Unilateral Mastication Evaluated Using Asymmetric Functional Tooth Units as a Risk Indicator for Hearing Loss.

BACKGROUND: Some previous studies reported hearing ability can be reduced by impaired masticatory ability, but there has been little evidence reported of an association between hearing loss and unilateral mastication. Therefore, this study aimed to investigate the relationship between unilateral mastication (UM), estimated from individual functional tooth units (FTUs), and hearing loss in a representative sample of Korean adults. METHODS: The analyzed data were obtained from 1,773 adults aged 40-89 years who participated in Korean national survey. Hearing loss was defined as a pure-tone average of >25 dB at frequencies of 0.5, 1, 2, and 4 kHz in either ear. In each subject, UM was calculated as the difference in the sums of the FTU scores, which is an index of posterior tooth occlusion, on the two sides of the oral cavity. The scores were used to classify the UM into low, moderate, and high. The adjusted odds ratios (aORs) and their 95% confidence intervals (CIs) were calculated in multivariable logistic regression analyses. RESULTS: When controlling for sociodemographic factors, the aOR for hearing loss was 3.12 (95% CI, 1.21-8.03) for high UM relative to low UM. This association remained in a fully-adjusted model containing factors related to noise exposure (aOR 2.88; 95% CI, 1.12-7.46). CONCLUSION: Adults with high UM as measured using FTUs showed a higher occurrence of hearing loss than those with low UM.

Explaining the Red Fluorescence Evident on the Surface of Failed Dental Implants: Case Reports.

INTRODUCTION: It is important to identify the reasons for implant failure when planning future dental treatment. No studies have distinguished the factors that affect implant failure by evaluating the appearance of failed fixtures. PURPOSE: This study investigated these factors by evaluating the surface of implant fixtures using quantitative light-induced fluorescence-digital (QLF-D), which involves detecting the red fluorescence emitted by porphyrin metabolized by oral bacteria in a mature biofilm. MATERIALS AND METHODS: The areas of red fluorescence in QLF-D images obtained from all aspects of the fixture surface were then analyzed using quantitative analysis software. RESULTS: Red fluorescence was evident on the surface of implants that failed after at least 2 years of occlusal loading and exhibited severe bone loss. Implants with no fluorescence exhibited a clean surface in blue-light images, and the bone loss could not be observed radiographically. CONCLUSIONS: The cases presented that failed dental implant surfaces caused by periimplantitis can be detected by the red fluorescence evident as QLF-D.

Prevention of dental erosion of a sports drink by nano-sized hydroxyapatite in situ study.

AIM: To evaluate the inhibitory effects of the sports drink containing nano-sized hydroxyapatite (nano-HA) on dental erosion in situ. DESIGN: The study had a single-blind, two-treatment crossover design. The two treatment groups were a control group (CG; Powerade only) and an experimental group (EG; 0.25% wt/vol nano-HA was added to Powerade). Ten subjects wore removable palatal appliances containing bovine enamel specimens. The appliances were immersed in each drink for 10 mins, 4 times a day for 10 days. The tooth surface microhardness (SMH) was tested, and the erosion depth and the morphology of the tooth surface were observed. The data were analysed by repeated measures anova and t-test. RESULTS: Between the baseline and the 10th day, SMH was decreased by 80% in the specimens of the CG (P < 0.001), whereas there was only a 6% decrease in the SMH of the specimens in the EG. An erosion depth of 12.70 ± 4.66 µm and an irregular tooth surface were observed on the 10th day in the specimens of the CG. No dental erosions, however, was observed in the specimens of the EG. CONCLUSIONS: The sports drink containing 0.25% nano-HA was effective in preventing dental erosion in situ.

Recovery percentage of remineralization according to severity of early caries.

