An Interdisciplinary Approach to the Treatment of Amelogenesis Imperfecta

INTRODUCTION

Amelogenesis imperfecta is a collection of genetic conditions that most often presents intraorally with generalized hypomineralization. Treatment requires a multidisciplinary approach and close professional collaboration. Although treatment methods vary, most patients initially require anterior composite restorations and posterior stainless steel crowns on high-risk teeth to allow for healthy psychosocial development and posterior function. Following growth and development, patients often require full-arch restorations in conjunction with crown lengthening surgery since hypomineralization and wear minimize available tooth structure. This case report documents the multidisciplinary treatment of a patient suffering from amelogenesis imperfecta and highlights the significance of interdisciplinary collaboration.

Amelogenesis imperfecta is an uncommon genetic condition affecting the enamel. More specifically, it causes hypomineralization or hypoplasia.¹ Epidemiologically, the disease prevalence ranges from 1:700 to 1:14,000.^2,3 The different classifications of the disease are organized either by clinical presentation or genetic mutation. Alterations to the secretory stage of tooth development can cause amelogenesis imperfecta via mutations in AMELX (X-linked) or ENAM (autosomal dominant) genes. Likewise, mutations in MMP20 and LKL4 genes (autosomal recessive) result in softer enamel.⁴ Amelogenesis imperfecta affects enamel of all teeth, and hypoplasia is often associated with discoloration and hypersensitivity.¹ Treatment of these patients is very challenging since restorations are required on every tooth. Moreover, the quality of the existing tooth structure can complicate the quality of final restorations as inadequate etching can result in less retention and more leakage. Coronal restorations in patients with amelogenesis imperfecta had a survival rate of 50% compared to a survival rate of 80% in patients with normal enamel.⁵ A conservative treatment option may include direct resin restorations, but this choice may only be a transitional treatment until patients finish growth.⁶ More often, full-coverage restorations are necessary for proper restoration and can be metal, stainless steel, ceramic, or porcelain-fused-to-metal.⁷ Full-coverage restorations in patients with amelogenesis imperfecta are predictable and comparable to full-coverage restorations placed in healthy patients.⁵ Because of the wear, most full-mouth cases require crown lengthening surgery in order to provide adequate tooth structure.⁸ Restoring and treating patients with amelogenesis imperfecta is a complicated task that requires an interdisciplinary approach and a comprehensive plan.

CASE REPORT

A 16-year-old healthy male presented to the Rutgers School of Dental Medicine with the following chief complaint: “I have a lot of sensitivity, and I want to fix my smile.” The patient was diagnosed with amelogenesis imperfecta during childhood and received composite restorations in the anterior teeth and stainless steel crowns on the permanent first molar teeth as a provisional means to restore the dentition prior to completion of growth.⁶ The patient had a history of irregular care over the last several years. His mother stated that her 16-year-old son was reluctant to smile, particularly around his peers in school. The clinical examination revealed defective enamel with dentin exposure, yellow discoloration, tooth sensitivity, and dental caries (Figures 1 to 3). The premolar teeth had short clinical crowns and radiographically revealed large pulp horns. The maxillary and mandibular second molars were covered partially with keratinized mucosa, indicating that passive eruption may not yet have been completed. The maxillary right second molar was completely covered by soft tissue and was radiographically shown to have coronal tooth resorption, called intracoronal resorption. The maxillary arch was oval in shape and exhibited slight constrictions, particularly in the premolar regions. Occlusal examination showed that there was a slight discrepancy between centric relation and maximum intercuspal position with posterior teeth interferences in all excursive movements. Due to the extent of the enamel defects, there was occlusal attrition of the premolars. This led to supra-eruption of the premolar teeth and maxillary canines, causing a reverse smile-line and large gingival display in the maxillary premolar region on the full smile. Although he presented with generalized occlusal attrition, there was no loss of vertical dimension due to the compensatory dentoalveolar movement of the premolar teeth and the presence of stainless steel crowns on the first molar teeth. Radiographically, the coronal portions of the teeth appeared to have a thin layer of enamel, a typical phenomenon of hypoplastic amelogenesis imperfecta. Bite-wing and periapical radiographic films indicated that the pulp horns of the mandibular premolars were close to the external occlusal surfaces of the teeth (Figure 4). Based on the clinical and radiographic findings, a diagnosis of amelogenesis imperfecta was made. This is associated with a thin or no enamel layer (hypoplastic teeth), dental caries, defective composite restorations, occlusal plane discrepancy, occlusal interferences, and unerupted third molar teeth. The patient was treatment planned for a full-mouth rehabilitation with full-coverage restorations. The goals of treatment were to protect the teeth, reduce teeth sensitivity, and restore normal tooth form, function, and aesthetics. The prognosis for the teeth was favorable except for the maxillary right second molar, which was planned for extraction. No implant was planned at this stage since there were occlusal contacts between teeth Nos. 3 and 31, which will maintain the tooth spatial position of tooth No. 31. However, the patient was informed to replace the missing tooth in the future if needed. Because involving third molars in the treatment would complicate the case, the decision was made to extract them at the early stage of the treatment even though they were not yet erupted.

