Randomized in situ evaluation of surface polishing protocols on the caries-protective effect of resin Infiltrant.

The aim of this placebo-controlled randomized in situ study was to evaluate the effect of different surface polishing protocols on enamel roughness, bacterial adhesion and caries-protective effect of a resin infiltrant. Seventy-five bovine enamel samples having artificial caries lesions were treated with a resinous infiltrant and afterwards randomly dividided into five polishing protocols: aluminum oxide flexible disks (Al2O3-Disks), silicon carbide tips (SIC-Tips), silicon carbide brush (SIC-Brush), silicon carbide polyester strips (SIC-Strips) or no polishing [negative control (NC)]. Average surface roughness (Ra) was assessed by profilometry. Samples were mounted in palatal appliances under a mesh for biofilm accumulation. Fifteen volunteers wore the intraoral appliances (14-days) and cariogenic challenge was triggered by sucrose solutions. Biofilm formed was collected for microbiological analysis of caries-related bacteria (Streptococcus mutans, Lactobacillus acidophilus) and demineralization was assessed by cross-sectional microhardness. Mean Knoop hardness numbers (Kg/mm2) were plotted over lesion depth (µm) and area under the lesion curve was subtracted from sound enamel to determine demineralization (ΔS, Kg/mm2xµm). Data were analyzed by ANOVA and post-hoc comparisons (α = 0.05). NC resulted in significantly higher Ra means than Al2O3-Disks and SIC-Strips. Bacterial counts were not significantly different between the groups (p > 0.05). Regards ΔS means, however none of the groups were significantly different to NC (6983.3 kg/mm2xµm /CI 4246.1-9720.5, p > 0.05). Conclusions: Polishing protocols (Al2O3-Disks, SIC-Strips) significantly decreseased roughness of infiltrated-enamel, however none of the polishing protocols could signicantly decrease bacterial counts nor resulted in significant less demineralization.

Development of a membrane for guided tissue regeneration: An in vitro study.

AIM: The aim of this study was to develop an alternative low-cost membrane for use in guided tissue regeneration (GTR). SETTING AND DESIGN: In vitro study. METHODS AND MATERIAL: In this study, a membrane prepared from a 335 mm sized opening nylon substrate, covered in aqueous resin derived from chitosan, was compared with a commercial material, a non-degradable expanded poly (tetrafluoroethylene). Nylon substrate samples 2.0 × 2.0 cm were covered by aqueous resin based on diluted chitosan solution into 1:05 or 1:10 by spin coating technique to produce from 06, 10, and 15 layers. The surfaces of these membranes were observed using optical microscopy. The physical properties were measured by hydration superficial energy measurements (ΔG) and a tensile test machine. STATISTICAL ANALYSIS: Statistical analysis was performed using the Student's t test at a significance level of 5%, using the BioEstat 2.0 program. RESULTS: The Δ G values of the nylon membrane covered by the 1:05 of chitosan with 15 layers were close to the commercial membrane's Δ G values. The tensile strength values of the nylon membrane covered by the 1:05 of chitosan with 15 layers were higher than the commercial membrane's (115.826 MPa, P < 0.05). CONCLUSION: Therefore, the membrane developed shows some favorable physical properties that could qualify it as a material candidate for use in guided tissue regeneration.

The effects of intrinsic and extrinsic acids on nanofilled and bulk fill resin composites: Roughness, surface hardness, and scanning electron microscopy analysis.

The objective of this study was to examine the effects of extrinsic or intrinsic acids on nanofilled and bulk fill resin materials in vitro. A total of 90 disks were prepared using dental restorative material (Filtek Z350XT, GrandioSO, Filtek Bulk Fill, X-tra fil). Thirty disks of each material were sub-divided into three groups (n = 10) that were immersed for 7 days in deionized water (DW), 5% citric acid (CA-pH 2.1), or 0.1% hydrochloric acid (HCl-pH = 1.2). Surface hardness and roughness (stylus profilometer by Ra parameter) analysis were performed before and after immersion. Morphological changes were evaluated by scanning electron microscopy. The data were analyzed by two-way ANOVA and Tukey's test (α = 0.05). All tested materials did not show significant differences in the effects of the DW, CA, or HCl solutions on surface roughness (p = .368). Likewise, the hardness loss was not affected by the solutions tested (p = .646), but there was a difference in the resin type (p = .002). Filtek Bulk Fill resin hardness was less affected, while Filtek Z350XT and GrandioSO presented the most hardness loss after 7 days of solution immersion. In terms of this experimental study, the results demonstrate the effectiveness of the mechanical properties (roughness and hardness surface) of nanofilled and bulk fill resin materials to resist erosion from extrinsic and intrinsic acids, therefore being potential candidates for dental applications.

