Long-term bonding to eroded dentin requires superficial bur preparation

Objectives

This study aims to evaluate the influence of different surface preparation techniques on long-term bonding effectiveness to eroded dentin.

Materials and methods

Dentin specimens were eroded by pH cycling or were left untreated as control, respectively. Five different “preparation” techniques were applied: (1) cleaning with pumice, (2) air abrasion, (3) silicon polisher, (4) proxo-shape, and (5) diamond bur. The three-step etch-and-rinse adhesive OptiBond FL (O-FL; Kerr) and the mild two-step self-etch adhesive Clearfil SE Bond (C-SE; Kuraray) were evaluated. Micro-tensile bond strength was measured after water storage for 24?h and 1?year. Fracture analysis was performed by stereomicroscopy and SEM. Interfaces were characterized by TEM. Differences were statistically analyzed with a linear mixed effects model (α?=?0.05).

Results

Erosion reduced bond strength in all groups, but this effect was less prominent when eroded dentin was prepared by diamond bur. Storage lowered bond strength in almost all groups significantly, but this ageing effect was more prominent for the eroded surfaces than for non-eroded controls. Whereas after 1-year control specimens revealed superior bond strength with the three-step etch-and-rinse adhesive (O-FL), the mild two-step self-etch adhesive (C-SE) revealed a better 1-year bond strength to eroded dentin. The interface at eroded dentin appeared very prone to degradation as was shown by the increased amount of adhesive failures and by the silver infiltration detected by TEM.

Conclusions and clinical relevance

Although a minimally invasive approach should clinically always be strived for, superficial preparation (or minimal roughening) with a diamond bur is recommendable for long-term bonding to eroded dentin.     

Influence of caries infiltrant contamination on shear bond strength of different adhesives to dentin

Objectives

To analyze whether the contamination with a caries infiltrant system impairs the adhesive performance of etch-and-rinse and self-etching adhesives on dentin.

Materials and methods

Dentin contamination with the caries infiltrant system (Icon, DMG) was simulated by applying either hydrochloric acid (15 % HCl, Icon Etch, 15 s), the resin infiltrant (Icon infiltrant, 4 min), or both prior to the application of the respective adhesives (each group n?=?10). In the control groups, the etch-and-rinse adhesive (Optibond FL, Kerr) and the self-etching adhesive (iBOND Self Etch, Hereaus) were applied without former contamination with the infiltrant system. Additionally, the adhesive performance of the resin infiltrant alone was tested. Shear bond strength of a nano-hybrid composite was analyzed after thermocycling (5,000×, 5–55°C) of the specimens and analyzed by ANOVA/Scheffé post hoc tests (p?<?0.05) and Weibull statistics. Failure mode was inspected under a stereomicroscope at?×?25 magnification.

Results

Contamination with the resin infiltrant alone did not impair shear bond strength, while contamination with hydrochloric acid or with hydrochloric acid and the resin infiltrant reduced shear bond strength (MPa) of the adhesives (Optibond FL: 20.5?±?3.6, iBOND Self Etch: 17.9?±?2.6) significantly. Hydrochloric acid contamination increased the number of adhesive failures. The adhesive performance of the caries infiltrant system alone was insufficient.

Conclusion

The contamination with the caries infiltrant system impaired the shear bond strength of conventional dental adhesives.

Clinical relevance

Contamination of the caries infiltrant system on dentin should be avoided due to the detrimental effect of hydrochloric acid etching.     

Three-year clinical evaluation of a two-step self-etch adhesive with or without selective enamel etching in non-carious cervical sclerotic lesions

Objective

The purpose of this prospective, controlled, randomized study was to evaluate the 3-year clinical performance of a two-step self-etch adhesive (AdheSE, Ivoclar Vivadent; Schaan, Liechtenstein) in non-carious cervical sclerotic lesions with or without selective acid-etching of the enamel margins.

Material and methods

Twenty-two patients (mean age 51.5) having at least two pairs of non-carious cervical sclerotic erosion?attrition?abfraction lesions with incisal or occlusal margins in the enamel and gingival margins in the dentin were included in the study. The two-step self-etch adhesive was applied following either the self-etch approach (AdheSE non-etch, n?=?52) or a similar application approach, including prior selective acid-etching of the enamel margins (AdheSE etch, n?=?52). Composite resin Point 4 (Kerr Corp; Orange, CA, USA) was used as the restorative material for all 104 restorations. The restorations were evaluated at baseline and after 1, 2, and 3 years, according to the modified USPHS criteria. Data were analyzed using McNemar’s test (p?<?0.05).

