Enamel Surface Morphology Research Articles

To What Extent is Primate Second Molar Enamel Occlusal Morphology Shaped by the Enamel-Dentine Junction?

The form of two hard tissues of the mammalian tooth, dentine and enamel, is the result of a combination of the phylogenetic inheritance of dental traits and the adaptive selection of these traits during evolution. Recent decades have been significant in unveiling developmental processes controlling tooth morphogenesis, dental variation and the origination of dental novelties. The enamel-dentine junction constitutes a precursor for the morphology of the outer enamel surface through growth of the enamel cap which may go along with the addition of original features. The relative contribution of these two tooth components to morphological variation and their respective response to natural selection is a major issue in paleoanthropology. This study will determine how much enamel morphology relies on the form of the enamel-dentine junction. The outer occlusal enamel surface and the enamel-dentine junction surface of 76 primate second upper molars are represented by polygonal meshes and investigated using tridimensional topometrical analysis. Quantitative criteria (elevation, inclination, orientation, curvature and occlusal patch count) are introduced to show that the enamel-dentine junction significantly constrains the topographical properties of the outer enamel surface. Our results show a significant correlation for elevation, orientation, inclination, curvature and occlusal complexity between the outer enamel surface and the enamel dentine junction for all studied primate taxa with the exception of four modern humans for curvature (p<0.05). Moreover, we show that, for all selected topometrical parameters apart from occlusal patch count, the recorded correlations significantly decrease along with enamel thickening in our sample. While preserving tooth integrity by providing resistance to wear and fractures, the variation of enamel thickness may modify the curvature present at the occlusal enamel surface in relation to enamel-dentine junction, potentially modifying dental functionalities such as blunt versus sharp dental tools. In terms of natural selection, there is a balance between increasing tooth resistance and maintaining efficient dental tools. In this sense the enamel cap acts as a functional buffer for the molar occlusal pattern. In primates, results suggest a primary emergence of dental novelties on the enamel-dentine junction and a secondary transposition of these novelties with no or minor modifications of dental functionalities by the enamel cap. Whereas enamel crenations have been reported by previous studies, our analysis do not support the presence of enamel tubercles without dentine relief nuclei. As is, the enamel cap is, at most, a secondary source of morphological novelty.

Ultrastructural evaluation of enamel surface morphology after tooth bleaching followed by the application of protective pastes.

The aim of the present in vitro study was to evaluate the morphology of bleached enamel surface followed by the application of different protective pastes. Specimens were prepared from 50 human incisors free of caries and defects. The bleaching procedure was performed with 35% hydrogen peroxide (Perfect Bleach Office+). For the remineralization treatment, different protective pastes (Tooth Mousse, MI Paste Plus, Remin Pro, and Profluorid Varnish) were evaluated. Specimens were randomly assigned to 10 groups of 5 specimens each. The specimens were analyzed under scanning electron microscopy. The superficial morphology of enamel was examined and scored as follows: 0, enamel with smooth surface morphology; 1, enamel with slight irregularities; 2, enamel with moderate irregularities; 3, enamel with accentuated irregularities. The photomicrographs were evaluated in a double-blind manner by three examiners, previously calibrated. Results were analyzed by a Kruskal-Wallis nonparametric test, at the significance level of 0.05. Dunn method posttest was applied for multiple comparisons. A different superficial morphology was observed among control group specimens and specimens treated with bleaching agent and protective pastes (p < 0.05). Enamel bleached showed pronounced surface changes and irregularities, significantly different from other groups except for groups 8 (enamel + Perfect Bleach Office+ + Remin Pro) and 10 (enamel + Perfect Bleach Office+ + Profluorid Varnish) (p > 0.05). The application of the tested pastes after bleaching is effective on repairing enamel surface morphology, demonstrating a higher efficacy for the CPP-ACP products compared to fluoridated ones. SCANNING 38:221-226, 2016. © 2015 Wiley Periodicals, Inc.

Protective effect of casein phosphopeptide-amorphous calcium phosphate on enamel erosion: Atomic force microscopy studies.

