July 30, 2010
By Dr. Rajkumar S Alle, BDS. MDS. DNB and Dr. Suma T, BDS. MDS.
Mini-screws used for skeletal anchorage offer many clinical advantages: small size,wide range of implantation sites,ease of insertion and removal, the ability to load forces immediately and rapid healing. The risk of injury to dental roots during placement is one of the greatest concerns with orthodontic mini-implants, especially when they are inserted between teeth. Placement of a mini-screw too close to the root can also result in insufficient bone remodeling around the screw and transmission of occlusal forces through the teeth to the screw, which can lead to implant failure.  Even though periodontal structures can heal after being injured by TADS,  it is important to carefully select insertion sites using clinical and radiographic evaluation of their anatomical details.
The wire guide suggested in this article has a simple design and does not disturb the existing appliance system, can be clearly located in the radiograph and the mini-screw can be easily inserted through the guide reducing the chance of implant misplacement.
The wire guide is fabricated using round 0.018 stainless steel wire (A.J.WILCOCK) (Fig. 01). A helix of 3 mm diameter is made at the center of the wire (Fig.02). The appropriate length is determined by the desired mini-screw insertion point (generally 5-6 mm apical to the alveolar crest). After vertical height is determined, two horizontal bends are place at the level of the adjacent brackets.
Once the mini-screw placement area has been determined clinically, a periapical radiograph is taken to show the location of adjacent roots. The wire guide is fabricated, as mentioned above, and secured with the help of a ligature or an ‘O’ ring. A periapical radiograph is taken to confirm the correct position of the helix for the mini-screw insertion. The mini-screw is inserted through the helix of the guide in the desired direction. The wire guide is disengaged after 3/4th of the mini-screw is driven in and then the mini-screw is completely inserted. Placement accuracy is reconfirmed clinically (Fig.03) and radiographically (Fig.04).
Figure 3, 4.
The use of mini-implants in orthodontics has phenomenally increased in the last few years due to the clear advantage of their clinical efficiency in anchorage control.
The critical issue about mini-implants is the location of the implant. It is very important to place the implant in a location that does not damage adjacent roots or other vital tissues. There are various methods mentioned in the literature; e.g. using a mesh placed in an inter-radicular area and radiogrphed to use as a guide to implant placement, or custom-made soldered wire guides placed both buccally and lingually and then radiographed to use as a guide.
The technique mentioned in the present article is simple and accurate because the implant is inserted through the helix of the guide, hence less chance for it to be misplaced. The existing orthodontic appliance is not disturbed and the implant guide can be disengaged without any difficulty.
This wire guide is simple in design, easy to fabricate, inexpensive and can be used with a variety of mini-screws.
Dr.Rajkumar S Alle
Professor & Head of the Department of Orthodontics & Dent
ofacial orthopedics Rajarajeshwari Institute of Dental Sciences, Bangalore, India
Assistant Pofessor of Orthodontics & Dentofacial orthopedics Rajarajeshwari Institute of Dental Sciences, Bangalore, India