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REVIEW ARTICLE
Year : 2021  |  Volume : 13  |  Issue : 1  |  Page : 17-27

A comprehensive update on crown-lengthening procedures with new concepts and inputs


Department of Periodontology and Oral Implantology, Maharashtra Institute of Dental Sciences and Research, Latur, Maharashtra, India

Date of Submission02-Oct-2020
Date of Decision07-Feb-2021
Date of Acceptance19-Feb-2021
Date of Web Publication26-Jun-2021

Correspondence Address:
Dr. Om Nemichand Baghele
Department of Periodontology and Oral Implantology, Maharashtra Institute of Dental Sciences and Research, Ambajogai Road, Vishwanathpuram, Latur - 413 512, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jicdro.jicdro_62_20

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   Abstract 


A majority of periodontal procedures performed today are related with clinical crown extension for esthetic or functional needs related to varied etiologies. The concepts and understanding about any particular treatment keep evolving and further refinements happen with each passing year. The objective of the review is to put forth the various new innovative inputs and concepts regarding crown-lengthening procedures (CLPs) as envisioned by the author and provide a relevant review on various surgical procedures. To the extent possible, a retrospective evaluation of the available literature on CLPs and associated treatment modalities were undertaken. Personal evaluations based on a cumulative understanding of various clinical situations being presented for CLPs across many years were instrumental in writing this review. A new perspective on need-based area-specific CLPs is presented in the review which can be appropriated with any presenting clinical scenario. The review also proposes a new categorization of apically repositioned flaps in multiple types, which may expand our surgical options. A new treatment algorithm based on proposed residual attached gingiva is introduced. The review also deals with a modified proposal for the restorative considerations and a CLP format for record keeping. The scope of CLPs is really wide and refinements in the treatment modalities are need of the hour. The expansion of CLP concept and innovative inputs will definitely appeal to an astute clinician.

Keywords: Apically repositioned flap, clinical crown extension, crown-lengthening procedure, crown-lengthening procedure decision algorithm, crown-lengthening procedure record sheet format, new classifications, periodontal osseous surgery, periodontal surgery, stepwise surgical protocol


How to cite this article:
Baghele ON. A comprehensive update on crown-lengthening procedures with new concepts and inputs. J Int Clin Dent Res Organ 2021;13:17-27

How to cite this URL:
Baghele ON. A comprehensive update on crown-lengthening procedures with new concepts and inputs. J Int Clin Dent Res Organ [serial online] 2021 [cited 2021 Dec 9];13:17-27. Available from: https://www.jicdro.org/text.asp?2021/13/1/17/319530




   Introduction Top


Crown-lengthening procedures (CLPs) are aimed at increasing the clinical crown height of a tooth either for the esthetic or restorative needs. The same is accomplished usually by surgical, orthodontic, or a combination of surgical and orthodontic procedures. Even though many clinicians advocate avoiding CLPs in favor of implant therapy, the long-term survival of CLP treated structurally-compromised teeth has been found to be quite acceptable at 78.4% at 10 years of service.[1] The cumulative success rate of such teeth is found to be 68% for teeth/patients followed for ≥15 years. Furthermore, the reasons for the extraction within this period were nearly unrelated to periodontal weakening (only 11% failures because of periodontal breakdown).[1] Moghaddam et al.[2] also noted a long-term survival rate of multidisciplinary-treated teeth (combined endodontic, periodontal, and prosthodontic treatment) was 83%–98%, for 245 teeth followed for at least 3 years to more than 10 years (3–5 years 98%, 5–10 years 96%, and ≥10 years 83%). Thus, CLPs are not only viable treatment modalities but also successful ones for long-term.

The review by Hempton and Dominici[3] explained about the rationale of CLP and the extent of osseous reduction. The readers can refer to their review for understanding the ferrule effect. Mele et al.[4] presented a very nice review about altered passive eruption (APE) and its management. They also summarized the literature from the various authors for re-establishing biologic width (BW). The summary suggested that, a 1–3 mm distance between bone crest and cementoenamel junction and ≥3 mm distance between bone crest and gingival margin (GM) should be maintained for BW.[4] A comprehensive literature review is presented by Majzoub et al.[5] A meta-analysis by Nobre et al.[6] dealt with the numerical aspects of CLP on adjacent and nonadjacent teeth, whereas Pilalas et al.[7] dealt with outcome of CLP in their systematic review and meta-analysis.

