Crowns and other extra-coronal restorations: Occlusal considerations and articulator selection (original) (raw)
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The arrangement of the interproximal interfaces in the human permanent dentition
Clinical Oral Investigations, 2013
The interproximal interface (IPI) is the interface between two adjacent teeth, i.e., the site where forces are transmitted along the dental arch. We investigated the IPI arrangement of the human permanent dentition. Specifically, the IPI morphometrical characteristics were studied and interpreted within a biomechanical framework. A novel in vivo IPI measurement was developed based on diversity in transillumination of Polyvinyl siloxane impression of the interproximal region. The study group included 30 subjects, aged 27, ±4.0 years. Eleven parameters were examined in each of the 26 IPIs of the permanent dentition. The IPI showed intra-arch similarity and interarch diversity between the tooth groups. The IPI shape was predominantly oval (60-100%), yet kidney-shaped in some molars (22-40%). From incisors to molars: the IPI increased significantly (p < 0.001) in size (1.72 to 6.05 mm(2)), occupied more of the proximal wall (7.8-12%), changed its orientation from vertical to horizontal (88.66-14.80°), and was mainly located in the buccal-occlusal quadrant of the proximal wall, chiefly in the molar teeth. The IPI is a product of proximal wall attrition and is dictated by the mastication forces, number of cusps, and crown inclination. IPI arrangement counteracts the adverse crowding effect of the anterior component of the mastication forces. The IPI characteristics found in the present study provide guidelines for crown and proximal filling restorations to meet dental physiology requirements. Further, IPI determines correct tooth alignment and proximal wall stripping applied to resolve arch length deficiency.
International Journal of Biomedicine
The aim of the study was to determine maximum bite force (MBF) and the percentage of bite force distribution at the position of maximum intercuspation for patients with fixed restorations. Methods and Results: This study enrolled 60 subjects [33(55%) female and 27(45%) male] divided into two groups: The control group (CG) included 30 patients with intact teeth; the experimental group (EG) included 30 patients with fixed restorations. In EG, occlusion was analyzed before and after fixed restoration insertion (FRI). We used the T-Scan III Computerized Occlusal Analysis System 7.0 (Tekscan Inc., South Boston, MA, USA) for analysis. The present study showed a significant difference in MBF between CG and EG before and after FRI (P<0.05). In the present study, there were no statistically significant differences in force distribution in the right and left half of the string between groups (P>0.05). Conclusion: Occlusal analysis with T-Scan III is the only method that enables us to es...
Occlusal contacts in maximum intercuspation in normal dentitions
Journal of Oral Rehabilitation, 2008
A cross-sectional study of the contacts in maximum intercuspation was undertaken using a method to identify occlusal contacts, which is indicated as satisfactory by modern research. The aims were to describe in subjects with normal dentitions and normally functioning masticatory systems: (a) the general distribution of contacts; (b) the numbers in the various classes and types of occlusal contacts; (c) the numbers of teeth without contact. A randomized sample of 18 women and 20 men was used. Classical theoretical proposals for the numbers, distribution and nature of occlusal contacts were not supported. Wide variability was evident and asymmetry of distribution on the right and left sides of individual subjects was common. Contacts with stabilizing tendencies involved the mandibular supporting cusps in 79% of occurrences. Overall, the difference in the number of contacts with stabilizing effects was not significantly different from the number with unstabilizing tendencies. Contacts with mechanically unstabilizing effects did not produce clinically discernible, unfavourable sequelae in the dentitions. Because of the sparse number of stabilizing contacts, interventions involving the occlusal surfaces should maintain or improve on the number of such contacts in maximum intercuspation.
Digital analysis of the occlusal contacts can be performed with the T-scan device (T Scan III, TekScan, Boston, USA). However, the thickness of the interocclusal T-scan sheet (100 μm) may lead to a displacement of the mandible. Thus, the aim of this study was to investigate the impact of the T-scan sheet on the position of the mandibular condyles in maximum intercuspidation. Twenty dentate subjects with healthy jaw function were enrolled in the study. An ultrasonic axiography device was used to measure the position of the condyles. Ten 3D condyle positions in maximum intercuspidation of the teeth were recorded: first the reference position without the sheet, then 3 times without the sheet, 3 times with the sheet, and finally again 3 times without the sheet. There was a statistically significant difference (Wilcoxon matched pairs test) between the condyle positions with and without the interocclusally positioned T-scan sheet (P < 0.0005). The T-scan device lead to a displacement of the condyles of about 1 mm mainly in ventral direction (P = 0.005). Thus, occlusal analysis is not performed in physiological, maximum intercuspidation. This has to be considered when interpreting the measured contact points.
