The effect of 904 nm low level laser on condylar growth in rats

Effect of low-level laser therapy on condylar growth in children treated with functional appliance: a preliminary study

Purpose

This study aimed to evaluate the skeletal and dentoalveolar changes achieved by combining low-level laser irradiation applied on the condyle area with twin-block therapy in growing class II malocclusion patients.

Methods

Fourteen patients (9 males, 5 females; mean age, 11.4 ± 2 years) with skeletal class II mandibular deficiency were recruited. They were divided into two groups (G 1: twin-block + low-level laser therapy, G 2: twin-block only). A semiconductor diode laser with a wavelength of 940 nm was applied on the condyle area (100 mW, 2.5 J, 3.9 J/cm²). The laser was applied twice a week in the first month and once a week in the second and third months, totalizing 16 sessions. Skeletal, dental, and soft-tissue cephalometric parameters were measured and compared at different treatment points.

Results

Mandibular length (Co-Gn) was significantly increased by 3.6 mm in the experiment group (3.16 SD) and 4.3 mm (4.4 SD) in the control group, with no significant difference between groups at every time point (P-value 0.949 at T2). Similarly, a statistically significant positive effect of treatment was found in both groups on ramus height (Co-Go), upper lip to E-Line, SNA angle, ANB angle, and U1/SN angle with no significant difference between groups.

Conclusion

Based on the results of this preliminary study, low-level laser irradiation with the used parameters seems to have no synergetic impact on the skeletal and dental outcomes of twin-block therapy over 9 months. However, more studies are needed to investigate the effect of low-level laser therapy on condylar growth during functional orthodontic treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41547-022-00158-x.

Evaluation of the Functional Treatment of Patients With Skeletal Class II Malocclusion Using Low-Level Laser Therapy-Assisted Twin-Block Appliance: A Three-Arm Randomized Controlled Trial

Background

Different techniques have been used to reduce functional treatment time including low-level laser therapy (LLLT), and the majority of studies have been conducted on animals. Therefore, the aim of the current study was to evaluate the effects of LLLT on improving orthodontic functional treatment using the Twin-Block (TB) appliance.

Materials and methods

This study was a three-arm, parallel-group randomized controlled trial. Patients were selected using the following inclusion criteria: skeletal Class II Division 1 malocclusion resulting from mandibular retrognathia (angle between the anterior cranial base and the NB plane (i.e., SNB angle): 73°-78°), the sagittal skeletal discrepancy angle (ANB angle) between 4° and 9°, and overjet between 5 and 9 mm. Forty-eight patients were randomly allocated into three equal groups. In the LLLT-TB group, the low-level laser device was used with a wavelength of 808 nm and power of 250 mW in addition to functional treatment with a Twin-Block appliance. The laser was applied on the skin at the bilateral temporomandibular joint (TMJ) regions, at five points, each point received 5 J of the laser for 20 seconds. The laser course was twice a week in the first month, every two weeks in the second month, and every three weeks up to the end of the treatment. The second group (the TB group) received functional treatment with a Twin-Block appliance, while patients in the third group (the untreated control group (UCG)) were observed for nine months without any intervention.

Results

There were statistically significant differences in treatment periods between the LLLT-TB group and the TB group (129 days and 235 days, respectively, P-value<0.001). The change in the effective mandibular length (Co-Gn) was the highest in the LLLT-TB group compared with the TB and the UCG groups (4.41 mm, 3.66 mm, and 1.07 mm, respectively; P-value<0.001).

Conclusions

The application of low-level laser therapy on the condylar regions accelerated the functional treatment in skeletal Class II malocclusion patients by approximately 45% and increased the bone growth and mandibular length. The improvement in the SNB angle was similar in both interventional groups. Irradiation of low-level laser stimulated bone growth at the condyles and did not cause anterior movement of the temporomandibular joint following functional orthopedic correction.

Effect of Strontium Ranelate on Condylar Growth during Mandibular Advancement in Rats

Objective

Strontium ranelate (SR), unlike other anti-osteoporotic agents, might not only prevent bone resorption but also might induce bone formation. The aim of this experimental study was to evaluate the effects of systemic SR on condylar growth during mandibular advancement (MA) in growing rats.

