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.

Surface Topography of Thermoplastic Appliance Materials Related to Sorption and Solubility in Artificial Saliva

(1) Background: PETG (polyethylene terephthalate glycol) is a transparent, inexpensive, and versatile thermoplastic biomaterial, and it is increasingly being used for a variety of medical applications in dentistry, orthopedics, tissue engineering, and surgery. It is known to have remarkable properties such as tensile strength, high ductility, and resistance to chemical insults and heat, but it can be affected by various environmental conditions. The aim of the present study was to evaluate the topographical characteristics of four thermoplastic dental appliance materials in relation to water sorption in simulated oral environments (artificial saliva samples with different pH values). (2) Methods: The following four types of PETG clear thermoplastic materials were selected for the present study: Leone (L), Crystal (C), Erkodur (E), and Duran (D). In relation to the desiccation and water-uptake stages, their water sorption (Wsp) and solubility (Wsl) were calculated, and the surface topographies were analyzed on two length scales. The surface roughness was determined using a contact profilometer, and nanoroughness measurements were generated by three-dimensional profiles using an atomic force microscope (AFM). Statistical analyses (one-way ANOVA and unpaired and paired Student t-tests) were performed. (3) Results: After saliva immersion, the weights of all samples increased, and the highest sorption was recorded in a basic environment. Among the materials, the water uptake for the L samples was the highest, and for E, it was the lowest. In relation to water solubility, significant values were registered for both the L and C samples' materials. After immersion and desiccation, a decreasing trend in microroughness was observed. The AFM high-resolution images reflected more irregular surfaces related to saliva immersion. (4) Conclusions: The sorption rates recorded in water-based artificial saliva were higher for basic pH levels, with significant differences between the samples. There were also significant differences related to the behaviors of the materials included in the study. In relation to roughness, on a microscale, the surfaces tended to be smoother after the saliva immersions, and on a nanoscale, they became more irregular.

Enhancing Orthodontic Renewal and Retention Techniques: A Systematic Review

Orthodontists have a variety of options available for retainers. Research in Orthodontics focuses on assessing outcomes important to clinicians; however, there is inconsistency in how these outcomes are selected and evaluated. This review sought to assess the effects of different orthodontic retainers on patients' quality of life (QoL). Various approaches were employed in this systematic review, and a thorough search was conducted across six databases. The review involved a comprehensive evaluation of six included studies, highlighting changes in dental structure post-treatment, emphasizing the role of extraction procedures and the quality of debonding in improving retention. The study identified key outcomes for orthodontic clinical trials, highlighting orthodontists' preferences for specific retainer types. Moreover, it discussed the impact of sociocultural influences on retention care. Involving patients actively in discussions about whether to end or extend the retention phase was deemed essential. Noteworthy improvements in occlusal outcomes were linked to extraction treatments. Gender and malocclusion severity influenced QoL before and after orthodontic treatment. The degree of improvement observed in the Class III malocclusion group was comparatively lower than that in the Class I and Class II groups. Orthodontic treatment was found to yield favorable psychological outcomes, as evidenced by notable enhancements in self-esteem and social engagement among individuals. Fixed appliances were shown to negatively affect oral health-related quality of life (OHRQoL), particularly for those with aesthetic and functional concerns. A consensus has been reached on the essential themes and outcomes that should be incorporated in clinical trials related to orthodontic retention for non-cleft and non-surgical cases.

Coffee Staining and Simulated Brushing Induced Color Changes and Surface Roughness of 3D-Printed Orthodontic Retainer Material

This in vitro study evaluated the influence of combined coffee staining and simulated brushing-induced color changes and surface roughness on 3D-printed orthodontic retainers. Specimens measuring 10 × 10 × 0.75 mm³ were obtained either by conventional vacuum forming or 3D printing at four print angulations (0°, 15°, 30°, and 45°) (n = 10). The prepared specimens were immersed in a coffee beverage and then mechanically brushed using a simulating device. The specimen's color difference (ΔE) and surface roughness (Ra) were quantified using a spectrophotometer and a non-contact profilometer, respectively. The highest and lowest mean ΔE values were recorded for the 3D-printed-45° (4.68 ± 2.07) and conventional (2.18 ± 0.87) groups, respectively. The overall mean comparison of ΔE between the conventional and 3D-printed groups was statistically significant (p < 0.01). After simulated brushing, all groups showed a statistically significant increase in the Ra values (p < 0.01). The highest Ra was in the 3D-printed-45° (1.009 ± 0.13 µm) and conventional (0.743 ± 0.12 µm) groups, respectively. The overall ΔE of 3D-printed orthodontic retainers was not comparable to conventional VFRs. Among the different angulations used to print the retainers, 15° angulations were the most efficient in terms of color changes and surface roughness and were comparable to conventional VFRs.

