CHAPTER 18 Restorative Dentistry
A dvances in preventive dentistry and their application in the private dental office, the widespread acceptance of communal fluoridation, and greater emphasis on dental health education have dramatically changed the nature of dental practice. Today the dentist devotes more time to preventive procedures and less time to the routine restoration of carious teeth.
Nevertheless, the restoration of carious lesions in primary and young permanent teeth continues to be among the important services that pediatric dentists and general practitioners provide for the children in their practices. Patients and fellow practitioners often judge dentists on the effectiveness of their preventive programs and the skill with which they perform routine operative procedures.
The restorative treatment plan must be prepared in conjunction with an individually tailored preventive program. Restoration of primary teeth differs significantly from restoration of permanent teeth, due in part to the differences in tooth morphology.
In 2002, the AAPD, with financial assistance from the American Society of Dentistry for Children, held a pediatric restorative dentistry consensus conference in San Antonio, Texas. Sixteen literature review and position papers were presented at the conference and numerous consensus statements about appropriate pediatric restorative materials and procedures were developed. The papers and consensus statements are compiled in the September/October 2002 issue 24 of Pediatric Dentistry.
Recent advances in the development of improved biomaterials for dental restorations have been rapid, and they continue to occur at a fast pace. This fact creates a significant challenge for dentists striving to remain at the cutting edge of dental technology. The more common restorative materials used in pediatric dentistry are composite and other resin systems, glass ionomers, silver amalgam alloys, and stainless steel alloys. Porcelain and cast metal alloy materials are also used in pediatric restorative dentistry but less frequently than those listed in the previous sentence.
Composite resins, glass ionomers, or some combination of the two are being used progressively more and silver amalgam progressively less in pediatric restorative dentistry. Many pediatric dentistry practices do not use silver amalgam at all; instead, some form of composite resin and/or glass ionomer is used. These materials have bonding capability. Glass ionomers may be considered pharmacologically therapeutic because they release fluoride over time; they also have minimal shrinkage during setting. Composite resins possess durability and superior esthetic qualities. When managed properly, both materials are capable of providing superior marginal sealing at the tooth–restorative material interface. The manufacturers of these materials have also combined them in an effort to join the primary advantages of each type of material. Berg has suggested that we think of these materials and their combinations on a continuum, with glass ionomer on the left, composite resin on the right, and the combined materials somewhere in between depending on the relative amounts of each material in the mix. Two major categories on the continuum are described as “resin-modified glass ionomer” (or “hybrid ionomer” or “light-cured glass ionomer”) and “compomers” (or “polyacid-modified composite resin” or “glass ionomer–modified composite resin”). A fifth formulation has been added on the right side of the continuum in the form of “flowable composite resin.” Berg points out that knowing the particular strengths and weaknesses of each type of material on the continuum will enhance the clinician’s ability to make the best choices for each individual restorative situation.2 Use of any of these restorative materials generally requires more effort and time than corresponding conventional amalgam restorations.
Despite its declining use, silver amalgam remains one of the most durable and cost-effective restorative materials. Success in using this filling material depends on adherence to certain principles of cavity preparation that do not always apply when materials on the glass ionomer–composite resin continuum are used. Some renewed interest in silver amalgam has occurred because of the development of “bonded amalgams.” Bonded amalgams are silver amalgam restorations that have been condensed into etched cavity preparations lined with a dentin-bonding agent and some material on the glass ionomer–composite resin continuum. Bonded amalgams require considerable extra effort and expense to place compared with conventional amalgam restorations. The improvements in tooth support and marginal integrity gained with these restorations have been demonstrated in many studies. Some longer-term studies, however, suggest that the advantages of bonded amalgams may be transient and relatively short-lived, possibly 1 year or less.3,4 In general, the use of bonded amalgams seems difficult to justify for the routine restoration of primary teeth because traditional silver amalgam should provide comparable quality more efficiently and cost effectively in most situations.
Stainless steel alloy is another commonly used pediatric restorative material. It is used extensively for full coronal coverage restorations of primary teeth. Stainless steel crowns have undoubtedly preserved the function of many primary teeth that otherwise would have been unrestorable. In addition, stainless steel crowns are often used to restore all posterior teeth in young patients with high risk for caries who exhibit multiple proximal lesions that could otherwise be restored with silver amalgam or esthetic materials. Crowns are used instead simply because they better protect all posterior tooth surfaces from developing additional caries and because the posterior crown restoration has proven to be the most durable and cost effective in the primary dentition. Anterior, as well as posterior, stainless steel crowns may have labial and/or occlusal resin or porcelain veneers to enhance esthetics.
