Crown Lengthening Procedure: Report of Two Cases

Crown lengthening is a surgical procedure designed to increase the extent of the supragingival tooth structure, so that the clinician can restore the tooth. Crown lengthening procedure is done to maintain normal biologic width and increase crown length for retention of prosthesis. Various techniques have been proposed to perform CLP, such as gingivectomy, undisplaced (cid:976)lap with or without osseous reduction, apically repositioned (cid:976)lap with or without bone reduction, and orthodontic forced eruption with or without (cid:976)ibrotomy. Selection of one of this CLP technique depends upon esthetics, clinical ratio of crown to root, structure of root, location of furcation, position of tooth and the capacity of the tooth to be restored. This case report illustrate two different methods of doing crown lengthening procedure the selection of case depends upon various soft tissue and hard tissue parameters. Owing to the various advantages, disadvantages and associated limitation with different methods, we opted for surgical CLP with scalpel method. Uneventful healing was observed in both our cases. No post-operative complications was observed in both cases. Thus to conclude success rate of CLP is high but appro-priate selection of case is required. In our case report both the methods of CLP shows signi(cid:976)icant result in increasing the crown length and maintaining the biological width.

A Crown lengthening is a surgical procedure designed to increase the extent of the supragingival tooth structure, so that the clinician can restore the tooth. Crown lengthening procedure is done to maintain normal biologic width and increase crown length for retention of prosthesis. Various techniques have been proposed to perform CLP, such as gingivectomy, undisplaced lap with or without osseous reduction, apically repositioned lap with or without bone reduction, and orthodontic forced eruption with or without ibrotomy. Selection of one of this CLP technique depends upon esthetics, clinical ratio of crown to root, structure of root, location of furcation, position of tooth and the capacity of the tooth to be restored. This case report illustrate two different methods of doing crown lengthening procedure the selection of case depends upon various soft tissue and hard tissue parameters. Owing to the various advantages, disadvantages and associated limitation with different methods, we opted for surgical CLP with scalpel method. Uneventful healing was observed in both our cases. No post-operative complications was observed in both cases. Thus to conclude success rate of CLP is high but appropriate selection of case is required. In our case report both the methods of CLP shows signi icant result in increasing the crown length and maintaining the biological width.

INTRODUCTION
American Academy of Periodontology Practice Proile Survey in 2003 said that crown lengthening procedure (CLP) is one of the most commonly performed periodontal surgery. (American Academy of Periodontology, 2003) In CLP it is often essential to gain both adequate resistance and retention form by achieving supracrestal tooth length (Palomo and Kopczyk, 1978;Lundergan and Hughes, 1996;Rosenberg et al., 1980Rosenberg et al., , 1999. Re-establishment of the biologic width is achieved to avoid impingement of restoration margins on the attachment apparatus. (Carnevale et al., 1983;Oakley et al., 1999) Various techniques have been proposed to perform CLP, such as gingivectomy, undisplaced lap with or without osseous reduction, apically repositioned lap with or without bone reduction, and orthodontic forced eruption with or without ibrotomy. Selection of one of this CLP technique depends upon esthetics, clinical ratio of crown to root, structure of root, location of furcation, position of tooth and the capacity of the tooth to be restored. (Anoop, 2018) (Garguilo, 1961) described the biologic width as "the zone of the root surface coronal to the alveolar crest to which the junctional epithelium and connective tissue are attached" which is approximately 2.04 mm. The dimension of the biologic width can vary based on the position of a tooth, from tooth to tooth, and from surface to surface on the same tooth. Crown margins which are located below gingiva can cause in lammation of gingiva leading to damage of biologic width, whereas crown margins present supra-gingivally did not cause gingival in lammation. (Ganji and John, 2012) Thus, CLP must be done so as to allow easy restorative treatment of the teeth which have short crown length. CLP also results in access for appropriate restorative measures having deep subgingival pathologies by giving adequate retention form.
This case report describes two methods of crown lengthening procedures in which normal biologic width is maintained and crown length is increased for retention of prosthesis.

Case 1
A 24-year-old systemically healthy male patient was referred to the department of Periodontics for crown lengthening procedure with #46. Patient had undergone endodontic treatment with #46 in department of Conservative dentistry, 1 week prior. Tooth had 1-2 mm PPD on mid-lingual surface and 2-3 mm in mid-mesial, mid-distal and mid-buccal region. CAL was 1-2 mm on mid-lingual surface and 2-3 mm in mid-mesial, mid-distal and mid-buccal region. Tooth was irm with no involvement of furcation area. Clinical crown length was 2 mm on the lingual side ( Figure 1) and on mesial, distal and buccal side it is 4-5mm. IOPA showed a normal interproximal bone level (Figure 2), and adequate root length. On the bases of CAL and radiograph, the amount of bone present was estimated to be 85% -90 %. Prognosis of tooth # 46 was determined to be fair. Overall prognosis was good with mild chronic gingival in lammation. Oral prophylaxis was done including scaling and polishing. Patient was instructed for proper oral hygiene measures and further, patient was appointed for CLP.

