Introduction
Orthodontic mini-implants are a widely accepted treatment modality in orthodontics; however, the failure rate is moderately high. Surface roughening is the golden standard in conventional oral implantology, and this may prove beneficial for orthodontic mini-implants as well. The objective of this systematic review is to assess the effect of surface roughening on the success rate of orthodontic mini-implants in both adolescent and adult patients undergoing orthodontic treatment.
Methods
Randomized studies comparing the success of surface-roughened and smooth, machined-surface orthodontic mini-implants were included. A literature search was conducted for 6 electronic databases (Pubmed/Medline, Embase, Cochrane, CINAHL, Web of Science, and Scopus), Clinical trial registry ( https://www.clinicaltrials.gov ), and grey literature (Google Scholar). A manual search of the reference lists of included studies was performed. Two authors independently performed the screening, data extraction, risk of bias, and quality assessments. The risk of bias was assessed with the Cochrane risk-of-bias 2.0 Tool. Data were synthesized using a random effect model meta-analysis presented as a forest plot. The certainty in the body of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation tool.
Results
A total of 4226 unique records were screened, and 6 of these were included in the quantitative analysis. Four additional articles were selected for a secondary outcome. A total of 364 orthodontic mini-implants were included in the primary outcome analysis. There was no statistically significant effect of surface roughening on the success of orthodontic mini-implants (odds ratio = 0.63 favoring roughened orthodontic mini-implants; 95% confidence interval, 0.35-1.14). The secondary outcome (ie, the overall failure rate of roughened orthodontic mini-implants) was 6% based on studies with high heterogeneity. Limitations of this study were the risk of bias, study imprecision, and possible publication bias, leading to a very low certainty in the body of evidence.
Conclusions
There is very low-quality evidence that there is no statistically significant effect of surface roughening on the success of orthodontic mini-implants in humans. The overall failure rate of surface-roughened orthodontic mini-implants was 6%.
Funding
No funding was received for this review.
Registration
This study was preregistered in the Prospective Register of Systematic Reviews (CRD42022371830).
Highlights
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Surface roughening did not significantly affect orthodontic mini-implant success.
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The overall failure rate of roughened orthodontic mini-implants was 6%.
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The quality of evidence on this topic is very low.
Introduction
The use of orthodontic mini-implants (OMIs) is a widely accepted treatment modality in clinical orthodontics. OMIs have several potential benefits over traditional anchorage methods, including a more effective anchorage and less reliance on patient cooperation. Failure rates reported in the literature are moderately high, with an overall failure rate between 11.5% and 15.9%. These rates vary for different insertion sites, with OMIs in the palate being more successful than OMIs in interradicular insertion sites. Multiple predictors for OMI failure have previously been systematically reviewed, including heavy smoking, placement in the mandible, and root contact. Age, gingival type at the insertion site, and implant dimensions have shown less correlation, as several studies have presented conflicting results. , The high failure rate and associated risk factors may discourage routine use of OMIs.
Primary stability of OMIs is provided by mechanical retention in bone after implantation. Secondary stability is then attained on adequate biologic responses leading to an effective osseointegration process and increases over time, provided that factors such as implant surface, biocompatibility, and loading conditions are favorable. , Because mechanical primary stability is already decreasing before biologic secondary stability is fully attained, a dip in total implant stability, known as the lag phase, often occurs. In an attempt to maintain primary stability over a longer period and, at the same time, to enhance secondary stability, the roughening of implant surfaces has emerged as the golden standard in conventional oral implantology. Clinical research has shown that surface roughening techniques such as sandblasting and/or acid etching lead to improved osseointegration, enhancing secondary stability compared with unmodified machined surfaces. Several invasive and noninvasive techniques are available to measure implant stability in conventional oral implantology. However, assessing OMI stability remains problematic, and various assessment methods show only moderate agreement. Because of the great heterogeneity in these objective implant stability measurement techniques, clinical outcome measures such as failure rates are of invaluable interest.
The success of surface roughening in conventional oral implantology suggests its promise for application with OMIs. If implant stability is enhanced similarly for OMIs and conventional dental implants, it is straightforward to assume a positive effect of surface roughening on OMI success. A recent systematic review of animal experimental data investigated the effects of surface roughening of OMIs. The authors reported significantly higher removal torque values for surface-roughened OMIs compared with that of machined-surface controls. These data consequently prove that surface roughening of OMIs increases secondary stability. However, these promising results should be interpreted with caution, as extrapolation of animal experimental data to daily clinical practice shows poor predictability, which is the rationale for our study. This systematic review aims to assess the effect of surface roughening on the success rate of orthodontic mini-implants in humans.
Material and methods
Protocol and registration
The protocol for this systematic review was registered in PROSPERO (CRD42022371830). The Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines were followed in the reporting of this systematic review.