In order to ensure proper delivery of care, an interdisciplinary approach, including prosthetic and periodontal collaboration, was required. Prior to treatment planning, irreversible hydrocolloid impressions (Jeltrate [Dentsply Sirona]) of the maxillary and mandibular arches were made to generate diagnostic stone casts. These casts were mounted in centric relation with a face-bow transfer on a semi-adjustable articulator (Hanau Wide Vue [Whip Mix]). A diagnostic wax-up was then constructed. Since the teeth exhibited large pulp horns, a conservative approach was made to open the vertical dimension by 2 mm in the premolar area and select a restorative material that would accept a minimum occlusal thickness yet restore aesthetics and function. In this case, all-ceramic lithium disilicate material was selected for the anterior and posterior teeth. Full-metal gold restorations were planned for restoration of the second molar teeth to the required restorative space. The first phase of the treatment involved caries control and the extraction of the third molars and the maxillary right second molar. This improved accessibility to the distal surfaces of the second molars. Initially, all teeth were prepared except for the second molars. The patient was provisionalized in the new vertical dimension of occlusion with full-arch splinted fixed temporaries made of milled PMMA resin material relined with chairside auto-polymerized resin material (ALIKE Temporary Crown and Bridge Resin [GC America]) (Figures 5 and 6). Flowable composite (Filtek Supreme Flowable Restorative [3M]) was added to the occlusal pit and fissure of the mandibular second molars to maintain the vertical position of these teeth until the crown lengthening was done, and these teeth were prepared to receive provisional crowns (Figure 7). The provisional restorations and increased vertical dimension were tested for 4 weeks. During this time, there were no TMD symptoms or difficulty in speech or swallowing reported by the patient. After confirming the patient’s comfort, he was seen in the postgraduate periodontics department for crown lengthening of the maxillary arch and mandibular posterior teeth. Prior to crown lengthening, surgical guides were fabricated on models depicting the desired level for the soft tissue. With the aid of the surgical guide, crown lengthening was completed to ensure proper space for biologic width and adequate retention and resistance form (Figure 8). The crown lengthening procedure entailed a full-thickness flap elevated to the mucogingival junction and a split-thickness flap apical to the mucogingival junction (Figure 9). This allowed precise apical repositioning of the flap at the crest following ostectomy and osteoplasty via 4-0 chromic gut sutures (FS2 Ethicon). Also, the amount of keratinized gingiva was maintained (Figure 10). Immediately after crown lengthening and before the flap was sutured, the second molar teeth were prepared, and the temporary crowns were fabricated to ensure the desired preparation design was achieved. After appropriate healing (Figure 11), the finish line margins of the teeth preparations were refined, and the patient received a second set of provisionals to ensure proper aesthetics and function (Figure 12). Prior to final impressions, the patient requested the treatment of pigmented gingiva, which was accomplished by using the Nd:YAG laser (PerioLase MVP-7 [Millennium Dental Technologies]). Maxillary and mandibular frenectomies were performed at the same time (Figure 13). The Nd:YAG laser has a 1,064-nm wavelength, which highly absorbs melanin and pigment, optimizing the depigmentation process.

RESULTS

Following healing, the patient was pleased with the aesthetic result (Figure 14). Four months after crown-lengthening surgery and laser therapy, intrasulcular preparations were impressed for delivery of the final prosthetics (Figures 15 to 19). The patient reported the disappearance of teeth sensitivity at the end of the treatment and during followup visits. Moreover, the patient received an aesthetic and functional result (Figures 20 to 22) that restored his functionality and psychosocial health as compared to his initial presentation. Regular maintenance is very crucial for long-term successful treatment. Therefore, he is being placed on a meticulous maintenance schedule of every 3 to 4 months. Oral hygiene has been continually reinforced, and the patient has been placed on PreviDent 5000 (Colgate) and Booster Toothpaste (Colgate).

DISCUSSION

Management of these patients is accomplished in 3 phases: temporary, transitional, and permanent.⁹ The temporary phase of care addresses the primary and mixed dentition, which requires a combination of composite restorations for aesthetic concerns and stainless steel posterior restorations. The transitional phase entails monitoring the patient’s growth and restorative status until the permanent dentition has completed eruption and the patient has ceased active growth. At this time, the patient enters the permanent phase, where a multidisciplinary team provides full-mouth rehabilitation. This case report illustrates the prosthetic and periodontal treatment of a patient entering the permanent phase of care. As Chen et al⁹ discuss, the patient was properly diagnosed at an early age when he received stainless steel posterior crowns to prevent caries progression and composite anterior restorations. Note that the direct anterior restorations were delivered primarily to improve psychosocial status. Studies regarding amelogenesis imperfecta patients indicate that without aesthetic restorations, their self-esteem decreases, and social dysfunction increases.¹⁰ Both indirect and direct restorations have been reported to restore teeth in patients with amelogenesis imperfecta. While guidelines to treat such patients are not yet available, indirect restorations have shown more predictable results when compared to direct restorations.¹¹ Previous research showed that the enamel and dentin in patients with amelogenesis imperfecta are associated with changed properties, which explains why direct restorations have a higher failure rate than indirect restorations. All-ceramic lithium disilicate material was chosen to restore the majority of the teeth in this case. Not only does lithium disilicate material provide excellent optical properties, but it also allows for minimal tooth preparation and possesses acceptable strength and longevity when bonded to tooth structure. Previous reports showed that all-metal, full-gold material would be the material of choice when restoring second molar teeth because of the minimal thickness needed and high fracture strength.