Microtensile bond strength of lithium disilicate ceramics to resin adhesives

PURPOSE

To evaluate the influence of the internal structure of lithium disilicate glass ceramics (LDC) on the microtensile bond strength to a resin adhesive using two surface treatments.

MATERIALS AND METHODS

Milling blocks of three types of LDC were sectioned (4 mm thick) using a precision cutting machine: IPS Empress 2 (conventional LDC), IPSe.max CAD (a refined crystal high strength LDC), and Celtra (zirconia reinforced LDC). Cut specimens received crystallization heat treatment as suggested by the manufacturers. Two surface treatments were performed on each group: hydrofluoric acid etching (HF) and airborne particle abrasion using 50-μm glass beads, while the as-cut surface served as control. Treated surfaces were examined using scanning electron microscopy (SEM). The disks were coated with a silane primer and bonded to pre-aged resin composite disks (Tetric EvoCeram) using a resin adhesive (Variolink II) and then stored in water for 3 months. Bonded specimens were sectioned into micro-bars (1x1x6 mm) and microtensile bond strength test (MTBS) was performed. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (α=0.05).

RESULTS

Statistical analysis revealed significant differences in microtensile bond strength values between different LDCs (F=67, p<0.001), different surface treatments (F=232, p<0.001), and interaction between LDC and surface treatments (F=10.6, p<0.001). Microtensile bond strength of Celtra ceramic (30.4±4.6 MPa) was significantly higher than both IPS Empress 2 (21.5±5.9 MPa) and IPSe.max ceramics (25.8±4.8 MPa), which had almost comparable MTBS values. SEM images demonstrated homogenous glassy matrix and reinforcing zirconia fillers characteristic of Celtra ceramic. Heat treatment resulted in growth and maturation of lithium disilicate crystals. Particle abrasion resulted in abrasion of the glass matrix and exposure of lithium disilicate crystals, while HF etching produced a microrough surface, which resulted in higher MTBS values and reduction in the percentage of adhesive failure for all groups.

CONCLUSIONS

Within the limitations of this study, bond strength to lithium disilicate ceramics depends on proper surface treatment and on the chemical composition of the glass ceramic.

Self-adhesive resin cements: adhesive performance to indirect restorative ceramics

PURPOSE

To evaluate the bonding performance of self-adhesive resin cements to zirconia and lithium disilicate in self- and dual-curing modes before and after thermocycling.

MATERIALS AND METHODS

Rectangular bars (3 mm high, 3 mm wide, 9 mm long) were manufactured from zirconia (Vita In-Ceram YZ for inLab, VITA) and lithium disilicate blocks (IPS e.max Press, Ivoclar Vivadent) (n=240 per material). Zirconia bars were sandblasted (35 μm Al2O3, 1.5 bar pressure). Lithium disilicate bars were HF etched (20 s, IPS Ceramic Etching Gel, Ivoclar Vivadent) and silanized with ESPE Sil (3M ESPE). Forty bars of zirconia were luted in twos perpendicular to each other as were 40 bars of lithium disilicate using RelyX Unicem Automix 2 (3M ESPE), G-Cem LinkAce (GC Europe) or Maxcem Elite (Kerr) in self- or dual-curing mode. Half of the specimens from each material were submitted to tensile bond strength (TBS) testing after 24-h storage in distilled water at 37°C, and half underwent TBS testing after thermocycling (5000 cycles, 5°C/55°C, 30-s dwell time). Bond strength values for each bonding substrate were analyzed using one-way ANOVA (Student-Newman- Keuls, α=0.05).

RESULTS

On zirconia, dual-curing resulted in significantly (p<0.05) higher tensile bond strengths compared to self-curing, with the exception of RelyX Unicem 2 after thermocycling. Thermocycling significantly (p<0.05) reduced the tensile bond strength of Maxcem Elite to zirconia in both curing modes. The TBS of self-adhesive cements to lithium disilicate showed no significant (p>0.05) difference between the different curing modes and after thermocycling.

CONCLUSION

For most of the investigated self-adhesive cements, bond strengths to zirconia were increased by dual curing; this was not true for lithium disilicate. For luting on zirconia with self-adhesive cements, dual curing is strongly recommended in clinical situations.

Chlorhexidine does not improve but preserves bond strength to eroded dentin

PURPOSE

To evaluate the effect of aqueous solutions of chlorhexidine digluconate (CHX) in different concentrations on bond strength to eroded dentin up to 6 months, using normal dentin as a control.

METHODS

Exposed flat dentin of extracted third molars was only ground with 600-grit SiC paper/1 minute (normal dentin - N), or subsequently eroded by a regular-cola soft-drink (eroded dentin - E). N and E were acid-etched, washed, dried and rehydrated with 1.5 μL, respectively, of distillated water (control - NC / EC); of 0.004% CHX (N0.004% / E0.004%); or of 2% CHX (N2% / E2%). Adper Single Bond 2 was applied in all specimens and resin composite buildups were constructed with Filtek Z350. Specimens were sectioned in beams, which were tested (μTBS) immediately or after 6 months of aging.

RESULTS

Microtensile bond strength to eroded dentin was always significantly lower than that to normal dentin. Application of tested CHX solutions did not exert a significant effect immediately; however, after aging, the 2% CHX prevented abrupt bond strength loss both to eroded and normal dentin.

Resin-based pit-and-fissure sealants: microleakage reduction and infiltration enhancement using a bonding agent

PURPOSE

To evaluate the marginal microleakage and the infiltration ability of pit-and-fissure sealants by applying the conventional sealing technique in comparison to using an additional bonding agent.

MATERIALS AND METHODS

Extracted non-carious permanent molars (n = 60) were first stored in sterile saline solution and then assigned to one of two groups: group C (control) was sealed (Helioseal F) by using the conventional technique, while in group BA (bonding agent), a bonding agent (OptiBond FL) was additionally applied prior to sealing. The teeth were thermocycled (1000 cycles, 5°C to 55°C, dwell time 30 s), then varnished and immersed in 5% methylene blue solution for 24 h. After embedding and sectioning each tooth into 6-12 slices, the presence of microleakage, unfilled areas, and air bubbles trapped in the sealant were assessed with a stereomicroscope.

RESULTS

A higher proportion of microleakage was found under sealants applied without the additional use of the bonding agent. A statistically significant difference in microleakage was noted between the groups (p = 0.045). Regarding the presence of unfilled areas, a statistically significant difference between the groups was observed (p < 0.001), especially since no unfilled areas were found at all in the samples of the group using the bonding agent. Regarding the amount of air bubbles trapped in the sealant, no statistically significant difference was observed between the two groups (p = 0.829).

CONCLUSION

Under these in vitro conditions, sealant procedures using an additional bonding agent applied beforehand significantly improved fissure infiltration and microleakage prevention significantly.

Ethanol-wet bonding and chlorhexidine improve resin-dentin bond durability: quantitative analysis using raman spectroscopy

PURPOSE

To directly test the effectiveness of ethanol-wet bonding (EW) in improving monomer infiltration into demineralized dentin through quantitative measurement of bis-GMA and TEG-DMA molar concentrations within hybrid layers, and to comprehensively evaluate the effect of EW and chlorhexidine on durability of resin-dentin bonds compared to conventional water-wet bonding (WW).

