ABSTRACT
AIM: The aim of the present study was to assess the alterations in morphology, roughness, and composition of the surfaces of a conventional and a flowable composite attachment engaged with aligners, and to evaluate the release of resin monomers and their derivatives in an aqueous environment. METHODS: Zirconia tooth-arch frames (nâ =â 20) and corresponding thermoformed PET-G aligners with bonded attachments comprising two composite materials (universal-C and flowable-F) were fabricated. The morphological features (stereomicroscopy), roughness (optical profilometry), and surface composition (ATR-FTIR) of the attachments were examined before and after immersion in water. To simulate intraoral use, the aligners were removed and re-seated to the frames four times per day for a 7-day immersion period. After testing, the eluents were analyzed by LC-MS/MS targeting the compounds Bis-GMA, UDMA, 2-HEMA, TEGDMA and BPA and by LC-HRMS for suspect screening of the leached dental material compounds and their degradation products. RESULTS: After testing, abrasion-induced defects were found on attachment surfaces such as scratches, marginal cracks, loss of surface texturing, and fractures. The morphological changes and debonding rate were greater in F. Comparisons (before-after testing) revealed a significantly lower Sc roughness parameter in F. The surface composition of the aligners after testing showed minor changes from the control, with insignificant differences in the degree of Câ =â C conversion, except for few cases with strong evidence of hydrolytic degradation. Targeted analysis results revealed a significant difference in the compounds released between Days 1 and 7 in both materials. Insignificant differences were found when C was compared with F in both timeframes. Several degradation products were detected on Day 7, with a strong reduction in the concentration of the targeted compounds. CONCLUSIONS: The use of aligners affects the surface characteristics and degradation rate of composite attachments in an aqueous environment, releasing monomers, and monomer hydrolysates within 1-week simulated use.
Subject(s)
Composite Resins , Materials Testing , Methacrylates , Surface Properties , Zirconium , Zirconium/chemistry , Composite Resins/chemistry , Methacrylates/chemistry , Polyethylene Glycols/chemistry , Polymethacrylic Acids/chemistry , Polyurethanes/chemistry , Bisphenol A-Glycidyl Methacrylate/chemistry , Dental Materials/chemistry , In Vitro Techniques , Humans , Tooth Movement Techniques/instrumentation , Tooth Movement Techniques/methods , Spectroscopy, Fourier Transform Infrared/methodsABSTRACT
The clinical application of aligners is accompanied by the ageing of the polymer appliances and the attachments used, which may result in inefficiency in reaching the predicted range of tooth movement, and release of compounds and microplastics in the oral cavity as a result of the friction, wear and attrition of the aligner and composite attachment. The purpose of this review is to present the mechanism and effects of in vivo ageing; describe the hydrolytic degradation of aligners and enzymatic degradation of composite attachments; examine the ageing pattern of aligners in vivo, under actual clinical scenarios; and identify a link to the discrepancy between predicted and actual clinical outcome. Lastly, strategies to deal with three potentially critical issues associated with the use of aligners, namely the necessity of weekly renewal, the dissimilar mechanical properties of aligner and attachment resulting in wear and plastic deformation of the aligner, and the development of integuments and biofilms with microbial colonization of the appliance, are discussed.
