Acid-etched Enamel Research Articles

Comparative study of the shear bond strength of composite resin bonded to enamel treated with acid etchant and erbium, chromium: Yttrium, scandium, gallium, garnet laser

Aim: The purpose of this investigation is in vitro comparison of the shear bond strength (SBS) of composite resin bonded to enamel pretreated with an acid etchant against enamel etched with erbium, chromium: yttrium, scandium, gallium, garnet (Er, Cr:YSGG) laser. Materials and Methods: Sixty premolars were sectioned mesiodistally and these 120 specimens were separated into two groups of 60 each (Groups A and B). In Group A (buccal surfaces), enamel surface was etched using 37% phosphoric acid for 15 s. In Group B (lingual surfaces), enamel was laser-etched at 2W for 10 s by Er, Cr:YSGG laser operational at 2780 nm with pulse duration of 140 μs and a frequency of 20 Hz. After application of bonding agent on all test samples, a transparent plastic cylinder of 1.5 mm × 3 mm was loaded with composite and bonded by light curing for 20 s. All the samples were subjected to SBS analysis using Instron Universal testing machine. Failure modes were observed under light microscope and grouped as adhesive, cohesive, and mixed. Failure mode distributions were compared using the Chi-square test. Results: SBS values obtained for acid-etched enamel were in the range of 7.12–28.36 megapascals (MPa) and for laser-etched enamel were in the range of 6.23–23.35 MPa. Mean SBS for acid-etched enamel was 15.77 ± 4.38 MPa, which was considerably greater (P < 0.01) than laser-etched enamel 11.24 ± 3.76 MPa. The Chi-square test revealed that the groups showed no statistically significant differences in bond failure modes. Conclusions: We concluded that the mean SBS of composite with acid etching is significantly higher as compared to Er, Cr: YSGG (operated at 2W for 10 s) laser-etched enamel.

Surface and interfacial analysis of sandblasted and acid-etched enamel for bonding orthodontic adhesives.

The purposes of this study were to characterize enamel surfaces treated with sandblasting, acid etching, or sandblasting followed by acid etching for bonding of orthodontic adhesives and to evaluate the enamel-adhesive interfaces. Buccal premolar surfaces were sandblasted, acid etched, sandblasted and subsequently acid etched, or left intact. For 2 treatments (acid etching and sandblasting plus acid etching), orthodontic brackets were bonded for resin infiltration assessment. Surface roughness and enamel loss were evaluated by optical profilometry, and surface morphology and elemental composition were examined by low-vacuum scanning electron microscope/energy dispersive x-ray analysis, whereas interfacial resin infiltration was assessed by high-vacuum scanning electron microscopy. Differences were statistically analyzed by 1-way analysis of variance and Tukey-Kramer multiple comparison tests or t tests (α = 0.05). The sandblasted and sandblasted-plus-acid-etched groups showed higher surface roughness values than the acid-etched group. Sandblasting plus acid etching removed more enamel than did sandblasting or acid etching alone. Sandblasting plus acid etching demonstrated a more uniform type I etching pattern, without alumina particles implanted in the enamel, unlike sandblasting. No difference was found in the extent of resin infiltration between the bonded acid-etched and sandblasted-plus-acid-etched groups, although the latter showed improved infiltration characteristics. Sandblasting-plus-acid-etching treatment creates a rough enamel surface, typical of type I etching, with the greatest extent of enamel loss, free of alumina interferences, demonstrating the same extent of resin infiltration as acid etching, but exhibiting improved infiltration quality.

