Enamel mineral loss

Triple-function carbon-based Ca2+ ion-selective pH ring microelectrode to study real-time bacteria-mediated hydroxyapatite corrosion

BACKGROUND

The local pH change mediated by the pathogenic bacterial species Streptococcus mutans plays a significant role in the corrosion of hydroxyapatite (HA) present in the tooth in the dynamic oral cavity. The acid produced by the bacteria decreases the local pH and releases Ca2+ ions from the HA. We studied the bacteria-mediated demineralization of HA by scanning electrochemical microscopy (SECM) after growing S. mutans biofilm on HA for 7 days.

RESULTS

We notably developed a triple-function SECM-compatible tip that could be positioned above the biofilm. It can also measure the pH and [Ca2+] change simultaneously above the biofilm-HA substrate. The triple-function SECM tip is a combination of a potentiometric pH sensor deposited with iridium oxide and a dual-function carbon-based Ca2+ ion-selective membrane electrode with a slope of 67 mV/pH and 34.3 mV/log [Ca2+], respectively. The distance-controlled triple-function SECM tip monitored real-time pH and [Ca2+] changes 30 μm above the S. mutans biofilm. The high temporal resolution pH data demonstrated that after approximately 20 min of sucrose addition, S. mutans started to produce acid to titrate the solution buffer, causing a pH change from 7.2 to 6.5 for HA and from 7.2 to 5 for the glass substrate. We observed that, after 30 min of acid production, ∼300 μM of Ca2+ ions were increased at pH 6.5 above the biofilm surface as a result of the pH change in the local microenvironment. After the release of Ca2+ from HA, the pH environment again shifted toward the neutral side, from 6.5 to 7.2. Therefore, precipitation of Ca2+ happens at the top of the biofilm, thus corroding the HA from underneath. For a glass substrate, in contrast, no Ca2+ ions were released, and the pH did not change back to 7.2. We were able to observe the dynamics of the HA demineralization-remineralization process simultaneously with our newly developed triple-function SECM tip or microprobe.

SIGNIFICANCE

This technique could notably advance the study of similar complex processes, such as bacteria-mediated corrosion in biomedical and environmental contexts.

The oral microbiome and oral and upper gastrointestinal diseases

Background

Microbiomes are essential components of the human body, and their populations are substantial. Under normal circumstances, microbiomes coexist harmoniously with the human body, but disturbances in this equilibrium can lead to various diseases. The oral microbiome is involved in the occurrence and development of many oral and gastrointestinal diseases. This review focuses on the relationship between oral microbiomes and oral and upper gastrointestinal diseases, and therapeutic strategies aiming to provide valuable insights for clinical prevention and treatment.

Methods

To identify relevant studies, we conducted searches in PubMed, Google Scholar, and Web of Science using keywords such as "oral microbiome," "oral flora, " "gastrointestinal disease, " without any date restrictions. Subsequently, the retrieved publications were subject to a narrative review.

Results

In this review, we found that oral microbiomes are closely related to oral and gastrointestinal diseases such as periodontitis, dental caries, reflux esophagitis, gastritis, and upper gastrointestinal tumors (mainly the malignant ones). Oral samples like saliva and buccal mucosa are not only easy to collect, but also display superior sample stability compared to gastrointestinal tissues. Consequently, analysis of the oral microbiome could potentially serve as an efficient preliminary screening method for high-risk groups before undergoing endoscopic examination. Besides, treatments based on the oral microbiomes could aid early diagnosis and treatment of these diseases.

Conclusions

Oral microbiomes are essential to oral and gastrointestinal diseases. Therapies centered on the oral microbiomes could facilitate the early detection and management of these conditions.

Effect of natural agents on the bond strength to eroded dentin

OBJECTIVE

This study evaluated the effect of bromelain and propolis extract on the bond strength (BS) of a universal adhesive system to eroded dentin.

MATERIALS AND METHODS

Sixty human molars with exposed dentin were halved, with one half protected by composite resin and the other subjected to erosive treatment followed by remineralization. After the erosive treatment, the composite resin was removed, and the teeth were randomly assigned to three groups (n = 20): Adhesive-Control System; Br-10%; Pr-16%. Following the treatments, composite resin blocks were built on the dentin surfaces and sticks of 0.9 mm2 were obtained and stored in distilled water at 37°C for 24 h and 6 months. After these periods, the sticks underwent bond strength testing and the data were analyzed using 2-way ANOVA, Bonferroni test, p < 0.05. Fracture patterns were observed using light microscope and scanning electron microscopy.

RESULTS

Irrespective of the substrate and aging duration, propolis demonstrated higher BS (p < 0.05) compared to the other treatments. Eroded dentin exhibited greater removal of the smear layer and dentinal tubules with a larger diameter than sound dentin, especially when treated with bromelain, resulting in the formation of resin tags.

CONCLUSIONS

Propolis consistently promoted the highest bond strength, irrespective of aging or substrate. Eroded dentin treated with propolis, or bromelain exhibited a higher prevalence of non-adhesive fractures and resin tag formation.

CLINICAL SIGNIFICANCE

Propolis shows promise for enhancing the longevity of adhesive restorations in eroded dentin due to its ability to promote high bond strength.

Introspection of the Etiopathological Mechanisms Underlying Noncarious Cervical Lesions: Analysis of the Different Theories and Their Impact on the Mineralized Structures of the Tooth

The noncarious cervical lesions (NCCLs) recognize an etiological framework of onset very different from the carious processes with etiology whose bacteria aggregated in a biofilm play a predominant role, leading in this way to the loss of the mineralized structure of the tooth. The pathological picture of the NCCLs, which manifests itself with a clinical picture of dental wear, differs from caries because it mainly recognizes a series of pathological processes, such as erosion, through the action of generally acidic chemical agents and abrasion, which is basically expressed through repeated mechanical trauma characteristic of tooth brushing. However, in the literature, there is no unanimous agreement in identifying only these two mechanisms, but there are some who propose a more marked role of anomalous occlusal loads, which would be unloaded on some teeth which, in addition to both erosive and abrasive mechanisms, would give rise to abfraction. Therefore, the aim of this review was to collect literature etio-pathological information and discuss the mechanisms underlying NCCLs.

Enamel Remineralization Efficacy of Coconut Milk and Lyophilized Coconut Extract in Different Concentrations on Demineralized Enamel Surfaces: An In-Vitro Study

Aim The current study's objective is to determine the remineralizing efficacy of freeze-dried lyophilized coconut extract and coconut milk made from freshly grated coconut on artificial carious lesions produced by pH cycling. Materials and methods Freshly extracted coconut pulp was split into two parts. The first half was blended to obtain coconut milk, and the second part was freeze-dried and lyophilized. Tooth slabs were prepared from extracted third molar teeth. After being demineralized for 72 hours, the tooth samples were remineralized by submerging them in the appropriate remineralizing solution, which is as follows: Group 1 received 25 mL of the Remineralization solution (the control); Group 2 received 2.5 g of coconut milk and 25 mL of the solution (1:1); and Group 3 received 5 g of coconut milk and 25 mL of the solution (2:1). 2.5 g of freeze-dried, lyophilized coconut extract was given to Group 4 along with 25 mL of remineralization solution (1:1), and 5 g of freeze-dried, lyophilized coconut extract was given to Group 5 along with 25 mL of remineralization solution (2:1). Microhardness and contact angle measurements were made. An Excel spreadsheet was filled up with values from after demineralization, and after remineralization. A statistical analysis was performed using SPSS 26.0 (IBM Corp., Armonk, NY). Using descriptive statistics, the pretreatment mean values for the microhardness and contact angle of the various groups were evaluated. Post-hoc Tukey tests were utilized to compare the analytic results of the various groups. Results Among the various concentrations of freshly extracted coconut milk, the contact angle in concentrations of 1:1 was 81.22 ± 1.62 deg, and that in concentrations of 2:1 was 88.01 ± 1.85 deg. Between the two concentrations of the lyophilized coconut extract group, the contact angle in 1:1 was 75.05 ± 2.29 deg, and in 2:1 was 71.37 ± 0.85 deg. In the coconut milk group, the value of microhardness was 261 ± 6.4 kg/cm2 at a lower concentration and 322 ± 3.9 kg/cm2 at a higher concentration. In the lyophilized coconut group, the lower concentration exhibited a microhardness of 211 ± 7.2 kg/cm2, whereas in the higher concentration, it was 324 ± 4.04 kg/cm2. Conclusion Of the various concentrations of coconut milk and lyophilized coconut used, coconut milk at a higher concentration exhibits the highest contact angle, and the latter at a higher concentration exhibits the lowest contact angle. In both groups, high concentrations of the material exhibited high microhardness values compared to lower concentrations of the same.

