Tooth Surface Research Articles

Prevalence of molar incisor hypomineralization and demands for treatment according to the severity of its clinical manifestation.

Assess the prevalence and severity of molar incisor hypomineralization (MIH) in children 6- to 12-year-old and correlate MIH severity with the complexity of treatment demands. Between March and October 2023, 2,136 children were screened for MIH by two calibrated examiners. MIH severity was categorized in mild, moderate, severe, and very severe. Treatment requirements were categorized in basic, intermediate, and complex. The prevalence of MIH was 15.5% (n = 331), 158 (47.7%) mild/moderate and 173 (52.3%) severe/very severe. Among the 126 children with atypical caries/restoration, cusp involvement was observed in 60.3%, endodontic treatment was necessary in 24.6%, only 15% needed restorations limited to two tooth surfaces with no cusp involvement. Extraction due to MIH was observed in 2.7%. The prevalence of MIH was in accordance with previous literature. Whenever a restorative treatment was necessary, it often involved multiple tooth surfaces and cusps. The complexity of treatment demands increased with age. It is necessary that oral health policymakers pay special attention to children with MIH to ensure appropriate treatment. MIH represents a challenge, especially severe cases with enamel post-eruptive breakdown and caries, requiring extensive restorations. MIH prevalence was assessed in a considerable large sample and the correlation between MIH severity and the complexity of treatment demands was analyzed. More than half of children exhibiting atypical caries/restorations required complex restorative treatment, involving multiple tooth surfaces and cusps. The manuscript prompts a reflection on the importance of evaluating whether the restoration will extend to cusp areas before determining the appropriate technique and material for treatment.

Impact of nanostructured additives in tooth bleaching agents on enhancing color change and reducing side effects: a scoping review.

This study aimed to determine whether incorporating nanostructured additives into bleaching agents enhances efficacy and reduces side effects while identifying gaps for further investigation. A comprehensive search was conducted in electronic databases, including PubMed/Medline, Embase, Scopus, and ISI Web of Science. Two reviewers independently screened articles based on predefined criteria, resolving discrepancies through discussion or consultation with a third reviewer. Data extraction focused on key details, including study design, interventions, and outcomes. Twenty-one articles were reviewed, consisting of nine clinical studies, one in vivo/in situ study, and 11 in vitro studies on tooth bleaching protocols. Hydrogen peroxide was the most commonly used bleaching agent. The primary nanostructured additives studied were titanium dioxide nanoparticles, polymeric carbamide peroxide nanoparticles, chitosan nanoparticles, nano-hydroxyapatite, SiO2/MgO/Fe2O3 nanocomposite spheres, and nano-bioactive glass. Most studies demonstrated an enhanced bleaching effect, reduced bleaching sensitivity, decreased cytotoxicity, reduced hydrogen peroxide penetration into the pulp chamber, and protection of the tooth surface against mineral and structural loss when nanostructured additives were incorporated into the bleaching agent. Incorporating nanostructured additives into tooth-bleaching agents improved efficacy and reduced side effects, especially with titanium oxide nanoparticles. Further clinical studies and systematic reviews are needed to establish strong evidence for safe clinical practice. Including nanostructured additives in bleaching agents, such as titanium oxide nanoparticles, might be a valuable approach to enhancing the bleaching potential while reducing bleaching sensitivity and cytotoxicity, offering safer alternatives for clinical protocols.

Validity of quantitative values of quantitative light-induced fluorescent (QLF) device for pulp diagnosis of teeth with cracks.