The aim of this study was to investigate the in vitro effect of a casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (GC Tooth Mousse- TM, GC Corporation, Tokyo, Japan) on preventing enamel erosion, by using Atomic Force Microscopy (AFM). 30 human incisors, were equally assigned to 6 groups: intact enamel, enamel + soft drink, enamel + TM, enamel + TM + soft drink, enamel + soft drink + TM, enamel + soft drink + TM + soft drink. Specimens were observed through atomic force microscopy (AFM). The most common topographical parameters were determined, such as the surface roughness (Rrms ). The use of soft drink on intact enamel has roughened the surface of the sample. The application of the CPP-ACP paste on non-treated enamel made the surface smoother. A significant decrease in roughness was seen after remineralization with CPP-ACP paste. Significant differences were recorded when comparing softened enamel with softened enamel remineralized with CPP-ACP paste. Comparing eroded enamel with demineralized/remineralized specimens, the application of a CPP-ACP paste leads to a significant reduction in roughness values. AFM images of enamel surface treated with CPP-ACP resulted in less morphological changes of the tooth substrate when compared with the only eroded enamel surface morphology; thus, indicating that CPP-ACP paste promoted remineralization. Specimens' surface roughness remained similar regardless that the protective agent is used before or after exposure to coke or between two demineralizing cycles. The results confirmed the effectiveness of the CPP-ACP paste on preventing enamel erosion produced by soft drinks.

Effect of enamel morphology on nanoscale adhesion forces of streptococcal bacteria : An AFM study.

We explore the influence of enamel surface morphology on nanoscale bacterial adhesion forces. Three dimensional morphology characteristics of enamel slices, which were treated with phosphoric acid (for 0 s, 5 s, 10 s, 20 s, and 30 s), were acquired. Adhesion forces of three initial colonizers (Streptococcus oralis, Streptococcus sanguinis, and Streptococcus mitis) and two cariogenic bacterial strains (Streptococcus mutans and Streptococcus sobrinus) with etched enamel surfaces were determined. Comparison of the forces was made by using bacterial probe method under atomic force microscope (AFM) in adhesion buffer. The results showed that enamel morphology was significantly altered by etching treatment. The roughness, peak-to-valley height, and valley-to-valley width of the depth profile, surface area, and volume increased linearly with acid exposure time, and reached the maximum at 30s, respectively. The adhesion forces of different strains increased accordingly with etching time. Adhesion forces of S. oralis, S. mitis, S. mutans, and S. sobrinus reached the maximum values of 0.81 nN, 0.84 nN, 0.73 nN, and 0.64 nN with enamel treated for 20s, respectively, whereas that of S. sanguinis at 10s (1.28nN), and dropped on coarser enamel surfaces. In conclusion, enamel micro-scale morphology may significantly alter the direct adhesion forces of bacteria. And there may be a threshold roughness for bacterial adhesion on enamel surface.

In-vivo evaluation of the surface roughness and morphology of enamel after bracket removal and polishing by different techniques

The aim of this study was to evaluate the surface roughness and morphology of enamel with a surface roughness tester and scanning electron microscopy after the removal of metal brackets and polishing. Ten orthodontic patients were selected for the study. At the conclusion of orthodontic treatment, their metal brackets were removed. For each patient, teeth on one side of the mouth were randomly chosen for finishing and polishing with aluminum oxide discs (n = 10). Teeth on the other side were finished with multilaminated carbide burs (n = 10). Dental replicas (before and after tooth polishing) were obtained with epoxy resin. Three surface roughness measurements were made in different directions with an angle of 120° among them, and a mean for each dental replica was calculated. The roughness data were statistically evaluated by repeated-measurements analysis of variance. Three specimens from each group were also used for scanning electron microscopy analysis. After resin removal, the average roughness in the carbide bur group (0.31 μm) was significantly greater than that in the aluminum oxide disc group (0.25 μm). The aluminum oxide disc polishing system resulted in less enamel roughness than did the multilaminated carbide bur system.

The impact of surface preparation on shear bond strength of metallic orthodontic brackets bonded with a resin-modified glass ionomer cement.

