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Purpose: To compare the impact of canine guided vs. bilateral balanced occlusion on oral health related quality of life (OHRQoL) as a patient-reported outcome measure., Methods: In this randomized single-blind crossover trial, 19 patients have been provided with new complete dentures in the maxilla and mandible. OHRQoL was assessed using the 49-item Oral Health Impact Profile (OHIP-49) before the start of the prosthodontic treatment (B), 3 months after insertion of the new dentures (T1), and 3 months after rework into the alternative concept (T2). Multilevel mixed-effect linear regression models were computed to determine the effect provided by the new set of dentures and the specific impact of the occlusal concept on OHRQoL using summary scores of the OHIP-49 and of a 19-items subset specific for edentulous patients (OHIP-EDENT)., Results: At baseline, participants' OHRQoL was substantially impaired indicated by an average OHIP-49 score of 42.1 points and an OHIP-EDENT score of 21.1 points. The effect of provision of a new set of complete dentures was a statistically significant decrease of 8.3 points (OHIP-49) and 4.0 points (OHIP-EDENT), respectively, representing a clinically relevant improvement in OHRQoL. When wearing dentures with bilateral balanced occlusion, participants showed on average 1.6 points higher OHIP-49 scores and 0.9 points higher OHIP-EDENT scores compared to canine guided dentures. This effect of the occlusal concept was neither statistically nor clinically significant., Conclusions: Both investigated occlusal concepts for complete dentures were comparable in their effect on patients' perceptions with none being considerably superior in terms of OHRQoL., (Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

This article presents the basic principles of dental occlusion and an overview of this subject area, which is important for dental professionals. Clinical relevance: A sound knowledge of dental occlusion is important in order to improve dental treatment outcome and achieve a long-lasting restoration.

Instability of our orthodontic treatment is not uncommon, in particular in the anterior teeth. Given that the mandible is constantly in movement and that the lower and upper teeth regularly meet head-on during normal functioning, one might ask: are the static and normative end of treatment objectives we generally target sufficient to ensure treatment stability?, (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

Aim: The aim of this study was to find out the nature of occlusion and tooth contact during various eccentric mandibular movements in young adults with class I occlusion., Materials and Methods: The sample consisted of 100 young adults with class I occlusion with full complement of teeth. Anterior disclusion in centric occlusion was demonstrated using a shim stock interposed between the upper and lower anteriors. Disclusion of posteriors was ascertained during 1.5 mm straight protusion and in edge-to-edge protrusion, visually as well as using a silk floss method. Posterior disclusion was also verified during lateroprotrusion and crossover. Besides these occlusal wear of teeth also were observed., Results: The results of this study showed that the anterior disclusion is seen only in one-fourth of the subjects compared to almost three-fourth showing posterior disclusion. Mutually protected occlusion was also seen only in one-fourth of the subjects. Canine protective mechanism is seen in a relatively large number of subjects, but it was not overwhelmingly predominant. No correlation could be established between cuspid wear and the type of occlusion. A relatively high percentage of subjects showed wear on posterior teeth when there was no posterior disclusion., Conclusion: From the above study it is seen that posterior disclusion is acknowledged as a common factor except when a bilateral balance is present. Since bilateral balance is harmful, the ideal occlusal relationship in eccentric movements is in favor of posterior disclusion. Posterior disclusion is easily obtainable when restorations are planned., Clinical Significance: From the findings and results it has been possible to make some contributions on the nature of tooth contacts and disclusion during various eccentric movements and compare it with the requirements of ideal occlusion.

