Influence of the size of the microgap on crestal bone changes around titanium implants. A histometric evaluation of unloaded non-submerged implants in the canine mandible

J. S. Hermann, J. D. Schoolfied, R. K. Schenk, D. Buser, D. L. Cochran

Research output: Contribution to journalArticlepeer-review

300 Scopus citations


Background: Endosseous implants can be placed according to a non-submerged or submerged approach and in 1- or 2-piece configurations. Recently, it was shown that peri-implant crestal bone changes differ significantly under such conditions and are dependent on a rough/smooth implant border in 1-piece implants and on the location of an interface (microgap) between the implant and abutment/restoration in 2-piece configurations. Several factors may influence the resultant level of the crestal bone under these conditions, including movements between implant components and the size of the microgap (interface) between the implant and abutment. However, no data are available on the impact of possible movements between these components or the impact of the size of the microgap (interface). The purpose of this study was to histometrically evaluate crestal bone changes around unloaded, 2-piece non-submerged titanium implants with 3 different microgap (interface) dimensions and between implants with components welded together or held together by a transocclusal screw. Methods: A total of 60 titanium implants were randomly placed in edentulous mandibular areas of 5 hounds forming 6 different implant subgroups (A through F). In general, all implants had a relatively smooth, machined suprabony portion 1 mm long, as well as a rough, sandblasted, and acid-etched (SLA) endosseous portion, all placed with their interface (microgap) 1 mm above the bone crest level and having abutments connected at the time of first-stage surgery. Implant types A, B, and C had a microgap of <10 μm, ∼50 μm, or ∼100 μm between implant components as did types D, E, and F, respectively. As a major difference, however, abutments and implants of types A, B, and C were laser-welded together, not allowing for any movements between components, as opposed to types D, E, and F, where abutments and implants were held together by abutment screws. Three months after implant placement, all animals were sacrificed. Non-decalcified histology was analyzed histometrically by evaluating peri-implant crestal bone changes. Results: For implants in the laser-welded group (A, B, and C), mean crestal bone levels were located at a distance from the interface (IF; microgap) to the first bone-to-implant contact (fBIC) of 1.06 ± 0.46 mm (standard deviation) for type A, 1.28 ± 0.47 mm for type B, and 1.17 ± 0.51 mm for type C. All implants of the non-welded group (D, E, and F) had significantly increased amounts of crestal bone loss, with 1.72 ± 0.49 mm for type D (P <0.01 compared to type A), 1.71 ± 0.43 mm for type E (P <0.02 compared to type B), and 1.65 ± 0.37 mm for type F (P <0.01 compared to type C). Conclusions: These findings demonstrate, as evaluated by non-decalcified histology under unloaded conditions in the canine mandible, that crestal bone changes around 2-piece, non-submerged titanium implants are significantly influenced by possible movements between implants and abutments, but not by the size of the microgap (interface). Thus, significant crestal bone loss occurs in 2-piece implant configurations even with the smallest-sized microgaps (<10 μm) in combination with possible movements between implant components.

Original languageEnglish (US)
Pages (from-to)1372-1383
Number of pages12
JournalJournal of periodontology
Issue number10
StatePublished - 2001


  • Alveolar bone/anatomy and histology
  • Animal studies
  • Dental implants, endosseous/methods
  • Dental implants/anatomy and histology
  • Follow-up studies
  • Titanium
  • Tooth movement

ASJC Scopus subject areas

  • Periodontics

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