Comparison of shear bond strength of universal adhesives on etched and nonetched enamel

BACKGROUND

The purpose of this study was to evaluate the effect of surface pretreatment with 37% phosphoric acid on the enamel bond strength of different universal adhesives.

METHODS

One hundred and sixty bovine permanent mandibular incisors freshly extracted were used as a substitute for human teeth. The materials tested in this study included 6 universal adhesives, and 2 self-etch adhesives as control. The teeth were assigned into 2 groups: In the first group, etching was performed using 37% phosphoric acid for 30 seconds. In the second group, no pretreatment agent was applied. After adhesive application, a nanohybrid composite resin was inserted into the enamel surface by packing the material into cylindrical-shaped plastic matrices. After storing, the specimens were placed in a universal testing machine. The normality of the data was calculated using the Kolmogorov-Smirnov test. Analysis of variance (ANOVA) was applied to determine whether significant differences in debond strength values existed among the various groups.

RESULTS

Groups with phosphoric acid pretreatment showed significantly higher shear bond strength values than groups with no enamel pretreatment (p<0.001). No significant variation in shear strength values was detected when comparing the different adhesive systems applied onto enamel after orthophosphoric acid application (p>0.05).

CONCLUSIONS

All adhesives provide similar bond strength values when enamel pretreatment is applied even if compositions are different. Bond strength values are lower than promised by manufacturers.

Plasma arc versus halogen light-curing of adhesive-precoated orthodontic brackets: a 12-month clinical study of bond failures

The purpose of this randomized clinical trial was to evaluate the performance of adhesive-precoated brackets cured with 2 different light-curing units (conventional halogen light and plasma arc light). Thirty patients treated with fixed appliances were included in the investigation. Each patient's mouth was divided by the split-mouth design into 4 quadrants. In 15 randomly selected patients, the maxillary left and mandibular right quadrants were cured with the halogen light, and the remaining quadrants were cured with the plasma arc light. In the other 15 patients, the quadrants were inverted. A total of 600 adhesive precoated stainless steel brackets were examined: 300 were cured with a conventional halogen light for 20 seconds, and the others were cured with the plasma arc light for 5 seconds. The number, cause, and date of bracket failures were recorded for each light-curing unit over 12 months. Statistical analysis was performed with the Fisher exact test, Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences in bond failure rates were found between the adhesive-precoated brackets cured with the halogen light and those cured with the plasma arc light; neither were any significant differences in performance found with each light-curing unit between the maxillary and mandibular arches. Plasma arc lights can be considered an advantageous alternative to conventional light curing, because they enable the clinician to reduce the curing time of adhesive-precoated orthodontic brackets without significantly affecting their bond failure rate.

Management of Periodontal Disease with Adjunctive Therapy with Ozone and Photobiomodulation (PBM): A Randomized Clinical Trial

Periodontitis is an inflammatory condition of the soft and hard tooth-supporting tissues, representing the first cause of tooth loss. In addition to standard mechanical debridement (Scaling and Root Planing, SRP), further approaches have been proposed as adjuncts. The aim of the present randomized clinical trial is to compare the efficacy of ozone or photobiomodulation (PBM) therapy in addition to SRP to treat periodontal disease. According to a split-mouth design, 240 pathological sites, corresponding to 30 periodontal patients, were randomly divided according to the professional oral hygiene protocol performed at baseline (T0) and after 1 (T1), 2 (T2), 3 (T3), 4 (T4), 5 (T5), and 6 (T6) months. A total of 120 sites underwent an ozonized water administration (ozone group), whereas the other 120 sites were treated with photobiomodulation (PBM group), both in addition to SRP. At every timepoint, the following clinical indexes were assessed: Probing Pocket Depth (PPD) (measured on six sites per element), Plaque Index (PI), and Bleeding on Probing (BOP). As regards PPD, significant intergroup differences were noticed from T5, with significantly lower values in the PBM group (p < 0.05), where values further decreased at T6 (p < 0.05). Both PI and BoP generally decreased from baseline to T6 in both groups; a significant difference was found between T0 and T1 among the groups (p < 0.05), with a progressively higher reduction in the PBM group among the time frames of the study, despite intergroup comparisons not being significant (p > 0.05). Both ozone and PBM appear to be effective adjuvant treatments to SRP, obtaining a slightly better outcome for the latter in the long term, with significant differences at T5 and T6 for PPD. However, because of the absence of standardized protocols for PBM considering both therapeutic and research purposes, no definitive conclusions can be reached, and further studies are required.