Leucine‐rich amelogenin peptide (LRAP) as a surface primer for biomimetic remineralization of superficial enamel defects: An in vitro study

This study was carried out to obtain more information about the assembly of hydroxyapatite bundles formed in the presence of Leucine-Rich Amelogenin Peptide (LRAP) and to evaluate its effect on the remineralization of enamel defects through a biomimetic approach. One or 2 mg/mL LRAP solutions containing 2.5 mM of Ca(+2) and 1.5 mM phosphate were prepared (pH = 7.2) and stored at 37 °C for 24 h. The products of the reaction were studied using atomic force microscopy (AFM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Vickers surface microhardness recovery (SMR%) of acid-etched bovine enamel, with or without LRAP surface treatment, were calculated to evaluate the influence of peptide on the lesion remineralization. Distilled water and 1 or 2 mg/mL LRAP solution (pH = 7.2) were applied on the lesions and the specimens were incubated in mineralization solution (2.5mM Ca(+2) , 1.5mM PO4 (-3) , pH = 7.2) for 24 h. One-way ANOVA and Tukey's multi-comparison tests were used for statistical analysis. The pattern of enamel surface repair was studied using FE-SEM. AFM showed the formation of highly organized hierarchical structures, composed of hydroxyapatite (HA) crystals, similar to the dental enamel microstructure. ANOVA procedure showed significant effect of peptide treatment on the calculated SMR% (p < 0.001). Tukey's test revealed that peptide treated groups had significantly higher values of SMR%. In conclusion, LRAP is able to regulate the formation of HA and enhances the remineralization of acid-etched enamel as a surface treatment agent.

Comparative Evaluation of Shear Bond Strength of Flowable Composite Bonded to Teeth Enamel with Laser Surface Treatment

Background: Acid etching of enamel appears to improve retention by selectively eroding certain hydroxyapatite formations and facilitating penetration by the development of resin tags. Aim of study: To evaluate shear bond strength (SBS) of flowable composite to non-lased and lased groups, compare the (SBS) of flowable composite between Total and Self-etch in non-lased and lased groups, and failure mode analysis.Materials and Methods: Forty bovine incisors were used, enamel surfaces was grounded by silicon carbide paper and samples were randomly assigned into two main groups (Group A: Non lased n=20, Group B: lased prepared n=20). Each main group was subdivided randomly according to the adhesive systems that used which are: total-etch adhesive and self-etch adhesive, which were applied to the prepared enamel surface according to manufacture instruction. Composite rod applied over the bonded area and cured. Samples were stored in distilled water at 370 for 24 hours. The evaluation of shear bond strength was employed by the use of universal testing machine. Results: The results of Student’s t-test showed that there was no significant difference between the lased and non-lased enamel groups (P= 0.311). One–way ANOVA test and Duncan's Multiple Range test that compare shear bond strength between total and self-etch adhesives showed no significant difference in both lased and non-lased enamel groups. Conclusion: The mean shear bond strength and enamel surface etching obtained with an Er,Cr:YSGG laser was not comparable to that obtained with nonlased enamel surface.

Effect of different monomer-based composites and acid etching pre-treatment of enamel on the microleakage using self-etch adhesives systems

Objective. To evaluate quantitatively the marginal microleakage of restorations carried out with self-etching adhesives with or without prior phosphoric enamel acid etching of silorane or methacrylate resin-based composite restorations subjected to thermal cycling. Materials and methods. Forty cavities were prepared at the proximal surface of bovine incisors and randomly divided according to the etching of the enamel and restorative system used. The groups were restored with methacrylate [Adper SE Plus adhesive (3M ESPE) + Filtek Z250 (3M ESPE)] or silorane [Filtek LS adhesive (3M ESPE) + Filtek LS composite (3M ESPE)] restorative systems, light-cured using a LED unit (Bluephase 16i, Vivadent). After restorative procedure and thermocycling (1000 cycles), the specimens were immersed in methylene blue for 2 h. The specimens were triturated and the powder was used for analysis in an absorbance spectrophotometer. Data were statistically analyzed by 2-way ANOVA (alpha = 0.05). Results. No statistical difference between the restorative materials tested with or without previous acid etching of enamel in Class II marginal microleakage was observed (p > 0.05). Conclusions. The use of acid etching prior to self-etching adhesives did not interfere on the microleakage of methacrylate- or silorane-based restorations.

