Systematic Review

By Dr. Debora Loli
Corresponding Author Dr. Debora Loli
Sapienza University of Rome - Department of Oral and MaxilloFacial Sciences, - Italy
Submitting Author Dr. Debora Loli

TADs failure rate, TADs, risk factors

Loli D. Temporary anchorage devices (TADs): failure rates and risk factors. WebmedCentral ORTHODONTICS 2017;8(11):WMC005392

This is an open-access article distributed under the terms of the Creative Commons Attribution License(CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Submitted on: 15 Nov 2017 12:05:03 AM GMT
Published on: 15 Nov 2017 05:51:01 AM GMT


Background: Temporary anchorage devices (TADs) are frequently used in orthodontics and had many indications but, before inserting them, clinicians have to respect some important rules, first of all an adequate preoperative preparation consisting of an exhaustive history, an accurate diagnosis report and a precise selection of implant site. Aim of this review is to evaluate the failure rates of the TADs implant and the reasons for the failure. Materials and methods: A systematic review was performed on principal medical databases. Results: The failure rates of TADs implants reported in literature vary from 0% to 40,8% with an overall mean value of 13,8%. Failure rates are higher when TADs are implanted in mandible than in maxilla. Failure can occur when screw-related problems such as screw too narrow with risk of fracture, operator-related problems such as the application of excessive pressure during insertion of a self-drilling screw that can fracture the tip of the screw and patient-related problems such as thin cortex and low density of bone are present. Conclusions: Failure of TADs implants has a high incidence and is associated to problems related to screw, operator or patient.


Anchorage is one of the limiting factors in orthodontics, and its control is essential for successful treatment outcomes. The term ‘orthodontic anchorage’ denotes the nature and degree of resistance to displacement offered by an anatomic unit. According to the intended treatment goals, desired tooth movements should, therefore, be maximized, and undesirable effects should be minimized. Traditionally, orthodontic therapy used teeth, extraoral and/or intermaxillary appliances for anchorage.

Since a patient’s cooperation is not always optimal, temporary anchorage devices (TADs) have been introduced.2

TADs are anchored in bone and removed after completion of the intended orthodontic tooth movement. They are designed to overcome the limitations of conventional orthodontic anchorage devices. Unlike orthodontic devices that have a single indication, such as distalizers or expanders, TADs are an orthodontic tool to aid in orthodontic anchorage planning and management. For this reason, they can be used in many clinical situations, limited only by the experience and knowledge of the clinician.3-6

The TADs are used to achieve any dental movement such as intrusion, extrusion, uprighting, mesialization and distalization. 3-6

Skeletal anchorage by TADs is indicated in all cases where forces acting on reactive units are undesirable and / or cannot be easily neutralized.7

We can classify contraindications to TADs in local and generals. Local contraindications are qualitative and/or quantitative deficiency of bone at site insertion site, free mucosa insertion, insertion into mandibular lingual side, insertion in close proximity to dental gems and / or deciduous teeth, insufficient oral hygiene conditions, recurrent stomatitis, osteomyelitis, radiotherapy in the cranial region. 8

General contraindications are immunodeficiency, corticosteroid and/or bisphosphonate therapy, alteration of blood coagulation, decompensated endocrine disorders, rheumatic diseases, bone metabolic pathology, liver cirrhosis, patient's inability to follow postoperative instructions.8

The insertion of a TADs is a very simple therapeutic procedure but requires respect for important rules, first of all an adequate preoperative preparation consisting of an exhaustive history and an accurate diagnosis report.

To select the TADs location, clinical data such as radiographic examinations, patterns, as well as treatment goals and the orthodontic system that will be implemented will be considered. A TADs for ideal operation requires stable bone anchorage (primary stability) and a positioning in the adherent gingiva.9.10

The interradicular distance and the radicular axis pattern can only be approximately evaluated on the OPT exam; therefore, it is good practice to evaluate in detail the interradicular distance to perform an endoral radiographic examination with the help of centering of the selected site.9-10 In some cases a CT scan can be useful.

