Comparison of transportation and centering ability using RECIPROC and iRace: A cone-beam computed tomography study

BACKGROUND AND AIM: Root canal treatment, especially in curved and constricted root canals, can be very difficult and time consuming. Several investigations have compared the reciprocating and full sequence motions in terms of shaping ability. The purpose of the present study was to compare the root canal transportation and centering ability of RECIPROC and iRace using cone-beam computed tomography (CBCT). METHODS: Thirty-two mesiobuccal (MB) root canals of maxillary first molars with curvature ranged 25-40 degrees were selected. Pre-instrumentation CBCT images were captured at 2, 4 and 6 mm distances from the root apex. Thirty samples were randomly divided into two groups (n = 15). After root canal preparation using either iRace or RECIPROC #25, post-instrumentation CBCT images were obtained at the same levels. Two specimens served as control group. Pre- and post-CBCT images were evaluated to measure root canal transportation and centering ability. Mann-Whitney and Friedman tests were used for statistical analysis. RESULTS: There was no significant difference between the groups (P > 0.05). CONCLUSION: iRace and RECIPROC maintained original root canal geometry and may be safe to be used in curved root canals. KEYWORDS: Cone-Beam Computed Tomography; Root Canal Preparation; Transportatio

Comparison of transportation and centering ability using RECIPROC and iRace: A cone-beam computed tomography study

BACKGROUND AND AIM: Root canal treatment, especially in curved and constricted root canals, can be very difficult and time consuming. Several investigations have compared the reciprocating and full sequence motions in terms of shaping ability. The purpose of the present study was to compare the root canal transportation and centering ability of RECIPROC and iRace using cone-beam computed tomography (CBCT). METHODS: Thirty-two mesiobuccal (MB) root canals of maxillary first molars with curvature ranged 25-40 degrees were selected. Pre-instrumentation CBCT images were captured at 2, 4 and 6 mm distances from the root apex. Thirty samples were randomly divided into two groups (n = 15). After root canal preparation using either iRace or RECIPROC #25, post-instrumentation CBCT images were obtained at the same levels. Two specimens served as control group. Pre- and post-CBCT images were evaluated to measure root canal transportation and centering ability. Mann-Whitney and Friedman tests were used for statistical analysis. RESULTS: There was no significant difference between the groups (P > 0.05). CONCLUSION: iRace and RECIPROC maintained original root canal geometry and may be safe to be used in curved root canals

mTOR/S6 Kinase Pathway Contributes to Astrocyte Survival during Ischemia*

Neurons are highly dependent on astrocyte survival during brain damage. To identify genes involved in astrocyte function during ischemia, we performed mRNA differential display in astrocytes after oxygen and glucose deprivation (OGD). We detected a robust down-regulation of S6 kinase 1 (S6K1) mRNA that was accompanied by a sharp decrease in protein levels and activity. OGD-induced apoptosis was increased by the combined deletion of S6K1 and S6K2 genes, as well as by treatment with rapamycin that inhibits S6K1 activity by acting on the upstream regulator mTOR (mammalian target of rapamycin). Astrocytes lacking S6K1 and S6K2 (S6K1;S6K2−/−) displayed a defect in BAD phosphorylation and in the expression of the anti-apoptotic factors Bcl-2 and Bcl-xL. Furthermore reactive oxygen species were increased while translation recovery was impaired in S6K-deficient astrocytes following OGD. Rescue of either S6K1 or S6K2 expression by adenoviral infection revealed that protective functions were specifically mediated by S6K1, because this isoform selectively promoted resistance to OGD and reduction of ROS levels. Finally, “in vivo” effects of S6K suppression were analyzed in the permanent middle cerebral artery occlusion model of ischemia, in which absence of S6K expression increased mortality and infarct volume. In summary, this article uncovers a protective role for astrocyte S6K1 against brain ischemia, indicating a functional pathway that senses nutrient and oxygen levels and may be beneficial for neuronal survival