Influence of violet LED and fluoride-containing carbamide peroxide bleaching gels on early-stage eroded/abraded teeth

PURPOSE

This study evaluated enamel with early-stage erosion/abrasion following bleaching with 20% and 45% carbamide peroxide (CP) gels containing fluoride (F) and irradiated with violet LED (LED).

METHODS

Enamel blocks were immersed in 1% citric acid (5 min) and artificial saliva (120 min) three times to produce early-stage enamel erosion. Simulated toothbrushing was performed only after the first saliva immersion, to provoke enamel abrasion. The erosive/abraded enamel samples were submitted to (n=10): LED/CP20, CP20, LED/CP20_F, CP20_F, LED/CP45, CP45, LED/CP45_F, CP45_F, LED, and control (without treatment). The pH of the gels was assessed, and color (ΔE₀₀) and whiteness index (ΔWI_D) changes were calculated after cycling (T₁), and 7 days from bleaching (T₂). Enamel surface roughness average (Ra) and Knoop microhardness (kg/mm², %SHR) were evaluated at baseline (T₀) at T₁ and T_2. Scanning electron microscopy evaluated the enamel surface morphology at T₂.

RESULTS

The gels' pH was neutral and CP20 and CP45 exhibited no differences in ΔE₀₀ and ΔWI_D (p>0.05) but LED increased these parameters for CP20_F and CP45. Erosion/abrasion significantly decreased mean kg/mm², and the LED group was the only one not increasing microhardness after bleaching (p>0.05). None of the groups fully recovered the initial microhardness. All groups exhibited %SHR similar to the control (p>0.05) and the increase in Ra was detected only after erosion/abrasion. CP20_F groups exhibited a more preserved enamel morphology.

CONCLUSION

Light irradiation combined with low-concentrated CP gel promoted a bleaching effect comparable to the high-concentrated CP. The bleaching protocols did not adversely impact the surface of early-stage eroded/abraded enamel.

Erosive effects of commercially available alcoholic beverages on enamel

This study aimed to investigate the effects of four alcoholic beverages on enamel erosion. Fifty enamel specimens were randomly allocated into the following five groups (n=10): group 1, water as negative control; group 2, red wine; group 3, white wine; group 4, distilled spirit; and group 5, beer. The specimens were immersed in the respective solution for a 16 h demineralization, followed by an 8 h remineralization in artificial saliva. Cyclic de- and re-mineralization were performed for 8 days. Surface roughness, microhardness and morphology of the enamel specimens were studied after the cycling. The results were analyzed by One-way ANOVA and Dunnett's post-hoc test (p<0.05). All investigated beverages showed an erosive effect on enamel. White wine had the highest erosive potential whereas distilled spirit had the least.

Fatigue and wear of human tooth enamel: A review

Human tooth enamel must withstand the cyclic contact forces, wear, and corrosion processes involved with typical oral functions. Furthermore, unlike other human tissues, dental enamel does not have a significant capacity for healing or self-repair and thus the longevity of natural teeth in the oral environment depends to a large degree on the fatigue and wear properties of enamel. The purpose of this review is to provide an overview of our understanding of the fatigue and wear mechanisms of human enamel and how they relate to in vivo observations of tooth damage in the complex oral environment. A key finding of this review is that fatigue and wear processes are closely related. For example, the presence of abrasive wear particles significantly lowers the forces needed to initiate contact fatigue cracking while subsurface fatigue crack propagation drives key delamination wear mechanisms during attrition or attrition-corrosion of enamel. Furthermore, this review seeks to bring a materials science and mechanical engineering perspective to fatigue and wear phenomena. In this regard, we see developing a mechanistic description of fatigue and wear, and understanding the interconnectivity of the processes, as essential for successfully modelling enamel fatigue and wear damage and developing strategies and treatments to improve the longevity of our natural teeth. Furthermore, we anticipate that this review will stimulate ideas for extending the lifetime of the natural tooth structure and will help highlight where our understanding is too limited and where additional research into fatigue and wear of human tooth enamel is warranted.

Effects of Carbonated Beverage Consumption on Oral pH and Bacterial Proliferation in Adolescents: A Randomized Crossover Clinical Trial

Sugary soft drinks modify salivary pH and favor bacterial proliferation and are associated with the development of caries. Information on the effects of consuming carbonated drinks without sucrose is limited. Methods: In this crossover clinical trial, salivary and dental biofilm pH were determined at 0, 5, 10, 15, 30, 45, and 60 min after the participants (n = 18) ingested a soft drink with sucrose, a soft drink with aspartame/acesulfame K, carbonated water, and plain water on different days. Dental biofilm cultures were conducted at 0- and 120-min. Results: Salivary pH decreased significantly after ingestion of the sucrose-containing soft drink when compared with the other types of beverages (median difference, -0.3--0.4, p ≤ 0.05), and the greatest difference was found with mineral water. A greater bacterial proliferation (Colony Forming Units [CFU]) was observed after ingestion of the drink with sucrose (↑310 × 103 CFU, p ≤ 0.01), followed by the drink with aspartame/acesulfame K (↑160 × 103 CFU, p ≤ 0.01) and carbonated water (↑60 × 103 CFU, p ≤ 0.05). No significant changes in bacterial proliferation were observed after the consumption of natural water. Conclusions: Ingestion of sucrose-containing soft drinks favors the acidification of salivary pH and the bacterial proliferation of dental biofilm. Although to a lesser extent, soft drinks containing aspartame/acesulfame K also favor bacterial proliferation.

Comparison of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro study

Aim

To investigate the cariostatic and remineralizing effect of two commercial silver diamine fluoride (SDF) preparations on enamel and dentinal caries using a bacterial plaque model.

Materials and methods

A total of 32 extracted primary molars were divided into two groups (n = 16), group I (FAgamin), and group II (SDF). Plaque bacterial model was used to induce caries on enamel and dentin. Preoperative evaluation of samples was done using confocal laser microscopy (CLSM) and energy-dispersive X-ray spectroscopy-scanning electron microscope (EDX-SEM). All samples were treated with test materials and evaluated for postoperative remineralization quantification.

Results

Energy-dispersive X-ray spectroscopy (EDX) revealed that mean preoperative levels (in weight %) of silver (Ag) and fluoride (F2) in carious enamel lesions were 0.0 and 0.0, which increased postoperatively to 11.40 and 31.05 for FAgamin and 13.61 and 31.87 for SDF, respectively. For dentinal caries, EDX revealed mean preoperative levels (in weight %) of Ag and F2 were 0.0 and 0.0, which increased to 11.47 and 48.71 for FAgamin and 10.16 and 47.82 for SDF, respectively postoperatively. Both the groups showed evident demineralization with exposed collagen under SEM. The mean value of enamel lesion depth for the group I and II were 38.64 and 39.30 µm, that reduced to 28.02 and 28.70 µm while for dentinal caries, the mean depth from 38.05 and 38.29 µm that reduced significantly to 28.96 and 30.10 µm, respectively (p < 0.001). Caries depth declined significantly after the application of both FAgamin and SDF (p < 0.001).

Conclusion

FAgamin and SDF show similar cariostatic and remineralization potential for dental caries. The bacterial plaque model used in this study is an efficient method to induce artificial carious lesions in teeth.

Clinical significance

A comparative evaluation of these two cariostatic and remineralizing agents will aid in identifying the efficacy of both commercial products in treating initial caries lesions in an effective noninvasive and child-friendly manner.

