Root Formation

According to Orban, development of the roots begins after enamel and dentin formation has reached the future cementoenamel junction (CEJ). The epithelial dental organ forms Hertwig’s epithelial root sheath, which initiates formation and molds the shape of the roots. Hertwig’s sheath takes the form of one or more epithelial tubes (depending on the number of roots of the tooth, one tube for each root). During root formation, the apical foramen of each root has a wide opening limited by the epithelial diaphragm. The dentinal walls diverge apically, and the shape of the pulp canal is like a wide-open tube. Each root contains one canal at this time, and the number of canals is the same as the number of roots ( Fig. 24-2, A ). When root length is established, the sheath disappears, but dentin deposition continues internally within the roots.

Faciolingual cross section of the mesial root of a mandibular primary molar.

A, Formation of the root at the time the root length is completed; only one canal is present. B, Differentiation of the root into separate canals by the continued, but incomplete deposition of dentin in central areas . Small fins and branches are present between the two canals. C, Canals are completely divided; root resorption has begun.

Differentiation of a root into separate canals, as in the mesial root of the mandibular molars, occurs by continued deposition of dentin. This narrows the isthmus between the walls of the canals and continues until the formation of dentin islands in the root canal and eventual division of the root into separate canals. During the process, communications exist between the canals as an isthmus and then as fins connecting the canals ( Fig. 24-2, B ). (See Chapter 12 for a complete description of pulp and dentin formation.)

As growth proceeds, the root canal is narrowed by continued deposition of dentin, and the pulp tissue is compressed. Additional deposition of dentin and cementum closes the apex of the tooth and creates the apical convergence of the root canals common to the completely formed tooth ( Fig. 24-2, C ) .

Root length is not completed until 1 to 4 years after a tooth erupts into the oral cavity. In the primary dentition, root length is completed in a shorter period than in the permanent tooth because of the shorter length of the primary roots.

The root-to-crown ratio of the primary teeth is greater than that of the permanent teeth. The primary roots are narrower than the permanent roots. The roots of the primary molars diverge more than those of the permanent teeth; this feature allows more room for the development of the crown of the succeeding premolar (see Fig. 24-1 ).

The primary tooth is unique insofar as resorption of the roots begins soon after formation of the root length has been completed. At this time, the morphology of the root canals roughly corresponds to the form and shape of the external anatomy of the teeth. Root resorption and the deposition of additional dentin within the root canal system, however, significantly change the number, size, and shape of the root canals within the primary tooth. A more detailed description of how this affects the primary teeth is presented later in this section.

It should be noted that most variations within the root canals of primary and permanent teeth are in the faciolingual plane; dental radiographs do not visualize this plane but show the mesiodistal plane. Therefore, when reviewing clinical radiographs, many of the variations that may be present are not visible. Figures 24-3 and 24-4 show silicone models of root canals, and Figure 24-5 shows a reconstructed digital image to illustrate morphology not visible with plain radiographs. The increasing availability of three-dimensional imaging techniques, such as cone beam computed tomography, is bringing greater understanding of such anatomic features to practicing clinicians.

Primary central incisors and silicone models of pulp canals.

A, Facial surfaces. B, Beginning resorption of roots on apical third of lingual surfaces. C, Models. Pulp canals were injected with silicone, and the tooth structure decalcified away, leaving a model of the root canal systems. Note the division of the canal in the model on the left.

Maxillary primary canine and silicone model of the root canal.

A, Mesial surface. B, Model of the root canal.

Three-dimensional tomographic images of a maxillary second primary molar.

A, Mesial view of primary molar with four root canals. Note the fins of pulp tissue between the distofacial and palatal canals. B, Same tooth from the distal view. Note the wide area of pulp tissue connection between the distofacial and palatal canals.

(Courtesy Paul Dummer and Sue Bryant, Cardiff University, Wales, UK.)

Primary Root Canal Anatomy

To treat the pulps of primary teeth successfully, the clinician must have a thorough knowledge of the anatomy of the primary root canal systems and the variations that exist within them. Understanding some of the variations in the primary root canal systems requires an understanding of root formation (see previous discussion and Box 24-1 ).

Primary Anterior Teeth

The morphology of root canals in primary anterior teeth resembles the form and shape of the roots of the teeth themselves (see Figs. 24-3 and 24-4 ). The permanent tooth bud lies lingual and apical to the primary anterior tooth, so physiologic root resorption of primary incisors and canines begins on the lingual aspect of the apical third of the roots (see Fig. 24-3, A ).

Maxillary Incisors

The root canals of maxillary primary incisors are almost round in cross section but somewhat compressed in a faciolingual direction. Commonly these teeth have one canal without bifurcations. Apical ramifications and accessory and lateral canals are rare but may occur (see Fig. 24-3 ).

Mandibular Incisors

The root canals of primary mandibular incisors are flattened on the mesial and distal surfaces and are sometimes grooved, progressing in an apical direction to an eventual division into two canals (facial and lingual). The presence of two canals is seen less than 10% of the time. Occasionally, lateral or accessory canals are observed.

Maxillary and Mandibular Canines

The root canals of primary maxillary and mandibular canines correspond to the exterior root shape: a rounded, triangular shape with the base toward the facial surface. Sometimes the lumen of the root canal is compressed in the mesiodistal dimension. The canines have the simplest root canal systems of all the primary teeth and offer few challenges during endodontic treatment. Bifurcation of the canal does not normally occur. Lateral canals and accessory canals are rare (see Fig. 24-4 ).

Primary Molars

Often, primary molars have the same number and position of roots as the corresponding permanent molars (see Fig. 24-5 ). Maxillary molars have three roots, two facial and one palatal; mandibular molars have two roots, mesial and distal. The roots of the primary molars are long and slender compared with crown length and width, and they diverge to allow for permanent tooth bud formation.

When full-length root formation has just been completed in the primary molars, only one root canal is present in each of the roots. The continued deposition of dentin internally may divide the root into two or more canals. During this process, communications exist between the canals and may remain in the fully developed primary tooth as isthmi or fins connecting the canals (see Fig. 24-2, B , and Fig. 24-5 ).

In primary teeth, the deposition of secondary dentin has been reported to occur after root-length completion. This may result in changes to the basic root canal morphology, producing variations and alterations in the number and size of the root canals. This deposition begins at about the time root resorption begins. Variations in form are more pronounced in teeth that show evidence of root resorption.

The greatest variation in morphology of the root canals occurs in the mesial roots of maxillary and mandibular primary molars. This variation originates in the apical region as a thinning of the narrow isthmus between the facial and lingual extremities of the apical pulp canals. Subsequent deposition of secondary dentin may produce complete separation of the root canal into two or more individual canals. Many fine connecting branches or lateral fibrils form a connecting network between the facial and lingual aspects of the root canals (see Fig. 24-5 ).

The variations found in the mesial roots of the primary molars are also found in the distal and lingual roots but to a lesser degree. Accessory canals, lateral canals, and apical ramifications of the pulp are common in primary molars, occurring in 10% to 20%.

In the primary molars, resorption usually begins on the inner surfaces of the roots next to the interradicular septum. The effects of resorption on canal anatomy and root canal filling on the primary teeth are discussed in detail later in this chapter.

Maxillary First Primary Molar

The maxillary first primary molar has two to four canals that correspond approximately to the exterior root form, with much variation. Usually, the palatal root is round and often longer than the two facial roots. Bifurcation of the mesiofacial root into two canals is common and occurs in approximately 75% of maxillary first primary molars.

Fusion of the palatal and distofacial roots occurs in approximately one third of maxillary first primary molars. In most of these teeth, two separate canals are present, with a very narrow isthmus connecting them. Islands of dentin may exist between the canals, with many connecting branches and fibrils.

Maxillary Second Primary Molar

The maxillary second primary molar has two to five canals roughly corresponding to the exterior root shape. The mesiofacial root usually bifurcates or contains two distinct canals. This occurs in approximately 85% to 95% of maxillary second primary molars.

Fusion of the palatal and distofacial roots may occur. These fused roots may have a common canal, two distinct canals, or two canals with a narrow connecting isthmus of dentin islands between them and many connecting branches or fibrils.

Mandibular First Primary Molar

The mandibular first primary molar usually has three canals, again corresponding approximately to the external root anatomy, but it may have two to four canals. It is reported that approximately 75% of the mesial roots contain two canals, whereas only 25% of the distal roots contain more than one canal.

Mandibular Second Primary Molar

The mandibular second primary molar may have two to five canals, but it usually has three. The mesial root has two canals approximately 85% of the time, whereas the distal root contains more than one canal only 25% of the time.

History and Characteristics of Pain

The character of any presenting pain is first identified in the history. Wherever possible, the distinction should be made between provoked and spontaneous pain.

