Effect of platform switching size and vertical implant depth on crestal bone remodeling – An histological animal study

Background

Functional and dimensional maintenance of the soft tissue seal in dental implants can determinate better long-term condition, and an adequate amount of bone around the implant reduces the risk of the abutment loosening from the implant.

Aim/Hypothesis

The present animal study aimed to analyze the possible relationship between the combination of different platform switching and vertical implant depth and remodeling of the crestal bone.

Material and Methods

Sixty conical Morse taper dental implants were placed in the tibia of 15 rabbits, hence 2 implants per tibia. Three different implant diameters were used, 3.5-mm, 4.0-mm and 4.5-mm (n = 3 × 20 implants). The implants were placed either 1-mm or 2.0-mm subcortically, based on a randomized allocation. A transmucosal healing abutment with a diameter of 3.3 mm and height of 3.5 mm was secured to the implants. Eight weeks after the implantation surgery, histological samples were prepared and analyzed quantitatively. The extent of new bone formation was appraised by two measurements. I.e., the relative area of new bone formed between the osteotomy wall and the vertical surface of the abutment (%), and the height from the implant shoulder to the most cervical crest of the new bone (mm). Parametric and nonparametric statistical tests were applied to assess the significance of observed group differences (n + 6 × 10 implants).

Results

New bone formation between the osteotomy wall and the vertical surface of the abutment cervically to the implant shoulder was observed in all 6 groups. The highest and lowest new bone formation measured by the bone height was observed respectively for the 3.5 mm implants placed 2 mm subcrestally (1.2 mm) versus the 4.0 and 4.5 mm implants placed 1 mm subcrestally (0.6 mm) (P < 0.001). The highest and lowest new bone formation measured by the percentage of the total area was observed respectively for the 3.5 mm (>120%) and the 4 and 4.5 mm (˜55%) implants.

Conclusion and Clinical Implications

In this animal model, both the implant diameter and vertical placement level influence the crestal bone behavior during the healing process.