Enamel Hardness Research Articles

Effects on Hardness and Elastic Modulus for DSS-8 Peptide Treatment on Remineralization of Human Dental Tissues.

Dental remineralization may be achieved by mediating the interactions between tooth surfaces with free ions and biomimetic peptides. We recently developed octuplet repeats of aspartate-serine-serine (DSS-8) peptide, which occurs in high abundance in naturally occurring proteins that are critical for tooth remineralization. In this paper, we evaluated the possible role of DSS-8 in enamel remineralization. Human enamel specimens were demineralized, exposed briefly to DSS-8 solution, and then exposed to concentrated ionic solutions that favor remineralization. Enamel nano-mechanical behaviors, hardness and elastic modulus, at various stages of treatment were determined by nanoindentation. The phase, microstructure and morphology of the resultant surfaces were characterized using the grazing incidence X-ray diffraction (GIXD), variable pressure scanning electron microscopy (VPSEM), and atomic force microscopy (AFM), respectively. Nanoindentation results show that the DSS-8 remineralization effectively improves the mechanical and elastic properties for demineralized enamel.

Change in surface hardness of enamel by a cola drink and a CPP–ACP paste

Objectives This in vitro study used surface microhardness to evaluate whether a paste containing casein phosphopeptide amorphous calcium phosphate (CPP–ACP) can reharden tooth enamel softened by a cola drink, and how different saliva-substitute solutions affect the enamel hardness. Methods Twenty-four bovine incisors, each tooth consisting of treatment and control halves, were immersed in a cola drink (Coke ®) for 8 min, then placed under a 0.4 mL/min drip with various saliva-substitute solutions. The saliva-substitute solutions were: saliva-like solution (SLS) with 1 ppm fluoride, SLS without fluoride, and Biotene ® mouthwash. CPP–ACP paste was applied to the treatment halves for 3 min at 0, 8, 24, and 36 h. Knoop microhardness measurements were performed at baseline, after the cola drink immersion, and after 24 and 48 h contact with saliva-substitute solution. Results Enamel hardness significantly decreased after immersion in cola drink (ANOVA, p < 0.05). After contact with saliva-like solutions for 48 h, those treated with CPP–ACP paste were significantly harder than those untreated regardless of the presence of 1 ppm fluoride in the saliva-like solution (ANOVA, p < 0.05). Biotene ® mouthwash significantly softened the enamel surface (ANOVA, p < 0.05). Two-way ANOVA showed significant effects of the CPP–ACP paste application and types of saliva-substitute solutions on the changes in surface hardness of the softened enamel at a significance level of 0.05. Conclusion The application of CPP–ACP paste with continuous replenishment of saliva-like solution for 48 h significantly hardened enamel softened by a cola drink. Biotene ® mouthwash softened enamel surface after 48 h contact.

Effects of New Formulas of Bleaching Gel and Fluoride Application on Enamel Microhardness: An In Vitro Study

This in vitro study evaluated the new formulas of bleaching products and the effect of subsequent applications of fluoride on the hardness of enamel during and after tooth bleaching. The crowns of 60 extracted intact human molars were sectioned longitudinally; the buccal part was embedded in acrylic resin, the occlusal part was ground flat, exposing enamel and dentin, and then polished. Baseline Knoop microhardness (KHN) of enamel was determined. The specimens were then randomly divided into six groups of 10 specimens, and each group was assigned to a specific 10% carbamide peroxide (CP) bleaching agent. A: Opalescence, B: Opalescence PF (3% potassium nitrate and 0.11% fluoride), C: Nite White Excel 3 (ACP), D: Opalescence + F (acidulated phosphate fluoride 1.23%), E: Opalescence PF + F, F: Nite White Excel 3 + F. The teeth were bleached for eight hours; after each procedure, the specimens were stored in artificial saliva at 37 degrees C. Immediately after day 21 of bleaching, the specimens in groups D, E and F received fluoride 1.23% for five minutes. KHN tests w ere performedbefore (baseline = control), during (14, 21) and two weeks (35 days) after the bleaching procedure and were statistically compared using ANOVA/Tukey's t-test (alpha < 0.05). The statistical analysis revealed no significant difference among the bleaching materials (p = 0.123). A significant enamel KHN reduction (p < 0.001) was observed for all bleaching materials, with no difference among them. Two weeks after bleaching, all the groups that received fluoride showed a significant increase in microhardness. For the new bleaching formulas, the enamel was restored to a value similar to baseline.

