Manoel Damião de Sousa Neto

In vitro fracture resistance of glass-fiber and cast metal posts with different lengths

STATEMENT OF PROBLEM Dental fractures can occur in endodontically treated teeth restored with posts. PURPOSE The purpose of this study was to evaluate the in vitro fracture resistance of roots with glass-fiber and metal posts of different lengths. MATERIAL AND METHODS Sixty endodontically treated maxillary canines were embedded in acrylic resin, except for 4 mm of the cervical area, after removing the clinical crowns. The post spaces were opened with a cylindrical bur at low speed attached to a surveyor, resulting in preparations with lengths of 6 mm (group 6 mm), 8 mm (group 8 mm), or 10 mm (group 10 mm). Each group was divided into 2 subgroups according to the post material: cast post and core or glass-fiber post (n=30). The posts were luted with dual-polymerizing resin cement (Panavia F). Cast posts and cores of Co-Cr (Resilient Plus) crowns were made and cemented with zinc phosphate. Specimens were subjected to increasing compressive load (N) until fracture. Data were analyzed with 2-way ANOVA and the Tukey-Kramer test (alpha =.05). RESULTS The ANOVA analysis indicated significant differences (P<.05) among the groups, and the Tukey test revealed no significant difference among the metal posts of 6-mm length (26.5 N +/-13.4), 8-mm length (25.2 N +/-13.9), and 10-mm length (17.1 N +/-5.2). Also, in the glass-fiber post group, there was no significant difference when posts of 8-mm length (13.4 N +/-11.0) were compared with the 6-mm (6.9 N +/-4.6) and 10-mm (31.7 N +/-13.1) groups. The 10-mm-long post displayed superior fracture resistance, and the 6-mm-long post showed significantly lower mean values (P<.001). CONCLUSIONS Within the limitations of this study, it was concluded that the glass-fiber post represents a viable alternative to the cast metal post, increasing the resistance to fracture of endodontically treated canines.

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.

Influence of the length of remaining root canal filling and post space preparation on the coronal leakage of Enterococcus faecalis

This study evaluated the sealing ability of different lengths of remaining root canal filling and post space preparation against coronal leakage of Enterococcus faecalis. Forty-one roots of maxillary incisors were biomechanically prepared, maintaining standardized canal diameter at the middle and coronal thirds. The roots were autoclaved and all subsequent steps were undertaken in a laminar flow chamber. The canals of 33 roots were obturated with AH Plus sealer and gutta-percha. The root canal fillings were reduced to 3 predetermined lengths (n=11): G1=6 mm, G2=4 mm and G3=2 mm. The remaining roots served as positive and negative controls. Bacterial leakage test apparatuses were fabricated with the roots attached to Eppendorf tubes keeping 2 mm of apex submerged in BHI in glass flasks. The specimens received an E. faecalis inoculum of 1 x 107 cfu/mL every 3 days and were observed for bacterial leakage daily during 60 days. Data were submitted to ANOVA, Tukeys test and Fishers test. At 60 days, G1 (6 mm) and G2 (4 mm) presented statistically similar results (p>0.05) (54.4% of specimens with bacterial leakage) and both groups differed significantly (p<0.01) from G3 (2 mm), which presented 100% of specimens with E. faecalis leakage. It may be concluded that the shortest endodontic obturation remnant leaked considerably more than the other lengths, although none of the tested conditions avoids coronal leakage of E. faecalis.

