Advances in orthodontic clear aligner materials

Biomechanics of clear aligner therapy: Assessing the influence of tooth position and flat trimline height in translational movements

OBJECTIVE

The present clear aligner therapy (CAT) research focuses on isolating and reporting the biomechanical performance for three separate teeth, three translational movements and two flat trimlines at different heights. By identifying key patterns, the research seeks to inform the development of improved aligner designs, ultimately enhancing the effectiveness of clinical orthodontic treatments.

MATERIALS AND METHODS

In an in vitro setting using the Orthodontic Force Simulator (OFS), the biomechanical response of 30 aligners was investigated on three different teeth of a straight symmetric maxillary dentition (central incisor, canine and first molar). Each tooth was tested under two flat trimline conditions (trimmed at gingival margin, TL0; extended 2.0 mm below, TL2) and for three types of translational movements (palatal translation, mesial translation and intrusion). Forces and moments were reported at the centre of resistance for each displaced tooth as well as the two neighbouring teeth, evaluating a total of 18 distinct scenarios.

RESULTS

Findings indicate significant variability in the biomechanical responses based on tooth location in the arch, trimline height and movement performed. For palatal translations, the palatal force required to perform the movement was observed highest in molar cases, followed by canine and incisor cases, with a notable difference in the distribution of side effects, indicating a strong influence of tooth anatomy and position in the arch. Similarly, in mesial translations and intrusions molars experienced greater forces and moments than the corresponding movements applied on canines and incisors, but uniquely dispersed for each configuration tested. Regarding the shape of the aligner, TL2 consistently showed improved control over orthodontic movements compared to TL0. Neighbouring teeth frequently displayed compensatory reactions up to about half of the intensity observed on the tooth being moved, with notable variations from case to case.

CONCLUSIONS

This research supports fundamental factors impacting CAT: Characteristic patterns in the direction and intensity of forces and moments are associated with each of the three translational movements tested. Tooth anatomy and arch location significantly influence the biomechanical performance of aligners, with an observed trend for molars to display higher forces and moments over canines and incisors, but distributed differently. The height of a flat trimline, specifically TL2, shows enhanced control over orthodontic movements. Additional findings revealed a compensatory activity of neighbouring teeth, which varies based on tooth region and movement type. It potentially could influence CAT outcomes negatively and merits attention in future investigations. These results support a tailored CAT method that improves aligner design for better force application. This method needs to be used alongside, and confirmed by, clinical knowledge. Future research should extend these findings to a wider range of clinical conditions for greater applicability in the day-to-day orthodontic practice.

Biocompatibility of variable thicknesses of a novel directly printed aligner in orthodontics

Direct printed aligners (DPAs) offer benefits like the ability to vary layer thickness within a single DPA and to 3D print custom-made removable orthodontic appliances. The biocompatibility of appliances made from Tera Harz TA-28 (Graphy Inc., Seoul, South Korea) depends on strict adherence to a standardized production and post-production protocol, including UV curing. Our aim was to evaluate whether design modifications that increase layer thickness require a longer UV curing time to ensure biocompatibility. Specimens with varying layer thickness were printed to high accuracy using Tera Harz TA-28 and the Asiga MAX 3D printer (Asiga SPS ™ technology, Sydney, Australia). UV curing durations were set at 20, 30 and 60 min. Cytotoxicity was evaluated using the AlamarBlue assay on human gingival fibroblasts. Cell viability decreased with increasing specimen thickness (significant for 2 mm [p < 0.001], 4 mm [p < 0.0001], and 6 mm [p < 0.01]) under the manufacturer-recommended 20-min UV curing. Extending the curing time did not improve cell viability. However, cell viability never decreased by more than 30%, meeting EN ISO 10993-5 standards for non-cytotoxicity. The standard 20-minute UV curing protocol ensures the biocompatibility and patient safety of Tera Harz TA-28 for material thicknesses up to 6 mm.

Impacts of surface wear of attachments on maxillary canine distalization with clear aligners: a three-dimensional finite element study

Objectives

This study established three-dimensional finite element models to explore the impacts of surface wear of attachments on maxillary canine distalization with clear aligners, thereby guiding the clinical application of attachments and enhancing the efficiency of clear aligner therapy.

Materials and methods

Finite element models of maxillary canine distalization, including the maxilla, dentition, periodontal ligament, attachments (in both initial and worn states), and clear aligners, were established. Two groups of attachments (vertical rectangular attachment and optimized root control attachment) and five working conditions representing different degrees of attachment wear (M0, M2, M4, M6, and M8) were designed for canine distalization. Tooth displacement and equivalent stress in the roots and periodontal ligaments were analyzed.

Results

The canines in both groups exhibited a tipping movement pattern under all working conditions. By M8, the distal displacement of the canine crown, the equivalent stress values in the roots, and the equivalent stress values in the periodontal ligaments in the rectangular attachment group decreased by 12.04%, 30.80%, and 16.48%, respectively, compared to M0. In the optimized root control attachment group, these values decreased by 24.98%, 34.69%, and 19.15%, respectively. However, under all working conditions, the canines in the rectangular attachment group presented greater displacement and stress. The greatest reduction in canine crown distal displacement and stress values was observed between M6 and M8 in the rectangular attachment group, but the efficiency of canine distalization was still 64.30% at M8, with minimal change. In the optimized root control attachment group, the greatest reduction was observed in M4-M6, and the efficiency of canine distalization decreased to less than 60% in response to M6.

Conclusion

The canines tended to tip when maxillary canine distalization was performed with clear aligners. Attachment wear led to a reduction in the efficiency of canine distalization. Compared with optimized root control attachments, the impact was less significant for rectangular attachments. Once optimized root control attachments have been in place for more than 4 months and maxillary canine distalization is still required, orthodontists should closely monitor the wear of these attachments. If necessary, timely restoration or rebonding of the attachments is recommended.

A study on the compressive strength of three-dimensional direct printing aligner material for specific designing of clear aligners

BACKGROUND

The demand for orthodontic treatment using clear aligners has been gradually increasing because of their superior esthetics compared with conventional fixed orthodontic therapy. This study aimed to evaluate and compare the compressive strength of three-dimensional direct printing aligners (3DPA) with that of conventional thermo-forming aligners (TFA) to determine their clinical applicability. In the experimental group, the 3DPA material TC-85 (TC-85 full) was used to create angular protrusions called rectangular pressure areas (RPA). A protrusion akin to the power ridge typically employed in conventional TFAs was created using glycol-modified polyethylene terephthalate (PETG; Control 1). RPA was created using the same TC-85 without filling the protrusions (TC-85 blank; Control 2). Compression cycle tests were conducted on an LTM 3 h electrodynamic testing machine (Zwick Roell, Germany), with 500 cycles and compression depths of 100, 300, 500, and 700 µm. Twenty specimens were tested for PETG, 17 for the TC-85 blank, and 19 for the TC-85 full.

RESULTS

Changes in the compressive force were assessed based on the material and thickness. The results indicated significantly higher and broader ranges of compressive strength for specimens fabricated with the 3DPA material TC-85 compared with those fabricated using PETG. Among the TC-85 specimens, TC-85 full demonstrated the highest statistically significant compressive strength .

CONCLUSIONS

3DPA technology enables precise modifications in the shape and inner thickness at specific dental sites, including the creation of ridges in targeted areas, of aligners. These alterations enhance the biomechanical capability of aligners to exert selective forces necessary for desired tooth movement while reducing the number of attachments, thereby demonstrating the clinical potential of 3D-printed aligners in orthodontic treatment.

Effect of post-processing on the surface, optical, mechanical, and dimensional properties of 3D-printed orthodontic clear retainers

OBJECTIVES

To address the high surface roughness and poor optical properties of three-dimensional (3D) printed orthodontic clear retainers, an alternative post-processing protocol was investigated with the goal of achieving improved surface, optical, and mechanical properties while preserving dimensional accuracy.

MATERIALS AND METHODS

Samples were prepared from two biocompatible methacrylate-based 3D-printing resins (Formlabs Dental LT Clear V2, NextDent OrthoFlex) and one thermoplastic material (Duran). For the 3D-printed resins, one group was post-processed by rinsing in isopropyl alcohol, while another group was centrifuged before post-curing in glycerine. Three different testing conditions were used: dry, wet (24-h water immersion), and aged (thermocycling for 10,000 cycles). Surface characteristics were evaluated qualitatively and quantitatively. Optical properties were assessed for transparency and colour stability, while mechanical properties were elicited from tensile and microhardness tests. Water sorption and solubility were calculated. Samples mounted on a dental model were scanned by micro-computed tomography to measure thickness and gap width.

RESULTS

3D-printed samples post-processed by centrifugation showed significantly decreased surface roughness and improved visible light transmission, colour stability, tensile strength, and hardness. The centrifuged samples showed significantly increased thickness, while designing an offset equal to this thickness improved the adaptation.

CONCLUSIONS

Post-processing by centrifugation produces surface coating that enhances the surface and optical properties of the 3D-printed orthodontic retainers, while curing in an oxygen-free environment improves their mechanical properties. Design modifications may be necessary for this protocol to ensure proper adaptation to the dentition.

CLINICAL RELEVANCE

Proper design and post-processing protocols are necessary to achieve the desired properties of orthodontic clear retainers.

Accuracy of Preliminary Maxillary Canine and Anchorage Tooth Movement in Premolar Extraction Cases Using 12 In-House Clear Aligners: A Randomised Control Trial Comparing Power Arm and Control

OBJECTIVES

To investigate maxillary canine movement accuracy and anchorage during space closure in first premolar extraction cases (maximum anchorage) using In-House Clear Aligners (IHCAs).