Current Concepts and Best Evidence on Strategies to Prevent Dental Erosion.

Dental erosion is a multifactorial condition associated with chemical, biological, and behavioral factors whereby a non-bacterial chemical process leads to an irreversible loss of dental structure. Consequences of this erosive process include painful sensitivity, susceptibility to further erosion, mechanical wear, changes in occlusion, exposure of dental pulp, and poor esthetics. Substantial evidence has revealed new insights to diagnosing early stages of dental erosion and enabling novel preventive approaches to control its progression. In the context of outpatient medical/dental practice, clinicians often encounter patients with progressive dental erosion. This article summarizes published research in this area of dentistry to suggest guidelines that are clinically oriented but scientifically fundamental. It is aimed at helping clinicians effectively integrate this information into their professional evaluations of dental erosion with regard to diagnosis, risk factors, clinical signs, assessment, and clinical preventive strategies and treatment. Clinicians should address patient diet habits, educate patients on prevalence data, and inform them regarding potential acidic interactions, such as medically induced acidic conditions, that may ultimately lead to tooth destruction. Prevention of dental erosion, including the recognition of initial erosive lesions and the implementation of the early intervention, involves the clinical expertise of both the dentist and physician.

Human In Situ Study of the effect of Bis(2-Methacryloyloxyethyl) Dimethylammonium Bromide Immobilized in Dental Composite on Controlling Mature Cariogenic Biofilm.

Cariogenic oral biofilms cause recurrent dental caries around composite restorations, resulting in unprosperous oral health and expensive restorative treatment. Quaternary ammonium monomers that can be copolymerized with dental resin systems have been explored for the modulation of dental plaque biofilm growth over dental composite surfaces. Here, for the first time, we investigated the effect of bis(2-methacryloyloxyethyl) dimethylammonium bromide (QADM) on human overlying mature oral biofilms grown intra-orally in human participants for 7⁻14 days. Seventeen volunteers wore palatal devices containing composite specimens containing 10% by mass of QADM or a control composite without QADM. After 7 and 14 days, the adherent biofilms were collected to determine bacterial counts via colony-forming unit (CFU) counts. Biofilm viability, chronological changes, and percentage coverage were also determined through live/dead staining. QADM composites caused a significant inhibition of Streptococcus mutans biofilm formation for up to seven days. No difference in the CFU values were found for the 14-day period. Our findings suggest that: (1) QADM composites were successful in inhibiting 1⁻3-day biofilms in the oral environment in vivo; (2) QADM significantly reduced the portion of the S. mutans group; and (3) stronger antibiofilm activity is required for the control of mature long-term cariogenic biofilms. Contact-killing strategies using dental materials aimed at preventing or at least reducing high numbers of cariogenic bacteria seem to be a promising approach in patients at high risk of the recurrence of dental caries around composites.

Ph-activated nano-amorphous calcium phosphate-based cement to reduce dental enamel demineralization.

Enamel demineralization is destructive, esthetically compromised, and costly complications for orthodontic patients. Nano-sized amorphous calcium phosphate (NACP) has been explored to address this challenge. The 20% NACP-loaded ortho-cement notably exhibited favorable behavior on reducing demineralization of enamel around brackets in a caries model designed to simulate the carious attack. The 20% NACP-loaded ortho-cement markedly promotes higher calcium and phosphate release at a low pH, and the mineral loss was almost two fold lower and carious lesion depth decreased the by 1/3. This novel approach is promising co-adjuvant route for prevention of dental caries dissemination in millions of patients under orthodontic treatment.

