Effects of Different Parameters of Diode Laser on Acceleration of Orthodontic Tooth Movement and Its Effect on Relapse: An Experimental Animal Study

Post-Orthodontic Relapse Prevention through Administration of a Novel Synthetic Carbonated Hydroxyapatite-Chitosan Hydrogel Derived from Blood Cockle Shell (Anadara granosa L.)

Relapse during passive orthodontic treatment is a major issue, with 70-90% frequency. This study examines whether blood cockle shells may be used to extract carbonated hydroxyapatite (CHA)-chitosan (CS). This study also aims to analyze the effect of CHA-CS on orthodontic relapse in rats. This study utilized 18 male Wistar rats which were randomly divided into two groups: CHA-CS and the control group (CG). The rats were subjected to a 35 cN orthodontic force for a duration of 7 days, after which the rats were conditioned to be passive. During this phase, the CHA-CS group received daily administration of CHA-CS hydrogel derived from the blood cockle shell. Subsequently, the appliances were detached to facilitate relapse. The distance between the mesial tips was measured using a digital caliper at three consecutive time points: 1, 5, and 7 days after debonding. The number of osteoblasts, osteoclasts, and fibroblasts was examined using hematoxylin-eosin staining. The data were subjected to statistical analysis using a t-test. The relapse distance of the CHA-CS group was lower than that of the control groups on day 7. Histological examinations using hematoxylin-eosin (HE) staining showed a significant increase in osteoblasts, a decrease in osteoclasts, and an increase in fibroblasts during orthodontic relapse movement (p < 0.05). This study found that blood cockle shell-derived CHA-CS may reduce orthodontic relapse by increasing osteoblasts and fibroblasts and by reducing the osteoclast number in rats.

In Vitro Effect of Photobiomodulation Therapy with 980 nm Diode Laser on Gene Expression of Key Regulators of Bone Remodeling by Human Periodontal Ligament Cells under Mild Orthodontic Forces

This study investigated the effect of photobiomodulation (PBM) with 980 nm diode laser as monotherapy and in combination with compressive and tensile orthodontic forces on expression of osteoprotegerin (OPG), receptor activator of nuclear factor-κB ligand (RANKL), sclerostin (SOST) and periostin (POSTN), by human periodontal ligament cells. Isolated cells were cultured and subjected to either tensile (10% elongation) or compressive forces (25 g cm-2 ) for 24 and 48 h. Subsequently, the cells received PBM (100 mW power, 3 or 6 J cm-2 energy density) immediately after load cycle. RT-PCR was applied to assess the genes expression. Data were analyzed by one-way ANOVA, followed by post hoc Tukey test (P ≤ 0.05). We found that PBM in combination with orthodontic forces led to upregulation of bone resorption genes (RANKL and SOST) at the pressure side and their downregulation at the tension side. The expression of osteogenic genes (OPG and POSTN) increased at the tension side and decreased at the pressure side. PBM alone did not affect gene expression. In conclusion, these findings suggest that this PBM protocol may be effective in enhancement of the gene expression in favor of bone remodeling acceleration that should be confirmed in future animal and human studies.

Comparing Circumferential Supracrestal Fiberotomy with Surgical Scalpel Versus Photobiomodulation in Orthodontic Relapse Reduction: A Clinical Trial

Objective: This investigation aimed to compare the efficacy of circumferential supracrestal fiberotomy (CSF) with surgical scalpel, laser CSF, and photobiomodulation for reduction of relapse after orthodontic tooth rotation. Background: Relapse is the tendency of teeth to move back to their preoperative position after removal of orthodontic appliances. Materials and methods: This randomized controlled clinical trial was conducted on 90 rotated teeth at the final stages of fixed orthodontic treatment. The teeth were randomly divided into six groups (n = 15) of (1) control (no intervention), (2) photobiomodulation alone (wavelength of 940 nm, 0.2 W, and 4 J/cm2), (3) conventional CSF, (4) laser CSF (wavelength of 940 nm, 1.5 W, and 4 J/cm2, and power density of 160 mW/cm2), (5) conventional CSF plus photobiomodulation, and (6) laser CSF plus photobiomodulation. Measurements were made on clinical photographs and dental casts using the AutoCAD software. Level of pain of patients was measured within the first 24 h after fiberotomy using a visual analog scale. Data were analyzed by ANOVA and Kruskal-Wallis test (α = 0.05). Results: The magnitude (p = 0.014) and percentage (p = 0.035) of relapse were significantly different among the six groups, and they were the highest in the control group followed by photobiomodulation alone, laser CSF, conventional CSF, conventional CSF plus photobiomodulation, and finally, laser CSF plus photobiomodulation. Moreover, photobiomodulation plus laser CSF and photobiomodulation plus conventional CSF had significantly different results from the other groups. The six groups had no significant difference in sulcus depth changes, gingival recession (difference in primary and secondary crown height), or pain score (p > 0.05). Conclusions: This study suggests that utilizing photobiomodulation combined with laser CSF or conventional CSF can be effective in reducing relapse. However, further clinical trials are required to support this idea. Iranian Registry of Clinical Trials (IRCT20210621051653N1).