MATERIALS AND METHODS

A three-step etch-and-rinse adhesive (70% bis-GMA/28.75%TEG-DMA) was applied to coronal dentin using a clinically relevant ethanol-wet bonding protocol (EW) or the conventional water-wet bonding (WW) technique. Bis-GMA and TEG-DMA molar concentrations at various positions across the resin/dentin interfaces formed by EW and WW were measured using micro-Raman spectroscopy. The experiment was repeated at the same positions after 7-month storage in phosphate buffer solution containing 0.1% sodium azide. The μTBS and hybrid layer morphology (TEM) of bonding groups with and without chlorhexidine application were compared immediately and after 1-year storage in terms of nanoleakage, collagen fibril diameter, collagen interfibrillar width, and hybrid layer thickness.

RESULTS

Specimens bonded with EW showed significantly higher monomer molar concentrations and μTBS throughout the hybrid layer immediately and after storage, providing direct evidence of superior infiltration of hydrophobic monomers in EW compared to WW. Microscopically, EW maintained interfibrillar width and hybrid layer thickness for resin infiltration and retention. The application of chlorhexidine further preserved collagen integrity and limited the degree of nanoleakage in EW after 1-year storage.

CONCLUSION

EW enhances infiltration of hydrophobic monomers into demineralized dentin. The results suggest that a more durable resin-dentin bond may be achieved with combined usage of a clinically relevant EW and chlorhexidine.

Effects of acid etching and adhesive treatments on host-derived cysteine cathepsin activity in dentin

PURPOSE

To analyze the effects of different processes during bonding on endogenous cysteine cathepsin activity in dentin.

MATERIALS AND METHODS

Dentin powder, prepared from extracted human third molars, was divided into 10 groups. Two lots of dentin powder were used to detect the effects of the procedure of protein extraction on endogenous cathepsin activity. The others were used to study effects of different acid-etching or adhesive treatments on enzyme activity. Concentrations of 37% phosphoric acid or 10% phosphoric acid, two etch-and-rinse adhesive systems, and two self-etching adhesive systems were used as dentin powder treatments. The untreated mineralized dentin powder was set as the control. After treatment, the proteins of each group were extracted. The total cathepsin activity in the extracts of each group was monitored with a fluorescence reader.

RESULTS

In the control group, there were no significant differences in cathepsin activity between the protein extract before EDTA treatment and the protein extract after EDTA treatment (p > 0.05). The cathepsin activities of the three different extracts in the 37% phosphoric acid-treated group were different from each other (p < 0.05). The two acid-etching groups and two etch-and-rinse groups showed significant enzyme activity reduction vs the control group (p < 0.05). There were no significant differences between those four groups (p > 0.05). Treating the dentin powder with any of the two self-etching adhesives resulted in an increase in cathepsin activity (p < 0.05).

CONCLUSIONS

The activity of cysteine cathepsins can be detected in dentin powder. Treatment with EDTA during protein extraction exerted an influence on cathepsin activity. Acid etching or etch-and-rinse adhesive systems may reduce the activity of endogenous cathepsins in dentin. Self-etching adhesive systems may increase the enzyme activity.

A feasible method to eliminate nanoleakage in dentin hybrid layers

PURPOSE

To determine whether high-pressure air blowing during adhesive application affects the infiltration of resin comonomers and nanoleakage manifestation in the resin/dentin interface under simulated pulpal pressure.

MATERIALS AND METHODS

Thirty mid-coronal dentin surfaces were bonded with an etch-and-rinse adhesive (Adper Single Bond 2) under simulated pulpal pressure. In the control group, the adhesive was thinned by ordinary air blowing with a pressure of 0.2 MPa, while in the experimental group, a high-pressure air blowing technique (pressure: 0.4 MPa) was used. All other procedures followed the manufacturer's instructions. Resin tag formation and nanoleakage in the bonding interface were evaluated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

RESULTS

When adhesive was thinned with high pressure air blowing, longer and more homogeneous resin tags were formed. The bonding interface demonstrated good overall morphology and integrity. Almost perfect infiltration of resin and no obvious nanoleakage were observed.

CONCLUSION

Thinning of adhesive with high-pressure air blowing provides a clinically feasible adjunctive procedure for better resin infiltration.

Enamel and dentin bond strength, interfacial ultramorphology and fluoride ion release of self-etching adhesives during a pH-cycling regime

PURPOSE

This study evaluated the effects of pH cycling on fluoride release and bond strength of two self-etching adhesive systems to both enamel and dentin. The ultramorphology of the interfaces produced by the adhesive systems were also analyzed.

MATERIALS AND METHODS

The buccal surfaces of bovine incisors were flattened to expose enamel and dentin, which were bonded with either Clearfil Protect Bond (CPB) or One-Up Bond F Plus (OBP). The bonded samples were prepared for microtensile bond strength (μTBS) testing, fluoride ion release, and transmission electron microscopy. pH cycling comprised demineralization (8 h/day) and remineralization (16 h/day) cycles for 8 days. The μTBS data were analyzed by two-way ANOVA, while fluoride release was analyzed using the Friedman and Wilcoxon tests.

RESULTS

The adhesives presented similar bond strengths to enamel. However, the dentin bond strength of CPB was higher than that of OBP. pH cycling did not influence enamel or dentin μTBS. The amount of fluoride released from the bonded enamel and dentin was low and varied among the groups. The morphological evaluation showed that the thickness of the dentin hybrid layers was similar for both adhesives.

CONCLUSION

The pH-cycling regime did not affect enamel or dentin bond strengths. In enamel, both the self-etching adhesives tested presented similar bond strengths, but in dentin, Clearfil Protect Bond showed higher dentin bonding than One-Up Bond F Plus.

Experimental self-etching HEMA-free adhesive systems: cytotoxicity and degree of conversion

The aim of this study was to evaluate the effect of replacing 2-hydroxyethyl methacrylate (HEMA) by methacrylate surfactant monomers on the cytotoxicity and degree of conversion of two-step self-etching dentin adhesive systems. Five HEMA-free adhesive systems were tested: Bis-EMA 10, Bis-EMA 30, PEG400, PEG400UDMA, PEG1000, and a HEMA group was used as positive control. The cytotoxicity of the experimental primers, with different monomer concentrations (2 or 20 wt%), and bond resins, containing 25 wt% surfactant, was assessed using murine fibroblast cell line 3T3 and the tetrazolium assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)). The degree of conversion of the bond resins was analyzed using Fourier transform infrared spectroscopy. The data were submitted to statistical analysis using level of significance set at P < 0.05. The PEG 1000 group obtained higher cell viability in comparison with HEMA in the 2 % primer. The cell survival rate using 20 % primer showed that PEG1000 and BIS-EMA 10 were less cytotoxic than HEMA. With regard to the eluate from bond resin, the data showed that the groups BIS-EMA 10, BIS-EMA 30 and PEG400UDMA were less cytotoxic than HEMA. No statistically significant difference was found among degrees of conversion of the experimental groups and HEMA. PEG 1000, BIS-EMA 10 and 30 monomers showed the biological potential for use in new adhesive system formulations since they showed lower cytotoxicity and similar degree of conversion when compared with the HEMA-containing group.

A simple technique for bonding lingual retainer

The present article describes an easy method to place a bonded lingual retainer. This technique is also helpful in limiting the flow of the acid etchant used for etching and also limiting the flow of the adhesive on to the lingual surfaces of the teeth.

Effect of Acid Etching on Long-term Microleakage of Nano Ionomer Restorations in Burand Laser-prepared Cavities in Primary Teeth

PURPOSE

The purpose of this study was to evaluate the effect of etching on marginal sealing of nanofilled resin-modified glass ionomer restorations in Class V cavities in primary teeth prepared with an Er, Cr:YSGG laser compared to bur preparation.

