Percentage of patients shifting to another treatment modality: An experience-guided decision.

OBJECTIVE: This study aimed to assess the frequency with which orthodontic patients decided to shift to another type of orthodontic appliance, among conventional metal brackets, ceramic brackets, lingual brackets and clear aligner, based on their personal experiences of pain, ulcers, bad breath, hygiene issues and social difficulties. MATERIAL AND METHODS: This study comprises of patients seeking orthodontic treatment. The sample (n = 500; age group = 19-25 years) was divided equally into four groups based on the treatment modality: conventional metal brackets, ceramic brackets, lingual brackets and clear aligner. Patients rated the questionnaire using a visual analogue scale, to assess variables (such as pain, ulcer etc) that impact various treatment modalities. Subsequently, patients from all groups provided feedback regarding their treatment experiences, and expressed their preference for an alternative modality. Intergroup comparison among the four groups was done using one-way analysis of variance with Tukey's HSD post-hoc test (p ≤ 0.05). RESULTS: Patients who received lingual brackets reported higher levels of pain and ulceration, as compared to those who received clear aligners. All four groups showed statistically significant differences for ulcers during treatment (p ≤ 0.05). Of the 125 patients who received conventional metal brackets, 28% expressed a preference for clear aligner therapy, while 20% preferred ceramic brackets. In the lingual group, 56% of 125 patients preferred clear aligner therapy, and 8% preferred ceramic brackets to complete their treatment. In the ceramic group, 83% did not want to switch, whereas 17% desired to switch to clear aligner, while in aligner group no patient desired to switch. CONCLUSIONS: A higher percentage of patients from lingual brackets group chose to shift to clear aligners, followed by conventional metal brackets group and by ceramic brackets group, in this descending order. The clear aligner group demonstrated fewer issues than the other treatment modalities.

Evaluation of enamel surface integrity after orthodontic bracket debonding: comparison of three different system.

OBJECTIVE: This study aimed to evaluate enamel surface integrity and time consumed during residual cement removal after bracket debonding using different adhesive removal burs with and without a dental loupe. MATERIAL AND METHODS: Sixty human-extracted premolars were collected, cleaned, mounted, and prepared for orthodontic bracket bonding. Teeth were randomly divided into three main groups (n = 20) based on the adhesive removal method: tungsten carbide system (TC), sof-lex discs system (SD), and diamond system (DB) groups. Then, each group was subdivided into two subgroups (naked eye and magnifying loupe subgroups). The brackets were bonded and then debonded after 24 h, and the Adhesive Remnant Index (ARI) was assessed. The adhesive remnants were removed by different systems, and the final polishing was performed by Silicone OneGloss. The enamel surface roughness was evaluated before bracketing (T0), after residual cement removal (T1), and finally after polishing (T2) using surface Mitutoyo SJ-210 profilometry and Scanning Electron Microscopy (SEM) to determine the Enamel Damage Index (EDI) score. The time consumed for adhesive removal was recorded in seconds. RESULTS: The Kruskal Wallis test showed a statistically significant difference in roughness values at T1 compared to T2 between subgroups (p < 0.001). When comparing EDI at T1 and T2, the Kruskal-Wallis H-test showed statistically significant differences in all subgroups. The pairwise comparisons revealed that EDI scores showed a statistically significant difference at T1 and T2 between DB vs. TC and SD (p = 0.015) but not between TC vs. SD (p = 1.000), indicating the highest roughness value observed in the DB group. The time for cement removal was significantly shorter in the magnifying loupe group than in the naked eye group and was shortest with the TC group, whereas the time was the longest with the DB group (p < 0.05). CONCLUSION: All three systems were clinically satisfactory for residual orthodontic adhesive removal. However, TC system produced the lowest enamel roughness, while the DB system created the greatest. The polishing step created smoother surfaces regardless of the systems used for resin removal.

Cleaning performance of electric toothbrushes around brackets applying different brushing forces: an in-vitro study.

