The International Journal of Periodontics & Restorative Dentistry

The International Journal of Periodontics & Restorative Dentistry

559 Failure of Orthodontic Mini-implants by Age, Sex, and Arch; Number of Primary Insertions; and Frequency of Reinsertions After Failure: An Analysis of the Failure Rate and Failure Rate Jong-Wan Kim, DDS, MSD, PhD 1 Nam-Ki Lee, DDS, MSD, PhD 2 Hye-Young Sim, DDS, MSD, PhD 3 Pil-Young Yun, DDS, MSD, PhD 4 Jong-Ho Lee, DDS, MSD, PhD 5 This study aimed to analyze and compare the failure rate of orthodontic miniimplants (OMIs) in terms of the number of implants (implant failure rate []) and patients (patient failure rate []) according to the age, sex, and arch of the patients, the number of primary insertions, and frequency of reinsertions after failure. A total of 394 OMIs (1.2 mm in diameter; 7. mm in length) were inserted in 125 patients (24 male and 11 female, mean age 21.95 ± 7.6 years). and were evaluated according to the age and sex of the patient, the number of primary insertions, and the frequency of reinsertions after failure. was 4.8% and was 18.27% after the first insertions. was higher than regardless of the number of OMIs inserted. increased with an increase in the frequency of reinsertions, reaching 66.67% after the fourth insertion, whereas decreased to 25.% after the second insertion and to 66.67% after the third and fourth insertions. The overall and were 4.8% and 19.29%, respectively. Although male patients, young patients, and location in the mandible showed higher and, there were no significant differences between and according to the sex, age, or arch. was higher than in this study, indicating that the treatment process could be more strongly affected by than. The failure rate can increase with the frequency of OMI reinsertions after failure. Sex, age, and arch may have no correlation with primary or recurrent OMI failure. Int J Periodontics Restorative Dent 16;36:559 565. doi: 1.1167/prd.2675 1 Clinical Associate Professor, Department of Orthodontics, Section of Dentistry, Seoul National University Bundang Hospital, Seongnam-si, Korea. 2 Associate Professor, Department of Orthodontics, Section of Dentistry, Seoul National University Bundang Hospital, Seongnam-si, Korea. 3 Assistant Professor, Department of Orthodontics, SMG-SNU Boramae Medical Center, Seoul, Korea. 4 Associate Professor, Department of Oral and Maxillofacial Surgery, Section of Dentistry, Seoul National University Bundang Hospital, Seongnam-si, Korea. 5 Professor, Department of Oral and Maxillofacial Surgery and Oral Cancer Center, School of Dentistry and Dental Research Institute, Seoul National University Dental Hospital, Seoul, Korea. Correspondence to: Dr Hye-Young Sim, Department of Dentistry, SMG-SNU Boramae Medical Center, Boramae-ro, Dongjak-gu, Seoul, 156-77, South Korea. Fax: +82-2-87-1476. Email: orthodo@hanmail.net 16 by Quintessence Publishing Co Inc. Orthodontic mini-implants (OMIs), 1,2 onplants, 3 and plates 4 are useful appliances for patients requiring maximum anchorage 5 or asymmetric force systems. 6 OMIs with the buccal alveolar bone as skeletal anchorage are preferred because they are small and can be easily inserted and removed. 7 However, small implants are associated with a higher failure rate 8 because of the small contact area between the implant surface and bone. Surgical plates and palatal implants for orthodontic anchorage reportedly have higher success rates. 9,1 The failure rate of OMIs, which are conventionally inserted into the buccal alveolar bone, was reported to be approximately 1% to 3%. 11 Occasional discrepancies have been observed between the reported failure rate and the actual failure rate of OMIs in the clinical setting, probably because the total number of patients may be lower than the total number of inserted OMIs when multiple OMIs are inserted in a single patient. Recurrent failure of OMIs in a patient can necessitate a change in the treatment strategy. 12 Other studies on the failure rate of OMIs have assessed the clinical failure rate on the basis of factors such as type and size of OMIs and patient age and sex. 13 15 It is necessary to evaluate the failure rate of OMIs in terms of the number of implants as well as the Volume 36, Number 4, 16