In Vitro Re-Hardening of Bleached Enamel Using Mineralizing Pastes: Toward Preventing Bacterial Colonization

The search for materials able to remineralize human hard tissues is a modern medical challenge. In this study, the protective effect on the enamel microhardness by a paste based on hydroxyapatite and sodium fluoride (Remin Pro) was evaluated after two different enamel bleaching procedures. Forty sound human incisors were randomly assigned to different treatments: bleaching with an in-office agent (Perfect Bleach Office+); bleaching with an at-home agent (Perfect Bleach); bleaching with the in-office agent followed by the prophylaxis paste; bleaching with the athome agent followed by the prophylaxis paste; no treatment (control). Bleaching was performed at 0, 8, 24 and 32 h, followed by a 3min remineralizing treatment in the subgroups designed to receive it. Specimens underwent a microhardness tester and a mean Vickers Hardness number was considered for each specimen. ANOVA exhibited significant differences among groups. Posthoc Tukey testing showed significant microhardness decrease after the application of both the two bleaching agents. The treatment with prophylaxis paste significantly increased the microhardness values of bleached enamel.

Effects of nanofillers on mechanical properties of fiber-reinforced composites polymerized with light-curing and additional postcuring

BACKGROUND

The purpose of the present study was to evaluate the effect of nanofillers on the mechanical properties of 2 sizes (diameters 0.6 and 0.9 mm) of conventional and nanofilled fiber-reinforced composites (FRCs) polymerized with conventional light-curing and additional postcuring.

METHODS

The FRCs samples were divided into 8 groups (10 specimens each). Conventional FRCs with glass fibers preimpregnated with polymethyl methacrylate (groups 1, 2, 3 and 4) and FRCs with impregnating solution containing 32% nanofilled resin (groups 5, 6, 7 and 8) were tested in 2 different sections (0.6 and 0.9 mm in diameter). Two different polymerizations were analyzed: hand light-curing for 40 seconds with an halogen light, and additional postcuring for 25 minutes in a light-curing oven. Each sample was evaluated with a 3-point bending test on a universal testing machine, after 48 hours of dry storage. All of the data were statistically analyzed.

RESULTS

After oven postcuring, nanofilled FRCs exhibited significantly higher load values than conventional FRCs. No significant differences were found when comparing conventional and nanofilled FRCs after hand light-curing. Moreover, 0.6-mm FRCs showed significantly lower load values than 0.9-mm FRCs, both for conventional and nanofilled FRCs.

CONCLUSIONS

Nanofilled FRCs showed higher load values after additional oven postcuring.

Travel beyond Clinical Uses of Fiber Reinforced Composites (FRCs) in Dentistry: A Review of Past Employments, Present Applications, and Future Perspectives

The reinforcement of resins with short or long fibers has multiple applications in various engineering and biomedical fields. The use of fiber reinforced composites (FRCs) in dentistry has been described in the literature from more than 40 years. In vitro studies evaluated mechanical properties such as flexural strength, fatigue resistance, fracture strength, layer thickness, bacterial adhesion, bonding characteristics with long fibers, woven fibers, and FRC posts. Also, multiple clinical applications such as replacement of missing teeth by resin-bonded adhesive fixed dental prostheses of various kinds, reinforcement elements of dentures or pontics, and direct construction of posts and cores have been investigated. In orthodontics, FRCs have been used also for active and passive orthodontic applications, such as anchorage units, en-masse movement units, and postorthodontic tooth retention. FRCs have been extensively tested in the literature, but today the advances in new technologies involving the introduction of nanofillers or new fibers along with understanding the design principles of FRC devices open new fields of research for these materials both in vitro and in vivo. The present review describes past and present applications of FRCs and introduces some future perspectives on the use of these materials.

