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Many different types of alloys are now available in the market to be used for dental restorations and fixed prostheses. The common criterion for all these fixed prosthodontic materials is the permanent existence of them in the oral cavity for prolonged time without the ability to be removed by the patient. Therefore, knowledge about the biocompatibility of dental alloys is of great importance. This article presents a literature review on the biocompatibility of dental alloys. A PubMed database search was conducted for studies pertaining to the biocompatibility of dental alloys. The search was limited to peer-reviewed articles published in English between 1985 and 2013. Available data revealed that substances are released from alloys into the surrounding tissues; mainly nickel, zinc, and copper. Some alloys such as nickelechromium alloy have shown to be cytotoxic in vitro. Also, elements released from gold alloy showed in vitro cytotoxic effect. Therefore, clinicians should give up assuming that gold alloy is completely inert and biocompatible with oral tissues. The clinical relevance of these findings remains unclear. Further in vitro studies, as well as controlled clinical trials, are needed due to possible exceptions.

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The objective of this study was to quantitatively investigate the elemental ion release from the fixed gold alloy and ceramic crowns into patient saliva. Twenty patients who participated in the study were divided into two equal groups; 1) full coverage type IV gold crowns and 2) full coverage CAD-CAM-fabricated ceramic crowns. Saliva collection and clinical evaluation of marginal integrity and gingival health were performed before crowns preparation, 3 months and 6 months after crowns placement. Clinical evaluations were conducted using California Dental Association criteria. Collected saliva samples were analysed for element release using inductively coupled plasma mass spectrometer. The zinc, copper, palladium, gold and silver were released from type IV gold crowns into saliva, while the silicon and aluminium were released from ceramic crowns. A clinically significant number of subjects had increased release of zinc from baseline to three-month recall and increased silicon release from baseline to both three-month and six-month recalls. For all elements, the subjects' counts for the case of three-month recall to six-month recall were never higher than that of the case of baseline to three-month recall except for palladium. No obvious adverse effects on marginal integrity or gingival health were noticed. Significant increased releases of zinc from cast gold crowns and silicon from CAD-CAM-fabricated ceramic crowns into the saliva were evident after 3 months of clinical service.

Purpose: This in vitro study aimed to evaluate the influence of fatigue loading on fracture resistance of endodontically treated molars restored with endocrowns using different machinable blocks. Methods: Endodontically treated mandibular first molars were prepared using a standardized method. Specimens were divided into 4 groups (n = 10). Anatomically shaped endocrowns groups were manufactured using VITA ENAMIC (VE) and KATANA Zirconia (KZ). Layered endocrowns groups were manufactured using IPS e.max CAD (EM) and BioHPP (BH). Half of the specimens of each group were subjected to fracture resistance test, while the other half were subjected to thermocycling and chewing simulation. After fatigue loading, specimens were loaded until failure. Specimens were examined using stereomicroscopy. Data were analyzed using ANOVA analysis of variance and Bonferroni post hoc test (α=0.05). Results: KZ group had the highest initial fracture resistance value (1810.20± 119.56 N) and BH had the lowest value (579.50± 76.15 N). The reduction of fracture resistance after fatigue loading was significant for KZ group (1588.30±216.25 N) and BH group (502.60±11.53 N) and non-significant to VE group (1101.70±77.05 N) and EM group (1112.10±74.12 N). Failure modes of KZ and EM groups showed high percentage of non-restorable fractures, while VE and BH groups showed high percentage of restorable fractures. Conclusions: Within the limitations of this study, the following can be concluded: Poly infiltrated ceramics should be considered as a proper material to be used as an endocrown material because of its ability to be restorable if failure occurred.