A Review of Selected Microstomia Prevention Appliances

Scientific Article

A review of selected microstomia prevention appliances

Lincoln B. Taylor, BSc, DDS, MS Jerry Walker, BS, DDS, MA

Abstract sues, and the live wire makea complete circuit, gener- 8 Perioral burns mayoccur due to electrical, thermal, or ating heat from 2500-3000°C. In a contact burn, the chemicalagents. The resultant contracture of the facial electrical current passes through the body along the tissue during healing causes limited oral access, compro- path of least resistance from the point of contact to the groundor exit site. mised esthetics, and other related problems. This article presents various microstomiaprevention appliances used The initial appearance of the electrical burn of the commissureis a grayish-white, coagulated lesion out- by dentists and hospital burn centers. These appliances 9 reflect different treatmentconcerns, ease of fabrication, age line with a rim of erythematous tissue. Twoto 4 weeks appropriateness, and cost effectiveness. An understand- later the eschar sloughs, leaving an ulceration. Thetis- ing of these factors and availabile applianceswill aid the sue is replaced by collagenous fibrous connective tis- clinician in selecting or developingthe best appliancefor sue. It takes up to 1 year for the postburn scar to be- burn patients. (Pediatr Dent 19:413-18, 1997) come stable due to the sphincteral action of the orbicularis oris muscle. acial burnscan occur as a result of electrical, ther- The burn is usually painless, and drooling of food al, or chemical injury. 1 Burns of the face may and saliva occurs because of destruction of the sensory F~nnvolve the oral cavity, and if left untreated, re- innervation of the lip. Bleeding mayoccur at the time sult in microstomia. Perioral facial burns maybe ei- of injury or secondary to vacuolation of the vascular endothelium due to rupture of the labial artery and ther partial or full thickness, which upon healing can y, cause tissue scarring and contraction 2 due to sphinc- vessel walls during the necrosis stage of healing, s teral action of the orbicularis oris muscle.3 Contrac- Dental dysplasia and malocclusion may occur de- tion can interfere with vocalization, facial expression, pendingon the severity, timing, and site of injury. The eating, oral hygiene, dental care, and in children may lip contracture in young children may cause lingual inclination and crowding of the teeth resulting in an- affect the developmentof facial structures if proper ~, treatment is not instituted immediately.2 The litera- terior crossbite or overbite. 10 ture has demonstrated that burn contractures and Management scar formation can be modified with pressure and General splinting. 4,s If early splint therapy is not provided, the resultant contracture, will require later surgical Although systemic complications occur infre- reconstruction. The reconstruction involves linear quently, the patient should be evaluated for such prob- release of the scar band with lateral advancementof lems as dehydration, hypothermia, shock, and cardiac the orbicularis oris muscle, recreation of modiolus arrhythmia, s Tetanus prevention is recommended,as labii,6 and reestablishment of vermilion continuity. is prophylactic antibiotic therapy for the severely A conservative appliance-therapy approach with no burnedpatient, s, 10-12 Topical antibiotic maybe used in 8 surgical consideration for approximately 1 year is the presence of secondary wound infection. It is considered to be the best approach. This literature re- thought that oral woundsdo not benefit from prophy- view presents various treatment appliances and the lactic systemic antibiotic therapy and when applied conditions required for their success. topically, these agents have soothing effect rather than any13 antibacterial action. Etiologyand characteristic Daily homecare with saline or hydrogen peroxide rinses and swabsmay be used to debride the necrotic tis- The commonscenario leading to oral electrical burns 8 involves preschool-age children chewing or sucking on sue and promoteformation of healthy granulation tissue. live electrical wires/There are two types of electrical Placementof a splint should be within 10-14 days of the burns, arc and contact. In an arc burn, the saliva, tis- initial injury to allow for proper approximationof the lip dimension before substantial healing has begun.