Subject(s)
Evidence-Based Dentistry , Publishing , Humans , Periodicals as Topic , Orthodontics/economicsABSTRACT
BACKGROUND: The aim of the present study was to investigate qualitatively and quantitatively the elution of substances from polyester-urethane (Invisalign™) aligners and resin composite attachments (Tetric EvoFlow) in vivo. METHODS: Patients (n = 11) treated with the aligners and attachments (16 per patient, without other composite restorations) for an average of 20 months, who were planned for attachment removed were enrolled in the study. Patients were instructed to rinse with 50 mL of distilled water upon entry and the rinsing solution was collected (before removal). Then, the attachments were removed with low-speed tungsten carbide burs for adhesive residue removal, a thorough water rinsing was performed immediately after the grinding process to discard grinding particle residues, and subsequently, after a second water-rinsing the solution was collected for analysis (after removal). The rinsing solutions were analyzed for targeted (LC-MS/MS: Bis-GMA, DCDMA, UDMA, BPA) and untargeted (LC-HRMS: screening of leached species and their degradation products) compounds. RESULTS: Targeted analysis revealed a significant reduction in BPA after attachment removal (4 times lower). Bis-GMA, DCDMA, UDMA were below the detection limit before removal but were all detectable after removal with Bis-GMA and UDMA at quantifiable levels. Untargeted analysis reviled the presence of mono-methacrylate transformation products of Bis-GMA (Bis-GMA-M1) and UDMA (UDMA-M1), UDMA without methacrylate moieties (UDMA-M2), and 4-(dimethylamino) benzoic acid (DMAB), the degradation product of the photo-initiator ethyl-4-(dimethylamino) benzoate (EDMAB), all after attachment removal. Several amino acids and endogenous metabolites were also found both before and after removal. CONCLUSIONS: Elevated levels of BPA were traced instantaneously in patients treated with Invisalign™ and flowable resin composite attachments for the testing period. BPA was reduced after attachment removal, but residual monomers and resin degradation products were found after removal. Alternative resin formulations and attachment materials may be utilized to reduce eluents.
Subject(s)
Composite Resins , Methacrylates , Polyurethanes , Humans , Polyurethanes/chemistry , Composite Resins/chemistry , Female , Male , Methacrylates/chemistry , Saliva/chemistry , Bisphenol A-Glycidyl Methacrylate/chemistry , Adult , Orthodontic Appliances, Removable , Polyesters/chemistry , para-Aminobenzoates/analysis , Young Adult , Adolescent , Tooth Movement Techniques/instrumentation , Tooth Movement Techniques/methods , Tandem Mass Spectrometry , Chromatography, LiquidABSTRACT
BACKGROUND: The minimal important difference (MID) is defined as the smallest difference that the patient perceives as important. Furthermore, the smallest worthwhile effect (SWE) is the important change measured with the benefit-harm trade-off method. The aim of this study was to evaluate the MID in orthodontic treatment duration to inform the decision regarding seeking procedures to accelerate orthodontic tooth movement and reduce treatment duration. METHODS: We constructed a survey eliciting views of the MID from adult participants from four countries undergoing orthodontic treatment. Ten questions addressed reduction in the treatment duration for both durations 12 and 24 months, and four questions were related to the reduction in treatment duration that the patients would require to undergo surgical or non-surgical adjunctive procedures. We applied a univariable random effects logistic regression model to examine the association between the participants' characteristics and the MID. Then, we fitted a multivariable logistic random effects regression including significant predictors. RESULTS: Four hundred and fifty adults, with a median age of 21 (interquartile range: 19-24), undergoing orthodontic treatment participated in the survey. Of the respondents, 60% considered 15 days as a trivial reduction from 12 months duration of therapy and 70% considered 15 days a trivial reduction from 24 months. Of the respondents, 48% considered the period of 2 months a moderate reduction from 12 months, and 60% considered 2 months a moderate reduction from 24 months. From these results, we inferred that patients considered reductions of approximately 1 month as the MID in the treatment duration for both 12 and 24 months. However, SWE was considerably more than the MID for most of the participants to decide undergoing surgical adjunctive procedures to reduce the time of therapy. The participants required smaller SWE to undergo non-surgical procedures compared to surgical procedures. CONCLUSION: The MID in the treatment duration is one month for both treatment durations 12 and 24 months. Patients require a greater SWE than the MID to undergo adjunctive procedures to shorten the duration, particularly for surgical procedures.
