Pathophysiology of Demineralization, Part II: Enamel White Spots, Cavitated Caries, and Bone Infection

Assessing the dental health needs of children in the paediatric intensive care unit

Many children admitted to paediatric intensive care units (PICUs) present with unmet dental health needs or develop these during their admission. It is important to maintain good oral health because suboptimal oral hygiene is linked to various dental and medical conditions, with intubated patients being at risk of developing hospital-acquired pneumonia. This article outlines the role of PICU nurses in identifying children's dental health needs by undertaking oral assessments when each child is admitted to the unit and by implementing national initiatives and guidelines on oral health. The article also details the findings of a service evaluation in the PICU at Evelina London Children's Hospital, England, which demonstrated the importance of maintaining good oral hygiene and the benefit of opportunistic dental treatment while children are admitted to the unit.

In situ remineralization of enamel caries lesions with a toothpaste supplemented with fluoride, amorphous calcium phosphate casein phosphopeptide and trimetaphosphate

OBJECTIVES

This in situ study aimed to evaluate the effect of a new toothpaste formulation containing fluoride (F), casein phosphopeptide amorphous calcium phosphate (CPP-ACP) and sodium trimetaphosphate (TMP) on the remineralization of initial caries lesions.

METHODS

This was a blind, crossover study, performed in 5 experimental phases with a duration of 3 days each. At first, the initial surface hardness (SH) and hardness after demineralization (SH1) were determined. Then, volunteers (n = 10) used palatal appliances containing 4 bovine enamel specimens with initial caries lesions. The treatment regimens were: 1) Placebo (No F-TMP-CPP-ACP), 2) 1100 ppm F (1100F), 3) 1100F+3 %TMP (1100F-TMP), 4) 1100F+10 %CPP-ACP (1100F-CPP-ACP) and 5) 1100F-CPP-ACP-TMP. After 3 days, the final surface hardness (post-remineralization) (SH2), percentage of surface hardness recovery (%SHR), integrated recovery of subsurface hardness (ΔIHR), fluoride- (F), calcium- (Ca) and phosphorus- (P) concentration in the enamel were determined. Data were analyzed by ANOVA (one-way, repeated measures) and Student-Newman-Keuls test (p < 0.05).

RESULTS

The enamel surface showed greater remineralization (SH2) when treated with 1100F-CPP-ACP-TMP (224.8KHN±1.6) compared to 1100F (163.9KHN±2.0) (p < 0.033). Treatment with 1100F-CPP-ACP-TMP led to remineralization of the subsurface lesion (ΔIHR) by 84 % and 91 % when compared to the 1100F and 1100F-CPP-ACP treatments (p < 0.05). For the F concentration values in the enamel, there was an increase of ⁓ 63 % compared to 1100F (p < 0.05). The Ca concentration in the enamel after 1100F-CPP-ACP-TMP treatment was significantly higher in ⁓ 65 %, ⁓ 28 % and ⁓ 15 % when compared to the 1100F, 1100F-CPP-ACP and 1100F-TMP treatments (p < 0.05). The highest concentration of P was observed for 1100F-ACP-CPP-TMP, which was ⁓ 41 % and ⁓ 17 % higher than the 1100F and 1100F-TMP treatments respectively (p < 0.05).

CONCLUSION

The result of this study demonstrates that the combined use of remineralizing agents (F, CPP-ACP, and TMP) in a single toothpaste formulation (1100F-CPP-ACP-TMP) significantly enhances mineral gain compared to conventional toothpaste, as evidenced by a short-term in situ model.

CLINICAL SIGNIFICANCE

The findings of our study offer essential insights for future investigations and potential clinical applications, especially for individuals with initial caries lesions.