PediatricDentistry- 19:6, 1997 AmericanAcademy of PediatricDentistry 413 Type Appliance Description, Impression Measurement (A;P;AP) Fabrication, and Placement Necessary for Cast Needed Advantages Disadvantages

Intraoral Maxillary Full acrylic coverage with Yes N/A None Poor compliance Full8 vestibular extension and with pre-choolers (PI acrylic covered wire post Monitor erupting for commisure support teeth

Mandibular Full acrylic coverage with Yes N/A None Poor compliance ~~1119 vestibular extension and with preschoolers (PI acrylic covered wire post Monitor erupting for commisure support teeth

Metal crown adapted on Yes Yes Reduces compliance None upper central incisor and 1st problems in or 2nd primary molars. Avoid pre-schoolers tooth preparation. Labial archwire soldered to crowns and acrylic post for the commissures.

Over- Same as above (Crown) but with Yes Yes Reduces compliance None denture acrylic overdenture with problems in (PI projecting post for commisures pre-schoolers Modified Upper Hawley retainer: Adam Yes Yes Minimalacrylic Limited to older Hawley clasps on the primary 2nd thus speaking and children retainer15 molars and a labial bow from eating not affected Monitor erupting (PI cuspid to cuspid. Two 0.036 Good retention teeth extends labially to form acrylic-covered post. Occlusal anterior bite plane.

Reverse A reverse headgear fitted to No Yes Parental and infant None Head- the face. Left and right cooperation gearI5 outer bows of the headgear Easy insertion and (MP) were reshaped to the removal commissures and covered with acrylic. This is positioned and shaped to maintain the lips at equidistance.

Poly- Polyvinyl stents made from Yes Yes Easy insertion and None vinyl mouthguards blanks. Each is removal intral 3 mm thick at mucogingival No intraoral/ (AD) junction, and enlarging towards commissural incisal/occlusal table (8 mm). ulceration

Extraoral Prefabricated consists of 2 Supported acrylic sections (fits into MPA2 mouth commissures) joined by No Yes Easy insertion and Potentiate tissue (NP) an adjustable stainless-steel removal breakdown with bar with thumbscrew closure Prefabricated thus excessive force (2-mm increments). immediate delivery Poor salivary Available: S, M, L, and XL Range of sizes retention 3.8-9.0 cm for accommodation Slow expansile force

414 American Academy ofpediatric Dentistry Pediatric Dentistry - 19:6, 1997 Acrylic The commissure is adapted with No Yes Easy insertion and None holder21 wax; the wax is invested in removal with finger (A) flask for boil-out. The wax is pressure, no lubrication replaced with heat curing resin. required Angle of bent wire is adjusted so that forces are applied distally and parallel to facial contour. The 2 acrylic commissures are adapted to an £2-steel wire self-curing resin

Vancouver U-shaped Kirschner wire is No Yes Inexpensive material Limited to orthosis14 covered with thermoplastic, Slow expansile force older children (A/P) The flat ends of the thermo- Easy insertion/ plastic are heated for attach- removal ment of the commissural ends, angled at 140° upwards and 160° backwards with respect to the wire spring. By the varing length of static wire bar, placed inside the U-wire, the desired pressure may be applied to the commissure.

Hyrax Consists of 2 acrylic No No Easy insertion/ None

Screw22 phalanges (fits into mouth removal (A/P) commissures) between which Slow expansile force is a Hyrax screw. Allows incremental expansion: 0.25 mm A—Active P—Passive A/P—Utilized active or passive as needed