This study compares the effect of tooth clenching and grinding on supra- and infrahyoid electromyographic (EMG) activity during different laterotrusive jaw posture tasks. The study included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance and 15 with bilateral group function. Bipolar surface electrodes were located on the left and right supra- and infrahyoid muscles. EMG activity was recorded during the following tasks: A. eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; B. clenching in right edge-to-edge lateral contact position; C. concentric grinding from right lateral edge-to-edge contact position to intercuspal position. EMG activity was not significantly different between tasks on the working side, nonworking side, or between both sides, in subjects with canine guidance or group function (Wilcoxon rank-sum test). When comparing EMG activity by occlusal scheme, no significant differences were found either on the working side or the non-working side (Mann-Whitney U test). This result suggests that supra- and infrahyoid EMG activity in its predominant stabilizing role of the hyoid bone is not significantly modified by the type of laterotrusive occlusal scheme.

Objectives: To test the hypothesis that there is no relationship between static occlusion and dynamic occlusion., Materials and Methods: The relationship between static and dynamic occlusion was investigated in a sample of 94 dental students (39 males and 55 females) with an age range of 21-30 years. Static occlusion was determined by intraoral examination. Dynamic occlusion was determined in regulated lateral (0.5 mm and 3 mm lateral to the intercuspal position) and protrusive movements of the mandible by intraoral examination with the aid of shimstock., Results: At the 0.5 mm lateral excursion, 24.5% had bilateral group function and 12.7% had bilateral canine guidance. At the 3 mm positions, the guidance pattern changed to a predominantly canine guidance. Fifty percent of subjects had bilateral canine guidance, and only 8.8% had bilateral group function. In terms of the anterior guidance pattern, a predominant anterior contact with posterior disocclusion (77.5%) was noted. Examination of the relationship between static and dynamic occlusions revealed that at the 0.5 mm position, the pattern of dynamic occlusion was different in relation to various static occlusion features but without reaching a significant level. While at the 3 mm position, the pattern of dynamic occlusion was significantly affected by incisor relationship. The distribution of protrusive excursion patterns was significantly influenced by incisor, canine, and molar relationships., Conclusions: The hypothesis is rejected. An association exists between dynamic occlusion and different aspects of static occlusion.

Occlusion is a basic tenet of dentistry. Not every patient should be treated for occlusal discrepancies--many patients will go a lifetime with a less than ideal occlusion and experience no symptoms. Many cases of headache and facial pain have nothing to do with occlusion. Nevertheless, I believe advanced training in occlusion is an extremely valuable and essential part of everyday dentistry. This training should start at the undergraduate level in the dental schools.

This study was designed to determine the effect of the occlusal scheme on masseter EMG activity at different jaw posture tasks. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance, and 15 with bilateral group function. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right masseter muscles. EMG activity was recorded during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge lateral contact position; C. maximal clenching in the edge-to-edge lateral contact position; D. grinding from edge-to-edge lateral contact position to intercuspal position. EMG activity in tasks B, C, and D was lower than in task A (mixed model with unstructured covariance matrix). EMG activity was not significantly different with canine guidance or group function. EMG activity recorded on the nonworking side was higher than the working side during task C, and no different between tasks B or D. On the nonworking side, EMG activity in task B was significantly lower than C and D, and similar between task C and D. On the working side, EMG activity was significantly higher in task D than C and B, and in task B significantly higher than task C. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.

Purpose: This study assessed the duration of different phases of the chewing cycle and the height of the masticatory cycle in relation to the type of lateral guidance., Materials and Methods: Fifty-three subjects with the same type of lateral guidance on both sides were categorized into 3 groups: anterior protected articulation, canine protection, and group function. Overbite was measured clinically. Border jaw movements were recorded using a Sirognathograph, and the lateral guidance angle in the frontal plane was measured. Jaw movements during unilateral chewing of peanuts were recorded on the frontal plane using the Sirognathograph connected to an electrocardiograph used for transcription. A single masticatory cycle was divided into opening, closing, and occlusal-level phases. Masticatory parameters were analyzed by one-way analysis of variance, correlations, the paired Student t test, and multiple linear regression., Results: Women showed significantly longer total cycle duration than men. Subjects with canine protection showed the highest lateral guidance angle and the highest chewing cycle duration. Subjects with anterior protected articulation exhibited significantly longer occlusal-level phases. Fifty-nine percent of the variation in duration of the occlusal-level phase can be explained by the type of lateral dental guidance, gender, and lateral guidance angle. Only overbite was a predictor of height of mastication., Conclusion: The type of lateral guidance, gender, and frontal guidance angle are correlated with the duration of the occlusal-level phase during unilateral chewing of peanuts. The height of mastication cannot be explained by the type of lateral guidance.