Provoked pain is usually triggered by a thermal or an osmotic stimulus (e.g., cold drinks, eating candy) and usually ceases when the stimulus is removed. This history is indicative of minor, reversible pulp inflammation. Provoked pain may sometimes be confused with that caused by interproximal impaction of food ( Fig. 24-6 ), soreness associated with tooth exfoliation, or eruption of permanent teeth.

Bone loss (and pain) caused by food impaction in interproximal space between primary molars.

A, First and second mandibular primary molars with caries and marginal bone loss caused by food impaction. B, Healthy bone after restoration of teeth.

By contrast, spontaneous pain is not consistently associated with an external stimulus, may arise at any time of the day, or may wake the child from sleep. In both primary and young permanent teeth, spontaneous pain and provoked pain that continues long after the causative factor has been withdrawn are usually associated with extensive, irreversible pulpal inflammation that extends into the root canals. Primary teeth with a history of spontaneous toothache are unreliable candidates for vital pulp therapy and should not be considered for any form of treatment short of pulpectomy or extraction. The situation is quite different for immature permanent teeth. Because the consequences of losing vital pulp functions are so serious, immature permanent teeth with a similar pain history should always be considered for pulpotomy, apexogenesis, or even regenerative techniques in an effort to safeguard tooth development (see later sections on immature permanent teeth).

Clinicians faced with an apparently graphic pain history should not neglect to conduct a proper clinical examination because other conditions, such as papillitis caused by interproximal food impaction, can mimic pulpal pain.

Equally, the absence of pain should not encourage clinical complacency because varying degrees of pulp degeneration or even complete necrosis can be encountered without any report of pain. Consequently, children may present without any complaint, despite extensive carious lesions and a draining sinus tract. Those who have developed early childhood caries (e.g., nursing bottle caries) may have no experience of their teeth feeling any other way and thus no special pain history to report.

Clinical Examination

A careful extraoral and intraoral examination is of great importance in identifying teeth with pulpal involvement. Signs such as tooth discoloration, gross caries, redness and swelling of the vestibulum, or a draining sinus tract may strongly suggest pulpal pathoses. In addition, attention should be paid to teeth with extensive fractured or missing restorations or restorations with recurrent caries. All may indicate involvement of the pulp through the relatively thin and porous dentin of the cavity floor.

Palpation, Percussion, and Mobility

Fluctuation, felt by palpating a swollen mucobuccal fold, may be the expression of an acute dentoalveolar abscess that may not be visualized yet externally. Bone destruction associated with a chronic dentoalveolar abscess may also be detected by palpation.

Although significant inflammatory bone loss can make primary teeth mobile, this is not a reliable, objective test of pulpal status. Teeth with varying degrees of pulpal inflammation may have very little mobility, whereas mobility can be significant during phases of active physiologic root resorption in primary teeth with healthy pulps.

Comparing the mobility of a suspicious tooth with its contralateral equivalent can be especially helpful in clarifying such quandaries. If a significant difference in mobility is noted, this, along with other diagnostic information, may suggest pulpal inflammation or necrosis.

Sensitivity to percussion may reveal a painful tooth in which pulpal breakdown has resulted in acute periradicular periodontitis. Exceptions include recently traumatized teeth. Care should be taken in percussing the teeth of children; Pinkham et al. recommend gentle use of a fingertip rather than the end of a dental mirror.

Pulp Tests

Standard electrical and thermal pulp provocation tests are of limited value in the primary dentition and in young permanent teeth with incompletely developed apices. Although these tests may indicate the presence of some vital responsive tissue, they do not give reliable data on the extent of pulpal inflammation. Many children with perfectly normal teeth do not respond to the electrical pulp tester, even at the higher settings. In addition, young patients may give unreliable responses to such provocation tests because of apprehension, fear, or general management problems.

The unreliability of electrical pulp testing in immature permanent teeth has been reported in several studies. Klein showed responses ranging from 11% in 6- to 11-year-olds with completely open apices to 79% in older children with complete root formation.

Thermal tests may be more reliable than electrical methods for determining the presence of vital responsive tissue in immature permanent teeth, and carbon dioxide snow has been shown to be more effective than ice and ethyl chloride. Heat is unreliable as a diagnostic test in young children.

Laser Doppler flowmetry has been reported to be reliable for diagnosing pulpal vitality in immature permanent teeth, but the equipment has not been perfected for clinical use and is cost prohibitive. It is also affected by blood pigmentation of the crown, or by the presence of large or full-coverage coronal restorations.

Radiographic Examination

The clinical examination should be supplemented where appropriate with high-quality radiographs. Interradicular (furcal) radiolucencies, a common finding in primary posterior teeth with pulpal pathoses, are best observed in bite wing radiographs. If the apical area cannot be clearly observed, a periapical view should be obtained. The integrity of the lamina dura of the affected tooth should be compared with that of adjacent or contralateral teeth.

Current radiographs are essential in examining for caries, restoration integrity, previous endodontic treatments, and resorptive and periapical changes in primary and young permanent teeth. In children, interpretation of radiographs is complicated by physiologic root resorption of primary teeth and incompletely formed roots of permanent teeth. If the clinician is not familiar with interpreting radiographs of children or does not have radiographs of good quality, these normal conditions can easily be misinterpreted as pathologic changes in need of treatment. In the case of immature permanent teeth, comparison of root formation with the contralateral tooth should always be considered.

The radiograph does not always demonstrate periapical pathosis, nor can the proximity of caries to the pulp always be accurately determined (see also Chapter 2 ). What may appear as an intact barrier of secondary or tertiary dentin overlying the pulp may actually be a perforated mass of irregularly mineralized and/or carious dentin overlying a pulp with extensive inflammation.

The presence of calcified masses within the pulp is an important diagnostic sign ( Fig. 24-7 ). Mild, chronic irritation to the pulp stimulates tertiary reactionary dentin formation. When the irritation is acute and rapid in onset, the defense mechanism may not have a chance to lay down reactionary dentin. When the disease process reaches the pulp, the pulp may form calcified masses away from the exposure site. These calcified masses can be associated with degeneration of the coronal pulp and inflammation of the radicular pulp in primary teeth. In the absence of other clinical evidence, it is unclear whether this warrants invasive treatment in all cases. Certainly for immature permanent teeth, the presence of calcific metamorphosis within the coronal pulp chamber would not in isolation warrant pulpectomy and root canal treatment.

Calcified mass in the pulp chamber.

Internal and external root resorption has occurred. The calcified mass (arrow) is an attempt to block a massive carious lesion. Because of the root resorption, this tooth should be extracted. Note the bone loss in the bifurcation area.

Pathologic changes in the periapical tissues surrounding primary molars are most often apparent in the bifurcation or trifurcation areas rather than at the apices (as generally seen in permanent teeth) (see Fig. 24-7 ). Pathologic bone and root resorption indicates advanced pulpal degeneration that has spread into the periapical tissues. The pulpal tissue may remain vital even with such advanced degenerative changes. Periapical radiolucencies of primary anterior teeth, like those in permanent teeth, are usually at the apices.

Internal resorption occurs frequently in the primary dentition after pulpal involvement. It is always associated with extensive inflammation, and it usually occurs in the molar root canals adjacent to the bifurcation or trifurcation area. Because of the thinness of primary molar roots, once the internal resorption becomes visible on radiographs, it has usually advanced to root perforation ( Fig. 24-8 ). In some instances, however, the process is reversible and self-correcting, and the resorbed area becomes filled with mineralized tissue. If a perforation of the root occurs in a primary tooth because of internal resorption, all forms of pulp therapy are contraindicated. The treatment of choice is observation (if the area of the resorption is confined to the tooth) or extraction (if the process has reached the bone).

Pulpotomy failure.

Note the internal resorption, which has perforated the pulp chamber floor and resulted in a furcal radiolucency.

In immature permanent teeth, it is often difficult to assess the extent of apical closure. Plain-film images are frequently misleading because under normal conditions, they show the mesiodistal plane of the tooth but give little information about the faciolingual dimension. Except for the maxillary central and lateral incisor, all other root canals of the permanent teeth are wider in the faciolingual plane than in the mesiodistal plane. The faciolingual aspect of the root canal is two to three times as wide as the mesiodistal width and is the last to become convergent apically as the root develops. Therefore, it is possible to have a dental radiograph showing an apically convergent root canal, whereas in the faciolingual plane, the root canal is divergent. Equally, canals that are apically diverging in the faciolingual view may be parallel or converging in the mesiodistal view. As mentioned, contemporary three-dimensional imaging techniques are beginning to improve understanding, both in the research laboratory ( Fig. 24-9 ) and in the clinic.

