Purpose: The aim of the study was to analyze the microchemistry of human bone in different regions of interest (ROIs) on histologic samples of implants retrieved postmortem by the innovative use of an environmental scanning electronic microscope (ESEM) connected to energy-dispersive x-ray spectroscopy (EDX).
Materials and methods: Maxillary and mandibular bone blocks with inserted implants (n = 12) were obtained postmortem from a patient. The histologic samples were observed uncoated using ESEM in quadrant backscattered condition. Two ROIs (approximately 750 × 500 μm) for each implant were analyzed corresponding to the cortical thread (cortical ROI) and the middle part of each implant (approximately 3.0 mm below; middle ROI). Different electron-dense bone tissue areas were detected through grayscale intensity quantification of ESEM images. Calcium (Ca), phosphorous (P), and titanium (Ti; atomic %) were evaluated by EDX, and Ca/P ratios were calculated and used as the index to identify areas with different mineralization. The presence of Ti contaminants was investigated by EDX microanalysis. Additional ROIs approximately 2.0 mm from the implant interface and not in connection with the implant surface were analyzed as the control.
Results: Four bone areas (BAs) with different degrees of mineralization (from 1 as the lowest mineralized to 4 as the highest mineralized) were identified by Ca and P content and by tissue electron density. BA1 (bone marrow areas) and BA2 (areas with active bone remodeling) proved to have low levels of Ca and P, while BA3 (mineralized new bone areas) and BA4 (control cortical bone) had higher content of Ca and P and higher electron density. Mandibular ROIs displayed higher percentages of BA3 and BA4, while maxillary ROIs revealed a greater presence of BA2 and moderate presence of BA1. Control bone showed a high percentage of BA4. Cortical and middle ROIs showed similar BA distribution within mandibular bone, whereas in maxillary bone, a slightly higher presence of BA1 was observed. Ti ions were detected in ROIs of all specimens; the atomic % significantly decreased in the most distant areas. Ti particles were observed close to the implant interface. Analyses 2.0 mm distant from the implant thread revealed low traces of Ti in healthy bone tissue.
Conclusion: The high percentage of BA3 and BA4 in mandibular blocks associated with low presence of BA2 suggested the fast formation of compact bone tissue after 7 months from the implant placement. The presence of BA2 in maxilla blocks suggested active bone remodeling still present after 7 months. Ti particles were observed throughout the ROIs with and without bone remodeling activity. ESEMEDX resulted as a suitable technique to obtain more complete information on microchemistry composition and density/mineralization of bone around implants. For clinical significance, maxillary and mandibular peri-implant bone revealed different mineralization patterns, which means different healing times. The presence of Ti particles at the bone-implant interface and ion translocation, likely due to wear forces in the times following the implant insertion, do not affect the bone remodeling process.