Quantitative Evaluation of Supracrestal Bone Growth Around Dental Implants

Objectives:

During the last decade, the need to augment the remaining osseous structure to house dental implants has increased as dental implant placement has increased. Regaining lost vertical bone height is generally acknowledged as the greatest bone augmentation challenge. Several approaches, from basic to complex have been proposed to meet this clinical challenge. The development of new animal models and the validation of high performing evaluation methods are essential for the objective assessment of experimental vertical bone augmentation outcomes.

The aim of the present study was to investigate a new surgical model achieving de novo supracrestal alveolar bone growth around dental implants, and to validate a quantitative evaluation method based on comparative analysis of three dimensional imaging and histomorphometry.

Methods:

Four different custom made titanium implants were placed in mandibles of four adult mini pigs such that the implant shoulder was located 2.5 mm above the bone crest. A cover abutment provided a protected space around the implant of 2.5 mm of width and height. After nine weeks of healing, the sites were extracted, embedded in PMMA and scanned with micro-computed tomography (microCT). A trilinear interpolation method was used to align the microCT images with the z-axis in voxel space. Bone volume density was computed within a virtual ring-mask positioned around the former supracrestal part of the implant. Subsequently, histomorphometric analysis was conducted on non-decalcified sections stained with a modified polychromatic Paragon staining.

Results:

Vertical supracrestal bone growth was successfully measured and quantified by micro-computed tomography (up to 71% volume regeneration), which appeared to be highly associated with the histomorphometrical results (up to 1.5 mm vertical bone regeneration).

Conclusions:

Micro-computed tomography and histomorphometry are very efficient, complementary methods. Applied to large animal models, these methods are essential for an accurate evaluation of bone augmentation around dental implants.