Influence of obturating techniques on root dentin crack propagation: A micro-computed tomography assessment.

AIM: The aim is to assess and compare the microcrack formation in radicular dentin after obturating the root canals with cold lateral condensation (CLC), warm vertical condensation (WVC), and injectable gutta-percha (IGP) techniques using micro-computed tomography (CT). MATERIALS AND METHODS: Human extracted mandibular premolar teeth (n = 60) were haphazardly assigned based on the obturation technique into three experimental groups (n = 20 each). Root canals are cleaned and shaped with M Two rotary files and 3% sodium hypochlorite irrigant. Cross-sectional images were taken with Micro-CT to record the baseline defects present on root samples. After root canal obturation either with CLC or WVC or injectable obturation techniques, micro-CT images were captured again to analyze the increase in the number and type of dentinal defects. Statistical analysis of data was performed using the Mann-Whitney U test and the Mcnemar test at 5% significance level. RESULTS: An increase in the number of radicular micro-cracks was identified in samples obturated with lateral condensation technique (1.66%). No change in the percentage of micro-cracks was recorded after obturation with warm vertical or injectable guttapercha (IGP) techniques (P > 0.05). The three obturation techniques were not statistically different in the occurrence of micro-cracks after obturation. CONCLUSION: The three obturating techniques tested showed no significant increase in radicular dentin defects' occurrence or propagation.

Knowledge and awareness on novel coronavirus spread among dental fraternities in Visakhapatnam, India: A questionnaire-based survey.

INTRODUCTION: The pandemic caused by novel coronavirus (severe acute respiratory syndrome coronavirus 2) in Wuhan, China, in December 2019 is a highly contagious disease. The World Health Organization has declared the outbreak of coronavirus diseases (COVID-19) as a global public health emergency. Currently, the research on novel coronavirus is still in the primary stage. The aim of this study is to assess the knowledge and awareness on COVID-19 disease and related infection control measures among the dental fraternity in Visakhapatnam - the smart city. METHODS: A total of 808 dentists from the Visakhapatnam region completed a questionnaire-based survey on the knowledge, awareness, and infection control measures related to COVID-19 infection. The questionnaire was tailored from the guidance and information for health-care workers issued by the US Centers for Disease Control and Prevention. Suitable sampling method was used for the collection of data and the distribution of responses was presented as percentages. Explanatory statistics were performed for all groups and subgroups based on the percentage of correct responses. Individual pair-wise comparisons were done using the Chi-square test for the percentage of correct responses. RESULTS: A total of 825 participated in the survey, of which 808 dentists completely answered the survey, and the response rate was 98%. Among the respondents, males and females are 46.8% and 53.2%, respectively. There was a statistically significant difference for all the questions solicited, among age groups (P = 0.001, 0.001) and occupation (P = 0.001, 0.001, 0.004). Private practitioners seem to more awareness compared to teaching faculty, undergraduates, and postgraduates, as they have answered correctly (>70%) for almost all the questions. CONCLUSION: The inputs from the survey help us throw some light and fill up lacunae where required. There is a strong need to implement periodic educational interventions and training programs on infection control practices for COVID-19 among dentists in particular. The information from this survey helps us to make necessary changes in implementing periodic educational webinars and stress on areas where necessary, which is important for the dental fraternity for protecting themselves and shielding our society from COVID-19.

Efficacy of hydroxyapatite and silica nanoparticles on erosive lesions remineralization.

AIM: The aim is to assess and compare the mineral gain and penetration depth of hydroxyapatite and silica nanoparticle infiltrates into artificially created erosive lesions of enamel and dentin. MATERIALS AND METHODS: Sixty extracted human molars were sectioned to obtain enamel and dentin samples (n = 60 each). They were demineralized using citric and formic acid, respectively, to create erosive lesions on enamel and dentin surfaces. Samples were assigned into nanohydroxyapatite (nHA) or nanosilica groups (n = 30 each) according to the infiltrant used. Half of the enamel and dentin samples in each group (n = 15) were analyzed after erosive attack for mineral loss, after infiltrant application for mineral gain, using energy-dispersive X-ray spectroscopy. In another half of the enamel and dentin samples (n = 15), the penetration depth of the nanoinfiltrants was analyzed using confocal microscopy. STATISTICAL ANALYSIS: To compare the overall mineral gain between groups, a dependent t-test was applied. The intergroup comparisons were made using one-way ANOVA followed by Tukey post hoc test for pairwise comparisons for both penetration depth and mineral gain. The significance level was set to P ≤ 0.05. RESULTS: The mineral gain in enamel was not statistically different between nHA and nanosilica infiltrants (P = 0.9950). nHA infiltrated dentin showed significantly more mineral gain (P = 0.0001) than nanosilica infiltrant. The depth of penetration of the nHA in enamel was statistically greater than that of nanosilica, but in dentin, the difference was not significant. CONCLUSION: nHA infiltrant performed better in mineral gain, and penetrated deeper into the demineralized erosive lesions, compared to nanosilica infiltrant in both enamel and dentin. The highest mineral precipitation and deeper penetration into both demineralized enamel and dentin was observed with nHA infiltrant compared to (as against) nanosilica infiltrant.

Microtensile bond strength of bulk-fill restorative composites to dentin.

BACKGROUND: To facilitate the easier placement of direct resin composite in deeper cavities, bulk fill composites have been introduced. The Mechanical stability of fillings in stress bearing areas restored with bulk-fill resin composites is still open to question, since long term clinical studies are not available so far. Thus, the objective of the study was to evaluate and compare the microtensile bond strength of three bulk-fill restorative composites with a nanohybrid composite. MATERIAL AND METHODS: Class I cavities were prepared on sixty extracted mandibular molars. Teeth were divided into 4 groups (n= 15 each) and in group I, the prepared cavities were restored with nanohybrid (Filtek Z250 XT) restorative composite in an incremental manner. In group II, III and IV, the bulk-fill composites (Filtek, Tetric EvoCeram, X-tra fil bulk-fill restoratives) were placed as a 4 mm single increment and light cured. The restored teeth were subjected to thermocycling and bond strength testing was done using instron testing machine. The mode of failure was assessed by scanning electron microscope (SEM). The bond strength values obtained in megapascals (MPa) were subjected to statistical analysis, using SPSS/PC version 20 software.One-way ANOVA was used for groupwise comparison of the bond strength. Tukey's Post Hoc test was used for pairwise comparisons among the groups. RESULTS: The highest mean bond strength was achieved with Filtek bulk-fill restorative showing statistically significant difference with Tetric EvoCeram bulk-fill (p< 0.003) and X-tra fil bulk-fill (p<0.001) composites. Adhesive failures are mostly observed with X-tra fil bulk fill composites, whereas mixed failures are more common with other bulk fill composites. CONCLUSIONS: Bulk-fill composites exhibited adequate bond strength to dentin and can be considered as restorative material of choice in posterior stress bearing areas. Key words:Bond strength, Bulk-fill restoratives, Configuration factor, Polymerization shrinkage.