Changes In Enamel Research Articles

Evaluation of enamel surface changes by different enamel conditioners and de-bonding procedure using optical coherence tomography: An in-vitro qualitative study

Introduction: The purpose of this study is to evaluate surface changes of enamel after using different enamel conditioning agents and bonding adhesives after de-bonding and clean-up of metal and ceramic brackets using optical coherence tomography. Method: Metal and ceramic brackets were bonded onto 120 pre-molars, divided into 4 groups [n=30] which were de-bonded after 24 hours. Enamel conditioners, bonding agents and adhesive resins of four different brands were used in each group. The images of enamel surface were captured with Optical Coherence Tomography [OCT] machine; pre-treatment (T0), post-etching (T1), after bracket de-bonding (T2) and post-cleanup (T3). A spectral domain optical coherence tomography system with 5?m axial spatial resolution was used. This was connected to a pre-configured computer system. A total of 480 images were evaluated for enamel surface evaluation. Results: OCT images obtained allowed us to evaluate the enamel surface after acid-etching and post de-bonding and clean-up procedures. 2D OCT analysis allowed in-depth analysis of enamel loss after various procedures. OCT also assisted in locating remnant adhesive layer after clean-up. Conclusion: OCT is a powerful clinical tool for the use in dentistry and can be used effectively to evaluate enamel surface loss after various procedures. Keywords: De-bonding Evaluation using Optical coherence tomography, Evaluation of enamel surface changes, Optical Coherence Tomography, OCT.

Strontium Uptake and Intra-Population 87Sr/86Sr Variability of Bones and Teeth—Controlled Feeding Experiments With Rodents (Rattus norvegicus, Cavia porcellus)

Strontium isotopes in biogenic apatite, especially enamel, are widely employed to determine provenance and track migration in palaeontology and archaeology. Body tissues record the 87Sr/86Sr of bioavailable Sr of ingested food and water. To identify non-local individuals, knowledge of the 87Sr/86Sr of a non-migratory population is required. However, varying factors such as tissue turnover rates, feeding selectivity, Sr content, digestibility of food, and the ingestion of mineral dust can influence body tissue 87Sr/86Sr. To evaluate the Sr contribution of diet and water to mammalian hard tissues 87Sr/86Sr, controlled feeding studies are necessary. Here we present 87Sr/86Sr from controlled feeding experiments with two rodent species (Rattus norvegicus, Cavia porcellus). Due to the continuous and fast incremental growth of rat and guinea pig incisors (~0.1 – 0.5 mm/day), their enamel is expected to record isotopic dietary changes. For Experiment-1: Diet Switch, animals were switched from their respective supplier food to a pelleted experimental diet containing either insect-, plant-, or meat-meal and a staggered-sampling approach was used to monitor the 87Sr/86Sr changes in rat incisor enamel and bone over the course of the experiment. In Experiment-2: Basic Diets, separated cohorts (n = 6) of rats and guinea pigs were fed one of the three pelleted diets and received tap water for 54 days. While the rat incisors showed a complete tissue turnover, the slower-growing guinea pig incisors partially retained supplier diet-related isotopic compositions. In addition, one group of rats fed plant-meal pellets received Sr-rich mineral water, demonstrating that drinking water can be an important Sr source in addition to diet. Additionally, a leaching experiment showed that only a small fraction of diet-related Sr is bioavailable. Finally, in Experiment-3: Dust Addition, guinea pigs were fed pellets with and without addition of 4% of isotopically distinct dust (loess or kaolin). Animals that received kaolin-containing pellets displayed increased enamel 87Sr/86Sr. Intra-population 87Sr/86Sr variability within each feeding group was small and thus we conclude that it should not affect interpretations of 87Sr/86Sr in provenance studies. However, the differences between bulk food and leachate 87Sr/86Sr highlight the importance of Sr bioavailability for provenance studies and Sr isoscapes.

Amelogenesis Imperfecta Enamel Changes, Amelogenin, and Dental Caries Susceptibility

There is great interest in identifying the subset of individuals in the population that are more susceptible to dental caries. We proposed that a portion of these particular individuals are more susceptible to dental caries due to changes in dental enamel that are related to amelogenin genomic variation. However, apparently amelogenin function can be impacted by inflammation, and this can lead to small changes in the structure of the dental enamel that later in life increases the risk of dental caries.

Color heterogeneity and individual color changes in dentin and enamel bleached in the presence of a metallic orthodontic bracket.