Buccolingual Inclination Control of Upper Central Incisors of Aligners: A Comparison with Conventional and Self-Ligating Brackets

OBJECTIVE

The upper incisors torque expression is essential for the orthodontic treatment accuracy. Various orthodontic devices are claimed to have different inclination control capacity. The purpose of this retrospective study was to compare the radiographic buccolingual inclination of upper incisors in patients treated with three different orthodontic techniques.

MATERIAL AND METHODS

Conventional brackets (Victory, 3M), self-ligating appliances (Damon Q, Ormco), and aligners (Invisalign, Align Technology) were tested. Cephalometric data of 25 patients with similar skeletal and dental pretreatment parameters were collected for each technique. Position changes of upper central incisors were assessed with radiographic evaluation before and after therapy. Three different parameters were considered: 11∧SnaSnp, 11∧Ocl and I+ TVL. All variables were measured before (T0) and after (T1) treatment and their variation over treatment was assessed.

RESULTS

When evaluating angular measurements, 11∧SnaSnp and 11∧Ocl angles showed the highest numeric variation with conventional brackets. Lowest values were reported with aligners. However, the differences among various techniques were not significant for both angles (P>0.05). Also I+ TVL linear value variation did not show significant differences among the different groups tested (P>0.05).

CONCLUSION

Conventional multibrackets appliance showed the highest incisal position variations over treatment, but the differences among various groups were not significantly different.

Surface discoloration of composite resins: Effects of staining and bleaching

BACKGROUND

The purpose of this in vitro study was to evaluate surface discoloration of three microhybrid composite resins (Esthet•X HD, Clearfil AP-X, Gradia Direct) and five nanohybrid composite resins (Ceram•X, GC Kalore, G-aenial, Grandio, GrandioSO), after staining and bleaching procedures.

MATERIALS AND METHODS

The composite resins were polymerized with a curing light (Celalux II, Voco, Cuxhaven, Germany) into 160 silicon molds (6,4 mm in diameter and 2 mm in thickness) to obtain identical specimens. Twenty samples for each composite resin were prepared. The specimens were polished using an automated polishing machine with the sequence of 600-, 800-, 1000-grit abrasive paper under water irrigation. The specimens were immersed in tea and distilled water: the specimens were dipped for 20 min, once a day (every 24 h), for 14 days into the drinks. The specimens were then bleached with carbamide peroxide at 17% (Perfect Bleach-Voco). The color of specimens was measured with a spectrophotometer according to the CIE L(*)a(*)b(*) system after light-polymerization of composite resin specimens, after 7 days, after 14 days, and after bleaching. The color difference h index (DEab(*)) between each measurement was calculated. Statistical analysis was made using analysis of variance (ANOVA).

RESULTS

All specimens showed a significant increase in staining with a similar trend and no significant differences between microhybrid and nanohybrid composite resins. After whitening procedures, materials tested showed both significant and unsignificant differences of the h index.

CONCLUSIONS

Microhybrid and nanohybrid composite resins had similar in vitro surface discoloration in tea. After bleaching, discoloration was removed from some composite resins tested.

Effect of blood contamination on shear bond strength of brackets bonded with conventional and self-etching primers

This study assessed the effect of blood contamination on the shear bond strength and bond failure site of 2 different orthodontic primers (Transbond XT and Transbond Plus Self-Etching Primer, both from 3M Unitek, Monrovia, Calif) used with adhesive-precoated brackets. Four different enamel surface conditions were tested: (1) dry, (2) blood contamination before priming, (3) blood contamination after priming, and (4) blood contamination before and after priming. Noncontaminated enamel surfaces had the highest bond strengths for both conventional and self-etching primers, which produced almost the same strength values. Under blood-contaminated conditions, both primers showed significantly reduced shear bond strengths. For the conventional primer, no significant differences were reported among the blood-contaminated groups, whereas when the self-etching primer was used, condition 4 reduced significantly the bond strength values. Significant differences in debond locations were found among the groups bonded with the 2 primers under the various enamel surface conditions.