Three-dimensional tomographic images of an immature maxillary canine.

A, Faciolingual view. B, Mesiodistal view. Such imaging techniques are bringing new anatomic awareness to both the research laboratory and the clinic.

(Courtesy Paul Dummer and Sue Bryant, Cardiff University, Wales, UK.)

In summary, radiographs add to the diagnostic process by visualizing the presence or absence of the following:

• 1.

  Deep caries with possible or definite pulp involvement

• 2.

  Deep restorations close to a pulp horn

• 3.

  A successful or failing pulp cap, pulpotomy, or pulpectomy

• 4.

  Changes within the pulp, such as calcific barrier formation, calcific metamorphosis, and pulp stones (denticles)

• 5.

  Pathologic root resorption, which may be internal (within the root canal) or external (affecting the root or the surrounding bone). Internal inflammatory resorption indicates inflammation of a vital pulp, whereas external inflammatory resorption demonstrates a nonvital pulp with extensive inflammation, including resorption of the adjacent bone. External, replacement resorption usually follows trauma and is discussed more fully in Chapters 16 and 20 .

• 6.

  Periapical and interradicular radiolucencies of bone. In primary molar teeth, any radiolucency associated with a nonvital tooth is usually located in the furcation area, not at the apices. This is because of the presence of accessory canals on the pulpal floor area. A bite wing film is frequently a useful diagnostic aid, particularly in maxillary molars where the developing premolar obscures the furca in a periapical radiograph.

• 7.

  The degree of root formation in young permanent teeth

It is important to emphasize once again that the clinician should be familiar with the normal factors that complicate interpretation of radiographs in children: larger bone marrow spaces, superimposition of developing tooth buds, normal resorption patterns of the teeth, and immature root apices.

Restorative Diagnosis: Pulpal Exposures and Hemorrhage

It has been reported that the size of the exposure, the appearance of the pulp, and the color and amount of hemorrhage are important factors in diagnosing the extent of inflammation in a pulp exposed by caries. The presence of excessive or deep purple hemorrhage from an exposed or amputated pulp is evidence of extensive inflammation in both primary and young permanent teeth. A true carious exposure is always accompanied by pulpal inflammation (see Chapter 13 ), and even a pinpoint carious exposure can be associated with pulpal inflammation ranging from minimal to extensive or even complete necrosis. However, massive exposure in primary teeth is always associated with widespread inflammation or necrosis and makes the tooth a poor candidate for any form of vital pulp therapy. As discussed previously, this rule does not apply for young permanent teeth with incomplete root development, where the premature loss of vital pulp functions is so catastrophic that every effort should be made to safeguard tooth development (see later section on the management of pulpal exposure in immature permanent teeth).

Sometimes a final working diagnosis can be reached only by direct evaluation of the pulp tissue, and a decision about treatment is made accordingly. For example, if a pulpotomy is planned in a primary molar, the bleeding from the amputation site should be normal, and hemostasis should be evident after 2 to 3 minutes of light pressure with a moistened cotton pellet. Significant bleeding beyond this point indicates inflammation of the radicular pulp, and a more radical treatment, such as pulpectomy or extraction, should be considered. Conversely, if a pulp polyp is present and bleeding stops normally after coronal pulp amputation, a pulpotomy may be performed instead of a more radical procedure.

In the case of an immature permanent tooth, persistent hemorrhage after several minutes of sodium hypochlorite application is an indication of serious pulp inflammation, and a tooth initially scheduled for a direct mineral trioxide aggregate (MTA) pulp cap may be a better candidate for a pulpotomy, apexification, or pulp regeneration (see later section on immature permanent teeth).

Guthrie et al. attempted to use the first drop of hemorrhage from an exposed pulp site as a diagnostic aid for determining the extent of degeneration within the pulp. A white blood cell differential count (i.e., hemogram) was made for each of 53 teeth included in the study. A detailed history was obtained, including percussion, electrical pulp testing, thermal tests, mobility, and history of pain. The teeth were extracted and histologically examined. On correlation of the histologic findings with the hemogram and history, it was determined that percussion, electrical and thermal pulp tests, and mobility were unreliable in establishing the degree of pulpal inflammation. The hemogram did not give reliable evidence of pulpal degeneration, although teeth with advanced degeneration of the pulp involving the root canals did have an elevated neutrophil count. A consistent finding of the study, however, was advanced degeneration of pulpal tissue in teeth with a history of spontaneous toothache.

The outward clinical signs of inflammation represent a succession of cellular, vascular, and immunologic processes involving many endogenous mediators. Inflammatory mediators (vascular mediated and cell released) and their role in pulpal inflammation have been the subject of much research. The relationship between the concentration of a known cell-released inflammatory mediator (prostaglandin E ₂ [PGE ₂ ]) in pulpal blood samples and treatment outcome after vital pulpotomy in extensively carious primary molars has been reported. Thirty-nine primary molars with no history of spontaneous pain had blood samples harvested from the radicular pulp stumps immediately after coronal pulp amputation. Enzyme immunoassay of the samples for PGE ₂ detected the inflammatory mediator in all samples. A wide range of concentrations was detected, and it was shown that the concentration of PGE ₂ detected correlated positively with radiologic signs of failure after treatment. The authors tempered their findings by describing the dependence upon a single inflammatory mediator to predict prognosis as oversimplistic and suggested the “trauma” of pulp amputation would stimulate prostaglandin production irrespective of the underlying inflammatory status of the tissue. Similarly, a rapid and low-cost, chairside diagnostic kit to assess the extent of pulp inflammation does not yet exist. Therefore, despite research in this area, clinicians still rely upon empiric clinical findings to diagnose the inflammatory status of the pulp.

Diagnosis After Traumatic Injuries in Children

The details of trauma management are considered in Chapter 20 . Injuries to the primary dentition are common, occurring in 1 in 3 children by the age of 5 years. Diagnosis after traumatic injuries requires consideration of other factors in addition to those previously discussed. The most frequent injury in the primary dentition is tooth displacement that occurs because the bone is less dense and the roots are shorter. Healing varies from normal without sequelae to canal calcification or pulpal necrosis. Canal calcification may vary from an amorphous material resembling osteodentin to partial or complete closure of the canal.

Pulp Diagnosis and Treatment Planning After Trauma

Treatment guidelines are almost nonexistent concerning healing and complications after trauma in primary teeth. The literature is devoid of histologic or microbiologic studies in this area. In a study of 545 traumatized primary maxillary incisors, Borum and Andreasen found that 53% developed pulpal necrosis, and 25% developed canal obliteration. The age of the patient, degree of tooth displacement, concurrent crown fracture, and amount of root resorption were factors influencing pulpal necrosis and calcification. Teeth with a coronal fracture were less likely to suffer mineralized obliteration of the root canal than those that had been luxated.

In deciding on the appropriate treatment, the proximity of the primary tooth to the permanent successor is an important consideration. The treatment least likely to damage the permanent tooth should be chosen. Studies present conflicting data on the merits of treating or extracting traumatized primary teeth. Some have suggested no relationship, whereas others have shown more extensive developmental disturbances if the primary tooth is treated and preserved.

Transient or permanent discoloration of the crown occurs in approximately 50% of traumatized primary incisors, varying from yellow to dark gray and usually becoming evident in 1 to 3 weeks. The yellow discolorations are frequently associated with canal calcification but are not commonly associated with pulp necrosis.

Pulpal necrosis ranging from 50% to 82% has been reported in traumatized primary incisors with dark gray discoloration, compared to 25% in those with no discoloration. Croll et al. pointed out that color change in the absence of other clinical findings is unreliable. The diagnosis of pulpal necrosis is usually based on dark gray color and radiographic evidence of periapical pathology or cessation of root development.

In immature permanent teeth, discoloration of the crown is also one of the best diagnostic indicators after traumatic injuries. Yellow or brown-tinted discoloration usually indicates calcification of the pulp space; a gray color is usually associated with pulpal necrosis. A return to normal after transient coronal discoloration and transient apical breakdown up to 4 months’ duration has also been reported.

Indirect Pulp Therapy in Primary Teeth

Indirect pulp treatment (IPT) in the primary dentition is considered a contemporary, effective approach to the management of a deep carious lesion in the absence of signs or symptoms of irreversible pulp pathosis. It involves the removal of caries to leave a layer of stained dentin at the cavity floor in areas where its removal would result in exposure of pulp tissue. A decision to use this treatment is derived from a thorough pain history, clinical and radiographic examination, direct evaluation of the cavity preparation, and a good knowledge of tooth anatomy and the caries process.

The aims of IPT are to arrest the carious process, provide conditions conducive to the formation of reactionary dentin, and promote remineralization of the altered dentin remaining. This in turn is expected to promote pulpal healing and preserve the vitality of the pulp.