Commisure appliances aged 2 years or younger.16'17 At this age, the child has Numerous appliances have been used to manage an incomplete primary dentition and is in the active oral burns. Selection of an appropriate microstomia- stage of tooth eruption. Retention of an appliance can prevention device for a patient should be based on age, be a significant problem. Fig 1 is an example of a max- the presence or absence of teeth, condition of the den- illary full-coverage acrylic denture base with posterior tition, type and extent of injury, patient's ability to com- palatal seal and two .032-in wires extending from the ply with the regimen of use, comfort, cosmetics, dura- bility, expense, complexity of fabrication, and need for repair and readjustment.14 There are two basic appliance types, tooth supported and tissue supported.15 Often, the tissue-supported appliances are indicated for infants who have few teeth, low tolerance for pain or discomfort, and lack the ability to understand the need for the appliance. Tooth-supported appliances may be designed for similar concerns but can either be further designated as removable or fixed. An- other method for categorizing these labial commissure devices are passive stents and dynamic widening devices. The passive stent is applied for immediate (early) burn treatment while the dynamic device is for a delayed treatment situation where contracture of the commissure had Figure 1. The maxillary full coverage denture base with posterior palatal seal. already begun. This report will be presented according to support location: intraoral- and extraoral-supported 8 appliances. The clinical characteristics of the appliances base. The posterior palatal seal and vestibular exten- are summarized in Table 1. sion provide its retention. The disadvantage as stated by Port et al.8 is the need for elbow restraints until the Intraoral appliances child accepts the appliance. Most electrical burns of the mouth occur in children In a response to this report, Silverglade18 claims a

Pediatric Dentistry - 19:6,1997 American Academy of Pediatric Dentistry 415 be a problem with subsequent lack of compliance. It appears to require a greater ability of the wearer to adequately control the appliance from being dislodged by the tongue during oral function (speech and mas- tication). Another removable appliance is the modified reverse-pull headgear (Fig 3). Schneider15 used a reverse- Figure 2a. The stainless Figure 2b. The stainless steel pull headgear modified to retain the lip commissure in steel crown fixed crown fixed cemented a 9-month-old male infant with an electrical burn. The cemented appliance with appliance with anterior and reverse headgear is normally used to manage skeletal anterior retention. posterior retention. maxillary retrusion as a positive-pressure appliance, (Courtesy of Silverglade) and was modified to avoid any orthopedic or orthodontic results. The outer bows were reshaped to the commissures with acrylic adaptation. The modified Hawley removable retainer appliance (Fig 4) offers a good alternative for the older, compli- ant patient with posterior teeth.20 The basic design is that of a maxillary Hawley retainer with Adams clasps on the decidous second molars and a labial bow extending from cuspid to cuspid. Two 0.036-in wires are Figure 4. Modified Hawley incoporated into the palatal acrylic and extended labi- Removable Retainer ally to form an acrylic, covered post for commisural appliance (Courtesy of T.H. support. The appliance is fabricated on a cast with con- Larson). sideration for appropriate placement of the post based Figure 3. The on commissure measurement. An anterior, acrylic, oc- modified reverse high success rate using a clusal, bite plane may be placed for additional support headgear. (Courtesy stainless-steel crown, fixed, to the post to minimize flexure and to allow mandibu- of P.E. Schneider) cemented appliance. The ap- lar function without occlusal interferences. The advan- pliance consists of metallic crowns, orthodontic wire, tages consist of good retention, minimal bulk of acrylic, and cold-cured acrylic. In situations where there are and excellent support for the acrylic, commissure- no erupted posterior teeth, a fixed overdenture type splinting posts. The minimal bulk of acrylic helps the of splint may be considered with metal crowns on the patient to speak and function normally.20 The only dis- anterior teeth (incisors can be surgically exposed). No advantage, as with most removable appliances, is the preparation of the teeth is required in the presence of patient's willingness to wear it as instructed. interproximal spacing. In the direct technique, an im- Compliance may be a problem for the patient, despite pression is obtained, the crowns are removed and then age or level of understanding, because of the intense pain placed in the impression material. The working model associated with appliance use, thus other treatment meth- with the crowns is produced for the acrylic adaption. ods may be sought, depending on the situation. In a case A labial arch wire is soldered to the stainless-steel report by MacMillan et al.,1 a 21-year-old female with self- crowns and enclosed in acrylic resin. The fixed appli- induced petrol burn was treated for perioral stricture in- ance, if not adapted or cemented adequately, may be corporating a polyvinyl, intraoral splint. The patient was removed by the child. The effectiveness of this fixed initially treated with an orthodontic headgear strap with appliance is dependent on the child's compliance and cervical and acrylic retractors for each commissure. The the skill of the dentist. device was poorly worn due to commissure ulcerations Fig 2 depicts another type of metal-crown, fixed with resultant abandonment. After 10 weeks the patient appliance. Only the cuspids are utilized for retention. returned with limited oral opening (lip separation of 20 Silverglade, however prefers the use of the crowned mm). An active, polyvinyl, intraoral splint was fabricated central incisor and the first or second molars for im- and is shown in Figs 5a and 5b. The limited opening re- proved retention. Mandibular retention has been con- quired sectioned, prefabricated, flexible, polyvinyl trays sidered by other authors. A mandibular acrylic splint for impression of the dental arches. Each section was small with an extended, unilateral, ovoid, acrylic post to the enough to be inserted into the oral aperture. The com- affected side was used to maintain the burned oral bined sections were used to produce a cast for the fabri- commissure of a 16-month-old boy.19 The splint cov- cation of the polyvinyl microstomia appliance. The appli- ered the mandibular arch, except for the primary den- ance was activated by progressively thickening (bulk) tition, and extended in the vestibule. The appliance from the mucogingival junction the incisal/occlusal of the may be fabricated as the previous maxillary appliance, teeth. The patient wore this continually for 2 days and except that the smaller central incisor is used, which thereafter during sleep. Three months later, the offers less retention. Retention of the appliance may patient's lip separation was 46 mm.

