Comparison of effectiveness of Low-Intensity Pulsed Ultrasound (LIPUS) Versus Low Level Laser Therapy (LLLT) on Healing of Wound Following Surgical Extraction of Mandibular Third Molar A Randomized control study

The surgical removal of mandibular third molars produces a significant degree of trauma to soft tissues and bony structures of oral cavity, resulting in release of inflammatory mediators.1 This produces postoperative signs and symptoms of pain, oedema and trismus, etc. Several therapeutic protocols such as use of various preoperative or postoperative antibiotic administration, different incisions, postoperative ice packs, corticosteroid administration by systemic, local or topical route are reported in literature for management of this postoperative sequelae and are constantly evolving.2

Accelerated healing after a surgical tooth extraction is important because it reduces the risk of infection, minimizes pain and discomfort, and facilitates faster recovery, allowing patients to resume normal activities sooner. Low level laser therapy and lowintensity pulsed ultrasound (LIPUS) are some of the more recently reported protocols that have been proven to reduce inflammatory mediators. Other methods for accelerated healing include topical melatonin application, platelet-rich fibrin (PRF) application, and axial micromovement, all of which have shown promise in promoting faster tissue regeneration and bone repair.

Laser is important in basic sciences, but mainly so in the diagnosis and treatment of the different pathologic conditions of the patients. It is electromagnetic radiation3 and is a source of light or radiation energy4; as it is not X-irradiation, it is not expected to produce a new generation of iatrogenic malignancies. Maiman described laser in the form of a ruby laser in

19605. LLL is a special type of laser that affects biologic systems through non-thermal means6. This area of investigation was initiated with the work of Mester et al. in 1967. Mester et al found the non-thermal properties of lasers on hair growth in mouse7.

LLLT is the application of light to a biological tissue to promote tissue regeneration. It has a photochemical effect; according to this effect, the light is absorbed and causes a chemical change8. The reason behind why this technique is termed ‘low-level’ is because the optimal levels of dose provided are lower than other forms of laser therapy such as those practiced for ablation, cutting, and thermal tissue coagulation9.

Ultrasound can be defined as sound wave or pressure wave with a frequency  above the limit of the human hearing range(16–20 kHz).The unit of ultrasound is Hertz or cycle per second. Being a propagating pressure wave, ultrasound is capable of transferring mechanical energy into the tissues. The energy of the ultrasound signal is transferred, propagated, or reflected depending on its frequency.10

In the year 1976, Duarte first reported that LIPUS stimulated the growth of bone healing of fresh fracture in experimental cortical defects and fibular osteotomy in rabbits and non-unions in humans. Similar findings have been reported in treatment of osteoradionecrosis, tibial fractures, distal radial fractures with findings such as reduction in healing time by 38-41%. The acceleration of callus formation in diabetic fractures has also been reported.11

LIPUS therapy has been widely accepted for enhancing endochondral bone formation.12 It has also been demonstrated to increase the blood flow near the injured area13. The therapeutic ultrasound used in LIPUS is harmless and does not require any subsequent surgeries14. It has been reported to have higher efficiency of the treatment, especially when it is performed in the initial stage of the impact. In addition, LIPUS treatment can be used along with the metallic fixtures, without causing any adverse side effects to the tissues.15

Apart from the use in orthopedic field, the clinical application of ultrasound therapy has now been extended to healing of maxillofacial bones.16 Konno et al further reported that LIPUS increased the acceleration of callus formation in the stimulation side compared with the nonstimulation side.17 LIPUS increases bone mineralization and stimulates fracture repair by converting the cartilaginous soft callus into mineralized callus, improving the stability of fracture union.18

In case of ultrasound therapy, the mechanical stimulation inherent to ultrasound waves translates into a biological response. LIPUS waves create nano-motion at the fracture site, where the mechanical signal is converted into biochemical signals intracellularly. It stimulates the production of cyclooxygenase 2, which promotes prostaglandin E2 (PGE2) production. PGE2 triggers osteogenic genes, which facilitate mineralization and endochondral ossification, thereby aiding in bony healing.19

Despite several in vitro and in vivo applications of lowintensity pulsed ultrasound (LIPUS) and low intensity laser therapy (LILT) , it remains an understudied feature of the oral and maxillofacial region. Based on the understanding of the mechanism of LIPUS and LILT , it is the goal of this study to objectively investigate the efficacy of lowintensity pulsed ultrasound  and low intensity laser therapy on wound healing following removal of an third molar.1