The aim of this study was to assess the effects of four enamel preparation techniques on shear bond strength (SBS) of brackets bonded with a resin-modified glass ionomer cement (RMGIC). Adhesive Remnant Index (ARI) and enamel surface roughness (Ra) were also investigated after cement removal. One hundred and forty-four human premolars were divided into four groups (n = 36 in each group) as follows: Group 1, 37% phosphoric acid (i.e. conventional); Group 2, sandblasting; Group 3, sodium hypochlorite and 37% phosphoric acid; and Group 4, sodium hypochlorite and sandblasting. Twenty-four hours after bonding, the brackets were debonded with an Instron machine using a crosshead speed of 1·0 mm/min; the ARI was evaluated by an image analyser system; the Ra was measured by profilometry; and the morphology of the tooth enamel surface was observed by scanning electron microscope evaluation. Data were submitted to ANOVA and the Kruskal-Wallis test (α = 0·05). Mean SBS values for Groups 1-4 were 13·86, 9·08, 17 and 9·63 MPa, respectively. Mean ARI for Groups 1-4 were 11·16, 2·06, 20·66 and 3·73%. The SBS and ARI showed statistically significant differences between the four groups (P<0·001). The Ra (μm) showed no significant differences between groups. Bracket bonding using RMGIC showed adequate adhesion for clinical use, and the type of enamel preparation had a significant influence.

Effect of various tooth whitening modalities on microhardness, surface roughness and surface morphology of the enamel

The purpose of this study was to evaluate the effect of four whitening modalities on surface enamel as assessed with microhardness tester, profilometer, and scanning electron microscopy (SEM). Whitening was performed according to manufacturer's directions for over-the-counter (OTC), dentist dispensed for home use (HW) and in-office (OW) whitening. Do-it-yourself (DIY) whitening consisted of a strawberry and baking soda mix. Additionally, negative and positive controls were used. A total of 120 enamel specimens were used for microhardness testing at baseline and post-whitening. Following microhardness testing specimens were prepared for SEM observations. A total of 120 enamel specimens were used for surface roughness testing at baseline and post-whitening (n = 20 per group). Rank-based Analysis of Covariance was performed to compare microhardness and surface roughness changes. Tests of hypotheses were two-sided with α = 0.05. There was a significant difference in Knoop hardness changes (ΔKHN) among the groups (Kruskal-Wallis test, p < 0.0001). Significant hardness reduction was observed in the positive control and DIY group (p < 0.0001). Mean surface roughness changes (ΔRa) were significantly different among the groups (Kruskal-Wallis test, p < 0.0001). Surface roughness increased in the OTC group (p = 0.03) and in the positive control (p < 0.0001). The four whitening modalities-DIY, OTC, HW and OW induced minimal surface morphology changes when observed with SEM. It can be concluded that none of the four whitening modalities adversely affected enamel surface morphology. However, caution should be advised when using a DIY regimen as it may affect enamel microhardness and an OTC product as it has the potential to increase surface roughness.

Comparative Evaluation of Two in -Office Bleaching Agents Using Two Different Light Sources- In Vivo Study

The purpose of this study was to evaluate and compare the effect of 35% Hydrogen Peroxide and 35% Carbamide peroxide in - office bleaching agents using plasma arc and laser light sources on colour change, enamel surface morphology and sensitivity on teeth. -in vivo study Material and method: This study was carried out on 12 patients in which four groups i.e. 35% carbamide peroxide and plasma arc (CPP), 35% carbamide peroxide and laser light source (CPL), 35% hydrogen peroxide and Plasma arc (HPP), 35% hydrogen peroxide and laser light source (HPL) were made in all the four quadrants in anterior teeth. Preoperative baseline shade and impression was taken and same was repeated post operatively. After bleaching procedure colour change was evaluated using VITA classic shade guide , change in enamel surface morphology was calculated on epoxy model using contact profilometer and tooth sensitivity was analyzed using VAS scale. Result: 35% Carbamide peroxide and plasma arc (CPP) group showed significant colour change followed by 35% hydrogen peroxide plasma arc (HPP) group, 35% hydrogen peroxide and lasers (HPL)group and 35% carbamide peroxide and laser (CPL)group whereas highest change in enamel surface morphology was observed in 35% hydrogen peroxide and laser light source (HPL) group followed by 35% carbamide peroxide and laser light source (CPL) group, 35% hydrogen peroxide plasma arc (HPP) group , 35% carbamide peroxide plasma arc (CPP) group. Conclusion: Carbamide peroxide 35 % using plasma arc presented greater colour change as compared to Hydrogen peroxide 35% using laser light source. Laser light source caused more change in enamel surface morphology as compared to plasma arc.