Throughout treatment with fixed orthodontic appliances, effective plaque control is crucial to maintaining dental health. This in-vitro study evaluated the cleaning performance of eleven different brush heads of seven electric toothbrushes (oscillating-rotating and sonic motions) and varying brushing forces around orthodontic brackets. Six Mini Diamond® Twin brackets were placed on black-stained front teeth. Teeth were coated with white titanium oxide and brushed in a machine six times for one minute with two different brushing forces (1 N and 1.5 N). Eleven different brush heads were evaluated (either oscillating-rotating or sonic movements). The teeth were scanned and planimetrically evaluated after brushing. Three detailed plaque areas (DPAs) were created: proximal (< 1 mm to bracket), mid-tier (1-2 mm to bracket), and distant (> 2 mm to bracket). The proportion of contaminated proximal, mid-tier, and distant surfaces (white regions) in relation to the respective DPA was calculated. Independent of brushing forces, places with a higher distance (> 2 mm) to the orthodontic bracket had the least amount of residual contamination, followed by areas with a minor (1-2 mm) and proximal distance (< 1 mm). In all of the brushes tested and for both estimated brushing forces, the region with the highest residual contamination was the proximal area. The brush heads of the Paro® Sonic toothbrush left the least amount of residual contamination. The cleaning performance of electric toothbrushes around brackets on upper incisors varied across the brushes examined. The proximal area has the most residual contamination. Furthermore, 9 out of 11 toothbrushes cleaned more successfully with 1.5 N than with 1 N brushing force.

Correlating Frictional Forces Generated by Different Bracket Types during Sliding and Surface Topography Using Scanning Electron Microscopy and Optical Profilometer.

AIM: The study aims to correlate the frictional forces (FF) of four different types of commercially available ceramic brackets to their surface topography. MATERIALS AND METHODS: Two monocrystalline (MC) brackets (CLEAR™, Adanta, Germany; Inspire ICE™, Ormco, USA), one polycrystalline (PC) bracket (Symetri Clear™, Ormco, USA), one clear hybrid esthetic bracket (DISCREET™, Adanta, Germany), and a stainless-steel (SS) bracket (Victory™, 3M Unitek, USA) served as control. Both static friction (SF) and kinetic friction (KF) were recorded during sliding using an Instron universal machine in dry settings. The bracket slot surface topography was evaluated. A scanning electron microscope (SEM) and a profilometer machine were used for assessment before and after sliding. RESULTS: Frictional forces values during sliding were as follows in descending order; Inspire ICE™, CLEAR™, DISCREET™, Symetri Clear™, and, lastly, Victory™. Also, DISCREET™ scored the highest in surface roughness (Sa) values followed by Symetri Clear™. None of the correlations were statistically significant. CONCLUSION: Frictional forces produced during sliding were not always directly related to surface roughness. Monocrystalline ceramic brackets appeared to have the greatest FF and a low surface roughness. Furthermore, DISCREET™ scored a very low frictional value comparable to metal brackets yet showed the highest surface roughness. Metal brackets exhibited the greatest surface smoothness before sliding and the least SF. CLINICAL SIGNIFICANCE: Predicting the FFs produced during sliding mechanics would help the practitioner while choosing the bracket system to be used, and while planning the treatment mechanics, how much force to deliver, and how much tooth movement to expect. How to cite this article: AlBadr AH, Talic NF. Correlating Frictional Forces Generated by Different Bracket Types during Sliding and Surface Topography Using Scanning Electron Microscopy and Optical Profilometer. J Contemp Dent Pract 2024;25(1):41-51.

[Bond strength of metal brackets to enamel with a Russian adhesive complex: an in vitro study]. / Sila adgezionnogo soedineniya emali zuba i metallicheskogo breketa, poluchennogo s pomoshch'yu otechestvennogo adgezivnogo kompleksa in vitro.