PURPOSE: To analyze the cutoff severity of early lesions according to recovery rate after fluoride treatment. METHODS: 100 specimens were demineralized over 3 to 40 days. Specimens were immersed in 2% sodium fluoride solution for 4 minutes, and then in artificial saliva for the rest of the total 24 hours. After 10-time repetition of this cycle, the deltaF recovery rates (R(deltaF,) %) were calculated from the deltaF values before (deltaF(base), %) and after (deltaF(tx), %) remineralization using the QLF-D system. For the discrimination of R(deltaF) based on deltaF(base), the sensitivities versus 1-specificities were analyzed in receiver operating characteristic (ROC) curves, the 95% confidence interval (CI) as well as the significance of differences. The histological features of lesions were observed and lesion depths were digitally measured by polarized light microscopy (PLM). A paired t-test was also performed to assess the differences in deltaF and lesion depth before and after applying fluoride. RESULTS: For a threshold recovery percentage of 40%, the suggested deltaF(base) cutoff value was -19.15%, whereas for a threshold recovery percentage of 50%, the suggested cutoff value was -14.60% (P < 0.0001). According to the QLF-D system and PLM analysis, recovery percentage was greater for shallower lesions. Based on fluoride treated recovery percentages, the findings suggested that it is possible for early caries lesions to make more than 50% recovery when the deltaF(base) value was greater than -14.60%. Visually and numerically, the relative recovery percentages were highest during the earlier stages of caries.

Image-guided in situ cancer vaccination with combination of multi-functional nano-adjuvant and an irreversible electroporation technique.

Cancer immunotherapy is a next-generation treatment strategy; however, its side effects limit its clinical translation. Here, a novel combination of a multi-functional nano-adjuvant (M-NA) prepared with an iron oxide/gold core and a cationic polymer shell via multilayer synthesis with CpG oligodeoxynucleotide (CpG-ODN) electrostatically complexed on its surface, and irreversible electroporation (IRE) technique was developed for effective image-guided in situ cancer vaccination. The M-NA can be retained long-term in the dense tumoral extracellular matrix after intratumoral injection and internalized by antigen-presenting cells (APCs). The IRE can induce immunogenic cell death. Indeed, in a mouse tumor model, the M-NA showed longer tumor retention time than free CpG-ODN. Compared with other treatments, the combined treatment significantly inhibited tumor growth with 100% survival rate for ∼60 days. The therapy induced the activation of cytotoxic lymphocytes and the maturation of APCs in vivo. This treatment could be effective in image-guided local cancer immunotherapy.

Antibacterial characteristics of Curcuma xanthorrhiza extract on Streptococcus mutans biofilm.

This study evaluated the antibacterial effects of a natural Curcuma xanthorrhiza extract (Xan) on a Streptococcus mutans biofilm by examining the bactericidal activity, inhibition of acidogenesis and morphological alteration. Xan was obtained from the roots of a medicinal plant in Indonesia, which has shown selective antibacterial effects on planktonic S. mutans. S. mutans biofilms were formed on slide glass over a 72 h period and treated with the following compounds for 5, 30, and 60 min: saline, 1% DMSO, 2 mg/ml chlorhexidine (CHX), and 0.1 mg/ml Xan. The Xan group exposed for 5 and 30 min showed significantly fewer colony forming units (CFU, 57.6 and 97.3%, respectively) than those exposed to 1% DMSO, the negative control group (P<0.05). These CFU were similar in number to those slides exposed to CHX, the positive control group. Xan showed similar bactericidal effect to that of CHX but the dose of Xan was one twentieth that of CHX. In addition, the biofilms treated with Xan and CHX maintained a neutral pH for 4 h, which indicates that Xan and CHX inhibit acid production. Scanning electron microscopy showed morphological changes in the cell wall and membrane of the Xan-treated biofilms; an uneven surface and a deformation in contour. Overall, natural Xan has strong bactericidal activity, inhibitory effects on acidogenesis, and alters the microstructure of S. mutans biofilm. In conclusion, Xan has potential in anti-S. mutans therapy for the prevention of dental caries.

Caries detection and quantification around stained pits and fissures in occlusal tooth surfaces with fluorescence.

