SEM analysis of the acid-etched enamel patterns promoted by acidic monomers and phosphoric acids

Effect of multi-layer applications of self-etch universal bonding agents on the adhesion of resin composite to enamel

To evaluate the effect of adhesive coats application on the enamel microtensile bond strength (µTBS) of universal adhesives, morphological etching pattern and their chemical interaction with hydroxyapatite (HA). Two universal adhesives were investigated: Scotchbond Universal (SBU, 3 M) and Prime&Bond Universal (PBU, Dentsply). The adhesives were applied in self-etching mode on bovine enamel (n = 8) in one (1L), two (2L) or three coats (3L) and light-cured as per manufacturers' instructions. As controls adhesives were applied to etched enamel (H3PO4-37% phosphoric acid). Bonded specimens were cut into sticks that were stored in deionized water for 24 h or 6 months prior to µTBS testing. Two-way ANOVA and Tukey's test were used for statistical analysis of bond strength with α = 5%. For morphological SEM analysis, enamel surfaces were treated as aforementioned and immediately rinsed with acetone. The intensity of monomer-calcium salt formation from each treatment was measured via infrared spectroscopy (ATR-FTIR). All treatments presented no significant reduction on µTBS after aging (p > 0.05). However, SBU attained highest µTBS when applied in 3L. PBU showed higher µTBS when applied to H3PO4 etched enamel than 1L or 2L. Etching pattern was enhanced by 3L application, particularly with PBU. Chemical interaction was notably higher for SBU than PBU, with no relevant differences with more layers or prior H3PO4-etching. The application of three adhesive coats of universal adhesives in self-etch mode using may enhance the bonding performance and etching pattern to enamel, surpassing the H3PO4-etched enamel bond for SBU. The chemical interaction with calcium from enamel is not affected by number of coats or prior phosphoric acid etching.

Evaluation of developmentally hypomineralised enamel after surface pretreatment with Papacarie Duo gel and different etching modes: an in vitro SEM and AFM study

PURPOSE

This study aimed at investigating the surface morphology and nanotopography of normal enamel (NE) and developmentally hypomineralised enamel (HE) when subjected to various pretreatment protocols under scanning electron microscopy (SEM) and atomic force microscopy (AFM).

METHODS

Sixteen NE, 16 creamy/white (CW) HE and 16 yellow/brown (YB) HE specimens sectioned from extracted hypomineralised first permanent molars (FPMs) were included in this study. They were randomly distributed into 12 experimental groups (n = 4). Each group involved the following: (1) deproteinisation with Papacarie Duo^® gel or no deproteinisation, and (2) the use of Scotchbond™ Universal Adhesive (Scotchbond) in self-etch (SE) mode or 37% phosphoric acid etchant. Subsequently, the surface morphology and nanotopography of pretreated enamel specimens were evaluated under SEM and AFM, respectively.

RESULTS

SEM observation showed that deproteinisation with Papacarie Duo^® gel before phosphoric acid etching led to favourable etching patterns. This was consistent across all groups irrespective of the type of enamel specimen and the severity of hypomineralisation. In contrast, AFM results identified three factors that influenced surface parameters: (1) type of enamel specimen, (2) severity of hypomineralisation and (3) etching mode. YB HE recorded higher surface roughness values than CW HE and NE when subjected to the same pretreatment protocol. Deproteinisation and the application of Scotchbond in SE mode led to minimal topographic changes; however, acid etching was associated with an increase in surface roughness.

CONCLUSION

Deproteinisation with Papacarie Duo^® gel followed by acid etching contributed to improved etching patterns on HE.

Subsurface enamel remineralization by Lyophilized Moringa leaf extract loaded varnish

OBJECTIVE

The objective of this study was to investigate enamel remineralization using lyophilized extract from Moringa Oleifera Leaves (MOL).

MATERIALS AND METHODS

A total of seventy-five teeth were selected and randomly divided into 5 equal groups (n = 15). All teeth were air dried for 30 s, two windows (right and left) were drawn on the labial surface of each tooth. The right window was set as the control and no etching or treatment was performed. The left window was etched for 30 s for all five groups. After etching, group I received no treatment, group II received plain varnish, group III received fluoride varnish, and finally groups IV and V received plain varnish loaded with 50 mg/ml and 200 mg/ml of lyophilized MOL extract respectively. All samples were then immersed in artificial saliva for 14 days. The specimens were examined under scanning electron microscope (SEM) and energy dispersive x-ray (EDX).

