Effectiveness of a low-intensity static magnetic field in accelerating upper canine retraction: a randomized controlled clinical trial.

INTRODUCTION: Neodymium-iron-boron magnets have been suggested as a contemporary method for accelerating the process of orthodontic tooth movement (OTM). A limited number of clinical trials evaluated their effectiveness in accelerating OTM which is desirable for both orthodontists and patients. The present study aimed to investigate the effectiveness of a low-intensity static magnetic field (SMF) in accelerating upper canine retraction movement. MATERIALS AND METHODS: Seventeen patients (mean age 20.76 ± 2.9 years) with their orthodontic treatment decision to extract the upper and lower first premolars due to bimaxillary protrusion malocclusion were included in this split-mouth study. Canine retraction was performed using Nickel-titanium (Ni-Ti) closed-coil springs (150 g of force on each side). The experimental side received SMF via an auxiliary wire that carried 4-neodymium iron-born magnets with an air gap of 2 mm between the magnets to produce a magnetic field density of 414 mT in the region corresponding to the lateral ligament of the upper canine. To determine the rate of upper canine retraction and upper molar drift, alginate impressions were taken once a month to create plaster casts, which were analyzed digitally via a three-dimensional method. RESULTS: The rate of upper canine retraction was significantly greater (P < 0.05) on the SMF side than that on the control side during the first and second months, with an overall duration (19.16%) that was greater than that on the control side. The peak acceleration occurred during the second month (38.09%). No significant differences in upper molar drift were detected between the experimental and control sides (P > 0.05). CONCLUSION: A low-intensity static magnetic field was effective at accelerating upper canine retraction. The difference between the two sides was statistically significant but may not be clinically significant. The SMF did not affect upper molar drift during the upper canine retraction phase. TRIAL REGISTRATION: The trial was retrospectively registered at the ISRCTN registry ( ISRCTN59092624 ) (31/05/2022).

Does the application of autologous injectable Platelet-Rich Fibrin (i-PRF) affect the patient's daily performance during the retraction of upper canines? A single-centre randomized split-mouth controlled trial.

BACKGROUND: Previous studies have assessed different aspects concerning the applications of i-PRF in the oral cavity. However, nothing is known regarding patients' perceptions of the injection of autologous platelet-rich fibrin (i-PRF). OBJECTIVES: To investigate patients' perceptions after injecting platelet-rich fibrin (i-PRF) in the course of retracting upper canines. METHODS: Twenty-one patients, whose treatments required extractions of both upper first premolars, were recruited. Extraction side was randomly allocated to the intervention or control sides. After the alignment phase, i-PRF was injected twice with a one-month interval on the buccal and palatal aspects of the extraction sites (intervention side). Patients' perceptions were evaluated with two questionnaires: the first was used to assess the level of pain, discomfort, swelling, eating and swallowing difficulties as well as jaw movement restriction after 1 h (T1), 2 h (T2), 6 h (T3), 24 h (T4) and 48 h (T5) of the second injection; the second questionnaire was used to assess the acceptance of the i-PRF injection and overall satisfaction with this technique at the end of canine retraction phase. Visual Analogue Scale (VAS) was adopted for this purpose. Wilcoxon Signed Rank Test was used to compare between both sides at all time points while Friedman's Test was the selected test for detecting variables' changes over time. Post-hoc Wilcoxon Matched-Pairs Signed-Rank Tests were applied when any of the results were significant. As to the multiplicity of tests, Bonferroni Correction was implemented. RESULTS: Pain and swelling levels were significantly higher on the experimental compared to the control sides at T1, T2, and T3 (P < 0.05), whereas they declined sharply and went back to almost normal values at T4 (after 24 h). At T5 they were 0. Discomfort and difficulty in mastication on intervention sides were significant only at T1 and T2. Pain, swelling, and chewing difficulties were significant (P < 0.001) during the 4 assessed time points. The increase was insignificant regarding swallowing difficulties and jaw movement limitations at all time intervals. CONCLUSIONS: Injecting autologous (i-PRF) during orthodontic canine retraction is a well-perceived and well-tolerated method due to the limited discomfort which significantly diminishes 24 h afterwards. TRIAL'S REGISTRATION: ClinicalTrials.gov (Identifier Number: NCT03399422. 16/01/2018).

Three-dimensional evaluation of the effects of injectable platelet rich fibrin (i-PRF) on alveolar bone and root length during orthodontic treatment: a randomized split mouth trial.

