3D-printed zirconia orthodontic brackets: Effect of printing method on dimensional accuracy.

OBJECTIVES: This study investigated the effect of additive manufacturing (AM) methods on the slot height dimensions and accuracy of 3D-printed orthodontic brackets. METHODS: A 3D model of a standard Mclaughlin Bennett Trevisi bracket was used as a reference to print the ceramic bracket in a 90° orientation using two representative AM methods: digital light processing (DLP) and material jetting (MJ). The dimensional accuracy and slot heights were determined using a scanning electron microscope and an optical scanner. Also, all specimens were analysed using the Geomagic Control X 3D inspection software. The root mean square (RMS) values were used for trueness and precision assessment. Statistical analyses were performed using an independent sample t-test. RESULTS: Slot height dimensions, trueness RMS, and precision RMS were statistically affected by different AM methods (p < .01). There was a significant difference between the different printing methods, with DLP meeting the tolerance requirements (mean slot height = 0.557 ± 0.018 mm) and MJ being slightly below them (mean slot height = 0.544 ± 0.021 mm). However, MJ significantly outperformed DLP in terms of accuracy. Among the two printing methods, MJ was associated with higher trueness (RMS = 0.025 ± 0.004 mm) and precision (RMS = 0.038 ± 0.005 mm). CONCLUSIONS: Both tested AM methods yielded clinically acceptable outcomes, with the RMS range set to ±100 µm and the slot height tolerance established at 0.549-0.569 mm. The MJ technology achieved the highest accuracy.

Deep learning for virtual orthodontic bracket removal: tool establishment and application.

OBJECTIVE: We aimed to develop a tool for virtual orthodontic bracket removal based on deep learning algorithms for feature extraction from bonded teeth and to demonstrate its application in a bracket position assessment scenario. MATERIALS AND METHODS: Our segmentation network for virtual bracket removal was trained using dataset A, containing 978 bonded teeth, 20 original teeth, and 20 brackets generated by scanners. The accuracy and segmentation time of the network were tested by dataset B, which included an additional 118 bonded teeth without knowing the original tooth morphology. This tool was then applied for bracket position assessment. The clinical crown center, bracket center, and orientations of separated teeth and brackets were extracted for analyzing the linear distribution and angular deviation of bonded brackets. RESULTS: This tool performed virtual bracket removal in 2.9 ms per tooth with accuracies of 98.93% and 97.42% (P < 0.01) in datasets A and B, respectively. The tooth surface and bracket characteristics were extracted and used to evaluate the results of manually bonded brackets by 49 orthodontists. Personal preferences for bracket angulation and bracket distribution were displayed graphically and tabularly. CONCLUSIONS: The tool's efficiency and precision are satisfactory, and it can be operated without original tooth data. It can be used to display the bonding deviation in the bracket position assessment scenario. CLINICAL SIGNIFICANCE: With the aid of this tool, unnecessary bracket removal can be avoided when evaluating bracket positions and modifying treatment plans. It has the potential to produce retainers and orthodontic devices prior to tooth debonding.

[Study on quantitative analysis of bracket-induced nonlinear response of labio-cheek soft tissue during the orthodontic process].

In the orthodontics process, intervention and sliding of an orthodontic bracket during the orthodontic process can arise large response of the labio-cheek soft tissue. Soft tissue damage and ulcers frequently happen at the early stage of orthodontic treatment. In the field of orthodontic medicine, qualitative analysis is always carried out through statistics of clinical cases, while quantitative explanation of bio-mechanical mechanism is lacking. For this purpose, finite element analysis of a three-dimensional labio-cheek-bracket-tooth model is conducted to quantify the bracket-induced mechanical response of the labio-cheek soft tissue, which involves complex coupling of contact nonlinearity, material nonlinearity and geometric nonlinearity. Firstly, based on the biological composition characteristics of labio-cheek, a second-order Ogden model is optimally selected to describe the adipose-like material of the labio-cheek soft tissue. Secondly, according to the characteristics of oral activity, a two-stage simulation model of bracket intervention and orthogonal sliding is established, and the key contact parameters are optimally set. Finally, the two-level analysis method of overall model and submodel is used to achieve efficient solution of high-precision strains in submodels based on the displacement boundary obtained from the overall model calculation. Calculation results with four typical tooth morphologies during orthodontic treatment show that: ① the maximum strain of soft tissue is distributed along the sharp edges of the bracket, consistent with the clinically observed profile of soft tissue deformation; ② the maximum strain of soft tissue is reduced as the teeth align, consistent with the clinical manifestation of common damage and ulcers at the beginning of orthodontic treatment and reduced patient discomfort at the end of treatment. The method in this paper can provide reference for relevant quantitative analysis studies in the field of orthodontic medical treatment at home and abroad, and further benefit to the product development analysis of new orthodontic devices.

