Functional Crown Lengthening

 The concept

The concept of crown lengthening was first introduced by D.W. Cohen (1962) and is presently a procedure that often employs some combination of tissue reduction or removal, osseous surgery, and / or orthodontics for tooth exposure. The amount of tooth structure exposed above the osseous crest (about 4mm) must be enough to provide for a stable dentogingival complex and biologic width to permit proper tooth preparation and account for an adequate marginal placement, thus ensuring a good marginal seal with retention for both provisional and final restorations

1 - To provide retention form to allow for proper tooth preparation

2 - impression procedures 

3 - placement of restorative margins 

Approaches for Crown lengthening

Gingivectomy: when there is an adequate band of Keratinized gingiva (KG) (≥2 mm) and distance from CEJ to alveolar bone crest is (≥2 mm)

Flap + Osseous Resection: when there is an adequate band of Keratinized gingiva (KG) (≥2 mm) and distance from CEJ to bone crest is (<2 mm).

Apically positioned flaps (APF):when there is an inadequate band of KG (<2 mm) and distance from CEJ to bone crest is (≥2 mm)

APF + Osseous resection: when there is an inadequate band of KG (<2 mm) and distance from CEJ to bone crest is (<2 mm)                    (Ong et al., 2011)

Orthodontic extrusion

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in this topic we will focus on functional crown lengthening 

first we will start with the most important biological factor 

to measure the patient biologic width 

there are 2 common methods 

 

  : the second biological parameter is

 : the third mechanical factor is

we should balance between benefits and risks during our decision making 

  , in some cases if we are going to encroach the proper crown root ratio

orthodontic extrusion maybe the ideal choice 

for getting into the surgical procedure let us visualize it through this animation

Animated illustration

Clinical Case Example 

preoperative photo showing deep caries margin 

trimming the gingival margin with thermacut bur

pre endodontic build up 

rubber dam isolation 

flap elevation

osseous removal to the desired depth

suturing 

2 weeks follow up

post operative

post operative periapical xray