Subject(s)
Orthodontics, Corrective , Humans , Female , Male , Time Factors , Young Adult , Orthodontics, Corrective/methods , Surveys and Questionnaires , Adult , Tooth Movement Techniques/methodsSubject(s)
Evidence-Based Dentistry , Publishing , Humans , Orthodontics/economics , Periodicals as TopicSubject(s)
Publishing , Publishing/economics , Humans , Evidence-Based Dentistry , Periodicals as TopicABSTRACT
The purpose of this study was to quantitatively evaluate adhesive remnants on the enamel surface following bracket debonding using a freezing element. Thirty-six sound premolars were used in this study. In each case, a bracket was bonded onto each tooth with conventional light-cured composite resin and de-bonded after one week. Freezing of the underlying composite through the bracket was performed immediately before debonding with a portable cryosurgical system (-55 °C). Specimens were divided into three groups according to the duration of freezing: a control group without freezing was used as a reference and two interventional groups with different durations of freezing (15 or 40 s). Brackets were removed by using debonding pliers to squeeze the wings of the bracket in an occluso-gingival manner. Adhesive remnants on the tooth were then quantitatively evaluated by stereo-microscopy. Pearson's Chi-squared test was used to investigate the relationship between the proportion of remaining resin and the group of teeth. In the control group, 100% of the composite remained on the enamel surface of all specimens. Significantly less adhesive remnants were found in the intervention groups (p = 0.001 for the 15 s group and p = 0.043 for the 40 s group). There was no significant difference between the two interventions (p = 0.165) in terms of the proportion of remaining adhesive remnants. Freezing of the bracket and the underlying adhesive resin prior to bracket debonding may favorably alter the behavioral pattern of composite fracture, thus reducing the extent of adhesive remnants on the enamel. Increasing the freezing time from 15 to 40 s did not exert significant effects on adhesive remnants following debonding. Further research now needs to investigate the effect of freezing on the mechanical properties of the adhesive remnants and its in-vivo effect on pulp vitality over both short- and long-terms.
Subject(s)
Composite Resins , Dental Debonding , Freezing , Orthodontic Brackets , Humans , Dental Debonding/methods , Composite Resins/chemistry , Dental Enamel , In Vitro Techniques , Resin Cements/chemistry , Dental Cements/chemistry , Bicuspid , Materials TestingABSTRACT
AIM: Two-phase treatment for children with Class II malocclusion with several functional appliances is still performed by many orthodontists, while the Activator and the Bionator appliances are two of the most popular ones. Aim of this study was to compare the skeletal and dentoalveolar effects of treatment with these two appliances. METHODS: Class II children treated with Activator or Bionator in the first phase, followed by a phase of fixed appliances were included. Skeletal and dentoalveolar parameters were assessed from lateral cephalograms and analysed with linear regressions at 5%. RESULTS: A total of 89 patients (mean age 10.0 years; 47% female) were included. During the first phase, Bionator increased less the SNB (difference in mean treatment-induced changes [MD] -0.7°; 95% confidence interval [CI] -1.3 to -0.2°; P=0.01) and decreased less the ANB angle (MD 0.6°; 95% CI 0 to 1.1°; P=0.03) compared to Activator. Activator slightly increased the facial axis and Bionator reduced it (MD -1.6°; 95% CI -2.3 to -0.8°; P<0.001). Compared to Activator, the Bionator retroclined more the upper incisors (MD -2.4°; 95% CI -4.6 to -0.2°; P=0.03) and increased more the interincisal angle (MD 2.9°; 95% CI 0.5 to 5.4°; P=0.02). After the second phase (6.2 years after baseline), the only differences were a reduced facial axis (MD -1.3°; 95% CI -2.2 to -0.3°; P=0.008) and an increased maxillary rotation (MD 0.9°; 95% CI 0 to 1.8°; P=0.04) with Bionator compared to Activator. CONCLUSION: Similar dentoalveolar effects were seen overall with two-phase treatment with either appliance, with Bionator being associated with more vertical increase compared to Activator.