MRI compatibility of orthodontic brackets and wires: systematic review article.

BACKGROUND: Before the magnetic resonance imaging (MRI) examination fixed orthodontic devices, such as brackets and wires, cause challenges not only for the orthodontist but also for the radiologist. Essentially, the MRI-safe scan of the fixed orthodontic tools requires a proper guideline in clinical practice. Therefore, this systematic review aimed to examine all aspects of MRI-safe scan, including artifact, thermal, and debonding effects, to identify any existing gaps in knowledge in this regard and develop an evidence-based protocol. METHODS: The Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statement was used in this study. The clinical question in "PIO" format was: "Does MRI examination influence the temperature of the orthodontic devices, the size of artifacts, and the debonding force in patients who have fixed orthodontic bracket and/or wire?" The search process was carried out in PubMed, PubMed Central, Scopus, and Google Scholar databases. The search resulted in 1310 articles. After selection according to the eligibility criteria, 18 studies were analyzed by two reviewers. The risk of bias was determined using the Quality In Prognosis Studies tool. RESULTS: Out of the eligible 18 studies, 10 articles examined the heating effect, 6 were about the debonding effect, and 11 measured the size of artifact regarding brackets and wires. Considering the quality assessment, the overall levels of evidence were high and medium. The published studies showed that heating and debonding effects during MRI exposure were not hazardous for patients. As some wires revealed higher temperature changes, it is suggested to remove the wire or insert a spacer between the appliances and the oral mucosa. Based on the material, ceramic and plastic brackets caused no relevant artifact and were MRI-safe. Stainless steel brackets and wires resulted in susceptibility artifacts in the orofacial region and could cause distortion in the frontal lobe, orbits, and pituitary gland. The retainer wires showed no relevant artifact. CONCLUSIONS: In conclusion, the thermal and debonding effects of the fixed orthodontic brackets and wires were irrelevant or resoluble; however, the size of the artifacts was clinically relevant and determined most significantly the feasibility of fixed brackets and wires in MRI examination.

Accuracy of bracket position using thermoplastic and 3D-printed indirect bonding trays.

AIM: The positional accuracy of bracket placement planned through tooth setup vs actual placement was evaluated by means of conventional thermoplastic indirect bonding trays and customized 3D-printed indirect bonding trays. MATERIALS AND METHODS: A total of 280 bracket positions placed on the crowns of 10 dental plaster models were evaluated. The manual setup method and a thermoplastic indirect bonding tray were used for the manual group. For the CAD/CAM group, the bracket was positioned using a digital setup and a corresponding 3D-printed tray. The positional accuracy of the bracket placement on the duplicated gypsum model using the trays was evaluated by means of 3D software. Six errors of bracket position (height, depth, mesiodistal, torque, rotation, and tip errors), including linear and angular errors, were measured. Differences in variables were compared across subgroups using the independent t test or the Mann-Whitney U test. RESULTS: Only the height error differed significantly (P < 0.05) between groups (manual: 0.2 mm; CAD/CAM: 0.12 mm). For both incisors and molars, the manual group showed significantly greater height errors than the CAD/CAM group (P < 0.05). The analysis of variance of the position error to the whole bracket showed statistically significant differences between tooth positions, linear measurements, and angular measurements (P < 0.05). CONCLUSION: A 3D-printed indirect bonding tray showed accuracy similar to that of conventional methods for bracket placement, with slightly greater bracket height accuracy. Further studies should strive to improve accuracy in terms of tooth positions.

Esthetics of Orthodontic Appliances: Objective Evaluation by Spectrophotometry vs Subjective Evaluation Using the Visual Analog Scale Method.

