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Implants for Orthodontic Anchorage: Success Rates and Reasons of Failures Juan C. Rodriguez, DDS,* Fernando Suarez, DDS,† Hsun-Liang Chan, DDS, MS,‡ Miguel Padial-Molina, DDS, PhD,§ and Hom-Lay Wang, DDS, MSD, PhDk
relatively common finding in the average individual is malocclusion. It may be caused by developmental or acquired deformity, agenesis, or tooth loss.1,2 In orthodontics, controlled forces are applied in specific directions to move teeth from improper locations into what is considered an “ideal” physiologic/esthetic location. To provide the movement, a steady and strong support known as orthodontic anchor is required.3 Anchorage, by definition, is a resistance to displacement provided by a static object. The most common anchor used is the own dentition of the patient; however, in some cases, the anchorage is limited or not enough. In such cases, alternative strategies might be applied to achieve the desired outcome. These alternatives to natural teeth can be the palate, the head, the neck, and foreign devices, such as plates, implants, or screws.4 Proffit5 stated that an important aspect of orthodontic treatment is maximizing the tooth movement that is desired, while minimizing undesirable side effects, hence
A
*Resident, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. †Visiting Scholar, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. ‡Adjunct Clinical Assistant Professor, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. §Research Fellow, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. kProfessor and Director, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI.
Reprint requests and correspondence to: Hom-Lay Wang, DDS, MSD, PhD, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, 1011 North University Avenue, Ann Arbor, MI 48109-1078, Phone: (734) 763-3383, Fax: (734) 9360374, E-mail: [email protected] ISSN 1056-6163/14/02302-155 Implant Dentistry Volume 23 Number 2 Copyright © 2014 by Lippincott Williams & Wilkins DOI: 10.1097/ID.0000000000000048
Introduction: The aims of this study were to analyze the success rate of mini-implants and miniscrews and to report the reasons behind them. Materials and Methods: An electronic literature search from PubMed databases and a hand search in implant- and orthodontic-related journals were performed until December 31, 2011. Human clinical studies in English that reported temporary anchorage devices used for orthodontic purpose with at least 6 months follow-up were included. In addition, the minimal number of implants had to be at least 10. Implants placed in maxilla, mandible, and hard palate were included. Results: The initial search resulted in 847 articles, of which 46 were further evaluated. Finally, 29
studies were qualified and classified into 2 groups: implants placed in maxilla and mandible (group 1) and implants placed in hard palate (group 2). A meta-analysis performed for groups 1 and 2 showed 87.8% and 93.8% survival rate, respectively. In addition, the most common cause for implants failure was surgery-related factors. Conclusion: Mini-implant survival rate is location dependent, with those placed in the palate showing higher success rates. In addition, failures most commonly occur because of surgery-related factors. (Implant Dent 2014;23:155–161) Key Words: mini-implants, miniscrews, temporary anchorage device, TAD, microimplant, orthodontic anchorage
when used as temporary anchorage devices (TADs), dental implants can certainly meet the need. The first application on TADs dates back to 1945, when Gainsforth and Higley6 placed Vitallium (a trademark for an alloy of 60% cobalt, 20% chromium, 5% molybdenum, and other components) screws in the ascending ramus of 6 dogs aiming to retract their canines. It was not until almost 30 years later that the first human case report was published. During the time of treatment, the incisors were elevated 6 mm and 25 degrees lingual to the original position.7 Like most implantable devices, miniimplants have several advantages, but
the decision to proceed with the use of these devices should be carefully evaluated mainly depending on the amount of anchorage needed, anatomy, the skills of the clinician, and the patients’ acceptance to the procedure. Skeletal anchorage can be classified according to their function as: (1) devices for asymmetrical tooth movements in all planes of space and (2) an alternative to orthognathic surgery.2 They can also be grouped into 2 main categories depending on their relation with bone. The first category includes osseointegrated dental implants, such as the orthodontic mini-implants, the retromolar implants, and the palatal implants.
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Table 1. Summary of the Reasons Grouped for Each Type of Failure Surgery-related
Orthodontic-related
Surgical complications
Patient-related
Implants lost during loading without specifying patient or surgical factors Inability to resist reciprocal forces
Lack of stability before loading Lack of surgical experience Improper implant selection
The second category derives from the surgical miniscrews and miniplates.7 The main differences between them are that devices from the second category are smaller in diameter, usually have a smooth surface, and are designed to be loaded shortly after insertion because they rely on primary mechanical stability as opposed to mini-implants, which mostly rely on osseointegration.3 Terms such as mini-implants, miniscrews, microimplants, and microscrews have been used to describe skeletal anchorage appliances.4 Implants and mini-implants refer to
Inadequate hygiene causing persistent inflammation Habitual factors (e.g. tongue pressure, traumatic tooth brushing) Patients dropouts
systems, which by definition imply that osseointegration is achieved before loading, whereas screws and other self-tapping devices do not anticipate osseointegration. Since 2004, it was agreed that the word mini-implant should be applied to palatal implants, miniscrews, and microscrews. However, intraoral extradental anchorage systems and TADs are other terms that have also been suggested to describe such devices.8–10 By definition, a mini-implant’s diameter should range from 1.2 to 2.3 mm and measure from 5 to 14 mm in length.
