The Role of Abutment Preparation Strategies in Optimizing the Bond Strength of Resin-Bonded Fixed Partial Dentures: An In Vitro Study

Introduction Prosthodontics has increasingly embraced minimally invasive techniques, with resin-bonded fixed partial dentures (RBFPDs) offering a conservative solution for anterior tooth replacement. The success of RBFPDs depends on the durability of the bond between the retainer and abutment, which might be influenced by tooth preparation design. This study aimed to compare the shear bond strength of RBFPDs across four abutment preparation designs to identify the optimal configurations for enhanced retention. Materials and methods This in vitro study was conducted at the Educare Institute of Dental Sciences in Malappuram, India. Forty acrylic samples, each with one maxillary central incisor and one canine, were divided into four groups (n = 10): Group A (control: 0.5 mm lingual reduction with chamfer), Group B (tram-line: three grooves, two lingual, one facio-proximal), Group C (lingual rest seat with one distolingual groove), and Group D (two vertical parallel grooves). Acrylic blocks were fabricated using standardized wax molds, and tooth preparation was performed using a diamond bur. Metal dies and cobalt-chromium retainers (Wironit, Bego, Bremen, Germany) were cast, abraded with 50 µm aluminum oxide, and cemented with a resin cement (Dentsply Sirona, Charlotte, NC, USA). The shear bond strength was tested using a universal testing machine (Instron 5944, Instron Corporation, Norwood, MA, USA) at 1 mm/min, with values recorded in Newtons (N). Statistical analysis was performed using one-way ANOVA and the post hoc Tukey test (p < 0.05). Results One-way ANOVA revealed significant differences in bond strength (p < 0.001). Group B exhibited the highest mean bond strength (370.49 ± 27.24 N), followed by Group D (273.19 ± 23.03 N), with Groups A (147.44 ± 9.46 N) and C (156.18 ± 9.66 N) showing lower, comparable values. Post hoc tests confirmed Group B's superiority (p < 0.001), with no significant difference between Groups A and C (p = 0.055). Conclusions The tram-line preparation significantly enhanced RBFPD retention, followed by the dual-groove design, supporting their use in conservative prosthodontics. Further in vivo studies are required to validate its clinical applicability.