Brain Functional Changes before, during, and after Clinical Pain.

This study used an emerging brain imaging technique, functional near-infrared spectroscopy (fNIRS), to investigate functional brain activation and connectivity that modulates sometimes traumatic pain experience in a clinical setting. Hemodynamic responses were recorded at bilateral somatosensory (S1) and prefrontal cortices (PFCs) from 12 patients with dentin hypersensitivity in a dental chair before, during, and after clinical pain. Clinical dental pain was triggered with 20 consecutive descending cold stimulations (32° to 0°C) to the affected teeth. We used a partial least squares path modeling framework to link patients' clinical pain experience with recorded hemodynamic responses at sequential stages and baseline resting-state functional connectivity (RSFC). Hemodynamic responses at PFC/S1 were sequentially elicited by expectation, cold detection, and pain perception at a high-level coefficient (coefficients: 0.92, 0.98, and 0.99, P < 0.05). We found that the pain ratings were positively affected only at a moderate level of coefficients by such sequence of functional activation (coefficient: 0.52, P < 0.05) and the baseline PFC-S1 RSFC (coefficient: 0.59, P < 0.05). Furthermore, when the dental pain had finally subsided, the PFC increased its functional connection with the affected S1 orofacial region contralateral to the pain stimulus and, in contrast, decreased with the ipsilateral homuncular S1 regions ( P < 0.05). Our study indicated for the first time that patients' clinical pain experience in the dental chair can be predicted concomitantly by their baseline functional connectivity between S1 and PFC, as well as their sequence of ongoing hemodynamic responses. In addition, this linked cascade of events had immediate after-effects on the patients' brain connectivity, even when clinical pain had already ceased. Our findings offer a better understating of the ongoing impact of affective and sensory experience in the brain before, during, and after clinical dental pain.

Imaging textural variation in the acoustoelastic coefficient of aluminum using surface acoustic waves.

Much interest has arisen in nonlinear acoustic techniques because of their reported sensitivity to variations in residual stress, fatigue life, and creep damage when compared to traditional linear ultrasonic techniques. However, there is also evidence that the nonlinear acoustic properties are also sensitive to material microstructure. As many industrially relevant materials have a polycrystalline structure, this could potentially complicate the monitoring of material processes when using nonlinear acoustics. Variations in the nonlinear acoustoelastic coefficient on the same length scale as the microstructure of a polycrystalline sample of aluminum are investigated in this paper. This is achieved by the development of a measurement protocol that allows imaging of the acoustoelastic response of a material across a samples surface at the same time as imaging the microstructure. The development, validation, and limitations of this technique are discussed. The nonlinear acoustic response is found to vary spatially by a large factor (>20) between different grains. A relationship is observed when the spatial variation of the acoustoelastic coefficient is compared to the variation in material microstructure.

School-based intervention for improving the oral health of children in southern Thailand.

OBJECTIVE: A two-year study assessed the benefit of an enhanced oral health promotion program combined with a closely supervised tooth brushing program in schools, using toothpaste containing 1,450 ppm F- and 1.5% arginine, on oral health and dental caries. METHODS: 15 southern Thailand schools and 3,706 pre-school children were recruited: 8 schools with 1,766 children as controls; 7 schools with 1,940 children in the intervention groups. Of the intervention schools five were classified as cooperative school and two as non-cooperative schools, based on the criteria of 80% participation in the prescribed tooth brushing activities. RESULTS: The DMFT and DMFS increments ("enamel and dentine") were 1.19 and 1.91 for the control group and 1.04 and 1.59 for the intervention groups. These represent 12.6% and 16.8% reductions in caries respectively. The DMFT and DMFS increments ("dentine threshold") were 0.26 and 0.44 for the control group and 0.19 and 0.29 for the intervention group, representing 26.9%, and 34.1% reductions in caries incidence respectively. For the more cooperative schools the benefits were greater: up to a 40.9% reduction in caries for DMFS ("dentine threshold"). At the 24 month examination there were significant improvements in dental plaque scores with greater improvements seen in the intervention group, greater still in the cooperative schools. CONCLUSIONS: This study documents the positive effect from use of fluoridated toothpaste (1,450 ppm F- and 1.5% arginine) administered by schoolteachers and undertaken via an enhanced school oral health program. Optimising oral health interventions for young children in Thai schools may have a significant impact on caries incidence resulting in reductions of up to 34% reductions in caries for all schools included in the study and up to 41% for the most cooperative.

