Crown lengthening andrestorative procedures in theesthetic zoneMATTEO MARZADORI*, MARTINA STEFANINI*, MATTEO SANGIORGI,ILHAM MOUNSSIF, CARLO MONACO & GIOVANNI ZUCCHELLI

Crown lengthening is one of the most common surgi-cal procedures in periodontal practice. A recent Ameri-can Academy of Periodontology survey reported thatapproximately 10% of all periodontal surgical proce-dures are performed in order to achieve gain in crownlength (1). The main indications of crown-lengtheningsurgical procedure include treatment of subgingivalcaries, crown or root fractures, altered passive erup-tion, cervical root resorption and short clinical abut-ment. The rationale of crown lengthening is to re-establish the biologic width (e.g. the natural distancebetween the base of the gingival sulcus and the heightof the alveolar bone) in a more apical position to avoida violation that may result in bone resorption, gingivalrecession, inflammation or hypertrophy.

The concept of biologic width stems from the clas-sic histologic study by Gargiulo et al. (13), who mea-sured the average dimension of the epithelialjunction (0.97 mm) and connective tissue attachment(1.07 mm) in humans. These values were summed toprovide the biologic width, yielding an averagedimension of 2.04 mm. A recent systematic review(22) found similar mean values of biologic width(2.15–2.30 mm), although considerable intra- andinterindividual variances were reported (subject sam-ple range: 0.20–6.73 mm). The integrity of the biologicwidth is considered a necessary step, in restorativeand prosthetic rehabilitations, to obtain and maintainhealthy soft tissues. While crown-lengthening proce-dures in posterior areas have been investigated indetail, crown lengthening performed for esthetic

reasons in anterior areas is still a matter of debate. Aliterature search on PubMed for ‘esthetic crownlengthening’ returned a list of 250 articles. Amongthese articles, there are no systematic reviews andonly a few controlled clinical trials (3, 5, 14, 16, 20).Moreover, anterior crown lengthening is oftendescribed as part of a multidisciplinary orthodonticand restorative treatment plan. For these reasons,although a number of surgical procedures aredescribed, an evidence-based technique is not avail-able and many questions still remain unanswered.The purpose of this paper is to focus on the descrip-tion of the surgical and restorative phases in theesthetic crown-lengthening procedure by answeringthe following questions: what is the ideal surgical flapdesign? how much supporting bone should beremoved? how should the position of the flap marginrelate to the alveolar bone at surgical closure? andhow should the healing phase be managed in relationto the timing and the position of the provisionalrestoration with respect to the gingival margin?

Soft- and hard-tissue management

Flap design (vestibular aspect)

The flap is designed by creating submarginal parabolicincisions, starting from the angular lines of the adja-cent teeth and crossing at the level of the interdentalpapillae, thereby reproducing the natural scalloping ofa patient’s gingival margin. Correct placement of theprimary incision is based on the probing depth and onthe amount of keratinized tissue available (4, 7). In apatient with an ‘adequate’ dimension of keratinized*Both authors contributed equally.

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Periodontology 2000, Vol. 77, 2018, 84–92 © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

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tissue, the distance of the primary incision from thegingival margin is proportional to the differences inprobing depth of the adjacent teeth (6). If the amountof keratinized tissue is ‘inadequate’, the primary inci-sion should be intrasulcular.

Flap elevation is a controversial issue. The litera-ture describes full-thickness (3, 19), split-thickness (2)and split-full-split-thickness approaches (4, 18, 25).The rationale of the split-thickness elevation is to pre-serve the periostium in order to minimize postsurgi-cal bone resorption and to facilitate the apicalsuturing of the flap. The full-thickness approach hasthe advantages of being easier to perform and ofgaining direct access to the bone than the split-full-split-thickness and full-thickness approaches. Thesplit-full-split-thickness approach merges the positiveaspects of both techniques: the papillae area is ele-vated split-thickness in order to obtain a precise post-surgical adaptation, while, apically, a full-thicknesselevation is made in order to gain access to the boneand to preserve the periosteum, which would other-wise be lost during osteoplasty, at the inner aspect ofthe flap. Once an adequate amount of bone has beenexposed, a split-thickness dissection can be per-formed to facilitate the apical anchorage of the flap inthe desired position (4, 7, 25).