RESULTS

SEM micrographs revealed that MOL extract loaded-varnish groups IV & V showed the most re-establishment of normal enamel architecture. Elemental analysis of the treated surfaces of Groups IV and V showed the surfaces treated by MOL loaded-varnish groups had significantly higher Ca, P, and O deposition than the fluoride varnish group.

CONCLUSION

MOL might be considered as a biomimetic material capable of guiding enamel tissue remineralization.

Microleakage of a Self-Adhesive Flowable Composite, a Self-Adhesive Fissure Sealant and a Conventional Fissure Sealant in Permanent Teeth with/without Saliva Contamination

Objectives:

Application of fissure sealants is a practical method for prevention of occlusal pit and fissure caries. Microleakage is an important factor affecting the success of fissure sealant treatment. This study aimed to assess the microleakage of a self-adhesive flowable composite, a self-adhesive fissure sealant and a conventional fissure sealant in permanent teeth with/without saliva contamination.

Materials and Methods:

This in vitro, experimental study evaluated 108 extracted human third molars, which were randomly divided into six groups (n=18) of control, Denu-Seal conventional fissure sealant applied on etched enamel with/without saliva contamination, Vertise Flow self-adhesive flowable composite applied on rinsed and dried enamel with/without saliva contamination and Prevent Seal self-adhesive fissure sealant applied on rinsed and dried enamel with/without saliva contamination. Microleakage was assessed using the dye penetration technique and subsequent observation of samples under a stereomicroscope. Data were analyzed using the Kruskal-Wallis and Tukey’s test.

Results:

Microleakage of the conventional fissure sealant with/without saliva contamination was significantly lower than that of other groups (P<0.05).

Conclusion:

Microleakage of the conventional fissure sealant is less than that of self-adhesive fissure sealant and self-adhesive composite, irrespective of saliva contamination.

Surface roughness and filler particles characterization of resin-based composites

The purpose of this study was to evaluate the surface roughness (Ra), and the morphology and composition of filler particles of different composites submitted to toothbrushing and water storage. Disc-shaped specimens (15 mm × 2 mm) were made from five composites: two conventional (Z100™, and Filtek™ Supreme Ultra Universal, 3M), one "quick-cure" (Estelite ∑ Quick, Tokuyama), one fluoride-releasing (Beautiful II, Shofu), and one self-adhering (Vertise Flow, Kerr) composite. Samples were finished/polished using aluminum oxide discs (Sof-Lex, 3M), and their surfaces were analyzed by profilometry (n = 5) and scanning electron microscopy (SEM; n = 3) at 1 week and after 30,000 toothbrushing cycles and 6-month water storage. Ra data were analyzed by two-way analysis of variance and Tukey's test (α = 0.05). Filler particles morphology and composition were analyzed by SEM and X-ray dispersive energy spectroscopy, respectively. Finishing/polishing resulted in similar Ra for all the composites, while toothbrushing and water storage increased the Ra of all the tested materials, also changing their surface morphology. Beautifil II and Vertise Flow presented the highest Ra after toothbrushing and water storage. Filler particles were mainly composed of silicon, zirconium, aluminum, barium, and ytterbium. Size and morphology of fillers, and composition of the tested composites influenced their Ra when samples were submitted to toothbrushing and water storage.

Clinical evaluation of a surface pre-reacted glass (S-PRG) filler-containing dental sealant placed with a self-etching primer/adhesive

AIMS

To clinically evaluate the retention rates and caries-prevention effect of a resin-based, non-etch and rinse, self-etch primed pit and fissure sealant containing Sealant Pre-reacted Glass Ionomer Cement (S-PRG) fillers, in comparison to a conventional resin-based sealant over an 18-month period.