The Quantitative Light-Induced Fluorescence (QLF) device provides both the visual information of crack lines on tooth surfaces and quantitative values for fluorescence reactions. The aim of this study was to evaluate the correlation and assess the usefulness of QLF quantitative values in pulp diagnosis of teeth with cracks. Pulp diagnosis was performed on 76 teeth with cracks according to the American Association of Endodontics's guidelines, and their QLF images were captured. The crack lines of the QLF images were quantitatively analyzed using the QLF software CrazeLineWizard01. QLF quantitative values (ΔF: fluorescence loss unit, ΔFmax: maximum of fluorescence loss unit, ΔR: red fluorescence gain unit, ΔRmax: maximum of red fluorescence gain unit) according to the pulp diagnosis of teeth with cracks were analyzed using one-way ANOVA. Multinomial logistic regression analysis was conducted to calculate the prediction of pulp diagnosis on QLF quantitative values. The correlation between the predicted pulp diagnosis and the clinical pulp diagnosis was compared using Pearson's correlation coefficient. ΔF and ΔF max decreased with the progression of pulp disease in cracked teeth, while ΔR and ΔR max increased. Significant differences were found between irreversible pulpitis and pulp necrosis (p < 0.05). Pearson correlation coefficients between predicted and clinical pulp diagnosis based on multinomial logistic regression analysis of QLF quantitative values ranged from 0.699 to 0.806. The accuracy of prediction​​was up to 82.1 % for reversible pulpitis, 73.1 % for irreversible pulpitis, and approximately 80.0 % for pulp necrosis. The quantitative values from the QLF device demonstrate its potential for predicting the severity of pulp disease caused by tooth cracks. The quantitative values of QLF images acquired with a QLF device, which provide visual information on crack lines of teeth through fluorescence reactions on the tooth surface, showed a significant correlation and predictive value for pulp diagnosis as pulp disease progressed in teeth with cracks.

The Most Promising Alternative to Mercury-containing Dental Restorations

The European Union Environmental Commission report and the United Nation Minamata Convention have legislated for phasing-out of mercury-containing dental materials use (dental amalgams) by 2030.1, 2 Several Scandinavian countries have already banned the use of dental amalgams, and this ban is expected to grow to other countries worldwide.2, 3 This creates a market gap for materials which can be used as an alternative to dental amalgams.4 Varieties of mercury-free dental materials have been clinically approved as posterior restorations; such as (1) resin-based composite materials, and (2) glass-based materials, including glass ionomers and glass hybrids. Using these types of dental materials will decrease the mercury’s risks on human’s health and also contribute significantly in the reduction of the environmental mercury pollution.5, 6 Recently, several clinical approaches to treat dental caries lesions have shifted the focus to preserving tooth structure and use of adhesive materials. Considering this, Minimally Intervention Dentistry (MID) has become a crucial concept which includes three aspects to fulfil the requirement of preventive and restorative dentistry; these are early caries diagnosis, enhance remineralisation and minimal cutting of tooth surfaces.7, 8 This approach is identified as an Atraumatic Restorative Treatment (ART). The ART technique was adopted in 1994 by the World Health Organisation (WHO) as an alternative technique for dental caries management in the developed countries either for treating deciduous and/or permanent dentitions.9 The high viscous glass ionomer cement (GIC) is approved as an ideal candidate material to be used with ART technique; such as GC Fuji IX®, KetacTM Molar and Glass Carbomer®.10, 11 One of the main advances in dental materials field is based on the modifications of the GIC chemical compositions, by introducing a bioactive glass in different particle sizes (for promoting remineralising ability) and/or using a highly molecular weight of poly- acrylic acid (for enhancing matrix strength).12 When bioactive glass-containing dental materials come into contact with body fluid, will undergo to a sequence of bioactivity reactions; which is summarised into (1) ion exchange, (2) dissolution and (3) precipitation stages, leading to formation of apatite crystals in fractions identical to those of the natural bone and tooth components.13 Formation of apatite crystals [hydroxyapatite-Ca10(PO4)6OH2 or fluorapatite-Ca10(PO4)6F2] in the bioactive glass-containing GICs occurs via delivering of calcium (Ca2+), phosphate (PO43), hydroxyl (OH-) and/or fluoride (F-) species at the interfaces between the GIC/tooth surfaces and/or the GIC/oral environment.14 For this reason, the bioactive glass-containing GICs are considered as the most promising alternative restorative materials for posterior cavities.

Pulp sensibility responses following complete and partial pulpotomy in mature permanent molars with carious pulpal exposure and symptomatic irreversible pulpitis: Analysis of pooled data from three randomized clinical trials.