This in-vitro study evaluated the color changes in enamel and dentin bleached in the presence of an orthodontic bracket, as well as the heterogeneity of the color and contribution of each tissue to the color change (CTCC). Enamel-dentin specimens from extracted bovine teeth were bleached before or after bracket removal or maintained without any treatment (control). The colors of the dentin and enamel were measured individually and after recombining these substrates. The changes in the color (ΔE00 ) and whitening index (ΔWID) were estimated by the color difference between the bleached specimens and those of the control. The CTCC was also calculated by recombining the tissues from different treatments. Images of specimens obtained from a stereomicroscope were used to analyze the color homogeneity within each tissue. The highest values of ΔE00 and ΔWID were observed in the specimens bleached in the absence of a bracket. Bleaching in the presence of a bracket resulted in enamel with a center that was whiter than the periphery. Dentin and enamel presented similar CTCC values. Tooth bleaching performed in the presence of a metallic bracket resulted in a reduced bleaching effect and increased color heterogeneity within both tissues. Tooth bleaching before the orthodontic bracket removal reduces the bleaching effect in both dentin and enamel. Moreover, a heterogeneous color of enamel surface can be observed after tooth bleaching in the presence of a nickel-free metallic orthodontic bracket.

Changes in enamel after bleaching pre-treatment with non-thermal atmospheric plasma

The aim of this study was to evaluate color change, mineral composition and topography of the enamel after the pre-treatment with non-thermal atmospheric plasma (NTAP) followed by 38% hydrogen peroxide (HP) bleaching.Buccal enamel of bovine incisors teeth was stained with black tea solution and then divided into five groups (n = 12), according to the plasma application time: PL1 (one minute) or PL2 (2 min) and number of HP applications: HP1 (one) and HP3 (three). The following groups were investigated: HP3, PL1+HP1, PL1+HP3, PL2+HP1 and PL2+HP3. Four color measurements: initial (untreated), after staining and after bleaching (first and second sessions), were performed using an intraoral spectrophotometer (Vita Easyshade). Energy Dispersive X-ray Spectroscopy (EDX) was used to analyze the mineral composition of the enamel before and after two bleaching sessions. Laser confocal microscopy was used to analyze the enamel topography.The pre-treatment with NTAP did not improve the whitening results. The use of NTAP preserves the concentration of calcium and phosphorus, only HP3 group experimented a significant decrease in the mineral concentration. All the bleached groups, with or without NTAP treatment increased their enamel roughness.The application of NTAP did not influence the color change, but it was important to maintain the mineral composition of bleached teeth. All the groups increased their roughness level.

Comparative Evaluation of Fluoride Release From Chemically Cured and Light-Cured Orthodontic Bonding Agents and Surface Alteration of Enamel: An in vitro Study

Introduction: Fluoride is known to reduce demineralization and enhance remineralization which is desirable around orthodontic brackets. Material and methods: This study was carried out to determine the rate of fluoride release, fluoride content of enamel, and surface alteration of enamel from orthodontic bonding agents. Thirty extracted maxillary first premolars were divided into 2 groups of 15 teeth each. Group A—teeth were bonded with a chemically cured orthodontic bonding agent containing fluoride (Rely-a-Bond, Reliance, Itasca) and group B—teeth were bonded with a light-cured orthodontic bonding agent containing fluoride (Light Bond Reliance, Itasca). All individual sample teeth were used to estimate fluoride release and fluoride content of enamel. The same samples were also used to evaluate enamel surface alterations. The rate of fluoride release from the above 2 orthodontic bonding agents were measured in artificial saliva on day 1, 2, 3, 4, 5, 6, 7, 14, 30, 60, and 90. The fluoride content of the enamel was evaluated on day “0” and day “90” of bonding. The samples were also evaluated for the surface changes in enamel using scanning electron microscope (SEM). Results: The results showed that (a) chemically cured and light-cured bonding agent showed a dramatic decrease in the concentration of fluoride release from day “1” to day “2,” (b) the concentration of fluoride release kept decreasing from day “1” to day “90” of measurement in both the groups, and (c) SEM of the bracket margins bonded with chemically cured bonding agent and light-cured bonding agent revealed particle depositions of irregular shape and size on day “90.” Conclusion: Light-cured bonding agent (Light Bond) released higher concentration of fluoride as compared to chemically cured bonding agent (Rely-a-Bond). Light-cured bonding agent (Light Bond) showed higher increase in fluoride content of enamel than chemically cured bonding agent (Rely-a-Bond).