METHODS

There were 81 children, aged 6-12 years old, who were randomly assigned to one of two sealant-groups, either the self-etch primed sealant (Beautisealant, Shofu) or the conventional etch and rinse sealant (Seal it, Spident). A total of 218 sealants of both groups were placed on first permanent molars with either sound surfaces (The International Caries Detection and Assessment System [ICDAS], code 0) or incipient enamel caries lesions (ICDAS code 1) according to the manufacturers' instructions. Each sealant restoration was independently evaluated in terms of retention and caries status at 6, 12 and 18 months. The data were statistically analysed with the Chi-squared test and z-test and the level of significance was preset at α = 0.05.

RESULTS

The differences between the complete retention rates of the two sealant groups were statistically significant in all periods of evaluation (p < 0.01). Survival rates of each sealant-group were comparable on sound (ICDAS 0) and enamel caries lesions (ICDAS1). Caries prevention effect of the two sealant groups was similar at the end of the evaluation period.

CONCLUSIONS

The clinical performance of the S-PRG filler-containing dental sealant placed with a self-etching primer was poor regarding its retention. Its significantly higher loss did not lead to more carious occlusal surfaces at the 18-month recall.

Effect of carbonated water manufactured by a soda carbonator on etched or sealed enamel

Objective

The purpose of this study was to determine the effects of carbonated water on etched or sealed enamel according to the carbonation level and the presence of calcium ions.

Methods

Carbonated water with different carbonation levels was manufactured by a soda carbonator. Seventy-five premolar teeth were randomly divided into a control group and 4 experimental groups in accordance with the carbonation level and the presence of calcium ions in the test solutions. After specimen preparation of the Unexposed, Etched, and Sealed enamel subgroups, all the specimens were submerged in each test solution for 15 minutes three times a day during 7 days. Microhardness tests on the Unexposed and Etched enamel subgroups were performed with 10 specimens from each group. Scanning electron microscopy (SEM) tests on the Unexposed, Etched, and Sealed enamel subgroups were performed with 5 specimens from each group. Microhardness changes in different groups were statistically compared using paired t-tests, the Wilcoxon signed rank test, and the Kruskal-Wallis test.

Results

The microhardness changes were significantly different between the groups (p = 0.000). The microhardness changes in all experimental groups except Group 3 (low-level carbonated water with calcium ions) were significantly greater than those in the Control group. SEM showed that etched areas of the specimen were affected by carbonated water and the magnitude of destruction varied between groups. Adhesive material was partially removed in groups exposed to carbonated water.

Conclusions

Carbonated water has negative effects on etched or sealed enamel, resulting in decreased microhardness and removal of the adhesive material.

Effect of Removal of Enamel on Rebonding Strength of Resin Composite to Enamel

Objective. To examine the effect of removing the surface layer of enamel on the rebonding strength of resin composite. Methods. Teeth in four groups (n = 10) were etched, a small amount of resin composite was bonded and debonded, then specimens in three groups were ground for different lengths of time (10 s, 20 s, 30 s) to remove an increasing amount of enamel, one group was left untouched. The teeth were bonded again and the bond strengths of 1st and 2nd bonding were compared and analysed against the amount of enamel loss in different groups (7 µm (±2); 12 µm (±1); 16 µm (±3)). Specimens were examined with SEM and by noncontacting optical profilometer. Results. Although results indicated higher rebonding strength with increasing enamel removal ANOVA showed low statistical differences between the groups (p > 0.05). However, values between first bonding and rebonding strengths differed significantly (p < 0.05) in the group that was not ground. SEM revealed that enamel-surfaces that were ground after debonding etched well, compared to the surfaces that still contained adhesive remnants. Conclusions. Removal of small amount of enamel refreshed the surface for rebonding. Rebonding strengths without grinding the surface before bonding were lower than bond strength to intact enamel.

Self-Etch Adhesive Systems: A Literature Review

This paper presents the state of the art of self-etch adhesive systems. Four topics are shown in this review and included: the historic of this category of bonding agents, bonding mechanism, characteristics/properties and the formation of acid-base resistant zone at enamel/dentin-adhesive interfaces. Also, advantages regarding etch-and-rinse systems and classifications of self-etch adhesive systems according to the number of steps and acidity are addressed. Finally, issues like the potential durability and clinical importance are discussed. Self-etch adhesive systems are promising materials because they are easy to use, bond chemically to tooth structure and maintain the dentin hydroxyapatite, which is important for the durability of the bonding.

