The Influence of Occlusal Trauma on Gingival Recession and Gingival Clefts

The aim of this study was to investigate the centric occlusal contact pattern in maximum intercuspation and to study the nature of occlusal contacts during maximum intercuspation to protrusive, lateroprotrusive and lateral excursive movements. Fifty subjects having gingival recession and ten subjects having gingival clefts belonging to age group of 18–25 years were selected after obtaining informed consent from the student’s population. The selected subjects were examined and the location and extent of gingival recession, gingival clefts and occlusal wear facets were recorded. The type of occlusion and the nature of occlusal contact in maximum intercuspation and eccentric mandibular movements were also recorded using articulating foil and shimstock. Chi square test, Fisher’s exact test (F) and Z test were used to statistically analyse the data obtained. Among the three occlusal concepts, gingival recession was more commonly related to group function than to canine protected occlusion. Canine protected occlusion was associated with gingival recession on the labial surface while in group function occlusion; the recession was distributed equally on the facial surface of the anterior as well as posterior teeth. Nearly all subjects showed interferences in protrusive, lateroprotrusive and lateral excursive movements on teeth showing gingival recession and gingival clefts. Occlusal wear was seen on all teeth having gingival clefts and on most teeth having gingival recession. These results suggest that occlusal interferences in maximum intercuspation and eccentric movements in one form or the other and absence of mutually protected occlusion can contribute to gingival lesions such as gingival recession and clefts.     

Anterior condylar displacement: Its diagnosis and treatment

A deflective slide in centric relation to centric occlusion does not necessarily mean anterior condylar displacement. Its diagnosis and treatment depend on the correlation of three factors: the direction and magnitude of the mandibular slide from centric relation to centric occlusion, the change in vertical dimension of occlusion during the slide, and the position of the condyles in the fossae when the teeth are in the maximum occlusion (centric occlusion).When the change in vertical dimension almost equals the amount of slide from the deflective contact in centric relation to maximum intercuspation, very little anterior condylar displacement would be expected. Conversely, with proportionately little change in vertical dimension, more anterior condylar translation is required for a given degree of anterior slide. Examples of each type of anterior slide were related to the TMJ radiographs of the condylar position. If the direction and magnitude of the deflective occlusal contact can be correlated with the TMJ radiographs, the centric relation is “functional,” and the clinically retruded mandibular position should be used. When this correlation does not exist, the centric relation is “dysfunctional,” and the terminal hinge position (retruded mandibular position) shouldnot be used for restorative or corrective procedures. Examples of anterior condylar displacement were given, including lateral deviation, with a comparison of “before” and “after” TMJ radiographs.     

A possible biomechanical role of occlusal cusp–fossa contact relationships

Summary Biomechanical features of occlusal contacts are important in understanding the role of the occlusion contributing to masticatory function. Cusp–fossa contact is the typical pattern of occlusion between upper and lower teeth. This includes static relations, such as that during clenching, and dynamic relations when mandibular teeth contact in function along the maxillary occlusal pathways, as during mastication. During clenching in the maximum intercuspal position (ICP), cuspal inclines may take the role of distributing the occlusal forces in multi‐directions thus preventing excessive point pressures on the individual tooth involved. During chewing movement on the functional side, the mandible moves slightly from buccal through the maximum ICP to the contralateral side. The part of the chewing cycle where occlusal contacts occur and the pathways taken by the mandible with teeth in occlusal contacts are determined by the morphology of the teeth. The degree of contact is associated with the activity of the jaw muscles. To obtain repeatable static and dynamic occlusal contact information provided by the morphology of the teeth, maximum voluntary clenching and chewing movements with maximum range are needed. In conclusion, in addition to the standard occlusal concepts of centric relation/centric occlusion and group function/cuspid protection relation, biomechanics in static and dynamic cusp–fossa relationships should be included to develop an understanding of occlusal harmony which includes no interfering or deflective contacts in functional occlusal contact.     

