A novel three-dimensional analysis of standardized bone defects by means of confocal scanner and micro-computed tomography

Objectives: The aim of the study was to introduce a novel three-dimensional (3D) method to quantify the relative amount of different tissue components in bone substitute-treated defects by means of integration of confocal laser imaging into micro-computed tomography (μCT) analysis. Materials and methods: One standardized semisaddle intraosseous defect was prepared in the mandibles of six minipigs and scanned by an optical scanner to capture the surface of the fresh defect in a 3D manner. Subsequently, all the defects were filled with a biphasic calcium phosphate material. The animals were divided into two groups of three animals each, which were allowed to heal for 3 and 8 weeks, respectively. μCT analysis followed the two healing periods and was performed on all defect locations. The data from optical scanning and μCT were used for three-dimensional evaluation of bone formation, nonmineralized tissue ratio, and graft degradation. The integration of confocal laser scanning into μCT analysis through a superimposition imaging procedure was conducted using the software Amira (Mercury Computer Systems, Chelmsford, MA, USA). Results: The feasibility of combining the confocal imaging into μCT data with regard to obtaining accurate 3D quantification was demonstrated. The amount of tissue components was identified and quantified in all the investigated samples. Quantitative analysis demonstrated that a significant increase in the amount of bone filling the defect was observed in vivo (p < 0.02) while a significant decrease in the amount of nonmineralized tissue occurred (p < 0.04). No difference in the amount of residual grafting material was detected between 3 and 8 weeks in vivo (p > 0.38). Conclusions: The combination of confocal imaging and micro-computed tomography techniques allows for analysis of different tissue types over time in vivo. This method has revealed to be a feasible alternative to current bone regeneration quantification methods. Clinical relevance: Assessment of bone formation in a large animal model is a key step in assessing the performance of new bone substitute materials. Reliable and accurate methods are needed for the analysis of the regenerative potential of new materials.