Marginal Accuracy of Ceramic Veneer Alloy Related to Different Alloy Fabrication Techniques, Ceramic Veneering Methods, Stages, and Sites of Fabrication.

Objectives:  Fabrication processes affect accuracy of restoration. This study compared marginal accuracy of ceramic veneer metal upon different metal substructure fabrication techniques, ceramic veneering methods, stages, and sites of restoration.

Material and methods:  A prepared premolar metal abutment was used to fabricate 96 metal substructures from 4 techniques: cast metal with traditionally impressed tooth (CmTt), cast metal with digitally milled wax (CmDw), sintered metal with digitally impressed tooth (SmDt), and sintered metal with digitally impressed stone model (SmDm). As-cast (A) substructures were degassed (D), opaqued (O), and contoured (C) with porcelain layering (Pl) or press-on (Pp) methods and glazed (G). Marginal fit was measured at A, D, O, C, and G stages, on buccal (Bu), lingual (Li), mesial (Me), and distal (Di) sites using silicone replica.

Statistical analysis:  Analysis of variance and Bonferroni test were analyzed for significant differences of marginal fit upon different factors (α = 0.05).

Results:  Significantly different accuracy was found upon metal substructures fabrication technique, veneering methods, stages, and sites of restoration (p < 0.05). SmDt and SmDm revealed significantly better accuracy than CmTt and CmDw (p < 0.05). Pp generated significantly better accuracy than Pl (p < 0.05). Significant increasing inaccuracy was found at D stage (p < 0.05). Me and Di sites exhibited larger inaccuracy than Bu and Li sites (p < 0.05). However, marginal inaccuracy for all groups was under clinically acceptable marginal fit.

Conclusions:  Increasing marginal inaccuracies upon stages of fabrication were noticed, with highly observed at the proximal site. Sintered metal provided better accuracy than cast metal, while press-on veneering generated better accuracy than the layering method. Porcelain press-on sintered metal was suggested for fabrication restoration.