Crown-LengtheningProcedure


Serge Dibart


HISTORY
There are two aspects to the crown lengthening procedure: aesthetic and functional. In both cases, the surgical proce- dure is aimed at reestablishing the biological width apical- ly while exposing more tooth structure. The biological width is defined as the sum of the junctional epithelium and supracrestal connective tissue attachment (Cohen 1962).
Gargiulo et al. (1961), who measured the human den- togingival junction, found that the average space occu- pied by the sum of the junctional epithelium and the supracrestal connective tissue fibers is 2.04 mm. Viola- tion of that space by restorations impinging on the biolog- ical width has been associated with gingival inflamma- tion, discomfort, gingival recession, alveolar bone loss, pocket formation, and the like (Parma-Benfenati et al.
1985; Tarnow et al. 1986; Tal et al. 1989).
To have a harmonious and successful long-term restora- tion, Ingber et al. (1977) advocated 3 mm of sound supracrestal tooth structure between bone and prosthetic margins, which allows for the reformation of the biological width plus sulcus depth. This can be achieved surgically (crown lengthening) or orthodontically (forced eruption) or by a combination of both (Ingber 1976; Pontoriero et al.1987; De Waal and Castellucci 1994).

INDICATIONS
• To improve the gummy smile of a patient with a high smile line
• To rehabilitate dentition that is compromised by the pres- ence of extensive caries, short clinical crowns, traumatic injuries, or severe parafunctional habits
• To restore gingival health when the biological width has been violated by a prosthetic restoration that is too close to the alveolar bone crest
Crown lengthening can be limited to the soft tissues when there is enough gingiva coronal to the alveolar bone, allow- ing for surgical modification of the gingival margins without the need for osseous recontouring (that is, pseudopockets in cases of gingival hyperplasia). An external or internal bevel gingivectomy (gingivoplasty) is the procedure of choice in these cases.
The biological width has not been compromised, and, as a result, the soft tissue pocket is eliminated and the teeth exposed without the need for osseous resection. Unfortu- nately, the majority of cases will involve bone recontouring as well as gingival resection to accommodate aesthetics and function. This is a more delicate procedure that requires exposing root surface, positioning gingival mar- gins at the desired height, and apically reestablishing the biological width.
The crown-lengthening procedure enables restorative den- tists to develop an adequate zone for crown retention with- out extending the crown margins deep into periodontal tis- sues. After the procedure, it is customary to wait 6–8 weeks before cementing the final restoration. In the aes- thetic zone, a waiting period of at least 6 months is recom- mended before final impression (Pontoriero & Carnevale
2001). This reduces the chances of gingival recession fol- lowing prosthetic crown insertion, specifically if there is a thin biotype.

A FEW WORDS ABOUT AESTHETICS
As the saying goes, “Beauty is in the eye of the beholder.” Oral aesthetics is part art and part science. The enhance- ment of a person’s smile culminates in the individualization of the general rules governing dental aesthetics for that person. Every patient is different, and yet a nice smile is the result of an orderly combination of several compo- nents. Knowing the general guidelines that make a smile appealing and tailoring them to an individual patient gives that smile uniqueness.
The aesthetic zone has been defined as the area encom- passed by the upper and lower lips (Saadoun & LeGall
1998). It is the harmonious relationship among the denti- tion (premolar to premolar), the periodontium (gingival line), and the lips that will make or break a smile.
In 1984, Tjan et al., after observing several hundred dental and hygiene students, defined a standard of normalcy in an aesthetic smile (Figs. 1 & 2).


ARMAMENTARIUM
This includes the basic kit plus crown-lengthening burrs and bone chisels.
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Figure 1. Apleasant smile line reveals 75%–100%of the maxillary anterior teeth and the interproximal gingiva only (68.94%of the sub- jects).The gingival margins of the central incisors and canines are located horizontally at the same level, whereas the gingival margins of the laterals are 2 mmbelow.The maxillary incisal curve is parallel with the lower lip (84.8%of the subjects). FromTjan et al. (1984


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Figure 2. The position of the anterior contact point progressing fromincisal to cervical and fromcentral incisors to canines ( horizontal lines). The location of the gingival zenith (black arrows), the most api- cal point of the gingival tissue, referencing the tooth axis, is distal on the maxillary central incisors and canines, and coincidental on lateral inci- sors (Rufenacht 2000).The golden percentage (25%, 15%, and 10%) is considered a starting point in designing the relative width of teeth in a beautiful smile. With all of these width ratios added together, the total canine-to-canine width becomes the golden percentage (Snow1999).

