Intercuspal contacts of the natural dentition in centric occlusion

Comparison of occlusal contact areas of class I and class II molar relationships at finishing using three-dimensional digital models

Objective

This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing.

Methods

Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models.

Results

Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078).

Conclusions

In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.

Effect of prosthodontic planning on intercuspal occlusal contacts: comparison of digital and conventional planning

BACKGROUND

Adequate occlusal contacts are critical for masticatory function. The aim of this study is to evaluate the intercuspal occlusal contacts following conventional and digital wax-ups.

METHODS

Stone casts of 15 patients undergoing prosthodontic treatment were gathered. Each cast was duplicated twice, so that conventional and digital wax-ups could be performed. To assess the occlusion, the following variables were evaluated: contact number per tooth (CNT), contact area per tooth (CAT) and contact accuracy. Further, the impact of tooth location in the arch was assessed.

RESULTS

The CNT and CAT after the wax-ups increased significantly following each wax-up, and this increase was more prominent for the posterior teeth than the anterior teeth. The conventional wax-up was associated with lower CNT than the digital wax-up, especially for the posterior teeth. On the other hand, the CAT was greater for the conventional wax-up than the digital wax-up for the anterior and posterior teeth. In terms of accuracy, the two wax-ups showed greater discrepancies than the pre-treatment casts, however, the magnitude of discrepancy was greater for the digital wax-up.

CONCLUSIONS

The two wax-ups improved the contact number and area. Despite the statistical variation between the wax-ups, the actual difference was minimal. Therefore, it could be speculated that the two wax-ups produced a similar outcome.

Tooth positioners and their effects on treatment outcome

Malocclusion can also be corrected by means of clear removable appliances called as "tooth positioners" or "aligners". A tooth positioner is used to control settling and to minimize or eliminate relapse of the teeth after an orthodontic treatment. In this article, a complete review of the objectives, course of treatment, fabrication, and the materials used for fabrication of tooth positioners along with their importance and disadvantages were discussed. Tooth positioners did improve the overall orthodontic treatment outcome as quantified by the ABO (American Board of orthodontics) objective scoring method. But once the initial occlusal contact was achieved, the vertical movement of teeth was found to be inhibited.

History of materials used for recording static and dynamic occlusal contact marks: a literature review

In the discipline of prosthetic dentistry it is important not only to examine the occlusion, but to be able to record, store, and transfer the information. Over the years many occlusion testing materials have been used. It has been suggested the clinical recording and transfer of information using waxes and other occlusion recording materials have disadvantages relating to inaccuracy and problems of manipulation. Therefore, there has been introduction of many new systems for recording occlusion contacts to overcome such problems. The correct physiological recovery of occlusion posses as much a challenge as ever for every dentist and technician. Even the smallest high spots measuring just a few microns can cause dysfunctions like temporo-mandibular pain. Occlusal proportions are being constantly changed with every procedure. Therefore, an understanding of the synergy of the teeth in static and dynamic occlusion forms the basis of good dentistry. The purpose of this review article is to give and overview of the various materials and methods that have been used to record occlusal contact marks. Key words:Occlusal contact marks, Occlusion indicators, Occlusion test materials, Occlusion recording materials.

A positional analyzer for measuring centric slide

Centric relation (CR) has been considered mainly as a position posterior to habitual occlusion or maximum intercuspation (MI). Awareness of the tooth contacts relationship in centric relation position of the mandible and diagnosing the case from this position is essential to consistently select treatment plans that will allow to treat to or very near to centric relation occlusion. Centric slide and other occlusal relationships are conceived of as positions, which can be studied in three dimensions. Clinically, the difference between the two occlusal positions namely CR and MI (centric slide) can easily be determined, but for a more precise evaluation of its length and directions, an occlusal analysis on articulator mounted casts is necessary. Study was under taken on the mounted casts of ten subjects on a semi adjustable articulator to which a stylus and recording table was devised and attached for measurement of CR-MI slide in the three planes namely anterior-posterior, medio-lateral and superior-inferior. It was found that there was a displacement from CR to MI (centric slide) in all the three planes and numerically the mean slide was 0.688 ± 0.623, 0.261 ± 0.627 and 0.127 ± 0.541 mm in the antero-posterior, medio- lateral and superior-inferior directions respectively. The stylus and table attachment may be an accurate indirect method to measure positional changes of the condyle in 3D.