Osteochondroma of the mandibular condyle: surgical excision followed by occlusal stabilization

Osteochondroma of the mandibular condyle in adults can be treated by surgical excision, condylectomy followed by costochondral graft or orthognathic surgery. Such complex treatment plan may not be appropriate for patients with old age, affected with chronic osteochondroma of the condyle. In this clinical report, we present a patient with osteochondroma of the condyle treated by surgical excision. The patient's postoperative occlusion was a contraindication for orthognathic surgery because of the severe abrasion of the teeth and the chronic compensation of the dentition to the deviated mandible. Surgical excision of the lesion was carried out under general anesthesia, and the remaining condylar head was salvaged as much as possible. No graft materials or posthodontic condyle reconstruction was carried out. Because there was no occlusal stop to secure the mandible in a centric relation position of the condyle, a stabilization splint was delivered to position the condyle in a relatively stable position. The stability of the condyle position was evaluated by follow-up cone beam computed tomographic scans of the pathologic and the contralateral condyle, along with clinical factors such as occlusal contact points and mandible movements assayed by ARCUSdigma (KaVo). After significant condylar position was achieved, full prosthodontic reconstruction was performed to both the patient's and the dentist's satisfaction.     

Full mouth rehabilitation on a bilateral condylar fractured patient using orthognathic surgery and dental implant

BACKGROUND

Mandibular displacement is a common complication of condylar fracture. In the mandibular displacement due to condylar fracture, it is difficult to restore both esthetics and function without using orthognathic surgery.

CASE DESCRIPTION

This clinical report described a full mouth rehabilitation in the patient with bilateral condylar fractures and displaced mandible using bilateral sagittal split ramus osteotomy (BSSRO) and simultaneous dental implant surgery. Mandibular position was determined by model surgery through the diagnostic wax up and restoration of fractured teeth. The precise amount of the mandibular shift can be obtained from the ideal intercuspation of remaining teeth.

CLINICAL IMPLICATION

Mandibular displacement by both condylar fractures can be successfully treated by orthognathic surgery. Determination of occlusal plane and visualization from diagnostic wax up are mandatory for mandibular repositioning of model surgery. Stable occlusion and regular recall check up are needed for long-term outcome.     

Clinical Study on the Analysis of Chewing Movements in Relation to Occlusion

The purpose of this study was to examine how the occlusal factor influences the chewing movement. The subjects were divided into two groups; one consisted of 10 subjects whose chewing patterns look like grinding movements, which we named “grinding type,” and another consisted of 15 subjects whose chewing patterns look like chopping movements, which we named “chopping type.” The distance of separation between the lower functional cusp tips and the upper teeth in centric occlusion and at lateral mandibular position was measured and analyzed in the two groups. In centric occlusion, the distancewas less in the chopping type than in the grinding type. On the contrary, at lateral mandibular position, the distance was less in the grinding type.

This study suggests that the chewing pattern has some relationship to occlusion, especially to the distance between the upper and the lower posterior teeth in the lateral mandibular position.     

Does the presence of an occlusal indicator product affect the contact forces between full dentitions?

Studies have explored occlusal marking interpretation, repeatability and accuracy. But, when an occlusion detection product is interposed between teeth, direct tooth–tooth occlusal contact relationships are replaced by tooth‐material‐tooth structures. Thus, the marks cannot reflect the original contacts. This has been shown for single tooth pair contacts. The purpose of this laboratory study was to similarly examine full dentitions. A dentiform was set into Class I centric occlusion with the mandible supported by a load cell. The maxillary arch was guided by precision slides. As the weighted (~52 N) upper assembly was lowered onto and raised off the mandibular arch, the loads on the mandible were measured. With and without (control) occlusal marking material, the steps were as follows: (cleaning – control 1 – material 1) … (cleaning – control 6 – material 6). The six materials were as follows: Accufilm I and II, Rudischhauser Thick and Thin, Hanel Articulating Silk and T‐Scan. Then, the six sets of (cleaning – control – material) measurements were repeated with the mandibular assembly shifted, in turn, by 0·1 mm in the Anterior, Posterior, Right and Left directions. The five (Centric and four 0·1 mm shifted) occlusal relationships produced grossly different tooth–tooth (control) load profiles. And, in general, these controls were affected, in different ways, by the marking products. Among the five conventional products, the Rudischhausers fared the worst and the electronic T‐Scan was an extreme outlier. Thus, in general, popular occlusal detection products alter the occlusal contact forces, and therefore, their markings cannot characterise the actual occlusion.     