How to cite this article

Kale YJ, Misal S, Dadpe MV, et al. Comparison of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro study. Int J Clin Pediatr Dent 2022;15(6):643-651.

An Assessment of Mineral Concentration of Dental Enamel Neighbouring Hypothetical Orthodontic Brackets Using X-ray Microtomography

OBJECTIVES

Differences in the mineral concentration (MC) level of dental enamel may represent a precursor of white spot lesions adjacent to fixed orthodontic brackets. The aim of the current in vitro study was to compare the MC level central, occlusal and cervical to orthodontic attachments.

METHODS AND MATERIALS

A total of 16 enamel blocks were obtained from sound human premolar samples extracted for orthodontic reasons. The buccal portion of the dental enamel blocks was divided into central, occlusal, and cervical regions and then imaged and measured to calculate the level of MC using quantitative X-ray microtomography methods (XMT) at each site.

RESULTS

There was a substantial variation in the mineral concentration with the lowest level being detected in the cervical region when compared with other regions. The MC of the gingival zone was significantly lower than that of the middle zone (P<0.05) and was insignificantly lower than that of the occlusal zone.

CONCLUSION

Within the limitations of the current study, it can be concluded that the cervical region of the permanent enamel had the lowest mineral concentration using XMT. The cervical region may therefore be more vulnerable to the development of white spot lesions (WSLs) adjacent to a fixed orthodontic appliance during orthodontic treatment.

CLINICAL SIGNIFICANCE

Using X-ray microtomography lower mineral concentration in the cervical region of the enamel was observed. This may make these areas particularly susceptible to demineralisation during fixed appliance-based orthodontic treatment and may influence the bond strength of fixed orthodontic attachments.

Quantitative Measurements of the Depth of Enamel Demineralization before and after Bleach: An In Vitro Study

Objective

This study is aimed at determining two main points. First, if the Canary System™ (CS), initially used to assess caries, can measure a decalcification depth of bleached enamel quantitatively, and second, whether or not whitening has a harmful effect on enamel. This device can be considered a useful tool in the clinical assessment of the progression of demineralization after bleaching.

Materials and Methods

This study collected sixty human premolars that are in a good state recently extracted for orthodontic reason. To properly disinfect and preserve the premolars, they were stored in a saline solution and later in distilled water for a period of two weeks to allow the premolars to rehydrate. Later, 24 hours before the experiment, the premolars were introduced into a solution of artificial saliva to acquire back their minerals. The mineral content of the teeth was measured by the Canary System™ before bleaching. The teeth were bleached with 30% hydrogen peroxide (fläsh HP 30%), 30 min per week and for 3 consecutive weeks to simulate the conditions of strong bleaching in the clinic. The extent of demineralized enamel was measured by the Canary System™ at three points on the enamel surface of each tooth. The data were averaged for each application of the bleaching product. The demineralization extent of the teeth was measured by the Canary System™ before and after bleaching. The significance level was set at 0.05, and SPSS version 26 was used. The data were analyzed by using Wilcoxon's and Student's tests.

Results

Mineral loss occurred after the first bleaching session; the Canary System™ detected a decalcification in the first bleaching session (532 ± 322 μm) compared to the other sessions (p ≤ 0.05), while no significant change was detected between the second and the third sessions (p > 0.05).

Conclusion

Based on the findings of the present study, under in vitro conditions, it was possible to measure the demineralization extent of bleached enamel with the Canary System™.

Risk prediction models for erosive wear in preschool-aged children: a prospective study

Background

Despite increasing prevalence, age-specific risk predictive models for erosive tooth wear in preschool-age children have not been developed. Identification of at-risk groups and the timely introduction of behavioural change or treatment will stop the progression of erosive wear in the permanent dentition. This study aimed to identify age-specific risk factors for erosive wear. Distinct risk prediction models for 3-year-old and 5-year-old children were developed.

Methods

A prospective cohort study included school-based clinical examinations and parent administered questionnaires for consented 3 and 5-year-old healthy children. Calibrated examiners measured the following health parameters under standardised conditions: erosion, using the Basic Erosive Wear Examination Index (BEWE), caries using the International Caries Detection and Assessment System (ICDAS), plaque and calculus according to the British Association for the Study of Community Dentistry (BASCD) scores, dental traumatic injuries and soft tissue lesions, salivary testing and BMI. Other health conditions were collected via a parent-administered questionnaire that explored oral- and general-health. Non parametric tests were utilised to explore the temporal relation of erosion with, demographic factors, oral hygiene habits, general health and dietary habits. Variables showing significance with a difference in BEWE cumulative score over time were utilised to develop two risk prediction models. The models were evaluated by Receiver Operating Characteristics analysis.

Results

Risk factors for the 3-year-old cohort (N = 336) included erosive wear (χ²(1, 92) = 12.829, p < 0.001), district (χ²(5, 92) = 17.032, p = 0.004) and family size (χ²(1, 92) = 4.547, p = 0.033). Risk factors for the 5-year-old cohort (N = 441) also included erosive wear (χ²(1, 144) = 4.768, p = 0.029), gender (χ²(1, 144) = 19.399, p < 0.001), consumption of iced tea (χ²(1, 144) = 8.872, p = 0.003) and dry mouth (χ²(1, 144) = 9.598, p = 0.002).

Conclusions

Predictive risk factors for 3-year-old children are based on demographic factors and are distinct from those for 5-year-old children based on biological and behavioural factors. Erosive wear is a risk factor for further wear in both age cohorts.

Comparative Evaluation of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations Using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro Study

Aim

To investigate the cariostatic and remineralizing effect of two commercial silver diamine fluoride (SDF) preparations on enamel and dentinal caries using a plaque bacterial model.

Materials and methods

Thirty-two extracted primary molars were divided into two groups (n = 16) as group I (Advantage Arrest) and group II (e-SDF). Plaque bacterial model was used to induce caries on enamel and dentin. Preoperative evaluation of samples was done using confocal laser scanning microscopy (CLSM) and energy-dispersive X-ray spectroscopy-scanning electron microscope (EDX-SEM). All samples were treated with test materials and evaluated for postoperative remineralization quantification.

Results

EDX revealed that mean preoperative levels (in weight%) of silver (Ag) and fluoride (F) in enamel carious lesions were 0.0 and 0.0, which increased postoperatively to 11.40 and 31.05 for Advantage Arrest and 13.61 and 31.87 for e-SDF, respectively. For dentinal caries, EDX revealed mean preoperative levels (in weight%) of Ag and F were 0.0 and 0.0, which increased to 11.47 and 48.71 for Advantage Arrest and 10.16 and 47.82 for e-SDF, respectively postoperatively. Both groups showed evident demineralization with exposed collagen under SEM. The mean values of enamel lesion depth for the group I and II were 38.64 and 39.30 µm, that reduced to 28.02 and 28.70 µm, while for dentinal caries, the mean depth from 38.05 to 38.29 µm that reduced significantly to 28.96 and 30.10 µm, respectively (p < 0.001). Caries depth declined significantly after the application of both Advantage Arrest and e-SDF (p < 0.001).

Conclusion

Advantage arrest and e-SDF show similar cariostatic and remineralization potential for dental caries. The plaque bacterial model used in this study is an efficient method to induce artificial carious lesions in teeth.

How to cite this article

Kale YJ, Misal S, Dadpe M, et al. Comparative Evaluation of Cariostatic and Remineralizing Potential of Two Commercial Silver Diamine Fluoride Preparations Using Confocal Laser Microscopy and EDX-SEM Spectroscopy: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(4):442-449.