Results

The retention rates for AdheSE non-etch were 100 %, 98 %, and 91.5 %; whereas, 100 %, 100 %, and 97.9 % retention rates were recorded for AdheSE etch after 1, 2, and 3 years, respectively. No significant differences were detected between the retention rates, marginal adaptation at the dentin side, secondary caries, and postoperative sensitivity (p?>?0.05). A significantly higher number of restorations in AdheSE non-etch group showed clinically acceptable slight marginal discoloration (p?=?0.0001) and clinically acceptable small marginal defects at the enamel side (p?=?0.008) than in the AdheSE etch group.

Conclusions

After 3 years, the two-step self-etch adhesive exhibited acceptable clinical performance with or without selective enamel etching in non-carious cervical sclerotic lesions.

Clinical relevance

Selective acid-etching of the enamel margins enhanced the performance of the two-step self-etch adhesive in terms of marginal discoloration and marginal adaptation at the enamel side.     

Five-year clinical performance of a HEMA-free one-step self-etch adhesive in noncarious cervical lesions

Objectives

The objective of this randomized controlled trial was to evaluate the clinical performance of a 2-hydroxyethyl methacrylate (HEMA)-free one-step adhesive.

Materials and methods

Two hundred sixty-seven cervical lesions in 52 patients were restored with the composite Gradia Direct (GC), bonded with either the one-step self-etch adhesive G-Bond (GC) or the three-step etch-and-rinse adhesive Optibond FL (Kerr) in a random order. The restorations were evaluated for retention, marginal integrity, marginal discoloration, and caries occurrence after 5 years. Specific statistics were used to account for the clustered data (multiple restorations per patient).

Results

The clinical success rate for G-Bond (87.4 %) was not significantly different from that of Optibond FL (90.9 %). Both adhesives showed progressive marginal deterioration, but G-Bond exhibited more small enamel defects and marginal discoloration, and unlike previous recalls, several restorations failed because of deep microleakage. Large sclerotic lesions were a significant risk factor for retention loss with G-Bond. Irrespective of the adhesive, almost all restorations with retention loss were located in the lower jaw.

Conclusion

After 5 years of clinical service, restorations bonded with the HEMA-free one-step adhesive did not need repair or replacement more often than those with the three-step etch-and-rinse adhesive, and both adhesives had a high retention rate (>90 %). There were indications that G-Bond did not (self-)etch enough in some clinical situations, as G-Bond exhibited more incisal defects and marginal discolorations, and sclerotic lesions were at higher risk of retention loss.

Clinical relevance

The clinical performance of the HEMA-free one-step adhesive was clinically acceptable after 5 years.     

Bonding and sealing ability of a new self-adhering flowable composite resin in class I restorations

Objectives

The aim of this study is to assess by means of shear bond strength tests (SBS), microleakage analysis (μLKG), and scanning electron microscopy (SEM) the bonding potential and sealing ability of a new self-adhering composite resin.

Materials and methods

SBS and μLKG of Vertise Flow (VF, Kerr) were measured and compared to the all-in-one adhesive systems G-Bond (GB, GC), AdheSE One (AO, Ivoclar Vivadent), Adper Easy Bond (EB, 3M ESPE), Xeno V (XV, Dentsply), and iBOND (iB, Heraeus Kulzer). For each system, 20 molars were tested for SBS on dentin (n?=?10) and enamel (n?=?10). For μLKG assessment, 12 premolars per group were selected and small, box-shaped cavities were made. After restoration, the teeth were immersed in 50 wt% silver nitrate solution for 24 h. For each group, 10 randomly selected specimens were processed for leakage calculations, while two of the specimens were examined under SEM. Between-group differences in SBS to dentin and μLKG were assessed using Kruskal–Wallis analysis of variance followed by the Dunn’s Multiple Range test. Enamel SBS data were analyzed with one-way ANOVA, followed by the Tukey test.