Flap design (palatal aspect)

The palatal flap is raised using the thinned palatalflap approach (9). As the palatal flap cannot bemoved apically, the position of the primary incisionmust anticipate the future configuration of the crestalbone and depends on the amount of crown lengthen-ing required and on the palatal vault anatomy. In thepresence of a shallow palatal vault the distance of theincision from the gingival margin is exclusivelyrelated to the amount of crown lengthening required.In the presence of a deep palatal vault, the soft-tissuethickness has to be taken into consideration, withthicker soft tissues necessitating a greater amount oftissue removal with the secondary palatal flap andmore pronounced apical repositioning of the flap.Hence, if the deep palatal vault has thick soft tissue,the primary incision should be less para-marginalthan if the deep palatal vault has thin tissues. Other-wise, there is a risk of incomplete coverage of thepalatal bone. In order to avoid excessive exposure ofpalatal bone, great care must be taken not to makethe incision too far from the gingival margin, espe-cially in the case of a shallow vault or a deep palatalvault with thick soft tissue.

After vestibular and palatal flap reflection, the softtissue delimited with the primary incisions isremoved using manual and ultrasonic devices.

Ostectomy

Ostectomy consists of the removal of supportingbone (bone connected to the root surface with peri-odontal ligament), and the amount of bone resectedis determined by the extent of the crown lengtheningrequired. Many authors have proposed a range of val-ues (3 mm to > 5 mm) for the amount of tooth struc-ture to be exposed during crown-lengtheningprocedures (12, 15–17, 21, 23). These ‘numbers’ arederived from the histologic description of the den-togingival complex by Gargiulo et al. (13). Althoughconsiderable variations were reported, the dimensionof the supra-osseous soft tissue was, on average,2.73 mm. Other authors (16, 18) proposed a methodto measure the individual biologic width dimensionusing presurgical, transmucosal probing. In particu-lar, Lanning et al. (16) reported a biologic width aver-age of 2.26 � 0.13 mm, while Perez et al. (18)measured a mean supra-osseous gingiva of 3.63 �0.64 (range: 2.67–5.00) mm. Although the mean val-ues of biologic width found in these studies are simi-lar, the significant range variability observed betweenpatients makes it reasonable to carry out presurgicalbiologic width or supra-osseous gingiva measure-ments in order to personalize the extent of boneremoval.

Osteoplasty

Osteoplasty consists of the removal of nonsupportingbone and aims to thin the vestibular and lingual/palatal aspects of alveolar bone and to eliminate anyosseous ledges or exostosis. It includes techniques ofvertical grooving and radicular blending aimed atestablishing physiologic osseous morphology androot prominence (4, 6). The amount of bone requiredto be removed has not been quantified in the litera-ture, and whether osteoplasty is needed requires asubjective clinical judgment. However, bone reduc-tion could be considered as complete when the flapcan be precisely adapted over the underlying bone.

Instrumentation

Bone is removed by high-speed drilling under copi-ous irrigation with sterile water. Aggressive, multita-pered drills can be used initially, followed by the useof diamond burs and handheld chisels to refine the

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bone surface. Care must be taken to remove all inter-proximal bone remnants (i.e. widow’s peaks) and toprevent inadvertent trauma to the teeth. Root planingof the exposed root surface is carried out using ultra-sonic and hand instruments to create a hard, smoothand clean root surface.

Flap suturing and positioning

The flap is sutured with vertical mattress suturesanchored to the periosteum with the rationale ofobtaining a tight adaption of the flap to the underly-ing tissues at the desired apical position.

Esthetic considerations

The goal of esthetic surgery is to mimic, as much aspossible, the natural aspect of soft tissues and to givea harmonious aspect to the surgical area. The presur-gical and surgical variables to be considered toachieve these objectives are:� The position of the vestibular incision. As the

vestibular flap can be precisely adapted to thebone crest and sutured at the desired position,the vestibular incision should be mostly guided byconsidering the final position of the mucogingivalline after flap suturing, with the purpose ofobtaining a uniform band of keratinized tissuearound the anterior teeth.