Methods

Fifty-six, 8-week-old Wistar male rats weighting 160-190 g were randomly divided into four groups; one control (n=14) and three experimental (n=14). Group 1: Control group, Group 2: SR (900mg/kg daily dose), Group 3: MA, Group 4: SR +MA. The amount and direction of mandibular growth were assessed by linear measurements on the computed tomography (CT) images taken on days 1, 15, and 30. For immunohistochemical evaluation, half of the subjects in the groups were sacrificed on the 15th day (early phase) and the rest of them on the 30th day (late phase). New cartilage and bone formation areas on the condyle were analyzed by using Sox9 and Osteopontin antibodies.

Results

Early and late CT images measurements showed no significant difference between the groups (p<0.05). However, there were significant differences between the control and experimental groups in the immunohistochemical assessment. Severe immunolocalization of SOX9 and Osteopontin was observed in Group 4, while the immunolocalization scores were moderate in Group 2 and Group 3. In addition, early histological findings were similar to late results in all groups.

Conclusion

In mandibular advancement therapy, Strontium ranelate could be therapeutically effective in avoiding relapse and reducing the duration of retention.

Three-Dimensional Assessment of Mandibular Condylar Volume and Position Subsequent to Twin Block Functional Therapy of Skeletal Class II Malocclusion Accompanied by Low-Level Laser Therapy

This study aimed to evaluate and compare the effect of low-level laser therapy (LLLT) on mandibular condylar volume and position following treatment of a Class II malocclusion with a twin block (TB) appliance employing cone beam computed tomography (CBCT). Twenty-four growing patients, aged 9–12 years, were randomly allocated into control and laser groups. All patients were treated with a TB appliance. The patients in the laser group were treated weekly with a gallium–aluminum–arsenide (GaAlAs) diode laser around the temporomandibular joint (TMJ) region for three months. CBCT images were obtained before and after TB therapy and the changes in TMJ and skeletal variables were evaluated and compared among and between the groups. In the laser group, the condylar volume of the right and left sides significantly increased by 213.3 mm³ and 231.2 mm³, respectively (p < 0.05), whereas in the control group it significantly increased by 225.2 mm³, and 244.2 mm³, respectively (p < 0.05), with forward and lateral positioning of both sides. Furthermore, effective mandibular, ramus, and corpus lengths were increased, which were not significant between the groups. Low-Level Laser therapy accomplished no considerable effect on mandibular condylar volume and position following the functional orthopedic treatment of skeletal Class II malocclusions using a TB appliance.

Photobiomodulation and Mandibular Advancement Modulates Cartilage Thickness and Matrix Deposition in the Mandibular Condyle

Objective: We evaluated the effects of photobiomodulation (PBM), mandibular advancement (MA), and the combination of both treatments (PBM+MA) on condylar growth, by the analysis of cartilage and bone formation, fibrillar collagen deposition, proteoglycan content, cell proliferation, and clastic cell index (CCI). Methods: Forty male Wistar rats were randomly assigned to CONTROL, PBM, positive control-MA, and PBM+MA groups. The appliance was worn 10 h/day. Laser was irradiated bilaterally on mandibular condyles in 8 alternate days (1 irradiation point per condyle) using the following parameters: 780 nm, 10 J/cm2, 40 mW, 1 W/cm2, 10 sec/point, 0.4 J/point, and cumulative dose per point: 3.2 J. PBM+MA received both treatments simultaneously. After 15 days, the animals were euthanized and the condyles dissected and embedded in paraffin. Histological sections from the intermediate portion of the condyle were used for morphometric analysis. The relative frequency (%) of fibrillar collagens was determined in sections stained with picrosirius red-hematoxylin under polarized light or Gömöri's method for reticular fibers. Proteoglycan content was evaluated by computerized photocolorimetric analysis. CCI was determined by tartrate-resistant acid phosphatase (TRAP), and proliferating cell nuclear antigen (PCNA) was detected by immunohistochemistry. Results: PBM and MA influenced condylar cartilage thickeness and matrix deposition, but none of the treatments affected significantly the area of the condyle. CCI were not influenced by the treatments, but clastic cells distribution was influenced by MA and PBM+MA treatments. There was no significant difference in proliferating cells among the groups. Conclusions: This study demonstrated that PBM and MA stimulates matrix deposition and cartilage thickening in the mandibular condyle, but was not able to demonstrate a synergistic effect between the treatments. Additional studies should be conducted to evaluate the possible synergistic effect between PBM and MA.