BACKGROUND: The era of using adhesives to fix brackets began in the 70s of the last century. There are eight generations of foreign-made adhesive systems for the restoration of teeth. However, until now, in orthodontics, the development of domestic adhesive systems with improved properties of adhesion of brackets to tooth enamel still important, especially in the posterior teeth. OBJECTIVE: The purpose of this work was to study the shear strength of fifth generation domestic adhesive between metal brackets and the enamel of molar teeth in laboratory conditions. MATERIAL AND METHODS: The study included 17 specimens of extracted maxillary molars embedded in acrylic resin blocks. Brackets from G&H Orthodontics (G&H Wire Company, USA) were fixed to the tooth enamel using the domestic Compofix (ortho) set. The enamel was treated with etching gel (37% phosphoric acid) for 30 seconds. Then the gel was washed off with water and the surface of the enamel was thoroughly dried. A primer was applied to the prepared surface with an applicator, inflated with a weak air flow for 5-10 seconds and photopolymerized for 20 seconds. The surface of the bracket was treated with degreaser, then a thin layer of adhesive was applied, and the sample was fixed to the enamel. Excess material was removed with an applicator. The samples were photopolymerized for 20 sec. Then, the shear bond strength of the adhesive was determined according to the method of GOST 31574-2012 on a (Zwick/Roell Z010 testing machine, Zwick, Germany). RESULTS: The shear strength of the adhesive joint obtained during the test is 13.54±1.01 MPa, the average value of the index of adhesive residues on the surface of the bracket was 23%±4%, which corresponds to the standard average values according to GOST. CONCLUSION: The tested domestic adhesive system of the fifth generation can be recommended for the practical work of an orthodontist.

Initial arch wires used in orthodontic treatment with fixed appliances.

