Hybrid-abutment-restoration: effect of material type on torque maintenance and fracture resistance after thermal aging

Abstract

Purpose: To evaluate the tightening torque maintenance with zirconia, lithium disilicate, and polyetheretherketone (PEEK) hybrid-abutment-crowns after thermal aging, in addition to assess the fracture resistance of hybridabutment-crowns fabricated with different materials. Materials and methods: Thirty implants were restored with identical hybrid-abutment-crowns, resembling the maxillary first premolar, fabricated from zirconia (Zr), lithium disilicate (L2), or ceramic-reinforced PEEK (PE). The three groups (n = 10) were constructed utilizing a Ti-base. After bonding, each restoration was secured in its respective implant with a torque of 25 Ncm. All restorations were subjected to thermal aging for 7000 cycles. The loosening torque was assessed utilizing the digital torque meter. Each restoration was subjected to fracture testing and the mode of failure was determined. Results: Zr group displayed the highest mean torque loss value (2.70 ± 0.59 Ncm) with the mean loosening torque value of 22.38 ± 0.68 Ncm. PE group displayed the lowest mean torque loss (2.55 ± 0.50 Ncm) with mean loosening torque value of 22.61 ± 0.59 Ncm. There was no significant difference between study groups regarding loosening torque (p = 0.68), torque loss (p = 0.80), and percentage of torque loss (p = 0.79). There was significant difference regarding the mean fracture load value between Zr and PE groups. However, there was no significant difference (p = 0.05) regarding mean fracture load value between L2 and PE groups. Conclusion: The hybrid-abutment-crown material does not affect the torque maintenance after thermal aging. Based on fracture load, zirconia hybrid-abutment-crown can be used, while lithium disilicate and PEEK hybridabutment-crowns may cautiously serve in premolar region.

Titanium Base Abutments in Implant Prosthodontics: A Literature Review

“…Zirconia crowns with titanium base were found to have higher fracture resistance than other materials, and they could be used in the premolar area. 45 Adolfi et al 44 assessed the fracture resistance of two different designs of assembling screw-retained zirconia crowns to titanium bases. In the first design, the titanium bases were cemented to the zirconia crowns using resin cement; in the second design, the zirconia crowns were fixed to titanium bases through a hexagonal connection notched in both the crowns and titanium bases.…”

“… 44 In a recent study, the amount of torque loss of titanium bases was evaluated after being bonded to zirconia, lithium disilicate, or polyetheretherketone restorations, 45 and the material of the superstructure was found to have no significant effect on the amount of torque loss. 45 …”

“…24 Several studies have investigated the effect of introducing titanium base abutments into implant-supported restorati ons. 24,27,[39][40][41][42][43][44][45] Different designs of zirconia abutments, including one-piece anatomic contour zirconia abutments and zirconia abutments with titanium inserts, have been examined for fracture strength tests after screwing them to titanium alloy implants with a regular diameter (4.1 mm). 24 Zirconia abutments with titanium inserts were found to have a remarkable increase in fracture resistance compared with the one-piece zirconia.…”

“…The authors reported that the amount of torque loss, stress concentration, and vertical misfit decreased significantly in the cement-retained restorations compared with the notched-retained restorations. 44 In a recent study, the amount of torque loss of titanium bases was evaluated after being bonded to zirconia, lithium disilicate, or polyetheretherketone restorations, 45 and the material of the superstructure was found to have no significant effect on the amount of torque loss. 45 Based on the aforementioned studies, the internal and marginal fit of titanium base abutments had comparable outcomes with other fabrication techniques.…”

“…44 In a recent study, the amount of torque loss of titanium bases was evaluated after being bonded to zirconia, lithium disilicate, or polyetheretherketone restorations, 45 and the material of the superstructure was found to have no significant effect on the amount of torque loss. 45 Based on the aforementioned studies, the internal and marginal fit of titanium base abutments had comparable outcomes with other fabrication techniques. However, the cement-retained restorations using titanium base abutments could have a better fit and less generated stress than the screw-retained restorations.…”