Development of a Clinically Relevant Index for Tooth Wear Treatment Needs

Background: This study aimed to develop a tooth wear classification system that combined the extent, severity, and aesthetic impact of tooth wear and correlated them with the most appropriate clinical management strategy. Methods: Three hundred photographs were used to develop a classification tool that contained four levels of severity and aesthetic impact (0, 1, 2, and 3) in three age groups of patients. Ten examiners assessed and classified the cases using validated forms. Additionally, they selected the recommended treatment modality for each level. The analysis was conducted using a coefficient correlation test. Results: The coefficient correlation for the severity was 0.81, 0.82 in the upper anterior and posterior segments, and 0.85 and 0.77 for the lower anterior and posterior segments, respectively. The aesthetic impact correlation coefficient was 0.84. Examiners had agreed that minor cases required monitoring or simple restorative interventions. The moderate-level cases had variety in the recommended management options depending on the aim of treatment. The severe level cases often required rehabilitation at an increased occlusal vertical dimension. Conclusion: Within the limitations of this preliminary study, a good agreement between the examiners was found using the provided tools. More strict criteria in the classification part of the tool can further improve the examiners’ agreement.

The quality of etched enamel in different regions and tooth types and its significance in bonding and the development of white spot lesions

OBJECTIVES

To quantify differences in the etch quality of enamel within and between human teeth, which has not previously been attempted.

MATERIALS AND METHODS

The buccal right and left halves of 27 extracted human teeth were randomly allocated to scanning electron microscopy (SEM) or micro-computed tomography (μCT) for evaluation. The buccal surfaces were pumiced, etched with 37% phosphoric acid gel etchant for 15 seconds, rinsed, and air dried. Each tooth was divided into three regions (incisal, middle, and cervical) and viewed after etching at 1200× magnification with SEM. The μCT scans were taken before and after etching to calculate apparent and material mineral densities.

RESULTS

SEM showed greater aprismatic enamel and poorer etch quality (ie, significantly less percentage enamel) for the posterior than anterior teeth and for the cervical region than for the incisal and middle regions of all teeth. Although there were no density differences prior to etching, μCT demonstrated that etching increased material density significantly more for the anterior than posterior teeth. Prior to etching, the enamel in the cervical regions was significantly less dense than the enamel in the middle or incisal regions. Etching significantly increased the material density of all three regions, which decreased initial regional differences. After etching, the apparent density of the cervical region remained significantly lower than the densities of the other two regions.

CONCLUSIONS

Based on SEM and μCT, there is greater aprismatic enamel and inferior etch quality in the cervical regions of all tooth types and is clinically significant in explaining the failure of sealant retention and the propensity for white spot lesions.

Evaluation of bactericidal effects of ultraviolet light C irradiation on cariogenic bacteria: An in vitro study

Backgrounds

Ultraviolet light C (UVL-C) irradiation has demonstrated an antimicrobial action against various pathogens. This study aimed to evaluate the bactericidal effect of UVL-C irradiation against cariogenic oral bacteria (Streptococcus mutans) in single layers and colonies grown on solid surfaces.

Methods

Two different experiments were performed. In the first experiment, a single layer of Streptococcus mutans bacteria on agar plates was exposed to UVL-C irradiation at energies from 0 to 21 mWs/cm². The second experiment was conducted to inhibit viability of bacterial colonies on solid surfaces. The samples were derived from saliva from a patient where bacteria were grown on plastic strips and then exposed to UVL-C. The highest energy was 1050 mWs/cm².

Results

Exposure to 21 mWs/cm² was bactericidal in single layers of Streptococcus mutans. The result for bacterial colonies on solid surfaces indicated only a bacteriostatic effect, even at energies of 1050 mWs/cm².

Conclusions

Ultraviolet light C exhibits bactericidal effects on single layers of Streptococcus mutans but has a limited effect on bacterial colonies in a biofilm. It is a matter of debate whether these in vitro results would have the same effect in clinical setting.

Enamel-like tissue regeneration by using biomimetic enamel matrix proteins

Enamel regeneration currently -is limited by our inability to duplicate artificially its complicated and well-aligned hydroxyapatite structure. The initial formation of enamel occurs in enamel organs where the ameloblasts secret enamel extracellular matrix formed a unique gel-like microenvironment. The enamel extracellular matrix is mainly composed by amelogenin and non-amelogenin. In this study, an innovative strategy was proposed to regenerate enamel-like tissue by constructing a microenvironment using biomimetic enamel matrix proteins (biomimetic EMPs) composed of modified leucine-rich amelogenin peptide (mLRAP) and non-amelogenin analog (NAA). Impressively, the regenerated enamel in this biomimetic EMPs on etched enamel surface produced prismatic structures, and showed similar mechanical properties to natural enamel. The results of X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) showed that regenerated crystal was hydroxyapatite. Molecular dynamics simulation analysis showed the binding energy between mLRAP and NAA were electrostatic forces and Van der Walls. These results introduced a promising strategy to induce crystal growth of enamel-like hydroxyapatite for biomimetic reproduction of materials with complicated hierarchical microstructures.

Protective effect of calcium silicate toothpaste on enamel erosion and abrasion in vitro

Objectives

To compare in vitro the effect of a toothpaste containing fluoride (F), calcium silicate (CaSi) and sodium phosphate salts to conventional toothpaste (NaF) on human enamel specimens submitted to erosive and abrasive challenges.

Methods

48 sound and 48 enamel samples pre-treated with 1% citric acid were divided into 4 groups (n = 12): Group 1- Non-fluoride toothpaste; Group 2- NaF toothpaste (1450 ppmF); Group 3- CaSi toothpaste (1450 ppmF; MFP); Group 4- Erosion only. The samples were subjected to pH cycling (3 cycles/day; 90s; 1% citric acid, pH 3.6) and to abrasion for 7 days. After the 1^st and the last cycle, they were submitted to abrasion (15s, 1.5N load), using a brushing machine, soft toothbrush and toothpaste slurry (1:3; 15ml/sample) and then immersed in the slurry for 45s. Samples were immersed in artificial saliva between the challenges. Enamel loss was evaluated using profilometry on days 3 and 7. Data were analysed by ANOVA and Tukey's test (p < 0.05).

Results

For sound enamel at baseline, mean (±SD) enamel loss (μm) for groups 1-4 on day 3 was 2.15 ± 0.35^a, 1.20 ± 0.22^b, 0.95 ± 0.19^b and 1.98 ± 0.32^a; on day 7 was 3.05 ± 0.40^a, 2.07 ± 0.32^b, 1.36 ± 0.33^c and 3.69 ± 0.27^d respectively. For acid-softened enamel at baseline, enamel loss on day 3 was 3.16 ± 0.19^a, 2.17 ± 0.14^b, 1.70 ± 0.11^c and 3.04 ± 0.19^a; on day 7 was 3.92 ± 0.25^a, 3.07 ± 0.13^b, 2.09 ± 0.15^c and 3.87 ± 0.25^a respectively.

Conclusions

Both F toothpastes led to significantly higher enamel protection from short-term erosion and abrasion in comparison to the non-F toothpaste and erosion only. In the longer term, CaSi toothpaste conferred significantly higher protection than NaF toothpaste.

Clinical significance

The results showed that for the longer term the CaSi toothpaste provided significantly higher protection than the NaF toothpaste, which indicates a good potential of the former to help prevent erosive tooth wear.

Influence of material type, thickness and storage on fracture resistance of CAD/CAM occlusal veneers

OBJECTIVES

The present study aimed to evaluate the effect of restoration thickness, CAD/CAM material, and 6 months of artificial saliva storage on the fracture resistance of occlusal veneers.

MATERIALS AND METHODS

A total of 84 intact maxillary molars were sectioned 4.0 mm occlusal to the cementoenamel junction to expose the dentine. The teeth were assigned into 3 main groups according to the type of restorative material (e.max CAD, Vita Enamic, and Lava Ultimate). In each group, the teeth were allocated into 2 subgroups (n = 14) according to restoration thickness (1.0 and 1.5 mm). The veneers were adhesively bonded using dual-cure self-adhesive luting agent. A total of 42 specimens comprising half the tested subgroups were stored in distilled water for 24-h before the test. The remaining half was stored in artificial saliva at 37 ± 1 °C in an incubator for 6 months. All specimens (n = 84) were subjected to 5000 thermal cycles between 5 and 55 °C ± 2 before the fracture resistance test. The maximum force at fracture was recorded in Newton. Failure mode was analyzed using a stereomicroscope. The results were analyzed using a parametric Three-way ANOVA test.

