Evaluation of fluoride effects on incipient caries lesion using the Q-Ray™ system

Abstract

As the global frequency of cavitated dental caries has decreased, more interest has been paid to the early detection of incipient non-cavitated dental caries. The Quantitative Light-Induced Fluorescence-Digital (QLF-D, Q-Ray™) device introduced recently is one of the computer-based incipient caries lesion detection devices that can subtly spot and quantify minimal changes in tooth minerals. The machine is capable of taking intra-oral cavity images, and has been utilized clinically as well. Meanwhile, the remineralization effect of fluoride has been sufficiently proven by multiple preceding studies. Still more studies are necessary to qualitatively show the degree and developments of short-time changes treated with fluoride application in an oral environment with a high risk of incipient caries becoming mature. Therefore, the present research sought to assess the remineralization recovery of incipient caries lesions after fluoride application by studying, first, pediatric patients with lesions among those with non-cavitated incipient caries lesions by utilizing the Q-Ray™ system. Second, the study aimed to discover the factors that affect remineralization recovery through fluoride application by a specialist. Third, based on the clinical database created during this process, the researcher aimed to identify the critical fluorescence loss amount (ΔF) to which the lesion could recover one or four weeks after fluoride treatment. The research was performed under the approval of the research review committee (IRB No. 2-2013-0043) at the Yonsei University College of Dentistry. At the start of this research, the research subjects underwent oral cavity examination, stimulated salivary flow examination, plaque measurements, oral hygiene state examination and oral prophylaxis. Incipient caries lesions found during the oral cavity examination were photographed with the Q-Ray™ system before and after the oral prophylaxis. After the image taking process, a 1.23% acidulated phosphate fluoride (APF) gel-based fluoride application was conducted for one minute. The subjects re-visited the hospital to take Q-Ray™ images again one week and four weeks after the fluoride application. Based on the Q-Ray™ images taken, the detected fluorescence loss of the incipient caries lesion was analyzed.One week after the fluoride application (31 subjects; 101 lesions), the recovered lesion group (N=68) improved in ΔF, ΔFmax, Area, and ΔQ compared to their pre-fluoride application state (p<0.0001). On the other hand, the unrecovered lesion group (N=33) showed worse ΔF and ΔFmax compared to their pre-fluoride application status (p<0.0001). Four weeks after the fluoride application (27 subjects; 90 lesions), the recovered group (N=53) improved in ΔF, ΔFmax, Area, and ΔQ (p<0.0001) compared to their pre-fluoride application status. The unrecovered lesion group (N=37) was found to show the opposite of the recovered group in every aspect (p<0.05). The logistic regression analysis found that ΔF(0) affected lesion recovery. Accordingly, we analyzed the degree of recovery in the three groups of lesions divided by the ΔF(0). No change was observed in group 1 (△F(0)≥-10%) one week after fluoride application. However, group 2 (-20%≤△F(0)<-10%) and group 3 (△F(0)<-20) were recovered about 12.01% and 29.05% one week after fluoride application (p<0.05).A receiver operating characteristic (ROC) curve analysis was conducted to identify the amount of critical fluorescence loss (ΔF(0)) up to which lesions can recover. The result of this analysis found that the lesions with fluorescence loss (ΔF(0)) of less than -11.8% and -13.0% could be recovered one week and 4 weeks after fluoride application, respectively.This clinical research has discovered the effect of fluoride on incipient caries lesion recovery and its extent, and that the severity of incipient caries lesions discovered in the first examination affected post-fluoride application remineralization recovery. In addition, by studying the cutoff point of fluorescence loss according to incipient caries lesion recovery, the researcher could more effectively investigate changes in the lesions of incipient caries patients by using the Q-Ray™ system within a shorter period of time. In this sense, the present research is expected to lay a cornerstone for the more proactive management of incipient caries lesions that will receive continued attention in the field of dentistry in the future.