Effect of occlusal reconstruction on cerebral blood flow and cerebral oxygen saturation in patients with malocclusion / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the effect of occlusal reconstruction on blood flow velocity and cerebral oxygen saturation in patients with malocclusion.</p><p><b>METHODS</b>Thirty-three patients with malocclusion treated with occlusal reconstruction in Department of Stomatology, Medical School of Huzhou Normal College from Feb 2011 to Oct 2013 were enrolled in the study. The systolic peak flow velocity (vs), end-diastolic peak flow (vd) , mean peak flow velocity (vm) of middle cerebral artery and the oxygen saturation (rScO2) in the brain were detected at rest or chewing status by using transcranial Doppler color ultrasonography and near-infrared spectroscopy, respectively.</p><p><b>RESULTS</b>In rest state, vm was significantly increased on 3 months after treatment, while vs and vd were significantly increased on 6 months after treatment and rScO2 were increased on 12 months after treatment (P<0.05). In chewing state, vs, vm, and rScO2 were increased on 3 months after treatment, and vd was increased on 6 months after treatment (P<0.05).</p><p><b>CONCLUSION</b>Occlusal reconstruction can increase blood flow velocity of middle cerebral artery and cerebral oxygen saturation and improve oxygen supply of the brain in patients with malocclusion.</p>

Marginal and internal fit of two different zirconium copings fabricated on the implant abutment / 中国医学科学院学报

<p><b>OBJECTIVE</b>To evaluate the accuracy of marginal and internal fit of the zirconium copings manufactured by two different computer-aided design(CAD)/computer-aided manufacturing(CAM)system on the implant abutment.</p><p><b>METHODS</b>Using different scanning mode,five Procera(®) zirconium copings and five Lava zirconium copings were fabricated on the same implant abutment, and then compared with five precious metal copings fabricated by traditional method. Fifteen abutment replica were made with die-stone and the copings were randomly cemented on them, then they were sectioned and invested. The marginal, shoulder, occlusal, and axial fit of each sample was measured by scanning electron microscopy (SEM).</p><p><b>RESULTS</b>There was no significant difference in marginal and axial fit among the three groups(P>0.05). Significant difference in occlusal fit was found among the three groups(P<0.05): Lava group showed better fit than the others(P<0.05)and Procera(®) group showed better fit than the control(P<0.05).</p><p><b>CONCLUSIONS</b>These two types of zirconium coping have clinically acceptable marginal and internal fit. The internal fit of zirconium coping may be affected by different manufacturing techniques.</p>

Effect of different irrigants on radicular dentin cleansing and resin tag formation after post space preparation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the effect of different root canal irrigants on smear layer removal and dentinal tubule opening of root canal surfaces after post space preparation.</p><p><b>METHODS</b>Thirty maxillary anteriors were endodontically treated. After post space preparation, the teeth were assigned to three groups with ten teeth each: group A, B, C. 3% H2O2, 15% ethylenediamine tetraacetic acid(EDTA), 15% EDTA and 3% NaClO were used as irrigant of group A, B, C. After post space irrigation, eight teeth of each group were examined under scanning electron microscope (SEM) for smear layer removal and dentinal tubule opening. The left two specimens were restored with fiber posts and prepared for evaluation of resin tag formation.</p><p><b>RESULTS</b>The cleansing effectiveness of group A, B and C was respectively 3.89 +/- 0.36, 1.77 +/- 0.30, 1.25 +/- 0.21. The dentinal tubule opening of group A, B and C was respectively (2.53 +/- 0.19), (3 11 +/- 023) (3.83 +/- 0.52) microm. The cleansing effectiveness and dentinal tubule opening of root canal surfaces were significantly affected by different root canal irrigants (P < 0.05). Excessive erosion of the dentin was observed in group C. Resin tag formation differed between the three irrigant groups, and group B showed excellent resin tag formation.</p><p><b>CONCLUSION</b>Irrigation with 15% EDTA after post space preparation can excellently remove the smear layer and improve dentinal tubule opening, permitting well penetration of resin adhesive into the dentinal tubules and collagen fibrillar structure.</p>

An experimental study on fracture resistance of metal-ceramic crowned incisors with different post-core systems / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate fracture resistance of metal-ceramic crown restored incisors with different post-and-core systems.</p><p><b>METHODS</b>Selected 40 intact maxillary central incisors were endodontically treated and then randomly assigned to four groups of 10 teeth each. Teeth in Group A were prepared to root canal with 10 mm in length, 1.6 mm in diameter and restored with fiber-reinforced posts and composite cores. Same final preparation but root canal with 1.5 mm in diameter was achieved for teeth in the other three groups. Teeth in Group B were restored with prefabricated titanium alloy posts and composite cores and teeth in Group C were restored with cast nickel-chromium post-cores. The posts were luted with a composite resin luting system, and metal-ceramic crowns were restored and cemented with the same luting system for all of the teeth in Group A, B and C. The other 10 teeth were restored with cast nickel-chromium post-cores and metal-ceramic crowns as a control, which were cemented with glass-ionomer cement. All restored teeth were thermo-cycled for 5000 cycles (5 degrees C/55 degrees C) as a fatigue test. The tooth was loaded in a universal testing machine at an angle of 135 degrees to the long-axis at the incisal edge with a cross-head speed of 1.5 mm/min until fracture. Fracture loads (N) and modes (repairable or catastrophic) were recorded. One-way ANOVA and SNK test were used to determine the significance of the failure loads between groups. Chi-square test was conducted for evaluation of the fracture mode.</p><p><b>RESULTS</b>The fracture loads from Group A, B, C and control group were (534.4 +/- 145.7) N, (499.8 +/- 168.9) N, (412.6 +/- 99.3) N, (337.4 +/- 121.2) N, respectively. A significant difference was existed among four groups (P < 0.05). The fracture loads of Group A and Group B were significantly higher than control group (P < 0.05). The repairable mode of fracture observed from Group A to control group was 80%, 40%, 20% and 30%, Group A had a significantly higher number of repairable fractures than those of the other groups (P < 0.05).</p><p><b>CONCLUSIONS</b>Within the limitations of this study, fiber-reinforced post has an excellent fracture resistance, and can be recommended as an alternative to cast post-cores, especially for incisor esthetic restoration.</p>

A comparative study of marginal microleakage using three different cements in ceramic crowns / 浙江大学学报·医学版

OBJECTIVE: To evaluate the marginal microleakage of IPS-Empress 2 all-ceramic crowns using three different cements. METHODS: Twenty-four IPS-Empress 2 all-ceramic crowns were built and luted onto standardly prepared human upper third molars using three different cements. All samples were thermocycled then submerged in 2% fuchsin for 24 hours. The marginal microleakage at tooth-cement and ceramic crown-cement interfaces was observed using light stereomicroscopy. RESULTS: The Panavia F adhesive luting system demonstrated the least microleakage(0.90+/-0.75, 0.46+/-0.37). Dyract compomer cement showed an intermediate level of microleakage (4.71+/-1.68, 5.28+/-1.48). Harvard zinc phosphate cement was associated with severe microleakage in all specimens( 6.99+/-0.04, 6.99+/-0.04). THe differences in microleakage among the three cements was highly significant(P<0.01). CONCLUSION: Panavia F adhesive luting system was the most effective dental cement to prevent microleakage. It can be used for IPS-Empress 2 posterior all-ceramic crowns.