Near‐IR image‐guided laser ablation of demineralization on tooth occlusal surfaces

Abstract

Introduction Studies have shown that reflectance images at near-IR wavelengths coincident with higher water absorption are well-suited for image-guided laser ablation of carious lesions since the contrast between sound and demineralized enamel is extremely high and interference from stains is minimized. The objective of this study was to demonstrate that near-IR reflectance images taken at a wavelength range of 1,500–1,700 nm can be used to guide a 9.3 μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. Methods The occlusal surfaces of ten sound human molars were used in this in vitro study. Shallow simulated caries lesions with random patterns and varying depth and position were produced on tooth occlusal surfaces. Sequential near-IR reflectance images at 1,500–1,700 nm were used to guide the laser for the selective removal of the demineralized enamel. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess selectivity. Results Images taken before and after lesion removal suggest that the demineralized areas were removed with high selectivity. Although the estimated volume of tissue ablated was typically higher than the initial lesion volume measured with PS-OCT, the volume of enamel removed by the laser correlated well with the initial lesion volume. Conclusion Sequential near-IR reflectance images at 1,500–1,700 nm can be used to guide a 9.3 μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces.

Selective ablation of dental caries using coaxial Co2 (9.3‐μm) and near‐IR (1880‐nm) lasers

“…In previous selective ablation experiments, the CO 2 laser caused surface roughening which caused higher reflectivity in irradiated areas and ultimately led to unnecessary tissue removal . However, in this study, the CO 2 laser did not cause any significant surface roughening that interfered with the NIR reflectance images (“Lesion Segmentation and Removal” section) as indicated in the final visible images (Fig.…”

“…Previous lesion detection algorithms relied on the user setting a global threshold to identify lesions . This was not ideal as it subjects the selective caries removal to user judgment and bias.…”

“…Previous studies established that NIR reflectance images can be used to guide a CO 2 laser for the selective removal of caries lesions on smooth and occlusal surfaces . This was accomplished by re‐iterating a four‐phase process until complete caries removal: taking the NIR reflectance image with an InGaAs camera, segmenting demineralization, generating ablation maps or look‐up tables (LUTs) of the caries lesion, and scanning the CO 2 laser over demineralized areas for removal.…”

Polarization Sensitive Optical Coherence Tomography: A Review of Technology and Applications

“…Processes such as demineralization lead to birefringence changes which can be observed by PS-OCT. PS-OCT was demonstrated for the assessment of early and advanced demineralization in dentin as well as in enamel (Figure 11d-e) [211][212][213][214]. Ablation of demineralized tooth structures was monitored by PS-OCT [215]. Demineralization was also investigated in tooth roots [216].…”

Development and Application of Optical Coherence Tomography (OCT)

“…Ablation of demineralized tooth structures was monitored by PS-OCT [215]. Demineralization was also investigated in tooth roots [216].…”