Three-dimensional studies allowed us to evaluate the thickness of the cortical and bone volume (the inter-root distance must be at least 3.1 mm for a screw of 1.6 mm in diameter) of the various inter-radicular, maxillary and mandibular sites by allowing the creation of visual maps for the detection of "safe zones" for the insertion of TADs.9-10

On this basis, purpose of this review is to evaluate the failure rates of the TADs implant and the reasons for the failure.


In order to evaluate success rates and failure reasons of TADs, a systematic review was performed on major databases: Pubmed (Medline) and Scopus). Keywords used were: TADs, miniscrews, success, failure rates. After this search, 44 articles were found.


Analyzing literature, failure rates of TADs implants vary from 0% to 40,8%.11-54

Papageorgiou in his metanalysis reported a mean incidence of failure of 13,5%.

Regarding factors associated with TADs implant failure, no difference in the miniscrew implant failure rates was observed for the following factors: patient sex and patient. The miniscrew implant's thread diameter and thread length were found not to be associated with the miniscrew implant failure rates. No significant differences of the miniscrew implant failure rates were observed with regard to side of placement and site of placement.55

Higher overall failure rates were observed when the miniscrew implants were inserted in the mandible than in the maxilla (19.3% and 12.0%, respectively).55

Melsen has identified risk factors of failure related to the screws, to the operator and to the patient8.

Screw-related problems are screw fracture that can occur if it is too narrow or the neck area is not strong enough to withstand the stress of removal (the solution is to choose a conical screw with a solid neck and a diameter appropriate to the quality of bone) and infections that can develop around the screw if the transmucosal portion is not entirely smooth. If a screw system with variable neck lengths is used, the clinician can select one that suits the particular implant site.8

Regarding operator-related problems, the first is the application of excessive pressure during insertion of a self-drilling screw that can fracture the tip of the screw.8 Overtightening a screw can cause it to loosen. It is crucial to stop turning the screw as soon as the smooth part of the neck has reached the periosteum. With a bracket-like screw head, the ligature should be placed on top of the screw in the slot perpendicular to the wire. Turning the ligature around the screw will make it impossible for the patient to keep the area free of inflammation. It is important not to wiggle the screw driver when removing it from the screw head. The screw driver will not stick if the long extension is removed before the part surrounding the screw.

Melsen said regarding patient-related problems that the prognosis for primary stability of a mini-implant is poor in cases where the cortex is thinner than .5mm and the density of the trabecular bone is low. 8

In patients with thick mucosa, the distance between the point of force application and the center of resistance of the screw will be greater than usual, thus generating a large moment when a force is applied.

Loosening can occur, even after primary stability has been achieved, if a screw is inserted in an area with considerable bone remodeling because of either the resorption of a deciduous tooth or post-extraction healing. As previous said, Mini-implants are contraindicated in patients with systemic alterations in the bone metabolism due to disease, medication, or heavy smoking.


Rate of failure in TADs implants is described in literature varying from 0 to 40,8%. The overall failure rate was 13.5%. Factors associated with the failure are insertion in the mandible, screw-related problems such as screw too narrow with risk of fracture, operator-related problems such as the application of excessive pressure during insertion of a self-drilling screw that can fracture the tip of the screw and patient-related problems such as thin cortex and low density of bone.



