An in vitro comparison of the dimensional stability of four 3D-printed models under various storage conditions.

OBJECTIVES: To investigate the dimensional stability of various 3D-printed models derived from resin and plant-based, biodegradable plastics (PLA) under specific storage conditions for a period of up to 21 weeks. MATERIALS AND METHODS: Four different printing materials, including Draft V2, study model 2, and Ortho model OD01 resins as well as PLA mineral, were evaluated over a 21-week period. Eighty 3D-printed models were divided equally into two groups, with one group stored in darkness and the other exposed to daylight. All models were stored at a constant room temperature (20°C). Measurements were taken at 7-week intervals using the Inspect 3D module in OnyxCeph software (Image Instruments GmbH, Chemnitz, Germany). RESULTS: Dimensional change was noted for all of the models with shrinkage of up to 0.26 mm over the study period. Most contraction occured from baseline to T1, although significant further contraction also arose from T1 to T2 (P < .001) and T1 to T3 (P < .001). More shrinkage was observed when exposed to daylight overall and for each resin type (P < .01). The least shrinkage was noted with Ortho model OD01 resin (0.16 mm, SD = 0.06), and the highest level of shrinkage was observed for Draft V2 resin (0.23 mm, SD = 0.06; P < .001). CONCLUSIONS: Shrinkage of 3D-printed models is pervasive, arising regardless of the material used (PLA or resin) and being independent of the brand or storage conditions. Consequently, immediate utilization of 3D printing for orthodontic appliance purposes may be preferable, with prolonged storage risking the manufacture of inaccurate orthodontic retainers and appliances.

Impact of fixed orthodontic retainers on oral health-related quality of life: a longitudinal prospective study.

OBJECTIVE: The aim of the present study was to assess the impact of orthodontic retainers on oral health-related quality of life (OHRQoL) in the short and long terms after orthodontic treatment. METHODS: Data from 45 patients up to three years after orthodontic treatment (T0) were analyzed. Patients were reassessed four years (T1) after T0. OHRQoL was measured using the OHIP-14 (Oral Health Impact Profile-14) questionnaire. The presence of a fixed retainer in the upper and/or lower arches, sex, and age were the predictive variables evaluated at T0 and T1. The occurrence of retainer fracture at T0 was clinically evaluated. Due to the COVID-19 pandemic, clinical examination on T1 was not possible, so the OHIP-14 and the self-perception of changes in teeth position and fracture of retainers were examined using an on-line questionnaire. RESULTS: At the initial examination, the presence of upper retainers had a negative impact on quality of life (p=0.018). The OHIP-14 value increased significantly from T0 to T1 (p=0.014), regardless of the presence of retainers. The fracture or debonding of the retainer reported by the patient was the only variable that had a negative impact on OHRQoL (p=0.05). CONCLUSION: The use of fixed upper retainers suggests a negative impact on the quality of life of the orthodontic patient after the end of orthodontic treatment. This impact, however, is negligible in the long term, except when associated with fracture or debonding. This study emphasizes the need for continuous follow-up of orthodontic patients during the retention period.

Environmental sustainability of post-orthodontic dental retainers: a comparative life-cycle assessment of Hawley and Essix retainers.

BACKGROUND: Environmental sustainability has been brought into the limelight due to the global climate crisis. This crisis is driven by human activities and even the healthcare sector is no exception. Within dentistry, orthodontics is a large global market; hence, the use of post-orthodontic retainers has a significant environmental footprint. The aim of this study was to determine the environmental sustainability of post-orthodontic retention using Hawley and Essix retainers. MATERIALS AND METHODS: A comparative life-cycle assessment (LCA) was carried out to compare the environmental impact of both retainers. All inputs and outputs were accounted for using the Ecoinvent database, v3.7.1, and openLCA software. Sixteen impact categories were used to determine their environmental burden. RESULTS: Of the 16 impact categories, the Hawley had a greater environmental burden than the Essix retainer in 12 categories. The Hawley's most significant contributors to its impact values are factory manufacturing and in-house production, with an average of 41.45% and 52.52%, respectively. For the Essix, the greatest contributor is factory manufacturing, with an average of 64.63%. However, when factoring in the lifespan of the retainers, the Essix would have a greater environmental impact than the Hawley retainer. LIMITATIONS: This study employed a comparative LCA. There were also assumptions made, but these were supported by research. CONCLUSIONS: On the basis of the evidence gathered in this study, Hawley retainers are more environmentally sustainable than Essix retainers. These results would better enable clinicians to factor in the environmental impact and make informed decisions on the choice of retainer type.