Subject(s)
Activator Appliances , Cephalometry , Malocclusion, Angle Class II , Maxilla , Orthodontic Appliances, Fixed , Humans , Malocclusion, Angle Class II/therapy , Female , Male , Child , Retrospective Studies , Mandible , Treatment Outcome , Orthodontic Appliance Design , Orthodontic Appliances, Functional , Incisor , Sella Turcica , Nasal Bone , Orthodontics, Corrective/instrumentation , Orthodontics, Corrective/methodsABSTRACT
OBJECTIVE: The curve of Spee is deemed important characteristic of the dentition for a balanced occlusion and distribution of masticatory forces, while orthodontic levelling of an accentuated curve of Spee is generally included as a treatment goal for deepbite correction. However, relapse is often seen and can be problematic. METHODS: A retrospective longitudinal study of predominantly young patients with a deep curve of Spee, who had been treated orthodontically with 0.018"-slot Edgewise fixed appliances, was performed. The depth of the curve of Spee was digitally measured before treatment (T1), at debond (T2), and an average of 7 years post-debond (T3) and analysed statistically at 5%. RESULTS: A total of 157 patients were included (56.7% female; 11.6-year-old at T1), 16.6% of which were treated with premolars extractions. Non-extraction treatment reduced the curve of Spee at the first premolar from 1.87 mm (T1) to 0.22 mm (T2), which relapsed 0.12 mm (T3; P = .04). The respective depths for the second premolar were 2.0 mm (T1), reduced to 0.80 mm (T2). No significant relapse was seen for the second premolar (0.08 mm; P > .05) or the first permanent molar (0.06 mm; P > .05). No overall significant differences in absolute relapse were seen between extraction and non-extraction patients, but premolar extractions were associated with less clinically relevant relapse at the first molar (odds ratio 0.27; 95%-confidence interval 0.08-0.88; P = .003). CONCLUSION: Steep curves of Spee can be satisfactorily levelled orthodontically with satisfactory stability in the long term, while premolar extractions might be associated with less relapse.
Subject(s)
Recurrence , Humans , Female , Longitudinal Studies , Retrospective Studies , Male , Child , Overbite/therapy , Orthodontic Appliances, Fixed , Adolescent , Tooth Extraction , Orthodontics, Corrective/methodsABSTRACT
OBJECTIVE: To evaluate the initial bacterial adherence and biofilm formation on novel restorative materials in paediatric dentistry and compare the results to stainless steel crown and primary enamel. MATERIALS AND METHODS: Twenty-five samples (Diameter = 4 mm) from five restorative materials (Tetric Power Fill light cured for 3 s or 10 s, Fuji II LC, Equia Forte HT Fil, Cention Forte, Stainless-steel crown) and primary enamel were prepared. Four samples served for recording of surface roughness (Ra) using a contact profilometer, 21 samples were incubated in stimulated human saliva for 2 h (initial bacterial adherence) and 72 h (biofilm formation) and served to determine ion releasing and bacterial growth. After 2 and 72 h, the number of colony-forming units (CFU) per ml was counted and expressed in Log10 CFU/ml. Data were analysed with two-way ANOVA and Tuckey's multiple comparisons test (p < 0.05). RESULTS: All tested materials showed similar initial bacterial adherence (p > 0.1). Stainless steel crown showed statistically significantly less biofilm formation than all other tested materials (p ≤ 0.02), except for Fuji II LC (p = 0.06). In terms of biofilm formation, the differences between all tested materials were not statistically significant (p ≥ 0.9). SIGNIFICANCE: Novel restorative materials in paediatric dentistry show similar initial bacterial adherence and biofilm formation. However, compared to other restorative materials, stainless steel crowns demonstrate the lowest level of biofilm formation. Ion-releasing materials may not necessarily show better antimicrobial properties than conventional materials.
