Where You Place, How You Load: A Scoping Review of the Determinants of Orthodontic Mini-Implant Success

Abstract

Objective: This scoping review identifies and analyzes factors influencing the effectiveness of orthodontic mini-implants and temporary anchorage devices in orthodontic treatments, including clinical applications, success rates, and associated complications. Methods: A systematic search was conducted across EBSCOhost, Ovid Medline, PubMed, Scopus, and Web of Science for peer-reviewed, English-language human studies published between 2013 and 2023 that examined determinants of mini-implants/temporary anchorage devices success or failure. Inclusion/exclusion criteria were predefined, and screening was performed in duplicate. Thirty-six studies met criteria. Results: Placement site and peri-implant oral hygiene/soft-tissue health were the most consistent contributors to success. Optimal sites varied by indication, supporting individualized planning. Greater implant length generally improved stability but must be balanced against anatomic limits and patient comfort. Temporary anchorage devices supported diverse movements (e.g., molar distalization; posterior/anterior intrusion). Findings for loading protocol, patient age, bone quality, and operator experience were mixed, reflecting heterogeneity in primary stability, force magnitude/vector, and outcome definitions. Conclusion: Mini-implants/temporary anchorage devices success is multifactorial. Emphasis on site-specific selection, hygiene management, appropriate implant dimensions, and patient-specific modifiers can optimize outcomes and minimize complications. Future studies should report standardized outcomes and explicit loading parameters to enable granular analyses of movement-specific biomechanics and evidence-based decision-making.

1. Introduction

The adoption of Temporary Anchorage Devices (TADs), also known as orthodontic mini-implants (MIs), has transformed contemporary orthodontics by providing a versatile, efficient form of anchorage that enhances the precision and control of tooth movement, particularly in complex malocclusions [1,2,3]. Beyond enabling maximum anchorage in extraction and non-extraction mechanics, TADs reduce unwanted reciprocal movements and anchorage loss, improving the predictability of en-masse retraction, vertical control in open-bite therapy, and correction of transverse discrepancies [3]. As use expands, clearly defining indications and the determinants of success are essential, alongside patient-reported outcomes (comfort, hygiene burden) and risk profiles to support shared decision-making.

Conventional appliances (e.g., braces, archwires, and elastics) remain effective but can struggle in severe crowding, unfavorable rotations/impactions, skeletal discrepancies, and open bites [3]. Their performance often depends on patient compliance and tooth-borne or extraoral anchorage, which may be variable or unstable (e.g., headgear wear time, and elastics causing incisor proclination or posterior extrusion) [3]. TADs address these limits by providing temporary, skeletal anchorage that is independent of patient compliance and existing dentition [1,3]. This innovation supports more controlled, efficient biomechanics [4,5]. Consequently, clinicians can apply force systems that are decoupled from reactive dental units, allowing lighter, more continuous forces and shorter biomechanics chains.

TADs are small-diameter implants [6], typically composed of biocompatible materials like titanium [7], which are temporarily inserted into alveolar or basal bone to serve as anchorage points. Unlike traditional reliance on adjacent teeth for support, TADs offer a direct, anchorage-stable approach to applying orthodontic forces [8]. This innovation broadens the indications for treatment, ranging from molar distalization, protraction, intrusion, and extrusion to facilitating more predictable control of skeletal structures. Common placement sites include interradicular areas, the anterior or paramedian palate, the infrazygomatic crest, and the mandibular buccal shelf, each chosen to balance cortical thickness, soft-tissue quality, and proximity to roots and vital structures. Consequently, TADs have expanded the orthodontic armamentarium and advanced personalized treatment strategies, allowing tailored and precise treatment plans that address the unique needs of each patient. Contemporary workflows may incorporate digital planning with CBCT, virtual root mapping, and insertion guides to enhance safety and accuracy, and many systems support immediate or early loading when primary stability is sufficient.

The clinical success reflects multiple determinants [9], including placement techniques and site, patient age, bone quality/thickness, soft-tissue health, biomechanics, and the host response can shape the outcomes of TAD-assisted orthodontic treatments. Primary stability is influenced by screw design (self-drilling vs. self-tapping), diameter/length, insertion torque, and the presence of keratinized tissue at the transmucosal interface. Attention to hygiene protocols, soft-tissue management (punch vs. flap), and careful assessment of anatomic limitations (sinus floor, nasal cavity, roots, neurovascular bundles) mitigates risk. Standardized definitions of “success” and “failure” (e.g., time-to-mobility, survival to treatment completion) are needed to harmonize outcomes across studies.