Different Brain Responses to Pain and Its Expectation in the Dental Chair.

A dental appointment commonly prompts fear of a painful experience, yet we have never fully understood how our brains react to the expectation of imminent tooth pain once in a dental chair. In our study, 21 patients with hypersensitive teeth were tested using nonpainful and painful stimuli in a clinical setting. Subjects were tested in a dental chair using functional near-infrared spectroscopy to measure cortical activity during a stepwise cold stimulation of a hypersensitive tooth, as well as nonpainful control stimulation on the same tooth. Patients' sensory-discriminative and emotional-cognitive cortical regions were studied through the transition of a neutral to a painful stimulation. In the putative somatosensory cortex contralateral to the stimulus, 2 well-defined hemodynamic peaks were detected in the homuncular orofacial region: the first peak during the nonpainful phase and a second peak after the pain threshold was reached. Moreover, in the upper-left and lower-right prefrontal cortices, there was a significant active hemodynamic response in only the first phase, before the pain. Subsequently, the same prefrontal cortical areas deactivated after a painful experience had been reached. Our study indicates for the first time that pain perception and expectation elicit different hemodynamic cortical responses in a dental clinical setting.

Dentists' perspectives on caries-related treatment decisions.

OBJECTIVE: To assess the impact of patient risk status on Colombian dentists' caries related treatment decisions for early to intermediate caries lesions (ICDAS code 2 to 4). METHODS: A web-based questionnaire assessed dentists' views on the management of early/intermediate lesions. The questionnaire included questions on demographic characteristics, five clinical scenarios with randomised levels of caries risk, and two questions on different clinical and radiographic sets of images with different thresholds of caries. RESULTS: Questionnaires were completed by 439 dentists. For the two scenarios describing occlusal lesions ICDAS code 2, dentists chose to provide a preventive option in 63% and 60% of the cases. For the approximal lesion ICDAS code 2, 81% of the dentists chose to restore. The main findings of the binary logistic regression analysis for the clinical scenarios suggest that for the ICDAS code 2 occlusal lesions, the odds of a high caries risk patient having restorations is higher than for a low caries risk patient. For the questions describing different clinical thresholds of caries, most dentists would restore at ICDAS code 2 (55%) and for the question showing different radiographic thresholds images, 65% of dentists would intervene operatively at the inner half of enamel. No significant differences with respect to risk were found for these questions with the logistic regression. CONCLUSION: The results of this study indicate that Colombian dentists have not yet fully adopted non-invasive treatment for early caries lesions.

Determination of the acoustoelastic coefficient for surface acoustic waves using dynamic acoustoelastography: an alternative to static strain.

The third-order elastic constants of a material are believed to be sensitive to residual stress, fatigue, and creep damage. The acoustoelastic coefficient is directly related to these third-order elastic constants. Several techniques have been developed to monitor the acoustoelastic coefficient using ultrasound. In this article, two techniques to impose stress on a sample are compared, one using the classical method of applying a static strain using a bending jig and the other applying a dynamic stress due to the presence of an acoustic wave. Results on aluminum samples are compared. Both techniques are found to produce similar values for the acoustoelastic coefficient. The dynamic strain technique however has the advantages that it can be applied to large, real world components, in situ, while ensuring the measurement takes place in the nondestructive, elastic regime.

Quantitative light-induced fluorescence to measure enamel remineralization in vitro.

UNLABELLED: The aim of this study was to compare the ability of quantitative light-induced fluorescence (QLF) and surface microhardness (SMH) to measure the remineralization of enamel subsurface lesions, using a pH-cycling model including treatment with 0-ppm, 550-ppm or 1,100-ppm sodium fluoride (NaF) dentifrices. METHODS: Subsurface lesions were created in human enamel specimens (n = 36) and exposed to a remineralization pH-cycling model for 14 days. The pH-cycling model was performed in an automated system where specimens were subjected to a demineralizing solution for 20 min and treatment for 1 min and were then remineralized for 7 h 39 min, 3 times daily. The treatments consisted of 3 NaF, silica-containing dentifrices (0 ppm F; 550 ppm F; 1,100 ppm F). The outcome variables were: change from baseline in surface hardness and percentage change from baseline in fluorescence. An ANCOVA explored differences between different treatment groups (at the p < 0.05 level). Associations between QLF and SMH were evaluated using Spearman's correlation coefficient. RESULTS: The percentage SMH changes were 14.9 ± 2.1%, 56.6 ± 9.6% and 103.9 ± 14.6% for the 0-, 550- and 1,100-ppm F dentifrices, respectively. The percentage fluorescence changes were 15.6 ± 7.1%, 59.8 ± 11.9% and 85 ± 13.2%, respectively. The differences between all pairwise comparisons were statistically significant for both methods (p = 0.001). QLF correlated with SMH (r = 0.67). CONCLUSIONS: Both the SMH and QLF methods demonstrated a significant F dose response for toothpaste in this in vitro remineralization model, and both methods were able to distinguish treatments with different F levels.

