Cross-sectional visual comparison of remineralization efficacy of various agents on early smooth surface caries of primary teeth with swept source optical coherence tomography

Abstract

Purpose: Sweptsource optical coherence tomography (SS-OCT) permits cross-sectional observation of surface/subsurface characteristics of enamel including early carious lesions (ECL) or remineralization non-invasively.This study aimed to visually compare the cross-sectional remineralizing efficacy of various agents on ICDAS-II scores-1&2 by using SS-OCT and histology.

Methods: Baseline SS-OCT (grey-scale/false-colour) and histology was performed on the randomly selected two samples with scores-1&2. Four remineralizing agents [fluoride-varnish (FV), CPP-ACP, nanohydroxy-paste (NHP) and silver-diamine-fluoride (SDF)]were evaluated for 2-or 6-weeks post-remineralization using SS-OCT and histology.

Results: Score-1&2 baseline SS-OCT images showed a linear-shaped demineralization with dentino-enamel junction (DEJ) visible; and bowl-shaped demineralization with DEJ invisible respectively. Remineralizing agents were assessed on the basis of their ability to remineralize the surface, subsurface and made visualize the DEJ in score-2. SS-OCT showed an outer growth layer in post-remineralization score-1, 2-weeks samples with FV and NHP. All the agents showed progressive subsurface remineralization in 6 weeks. Active lesions showed rapid uptake of minerals on surface. Subsurface mineralization in pigmented score-2 matched sound enamel with NHP and SDF. Surface remineralization was comparable in FV and SDF followed by NHP. SDF demonstrated deeper subsurface remineralization followed by NHP and CPP-ACP.

Conclusion: SS-OCT images correlated to histology. SS-OCT could monitor surface/subsurface in-situde/remineralization activity non-invasively.

Keywords: Early carious lesions; Enamel; ICDAS-II; Remineralization; SS-OCT; Smooth surface caries.

Fig. 1

Scanning of samples with SS-OCT.

Fig. 2

Distribution of samples.

Fig. 3

Baseline Observation A-i) score-1.ii) & iv) Linear shapedlesion-limited to outer third of enamel (red arrow). Clearly demarcated lesion boundary from sound enamel (deep blue). Additional finding: developmental defect projecting from DEJ towards the surface (white arrows). Both the findings, correlating with the SS-OCT (red arrow). B-i-iv) Score-1 (red box) with DEJ involvement as an additional finding (green arrow and red braces), correlating to histology -DEJ is not sharp below yellow line (red braces). C-i) score-2.ii) & iii) Deep bowl-shapedlesiontapering towards the DEJ (white arrows). DEJ is not visible.iv) Bowl shaped chalky white lesion (red box) up to DEJ, correlating with the SS-OCT.

Fig. 4

Post-remineralization ICDAS-II score-1&2 using FVA-i) score-1. ii) &iii) Rapid remineralization (Red arrow) above surface. Outer third of subsurface -initial remineralization (white arrow).iv) No identifiable remineralization.B-i) score-1. Roughened surface - active lesion.ii) & iii) Yellow interspersed with thicker red on the surface and in outer half of subsurface -rapid surface remineralization (red arrow). iv) Roughened surface but no identifiable remineralization.C-i) score-2. ii) & iii) Rapid surface remineralization (red arrow) and initial remineralization (white arrow)respectively.iv) Score-2 involving DEJ. D-i) Pigmented score-2. ii) & iii) Bright-white and line of red on the surface (red arrow). Dense, thicker band on the outer half of subsurface -increased remineralization with time (white arrow). Band like remineralization of subsurface - reduced depth of pigmented ECL. DEJ, visible as a faint line.iv) Brown colour on surface and chalky white lesion - healed or no priorly involved DEJ.

Fig. 5

Post-remineralization ICDAS-II score-1&2 using CPP-ACP A-i) score-1, rough surface. ii) & iii) Outer third of subsurface (white arrow) - initial remineralization. Active lesion (red arrow) -rapid surface mineralization. iv) Intact surface but no identifiable remineralization.B-i) score-1. ii) & iii) Band in the outer half of subsurface; band of red interspersed with yellow (between white and red arrows)- dense subsurface remineralization at 6 weeks. iv) Outer subsurface as smooth with chalky white enamel in inner two third.C-i) score-2 (both white and pigmented areas) – no marked improvement. ii) & iii) Outer half of enamel -initial subsurface remineralization. Reduced depth of demineralized subsurface & pigmented surface, has minimal surface remineralization (red arrow) with almost healed subsurface (white arrow). DEJ became visible.iv)Small area of smooth subsurfacecorrelate to the area with white and red arrows in SS-OCT. Chalky white area around smooth area up to DEJ is observed.D-i) score-2. ii) & iii) Majorly blue on the surface depicting mature phase of remineralization. Yellow with red, site of active lesion (red arrow). Blue coloured subsurface (red box) -mature phase; beneath this, yellow -remineralizing front of the lesion (white arrows). iv) Chalky white lesion involving DEJ. Activity observed in SS-OCT is not identifiable.

Fig. 6

Post-remineralization ICDAS-II score-1&2 using NHP. A-i) score-1.ii) & iii) Rapid mineralization (red arrow). Outer third of subsurface - initial remineralization (white arrow). DEJ became faintly visible. iv) Elevated surface correlating SS-OCT.B-i) score-1.ii) & iii) Red interspersed with blue and yellow on surface - initial to mature remineralizing phase (red arrow). Yellow interspersed with red in outer third of subsurface (white arrow). Accidental finding of DEJ involvement with apparently normal surface (broken red circle).iv) No demineralized ECL, correlating SS-OCT.C-i) score-2.ii) & iii) Layer of red - rapid remineralization of surface(red arrow). Bowl shaped less dense white (grey scale) and blue & yellow in the outer half of enamel-initial to mature phase of subsurface remineralization (white arrow). iv) Chalky white ECL involving DEJ. D-i) score-2.ii) & iii) Surface -mature phase of remineralization (red arrow). Less dense white and blue with yellow in the outer half of subsurface - initial to mature phase of remineralization (white arrow). Accidental finding of DEJ involvement underneath normal surface (green arrow).iv) Chalky white inner subsurface underneath smooth outer third with DEJ involvement correlate SS-OCT.

Fig. 7

Post-remineralization ICDAS-II score-1&2 using SDF. A-i) score-1.ii) & iii) Rapid surface remineralization on active lesion (red arrow). Outer third of enamel-initial phase of subsurface remineralization (white arrow). Additionally, mineral uptake, seen as yellow in the cracks of enamel.iv) Black staining on the surface and subsurface.B-i) score-1.ii) & iii) Red interspersed with yellow on the surface - initial phase of surface remineralization (red arrow). Dense yellow interspersed with red in the subsurface -almost full depth remineralization with time (white arrows). iv) Stained full thickness enamel up to DEJ.C-i) score-2.ii) & iii) Rapid surface remineralization (red arrow). Dense-yellow in the outer half of enamel, near the red line -initial phase of subsurface remineralization (white arrow). iv) Black stained lesion and DEJ including part of dentine.D-i) score-2.ii) & iii) Rapid surface remineralization (red arrow). Outer half of enamel - initial phase of subsurface remineralization (white arrow). iv) Black stained lesion and DEJ including part of dentine.