Erosive potential of processed and fresh orange juice on human enamel.

PURPOSE: The purpose of this study was to analyze the erosive potential of processed and fresh orange juice on human enamel. METHODS: Sixty enamel slabs, incubated in human saliva to develop acquired pellicle, were exposed to processed and freshly squeezed juice from oranges and lime oranges. Daily erosive cycles were performed by immersing the slabs in the juices for 20 minutes over five days. During the intervals, the samples were immersed in artificial saliva. The pH, titratable acidity (TA), and buffer capacity (ß) of the juices were determined. Analysis of variance and Tukey's tests were used to compare the percentage of surface hardness loss and the amount of wear between groups. RESULTS: The ranges of pH, TA, and ß were 3.66 to 3.75, 3.33 to 110 mmol/L, and 2.98 to 40.97 mmol/L × pH, respectively. A similar erosive potential was found for all groups, except for the lime orange juices (P<.05). CONCLUSION: Both processed and freshly squeezed orange juices were erosive to enamel. However, the lime orange juice was acidless and, therefore, not able to produce any significant changes in enamel.

The influence of dentin demineralization on morphological features of cavities using Er:YAG laser.

OBJECTIVE: The purpose of this study was to evaluate the influence of erbium-doped: yttrium-aluminum-garnet (Er:YAG) laser parameters and different degrees of demineralization on morphological features, diameter, and depth of prepared cavities. BACKGROUND DATA: Minimally invasive dentin caries removal has been recommended. Ablation of deep caries lesions using Er:YAG laser should preserve remaining demineralized dentin; however, the influence of the degree of mineralization of this substrate had not been entirely described. MATERIALS AND METHODS: A randomized, factorial design was used to study the effects of two factors. Laser parameter was tested at two levels (250 mJ/4 Hz vs. 200 mJ/2 Hz) and degree of demineralization was tested at four levels (control, two-four-eight cycles). Twelve slabs of human dentin were divided into four groups according to the number of cycles induced by pH-cycling: G1, zero cycles; G2, two cycles, G3, four cycles, and G4, eight cycles. An Er:YAG laser was used at an output energy of 250 mJ/4 Hz and 200 mJ/2 Hz for all groups, for 10 sec at 12 mm distance focus/object. Circumference and depth of the cavities were measured on scanning electron microscopy (SEM) images using image analysis software. The mean values were subjected to two way analysis of variance (ANOVA) and Tukey tests. RESULTS: When using 250 mJ/4 Hz, the mean values of circumferential area increased significantly in relation to control (503.54 µm(2)) with increasing demineralization level (eight cycles) (555.45 µm(2)). Regardless of the demineralization level, there was also significant statistical difference in the studied measurements of the cavities when 250 mJ/4 Hz and 200 mJ/2 Hz were used. SEM also showed that laser cavity preparations left no smear layer, and the dentinal tubules were clear. CONCLUSIONS: The circumferential area and depth measurements were affected by laser parameter and demineralization level (eight cycles). Energy level output represents a relevant factor for increased circumferential area and depth measurements. High demineralized artificially caries-affected dentin may also imply higher ablation. Appropriated parameter of laser pulse frequency/power density for demineralized dentin should be used for effective less-invasive caries treatment.

Effects of diode laser therapy and stannous fluoride on dentin resistance under different erosive acid attacks.

OBJECTIVE: This in vitro study aimed to evaluate the effect of a low intensity diode laser (λ=808 nm; 60 J/cm2) associated with stannous fluoride on the inhibition of dentin erosion by assessing percentage of superficial hardness loss (%SHL) and calcium release into the acid solution. MATERIALS AND METHODS: Human root dentin slabs were assigned to eight groups (n=10), according to treatments (control, stannous fluoride, diode laser therapy, and the combination of stannous fluoride and laser therapy), and acid challenge (hydrochloridric or citric acid). All slabs were subjected to a previous 2 h acquired pellicle formation; laser and fluoride treatments were performed according to the groups. Subsequently, the slabs were exposed to erosive challenge (0.01 M hydrochloridric acid or citric acid 1% for 60 sec). Additionally, calcium released into the acid solution during erosive challenge was analyzed by photometric test. Data were analyzed by ANOVA followed by Tukey's test (p<0.05). RESULTS: Mean values (±SD) for %SHL of treated groups did not present statistically significant differences, regardless of the erosive challenge. However, in relation to released calcium concentration, groups treated with laser presented statistically significant lower calcium loss under hydrochloridric acid challenge (p<0.001). To groups under citric acid attack, only the combination of treatments (p=0.037) was able to show a protective effect on dentin. CONCLUSIONS: Under the conditions of this study, 808 nm diode laser with or without stannous fluoride could effectively reduce dentin surface loss under both acid exposures. Only calcium concentration analysis was sensitive enough to measure the effects under the tested conditions.

