Statement - ZZI 01/2011

The use of implants for skeletal anchorage in orthodontics
Recommendations for: Anchorage in orthodontics

F. P. Strietzel1, H. Wehrbein2

Introduction

Endosseous implants for orthodontic anchorage are used more and more frequently in orthodontic treatment for movement of larger groups of teeth or single teeth without loading other teeth. Also, in situations with no or only very limited existing conventional anchorage options in the case of hypodontia, after tooth loss or in patients with periodontally compromised teeth, implants for orthodontic anchorage provide an alternative to extraoral anchorage.

The procedure as well as the application and choice of implants always depend on the long-term treatment aims. On the one hand, there is the option of placing conventional implants in the position of one (or more) abutments for the subsequent prosthetic restoration and then move the teeth or tooth groups into the planned position using orthodontic anchorage and retain the restoration on these implants at a later stage. These implants are intended to remain in the alveolar ridge. On the other hand, orthodontic forces can be applied to teeth or groups of teeth using special implants. Subsequent to completion of orthodontic treatment these implants, which are only intended for orthodontic anchorage, are removed again.

These basic considerations regarding the type and functional life of the implants to be placed also include the special demands on the implants, the range of pre-implantological diagnoses as well as the risks and possible complications to be taken into account during treatment planning, which should be assessed to avoid forensic complications. The patient should also be informed of these prior to treatment.

The complexity of the planning and implementation when using implants for orthodontic anchorage and possible integration in the prosthetic restoration later often requires the interdisciplinary teamwork of colleagues in different specialist fields.

The scientific literature available on the clinical use of implants for orthodontic anchorage consists of case reports and also prospective studies [15, 34].

 

Indication

Defining the indication on the use of implants for orthodontic anchorage requires orthodontists during treatment planning to assess the advantages and disadvantages of alternative treatment procedures and to take into consideration the individual characteristics of the patient (e. g. general medical history, characteristics of the disorder that requires orthodontic treatment, anatomical characteristics at the planned insertion site, age, oral hygiene behaviour, compliance of the patient, support of the therapeutic procedure by the parents or guardians in the case of minor patients). Implants are used as anchorage elements in the following indications in particular: tooth intrusion and extrusion, treatment of teeth misalignment, asymmetrical tooth movement in all planes, increase of anchorage, especially where there is insufficient conventional anchorage, orthodontic space closure, correction of malocclusion, in general for anchorage in orthodontic tooth movement to avoid undesired reactive forces as well as to provide an alternative to orthodontic surgery [14, 17, 25, 26].

Detailed consultation is required with all colleagues involved in the treatment with regard to age and growth phase of the jaw and facial skeleton and the resulting characteristics in relation to the timing of the implant-supported therapy in the overall treatment process. In addition to the growth phases of the jaw and facial skeleton, when planning placement of an implant consideration should also be given to the development of the alveolar process, which accompanies the vertical development of the teeth. When choosing the time of implant placement, there should be a discussion of the comparative advantages and disadvantages of implant treatment, which could result from a subsequent tooth-borne prosthetic restoration and suspension of the jaw growth at the implant site [3].

 

Selection of the implant systems

Selection of the implant systems depends on the treatment plan and the anatomical conditions. While conventional implant systems provide options for prosthetic treatment they do not always also have the means of anchorage for orthodontic force application that are coordinated to the respective implant system, however, these features are incorporated in implants which are used exclusively for orthodontic purposes.

Conventional implants are used in different diameters and lengths, depending on the region of implant placement and the planned dental restoration to be fitted on the implant. Selection of the implants with regard to the implant system, dimensions and positioning requires interdisciplinary consultation. The load-free healing periods should follow the previously existing recommendations regarding the respective implant systems and take into consideration the primary stability and dimensions of the implant as well as the bone quality.

The length and diameter of implants intended exclusively for orthodontic anchorage should be as small as possible to allow them also to be used in the interdental region and to keep the size of the defect as small as possible after their removal; the implant body and orthodontic anchorage device should, however, also be able to withstand the applied forces.

Orthodontic implants are mainly used in the palate or the alveolar process. Palatal implants are intended for placement in the median line or paramedian region. Their diameter is comparable to that of standard implants, their endosseous surface design has a rough texture, their intraosseous length, however, is reduced to correspond with the limited vertical bone availability of the palatal process of the maxilla [39]. Placement of these implants is generally minimally invasive (Fig. 1). The aim is to achieve osseointegration with these implants and therefore a load-free healing phase of between two and three months is required [2, 19, 24, 39, 40, 41]. However, shortening of the healing phase is discussed in favour of immediate orthodontic anchorage if constant forces are used [9]. As these implants have been osseointegrated they generally have to be explanted following completion of orthodontic treatment using a surgical procedure that is as minimally invasive and structure conserving as possible. This may be regarded as a disadvantage in comparison with mini-screw or microscrew implants.

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