Prior to the 2004 AAO meeting in Orlando, a discussion group convened to discuss one of the most popular topics in orthodontics of recent - the topic of “temporary anchorage devices” (TADs). This event was hosted by 3M-Unitek and featured a number of presentations by orthodontists using and/or developing these temporary anchorage devices. A moderated general discussion on relevant issues followed. The day went exceptionally well and developed into an unofficial consensus group on this topic. Presentations and discussions centered on small diameter implants as opposed to palatal/conventional dental implants or onplants. The group felt very strongly that the information presented and discussed was extremely useful, timely, and educational and that this information should be shared with all interested in this topic. The following is a summary of the group’s consensus or lack thereof on certain issues.

The overall broad objective for the meeting was to review the current status of TADs and the future impact they may have on treatment planning and execution of the treatment plan. The open-ended question posed to the group was "Are we adapting current procedures to new techniques or are we trying to adapt new techniques to current procedures and materials?"

Presentations were made by: Dr.’s Jason Cope, Axel Bumann, Dietmar Segner, Dagmar Ibe, Antonio Costa, George Anka, Birte Melsen and Hee-Moon Kyung (not present - presentation by digital means).

Nomenclature
The term temporary anchorage device refers to all variations of implants, screws, pins and onplants placed specifically for the purpose of providing orthodontic anchorage that are removed upon completion of biomechanical therapy. Although there was no general agreement on one term to be used, it was voiced that "mini-implant" is more appropriate than "micro-implant" from the perspective of scientific nomenclature since "micro" means 10-6. The shape and design indicate that "screw" is more appropriate, however to avoid negative connotations, the group favored words such as "pin" or "implant" or "device".

Regulatory Issues
The group was aware of TADs that have received the European CE (insert symbol) approval, however the group was unaware of US FDA approval although it was noted that at least one TAD is available in the US. The group was pleased that outcomes of success and failure are being reported from groups developing and using TADs.

Indications
It seemed that there were two major areas and indications for use of TAD’s: (1) in the correction of skeletal discrepancies and (2) in the correction of dental discrepancies. In the former, clinical cases were shown where TADs were used to assist in the correction of antero-posterior and vertical discrepancies. In one case, TADs were used for direct inter-maxillary fixation following orthognathic surgery. However, a common concern was the stability of skeletal correction using TADs. Surgical correction is more likely to change neuromuscular imbalances, leading to a more stable correction. However this can not be proven at this time because of the lack of studies in this area. The group called for long-term stability studies using TADs. In category of correction of dental discrepancies, applications of TADs were shown for: (1) antero-posterior tooth movements, (2) molar uprighting, (3) intrusion/extrusion of single and multiple teeth. In most cases TADs were used to supplement dental anchorage, however in some applications TADs were used as the sole source of anchorage. Overall the group felt that there are many possible indications and applications for TADs and they serve as an invaluable component of the orthodontic armamentarium. In addition, it was noted that biomechanics need to be design to optimize the use of TADs.
The question re growing vs non growing patients was issued with voice of skepticism from some participants on placing TAD`s on young growing patients. Concensus within the group was that the growing patient was not considered to be contra-indicated per se ( James correct or??)

Design of TADs
Overall there was good general consensus on the design of TADs.
Size
A diameter of 1.2 to 2.0 mm seemed to be adequate. Of note, some of these figures refer to the core diameter of the implant without threads and some include the threads in this measurement. A concern with devices featuring core diameters smaller than 1.2 mm was breakage. A call for slightly larger diameter "emergency" implants was made for situations where good mechanical interlocking of the threads does not take place.
Length
A variety of lengths approximating 6, 9, and 12 mm was popular and could be used in most situations. A tapering/conical design was favored.
Head
The group favored a head design that featured a 0.022" archwire slot(s) facilitating connection to the archwire. There was a preference for designs allowing for retention and use of light-cured composite resin to stabilize the archwire. This method of retention was favored over cap designs. It was felt that this system allowed for cleanliness and stability, two factors that contribute to success of TADs.
Surfaces
There was agreement that the device should have smooth polished surfaces. This is important at the collar where there is contact with the gingival mucosa to minimize irritation and inflammation. Smooth surfaces are also important on the threads to prevent osseointegration and allowing for easy removal.