La evolución de los métodos y herramientas para la detección de caries.

Las enfermedades bucales son un problema en la sociedad actual, siendo una de las más relevantes la caries, la cual ha sido considerada como una de las enfermedades más prevalentes a nivel mundial debido a que produce cambios en el esmalte dental y dentina. En la actualidad, cada vez es más resaltable el hecho de la evolución de la tecnología, y no solo en la vida cotidiana, también en el ámbito de la salud, y es que existen equipos tecnológicos que ayudan en la salud bucal, siendo capaces de manipular información de manera digital; es decir, almacenan la información mediante una serie de impulsos eléctricos basados en un sistema binario, lo cual hace posible que la información sea interpretada sin ninguna posibilidad de error.

Differences in the Natural Enamel Surface and Acquired Enamel Pellicle following Exposure to Citric or Hydrochloric Acid

Objectives: The aim of this study was to investigate variations in the interaction between enamel, that is, the acquired enamel pellicle (AEP) and citric or hydrochloric acid. Materials and Methods: A 24-h AEP was formed on natural enamel specimens (n = 40) from pooled whole mouth human saliva. Samples were randomly allocated to citric (0.3%, pH 3.2) or hydrochloric (HCl) acid (0.01 M, pH 2.38) exposure for 30 or 300 s. The total protein concentration (TPC), and phosphorous and calcium concentrations of the pellicle were determined before and after acid exposure, and again after re-immersion in saliva. Surface roughness and tandem scanning confocal microscopy imaging were used to assess enamel changes. Results: After 300 s of citric acid exposure, the mean ± SD TPC reduced from 5.1 ± 1.1 to 3.5 ± 1.1 mg/mL (p < 0.05). In contrast, after 300 s of HCl exposure, the mean TPC did not reduce significantly from baseline (6.6 ± 1.1 to 5.7 ± 0.7 mg/mL) but was significantly reduced in the reformed pellicle to 4.9 ± 1.2 mg/mL (p < 0.001). This reduction occurred after significant release of calcium and phosphorous from the enamel surface (p < 0.001). Thirty seconds of exposure to either acid had no obvious effect on the AEP. The surface roughness of the enamel decreased after acid exposure but no differences between groups was observed. Conclusions: These findings indicate that citric acid interacted with proteins in the AEP upon contact, offering enamel protection. In contrast, HCl appeared to bypass the pellicle, and reduced protein was observed only after changes in the enamel chemical composition.

The effect of carbamide peroxide on surface enamel structural changes and streptococcus mutans attachment

Background: Home bleaching with carbamide peroxide is commonly used due to its high success rate and minimum side effects. Although home bleaching is safe, it causes structural changes in surface enamel, thereby facilitating Streptococcus mutans attachment on the enamel surface. Objectives: This study aimed to determine the effect of carbamide peroxide concentration on surface enamel structural changes and S. mutans attachment. Methods: Healthy, caries-free, and calculus-free upper first premolars were divided into 10%, 15%, and 35% carbamide peroxide concentration groups, with five samples in each group. Structural changes in the surface enamel of the teeth before and after the bleaching procedure were assessed subjectively based on observations using a stereomicroscope at × 40. The samples were inoculated in S. mutans culture and incubated for 24 h (37°C) in anaerobic conditions. The samples were then washed with phosphate-buffered saline, and bacterial attachment was released by vortexing for 1 min. Bacterial attachment was assessed using a turbidimetry test and total plate count test. Result: Structural changes in enamel were observed in the samples exposed to carbamide peroxide 35%. The results of an analysis of variance test revealed a significant difference (P

Effect of mouth rinses on tooth enamel surface

This study aims to evaluate the effect of mouth rinses on the color, microhardness, and surface roughness of tooth enamel. Sixty dental blocks were collected from human third molars and divided in five groups (n = 12): the control group (CG) without immersion in mouth rinse, Listerine Zero, Colgate Plax Fresh Mint, Listerine Whitening, and Colgate Luminous White. The groups were subjected to initial color analysis; the microhardness and roughness of the enamel surfaces were evaluated. Next, the samples were subjected to immersion in mouth rinses or brushing with conventional fluoride toothpaste (CG) according to the manufacturer's instructions; after a 12-week treatment, the color, microhardness, and roughness were once again assessed and compared with the initial analysis. Data were tabulated and analyzed through a two-way analysis of variance (ANOVA) (color and roughness) followed by Tukey's test. Microhardness was analyzed through the Kruskal-Wallis test followed by Dunn's test; the level of significance was 5%. All groups immersed in mouth rinses had a higher level of microhardness loss than CG; additionally, all groups showed changes in the enamel surface. Enamel surface loss was observed using a roughness test, and the mouth rinses promoted a higher level of color changes than CG. Given the results, it can be concluded that the mouth rinses led to significant changes in tooth enamel.