BACKGROUND: Initial arch wires are the first arch wires inserted into fixed appliance at the beginning of orthodontic treatment. With a number of different types of orthodontic arch wires available for initial tooth alignment, it is important to understand which are most efficient and which cause the least amount of root resorption and pain during the initial aligning stage of treatment. This is the third update of a Cochrane review first published in 2010. OBJECTIVES: To assess the effects of initial arch wires for the alignment of teeth with fixed orthodontic braces, in terms of the rate of tooth alignment, amount of root resorption accompanying tooth movement, and intensity of pain experienced by patients during the initial alignment stage of treatment. SEARCH METHODS: We searched Cochrane Oral Health's Trials Register, CENTRAL, MEDLINE, Embase, and two ongoing trials registries on 4 July 2022. SELECTION CRITERIA: We included randomised controlled trials (RCTs) of different initial arch wires used to align teeth with fixed orthodontic braces. We included people with full-arch fixed orthodontic appliances on the upper arch, lower arch, or both arches. DATA COLLECTION AND ANALYSIS: Two independent review authors were responsible for study selection, data extraction, and assessment of risk of bias in included studies. We contacted corresponding authors of included studies to obtain missing information. We resolved disagreements by discussion between the review authors. Our main outcomes were alignment rate (movement of teeth in mm), root resorption, time to alignment, and intensity of pain measured on a 100-mm visual analogue scale (VAS). We pooled data from studies with similar interventions and outcomes using random-effects models. We reported mean differences (MDs) with 95% confidence intervals (CIs) for continuous data, risk ratios (RRs) with 95% CIs for dichotomous data, and alignment rate ratios with 95% CIs for time-to-event data. Two independent review authors assessed the certainty of evidence. We resolved disagreements by discussion between the review authors. MAIN RESULTS: We included 29 RCTs with 1915 participants (2581 arches) in this review. Studies were generally small (sample sizes ranged from 14 to 200 participants). Duration of follow-up varied between three days and six months. Eleven studies received funding, six received no funding, and 12 provided no information about funding sources. We judged eight studies at high risk of bias, nine at low risk, and 12 at unclear risk. We grouped the studies into six main comparisons. Multistrand stainless steel wires versus wires composed of other materials Six studies with 409 participants (545 arches) evaluated multistrand stainless steel (StSt) wires versus wires composed of other materials. We are very uncertain about the effect of multistrand StSt wires versus other wires on alignment rate (4 studies, 281 participants, 417 arches; very low-certainty evidence). There may be little to no difference between multistrand StSt wires and other wires in terms of intensity of pain (MD -2.68 mm, 95% CI -6.75 to 1.38; 2 studies, 127 participants, 127 arches; low-certainty evidence). Conventional nickel-titanium wires versus superelastic nickel-titanium wires Four studies with 266 participants (274 arches) evaluated conventional nickel-titanium (NiTi) wires versus superelastic NiTi wires. There may be little to no difference between the different wire types in terms of alignment rate (124 participants, 124 arches, 2 studies; low-certainty evidence) and intensity of pain (MD -0.29 mm, 95% CI -1.10 to 0.52; 2 studies, 142 participants, 150 arches; low-certainty evidence). Conventional nickel-titanium wires versus thermoelastic copper-nickel-titanium wires Three studies with 210 participants (210 arches) evaluated conventional Ni-Ti versus thermoelastic copper-nickel-titanium (CuNiTi) wires. We are very uncertain about the effects of the different arch wires on alignment rate (1 study, 66 participants, 66 arches; very low-certainty evidence). There may be little to no difference between conventional NiTi wires and thermoelastic CuNiTi wires in terms of time to alignment (alignment rate ratio 1.30, 95% CI 0.68 to 2.50; 1 study, 60 participants, 60 arches; low-certainty evidence). Superelastic nickel-titanium wires versus thermoelastic nickel-titanium wires Twelve studies with 703 participants (936 arches) evaluated superelastic NiTi versus thermoelastic NiTi wires. There may be little to no difference between superelastic NiTi wires and thermoelastic NiTi wires in alignment rate at four weeks (MD -0.28 mm, 95% CI 0.62 to 0.06; 5 studies, 183 participants, 183 arches; low-certainty evidence). We are very uncertain about the effects of the different wires on root resorption (2 studies, 52 participants, 312 teeth; very low-certainty evidence). Superelastic NiTi wires compared with thermoelastic NiTi wires may result in a slight increase in time to alignment (MD 0.5 months, 95% CI 0.21 to 0.79; 1 study, 32 participants, 32 arches; low-certainty evidence) but are probably associated with a slight increase in intensity of pain (MD 6.96 mm, 95% CI 1.82 to 12.10; 3 studies, 94 participants, 138 arches, moderate-certainty evidence). Single-strand superelastic nickel-titanium wires versus coaxial superelastic nickel-titanium wires Three studies with 104 participants (104 arches) evaluated single-strand superelastic NiTi versus coaxial superelastic NiTi wires. Use of single-strand superelastic NiTi wires compared with coaxial superelastic NiTi wires probably results in a slight reduction in alignment rate at four weeks (MD -2.64 mm, 95% CI -4.61 to -0.67; 2 studies, 64 participants, 64 arches, moderate-certainty evidence). Different sizes of nickel-titanium wires Two studies with 149 participants (232 arches) compared different types of NiTi wires. There may be little to no difference between different sizes of NiTi wires in terms of pain (low-certainty evidence). AUTHORS' CONCLUSIONS: Superelastic NiTi wires probably produce slightly more pain after one day than thermoelastic NiTi wires, and single-strand superelastic NiTi wires probably have a lower alignment rate over four weeks compared with coaxial superelastic NiTi wires. All other evidence on alignment rate, root resorption, time to alignment, and pain is of low or very low certainty in all comparisons. Therefore, there is insufficient evidence to determine whether any particular arch wire material or size is superior to any other. The findings of this review are imprecise and unreliable; well-designed larger studies are needed to give better estimates of the benefits and harms of different arch wires. Orthodontists should exercise caution when interpreting the findings of this review and be prepared to adapt their treatment plans based on individual patient needs.

A scanning electron microscopy investigation of the precision of three orthodontic bracket slot systems.

OBJECTIVE: One of the most imprortant factors in achieving ideal teeth positions is the precision of the slot dimensions of orthodontic brackets into the archwires are inserted.This study aimed to assess the accuracy of the dimensions of orthodontic bracket slots and molar buccal tube apertures and to compare them with the specifications provided by the manufacturers. METHOD: A total of sixty brackets and ten molar buccal tubes with varying slot heights were examined using a scanning electron microscope from the mesial side. The dimensions and morphology of these bracket slots and buccal tubes apertures were assessed using the AutoCAD Software. A one-sample t-test was conducted to compare the measurements with the values provided by the manufacturer. RESULTS: The findings of the present study indicated that the height of the measured bracket slots and buccal tube apertures dimensions were significantly larger than the actual dimensions and exhibiting divergent walls. On the other hand, the depth of the brackets slots showed significantly smaller values than the actual one. CONCLUSION: A need for careful consideration when selecting a commercially accessible brand for everyday use is essential as certain materials may not meet acceptable standards.