Subject(s)
Anti-Infective Agents , Pediatric Dentistry , Child , Humans , Stainless Steel , Dental Materials , Biofilms , Materials TestingABSTRACT
PURPOSE: The purpose of this study was to assess differences in the fundamental mechanical properties of resin-made three-dimensional (3D) printed orthodontic aligners according to the printing orientation. METHODS: Twenty resin 3D-printed dumbbell-shaped specimens and 20 orthodontic aligners were fabricated and postcured in nitrogen. Half of the specimens and aligners were built in horizontal (H), the other half in vertical (V) directions. The dumbbell-shaped specimens were loaded in a tensile testing machine, while parts of the aligners were embedded in acrylic resin, ground, polished, and then underwent instrumented indentation testing (IIT). Mechanical properties that were assessed included the yield strength (YS), breaking strength (BS), plastic strain (ε), Martens hardness (HM), indentation modulus (EIT), elastic index (ηIT), and indentation relaxation (RIT). Data were analyzed statistically with independent ttests or Mann-Whitney tests at αâ¯= 5%. RESULTS: No significant differences were found between specimens or aligners printed either in a horizontal or a vertical direction (Pâ¯> 0.05 in all instances). Overall, the 3D-printed aligners showed acceptable mechanical propertied in terms of YS (mean 19.2â¯MPa; standard deviation [SD] 1.7â¯MPa), BS (mean 19.6â¯MPa; SD 1.2â¯MPa), ε (mean 77%; SD 11%), HM (median 89.0â¯N/mm2; interquartile range [IQR] 84.5-90.0 NN/m2), EIT (median 2670.5â¯MPa; IQR 2645.0-2726.0â¯MPa), ηIT (median 27.5%; IQR 25.9-28.1%), and RIT (mean 65.1%; SD 3.5%). CONCLUSION: Printing direction seemed to have no effect on the mechanical properties of 3D-printed resin aligners, which are promising for orthodontic use.
ABSTRACT
INTRODUCTION: This study aimed to discover the genetic and environmental factors that contribute to the mandibular development of untreated monozygotic and dizygotic twins. MATERIAL AND METHODS: The sample, taken from the Forsyth Moorrees Twin Study, included 52 untreated monozygotic twins (36 male, 16 female) and 46 untreated dizygotic twins (23 male, 23 female). At the ages of 12 and 17, lateral cephalograms were collected and traced to assess total mandibular length, mandibular ramus length, mandibular corpus length, gonial angle, SNB, and bony chin prominence. The genetic and environmental components of variation were assessed using multilevel mixed-effects structural equation modelling. RESULTS: At 12 years of age, high additive genetic influences were observed for total mandibular length (74%), gonial angle (76%), SNB (41%), and bony chin prominence (64%), whereas strong dominant genetic components were observed for corpus length (72%), and mandibular ramus length was under unique environment influence (54%). At 17 years of age, only total mandibular length (45%), ramus length (53%), gonial angle (76%), and bony chin prominence (68%) were under strong additive genetic control, while the remainder were under strong dominant genetic control. CONCLUSIONS: Although monozygotic and dizygotic twins share at least a portion of their DNA, additive, dominant, or environmental components were discovered during adolescence. Nonetheless, by the age of 17, the majority of the mandibular traits are under either additive or dominant genetic impact.