Acid etching of human enamel in clinical applications: A systematic review

The laboratory-based enamel acid-etching doctrine with 30% to 50% phosphoric acid for 60 seconds to generate the maximum amount of Type 1 and/or Type 2 etch pattern has been established for more than 30 years. However, this recommendation may not be clinically relevant. The purpose of this systematic review was to compare clinically accepted protocols of enamel acid etching with the laboratory protocol. Studies were identified by searching 4 electronic databases: Medline, CINAHL Plus, Embase, and Cochrane Library. The final search was run on November 8, 2012. All clinical studies published in English that investigated enamel acid pretreatment methods on human permanent teeth were included. Additional publications were obtained from the reference lists of the included studies. The clinical evidence of all included studies was tabulated. Initially, 4543 publications were retrieved from the databases. A total of 4508 articles were excluded, including 2285 duplicates, 1805 publications according to exclusion criteria by their titles and abstracts, 368 laboratory articles, 49 reviews, and 1 pilot study. Only 1 study was added from reference lists of the included studies. Finally, 36 clinical publications were included. The included clinical studies provided different levels of clinical evidence on the efficacy of acid-etching protocols to enable successful enamel adhesion. Clinical protocols of enamel acid etching differ from the laboratory-generated doctrine, which may imply that maximization of the Type 1 and/or Type 2 etch pattern is not important in the clinical acid etching of human enamel.

Comparison of shear bond strength of composite resin to enamel surface with laser etching versus acid etching: An in vitro evaluation.

Introduction:The aim of the study is in vitro evaluation of the shear bond strength of composite resin bonded to enamel which is pretreated using acid etchant and Er,Cr:Ysgg.Materials and Methods:40 extracted human teeth were divided in two groups of 20 each (Groups A and B). In Group A, prepared surface of enamel was etched using 37% phosphoric acid (Scotchbond, 3M). In Group B, enamel was surface treated by a an Er, Cr: YSGG laser system (Waterlase MD, Biolase Technology Inc., San Clemente, CA, USA) operating at a wavelength of 2,780 nm and having a pulse duration of 140-200 microsecond with a repetition rate of 20 Hz and 40 Hz. Bonding agent ((Scotchbond Multipurpose, 3M) was applied over the test areas on 20 samples of Groups A and B each, and light cured. Composite resin (Ceram X duo Nanoceramic restorative, Densply) was applied onto the test areas as a 3 × 3 mm diameter bid, and light cured. The samples were tested for shear bond strength.Results:Mean shear bond strength for acid-etched enamel (26.41 ± 0.66MPa, range 25.155 to 27.150 MPa) was significantly higher (P < 0.01) than for laser-etched enamel (16.23 ± 0.71MPa, range 15.233 to 17.334 MPa).Conclusions:For enamel surface, mean shear bond strength of bonded composite obtained after laser etching were significantly lower than those obtained after acid etching.

Effect of adhesive application on the shear bond strength of refrigerated and pre-heated of different composite resins to orthodontic molar tubes

Objective: To evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic tubes to acid-etched human enamel using different temperatures and orthodontic composite resins. Methods: One hundred and twenty metal tubes were bonded to human third molars, which were randomly divided into three groups depending on the composite used: Transbond XT (XT); Transbond Supreme LV (LV); and Light Bond (LB). Each group was divided into four subgroups depending on the temperature (5°, 20°, 40°, and 60°) applied to the composite before cementing. For each experimental subgroup, half the specimens were bonded in combination with XT Primer. After 72 h, a SBS test was performed using a universal testing machine. Statistical analysis was performed using ANOVA, post hoc intergroup comparisons, chi-square test, and linear regression. Two representative molar surfaces from each subgroup were assessed under Scanning electron microscope. Results: The composite type only influenced XT regarding LB. The use of adhesive does not affect the SBS values of any composite. The flowable composites with adhesive containing zirconia (LV) as a filler showed lower SBS when cooled to 5 °C and when increases the temperature from 40 °C. Whether adhesive was used or not, composites with silica as filler (LB) showed lower SBS at 60 °C and increased to 5 °C. Conclusions: For all composites, from 20 °C, SBS values tend to increased and started to decline at 40°C except when adhesive is applied to the quartz-filled composite, which continues to increase, and the silica-filled composite without adhesive, which tend to decreases from 5 °C.

