[Effect of different frequencies of Er:YAG laser on bond properties of zirconia ceramic]

PURPOSE

The effect of different frequencies of Er:YAG laser on bond properties of zirconia ceramic was investigated.

METHODS

3 mm×3 mm ×2 mm Y-TZP blocks were randomly divided into 6 groups（n=5）：control group (C)，sandblasting group (SB) and Er:YAG laser group (A1-A4) in which the frequencies were 5, 10, 15 and 20 Hz, respectively, IPS e.max Press ceramics were used as group B. Scanning electron microscope (SEM) images were recorded for each group. The ceramics were bonded to teeth. After being stored in a constant temperature water bath at 37 ℃ for 24 hours, shear test was performed with universal testing machine. Fracture modes were evaluated with stereomicroscope. The data were analyzed with SPSS 26.0 software package. RESULTS：SEM showed that compared with the control group (C)，the surface of Y-TZP treated by Er:YAG laser with different frequencies became rough. The results of shear test showed that the highest bond strength value for IPS e.max Press ceramics group(B) was (13.15±2.97) MPa, followed by sandblasting group (SB): (7.78±0.97) MPa, and 10 Hz group (A2): (7.13±0.75) MPa. There was no significant difference between sandblasting group (SB) and 10Hz group(A2) (P>0.05). Fracture modes of the control group (C) were mainly interface fracture of Y-TZP and resin cement；most of the fracture modes of Er:YAG laser and sandblasting group (SB) were interface fracture of Y-TZP and resin cement，a few of mixed fracture and cohesion fracture of resin cement；and the fracture modes of IPS e.max Press ceramics group(B) were all mixed fracture. CONCLUSIONS：Er:YAG laser with 10 Hz can replace 110 μm Al2O3 sandblasting for surface modification of Y-TZP, in order to increase the bonding strength between Y-TZP and resin cement.

Surface treatment of RMGIC to composite resin using different photosensitizers and lasers: A bond assessment of closed Sandwich restoration

AIM

The aim of present study was to assess and compare different conditioning methods (laser, PDT and conventional) on shear bond strength (SBS) of resin modified glass ionomer cement (RMGIC) bonded to composite (sandwich technique).

MATERIAL AND METHODS

Fifty specimens were prepared from RMGIC and were packed in a teflon mould placed on glass slab. Through each of the glass slab the cement was light cured for 20 s. Now samples were randomly allocated into five groups (n = 10) according to pre-treatment protocols. In group 1 RMGIC were conditioned with MBP using PDT, Samples in group 2 treated with Er,Cr:YSGG (ECYL), group 3 pre-treated with Nd:YAG laser (NYL), samples in group 4 surface conditioned with air abrasion (AA) and group 5 conditioned with 37 % phosphoric acid (PA). Specimens after conditioning were rinsed with distilled water. Adhesive Adper Single Bond 2 was applied on treated surface of RMGIC and cured. Teflon mold was utilized to hold the composite Filtek Z250 in an incremental technique. For SBS testing all specimens were placed under shear knife edge at 1 K N at a speed of 0.5mm2 until bond failure. Optical microscope was used to evaluate failure pattern at 10x magnification. The data of SBS in Megapascal were subjected to statistical test. Analysis of variance was followed by Post hoc test with level of significance at 5 %.

RESULT

The maximum SBS was found in group 5 RMGIC conditioned with 37 % PA (16.45 ± 0.32 MPa). Whereas, group 1 (MBP, PDT) demonstrated significantly lower bond integrity (9.82 ± 1.08 MPa) compared to all experimental groups. Bond integrity of RMGIC surface treated with MBP, PDT (9.82 ± 1.08 MPa), group 3 lased with NYL (11.47 ± 0.53 MPa) and samples in group 4 conditioned with AA (11.23 ± 0.47 MPa) were comparable (p > 0.05).

CONCLUSION

ECYL has a potential to be used for conditioning of RMGIC prior to composite restoration (sandwich technique). MBP at 100 mg/L deteriorates SBS of composite to RMGIC.