A primary consequence of sleep bruxism is severe tooth wear. Although an occlusal splint is able to protect teeth, grinding may continue on its surface. This clinical report describes an approach to restore canine guidance on an occlusal splint, with amalgam, for a patient with sleep bruxism. This procedure allowed maintenance of the canine guidance for a period of time longer than 3 months, postponing the fabrication of a new splint.

The aim of this study was to examine the relationship between lateral retrusive and lateral protrusive tooth guidance and temporomandibular joint disc displacement. The control group comprised 55 symptomless students and dental nurses. The patient group consisted of 117 patients (90 women and 27 men). Fifty-four patients had temporomandibular joint clicking on the right side and 63 patients had clicking on the left side. The incidence of ipsilateral lateral retrusive tooth guidance was significantly higher in the patient group (87%) than in the control group (18.5%).

This study was conducted to determine the effects of laterotrusive occlusal scheme and body position on bilateral sternocleidomastoid electromyographic (EMG) activity. The study was performed on 20 healthy subjects with natural dentition and bilateral molar support. During laterotrusive occlusal excursion (working side), each individual had to present canine guidance on one side and group function on the opposite side, without balancing-side contacts. Integrated EMG (IEMG) recordings were performed by placing bipolar surface electrodes on the right and left sternocleidomastoid muscles. IEMG activity was recorded seated upright with the head unsupported and in the right and the left lateral decubitus body positions (head, neck and body horizontally aligned), under the following experimental conditions: 1. Maximal voluntary clenching in the intercuspal position; 2. Laterotrusive occlusal excursion with canine guidance; 3. Laterotrusive occlusal excursion with group function. Bilateral sternocleidomastoid IEMG activity with canine guidance or group function was significantly lower than the intercuspal position in both body positions. In the seated upright position, significantly lower activity was observed with canine guidance than in group function. In the lateral decubitus position activity was similar with both laterotrusive occlusal schemes and significantly higher than seated upright. Results suggest that both laterotrusive occlusal scheme and body position have significant influence on sternocleidomastoid IEMG activity. The clinical relevance of both factors is discussed.

The research of the predominant occlusal function during mandibular movements of laterality at the topic African melanoderme, drove authors of this survey to: select 52 healthy topics (11 women and 41 men), aged of 22 to 33 years old observe and note at every topic the presence and the nature of contacts or their possible absence of the working side during the movement of deduction. Observations done as well directly in mouth, that on models put in semi-adaptable articulators, permitted to note that the function of posterior group is more the recovered so much at women that at men, at the young adults and at adults.

Statement of Problem: Limited knowledge exists about the interaction between dental morphology and mandibular excursive movements., Purpose: This study evaluated dental guidance in lateral excursive movement and its relationship to jaw motion in unilateral chewing., Material and Methods: Three-dimensional mandibular movement paths (in lateral guiding movements and in the final part of a monolateral chewing stroke) were collected with automated infrared motion analysis in 22 subjects with complete, permanent dentitions. On 2 traces selected from the recorded movements, the angular values projected in all planes of space obtained from 2 lines tangent to a point at a distance of 2.5 mm from maximum intercuspation were used to calculate a canine and a molar dental guidance ratio (DGR). Descriptive statistics were computed for the DGRs in the 3 spatial planes., Results: Assuming masticatory movements of any given subject are restricted or guided by dental anatomy, a value below 100% of the DGR was expected. This was true for the frontal plane only, with mean values of approximately 80% (working-side movements, canines, and molars) and approximately 60% (nonworking-side movements for both molars and canines). In the horizontal and sagittal planes, mean values between 102% and 137% were found., Conclusion: Within the limitations of this study, masticatory movement was within the physical borders dictated by dental anatomy in the frontal plane only.