Self-etch bonding agent beneath sealant: Bond strength for laser-irradiated enamel.

Objectives:This study evaluated the in vitro shear bond strength (SBS) of a resin-based pit-and-fissure sealant (Fluroshield [F], Dentsply/Caulk) associated with either an etch-and-rinse (Adper Single Bond 2 [SB], 3M/ESPE) or a two-step self-etch adhesive system (Adper SE Plus [SE], 3M/ESPE) on Er: YAG laser-irradiated enamel.Materials and Methods:Seventeen sound third molar crowns were embedded in acrylic resin, and the mesial–distal enamel surfaces were flattened. The enamel sites were irradiated with a 2.94-μm wavelength Er: YAG laser (120 mJ, 4 Hz, noncontact mode/17 mm, 20 s). The specimens were randomly assigned to three groups according to the bonding technique: I - 37% phosphoric acid etching + SB + F; II - SE + F and III - F applied to acid-etched enamel, without an intermediate layer of bonding agent. In all of the groups, a 3-mm diameter enamel-bonding site was demarcated and the sealant cylinders were bonded. After 24 hours in distilled water, the shear bond strength was tested at a crosshead speed of 0.5 mm/minute. The data were analyzed by one-way ANOVA and Tukey's test. The debonded specimens were examined with a stereomicroscope to assess the failure modes.Results:The mean SBS values in MPa were I = 6.39 (±1.44); II = 9.50 (±2.79); and III = 5.26 (±1.82). No statistically significant differences were observed between groups I and III; SE/F presented a significantly higher SBS than that of the other groups (P = 0.001). With regard to the failure mode, groups I (65%) and II (75%) presented adhesive failures, while group III showed 50% adhesive failure. Cohesive failure did not occur.Conclusion:The application of the two-step self-etch bonding agent (Adper SE Plus) beneath the resin pit-and-fissure sealant placement resulted in a significantly higher bond strength for the Er:YAG laser-irradiated enamel.

Tricalcium silicate induces enamel remineralization in human saliva

Background/purposeSevere tooth demineralization by production of acid leads to dental caries. In this study, we investigate the repairing effect of tricalcium silicate (Ca3SiO4) ceramics on acid-etched enamel in natural human saliva. Materials and methodsThe demineralization of enamel discs was simulated with citric acid, and they were then brushed with Ca3SiO4 paste. The treated discs were placed in human saliva for 1 day or 3 days at 36.5°C, and then the surface morphologies and structures were observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). ResultsCa3SiO4 ceramics can induce enamel remineralization in human saliva and form a compact Ca–P mineralized layer onto the etched enamel surface. After soaking for 1 day, the thickness was 200–250 nm and the interface bonded well. The chemical components and structure of the mineralized layer were similar to those of the enamel matrix. After soaking for 3 days, the surface roughness of the enamel surface became lower. ConclusionThe bioactive Ca3SiO4 repaired the acid-etched enamel successfully and protected the demineralized teeth.

