Retention of fiber posts in different dentin regions: An in vitro study.

Aim: The aim of this study was to evaluate the influence of different regions of dentin within the post space on the retention of fiber posts. Materials and Methods: Ten human incisors with straight roots were selected for this study. Endodontic treatment of the specimens was done. The post spaces were created immediately after obturation and the posts were luted with dual-cure resin cement. Approximately 2.5-mm-thick sections were made from the coronal, middle, and apical thirds of the post space and thus we had three groups: Group I: Cervical, Group II: Middle, Group III: Apical. The specimens were tested on a universal testing machine. Statistical analysis was done using the unpaired Student's t-test and one-way ANOVA test. Result: The best push-out strength was obtained with the apical sections (14.69±0.298 MPa), followed by the middle (10.66±0.34 MPa) and cervical sections (9.73±0.42 MPa). Conclusion: highest pust out strengths were obtained in apical sections followed by middle and coronal.

Regional bond strengths to root canal dentin of fiber posts luted with three cementation systems

This study evaluated the influence of the cementation system on the regional push-out bond strength and failure pattern of fiber posts to radicular dentin. The roots of 48 extracted human incisors were prepared and divided into 3 groups (n=16), according to the cementation system: AdperScotchbond Multi-Purpose + resin cement RelyX ARC (SBMP+ARC); Adper SingleBond 2 + RelyX ARC (SB+ARC) and; RelyX U100 self-adhesive resin cement (U100). The posts were cemented as per manufacturer’s instructions for each cementation system. After 1 week, the roots were sectioned transversely into 6 discs. Two discs were obtained from the cervical, middle and apical thirds and the push-out test was carried out. The failure pattern was examined on all debonded specimens. The data were analyzed by two-way repeated measures ANOVA and Tukey’s test. When U100 was used, no statistically significant difference (p>0.05) was observed among the different root regions. Statistically higher push-out bond strength values were detected in the cervical third for SBMP+ARC and SB+ARC (p<0.05). The U100 showed significantly more mixed failures than SBMP+ARC in the apical third (p<0.05). In conclusion, the self-adhesive cement RelyX U100 was the only cement not sensitive to the root canal region.

Esse estudo avaliou a influência do sistema de cimentação na resistência de união regional e os padrões de fratura de pinos de fibra à dentina radicular. As raízes de 48 incisivos humanos extraídos foram preparadas e divididas em 3 grupos (n=16) de acordo com o sistema de cimentação: AdperScotchbond Multi-Purpose + cimento resinoso RelyX ARC (SBMP+ARC); AdperSingle Bond 2 + RelyX ARC (SB+ARC) e cimento resinoso autoadesivo RelyX U100 (U100). Os pinos foram cimentados conforme as recomendações dos fabricantes para cada sistema de cimentação. Após uma semana, as raízes foram seccionadas transversalmente em 6 discos. Dois discos foram obtidos para os terços coronário, médio e apical e o teste de push-out foi realizado. O padrão de fratura foi avaliado em todos os espécimes. Os dados obtidos foram analisados através dos testes ANOVA dois fatores e Tukey. Quando o cimento U100 foi testado, não foram observadas diferenças significativas (p>0,05) entre as diferentes regiões radiculares. Valores de resistência de união significativamente superiores foram encontrados no terço coronário para SBMP+ARC e SB+ARC (p<0,05). O U100 apresentou significativamente mais fraturas mistas que o SBMP+ARC no terço apical (p<0,05). Conclui-se que o cimento resinoso autoadesivo RelyX U100 foi o único cimento não afetado pela região do canal radicular.

Mandibular behavior in the treatment of skeletal class II malocclusion: a 5-year post-retention analysis

Aim: This study aimed to assess mandibular behavior in Class II subjects subjected to full orthodontic treatment with standard edgewise appliance and cervical headgear (Kloehn appliance) during the pubertal growth spurt period. Methods: Lateral cephalometric radiographs of 40 patients (21 females and 19 males) were performed at the beginning of the treatment (T0), at its end (T1) and at 5-year post-retention phase (T2) in order to quantify the cephalometric measurements (8 angular and 3 linear), representing the mandibular behavior in the anteroposterior and vertical senses. The mean age of female patients at T0, T1 and T2 was 11.4, 15 and 26 years, respectively, and for male patients it was 12.2, 16.7 and 28 years, respectively. All patients were treated in just one phase without extractions and not associating Class II intermaxillary elastics. Results: The effective treatment of skeletal Class II malocclusion with conventional Edgewise fixed appliance and Kloehn cervical headgear did not interfere in the direction and amount of mandibular growth as well as remodeling at it is inferior border, with no influence in anti-clockwise rotation of the mandible. Themandibular growth was also observed after the orthodontic treatment, suggesting that it is influenced bygenetic factors. Conclusion: These observations may lead to the peculation that growing patients with skeletal Class II malocclusion and low mandibular plane are conducive to a good treatment and long-term stability.

Effects of endodontic instrument taper on post retention of central or lateral maxillary incisors in vitro / 实用口腔医学杂志

Objective:To evaluate the effects of various tapers of canal preparations on the retention of cast posts in endodontically treated upper incisors in vitro.Methods: Forty human central or lateral maxillary incisors were prepared by removing the clinical crown at 1 mm above the approximal CEJ and treated the canals with instruments of varying tapers. The groups comprising 10 teeth of each group were divided as follows: Taper 0.02 /15~40#SS (stainless steel K-files) with step-back technique as control, PF (ProFile)OS 3#/0.06 with taper 0.06/PF 25#/ in apical third, PF OS 4#/0.07 with taper PF 0.06/30# in apical third, PF OS 5#/0.08 with PF taper 0.06/35# in apical third. Then, canals were filled with gutta percha and AH Plus sealer using vertical condensation technique with a level of 5 mm of gutta-percha left in the apical segment of the root. Metal cast posts were made by direct method and then the post was cemented with HY-BOND GLASIONMER CX (Shofu,Inc)cement. The roots were fixed in copper rings with mounting plaster and mounted on a WD-5A machine.The posts were subjected to gradually increasing vertical tensile force until dislodgment of the post occurred. Force (N) required to dislodge the post was obtained for each tooth, and the average force of the groups was compared using a one-way ANOVA and SNK multiple comparisons with SAS V8.1. Results:The highest resistance to dislodgment was obtained with PF OS 4#/0.07, whereas the lowest was obtained by the PF OS 3#/0.06. Nonstatistical difference was found between Taper 0.02 /15~40# and PF OS 3#/0.06. PF OS 4#/0.07 was statistically superior to Taper 0.02 /15~40# and PF OS 3#/0.06 but not PF OS 5#/0.08. Conclusion: The retention of posts is affected strongly with the increase in the diameter than with the increase in the taper angle. PF OS 4#/0.07 with taper PF 0.06/30# in apical third seems to be the best taper for maximal resistance to post dislodgment.