Eligibility criteria
The PICO (patient problem or population, intervention, comparison, and outcomes) format was applied to define the following inclusion criteria: (1) population (P): adolescent or adult patients undergoing treatment with OMIs; (2) intervention (I): surface-treated OMIs with increased roughness; (3) comparison (C): untreated, machined-surface OMIs; and (4) outcome (O): success.
Success was defined as the OMI being present and loadable (ie, with clinical mobility <1 mm) at the end of mini-implant treatment. A secondary outcome was defined as the overall failure rate of only the surface-roughened group. Only (split-mouth) randomized controlled trials (RCTs) were included for the primary outcome. For the secondary outcome, prospective nonrandomized studies with or without controls were also included.
The following exclusion criteria were defined: (1) animal, cadaver, or in vitro research; (2) review articles, case reports, or case series; (3) studies that included patients with syndromes involving the craniofacial area; (4) studies that included patients with periodontal disease; or (5) studies with multiple surface characteristics within the same orthodontic mini-implant (eg, split screw design).
Information sources and search strategy
A comprehensive search up until July 10, 2023, was performed using electronic databases: PubMed/Medline, Embase, Cochrane, CINAHL, Web of Science, and Scopus. Combinations of keywords, appropriate truncations, and filters were used without date or language restriction, resulting in search strategies provided in Supplementary Table I . A grey literature search was conducted using Google Scholar. Combinations of short search strings from parts of the developed search strategies were used as entry terms, and the first 50 result pages were reviewed. The clinical trials registry ( https://www.clinicaltrials.gov ) was screened for trials. In addition, references of included studies were manually searched to identify any missing studies.
Study selection and data collection
All studies were imported into EndNote (version 20, Clarivate, Philadelphia, Pa) and scanned for duplicates. To ensure blinding during the selection process, Rayyan web-based software ( http://rayyan.qcri.org ) was used. Two authors (M.C.T.vdB. and J.W.M.H.) independently screened titles and abstracts to exclude studies that did not meet the inclusion criteria. A full-text analysis of the remaining studies was independently performed by the same reviewers. Any disagreements were resolved by discussion. Data extraction was independently performed by 2 authors (M.C.T.vdB. and J.W.M.H.). All studies were screened for general study and design characteristics. The extracted data consisted of surgical procedures, implant dimensions, treatment duration, type of surface modification, information on missing data, and outcome data relating to success. For the primary outcome, all odds ratios (ORs) for OMI failure were extracted or manually calculated on the basis of paired data analysis when possible. When only analyses ignoring the pairing in the data were reported or when data were incomplete or unclear, the first and last authors were contacted weekly (up to 3 times) by e-mail. If the authors did not respond, unpaired data were extracted. For the secondary outcome, the total number of surface-treated mini-implants, the incidence of failure, and information about missing or excluded units were extracted.
Risk of bias and quality assessment
Two authors (M.C.T.vdB. and J.W.M.H.) independently assessed the risk of bias for each (split-mouth) randomized controlled trial using the Cochrane risk-of-bias 2.0 tool. The domains of the randomization process, deviations from the intended intervention, missing outcome data, measurement of the outcome, and selection of the reported result were scored as either low risk of bias, some concerns, or high risk of bias. An overall risk-of-bias judgment was given on the basis of these 5 domains.
The same authors independently assessed study quality for each study included for the secondary outcome using the National Institutes of Health quality assessment tool. The tool consists of 14 yes or no questions; of which, 5 were not applicable to our included studies. Items answered with the following responses: no, cannot determine, or not reported were indicative of potential quality issues, and a rationale was provided when authors felt there was indeed an effect on study quality. A judgment of overall quality was then given as poor, fair, or good.
Any disagreements in determining the risk of bias and quality assessment were resolved by discussion.
Data synthesis
Statistical analysis and the creation of plots were carried out using the R software (version 4.1.3; R Core Team, Vienna, Austria). A meta-analysis was conducted for the primary outcome by pooling ORs with corresponding 95% confidence intervals (CIs) for OMI failure. Heterogeneity was evaluated by inspecting study characteristics and I 2 statistics. A fixed effects model was chosen when no serious heterogeneity was suspected. A random intercept logistic regression model was chosen for all other analyses. Because of the underreporting of paired data analyses, the primary data synthesis was performed using unpaired data for all included studies. A sensitivity analysis was performed to investigate the robustness of the results by excluding high risk of bias studies from the meta-analysis. An additional sensitivity analysis was planned using the level of pairing of studies reporting paired data analyses. Furthermore, the overall failure rate for surface-treated mini-implants with increased roughness was calculated by pooling the reported proportions of failures. Because of statistical heterogeneity within the results of the studies included in the secondary outcome, a random effects model was chosen.
For all analyses, 95% CIs were reported. Publication bias was planned to be investigated by visual inspection of funnel plots if >10 studies were included. The certainty in the body of evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool.