METHODS

Standard Class V cavities were prepared on the buccal surfaces of 56 extracted primary canines that were randomly divided into four groups of 14 teeth each, according to laser or bur preparation and whether acid etching was used or not in the cavity. All cavities were restored with Nano primer/Ketac N100. After storage for six months in water and 2,000 thermal cycles, the specimens were placed in a one percent basic fuchsin dye solution. Dye penetration was evaluated with a stereomicroscope. The data were analyzed via nonparametric tests (P<.05).

RESULTS

Etching in bur- and laser-prepared cavities significantly reduced enamel microleakage (P=.031 and P=.001, respectively). At the dentin margin, etching significantly increased microleakage in bur-prepared cavities (P=.009) and significantly decreased it in laser-prepared cavities (P=.009).

CONCLUSIONS

Etching may improve the sealing ability of Ketac N100 at both margins in laser-prepared cavities and at the enamel margin in bur-prepared cavities. It had an adverse effect on dentinal sealing in aged Ketac N100 restorations in primary teeth.

Rubber dam isolation--key to success in diastema closure technique with direct composite resin

The use of direct composite resin for diastema closure has technique advantages, including that the restorative procedure can be carried out in one appointment at a reasonable cost and without the removal of sound tooth structure. The use of a rubber dam for closing diastemas with composite resin is of paramount importance as it prevents moisture contamination and ensures increased gingival retraction compared to other techniques. This provides better access to the cervical area of the tooth, facilitating proper placement of resin to recreate the natural anatomical contours and contact point. Thus, there is a more natural adaptation of the restoration to the gingival tissue, avoiding a space between the papilla and the restored tooth. To illustrate the advantages of this technique, two diastema closure cases are presented using direct composite resin with rubber dam isolation.

Clinical performance of chairside CAD/CAM feldspathic ceramic posterior shoulder crowns and endocrowns up to 12 years

In 55 patients, 25 endocrowns (test) and 40 shoulder crowns (control) were produced chairside in a private practice using the Cerec 3 (CAD/CAM) method and Vita Mark II feldspathic ceramic. The crowns were examined at baseline and after up to 12 years using modified USPHS criteria. The survival estimate was assessed by Kaplan-Meier analysis. The 12 years survival estimate of the shoulder crowns was 95% on molars and 94.7% on premolars. Endocrowns showed 90.5% survival on molars and 75% on premolars. Statistically, the differences between the survival estimates were not significant (P > 0.05). The longevity of Vita Mark II Cerec 3 shoulder crowns on molars and premolars, as well as of endocrowns on molars, proved to be--for private practice--a very acceptable result, while the premolar endocrowns tended to show a higher risk for failure.

Facilitating Direct Bonding for Lingual Retainers

Directly bonded lingual retainers are not always easy because the available techniques do not keep the wire totally stable in position and there is risk of moist contamination. Indirect methods help to keep a moist-free environment and reduce chair time but have other drawbacks, such as lack of control over the composite placement leading to adhesive-tooth failure or undesirable flow of adhesive to gingival embrasures. The purpose of this report is to show a direct bonding method, helped by a laboratory made acrylic guide, which has benefits of direct and indirect techniques.

The non-vital discolored central incisor dilemma

The restoration of anterior teeth is frequently a demanding mission. Patients generally have high expectations for the anterior region, which makes the emotional side of treatment especially important. When this involves discolored endodontically treated teeth, consensus can hardly ever be found as to the chosen approach. Bleaching with direct composites is undoubtedly the most conservative choice for these cases. However, this may require more maintenance (touch-up bleaching and repairs) in the long term, which is an important issue for adult patients. On the other hand, bonded porcelain veneers represent a more 'high-end' option, as they recover the original biomechanics of the intact tooth, allow an optimal masking of the substrate, remain stable, and have a reasonable biological cost when compared to full-coverage crowns. This strategy is explained in this article and documented with a clinical case. We describe treatment planning based on the biomimetic concept, taking into consideration what is possible with current materials and techniques when combined with the patient's particular needs, including the introduction of an innovative step during dentin sealing--the microsuction. The laboratory work was totally accomplished by 'teledentistry', with no direct contact between the dental technologist and the patient.

Adhesive luting of new CAD/CAM materials

OBJECTIVE

To evaluate the adhesive bonding performance of recently introduced tooth-colored CAD/CAM materials after different pretreatment protocols and using different luting materials.

MATERIALS AND METHODS

The CAD/CAM materials under investigation were e.max CAD (lithium disilicate glass ceramic; Ivoclar Vivadent, Schaan, Liechtenstein), Celtra Duo (zirconia-reinforced lithium disilicate ceramic; Dentsply DeTrey, Konstanz, Germany), Lava Ultimate (resin nano ceramic; 3M ESPE, Neuss, Germany), and Enamic (resin infiltrated ceramic; Vita, Bad Säckingen, Germany). A total of 240 blocks (n = 5) received various pretreatments (no pretreatment, silane, sandblasting, sandblasting + silane, hydrofluoric acid, hydrofluoric acid + silane), and then different classes of adhesive luting composites were applied (adhesive: Prime&Bond XP + SCA + Calibra; Dentsply DeTrey; self adhesive: RelyX Unicem; 3M ESPE). After 24 h water storage and 10,000 thermocycles (5°C/55°C), specimens were cut into beams and microtensile bond strengths were recorded.

RESULTS

Bonding performance of recent CAD/CAM materials was clearly influenced by the pretreatment method (P < 0.05). In general, significantly higher μ-TBS values were recorded for the ceramic materials compared to the hybrid materials (P < 0.05). Among the hybrid materials, Enamic exhibited higher bond strengths than Lava Ultimate (P < 0.05). However, despite the differences found, all materials showed a high level of bonding performance, being sufficient to withstand intraoral chewing forces during mastication.

CONCLUSION

When pretreated as recommended by the manufacturers, recent tooth-colored CAD/CAM materials show an encouraging bonding performance for adhesive luting.

Esthetic non-invasive IPS e.max CAD veneers using the Cerec system: Two case reports

Incisors can sometimes become discolored due to trauma. In most cases, the trauma involves complicated fractures of dentin and enamel that necessitates immediate restorative treatment. In some cases, the trauma is minor and does not involve any structural damage to the tooth. In these cases, the pulp tissue reacts to the trauma, causing discoloration. In the following two cases involving anterior teeth, there were no changes visible at the apex of the incisor. We assumed that the pulp tissue remained vital to some degree and was able to react in several ways to the trauma. In both cases, we saw a change in color of a central incisor, combined with an irregularity in the position of the anterior teeth. The patients involved both explicitly wished to alter the color of the darker incisor in order to restore the harmony of their smiles.

Influence of Etching Protocol and Silane Treatment with a Universal Adhesive on Lithium Disilicate Bond Strength

OBJECTIVES

To measure the effects of hydrofluoric acid (HF) etching and silane prior to the application of a universal adhesive on the bond strength between lithium disilicate and a resin.

METHODS AND MATERIALS

Sixty blocks of lithium disilicate (e.max CAD, Ivoclar Vivadent) were sectioned into coupons and polished. Specimens were divided into six groups (n=10) based on surface pretreatments, as follows: 1) no treatment (control); 2) 5% HF etch for 20 seconds (5HF); 3) 9.5% HF etch for 60 seconds (9.5HF); 4) silane with no HF (S); 5) 5% HF for 20 seconds + silane (5HFS); and 6) 9.5% HF for 60 seconds + silane (9.5HFS). All etching was followed by rinsing, and all silane was applied in one coat for 20 seconds and then dried. The universal adhesive (Scotchbond Universal, 3M ESPE) was applied onto the pretreated ceramic surface, air thinned, and light cured for 10 seconds. A 1.5-mm-diameter plastic tube filled with Z100 composite (3M ESPE) was applied over the bonded ceramic surface and light cured for 20 seconds on all four sides. The specimens were thermocycled for 10,000 cycles (5°C-50°C/15 s dwell time). Specimens were loaded until failure using a universal testing machine at a crosshead speed of 1 mm/min. The peak failure load was used to calculate the shear bond strength. Scanning electron microscopy images were taken of representative e.max specimens from each group.

