Analysis of cariogenic biofilms by using a swept-source optical coherence tomography in vitro.

OBJECTIVE: The objective was to measure the thickness of Streptococcus mutans (S. mutans) biofilms forming in an oral biofilm reactor (OBR) by using a noninvasive swept-source optical coherence tomography (SS-OCT) system at every 4 h time interval until 20 h and analyze the correlations with the amounts of biofilms. METHODS: S. mutans biofilms were formed on square-shaped bovine enamel blocks inside an OBR. Biofilms were analyzed at every 4 h stage (4 h, 8 h, 12 h, 16 h and 20 h) using a SS-OCT system and a laser scanning confocal microscope (LSCM). The amounts of biofilms were measured at each stage by separating the water insoluble glucan (WIG) and bacterial cells. Co-relationships between the SS-OCT measured biofilm thickness and the amounts of adhered biofilms were analyzed. RESULTS: The thickness of biofilms detected on SS-OCT images at 4 h stage was 0.059 ± 0.029 (Av ± SD) mm which increased time-dependently in a linear fashion after 8 h stage and reached to 0.435 ± 0.159 mm at 20 h stage and the correlation coefficient was about 0.89. The amounts of biofilms; bacterial optical density (OD) and WIG concentration increased time-dependently were 0.035 ± 0.008 / mm2 and 10.328 ± 2.492 µg/ mm2 respectively at 20 h stage. Correlation coefficients of 0.66 between 'the amounts of bacteria' and 'biofilm thickness on OCT' and 0.67 between 'the amounts of WIG' and 'biofilm thickness on OCT' were obtained, suggesting that there was a relatively positive correlation between them. CONCLUSION: The SS-OCT can be a useful tool to measure time-dependent growth of biofilms. Further studies are needed in order to assess biofilms using SS-OCT more accurately.

Effect of Attenuated Light Through Translucent Zirconia on the Interfacial Adaptation and Polymerization of Resin Cements.

PURPOSE: The first objective was to determine if dual-curing of resin cement with reduced light could affect interfacial adaptations of zirconia restoration. The second objective was to examine whether cement type and pretreatment method of universal adhesive affected interfacial adaptation. The final objective was to compare the polymerization degree of cement under different reduced-light conditions. MATERIALS AND METHODS: Inlay cavities were prepared on extracted third molars. Translucent zirconia restorations were milled using Katana UTML (Kuraray Noritake) in three groups with restoration thicknesses of 1, 2, and 3 mm, respectively. Each group had three subgroups using different cementation methods. For subgroup 1, restorations were cemented with self-adhesive cement. For subgroup 2, universal adhesive was applied and light cured. After the restoration was seated with conventional resin cement, light curing was performed. For subgroup 3, after adhesive was applied, the restoration was seated with conventional resin cement. Light curing was performed for the adhesive and cement simultaneously. After thermocycling, interfacial adaptation at the restoration-tooth interface was investigated using swept-source optical coherence tomography imaging. Finally, polymerization shrinkage of the cement was measured using a linometer and compared under the conditions of different zirconia thicknesses and light-curing durations. RESULTS: Interfacial adaptation varied signficantly depending on the zirconia thickness, pretreatment, polymerization mode and cements used (p < 0.05). The effects of the adhesive and polymerization shrinkage differed signficantly, depending on the reduced light under the zirconia (p < 0.05). CONCLUSION: Lower curing-light irradiance may lead to inferior adaptation and lower polymerization of the cement. Polymerization of resin cement can differ depending on the light irradiance and exposure duration.

Evaluation of Incipient Enamel Caries at Smooth Tooth Surfaces Using SS-OCT.

(1) Background: Dental caries, if diagnosed at the initial stage, can be arrested and remineralized by a non-operative therapeutic approach preserving tooth structure. Accurate and reproducible diagnostic procedure is required for the successful management of incipient caries. The aim of this study was to evaluate the diagnostic accuracy of 3D swept-source optical coherence tomography (3D SS-OCT) for enamel caries at smooth tooth surface if the lesion was with remineralization. (2) Methods: Forty-seven tooth surfaces of 24 extracted human teeth visibly with/without enamel caries (ICDAS code 0−3) were selected and used in this study. The tooth surfaces of investigation site were cleaned and visually examined by four dentists. After the visual inspection, SS-OCT scanning was performed onto the enamel surfaces to construct a 3D image. The 2D tomographic images of the investigation site were chosen from the 3D dataset and dynamically displayed in video and evaluated by the examiners. A five-rank scale was used to score the level of enamel caries according to the following; 1: Intact enamel. 2: Noncavitated lesion with remineralization. 3: Superficial noncavitated lesion without remineralization. 4: Deep nonvacitated lesion without remineralization. 5: Enamel lesion with cavitation. Sensitivity and specificity for 3D OCT image and visual inspection were calculated. Diagnostic accuracy of each diagnostic method was calculated using weighted kappa. Statistical significance was defined at p = 0.05. (3) Results: 3D SS-OCT could clearly depict enamel caries at smooth tooth surface as a bright zone, based on the increased backscattering signal. It was noted that 3D SS-OCT showed higher sensitivity for the diagnosis of remineralized lesions and deep enamel lesions without cavitation, as well as cavitated enamel lesions (p < 0.05). No significant difference of specificity was observed between the two diagnostic methods (p > 0.05). Furthermore, 3D SS-OCT showed higher diagnostic accuracy than visual inspection (p < 0.05). (4) Conclusions: Within the limitations of this in vitro study, 3D SS-OCT showed higher diagnostic capacity for smooth surface enamel caries than visual inspection and could also discriminate lesion remineralization of enamel caries.

