Shear bond strength of different retainer wires and bonding adhesives in consideration of the pretreatment process

The Micromechanical Properties and Surface Roughness of Orthodontic Retainer Wires-An In Vitro Analysis

BACKGROUND

Despite the large variety of retainer wires available, no studies could be found comparing the micromechanical properties and surface roughness of different retainer wires. Such characteristics affect the survival of the fixed retainer in terms of both fracture resistance and resistance to debonding from the tooth. Therefore, the aim of the present study was to examine and compare those characteristics in popular retainer wires.

METHODS

six different popular orthodontic retainer wires were subjected to instrumental indentation based on the Oliver and Pharr method. The geometric surface structure was analysed using a non-contact profilometer.

RESULTS

stainless steel wires had a higher hardness and a higher elastic modulus compared to titanium wires and white gold chain. The titanium wire and the white gold chain showed much more roughness than other wires.

CONCLUSIONS

stainless steel wires are the most resistant, considering both the shape retention capacity and the ability to resist abrasive wear. The titanium wire showed the lowest hardness and, thus, the highest susceptibility to deformation. Bond-a-braid, Retainium and Orthoflex white gold are more resistant to fracture than other steel wires. Titanium wire and chain retainer wires have more roughness, which is a great advantage in terms of mechanical adhesion to composite materials.

Mechanical properties of combined packable and high-filled flowable composite used for the fixed retainer: an in vitro study

BACKGROUND

Clinicians often utilize both flowable and packable composites concurrently in bonding fixed retainers. Thus, this study aimed to assess the synergistic effect of these composites in the bonding process.

METHODS

This in vitro study divided specimens into three groups: flowable composite (nano-hybrid, Tetric N-Flow, Ivoclar Vivadent), packable composite (nano-hybrid, Tetric N-ceram, Ivoclar Vivadent), and combined use of flowable and packable composite. Shear bond strength (SBS), adhesive remnant index (ARI), and wire pull-out resistance were compared among the groups. Statistical analyses were conducted using ANOVA and Tukey tests to compare study groups. Additionally, Chi-square and Kruskal-Wallis tests were employed to analyze the ARI index among the groups.

RESULTS

ANOVA results indicated no statistically significant differences among test groups (P = 0.129) regarding SBS. However, a significant difference existed between flowable and packable composite groups (P = 0.01) regarding ARI scores. Among the study groups, flowable composite exhibited the highest frequencies of ARI scores of 1 and 2, whereas packable composite showed the highest frequency of ARI scores of 0. The combined group had higher frequencies of ARI scores of 0 and 1 compared to the flowable composite. The wire pull-out test revealed that the combined application of flowable and packable composite resulted in significantly lower detachments compared to the packable composite alone (P = 0.008). However, no significant differences were observed in the comparisons between the flowable-packable (P = 0.522) and combined-flowable (P = 0.128) groups.

CONCLUSION

The combined use of flowable and packable composites for fixed retainers demonstrated adequate shear bond strength and ideal ARI scores, suggesting it as a suitable adhesive system for bonding orthodontic fixed retainers.

Comparison of six different CAD/CAM retainers vs. the stainless steel twistflex retainer: an in vitro investigation of survival rate and stability

PURPOSE

To compare failure rates and maximum load capacity (F_max) of six different computer-aided design/computer-aided manufacturing (CAD/CAM) retainers with those of the hand-bent five-stranded stainless steel twistflex retainer.

MATERIALS AND METHODS

Six groups (n = 8 per group) of commercially available CAD/CAM retainers (cobalt-chromium [CoCr], titanium grade 5 [Ti5], nickel-titanium [NiTi], zirconia [ZrO₂], polyetheretherketone [PEEK], and gold) and twistflex retainers were tested for long-term sufficiency and for F_max using a self-developed in vitro model. All retainer models underwent a simulated ageing process of about 15 years (1,200,000 chewing cycles with a force magnitude of 65 N at 45° followed by storage in water at 37 °C for 30 days). If retainers did not debond or break during ageing, their F_max was determined in a universal testing machine. Data were statistically analysed using Kruskal-Wallis and Mann-Whitney U‑tests.