In Situ Response of Nanostructured Hybrid Fluoridated Restorative Composites on Enamel Demineralization, Surface Roughness and Ion Release.

Recurrent caries at the tooth-restoration margins is the main reason for composite failure. Fluoride-releasing nanohybrid composite resin may reduce the recurrent caries rates. A fluoride-releasing resin (FCR) and non-fluoride-releasing resin (CR) were tested using an in situ model. Demineralization (ΔS), ion release and surface roughness of composite specimens were determined. The F concentration in the group FCR was higher than the CR group. ΔS (Mean ± SD) was 2579 ± 1582 and 1705 ± 1292, respectively, for FCR and CR. Surfaces roughness was altered by biofilm accumulation. The hybrid fluorated restorative composites containing nanoparticles have a slight anticaries action without alteration of surface smoothness of the material.

Fluoride releasing and enamel demineralization around orthodontic brackets by fluoride-releasing composite containing nanoparticles.

INTRODUCTION: Fluoride-containing materials have been suggested to control enamel demineralization around orthodontic brackets during the treatment with fixed appliances. The improvement of their properties has been made through innovations, such as the application of nanotechnology by incorporation of nanofillers. OBJECTIVE: This in vitro study evaluated the capacity of fluoride releasing and enamel demineralization inhibition of fluoride-releasing nanofilled cement around orthodontic brackets using an artificial caries biofilm model. MATERIALS AND METHODS: Forty bovine enamel discs were selected by evaluating surface microhardness and randomized into four groups (n = 10): non-fluoride-releasing microfilled composite, fluoride-releasing microfilled composite, resin-modified glass ionomer cement (RMGI), and fluoride-releasing nanofilled composite (FN). After brackets bonding in each disc, the specimens were subjected to a cariogenic challenge through a Streptococcus mutans biofilm model. After the experimental period, the biofilm formed around the brackets was collected for fluoride analysis and the mineral loss around the brackets was determined by integrated demineralization via cross-sectional microhardness measurement at 20 and 70 µm from the bracket margin. Additionally, samples of each group were subjected to energy-dispersive X-ray spectroscopy (EDX) analysis examined under a scanning electron microscopy (SEM). ANOVA followed by Tukey test were applied for fluoride concentration and mineral loss data, respectively. RESULTS: At both distances, only RMGI statistically differed from the other groups presenting the lowest demineralization, although there was a trend to a lower demineralization of enamel around brackets in FN group. Similar condition was found to fluoride concentration and EDX/SEM analysis. CONCLUSIONS: Under the cariogenic exposure condition of this study, the fluoride-releasing nanofilled material had similar performance to fluoride-releasing microfilled materials. CLINICAL RELEVANCE: The presence of nanofillers in the fluoride-releasing materials studied did not promote further benefits against caries lesion development around brackets and presented inferior demineralization inhibition than the resin-modified glass ionomer material.

Dentin erosion by whitening mouthwash associated to toothbrushing abrasion: a focus variation 3D scanning microscopy study.