Influence of etchant type on the shear bond strength of orthodontic brackets to enamel.

The aim of this study was to evaluate the influence of the type of etchant on the shear bond strength (SBS) of metallic brackets to enamel and the Adhesive Remnant Index (ARI) after debonding. A total of 30 mandibular and maxillary premolars were randomly distributed into groups (n = 10) treated with 1 of 3 enamel surface-conditioning agents: 35% phosphoric acid (PA), 35% glycolic acid (GA), or 35% ferulic acid (FA). The designated acid was applied to the buccal enamel surface of the tooth for 20 seconds, and the tooth was then rinsed with distilled water for 20 seconds and air dried for 5 seconds. A metal bracket was bonded to the prepared surface with light-cured orthodontic resin. After 24 hours, the bracket-tooth interface was submitted to SBS testing in a universal testing machine at a speed of 0.5 mm/min. After debonding, the enamel surface was observed under a stereomicroscope (×20 magnification) to determine the ARI. The generalized linear models showed that the PA and GA groups presented significantly higher SBSs than the FA group (P = 0.0003). The ARI was significantly higher in specimens treated with PA than with the other acids (P < 0.05; Kruskal-Wallis and Dunn tests), with a larger quantity of adhesive remaining adhered to the tooth. Both PA and GA are effective for bonding brackets, but GA resulted in a lower percentage of adhesive remnant adhered to the enamel.

In-vitro effect of a single application of CPP-ACP pastes and different fluoridated solutions on the prevention of dental caries around orthodontic brackets.

OBJECTIVE: To assess the in-vitro effect of single applications of CPP-ACP pastes and different fluoridated solutions on the prevention of dental caries around orthodontic brackets. MATERIAL AND METHODS: Tooth/bracket sets (n=65) were immersed in artificial saliva (1h at 37ºC) and randomly subjected to single applications (100µL; 1min) of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP emulsion), CPP-ACP with fluoride (CPP-ACPF emulsion), solutions of titanium tetrafluoride (TiF4) or sodium fluoride (NaF), or no treatment (CG). Multispecies biofilm (5 x 105 CFU/mL) was formed in the presence of 2% sucrose. After 24 h, the pH and the concentration of total soluble fluoride (TSF) were analyzed by culture medium. The presence of active white spot lesions (WSL) evaluated by macroscopic examination and the percent surface mineral loss (%SML) were analyzed. Also, the topography of enamel was detected by analysis of scanning electron microscopy (SEM). The data was assessed by chi-square, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). RESULTS: Fluoride-containing compounds led to a smaller pH reduction than did CPP-ACP and CG (p<0.05). There was difference in TSF between the groups (p<0.05), denoted as TiF4> NaF > CPP-ACPF > CPP-ACP > CG. Regarding the presence of WSL and %SML, the NaF group obtained lower values (p<0.05), while TiF4 and CPP-ACPF were similar (p>0.05). SEM demonstrated that fluoride-free groups had a larger surface dissolution. CONCLUSION: Fluoridated groups including solutions and CPP-ACPF were more effective than CPP-ACP in reducing enamel demineralization around orthodontic brackets after a single application.

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.

New generation of orthodontic devices and materials with bioactive capacities to improve enamel demineralization.

OBJECTIVE: The article reviewed novel orthodontic devices and materials with bioactive capacities in recent years and elaborated on their properties, aiming to provide guidance and reference for future scientific research and clinical applications. DATA, SOURCES AND STUDY SELECTION: Researches on remineralization, protein repellent, antimicrobial activity and multifunctional novel bioactive orthodontic devices and materials were included. The search of articles was carried out in Web of Science, PubMed, Medline and Scopus. CONCLUSIONS: The new generation of orthodontic devices and materials with bioactive capacities has broad application prospects. However, most of the current studies are limited to in vitro studies and cannot explore the true effects of various bioactive devices and materials applied in oral environments. More research, especially in vivo researches, is needed to assist in clinical application. CLINICAL SIGNIFICANCE: Enamel demineralization (ED) is a common complication in orthodontic treatments. Prolonged ED can lead to dental caries, impacting both the aesthetics and health of teeth. It is of great significance to develop antibacterial orthodontic devices and materials that can inhibit bacterial accumulation and prevent ED. However, materials with only preventive effect may fall short of addressing actual needs. Hence, the development of novel bioactive orthodontic materials with remineralizing abilities is imperative. The article reviewed the recent advancements in bioactive orthodontic devices and materials, offering guidance and serving as a reference for future scientific research and clinical applications.

