Post-Burn Microstomia Prevention: Application of a New Therapeutic Device

Introduction

 Perioral burns may be the result of electrical, thermal, or chemical injuries (1). During healing of such injuries, contraction of peri-oral tissues causes limited oral access compromising esthetics and speaking. In children this may lead to alteration of developing facial structures if proper treatment is not received immediately. Perioral facial burns may be partial or full thickness, which upon healing can cause tissue scarring and contraction due to the sphincteral action of the orbicularis oris muscle (2, 3). Burn contractures and scar formation can be modified by application of pressure and employment of certain appliances that place tissues under tension (4, 5). Splint therapy should be initiated in the early stages of healing, otherwise tissue contracture will take place, making further surgical intervention a necessity. Such surgical procedures include linear release of the scar band with lateral advancement of orbicularis oris muscle that restore modiolus labii and vermilion continuity (6). A one-year conservative appliance-therapy with no surgical intervention is considered to be the best approach (7).

 Two to four weeks after burning, collagenous fibrous connective tissue replaces injured tissues. It takes up to 1 year for the postburn scar to form as the result of the sphincteral action of the orbicularis oris muscle. The burn is usually painless and accompanied by drooling of food and saliva because of destructed lip sensory innervations (7).

 Post-burn scars are proportional to the depth of the burn injury and therefore inevitable, even with the best treatments available. Except for superficial dermal burns, all deeper burns (2nd degree deep dermal and full thickness) heal by scar formation. Post-burn scars can be minimized through application of various physical therapies and plastic surgery, however scar formation cannot be prevented (7).

 Understanding wound healing is not only a necessity in management of burn wounds but is also useful for prevention, treatment,  and minimizing post-burn scars and tissue contractures (8). A burn wound can heal by restitution (complete regeneration) or substitution.

Restitution can only take place when skin is burnt as deep as stratum papillare and all the specialized cells of the organ are present. In such cases, epithelial appendages from which epithelial cells are derived consist of pilosebaceous units and sweat glands in central portion and periphery of wound edges. Cellular interactions that take place subsequent to a burn incident include detachment, migration, proliferation and differentiation of cells. If burn is deeper into zone of stratum reticulare, the defect will be covered by unspecialized connective tissue. This burn wound healing is called substitution. Final wound healing demonstrates some degree of cicatrix formation. Full thickness loss of skin, wound contraction and epithelialization from wound margins lead to contractures (7).

 Contraction is an active biological procedure causing concentric reduction in wound size that takes place in open wounds with skin loss. Reduction in size of the wound reduce connective tissue deposition to decrease epithelialization required. Wound contraction which involves fibroblasts, myofibroblasts and collagen deposition, is considered satisfactory when tissue loss is minimal in a non-critical area surrounded by loose skin (7).

Scar contracture is the end result of wound healing contraction. But in some areas of the body like in perioral areas this contracture can be problematic (8).

Daily home care regimens using saline or hydrogen peroxide rinses and swabs may be used to debride the necrotic tissue to promote formation of healthy granulation tissue (9).

In order to achieve proper lip dimension, application of a splint device should take place within 10-14 days of initial injury before substantial healing occurs (7).

Selection of an appropriate device for each patient to prevent microstomia is based on age, presence or absence of teeth, dentition, injury type, patient's compliance, comfort, cosmetics, durability, expense, complexity of fabrication and need for repair and readjustment (10).

 Microstomia prevention appliances (MPA) could be classified three different ways. First, based on support type: Tooth supported and tissue supported (11). Tissue-supported ones are often indicated for infants who have fewer teeth, low discomfort tolerance, and lack of understanding the need for appliance. Tooth-supported appliances may be designed for similar concerns and can further be designated as removable or fixed (11).

 Second way to classify these labial commissure devices depends if it is active or passive. When treatment of a burn is to proceed immediately, application of a passive stent is treatment of choice (11). The last classification is based on support location and consists of intraoral- and extraoral-supported appliances (11).

Universal application of MPAs in facial burns is expected to decrease surgical need for reconstruction of burn sites in future. Among goals of appliance therapy, following can be mentioned:

1.Restore function and esthetics

2.Promote tissue healing

3.Reduce scarring

4.Improve symmetry

5.Maintain size of the oral stoma (11).

The purpose of this paper is to describe an equipment used in preventing burns microstomia in edentulous patients.

Case Techniques

The patient was a 50-year-old woman who had fallen into an oven 3 months ago and had a 3^rd degree burn. (figure.1)

 She has been treated with medicinal and palliative treatments after the incident.  Due to burn scar that involved all her peri-oral tissues, she had progressive microstomia. (figure.2)

 Therefore, her plastic surgeon referred her to Mashhad faculty of dentistry to have a microstomia prevention device fabricated for her in order to prevent further progression of microstomia. Since patient was completely edentulous, we decided to fabricate a tissue- supported appliance that could place the commissural tissues of the lip under tension using support provided by tissues of the upper and lower lips. This could prevent progression of microstomia.

 The first step was to take impressions. We gently heated and softened 3 wafers of rose wax (betadent, modeling wax) and used them to make impressions of lips. These impressions were then flasked and frames for the upper and lower lips were fabricated with translucent heat-cure acrylic resin (Germany, Springen, Dentaurum, Orthocryl). After finishing and polishing the frames, we checked them on patient’s lips. We marked one point on each side of each frame. The pointed marks on frames were approximately 15mm away from outer border of the frames and opposite each other. We drilled a 1 cm diameter hole on each point we had marked. In the lower lip frame, we placed a 8mm diameter nut in each hole and bonded the nut to the frame using auto-polymerizing acrylic resin. 10 cm long bolts were screwed through the nuts placed in the lower lip frame and their ends were stabilized in holes in the upper lip frame with auto-polymerizing acrylic resin. (figure.3) 

 On the other end of the bolts, we made egg-shaped handles using auto-polymerizing acrylic resin in order to enable the patient to open the bolts. (figure.4)

 Opening the bolts would place the patient’s mouth under dynamic tension and lead to a greater amount of mouth opening for the patient. (figure.5) Patient was instructed to open bolts once a week till the desired result was acquired.