Crown Lengthening for Esthetics and Retention: An Overview & Case Series

INTRODUCTION

The concept of crown lengthening encompasses a combination of soft and or hard tissue reduction and or orthodontic extrusion. An ideal anterior appearance necessitates healthy and inflammation-free periodontal tissues. Garguilo¹ described various components of the periodontium, giving mean dimensions of 1.07 mm for the connective tissue, 0.97 mm for the epithelial attachment and 0.69 mm for the sulcus depth. Based on this biologic width is considered to be 2.04mm. Similar findings were also reported by Vacek et al. Ingber and others² observed that the presence of caries or restorations in close proximity to the alveolar crest may lead to inflammation and bone loss due to violation of the biologic width. Hence, they recommended that the restorative margin be a minimum of 3 mm coronal to the alveolar crest, suggesting that this margin could be achieved through a surgical intervention known as crown-lengthening surgery. Some authors have questioned the necessity of this procedure, suggesting that if the biologic width is invaded, the body can re-establish the necessary dimensions on its own over time³ . However, it is generally accepted that crown-lengthening surgery helps to relocate the alveolar crest at a sufficient apical distance to allow room for adequate crown preparation and reattachment of the epithelium and connective tissue⁴ .

Furthermore, by altering the inciso-gingival length and mesiodistal width of the periodontal tissues in the anterior maxillary region, the crown-lengthening procedure can build a harmonious appearance and improve the symmetry of the tissues.

Good communication between the restorative dentist and the periodontist is important to achieve optimal results with crown-lengthening surgery, particularly in esthetically demanding cases. In addition to establishing the smile line, the restorative dentist evaluates the anterior and posterior occlusal planes for harmony and balance, as well as the anterior and posterior gingival contours. This information allows the restorative dentist to determine the ideal incisogingival length and mesiodistal width of the anterior maxillary teeth. On the basis of these projections, the periodontist recontours and relocates the gingival margin and the alveolar crest to achieve both an esthetically pleasing appearance and periodontal health.

Definitions and terminology:

• Crown lengthening surgery: The surgical procedure conducted to expose adequate clinical crown to prevent the placement of the crown margin in to the area of biologic width.
• Biologic width: The dimension of the soft tissue, which is attached to the portion of the tooth coronal to the crest of the alveolar bone (Gargiulo et al 1961).
• Clinical crown: It is that portion of the tooth that extends occlusally or incisally from the investing soft tissue, usually the gingiva (American Academy of Periodontology 1992) or the tooth structure visible to the dentist or portion of tooth structure located coronal to the margin of gingiva.

Objectives of Crown Lengthening Surgery

• Removal of subgingival caries.
• Preservation and of maintenance of restorations.
• Cosmetic improvement.
• Enabling restorations without impinging on biologic width.
• Facilitation of improved oral hygiene.  

Indications of Crown Lengthening Surgery

• Sub gingival caries or fracture.
• Inadequate clinical crown for retention.
• Unequal or unaesthetic gingival heights.
• Short clinical crowns with or without aesthetic deficiencies.
• Teeth shortened by incomplete exposure of anatomical crown.

Contraindications of Crown Lengthening Surgery 

• Surgery would create an unaesthetic outcome. 
• Deep caries or fracture that would require excessive bone removal on contiguous teeth. 
• The tooth in a poor restorative risk. 
• Inadequate crown root ratio 
• Inadequate predictability

Limitations to lengthening the clinical crown 

• Importance of tooth in dental arch 
• Subgingival caries and degree of extension of the clinical crown fracture apically residual amount of supporting bone after crown lengthening .
• The degree of periodontal support lost from the adjacent tooth. 
• Increasing tooth mobility due to diminished supporting tissue and its influence on occlusion possible esthetic and speech defects.
• Whether proper plaque control can be maintained after the placement of restorations

Considerations for surgical crown lengthening procedure for restorative function:

The clinical height of the crown of a tooth can be increased by the removal of the coronal portion of the periodontium together with crestal bone, using standard periodontal flap procedures. It is always necessary to use a flap procedure, unless the clinical crown is shorter than the anatomical crown, in which case gingivectomy procedures will suffice.