Exposure to Secondhand Smoke Impairs Fracture Healing in Rats

BackgroundNonsmokers may be affected by environmental tobacco smoke (secondhand smoke), but the effects of such exposure on fracture healing have not been well studied.Questions/purposesTo explore the possible effects of passive inhalation of tobacco smoke on the healing of a diaphyseal fracture in femurs of rats. We hypothesized that secondhand exposure to tobacco smoke adversely affects fracture healing.MethodsA mid-diaphyseal fracture was created in the femur of 41 female Wistar rats and fixed with an intramedullary metallic pin; 14 rats were excluded (nine for inadequate fractures and five for K wire extrusion). Tobacco exposure was provided by a smoking machine on a daily basis of four cigarettes a day. Each cigarette yielded 10 mg tar and 0.8 mg nicotine, and was puffed by alternating injections of fresh air for 30 seconds and smoke air for 15 seconds. The smoke exposure was previously adjusted to provide serum levels of cotinine similar to human secondhand tobacco exposure. Cotinine is a predominant catabolite of nicotine that is used as a biological biomarker for exposure to tobacco smoke. In one group (n = 11), the animals were intermittently exposed to tobacco smoke before sustaining the fracture but not afterward. In another group (n = 7), the exposure occurred before and after the fracture. The control group (n = 9) was sham-exposed before and after the fracture. We evaluated the specimens 28 days after bone fracture. The callus quality was measured by dual-energy x-ray absorptiometry (bone mineral density [BMD], bone mineral content [BMC], and callus area), μCT (callus volume and woven bone fraction), and mechanical bending (maximum force and stiffness).ResultsTobacco exposure resulted in delayed bone callus formation, which is represented by decreased BMD (Control: 0.302 ± 0.008 g/cm2 vs Preexposed: 0.199 ± 0.008 g/cm2 and Pre- and Postexposed: 0.146 ± 0.009 g/cm2; mean difference = 0.103 g/cm2, 95% CI, 0.094–0.112 g/cm2and mean difference = 0.156 g/cm2, 95% CI, 0.147–0.167 g/cm2; p < 0.01), BMC (Control: 0.133 ± 0.005 g vs Preexposed: 0.085 ± 0.0034 g and Pre- and Postexposed: 0.048 ± 0.003 g; mean difference = 0.048 g, 95% CI, 0.045–0.052 g and mean difference = 0.085 g, 95% CI, 0.088–0.090 g; p < 0.01), callus volume (Control: 7.656 ± 1.963 mm3 vs Preexposed: 17.952 ± 1.600 mm3 and Pre- and Postexposed: 40.410 ± 3.340 mm3; mean difference = −10.30 mm3, 95% CI, −14.12 to 6.471 mm3 and mean difference, −32.75 mm3, 95% CI, −36.58 to 28.93 mm3; p < 0.01), woven bone fraction (Control: 42.076 ± 3.877% vs Preexposed: 16.655 ± 3.021% and Pre- and Postexposed: 8.015 ± 1.565%, mean difference = 0.103%, 95% CI, 0.094–0.112% and mean difference = 0.156%, 95% CI, 0.147–0.166%; p < 0.01), maximum force (Control: 427.122 ± 63.952 N.mm vs Preexposed: 149.230 ± 67.189 N.mm and Pre- and Postexposed: 123.130 ± 38.206 N.mm, mean difference = 277.9 N.mm, 95% CI, 201.1–354.7 N.mm and mean difference = 304 N.mm, 95% CI, 213.2–394.8 N.mm; p < 0.01) and stiffness (Control: 491.397 ± 96.444 N.mm/mm vs Preexposed: 73.157 ± 36.511 N.mm/mm and Pre- and Postexposed: 154.049 ± 134.939 N.mm/mm, mean difference = 418.2 N.mm/mm, 95% CI, 306.3–530.1 N.mm/mm and mean difference = 337.3 N.mm/mm, 95% CI, 188.8–485.9 N.mm/mm; p < 0. 01).ConclusionsRats exposed to tobacco smoke showed delayed fracture healing and callus that was characterized by decreased maturity, density, and mechanical resistance, which was confirmed by all assessment methods of this study. Such effects were more evident when animals were exposed to tobacco smoke before and after the fracture. Future studies should be done in human passive smokers to confirm or refute our findings on fracture callus formation.Clinical RelevanceThe potential hazardous effects of secondhand smoke on fracture healing in rodents should stimulate future clinical studies in human passive smokers.

Effect of the diameter on Cu-Al post retention

This study compared the resistance to removal by traction of abraded cylindrical metal cast posts of Cu-Al (Goldent-LA). The posts had constant length (9 mm) and three different diameters (0.9, 1.3 and 1.7 mm), and were cemented with zinc phosphate cement. The crowns of 36 sound maxillary canines were sectioned, the roots were immersed in resin blocks and the root canals were endodontically treated. The teeth were divided into three groups to be prepared and standardized with the use of a parallelometer with the following burs: Group 1 Largo n. 2; Group 2--Largo n. 4; Group 3--Largo n. 6. The posts were molded with chemically activated resin and after casting they were abraded and their dimensions were confirmed with a digital caliper. After cementation of the posts in the prepared root canals, the samples were kept at 37 degrees C in distilled water for 7 days and subsequently submitted to the traction test in a universal testing machine (Instron 4444). The results showed no statistical difference between the groups. Diameter variation (0.9 mm, 1.3 mm and 1.7 mm) in abraded cylindrical posts cemented with zinc phosphate did not affect resistance to removal.

Micro-CT evaluation of root and canal morphology of mandibular first premolars with radicular grooves

The aim of this study was to evaluate morphological features of 70 single-rooted mandibular first premolars with radicular grooves (RG) using micro-CT technology. Teeth were scanned and evaluated regarding the morphology of the roots and root canals as well as length, depth and percentage frequency location of the RG. Volume, surface area and Structure Model Index (SMI) of the canals were measured for the full root length. Two-dimensional parameters and frequency of canal orifices were evaluated at 1, 2, and 3 mm levels from the apical foramen. The number of accessory canals, the dentinal thickness, and cross-sectional appearance of the canal at different root levels were also recorded. Expression of deep grooves was observed in 21.42% of the sample. Mean lengths of root and RG were 13.43 mm and 8.5 mm, respectively, while depth of the RG ranged from 0.75 to 1.13 mm. Mean canal volume, surface area and SMI were 10.78 mm3, 58.51 mm2, and 2.84, respectively. Apical delta was present in 4.35% of the sample and accessory canals were observed mostly at the middle and apical thirds. Two-dimensional parameters indicated an oval-shaped cross-sectional appearance of the root canal with a high percentage frequency of canal divisions (87.15%). Canal configuration type V (58.57%) was the most prevalent. C-shaped configuration was observed in 13 premolars (18.57%), whereas dentinal thickness ranged from 1.0 to 1.31 mm. Radicular grooves in mandibular first premolars was associated with the occurrence of several anatomical complexities, including C-shaped canals and divisions of the main root canal.

