On

Respect Biology ,,  



Objectives

This surgical procedure is aimed at reestablishing the biological width apically while exposing more tooth structure. The biological width is defined as the sum of the junctional epithelium and supracrestal connective tissue attachment. The average space occupied by the sum of the junctional epithelium and the supracrestal connective tissue fibers is 2.04 mm. Violation of that space by restorations impinging on the biological width has been associated with gingival inflammation, discomfort, gingival recession, alveolar bone loss, pocket formation, and the like.

To have a harmonious and successful long-term restoration, it is advocated to keep 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.


Indications
  • To improve the gummy smile of a patient with a high smile line.
  • To rehabilitate dentition that is compromised by the presence 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, allowing for surgical modification of the gingival margins without the need for osseous recontouring (i.e., 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. Unfortunately, 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 margins at the desired height, and apically reestablishing the biological width.
The crown lengthening procedure enables restorative dentists to develop an adequate zone for crown retention without extending the crown margins deep into periodontal tissues. After the procedure, it is customary to wait 6–8 weeks before cementing the final restoration.
In the aesthetic zone, a waiting period of at least 6 months is recommended before final impression. This reduces the chances of gingival recession following prosthetic crown insertion, specifically if there is a thin biotype.


A pleasant smile line reveals 75–100% of the maxillary anterior teeth and the interproximal gingiva only (68.94% of the subjects). 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 mm below. The maxillary incisal curve is parallel with the lower lip (84.8% of the subjects). 


The position of the anterior contact point progressing from incisal to cervical and from central incisors to canines (horizontal lines). The location of the gingival zenith (black arrows), the most apical point of the gingival tissue, referencing the tooth axis, is distal on the maxillary central incisors and canines, and coincidental on lateral incisors. 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.


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 or Orban (in case of external bevel gingivectomy), or a no. 15 blade (internal bevel gingivectomy) is used to eliminate that excess gingiva. 

Gingival hyperplasia secondary to the daily use of Dilantin (phenytoin). This excessive tissue affects patients’ dental aesthetics and function.

The mouth of the 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 environment. as there is no need for osseous recontouring, the biological width is undisturbed.

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.
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 restoration. 

Case 1 : 

 
The mouth of a 42-year-old woman unhappy with her smile. Her lip line shows maxillary gingiva, iatrogenic dentistry and erroneous gingival margin positions. 
Intraoral photography shows a poorly designed prosthesis, severe overbite, faulty crown margins and severely decayed teeth.

Diagnostic wax-up from which a surgical guide will be created.

The provisional restorations are removed, and the surgical guide created from the wax-up is inserted. This guides the surgeon to position the new gingival 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 new gingival architecture.


The full-thickness flap is elevated, and the osseous recontouring is done to expose the new tooth structure that will recieve the new prosthetic margins.   A 3-mm space between the bone crest and the planned new prosthetic margins is imperative for successful restorations.


The falps are secured with a continuous sling and vertical mattress suture.

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

 Case 2 :

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

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

A patient’s mouth rehabilitated aesthetically and functionally with individual PFM crowns. 


Case 3 :


A female patient wanted an esthetic restoration of the entire maxillary arch. The initial situation showing severe wear of the anterior maxillary teeth accompanied by osseous regression and modification of the gingival level.

Esthetic crown lengthening with apically positioned flap in order to restore the dental proportions.

The final situation ; lithium disilicate pressed crowns.



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. 

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

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 & 9. They should be situated above the gingival margins of the lateral incisors.

Two short vertical buccal incisions at the line angles of teeth 8 & 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.

A submarginal incision mimicking the final gingival margin levels of teeth 8 & 9 will help connect the two verticals .


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

Crestal bone is removed with a chisel or a burr to have 3 mm of space between the anticipated prosthetic margins and the  alveolar bone. 

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

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

Final veneers 4 months later.


Reference : PRACTICAL PERIODONTAL PLASTIC SURGERY edited by Serge Debart.