Since their introduction, many indications, techniques, materials, and designs have been described.1,11–13 Currently, mini-implants are commonly used in aid of orthodontic treatments; however, the reasons for failures have not been investigated in depth (Table 1). Hence, it was the goal of this article to provide a comprehensive review of the literature on evaluating the reasons of failures and a metaanalysis of success for mini-implants for orthodontic anchorage.
MATERIALS
AND
METHODS
A search of electronic databases, including Ovid (MEDLINE), PubMed, and Cochrane Central for studies published before January 2012 in English was performed by 2 examiners (J.C.R. and F.S.). Only articles published in English and in human subjects were included. The search terms used were a combination of: “implant for orthodontic anchorage,” “miniscrew,” “mini screw,” “mini-implant,” “miniimplant,” “temporary anchorage device,” “ palatal implant,” and “Onplant.” A search for references in the included articles was performed. In
Table 2. Analysis of the Failures Occurred
TAD Location Interdental
Palatal
Author and Year 30
Antoszewka et al, 2009 Berens et al, 200613 Garfinkle et al, 200636 Kuroda et al, 2007a51 Motoyoshi et al, 200635 Tseng et al, 200656 Total % Arcuri et al. 200743 Asscherick et al. 201044 Benson et al. 200745 Feldmann & Bondemark 200831 Gollner et al. 200946 Jung et al. 201058 Jung et al. 2011a47 Jung et al. 2011b46 Mannchen et al. 200841 Sandler et al. 200832 Wehrbein & Gollner 200911 Total %
Reasons for Failures
No. of implants
No. of Failures
Surgery-related
Ortho-related
Patient-related
350 239 82 216 124 45 1056
23 36 20 15 18 4 116 100 1 3 2 2 4 2 11 2 3 4 2 36 100
0 36 20 15 18 2 91 78.45 0 1 2 1 1 1 9 1 2 2 2 22 61.11
23 0 0 0 0 0 23 19.83 0 0 0 1 3 0 2 0 1 0 0 7 19.44
0 0 0 0 0 2 2 1.72 1 2 0 0 0 1 0 1 0 2 0 7 19.44
16 34 25 30 76 41 239 41 70 26 22 620
177 41 34 34 60 N/S 0 N/S 0 61 201 351 44 31 103 18 135 1290 173 82 48 16 156 N/S 260 N/S 32 63 279 427 80 56 124 27 268 2091 350 239 82 50 216 116 260 407 32 134 480 778 124 87 227 45 414 4041 19.2 16 Until treatment Until treatment 12 12 22 Until treatment 9 12 .8 12.21 6 6 15 16 .6 Pts indicates patients; No, number; Imp, implant; Max, maxillary; Mand, mandibular; N/S, not specified.
57
56
34
55
35
33
40
39
54
53
52
50
51
49
36
13
30
Retrospective Retrospective Prospective Prospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Prospective Retrospective Prospective Retrospective Prospective
130 85 13 21 110 75 140 168 16 51 209 306 41 32 87 25 166 1675
Mand Max
Antoszewska et al, 2009 Berens et al, 2006 Garfinkle et al, 2008 Junstens et al, 2008 Kuroda et al, 2007a Kuroda et al, 2007b Lee et al, 2010 Lim et al, 2011 Liou et al, 2004 Miyawaki et al, 2003 Moon et al, 2008 Moon et al, 2010 Motoyoshi et al, 2006 Motoyoshi et al, 2007 Park et al, 2006 Tseng et al, 2006 Wu et al, 2009 Total
No Pts Study Design Author Reference No.
