In-vitro and in-vivo comparative studies of treatment effects on enamel demineralization during orthodontic therapy: implications for clinical early-intervention strategy

Abstract

Objectives: This study aimed to investigate if CPP-ACP / infiltrating resin was superior in treating enamel demineralization during orthodontic therapy compared with fluoride varnish, in order to provide early-intervention implications for dental professionals.

Materials and methods: In the in-vitro study, premolars were grouped into four: remineralization with fluoride varnish / CPP-ACP, sealing with infiltrating resin, and negative control. Experimental demineralization of enamel surfaces was analyzed using techniques of QLF, SEM, EDS and micro-hardness testing. An in-vivo intervention study was conducted on patients randomly assigned into three groups. At the baseline and every-3-month follow-up, QLF parameters were compared temporally and parallelly to yield potential implications for promotion in clinical practice.

Results: The in-vitro study performed on 48 experimental tooth surfaces demonstrated that sealing with infiltrating resin reduced enamel surface porosity and increased surface micro-hardness significantly. In the in-vivo intervention study on 163 tooth surfaces, it was suggested that for those who meet the criteria of -10 < ΔF < -6 and - 1000 < ΔQ < -20 at the baseline, all these treatment methods could achieve acceptable outcomes; with the rising of absolute values of ΔF and ΔQ, sealing with infiltrating resin showed more evident advantages.

Conclusion: For enamel demineralization during orthodontic therapy, all the treatment methods involved in this study showed acceptable effectiveness but had respective characteristics in treatment effects. QLF parameters could be used as indicators for clinical early-intervention strategy with regards to this clinical issue.

Clinical relevance: With QLF parameters, clinical early-intervention strategy for enamel demineralization during orthodontic therapy could be optimized.

Keywords: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP); Enamel demineralization; Infiltrating resin; Orthodontic therapy; Quantitative light-induced fluorescence (QLF).

Fig. 1

Schematic diagram of the in-vitro experiment

Fig. 2

Comparative analysis of QLF, electron microscopy scanning, and hardness measurement in vitro. ^*, P < 0.05. ^**, P < 0.01. ^***, P < 0.001

Fig. 3

Representative enamel surface morphology under SEM. (a) Normal enamel surface; (b & c) Demineralized enamel surfaces; (d) Enamel surface after treatment with fluoride varnish (Group A); (e) Enamel surface after treatment with CPP-ACP (Group B); (f) Enamel surface after treatment with infiltrating resin (Group C)

Fig. 4

Temporal variations in indices of clinical examination and QLF parameters

Fig. 5

Graphical summary of methods and main findings of the present study