Evaluation of tooth wear by estimating enamel thickness with quantitative light-induced fluorescence technology

Evaluation of residual dentin thickness using quantitative light-induced fluorescence technology

This study aimed to determine whether a correlation exists between residual dentin thickness and quantitative light-induced fluorescence (QLF) values and, if so, to analyze its tendencies. Forty extracted sound human molars were assigned to filled and unfilled groups. The teeth were submerged in a mold with clear acrylic resin. Red utility wax was inserted into the pulp chamber space in the filled group to simulate vital pulp. The specimen was sectioned longitudinally to observe the inside of the pulp space. The samples were cut horizontally from the highest point of the pulp space 2 mm apart. QLF images were then taken of 2 mm, 1 mm, and 0.5 mm samples using the QLF-D Biluminator™ 2 + system. Three operators independently evaluated the QLF images, and the statistical analysis was conducted using one-way analysis of variance, Pearson correlation coefficients, and intraclass correlation coefficients. In the filled group, the mean ΔF values for residual dentin thicknesses of 2 mm, 1 mm, and 0.5 mm were - 3.22, - 7.84, and  - 11.52, respectively. In the unfilled group, the mean ΔF values were 0, - 6.90, and - 10.14, respectively. A positive correlation was found between residual dentin thickness and ΔF values (P < 0.05). The intraclass correlation coefficients for observations made by the three operators for the filled and unfilled groups were 0.831 and 0.917, respectively (P < 0.05). In conclusion, residual dentin thickness and ΔF values were significantly correlated and had a highly positive correlation regardless of the QLF device operator.

Tooth Wear and Tribological Investigations in Dentistry

Dental or tooth wear is a physiological process in the life cycle of teeth. Loss of the occlusal surface may cause excessive tooth wear. Several factors may contribute to tooth wear with different intensities and duration in the oral cavity. The oral cavity is generally compared to a tribological system to determine the various types of wear between teeth and restorative materials and assess the amount of dental wear. However, it is challenging to investigate in vitro and in vivo wear owing to the complexity of tooth wear; thus, a clear correlation between in vitro and in vivo data could not be established. This review is aimed at providing an insight into the etiology of tooth wear and tribological investigations in dentistry.

Association between incisor positions and amount of interdental stripping in patients undergoing orthodontic treatment

INTRODUCTION

The study aimed to investigate the effect of a nonextraction treatment approach with interdental stripping (IDS) on the dentofacial structures in patients with dental and skeletal Class I, II, and III malocclusions.

METHODS

A total of 60 patients with mild-to-moderate crowding of the teeth and nonsevere skeletal malocclusion were included and divided into 3 groups: Class I, Class II, and Class III groups (n = 20 per group). In all patients, nonextraction orthodontic treatment was administered, and those who underwent IDS at the jaw quadrants as needed were evaluated. For pretreatment and posttreatment evaluation, lateral cephalometric radiography and 3-dimensional dental model scans were acquired for each patient. For statistical analysis, paired-samples t test and 1-way analysis of variance with Tukey post-hoc test were used for parametric variables, whereas the Wilcoxon paired signed rank test and Kruskal-Wallis test with Dunn post-hoc test were used for nonparametric variables.

RESULTS

An increase in the maxillary incisor angle was observed in patients with Class I and Class III malocclusions, whereas a decrease was observed in patients with a Class II malocclusion (P < 0.05). Mandibular incisor angles were significantly increased in the Class II malocclusion group (P < 0.05) but unchanged in the other groups. IDS was more frequently applied to the posterior aspect of the maxilla and mandible in patients with a Class II malocclusion than in patients with other malocclusion types, and the amount of IDS at the anterior aspect of the mandible was significantly higher in the Class III group.

CONCLUSIONS

Combined nonextraction orthodontic treatment and IDS yielded successful treatment outcomes. IDS application was localized to different jaw regions according to the different malocclusion types.

Optical detection of the potential for tooth discoloration from children's beverages by quantitative light-induced fluorescence technology

BACKGROUND

Some beverages are known to cause extrinsic staining on the tooth. This study investigated the degree of pigmentation caused by children's acidic beverages, and to confirm the possibility of the quantitative light-induced fluorescence (QLF) technology in assessing staining of the tooth.

METHODS

Bovine tooth specimens were subjected to an 8-day pH-cycling model, using six children's beverages (experimental groups) and a cola (control group), and a remineralizing solution. Before and after the pH-cycling, white-light and fluorescence images of the enamel surface were photographed with a QLF to evaluate color change (ΔE_after) and fluorescence loss (ΔF_after), respectively. Paired t-test was used to compare the tooth colors obtained before and after the pH-cycling. Spearman correlation analysis was performed to examine the correlation between the ΔE_after and ΔF_after values.

RESULTS

Median ΔE_after values of all the beverages ranged from 1.33 to 20.42, showing the greatest value in Koal-Koal Koala™ (KKK, p < 0.001). The ΔE_after was correlated with ΔF_after value negatively (ρ=-0.611, p < 0.001). The median ΔF_after varied by beverages (-38.86-0.00) and KKK caused the greatest value.