The Remineralization Potential of Fluoride, Casein Phosphopeptide-Amorphous Calcium Phosphate, and Chicken Eggshell on Enamel Lesions: An In Vitro Study

Background and objective The effectiveness of various remineralizing agents, including fluoride varnish, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), and chicken eggshell powder (CESP), in improving enamel surface microhardness (SMH) is of clinical interest. This in vitro study aimed to evaluate and compare SMH changes in the enamel after treatment with these agents. Materials and methods An in vitro study was conducted in which 40 human premolars extracted for orthodontic reasons were sectioned into four enamel sections, which were randomly allocated into four groups: group A (fluoride varnish), group B (CPP-ACP cream), group C (CESP), and group D (control). Group A was treated with a thin layer of fluoride varnish (MI Varnish®, GC Corp., Tokyo, Japan), which was left to absorb for 20 s before air drying. Group B specimens were treated with CPP-ACP cream (GC Tooth Mousse®; GC Corp.) for at least three minutes. Group C received CESP application to the enamel surface, which was allowed to absorb for five minutes. Group D (the control group) did not receive any surface treatment. Artificial carious lesions were induced using a demineralization solution and pH cycling for five days. The treated samples were stored in artificial saliva for 21 days at 37 °C. The SMH was assessed using a Vickers microhardness tester at baseline, post-demineralization, and post-treatment. Statistical analyses included paired t-test, one-way analysis of variance (ANOVA), and Tukey's post-hoc test. Results After demineralization, SMH significantly decreased in all groups (p<0.05). After treatment with various remineralizing agents, groups A, B, and C demonstrated significant improvement in SMH compared to the control group (p<0.05). Group C exhibited the greatest improvement in SMH, followed by groups A and B. The difference in the SMH between the treatment groups was statistically significant (p<0.05). Conclusions All three remineralizing agents effectively increased SMH, with CESP showing superior results. Fluoride varnish and CPP-ACP also demonstrated substantial remineralization potential. Further in vivo studies are required to validate these findings in a clinical setting.

Nano-Hydroxyapatite toothpaste of rice field snail shell combined with basil leaf extract as a remineralizing and antibacterial agent to prevent dental caries

Background

This study aimed to compare rice snail shell nano-hydroxyapatite (nano-HAp) toothpaste combined with basil leaf extract and 1450 ppm fluoridated herbal toothpaste as remineralizing and antibacterial agents.

Material and Methods

Experimental toothpastes were prepared with different concentrations of nano-HAp (5% nano-HAp, 10% nano-HAp) and a fixed concentration of basil leaf extract (5% extract). 24 bovine tooth enamel samples were divided into 4 treatment groups. After 6 days of pH cycling, surface microhardness was tested using Vickers Microhardness Test and microporosity was observed using Scanning Electron Microscopy (SEM). The pitting diffusion method was used to test the antibacterial activity of toothpaste against Streptococcus mutans and Lactobacillus acidophilus.

Results

Enamel surface microhardness showed an increase with increasing nano-HAp concentration, while fluoride toothpaste showed the highest level of surface microhardness. Microporosity observation showed the disappearance of microporosity as nano-HAp concentration increased, while fluoride toothpaste still left microporosity. Antibacterial activity of the toothpaste showed that the mean inhibition zone of each group was not significantly different with a very strong inhibition zone.

Conclusions

Rice snail shell nano-HAp toothpaste combined with 5% basil leaf extract is effective as a remineralizing agent by reducing the level of tooth enamel microporosity but cannot match 1450 ppm fluoride toothpaste in increasing surface hardness. In addition, nano-hydroxyapatite toothpaste of paddy field snail shell combined with 5% basil leaf extract is effective as an antibacterial agent for preventing dental caries because it has antibacterial activity equivalent to 1450 ppm fluoride herbal toothpaste. Key words:Nano-hydroxyapatite, basil leaf extract, toothpaste, remineralization, antibacterial.

Comparative evaluation of remineralizing efficacy of calcium sodium phosphosilicate, ginger, turmeric, and fluoride

Background

White lesions, also known as white spots, are the earliest signs of tooth decay. At this stage, noninvasive preventive treatments, such as fluoride application, can help to slow down or even reverse the progression of white lesions. For decades, fluoride has held the spotlight as the go-to agent in oral preventive care, demonstrating significant remineralizing power. Recent scientific literature reveals a growing interest in alternative products as natural substances that demonstrate potential remineralizing effects on tooth enamel. This in vitro study aimed to evaluate the potential remineralizing effect of calcium sodium phosphosilicate (CSP), ginger, and turmeric.