RESULTS

Twistflex retainers did not fail (0/8) during ageing and had the highest F_max (445 N ± 51 N). Ti5 retainers were the only CAD/CAM retainers that also did not fail (0/8) and had similar F_max values (374 N ± 62 N). All other CAD/CAM retainers had higher failure rates during ageing and significantly lower F_max values (p < 0.01; ZrO₂: 1/8, 168 N ± 52 N; gold: 3/8, 130 N ± 52 N; NiTi: 5/8, 162 N ± 132 N; CoCr: 6/8, 122 N ± 100 N; PEEK: 8/8, 65 ± 0 N). Failure was due to breakage in the NiTi retainers and debonding in all other retainers.

CONCLUSION

Twistflex retainers remain the gold standard regarding biomechanical properties and long-term sufficiency. Of the CAD/CAM retainers tested, Ti5 retainers seem to be the most suitable alternative. In contrast, all other CAD/CAM retainers investigated in this study showed high failure rates and had significantly lower F_max values.

Comparison of the debonding force of metal, glass and polyethylene Fiber reinforced composite retainers: Mechanical and finite element analyses

OBJECTIVE

The studies evaluating the efficiency of fiber reinforce composite (FRC) retainers are few and contradictory. This study aimed to compare the debonding force of metal, glass FRC (GFRC) and polyethylene FRC (PFRC) retainers, assess the interactions between the materials and forces, and pattern of load distribution by finite element analysis (FEA).

MATERIALS AND METHODS

Forty-eight sound lower incisors were collected and randomly assigned to 3 groups (n=8; each sample included 2 teeth). Next, 15mm of the three retainers (multi-stranded metal wire, GFRC, and PFRC) were bonded to the lingual surface of the teeth and debonding force was measured by a universal testing machine. For FEA, 3D models were designed. The data related to geometrical models and material properties were transferred to ANSYS software. A 187-Newton load was applied to the incisal edge of the two centrals. Then different parameters were assessed. The three groups were compared by one-way Anova and Tukey's test. Type one error was considered to be 0.05.

RESULTS

The debonding force decreased in the order: Metal (143.71N)≥GFRC (108.29N)>PFRC (45.08N). The difference between metal retainer and GFRC was not significant. In contrast, PFRC group showed significantly lower debonding force compared to other groups (P<0.05). FEA showed stress peak value in metal-composite interface. Maximum total deformation was noted in central, followed by lateral and canine.

CONCLUSIONS

Glass-FRC can serve as an alternative to metal retainers as the difference in debonding force is not significant. However, the difficulty of repairing or replacing the Glass-FRC should be taken into account given the large number of failure in the interproximal dental area.

Comparison of microleakage and shear bond strength of ribbon and twisted wire retainers bonded on human mandibular incisors with two different types of adhesives with and without primer: An in-vitro study

BACKGROUND AND OBJECTIVES

Shear bond strength and microleakage are the success factors of fixed retainers. Recently, primer-free composites were introduced to reduce chair time. The main objectives of this study were to compare the shear bond strength (SBS) and microleakage of GC Ortho Connect^TM Flow (OF) and Transbond^TM XT (TXT) with two types of common retainer wires (0.0175-inch twisted wire and 0.028×.0.008-inch ribbon dead soft wire retainers). The secondary objectives of the study were to compare enamel-adhesive interface and wire-adhesive interface microleakages.

MATERIALS AND METHODS

This in vitro study was conducted on 132 human mandibular incisors (96 for bond strength and 36 for microleakage). The teeth were randomly divided into four groups for use of ribbon and twisted wires with OF and TXT adhesives. The bond strength was measured by a universal testing machine. Microleakage was evaluated by the dye penetration test using 0.05% fuchsine. Data were analysed by two-way ANOVA (alpha=0.05).