The contribution of chemical bonding to the short- and long-term enamel bond strengths

ObjectivesMDP (10-methacryloyloxydecyl dihydrogenphosphate) has been proven to possess chemical bonding ability to tooth hard tissues, but its contribution to the enamel bond strength has not been recognized. The aim of this study was to investigate the contribution of chemical bonding to the short- and long-term bovine enamel micro-tensile bond strengths (μTBS). MethodsThe acid-etched enamel surfaces were treated without any primer (control) or with one of three MDP-containing primers (containing different ratio of MDP/HEMA/Bis-GMA, Kuraray Co.) for 5s, water-sprayed and air-dried. Subsequently, the pretreated enamel surfaces were applied with an etch-and-rinse adhesive Durafill Bond (Heraeus Kulzer) and placed with composite resin Durafill VS (Heraeus Kulzer). The specimens were prepared for μTBS tests after 24-h or 1-yr water storage. The etched enamel surfaces treated with or without MDP-containing primers were analyzed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). ResultsThe acid-etched enamel treated with the MDP-primers for a very short time could produce the greater enamel μTBS than the control did (p<0.05), and change enamel micromorphology. No significant different μTBS were found between 24-h and 1-yr water storage (p>0.05). The chemical bonding of MDP on the enamel surfaces was re-confirmed by XPS. SignificanceThe additional chemical bonding of MDP around the enamel crystallites of the etched enamel substrate could significantly increase the short- and long-term enamel μTBS, and their μTBS surpass those of the etch-and-rinse adhesive alone.

Hydroxyapatite-anchored dendrimer for in situ remineralization of human tooth enamel

In situ remineralization of hydroxyapatite (HA) on human tooth enamel surface induced by organic matrices is of great interest in the fields of material science and stomatology. In order to mimic the organic matrices induced biomineralization process in developing enamel and enhance the binding strength at the remineralization interface, carboxyl-terminated poly(amido amine) (PAMAM–COOH)—alendronate (ALN) conjugate (ALN–PAMAM–COOH) was synthesized and characterized. PAMAM–COOH has a highly ordered architecture and is capable of promoting the HA crystallization process. ALN is conjugated on PAMAM–COOH due to its specific adsorption on HA (the main component of tooth enamel), resulting in increased binding strength which is tight enough to resist phosphate buffered saline (PBS) rinsing as compared with that of PAMAM–COOH alone. While incubated in artificial saliva, ALN–PAMAM–COOH could induce in situ remineralization of HA on acid-etched enamel, and the regenerated HA has the nanorod-like crystal structure similar to that of human tooth enamel. The hardness of acid-etched enamel samples treated by ALN–PAMAM–COOH can recover up to 95.5% of the original value with strong adhesion force. In vivo experiment also demonstrates that ALN–PAMAM–COOH is effective in repairing acid-etched enamel in the oral cavity. Overall, these results suggest that ALN–PAMAM–COOH is highly promising as a restorative biomaterial for in situ remineralization of human tooth enamel.

Effect of adhesive application on the shear bond strength of flowable composite resins and APC plus to orthodontic molar tubes

Objectives: To evaluate the effect of adhesive application on the shear bond strength (SBS) of orthodontic tubes to acid-etched human enamel when using different flowable composite resins and the APC Plus system (APC). Study design: One hundred metal tubes were bonded to human third molars, which were randomly divided into five groups: Tetric EvoFlow (TF); Wave mv Flow (W); Transbond Supreme LV (S); Transbond XT (XT); and APC. For each experimental group, half of the specimens were bonded in combination with Transbond XT adhesive. After 72 h, an SBS test was performed using a universal testing machine. Two-way analysis of variance (ANOVA) was run for multiple comparison tests and for comparing the mean SBS among the 10 subgroups to evaluate the effect of both the composite and the adhesive factors. Then, a Student-Newman-Keuls test was used for pairwise comparisons using the highest mean SBS group as reference. Adhesive Remnant Index scores were determined for the teeth after failure and compared by χ 2-test. Two representative molar surfaces from the 10 subgroups were assessed under scanning electron microscope. Results: The application of adhesive did not have a significant effect, but there was a marked tendency toward the influence of the factor composite on SBS. The mean SBS of tubes bonded with XT with adhesive was significantly higher than that of those bonded with APC with adhesive, TF with and without adhesive, and S with adhesive. Conclusion: Flowable composites and the APC system without intermediate bonding resin could be conveniently applied for orthodontic tube bonding.