Comparison of efficacy of thermoplastic retainer with round and rectangular bonded lingual wire retainer in the mandible two years after orthodontic treatment: a randomised controlled trial.

OBJECTIVE: To analyse three protocols in maintaining the stability of orthodontic therapy results and their effect on gingival health. MATERIALS AND METHODS: Sixty-six subjects (pre-therapeutic age 11-18 years; 68% female) randomly allocated into three retention groups of equal size were analysed. The first group had a 0.673 × 0.268 mm (0.027 × 0.011 inches) rectangular braided steel retention wire bonded to the lingual surfaces of all mandibular teeth from canine to canine, and the second group had a 0.406 mm (0.016 inches) round twisted steel wire. The third group was the control, without wires, and only with vacuum-formed retainers. All three groups had vacuum-formed removable retainers in the maxilla. The frequency of wire detachment/breakage/loss of retainer, the occurrence of crowding of mandibular incisors, and changes in intercanine width and gingival health were monitored. RESULTS: Incidence and severity of relapse differed between groups (p = 0.001 and 0.049) being most common in the removable retainer group (incidence 68.2%; severity 0.7 ± 1.0 mm), followed by the round wire group (36.4%; 0.5 ± 1.2 mm) and rectangular wire group (13.6%; 0.1 ± 0.1 mm). The intercanine width decreased more without a bonded retainer (incidence 68.2%; severity 0.5 ± 0.7 mm) and with the round wire more (45.5%; 0.5 ± 0.7 mm) than with the rectangular (27.3%; 0.1 ± 0.3 mm). The difference was significant for incidence (p = 0.025), but not severity. Detaching of the wires/breakage/loss of retainer was similar. There were no significant differences in the accumulation of biofilm, calculus and gingivitis between appliances. CONCLUSION: A rectangular wire is the most effective in retention, and the impact of retention appliances on gingival health is similar. TRIAL REGISTRATION: ClinicalTrials.gov, NCT05121220. Registered 02 October 2021 - Retrospectively registered. CLINICAL RELEVANCE: Studying guidelines for reducing relapse, proper use of materials and appliances, the behavior of retention wires according to their profile in the retention phase, and possibilities of maintaining oral health will contribute to improving the stability of orthodontic therapy results.

Stability, survival, patient satisfaction, and cost-minimization of CAD/CAM versus conventional multistranded fixed retainers in orthodontic patients: a 2-year follow-up of a two-centre randomized controlled trial.

BACKGROUND: CAD/CAM (computer-aided design/computer-aided manufacturing) fixed retainers (FRs) as an alternative to multistranded FRs to maintain orthodontic treatment outcome. OBJECTIVES: The primary aim was to compare CAD/CAM versus conventional multistranded FRs in terms of stability until 2 years. Secondary outcomes were failure rates, patient satisfaction, and cost-minimization. TRIAL DESIGN: 2-arm parallel, two-centre randomized controlled trial. METHODS: Patients were randomized to CAD/CAM or conventional FRs in both arches, in a 1:1 ratio and blocks of four. Allocation concealment was secured by using sequentially numbered envelopes. Patients were blinded. FRs were bonded at the end of treatment, and patients were recalled after 12 and 24 months. First-time retainer failures were recorded and digital impressions were taken. Arch widths and lengths, as well as Little's Irregularity Index (LII), were measured. Additionally, patients answered satisfaction questionnaires. Linear mixed models were applied for measurements and patient satisfaction. Survival analyses were estimated with Kaplan-Meier curves, along with Cox-regression modelling. Cost-minimization analysis was undertaken. RESULTS: One hundred and eighty-one patients were randomized (98 in Centre 1, and 83 in Centre 2): 90 in CAD/CAM and 91 in conventional group. One hundred and fifty three patients attended T24 follow-up. There were no significant differences in LII and arch dimensions between groups for failure-free patients. Within 24 months, 34% maxillary CAD/CAM FRs and 38% maxillary conventional FRs failed, along with 42% mandibular CAD/CAM FRs and 40% mandibular conventional FRs, with no significant difference in survival between groups (hazard ratios conventional to CAD/CAM: maxillary arch: 1.20 [P = 0.46], mandibular arch: 0.98 [P = 0.94]). There were no significant differences in patient satisfaction between groups. No harms were observed. Cost-minimization analysis showed that CAD/CAM FRs were slightly cheaper than conventional FRs. CONCLUSIONS: There were no clinically significant differences in LII, arch widths, and lengths between CAD/CAM and conventional FRs after 24 months. There were no differences in failures and patient satisfaction between groups. CAD/CAM FRs were slightly cheaper than conventional FRs. TRIAL REGISTRATION: ClinicalTrials.gov NCT04389879.