BACKGROUND: The role of injectable platelet rich fibrin (i-PRF) in orthodontic treatment has not been investigated with focus on its effect on dental and bony periodontal elements. OBJECTIVE: To evaluate the efficacy of i-PRF in bone preservation and prevention of root resorption. METHODS: A randomized split-mouth controlled trial included 21 patients aged 16-28 years (20.85 ± 3.85), who were treated for Class II malocclusion with the extraction of the maxillary first premolars. Right and left sides were randomly allocated to either experimental treated with i-PRF or control sides. After the leveling and alignment phase, the canines were retracted with 150gm forces. The i-PRF was prepared from the blood of each patient following a precise protocol, then injected immediately before canine retraction on the buccal and palatal aspects of the extraction sites. Localized maxillary cone beam computed tomography scans were taken before and after canine retraction to measure alveolar bone height and thickness and canine root length (indicative of root resorption), and the presence of dehiscence and fenestration. Paired sample t-tests and Wilcoxon signed rank tests were used to compare the changes between groups. RESULTS: No statistically significant differences in bone height, bone thickness were found between sides and between pre- and post-retraction period. However, root length was reduced post retraction but did not differ between sides. In both groups, postoperative dehiscence was observed buccally and palatally and fenestrations were recorded on only the buccal aspect. CONCLUSIONS: I-PRF did not affect bone quality during canine retraction or prevent canine root resorption. I-PRF did not reduce the prevalence of dehiscence and fenestration. Trial registration ClinicalTrials.gov (identifier number: NCT03399760. 16/01/2018).

Effect of injectable platelet-rich fibrin (i-PRF) in accelerating orthodontic tooth movement : A randomized split-mouth-controlled trial.

BACKGROUND: The role of platelet-rich fibrin (PRF) in accelerating orthodontic tooth movement has been controversially discussed in available clinical studies. OBJECTIVE: To investigate the effectiveness of i­PRF in accelerating maxillary canine retraction. MATERIALS AND METHODS: A split-mouth design was applied in 21 participants (6 men, 15 women; mean age: 20.85 ± 3.85 years) whose class II division I malocclusion required the extraction of both maxillary first premolars. The right and left canines were randomized into intervention and control sides. After the initial leveling and alignment phase and immediately before canine retraction, i­PRF obtained from the brachial vein was injected into the mucosa on the buccal and palatal aspects of the intervention sides. The injection was repeated one month later. Study casts were taken at the initiation of canine retraction (T0) and at monthly visits up to 5 months (T1 through T5). The paired t­test was used to compare the total and monthly rates of canine retraction, canine rotation, and anchorage loss. RESULTS: The average rates of canine retraction were greater on the experimental side at T2, T3, and T4, but this difference with the control side was statistically significantly different only at T2 (P < 0.05). Differences in canine rotation and anchorage loss were not statistically significant. CONCLUSION: The rates of canine retraction following the injection of platelet-rich fibrin were not statistically significantly greater on the experimental than the control sides except at the second month (T2). This apparently transient rate of tooth movement indicates that repeated injections might be needed for sustained effects, a premise meriting more focused research.

The Genetic Architecture of Intra-Species Hybrid Mito-Nuclear Epistasis.

Genetic variants that are neutral within, but deleterious between, populations (Dobzhansky-Muller Incompatibilities) are thought to initiate hybrid dysfunction and then to accumulate and complete the speciation process. To identify the types of genetic differences that might initiate speciation, it is useful to study inter-population (intra-species) hybrids that exhibit reduced fitness. In Caenorhabditis briggsae, a close relative of the nematode C. elegans, such minor genetic incompatibilities have been identified. One incompatibility between the mitochondrial and nuclear genomes reduces the fitness of some hybrids. To understand the nuclear genetic architecture of this epistatic interaction, we constructed two sets of recombinant inbred lines by hybridizing two genetically diverse wild populations. In such lines, selection is able to eliminate deleterious combinations of alleles derived from the two parental populations. The genotypes of surviving hybrid lines thus reveal favorable allele combinations at loci experiencing selection. Our genotype data from the resulting lines are consistent with the interpretation that the X alleles participate in epistatic interactions with autosomes and the mitochondrial genome. We evaluate this possibility given predictions that mitochondria-X epistasis should be more prevalent than between mitochondria and autosomes. Our empirical identification of inter-genomic linkage disequilibrium supports the body of literature indicating that the accumulation of mito-nuclear genetic incompatibilities might initiate the speciation process through the generation of less-fit inter-population hybrids.