The objective of pulpotomy is to preserve the pulp vitality. However, the assessment of pulpal status following pulpotomy is often overlooked. This retrospective analysis aimed to compare the pulp responses to EPT (Electric pulp test) and cold test in mature permanent molars that have undergone either complete pulpotomy (CP) or partial pulpotomy (PP) for managing carious pulpal exposure and symptomatic irreversible pulpitis (SIP) and completed 12 months follow-up. This retrospective analysis pooled data from three randomized clinical trials of pulpotomy (one using CP and two using PP) conducted in the Department of Conservative Dentistry and Endodontics of the Postgraduate Institute of Dental Sciences, Rohtak, from December 2020 to May 2024. The present study included a total of 220 cariously exposed mature permanent molars with SIP, that underwent either CP (n = 45) or PP (n = 175) using ProRoot Mineral Trioxide Aggregate, and were followed-up for 12 months. The teeth were evaluated for outcomes (clinical and radiographic), and pulp sensibility responses to EPT and the cold test, both individually and collectively as positive response to either test. Pulp sensibility responses were further analysed following teeth distribution considering variables like age, gender, number of tooth surfaces restored, preoperative pain intensity and hard tissue formation. Statistical analysis was performed using the Chi-squared test, Fisher's exact test and Mann-Whitney U-test, with significance at p < .05. At 12 months follow-up, 209 of 220 teeth analysed had a successful pulpotomy outcome. Amongst these, PP-treated teeth responded more predictably to EPT and cold test as compared to CP-treated teeth. However, the difference was significant with EPT analysis only (p = .001). The proportion of teeth with a positive response was significantly higher in both the groups, when considering a combined positive response to either EPT or cold test, compared to the positive response to each test alone (p < .001). None of the included variables influenced the pulp sensibility responses in either group (p > .05). PP-treated teeth responded more predictably to EPT and cold test than CP-treated teeth. Future studies must consider positive response to either EPT or the cold test collectively, whilst assessing the pulpal status following CP and PP.

A Randomized Clinical Study Investigating the Stain Removal Efficacy of Two Experimental Dentifrices.

This study aims to evaluate extrinsic tooth stain removal and whitening efficacy of two experimental dentifrices containing (i) 5% sodium tripolyphosphate (STP)/1% micronized alumina or (ii) 5% STP/1% micronized alumina with abrasive silica (ED2) compared to a regular fluoride dentifrice (RFD) following 8 weeks of use. This was a single-center, randomized, controlled, blind, three-arm, stratified, parallel-group study. Eligible participants underwent clinical assessment of stain on the facial/lingual surfaces of maxillary and mandibular teeth using the modified Lobene stain index (MLSI), and shade of the facial surfaces of the central and lateral maxillary incisors using the VITA Bleachedguide 3D-Master (VITA) shade guide. Participants brushed twice daily with their assigned dentifrice and returned to the clinic for clinical assessments at weeks 4 and 8. A total of 272 participants completed the study (281 screened, 279 randomized). Both experimental dentifrices demonstrated statistically significant reduction from baseline and significant differences compared to RFD for MLSI and VITA shade scores at 4 and 8 weeks. 10 treatment-related treatment-emergent adverse events were reported in seven participants. All were resolved at the end of the study. This study demonstrated that dentifrices containing 5% STP/1% micronized alumina provide enhanced stain removal and shade improvements compared to a regular dentifrice. Study treatments were generally well tolerated. A low-abrasion daily-use fluoride dentifrice containing 1% micronized alumina and 5% STP, suitable for people at risk of erosive toothwear and/or dentin hypersensitivity, can provide clinically meaningful superior reductions in tooth stain, which translates into a visibly noticeable improvement in tooth shade.

In vitro early proximal caries detection using trilateral short-wave infrared reflection at 1050 and 1550 nm.