This review is a treatise on therapeutic considerations for CLPs. The author has addressed new innovative inputs regarding classifying CLP requirement, osseous surgery and an expanded stratification/categorization of apically repositioned flaps (ARFs), and a simplified decision algorithm based on the presence of residual attached gingiva (AG) in proposed case of CLP.

Broad therapeutic consideration (classification)

Although various surgical, orthodontic, or combination procedures have been suggested to achieve increased crown length, many of the procedures can be basically combined under the following categories (this categorization includes any clinical situation):

  • Category-1: Repositioning of the buccal GMs alone apically [Figure 1]
  • Category-2: Repositioning of the buccal and interdental GMs apically [Figure 2]
  • Category-3: Repositioning of the whole periodontal complex, the buccal, interdental, and lingual GMs apically [Figure 3]
  • Category-4: Moving the tooth coronally but keeping the periodontal complex at the existing level or slight coronal repositioning [Figure 4] and
  • Category-5: Moving the tooth coronally as well as repositioning the periodontal complex apically [Figure 5] either partly or completely (as in Categories 1, 2, and 3).
Figure 1: This excessive gingival display is because of the altered passive eruption and inflammation. It's a Category 1 crown lengthening procedure case where apical repositioning of only buccal tissues will suffice

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Figure 2: A full mouth rehabilitation case with multiple uneven gingival margins with deleterious parafunctional habits. It's a Category 2 crown lengthening procedure case which can be managed by apically relocating the buccal gingival margins and to certain extent the interdental papillae

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Figure 3: A case where multiple Category-3 crown lengthening procedures are required to save the natural dentition. An apically repositioned flap will be appropriate for preserving and augmenting the attached gingiva. A full-mouth rehabilitation strategy is necessary for this case

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Figure 4: A case of fractured and cavitated canine with the patient having strong desire for saving the natural tooth. This should be managed with Category 4 crown lengthening procedure approach by orthodontic extrusion and without relocating the gingival margins. A small coronal migration (about 1 mm) of gingival margin can be tolerated with orthodontic extrusion

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Figure 5: A case of endodontic perforation at cervical level. This type of clinical presentation can be best treated with Category 5 crown lengthening procedure approach, where apical repositioning of periodontal tissues as well as coronal orthodontic extrusion will achieve lasting results

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This classification is covered under Copyright Registration No. L- 98983/2021 on the Author's name with Govt. of India, Copyright Office. All of the above procedures are successfully done,[3],[4],[5],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22] but not categorized as so. Crown-lengthening (CL) approaches to each of the above considerations are different. These options require interplay between soft-tissue surgery, hard-tissue surgery, orthodontics, and various combinations of these. Approaches such as single buccal flap, ARF, internal bevel (IB) gingivectomy, external bevel gingivectomy, gingivoplasty, ostectomy, and osteoplasty should be considered cautiously after evaluating the patient thoroughly.

