Crown Lengthening

Crown Lengthening Esthetic Parameters Clinically, the patient’s tissue biotype is classified according to how thick or thins the supporting bone and gingival soft tissues are defined. Becker and Oschenbein (1997) Three distinct types; pronounced scalloped, scalloped and flat. • A thin periodontium will be pronounced scalloped or scalloped. •

A thick periodontium will present with flat gingival architecture, and usually be supported by thick buccal and lingual plates of alveolar bone.

Response to inflammation, restorative and surgical injury: Thin-scalloped periodontium → some degree of soft-tissue recession. Thick flat periodontium →resists recession and reacts with pocket formation. In the aesthetic zone: •

It is extremely important to identify the position of the midline, and the amount of teeth and the soft tissues visible not only from the frontal view but also from the lateral view, both with the lip at rest and when smiling.

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It is sometimes better to make compromises and understand that residual pocket depths may be maintainable.

• Nonsurgical therapy can keep interproximal papilla intact and is more desirable as compared to the esthetic problems associated with pocket elimination and the creation of “black triangles.” Esthetic periodontal defects include: •

Residual gingival/periodontal defects.

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Violations of biologic width.

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Gingival asymmetries. 1

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Inadequate amount of gingival.

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Gingival recessions.

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Deficient pontic areas.

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Frena impinging on the gingival margin.

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Excessive gingival display.

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Deficient interproximal papillae.

The biologic Zone The biological width The physiological dentogingival junction of natural teeth (“the biological width”) includes: •

The length of the epithelial attachment.

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The length of the connective- tissue attachment .

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The depth of the sulcus.

The mean value of the biological width around a natural tooth is 2.04 mm- 2.73 mm. Keep in mind: •

This dimension is an average of a range of attachment heights.

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There are several variations in dimension of the biologic width between individuals as well as within the same person, depending on the location of the tooth in the dental arch.

Crown Lengthening Aim: To increase the extent of the supragingival tooth structure for restorative or esthetic purposes by apically positioning the gingival margin, removing bone, or both. Rrationale: •

Obtaining physiological or biologic width for the periodontal-restorative interrelationship.

• A minimum of two millimeters of tooth surface should be available above the alveolar bone crest for tissue attachment. Therefore the biologic width is two millimeters (1 mm for connective tissue above crestal bone and 1 mm for epithelial attachment) + sulcus depth (1mm) and resistance form (1-2 mm). Restorations that invade the zone of biologic width will cause inflammation, bone loss and periodontal pocketing. Indications: a) Caries.

b) Tooth fracture.

c) External resorption.

d) Short clinical crowns e) Loss of tooth structure through attrition and abrasion. Contra-indications: 1- When postsurgical healing will result in significant exposure of inaccessible molar or premolar furcations. 2 - If Reduction of the supporting bone will result in a poor crown- root ratio. 3

3- When postsurgical esthetics will be compromised (orthodontic forced eruption may be an alternative). 4 - If there is no attached or keratinized gingiva and the patient will not accept mucogingival surgery prior to crown lengthening. 5 - In cases with thin periodontium and dehiscence or fenestration of alveolar bone (severe postsurgical gingival recession is likely). 6 - If the prognosis of the tooth to be lengthened is poor and adjacent teeth have a fair to good prognosis to act as abutments for a fixed or removable partial denture. Presurgical Planning: •

Evaluation of periapical radiographs and periodontal charting including: probing depths, width of keratinized gingiva, thickness of the periodontium including soft tissues and bone, to estimate how much bone will need to be removed prior to surgery.

• When the keratinized gingiva is 2 mm or less, intrasulular incisions are indicated. •

In cases with wide zone of keratinized gingiva, facial incisions are made with a scallop design, i.e., 0.5-1 mm buccal or lingual to the sulcus.

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If the width of keratinized gingiva is a millimeter or less and the thickness of the tissue is at least 1 mm, a partial thickness flap should be considered. (Fig.2)

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Positioning a partial thickness flap apical to the alveolar crest at a distance equal to the width of remaining keratinized tissue will result in:

o Doubling of the width of the keratinized tissue. o Allows for precise flap placement because periosteal suturing can be

utilized.

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Fig.2 Split thickness flap • Probing of the sulcus depth and sounding the underlying bone will assist the clinician in flap design. •

Wherever bone is to be a reduced, full thickness flap are indicated.

• If periodontal pockets are present, incisions should be planned that will allow for apical positioning of the flap. • A free gingival soft tissue, pedicle or connective tissue graft is indicated when only alveolar mucosa covers the facial surface of a tooth that requires crown lengthening. Gingival grafting establishing at least 2 mm of keratinized gingiva should precede lengthening of the clinical crown. Surgical procedure : 1- Initial incisions: •

Local anesthesia, using Lidocaine 2% with epinephrine 1:100,000.