Resin bond strength to zirconia: effects of surface treatments and resin cements

This in vitro study evaluated the effect of surface treatments on the microshear bond strength between zirconia and 2 different resin cements. Thirty sintered zirconia blocks (15.5 × 19.0 × 39.0 mm) were allocated into 10 groups according to 2 factors: surface treatment (control [10% isopropyl alcohol], silica coating, primer, hot etching solution, or glaze) and resin cement (conventional dual-curing [Multilink Automix] or self-adhesive [RelyX U100]). Three cement cylinders (0.7-mm diameter × 1.5-mm height) were made on the surface of each zirconia block. The specimens were stored in water for 6 months at 37°C and then submitted to microshear bond strength tests (n = 9 per surface treatment group). The bond strength data were analyzed statistically with Kruskal-Wallis and Dunn tests (P < 0.05). The contact angle was measured with a goniometer on separate surface-treated disc specimens (n = 2 per group). The greatest mean (SD) bond strength values, regardless of cement type, were reported for the groups with the glaze surface treatment: conventional cement, 13.1 (0.26) MPa; and self-adhesive cement, 20.1 (0.23) MPa. The next greatest mean (SD) values were found in the silica coating groups: conventional cement, 7.94 (0.09) MPa; and self-adhesive cement, 9.8 (0.10) MPa. The self-adhesive cement groups presented the greatest bond strength values, except when the primer surface treatment was applied. The zirconia treated with the hot etching solution presented the greatest mean contact angle, 78.23 (SD 1.34) degrees, and bond strengths that were among the lowest achieved, suggesting that low wettability may have influenced bond strengths.

Improvement of Total Etching Dentin Bonding with Subpressure

This study aimed to investigate the effects of subpressure on the bond properties of total-etching adhesive to dentin. Thirty-six caries-free premolars were sectioned parallel to the occlusal plane and randomly divided into four groups (n = 9): a control group (C, no treatment) and three subpressure groups, which were treated under 0.8, 0.6 or 0.4 bar after applying adhesives, named S8, S6 and S4, respectively. Afterward, resin was bonded to the dentin surface, and 27 beams (1.0 mm × 1.0 mm) of each group were sectioned. One was selected to observe the bonding interface from each group by SEM. Each group was divided into two subgroups (n = 13): 24 hours of water storage (I) and 10,000 thermocycling (A). The microtensile bond strength (μTBS), failure modes and nanoleakage expression were evaluated. SEM results showed that the subpressure groups had longer and denser resin tags. The μTBS of the subpressure groups was higher than that of the control group (p < 0.05). The subpressure groups were dominated by mixed failure, whereas main interfacial failure appeared in group C. The subpressure groups showed less silver deposition than the control group (p < 0.05). The subpressure technique may remarkably improve bonding strength and decrease nanoleakage on total-etching bonding.

Effectiveness of Disposable (Single-use) Tips for Dental Air-water Syringes

BACKGROUND

Single-use dental syringe (SUS) tips eliminate cross-infection risks. Many dental materials are moisture sensitive; therefore bonding could be affected by remaining moisture from SUS tips.

METHODS

An air-water syringe was calibrated to 50 PSI and the air pressure measured. SUS tips were then attached and pressure re-measured. Seven tips were tested; moisture content and spray pattern were investigated. Ethical approval was granted. Twenty third molar teeth were sectioned, stored in phosphate buffered saline and randomly allocated into groups with a SUS tip. They were mounted in acrylic and polished. Specimens were dried with a tip under standardised conditions, treated using a 3-step etch-prime-bond technique, then had a post bonded perpendicular to the dentine surface. The force to detach them was measured. Data were analysed using one-way analysis of variance (ANOVA) and Chi-squared tests.

RESULTS

The difference in output pressure between groups proved significant (p < 0.001). Tensile force at failure was significantly different between groups (p = 0.19).

CONCLUSIONS

The pressure output of the syringe and bond strength are influenced by the SUS tip.

Preparing and Restoring Composite Resin Restorations. The Advantage of High Magnification Loupes or the Dental Surgical Operating Microscope

Use of magnification, such as 6x to 8x binocular surgical loupes or the surgical operating microscope, combined with co-axial illumination, may facilitate the creation of stable composite resin restorations that are less likely to develop caries, cracks or margin stains over years of service. Microscopes facilitate observation of clinically relevant microscopic visual details, such as microscopic amounts of demineralization or caries at preparation margins; microscopic areas of soft, decayed tooth structure; microscopic amounts of moisture contamination of the preparation during bonding; or microscopic marginal gaps in the composite. Preventing microscope-level errors in composite fabrication can result in a composite restoration that, at initial placement, appears perfect when viewed under 6x to 8x magnification and which also is free of secondary caries, marginal staining or cracks at multi-year follow-up visits.