Noninvasive cross-sectional imaging of proximal caries using swept-source optical coherence tomography (SS-OCT) in vivo.

The aim of this study was to determine the diagnostic accuracy of swept-source optical coherent tomography (SS-OCT) in detecting and estimating the depth of proximal caries in posterior teeth in vivo. SS-OCT images and bitewing radiographs were obtained from 86 proximal surfaces of 53 patients. Six examiners scored the locations according to a caries lesion depth scale (0-4) using SS-OCT and the radiographs. The results were compared with clinical observations obtained after the treatment. SS-OCT could detect the presence of proximal caries in tomograms that were synthesized based on the backscatter signal obtained from the proximal carious lesion through occlusal enamel. SS-OCT showed significantly higher sensitivity and larger area under the receiver operating characteristic curve than radiographs for the detection of cavitated enamel lesions and dentin caries (Student's t -test, p < 0.05). SS-OCT appears to be a more reliable and accurate method than bitewing radiographs for the detection and estimation of the depth of proximal lesions in the clinical environment.

Validation of swept source optical coherence tomography (SS-OCT) for the diagnosis of smooth surface caries in vitro.

OBJECTIVE: An accurate evaluation of the extent of dental caries and possible progress of the lesion from enamel into dentin is very important in clinical dentistry. Dentists need an imaging technology that can noninvasively and reliably quantify the extent of caries. This study aimed to evaluate the effectiveness of non-polarized swept source optical coherence tomography (OCT) in evaluating the extent of caries on smooth enamel surfaces. METHODS: One-hundred and twenty-seven investigation sites on the enamel surfaces of 93 extracted teeth were selected randomly and examined visually. The presence and extent of caries were scored by experienced and inexperienced dentists using each observation method (0: no caries; 1: enamel demineralization without surface breakdown; 2: enamel breakdown due to caries; 3: deep caries involving the dentin). The same locations were then examined using OCT, following which the teeth were sectioned using a diamond saw and viewed directly under a confocal laser scanning microscope (CLSM). Sensitivity and specificity indices for OCT and VI were calculated and compared. The results were analysed statistically using receiver operating characteristic (ROC) curves. RESULTS: Enamel and dentin caries were outlined by a visible boundary on the cross-sectional OCT images. The modality showed superior results for the detection of dentinal caries; higher sensitivity and Az values could be obtained in the ROC curves, especially by experienced dentists. CONCLUSIONS: Cross-sectional imaging of the natural caries lesions on smooth enamel surface by OCT enables efficient diagnosis of the lesion type, extent and dentin involvement. CLINICAL SIGNIFICANCE: SS-OCT can demonstrate the cross-sectional image of smooth surface enamel caries as highlighted zone in tomogram. It is crucial to determine the extent of the lesion, whether it reaches beyond DEJ or not by a non-invasive and safe technique. OCT can give clinicians information about internal tooth structure and will help clinical decision making on surgical intervention.

3D evaluation of composite resin restoration at practical training using swept-source optical coherence tomography (SS-OCT).

Internal adaptation of restorations to the cavity wall is one of the important topics in clinical dentistry. The purpose of this study was to investigate the possibility to utilize the non-invasive tomographic imaging system for teaching the importance of cavity adaptation at dental school pre-clinical training. Swept-source optical coherence tomography (SS-OCT) was used for detection of marginal and internal defects in the composite resin restorations as an educational device. Class 1 and Class 2 composite restorations to melamine resin molar tooth were assigned to the students and prepared during the skill test, and SS-OCT imaging was performed to evaluate students' works. SS-OCT could detect the internal gaps and voids within the restorations in tomography images synthesized based on the backscatter signal from within the restoration. It is suggested that the SS-OCT is promising diagnostic modality, as well as educational imaging device for the detection of internal gaps in adhesive restorations.