RESULTS

The results of the Three-way ANOVA test revealed that material type and restoration thickness significantly affected fracture resistance values (p < 0.5), while 6 months of storage in artificial saliva had no significant effect on mean fracture resistance values (p˃0.5). The most common failure patterns in CAD/CAM resin composite and polymer-infiltrated ceramics were scores I and score II. For glass ceramic groups, score IV and III were more dominant.

CONCLUSIONS

All the tested CAD/CAM restorations in both thicknesses exhibited fracture resistance values exceeding normal and parafunctional bite forces. Polymer-infiltrated ceramics and CAD/CAM resin composite veneers showed more favorable fracture patterns.

Fluoride dentifrice containing calcium silicate and sodium phosphate salts on dental erosion: In vitro study

OBJECTIVE

To investigate the effect of a commercial dentifrice containing fluoride, calcium silicate, and sodium phosphate and its dual phase gel serum to prevent erosive tooth wear in enamel.

METHODS

Forty-eight enamel specimens were selected by surface hardness and randomly allocated into 4 groups (n = 12) according to the commercial toothpastes: non-fluoridated (NF); 1100 ppm Stannous fluoride (SnF₂); 1450 ppm MFP + calcium silicate + sodium phosphate (CSSP); CSSP + dual-phase gel (CSSP + Serum). Cyclic experiments were repeated 3x / day for five days, including an erosive challenge with 0.05 M citric acid (pH 3.75 for 30 s), treatment with toothpaste slurries (1 min), and remineralization with artificial saliva (pH 7.0 for 60 min). Surface alterations were determined by stylus profilometry (μm) and scanning electron microscopy (SEM). Data were analyzed by ANOVA and Tukey tests (α = 0.05).

RESULTS

SnF₂, CSSP and CSSP + Serum significantly reduce surface wear compared to NF treated group. Besides, there were no significant differences among SnF₂, CSSP and CSSP + Serum. In micrographs of both groups treated with CSSP, the surface demonstrates the presence of a protective layer as a deposition of particles.

CONCLUSIONS

Dentifrice containing calcium silicate and sodium phosphate with or without the dual-phase gel was able to prevent the erosive tooth wear.

Comparative Effect of Calcium Mesoporous Silica Versus Calcium and/or Fluoride Products Against Dental Erosion

The aim of this study was to compare the effects of a single application of a new calcium mesoporous silica nanoparticle (Ca2+-MSN) versus other calcium and/or fluoride products against dental erosion. Enamel blocks were half-covered and assigned to six groups (n = 10): Ca2+-MSNs; casein phosphopeptide-amorphous calcium phosphate mousse (CPP-ACP); CPP-ACP/F- (900 ppm F-); titanium tetrafluoride (TiF4 1%); sodium fluoride (NaF 1.36%); and Milli-Q® water (negative control). A single application for each product was completed on the exposed areas of the blocks and were submitted to an erosive challenge. Differences in volumetric roughness (Sa), and tooth structure loss (TSL) by use of three-dimensional noncontact optical profilometry were evaluate. Scanning electron microscopy (SEM) was performed. Analysis of variance and Tukey's test for Sa and the Kruskal-Wallis and Mann-Whitney U tests (p< 0.05) for TSL, respectively. Results: When evaluating Sa, all products presented differences in roughness when compared with the control group (p< 0.05) but not with each other (p > 0.05). However, when analyzing the TSL, it was observed that Ca2+-MSNs, TiF4, and NaF were more effective in preventing dental erosion versus CPP-ACP, CPP-ACP/F-, and Milli-Q® water (p< 0.05). In the SEM images, the negative control presented the worst loss of dental structure, with more porous enamel. Ca2+-MSNs were as effective as TiF4 and NaF to reduce the tooth structure loss.

BARIATRIC SURGERY IMPACT ON GASTROESOPHAGEAL REFLUX AND DENTAL WEAR: A SYSTEMATIC REVIEW

Introduction:

Several oral problems may be perceived in individuals who were submitted to bariatric surgery, due to metabolic and behavioral changes relative to diet and oral hygiene. Tooth wear appears to suffer impact after bariatric surgery, because there may be an increase in gastroesophageal reflux.

Objective:

To systematically review the literature regarding the impact of bariatric surgery on gastroesophageal reflux and tooth wear.

Method:

The following databases were accessed by two independent, calibrated examiners: PubMed, Medline, Lilacs, Scielo and Cochrane using the following descriptors: “bariatric surgery” AND “dental erosion” OR “bariatric surgery” AND “dental erosion” AND “gastroesophageal reflux disease”. After excluding duplicate studies, 12 studies were initially evaluated by the title and abstract. The excluded studies were those without relevance to the present research, literature review studies and case reports. Thus, four articles were included in this study. All the articles evaluated indicated high association between gastroesophageal reflux and tooth wear in patients submitted to bariatric surgery. Association of these outcomes was more evident six months after the surgical procedure.

Conclusion:

Patients submitted to bariatric surgery showed higher prevalence of gastroesophageal reflux and tooth wear.

Defense Mechanisms Against Acid Exposure by Dental Enamel Formation, Saliva and Pancreatic Juice Production

The pancreas, the salivary glands and the dental enamel producing ameloblasts have marked developmental, structural and functional similarities. One of the most striking similarities is their bicarbonate-rich secretory product, serving acid neutralization. An important difference between them is that while pancreatic juice and saliva are delivered into a lumen where they can be collected and analyzed, ameloblasts produce locally precipitating hydroxyapatite which cannot be easily studied. Interestingly, the ion and protein secretion by the pancreas, the salivary glands, and maturation ameloblasts are all two-step processes, of course with significant differences too. As they all have to defend against acid exposure by producing extremely large quantities of bicarbonate, the failure of this function leads to deteriorating consequences. The aim of the present review is to describe and characterize the defense mechanisms of the pancreas, the salivary glands and enamel-producing ameloblasts against acid exposure and to compare their functional capabilities to do this by producing bicarbonate.

Assessing the Effect of Low Calorie Soda Beverages on Primary Tooth Enamel: An In Vitro Study

Objective: The purpose of this study was to evaluate the effect of low calorie soda beverages on the enamel of primary teeth. Study Design: Fifty enamel slabs were prepared from twenty primary extracted teeth and were equally divided into five groups: a) 0.9% NaCl (Control), b) Coca-Cola Classic (Sucrose), c) Diet Coke (Aspartame), d) Zevia Cola (Erythritol), e) Coca-Cola Life (Stevia). Each specimen was exposed to the beverage for a total of sixty minutes. Enamel surface roughness was measured before and after the exposures using a LEXT OLS4000 3D Laser Measuring Microscope. Results: All tested sodas resulted to a statistically significant change on the surface roughness of the enamel (p =.000). However, this effect did not differ significantly between the different treatment groups (p =.103). Conclusions: Both regular soda and low calorie soda containing different commercial sweeteners appear to have an effect on the surface morphology of primary tooth enamel. Thus, it is important to discourage the intake of any type of soda as part of the dietary advice provided in the dental office.

The effects of 8DSS peptide on remineralization in a rat model of enamel caries evaluated by two nondestructive techniques

Nowadays, dental caries is one of the most common oral health problems, affecting most individuals. It has been found that, by remineralizing enamel at an early stage in the formation of enamel caries, teeth can be effectively protected from dental caries. In this work, a peptide with eight repetitive sequences of aspartate-serine-serine (8DSS) is applied as the bio-mineralizer in an in-vivo rat enamel caries model. Nondestructive quantitative light-induced fluorescence-digital (QLF-D) imaging and micro-computed tomography (micro-CT) are used to evaluate the remineralization of enamel carious lesions by measuring the total fluorescence radiance loss of the molar area (Δ Q_Total), acquired using QLF-D imaging, and the mineral density and residual molar enamel volume, acquired using micro-CT. Correlations are explored between Δ Q_Total and mineral density (strong correlation, r = 0.8000, p < 0.001) and Δ Q_Total and residual molar enamel volume (moderate correlation, r = 0.6375, p < 0.001). Our results demonstrate that 8DSS is a promising in-vivo remineralization agent that exhibits comparable effects to NaF ( p < 0.05), which has been verified using the classical Keyes method. Moreover, the nondestructive QLF-D and micro-CT methods can be combined to quantify the remineralization of enamel carious lesions three-dimensionally in vivo, making them broadly applicable in quantifying hard tissues.