AIM AND OBJECTIVE: In this study, we quantified the color of brackets and archwire appliances for an objective evaluation and investigated its relationship with subjective esthetic evaluation. MATERIALS AND METHODS: Five types of commercially available brackets (ceramic brackets C1, C2, and C3; plastic brackets P1 and P2) and three types of archwires (coated nickel-titanium archwires W1, W2, and W3) were used. The reflectance (%) and color (lightness: L*, hue: a*, b*) of each sample were quantified using a spectrophotometer (n = 5). Fifteen combinations of brackets and archwires were used. The esthetic evaluation was performed using the visual analog scale (VAS) method, and responses were obtained from 30 laypersons and 15 orthodontists. The mean VAS score was calculated, and the relationship between the reflectance and color of the bracket and archwire was discussed. RESULTS: The reflectance and L* of the brackets showed significantly higher values for C3 and C1 than for the others and lower values for P1 and P2. The reflectance and L* of the archwire showed significant differences among all samples. There was a high positive correlation between the reflectance and L*. There were statistically significant positive correlations between the layperson and orthodontist groups, between the VAS score and reflectivity, and between VAS score and L*. CONCLUSION: Our results showed that as the lightness and reflectance of the brackets and archwires increased, the subjective evaluation concerning their esthetic value was higher. CLINICAL SIGNIFICANCE: It is extremely difficult to evaluate esthetics despite the fact that patients' demands for esthetics have been increasing in recent years. If a method for evaluating esthetics is established, it should help in the development and selection of esthetic devices. The results of this study will facilitate the development of future study designs.

Assessment on the Precision of the Orthodontic Bracket Slot Dimensions Using Micro-computed Tomography (Micro-CT).

AIM: To evaluate the precision of the orthodontic bracket slot dimensions of 0.022 inch and to compare them with those of the manufacturers' specifications. MATERIALS AND METHODS: The slots of upper-right central incisor brackets (n = 5) from 11 commercial bracket systems of three different manufacturers (3M Unitek: Victory Mini Metal, Clarity, SmartClip, Clarity SL; ORMCO/SYBRON: Mini Diamond Twin, Damon Q, Damon Clear; Dentsply/GAC: Ovation, Mystique, In-Ovation R, In-Ovation C) were measured. The orthodontic brackets were scanned using micro-computed tomography (micro-CT), and the bracket slots were measured using micro-CT images. The slot was measured at four different surfaces (occlusal, gingival, base, and face) for both mesial and distal sites. Data were subjected to ANOVA and unpaired t-tests. A p-value of ≤0.05 was considered statistically significant. RESULTS: All brackets had slot dimensions that were significantly larger (p < 0.05) than the stated 0.022 inch. 3M-victory were 11.99% larger (0.02509 inch) and the closest to the stated dimension and the ORM-Damon C were 24.07% larger (0.02948 inch) than the quoted slot size of 0.022 inch. Comparison between mesial and distal sides showed that 91% of the bracket slots were asymmetrical at their bases and 100% asymmetrical at their faces. All of the bracket system showed divergent walls from base to face with values ranging from 1.96 (3M-SmartClip) to 26.58% (ORM-Damon C). CONCLUSION: The actual measurements of 11 bracket systems from three different manufacturers were more substantial than the manufacturers' specifications, and the walls of the slots diverged from the bracket bases in all of the tested bracket system. CLINICAL SIGNIFICANCE: Orthodontic bracket slots vary significantly from that of the manufacturers' specification. The orthodontist should anticipate such shortcomings and be able to modify treatment mechanics through additional wire bending in three spatial planes.

Impact of Fluoridated and Non-fluoridated Mouth Rinses on Frictional Resistance between Orthodontic Archwire and Bracket: A Comparative Study.

AIM AND OBJECTIVE: The present study aimed to assess the effect of fluoridated and nonfluoridated mouth ri nses on resistance to friction between orthodontic bracket and archwire. MATERIALS AND METHODS: This study comprises 60 premolar stainless steel (SS) brackets with 0.022 inches slot size. The 0.019 × 0.025 dimensions SS archwires were cut into 5 cm long specimens. They were grouped into three main categories, group I: artificial saliva (control solution), group II: Aloe Dent mouthwash (ALO), and group III: 0.05% sodium fluoride mouthwash. The specimens from each group were either immersed in the test solution or in the control solution for 10 hours. Later, the specimens were transferred to an incubator maintained at 37°C. Post 10 hours, the specimens were immersed for 30 minutes in distilled water. A scanning electron microscope was used to study the surface morphology and a universal testing machine was used to measure the frictional resistance. RESULTS: The distribution of normality for three study groups' recorded data was checked using Shapiro-Wilk test. The highest frictional resistance (1.94 ± 0.02) was demonstrated by specimens immersed in 0.05% sodium fluoride mouthwash than those immersed in Aloe Dent mouthwash (1.28 ± 0.66) and artificial saliva (1.10 ± 0.32). The difference found between the groups by an analysis of covariance was statistically significant. The highest surface roughness (22.30 ± 0.12) was revealed by specimens immersed in 0.05% sodium fluoride mouthwash than those immersed in Aloe Dent mouthwash (18.28 ± 0.26) and artificial saliva (15.86 ± 0.42). A statistically significant difference between the groups was shown by an analysis of covariance. CONCLUSION: After considering the drawbacks of this study, we conclude that specimens immersed in Aloe Dent mouthwash demonstrated less frictional resistance and surface roughness when compared to those immersed in 0.05% sodium fluoride mouthwash. CLINICAL SIGNIFICANCE: During sliding mechanism, the frictional resistance between orthodontic archwire and brackets imposes problems, such as lessening the applied force and movement of tooth, and also results in anchorage loss. So, orthodontists should always take care while prescribing mouthwashes to reduce their effects on the friction.