The clinicians are also concerned about periodontal osseous architecture (OA). Getting positive OA always remained a pertinent question with whichever approach you utilize for CLP. A negative OA may be detrimental to long-term health of periodontium, but whether a flat architecture remains stable for years is yet unknown with certainty. Quite often, it is necessary to reduce a lot of supporting bone to achieve positive OA. While doing ostectomy for CLP, we recommend keeping at least 7 mm of the root supported by sound alveolar bone, reducing more than that may compromise the periodontal health and in the anterior segments may not achieve desired esthetics. This is the average recommendation derived from Craft et al.[23] and Paoli et al.[24] The accepted average root length[23] is 13.63 mm, consider it as approximately 14 mm. Paoli et al.[24] mention that, a minimum of 5 mm of supra-alveolar root should be exposed for CL. They also mention that if the root length is around 10 mm, then mobility may develop. To err on the better side of preservation, we have postulated a minimum of 7 mm of the root should be in the alveolar housing. Keeping in mind above limitations in single-rooted teeth and furcation invasions in the multi-rooted teeth (if not accompanied by hemisection or root resection), we recommend a more conservative option in the form of achieving a flat OA rather than an ideal positive architecture. A flat architecture with good postoperative soft-tissue healing accompanied by appropriate restorative dentistry may last for years as compared to achieving positive architecture sacrificing the sacred supporting bone. Almost always the Category-1 outcome will be “positive architecture with accentuated scalloping,” for other categories a “positive” or “flat” architecture would be appropriate. Eventually such architecture may not pose any problems in the future. With appropriate indications in place, partial CLPs as explained in Categories-1 and 2 above will give best results in terms of preserving architecture.

Considerations of crown-lengthening procedures with restorative modality

In case of CLPs wherever future restorations, in the form of Class-II restorations, Class-V restorations, inlays, onlays, laminates, veneers, partial or full crowns, or abutments for cast partial dentures, are going to be placed, following considerations should be analyzed and followed:

Class-X: No requirement of any restorations, crowns, veneers, etc.

  • Class-1: Pre-CLP restorations (temporary, intermediate or permanent)
  • Class-2: Permanent restorations during CLP
  • Class-3: CLP with immediate temporary crowns just before or after suturing
  • Class-4: CLP with early (7 days to 3 months) temporary crowns
  • Class-5: CLP with late (3 months to 6 months) temporary crowns
  • Class-6: CLP without temporary crowns.


This classification is awaiting copyright registration on the Author's name under application no. 20671/2020-CO/L with Govt. of India, Copyright Office. A scenario where Class-II caries is present and the gingival floor is apical to the GM and a partial or circumferential CLP is required for the placement of proper restorative margins, then for such teeth, a pre-CLP restoration can be placed which may be of intermediate or permanent nature. Better to place an intermediate restoration which will be replaced with permanent restoration postmaturation of gingival tissues. A permanent restoration in the form of silver amalgam can also be done beforehand and then during CLP any overhang or contour corrections can be done before suturing. If the restorations are composites or inlays, it is advisable to place interim restorations before CLP and final restorations only after complete healing.

Not infrequently Class-V lesions (caries or cervical abrasions) have apical margins inaccessible for restorations, and even if restorations are done, they are difficult for finishing and flushing. Isolation is frequently troublesome. In such situations, CLP along with final restorations can be planned and executed without any trouble. Tseng et al.[8] and Starr[16] presented the series of cases of permanent fillings along with CLPs. In many CLP cases, it is required to place the immediate crowns for esthetic/functional reasons or as demanded by the patient. In such situations, we recommend using prefabricated polycarbonate crowns or custom-made temporary crowns on the scored diagnostic models. These crowns can be checked for fit during the CLP procedure accompanied by crown preparation. Osteoplasty procedures become more appropriate if we have a predetermined appropriately fitting temporary crown which is used during the procedure. Such a crown can be cemented with temporary or permanent luting cement before suture placement or just after suture placement, but excess cement can be best removed if it is done before suturing.

Early temporary crowns can be done up to 3 months from suture removal appointment. If it is done after 3 months, it can be denoted as late placement. Here, crown preparation can be done till the desired levels or just short of final placement of crown margins. These crowns can be kept till the GM matures completely. GMs will take more time for maturation where ARF is done as compared to where only gingivectomy was done. Sometimes, you can keep the teeth undergone CLP without any temporary crowns till final healing takes place, at which point final restorations are given. Each consideration should be evaluated properly before executing the final treatment with the entire required paraphernalia ready beforehand. A scheme for staging of the different CLPs is presented by Marzadori et al.[9]. One should try to incorporate all the morphological determinants of tooth and tissue anatomy while doing CLP along with restorations. A concept of periodontal morphology and tooth surface topography is put forth by Smukler and Chaibi,[25] where they mentioned that, the final determinant of gingival and osseous form is the surface topography of the tooth. This observation may indicate changing surface topography of the teeth undergoing CLP or incorporate the changes in temporary or final restorations.

