Complication incidence of two implant systems up to six years: a comparison between internal and external connection implants.
OBJECTIVE
This study was conducted to compare the cumulative survival rates (CSRs) and the incidence of postloading complications (PLCs) between a bone-level internal connection system (ICS-BL) and an external connection system (ECS).


METHODS
The medical records of patients treated with either a ICS-BL or ECS between 2007 and 2010 at Asan Medical Center were reviewed. PLCs were divided into two categories: biological and technical. Biological complications included >4 mm of probing pocket depth, thread exposure in radiographs, and soft tissue complications, whereas technical complications included chipping of the veneering material, fracture of the implant, fracture of the crown, loosening or fracture of the abutment or screw, loss of retention, and loss of access hole filling material. CSRs were determined by a life-table analysis and compared using the log-rank chi-square test. The incidence of PLC was compared with the Pearson chi-squared test.


RESULTS
A total of 2,651 implants in 1,074 patients (1,167 ICS-BLs in 551 patients and 1,484 ECSs in 523 patients) were analyzed. The average observation periods were 3.4 years for the ICS-BLs and 3.1 years for the ECSs. The six-year CSR of all implants was 96.1% (94.9% for the ICS-BLs and 97.1% for the ECSs, P=0.619). Soft tissue complications were more frequent with the ECSs (P=0.005) and loosening or fracture of the abutment or screw occurred more frequently with the ICS-BLs (P<0.001).


CONCLUSIONS
Within the limitations of this study, the ICS-BL was more prone to technical complications while the ECS was more vulnerable to biological complications.
Department of Periodontics, Asan Medical Center, Seoul, Korea.
Sung-Wook
0000-0002-7122-9692
SW
Chae
Department of Periodontics, Asan Medical Center, Seoul, Korea. ; Department of Dentistry, University of Ulsan College of Medicine, Seoul, Korea.
Young-Sung
0000-0003-2674-3649
YS
Kim
Department of Periodontology, Dental Research Institute, Seoul National University School of Dentistry, Seoul, Korea.
Yong-Moo
0000-0002-5619-3847
YM
Lee
Department of Periodontics, Asan Medical Center, Seoul, Korea.
Won-Kyung
0000-0003-2557-1646
WK
Kim
Department of Periodontics, Asan Medical Center, Seoul, Korea.
Young-Kyoo
0000-0001-7065-282X
YK
Lee
Department of Periodontics, Asan Medical Center, Seoul, Korea. ; Department of Dentistry, University of Ulsan College of Medicine, Seoul, Korea.
Su-Hwan
0000-0002-3431-453X
SH
Kim
Dental implant-abutment design; Dental implants; Retrospective studies; Survival rate