In planning the biomechanical aspects of orthodontic treatment for a specific patient, it is imperative that the orthodontist consider not only the forces required for the necessary tooth movement to achieve the patient’s objectives, but also the undesired tooth movement that may occur in response to these forces.
In the past, orthodontists have searched for the perfect anchorage in order to minimize these undesired tooth movements. Headgear, elastics, adjacent teeth, and any number of appliances have been suggested as anchorage in the past; however, the main drawback was that they all relied on patient compliance in order to be successful.
Implant anchorage has burst onto the clinical orthodontic scene in order to assist the orthodontist in controlling tooth movement. The primary advantage over the previously mentioned forms of anchorage is that implants provide skeletal anchorage, which is undoubtedly more predictable and stable than methods requiring patient compliance. While there are many types of implants available, this article will examine three categories that may be useful to today’s orthodontist: cylindrical, miniplate and miniscrew.
Cylindrical implants are the most common type on the market today. Retromolar implants, as well as the traditional abutment implants used for restorative therapies, fall into this category. These implants are highly predictable with regard to success of the implant itself; however, there are important considerations and potential limitations to their use. In general, these implants are primarily useful as anchor units to control anterior-posterior (A-P) movements in orthodontics.
A minimum of 4-6 months is needed for osseointegration of the implant prior to use as an anchorage unit. Finally, implants that are to be used as abutments for future restorative treatment require careful planning and coordination between the orthodontist, oral surgeon, and restorative dentist. Inadequate planning from the onset may result in failure of the implant, a minimally useful anchor unit for the orthodontist, or a poorly positioned implant for the restorative dentist.
Traditional miniplate implants have been used by oral surgeons for decades and are highly predictable in their success after placement. These plates are placed and retained in the skeletal anchorage unit by screws engaging the cortical bone. The most common areas for placement for orthodontic use are in the zygomatic strut in the maxilla and the buccal aspect of the body of the mandible.
Miniplate anchorage may be effective in controlling anchorage in the vertical and anterior-posterior planes, and therefore offers the orthodontist a particular advantage in treating skeletal open bite malocclusions. Although an 8-week healing period was initially recommended, there is debate in the current literature as to whether immediate loading of miniplates may be possible. Once in place, true molar intrusion of either maxillary or mandibular molars may be achieved by connecting elastic thread, rubber bands, ligatures, or niti coils between the molar(s) and the anchorage unit.
A disadvantage to using miniplates as anchorage is that a full thickness flap is required for their placement, and the plates must be retrieved after termination of treatment. Miniplates do offer advantages over other implant options in that they do not move, they are low profile, and the attachment for clinical use may be easily accessed for adjustment by the orthodontist.
Miniscrew implants have recently become a very hot item with regard to implant anchorage, primarily based on their ease of placement and retrieval. These screws may be placed by the dentist using only local anesthetic and retrieved, in some cases, using only topical anesthetic. Once placed, the miniscrew is available for immediate load placement in conjunction with the specified treatment plan.
Because miniscrews are retained in the interdental and interradicular alveolar crest, osseointegration is not required. However, because osseointegration is not required, the possibility exists that minor movement of the miniscrews (loss of anchorage) may occur. A final important consideration in the placement of miniscrews is the precise placement between the roots of adjacent teeth and the risks that may be associated with such a technique.
Without question, implants have changed, and will continue to change, the way orthodontists approach tooth movement. Movements of teeth that were previously thought difficult—if not impossible—may now be possible using implants as anchorage.
As I have described, there are a number of different types of implants being commonly used; however, there is no perfect implant. The orthodontist and oral surgeon must carefully consider and weigh the options for implants and their advantages and disadvantages to determine which implant to utilize for each individual patient. Regardless of personal preferences of surgeons and orthodontists, implants have provided orthodontics with a new horizon that is exciting for patients and doctors alike.