Sequence of treatment

As it is well said, “if you fail to plan then you are planning to fail,” it is very crucial to understand the clinical scenario and to predict the possible complications or limitations that can occur in a case as every case is unique. Based on thorough clinical examination and with the use of various auxiliaries such as radiographs and preoperative models and after critically evaluating the clinical situation of the dentition, a step by step sequence of treatment should be followed to get best possible long-term outcome of surgery.

Incorporating refreshed understanding of CLPs, a modified sequence based on Allen[26] model is presented here. The sequence of treatment procedure to be followed is summarized in [Table 1]. Timelines for restorative management post-CLP are outlined by Marzadori et al.[9] and Zucchelli et al.[27] The timeline for CLP as mentioned by Zucchelli et al.,[27] suggests taking final impressions at 6 months or more when there is no observable growth of interdental papilla between two appointments.
Table No. 1: Sequence of treatment for CLPs

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Pro forma for crown-lengthening procedure

A usable pro forma or data-sheet for CLP has been designed for recording the measurements of various landmarks, which is to be preserved for any medico-legal issues as well [Table 2]. For reproducible measurements, definitive record keeping and clinical research an acrylic stent should be used. One such good design of stent is explained by Smukler and Chaibi.[25]
Table 2: Record sheet for crown lengthening procedures. CLP=Crown lengthening procedure; MB=Mesiobuccal; MIDB=Midbuccal; DB=Distobuccal; L=Lingual; ML=Mesiolingual; MIDL=Midlingual; DL=Distolingual; CEJ=Cemento–enamel junction; GM=Gingival margin; MGJ=Mucogingival junction and tooth #Tooth number

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Bone surgery

Conventionally, periodontal ostectomy and osteoplasty (OnO) are conducted using manual as well as rotary instruments. Rongeurs, bone files, bone scrapers, and chisels are the manual instruments for the said purpose. The rotary instruments of choice are usually carbide and diamond burs of various sizes to be used along with micromotors. These require a continuous saline irrigation from an assistant to prevent desiccation of tissues during OnO. This type of irrigation is dependent on the assistant's expertise, which may not suffice every time. At occasions, it is inconvenient to use such a provision, especially in the posterior areas. To have enough, continuous and uninterrupted supply of irrigants during the surgery, we suggest using self-irrigating air-motors, physio-dispensers used for implant surgery, piezoelectric bone surgery devices, or even air-rotors. The simplest and cost-effective devices are air-motors and air-rotors, which can be attached with appropriate carbide or diamond burs. The area of concern is nature of irrigant while using air-motors or air-rotors. The liquid reservoirs attached to dental chair should be compulsorily filled with distilled water, bottled mineral drinking water, or normal saline. It is pretty easier to use these devices for reducing interdental bone, especially when the interproximal area is very restricted and also to remove very small amounts of bone wherever required. When the tooth is not root canal treated or does not require any restorations or interdental spaces are too narrow, the use of air-rotor with smaller diamonds is easier and good control can be exercised. We have not encountered any adverse effects of using air-rotors for the same, even though there is a theoretical chance of leading to air emphysema. Fortunately, the incidence of iatrogenic emphysema secondary to orodental procedures is very low, that too for periodontal procedures the lowest,[28] and none had been reported following a CLP till now. However, we propose taking appropriate precautions.

What is “adequate” attached gingiva?

The adequacy of AG and keratinized gingiva (KG) was always shrouded in mystery, especially during CLPs. All the reported algorithms are based vaguely on adequacy or inadequacy of AG or just a mention of, x or y amount of KG if present, then do this particular procedure or that. The uniqueness of our decision-making process lies in the consideration of AG.