RESULTS

No significant difference was noted in bond strength among the four groups (P>0.05). However, the microleakage of OF was significantly higher than that of TXT at both the enamel-adhesive and wire-adhesive interfaces (P<0.001). The microleakage at the wire-adhesive and enamel-adhesive interface was not significantly different in groups 1 and 4 and was significant in group 2 and 3.

CONCLUSION

Type of adhesive significantly affected the microleakage, and OF resulted in higher microleakage than TXT at both the enamel-adhesive and wire-adhesive interfaces. Type of wire had no significant effect on microleakage. Although OF showed comparable SBS to TXT, its higher microleakage may compromise its successful long-term clinical service.

Orthodontic Fixed Retainer and Unwanted Movements of Lower Anterior Teeth: A Case Report

The use of fixed retainers at the end of an orthodontic treatment has become a standard practice. Nonetheless, orthodontic relapse can still occur, requiring retreatment in the most severe cases. This case report describes a patient with a mandibular canine to canine fixed retainer presenting uncontrolled torque on all lower anterior teeth, probably due to tongue thrust and/or activation of the wire. Multibracket orthodontic treatment was performed, and an orthodontic lingual sectional was used to control (reposition) the root movement of the lower right cuspid. This case highlights the need for clinicians and patients to be aware of the potential problems associated with bonded retainers. In addition, patients with an orthodontic fixed retainer need regular short-term observation by an orthodontist in order to detect any adverse movements and long-term control by a general dentist.

Preparation of Nano-Apatite Grafted Glass-Fiber-Reinforced Composites for Orthodontic Application: Mechanical and In Vitro Biofilm Analysis

This study aimed to fabricate nano-hydroxyapatite (nHA) grafted/non-grafted E-glass-fiber-based (nHA/EG) and E-glass fiber (EG) orthodontic retainers and to compare their properties with commercially available retainers. Stainless-steel (SS) retainers and everStick Ortho (EST) were used as control groups. The retainers were evaluated with Raman spectroscopy and bonded to bovine teeth. The samples were fatigued under cyclic loading (120,000 cycles) followed by static load testing. The failure behavior was evaluated under an optical microscope and scanning electron microscope. The strain growth on the orthodontic retainers was assessed (48h and 168h) by an adhesion test using Staphylococcus aureus and Candida albicans. The characteristic peaks of resin and glass fibers were observed, and the debonding force results showed a significant difference among all of the groups. SS retainers showed the highest bonding force, whereas nHA/EG retainers showed a non-significant difference from EG and EST retainers. SS retainers’ failure mode occurred mainly at the retainer–composite interface, while breakage occurred in glass-fiber-based retainers. The strains’ adhesion to EST and EG was reduced with time. However, it was increased with nHA/EG. Fabrication of nHA/EG retainers was successfully achieved and showed better debonding force compared to other glass-fiber-based groups, whereas non-linear behavior was observed for the strains’ adhesion.

Universal Adhesive for Fixed Retainer Bonding: In Vitro Evaluation and Randomized Clinical Trial

This study aims to assess the efficacy of a universal adhesive (Scotchbond Universal, 3M ESPE) (SB) in total-etch mode, compared to a traditional orthodontic primer (Transbond XT Primer, 3M ESPE) (XT Primer), to perform bonding of orthodontic fixed retainers along with the Transbond XT Light Cure Adhesive Paste (3M ESPE). For the in vitro study, a round section wire (Ortosmail Krugg) was bonded using XT Primer for 20 bovine incisors (Group 1) and SB for other 20 (Group 2). Samples were debonded in a universal testing machine applying a tangential force to specimens (crosshead speed of 1 millimeter per minute). Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. For the in vivo study, 100 patients needing upper and lower canine-to-canine fixed retainers after orthodontic treatment were randomly assigned to two groups of 50 participants each, i.e., group 1 (retainer bonding with XT Primer) and group 2 (retainer bonding with SB). Over two years, examinations were carried out monthly, and detachments were registered by considering the teeth and arches affected. In vitro, no statistically significant differences in SBS and ARI scores were demonstrated between the two groups, both showing a mean bond strength of about 12 MPa and major frequency of ARI “2” (>50% remnant adhesive on the enamel). Conversely, a significantly lower failure rate over 2 years was assessed clinically for group 2 in both arches. Independently of the adhesive and arch, incisors reported a significantly higher failure rate than canines. Scotchbond Universal used in total-etch mode could be a valid alternative to the traditional orthodontic Transbond XT Primer.

