Temporary Anchorage Devices:

I have previously written about mini-screws and mini-plates, also called Temporary Anchorage Devices (TAD’s) for absolute anchorage in orthodontic treatment in past newsletters however there have been numerous advances in appliance design, use and application. I am using TAD’s more frequently in my treatment plans and have been applying these techniques along with incorporating the latest advancements in orthodontic appliances.

The two major types of TAD’s are mini-screws and mini-plates. Mini-screws have the major advantage of being simpler to use and applicable for a wide range of areas. The typical areas of placement include alveolar bone, the retromolar pad area, the palate and/or the symphysis. The screws are self-drilling, easy to place, comfortable and hygienic. They can be immediately loaded and resist 200-250 grams of force, sufficient to move 2-3 teeth simultaneously or to support molar stabilization. They are easily removed and are quite economical (about $300.)

This patient, T.K., age 40 requires distalization of the maxillary left posterior segment into Class I molar and canine position (Figure A). Typically a tooth would be removed or elastics worn, however T.K. was unwilling to have a tooth removed and elastics would have negative side effects on the lower dentition. A mini-implant was placed under topical anesthesia and loaded that same day (Figure B). Four months later (Figure C) you can see the second molar is now Class I and there is adequate space to retract the premolars and canine into a Class I occlusion. Invisalign is slated to finish treatment.

Mini-plates are adapted from oral surgical bone-plates yet they are also temporary; removed after the orthodontic movement is complete. Mini-plates are often used when multiple teeth need to be moved. Examples of use are with open bites due to over-erupted maxillary posterior teeth. By impacting the posterior teeth, the bite can be closed. The major drawback to the min-plate is the required surgical placement and removal; however this procedure is less invasive than a typical orthognathic jaw surgery.

Patient I.N. was 12 years old when she first presented for orthodontics. She had a significant open bite due to a crossbite and over-eruption of the posterior maxillary dentition (vertical maxillary excess) which during growth can cause a counter-clockwise rotation of the mandible resulting in a long lower face and “slack-jaw” appearance (Figure D). Expansion with an appliance or braces would increase the open bite so additional measures were necessary to prevent further adverse growth. Initial plans were to use headgear and extractions to close the bite, align the dentition and prevent any further downward growth of the maxilla. Unfortunately the patient was not complaint with visits or wearing the headgear so we were left with a non-growing patient who required orthognathic surgery. In fact we were left with a greater open bite that when we started due to the non-compliance while the crossbite was slowly corrected (Figure E). Note the lengthened lower face height. Two zygomatic and two palatal mini-implants were placed to intrude the maxillary premolars to second molars. A custom-designed appliance to maintain arch width and prevent unwanted side-effects on the teeth as they were intruded was fabricated and cemented 7/06. Figure F shows the change in the patients profile and full closure of the anterior open bite. This was accomplished in 5 ½ months.

In addition to “mini” implants, traditional implants can be used for orthodontic anchorage and can also be “temporary” or permanent. Recently we have used palatally-placed dental impants for anchorage. In these cases, an appliance is attached to the palatal implant and then bonded to the teeth for anchorage. Once the movement is complete, we can remove these implants.

Patient M.V. required bilateral molar distalzation into Class I. Again esthetics was a concern and extractions would be detrimental to her profile (Figure G). We had a palatal implant (Figure H) placed and a Trans-Palatal Arch Appliance attached to the implant and bonded to the first premolars. Springs were placed to distalize the molars. Once this was accomplished we removed the bonding from the premolars and bonded the TPA appliance to the second molars (Figure I - note the molars have distalized significantly; second molars are “super” Class I). The TPA will hold the second molar position while we retract the canines and premolars to Class I. Once the canines are Class I the patient will have Invisalign to align the anterior dentition.

It has become readily apparent that the use of these devices can help reduce the need for orthognathic surgery. Certain malocclusions such as over-erupted and tipped teeth, open bites, and pseudo-Class III dentitions can be successfully treated with TAD’s. With the increase in multidisciplinary treatment, TAD’s are allowing us to treat a greater spectrum of patients, from the teenager with excessive maxillary growth to the mature adult with a mutilated dentition. Now these dentitions can be aligned and bites corrected much faster, more reliably and with increased comfort, all of which improve the result of your restorative plans & enhance your patient’s experience. It’s a win-win-win for all of us.

It is amazing to see how the field of orthodontics has been revolutionized in the past few years, and I hope that this letter will increase your knowledge of these fascinating developments. Not only are we seeing a reduction in treatment time due to our “frictionless” brace technology, the addition of these temporary anchorage devices will make many malocclusions treatable without extractions or surgery. As with any of my correspondence or newsletters, if you have any questions or a specific case that you would like to discuss, please do not hesitate to call or email me.