Inhibitory Effect of Synthetic Nano-Hydroxyapatite on Dental Caries

The objective of this study was to investigate the inhibitory effect of the synthetic nanohydroxyapatite (HA) on dental caries. The nano-HA was synthesized by using the depositing reaction of Ca (H2PO4)2. The artificial dental caries was made by using sour solution and inoculating Streptococcus mutans (S.mutans) to the Sprague-Dawley (SD) rat’s mouth respectively. After mineralization of solution of nano-HA for 10 days, the hardness of enamel was measured. The inhibitory effect of the synthetic nano-HA on dental caries was detected by gargling way to rinse the rat tooth with the solution of nano-HA in the animal test. Transmission electron microscopy (TEM) revealed that the dried HA particles were needle-like with ф5-20nm×60nm and the sintered HA particles were spherical with less than 100nm. The remineralized test indicated that the solution of nano-HA with different shapes enhanced the hardness of artificial caries and improved the remineralization of artificial caries. The animal test showed that the dried nano-HA had the inhibitory effect on dental caries. The good absorptive effect of the nano-HA on both the saliva protein and the glucans leads to the development of interventions that could reduce or modify bacterial colonization of tooth surfaces.

Ectopic Expression of Dentin Sialoprotein during Amelogenesis Hardens Bulk Enamel

Dentin sialophosphpoprotein (Dspp) is transiently expressed in the early stage of secretory ameloblasts. The secretion of ameloblast-derived Dspp is short-lived, correlates to the establishment of the dentinoenamel junction (DEJ), and is consistent with Dspp having a role in producing the specialized first-formed harder enamel adjacent to the DEJ. Crack diffusion by branching and dissipation within this specialized first-formed enamel close to the DEJ prevents catastrophic interfacial damage and tooth failure. Once Dspp is secreted, it is subjected to proteolytic cleavage that results in two distinct proteins referred to as dentin sialoprotein (Dsp) and dentin phosphoprotein (Dpp). The purpose of this study was to investigate the biological and mechanical contribution of Dsp and Dpp to enamel formation. Transgenic mice were engineered to overexpress either Dsp or Dpp in their enamel organs. The mechanical properties (hardness and toughness) of the mature enamel of transgenic mice were compared with genetically matched and age-matched nontransgenic animals. Dsp and Dpp contributions to enamel formation greatly differed. The inclusion of Dsp in bulk enamel significantly and uniformly increased enamel hardness (20%), whereas the inclusion of Dpp weakened the bulk enamel. Thus, Dsp appears to make a unique contribution to the physical properties of the DEJ. Dsp transgenic animals have been engineered with superior enamel mechanical properties.

Depth‐dependent mechanical properties of enamel by nanoindentation

Nanoindentation has recently emerged to be the primary method to study the mechanical behavior and reliability of human enamel. Its hardness and elastic modulus were generally reported as average values with standard deviations that were calculated from the results of multiple nanoindentation testing. In such an approach, it is assumed that the mechanical properties of human enamel are constant, independent of testing parameters, like indent depth and loading rate. However, little is known if they affect the measurements. In this study, we investigated the dependence of the hardness and elastic modulus of human enamel on the indent depth. We found that in a depth range from 100 to 2000 nm the elastic moduli continuously decreased from approximately 104 to 70 GPa, and the hardnesses decreased from approximately 5.7 to 3.6 GPa. We then considered human enamel as a fiber-reinforced composite, and used the celebrated rule of mixture theory to quantify the upper and lower bounds of the elastic moduli, which were shown to cover the values measured in the current study and previous studies. Accordingly, we attributed the depth dependence of the hardness and modulus to the continuous microstructure evolution induced by the nanoindenter tip.

