Effect of Frequent Application of Low-Level Laser Therapy on Corticotomized Tooth Movement in Dogs: A Pilot Study

Protraction of Mandibular Second Molar for Substitution of Adjacent Missing First Molar With a Mini-Implant-Anchored Albert Loop Appliance

Protraction of mandibular posterior teeth into edentulous regions is challenging in clinical practice. This case demonstrated a minor tooth movement of a mandibular second molar to substitute its adjacent missing first molar in a 15-year-old female. An efficient bodily movement of the mandibular second molar was achieved through a mini-implant-anchored protraction loop appliance. With this carefully designed biomechanical system, over 10-mm molar protraction was accomplished within 14 months without mesial or lingual tipping. The adjacent third molar erupted spontaneously during the protraction process and drafted mesially. Through brackets and segmented archwire after the protraction, the second and third molars were successfully protracted and good buccal interdigitation was achieved. The combination of the Albert protraction loop and mini-implant allows for more efficient protraction of the mandibular molars, avoiding mesial tipping and lingual rotation of the molars.

The effects of a corticotomy on space closure by molar protraction using TSADs in patients with missing mandibular first molars

INTRODUCTION

The purpose of this study was to evaluate the effects of a triangular-shaped corticotomy on the protraction of second and third molars in patients with missing mandibular first molars.

SUBJECTS AND METHODS

The corticotomy and non-corticotomy groups consisted of sixteen first molars in fifteen patients (28.6 ± 9.4 years) and nineteen first molars in fifteen patients (26.6 ± 8.4 years), respectively. A triangular-shaped corticotomy was performed between the second premolar and molar. Temporary skeletal anchorage devices (TSADs) were placed between the first and second premolars in both groups. Mandibular dentition variables were measured on the pre and post-treatment panoramic radiographs and lateral cephalograms. Analysis of covariance was performed.

RESULTS

The corticotomy group exhibited 2.8 mm more inter-radicular correction between the second molar to second premolar roots (P < .001) and 1.6 mm more inter-radicular distance correction between the third molar to second premolar roots compared to the non-corticotomy group (P < .01). The corticotomy group required 5.5 months less treatment time for space closure (P < .05), but the total treatment time was the same for both groups.

CONCLUSIONS

The inter-radicular distance between the mandibular second premolar and molar and treatment times for space closure was significantly reduced in the corticotomy group.

Efficacy of Flat-Top Hand-Piece Using 980 nm Diode Laser Photobiomodulation on Socket Healing after Extraction: Split-Mouth Experimental Model in Dogs

The objective was to evaluate the effect of photobiomodulation (PBM) using 980 nm diode laser therapy (0.60 W, 0.77 W cm^-2 , 36 J, 46 J cm^-2 , 60 s) irradiated in continuous wave mode by flat-top hand-piece on socket healing in the maxilla and mandible. A split-mouth experimental design was performed on 6 dogs. The 3^rd premolar tooth was extracted from the maxilla and mandibles for both sides. The right-sided sockets were irradiated (PBM group), and the left-sided sockets were kept as control. Irradiation was done after extraction and at 48-h interval for 14 days. Both the buccal and lingual sides were irradiated to reach a total irradiation time of 120 s. Bone density was evaluated at 3, 4 and 5 weeks using cone beam computed tomography. We showed that maxillary sockets in the PBM group had higher bone density compared to control one at 3, 4, 5 weeks (P = 0.029, <0.001, <0.001), respectively. Mandibular sockets revealed no significant difference between PBM and control at 3 weeks (P = 0.347), while at 4 and 5 weeks PBM group showed higher bone density (P = 0.004, <0.001). In both groups, there was a significant increase (P < 0.001) in bone density by time which was higher in the PBM group. We concluded that PBM using a flat-top hand-piece of 980-nm improved the bone density of extraction sockets.

Corticotomy for orthodontic tooth movement

Corticotomy was introduced as a surgical procedure to shorten orthodontic treatment time. Corticotomy removes the cortical bone that strongly resists orthodontic force in the jaw and keeps the marrow bone to maintain blood circulation and continuity of bone tissues to reduce risk of necrosis and facilitate tooth movement. In the 21st century, the concept of regional acceleratory phenomenon was introduced and the development of the skeletal anchorage system using screw and plate enabled application of orthopedic force beyond conventional orthodontic force, so corticotomy has been applied to more cases. Also, various modified methods of minimally invasive techniques have been introduced to reduce the patient's discomfort due to surgical intervention and complications after surgery. We will review the history of corticotomy, its mechanism of action, and various modified procedures and indications.

