Evaluation of the effect of low-level diode laser therapy applied during the bone consolidation period following mandibular distraction osteogenesis in the human

Abstract

The aim of this study was to evaluate the effect of low-level laser therapy (LLLT) on new bone formation obtained by distraction osteogenesis in the early consolidation period. Ten selected patients with bilateral mandibular retrusion seen at the Nasser Institute Hospital, Egypt between June 2009 and June 2012 underwent this clinical trial; seven were female and three were male, and their mean age was 31 ± 5.1 years. The left mandible of each patient was assigned to group A ( n = 10) and the right mandible to group B ( n = 10); mandibular distraction osteogenesis was performed on both sides and then LLLT was used in group B only. The amounts of bone acquired were compared according to their radiographic density on digital panoramic radiographs after 6, 12, 24, and 54 days of consolidation. Statistically significant differences in bone density were found between the two groups. Group B showed bone consolidation and growth differences on day 6 ( P = 0.402), day 12 ( P = 0.006), day 24 ( P = 0.021), and day 54 ( P = 0.028). The use of LLLT on distracted bone was found to increase the quality and quantity of bone and to shorten the consolidation period, allowing early removal of the distractor and resulting in decreased morbidity and relapse.

Distraction osteogenesis (DO) is a technique for inducing new bone formation. After an osteotomy or corticotomy, the bony segments are separated and then gradual tension is applied to the callus connecting the separated bony segments using an external or internal fixation device, thereby lengthening the bone. This is followed by a consolidation phase in which the bone continues to heal.

DO has become an increasingly used alternative method for facial bone reconstruction, with promising results. However, the long-term stability of the results obtained with DO only is not well documented, and reports of instability and relapse can be found in the literature.

The gradual tension applied to the fracture gap activates the transformation of mesenchymal cells into osteoblasts and fibroblasts secreting type I collagen, which is organized into fibrils. The periosteal and endosteal surfaces on either side of the fracture gap are rapidly revascularized, and woven bone extends rapidly into the collagen fibrils. This inter-zone remains relatively avascular, but becomes vascularized and mineralized rapidly once distraction ceases during the consolidation phase.

Previous research aimed at increasing the quality and quantity of the newly formed bone obtained by DO, using supplements that promote osteogenesis such as hyperbaric oxygen or low-level laser therapy (LLLT), has been performed only in experimental animals. This research has sought to enhance the new bone growth and maturation in order to shorten the DO period by decreasing the duration of application.

LLLT has been shown to be effective in wound healing, collagen synthesis, matrix deposition, angiogenesis, epithelialization, and osteogenesis. LLLT increases osteogenesis by activating osteoblasts, increases the quality and quantity of bone that is augmented by DO, and reduces the time to maturation, with a marked reduction in osteoclast maturation and action.

The effect of DO in combination with LLLT has been evaluated only in experimental animals and has been shown to increase both bone mineral density and torsional strength by many authors ( Table 1 ).

Table 1
Experimental studies showing the effects of LLLT on distracted mandibles.
Study [Ref.] Type of animal Type of laser used Method of assessment Conclusion
Miloro et al. (2007) Adult female New Zealand white rabbits ( n = 9) GaAlAs – 820 nm Radiographs using a bone healing score; histological examination using H&E dyes LLLT accelerated the process of bone healing during the consolidation period
Cerqueira et al. (2007) Sheep ( n = 18) GaAlAs – 830 nm Microscopic analysis using H&E dyes The laser was more favourable when used in the consolidation period, after bone elongation
Hübler et al. (2010) Adult male New Zealand rabbits ( Oryctolagus cuniculus ) ( n = 5) GaAlAs – 830 nm X-ray fluorescence spectroscopy LLLT had a positive effect on the regeneration of newly formed bone
Kreisner et al. (2010) Adult male New Zealand rabbits ( Oryctolagus cuniculus ) ( n = 10) GaAlAs – 830 nm Microscopic analysis using H&E dyes LLLT had a positive effect on the quality of bone sites, allowing early removal of the distractors, and consequently reducing the total treatment time
Freddo et al. (2012) Female Corriedale sheep ( n = 5) GaAlAs – 830 nm CT imaging LLLT provided numerous benefits when applied during the bone consolidation period, as it promoted an increase in hardness and modulus of elasticity values
De Conto et al. (2013) Male New Zealand white rabbits (order Lagomorpha , genus
Oryctolagus , species O. cuniculus ) ( n = 24)
GaAlAs–830 nm Microscopic analysis using H&E dyes and histomorphometric analysis The application of LLLT following the irradiation protocol used in this study had a positive effect on the tissue repair process in a rabbit model of mandibular fracture and distraction
Kan et al. 2014 Female New Zealand white rabbits ( n = 16) GaAlAs–808 nm Micro-CT analysis; analysis of plain radiographs; histology and histomorphometry LLLT application in the distraction period activated bone healing; LLLT may decrease the distraction period

LLLT, low-level laser therapy; H&E, haematoxylin and eosin; CT, computed tomography.