  1. Nanda RS, Kierl MJ. Prediction of cooperation in orthodontic treatment. American Journal of Orthodontics and Dentofacial Orthopedics. 1992; 102: 15–21.
  2. Schatzle M, Mannchen R, Zwahlen M, Lang NP. Survival and failure rates of orthodontic temporary anchorage devices: a systematic review. Clin. Oral Impl. Res. 20, 2009; 1351–1359.
  3. Miyawaki S, Koyama I, Inoue M, Mishima K, Sugahara T, Takano-Yamamoto T. Factors associated with the stability of titanium screws placed in the posterior region for orthodontic anchorage. Am J Orthod Dentofacial Orthop 2003;124:373-8. 13.
  4. Costa A, Raffaini M, Melsen B. Miniscrews as orthodontic anchorage: a preliminary report. Int J Adult Orthod Orthognath Surg 1998;13:201-9. 14.
  5.  Freudenthaler JW, Haas R, Bantleon HP. Bicortical titanium screws for critical orthodontic anchorage in the mandible: a preliminary report on clinical applications. Clin Oral Implants Res 2001;12:358-63. 15.
  6. Fritz U, Ehmer A, Diedrich P. Clinical suitability of titanium miniscrews for orthodontic anchorage-preliminary experiences. J Orofac Orthop 2004;65:410-8
  7.  Creekmore TD, Eklund MK (1983) The possibility of skeletal anchorage. Journal of Clinical Orthodontics 1983;17: 266–269.
  8. Melsen B. Mini-implants? Where are we? J Clin Orthod 2005;39:539-47.
  9. Poggio PM, Incorvati C, Velo S, Carano A. "Safe zones": a guide for miniscrew positioning in the maxillary and mandibular arch. Angle Orthod. 2006 Mar;76(2):191-7.
  10. Ludwig B, Glasl B, Bowman SJ, Wilmes B, Kinzinger GSM, Lisson JA. Anatomical Guidelines for Miniscrew Insertion: Palatal Sites. J Clin Orthod. 2011 Aug;45(8):433-41; quiz 467.
  11. Aboul-Ela SMBE. Miniscrew implant-supported maxillary canine retraction with and without corticotomy-facilitated orthodontics. Am J Orthod Dentofacial Orthop 2011;139:252-9.
  12. Alves M Jr, Baratieri C, Nojima LI. Assessment of mini-implant displacement using cone beam computed tomography. Clin Oral Implants Res 2011;22:1151-6.
  13. Apel S, Apel C, Morea C, Tortamano A, Dominguez GC, Conrads G. Microflora associated with successful and failed orthodontic mini-implants. Clin Oral Implants Res 2009;20:1186-90.
  14. Baek SH, Kim BM, Kyung SH, Lim JK, Kim YH. Success rate and risk factors associated with mini-implants reinstalled in the maxilla. Angle Orthod 2008;78:895-901.
  15. Basha AG, Shantaraj R, Mogegowda SB. Comparative study between conventional en-masse retraction (sliding mechanics) and en-masse retraction using orthodontic micro implant. Implant Dent 2010;19:128-36.
  16.  Bayat E, Bauss O. Effect of smoking on the failure rates of orthodontic miniscrews. J Orofac Orthop 2010;71:117-24. 53. Berens A, Wiechmann D, Dempf R. Mini- and micro-screws for temporary skeletal anchorage in orthodontic therapy. J Orofac Orthop 2006;67:450-8.
  17. Chaddad K, Ferreira AFH, Geurs N, Reddy MS. Influence of surface characteristics on survival rates of mini-implants. Angle Orthod 2008;78:107-13.
  18. Cheng SJ, Tseng IY, Lee JJ, Kok SH. A prospective study of the risk factors associated with failure of mini-implants used for orthodontic anchorage. Int J Oral Maxillofac Implants 2004;19:100-6.
  19. El-Beialy AR, Abou-El-Ezz AM, Attia KH, El-Bialy AM, Mostafa YA. Loss of anchorage of miniscrews: a 3-dimensional assessment. Am J Orthod Dentofacial Orthop 2009;136:700-7.
  20. Freudenthaler JW, Bantleon HP, Haas R. Bicortical titanium screws for critical orthodontic anchorage in the mandible: a preliminary report on clinical applications. Clin Oral Implants Res 2001;12:358-63.
  21. Fritz U, Ehmer A, Diedrich P. Clinical suitability of titanium microscrews for orthodontic anchorage: preliminary experiences. J Orofac Orthop 2004;65:410-8.