Bond strength and bioactivity of Zn-doped dental adhesives promoted by load cycling

The purpose of this study was to evaluate if mechanical loading influences bioactivity and bond strength at the resin-dentin interface after bonding with Zn-doped etch-and-rinse adhesives. Dentin surfaces were subjected to demineralization by 37% phosphoric acid (PA) or 0.5 M ethylenediaminetetraacetic acid (EDTA). Single bond (SB) adhesive—3M ESPE—SB+ZnO particles 20 wt% and SB+ZnCl2 2 wt% were applied on treated dentin to create the groups PA+SB, SB+ZnO, SB+ZnCl2, EDTA+SB, EDTA+ZnO, and EDTA+ZnCl2. Bonded interfaces were stored in simulated body fluid for 24 h and tested or submitted to mechanical loading. Microtensile bond strength (MTBS) was assessed. Debonded dentin surfaces were studied by high-resolution scanning electron microscopy. Remineralization of the bonded interfaces was assessed by atomic force microscope imaging/nanoindentation, Raman spectroscopy/cluster analysis, and Masson's trichrome staining. Load cycling (LC) produced reduction in MTBS in all PA+SB, and no change was encountered in EDTA+SB specimens, regardless of zinc doping. LC increased the mineralization and crystallographic maturity at the interface; a higher effect was noticed when using ZnO. Trichrome staining reflected a narrow demineralized dentin matrix after loading of dentin surfaces that were treated with SB-doped adhesives. This correlates with an increase in mineral platforms or plate-like multilayered crystals in PA or EDTA-treated dentin surfaces, respectively.

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.

Kansal Separator As an Effective Fixed Retainer Stabilizer

Fixed bonded retainers are increasingly being recommended as the only way to ensure long-term stability of an orthodontic treatment result. However, frequent debonding of the fixed bonded retainer is a constant source of frustration for the orthodontist. Bond failure is most commonly attributed to the difficulty encountered in stabilizing the retainer wire in the precise position during the bonding process. This paper presents a clinical approach that makes use of Kansal Separator; a self-secured orthodontic spring separator as a simple, efficient, and dependable fixed retainer stabilizer.

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.

A simple technique for the direct bonding of a lingual retainer: a clinical hint

The direct bonding of a fixed wire retainer often poses clinical difficulties. While there are several possible techniques, the present paper describes a simple method employing a ball clasp (S handle) to assist in the stabilisation of the wire to be attached. The advantages and disadvantages are indicated.

Effect of air moisture content on adhesion to dentine: a comparison of dental air/water syringe tips

This study aimed to evaluate the spray pattern and air moisture content produced by single-use syringe and multiple-use syringe tips. The drying efficacy was evaluated by analyzing the spray and by detecting the presence of moisture in the air blast through the tips. Single-use tips had a more consistent spray pattern and produced a moisture-free airflow compared to the multiple-use tips. The differences were statistically significant. Adhesion to dentine between tooth preparations dried with the two tips was evaluated using a tensile test. The differences were statistically insignificant.

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.

Measurement and comparison of bracket transfer accuracy of five indirect bonding techniques

OBJECTIVE

To measure and compare bracket transfer accuracy of five indirect bonding (IDB) techniques.

MATERIALS AND METHODS

Five IDB techniques were studied: double polyvinyl siloxane (double-PVS), double vacuum-form (double-VF), polyvinyl siloxane vacuum-form (PVS-VF), polyvinyl siloxane putty (PVS-putty), and single vacuum-form (single-VF). Brackets were bonded on 25 identical stone working models. IDB trays were fabricated over working models (n  =  5 per technique) to transfer brackets to another 25 identical stone patient models. The mesiodistal (M-D), occlusogingival (O-G), and faciolingual (F-L) positions of each bracket were measured on the working and patient models using digital photography (M-D, O-G) and calipers (F-L). Paired t-tests were used to compare bracket positions between working and patient models, and analysis of variance was used to compare bracket transfer accuracy among the five techniques.

RESULTS

Between the working and patient models, double-VF had the most teeth with significant differences (n  =  6) and PVS-VF the fewest (n  =  1; P < .05). With one exception, all significant differences were ≤0.26 mm and most (65%) were ≤0.13 mm. When the techniques were compared, bracket transfer accuracy was similar for double-PVS, PVS-putty, and PVS-VF, whereas double-VF and single-VF showed significantly less accuracy in the O-G direction.

CONCLUSIONS

Although overall differences in bracket position were relatively small, silicone-based trays had consistently high accuracy in transferring brackets, whereas methods that exclusively used vacuum-formed trays were less consistent.

Effortless stabilization of lingual retainer wire using customized clip

The accurate positioning of the fixed lingual bonded retainer wire is one of the challenging processes in bonding fixed retainer. Though several methods have been introduced to stabilize the lingual bonded retainer, each technique has an inherent draw back. To overcome this we have designed a customized clip which is similar to Kesling Seperator to aid in accurate and precise positioning of lingual retainer wire.

The effect of different bracket base cleaning method on shear bond strength of rebonded brackets

AIM

To assess the effect of different bracket base conditioning method on shear bond strength (SBS) of rebonded brackets.