� Interdental soft tissues. The interdental soft tis-sues should be left in place if no interproximalcrown lengthening is required. This is the case if apatient is affected by buccal passive altered erup-tion requiring restorative rehabilitation.

o Ostectomy (Fig. 1). The tooth that will have thebuccal bone crest most apically displaced afterostectomy (for a restorative, ferrule effect, oresthetic or periodontal reasons) has to beconsidered as the ‘guiding tooth’. Once the guid-ing tooth is identified, the extent of the ostec-tomy on the adjacent teeth should respect thefollowing esthetic proportion parameters: theapicocoronal position of the bone crest shouldbe at the same level of homologous contralateralelements; the position of the bone crest of thecentral incisors should be at the same level ormore coronal to the bone crest of the canines;and the position of the bone crest of the lateralincisors should be more coronal to the bonecrest of the central incisors and canines.

� Osteoplasty. The osteoplasty must be performedaccurately in order to establish physiologic andharmonious vestibular bone morphology. Howthe bone thickness is managed has a direct influ-ence on the appearance and rebound of soft tis-sues and the tooth-emergence profiles.

Soft-tissue rebound

The regrowth of soft tissue after the crown-lengthen-ing procedure has been investigated in detail. Br€aggeret al. (5), performed a study on 25 patients to assesschanges in the soft-tissue level after a crown-length-ening procedure with a 6-month follow-up. Immedi-ately after suturing, the surgical procedure resulted inapical displacement of the soft-tissue margin by anaverage distance of 1.32 mm. At 6 months, stableperiodontal tissues with minimal changes in the

A B

Fig. 1. Ostectomy with esthetic proportion parameters. (A)The right lateral incisor is the ‘guiding’ tooth being thetooth in which the buccal bone crest has to be more api-cally displaced because of the need to establish the idealdistance between the bone crest and the compositerestorations. (B) The buccal and interdental bone crest ofall other teeth included in the flap design have been modi-fied in order to accomplish the esthetic proportion criteria:same level of the bone crest at homologous contralateralelements, buccal bone crest of the lateral incisors more

coronally displaced with respect to the central incisors,buccal bone crest of the central incisors more coronallydisplaced with respect to canine bone crests (white dotlines). Also the interdental bone between lateral andcanine should be at the same level of the contralateral oneand more apical with respect to the interdental bone levelbetween lateral incisor and central incisor which should beapical to the interdental bone height between central inci-sors (black lines). This is critical for the final estheticappearance of the interdental papillae.

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gingival margin levels were reported. These data werepartially confirmed by Lanning et al. (16), in a studyon 18 patients. These authors observed no significantchange in the position of the free gingival marginbetween 3- and 6-month time points (7.64 � 0.32and 7.90 � 0.30 mm, respectively). As no postsurgicalmeasures of the free gingival margin were provided, acomparison between baseline (after flap suturing)and 3- to 6-month time points is not possible. Con-versely, Pontoriero & Carnevale (20), in a study on 30patients, found significant alterations of the marginalperiodontal tissues from the immediate postsurgicallevel (4.8 � 1.7 mm interproximally and5.7 � 2.4 mm buccolingually) over a 12-month heal-ing period (1.6 � 1.4 mm interproximally and2.8 � 2.6 mm buccolingually), indicating significantcoronal displacement of the newly formed soft-tissuemargin. Moreover, a different pattern in the healingresponse between different tissue biotypes wasobserved, with the coronal regrowth at interproxi-mal and buccal/lingual sites being significantlymore pronounced in patients with a thick tissuebiotype than in patients with a thin tissue biotype.The tendency for a coronal shift of the soft-tissuemargin during healing was also confirmed by Perezet al. (18), Arora et al. (3), and Deas et al. (10), onstudies with 6 months of follow-up. In particular,Arora et al. (3) and Deas et al. (10) related the tissuerebound to the postsurgical flap position, observinggreater growth when flaps were positioned closer tothe alveolar crest. These findings underline theimportance of a presurgical evaluation by the clini-cian, and the extent of the ostectomy should beconsidered according to the tissue biotype. Also, theclinician should be aware that the position of theflap directly influences the soft-tissue rebound andaccordingly should choose an appropriate suturetechnique.