Results

On dentin and enamel, VF recorded the lowest SBS values that were statistically comparable to those measured by GB, iB, and AO. μLKG analysis showed the lowest percentage of stained interface for VF. Significantly greater extent of infiltration was seen for iB and EB.

Conclusions

Although VF resulted in lower bond strengths values on either dental substrate, better marginal sealing ability was visualized in comparison with all-in-one adhesive systems.

Clinical relevance

The results of the present study demonstrated satisfactory in vitro outcome of the self-adhering flowable composite resin VF when used to restore class I cavities.     

Retention of tooth-colored restorations in non-carious cervical lesions—a systematic review

Objectives

The aim of this review was to assess the effect of different adhesive systems and tooth preparation on the retention of tooth-colored restorative materials placed in non-carious cervical lesions (NCCLs).

Methods

Randomized clinical trials with a minimum of 3 years of follow-up that evaluated the effectiveness of tooth-colored materials, adhesive systems, and preparation techniques for the restoration of NCCLs were selected. The Cochrane Central Register of Controlled Trials (CENTRAL), EMBASE (OVID), the Latin American and Caribbean Health Sciences Literature database (LILACS), and Medline (OVID) electronic databases were searched from 1990 to 2013.

Results

Twenty-seven randomized clinical trials were included and reviewed. Meta-analysis was used to determine the relative risk of loss of tooth-colored NCCL restorations between different categories of adhesive systems. The effect of tooth preparation could not be similarly analyzed.

Conclusion

The current best evidence indicates that a glass ionomer cement has a significantly lower risk of loss of a NCCL restoration compared to either a three-step etch-and-rinse or a two-step etch-and-rinse adhesive system; a three-step etch-and-rinse adhesive system has a significantly lower risk of loss of a NCCL restoration compared to a two-step etch-and-rinse adhesive system. No significant difference could be observed in the risk of loss of a tooth-colored NCCL restoration between a three-step etch-and-rinse adhesive system and either a two-step self-etch or a one-step self-etch adhesive system.     

Leistungsvermögen unterschiedlicher Adhäsive im Milchgebiss

Background

In the post-amalgam era, adhesive measures are clinical routine in pediatric dentistry; however, it is not automatically effective to transfer bonding knowledge from permanent to deciduous teeth because the micromorphological issues are completely different.

Methods

In addition to a review of the current literature, this paper presents the results of own investigations on bonding to primary tooth enamel and dentin in milk teeth and the marginal quality which can be achieved.

Results

Important conclusions are: bonding to deciduous enamel is possible after removal of the outer prismless layer, with phosphoric acid being the predominant and most reliable method. Deciduous tooth dentin is less mineralized and therefore as a rule easy to pretreat and bond with self-etching adhesives. Phosphoric acid etching of primary dentin is not recommended. Multistep adhesives show fewer advantages in milk teeth than in the permanent dentition. Altogether, self-etching adhesives exhibit several handling advantages which make them the treatment option of choice in children. Selective phosphoric acid etching can be recommended especially in anterior restorations but in posterior teeth only in the occlusal cavity segment.     

Effect of proximal box elevation with resin composite on marginal quality of ceramic inlays in vitro

Objectives

The objective of this study was to evaluate the marginal quality and resin–resin transition of milled CAD/CAM glass–ceramic inlays in deep proximal cavities with and without 3-mm proximal box elevation (PBE) using resin composites before and after thermomechanical loading.

Materials and methods

MOD cavities with one proximal box beneath the cementoenamel junction were prepared in 48 extracted human third molars. Proximal boxes ending in dentin were elevated for 3 mm with different resin composites (RelyX Unicem, G-Cem, and Maxcem Elite as self-adhesive resin cements and Clearfil Majesty Posterior as restorative resin composite in one or three layers bonded with AdheSE) or left untreated. IPS Empress CAD inlays were luted with Syntac and Variolink II (n?=?8). Marginal quality as well as the PBE–ceramic interface were analyzed under an SEM using epoxy resin replicas before and after thermomechanical loading (100,000?×?50 N and 2,500 thermocycles between +5°C and +55°C).

