Graziela Bianchi Leoni

Micro-computed tomographic analysis of the root canal morphology of mandibular incisors.

INTRODUCTION This study aimed to describe the anatomy of mandibular central and lateral incisors using micro-computed tomographic imaging. METHODS One hundred mandibular incisors were scanned in a micro-computed tomographic device using an isotropic resolution of 22.9 μm. The anatomy of each tooth (length of the roots, presence and location of accessory canals and apical deltas, and number of canals) as well as the 2- and 3-dimensional morphologic aspects of the canal (area, roundness, diameter, volume, surface area, and structure model index) were evaluated. Data were statistically compared using the Student t test (alpha = 0.05). RESULTS The mean lengths of the mandibular central and lateral incisors were 20.71 and 21.56 mm, respectively. Most of the central (60%) and lateral (74%) incisors had no accessory canals. An apical delta was observed in only 1 specimen. The cross-section analysis of the apical third showed the presence of 1, 2, or 3 canal orifices. No statistical difference was observed in the comparison of the 2- and 3-dimensional morphologic parameters between central and lateral incisors (P < .05). The qualitative analyses of the 3-dimensional models of the root canal systems of the central and lateral incisor teeth confirm that the most prevalent configurations were Vertuccis types I (50% and 62%, respectively) and III (28%). CONCLUSIONS Overall, mandibular central and lateral incisors were similar in terms of the 2- and 3-dimensional analyzed parameters. Vertuccis types I and III were the most prevalent canal configurations of the mandibular incisors; however, 8 new types have also been described.

Histologic and Micro–Computed Tomographic Analyses of Replanted Teeth Stored in Different Kind of Media

INTRODUCTION Coconut water (CW) and soy milk (SM) have been proposed as storage media for avulsed teeth because of their nutrients that preserve cell viability. The present study investigated the periodontal healing process of dog teeth replanted after storage in CW, SM, and whole milk (WM) using micro-computed tomographic (μCT) and histologic analyses compared with immediate tooth replantation. METHODS Forty roots of 10 adult beagle dogs were extracted and subjected to the following protocols: immediate replantation after extraction (control), stored in CW with an adjusted pH, and SM and WM for 50 minutes before replantation. The animals were euthanized 28 days postoperatively, and the obtained specimens were scanned using a μCT scanner and subjected to routine processing for histometric analyses under an optical microscope. RESULTS CW and SM performed similarly to WM; however, SM showed significantly higher ankylosis than the control group. CONCLUSIONS Additionally, this study showed that the combined use of histologic analysis and μCT is a promising method to better identify tooth resorption and the repair process and to evaluate the total extension of the periodontium. CW as a storage medium is a promising transport media for avulsed teeth.

The Radix Entomolaris and Paramolaris: A Micro–Computed Tomographic Study of 3-rooted Mandibular First Molars

INTRODUCTION The morphology of the supernumerary third root (radix) in mandibular first molars was examined by micro-computed tomography (μCT) scanning. METHODS Nineteen permanent mandibular first molars with radix were scanned in a μCT device to evaluate their morphology with respect to root length, root curvature direction, location of radix, apical foramen, accessory canals and apical deltas, and distance between canal orifices as well as 2- and 3-dimensional parameters of the canals (number, area, roundness, major/minor diameter, volume, surface area, and structure model index). Quantitative data were analyzed by 1-way analysis of variance and the Tukey test (α = 0.05). RESULTS The mean length of the mesial, distal, and radix roots was 20.36 ± 1.73 mm, 20.0 ± 1.83 mm, and 18.09 ± 1.68 mm, respectively. The radix was located distolingually (n = 16), mesiolingually (n = 1), and distobuccally (n = 2). In a proximal view, most radix roots had a severe curvature with buccal orientation and a buccally displaced apical foramen. The spatial configuration of the canal orifices on the pulp chamber floor was mostly in a trapezoidal shape. The radix root canal orifice was usually covered by a dentinal projection. The radix differed significantly from the mesial and distal roots for all evaluated 3-dimensional parameters (P < .05). The radix canal had a more circular shape in the apical third, and the mean size of the minor diameter 1 mm short of the foramen was 0.25 ± 0.10 mm. CONCLUSIONS The radix root is an important and challenging anatomic variation of mandibular first molars, which usually has a severe curvature with a predominantly distolingual location, and a narrow root canal with difficult access.

