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Year : 2012  |  Volume : 4  |  Issue : 1  |  Page : 3-6

Therapeutic ultrasound - The healing sound and its applications in oral diseases: The review of literature

1 Department of Oral Medicine and Radiology, Vishnu Dental College, Bhimavaram, Andhra Pradesh, India
2 Department of Oral Medicine and Radiology, SIBAR Institute of Dental Sciences, Guntur, Andhra Pradesh, India

Date of Web Publication10-Sep-2012

Correspondence Address:
Jyothirmai Koneru
Department of Oral Medicine and Radiology, Vishnu Dental College, Bhimavaram, Andhra Pradesh
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0975-8844.99873

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The application of medical ultrasound was mainly centered on the soft tissue diagnostic imaging until now. Recently, its use has been widened and adopted for various therapeutic purposes. It has been reported to facilitate the healing of bone fractures, wounds, apthous ulcers and temporomandibular disorders. In addition, ultrasound has also been shown to facilitate delivery of chemotherapeutic drugs into tumors, promote gene therapy to targeted tissues, and deliver thrombolytic drugs into blood clots. This article reviews the principles and current status of ultrasound-based treatments.

Keywords: Apthous ulcer, cavitation, fracture healing, sonoporation, therapy, ultrasound

How to cite this article:
Koneru J, Alaparthi R, Yalamanchali S, Reddy R S. Therapeutic ultrasound - The healing sound and its applications in oral diseases: The review of literature. J Orofac Sci 2012;4:3-6

How to cite this URL:
Koneru J, Alaparthi R, Yalamanchali S, Reddy R S. Therapeutic ultrasound - The healing sound and its applications in oral diseases: The review of literature. J Orofac Sci [serial online] 2012 [cited 2021 Aug 3];4:3-6. Available from:

  Introduction Top

Ultrasound (US) has wide and varied range of applications in the diagnostic field of medicine. It is like a stethoscope in the hands of radiologist when used to examine the underlying pathological conditions. [1] The use of US in the field of medicine had, nonetheless initially started with its applications in therapy rather than diagnosis, utilizing its thermal and disruptive effects on animal tissues. It was in the 1940's that US was used experimentally as a possible diagnostic tool in medicine. Now US is certainly the most widely used soft tissue imaging modality. However, tremendous research has been done on the US in the last few decades in the therapeutic field of medicine. [2]

Ultrasound is defined as sound wave oscillating at a frequency greater than 20,000 cycles per second (Hz). Therapeutic US has a frequency of between 0.7 MHz and 3.3 MHz. These frequencies are able to reach tissue depths of two to five centimeters. [3]

  Thermal and Non-Thermal ­Effects Top

The therapeutic effects of US are derived from both its thermal and non-thermal properties. At intensities of 1-1.5 Watts/ cm 2 , sound waves cause tissue vibration that creates heat in the treatment field. Secondary effects from the production of heat include increasing blood flow to tissue, which delivers important nutrients and removes waste. This is the US mode traditionally used for therapy in musculoskeletal conditions such as spasm. Thermal effects usually last for 5-10 minutes following treatment. [4]

The non-thermal effects of US are achieved at intensities of <0.3-1Watts/ cm 2 . This intensity produces waves which exert pressure on the cell walls, caused by cavitation and micro-streaming. Cavitation can be described as the effects of the sound waves on the fluid within the cell. Bubbles form and begin to expand and contract, causing increased diffusion across the membrane and increased cellular activity. Acoustic micro-streaming is the result of pressure forming in the fluid surrounding a cell, which facilitates components required for tissue healing. These effects cause changes in cell membrane permeability and thus the diffusion of cellular metabolites causing edema reduction, pain modulation, and increased capillary density which, in turn, increases local circulation. [5]

US therapies can broadly be divided into '-high-' power and '-low-' power therapies. High power applications include high intensity focused US (HIFU) and lithotripsy. Low power US encompasses sonophoresis, sonoporation, gene therapy and bone healing. [6] In high intensity focused US (HIFU), the high-intensity US beam is localized to a small focal point, resulting in thermal damage, or thermo coagulation. This minimizes side effects by ablating only the intended volume of tissue. [7] similarly, shock waves from a lithotripter penetrate the body to comminute kidney stones, salivary stones and transcutaneous US enhances the transport of chemotherapy agents. [8]

This review will describe the most frequently used applications of US for therapy pertaining to oral pathologies. Ultrasonically driven devices (used for example in surgery and periodontics) and lithotripsy have not been included.