416 American Academy of Pediatric Dentistry Pediatric Dentistry -19:6,1997 Figure 5a. Flexible Impression tray was Figure 5b. The intraoral stents were Figure 6. The microstomia made using polyvinyl mouthguard processed using polyvinyl mouth- prevention appliance with two blanks and upper and lower study guard blanks. The stents extended to acrylic sections. The arrow on the obtained from a randomly selected the second premolar teeth and were 8 device is used for adjusting the female patient. The polyvinyl moulds mm thick at the level of the incisal/ appliance with respect to the were sectioned into equal parts and occlusal table. (Courtesy of A.R.G. patient's eye pupil. perforated. Each sectioned was then MacMillan) used to obtain an aliginate impression to produce the burn patient's study developed by the Vancouver General Hospital. This de- model. (Courtesy of A.R.G. MacMillan) vice is easily removed by the patient, inexpensive, uncom- plicated in adjustment, requires no moulage for fabrica- Extraoral Appliances tion, and no anesthesia is necessary.14 The appliance can Hartford and associates at the University of Iowa be fabricated in 30 min. The appliance is fabricated from Hospitals and Clinics (UIHC) developed a microstomia Kirschner wire (10 cm length, 1.1 mm diameter) and a prevention appliance (MPA, Fig 6, MPA Incorporation, outrigger wire (3-5 cm length, 2 mm diameter). The Dallas, TX), which has been used since 1972.2 The MPA Kirschner wire is bent into a U shape, based on the com- consists of an adjustable stainless-steel bar with thumb- missural distance, to form the spring portion of the ap- screw closure between two acrylic sections that fit pliance. The low thermoplastic material is adapted to both around the oral commisures. The appliance is available wires at 65-70°C. The encased outrigger wire is used to in small, large, and extra large, ranging from 3.8 to 9.0 form the commisural piece which is then heated and cm, each with 2-mm increments for a finer fit. The range adapted to the ends of encased U-shaped portion. The is for accommodating mouths of small children to commissural portion is angled at 140° upward and 160° adults. The appliance may be used as an active or pas- backward with respect to the wire spring. If a passive de- sive appliance. The acrylic section has an arrow demar- vice is required, then holes 2 mm in diameter and 2-3 mm cation to determine expansion. The expansion is based deep are drilled into both sides of the spring. A piece of on the interpupillary width of the patient's eye, which outrigger wire is cut and fitted into the holes to act as a corresponds to the commissure-to-commissure width. static bar and to maintain the desired pressure to the com- The device is removed only for oral care, eating, and missures. Without the bar, the device is dynamic. The visitations. The advantage of the appliance is its device is inserted and removed without the bar. Horizon- availablilty, immediate delivery, insertion and removal tal pressure is altered by pulling the spring further apart. by patient or family member with minimal discomfort, Pressure to the commissure may be altered by increasing and cost-effectiveness. The most common complaint is or decreasing the bar length. Vertical opening of the oral secretions because the lip borders are held apart.2 mouth may be increased by increasing the size of the com- As it is an active appliance, there is the potential for missural opening. The advantages of the VMO appliance breakdown of viable tissue if too much pressure is ap- are that it does not require the presence of teeth, making plied. Madjar et al.21 presented a simplified, easily made a mold, expensive materials, or professional fabrication. widening device that consisted of two labial commis- Also, it applies graduated pressure in the horizontal sure acrylic holders connected with an omega-shaped and vertical directions. It is recommended for older chil- stainless-steel wire. The device is fabricated using dren (> 2 years) if warmed base-plate wax cut to one-third the width of compliance is not the commissure. The wax is then molded to the angle a problem. of the mouth labially and lingually. The wax is adjusted Another dy- to increase the exit angle of the mouth. The wax pat- namic appliance terns are flasked and replaced by heat-cured acrylic is the individual resin. The wire is adapted by autopolymerizing acrylic mouth splint with for anchorage to the labial commissures. The bent wire a Hyrax screw may be activated to accommodate expansile (lateral (Dentarum, West and distal) force on the lip commissures. Germany) devel- A similar device to the UIHC appliance is the Figure 7. Static Vancouver oped in Israel at microstomia orthosis in use. Vancouver microstomia orthosis (VMO, Fig 7) which was Hebrew Univer-