Transenamel and Transdentinal Penetration of Hydrogen Peroxide Applied to Cracked or Microabrasioned Enamel

The present study evaluated transenamel and transdentinal penetration of hydrogen peroxide during tooth whitening recognized in altered enamel by the presence of cracks or microabrasion. We used 72 experimental units (n=20) obtained from bovine incisors: GI-sound enamel; GII-teeth showing visible enamel cracks (4 mm to 5.7 mm in length); and GIII-microabrasioned enamel. The 12 remaining specimens were used to analyze the enamel surface morphology using scanning electron microscopy. The specimens were cylindrical and 5.7 mm in diameter and 3.5 mm thick. A product based on 35% hydrogen peroxide was used for bleaching, following the manufacturer's recommendations for use. To quantify the H2O2 penetration, the specimens were placed in artificial pulp chambers containing an acetate buffer solution. After bleaching, the solution was collected and adequately proportioned with leucocrystal violet, peroxidase enzyme, and deionized water. The resulting solution was evaluated using ultraviolet visible reflectance spectrophotometer equipment. The data were analyzed by analysis of variance (ANOVA) and Fisher's PLSD at a significance level of 0.05, and significant differences in the penetration of peroxide in different substrate conditions were observed (p<0.0001). The penetration of hydrogen peroxide was more intense in cracked teeth. The group in which the enamel was microabraded showed intermediate values when compared to the control group. Microabrasion and the presence of cracks in the enamel make this substrate more susceptible to penetration of hydrogen peroxide during in-office whitening.

Remineralisation of Carious Lesions and Fluoride Uptake by Enamel Exposed to Various Fluoride Dentifrices In Vitro

To evaluate the relative performance of fluoride (F) dentifrices to promote remineralisation and enamel F acquisition using an in vitro pH-cycling model. Enamel surface morphology was investigated. Thirty-six white spot lesions and 36 sound enamel sections from extracted premolars and molars were randomly assigned to 8 experimental groups and a placebo group. Eight commercially available brands of Fdentifrices were used: A. 0.8% monofluorophospate (MFP)-silica; B. 0.8% MFP-calcium carbonate and calcium phosphate; C. 0.8% MFP-calcium carbonate and calcium phosphate; D. 0.76% MFP-aluminium hydroxide; E. 0.24% sodium fluoride (NaF)-silica and sodium pyrophosphate; F. 0.24% NaF-silica and sodium pyrophosphate; G. 0.76% MFP and 0.10% NaF-dicalcium phosphate and sodium pyrophosphate (1450 ppm F); H. 0.76% MFP and 0.33% NaF-silica (2500 ppm F). The placebo (I) contained non-fluoridated silica. The cycling regimen comprised the following: three 2-min and one 4-min daily treatments with dentifrice slurries, rinsed with water and stored in fresh whole saliva at 37°C until the next experimental day, when specimens were activated in acid buffer solutions prior to each dentifrice treatment. This pH cycling continued for 21 consecutive days. Lesion depths and size were measured using a polarising microscope and enamel F uptake was determined using the acid-etch biopsy technique. The morphology of enamel surfaces was examined using scanning electron microscopy. The data were statistically analysed using Student's t-test, analysis of variance (ANOVA) and Pearson's correlation coefficient (r). All tested fluoride dentifrices significantly enhanced remineralisation by reducing the lesion depths from 6.4 to 17.1 µm and lesion sizes by 10% to 34% relative to the pre-cycling measurements. Overall, the degree of remineralisation was as follows: NaF-silica-pyrophosphate dentifrices (1000 ppm F) averaged 41%; NaF/MFP-silica (1500/1000 ppm F) 38%; MFP/NaF-dicalcium phosphate (1000/450 ppm F) 30%; MFP dentifrices (1000 ppm F) ranged from 15 to 23%. Enamel F uptake by NaF and NaF/MFP was significantly greater than MFP dentifrices (P < 0.05 to P < 0.001), with the area under the depth curve being 2.4 and 2.2 times greater, respectively. At all enamel depths, fluoride dentifrices significantly increased F concentrations relative to the control (P < 0.001). A strong correlation was found between ionic F levels in dentifrices and their efficacy. Dentifrices produced different enamel surface morphologies. The present study demonstrates that commercially available dentifrices vary in their degree of effectiveness and mode of action depending on formulations.