This scoping review synthesizes recent evidence on the use of TADs/MIs in orthodontics and the determinants of success and failure, summarizing indications, benefits, complications, and evidence gaps. Specifically, we map clinical indications to preferred sites and device characteristics, compare immediate versus delayed loading approaches, and describe common complications with prevention and management strategies.

2. Methods

This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines [10] and the Joanna Briggs Institute guidance for scoping reviews [11] to analyze literature related to TAD and/or MIs in orthodontic treatment. The primary objective was to synthesize articles focusing on human-based studies published between 2013 and 2023. The review specifically addressed determinants of success and causes of failure of orthodontic MIs.

2.1. Search Strategy and Eligibility Criteria

We conducted a comprehensive scoping review to identify research articles published between 2013 and 2023, focusing on the factors influencing the success or failure of TADs or orthodontic MIs. The inclusion criteria consisted of peer-reviewed articles on human-based studies written in English, with a specific focus on TADs or MIs and their success or failure factors. Articles excluded from the review were those published before 2013, non-peer-reviewed articles, non-human studies, studies not addressing TADs or MIs, articles not investigating success or failure factors, non-English articles, review articles, and case reports/case series. The detailed inclusion and exclusion criteria are summarized in

Table 1. Inclusion and exclusion criteria.

Inclusion Criteria	Exclusion Criteria
- Articles published between 2013 and 2023 - Published peer-reviewed articles - Human-based studies - Focus on temporary anchorage devices/mini-implants - Investigate factors that lead to the success or failure of TADs - English-language articles	- Unpublished or non peer-reviewed - Review articles - Commentaries - Opinions - Case studies

.

These criteria were established to ensure that the review concentrated on recent, high-quality studies pertinent to the factors affecting the success or failure of TADs in orthodontics. Limiting the search to articles from the past ten years ensured that the most current and relevant information was included, reflecting the latest advancements and trends in the field. By requiring peer-reviewed articles, we ensured that the selected studies adhered to rigorous research standards, ensuring reliability and validity of the findings. Restricting the review to English-language articles helped maintain consistency and accuracy in interpretation, avoiding potential translation errors that could compromise the integrity of the analysis.

The focus on human-based studies was essential to ensure the direct applicability and relevance of the findings to clinical orthodontic practice, thereby enhancing the practical implications of the review. Furthermore, the deliberate exclusion of review articles and case studies was aimed at promoting the synthesis of original data and findings from larger-scale research. This approach ensured that the review added unique value to the existing body of knowledge by highlighting empirical research and perspectives, ultimately contributing to a more comprehensive and up-to-date understanding of the factors that influence the success or failure of TADs in orthodontic treatment. The primary determinants were placement/site and local bone quality, peri-implant soft-tissue health/oral hygiene, device geometry (length/diameter/thread), loading parameters (timing, magnitude, vector); host modifiers (age/skeletal maturity, smoking, and periodontal status). The primary outcomes were success (survival to treatment completion, or absence of mobility/inflammation at prespecified timepoints) and failure (mobility, loss of stability, removal). By specifically concentrating on articles investigating the success or failure factors of TADs, this review aimed to provide valuable insights into the optimal use of these devices in orthodontic practice, potentially improving treatment outcomes and patient care.

2.2. Database Search and Terms

To identify relevant articles for this review, we conducted a comprehensive search across 5 databases, including EBSCOhost, Ovid Medline, PubMed, Scopus, and the Web of Science. Our search strategy was carefully designed to capture the full scope of research on TADs and MIs in orthodontics.

The search terms were strategically chosen to ensure broad coverage while maintaining specificity to our research focus. We used a combination of MeSH terms and free-text keywords related to orthodontics and MIs. The core search string included: (“Orthodontics” [Mesh] OR “Orthodontics, Corrective” [Mesh] OR “Orthodontics, Interceptive” [Mesh]) AND (“Mini implants” [tiab] OR “mini-implants” [tiab] OR “orthodontic mini-implants” [tiab] OR “orthodontic mini-implants” [tiab] OR “temporary anchorage device” [tiab]). This search strategy was tailored to each database to account for differences in indexing and search capabilities. In databases without MeSH terms, we expanded our keyword list to include synonyms and related terms, ensuring comprehensive coverage, as shown in

Table 2. Databases and Search Strategies.

