Nonlinear visco-elastic finite element analysis of porcelain veneers: a submodelling approach to strain and stress distributions in adhesive and resin cement.

PURPOSE: To assess under load the biomechanical behavior of the cementing system of feldspathic vs alumina porcelain veneers. MATERIALS AND METHODS: A 3D model of a maxillary central incisor, the periodontal ligament (PDL) and the alveolar bone was generated. Incisors restored with alumina and feldspathic porcelain veneers were compared to a natural sound tooth. Enamel, cementum, cancellous and cortical bone were considered isotropic elastic materials; conversely, dentin was designated as orthotropic. The nonlinear visco-elatic behavior of the PDL was considered. The adhesive layers were modelled using spring elements. A 50-N load at a 60-degree angle to the tooth's longitudinal axis was applied and validated. Stress concentration in the interfacial volumes of the main models was identified and submodelled in a new environment. RESULTS: Regarding tooth structure, strain concentrations were observed in the root dentin below the CEJ. As to the cement layer, tensile stresses concentrated in the palatal margin of the adhesive complex. CONCLUSION: Despite the effects on tooth deformation, the rigidity of the veneer did not affect the stress distributions in the cement layer or in the adhesive layers. In both cases, the palatal and cervical margins seemed to be the most stressed areas.

The effects of dietary naringenin supplementation on physiological changes in molar crestal alveolar bone-cemento-enamel junction distance in young rats.

The objective of this study was to evaluate the influence of dietary naringenin (NAR) supplementation on physiological molar crestal alveolar bone (CAB)-cemento-enamel junction (CEJ) distances in young male albino rats. The effects of diets supplemented with 0.09%, 0.18%, 0.36%, and 0.72% NAR, at the expense of dextrose, were tested on 40 young rats, divided equally into five groups, for a period of 42 days. Rat skulls were defleshed, and CAB-CEJ distance was scored according to the modified method of Keyes and Gold. Data were analyzed using one-way analysis of variance, post hoc Tukey's test, and Spearman's (R(2)) correlation. P < .05 was used to reject the null hypothesis. NAR showed a statistically significant inverse dose-dependent relationship on CAB-lingual alveolar bone distance (P < .05). In all cases lingual CAB-CEJ distance was larger than buccal CAB-CEJ distance. Thus dietary NAR supplementation was shown to significantly reduce molar CAB-CEJ distance (P < .001-.05) during alveolar development in young male rats.

The effects of dietary bioflavonoid (rutin, quercetin, and naringin) supplementation on physiological changes in molar crestal alveolar bone-cemento-enamel junction distance in young rats.

The objective of this study was to evaluate the influence of dietary bioflavonoid (rutin [R], quercetin [Q], and naringin [N]) supplementation on physiological molar crestal alveolar bone(CAB)-cemento-enamel junction (CEJ) distances in young male albino rats. The effects of diets supplemented with 0.57% R, Q, or N, at the expense of dextrose, were tested on 40 young rats, divided into four groups, for a period of 42 days. Rat skulls were defleshed, and CAB-CEJ distance was scored according to the modified method of Keyes and Gold (Oral Surg Oral Med Oral Pathol 1955;8:492). Data were analyzed using one-way analysis of variance, post hoc Tukey's test, and Spearman's (R(2)) correlation. P <.05 was used to reject the null hypothesis. The N group demonstrated the lowest CAB-CEJ distance, followed by the R and Q groups (P <.001-.05), except in the mandibular lingual region, where the Q group had a lower CAB-CEJ distance than the N and R groups (P <.05). The control group showed the largest CAB-CEJ distances. Dietary bioflavonoid supplementation was shown to significantly reduce molar CAB-CEJ distance (P <.001-.05) during alveolar development in male young rats.