The effects of low-level laser therapy on condylar growth with a mandibular advancement appliance in rats

OBJECTIVE

The aim of this study was to evaluate the effects of low-level laser therapy (LLLT) on condylar growth with a mandibular advancement appliance in rats.

BACKGROUND DATA

Researchers studied new methods such as laser, for mandibular condyle growth stimulation and acceleration with or without functional appliances in experimental animals, but the specific mechanism and laser energy density values for condylar biostimulation and bone cell activities are still unknown.

METHODS

Forty-eight 8-week-old male Wistar albino rats weighing between 260 and 280 g were randomly divided into four groups. Group I was the control group; group II was the mandibular advancement appliance group; group III was the 8 J/cm(2) (0.25 W, 20 sec) laser irradiation with mandibular advancement appliance group; and group IV was the 10 J/cm(2) (0.25 W, 25 sec) laser irradiation with mandibular advancement appliance group. Experimental rats in groups III and IV were stimulated with a low-level laser in the temporomandibular joint region bilaterally 15 times over 30 days. Morphological changes in the mandible were evaluated with lateral radiographs before and after the study with selected linear and angular measurements. Pearson correlation test, Friedman, Kruskal-Wallis, and Mann-Whitney U tests were used for statistical analysis.

RESULTS

According the lateral radiograph results, the growth of mandibles in the experimental groups was significantly more than that of the control group (p<0.05). Group III also showed greater mandibular growth than the other groups (p<0.05).

CONCLUSIONS

We concluded that an intraoral appliance with LLLT, including chosen parameters, can stimulate condylar growth and increase mandibular advancement.

Guideline for the prevention of oral and oropharyngeal mucositis in children receiving treatment for cancer or undergoing haematopoietic stem cell transplantation

PURPOSE

To develop an evidence-based clinical practice guideline for the prevention of oral mucositis in children (0-18 years) receiving treatment for cancer or undergoing haematopoietic stem cell transplantation (HSCT).

METHODS

The Mucositis Prevention Guideline Development Group was interdisciplinary and included internationally recognised experts in paediatric mucositis. For the evidence review, we included randomised controlled trials (RCTs) conducted in either children or adults evaluating the following interventions selected according to prespecified criteria: cryotherapy, low level light therapy (LLLT) and keratinocyte growth factor (KGF). We also examined RCTs of any intervention conducted in children. For all systematic reviews, we synthesised the occurrence of severe oral mucositis. The Grades of Recommendation, Assessment, Development and Evaluation approach was used to describe quality of evidence and strength of recommendations.

RESULTS

We suggest cryotherapy or LLLT may be offered to cooperative children receiving chemotherapy or HSCT conditioning with regimens associated with a high rate of mucositis. We also suggest KGF may be offered to children receiving HSCT conditioning with regimens associated with a high rate of severe mucositis. However, KGF use merits caution as there is a lack of efficacy and toxicity data in children, and a lack of long-term follow-up data in paediatric cancers. No other interventions were recommended for oral mucositis prevention in children.

CONCLUSIONS

All three specific interventions evaluated in this clinical practice guideline were associated with a weak recommendation for use. There may be important organisational and cost barriers to the adoption of LLLT and KGF. Considerations for implementation and key research gaps are highlighted.

Low power laser stimulation of the bone consolidation in tibial fractures of rats: a radiologic and histopathological analysis

The objective of this study is to analyze the effectiveness of low power laser irradiation in the bone consolidation of tibial fractures in rats. An experimental, comparative, prospective study with control group was designed. Twenty Wistar rats were grouped into control (n = 10) and experimental groups (n = 10). A tibial fracture, with a mechanical drill, was inflicted in all rats. The experimental group received ten days of low power arsenide-gallium laser irradiation of 850 nm (KLD, Sao Paulo, Brasil)-100 mW, 8 J/cm(2), 64 s. Before and after the laser treatment, a radiologic analysis was carried out in both groups, in which the rats were graded from 0 to IV according the Montoya scale of bone consolidation. Also, we histopathologically analyzed the bone to estimate the proliferation of fibroblasts, bone matrix, and angiogénesis with a microscopy, which were graded as I (thin layer of fibroblasts and osteoid matrix), II (thick layer of fibroblasts and osteoid matrix), or III (thick layer of fibroblasts and osteoid matrix and new blood vessels). Radiologic data showed that the experimental group had a higher bone consolidation of Montoya scale after ten days of laser irradiation compared to control group (P < 0.004). Histopathologic data showed more fibroblasts and angiogenesis presence in the group receiving laser irradiation, compared to control group (P < .002). The low power laser radiation therapy may expedite the bone repair after tibial fractures in rats, according to radiologic and histopathologic analysis.