Effect of casein phosphopeptide - amorphous calcium phosphate on hardness of enamel eroded by a cola drink

Effect of casein phosphopeptide - amorphous calcium phosphate on hardness of enamel eroded by a cola drink

Erosive effect of an antihistamine‐containing syrup on primary enamel and its reduction by fluoride dentifrice

This study evaluated the action of an antihistamine-containing syrup (Claritin D) on enamel that was subsequently submitted or not to applications of fluoride dentifrice. METHODS; Two hundred sixty-four slices (n=44 per subgroup) prepared from exfoliated primary molars were evaluated in hardness tests. Six subgroups were submitted to different treatments for 10 days. The controls underwent pH cycling with (positive control) or without (negative control) three daily immersions in fluoride dentifrice/distilled water slurry. The test subgroups related to daytime use of the antihistamine syrup underwent pH cycling and two 5-min applications of Claritin D, coupled or not to the three daily immersions in the fluoride slurry. The subgroups related to nocturnal use of the syrup were submitted to the same procedures of daytime subgroups, respectively, but with one of the applications of Claritin D lasting for 8 h. The median hardness values obtained after use of the syrup were significantly lower than the initial ones. Equivalent values for subgroups submitted to fluoride applications in addition to treatment with the syrup were significantly higher. It was concluded that the antihistamine-containing syrup reduced the hardness of primary enamel and that, in this experiment, the use of fluoride dentifrice was able to diminish this erosive effect.

Effects of Nd:YAG Laser on Enamel Microhardness and Dental Plaque Composition: Anin SituStudy

This study evaluated Knoop microhardness (KHN) and dental plaque composition of human enamel irradiated with Nd:YAG laser and subjected to in situ cariogenic challenge. Although in vitro studies have shown that Nd:YAG laser irradiation results in a reduction of enamel mineral loss after acid challenge, this hypothesis has not been tested using an in situ caries model. Acrylic devices containing lased and non-lased human enamel slabs were used for 28 days by eight subjects highly colonized by S. mutans. Devices were immersed in a sucrose solution (20%) eight times daily in order to better simulate the cariogenic challenge. After the experimental period, no differences in dental plaque composition were observed between lased and non-lased enamel slabs indicating that all slabs were exposed to equivalent cariogenic challenges. Cross sections of enamel slabs were then measured for Knoop microhardness at 10, 20, 40, 60, 80, 120, and 180 microm in depth from the outer exposed surface. Un-lased enamel slabs not subjected to the in situ cariogenic challenge were also used as control. Enamel slabs from the two in situ groups exhibited lower hardness when compared to control. Lased enamel showed higher hardness values up to 60 microm in depth than the un-lased enamel exposed to in situ cariogenic challenge. The results suggest that the irradiation of Nd:YAG laser of human enamel appears to be effective for increasing enamel hardness and thus decreasing the effect of acid attack.

Hardness of enamel exposed to Coca‐Cola® and artificial saliva

The purpose of this study was to determine the rate of change in indentation hardness of enamel in permanent teeth exposed to Coca-Cola. In a further experiment, the ability of a commercially available artificial saliva to remineralize enamel treated with Coca-Cola was tested. Ten enamel specimens were randomly chosen to be treated with Coca-Cola (experimental groups) and seven with water (control group). The fluids were applied for 1, 2, 3 h and overnight (15 h), washed off with a few drops of water and the moist enamel indentation hardness tested after each interval. With Coca-Cola treatment, the mean enamel hardness was 92.6% (s.d. = 7.9) of the original baseline hardness after 1 h, 93.25% (s.d. = 10.15) after 2 h, 85.7% (s.d. = 12.03) after 3 h and 80.3% after 15 h. The mean indentation hardness of control specimens treated with water was 108.7% (s.d. = 16.09) of the original hardness after 1 h, 99.09% (s.d. = 18.98) after 2 h, 98.97% (s.d. =11.24) after 3 h and 98.42% (s.d. = 22.78) after 15 h. In a separate experiment, the hardness of 9 enamel specimens was tested, as previously described, before and after treatment with Coca-Cola overnight and again after application of artificial saliva for 3 min. Coca-Cola reduced the mean indentation hardness of enamel in the teeth, but the hardness was partially restored with artificial saliva (Salivart) and increased by 18% from the demineralized enamel hardness.