RESULTS

A two-way analysis of variance (ANOVA) determined that there were significant differences between HF etching, silane treatment, and the interaction between HF and silane treatment (p<0.01). Silane treatment provided higher shear bond strength regardless of the use or concentration of the HF etchant. Individual one-way ANOVA and Tukey post hoc analyses were performed for each silane group. Shear bond strength values for each etch time were significantly different (p<0.01) and could be divided into significantly different groups based on silane treatment: no silane treatment: 0 HF < 5% HF < 9.5% HF; and RelyX silane treatment: 0 HF < 5% HF and 9.5% HF.

CONCLUSIONS

Both HF and silane treatment significantly improved the bond strength between resin and lithium disilicate when used with a universal adhesive.

Two-year clinical performance of dimethacrylatebased composite restorations repaired with a silorane-based composite

PURPOSE

To investigate the clinical performance of a silorane-based composite resin used for repairing dimethacrylate- based composite restorations.

MATERIALS AND METHODS

One operator repaired defective dimethacrylate-based resin restorations that were randomly assigned to one of two treatment groups: control (n=50), repaired with Adper SE Plus and Filtek P60 Posterior Restorative (3M ESPE); or test (n=50), repaired with P90 System Adhesive Self-Etch Primer and Bond and Filtek P90 Low Shrink Posterior Restorative (3M ESPE). After 1 week, restorations were finished and polished. Two calibrated examiners (weighted Kappa≥0.78) evaluated the repaired restorations, blindly and independently, at baseline, after 6 months, 1 and 2 years. The parameters examined were marginal adaptation, anatomic form, surface roughness, marginal discoloration, postoperative sensitivity, and secondary caries. The restorations were classified as Alfa, Bravo, or Charlie, according to modified US Public Health Service criteria. Variation in the levels of clinical parameters over time was evaluated by Friedman's ANOVA (α=0.05). The Mann-Whitney test assessed the differences between the materials for all clinical criteria at baseline, 6-month, 1- and 2-year recalls (α=0.05). The Wilcoxon test compared each composite resin for all clinical criteria at the same recalls (α=0.05).

RESULTS

After two years, 79 repaired restorations were re-examined. No statistically significant differences were found between the materials at baseline or at the 2-year recall (p>0.05). Comparing baseline and 2-year recall, there was a statistically significant difference for marginal discoloration (p=0.029) in silorane-based composite restorations.

CONCLUSION

After two years, the clinical performance of the silorane-based composite was similar to that of the dimethacrylate-based composite when used to make repairs.

Selective infiltrated etching to surface treat zirconia using a modified glass agent

PURPOSE

The surface roughness of zirconia specimens and the bond strength of zirconia and resin cements were evaluated after selective infiltrated etching (SIE) surface treatment using a modified glass agent.

MATERIALS AND METHODS

One hundred twenty zirconia specimens were divided into four groups according to surface treatment method: untreated control (C), airborne particle abrasion (A), airborne particle abrasion followed by SIE treatment using a modified glass agent (A-SIE), and SIE treatment using a modified glass agent without airborne particle abrasion (SIE). The surface morphology and roughness of the specimens were examined before and after treatment using scanning electron and atomic force microscopy. The specimens were then cemented to resin blocks with a 4-META resin luting system (Superbond C&B). The shear bond strength of the zirconia/ resin interface was measured before and after thermocycling and fatigue testing.

RESULTS

The surface roughness and shear bond strength values of the SIE group were higher than those of the other three zirconia groups. The surface roughness (Ra) values were 8.10, 8.34, 9.42, and 12.42 μm for the C, A, A-SIE, and SIE groups, respectively, with significant differences between SIE and the C and A groups (p<0.05). The shear bond strength values before thermocycling and fatigue testing were 23.37, 23.38, 25.82, and 28.67 MPa for the C, A, A-SIE, and SIE groups, respectively. These values did not decrease after 10,000 cycles of thermocycling for the surface-treated groups, but did decrease for the untreated control group (C).

CONCLUSION

SIE treatment using a modified glass agent can increase surface roughness and the bond strength between zirconia and resin cements. The shear bond strength did not decrease after thermocycling and fatigue testing.

A clinical comparison of bracket bond failures in association with direct and indirect bonding

OBJECTIVE

To compare bond failure rates between direct and indirect techniques for bonding orthodontic brackets.

DESIGN

A two-centre single blinded prospective randomized controlled clinical trial.

MATERIALS AND METHODS

This study was undertaken at the Birmingham Dental Hospital and Good Hope Hospital, Sutton Coldfield. Thirty-three subjects meeting the inclusion criteria were selected from orthodontic waiting lists and assigned to either of two study groups according to a split-mouth study design. The number and site of bracket failures between tooth types was recorded over 1 year. Statistical analysis was carried out using chi-square tests.

RESULTS

Brackets were lost from 14 of the 553 teeth bonded, giving an overall bond failure rate of 2.5%. There were no significant differences in bond failures between direct and indirect bonding or in the tooth types of the failures.

CONCLUSIONS

There was no significant difference in the bond failure rates between direct and indirect bonding.

Does the method of caries induction influence the bond strength to dentin of primary teeth?

PURPOSE

To evaluate the effect of chemical and microbiological methods of caries induction on microtensile bond strength (μTBS) of current adhesive systems to primary dentin.

MATERIALS AND METHODS

Flat dentin surfaces from 36 primary molars were assigned to 3 groups according to the method of inducing caries-affected dentin: (1) control (sound dentin); (2) pH cycling; and (3) microbiological. In both methods, teeth were submitted to caries induction for 14 days, and the sound dentin was stored in distilled water for the same period. Specimens were then randomly reassigned according to adhesive system: a two-step etch-and-rinse adhesive (Adper Single Bond 2) or a two-step self-etching system (Clearfil SE Bond). Composite buildups were constructed and the teeth were sectioned to obtain bonded sticks (0.8 mm2) to be tested for microtensile bond strength. The μTBS means were analyzed by two-way ANOVA and Tukey's tests (α = 0.05). Failure mode was evaluated using a stereomicroscope (400X).

RESULTS

Both methods of caries induction resulted in lower μTBS values (with no significant difference between them) than those obtained for sound dentin. Adhesive systems showed similar bond strength values. The percentage of premature failure was higher in the microbiological group, regardless of adhesive system.

CONCLUSION

Microbiological and pH-cycling methods are both suitable for simulating caries-affected dentin for bonding evaluations in primary teeth.

Influence of PEEK surface modification on surface properties and bond strength to veneering resin composites

PURPOSE

To test the impact of mechanical and chemical treatments of PEEK on surface roughness (SR), surface free energy (SFE), and tensile bond strength (TBS) to veneering resin composites.