This in vitro study evaluated the diagnostic potential of short-wave infrared reflection (SWIRR) at 1050 and 1550 nm for proximal caries detection from the occlusal, buccal, and lingual surfaces of posterior teeth under clinically relevant conditions. Bitewing radiography (BWR) was the alternative index test and micro-computed tomography (μCT) was the reference standard. Two hundred and fifty proximal surfaces of extracted human teeth were examined using SWIRR at 1050 and 1550 nm and BWR. SWIRR, BWR, and μCT findings were evaluated twice by 2 trained examiners. SWIRR images were evaluated from occlusal and trilateral (occlusal, buccal, and lingual combined) views. Sensitivity, specificity, and area under the curves were calculated. Reliability assessment was performed using κ statistics. Short-wave infrared reflection (1050 nm) showed sensitivity of 0.44 for occlusal and 0.55 for trilateral assessment, paired with specificity of 0.96 and 0.90, whereas SWIRR (1550 nm) showed sensitivity of 0.73 and 0.85 paired with specificity of 0.76 and 0.59. Compared to occlusal view, trilateral SWIRR view revealed ≈10% higher sensitivity and lower specificity. BWR revealed lowest sensitivity (0.30) and highest specificity (0.99). Over- and underestimation of caries demonstrated opposite trends: from 1050 to 1550 nm, overestimation of trilateral SWIRR increased (0.08-0.29), while underestimation decreased (0.15-0.06). Trilateral SWIRR has higher sensitivity and lower specificity for proximal caries, than occlusal SWIRR. For trilateral SWIRR, wavelengths around 1050 nm are more suitable, while 1550 nm is better for occlusal examinations. A combination of SWIRR at 1050 and 1550 nm may exhibit a balanced sensitivity and specificity for proximal caries.

In vitro evaluation and comparison of the abrasive capacity of zirconia whitening toothpaste at different concentrations on the radicular dentin surface of human teeth

In vitro evaluation and comparison of the abrasive capacity of zirconia whitening toothpaste at different concentrations on the radicular dentin surface of human teeth

Morphological study of hard dental tissue condition with various types of dental deposits

Today, it has been established that the primary factor in preventing dental caries is controlling the level and type of dental deposits. However, the literature has not yet addressed the specific morphological changes in the hard dental tissues when non-mineralized and mineralized dental plaque is present on the tooth surface. The aim of this study was to examine the microscopic structure of the cuticle and hard dental tissues and to assess the X-ray spectral changes associated with different types of dental deposits. Epimicroscopic and X-ray spectral examinations were performed on 32 teeth with various types of supragingival deposits, extracted for orthodontic and surgical indications. Each tooth was cut in the vestibulo-oral direction using a diamond bur at low speed, then one half was polished, stained with PAS-Alcian blue, and photographed at different magnifications in epiprojection. Samples were carbon-coated in a vacuum chamber, and the inorganic components in the cuticle and mineralized deposits were assessed using the Link AN 10.85s micro X-ray analyzer. Thin sections of the other tooth halves were prepared, stained with PAS-Alcian blue, and examined under the “Olympus” microscope at various magnifications. Statistical analysis was performed using standard parametric methods with “Statistica 6.0” and “Microsoft Excel 2002” software. Significant findings in the hard dental tissues included the presence of non-mineralized (soft plaque, dental biofilm), mineralized (dental calculus), and smoker's plaque. In areas with soft plaque, enamel prisms remained intact, with no changes in the enamel-dentin junction or dentin, though the cuticle was nearly absent. In areas with dental biofilm, enamel thickening, the absence of characteristic enamel prism patterns, fragmentation of the reticular layer, and formation of interglobular dentin were observed. Morphological changes in mineralized deposits included enamel thinning, prism disorganization, localized hypermineralization, destroyed enamel-dentin junctions, and “dead tracts” in the dentin. In cases with smoker's plaque, nicotine pigment accumulated in Retzius line biomineralization zones, along with thickening of the reticular layer and “dead tracts” in the deeper dentin layers. A comparison of the main inorganic components (Ca, P, Mg, Ca/P) in the cuticle and mineralized deposits showed significant differences in phosphate, magnesium, and Ca/P ratios, indicating disrupted metabolic processes at the “enamel-oral fluid” interface, promoting calculus formation. Thus, the morphological and X-ray spectral changes observed in the enamel and surrounding tissues provide an objective assessment of tissue condition with various types of deposits. These findings should be considered in selecting a scaling method.