Disinclusion of unerupted teeth by mean of self-ligating brackets: effect of blood contamination on shear bond strength

OBJECTIVES

The aim of this study was to assess the effect of blood contamination on the shear bond strength and failure site of three different orthodontic self-ligating brackets.

STUDY DESIGN

240 bovine permanent mandibular incisors were randomly divided into 12 groups of 20 specimens each. Orthodontic self-ligating brackets were tested under four different enamel surface conditions: a) dry, b) blood contamination before priming, c) blood contamination after priming, d) blood contamination before and after priming. Brackets were bonded to the teeth and subsequently tested using a Instron universal testing machine. Shear bond strength values and adhesive failure rate were recorded. Statistical analysis was performed using ANOVA and Tukey tests (strength values), and Chi squared test (ARI Scores).

RESULTS

Non-contaminated enamel surfaces showed highest bond strengths for all self ligating brackets. Under blood-contamination shear bond strengths lowered for all brackets tested. Groups contaminated before and after primer application showed the lowest shear bond strength. Significant differences in debond locations were found among the groups under the various enamel surface conditions.

CONCLUSIONS

Blood contamination of enamel during the bonding procedure lowers bond strength values of self ligating brackets, expecially when contamination occur in different times of the bonding procedure.

Flexural strengths of conventional and nanofilled fiber-reinforced composites: a three-point bending test

OBJECTIVES

The purpose of this study was to evaluate the effect of the introduction of nanofillers on the mechanical properties of fiber-reinforced composites (FRCs) for stabilization and conservative treatment of multiple traumatized anterior teeth. In particular, the aim of the research was to point out the force levels of two sizes (diameters 0.6 and 0.9 mm) of both conventional and nanofilled FRCs.

METHODS

Eighty FRCs samples were divided into eight groups, each consisting of 10 specimens. Conventional (groups 1, 2, 3, and 4) and nanofilled (groups 5, 6, 7, and 8) FRC samples were evaluated. Each FRC was tested in two diameters (0.6 and 0.9 mm) and under two deflections (1 and 2 mm). Each sample was polymerized with the same halogen curing unit and then evaluated with a 3-point bending test on a universal testing machine after 48 h of dry storage.

RESULTS

Nanofilled FRCs showed significantly higher load values than conventional FRCs. Moreover, 0.9-mm-diameter FRCs showed significantly higher load value than 0.6-mm-diameter FRCs. Specimens tested at 2-mm deflection showed significantly higher load values than those tested at 1-mm deflection.

CONCLUSIONS

Nanofilled FRCs showed significantly higher load values than conventional FRCs. Higher flexural strength values were recorded with 1-mm deflection for both FRC tested.

Properties of CAD/CAM 3D Printing Dental Materials and Their Clinical Applications in Orthodontics: Where Are We Now?

In the last years, both medicine and dentistry have come across a revolution represented by the introduction of more and more digital technologies for both diagnostic and therapeutic purposes. Additive manufacturing is a relatively new technology consisting of a computer-aided design and computer-aided manufacturing (CAD/CAM) workflow, which allows the substitution of many materials with digital data. This process requires three fundamental steps represented by the digitalization of an item through a scanner, the editing of the data acquired using a software, and the manufacturing technology to transform the digital data into a final product, respectively. This narrative review aims to discuss the recent introduction in dentistry of the abovementioned digital workflow. The main advantages and disadvantages of the process will be discussed, along with a brief description of the possible applications on orthodontics.

Ozonized Gel Against Four Candida Species: A Pilot Study and Clinical Perspectives

Ozone therapy can display a wide range of clinical beneficial effects, including antimicrobial, immune-stimulant, analgesic, anti-hypoxic actions. However, there is still a paucity of data regarding the ozone fungicide activity. Oral Candida is the most common fungal infection in the mouth among denture wearers and people with weakened immune systems. In the case of generalized candidiasis or immunocompromised patients, systemic therapy is needed, while localized infections are treated with topic medications. However, many Candida strains are resistant to antifungal drugs. The aim of this preliminary analysis is to evaluate the antimycotic efficacy of a new ozonided oil (GeliO3), as a possible terapeutic alternative in local treatments of these infections, compared to chlorhexidine digluconate (Plak gel®). Chlorhexidine is a chemical synthesis disinfectant with a broad-spectrum antiseptic action, active against bacteria and fungi. Antimycotic activity was tested against the following four Candida species: C. albicans, C. parapsilosis, C. glabrata, C. tropicalis, through an agar diffusion method. No significant differences were found between the growth inhibition zone diameters of the ozonized gel and chlorhexidine. The results indicated that the ozonized gel may help to combat Candida infections. Moreover, useful applications could be used to counteract Candida colonization of endosseous implants.