The maintenance of a clean operating field during cavity preparation and placement of the restorative material helps ensure efficient operation and development of a serviceable restoration that will maintain the tooth and the integrity of the developing occlusion.
The armamentarium consists of 5- × 5-inch sheets of medium latex, a rubber dam punch, clamp forceps, a selection of clamps, a flat-blade instrument, dental floss, and a rubber dam frame. If one visualizes an approximately 1¼-inch square in the center of a sheet of rubber dam, each corner of the square indicates where the punch holes for the clamp-bearing tooth in each of the four quadrants of the mouth are to be made (Fig. 18-1). As experience is gained in applying the dam, the dentist and assistant will soon learn the proper location for punching the holes. If the holes are punched too far apart, the dam will not readily fit between the contact areas. In addition, the greater bulk of material between the teeth will greatly increase the possibility that the rubber will become a barrier to proximal surface preparation. Conversely, if the holes are punched too close together, salivary leakage will contaminate the operating field. In general, the holes should be punched the same distance apart as the holes on the cutting table of the rubber dam punch.
The large punch hole is used for the clamp-bearing tooth and for most permanent molars. The medium-sized punch hole generally is used for the premolars and primary molars. The second smallest hole is used for maxillary permanent incisors, whereas the smallest hole is adequate for the primary incisors and lower permanent incisors.
The operator will soon develop a personal preference for which clamps to use to secure the dam in isolating different areas in the mouth. Unless the clamp is firmly anchored to the tooth, the tension of the stretched rubber will easily dislodge it. Therefore the proper selection of a clamp is of utmost importance. It is recommended that the clamp be tried on the tooth before the rubber dam is placed to ascertain that the clamp can be securely seated and will not be easily dislodged by the probing tongue, lip, or cheek musculature. An 18-inch length of dental floss should be doubled and securely fastened to the bow of the clamp. The floss will facilitate retrieval in the unlikely event that the clamp slips and falls toward the pharynx (Fig. 18-2).
The following procedure is recommended for rubber dam application (Fig. 18-3). The previously selected and ligated clamp is placed in the rubber dam. The dentist grasps the clamp forceps with the clamp engaged. The assistant, seated to the left of the patient (the dentist is right-handed in this example), grasps the upper corners of the dam with the right hand and the lower left corner between the left thumb and index finger. The dam is moved toward the patient’s face as the dentist carries the clamp to the tooth while holding the lower right portion of the dam. After securing the clamp on the tooth, the dentist transfers the clamp forceps to the assistant, who receives it while continuing to hold the upper corners of the dam with the right hand. The dentist then places the frame over the rubber dam. Together the assistant and dentist attach the corners of the dam to the frame. The flat blade of a plastic instrument or a right-angle explorer may be used to remove the rubber dam material from the wings of the clamp and to complete the seal around the clamped tooth. If necessary, light finger pressure may seat the clamp securely by moving it cervically on the tooth. If additional teeth are to be isolated, the rubber is stretched over them, and the excess rubber between the punched holes is placed between the contact areas with the aid of dental floss. The most anterior tooth and others if necessary are ligated to aid in the retention of the dam and the prevention of cervical leakage. The free ends of the floss are allowed to remain, because they may aid in the further retraction of the gingival tissue or the patient’s lip during the operative procedure. At the end of the operative procedure, the length of floss will also aid in removing the ligature.
Figure 18-3 A, The dental assistant holds the top and lower right corners of the rubber dam as the dentist holds the lower left corner and carries the clamp to the tooth. B, The assistant and dentist attach the corners of the rubber dam to the frame. C, Dental floss is used to carry the rubber dam between the teeth. D, The teeth are isolated and ready for the operative procedure.
(A, B, and C Courtesy of Dr. Richard Troyer.)
When a quadrant of restorations in the primary dentition is planned and no pulp therapy is anticipated, Croll recommends the “slit-dam method.”6 One long opening is made in the dam, and the entire quadrant is isolated without interseptal dam material between the teeth.
It is unwise to include more teeth in the rubber dam than are necessary to isolate the working area adequately. If the first or second permanent molar is the only tooth in the quadrant that is carious and if it requires only an occlusal preparation, it is often desirable to punch only one hole in the dam and to isolate the single tooth (Fig. 18-4). This procedure will require only seconds and will save many minutes.
