1. A procedure that clinical height of the crown increased by removal of the coronal portion of periodontium with crestal bone. There must be at least 3 mm between most apical extension of restorative margin and crestal bone.
1.1. Anatomical factors to consider
1.1.1. Soft tissue — aesthetic considerations
1.1.1.1. Minimum of two central incisor teeth or all six anterior teeth may need to be crown lengthened
1.1.1.2. To produce acceptable aesthetics:
1.1.1.3. If only one tooth requires crown lengthening, in order to gain even gingival heights:
1.1.1.3.1. Orthodontic eruption which is then followed by surgery.
1.1.1.4. If restorations are to be placed with their margins just sub-gingival, it is prudent to wait until :
1.1.1.4.1. 6 months after surgery to be certain that no further change in after surgery and before the position of the gingival margin takes place.
1.1.2. Shape of single-rooted teeth
1.1.2.1. where tooth tend to be cylindrical or if there is sufficient room at the level of the amelo-cemental junction to make the preparation, then extending the length of the clinical crown in an apical direction.
1.1.2.1.1. If there is insufficient room at the ACJ , or if the tooth tapers significfntly from that point,These require bevelled margins which need less tooth reduction in the marginal areas. The use of a metal collar has aesthetic implications if the patient has a high lip-line.
1.1.3. 3
1.1.4. 4
1.1.5. Muscle insertion
1.1.5.1. When apically re-positioning a mucogingival flap after bone removal to partially expose the root of the tooth, the space available to accommodate the flap is determined by the muscle insertion.
1.1.5.1.1. A shallow vestibule due to the attachment of buccinator and mentalis muscles limits the space available to accommodate the re-positioned muco-gingival flap which will in turn limit the amount of coronal extension possible.
1.1.6. 6