Elemental composition, corrosion resistance and mechanical properties of computer-aided design and computer-aided manufacturing fixed retainers versus conventional fixed retainers.

PURPOSE: To investigate the elemental composition, corrosion resistance, and mechanical properties of computer-aided design and computer-aided manufacturing (CAD-CAM) retainers versus conventional fixed retainers (FRs). METHODS: Eight different retainer wires were investigated. Energy dispersive X-ray spectroscopy was used to determine the elemental composition. Leakage was analysed according to ISO 10271:2020 guidelines. Hardness was tested using the Vickers method with a load of 0.3 kg. The tensile force and tensile strength were evaluated. Multiple comparisons among wires of hardness, tensile force, and strength were conducted using the Welch t-test, with Bonferroni correction. RESULTS: Nickel was present in all wires. The CAD-CAM-FR wire, which contained more nickel than the other wires, had no measurable leakage. The gold-plated wires had the highest total leakage, but did not exceed the ISO standard limit. The hardness of the stainless-steel twisted wires was the highest and that of the CAD-CAM-FR wire was the lowest. The tensile strength of the CAD-CAM-FR wire was significantly lower than that of the other wires and similar to the other twisted-wire retainers. CONCLUSION: The CAD-CAM-FR wire is likely to have high corrosion resistance and flexibility due to its low hardness.

Relapse and failure rates between CAD/CAM and conventional fixed retainers: a 2-year follow-up of a randomized controlled clinical trial.

BACKGROUND: Retention has been always considered a major challenge in orthodontics. Recently computer-aided design/computer-aided manufacturing (CAD/CAM) fixed retainers (FRs) have been introduced as a marked development in retainer technology, offering potential advantages. OBJECTIVE: The objective of this study was to compare the differences in relapse and failure rates in patients treated with FRs using CAD/CAM technology, lab-based technique, and chairside method. TRIAL DESIGN: A double-blinded, prospective, randomized controlled clinical trial was conducted over a 2-year period at a single centre. INTERVENTIONS: These patients were divided into three groups: CAD/CAM group with multistranded Stainless Steel wires (CAD/CAM, n = 14), lab group with the same multistranded wires (lab, n = 15), and a chairside group with Stainless Steel Ortho-FlexTech wires (chairside, n = 14). OUTCOMES: Inter-canine width (ICW) and Little's irregularity index were digitally measured from scans at the orthodontic debonding (T1), 6-month retention (T2), 1-year retention (T3), and 2-year retention (T4) visits. All forms of failure were documented and analyzed. RANDOMIZATION: Participants were randomly assigned to the three groups using online randomization software (randomization.com) by a statistician who was not involved in the study. BLINDING: Patients were blinded in terms of the FR group to which they were each randomly assigned. The principal investigator was blinded upon data analysis since patients' records were coded to minimize observer and measurement bias. RESULTS: Initially 81 patients were assessed for eligibility. Seventy-five patients were randomly allocated into the three study groups. After 2-year follow-up, 43 patients came back for the follow-up and were analyzed. The CAD/CAM group showed significantly less reduction in ICW compared to the chairside group at all time intervals (P < .05) and compared to the lab group at 6 months (P = .038). In terms of LII, the CAD/CAM group exhibited significantly less change than the chairside and lab groups at all time intervals (P < .05). The CAD/CAM group had the lowest failure rate (21.4%), followed by chairside group (28.6%) and then lab group (33.3%), however the differences were insignificant. No harms were observed in the current study. CONCLUSION: Within 2 years of fixed retention, CAD/CAM FRs showed significantly less relapse than lab-based and chairside FRs. However, there was no significant difference in failure rates among the groups. TRIAL REGISTRATION: NCT05915273.