Effects of dentifrices on mechanical resistance of dentin and restorative materials after erosion and abrasion

The aim of this study was to evaluate the mechanical resistance of dentin and restorative materials submitted to erosive/abrasive challenges with different dentifrices. The dentin was restored using a resin-modified glass-ionomer (RMGIC) or a composite resin (RC). One hemiface of the sample was protected, and the other was subdivided according to the applied dentifrice (n = 10): without fluoride (SF), sodium fluoride (NaF) and stannous fluoride (SnF). The specimens were submitted to erosive/abrasive cycles, the varnish was removed, and the Martens hardness (HMV) and elastic modulus (Eit) were evaluated. The data were analyzed by repeated two-way ANOVA measurements and Tukey tests (alpha = 0.05). When analyzing the HMV on the test side, there was no influence of the dentifrices in the dentin; however, the orders of NaF < SnF = SF in RC and SnF > NaF = SF in RMGIC were observed. Comparing the treated surfaces, there were no differences in the dentin, and only the SF since CR presented an HMV superior to that of RMGIC. Comparing control and test sides, both dentins obtained a decreased HMV after the erosive/abrasive challenge; for the restorative materials, superior values were found only for SnF in the RMGIC. The Eit values were influenced more by the dentifrices on the test side for the dentin adjacent to the RMGIC, with the lowest values shown for the SF, and for both materials, the highest values were shown for the SnF group. No differences were found when comparing each dentin treated with the same dentifrice; however, the RMGIC presented a superior Eit than the CR when brushed with both dentifrices with a fluoride. Comparing the control and test sides, the same results were obtained for the HMV. The dentifrices showed little influence on the dentin substrate, whereas the dentifrice with SnF enhanced the mechanical properties of the restorative materials, which was more evident in the RMGIC.

Remineralisation of enamel with silver diamine fluoride and sodium fluoride

OBJECTIVE

To evaluate the remineralising effect of the adjunctive application of 38% silver diamine fluoride (SDF) solution and 5% sodium fluoride (NaF) varnish on artificial enamel caries lesions.

METHODS

Forty-eight demineralised enamel specimens were allocated into four groups. Group 1 received 38% SDF and 5% NaF; Group 2 received 38% SDF; Group 3 received 5% NaF; and Group 4 received deionized water. After pH cycling, the surface morphology and fluoride content of the specimens were studied via scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS). The lesion depth and crystal characteristics were assessed using micro-computed tomography and X-ray diffraction (XRD) respectively. The crystallization reaction was performed by incubating hydroxyapatite powder with NaF or SDF for 48h. The precipitates were studied via transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).

RESULTS

SEM demonstrated the destruction of the enamel surface in Group 4. EDS revealed that the mean fluoride weight percentage of Groups 1-4 were 1.28±0.15, 1.33±0.19, 1.03±0.09 and 0.87±0.04 respectively. The mean lesion depths of Groups 1-4 were 129±14μm, 131±16μm, 153±10μm and 181±21μm respectively. The addition of NaF to SDF did not reduce the lesion depths (p=0.779). XRD revealed that silver chloride formed as a main product in Groups 1 and 2. Meanwhile, TEM analysis indicated that silver nanoparticles were incorporated into hydroxyapatite crystal in SDF-treated hydroxyapatite. XPS spectra suggested that the chemical state of the silver was metallic.

SIGNIFICANCE

The adjunctive application of SDF and NaF varnish had a similar remineralising effect to that of SDF on enamel caries.

Non-carious cervical lesions and risk factors: A case-control study

OBJECTIVES

To evaluate whether the presence of non-carious cervical lesions (NCCLs) was related to the considered risk factors and to show the corresponding odds ratio in a predictive model.

METHODS

The sample was 280 dentistry students. In an initial clinical examination, 140 cases were selected that presented one or more teeth with non-carious cervical wear. For each case, a similar sex and age control without any tooth with non-carious cervical lesions was selected. An occlusal examination and periodontal probing were performed in all cases and controls by skilled dentists. All the subjects answered a questionnaire referring to factors of brushing, bruxism, preferred chewing side, consumption of extrinsic acids and the presence of intrinsic acids. Data were analysed by means of univariate and multivariate logistic regression.

RESULTS

Of all the study variables, only the protrusion interferences, interferences on the non-working side, the brushing force, CPITN value and the consumption of salads increase the risk of NCCLs in the univariate regression. The best predictive model was formed by the combination of CPITN variables >1, the consumption of acidic salads, self-reported bruxism, brushing force and attrition. However, it only correctly classifies 68.75% of subjects.

CONCLUSIONS

This study supports the multifactorial aetiology of NCCLs, the combination of several factors being necessary to explain their presence. The risk factors that make up the predictive model are not sufficient to explain the appearance of NCCLs. Dentists should take into account all these risk factors in prevention, diagnosis and treatment.

Sol-gel bioglasses in dental and periodontal regeneration: A systematic review

Due to their osteoconductive and osteoinductive abilities, bioglasses (BGs) have attracted attention in tissue engineering, especially for mineralized tissue. The aim of this study is to review the current state of the art on the effects of BGs produced by sol-gel on cells for dental and periodontal regeneration. The study also discusses associated antibacterial properties. The research was performed by considering the Preferred Reporting Items for Systematic Reviews and the Meta-Analyses (PRISMA) statement. The research ranged 5 years' window time (from January, 01, 2012, to August, 31, 2017) and the relevant studies were identified based on the inclusion/exclusion criteria. A total of 45 articles were selected from 244 initial returns, plus seven further articles coming from other sources were selected for the same purpose. From this systematic study, it is revealed that only 13 of the 52 articles have proved both the ability of BGs to differentiate dental cells at genetic level and their ability of triggering cell-mediated mineralization, but only six of them showed, along with cells, the antibacterial properties of the glasses. This review shows that sol-gel BGs are not toxic, can sustain cell proliferation and differentiation at a genetic level, and can keep the bacterial population under control. Moreover, a standard methodology and an ideal material are suggested. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1210-1227, 2019.

Cariology education for undergraduate Brazilian dental students

ABSTRACT This study sought to provide an overview of current cariology education for undergraduate Brazilian dental students. Data collection was via a Portuguese version of a 12-item questionnaire (Schulte et al., 2011) that was sent to all Brazilian dental schools (n = 219). The response rate was 57.0% (n = 125). Of the schools that returned the questionnaire, 84.8% supported the development of a Brazilian cariology curriculum. The units responsible for teaching cariology were predominantly operative dentistry (49.6%), pediatric dentistry (49.6%), dental public health (44.8%), and cariology (32%). Theoretical teaching of cariology (74.4%) and pre-clinical exercises (63.2%) were cited to occur mainly during the second year of the course, while clinical activities were placed in the third (71.2%) and fourth (64.8%) years. Among respondents, 76.8% of the schools included dental erosion and 86.4% included defects of dental hard tissues, such as abrasion, in teaching cariology. This survey was able to determine the panorama of cariology education in Brazil and to detect some differences among Brazilian geographic areas. The promotion of a workshop to discuss the topics that should be taught to undergraduate dental students and the development of a Brazilian core curriculum in cariology would be likely to reduce the differences in teaching cariology in Brazil.

