IADR Abstract Archives
Mapping Dentin Biostability in Situ With Spectroscopies
Objectives: Bond to the deeper portion of dentin is known to degrade more rapidly than to the superficial part. Previous studies relate the phenomenon to the differential distribution of endogenous collagenolytic enzymes. Nevertheless, study regarding the biostability in different depths of dentin itself is still lacking. The objective of this study was therefore to investigate the biostability along longitudinal dentin sections. By mapping the acid-etched surface, the biostability was defined with the spatial distribution of organic matrix remnant after collagenase degradation.
Methods: Organic matrix on longitudinal dentin sections was exposed with 37% phosphoric acid etching for 30s. Afterwards, specimens were subjected to collagenase challenge (100ug/ml from Clostridium histolyticum, Sigma) for 4 hours, while those not treated with collagenase were served as controls. All specimens were extensively rinsed for 3 times after etched and after collagenase degradation. Then, the specimens were sequentially dehydrated in ethanol for subsequent observation. The specimens were first analyzed with non-contact refractive Fourier-transform infrared (FTIR) spectroscopy to map the matrix-to-mineral ratio (area ratio of amide I and phosphates) across the surface. Finally, elements on the surfaces were resolved with energy-despersive adsorption x-ray (EDAX) spectroscopy. SEM images of the demineralized dentin surface were captured as well.
Results: Both matrix-to-mineral ratio (FTIR) and carbon percentage (EDAX) gradually decreased from DEJ to pulp in all samples after collagenase degradation. The gradient was revealed in SEM images as well. The results clearly suggested that superficial dentin was more resistant to collagenase challenge.
Conclusions: After challenged by collagenase, gradient of organic matrix remnants is observed on the longitudinal sections of dentin. The unique phenomenon is reported for the first time, and it adequately explains the faster bond deterioration in deeper dentin. The findings bring us deeper insights into the depth-dependent bond instability and open up new research possibilities in the future.
Methods: Organic matrix on longitudinal dentin sections was exposed with 37% phosphoric acid etching for 30s. Afterwards, specimens were subjected to collagenase challenge (100ug/ml from Clostridium histolyticum, Sigma) for 4 hours, while those not treated with collagenase were served as controls. All specimens were extensively rinsed for 3 times after etched and after collagenase degradation. Then, the specimens were sequentially dehydrated in ethanol for subsequent observation. The specimens were first analyzed with non-contact refractive Fourier-transform infrared (FTIR) spectroscopy to map the matrix-to-mineral ratio (area ratio of amide I and phosphates) across the surface. Finally, elements on the surfaces were resolved with energy-despersive adsorption x-ray (EDAX) spectroscopy. SEM images of the demineralized dentin surface were captured as well.
Results: Both matrix-to-mineral ratio (FTIR) and carbon percentage (EDAX) gradually decreased from DEJ to pulp in all samples after collagenase degradation. The gradient was revealed in SEM images as well. The results clearly suggested that superficial dentin was more resistant to collagenase challenge.
Conclusions: After challenged by collagenase, gradient of organic matrix remnants is observed on the longitudinal sections of dentin. The unique phenomenon is reported for the first time, and it adequately explains the faster bond deterioration in deeper dentin. The findings bring us deeper insights into the depth-dependent bond instability and open up new research possibilities in the future.