Masticatory performance, maximum occlusal force, and occlusal contact area in patients with bilaterally missing molars and distal extension removable partial dentures.

PURPOSE: The aim of this study was to compare the masticatory performance, maximum occlusal force, and occlusal contact area of subjects with bilaterally missing molars, treated either with the shortened dental arch (SDA) concept or with distal extension removable partial dentures (RPDs), during a 1-year follow-up. MATERIALS AND METHODS: This study included three groups of 10 subjects each, in which SDA and RPD groups displayed bilateral molar loss in the mandible. Subjects with complete natural dentition (CD) served as the control group. Masticatory performance was evaluated by the multiple sieve method. Standard cubes (edge length: 8 mm, 0.9 g) shaped from a high viscosity polysiloxane molding material (Zetaplus, Zhermack) were used as the test food. Maximum occlusal force (N) and occlusal contact area (mm2) were evaluated using dental prescale films. RESULTS: No statistically significant differences regarding masticatory performance between the groups or evaluation periods were demonstrated. In the RPD group, masticatory performance with and without prostheses showed no significant differences. SDA patients showed significantly lower contact area and occlusal force than both the CD and RPD groups (P < .05). CONCLUSION: SDA can be an alternative to distal extension RPDs with respect to masticatory performance in subjects with bilaterally missing molars in one dental arch, despite remarkable reductions in maximum occlusal force and occlusal contact area.

The effect of occlusal contacts on adjacent tooth.

PURPOSE: The purpose of this study was to clarify the influence of changes of occlusal contacts on adjacent tooth displacement during articulation. MATERIALS AND METHODS: The amount and direction of displacement of the maxillary left first molar and adjacent teeth were measured using a displacement transducer, Type M-3. Seven subjects were included in this study. On the maxillary left first molar, 8 experimental occlusal contact points were established using platinum foil and these were divided into 2 groups, the buccal and lingual groups, which corresponded to the buccal and lingual cusps, respectively. RESULTS: During clenching, the buccal group showed differences in the direction of the tooth displacement paths among the 3 teeth (second premolar, first and second molar), but there was no difference in the lingual group and the direction of displacement of these 3 teeth was similar to the natural teeth. CONCLUSION: It is necessary to make at least one lingual occlusal contact point to obtain displacement of not only the abutment tooth but also the adjacent teeth.

Rehabilitation of occlusal support by removable partial dentures with free-end saddles.

This study aimed to assess the level of restored occlusal support by removable partial dentures with free-end saddles. The maximal clenching force of 61 subjects was measured using pressure sensitive film with and without their dentures. The restored level of occlusal support was estimated from the shift of the occlusal load centre. In comparison with previous results of experimental occlusions using splints for eight normal dentate subjects, the restored level using dentures ranged from 40-60% of that of natural teeth. The analysis of the shift of the occlusal load centre could reasonably evaluate the prostheses from the standpoint of occlusal support.

A new approach to evaluating occlusal support by analyzing the center of the bite force.

The aim of this study was to create a standard for occlusal support in the diagnosis and evaluation of prosthetic treatment. In experimental occlusion, the maximal bite force of eight normal dentates was measured by pressure-sensitive film over the whole dentition using splints divided into nine pieces. The occlusal contact was altered by exchanging splint pieces according to the shortened dental arch concept. The occlusal load center (OLC) was located on a graph set up with reference to the size of the individual dental arch. The occlusal supporting index (SI) and the rehabilitation index (RI) were calculated from the locations of the OLC corresponding to each occlusal contact. Differences in numbers and distribution of occlusal stops could clearly be distinguished by the location of the OLC. Though the SI showed a strong positive correlation with maximal bite force, it is proposed that the number of occlusal stops, or occlusal units, provides the most effective index for quantitative parameters of occlusal support in clinical use. From the standpoint of bite force, analysis of the RI is suggested as a useful method of objectively evaluating the recovery of occlusal support with prosthetic treatment.