Risk factors and patterns related to dental caries evaluated with caries assessment spectrum and treatment (cast) among schoolchildren of Bhubaneswar, India

To determine the complete range of carious conditions and furthermore to compare the risk factors and patterns of dental caries amongst schoolchildren aged 12 and 15 years in Bhubaneswar. Cross-sectional descriptive survey was performed among 800 schoolchildren to assess the dental caries status by Caries Assessment Spectrum and Treatment (CAST) scoring. Chi-square, parametric t-test, one-way ANOVA with post hoc Bonferroni and stepwise multiple linear regression were utilized for statistical analysis. Study population comprised of 476 (59.5%) boys and 324 (40.5%) girls, of which 356 (44.5%) and 444 (55.5%) represented the 12- and 15-years age group respectively. Prevalence of dental caries was 60.6% (Mean 0.38+0.545). Younger age group children presented a significant (p<0.05) lower caries prevalence (54.8%) as against 65.3% in 15 years children. Majority, 189 (23.6%) revealed distinct visual change in enamel (code 3). Acuteness of disease constructed on maximum CAST score for each subject showed that teeth with morbidity (28.5%) is higher followed by reversible pre-morbidity (23.6%) and serious morbidity (6.5%). Predominantly first molars were generally influenced. Significant interpreters in plunging order for DMFT were frequency of cleaning teeth and sweet score. A creative instrument named CAST index describes full continuum of dental caries. Its utilization in epidemiological studies is exceptionally encouraging as it is less tedious and more cost effective. It can possibly be a useful tool for planning caries control programs in both individual and community levels.

An In Vivo Investigation of Diagnostic Performance of DIAGNOdent Pen and the Canary System for Assessment and Monitoring Enamel Caries under Fissure Sealants.

ABSTRACTAim and Objectives:The aim of this study was to evaluate and compare the diagnostic performance of a quantitative light-induced fluorescence (DIAGNOdent pen [DP]) and a photothermal radiometry (Canary System [CS]) for assessment and monitoring occlusal enamel caries under fissure sealants placed on young permanent teeth.Materials and Methods:Forty-five patients of mean age 9.96 (1.4) years, having at least two occlusal surface sites of non-cavitated lesions (International Caries Detection and Assessment System [ICDAS], 1–3 at baseline), were assigned for this clinical study as per specific inclusion/exclusion criteria. A total of 90 permanent teeth were examined using a visual examination method (ICDAS), a quantitative light-induced fluorescence (DP), and a photothermal radiometry (CS). Teeth were randomly divided into two groups based on the type of fissure sealants: a resin sealant and a glass-ionomer sealant. Sealants were placed over the study sites, and caries assessment was performed with each caries detection method at 3- and 6-month recall appointments. Numerical data were presented as mean, standard deviation, median, and interquartile range values. Qualitative data were presented as frequencies and percentages. Receiver operating characteristic (ROC) curve was constructed to determine the diagnostic accuracy measures of the two modalities and compared using z-statistic. ROC curve analysis was performed with MedCalc software, Ostend, Belgium, version 11.3 for Windows (MedCalc Software). Changes by time in caries progression were analyzed using McNemar test and Cochran Q test. The significance level was set at P ≤ 0.05. Statistical analysis was performed with the IBM Statistical Package for the Social Sciences (SPSS) software for Windows, version 23.0 (IBM, Armonk, New York).Results:The CS and DP were able to distinguish between sound and carious tissue beneath fully and partially retained sealants at 6-month follow-up with an accuracy of 46.7% and 33.4%, respectively.Conclusion:The diagnostic performance of the CS and DP are acceptable and can be considered as useful adjunct tools in the clinical evaluation and monitoring the changes in enamel due to lesion progression under fissure sealants. However, in the clinical setting, sensitivity and specificity of these devices may be influenced by the sealant type, thickness, retention, and the differences in the lesion characteristics over time.