MATERIALS AND METHODS

A randomised controlled trial with a split-mouth design recruited 16 adults in university setting. Each patient was randomly assigned by side for canine retraction using 12 IHCAs to both the experimental palatal power arm (Pa) and non-Pa control (C). Accuracy was assessed using GOM Inspect by superimposing the virtual and actual digital models between pretreatment and 12th IHCA. Paired t-test or Wilcoxon signed-rank test was used to compare virtual-power arm (VPa) versus actual-power arm (APa) and virtual-control (VC) versus actual-control (AC). Root mean square error (RMSE) was calculated.

RESULTS

Pa displayed a significant difference in preliminary canine distalisation (VPa 2.0 mm vs. APa 2.4 mm), while the control did not differ. Both Pa and control exhibited significantly greater actual distal crown tipping than virtual movement (VPa 4.4° vs. APa -6.3°/VC 4.4° vs. AC -4.3°). AC achieved more canine rotation than VC. RMSE was slightly greater in Pa than control for canine distalisation (Pa 0.6 vs. C 0.55 mm) and distal crown tipping (Pa 10.9° vs. C 8.99°). Conversely, Pa displayed better accuracy in canine rotation. For anchorage, Pa and control exhibited significantly greater actual mesialisation and mesial tipping than virtual. RMSE for anchorage mesialisation and mesial tipping were comparable between Pa and control.

CONCLUSIONS

Preliminary canine retraction using Pa may result in greater error in distal crown tipping but less rotation than control.

TRIAL REGISTRATION

ISRCTN 14020146 by the International Standard Randomised Controlled Trial Registry.

Dynamics of the oral microbiome during orthodontic treatment and antimicrobial advances for orthodontic appliances

The oral microbiome plays an important role in human health, and an imbalance of the oral microbiome could lead to oral and systemic diseases. Orthodontic treatment is an effective method to correct malocclusion. However, it is associated with many adverse effects, including white spot lesions, caries, gingivitis, periodontitis, halitosis, and even some systematic diseases. Undoubtedly, increased difficulty in oral hygiene maintenance and oral microbial disturbances are the main factors in developing these adverse effects. The present article briefly illustrates the characteristics of different ecological niches (including saliva, soft tissue surfaces of the oral mucosa, and hard tissue surfaces of the teeth) inhabited by oral microorganisms. According to the investigations conducted since 2014, we comprehensively elucidate the alterations of the oral microbiome in saliva, dental plaque, and other ecological niches after the introduction of orthodontic appliances. Finally, we provide a detailed review of recent advances in the antimicrobial properties of different orthodontic appliances. This article will provide researchers with a profound understanding of the underlying mechanisms of the effects of orthodontic appliances on human health and provide direction for further research on the antimicrobial properties of orthodontic appliances.

In Vitro Comparison of the Effectiveness of Different Attachment Shapes and Locations on Extrusion of the Upper Left Lateral Incisor Using Thermoplastic Aligners

OBJECTIVES

The aim of this study was to compare the effectiveness of different attachment shapes and locations on the extrusion of the upper left lateral incisor (UL2) using thermoplastic aligners.

MATERIALS AND METHODS

Seven typodonts were digitally printed with hemi-ellipsoid or rectangular attachments in the incisal, middle or cervical third of the UL2. Five clear aligners were fabricated for each typodont; each was tested twice. Forces and moments were measured with an orthodontic force tester during 0.2 mm simulated extrusion of the UL2. Analysis of variance (ANOVA) was used to determine the effects of group, tooth, and the group-by-tooth interaction on the outcomes. A two-sided 5% significance level was used for all tests.

RESULTS

Altering attachment shape and location had a statistically significant effect on the forces and moments generated in each trial (p < 0.01), except for rectangular incisal and hemi-ellipsoid cervical (p > 0.05). The rectangular middle attachment generated the highest extrusive force (Fz = 7.498 N), followed by hemi-ellipsoid cervical (Fz = 6.338 N) and rectangular incisal (Fz = 5.948 N).

CONCLUSIONS

Varying direct attachment shape and location on the UL2 during extrusion has a significant effect on the forces and moments generated by thermoplastic aligners. The rectangular attachment located in the middle third generated the most effective extrusive force and least unwanted moment. For anchorage teeth, hemi-ellipsoid attachments located in the cervical third were found to be the most effective in minimising the reciprocal intrusive forces and unwanted moments.

The biomechanical effects of clear aligner trimline designs and extensions on orthodontic tooth movement: a systematic review

BACKGROUND

Clear aligner treatment (CAT) has emerged as an effective alternative to conventional multibracket systems in orthodontics. The trimline design and extension of aligners may significantly influence their biomechanical performance and tooth movement efficacy.

AIM

To systematically review the biomechanical effects of different aligner trimline designs and extensions on orthodontic tooth movement.

METHODS

A systematic search was conducted across PubMed, Scopus, Embase, ProQuest Dissertations & Theses Global, and Google Scholar for studies published between January 2000 and August 2024. The review included any types of empirical research focusing on the influence of trimline of orthodontic aligners on tooth movement efficacy conducted between January 2000 and August 2024. The Risk of Bias In Non-randomized Studies of Interventions (ROBINS-I) tool was used for quality assessment.

RESULTS

Twelve studies met the inclusion criteria, all assessed as having low to moderate risk of bias. Aligner trimline design significantly influenced orthodontic tooth movement efficacy through two primary mechanisms: enhanced force delivery and increased aligner retention. Aligners with straight and extended margins generally exerted higher forces and moments compared to scalloped or shorter designs. This resulted in greater tooth displacement for certain movements, particularly intrusion, translation, tipping, and root torquing. Extended trimlines also demonstrated superior retention. However, the effects varied depending on the type of tooth movement.

CONCLUSION

Aligner trimline designs and extensions can significantly influence biomechanical performance and tooth movement efficacy in CAT. Straight extended trimlines generally demonstrate superior force delivery and retention, leading to more predictable clinical outcomes. This could reduce the need for revisions, thereby decreasing overall treatment time and increasing patient satisfaction. However, further research is needed to investigate the interactions between aligner trimline designs and other factors to develop evidence-based guidelines for their optimal combination in various clinical scenarios.

The 'roller coaster effect' in premolar extraction cases: clear aligners vs. straight-wire appliance

OBJECTIVES

This study aimed to quantitatively investigate the intractable 'roller coaster effect' (RCE) that occurs in premolar extraction cases treated with clear aligner therapy (CAT) or straight-wire appliance (SWA).

METHODS

Protrusion cases treated with extraction of bilateral first premolars were included. Pre- and post-treatment cephalograms were obtained to measure the bending angle of occlusal plane (BAOP), namely the occlusal intersection angle between the anterior occlusal plane (AOP) and posterior occlusal plane (POP). BAOP is proposed as the indicator for quantifying RCE in this study.

RESULTS

In the maxillary dentition, BAOP significantly decreased from 177.50 ± 5.57° to 171.10 ± 3.32° in the SWA group (n = 30), and from 178.00 ± 4.66° to 168.10 ± 5.63° in the CAT group (n = 36). In the mandibular dentition, BAOP had no significant change (from 164.90 ± 5.00° to 164.30 ± 6.40°) in the SWA group (n = 29), while significantly decreased from 163.40 ± 6.36° to 155.90 ± 7.48° in the CAT group (n = 37). In the both dentitions, the post-treatment BAOP was significantly smaller in the CAT compared to SWA group. Decrease of BAOP in the CAT group resulted from bending of the AOP rather than POP. Multiple linear regression analysis revealed that the mandibular canine crown length had a positive correlation with the mandibular post-treatment BAOP.

LIMITATIONS

Only two-dimensional cephalometric measurements were conducted.

CONCLUSIONS

In premolar extraction cases, CAT undergoes more severe RCE at completion of its first-phase treatment compared to SWA at the end of treatment. Longer mandibular canine crown may mitigate mandibular RCE in CAT.

Bonding positional accuracy of attachments and marginal adaptation of in-house aligners - A quality improvement laboratory study

OBJECTIVES

To evaluate the 3D accuracy of attachment positioning and the adaptation of aligners to attachments using in-house templates made with either polyethylene terephthalate glycol (PETG) or ethylene-vinyl acetate (EVA) and either pressure or vacuum thermoforming machines.

MATERIALS AND METHODS

Overall, 140 test specimens were resin-printed. Templates for the attachment bonding were made with 1-mm EVA or 0.5-mm PETG laminates. Orthodontic aligners were manufactured with 0.75-mm PETG. The thermoplastification process was carried out using either vacuum or pressure machines. The positional differences between the virtual and bonded attachments were assessed in the X, Y and Z coordinates. The marginal adaptation between the aligners and the attachments was measured.

RESULTS

Minor inaccuracies in the positioning of the attachments were observed in all combinations of thermoforming machines and plastic laminates used to fabricate the templates, mainly in the superior-inferior (Z) dimension. PETG performed better than EVA in the anterior region (p < .05). No association was found between thermoplastification machines and the accuracy of the positioning of the attachments (p > .05). While small misadaptations between the aligners and the attachments were observed, the EVA templates performed better than the PETG templates.

CONCLUSIONS

The inaccuracy of the attachment positioning and the misadaptation of the aligners to the attachments were slight. The vacuum and pressure thermoplastification machines showed no difference in attachment positioning accuracy. The PETG template was better than the EVA template in the anterior region, but the EVA attachments presented a better adaptation to the aligners than the PETG attachments.

Effect of thermomechanical ageing on force transmission by orthodontic aligners made of different thermoformed materials: An experimental study

OBJECTIVES

Investigating the impact of thermal and mechanical loading on the force generation of orthodontic aligners made from various thermoplastic materials and different compositions.

MATERIALS AND METHODS

Five distinct materials were utilized including, three multi-layer (Zendura FLX, Zendura VIVA, CA Pro) and two single-layer (Zendura A and Duran). A total of 50 thermoformed aligners (n = 10) underwent a 48-hour ageing protocol, which involved mechanical loading resulting from a 0.2 mm facial malalignment of the upper right central incisor (Tooth 11) and thermal ageing through storage in warm distilled water at 37°C. The force exerted on Tooth 11 of a resin model was measured both before and after ageing using pressure-sensitive films and a biomechanical setup.

