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.

Game-based learning in orthodontic education: a systematic review.

OBJECTIVE: To evaluate educational impact of game-based learning (GBL) in orthodontic education. METHODS: A systematic search was undertaken across four databases (Scopus, PubMed, ProQuest Dissertations & Theses Global, and Google Scholar) to identify relevant articles published from January 2000 to December 2023. Additionally, the reference lists of identified literature were examined to further search for relevant literature. The last search was performed on 28 January 2024. RESULTS: Following the article selection process, seven articles were included in this systematic review, comprising four randomized control trials and three questionnaire surveys. Six articles were assessed to have a moderate risk of biases, whereas one research exhibited a low risk of bias. GBL interventions assessed in five articles were designed in digital format, while one study implemented evaluated traditional learning, and another employed a card game format. Two RCTs indicated a greater effectiveness of GBL in enhancing learner performance compared to traditional learning methods, while one article found no significant difference. Across all articles, positive perceptions of GBL were consistently highlighted at both undergraduate and postgraduate levels. CONCLUSION: This systematic review supports the potential of GBL in orthodontic education. The implementation of GBL is recommended to integrate entertaining and educational elements, fostering learner performance within engaging learning environments. However, it is imperative to acknowledge that the overall quality of evidence is limited, primarily due to the moderate risk of biases identified in six of the included articles. Consequently, further high-quality experimental studies are required to validate the effectiveness of GBL in orthodontic education.

The accuracy of virtual setup in simulating treatment outcomes in orthodontic practice: a systematic review.

OBJECTIVES: To evaluate the accuracy of virtual orthodontic setup in simulating treatment outcomes and to determine whether virtual setup should be used in orthodontic practice and education. MATERIALS AND METHODS: A systematic search was performed in five electronic databases: PubMed, Scopus, Embase, ProQuest Dissertations & Theses Global, and Google Scholar from January 2000 to November 2022 to identify all potentially relevant evidence. The reference lists of identified articles were also screened for relevant literature. The last search was conducted on 30 November 2022. RESULTS: This systematic review included twenty-one articles, where all of them were assessed as moderate risk of bias. The extracted data were categorized into three groups, which were: (1) Virtual setup and manual setup; (2) Virtual setup and actual outcomes in clear aligner treatment; (3) Virtual setup and actual outcomes in fixed appliance treatment. There appeared to be statistically significant differences between virtual setups and actual treatment outcomes, however the discrepancies were clinically acceptable. CONCLUSION: This systematic review supports the use of orthodontic virtual setups, and therefore they should be implemented in orthodontic practice and education with clinically acceptable accuracy. However, high-quality research should be required to confirm the accuracy of virtual setups in simulating treatment outcomes.

Accuracy of the Intraoral Scanner for Detection of Tooth Wear.

OBJECTIVE: The aim of this work was to study the accuracy of the intraoral scanner for detection of tooth wear in natural teeth by using micro-computed tomography (micro-CT) as a gold standard. MATERIALS AND METHODS: Twenty premolars were prepared, fixed in acrylic blocks, and scanned with an intraoral scanner (iTero Element® 2) and micro-CT for baseline reference images before artificial tooth wear induction. The samples were then scrubbed with abrasive sandpaper 20 times and scanned with the intraoral scanner. They were then superimposed with the reference images utilising the "TimeLapse" feature of the scanner until the abraded area appeared yellow, indicating tooth surface loss in the 50-200 µm range. The same samples were then rescanned by micro-CT to measure the actual tooth surface loss. This procedure was repeated for the subsequent experimental tooth surface loss of 200-400 µm range (orange areas) and 400-750 µm range (red areas). The collected data were analysed for sensitivity, positive predictive value (PPV), and accuracy. Level of statistical significance was set at .05. RESULTS: In the detection of experimental tooth surface loss, the specificity, PPV, and accuracy of the intraoral scanner were 98%, 98%, and 97%, respectively. CONCLUSIONS: The iTero® intraoral scanner can be recommended to be a suitable screening tool for tooth wear in routine dental practice.

Influence of functional and esthetic expectations on orthodontic pain.

OBJECTIVES: To investigate the effect of orthodontic treatment outcome (OTO) expectations on the level of pain intensity experienced after orthodontic elastomeric separation (OES). MATERIALS AND METHODS: A total of 100 orthodontic patients (74 female and 26 male, age 14 years and above) from the Faculty of Dentistry, Mahidol University were enrolled. Before OES, questionnaires were administered to obtain patients' expectations regarding various aspects of OTO as well as OES pain expectations. Real-time self-reported pain intensity from OES at the maxillary and mandibular first permanent molars was obtained before and immediately after separator placement and at 6 h, 24 h, and then every day until day 7 after OES. Data were analyzed for the relationship between OTO expectations and OES pain intensity. The level of significance was set at 0.05. RESULTS: The maximum OES pain intensity occurred on day 2 after OES and gradually decreased to the pretreatment level on day 7. The degree of facial, tooth alignment, masticatory function improvement expectations, and a high level of OES pain expectations were significantly associated with the severity of OES pain after separator placement. CONCLUSION: Esthetic and functional expectations of OTO were significantly associated with OES pain intensity. Thus, knowledge about esthetic and functional expectations may help to predict patient's pain response to orthodontic treatment.