Effects of Antioxidants on the Shear Bond Strength of Orthodontic Brackets Bonded to Bleached Human Teeth: An In Vitro Study.

AIM: The aim of this study was to evaluate the effects of different concentrations of sodium ascorbate (SA), green tea (GT), and chamomile (CM) on the shear bond strength (SBS) of metal orthodontic brackets bonded to teeth bleached with 40% hydrogen peroxide (HP). MATERIALS AND METHODS: Ninety-four sound premolars were divided into eight groups: group I (control + no bleaching), group II (bleaching + immediate bonding), group III (bleaching + 10% SA), group IV (bleaching + 35% SA), group V (bleaching + 0.5% GT), group VI (bleaching + 1% GT), group VII (bleaching + 0.5% CM), and group VIII (bleaching + 1% CM). In groups III-VIII, teeth were treated with the antioxidants for 10 minutes after bleaching with 40% HP, but before bonding. All the specimens were bonded with the resilience adhesive, and the SBS was tested with a universal testing machine (Instron 5965). The cross-head speed to break the bond was 1 mm/minute. The adhesive remnant index (ARI) was tested under 50× magnification. One-way analysis of variance, Tukey's post hoc, and Chi-squared tests were used for analysis (p ≤ 0.05). RESULTS: The differences in SBS among the eight tested groups were highly significant (p < 0.001). Comparison of the eight groups using Tukey's post hoc test revealed significantly lower SBS (p < 0.001) in test groups II, III, IV, and VIII than in group I. Adhesive remnant index scores showed significant intergroup differences (p = 0.005). Most groups had a failure score of 1 (<50% of the bonding material adhering to the tooth), whereas groups II and VIII showed a failure score of 0 (no material adhering to the tooth). CONCLUSION: Bond strength can be enhanced by using 0.5% or 1% GT or 0.5% CM to allow bracket bonding immediately after bleaching. CLINICAL SIGNIFICANCE: The use of antioxidants would allow clinicians to bleach teeth before orthodontic treatment without delaying bonding.

Evaluation of Different Pretreatment Efficacy with Fluoride-releasing Material on Shear Bond Strength of Orthodontic Bracket: An In Vitro Study.

AIM: The aim of this study was to assess the efficacy of different pretreatments with fluoride-releasing material on shear bond strength (SBS) of orthodontic bracket. MATERIALS AND METHODS: A total of 60 human mandibular premolars were taken in this study. These samples were stored in periodically changed distilled water at room temperature so as to stop bacterial growth. All samples were randomized to three pretreatment groups: group I, acid etching; group II, fluoride varnish; group III, casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste. Later, Transbond XT was applied on brackets made of stainless steel and brackets were centered buccally and then light-cured. The INSTRON universal machine was used to measure SBS. Based on the values, the adhesive remnant index (ARI) was estimated. RESULTS: The maximum SBS was seen in group III (18.84 µ 1.04), followed by group II (14.18 µ 0.23), and the minimum bond strength was found in group I (13.90 µ 1.22). The one-way analysis of variance (ANOVA) showed high statistically significant difference within the pretreatment groups. The pretreatment group comparisons showed statistically significant difference between group I vs group III and group II vs group III. Score 0 was more in group III [8 (40%)] followed by group II [4 (20%)] and group I [2 (10%)]. The lowest number of score 3 was found in CPP-ACP paste group. After comparing the ARI scores within the groups, the Chi-square test showed a probability of 0.001 which was statistically significant. CONCLUSION: Our study established that the CPP-ACP paste pretreatment improves the SBS of orthodontic bracket significantly followed by fluoride varnish and acid etching. CLINICAL SIGNIFICANCE: The bond strength of orthodontic brackets that were bonded should be adequate to resist orthodontic forces applied during treatment. The effect of the adhesive material to improve the adequate bond strength depends on the efficient pretreatment methods.