Taking into account the reported positive influences of LLLT on experimental mandibular DO, it was decided to investigate the potential effect of a diode laser (905 nm) on the process of bone regeneration during the consolidation phase after human mandibular DO, with the aim of reducing the duration of distraction and thus the complications associated with a long-term distractor device.

Patients and methods

The clinical trial design and protocol of this study were approved by the research ethics committees of Nasser Institute Hospital and Salman Bin Abdulaziz University. All patients underwent surgery in the Oral and Maxillofacial Surgery Department of the Nasser Institute Hospital in Cairo, Egypt.

Ten patients with bilateral mandibular retrusion were selected; seven were female (70%) and three were male (30%), and their mean age was 31 ± 5.1 years (range 18–46 years). These patients were seen over a 3-year period, from June 2009 to June 2012. The patients were treated under the guidelines of the hospital after they had been informed of the risks and benefits of the planned procedures. All provided written informed consent to participate in this study.

The study patients had a skeletal class II malocclusion with mandibular retrusion, either acquired congenitally or from a trauma. All patients had a clinical indication for bilateral mandibular DO, with no evidence of other systemic disease, following clinical examination and full radiological and laboratory investigations. Patients who had undergone a previous mandibular tumour resection, those aged <18 years, and tobacco smokers were excluded.

As the patients had bilateral mandibular retrusion, the left mandible of each patient was assigned to group A ( n = 10) and the right mandible to group B ( n = 10). Group A underwent DO only using a mandibular distractor (Multi-Guide II System; Stryker GmbH, Duisburg, Germany) and group B underwent DO followed by LLLT (gallium–arsenide (GaAs), 905 nm). The LLLT was applied as adjuvant therapy, with a fixed duration and equal intensity of exposure, from day 1 of the consolidation period to day 24 of consolidation.

Surgical procedure

The surgical procedure was carried out according to the technique of McCarthy et al., with the patients under general anaesthesia with nasotracheal intubation.

The surgical field was prepared and disinfected with iodine solution before the operation. All patients were treated with bilateral external distraction devices (Stryker Multi-Guide II System). The operation was performed intraorally by raising a mucoperiosteal flap in the third molar area; the third molar tooth germ was removed, if present, 3 months before distractor placement. In order to advance the mandible, the osteotomy was performed in the mandibular body just anterior to the gonial angle; great care was taken to remain monocortical with the reciprocating saw, completing the osteotomy with a 4-mm osteotome to preserve the inferior alveolar nerve. While planning a forward distraction vector, four extraoral pins were placed bicortically through the cheek across the planned osteotomy line and two extraoral bidirectional mandibular devices were fixed on each side of the mandible. It is important to place the device parallel to the mandibular body in order to advance the retruded mandible.

Distraction protocol

The distraction device was not activated during the first 5 days of the post-osteotomy period (the latency period); it was only checked and washed with 1% iodophor alcohol. The device was activated on day 6 postoperative and activation was continued for 7–14 days (total activation time between 7 and 14 days). The activation rate was 0.5 mm twice a day (1 mm/day), depending on the planned mandibular lengthening required for each patient ( Fig. 1 ). The consolidation period following the activation period lasted 30 days; the distractor was removed and replaced with mini titanium plates on day 1 of the consolidation period.

Fig. 1
Stryker Multi-Guide II System (during the activation period).

Laser therapy protocol (during the consolidation period)

During the consolidation period, each patient’s right mandible (group B) underwent LLLT. An ASA IDEA Terza GaAs laser device (Lasermedico, Herzele, Belgium) was used (laser wavelength of 905 nm and power of 500 mW). This was applied at four different points across the osteotomy area: the first two points were located on the lateral surface, while the other two points were located on the inferior body of the right mandible) ( Fig. 2 ). A total of 20 J/cm 2 was applied – 5 J/cm 2 applied to each point in a continuous contact mode, for 2 min, for 12 sessions.

Fig. 2
Application of diode laser irradiation: (A) lateral surface and (B) inferior border.