RESULTS

Before ageing, pressure-sensitive films recorded normal contact forces ranging from 83.1 to 149.7 N, while the biomechanical setup measured resultant forces ranging from 0.1 to 0.5 N, with lingual forces exceeding facial forces. Multi-layer materials exhibited lower force magnitudes compared to single-layer materials. After ageing, a significant reduction in force was observed, with some materials experiencing up to a 50% decrease. Notably, multi-layer materials, especially Zendura VIVA, exhibited lower force decay.

CONCLUSIONS

The force generated by aligners is influenced by both the aligner material and the direction of movement. Multi-layer materials exhibit superior performance compared to single-layer materials, primarily because of their lower initial force, which enhances patient comfort, and their capability to maintain consistent force application even after undergoing ageing.

Effects of aging on the tensile strength and surface condition of orthodontic aligners: a comparative study of five models

BACKGROUND/OBJECTIVE

The objective of this study is to determine the effect of aging on tensile strength and surface condition of orthodontic aligners on days 0, 1, 5, 7, 10, and 14.

MATERIALS/METHODS

The total sample of 80 aligners included five brands (Accusmile®, Angel®, GRAPHY®, Invisalign® and Suresmile®) were placed in a thermocycler to imitate the temperature variations of the oral cavity and accelerate aging for 50, 250, 350, 500, and 700 cycles. The mechanical tensile properties (Young's modulus E, yield strength YS, maximum elastic stress MES, Ultimate Tensile Strength UTS, and maximum stress MS) were measured by Universal Testing Machine at a rate of 5 mm of deformation per minute for 4 minutes. Microscopic observations were made under a voltage of 10 kV at magnifications times 50, 250, 500, 1000, and 2500 after cleaning with ethanol and ultrasound then metallization with gold.

RESULTS

YS and MES of Angel® aligners are statistically reduced after five days of aging (P = .003). Aligners from the most rigid to the most flexible are (decreasing E): Accusmile® > GRAPHY® > Suresmile® > Invisalign® > Angel®. Surface conditions also deteriorated with aging (appearance of scratches, porosity, cracks, etc.). GRAPHY® aligners are more heterogeneous and weaker than others.

LIMITS

In vitro study.

CONCLUSION

Mechanical properties of Accusmile®, GRAPHY®, Invisalign®, and Suresmile® were not affected by aging. YS and MES were reduced from day 5 for Angel® aligners. Surface conditions are also altered by aging.

The new additive era of orthodontics: 3D-printed aligners and shape memory polymers-the latest trend-and their environmental implications

The era of printed aligners has just began in the orthodontic field. Orthodontists have become more interested in 3D-printed in-office aligners. Treatment due to this technology can become faster and more efficient. Advantages highlighted by newly introduced materials for manufacturing processes of 3D aligners present the possibility of overcoming limitations faced by thermoformed aligners, making them a potential replacement of thermoformed aligner. Advances in aligner material, especially shape memory polymers, have the potential to bring about radical transformations in the clinical applications of clear aligner therapy. Safety and cytotoxicity of printable resins along with its mechanical properties must be scientifically studied extensively before it is cleared for clinical use. In addition, with the increased use of aligners, awareness of the environmental burden of plastic waste should be emphasized. Attention should be directed into the development of recyclable materials for aligners along with establishing clear recycling guidelines and patient education programs on proper recycling methods. With the introduction of Graphy's clear biocompatible photocurable resin, which is equipped with a shape-memory function and is printed in an environmental friendly way by reducing carbon emissions. Direct 3D printing represents the future of clear aligner therapy, and more studies to test these new technologies and materials are required.

Seeking orderness out of the orderless movements: an up-to-date review of the biomechanics in clear aligners

INTRODUCTION

Although with increasing popularity due to aesthetic appeal and comfort, clear aligners (CAs) are facing challenges in efficacy and predictability. Advancement in the underlying biomechanical field is crucial to addressing these challenges. This paper endeavors to provide a comprehensive framework for understanding the biomechanics of CA and enlightening biomechanics-based improvements on treatment strategies.

METHODS

A thorough review of the English-language literature accessible through PubMed and Google Scholar, without any publication year restrictions, was undertaken to unravel the biomechanical aspects of CA.

RESULTS

This review presented an up-to-date understanding of aligner biomechanics arranged by the framework of the material-dependent mechanical characteristics of CA, the geometric characteristics-dependent force transmission of the CA system, methods for studying the biomechanics of CA, and the biomechanical analyses for different types of tooth movement.

CONCLUSIONS

Biomechanics should be the fundamental concern for concepts, methods and adjuncts attempting to enhance the accuracy and predictability of tooth movement induced by CA. Improvement on material properties and alteration of geometric design of CA are two main approaches to develop biomechanically optimized force system. Exploration of real-world force sensing and monitoring system would make substantial progresses in aligner biomechanics.

Viscoelastic and antimicrobial dental care bioplastic with recyclable life cycle

Medical plastic-appliance-based healthcare services, especially in dentistry, generate tremendous amounts of plastic waste. Given the physiological features of our mouth, it is desirable to substitute dental care plastics with viscoelastic and antimicrobial bioplastics. Herein, we develop a medical-grade and sustainable bioplastic that is viscoelastic enough to align the tooth positions, resists microbial contamination, and exhibits recyclable life cycles. In particular, we devise a molecular template involving entanglement-inducing and antimicrobial groups and prepare a silk fibroin-based dental care bioplastic. The generated compactly entangled structure endows great flexibility, toughness, and viscoelasticity. Therefore, a satisfactory orthodontic outcome is accomplished, as demonstrated by the progressive alignment of male rabbit incisors within the 2.5 mm range. Moreover, the prepared bioplastic exhibits resistance to pathogenic colonization of intraoral microbes such as Streptococcaceae and Veillonellaceae. Because the disentanglement of entangled domains enables selective separation and extraction of the components, the bioplastic can be recycled into a mechanically identical one. The proposed medical-grade and sustainable bioplastic could potentially contribute to a green healthcare future.

Effect of endodontically treated teeth on prosthetically guided orthodontics with clear aligners: a case series

BACKGROUND

Prosthetically guided orthodontics (PGO) can correct the malocclusion for better prosthetic rehabilitation in esthetic rehabilitation. Unlike conventional orthodontic treatment, only minor tooth movement is designed in PGO according to the requirement of subsequent restoration. For better appearance during the treatment, PGO is often performed with clear aligners, which have no metal brackets. It has been proven that the PGO with clear aligners can achieve generally satisfactory outcomes. However, its risk has not been fully known due to the paucity of relevant studies.

CASE PRESENTATION

Three patients who needed esthetic rehabilitation with mild malocclusion were included in this study. After evaluation, a prosthetic solution alone was considered insufficient to provide optimal outcomes. Thus, they were treated using PGO with clear aligners (Invisalign Go, Align Technology, Santa Clara, California, USA) and accomplished prosthetic rehabilitation subsequently. Dental history and X-ray examination revealed that endodontically treated teeth (ETT) existed in all the cases. Intraoral photographs were collected to compare the pre-treatment and post-treatment dentition. After PGO, posterior ETT did not maintain their position as scheduled and lost occlusal contacts, while all the anterior teeth, including anterior ETT, were moved to the designed position. Corresponding prosthetic rehabilitation was used to solve it after consulting with the patients.

CONCLUSIONS

Occlusal contact loss of posterior ETT is a potential risk in PGO with clear aligners, affecting the orthodontic result.

Cytotoxicity assessment of eluates from vacuum-forming thermoplastics

OBJECTIVES

This study aimed to evaluate possible cytotoxic effects of thermoplastic materials commonly used for occlusal splints and orthodontic appliances.

METHODS

Seven thermoplastics were included: three variants of the Essix sheets (C+, Plus, and Tray Rite; Dentsply Sirona), three thermoplastics (Bleach Heavy, Splint, and X-Heavy; Cavex Holland) and Invisalign (Align Technology). Cylindrical specimens (n = 24; 10 mm diameter) were incubated in cell culture medium for 24 h and 14 days. After incubation, the medium was collected, serially diluted, and dosed to primary human gingival fibroblasts in triplicate. Medium processed like the samples was used as negative control. Cell viability was evaluated by XTT and LDH assay to assess metabolic activity and membrane integrity, respectively. Next, cell cycle was assessed with flow cytometry after exposing HGFs to undiluted extracts.

RESULTS

The 24-hour and 14-day extracts did not evoke cytotoxicity after 24-hour incubation. No significant differences in cell viability (one-way ANOVA, p > 0.05 ) in the XTT and LDH assays or in cell cycle distribution between the different materials (two-way ANOVA, p > 0.05 ).

CONCLUSION

The thermoplastics tested in the study showed no evident in-vitro cytotoxic effects. Further investigation should focus on determining which compounds are released from thermoplastic materials and assessing potential toxicity related to exposure to these compounds.

CLINICAL SIGNIFICANCE

Our study adds to the growing body of evidence on the biocompatibility of dental thermoplastics. This can aid clinical decision-making, as thermoplastics are expected to be safe to use in terms of cytotoxicity.

Biofilm formation of Streptococcus mutans, Streptococcus sanguinis, Staphylococcus epidermidis, Staphylococcus aureus, Lactobacillus casei, and Candida Albicans on 5 thermoform and 3D printed orthodontic clear aligner and retainer materials at 3 time points: an in vitro study

INTRODUCTION

Orthodontic clear aligners and retainers have numerous advantages that is making them ever increasingly popular. However, they might, similar to any other oral appliance, contribute to biofilm formation and finally dental caries or white spot lesions or gingival inflammations. The literature on biofilm formation on orthodontic clear appliances is very scarce and limited to a few microorganisms and materials. Therefore, this experimental study evaluated the biofilm formation on 5 thermoformed and 3D printed CAD/CAM orthodontic retainers in 3 intervals.

