Change in surface hardness of enamel by a cola drink and a CPP-ACP paste

D. Tantbirojn, A. Huang, M. D. Ericson, S. Poolthong

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


Objectives: This in vitro study used surface microhardness to evaluate whether a paste containing casein phosphopeptide amorphous calcium phosphate (CPP-ACP) can reharden tooth enamel softened by a cola drink, and how different saliva-substitute solutions affect the enamel hardness. Methods: Twenty-four bovine incisors, each tooth consisting of treatment and control halves, were immersed in a cola drink (Coke®) for 8 min, then placed under a 0.4 mL/min drip with various saliva-substitute solutions. The saliva-substitute solutions were: saliva-like solution (SLS) with 1 ppm fluoride, SLS without fluoride, and Biotene® mouthwash. CPP-ACP paste was applied to the treatment halves for 3 min at 0, 8, 24, and 36 h. Knoop microhardness measurements were performed at baseline, after the cola drink immersion, and after 24 and 48 h contact with saliva-substitute solution. Results: Enamel hardness significantly decreased after immersion in cola drink (ANOVA, p < 0.05). After contact with saliva-like solutions for 48 h, those treated with CPP-ACP paste were significantly harder than those untreated regardless of the presence of 1 ppm fluoride in the saliva-like solution (ANOVA, p < 0.05). Biotene® mouthwash significantly softened the enamel surface (ANOVA, p < 0.05). Two-way ANOVA showed significant effects of the CPP-ACP paste application and types of saliva-substitute solutions on the changes in surface hardness of the softened enamel at a significance level of 0.05. Conclusion: The application of CPP-ACP paste with continuous replenishment of saliva-like solution for 48 h significantly hardened enamel softened by a cola drink. Biotene® mouthwash softened enamel surface after 48 h contact.

Original languageEnglish (US)
Pages (from-to)74-79
Number of pages6
JournalJournal of Dentistry
Issue number1
StatePublished - Jan 2008

Bibliographical note

Funding Information:
This study is supported in part by a Summer Research Fellow Program, University of Minnesota School of Dentistry, Nontenured Faculty Award, 3M Foundation, and the Minnesota Dental Research Center for Biomaterials and Biomechanics. The authors would like to thank Dr. A. Versluis for proof reading the manuscript.


  • Biotene mouthwash
  • Cola
  • Enamel
  • Saliva-substitute solution
  • Surface hardness


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