Stability and failure rate during 3 years of fixed retention: A follow-up of an randomized clinical trial on adolescents with four different lingual retainers.

OBJECTIVE: To evaluate stability outcomes and failure rates associated with four types of lingual retainers: (1) dead-soft wire, (2) multistrand stainless steel (SS) wire, (3) CAD/CAM nitinol, and (4) connected bonding pads (CBPs) after 3 years of retention. METHODS: This study enrolled 96 patients (66 females, 30 males) with a median age of 19 years with four types of lingual retainers: (1) 0.016 × 0.022-inch dead-soft wire, (2) 0.0215-inch five-strand SS wire, (3) 0.014 × 0.014-inch CAD/CAM nitinol wire, and (4) CBPs. The irregularity index, intercanine distances, and arch lengths were obtained and used to evaluate mandibular stability. Failure rates were also assessed during this study. Data were statistically analysed. RESULTS: Irregularity increased, whereas intercanine width and arch length decreased after 3 years of retention. The greatest irregularity was associated with the CBPs and the least with the CAD/CAM retainers. Changes in stability measurements were significantly higher in the dead-soft wire and CBPs than those in the CAD/CAM nitinol and multistrand SS wires. Parallel to these changes, the frequency of failure yielded similar results with the same significance between the groups. The failure rate of CBPs, in contrast to the CAD/CAM nitinol and multistrand SS wires, was significantly higher in the right quadrant (P < .05). CONCLUSION: After taking the 3-year results into consideration, CAD/CAM nitinol and multistrand SS wires were found to be more successful than the others in maintaining mandibular stability. The most failures were observed with CBPs after 3 years of retention.

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.

Patients' perception of orthodontic retainers: a systematic review.

BACKGROUND: Orthodontic retainers are widely used to prevent relapses after orthodontic treatment; however, evidence about patients' perceptions of retainers is lacking. OBJECTIVE: To assess patients' perception of orthodontic retainers. SEARCH METHODS: PubMed, Web of Science, Scopus, LILACS, LIVIVO, Cochrane Library, and gray literature (Google Scholar) were searched without date or language restrictions. A manual search of the reference lists of the included articles was also performed. SELECTION CRITERIA: Studies comparing patients' perceptions of wearing orthodontic retainers were included. DATA COLLECTION AND ANALYSIS: According to the study design, the risk of bias (RoB) assessment was performed using RoB 2.0 or ROBINS-I. The level of evidence was assessed through the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) tool. RESULTS: Seventeen studies met the eligibility criteria. After the RoB assessment, 12 randomized controlled trials presented a high RoB, and 4 non-randomized controlled trials presented a moderate RoB. The certainty of evidence was classified as very low for the four assessed outcomes. The studies generally reported an initial temporary negative impact of orthodontic retainers. Different esthetic, functional, and ease-of-use advantages are reported using removable and fixed retainers. A quantitative analysis was not performed due to the considerable clinical and methodological heterogeneity among the studies. CONCLUSION: The current evidence, although very limited, suggests that orthodontic retainers have an initial negative impact related to discomfort and functional limitations, but they seem to regress over time. There is a preference for thermoplastic over Hawley-type retainers. However, thermoplastic retainers cause different functional difficulties, and bonded retainers present the advantage of affecting speech function less than orthodontic removable retainers, although they can facilitate oral hygiene problems. REGISTRATION: PROSPERO (CRD42022306665).

Effects of three orthodontic retainers on periodontal pathogens and periodontal parameters.