We are proposing a scheme where only the “amount of projected residual AG” should be considered for decision-making. The process is simple, determine preoperative width of AG and also determine the extent of CL, especially on the buccal aspect. Here, the extent of CL is equivalent to “future position of the GM.” ARF or free gingival grafting combined with CL or two-stage procedure is indicated in situations where there is no attached tissue on the buccal side. In situations where the AG is 4 mm and extent of CL is 3 mm, then you will be left with only 1 mm of AG if you do a gingivectomy procedure. In such situations, the residual AG would be 1 mm; we are giving more importance to this residual AG rather than the preoperative levels. We are considering it is adequate only when the “residual AG” is more than 2 mm. Less than 2 mm do ARF and more than 2 mm gingivectomy. We continue to use the Lang and Löe[29] guideline as 2 mm of width of KG which equals to 1 mm of width of AG as “adequate” for natural teeth. The AAP regeneration workshop[30] states that, “there is enough clinical evidence to support maintaining an adequate band of gingiva for intracrevicular margin restorations,” whereas Agudio et al.[31] found that over a period of time (average 15-year follow-up) untreated homologous contralateral sites were presented with increased recession as compared to the sites treated with grafting procedures. Clinically, it is still difficult to measure 1 mm and recently traditional “statistical significance” was fiercely doubted by world's top scientists.[32] 2 mm looks to be a better “clinically significant” value which we considered as the reference value. Following CLP techniques are described on the basis of concepts discussed till now.

Techniques to perform crown-lengthening procedure

The surgical techniques for CLPs were evolved over a period of time and now there is an array of procedures available. Representative classifications for CLPs are presented as supplementary file [Supplementary File 1]. While Lee's classification[10] tells you what to expect underneath and about AG if you happen to place your first incision at required crown length, Sonick's classification[11] is based on the requirement for soft-tissue or hard-tissue surgery. Following is a short description of techniques based on the available literature and author's experience.

Crown-lengthening procedure by external bevel gingivectomy: (Category-1, 2 or 3 crown-lengthening procedure)

It is the procedure in which only the gingival portion is excised. It is recommended when there is adequate sulcus depth and KG, and the crest of bone is at least 3 mm or more apical to the proposed GM. It should only be done when the remaining residual AG is more than 1 mm in case of teeth not requiring any restoration or more than 2 mm where restorations are required.

The gingivectomy can be performed well with a conventional scalpel blade, periodontal knives, electrocautery, or with lasers. Sometimes, if you are not getting a proper angle with scalpel blade, an angulated blade handle is recommended. In an indicated patient, bleeding points are marked and incisions placed using Kirkland knife or scalpel making 450 bevel toward tooth surface creating the normal-scalloped pattern of gingiva. Finally, the excised mass of gingiva removed followed by the removal of calculus, if present, and gingivoplasty, if needed. The purpose of gingivoplasty is to further reduce the bulk of gingiva, thinning of interdental papilla as per the requirement and finalization of the gingival contour. The area is then covered with periodontal dressing, to protect the beveled raw area. Adequate width of keratinized tissue of at least 3 mm should form after the surgery in the presence of subgingival/intracrevicular restoration margins.

Gingivectomy with buccal flap reflection with papillary retention: (Category-1 crown-lengthening procedure)

A slightly different approach for CLP in the anterior maxilla with loss of interdental papillae is reported by Kilic et al.[12]. This technique can be utilized when the gingiva shows a flat contour, adequate residual AG present after gingivectomy and OnO is required for apically repositioning the bone crest only on mid-and para-buccal areas. A contoured gingivectomy incision is given on the buccal aspect; mini vertical incisions are given on mesial and distal aspects of each interdental papillae, and then, a buccal horizontal incision given 2–3 mm apical to the crest of the interdental papilla to save the entire papilla. The gingivectomy is completed by removing incised gingiva and a full-thickness flap elevated on the buccal side. Appropriate buccal bone reduction is done and the flap closed in close-approximation with the retained papillae.