Results

Bonding glass–ceramic directly to dentin showed the highest amounts of gap-free margins in dentin (92%, p?<?0.05). Bonded resin composite applied in three layers achieved 84% gap-free margins in dentin; PBE with self-adhesive resin cements exhibited significantly more gaps in dentin (p?<?0.05).

Conclusions

With a meticulous layering technique and bonded resin composite, PBE may be an alternative to ceramic bonding to dentin. Self-adhesive resin cements seem not suitable for this indication.

Clinical relevance

For deep proximal boxes ending in dentin, a PBE may be an alternative to conventional techniques.     

Brushing force of manual and sonic toothbrushes affects dental hard tissue abrasion

Objectives

This study aimed to determine the brushing forces applied during in vivo toothbrushing with manual and sonic toothbrushes and to analyse the effect of these brushing forces on abrasion of sound and eroded enamel and dentin in vitro.

Materials and methods

Brushing forces of a manual and two sonic toothbrushes (low and high frequency mode) were measured in 27 adults before and after instruction of the respective brushing technique and statistically analysed by repeated measures analysis of variance (ANOVA). In the in vitro experiment, sound and eroded enamel and dentin specimens (each subgroup n?=?12) were brushed in an automatic brushing machine with the respective brushing forces using a fluoridated toothpaste slurry. Abrasion was determined by profilometry and statistically analysed by one-way ANOVA.

Results

Average brushing force of the manual toothbrush (1.6?±?0.3 N) was significantly higher than for the sonic toothbrushes (0.9?±?0.2 N), which were not significantly different from each other. Brushing force prior and after instruction of the brushing technique was not significantly different. The manual toothbrush caused highest abrasion of sound and eroded dentin, but lowest on sound enamel. No significant differences were detected on eroded enamel.

Conclusion

Brushing forces of manual and sonic toothbrushes are different and affect their abrasive capacity.

Clinical significance

Patients with severe tooth wear and exposed and/or eroded dentin surfaces should use sonic toothbrushes to reduce abrasion, while patients without tooth wear or with erosive lesions confining only to enamel do not benefit from sonic toothbrushes with regard to abrasion.     

Marginal adaptation of class V composite restorations submitted to thermal and mechanical cycling

Objective:

This study evaluated the effect of the margin location and an adhesive system on the marginal adaptation of composite restorations.

Material and Methods:

Class V cavities were prepared in bovine teeth with the gingival margin on the dentin and the incisal margin on the enamel. The cavities were restored with a micro-hybrid composite resin using an etch-and-rinse [Single Bond 2 (SB)] or a self-etching adhesive [Clearfil SE Bond (CL)]. After finishing and polishing the restorations, epoxy replicas were prepared. The marginal adaptation was analyzed using scanning electronic microscopy (SEM, 500 x magnification). The higher gap width in each margin was recorded (T0). After the first evaluation, the samples were submitted to thermal cycling (2,000 cycles of 5ºC±2ºC followed by 55ºC±2ºC - T1) and mechanical cycling (100,000 cycles of 50 kN and 2 Hz - T2). Replicas of samples were rebuilt after each cycling and analyzed under SEM. The data were submitted to Mann-Whitney, Wilcoxon and Friedman testing (a=0.05).

Results:

The SB presented higher gaps in the dentin than the enamel, while there was no difference between the substrate for the CL. In the dentin, the CL showed better marginal sealing than the SB. The opposite occurred in the enamel. There were no significant differences between the baseline, thermal and mechanical cycling for any experimental condition.

Conclusions:

The outcomes of the present study showed that the adhesive system and margin location have an important effect on the marginal adaptation of composite restorations.     

Self-etch adhesives for the bonding of orthodontic brackets: faster, stronger, safer?

Objectives

This study aimed to evaluate the performance of accelerating procedures for bonding of orthodontic brackets in vitro by comparing different adhesives (etch-and-rinse, self-etch) and polymerization procedures (curing devices, time). The performance was characterized by three parameters: (1) the bond strength achieved, (2) the incidence of enamel damage, and (3) the extent of residual composite on the tooth.

Materials and methods

Bracket bonding was performed on 500 extracted human teeth after application of either an etch-and-rinse adhesive or a one-step self-etch adhesive. Two different two-component self-etch adhesives (Clearfil SE and Transbond Plus) and two single-component self-etch adhesives (Ideal and iBond) were investigated after using different polymerization procedures (light-emitting diode for 10 or 20 s or plasma arc curing device for 3 or 6 s). The bond strength, incidence of enamel damage, and extent of residual composite on the tooth were measured.