Subject(s)
Twins, Dizygotic , Twins, Monozygotic , Adolescent , Female , Humans , Male , Environment , Mandible , Retrospective Studies , Twins, Dizygotic/genetics , Twins, Monozygotic/genetics , Cohort StudiesABSTRACT
OBJECTIVE: The objective of this study was to examine the impact of intraoral aging on the mechanical properties of directly printed aligners (DPA) compared to thermoformed aligners (TA). MATERIALS AND METHODS: This prospective in vivo experiment included three types of aligners: DPAs (group DP) fabricated from Tera Harz TC-85 DAC resin (Graphy, Korea), TA (group INV) made from a polyurethane-based polymer (Align Technology, Inc., CA, USA), and TA (group DUR) made from polyethylene glycol terephthalate based polymer (Scheu-Dental, Germany). Each group was categorized into retrieved (Clin) and unused aligners (Ctr). Thirty patients (10 per group) wore the aligners for 7 days, thereby generating the retrieved samples. Thirty unused aligners were employed as control samples. The following mechanical properties were determined: Martens Hardness (HM), indentation modulus (EIT), elastic index (ηIT), and indentation relaxation (RIT). Intergroup comparisons were conducted using ANOVA/Kruskal-Wallis test. Comparisons between retrieved and control samples were done using Wilcoxon-Mann-Whitney-U/Student's t-test/Welch's test. RESULTS: Statistically significant differences between the groups were found for both control and used samples (Pâ <â .001). Pairwise comparisons also revealed significant differences between the samples. The mechanical properties did not differ significantly between unused and retrieved INV- and DUR-aligners, whereas for DP-aligners significant differences for ηIT and RIT were found following intraoral service (P-values .012 and .002, respectively). CONCLUSIONS: Group DUR showed generally more favorable mechanical properties compared to DP and INV. The much higher RIT and EIT in DP aligners suggest their higher rigidity and force decay, which could compromise their clinical efficacy.
Subject(s)
Mechanical Phenomena , Polyurethanes , Humans , Prospective Studies , Hardness , Polyethylene Glycols , Materials TestingABSTRACT
The aim of this study was to assess the percentage degree of cure (DC%) of 2-mm-thick resin composite attachments used for aligner treatment. Three types of aligner - two thermoformed aligners (Clear Aligner [CLA], polyethylene terephthalate glycol modified; and Invisalign [INV], polyester urethane) and a three-dimensional-printed aligner (Graphy TC-85DAC [GRP], an acrylate-methacrylate copolymer) - were selected, along with two universal resin composites (3M Filtek Universal [FTU] and Charisma Topaz ONE [CTO]). Samples of each composite were placed under each aligner, and the degree of cure of each composite was evaluated on the top (facing the aligner) and the bottom (facing the substrate) attachment surfaces after curing. Five specimens were used per combination of aligner and composite, and an additional group of composites irradiated without aligners served as the control. The DC% measurements were performed using attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. The DC% across the aligners were (median values) 33.8%-44.8% for CLA, 33.6%-40.8% for INV, 32.8%-40.6% for GRP, and 40.0%-51.7% for the control group. The DC% values of the attachments cured under any aligner were significantly lower than that of the corresponding control, with the values recorded on the top surfaces being 6% higher than those on the bottom surfaces after adjusting for aligner group and composite type.
Subject(s)
Methacrylates , Polymers , Methacrylates/chemistryABSTRACT
AIM: To identify practices of assessment of gender effects in research articles in orthodontics and detect whether there were significant differences in the treatment effects on outcomes according to gender. MATERIALS AND METHODS: Four major orthodontic journals were sought over a 3-year period to identify publications which included assessment of gender effects on outcomes in their reporting. Data were extracted on the following characteristics: journal, year of publication, region of authorship, and study design. For the studies including reporting of gender effects, whether a significant effect existed was further documented. Additionally, for these studies, data were extracted on population, sample size per gender, treatment, comparison, outcome type, and nature and whether gender analysis was based on subgroup testing or included as a main effect. Descriptive statistics, cross-tabulations, univariable, and multivariable regression models were utilized as appropriate. RESULTS: A total of 718 research articles were eligible for inclusion out of a pool of 1,132 screened articles. Of those, 95 reported on any type of analysis on gender effects (95/718; 13.2%). In the 95 studies that reported assessment of gender effects, it was clear that the majority did not detect significant gender-related differences across the documented outcomes (range of frequency distribution for significant gender differences across all outcomes: 0-50%). Twenty-two articles overall (22/95; 23.2%) described a significant gender effect classified by outcome, 12 favoring female and 10 favoring male participants. Patterns of efficacy and adverse outcomes were schemed either favoring female (root resorption: 4/10; 40.0%, periodontal outcomes: 3/11; 27.3%) or male (cephalometric/growth changes following orthodontic treatment: 4/17; 23.5%) patients across the 22 studies with significant effects. Appropriately designed and adequately powered statistical analyses, with gender effect assessment as a main effect in a multivariable regression model was associated with 6.53 times higher odds for identifying significant gender effects (ORâ =â 6.53; 95% CI: 2.15, 19.8; Pâ =â .001). CONCLUSIONS: A very small proportion of research studies included gender effect assessment in their analyses. Of those, a quarter described significant effects. Nevertheless, careful analysis planning and strategies should be prioritized to allow for any meaningful interpretation.
