RESUMEN
PURPOSE: The purpose of this study was to compare the three-dimensional accuracy of indirect plastic impression copings and direct implant-level impression copings from three implant systems (Nobel Biocare [NB], Biomet 3i [3i], and Straumann [STR]) at three interimplant buccolingual angulations (0, 8, and 15 degrees). MATERIALS AND METHODS: Two-implant master models were used to simulate a three-unit implant fixed partial denture. Test models were made from Impregum impressions using direct implant-level impression copings (DR). Abutments were then connected to the master models for impressions using the plastic impression copings (INDR) at three different angulations for a total of 18 test groups (n = 5 in each group). A coordinate measuring machine was used to measure linear distortions, three-dimensional (3D) distortions, angular distortions, and absolute angular distortions between the master and test models. RESULTS: Three-way analysis of variance showed that the implant system had a significant effect on 3D distortions and absolute angular distortions in the x- and y-axes. Interimplant angulation had a significant effect on 3D distortions and absolute angular distortions in the y-axis. Impression technique had a significant effect on absolute angular distortions in the y-axis. With DR, the NB and 3i systems were not significantly different. With INDR, 3i appeared to have less distortion than the other systems. Interimplant angulations did not significantly affect the accuracy of NBDR, 3iINDR, and STRINDR. The accuracy of INDR and DR was comparable at all interimplant angulations for 3i and STR. For NB, INDR was comparable to DR at 0 and 8 degrees but was less accurate at 15 degrees. CONCLUSIONS: Three-dimensional accuracy of implant impressions varied with implant system, interimplant angulation, and impression technique.
Asunto(s)
Materiales de Impresión Dental , Técnica de Impresión Dental , Dentadura Parcial Fija , Modelos Dentales , Resinas Sintéticas , Pilares Dentales , Humanos , Plásticos , PolivinilosRESUMEN
STATEMENT OF PROBLEM: In badly damaged teeth and teeth with short clinical crown heights, the placement of foundation restorations has been advocated to permit the development of retention and resistance form. However, there is little information on the effect of these foundation restorations on the clinical performance of the definitive restoration. PURPOSE: The purpose of this study was to evaluate the load fatigue performance of teeth restored with posts and cores, with varying tooth heights, and to compare them with similar groups having no posts and cores. A secondary purpose was to determine whether a critical tooth height existed at which the placement of a foundation restoration resulted in no significant difference in the load fatigue performance. MATERIAL AND METHODS: Three test groups (n=10) with prepared tooth heights of 2, 3, and 4 mm were tested. These were compared with another 3 groups with similar tooth heights that were restored with prefabricated titanium posts and core heights of 4, 3, and 2 mm, respectively. Cast complete crowns were then fabricated and cemented with zinc phosphate cement. A fatigue load of 58.8 N was applied at an angle of 135 degrees to the long axis of each crown-tooth specimen. The number of cycles to preliminary failure was determined. Significant differences in cycles to preliminary failure were assessed with 1-way ANOVA, followed by Tukey HSD tests (α=.05). RESULTS: The group with the greatest preparation height (4 mm) and a 2-mm post-retained foundation had the highest number of cycles to preliminary failure (437,701), while the group with the shortest preparation height and no foundation had the lowest number of cycles (53,806). The Tukey HSD multiple comparison tests showed that for all 3 tooth heights, groups with foundation restorations had a significantly higher number of cycles to preliminary failure than those without foundation restorations. CONCLUSIONS: For a given tooth height, teeth restored with foundation restorations had a significantly better load fatigue performance than those with no foundation restoration.
Asunto(s)
Coronas , Restauración Dental Permanente/métodos , Análisis del Estrés Dental , Técnica de Perno Muñón , Corona del Diente/patología , Preparación Protodóncica del Diente/métodos , Diente no Vital/terapia , Análisis de Varianza , Diente Premolar , Fuerza de la Mordida , Aleaciones Dentales , Humanos , Estadísticas no ParamétricasRESUMEN
STATEMENT OF PROBLEM: Resin cements have gained popularity over the past few years because of their improved physical properties. There is a need to test these cements under fatigue loading, as there is growing recognition that fatigue testing is more clinically relevant than traditional monotonic static tests. PURPOSE: This study investigated the load-fatigue performance of complete gold crowns cemented with 4 types of resin cement. MATERIAL AND METHODS: Four resin cements (C & B Opaque [CBO], Calibra Esthetic [CE], RelyX Unicem [RU], and Panavia F [PF]) and a control, zinc phosphate cement (HY-Bond [HBZPC]) were tested. Fifty human maxillary premolars were prepared to an occluso-cervical dimension of 4 mm and a convergence angle of 20 degrees. Complete gold crowns were cast (Strator 3) and cemented with 1 of the 5 cements (n=10). A fatigue load of 73.5 N was applied at an angle of 135 degrees to the long axis of each tooth-crown specimen. Preliminary failure was defined as the propagation of a crack in or around the crown luting cement layer. The number of cycles to preliminary failure and the cement failure location were determined. Significant differences in cycles to preliminary failure were assessed by the nonparametric Kruskal-Wallis test, with follow-up Mann-Whitney tests (alpha=.05). RESULTS: Group CE had the highest rank of cycles to preliminary failure, while HBZPC had the lowest cycles to preliminary failure. Group CE had a significantly higher failure cycle count compared to PF (P=.016), RU (P=.001), and HBZPC (P<.001), but was not significantly different from CBO (P=.112). There was no significant difference in the failure cycle count between RU and HBZPC (P=.070). CONCLUSION: Not all tested resin cements had a superior fatigue life when compared with zinc phosphate cement. Of the 4 resin cement groups, Groups CE, CBO, and PF were significantly superior to HBZPC.