Effects of a low level laser on periodontal tissue in hypofunctional teeth

Malocclusions, such as an open bite and high canines, are often encountered in orthodontic practice. Teeth without occlusal stimuli are known as hypofunctional teeth, and numerous atrophic changes have been reported in the periodontal tissue, including reductions in blood vessels in the periodontal ligament (PDL), heavy root resorption, and reduced bone mineral density (BMD) in the alveolar bone. Low Level Laser (LLL) has been shown to have a positive effect on bone formation and the vasculature. Although the recovery of hypofunctional teeth remains unclear, LLL is expected to have a positive influence on periodontal tissue in occlusal hypofunction. The aim of the present study was to elucidate the relationship between LLL and periodontal tissue in occlusal hypofunction. Twenty-four male rats aged 5 weeks were randomly divided into control and hypofunctional groups. An anterior metal cap and bite plate were attached to the maxillary and mandibular incisors in the hypofunctional group to simulate occlusal hypofunction in the molars. LLL irradiation was applied to the maxillary first molar through the gingival sulcus in half of the rats. Rats were divided into four groups; control, control+LLL, hypofunctional, and hypofunctional+LLL. Exposure to LLL irradiation was performed for 3 minutes every other day for 2 weeks. Animals were examined by Micro-CT at 5 and 7 weeks and were subsequently sacrificed. Heads were resected and examined histologically and immunohistologically. The hypofunctional group had obvious stricture of the PDL. However, no significant differences were observed in the PDL and alveolar bone between the hypofunctional+LLL and the control groups. In addition, the expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF)-positive cells were higher in the hypofunctional + LLL group than in the hypofunctional group. These results indicated that LLL enhanced the production of bFGF and VEGF in the periodontal tissue of hypofunctional teeth.

Radiodensitometric Assessment of the Effect of Pulsed Electromagnetic Field Stimulation Versus Low Intensity Laser Irradiation on Mandibular Fracture Repair: A Preliminary Clinical Trial

PURPOSE

Closed reduction of mandibular fractures usually entails a relatively long period of immobilization, with the subsequent delay of rehabilitation. Therefore, shorter immobilization period with various approaches to protect or enhance bone healing have been investigated. The aim of this study was to analyze the effects of pulsed electromagnetic field (PEMF) and low intensity laser irradiation (LILI) on the fracture healing process, through radiodensitometric assessment of the bone callus.

PATIENTS AND METHODS

Eighteen patients with mandibular fractures at the tooth bearing area participated in this prospective study. They were treated by closed reduction using maxillo-mandibular fixation (MMF) and were consecutively assigned into 1 of 3 groups. In group A, the fracture sites were exposed to PEMF for 2 h daily for 12 days. In group B, the fracture sites were exposed to LILI on the tenth and twelfth postoperative days (2 sessions of 6 min per day 2 h apart). The fracture sites in group C acted as controls. MMF was maintained for 2 weeks in group A and 4 weeks in groups B and C. The bone fracture healing was evaluated clinically by investigating the union of the fractured segments and radiographically using computerized densitometry. The union of the fractured segments was tested by manual manipulation and the occlusion was assessed upon removal of MMF. Standardized digital panoramic radiographs were performed for each patient, immediately postoperatively as well as at 2 and 4 weeks. The digital images were manipulated using the IDRISI software. A rectangular area of 10 × 15 mm was drawn along the center of the fracture line. The obtained densitometry values were expressed in gray levels from 0 to 256. The collected data were then tabulated and statistically analyzed.

RESULTS

After releasing the MMF, the bimanual mobility test of the fractured segments in all patients showed stability of the segments. The preinjury occlusion was maintained in all patients. The postoperative radiographs of all patients revealed good bony alignment of the bony segments. In all groups, comparison between the study intervals with respect to both means and changes percentages of the bone density values showed insignificant differences. At 2nd postoperative week, the mean bone density at the fracture sites decreased by 4.74, 6.6 and 27.89 % in groups A, B and C respectively. The period from the 2nd to the 4th postoperative weeks showed increase in the bone density by 1.49, 1.95 and 14.12 % in groups A, B and C respectively. Insignificant difference was found between the means of bone densities of group A and B throughout the study intervals. On the other hand, both groups showed insignificant difference with group C immediately postoperative and significant increase in bone density at the 2nd and 4th postoperative weeks.