Table 3. Summary of Implants Placed in the Maxilla and Mandible (Group 1)
Mean Follow-up Period (mo)
No Imp
Location
Length (mm)
6.0–8.0 N/S 6.0 8.0 and 10.0 6.0–12.0 7.0 and 11.0 8.5 6.0–10.0 17.0 6.0, 11.0, 14.0 8.0 8.0 8.0 8.0 5.0–15.0 8.0–14.0 7.8–10.0
Width (mm)
1.2–1.8 1.3, 1.6, 2.0 1.6 1.6–2.0 1.3 2.0–2.3 1.8 1.6–1.8 2 1, 1.5, 2.3 1.6 1.6 1.6 1.6 1.2–2.0 2 1.1–1.7
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addition, hand search from January 2000 to December 2011 was conducted in implant-related dental journals, including American Journal of Orthodontics and Dentofacial Orthopedics, Journal of Oral and Maxillofacial Surgery, Journal of Orofacial Orthopedics, Clinical Oral Implants Research, Clinical Oral Investigations, Clinical Implant Dentistry and Related Research, European Journal of Orthodontics, The Angle Orthodontist, The International Journal of Oral & Maxillofacial Implants, and International Journal of Oral and Maxillofacial Surgery. Articles were included if they fulfilled the following criteria (Table 2): human clinical trial that evaluated either survival or success of orthodontic miniimplants placed in maxilla, mandible, and palate; at least 10 implants with a minimum follow-up of 6 months. However, articles were excluded if they had less than 10 implants, less than 6 months of follow-up, animal studies, review articles or case reports, and data combined with miniplates. Studies were also excluded if the implants were used for any other purpose beside orthodontic anchorage. Potential articles were independently reviewed in fulltext by 2 examiners (J.C.R. and F.S.). The final decision on the included articles was made with mutual agreements of the 2 examiners (Table 3). Understanding that mini-implants might perform differently depending on anatomic locations, the weighed mean survival rates with 95% confidence interval (CI) were calculated separately for: (1) the mini-implants that were placed at the interdental space of the maxilla and mandible and (2) those placed in the palate. The number of fixtures and survival rate from each included article were retrieved and inserted into the statistical software (Comprehensive Meta-analysis). The random model was selected for the meta-analyses. The survival rate of each study and the weighed mean survival rate were computed into a forest plot.
RESULTS The screening process was represented in Figure 1. The initial
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screening yielded a total of 847 articles. After initial screening of their titles and abstracts, 801 articles were excluded because they did not meet the inclusion criteria, and 46 articles were further evaluated in full text (Table 4). After a final revision, 29 articles were selected for this systematic review. Interexaminer agreement in article selection was 0.9. The reasons of exclusion after full-text evaluation included: insufficient follow-up,14–18 data combined or not well differentiated with miniplates,19–22 review articles or case reports,23–28 and non-human study.29 For a more detailed explanation, please refer to Table 5.
Fig. 1. Flow chart of the screening process.
Table 4. Summary of Implants Placed in the Palate (Group 2) Reference No. 43 44 45 38 31 46 58 47 48 41 32 11
Author
Study Design
No Pts
Arcuri et al, 2007 Asscherick et al, 2010 Benson et al, 2007 Borsos et al, 2008 Feldmann et al, 2008 Göllner et al, 2009 Jung et al, 201057 Jung et al, 2011a Jung et al, 2011b Männchen et al, 2008 Sandler et al, 2008 Wehrbein et al, 2009 Total
Retrospective Prospective RCT Prospective RCT Retrospective RCT Retrospective RCT Prospective RCT Prospective
14 33 25 16 30 76 41 239 41 70 26 22 636
Mean Follow-up Period (mo) 22 22 N/A Until treatment Until treatment Until treatment 6 33 6 19 26 21
No Imp
Length (mm)
Width (mm)
16 34 25 16 30 76 41 239 41 70 26 22 633
6.0–4.0 4.0–6.0 6.0 4.0 4.0 4.0–6.0 4.2 4.0–4.2–6.0 4.0–6.0 4.0–6.0 4.0 4.0–6.0
3.3 3.3–4.0 N/A 4.1 3.3 3.3 4.1 3.3–4.0–4.1 4.1–4.2 3.3–4.0 3.3–4.0 N/A
Pts indicates patients; No, number; Imp, implant; Max, maxillary; Mand, mandibular; N/S, not specified.
Table 5. Excluded Articles Reason for Exclusion
Excluded Article
Insufficient follow-up
Chaddad et al, 200814 Crismani et al, 200615 Jackson et al, 200816 Schaltze et al, 200917 Wiechmann, 200718 Chen et al, 200719 Chen et al, 200820 Cheng, 200421 Yao, 200822 Hoste et al, 200824 Li et al, 201125 McGuire et al, 200626 Motoyoshi et al, 201127 Ohashi et al, 200628 Wehrbein et al, 200723 Migliorati et al, 201229
Data combined with miniplates
Review articles or case reports
Non-human study
The meta-analysis showed that the weighted mean survival rate of maxillary and mandibular implants is 87.8% (95% CI) (Fig. 2), whereas a survival rate of 93.8% (95% CI) was found for palatal implants (Fig. 3). Further analysis was performed for the failures occurred and the reasons of their occurrence. For mandibular and maxillary implants, 116 of 1056 implants failed, of which 78.45%, 19.83%, and 1.72% failed because of surgery-related, orthodontic-related, and patient-related reasons, respectively (Table 2). However, 620 palatal implants were analyzed and 36 of them failed. The reasons for their failures were 61.11%, 19.44%, and 19.44% for surgery-related, orthodonticrelated, and patient-related reasons, respectively.