METHODS

In this in vitro study, 345 specimens (270 test discs and 45 negative controls) were created from fabricated retainers. Retainers included a 3D printed CAD/CAM material (Detax) and four thermoformed retainers [Erkodent (polyethylene terephthalate glycol [PETG]); EasyVac (polyethylene); DB (polyester based on terephthalic acid); and Clear Tech]. They were all 1 mm thick, and all completely fabricated, i.e., heated or printed. The discs were placed in 96-well plates. Microorganisms were cultured on 270 discs for 24 h (90 discs), 72 h (90 other discs), and 5 days or 120 h (90 other discs). Biofilm formation of the strains and negative controls was measured using the microtiter plate assay by ELISA reading. The microbes' ability to produce biofilm was categorized based on the comparison of average optical density (OD) of tests versus a cut-off point OD (ODc) calculated as the average of the OD of corresponding negative controls plus 3× its standard deviation: non-biofilm former [OD ≤ ODc], weak biofilm former [ODc < OD ≤ (2 × ODc)], moderate biofilm former [(2 × ODc) < OD ≤ (4 × ODc)], and strong biofilm former [(4 × ODc) < OD]. These were also converted to ranked scores between zero (no biofilm) and 3. The difference between ODs with control ODs were calculated. These were analyzed using 3-way ANOVA, 2-way ANOVA, and Tukey tests (α = 0.05, α = 0.008).

RESULTS

The 3-way ANOVA showed that the overall difference among the ΔODs of 5 retainers (all microorganisms and all intervals combined, n = 270) was not significant (F = 1.860, P = 0.119). Nevertheless, the difference among 3 intervals (F = 31.607, P = 0.0000) and the difference among the 6 microorganisms (F = 24.044, P = 0.0000) were significant. According to the Tukey test, the differences between the 1st interval with either of the other two intervals was significant (both P values = 0.000). There were significant differences between Candida albicans with all other organisms (all 5 P values = 0.0000). All other pairwise comparisons were insignificant (all 10 P values ≥ 0.1). After taking the averages of the 3 intervals, the order of the biofilm generation for different materials were as follows: Detax (average score: 1.56), Easyvac (1.67), Erkodent (1.78), Clear Tech (1.83), BD (2.28).

CONCLUSIONS

As far as these 6 microorganisms are of concern, there might not be a significant overall difference among the clear retainer materials tested in this study. A significant overall increase was observed between the first and third days, which later did not significantly increase more until day 5. The Candida albicans biofilm was more intense than the tested 5 bacteria, which themselves showed rather similar growth patterns to each other.

Assessment of patients' knowledge and preferences for the use of orthodontic aligners

OBJECTIVE

To evaluate the knowledge and preference of patients treated at a Dental School in Jaraguá do Sul, Brazil, about using aligners and the reasons for choosing this device as a treatment option.

DESIGN

A cross-sectional study.

PARTICIPANTS

A total of 82 participants aged 18-45 years recruited at a screening clinic.

METHODS

A questionnaire was completed in person using a tablet with digital forms.

RESULTS

Almost half of the participants (49%) knew about aligners; 40% were aged 18-24 years, and 77% were female. When observing the images of the types of orthodontic appliances, the aligners had an acceptance rate of 80%. Among the reasons that led to the preference for choosing aligners, 68% cited aesthetics and 42% comfort.

CONCLUSION

Recently, clear aligners have become a popular choice for orthodontic treatment, particularly among adults. Despite their popularity and effectiveness, many patients still need more information about aligner treatment. Over half of the respondents did not know what orthodontic aligners were. Younger participants had more knowledge about aligners than older participants. Patients still need more knowledge about the types of appliances available for orthodontic treatment. When presented with images of the kinds of devices available, almost 80% of participants showed greater satisfaction with aligners.

Prospects for 3D-printing of clear aligners—a narrative review

Clear aligner therapy is a rapidly developing orthodontic treatment. 3D-printing technology, which enables the creation of complex geometric structures with high precision, has been used in dentistry. This article aims to summarize the various aspects of 3D-printing clear aligners and give an outlook on their future development. The traditional thermoforming technology is introduced and the principle and application of 3D-printed clear aligners and materials are introduced, as well as the application prospects of 3D-printed clear aligners. According to PRISMA statement, the relevant literature of 3D-printing clear aligner was searched in PubMed, Web of Science, Embase and other databases. We searched the related words in the MESH database and then carried out advanced searches. We read systematic review and conference papers to find the articles related to the subject and manually added and excluded articles by reading the title and abstract. The production of clear aligners combines computer-aided 3D analysis, personalized design and digital molding technology. The thickness and edges of the 3D-printed clear aligner can be digitally controlled, which allows appliance more efficiently fitted. Presently, the array of clear resins suitable for 3D-printing include photo polymeric clear methacrylate-based resin (Dental LT) (Form Labs, Somerville, Mass), aliphatic vinyl ester-polyurethane polymer (Tera Harz TC-85) (Graphy, Seoul, South Korea). They all have good biocompatibility. But no such material is currently approved on the market. Developing biocompatible resins and further improving the material’s mechanical properties will be critical for the combination of 3D-printing and clear aligners. However, the literature on 3D-printed clear aligners is limited and lacks clinical application. Further in vivo and in vitro tests, as well as additional exploration in conjunction with corresponding cytological tests, are required for the research on available materials and machinery for 3D-printing clear aligners.

Revolutionizing Smiles: Advancing Orthodontics Through Digital Innovation

Orthodontics is undergoing a digital revolution, transforming traditional techniques with modern technology. This evolution is driven by the need for precise diagnosis and treatment planning. Digital platforms, including digital radiography and cone beam computed tomography (CBCT), are replacing conventional methods, enhancing documentation, analysis, and appliance production. Three-dimensional imaging enables customized treatment plans and appliance design using computer-aided design and computer-aided manufacture (CAD/CAM). Integration of digital models and software facilitates treatment simulation and patient communication. Digital videography enhances diagnostic capabilities. Embracing digital processes is essential for improved patient care and practice efficiency in orthodontics. This review article on digital orthodontics aims to provide a comprehensive overview and critical analysis of the current advancements, technologies, applications, benefits, and challenges in the field of orthodontics utilizing digital tools and technologies.

Awareness and Perception of Dental, Medical, and Paramedical Students Toward the Use of Clear Aligners in Orthodontic Treatment in Belagavi, India

Background The advent of clear aligners represents a significant shift in orthodontic treatment, offering an aesthetic and convenient alternative to traditional braces and helping maintain better oral hygiene as it is removable. This study investigates the awareness and perception of clear aligners among dental, medical, and paramedical students in Belagavi, India. Methodology A cross-sectional, observational study was conducted in February 2024 among students from a private medical university in Belagavi. A validated questionnaire (content validity ratio = 0.88; Cronbach's alpha coefficient = 0.86), developed through expert consultation and pilot testing, assessed the awareness and perception of students on clear aligners. Simple random sampling was used to select 480 participants. Data were analyzed using the chi-square test, analysis of variance, Pearson correlation coefficient, and binary logistic regression. Results The study found that awareness and perception of clear aligners were the lowest among medical and paramedical students in comparison with dental students. A positive linear correlation was seen between awareness and perception scores. When specialty was taken into consideration, medical/dental students were 2.55 times more aware and had 2.78 times more positive perceptions toward clear aligners compared to paramedical students. Conclusions There was a notable disparity in the awareness and perception of clear aligners among dental, medical, and paramedical students. Medical and paramedical students displayed lower awareness and unfavorable perception toward clear aligners in comparison with dental students.

Investigation of Different Miniscrew Head Designs by Finite Element Analysis

Objective

To determine the optimum miniscrew head design in orthodontic treatments for primary stability and compare stress distribution on a representative bone structure.

Methods

Miniscrews with cross heads, mushroom-shaped heads, button heads, bracket heads, and through-hole heads were compared using finite element analysis. Miniscrews, whose three-dimensional drawings were completed using the SolidWorks computer-aided software package, were inserted in the bone block. Orthodontic force was applied to the head, and stress distributions, strains, and total deformations were investigated.

Results

The lowest von Mises stress of 5.67 MPa was obtained using the bracket head. On the other hand, the highest von Mises stress of 22.4 MPa was found with the button head. Through mesh convergence analysis, the most appropriate mesh size was determined to be 0.5 mm; approximately 230,000 elements were formed for each model.

Conclusion

Because the need for low stress is substantial for the primary stability of the miniscrew, this study demonstrated that the bracket head miniscrew is the optimal head design. In addition, it is posited that the success rate of orthodontic anchorage treatments will increase when bracket head miniscrews are used.

Finite element analysis of the mechanical behavior of 3D printed orthodontic attachments used in aligner treatment

The composite attachment loss during orthodontic clear aligner therapy is an adverse event that commonly happens in clinical practice and can affect the overall outcome and length of treatment. The aim of our research is to provide a basis for the further study of an innovative digital protocol and application method for orthodontic aligner attachments. Two 3D models were designed, one based on the proposed protocol and the other on the conventional method for aligner attachment application. Four attachment shapes were used to identify the maximum values for the von Mises equivalent stresses, the maximum displacements values and the areas in which these values were recorded through FEM analysis. The results of the mechanical simulation show lower values of von Mises stress recorded in the 3D printed attachments assemblies, independent of their shape, when simulated under the same boundary and load conditions. The trapezoidal prism shaped 3D printed model has a 3.7 times smaller displacement value (0.088 [mm]) compared to the adhesive resin model (0.326 [mm]). In conclusion, the proposed protocol for aligner attachments and the introduction of innovative materials is a promising method of solving conventional attachment problems in current orthodontic treatments.