Reconsidering the Double Etching of Enamel: Do Self-etching Primers Contaminate Phosphoric Acid-etched Enamel?

To evaluate the composite-to-enamel bond following double etching of the enamel using phosphoric acid and different self-etching (SE) bonding systems with and without the application of their respective acidic primers. The enamel surfaces of 90 human molars were ground (600 grit) flat and randomly divided into nine groups (n = 10). Three two-step SE systems (AdheSE, ASE; Clearfil SE Bond, CSE; OptiBond Solo Plus SE, OSE) were tested, both with and without primer application on enamel pre-etched with phosphoric acid under dry bonding conditions. As the controls, the SE systems were applied according to their original directions without pre-etching. All the specimens were built up with a microhybrid composite resin (Arabesk Top). After water storage for 24 h at 37°C, the bonded specimens were sheared to failure in the Zwicki 1120. Etching and failure patterns were evaluated using a scanning electron microscope (SEM). Shear bond strength was analyzed with two-way ANOVA and Tukey's test. Failure modes were analyzed with Fisher's exact test. Without pre-etching, CSE showed significantly higher bond strengths than ASE and OSE (p < 0.05). Enamel etching prior to the application of the SE systems tended to result in higher bond strengths, but significantly increased the values only for ASE (p < 0.05). Contamination of the pre-etched enamel with the SE primer decreased the bond strength by values of 19% for ASE (p > 0.05), 36% for CSE (p < 0.05), and 75% for OSE (p < 0.05). SEM analysis showed that omission of the priming step significantly increased the number of cohesive failures within the resin for OSE (p < 0.0001). Additional etching with phosphoric acid before the application of SE systems does not necessarily result in better enamel bonding, since unavoidable primer contamination of the pre-etched enamel was shown to significantly reduce the bond strength for two of the three systems tested.

Effect of ethanol-wet-bonding technique on resin–enamel bonds

Background/purposeIt was reported that more stable resin--dentin bonds were achieved by using ethanol-wet bonding. Because it would be difficult to saturate acid-etched dentin with ethanol without saturation enamel, the study was conducted to evaluate the microtensile bond strength (μTBS) of adhesive resins bonded to enamel using water- and ethanol-wet-bonding techniques. Materials and methodsFlat enamel surfaces from extracted bovine incisor teeth were conditioned with 37% H3PO4 (for 15 seconds) before bonding. Two commercial adhesives (Single Bond 2 and All Bond 3) were applied to enamel using water- and ethanol-wet-bonding techniques (for 1 minute) as follows: group I, Single Bond 2 and water-wet bonding; group II, All Bond 3 and water-wet bonding; group III, Single Bond 2 and ethanol-wet-bonding; and group IV, All Bond 3 and ethanol-wet-bonding. Resin-bonded teeth were stored in distilled water (for 24 hours) and sectioned in beams for μTBS testing. μTBS results were analyzed by a two-way ANOVA and LSD test. The resin–enamel interfaces were examined by SEM. ResultsThe following mean μTBS values were obtained: 17.4 MPa for group I, 26.4 MPa for group II, 28.7 MPa for group III, and 31 MPa for group IV. For both adhesives, the obtained adhesive-enamel μTBS values with the ethanol-wet-bonding technique were significantly higher than those of the water-wet-bonding technique (P < 0.05). ConclusionThe ethanol-wet-bonding technique may increase the bond strength of commercial adhesives to enamel. The chemical composition of the adhesives can affect the bond strength of adhesives when bonding to acid-etched enamel, using the ethanol-wet-bonding technique. Some adhesive systems used in the present study may simultaneously be applied to enamel and dentin using ethanol-wet-bonding. Furthermore, deploying ethanol-wet-bonding for the tested commercial adhesives to enamel can increase the adhesion abilities of these adhesives to enamel.