Placement of TADs
In this area there was general agreement on techniques, however there was considerable discussion on who should place the device.

Local Anaesthesia
Traditional administration of local anaesthesia was used to place TADs, however it was not used on lingual surfaces if the TAD was being placed on the buccal. The rationale is that the patient would feel pain and react to warn the operator if the drill or the implant were placed too far. Aneasthetic was not required for removal of TADs in approximately 90% of the cases.

Tissue Penetration
The group felt strongly that prior to surgery the area should be cleaned and debrided. Patients should be asked to first brush and then rinse with chlorhexidine. Penetration of the tissue is accomplished with a circular tissue biopsy punch, leaving cleanly cut tissue margins that closely approximate the collar of the TAD. This prevents leakage and bacterial invasion around the TAD. It was felt that tissue fragments contribute to plaque retention and leakage around the TAD leading to inflammation and possibly failure. It was remarked that the “single largest cause of failure is inflammation and less related to the implant design”. Penetration through attached gingival was preferred over unattached gingival as this area seemed to be more amenable to cleansing and the tissues were more closely adapted around the TAD. Overall less inflammation was observed in this area. Oral hygiene and homecare is very important to success. Very mobile tissues such as those around frenum (is it frenum or frenulum? ) should be avoided.

Antibiotics and Anti-inflammatory drugs
In general antibiotics were not used unless there was a specific medical indication. It was stressed that good surgical protocol should be used to ensure asepsis and overall success. Contamination of the drills and TADs should be avoided by preventing contact with other surfaces and tissues prior to their placement into the bone. In general anti-inflammatory drugs were not used in conjunction with the procedure.

Revolutions (RPM) and Torque
It was felt that drilling the bone using “controlled RPM” was essential for success. A recommendation was made to use slow speed (800-1500 rpm) with low pressure on the bone. A discussion ensued on whether water-spray cooling was necessary since the water does not reach the tip of the drill and the drill is relatively small. Nevertheless it was felt that good surgical technique should be followed and a suggestion was made to pre-cool the instruments prior to surgery. Placement of the devices can be done by: (1) hand using finger pressure and a driver/thimble, (2) use of an adjustable torque wrench, (3) electric handpiece (with rotational and torque limits). There was no preference for any of the above methods and all were used. Although the amount of torque required to place the device is not established, it was felt that a safety margin should be used. For example if studies show that a particular device fails at 25 Newtons of force, a maximum limit of 20 Newtons be used during device placement to avoid breakage.

Pre-Drilling vs. Self-tapping
There was no consensus on designs of TADs that require pre-drilling the bone vs. self-tapping designs.

Positional Planning and Direction
It was felt that use of panoramic and/or peri-apical radiographs was for positional planning was acceptable, although 3-dimensional imaging would be ideal. The accuracy of 2-dimensional radiographs could be improved with the use of wire/markers. Ideally TADs should be placed perpendicular to the bone surface however this is not always achievable, particularly in areas with difficult access. It was reported that deviations off perpendicular by 10 degrees is generally acceptable, however deviations of 20 degrees or more are not. Placement in the region of the apical thirds of teeth was favored since the roots are more tapered in this location and the alveolar bone thickness is greater. In addition, it was felt that a post-operative radiograph was not generally necessary, particularly using 2-dimensional imaging since the images do reveal the true perspective and position of the device. Furthermore, surgical complications such as drilling into a dental root “could be felt” during placement since the density of the root is much different than bone.

Who should place it?
There was considerable discussion on whether the orthodontist, oral surgeon or general dentist should place TADs. It was agreed that the orthodontist is by far in the best position to understand the case, the biomechanics, and optimal sites for the TADs and for these reasons they should place them. Other benefits are cost and efficiency of appointments. The cost of placement of TADs by the orthodontist ranged from no additional cost to the patient to approximately $200 each. In the situations where there was no additional cost to the patient, the service is embedded into a total treatment fee much like placement of other appliances. The cost of TADs for the orthodontist range from approximately $30 to $60. From the perspective of appointments and time efficiency, no additional appointments are necessary if the TADs are placed by the orthodontist. The orthodontists in the discussion group with experience in TAD placement indicated that it was a 5 to 15 minute procedure including the administration of anaesthesia. The TADs were also removed the orthodontists. It was also recognized that many orthodontists in North America are reluctant to do so since it involves administration of local anaesthetic and a minor surgical procedure. However it was also recognized that in the overall spectrum of dental procedure placement of TADs is relatively straightforward. In addition the AAO’s practice insurance has been modified to provide coverage to orthodontists for performing TAD placement. Placement of TADs by the oral surgeon or other specialist added very significant costs ranging from $200/TAD to $1000 for other designs to the cost of treatment. In some cases this would be prohibitive. A benefit of placement by the oral surgeon is that he/she could be in a better position to remove the TAD if it broke during placement. Although some general dentists are placing TADs it was generally agreed that they are in the worst position to place them, particularly if they have no additional training in orthodontics and oral surgery.