The aim of this study was to determine the erosive potential of hydrogen peroxide (HP) containing mouthwash on dentin assessed by Focus variation three-dimensional (3D) microscopy. Twenty dentin slabs were selected and randomly allocated into two groups (n = 10): DW--Distilled water (pH = 7.27) and HP-1.5% (pH = 3.78). Each specimen was cyclically demineralized (4 × 60 s/day, 10 days) with HP or DW and brushed 3×/day (200 g, 150 strokes--toothpaste with 1,450 ppmF as NaF). Between the challenges, the specimens were exposed to artificial saliva. Afterward, dentin loss was analyzed using focus variation 3D microscopy, and the data were submitted to unpaired t-test (α = 0.05). Statistically significant difference was found between the mean wear rate (µm, ±SD) of HP (1.98 ± 0.51) and DW (1.45 ± 0.39). The results suggest that the use of HP-containing mouthwash associated to brushing may increase the risk of tissue loss and focus variation 3D microscopy may be used as a technique for quantifying dental wear.

Comparison of methods for quantifying dental wear caused by erosion and abrasion.

Various methods have been applied to evaluate the effect of erosion and abrasion. So, the aim of this study was to check the applicability of stylus profilometry (SP), surface hardness (SH) and focus-variation 3D microscopy (FVM) to the analysis of human enamel and dentin subjected to erosion/abrasion. The samples were randomly allocated into four groups (n = 10): G1-enamel/erosion, G2-enamel/erosion plus abrasion, G3-dentin/erosion, and G4-dentin/erosion plus abrasion. The specimens were selected by their surface hardness, and they were subjected to cycles of demineralization (Coca-Cola®-60 s) and remineralization (artificial saliva-60 min). For groups G2 and G4, the remineralization procedures were followed by toothbrushing (150 strokes). The above cycle was repeated 3×/day during 5 days. The samples were assessed using SH, SP, and FVM. For each substrate, the groups were compared using an unpaired t-test, and Pearson correlation coefficients were calculated (α = 5%). For enamel, both profilometry technique showed greater surface loss when the erosion and abrasion processes were combined (P <0.05). The correlation analysis did not reveal any relationships among SH, SP, and FVM to G2 and G4. There were significant correlation coefficients (-0.70 and -0.67) for the comparisons between the FVM and SH methods in enamel and dentin, respectively, in G1 and G3. Choosing the ideal technique for the analysis of erosion depends on the type of dental substrate. SP was not sufficiently sensitive to measure the effects on dentin of erosion or erosion/abrasion. However, SP, FVM and SH were adequate for the detection of tissue loss and demineralization in enamel.

The effect of diode laser irradiation on dentin as a preventive measure against dental erosion: an in vitro study.

Increasing rates of non-carious cervical lesions due to dental erosion, exposure of dentinal tubules, and hypersensitivity to environmental stimuli have led to the development of new prevention strategies. This study evaluated the effects of a low-intensity diode laser (λ = 808 nm) on the dentinal chemical composition and prevention of demineralization. In addition, the study monitored temperature changes during the course of irradiation. Forty dentin specimens were randomly allocated into four groups (n = 10): G1 - No treatment (control), G2 - irradiated with 15 J/cm(2), G3 - irradiated with 30 J/cm(2), and G4 - irradiated with 60 J/cm(2). Each specimen was partially covered with nail varnish, treated according to the group irradiation levels, and exposed to an erosive challenge (1.0 M hydrochloric acid) for 5 min. Afterwards, dentin loss was profilometrically analyzed and examined by scanning electron microscopy (SEM) combined with energy dispersive X-ray (EDX). Intrapulpal temperatures were measured during the dentin irradiation. One-way ANOVA and Tukey tests (p < 0.05) were performed to assess differences. For all irradiated groups, intrapulpal temperature changes were less than 3°C. The G2 group showed statistically significant differences when compared to the other groups, representing the lowest temperature increase. A quantitative element analysis via EDX did not significantly differ (p < 0.05) for Ca, P, F, O, or C between the four groups when measured after irradiation/erosion. The mean wear rates (± SD, µm) were 35.66 ± 7.28; 40.70 ± 5.03; 38.17 ± 10.81 and 25.25 ± 6.87 for G1-G4, respectively. The G4 group statistically differed from all other groups representing the lowest wear rate. These results suggest that dentin irradiation, using a diode laser with levels set at 60 J/cm(2), may induce inhibitory effects on root dentin demineralization without causing any harmful thermal effects. However, the exact mechanism of the action of the laser remains unclear.