There must be at least 3 mm between the most apical extension of any restorative margin and the crest of the alveolar bone which includes an average sulcus depth of 0.69 mm, epithelial attachment of 0.97 mm and connective tissue attachment of 1.07 mm. These proportions between bone crest, epithelium and connective tissue attachment remain constant. The sum of the connective tissue and epithelial attachments i.e. the distance from the alveolar crest to the base of the gingival sulcus is referred to as the 'biological width'⁵ .

Restorative procedures cause resorption of crestal bone and migration of the junction epithelium until the necessary 'biological width' has been re-established. The need to maintain it influences the amount of bone removal required during crown lengthening surgery. Once the clinician has decided on the clinical crown height necessary to restore the tooth, not only must sufficient bone be removed to achieve the desired crown height but the biological width must be taken into account. Failure to do so will result in inflammation. Where gingival tissue is thin, this can lead to recession and exposure of crown margins originally placed within the sulcus with an adverse effect on the aesthetics.

Considerations for crown lengthening for esthetics:

Excessive gingival display during smile may give unaesthetic appearance. Such cases may require surgical crown lengthening procedure to enhance the smile of the patients. Components of esthetically pleasing and well balanced smile have been extensively reviewed^6,7. Various factors that need to be considered during this procedure are gingival line, inter papillary line and occlusal plane. The objective here is to obtain parallelism of the horizontal gingival and incisal planes with the interpapillary lines. Increase in the crown length can be achieved by gingivectomy or apically positioned flap with or without osteoctomy. Selection of the procedure is governed by the sulcus depth, location of alveolar crest, width of the attached gingiva etc. 

CASE SERIES:

Here are few series of case reports on aesthetic and restorative crown lengthening procedures.

Case report 1(Fig1-6):

A 25-year-old man presented to the Department of Periodontics, A.M.E's Dental College & Hospital requesting “better-looking teeth.” His medical history was noncontributory, and he denied a history of smoking or alcohol consumption. Extra oral examination revealed no significant findings. His face was symmetric and had a straight profile. His smile line extended to the second premolars, and smiling displayed approximately 3 mm of gingival tissue. Dental examination revealed that the crown of tooth 22, which had been treated endodontically, had a fracture extending subgingivally. The same tooth was orthodontically extruded, but failed to provide adequate clinical crown exposure (fig.1).

Periodontal examination revealed good oral hygiene with minimal plaque and calculus deposits. The gingiva was pink and firm and the papillae were intact. Clinical examination revealed shallow probing depths, no mobility and adequate amounts of keratinized attached gingiva.

Review of the full mouth X-rays revealed no significant findings. The crestal bone level was within normal limits, and the crown to root ratio was favorable (fig.2). Occlusal analysis revealed an Angle's class I relationship, with 70% overbite and 2 mm of over jet. No signs of fremitus test positive were observed. The patient had adequate anterior guidance upon protrusion and adequate group function upon lateral excursions. After discussion with the restorative dentist, crown-lengthening was recommended to allow a healthy, optimal relationship between the teeth and the periodontium.

The initial inverse bevel incision was performed so as to achieve the ideal contour on the anterior teeth. This incision is carried out in a parabolic manner, with the most apical point or gingival zenith for the lateral incisor and extending incision to the adjacent teeth. The papillae were raised in a splitthickness fashion, and this process was followed by creation of a full-thickness flap apically (fig.3). Thus, the papillae were kept intact palatally to avoid tissue recession. Osseous resection, performed only on the buccal surface, exposed 3 mm of root surface from the gingival margin to the alveolar crest; this allowed for attachment of the junctional epithelium and connective tissue. The flap was apically repositioned and sutured with 5-0 silk suture(fig.4). Chlorhexidine rinse 0.12% bid was prescribed for 2 weeks, and the patient was given appropriate postoperative instructions.

Final preparation of the teeth began a half year later, since gingival recession can occur as long as 6 months after the surgery. Care was taken to ensure that the margins of the temporary crown were smooth and closely adapted to ensure gingival health. Fig 6.4months post operative photograph.

