Effect of antioxidant on orthodontic bracket bond strength after vital bleaching

The objective of this study is to compare the neutralization effect of various antioxidant agents on the bond strength of composite resins on stainless steel and ceramic brackets immediately bonded to previously bleached teeth. Materials and Methods: One hundred and sixty human maxillary premolars were used for the study. Teeth were divided into four groups (n = 40): Group 1 (control), Group 2 (bleached), Group 3 (sodium ascorbate), and Group 4 (tocopherol acetate). Each group was divided into two subgroups, one was bonded with stainless steel and other with ceramic brackets using 3M Transbond XT. Universal testing machine was used to determine the shear bond strength (SBS). Results: Among the metal brackets, Group 1A had the highest SBS (12.18 + 1.41 MPa) and Group 2A had the least SBS (6.18 + 1.49 MPa). Weibull analysis indicated that bond strength for a 90% probability of failure was highest for Group 1A (13.99 MPa) and lowest for Group 2A (8.49 MPa). For ceramic brackets, Group 1B had the highest SBS (13.80 + 1.69 MPa) and Group 2B had the least SBS (8.05 + 1.85 MPa). Weibull analysis indicated that bond strength for a 90% probability of failure was highest for Group 1B (14.61 MPa) and lowest for Group 2B (8.85MPa). Conclusion: The in vitro study showed that bleaching reduced the SBS significantly, and this could be effectively reversed by the application of antioxidants in both metal and ceramic brackets.

Ergonomic risk factors and their association with musculoskeletal disorders among Indian dentist: A preliminary study using Rapid Upper Limb Assessment.

Context: Ergonomics is the scientific study of people and their work. The manufacturers typically do not design to accommodate the dimensions of the individual user. Work‑related musculoskeletal disorders (MSDs) have emerged as major health problem among workers in both industrialized and industrially developing countries. Rapid Upper Limb Assessment (RULA) was developed to investigate the exposure of the individual workers to risk factors associated with work‑related upper limb disorders. Aims: The assessment of the posture using RULA, which is quick reliable tool to determine the posture, has not been done in the Indian dentist population, indicating the need for the same. Settings and Design: A total of 104 subjects were included from New Delhi/NCR. Subjects and Methods: The procedure was explained, and the questionnaire was distributed and assessment was done using RULA. The MSDs can be recorded using the standard Nordic questionnaire. Statistical Analysis Used: The data were collected from 104 subjects out of the 192 evaluated and was statistically analyzed using SPSS software. Results: The study sample included 70 male and 34 female dentists. The posture of the subjects and the MSDs are not associated with a significant difference as according to Pearson’s Chi‑square test (0.231). Conclusions: RULA can be used as a screening tool for postural risks following a short training session regardless of the assessor’s experience in postural risk assessments.

A comparative evaluation of tray spacer thickness and repeat pour on the accuracy of monophasic polyvinyl siloxane impression material: In vitro study.

Purpose: This study was aimed to determine the effect of various tray spacer thickness and subsequent repeated pours on the accuracy and dimensional stability of the impression made from monophasic polyvinyl siloxane material. Materials and Methods: Custom trays with different spacer thickness (2, 4 and 6 mm) were used for making an impression of a master model simulating 3 unit fixed partial denture with monophasic polyvinyl siloxane material. These impressions were poured with die stone and repoured. Distance between the reference points were measured and subjected to statistical analysis. Result: Casts obtained from 1 st , 2 nd and 3 rd pour of the impression in 2, 4 and 6 mm spacer thickness tray have similar dimensional accuracy amongst each other and with the master model except in molar diameter and inter-abutment distances of cast obtained from 6 mm spacer thickness tray. Conclusion: The vertical distance of stone dies were decreased, whereas horizontal distance increased as the thickness of impression material is increased. There were statistically non-significant changes occurring among the repeated pours in 2, 4 and 6 mm spacer thickness. Clinical Implication: 2 and 4 mm spacer thickness are acceptable for making an impression for three unit fixed partial denture with monophasic polyvinyl siloxane material and it was not affected by two subsequent (1 st and 2 nd ) repeated pours.