The relationship between bite force and oral sensation during biting in molars

BACKGROUND

In prosthodontic treatment, the occlusal form should be designed such that bite force is applied at the position that has higher load-bearing capacity and is comfortable for the patient. The purpose of this study was to clarify the differences in bite force and occlusal sensation with different loading positions on the occlusal surface.

METHODS

Twelve healthy subjects were recruited for this study. Bite force and occlusal sensation were measured at five loading points on the upper and lower left first molars. Occlusal sensation was evaluated using a Visual Analogue Scale (VAS).

RESULTS

Bite forces on the lingual side of the upper first molar and the buccal side of the lower first molar were significantly higher and VAS scores were significantly lower, i.e. the subjects felt less discomfort during biting on the buccal side of the upper first molar and the lingual side of the lower first molar compared to the other side of each molar.

CONCLUSIONS

Loading on the occlusal surfaces of the functional cusps of the upper and lower first molars produces more load-bearing capacity and is more comfortable than loading on the non-functional cusps.

Occlusal Contact Changes with Removable and Bonded Retainers in a 1-Year Retention Period

Objective: To test the hypothesis that there is no difference in the number of occlusal contacts in centric occlusion in patients treated with bonded and removable retention procedures and a control group during a 1-year retention period.

Materials and Methods: Twenty-five patients received a removable Hawley retainer, and 25 patients received maxillary and mandibular bonded retainers. The retainer patients were compared with 20 control subjects with normal occlusions. Silicone-based impression bites were used to record occlusal contacts. Paired-sample t-test, analysis of variance (ANOVA), and Tukey tests were used to evaluate intragroup and intergroup differences.

Results: An increased number of occlusal contacts were recorded in total-arch and posterior combined (actual/near) teeth during the retention period as compared with the control group. In the Hawley group, actual and total contacts on the first and second molar and actual contacts on the premolar and canine showed statistically significant increases. In the bonded retainer group, near and total contacts on the first and second molars and premolars showed statistically significant increases. Slight occlusal changes were seen in the control sample during the observation period, presumably from growth and development. ANOVA comparisons of total contacts of anterior and posterior teeth indicated statistically significant differences in the three groups on posterior segments.

Conclusions: The hypothesis is rejected. Both retention procedures allowed relative vertical movement of the posterior teeth, but the number of contacts on the posterior segment was increased more in the bonded retainer group than in the Hawley and control groups at the end of retention.

Tooth Positioner Effects on Occlusal Contacts and Treatment Outcomes

Objective: To determine if an increase in tooth contacts is the principal effect of tooth positioner wear.

Materials and Methods: Patient charts from a consecutive series were reviewed until a sample of 100 cases that used a tooth positioner was obtained. One hundred control cases were randomly selected from patients treated at the same period. Malocclusion severity and finished occlusion were assessed with the American Board of Orthodontics (ABO) Discrepancy Index (DI) and Objective Grading System (OGS) score, respectively. Finish casts for each patient were mounted on a Galleti articulator. Occlusal registrations were obtained with silicone-based impression material from casts fabricated from impressions taken at the time of fixed appliance removal (control) or at the end of the tooth positioner treatment (experimental). The number of the perforations and transparent areas on the occlusal registrations were quantified.

Results: There was no significant difference (P = .20) in the number of total occlusal contacts between the two groups. However, the OGS score of the tooth positioner group (16.7) was significantly (P = .0009) better than for the control group (19.9).

Conclusions: Tooth positioners were effective in improving the occlusal finish, but the effects were independent of an increase in occlusal contacts. Positioners primarily improved first order alignment by tipping teeth into an improved intercuspation.

