A comparative study between replica and cementation techniques in the evaluation of internal and marginal misfits of single crowns.

STATEMENT OF PROBLEM: Systematic reviews about the internal and marginal misfits of fixed prostheses have identified a limited number of clinical studies, suggesting the need for further research on the subject. Although the replica technique has been described as suitable for this purpose, few studies have validated it. PURPOSE: The purpose of this in vitro study was to compare the ability of a nondestructive replica technique and a destructive cementation technique to assess internal and marginal misfits of zirconia copings, considering current materials and designs. MATERIAL AND METHODS: Twelve anatomic prefabricated abutments (Neodent) were used to manufacture zirconia copings following the Ceramill (Amann Girrbach AG) (n=6) and Lava (3M ESPE) (n=6) systems. Replications of the cementation line were obtained with polyvinyl siloxane for the replica technique, and the copings were then cemented and sectioned to obtain 5 surfaces (buccal, palatal, mesial, distal, and incisal) and the linear and angle regions (internal axiogingival and axioincisal angles). The thickness of the cement line and silicone film was measured at 45 reference points on each abutment. A total of 540 measurements were made with an optical microscope with a digital camera at magnifications of x100 and x200. Data were analyzed by repeated-measures ANOVA and the Bonferroni multiple comparison tests (alpha=.05). RESULTS: In the internal misfit evaluation, the mean values observed for the cementation technique and replica technique were as follows: angle regions, 70.6 mum and 72.2 mum; linear regions, 59.1 mum and 59.6 mum; incisal surface, 139.0 mum and 139.8 mum; buccal surface, 72.4 mum and 73.8 mum; palatal surface, 73.1 mum and 75.2 mum; mesial surface, 74.1 mum and 73.8 mum; distal surface, 75.0 mum and 76.3 mum; and overall mean, 73.6 mum and 74.8 mum, respectively. In the evaluation of the marginal misfit, the mean values found were: buccal surface, 36.7 mum and 37.8 mum; palatal surface, 37.5 mum and 36.8 mum; mesial surface, 44.0 mum and 43.7 mum; and distal surface, 44.6 mum and 45.2 mum, respectively. No significant differences were found between the 2 techniques for all locations and systems (P>.05). CONCLUSIONS: Within the limitations of this in vitro study, both techniques presented the same ability to assess the internal and marginal misfits when the location and overall mean averages were evaluated (P>.05).