The Influence of Thickness on the Mechanical Behaviors of 3D Printing Resins for Orthodontic Retainers

This study aimed to evaluate the mechanical behaviors of thermoformed and 3D-printed retainers with different thicknesses. Thermoformed retainers (Duran) and 3D-printed retainers (Dental LT Clear V2 and NextDent Ortho Flex) were fabricated at thicknesses of 0.5, 0.75, and 1 mm. Five samples of each material were subjected to compression, tensile, and flexural testing with the universal testing machine (Instron Ltd., Buckinghamshire, England). The results revealed that the mechanical behaviors were significantly influenced by thickness in each type of material. The increased thickness tended to increase strength and modulus in all three tests. However, Dental LT Clear V2 and Duran showed that flexural strength and modulus were inversely related to thickness. The compressive test revealed significantly greater compressive resistance in 3D-printed groups, except for the NextDent Ortho Flex at 0.5 mm. The tensile test showed that Dental LT Clear V2 at all thicknesses demonstrated significantly higher tensile strength and modulus, while NextDent Ortho Flex was significantly lowest at any thickness in tensile and flexural properties. In conclusion, the thickness significantly influenced the mechanical behaviors of the 3D-printed retainers. The 0.75 mm thickness of Dental LT Clear V2 could be considered as an alternative to fabricated retainers due to its similar mechanical properties compared with the thermoformed material.

Effects of different tooth movement patterns and aligner thicknesses on maxillary arch expansion with clear aligners: a three-dimensional finite element study

Objectives

The objective of this study was to investigate the biomechanical effects of different tooth movement patterns and aligner thicknesses on teeth and periodontal tissues during maxillary arch expansion with clear aligners, to facilitate more precise and efficient clinical orthodontic treatments.

Methods

Three-dimensional models including teeth, maxilla, periodontal ligament, and aligner were constructed and subjected to finite element analysis. Tooth displacement trends and periodontal ligament stresses were measured for seven tooth displacement patterns (divided into three categories including overall movement of premolars and molars with gradually increasing molar expansion in each step; distributed movement of premolars and molars; and alternating movement between premolars and molars at intervals) and two aligner thicknesses (0.5 mm and 0.75 mm) during maxillary arch expansion with clear aligners.

Results

When expanding the maxillary arch with clear aligners, the effective expansion of the target teeth mainly showed a tilting movement trend. Increasing the amount of molar expansion increased the buccal displacement of the first molar but decreased the buccal displacement of the premolars. The mean buccal displacement of the target teeth was greater in the posterior teeth interval alternating movement group (0.026 mm) than in the premolar/molar distributed movement group (0.016 mm) and the overall movement group (0.015 mm). Increasing aligner thickness resulted in greater buccal displacement of the crowns and increased stress on the periodontal ligaments.

Conclusion

Increasing the amount of molar expansion reduces the efficiency of premolar expansion. Alternating movement of premolars and molars at intervals achieves a higher arch expansion efficiency, but attention should be paid to the anchorage of adjacent teeth. Increasing the thickness of the aligner increases the expansion efficiency but may also increase the burden on the periodontal tissues.

Construction of Zwitterionic Coatings with Lubricating and Antiadhesive Properties for Invisible Aligner Applications

Invisible aligners have been widely used in orthodontic treatment but still present issues with plaque formation and oral mucosa abrasion, which can lead to complicated oral diseases. To address these issues, hydrophilic poly(sulfobetaine methacrylate) (polySBMA) coatings with lubricating, antifouling, and antiadhesive properties have been developed on the aligner materials (i.e., polyethylene terephthalate glycol, PETG) via a simple and feasible glycidyl methacrylate (GMA)-assisted coating strategy. Poly(GMA-co-SBMA) is grafted onto the aminated PETG surface via the ring-opening reaction of GMA (i.e., "grafting to" approach to obtain G-co-S coating), or a polySBMA layer is formed on the GMA-grafted PETG surface via free radical polymerization (i.e., "grafting from" approach to obtain G-g-S coating). The G-co-S and G-g-S coatings significantly reduce the friction coefficient of PETG surface. Protein adsorption, bacterial adhesion, and biofilm formation on the G-co-S- and G-g-S-coated surfaces are significantly inhibited. The performance of the coatings remains stable after storage in air or artificial saliva for 2 weeks. Both coatings demonstrate good biocompatibility in vitro and is not caused irritation to the oral mucosa of rats in vivo over 2 weeks. This study proposes a promising strategy for the development of invisible aligners with improved performance, which is beneficial for oral health treatment.

Thickness Variations of Thermoformed and 3D-Printed Clear Aligners

Objective

To assess thickness variations of thermoformed and 3D-printed clear aligners.

Materials and Methods

Six different thermoplastic materials with different initial thicknesses were used for aligner thermoforming using Biostar® device (Biostar®, SCHEU-DENTAL GmbH, Iserlohn, Germany). Also, two different dental resins were used to create the printed aligners in three digitally designed thicknesses using IZZI Direct printer (3Dtech, Zagreb, Croatia). The aligners were measured using an electronic micrometer (ELECTRONIC UNIVERSAL MICROMETER, Schut Geometrical Metrology, Groningen, The Netherlands, accuracy: 0.001 mm) on a total of 20 points per aligner. Statistical analysis was performed using the JASP program (JASP, University of Amsterdam, Amsterdam, The Netherlands).

Results

The difference between the thermoformed and printed groups was statistically significant. Significant differences between different thermoformed materials and between 3D-printed materials were found. The thickness of thermoformed aligners deviated more in the upper jaw, whereas the thickness of printed aligners deviated more in the lower jaw. Both differences were statistically significant. The greatest average deviation from the initial thickness was found in Duran 0.75; Erkodur 0.6; Erkoloc-Pro 1.0; IZZI 0.5; NextDent 0.6 and NextDent A 0.6. NextDent group had the lowest deviations for all teeth of both jaws, except for upper and lower first molar where NextDent A group was more accurate.

Conclusions

Thermoformed aligners showed decreased values, while printed ones showed mostly increased values compared to the original material thickness. The highest mean deviation belonged to IZZI group, and the NextDent group had the lowest mean deviation. The thickness of both aligners was thinner at the edges compared to the thickness at cusps and fissures.

Mechanical and Electrical Properties of Polyethylene Terephthalate Glycol/Antimony Tin Oxide Nanocomposites in Material Extrusion 3D Printing

In this study, poly (ethylene terephthalate) (PETG) was combined with Antimony-doped Tin Oxide (ATO) to create five different composites (2.0-10.0 wt.% ATO). The PETG/ATO filaments were extruded and supplied to a material extrusion (MEX) 3D printer to fabricate the specimens following international standards. Various tests were conducted on thermal, rheological, mechanical, and morphological properties. The mechanical performance of the prepared nanocomposites was evaluated using flexural, tensile, microhardness, and Charpy impact tests. The dielectric and electrical properties of the prepared composites were evaluated over a broad frequency range. The dimensional accuracy and porosity of the 3D printed structure were assessed using micro-computed tomography. Other investigations include scanning electron microscopy and energy-dispersive X-ray spectroscopy, which were performed to investigate the structures and morphologies of the samples. The PETG/6.0 wt.% ATO composite presented the highest mechanical performance (21% increase over the pure polymer in tensile strength). The results show the potential of such nanocomposites when enhanced mechanical performance is required in MEX 3D printing applications, in which PETG is the most commonly used polymer.

Effect of thermomechanical aging on force system of orthodontic aligners made of different thermoformed materials : An in vitro study

PURPOSE

The aim was to investigate the effect of aging by thermocycling and mechanical loading on forces and moments generated by orthodontic clear aligners made from different thermoplastic materials.

METHODS

A total of 25 thermoformed aligners made from 5 different materials, i.e., Essix ACE® and Essix® PLUS™ (Dentsply Sirona, Bensheim, Germany), Invisalign® (Align Technology, San Jose, CA, USA), Duran®+ (Iserlohn, Germany), Zendura™ (Fremont, CA, USA), underwent a 14-day aging protocol involving mechanical loading (a 0.2 mm vestibular malalignment of the upper left second premolar [tooth 25]) and thermocycling in deionized water (temperature range 5-55 °C). The 3D forces/moments exerted on tooth 25 of a resin model were measured at three time points: before aging (day 0), after 2 days and after 14 days of aging.

RESULTS

Before aging, extrusion-intrusion forces were 0.6-3.0 N, orovestibular forces were 1.7-2.3 N, and moments as mesiodistal rotation were 0.3-42.1 Nmm. In all directions, multilayer Invisalign® exhibited the lowest force/moment magnitudes. After aging, all materials showed a significant force/moment decay within the first 2 days, except Invisalign® for orovestibular and vertical translation. However, following thermomechanical aging, Duran®+ and Zendura™ aligners had equivalent or even higher vestibular forces (direction of mechanical load).

CONCLUSION

Thermomechanical aging significantly reduced forces and moments during the first 48 h. Multilayer aligner materials exhibit lower initial forces and moments than single-layer ones, and were less influenced by aging. Material hardening was observed after subjecting some of the aligner materials to mechanical loading. Thus, orthodontists should be aware of possible deterioration of orthodontic aligners over time. This work also sheds light on how material selection impacts the mechanical behavior of aligners and may provide valuable guidance regarding optimal timing for the aligner changing protocol.

A comparison of the upper anterior teeth movements with optimized and conventional attachment

Background

Invisalign® attachments are divided into two main groups: the conventional group and the optimized group, which is also known as the SmartForce™. The aim of this study is to compare the movements produced by an optimized crescent-shaped attachment in superior incisor teeth with the movements produced by a conventional rectangular attachment (vertical and horizontal) in the same teeth.

