Journal of Dental Medicine

Statement of Problem: One of newly presented base metal alloys (Minalux) is produced according to VeraBond2 alloy (Ni- Cr base) composition. Several studies showed that, cytotoxicity of base metal alloys can be occurred due to corrosion and element release.

Purpose: This study evaluated the biocompatibility of these two base metal alloys in three steps: as cast, after polishing and after porcelain firing cycles. Release of Ni and Cr ions were measured to determine if there is any difference between these two alloys.

Materials and Methods: Samples of two base metal alloys were subjected to Neutral Red Assay, MTT Assay and Trypan Blue for biocompatibility tests. Fibroblast Balb/c 3T3 cells were used for cell culture. Samples were contacted directly with cells in 37ºc and 5% Co2 concentration for 72 hours. Teflon samples were used as negative control. ANOVA test was used to compare different groups of two alloys. In addition, the release of Ni and Cr ions in to saline solution was measured by means of atomic absorption spectrometry.

Results: MTT and Trypan Blue didn’t show any significant difference between Minalux, VeraBond2 and Teflon. Neutral Red Assay showed no significant difference between these two base metal alloys but as cast group was higher in cytotoxicity in comparisons with polished and firing groups in both two alloys. Release of Cr ion was non detectable (Cr < 1 PPB) but Ni ion was measured and Ni release was significantly different in as cast groups (P=0.007) of two alloys.

Conclusion: There is no significant difference between cytotoxicity of two base metal alloys and polishing and firing can decrease cytotoxicity of both alloys.

Background and Aims: Constant dynamic and static activities are considered as the main cause of musculoskeletal problems among dentists. The aim of this study was to evaluate the musculoskeletal problems and related factors among dentists in specialized clinics and dental schools in Tehran in 2014 using the REBA method.

Materials and Methods: In this cross-sectional study, the dentists from clinics of dental schools in Tehran were selected as individual targets. Nordic anddemopghrphic questionnaire were completed through interview from dentists. In order to assess the musculoskeletal disorders, REBA method (Rapid Entire Body Assessment) was used. In this method, positions and postures of the dentists during their work was observed and recorded. Data was analyzed using Regression Logestic test.

Results: The obtained results showed that among 100 dentist, 6% were in the very high risk (15-11) for musculoskeletal problems and 17% and 25% were in high-risk (10-8) and average risk (7-4), respectively. Based on the findings from Nordic questionnaire, the most skeletal- muscle travail were related to the neck (60%), lumbar (58%) and rear (46%) consequently. It seemed that factors such as gender, body mass index (BMI), height, specialty, body posture during the work (standing or sitting), smoking and using the direct or indirect vision, had an impact on the musculoskeletal disorders.

Conclusion: Findings from the final scoring of REBA showed that a high percentage of dentists were struggling with skeletal- muscle problems and they were in moderate to high range of risk for these type of disorders.