Forced eruption allows reduction
of the bony pocket without
surgically taking off bone.
One way orthodontics is used in treating periodontal disease is forced tooth eruption. When a tooth is moved orthodontically, the bone will follow the tooth as long as there is no inflammation. Thus if there is a bone pocket next to the tooth, it may be possible to erupt the tooth out of the defect. In the illustration below, there is a 4mm bone pocket next to the tooth. If pocket elimination surgery were used to correct the pocket, much of the adjacent bone would have to be ground away to allow the gum to again connect to the tooth next to the bone.
However, if the tooth is extruded 4 mm, the bone will follow it up until it is level with the adjacent bone. The pocket is now gone, without bony surgery. Also, because the height of the tooth must remain the same so the patient's bite won't be affected, the top of the tooth is reduced as the eruption progresses. This normally can be done without causing the tooth to need a filling or crown. By shortening the part of the crown out of the bone, the ratio of tooth in bone to that out of bone (the crown/root ratio) improves. This stabilizes the tooth, and makes it stronger. In this example the crown/root ratio has improved from 10/6 to 6/6.
Another common use for forced eruption is to allow better access to deep decay. While the gum and bone can be surgically removed until the decay is seen (See Crown Lengthening), this may create a high gum line and a cosmetic problem with front teeth. By erupting the decayed tooth, the adjacent teeth are not affected when exposing the decay. In this case study, the deep decay is clearly seen on the pre-operative x-ray. After orthodontically extruding the tooth, the new x-ray shows the decay much nearer the gum surface.
When the gum is reflected, the decay is easily seen. Note that the bone erupted along with the tooth, and is now too high on the extruded tooth. That bone is leveled with the adjacent bone, and the gum closed. Note that no bone on the adjacent teeth needed to be moved higher. The final x-ray shows the bone level the same as with the pre-operative x-ray, while access for a crown has been achieved.
Decay under a crown, near the bone margin. Note position of decay relative to adjacent tooth.
Tooth extruded.
Note bone followed tooth as it erupted.
Orthodontics to extrude the decayed tooth performed. Note gum and bone hasfollowed the extrusion.
Gum reflected to access decay.
Note bone that moved with tooth.
Excess bone levelled to adjacent bone,
giving excellent access to decay.
Gum sutured closed. Note gum has stayed level with the adjacent teeth, while decay is now accessible.
Final x-ray showing crown with level bone in normal position.
Clinical results with esthetics preserved.