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Fig. 2. A meta-analysis evaluating survival rates of orthodontic implants in maxilla and mandible.
Fig. 3. A meta-analysis evaluating survival rates of orthodontic implants in palate.
DISCUSSION As we focused our efforts in identifying the success rates of orthodontic mini-implants reported in the literature, we encountered several variation and opinions to this term. However, the most common label of success was a mini-implant that remained static, with no signs of inflammation, and that supported the orthodontic forces applied to the device throughout the entire length of the orthodontic treatment.30,31 Due to the fact that we focused our meta-analysis in the behavior of different devices that serve the same purpose, we inherited certain criteria that were mandatory for each system to be considered successful. Osseointegration, for example, was an absolute factor that needed to be present when we analyzed the data from palatal implants and certain systems that were inserted into the mandible and maxilla and relied on it31,32; nevertheless, it was not taken into consideration to judge the behavior of
systems that performed on mechanical retention or stability.33–35 For these reasons, we had to dissect each article revised to be certain that there were no overlapping definitions of success/ survival, and although some articles divided their success rates into other variables, including location, type of movement, time of loading, effectiveness, and overall patient satisfaction, we found that differences in the final outcomes were not statistically significant among them.36,37 We included success rates from articles where the authors clearly stated that the devices used as orthodontic anchors were effective for the use of reciprocal forces throughout the entire length of the treatment, no signs of severe inflammation or suppuration, they were osseointegrated when needed or they had no mobility, and that they were clinically effective. It has also been shown in the literature the different causes why an implant may fail, including but not limited to patients and surgery-related
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factors. Nonetheless, due to the purpose of this specific type of implants used as anchorage devices, orthodontics parameters, such as the force applied, the loading time, and the position in the arches, may also play a role in its failures. In this article, 3 different categories were created to group the reasons why implant fails. These categories are surgical, orthodontic, and patient-related factors. Implants failed due to surgical factors are attributed by the following: poor surgical technique, lack of implant primary stability, implants lost due to reverse torque, implants failed during healing without any other contributing factor, implants placed in wrong anatomical position, and implants with unfavorable characteristics that lead to implant loosening, and finally, implants that failed to osseointegrate. However, orthodontic factors included loss after initial loading, when the implant was unable to resist reciprocal forces and when they were lost during orthodontic load. Finally, patients factor attributed to failures related to inadequate hygiene, patients who reported tongue thrusting or brushing the area, persistent inflammation, and patient dropouts. Yet another variable that may alter success rates is location, most commonly mini-implants are placed in the vestibular areas of the posterior jaws or in the midpalatal suture.2,38 In miniimplants placed in the mid palatal suture, we found success rates of 93%, which indicated a very positive outcome. In the case of mini-implants placed in the mandible and maxilla, there was no evident consensus for a healing period, and in some cases, the authors loaded immediately, and in others, they waited between 1 and 12 weeks, with no statistical significance in the outcomes.39–41 With regards to loading time, no clear guideline is available in the literature. It will depend on the type of implant, the material, and the final purpose of the device.12 In clinical situations were primary stability and bone-to-implant contact is adequate, the clinician may take the risk of indicating immediate or early loading. In several cases, it was reported that at the time of insertion and up to 1 week after placement, higher primary stability and insertion torque were achieved in the mandible. However, after a healing
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period of 3 weeks in average, the stability and success rates were slightly higher in the maxilla compared with mandible, and the difference was even more pronounced past the 5- to 7-week period.34–42 This article provides updated information on survival rates of implant used for orthodontic anchorage and an analysis of the failures and their reasons, which for the best of our knowledge, has never been studied before.
CONCLUSION After analyzing a total of 29 articles,11,31,32,41,43–48 divided by location, 12 articles evaluated palatal implants11,31,32,38,41,43–48 while 17 aranalyzed ticles13,30,33–36,39,40,49–57 maxillary and mandibular implants. Available evidence showed miniimplants as a reliable treatment option with high survival rates regardless of the position in the arch; nonetheless, higher survival rate was associated with implants placed in the palate (93.8%) than in other locations (87.8%). As regards to the occurrence of the failures, 78.45% were surgery related, makingmini-implants for orthodontic anchorage, a technique sensitive procedure with a steep learning curve.
DISCLOSURE The authors claim to have no financial interests, either directly or indirectly, in the products or information listed in the article. This article was partially supported by the University of Michigan Periodontal Graduate Student Research Fund.
