Temporary Anchorage Device (TAD) or Mini (screw ,implant)

Temporary Anchorage Device (TAD) or Mini (screw ,implant)

بسم الله الرحمن الرحيم

By: Dr. Khaled Mohamed Wafaie

• Mini-implants have become a routine anchorage method in orthodontic practice given their high predictability and scientifically proven benefits. The small size of miniscrew implants allows them to be placed into bone between the teeth, thus expanding their clinical applications. With more patients treated with screw implants as ((anchorage)), their stability is gathering attention. Despite their tremendous success in facilitating treatment outcomes, the implant failure rates are widely variable and could be as high as ( 10-30%))

Success in mini-implant orthodontics is defined as a

mini-screw with minimal mobility and inflammation and

the ability to obtain full functional correction either through direct or indirect

anchorage.

• Various factors affecting success;• I.            Implant dependent• II.            Operator dependent• III.            Patient dependent

I .Implant dependent factors

• A)Shape:• 1) conical : torque measurements suggest

that a conical screw design will provide greater primary stability

• 2)cylindrical :superiority was evident in the pullout tests.

• # All the miniscrews’ primary stability rose after drill-free insertion.

B)Dimension: 1)Length : a) long = more forces = breakage . B) longer than 10 mm could result in greater risk of iatrogenic perforation .

2. Diameter and Trans-gingival Collar:#increase diameter = increase success but increase proximity of the root so use diameters of 1.2, 1.5, and 2.3 mm .

II- Operator related factors :

1. Selection of implant site: 0.5-1 mm to nearest vital structure .

# For proper position : 5 mm from CEJ and x-ray .

2. Bone density: D1, D2, D3 are optimal for self-drilling miniscrews D4 not preferred.

3. Soft tissue considerations

4. Placement technique: small amount of local anesthetic is sufficient . 1.Surgical technique: Ideally a pilot

drill should be 0.2 to 0.5 mm less than the implant diameter, and the depth should be less to obtain proper initial mechanical stability.

• 2. Self drilling method: The self-drilling Implant has high placement torque and high bone-implant contact values. This procedure is contraindicated in the posterior and inferior aspects of the mandible since they have been reported to have a high breakage rate.

• Used in maxilla

3. Direction of placement and Insertion angle: Angulation of the bone surface needs to be moderate, a 45 degree angulation relative to the occlusal plane is considered acceptable oblique insertion is advantageous to avoid possible root damage .

Excessive angulation may weaken the cortical bone structure and part of the threaded portion may be exposed on buccal side.

• 4. Implant placement torque: Motoyoshi et al recommended an implant placement torque range of 5 to 10Ncm. Very high insertion torques leads to higher failure rates due to excessive bone compression.

• 5. Loading protocol: involves immediate loading or a waiting period of 2 weeks to apply orthodontic forces.14 Most mini-implants can withstand 100 to 200 g of horizontal immediate loading successfully.

• 6. Minimizing soft tissue over growth: This can be done by placing of a healing abutment cap, a wax pellet, or an elastic separator.

• #Using Chlorhexidine mouthwash slows down epithelialisation.

• 7. Using mini-plates: The connection of two mini-implants with mini- plate provides a stable anchorage system and improves the versatility of the device.1

• 8. Sterilization and asepsis are mandatory throughout the procedure.

• 9. Clinician experience and skill do contribute to the success of mini implants.

III -Patient dependent factor-

• Along with regular tooth-brushing, Chlorhexidine (0.12%, 10 ml) mouthwash is recommended. Patient should be explained about the importance of oral hygiene and motivated at every visit.

Removing miniscrews

Conclusion;

• Orthodontic mini-implants are a powerful aid for the orthodontic practitioner in resolving challenging malocclusions but, Implant failure might delay treatment time. A good knowledge of factors affecting miniscrew success will help us to increase their success rate, thereby achieving desired treatment results and save chair-side time.

Uses of miniscrews

• 1) intrusion of molars to treat open bite

•2)retraction or firing of teeth

• 3)Extrusion of posteriors in opposing arch to treat deep bite.• Extrusion of anteriors in the

same arch to treat open bite.

• 4) up righting tilted teeth

• 5) lingual orthodontics , substitute to (Transpalatal arch or nance appliance)

•Researches

Failure rates and associated risk factors of orthodontic miniscrew implants: a meta-

analysis.Department of Oral Technology, School of Dentistry, University of

Bonn, Bonn, Germany.• Fifty-two studies were included for the overall

miniscrew implant failure rate and 30 studies for the investigation of risk factors. From the 4987 miniscrew implants used in 2281 patients, the overall failure rate was 13.5% (95% confidence interval, 11.5-15.8).

manual vs. motor-driven mini-screw insertion:

• Methods• We retrospectively reviewed 429 orthodontic

mini-screw placements in 286 patients (102 in men and 327 in women) between 2005 and 2010 at private practice. Age, gender, mini-screw length, and insertion site were cross-tabulated against the insertion methods. The Cochran-Mantel-Haenszel test was performed to compare the success rates of the 2 insertion methods.

• Results• The motor-driven method was used for 228 mini-screws

and the manual method for the remaining 201 mini-screws. The success rates were similar in both men and women irrespective of the insertion method used. With respect to mini-screw length, no difference in success rates was found between motor and hand drivers for the 6-mm-long mini-screws (68.1% and 69.5% with the engine driver and hand driver, respectively). However, the 8-mm-long mini-screws exhibited significantly higher success rates (90.4%, p < 0.01) than did the 6-mm-long mini-screws when placed with the engine driver. The overall success rate was also significantly higher in the maxilla (p < 0.05) when the engine driver was used. Success rates were similar among all age groups regardless of the insertion method used.