A 48-month Clinical Evaluation of Fissure Sealants Placed With Different Adhesive Systems

Aim

To compare the retention rates of a nanofilled occlusal fissure sealant placed with the use of an etch-and-rinse or a self-etch adhesive over 48 months.

Materials and Methods

The authors enrolled 244 teeth, each with no restoration or sealant and no detectable caries, from 16 patients. The sealants were placed with Solobond M two-step etch-and-rinse adhesive or Futurabond NR one-step self-etch adhesive by four previously calibrated dentists using a table of random numbers. After completion of the adhesive application, a nanofilled sealant, Grandio Seal, was applied and light-cured. Two other calibrated examiners, who were unaware of which adhesive had been used, independently evaluated the sealants at baseline and at 12-, 24-, 36-, and 48-month recalls. Each sealant was evaluated in terms of caries formation being present or absent and retention using the following criteria: 1 = completely retained, 2 = partial loss, and 3 = total loss. The Pearson χ2 test was used to evaluate differences in retention rates among the sealants used with different adhesives for each evaluation period.

Results

The retention rates for sealants in the Solobond M group were significantly higher than those in the Futurabond NR group in all periods of evaluation (p&lt;0.05). No statistically significant difference between the retention rates for premolars and molars was found at each evaluation period (p&gt;0.05). There was no new caries formation throughout the 48-month recall period.

Conclusion

Fissure sealants placed with etch-and-rinse adhesive showed better retention rates than those placed with self-etch adhesive.

Fatigue of the resin-enamel bonded interface and the mechanisms of failure

The durability of adhesive bonds to enamel and dentin and the mechanisms of degradation caused by cyclic loading are important to the survival of composite restorations. In this study a novel method of evaluation was used to determine the strength of resin-enamel bonded interfaces under oth static and cyclic loading, and to identify the mechanisms of failure. Specimens with twin interfaces of enamel bonded to commercial resin composite were loaded in monotonic and cyclic 4-point flexure to failure within a hydrated environment. Results for the resin-enamel interface were compared with those for the resin composite (control) and values reported for resin-dentin adhesive bonds. Under both modes of loading the strength of the resin-enamel interface was significantly (p≤0.0001) lower than that of the resin composite and the resin-dentin bonded interface. Fatigue failure of the interface occurred predominantly by fracture of enamel, adjacent to the interface, and not due to adhesive failures. In the absence of water aging or acid production of biofilms, the durability of adhesive bonds to enamel is lower than that achieved in dentin bonding.

Effects of buccal and lingual enamel sandblasting on shear bond strength of orthodontic brackets bonded with a self-etching primer

The purpose of this study was to evaluate the effects of sandblasting on the initial shear bond strength (SBS) and on the bracket/adhesive failure mode of orthodontic brackets bonded on buccal and lingual enamel using a self-etching primer (SEP). The brackets were bonded using a SEP and composite resin on the buccal and lingual surfaces of 30 premolars with intact enamel and 30 premolars pretreated by sandblasting with 50 μm aluminum-oxide. Student's paired t-test was used to compare the groups for differences in SBS and a multiple Chi(2) test was performed to compare the bond failure mode. It was shown that sandblasting increases significantly SBS of the SEP on the buccal surfaces but the increase on the lingual surfaces is not statistically significant. A comparison of the adhesive remnant index scores indicated that there was more residual adhesive remaining on the teeth that were treated by sandblasting than on the teeth with intact enamel. Besides, there is no statistical difference between SBS of the SEP on buccal and lingual surfaces with intact enamel. Therefore, we can conclude that sandblasting improves the bond between buccal and lingual enamel and resin ant that the SEP provides the same SBS on buccal and lingual intact surfaces.

Bond strength of one-step self-etch adhesives and their predecessors to ground versus unground enamel

OBJECTIVE

The aim of this study was to compare the shear bond strength of several self-etch adhesives to their two-step predecessors to ground and unground enamel.