Measuring initial enamel erosion with quantitative light-induced fluorescence and optical coherence tomography: an in vitro validation study.

BACKGROUND: Measurement of initial enamel erosion is currently limited to in vitro methods. Optical coherence tomography (OCT) and quantitative light-induced fluorescence (QLF) have been used clinically to study advanced erosion. Little is known about their potential on initial enamel erosion. OBJECTIVES: To evaluate the sensitivity of QLF and OCT in detecting initial dental erosion in vitro. METHODS: 12 human incisors were embedded in resin except for a window on the buccal surface. Bonding agent was applied to half of the window, creating an exposed and non-exposed area. Baseline measurements were taken with QLF, OCT and surface microhardness. Samples were immersed in orange juice for 60 min and measurements taken stepwise every 10 min. QLF was used to compare the loss of fluorescence between the two areas. The OCT system, OCS1300SS (Thorlabs Ltd.), was used to record the intensity of backscattered light of both areas. Multiple linear regression and paired t test were used to compare the change of the outcome measures. RESULTS: All 3 instruments demonstrated significant dose responses with the erosive challenge interval (p < 0.05) and a detection threshold of 10 min from baseline. Thereafter, surface microhardness demonstrated significant changes after every 10 min of erosion, QLF at 4 erosive intervals (20, 40, 50 and 60 min) while OCT at only 2 (50 and 60 min). CONCLUSION: It can be concluded that OCT and QLF were able to detect demineralization after 10 min of erosive challenge and could be used to monitor the progression of demineralization of initial enamel erosion in vitro.

A clinical investigation using quantitative light-induced fluorescence (QLF) of the anticaries efficacy of a dentifrice containing 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate.

OBJECTIVE: The purpose of this study was to assess the ability of a new dentifrice containing arginine, an insoluble calcium compound, and fluoride to arrest or reverse naturally occurring buccal caries lesions measured using Quantitative Light-induced Fluorescence (QLF). METHODS: Three study groups used dentifrices which contained 1) 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate (experimental), 2) 1450 ppm fluoride as sodium monofluorophosphate (positive control), and 3) no fluoride (negative control). All three dentifrices were formulated in the same calcium base. The study participants were from three schools in the city of Chengdu, Sichuan Province, China. A total of 446 of 450 recruited subjects completed the study. Of these, 147 were in the experimental, 148 in the positive control, and 151 in the negative control groups. The initial age of the children was 10-12 years (mean 11.4 +/- 0.54); 47.5% were female. RESULTS: Using QLF, assessments of buccal caries lesions were made at baseline and after three and six months of product use. For AQ, representing lesion volume, the baseline mean value for the three groups was 27.30, and at the three-month examination the mean values were 16.76, 19.25, and 25.89 for the experimental, positive, and negative control dentifrices, respectively. This represents improvements from baseline of 38.6%, 29.5%, and 5.2%. At six months, the deltaQ values for the three groups were 13.46, 18.47, and 24.18, representing improvements from baseline of 50.7%, 32.3%, and 11.4%. For all QLF metrics, deltaF (loss of fluorescence), area, and deltaQ, the differences between the negative control and both the experimental and positive control groups were statistically significant (p < or = 0.01). The differences between the experimental and positive control groups attained statistical significance for deltaQ (p < or = 0.003) at the six-month examination. CONCLUSION: It is concluded that both of the fluoride-containing toothpastes are significantly better at arresting and reversing buccal caries lesions than the non-fluoride toothpaste. Furthermore, it is concluded that the new dentifrice containing arginine, an insoluble calcium compound, and fluoride provides significantly greater anticaries benefit than a dentifrice containing fluoride alone.

A clinical investigation of the efficacy of a dentifrice containing 1.5% arginine and 1450 ppm fluoride, as sodium monofluorophosphate in a calcium base, on primary root caries.