The objective of this study was to compare and evaluate the changes in periodontal pathogens and periodontal status within 6 months of wearing three orthodontic retainers, namely, vacuum-formed retainer (VFR), Hawley retainer (HR), and lingual fixed retainer (LR). In total, 48 patients who underwent orthodontic treatment with ordinary metal brackets were divided into VFR, HR, and LR groups (n = 16 per group). Saliva samples were collected at the time of debonding (T0) and after 1 month (T1), 3 months (T2), and 6 months (T3). Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa) were quantitatively analyzed using real-time PCR. Gingival index (GI), plaque index (PLI), and probing depth (PD) were measured at the four time points to evaluate changes in periodontal state. SPSS20.0 software was used to analyze the data, and P < 0.05 was considered statistically significant. The trial was registered at the Chinese Clinical Trial Registry (ChiCTR2300073704), the registration was retrospective. Compared to baseline (T0) values, Pg, Aa, GI, PLI, and PD were significantly decreased in all three groups 1 month after wearing the retainer (p < 0.05). Significant differences were observed in Aa at T3 among the three groups, whereby the HR group exhibited significantly better results compared to the VFR and LR groups (p < 0.05). Differences were found among the three groups' Porphyromonas gingivalis at T3, and the HR group was significantly better than the VFR and LR groups (P < 0.05). From T1 to T2, GI, PLI, and PD of the three groups tended to be stable, however differences were observed at T3, with the PLI and PD of the HR group being the lowest among the three groups (p < 0.05). Regardless of the type of retainer used, the periodontal condition of patients was significantly improved after removal of the metal brackets. After 6 months of retainer use, the Hawley retainer was superior to vacuum-formed retainer and lingual fixed retainer with regard to Pg, Aa, and periodontal clinical parameters.

[Evaluation of the effect of 3D printing resin splint based on the retention effect of orthodontic treatment in patients with periodontal disease].

PURPOSE: To investigate the difference in the retention effect of 3D printing resin splint and Hawley retainer combined with lingual retention wire in periodontal disease patients after orthodontic treatment. METHODS: Forty patients who finished orthodontic treatment for periodontal disease from January 2021 to February 2022 were selected and divided into experimental group and control group according to the random number table method, with 20 patients in each group. Patients in the experimental group used 3D printing resin splint for retention, while patients in the control group used Hawley retainer combined with a lingual retention wire for retention. The chair-side operation time of the retainers was recorded for both groups. The maxillary and mandibular cuspid width, molar width, overjet, overbite and irregularity index were measured at 1 month and 6 months after orthodontic treatment in both groups. Statistical analysis was performed with SPSS 12.0 software package. RESULTS: The mean time for chair-side manipulation of experimental group and control group was 8.23, 11.17 min, respectively. The difference between the two groups was statistically significant (P＜0.05) when comparing the width of the maxillary and mandibular cusps, the width of the molars, overjet, overbite and the irregularity index after 1 month and 6 months of wear of the retainers, which were significantly greater in the experimental group than in the control group at 6 months(P＜0.05). CONCLUSIONS: 3D printing resin splint, with short chair-side manipulation time, was more effective than Hawley retainer combined with a lingual retention wire, and the efficacy of both groups was otherwise generally consistent.

The prevalence of the failure of fixed orthodontic bonded retainers: a systematic review and meta-analysis.

OBJECTIVES: To systematically assess the scientific literature for the prevalence of failure rate of fixed orthodontic bonded retainer (FOBR). METHOD: Randomized clinical trials (RCTs) and prospective non-RCTs involving participants who had FOBR fitted were included. The Cochrane Central Register of Controlled Trials, Web of science, MEDLINE, and EMBASE via OVID were searched from inception to January 2023. Risk of bias was assessed using the Cochrane RoB 2 and Newcastle-Ottawa tools. The main outcome was the failure rate of FOBRs. The secondary outcome was to identify factors that can influence the failure of FOBR. Meta-analyses and sensitivity analyses were undertaken using Revman, version5.4. A random-effects model was used. Quality assessment using Grading of Recommendations Assessment, Development, and Evaluation. RESULTS: Thirty-four studies (25 RCTs and 9 prospective clinical studies) (3484 participants) were included in this review. The overall failure rate of bonded retainers, after excluding high-risk studies, was 35.22% (95% confidence interval [CI] 27.46-42.98). The failure rate is increased with the duration of follow up; with short-term follow-up rate 24.18% (95% CI 20.16-28.21), medium-term follow up 40.09% (95% CI 30.92-49.26), and long-term follow up 53.85% (95% CI 40.31-67.39). There is a low level of evidence to suggest there is no statistically significant difference in the failure rate of fixed retainers using direct versus indirect bonding methods, using liquid resin versus without liquid resin, and fibre-reinforced composite retainers compared to multi-stranded stainless steel retainers. DISCUSSION: There is low-quality evidence to suggest that the failure rate of FOBR is relatively high. There is a need for high-quality, well-reported clinical studies to assess factors that can influence the failure rate of FOBR. REGISTRATION: CRD42021190910.