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A minimal of three teeth are exposed, at least one tooth on each side of the tooth to be surgically lengthened.

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Using a #15 scalpel blade an inverse bevel incision approximately 1 mm from the free gingival margin with a scalloped design is made (Scalloped incisions should not be used when the width of keratinized tissue is less than 2mm}. 5

• Thin keratinized gingiva requires an intra sulcular incision. •

A vertical releasing incision is cut at a 45o angle at the mesiobuccal line angle of the tooth.

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On the palatal aspect, the same parabolic inverse bevel incision design is performed.

• Vertical releasing incisions cut at a 45o angle enhance flap coadaptation. Vertical releasing incisions should be made at the line angles of the teeth so that papillary tissue is available to affix the suture (Fig. 3)

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Fig. 3: Vertical releasing incision and reflection of full thickness flap 2- Full thickness flap elevation: •

Placing#7 K-N knife inserted into the initial incisions, the flap is elevated from the bone.

• Some clinicians prefer to use a periosteal elevator to free the flap. • Controlled pressure is directed toward the bone at the base of the incision. Using the back of the instrument, in this case the #7 K-N knife, to reinforce the flap, short pushing strokes will free the underlying periosteum and connective tissue from the bone. The #7 K-N knife is especially helpful in elevating the palatal flap by performing a “cut-back” procedure, freeing the flap from the bone.

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3-Removing connective and granulation tissue: •

Using the #7 K-N knife into the sulcus and parallel to the tooth surface, the connective tissue collar is excised and elevated from the tooth surface. Interproximal tissue is removed with the #Buck knife. Connective and granulation tissue tags are removed from the tooth and intrabony craters using a #4 curette.

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Once the craters and tooth are free of tissue, the root is examined and planed free of calculus and roughness.

• Most crown lengthening procedures do not require root planing since periodontal pockets normally are not associated with this procedure. •

It is important to root plane only those surfaces of the tooth that have been exposed to the oral environment.

• Connective tissue and periodontal ligament fibers should be spared injury so that wound healing will result in connective tissue reattachment rather than repair with a long junctional epithelium. •

4- Bone reduction steps:

• Based on presurgical planning and the bony topography approximating the crown to be lengthened, measurements are made from the margin of the fractured tooth to the crest of the alveolar bone. • To establish the proper soft tissue dimension and adequate retention/ resistance form, the clinician should measure 4-5 mm from the fractured margin to the crest of the alveolar bone. • If there are intrabony craters, the measurements should allow for reduction of these craters.

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• When ostectomy/osteoplasty is completed, the bone should have physiologic osseous architecture i.e., interproximal bone more coronal to the facial and lingual radicular bone. •

The alveolar crest will parallel the cementoenamel junction. (Fig 4)

Fig. 4: Steps of bone reduction

• Bone is reduced with either hand or rotary instruments. • Where the bone is thick, round diamond burs are used in a high speed handpiece with copious water spray from the handpiece or external irrigation. • Many periodontists will use a round carbide bur to reduce the bone but extra care is necessary to avoid nicking the tooth. •

The rotating bur is lightly stroked against the bone in a paintbrush fashion. Smaller areas of bone reduction are completed with the Ochsenbien Chisel used in a twisting or pushing stroke.

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When lengthening of the clinical crown involves molar and maxillary first premolar teeth, care must be taken to avoid exposing furcations and grooves. Further opening of the furcation will compromise the prognosis of the tooth, causing a plaque trap, inhibiting oral hygiene and periodontal maintenance.

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5- Flap suturing-closure: • When the bony architecture is of equal height on the buccal and lingual surface, simple interrupted sutures are appropriate. •

In esthetic areas and where the tissues are thin, small monofilament suture, e.g. 4-0 or 5-0 Gut or GoreTex® suture, provide for ideal closure with minimal scarring or tissue necrosis.

Excessive gingival display •

In most patients, the lower edge of the upper lip assumes a "gum-wing" profile which limits the amount of gingiva that is exposed when a person smiles. Patients who have a high lip line expose a broad zone of gingival tissue and may often express concern about their "gummy smile".

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The dentist may, if necessary, modify/control the form of the teeth and interdental papillae as well as the position of the gingival margins and the incisal edges of the teeth.

• In the young adult with an intact periodontium the gingival margin normally resides about 1 mm coronal to the cemento-enamel junction. •

Some patients may have a height of free gingiva that is greater than 1 mm, resulting in an unproportional appearance of the clinical crown.

• If such a patient complains about their "small front teeth" and the periodontium is of a thin biotype, full exposure of the anatomical crown can be accomplished by a gingivecomy/gingivoplasty procedure. • If the periodontium is of the thick biotype and there is a bony ledge at the osseous crest, an apically positioned flap procedure should be performed. This will allow for osseous recontouring. 9

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