Occlusal discoloration due to staining frequently occurs on the pits and fissures of teeth. Noncariogenic discoloration (non-CD) refers to the attachment of staining chromogens to sound surfaces, whereas cariogenic discoloration (CD) represents the discoloration of porous structures due to bacterial metabolites and mineral loss from the enamel surface. This study evaluated whether it is possible to distinguish between non-CD and CD on stained occlusal surfaces with fluorescence assessed by the quantitative light-induced fluorescence (QLF) technology. Sixty-two extracted human permanent teeth with suspected discolorations on the pit and fissure were examined. The maximum values of fluorescence loss (ΔFmax) and red fluorescence gain (ΔRmax) were calculated using QLF images. Using histology as the gold standard, it was found that 12 teeth were sound (non-CD), while 50 teeth had enamel and dentine caries (CD). The validity tests at the enamel histological caries level, ΔRmax (ρ = 0.80) were strongly correlated with the histology (P < 0.001). At the optimum threshold (105.0) of ΔRmax, it showed high levels of sensitivity and specificity (0.96 and 0.83, respectively). Therefore, QLF can be used to distinguish non-CD from CD on occlusal surfaces using red fluorescence values with high validity.

Detection and Analysis of Enamel Cracks by Quantitative Light-induced Fluorescence Technology.

INTRODUCTION: The ability to accurately detect tooth cracks and quantify their depth would allow the prediction of crack progression and treatment success. The aim of this in vitro study was to determine the capabilities of quantitative light-induced fluorescence (QLF) technology in the detection of enamel cracks. METHODS: Ninety-six extracted human teeth were selected for examining naturally existing or suspected cracked teeth surfaces using a photocuring unit. QLF performed with a digital camera (QLF-D) images were used to assess the ability to detect enamel cracks based on the maximum fluorescence loss value (ΔFmax, %), which was then analyzed using the QLF-D software. A histologic evaluation was then performed in which the samples were sectioned and observed with the aid of a polarized light microscope. The relationship between ΔFmax and the histology findings was assessed based on the Spearman rank correlation. The sensitivity and specificity were calculated to evaluate the validity of using QLF-D to analyze enamel inner-half cracks and cracks extending to the dentin-enamel junction. RESULTS: There was a strong correlation between the results of histologic evaluations of enamel cracks and the ΔFmax value, with a correlation coefficient of 0.84. The diagnostic accuracy of QLF-D had a sensitivity of 0.87 and a specificity of 0.98 for enamel inner-half cracks and a sensitivity of 0.90 and a specificity of 1.0 for cracks extending to the dentin-enamel junction. CONCLUSIONS: These results indicate that QLF technology would be a useful clinical tool for diagnosing enamel cracks, especially given that this is a nondestructive method.

Assessing the use of Quantitative Light-induced Fluorescence-Digital as a clinical plaque assessment.

BACKGROUND: The aims of this study were to compare the relationship between red fluorescent plaque (RF plaque) area by Quantitative Light-induced Fluorescence-Digital (QLF-D) and disclosed plaque area by two-tone disclosure, and to assess the bacterial composition of the RF plaque by real time-PCR. METHODS: Fifty healthy subjects were included and 600 facial surfaces of their anterior teeth were examined. QLF-D was taken on two separate occasions (before and after disclosing), and the RF plaque area was calculated based on Plaque Percent Index (PPI). After disclosing, the stained plaque area was analyzed to investigate the relationship with the RF plaque area. The relationship was evaluated using Pearson correlation and paired t-test. Then, the RF and non-red fluorescent (non-RF) plaque samples were obtained from the same subject for real-time PCR test. Total 10 plaque samples were compared the ratio of the 6 of bacteria using Wilcoxon signed rank test. RESULTS: Regarding the paired t-test, the blue-staining plaque area (9.3±9.2) showed significantly similarity with the RF plaque area (9.1±14.9, p=0.80) at ΔR20, however, the red-staining plaque area (31.6±20.9) presented difference from the RF plaque area (p<0.0001). In addition, bacterial composition of Prevotella intermedia and Streptococcus anginosus was associated with substantially more the RF plaque than the non-RF plaque (p<0.05). CONCLUSIONS: The plaque assessment method using QLF-D has potential to detect mature plaque, and the plaque area was associated with the blue-staining area using two-tone disclosure.

Plaque autofluorescence as potential diagnostic targets for oral malodor.