The crowns of the primary teeth are smaller but more bulbous than the corresponding permanent teeth, and the molars are bell-shaped, with a definite constriction in the cervical region. The characteristic sharp lingual inclination occlusally of the facial surfaces results in the formation of a distinct faciogingival ridge that ends abruptly at the cementoenamel junction. The sharp constriction at the neck of the primary molar necessitates special care in the formation of the gingival floor during class II cavity preparation. The buccal and lingual surfaces of the molars converging sharply occlusally form a narrow occlusal surface or food table; this is especially true of the first primary molar.
The pulpal outline of the primary teeth follows the dentoenamel junction more closely than that of the permanent teeth. The pulpal horns are longer and more pointed than the cusps would indicate. The dentin also has less bulk or thickness, and so the pulp is proportionately larger than that of the permanent teeth. The enamel of the primary teeth is thin but of uniform thickness. The enamel surface tends to be parallel to the dentinoenamel junction.
Traditional cavity preparations for class I and class II lesions include areas that have carious involvement and, in addition, those areas that retain food and plaque material and may be considered areas of potential carious involvement. A flat pulpal floor is generally advocated. However, a sharp angle between the pulpal floor and the axial wall of a two-surface preparation should be avoided. Rounded angles throughout the preparation will result in less concentration of stresses and will permit better adaptation of the restorative material into the extremities of the preparation.
Although the traditional class I cavity preparation and restoration may occasionally be the most practical treatment for a tooth in certain circumstances, such treatment is currently obsolete for most class I lesions. The traditional treatment has been replaced, for the most part, by conservative caries excavation and restoration using a combination of bonding restorative and sealant materials (see Chapter 17).
Likewise, the traditional class II cavity preparation and restoration, although not yet considered obsolete, is currently used less frequently as steadily improving restorative materials with therapeutic and bonding capability are developed. In the traditional class II cavity preparation for amalgam, the buccal and lingual extensions should be carried to self-cleansing areas. The cavity design should have greater buccal and lingual extension at the cervical area of the preparation to clear contact with the adjacent tooth. This divergent pattern is necessary because of the broad, flat contact areas of the primary molars and because of the distinct buccal bulge in the gingival third. Ideally, the width of the preparation at the isthmus should be approximately one-third the intercuspal dimension (Fig. 18-5). The axiopulpal line angle should be beveled or grooved to reduce the concentration of stresses and to provide greater bulk of material in this area, which is vulnerable to fracture.
Because many occlusal fractures of amalgam restorations are caused by sharp opposing cusps, it is advisable to identify these potentially damaging cusps with articulating paper before cavity preparation. The slight reduction and rounding of a sharp opposing cusp will reduce the number of such fractures.
The steps in the preparation of a cavity in a primary tooth are not difficult but do require precise operator control. Many authorities advocate the use of small, rounded-end carbide burs in the high-speed handpiece to establish the cavity outline and perform the gross preparation. For efficiency and convenience, all necessary high-speed instrumentation for a given preparation may be completed with a single bur in most situations. Therefore the dentist should select the bur that is best designed to accomplish all the high-speed cutting required for the procedure being planned. Fig. 18-6 illustrates four high-speed carbide burs designed to cut efficiently and yet allow conservative cavity preparations with rounded line angles and point angles. Alternatively, cavity preparations may be made with aluminum oxide air abrasion systems or with laser systems approved for hard-tissue procedures, when indications allow.
During the routine examination of a child younger than 2 years of age, the dentist may occasionally discover a small but definite carious lesion in the central fossa of one or two first primary molars, with all other teeth being sound. Thus restorative needs are present but minimal. Because of the child’s psychological immaturity and because it is usually impossible to establish effective communication with the child, the parent should hold the child on his or her lap in the dental chair. This helps the child feel more secure and provides a better opportunity to restrain the child’s movement during the operative procedure. The small-cavity preparation may be made without the aid of a rubber dam or local anesthetic. A No. 329 or No. 330 bur is used to open the decayed area and extend the cavosurface margin only to the extent of the carious lesion. If the patient is resistant (usually), completing the preparation with an air abrasion or laser system would be inconvenient. The preparation can be completed in just a few seconds. Restoring the tooth with amalgam or a resin-modified glass ionomer arrests the decay and at least temporarily prevents further tooth destruction without a lengthy or involved dental appointment for the child. If the child is cooperative, a preventive resin restoration, preceded by application of a dentin-bonding agent, may be used.
If an amalgam restoration is planned, the first step in the preparation of an extensive class I cavity is to plane back the enamel that overhangs the extensive carious lesion. Then the cavity preparation should be extended throughout the remaining grooves and anatomic oc/>