The Protocol of Low-level Laser Therapy in Orthodontic Practice: A Scoping Review of Literature.

Low-level laser therapy (LLLT) has been widely investigated as an adjunct technique for orthodontic treatment due to photobiomodulation effect. LLLT appears to be supportive for an orthodontic practice in terms of tooth movement acceleration, pain relief, and root resorption management. The decrease in these adverse effects will enhance the compliance in orthodontic patients, which could positively impact treatment outcomes. However, there seemed to be inconsistency in the impact of LLLT as well as its laser and treatment parameters. This scoping review aimed to evaluate the impact of different irradiation parameters on tooth movement acceleration, pain relief, and root resorption as well as to construct a protocol of LLLT in orthodontic practice. The search was conducted across PubMed, Scopus, Web of Science, Embase, Google Scholar, and the reference lists of identified articles. The last search was conducted on October 10, 2021 to identify experiments in humans regarding the application of LLLT as noninvasive treatment in orthodontic practice published between 2010 and 2021. However, they were excluded if they were not clinical research, if they did not report the source of laser, or if they were not relevant to tooth movement, pain perception, and root resorption, or if they were not available in English or in full-text. Following the systematic search and selection process, 60 articles were included in this review. A majority of included articles were published in the past few years. The findings of this review supported the application of LLLT in orthodontic practice with purposes of tooth movement acceleration and pain reduction. The positive impact of LLLT on root resorption had not been clearly evident yet. As this review demonstrated heterogeneity of both laser and treatment parameters, further research should be required to ensure the effectiveness of its specific parameters in orthodontic practice.

A Novel Alveolar Distractor Incorporating Nickel-Titanium Alloy Springs: A Preliminary In Vitro Study.

A new design of an alveolar distractor using nickel−titanium (NiTi) open-coil springs was developed and investigated to produce distraction forces against the tensile forces of porcine attached gingiva to simulate human gingiva. We subjected 15 mm long NiTi open-coil springs (Highland and ORMCO) with three levels of forces (light, medium and heavy) to mechanical testing in a 37 ± 1 °C water bath. Ten strips of porcine mandibular attached gingiva were subjected to tensile tests to determine the resistance force. The forces from the springs were compared with the tensile forces from the porcine attached gingiva. Data between groups were analyzed with independent-samples T-tests (p-value < 0.05). The tensile strength and the Young modulus were greater in buccal compared to lingual porcine attached gingiva. Compared to other spring dimensions and companies, forces generated from 0.014 × 0.036″ ORMCO springs were the highest and could overcome the tensile resistance from porcine attached gingiva over the longest distraction range of 1.6 mm. This preliminary in vitro study introduced a new design of an alveolar distractor incorporated with NiTi open-coil springs that could generate light and continuous forces to overcome the resistance from porcine attached gingiva.

The Effects of Temperature and Time of Heat Treatment on Thermo-Mechanical Properties of Custom-Made NiTi Orthodontic Closed Coil Springs.

Nickel-Titanium (NiTi) springs have been increasingly used in orthodontics; however, no optimum condition of heat treatment has been reported. Therefore, this research was conducted to determine the optimum heat-treatment temperature and duration for the fabrication of NiTi-closed coil springs by investigating their effects on thermo-mechanical properties. As-drawn straight NiTi wires of 0.2 mm diameter were used to fabricate closed coil springs of 0.9 mm lumen diameter. The springs were heat-treated at three different temperatures (400, 450, and 500 °C) with three different durations (20, 40, and 60 min). Electron Probe Micro-Analysis (EPMA) and Differential Scanning Calorimetry (DSC) were used to investigate element composition and thermo-mechanical properties, respectively. Custom-made NiTi closed coil springs composed of 49.41%-Ti and 50.57%-Ni by atomic weight, where their DSC curves of 500 °C presented the obvious endothermic and exothermic peaks, and the austenite finish temperature (Af) were approximately 25 °C. With increasing temperature, deactivation curves presented decreased plateau slopes generating higher superelastic ratios (SE ratios). At 500 °C, closed coil springs showed superelastic tendency with lower stress hysteresis. The thermo-mechanical properties were significantly influenced by heat-treatment temperature rather than duration. The optimum parameter appeared to be 500 °C for 40 min to produce appropriate force delivery levels, relatively low plateau slope, and lower hysteresis for orthodontic use.