Pediatric Dentistry - 19:6,1997 American Academy of Pediatric Dentistry 417 sity-Hadassah School of Dental Medicine.22An indi- Dr. Taylor, was formerly assistant professor at the University of vidual lip tray is used to obtain an impression from Tennessee, Dunn Dental Building, Department of Pediatric Den- tistry, Memphis, Tennessee, and is in private practice in Oviedo, which a cast of the region of the lips is produced. The Florida. Dr. Walker is professor and clinical director at the Uni- cast is used to fabricate the pink, acrylic-resin splint with versity of Iowa, College of Dentistry, Department of Pediatric Den- a Hyrax screw. The horizontal splint provides an open- tistry, Iowa City, Iowa. ing of 14 mm that may be achieved in 2 weeks, activat- 1. MacMillan AR, Oliver AJ, Richardson L, Reade PC: An in- ing the screw only every other day, due to the pain extraoral splint for the prevention of microstomia from facial perienced. The appliance is used as much as possible burns. Burns 17:72-74,1991. during resting periods.22 2. Heinle JA, Kealey GP, Cram AE, Hartford CE: The microstomia prevention appliance: 14 years of clinical experience. Determining oral dimension J Burn Care Rehabil9:90-91,1988. 3. Peacock EE Jr. Wound Repair, 3rd ed Philadelphia: WB Although some authors did not provide informa- Saunders Co, 1984, pp 445. tion on oral or facial dimension for appliance deliv- 4. Evans EB, Larson DL, Abston S, Willis B: Prevention and ery, the preburn commisural dimensions must be correction of deformity after severe burns. Surg Clin North Am 50:1361-75,1970, determined to achieve the most esthetic and func- 5. Larson DL, Abston S, Evans EB, Dobrkovsky M, Linares tional results after healing. HA: Techniques for decreasing scar formation and Silverglade et al.23determines the post (tusk) place- contractures in the burned patient. J Trauma 11:807-23, ment from vertical and horizontal measurements. The 1971. vertical position is determined from the incisal edge of 6. Pensler JM, Rosenthal A Reconstruction of the oral commissure after an electrical burn. J Burn.Care Rehab 11:50-53, the maxillary central incisors in an imaginary line from 1990. commissure to commisure. The horizontal measure- 7. Needleman HL, Berkowitz RJ: Electric trauma to the oral ment is determined by measuring the distance from the tissue of children. ASDC J Dent Child 41:19-22,1974. unaffected commisures to the midline. If both 8. Port RM, Cooley RO: Treatment of electrical burns of the oral and perioral tissues in children. J Am Dent Assoc commisures are involved, then the horizontal position 112352-54,1986. is at the posterior embrasure of the canines. Another 9. Ackerman AB, Goldfaden GL: Electrical bums of the mouth determinant in bilateral burns is the interpupillary in children. Arch Dermatol 104:308-11,1971. width of the eye. 10. Donly KJ, Nowak AJ: Oral electrical burns: etiology, mani- festations, and treatment. Gen Dent 36:103-107,1988. Conclusion 11. Leake JE, Curtin JW: Electrical burns of the mouth in children. Clin Plast Surg 11:669-83,1984. The use of MPAs in facial burns is the standard of 12. Holt GR, Parel S, Richardson DS, Kittle PE: The prosthetic care and definitely offers several advantages for the management of oral commissure burns. Laryngoscope future. It eliminates or reduces the extent of surgical 92~407-11,1982. 