Materials and Methods

This in vitro study was designed to evaluate the remineralizing effects of various materials on the enamel of extracted human teeth. The aim was to compare the effectiveness of these different substances in promoting enamel remineralization. Enamel blocks were prepared and were divided into seven experimental groups: CSP, fluoride toothpaste, nonfluoride toothpaste, turmeric, ginger, fluoride varnish, and distilled water. In this study, sample mineralization is assessed through the quantitative photo-induced fluorescence test before demineralization, after demineralization, and after remineralization. Statistical analysis of the data was conducted using a one-factor analysis of variance test. The significance level was set at P < 0.05.

Results

The best results were obtained by groups treated with turmeric (P < 0.0001), Enamelast fluoride varnish (P < 0.0001), and NovaMin (P < 0.01), as compared to other remineralizing treatments.

Conclusion

While fluoride has undeniably revolutionized oral preventive care, the exploration of alternative products as natural substances and innovative compounds in recent scientific literature signals a shift in focus toward safer and potentially more diverse options.

Incidence, severity, and risk factors for white spot lesions in adolescent patients treated with clear aligners

OBJECTIVES

This study was aimed to clarify the incidence, severity, and clinical risk factors for white spot lesions (WSLs) in adolescent patients treated with clear aligners.

METHODS

Pre-treatment and post-treatment intraoral photographs of 203 adolescent patients undergoing clear aligner therapy were retrospectively evaluated to assess the occurrence and severity of WSLs. Information on patients' general oral condition and orthodontic treatment was collected from clinical medical documents, retrospective questionnaires, and ClinCheck® software. Independent risk factors and model performance were determined by multivariate logistic regression and receiver operating characteristic curve analysis.

RESULTS

Thirty-five percent of adolescent patients developed WSLs during clear aligner treatment. Logistic regression analysis revealed that the presence of WSLs before treatment (OR 2.484, 95% CI 1.245-4.957), frequency of drinking carbonated beverages (OR 1.508, 95% CI 1.045-2.177), and number of anterior attachments (OR 2.192, 95% CI 1.502-3.198) were risk factors for the occurrence of WSLs in adolescent patients treated with clear aligners (P < .05), whereas the number of times they brushed each day (OR 0.656, 95% CI 0.454-0.947) and frequency of aligner cleaning after eating while wearing them (OR 0.611, 95% CI 0.433-0.861) were protective factors against WSLs (P < .05).

CONCLUSIONS

The incidence of WSLs was high in adolescent patients treated with clear aligners. Few brushings each day, pre-treatment WSLs, a high frequency of drinking carbonated beverages, a low frequency of aligner cleaning after eating while wearing them, and a high number of anterior attachments are strongly associated with the development of WSLs in adolescent patients treated with clear aligners.

The Effect of Formulated Dentin Remineralizing Gel Containing Hydroxyapatite, Fluoride, and Bioactive Glass on Dentin Microhardness: An In Vitro Study

Objectives

This study aimed to develop a gel with dentin-remineralizing properties, integrating nano-hydroxyapatite (nHA), sodium fluoride (NaF), and bioactive glass (BG).

Materials and Methods

The enamel layer of 40 bovine incisors was removed. The samples were allocated into four groups of 10 each, based on varying concentrations of nHA, BG, and NaF in the gel compositions (wt%): (1) 2.5%-7.5%-0.05%, (2) 5%-5%-0.05%, (3) 7.5%-2.5%-0.05%, and (4) a control group with a base gel lacking remineralizing agents. After 8 hr of demineralization, the dentin surface microhardness was measured at depths of 30, 60, and 140 µm. After a 20-day pH cycling, the percentage of surface microhardness recovery (SMHR%) was measured and compared among the groups using the ANOVA and Tukey HSD post hoc tests (α = 0.05). Scanning electron microscopy analysis evaluated each specimen's superficial morphology.

Results

At all depths, the SMHR% of the Group 2 and Group 3 was significantly higher than the control group (p  < 0.05). The SMHR% Group 1 (67.39% ± 29.34%) was significantly higher than the control group (-21.24% ± 51.72%) only at the depth of 30 μm (p = 0.047). Group 3 had higher SMHR% than Group 2 at all depths; however, the difference was not statistically significant. Moreover, the SMHR% of Group 3 was significantly higher than that of Group 1 at depths of 30 μm (187. 94% ± 68.95% vs. 67.39% ± 29.34%; p = 0.005) and 60 μm (179.55% ± 75.96% vs. 64.34% ± 41.96%; p = 0.043). Surface deposition and tubule occlusion were observed in the Groups 2 and 3 samples, which was more prominent in the latter.

