Effect of incisal preparation design on the fracture strength of monolithic zirconia‐reinforced lithium silicate laminate veneers

Abstract

PurposeThis study aimed to assess the fracture resistance of monolithic zirconia‐reinforced lithium silicate laminate veneers (LVs) fabricated on various incisal preparation designs.Materials and methodsSixty maxillary central incisors with various preparation designs were 3D‐printed, 15 each, including preparation for: (1) LV with feathered‐edge design; (2) LV with butt‐joint design; (3) LV with palatal chamfer; and (4) full‐coverage crown. Restorations were then designed and manufactured from zirconia‐reinforced lithium silicate (ZLS) following the contour of a pre‐operation scan. Restorations were bonded to the assigned preparation using resin cement and following the manufacturer's instructions. Specimens were then subjected to 10,000 thermocycles at 5 to 55°C with a dwell time of 30 s. The fracture strength of specimens was then assessed using a universal testing machine at a crosshead speed of 1.0 mm/min. One‐way ANOVA and Bonferroni correction multiple comparisons were used to assess the fracture strength differences between the test groups (α = 0.001). Descriptive fractographic analysis of specimens was carried out with scanning electron microscopy images.ResultsComplete coverage crown and LV with palatal chamfer design had the highest fracture resistance values (781.4 ± 151.4 and 618.2 ± 112.6 N, respectively). Single crown and LV with palatal chamfer had no significant difference in fracture strength (p > 05). LV with feathered‐edge and butt‐joint designs provided significantly (p < 05) lower fracture resistance than complete coverage crown and LV with palatal chamfer design.ConclusionThe fracture resistance of chairside milled ZLS veneers was significantly influenced by the incisal preparation designs tested. Within the limitation of this study, when excessive occlusal forces are expected, LV with palatal chamfer display is the most conservative method of fabricating an indirect restoration.

Clinical Survival Rate and Laboratory Failure of Dental Veneers: A Narrative Literature Review

“…Fracture failures can be amplified by the presence of parafunctional activities [7]; therefore, a night guard is recommended for patients. Dentists need to examine occlusions carefully, especially for any parafunctional habits such as bruxism, before initiating treatment and after cementation of the veneers because an unfavorable occlusion is the leading cause of fracture failure [9].…”

“…Frequently, fractures occur at the cervical onethird because the enamel is thinner, resulting in dentin exposure that may compromise longevity [8]. The causes of fractures in veneers are summarized in Table 1 [7,[9][10][11][12][13][14][15][16][17][18].…”

“…Sharp angles or inadequate tooth reduction; extension of the preparation to the palatal surface [9]; incisal coverage for maxillary canine [14]; not restoring a cavity to obtain a thick cement layer [12]; occlusal/labial thicknesses: labial thicknesses of ultrathin veneers should be 0.5/0.4 mm for premolar teeth [15].…”

“…They also found no significant difference in the failure loads between the window preparation with incisal reduction when compared with the three-quarters veneer preparation design. Jurado et al [9] reported that complete coverage crowns and veneers with palatal chamfers had the highest fracture resistance values. Single crowns and veneers with palatal chamfer showed no significant difference in fracture strength.…”

Ultra-Translucent Zirconia Laminate Veneers: The Influence of Restoration Thickness and Stump Tooth-Shade

“…To ensure the success of zirconia laminate veneers in terms of mechanical properties and esthetic demands, it is crucial to balance their translucency and color matching with natural teeth [13][14][15][16]. Although zirconia ceramics exhibit partial translucency, variations in light transmission have been reported, which can impact the aesthetic outcome [17][18][19].…”