The effect of LED photobiomodulation on the proliferation and osteoblastic differentiation of periodontal ligament stem cells: in vitro.

BACKGROUND: The aim of this study was to investigate the influence of three different light-emitting diode (LED) wavelengths on the proliferation and osteoblastic differentiation of periodontal ligament stem cells (PDLSCs) in vitro. METHODS: PDLSCs seeded on 96- and 24-well plates, for proliferation and osteoblastic differentiation, respectively, were irradiated daily by LED light with peak emission wavelengths of 630, 680, and 830 nm at constant energy densities of 3.5 J/cm2. Cultures were grown for 8 days for the proliferation assay, 10 days for the alkaline phosphatase (ALP) assay, and 28 days for Alizarin red staining. Mitochondrial activity, ALP enzyme level, and the ability to form calcium phosphate deposits were measured and compared across cultures. RESULTS: Results obtained from statistical analysis of the experimental data indicated that the rate of proliferation (P < 0.05) in 830-nm irradiated cultures were significantly higher than the control samples at day 6 and 8; whereas, for the 630- and 680-nm groups, test results showed lower proliferation rates at day 8. For osteoblastic differentiation, significantly greater mineralization than the control samples was detected in the red-light groups (630 and 680 nm) during the late differentiation period (P < 0.001), which was supported by a higher ALP activity of the 630- and 680-nm groups in the early stage (P < 0.01). CONCLUSION: The results of this study demonstrate that the PDLSCs responded differently to specific LED wavelengths. For enhancing cellular proliferation, 830-nm LED irradiation was more effective. On the other hand, the wavelengths of 630 and 680 nm were better for stimulating osteoblastic differentiation.

The effect of light-emitting diode irradiation at different wavelengths on calcification of osteoblast-like cells in 3D culture.

This study aimed to investigate the effect of four different light-emitting diode (LED) wavelengths on calcification and proliferation of osteoblast-like cells in vitro. MC3T3-E1 cells were seeded within three-dimensional collagen scaffolds and irradiated daily by LED light with peak emission wavelengths of 630-, 680-, 760- and 830-nm at constant fluency of 3.1 J/cm(2) (irradiance intensity 2 mW/cm(2)). Cultures were measured for calcium content at day 0, 7, 14, 21, 28, 35 and 42. The significant enhancement in calcium content was observed at the early stage of culture (days 7 and 14) (p<;0.05). After that, the calcium content of irradiated groups was similar to that of the controls group. This suggests the transient effect of light irradiation on osteoblastic cell calcification. Only 680-nm irradiated samples revealed a significant enhancement of calcium content until the late stages of culture (from days 21 to 42) (p<;0.001). The cyclin D mRNA expression that was investigated 3 hours after stimulation at day3 also show that the 680-nm LED irradiation can enhance cyclin D expression more than others. For enhancing bone mineralization, LED irradiation at the 680-nm is more effective than those at 630-, 760- and 830-nm. Further studies should be investigated in order to obtain the most effective parameters of LLLI on bone regeneration in clinical setting.

The effect of different surface preparation techniques on the survival probabilities of orthodontic brackets bonded to nanofill composite resin.

OBJECTIVE: To analyze the survival probabilities of different surface preparation techniques for bonding brackets to nanofill composite resin. DESIGN: In vitro, laboratory study. SETTING: Mahidol University, Bangkok, Thailand. MATERIALS AND METHODS: Thirty-five nanofill composite resin specimens/group were subjected to four surface preparation techniques as follows: (1) sandblast using aluminium oxide powder of 90 microm; (2) abrasion using diamond bur; (3) hydrofluoric acid etching for 2 min; and (4) 37% orthophosphoric acid etching for 30 s. Plastic conditioner was applied then brackets were bonded. Shear bond strength tests were carried out on a universal testing machine. MAIN OUTCOME MEASURES: Shear bond strength (MPa) and debonding force (N) were analyzed using Weibull analysis. RESULTS: The maximum stress and debonding force levels with a 95% probability of survival ranking from highest to lowest were: (1) sandblast group (4.2 MPa, 45.5 N); (2) diamond bur group (2.2 MPa, 25.3 N); (3) orthophosphoric group (1.9 MPa, 19.8 N); and (4) hydrofluoric group (0.8 MPa, 10.9 N). There was a significant difference in the adhesive remnant index scores between the surface preparation techniques (chi squared P<0.001). CONCLUSION: Bonding orthodontic brackets to nanofill composite resin materials may result in lower bond strengths and special surface preparation techniques might be required to avoid increased numbers of bond failures. Surface treatment with sandblasting followed by plastic conditioner could increase the survival probability. The use of a diamond bur, orthophosphoric etching or hydrofluoric etching cannot be recommended.