Clinical Effectiveness of a Patient-tailored Orthosis Based on 3-dimensional (3D) Scanner Modeling and 3D Printing Technology for Microstomia Caused by Burns : Pilot Study

Introduction Microstomia is defined as a mouth size that becomes so small that it interferes with oral functions such as oral hygiene care, eating, and speaking with oral function after trauma, facial burns, or surgical procedures for skin cancer, although the exact definition is ambiguous due to cultural differences and standards in each country. Therfore, the diagnosis is defined by functional decline and patient-reported discomfort (1). The cause of microstomia are divided into intraoral and perioral causes. Damage to the sphincter action of the orbicularis oris muscles due to perioral causes, such as burns or trauma, causes contracture which limits lip movement when eating or specking. In the cases of burns around the mouth, the degree of functional impairment varies depending on the extent and depth of the scar. Hypertrophic scars occur in deep second burns or more, and the scar increases as it undergoes the inflammatory, proliferative, and remodeling stages of scar healing. Scar formation increases for several months after burn injury, causing abnormal movement of the surrounding tissue and the scar sites (2). There are various causes of microtomia and various symptoms depending on the severity of the damage, so various attempts are being made to improve the symptoms (3). Conservative treatment generally includes physical therapy and massage to improve facial muscle movement and the use of orthosis to prevent the progression of microstomia. To prevent the progression of microstomia during the healing process of scars after trauma or burns, it is recommended to apply a brace within 10 to 14 days after the injury, but ready-made orthosises are difficult to apply to mouth that are too small, children, or those with severe deformities. The creating of a mouthpiece applied to patient with microstomia in the acute phase is a challenging task tha must be realized to improve clinical outcomes.

Optical three-dimensional (3D) scanning and 3D printing are being used for medical applications such as accurate visualization, precise preoperative anatomical measurements, and patient-specific guides (4). These technologies can be used to manufacture patient-specific orthosis for preventing post burn contractures (5). The technologies have the advantage of saving time and cost in the production of personalized devices and of being able to accurately measure the paricipant's body (6, 7). 3D scanning and printing technology is used for patient-specific body measurements on curved body parts such as the face, hands, and neck, which are difficult to apply with ready-made orthosis (5, 6, 8, 9). The ideal personalized 3D orthosis wound be created by scanning to get the most realistic and accurate outline of the body (10).

There has been little research on the use of 3D scanning modeling technology to produce mouthpiece for patients with microstomia caused by surgery including split thickness skin grafting after burns or cancer operations. This study aimed to confirm the clinical effectiveness of applying patient-tailored mouthpiece using 3D scanning and 3D printing technology to microstomia caused by burns.

Material and Methods Study design This was a pilot study. The protocol was approved by out institution's research ethics committee and registered in ClinicalTrials. The study adhered to the principles of the Declaration of Helsinki, and informed consent was obtained from all participants prior to enrollment. This was conducted in compliance with the TITAN Guidelines 2025 (11).

Participants All participants were admitted to the Department of Rehabilitation Medicine for the first time after complete epithelialization of the wound. Eligible inclusion criteria are defined as participants who underwent skin grafting after suffering from deep second- or third degree burns around the mouth, and who complained of difficulties in daily life such as difficulty in eating, pronunciation, and oral hygine care due to microstomia (Figure 1). Exclusion criteria included patients diagnosed with limited temporomandibular joint movement after or before burn injury, at risk of skin damage when wearing an open mouthpiece, with bleeding at the scar site or scar at risk of epidermal damage, with peripheral vascular diseases with reduced blood circulation, and who withdrew consent.