RESUMEN
BACKGROUND:Someone regards that treatments such as root canal therapy and post-core restoration can increase the fracture probability of teeth. Can fiber reinforced composite post enhance the fracture resistance of the severe wedge-shaped defected premolar? Three-dimensional finite element can simplify complex dental systems into a model analyzed by computer, and conduct biomechanical research through the model analysis. OBJECTIVE:To analyze the stress distribution of sever wedge-shaped defected first premolar which restored by fiber reinforced composite post and composite resin. METHODS:We established the three-dimensional finite element models of severe wedge-shaped defected maxil ary first premolar before and after restoration with fiber reinforced composite post and composite resin. The maximum bite force was designed to 267 N that was applied at 45° angle. Then, we analyzed the distribution of maximum principal stress in finite element models. RESULTS AND CONCLUSION:The maximum principal stress was concentrated in the tip of defected region. After restoration, the distribution of maximum principal stress was similar to that of the normal premolar, and the tensile stress was distributed uniformly in the upper-central part of buccal root. It may be beneficial for improving fracture resistance ability of severe wedge-shaped-defect premolar by restoration with fiber reinforced composite post and composite resin.
RESUMEN
BACKGROUND:Previous studies show that the fracture resistant force of endodonticaly treated teeth can be improved by post. But this idea has been controversial in recent years. Many scholars believe that the root canal preparation might weaken dental root the post increases the risk of tooth fracture. OBJECTIVE: To evaluate the fracture resistance ability of severe wedge-shaped-defect premolar to oblique loading, which was restored with fiber reinforced composite posts by different therapy methods. METHODS:A total of 50 human maxilary premolars were randomly divided into five groups, with ten teeth in each group. They were given folowing treatments: Group A: 10 untreated premolars; Rest 40 premolars of Groups B, C, D and E were prepared 1/3 bucco-lingual distance for artificial severe wedge-shaped defects at the buccal cervix. Group B: untreated severe wedge-shaped defects premolars; Group C: severe wedge-shaped defects premolars were endodonticaly treated, remaining dentin over hang above the wedge shaped defect, LuxaPost posts reinforced in buccal canal and lingual canal, LuxaCore composite resin restored dentin defect; Group D: severe wedge-shaped defects premolars were endodonticaly treated, LuxaPost posts reinforced in buccal canal and lingual canal, LuxaCore composite resin restored dentin defect, and then covered with ful metal crown; Group E: severe wedge-shaped defects premolars were endodonticaly treated, removing dentin over hang above the wedge shaped defect, LuxaPost posts reinforced in buccal canal and lingual canal, restored with LuxaCore composite resin, and then covered with ful metal crown. Fracture resistance of each specimen was measured in each group. RESULTS AND CONCLUSION: The fracture strength of each group were Group A (1 002.69±147.62) N, Group B (439.28±66.34) N, Group C (958.30±101.23) N, Group D (1 207.09±143.48) N, and Group E (1 056.44±139.30) N. Group D had the highest fracture strength (P < 0.01), while Group B had the lowest fracture strength (P < 0.01). There were no significant difference among the fracture strength of Group A, Group C and Group E. Our findings indicated that the fracture resistance of the severe wedge-shaped defected premolar can be improved by fiber reinforced composite post and dentin above wedge shaped defect remained.
RESUMEN
Biological performances of Ni-Cr porcelain alloy are highly correlated with released metallic ions. Released metal ions from Ni-Cr porcelain alloy, particularly Ni, Be can induce inflammation of the adjacent periodontal tissue and oral mucosa. In vitro evidence has indicated that the immune response can be altered by various metal ions. Allergic reactions due to metallic dental restorations have been documented. Ni has especially been identified as being highly allergenic. The cytotoxicity and corrosion level of Ni-Cr porcelain alloy is increased after recasting. The Ni-Cr porcelain alloy produced according to technology requirements has good biological safety. Ni-Cr porcelain alloy released a few of metal ions which might induce allergy and density of adjacent periodontal tissues, for the stimulation effect of these metal ions. There is no evidence to suggest that Ni-Cr porcelain alloy restorations has systemic toxicity or carcinogenic/genotoxic effect to human.