Crown lengthening procedure in the management of amelogenesis imperfecta.

Full mouth rehabilitation includes a promising treatment planning and execution thus fulfilling esthetic, occlusal, and functional parameters maintaining the harmony of the stomatognathic system. Crown lengthening procedures have become an integral component of the esthetic armamentarium and are utilized with increasing frequency to enhance the appearance of restorations placed in the esthetic zone. Crown lengthening plays a role to create healthy relationship of the gingiva and bone levels so as to gain access to more of the tooth which can be restored, if it is badly worn, decayed or fractured, below the gum line. This paper highlights the full mouth crown lengthening procedure performed on a patient with amelogenesis imperfecta.

Achieving an appealing and an esthetic smile is no longer a dream. With the increasing popularity of esthetic related treatment procedures, an understanding of the therapeutic synergies brought about by an interdisciplinary approach should be developed.

Symmetrical smiles are considered esthetically pleasing, ideally there should be 1 mm of gingiva visible when smiling.[1] In a disorder like amelogenesis imperfecta (AI) which is characterized by defects in enamel, resulting in poor dental esthetics. Full mouth fixed bridges can rehabilitate them. However, the extensive loss of tooth structure renders the clinical crown height inadequate for the placement of restorations and so clinical crown lengthening is required.[2] When planning for clinical crown lengthening procedures, it is necessary to identify whether the biologic width will be infringed. If encroached upon, this may lead to a gingival recession in thin tissue biotypes or hyperplasia in thick tissue biotypes.[3] This case report emphasizes the significance of crown lengthening procedure in achieving harmonious restoration in a patient with AI.

Amelogenesis imperfecta is a hereditary disorder that disturbs the formation of dental enamel both in the primary and permanent dentition.[4] It results in the poor development or complete absence of the enamel of the teeth and occurs in the general population in an approximate range of 1 in 14,000–1 in 16,000.[4]

Dental features associated with AI include quantitative and qualitative enamel deficiencies, taurodontism, pulpal calcification and root malformations, failed tooth eruption, and impaction of permanent teeth, progressive root and congenitally missing teeth, crown resorption, and anterior and posterior open bite occlusions.[5]

Amelogenesis imperfecta may create an esthetic problem, dentinal hypersensitivity, and attrition. Pitted enamel surfaces may predispose teeth to plaque accumulation. Oral hygiene has to be maintained at a high level if a favorable long-term prognosis for restorative procedures is to be achieved. This case report outlines an interdisciplinary approach involving periodontics, prosthodontics, and endodontics in the management of a patient with AI and the significance of crown lengthening in maintaining a healthy periodontium upon which esthetic and functional rehabilitation are done.

Case Report

An 18-year-old female patient was referred from the Department of Prosthodontics regarding inadequate clinical crown heights for full mouth prosthetic rehabilitation. On intra-oral examination, the patient revealed short clinical crowns, occlusal wear with exposed dentin in the posterior teeth, and asymmetry of the gingival contours in the anterior teeth. The teeth were yellowish with the lack of contact points and revealed the absence of enamel in all the teeth [Figures 1–3].

Figure 1

Preoperative photograph

Figure 3

Orthopantomograph showing short crowns with taurodontism

Clinical presentation showing short clinical crowns

In consultation with the patient full maxillary and mandibular rehabilitation with porcelain fused metal (PFM) crowns extending to the second molars was considered to be the best therapeutic option. As the clinical crowns were inadequate for the placement of the PFM crowns, a full mouth surgical crown lengthening was planned.

Presurgical evaluation

Due to deficiency of sufficient tooth structure for prosthetic rehabilitation intentional endodontic therapy was done for 11, 12, 13, 21, 22, 23, 31, 32, 33, 41, 42, 43. Coronal restorations carried out using glass ionomer cement.

Once the crown lengthening procedure has been decided the patient's smile line gingival esthetic line, crown root ratio are evaluated, and the anticipated finish line is determined prior to the surgery. The biologic width determines the amount of bone to be removed.

Crown lengthening procedure

Under the administration of 2% lignocaine sulcular and vertical releasing incisions were placed and a full mucoperiosteal flap was elevated in the labial and palatal/lingual aspects of the operated teeth. Respective osseous procedures were performed using rotary instruments to achieve exposure of sufficient tooth structure coronal to the alveolar crest [Figure 4].

Figure 4

Intraoperative: After ostectomy

The flaps were sutured at the level of the alveolar crest with interrupted sutures. The surgical site was covered with periodontal dressing.

Prosthodontic rehabilitation

Three months after crown lengthening procedure, tooth preparation was done. Provisional restorations were placed. Final tooth preparation was done after 6 months. Full mouth Porcelain fused to ceramic crowns placed, occlusion evaluated. Oral hygiene instructions are given and periodic maintenance visits advised [Figures 5–9].

Figure 5

Postoperative healing

Figure 9

Postoperative smile

Tooth preparation with supra gingival margins

Final restoration

Postoperative profile

Discussion

Massive loss of tooth substance in AI results, in short, clinical crown heights that compromise the retention and resistance of the restorations necessitating crown lengthening procedures. The primary objective of the crown lengthening procedure is the restoration of the adequate biological width. Biologic width is the physiologic dimension of the junctional epithelium and connective tissue attachment which is relatively constant at approximately[1]0.07 mm of connective tissue attachment, 0.97 mm of junctional epithelium, and 0.69 mm of gingival sulcus.[6] Infringement on the biologic width by the placement of a restoration within its zone may result in gingival inflammation,[7] pocket formation and alveolar bone loss.[8] Hence, it is recommended that there should be at least 3.0 mm between the restoration margins and bone crest.[910]

Surgical crown lengthening includes the removal of soft tissue or both soft tissue and alveolar bone. Reduction of soft tissue alone is indicated if there is adequate attached gingival and more than 3 mm of tissue coronal to the bone graft. This may be accomplished by either gingivectomy or flap technique, which allows for adequate biologic width when the restoration is placed 0.5 mm within the gingival sulcus.[1112]

The time interval between the surgical procedure and final preparation and placement of restorations are much important. It has been reported that the marginal periodontal tissue show a tendency to grow coronally after surgery.[12]

The amount of tissue rebound seems related to the position of the flap relative to the alveolar crest at suturing.[13] Hence, it is critical that proper crown height be established during surgery without relying on flap placement at the osseous crest.

It has been suggested that considering the postsurgical coronal rebound of the marginal periodontium, the final preparation and restorations be delayed for 12 months after the crown lengthening procedure and that any intermediate preparations be delayed for at least 6 weeks after surgery.[9] In situations where the restorations cannot be delayed, the restoration margins can be placed coronal to the gingival margin so that when the tissues grow coronally the restoration margins may shift to an acceptable subgingival position.[11]

Conclusion

Early treatment of a patient with AI disorder can prevent progressive damage of dentition and the psychological impact of this condition. When crown lengthening procedure is required for prosthodontic rehabilitation, the biologic width needs to be considered. The understanding of the relationship between periodontal tissues and restorative dentistry is paramount to ensure adequate form, function, esthetics, and comfort of the dentition.