The aim of this study was to determine whether the degree of tongue and interdental plaque can be used to assess oral malodor by quantifying their fluorescence as detected using quantitative light-induced fluorescence (QLF) technology. Ninety-nine subjects who complained of oral malodor were included. The level of oral malodor was quantified using the organoleptic score (OLS) and the concentration of volatile sulfur compounds (VSCs). The fluorescence properties of tongue and interdental plaque were quantified as scores calculated by multiplying the intensity and area of fluorescence in QLF-digital images, and the combined plaque fluorescence (CPF) score was obtained by summing the scores for the two regions. The associations of the scores with malodor levels and the diagnostic accuracy of the CPF score were analyzed. The two plaque fluorescence scores and their combined score differed significantly with the level of oral malodor (p<0.001). The CPF score was moderately correlated with OLS (r=0.64) and VSC levels (r=0.54), and its area under the receiver operating characteristic curve was 0.77 for identifying subjects with definite oral malodor (OLS≥2). In conclusion, plaque fluorescence from tongue and interdental sites as detected using QLF technology can be used to assess the level of oral malodor.

Short-term improvement of masticatory function after implant restoration.

PURPOSE: Dental implants present several advantages over other tooth replacement options. However, there has been little research on masticatory function in relation to implant treatment. Therefore, the aim of the present study was to evaluate the improvement of masticatory function two weeks after implant restoration. METHODS: Masticatory ability was evaluated with the subjective food intake ability (FIA) and objective mixing ability index (MAI) methods. Fifty-four subjects with first and second missing molars completed the study. The subjects were asked to complete a self-reported questionnaire about 30 different food items, and to chew wax samples 10 times both before and two weeks after implant restoration. A total of 108 waxes were analyzed with an image analysis program. RESULTS: Dental implant restoration for lost molar teeth on one side increased the FIA score by 9.0% (P<0.0001). The MAI score also increased, by 14.3% after implant restoration (P<0.0001). Comparison between the good and poor mastication groups, which were subdivided based on the median MAI score before implant restoration, showed that the FIA score of the poor group was enhanced 1.1-fold while its MAI score was enhanced 2.0-fold two weeks after an implant surgery. CONCLUSIONS: Using the FIA and MAI assessment methods, this study showed that masticatory function was improved two weeks after implant restoration. In particular, the enhancement of masticatory function by implant restoration was greater in patients with relatively poor initial mastication than in those with good initial mastication.

Validity and reliability of autofluorescence-based quantification method of dental plaque.

BACKGROUND: The aim of this study was to evaluate validity and reliability of autofluorescence-based plaque quantification (APQ) method. METHODS: The facial surfaces of 600 sound anterior teeth of 50 subjects were examined. The subjects received dental plaque examination using Turesky modified Quigley Hein plaque index (QHI) and Silness & Löe plaque index (SLI). The autofluorescence images were taken before the plaque examination with Quantitative Light-induced Fluorescence-Digital, and plaque percent index (PPI) was calculated. Correlation between two existing plaque indices and the PPI of the APQ method was evaluated to find which level of plaque redness on tooth (ΔR) by the APQ method shows the highest correlation. The area under the ROC curve (AUC) analysis and intra- and inter-examiner reliability tests were performed. RESULTS: The PPIΔR20 of the APQ method showed a moderate correlation with two existing plaque indices (rho of QHI=0.48, SLI=0.51). This methodology fell in the fair category and it had an excellent reliability. The APQ method also showed possibility to detect heavy plaque with fair validity. CONCLUSIONS: The APQ method demonstrated excellent reliability, and fair validity, compared with 2 conventional indices. The plaque quantification described has the potential to be used in clinical evaluation of oral hygiene procedures.

Chlorhexidine-releasing orthodontic elastomerics.