MATERIALS AND METHODS

PEEK specimens (N = 680) were fabricated and divided into treatment groups (n = 170/group): 1. air abrasion (AIA); 2. etching with piranha solution (PIS); 3. air abrasion + piranha acid etching (AIP); and 4. no treatment (NO). Ten specimens of each treatment group were assessed with a contact angle measuring device and profilometer to determine SFE and SR, respectively. The remaining 160 specimens of each group were divided into subgroups according to coupling method (n = 32/subgroup): 1. Monobond Plus/ Heliobond (MH); 2. Visio.link (VL); 3. Clearfil Ceramic Primer (CCP); 4. Signum PEEK Bond (SPB); and 5. control, no coupling (CG). Specimens were veneered using Signum Composite/SiCo or Signum Ceramis/SiCe (both: n = 16), incubated in water (60 days at 37°C) and thermocycled (5000 cycles of 5°C/55°C). TBS was measured and data analyzed by three- and one-way ANOVA, Kruskal-Wallis and Mann-Whitney tests (p < 0.05).

RESULTS

A significant effect of surface treatment (p < 0.001) and coupling agent application (p < 0.001) on TBS was observed. AIA specimens with/without PIS showed the highest SFE, SR, and TBS. No differences were measured between PIS and NO, and between AIA and AIP. When no coupling agent was used, no adhesion was obtained. CCP resulted in low adhesion values, whereas MH, SPB, and VL exhibited increased TBS. No significant impact of the veneering resin composite on TBS was found (p = 0.424).

CONCLUSION

AIA and AIP combined with VL, SPB, and MH can be recommended for clinical use.

[Effect of dentin proteoglycans on the bonding properties of dentin]

OBJECTIVE

To investigate the potential effect of proteoglycan (PG) and glycosaminoglycan (GAG) on the bonding of etch and rinse adhesive to dentin, in order to improve the bonding effect of dentin.

METHODS

Forty-two extracted molars were used to obtain standard dentin bonding surface, and the specimens were etched for 15 s with 37% phosphoric acid and divided into three groups using a table of random numbers. Then the three groups undergone different incubating procedures as follow: specimens in chondroitinase ABC (C-ABC) group were incubated with C-ABC at 37 °C for 48 h in vibrator. Specimens in trypsin (TRY) group were incubated with trypsin, and specimens in the control group were incubated with deionized water for 48 h in the oscillators. Then specimens in each group were randomly assigned into two subgroups, A (Adper(TM) Single Bond 2) and B (Prime & Bond NT) (n = 7). The microtensile bond strength (µTBS), fracture mode and bonding interface morphology of the specimens were evaluated via microtensile testing, stereo microscope and field emission scanning electron microscopy (FE-SEM) respectively after specimens being incubated in 37 °C water for 24 h.

RESULTS

The immediate µTBS of C-ABC group bonding with adhesive A and B [(32.9±2.5) and (26.8±2.2) MPa] were significantly lower than that of the control group [(40.7±3.3) and (34.6±3.7) MPa] (P < 0.05). While the immediate µTBS of TRY group [(49.0 ± 3.6) and (44.5 ± 3.0) MPa] were significantly higher than that of the control group(P < 0.05).

CONCLUSIONS

Dentin PG participates in the dentin bonding process. Removal of PG increased the immediate µTBS of dentin and total etching adhesives, while removal of GAG decreased the immediate µTBS.

Microhardness evaluation of enamel adjacent to an improved GIC sealant after different enamel pre-treatment procedures

AIM

This in vitro study was carried out to evaluate the microhardness of enamel adjacent to a glass ionomer cement (GIC) with high fluoride content used as a sealant (Fuji Triage, GC Corp., Japan) after laser, bur or air abrasion treatment procedures.

STUDY DESIGN

200 freshly extracted non-carious human molars were divided into 10 experimental groups according to the enamel pre-treatment method: A air abrasion (Mach 4.1 Kreativ Inc., USA); AP, Air abrasion + conditioning with 20% polyacrylic acid (GC cavity conditioner); L, Er,Cr:YSGG laser application (Waterlase, Biolase Technology, Inc., San Clemente, USA); LP, Er,Cr:YSGG laser application and fissure conditioning; B, ameloplasty carried out with a diamond bur especially designed for preparing fissures (Komet #8833); BP, ameloplasty + fissure conditioning; P, application of 20% polyacrylic acid and all fissures sealed with GIC; C, no fissure treatment, the material was applied directly to the fissures (control); R, application of 37% orthophosphoric acid and fissures sealed with a resin-based sealant (Fissurit; Voco, Germany) (control); N, no treatment (control). Half of each group of teeth were left in artificial saliva for one month and the rest for three months. The teeth were then sectioned and microhardness was measured using a Vickers test apparatus. Kruskal-Wallis, Mann-Whitney U and Dunn's multiple comparison tests were carried out (5% significance).

RESULTS

After one month results regarding hardness at the base and lateral walls of fissures were significantly higher in groups A, AP, L, LP, B, BP, P and C than in groups R and N (p<0.01), but no difference was seen between the treatment procedures. The results after three months produced similar findings with evenly increased values for all groups.

CONCLUSION

The results of this study showed that the tested GIC with a higher fluoride content seemed to improve the enamel hardness of the fissure enamel and could be regarded as an alternative material in cases where resin sealant applications are questionable.

Polymer nanocarriers for dentin adhesion

To obtain more durable adhesion to dentin, and to protect collagen fibrils of the dentin matrix from degradation, calcium- and phosphate-releasing particles have been incorporated into the dental adhesive procedure. The aim of the present study was to incorporate zinc-loaded polymeric nanocarriers into a dental adhesive system to facilitate inhibition of matrix metalloproteinases (MMPs)-mediated collagen degradation and to provide calcium ions for mineral deposition within the resin-dentin bonded interface. PolymP- N : Active nanoparticles (nanoMyP) were zinc-loaded through 30-minute ZnCl2 immersion and tested for bioactivity by means of 7 days' immersion in simulated body fluid solution (the Kokubo test). Zinc-loading and calcium phosphate depositions were examined by scanning and transmission electron microscopy, elemental analysis, and x-ray diffraction. Nanoparticles in ethanol solution infiltrated into phosphoric-acid-etched human dentin and Single Bond (3M/ESPE) were applied to determine whether the nanoparticles interfered with bonding. Debonded sticks were analyzed by scanning electron microscopy. A metalloproteinase collagen degradation assay was also performed in resin-infiltrated dentin with and without nanoparticles, measuring C-terminal telopeptide of type I collagen (ICTP) concentration in supernatants, after 4 wk of immersion in artificial saliva. Numerical data were analyzed by analysis of variance (ANOVA) and Student-Newman-Keuls multiple comparisons tests (p < .05). Nanoparticles were effectively zinc-loaded and were shown to have a chelating effect, retaining calcium regardless of zinc incorporation. Nanoparticles failed to infiltrate demineralized intertubular dentin and remained on top of the hybrid layer, without altering bond strength. Calcium and phosphorus were found covering nanoparticles at the hybrid layer, after 24 h. Nanoparticle application in etched dentin also reduced MMP-mediated collagen degradation. Tested nanoparticles may be incorporated into dental adhesive systems to provide the appropriate environment in which dentin MMP collagen degradation is inhibited and mineral growth can occur.

Microleakage of inlay ceramic systems luted with self-adhesive resin cements

PURPOSE

To evaluate the microleakage of Cerec 3, IPS e.max Press, and Turkom-Cera inlays cemented with three self-adhesive resin cements.

MATERIALS AND METHODS

Ninety standardized class III MOD cavities were prepared in intact human mandibular third molars. Ceramic inlays were fabricated according to the manufacturer's instructions and were cemented using three self-adhesive resin cements (RelyX Unicem, Smartcem 2, and SpeedCEM). The specimens were stored in distilled water at 37°C for 24 h and subjected to 1000 thermocycles in water between 5°C and 55°C with a dwell time of 30 s. Subsequently, the specimens were subjected to 100,000 cycles of mechanical loading of 50 N at 1.6 Hz in 37°C water. The specimens were immersed in 0.5% basic fuchsine for 24 h and were sectioned using a low-speed diamond blade. The percentage of dye leakage at the tooth/restoration interface was measured and compared by Kruskal-Wallis tests with Bonferonni correction and Mann-Whitney U-tests at a significance level of p<0.05.

