The functional range of tooth contact in lateral gliding movements

Effect of prosthodontic planning on lateral occlusion scheme: a comparison between conventional and digital planning

Recently, digital wax-up is proposed as a tool to aid prosthodontic planning. However, there are no data about the effect of prosthodontic planning on lateral occlusion scheme.

OBJECTIVE

This study aims to evaluate the impact of conventional and digital prosthodontic planning on lateral occlusion scheme.

MATERIAL AND METHODS

Dental models of 10 patients were collected. All models had Angle Class I occlusion and were undergoing prosthodontic treatment that would influence the lateral occlusion scheme. Each set of models had received both conventional wax-up and digital wax-up. In relation to the lateral occlusion scheme, the following variables were evaluated: the prevalence of the different lateral occlusion scheme, number of contacting teeth and percentage of each contacting tooth. Four excursive positions on the working side were included: 0.5, 1.0, 2.0 and 3.0 mm from the maximal intercuspation position.

RESULTS

The lateral occlusion scheme of the two wax-up models was subjected to alterations following excursion. There was a tendency for the prevalence of canine-guided occlusion to increase and for the prevalence of group function occlusion to decrease with increasing excursion. The number of contacting teeth was decreasing with the increasing magnitude of excursion. For the 0.5 mm and 1.0 mm positions, the two wax-ups had significantly greater contacts than the pre-treatment models, while at the 2.0 mm and 3.0 mm positions, all the models were similar. For all models, canines were the most commonly contacting teeth, followed by the teeth adjacent to them. No difference was observed between the two wax-ups in relation to the number of contacting teeth.

CONCLUSION

Although the prosthodontic planning had influenced the pattern of the lateral occlusion scheme and contacts, there was no difference between the conventional and digital prosthodontic planning.

A clinical study to determine the pattern of occlusal contacts in lateral positions and its validity in classifying guidance patterns

The existing classification systems like canine-guided and group function are insufficient to classify all clinical conditions and chances of subjective variations are always there, as there is no standardization in examination method. Hence a study was planned to find out the frequency of tooth contacts in different lateral positions and to assess whether existing occlusal schemes like canine protection and group function can classify all occlusal guidance in the natural dentition. 100 systematically healthy undergraduate students between the age group of 18 to 25 years were selected. Occlusal contacts were examined with shim stock in lateral positions, 0.5, 1, 2, and 3 mm from the maximum intercuspation. Frequency of tooth contacts in different lateral positions was examined. The SPSS version 15.0 statistical software and Chi- Square test were used for statistical analysis. Out of all the four lateral positions, 0.5 mm position showed maximum contacts which progressively decreases for further positions. Out of all teeth, canine showed consistent contact frequency throughout all four positions. Most contact patterns belonged to group function, and a few to canine protection. Majority of the contact patterns were those other than canine protection and group function and were unclassifiable. On the basis of the results of this study, it does not seem appropriate to describe and classify the patterns of occlusal contact using only existing classification system. A clear description regarding the position of mandible should be included in definition for research as well as clinical situations. Here an attempt is made to classify eccentric occlusal contact at different lateral positions so as to get consistent result for future studies.

Relationship between pattern of masticatory path and state of lateral occlusal contact

The purpose of this study is to clarify whether the state of occlusal contact on lateral excursion is related to the pattern of masticatory movement path. The masticatory movement during mastication of softened chewing gum and the occlusal contact on lateral sliding of the mandible by 1 mm (L1), 2 mm (L2) and 3 mm (L3) were recorded in 50 healthy subjects. The path of masticatory movement was classified into one of seven patterns. The number of teeth involved in the occlusal contact in each pattern was investigated and compared among different lateral occlusal positions. The occlusal contact was then classified into 15 types based on one or a combination of the following four regions; incisal region, canine region, premolar region and molar region. The number of occlusal contact type for each pattern was investigated and compared among patterns. The number of teeth involved in occlusal contact decreased as the degree of lateral excursion increased, and significant differences were observed among the lateral occlusal positions (P < 0.001). The occlusal contact tended to decrease in the molar region and increase in the canine or premolar regions as the degree of the lateral excursion increased. When comparing among patterns, significant differences were observed at L2 and L3 (L2; P < 0.001, L3; P = 0.030) but not at L1 (P = 0.318). The difference was remarkable at L2. It was suggested that the state of occlusal contact at L2 and L3, particularly at L2 was related to the masticatory path pattern.