MATERIALS AND METHODS

Eighty brackets were bonded to freshly extracted premolar teeth using light cured composite adhesive. SBS was measured for 20 random samples as control group (G1). After debonding, 60 debonded brackets were allocated randomly into three groups of bracket base conditioning methods to remove the remaining adhesives. G2: bracket base cleaned with slow speed round carbide bur (CB), G3: cleaned with ultrasonic scaler (US), G4: cleaned with sandblasting (SB). After that, brackets were rebonded in the same manner as frst bonding and SBS was measured. Modifed adhesive remnant index (ARI) was recorded for all groups.

RESULTS

SBS for new brackets was 11.95 MPa followed by 11.65 MPa for G2, 11.56 MPa for G4 and 11.04 MPa for G3 group. There were no statistically signifcant differences between all groups (p = 0.946). In all groups, failure mode showed that the majority of adhesive composite remained on the bracket base with ARI of 4. There was no statistically signifcant difference between all groups in ARI (p = 0.584).

CONCLUSION

In-offce methods; slow speed CB and US are effective, quick and cheap methods for bracket base cleaning for rebonding.

Isolite vs cotton roll isolation in the placement of dental sealants

PURPOSE

The purpose of this split-mouth, randomized, controlled trial was to evaluate the retention rates of sealants placed under Isolite vs cotton roll isolation.

METHODS

A convenience sample of 29 patients, with a mean age of 9.8 years and a total of 96 teeth, was included in this study. Matched contralateral pairs of first and second molars were randomized to receive sealants with Isolite or cotton roll isolation. All sealants were performed by one standardized operator. Sealants were placed on first and second permanent molars that had a matched contralateral molar requiring a sealant as well. Photographs were taken of the sealants on the day of placement, and at 6-month and 12-month recalls. Photographs were viewed, and retention of the sealants was evaluated and scored by three calibrated pediatric dentists. The scores were analyzed via Mann-Whitney U and chi-square tests.

RESULTS

There were no significant differences in the retention rates between sealants placed using Isolite isolation compared with cotton roll isolation.

CONCLUSION

Isolite and cotton roll isolation both appear to be equally effective in creating a favorable environment for sealant placement by a single operator.

The direct way of indirect bonding--the combined effect

The placement of orthodontic bonded brackets may be accomplished by either a direct or indirect technique. Most orthodontists will agree that brackets can be positioned more accurately on study casts than directly on teeth in the mouth. And, also direct bonding is more demanding to the orthodontist. Yet, very few orthodontists routinely use an indirect bonding technique. The reasons commonly given for not using the indirect method are difficulty in achieving consistent and predictable adhesion to the teeth, excess of composite around the bracket margins, failure to get all the brackets to adhere to the teeth e the expense of the materials. These disadvantages can be overcome by a new simplified method of bonding outlined in this article; additionally it has advantages of direct bonding also.

A simple bracket placement gauge

Various techniques for placement of orthodontic brackets have been described. Metallic jigs or instruments are available for bracket placement at a desired height. The present article describes a simple bracket placement gauge to position the brackets accurately during bonding procedure.

Effectiveness of an indirect bonding technique in reducing plaque accumulation around braces

OBJECTIVE

To evaluate if the use of an indirect braces bonding protocol for localized enamel etching and adhesive application could help reduce plaque accumulation and demineralization around the brackets compared with a conventional direct-bonding technique.

MATERIALS AND METHODS

Thirty patients were bonded with a split-mouth approach: two randomly selected opposite quadrants were used as the test sides and the other two as control sides. During the first 6 months, the plaque presence around the braces was recorded monthly according to a plaque accumulation index (PAI), as was the presence of demineralization. PAI values were measured at each of the four bracket sides for every bonded tooth. Analysis of variance was used to identify significant differences between different bracket margins and between test and control sides.

RESULTS

Test and control sides differed significantly for PAI measurements from t(1) (1 month after bonding) to t(4) (4 months after bonding), with the highest value of significance (P < .001) at t(1) but with no significant differences from t(5) to t(7) (treatment end). Considering whole-mouth results, different bracket margin PAI scores did not differ significantly. PAI scores were higher at t(1) and progressively decreased during the treatment. At debonding, the onset of 21 new white spots was recorded overall for the control sides and eight new white spots for the test sides.

CONCLUSION

Especially during the first 4 months after brackets placement, this indirect bonding protocol allowed for significant reduction in plaque accumulation around the braces and reduced onset of white spots during the orthodontic treatment.

A comparison of traditional and computer-aided bracket placement methods

OBJECTIVE

To test the hypothesis that there is no difference in the accuracy of bracket placement produced by OrthoCAD iQ indirect bonding (IDB) and that of an in-house fabricated IDB system by measuring the quality of intra-arch dental alignment at the end of simulated orthodontic treatment.