Provisional and definitiveprosthetic management

Management of the provisional prosthetic restorationis a fundamental step in the esthetic rehabilitationprocess that often troubles both the clinician and thepatient. Three procedures can be adopted based onthe time point when the teeth are prepared and on theposition of the margins of the prosthesis with respectto the gingival margin: (i) intra-operative tooth prepa-ration and relining of the provisional restoration; (ii)early tooth preparation and relining of the provisional

restoration; and (iii) delayed tooth preparation andrelining of the provisional restoration.

Intra-operative tooth preparation andprovisional relining

In this approach, tooth preparation is carried out dur-ing surgery, after ostectomy and osteoplasty, usuallywith the use of diamond burs. Abutments are pre-pared with knife-edge margins at the bone crest level.The intra-operative preparation offers the followingadvantages: elimination of undercuts; root proximitycorrection; and smoothing and cleansing of root sur-faces by removing calculus and necrotic cement rem-nants. After preparation of abutments the provisionalrestoration can be relined during surgery or immedi-ately after suturing. Prosthetic margins should bepositioned at a distance of at least 1 mm from the gin-gival level and constantly monitored in order not tointerfere with the healing of soft tissue. The frequencywith which the provisional restoration is modified isrelated to the expected soft-tissue rebound (i.e. theposition of the flap at time of suturing and the gingivalbiotype) (6). The final prosthesis can be deliveredwhen soft-tissue stability is observed.

Early tooth preparation and provisionalrelining

In this approach tooth preparation occurs after 3weeks from the surgery (25). During this period, thepresurgical provisional restoration is left in place. Therationale for this approach is to manage the provi-sional prosthetic steps after the initial healing hastaken place and following restoration of the connec-tive tissue attachment (i.e. the re-establishment ofthe biologic width and during the maturation phaseof the soft tissues). In the first 3 weeks after surgery,approximately 1 mm of bone surrounding the teethinvolved in the surgery resorbs and leaves a portionof healthy root cementum available for connectivetissue attachment to re-form, in a more apical posi-tion (24). The area previously occupied by the con-nective tissue attachment, where intra-operative rootplaning was performed, is now a hard, smooth andclean surface onto which the junctional epitheliumcan adhere (8). Three weeks after surgery, the probingdepth is zero and the sulcus and the interdentalpapillae are still absent. From a clinical point of view,the tooth structure that, after the soft-tissue matura-tion, will become subgingival is now still supragingi-val, thus facilitating management of the provisionalprosthetic restoration. The abutment preparation is

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now performed at, or close to, the gingival level witha knife-edge margin and using the healed soft-tissuemargin as a guide. A new provisional restoration isrelined at the same level. The early tooth preparationoffers the following advantages (25): less aggressiveabutment preparation; the provisional prostheticphase does not interfere with the re-establishment ofthe biologic width; no need for provisional relining atthe end of surgery; easy supragingival knife-edgepreparation using the healed soft-tissue margin as aguide; easy supragingival relining of the provisionalrestoration in a rested patient with no bleeding; con-ditioning of the soft tissues during the maximal

regrowth period; and no need for retraction cordsduring abutment preparation and relining of the pro-visional restoration (necessary in the case of delayedtooth preparation and provisional relining).

The provisional restorations are modified furtheronly in the interdental aspect, thus avoiding unes-thetic exposure of tooth structure during the entirehealing phase. This also minimizes hypersensitivity.The contact point is initially positioned at a distanceof 3 mm from the interdental soft tissues and is pro-gressively shifted in a more coronal position, a mil-limeter at a time, as the interdental space is filled bythe soft-tissue regrowth. Also, the convergence of the

A

B

Fig. 2. Crown lengthening for esthetic reasons. (A) Patient complaints about the previous esthetic treatment. (B) Intraoralradiographs showing no interdental bone loss.

A B C

Fig. 3. (A) Pre-surgical phase. (B) Removal of the old restorations. (C) Abutment reconstruction.

A B

Fig. 4. (A) Gummy smile. (B) First provisional restorations.

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A B C

Fig. 6. Three weeks after the surgery. (A) Feather-edge abutment preparation using the soft tissues as a guide. (B) 7 weeksafter the surgery, the papillae fill the interdental spaces. (C) The convergence of the provisional interproximal surfaces ismodified and the contact point shifted coronally to allow further growth of the papillae.

A B C

Fig. 7. Soft tissues maturation phase. (A) 3 months after the surgery the interdental spaces are filled. (B) 6 months aftersurgery, soft tissues are mature and ready for the final impression. (C) Digital impression.