Case report 2 (Fig7-13):

A 22 yr male patient presented to the department of periodontics, AME'S dental college and hospital referred from the Department of Endodontics for crown lengthening procedure. His medical history was non contributory and had no history of smoking or tobacco chewing, and alcohol consumption. Extra oral examination revealed no significant findings. He had a straight profile and smile line extending to the second premolars. Dental examination showed insufficient crown length i.r.w 15 (fig 7). Periodontal examination revealed good oral hygiene with minimal plaque and calculus deposits and probing depth ranging from 1- 3mm. After discussion with the restorative dentist, surgical crown lengthening was considered to avoid violation of biological width. Apically repositioned flap with osteoctomy was carried out under local anesthesia in relation to 15 (fig 8,9,10). Post surgical instructions were given and patient was recalled after a week. Patient was followed up for a period of 2months following which the crown build up was done and the crown was replaced (fig11,12) and patient was recalled every one month for check up. Photograph following 6 months with healthy periodontal tissues free of inflammation (fig.13).

Here are few series of case reports on Esthetic Crown Lengthening Procedures.

Case Report 1 (Fig14-21):

A systemically healthy 25 yrs female patient reported to the department of periodontics, AME'S dental college and hospital with a chief complaint of gummy smile with smile nd nd line extending from 2 premolar to 2 premolar (fig 20). She had a straight profile. Intra oral examination revealed good oral hygiene, with the probing depth ranging from 2-3mm.

After the case analysis surgical crown lengthening by external bevel gingivectomy was considered. After the phase I therapy, patient was considered for crown lengthening procedure under local anesthesia. Trans gingival probing was done and sulcus depths were marked following which external bevel gingivectomy was done. Hemostasis was achieved, periodontal dressing was given (fig14-17), after which the patient was given post surgical instructions and was recalled after a week for check up.

Case Report 2 (Fig 21a-25b):

A systemically healthy male patient of 22yrs reported to the department AME'S dental college and hospital with a chief complaint of gummy smile with smile line extending from 15 to25. Extra oral examination showed no abnormalities, intra oral examination showed good oral hygiene and probing depths ranging from 2-3mm. After the thorough case analysis surgical crown lengthening was considered. Gingivectomy was done under LA to obtain the desired crown length. Oral hygiene instructions were given patient was advised to use chlorhexidine mouth wash for next one week and the patient was recalled for check up after 15 days.

DISCUSSION

The goal of surgical crown lengthening is to provide the restorative dentist with sufficient clinical crown to permit optimum restoration of a tooth. The "biologic width" is of prime concern during surgical crown lengthening and the minimum desired distance achieved immediately post surgically from the crest of alveolar bone to the margin of the planned restoration has been proposed to be at least 3 mm⁵ .

Surgical crown lengthening procedures can form an essential adjunct to the restorative management of teeth affected by tooth surface loss. There are occasions when the restorative procedures cannot be completed without them. Periodontal surgery is another adjunctive procedure that must be considered at an early stage in planning restorative care. It is one of the frequently indicated strategies for assisting in creating adequate mechanical, occlusal and aesthetics outcomes in restorative treatment.

While many situations require it, crown-lengthening surgery is often underutilized. Because of this, too much reliability is placed on post and core restorations and deep sub gingival margin placement to gain adequate retention for restorative purposes (Alien 1993). This often leads to root fractures in the case of post and core restorations, and violation of the biologic width in the case of deep sub gingival margins. These factors contribute to greater expense and frustration for the patient, hence further complicating restorative and periodontal therapy.

Ramfjord et al³ (1988) have questioned the necessity of this procedure, suggesting that if the biologic width is invaded, the body can re-establish the necessary dimensions on its own over time. However, it is generally accepted that crown-lengthening surgery helps to relocate the alveolar crest at a sufficient apical distance to allow room for adequate crown preparation and reattachment of the epithelium and connective tissue.

Crown lengthening considered for enhancing the esthetics of the patients with gummy smile needs a careful presurgical analysis such as gingival anatomic crown relationship and the alveolar crest-CEJ relationship.⁸

CONCLUSION

Surgical crown lengthening remains an essential adjunct to the restorative management of teeth affected by tooth surface loss. In addition it also plays an important role in enhancing the smile of the patients with short clinical crowns. However careful clinical assessment, presurgical analysis and appropriate decision making are important for successful outcome of any procedure.