Technique

The clinical steps in IPT may be divided into stages involving partial caries removal, placement of an antibacterial agent, and restoration of the crown in a way that provides the optimum coronal seal.

Some studies of IPT in primary teeth have advocated a two-stage approach. After initial partial caries removal without local anesthetic, the cavity was restored for 1 to 3 months, using a reinforced zinc oxide–eugenol (ZOE) cement or glass ionomer restoration. After this, further caries removal and definitive restoration were undertaken under local anesthesia. It has been suggested that this approach may have a use in the very young or very anxious child, but it may be argued that a single-visit approach is more appropriate and successful. Thinner dentin in the primary tooth compared with the permanent tooth may result in a higher risk of pulp exposure if a primary tooth is reentered to remove residual caries.

The following technique is based on a recommended approach :

• 1.

  Local anesthetic

• 2.

  Isolation with a rubber dam

• 3.

  Removal of all caries at the enamel-dentin junction of the cavity, ensuring caries-free walls

• 4.

  Judicious removal of soft, deep carious dentin, using large, round steel burs (#6 to #8). Hand excavators should be used only to remove caries at the dentino­enamel junction and should be angled outward at the DEJ, with care taken not to produce a pulp exposure.

• 5.

  Placement of an appropriate lining material, such as glass ionomer cement, hard-setting calcium hydroxide (Ca(OH) ₂ ). ZOE, or a directly bonded restoration

• 6.

  Definitive restoration providing the optimal coronal seal, such as an adhesive restoration or preformed metal (stainless steel) crown

Unfortunately, the evidence currently is insufficient to promote a definitive choice for the lining material placed over the residual stained dentin. Studies show good success rates for resin-modified glass ionomer lining/restoration, self-etching adhesive systems, and Ca(OH) ₂ linings.

Although additional prospective clinical evaluation of IPT is required, studies involving the primary dentition show good success rates (over 90% at 3 years). However, it has been suggested that a successful outcome is highly dependent upon obtaining the optimal coronal seal to eradicate the nutrient supply to residual cariogenic microorganisms. When intracoronal amalgam restorations were compared with extracoronal preformed metal (stainless steel) crowns after IPT, failure was 7.7 times more likely with the amalgam restorations. Adhesive restorations also were reported to provide the optimal coronal seal after pulp therapy. Therefore, to secure the best possible outcome after IPT, or indeed after any pulp therapy for the primary tooth, definitive restoration should involve a bonded restoration and/or preformed metal (stainless steel) crown.

The Hall Technique

The Hall technique, an emerging method of managing dental caries in primary molars, is noteworthy in this section on indirect pulp therapy. The technique was introduced by Dr. Norna Hall, a primary care clinician in Scotland, who was overwhelmed by the number of children with dental caries. In Scotland, by the age of just 5 years, 55% of children had visible decay into dentin, and 16% had experienced tooth extraction. In response, this clinician decided to manage lesions in primary molars (that were symptom free and free of radiographic signs of periradicular pathology) by cementing a preformed metal (stainless steel) crown in place without local anesthesia, tooth preparation, or any attempt at caries removal. This is viewed in the United Kingdom as an undoubtedly novel approach to caries management and caught the attention of clinical academics in Scotland. Audit data from Hall’s records indicate that her technique may have results similar to those for more conventional approaches in the primary care setting.

Subsequently, a randomized, controlled clinical trial was undertaken comparing the Hall technique with conventional restorations in carious primary molars in primary care. Interestingly, the Hall technique was preferred to conventional restorations by most children, guardians, and clinicians. After a review period of 2 years, in which the teeth managed using Hall preformed metal (stainless steel) crowns were compared with conventional restorations, the “Hall crowns” showed better treatment outcomes for both pulpal health and restoration longevity. In the United Kingdom, this has further stimulated an ongoing debate over whether restorative treatment provided by general clinicians in primary care is an effective way of managing caries in the primary dentition.

Certainly this new and novel approach would appear to encompass present-day theory. Potentially cariogenic microorganisms require a very specific environment to start or progress a carious lesion. By sealing the lesion within the tooth, this removes the nutrient supply and stops or slows the lesion’s progress. Nevertheless, obtaining an effective and complete coronal seal should be of utmost concern.

Direct Pulp Capping in Primary Teeth

The life span of the average primary tooth from initial development to exfoliation is significantly shorter than that of a permanent tooth. Primary teeth undergo dramatic physiologic and physical changes over a relatively short period. Clinicians should keep in mind that pulp tissue is not static in nature, and outcomes for the same procedure may differ, depending on the age of the patient. Furthermore, because of the aging process within dental pulp, the likelihood of successful pulp capping diminishes with age. This may be explained by the increase in intrapulpal fibrous and calcific deposits seen with aging, together with a reduction in both pulpal volume and pulp fibroblast proliferation.

Direct pulp capping should not be performed on carious pulpal exposures in primary teeth. Guidelines developed by both the American Academy of Pediatric Dentistry (AAPD) and the British Society of Paediatric Dentistry (BSPD) recommend that direct pulp capping should be reserved only for small mechanical or traumatic exposures in primary teeth. Under these circumstances, it is presumed that the conditions for a favorable pulpal response are optimal.

Pulpotomy in Primary Teeth

The AAPD guidelines for pulp therapy for primary and young permanent teeth describe the pulpotomy procedure in primary teeth as the amputation of the affected or infected coronal portion of the dental pulp, preserving the vitality and function of all or part of the remaining radicular pulp. Evidence of successful pulp therapy includes the features listed in Box 24-2 .

Complete amputation of the coronal pulp is the norm for pulpotomy procedures performed on the cariously exposed vital pulps of primary teeth. After this, and once hemostasis has been achieved, a decision is made on the wound dressing or technique to apply to the pulp stumps.

The following are some of the available options. The success of all procedures depends upon ensuring that the residual pulp tissue is correctly diagnosed as healthy or reversibly inflamed.

• •

  Hemostasis and maintenance of vital tissue (e.g., ferric sulfate solution, electrosurgery, laser)

• •

  Dentin bridge formation and maintenance of vital tissue (e.g., MTA)

• •

  Superficial (partial) pulp tissue fixation and maintenance of vital tissue (e.g., dilute formocresol solution, gluta­raldehyde solution)

Many pharmacotherapeutic agents have been used for pulp therapy in the past. Formocresol has been the most popular agent, mainly because of its ease of use and good clinical success. Nonetheless, formocresol, and in particular one of its constituents, formaldehyde (FAD), has come under close scrutiny because of reported concerns related to the systemic distribution of FAD and its potential for toxicity, allergenicity, carcinogenicity, and mutagenicity. Other medicaments (e.g., glutaraldehyde, Ca(OH) ₂ , collagen, ferric sulfate, MTA) have been suggested as possible replacements. However, varying success rates and questions about the safety of these materials make it clear that additional research is required on the use of these and other pharmacotherapeutic agents.

Nonpharmacologic hemostatic techniques have been recommended, including electrosurgery and laser therapy. Research involving human clinical trials on both these techniques is sparse; nevertheless, electrosurgical pulpotomy currently is taught in several dental schools. Comprehensive reviews of the techniques and agents used in vital pulp therapy and discussion of possible new modalities are available in the literature.

Indications and Contraindications for Pulpotomy

Pulpotomy is indicated for pulp exposure on primary teeth in which the inflammation or infection is judged to be confined to the coronal pulp. If inflammation has spread into the tissues within the root canals, the tooth should be considered a candidate for pulpectomy and root canal filling or extraction. The contraindications to pulpotomy on a primary tooth are outlined in Box 24-3 .

Technique

Pulpotomy is used for primary teeth with radicular pulp tissue judged to be free of inflammation and infection. Compromise on this principle leads to a diminished success rate. If inflamed vital (coronal) pulp tissue is amputated to leave residual healthy pulp tissue (radicular), the tissue remaining has the capacity to remain healthy if managed correctly. The overall success of vital pulp therapy in the primary dentition depends upon several factors:

• •

  Effective control of infection

• •

  Complete removal of inflamed coronal pulp tissue

• •

  Appropriate wound dressing

• •

  An effective coronal seal during and after treatment

An accurate diagnosis of pulp status is very important in aiding appropriate pulpal management. However, this can be challenging, particularly in young children. The following points highlight the diagnostic aids available.

• •

  An accurate pain history is helpful for determining the possible stage or extent of pulpal inflammation, but it may be difficult to elicit such information from a child.

• •

  Radiographic findings can guide treatment decisions. Pretreatment radiographs are essential to assess the extent of the carious lesion and its proximity to the pulp horns or chamber. They also provide information about periradicular pathosis.