  Ultrasound in Healing Top

The use of US as a therapeutic approach in bone healing has a history of more than half a century. The first study regarding the effects of ultrasound on bone healing was published in 1950 by Maintz. This research stated that US at high intensities caused thermal damage in bone and lower intensity doses lead to new periosteal bone formation. Two years later, Corradi and Cozzolino, showed that continuous wave ultrasound at 800 kHz and 1.5 W/cm2 stimulated new callus formation along the fracture line in the radial bones of rabbits. [9] In an attempt to reduce the thermal damage to bone and stimulate bone growth, Shiro advocated the use of lower doses and a pulsed ultrasound application. [6]

The effects of ultrasound on bone tissue repair are caused by a multiple mechanisms. Physical effects are due to the vibrations generated in all tissue components, including intracellular and extracellular fluids and cell membranes, which produce a micro massage effect in tissues, causing mechanical stimulation. [10] It has also been shown that US application increases synthesis of angiogenesis-related cytokines such as interleukin, fibroblast growth factor, and vascular endothelial growth factor. The rate of angiogenesis is one of the basic elements in the bone healing process. In soft tissue wound healing thermal US has been used in the late stages (remodeling phase) to improve scar and wound outcome. [11],[12]

  Ultrasound for Treatment of Microbial Disease Top

The science of photodynamic antimicrobial chemotherapy (PACT) utilizes photo sensitizers and light of appropriate wavelength to produce highly reactive free radical species which then destroy the microbial pathogens. PACT has been shown to be ineffective against some microbia because of the limited tissue penetration of visible light. Recently, some photo sensitizers have been discovered which produce free radicals on irradiation with US. These photo sensitizers are termed sonosensitizers (SS). Focused US can penetrate into tissue more deeply than light and can be focused into a small region to activate SS, which was termed sonodynamic therapy (SDT), whose mechanism is similar to PDT which has promising antimicrobial strategy against bacteria, yeasts, viruses and parasites. [13]

  Ultrasound for Treatment of Recurrent Apthous Stomatitis Top

Recurrent apthous stomatitis (RAS) is the most common disease of the oral mucosa. In spite of its high prevalence rate, the cause of this disorder remains obscure. Current evidence strongly supports a role of immune dysfunction, although specific defect has not been identified. There is no uniformly effective therapy for this potentially debilitating disorder.

The use of low intensity US in the form of an ultrasonic tooth brush has been shown to provide a therapeutic benefit in a number of clinical settings, primarily by accelerating the wound healing. Using low intensity US avoids excessive tissue heating and the physiologic responses noted in tissue exposed to these ultrasonic waves are the result of non-thermal effects. One such response is a change in cellular membrane permeability. Other effects include stimulation of fibroblasts and macrophages, increased angiogenesis, promotion of granulation tissue formation, and alteration of oral microflora. This, if any, of these physiologic responses plays a role in the improvement of RAS cannot be determined, although improved oral hygiene, modulation of the inflammatory response, and enhanced wound healing would logically be important factors.

It was demonstrated the use of ultrasonic tooth brush twice daily decreased the number of lesions existing as well as decreased the number of lesions that develop. [14]

  Ultrasound for Treatment of Temporomandibular Disorders Top

The therapeutic efficacy of US alone in the temporomandibular disorders is lacking and it is always used in the combination of electrical stimulation. The therapeutic effect of US is reported to be due to its thermal properties. [15]

  Sonoporation Top

Sonoporation, or cellular sonication, is the use of US for modifying the permeability of the cell plasma membrane. This technique is performed with a commercially available sonoporator. Sonoporation is used in the delivery of therapeutic agents including genetic material, proteins, and chemotherapeutic agents into the cell, in a cell disruption process called transfection or transformation. It employs the acoustic cavitation of microbubbles to enhance delivery of these large molecules. This technique is similar to, and in some cases found superior to, electroporation.

Thus, sonoporation is a promising drug delivery and gene therapy technique, which unlike other methods of transfection or chemotherapy, combines the capability of enhancing gene and drug transfer with the possibility of restricting this effect to the desired area and the desired time. [16],[17]

  Sonothrombolysis Top

A number of investigators demonstrated that US can aid the dissolution of blood clots either on its own or in combination with microbubble contrast agents and fibrinolytic drugs. [18] This is known as sonothrombolysis. It has been proposed that streaming may facilitate the permeation of the drug into the clot, or that the mechanical action of the ultrasound affects the fibrin mesh, allowing better access for the drug. [6] There is also evidence that cavitation may be key in producing effects. [19]

  Hemostasis and Vascular Occlusion Top

Experimental evidence that HIFU can seal blood vessels and halt flow in vessels has been demonstrated by a number of investigators. The range of intensities used is 400-6500W/cm 2 . Selective occlusion of blood vessels may be useful in the treatment of cancer where it might be useful to cut off feeder vessels to the tumor. The mechanism by which hemostasis is achieved is a combination of tissue disruption, release of coagulation induction factors and platelet activation. [6]

  Adverse Effects of Therapeutic Ultrasound Top

Animal studies using pulsed 2MHz ultrasound exposure for 3 minutes reported capillary bleeding in the lung due to the effects of cavitation. However the observed hemorrhage was mild and reversible with no structural damage to the alveolar architecture. [20],[21]

The therapeutic potential of US is extremely promising, but further progress is necessary, notably in the area of the generation of ultrasonic waves. Compared with other medical ultrasonic techniques such as those used in diagnostics, transducers for therapeutic applications have specific requirements. Generation of high power acoustic waves must be precisely localized and controlled in amplitude. These requirements guarantee an improved degree of reliability and safety while taking into account the use of a larger amount of electrical and acoustical energy. New piezocomposite technologies offer performances that have proved to be particularly well adapted for such applications. [22]

  Conclusion Top

Therapeutic applications of US have been employed for over three decades with little documented evidence of adverse effect. While more studies on the bio effects of US are needed to better understand its impact on the body, its use as a therapeutic agent is becoming more widespread primarily because of the medical and cost benefits that could be realized by the non-invasive nature of the procedure. In the near future US will be an efficient therapeutic tool for the treatment of pathological conditions.