RESULTS

Microleakage at the RelyX Unicem interface was lower than that with Smartcem 2 and SpeedCEM resin cements (p<0.05). Microleakage of the Turkom-Cera system was higher than Cerec 3 and IPS e.max Press ceramic inlays (p<0.05).

CONCLUSIONS

Regardless of the ceramic system and self-adhesive resin cement used, dentin margins were associated with higher microleakage than enamel margins.

Clinical survival of anterior metal-ceramic and all-ceramic cantilever resin-bonded fixed dental prostheses over a period of 60 months

PURPOSE

To evaluate the survival of maxillary anterior cantilever resin-bonded metalceramic (MC) and all-ceramic (AC) fixed dental prostheses (RBFDPs).

MATERIALS AND METHODS

Between August 2007 and December 2009, 40 patients received 40 RBFDPs made of either cobalt-chromium-ceramic (n = 20) or glass-infiltrated alumina (In-Ceram, Vident; n = 20) and were followed up until December 2012. Restorations were adhesively cemented (Panavia 21, Kuraray).

RESULTS

Two fractures were observed with AC. No debondings were observed with MC (n = 0) but were observed with AC (n = 3). The difference in survival rates of MC and AC was not significant (MC: 100%; AC: 90%; P = .15) (Kaplan-Meier method, confidence interval = 95%).

CONCLUSIONS

Cantilever AC RBFDPs could be a promising alternative to MC RBFDPs for replacement of missing anterior incisors, provided that no mechanical complications were experienced with the latter.

Cuspal flexure, depth-of-cure, and bond integrity of bulk-fill composites

PURPOSE

Evaluate cuspal flexure caused by polymerization shrinkage stress, bond integrity, and depth-of-cure of bulk-fill composites.

METHODS

Twenty-eight extracted permanent molars were mounted in stainless steel rings. Slot-shaped Class II mesio-occlusal-distal preparations (four mm deep) were restored with Filtek Supreme Ultra (control; two two-mm increments) and bulk-fill composites (Tetric EvoCeram, Venus, Filtek Bulk Fill). The teeth were digitized using a 3D scanner before and after restoration. Before- and after-restoration scans were aligned, and cuspal flexure was calculated. Bond integrity along occlusal interfaces was assessed by dye penetration and measured after overnight immersion in basic fuchsin dye and cross-sectioning. Depth-of-cure was determined on the cross-sections using Vickers hardness. Statistical analysis was performed with one-way analysis of variance.

RESULTS

All composites caused inward cuspal flexure (10.4 to 13.6 μm). No statistical difference in flexure was found among the composites (P=.07). No significant difference in microhardness at any restoration depths was found for any composite (.35<P<.99). Dye penetration showed comparable bonding along occlusal interfaces for the tested composites.

CONCLUSIONS

Bulk-fill composites cured all the way through four-mm restoration depths. Cuspal flexure, caused by polymerization shrinkage, and bond integrity were not different between teeth restored with the bulk-fill and conventional incrementally placed restorative composites.

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.

Effect of different surface treatments on the shear and microtensile bond strength of resin-modified glass ionomer cement to dentin

OBJECTIVE

The aim of this study was to evaluate the effect of different surface treatments on the microtensile bond strength (μTBS) and shear bond strength (SBS) of resin-modified glass ionomer cement (RMGIC) to dentin.

MATERIALS AND METHODS

Fifty-two extracted human molars were flattened to obtain dentin surfaces. For SBS assessment 40 teeth were divided into four groups according to their surface treatments (acid etching, Er:YAG laser QSP mode, Er:YAG laser MSP mode and control-SiC) (n = 10). A plastic cylinder was placed over the differently treated dentin surfaces and RMGIC was placed into the rings and polymerized. Twelve teeth were used for the μTBS test. The treated dentin surfaces described above were restored with 4 mm high RMGIC and light cured; then, the specimens were sectioned into serial sticks (n = 15) and μTBS and SBS were tested for failure in a testing machine with a 1 mm/min crosshead speed. The data were analyzed by one-way ANOVA and Tukey HSD tests (α = 0.05).

RESULTS

Acid etching showed significantly higher SBS than the other groups (p < 0.05). Er:YAG QSP and MSP-treated groups showed higher SBS values than the control group, but the difference was not statistically significant (p > 0.05). Er:YAG MSP showed the highest μTBS value followed by acid etching, whereas the control group exhibited the lowest value (p < 0.05) and the differences between the control group and Er:YAG QSP were not significant (p > 0.05).

CONCLUSIONS

The application of Er:YAG MSP mode and acid etching to dentin can be used for improving the bond strength of RMGIC.

Stability of two resin combinations used as sealants against toothbrush abrasion and acid challenge in vitro

OBJECTIVE

To test the stability of two conventional adhesives when combined with a low-viscosity caries infiltrant used for sealing sound enamel against toothbrush abrasion and acid challenge in vitro.

MATERIALS AND METHODS

Bovine enamel discs (Ø = 3 mm) randomly assigned to three groups (n = 10/group) were etched with 37% phosphoric acid for 30 s and treated with resins of different monomer contents forming three test groups: (1) Untreated specimens (Control); (2) Infiltrant (Icon, DMG) + conventional enamel bonding adhesive (Heliobond, Ivoclar Vivadent); and (3) Infiltrant + conventional orthodontic adhesive (Transbond XT Primer, 3M Unitek). All specimens were immersed in hydrochloric acid (pH 2.6) for up to 9 days, during which they were exposed to 1825 toothbrush-strokes per day. Calcium dissolution was assessed using Arsenazo III method at 24-h intervals. Data were analyzed by Kruskal-Wallis and Wilcoxon signed ranks tests.

RESULTS

Cumulative calcium dissolution for the untreated specimens (39.75 ± 7.32 μmol/ml) exceeded the sealed groups (Icon + Heliobond: 23.44 ± 7.03 μmol/ml; Icon + Transbond XT Primer: 22.17 ± 5.34 μmol/ml). Untreated specimens presented a relatively constant calcium dissolution rate throughout the experimental period, whereas the sealed groups presented a gradual increase indicating weakening of the seal by toothbrush abrasion. Both sealed groups presented significantly lower daily calcium dissolution at all time points compared to the control, except for Group 2 on the last measurement day.

CONCLUSIONS

Low-viscosity caries infiltrant application on sound enamel prior to conventional resin application provided a protective effect against enamel demineralization, but this effect was not stable when challenged mechanically by toothbrush abrasion.

Evaluation of surface roughness and bond strength of quartz fiber posts after various pre-treatments

PURPOSE

Debonding at the post-adhesive interface is a major problem for quartz fiber posts. The objective of this study was to evaluate surface roughness and bond strength of quartz fiber posts after various surface treatments.

MATERIALS AND METHODS

Sixty-six quartz fiber posts were randomly divided into six experimental groups (n = 11) including group C, untreated (control); group SB, sandblasted; group SC, silica coated; group HF, hydrofluoric acid-etched; group N, Nd:YAG laser irradiated; group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. They were then bonded to resin cement and tensile bond strength was determined in a universal testing machine. Furthermore, two-way ANOVA and post hoc comparison tests (α = 0.05) were performed on all data.