MATERIALS AND METHODS

Twenty-eight artificial teeth were arranged to resemble a typical preorthodontic malocclusion. Forty-six sets of models were duplicated from the original malocclusion and randomly divided into two sample groups. Half of the models had their bracket positions selected by OrthoCAD, while the others were completed by a combination of faculty and residents in a university orthodontic department. Indirect bonding trays were fabricated for each sample and the brackets were transferred back to the original malocclusion following typical bonding protocol. The individual teeth were ligated on a .021 × .025-inch stainless steel archwire to simulate their posttreatment positions. The two sample groups were compared using the objective grading system (OGS) originally designed by the American Board of Orthodontics.

RESULTS

The mean total OGS score for the OrthoCAD sample group was 39.25 points, while the traditional IDB technique scored 41.00 points. No statistical difference was found between total scores or any of the four components evaluated. Similar ranges of scores were observed, with the OrthoCAD group scoring from 30 to 52 points and the traditional IDB group scoring from 33 to 53 points.

CONCLUSIONS

The hypothesis is not accepted. OrthoCAD iQ does not currently offer a system that can position orthodontic brackets better or more reliably than traditional indirect bonding techniques.

Standardized bonding protocol posterior porcelain restorations

Strict adherence to a carefully designed protocol for the cementation of posterior porcelain restorations allows for a reliable and minimally invasive procedure. Though such a thorough protocol for porcelain cementation may initially seem time consuming or over-engineered, it is quickly learned and can be applied in nearly all situations. As with many practices in dentistry, the cementation is but the final step in the creation of a beautiful, minimally invasive, and durable restoration that lies at the end of a long line of procedures. All these procedures must also be completed at equivalent levels of excellence to ensure a successful result (Figures 10 to 12).

A modified bracket-positioning gauge

Various techniques for improving bracket positioning with different kinds of instruments have been described. This article describes the use of a modified bracket-positioning gauge for accurate placement of brackets during orthodontic bonding.

Comparison of shear bond strength of orthodontic brackets bonded with light emitting diode (LED)

Light-emitting diode (LED) light curing units (LCU) have recently been used to polymerize resin-based orthodontic adhesives and preliminary studies indicate their use has been successful. The objectives of this study were to evaluate the shear bond strength (SBS) oforthodontic brackets bonded to enamel with a LED LCU (LEDMAX 4, Hilux, Kulzer comp.) at 10, 20 and 40 seconds and comparing them with that of 40 seconds light exposure from a conventional halogen-based LCU (Hilux unit, Heraeus Kulzer comp.). Also to assess the amount of adhesive remaining on the tooth after debonding using Adhesive Remnant Index (ARI). 120 extracted human premolars were divided into 4 groups of 30 each. After photo polymerization, all the samples were stored in distilled water at 37 degrees C for 24 hours and then subjected to a shear force with universal testing machine until bracket failure. All the recordings were evaluated statistically ANOVA and Turkey tests revealed that, no statistically significant differences were found among the shear bond strengths of 40 sec halogen (10.15 +/- 1.55), 20 sec LED (9.58 +/- 1.71) and 40 sec LED (10.34 +/- 1.83) cured groups; but the bond strength of 10 sec cure LED group (7.56 +/- 1.47) showed significantly lower than the other groups. Chi-square comparisons indicated that there were no significant differences in the ARI scores between the 4 groups tested. The results of this study are promising for orthodontic application of LED curing units in clinics, but further in vivo trials should be performed before validation.

[Methods for bonding Incognito brackets using a photo-polymerizable bonding agent]

The bonding procedures used in the Incognito system are now well known. Practitioners can work with either a protocol for Maximum-cure which utilizes a hydrophobic and chemo-polymerizable adhesive or an adhesive that is dual and hydrophilic, the association Nexus 3/Excite. Clinically the two protocols provide equivalent results in the quality of the bonding seal for attachments. They are simple to use, but in applying them practitioners must scrupulously follow the manufacturer's recommended stages of procedure.

[Optimal direct bonding methods]

The author explains in this clinical note how the direct bonding method can be most efficiently utilized. He suggests that precision of placement and comfort for patients can be improved if the following two rules are respected: the attachments must be kept horizontal and the substrate must remain immobile.

[Methods for bonding Incognito brackets using a chemo-polymerizable bonding agent]

An indirect method is used to bond Incognito attachments. This article will give a step-by-step outline of the procedure that employs a traditional chemo-polymerized bonding agent carried in a silicone splint. Using this guide, every practitioner will be able to use a proven technique to achieve the same anticipated results.

Creating certainty and confidence with indirect bonding

Indirect bonding offers a superior method of adhering brackets to teeth, but few orthodontists use it. The neglect of this procedure has many origins, including expense, lack of expertise, and inconsistent results. This paper presents an indirect-bonding method that can be used to expedite bonding appointments and make them more pleasant for patients and clinicians alike.

