Fracture strength and energy-dispersive spectroscopy analysis of 3-unit fixed partial dentures fabricated from different monolithic zirconia materials.

STATEMENT OF PROBLEM: Mastication forces in different regions affect the survival of multiunit posterior restorations. The fracture strength of 3-unit posterior monolithic zirconia fixed partial dentures (FPDs) and their fracture patterns require investigation. PURPOSE: The purpose of this in vitro study was to evaluate and compare the fracture strength and fracture pattern of 3-unit posterior FPDs fabricated from different monolithic zirconia materials. MATERIAL AND METHODS: Thirty 3-unit FPDs were fabricated from BruxZir, FireZr, and Upcera (n=10 per group). Energy-dispersive spectroscopy analysis was performed on 2 selected specimens from each group. All specimens were exposed to a mastication simulator for 1.2×106 cycles and then monotonically loaded to fracture at a crosshead speed of 1 mm/min. The surfaces of a selected fractured specimen were examined at magnifications of ×25 and ×500 with scanning electron microscopy. Conformity to normal distribution was evaluated with the Shapiro-Wilk test. One-way analysis of variance was used to compare the normally distributed initial crack formation load F initial (Fi) and catastrophic failure strength F maximum (Fm) means by group. Weibull statistics were calculated by using the maximum likelihood estimation method. The chi-square test was used to compare shape and scale parameters (α=.05). RESULTS: The mean Fm values were fail1878.9 N for Upcera, 2177.8 N for BruxZir, and 2229.4 N for FireZr. Upcera and BruxZir showed statistically significant differences for the Fm mean values (P=.039). The differences between the fracture type distributions according to the groups were statistically similar (P>.05). For Fi, Upcera presented the highest Weibull modulus value (2.199), FireZr had the lowest (1.594), while for Fm, BruxZir had the highest Weibull modulus value (9.267) and FireZr the lowest (6.572). CONCLUSIONS: Using the zirconia materials BruxZir, FireZr, and Upcera resulted in high Fm values after aging procedures. With all materials, the fractures were most commonly found in the connector areas in the tested FPDs.

Evaluation of the relationship between GOHAI, MNA and the dental hygiene of using denture wearers for older patients.

BACKGROUND: The use of removable dentures increase due to tooth loss that occurs with ageing. The relationship between age, use of removable dentures and nutrition is important. OBJECTIVE: To evaluate the effectiveness of the GOHAI, the MNA, and the dental hygiene of older patients using dental prostheses. METHODS: This was a cross-sectional study of people over 65 who used removable prostheses in at least one jaw (partial or complete denture) for a minimum of 6 months (n = 120). The data were collected using questionnaires of a qualified examiner and oral clinical tests with interviewers in person. The subjects' nutritional status was assessed by a Turkish version of the mini nutritional assessment (MNA). GOHAI questionnaire was used to evaluate those aspects considered to have an impact on the quality of life of the older population, such as functional limitation, aesthetic dissatisfaction, chewing discomfort, avoidance of particular food, out-of-social contacts and self-medication administered for dental pain. RESULTS: There was no statistically significant correlation between the GOHAI score and sociodemographic and intraoral data (p > .050). A negative correlation was found between age and MNA. A statistically significant difference was found between the MNA score's median values according to the participant's education level, type of prosthesis, and marital status (p < .050). Good was determined as the highest GOHAI category with 54%. CONCLUSION: There is a negative correlation between age and MNA. The risk of malnutrition increases with age. Since the oral condition also affects the patient's systemic condition, the team caring for geriatric patients must bring these people to the maximum level of life in a multidisciplinary manner.

Effect of mastication simulation on the phase transformation of posterior 3-unit monolithic zirconia fixed dental prostheses.

STATEMENT OF PROBLEM: Monolithic zirconia restorations are directly exposed to cyclic loads and temperature changes in the oral cavity after cementation. These stresses may reduce the long-term success of the material by causing uncontrolled phase transformations within the zirconia. PURPOSE: The purpose of this in vitro study was to evaluate the effect of mastication simulation and different measurement points on the phase transformation of posterior 3-unit monolithic zirconia partial fixed dental prostheses (FDPs) in the posterior region. MATERIAL AND METHODS: Posterior 3-unit FDPs of monolithic yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP), including BruxZir Shaded (group B), FireZr (group F), and Upcera (group U) (n=10), were machined from presintered blocks. All specimens were exposed to mastication simulation (240 000 cycles/1.7 Hz/50 N). The monoclinic phase content was evaluated by X-ray diffraction (XRD). Phase transformation was measured at the mesial connector (group M), distal connector (group D), and pontic regions (group P) before and after mastication simulation. The relative monoclinic phase amount (Xm) was calculated for all specimens. The data were analyzed by ANOVA and post hoc tests (α=.05). RESULTS: According to XRD analysis, Xm for all groups and regions showed higher results after aging than before aging (P<.05). Group B has the lowest Xm among the groups. Group B showed a statistically significant difference compared with both group F and group U (P<.05). There was no significant difference between group F and group U (P>.05). When the regions were evaluated regardless of brand and the groups were evaluated in terms of regions, no statistically significant difference was observed between connectors and the pontic region (P>.05). CONCLUSIONS: Mastication simulation causes an increase in the Xm. However, this increase was unlikely to be clinically significant. There may be differences in phase transformation depending on the contents of the brands and sintering procedures. Variations in the phase quantity were independent of the connector regions and pontic for FDPs.