METHODS

Seventy-five extracted, non-carious human third molar teeth were selected for this study. The buccal surfaces of each tooth were mechanically ground to obtain flat enamel surfaces (ground enamel), while the lingual surfaces were left intact (unground enamel). The teeth were randomly divided into five groups according to the adhesive systems (n=15): one-step self-etch adhesive - Clearfil S3 Bond, its two-step predecessor - Clearfil SE Bond, one-step self-etch adhesive - AdheSE One, and its two-step predecessor - AdheSE, and a two-step etch-and-rinse adhesive - Adper Single Bond 2(control). After application of the adhesives to the buccal and lingual enamel surfaces of each tooth, a cylindrical capsule filled with a hybrid composite resin (TPH) was seated against the surfaces. The specimens were stored in distilled water at 37°C for 24 hours, followed by thermocy-cling (5°C-55°C/500 cycles). They were subjected to shear bond strength test in a universal testing machine at a crosshead speed of 1.0 mm/minute. The data were compared using a two-way ANOVA, followed by Bonferroni test at P<.05.

RESULTS

All adhesives exhibited statistically similar bond strengths to ground and unground enamel except for the etch-and-rinse adhesive that showed significantly higher bond strengths than the self-etch adhesives (P<.05). No significant differences in bond strength values were observed between ground and unground enamel for any of the adhesives tested (P=.17).

CONCLUSION

Similar bond strengths to ground and unground enamel were achieved with one-step self-etch adhesives and their predecessors. Enamel preparation did not influence the bonding performance of the adhesives tested.

Identification of a protein-containing enamel matrix layer which bridges with the dentine-enamel junction of adult human teeth

OBJECTIVE

To investigate the ultrastructure and chemical composition of the dentine-enamel junction and adjacent enamel of minimally processed third molar tooth sections.

DESIGN

Undecalcified human third molar erupted teeth were sectioned and etched with 4% EDTA or 37% phosphoric acid prior to visualization by scanning electron microscopy. Confocal Raman spectroscopy was carried out at 50 μm and more than 400 μm away from the dentine-enamel junction before and after mild etching.

RESULTS

A novel organic protein-containing enamel matrix layer was identified for the first time using scanning electron microscopy of etched bucco-lingual sections of crowns. This layer resembles a three-dimensional fibrous meshwork that is visually distinct from enamel "tufts". Previous studies have generally used harsher solvent conditions which likely removed this layer and precluded its prior characterization. The shape of the organic enamel layer generally reflected that of sheath regions of enamel rods and extended from the dentine-enamel junction about 100-400 μm into the cuspal enamel. This layer exhibited a Raman CH stretching peak at ∼2931 cm(-1) characteristic of proteins and this signal correlated directly with the presence and location of the matrix layer as identified by scanning electron microscopy.

CONCLUSIONS

The enamel protein layer was most prominent close to the dentine-enamel junction and was largely absent in cuspal enamel >400 μm away from the dentine enamel junction. We hypothesize that this protein containing matrix layer could provide an important biomechanical linkage between the enamel and the dentine-enamel junction and by extension, with the dentine, of the adult tooth (246 words).

In Vitro Secondary Caries Inhibition by Adhesive Systems in Enamel Around Composite Restorations

The ability of the adhesive system to inhibit secondary caries was similar among the materials tested, according to the enamel mineral content around restorations.

Enamel susceptibility to red wine staining after 35% hydrogen peroxide bleaching

Concern has been expressed regarding the staining of enamel surface by different beverages after bleaching. This study investigated the influence of 35% hydrogen peroxide bleaching agents on enamel surface stained with wine after whitening treatments. Flat and polished bovine enamel surfaces were submitted to two commercially available 35% hydrogen peroxide bleaching agents or kept in 100% humidity, as a control group (n = 10). Specimens of all groups were immersed in red wine for 48 h at 37°C, immediately, 24 h or 1 week after treatments. All specimens were ground into powder and prepared for the spectrophotometric analysis. Data were subjected to two-way analysis of variance and Fisher's PLSD test at 5% significance level. The amount of wine pigments uptake by enamel submitted to bleaching treatments was statistically higher than that of control group, independently of the evaluation time. Results suggested that wine staining susceptibility was increased by bleaching treatments.

Clinical Evaluation of a Nanofilled Fissure Sealant Placed with Different Adhesive Systems: 24-month Results

The use of an etch-and-rinse adhesive prior to the placement of sealants yielded better retention than did the use of a self-etch adhesive.