Combined Digital/Conventional Technique for Rehabilitation of a Patient With Epidermolysis Bullosa: A Case Letter

Epidermolysis bullosa (EB) includes a group of rare hereditary mucocutaneous disorders with multiple oral and systemic manifestations characterized by mechanical fragility of the skin and the formation of vesicles and blisters induced by trauma or friction.^1–4  Based on the level of tissue separation and blister development, there are 4 major groups of EB including epidemolysis simplex, junctional EB, dystrophic EB, and Kindler syndrome (mixed type). The most common location is the oral mucosa, and the most aggressive form is recessive dystrophic epidermolysis bullosa (RDEB).^5,6 

Oral manifestations include the frequent occurrence of blisters, erosions, and scars that result in restricted mouth opening, ankyloglossia, the obliteration of buccal sulci, perioral stricture, severe periodontal disease, early loss of dentition, alveolar bone resorption, maxillary atrophy with mandibular prognathism, increased mandibular angle, and an increased risk of oral carcinoma. Caries and severe periodontal disease are often found because of poor manual dexterity and consequently poor oral hygiene and difficulty in routine dental care.^2,4,7,8 

The systemic features of EB comprise blisters on much of the body, predominantly in areas of friction such as the feet, knees, hands, and elbows, leaving painful ulcers that heal by soft-tissue contraction and scarring. In its most severe forms (junctional and dystrophic EB), the tissue contraction often causes digital syndactyly, which can lead to the formation of clawlike hands or stumps, and stenosis of the upper esophagus, resulting in dysphagia or esophageal obstruction.^2,3,7 

Routine oral hygiene such as tooth brushing and normal dental treatments can cause blisters and bullae on the oral mucosa in such patients.^9,10  Dental treatment has changed considerably in recent years for patients with EB.¹¹  The latest studies^12,13  have found that dental implants can be used successfully in these patients and can result in better outcomes in comparison with conventional prosthetic approaches. Because only the skin and mucosa are involved in the disorder, implant osseointegration should not be affected by EB.⁷ 

Treatment modalities for completely edentulous patients with EB are limited.²  The conventional denture is not a suitable option, because it can cause the recurrent formation of lesions induced by the movement and friction of the denture on the mucosa.^2,4  This has been observed with implant-tissue–supported overdentures as well, but with less severity.¹²  Therefore, the use of implant and fixed prostheses results in better outcomes in terms of blister occurrence and patient comfort.

The primary issues in treating EB patients are the restricted mouth opening and blister formation induced by the treatment procedures, making all steps of the prosthetic rehabilitation difficult, from the primary impressions to the fabrication of the prostheses. Conventional methods, especially impression making, result in injuries, bleeding, and discomfort for the patient.⁷  The best method for making impressions in such patients is still questionable. Digital impressions require no impression materials or trays, which could reduce the possibility of blister formation and patient discomfort, but they have limitations. Following is a description of the oral rehabilitation of a completely edentulous EB patient with fixed implant-supported prostheses on 4 dental implants using a combination of digital and conventional methods.