Effect of hydrogen-peroxide-based home bleaching agents on enamel hardness

The aim of this in vitro study was to examine the effect of four commercial hydrogen-peroxide-based home bleaching agents on enamel microhardness. Fifteen human molars conserved in water for no more than 3 months were sectioned mesio-distally. The buccal and lingual surfaces were included in self curing acrylic resin, and the 30 specimens were ground until 600 grid (n=6). At baseline, 6 indentations (Vickers) were made on each of the 6 surfaces of each group, under load of 100g for 30s. Bleaching procedure was performed for 2 weeks with: 4.5% hydrogen-peroxide (Perfecta, Premier), 5.5% hydrogen-peroxide (DayWhite, Discus Dental), 7.5% hydrogenperoxide (DayWhite, Discus Dental), a polyethylene-strip whitening system containing 5.3% hydrogen-peroxide (Whitestrips, Procter&Gamble) and 10% carbamide peroxide (Opalescence, Ultradent) was used as control. After bleaching time, the specimens were rinsed and maintained in fresh artificial saliva, changed daily. A t-test compared each bleaching agent before and after treatment. The results showed that none of the five commercial home bleaching agents reduced the enamel microhardness. I t was concluded that all the five commercial home bleaching agents evaluated in our study showed no adverse effects on enamel microhardness.

Erosive effects of common beverages on extracted premolar teeth

Dental erosion is highly prevalent today, and acidic drinks are thought to be an important cause. The aim of the present investigation was to determine the erosive potential of a range of common beverages on extracted human teeth. The beverages were tested for their individual pHs using a pH meter. The clinical effects of the most erosive beverages were determined by the degree of etching and Vickers microhardness of enamel. The results showed that many common beverages have pHs sufficiently low to cause enamel erosion. Lime juice concentrate (pH 2.1) had the lowest pH, followed by Coca-cola and Pepsi (both with pH 2.3) and Lucozade (pH 2.5). The erosive potential of these beverages was demonstrated by the deep etching of the enamel after five minutes. The Vickers Hardness of enamel was reduced by about 50 per cent in the case of lime juice (p < 0.001) and 24 per cent in the case of Coca-cola (p < 0.004). Addition of saliva to 50 per cent (v/v) of Coca-cola completely reversed the erosive effects on the enamel. Although only a few of the beverages with the lowest pHs were tested, the present study showed that the most acidic drinks had the greatest erosive effects on enamel. While saliva was protective against erosion, relatively large volumes were required to neutralize the acidity.

RBS and XPS analyses of the composite calcium phosphate coatings for biomedical applications

The calcium phosphate coatings on metallic implants are widely used for biomedical applications. The calcium phosphate coatings require mechanical strength, strong adhesion to the metallic implants, chemical stability and low dissolution into the human body fluid for stable functioning in the corrosive environment of the human body. In this study, a novel approach for improving the calcium phosphate coatings is utilized by adding trace metallic element into the coatings. We focused on teeth enamel, which is the hardest calcium phosphate tissue in the human body. Zn concentration increases exponentially from the interior to the surface of the enamel. As the Zn concentration increases, so the local hardness increases. Our previous studies suggest that Zn has influence on the hardness and other properties of enamel, calcium phosphate tissue. Calcium phosphate coatings doped with Zn was fabricated and characterized. The atomic composition and chemical state were investigated by using Rutherford backscattering spectroscopy (RBS) and X-ray photoelectron spectrometer (XPS), respectively. Scratch test was also carried out for measuring the adhesion of the coatings.

Effect of acidic food and drinks on surface hardness of enamel, dentine, and tooth-coloured filling materials

The purpose of this study was to determine the effect of acidic food and drinks (Cola soft drink, drinking yogurt, orange juice, sports drink, Tom-yum soup) on surface hardness of various substrates (enamel, dentine, universal composite, microfilled composite, conventional glass ionomer, resin-modified glass ionomer, polyacid-modified resin composite). Specimens (n = 10) were alternately immersed, 5 s each, in food or drinks and in artificial saliva for 10 cycles. Baseline and post-immersion Vickers hardness were compared using paired t-test. The difference in hardness between the groups was analysed with one-way ANOVA followed by a least significant different (LSD) test. Cola soft drink significantly reduced surface hardness of enamel, dentine, microfilled composite, and resin modified glass ionomer (p < 0.05). Orange juice and sports drink significantly reduced surface hardness of enamel (p < 0.05). Drinking yogurt and Tom-yum soup did not reduce surface hardness of any substrate. This in vitro study confirms the erosive potential of certain acidic food and drinks that public should be aware of.

Effects of Nd:YAG laser on dental enamel.

