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Histologic and histomorphometric evaluation of peri-implant bone of immediate or delayed occlusal-loaded non-splinted implants in the posterior mandible – an experimental study in monkeys

Authors

  • Rie Stokholm,

    Corresponding author
    1. Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University, Aarhus, Denmark
    • Corresponding author:

      Rie Stokholm, PhD student

      Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University

      Vennelyst Boulevard 9, DK- 8000 Aarhus C, Denmark

      Tel.: +45 87 168 098

      Fax: + 45 86 196 029

      e-mail: rie.stokholm@odontologi.au.dk

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  • Flemming Isidor,

    1. Section of Prosthetic Dentistry, Department of Dentistry, Aarhus University, Aarhus, Denmark
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  • Jens R. Nyengaard

    1. Stereology and Electron Microscopy Laboratory, Centre for Stochastic Geometry and Advanced Bioimaging, Aarhus University, Aarhus, Denmark
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Abstract

Objectives

The primary aim of this study was to compare the bone reaction around immediate-loaded non-splinted single implants vs. delayed loaded non-splinted single implants placed in healed ridges in the posterior mandible.

Materials and methods

Six adult Macaca Fascicularis monkeys were used in this study. The first and second premolars and the first molar were extracted in both sides of the mandible. After 3 months of healing, four implants (Replace Select Tapered; Nobel Biocare, Gothenburg, Sweden) with a moderately rough surface (TiUnite, Nobel Biocare) were placed in the edentulous areas of each monkey, two in each side. The implants had a length of 10 mm and a diameter of 3.5 mm. Four groups of varying time and occlusal loading aspects were created: (i) control group: implant placed non-loaded for 3 months; (ii) immediate loaded: implant placed and loaded immediately for 3 months; (iii) immediate loaded: implant placed and loaded immediately for 6 months; and (iv) delayed loaded: implant placed submerged for 3 months and then loaded for 3 months. At the loaded implants, after a second stage surgery, a composite crown was made directly on an abutment mounted on the implant reinsuring simultaneous occlusal contact on the implant crown and the neighboring teeth. After euthanization of the animals, histologic specimens were quantified in the light microscope.

Results

All implants were clinically, radiographically, and histologically osseointegrated at the time of euthanization and with only mild signs of inflammation in the peri-implant mucosa. The histologic marginal bone level was located on average 1.14–1.74 mm apical to the margin of the implants in the various groups. The average bone-to-implant contact (BIC) varied between 55% and 65% and the average bone density (i.e., the proportion of mineralized bone tissue from the implant surface and to a distance of 1 mm lateral to the implant) varied between 30.6% and 34.2%. No statistical significant differences between groups were observed in the above-stated histomorphometric parameters.

Conclusions

Similar histologic and histomorphometric findings were observed in immediately and delayed loaded non-splinted implants placed in the posterior mandible of macaque monkeys.

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