Before presenting 'how' the examination and recording of the occlusion may be achieved, some attempt should be made to justify 'why' it is necessary. It may appear to be a strange way of justifying the need to examine the patient's occlusion, but this will initially involve a study of the influences of mandibular movements.

Occlusion through successive phases of dental eruption was the concern of many authors. So that the progressive installation of occlusion is made harmonious way, it is necessary that the dental eruption sequences proceed correctly. The authors have studied rhythm appearance of permanent teeth, and they have determined the average eruption age of canines, first, second premolar and second molar. The results are given for the 574 children of the sample and following to the sex.

Functional occlusion and periodontal health were investigated after orthodontic treatment that involved extraction of second molars and after eruption of the third molars in 37 patients (25 female, 12 male). The mean age was 21 years 9 months (range, 16 years 1 month-30 years 5 months). The third permanent molars invariably erupted into a position that maintained good functional occlusion. Sixty-three percent of patients had canine guidance in lateral excursion; the remainder of patients had satisfactory group function. There were only 2 non-working side interferences in the sample, 1 from a recently erupted mandibular third molar. The periodontal health of the sample was generally excellent. Plaque score and bleeding on probing was very low (1.7% of sites). Periodontal health around both maxillary and mandibular teeth was extremely good. When attachment loss was assessed, 2238 of 2240 sites were clinically healthy. One patient, who had generally poor oral hygiene, had a 4-mm probing depth interproximally on the maxillary first and third molar contact. There was no correlation between periodontal health and mandibular third molar position. Therefore, both functional occlusion and periodontal health in the sample were good after loss of second permanent molars and eruption of the third molars.

Statement of Problem: The analysis of occlusal contacts on mounted diagnostic casts is an important task in prosthetic diagnostics. However, it is still restricted mainly to qualitative aspects because existing measuring techniques fail to provide 3-dimensional data for more than a few single points in acceptable time., Purpose: The aim of this study was to develop a method for quantifying occlusal contacts and paths by using anatomically oriented diagnostic casts and to design the method to allow fast acquisition of digital 3-dimensional coordinates., Material and Methods: Plaster casts with color-marked contacts were digitized optically with a profilometric system based on the fringe projection technique. Digital camera images taken simultaneously were used to define the contact areas by marking them either manually or automatically with the help of image-processing routines. Three-dimensional coordinates were determined by finding the corresponding points within the profilometric data set., Results: Color-marked contact areas on diagnostic casts were successfully digitized with a computer-controlled, automatic setup in approximately 30 seconds. The accuracy of the acquired 3-dimensional data was estimated to be better than 60 microm in lateral and 30 microm in height resolution. The data set was visualized and evaluated in a skull related coordinate system., Summary: This study verified the use of a new tool to quantify color-marked occlusal contacts on diagnostic casts in terms of spatial coordinates. The resulting digital data may be stored easily and analyzed numerically as well as visualized 3-dimensionally with computer graphic equipment. Because the anatomic orientation of the casts is maintained throughout the measurement process, it is possible to compare the data with electronically registered condyle paths and therefore to investigate, for example, their relation to the corresponding guidance paths of the frontal teeth and the canines in dynamic occlusion.

With the emphasis placed on esthetics today, anterior guidance has an important role in the development of a stable, anatomic, functional, and esthetic result. To develop a predictable and stable result requires a multidisciplinary approach to esthetics and function. The orthodontist is a major contributor in helping the restorative dentist achieve the anatomic and functional harmony that is needed for long-term stable function and esthetics. Harmony in function creates long-lasting smiles. In their continued quest for optimal results, and as members of their interdisciplinary teams, orthodontists should remind themselves of what Gottlieb wrote in 1986 in an editorial in the Journal of Clinical Orthodontics: "There is a difference between a beautiful alignment of teeth and an alignment of beautiful teeth. The orthodontist's job is not complete until there is a beautiful alignment of beautiful teeth."