Validation of a Real-Time ISE Methodology to Quantify the Influence of Inhibitors of Demineralization Kinetics in vitro Using a Hydroxyapatite Model System

The aim was to validate a novel protocol to measure the cariostatic efficacies of demineralization inhibitors by repeating previous SMR (scanning microradiography) studies investigating the dose response of Zn2+ and F- on demineralization kinetics in vitro using real-time Ca2+ ion selective electrodes (ISEs). In this study, Ca2+ release was used as a proxy for the extent of demineralization. Forty-eight hydroxyapatite (HAP) discs were allocated into 16 groups (n = 3) and adding either increasing [Zn2+], or [F-], similar to those used in the previous SMR studies. Each HAP disc was immersed in 50 mL, pH 4.0, buffered acetic acid for 1 h, and real-time ISE methodology was used to monitor the rate of increase in [Ca2+] in the demineralization solution. Next, either zinc acetate or sodium fluoride was added into each demineralization solution accordingly. Then after each [Zn2+] or [F-] addition, the HAP disc was further demineralized for 1 h, and ISE measurements were continued. The percentage reduction in the rate of calcium loss from hydroxyapatite (PRCLHAP) at each [Zn2+] or [F-] was calculated from the decrease in Ca2+ release rate, similar to that used in the previous SMR studies. A log-linear relationship between mean PRCLHAP and inhibitor concentration was found for both Zn2+ and F-, similar to that reported for each ion in the previous SMR studies. In conclusion, real-time Ca2+ ISE systems can be used to measure the cariostatic efficacies of demineralization inhibitors.

Evaluation of calcium and magnesium contents in tooth enamel without any pathological changes: in vitro preliminary study

Enamel is the structure that covers the entire clinical crown of a tooth. It enables to chew and crush food, and gives a final shape to the crowns of teeth. To evaluate calcium and magnesium contents in tooth enamel and analyse relationships between the study minerals extracted human permanent teeth were cut at every 150 microns and subjected into acid biopsy. The amounts of calcium and magnesium were assessed in the laboratory using atomic absorption spectroscopy with an air/acetylene flame. The lowest calcium and magnesium contents were found on the enamel surface of the teeth. Statistically significant correlation between the calcium and magnesium concentrations was found at a depth between 150 and 900 µm. Calcium and magnesium contents increased with increasing enamel depth. Calcium and magnesium deposits appeared to be stable through all the enamel layers studied. It would be suggested that mineralization/demineralization affect only external layer of the enamel, whereas deeper layers are not affected by these processes.

Effect of Different Computer-aided Design/Computer-aided Manufacturing (CAD/CAM) Materials and Thicknesses on the Fracture Resistance of Occlusal Veneers

The aim was to evaluate, in vitro, the influence of different computer-aided design/computer-aided manufacturing (CAD/CAM) materials (IPS e.max CAD, Vita Enamic, and Lava Ultimate) and thicknesses (0.6 mm and 1.5 mm) on the fracture resistance of occlusal veneers. Sixty human third molars were prepared to simulate advanced erosion of the occlusal surface, and the teeth were randomly divided into six experimental groups (n=10) according to the material and thickness used to build the veneers. Ten sound teeth formed the control group. The veneers were adhesively luted and submitted to mechanical cyclic loading (1 million cycles at 200-N load). The fracture resistance test was performed in a universal testing machine. The failures were classified as "reparable" and "irreparable." According to two-way analysis of variance and the Tukey test, the interaction (material × thickness) was significant ( p=0.013). The highest fracture resistance was obtained for IPS e.max CAD at a 1.5-mm thickness (4995 N) and was significantly higher compared to the other experimental groups ( p<0.05). The lowest fracture resistance was obtained for Vita Enamic at 0.6 mm (2973 N), although this resistance was not significantly different from those for IPS e.max CAD at 0.6 mm (3067 N), Lava Ultimate at 0.6 mm (3384 N), Vita Enamic at 1.5 mm (3540 N), and Lava Ultimate at 1.5 mm (3584 N) ( p>0.05). The experimental groups did not differ significantly from the sound teeth (3991 N) ( p>0.05). The failures were predominantly repairable. The occlusal veneers of IPS e.max CAD, Vita Enamic, and Lava Ultimate, with thicknesses of 0.6 mm and 1.5 mm, obtained fracture resistances similar to those associated with sound teeth.

Effects of Fluoride on Two Chemical Models of Enamel Demineralization

This study evaluated the effects of fluoride on subsurface enamel demineralization induced by two commonly used chemical models. Forty-eight enamel blocks were demineralized at pH = 5.0 by an acetate buffer (Group 1), a lactate buffer (Group 2), an acetate buffer with 0.02 ppm fluoride (Group 3) and a lactate buffer with 0.02 ppm fluoride (Group 4) at 25 °C for 3 weeks. The surface destruction percentage (SDP), mineral loss and lesion depth of the blocks were studied using micro-computed tomography. An elemental analysis of the enamel surface was evaluated using an energy-dispersive X-ray spectroscopy. Surface micro-hardness was determined by the Knoop Hardness Test. The mean lesion depth of Groups 1 through 4 were 134.1 ± 27.2 μm, 96.1 ± 16.5 μm, 97.5 ± 22.4 μm and 91.1 ± 16.2 μm, respectively (p < 0.001; group 1 > 2, 3 > 4). The SDPs of groups 1 through 4 were 7.8 ± 8.93%, 0.71 ± 1.6%, 0.36 ± 1.70% and 1.36 ± 2.94% (p < 0.001; group 1 > 2, 3, 4). The fluoride in mean weight percentages of groups 1 through 4 were 1.12 ± 0.24%, 1.10 ± 0.20%, 1.45 ± 0.40% and 1.51 ± 0.51%, respectively (p < 0.001; group 3, 4 > 1, 2). The mean Knoop hardness values of groups 1 through 4 were 27.5 ± 13.3, 39.7 ± 19.3, 73.6 ± 44.2 and 91.0 ± 57.2, respectively (p < 0.001; group 4 > 3 > 2 > 1). The chemical model using an acetate buffer solution created significantly deeper zones of subsurface demineralization on enamel than the lactate buffer solution. An acetate buffer may damage the enamel surface, but the surface damage can be prevented by adding fluoride.

A Novel Kinetic Method to Measure Apparent Solubility Product of Bulk Human Enamel

Introduction: Tooth enamel mineral loss is influenced by its solubility product value, which is fundamental to the understanding of de- and remineralization resulting from a carious or erosive challenge. Published pKsp values for human enamel and hydroxyapatite range from 110 to 126 suggesting a heterogeneous nature of enamel solubility. However, this range of values may also result from the variety of methods used, e.g., some authors reporting values for suspensions of enamel powder and others for bulk enamel. The aim of this study was to develop a method to measure the solubility of bulk human enamel under controlled in vitro conditions simulating demineralization behavior of enamel within the oral environment using scanning microradiography (SMR). SMR was used to monitor real-time changes in enamel demineralization rates at increasing calcium concentrations in a caries simulating demineralization solution until the concentration at which thermodynamic equilibrium between enamel and solution was achieved. Method: 2 mm thick caries free erupted human enamel slabs with the natural buccal surfaces exposed were placed in SMR cells exposed to circulating caries-simulating 2.0 L 0.1 M pH = 4.0 acetic acid, at 25°C. SMR was used to continuously measure in real-time the decrease in mineral mass during the demineralization at 5 different points from on each slab. Demineralization rates were calculated from a linear regression curve of projected mineral mass against demineralization time. Changes in the demineralization rates were monitored following a series of successive increases in calcium (and phosphate at hydroxyapatite stoichiometric ratios of Ca:P 1.67) were added to the demineralizing solution, until demineralization ceased. The pH was maintained constant throughout. Results: Demineralization halted when the calcium concentration was ~30 mM. At higher calcium concentrations, mineral deposition (remineralization) occurred. By comparison with results from speciation software calculations for the calcium phosphate ternary system, this result suggests that the bulk solubility product of enamel (pKsp_BEnamel) under the conditions used is 121. Discussion: The apparent pKsp_BEnamel under these conditions was higher than many previous reported values, and much closer to those previously reported for HAp. However, this is a bulk value, and does not reflect that enamel is a heterogeneous material, nor the influence of ionic inclusions.

