The Effect of Preparation Design and Thermal Cycling on the Marginal Accuracy of Hybrid Ceramic Laminate Veneers

Aim: This study investigated the effect of preparation design and thermal cycling on the marginal accuracy of hybrid ceramic laminate veneers.Materials and Methods: A total of twenty 3D printed dies of central incisors prepared with 2 preparation designs; butt joint and palatal wrap design were fabricated.Each type of preparation was assigned into 2 subgroups (n=5/ each subgroup) according to the type of material used for fabrication of the laminate veneer; hybrid ceramic and lithium disilicate (served as control).Marginal discrepancy was evaluated using a digital microscope before and after thermocycling.Results: Statistically analysis of marginal gaps revealed that before thermocycling, butt joint design demonstrated larger average marginal gaps compared to palatal wrap design in both Enamic (76.18±0.07)and E-max (76.11±0.09µm).While smaller gaps was recorded in palatal wrap design E-max (63.27±0.28µm) and Enamic (63.21±0.05).After thermocycling, palatal wrap design showed larger average marginal gaps in E-max (166.75 ±16.67 µm) and Enamic (157.52±15.44);while a significantly lower gap was recorded in butt joint design for Enamic (137.41±0.2) and E-max (137.41±0.09µm).There was no statistical significant difference between marginal gaps in Emax and Enamic within the same preparation design.Conclusion: Before thermocycling, the palatal wrap design laminate veneers showed smaller marginal gaps compared to butt joint.Thermalcycling caused a detrimental increase in marginal gaps .The effect of thermocycling was more profound on palatal wrap design veneers.The marginal accuracy of hybrid ceramic laminate veneers were statistically comparable to that of lithium disilicate.