• •

  Clinically, pulpal involvement can be assessed immediately after caries removal by a very careful search for evidence of a pulp exposure.

Technique for Coronal Pulp Amputation

Removal of the coronal pulp tissue is a process common to whichever pulpotomy procedure is chosen for the cariously exposed vital primary tooth. After successful coronal amputation and hemostasis ( Fig. 24-10, A and B ), the subsequent management of the radicular pulp stumps is defined by which pulpotomy technique the clinician chooses. For example, once hemostasis has been achieved, a wound dressing may be applied to the pulp wounds or, alternatively, the exposed tissue might be subjected to electrosurgery or laser application. Figure 24-10, C to H provides a schematic overview of the options and expected outcomes.

Three different approaches to the radicular pulp after coronal pulp amputation during pulpotomy in an extensively carious primary molar.

A, Primary molar with caries extending to the pulp. Note the inflammatory response in the coronal pulp. B, The tooth has undergone removal of the coronal pulp. The radicular pulp tissue is healthy and has stopped bleeding. C, A 1 : 5 dilute solution of formocresol may be applied to the pulp stumps for 5 minutes. This produces partial tissue fixation, which is greatest near the point of application. D, Intracoronal restoration: zinc oxide eugenol (ZOE) is placed directly over the pulp stumps, and an intracoronal restoration is placed. Vital radicular pulp may remain apically. E, A 15.5% ferric sulfate solution is applied to the pulp stumps for 15 seconds. This produces mechanical blockage of open capillaries by a protein-iron complex. F, Intracoronal restoration has been provided as in D. Healthy, vital pulp tissue remains in the root canals. G, Mineral trioxide aggregate (MTA) is placed directly over the radicular pulp stumps, and an intracoronal restoration is provided as before. H, The radicular pulp tissue remains vital beneath the MTA; a calcific bridge may form over time beneath the MTA.

Stages of the Technique for Coronal Pulp Amputation

• 1.

  After the initial diagnosis of probable vital pulpal involvement, the primary tooth is anesthetized and isolated with a rubber dam.

• 2.

  All caries is removed, and the observation of bleeding from exposure sites indicates vital (if inflamed) coronal pulp tissue ( Fig. 24-11, A and B ).

  

  Clinical stages of a vital pulpotomy using ferric sulfate solution.

  A, Extensive dental caries affecting a mandibular first primary molar. Note the proximity of the radiographic lesion to the mesial pulp horn. B, Caries removal, showing a carious pulpal exposure; bleeding is evident. C, Partial unroofing of the pulp chamber; note the bleeding coronal pulp before amputation. D, Roof of pulp chamber removed completely. E, A 15.5% solution of ferric sulfate is applied to the radicular pulp stumps with a dento-infuser tip supplied by the manufacturer. F, Hemostasis is evident at the radicular pulp stumps. G, Definitive restoration involves placement of zinc oxide eugenol, overlaid with glass ionomer intracoronally, followed by a preformed metal (stainless steel) crown.

  (Courtesy Vidya Srinivasan, Edinburgh Dental Institute, Scotland, UK.)

• 3.

  The entire roof of the pulp chamber is removed using a high-speed non–end cutting bur and copious water spray.

• 4.

  All the coronal pulp is amputated with a slow-speed #6 or #8 round bur or spoon excavator. Care must be exercised to fully unroof the chamber and extirpate all filaments of the coronal pulp ( Fig. 24-11, C and D ). If any filaments remain in the pulp chamber, hemorrhage will be impossible to control.

• 5.

  The pulp chamber is thoroughly washed with sterile water or saline to remove all debris, and the site is dried by vacuum and sterile cotton pellets.

• 6.

  Hemorrhage is controlled by slightly moistened cotton pellets (wetted and blotted almost dry) placed against the stumps of the pulp at the openings of the root canals. Completely dry cotton pellets should not be used; fibers of the cotton will be incorporated into the clot, and when the pellet is removed, hemorrhage will result. Dry cotton pellets are placed over the moist pellets, and pressure is exerted on the mass. Hemorrhage should be controlled in this manner within 3 minutes. It may be necessary to change the pellets to control all hemorrhage.

• 7.

  If bleeding persists, the clinician should carefully check that all tissues of the pulp were removed from the pulp chamber and that the amputation site is clean. If the bleeding persists from one of the canals, that canal can be reentered with a small round bur to amputate the suspected inflamed tissue; the canal then is rinsed again, and cotton pellet pressure is applied.

• 8.

  If hemostasis is not achieved within 2 to 3 minutes, the pulp tissue within the canals is probably inflamed, and the tooth is not a candidate for a pulpotomy. The clinician should then proceed with pulpectomy, or the tooth should be extracted.

Once bleeding has stopped at the radicular pulp stumps, the wounds are managed according to one of the following pulpotomy techniques (see Fig. 24-10 ):

• •

  Application of dilute formocresol solution for 5 minutes

• •

  Application of 15.5% ferric sulfate solution for 15 seconds ( Fig. 24-11, E and F )

• •

  Permanent placement of MTA

• •

  Electrosurgical manipulation of the wound surfaces

• •

  Laser manipulation of the wound surfaces

Figure 24-11, G shows the treated tooth restored with a preformed metal crown.

Formocresol Pulpotomy

Technique (See Fig. 24-10, C and D )

• 1.

  After coronal pulp amputation and once hemostasis has been achieved, a cotton pellet moistened with one-fifth dilution formocresol solution ( Box 24-4 ) is blotted to remove excess formocresol and then placed in direct contact with the pulp stumps for 5 minutes. Formocresol is caustic and creates a severe tissue burn if allowed to touch the gingiva.

  Box 24-4

  Formulation of a One-Fifth Dilution of Formocresol Solution

  Mix 1 part Buckley’s formocresol solution with:

  • •

    1 part distilled water

  • •

    3 parts glycerin

• 2.

  When the pellet is removed, the tissue appears brown, and no hemorrhage should be evident.

• 3.

  If an area of the pulp was not in contact with the medication, the procedure must be repeated for that tissue. Small cotton pellets for applying the medication usually work best because they allow closer approximation of the material to the pulp.

• 4.

  A cement base of ZOE is placed over the pulp stumps and allowed to set. The tooth may then be restored permanently.

• 5.

  The restoration of choice is a preformed metal (stainless steel) crown for primary molars. On anterior primary teeth, a composite tooth-colored restoration is the treatment of choice unless the tooth is so badly broken down that it requires a crown.

The use of formocresol in dentistry remains controversial. Formaldehyde, a volatile organic compound, is toxic and corrosive, especially at the point of contact. Formocresol’s other active constituent, cresol, is also an irritant and corrosive in nature.

Local and Systemic Accumulation of Formaldehyde

Localized accumulation of formocresol or FAD has been demonstrated in pulp, dentin, periodontal ligament, and bone surrounding the apices of pulpotomized teeth.

Although animal studies have identified radioisotope-labeled formocresol or FAD in major organs after systemic injection or multiple pulpotomies, researchers concluded that the doses of formocresol were far in excess of those used in normal clinical practice. Therefore, it has been suggested that the findings should not be extrapolated to clinical use in humans. More recently, a review of the safety of formocresol, including FAD metabolism, suggested that FAD is rapidly metabolized, so the findings of previous studies may have been identifying FAD metabolites systemically and not FAD itself. Notwithstanding this, the amount of formocresol absorbed systemically by way of the pulpotomy route is small and may not contraindicate use of the drug.

Formocresol as an Allergen

The results of studies investigating the allergenic risks of formocresol are equivocal. Studies have shown no evidence of an allergic response in nonpresensitized animals, and presensitized animals showed only a weak allergic potential. However, demonstration of an immune response to formocresol-fixed, autologous tissue implanted in connective tissues or injected into root canals has been reported.

Is Formocresol Carcinogenic?

With respect to mutagenicity and carcinogenicity, it is generally accepted that FAD is genotoxic in vitro, inducing mutations and DNA damage in cells from a variety of organisms, including humans. The possible link between FAD and carcinogenesis has been investigated in the field of occupational health medicine. In a review of several large longitudinal studies, the International Agency for Research on Cancer (IARC) reported that “sufficient evidence” exists that FAD had caused nasopharyngeal cancer in humans. This was suggested to be linked to a localized combination of irritation and genotoxicity of FAD, which repeat-dose inhalation studies using rodents has corroborated. In the dental context, the amount of FAD in a diluted solution of formocresol is small, but no data are available on the amounts of FAD vapor inhaled by patients or dental personnel during pulpotomy procedures and whether this may constitute a potential risk. Moreover, the often disregarded cresol ingredient itself may pose a genotoxic risk to mammalian cells. Formocresol solution used in pulpotomies in children has been reported as genotoxic after postpulpotomy harvested lymphocyte cultures displaying significantly increased chromosomal aberrations were compared with nonpulpotomized controls.