Gingivectomy followed by full-thickness flap: (Category-1, 2 or 3 crown-lengthening procedure)

This is essentially same as that of IB gingivectomy or IB flap approach for CLP, with the exception that, the case should have very good width of AG (even after gingivectomy the residual AG should be >2 mm), the teeth are indicated for restorations, some form of bonded or prefabricated restorations are used for reference and a surgical guide or prefabricated temporaries. A representative case is presented by Trushkowsky et al.[13] using digital smile design as a concept for digital appropriation of the clinical workflow and making a surgical stent. The stent is used for giving the first scalloped gingivectomy incision, which may or may not be in an IB fashion, i.e., it can be perpendicular to the gingival surface too; that is one of the reasons for discussing it separately. Once this is completed, the stent is removed. At this point, especially for maxillary anterior teeth, confirm the need for papillary reduction or involving the palatal aspect, as this can be best performed with single buccal flap approach. If both of these are not required, give a crevicular incision and in continuation with that the papillary incision keeping the palatal portions of the papillae intact. Remove the collar of the tissue, achieve hemostasis and cement your provisional restorations or complete bonded restorations with the newly defined apical extension. Now raise a full-thickness flap, don't extend to or beyond MGJ, visualize bone and do OnO till exactly 3 mm from the restoration margin in a scalloped fashion and suture appropriately keeping GMs at the restoration margin. If conditions are favorable, this procedure will probably give the best results. The same procedure with a surgical stent can be followed for APE management even without the requirement for restorations.

Crown-lengthening procedure by flap surgery with and without osseous surgery: Internal bevel gingivectomy with and without osseous surgery: (Category-3 crown-lengthening procedure)

These surgeries should be seen as buccal and lingual both-sided surgical procedures without any coronal or apical repositioning of the flap. The apical relocation of the GM and interdental papilla happens secondary to soft-tissue resection alone or any combination with hard-tissue resection. The palatal/lingual approach is also usually same as followed on buccal aspect.

Flap Surgery Approach without Osseous Resection

It is indicated when after excising the gingiva for CLP, adequate amount of KG persists. If you desire to visualize root surfaces and osseous crest even without an actual need for osseous correction this is the method of choice. Furthermore, when the marginal tissues are too thick and require a knife-edged marginal adaptation, IB incision will give a better outcome. This can be a method of choice in a case with periodontitis presenting shallow pockets which are not extending till MGJ.

After local anesthesia, primary or inverse bevel incision is placed after marking bleeding points. Bleeding points should be marked at or just coronal to the future position of GM, it should be irrespective of the pocket depths present. It is followed by the placement of crevicular incision to the level of alveolar bone to detach the connective tissue attachment followed by reflection of flap and third or interdental incision placement to remove the tissue tags. It is similar to modified Widman flap with only difference in the location of the first incision. The flap should be reflected minimally to check for calculus deposits and to ascertain alveolar crest contour. If you happen to breach the MGJ, there are the chances of unplanned coronal repositioning during suturing. After the area is debrided properly, copious irrigations should be done and flaps sutured.

Flap Surgery with Osseous Resection

It is one of the favored procedures for CLP. As discussed above, IB flap approach is indicated whenever after resection of the gingiva, there remains at least 2 mm of AG. In addition, OnO is indicated when the distance between proposed GM on tooth/root surface and the underlying alveolar bone is <3 mm. The coronoapical distance of 3 mm from GM to the alveolar crest will re-establish the BW.

The soft-tissue procedure is essentially the same as “flap surgery without osseous resection,” except that here you may require raising the flap little bit more to visualize the bone properly for resection and instrumentation. Following adequate local anesthesia, incisions are placed as mentioned above followed by reflection of full-thickness mucoperiosteal flap. Ostectomy is performed as discussed in bone surgery section and observing the principles of osseous reduction. With the use of high-speed or low-speed hand-pieces, major chunks of the bone can be removed. It is followed by the removal of thin bone adjacent to tooth using hand instruments or Ochsenbein chisel followed by the use of curettes on root/tooth surfaces and bone. The bone level should be assessed carefully after ostectomy procedure such that it is placed 3 mm apical to the proposed GM circumferentially. If the requirement of supragingival tooth height is 3 mm, then the supra-alveolar tooth height should be 6 mm. The flaps are sutured primarily and instructions given.

