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.

Stability, survival, and patient satisfaction with CAD/CAM versus conventional multistranded fixed retainers in orthodontic patients: a 6-month follow-up of a two-centre randomized controlled clinical trial.

OBJECTIVES: The primary aim of this two-arm parallel two-centre randomized controlled trial was to compare computer-aided design and computer-aided manufacturing (CAD/CAM) versus conventional multistranded fixed retainers (FRs) in terms of stability over 6 months. Secondary outcomes were failure rates and patient satisfaction. METHODS: Patients were randomized to CAD/CAM or conventional FRs in both arches, in 1:1 ratio and blocks of four. Allocation concealment was secured by using sequentially numbered envelopes. Patients were blinded. Retainers were bonded at the end of orthodontic treatment (T0), and patients were recalled after 1 (T1), 3 (T3), and 6 (T6) 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. RESULTS: One hundred and eighty-one patients were randomized (98 in Centre 1, and 83 in Centre 2): Ninety in the CAD/CAM group and 91 in the conventional group. Three subjects dropped out at baseline, as they did not attend any of the follow-up appointments.168 patients attended the T6 visit. There were no significant differences in arch dimensions between T0 and T6, whilst the LII was different only in the CAD/CAM group (mean difference: 0.2 mm; 95% confidence interval: 0.1 to 0.4; P < 0.001). Within 6 months, 39 upper retainers (19 out of 88 CAD/CAM and 20 out of 90 conventional retainers) and 52 lower retainers failed (26 out of 88 CAD/CAM and 26 out of 90 conventional retainers), with no significant difference between the survival of both types of retainers (hazard ratios conventional to CAD/CAM: upper arch: 0.99 [P =0.99], lower arch: 0.93 [P = 0.80]). There were no significant changes in patient satisfaction between the groups. No harms were observed. CONCLUSIONS: There were no clinically significant differences in LII, arch widths and lengths between CAD/CAM and conventional retainers after 6 months. There was no difference in failures and in patient satisfaction between both types of FRs. REGISTRATION: ClinicalTrials.gov NCT04389879.

Irisin reduces orthodontic tooth movement in rats by promoting the osteogenic potential in the periodontal ligament.

OBJECTIVES: Positive effects of irisin on osteogenic differentiation of periodontal ligament (PDL) cells have been identified previously, this study aims to examine its effect on orthodontic tooth movement (OTM) in vivo. MATERIALS AND METHODS: The maxillary right first molars of male Wistar rats (n = 21) were moved mesially for 14 days, with submucosal injection of two dosages of irisin (0.1 or 1 µg) or phosphate-buffered saline (control) every third day. OTM was recorded by feeler gauge and micro-computed tomography (µCT). Alveolar bone and root volume were analysed using µCT, and plasma irisin levels by ELISA. Histological characteristics of PDL tissues were examined, and the expression of collagen type I, periostin, osteocalcin (OCN), von Willebrand factor (vWF) and fibronectin type III domain-containing protein 5 (FNDC5) in PDL was evaluated by immunofluorescence staining. RESULTS: Repeated 1 µg irisin injections suppressed OTM on days 6, 9, and 12. No significant differences were observed in OTM in the 0.1 µg irisin group, or in bone morphometric parameters, root volume or plasma irisin, compared to control. Resorption lacunae and hyalinization were found at the PDL-bone interface on the compression side in the control, whereas they were scarce after irisin administration. The expression of collagen type I, periostin, OCN, vWF, and FNDC5 in PDL was enhanced by irisin administration. LIMITATIONS: The feeler gauge method may overestimate OTM. CONCLUSIONS: Submucosal irisin injection reduced OTM by enhancing osteogenic potential of PDL, and this effect was more significant on the compression side.

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.

FNDC5/irisin is expressed and regulated differently in human periodontal ligament cells, dental pulp stem cells and osteoblasts.

OBJECTIVE: To examine the expression and regulation of fibronectin type III domain-containing protein 5/irisin (FNDC5/irisin) in primary human periodontal ligament (hPDL) cells, dental pulp stem cells (hDPCs) and osteoblasts (hOBs). METHODS: FNDC5/irisin was identified in sections of paraffin embedded rat maxillae, cryo-sections of 3D cultured spheroids hPDL cells, hDPCs and hOBs, 2D cultured hPDL cells, hDPCs and hOBs by immunohistochemistry. The expression of FNDC5/irisin was identified by qPCR, followed by sequencing of the qPCR product. Regulation of FNDC5/irisin expression in hPDL cells, hDPCs and hOBs were evaluated after administration of different concentrations of irisin and all-trans retinoic acid (ATRA). qPCR and ELISA were used to identify expression and secretion of FNDC5/irisin in odontoblast-like differentiation of hDPCs. RESULTS: FNDC5/irisin was confirmed to be present in rat periodontium and dental pulp regions, as well as in 2D and 3D cultured hPDL cells, hDPCs and hOBs. BLAST analyses verified the generated nucleotide alignments matched human FNDC5/irisin. FNDC5/irisin gene expression was enhanced during odontoblast-like differentiation of hDPCs whereas the secretion of the protein was decreased compared to control. The protein signals in rat periodontal and pulpal tissues were higher than that of alveolar bone, and the expression of FNDC5/irisin was differently regulated by recombinant irisin and ATRA in hPDL cells and hDPCs compared to hOBs. CONCLUSIONS: FNDC5/irisin expression was verified in rodent periodontium and dental pulp, and in hPDL cells, hDPCs and hOBs. The FNDC5/irisin expression was regulated by recombinant irisin and ATRA. Finally, expression and secretion of FNDC5/irisin were affected during odontoblast-like differentiation of hDPCs.

STIM1 R304W in mice causes subgingival hair growth and an increased fraction of trabecular bone.

Calcium signaling plays a central role in bone development and homeostasis. Store operated calcium entry (SOCE) is an important calcium influx pathway mediated by calcium release activated calcium (CRAC) channels in the plasma membrane. Stromal interaction molecule 1 (STIM1) is an endoplasmic reticulum calcium sensing protein important for SOCE. We generated a mouse model expressing the STIM1 R304W mutation, causing Stormorken syndrome in humans. Stim1R304W/R304W mice showed perinatal lethality, and the only three animals that survived into adulthood presented with reduced growth, low body weight, and thoracic kyphosis. Radiographs revealed a reduced number of ribs in the Stim1R304W/R304W mice. Microcomputed tomography data revealed decreased cortical bone thickness and increased trabecular bone volume fraction in Stim1R304W/R304W mice, which had thinner and more compact bone compared to wild type mice. The Stim1R304W/+ mice showed an intermediate phenotype. Histological analyses showed that the Stim1R304W/R304W mice had abnormal bone architecture, with markedly increased number of trabeculae and reduced bone marrow cavity. Homozygous mice showed STIM1 positive osteocytes and osteoblasts. These findings highlight the critical role of the gain-of-function (GoF) STIM1 R304W protein in skeletal development and homeostasis in mice. Furthermore, the novel feature of bilateral subgingival hair growth on the lower incisors in the Stim1R304W/R304W mice and 25 % of the heterozygous mice indicate that the GoF STIM1 R304W protein also induces an abnormal epithelial cell fate.