RESULTS

The highest mean force value was observed in group SB and followed by group E. Tukey's HSD test showed that there was no statistical difference between group SB and group E (p = 0.673). The highest mean roughness value was observed in group SB and a significant difference was found between group SB and all other groups (p < 0.001). This study reveals that sandblasting and Er:YAG laser irradiation provided a significant increase in bond strength between quartz fiber posts and resin cement.

CONCLUSIONS

Sandblasting or Er:YAG laser-irradiation of the surface of the quartz fiber post before cementation is recommended for increasing retention.

Adhesion between glass fiber posts and resin cement: evaluation of bond strength after various pre-treatments

PURPOSE

To evaluate surface roughness and bond strength of glass fiber posts to a resin cement after various surface treatments.

MATERIALS AND METHODS

Sixty individually formed glass fiber posts with a diameter of 1.5 mm and a length of 20 mm were used for this study. They were randomly assigned to six groups of pre-treatment (n = 10/group): Group C, untreated (control); Group SB, sandblasted; Group SC, silica coated; Group HF, hydrofluoric acid-etched; Group N, Nd:YAG laser irradiated; Group E, Er:YAG laser irradiated. Surface roughness of the posts was measured before and after pre-treatment. The posts were then bonded to resin cement and tensile bond strengths were determined in a universal testing machine. For statistical analysis, two-way ANOVA and post-hoc comparison tests (α = 0.05) were performed.

RESULTS

The highest bond strength value was observed in group HF, followed by group SC. There was a statistically significant difference in bond strength between group C and groups HF, SC and E (p < 0.001, p = 0.002 and p = 0.041, respectively). Posts of group SB and group N showed the highest surface roughness.

CONCLUSIONS

The findings of the present study reveal that hydrofluoric acid-etching, silica coating and Er:YAG laser irradiation provided a significant increase in bond strength between glass fiber posts and resin cement.

Effect of sonic application mode on the resin-dentin bond strength and dentin permeability of self-etching systems

PURPOSE

To compare manual and sonic adhesive application modes in terms of the permeability and microtensile bond strength of a self-etching adhesive applied in the one-step or two-step protocol.

MATERIALS AND METHODS

Self-etching All Bond SE (Bisco) was applied as a one- or a two-step adhesive under manual or sonic vibration modes on flat occlusal dentin surfaces of 64 human molars. Half of the teeth were used to measure the hydraulic conductance of dentin at 200 cm H₂O hydrostatic pressure for 5 min immediately after the adhesive application. In the other half, composite buildups (Opallis) were constructed incrementally to create resin-dentin sticks with a cross-sectional area of 0.8 mm² to be tested in tension (0.5 mm/min) immediately after restoration placement. Data were analyzed using a two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

The fluid conductance of dentin was significantly reduced by the sonic vibration mode for both adhesives, but no effect on the bond strength values was observed for either adhesive.

CONCLUSION

The sonic application mode at an oscillating frequency of 170 Hz can reduce the fluid conductance of the one- and two-step All Bond SE adhesive when applied on dentin.

Effect of sulfuric acid etching of polyetheretherketone on the shear bond strength to resin cements

PURPOSE

To examine the influence of etching duration on the bond strength of PEEK substrate in combination with different resin composite cements.

MATERIALS AND METHODS

In total, 448 PEEK specimens were fabricated, etched with sulfuric acid for 5, 15, 30, 60, 90, 120, and 300 s and then luted with two conventional resin cements (RelyX ARC and Variolink II) and one self-adhesive resin cement (Clearfil SA Cement) (n = 18/subgroup). Non-etched specimens served as the control group. Specimens were stored in distilled water for 28 days at 37°C and shear bond strengths were measured. Data were analyzed nonparametrically using Kruskal-Wallis-H (p < 0.05).

RESULTS

Non-etched PEEK demonstrated no bond strength to resin composite cements. The optimal etching duration varied with the type of resin composite: 60 s for RelyX ARC (15.3 ± 7.2 MPa), 90 s for Variolink II (15.2 ± 7.2 MPa), and 120 s for Clearfil SA Cement (6.4 ± 5.9 MPa). Regardless of etching duration, however, the self-etching resin composite cement showed significantly lower shear bond strength values when compared to groups luted with the conventional resin composites.

CONCLUSION

Although sulfuric acid seems to be suitable and effective for PEEK surface pre-treatment, further investigations are required to examine the effect of other adhesive systems and cements.

The effect of antibacterial agents on fissure sealant microleakage: a 6-month in vitro study

PURPOSE

To evaluate microleakage from an antibacterial adhesive and bonding agent added to the ssure sealant on intact enamel.

MATERIALS AND METHODS

One hundred twenty sound third mandibular molars were randomly divided into 6 groups of 20 teeth each. Occlusal pits and ssures were sealed with un lled sealant material (Clinpro, 3M) after pretreatment with 1. phosphoric acid etching (control); 2. acid etching + Adper Single Bond 2 (SB, 3M); 3. chlorhexidine digluconate (CHX, Ultradent) + acid etching; 4. CHX + acid etching + SB; 5. acid etching + Clear l Protect Bond (CPB, Kuraray) 6. CPB alone. After 6-month water storage and thermocycling, the specimens were placed in 0.5% fuschin, sectioned and evaluated under a digital microscope. The data were compared between groups with Kruskal-Wallis and Mann-Whitney tests.

RESULTS

Differences between groups were statistically signi cant at P < 0.05. Acid etching alone and with SB showed the lowest microleakage, followed by acid etching + CPB. Chlorhexidine with and without bonding agent showed the greatest microleakage.

CONCLUSION

Conventional acid etching alone or with a one-bottle adhesive were the two most effective methods of reducing microleakage from ssures. Acid etching together with a self-etching adhesive showed better results than self-etching alone. Appling CHX increased microleakage in sealed teeth.

Sealing of silorane-based composite in laser-prepared primary teeth: effect of acid etching

PURPOSE

The purpose of this study was to evaluate the influence of prior etching on the sealing of silorane composite restorations in Class V cavity preparations prepared with an Er,Cr:YSGG laser compared to bur preparation in primary teeth.

METHODS

Standard Class V cavity preparations were prepared on the buccal surfaces of 56 extracted primary canines and randomly divided into four groups of 14 teeth each, according to laser or bur preparation and the use of prior acid etching in the preparation. All cavity preparations were restored with silorane adhesive and silorane composite. After water storage and thermocycling, the specimens were placed in 0.5 percent basic fuchsin dye solution. Dye penetration was evaluated with a stereomicroscope. The data were analyzed with nonparametric tests (P=.05).

RESULTS

Laser preparation and prior etching in bur-prepared cavity preparation had no significant effect on enamel sealing (P>.05), but significantly increased microleakage at the dentin margin (P<.001 and P=.001, respectively). Prior etching in laser-prepared cavity preparations significantly improved sealing at the enamel and dentin margins (P=.009 and P=.003, respectively).

CONCLUSIONS

Prior acid etching may be necessary to ensure good marginal sealing when laser preparation is used. However, this step is not required when bur cutting is used in primary teeth.

Effect of etching time and resin bond on the flexural strength of IPS e.max Press glass ceramic

OBJECTIVE

To evaluate the effect of hydrofluoric acid (HFA) etching time and resin cement bond on the flexural strength of IPS e.max(®) Press glass ceramic.