Force Application

Immediate vs. Delayed Loading
Experience with TADs indicated that they should be loaded immediately or after 6 weeks. It seemed that the worst time to load them was at 2 weeks. However, it was also noted that there is no commonly accepted time at which the implant was loaded, but it was felt that initial stabilization of the TAD was essential to its success. It was noted that palatally placed TADs may fail if the patient’s tongue continually jiggles the device during healing. The group questioned whether the time of initial loading could be optimized in relation to the quality of bone and called for histological studies on this topic. Additionally further studies on the bone’s response to effects of biomechanical forces over time are required.

Biomechanics
Appropriate design of connecting archwires was thought to be important to success. It was noted that occlusal forces directed to the TAD would lead to its failure and that shear forces on the device should be avoided. The biomechanical design and "line of action" on the implant should be well thought out. For example, intrusion of incisors with TADs placed in the anterior could also produce undesirable incisor proclination and in this situation the TAD could be placed in the posterior to supplement traditional anchorage and conventional archwire biomechanics could be used to intrude the incisors.

Due to the nature of their force delivery coil springs were preferred over elastomeric C-Chains. However a recommendation was made to redesign the attachment loops on the ends of coil springs to allow for simple placement over the head of the TAD.

Complications and Failure
Failure
Early reports on the success of TADs ranged from 60 to 85% however recent reports are much closer to the higher rate. The reasons for this wide range are various. Some researchers included in this figure all failures during development and prototyping of various designs and refinement of their placement techniques. It seems that using the latest TAD designs and appropriate placement techniques the success of TADs in recent years has risen dramatically. However, it was noted that TADs seems to be more successful in the maxilla compared to the mandible and more successful in adults compared to children. Overall the group noted that further studies on success and failure are forthcoming and essential to the advancement of TADs into common clinical practice.

Complications
Major complications discussed were breakage and damage to adjacent tooth roots. It seems that device breakage is a problem of the past. Recent designs in conjunction with proper placement techniques are sufficient to prevent this complication. However, when breakage of the TAD occurred, it was removed with a root tip plier. Deeply embedded fragments were left in place. The other major complication discussed was damage to tooth roots. Although there is very little literature on this topic, it was mentioned that in the oral surgery literature, minor root damage during surgery heals with no major consequence. However, it was also noted that in these reports the teeth were not moved subsequent to the root damage and that additional movement could exasperate the situation. A further unresolved complication is the movement of a tooth into the TAD. It was noted that this complication has not been reported in the literature.

Long-term Stability
Long-term stability of treatment was a concern particularly in cases of vertical correction to avoid orthognathic surgery. It was noted that orthognathic surgery dramatically changes the oral environment relative to TADs and for this reason the etiology for the malocclusion may still be present. However, it was also noted that a few long-term cases (over two years) have been reported. There was agreement that further studies on long-term stability are invaluable since TADs are becoming a serious treatment alternative to some forms of orthognathic surgery.

Other Issues

Litigation
It seems that fear of litigation is one of the major barriers for orthodontists in the US to place TADs despite the fact that there is no known litigation in this area. The group felt that it was important to educate orthodontists on this topic and not over-simplify the procedure and the risks.

Acceptance
It was recognized that TADs are not widely accepted in the orthodontic community in the US and this may eliminate a viable treatment modality for some patients. The group felt that it was important for professional orthodontic organizations to develop consensus statements on the use of TADs.

Suggestions

A suggestion was made to provide typodonts for training orthodontists on the placement of TADs. The typodont would have a number of possible placement sites marked. The sites correspond to locations of optimal cortical bone thickness.

Summary by :
Dr. James Mah