Dose analysis of photobiomodulation therapy on osteoblast, osteoclast, and osteocyte

The objective of this study was to evaluate the effects of varying light doses on the viability and cellular activity of osteoblasts, osteocytes, and osteoclasts. A light application device was developed to apply 940-nm wavelength light from light-emitting diodes on three cultured cells, MC3T3-E1, MLO-A5, and RANKL-treated RAW264.7 cells. The doses (energy density) on cells were 0, 1, 5, and 7.5  J  /  cm2. The corresponding light power densities at the cell site were 0, 1.67, 8.33, and 12.5  mW  /  cm2, respectively, and the duration was 10 min. The results showed that the three cell types respond differently to light and their responses were dose dependent. Low-dose treatment (1  J  /  cm2) enhanced osteoblast proliferation, osteoclast differentiation, and osteoclastic bone resorption activity. Osteocyte proliferation was not affected by both low- and high-dose (5  J  /  cm2) treatments. While 1  J  /  cm2 did not affect viability of all three cell types, 5  J  /  cm2 significantly decreased viability of osteocytes and osteoclasts. Osteoblast viability was negatively impacted by the higher dose (7.5  J  /  cm2). The findings suggest that optimal doses exist for osteoblast and osteoclast, which can stimulate cell activities, and there is a safe dose range for each type of cell tested.

Low-level laser therapy stimulates bone metabolism and inhibits root resorption during tooth movement in a rodent model

This study evaluated the biological effects of low-level laser therapy (LLLT) on bone remodeling, tooth displacement and root resorption, occurred during the orthodontic tooth movement. Upper first molars of a total of sixty-eight male rats were subjected to orthodontic tooth movement and euthanized on days 3, 6, 9, 14 and 21 days and divided as negative control, control and LLLT group. Tooth displacement and histomorphometric analysis were performed in all animals; scanning electron microscopy analysis was done on days 3, 6 and 9, as well as the immunohistochemistry analysis of RANKL/OPG and TRAP markers. Volumetric changes in alveolar bone were analyzed using MicroCT images on days 14 and 21. LLLT influenced bone resorption by increasing the number of TRAP-positive osteoclasts and the RANKL expression at the compression side. This resulted in less alveolar bone and hyalinization areas on days 6, 9 and 14. LLLT also induced less bone volume and density, facilitating significant acceleration of tooth movement and potential reduction in root resorption besides stimulating bone formation at the tension side by enhancing OPG expression, increasing trabecular thickness and bone volume on day 21. Taken together, our results indicate that LLLT can stimulate bone remodeling reducing root resorption in a rat model. LLLT improves tooth movement via bone formation and bone resorption in a rat model.

New methodology for evaluating osteoclastic activity induced by orthodontic load

Orthodontic tooth movement (OTM) is a dynamic process of bone modeling involving osteoclast-driven resorption on the compression side. Consequently, to estimate the influence of various situations on tooth movement, experimental studies need to analyze this cell. Objectives The aim of this study was to test and validate a new method for evaluating osteoclastic activity stimulated by mechanical loading based on the fractal analysis of the periodontal ligament (PDL)-bone interface. Material and Methods The mandibular right first molars of 14 rabbits were tipped mesially by a coil spring exerting a constant force of 85 cN. To evaluate the actual influence of osteoclasts on fractal dimension of bone surface, alendronate (3 mg/Kg) was injected weekly in seven of those rabbits. After 21 days, the animals were killed and their jaws were processed for histological evaluation. Osteoclast counts and fractal analysis (by the box counting method) of the PDL-bone interface were performed in histological sections of the right and left sides of the mandible. Results An increase in the number of osteoclasts and in fractal dimension after OTM only happened when alendronate was not administered. Strong correlation was found between the number of osteoclasts and fractal dimension. Conclusions Our results suggest that osteoclastic activity leads to an increase in bone surface irregularity, which can be quantified by its fractal dimension. This makes fractal analysis by the box counting method a potential tool for the assessment of osteoclastic activity on bone surfaces in microscopic examination.