  22. Garfinkle JS, Cunningham LL Jr, Beeman CS, Kluemper GT, Hicks EP, Kim MO. Evaluation of orthodontic mini-implant anchorage in premolar extraction therapy in adolescents. Am J Orthod Dentofacial Orthop 2008;133:642-53.
  23. Gelgor IE, Buyukyilmaz T, Karaman AI, Dolanmaz D, Kalayci A. Intraosseous screw-supported upper molar distalization. Angle Orthod 2004;74:838-50.
  24. Gelgor IE, Karaman AI, Buyukyilmaz T. Comparison of 2 distalization systems supported by intraosseous screws. Am J Orthod Dentofacial Orthop 2007;131:161.e1-8.
  25. Hedayati Z, Hashemi S, Zamiri B, Fattahi H. Anchorage value of surgical titanium screws in orthodontic tooth movement. Int J Oral Maxillofac Surg 2007;36:588-92.
  26. Herman RJ, Currier GF, Miyake A. Mini-implant anchorage for maxillary canine retraction: a pilot study. Am J Orthod Dentofacial Orthop 2006;130:228-35.
  27. . Justens E, De Bruyn H. Clinical outcome of mini-screws used as orthodontic anchorage. Clin Implant Dent Relat Res 2008;10: 174-80.
  28. Kim SH, Kang SM, Choi YS, Kook YA, Chung KR, Huang JC. Conebeam computed tomography evaluation of mini-implants after placement: is root proximity a major risk factor for failure? Am J Orthod Dentofacial Orthop 2010;138:264-76.
  29. Kim YH, Yang SM, Kim S, Lee JY, Kim KE, Gianelly AA, et al. Midpalatal miniscrews for orthodontic anchorage: factors affecting clinical success. Am J Orthod Dentofacial Orthop 2010;137: 66-72.
  30. Kuroda S, Yamada K, Deguchi T, Hashimoto T, Kyung HM, Yamamoto TT. Root proximity is a major factor for screw failure in orthodontic anchorage. Am J Orthod Dentofacial Orthop 2007; 131(Suppl):S68-73.
  31. Lehnen S, McDonald F, Bourauel C, J€ager A, Baxmann M. Expectations, acceptance and preferences of patients in treatment with orthodontic mini-implants. J Orofac Orthop 2011;72: 214-22.
  32. Liu Y, Ding W, Liu J, Li Q. Comparison of the differences in cephalometric parameters after active orthodontic treatment applying mini-screw implants or transpalatal arches in adult patients with bialveolar dental protrusion. J Oral Rehabil 2009;36:687-95.
  33. Luzi C, Verna C, Melsen B. A prospective clinical investigation of the failure rate of immediately loaded mini-implants used for orthodontic anchorage. Prog Orthod 2007;8:192-201.
  34. Miyazawa K, Kawaguchi M, Tabuchi M, Goto S. Accurate presurgical determination for self-drilling miniscrew implant placement using surgical guides and cone-beam computed tomography. Eur J Orthod 2010;32:735-40
  35. Motoyoshi M, Hirabayashi M, Uemura M, Shimizu N. Recommended placement torque when tightening an orthodontic miniimplant. Clin Oral Implants Res 2006;17:109-14.
  36. Motoyoshi M, Matsuoka M, Shimizu N. Application of orthodontic mini-implants in adolescents. Int J Oral Maxillofac Surg 2007; 36:695-9.
  37. . Motoyoshi M, Yoshida T, Ono A, Shimizu N. Effect of cortical bone thickness and implant placement torque on stability of orthodontic mini-implants. Int J Oral Maxillofac Implants 2007;22: 779-84.
  38. Motoyoshi M, Inaba M, Ono A, Ueno S, Shimizu N. The effect of cortical bone thickness on the stability of orthodontic miniimplants and on the stress distribution in surrounding bone. Int J Oral Maxillofac Surg 2009;38:13-8.
  39. Motoyoshi M, Uemura M, Ono A, Okazaki K, Shigeeda T, Shimizu N. Factors affecting the long-term stability of orthodontic mini-implants. Am J Orthod Dentofacial Orthop 2010;137: 588.e1-5.
  40. Oh YH, Park HS, Kwon TG. Treatment effects of microimplantaided sliding mechanics on distal retraction of posterior teeth. Am J Orthod Dentofacial Orthop 2011;139:470-81.
  41. Park H, Yoon DY, Park C, Jeoung SH. Treatment effects and anchorage potential of sliding mechanics with titanium screws compared with the Tweed-Merrifield technique. Am J Orthod Dentofacial Orthop 2008;133:593-600.
