The masticatory system is composed of the jaws, the temporomandibular joints, the muscles of mastication, the nervous system, the teeth with their occlusal complexes, and the periodontal ligament. These components are physiologically and morphologically synchronized when function is normal. Within certain tolerance limits, the masticatory system can adapt to deviations from the norm (compensation, adaptation). However, if severe alterations or diseases occur in any one of the component parts of the masticatory system, the other components may also be affected (de-compensation or regressive adaptation; Bumann & Lotzmann 1999, Color Atlas of Dental Medicine: TMJ Disorders and Oro-facial Pain).
Functional disturbances do not elicit periodontitis! Nevertheless, such disturbances must be recognized and treated because they elicit alterations in masticatory musculature and temporomandibular joint function as well as excessive amounts of tooth abrasion, increased tooth mobility and the progression of any existing periodontitis (Ramfjord & Ash 1983). This chapter will present:
• Normal function – Physiologic tooth mobility
• Disturbed function – Occlusal periodontal trauma
• Therapy for functional disturbances: Bite guards
The complexity of the stomatognathic system makes it difficult to define the term “normal function.” It is only possible to describe physiologic data and norms for the individual components:
Normal chewing force is dependent on the type of food consumed. When eating pudding or puree etc., chewing force is quite low as measured in Newtons (1 Newton = 1 kg x m/s2= ca. 100 p), while chewing tough meat, ca. 150 N (ca. 15 kp); even with very hard foodstuffs, chewing force seldom exceeds 200 N (Ammann 1980).
The “normal” temporal loading of the periodontium is short. The occlusal forces that are imposed upon the periodontium during chewing and swallowing are intermittent in character. The duration of a chewing maneuver is only about 0.1 – 0.4 seconds. During swallowing (even of saliva) the periodontium is loaded for only ca. 1 second. If these maneuvers are summed over a 24-hour period, it is revealed that only 15–20 minutes of peak loading occurs per day (Graf 1969).
The “normal” direction of forces that are imposed upon the periodontium during chewing is extremely variable. The ideal direction of loading would be vertical/axial because this would ensure that all periodontal fibers and the alveolar process would be loaded evenly. Such equal loading does not occur even in centric occlusion. During chewing, on the other hand, alternating and combined forces are exerted primarily from the horizontal/orofacial and vertical directions (Graf et al. 1974, Graf & Geering 1977).
The “syndesmotic mechanism” by which the teeth are supported within their alveoli, and the elasticity of the entire alveolar process provide for a measurable physiologic tooth mobility in horizontal, vertical and rotational directions (Periodontometer, Mühlemann 1967; “Periotest,” Schulte et al. 1983).
Tooth mobility varies in daily as well as larger cycles (biorhythm): Teeth are more mobile in the morning than in the evening (Himmel et al. 1957). In addition, each type of tooth exhibits characteristic mobility depending upon the surface area available for insertion of periodontal ligament fibers into cementum, and also according to root number, root length and root diameter (Fig. 1130).
Increased Tooth Mobility
Elevated tooth mobility may result from occlusal trauma or quantitative bone loss due to periodontitis (Figs. 1131/1132). Increased tooth mobility alone is not a criterion of periodontal health or disease.
Initial Periodontal Tooth Mobility (A)
This is defined as the first phase of movement of a tooth after loading at 1 N (ca. 100 p) in the orofacial direction. The tooth moves relatively easily within its alveolus. Some periodontal ligament fiber bundles are stretched, others relaxed, but significant deformation of the alveolar process does not occur.
Initial tooth mobility is relatively high: It is a function of the width of the periodontal ligament space and the histologic structure of the periodontium; depending on the tooth type, it can range from 0.05 –0.10 mm.
Secondary Periodontal Tooth Mobility (B)
This is measured after application of 5 N in the orofacial direction. At this magnitude of force, delivered via the stretched periodontal ligament fibers, the entire alveolar process is deformed and this resists additional deflection of the tooth.
Variations in periodontal tooth mobility in a healthy periodontium depend upon the mass and quality of the alveolar bone. The normal periodontal tooth mobility ranges from 0.06 to 0.15 mm, depending upon tooth type.