CONCLUSIONS

Short period immobilization of mandibular fractures for 2 weeks supplemented with PEMF is recommended. Further studies are needed to evaluate the efficacy of LILI as a supplement to reduce the mandibular fracture immobilization period.

The effects of low-level laser therapy, 670 nm, on epiphyseal growth in rats

The longitudinal growth of long bones is attributed to epiphyseal growth. However, the effects of low-level laser therapy (LLLT) in such structures has still not been studied extensively in the literature. Therefore, the aim of this study was to evaluate the use of LLLT, 670 nm, at three different doses on the epiphyseal growth of the right tibia of rats. Twenty-one Wistar rats, aged four weeks, were subjected to the application of LLLT, with dosage according to the group (G4: were submitted to the application of 4 J/cm²; G8: were submitted to the application of 8 J/cm²; G16: were submitted to the application of 16 J/cm²). After completion of protocol they were kept until they were 14 weeks of age and then submitted to a radiological examination (evaluation of limb length) and euthanised. The histological analysis of the growth plates (total thickness and hypertrophic and proliferative zones) was then performed. Comparisons were made with the untreated left tibia. No differences were observed in any of the reviews (radiological and histological), when comparing the right sides (treated) to the left (untreated). It was concluded that the treatment with LLLT within the parameters used caused changes neither in areas of the epiphyseal cartilage nor in the final length of limbs.

Low-level laser on femoral growth plate in rats

PURPOSE

To determine the influence of low-level laser therapy on femoral growth plate in rats.

METHODS

Thirty male Wistar rats aged 40 days were divided into two groups, G1 and G2. In G1 the area of the distal growth plate of the right femur was irradiated at one point using GaAlAs laser 830 nm wavelength, output power of 40 mW, at an energy density of 10 J/cm(2). The irradiation was performed daily for a maximum of 21 days. The same procedure was done in G2, but the probe was turned off. Five animals in each group were euthanized on days 7, 14 and 21 and submitted to histomorphometric analysis.

RESULTS

In both groups the growth plate was radiographically visible at all moments from both craniocaudal and mediolateral views. On the 21st day percentage of femoral longitudinal length was higher in G2 than G1 compared to basal value while hypertrophic zone chondrocyte numbers were higher in G1 than G2. Calcified cartilage zone was greater in G1 than in G2 at all evaluation moments. Angiogenesis was higher in G1 than in G2 at 14th and 21st days.

CONCLUSION

The low-level laser therapy negatively influenced the distal femoral growth plate.

The effect of low level laser on condylar growth during mandibular advancement in rabbits

INTRODUCTION

It has been shown that Low Level Laser (LLL) has a positive effect on bone formation. The aim of this study was to evaluate the effect of low level laser on condylar growth during mandibular advancement in rabbits.

MATERIALS AND METHODS

Continuous forward mandibular advancement was performed in fourteen male Albino rabbits with the mean age of 8 weeks and the mean weight of 1.5 ± 0.5 kg, with acrylic inclined planes. The rabbits were randomly assigned into two groups after 4 weeks. LLL (KLO3: wave length 630 nm) was irradiated at 3 points around the TMJ, through the skin in the first group. The exposure was performed for 3 minutes at each point (a total of 9 minutes) once a day for 3 weeks. The control group was not exposed to any irradiation. The rabbits in both groups were sacrificed after two months and the histological evaluation of TMJ was performed to compare fibrous tissue, cartilage, and new bone formation in condylar region in both groups. Disc displacement was also detected in both groups. Student's t-test, Exact Fisher and Chi square tests were used for the statistical analysis.

RESULTS

The formation of fibrous tissue was significantly lower, while bone formation was significantly greater in lased group as compared with control group. The thickness of cartilage did not differ significantly between two groups.

CONCLUSION

Irradiation of LLL (KLO3) during mandibular advancement in rabbits, increases bone formation in condylar region, while neither increase in the cartilage thickness nor fibrous tissues was observed.