Influence of microgap location and configuration on radiographic bone loss around submerged implants: an experimental study in dogs.
OBJECTIVE
The vertical location of the implant-abutment connection influences the subsequent reaction of the peri-implant bone. It is not known, however, whether any additional influence is exerted by different microgap configurations. Therefore, the radiographic bone reactions of two different implant systems were monitored for 6 months.


METHODS
In eight mongrel dogs, two implants with an internal Morse-taper connection (INT group) were placed on one side of the mandible; the contralateral side received two implants with an external-hex connection (EXT group). On each side, one implant was aligned at the bone level (equicrestal) and the second implant was placed 1.5 mm subcrestal. Healing abutments were placed 3 months after submerged healing, and the implants were maintained for another 3 months without prosthetic loading. At implant placement and after 1, 2, 3, 4, 5, and 6 months, standardized radiographs were obtained, and peri-implant bone levels were measured with regard to microgap location and evaluated statistically.


RESULTS
All implants osseointegrated clinically and radiographically. The overall mean bone loss was 0.68 ± 0.59 mm in the equicrestal INT group, 1.32 ± 0.49 mm in the equicrestal EXT group, 0.76 ± 0.49 mm in the subcrestal INT group, and 1.88 ± 0.81 mm in the subcrestal EXT group. The differences between the INT and EXT groups were statistically significant (paired t tests). The first significant differences between the internal and external groups were seen at month 1 in the subcrestal groups and at 3 months in the equicrestal groups. Bone loss was most pronounced in the subcrestal EXT group.


CONCLUSIONS
Within the limits of this study, different microgap configurations can cause different amounts of bone loss, even before prosthetic loading. Subcrestal placement of a butt-joint microgap design may lead to more pronounced radiographic bone loss.
Department of Prosthodontics, Propaeduetics and Dental Materials, School of Dentistry, Christian-Albrechts-University at Kiel, Germany. dw@max-17.de
Dietmar
D
Weng
Maria Jose Hitomi
MJ
Nagata
Alvaro Francisco Hitomi
AF
Bosco
Luiz Gustavo Nascimento
LG
de Melo
D016301:Alveolar Bone Loss / Q000000981:diagnostic imaging*; D000539:Alveolar Process / Q000000981:diagnostic imaging; D000818:Animals; D001641:Bicuspid; D000044:Dental Abutments; D059605:Dental Implant-Abutment Design; D015921:Dental Implants; D018772:Dental Marginal Adaptation; D017267:Dental Prosthesis Design; D004285:Dogs; D008334:Mandible / Q000000981:diagnostic imaging / Q000601:surgery; D008963:Molar; D016348:Osseointegration / Q000502:physiology; D010027:Osteotomy / Q000379:methods; D011859:Radiography; D013499:Surface Properties; D013997:Time Factors; D020390:Tooth Socket / Q000000981:diagnostic imaging / Q000601:surgery
D015921:Dental Implants