Comparative study of the effect of Er:YAG and Er:Cr;YSGG lasers on porcelain: etching for the bonding of orthodontic brackets.

This study investigated the effect of Er:YAG (smart 2940 Dplus, DEKA, Italy) and Er:CrYSGG (Waterlase iPlus, Biolase, USA) lasers on the shear bond strength (SBS) between the orthodontic brackets and dental porcelain in comparison with conventional acid etching with 9% hydrofluoric acid (HF, Ultradent, USA). A total of 60 specimens of maxillary incisor crown were prepared and randomly assigned to five groups; each group was subjected to a different porcelain surface conditioning: (1) etching with the 9% HF for 2 min; (2) etching with the 9% HF for 2 min followed by irradiation with the Er:CrYSGG laser (3-W power, 10-Hz frequency for 10 s); (3) etching with the 9% HF for 2 min followed by irradiation with the Er:YAG laser (3-W power, 10-Hz frequency for 10 s); (4) Irradiation with the Er:CrYSGG laser (3-W power, 10-Hz frequency for 10 s without acid etching) and (5) irradiation with the Er:YAG laser (3-W power,10-Hz frequency for 10 s without acid etching). After using Transbond XT primer and Transbond XT adhesive, the metal brackets (Dentaurum, Germany equilibrium 2, optimal design) bonded to the conditioned porcelain surface. Subsequently, the specimens were thermocycled for 5000 cycles and then debonded using the Universal Testing Machine (Zwick). In each group, one specimen was not bonded to brackets to allow further examination with electron microscopy. After debonding, the specimens were examined by stereomicroscope to determine their adhesive remnant index (ARI). The average SBS [Mean (SD)] values in the five groups were as follows: HF (32.58 ± 9.21 MPa), Er:CrYSGG + HF (27.81 ± 7.66 MPa), Er:YAG + HF (23.08 ± 9.55 MPa), Er:CrYSGG (14.11 ± 9.35 MPa), and Er:YAG (6.30 ± 3.09 MPa). A statistically significant difference in SBS existed between the first three groups and the two laser groups (df = 4, F = 18.555, p < 0.001). Evaluation of ARI values showed that bond failures in the first three groups were mostly of cohesive and mixed types, but in the laser groups, they were mostly adhesive. Chi-square was not significant between groups (p = 0.219). The Er:YAG laser with the stated specifications is not a suitable alternative to HF etching. In the case of Er:CrYSGG laser, although the conditioning outcome met the bond strength requirement for orthodontic brackets (that is, 6-8 MPa). Therefore, the bond strength must be further improved by fine-tuning the irradiation details.

Comparative efficacy of Er,Cr:YSGG and Er:YAG lasers for etching of composite for orthodontic bracket bonding.

Several techniques have been proposed to obtain a durable bond, and the efficacy of these techniques is assessed by measuring parameters such as bond strength. Laser has provided a bond strength as high as that of acid etching in vitro and has simpler use with shorter clinical time compared to acid etching. This study aimed to compare the efficacy of Er:YAG and Er,Cr:YSGG lasers for etching and bonding of composite to orthodontic brackets. No previous study has evaluated the effect of these particular types of laser. A total of 70 composite blocks were randomly divided into five groups (n = 14): group 1, etching with phosphoric acid for 20 s; group 2, Er:YAG laser irradiation with 2 W power for 10 s; group 3, Er:YAG laser with 3 W power for 10 s; group 4, Er,Cr:YSGG laser with 2 W power for 10 s; group 5, Er,Cr:YSGG laser with 3 W power for 10 s. Metal brackets were then bonded to composites, and after 5000 thermal cycles, they were subjected to shear bond strength test in a universal testing machine after 24 h of water storage. One sample of each group was evaluated under a scanning electron microscope (SEM) to assess changes in composite surface after etching. The adhesive remnant index (ARI) was calculated under a stereomicroscope. Data were statistically analyzed. The mean and standard deviation of shear bond strength were 18.65 ± 3.36, 19.68 ± 5.34, 21.31 ± 4.03, 17.38 ± 6.94, and 16.45 ± 4.26 MPa in groups 1-5, respectively. The ARI scores showed that the bond failure mode in all groups was mainly mixed. The groups were not significantly different in terms of shear bond strength. Er:YAG and Er,Cr:YSGG lasers with the mentioned parameters yield optimal shear bond strength and can be used as an alternative to acid etching for bracket bond to composite.