The effect of different types of canine guidance on the patterns of laterotrusive tracing at the incisal point and the relationship between the laterotrusive inclinations and the working side condylar movements were investigated in 42 young subjects. The subjects were divided into M and D groups according to their mesial and distal canine guidance, and were also divided into protrusive laterotrusion (PL) and retrusive laterotrusion (RL) groups according to their laterotrusive tracing patterns. No differences of laterotrusive inclinations and working side condylar movements were found between the M and D groups. The laterotrusive tracing pattern had no corresponding association with the type of canine guidance. In relation to the movements of the working side condyles, significant differences were found between the PL and RL groups. The condyles moved laterally and posteriorly in the RL group, but moved lateral and inferior in the PL one. The distance of condylar movement in the X direction was correlated with the horizontal and sagittal inclinations of laterotrusion. The results indicate that the movements of the working side condyle were affected functionally by the laterotrusion, but not by either the mesial or the distal type of canine guidance.

The dental-arch surfaces preferentially used in mastication were studied by measuring functional and occlusal surface areas and comparing these to the number of chews required to swallow foods of different texture properties. The functional surface of the teeth was defined as the total area of visible wear facets on post-incisal teeth, adding to it the contacting areas of restored teeth where no facets were visible. Occlusal surface area was taken as the total area of the occluding parts of post-incisal teeth. Both surfaces were measured with computer image processing on dental-stone casts of the teeth of 31 young adults. Functional surface areas (mean 168 mm(2), four quadrants) were positively correlated with occlusal surface areas (mean 739 mm(2), four quadrants). The left:right area ratios were more variable for functional than for occlusal surfaces. Functional surface-area ratios markedly different from 1.0 might reflect functional side-preponderance of masticatory activity. Correlations between tooth surface area and the number of cycles were examined with five different food samples of known texture during side-imposed mastication. Depending on the elastic moduli of the foods, significant negative correlations were found between the left:right ratios of functional or occlusal surface areas and the left:right ratios of cycle numbers. The rheological properties of the food particles chewed were assumed to be the key factor in the correlations with either the functional or anatomical occlusal surfaces.

The purpose of this study was to evaluate the relationship between the clenching level and the intercuspal contact area in different regions of the dental arch. Twenty-five healthy subjects with natural normal dentitions and good occlusal support performed clenching tasks in the intercuspal position at four different levels (10, 30, 70 and 100% levels of maximum voluntary contraction) through EMG visual feedback from bilateral masseter and anterior temporal muscles. Simultaneously, the occlusal contacts were recorded with a silicone occlusal contact checking material (Black Silicone, GC Dental Industrial Corp., Tokyo, Japan). The occlusal records were analysed by an image analyser. Every area of the thickness less than 50 microm was determined to be an occlusal contact area. The occlusal contact areas on the anterior teeth (incisors and canines), the premolars (first and second premolars) and the molars (first and second molars) were calculated separately. The posterior occlusal contact area increased with an increase in the clenching levels but that of the anterior did not. The results of this study indicate that the increase in clenching forces affects the anterior and posterior occlusal contact areas differently.

This study aimed to assess mandibular mobility and the prevalence of functional occlusal contacts in subjects treated to a Class 1 incisor relationship by fixed orthodontic appliance therapy. Two hundred and thirty subjects participated (mean age=18 years) of whom 42 underwent orthognathic surgery. All subjects were in retention with a mean time of 7 months between debond and examination. Maximal mandibular opening, lateral and protrusive excursions were all significantly reduced in the surgical cases compared to the non-surgical group. Centric and eccentric non-ideal occlusal contacts were not different between surgical and non-surgical groups. Non-working side contacts occurred in 30% of subjects, posterior contacts on protrusion in 20% and RCP-ICP prematurities in 18% of subjects. Non-working side contacts were significantly more frequent in post-graduate cases compared to staff cases (P<0.05). An overbite less than the mean of 2.4 mm resulted in a reduced likelihood of canine guidance on the working side (P<0.001) and an increased frequency of non-working side contacts and posterior contacts on protrusion (P<0.001).

