Screw- vs Cement-implant–retained Restorations: An Experimental Study in the Beagle. Part 1. Screw and Abutment Loosening

Abstract

The causes of implant failures can be biological or mechanical. The mechanical causes include fracture of the implant, fracture of the abutment, and loosening of the abutment. Numerous studies show that abutment loosening constitutes one of the marked implant postsurgery complications requiring clinical intervention. The aim of the present study was to evaluate the incidence of the screw loosening in screwed or cemented abutments. Six adult male Beagles were used. In each dog, the first molars and 2 premolars were extracted. The sutures were removed after 7 days. After 3 months, 10 implants were placed in each dog, 5 in the right mandible and 5 in the left mandible. The abutments either were screwed in (n=30) by applying a total strength of 30 N/cm or were cemented (n=30). After 12 months, 8 (27%) loosened screws were present in screwed abutments, whereas no abutment loosening was observed in cemented abutments (P = .0001). Screwed abutments are often submitted to nonaxial loads that determine screw and abutment loosening.

Loosening of the fixing screw in single implant crowns: predisposing factors, prevention and treatment options

“…A clinical‐experimental study of particular interest was performed with dogs, where similar cement‐retained or screw‐retained FDPs were placed bilaterally in the same arch (split‐mouth). After 12 months of clinical function, a loosening of the screw was observed in 27% of screw‐retained restorations and 0% in the cement‐retained . In the same study, it was stated that the proper treatment of the problem is the replacement of the screw.…”

“…The results reported in different studies are contradictory. Some report higher incidence of screw loosening in screw‐retained and others in cement‐retained restorations …”

Mechanism of and factors associated with the loosening of the implant abutment screw: A review

“…These complications mainly include peri‐mucositis, peri‐implantitis, loosening or fracturing of the abutment screw, fracturing of the abutment or superstructure, crown loosening, or porcelain cracking . Among these, the loosening of the abutment screw is one of the most common mechanical complications . The incidence rate of abutment screw loosening reaches 5.3% in the first year after loading, and 5.8%‐12.7% after the 5‐year follow‐up .…”

Effect of luting space and cements on retention of implant supported crowns fabricated by laser sintering

“…[4][5] Although no consensus has been reached regarding the superiority of any method of retention, cement retention is more popular because of lower complication rates and higher fracture resistance of veneering ceramics. [6][7][8][9][10][11] It also offers the advantages of passive fit, improved esthetics, favorable occlusal surface by…”