Influence of matrix type on surface roughness of three resins for provisional crowns and fixed partial dentures.

PURPOSE: This study evaluated the effect of matrix type on the surface roughness of resins for provisional crowns and fixed partial dentures. MATERIALS AND METHODS: Ninety specimens of two acrylic resins (Trim II, Tab2000) and one bis-acryl composite (Protemp II Garant) were fabricated using one of three matrices: irreversible hydrocolloid (Cavex CA37), poly(vinyl siloxane) (Aquasil) or vacuum-formed matrix (Bio-flow Hard). The sample size for each resin-matrix combination was 10. The vestibular face of one natural maxillary central incisor was used as a model to fabricate all the specimens, following the custom fabrication technique. The average roughness measurements, Ra (mum), were obtained using a profilometer, and the data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests. The results were contrasted against the surface roughness of the tooth using a one-sample t-test. RESULTS: Aquasil and vacuum-formed matrix had a smoother surface than Cavex CA37 regardless of the resin tested (p < 0.05). Protemp II Garant had the smoothest surface regardless of the matrix used, with no significant differences when polymerized against the three different matrices. Trim II polymerized against Cavex CA37 had a rougher (p < 0.05) surface than Aquasil or vacuum-formed matrix. Tab2000 had the smoothest surface (p < 0.05) when polymerized against a vacuum-formed matrix. CONCLUSIONS: There is no universal matrix that produces the smoothest surface: this depends on the compatibility between the resin and the matrix. Protemp II Garant polymerized against Cavex CA37 matrix yields a surface that is smooth enough not to require polishing unless this surface is adjusted.

Influence of static and dynamic occlusal characteristics and muscle force on masticatory performance in dentate adults.

Masticatory performance is the outcome of a complex interplay of several factors. This study was carried out to determine the relationship between masticatory performance and several muscular-related and occlusion-related factors in a population with a full or near-full complement of natural teeth. One-hundred dentate young adults participated in this cross-sectional study. Maximum muscular force with jaw, hand, tongue, and cheek were measured by means of a gnatodynamometer. Occlusal contact area and number of teeth in contact were determined in the maximal intercuspal position and in a 1.5-mm right and left lateral excursion by means of interocclusal registrations that were scanned and analysed using image software. Masticatory performance was determined by sieving the Optosil particles resulting from 20 chewing cycles. Stepwise multiple linear regression analysis showed that the maximum bite force in the region of the first molar had the best correlation with masticatory performance and explained 36% of its variation. Static occlusion characteristics such as occlusal contact area, the lack of lateral crossbite and the number of anterior teeth in contact explained an additional 9% of the variation in masticatory performance. These findings suggest that variables related to dynamic occlusion or tongue or cheek force do not enhance the prediction of masticatory performance.

Relationship between chewing side preference and handedness and lateral asymmetry of peripheral factors.

OBJECTIVE: To determine whether chewing side preference is related to handedness and lateral asymmetry of occlusal characteristics, muscular force and temporomandibular disorders (TMD) in a dentate population. DESIGN: One hundred and seventeen dentate adults participated in this cross-sectional study. Static and dynamic occlusal characteristics were determined at the maximal intercuspal position and at the lateral excursions by scanning interocclusal records and analysing them using image software. Unilateral maximum bite force and finger-thumb grip force were measured by means of a gnathodynamometer. TMD were assessed according to the Research Diagnostic Criteria for TMD. Chewing side preference and masticatory laterality were determined by observing the jaw's movement while each subject chewed silicone. Asymmetry or side difference of the variables was calculated. Correlation between side difference variables and masticatory laterality was studied using Spearman correlation coefficient. RESULTS: Fifty-nine subjects chewed on the right, 15 on the left and 43 chewed on both sides. There was no relationship between preferred chewing side and handedness, lateral asymmetry of TMD or side difference in finger-thumb grip force. Significant and positive correlations were observed between masticatory laterality and side differences in bite force and side differences in occlusal contact area at intercuspal position (P<0.01). CONCLUSIONS: Chewing side preference in a dentate population is related to lateral asymmetry of bite force and asymmetry of occlusal contact area at the intercuspal position but not to handedness.