Assessment of efficacy of two chlorhexidine mouthrinses on oral hygiene and gingival health in adolescents wearing two types of orthodontic brackets.

OBJECTIVE: To investigate the efficacy of two formulations of chlorhexidine 0.2% (CHX) mouthrinses in terms of oral hygiene and gingival health status in adolescents with fixed orthodontic appliances wearing two different types of brackets during 18 weeks. STUDY POPULATION AND METHODOLOGY: Eighty subjects were randomly divided into two equal groups according to brackets type: (i) metal-stainless steel, (ii) ceramic. Four weeks after the placement of the fixed orthodontic appliances the subjects from each group were randomly allocated into two equal subgroups and were provided with two different mouthrinses for 14 days: (i) alcohol-free CHX, (ii) CHX with antidiscoloration system (CHX-ADS). Assessment was carried out according to gingival index (GI) and oral hygiene index-simplified (OHI-S) performed prior to the placement of the appliance (t1 ), 6 weeks (t2 ), and 18 weeks (t3 ) after the placement. To analyse the data, two-way mixed model MANOVA. Pearson correlations, one-way ANOVA and Independent Samples t test were conducted. RESULTS: Statistically significant decrease in GI and OHI-S indices after 6 weeks and then increase after 18 weeks for all groups was found. Both GI and OHI-S values were lower in subjects wearing ceramic brackets, with statistically significant difference for GI after the usage of the mouthrinse for 14 days, at t2 (P<.05). CONCLUSION: The results revealed that the ceramic brackets as well as usage of CHX-ADS resulted in improved gingival status.

Ion Release and Galvanic Corrosion of Different Orthodontic Brackets and Wires in Artificial Saliva.

INTRODUCTION: To investigate the galvanic corrosion of brackets manufactured by four different companies coupled with stainless steel (SS) or nickel-titanium (NiTi) wires in an artificial saliva solution. MATERIALS AND METHODS: A total of 24 mandibular central incisor Roth brackets of four different manufacturers (American Orthodontics, Dentaurum, Shinye, ORJ) were used in this experimental study. These brackets were immersed in artificial saliva along with SS or NiTi orthodontic wires (0.016'', round) for 28 days. The electric potential difference of each bracket/ wire coupled with a saturated calomel reference electrode was measured via a voltmeter and recorded constantly. Corrosion rate (CR) was calculated, and release of ions was measured with an atomic absorption spectrometer. Stereomicroscope was used to evaluate all samples. Then, samples with corrosion were further assessed by scanning electron microscope and energy-dispersive X-ray spectroscopy. Two-way analysis of variance was used to analyze data. RESULTS: Among ions evaluated, release of nickel ions from Shinye brackets was significantly higher than that of other brackets. The mean potential difference was significantly lower in specimens containing a couple of Shinye brackets and SS wire compared with other specimens. No significant difference was observed in the mean CR of various groups (p > 0.05). Microscopic evaluation showed corrosion in two samples only: Shinye bracket coupled with SS wire and American Orthodontics bracket coupled with NiTi wire. CONCLUSION: Shinye brackets coupled with SS wire showed more susceptibility to galvanic corrosion. There were no significant differences among specimens in terms of the CR or released ions except the release of Ni ions, which was higher in Shinye brackets.

The effect of antimicrobial agents on bond strength of orthodontic adhesives: a meta-analysis of in vitro studies.

Antimicrobial orthodontic adhesives aim to reduce white spot lesions' incidence in orthodontic patients, but they should not jeopardizing its properties. Systematic review and meta-analysis were performed to answer the question whether the association of antimicrobial agents with orthodontic adhesives compromises its mechanical properties and whether there is a superior antimicrobial agent. PubMed and Scopus databases. In vitro studies comparing shear bond strength of conventional photo-activated orthodontic adhesives to antimicrobial photo-activated orthodontic adhesives were considered eligible. Search terms included the following: orthodontics, orthodontic, antimicrobial, antibacterial, bactericidal, adhesive, resin, resin composite, bonding agent, bonding system, and bond strength. The searches yielded 494 citations, which turned into 467 after duplicates were discarded. Titles and abstracts were read and 13 publications were selected for full-text reading. Twelve studies were included in the meta-analysis. The global analysis showed no statistically significant difference between control and experimental groups. In the subgroup analysis, only the chlorhexidine subgroup showed a statistically significant difference, where the control groups had higher bond strength than the experimental groups. Many studies on in vitro orthodontic bond strength fail to report test conditions that could affect their outcomes. The pooled in vitro data suggest that adding an antimicrobial agent to an orthodontic adhesive system does not influence bond strength to enamel. It is not possible to state which antimicrobial agent is better to be associated.