Conclusions

Combining 7.5% nHA, 2.5% BG, and 0.05% NaF could potentially remineralize primary carious lesions.

Effectiveness of Fluoride Varnishes for White Spot Lesion Prevention and Remineralization during Orthodontic Treatment: A Randomized Controlled Trial

INTRODUCTION

This study investigated the effectiveness of titanium tetrafluoride (TiF4) varnish compared to sodium fluoride (NaF) varnish for preventing and remineralizing white spot lesions (WSLs) in individuals undergoing orthodontic treatment.

METHODS

This randomized, placebo-controlled, and double-blinded study was conducted with sixty-five adolescents who were selected based on caries activity and then randomized into three parallel groups: G1 (placebo varnish), G2 (5% NaF varnish), and G3 (4% TiF4 varnish). Volunteers received varnish application weekly for the first 4 weeks, after 6 (T1) and 12 (T2) months. The measured outcomes included prevention of new WSLs and reversal/progression of WSLs, assessed by Nyvad and International Caries Detection and Assessment System (ICDAS) indices, as well as quantitative light-induced fluorescence. χ2, ANOVA, and Kruskall-Wallis tests were applied. The level of significance was set at 0.05, and post hoc Bonferroni test for p values was performed to correct for multiple comparisons.

RESULTS

1,274 teeth were included; 70.5% were Nyvad 0, and 29.5% were Nyvad 1, with no differences between the groups at baseline (T0). Regarding ICDAS, 70.5% were ICDAS 0, 21.6% were ICDAS 1, and 7.9% were ICDAS 2. G1 showed an increasing prevalence of WSLs at T1 and maintained stable at T2; G2 exhibited a decline at T2, while G3 experienced a decrease at T1 and T2 (p < 0.01). Incidence of WSLs at T2 was 10.2% (G1), 5.6% (G2), and 1.4% (G3). The percentage of teeth initially scored as Nyvad 0 that progressed to Nyvad 1 was 13%, 6.8%, and 1% for G1, G2, and G3, respectively. Conversely, the percentage of teeth initially scored as Nyvad 1 that regressed to Nyvad 0 or Nyvad 2 (T0-T2) was 14%, 49.3%, and 74.4%, respectively (p < 0.001). As for the ICDAS index, regression was observed in 6.5%, 17.8%, and 24%, while progression was observed in 14.9%, 7.7% and 0.9% for G1, G2, and G3, respectively (p < 0.001). Significant differences among the 3 groups for integrated fluorescence loss (mean ± SD, G1: -14.28 ± 9.47, G2: -11.10 ± 11.49, and G3: -6.77 ± 11.00) were found at T2 (p < 0.01).

CONCLUSION

Both varnishes demonstrated the ability to prevent and remineralize WSLs. However, TiF4 varnish exhibited the most effective control over WSLs during the 12-month orthodontic treatment.

Effectiveness of fluoride mouthrinse in prevention of demineralization during fixed orthodontic treatment: A systematic review and meta-analysis

Enamel demineralization is a very common occurrence around bonded brackets in an orthodontic practice. Fluoride (FLR) applications have been used to prevent decalcification and further progression of white spot lesions. The purpose of this systematic review and meta-analysis was to systematically appraise available literature on the effectiveness of fluoride mouthrinse in the prevention of demineralization around fixed orthodontic appliances. A search was conducted for randomized controlled clinical trials among four electronic databases (MEDLINE, Google Scholar, PubMed, and Cochrane Review) through MeSH terms and keywords. Studies were excluded if random allocation was not conducted, or if they were animal or in vitro studies. About 146 articles were screened and 5 studies were selected for the present review. Only two studies were selected for MA due to variations in the measurement of outcomes among studies. This review concluded that rinsing with FLR in the course of the fixed orthodontic treatment lessens demineralization around the bracket. Using FLR mouthrinse to inhibit the formation of white spot lesions or dental caries in patients with multiple cavities or restoration can be considered in clinical practice.