Is skeletal stability after bimaxillary surgery for skeletal class III deformity related to surgical occlusal contact?

A stable occlusion at the time of surgery is considered important for post-surgical stability after orthognathic surgery. The aim of this study was to determine whether skeletal stability after bimaxillary surgery using a surgery-first approach for skeletal class III deformity is related to the surgical occlusal contact or surgical change. Forty-two adult patients with a skeletal class III deformity corrected by Le Fort I osteotomy and bilateral sagittal split osteotomy with a surgery-first approach were studied. Dental models were set and used to measure the surgical occlusal contact, including contact distribution, contact number, and contact area. Cone beam computed tomography was used to measure the surgical change (amount and rotation) and post-surgical skeletal stability. The relationship between skeletal stability and surgical occlusal contact or surgical change was evaluated. No relationship was found between maxillary or mandibular stability and surgical occlusal contact. However, a significant relationship was found between maxillary and mandibular stability and the amount and rotation of surgical change. The results suggest that in the surgical-orthodontic correction of skeletal class III deformity with a surgery-first approach, the post-surgical skeletal stability is not related to the surgical occlusal contact but is related to the surgical change.     

A comparison of the signs of temporomandibular joint dysfunction and occlusal discrepancies in a symptom-free population of men and women

To date, there has been no conclusive explanation for the predominance of female patients with temporomandibular joint (TMJ) dysfunction. The purpose of this study was to survey a normal population without symptoms for the presence of certain putative signs of TMJ dysfunction in association with certain signs of occlusal discrepancy and to determine the presence of any gender variation. The subjects (217 men and 217 women) were examined for the presence of three putative signs of TMJ dysfunction: limited mandibular opening (under 37 mm), deviation on opening, and joint sounds. The subjects were also examined for the presence of four signs of occlusal discrepancy: an anterior slide from centric relation (CR) to centric occlusion (CO), lateral slide from CR to CO, nonworking occlusal contacts, and working disclusive contacts distal to the canines. CR is the mandibular position at which the condyles are in their most superior position on the posterior aspect of the articular tubercles. CO is the mandibular position at which the mandibular and maxillary teeth are in maximum intercuspation. There were no significant differences in the prevalence of the putative signs of TMJ dysfunction and occlusal discrepancy between men and women. It was concluded that factors other than the presence of these signs of TMJ dysfunction and occlusal discrepancy are responsible for the high predominance of female patients with TMJ dysfunction.     

COMPARATIVE EVALUATION OF THE EFFICACY OF OCCLUSAL SPLINTS FABRICATED IN CENTRIC RELATION OR MAXIMUM INTERCUSPATION IN TEMPOROMANDIBULAR DISORDERS PATIENTS

Fabrication of occlusal splints in centric relation for temporomandibular disorders (TMD) patients is arguable, since this position has been defined for asymptomatic stomatognathic system. Thus, maximum intercuspation might be employed in patients with occlusal stability, eliminating the need for interocclusal records. This study compared occlusal splints fabricated in centric relation and maximum intercuspation in muscle pain reduction of TMD patients. Twenty patients with TMD of myogenous origin and bruxism were divided into 2 groups treated with splints in maximum intercuspation (I) or centric relation (II). Clinical, electrognathographic and electromyographic examinations were performed before and 3 months after therapy. Data were analyzed by the Student''s t test. Differences at 5% level of probability were considered statistically significant. There was a remarkable reduction in pain symptomatology, without statistically significant differences (p>0.05) between the groups. There was mandibular repositioning during therapy, as demonstrated by the change in occlusal contacts on the splints. Electrognathographic examination demonstrated a significant increase in maximum left lateral movement for group I and right lateral movement for group II (p<0.05). There were no significant differences (p>0.05) in the electromyographic activities at rest after utilization of both splints. In conclusion, both occlusal splints were effective for pain control and presented similar action. The results suggest that maximum intercuspation may be used for fabrication of occlusal splints in patients with occlusal stability without large discrepancies between centric relation and maximum intercuspation. Moreover, this technique is simpler and less expensive.     

