Van Assche Nele, Collaert Bruno, Coucke Wim, Quirynen Marc
Department of periodontology, Catholic University Leuven, Leuven, Belgium.
J Clin Periodontol. 2008 Jan;35(1):76-9. doi: 10.1111/j.1600-051X.2007.01158.x.
This retrospective study aimed to determine the consequence of early cover screw exposure on peri-implant marginal bone level.
Sixty Astra Tech MicroThread implants installed in partially edentulous jaws were compared: 20 implants were placed following a two-stage procedure and were unintentionally exposed to the oral cavity (two-stage exposed), 20 implants were placed following a two-stage procedure and were surgically exposed after a subgingival healing time of 3-6 months (two-stage submerged), and 20 implants were placed following a one-stage surgical protocol (one-stage). Digital radiographs were taken at implant placement for all implants, and after abutment surgery for the two-stage exposed and two-stage submerged groups or after 3 months for the one-stage group. Bone loss mesially and distally was measured with an on-screen cursor after calibration.
Mean bone re-modelling was 1.96 mm (range: 0.2-3.2 mm) around the two-stage exposed implants, 0.01 mm (range: 0.0-0.3 mm) around the two-stage submerged implants and 0.14 mm (range: 0.0-1.2 mm) around the one-stage implants.
The unintentional perforation of two-stage implants resulted in significant bone destruction, probably because the biological width was not considered.