Results
Study selection
The electronic database search resulted in a total of 6763 articles. Of these, 1815 were identified in PubMed, 1296 in Embase, 124 in Cochrane, 86 in CINAHL, 1213 in Web of Science, 1713 in Scopus, 16 in the clinical trials registry, and 500 in Google Scholar. No additional results were obtained by manual search of reference lists. After removing duplicates, a total of 4226 articles remained. After screening of titles and abstracts, 26 articles were selected for full-text analysis. Of these, 16 were excluded on the basis of the eligibility criteria. A list of excluded articles and the justification can be found in Supplementary Table II . The 10 remaining articles were included for the secondary outcome (ie, overall failure rate analysis of surface-treated OMIs). , , Finally, 4 of these articles were excluded from the primary outcome analysis on the basis of the study design. This resulted in a total of 6 articles included for quantitative synthesis of the primary outcome ( Fig 1 ). , ,
Study characteristics
Characteristics of the included studies and their respective OMI protocols are described in detail in Tables I and II . All but 1 study reported that sex included more females than males. OMIs were mostly used in conjunction with fixed appliances in a variety of clinical situations, including en masse retraction, total arch distalization, or posterior intrusion. OMI surface treatments were either large grit sandblasting and acid etching (SLA), acid etching (AE), or anodization. The planned observation period was until the end of treatment for most studies, whereas 3 studies used 6 months, 9-12 months, or until the end of loading. Surgical protocol, implant dimensions, loading protocol, and applied force differed between studies. Of the 6 included split-mouth RCTs, 5 directly reported on OMI success as defined in this study, and 1 reported only whether implants were lost.
| Study | Design | Orthodontic treatment | End of observation | No. of patients (M/F) | |
|---|---|---|---|---|---|
| Primary and secondary outcome | Bratu 2014 | Split-mouth RCT | Various clinical situations | End of treatment | 20 (20/0) |
| Hammad 2017 | Split-mouth RCT | En masse retraction of maxillary anterior 6 | 9-12 mo | 27 (0/27) | |
| Manni 2022 | Split-mouth RCT | Prevention of mandibular incisor flaring during Herbst therapy | End of Herbst treatment | 39 (16/23) | |
| Moghaddam 2021 | Split-mouth RCT | En masse retraction of maxillary anterior 6 | End of treatment | 31 (8/23) | |
| Park 2019 | Split-mouth RCT | En masse retraction, total arch distilization, maxillary posterior intrusion | End of treatment | 40 (13/27) | |
| Ravi 2023 | Split-mouth RCT | Premolar extraction | End of treatment | 9 (NR) | |
| Secondary outcome only | Calderón 2011 | NRSI | Space closure | 6 mo | 13 (6/7) |
| Chaddad 2008 | Split-mouth quasi-RCT | NR | End of treatment | 10 (NR) | |
| Kim 2008 | NRSI | Various clinical situations | End of loading or later | 37 (9/28) | |
| Lee 2010 | NRSI | Premolar extraction | End of treatment | 141 (NR) |
| Study | Surface treatment | Incision or raised flap | Predrilling | Length (mm) | Diameter (mm) | Loading protocol | Insertion site | |
|---|---|---|---|---|---|---|---|---|
| Primary and secondary outcome | Bratu 2014 | SLA | Yes | No | 10.0 | 1.6 | Immediate: 250 g of force | Mn, various locations |
| Hammad 2017 | AN | No | No | 8.0 | 1.8 | Delayed 2 wk: 200 g of force | Mx, between M1 and P2 | |
| Manni 2022 | AE | NR | No | 8.0 | 1.2 or 1.4 | Immediate: 150 g of force | Mn, between M1 and P2 or P2 and P1 | |
| Moghaddam 2021 | SLA | No | No | 10.0 | 1.6 | Delayed 6 wk: 250 g of force | Mx, between M1 and P2 | |
| Park 2019 | AE | NR | No | 6.0 | 1.6 | Delayed 4 wk: 100-200 g of force | Mx and Mn, mainly between M1 and P2 | |
| Ravi 2023 | SLA | NR | NR | 8.0 | 2.0 | Delayed 4 wk: 150 g of force | Mx and Mn, between M1 and P2 | |
| Secondary outcome only | Calderón 2011 | SLA | NR | NR | 6.0, 8.0, or 10.0 | NR | Delayed 4 wk: 150 g of force | Mx and Mn, various locations |
| Chaddad 2008 | SLA | No | Yes | 8.5, 9.5, or 10.5 | 1.8 | Immediate: 50-100 g of force; after 2 wk: 250 g of force | Mx and Mn, posterior | |
| Kim 2008 | SLA | Tissue punch | Yes | 8.5 | 1.8 | Delayed 4 wk: 200-450 g of force | Mx, between M1 and P2 | |
| Lee 2010 | SLA | Yes | Yes | 8.5 | 1.8 | Delayed 8 wk: force: NR | Mx, between M1 and P2 |
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