  42. Polat-Ozsoy O, Arman-Ozcirpici A, Veziroglu F. Miniscrews for upper incisor intrusion. Eur J Orthod 2009;31:412-6.
  43. Suzuki EY, Suzuki B. Placement and removal torque values of orthodontic miniscrew implants. Am J Orthod Dentofacial Orthop 2011;139:669-78.
  44. Thiruvenkatachari B, Pavithranand A, Rajasigamani K, Kyung HM. Comparison and measurement of the amount of anchorage loss of the molars with and without the use of implant anchorage during canine retraction. Am J Orthod Dentofacial Orthop 2006;129:551-4.
  45.  Turkoz C¸, Atac¸ MS, Tuncer C, Balos¸ Tuncer B, Kaan E. The effect of drill-free and drilling methods on the stability of mini-implants under early orthodontic loading in adolescent patients. Eur J Orthod 2011;33:533-6.
  46. Upadhyay M, Yadav S, Patil S. Mini-implant anchorage for enmasse retraction of maxillary anterior teeth: a clinical cephalometric study. Am J Orthod Dentofacial Orthop 2008;134: 803-10.
  47. Upadhyay M, Yadav S, Nagaraj K, Nanda R. Dentoskeletal and soft tissue effects of mini-implants in Class II, division 1 patients. Angle Orthod 2009;79:240-7.
  48. Viwattanatipa N, Thanakitcharu S, Uttraravichien A, Pitiphat W. Survival analyses of surgical miniscrews as orthodontic anchorage. Am J Orthod Dentofacial Orthop 2009;136:29-36.
  49. Wilmes B, Olthoff G, Drescher D. Comparison of skeletal and conventional anchorage methods in conjunction with pre-operative decompensation of a skeletal Class III malocclusion. J Orofac Orthop 2009;70:297-305.
  50. Liou EJW, Pai BCJ, Lin JCY. Do miniscrews remain stationary under orthodontic forces? Am J Orthod Dentofacial Orthop 2004; 16:42-7
  51. Upadhyay M, Yadav S, Nagaraj K, Patil S. Treatment effects of mini-implants for en-masse retraction of anterior teeth in bialveolar dental protrusion patients: a randomized controlled trial. Am J Orthod Dentofacial Orthop 2008;134:18-29.
  52. Park HS, Jeong SH, Kwon OW. Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofacial Orthop 2006;130:18-25.
  53. Maddalone M, Ferrari M, Barrila S, Arrigoni P, Stanizzi A. Intrusive mechanics in orthodontics by the use of TAD. Dent Cadmos 2010;78:97-106.
  54. Shi YT, Ping Y, Shan LH, Song JS, Qiu ZX. Stability of miniimplant during orthodontic treatment as anchorage. J Clin Rehabil Tissue Eng Res 2008;12:5109-12.
  55. Papageorgiou SN, Zogakis PI, Papadopoulos MA. Failure rates and associated risk factors of orthodontic miniscrew implants:A meta-analysis. Am J Orthod Dentofacial Orth 2012;142:577-95.

Source(s) of Funding


Competing Interests


0 reviews posted so far

0 comments posted so far

Please use this functionality to flag objectionable, inappropriate, inaccurate, and offensive content to WebmedCentral Team and the authors.


Author Comments
0 comments posted so far


What is article Popularity?

Article popularity is calculated by considering the scores: age of the article
Popularity = (P - 1) / (T + 2)^1.5
P : points is the sum of individual scores, which includes article Views, Downloads, Reviews, Comments and their weightage

Scores   Weightage
Views Points X 1
Download Points X 2
Comment Points X 5
Review Points X 10
Points= sum(Views Points + Download Points + Comment Points + Review Points)
T : time since submission in hours.
P is subtracted by 1 to negate submitter's vote.
Age factor is (time since submission in hours plus two) to the power of 1.5.factor.

How Article Quality Works?

For each article Authors/Readers, Reviewers and WMC Editors can review/rate the articles. These ratings are used to determine Feedback Scores.

In most cases, article receive ratings in the range of 0 to 10. We calculate average of all the ratings and consider it as article quality.

Quality=Average(Authors/Readers Ratings + Reviewers Ratings + WMC Editor Ratings)