Two-staged surgery for crown-lengthening procedures: (Category-1)

In esthetically demanding areas with high patient expectations and presence of adequate amounts of AG, a two-staged surgical approach can be followed. In the first-stage surgery, a full-thickness flap is elevated essentially for repositioning the alveolar crest apically and closing the flap to preoperative levels. The OnO is done to the level which will allow a gingivectomy in the second-stage surgery and would not violate the BW. After 2–3 months of healing following first surgery, a simple gingivectomy is performed with the help of surgical blades or laser.[10],[33]

Apically repositioned flap with or without ostectomy: (Categories-1, 2, or 3)

These procedures are the most preferred CLPs by the author. A variety of ARFs can be undertaken depending upon clinical situations. When there are doubts, this is the best type of procedure to be undertaken. [Table 3] [also Supplementary File 2] shows various types of ARFs: e.g., ARF Type-5 indicates an ARF done by giving crevicular incision with releasing incisions, elevating full-then-partial-thickness flap, and accompanied by no bone reduction but only single buccal flap approach is taken preserving interdental papillae and no suturing only periodontal dressing stabilization. Thus various combinations of ARFs are possible with the 17 different parameters presented for doing an ARF. This classification is proposed by the author who considers ARF Types 7 and 8 best for the maxillary anterior areas when palatal intervention is not needed and ARF types 58, 59, and 60 best for any quadrants where circumferential CLPs are required and GM is thick or marginal inflammation is present or presence of mild-to moderate pockets. All of these procedures attempt to increase the width of AG while giving you a lengthened clinical crown. The author has presented with 60 different types of ARFs, many more are possible with other combinations as well (Supplementary File 2). This same classification can be utilized for ARFs around implants to increase the width of attached tissue. For a discussion on split thickness, full-thickness or split-full-split thickness flap elevation the reader can refer to Marzadori et al.[9] The concept of sub-marginal and para-marginal incisions for single-flap approach as described by these authors is similar to an IB incision with may be a less angulated blade. This IB incision can be given as a continuous incision or given on each tooth starting and ending at GMs in a parabolic or half-moon shaped curve creating a proper contour of gingiva leaving an extension like a papilla in the interproximal regions. The collar of the tissue is then resected by giving crevicular incisions on the teeth and in continuation with these crevicular incisions, a vertical (corono-apical) incision keeping the sides of the blade parallel with the mesio-distal plane is given for the interdental papilla keeping the palatal portion of the papilla intact.
Table 3: Classification and categorization of apically repositioned flaps

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Zucchelli et al.[27] described a surgical technique for ARF starting with IB incisions, raising partial, full, and partial-thickness flaps on the buccal side and thinned-palatal flaps. Following OnO, the flaps were sutured at alveolar crests keeping the interdental bone bare for secondary intention healing. Paolantoni et al.[14] compared three different types of CLPs in the anterior maxilla (a papilla-preservation CLP, ARF with buccal approach and ARF with buccal and palatal approach) and concluded that the papilla-preservation CLP, similar to that of conventional papilla-preservation flaps, can be a viable option for CLP. Many of such procedures involving ARF and also any type of ARF can be explained or formulated from the accompanying table [Supplementary File-2].

If gingivectomy or IB flap approach for CLP will leave a residual AG of <2 mm, ARF with or without osseous surgery is indicated. Any clinician who is desirous of providing a maximum width of AG and/or increasing the vestibular depth, ARFs should be the first choice.

Friedman(1962),[34] classification [Supplementary File 1] for the initial incision placement for ARFs to achieve pocket reduction according to the amount of KG present may not be relevant today in the era of regenerative periodontics, but this may be considered for CLPs by ARFs as discussed above. Lee[33] states that the use of full-thickness flaps to preserve the entire dimension of the dentogingival complex, followed by adequate osseous resection measured from a restorative landmark to ensure sufficient bone removal and avoidance of periosteal sutures to apically position the flap, will result in increased GM predictability after CLP.