Subject(s)
Orthodontics , Research Design , Humans , Male , Female , Cross-Sectional Studies , Sample Size , AuthorshipABSTRACT
OBJECTIVES: Three-dimensional (3D)-printed aligners present a promising orthodontic treatment modality, whose clinical success largely depends on the material's mechanical properties. The aim of this study was to evaluate the mechanical properties of resin-made 3D-printed aligners and assess the effect of two different post-curing conditions. MATERIALS AND METHODS: Forty dumbbell-shaped specimens and 40 resin aligners were 3D-printed and divided into four equal groups according to post-curing conditions: presence or absence of oxygen during post-curing and water heat treatment at 85°C for 15 s or none. Samples from the central incisor of the aligner (nâ =â 5/group) were studied by Attenuated Total Reflection Fourier-transform infrared spectroscopy (ATR-FTIR). The dumbbell-shaped specimens were loaded up to fracture under tensile mode and yield strength, ultimate tensile strength, elastic and plastic strain were calculated. The first mandibular molar area from 3D-printed aligners (nâ =â 10/group) was cut and embedded in acrylic resin and then underwent metallographic grinding and polishing followed by instrumented indentation testing to determine the following mechanical properties: Martens hardness, indentation modulus, elastic index, and indentation relaxation. After descriptive statistics, differences according to each post-curing protocol, as well as their combination, were analyzed with linear regression modeling at a 5% significance level. RESULTS: All groups showed identical ATR-FTIR spectra, while no statistically significant effects were seen for either post-curing protocol (N2 presence and heat treatment) or their combination (Pâ >â .05 in all instances). CONCLUSIONS: The mechanical properties of 3D-printed resin aligners were not considerably affected either by post-curing in N2 atmosphere or heat treatment.
Subject(s)
Hot Temperature , Tooth , Humans , Hardness , Printing, Three-Dimensional , Materials Testing , Surface PropertiesABSTRACT
This review covers aspects of orthodontic materials, appliance fabrication and bonding, crossing scientific fields and presenting recent advances in science and technology. Its purpose is to familiarize the reader with developments on these issues, indicate possible future applications of such pioneering approaches, and report the current status in orthodontics. The first section of this review covers shape-memory polymer wires, several misconceptions arising from the recent introduction of novel three-dimensional (3D)-printed aligners (mistakenly termed shape-memory polymers only because they present a certain degree of rebound capacity, as most non-stiff alloys or polymers do), frictionless surfaces enabling resistance-less sliding, self-healing materials for effective handling of fractured plastic/ceramic brackets, self-cleaning materials to minimize microbial attachment or plaque build-up on orthodontic appliances, elastomers with reduced force relaxation and extended stretching capacity to address the problem of inadequate force application during wire-engagement in the bracket slot, biomimetic (non-etching mediated) adhesive attachment to surfaces based on the model of the gecko and the mussel, and command-debond adhesives as options for an atraumatic debonding. This review's second section deals with the recent and largely unsubstantiated application of 3D-printed alloys and polymers in orthodontics and aspects of planning, material fabrication, and appliance design.