CONCLUSIONS

The cola and 6 children's beverages showed the possibility for discoloration on the tooth. The QLF technology may enable monitoring the discoloration induced on the tooth surface by acidic beverage.

Detection of dentin-exposed occlusal/incisal tooth wear using quantitative light-induced fluorescence technology

OBJECTIVES

To prolong tooth life expectancy, tooth wear resulting in dentin exposure should be detected early. However, the most objective methods are clinically limited. We validated fluorescence parameters for distinguishing enamel from dentin-exposed wear in clinical images.

METHODS

Quantitative light-induced fluorescence (QLF) images of 73 adults (age range: 22-48 years, mean: 33.81 ± 7.71 years), including 1949 teeth with varying tooth wear degrees, without restorations, caries, or cusp area fractures, were used to calculate the ΔF_wear values. Areas-of-interest (AOIs) were selected from QLF images; the ΔF_wear values and the tooth wear index (TWI) were calculated for each tooth. The ΔF_wear values were compared according to the TWI scores. The optimum ΔF_wear values for distinguishing enamel and dentin-exposed wear were determined using the receiver operating characteristic (ROC) curve analysis.

RESULTS

Overall, 1949 AOIs were evaluated. The median ΔF_wear values for teeth with TWI scores 0, 1, and 2 (5.7 %, 10.3 %, and 17.0 %) differed significantly (P < 0.001). The optimum cutoff ΔF_wear values were 12.1 and 14.7 in the anterior and posterior teeth, respectively; the corresponding areas under the ROC values (AUROCs) were 0.86 and 0.93 (sensitivity: 0.79 and 0.85; specificity: 0.79 and 0.85, respectively). The ΔF_wear cutoff values for different age groups were within a range (12.7-13.7) and showed high validity (sensitivity, specificity, and AUROC: 0.78, 0.77-0.78, and 0.87-0.88, respectively).

CONCLUSIONS

At the optimum threshold, the ΔF_wear values showed high validity for distinguishing dentin exposure in worn teeth (AUROC: 0.87‒0.93) and could determine pathological tooth wear, particularly in posterior teeth.

CLINICAL SIGNIFICANCE

We demonstrated the feasibility of using QLF to detect dentin-exposed tooth wear and present optimal thresholds according to age. In addition, we confirmed the possibility using such image data for objective and cost-effective epidemiological investigation and application in tele-dentistry.

Quantitative light-induced fluorescence as a potential tool for detection of enamel chemical composition

BACKGROUND

Little is known about how the chemical composition of enamel affects the optical properties of teeth, but advances in technology allow this to be studied using white-light and fluorescent images. This study aimed to identify the variation in enamel chemical composition that may affect tooth optical properties, such as tooth color and autofluorescence.

METHODS

Sixty-one specimens of extracted human molars were prepared. Raman spectrometry was used to assess chemical composition of enamel, and tooth color, and autofluorescence from enamel were evaluated by quantitative light-induced fluorescence (QLF) images. Pearson correlation and multiple linear regression analyses were used.

RESULTS

Enamel fluorescence was related to enamel composition rather than tooth color. The b* value from the fluorescence image had a moderate correlation with crystallinity (full-width at half-maximum: r = -0.433, p < 0.001) and laser-induced fluorescence intensity (r = 0.450, p < 0.001) from Raman spectroscopy. In multiple linear regression analysis, the chemical composition of the tooth had a significant effect on the b* value from the fluorescent image (R² = 0.433, p < 0.001). In contrast, tooth color values (L*, a*, and b*) were not correlated with chemical composition.

CONCLUSIONS

The present study revealed that enamel autofluorescence in QLF was related to chemical composition of the enamel, particularly the inorganic‒organic interface. While enamel chemical composition can be detected only in a laboratory environment, enamel fluorescence by QLF may enable estimation in a dental clinic, which has implications for the field of tooth bleaching or esthetic restorative materials.

Diagnosis and management of cracked tooth by quantitative light-induced fluorescence technology

INTRODUCTION

The aim of this case report was to describe the process of diagnosis and treatment of a cracked tooth using quantitative light-induced fluorescence (QLF).

CASE REPORT

A 43-year-old male presented at our dental clinic with a complaint of cold pain in #17 tooth. A routine oral examination with radiography was performed for evaluation of the oral condition and treatment planning. Additionally, QLF image capture was performed using Qraycam and Qraypen (AIOBIO, Seoul, Republic of Korea), to collect white-light and fluorescence images. The #17 tooth was observed to have a crack line, showing red fluorescence, from the distal to mesial aspect on the occlusal surface. Even though there was no visible root fracture in the radiographic image, bone loss was observed. Therefore, we performed periodontal treatment. One month later, a root canal treatment was performed because the patient still complained of pain in the #17 tooth. During this treatment, one fluorescent image and one white light image set was captured with the Qraypen. A crack line showing red fluorescence was observed, while the line was not visible to the naked eye. After treatment, the patient has had no complaint related to this tooth for 3 years until today.

CONCLUSIONS

Clinically, use of QLF confirmed the presence of a crack before and during a root canal treatment. Therefore, it is postulated that the QLF technology could objectively facilitate the diagnosis and treatment of a cracked tooth.