Occlusal control of mandibular elevator muscles

Occlusal stability and mandibular elevator muscle function was studied in 25 women (20–30 yr of age). They had 27–32 fully erupted teeth with few treated occlusal surfaces, and craniomandibular function including mandibular mobility was normal. The aim was to analyze the influence of natural patterns of occlusal contact on electromyographic activity, unaffected by pain and functional disorders. Occlusal stability was assessed in the intercuspal and in lateral contact positions as the number of teeth with physical contact and the number of opposing pairs of teeth in contact. Electromyographic activity was recorded by surface electrodes over anterior and posterior temporalis and masseter muscles. In general, positive correlations were found between occlusal stability in intercuspal position and moderate to strong static and dynamic contractions, most significant in masseter muscles, indicating that forceful contraction of these muscles implies stable occlusion. Systematically, the duration of activity during chewing was negatively correlated with occlusal stability in the intercuspal position, most pronounced in working-side muscles. This pointed to shorter contractions with stable occlusion and is interpreted as the result of less need for stabilizing activity. It is concluded, that the correlations between occlusal stability and elevator muscle function are probably based on feedback mechanisms from periodontal pressoreceptors.     

Accuracy of check-bite registration and centric condylar position

In a dentate subject a jaw relation can either be determined in maximum intercuspation and is as such given by the occlusal morphology, or the mandibular position can be allocated according to the centric position of the condyles. For comprehensive restorative treatment or analytic measures of the occlusion it is important to record the centric condylar position. Various registration methods have been described in the literature, but there is no consensus on which is the 'best'. The aim of the present study was therefore to assess the accuracy of various registration methods and evaluate a possible influence of the used materials. Four dentists were involved in the clinical part of the study, another was responsible for the measurements. Impressions were taken from 81 fully dentate volunteers. The casts were mounted by face-bow transfer and central-bearing-point (CBP) registration into Dentatus articulators. Subsequently the centric condylar position was determined with six different methods and materials, respectively. Each method was reproduced twice so that a total of 18 registrations was performed per patient. The mandibular positions which resulted from the individual registrations were then repeatedly compared in the condylar area using a computer supported specially modified measuring articulator. The accuracy was found best for the unrefined wax wafer registration (x=0.33 mm) and with an average of 0.44 mm worst when using acrylic wafers. The CBP and frontal jig methods as well as tin-foil and refined wax wafers showed an accuracy in-between these boundaries. The biggest measured mandibular displacement between any two registrations were considerably 2.0 mm. However, the described differences in accuracy between the various methods and materials proved statistically not significant. All investigated jaw registrations showed an accuracy of about 20 times the tactile fine sensibility of natural teeth which has to be taken into account when inserting fixed prosthetic restorations in centric condylar position. Despite meticulous clinical and technical procedures small occlusal adjustments are therefore almost unavoidable.     

Dental plaque and caries on permanent first molar occlusal surfaces in relation to sagittal occlusion