Is there such a thing as a 'healthy occlusion'?: lessons from history

Opinions on occlusion and its link to oral health could not be more diverse. These opinions are used as justification for an equally diverse range of treatments for so-called occlusally related problems, from heavy wear to chronic orofacial pain. Many claim to have evidence to back up their opinions, although much of it appears to be from a very weak source or based on clinical experience. The strongest case appears to be made by those who believe there is no link, by virtue of a lack of evidence to support its existence. Yet for many clinicians, it is a self-evident truth that occlusion must be related in some way to the function and dysfunction of the stomatognathic system. This article uses historical research to highlight where the pro-occlusionists may be going wrong. It also offers a new concept, based on anthropological studies, that indicates occlusion's link to oral health, and explains why most patients appear to have no occlusal problems for most of the time. This theory needs to be tested by researchers to establish its validity. In the meantime, dentists who feel the need to treat occlusal problems will find it supports a very conservative approach to care.

Effects of laterotrusive occlusal scheme and body position on bilateral sternocleidomastoid EMG activity

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.

Comparison of unilateral chewing movements vs. dental guidance through the dental guidance ratio

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.

Functional occlusion: I. A review

The features that constitute an "ideal" functional occlusion have not been conclusively established. Orthodontic treatment has the capacity to change static and functional occlusal relationships fundamentally. In this article, we present the evidence on which features of the occlusion are reported to be detrimental to the teeth and masticatory system Deficiencies in this research area are highlighted, together with the need for prospective longitudinal trials to clarify the requirements of an ideal functional occlusion Based on the existing evidence this paper suggests which occlusal features may be significant in producing an "ideal" functional occlusion As no long-term studies exist to measure the impact of non-ideal occlusal relationships on the dentition, it is debatable whether orthodontic treatment should be prolonged in order to ensure that "ideal" occlusal contacts are achieved As the occlusion tends to "settle" in the period following appliance removal, we propose that it may be more appropriate to examine the functional occlusal relationships after retention has ceased rather than prolong active orthodontic treatment to achieve "ideal" functional occlusal goals.

Validity of the examination method of occlusal contact pattern relating to mandibular position

OBJECTIVE

This study was based on the hypothesis that conflicting findings and inconclusive consensus regarding the role of occlusal factors in the masticatory system are due to the variations in the definitions and methods used to describe and examine the occlusal factors. The object of this study was to determine whether contact patterns during lateral movement vary with mandibular positions and whether the contact pattern in lateral positions close to the maximum intercuspation has characteristics distinct from those in an edge-to-edge position.

METHODS

Occlusal contacts of 86 young adults were examined using shim stock in regulated lateral positions: 0.5, 1, 2 and 3 mm from the maximum intercuspation, where the 0.5, 1 and 2 mm positions were defined as lateral positions close to the maximum intercuspation and the 3 mm position as an edge-to-edge position.

RESULTS

The occlusal contact pattern in the 0.5 mm position showed a marked prevalence of posterior tooth contacts on the working and the non-working sides, compared with the 1, 2 and 3 mm positions. The occlusal contact pattern in the 3 mm position predicted the presence or absence of the occlusal contact in the 1 and 2 mm positions (sensitivity > 0.7) but not in the 0.5 mm position (sensitivity < 0.6).

