August, 2005
Non-Invasive Mini Plates
Recently, different systems for absolute anchorage appeared to help orthodontic treatment and improve final results.
A. Korrodi Ritto DDS, PHD
Titanium anchor plates have been used in orthodontics for correction of skeletal open bite and Class III malocclusions, increasing anchorage during treatment. Usually they are temporally fixed on the cortical plate of the mandible or maxilla with titanium monocortical miniscrews.
Once soft tissue surrounding the miniplate is healed, the anchor plate can be loaded immediately. The use of micro implants in edentulous areas has been well described in the literature. Two micro implants can be placed together and after build up composite a bracket is bonded.
The recent development of Bracket head type micro implants allowed this approach in an easy way. However, it is not possible to make a three dimensional activation without debonding the bracket or replacing the bracket head type micro implant. Moreover in posterior edentoulous areas the bone usually has poor quality, and failures can occur when force is applied specially in maxilla. Anchor plates can also be used in a different way then the traditional method (placed surgically on the cortical bone) in cases without posterior teeth and when a three-dimensional control will be necessary – non-invasive mini plates.
The anchor plate shape is chosen according to the situation and adapted to the gengivae. It is inserted and tied to the BH micro implants. A bracket is then bonded in the desired position (angulation and vertical high). The shape of the plate can be changed with a plier to control the horizontal or sagital direction.
Clinical Case
A thirty years old female was sent by his dentist to align the upper front teeth before prosthesis rehabilitation. She presented a moderate crowding, lack of space for #22 and canine cross bite on both sides. She doesn’t have posterior teeth on the upper jaw, and on the lower the #48 will be extracted and the #38 will be restored (Figure 1.).
Figure 1. Patient before treatment. Lack of space for tooth #22, moderate crowding and bilateral cross bite.
Treatment Plan
Due to the missing teeth there is no support for orthodontic treatment. It was decided to treat the patient with temporary anchorage devices. It was planed to place a miniplate on the left side fixed with two micro implants, and one micro implant on the right side (Figure 2.).
Figure 2. Mini plate adapted on a plaster model. The mini plate is inserted into the Bracket Head type micro implant slot, the length is choosen to avoid occlusal interference and the position is adjusted to allow a bonded bracket.
Treatment
Two micro implants bracket head type with 1,5mm diameter and with 7 and 8 mm length were placed distal to #23. Another micro implant was placed distal to #13. They are left in place for one month before starting with fixed appliance, to evaluate the stability (Figure 3.).
A mini plate was adapted on a plaster model and activated to produce a vestibular force on #23 when in place (Figure 2.).
The fixed appliance was bonded, and the mini plate was placed one month after into the slots of the bracket head type micro implant. A bracket was bonded on the mini plate (Figure 4.). One month later the mini plate was activated to increase the vestibular force on #23 to correct the cross bite (Figure 5., 6.).
The treatment was done in 3 months (with fixed appliance bonded), and a retainer was done for night time use. The cross bite was corrected and teeth aligned.
Figure 3. Bracket Head type micro implants placed and left in place for one month to evaluate the stability.
Figure 4. Non invasive mini plate in place with the bracket bonded in a higher position to initialize the cross bite correction.
Figure 5. Mini plate activated in a vestibular direction to correct the cross bite.
Figure 6. Cross bite corrected and all teeth aligned.
Figure 7. End of treatment. Teeth were aligned and cross bite corrected. Even without posterior teeth it is possible nowadays to make orthodontic treatments.
Conclusion
One of the advantages of skeletal anchorage is the possibility of treat patients without enough teeth support. Non-invasive mini plates are important in such cases, because they can be activated during treatment in any direction.
Because mini plates are fixed with more then one screw, the stability is greater then with only one micro implant.
References
1. Ritto A.K., Kyung H.M. Solutions with Micro Implants. Ortodontia Journal 8:6-13; 2004.
2. Ritto A.K., Kyung H.M. Soluções com micro implantes. Orthodontic Cyberjournal www.oc-j.com 2004
3. Ritto A.K. Micro Implants in Orthodontics. Int. Journal of Orthod. 15 (3): 22-24; 2004
4. Ritto A.K. Easy movements with mini implants. Thai Journal Orthod. (in press).
5. Ritto A.K., Kyung H.M. Bracket Head Micro implants. Ortodontia Journal 9:50-66; 2004
6. Ritto A.K. Micro implants in Orthodontics – a useful tool to treat cases without teeth support. Jornal Ibero Americano de Ortodontia (in press)
7. Ritto A.K. Resorbable screws for orthodontic anchorage. Orthodontic cyberjournal, June 2005.
8. Ritto A.K. Micro implants – other options. Ortodontia Journal (in press)
Contributed by:
A. Korrodi Ritto
Specialist in Orthodontics, Vice President of Portuguese Orthodontic and Orthopaedic Society.