Assessment of Microleakage of Class V Composite Resin Restoration Following Erbium-Doped Yttrium Aluminum Garnet (Er:YAG) Laser Conditioning and Acid Etching with Two Different Bonding Systems.

The use of laser for cavity preparation or conditioning of dentin and enamelsurfaces as an alternative for dental tissue acid-etch have increased in recent years. Theaim of this in vitro study was to compare microleakage at enamel-composite and dentincompositeinterfaces following Erbium-Doped Yttrium Aluminum Garnet(Er:YAG) laserconditioning or acid-etching of enamel and dentin, hybridized with different bonding systems. Class V cavities were prepared on the lingual and buccal surfaces of 50 recentlyextracted intact human posterior teeth with occlusal margin in the enamel and gingival marginin the dentin. The cavities were randomly assigned to five groups: group1:conditioned withlaser (Energy=120mJ, Frequency=10Hz, Pulse duration=100μs for Enamel and Energy=80mJ,Frequency=10Hz, Pulse duration=100μs for Dentin) + Optibond FL, group2:conditioned withlaser + etching with 35% phosphoric acid + Optibond FL, group3:conditioned with laser+ Clearfil SE Bond, group 4 (control):acid etched with 35% phosphoric acid + OptibondFL, group 5 (control): Clearfil SE Bond. All cavities were restored using Point 4 compositeresin. All samples were stored in distilled water at 37°c for 24 h, then were thermocycled for500 cycles and immersed in 50% silver nitrate solution for 24 h. The teeth were sectionedbucco-lingually to evaluate the dye penetration. Kruskal-Wallis & Mann-Whitney testswere used for statistical analysis. In occlusal margins, the least microleakage showed in groups 2, 4 and 5. Themaximum microleakage was observed in group 3 (P=0.009). In gingival margins, the leastmicroleakage was recorded in group2, while the most microleakage was found in group5 (P=0.001). Differences between 5 study groups were statistically significant (P<0.05).The microleakage scores were higher at the gingival margins. The use of the Er:YAG laser for conditioning with different dentin adhesivesystems influenced the marginal sealing of composite resin restorations.

Influence of enamel acid etching on mechanical properties after thermo-mechanical aging

Influence of enamel acid etching on mechanical properties after thermo-mechanical aging

Er:YAG Laser-Roughened Enamel Promotes Osteoblastic Differentiation

The aim of this study was to test whether Er:YAG laser-etched enamel of human teeth could act as a biologically active scaffold for tissue regeneration. Hydroxylapatite (HA) with rough surface created by acid etching treatment has been used as a scaffold for tissue engineering. However, whether tooth HA can be a scaffold for osteoblastic cell seeding is still unclear. Enamel samples from human teeth were pretreated with an Er:YAG laser to create a rough surface. Then the surface of the laser-treated enamel was examined using a surface roughness profilometer and a scanning electron microscope. In addition, static water contact angles of the Er:YAG laser-treated enamel samples were measured using goniometry. To observe the effects of cell behavior on an Er:YAG laser-roughened enamel surface, we cultured MG63 osteoblast-like cells on the surface-modified enamel samples. Alkaline phosphatase activity, a marker of cell proliferation and differentiation, was monitored and compared with that in untreated control and acid-etched enamel samples. Er:YAG laser treatment significantly improved the surface roughness of the enamel samples. Furthermore, MG63 osteoblast-like cells cultured on the Er:YAG laser-roughened enamel surface expressed more alkaline phosphatase activity and exhibited greater degrees of cellular differentiation than did cells that had been cultured on untreated enamel samples. These results demonstrate that Er:YAG laser-roughened enamel promotes osteoblastic differentiation. This finding suggests that Er:YAG laser-roughened enamel surfaces can potentially serve as a scaffold for tissue engineering.

Clinical effectiveness of direct class II restorations - a meta-analysis.