Databases and Search Date	Search Strategy & Filters	Results
Dentistry & Oral Sciences Source (EBSCOhost) https://web.p.ebscohost.com/ehost/search/advanced?vid=0&sid=cb491755-8714-4139-8948-384b93edcb90%40redis (accessed on 13 September 2023)	(((“Orthodontics”) OR (“Orthodontics, Corrective”) OR (“Corrective Orthodontics”) OR (“Orthodontics, Interceptive”) OR (“Interceptive Orthodontics”)) AND ((“men”) OR (“women”) OR (“patient”) OR (“female”) OR (“male”) OR (“subjects”) OR (“adult”) OR (“human”))) AND TI ((“Mini implants”) OR (“mini-implants”) OR (“orthodontic mini implants”) OR (“orthodontic mini-implants”) OR (“temporary anchorage device”)) OR AB ((“Mini implants”) OR (“mini-implants”) OR (“orthodontic mini implants”) OR (“orthodontic mini-implants”) OR (“temporary anchorage device”)) Filters: 2013–2023 & English	125
Ovid Medline https://ovidsp.dc2.ovid.com/ovid-new-a/ovidweb.cgi (accessed on 13 September 2023)	((Orthodontics or Orthodontics, Corrective or Corrective Orthodontics or Orthodontics, Interceptive or Interceptive Orthodontics) and (men or women or patient or female or male or subjects or adult or human)).af. and (Mini implants or mini-implants or orthodontic mini implants or orthodontic mini-implants or temporary anchorage device).ab. and (Mini implants or mini-implants or orthodontic mini implants or orthodontic mini-implants or temporary anchorage device).ti. Filters: 2013–2023	58
PubMed https://pubmed.ncbi.nlm.nih.gov/?otool=nvujrolib (accessed on 13 September 2023)	(“Orthodontics” [Mesh] OR “Orthodontics, Corrective” [Mesh] OR “Orthodontics, Interceptive” [Mesh]) AND (“Mini implants” [tiab] OR “mini-implants” [tiab] OR “orthodontic mini implants” [tiab] OR “orthodontic mini-implants” [tiab] OR “temporary anchorage device” [tiab]) Filters: Human, English, & 2013–2023	284
Scopus https://www.scopus.com/search/form.uri?display=basic#basic (accessed on 13 September 2023)	(TITLE-ABS-KEY (((“Orthodontics”) OR (“Orthodontics, Corrective”) OR (“Corrective Orthodontics”) OR (“Orthodontics, Interceptive”) OR (“Interceptive Orthodontics”)) AND ((“Mini implants”) OR (“mini-implants”) OR (“orthodontic mini implants”) OR (“orthodontic mini-implants”) OR (“temporary anchorage device”))) AND ALL (((“men”) OR (“women”) OR (“patient”) OR (“female”) OR (“male”) OR (“subjects”) OR (“adult”) OR (“human”))) AND NOT ALL ((“animal models”))) AND (LIMIT-TO (SUBJAREA, “DENT”)) AND (LIMIT-TO (LANGUAGE, “English”)) AND (LIMIT-TO (EXACTKEYWORD, “Human”) OR LIMIT-TO (EXACTKEYWORD, “Humans”) OR LIMIT-TO (EXACTKEYWORD, “Orthodontic Anchorage Procedures”)) Filters: Human, English, & 2013–2023	155
Web of Science https://www.webofscience.com/wos/woscc/basic-search (accessed on 13 September 2023)	ALL = ((“Orthodontics”) OR (“Orthodontics, Corrective”) OR (“Corrective Orthodontics”) OR (“Orthodontics, Interceptive”) OR (“Interceptive Orthodontics”)) AND TS = ((“Mini implants”) OR (“mini-implants”) OR (“orthodontic mini implants”) OR (“orthodontic mini-implants”) OR (“temporary anchorage device”)) AND ALL = ((“men”) OR (“women”) OR (“patient”) OR (“female”) OR (“male”) OR (“subjects”) OR (“adult”) OR (“human”)) NOT ALL = ((“animal models”)) Filters: Human, English, & 2013–2023	130

.