Shear bond strength and SEM morphology evaluation of different dental adhesives to enamel prepared with ER:YAG laser

Context:Early observations of enamel surfaces prepared by erbium lasers motivated clinicians to use laser as an alternative to chemical etching.Aims:Evaluate shear bond strength (SBS) values of different dental adhesives on Erbium:Yttrium Aluminum Garnet (Er:YAG) laser prepared enamel and to evaluate possible etching patterns correlations between dental adhesives and SBS values.Subjects and Methods:One hundred bovine incisors were randomly assigned to SBS tests on enamel (n = 15) and to enamel morphology analysis (n = 5) after Er:YAG laser preparation as follows: Group I – 37% phosphoric acid (PA)+ ExciTE®; Group II – ExciTE®; Group III – AdheSE® self-etching; Group IV – FuturaBond® no-rinse. NR; Group V – Xeno® V. Teeth were treated with the adhesive systems and subjected to thermal cycling. SBS were performed in a universal testing machine at 5 mm/min.Statistical Analysis Used:One-way ANOVA and post-hoc tests (P < 0.05). For the morphology evaluation, specimens were immersed in Ethylenediamine tetraacetic acid (EDTA) and the etching pattern analyzed under Scanning Electron Microscope (SEM).Results:Mean bond strengths were Group I – 47.17 ± 1.61 MPa (type I etching pattern); Group II – 32.56 ± 1.64 MPa, Group III – 29.10 ± 1.34 MPa, Group IV – 23.32 ± 1.53 MPa (type III etching pattern); Group V – 24.43 MPa ± 1.55 (type II etching pattern).Conclusions:Different adhesive systems yielded significantly different SBSs. Acid etching significantly increased the adhesion in laser treated enamel. No differences in SBS values were obtained between AdheSE® and ExciTE® without condition with PA. FuturaBond® NR and Xeno® V showed similar SBS, which was lower in comparison to the others adhesives. No correlation between enamel surface morphology and SBS values was observed, except when PA was used.

Repeated bonding of fixed retainer increases the risk of enamel fracture

The aim of this study was to investigate the influences of repeated bonding, using 2 different orthodontic adhesive systems, on the shear bond strength (SBS) and the enamel surface morphology. Sixty premolars were divided into 2 groups (n = 30), and either Transbond XT (T group) or Fuji Ortho LC (F group) adhesives were used. SBS was measured 24 h after bonding, using a universal testing machine. Then, the enamel surfaces were investigated and the mode of failure was described using adhesive remnant index (ARI) scores. After each debonding, 10 teeth from each group were examined by scanning electron microscopy to determine the penetration of adhesives, the length of resin tags, and the state of the enamel surface. The other teeth were subjected to two more bonding/debonding procedures. In T group, the second debonding sequences had significantly higher bond strengths than the other sequences. The length of resin tags was greatest in the second debonding sequence, although there was no significant difference. In F group, the SBS increased with further rebonding and the failure mode tended towards cohesive failure. In both groups, the ARI scores increased with rebonding. Enamel loss could have occurred with both adhesives, although the surfaces appeared unchanged to the naked eye. From this study, we suggest that enamel damage caused by repeated bonding is of concern. To prevent bond failure, we should pay attention to the adhesion method used for bondable retainers.

Histomorphologic Alterations and Human Enamel after Repeated Applications of a Bleaching Agent

The objective of the study was to analyse the histomorphology of enamel after repeated applications of a professional bleaching regimen. Enamel specimens were obtained from buccal surfaces of 20 extracted human incisors. Two specimens were obtained for each tooth. Half of each tooth was maintained in distilled water and served as control; the other part was treated with a 38 percent hydrogen peroxide professional bleaching agent. The treated specimens were divided in four groups: in group 1, the professional bleaching protocol suggested by the manufacturer was applied once; in group 2, the same protocol was repeated twice; in group 3, three times; in group 4, four times. Between bleaching applications and before SEM evaluation, enamel specimens were maintained in artificial saliva for 1 week. Enamel specimens for each group were submitted to a qualitative scanning electron microscopy (SEM) analysis (200X, 500X, 1000X, 3000X), comparing the treated specimens with the related control enamel. Results of the SEM analysis showed no relevant alteration on the enamel surfaces, when the bleaching protocol was applied once or twice. However, significant changes of enamel surface morphology were SEM observed in groups 3 and 4, suggesting a predominance of depressions when bleaching procedure was repeated three or four times. From the results of this in vitro study, it is possible to state that bleaching procedures should not be carried out indiscriminately. SEM analysis showed important alterations of the prismatic structure of the enamel when the bleaching protocol was applied three and four times.

