Effect of Arch Size and Implant Angulations on the Accuracy of Implant Impressions.

PURPOSE: To evaluate the effects of arch size and implant angulation on the accuracy of implant impressions. MATERIALS AND METHODS: Four different resin models (small and large) of edentulous maxilla were fabricated and four implants were inserted (Blossom®, ø 4.75 × 10 mm) in each model. Implants were either parallel or angled 25° buccally. Forty working casts (small parallel, small angled, large parallel, and large angled) were fabricated in dental stone (n=10). For each implant, linear and angular displacements were measured using a coordinate-measuring machine (CMM) and mean values were analyzed by univariate analysis (α = 0.05). RESULTS: Arch size did not affect the linear or angular displacement (P ⟩ .05). However, the implant angulation had a marked influence on the linear displacement (P ⟨ .05). The largest linear displacement occurred in implant no. 4 of angled small groups. CONCLUSION: Regardless of arch size, linear and angular accuracy of implant impression varied with the implant angulation.

The effect of environmental pressure and resin cements on the push-out bond strength of a quartz fiber post to teeth root canals.

AIM: To evaluate the effect of environmental pressure changes on the bond strength between a fiber post and one of three resin cements using different mixing methods and modes of application. METHODOLOGY: Sixty single-canal human teeth were divided into three groups (n = 20) and endodontically treated. Post spaces were prepared, and a quartz fiber post was secured with either a self-adhesive machine-mixed cement (RelyX Unicem, Aplicap), a self-adhesive hand-mixed cement (RelyX Unicem), or a self-etching dual-cured resin cement (Panavia F2). Half of each group was subjected to 24 pressure cycles from 0 to 5 atmospheres. The mean push-out bond strength of the posts was calculated and statistically analyzed using ANOVA and Tukey tests (α = 0.05). RESULTS: Regardless of the pressure, Unicem Aplicap achieved the highest bond strength (P < 0.05). The bond strengths of all groups were significantly lower after they were subjected to the pressure cycles (P < 0.003), and they were lower in the apical regions. CONCLUSION: Bond strengths between the fiber post and root canal can be affected by environmental pressure while the type of resin cements, their mixing methods and modes of application incorporated lower porosity, achieving higher bond strength.

Effect of artificial saliva and pH on shear bond strength of resin cements to zirconia-based ceramic.

The aim of the present study was to evaluate the effect of media with different pH on shear and strength of resin cements to zirconia-based ceramics. Sixty rectangularly shaped specimens made of a zirconia based ceramic (Cercon, Dentsply) were prepared, air-blasted with 110 microm aluminum oxide particles (Al203) and randomly assigned into three groups (n = 30). A universal resin composite (Filtek Z250, 3M/ESPE) was bonded to each specimen using one of the following three cements: Calibra (Dentsply), Panavia F2 (kurary) and Unicem (3M/ESPE). Specimens were thermal cycled and stored in one of the following three media for two weeks: water at pH = 7, saliva at pH = 7 and saliva at pH = 3.5. The mean shear bond strength of each group was analyzed using the Kruskal-Wallis test (alpha = 0.05). The modes of failure were recorded using a streomicroscope. All specimens in the Calibra groups showed premature debonding. No significant difference was found between the two other cements or different media. The failure modes in the two latter cements were predominantly adhesive. Despite the adverse effect of acidic media on the properties of restorative materials, the media did not significantly influence the bond strength of MDP-containing resin cement and a self-adhesive cement to a zirconia- based ceramic.

Comparison of two techniques for evaluation of coronal leakage along of a glass fiber post.

OBJECTIVE: Contradictory results have been reported over microleakage studies of restorative materials and methods. Despite the number of publications on leakage there are few evidences comparing the different microleakage evaluation methods. The purpose of the present study was to compare the clearing technique and longitudinal sectioning in the evaluation of dye penetration along a glass fiber post. MATERIALS AND METHODS: Fifteen single-rooted human teeth were endontically prepared and obturated with gutta percha points and a resin based sealer (AH26). A glass fiber post (Glassix) was cemented into each post space with a dual polymerizing resin cement (Varilink II) and the composite core (Tetric Ceram) was fabricated. Specimens were immersed in Indian ink solution for 72 hours after completion of 1500 cycles of thermal cycling. Then demineralized, cleared and evaluated for the deepest length of dye penetration using a stereomicroscope. Specimens were then cut longitudinally and the length of penetration was measured again by the same instrument. The mean difference of the penetrated length was analyzed by two methods using the paired t test and an analysis of correlation (α = 0.05). RESULTS: No significant difference was found in the mean microleakage measured by the two methods (P= 0.07). Significant correlation was found between them (P=0.0001, r= 0.9) CONCLUSION: The clearing technique and longitudinal sectioning showed the same results in microleakage of Glassix post and composite core within the limitation of the present study.