How sandblasting on lingual surfaces can be carried out with minimum enamel damage: An in vitro study on human teeth

OBJECTIVE

The aim was to assess the extent of enamel damage sandblasting might cause and to identify a combination of sandblasting durations and MicroEtcher nozzle-tooth surface distance (NTD) resulting in the least enamel damage.

MATERIALS AND METHODS

Lingual surfaces of 30 human teeth were sandblasted with 2 different distances: 1, 2mm and 3 different durations: 1, 2, 3s and photographed using a light microscope. The cavity depth and diameter of the sandblasted teeth were measured on the light microscope's pictures. A pilot study was performed to minimize possible combinations of sandblasting durations and distances. To validate the measurement method, sandblasted teeth were ground cut for comparison. Inter-examiner reliability was assessed with Bland-Altman analysis. Mann-Whitney U-test was used to detect cavity and diameter changes for every sandblasting duration and NTD combination.

RESULTS

From the pilot study sandblasting durations 1,2 and 3s and NTD<2mm were chosen. The cavity diameter of the sandblasted area did not change with increased sandblasting duration nor NTD (P>0.05). The cavity depth of the sandblasted area increased statistically with an increased sandblasting duration (P<0.05) but did not increase with an increase NTD (P>0.05). The 95% limits of inter-examiner agreement were narrow.

CONCLUSION

All distance and duration combinations tested caused enamel damage. Sandblasting duration had greater impact on the cavity depth than the NTD. The blasting duration should, therefore, not exceed 2s and the NTD should be held at maximum 2mm to minimize the risk of unintentional spread.

Comparison of lithium disilicate-reinforced glass ceramic surface treatment with hydrofluoric acid, Nd:YAG, and CO2 lasers on shear bond strength of metal brackets

OBJECTIVES

To evaluate and compare the effects of different surface conditioning methods of lithium disilicate-reinforced ceramic on shear bond strength (SBS) of metallic brackets.

MATERIALS AND METHODS

Thirty-six lithium disilicate ceramic blocks mounted in acrylic resin blocks were assigned to 3 groups (n = 12): 9.6% hydrofluoric acid (HF); neodymium-doped yttrium aluminium garnet (Nd:YAG) laser; and carbon dioxide (CO₂) laser. The glass ceramic surfaces were primed with a silane, and the brackets were bonded using a light-cured composite resin. SBS test was carried out in a universal testing machine at 0.5 mm/min crosshead speed until the brackets were debonded. The remaining adhesive was evaluated under a stereomicroscope in terms of the adhesive remnant index (ARI). The surface hardness was determined with a 100-gr force using a microhardness tester. Glass ceramic surface changes were evaluated using the scanning electron microscope. One-way ANOVA and post hoc Tamhane tests were used to compare microhardness values, and Kruskal-Wallis and Mann-Whitney U tests were used to analyze SBS values and ARI.

RESULTS

The median and interquartile range of SBS values in 3 groups were 6.48 (1.56-15.18), 1.26 (0.83-1.67), and 0.99 MPa (0.70-2.10), respectively. Microhardness analysis revealed significant differences between the CO₂ laser and intact porcelain groups (P = 0.003), without significant differences between the other groups. Group 1 exhibited the highest ARI.

CONCLUSION

Neither CO₂ nor Nd:YAG lasers resulted in adequate surface changes for bonding of brackets on ceramics compared with the samples conditioned with HF. CO₂ laser decreased the microhardness of ceramics.

CLINICAL RELEVANCE

Surface conditioning with HF resulted in clinically acceptable SBS values.