Despite these concerns, the formocresol pulpotomy continues to be one treatment choice available for primary teeth with vital, carious exposures of the pulp in which inflammation or degeneration is judged to be confined to the coronal pulp. The last reported worldwide survey of dental schools (in 1989) showed that most pediatric dentistry departments and pediatric dentists advocated the formocresol pulpotomy technique, and it may still be widely used in clinical practice. In the United Kingdom, since 2004, a general trend away from using formocresol has been noted, driven by several factors, such as difficulty obtaining the medicament, concerns related to its safety, and promising clinical results for newer, nonaldehyde techniques. However, the recent U.K. clinical guideline, Pulp Therapy for Primary Molars, still includes the formocresol pulpotomy as an option, as do the AAPD guidelines. Although formocresol pulpotomy is still taught in predoctoral pediatric dentistry programs in the United States, consensus is lacking on its use for vital pulp therapy in primary teeth.

The current formocresol pulpotomy technique is a modification of the technique reported by Sweet in 1930. The effect of formocresol on pulp tissue (i.e., the amount of tissue fixation) is controlled by the quantity that diffuses into the tissue and depends on the duration of application, the concentration used, the method of application, or a combination of these factors.

A one-fifth dilution formocresol solution has been widely advocated based on the outcomes of both in vitro and in vivo studies comparing dilute formocresol (see Box 24-4 ) with the undiluted solution ( Table 24-1 ). Histochemical investigations comparing dilute and undiluted formocresol noted little difference between initial effects on pulp tissue fixation but earlier recovery of enzyme activity and improvement in the rate of recovery from the localized cytotoxic effects of formocresol with diluted formocresol. Clinical studies have shown diluted formocresol to be as successful as full-strength formocresol.

There is enough evidence today to conclude that if formocresol is to be used at all, the one-fifth concentration should be preferred for pulpotomy procedures because it is as effective as and less damaging than the traditional preparation.

Formocresol and the Permanent Successor

The fear of damage to the succedaneous tooth has been offered as an argument against formocresol pulpotomy on primary teeth. Results from studies are inconsistent, ranging from the same incidence of enamel defects in treated and untreated contralateral teeth to an increase in defects and positional alterations of the underlying permanent tooth. It should be pointed out that studies of this nature are follow-up studies long after treatment, and the researchers had no knowledge of the existing status of the pulp before pulpotomy.

The effect of a formocresol pulpotomy upon the exfoliation time of primary molars is also equivocal; some studies found no consistent effect, and others reported early exfoliation.

Unlike the tissue response to Ca(OH) ₂ or MTA, no dentin bridge should be anticipated after formocresol is applied to exposed pulp tissue (see Fig. 24-10, C and D ). However, narrowing of the root canal through the continued deposition of dentin by the preserved radicular pulp may be observed in some cases ( Fig. 24-12 ).

Narrowing of the apical region of the root canal after formocresol pulpotomy.

Histologic section of a tooth showing deposition of new dentin along the walls of the apical region of the root canal.

Criteria for Success

Failure of a formocresol pulpotomy is usually detected on radiographs (see Fig. 24-8 ). The first signs of failure are often internal resorption of the root adjacent to the area where the formocresol was applied. This may be accompanied by external resorption, especially as the failure progresses. Sometimes, however, the internal resorption is self-corrected with deposition of calcified tissue. In the primary molars, radiolucency develops in the bifurcation or trifurcation area. In the anterior teeth, a radiolucent area may develop at the apices or lateral to the roots. With more destruction, the tooth becomes excessively mobile; a sinus tract usually develops. It is rare for pain to occur with the failure of a formocresol pulpotomy. Consequently, unless patients receive follow-up checks after a formocresol pulpotomy, failure may go undetected. When the tooth loosens and is eventually exfoliated, the parents and child may consider the circumstances normal.

The development of cystic lesions after pulp therapy in primary molars has been reported. An amorphous, eosinophilic material shown to contain phenolic groupings similar to those present in medicaments was found in the lesions. Myers et al. have observed furcal lesions in untreated, pulpally involved primary molars containing granulomatous tissue with stratified squamous epithelium, which suggests the potential for cyst formation. In a subsequent study involving failed, pulpotomized primary molars, most specimens were diagnosed as furcation cysts. These findings emphasize the importance of periodic follow-up to endodontic treatment on primary teeth. Figure 24-13 shows a favorable long-term outcome after a formocresol pulpotomy in a mandibular primary molar.

Five-year follow-up of a primary tooth treated by formocresol pulpotomy.

A, Pretreatment radiograph showing deep caries on the lower right first and second primary molars. B, One-year posttreatment radiograph. C, Five-year follow-up radiograph. Note the eruption of the lower right first permanent molar and first bicuspid.

Glutaraldehyde Pulpotomy

Glutaraldehyde has been suggested as an alternative to formocresol as a tissue fixative for vital pulpotomy. Histologic studies showed that it produced rapid surface fixation of pulp tissue but with limited depth of penetration, so a larger amount of radicular pulp tissue remained vital. Fixed pulp tissue may be replaced with dense collagenous tissue over time. Studies have also demonstrated less systemic distribution than was thought to occur with formocresol.

Glutaraldehyde has been shown to be rapidly metabolized with little toxic effect. It has also been demonstrated that although glutaraldehyde has antigenic action similar to that of formocresol, it is of a lower potential. However, there are perceived problems with the use of gluta­raldehyde as a pulpotomy agent:

• •

  Glutaraldehyde solutions are reported to be unstable.

• •

  Neither the optimum concentration nor optimal duration of application of glutaraldehyde solution have been established conclusively.

• •

  Clinical studies reported increasing failure rates with increasing time after pulpotomy, with lower levels of clinical success than with formocresol.

Despite its perceived enhanced safety compared with formocresol, glutaraldehyde has not gained favor over formocresol for pulpotomy in the primary dentition.

Ferric Sulfate Pulpotomy

Technique

• 1.

  After completion of coronal pulp amputation and achievement of hemostasis with moist cotton pellets, a 15.5% solution of ferric sulfate is applied to the radicular pulp stumps for 10 to 15 seconds.

• 2.

  The ferric sulfate may be applied using a cotton pellet or by allowing small droplets of the solution to drip from a burnisher tip onto the surface of the pulp tissue. One manufacturer also supplies a special dento-infuser tip for this purpose (Astringident, Ultradent Products, Salt Lake City, Utah) (see Fig. 24-10, E , and Fig. 24-11, E ).

• 3.

  Upon removal of the cotton pellet, the wounds appear brown, and no bleeding should be evident. If a small amount of residual bleeding occurs, one further application of ferric sulfate should be considered.

• 4.

  A cement base of ZOE is placed over the pulp stumps and allowed to set. The tooth may then be restored permanently as described for the formocresol pulpotomy (see Fig. 24-10, F ).

Ferric sulfate is well esablished as a hemostatic agent for crown and bridge impressions. Its hemostatic action occurs by the reaction of blood with ferric and sulfate ions within the acidic pH of the solution. The agglutinated proteins form plugs that occlude the capillary orifices and prevent blood clot formation. Initially the use of ferric sulfate was recommended as a hemostatic agent during Ca(OH) ₂ pulpotomy on the grounds that it may prevent problems arising from clot formation after coronal pulp amputation and minimize the chances for inflammation and internal resorption ; some consider these to be important factors contributing to the failure of pulpotomies using Ca(OH) ₂ . The first documented use of ferric sulfate in this way was in primate teeth.

The use of ferric sulfate itself as a hemostatic pulpotomy agent was investigated by researchers using animal models (rat and baboon ). Published clinical studies using ferric sulfate as a pulpotomy medicament have included both prospective comparative and retrospective designs.

In all the comparative studies, formocresol was included as the gold standard. The materials and methods used in all these studies are similar, which allows more meaningful comparison of their findings. Pulpotomies were performed in primary molars of healthy children who were selected on the basis of symptomless exposure of vital pulp by caries, absence of clinical or radiographic evidence of pulp degeneration, and possibility of proper restoration.

In all of the aforementioned ferric sulfate studies, the teeth were treated using the pulpotomy technique already outlined, and the teeth were restored with preformed metal (stainless steel) crowns. In a study by Papagiannoulis, half of the teeth were restored with composite resin and the remaining half with preformed metal (stainless steel) crowns.