Occlusal trauma is defined as “microscopic alterations of periodontal structures in the area of the periodontal ligament, which become manifest clinically in (reversible) elevation of tooth mobility” (Mühlemann et al. 1956, Mühlemann & Herzog 1961).
That an excess of pro-inflammatory mediators could increase occlusal trauma is suspected, but has not yet been proven.
Occlusal trauma causes histologic alterations in the periodontium: Circulatory disturbances, thrombosis of PDL vasculature, edematisation and hyalinazation of collagen fibers, inflammatory cell infiltration, nuclear pyknosis of osteoblasts, cementoblasts and fibroblasts, as well as increases in vasculature diameter (Svanberg & Lindhe 1974). The periodontal ligament space adapts by becoming wider (“hourglass shape”), and this is manifested clinically by elevated mobility and radiographic evidence such as triangulation.
Clinical experiments have proved that abnormal occlusal forces cause neither gingivitis nor periodontitis. However, the progression of an already existent periodontitis may be accelerated, especially during active stages of disease (Svanberg & Lindhe 1974; Polson et al. 1976a, b; Lindhe & Ericcson 1982; Pihlstrom 1986; Hanamura et al. 1987).
Adaptation to Unphysiologic Forces—Adaptive Phase
Even without treatment, the periodontium may adapt to long-term occlusal trauma. The PDL space remains wide, but retains its normal histologic appearance. Tooth mobility may remain elevated, but does not increase in severity (Nyman & Lindhe 1976).
Progressive Mobility with Unphysiologic Forces (Lack of Adaptation)—Progressive Phase
Heavy, continuous, abnormal occlusal forces may lead to progressively increasing tooth mobility, and function may be negatively influenced. The elimination of the causes of the trauma is then of primary importance.
When parafunctional habits (e. g., bruxism) result in occlusal periodontal trauma (increasing tooth mobility) or to progression of periodontitis, the dentition should undergo selective occlusal grinding and wear facets should be eliminated.
However, selective grinding is often impossible due to spasm in the masticatory musculature. Reciprocal functional relationships exist among occlusion, the periodontal ligament, TMJ, masticatory musculature, and the central nervous system (CNS). The activity of the CNS may also be significantly influenced by psychic factors (Graber 1985).
Such central nervous system hyperactivity is relieved through elevated tone within the masticatory musculature (clenching or possibly also bruxism). In such situations, if occlusal disharmonies are also present, a “vicious circle” is created which can best be broken through use of an occlusal bite guard, e. g., the Michigan splint (Ramfjord & Ash 1983). The result is that the occlusion is taken out of the “circle” and the masticatory musculature relaxes. In most cases, selective occlusal grinding can then be accomplished after only a few weeks (removal of premature contacts and/or elimination of balancing side interferences).
Periodontal and Esthetic Corrections
Anomalies of tooth position in a periodontally compromised dentition can be characterized as:
• Anomalies that have existed since tooth eruption
• Anomalies that have resulted from periodontitis (or functional disturbances)
A direct, causal relationship between existing dental malocclusion and periodontitis is difficult to document (Hug 1982, Zachrisson 1997, Ong et al. 1998, Thilander 1998). Dental crowding always makes plaque control more difficult. This leads to increased plaque retention, the consequence of which is increased gingival inflammation (Fig. 248).
But tooth migration must be differentiated from other anomalies; it only occurs over the course of time, and not seldom as a symptom/result of periodontitis. These sorts of intraoral manifestations frequently create esthetic problems for the patient, including:
• Protrusion of the maxillary anterior teeth
• Tooth elongation
• Tooth tipping
The factors involved in the etiologic development of dental malocclusion following loss of periodontal support are not always obvious. Possible/probable causes include occlusal disharmonies (tooth tipping following tooth loss), oral para-functions such as tongue thrust or lip biting, occupation-related peculiarities such as holding nails or pins between the teeth, the playing of wind instruments etc. It has also been shown that not only the granulation tissue present in a deep periodontal pocket may exert a force that causes drifting, but that intact supracrestal fibers on the “healthy” side of a tooth may exert a pull resulting in tooth migration.
Periodontal therapy must be completed before any orthodontic treatment is begun. The advantages and disadvantages of orthodontics must be considered. Is the treatment motivated by functional or esthetic concerns? Could the problem be solved by other means, e. g., by functional, morphologic or esthetic odontoplasty, or through prosthetic means?
