Volumetric Bone Measurement Around Dental Implants Using 3D Image Superimposition: A Methodological and Clinical Pilot Study.

PURPOSE: This study describes the development of a methodology for using three-dimensional (3D) image superimposition to measure volumetric changes in bone level around dental implants in comparison with linear measures. MATERIALS AND METHODS: The sample was comprised of 46 dental implants of 6-mm length and 4.1-mm diameter placed in the posterior maxilla and posterior mandible in 20 patients. All implants received screw-retained single crowns. Radiographic images were taken using cone beam computed tomography (CBCT) and digital periapical radiography after implantation and after 12 and 24 months of functional loading (after crown installation). Tridimensional reconstructions of the bone perimeter closest to the implant were developed, superimposed, and volumetrically measured. Linear measures of bone levels were recorded in periapical radiography images. A multilevel regression model tested volumetric and linear bone loss. RESULTS: The mean peri-implant linear bone loss for the first and second years was 0.2 ± 0.4 mm and 0.1 ± 0.2 mm, respectively, and the mean volumetric bone loss for the first and second years was 7.2 ± 6.1 mm³ and 6.4 ± 7.8 mm³, respectively. It was estimated that an increase of 1 mm of linear bone loss was associated with a mean volumetric bone loss of approximately 14 mm³ (P < .001). CONCLUSION: The findings showed that linear and volumetric bone loss measures are related. Measuring volumetric bone changes around implants is possible provided that the CBCT images have proper contrast and sharpness, particularly around the implant outline. Improvements in image quality and in the filters for bone tissue detection would be important for this methodology to be made faster and used clinically.

Characterization of the interface between cast-to Co-Cr implant cylinders and cast Co-Cr alloys.

STATEMENT OF PROBLEM: The affordable Co-Cr cast alloy should provide an ideal interface with prefabricated cast-to cylinders from the same alloy family. The alloy microstructures should be maintained up to the interface, and porosities and reaction regions should be absent, and sufficient bond strength between alloys should be provided. PURPOSE: The purpose of this in vitro study was to evaluate the metallurgical interfacial compatibility between Co-Cr dental casting alloys and a prefabricated Co-Cr dental implant cast-to-cylinder. MATERIAL AND METHODS: A Co-Cr alloy was cast to Co-Cr implant cylinders. Specimens were cross-sectioned longitudinally and divided into as-cast and heat-treated groups. The microstructures of specimens were evaluated by optical and scanning electron microscopy. The elemental composition of as-received prefabricated implant cylinders and diffusion characteristics of cast interfacial regions were determined by energy dispersive x-ray spectroscopy. Vickers hardness values were defined across the interface on cast specimens and for the as-received implant cylinders. ANOVA and Tukey honest significant differences tests were used for the statistical evaluation of hardness values. RESULTS: No significant reaction regions or porosity were present in the interface. Microstructural aspect and interdiffusion indicated a metal-metal bond between the Co-Cr implant cylinder and cast alloy. Mean hardness values demonstrated a significant rise across the interface (373.5 ±12.8; 363.8 ±12.6, respectively) from the wrought cylinder (338.6 ±10.5; 329 ±9.7, respectively) to the cast alloy (399.8 ±7.4; 392.3 ±10.3, respectively) for the as-cast and heat-treated conditions, respectively. CONCLUSIONS: Co-Cr casting alloy cast on to prefabricated Co-Cr implant cylinders provided interfaces which appear to fulfill the requirements of the established criteria.