A 36-year-old white man was referred to the Department of Prosthodontics, School of Dentistry, at the Tehran University of Medical Sciences, where he was diagnosed with RDEB. He was completely edentulous and asked to have his missing teeth replaced. An extraoral examination revealed blisters all over his body, predominantly on his feet and hands, digital syndactyly, and restricted mouth opening. The intraoral examination found an obliterated vestibule, denuded tongue (lack of papillae), and alveolar bone resorption. After the diagnostic and cone-beam computerized tomography evaluation and because of the bone atrophy and restricted mouth opening, it was decided to place 4 implants in each arch to fabricate a shortened dental arch, screw-retained, metal-ceramic prosthesis. The surgery was performed under general anesthesia using the open-flap technique, because of the bone atrophy and requirement of direct access to the field for optimal positioning of the implants. Full mucoperiosteal flaps were carefully raised without a release incision to minimize the likelihood of tissue injury. Eight implants (Implantium, Dentium, Gyeonggi, South Korea) were placed using 1-stage surgery (Figure 1). For implant placement, the osteotome and conventional rotary techniques were used in the maxilla and mandible, respectively. Six months after implant placement, the peri-implant tissues were in good condition, and implant osseointegration was verified by both radiologic and clinical evaluations. Because of the patient's severe microstomia, it was impossible to use an impression tray intraorally. Therefore, the digital-impression technique was chosen and an intraoral scanning device (Trios, 3shape, Copenhagen, Denmark) was used. For the maxilla, scan bodies (Scanbody 3D-Guide, NT-Trading, Karlsruhe, Germany) were placed in the maxilla, and a full-arch scan was performed (Figure 2a and b). To assist with the virtual designing, digital master casts were obtained from the digital scans. Because of limitations such as the lack of isolation and the presence of movable tissues, we were unable to obtain a suitable scan of the mandible, and the resulting file was not perfect. However, a recording of the jaw relations was needed. Software (Exocad DentalCAD, Exocad, Darmstadt, Germany) was used to design 1-piece bar substructure-splinting implants with internal nonhex connections for both arches (Figure 2c and d). Polymethylmathacrylate (maxilla) and resin (mandible) blocks were fabricated using a milling unit (Arum milling machine, Dowoom, Daejeon, Korea; Figure 3a and b) and tried in (Figure 3c). The milled bar for the mandible was cut into 4 individual parts, placed in the mouth, and intraorally splinted to each other with a resin pattern (Pattern Resin LS, GC America, Alsip, Ill; Figure 3d). Wax rims were then formed on the bars (Figure 3e and f). The upper wax rim was verified by the smile line and amount of tooth showing both at rest and while smiling. The corners of the mouth verified the lower wax rim. The wax rims were eventually finalized based on the determined occlusal vertical dimension. Because the jaw relations were digitally recorded, each jaw was scanned with the bar present to allow the software to be used to determine the bite registration. In the next stage, full contour restorations were designed according to the verified wax rims in the form of shortened dental arches (to the first premolar). The cut-back framework was designed to achieve a uniform thickness of the porcelain layer (Figure 4a), and the frameworks were milled with a milling unit (Arum milling machine). At the next appointment, the milled metal frameworks were tried in, and the passivity, occlusal plane, and amount of tooth showing were checked. A centric relation record was made using vinyl polysiloxane (VPS) bite registration material (Futar D, Kettenbach, Hesse, Germany). To record the soft tissue under the pontics more meticulously, adhesive material (Panasil Adhesive, Kettenbach) for silicone impressions was applied on the bottom side of the metal frameworks and dried. The assembly was then placed intraorally and secured, and a light-body VPS impression material (Panasil Initial Contact Regular, Kettenbach) was injected under the pontics and around the implants to record the soft tissue (Figure 4b and c). The associated implant analogues were secured, and definitive casts were fabricated and mounted on an arcon semiadjustable articulator (HANAU Wide-View, Whip Mix, Louisville, Ky). Layering was performed with porcelain shade A2 (GC Initial, GC America), the try-in was performed, and then it was glazed (Figure 5a). In the final session, the screw-retained prostheses were secured with a torque of 25 N/cm² (Figure 5b), and the screw access holes were filled with the composite resin and light cured. The postoperative instructions were to use a soft bristle toothbrush, which could be further softened by soaking in warm or hot water, after every meal; use clean gauze when blisters were present in the mouth and brushing was not possible; rinse with water after each meal; and use an alcohol-free formulation of chlorhexidine 0.12% (twice a day for 2 weeks every 3 months). Follow-up appointments were scheduled at 1 month, every 3 months for the first year, and then every 6 months. During 18 months of follow-up, the patient was satisfied with the prosthesis and did not report any discomfort.

There were some difficulties during the implant placement, including with the soft-tissue handling, the formation of a bleeding blister induced by the trauma, and requiring sterile saline solution irrigation. To reduce the possibility of tissue injury and shear forces, the patient's lips and the mucosa prone to blister formation were lubricated repeatedly and irrigation with sterile saline solution was minimized.

Fixed implant-supported prostheses are preferred in RDEB patients, because in a fixed rehabilitation, there is no need to remove and place the restoration, and the risk of trauma inducing blister development is reduced because of the lack of contact with the oral mucosa. A short dental arch rehabilitation supported by 4 anterior implants in those areas can also be chosen as a treatment option in the RDEB patient.

A clinical series by Peñarrocha et al¹⁴  compared the level of satisfaction between implant-supported fixed and overdenture prostheses in RDEB patients. Both types of prostheses demonstrated good outcomes. The patients with fixed prostheses had slightly higher satisfaction levels (mean, 9.6) than the patients with overdentures (mean, 8.8). Peñarrocha-Diago et al¹²  treated all EB patients with implant-tissue supported overdentures and found that recurrent blisters developed in the areas of mucosal contact in the EB patients. They suggested the blisters resulted from the movement and mechanical friction of the prosthesis on the oral mucosa. Letelier et al¹⁰  have stated that fixed implant-supported prostheses are more suitable than overdentures for patients with severe forms of EB (eg, RDEB), because they cause less irritation.

In addition to the advantages of the digital impression procedure in RDEB patients previously mentioned, this technique also has some advantages over conventional methods in healthy patients, such as less distortion of the impression materials and improved patient acceptance.¹⁵  However, this technique does have some difficulties. The major problems during scanning were the movable tissues and the presence of bleeding and saliva, which led to the use of some conventional methods. With future advancements and improved capabilities in intraoral scanners, the digital impression technique may soon be a suitable alternative method in RDEB patients.

Abbreviations

EB:

epidermolysis bullosa

RDEB:

recessive dystrophic epidermolysis bullosa

VPS:

vinyl polysiloxane

The authors declare that there are no conflicts of interest.