Importance of bicarbonate transport in pH control during amelogenesis - need for functional studies

Dental enamel, the hardest mammalian tissue, is produced by ameloblasts. Ameloblasts show many similarities to other transporting epithelia although their secretory product, the enamel matrix, is quite different. Ameloblasts direct the formation of hydroxyapatite crystals, which liberate large quantities of protons that then need to be buffered to allow mineralization to proceed. Buffering requires a tight pH regulation and secretion of bicarbonate by ameloblasts. Many investigations have used immunohistochemical and knockout studies to determine the effects of these genes on enamel formation, but up till recently very little functional data were available for mineral ion transport. To address this, we developed a novel 2D in vitro model using HAT-7 ameloblast cells. HAT-7 cells can be polarized and develop functional tight junctions. Furthermore, they are able to accumulate bicarbonate ions from the basolateral to the apical fluid spaces. We propose that in the future, the HAT-7 2D system along with similar cellular models will be useful to functionally model ion transport processes during amelogenesis. Additionally, we also suggest that similar approaches will allow a better understanding of the regulation of the cycling process in maturation-stage ameloblasts, and the pH sensory mechanisms, which are required to develop sound, healthy enamel.

[Increased oral fluid remineraling function by endogenous and exogenous saturation methods of its mineral complexes]

RELEVANCE

One of the most common problems in modern caries prevention is the development of techniques to increase tooth resistance to the effects of cariogenic factors. Therefore, research is needed to study the chemical composition of tissues like teeth and body fluids surrounding the tooth to prevent demineralization process. The purpose of determining the effectiveness of work- and correlation relationship between endo saturation exogenous methods oral liquid mineral complexes.

MATERIAL AND METHODS

In 95 patients analyzed the chemical composition and structure of the oral fluid by IR spectroscopy. For the collection of IR spectra used Verteh-70 spectrometer ('Bruker', Germany) and the prefix of frustrated total internal reflection PLATINUM ATR diamond prism.

RESULTS AND DISCUSSION

A correlation between the use of endogenous and exogenous methods of caries prevention, in favor of the former, as well as changes in the mineral-organic and phosphate-carbon ratio in the dry residues of oral fluid.

Effect of Tannic Acid on the Protective Properties of the in situ Formed Pellicle

OBJECTIVES

In the present in situ/ex vivo study the impact of tannic acid on the erosion-protective properties of the enamel pellicle was tested. Additionally, the antiadherent and antibacterial effects of tannic acid were evaluated.

METHODS

The pellicle was formed in situ on bovine enamel samples fixed on individual splints worn by 6 subjects. Following 1 min of pellicle formation the volunteers rinsed for 10 min with tannic acid. After further oral exposure for 19 min, 109 min, and 8 h overnight, respectively, slabs were incubated in HCl ex vivo (pH 2.0, 2.3, 3.0) over 120 s. Subsequently, kinetics of calcium and phosphate release were measured photometrically. Samples after a 1-min fluoride mouth rinse as well as enamel samples with and without a 30-min in situ pellicle served as controls. Antiadherent effects were evaluated after a 1-min rinse with tannic acid and oral exposure of the slabs overnight. DAPI (4',6-diamidino-2-phenylindole) combined with concanavalin A staining and live/dead staining was used for fluorescence microscopic visualization and quantification of adherent bacteria and glucans. Modification of the pellicle's ultrastructure by tannic acid was evaluated by transmission electron microscopy (TEM).

RESULTS

Tannic acid significantly improved the erosion-protective properties of the pellicle in a pH-dependent manner. Bacterial adherence and glucan formation on enamel were significantly reduced after rinses with tannic acid as investigated by fluorescence microscopy. TEM imaging indicated that rinsing with tannic acid yielded a sustainable modification of the pellicle; it was distinctly more electron dense.

CONCLUSION

Tannic acid offers an effective and sustainable approach for the prevention of caries and erosion.

Tooth wear and quality of life among adults in the United Kingdom

OBJECTIVE

To explore the association between tooth wear and quality of life among adults in the United Kingdom, independently of sociodemographic factors and other common oral conditions.

METHODS

We used data from 5654 dentate adults who participated in the 2009 Adult Dental Health Survey. Tooth wear was assessed during clinical examination and classified as none, mild, moderate and severe based on the worst affected tooth recorded. The numbers of teeth with mild, moderate and severe tooth wear were used as alternative measures. Oral impacts on quality of life were measured using the short form of the Oral Health Impact Profile (OHIP-14). The associations between tooth wear measures and OHIP-14 total and domain scores were tested in negative binomial regression models adjusting for sociodemographic and clinical factors.

RESULTS

Overall, 62% of participants had mild, 13% moderate and 2% severe tooth wear. Adults with severe tooth wear had a crude OHIP-14 total score higher than those without tooth wear (Rate Ratio: 1.90; 95% Confidence Interval: 1.32-2.75). This association was attenuated after adjustment for confounders, particularly for other oral conditions (1.25; 95% CI: 0.90-1.73). Moreover, adults with severe tooth wear reported higher OHIP-14 domain scores in psychological discomfort (1.15; 95% CI: 1.06-1.25) and psychological disability (1.18; 95% CI: 1.10-1.30) than those without such condition. There was also evidence of a dose-response relationship; with higher OHIP-14 domain scores according to the number of teeth with severe tooth wear.

CONCLUSION

This nationwide study among UK adults shows that severe tooth wear was negatively associated with psychological impacts on people's life.

CLINICAL SIGNIFICANCE

Dentist should consider not only the patients' clinical characteristics, but also their impacts on quality of life and provide preventive or restorative management accordingly.

Effectiveness of resin-based materials against erosive and abrasive enamel wear

OBJECTIVE

The objective of this study was to test the effectiveness of resin-based materials against erosive enamel wear under erosive and abrasive challenges by orange juice and tooth brushing.

METHODS

Fifty enamel specimens from third molars were assigned to five groups: ICON resin infiltration with no etching (ICON-NE), ICON resin infiltration with 15 % HCl etching (ICON-AE), Seal & Protect sealant (S&P), Tetric EvoFlow (TEF), and control. Erosive lesions were first created on enamel, then treated with resin-based materials. Erosive and abrasive challenges by orange juice and tooth brushing were repeated after treatments. Erosive wear of the treated areas was measured with 3D scanning microscopy, and data were analyzed using ANOVA and paired t tests.

RESULTS

Treatments with ICON, S&P, and TEF created a protective material coating of 4.5 ± 1.9 μm, 44.3 ± 8.1 μm, and 84.6 ± 15.7 μm in thickness on the lesion surfaces, respectively. After 15 cycles of erosive and abrasive challenges, enamel or material losses were 21.9 ± 2.3 μm for control, 24.5 ± 4.0 μm for ICON-NE, 24.6 ± 7.4 μm for ICON-AE, 11.2 ± 4.1 μm for S&P, and 3.9 ± 1.9 μm for TEF, respectively. The protective coatings were completely lost in the ICON infiltration groups but remained intact in both the S&P and TEF groups after erosive and abrasive challenges.

CONCLUSION

In contrast to a resin sealant and a flowable composite, ICON infiltration resin was not effective in protecting enamel surfaces from erosive and abrasive wear.

CLINICAL RELEVANCE

Sealant and flowable composite resin may create protective coatings on eroded enamel surfaces and prevent further tissue loss.

Analysis of Dental Enamel Surface Submitted to Fruit Juice Plus Soymilk by Micro X-Ray Fluorescence: In Vitro Study

OBJECTIVE

This paper aimed to analyze the in vitro industrialized fruit juices effect plus soy to establish the erosive potential of these solutions.

MATERIALS AND METHODS

Seventy bovine incisors were selected after being evaluated under stereomicroscope. Their crowns were prepared and randomly divided into 7 groups, using microhardness with allocation criteria. The crowns were submitted to the fruit juice plus soy during 15 days, twice a day. The pH values, acid titration, and Knoop microhardness were recorded and the specimens were evaluated using X-ray microfluorescence (µXRF).

RESULTS

The pH average for all juices and after 3 days was significantly below the critical value for dental erosion. In average, the pH value decreases 14% comparing initial time and pH after 3 days. Comparing before and after, there was a 49% microhardness decrease measured in groups (p < 0.05). Groups G1, G2, G5, and G6 are above this average. The analysis by μXRF showed a decrease of approximately 7% Ca and 4% P on bovine crowns surface. Florida (FL) statistical analysis showed a statistically significant 1 difference between groups. Thus, a tooth chance to suffer demineralization due to industrialized fruit juices plus soy is real.