More than five hundred million direct dental restorations are placed each year worldwide. In about 55% of the cases, resin composites or compomers are used, and in 45% amalgam. The longevity of posterior resin restorations is well documented. However, data on resin composites that are placed without enamel/dentin conditioning and resin composites placed with self-etching adhesive systems are missing. The database SCOPUS was searched for clinical trials on posterior resin composites without restricting the search to the year of publication. The inclusion criteria were: (1) prospective clinical trial with at least 2 years of observation; (2) minimum number of restorations at last recall = 20; (3) report on dropout rate; (4) report of operative technique and materials used; (5) utilization of Ryge or modified Ryge evaluation criteria. For amalgam, only those studies were included that directly compared composite resin restorations with amalgam. For the statistical analysis, a linear mixed model was used with random effects to account for the heterogeneity between the studies. P-values under 0.05 were considered significant. Of the 373 clinical trials, 59 studies met the inclusion criteria. In 70% of the studies, Class II and Class I restorations had been placed. The overall success rate of composite resin restorations was about 90% after 10 years, which was not different from that of amalgam. Restorations with compomers had a significantly lower longevity. The main reason for replacement were bulk fractures and caries adjacent to restorations. Both of these incidents were infrequent in most studies and accounted only for about 6% of all replaced restorations after 10 years. Restorations with macrofilled composites and compomer suffered significantly more loss of anatomical form than restorations with other types of material. Restorations that were placed without enamel acid etching and a dentin bonding agent showed significantly more marginal staining and detectable margins compared to those restorations placed using the enamel-etch or etch-and-rinse technique; restorations with self-etching systems were between the other groups. Restorations with compomer suffered significantly more chippings (repairable fracture) than restorations with other materials, which did not statistically differ among each other. Restorations that were placed with a rubber-dam showed significantly fewer material fractures that needed replacement, and this also had a significant effect on the overall longevity. Restorations with hybrid and microfilled composites that were placed with the enamel-etching technique and rubber-dam showed the best overall performance; the longevity of these restorations was similar to amalgam restorations. Compomer restorations, restorations placed with macrofilled composites, and resin restorations with no-etching or self-etching adhesives demonstrated significant shortcomings and shorter longevity.

Four-year clinical evaluation of a self-adhesive luting agent for ceramic inlays

The aim of this randomized controlled clinical trial was to evaluate the 4-year clinical performance of a self-adhesive resin cement, RelyX Unicem (3M ESPE), used for cementation of ceramic inlays. In addition, the influence of selectively acid-etching enamel prior to luting on the clinical performance of the restorations was assessed. Sixty-two IPS Empress 2 inlays/onlays were placed in 31 patients by two experienced clinicians. The restorations were luted with RelyX Unicem with (=experimental group: E) or without (=control group: NE) prior enamel etching with phosphoric acid. At baseline, 6 months, and 1, 2, and 4 years after placement, the restorations were assessed by two calibrated investigators using modified USPHS criteria. Ten selected samples of each group were investigated under SEM regarding morphological changes at the cement-inlay interface. The recall rate at 4 years was 97%. Two restorations (1 E, 1 NE) were lost, and one (E) had to be replaced due to inlay and tooth fracture resulting in a survival rate of 95%. No significant differences between the experimental and control group were noticed regarding all criteria (McNemar, p < 0.05). An obvious deterioration in marginal integrity was observed after 4 years as only 5% (E = 7%; NE = 3%) of the restorations exhibited an excellent marginal adaptation. In 90% of the restorations small, still clinically acceptable marginal deficiencies were observed. SEM of the luting gap showed an increased wear of the RelyX Unicem cement over the 4-year period. The self-adhesive luting cement RelyX Unicem can be recommended for bonding of ceramic inlays/onlays. Additional selective enamel etching does not improve the clinical performance of the restorations within the 4-year period. The self-adhesive resin composite RelyX Unicem showed acceptable clinical performance after 4 years of clinical service.