OBJECTIVE: The purpose of this six-month study was to assess the ability of a new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, as sodium monofluorophosphate, to arrest and reverse primary root caries lesions in adults. METHODS: Three test groups used dentifrices which contained either: 1) 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate in a calcium base (experimental); 2) 1450 ppm fluoride as sodium fluoride in a silica base (positive control); or 3) no fluoride in a calcium base (negative control). The study participants were residents of the city of Chengdu, Sichuan Province, China. In order to take part, subjects had to have at least one non-cavitated primary root caries lesion. A total of 412 subjects completed the study. They were aged from 50 to 70 years (mean age 64 +/- 4.1 years) and 53.6% were female. Efficacy for arresting and reversal of primary root caries was assessed by clinical hardness measures and through the use of the Electrical Caries Monitor. RESULTS: After three months of product use, clinical hardness measures showed that 27.7%, 24.6%, and 13.1% of lesions had improved in the experimental, positive, and negative control groups, respectively, and 0.7%, 4.5%, and 16.8% had become worse, respectively. The differences in the distribution of lesion change between the negative control group and both the experimental (p < 0.001) and positive control (p = 0.001) were statistically significant. The Electrical Caries Monitor was also used as an objective measure of lesion severity. The end values increased from baseline to the three-month examinations, but none of the differences between the groups attained statistical significance. After six months, clinical hardness measures showed that only one lesion (0.7%) was worse than at the baseline examination-in the experimental group compared to 9.0% and 18.2% in the positive and negative control groups, respectively. In addition, 61.7%, 56.0%, and 27.0%, respectively, showed improvement for the three groups. The differences in the distribution of lesion change scores between the negative control group and both the experimental (p < 0.001) and positive control (p < 0.001) were statistically significant, as was the difference between the experimental group and the positive control (p = 0.006). The Electrical Caries Monitor end values for the experimental, positive, and negative control groups at the six-month examination were 7.9, 1.9 mega omega(s), and 387 kilo omegas(s), respectively. The differences between the negative control group and both the experimental (p < 0.001) and positive control (p < 0.001) were statistically significant. The difference between the experimental and positive control groups was also statistically significant (p = 0.03). CONCLUSION: It is concluded that the new toothpaste containing 1.5% arginine and 1450 ppm fluoride, as sodium monofluorophosphate in a calcium base, provided greater anticaries benefits than a conventional toothpaste containing 1450 ppm fluoride. Both fluoride toothpastes demonstrated greater benefits than non-fluoride toothpaste.

Two-year caries clinical study of the efficacy of novel dentifrices containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm fluoride.

A 2-year double-blind randomized three-treatment controlled parallel-group clinical study compared the anti-caries efficacy of two dentifrices containing 1.5% arginine, an insoluble calcium compound (di-calcium phosphate or calcium carbonate) and 1,450 ppm fluoride (F), as sodium monofluorophosphate, to a control dentifrice containing 1,450 ppm F, as sodium fluoride, in a silica base. The 6,000 participants were from Bangkok, Thailand and aged 6-12 years initially. They were instructed to brush twice daily, in the morning and evening, with their randomly assigned dentifrice. Three trained and calibrated dentists examined the children at baseline and after 1 and 2 years using the National Institute of Dental Research Diagnostic Procedures and Criteria. The number of decayed, missing and filled teeth (DMFT) and surfaces (DMFS) for the three study groups were very similar at baseline, with no statistically significant differences among groups. After 1 year, there were no statistically significant differences in caries increments among the three groups. After 2 years, the two groups using the dentifrices containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm F had statistically significantly (p < 0.02) lower DMFT increments (21.0 and 17.7% reductions, respectively) and DMFS increments (16.5 and 16.5%) compared to the control dentifrice. The differences between the two groups using the new dentifrices were not statistically significant. The results of this pivotal clinical study support the conclusion that dentifrices containing 1.5% arginine, an insoluble calcium compound and 1,450 ppm F provide significantly greater protection against caries lesion cavitation, in a low to moderate caries risk population, than dentifrices containing 1,450 ppm F alone.

The caries continuum: opportunities to detect, treat and monitor the re-mineralization of early caries lesions.

