Dentinal microcracks on freshly extracted teeth: the impact of the extraction technique.

AIM: To evaluate the incidence of root dentinal microcracks after two extraction techniques through micro-computed tomographic (micro-CT) analysis. METHODOLOGY: Thirty pairs of premolars, extracted for orthodontic reasons, were assigned to two experimental groups, following a split-mouth design (n = 30): traumatic technique group (TTG) - teeth extracted following a conventional protocol using forceps, and an atraumatic technique group (ATG) - teeth extracted following an atraumatic technique protocol in which the root was gently detached from the periodontal ligament using a periotome. All teeth were immediately immersed in distilled water and scanned in a micro-CT device within 72 h following the extraction. The assessment of the images was completed on cross-section images by two masked evaluators. The Mann-Whitney test was used to assess the significant differences between the groups regarding the number of cross-sections displaying microcracks whilst the Fischer's exact test was used to assess differences in the frequency of specimens with defects (P < 0.05). RESULTS: A total of 52 750 micro-CT cross-sectional images were evaluated. A total of 352 cross-sections had at least one dentinal defect. Microcracks were observed in five teeth of the TTG group (n = 352 slices) and in two teeth of the ATG group (n = 103 slices). The statistical analysis used was unable to detect a significant difference between the groups in terms of the number of dentinal microcracks (P = 0.233) and in the frequency of teeth displaying microcracks (P = 0.424). CONCLUSION: A small number of sound teeth without endodontic treatment had dentinal microcracks regardless of the extraction technique applied. No difference was noticed between the traumatic and atraumatic techniques in the incidence of microcracks.

Climatic variables drive temporal patterns of α and ß diversities of dung beetles.

Understanding the mechanisms underpinning spatiotemporal diversity patterns of biological communities is a major goal of ecology. We aimed to test two ecological hypotheses: (i) temporal patterns of ß-diversity will mostly be driven by nestedness, with a loss of species from summer to winter, and (ii) nestedness values will correlate with climatic variables instead of turnover values, indicating either a loss of species during winter or a gain of species during summer. We sampled dung beetles using standardized sampling protocols along a year in four Atlantic forest sites: two at the northwest and two at the central region of Rio Grande do Sul state, southern Brazil. We partitioned temporal patterns of ß-diversity into turnover and nestedness in order to investigate if community changes are driven by species substitution or gain/loss across time. Our results highlighted five main findings: (i) dung beetle composition varied more with sites than site geographic position; (ii) there was almost one and a half 'true' dung beetle assemblages regarding the spatial distribution of species weighed by abundance; (iii) we found a positive influence of mean temperature and a negative influence of relative humidity on both species richness and abundance; (iv) both spatial and temporal dissimilarity among sites were dominated by species replacement, while the relative importance of nestedness was higher in temporal than spatial patterns; (v) there was an effect of precipitation and relative humidity on temporal patterns of ß-diversity components, but these effects were site-dependent. Contrary to our expectations, the ß-diversity component of turnover dominated both spatial and temporal patterns in dung beetle dissimilarity among sites and months. Distinct climatic variables affected differently the α-diversity and ß-diversity components of dung beetle assemblages. Partitioning ß-diversity into temporal components is a promising approach to unveil patterns of the community dynamics and to produce insights on mechanisms underlying such patterns.