Comparison of the effect of sodium bicarbonate and glycine air polishing systems on tooth surface roughness: An atomic force microscopic analysis.

A variety of prophylactic materials are used in the dental office for the removal of stains and calculus. To evaluate tooth surface changes caused by the application of air abrasive powders (sodium bicarbonate, SBAP and glycine air powder, GPAP) along with scaling and root planing (SRP), under atomic force microscope (AFM) and to analyze the histological soft tissue changes caused by these agents, using light microscopy. This study was conducted in two phases: in vitro and in vivo. In the in vitro phase, hard tissue analysis was done under AFM following air powder polishing. Eighteen extracted teeth were chosen. SRP and tooth sectioning were carried out. Subsequently, each section of the tooth was mounted on a glass plate with self-cure acrylic resin and air polished using SBAP and GPAP. In the vivo phase, the soft tissue was analyzed under a light microscope for surface roughness. A biopsy specimen was taken from patients who had received phase I therapy, and flap surgery was planned using a modified Widman flap technique. This study compared surface changes in enamel and cementum, under AFM, as indicated by RA after SRP, SRP and SBAP, and SRP and GPAP; comparisons were then drawn across the three groups. The mean AFM values were 108.5 and 144.7, 102.7 and 81.7, and 95.6 and 7.4, at the crown and root, for SRP, SRP and SBAP, and SRP and GPAP interventions, respectively. GPAP was the least rough on soft tissues. SBAP and GPAP were better than hand instrumentation as indicated by AFM and histological section analysis.

MOLAR-INCISOR MALFORMATION: A NARRATIVE REVIEW

Introduction: “Molar-incisor malformation” (MIM) or “Molar root-incisor malformation” is a recently reported dental anomaly of unknown etiology, possibly associated with systemic complications, which affects the development of first permanent molar roots and dental enamel of central incisors. Objective: To conduct a literature review on “Molarincisor malformation”, also known as “Molar root-incisor malformation”, discussing its clinical, radiographic/tomographic and microscopic aspects; differential diagnosis and treatment possibilities. Sources of data: Electronic search was performed on the MEDLINE database in March 2021, without limit regarding the year of publication. The terms used were “molar-incisor malformation”, “molar-root incisor malformation”, “root malformation”, “root development”, “tooth roots”, “abnormalities”. Synthesis of data: Fifteen articles, most of them case series, were included. In general, medical historyrevealed clinical complications during pregnancy and / or the first years of life. Clinical features included tooth enamel defects in the cervical region of incisors and marked mobility of permanent molars and incisors. Radiographically, partially obliterated pulp chambers, short, thin and incomplete roots of first permanent molars and incisors, were observed. Microscopically, the occurrence of a hypercalcified dentin layer, in the form of a lens, inside the pulp chamber, at the level of the cementum-enamel junction, called“mineralized cervical diaphragm”, was reported. Conclusion: “Molar-incisor malformation” is an anomaly characterized by changes in root development, pulp chamber and enamel in permanent molars and incisors. The differential diagnosis includes Dentin Dysplasia type I and Regional Odontodysplasia. Medical and familyhistories are essential for the final diagnosis, and treatment, which despite not having an established protocol, requires a multidisciplinary approach and conventional treatments such as tooth extraction, endodontics, orthodontics, and dental implants.

Evaluation of mineral loss in primary and permanent human enamel samples subjected to chemical demineralization by international caries detection and assessment system II and quantitative light-induced fluorescence™: An in vitro study.