A B C

Fig. 8. (A) 1 year after cementation of the final restoration. (B) 3 years after cementation. (C) Radiographic control at3 years.

A B C

D E F

Fig. 5. The gummy smile, the absence of interdentalbone loss and the adequate interdental and palatal abut-ment height suggest only buccal crown lengthening pro-cedure to be performed. (A) Flap design: paramarginalincisions. (B) Split-Full-Split thickness flap elevation. (C)Removal of the marginal tissue and de-epithelization of

the papillae. (D) Osteoplasty and ostectomy performedfollowing the esthetic proportion criteria. (E) Apicallypositioned flap and provisional replacement with noneed of relining. (F) Soft tissue healing after 2 weeks:time for the impression for the new provisionalrestoration.

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A B

Fig. 10. Pre-surgical phase. (A) Removal of the old restorations. (B) New temporary crown in position.

A B C

D E F

Fig. 11. (A) Bone recountouring (ostectomy and osteo-plasty) was performed on the buccal and palatal aspects.No intrasurgical abutments preparation was performed.(B) The position of the buccal crest respects the aestheticproportion criteria independently of the previous length of

the temporary crowns. (C) Sutures of the apically posi-tioned buccal flap. (D) Sutures of the apically positionedthinned palatal flap. (E) Temporary crowns in positionwith no need of rebasement. (F) 2 weeks after surgery atthe time of suture removal.

A B C

Fig. 12. Three weeks after surgery. Early restorative phase. (A) Before abutment preparation. (B) After feather edge abut-ment preparation. (C) Rebasement of the temporary crowns.

A B

Fig. 9. Crown lengthening for esthetic reasons. (A) Patient complaints about the previous esthetic treatment. (B) Intraoralradiographs showing mild horizontal bone loss.

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provisional interproximal surfaces is gradually aug-mented, to maximize the regrowth of the interdentalpapillae. The frequency of the provisional modifica-tions is related to the expected soft-tissue rebound.The time for the final impression is specifically cho-sen in each patient when, at the last control visit,there is no further growth of the interdental papillaewith respect to the last contact point of the temporarycrowns (25). An example of esthetic crown lengthen-ing limited to the buccal aspect and early restorative

phase is shown in Figs 2–8. An example of estheticcrown lengthening and early restorative phase isshown in Figs 9–14.

Delayed tooth preparation andprovisional relining

This approach is based on the concept of not interfer-ing with healing of the soft tissues (11). After thecrown-lengthening procedure, the margins of the

A

C

B

Fig. 14. (A) 1 year after cementation of the final restoration. (B) 3 years after cementation. (C) Radiographic control at3 years.

Fig. 15. Staging of the different crown lengthening prosthetic procedures.

A B

Fig. 13. (A) Intermediate (4 months) maturation phase after modification of the temporary crowns. (B) 6 months after thesurgery at the time of final impression.

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provisional restoration are maintained at the presurgi-cal level until soft-tissue stability is achieved (9–12months). At this point, the final abutment preparationis performed and the final prosthesis is delivered.

Conclusions

Despite the fact that crown lengthening in estheticareas is a widely used clinical procedure, there is a lackof evidence in the literature regarding the descriptionof both surgical and prosthetic procedures. However,some indications can be summarized:� The objective of resective surgery is to obtain an

increase in the clinical crown length. To achievethis, hard and soft tissues must be thinned asmuch as possible in order to minimize the amountof supporting bone removal (ostectomy):o The surgical papillae should be elevated in a

split-thickness manner.o The palatal flap should be elevated using the

‘thinned palatal flap approach’.o The nonsupportive bone should be thinned to

obtain a precise flap adaptation.o The buccal ostectomy should be performed,

after choosing the guiding tooth, following theesthetic proportion parameters.

� Regrowth of soft tissue after the crown-lengthen-ing procedure is dependent on individual patientfactors and the timing of the placement of thefinal restoration should be chosen accordingly.

� The provisional prosthetic restoration phaseshould start 3 weeks after the surgery in order notto interfere with the re-establishment of the bio-logic width and to condition the soft tissues dur-ing the period of maximal regrowth.

Figure 15 summarizes the staging of crown-lengthen-ing prosthetic procedures.

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