The aim of this review is to discuss dental caries as a dynamic process of de-mineralization and re-mineralization with progression, arrest or reversal of lesions reflecting the balance between them. The need for new clinical trial designs to assess oral care products which reflect and monitor these processes is highlighted and discussed. The research evidence to support the use of two state-of-the-art methods that focus on re-mineralization of natural root caries lesions and natural enamel lesions is described. The use of the Electrical Caries Monitor (ECM) in combination with clinical scoring of lesions to assess the hardness of root dentin and the use of Quantitative Light-induced Fluorescence (QLF) to measure enamel lesions are described together with a number of studies that have employed the methods to assess the efficacy of oral care products. It can be concluded that quantification of the re-mineralization provided by oral care products assessed using both buccal caries and root caries study designs is a valid approach to developing understanding of the mechanism of action of a new technology and to establishing its clinical efficacy in respect of arresting and reversing early caries lesions, and it complements, enhances and may ultimately supplant the information from a conventional two- to three-year clinical trial measuring effects at the cavitation level.

The anti-caries efficacy of a dentifrice containing 1.5% arginine and 1450 ppm fluoride as sodium monofluorophosphate assessed using Quantitative Light-induced Fluorescence (QLF).

OBJECTIVE: To compare the efficacy of a new dentifrice containing 1.5% arginine, an insoluble calcium compound and 1450 ppm fluoride to arrest and reverse naturally occurring buccal caries lesions in children relative to a positive control dentifrice containing 1450 ppm fluoride alone. STUDY DESIGN: Participants from Chengdu, Sichuan Province, China tested three dentifrices: a new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, as sodium monofluorophosphate, a positive control dentifrice containing 1450 ppm fluoride, as sodium fluoride, in a silica base, and a matched negative control dentifrice without arginine and fluoride. Quantitative Light-induced Fluorescence (QLF) was used to assess buccal caries lesions at baseline and after 3 and 6 months of product use. RESULTS: 438 participants (initial age 9-13 years (mean 11.1±0.78) and 48.6% female) completed the study. No adverse events attributable to the products were reported during the course of the study. The subject mean ΔQ (mm(2)%), representing lesion volume, was 27.26 at baseline. After 6 months of product use, the ΔQ values for the arginine-containing, positive and negative control dentifrices were 13.46, 17.99 and 23.70 representing improvements from baseline of 50.6%, 34.0% and 13.1%. After 6 months product use, the differences between the pair wise comparisons for all three groups were statistically significant (p<0.01). The arginine-containing dentifrice demonstrated an improvement after only 3 months that was almost identical to that achieved by the conventional 1450 ppm fluoride dentifrice after 6 months. CONCLUSION: The new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride provides statistically significantly superior efficacy in arresting and reversing buccal caries lesions to a conventional dentifrice containing 1450 ppm fluoride alone.

Comparison of the efficacy of a dentifrice containing 1.5% arginine and 1450 ppm fluoride to a dentifrice containing 1450 ppm fluoride alone in the management of early coronal caries as assessed using Quantitative Light-induced Fluorescence.

OBJECTIVE: To compare the efficacy of a new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride to a matched, positive control dentifrice containing 1450 ppm fluoride in arresting and reversing early coronal caries lesions in children using Quantitative Light-induced Fluorescence (QLF). STUDY DESIGN: 331 children from Chiang Mai, Thailand, aged 7-14 years, with one or more visible early enamel caries lesions on the upper anterior teeth, completed the study. The new dentifrice contained 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, as sodium monofluorophosphate; the matched positive control contained 1450 ppm fluoride only. Subjects brushed twice daily at home and additionally once on school days under teacher's supervision. Digital images of the upper six anterior teeth were captured at the baseline, 3- and 6-month examinations using a custom apparatus for reproducible acquisition of Quantitative Light-induced Fluorescence data. RESULTS: At the 3-month examination, the ΔQ (representing lesion volume) for the test group decreased from a mean of 28.62 at baseline to 20.53 mm(2)% and for the positive control group to 23.38 mm(2)%. The difference between groups was not statistically significant (p=0.055). At the 6-month examination, the ΔQ decreased for the test group to 15.85 mm(2)% and for the positive control group to 20.35 mm(2)%. The difference between groups was statistically significant (p<0.001). CONCLUSION: A new dentifrice containing 1.5% arginine, an insoluble calcium compound, and 1450 ppm fluoride, as sodium monofluorophosphate, provided statistically significant superior efficacy in arresting and reversing active coronal caries lesions in children than brushing with a matched positive control dentifrice containing fluoride alone.