Direct 3D-Printed Orthodontic Retainers. A Systematic Review

Three-dimensional (3D) printing technology has shed light on many fields in medicine and dentistry, including orthodontics. Direct 3D-printed prosthetics, implants or surgical devices are well-documented. The fabrication of orthodontic retainers using CAD technology and additive manufacturing is an emerging trend but the available data are scarce. The research approach of the present review included keywords in Medline, Scopus, Cochrane Library and Google Scholar up to December 2022. The searching process concluded with five studies eligible for our project. Three of them investigated directly 3D-printed clear retainers in vitro. The other two studies investigated directly 3D-printed fixed retainers. Among them, one study was in vitro and the second was a prospective clinical trial. Directly 3D-printed retainers can be evolved over time as a good alternative to all the conventional materials for retention. Devices that are 3D-printed are more time and cost efficient, offer more comfortable procedures for both practitioners and patients and the materials used in additive manufacturing can solve aesthetic problems, periodontal issues or problems with the interference of these materials with magnetic resonance imaging (MRI). More well-designed prospective clinical trials are necessary for more evaluable results.

Wear and fatigue resistance: An in-vitro comparison of three polyethylene terephthalate glycol and thermoplastic polyurethane materials for vacuum-formed retainers

OBJECTIVE

To test the wear and fatigue resistance of three materials (Essix ACE®, Taglus®, and Zendura A®) for the fabrication of vacuum-formed retainers in an artificial oral environment.

MATERIAL AND METHODS

Wear resistance was tested by subjecting 21 retainers of each Essix ACE®, Taglus®, and Zendura A® to 12,000 wear cycles at 75N to simulate one year of retainer wear with moderate nighttime bruxing. Post-wear retainer thickness was compared to baseline measurements to calculate wear depth. Fatigue resistance was tested by flexing 15 retainers of each material at an angle of 25 degrees for 1,825 cycles to simulate one year of removing and reinserting a retainer five times per day. Retainers were visually inspected for fractures. Pairwise t-tests with correction using Tukey's method were used to determine significant differences between materials.

RESULTS

The mean wear depths were 0.155±0.021mm, 0.168±0.031mm, and 0.096±0.033mm for Essix ACE®, Taglus®, and Zendura A®, respectively. The wear depth of Zendura A® was significantly lower than that of both Essix ACE® (P<0.001) and Taglus® (P<0.001). There was no significant difference in wear depth between Essix ACE® and Taglus® (P=0.312). Under the parameters set for the fatigue resistance test, fractures did not occur on any of the tested materials.

CONCLUSIONS

Under the assumption of moderate nighttime bruxing for one year, Zendura A® is the most wear-resistant among the materials tested. With the assumption of retainer removal and reinsertion five times per day for one year, all three materials tested have the same ability to resist fatigue.

Orthodontic treatment with miniscrew anchorage: Analysis of quality of information on YouTube

INTRODUCTION

The evaluation of the quality of information (QOI) and clarity of information (COI) among oral health-related videos on the video-streaming Web site YouTube is scarce. This study evaluated QOI and COI regarding temporary anchorage devices contained within videos uploaded by dental professionals (DPs) on YouTube.

METHODS

YouTube videos were systematically acquired with 4 search terms. The top 50 videos per search term by the number of views were stored in a YouTube account. A set of inclusion/exclusion criteria were applied, videos were assessed for viewing characteristics, a 4-point scoring system (0-3) was applied to evaluate QOI in 10 predetermined domains, and a 3-point scoring system (0-2) was applied to evaluate COI. Descriptive statistical analyses and intrarater and interrater reliability tests were performed.

RESULTS

Strong intrarater and interrater reliability scores were observed. Sixty-three videos from the top 58 most-viewed DPs were viewed 1,395,471 times (range, 414-124,939). Most DPs originated from the United States (20%), and orthodontists (62%) uploaded most of the videos. The mean number of reported domains was 2.03 ± 2.40 (out of 10). The mean overall QOI score per domain was 0.36 ± 0.79 (out of 3). The "Placement of miniscrews" domain scored highest (1.23 ± 0.75). The "Cost of miniscrews placement" domain scored the lowest (0.03 ± 0.25). The mean overall QOI score per DP was 3.59 ± 5.64 (out of 30). The COI in 32 videos was immeasurable, and only 2 avoided using technical words.

CONCLUSIONS

The QOI related to temporary anchorage devices contained within videos provided by DPs through the YouTube Web site is deficient, particularly in the cost of placement. Orthodontists should be aware of the importance of YouTube as an information resource and ensure that videos related to temporary anchorage devices contain comprehensive and evidence-based information.

Evaluation of relapse with thermoplastic retainers equipped with microsensors

OBJECTIVES

To examine relapse with thermoplastic retainers equipped with microsensors 1 year after treatment.