Material and Methods

This retrospective study examined the movement table of the initial ClinCheck® and the first refinement of 95 patients (mean age 44.18 ± 4.125, 40 males and 55 females). It represented 147 upper incisors divided into two groups: 87 with rectangular attachment and 60 with optimized attachment. Applying Kravitz's accuracy formula for each movement and each tooth of interest (with attachments of interest), we underlined the effectiveness of each attachment. Mann-Whitney U test, Kruskal-Wallis test, and Pearson and Spearman correlation coefficients were used for statistical analysis.

Results

The accuracies of rotation, mesio-distal angulation and vestibulo-lingual inclination are highly significantly related to the type of attachment used on the upper lateral incisor. The optimized attachment presented greater accuracy in the rotation of the lateral incisors than the conventional attachment. However, conventional vertical attachment showed a higher accuracy (p<.01) in the mesio-distal angulation and horizontal attachments showed a higher accuracy (p<.01) in the vestibulo-lingual inclination in the same group of teeth.

Conclusions

Optimized attachments rotate better lateral incisors; conventional vertical attachments are more efficient to improve mesio-distal angulation; and horizontal attachments serve best for torque movements. Key words:Orthodontics, clear aligners, orthodontic tooth movements, attachments.

The accuracy and retention of presurgical infant orthopaedics constructed from different polymer materials: A comparative study

Objectives

This laboratory-based study aimed to evaluate and compare the accuracy and retention of moulding plates when used as pre-surgical orthopaedic appliances (PSIOs) for infants with cleft lip and/or palate (CL/P).

Methods

Ten moulding plates were fabricated from three different materials (total sample size: 30), including polymethyl methacrylate (PMMA), a hard clear aligner (PET-G polymer), and a dual-layered hard and soft clear aligner (mixed PET-G/EVA) on ten three-dimensional (3D) printed working models. Accuracy was evaluated by measuring the virtual gap between the data acquired from the moulding plate and the working model after the optical scanning at each of the designated 36 points for each plate. Exocad software was used to facilitate all virtual alignments and measurements. Retention was measured using a digital gauge that quantified the traction force required to separate the plates from the retention test cast (a soft resin printed cast).

Results

PET-G plates exhibited the best fit with the working cast, with overall adaptations of 0.146 ± 0.012 for PET-G, 0.250 ± 0.073 for PET-G/EVA, and 0.294 ± 0.113 for PMMA. For region-specific misfit, PET-G plates exhibited superior accuracy across all regions, with mean discrepancies of 0.16 ± 0.08 mm, 0.15 ± 0.061 mm, and 0.12 ± 0.128 mm in the anterior, middle, and posterior regions, respectively. Retention for PET-G was significantly higher than the other materials, with a mean of 3.34 N ± 0.487, as opposed to 1.65 N ± 0.331for PMMA and 1.27 N ± 0.239 for PET-G/EVA (P < 0.05).

Conclusions

Moulding plates constructed from PET-G exhibited a better fit and higher retention than those made from PET-G/EVA and PMMA.

Clinical significance

Collectively, our findings suggest that the selection of PET-G for PSIO appliances could have clinical significance by potentially improving treatment outcomes in infants with CL/P.

Effects of different patterns of movement for correcting a deep curve of Spee with clear aligners on the anterior teeth: a finite element analysis

OBJECTIVE

To analyse the anterior teeth effects of clear aligners on five different patterns of mandibular molar movement and to define the most effective configuration to be implemented with clear aligners through finite element analysis.

METHODS

A three-dimensional mandibular model with a deep overbite in the mandible was constructed using cone beam computerized tomography (CBCT) data. The model included the mandibular dentition, mandibular periodontal ligaments, attachments, and aligners. Five models were created: (1) configuration A: second molar distalization (0.25 mm); (2) configuration B: second molar distalization (0.25 mm), first molar extrusion (0.15 mm); (3) configuration C: second molar distalization (0.25 mmm), first and second premolar extrusion(0.15 mm); (4) configuration D: second molar distalization (0.25 mm), first molar and first/second premolar extrusion(0.15 mm); and (5) configuration E: second molar distalization (0.25 mm), first molar and first/second premolar extrusion (0.15 mm), first molar and first/second premolar expansion (0.15 mm).

RESULTS

In all configurations, the anterior teeth exhibited labial tipping and the mandibular central incisor of configuration E showed the highest labial tipping. Configuration E demonstrated a relatively minor impact on mandibular molars distalization compared with configuration A. Configuration A showed the highest distal displacement value, and configuration E produced the lowest displacement value. Configuration E caused the highest periodontal ligament (PDL) pressure of the central and lateral incisors. The differences in the canines between configurations C and D,were not significant, and the stress distribution differed among the five groups.

CONCLUSIONS

All patterns utilizing clear aligners facilitated mandibular molar distalization. Extruding the premolars and second molar distalization at the same time had little impact on second molar distalization; When expansion and extrusion were simultaneously performed during the distalization of mandibular molars, our prime consideration was the alveolar bone on the labial side of the anterior teeth to prevent the occurrence of gingival recession, dehiscence, and fenestration. Due to the lack of consideration for periodontal tissues in this study, clinical protocols should be designed based on the periodontal status of the mandibular anterior teeth.

Three-dimensional microanalysis of tooth movement during the first 6 months of orthodontic double retention

INTRODUCTION

This study performed a 3-dimensional analysis of tooth movement during orthodontic retention to assess the effectiveness of double retention (fixed and removable) in preventing undesired tooth movement.

METHODS

One hundred randomly selected patients were included at the initiation of double orthodontic retention with fixed retainers and vacuum-formed splints (recommended to be worn 22 h/d) in both arches. Intraoral scans were performed directly (T0), 1 month (n = 88), 3 months (T2) (n = 78), and 6 months (T3) (n = 66) after retainer bonding. Nine reference points were marked on each tooth in every patient. Subsequent scans were superimposed, and point displacement was calculated. Statistical analysis was performed using the R statistical software (version 4.2.2; R Core Team, Vienna, Austria).

RESULTS

Sample size calculation determined at least 55 patients were needed. The total dropout between T0 and T3 was 34 patients (did not show up for appointment). The median absolute displacement value of a single point between T0 and T3 was 0.015 mm. The most stable teeth were mandibular central incisors, whereas the least stable were mandibular molars. Most tooth displacements occurred between T0 and T2, then slowed down significantly.

CONCLUSIONS

Double orthodontic retention prevents major tooth displacements in most patients during the first 6 months of retention; however, larger, unpredictable single-tooth displacement may occur in individual patients.

The effect of enhanced structure in the posterior segment of clear aligners during anterior retraction: a three-dimensional finite element and experimental model analysis

BACKGROUND

Mesial tipping of posterior teeth occurs frequently during space closure with clear aligners (CAs). In this study, we proposed a new modification of CA by localized thickening of the aligner to form the enhanced structure and investigate its biomechanical effect during anterior retraction.

METHODS

Two methods were employed in this study. First, a finite element (FE) model was constructed, which included alveolar bone, the first premolars extracted maxillary dentition, periodontal ligaments (PDL), attachments and aligners. The second method involved an experimental model-a measuring device using multi-axis transducers and vacuum thermoforming aligners. Two groups were formed: (1) The control group used common CAs and (2) the enhanced structure group used partially thickened CAs.

RESULTS

FE model revealed that the enhanced structure improved the biomechanics during anterior retraction. Specifically, the second premolar, which had a smaller PDL area, experienced a smaller protraction force and moment, making it less likely to tip mesially. In the same vein, the molars could resist movement due to their larger PDL area even though they were applied larger forces. The resultant force of the posterior tooth was closer to the center of resistance, reducing the tipping moment. The canine was applied a larger retraction force and moment, resulting in sufficient retraction of anterior teeth. The experimental model demonstrated a similar trend in force variation as the FE model.

CONCLUSIONS

Enhanced structure allowed force distribution more in accordance with optimal principles of biomechanics during the extraction space closure while permitting less mesial tipping and anchorage loss of posterior teeth and better retraction of anterior teeth. Thus, enhanced structure alleviated the roller coaster effect associated with extraction cases and offered a new possibility for anchorage reinforcement in clear aligner therapy.

Bioceramic micro-fillers reinforce antibiofilm and remineralization properties of clear aligner attachment materials

Introduction: Clear aligners, while offering a more hygienic alternative to fixed appliances, are still associated with challenges including plaque accumulation and enamel demineralization. The aim of the present study was to investigate the antibiofilm and remineralization effectiveness of innovative flowable composite attachments containing bioceramic micro-fillers. Methods: Four experimental attachments were formulated and bonded to human enamel specimens: 3M Filtek Supreme flowable composite (Filtek SF) + 10% bioactive glass 45S5 (BAG), Filtek SF + 30% BAG, Filtek SF + 10% Bredigite (BRT), Filtek SF + 30% BRT. Plaque biofilms were grown on the bonded enamel using a standardized protocol and the biofilm-killing effect was assessed by confocal laser scanning microscopy and scanning electron microscopy. Vickers microhardness was measured to evaluate the remineralization effect of the attachments containing bioceramic fillers after acid challenge. Shear bond test was performed to assess the bonding strength. Results: Attachments with bioceramic fillers significantly inhibited plaque biofilm growth in 3 weeks on enamel, contributing over 20% bacterial cell killing in 10% filler groups and over 30% killing in 30% filler groups. All four experimental groups demonstrated significantly higher microhardness values than the control group without fillers on the attachment side. The shear bonding strength was not compromised in the attachments with micro-fillers. Discussion: Proper incorporation of bioceramic micro-fillers in attachments provides an innovative approach for clear aligner therapy with reinforced antibiofilm and remineralization effects without weakening shear bonding strength.