White spot lesions in fixed orthodontic treatment: Etiology, pathophysiology, diagnosis, treatment, and future research perspectives

White spot lesions (WSLs) refer to localized areas of hypo-mineralization limited to the enamel of the teeth surface, which is noticeable clinically to the naked eye on drying of the teeth. During fixed orthodontic treatment, it is very hard for the patient to maintain excellent oral hygiene as the brackets, bands, wires, elastics, and other appliances and attachments worn intra-orally provide a platform for food retention, plaque formation, and then colonization by acidogenic bacteria like Streptococcus mutans and Lactobacillus. This review aims to elaborate and focus on etiology, pathophysiology, diagnosis, treatment aspect, and future scope for research about the WSLs occurring due to fixed orthodontic treatment.

Efficacy of Glass Ionomer Cement as Pit and Fissure Sealant in Permanent First Molars

Background/Objectives Pit and fissure caries constitute a predominant portion, approximately 90% in permanent posterior teeth and 44% in primary teeth among children and adolescents. Among various preventive modalities, pit and fissure sealants play a pivotal role in safeguarding these vulnerable areas. Categorized by materials such as glass ionomer, composites, and polyacid-modified glass ionomers, these sealants offer effective protection. This study aims to evaluate the efficacy of glass ionomer-based pit and fissure sealants in terms of retention rate at 12-month post-procedure period in permanent first molars. Methodology This study was conducted at the Department of Operative Dentistry, Nishtar Institute of Dentistry, Multan, Pakistan. Fifty-six children, aged 7 to 12 years, presenting with pit and fissure caries in permanent first molar teeth were enrolled. Glass ionomer sealant was meticulously applied to the affected pits and fissures. The efficacy was assessed after 12 months based on predefined criteria. Results The age of participants ranged from 7 to 12 years, with a mean age of 9.24 ± 1.38 years. Among the 56 patients, 23 (41.2%) were male and 33 (58.8%) were female. Sealant retention was noted in 31 (55.35%) patients, while 25 (44.65%) experienced sealant loss. In the 7 to 9-year age group, 19 demonstrated complete sealant retention, whereas in the 10 to 12-year age group, 12 exhibited complete retention. Concerning gender distribution, 17 males and 14 females exhibited complete sealant retention. Conclusion Glass ionomer-based sealants demonstrate excellent properties for pit and fissure sealing owing to their low technique sensitivity, cost-effectiveness, and favorable retention rates. Therefore, they represent an optimal choice for this preventive dental procedure.

The Influence of Dental Virtualization, Restoration Types, and Placement Angles on the Trueness and Contact Space in 3D-Printed Crowns: A Comprehensive Exploration

The current digital dentistry workflow has streamlined dental restoration production, but the effectiveness of digital virtual design and 3D printing for restorations still needs evaluation. This study explores the impact of model-free digital design and 3D-printing placement angles on restorations, including single crowns and long bridges produced with and without casts. The restorations are 3D printed using resin at placement angles of 0°, 60°, and 90°. Each group of samples was replicated ten times, resulting in a total of 120 restorations. The Root Mean Square Error (RMSE) value was used to evaluate the surface integrity of the restoration. In addition, the contact space, edge gap, and occlusal space of restorations produced by different processes were recorded. The results indicate that there was no significant difference in the RMSE value of the crown group (p > 0.05). Changing the bridge restoration angle from 0° to 90° resulted in RMSE values increasing by 2.02 times (without casts) and 2.39 times (with casts). Furthermore, the marginal gaps in the crown group were all less than 60 μm, indicating good adaptation. In contrast, the bridge group showed a significant increase in marginal gaps at higher placement angles (p > 0.05). Based on the findings, virtual fabrication without casts does not compromise the accuracy of dental restorations. When the position of the long bridge exceeds 60 degrees, the error will increase. Therefore, designs without casts and parallel placement result in higher accuracy for dental restorations.

The Effect of Biomimetic Remineralization of Calcium Phosphate Ion Clusters-Treated Enamel Surfaces on Bracket Shear Bond Strength

Purpose

To evaluate the remineralization effect of calcium phosphate ion clusters (CPICs) on demineralized enamel surfaces and their effects on bracket shear bond strength.

Patients and Methods

Extracted premolars were prepared in resin blocks. The samples in the form of resin blocks were divided into five experimental groups: control group, demineralized group, and groups of CPIC solution treatment for 30, 60, and 90s. The specimens were examined using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), microhardness testing, micro-computed tomography (micro-CT) assessment, shear bond strength (SBS) test, and adhesive remnant index (ARI) score.