Flapless crown-lengthening procedure: (Category-1)

A minimally invasive flapless CLP with attendant OnO is possible and has shown equivalent results.[15] IB incisions are given at the future position of GM, and with the help of sulcular incisions, the gingival tissue is removed, this is akin to IB gingivectomy. Then, bone is removed and recontoured using microchisels, through incisions, without flap elevation. The root surfaces were carefully planned and a required distance of 3 mm between bone crest and GM is achieved, sutures are avoided. Even though Ribeiro et al.[15] proposed this technique for esthetic CLP in patients with APE, the same can be performed for other indications provided there is ≥2 mm residual AG post IB incision.

Thinned palatal flap

Palatal flap management can be a tricky exercise. As has been mentioned earlier, there may be absolutely no requirement to touch the palatal tissues and palatal portion of the interdental papillae to extensive resections. If there are enough indications to preserve the papillae, don't touch the palatal mucosa and do only a buccal-sided procedure. If there are indications to apically reposition the interdental papillae and palatal mucosal margin, then that can be achieved with different techniques depending upon the extent of repositioning. The thickness of the palatal mucosa and the presence of rugae may pose challenges to raise a proper palatal flap. Only gingivectomy-type resection on the palatal side almost always won't work, unless there is deep pocketing and horizontal bone loss. One approach is to give a straight palatal incision at proposed mucosal margin and removing all of the tissue coronal to it, doing necessary OnO and then after suturing let it heal by secondary intention. However, the gold standard technique on the palatal side is an internally bevelled accentuated-scalloped flap approach. After ascertaining the future position of the mucosal margin, a continuous deep scalloped incision in an IB fashion is given. This incision can also be given in half-moon shaped fashion starting from the mucosal margin of one tooth to another tooth. Then, the collar of the tissue is separated from the attachment by crevicular and interdental incisions. Bone recontouring is done and flaps closed. Another approach is a “thinned palatal flap” with the concepts of “primary” and “secondary” flaps. A representative case is presented by de Waal and Castellucci.[35] A palatal IB scalloped incision is given approximating the future mucosal margin after giving internally beveled palatal vertical incisions on either side. The outer “primary” flap is then trimmed to approximately 1.5 mm, separating it from the inner “secondary” flap. The inner portions are then separated and removed. This type of flap gives good access for OnO and thinner mucosal margin.

It is beyond the scope of this article to discuss about other treatment modalities such as surgical or orthodontic extrusion or lip repositioning.


   Conclusion Top


Increase in clinical crown length is the outcome desirable for multiple indications. We do face various clinical situations where partial, full, or extensive CLs are required. Every presented case is different and we should deal with them with unique and long-lasting solutions. The requirements for restorations with lengthened crowns are also varied. The soft and hard tissue morphological features at the surgical sites are unique, and the procedure is definitive and nonreversible. The treating clinician should be aware of the patient requirements, the feasibility and various techniques available to achieve the goal. Still today, saving a natural tooth is much more predictable and satisfying exercise for both, the patient and the doctor. The concepts proposed here can be utilized like this, “a Class-X, Category-1 CLP by external bevel gingivectomy,” will indicate a CLP which is done by gingivectomy where no restorations were indicated and only buccal side GM shifted apically. Similarly, 'a Class-3, Category-3 CLP by ARF Type-58' will indicate a circumferential CLP accomplished by ARF where temporary crowns were placed just before or after suturing and the ARF involved IB incision, releasing incisions, osseous surgery, both sided flap, full thickness elevation, and suturing buccal flap 2–4 mm apical to newly created osseous crest with periodontal dressing.

Acknowledgment

I would like to thank Dr. Amarpreet Tuteja who initiated myself into writing this manuscript. I acknowledge Dr. Mangala Baghele for being my moral support. I thank Dr. Ashish Deshpande, Dr. Rajesh Iyer, Dr. Sachin Lad and Dr. Meghna Wandekar who keep crown-lengthening cases in their offices for me to operate for the last 16 years. I also thank Dr. Abhay Kolte for some critical inputs.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.


   Supplementary file Top



   Supplementary file 1: Classification of CLPs Top







   References Top


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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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