Orthodontic adhesive loaded with different proportions of ZrO2 silver-doped nanoparticles: An in vitro µTBS, SEM, EDX, FTIR, and antimicrobial analysis.

Zirconium dioxide silver-doped nanoparticles (ZrO2AgDNPs) impacts the adhesive material in terms of its physical characteristics, antimicrobial properties, degree of conversion (DC), and micro-tensile bond strength (µTBS) of orthodontic brackets to the enamel surface. A comprehensive methodological analysis utilizing a range of analytical techniques, including scanning electron microscopy coupled with energy-dispersive x-ray spectroscopy (EDX), Fourier-transform infrared (FTIR) spectroscopy, DC analysis, and µTBS testing. A light-curable orthodontic adhesive, specifically Transbond XT, was combined with ZrO2AgDNPs at 2.5% and 5%. As a control, an adhesive with no incorporation of ZrO2AgDNPs was also prepared. The tooth samples were divided into three groups based on the weightage of NPs: group 1: 0% ZrO2AgDNPs (control), group 2: 2.5 wt% ZrO2AgDNPs, and group 3: 5 wt% ZrO2AgDNPs. EDX graph demonstrated silver (Ag), Zirconium (Zr), and Oxygen (O2), The antibacterial efficacy of adhesives with different concentrations of NPs (0%, 2.5%, and 5%) was assessed using the pour plate method. The FTIR spectra were analyzed to identify peaks at 1607 cm-1 corresponding to aromatic CC bonds and the peaks at 1638 cm-1 indicating the presence of aliphatic CC bonds. The µTBS was assessed using universal testing machine (UTM) and bond failure of orthodontic brackets was seen using adhesive remanent index (ARI) analysis. Kruskal-Wallis test assessed the disparities in survival rates of Streptococcus mutans. Analysis of variance (ANOVA) and post hoc Tukey multiple comparisons test calculated µTBS values. The lowest µTBS was observed in group 1 adhesive loaded with 0% ZrO2AgDNPs (21.25 ± 1.22 MPa). Whereas, the highest µTBS was found in group 3 (26.19 ± 1.07 MPa) adhesive loaded with 5% ZrO2AgDNPs. ZrO2AgDNPs in orthodontic adhesive improved µTBS and has acceptable antibacterial activity against S mutans. ZrO2AgDNPs at 5% by weight can be used in orthodontic adhesive alternative to the conventional method of orthodontic adhesive for bracket bonding. RESEARCH HIGHLIGHTS: The highest µTBS was found in orthodontic adhesive loaded with 5% ZrO2AgDNPs. ARI analysis indicates that the majority of the failures fell between 0 and 1 among all investigated groups. The colony-forming unit count of S. mutans was significantly less in orthodontic adhesive loaded with nanoparticles compared with control. The 0% ZrO2AgDNPs adhesive showed the highest DC.

Aligner biomechanics: Where we are now and where we are heading for.

Aligner orthodontics has gained significant popularity as an alternative to traditional braces because of its aesthetic appeal and comfort. The biomechanical principles that underlie aligner orthodontics play a crucial role in achieving successful outcomes. The biomechanics of aligner orthodontics revolve around controlled force application, tooth movement, and tissue response. Efficient biomechanics in aligner orthodontics involves consideration of attachment design and optimized force systems. Attachments are tooth-colored shapes bonded to teeth, aiding in torque, rotation, and extrusion movements. Optimized force systems ensure that forces are directed along the desired movement path, reducing unnecessary strain on surrounding tissues. Understanding and manipulating the biomechanics of aligner orthodontics is essential for orthodontists to achieve optimal treatment outcomes. This approach requires careful treatment planning, considering the mechanics required for each patient's specific malocclusion. As aligner orthodontics continues to evolve, advances in material science and treatment planning software contribute to refining biomechanical strategies, enhancing treatment efficiency, and expanding the scope of cases that can be successfully treated with aligners.