56 Fig 1 (left) Design illustration (a) and photograph (b) of the mini-implant, which had a diameter of 1.2 mm and a length of 7. mm. 8.9 7. Fig 2 (below) Intraoral photos of cases using OMIs. (a) OMIs were used in the maxilla and mandible in a Class I extraction case. (b) OMIs in the maxilla in a Class II extraction case. (c) OMIs were used in the mandible in a Class III nonextraction case. a 1.2 b a b c a b Fig 3 Lateral cephalometric radiographs of a case using OMIs for retraction of anterior teeth after the first premolars extraction. (a) Pretreatment. (b) During treatment. (c) Posttreatment. c number of patients, because the treatment strategy can be affected by the failure of even a single OMI in a patient. OMIs can be reinserted after failure, although the failure rate of reinserted OMIs has not been evaluated to date. Furthermore, the influence of age and sex on primary and recurrent failure rates needs to be investigated. This study was performed to evaluate the failure rate of OMIs in terms of the number of implants (implant failure rate []) and the number of patients (patient failure rate []) according to the age, sex, and arch of the patient, number of primary insertions, and frequency of reinsertions after failure. Materials and methods The OMIs used in this study (Miangang, Biomaterialskorea) were manufactured from grade 5 titanium and had a diameter of 1.2 mm and a length of 7. mm (Fig 1). A total of 394 OMIs were inserted into the buccal alveolar bone in the posterior regions of 125 patients (24 male and 11 female; overall mean age 21.95 ± 7.6 years; mean age for males 19. ± 5.87 years; mean age for females 22.64 ± 7.79 years) from July 6 to May 1 at National University Budang Hospital (Figs 2 and 3). s with medical or dental problems such as diabetes, osteoporosis, osteopenia, or uncontrolled periodontitis were excluded from The International Journal of Periodontics & Restorative Dentistry

561 Table 1 failure rate () and implant failure rate () by number of primary insertions in a patient Primary insertions P* 1 11 1 9.9 11 1 9.9 1.*** 2 64 24 37.5 128 27 21.9.15** 3 1 6 6. 3 8 26.67.123*** 4 38 18 47.37 152 21 13.82.** 5 1 1 1. 5 1..333*** 6 1 1 1. 6 2 33.33.429*** Total 125 51 4.8 332 6 18.7.** *Significant differences between and. **Significant difference by chi-square test. ***Significant difference by Fisher exact test. Table 2 failure rate () and implant failure rate () after reinsertions following failure of primary orthodontic mini-implants Reinsertions P* 1 125 51 4.8 332 6 18.7.** 2 44 11 25. 52 11 21.15.655** 3 7 3 42.86 7 3 42.86 1.*** 4 3 2 66.67 3 2 66.67 1.*** *Significant differences between and. **Significant difference by chi-square test. ***Significant difference by Fisher exact test. the study. Clinical failure of an OMI was determined when the implant was exfoliated or not firm in the alveolar bone with mobility or pain. Gingival proliferation around the OMI or gingival coverage of the OMI was not considered OMI failure. The patients were classified into six groups according to the number (1 to 6) of primary OMIs inserted. was calculated by dividing the number of failed OMIs by the total number of OMIs in each group. was calculated by dividing the number of patients with OMI failure by the total number of patients in each group. and after the first, second, third, and fourth insertions after failure were calculated and compared. The values were also obtained for patients stratified by sex, age, and arch. The evaluated age range was 1 to 58 years. When OMIs were inserted in the same patient at different times, the age of the patient was considered according to the date at each insertion. Results and after the primary insertion were 4.8% and 18.27%, respectively (Table 1). When and were analyzed according to the number of primary insertions, the highest values (6.% and 26.67%, respectively) were observed for the group that received three OMIs (Fig 4). All groups except the group that received a single OMI showed higher values compared with values. increased with an increase in the frequency of reinsertions after OMI failure, reaching 66.67% after the fourth insertion (Table 2, Fig 5). However, decreased to 25.% after the second insertion and increased again after the third and fourth insertions, eventually reaching 66.67%. Volume 36, Number 4, 16

562 1 1 8 8 Failure rate 6 4 Failure rate 6 4 1 2 3 4 5 6 1 2 3 4 Primary insertions in a patient Reinsertions Fig 4 and by number of primary insertions in a patient. Fig 5 and by frequency of reinsertions. Table 3 failure rate (), implant failure rate (), and mean number of inserted and failed implants by patient sex Sex Average number of inserted implants Average number of failed implants P* Male 24 11 45.83 74 18 24.32 3.8.75.45 Female 11 4 39.6 3 58 18.13 3.17.57. Total 125 51 4.8 394 76 19.29 3.15.61. P**.577.223 *Significant differences by chi-square test between and. **Significant differences by chi-square test between male and female patients. Table 4 failure rate (), implant failure rate (), and mean number of inserted and failed implants by patient age Age Average number of inserted implants Average number of failed implants P* 1 19 5 23 46. 157 33 21.2 3.14.66.1 29 56 19 33.93 176 29 16.48 3.14.52.5 3 58 21 7 33.33 61 1 16.39 2.9.48.99 P**.383.518 *Significant differences by chi-square test between and. **Significant differences by chi-square test test among age groups. The overall and for primary and subsequent insertions were 4.8% and 19.29%, respectively (Table 3). Both and were higher in males (45.83% and 24.32%, respectively) than in females (39.6% and 18.13%, respectively), although the differences were not significant (Fig 6). The mean number The International Journal of Periodontics & Restorative Dentistry