Results

Single-component self-etch adhesives gave the lowest bond strengths. No significant difference in bond strength could be detected between the two-component self-etch adhesives and the etch-and-rinse method. There was a 70.3 % risk for enamel damage at bond strengths above 12 MPa, but only 5 % risk below 12 MPa and no risk below 8.2 MPa. The risk of enamel damage increased by an odds ratio increment of 1.3 for each additional MPa above 8.2 MPa.

Conclusion

Single-component self-etch adhesives showed the lowest bond strengths, caused limited enamel damage, and generally left less residual composite on the tooth.

Clinical relevance

The nature of the adhesive greatly influences the resultant bond strength, the risk of enamel damage, and the extent of residual composite on the teeth.     

Hydrolytic stability of three-step etch-and-rinse adhesives in occlusal class-I cavities

Objectives

A dental adhesive without small and hydrophilic monomers such as 2-hydroxyethyl methacrylate (HEMA) and triethylene glycol dimethacrylate (TEGDMA) would be beneficial in order to avoid contact allergies. However, these monomers are important to increase infiltration and polymerization of the adhesive. Therefore, the purpose of this study was to evaluate the bonding effectiveness and bond durability of a more hydrophobic and biocompatible adhesive as compared to a conventional three-step etch-and-rinse adhesive.

Methods

Sixteen non-carious human third molars were used to determine the micro-tensile bond strength testing (μTBS) and interfacial ultrastructure by transmission electron microscopy (TEM) of the more hydrophobic cmf adhesive system (Saremco) adhesive as compared to the control OptiBond FL (Kerr).

Results

The more hydrophobic and biocompatible three-step etch-and-rinse adhesive was able to produce a reasonable short-time bonding effectiveness. In the long term, the collagen fibrils in the hybrid layer were not effectively protected and were prone to hydrolytic degradation. As a result, long-term bonding effectiveness of this novel adhesive was very low.

Conclusions

Application of a more hydrophobic adhesive without altering the application procedure considerably results in a reduced durability of the created bond

Clinical relevance

Omitting small and hydrophilic components from the adhesive formulation may impair the durability of your composite restoration.     

Radiopacity of dental restorative materials

Objectives

Radiopacity of dental materials enables clinician to radiographically diagnose secondary caries and marginal defects which are usually located on the proximal gingival margin. The aim of this study was to measure the radiopacity of 33 conventional resin composites, 16 flowable resin composites, and 7 glass ionomer cements and to compare the results with the radiopacity values declared by the manufacturers.

Materials and methods

From each restorative material, six 2-mm-thick disk-shaped specimens were fabricated and eight 2-mm-thick sections of teeth were made and used as reference. The material samples and tooth sections were digitally radiographed together with the aluminum stepwedge. Gray values were obtained from the radiographic images and radiopacity values were calculated and statistically analyzed. Post hoc Tukey’s honestly significant difference test was used to calculate significant differences in radiopacity values between materials and reference dentin and enamel values.

Results

The radiopacity values of all 56 restorative materials were above the dentin reference radiopacity value; however, 4 out of 33 conventional composites and 3 out of 16 flowable resin composites had significantly lower radiopacity than enamel (p?<?0.05). There were up to 1.53 mm eq Al differences between the measured and the manufacturers’ declared radiopacity values of some materials.

Conclusions

Majority of the materials exceed enamel radiopacity and would not hamper radiographic diagnosis of secondary caries. However, manufacturers’ data are not always reliable.

Clinical relevance

Materials with radiopacity lower than enamel might be misinterpreted as secondary enamel caries on radiographic images, especially when applied as initial increment on the proximal gingival margin.     

Microleakage in conservative cavities varying the preparation method and surface treatment

Objective

To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems.

Material and Methods

Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV -self-priming etchant (Tyrian-SPe). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey’s test (α=0.05).

Results

Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV -self-priming etchant (Tyrian-SPe). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey’s test (α=0.05).

Conclusion

Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins.     