A study to investigate the bond strengths of orthodontic brackets bonded to prosthetic acrylic teeth.

INTRODUCTION: In this study, we compared the shear bond strengths of five different adhesive techniques for attaching metal orthodontic brackets onto acrylic pontics. MATERIALS AND METHODS: Two hundred upper left lateral incisor acrylic teeth with bonded brackets were divided into five groups - composite alone (control), composite following sandblasting, composite held with a mechanical undercut, cyanoacrylate adhesive and Panavia(®). The initial bond strength was tested using the Instron Universal Testing Machine. The fatigue bond strength was tested by subjecting each bracket to 5000 repetitive low-load cycles at 50% of the mean shear bond strength using the Dartec machine at 2 Hz. RESULTS: Cyanoacrylate adhesive statistically exhibited the highest mean bond strength (19·82 MPa). This was followed by the mechanical undercut group (17·69 MPa) and the sandblasted group (17·18 MPa). There was no statistically significant difference when considering the effect of fatiguing (p = 0·238) as well as the interaction between the adhesive technique and the effect of fatiguing on the bond strength (p = 0·440). CONCLUSION: The initial and fatigue bond strengths of the cyanoacrylate adhesive, sandblasted and undercut groups were significantly higher than the control and Panavia(®) groups when tested under laboratory conditions.

The effect of orthodontic bracket base shape on shear bond strength to human enamel, an in vitro study.

The purpose of this study was to evaluate the in vitro effect of orthodontic bracket base shape on shear bond strength (SBS) to human enamel and assess the nature of debonding fractures using the Adhesive Remnant Index (ARI). Orthodontic brackets with different-shaped bases (flower, heart, rectangle) were bonded to 120 extracted human third molars. Shear bond strength was measured using a Servohydraulic Test System at 24 h and 2 months after bonding. Adhesive Remnant Index scores were evaluated under 10x magnification to assess the amount of resin left on the tooth. The control bracket (rectangular base shape) had the highest mean SBS (26.8 ± 8.2 megapascals [MPa]), and significantly differed from the flower (17.2 ± 4.4 MPa) and heart (18.9 ± 3.5 MPa) base shapes (p < 0.001). The mean SBS between debonding times at 24 h (21.5 ± 7.4 MPa) and 2 months (20.4 ± 6.7 MPa) were not statistically significant (p > 0.05). Analysis of ARI scores showed a significant difference between flower-24 h versus heart-2 months (p = 0.039), flower-24 h versus heart-24 h (p = 0.004), and control-2 months versus heart-24 h (p = 0.015). Bracket base shape influenced SBS, with the rectangular base shape having a higher mean SBS compared to flower and heart base shapes. Variations in ARI scores occurred based on bracket shape and were of a mixed adhesive-cohesive nature. All bracket shapes had bond strengths above the clinically acceptable range of 6-8 MPa, and may thus provide adequate SBS in a clinical situation.

Assessing the physico-mechanical, anti-bacterial, and anti-demineralization properties of orthodontic resin composite containing different concentrations of photoactivated zinc oxide nanoparticles on Streptococcus mutans biofilm around ceramic and metal orthodontic brackets: An ex vivo study.