The lateral leeway in the habitual intercuspation: experimental studies and literature review

The habitual intercuspation is used ubiquitous for manufacturing small dental restorations. However, a little is known on its precision. The aim of the present study was therefore to investigate the unambiguity and accuracy of the habitual occlusion in mounted plaster casts from fully dentate persons. Eighty-one fully dentate volunteers, 36 women and 45 men aged 26.8 +/- 6.2 years (18-55 years), with minor fillings and no signs or symptoms of TMD took part in the experiments. Silicone impressions were taken, poured with stone plaster and the obtained casts mounted into Dentatus ARL(R)- articulators using an individual face bow transfer. Subsequently, the models were transferred to a custom-made measuring articulator where the lateral leeway and the accuracy of the hand-held habitual intercuspation were quantified in the condylar area. Measurements were repeated seven times with the upper cast pushed either to the maximum right or the maximum left intercuspation. The hand-held habitual intercuspation of upper and lower cast proved ambiguous in 57% of pairs of casts. The average lateral leeway of the habitual intercuspation in the condylar area was 0.10 +/- 0.05 mm (0-0.51 mm; median 0.07 mm) between the maximum right and left occlusal positions. The average accuracy of three repeated measurements was 0.22 +/- 0.09 mm (0.02-1.17 mm; median 0.16 mm). Natural occlusal surfaces in a full dentition do not guarantee an unambiguous habitual intercuspation of the plaster casts. The described leeway and technical limits might be possible causes for occlusal adjustments that are sometimes necessary when inserting restorations manufactured in habitual intercuspation.

Occlusal contacts with different retention procedures in 1-year follow-up period

INTRODUCTION

The aim of this follow-up study was to evaluate the number of contacts in centric occlusion during a 1-year retention period in patients treated with 2 retention procedures and in a control sample.

METHODS

Twenty patients received modified wraparound Hawley retainers, and 20 received maxillary Jensen plates with mandibular fixed retainers. These retention patients were compared with a control group of 20 subjects with normal occlusions. Silicone-based impression bites were used to record occlusal contacts. Paired and independent-sample t tests were used to evaluate intragroup and intergroup differences.

RESULTS

Contacts increased in the total arch and the posterior combined (actual/near) during the retention period compared with the control group. In the Hawley retainer group, actual contacts on the second molars (P <.05), near contacts on the premolars (P <.05), and total contacts on the first molars (P <.05) and premolars (P <.01) had statistically significant increases. In the maxillary Jensen plate and mandibular fixed lingual retainer group, the number of actual contacts on the posterior segment increased. Actual contacts on the first molars (P <.01), second molars (P <.01), premolars (P <.05), and canines (P <.05), and total contacts on the first (P <.05) and second (P <.05) molars had statistically significant increases. During the observation period, some slight occlusal changes were seen in the control sample, presumably from growth and development. At the end of the study, during the 1-year follow-up period, no statistically significant occlusal contact differences were observed in the 3 groups.

CONCLUSIONS

Retention procedures carried out in this study allowed relative vertical movement of the posterior teeth.

Reliability of recording static and dynamic occlusal contact marks using transparent acetate sheet

STATEMENT OF PROBLEM

Inaccuracy in the transfer of information between clinician and technician regarding occlusal contacts can cause problems when fabricating indirect restorations, which can result in frustration for the dentist, technician, and patient. Few studies have considered the reproducibility of recording marked occlusal contacts.

PURPOSE

This study aimed to test the reproducibility of a quick and simple means of recording marked occlusal contacts.

MATERIAL AND METHODS

The static and dynamic occlusal contacts of 29 subjects, with no missing functional units, were marked using articulating paper. Three clinicians with varying clinical experience (3-10 years after graduation from dental school) were asked to independently record the marked occlusal contacts using a transparent acetate sheet. The results were analyzed for Kappa agreement.

RESULTS

For the static occlusion, Kappa values of agreement between pairs of examiners were 0.88, 0.86, and 0.85, respectively, all indicating "almost perfect agreement." For the dynamic occlusion, the range of Kappa agreement between pairs of examiners produced a median of 0.91, 0.88, and 0.85, respectively, indicating almost perfect strength of agreement.