Light-activation of resin cement through ceramic: relationship between irradiance intensity and bond strength to dentin

This study investigated the relationship between the irradiance transmitted through ceramic and the bond strength of a resin cement to dentin. After application of an adhesive system, elastomer molds with cylindrical orifices (1.2 mm in diameter) were placed onto bovine dentin surfaces and filled with a photoactivated luting agent (Enforce; Dentsply Caulk). Light-activation was performed through a 0.6-mm-thick ceramic disc using different intensities: 250, 400, 550, 700, or 850 mW/cm(2). Control specimens were irradiated without ceramic (1050 mW/cm(2)). The radiant exposure was kept at 30 J/cm(2). Light spectral distribution was analyzed with a spectrometer. Microshear test was conducted and modes of failure were classified under SEM. Bond strength data were analyzed with ANOVA and Student-Newman-Keuls' test (alpha < or = 0.05), and failure scores with the Kruskal-Wallis test (alpha < or = 0.05). A linear regression model assessed the relationship between irradiance and bond strength. Groups light-cured at 250 and 400 mW/cm(2) presented lower bond strengths than groups activated at 850 and 1050 mW/cm(2). The linear regression showed that a decrease in light irradiance predicts a decrease in bond strength (r(2) = 0.955; p = 0.004). A predominance of mixed failures was observed. No significant alteration in the spectral wavelengths was observed. Despite the constant energy dose, the bond strength was dependent upon the irradiance level.

Effect of high-intensity LED units at reduced curing time on in vitro bond strength of orthodontic brackets

AIM

To compare the shear bond strength of stainless steel brackets obtained by 3 high-intensive light-emitting diode (LED) units with conventional halogen polymerization.

METHODS

A standard light-curing adhesive paste was used to bond brackets using different lamps and curing times. Eighty permanent bovine incisors were obtained and randomly divided into 4 groups. The first group was bonded using a high-output halogen lamp for 20 seconds, which served as a positive control. The other 3 groups were bonded with high-intensive LED curing devices for 10 seconds. After 30 minutes, a universal testing machine was used to apply an occlusal shear force directly to the enamel-bracket interface at a speed of 0.5 mm/minute. The groups were compared using Kruskal-Wallis test.

RESULTS

Mean results and standard deviations for the groups were: group 1 = 11.22 MPa (1.68), group 2 = 10.35 MPa (1.92), group 3 = 11.19 MPa (2.62), and group 4 = 11.82 MPa (2.09). No significant difference was observed in the bond strengths of the 4 groups evaluated (P = . 176).

CONCLUSIONS

Under the conditions of the present study, the high-intensity LED units with reduced light-curing time bonded brackets to etched tooth enamel as well as the halogen-based light-curing units.

Shear bond strength of a light-cured veneering composite to fiber-reinforced composite substrates

PURPOSE

The aim of this study was to compare the shear bond strength of a veneering composite to 2 differently treated fiber-reinforced composite (FRC) substrates and to a base metal alloy.

MATERIALS AND METHODS

A veneering composite (SR Adoro) was bonded to the following substrates: (1) a nickel-chromium base metal alloy (control, group A), (2) an FRC substructure (Vectris) with a flat surface (group B), and (3) an FRC substructure (Vectris) with retentive rods 0.5 x 0.5 mm in cross section and 10 mm in length, positioned parallel to each other at a distance of 0.5 mm (group C). Thirty-nine specimens were fabricated and divided into 3 groups of equal size. All specimens were thermocycled for 5,000 cycles at 5 degrees C and 55 degrees C with dwell time of 30 seconds in each bath. Evaluation of shear bond strength was performed at a constant crosshead speed of 0.5 mm/min according to ISO 10477.

RESULTS

The mean values for the shear bond strength were 19.29 MPa for the control group (group A), 16.66 MPa for group B, and 16.74 MPa for group C. Despite a tendency to higher bond strength of group A specimens, no statistically significant difference was recorded between the groups (P > .05).

CONCLUSIONS

No statistically significant difference was found between the metal and FRC substructures. Retentive rods on the FRO substructure do not seem to increase the bond strength significantly.

A pilot study for evaluation of bond strength of orthodontic brackets to enamel using a new impact test machine

We report an in-vitro pilot study to assess the ability of a new impact test machine to evaluate bond strength of orthodontic brackets to tooth enamel. A total of 37 extracted premolar teeth were bonded with APC Plus MBT Victory orthodontic brackets. Bond strength was tested using a new pendulum-based instrumented impact test machine. The maximum stress, the impact energy and interaction time required to debond the brackets were recorded. Of the total tested, 9 samples were successfully debonded with no obvious damage to the tooth surface although 28 samples fractured through the enamel and dentine. There was a statistically significant difference between the maximum stress required to debond the bracket and that required to fracture the tooth, a higher stress being required to debond the bracket. Significantly less stress was required to fracture older teeth. The high incidence of tooth fracture suggests a need to modify the impact test protocol. The lack of a simulated periodontal ligament, which is present clinically and acts as a shock absorber, may have contributed to the high failure rate, although the striking position of the pendulum also needs to be considered.