This study examines the influence of sagittal occlusion on occlusal plaque formation in permanent first molars (PFM) in 72 7–10-yr-olds before loss of primary second molars. Of a total of 288 PFM, 140 (49%) were sealed and 23 (8%) filled. Occlusal plaque was recorded at two levels of examination: 1) visible plaque on the entire surface and 2) detailed macromorphologic mapping. Enamel caries was recorded after professional tooth cleaning. After 48 h without tooth brushing, plaque examinations were repeated. Stone models were used for 1) identification of interocclusal contact areas and 2) classification of sagittal molar occlusion. The detailed mapping of plaque on unfilled surfaces showed a clear pattern of preferential locations related to the macromorphology of the occlusal surfaces. Active caries was restricted to those anatomic structures where plaque accumulated. 48-h median plaque values on mandibular molars in normal and with one cusp distal occlusion were significantly lower ( P < 0.01) compared to surfaces in 1/4, 1/2 and 3/4 distal molar occlusion. Maxillary molars with normal and with 1 cusp distal occlusion had lower median plaque values than other sagittal occlusion categories. In general, however, plaque scores were higher in maxillary teeth because more than 2/3 of these teeth were without occlusal contact in the distal part. Mandibular occlusal surfaces in normal and with one cusp distal occlusion had significantly fewer active lesions than teeth with 1/4, 1/2 and 3/4 cusp distal occlusion. The significant influence of variations in sagittal molar relation on occlusal plaque formation and caries initiation occurring in fully erupted PFM before loss of primary second molars thus supports the view that physical forces operating during mastication are an important factor for colonization and growth of bacteria with cariogenic potential.     

Cephalometric analysis: comparisons between maximum intercuspation and centric relation.

Cephalometric analyses were made of forty-six preorthodontic patients with the mandibular teeth in maximum intercuspation. A Centric-Ceph was used and the analysis was repeated on these patients with the mandible in centric relation. The following conclusions are drawn: 1. No clinically useful prediction may be made from cephalometric radiographs concerning the amount of mandibular deflection from centric relation to maximum intercuspation of teeth. 2. There are differences in cephalometric measurements with the mandible in the two different positions. However, with the exception of a few cases, the differences are slight. 3. The individual cases that have the largest discrepancies tend to be Class II malocclusion cases. The orthodontist should be aware of those cases and be prepared to articulate them for diagnosis.     

A discussion of some factors of relevance to the occlusion of complete dentures

There exists general agreement that in the construction of complete dentures the accurate positioning of the plane of occlusion is essential for correct denture function. Yet rarely does a prosthodontist give detailed instructions concerning the positioning of this plane to the technician who is to set the teeth. In this paper the three-dimensional location and form of the occlusal plane is discussed. For both anatomical and mechanical reasons the author favours the use of the mandibular rather than the maxillary record rim as the clinical determinant of the level of the artificial occlusion. A change in the method of setting the face-bow is recommended to allow for the difference between the cranial Frankfort plane and the axis-orbital plane of the articulator. Arguments are advanced to support the proposal that artificial teeth should be set to an intercuspal location forward of centric relation; and that the form of the antero-posterior compensating curve of the artificial dentition should be determined by the clinician before the teeth are set to the registration rims.     

Clinical protocol for occlusal adjustment: Rationale and application

Background: Occlusal adjustment can optimize the result of orthodontics, orthognathic surgery, and comprehensive restoration, and resolve adverse forces to the dentition that affect the entire masticatory system. Mounted diagnostic casts and computerized occlusal analysis offer complementary advantages for evaluating occlusal problems. Predictable occlusal adjustment is facilitated by precise, measured documentation of occlusal force by computerized occlusal analysis.

Clinical presentation: A conservative, structural correction of a pronounced, chronic occlusal problem by additive and subtractive occlusal adjustment was performed after a previous failed occlusal adjustment. The patient’s chief concerns were significant anterior teeth fremitus in maximum intercuspation and “pain in the teeth and a poor bite” after 30+ adjustments over 2.5 years.

Clinical Relevance: Confirmation of specific criteria for a therapeutic occlusion resolved the anterior teeth fremitus and uneven bite. Traumatic occlusal contact on posterior teeth may elicit protective mandibular repositioning affecting anterior teeth relationships and should be considered during comprehensive diagnosis.     

Posterior unilateral condylar displacement: its diagnosis and treatment.