CONCLUSIONS

The results suggest that marking occlusal contacts on a transparent acetate sheet provides a simple means of recording static and dynamic occlusal contacts with a high degree of reproducibility.

Unilateral temporomandibular disorder and asymmetry of occlusal contacts

STATEMENT OF PROBLEM

The relationship between temporomandibular disorders and occlusal tooth contacts is unclear and controversial.

PURPOSE

This study assessed whether unilateral temporomandibular disorders were associated with the absence of bilateral symmetry in the number of occlusal contacts.

MATERIAL AND METHODS

Fifteen university dental students who had complete natural dentition and normal occlusion and exhibited unilateral signs and symptoms of temporomandibular disorders were compared to 15 age- and sex-matched healthy control subjects. All participants met specific inclusion and exclusion criteria. Occlusal contacts were recorded in the intercuspal position with wax registrations. Dental impressions were made and poured in type I stone. Contacts were classified according to location and intensity. Four experienced dentists using an established protocol made all measurements. Assessment of the reliability of the occlusal registration procedure showed a small (<4%) within-subject variability. Statistical analysis was based on the binomial distribution and nonparametric tests (P < .05).

RESULTS

Subjects with unilateral temporomandibular disorders had greater bilateral difference in the number of contacts than controls. The median (95% confidence interval) difference was 3 (2 to 4) and 2 (1 to 2), respectively. In unilateral temporomandibular disorder subjects, the number of occlusal contacts was greater on the side with, rather than without, disorder (median number 20 vs. 16). The median (95% confidence interval) difference between sides with and without unilateral temporomandibular disorders was 3 (2 to 4) for all contacts and 2 (1 to 3) for contacts on the posterior teeth.

CONCLUSION

Within the population of this study, a weak association was found between unilateral temporomandibular disorders and asymmetry in the number of occlusal contacts.

Inter- and intra-operator reliability of the recording of occlusal contacts using 'occlusal sketch' acetate technique

OBJECTIVES

To develop a simple way of recording occlusal contacts with proven inter- and intra-operator reliability.

SETTING

Clinical skills laboratory in the University Dental Hospital of Manchester.

MATERIALS AND METHODS

The marked static occlusal contacts of 20 sets of models were recorded in a pseudo-clinical situation, by three dentists and in addition by one dentist on two occasions using a schematic representation of the dental arch - the 'occlusal sketch'.

RESULTS

The median of Kappa agreement for inter- and intra-operator reliability was almost perfect.

CONCLUSIONS

The occlusal sketch is a simple, inexpensive and easy way of recording the results of an occlusal examination using marking papers.

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.

Digital imaging of occlusal contacts in the intercuspal position

PURPOSE

The purpose of this study was to develop an approach to the measurement of occlusal contact area and location using digitized video images of occlusal records.

MATERIALS AND METHODS

Five occlusal records in the intercuspal position were made using a polyvinylsiloxane material on five subjects with intact, natural dentition. In regions of occlusal contact, the material showed a minimal film thickness without perforation. A dental cast of the mandibular arch was video digitized and followed by digitization of each of the five occlusal records in place on the cast. An impression of a calibration stepwedge was video digitized to provide the relationship between impression material thickness and pixel density.

RESULTS

Contact surface areas ranged from 0.02 to 3.16 mm2 between subjects. The contact positions on a single tooth determined in five records from a single individual showed coefficients of variation between 7.4% to 36.1%. Large variations in contact size were found in this group of five records from a single individual (coefficient of variation ranged from 10.8% to 156.7%). The large difference in contact size between records may be due to variations in biting force at the time the records were made. When the cast position was changed and records redigitized, the mean area of the contact was not significantly different (P > .20) from measurements at the original position.

CONCLUSIONS

For the small sample evaluated, a large variation in occlusal contact size was found in the five records. The occlusal contact location was consistent in the five records. The measurement method developed seems to provide reliable measures of occlusal contact surface area and location.

