Fracture resistance of maxillary premolar veneers using various preparation designs

PURPOSE: Veneers for maxillary premolars are commonly included in treatment plans for patients with a wide smile who request enhancement of all teeth in the smile zone. However, limited data are available regarding the influence of different premolar veneer designs on fracture resistance. Therefore, this in vitro study aimed to evaluate and compare the fracture resistance of maxillary premolar veneer preparations with feather-edge (FeV), butt-joint (BuV), preparation extending to the central groove (CeV), and conventional full-coverage crowns (FC) as the control. MATERIALS AND METHODS: Four maxillary right first premolar typodont teeth were prepared: three for veneer designs (FeV, BuV, and CeV) and one for a full-coverage crown (FC). A total of 60 restorations (n = 15 per group) were milled from lithium disilicate and cemented to printed dies. All restorations underwent artificial aging with 10,000 thermal cycles between 5°C and 55°C, followed by load-to-fracture testing. Fracture resistance values were recorded. Statistical comparisons were performed using one-way ANOVA with Tukey post hoc tests (α = 0.05). In addition, fracture patterns were evaluated descriptively using scanning electron microscope images. RESULTS: Fracture resistance differed significantly among the veneer and crown groups (p < 0.05). Among the veneers, CeV demonstrated the highest fracture resistance (668 N), followed by BuV (531 N), while FeV showed the lowest values (492 N). The control group (FC) exhibited the highest overall fracture resistance (911 N), exceeding all veneer groups. CONCLUSIONS: Maxillary premolar veneer preparations extending to the central groove demonstrated higher fracture resistance than feather-edge and butt-joint designs. Conventional full-coverage crowns exhibited higher fracture resistance than any veneer design. These findings may guide clinicians in selecting the appropriate veneer preparation design for patients with wide smiles that display premolar teeth.