IADR Abstract Archives
Retention Durability of One-Retainer Versus Two-Retainer Posterior RBFDPs
Objectives: To evaluate the effect of different preparation/framework designs on the retention of monolithic zirconia posterior RBFDPs replacing premolars.
Methods: Extracted caries-free human premolars and third molars were embedded in autocuring resin to create models with an edentulous space of premolar width (7.5 mm). Abutment teeth were prepared according to six groups (n=8): NU1, one upper-molar retainer with narrow rest; NU2, two upper retainers with narrow rests; WU1, one upper-molar retainer with wide rest; WU2, two upper retainers with wide rests; WL1, one lower-molar retainer with wide rest; WL2, two-retainers with wide rests. RBFDPs were milled from monolithic zirconia (KATANA Zirconia HT), and were adhesively bonded using Panavia V5 with corresponding primers. RBFDPs underwent thermodynamic loading (49N, 1,200,000 cycles, 0.3 mm horizontal movement). The loading point was located at the 30°-buccal slope, 1 mm from the buccal cusp and 2 mm from the central fissure of the pontic. Debonding was performed with 1 or 2 wire loops applied interproximally between the tooth/teeth and the pontic basis in a universal testing machine at a crosshead speed of 2 mm/min. The tensile force required for the failure (debonding or fractures) was recorded. Failure modes were evaluated using a microscope. The data distribution was tested by Shapiro-Wilk and analyzed by three-way ANOVA.
Results: Survival rate after chewing simulator were 75% for NU1 group and 100% for all other groups. The tensile force ranged from 310±224 N (NU1) to 927±292 N (NU2). Two-retainer designs failed at significantly higher tensile forces than designs with one retainer (p≤0.05). There were no significant differences between upper and lower designs or rest widths.
Conclusions: Although RBFDPs with two retainers withstood higher debonding forces, RBFDPs with one retainer have also a high potential for a clinical treatment because of the high debonding forces measured here.
Methods: Extracted caries-free human premolars and third molars were embedded in autocuring resin to create models with an edentulous space of premolar width (7.5 mm). Abutment teeth were prepared according to six groups (n=8): NU1, one upper-molar retainer with narrow rest; NU2, two upper retainers with narrow rests; WU1, one upper-molar retainer with wide rest; WU2, two upper retainers with wide rests; WL1, one lower-molar retainer with wide rest; WL2, two-retainers with wide rests. RBFDPs were milled from monolithic zirconia (KATANA Zirconia HT), and were adhesively bonded using Panavia V5 with corresponding primers. RBFDPs underwent thermodynamic loading (49N, 1,200,000 cycles, 0.3 mm horizontal movement). The loading point was located at the 30°-buccal slope, 1 mm from the buccal cusp and 2 mm from the central fissure of the pontic. Debonding was performed with 1 or 2 wire loops applied interproximally between the tooth/teeth and the pontic basis in a universal testing machine at a crosshead speed of 2 mm/min. The tensile force required for the failure (debonding or fractures) was recorded. Failure modes were evaluated using a microscope. The data distribution was tested by Shapiro-Wilk and analyzed by three-way ANOVA.
Results: Survival rate after chewing simulator were 75% for NU1 group and 100% for all other groups. The tensile force ranged from 310±224 N (NU1) to 927±292 N (NU2). Two-retainer designs failed at significantly higher tensile forces than designs with one retainer (p≤0.05). There were no significant differences between upper and lower designs or rest widths.
Conclusions: Although RBFDPs with two retainers withstood higher debonding forces, RBFDPs with one retainer have also a high potential for a clinical treatment because of the high debonding forces measured here.