Analysing the potential of hydrophilic adhesive systems to optimise orthodontic bracket rebonding

Introduction

Bond failure during fixed orthodontic treatment is a frequently occurring problem. As bracket rebonding is associated with reduced shear bond strength, the aim of the present investigation is to analyse the effect of different innovative rebonding systems to identify optimised rebonding protocols for orthodontic patient care.

Methods

Metallic brackets were bonded to the frontal enamel surfaces of 240 bovine lower incisors embedded in resin bases. Teeth were randomly divided into two major experimental groups: in group 1 a hydrophilic primer (Assure™ PLUS) was compared to commonly used orthodontic adhesives (Transbond XT™, BrackFix®, Grengloo™) and a zero control. In group 2 different rebonding systems were analysed using a hydrophilic primer (Assure™ PLUS), a methyl methacrylate-consisting primer (Plastic Conditioner) and a conventional adhesive (Transbond XT™). All teeth were tested for shear bond strength according to the DIN-13990 standard, the Adhesive Remnant Index and enamel fracture rate.

Results

The hydrophilic primer enhanced shear bond strength at first bonding (Assure™ PLUS 20.29 ± 4.95 MPa vs. Transbond XT™ 18.45 ± 2.57 MPa; BrackFix® 17 ± 5.2 MPa; Grengloo™ 19.08 ± 3.19 MPa; Meron 8.7 ± 3.9 MPa) and second bonding (Assure™ PLUS 16.76 ± 3.71 MPa vs. Transbond XT™ 13.06 ± 3.19 MPa). Using Plastic Conditioner did not seem to improve shear bond strength at rebonding (13.57 ± 2.94). When enamel etching was left out, required shear bond strength could not be achieved (Plastic Conditioner + Assure™ PLUS 8.12 ± 3.34 MPa; Plastic Conditioner: 3.7 ± 1.95 MPa). Hydrophilic priming systems showed decreased ARI-scores (second bonding: 2.63) and increased enamel fracture rates (first bonding: 55%; second bonding 21,05%).

Conclusions

Based on the present study we found that rebonding strength could be compensated by the use of hydrophilic priming systems. The additional use of a methyl methacrylate-consisting primer does not seem to enhance shear bond strength. No etching approaches resulted in non-sufficient bond strength.

Effect of the caries-protective self-assembling peptide P11-4 on shear bond strength of metal brackets

Purpose

During orthodontic treatment with fixed appliances, demineralization around brackets often occurs. The aim of this in vitro study was to investigate the effect of the caries-protective self-assembling peptide P11‑4 (SAP P11-4) on the shear bond strength of metal brackets.

Methods

In all, 45 extracted human wisdom teeth were available for the study. The teeth were randomly divided into 3 groups (each n = 15) and pretreated as follows: test group 1: application of SAP P11‑4 (Curodont Repair, Windisch, Switzerland) and storage for 24 h in artificial saliva; test group 2: application of SAP P11‑4; control group: no pretreatment with SAP P11‑4. A conventional metal maxillary incisor bracket (Discovery, Dentaurum, Ispringen) was adhesively bonded to each buccal surface. The shear bond strength was tested according to DIN 13990. After shearing, the Adhesive Remnant Index (ARI) was determined microscopically (10 × magnification). Analysis of variance (ANOVA) was used to check the groups for significant differences (α = 0.05). The distribution of the ARI scores was determined with the χ ² test.

Results

There was no significant difference in shear forces between the groups (p = 0.121): test group 1 = 17.0 ± 4.51 MPa, test group 2 = 14.01 ± 2.51 MPa, control group 15.54 ± 4.34 MPa. The distribution of the ARI scores between the groups did not vary (p-values = 0.052–0.819).

Conclusion

The application of the caries protective SAP P11‑4 before bonding of brackets did not affect the shear bond strength. Therefore, pretreatment of the enamel surface with SAP P11‑4 shortly before bracket insertion can be considered.

The lingual enamel morphology and bracket shear bond strength influenced by Nd:YAG laser and aluminum oxide sandblasting preconditioning

OBJECTIVES

This study aimed to investigate the influence of Nd:YAG laser and aluminum oxide sandblasting on the shear bond strength (SBS) of lingual brackets and to optically analyze the behavior of the enamel morphology.