  References Top

1.Whaites E. Essentials of dental radiography and radiology. 3rd ed. Philadelphia: Elsevier Publications; 2003. p. 191-208.  Back to cited text no. 1
2.El Bialy T. Therapeutic ultrasound applications in craniofacial growth, healing and tissue engineering. Rejuvenation Res 2007;10:367-72.  Back to cited text no. 2
3.Curry TS, Dowdey JE, Murry Jr RC. Christensen's Physics of diagnostic radiology. In: Carlisle ML, editor. 4th ed. Philadelphia: Lea and Febiger; 1983. p. 351-400.  Back to cited text no. 3
4.Dyson M. Therapeutic application of ultrasound. Clin Diagnost Ultrasound 1985;16:121-34.  Back to cited text no. 4
5.Dyson M. Mechanisms involved in therapeutic ultrasound. Physiotherapy 1987;73:116-20.  Back to cited text no. 5
6.Ter Haar G. Therapeutic applications of ultrasound. Prog Biophys Mol Biol 2007;93:111-29.  Back to cited text no. 6
7.Lynn LG, Zwemer RL, Chick AJ, Miller AE. A new method for the generation and use of focused ultrasound in experimental biology. J Gen Physiol 1992;26:179-93.  Back to cited text no. 7
8.Bailey MR, Khokhlova VA, Sapozhnikov OA, Kargl SG, Crum LA. Physical mechanisms of the therapeutic effect of ultrasound. Acoust Phys 2003;49:369-88.   Back to cited text no. 8
9.Schortinghuis J, Stegenga B, Raghoebar GM, de Bont LG. Ultrasound stimulation of maxillofacial bone healing. Crit Rev Oral Biol Med 2003;14:63-74.  Back to cited text no. 9
10.Erdogan O, Esen E. Biological aspects and clinical importance of ultrasound therapy in bone healing. J Ultrasound Med 2009;28:765-76.  Back to cited text no. 10
11.Kerr EN, Mealey BL, Noujeim ME, Lasho DJ, Nummikoski PV, Mellonig JT. The effect of ultrasound on bone dimensional changes following extraction: A pilot study. J Periodontol 2008;79:283-90.  Back to cited text no. 11
12.Ikai H, Tamura T, Watanabe T. Low-intensity pulsed ultrasound accelerates periodontal wound healing after flap surgery. J Periodont Res 2008;43:212-6.  Back to cited text no. 12
13.Maa X, Pan H, Wu G, Yang Z, Jilin Y. Ultrasound may be exploited for the treatment of microbial diseases. Med Hypotheses 2009;73:18-9.  Back to cited text no. 13
14.Brice SL. Clinical evaluation of the use of low intensity ultrasound in the treatment of recurrent apthous stomatitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997;83:14-20.  Back to cited text no. 14
15.Mohl ND, Ohrbach RK, Crow HC, Gross AJ. Devices for the diagnosis and treatment of temporomandibular disorders. Part III: Thermography, ultrasound, electrical stimulation, and electromyographic biofeedback. J Prosthet Dent 1990;63:472-7.  Back to cited text no. 15
16.Pitt WG, Husseini GA, Staples BJ. Ultrasonic Drug Delivery - A General Review. Expert Opin Drug Deliv 2004;1:37-56.  Back to cited text no. 16
17.Maeda H, Tominaga K, Iwanaga K, Nagao F, Habu M, Tsujisawa T, et al. Targeted drug delivery system for oral cancer therapy using sonoporation. J Oral Pathol Med 2009;38:572-9.  Back to cited text no. 17
18.Hernot S, Klibanov AL. Microbubbles in Ultrasound-Triggered Drug and Gene Delivery. Adv Drug Deliv Rev 2008;60:1153-66.  Back to cited text no. 18
19.Porter TR, LeVeen RF, Fox R, Kricsfeld A, Xie F. Thrombolytic enhancement with perfluorocarbon-exposed sonicated dextrose albumin microbubbles. Am Heart J 1996;132:964-8.  Back to cited text no. 19
20.Dalecki D, Raeman CH, Child SZ, Carstensen EL. Intestinal hemorrhage from exposure to pulsed ultrasound. Ultrasound Med Biol 1995;21:1067-72.  Back to cited text no. 20
21.Tarantal AF, Canfield DR. Ultrasound-induced lung hemorrhage in the monkey. Ultrasound Med Biol 1994;20:65-72.  Back to cited text no. 21
22.Chapelon JY, Cathignol D, Cain C, Ebbini E, Kluiwstra JU, Sapozhnikov OA, et al. New piezoelectric transducers for therapeutic ultrasound. Ultrasound Med Biol 2000;26:153-9.  Back to cited text no. 22

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