Crown Lengthening

Not all crowns are made the same.  Some crowns have good contacts and occlusion.  That’s all that patients can tell.  But what is underneath the crown?  No one knows except you, your assistant and lab technician.  What I am trying to say is that not all crowns have good retention, good margin and ferrule on sound tooth structure. So, how can you make your prep meet these requirements?  To satisfy these requirements, there has to be enough tooth structure exposed supragingivally.  Deep subgingival preps can make impression taking difficult and impinge on the biological width and cause persistent gingival inflammation and subsequent periodontal disease.

Gingivectomy

Gingivectomy  can be done when bone level is sufficiently low enough and only soft tissue needs to be removed.  Then, what is the minimum distance from the crown margin to the bone?  Most authorities agree that 3 mm is the distance needed from the crown margin to the bone.

Laser and electrosurge

Sometimes laser and electrosurge can be used to expose tooth structure, but these instruments have limitations.  Laser and electrosurge can be used to remove soft tissue but not bone.  Some lasers are claimed to do efficient crown lengthening.  These, however, can not be used effectively to perform bone removal.  Crown lengthening requires bone removal apically and contouring of bone thereafter.

Crown lengthening

Crown lengthening as described by periodontal literature require flap reflection.  Then remove enough bone to have the 3 mm distance required.  Contour the bone so that the bone structure is positive with no craters or ledges. If craters and ledges are present the soft tissue will become thick and hinder good impression taking in addition to ending with deep probing depth after the restoration is cemented.  And don’t forget to plane the root surfaces.  If you don’t then you might end up with low bone level but high attached periodontal ligament and still violating the biologic width.  Before suturing, make sure the flaps are laying without tension and preferably below your crown margin (imaginary margin if the tooth does not have the final margin).  Flaps will not lay correctly if you do not contour the surrounding bone properly.  Sutures need to be removed within 7 to 10 days.  If everything is done correctly, impression can be made between 3 to 6 weeks for posterior teeth and much longer for anterior teeth where soft tissue esthetics is important.

Patients should be informed before the surgery about some transient sensitivity to cold and recession on the tooth and sometimes on the adjacent teeth as well.  A good crown lengthening makes restorative dentistry so much easier and enjoyable.