MATERIALS AND METHODS

Thirty-five bovines' incisors teeth were divided into 5 groups (n = 7), according to the surface preconditioning: G1, control group; G2, Nd:YAG laser; G3, laser + aluminum oxide sandblasting (Al₂O₃); G4, Al₂O₃; and G5, Al₂O₃ + laser. All groups had lingual brackets bonded and shear debonded after 72 h. SBS values were analyzed, and the enamel morphology was evaluated by optical coherence tomography (OCT) and scanning electron microscope (SEM), before and after preconditioning surface. The optical attenuation coefficient (α) analysis was obtained from OCT images. Data analysis used the ANOVA test, followed by post hoc Tukey, Kruskal Wallis, and post hoc Dunn tests (significance of 5%).

RESULTS

The SBS values presented similarly among groups, but the value of α showed statistical difference (p-value = 0.0124) between G3 and G5 with the others. Optical analyses indicated a melting on the enamel that suffered laser irradiation for G2 and G5 and crystal surface disorganization for G4. Sandblasting partially removes the melting of the laser effect (G3).

CONCLUSION

The sandblasting is a dispensable step for bonding lingual brackets, and the melting of the enamel after laser irradiation does not compromise the bracket adhesive resistance.

CLINICAL RELEVANCE

The Nd:YAG laser became an interesting tool to prevent caries and decrease prevalence of white spot lesions in orthodontic treatments, without systemic effects in patients with genetic high risks of caries.

Evaluation of bond strength of molar orthodontic tubes subjected to reinforcement with flowable and bonding resins

OBJECTIVE

The goal was to evaluate the adhesive shear bond strength (SBS) of orthodontic tubes bonded to molar teeth and reinforced with Transbond XT (3M Science, St. Paul, MN, USA) and flowable resin.

MATERIALS AND METHODS

In all, 120 molar teeth, previously extracted from patients with a mean age of 30 were included. Orthodontic molar tubes were bonded on the vestibular surface of these teeth with one of two types of adhesive (Transbond XT [3M Science, St. Paul, MN, USA] or Orthobond [Morelli, Sorocaba, Brazil]). Each of these groups was subsequently divided into four further groups: control and those subjected to the use of resin reinforcement on the occlusal surface of the bonded tubes with one of three materials (Transbond XT, Tetric N Flow [Ivoclar Vivadent, Ellwangen, Germany], Z 350 Flow [3M Science, St. Paul, MN, USA]). SBS and adhesive remnant index tests were performed to evaluate bond strength and type of fracture of the tubes bonded with the different methods.

RESULTS

The use of resin reinforcement with Transbond XT significantly increased the SBS of tubes bonded with both materials. Flowable composites did not increase the SBS when used as a reinforcement. Less than 50% of the adhesive remained on the vestibular surface after the SBS test in most samples of all groups.

CONCLUSION

Transbond XT orthodontic adhesive and Orthobond adhesive had appropriate bonding strengths for clinical use. Furthermore, the use of a resinous reinforcement with Transbond XT significantly increased the SBS of tubes bonded. However this technique with flowable adhesives (Tetric N Flow and Z350 Flow) did not significantly increase SBS when orthodontic tubes were bonded with Transbond XT or Orthobond.

Fear of the Relapse: Effect of Composite Type on Adhesion Efficacy of Upper and Lower Orthodontic Fixed Retainers: In Vitro Investigation and Randomized Clinical Trial