Whole-body vibration improves fracture healing and bone quality in rats with ovariectomy-induced osteoporosis

PURPOSE To investigate the effect of vibration therapy on the bone callus of fractured femurs and the bone quality of intact femurs in ovariectomized rats. METHODS Fifty-six rats aged seven weeks were divided into four groups: control with femoral fracture (CON, n=14), ovariectomized with femoral fracture (OVX, n=14), control with femoral fracture plus vibration therapy (CON+VT, n=14), and ovariectomized with femoral fracture plus vibration therapy (OVX+VT, n=14). Three months after ovariectomy or sham surgery, a complete fracture was produced at the femoral mid-diaphysis and stabilized with a 1-mm-diameter intramedullary Kirschner wire. X-rays confirmed the fracture alignment and fixation. Three days later, the VT groups underwent vibration therapy (1 mm, 60 Hz for 20 minutes, three times per week for 14 or 28 days). The bone and callus quality were assessed by densitometry, three-dimensional microstructure, and mechanical test. RESULTS Ovariectomized rats exhibited a substantial loss of bone mass and severe impairment in bone microarchitecture, both in the non-fractured femur and the bone callus. Whole-body vibration therapy exerted an important role in ameliorating the bone and fracture callus parameters in the osteoporotic bone. CONCLUSION Vibration therapy improved bone quality and the quality of the fracture bone callus in ovariectomized rats.

A Novel Dentin Push-out Bond Strength Model That Uses Micro-Computed Tomography.

INTRODUCTION Current push-out experimental methods used in endodontic research should be improved. This study introduced a novel dentin push-out bond strength model that uses micro-computed tomography (μCT). METHODS Roots filled with gutta-percha cones and different resin-based sealers (n = 10) were sectioned transversely to obtain two 2-mm-thick slices per root third. The first slice was subjected to a push-out test by using a material testing stage fitted inside a μCT scanner. The apparatus was scanned before and after the test to evaluate areas of filling material ruptures. The images provided by μCT were also used to generate models for a 3-dimensional finite element analysis. Confocal laser scanning microscopy was used to assess failure modes after the test and to measure interfacial gaps in slices not subjected to push-out. Bond-strength and gap data were statistically analyzed (P < .05). RESULTS Proper coefficients of variation (average less than 30%) were observed for all the experimental conditions. The finite element analysis helped explain the results of bond strength and root-filling ruptures. A significant, moderate, indirect correlation was observed between the bond strength and gaps. CONCLUSIONS The micromechanical model with the μCT images resulted in a consistent root-filling bond strength evaluation.

Swimming Activity Prevents the Unloading Induced Loss of Bone Mass, Architecture, and Strength in Rats.

We investigated whether swimming activity associated with a three-week period of hypoactivity could prevent the deleterious effects of disuse on the tibias of tail-suspended rats. Forty Wistar rats were divided into five groups: (HS) permanently hindlimb suspension rats; (HS + Swim) rats submitted to unloading interrupted by swimming exercise; (HS + WB) hindlimb suspension rats with interruption for regular weight bearing for the same length of time as the HS+Swim rats; (Control) control rats that were allowed regular cage activities; and (Control + Swim) control rats that underwent swimming exercise. At the end of the experiment, bone mineral density, bone strength, and trabecular quantification were analyzed. The hindlimb-suspended rats exhibited bone quality loss (significant decrease in BMD, bone strength, and deterioration of trabecular and cortical bone architecture; decrease in BV/TV, TbN, TbTh, ConnD, CtV, and CtTh; and increase in TbSp) when compared to control rats. In contrast, trained rats showed a significant increase of 43% in bone mass, 29% in bone strength, 58% in trabecular thickness, 85% in bone volume, 27% in trabeculae number, and 30% in cortical volume, when compared to the hindlimb-suspended rats. We conclude that swimming activity not only ameliorates but also fully prevents the deleterious effects on bone quality in osteopenic rats.

Comparison of Two Techniques for Selection of Master Gutta-Percha Cone Using Micro-Computed Tomography

This study used micro-computed tomography (micro-CT) to evaluate the fit of the master gutta-percha cone at time of cone fit, gutta-percha volume in the filling material, and the filling material volume in relation to the canal at the apical limit of the working length. Root canals of 20 maxillary central incisors were prepared with rotary instruments and distributed into two groups (n=10). The gutta-percha cone tip was either plasticized (apical thermal impression technique - ATI) or not (conventional technique - CT), and its apical fit was checked. The apical 1 mm of working length was examined with a micro-CT, canals were filled with gutta-percha and sealer, and new micro-CT scans were obtained. In CT, gutta-percha filled 35.83 ± 15.05% of the canal at cone selection and 38.72 ± 11.64% after filling. In ATI, these values were 23.14 ± 7.74% and 26.98 ± 20.40%, respectively. Gutta-percha volume in the filling material, and filling material volume in relation to the canal were, respectively, 61.28 ± 11.64% and 87.76 ± 9.98% for CT, and 73.00 ± 20.41% and 89.96 ± 9.08% for ATI. No significant difference was found between cone selection and after canal filling, for either CT (p=0.593) or ATI (p=0.4975). The techniques did not differ significantly with respect to gutta-percha volume in the filling material (p=0.132) and filling material volume in relation to the canal (p=0.612). An ideal fit of the master gutta-percha cone at working length was not achieved regardless of the cone selection technique, and the material-filled area was similar for both techniques.

