Microhardness Of Human Enamel Research Articles

Effect of resin infiltration and bleaching on surface roughness and microhardness of human enamel with induced white spot lesions

Objective: To comparatively evaluate the effect of resin infiltration, bleaching and bleaching followed by resininfiltration on the surface roughness and microhardness of human enamel with induced white spot lesions(WSLs) and their resistance to acidic challenge. Material and Methods: Sixty human specimens were randomlydivided into three groups (n=20) according to the treatment modality applied; group I Icon® resin infiltration,group II bleaching and group III bleaching followed by Icon® resin infiltration. For each treatment modality, 10specimens were tested for surface roughness and another 10 for microhardness. WSLs were artificially inducedin all specimens and after treatment, all specimens were subjected to acidic challenge. Surface roughness wasmeasured by the tapping mode of the atomic force microscope (AFM) and microhardness was measured bydigital Vickers hardness tester at baseline, after induction of WSLs, after treatment and after acidic challenge.Results: Groups I and III showed significant reduction in surface roughness after treatment, while group II showedsignificant increase. Groups I and III showed significant increase in the microhardness after treatment, whilegroup II showed insignificant increase. The three tested groups showed significant increase in surface roughnessvalues and significant reduction in microhardness after acidic challenge. Conclusion: Resin infiltration andbleaching followed by resin infiltration reduced the surface roughness and enhanced the microhardness of theWSLs. The three treatment modalities failed to resist acidic challenge resulting in increasing surface roughnessand reducing microhardness.KEYWORDSAFM; Bleaching; Microhardness; Resin infiltration; White spot lesions.

Effect of different non-invasive and micro-invasive treatment modalities of white spot lesions on microhardness of human enamel

Aim: to investigate effect of different treatment modalities of white spot lesions on microhardness of human enamel. Materials and methods: twenty-four recently extracted sound human maxillary incisor teeth were collected. Teeth were divided at random into six groups (10 each) that were summarized as follows: Group 1: sound unprepared teeth (base line control); Groups 2: demineralized enamel (negative control), Group 3: Demineralized enamel treated by resin infiltration (ICON), Group 4: demineralized enamel treated by bioactive glass (Sylc powder) as remineralizing agent, Group 5: demineralized enamel treated by fluoride varnish ( positive control), Group 6: Demineralized enamel treated by microabrasion. Teeth were embedded in the acrylic blocks with their labial surface flushed with the flat surface of the mold. All specimens except the base line control specimens were demineralized. Each group was treated with the assigned treatment according to manufacturer’s recommendations. The microhardness measurements were performed using a Vickers Microhardness Tester with a Vickers diamond indenter and a 20X objective lens. Results: showed that there was a statistically significant difference in MH values between different study groups (P<0.001). The significantly highest MH mean values were recorded in (microabrasion), (sound enamel), (resin infiltration), and (Sylc powder) groups, which did not differ significantly. This was followed by the mean value of (fluoride varnish) group. While (demineralized enamel) group yielded significantly lowest MH values. Conclusions: among the tested treatment modalities, microabrasion, resin infiltrant as well as bioactive glass air abrasion improved enamel surface microhardness in comparison to fluoride varnish.

Effects of charcoal-based whitening toothpastes on human enamel in terms of color, surface roughness, and microhardness: an in vitro study.

Charcoal based oral care products have gained popularity in the last few years. The aim of this in vitro study was to compare the effects of different charcoal based whitening toothpastes on color, surface roughness and microhardness of human enamel. Forty-eight specimens obtained from human permanent upper incisor teeth were randomly divided into 4 groups(n=12):Group-1:Colgate Total 12(CT); Group-2:Body Kingdom(BK); Group-3:Black is White(BW), Group-4:Colgate optic white(COW). Following 4 days cycle of darkening(2-min chlorhexidine and 60-min black tea per day), a 12- week brushing(twice daily for 1 min)was performed. Color of specimens was measured using a spectrophotometer. A contact type profilometer was used to measure surface roughness (Ra) and Vicker's hardness tester was used for the changes in microhardness(VHN). A representative sample from each group was visualized by SEM. Data were analyzed by One-way ANOVA, Welch, Fisher's, Kruskall-Wallis, Wilcoxon Sign Rank and Paired t-tests(p<0.05). After 12- week brushing, no differences were found among the groups in terms of color change(p=0.989). All toothpastes tested showed no clinically acceptable whitening performances. A substantial increase in surface roughness was found in all groups, except BW(p<0.05). An increase was found in microhardness with CT(p=0.013), while no changes were found with BK, BW and COW(p>0.05).Only few scratches were observed on the enamel surfaces by SEM evaluations. Twelve week brushing with charcoal based whitening toothpastes and a regular fluoridated toothpastepresented similar effects in color of enamel. Surface roughness was increased(except BW) while microhardness was not affected(except CT) with charcoal based whitening toothpastes. Charcoal based whitening toothpastes do not promise to whiten the human permanent teeth and their effects on enamel abrasion should not be disregarded.