The aim of this laboratory and clinical study is to determine the reliability of the flowable nanocomposite Filtek Supreme XTE (FL) for the adhesion of orthodontic retainers, compared to highly filled orthodontic resin Transbond XT (XT). Portions of a round section multistranded wire (Ortosmail Krugg) were bonded to 40 bovine incisors with Scotchbond Universal in total-etch modality. For group one (XT, 20 samples), the orthodontic resin was used, whereas in group two (FL, 20 samples), the flowable one. Specimens were placed into a universal testing machine which applied a shear force on retainers with a crosshead speed of one/minute. Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. In the clinical trial, 100 patients requiring a canine-to-canine palatal and lingual retainer were randomly divided into two groups, according to the resin used for bonding procedure: the orthodontic in group one (XT, 50 participants) and the flowable in group two (FL, 50 participants). Monthly visits were carried out over a 24-month follow up to assess any detachment occurring on teeth of both arches. All data were submitted to statistical analysis. In vitro, FL reported a significant lower mean SBS, whereas no significant differences in ARI were reported between the two groups which both showed a major frequency of scores “1” and “2”. At the end of the 24-month follow up, FL reported significantly higher failure rates in both arches besides a significantly lower survival rate starting from the sixth month after retainers bonding. According to the results assessed in vitro and clinically, XT would be preferable to FL when performing retainers bonding procedure.

Adhesive luting of orthodontic devices to silica-based ceramic crowns-comparison of shear bond strength and surface properties

OBJECTIVES

The aim of this study was to analyse the impact of different clinical conditioning approaches and an ammonium polyfluoride- and trimethoxysilylpropyl methacrylate-based experimental primer for intraoral luting of buccal tubes on silica-based ceramic surfaces.

MATERIALS AND METHODS

A total of 60 leucite-reinforced glass ceramic molar crowns were conditioned using different methods (n = 10): I-roughening, hydrofluoric acid, silane; II-roughening, silane; III-roughening, experimental coupling agent; IV-experimental coupling agent; V-roughening; VI-no treatment. A buccal tube was adhesively luted to the ceramic surface. Subsequently, water storage, thermocycling and chewing simulation were carried out. The shear bond strength (SBS) was determined, and changes in the surface were assessed.

RESULTS

All tubes of the control group (group VI) debonded after incubation. The conditioning methods using coupling agents revealed mean values for SBS of 61.56 MPa (group I), 45.53 MPa (group III), 41.65 MPa (group II), and 23.14 MPa (group IV). In groups I-III, both composite residues and cracks/tear-outs were detected.

CONCLUSIONS

The conditioning of silicate ceramic surfaces with a suitable coupling agent system appears to allow sufficient adhesive luting of buccal tubes. The intraoral luting of fixed appliance elements on silicate ceramic surfaces using an ammonium polyfluoride- and trimethoxysilylpropyl methacrylate-based ceramic primer can withstand orthodontic forces.

CLINICAL RELEVANCE

Ammonium polyfluoride- and trimethoxysilylpropyl methacrylate-based ceramic primers revealed promising results for the intraoral adhesive luting of orthodontic devices to silica-based ceramic crowns.

Influence of enamel sealing with a light-cured filled sealant before bracket bonding on the bond failure rate during fixed orthodontic therapy

PURPOSE

Fluoride-containing adhesives for enamel sealing are commonly used for the prevention of white spot lesions during fixed orthodontic treatment. Thus, we examined whether enamel sealing with L.E.D. ProSeal® (Reliance Orthodontic Products Inc., Itasca, IL, USA) before bracket bonding increases the rate of bond failure during orthodontic treatment.

METHODS

In 20 adolescents (11-16 years, 10 male/10 female) at the start of fixed therapy, self-ligating SmartClip™SL3 metal brackets (3M Unitek, Monovia, CA, USA) were bonded to cleaned and conditioned (40% H₃PO₄, 30 s) buccal enamel surfaces of all permanent teeth except molars using Transbond™ XT (3M Unitek). In a split-mouth design, either L.E.D. ProSeal® (1st/3rd quadrant) or Clinpro™ XT Varnish (2nd/4th quadrant; 3M Unitek) was applied to enamel surfaces before (ProSeal®) or after (Clinpro™ XT Varnish) bracket bonding (200 teeth each; light curing: 20 s, Ortholux™ Luminous, 3M Unitek). Cumulative bond failure as total number of teeth with bracket detachment since start of therapy was documented every 3 months for a total of 12 months.