Arresting Early Childhood Caries with Silver Diamine Fluoride Gel Among Preschool Children: Protocol for a Randomised Clinical Trial.

Background: The World Health Organisation (WHO) included silver diamine fluoride (SDF) in the WHO Model List of Essential Medicines for the management of early childhood caries. SDF is typically available as a 38% aqueous solution, which is watery to apply. A 38% SDF gel has recently been developed, but its caries-arrest effectiveness remains unsubstantiated. The objective of this study is to determine whether the efficacy of a 38% SDF gel is non-inferior to a 38% SDF solution in arresting early childhood caries. Methods: This is a 30-month, randomised, active-controlled, parallel-group non-inferiority pragmatic clinical trial with two arms. The hypothesis is that the 38% SDF gel is not worse than the 38% SDF solution by a non-inferiority margin of 10% caries-arrest rate when applied semi-annually to preschool children. This trial will recruit 630 3-year-old kindergarten children through block randomisation to receive either an application of SDF gel or SDF solution on cavitated carious lesions in their primary teeth every 6 months. The primary outcome is the proportion of soft (active) carious tooth surfaces that turn hard (arrested) at the 30-month follow-up. The same calibrated dentist will conduct 6-monthly dental examinations in the kindergartens to assess the status of carious lesions over 30 months. The examiner, the children, and parents will be blinded to treatments. The parents will be surveyed on their child's oral health-related behaviours and socioeconomic background to allow adjustment for effect modification. Results: If the anticipated results are obtained, clinicians can use the 38% SDF gel as an alternative of the 38% SDF solution in arresting early childhood caries. Conclusions: As SDF gel is cost-effective, non-invasive, and non-aerosol-generating, it can be widely recommended for caries control. Trial registration: ClinicalTrials.gov NCT06241261. Registered on 7 February 2024.

Geometric generation and meshing characteristics analysis of a new S-shaped gear drive

A new type of S-shaped gear drive with a tooth profile combining involute and circular-arc curves is proposed in this paper. Tooth profile design includes convex involute, convex circular-arc, concave involute, and concave circular-arc curves is carried out. Geometric generation and mathematical model of tooth surfaces of the S-shaped gear are established based on imaginary rack method. Utilizing Hertz contact theory, the calculation formula of contact stress of tooth surfaces is provided. Furthermore, simulation analysis of contact stress based on finite element method under various working conditions is studied using ANSYS/Workbench software. And the comparisons of stress results with general involute gear are also provided. Dynamic characteristics analysis of the generated tooth surfaces is put forward using the established virtual prototype. Normal contact force, circumferential force, axial force and radial force of tooth surfaces both S-shaped gear and involute gear are analyzed. Research results show that the developed S-shaped gear has better transmission performance than involute gear. Further study on dynamic analysis and manufacturing method will be carried out.

The Effect of Thermocycling on the Shear Bond Strength of Flash-free Brackets and Healing Dynamics of Enamel Microcracks: An In vitro Study.