Assessment of the effectiveness of two different orthodontic retention protocols.

INTRODUCTION: The main goal of orthodontic retention is to keep the teeth in their corrected positions. Fixed or removable retainers are the most common types of retainers used during the retention phase. For the maxilla, various types of retainers have been described, including the vacuum-formed retainers and Hawley retainers. Fixed retainers are used for the lower jaw.

A comparative evaluation of mechanical wear of adhesives used for bonded retainers that underwent brushing for 1 hour under 36 mm of linear action, using computer-aided 3D scan-an in vitro study.

OBJECTIVES: The aim of the present study was to comparatively evaluate the mechanical wear of adhesives used in bonded retainers. MATERIALS AND METHODS: Eighty mandibular acrylic teeth were included in the study that were divided into 4 different groups based upon the composite used. Each acrylic tooth was bonded with a retainer wire and composite of their respective group (Heliosit, Restofill, Tetric-N-flow, and Filtek Z350 XT). These bonded acrylic teeth were subjected to 3D scan in order to evaluate the volume and surface area of the composite. The 3D scans were recorded using MEDIT 3D scanner. After evaluating, the samples were subjected to brushing with the aid of a custom-made brushing simulator using a toothbrush with soft bristles and toothpaste slurry. The samples were subjected to 1 hr of brushing. These samples were again subjected to 3D scans to evaluate (post-test volume and surface area) and underwent statistical analysis. RESULTS: The results showed the Heliosit group exhibited the highest mean volume (1.76 mm3) and surface area (4.81 mm2) difference between the pre-test and post-test values whereas the least mean volume difference (1.10 mm3) and surface area difference (3.21 mm2) were seen in the Tetric-N-flow group. CONCLUSION: All the four composites underwent change in the mean surface area and volume after being subjected to brushing, suggesting that the composites routinely used for bonding fixed bonded lingual retainers are subjected to changes due to abrasion. The Heliosit group, which showed least filler loading among the 4 composites, exhibited least resistance to wear, whereas the Tetric-N-flow group which had highest filler loading among the composites exhibited highest resistance to wear. CLINICAL RELEVANCE: The most crucial phase during orthodontic treatment is the retention phase. This phase is responsible for the long-term results of the treatment. The retainers that are placed in the oral cavity are subjected to changes due to oral environment, chemical changes, and mechanical changes. These changes have a direct effect on the retainers, which tend to alter their properties. Thus, the effects of these changes are to be studied thoroughly.

Preclinical in vitro study of streptococcus mutans accumulation in three fixed retainer designs: Microbiological assay.

The use of fixed retainers in the lower arch is frequent; however, its presence increases the accumulation of biofilm and dental calculus. The objective of this research was to evaluate, in vitro, the accumulation of Streptococcus mutans (S. mutans) in 3 designs of fixed retainers. Nine models were reproduced in heat-cured acrylic resin and divided into groups: straight retainer (SR), retainer with vertical strap (RVS), retainer with horizontal strap (RHS). The accumulation of S. mutans was assessed using the MTT assay (3-4,5-dimethyl-thiazol-2-yl-2,5-diphenyltetrazolium bromide) and then measured using an automated reader. The RHS group showed less biofilm accumulation compared to the other groups (p<0.05). The distance between the tooth surface and the retainer showed a strong negative correlation with biofilm accumulation (rs=-0.79, p=0.00037). The RHS showed significantly less accumulation of S. mutans due to the distance between the retainer and the tooth surface. This research provides relevant data for a future randomized clinical trial.