Influence of brush type as a carrier of adhesive solutions and paper points as an adhesive-excess remover on the resin bond to root dentin

PURPOSE

To evaluate the influence of the brush type as a carrier of priming adhesive solutions and the use of paper points as a remover of the excess of these solutions on the push-out bond strength of resin cement to bovine root dentin. The null hypotheses were that brush type and the use of paper points do not affect the bond strength.

MATERIALS AND METHODS

The canals of 80 single-root bovine roots (16 mm in length) were prepared at 12 mm using the preparation drill (FRC Postec Plus, Ivoclar). Half of each root was embedded in acrylic resin and the specimens were divided into 8 groups, considering the factors "brush type" (4 levels) and "paper point" (2 levels) (n = 10): Gr 1: small microbrush (Cavi-Tip, SDI); Gr 2: Microbrush (Dentsply); Gr 3: Endobrush (Bisco); Gr 4: conventional brush (Bisco); Gr 5: Cavi-Tip (SDI) + paper points; Gr 6: Microbrush (Dentsply) + paper points; Gr 7: Endobrush (Bisco) + paper points; Gr 8: conventional brush (Bisco) + paper points. The root dentin was treated with a multistep total-etch adhesive system (All Bond 2). The adhesive system was applied using each microbrush, with and without using paper points. One fiber post was molded with addition silicon and 80 posts were made of resin cement (Duolink). The resin posts were luted (Duolink resin cement), and the specimens were stored for 24 h in water at 37 degrees C. Each specimen was cut into 4 disk-shaped samples (1.8 mm in thickness), which were submitted to the push-out test.

RESULTS

The brush type (p < 0.0001) (small microbrush > microbrush = endobrush = conventional brush) and the use of paper points (p = 0.0001) (with > without) influenced the bond strength significantly (two-way ANOVA). The null hypotheses were rejected.

CONCLUSION

The smallest brush (Cavi-Tip) and the use of paper points significantly improved the resin bond to bovine root dentin.

Retention of zirconia ceramic copings bonded to titanium abutments

PURPOSE

The aim of this study was to evaluate the effect of 2 surface conditioning methods and 2 luting-gap sizes on the retention and durability of zirconia ceramic copings bonded to titanium abutments.

MATERIALS AND METHODS

Zirconia ceramic copings (Camlog Biotechnologies, Winsheim, Germany) with a luting-gap size of either 30 microm or 60 microm were bonded to titanium abutments (Camlog Biotechnologies) using the composite resin cement Panavia F (Kuraray, Osaka, Japan). The bonding surfaces of the zirconia ceramic copings were either (a) pretreated with airborne particle abrasion and cleaned with alcohol or (b) just cleaned with alcohol, whereas the bonding surfaces of all titanium abutments had been abraded and cleaned. After the specimens had been stressed for either 1, 30, 60, or 150 days by water and thermal cycling, retention was measured.

RESULTS

The surface conditioning method, luting-gap size, and storage time significantly (P = .001; 3-way analysis of variance [ANOVA]) influenced retention. Air abrasion increased the retention significantly. Failure modes were predominantly adhesive. Air-abraded copings bonded with 30-microm luting gap achieved significantly greater retention than those bonded with a 60-microm luting gap.

CONCLUSION

Surface conditioning methods and the size of the luting gap have a significant influence on the retention of Camlog zirconia ceramic copings bonded to Camlog titanium abutments.

Micro-shear bond strength of Er:YAG-laser-treated dentin

This study tested if dentin adhesion is affected by Er:YAG laser. Ninety dentin disks were divided in groups (n = 10): G1, control; G2, Er:YAG laser 150 mJ, 90 degrees contact, 38.8 J/cm(2); G3, Er:YAG laser 70 mJ, 90 degrees contact, 18.1 J/cm(2); G4, Er:YAG laser 150 mJ, 90 degrees non-contact, 1.44 J/cm(2); G5, Er:YAG laser 70 mJ, 90 degrees non-contact, 0.67 J/cm(2); G6, Er:YAG laser 150 mJ, 45 degrees contact, 37.5 J/cm(2); G7, Er:YAG laser 70 mJ, 45 degrees contact, 17.5 J/cm(2); G8, Er:YAG laser 150 mJ, 45 degrees non-contact, 1.55 J/cm(2); and G9, Er:YAG laser 70 mJ, 45 degrees non-contact, 0.72 J/cm(2). Bonding procedures were carried out and the micro-shear-bond strength (MSBS) test was performed. The adhesive surfaces were analyzed under SEM. Two-way ANOVA and multiple comparison tests revealed that MSBS was significantly influenced by the laser irradiation (p < 0.05). Mean values (MPa) of the MSBS test were: G1 (44.97 +/- 6.36), G2 (23.83 +/- 2.46), G3 (30.26 +/- 2.57), G4 (35.29 +/- 3.74), G5 (41.90 +/- 4.95), G6 (27.48 +/- 2.11), G7 (34.61 +/- 2.91), G8 (37.16 +/- 1.96), and G9 (41.74 +/- 1.60). It was concluded that the Er:YAG laser can constitute an alternative tool for dentin treatment before bonding procedures.