Fabrication of a novel aesthetic orthodontic bracket and evaluation of friction properties between PEEK and stainless steel wires.

BACKGROUND: Polyetheretherketone (PEEK) is a polyaromatic semi-crystalline thermoplastic polymer with mechanical and lubrication properties favorable for biomedical applications. Despite of its aesthetic appearance, ceramic brackets are unsatisfactory in brittleness and thickness, while PEEK is a potential material for aesthetic orthodontic brackets. OBJECTIVE: To fabricate a novel aesthetic orthodontic bracket and evaluate friction properties of PEEK and stainless steel wires. METHODS: All polyether ether ketone (PEEK) and ceramic samples disks were made into disks (diameter, 5 mm; thickness, 2 mm). The tested surfaces of PEEK were ground with #600, #800 and #1200 SiC papers, followed by polishing with Sof-Lex kit (3M ESPE, USA). The surface roughness was tested using a laser profilometer device (VK-X200, Keyence, Japan). The COFs of the specimens and stainless steel (SS) archwires were tested using a Universal Micro-Tribotester (UMT-3, Bruker, USA). The wear scratches on the materials' surfaces were examined by using a scanning electron microscope (SEM) (Hitachi SU8010). The elastic modulus and hardness of samples were examined with a nano-indenter (XP, Keysight Technologies, USA). RESULTS: The mean surface roughness of PEEK and Ceramic are 0.320 ± 0.028 µm and 0.343 ± 0.044 µm, respectively. PEEK has a lower Friction coefficient than Ceramic and the difference between the two groups was statistically significant (P< 0.05). The abrasive wear of Ceramic was the main wear style and was characterized by the observation of chipping fractures, while PEEK surface looked smooth without obvious scale-like desquamations and granular debris, indicating adhesive wear. CONCLUSION: Within the limitations of the present study, PEEK shows lower coefficient of friction than ceramic. PEEK has excellent properties such as low friction coefficient, smooth surface and good mechanical properties, and thus meets the requirements for orthodontic brackets. It is considered as a potential bracket material with both low friction and aesthetic performance.

Evaluation of the shear bond strength of various adhesives on the surface of enamel irradiated with various doses of radiotherapy.

INTRODUCTION: We aimed to compare the shear bond strength (SBS) forces on the enamel surface with 2 adhesives after treatment with various radiation doses. METHODS: A total of 120 premolars were included in the study. The teeth were randomly divided into 5 main groups (n = 24): negative control (without aging), positive control (with aging), 40 Gy, 60 Gy, and 70 Gy radiation. The 40 Gy, 60 Gy, and 70 Gy groups underwent conventional radiotherapy 5 days a week with a dose of 2 Gy each day. After the radiotherapy, all samples except the negative control group were subjected to thermal cycle aging. In all 5 groups, the specimens were divided into 2 subgroups, and half were bonded using 2 adhesives. After bonding, the universal Shimadzu test device was used to analyze the SBS. After the test, the tooth surfaces were examined under a stereomicroscope to determine the adhesive remnant index. RESULTS: When adhesives were compared, Biofix adhesive's bond strength value was statistically higher in the 40 Gy group than in the Transbond XT group (P = 0.001). The SBS value was higher in all irradiated groups than in nonirradiated groups (P = 0.001). When the adhesive remnant index score was analyzed, no significant difference was found among the groups. CONCLUSIONS: The SBS increased in irradiated teeth compared with unirradiated teeth, and the SBS values of both adhesives were within the acceptable limits in all radiation groups.

Lingual bracket transfer accuracy of double vacuum-formed indirect bonding tray using 3D-printed model: an in vivo study.