Alterations in the surface roughness and porosity parameters of directly printed and Invisalign aligners after 1 week of intraoral usage: An in vivo prospective investigation

INTRODUCTION

Direct printing of clear aligners could be the next paradigm shift in modern orthodontics and can potentially overcome the limitation of the indirect production method. This study investigated the effects of 1 week of intraoral usage on the surface roughness parameters of directly printed aligners (DPAs) and commercially produced Invisalign aligners compared with their unused control counterparts using confocal laser scanning microscopy.

METHODS

The study consisted of 4 groups with 34 samples per group. Unused control aligners were allocated to the control groups (DP-Ctr and INV-Ctr). Sixty-eight patients undergoing clear aligner therapy were allocated to group DP-Clin (patients in therapy using DPAs made from TC-85 DAC resin) and group INV-Clin (patients provided with Invisalign aligners). After 1 week of intraoral usage, the aligners were retrieved from the patients in groups DP-Clin and INV-Clin. Samples were made from the buccal surface of the maxillary right central incisor of each aligner and underwent surface roughness and porosity measuring using confocal laser scanning microscopy. The arithmetic mean deviation of the profile, root mean square deviation, maximum peak height, maximum valley depth, maximum height difference among the highest peak and deepest valley, void volume, and void count were measured. Descriptive analysis and median (quantile) regression models were used for data analysis of this experiment.

RESULTS

One week of intraoral usage significantly increased the surface roughness and porosity of DPAs. In contrast, a significant reduction in the surface roughness and porosity parameters of Invisalign aligners was recorded after intraoral service.

CONCLUSIONS

This study suggests an increase in the surface roughness and surface porosity of DPAs following 1 week of intraoral usage, which might lead to an increase in bacterial adhesion and biofilm formation in these aligners.

Three-dimensional measurement and analysis of Mandibular Molar Distalization assisted by micro-implant anchorage combined with clear aligner

Objective

To investigate the effect of micro-implant anchorage combined with a clear aligner on the efficiency of mandibular molar distalization and the protection of anterior teeth anchorage, provide reference for clinical scheme design.

Methods

This is a prospective study. Seventeen patients who were treated in the Orthodontics Department of the Hospital of Stomatology affiliated to Fujian Medical University from 2019 to 2021 and used Invisalign clear aligners to move mandibular molars distally were included and divided into two groups according to anchorage types: Group-A and Group-B. Group-A (ten cases) were treated without micro-implant anchorage, while Group-B (seven cases) were treated with micro-implant anchorage nails for enhanced anchorage. The effect of micro-implant anchorage on crown and root distal movement of mandibular molars and the difference in three-dimensional movement between mandibular molars and mandibular central incisors were analyzed.

Results

The crown distalization efficiency of mandibular first and second molars in Group-B was 68.66% and 71.02%, respectively, which were higher than those in Group-A(p<0.05). The mandibular central incisors in Group-A showed labial displacement and a small amount of elongation, while those in Group-B showed less anchorage loss(p<0.05). In Group-A, the crown was tilted in the distal direction and moved in the buccal direction during mandibular molar distalization(p<0.05). While in Group-B, the crown was tilted in the distal directio (p<0.05) and the mandibular second molar was depressed(p<0.05).

Conclusion

In the process of mandibular molar distalization assisted by micro-implant anchorage combined with a clear aligner, better protects the anchorage of the mandibular central incisor and improves the efficiency of the molar crown distalization.

In vitro analysis of the influence of the thermocycling and the applied force on orthodontic clear aligners

The mechanical properties of polyurethane dental aligners have been studied in an oral environment at 37°C and subjected to thermal cycling between 5°C and 55°C for long periods of time at different mechanical stresses. The aim is to determine the efficacy of the orthodontic aligner at different stress levels, the effect of thermal cycling with therapy time on tooth position correction. Sixty aligners with the same design were studied applying tensions of 0, 3 and 30 N and determining the deformation at different times from 1 to 760 h. Half of these aligners were subjected to stresses submerged in artificial saliva at 37°C and the other half were subjected to thermal cycles between 2°C and 55°C in salivary medium. Deformation was determined using a high-resolution stereo magnifier and ImageJ image analysis software. Water adsorption by the polyurethane was determined at the different test times. The results showed that in the unloaded aligners there is no appreciable deformation, but with thermal cycling there is a light shrinkage of the aligner due to the semi-crystallization process (ordering of polymeric chains) of the polyurethane. When applying loads of 3 and 30 N, creep curves with constant deformation transition zones can be seen. The transition zones decrease as the applied mechanical load increases. In addition, the significant effect of thermal cycling on the reduction of the transition zone of the aligners has been demonstrated. The transition zones are optimal for dental correction as constant stresses are exerted for tooth movement. The effect of thermal cycling shortens the constant deformation zone and reduces tooth alignment time. It was observed that the absorption of water in the aligner is constant after 1 h of immersion and does not exceed 0.4% by weight of absorbed water.

Differential Stability of One-layer and Three-layer Orthodontic Aligner Blends under Thermocycling: Implications for Clinical Durability

Objectives

To optimize the therapeutic usefulness of aligners, it is crucial to understand how their mechanical properties alter with time.

Materials and methods

Specimens from four different brands, including Duran+, CA® Pro, Zendura A, and Zendura FLX, were produced for material testing of thermoplastic orthodontic aligners (TOA) using dimensions measuring 4mm x 10mm. Each brand's 24 samples were split into three groups as follows: G1 being thermoformed, G2 being thermoformed and underwent 500 thermocycles (simulating 7 days), and G3 being thermoformed and underwent 1000 thermocycles (simulating 14 days). Surface roughness, modulus of elasticity in bending, and spectrophotometry were used to assess the effect of aging on TOAs.

Results

After 1000 thermocycles, Duran+ had the highest modulus of elasticity and differed statistically from all other groups. The intragroup comparison showed that only Duran+'s elastic modulus significantly changed after 1000 thermocycles in comparison with the control group. Surface roughness values (Ra), did not statistically differ among brands or thermocycling group measures. The change in chemical properties was not significant in any brand.

Conclusion

One-layer PETG (Duran+) failed to demonstrate stability after in vitro aging, thus suggesting that clinicians should be aware of the change in mechanical properties when using one-layer PETG (Duran +) in a 2 weeks regime.

Construction of silver-coated high translucent zirconia implanting abutment material and its property of antibacterial

High translucent zirconia (HTZ) has excellent mechanical properties, biocompatibility, and good semi-translucency making it an ideal material for aesthetic anterior dental implant abutments without antibacterial properties. In the oral environment, the surface of the abutment material is susceptible to microbial adhesion and biofilm formation, which can lead to infection or peri-implantitis and even implant failure. This study aims to promote the formation of a biological seal at the implant-soft tissue interface by modifying the HTZ surface, using the load-bearing capacity of the aluminosilicate porous structure and the broad-spectrum antibacterial effect of silver nanoparticles to prevent peri-implant bacterial infection and inflammation and to improve the success rate and prolong the use of the implant. FE-SEM (field emission scanning electron microscopes), EDS (energy dispersive spectroscopy), and XPS (X-ray photoelectron spectroscopy) results showed that aluminosilicate non-vacuum sintering can form open micro- and nanoporous structures on HTZ surfaces, and that porous aluminosilicate coatings obtain a larger number, smaller size, and more uniformly shaped silver nanoparticles than smooth aluminosilicate coatings, and could be deposited deeper in the coating. The ICP-AES (inductively coupled plasma-atomic emission spectroscopy) results showed that the early silver ion release of both the smooth silver coating and the porous silver coating was obvious, the silver ion concentration released by the former was higher than that of the latter. However, the silver ion concentration released by the porous silver coating was higher than that of the smooth coating when the release slowed down. Both smooth and porous silver coatings both inhibited E. coli (Escherichia coli), S. aureus (Staphylococcus aureus), and L. acidophilus (L. acidophilus), and porous silver coatings had stronger antibacterial properties. The silver coating was successfully constructed on the surface of HTZ, through aluminium silicate sintering and silver nitrate solution impregnation. It was found that the high concentration environment of silver nitrate solution was more advantageous for nano-Ag deposition, and the non-vacuum sintered porous surface was able to obtain a larger number of nano-Ag particles with smaller sizes. The porous Ag coating exhibited superior antibacterial properties. It was suggested that the HTZ with silver coating had clinical application, and good antibacterial properties that can improve the survival rate and service life of implants.

Accuracy and Retention of Molding Plates Used for Infants with Cleft Lip and Palate Fabricated from Different Materials: A Cross-Sectional Clinical Study

OBJECTIVES

The study aimed to comparatively assess the accuracy and retention of molding plates made of polyethylene terephthalate modified with glycol (PET-G) and polymethyl methacrylate (PMMA) materials, while also investigating the effect of adhesive addition on retention.

DESIGN

A cross-sectional clinical study.

PATIENTS/SETTING

The study included 30 infants diagnosed with non-syndromic cleft lip and palate (16 unilateral, 14 bilateral). Two molding plates were fabricated for each infant, and their accuracy and retention were evaluated. The data were analyzed using independent t-tests, Mann-Whitney U tests, and Wilcoxon rank tests.

MAIN OUTCOME MEASURES

Accuracy: The accuracy of the molding plates was assessed by measuring the virtual gap between the inner surface of the plates and their working cast using Exocad software. The accuracy was evaluated in different regions (anterior, middle, and posterior) and compared between PET-G and PMMA materials. Retention: The retention of the molding plates was measured using a digital force gauge, which recorded the force required to dislodge the plates from the infant's mouth. The retention was compared between PET-G and PMMA materials, as well as the effect of adhesive addition on retention. Overall adaptation; PET-G plates showed a significantly smaller gap (mean= 0.264 ±0.106) compared to PMMA (mean= 0.362 ±0.130). Region-specific adaptation: PET-G plates demonstrated better accuracy in all regions (means of anterior =0.246, middle =0.262, posterior =0.282 µm). Significant differences in accuracy were observed in the middle and posterior regions compared to PMMA. Retention assessment revealed that the PET-G groups (with or without adhesive) exhibited significantly higher retention compared to the PMMA groups (P<0.01).