The Role of Intercondylar Distance in the Posterior Teeth Arrangement
The objective of this study was to determine the relationship of intercondylar distance with maxillary intermolar distance. It was cross-sectional comparative study and was conducted at the Department of Prosthodontics, Lahore Medical and Dental College, Lahore from June 2011 to November 2011. A total of 250 dentate subjects were selected according to the inclusion criteria. The impression of the maxillary arch was obtained using alginate. The vernier caliper was used to measure the distance between the mesiobuccal cusp tips of maxillary first molars. With the help of an arbitrary facebow the intercondylar distance was recorded. The distance obtained between the two condylar rods was measured in millimeters with the vernier caliper. Every distance was measured three times to ensure the accuracy and the mean was taken. The data were recorded on the proforma for the statistical analysis. Pearson correlation coefficients (r) for the intercondylar distance and maxillary intermolar showe...
Acta Facultatis Medicae Naissensis
S U M MA R Y Among many factors influencing human beauty, the correct position of the upper front teeth, including central incisors, is undoubtedly of particular importance. When determining the intermaxillary relationship, an important phase is determination of the medial line of a person's face or places of contact of the upper central incisors. The aim of this study was to test the hypothesis that the place of mutual contact of the upper central incisors in most cases coincided with the central groove of the lower lip. Examination included two groups of respondents. The first group consisted of 100 female and the second of 100 male respondents, with age range from 18 to 30 years. A starting point in measuring was the central groove of the lower lip. Measuring the horizontal distance of the central groove of the lower lip and the mutual contact of the upper central incisors was performed with a slight touch of the upper teeth with the lower lip. The measurement was performed using a digital vernier SH, with the resolution of 0.01 mm. After performing statistical analysis, the results showed that in a large percentage of cases, the central groove of the lower lip coincided with the point of mutual contact of the upper central incisors. The point of contact of the upper incisors can be determined simply by transferring the position of the groove to the upper interocclusal rim,with a slight contact between the lips and interocclusal rim.
Is Centric Relation and Centric Occlusion Discrepancy an Enigma? An Orthodontic Perspective
JOURNAL OF CLINICAL AND DIAGNOSTIC RESEARCH
Centric Relation (CR) and Centric Occlusion (CO) are commonly used references in clinical dentistry. CR represents bone-tobone contact independent of teeth contact, while CO refers to occlusal contact between the maxillary and mandibular teeth. The coincidence or discrepancy between CR and CO has been the subject of many challenging debates. These reference positions of the mandible typically do not align in natural dentition. When a discrepancy exists, the mandible slides from CR to CO to stabilise the occlusion. Such functional interferences can result in occlusal wear, excessive tooth mobility, poor periodontal health, temporomandibular joint dysfunction, and myofascial pain. Orthodontists who follow gnathologic occlusion recommend using study models mounted on articulators in the CR position to coincide with the treatment of CR-ICP (Maximal Intercuspal Position - ICP). Generally, a discrepancy of 1.5 mm in the vertical and horizontal planes and 0.5 mm in the transverse plane is ...
Introduction: Occlusal plane is the average plane established by incisal and occlusal surfaces of teeth. Various anatomic landmarks are used to determine this missing component of occlusion which is lost with the loss of teeth. However, variation has been observed in the orientation of occlusal plane determined clinically with different anatomical landmarks as references. Objective: This study was undertaken to determine the relation of intraoral anatomic soft tissue landmarks, namely, retromolar pad and parotid papilla with occlusal plane in natural dentition. Materials and Methods: Irreversible hydrocolloid impressions of 100 edentulous individuals (50 males and 50 females) were made to get the models. A 16 gauge wire was extended from mandibular occlusion plane posteriorly up to retromolar pad to establish their relationship. Furthermore, vertical distance of apex of parotid papilla to maxillary molar cusp tip it opposed (distobuccal cusp of maxillary first molar or mesiobuccal cusp of maxillary second molar), and mandibular molar cusp tip (to which parotid papilla apposed) was measured when the teeth were in maximal intercuspal position. Results: This study determined that the natural occlusal plane is oriented posteriorly at the level corresponding with the lower third of retromolar pad. Mean distance of parotid papilla above the corresponding maxillary cusp tip (while in occlusion) was 5.048 mm, and mean distance of Parotid papilla above the corresponding mandibular molar cusp tip (while in occlusion) was determined to be 3.602 mm. The difference in observed means between males and females or between right and left side was not statistically significant.