Results

The SEM images revealed epitaxial growth of enamel and a decrease in the thickness of the demineralized enamel layer when treated with CPIC solution. The EDX analysis revealed an increase in the Ca/P ratio in the CPIC-treated groups. The microhardness value significantly increased when treated with CPICs; however, it showed a lower value than that of the sound enamel groups. As a result of the micro-CT test, radiolucency decreased gradually as the CPIC treatment time increased. The SBS test and ARI score results showed an improvement in bonding stability after treatment with CPICs.

Conclusion

We demonstrated an enamel biomodification approach using CPIC solution treatment, which is a promising strategy for enamel remineralization. Specifically, remineralization of demineralized enamel improves the orthodontic bracket SBS.

Instant identification of dental white spot using K-means algorithm via laser-induced fluorescence and associated hyperspectral imaging

Dental caries (DC) is a chronic illness that affects 2 billion individuals worldwide, with 520 million of those suffering from it in their primary teeth. It is apparent that early DC detection and subsequent minimally invasive therapy are crucial clinical requirements. The first reversible clinical indication of demineralization is dental white spot (DWS) lesions. However, diagnosing DWS poses extreme challenges for practitioners. In this investigation, a customized laser-induced fluorescence system with a hyperspectral imaging (HI) camera and a non-ionization laser light supply was created for DWS localization and early DC detection. A UV laser diode source with a wavelength of 395 nm was used for light stimulation for the 10 test samples of teeth. The emitted signature of the main tooth components, including dentin, DWS, enamel, and DC, was recorded. An attempt was made to increase the system's sensitivity to the fluorescent signal by applying a logarithmic scale to the spectral signature. Moreover, further discrimination may be achieved by signal strength. We identified that the fluorescent signal's peak intensity at 771 nm works best for discriminating DWS from normal areas, or DC. For characterizing dentin, the re-emitted frequency at 500 nm has the maximum intensity. Next, we presented our imaging grouping strategy that combines visual enhancement through a moving average, MA, filtering and segmenting an image using K-means clustering (K-mc) (K = 8) for instant and precise DWS grouping for the constructed HI images at (500 nm and 771 nm). Despite the tiny structure and its DWS white appearance, our approach could successfully demarcate the DWS on the tested teeth. Dental examiners might benefit from our simple, non-invasive, non-ionizing optical diagnosis approach to help them make their first assessments and experience accurate and exact delineation of the DWS to obtain immediate and higher rates of early-stage DC detection.

The Relationship between Sleep, Chronotype, and Dental Caries-A Narrative Review

This article provides an overview of how sleep and circadian rhythm disturbances mutually influence the occurrence of dental caries and how it is possible to reduce the risk of circadian rhythm disturbances, sleep, and associated adverse effects. Dental caries is a global problem worldwide that contributes to sociological limitations. Numerous factors influence the occurrence of dental caries, from socioeconomic factors to cariogenic bacteria, dietary habits, and oral hygiene. However, sleep disorders and circadian rhythm disturbances represent a new approach in the fight against the increasing prevalence of dental caries worldwide. Bacteria in the oral cavity and the oral microbiome are mainly responsible for the development of caries, and saliva plays an important role in their regulation. The circadian rhythm regulates numerous physiological functions, including sleep and saliva production. Disturbances in sleep and circadian rhythms affect saliva production, which impacts the development of dental caries, as saliva is necessary for regulating and maintaining oral health, especially for controlling oral infections. A person's preference for a particular time of day depends on the circadian rhythm called chronotype. Individuals with an evening chronotype have a less healthy lifestyle that can lead to a higher caries risk than individuals with a morning chronotype. Because circadian rhythms are critical to maintaining sleep homeostasis and oral health, sleep disturbances can disrupt circadian rhythms and lead to a vicious cycle.

Synchrotron X-ray Studies of the Structural and Functional Hierarchies in Mineralised Human Dental Enamel: A State-of-the-Art Review

Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical-chemical-structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.

Stoichiometric models of sucrose and glucose fermentation by oral streptococci: Implications for free acid formation and enamel demineralization

OBJECTIVES

The objective of this study is to develop stoichiometric models of sugar fermentation and cell biosynthesis for model cariogenic Streptococcus mutans and non-cariogenic Streptococcus sanguinis to better understand and predict metabolic product formation.