EROSIVE POTENTIAL OF SPORTS BEVERAGES ON HUMAN ENAMEL “IN VITRO”

ABSTRACT Introduction: The low pH of sports drinks may cause tooth enamel demineralization. Objective: To measure Vickers hardness of human enamel exposed to sports drinks. Methods: Human molars were used to collect the enamel samples. Each sample had a test surface (exposed to the drinks) and a control surface (unexposed). The samples were exposed to isotonic drinks Gatorade and Powerade, and to maltodextrin drinks Malto Advanced and Malto Active, for 10 minutes every 12 hours over 30 days. The Vickers microhardness test was conducted with three indentations on each surface. The mean of the indentations within each group was considered in the statistical analysis. Sports drinks variables were analyzed with ANOVA/Tukey (p≤0.01). The independent t-test was used in the comparison between the control and test surfaces of each drink (p ≤ 0.05). Results: Enamel exposure to Gatorade (p = 0.000) Malto Advanced (p = 0.000) and Malto Active (p = 0.000) was seen to significantly reduce microhardness, while the isotonic drink Powerade had no significant effect on enamel (p = 0.248). Conclusion: It was concluded that with the exception of the isotonic drink Powerade, all the sports drinks tested caused a reduction in the microhardness of human enamel. Evidence Level III; Therapeutic studies - Investigating the Results of Treatment.

Chemical Composition and Microhardness of Human Enamel Treated with Fluoridated Whintening Agents. A Study in Situ.

Background:Dental whitening has been increasingly sought out to improve dental aesthetics, but may cause chemical and morphological changes in dental enamel surfaces.Objective:Assess in situ the effects of high-concentration hydrogen peroxide with and without fluoride on human dental enamel using the ion chromatography test (IC) and the Knoop hardness test (KHN).Material and Methods:Nineteen enamel specimens were prepared using third human molars. These specimens were fixed on molars of volunteers and were divided into groups: OP38-Opalescence Boost PF38%, PO37-Pola Office 37.5% and CO-Control group. For chemical analysis (n= 3), the dentin layer was removed, keeping only the enamel, which was subjected to acidic digestion by microwave radiation. It was necessary to perform sample dilutions for the elements fluorine (F), calcium (Ca) and phosphorus (P) for quantification using the IC test. The KHN (n= 5) was performed before and after the treatments. Five indentations were made, separated by 100 µm, for each specimen using a load of 25 gf for 5 seconds in the microdurometer. The data were analyzed using ANOVA with a 5% significance level.Results:The OP38 group had the largest concentrations of F, Ca and P ions. The PO37 group showed the lowest concentrations of F and Ca ions. The average KHN was not significantly different between the OP38 and PO37 groups.Conclusion:Enamel whitened with hydrogen peroxide containing fluoride had greater concentrations of F, Ca and P ions. The presence of fluoride in the whitening agent did not influence the enamel microhardness.

Effect of organic versus inorganic fluoride on enamel microhardness: An in vitro study

Introduction:Dental caries is one of the most prevalent infectious diseases affecting the human dentition. Fluorides are effective anti-carious agents and have been widely used for caries prevention in the form of systemic and topical fluorides. Neutral sodium fluoride (NaF) is commonly used as a topical fluoride agent. A special category of topical fluorides are organic fluorides in the form of amine fluorides (AmF). Researchers have reported that AmF is superior to inorganic fluorides in improving the caries resistance of enamel due to the significant anti-enzyme effect of the organic fragment.Aim:The aim of the present study was to compare the enamel surface micro hardness after topical application of NaF and AmF solutions.Materials and Methods:Twenty fresh samples of sound human enamel were treated with demineralizing solution for 72 h and divided into Group A (treated with NaF) and Group B (treated with AmF) solutions for 3 min twice daily for 7 days. In between treatment, the samples were stored in artificial saliva. The enamel surface hardness was measured with Vickers hardness test at baseline, post-demineralization and post-treatment with two different fluoride solutions (NaF and AmF) and a comparative analysis was made.Results:The increase in mean micro hardness of human enamel after treatment with AmF application was found to be statistically significant (P < 0.01) when compared to the mean micro hardness after treatment with NaF.Conclusion:Fluoride enhances the remineralization process by accelerating the growth of enamel crystals that have been demineralized. It can be concluded from the present study that AmF compounds result in a marked increase in enamel micro hardness when compared to NaF.

In vitro action of various carbamide peroxide gel bleaching agents on the micro hardness of human enamel

Aims and Objectives:The study was undertaken to evaluate the effects of different carbamide peroxide based gels on micro hardness of enamel exposed to these agents for a period of 8 h daily for a total of 1 week.Materials and Methods:Thirty enamel specimens of 5 × 5-mm dimensions were sectioned from labial surface of maxillary incisor teeth and were embedded in Bakelite. Each block is polished to facilitate micro hardness testing. Pre-bleaching hardness values of 30 samples were measured using Vickers micro hardness tester. After exposing the specimens for different agents for 8 h daily for 1 week, post-exposure micro hardness values were taken and evaluated.Conclusion:With increase in concentration of carbamide peroxide gel from 10% to 16%, mean micro hardness values decreased but to an insignificant level.

