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Fit of titanium and a base metal alloy metal-ceramic crown.

STATEMENT OF PROBLEM Titanium has been widely used in dental implantology. However, problems remain for use of titanium in prosthodontics. PURPOSE This study evaluated the marginal and inner fit of metal-ceramic restorations and frameworks made with a nickel-chromium alloy (Remanium CS) and a commercially pure titanium (Rematitan). Fit was compared with SEM before and after firing of ceramic materials. MATERIAL AND METHODS Sixteen metal frameworks were cast with each casting material, 8 frameworks were used directly to evaluate measurements for fit (RCS: Remanium CS frameworks and TI: Rematitan frameworks). Porcelain was applied on the other 8 frameworks (RCSP: Remanium CS-porcelain and TIP: Rematitan-porcelain), fired, and then the fit was measured. Measurements were recorded at 3 points for marginal fit evaluation and at 3 points for inner fit. RESULTS Significant differences were recorded among the occlusal (JK) values of groups tested (P <.05). Marginal fit and inner fit of Remanium CS frameworks were better than Rematitan frameworks. However, there were no substantial differences detected among groups after firing the ceramic superstructures. CONCLUSION The fit of the base metal alloy metal-ceramic crowns was better than the commercially pure titanium metal-ceramic crowns. However, both artificial crowns were clinically acceptable.

Stress analysis of effects of nonrigid connectors on fixed partial dentures with pier abutments

STATEMENT OF PROBLEM In some patients, the pattern of missing teeth may require the use of a fixed partial denture (FPD) with an intermediate pier abutment. Information is needed regarding the biomechanical behavior and the position of a nonrigid connector for this treatment option. PURPOSE The purpose of this study was to evaluate, by means of finite element method (FEM), the effects of rigid and nonrigid design types on stress distribution for 5-unit FPDs with pier abutments. MATERIAL AND METHODS A 3-dimensional cross-section FEM model (SAP 2000) simulating a 5-unit metal ceramic FPD with a pier abutment with rigid or nonrigid designs (connector location at the mesial region of the second molar, at the distal region of the second premolar, at the mesial region of the second premolar, and at the distal region of the canine) was developed. In the model, the canine, second premolar, and second molar served as abutments. A supporting periodontal ligament and alveolar bone (cortical and trabecular) were modeled. A 50-N static vertical occlusal load was applied on the cusp of each abutment to calculate the stress distributions. Three different types of load were evaluated: loading of all cusps to simulate maximum centric occlusion contacts, loading of the canine to simulate a single anterior contact, and loading of the second molar to simulate a posterior contact. RESULTS The analysis of the von Mises stress values revealed that maximum stress concentrations were located at the load areas for all models. Also, for all models, the highest stress values were located at connectors and cervical regions of abutment teeth, especially at the pier abutment. CONCLUSIONS The area of maximum stress concentration at the pier abutment was decreased by the use of a nonrigid connector at the distal region of the second premolar.