BACKGROUND AND PURPOSE: The aim of this study was to evaluate the physico-mechanical, anti-bacterial, and anti-demineralization properties of orthodontic resin composite containing photoactivated zinc oxide nanoparticles (ZnONPs) on Streptococcus mutans biofilm around ceramic and metal brackets. MATERIAL AND METHODS: Following the minimum inhibitory concentration (MIC) determination for ZnONPs, shear bond strength (SBS) was tested for composites containing different concentrations of ZnONPs. The chosen concentration was used to evaluate the microleakage, anti-bacterial, and anti-demineralization properties. RESULTS: Adding 50µg/mL of ZnONPs to the orthodontic composite did not negatively affect its physico-mechanical properties. ZnONPs (50µg/mL)-mediated aPDT and 0.2% chlorhexidine significantly (P=0.000) reduced S. mutans biofilms compared to the phosphate-buffered saline (PBS) groups (metal/PBS=7.47±0.7×106, and ceramic/PBS=7.47±0.7×106), with the lowest colony count observed in these groups (metal/chlorhexidine=1.06±0.4×105, ceramic/chlorhexidine=1±0.2×105, metal/ZnONPs-mediated aPDT=1.33±0.3×105, and ceramic/ZnONPs-mediated aPDT=1.2±0.3×105). Sodium fluoride varnish and ZnONPs-mediated aPDT showed the highest efficacy in anti-demineralization and significantly improving the enamel surface microhardness compared to the artificial saliva, especially in ceramic bracket groups (524.17±42.78N and 441.00±29.48N, 394.17±46.83N, P=0.000, and P=0.003, respectively). CONCLUSION: ZnONPs (50µg/mL)-mediated aPDT effectively inhibited S. mutans biofilm and promoted anti-demineralization without adverse effects on the physico-mechanical properties of the composite resin. These results suggest the potential of this method in preventing white spot lesions during orthodontic treatment.

Does surface priming increase the bond strength of orthodontic brackets? An experimental study.

OBJECTIVE: To evaluate the effects of metal primer II (MP II) on the shear bond strength (SBS) of orthodontic brackets bonded to teeth and bis-acryl composite provisional material (Bis-Acryl). MATERIAL AND METHODS: Twenty extracted human premolars specimens and 20 premolar shaped Bis-Acryl specimens were obtained and randomly divided into two surface groups. The first group consisted of human premolars (T) bonded to brackets in the conventional way while in the second (T-MP) MP II was applied on the bracket base before bonding. Similarly, one group of provisional material (PM) was prepared according to conventional treatment and another with the application of MP-II metal bonder (PM-MP). In all cases Ortho-brackets (Victory Series, 3 M) were bonded employing Transbond XT resin cement. Then the brackets were debonded under shear and the results were statistically analyzed by two-way analysis of variance and Holm Sidak at α = .05. The debonded surfaces of all specimens were examined by light microscopy and the Adhesive Remnant Index (ARI) was recorded. RESULTS: The SBS results exhibited significant differences er (p < .001). For both the T and TM the application of MP-II increased the SBS compared to respective control groups (p < .001). The T-C group was found inferior compared to PM-C (p < .001) and the same is true for the comparison between T-MP and PM-MP (p < .001). ARI indexes demonstrated that the tooth groups were characterized by a predominantly adhesive failure at the resin-dentin interface. In contrast, the control group for provisional crowns (PM-C) showed a predominantly cohesive failure mode, which moved to predominantly adhesive after the application of MP II. CONCLUSION: The application of MP II enhances the SBS on both, human enamel and provisional crown materials.

Biofilm volume and acidification within initial biofilms formed in situ on buccally and palatally exposed bracket material.

PURPOSE: Acidification by bacterial biofilms at the bracket/tooth interface is one of the most common problems in fixed orthodontic treatments, which can lead to white spot lesions (WSL) and caries. As lingual brackets were shown to exhibit reduced WSL formation clinically, the aim of this in situ study was to compare initial intraoral biofilm formation and acidification on bracket-like specimens placed buccally and palatally in the upper jaw as a possible cause for this observation. METHODS: Intraoral biofilm was collected from splints equipped with buccally and palatally exposed test specimens, which were worn by 12 volunteers for a total of 48 h. The test specimens consisted of standard bracket material cylinders on top of a hydroxyapatite disc to represent the bracket/tooth interface. They were analyzed for three-dimensional biofilm volume and live/dead distribution by fluorescence staining and confocal laser scanning microscopy as well as for acidification by fluorescence-based pH ratiometry. RESULTS: Similar general biofilm morphology with regard to volume and viability could be detected for buccally and palatally exposed specimens. For pH values, biofilms from both positions showed increased acidification at the bottom layer. Interestingly, the pH value at the top layers of the biofilms was slightly lower on palatally than on buccally exposed specimens, which may likely be due to anatomic conditions. CONCLUSION: Based on the results of this study, initial intraoral biofilm formation and acidification is almost similar on the bracket material/biomimetic tooth interface when placed buccally or palatally in the upper jaw. As lingual brackets were shown to exhibit reduced WSL formation clinically, future studies should investigate further factors like bracket geometry.