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Implants for Orthodontic Anchorage: Success Rates and Reasons of Failures Juan C. Rodriguez, DDS,* Fernando Suarez, DDS,† Hsun-Liang Chan, DDS, MS,‡ Miguel Padial-Molina, DDS, PhD,§ and Hom-Lay Wang, DDS, MSD, PhDk
relatively common finding in the average individual is malocclusion. It may be caused by developmental or acquired deformity, agenesis, or tooth loss.1,2 In orthodontics, controlled forces are applied in specific directions to move teeth from improper locations into what is considered an “ideal” physiologic/esthetic location. To provide the movement, a steady and strong support known as orthodontic anchor is required.3 Anchorage, by definition, is a resistance to displacement provided by a static object. The most common anchor used is the own dentition of the patient; however, in some cases, the anchorage is limited or not enough. In such cases, alternative strategies might be applied to achieve the desired outcome. These alternatives to natural teeth can be the palate, the head, the neck, and foreign devices, such as plates, implants, or screws.4 Proffit5 stated that an important aspect of orthodontic treatment is maximizing the tooth movement that is desired, while minimizing undesirable side effects, hence
A
*Resident, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. †Visiting Scholar, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. ‡Adjunct Clinical Assistant Professor, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. §Research Fellow, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI. kProfessor and Director, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, Ann Arbor, MI.
Reprint requests and correspondence to: Hom-Lay Wang, DDS, MSD, PhD, Department of Periodontics and Oral Medicine, University of Michigan School of Dentistry, 1011 North University Avenue, Ann Arbor, MI 48109-1078, Phone: (734) 763-3383, Fax: (734) 9360374, E-mail: [email protected] ISSN 1056-6163/14/02302-155 Implant Dentistry Volume 23 Number 2 Copyright © 2014 by Lippincott Williams & Wilkins DOI: 10.1097/ID.0000000000000048
Introduction: The aims of this study were to analyze the success rate of mini-implants and miniscrews and to report the reasons behind them. Materials and Methods: An electronic literature search from PubMed databases and a hand search in implant- and orthodontic-related journals were performed until December 31, 2011. Human clinical studies in English that reported temporary anchorage devices used for orthodontic purpose with at least 6 months follow-up were included. In addition, the minimal number of implants had to be at least 10. Implants placed in maxilla, mandible, and hard palate were included. Results: The initial search resulted in 847 articles, of which 46 were further evaluated. Finally, 29
studies were qualified and classified into 2 groups: implants placed in maxilla and mandible (group 1) and implants placed in hard palate (group 2). A meta-analysis performed for groups 1 and 2 showed 87.8% and 93.8% survival rate, respectively. In addition, the most common cause for implants failure was surgery-related factors. Conclusion: Mini-implant survival rate is location dependent, with those placed in the palate showing higher success rates. In addition, failures most commonly occur because of surgery-related factors. (Implant Dent 2014;23:155–161) Key Words: mini-implants, miniscrews, temporary anchorage device, TAD, microimplant, orthodontic anchorage
when used as temporary anchorage devices (TADs), dental implants can certainly meet the need. The first application on TADs dates back to 1945, when Gainsforth and Higley6 placed Vitallium (a trademark for an alloy of 60% cobalt, 20% chromium, 5% molybdenum, and other components) screws in the ascending ramus of 6 dogs aiming to retract their canines. It was not until almost 30 years later that the first human case report was published. During the time of treatment, the incisors were elevated 6 mm and 25 degrees lingual to the original position.7 Like most implantable devices, miniimplants have several advantages, but
the decision to proceed with the use of these devices should be carefully evaluated mainly depending on the amount of anchorage needed, anatomy, the skills of the clinician, and the patients’ acceptance to the procedure. Skeletal anchorage can be classified according to their function as: (1) devices for asymmetrical tooth movements in all planes of space and (2) an alternative to orthognathic surgery.2 They can also be grouped into 2 main categories depending on their relation with bone. The first category includes osseointegrated dental implants, such as the orthodontic mini-implants, the retromolar implants, and the palatal implants.
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Table 1. Summary of the Reasons Grouped for Each Type of Failure Surgery-related
Orthodontic-related
Surgical complications
Patient-related
Implants lost during loading without specifying patient or surgical factors Inability to resist reciprocal forces
Lack of stability before loading Lack of surgical experience Improper implant selection
The second category derives from the surgical miniscrews and miniplates.7 The main differences between them are that devices from the second category are smaller in diameter, usually have a smooth surface, and are designed to be loaded shortly after insertion because they rely on primary mechanical stability as opposed to mini-implants, which mostly rely on osseointegration.3 Terms such as mini-implants, miniscrews, microimplants, and microscrews have been used to describe skeletal anchorage appliances.4 Implants and mini-implants refer to
Inadequate hygiene causing persistent inflammation Habitual factors (e.g. tongue pressure, traumatic tooth brushing) Patients dropouts
systems, which by definition imply that osseointegration is achieved before loading, whereas screws and other self-tapping devices do not anticipate osseointegration. Since 2004, it was agreed that the word mini-implant should be applied to palatal implants, miniscrews, and microscrews. However, intraoral extradental anchorage systems and TADs are other terms that have also been suggested to describe such devices.8–10 By definition, a mini-implant’s diameter should range from 1.2 to 2.3 mm and measure from 5 to 14 mm in length.