The aim of this study was to identify the best combination of chlorhexidine (CHX) with orthodontic elastomerics for prevention of oral disease in orthodontic patients. We used ethyl cellulose (EC) as the polymer, and experimental groups were divided into five groups according to differences in solvent (i.e., ethanol; EtOH, dichloromethane; DCM). CHX release from the coated elastomerics was evaluated with a UV spectrophotometer and observed by scanning electron microscope (SEM). The antimicrobial release increased over time for 48 h in Group 3 (CDA+EC+30% EtOH/70% DCM), exhibiting the longest sustained-release characteristics (p<0.001). It also showed the highest antimicrobial properties, which was confirmed by inhibition zone testing using S. mutans (p<0.05). All groups were not affected when tensile force was tested in the coated elastomerics. We conclude that the antibacterial effect of CHX can be adjusted according to combinations of polymers and solvents. Group 3 exhibited the best substantivity and antimicrobial properties.

Validation of quantitative light-induced fluorescence-digital (QLF-D) for the detection of approximal caries in vitro.

OBJECTIVES: Detection of approximal caries lesions can be difficult due to their anatomical position. This study aimed to assess the ability of the quantitative light-induced fluorescence-digital (QLF-D) in detecting approximal caries, and to compare the performance with those of the International Caries Detection and Assessment System II (ICDAS II) and digital radiography (DR). METHODS: Extracted permanent teeth (n=100) were selected and mounted in pairs. The simulation pairs were assessed by one calibrated dentist using each detection method. After all the examinations, the teeth (n=95) were sectioned and examined histologically as gold standard. The modalities were compared in terms of sensitivity, specificity, areas under receiver operating characteristic curves (AUROC) for enamel (D1) and dentine (D3) levels. The intra-examiner reliability was assessed for all modalities. RESULTS: At D1 threshold, the ICDAS II presented the highest sensitivity (0.80) while the DR showed the highest specificity (0.89); however, the methods with the greatest AUC values at D1 threshold were DR and QLF-D (0.80 and 0.80 respectively). At D3 threshold, the methods with the highest sensitivity were ICDAS II and QLF-D (0.64 and 0.64 respectively) while the method with the lowest sensitivity was DR (0.50). However, with regard to the AUC values at D3 threshold, the QLF-D presented the highest value (0.76). All modalities showed to have excellent intra-examiner reliability. CONCLUSIONS: The newly developed QLF-D was not only able to detect proximal caries, but also showed to have comparable performance to the visual inspection and radiography in detecting proximal caries. CLINICAL SIGNIFICANCE: QLF-D has the potential to be a useful detection method for proximal caries.

Desensitizing efficacy of nano-carbonate apatite dentifrice and Er,Cr:YSGG laser: a randomized clinical trial.

OBJECTIVE: The aim of this study was to evaluate the desensitizing effects of a dentifrice containing nano-carbonate apatite (n-CAP) and Er,Cr:YSGG laser in the treatment of dentin hypersensitivity. BACKGROUND DATA: Most studies of hypersensitivity treatment have been conducted with different methods of professional treatment and self-care in each study. Moreover, clinical studies that compare self-care and professional treatment have not yet been published. METHODS: Eighty-two patients with dentin hypersensitivity were divided randomly into three groups: (1) a control group with strontium chloride dentifrice (SC), (2) n-CAP dentifrice (n-CAP), and (3) an Er,Cr:YSGG laser (laser) group. The study was conducted for 4 weeks: a treatment period of 2 weeks and a maintenance period of 2 subsequent weeks. The SC and n-CAP groups were instructed to brush their teeth twice a day for 1 min. The laser group visited twice at 1 week intervals for irradiation of the sensitive teeth. The desensitizing effect was evaluated by assessing the tactile sensitivity using the visual analogue scale (VAS), and evaporative air sensitivity was determined using an air blast score (ABS). RESULTS: The n-CAP group and the laser group showed significantly different desensitizing effects in VAS after 4 weeks (69% and 63%, respectively) and a 33% (p<0.05) and 3% (p>0.05) desensitizing effect, respectively, in VAS during the maintenance period. CONCLUSIONS: The n-CAP and the laser were effective in reducing dentin hypersensitivity. The laser had a superior desensitizing effect at the initial stage, whereas the n-CAP maintained its effect for a relatively longer time in clinical situations.

Validity of screening methods for periodontitis using salivary hemoglobin level and self-report questionnaires in people with disabilities.