Caries prevention should be an important goal of the dentistry practitioner. In addition to traditional preventive techniques, laser beam has been a recent suggestion. This study aimed to evaluate Nd:YAG laser treatment effects on dental enamel surfaces, irradiated at different energy levels, by scanning electron microscopy (SEM) observations and surface micro-hardness tests to evaluate if caries prevention can be achieved by laser treatment. Forty human teeth were divided in four groups of 10 specimens each: in three groups the enamel surface was treated with three different laser beam energy levels, 60, 120 and 160 mJ, in one group the enamel was not lased. Five samples from each group were subjected to the Vickers microhardness test and five samples underwent SEM investigation. Results of the microhardness test demonstrated no significant differences between treated and non-treated dental enamel samples. SEM observation demonstrated a rougher enamel surface in all treated groups: the 60 mJ treated group showed tooth surfaces with vertical scratches, the 120 mJ treated group showed the enamel surface covered by craters and cracks, and the 160 mJ treated group showed a completely changed enamel structure with columns separated by voids and with a glass-like surface. These investigations demonstrated that dental enamel laser treatment at low energy levels (not >60 mJ) produces a protective glass-like surface, without the loss of its integrity and could be an advisable technique to prevent caries. Higher energy laser treatment leads to modifications of the enamel morphology such as craters and cracks, even if it does not cause any change in enamel hardness characteristics, which could be more useful in conservative dentistry.

Human enamel erosion in constant composition citric acid solutions as a function of degree of saturation with respect to hydroxyapatite

The objective of this study was to investigate human enamel erosion under constant composition conditions, as a function of solution degree of saturation (DS) with respect to hydroxyapatite. The experimental conditions were relevant to the initial stages of enamel erosion by soft drinks. Nanoindentation was used to compare enamel surface softening caused by a control mineral water and two citric acid solutions with DS = 0.000 and DS = 0.032, both having pH 3.30. Enamel hardness and reduced elastic modulus were measured after 0, 30, 60, 120, 300 and 600 s exposure. A statistically significant change in enamel hardness was detected after 30 s exposure to both citric acid solutions, indicating that nanoindentation is extremely sensitive to the initial stages of erosion. There was a statistically significant difference between the mechanical properties of enamel exposed to the two citric acid solutions after 30, 60 and 120 s. At these times, the solution with DS = 0.000 caused twice as much enamel softening as that with DS = 0.032. This demonstrates that it may be possible to design a soft drink with a low erosive potential and a good taste by a small change in DS, at a typical drink pH.

Nanoindentation study of human premolars subjected to bleaching agent

Bleaching of teeth is gaining popularity due to cosmetic reasons. However, the effect it has on teeth is still largely unknown. This paper seeks to evaluate the effect of a bleaching agent, 30% hydrogen peroxide, on the nanomechanical properties of dentin and enamel using the nanoindentation technique. The Young's modulus and hardness obtained from nanoindentation before and after bleaching were compared. Five newly extracted human premolars were used. Nanoindentation was first done on the sliced enamel and dentin regions to determine their mechanical properties. One batch of samples was kept in Hank's balanced salt solution as control while the other was bleached in 30% hydrogen peroxide for 24 h. The same number of nanoindentations was then done near the previously indented regions for both the control and bleached samples and the results compared. Using paired sample t-tests with α = 0.05 , it was found that there were no significant differences in both the Young's modulus and hardness of dentin and enamel kept in control. However, the mechanical properties of the bleached dentin were significantly decreased. For intertubular dentin, the mean hardness decreased by 29–55% and the mean Young's modulus decreased by 19–43%. For enamel, the mean hardness decreased by 13–32% while the mean Young's modulus decreased by 18–32%. The exact mechanism by which hydrogen peroxide affects the dentin and enamel has yet to be fully elucidated. However, it is observed to have an undermining effect on the nanomechanical properties of teeth.

Effect of different peroxide bleaching regimens and subsequent fluoridation on the hardness of human enamel and dentin