Radiotherapy does not impair dentin adhesive properties in head and neck cancer patients

Objectives

This study evaluated the influence of radiotherapy on the dentin bond strength of teeth extracted from patients who had undergone head and neck radiotherapy.

Materials and methods

A total of 36 samples were divided into two experimental groups: group I (control group, n?=?18) and group II (in vivo irradiated group, n?=?18). Groups I and II were further separated into three subgroups (six specimens per subgroup), which were further assigned to the three adhesive system protocols employed: Single Bond 2 (SB) (3M ESPE), Easy Bond (EB) (3M ESPE) and Clearfil SE Bond (CSE) (Kuraray). The adhesive systems were applied to the prepared surface according to the manufacturers’ instructions and restored using composite resin (Filtek Supreme, 3M ESPE). After 24 h in deionised water (37^oC), teeth were horizontally and vertically cut to obtain beam specimens with a cross-section area of 0.8?±?1.0 mm². Specimens were tested in tension using a universal testing machine at a cross-speed of 0.5 mm/min. Fracture patterns were observed under SEM. Data was analysed by two-way analysis of variance (p?≤?0.05).

Results

No statistically significant difference was found between the irradiated (R/SB?=?44.66?±?10.12 MPa; R/EB?=?41.48?±?12.71 MPa; and R/CSE?=?46.01?±?6.98 MPa) and control group (C/SB?=?39.12?±?9.51 MPa; C/EB?=?42.40?±?6.66 MPa; and C/CSE?=?36.58?±?7.06 MPa) for any of the adhesive systems. All groups presented a predominance of mixed fracture modes.

Conclusion

Head and neck radiotherapy did not affect dentin bond strength for the adhesive materials tested in this study.     

Shear bond strength of a self-adhering flowable composite when used for lingual retainer bonding

Objective

The goal of this work was to assess the shear bond strength (SBS) and fracture mode of a self-adhering flowable composite when used after thermocycling for lingual retainer bonding.

Materials and methods

A total of 80 human mandibular incisor teeth were categorized into four equal groups: group 1: Vertise? Flow (VF) without acid etching; group 2: VF with acid etching; group 3: VF with a self-etching bonding agent accompanied by an additional acid etching; group 4: Transbond LR control. Either VF or Transbond LR was applied to the lingual surface of the teeth by packing the material into cylindrical plastic matrices to simulate the lingual retainer bonding area. After all teeth were thermocycled (5000 cycles, 5 and 55?°C), fracture modes were examined under ×20 magnification. The SBS data were assessed via analysis of variance (ANOVA) and Tukey’s tests. Fracture modes were analyzed by the χ² test at a significance level of 0.05.

Results

Statistically significant differences in SBS values between groups (p??<?0.001). In all the self-adhering flowable composite groups, the adhesive type (tooth–composite interface) fracture occurred more frequently than cohesive and mixed-type fractures.

Conclusion

When applied to bond lingual retainers to unetched enamel or with self-etching bonding agent accompanied by an additional acid etching, Vertise? Flow resulted in a significant decrease in bond strength.     

Shear bond strength of orthodontic brackets bonded with a new self-adhering flowable resin composite

Objectives

This study aims to assess the shear bond strength (SBS) to enamel and the distribution of failure modes of brackets bonded using a new self-adhering flowable resin composite (Vertise Flow, VF), with or without preliminary phosphoric acid etching (PAE).

Materials and methods

Eighty extracted premolars were randomly divided into four groups (n?=?20): (1) etch-and-rinse adhesive (E&R), PAE/Transbond XT Primer/Transbond XT Paste (3M Unitek); (2) self-etch adhesive (SE), Transbond Plus Self–Etching Primer (3M Unitek)/Transbond XT Paste; (3) VF; (4) PAE/VF. In each group, 10 bracketed teeth were debonded within 30 min, while the remaining teeth were subjected to thermocycling before testing. SBS and adhesive remnant index were recorded.

Results

SE measured significantly lower early SBS than PAE/VF. Early SBSs recorded by VF were slightly higher yet statistically similar to those of E&R. Such levels of adhesion were achieved by VF regardless of preliminary PAE. After thermocycling, VF measured the lowest SBS. When debonded early, VF and SE tended to leave less residues on enamel surface than E&R. After thermocycling, the failure pattern changed significantly for VF and PAE/VF specimens that all exhibited adhesive failures at the tooth–bracket interface.

