NEW CONTROLLED BONE EXPANSION TECHNIQUE: MULTI-DISCIPLINE CLINICAL CASE (SURGICAL AND ORTHODONTIC PART)
In implant-prosthetic rehabilitation, the presence of horizontal or vertical bone re-absorptions represents one of the most frequent anatomic limits impeding implant positioning. When bone areas are not suitable for implant positioning, reconstruction techniques can be used to restore bone anatomy. These techniques allow implant inserting of appropriate number and length for a correct dental arch restore.
In case of severe horizontal crest atrophies, the technique used to restore a correct vestibular-oral dimension, are the following:
- regenerative techniques (Guided Bone Regeneration);
- bone grafts;
- expansion techniques;
- bone distraction;
- crest sagital osteothomy (ERE);
- extension Crest ;
- combined techniques (regenerative techniques, expansive techniques)
Edentulous bridge expansion (ERE) technique has been created in 1986 and presented 2 years later by Dr. Bruschi and Dr. Scipioni. The technique has been improved during the past years. Nowadays, it is used to reestablish orofacial dimensions suitable for alveolar atrophic crests during implant introduction without membrane induction and without bone-inductor or bone-conductor materials induction.
A study conducted on edentul sites treated with ERE technique confirmed that in the intraosseous rupture surgically created there is a complete bone regeneration. Interestingly, the same bone integration level is obtained on control sites treated with a traditional surgical implant technique. This technique uses the normal regenerative potential of the spongy bone, improved by a careful surgical approach with a periosteum conservation, together with recovery techniques by second intention. Intra-osseous rupture is, at first, filled by a clot; in the next days (about 40), there begins the formation of osteoid tissue that progressively (after 90-120 days) matures by increase in matrix mineralization and transformation of osteoblasts in osteocytes.
There are two principal prerequisites for bone regeneration after slit crest:
- a solid nutritional basis, with a minimum thickness of 1-1,5 mm of osseous flaps;
- an abundant blood flow necessary for newborn trabeculars.
This allows to avoid fenestrations, dehiscences or necrosis of vestibular osseous plate during the introduction and recovery phases of osteointegrated implants.
ERE technique is indicated in blade knife crests with a height of 10 mm minimum and a thickness of 4 mm minimum. It is performed by a crestal cut to release a flap of partial thickness edge in a vestibular and palatal direction. If necessary, two cuts are carried out in the mesial and distal limits of the surgical area. After the edges are raised, we proceed with cutting the bone in the crest center (5-7 mm deep); secondarily, we carry out two parallel trans-periosteal cuts. Thus, there result two vertical grooves in the vestibular cortical plan. A scalpel is inserted in the crest incision and beaten softly with a percussion hammer, until it reaches the lower part of the crack; at this point the scalpel will be used as a lever to dislocate the buccal plate in a vestibular direction.
The recovery period of implants inserted with the ERE technique is identical to the prescribed period for classic procedures. Nowadays, there seems to be a higher stability of the bone regenerated by bone expansion through time than that obtained by guided bone regeneration (GBR) techniques that tend to reabsorbed through time.
The disadvantage of the ERE technique is the risk of fracture of the vestibular wedge during the scalpel action, not being able to control the power during hammering. To avoid this risk the flap is cut at a partial thickness to guarantee blood flow of the cortical bone in case of fracture. On one hand the partial thickness flap preserves us from this risk, on the other hand not detaching the periosteum does not enable us to associate bone regeneration techniques.
Some years ago the Extension crest technique was presented.This technique, following incision in crest and bone expansion of 2 mm, is based on the insertion of a 2 mm thick distractor, activated by a screw and immediately bringing to the superior dental arch, or after a few days to the inferior arch to the crest expansion. This technique permits to control the expansion and to make it more predictable. A big disadvantage, instead, is the tool thickness. Actually, there exist 3 mm diameter implants of predictable use. Therefore, when the bone is expanded of 2 mm to introduce the Extension Crest there would be only 1 mm of expansion left for implant insertion. For all these reasons in the clinical practice during these last 4 years we tried to improve a controlled bone expansion technique that allows us to give predictability to the technique of bone expansion in order to obtain the detachment of a total thickness flap and so to associate guided osseous regeneration techniques.
The use of the scalpel cannot be foreseen and its’ power not being continuous may cause the fracture of the bone fragment with its consequent dislocation. Controlled osseous technique includes the use of manual screw expanders. Manual screw expanders can be checked more easily by the user, they allow to check with a ratcher its expansion power. In particular, they allow minimum expansion movements, each screw movement being of 0,2 mm. These screws should have a decreasing in its conical shape. This reduces expansion powers on the crest edge which is usually the weakest point.
The patient of this case presented a medial survey until the apex of the element n.11 caused by a root fracture not immediately diagnosed and a 3 mm diasteme between the 2 superior central teeth. The extraction of this element was thus necessary as was the consequent implant rehabilitation following 9 months from the extraction. Meanwhile, it was necessary to put a temporary prosthesis on the edentule saddle and considering that the patient wanted to fill the space between the two central teeth it was also required an orthodontic movement to improve in a mesial-distal way the space for a future implant site and the prosthetic dental crown. The patient declined at the same time the multibrackets vestibular therapy which would have allowed at the same time the maintainance of the temporary tooth.