If the decision is made to proceed with orthodontic therapy, depending upon the diagnosis, goal of treatment and difficulty of the proposed therapy, the myriad of therapeutic possibilities include simple wire ligatures, removable apparatus and fixed brackets on the facial/buccal or even – almost invisibly – on the oral/lingual aspect of the dentition. The choice will depend in many cases on the desires of the (adult) patient. Patients exhibiting difficulties in adequate plaque control may also lead to compromises (e. g., removable devices).
In a dentition with periodontitis, orthodontic treatment always represents an additional trauma for the remaining tooth-supporting structures. Tooth mobility increases in virtually every orthodontic case. This is fully comparable to the situation following occlusal trauma. Following orthodontic therapy, long-term retention is always required in a periodontally compromised dentition, at least in the form of semi-permanent splinting (p. 473) or a night guard.
A 46-year-old female suffered from chronic and advanced periodontitis. In addition to bacterial infection (plaque), the etiology included severe psychic stress for family reasons, and the patient was overworked and weary.
The functional analysis revealed premature contacts between teeth 13, 14 and 45, 44, with a slight deviation from the left side anteriorally; this caused the maxillary anterior teeth to be mildly traumatized. Figures 1136 and 1138 depict the clinical view after initial periodontal therapy and subsequent surgical treatment.
Figure 1137 shows the probing depths and radiographic appearance before any periodontal treatment. Initially the clinical values were
|PI: 70 %||BOP: 69 %|
During the periodontal therapy, protrusion and diastemata occurred and these bothered the patient. She desired esthetic improvement of her situation. Orthodontic treatment and conservative restorative therapy were indicated.
It is not necessary to prosthetically close every space in the dental arch. If the occlusion is stable and there is adequate periodontal/anatomic support, no drifting of the adjacent teeth should occur.
However, in a periodontally compromised dentition, tipping of a second molar into a first molar extraction site is common. The mesial tipping of the second molar leads to a plaque-retentive niche, which promotes the development of a deeper periodontal pocket (Ericsson 1986).
This was the case presented by a 48-year-old female with moderate periodontitis.
Tooth 38 was extracted during initial therapy, for endodontic reasons. Both mandibular second molars were uprighted during a 7-month period. The tooth movement was accomplished with an appliance incorporating a bite plane extending distally to the bicuspid area, a labial bow, and activatable uprighting springs for the molars.
Instead of the two fixed bridges, one might have considered dental implants to replace the missing first molars (Fig. 1145).
A 56-year-old female complained of esthetic problems in the maxillary anterior segment (tooth migration and mild gingival recession, “long teeth”). A small diastema had been present even at age 20, but had become much wider during the previous ten years. This led the patient to seek possibilities for space closure and resultant esthetic improvement.
The patient was unaware of any other gingival problems. She smoked ca. 10 cigarettes per day, but stopped smoking during the treatment phase. Despite the relatively high plaque index, the gingiva did not exhibit significant inflammatory symptoms. In the maxillary anterior region, pocket probing depths up to 7 mm were detected. Tooth 21 exhibited significant attachment loss up to two-thirds of the root length.
|PI: 68 %||BOP: 58 %||TM: see Fig. 1151|
Following periodontal therapy, a “simple” orthodontic treatment was planned for the maxillary anterior region.
|•PI 68 %
•BOP 58 %
• PI < 10 %
•BOP <10 %
A 14-year-old female was referred because of extremely severe gingivitis and malpositioning of the maxillary right canine, which caused a plaque-retentive niche. This young girl’s oral hygiene was miserable. The patient proved extremely difficult to motivate. The erythematous, edematous, swollen gingiva bled at the slightest touch. Following initial periodontal therapy, a removable orthodontic appliance was selected in favor of a fixed appliance because of the unreliable patient compliance. Fixed orthodontic apparatus collects plaque biofilm readily and demand a higher level of oral hygiene from the patient.
A removable appliance can easily be cleaned when removed from the mouth, and also permits improved oral hygiene of the teeth. Financial considerations may also be a factor in the selection of fixed or removable orthodontic appliances.
|PI: 87 %||BOP: 80 %|
|Pseudopockets up to 7 mm|
During orthodontic therapy, the patient’s oral hygiene improved following repeated OHI and motivation.