SOFT TISSUE CROWN LENGTHENING
Soft tissue crown lengthening is best accomplished with an external or internal bevel gingivectomy. The alveolar bone is left intact, the depth of the soft tissue pocket is marked with a probe (bleeding points) and a gingivectomy knife, Kirkland (Hu-Friedy, Chicago, IL, USA) or Orban (Hu- Friedy) (in case of external bevel gingivectomy), or a no.
15 blade (internal bevel gingivectomy) is used to eliminate that excess gingival (Figs. 3 and 4).

HARD TISSUE CROWN LENGTHENING
The optimal gingival line (margins) is determined after careful evaluation of the diagnostic waxup. A surgical guide is prepared from the waxup model that will help the surgeon re-create the ideal gingival line in the mouth. Using a no. 15 blade as a pencil, the surgeon outlines the incision and, following the surgical guide, keeps the blade at an angle to create a coronal internal bevel

 
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Figure 3. Gingival hyperplasia secondary to the daily use of Dilan- tin (phenytoin).This excessive tissue affects patients’ dental aesthetics and function



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Figure 4. The mouth of a patient after minor orthodontic treatment and full-mouth external bevel gingivectomy. Hyperplastic gingival tissue has been surgically eliminated and the teeth exposed to the oral envi- ronment. As there is no need for osseous recontouring, the biological width is undisturbed.
The full-thickness flap is then reflected, the secondary flap discarded, and the bone exposed. Using burrs or bone chisels, the alveolar bone is recontoured to create a 3-mm space between the bone and the anticipated new margins. The flaps are sutured back in place and the area left to heal for about 3 weeks before repreparing the teeth (supragingivally) and relining the temporaries. A waiting period of about 6 months, in temporaries, is recommended in the aesthetic zone before final preparation and restora- tion (Figs.5–14


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Figure 5. The mouth of a 42-year-old woman unhappy with her smile. Her lip line shows maxillary gingiva, iatrogenic dentistry, and erro- neous gingival margin positions


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Figure 6. Intraoral photography shows a poorly designed prosthe- sis, severe overbite, faulty crown margins, and severely decayed teeth


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Figure 7. Diagnostic waxup fromwhich a surgical guide will be created.



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Figure.8. The provisional restorations are removed, and the surgi- cal guide created fromthe waxup is inserted.This guides the surgeon to position the newgingival margins to the desired levels.The surgical incision follows the surgical guide closely to give the restorative dentist the precise amount of tooth structure needed to create a newgingival architecture



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Figure 9. The full-thickness flap is elevated, and the osseous recontouring is done to expose the newtooth structure that will receive the newprosthetic margins. A3-mmspace between the bone crest and the planned newprosthetic margins is imperative for successful restora




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 Figure 10. The flaps are secured with a continuous sling and verti- cal mattress suture.




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Figure 11. The final prosthesis is inserted 1 year later.The teeth have been customized to fit the patient’s morphogenetic type.




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Figure 12. The mouth of a patient who has amelogenesis imperfec- ta. Extensive decay and short clinical crowns make it difficult for proper rehabilitation without crown lengthening.




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Figure 13. The surgical crown-lengthening procedure performed with removal of hard and soft tissues.





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Figure 14. Apatient’s mouth rehabilitated aesthetically and func- tionally with individual porcelain fused to metal crowns.





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Figure 15. The mouth of a 40-year-old woman unhappy with her smile. She seeks help to improve her appearance and boost her self- confidence.


MICROSURGICAL CROWN LENGTHENING
In the areas of high aesthetic demand, where papilla and soft tissue conservation is of paramount importance, the use of a microsurgical technique is recommended. There will be smaller incisions, which will not involve the papillae.
Flap reflection is minimal, and the sutures enable a very close adaptation of the flaps. This, in turn, results in minimal inflammation, scarring, and patient discomfort. Because of the minimally invasive nature of the procedures and the superior wound adaptation, quick healing and enhanced aesthetics are to be expected (Figs. 15–23)




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Figure 15. The mouth of a 40-year-old woman unhappy with her smile. She seeks help to improve her appearance and boost her self- confidence.