This study evaluates long-term shear bond strength (SBS) and enamel micro cracks (MCs) healing after using adhesive pre-coated brackets (APC). A total of eighty extracted human premolar teeth were randomly divided into four experimental groups (n = 20 per group): Control group: Teeth underwent indentation but no bracket bonding; group II : Teeth were subjected to indentation without exposure to thermocycling; group III: Teeth experienced both indentation and thermocycling; group IV: No indentation was applied to the teeth; groups III and IV were further divided into two subgroups to simulate different clinical timelines: Subgroup A (n = 10): Teeth underwent 5,000 thermocycles, equivalent to six months of clinical use. Subgroup B (n = 10): Teeth were subjected to 10,000 thermocycles, representing 12 months of use. All precoated brackets underwent debonding with a universal testing machine to assess the SBS, and the adhesive remnant index (ARI) was scored to evaluate the amount of adhesive left on the tooth surface. The study also examined horizontal and vertical enamel cracks, both pre- and post-intervention, across all groups. Crack healing was quantitatively assessed using computer-assisted digital image analysis to ensure precision. For statistical evaluation, ANOVA, Kruskal-Wallis H-test, and Tukey's post-hoc tests were applied to assess differences among the groups. The Kruskal-Wallis H-test demonstrated no significant ARI difference between the groups (p = 0.790). A one-way ANOVA showed a significant difference among all groups (p < 0.001), with lower values observed in the group with indentation without thermocycling compared to all other groups and the groups with 5,000 thermocycles compared to the groups with, 10,000 thermocycles. Crack healing was observed in the control and second groups, and cracks were directly proportional to the number of thermocycles and SBS values. The study showed that APC FF's SBS increased, and thermal aging did not change the failure pattern. Thermocyclers and SBS affected enamel cracks. The bond strength of pre-coated brackets and microcrack healing gradually increased with time, while the pattern of bond failure did not change. How to cite this article: Shamsan H, Albelasy NF, Farahat DS, et al. The Effect of Thermocycling on the Shear Bond Strength of Flash-free Brackets and Healing Dynamics of Enamel Microcracks: An In vitro Study. J Contemp Dent Pract 2024;25(9):836-845.

Effects of discrete fibre reinforcements on the wear resistance behaviour of polyamide-based spur gears

Abstract In many situations, the polymer gears are the perfect replacement for traditional metal gears. Compared to metal gears, the polymer gears will generate more heat at the gear tooth contact surface and more wear loss. Hence, this study aims to decrease the wear loss and increase the load-carrying capacity of the polymer gears. To achieve this, the reinforcement materials were added to the base polymer gear material. In this study, Nylon-66 was chosen as the polymer matrix material and an isolated glass fibre and steel grid were used as the reinforcement materials. Three different types of polymer spur gears such as Polyamide Gear (Nylon-66), Reinforced Polyamide Gear (Nylon-66+Glass Fibre), and Hybrid Glass Fiber Steel Grid Gear (Nylon-66+Glass Fibre+Steel Grid) named PG, RPG and HGFSGG were fabricated using injection moulding machine and each type of gears were compared for wear loss and specific wear rate under the similar testing conditions. The wear test was performed in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) test rig at 1500 rpm with an applied load of 20 N for 12.5 hours continuously. From the test results, it was identified that HGFSGG polymer spur gears have exhibited a lower surface temperature and better wear properties compared to the other two types of spur gears. From the Scanning Electron Microscope (SEM) analysis, it was noticed that the PG spur gear exhibited deep and uniform wear at the gear tooth surface. In contrast, RPG spur gear exhibited glass fibre distortion and abrasive-type wear. The SEM micrograph of HGFSGG spur gear reveals the presence of very few surface flaws in the gear tooth surface.

Revolutionizing Laminate Veneer Bonding: Laser Versus Acid Etching of Enamel.

This study is designed to explore the effect of Er,Cr:YSGG laser tooth etching versus that of conventional tooth surface treatment on the shear bond strength of ceramic laminate veneers. Seventy-six maxillary premolars were assigned to two groups (n = 38) according to the type of enamel surface treatment approach. Group 1: samples treated with the conventional acid-etch protocol. Group 2: samples subjected to Er,Cr:YSGG laser. Light-curing resin cement was used to bond the restoration to the tooth and specimens were thermocycled for 30,000 cycles. Shear bond strength testing was conducted on all the specimens. The samples were observed using a scanning electron microscope to record enamel topography and a stereomicroscope to monitor the mode of failure. P ≤ 0.05 was considered significant. There were no statistically significant differences between the acidetch and laser enamel surface treatment groups for the shear bond strength values at maximum load (MPa) (p-value = .627). There was a significantly higher proportion of cohesive failure in the acid-etch group compared to the laser treatment group and a significantly lower proportion of mixed failure in group 1 compared to group 2 (p-value = .022). Concerning the bond strength of the laminate veneer, the effects of laser and traditional acid etching on the enamel surface were the same. Enamel surfaces can be successfully etched using a laser as an alternative to the traditional acid-etch method.

Effects of Lacticaseibacillus paracasei L9 on Oral Microbiota and Cariogenic Factors in Streptococcus mutans-Infected Mice.

