Crown width/crown length ratio and GW could represent surrogate parameters to anticipate the gingival thickness at the cementoenamel junction, whereas CW/CL might also be an indicator for alveolar bone crest thickness. Periodontal probing has a limited prognostic value for these tissue dimensions.

This study monitored experimental peri‐implant tissue breakdown around hydroxyapatite (HA)‐coated titanium dental implants. Thirty‐two HA‐coated cylindrical implants, in groups of two, were bilaterally inserted in the posterior maxilla and mandible in 4 Macaca mulatta monkeys. Two months after healing‐abutment connection, a 2‐month plaque control program was initiated. Clinical and radiographic recordings and peri‐implant submucosal microbial samples were then obtained (baseline). Cotton ligatures were next placed around the healing‐abutments and plaque control measures were abandoned. Clinical and radiographic recordings were repeated at 5 and 10 months post‐baseline. Microbial samples were repeated at 10 months post‐baseline, and ligatures were removed. Clinical, radiographic, and microbial examinations were again repeated at 11 months post‐baseline. Mean modified plaque index (mPI; P < 0.01), gingival index (Gl; P < 0.01), and bleeding on probing (BOP; P < 0.05) scores increased over the plaque accumulation period. The mPI, and GI scores decreased after ligature removal (P < 0.001). Mean probing depth (PD) and clinical attachment level (AL) increased between baseline and the 5‐ and 10‐month examinations (ΔPD 3.0 mm; Δ 2.7 mm; P < 0.05). PD values were reduced following ligature removal (P < 0.05). AL values and BP scores remained unchanged. A significant negative correlation was found between induced defect depth and width of keratinized mucosa at baseline (P = 0.03). At baseline, the submucosal microbiota was dominated by coccoid cells. Following ligature placement, the microbiota included a large proportion of Gram‐negative anaerobic rods, predominantly Porphyromonas gingivalis, Bacteroides forsythus, and Fusobacterium species as well as beta‐hemolytic streptococci. Ligature removal had a limited effect on the composition of the submucosal microbiota. This non‐human primate study indicates that ligature‐enhanced plaque accumulation is a precursor of progressive peri‐implant tissue breakdown around HA‐coated implants. The associated microbiota resembles that of peri‐implantitis and destructive periodontal disease in humans. This preclinical model may be useful to study modalities aimed at arresting peri‐implant tissue breakdown and at regeneration of bone in peri‐implantitis defects. J Periodontol 1997;68:59–66.

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The observations in this study point to a substantial native osteogenic potential of the alveolar process that has previously not been explored and show that surgical reentry observations of new bone formation may not necessarily indicate that osseointegration has occurred. Bone formation in control defects was substantially greater than predicted, limiting the value of adding an osteoinductive biologic construct.