Surgical procedure
Under local anesthesia (Rathi et al., 2019;Pawar et al., 2017) a crevicular incision was made on the buccal and the lingual side of tooth # 46. Full thickness lap re lection was done on both sides (Figure 3). To maintain a biologic width post-operatively (during crown placement), 3-4 mm osseous reduction on the lingual side was made with the help of micromotor and round carbide bur with 0.23 mm diameter (HM1T-023) under copious irrigation of normal saline (Figure 4). Following the procedure, desirable crown length was achieved. After attaining heamostasis, laps were positioned apically using interrupted and periosteal sutures at api-        cal end ( Figure 5). The periodontal pack was placed.
Periodontal pack and suture removal was done after 7 days of surgery ( Figure 6). Post-operative evaluation after 7 days revealed uneventful healing and 4 mm of desirable crown length with tooth # 46, suficient for crown placement. Patient's re-evaluation was done after 21 days to check for complete healing. Furthermore, patient was referred to department of Prosthodontics after 12 weeks (Oakley et al., 1999;Reddy et al., 2019) for placement of PFM crown with 46.

Case 2
A 25-year-old male patient was referred to the department of Periodontics for crown lengthening procedure with #16. On intra-oral examination, it was observed that endodontic treatment was performed with tooth #16. Tooth had 3-4 mm PPD on the mid-palatal surface ( Figure 7) and 2-3 mm in mid-mesial, mid-distal and mid-buccal region. Tooth was irm with no involvement of furcation area. CAL was 1-2 mm on mid-palatal surface and 2-3 mm in mid-mesial, mid-distal and mid-buccal region. Clinical crown length was 2 mm on the palatal side ( Figure 1) and on mesial, distal and buccal side it is 4-5mm.
Reduction of only soft tissue was indicated in this case as there was adequate attached gingiva and more than 3 mm of the soft tissue was present above the crest of the bone.
Under local anesthesia the pocket on palatal side was marked with the help of pocket marker (Figure 8). Incision with blade no # 15 was given starting 1 mm apical to the marking and is directed coronally to the point between the base of the pocket to the crest of the alveolar bone (Figure 9). The incision given was close to the crest of bone but did not expose it ( Figure 10). Soft tissue above the bone was removed. Adequate crown length for prosthetic replacement, considering the biologic width was achieved. Periodontal pack was given to protect the raw wound ( Figure 11).
Periodontal pack removal was done 7 days after surgery. Post operative evaluation after 7 days (Figure 12) reveled uneventful healing and 4 mm of desirable crown length with tooth # 16. Patient's reevaluation was done after 21 days to check for complete healing. Furthermore, patient was referred to the department of Prosthodontics 12 weeks postoperatively for placement of PFM crown with # 16. (Oakley et al., 1999)

DISCUSSION
The concept of CLP was given by D. W. Cohen (1962). (Pawar et al., 2017) The purpose of CLP is to avoid the violation of biologic width that may occur due to placement of subgingival margin of crown in order to get adequate retention form in short clinical crown cases. Violation of biologic width results into injury to the periodontium, leading to in lammation of gingiva, loss of attachment level and resorption of bone. (Reddy et al., 2019) The objective of CLP is to provide suf icient clinical crown for tooth restoration. The indications of CLP are subgingival fracture, naturally short clinical crown due to non-exposure of anatomic crown, teeth shortened by extensive caries or fracture and subgingival/ root caries. (Gupta et al., 2015) In a clinical and radiographic study, it was seen that surgical extrusion technique have few advantages over the other conventional CLP techniques like preservation of the position of gingival margin and interproximal papilla. (Nethravathy et al., 2013) However, (Andreasen, 1970) reported that surgical extrusion can cause marginal bone loss and apical root resorption.
CLP can be carried out by various instruments such as scalpels, cautery and lasers which have their own advantages, disadvantages (Table 1). (Ashwini et al., 2018;Kelman et al., 2009) Owing to the above mentioned advantages, disadvantages and associated limitation with different methods, we opted for surgical CLP with scalpel method. Uneventful healing was observed in both our cases. No post-operative complications was observed in both cases.

CONCLUSIONS
When a crown placement is to be done, the maintenance of an intact, healthy periodontium and appropriate crown length is necessary to maintain the tooth. CLP is practical to perform which facilitate restorative therapy and improves the esthetic appearance. Success rate of CLP is high but appropriate selection of case is required. In our case reports, both the cases showed signi icant result in increasing the clinical crown length while maintaining the biological width post crown placement.