Prospective Studies

In a study by Fei et al., 27 teeth were included in the formocresol group and 29 in the ferric sulfate group. Although the sample size was small, the recall rate was excellent, and in the 3- and 6-month intervals, no statistically significant difference was found between the two groups. However, at the end of this 1-year study, a statistically significant difference was seen in the success rate in favor of ferric sulfate (97% for ferric sulfate, 78% for formocresol). The most frequent evidence of failure in this short-term study in both groups was furcation radiolucency. In a study by Fuks, the sample consisted of 37 teeth in the formocresol group and 55 in the ferric sulfate group. The follow-up period ranged from 6 to 34 months, with a mean of 20.5 months. In this study, the sample size was bigger and the evaluation period much longer than in the previous one. The total success rate between the two groups over the total period of 34 months did not present any statistically significant difference; it was 92.7% for ferric sulfate and 83.8% for formocresol. Calcific metamorphosis and internal resorption were the most common radiographic findings. In this study, internal resorption that was stable and unchanged throughout the study was not recorded as failure.

In a later study by Ibricevic and Al-Jame, 34 teeth were used in each group, and identical results were obtained 24 months after treatment for both ferric sulfate and formocresol: a 97% total success rate was recorded. In each group, only one tooth showed internal resorption and was therefore considered a failure.

The results of a larger comparative study were published in 2002. The sample comprised 133 pulpotomy-treated molars of 90 children from 3 to 10 years old, with a mean age of 6.2 years. Sixty teeth (45%) were treated with formocresol and 73 (55%) with ferric sulfate. The number of teeth restored with either a stainless steel crown or a composite resin material was almost equal within each group. After 36 months, the clinical success rate was 97.3% for formocresol and 90.3% for ferric sulfate, but the difference in success rate between the two groups was reported to be statistically insignificant. The radiographic success rate was 78.3% for formocresol and 74% for ferric sulfate, again with no statistically significant difference between them. This success rate seems to be the lowest recorded compared with the previously mentioned comparative studies. The study’s author believed that this finding could be due to three reasons: (1) the larger sample size, (2) the very good recall rate, which increased the possibility to observe and locate more failures; and (3) the very strict radiographic assessment. Internal resorption was the most common radiographic finding for both treatments, with no statistically significant difference between ferric sulfate and formocresol. However, most cases classified initially as failures because of internal resorption remained stable throughout the 36-month observation period, and in two cases the respective areas were self-filled with reparative hard tissue. Based on this observation, the data were reevaluated, and only cases of internal resorption that were either extensive in size or progressing with time were considered as failures. After the reevaluation, the overall success rate became 78.7% for ferric sulfate and 85% for formocresol, with no statistically significant difference between them. The survival rate of the treated teeth after 6 months was 98% for both treatments and then 97% for ferric sulfate and 94% for formocresol after 1 year. These figures decreased with time for both groups, and the survival rate dropped to 81% for ferric sulfate and 78% for formocresol from 25 to 36 months.

Retrospective Studies

In a retrospective study published in 2000 by Smith et al., ferric sulfate pulpotomies performed over a period of 5 years by a private pediatric dentist were evaluated. The clinical success rate was very high: 99% up to 36 months and no further failures after 36 months. The radiographic success varied from 80% for the 4- to 12-month period, 74% for the 13- to 24-month period, 81% for the 25- to 36-month period, and 74% for the over 36-month period. The estimated tooth survival time was very high, starting with 99% up to 10 months and dropping to 80% after 43 months. The two most common radiographic findings in this study were calcific metamorphosis and internal resorption. The records in this study showed that 13 teeth that presented with internal resorption did not develop osseous lesions for the period of 43 months.

A second retrospective study, published 2 years later in 2002, reported results comparing different pulpotomy treatments; 83 formocresol pulpotomies, 45 ferric sulfate pulpotomies, and 74 pulpotomies treated with a combination of ferric sulfate and formocresol were selected from the records of children treated in a public clinic at different times and by different clinicians. The initial results showed that the total success rate was similar in the three groups, but after a 36-month follow-up, the success rate was better for formocresol than for ferric sulfate, and the combination of the two agents was the worst. The last finding is not surprising because the teeth were treated initially with ferric sulfate for hemostasis and then with formocresol, and they had a poor prognosis (i.e., hyperemic and/or symptomatic). As pointed out by the authors, this study had several shortcomings, the most serious being that the pulpotomies were performed by many clinicians of different levels of experience and expertise; the criteria for selection of cases were not strictly defined; and the radiographs were not always satisfactory, compromising accurate evaluation of the periradicular and furcal areas of the treated teeth.

The studies described demonstrate a higher success rate for both ferric sulfate and formocresol in those with shorter observation times and smaller sample sizes. As the sample size increases and the observation period becomes longer, the success rate drops; this holds true for both ferric sulfate and formocresol pulpotomies. The most important finding is that no statistically significant differences in the success rates between ferric sulfate and formocresol existed, with the exception of one short-term study in which a statistically significant difference was observed in favor of ferric sulfate at the 1-year period. In all the reviewed studies (prospective and retrospective), both ferric sulfate and formocresol treatments gave very good results with high tooth survival rates. Moreover, the type of restoration (stainless steel crown or composite resin) was not reported to influence the success rate for either pulpotomy agent.

Clinical Outcome

In one study, the cases of internal resorption that remained unchanged throughout the 36-month observation period were not considered as failures in the final examination of the results. Others proposed that internal resorption should not be considered as pulpotomy failure and based this proposal on the fact that none of the teeth with internal resorption in their sample developed an osseous lesion. This proposal may be accepted only in cases of minimal or unchanged internal resorption; not for severe or progressive resorption. Internal resorption may indicate pulp inflammation that is expected at the amputation site after pulpotomy. However, if the inflammation can be restricted and confined to a very small part of the pulp while the remainder is healthy, the resorption process will cease or even self-heal by the apposition of hard tissue and therefore will not be a failure. In all the other cases, internal resorption indicates irreversible or extensive inflammation and should be considered a failure.

It can be seen from these studies and the results of a meta-analysis that for human carious primary molars with reversible coronal pulpitis, ferric sulfate and formocresol pulpotomies give similarly good clinical and radiographic results, with high tooth survival rates and no statistically significant differences in success rates. These findings agreed with an earlier Cochrane Review of pulp treatment for extensive decay in primary teeth.

Based on these studies, ferric sulfate can be used instead of formocresol for treatment periods up to 36 months.

Mineral Trioxide Aggregate Pulpotomy

Technique

• 1.

  After completion of coronal pulp amputation and achievement of hemostasis with moist cotton pellets, MTA powder is mixed with sterile water until the powder is adherent. Excess moisture is removed from the powder by placing a dry paper point into the mixture to act as a moisture wick.

• 2.

  The MTA may be applied to the pulp tissue using an excavator or retrograde amalgam carrier, ensuring enough material to completely cover the exposed pulp tissue to a depth of 3 to 4 mm (see Fig. 24-10, G ).

• 3.

  The MTA mixture is gently packed over the pulp tissue using the blunt end of a large paper point and a broad-ended amalgam compactor. This layer of MTA is a permanent wound dressing.

• 4.

  A cement base of ZOE or glass ionomer cement is placed gently over the MTA and allowed to set. The MTA will take several hours to reach its optimum physical strength, so care must be taken to ensure an intact layer of MTA is in contact with the pulp tissue.

• 5.

  The tooth may then be restored permanently as described for the formocresol pulpotomy.

MTA used as a pulp capping agent in monkey teeth showed the pulp tissue responses to MTA to be superior to those produced using Ca(OH) ₂ . Similar results were found when human intact third molars were used to compare the effect of pulp capping with MTA and Ca(OH) ₂ . MTA was found to maintain pulp integrity after pulp capping and pulpotomy in animal studies and to have a dentinogenic effect on the pulp expressed by the induction of dentin bridge formation (see Fig. 24-10, H ) where it touches the pulp tissue.

Clinical Studies

One of the first preliminary studies published comparing MTA with formocresol in humans involved 45 pulpotomy-treated primary molars in 26 children with a mean age of 6 years, 5 months. Clinical and radiographic follow-up ranged between 6 and 30 months, involving 18 children with 32 teeth. Internal resorption was seen in one molar treated with formocresol (17 months after treatment). None of the teeth from the MTA group presented any clinical or radiographic pathosis. Pulp canal obliteration was observed in 9 of 32 (28%) molars evaluated.

Preliminary results of a 3-year prospective follow-up study comparing MTA with formocresol were reported at a scientific congress. Pulpotomies were undertaken on 60 primary molars in 22 children aged 2 to 8 years, each needing at least two pulpotomies. Each child received at least one MTA and one formocresol pulpotomy, followed by application of a preformed metal (stainless steel) crown. Six months after treatment, seven teeth of the formocresol group and two of the MTA group presented abnormal radiographic findings, but these differences were not statistically significant.

