Influence of tooth surface roughness and type of cement on retention of complete cast crowns.
ABSTRACT Bond strength of luting cements to dentin is a critical consideration for success of cast restorations.
This study determined the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of respective cemented restorations.
Ninety artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a milling machine on extracted human teeth. Diamond, tungsten carbide finishing, and cross-cut carbide burs of similar shape were used. The crowns in each group were randomly subdivided into three subgroups of 10 for the three luting cements selected for this study: zinc phosphate cement (Fleck's), glass ionomer cement (Ketac-Cem), and adhesive resin cement (Panavia-EX). Retention was evaluated by measuring the tensile load required to dislodge the artificial crowns from tooth preparations with an Instron testing machine.
Analysis of forces with parametric analysis of variance and Tukey's Studentized Range (HSD) disclosed a statistically significant difference for both luting cement and finishing burs (p < 0.001). A statistically significant interaction effect (p < 0.001) was also found. The greatest retention value (372.9 N) was for tooth preparations refined with carbide burs and cemented with Panavia-EX cement. However, the least retention value (201.6 N) was for tooth preparations completed with finishing burs and luted with zinc phosphate cement.
Significant differences were found among all three cements for finishing burs. However, there was a difference only between Panavia-EX cement and the other two cements for tungsten carbide burs. For diamond rotary instruments, zinc phosphate cement was significantly different from glass ionomer and Panavia-EX cements.
Article: Various conditioning methods for root canals influencing the tensile strength of titanium posts.[show abstract] [hide abstract]
ABSTRACT: Conditioning the root canal is frequently advised to achieve high post-retention when resin composite luting cements are used. However, manufacturers' instructions for this purpose differ widely from one another. The aim of this study was to compare the tensile bond strengths of passive, tapered, titanium root posts that were luted with four different resin composite cements (Compolute Aplicap, Flexi-Flow cem, Panavia 21 EX, Twinlook) in the root canals at three conditions, namely (i) no conditioning, (ii) etching with 37% phosphoric acid, and (iii) etching + bonding agent application. Panavia 21 EX was further tested after using the primer for the post-surface according to the manufacturer's recommendations. The posts luted with zinc phosphate cement (Tenet) acted as the control group. Following endodontic preparation of 140 intact anterior teeth with hand instruments, the post-spaces were prepared using the opening drills of the corresponding size of the posts. The samples were first stored in water at 37 degrees C for 24 h and then thermocycled (5000 cycles, 5-55 degrees C, 30 s). The tensile strength values were measured with the universal testing machine at a crosshead speed of 0.5 mm min(-1). The data were analysed statistically using anova and corrected with Scheffé test due to the significance levels (P < 0.05). The tensile bond strengths of the titanium posts after luting with various cements and thermocycling were affected by the conditioning systems used for the root canals. Tensile bond strengths were the highest with Flexi-Flow (475 +/- 78 N) followed in descending order by Panavia 21 EX (442 +/- 97 N), Twinlook (430 +/- 78 N) and Compolute Aplicap (352 +/- 76 N) after conditioning the root canal. The use of primer on the post improved the tensile bond strength compared with the non-conditioned group for the Panavia 21 EX group (375 +/- 77 N) (P < 0.001). Tensile bond strengths obtained after luting the posts with zinc phosphate cement (414 +/- 102 N) were not significantly different (P < 0.05) than those of resin composite cements. Although the importance of conditioning the root canal was evident for Panavia 21 EX, it was not the case for the other luting cements tested.Journal of Oral Rehabilitation 09/2004; 31(9):890-4. · 1.53 Impact Factor
Article: Influence of tooth preparation taper and cement type on recementation strength of complete metal crowns.[show abstract] [hide abstract]
ABSTRACT: Clinical studies have shown that lack of retention is one of the major causes of fixed dental prosthesis failure. The purpose of this study was to determine the relationship between the convergence angle of a complete metal crown tooth preparation and the recementation strength for restorations cemented with conventional and adhesive cements. One hundred twenty artificial crowns were cast for standardized complete metal crown tooth preparations accomplished with the use of a milling machine on extracted human teeth. Three different tapers, 5, 12, and 25 degrees, were used (n=40). The crowns in each group were subdivided into 4 subgroups (n=10) according to the luting cement: zinc phosphate cement (Fleck's), glass ionomer cement (Ketac-Cem), and adhesive resin cements (Panavia 21 and C&B-Metabond). Retention was evaluated by measuring the tensile force required to dislodge the crowns from the tooth preparations in a universal testing machine. Subsequently, the tooth preparations were scraped clean and polished with prophylaxis paste, and the intaglio surfaces of the artificial crowns were ultrasonically cleaned and airborne-particle abraded with 50-mum aluminum oxide powder prior to recementation. The data were analyzed with 3-way repeated-measures ANOVA and Tukey's HSD test (alpha=.05). Analysis of measurements disclosed a significant difference for taper and luting cement (P<.001); however, their interaction was not significant. Also, there was a statistically significant difference between the retention of the first cementation and the second cementation (P<.001). However, the interaction was not significant with taper or cement. Regardless of the taper used, Panavia 21 cement exhibited the highest mean initial retention, but the difference was not significantly different from the recementation retentive strength. Tooth preparation taper and type of luting cement had a direct effect on the recementation strength of complete metal crowns.The Journal of prosthetic dentistry 12/2009; 102(6):354-61. · 1.22 Impact Factor
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ABSTRACT: INTRODUCTION Crown displacement often occurs because the features of tooth preparations do not counteract the forces directed against restorations. OBJECTIVE The purpose of this study was to evaluate the effect of preparation designs on retention and resistance of fixed restorations. METHOD The study was performed on 64 differently sized stainless steel dies. Also, caps which were used for evaluated retention were made of stainless steel for each die. After cementing the caps on experimental dies, measuring of necessary tensile forces to separate cemented caps from dies was done. Caps, which were made of a silver-palladium alloy with a slope of 60° to the longitudinal axis formed on the occlusal surface, were used for evaluating resistance. A sudden drop in load pressure recorded by the test machine indicated failure for that cap. RESULTS A significant difference was found between the tensile force required to remove the caps from the dies with different length (p<0.05) and different taper (p<0.01). The greatest retentive strengths (2579.2 N and 2989.8 N) were noticed in experimental dies with the greatest length and smallest taper. No statistically significant (p>0.05) differences were found between tensile loads for caps cemented on dies with different diameter. Although there was an apparent slight increase in resistance values for caps on dies with smaller tapers, the increase in resistance for those preparation designs was not statistically significant. There was a significant difference among the resistance values for caps on dies with different length (p<0.01) and diameter (p<0.05). CONCLUSION In the light of the results obtained, it could be reasonably concluded that retention and resistance of the restoration is in inverse proportion to convergence angle of the prepared teeth. But, at a constant convergence angle, retention and resistance increase with rising length and diameter.Srpski Arhiv za Celokupno Lekarstvo. 01/2008;