Bleaching of teeth by "in-office" or "home" bleaching techniques are popular methods of whitening teeth. However, bleaching may reduce the surface hardness of enamel and dentin. The purpose of this study was to evaluate (1) the effect of different concentrations of 2 "in-office bleaching" and 2 "home bleaching" agents applied for different time periods on the hardness of enamel and dentin and (2) the effect of subsequent immersion in a low-concentration fluoride solution on the hardness of bleached enamel and dentin. The enamel and dentin of 12 extracted intact human molar teeth were sectioned lengthwise, ground, polished, embedded in acrylic resin and divided into 4 groups each (n=12). An area of approximately 5 x 5 mm of enamel and dentin tested for Knoop hardness number (KHN; kg/mm 2 ) at a load of 100 g for 20 seconds (baseline). The specimens were stored in distilled water for 1 hour and the microhardness testing repeated as a control group. The groups were bleached as follows: Group OX and Group OQ were bleached "in office" with Opalescence Xtra (35% hydrogen peroxide) and Opalescence Quick (35% carbamide peroxide), respectively, for 5, 15, or 35 minutes and retested for KHN at the end of each time period. "Home bleaching" products Opalescence F (15% carbamide peroxide) and Opalescence (10% carbamide peroxide) were applied in 14-hour applications at 24-hour intervals to Groups OF and O, respectively, which were then tested for KHN. Specimens were immersed in 0.05% fluoride solution (Meridol) for 5 minutes and retested for KHN. The hardness values were analyzed by 2-way ANOVA and Scheffe post hoc test (alpha=.05). Comparisons of KHN between each time and the baseline measurement for each group were of interest. Significant decreases in KHN of enamel and dentin were found after bleaching for all test groups, dependent on the accumulated bleaching time. Group OX showed a 25% KHN reduction for enamel and 22% for dentin after 35 minutes bleaching (P < .0001). Group OQ showed a 13% KHN reduction (P < .0001) for enamel and 10% for dentin after 35 minutes (P < .005). Group OF showed a KHN reduction of 14% for enamel (P < .05) and 9% for dentin (P < .0001) after 14 hours bleaching, and Group O showed an 18% reduction in enamel (P < .0001) and 13% in dentin (P < .0001) for the same period. Fluoridation completely restored the softened dental tissues. The "in-office" bleaching technique reduced the hardness significantly more than the "home" bleaching technique. Low-concentration fluoride mouth rinse (Meridol) restored the softened dental tissues.

Protective effect of the in situ formed short-term salivary pellicle

Salivary pellicle, as previously investigated, protects the enamel surface after certain processes of maturation against the influence of acidic agents. The aim of the present study was to investigate the protective effect of the short-term salivary pellicle formed in situ over periods of 3, 60 and 120 min. Six human volunteers used intraoral acrylic splints with bovine enamel samples fixed at the buccal and palatal sites of the maxillary first molars and second premolars. Enamel specimens ( n = 252) with and without pellicle were immersed for 60 s in 1.0% citric acid solution under agitation. Knoop surface hardness (KHN) of uneroded polished enamel was measured as a baseline and estimated immediately after erosive treatment reflecting the microhardness loss (ΔKHN). The amounts of calcium dissolved from the eroded enamel surface were analysed by atomic absorption spectroscopy and scored in mg/l per 10 mm 2 of enamel surface area. In addition, the scanning electron microscope was used for the micromorphological examination of the erosive alterations of the enamel surface. The average microhardness loss values after erosion of the enamel samples with buccally/palatally formed pellicle layers were measured as 139.1/144.9 ΔKHN for 3 min pellicle, 145.9/146.9 ΔKHN for 60 min pellicle and 141.7/138.6 ΔKHN for 120 min pellicle. Calcium release values from the specimens with buccal/palatal pellicles were amounted to 15.0/14.9, 16.5/15.9 and 15.3/17.4 mg/l per 10 mm 2 for 3, 60 and 120 min-old pellicles, respectively. No significant differences were related to the pellicle formation time and intraoral site (buccal or palatal) in all tested series (ANOVA, P < 0.05). However, significant protection of the enamel surface provided by the pellicle layer was observed on all pellicle-covered surfaces if compared to the non-covered enamel samples (calcium release: 25.6 mg/l per 10 mm 2; microhardness loss 187.0 ΔKHN). These data were in accordance with the morphologic alterations caused by citric acid on the pellicle-covered and pellicle non-covered specimens. It could be concluded that salivary pellicle formed in situ within a period of 3 min offers protection of enamel against citric acid. However, pellicle does not completely inhibit the erosive action of citric acid under the conditions of the present study.

An Evaluation of Surface Hardness, Roughness and Wear of Restorative Composites, Porcelain, and Enamel Following Abrasion by Enamel

An Evaluation of Surface Hardness, Roughness and Wear of Restorative Composites, Porcelain, and Enamel Following Abrasion by Enamel