BACKGROUND: The aim of this study is to evaluate the validity of screening methods in predicting periodontitis in people with disabilities using the objective salivary hemoglobin level, a subjective self-report questionnaire, and a combined model of the two methods with demographic characteristics. METHODS: The participants were 195 patients with disabilities aged >18 years who were examined using the community periodontal index (CPI), salivary hemoglobin level, and answers to 10 self-report questions (n = 192). Multivariable logistic regression and receiver operating characteristic (ROC) curve analysis were performed to evaluate the validity of the methods and the combined model in predicting the prevalence of ≥CPI 3 (probing depth [PD] ≥4 mm) or CPI 4 (PD ≥6 mm). RESULTS: Overall, 75.9% of the study group (148 of 195) were diagnosed with ≥CPI 3, and 38.5% of the study group (75 of 195) were diagnosed with CPI 4. The areas under the ROC curve (AUCs) of the salivary hemoglobin level were 0.578 (sensitivity of 41% and specificity of 77%) and 0.662 (sensitivity of 53% and specificity of 75%) for predicting the prevalence of ≥CPI 3 and CPI 4, respectively. Multivariable modeling incorporating four different questions for predicting ≥CPI 3 or CPI 4 indicated higher AUCs of 0.710 and 0.732, respectively, yielding higher sensitivity (55% for ≥CPI 3 and 69% for CPI 4) than that of salivary hemoglobin level. The most useful prediction models for ≥CPI 3 or CPI 4 were combined models, which yielded AUCs of 0.773 and 0.807, respectively, with sensitivity values of 70% and specificity values >75%. CONCLUSION: The salivary hemoglobin level, self-report questionnaire, and the combined method demonstrated screening potential that could predict the population prevalence of ≥CPI 3 or CPI 4.

Mercury distribution and concentration in rats fed powdered dental amalgam.

The aim was to evaluate the distribution and elimination of mercury in the tissues of rats exposed to powdered dental amalgam. The study comprised of three groups: the first (A) was an unexposed control, the second (B) was fed 8.3mg of powdered amalgam weekly for 12 weeks, and the third (C) was fed 25.0mg of powdered amalgam weekly for 4 weeks followed by either a 4- or 8-week period of non-exposure. The total amount of amalgam administered in each of the latter two groups was 0.1g. Animals were killed at 4, 8 and 12 weeks, and their kidneys, liver and brains were removed. Mercury present in tissues from one side was analysed by cold-vapour atomic absorption spectrometry; tissues from the other side were stained autometallographically. No mercury was detected in any tissue of control group A. In group B, the mercury concentration in the kidneys was significantly higher than that of the control, whereas in group C, the mercury concentration in both the liver and kidneys decreased significantly during the period of non-exposure. Mercury was not detected in brain tissue from any group. The light-microscopic findings were in agreement with the quantitative results. Mercury grains were most common in the renal cortex, especially in the proximal tubule. Although there was some mercury accumulation in the tissues of the two experimental groups, no pathological reactions were noted. These data suggest that, in the rat, the ingestion of dental amalgam in small quantities for a limited period does not lead to morphological changes in the liver, brain or kidneys. It seems likely that mercury does not accumulate in brain tissue and that any accumulation in the kidneys and liver is at least partially reduced after ingestion ceases.

Modification of surface pre-treatment for resin infiltration to mask natural white spot lesions.

