Effect of Circumferential and Axial Grooves on the Retention of Provisionally Cement-Retained Implant-Supported Crowns (In Vitro Study)

Abstract

Introduction: Retention of provisionallycemented implant-supported restorations plays an important role in success of the treatment. Uncementedrestorations may cause several problems such as restoration swallowing, increased bone loss and prosthesis failure. Therefore, suitable cementcompromising between retention and retrievability as well as extra-means of abutment retention might be preferable for durable implantrestorations.Objectives: This study introduced circumferential and axial grooves on implant abutments as retentive promoters and evaluated their effect on theretention of crown copings cemented to implant abutments with provisional luting cements.Materials and methods: Twenty straight titanium implant abutments were divided into 4 groups (n=5): without grooves, with 1 axial groove, with2 circumferential grooves, and with 3 circumferential grooves. Twenty nickel chromium crown copings were fabricated to fit all 20 abutments. Thecopings were cemented to each group of abutments with non-eugenol provisional cement. After storage for 24 hours in 100% humidity at 37°C,specimens were subjected to 500 cycles of thermal cycling, then 5000 cycles of compressive load to simulate the thermal and mechanical stresses inthe oral environment. Tensile strengths were conducted with a universal testing machine and tensile stresses were recorded in Newton. After theretention test, the copings and abutments were evaluated for cement failure mode with Stereoscopic Microscope. Collected data were analyzedusing one-way analysis of variance (ANOVA) and Tukey’s HSD tests (α=.05).Results: The mean tensile strength of the three circumferential grooves was significantly higher than the other groups (P<0.001) while there was nosignificant difference between the axial groove and control group (P=0.999). The cement failure mode was generally adhesive in nature, althoughsome mixed failures were observed.Conclusion The surface modification of an implant abutment by means of circumferential grooves was found to be an effective method ofimproving the retention of crown copings cemented with non-eugenol cement.