Ultrasound evaluation of consolidation

The ultrasound device used for examination of consolidation was the Sonoline G50 (1998) (Siemens, Germany). A clear ultrasound gel was applied to the patient’s skin surface with minimal pressure to avoid pain. The ultrasonic transducer used was a 7.5-MHz linear phased array and the ultrasound waves were oriented at a 90-degree angle to the bone surface. Ultrasound examination of the distraction gap was done at three fixed points for all patients and both groups: the first point was at the upper border of the alveolus, the second at the lower border of the mandible, and the third in the middle part; measurements were recorded in centimetres. Both the distraction gap and bony margins were examined for echogenicity as a sign of bone healing. The distraction gap was evaluated during active distraction, on day 1 of the consolidation period, and then on day 4 (after two LLLT sessions), day 8 (after four LLLT sessions), and day 16 (after eight LLLT sessions) of the consolidation period. Ultrasound examination was not possible during the early postoperative period, as postoperative oedema interfered with imaging.

Analysis of digital panoramic radiographs

Digital panoramic radiographs were obtained using a PLANMECA ProMaX (Planmeca Oy, Finland; 54–84 kV, 1–16 mA, 2.8–12 s, and 400 voxel size) for all patients (both groups) before surgery and on day 6 (after three LLLT sessions), day 12 (after six LLLT sessions), day 24 (after 12 LLLT sessions), and day 54 (1 month after 12 LLLT sessions) of the consolidation period–thus a total five exposures.

Measurement of bone density

Bone density was calculated from the panoramic radiographs using Digora software for Windows (Soredex, Milwaukee, WI, USA) in the selected area of the distracted bone, and was recorded in units of g/cm 2 . The following technique was used: A line was drawn in the distracted area by joining two points, the first at the upper border and the second at the lower border in the centre on the digital panoramic radiograph; Digora software was used to calculate and report the maximum, minimum, and mean density in this region. A radiologist experienced in using Digora software did all measurements for both the right and left distracted areas after 3, 6, and 12 sessions of laser irradiation, and at 1 month after 12 sessions of laser irradiation. The mandibular bone density data obtained for both groups were collected and analyzed statistically.

Statistical analysis

Data were presented as the mean and standard deviation (SD) values. The data showed a parametric distribution, hence the Student t -test was used to compare the results of the radiated and irradiated mandible sides. The paired t -test or McNemar test was used to compare parameters at different time points. The level of significance was set at P ≤ 0.05. The statistical analysis was performed using IBM SPSS Statistics for Windows, version 20.0 (IBM Corp., Armonk, NY, USA).

Results

Ultrasound evaluation

The anterior distal and proximal mandibular cortices were identifiable as a ‘double hyper-reflecting layer’ in the longitudinal ultrasound images ( Fig. 3 ), a sign confirming the size of the distraction gap.

Fig. 3
Comparison of representative longitudinal ultrasound images obtained during distraction osteogenesis treatment in the two study groups (group A, no LLLT; group B, LLLT applied). The white arrow indicates the location of the distraction gap for both groups.

Comparisons were made between the ultrasound images, and the echogenicity of the callus was found to increase locally and temporally. During active distraction and on day 1 of the consolidation period, echogenic flecks were distributed randomly in the distraction gap in both groups ( Table 2 and Fig. 4 ). Following further mandibular lengthening, echogenic streaks were noticed that had an increased echogenicity. In group B, on day 4 of the consolidation period (after two sessions of laser irradiation), these streaks showed greater echogenicity in the distal and proximal regions; however, the echogenic streaks were still not joined together. On day 8 of the consolidation period (after four sessions of laser irradiation), the discontinuity of the bone callus had almost disappeared and hyper-echogenicity had started to develop in the anterior part of the distraction gap. On day 16 of the consolidation period (after eight sessions of laser irradiation), full consolidation of the bone callus and the complete disappearance of the distraction gap had occurred in the posterior part of the callus and was detected by multiple ultrasound reflections. In group A, discontinuity of the bone callus was still apparent on day 16 of the consolidation period.

Table 2
Measurements of the distraction gap during the consolidation period (in centimetres).
Distraction period Consolidation period
Middle of the period Day 1 Day 4 Day 8 Day 16
Group A Group B Group A Group B Group A Group B Group A Group B Group A Group B
Upper point (cm) 0.75 0.74 1.72 1.54 1.62 0.91 1.12 0.43 0.6 0
Middle point (cm) 0.72 0.73 1.44 1.53 1.38 0.83 0.94 0.37 0.54 0
Lower point (cm) 0.78 0.79 1.67 1.8 1.59 0.78 0.96 0.39 0.67 0
Mean ± SD 0.75 ± 0.03 0.75 ± 0.03 1.61 ± 0.149 1.62 ± 0.153 1.53 ± 0.13 0.84 ± 0.066 1.01 ± 0.099 0.397 ± 0.031 0.75 ± 0.112 0
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Jan 17, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Evaluation of the effect of low-level diode laser therapy applied during the bone consolidation period following mandibular distraction osteogenesis in the human
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