Since their introduction, many indications, techniques, materials, and designs have been described.1,11–13 Currently, mini-implants are commonly used in aid of orthodontic treatments; however, the reasons for failures have not been investigated in depth (Table 1). Hence, it was the goal of this article to provide a comprehensive review of the literature on evaluating the reasons of failures and a metaanalysis of success for mini-implants for orthodontic anchorage.
MATERIALS
AND
METHODS
A search of electronic databases, including Ovid (MEDLINE), PubMed, and Cochrane Central for studies published before January 2012 in English was performed by 2 examiners (J.C.R. and F.S.). Only articles published in English and in human subjects were included. The search terms used were a combination of: “implant for orthodontic anchorage,” “miniscrew,” “mini screw,” “mini-implant,” “miniimplant,” “temporary anchorage device,” “ palatal implant,” and “Onplant.” A search for references in the included articles was performed. In
Table 2. Analysis of the Failures Occurred
TAD Location Interdental
Palatal
Author and Year 30
Antoszewka et al, 2009 Berens et al, 200613 Garfinkle et al, 200636 Kuroda et al, 2007a51 Motoyoshi et al, 200635 Tseng et al, 200656 Total % Arcuri et al. 200743 Asscherick et al. 201044 Benson et al. 200745 Feldmann & Bondemark 200831 Gollner et al. 200946 Jung et al. 201058 Jung et al. 2011a47 Jung et al. 2011b46 Mannchen et al. 200841 Sandler et al. 200832 Wehrbein & Gollner 200911 Total %
Reasons for Failures
No. of implants
No. of Failures
Surgery-related
Ortho-related
Patient-related
350 239 82 216 124 45 1056
23 36 20 15 18 4 116 100 1 3 2 2 4 2 11 2 3 4 2 36 100
0 36 20 15 18 2 91 78.45 0 1 2 1 1 1 9 1 2 2 2 22 61.11
23 0 0 0 0 0 23 19.83 0 0 0 1 3 0 2 0 1 0 0 7 19.44
0 0 0 0 0 2 2 1.72 1 2 0 0 0 1 0 1 0 2 0 7 19.44
16 34 25 30 76 41 239 41 70 26 22 620
177 41 34 34 60 N/S 0 N/S 0 61 201 351 44 31 103 18 135 1290 173 82 48 16 156 N/S 260 N/S 32 63 279 427 80 56 124 27 268 2091 350 239 82 50 216 116 260 407 32 134 480 778 124 87 227 45 414 4041 19.2 16 Until treatment Until treatment 12 12 22 Until treatment 9 12 .8 12.21 6 6 15 16 .6 Pts indicates patients; No, number; Imp, implant; Max, maxillary; Mand, mandibular; N/S, not specified.
57
56
34
55
35
33
40
39
54
53
52
50
51
49
36
13
30
Retrospective Retrospective Prospective Prospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Retrospective Prospective Retrospective Prospective Retrospective Prospective
130 85 13 21 110 75 140 168 16 51 209 306 41 32 87 25 166 1675
Mand Max
Antoszewska et al, 2009 Berens et al, 2006 Garfinkle et al, 2008 Junstens et al, 2008 Kuroda et al, 2007a Kuroda et al, 2007b Lee et al, 2010 Lim et al, 2011 Liou et al, 2004 Miyawaki et al, 2003 Moon et al, 2008 Moon et al, 2010 Motoyoshi et al, 2006 Motoyoshi et al, 2007 Park et al, 2006 Tseng et al, 2006 Wu et al, 2009 Total
No Pts Study Design Author Reference No.