Conclusions

VF achieved early bracket SBSs similar to E&R. Following thermocycling, VF and PAE/VF manifested a significant decrease in SBS.

Clinical relevance

Although the simplified handling and the satisfactory early SBS of VF may prompt its use for bracket bonding, the decrease in retention noted after thermocycling warns that the issue of bond durability should be thoroughly addressed prior to endorsing this clinical application of VF.     

Evaluation of bovine and human teeth exposed to thermocycling for microleakage under bonded metal brackets

Introduction

Bovine teeth are commonly used as substitutes for human teeth in scientific investigations. The present study was performed in vitro with the objective of comparing bovine and human enamel subjected to thermocycling for microleakage beneath metal brackets.

Materials and methods

A total of 50 bovine and human teeth (25 per group) void of defects or carious decay were extracted and stored in chloramine B (0.5%). A light-curing adhesive (Transbond? XT) was used as instructed by the manufacturer (3M Unitek, Monrovia, CA, USA) to bond a metal bracket (discovery®; Dentaurum, Ispringen, Germany) to the surface of each tooth following 30 s of enamel etching (phosphoric acid 35%). After 24 h of dye penetration in methylene blue (0.5%), the cervical and incisal bracket surfaces were analyzed by light microscopy for excess bonding material, dye penetration, and microleakage at the bracket–adhesive and adhesive–enamel interfaces. Staining and evaluation was repeated after thermocycling (5000 cycles at 5/55 °C).

Results

Before thermocycling, the number of human teeth showing marginal gaps was one-third the number of bovine teeth (p<0.001). After thermocycling, the distribution of gaps was similar (p=0.180). The adhesive–enamel interface was most frequently affected (on 74% of human and 64% of bovine teeth). No dye penetration in either group after examining a horizontal slice through the bracket basis was observed.

Conclusion

Immediately after bonding, less microleakage was observed around the base of metal brackets on human than bovine teeth. These marginal gaps were, however, superficial in both groups, none of them involving deep penetration of dye under the bracket base.     

Effect of selective enamel etching on clinical performance of CAD/CAM partial ceramic crowns luted with a self-adhesive resin cement

Objectives

This study was conducted to evaluate a self-adhesive resin luting cement [RelyX Unicem 3MESPE–RXU] for luting partial ceramic crowns (PCCs) with and without selective enamel etching in a prospective, randomized clinical trial.

Materials and methods

Thirty-four patients had received the intended treatment. Two PCCs (Vita Mark II; Cerec 3D; Sirona) had been placed in a split-mouth design: one with RXU without enamel etching (RXU), the other with RXU with selective enamel etching (RXU?+?E). Restorations were evaluated at baseline (BL) and after 12, 24, and 36 months (USPHS criteria). For statistical analysis, the Chi-square test was applied (α?=?0.05). Clinical survival of all restorations (n?=?68) after 3 years was determined using Kaplan–Meier analysis.

Results

Twenty three patients (12 male/11 female) were available for clinical evaluation after 3 years. 19 RXU-PCCs were placed in molars, four in premolars, 18 RXU?+?E–PCCs in molars, five in premolars. Concerning clinical changes, no significant differences were found between luting strategies RXU/RXU?+?E at all recalls. Statistically significant changes over time were observed for marginal adaptation and marginal discoloration between BL and 36 m for RXU and RXU?+?E. For RXU?+?E, postoperative hypersensitivities decreased significantly from BL (n?=?6) to 36 m (n?=?0). Of the 68 restorations originally included, eight RXU and four RXU?+?E restorations failed. At 3 years, Kaplan–Meier survival of RXU was 72.9 %, that of RXU?+?E 87.6 %. Survival rates were not statistically significant different.

Conclusions

Although clinical survival of RXU?+?E is slightly better at 3 years, restorations of both groups perform similar with respect to clinical changes over time as evaluated by modified USPHS criteria.

Clinical relevance

The self-adhesive resin cement RXU can be used in conjunction with selective enamel etching, because survival rates of PCCs in the RXU?+?E group were not lower but, as a trend, even better than without enamel etching.