Fall 2000 Presentation Summary:

Since the first Branemark dental team was created at the University of the Pacific in 1981, Dr. Roberts has been involved with dental implants and has been an innovator in the arena of orthodontic/prosthetic applications.

Anterior Implants

In cases involving anterior implants, the prosthodontist and the orthodontist cooperate. Driven by esthetic concerns, these specialists seek to orient the teeth around an ideal prosthetic restoration, with a symmetrical gingival line and pleasing gingival/dental display.

Pretreatment planning is critical. When an implant is part of the orthodontic result, one should consider using Ward Smalley's planning procedure to locate the implant. If the primary purpose of the implant is to provide orthodontic anchorage, the precise location is less critical. Dr. Roberts feels that occlusograms, panoramic X-rays or mounted models suffice in these situations.

When the orthodontist finishes a case that is planned for implant restoration, seven millimeters is considered an optimal space for an anterior implant at the root apex. However, this step is often completed well before the implant may be placed and considerable dental compensations may subsequently occur as a result of growth and occlusal settling. For example, mandibular growth can cause flaring of upper incisors. As incisal edges splay but do not spread apart, the apices come closer together. Some options can help to avoid this potential complication during retention: Very close adaptation of the labial archwire to prevent any root movement; an acrylic layer added to the labial wire; a bonded retainer; or a resin-bonded acrylic bridge. Dr. Roberts advises against using retainers that use a labial elastic from cuspid to cuspid.

Tissue Engineering

Thanks to advances in surgery that can alter soft tissue and bone morphology, we now need to consider the form of the supporting tissue as a treatment planning issue. One can use local bone remodeling to develop alveolar bone in a deficient area. Soft tissue will follow, more predictably than when only using periodontal surgery.

Dr. Roberts presented several examples to illustrate this contention. In one, he used an implant-supported bridge as anchorage to move incisors along with supporting hard tissue into an extensive surgical defect. He moved a premolar and the supporting bone into the middle of the maxillary sinus using anchorage derived from an implant distal to the sinus. Teeth moved into atrophic knife-edge alveolar areas appear to bring along their soft and hard tissue support.

Caveats

When planning treatments that involve bone manipulative procedures, you need to take the patient's systemic health into consideration early on. Diabetes must be controlled and monitored. Osteopenia and osteoporosis are the most common conditions encountered with reconstruction patients. For patients taking medications that inhibit bone formation (calcitonin and bisphosphonates), you will need to provide hormonal management during the active phase of orthodontic treatment.

In cases where you suspect a syndrome, order a genetic workup to identify specific conditions. Ectodermal dysplasia or other trichodental are not uncommon.

Anchorage Implants

A most innovative use of implants as orthodontic anchorage units is placing the temporary implant in the retromolar area buccal to the base of the vertical ramus. Dr. Roberts demonstrated his ability to reverse skeletal and dental compensations resulting from loss of teeth and collapsed vertical dimension.

A typical patient will present flared upper incisors, crowded, lingually displaced lower incisors, increased overbite, and severely tipped second and/or third molars. To reverse such compensations, vertical dimension must first be restored using restorative procedures, implants, or orthotics. Once reversed, you can then advance and align lower anteriors, and retract the upper incisors. The lower cuspid, stabilized by the retromolar implant, becomes the linchpin for molar uprighting.Using an 019x025 titanium alloy anchorage wire from the implant to a vertical slot on the cuspid bracket, Dr. Roberts connects the cuspid to the implant. He then uses a sectional archwire from the cuspid bracket slot to molar tubes to provide uprighting forces. Ligating the sectional archwire to the anchorage wire will prevent extrusion. As the tipped second and third molars upright, mesial force can be applied to move into the missing molar space. Without implant anchorage these movements would be impossible.

Dr. Roberts suggested that retromolar anchorage can also be used in cases with congenitally missing bicuspids or loss of bicuspids due to caries.

Maxillary Retromolar Anchorage

Using an implant distal to a terminal upper molar is more problematic given the steep learning curve for implant and anchorage wire placement. Dr. Roberts recommends that you schedule ample time for initial attempts by the surgeon and the orthodontist. He suggests diagnostic procedures on a typodont prior to surgery.

The basic procedure for maxillary retromolar anchorage implant placement is as follows:

Make a triangular flap distal and buccal to the terminal molar. Avoid reflecting tissue buccal to the terminal molar as this will impede healing of the incision in the presence of the anchorage wire. Place a standard 3.75 x 7-mm Branemark implant. Immediately load the fixture by engaging the threads in cortical bone to permit immediate loading of the fixture, avoiding bone tapping or countersinking. The implant flange should rest on periosteum. Secure the anchorage wire to the cover screw; it should emerge passively through the closed incision. After two weeks, the incision should have healed enough to permit activation of the anchorage wire. Then you can insert the anterior terminus of the TMA anchorage wire into the vertical slot on the cuspid bracket. To avoid extrusion of the cuspid, leave it free to move vertically in the slot. Next, place the segmental wire to upright molars, ligating the anchorage wire to the uprighting wire to prevent extrusion. Upon completion of the orthodontics, the surgeon can remove the anchorage implant from the retromolar fossa.

Ankylosed Teeth

Ankylosed teeth pose serious problems because they cannot be moved, and they never seem to be in the right place. You might luxate and extrude one, but translation is not feasible. Dr. Roberts has developed a protocol for intentionally inducing fatigue fracture into bone to permit bodily movement of an ankylosed tooth. Tooth movement results when one applies sufficient pressure to induce an osteogenic reaction. Additional force induces a hypertrophic response, and eventually, supporting bone is pushed into fatigue failure as pressure is increased.

If you apply force from implant anchorage that is high enough to produce fatigue damage, the small area of ankylosis fractures and the tooth abruptly moves one or two millimeters within the confines of its alveolar socket, and then inevitably resumes its ankylosed state. Two or three applications of force in the fatigue failure range will result in significant orthodontic movement of an ankylosed tooth.

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