Depth‐Profiling of Crystal Structure, Texture, and Microhardness in a Functionally Graded Tooth Enamel

The graded nature of crystal structure, texture, and microhardness of human enamel has been characterized by grazing‐incidence synchrotron radiation diffraction and Vickers indentation. Results show that the composition of tooth enamel consists mainly of calcium apatite or hydroxyapatite (HAP). The HAP crystals formed near the occlusal surface are aligned approximately orthogonal to each other between the axial and occlusal sections. In addition, the tooth enamel has been shown to be a hierarchical graded biomaterial with a distinct gradation in crystallinity, texture, crystallite size, and hardness, which is somewhat akin to that of the fibrous microstructures found in natural plants. A “graded‐interface” approach is proposed as a biomimetic model for designing new dental or restorative materials as well as for joining of dissimilar materials.

Effect of home bleaching agents on the microhardness of human enamel and dentin

In this study, the effects of home bleaching agents that contains carbamide peroxide (in different concentrations such as 10 and 15%) on the surface hardness of human enamel and dentine were evaluated. The buccal surfaces of 90 recently extracted human mandibular anterior teeth were used. The specimens in the dentine group were ground to expose of dentine surface. Then, samples in both enamel and dentine group were randomly divided into six main groups with 15 in each group. In the group 1 and 4, 15% carbamide peroxide was applied to the enamel and dentine surfaces and then the teeth were left in an incubator at 37 degrees C and 100% humidity for 4 h first, then left 28 h after repeating the same procedures seven times. The teeth were treated with 10% carbamide peroxide in groups 2 and 5 and distilled water in groups 3 and 6 (control groups), using the same procedures. Vicker's microhardness of enamel and dentine were assessed on each tooth before and after each treatment period (4 and 28 h). The hardness of control group specimens was also obtained after 4 h in distilled water and then after 28 h. For statistical analysis one-way ANOVA and post-hoc Tukey tests were used. For both 10 and 15%, there were no statistically significant differences between the untreated control specimens and the specimens treated with the bleaching materials for enamel and dentine at any given measurement time (P > 0.05). Nevertheless, in vivo use of bleaching agents on tooth hard tissues requires further analysis.

The effect of propolis exposure on microhardness of human enamel in vitro.

Propolis is a resinous wax-like material that is used by bees as a glue-like matrix in their hives. The in vitro effect of propolis solutions was investigated on the microhardness of human dental enamel. The calcium concentration of the solution was 7.8 ppm, the pH values varied between 5 and 6. The fluoride concentration was negligible. The Vickers hardness number of exposed enamel showed a steady increase with the percentage of propolis in the solution. The microhardness increase may be attributed to particular components of mineralization activity in propolis.

Effect of chloroform, xylene, and halothane on enamel and dentin microhardness of human teeth

Objective. The purpose of this study was to assess in vitro the effect of commonly used gutta-percha solvents on the microhardness of human enamel and dentin. Study Design. Crowns of human teeth were cut and treated with chloroform, xylene, and halothane. Treatment consisted of exposing the specimens for 5 or 15 minutes to the test solvents. Acid-treated and saline-treated specimens served as controls. After each treatment period, the specimens were rinsed, dried, and prepared for Vicker’s microhardness analysis. Vicker’s microhardness values for each specimen were recorded before and after treatment, and the differences were statistically compared. Results. A statistically significant decrease in enamel and dentin microhardness was found in most solvent-treated groups; the amount of the decrease was directly related to the exposure time. Conclusions. Chloroform, xylene, and halothane may cause a significant softening effect on both enamel and dentin. This softening is already apparent after 5 minutes of treatment.( Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;87:366-8)

Effect of hydrogen peroxide and sodium perborate on the microhardness of human enamel and dentin

The effect of 30% hydrogen peroxide and a paste of sodium perborate mixed with hydrogen peroxide at different temperatures and time intervals on the microhardness of human enamel and dentin was examined. Intact extracted human teeth were sectioned, embedded in acrylic resin, polished, and divided into four test groups related to surface treatment. The groups were 30% hydrogen peroxide at 37 degrees C, 30% hydrogen peroxide at 50 degrees C in an illuminated chamber, a paste of sodium perborate mixed with hydrogen peroxide at 37 degrees C, and a paste of sodium perborate mixed with hydrogen peroxide at 50 degrees C in an illuminated chamber. Teeth treated with distilled water at either 37 degrees C or 50 degrees C served as controls. The results indicated that treatment with 30% hydrogen peroxide reduced the microhardness of both enamel and dentin. This reduction was statistically significant after 5-min treatment for the dentin and after 15-min treatment for the enamel (p < 0.05). Treatment with sodium perborate mixed with hydrogen peroxide did not alter the microhardness of either the enamel or dentin at the tested temperatures and time intervals. It is therefore suggested that the use of high concentrations of hydrogen peroxide for bleaching purposes should be limited. Sodium perborate appears to be a less damaging bleaching agent.