Surface Morphological Changes in Human Enamel Following Bleaching: An in vitro Scanning Electron Microscopic Study

The purpose of this study was to evaluate, using scanning electron microscopy (SEM), the morphological and structural changes of the enamel induced by three bleaching agents namely old McInnes solution, modified McInnes solution and 10% carbamide peroxide gel at different time intervals. Fifteen freshly extracted noncarious human central incisors with intact enamel surface were selected. The teeth were sectioned at the cementoenamel junction separating the crown portion from the root using a diamond separating disk. Following this, the samples were subjected to three different bleaching agents: Group 1: Old McInnes solution, group 2: modified McInnes solution and group 3: 10% carbamide peroxide for a period of 15, 30 and 60 minutes, 24 and 30 hours time interval. The sample stubs were subjected to scanning electron microscope and were photographed at 2000 and 10,000 magnifications. The present study revealed no indication of either etching or significant change in surface morphology of enamel when evaluated under scanning electron microscope after 6 weeks treatment with various bleaching agents. Morphological alterations in bleached enamel are both concentration and time dependent.

A Comparative Study of Different Bleaching Agents on the Morphology of Human Enamel: An in vitro SEM Study

The purpose of the study was to compare two different commercial bleaching agents, Opalescence with Colgate Platinum, and 30% phosphoric acid used as aggressive agent on the morphology of human enamel. Ten freshly extracted, noncarious, human maxillary central incisors extracted for periodontal reasons were used in this study. The labial surface of the disinfected teeth were polished using a polishing paste with the help of rubber cup and a slow speed handpiece. Each tooth was sectioned at cement-enamel junction and the crown was separated into four specimens, all taken from labial surface. Group 1 was treated with Colgate Platinum for 7 hours, group 2 with Opalescence for 7 hours, group 3 was treated with 30% phosphoric acid for 30 seconds and group 4 was untreated and used as control. After the treatment period, the specimens were washed with normal saline and stored in sterile bottle and sealed. Photomicrographs obtained from the scanning electron microscopy (SEM) after surface treatments were examined for no alteration, slight alteration, moderate alteration and severe alterations. The specimens treated with commercial bleaching agents revealed no enamel surface morphologic alterations compared to control group. The specimen treated with phosphoric acid showed severe alterations. Ten percent carbamide peroxide evaluated in this study does not etch tooth enamel or alter enamel surface morphology as do conventional etching techniques. Carbamine peroxide is a safe and effective tooth whitening agent even when used for extended period of time. The enamel surface remains smooth which reduces caries due to plaque collection.

Evaluation of Primary Tooth Enamel Surface Morphology and Microhardness after Nd: YAG Laser Irradiation and APF Gel Treatment—An in vitro study

Laser irradiation and fluoride has been used as a preventive tool to combat dental caries in permanent teeth, but little has been done for primary teeth which are more prone to caries. The purpose of this study was to evaluate microhardness alterations in the primary tooth enamel after Nd-YAG laser irradiation alone and combined with topical fluoride treatment either before or after Nd-YAG laser irradiation. Ten primary molars were sectioned and assigned randomly to: control group, Nd-YAG laser irradiation, Nd-YAG lasing before APF and APF followed by Nd-YAG lasing. The groups were evaluated for microhardness. Surface morphological changes were observed using SEM. Statistical comparisons were performed. The control group's SEM showed a relatively smooth enamel surface and lasing group had fine cracks and porosities. In the lasing + fluoride group a homogenous confluent surface was seen. In the fluoride + lasing group an irregular contour with marked crack propagation was noted. There was a significant increase in the microhardness of the treatment groups. Nd-YAG laser irradiation and combined APF treatment of the primary tooth enamel gave morphologically hardened enamel surface which can be a protective barrier against a cariogenic attack.