OBJECTIVES: The aims of this study were to investigate an alternative pre-treatment method for resin infiltration using 37% H3PO4 with a brush applicator and to evaluate the penetration effect of the infiltrant for masking the natural white spot lesions (WSLs) in human teeth. METHODS: Seventy extracted human molars and pre-molars with non-cavitated WSLs were collected. Thirty teeth met criteria of ICDAS code 2, and were sectioned, providing a total of sixty paired halves. For the control group, 15% HCl gel was applied for 120s, and 37% H3PO4, gel was gently rubbed with a brush applicator for 30s to the experimental group. Also, to evaluate the penetration effect of the infiltrant by pre-treatment, the specimens were treated with the infiltrant (Icon®). Thicknesses of the removed surfaces and percentages of the infiltrated areas (IA%) were evaluated by CLSM, and micro-morphological changes were observed by SEM. RESULTS: The mean thicknesses of removed surface layers were significantly different between the control group (36±7.62µm) and the experimental group (13±2.76µm) (p<0.001). But, the means of IA% were similar in both groups (p>0.05). In the SEM images, the prism cores were preferentially dissolved in the control group, while the prism peripheries were preferentially dissolved in the experimental group. CONCLUSIONS: Applying 37% H3PO4 gel with an applicator brush for 30s could increase the permeability and minimize removal of the surface layer of natural WSLs. Moreover, the effect of resin infiltration was similar to the control group which was pretreated 15% HCl gel for 120s in vitro study. CLINICAL SIGNIFICANCE: For resin infiltration, applying 37% H3PO4 gel with a brush applicator can preserve the protective surface layers of the WSLs with reduced application time.

Effect of a new combined therapy with nano-carbonate apatite and CO2 laser on dentin hypersensitivity in an in situ model.

OBJECTIVE: The aim of this study was to determine the occluding effects of a combination of dentifrice containing nano-carbonate apatite (n-CAP) and CO2 laser on dentinal tubules, and to evaluate the acid resistance of this combination after 4 days of treatment, by using an in situ model. BACKGROUND DATA: The synergic effect of this combination was demonstrated in an in vitro study. METHODS: This was a two period crossover, single-blind, randomized, four-treatment, split-mouth study. Ten healthy participants wore lower intraoral appliances during the treatment period. Specimens were divided into the following four groups: no treatment (control group), tooth-brushing using 20% n-CAP dentifrice (n-CAP group), CO2 laser irradiation (laser group), and laser irradiation after n-CAP application (combined group). Occluding effects were evaluated on 2 days (days 1 and 2), and then acid challenge was performed using grape juice on 2 days (days 3 and 4). All of the specimen surfaces were evaluated by a scanning electron microscope. RESULTS: The combined group showed a better occluding effect than control group compared with other treatment groups, and this effect was 20% higher than that in the n-CAP group. Also, the combined group had the smallest open dentinal tubular area among all of the treatment groups. CONCLUSIONS: The combined therapy is a promising method for ensuring a long-lasting effect of dentin hypersensitivity treatment in clinical practice.

Monitoring the maturation process of a dental microcosm biofilm using the Quantitative Light-induced Fluorescence-Digital (QLF-D).

OBJECTIVE: The aim of this study was to investigate whether Quantitative Light-induced Fluorescence-Digital (QLF-D) could monitor the degree of maturation of dental microcosm biofilms by observing the red fluorescence emitted from the biofilms. METHODS: Dental microcosm the biofilms were grown on bovine enamel discs. They were initiated from human saliva, and then grown in 0.5% sucrose growth media for 10 days. On days 1, 2, 3, 7, and 10 after the inoculation, fluorescence images of the biofilms were captured using the QLF-D and the red fluorescence intensity was quantified by calculating the red/green ratio (R/G value). Total and aciduric bacteria within the biofilms were counted, and the degree of demineralization was evaluated by measuring the percentage of surface microhardness change (ΔVHN) and lesion depth in the enamel. RESULTS: The R/G values of the biofilms assessed by the QLF-D increased significantly over time up to 7 days after inoculation (p<0.0001). The R/G values showed significant positive correlations with the total bacterial CFUs (r=0.74, p=0.001), aciduric bacterial CFUs (r=0.85, p=0.001), ΔVHN (r=0.65, p=0.001), and lesion depth in the enamel (r=0.82, p=0.001) according to the maturation time. CONCLUSIONS: The red fluorescence detected by the QLF-D increased according to biofilm maturation and was significantly associated with the cariogenicity of the biofilm. Therefore, this device could be used to monitor the degree of biofilm maturation by observing the red fluorescence emitted from cariogenic biofilms. CLINICAL SIGNIFICANCE: The QLF-D enables the detection of a mature dental plaque and monitoring of its cariogenic status by observing the plaque fluorescence non-destructively, in real time.