Influence of bond quality on failure load of leucite- and lithia disilicate–based ceramics

STATEMENT OF PROBLEM

The long-term survival of bonded ceramic restorations for posterior teeth is a clinical concern. The durability of the bond between the ceramic and dentin during clinical service is a factor in the load-bearing capacity of the restoration.

PURPOSE

This study aimed to evaluate the effect of interfacial bonding quality on the interface failure initiation loads of 2 all-ceramic systems.

MATERIAL AND METHODS

One leucite-reinforced ceramic, IPS Empress (E1), and 1 lithia disilicate glass-ceramic, IPS Empress 2 (E2), were used to form disks 8.5 mm in diameter, with an approximate 1.35-mm total thickness (n=45). The ceramic specimens were fabricated in a manner that simulated their clinical application. The E1 specimens were fabricated using the staining technique, and the E2 specimens were made using a layering technique. Completed disks of each ceramic system were divided into 3 subgroups (n=15) that were subsequently cemented using 1 of 3 bonding conditions (Control, Cer, Sub). The control group followed ideal bonding protocol, whereas groups Cer and Sub had bonds that were compromised between the cement and the ceramic (Cer) or the substrate and the cement (Sub). All luted specimens were loaded at the center with a 10-mm-diameter ball indenter at a crosshead speed of 0.01 mm/min in a universal testing machine. Intermittent loads were applied in increasing increments of 50 N until a fracture could be observed in the ceramic substrate by transillumination with x2.6 optical magnification. The maximum load applied prior to crack observation was recorded as the failure initiation load. Survival analytical methods were used to determine differences between groups.

RESULTS

The characteristic fracture initiation loads ranged from 223.5 to 760.6 N. Group E2 had the greatest mean observed load to failure (715.6 N), which was significantly greater than group E1 (P<.001). For both the E1 and E2 ceramic systems, the control groups had significantly greater mean fracture initiation loads than either of the interface-inhibited Cer and Sub groups.

CONCLUSIONS

Poor bond quality at either the ceramic-cement or dentin-cement interface can significantly reduce the fracture initiation load-bearing capacity of ceramic disks bonded to compliant dentin-like substrates. For the E2 ceramic material, disruption of the ceramic-cement interface had a more detrimental effect on the load-bearing capacity of the simulated restoration than the disruption of the cement-dentin interface.

Personalized orthodontic bracket height in relation to marginal ridges

Correct bracket placement should level both the marginal ridges and the occlusional plane. The authors describe the laboratory and clinical procedures of placing brackets in relation to the marginal ridge. The ray set is a device that allows each tooth to be dealt with an individual unit, virtually isolating it from the rest of the arch and analyzing its position in a 3-dimensional control system that determines the first-, second-, and third-order values, which the clinician needs or which must be written into the slots. The ray set makes it possible to develop and simplify bracket placement methods without a preliminary set-up, while taking an accurate reading of the marginal ridge to establish the height of slots. This procedure can be used with all multibracket techniques (vestibular and lingual) aiming to properly level the occlusal plane, thereby ensuring the correct final occlusion.

Effects of light-emitting diode and halogen light curing techniques on ceramic brackets bonded to porcelain surfaces

The objectives of this study were to test the efficiency of LED curing devices in bonding ceramic brackets to porcelain surfaces and to compare the effects of LED and halogen curing techniques on shear bond strength of ceramic brackets. A total of 20 glazed porcelain facets were randomly divided into two groups of 10. Porcelain surfaces were etched with 9.6% hydrofluoric acid for 2 minutes, and silane was applied on the etched porcelain surface. Ceramic brackets were bonded with an LC composite resin cured with soft start mode LED and a halogen light. Bond strengths, as determined in the shear mode, were higher in the LED group (P < .001). LED curing units with the soft start polymerization mode were more effective than halogen curing units in bonding ceramic brackets on porcelain surfaces. The type of curing light must be considered as an important factor affecting bond strength of ceramic brackets on porcelain surfaces.