CONCLUSION

The occlusal contact patterns during lateral movement varied greatly with mandibular positions. The examination method of the occlusal contact pattern in one unregulated position will be invalid. It is necessary to distinguish the occlusal contact patterns between a position close to the maximum intercuspation and an edge-to-edge position when investigating its role in the masticatory system and in oral disease.

Pattern of occlusal contacts in lateral positions: canine protection and group function validity in classifying guidance patterns

STATEMENT OF PROBLEM

The concept of canine protection and group function lack consistency in the definitions and examining methods, and a valid system for evaluating and classifying occlusal contact patterns has not been established.

PURPOSE

This study assessed the use of canine protection and group function in classifying occlusal guidance in the natural dentition.

MATERIAL AND METHODS

Occlusal contacts of 86 young adults were examined with shim stock in regulated lateral positions, 0.5,1,2 and 3 mm from the maximum intercuspation. The patterns of occlusal contacts varying with the lateral position were described.

RESULTS

Focusing on the working-side contact only, most contact patterns belonged to group function, and a few to canine protection. Focusing on both the working and nonworking side contacts, nearly half the contact patterns were those other than canine protection and group function and were classified into balanced occlusion.

CONCLUSION

The validity of the classification system using canine protection and group function is questionable. A new classification system of occlusal guidance is desirable.

Masticatory tooth contact patterns: predicted and observed cuspid and first molar contacts in cuspid and group function

Using the mouth as an "in vivo articulator," the bilateral nonmasticatory ("empty") contact patterns of opposing cuspid and first molar teeth were determined in two healthy subjects with well-defined cuspid function and two healthy subjects with well-defined group function. The electronically recorded "empty" contact patterns pertained to the static intercuspal position and dynamic laterotrusion to the right and the left. On the basis of the "empty" tooth contact patterns and the number of electronically recorded masticatory cycles of one masticatory sequence, we postulated two simple models that attempted to predict the masticatory ("functional") tooth contacts of one sequence of unilateral mastication of apple and banana. Statistical comparisons between the predictions of the two models and the actual ("functional") contacts of in vivo mastication showed that the models predicted fairly well the observed tooth contacts on the nonchewing-side of the mouth, but not the observed tooth contacts on the chewing-side of the mouth. In consequence, "empty" (nonmasticatory) tooth contact patterns should not be equated with "functional" (masticatory) tooth contact patterns.

Temporomandibular joint dysfunction and flat lateral guidances: a clinical association

Temporomandibular joint alterations have been associated with abnormal mandibular movements in the open/close cycles and in the laterotrusive border movements. The quantitative analysis of these movements could allow a better or earlier diagnosis for patients and offer some insight into the pathophysiology of the disorder. Maximum opening and mandibular laterotrusive border movements were studied and measured in a group of 165 patients with a considerable lateral deviation (equal to or greater than 5mm) in maximum opening. Movements were directly performed by the patients and recorded with a mandibular kinesiography. The slope of the lateral guidance (frontal plane projection) was measured in the first millimeters of motion and started from the maximum intercuspal position. On average, slopes were significantly flatter on the same side with the opening deviation. These slopes were significantly flatter than previously published physiologic ranges, whereas contralateral slopes were similar to normal references. The results may be explained by a correlation between the insufficient lateral protection and a temporomandibular mandibular joint dysfunction (ipsilateral low mobility).

Tooth contact during dynamic lateral excursion in young adults

Tooth contact in mediotrusion as well as the signs and symptoms of periodontal and mandibular dysfunction were recorded in healthy patients aged between 20 and 31 with Angle class I or II. Non-functional side contact (NFSC) was found in 94% of the patients, indicating that it is a common phenomenon. In cases of NFSC, the entire range of movement, and not only the final stage of tip-to-tip contact on the working side, should be recorded. Slight positive mobility with tooth faceting, as compared to the adjacent and contralateral teeth, was observed in 56 patients. There was no correlation between mediotrusion and mandibular dysfunction. The cumulative effects of NFSC are not well documented, and longitudinal follow-up studies should be carried out to clarify these.