Biomechanical Characteristics of Maxillary Molar Distalization Using Different Attachments with Clear Aligners: A 3-Dimensional Finite Element Analysis

This study aimed to compare the biomechanical characteristics of maxillary teeth in molar distalization with different orthodontic attachments. A 3-dimensional finite model of maxillary molar distalization with clear aligners was generated by computed tomography and contained different components. Four models—non-attachment (model A), horizontal rectangular attachment (model B), vertical rectangular attachment (model C), and combined attachment (model D)—were set up. The modalities of molar distalization were simulated using a finite element analysis. The results showed that the minimum displacement (rotation center) of the second molar in models A and B was located at the root furcation. In model C, the minimum displacement was located in the middle third of the palatal root. In model D, the minimum displacement was located at the apical third of the root. The anchorage teeth in all the four groups tended to have mesial tipping movement. Models B and D had more uniform stress distribution of the periodontal ligament than models A and C. Models with attachment had a larger tooth displacement pattern than that without attachment. Collectively, if molar distalization is planned before treatment, the appropriate application of attachments can help achieve the desired tooth movements more efficiently.

Effect of 970 nm low-level laser therapy on orthodontic tooth movement during Class II intermaxillary elastics treatment: a RCT

This prospective randomized clinical trial aimed to evaluate the effect of low-level laser therapy on tooth movement during Class II intermaxillary elastics treatment. Forty-two patients with Class II malocclusion were included, and their maxillary quadrants were allocated into two groups: treatment with an active diode laser and a placebo group. In each group, the time taken to obtain Class I occlusion after 6 months, rate of movement, total displacement of the maxillary canine to Class I occlusion and pain were recorded. The time to reach Class I occlusion in the active laser group (2.46 ± 2.1 months) was not significantly different from that in the placebo group (2.48 ± 2.0 months) (p = 0.938). Interestingly, the total distance of movement on the active laser side (2.27 ± 1.5 mm) was significantly greater than that on the placebo side (1.64 ± 1.3 mm) (p = 0.009). The pain levels on days 1, 2 and 3 were not significantly different between the laser and placebo sections. The rate of distance change toward Class I occlusion in the laser group (1.1 ± 0.7 mm/month) was significantly higher than that in the placebo group (0.74 ± 0.6 mm/month) (p = 0.037). Low-level laser therapy (970 nm) did not reduce the time needed to obtain Class I occlusion, but a significant acceleration in tooth movement was observed in the irradiated group.

Trial registration: NCT02181439. Registered 04 July 2014—https://www.clinicaltrials.gov/ct2/results?term=cinelaser.

Effect of Photobiomodulation on Relapse in an Experimental Rapid Maxillary Expansion Model in Rat

Rapid maxillary expansion (RME) is performed on transversely deficient maxilla. As all orthodontic treatments, retention is important in maintaining therapeutic outcomes. Fixed /removable retainers are used post-RME causing hygiene and compliance problems. Given photobiomodulation's positive effects on the quantity and quality of bone regeneration, its effect on post-RME relapse was studied. Thirty Sprague Dawley rats were randomly divided into group R, non-irradiated RME-treated (n = 12), group P, irradiated RME-treated (n = 12) and group C, non-RME non-irradiated (n = 6). A 1.5 mm metal ring inserted between maxillary incisors at days 0 and 15 was expanded until 1.5 mm space was obtained at day 30. In group P, Ga-Al-As diode laser (810 nm, 100 mW, 4J/cm² , 30 secs) was applied on days 0, 2, 4, 6, 8, 10, 12 and 14 as predictor variable. The relapse was measured as the space lost between incisors for 30 days after appliance removal (primary outcome variable) and compared with t-test. In week 2, space loss in group P was significantly lower (P < 0.05) than all other groups. The relapse during weeks 2 and 3 was significantly lower in group P than group R. However, no significant difference in relapse amount was found between groups during first and fourth week. There was a significant difference (P < 0.05) between groups in relapse rates (secondary outcome variable) but not in total relapse after 4 weeks. Photobiomodulation proved beneficial in resisting relapse in our study, and it is suggested to be continued until the end of expansion.

Micro-osteo perforation effects as an intervention on canine retraction

Objective

To evaluate the rate of canine retraction, mesial movement of molar and pain perception in maxillary first premolar extraction patients with or without flapless cortical perforations (FCPs).

Methods

Thirty adult patients with class II div I malocclusion were randomly allocated with the help of SPSS software to either perforation or conventional group for carrying out this randomized parallel group-controlled trial in 1:1 ratio. Maxillary first premolars were extracted and after canine retraction, distance between the tip of the canine and midpoint of incisal edge and the distance between the cervical midpoints on the height of contour of respective cinguli was measured. Also, mesial movement of molar and pain perception were assessed in both groups. Three bilateral cortical FCP of 1.5 mm diameter were made in the perforation group. Data were analyzed with the help of SPSS software with an intention-to-treat the FCP approach.

Results

Significant canine retraction in patients with FCP (mean retraction of 6.68 ± 0.60 [measured at crown tip level] and 5.97 ± 0.71 mm [measured at mid cervical level]) was revealed, while patients with conventional mechanics had mean retraction of 2.54 ± 0.49 and 2.33 ± 0.46 mm. Mesial movement of molar also showed significant difference (FCP = 0.48 ± 0.11 mm and Conventional = 0.65 ± 0.19 mm). Pain perception in control group was significantly lower in day 1 and 2.

Conclusion

FCPs are an effective method of accelerating the rate of canine retractions by 2–3 fold of tooth movement, however, pain perception was high in day 1 and 2.