METHODS

Streptococcus mutans (strain UA159) and Streptococcus sanguinis (strain DSS-10) were grown separately in bioreactors fed brain heart infusion broth supplemented with either sucrose or glucose at 37 °C. Cell mass concentration and fermentation products were measured at different hydraulic residence times (HRT) to determine cell growth yield.

RESULTS

Sucrose growth yields were 0.080 ± 0.0078 g cell/g and 0.18 ± 0.031 g cell/g for S. sanguinis and S. mutans, respectively. For glucose, this reversed, with S. sanguinis having a yield of 0.10 ± 0.0080 g cell/g and S. mutans 0.053 ± 0.0064 g cell/g. Stoichiometric equations to predict free acid concentrations were developed for each test case. Results demonstrate that S. sanguinis produces more free acid at a given pH than S. mutans due to lesser cell yield and production of more acetic acid. Greater amounts of free acid were produced at the shortest HRT of 2.5 hr compared to longer HRTs for both microorganisms and substrates.

SIGNIFICANCE

The finding that the non-cariogenic S. sanguinis produces greater amounts of free acids than S. mutans strongly suggests that bacterial physiology and environmental factors affecting substrate/metabolite mass transfer play a much greater role in tooth or enamel/dentin demineralization than acidogenesis. These findings enhance the understanding of fermentation production by oral streptococci and provide useful data for comparing studies under different environmental conditions.

Noncarious cervical lesions: Morphology and progression, prevalence, etiology, pathophysiology, and clinical guidelines for restoration

PURPOSE

To synthesize the literature regarding noncarious cervical lesions (NCCLs) and propose clinical guidelines when lesion restoration is indicated.

MATERIAL AND METHODS

A PubMed search was performed related to NCCL morphology, progression, prevalence, etiology, pathophysiology, and restoration.

RESULTS

NCCLs form as either rounded (saucerlike) depressions with smooth, featureless surfaces that progress mainly in height or as V-shaped indentations that increase in both height and depth. Prevalence ranges from less than 10% to over 90% and increases with age. Common locations are the facial surfaces of maxillary premolars. They have a multifactorial etiology due to personal habits such as excessive horizontal toothbrushing and consumption of acidic foods and drinks. Occlusal factors have been identified as contributing to the prevalence of NCCLs in some studies, whereas other studies indicate there is no relationship. The concept of abfraction has been proposed whereby mechanical stress from occlusal loading plays a role in the development and progression of NCCLs with publications supporting the concept and others indicating it lacks the required clinical documentation. Regardless of the development mechanism, demineralization occurs and they are one of the most common demineralization diseases in the body. Treatment should be managed conservatively through preventive intervention with restorative treatment delayed until it becomes necessary due to factors such as lesion progression, impact on patient's quality of life, sensitivity, poor esthetics, and food collection may necessitate restoration. Composite resins are commonly used to restore NCCLs although other materials such as glass ionomer and resin-modified glass ionomer are also used. Sclerotic dentin does not etch like normal dentin and therefore it has been recommended to texture the dentin surface with a fine rotary diamond instrument to improve restoration retention. Some clinicians use mechanical retention to increase retention. Beveling of enamel is used to increase the bonding area and retention as well as enhance the esthetic result by gradually creating a color change between the restoration and tooth. Both multistep and single-step adhesives have been used. Dentin etching should be increased to 30 seconds due to the sclerotic dentin with the adhesive agent applied using a light scrubbing motion for 20 seconds but without excessive force that induces substantial bending of a disposable applicator. Both flowable and sculptable composite resins have been successfully used with some clinicians applying and polymerizing a layer of flowable composite resin and then adding an external layer of sculptable composite resin to provide enhanced resistance to wear. When caries is present, silver diamine fluoride has been used to arrest the caries rather than restore the lesion.