INTRODUCTION: This study aimed to assess the transfer accuracy of a digital indirect bonding method for lingual brackets using double vacuum-formed trays in vivo. METHODS: Twenty-five patients in need of lingual orthodontic treatment were consecutively recruited. Bracket placement was performed on ideal setups, followed by fabricating indirect bonding trays through vacuum-forming on 3-dimensional printed models. Transfer accuracy was measured at each bracket after superimpositions of postbonding scans and reference data. One-tailed t tests were used to determine whether bracket deviations were within the limit of 0.5 mm and 2° for linear and angular dimensions, respectively. RESULTS: A total of 611 lingual brackets were evaluated. Mean linear transfer errors were 0.06 mm, 0.09 mm, and 0.12 mm, with frequencies of deviations within the 0.5 mm limit of 99.7%, 99.8%, and 98.0% for mesiodistal, buccolingual, and occlusogingival dimensions, respectively. Regarding angular measurements, mean transfer errors were 1.28°, 1.73°, and 2.96°, with frequencies of deviations within the 2° limit of 81.0%, 68.9%, and 51.1% for rotation, tip, and torque, respectively. Mean errors fell within the clinically accepted limits for all linear dimensions and rotation but exceeded the limit for tip and torque. CONCLUSIONS: Lingual bracket indirect bonding using double vacuum-formed trays fabricated on 3-dimensional printed models has high transfer accuracy in the mesiodistal, buccolingual, and occlusogingival dimensions and rotation. However, the transfer of tip and torque is less accurate.

In vitro evaluation of an easy-to-remove orthodontic adhesive with photochromic property.

OBJECTIVES: To develop a photochromic bracket adhesive (PCA) with modification using photochromic material and evaluate the biocompatibility, bond strength, photochromic property, and adhesive removal efficiency. MATERIALS AND METHODS: The resin-modified glass ionomer powder was mixed with the photochromic material and then blended with the liquid agent to form PCA. Biocompatibility was evaluated by CCK-8 kit, and shear bond strength (SBS) was measured. Stereoscopic microscopy and quantitative color analysis were used to assess the photochromic property. Bracket bonding and debonding procedures were performed on a head simulator with the assistance of an ultraviolet radiator. The effectiveness of adhesive removal during bonding and debonding procedures was assessed using a stereomicroscope. Removal time was recorded, and the enamel damage index after debonding was analyzed. RESULTS: CCK-8 assay and SBS test indicated that 5wt.% mixing ratios of the photochromic material did not compromise the biocompatibility and SBS of the adhesive (PCA5). PCA5 showed photochromic properties and could help the operator remove adhesive more thoroughly without increasing enamel damage. CONCLUSIONS: Photochromic adhesive (PCA5) can be good for orthodontic adhesive removal and therefore has good clinical translation potential.

Shear bond strength of orthodontic brackets bonded to high-translucent dental zirconia with different surface treatments: An in vitro study.

PURPOSE: The objective of this study was to compare the shear bond strengths of orthodontic brackets bonded to translucent dental zirconia samples which are anatomically accurate and treated with various surface treatments. METHODS: This in vitro study included 156 samples from 3 brands of high-translucent zirconia split into a control group and 4 surface treatment groups: 9.6% hydrofluoric acid etching, 50-micron aluminium oxide particle air abrasion, and 30-micron tribochemical silica coating (TBS) particle air abrasion with and without silane application. After surface treatment, all groups were primed with a 10-MDP primer and bonded to metal orthodontic brackets. Shear bond strength (SBS) was tested and results were compared between all groups. Data analysis consisted of a balanced two-factor factorial ANOVA, a Shapiro-Wilks test, and a non-parametric permutation test. The significance level was set at 0.05. RESULTS: Among all surface treatments, aluminium oxide particle abrasion produced significantly higher SBS (P≤0.002). Lava™ Plus zirconia samples had significantly higher SBS than Cercon® samples (P<0.0001). TBS surface treatment produced significantly higher SBS on Lava™ Plus samples than it did on the other zirconia brands (P=0.032). CONCLUSIONS: This study indicated that mechanical abrasion using aluminium oxide in combination with a 10-MDP primer creates a higher SBS to high-translucent zirconia than the bond created by tribochemical silica coating. Also, there was no significant difference in ARI regardless of zirconia brand or surface preparation.