Table 3. Summary of Implants Placed in the Maxilla and Mandible (Group 1)
Mean Follow-up Period (mo)
No Imp
Location
Length (mm)
6.0–8.0 N/S 6.0 8.0 and 10.0 6.0–12.0 7.0 and 11.0 8.5 6.0–10.0 17.0 6.0, 11.0, 14.0 8.0 8.0 8.0 8.0 5.0–15.0 8.0–14.0 7.8–10.0
Width (mm)
1.2–1.8 1.3, 1.6, 2.0 1.6 1.6–2.0 1.3 2.0–2.3 1.8 1.6–1.8 2 1, 1.5, 2.3 1.6 1.6 1.6 1.6 1.2–2.0 2 1.1–1.7
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addition, hand search from January 2000 to December 2011 was conducted in implant-related dental journals, including American Journal of Orthodontics and Dentofacial Orthopedics, Journal of Oral and Maxillofacial Surgery, Journal of Orofacial Orthopedics, Clinical Oral Implants Research, Clinical Oral Investigations, Clinical Implant Dentistry and Related Research, European Journal of Orthodontics, The Angle Orthodontist, The International Journal of Oral & Maxillofacial Implants, and International Journal of Oral and Maxillofacial Surgery. Articles were included if they fulfilled the following criteria (Table 2): human clinical trial that evaluated either survival or success of orthodontic miniimplants placed in maxilla, mandible, and palate; at least 10 implants with a minimum follow-up of 6 months. However, articles were excluded if they had less than 10 implants, less than 6 months of follow-up, animal studies, review articles or case reports, and data combined with miniplates. Studies were also excluded if the implants were used for any other purpose beside orthodontic anchorage. Potential articles were independently reviewed in fulltext by 2 examiners (J.C.R. and F.S.). The final decision on the included articles was made with mutual agreements of the 2 examiners (Table 3). Understanding that mini-implants might perform differently depending on anatomic locations, the weighed mean survival rates with 95% confidence interval (CI) were calculated separately for: (1) the mini-implants that were placed at the interdental space of the maxilla and mandible and (2) those placed in the palate. The number of fixtures and survival rate from each included article were retrieved and inserted into the statistical software (Comprehensive Meta-analysis). The random model was selected for the meta-analyses. The survival rate of each study and the weighed mean survival rate were computed into a forest plot.
RESULTS The screening process was represented in Figure 1. The initial
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screening yielded a total of 847 articles. After initial screening of their titles and abstracts, 801 articles were excluded because they did not meet the inclusion criteria, and 46 articles were further evaluated in full text (Table 4). After a final revision, 29 articles were selected for this systematic review. Interexaminer agreement in article selection was 0.9. The reasons of exclusion after full-text evaluation included: insufficient follow-up,14–18 data combined or not well differentiated with miniplates,19–22 review articles or case reports,23–28 and non-human study.29 For a more detailed explanation, please refer to Table 5.
Fig. 1. Flow chart of the screening process.
Table 4. Summary of Implants Placed in the Palate (Group 2) Reference No. 43 44 45 38 31 46 58 47 48 41 32 11
Author
Study Design
No Pts
Arcuri et al, 2007 Asscherick et al, 2010 Benson et al, 2007 Borsos et al, 2008 Feldmann et al, 2008 Göllner et al, 2009 Jung et al, 201057 Jung et al, 2011a Jung et al, 2011b Männchen et al, 2008 Sandler et al, 2008 Wehrbein et al, 2009 Total
Retrospective Prospective RCT Prospective RCT Retrospective RCT Retrospective RCT Prospective RCT Prospective
14 33 25 16 30 76 41 239 41 70 26 22 636
Mean Follow-up Period (mo) 22 22 N/A Until treatment Until treatment Until treatment 6 33 6 19 26 21
No Imp
Length (mm)
Width (mm)
16 34 25 16 30 76 41 239 41 70 26 22 633
6.0–4.0 4.0–6.0 6.0 4.0 4.0 4.0–6.0 4.2 4.0–4.2–6.0 4.0–6.0 4.0–6.0 4.0 4.0–6.0
3.3 3.3–4.0 N/A 4.1 3.3 3.3 4.1 3.3–4.0–4.1 4.1–4.2 3.3–4.0 3.3–4.0 N/A
Pts indicates patients; No, number; Imp, implant; Max, maxillary; Mand, mandibular; N/S, not specified.
Table 5. Excluded Articles Reason for Exclusion
Excluded Article
Insufficient follow-up
Chaddad et al, 200814 Crismani et al, 200615 Jackson et al, 200816 Schaltze et al, 200917 Wiechmann, 200718 Chen et al, 200719 Chen et al, 200820 Cheng, 200421 Yao, 200822 Hoste et al, 200824 Li et al, 201125 McGuire et al, 200626 Motoyoshi et al, 201127 Ohashi et al, 200628 Wehrbein et al, 200723 Migliorati et al, 201229
Data combined with miniplates
Review articles or case reports
Non-human study
The meta-analysis showed that the weighted mean survival rate of maxillary and mandibular implants is 87.8% (95% CI) (Fig. 2), whereas a survival rate of 93.8% (95% CI) was found for palatal implants (Fig. 3). Further analysis was performed for the failures occurred and the reasons of their occurrence. For mandibular and maxillary implants, 116 of 1056 implants failed, of which 78.45%, 19.83%, and 1.72% failed because of surgery-related, orthodontic-related, and patient-related reasons, respectively (Table 2). However, 620 palatal implants were analyzed and 36 of them failed. The reasons for their failures were 61.11%, 19.44%, and 19.44% for surgery-related, orthodonticrelated, and patient-related reasons, respectively.