The significance, value and indication for immobilizing mobile teeth by means of permanent splinting remain controversial as a periodontal therapeutic technique. In order to clarify whether there exist any true indications for splinting, one must first consider the causes of tooth mobility:
• Quantitative loss of tooth-supporting structures due to periodontitis
• Qualitative alterations of tooth-supporting structures resulting from occlusal trauma, above all parafunctions
• Short-term trauma to the periodontium due to treatment for periodontitis
• Tooth mobility caused by accidental trauma
• Combinations of the above
Mobile teeth whose degree of mobility is not increasing (elevated versus progressing tooth mobility), generally do not require splinting. Exceptions to this general rule include accidental trauma, and the elimination of severe parafunctions using temporary bite plates (p. 462, “Function—Functional therapy”). Tooth mobility caused by occlusal trauma should be treated primarily by selective occlusal adjustment (Vollmer & Rateitschak 1975), i. e., premature contacts and disturbances in lateral or protrusive excursions of the mandible should be diagnosed and eliminated.
Following selective occlusal grinding to remove parafunctions, bruxism such as clenching and improperly targeted loading, physiologic forces are distributed onto the entire dentition. Selective occlusal odontoplasty is targeted to remove the etiologic factors of parafunctions, the “trigger” factors, e. g., premature contacts, balancing side interferences etc.
In addition to purely occlusal disharmonies, psychic components may also be partially responsible for parafunctions and therefore also for tooth mobility. A combination of local treatment such as selective grinding combined with splinting may possibly be supported by psychopharmacologic medications, but only after consultation with the patient’s physician.
In recent years, splinting/stabilization of individual teeth or entire dental arches has become much more common because of the increased use of regenerative treatment methods. If the goal of treatment is not only new bone formation but also especially “new attachment,” i. e., the regeneration of all periodontal structures after treatment, this will most likely occur through some minimal temporary stabilization of the treated (mobile) teeth (to prevent dislodgment of the coagulum from the root surface).
Following all types of pocket treatment, the pocket fills with blood. The fibrin net of the coagulum closely approximates the conditioned root surface. The organization of this coagulum, the formation of new periodontal structures (by periodontal ligament fibroblasts) requires several weeks. If a tooth is constantly mobile during this healing phase, the attachment (adhesins!) to the root surface will be significantly disturbed.
The demand for “stabilization” of the treated teeth is especially important after the use of regenerative techniques such as the implantation of bone and bone-replacement materials, and the GTR technique, as well as the use of growth factors and matrix proteins, and even combinations of these methods. Additional indications are illustrated below.
Elevated Tooth Mobility—Etiology, Treatment
The table below (modified from Flemmig 1993) attempts to define the causes and the necessary therapies for elevated tooth mobility; discussions in this regard are also dependent upon changes in the radiographic appearance of the periodontal ligament space (occlusal trauma) and clinical attachment loss.
Indications for Various Types of Splinting
• Temporary or semi-permanent: These protect against further trauma caused by occlusal and oral parafunctions (e. g., tongue pressing, “sucking”). It can be used as an emergency procedure with extremely mobile teeth. It also can serve to reduce trauma—mechanical, instrumental—during periodontitis therapy.
• Semi-permanent/permanent: This can enhance masticatory comfort when teeth are highly mobile; also to stabilize the teeth during periodontal healing phases, especially following regenerative therapies.
Awaiting the long-term prognosis.
Retention following orthodontic treatment.
• Permanent: Used for complex oral rehabilitation where abutments are highly mobile or where only few abutments must support the reconstruction, particularly when such abutment teeth have minimal periodontal support. Distribution of occlusal forces when parafunctions cannot be eliminated. In such cases, without splinting, there is a danger of progressively increasing tooth mobility and tooth migration (Nyman & Lindhe 1979).
The simple wire ligature may serve as a fixed splint for a few days to several weeks. Wire ligatures are seldom used today, however, primarily because of the esthetic considerations. A more commonly used fixed splint is the acid-etch composite resin splint without tooth preparation, and sometimes with cavity preparation. Such a splint can be quickly applied with a rubber dam in place; however, it is a temporary measure because adhesion of the resin to the tooth structure is not strong enough without additional mechanical retention (cavity preparation, grooves etc.). Fracture of such splints is common if more than 3–4 teeth are included.