13. Palin WE Jr, Sadove AM, Jones JE, Judson WF, Stambaugh reconstruction needed. The appliance should restore HD: Oral electrical burns in a pediatric population. J Oral function and esthetics, promote tissue healing, reduce Med 4217-21,1987. scarring, improve symmetry, and maintain the size of 14. Conine TA, Carlow DL, Stevenson-Moore P: The Vancouver the oral stoma.I5The use of any appliance is dependent microstomia orthosis. J Prosthet Dent 61:476-83,1989. on its availability, the clinician’s knowledge, and the 15. Schneider PE: Infant commissural burn management with reverse pull headgear. Pediatr Dent 10:34-38,1988. ability to fabricate the appliance. Compliance is the 16. Thomson HG, Juckes AW, Farmer AW: Electrical burns to most important factor for determining the appropriate- the mouth of children. Plastic Reconstr Surg 35:46&77,1965. ness of an appliance best suited for the patient. Appli- 17. Gifford GH Jr, Marty AT, MacCollum DW: The manage- ance retention, compatibility with tissue-bearing areas, ment of electrical mouth burns in children. Pediatrics and comfort potentially solicit compliance. 47113-19,1977. 18. Silverglade D: Fixed-cemented appliance for oral electrical Certain tissue-supported appliances are indicated bums [letter]. J Am Dent Assoc 112806,1986. for infants and children because of few teeth, low tol- 19. Salman RA, Glickman RS, Super S Splint therapy for elec- erance for discomfort, ease of insertion, and low ex- trical burns of the oral commisure in children. ASDC J Dent pense. The tooth-supported appliances are best used in Child 54:161-64,1987. older, cooperative children because they can be 20. Cooney BM: Conservative management of oral electrical burns: report of a case successfully treated. Int J Orthod stablized intraorally and withstand oral contraction 24:12-15,1986. forces. The disadvantages for both appliances are pa- 21. Madjar D, Shifman A, Kusner W: Dynamic labial commis- tient compliance and adequacy in maintaining an op- sure widening device for the facial burn patient. Quintes- timal position to reduce complications caused by sence Int 18:361-63,1987. 22. Sela M, Tubiana I: A mouth splint for severe bums of the contractures. A more predictable outcome occurs with head and neck. J Prosthetic Dentistry 62:679-81,1989. splinting for at least 6 to 8 months to facilitate scar 23. Silverglade D, Ruberg RL: Nonsurgical management of maturation. Surgical reconstruction may then be deter- burns to the lips and commissures. Clin Plast Surg 13537- mined after a 1-year follow-up.6 94, 1986.

418 American Academy of Pediatric Dentistry Pediatric Dentistry - 19:6,1997