Shear bond strength of self-ligating brackets

The aim of this study was to compare the shear bond strength (SBS) and adhesive remnant index (ARI) scores of conventional and self-ligating brackets. Conventional stainless steel brackets (group 1, Step; Leone) and three different passive and interactive self-ligating brackets (group 2, Smart Clip, 3M Unitek; group 3, Quick, Forestadent; and group 4, Damon 3MX, Ormco) were tested. Four groups of 20 specimens each were bonded with an adhesive system (Ortho Solo primer, Ormco and Transbond XT resin, 3M Unitek) onto bovine enamel and subsequently tested using an Instron universal testing machine. SBS values and adhesive failure rate were recorded. Statistical analysis was performed with analysis of variance and Scheffé tests to determine bond strength values, whereas a chi-square test was used for ARI scores. Groups 2 and 4 showed significantly higher SBS values than the other two groups. Moreover, groups 1 and 3 showed a higher frequency of ARI score 1, whereas groups 2 and 4 showed higher frequency of ARI score 2. All the brackets demonstrated a clinically adequate SBS.

Shear bond strength of one-step self-etch adhesives to enamel: effect of acid pretreatment

AIM

The purposes of this study were to evaluate the effect of surface pretreatment with phosphoric acid on the enamel bond strength of four-one-step self-etch adhesives with different pH values.

MATERIAL AND METHODS

One hundred bovine permanent mandibular incisors were used. The materials used in this study included four-one-step self-etch adhesives with different pH values: Adper(™) Easy Bond Self-Etch Adhesive (ph = 0,8-1), Futurabond NR (ph = 1,4), G-aenial Bond (ph = 1,5), Clearfil(3) S Bond (ph = 2,7). One two-step self-etch adhesive (Clearfil SE Bond/ph = 0,8-1) was used as control. The teeth were assigned into two subgroups according to bonding procedure. In the first subgroup (n = 50), no pretreatment agent was applied. In the second subgroup (n = 50), etching was performed using 37% phosphoric acid for 30 s. After adhesive systems application, a nanohybrid composite resin was inserted into the enamel surface. The specimens were placed in a universal testing machine (Model 3343, Instron Corp., Canton, Mass., USA). After the testing procedure, the fractured surfaces were examined with an optical microscope at a magnification of 10× to determine failure modes. The adhesive remnant index (ARI) was used to assess the amount of adhesive left on the enamel surface.

RESULTS

Descriptive statistics of the shear bond strength and frequency distribution of ARI scores were calculated.

CONCLUSIONS

Enamel pretreatment with phosphoric acid significantly increased bond strength values of all the adhesives tested. No significant differences in bond strength were detected among the four different one-step self-etch adhesives with different pH. Two-step self-etch adhesive showed the highest bond strength.

A 12 month clinical study of bond failures of recycled versus new stainless steel orthodontic brackets

The purpose of this prospective longitudinal randomized study was to compare the clinical performance of recycled brackets with that of new stainless steel brackets (Orthos). Twenty patients treated with fixed appliances were included in the investigation. Using a 'split-mouth' design, the dentition of each patient was divided into four quadrants. In 11 randomly selected patients, the maxillary left and mandibular right quadrants were bonded with recycled brackets, and the remaining quadrants with new stainless steel brackets. In the other nine patients the quadrants were inverted. Three hundred and ten stainless steel brackets were examined: 156 were recycled and the remaining 154 were new. All the brackets were bonded with a self-cured resin-modified glass ionomer (GC Fuji Ortho). The number, cause, and date of bracket failures were recorded over 12 months. Statistical analysis was performed by means of a paired t-test, Kaplan-Meier survival estimates, and the log-rank test. No statistically significant differences were found between: (a) the total bond failure rate of recycled and new stainless steel brackets; (b) the upper and lower arches; (c) the anterior and posterior segments. These findings demonstrate that recycling metallic orthodontic brackets can be of benefit to the profession, both economically and ecologically, as long as the orthodontist is aware of the various aspects of the recycling methods, and that patients are informed about the type of bracket that will be used for their treatment.