Influence of occlusal force and mandibular position on tooth contacts in lateral excursive movements

The diagnosis and treatment of occlusal disharmonies requires an understanding of the variables that affect occluding tooth contacts. Quantitative recordings of tooth contacts and near tooth contacts are necessary for detailed analysis of occlusion. In this study, different thicknesses of registration strips were used to assess the influence of occlusal force and mandibular position on tooth contacts and clearance. This assessment was made for nonworking side molars and working side premolars. There was a significant decrease in clearance with increased occlusal force on both the nonworking and the working sides. A significant increase of clearance was noted as the mandible moved to the most lateral position on the nonworking side. These results indicate that the variables of occlusal force and mandibular position represent potential sources of disparity in the recording of tooth contacts. These variables should be considered when occlusal examination procedures are conducted.

Evaluation of three occlusal examination methods used to record tooth contacts in lateral excursive movements

Accurate and repeatable methods for recording tooth contacts are required for the clinical management of problems related to occlusion. A thorough understanding of the materials and procedures used in these methods is important to achieve desirable results in the treatment of such problems. This study compared three occlusal examination methods to determine the influence of materials and procedures on the number of tooth contacts recorded. Tooth contacts were analyzed at two lateral mandibular positions with each method. It was found that the method that uses black silicone recorded the highest number of tooth contacts. Thus the most frequent type of occlusal pattern observed was full-balanced occlusion. This study suggested that the disparities of results reported in literature on occlusal contact patterns could be the result of the different materials and methods used for occlusal registration.

Mandibular elevator muscles: physiology, action, and effect of dental occlusion

In spite of differences in embryologic origin, central nervous organization, and muscle fiber distribution, the physiology and action of mandibular elevator muscles are comparable to those of skeletal muscles of the limbs, back, and shoulder. They also share the same age-, sex-, and activity-related variations of muscular strength. With respect to pathogenesis, the type of muscular performance associated with the development of fatigue, discomfort, and pain in mandibular elevators seems to be influenced by the dental occlusion. Clinical research comparing the extent of occlusal contact in patients and controls as well as epidemiologic studies have shown reduced occlusal support to be a risk factor in the development of craniomandibular disorders. In healthy subjects with full natural dentition, occlusal support in the intercuspal position generally amounts to 12-14 pairs of contacting teeth, with predominance of contact on first and second molars. The extent of occlusal contact clearly affects electric muscle activity, bite force, jaw movements, and masticatory efficiency. Neurophysiologic evidence of receptor activity and reflex interaction with the basic motor programs of craniomandibular muscles tends to indicate that the peripheral occlusal control of the elevator muscles is provided by feedback from periodontal pressoreceptors. With stable intercuspal support, especially from posterior teeth, elevator muscles are activated strongly during biting and chewing with a high degree of force and masticatory efficiency, and with relatively short contractions, allowing for pauses. These variables of muscle contraction seem, in general, to strengthen the muscles and prevent discomfort. Therefore, occlusal stability keeps the muscles fit, and enables the masticatory system to meet its functional demands.

Pattern of tooth contacts in eccentric mandibular positions in young adults

Tooth contact patterns in laterotrusion, protrusion of the mandible, and in the retruded position were recorded in young men with varying types of occlusion. The tooth contacts were recorded clinically with alginate (irreversible hydrocolloid) indices. In addition, the functional state of the masticatory system was evaluated by the recording of signs and symptoms of mandibular dysfunction and of the abrasion of the teeth. On protrusion, most subjects had contacts only on anterior teeth. Protrusive contacts only on posterior teeth were rare. On laterotrusion, most subjects had group function on the functional side. Contact on the nonfunctional side was found in half of the subjects in a 1.5 mm laterotrusive position and in one third of them in a 3 mm laterotrusive position. No correlation between the types of tooth contacts and mandibular dysfunction was found.