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Figure 16. The mouth of the same patient after caries control and temporization.The condition has somewhat improved but notice the erroneous position of the gingival margins of teeth 8 and 9.They should be situated above the gingival margins of the lateral incisors.




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Figure 17. Two short vertical buccal incisions at the line angles of teeth 8 and 9 are made with a microblade leaving papillae and frenum intact.The mesial incisions are hidden in the labial frenum; this allows for invisible scarring.




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Figure 18. Asubmarginal incision mimicking the final gingival mar- gin levels of teeth 8 and 9 will help connect the two verticals.





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Figure 19. The full-thickness flaps are reflected just enough to expose crestal bone.The interdental papilla is left alone; this enhances a positive aesthetic outcome.




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Figure 20. Crestal bone is removed with a chisel or a burr to have 3 mmof space between the anticipated prosthetic margins and the alveo- lar bone.




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Figure 21. The flaps are sutured back in place with resorbable 7-0 microsutures.The number and position of the microsutures enable a close adaptation of the flaps and subsequent rapid healing.




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Figure 22. The mouth of the patient 1 week later. Notice the quality of the wound healing.




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Figure 23. Final veneers 4 months later.



REFERENCES
Cohen, D.W. (1962) Periodontal preparation of the mouth for restora- tive dentistry. Presented at the Walter Reed Army Medical Center, Washington, DC, 3 June 1962.
De Waal, H., & Castellucci, G. (1994) The importance of restorative margin placement to the biologic width and periodontal health. Part II. International Journal of Periodontics and Restorative Dentistry
14, 70–83.
Gargiulo, A.W., Wentz, F.M., & Orban, B. (1961) Dimensions and rela- tions of the dentogingival junction in humans. Journal of Periodon- tology 32, 261–267.
Ingber, J.S. (1976) Forced eruption. Part II. A method of treating nonre- storable teeth: Periodontal and restorative considerations. Journal of Periodontology 47, 203–213.
Ingber, F.J.S., Rose, L.F., & Coslet, J.G. (1977) The biologic width: A
concept in periodontics and restorative dentistry. Alpha Omegan
10, 62–65.
Parma-Benfenati, S., Fugazzotto, P.A., & Ruben, M.P. (1985) The effect of restorative margins on the post-surgical development and nature of the periodontium. Part I. International Journal of Peri- odontics and Restorative Dentistry 5(6), 30–51.
Pontoriero, R., & Carnevale, G. (2001) Surgical crown lengthening: A
12-month clinical wound healing study. Journal of Periodontology
72, 841–848.
Pontoriero, R., Celenza, F., Jr., Ricci, G., & Carnevale, M. (1987) Rapid extrusion with fiber resection: A combined orthodontic-periodontic treatment modality. International Journal of Periodontics and Restorative Dentistry 5, 30–43.
Rufenacht, C.R. (2000) Principles of Esthetic Integration. London: Quintessence, 13–36.
Saadoun, A.P., & LeGall, M.G. (1998) Periodontal implications in implant treatment planning for aesthetic results. Practical Peri- odontics and Aesthetic Dentistry 10, 655–664.
Snow, S.R. (1999) Esthetic smile analysis of maxillary anterior tooth width: The golden percentage. Journal of Esthetic Dentistry 11,
177–184.
Tal, H., Soldinger, M., Dreiangel, A., & Pitaru, S. (1989) Periodontal response to long-term abuse of the gingival attachment by supracrestal amalgam restorations. Journal of Clinical Periodontology
16, 654–689.
Tarnow, D., Sthal, S.S., Magner, A., & Zamzok, J. (1986) Human gin- gival attachment responses to subgingival crown placement– marginal remodeling. Journal of Clinical Periodontology 13,
563–569.
Tjan, A.H., Miller, G.D., & The, J.G. (1984) Some esthetic factors in a smile. Journal of Prosthetic Dentistry 51, 24–28.

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