A removable, temporary splint can be made of acrylic resin pulled under vacuum, used only for a short period of retention for individual teeth.
Such splints were formerly used as a “bite guard” in the treatment of oral parafunctions. This approach proved not to be particularly effective and today the “Michigan splint” fabricated in a professional dental laboratory predominates.
The most frequently employed fixed, semi-permanent splint in the anterior region, which can remain in situ for months or even years, is splinting via composite resin (acid-etch technique) in combination with tooth preparation. It is often possible to simply remove all of the old anterior tooth restorations and subsequently incorporate the composite resin splint. The practical procedure is identical to the placement of composite restorations with the acid-etch technique.
The splint absolutely must be prepared with the rubber dam in place: Even tiny amounts of moisture after etching the enamel and during application of bonding and composite material will weaken the splint. Light-polymerized resin is recommended for this type of splint because of its long working time.
Removable semi-permanent splints may be fabricated as cast chrome-cobalt alloy frameworks incorporating typical partial denture clasps. This type of splint is indicated today only for wearing at night, often as a retentive appliance following orthodontic or surgical therapy.
Soon after introduction of the acid-etch technique for anterior restorations, the so-called adhesive bridges and adhesive splints were propagated (Rochette 1973).
In recent years, this technique had been refined. In particular, various methods for enamel preparation have been developed, that ensure adequate retention of such reconstructions following only very conservative tooth preparation (Marinello et al. 1987, 1988). When splinting in the anterior segments, the proximal surfaces of the teeth are rendered parallel, and fine grooves are prepared. For occlusal support, shallow, peg-shaped depressions at the margin and above the lingual tubercle are created. The incisal edges are not included, for esthetic reasons.
In contrast to semi-permanent splints that simply bond adjacent teeth with acid-etch resin, bridges and splints prepared with the acid-etch technique can serve for definitive immobilization of mobile teeth (cf. p. 479).
In cases of advanced, aggressive periodontitis, the stability of the periodontal treatment result must be observed over an extended period of time before seating a definitive, fixed replacement. In order to avoid any trauma to highly mobile teeth during this consolidation phase, the use of a fixed long-term temporary may be warranted (p. 480).
Because of dental fear, this 48-year-old male had not visited the dentist for many years. Severe tooth mobility and migration, especially in the maxillary anterior segment, and spontaneous tooth exfoliation in the mandible finally led him to our clinic. The patient was a heavy smoker and was experiencing psychological problems (divorce). In the mandible, it was necessary initially to fabricate a complete denture (dental implants later?). In the maxilla, all of his teeth were retained, with the exception of tooth 27. Following initial periodontal therapy, open root cleaning/planing was performed (in some cases with temporary wire ligature retention) and thereafter minor orthodontic corrections:
|PI: 70 %||BOP: 56 %||TM: Grade 3|
The clinical view and radiographs are depicted. When treatment was initiated, the patient was Aa positive.
In advanced periodontitis cases it is frequently not possible to maintain all of the teeth. During the treatment planning stage, teeth that are hopeless must be identified and extracted early on, because these teeth represent bacterial reservoirs. Such teeth can enhance the microbial re-colonization of other teeth (esthetics, temporaries?).
During initial therapy or at the very latest during surgical interventions it must be determined whether additional teeth must be sacrificed. In addition to the extent of periodontal attachment loss, other factors also play a role in the decision-making process:
• Must the lost tooth actually be replaced?
• Might an exclusively premolar occlusion be satisfactory? (Käyser 1981; De Boever 1978, 1984)
• Must every missing tooth absolutely be replaced, e. g., missing first molar and stable occlusion?
• How important is the tooth as a strategic abutment for dental reconstruction?
• Are there significant endodontic problems?
• Are there inherited or genetic risk factors?
• What is the overall prognosis for the entire dentition?
Last but not least, the type of comprehensive dental reconstruction is less important than the ultimate maintenance or rebuilding of masticatory function, speech and (more and more today) esthetics; in short, the oral/dental satisfaction of each individual patient.
This chapter, Perio-prosthetics 1/Standard Techniques presents the following themes: