Sorptivity of water in enamel for categorizing caries lesions

Siew Chen Gan, Alex Siu Lun Fok, Rana A. Sedky, Prema Sukumaran, Hooi Pin Chew

Research output: Contribution to journalArticlepeer-review

Abstract

Objective: The aim of this research was to determine the association between sorptivity of water and the state of mineralization in carious enamel of different stages of severity. Methods: As a preliminary work, water droplets of 1.5 μL were placed on the surfaces of hydroxyapatite (HA) discs of different densities. The water droplet profile was dynamically recorded every second over a period of 10 s using a contact angle meter to determine the relationship between sorptivity and density. To measure and calculate sorptivity on enamel surfaces, varnish was painted on the labial surface of 96 extracted caries-free human teeth, leaving two 1.4 ± 0.1 mm diameter circular exposed test sites. The specimens were randomly divided into 6 groups (n = 16) and subjected to 0(G0), 7(G7), 14(G14), 21(G21), 28(G28) and 35(G35) days of pH cycling, respectively. A 0.7 μL water droplet was placed on each exposed site and Optical Coherence Tomography was used to measure its height every 10 seconds for 2 min. Sorptivity was computed by considering sorption equations and Washburn's analysis of capillary kinetics and correction for evaporation was also performed. Micro-Computed Tomography scans of the specimens were obtained and delta Z (ΔZ) is the parameter used to measure mineral loss. ΔZ at 10 μm (ΔZ10) and 50 μm (ΔZ50) from the surface were calculated. One-way ANOVA and Post-hoc Tukey tests were used to compare sorptivity between groups and bivariate correlations were used to analyze the association between sorptivity and ΔZ. Results: Sorptivity was found to be inversely and linearly correlated with HA density with R2 value of 0.95. With enamel, there is a general trend of increase in mean sorptivity from G0 to G35, except for a decrease in G21. The same trends were observed for both ΔZ10 and ΔZ50. The decrease in sorptivity in G21 coincided with the presence of a surface hypermineralized layer in G21 samples. Post-hoc Tukey showed significant differences in mean sorptivity between G0 and G14, G0 and G21 as well as G14 and G21. Post-hoc Dunnett's T3 showed significant differences for ΔZ10 between G0 and G14 as well as G14 and G21. Significant correlation between mean sorptivity and ΔZ10 was detected with Pearson correlation coefficient of 0.461. For ΔZ50, post-hoc Tukey showed significant differences between G0 and G14 but no significant difference was detected between G14 and G21. No correlations were detected between mean sorptivity and ΔZ50. Significance: Sorptivity was found to be inversely and linearly correlated with HA density with R2 value of 0.95. With enamel, there is a general trend of increase in mean sorptivity from G0 to G35, except for a decrease in G21. The same trends were observed for both ΔZ10 and ΔZ50. The decrease in sorptivity in G21 coincided with the presence of a surface hypermineralized layer in G21 samples.

Original languageEnglish (US)
Pages (from-to)1379-1387
Number of pages9
JournalDental Materials
Volume36
Issue number11
DOIs
StatePublished - Nov 2020

Bibliographical note

Funding Information:
This study was partially supported by High Impact Research MoE Grant UM.C/625/1/HIR/MoE/DENT/11 from the Ministry of Education Malaysia. Rana Sedky would like to thank the MDRCBB for providing her with a 3Mgives KOL Scholarship and for hosting her visit, during which part of this study was carried out. The authors wish to acknowledge the contribution of Dr Brian Holmes for statistical support and Professor Changquan Calvin Sun for providing the HA discs used in this study. We also would like to express our sincere gratitude to the laboratory staff of the Biomaterials Lab at Faculty of Dentistry University of Malaya and Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota for the technical support provided throughout this research.

Funding Information:
This study was partially supported by High Impact Research MoE Grant UM.C/625/1/HIR/MoE/DENT/11 from the Ministry of Education Malaysia . Rana Sedky would like to thank the MDRCBB for providing her with a 3Mgives KOL Scholarship and for hosting her visit, during which part of this study was carried out.

Keywords

  • Absorption rate
  • Caries detection
  • Computed tomography
  • Delta Z
  • Demineralization
  • Enamel caries
  • Micro-CT
  • Optical Coherence Tomography
  • Sorptivity
  • Surface layer

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