More promising results were observed in a more extensive study by Holan et al. that included part of the material presented by Eidelman et al. and a longer follow-up time. Holan and colleagues assessed the long-term success rate of pulpotomy in primary molars with carious pulp exposure using MTA or formocresol as pulp dressing agents. Sixty-four primary molars of 35 children were treated by a conventional pulpotomy technique. After removal of the coronal pulp and hemostasis, the pulp stumps were covered with MTA in the experimental group. In the control group, formocresol was placed with a cotton pellet over the pulp stumps for 5 minutes and then removed; the pulp stumps were then covered with ZOE paste. Eight teeth from each group were restored with an amalgam restoration, and all others were covered with a preformed metal (stainless steel) crown. Thirty-three children with 62 teeth (29 treated with formocresol and 33 with MTA) were available for long-term clinical and radiographic evaluation. Follow-up ranged from 4 to 74 months, with a mean follow-up time of 38 months and with no difference between the groups. Twenty-nine teeth were followed until natural exfoliation (mean, 33 months). Failures were detected after a mean period of 16 months (range, 4 to 30 months). The success rate of pulpotomy was 97% for MTA (one failure) and 83% for formocresol (five failures). Eight teeth showed internal resorption. In four (two from each group), progress of the resorption process stopped, and the pulp tissue was replaced by a radiopaque calcified tissue. Pulp canal obliteration was observed in 55% (34 of 62) of the evaluated molars. This finding, which was not considered a failure, was detected in 58% (19 of 33) of the MTA and in 52% (15 of 29) of the formocresol group. The authors concluded that MTA showed a higher long-term clinical and radiographic success rate than formocresol as a dressing material following pulpotomy in primary molars and recommended it as a suitable replacement for formocresol.

The clinical, radiographic, and histologic effects of gray MTA, white MTA, and formocresol as pulp dressings in pulpotomy-treated primary teeth have been reported. This involved 24 children with a mean age of 6 years (range, 4 to 8 years), each with at least three primary molars requiring pulpotomy, for the clinical and radiographic part of the study. An additional 15 carious primary teeth planned for serial extractions were selected for the histologic part of the study. All the teeth were evaluated periodically for 12 months except those selected for histologic evaluation; these were extracted 6 months after treatment. Sixty pulpotomy-treated teeth in 20 children were reviewed; of these, one tooth (gray MTA) exfoliated normally, and six teeth (four white MTA and two formocresol) failed because of abscesses. All the remaining 53 teeth showed success clinically and on radiographs. Pulp canal obliteration was found in 11 teeth treated with gray MTA and one treated with white MTA. The histologic evaluation demonstrated that both types of MTA induced thick dentin bridges, whereas in the formocresol group these were thin and poorly calcified. The pulpal architecture observed with the gray MTA was closer to normal than the white MTA, which presented a dense fibrotic pattern with isolated pulp calcification. These authors concluded that gray MTA was better than both white MTA and formocresol as a pulp dressing for pulpotomy-treated primary teeth. More recently, MTA pulpotomies were compared with Ca(OH) ₂ and ferric sulfate, with reported results showing that MTA is a suitable pulpotomy agent.

The growing evidence from clinical studies and a systematic review allows MTA to be recommended as an effective pul­potomy agent in primary teeth.

MTA is commercially available in the United States as ProRoot MTA (DENTSPLY Tulsa Dental Specialties, Tulsa, OK). Angelus MTA (Angelus Indústria de Produtos Odontológicos, Londrina, Brazil) is also available in Latin America and Europe. ProRoot MTA is considered expensive, particularly because it is retailed in cartons containing a number of sealed 1-g packets. The composition of MTA is similar to that of cement used in the building industry, and such material should be kept dry during storage because contact with moist air leads to “air setting,” which affects the powder’s physical properties. The same could be applied to the “clinical grade” cement, and the manufacturer of ProRoot MTA recommends the 1-g sachet as single use, which would be expensive. The unused MTA remaining in a sachet may actually be stored for up to a further 4 weeks in a water-tight, air-tight container such as an Eppendorf tube (Eppendorf UK, Cambridge, Great Britain, UK), reducing its cost. It has been suggested that the MTA powder can be stored indefinitely if the corner of the packet is folded firmly and the packet is stored in a sealable plastic bag. Angelus MTA is presented in a sealable glass vial, with the recommendation that 1 g may provide up to seven treatments. Care must be taken not to contaminate the MTA powder when it is dispensed.

Electrosurgical Pulpotomy

Technique

The steps in the electrosurgical pulpotomy technique are basically the same as those for the formocresol technique through the removal of the coronal pulp tissue.

• 1.

  Large sterile cotton pellets are placed in contact with the pulp, and pressure is applied to obtain hemostasis.

• 2.

  The Hyfrecator Plus 7-797 (Birtcher Medical Systems, El Paso, Texas) is set at 40% power (high at 12 W), and the 705-A dental electrode is used to deliver the electric arc. The cotton pellets are quickly removed, and the electrode is placed 1 to 2 mm above the pulpal stump.

• 3.

  The electric arc is allowed to bridge the gap to the pulpal stump for 1 second, followed by a cool-down period of 5 seconds. Heat and electrical transfer are minimized by keeping the electrode as far from the pulpal stump and tooth structure as possible while still allowing electric arcing.

• 4.

  If necessary, this procedure may be repeated up to a maximum of three times. The procedure is then repeated for the next pulpal stump.

• 5.

  When the procedure is properly performed, the pulpal stumps appear dry and completely blackened.

• 6.

  The chamber is filled with ZOE placed directly against the pulpal stumps. Research by Fishman has shown no difference between ZOE and Ca(OH) ₂ as the dressing. The tooth should then be restored with a preformed metal (stainless steel) crown.

Although electrocoagulation on the pulps of teeth was reported in 1957, it was a decade later that Mack became the first U.S. clinician to routinely perform electrosurgical pulpotomies. Oringer also strongly advocated this technique in his 1975 text on electrosurgery.

Electrosurgery is a nonpharmacologic, hemostatic pulpotomy technique used directly on the radicular pulp stumps after coronal pulp amputation. Depending on the currents used and thus the heat generated, incision, coagulation, or electrofulguration can occur. Electrosurgical pulpotomy carbonizes and denatures pulp tissue, producing a layer of coagulative necrosis. This acts as a barrier between the lining material and healthy pulp tissue below.

Several clinical studies have produced results comparable to those found with the use of formocresol. Conflicting results have been reported from histologic studies, ranging from results comparable to formocresol pulpotomy to pathologic root resorption with periapical and furcal involvement. A retrospective human study in 1993 showed a success rate of 99% for primary molars undergoing electrosurgical pulpotomies. Compared with a formocresol pulpotomy study of similar design, the success rate of the electrosurgery technique was shown to be significantly higher. A more recent study compared the use of two different base lining materials during electrosurgical pulpotomy. Success rates at 12 months were high for both groups, 98% and 96% for ZOE and zinc polycarboxylate cements, respectively.

Laser Pulpotomy

Several reports have appeared in the literature on the use of the carbon dioxide laser for performing vital pulpotomies on primary teeth. Elliott et al. compared the use of the laser with formocresol in caries-free, primary cuspid teeth that were scheduled for extraction in children between 6 and 10 years of age. Thirty teeth were included in the study. No significant differences were found between the formocresol and laser-treated groups. Areas of isolated internal resorption were identified in one of the formocresol-treated teeth and two of the laser-treated teeth. These authors concluded that on the basis of symptomatic, clinical, and histologic findings, the carbon dioxide laser appeared to compare favorably with formocresol treatment. It was suggested that additional studies be conducted to establish the ideal applied laser energy to maximize optimum residual pulpal response and to explore the effects of laser pulpotomy upon pulps previously exposed by carious lesions.

Liu et al. reported the use of the laser on primary teeth with vital carious pulpal exposures. Thirty-three teeth, 21 primary molars and 12 primary canines, were treated and observed for 12 to 27 months. All were clinically successful, and only one showed evidence of internal resorption at the 6-month follow-up visit. The authors observed complete calcification on radiographs after 9 months in approximately half of the treated teeth.

On the basis of these initial studies, the use of the carbon dioxide laser could be considered a viable alternative to formocresol. More randomized controlled human clinical trials are recommended.

In summary, the search for alternatives to the formocresol pulpotomy in cariously exposed vital primary teeth has yet to reveal an agent, instrument, or technique that has unequivocal long-term clinical success rates better than those of formocresol, although MTA is beginning to show evidence of excellent success rates in comparative studies. Until such an agent, instrument, or technique is found, ferric sulfate, MTA, or formocresol (one-fifth dilution) can be used with equal confidence in primary tooth pulpotomies.