The local administration of parathyroid hormone encourages the healing of bone defects in the rat calvaria: Micro-computed tomography, histological and histomorphometric evaluation

OBJECTIVE To evaluate the effect of a single-dose local administration of PTH on bone healing in rat calvarial bone defects by means of micro-computed tomography, histological and histomorphometric analysis. DESIGN Critical-size cranial osteotomy defects were created in 42 male rats. The animals were randomly divided into 3 groups. In the C Group, the bone defect was only filled with a blood clot. In the S Group, it was filled with a collagen sponge and covered with bovine cortical membrane. In the PTH Group, the defect was filled with a collagen sponge soaked with PTH and covered with bovine cortical membrane. The groups were further split in two for euthanasia 15 and 60days post-surgery. Data was statistically analyzed with t-tests for independent samples or the nonparametric Mann-Whitney test when applicable. Intragroup comparisons were analyzed with paired t-tests (p<0.05). RESULTS Micro-CT analysis results did not demonstrate statistically significant intergroup differences. At 15days post-surgery, the histomorphometric analysis showed that the PTH Group exhibited a significantly higher percentage of bone formation compared with the S Group. At 60days post-surgery, a higher percentage of new bone was observed in the PTH group. CONCLUSION The results suggest that the local administration of PTH encouraged the bone healing in critical-size calvarial defects in rats.

The effect of ovariectomy and 2 antiresorptive therapeutic agents on bone response in rats: A 3-dimensional imaging analysis

OBJECTIVE The aim of this study was to evaluate bone mineral density (BMD) and microarchitecture in femurs and maxillary bones of ovariectomized (OVX) rats treated or not treated with alendronate (ALD) or odanacatib (ODN). STUDY DESIGN Twenty rats were divided into groups: SHAM, OVX, OVX/ALD, and OVX/ODN. After 12 weeks, the femurs and maxillae were removed and subjected to 3-dimensional analysis by micro-computed tomography. Results were analyzed with 1-way analysis of variance and Tukeys post hoc test (α = 0.05). RESULTS OVX decreased maxillary and femoral BMD and altered femoral microarchitecture (P < .05). The drugs increased BMD of both types of bones, but only ALD maintained the phenotype similar to the SHAM group. The action of ALD was limited to the femoral trabecular separation (Tb.Sp). OVX and the drugs had no effect on the microarchitecture of the maxilla (P > .05). CONCLUSIONS ALD and ODN therapy increased BMD in both bones after ovariectomy. ALD was more successful than ODN in preserving the morphology of bone similar to the SHAM group. ALD maintained the phenotype for Tb.Sp in the femur, but ODN did not. In the maxillae, neither ovariectomy nor the 2 antiresorptive drugs had significant effects on microarchitecture.

Ovariectomy Exacerbates Apical Periodontitis in Rats with an Increase in Expression of Proinflammatory Cytokines and Matrix Metalloproteinases

Introduction: The aim of this study was to evaluate the gene expression of proinflammatory cytokines, matrix metalloproteinases (MMPs), and cathepsin K in apical periodontitis (AP) and the volume of lesions in ovariectomized and sham‐operated rats. Methods: Twenty 12‐week‐old female Wistar rats were subjected to ovariectomy (OVX) or sham surgery. After 9 weeks, access cavities were prepared in the maxillary and mandibular first molars, pulp tissue was removed, and canals were exposed to the oral environment during 21 days for the induction of AP. The groups were as follows: sham, OVX, sham+AP, and OVX+AP. Animals were euthanized, and blocks containing the maxillary first molar and the surrounding bone were removed for quantification of proinflammatory cytokines cathepsin K and MMP genes by real‐time polymerase chain reaction. The hemimandibles containing the mandibular first molars were used for analysis of the AP lesion volume by micro–computed tomographic imaging. Results: AP in OVX rats showed an increased expression of interleukin 1 beta, tumor necrosis factor alpha, interleukin 6, MMP‐8, and MMP‐13 (P < .05). OVX alone, without AP induction, did not affect the expression of the evaluated genes. Additionally, AP induced an increase in cathepsin K expression, without significant differences between AP in the sham and OVX groups (P > .05). Micro–computed tomographic imaging showed a significantly greater AP lesion mean volume in OVX compared with sham animals (P < .05). Conclusions: AP lesions in ovariectomized rats are larger and have an increased expression of proinflammatory cytokines and MMPs, indicating that the infection combined with ovariectomy has an important role in the regulation of these signaling molecules and enzymes during the development of AP. Based on that, it may be assumed that the hypoestrogenic condition aggravates inflammation and degradation of extracellular matrix components in AP, which may provide insight into understanding the development of AP in female postmenopausal patients. HIGHLIGHTSFew studies evaluated apical periodontitis (AP) in OVX animals; none evaluated AP volume.Little attention has been given to the mediators that regulate this process.No study has assessed the role of matrix metalloproteinases (MMPs).This study was the first to evaluate proinflammatory cytokines and MMPs in AP of OVX rats.The hypoestrogenic condition aggravates inflammation and MMP expression in AP.Insight was provided into understanding AP in female postmenopausal patients.