Effect of various adhesive systems on the shear bond strength of fiber-reinforced composite

INTRODUCTION

The purpose of this study was to evaluate the effect of 3 adhesive systems on the shear bond strength of a fiber-reinforced composite (FRC).

METHODS

Sixty bovine permanent mandibular incisors were randomly divided into 3 groups of 20. The FRCs (Ortho, Stick Teck Ltd, Turku, Finland) were bonded to the teeth with 3 adhesive systems (Tetric Flow [Ivoclar-Vivadent, Schaan, Liechtenstein], Transbond XT [Unitek/3M, Monrovia, Calif], and Fuji Ortho LC [GC Europe, Leuven, Belgium]). After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. Analysis of variance and the Sheffé post-hoc tests were used at a significance level of P < .05.

RESULTS

ANOVA indicated significant differences among the various groups. Fibers bonded with Transbond XT showed significantly higher shear bond strengths than the other 2 groups. No significant differences in shear bond strength values were reported between Tetric Flow and Fuji Ortho LC. No significant differences in debond locations (ARI scores) were found among the various groups.

CONCLUSIONS

For maximum bond strength, use Transbond XT for direct bonding of FRC.

Glass Fiber Reinforced Composite Orthodontic Retainer: In Vitro Effect of Tooth Brushing on the Surface Wear and Mechanical Properties

Fiber reinforced composites (FRCs) are metal free materials that have many applications in dentistry. In clinical orthodontics, they are used as retainers after active treatment in order to avoid relapse. However, although the modulus of the elasticity of FRCs is low, the rigidity of the material in the form of a relatively thick retainer with a surface cover of a flowable resin composite is known to have higher structural rigidity than stainless steel splints. The aim of the present study is to measure load and bending stress of stainless steel wires, as well as flowable resin composite covered and spot‑bonded FRC retainer materials after tooth brushing. These materials were tested with a three point bending test for three different conditions: no brushing, 26 min of brushing, and 60 min of brushing. SEM images were taken before and after different times of tooth brushing. Results showed that stainless steel was not significantly affected by tooth brushing. On the other hand, a significant reduction of values at maximum load at fracture was reported for both FRC groups, and uncovered FRCs were most affected. Concerning maximum bending stress, no significant reduction by pretreatment conditions was reported for the materials tested. SEM images showed no evident wear for stainless steel. Flowable resin composite covered FRCs showed some signs of composite wear, whereas spot‑bonded FRCs, i.e., without the surface cover of a flowable resin composite, showed signs of wear on the FRC and exposed glass fibers from the FRC's polymer matrix. Because of the significant changes of the reduction of maximum load values and the wear for spot‑bonded FRCs, this technique needs further in vitro and in vivo tests before it can be performed routinely in clinical practice.

Epidemiological survey of different clinical techniques of orthodontic bracket debonding and enamel polishing

OBJECTIVES

To conduct an epidemiological survey of the orthodontic debonding techniques in Italy, and describe the most commonly used methods to remove the brackets and adhesive from the tooth surfaces.

MATERIALS AND METHODS

A survey consisting of 6 questions about bracket debonding methods and instruments used was emailed to 1000 orthodontists, who were members of the Italian Orthodontics Society (SIDO. Clinicians were characterized by different sex, age, origin, and professional experience.