CONCLUSION

PET-G plates demonstrated superior accuracy and retention compared to PMMA, with a significant difference observed in both accuracy and retention. Furthermore, the addition of denture adhesive had a positive effect on retention for both materials.

Orthodontic Aligners: Current Perspectives for the Modern Orthodontic Office

Orthodontic aligners are changing the practice of orthodontics. This system of orthodontic appliances is becoming the mainstay appliance of choice for orthodontic offices in many countries. Patient preferences and lifestyle needs have made this appliance the primary choice when seeking care. In the early days, appliances lacked the efficiency and effectiveness of traditional bracket-wire systems, but modern systems are now able to handle a more comprehensive orthodontic caseload. Current systems provide newer biomechanical strategies and artificial intelligence-driven tooth movements for better outcomes. These improvements now mean that an orthodontist can be better prepared to manage a larger number of orthodontic malocclusions. This paper aims to discuss some of the evolution of orthodontic aligners and to describe to orthodontists the fundamentals of aligner therapy. In addition, it will provide an evidence-based outcome to the existing treatment outcomes in the current literature.

Clear Aligner Therapy: Up to date review article

The advantages of Clear Aligners Therapy (CAT) include the braces being virtually invisible, comfortable to wear, and removable for eating and brushing; that way, CAT can be used to treat a wide range of orthodontic issues. In 1999, the company Align Technology introduced the frst commercial clear aligner system called Invisalign. The Invisalign system was initially only available to orthodontists, but later became available to general dentists as well. The system quickly gained popularity among patients who were looking for a more discreet and comfortable alternative to traditional braces. In 2000, Align Technology received FDA clearance for the Invisalign system, which further increased its popularity. The biomechanics of clear aligners involve the use of custom-made tooth aligners that are specifcally shaped to guide teeth into desired positions. These aligners are typically made from flexible materials such as polyurethane or ethylene vinyl acetate and are adjusted to apply the necessary forces for tooth movement. Attachment devices, such as power ridges or buttons, are often used to enhance or assist in specifc tooth movements and for retention of the aligner. The use of attachments allows for the exertion of desired force on the teeth, which is crucial for the success of Clear Aligner Therapy. CAT should be used if patients are concerned about the esthetic appearances of their teeth-for example, actors and other individuals that rely on their appearances in public in a professional context-and if the misalignment is not severe, so that clear aligners can still work. One should not use CAT in cases of severe crowding or spacing issues that require extractions. If the patient has complex jaw discrepancies or skeletal issues or if teeth need to be moved extensively in multiple directions, CAT is likely not going to be strong enough. In conclusion, Clear Aligner Therapy is a safe, effective, and convenient orthodontic treatment option that offers patients a virtually invisible way to achieve a straighter, more beautiful smile. With continued advancements in technology and a growing body of research supporting its effectiveness, the future of Clear Aligner Therapy looks bright.

Coronal Repercussions of the Maxillary Central Incisor Torque in the First Set of Aligners: A Retrospective Study

Coronal torque is one of the key factors in orthodontic treatment. An adequate torque value has an impact on aesthetics and soft tissue profile. The aim of this quantitative, comparative and observational longitudinal cohort study was to analyze the efficacy of the maxillary central incisor coronal torque in the Invisalign® system and evaluate the relation between coronal torque movement and patient's facial biotype. In total, 27 patients were selected. The planned movements (TP) were obtained from the Invisalign Doctor Site® using mathematical formulas that consider the T0 measurements. Pre-treatment (T0) and after full use of the first set of aligners (T1) scanners were evaluated using Geomagic® Control X TM by superimposing T0 and T1 models using a transverse plane and the long axis of the tooth crown. IBM® SPSS® software was used for statistical purposes. We found statistically significant differences between T0 and T1 in pro-inclination and retro-inclination, as well as between achieved and planned values in pro-inclination (p = 0.011). We verified that hyperdivergent clinical cases presented higher mean values of coronal torque, and hypodivergent cases presented lower values. In pro-inclination, the differences between the planned and achieved values were greater in hypodivergent cases and smaller in hyperdivergent cases. In retro-inclination, the differences between the planned and achieved values were greater in normodivergent cases and smaller in hypodivergent cases. This study highlights that inefficacy is more accentuated in pro-inclination. Aligners are an effective tool for producing coronal repercussions of torque movement, being more effective in retro-inclination.

Development of an antibacterial polypropylene/polyurethane composite membrane for invisible orthodontics application

In virtue of the advantages, such as aesthetics, designability, convenient removal, and comfortable experience, invisible orthodontics (IO) have been widely recognized and accepted by the public. However, most of the membranes currently used for IO only meet the requirement of shape retention. Other vital functions, like antibacterial and antifouling activities, are neglected. Herein, antibacterial composite membranes (ACMs) containing polypropylene (PP), thermoplastic polyurethane (TPU) and poly (hexamethylene guanidine) hydrochloride-sodium stearate (PHMG-SS) were facilely manufactured through the hot-pressing membrane forming technology. ACMs were conferred with favorable transparency (∼70% in the visible light range) and excellent antibacterial ability. Experiment results demonstrated that bactericidal rates of ACMs against Staphylococcus aureus, Escherichia coli and Streptococcus mutans were larger than 99.99%. Noticeably, the amount of protein adhered on the surface of ACMs was only 28.1 μg/cm², showing ideal antifouling performance. Collectively, the mutifunctional ACMs in the study are expected to be prominent alternatives for existing IO.

Comparison of translucency, thickness, and gap width of thermoformed and 3D-printed clear aligners using micro-CT and spectrophotometer

The present study compared the thickness and gap width of thermoformed and 3D-printed clear aligners (CAs) using micro-computed tomography (micro-CT) and evaluated their translucency using spectrophotometer. Four groups of CAs were tested: thermoformed with polyethylene terephthalate glycol (TS) or copolyester-elastomer combination (TM), and 3D-printed TC-85 cleaned with alcohol (PA) or with centrifuge (PC). CIELab coordinates were measured (n = 10) to evaluate translucency. CAs (n = 10) were fitted onto respective models and micro-CT was performed to evaluate the thickness and gap width. Thickness and gap width were measured for different tooth type and location in sagittal sections on all sides. The PC group showed significantly higher translucency than the PA group, which was similar to the TS and TM groups (p < 0.01). After the manufacturing process, thickness reduction was observed in the thermoformed groups, whereas thickness increase was observed in the 3D printed-groups. The TM group showed the least gap width amongst the groups (p < 0.01). Thermoformed and 3D-printed CAs had significantly varied thicknesses and regions of best fit depending on the tooth type and location. Differences in the translucency and thickness of the 3D-printed CAs were observed depending on the cleaning methods.

Microbiological evaluation in invisible aligner chemical cleaning methods against Candida albicans and Streptococcus mutans

INTRODUCTION

This study aimed to assess the efficacy of chemical agents in removing Candida albicans and Streptococcus mutans biofilm from invisible aligners.

METHODS

The samples were made of EX30 Invisalign trays, biofilm was cultured by standardized suspensions of C. albicans ATCC strain and S. mutans clinical strain on the sample. The treatments used were 0.5% sodium hypochlorite (NaClO) (20 minutes), 1% NaClO (10 minutes), chlorhexidine (5 minutes), peroxide (15 minutes), and orthophosphoric acid (15 seconds). The control group received phosphate-buffered saline for 10 minutes. The colony-forming units per milliliter of each microorganism were determined by serial dilutions seeded in plates with selective culture mediums for each one. Data were analyzed by the Kruskal-Wallis and Conover-Iman tests at an α of 0.05.

RESULTS

For the C. albicans biofilm group, the control group had 9.7 Log10 of microorganism growth, and all treatment groups had statistically significant biofilm reduction, in which chlorhexidine presented the highest inhibition of 3 Log10, followed by alkaline peroxide and orthophosphoric acid both with 2.6 Log10, 1% NaClO (2.5 Log10), and 0.5% NaClO (2 Log10). As for S. mutans, the control group had 8.9 Log10 of growth, and a total microorganism inhibition was reached by chlorhexidine, 1% NaClO, and orthophosphoric acid, whereas alkaline peroxide inhibited growth to 7.9 Log10 and 0.5% NaClO 5.1 Log10.

CONCLUSIONS

Within the limitations, chlorhexidine and orthophosphoric acid had greater efficacy in both biofilms. In addition, 1% NaClO and alkaline peroxide also had significant effects; therefore, their incorporation aligners disinfection protocols are valid.

Resistance of PETG Materials on Thermocycling and Brushing

The aim was to assess the impact of thermocycling and brushing on the surface roughness and mass of PETG material-the most commonly used for orthodontic retainers. A total of 96 specimens were exposed to thermocycling and brushing with three different kinds of toothbrushes depending on the number and thickness of the bristles. Surface roughness and mass were evaluated three times: initially, after thermocycling, and after brushing. In all four brands, both thermocycling and brushing increased surface roughness significantly (p < 0.001), with Biolon having the lowest and Track A having the highest. In terms of brushing, only Biolon samples showed statistically significant increased roughness after brushing with all three types of brushes, in comparison to Erkodur A1, where differences were not statistically significant. Thermocycling increased the mass of all samples, but a statistically significant difference was found only in Biolon (p = 0.0203), while after brushing, decreased mass was found in all specimens, statistically significant only in Essix C+ (CS 1560: p = 0.016). PETG material showed instability when exposed to external influences- thermocycling produced an increase in roughness and mass, and brushing mostly caused an increase in roughness and decrease in mass. Erkodur A1 demonstrated the greatest stability, whereas Biolon demonstrated the lowest.