Effect of Preparation Design on the Fracture Resistance of Partial Laminate Veneers. An In-vitro Study

Objectives. To evaluate the effect of two preparation designs of partial laminate veneers on the fracture resistance of anterior teeth with full and half incisal edge fracture. Materials and Methods. 48 upper central incisors were divided into four equal groups: two groups simulated completely fractured incisal edge: Group (Full/Cham): with chamfer design and Group (Full/Bev): with bevel design and two groups simulated half fractured incisal edge: Group (Half/Cham): with chamfer design and Group (Half/Bev): with bevel design. Lithium disilicate partial veneers were constructed and cemented using light-curing resin cement. All samples were mounted on universal testing machine to test their fracture resistance. Fractured samples were categorized as restorable or non-restorable based on the crack/fracture extension relative to the cemento-enamel junction. Results. Group (Full/Cham): (361.05 ± 11.39 N) had significantly the highest fracture resistance, followed by Group (Full/Bev): (207.1 ± 10.85 N), while Group (Half/Cham): (123.16 ± 6.63 N) and Group (Half/Bev): (123.75 ± 6.12 N) had significantly the lowest values with insignificant difference between them. All teeth with half incisal edge fracture revealed restorable fractures, while with full incisal edge fracture the percentage dropped to third (33.3%). Conclusions. In full incisal edge fractures, chamfer design had better fracture resistance than bevel design. While in half incisal edge fractures, both designs had similar fracture resistance and restorable mode of failure. Clinical Relevance. The innovative chamfer and bevel designs of partial laminate veneers can be used as a highly conservative approach to restore anterior teeth with full or half fractured incisal edge.