RESULTS

Overall, 267 surveys were returned, representing a response rate of 26.7% of the participants interviewed. The 0.2% of the orthodontists responded, via email, confirming that they were not interested, while 3% of the questionnaires were sent back not completed. The 70.1% of the clinicians interviewed did not return any response. Overall, 64% of SIDO members (orthodontists) did not detect any enamel damage after debonding. The brackets used most frequently (89.14%) in clinical practice were the metal ones. The most commonly used pliers for bracket removal were cutters (37.08%) and bracket removal pliers (34.83%). For adhesive removal, low speed tungsten carbide burs under irrigation were the most widely utilized method for adhesive removal (40.08%), followed by high speed carbide burs (14.19%), and diamond burs (14.19%). The most frequently used instruments for polishing after debonding were rubber cups (36.70%) and abrasive discs (21.35%). The 31.21% of the orthodontists found esthetic enamel changes before bonding versus after debonding.

CONCLUSIONS

This survey showed the high variability of different methods for bracket debonding, adhesive removal, and tooth polishing. The collected answers indicate that most orthodontists have developed their own armamentarium of debonding and polishing, basing their method on trials and errors.

Effects of blood contamination on the shear bond strengths of conventional and hydrophilic primers

The purpose of this study was to assess the effect of blood contamination on the shear bond strength and failure site of 2 orthodontic primers (Transbond XT and Transbond MIP; 3M/Unitek, Monrovia, Calif) when used with adhesive-precoated brackets (APC II brackets; 3M/Unitek). One hundred twenty bovine permanent mandibular incisors were randomly divided into 8 groups; each group contained 15 specimens. Each primer-adhesive combination was tested under a different enamel surface condition: dry, blood contamination before priming, blood contamination after priming, or blood contamination before and after priming. Stainless steel APC II brackets were bonded to the teeth. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for shear bond strength. Noncontaminated enamel surfaces had the highest bond strengths for both conventional and hydrophilic primers; their values were almost the same. Under blood-contaminated conditions, both primers showed significantly lower shear bond strengths. For each type of primer, no significant differences were reported among the blood-contaminated groups. Significant differences in debond locations were found among the groups bonded with the 2 primers under the various enamel surface conditions. Blood contamination of enamel during the bonding procedure of conventional and hydrophilic primers significantly lowers their bond strength values and might produce a bond strength that is not clinically adequate.

Reconditioning of self-ligating brackets

OBJECTIVE

To test the null hypothesis that there is no significant difference in the shear bond strength (SBS) and Adhesive Remnant Index (ARI) scores of new vs reconditioned self-ligating brackets.

MATERIALS AND METHODS

One hundred and twenty permanent extracted bovine teeth were embedded in resin blocks. Three different new and reconditioned self-ligating orthodontic brackets (Smart Clip [3M Unitek]; Quick [Forestadent]; and Damon3MX [Ormco]) were tested. Scanning electron microphotographs of the different new (groups 1, 3, and 5) and reconditioned (groups 2, 4, and 6) bracket bases were taken before starting the experiments. Brackets were then bonded to the teeth using an orthodontic adhesive and were then tested in shear mode using an Instron Universal Testing Machine. ARI scores were then recorded. Statistical analysis was performed to determine significant differences in SBS and ARI Scores.

RESULTS

Smart Clip and Damon3MX reconditioned brackets showed significantly lower SBS than did new ones. On the contrary, Quick reconditioned brackets showed significantly higher SBS than did new ones. No significant differences in ARI scores were found after the reconditioning process for the three different brackets tested.

CONCLUSION

The in-office reconditioning procedure alters the SBS of self-ligating brackets, although SBS values still remain clinically acceptable.

Shear bond strength of fibre-reinforced composite nets using two different adhesive systems

The purpose of this study was to evaluate the effect of two different adhesive systems (Tetric Flow and Transbond XT) in combination with fibre-reinforced composites (FRC) net (Ever Stick) on the shear bond strength (SBS) of orthodontic brackets. Eighty bovine permanent mandibular incisors were randomly divided into four equal groups. Stainless steel maxillary central incisor brackets with a 0.018 inch slot (DB Leone) were bonded to the teeth using the two different adhesive systems. Fifty per cent of the brackets were bonded without and 50 per cent with a FRC net under the bracket base. After bonding, all samples were stored in distilled water at room temperature for 24 hours and subsequently tested for SBS. Analysis of variance indicated significant differences among the various groups. Brackets bonded with FRC nets under the base showed a significantly lower SBS than those bonded without nets (P < 0.05). Moreover, teeth bonded with Transbond XT showed a significantly higher SBS than the other groups. Additionally, significant differences in debond locations [adhesive remnant index (ARI) score] were found among the various groups. Transbond XT can successfully be used for direct bonding of FRC nets, thus improving their SBS values.