Effect of bonded and removable retainers on occlusal settling after orthodontic treatment: A systematic review and meta-analysis.

This systematic review and meta-analysis aimed to summarize the effectiveness of bonded and removable retainers (the Hawley and Essix retainers) in terms of improving occlusal settling (occlusal contact points/areas) after orthodontic treatment. We searched the Cochrane Library, PubMed, CINAHL Plus, and Dental & Oral Sciences Source (DOSS), as well as SIGLE, Google Scholar and ClinicalTrials.gov for eligible studies. We included randomized and non-randomized controlled trials along with cohort studies. Studies that reported occlusal contacts/areas during retention with fixed bonded and removable retainers were included. To assess the quality of the randomized controlled trials (RCTs), the Cochrane Collaboration risk-of-bias (RoB) tool was utilized, whereas the Newcastle-Ottawa Scale (NOS) was used to assess the quality of cohort studies.We included 6 articles in our systematic review after scrutinizing 219 articles and eliminating the illegible ones based on duplication, titles, abstracts, and objectives. Bonded retainers (BRs) allowed faster and better posterior occlusal settling as compared to the Hawley retainer (HR). However, HR showed good occlusal settling in the anterior dental arch. The Essix retainer (ER) showed a decrease in occlusal contact during the retention phase. Meta-analysis showed no statistically significant difference between BRs and removable retainers. In conclusion, HR allowed better overall occlusal settling as compared to other retainers. However, BRs allowed faster settling in the posterior tooth region. The Essix retainer showed poor settling of occlusion. Overall, there is an insufficient number of high-quality RCTs to provide additional evidence, and further high-quality RCTs are needed.

A comparison of CAD/CAM-based fixed retainers versus conventional fixed retainers in orthodontic patients: a systematic review and network meta-analysis.

OBJECTIVE: Comparing computer-aided design and computer-aided manufacturing (CAD/CAM) fixed retainers and conventional fixed retainers for their effectiveness in orthodontic patients using systematic review and meta-analysis of literature. SEARCH METHODS: A comprehensive search was conducted in MEDLINE, Web of Science, EMBASE, Scopus, Cochrane's CENTRAL, Google Scholar, Ovid, and LILACS up to May 2023, with no language or date restrictions. SELECTION CRITERIA: Only randomized clinical trials (RCTs) that complied with PICO questions were included, and the Cochrane Risk of Bias 2.0 (RoB 2) tool was used to assess the risk of bias in the included studies. DATA COLLECTION AND ANALYSIS: Using custom-piloted forms, relevant data were retrieved from the included studies. Then a random-effects inverse variance meta-analysis was used to pool the results. Primary outcomes were stability of treatment results measured through dental cast measurements and periodontal status, while secondary outcomes were failure rates and patient-reported outcomes. RESULTS: Seven RCTs with 601 participants were included in the review. In the short term (≤6 months), the meta-analysis showed no significant differences in inter-canine distance or arch length between CAD/CAM and conventional fixed retainers in mandibular retainers. However, for Little's irregularity index, single-stranded stainless-steel retainers were notably worse than Ni-Ti CAD/CAM retainers at 3 and 6 months, while multi-stranded stainless-steel retainers only diverged from CAD/CAM at the 6-month milestone, despite the overall clinical inconsequence of these changes. CAD/CAM retainers were associated with a lower plaque index than traditional retainers but no significant difference in gingival index. Failure rates did not differ significantly between CAD/CAM and other types of retainers in mandibular retainers. Nonetheless, one study had a high amount of CAD/CAM retainer failures leading to the study being stopped. CONCLUSIONS: In the short term, CAD/CAM fixed retainers show promise as an alternative to traditional retainers. They may enhance periodontal health, as indicated by lower plaque index scores than conventional retainers. However, extensive research is needed to determine the long-term durability and effectiveness of CAD/CAM retainers in orthodontic treatment, particularly regarding their failure rate. Until comprehensive evidence is available, the use of CAD/CAM retainers should be tailored for each case. REGISTRATION: The protocol for this systematic review was registered at PROSPERO with the ID CRD42023412741.