563 1 1 8 8 Failure rate 6 4 Failure rate 6 4 Male Female Total 1 19 29 3 58 Sex Age (y) Fig 6 and by patient sex. Fig 7 and by patient age. Table 5 failure rate (), implant failure rate (), and mean number of inserted and failed implants by arch Arch Average number of inserted implants Average number of failed implants P* Maxilla 96 25 26.4 199 34 17.9 2.7.35.72 Mandible 92 29 31.52 195 42 21.54 2.12.46.67 P**.46.263 *Significant differences by chi-square test between and. **Significant differences by chi-square test test between maxilla and mandible. of OMIs inserted was 3.15 overall, 3.8 in males, and 3.17 in females. The mean number of failed OMIs was.61 overall,.75 in males, and.57 in females. and did not show any significant differences among the different age groups (1 19 years, 46.% and 21.2%, respectively; 29 years, 33.93% and 16.48%, respectively; and 3 58 years, 33.33% and 16.39%, respectively; Table 4, Fig 7). However, was higher than in all age groups and in both sexes. In the comparison between maxilla and mandible, the and in the mandible (31.52% and 21.54%, respectively) were higher than in maxilla (26.4% and 17.9%, respectively), although the differences were not significant (Table 5, Fig 8). The mean numbers of OMIs inserted were 2.7 in maxillae and 2.12 in mandibles. The mean numbers of failed OMIs were.35 in maxillae and.46 in mandibles. Failure rate 1 8 6 4 Maxilla Arch Fig 8 and by patient arch. Mandible Volume 36, Number 4, 16

564 Discussion This study evaluated the failure rate of OMIs () and according to the sex, age, and arch of the patients, the number of primary insertions, and the frequency of reinsertions after failure. The success rate of OMIs reported in some studies was higher than 9%, 1 or approximately 83.8% ± 7.4%. 16 However, the success rate observed in clinical practice is sometimes different from that found in these reported rates, probably because clinicians may calculate the failure rate as, not. can be generally higher than because multiple implants may be inserted in a single patient. In the present study, the was 6.% in the group that initially received three implants and 47.37% in the group that initially received four implants, while the corresponding s were 26.67% and 13.82%, respectively. This indicates that the probability of failure was once in every two patients in the groups that initially received three or four implants. Therefore, the actual clinical failure rate may be higher than the reported failure rate. In patients who receive two to four OMIs, the failure of even one OMI can result in a delay in treatment or necessitate a change in the treatment strategy. 12 A high indicates a higher number of patients with failed implants, and this can affect the treatment strategy more significantly than the failure rates reported in other studies. Therefore, when inserting multiple OMIs in a patient, clinicians should consider inserting additional OMIs at the same site of local anesthesia for use in the event of failure, keeping in mind the high for cases of multiple insertions. In particular, additional OMIs could be helpful in the group that received three OMIs because and were highest in this group. In this study, decreased from 4.8% after the first insertion to 25.% after the second insertion, indicating a decrease in the OMI failure rate. However, increased from 18.7% after the first insertion to 21.15%, 42.86%, and 66.67% after the second, third, and fourth insertions, respectively, indicating an increase in the failure rate with an increase in the frequency of reinsertions. also increased after the third and fourth insertions to reach 66.67%. decreased after the second insertion, probably because only one OMI may have been reinserted per patient. These results indicate that clinicians should make an effort to prevent the initial failure of OMIs, with even more careful efforts to prevent failure after reinsertion. Other studies showed that the in the maxilla was higher than in the mandible. 17,18 In this study, and in the maxilla were higher, although there was no significant difference between maxilla and mandible. Some clinical studies have reported that was higher for young patients 19 and women than for older patients and men. However, in this study and were not influenced by age or sex. The higher failure rates in younger patients and female patients may be attributed to a higher number of OMIs inserted in these patient populations than in older patients or male patients. Furthermore, because the number of patients who visit dental clinics is higher among young individuals and females than among older individuals and males, 21 clinicians may encounter OMI failures more frequently in young or female patients than in older or male patients, giving them a false impression that OMIs are less stable in the former two populations than in the latter two. Clinicians should consider that there may not be any correlation between OMI failure and age or sex. 13,22 Therefore, efforts to prevent failure after primary OMI insertion and the insertion of additional OMIs should be implemented regardless of the age or sex of the patient. Moreover, further studies about the failure times after insertion and orthodontic loading would be helpful for clinical application of orthodontic mini-implants. Conclusions The results of this study showed that was higher than, regardless of the number of primary insertions. Clinicians should insert additional OMIs at the same site when inserting multiple OMIs in a single patient. The failure rate can increase with an increase in the frequency of reinsertions. Clinicians should therefore make every effort to prevent failure after primary or subsequent insertions. Although male patients, young patients, and mandibular treatment sites showed higher and, there were no significant The International Journal of Periodontics & Restorative Dentistry