The relationship between anterior guidance and the mesiodistal inclination of the lower incisors relative to the existence of temporomandibular joint (TMJ) noise was investigated. One hundred and thirty-four individuals, 21 to 40 years of age (mean age 23.8; 104 men and 30 women), were examined. A highly significant correlation was observed between the mean lower-incisor inclination and the difference in steepness between the right and left anterior guidances in the subject group showing TMJ noise (P<0.001), whereas no significant correlation was observed in the group without TMJ noise.

The lack of easily measurable, objective physiological activity parameters of the masseter and temporalis muscle during jaw movements in humans has led to the consideration to revise data of surface electromyographies (EMGs) by applying a computerized quantification method. The aim of this follow-up analysis was to get quantitative data out of EMG-records of an earlier study. These records were obtained with two different splints, splint 1 providing an anterior front-canine guidance and splint 2 providing bilateral balanced occlusion. Utilizing a computer aided integration method led to numeric results which statistically proves the prediction of the previous investigation. Applying the integration method, the EMG raw signal was transformed into area-values which enabled a statistical work up of the data. Wilcoxon test statistics shows a significant (P<0.05) lower muscle activity in patients wearing dentures providing anterior front-canine guidance compared to those with balanced occlusion. It is concluded that the neuromuscular activity of the elevator muscles is highly reproducible and that the neuromuscular function is similar in edentulous subjects to that found in people with natural teeth. Furthermore, the study statistically proves earlier visual data that all those subjects, whose muscle activities were observed with anterior guidance (splint 1) compared to bilateral balanced occlusion (splint 2) showed significantly lower values with regard to subjects wearing splint 2.

Purpose: The purpose of this study was to investigate the effect of an altered inclination of the canine guidance on the pattern of the condylar movements during laterotrusion., Materials and Methods: The inclination of the canine guidance was steepened approximately 10 degrees by attaching a metal overlay to the lingual surface of the maxillary working-side canine. The laterotrusive movements of 20 young adults were measured using a three-dimensional mandibular movement analyzing system before and after alteration of the canine guidance. The difference between anterior, lateral, and inferior components of the working- and nonworking-side condylar movements, the Bennett angle, and the sagittal inclination of the nonworking-side condylar path before and after steepening of the canine guidance was evaluated by a paired t test., Results: After the canine guidance was steepened, the working-side condyle moved even more anteriorly and inferiorly. In contrast, little change was found in the direction and the amount of the nonworking-side condylar movement., Conclusion: The results of this study suggest that there is a relationship between the steepness of canine guidance and the pattern of the working-side condylar movement. but not between the steepness of the canine guidance and the pattern of the nonworking-side condylar movement.

In 46 non-patients and 46 patients, the authors examined the presence (+) and absence (-) of canine tooth guidance (CG), i.e. dynamic dental articulation events in contrast to static dental occlusion events. During a right and a left laterotrusion of the mandible, the number of simple, mutually exclusive and exhaustive tooth guidance events (possibilities) was four. In addition, the authors examined the associations between temporomandibular joint (TMJ) sounds and canine guidance events. In non-patients, CG+ was relatively infrequent (30%), and CG- was relatively frequent (70%). In patients, CG+ was relatively infrequent (22%), and CG- was relatively frequent (78%). In both non-patients and patients, bilateral CG+ was rather infrequent (15%). In both non-patients and patients with the presence of TMJ sounds, CG+ was relatively infrequent (38%) while CG- was relatively frequent (61%). In non-patients as well as patients, no evidence was found that distal CG+ (putative lateral retrusive guidance) was associated with ipsilateral TMJ sounds (relative risk = 0%), nor that the association between mesial CG+ (putative lateral protrusive guidance) and ipsilateral TMJ sounds was beyond that of mere chance (relative risk = 50%).