Critical appraisal: bulk-fill flowable composite resins

Recent developed flowable composite resins have been marketed for bulk filling of preparations or replacement of dentin in a single increment. The obvious attraction of these materials-quicker placement of restorations-has rapidly made them very popular despite the limited in vitro data and lack of clinical studies. This Critical Appraisal will review some of the available in vitro literature on the topic and summarize the available knowledge in this new category of restorative materials.

Influence of Different Surface Pretreatments on Shear Bond Strength of an Adhesive Resin Cement to Various Zirconia Ceramics

The aim of this in vitro study was to assess the influence of surface pretreatment on shear bond strength (SBS) of an adhesive resin cement (G-CEM Link Force TM, GC Corporation, Tokyo, Japan) to three different yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramics: (1) Copran Zirconia Monolith HT, COP; (2) Katana ML Zirconia, KAT; and (3) Metoxit Z-CAD HTL Zirconia, MET. In total, 45 cylinders (5 mm in diameter, 1 mm height) for each type of zirconia ceramic were prepared used a computer-aided design and computer-aided manufacturing (CAD/CAM) machine (software CEREC 4.2). Each type of zirconia was subdivided into three groups and each group received a different surface pretreatment; 15 samples were not conditioned as control (groups COP 1, KAT 1, MET 1), 15 samples were air-borne particle abraded with aluminum dioxide particles of 50-μm size at 0.3 MPa for 20 s (groups COP 2, KAT 2, MET 2), and 15 samples were hot-etched with a solution of hydrochloric acid and ferric chloride (groups COP 3, KAT 3, MET 3). After specimen fabrication, the adhesive cement-ceramic interface was analyzed using an SBS test. Subsequently, the adhesive remnant index (ARI) was measured. Data were submitted to statistical analysis. Air-borne particle abraded specimens showed the highest SBS values for COP and KAT groups. For MET, no significant difference was reported between air-borne particle abraded specimens and untreated controls. The lowest values were detected for acid-etched groups. A higher frequency of ARI = "1" and ARI = "2" was reported in control and air-borne particle abraded groups, whereas ARI = "3" was detected in hot-etched groups. No correlation was found between ARI score and shear bond strength. Air-borne particle abrasion is considered the best treatment for Zirconia Copran and Zirconia Katana ML, if it is followed by using dual-curing resin cement.

Bending Properties of Fiber-Reinforced Composites Retainers Bonded with Spot-Composite Coverage

Orthodontic and periodontal splints are prepared with round or flat metallic wires. As these devices cannot be used in patients with allergy to metals or with aesthetic demands, fiber-reinforced composite (FRC) retainers have been introduced. Stiffness of FRC materials could reduce physiologic tooth movement. In order to lower rigidity of conventional FRC retainers, a modified construction technique that provided a partial (spot) composite coverage of the fiber has been tested and compared with metallic splints and full-bonded FRCs. Flat (Bond-a-Braid, Reliance Orthodontic Products) and round (Penta-one 0155, Masel Orthodontics) stainless steel splints, conventional FRC splints, and experimental spot-bonded FRC retainers (Everstick Ortho, StickTech) were investigated. The strength to bend the retainers at 0.1 mm deflection and at maximum load was measured with a modified Frasaco model. No significant differences were reported among load values of stainless steel wires and experimental spot-bonded FRC retainers at 0.1 mm deflection. Higher strength values were recoded for conventional full-bonded FRCs. At maximum load no significant differences were reported between metallic splints (flat and round) and experimental spot-bonded FRCs, and no significant differences were reported between spot- and full-bonded FRC splints. These results encourage further tests in order to evaluate clinical applications of experimental spot-bonded FRC retainers.