The effect of fluoride therapies on the morphology of bleached human dental enamel

The aim of this in vitro study was to evaluate qualitatively the surface morphology of enamel bleached with 35% hydrogen peroxide (HP) followed by application of fluoridated agents. Forty intact pre molars were randomly distributed into four groups (n = 10), treated as follows: Group I (control group) remained stored in artificial saliva at 37 °C, Group II - 35% HP; Group III - 35% HP + acidulated fluoride (1.23%) and Group IV - 35% HP + neutral fluoride (2%). The experimental groups received three applications of bleaching gel and after the last application all specimens were polished. This procedure was repeated after 7 and 14 days, and during the intervals of applications, the specimens were stored in artificial saliva at 37°C. Scanning electron microscopy (SEM) analysis showed superficial irregularities and porosities to varying degrees in bleached enamel compared to control group. Sample evaluation was made by attributing scores, and data were statistically analyzed using Kruskal-Wallis and Dunn tests (P < 0.05). SEM qualitative investigation demonstrated that 35% hydrogen peroxide affected human dental enamel morphology, producing porosities, depressions, and superficial irregularities at various degrees. These morphological changes were higher after the application of 1.23% acidulated fluoride gel.

Chemical analysis and surface morphology of enamel following ozone application with different concentrations and exposure times

This study aimed to determine the effect of different ozone concentrations applied with different exposure times on the chemical composition and the surface morphology of enamel. Twenty human mandibular molars were divided into four groups according to ozone concentration and exposure times. Group A received 90 μg of ozone/ml oxygen for 1 min, group B received 90 μg of ozone/ml oxygen for 2 min, group C received 120 μg of ozone/ml oxygen for 1 min and group D received 120 μg of ozone/ml oxygen for 2 min. The ozone source was from a medical ozone generator equipped with a device to adjust the concentration. Buccal surfaces of teeth were tested before and after ozone application so that each tooth served as a control for itself, using Environmental Scanning Electron Microscope (ESEM) connected to an Electron Dispersive Analytical X-ray (EDAX). Changes in calcium and phosphorus percentage levels were recorded and the Ca/P ratio was calculated. The values were statistically analyzed using the one-way ANOVA test with a level of significance set at P ⩽ 0.05. No statistical significant difference was found between the control and the tested groups in minerals content or ratio as P > 0.05. ESEM images showed enamel surface roughness with 2 min ozone exposure times. High ozone concentration with prolonged exposure time does not change the chemical composition of enamel. Applying ozone for 2 min alters the surface morphology of enamel causing variable degrees of roughness. Using high ozone concentrations with prolonged exposure times for caries reversal or prevention and for bleaching may be contraindicated if this changes the surface morphology of enamel.

Effect of 10% Sodium Ascorbate on Bleached Bovine Enamel Surface Morphology and Microhardness

Sodium ascorbate has recently been suggested to compensate decreased bond strength of composite resin to bleached tooth surfaces. The aim of present study was to evaluate the effect of 10% sodium ascorbate on bleached bovine enamel morphology and microhardness considering the possibility of its effect on enamel surface characteristics. A total of 69 bovine enamel slabs were prepared and mounted in acrylic resin. Subsequent to polishing, they were randomly divided into 3 groups of 23 specimens each; 3 for Scanning Electron Microscopy (SEM) analysis and 20 for hardness test. In group 1 the specimens were immersed in distilled water as control group; in group 2 the specimens were bleached with 35% carbamide peroxide for 30 min a week for 3 consecutive weeks; and in group 3 the specimens were exposed to 10% sodium ascorbate for 30 min subsequent to bleaching similar to group 1. After 3 weeks Vickers hardness of the specimens was measured at 3 points with equal distances from each other under a force of 50 g. The mean of the hardness values of each specimen was calculated and data was analyzed by one-way ANOVA (P < 0.05). The highest and lowest microhardness values were observed in group 1 and group 2, respectively. However, there were no statistically significant differences in microhardness between the groups (P = 0.12). The use of 35% carbamide peroxide alone or with 10% sodium ascorbate does not affect bovine enamel hardness. SEM analysis showed a network of sodium ascorbate adsorbed to the bleached enamel surface.

The effects of different phosphoric acid concentrations on surface enamel.

The purpose of this study was to evaluate the effects of different acid concentrations on the enamel surface morphology. The buccal surfaces of 25 extracted premolars from young patients were etched with 40%, 20%, 10%, 5%, and 2% phosphoric acid solutions for 60 seconds. The specimens were examined with a scanning electron microscope in the occlusal, central, and cervical regions. A great variation of the etching patterns was observed in almost all test groups. The extent of the appearance of prism outlines was smaller in the cervical region and at lower acid concentrations. The advantages and disadvantages of the use of lower concentrated acids are discussed.