2.3. Selection Process

Screening was performed in duplicate by three independent reviewers (J.G., A.H., and S.L.) using a pilot-tested decision guide. Conflicts at title/abstract and full-text stages were logged and resolved in scheduled consensus meetings. When consensus was not reached, a senior reviewer (M.H. or A.M.) provided adjudication. In total, six title/abstract records and five full-text articles required consensus; senior adjudication occurred in three instances. These steps reduced the risk of selection bias and ensured reproducibility. We extracted key data points in full-text articles, including study design, sample characteristics, TAD/MI type, placement protocol, success rates, and factors influencing outcomes. To maintain data integrity, we used double, independent data extraction, with two team members extracting from each article and cross-verifying results.

2.4. Quality Assurance and Synthesis

To enhance quality control, senior team members (M.H. and A.M.) performed random spot-checks, and the team held calibration meetings to address challenging articles or conflicting interpretations. Data synthesis combined descriptive statistics of success and failure patterns with thematic analysis of determinants (e.g., placement technique and site, patient-specific variables, biomechanics, post-insertion care). We also conducted a gap analysis to identify under-studied areas and inform future research priorities.

Because outcome definitions and follow-up windows varied widely, we used a prespecified synthesis strategy. We (1) classified outcomes into two families—survival-to-treatment-completion (STTC) vs. clinical stability at fixed timepoints; (2) mapped determinants to mechanistic domains (bone quality/site, primary stability, load parameters, host factors); (3) summarized direction of effect using structured vote-counting; and (4) performed sensitivity narrations by outcome family and typical follow-up window. Where reported, we extracted insertion torque and approximate force levels to contextualize “immediate” vs. “delayed” loading.

3. Results

3.1. Article Selection

Figure 1 provides a PRISMA-ScR-style flow diagram of the article selection process. Initially, 752 records were identified. After duplicate removal, 518 unique articles remained and underwent title/abstract screening against predefined eligibility criteria. Three hundred thirteen (313) articles were retained for full-text review. Following in-depth assessment for relevance and methodological suitability, 36 studies were included in the final synthesis.

3.2. Study Designs

The review encompassed a range of study designs, with retrospective designs predominating. Of the 36 studies: retrospective (n = 11; 30.6%), retrospective cohort (n = 4; 11.1%), cohort (n = 3; 8.3%), prospective (n = 3; 8.3%), cross-sectional (n = 2; 5.6%), longitudinal (n = 2; 5.6%), prospective clinical trial (n = 2; 5.6%), randomized clinical trial (n = 3; 8.3%), retrospective cross-sectional (n = 2; 5.6%), case–control (n = 1; 2.8%), longitudinal prospective (n = 1; 2.8%), prospective cohort (n = 1; 2.8%), and randomized case–control (n = 1; 2.8%). (

Table 3. Study design of the reviewed articles.

Study Design	Count (%)
Retrospective	11 (30.6%)
Retrospective Cohort	4 (11.1%)
Cohort	3 (8.3%)
Prospective	3 (8.3%)
Cross-sectional	2 (5.6%)
Longitudinal	2 (5.6%)
Prospective Clinical Trial	2 (5.6%)
Randomized Clinical Trial	3 (8.3%)
Retrospective Cross-sectional	2 (5.6%)
Case–control	1 (2.8%)
Longitudinal Prospective	1 (2.8%)
Prospective Cohort	1 (2.8%)
Randomized Case–control	1 (2.8%)

).

3.3. Factors Leading to MI/TAD Success

A comprehensive review of 36 articles revealed that placement location and peri-implant tissue health (oral hygiene/inflammation) were the most prevalent factors contributing to the success of MIs and temporary anchorage devices during orthodontic treatment. Placement location was identified as a significant factor in 52.8% (19/36) of the studies analyzed [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]. Within this subset, 26.32% (5/19) reported higher success rates for maxillary placement [15,19,21,22,28], while 10.53% (2/19) favored mandibular placement [12,20]. Palatal placement was deemed superior to buccal placement in 21.05% (4/19) of the location-focused studies [14,25,27,31], with one study indicating lingual placement as the least favorable option [22]. Interestingly, 10.53% (2/19) of these studies reported higher success rates for left-side placement [26,29], while 5.26% (1/19) favored the right side [13]. Bone quality at the insertion site emerged as a critical factor, with 15.79% (3/19) of the location-focused studies emphasizing the importance of bone density, thickness, and volume for increased success rates [16,17,23]. These studies investigated various placement locations, including the infrazygomatic crest, the area between the first and second molars in the maxilla, and the median anterior palate. Additionally, oral hygiene was identified as a contributing factor in 36.1% (13/36) of the total studies reviewed, with all 13 studies correlating good oral hygiene and/or lack of inflammation with higher success rates (Table 4) [13,14,15,19,23,25,26,29,32,33,34,35,36].