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.

Analysis of kinematic, kinetic and electromyographic patterns during root canal preparation with rotary and manual instruments

Objective This study assessed the muscular activity during root canal preparation through kinematics, kinetics, and electromyography (EMG). Material and Methods The operators prepared one canal with RaCe rotary instruments and another with Flexo-files. The kinematics of the major joints was reconstructed using an optoelectronic system and electromyographic responses of the flexor carpi radialis, extensor carpi radialis, brachioradialis, biceps brachii, triceps brachii, middle deltoid, and upper trapezius were recorded. The joint torques of the shoulder, elbow and wrist were calculated using inverse dynamics. In the kinematic analysis, angular movements of the wrist and elbow were classified as low risk factors for work-related musculoskeletal disorders. With respect to the shoulder, the classification was medium-risk. Results There was no significant difference revealed by the kinetic reports. The EMG results showed that for the middle deltoid and upper trapezius the rotary instrumentation elicited higher values. The flexor carpi radialis and extensor carpi radialis, as well as the brachioradialis showed a higher value with the manual method. Conclusion The muscular recruitment for accomplishment of articular movements for root canal preparation with either the rotary or manual techniques is distinct. Nevertheless, the rotary instrument presented less difficulty in the generation of the joint torque in each articulation, thus, presenting a greater uniformity of joint torques.

Efficacy of Different Cone-beam Computed Tomographic Protocols in the Identification of Mesiobuccal Canals of Maxillary First Molars: A Tomographic and Ex Vivo Study

Introduction: Complementary methods of anatomic diagnosis, including cone‐beam computed tomographic (CBCT) imaging, may be useful in the diagnosis of mesiobuccal (MB) canals of maxillary molars. Methods: Thirty‐five maxillary first molars were subjected to ex vivo analysis and 4 CBCT protocols: i‐CAT Classic (Imaging Sciences International, Hatfield, PA) (ICC group), i‐CAT Next Generation (Imaging Sciences International) (ICN group), PreXion 3D (PreXion, San Mateo, CA) (16.8‐second acquisition time; PX1 group), and PreXion 3D (33.5‐second acquisition time; PX2 group). The images were evaluated by 2 calibrated endodontists who kept records following protocols previously published in the literature. Micro–computed tomographic imaging was used as the control. Results: The correct identification of anatomic variations of MB roots was 54.3% (n = 19) in the ICC group, 65.7% (n = 23) in the ICN group, and 80.0% (n = 28) in the PX1 and PX2 groups. The probability of agreement between the ICC and the control groups was significantly different from the probability of agreement with the PX1 (P < .05) and PX2 (P < .05) groups. The other groups showed no significant differences compared with the control group. There was no difference in the probability of agreement between the tomographic protocols and the ex vivo results. Conclusions: The PX1 and PX2 groups were more effective for the diagnosis of MB canals. PX1 is the most suitable because it results in a shorter radiation time and diagnostic imaging similar to PX2. The single‐canal anatomy was the most prevalent in the study. HIGHLIGHTSThe i‐CAT Classic protocol resulted in fewer diagnoses of mesiobuccal (MB) canals of maxillary molars.The PreXion 3‐dimensional protocols were more effective for the diagnosis of MB canals of maxillary molars.There was no difference in the probability of agreement between the tomographic protocols and the ex vivo result.Type I anatomy was the most prevalent in this study.

Cervical microleakage in root canals treated with Er:YAG and Nd:YAG laser

Cervical microleakage was evaluated in sealed root canals previously treated with Er:YAG and Nd:YAG lasers. Ninety-two single-rooted maxillary human canines were prepared with the crown-down technique and irrigated with distilled and deionized water. The samples were distributed randomly into 9 groups of 10 teeth each. One tooth was used as a positive control and one as a negative control. In group I, 1.2 ml of EDTAC was applied during 5 min. In groups II to V, radicular dentine was irradiated with Er:YAG laser (Opus 20, Opus Dent, Israel) at the following parameters: 200 mJ and 8 Hz, 200 mJ and 16 Hz, 400 mJ and 8 Hz, or 400 mJ and 16Hz, respectively, for 60 s. In groups VI to IX, radicular dentine was irradiated with Nd:YAG laser (Fotona Medical Lasers, Slovenia) at 10 Hz and 1 W, 10 Hz and 2 W, 15 Hz and 1 W, or 15 Hz and 2 W, respectively, for 60 s. The canals were then sealed by the lateral condensation technique with an epoxy resin-based sealer. The roots were immersed in India ink for 15 days and then cleared to visualize the level of cervical microleakage with a measurement microscope. The results were evaluated by the Kruskal-Wallis test, which showed no statistical significance (p>0.01) for parameter variations of the Er:YAG laser when compared to the control group. However, the increase in frequency and potency for Nd:YAG laser decreased the microleakage when compared to the control group.