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Fig. 2. A meta-analysis evaluating survival rates of orthodontic implants in maxilla and mandible.
Fig. 3. A meta-analysis evaluating survival rates of orthodontic implants in palate.
DISCUSSION As we focused our efforts in identifying the success rates of orthodontic mini-implants reported in the literature, we encountered several variation and opinions to this term. However, the most common label of success was a mini-implant that remained static, with no signs of inflammation, and that supported the orthodontic forces applied to the device throughout the entire length of the orthodontic treatment.30,31 Due to the fact that we focused our meta-analysis in the behavior of different devices that serve the same purpose, we inherited certain criteria that were mandatory for each system to be considered successful. Osseointegration, for example, was an absolute factor that needed to be present when we analyzed the data from palatal implants and certain systems that were inserted into the mandible and maxilla and relied on it31,32; nevertheless, it was not taken into consideration to judge the behavior of
systems that performed on mechanical retention or stability.33–35 For these reasons, we had to dissect each article revised to be certain that there were no overlapping definitions of success/ survival, and although some articles divided their success rates into other variables, including location, type of movement, time of loading, effectiveness, and overall patient satisfaction, we found that differences in the final outcomes were not statistically significant among them.36,37 We included success rates from articles where the authors clearly stated that the devices used as orthodontic anchors were effective for the use of reciprocal forces throughout the entire length of the treatment, no signs of severe inflammation or suppuration, they were osseointegrated when needed or they had no mobility, and that they were clinically effective. It has also been shown in the literature the different causes why an implant may fail, including but not limited to patients and surgery-related
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factors. Nonetheless, due to the purpose of this specific type of implants used as anchorage devices, orthodontics parameters, such as the force applied, the loading time, and the position in the arches, may also play a role in its failures. In this article, 3 different categories were created to group the reasons why implant fails. These categories are surgical, orthodontic, and patient-related factors. Implants failed due to surgical factors are attributed by the following: poor surgical technique, lack of implant primary stability, implants lost due to reverse torque, implants failed during healing without any other contributing factor, implants placed in wrong anatomical position, and implants with unfavorable characteristics that lead to implant loosening, and finally, implants that failed to osseointegrate. However, orthodontic factors included loss after initial loading, when the implant was unable to resist reciprocal forces and when they were lost during orthodontic load. Finally, patients factor attributed to failures related to inadequate hygiene, patients who reported tongue thrusting or brushing the area, persistent inflammation, and patient dropouts. Yet another variable that may alter success rates is location, most commonly mini-implants are placed in the vestibular areas of the posterior jaws or in the midpalatal suture.2,38 In miniimplants placed in the mid palatal suture, we found success rates of 93%, which indicated a very positive outcome. In the case of mini-implants placed in the mandible and maxilla, there was no evident consensus for a healing period, and in some cases, the authors loaded immediately, and in others, they waited between 1 and 12 weeks, with no statistical significance in the outcomes.39–41 With regards to loading time, no clear guideline is available in the literature. It will depend on the type of implant, the material, and the final purpose of the device.12 In clinical situations were primary stability and bone-to-implant contact is adequate, the clinician may take the risk of indicating immediate or early loading. In several cases, it was reported that at the time of insertion and up to 1 week after placement, higher primary stability and insertion torque were achieved in the mandible. However, after a healing
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period of 3 weeks in average, the stability and success rates were slightly higher in the maxilla compared with mandible, and the difference was even more pronounced past the 5- to 7-week period.34–42 This article provides updated information on survival rates of implant used for orthodontic anchorage and an analysis of the failures and their reasons, which for the best of our knowledge, has never been studied before.
CONCLUSION After analyzing a total of 29 articles,11,31,32,41,43–48 divided by location, 12 articles evaluated palatal implants11,31,32,38,41,43–48 while 17 aranalyzed ticles13,30,33–36,39,40,49–57 maxillary and mandibular implants. Available evidence showed miniimplants as a reliable treatment option with high survival rates regardless of the position in the arch; nonetheless, higher survival rate was associated with implants placed in the palate (93.8%) than in other locations (87.8%). As regards to the occurrence of the failures, 78.45% were surgery related, makingmini-implants for orthodontic anchorage, a technique sensitive procedure with a steep learning curve.
DISCLOSURE The authors claim to have no financial interests, either directly or indirectly, in the products or information listed in the article. This article was partially supported by the University of Michigan Periodontal Graduate Student Research Fund.
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