MATERIALS AND METHODS

A total of 42 patients (29 females, 13 males) treated with four premolar extractions were included in this study. Thermoplastic appliances equipped with TheraMon microsensors (Handelsagentur Gschladt, Hargelsberg, Austria) were used to assess daily wear time (DWT), and the patients were monitored at 2-month intervals for a period of 12 months. At the end of the follow-up, the following two groups were formed based on the mean DWT: short wear time (SWT; <9 h/d) and long wear time (LWT; ≥9 h/d). Digital models were constructed before treatment (T0), at debonding (T1), and 6 months (T2) and 12 months (T3) after debonding. Little's Irregularity Index (LII) and the intercanine and intermolar widths, arch lengths, overjet, and overbite were calculated based on the digital models. Data were analyzed statistically.

RESULTS

Irregularity and overjet increased, whereas transverse measurements and arch lengths decreased with time in both groups. During the retention period, overbite decreased in the SWT group but increased in the LWT group. There were significant differences between groups only in mandibular irregularity. The LII values of the SWT group were significantly higher than those of the LWT group for the T1-T2 and T1-T3 time intervals (P < .05).

CONCLUSIONS

A mean DWT less than 9 hours/day was inadequate for controlling irregularity within clinically acceptable limits. A wear time of at least 9 h/d is recommended for the maintenance of mandibular anterior alignment.

Orthodontic Bonded Retainers: a Narrative Review

Indefinite retention is now considered essential to prevent relapse after orthodontic treatment. Compliance with removable retainer wear is suboptimal and appears to decline with time post-treatment. As a result, use of bonded retainers may become more commonplace in the future. In this narrative review, the characteristics of bonded retainers are outlined and a summary of the evidence from randomized clinical trials regarding their effectiveness is provided. Guidance is also offered regarding care and maintenance.

CPD/Clinical Relevance: All general dental practitioners (GDPs) should be familiar with types of bonded retainers, evidence relating to their effectiveness and the GDP's role regarding their care and maintenance.

A survey of retention and retainer practices of orthodontists in Australia

Objective

To survey retention and retainer practices of orthodontists in Australia.

Methods

A pilot-tested e-survey was distributed to 502 eligible members of the Australian Society of Orthodontists (ASO). The questions addressed participant background information, preferred retainer and retention practices, retainer characteristics and factors influencing retainer choice. Statistical analyses were performed using PASWH version 18.

Results

The response rate was 58%. Thermoplastic retainers (TRs) were the most commonly chosen retainer in the maxilla (39.4%) and bonded retainers (BRs) were most commonly chosen in the mandible (38.5%). An initial period of full-time wear of removable retainers (RRs) was prescribed by 37.7–48.3%. ‘Night/sleeping with reducing frequency over time’ was the most commonly prescribed part-time RR wear practice (28.1-33.5%).

Indefinite retainer wear was recommended by 85.3-87.4% of orthodontists. Indefinite retainer checks were carried out by 19.1-19.8% of orthodontists while 28.9-43.6% were ‘not happy’ for general dental practitioners (GDPs) to continue retention checks. Adjunctive retention practices were used by 25.6-72.8%. Pre-fabrication TR sheet thickness of 1.0 mm (68%) and polypropylene co-polymer/ethylene material type (55.8%) were most commonly used. Vacuum-forming was the preferred mode of TR fabrication by 48.4%. ‘Stainless steel single strand round’ was the most commonly used BR material type (33.4%). BR bonded to 12-22 (bonded to four teeth) was the most common BR design in the maxilla (48.8%) and 33-43 (bonded to six teeth) was most commonly chosen for the mandible (81.5%). Inadvertent tooth movement associated with BRs was observed by 62%. The orthodontist factor that most influenced retainer choice was the nature of the pretreatment malocclusion (88%).

Conclusion

Although there is agreement that retention is indefinite, orthodontic retention practices and retainer characteristics vary considerably between orthodontists in Australia. Greater communication between orthodontists and GDPs is required to effectively manage retention over the long term.

Valid consent and orthodontic treatment

Valid patient consent is a legal and ethical principle that is fundamental to healthcare provision. Oral health practitioners (OHPs) must understand the principles that need to be addressed to ensure that the consent given by a patient is valid. Failure to obtain consent may result in a negligence claim or a complaint of professional misconduct against the OHP. Orthodontic treatment is mostly elective but is not without risk to the patient. Obtaining and maintaining valid consent for orthodontic treatment presents additional challenges in comparison with other dental procedures as the treatment lasts over a longer time and is most commonly performed in adolescents. In addition, prospective patients need to be informed regarding ‘lifelong’ management in the retention phase to minimise the risk of relapse. The present paper outlines the principles of valid consent with particular regard to orthodontic treatment in the adolescent patient. OHPs must ensure that they are satisfied that the competent patient has the capacity to voluntarily consent. Clinicians must also recognise that valid consent is not a one-off ‘tick the box’ procedural exercise but an ongoing process of effective information sharing in light of changing laws and an ever-changing scientific evidence base within a patient-centred model of healthcare.