The effect of canine guidance of a full-arch maxillary flat occlusal splint on the level of activation of the anterior and posterior, temporal, masseter and suprahyoid muscles during maximal clenching, were studied in 14 subjects without craniomandibular disorders. The results revealed that, the level of electromyographic activity of anterior and posterior temporal and suprahyoid muscles during maximal clenching on the occlusal splint in habitual closure was unchanged, as compared to biting in the intercuspal position (ICP), while the activity in the masseter muscle, on average, was increased slightly (13 percent). In contrast, the level of activation of the jaw elevator muscles decreased significantly during maximal clenching on the cuspid ramp of the splint, as compared to the biting in ICP or clenching on the splint. However, the degree of reduction of activity was not symmetrical, and was most pronounced in the masseter muscle of the biting side and in the anterior and posterior temporal muscles of the non-biting side. No significant difference was observed in the activity of the suprahyoid muscles.

The purpose of this study was to evaluate the effects of a change in the lateral anterior guidance pathway on the lateral border movement pathway of mandible. The results showed that altered occlusal guidance reproducibly and reversibly changed (increased) the lateral border movement area in two subjects who had unilaterally restricted lateral border movements.

Mandibular border movements were studied in a group of 74 healthy young men and women with sound dentitions and class I molar relationships. Movements were directly performed by the subjects and recorded with a mandibular kinesiograph, and slopes of the first millimeters of motion in the anterior and lateral guidances were calculated. In anterior guidance, the sagittal plane slope was steeper in men than in women, whereas the horizontal plane slope showed no gender differences. In the lateral guidances, frontal plane slopes were steeper in men than in women, with no side differences. The horizontal plane slope presented no side or sex differences. Most of the subjects demonstrated asymmetric guidances for both protrusive and the laterotrusive movements. These findings suggest that criteria for defining the norm should include asymptomatic asymmetry instead of strict morphologic symmetric appearance.

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.

Through electrognathography and surface electromyography of the right and left masseter muscle (MM), this methodologic study examined the excentric (lengthening) and concentric (shortening) contractions of brief (2000 ms) voluntary teeth grinding performed through canine as well as group function of the opposing teeth. We inferred that the most anterior and superior portions of the right and left MM were lengthened and shortened by at least 4.23 mm (right MM) and 4.82 mm (left MM). For the negative work efforts (excentric contractions) of canine function, the tensions of the ipsilateral MM ranged from 10 to 20% MVC and those of the contralateral MM from 4 to 14% MVC. For the positive work efforts (concentric contractions) of canine function, the tensions of the ipsilateral MM ranged from 11 to 44% MVC and those of the contralateral MM from 20 to 41% MVC. A comparison between canine and group function showed that the negative as well as positive work efforts of group function exceeded those of canine function.

Seven women patients at Tufts University School of Dental Medicine were evaluated for the subjective symptoms of a myofascial pain dysfunction. Each patient was evaluated by an occlusal analysis of the T-Scan computer to determine posterior disclusion time during excursive movements, and EMG analysis of the masseter and temporalis muscles. Each patient was then treated occlusally by developing immediate complete anterior guidance. This adjustment process involved the removal of all lateral and protrusive interferences prior to habitual closure adjustments. No attempt was made to retrude the mandible in centric relation, and splints were not used to deprogram the musculature before adjustment. In this study, protrusive movements and interferences were not examined, and there was no control group. Posttreatment EMG and T-Scan computer analyses revealed that by shortening disclusion times to less than 0.5 second in any lateral excursions, muscle function returned to normal in all seven patients in approximately 1 month's time. A direct correlation seemed to exist between contractile muscle activity and disclusion time. Lengthy disclusion time leads to excessive muscle activity that introduces spasm and fatigue of the masseter and temporal muscles. These results indicated that a partial explanation of the etiology of MPDS may be the time the molars and nonworking premolars remain in contact during excursive movements--a phenomenon termed "disclusion time."