The purpose of the study was to understand the mineral loss in primary and permanent enamel samples and an attempt is made to standardize the process of chemical demineralization to generate more meaningful results in research studies involving the remineralization of demineralized samples. Due to variability among enamel samples theoretically, it is impossible to standardize demineralization by running time-based chemical demineralization cycle without frequent monitoring. Instead of carrying out demineralization cycles for a fixed duration of time, we quantified the mineral loss 24 hourly using the International Caries Detection and Assessment System (ICDAS) and Quantitative Light-induced Fluorescence System (QLF™). Twenty primary and permanent enamel samples were subjected to demineralization, and ICDAS and QLF™ evaluation were done at 0, 24, 48, 72, 96, 120, 144, and 168 h of demineralization. The first visual change in permanent enamel is appreciated at 24 h (ICDAS II code1, QLF™ code1 -16.353 - ΔF) of demineralization, at 48 h (ICDAS II code2, QLF™ code2, -24.515 - ΔF), there was localized white spot lesion in permanent enamel and remained until 96 h (ICDAS II code 2, QLF™ code 2, -25.739 - ΔF) of demineralization. In primary samples, distinct visual change was seen at 24 h (ICDAS II code2, QLF™ code2, -19.431 - ΔF), and at 48 h clinically, there was a distinct visual change, but optically mild enamel breakdown was appreciated (ICADSII code 2 QLF™ code3, -27.201 - ΔF), which remained constant till 120 h of demineralization (ICDAS II code2 QLF™ code3 -37.645 - ΔF). Different samples demineralize at different rates. The demineralization in primary samples was 1.25 times higher than permanent samples. Recommendation: due to inherent variability in the samples continuous monitoring of the demineralization process on a 24 hourly basis is required to standardize the process.

Aesthetic perceptions and social judgments about different enamel opacities.

This study aimed to evaluate adolescents' aesthetic perceptions and their social judgments regarding different enamel opacities. Sample size was calculated and resulted in the inclusion of 100 adolescents (aged 10 to 15 years) from a public school in Jequié, Bahia, Brazil. Images of enamel opacities were manipulated to create aesthetic enamel defects, such as enamel color changes (unilateral and bilateral white opacity, unilateral and bilateral yellowish opacity, and unilateral and bilateral yellowish opacity with loss of structure). The images of the opacities were based on Fédération Dentaire Internationale's Developmental Defects of Enamel (DDE) Index. Aesthetic perception and social judgments were evaluated using a validated questionnaire with 12 questions (six positive and six negative points) on social aspects, considering the six manipulated images and the control. The photographic analyses were projected one-by-one by computer to adolescents individually in a classroom. Participants had one minute to observe each image and answer the questionnaire. The data were analyzed by descriptions, and the Friedman Wilcoxon test (p < 0.05). The results indicate that all opacities negatively impacted social judgment (p < 0.001). The enamel aesthetic defects most affecting an individual's perception were bilateral yellow opacity with or without loss of structure (p < 0.001). Regarding social judgment, all participants showed a negative perception of all the tested opacity types (p < 0.001). In conclusion, even opacities presenting only a color change caused aesthetic dissatisfaction to the individuals and changes in their social judgment toward others. Color changes in dental enamel have several aesthetic consequences.

Effect of two kinds of materials on the prevention of early erosive enamel wear

Objective: To investigate the preventive effect of resin infiltration and adhesive on early erosive enamel wear. Methods: Orthodontic reduction premolars collected from Central Laboratory of Nanjing Stomatological Hospital, Medical School of Nanjing University were used to prepare 70 specimens. Forty samples were divided into eight groups (n=5) and treated with different conditions (pH=1.6, 2.4, 3.2 or 4.0 hydrochloric acid solution, etching time was 30 or 60 s), and the conditions for obtaining early erosive enamel samples were selected. Based on this procedure, thirty early erosive enamel samples were made and divided into three groups: control group, resin infiltration group, and adhesive group. And the treatment of 30 days acid abrasion cycle was carried out. Confocal microscopy was used to measure the thickness changes of enamel or material before and after cycle. Results: Early erosive enamel samples was obtained when pH was 4.0 and etching time was 60 s. After 30 days cycle, the wear of enamel was (29.71±6.72) μm in control group, (5.60±2.24) μm in resin infiltration group and (2.89±1.03) μm in adhesive group. In infiltration group and adhesive group, lower enamel was not affected by the cycle, and the material loss ratios of the infiltration resin group and adhesive group were 0.41±0.14 and 0.29±0.13, respectively. The ratio of material loss was not significantly different (P>0.05). But infiltration group lost (12.95±2.22) μm of enamel during the application of the material. Conclusions: Resin infiltration and adhesive have the same short-term protective effect against early erosive enamel wear. Adhesive has less damage to enamel and better effect.

Prevalence and contributing factors of dental caries of 6-year-old children in four regions of China.