RESULTS

Cumulative bond failure was higher for enamel sealing before bonding from 6 months onward reaching significance at 12 months (34/200) compared to sealing after bonding (24/200): p = 0.038; Cramér's V = 0.488; odds ratio (OR) = 1.5; relative risk (RR) = 1.4. The higher loss rate was limited to the lower arch, but evident within 3 months reaching significance at 9 and 12 months (p = 0.019/0.011, V = 0.636/0.630; OR = 1.7/1.75, RR = 1.5/1.6). In general, cumulative bond failure at 12 months was higher in the lower arch, but this was only significant for teeth sealed before bonding (p = 0.001, V = 0.303, OR = 3.4, RR = 2.8).

CONCLUSIONS

Enamel sealing with L.E.D. ProSeal® should be performed after bracket bonding to prevent increased bond failure and bracket loss in the lower dental arch.

The influence of enamel sandblasting on the shear bond strength and fractography of the bracket-adhesive-enamel complex tested in vitro by the DIN 13990:2017-04 standard

OBJECTIVES

This study was conducted in order to investigate whether enamel sandblasting as an adjunct or substitute to the acid-etch technique has an effect on the shear bond strength (SBS) and fractography of the bracket-adhesive-enamel complex using the DIN 13990:2017-04 standard.

MATERIALS AND METHODS

Upper central incisor brackets (discovery®, Dentaurum, Germany) were bonded using Transbond XT™ (3M Unitek, Germany) on bovine incisors prepared by four different methods (15 samples each): sandblasting with 27 μm Al₂O₃ at 1.2 bar (s), acid etching with 37.4% phosphoric acid (a), sandblasting with 27 μm Al₂O₃ at 1.2 bar followed by acid etching (s1a), and sandblasting with 50 μm Al₂O₃ at 5.7 bar followed by acid etching (s2a). The SBS and adhesive remnant index (ARI) were measured, followed by one-way analysis of variance and Fisher's exact tests at 5%.

RESULTS

The SBS in groups s (5.6 ± 2.2 MPa), a (17.1 ± 4.3 MPa), s1a (18.3 ± 4.3 MPa), and s2a (18.5 ± 4.6 MPa) indicated that the s group was significantly inferior to all the other groups (p < 0.001). Likewise, the ARI analysis indicated a different performance of the s group (mostly ARI of 0) compared to the other groups (p < 0.001) and a tendency for different ARI between the a and s1a/s2a groups.

CONCLUSIONS

In vitro enamel sandblasting could not substitute acid etching and did not offer improved SBS when used before acid etching, regardless of air pressure and powder granulation. Sandblasting without acid etching produced less residual resin on the tooth after debonding.

CLINICAL RELEVANCE

The clinical use of adjunct enamel sandblasting prior to etching to enhance SBS has to be questioned.

The effect of prior sandblasting of the wire on the shear bond strength of two different types of lingual retainers

PURPOSE

The aim of this study was to evaluate the effect of total surface sandblasting on the shear bond strength of two different retainer wires. The null hypothesis was that there is no difference in the bond strength of the two types of lingual retainer wires when they are sandblasted.

MATERIALS AND METHODS

One hundred and sixty human premolar teeth were equally divided into four groups (n=40). A pair of teeth was embedded in self-curing acrylic resin and polished. Retainer wires were applied on the etched and rinsed surfaces of the teeth. Four retainers were used: group 1: braided retainer (0.010×0.028″, Ortho Technology); group 2: sandblasted braided retainer (0.010×0.028″, Ortho Technology); group 3: coaxial retainer (0.0215″ Coaxial, 3M) and group 4: sandblasted coaxial retainer (0.0215″ Coaxial, 3M). The specimens were tested using a universal test machine in shear mode with a crosshead speed of one mm/min.

RESULTS

One-way analysis of variance (Anova) was used to determine the significant differences among the groups. There was no significant difference (P=0.117) among the groups according to this test.

CONCLUSIONS

The null hypothesis was accepted. There was no statistically significant difference among the shear bond strength values of the four groups.