METHODS

Two hundred and ten bars, 25mm×3mm×2mm, were made from IPS e.max(®) Press ingots through lost-wax, hot-pressed ceramic fabrication technology and randomly divided into five groups with forty-two per group after polishing. The ceramic surfaces of different groups were etched by 9.5% hydrofluoric acid gel for 0, 20, 40, 60 and 120s respectively. Two specimens of each group were selected randomly to examine the surface roughness and 3-dimensional topography with atomic force microscope (AFM), and microstructure was analyzed by the field emission scanning electron microscope (FE-SEM). Then each group were subdivided into two subgroups (n=20). One subgroup of this material was selected to receive a thin (approximately 0.1mm) layer of resin luting agent (Variolink N) whereas the other subgroup remained unaltered. Half of subgroup's specimens were thermocycled 10,000 times before a 3-point bending test in order to determine the flexural strength. Interface between resin cement and ceramic was examined with field emission scanning electronic microscope.

RESULTS

Roughness values increased with increasing etching time. The mean flexural strength values of group 0s, 20s, 40s, 60s and 120s were 384±33, 347±43, 330±53, 327±67 and 317±41MPa respectively. Increasing HF etching times reduced the mean flexural strength (p<0.05). However, the mean flexural strength of each group, except group 0s, increased significantly to 420±31, 435±50, 400±39 and 412±58MPa after the application of dual-curing resin cement. In the present investigation, no significant differences after thermocycling on the flexural strengths were evident.

SIGNIFICANCE

Overtime HF etching could have a wakening effect on IPS e.max(®) Press glass ceramic, but resin cement bonding to appropriately etched surface would strengthen the dental ceramic.

Efficiency and patient satisfaction with the Isolite system versus rubber dam for sealant placement in pediatric patients

PURPOSE

The purpose of this clinical study was to compare the chair time and degree of patient satisfaction after use of the Isolite system (IS) versus rubber dam (RD) during the application of pit and fissure sealants.

METHODS

The patients included in this study ranged from seven to 16 years old. In each subject, pit and fissure sealants were applied to one permanent molar in each quadrant. IS dental isolation was used on one side; RD isolation was used on the other side. Chair time was assessed using a stopwatch, and patient acceptance was evaluated using a questionnaire.

RESULTS

Forty-two subjects (23 females and 19 males) were enrolled in the study. The average chair time was 19.36 minutes for the application of pit and fissure sealants on the RD side; average chair time was 10 minutes for the IS side (P<.001). Sixty-nine percent of the subjects were more comfortable using IS, while 31 percent found RD to be more comfortable (P=.02).

CONCLUSION

Isolite is a viable alternative to the conventional rubber dam. The use of Isolite is associated with reduced chair time and greater patient satisfaction.

Comparison of fracture resistance in post restorations in primary maxillary incisors

AIM

This in vitro study aimed to test the fracture resistance of 4 different posts used in the restoration of severely decayed primary incisors.

MATERIALS AND METHODS

Fifty primary incisors were selected for this study and sectioned 1 mm above the CEJ. After filing and irrigation of the root canal space, the canals were obturated with Metapex and 3 mm of post space was prepared inside the canals. Intact glass fiber posts, split-ended glass fiber posts, composite resin posts, and orthodontic γ 'gamma' wire posts were used as intracanal posts and the final composite resin restoration was placed using a paediatric strip crown. After thermocycling of the specimens, the fracture resistance was measured using a universal testing machine.

RESULTS

The mean fracture resistance of split- ended glass fiber posts was higher than the other groups, however, there was no significant difference between any of the groups (P>0.05).

CONCLUSION

Split-ended glass fiber posts seem to be a more appropriate option for full coverage restorations in primary incisors.

Performance of a new one-step multi-mode adhesive on etched vs non-etched enamel on bond strength and interfacial morphology

PURPOSE

To compare microtensile bond strength (μTBS) and interfacial morphology of a new one-step multimode adhesive with a two-step self-etching adhesive and two etch-and-rinse adhesives systems on enamel.

MATERIALS AND METHODS

Thirty human third molars were sectioned to obtain two enamel fragments. For μTBS, 48 enamel surfaces were ground using 600-grit SiC paper and randomly assigned into 6 groups (n = 8): nonetched Scotchbond Universal [SBU]; etched SBU [SBU-et]; non-etched Clearfil SE Bond [CSE]; etched CSE [CSE-et]; Scotchbond Multi-PURPOSE [SBMP]; Excite [EX]. The etched specimens were conditioned with 37% phosphoric acid for 30 s, each adhesive system was applied according to manufacturers' instructions, and composite resin blocks (Filtek Supreme Plus, 3M ESPE) were incrementally built up. Specimens were sectioned into beams with a cross-sectional area of 0.8-mm2 and tested under tension (1 mm/min). The data were analyzed with oneway ANOVA and Fisher's PLSD (α = 0.05). For interface analysis, two samples from each group were embedded in epoxy resin, polished, and then observed using scanning electron microscopy (SEM).

RESULTS

The μTBS values (in MPa) and the standard deviations were: SBU = 27.4 (8.5); SBU-et = 33.6 (9.3); CSE = 28.5 (8.3); CSE-et = 34.2 (9.0); SBMP = 30.4 (11.0); EX = 23.3 (8.2). CSE-et and SBU-et presented the highest bond strength values, followed by SBMP, CSE, and SBU which did not differ significantly from each other. EX showed the statistically significantly lowest bond strength values. SEM images of interfaces from etched samples showed long adhesive-resin tags penetrating into demineralized enamel.

CONCLUSIONS

Preliminary etching of enamel significantly increased bond strength for the new one-step multimode adhesive SBU and two-step self-etching adhesive CSE.

Influence of the number of adhesive layers on adhesive interface properties under cariogenic challenge using streptococcus mutans

PURPOSE

To test the hypothesis that the number of adhesive layers influences the adhesive interface properties under cariogenic challenge conditions using a Streptococcus mutans model.

MATERIALS AND METHODS

Bovine teeth (n = 90) were sectioned into blocks of 5 mm and divided into two groups for microleakage testing (n = 60) and tensile bond strength testing (n = 30). In each group, the samples were subdivided into subgroups according to the number of adhesive layers applied on the dentin: one (SB1), two (SB2), and three adhesive layers (SB3). The samples of the control groups were placed in BHI broth medium supplemented with 2% sucrose without microorganisms, and the experimental groups were submitted to Streptococcus mutans American Type Culture Collection (ATCC) for 5 days. For the tensile strength test, samples were sectioned into 1-mm-thick slices and submitted to a constant load of 0.5 mm/min in a universal testing machine. Fractured surfaces were analyzed and characterized as adhesive, cohesive, or mixed. The microleakage test was performed with silver nitrate solution.

RESULTS

In experimental groups, the tensile test revealed a statistically significant difference between the one- (18.59 ± 5.3) and three-layer (11.28 ± 5.0) groups (p < 0.001; ANOVA and Tukey's test). The adhesive failure mode was slightly more frequent in the one- (60%) and three-layer (80%) adhesive application groups. On the other hand, the microleakage levels of all experimental groups were statistically similar (Kruskal-Wallis; p > 0.05).

CONCLUSION

The experimental conditions influenced tensile properties and failure modes of different adhesive interfaces; however, they did not influence microleakage.

Conservative restorations combined with gingival zenith contour technique

The symmetry, shape, contour, and size of teeth play an important role in the esthetics of the anterior maxillary region of the mouth. However, abnormalities in symmetry and contour can considerably influence the esthetic parameters. Consequently, rehabilitation performed in this region can be challenging and, frequently, multidisciplinary treatment planning that includes esthetics, function, structure, and biologic aspects is paramount. The high demand for esthetic rehabilitations has, therefore, allowed the effective use of minimally invasive techniques to obtain results that mimic natural teeth. This article presents a case report in which both esthetic and functional rehabilitation were obtained by recontouring the gingival zenith followed by placing ultraconservative porcelain veneers.