Anterior guidance and the condylar path have been considered independent factors. In a recent study, it was revealed that the anterior guidance influenced the working condylar path and even changed when the lateral incisal path deviated from the optimal orbit. This supports the hypothesis that anterior guidance and condylar path are dependent factors. When setting anterior guidance, it is recommended to set the working condyle so that it moves straight outward along the transverse horizontal axis. The angle of hinge rotation created by the angular difference between anterior guidance and condylar path assists the posterior disclusion, but is not solely responsible. The anatomy of the cusps is created by establishing the appropriate form of the posterior cusps aligned to the condylar path so that it also contributes to posterior disclusion. Posterior disclusion is crucial in controlling harmful lateral forces. The molars must disclude slightly more than the deviation in the condylar path to avoid occlusal interferences.

This study compared the performance of a new computerized occlusal analysis (T-Scan) system with that of Accufilm and Shimstock foil for the registration of tooth contacts on a laboratory model. Induced interceptive contacts were created on epoxy models in a mechanical closing device and the occlusal contacts were recorded for each registration method. The traditional methods were similar to the computerized analysis but the T-Scan system provided additional differential diagnostic information in force and time modes for an improved occlusal analysis.

The relationship between static occlusion and functional occlusion was evaluated in 101 dental and dental hygiene students. The sample was selected from a population of 467 students who were enrolled at one dental school during the 1987-1988 academic year based upon the following criteria: age range 18 to 32 years; caucasian race; no prior orthodontic treatment; at least 28 natural teeth present; no occlusal adjustments; and no large restorations, crowns or bridges. Fifty-two (52) of the subjects possessed "normal" static occlusion, 26 had a Class I malocclusion, 16 were found to have a Class II malocclusion, and 7 had a Class III malocclusion. The majority (i.e., 75%) of the 101 subjects possessed non-working (balancing) functional contacts. Seventy-five (75) of the subjects possessed balanced occlusion, nine had canine-protected occlusion, nine possessed group function occlusion, and eight had mixed canine-protected/group functional occlusion. This study found no statistically significant relationship between static occlusion and functional occlusion, however, there was a trend for balanced occlusion to be more often associated with "normal" (ideal) static occlusion.

Anterior guidance, which can be categorized as group function or canine guidance, is essential for esthetics, phonetics, and mastication. This article reviews the historical development and philosophies of both occlusal schemes. There is no scientific evidence that supports one occlusal scheme over the other. Where anterior guidance must be reestablished or where it changes, there currently appear to be more authorities who favor canine guidance over group function.

The effects of balancing-side tooth contacts on temporomandibular joint loads are unclear. We used a 3-D computer model to calculate the magnitude and direction of temporomandibular reaction forces during simulated clenching on interocclusal acrylic resin shims and between natural teeth. Muscle tensions were proportioned according to the task modeled. Working-side tooth contacts included the canine alone, as well as group function, and occlusal loads were progressively shifted toward a posterior contralateral simple balancing contact. In the acrylic resin shim experiments, group function with simple balancing contact yielded the highest forces at the load point and at both temporomandibular joints. Movement of the occlusal load toward the balancing side produced greater, anteriorly oriented forces on the working condyle. For natural teeth, changes in the angle of resultant tooth force (simulating facet angulation) greatly influenced condylar forces. As the occlusal load moved toward the balancing side, greater and more laterally oriented forces were produced on the balancing condyle. Unilateral clenching on the canine produced the least condylar and bite forces. The simulation involving natural teeth offers a possible explanation for deviations in form and osteoarthrosis at the temporomandibular joints.