Reliability of the evaluation of occlusal contacts in the intercuspal position

Reliability of clinical measurement is essential to any clinical discipline. This investigation assessed intraexaminer and interexaminer reliability achieved in identifying contacting teeth in the intercuspal position. Shim stock and an articulating film were compared in the evaluation of occlusal contacts of 337 antagonist occlusal pairs in 24 young adults by two examiners. Results were compared by use of a simple proportion of agreement and, when possible, the Kappa statistical test that corrects for chance agreement. Shim stock displayed better reliability than articulating film and appeared suitable for clinical measurement of occlusal contacts in intercuspal position.

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.

Occlusal contact changes after the active phase of orthodontic treatment

Occlusal contacts in maximum intercuspidation were recorded at the end of active orthodontic treatment and 3 months into the retention period. Hawley retainer, tooth positioner, and nontreated normal occlusion groups of 10 subjects were examined for change in the number and location of occlusal contacts. Soft silicone-base impression materials were used to make interocclusal registrations. The contacts were then transferred onto the study models, and standard photographs of each model were taken. To determine any locational changes, superimposition of the first registration photograph on the second one was done. Significant difference in the number of total contacts between the treated groups and the control sample was recorded at both time periods. Use of a tooth positioner as a retainer did not show any additional gain of contacts in the positioner group when compared with the Hawley retainer group. No significant change in the location of contacts occurred during the period of observation.

Computerized occlusal analysis: an evaluation of the sensors

Dentists traditionally depend on their experiences to evaluate occlusion. A computerized system, that enables an objective analysis of dental occlusion has been developed and is currently available. A key component of the system is the disposable sensor. This research tested the sensors' validity and reliability in detection of known interceptive occlusal contact and discovered that the sensors were valid when used just twice.

Number and location of occlusal contacts in intercuspal position

Records of intercuspal position were made in 45 healthy young adults with morphologically normal occlusions. The observed perforations were analyzed according to the frequency of occlusal contacts. Most subjects had asymmetric distribution in number and location of occlusal contacts. Regardless of symmetry, a significantly higher number of subjects had approximately seven contacts on each side that were located between all posterior teeth. Contacts were most frequent between maxillary and mandibular first and second molars.

Unilateral, isometric bite force in 8-68-year-old women and men related to occlusal factors

Unilateral bite force was studied in 63 women and 59 men, 8-68 yr of age. The subjects had a minimum of 24 teeth and no symptoms or signs of disorders of the craniomandibular system. Bite force was stronger in men (522 N) than in women (441 N). It increased with age until 25 yr (P less than 0.0001). The level decreased significantly after this age in women, whereas it only tended to decrease in men and not until after 45 yr of age. Body height was positively associated with force. However, the strongest correlation (r: 0.43-0.49, P less than 0.01) with adult bite force was occlusal contact. The normal bite-force values with important determining factors provide reference data for screening of elevator muscle strength in routine examination of craniomandibular function.

The cantilever fixed partial denture: a 10-year follow-up

A 10-year study of patients with cantilever fixed partial dentures suggests that these prostheses can be used for both anterior and posterior replacements. Guidelines for cantilever prostheses are described. Fixed cantilever prostheses are favorable alternatives to certain types of unilateral removable partial dentures. Proper oral hygiene is essential.

Reproducibility of occlusal marking techniques

Our study was designed to (1) test clinically the reproducibility of the NPT by comparing two consecutive occlusal records and records made at 1-month intervals (2) test the reproducibility of a color-marking technique under the same conditions, and (3) compare the location of occlusal contacts as registered by these two techniques. Results showed that neither technique is highly reproducible. However, the NPT is more reproducible than the CMT. The advantages and disadvantages of the NPT and the CMT were described. It was suggested that more research should be conducted to improve the accuracy of occlusal record techniques.

Mandibular reference positions

An overview is presented of the mandibular reference positions of centric occlusion, centric relation and centric relation occlusion, and the position of rest. Clinical applications of the different positions are discussed on the basis of the physiology of the mandibular locomotor system.