BackgroundFrom 2005 to 2015, the prevalence of dental caries in both primary and permanent dentitions was significantly increased in China. Previous studies have shown that the prevalence of permanent dental caries in school-aged children had already reached 19.7%–54.0%, 97.5% affecting first permanent molars. This study aimed to investigate the prevalence and contributing factors of dental caries in 6-year-old children in four regions of China to provide information for oral health promotion programs.MethodsA randomized cluster sampling method was employed in the study. All 6-year-old first grade children from the selected schools were invited to receive a clinical oral examination. Dental caries were diagnosed according to the World Health Organization criteria. The erupting first permanent molars were recorded using the modified International Caries Detection Assessment System. Questionnaires assessing children’s oral health-related behaviors and their caretakers’ oral health awareness and attitudes were completed by the children’s parents or guardians.ResultsOverall, 4,936 6-year-old school children participated in the survey. The prevalence of caries among these children was 87.7%, with a mean number of decayed, missing and filled teeth of 6.04 (SD, 4.24). In primary dentition, the caries prevalence was 87.7%, and the mean dmft score was 6.01 (SD, 4.22). In permanent dentition, the caries prevalence was 2.0%, the mean DFS score was 0.04 (SD, 0.31). All permanent dental caries occurred on the first permanent molars. Carious tooth surfaces were identified as modified ICDAS code “A” to indicate initial caries and distinct visual change in enamel. The mean DAS score of non-cavitated caries in the first permanent molars was 0.18 (SD, 0.67). Logistic regression analysis showed that regional and gender factors were significantly related to the caries experience of these children.ConclusionsThe 6-year-old children from four regions of China had sever primary dental caries and the first permanent molars were at high risk for dental caries. It is critical to protect permanent teeth from caries as early as the eruption of the first permanent molars.

Detection threshold of non-contacting laser profilometry and influence of thermal variation on characterisation of early surface form and textural changes in natural human enamel

ObjectivesTo determine the detection threshold of non-contacting laser profilometry (NCLP) measuring surface form and surface roughness change in natural human enamel in vitro, characterise how ambient scanning thermal variation affects NCLP measurement, and calculate bulk enamel loss in natural human enamel. MethodsNCLP repeatability and reproducibility accuracy was determined by consecutively scanning natural human enamel samples with/without sample repositioning. Ambient thermal variation and NCLP sensor displacement over short (30 s), medium (20 min), and long (2 h) scanning periods were evaluated for their standard deviation. Natural human enamel specimens (n = 12) were eroded using citric acid (0.3% w/w pH3.2) for 5, 10, and 15 min and characterised using surface profilometry, tandem scanning confocal microscopy (TSM), and optical coherence tomography (OCT). ResultsRepeatability and reproducibility error of NCLP for surface form was 0.28 μm and 0.43 μm, and for surface roughness 0.07 μm and 0.08 μm. Ambient thermal variation resulted in NCLP sensor displacement of 0.56 μm and 1.05 μm over medium and long scanning periods. Wear scar depth (μm) was calculated between 0.72–1.61 at 5 min, 1.72–3.06 at 10 min, and 3.40–7.06 at 15 min. Mean (SD) surface roughness (μm) was 1.13 (0.13), 1.52 (0.23), 1.44 (0.19), and 1.43 (0.21) at baseline, 5, 10, and 15 min. Qualitative image analysis indicated erosive change at the surface level, progressing after increasing erosion time. SignificanceMinimum detectable limits for NCLP measuring surface form and surface roughness changes were characterised. Ambient thermal variation, subsequent sensor displacement, and its impact on NCLP performance were characterised. Dental erosion lesions in natural human enamel could be characterised using surface profilometry, surface roughness, OCT, and TSM. Step height formation could be calculated within NCLP and temperature operating limits using profile superimposition and profile subtraction techniques.Natural enamel samples can now be used in in-vitro studies to investigate the formation and development of early acid erosive tooth wear, as well as the assessment of methods for enamel lesion remineralisation and repair.

The dehydration effect on mechanical properties of tooth enamel

Exploring the subtle mechanical property changes of tooth enamel in different conditions is important for dental research. However, some experimental results can be deceptive and may lead to misunderstanding. In particular, we show the dehydration associated with increased mechanical properties of tooth enamel as monitored by Nanomechanical System Testing (NST) can be misleading. The results indicate that the friction coefficient decreased with an increase of hardness of enamel upon dehydration, which appears to imply that dehydrated enamel has better mechanical properties than hydrated enamel. However, more critical scrutiny of the actual situation, suggests dehydrated teeth enamel are more prone to damage and greater wear. To appreciate the basis for the contrast between the experimental results and reality of natural hydrated enamel, which has better resistance to wear, and is critical for an understanding of the aetiology of enamel resistance to fracture.