565 differences between and according to patient sex, age, or arch. Efforts to prevent failure should be made regardless of these factors. Acknowledgments This study was supported by grant no. 4-11-56 from the SNUBH Research Fund and was approved by the Institutional Review Board of Seoul National University Bundang Hospital (B-111-115-11). The authors reported no conflicts of interest related to this study. References 1. Umemori M, Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open-bite correction. Am J Orthod Dentofacial Orthop 1999;115:166 174. 2. Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod 1997;31: 763 767. 3. Block MS, Hoffman DR. A new device for absolute anchorage for orthodontics. Am J Orthod Dentofacial Orthop 1995;17:251 258. 4. Kook YA, Lee DH, Kim SH, Chung KR. Design improvements in the modified C-palatal plate for molar distalization. J Clin Orthod 13;47:241 248. 5. Basha AG, Shantaraj R, Mogegowda SB. Comparative study between conventional en-masse retraction (sliding mechanics) and en-masse retraction using orthodontic micro implant. Dent 1;19:128 136. 6. Park HS, Oh YH. Forced eruption of a labially impacted canine using joined micro-implants. J Clin Orthod 1;44: 18 113. 7. Costa A, Raffainl M, Melsen B. Miniscrews as orthodontic anchorage: A preliminary report. Int J Adult Orthodon Orthognath Surg 1998;13:1 9. 8. Moheng P, Feryn JM. Clinical and biologic factors related to oral implant failure: A 2-year follow-up study. Dent 5;14:281 288. 9. Schätzle M, Männchen R, Zwahlen M, Lang NP. Survival and failure rates of orthodontic temporary anchorage devices: A systematic review. Clin Oral s Res 9;:1351 1359. 1. Park HS, Jeong SH, Kwon OW. Factors affecting the clinical success of screw implants used as orthodontic anchorage. Am J Orthod Dentofacial Orthop 6; 13:18 25. 11. Reynders R, Ronchi L, Bipat S. Miniimplants in orthodontics: A systematic review of the literature. Am J Orthod Dentofacial Orthop 9;135:564. e561 e519. 12. Lee JH, Choo H, Kim SH, Chung KR, Giannuzzi LA, Ngan P. Replacing a failed mini-implant with a miniplate to prevent interruption during orthodontic treatment. Am J Orthod Dentofacial Orthop 11;139:849 857. 13. Wu TY, Kuang SH, Wu CH. Factors associated with the stability of mini-implants for orthodontic anchorage: A study of 414 samples in Taiwan. J Oral Maxillofac Surg 9;67:1595 1599. 14. 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 3;124:373 378. 15. Moon CH, Lee DG, Lee HS, Im JS, Baek SH. Factors associated with the success rate of orthodontic miniscrews placed in the upper and lower posterior buccal region. Angle Orthod 8;78:11 16. 16. Crismani AG, Bertl MH, Celar AG, Bantleon HP, Burstone CJ. Miniscrews in orthodontic treatment: Review and analysis of published clinical trials. Am J Orthod Dentofacial Orthop 1;137:18 113. 17. Kim JS, Choi SH, Cha SK, et al. Comparison of success rates of orthodontic miniscrews by the insertion method. Korean J Orthod 12;42:242 248. 18. Papageorgiou SN, Zogakis IP, Papadopoulos MA. Failure rates and associated risk factors of orthodontic miniscrew implants: A meta-analysis. Am J Orthod Dentofacial Orthop 12;142:577 595. e577. 19. Lee SJ, Ahn SJ, Lee JW, Kim SH, Kim TW. Survival analysis of orthodontic mini-implants. Am J Orthod Dentofacial Orthop 1;137:194 199.. 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 8;78: 895 91. 21. Huang GJ, Marston BE, del Aguila MA. Orthodontic care in an insured population in Washington: Demographic factors. Am J Orthod Dentofacial Orthop 4; 125:741 746. 22. Reynders RM. Low quality evidence on the stability of orthodontic mini-implants. Evid Based Dent 13;14:78 8. Volume 36, Number 4, 16