In the pathogenesis of dental caries, Streptococcus mutans (S. mutans) plays a central role. S. mutans can produce extracellular polysaccharides, which can help the bacteria form biofilms on the tooth surface, create a stable living environment, and hinder the removal of bacteria by natural defense substances in the oral cavity such as saliva. Meanwhile, the oral microbiota and dietary habits exert long-term influences on its development. This study, employing the BALB/c mouse model, explored the effects of L. paracasei L9 on dental caries. In the experiment, mice underwent the S. mutans inoculation and were subsequently treated with L. paracasei L9 or S. salivarius K12 for 28 consecutive days. The results showed that L. paracasei L9 significantly ameliorated early enamel caries, and both L. paracasei L9 and S. salivarius K12 cooperatively downregulated the expressions of critical cariogenic factors, effectively suppressing the initial adhesion of S. mutans and the formation of dental plaques. L. paracasei L9 reshaped the oral microbiota of caries-affected mice, selectively reducing pathogens abundances and augmenting abundances of probiotics such as Lactobacillaceae and Streptococcus salivarius. This study offers a strategic approach for the management of dental caries, highlighting the potential of these probiotics in the field of oral health.

Multiancestry Genome-Wide Association Study of Early Childhood Caries.

Early childhood caries (ECC) is the most common noncommunicable childhood disease-an important health problem with known environmental and social/behavioral influences lacking consensus genetic risk loci. To address this knowledge gap, we conducted a genome-wide association study of ECC in a multiancestry population of U.S. preschool-age children (N = 6,103) ages 3 to 5 y participating in a community-based epidemiologic study of early childhood oral health. Calibrated examiners used International Caries Detection and Assessment System criteria to measure ECC; the primary trait was the number of primary tooth surfaces with caries experience (i.e., dmfs index). We estimated heritability and concordance rates and conducted genome-wide association analyses to estimate overall genetic effects as well as stratified by sex, household water fluoride, and dietary sugar and leveraged combined gene/gene-environment effects using 2-degree-of-freedom joint tests. Common genetic variants explained 24% of ECC phenotypic variance among unrelated individuals, while concordance rates were 0.64 (95% confidence interval [CI] = 0.42-0.79) among monozygotic twins and 0.44 (95% CI = 0.34-0.53) among first-degree relatives. Across all analyses, we identified 21 novel nonoverlapping genome-wide significant loci (P < 5 × 10-8) and 1 genome-wide significant gene (TAAR6) associated with ECC. The taste receptor activity gene set, with known roles in chemosensing, bacterial recognition, and innate immunity in the oral cavity, was strongly associated with ECC. While no locus remained significant after studywise multiple-testing correction, 3 loci were nominally significant (P < 0.05) and directionally consistent in external cohorts of 285,248 adults (rs1442369, DLGAP1 and rs74606067, RP11-856F16.2) and 18,994 children (rs71327750, SLC41A3). Meanwhile, the strongest marker known to be associated with adult caries (rs1122171, tagging the long noncoding RNA PITX1-AS1) was nominally significant (P = 0.01) and directionally consistent with ECC in our study. Taken together, the results of this study add to the genomics knowledge base for early childhood caries, offer several plausible candidates for future mechanistic studies, and underscore the importance of accounting for sex and pertinent environmental exposures in genetic investigations.

The microbiome alterations of supragingival plaque among adolescents using clear aligners: a metagenomic sequencing analysis