CONCLUSIONS

Noncarious cervical lesions (NCCLs) form as smooth saucerlike depressions or as V-shaped notches. Prevalence values as high as 90% and as low as 10% have been reported due to habits such as excessive toothbrushing and an acidic diet. Occlusal factors have been proposed as contributing to their presence but it remains controversial. Publications have both supported and challenged the concept of abfraction. They are one of the most common demineralization diseases in the body. Conservative treatment through prevention is recommended with restorative treatment delayed as long as possible. When treatment is needed, composite resins are commonly used with proposed restorative guidelines including texturing the sclerotic dentin, beveling the enamel, potential use of mechanical retention, 30 seconds of acid etching, and use of either multistep or single-step adhesives in conjunction with a light scrubbing motion for 20 seconds without excessive force placed on disposable applicators.

Enhancement of chlorhexidine activity against planktonic and biofilm forms of oral streptococci by two Croton spp. essential oils from the Caatinga biome

This work investigates the ability of two Croton spp. essential oils (EO) to enhance chlorhexidine (CHX) activity against oral streptococci. EO's chemical composition of Croton argyrophyllus and C. pluriglandulosus was determined by GC-MS/FID. The microbial growth kinetics and minimum inhibitory concentration (MIC) of EOs and CHX were determined, followed by their synergism against S. mutans UA159 and ATCC 25175, S. salivarius ATCC 7073 and S. sp. ATCC 15300. The microplate-based method was used to determine the EO/CHX activity against 24-h-old biofilms. The major compounds were α-pinene (54.74%) and bicyclogermacrene (16.08%) for EOAr and 1,8-cineole (17.41%), methyleugenol (16.06%) and elemicin (15.99%) for EOPg. Both EO had MIC around 16,000 µg/mL. EOs/CHX presented a synergistic effect against most strains (FICi from 0.133 to 0.375), and OE/CHX-treated biofilms showed a reduction in biomass and cell viability compared to CHX, only (p < 0.01). Thus, the EOs works as natural adjuvants for CHX.

[The results of the study of the focus of initial caries of human tooth enamel in vitro using atomic force microscopy]

OBJECTIVE

Identify structural disorders of the surface of the enamel of a human tooth during the development of the carious process in the «white spot» stage using atomic force microscopy (AFM).

MATERIAL AND METODS

The studies were carried out on 10 molar samples in areas with initial caries in the white spot stage. 6 areas of initial caries were scanned using the atomic force microscope Cetus Light (Nano Scan Technology, Russia) in semi-contact mode. Criteria were proposed for comparing the results of AFM scanning of tooth enamel surface samples and, based on them, the nature of the main structural disorders of the enamel surface in the affected area was determined.

RESULTS

For all the samples studied, the healthy enamel surface was smoother compared to the enamel in the area of the clinically visible «white spot» and in the immediate vicinity of it. The heterogeneity of the enamel surface in the center of the white spot» for all the samples studied was at least 60% higher than at the edge of the process. It was revealed that the heterogeneity of the surface outside the clinically visible white spot at a distance of less than 1 mm from its perimeter is at least 30% higher than that of healthy tissue of the same tooth. It is shown that the heterogeneity of the enamel surface in the center of the caries area in the white spot stage is at least 4 times greater than the heterogeneity of the surface of the healthy enamel of the same tooth, which indicates its demineralization.

CONCLUSION

The established features of the spread of the initial carious process can be used in clinical practice for the diagnosis and dynamic observation of the processes of enamel demineralization.

Resin Infiltration of Non-Cavitated Enamel Lesions in Paediatric Dentistry: A Narrative Review

The resin infiltration (RI) technique was introduced as one of the minimal intervention dentistry strategies in addressing dental caries among the paediatric population. This technique used the low-viscosity resin monomer to infiltrate the non-cavitated carious lesion and other developmental enamel porosities, thus allowing the conservation of the tooth structure. This narrative review aims to explore the value of RI in Paediatric Dentistry. Through our search of the literature, the development of the material, their clinical applications and shortcomings, as well as the innovation that has been carried out to improve the current RI, were discussed. There are number of high-level evidence supporting the use of RI in arresting non-cavitated proximal caries lesions in primary and permanent teeth, but its efficacy in managing anterior white spot lesions is still unclear. Limited penetration depth, not radiopaque and questionable long-term colour and material stability were among the limitation of the material. Various laboratory-based studies have been conducted to improve the current properties of RI. Nevertheless, RI has emerged as one of the important micro-invasive techniques in addressing non-cavitated and anterior white-spot enamel lesions in children and adolescents with great success.