The treatment procedure for posterior unilateral condylar displacement has been described. An acrylic resin repositioning prosthesis may be used to decrease trismus. Occlusal adjustment permits lateral freedom for mandibular movement to the opposite side which provides a dual, or a therapeutic, centric occlusion as well as the existing dysfunctional centric relation. This permits the patient's physiologic adaptive mechanism to choose between the existing dysfunctional centric relation, which resulted in unilateral condylar retrusion and pain, or a therapeutic centric occlusion which is aimed at anterior unilateral condylar repositioning. Over long period of time, muscle reprogramming produces maximum intercuspation of teeth in the planned therapeutic centric occlusion rather than in the original dysfunctional position. No explanation has been established for this phenomenon. It is important, however, to provide a technique that permits physiologic adaptability over a period of time. It should be emphasized that this is not TMJ "remodeling" but a functional change in the position of the jaw. The treatment objectives of bilateral and unilateral posterior condylar displacement are similar, but the clinical techniques are completely different. In either instance, TMJ radiographs are necessary to establish the diagnosis and treatment, as well as to document the postoperative results.     

Bruxism and trauma from occlusion. An experimental model in Macaca monkeys

The present study describes an experimental approach for inducing bruxism and trauma from occlusion in animals. Gold occlusal cap splints overlaying the maxillary premolar and molar teeth were inserted in eight Macaca irus monkeys. The cap splints were designed to raise the vertical dimension of occlusion by 3--4 mm and were adjusted to a balanced occlusion with the mandible in an unstrained retruded position. The splint on the right side (test side) was given a tight occlusion with the opposing mandibular teeth, whereas the splint on the left side (reference side) had only small occlusal contact areas. Before insertion of the splints, the monkeys had slight gingivitis but no alveolar bone loss. The cap splints were in situ for 4 weeks. During this period the monkeys showed distinct signs of bruxism. The mandibular teeth on the test side showed increased mobility and there was radiographic evidence of breakdown of marginal and interradicular alveolar bone. Mean GI increased significantly on the test side and in two animals gingival abscesses developed. Deep intrabony pockets persisted adjacent to these teeth. Only slight gingival and radiographic changes were seen adjacent to the teeth on the control side. From the present experimental study there was no overall clinical or histological evidence that bruxism had caused a progression of gingivitis to destructive, chronic marginal periodontitis.     

浅谈咬合修复重建中的（牙合）学问题

与颌位问题是学研究中的核心问题。咬合重建特指采用修复手段在正确的颌位关系下恢复正常咬合接触的治疗方法，主要针对口内仍存留有大量天然牙，但丧失了稳定的咬合接触关系，需要以修复的方法重新建立稳定咬合关系的情况而展开。由于存留的大量天然牙有活跃的牙周反射活动，重建后的咬合关系在行使咬合功能时受到复杂的神经反馈调节作用，因此咬合重建与普通的活动修复治疗相比有更高的技术要求。本文主要讨论有关颌位关系和咬合接触问题。确定正常颌位关系是建立正常咬合关系的基础，建立正常咬合接触关系从而恢复正常咬合功能是咬合重建的目标。     

The role of the general practitioner in restoring patients with temporomandibular joint dysfunction

Treatment of temporomandibular joint pain, resulting from occlusal dysfunction, is divided into two phases. First, occlusal splint therapy is used to eliminate the initial signs and symptoms and to achieve stability in centric relation. In the second phase of treatment the occlusion is adjusted and, if indicated, restored by means of crown and bridge procedures. Casts, properly mounted in a semi-adjustable articulator, with the lower cast mounted in centric relation, can be extremely helpful for an occlusal analysis and a diagnostic occlusal adjustment in the articulator. Each occlusal adjustment procedure in the mouth should be preceded by an initial study, occlusal analysis and occlusal adjustment on articulator mounted casts. The two main criteria for restoring the occlusion are: maximum intercuspation occurring in centric relation and disocclusion of the posterior teeth during excursive movements by means of anterior guidance. Patients with a history of temporomandibular joint pain and dysfunction usually have a limited adaptive capacity of even the smallest occlusal imperfection. In order to cope with the occlusal restoration of patients with such a low level of occlusal tolerance the final crowns and bridges should be cemented temporarily for a period of at least 3 months. A matt gold surface will be very helpful to locate undesirable occlusal contacts during temporary cementation.