BackgroundWhite spot lesions (WSLs) may develop in adolescents undergoing clear aligner (CA) therapy with poor oral hygiene. The specific effects of CAs on the microbial composition and functional characteristics of supragingival plaques remain unclear. The present study investigated the shift in the supragingival microbial community induced by CAs in adolescents through metagenomic technology.MethodsFifteen adolescents (12–15 years old) with Invisalign appliances were recruited. Supragingival plaque specimens were obtained twice, before treatment (T1) and three months after treatment (T2). All the bacterial plaque specimens were analyzed for microbial communities and functions using metagenomic analyses.ResultsA total of 2,840,242,722 reads disclosed 180 phyla, 3,975 genera, and 16,497 microbiome species. During the first three months, the microbial community was relatively stable. The genus level revealed a higher relative abundance of Capnocytophaga, Neisseria, and Arachnia in the T2 period. Furthermore, the functional analysis suggested that the relative abundances of folate biosynthesis, biotin metabolism and biofilm formation-vibrio cholerae were increased in the T2 period compared to the T1 period. Finally, virulence factor analysis demonstrated that the relative abundance of genes associated with type IV pili (VF0082) and polar flagella (VF0473) was higher in the T2 period than in the T1 period.ConclusionIn adolescents undergoing CA therapy with poor plaque control, caries progresses quickly within three months and noticeable WSLs develop on the tooth surface. Although the microbial community remained relatively steady and CA therapy did not cause significant changes in the overall functional gene composition in the first three months, virulence factors, including type IV pili and flagella, were more abundant and actively contributed to microorganism adhesion and biofilm formation.

Analysis of spur gears drilled with radial holes on teeth surface for effective weight reduction

Analysis of spur gears drilled with radial holes on teeth surface for effective weight reduction

Morphological assessment of mandible: Way to effective anaesthesia

The biggest bone in the human skull, the mandible shapes the inferior third of the face and forms the lower jawline. The inferior alveolar nerve and vessels enter the mandibular canal through the mandibular foramen, which punctures the internal surface of the ramus. It is located at the level of the occlusal surfaces of the lower teeth, midway between the anterior and posterior borders of the ramus, and ends at the mental foramen. Most people have a single mandibular canal, while there are some variations in shape (oval, round, or pear-shaped) and whether an accessory canal can be distinguished (canal bifurcation). Failure of inferior alveolar nerve block (IANB) anesthesia can be attributed to these anatomical variables as well as operator technique. The anesthetic solution is administered as near to the mandibular foramen as feasible by adhering to the landmarks. Repeated injections of the local anesthetic solution in children due to IANB failure can be a tiresome task since they may cause the kid to behave negatively and there is a chance that the solution will be administered in excess of the safe suggested dosage. Data regarding the shifting position of the mandibular foramen from childhood to puberty is lacking in the literature. In light of this, this research was carried out to evaluate, using radiographic techniques, how the mandibular foramen's locations change as a kid grows and develops from childhood to adolescent.

Near-infrared light transillumination (NIR-LT) vs clinical-visual inspection/FOTI to detect interproximal caries lesions in vivo.

To evaluate the ability of near-infrared light transillumination (NIR-LT) to detect interproximal enamel and dentinal caries lesions compared to clinical-visual inspection aided by fiber-optic transillumination (FOTI). From 170 Finnish adolescents aged 15 to 17 years, 5,294 interproximal surfaces of premolars and molars were examined first clinical-visually aided by FOTI (VI&#43;FOTI) using the International Caries Detection and Assessment System (ICDAS) classification. Subsequently, the surfaces were examined using NIR-LT. The extent of lesions was determined using the modified NIR-LT classification based on the Söchtig criteria. For the analyses, data on maxillary and mandibular premolars and molars were combined. Distributions of lesions were presented as frequencies. Differences between VI&#43;FOTI and NIR-LT at the tooth and tooth surface levels were analyzed by chi-square and Fisher exact tests. Sensitivity and specificity of the NIR-LT method to detect any lesion was performed using VI&#43;FOTI as the gold standard. By VI&#43;FOTI, 92.4% surfaces were classified as sound and by NIR-LT, 88.2%. Enamel caries lesions were found on 7.0% of the surfaces by VI&#43;FOTI and on 11.6% by NIR-LT. Nearly double the number of enamel lesions were identified by NIR-LT for all examined teeth groups, except for mandibular molars where this was 1.3-fold. In 66% of the surfaces, the differences between NIR-LT and VI&#43;FOTI findings were statistically significant (P .001). The sensitivity for all teeth of NIR-LT was 48.4% and the specificity was 91.1%. Radiation-free NIR-LT method shows considerable potential as a supplementary method for early detection of caries lesions among low-caries prevalence adolescents.