Age was considered a factor in 19.4% (7/36) of the studies [13,19,24,35,37,38,39], with 71.43% (5/7) reporting higher success rates in older age groups [19,24,35,37,38], while 28.57% (2/7) favored younger patients for MI success [13,39]. The length of TADs and MIs was addressed in 19.4% (7/36) of the studies, with unanimous agreement that increased length correlates with improved success rates [12,13,21,30,33,40,41]. Loading protocols as a success factor was mentioned in 16.7% (6/36) of the studies [13,15,20,22,35,37], yielding conflicting results. Equal numbers of studies (33.33% each) supported immediate loading [35,37] and delayed loading for higher success rates [20,22], while the remaining 33.33% concluded that excess load led to higher failure rates [13,15]. Finally, 8.3% (3/36) of the studies indicated that MI success rates were higher when placed by experienced clinicians over resident surgeons (Table 4) [13,28,42]. Inconsistencies between “immediate” and “delayed” loading across studies can be explained by moderators—cortical thickness/site, insertion torque (proxy for primary stability), and the magnitude and vector of applied forces—rather than timing per se. Gentle initial forces with gradual escalation appear prudent when primary stability is borderline. Operator experience and workflow (freehand vs. guided) may narrow or widen the safety window for immediate loading.

Table 4. Summary of study findings.

Authors	Type of Orthodontic Movement	Placement Location	Success Factors
Abu et al. (2023) [30]	Numerous orthodontic tooth movements	Alveolar Ridge	Mini-implants were more likely to be successful with an increased length. Success rate increased when two mini-implants were splinted together.
Ağlarcı et al. (2016) [36]	Protrusion (maxillary & mandibular incisors) and Protraction of maxilla	Between mandibular lateral and canine teeth and maxillary second premolar and first molar.	Poor oral hygiene increased the rate of failure
Aly et al. (2018) [35]	Intrusion (molar) Retraction, Distalization (molar)	Maxillary and mandibular arches	The higher age group (>20 years), good oral hygiene, and immediate loading had a higher success rate
Arqub et al. (2021) [31]	Distalization, expansion, intrusion, or protraction	palatal mini-implants- paramedian or sutural, anteroposterior location (mesial to canine, canine to the second premolar, or distal to the second premolar) and buccal mini-implants (interradicular, infrazygomatic, or buccal shelf)	Palatal Implants: Lowest survival rate when used for and posterior segment protraction had the highest survival rate. Buccal Implants: Lower survival rate in males and when treating class III malocclusion. Treating class II malocclusion had the highest survival rate. Location—palatal shelf had the highest survival rate and the buccal shelf had the lowest survival rate
Azeem et al. (2019) [42]	Numerous orthodontic tooth movements	Maxillary tuberosity	Mini-implants placed by an operator with little experience was more likely to fail
Azeem et al. (2019) [29]	Uprighting (molar)	Placed in the buccal retromolar area, at the distobuccal surface of the second molars, between the anterior border of the mandibular ramus and the temporal crest	Mini-implants placed on the right side and when there was inflammation had a higher failure rate
Bearn & Alharbi (2015) [28]	Numerous orthodontic tooth movements	Various locations	Mini-implants were more successful when placed in the maxilla compared to the mandible and by clinicians with more experience
Bratu et al. (2014) [43]	Numerous orthodontic tooth movements	Various locations	Sandblasting and acid etching increased mini-implant success rate
Bungau et al. (2022) [27]	Intrusion (molar & incisor) and uprighting (molar)	Buccal maxillary area, the infrazygomatic region, palatal area, buccal mandibular area and lingual area	Mini-implants placed in the palatal region were more successful than when placed in the buccal mandibular region. The highest rejection rate occurred within the first month of placement.
Garg & Gupta (2015) [26]	Retraction (anterior teeth)	Second premolar and first molar (zygomatic buttress) in maxilla and mandible	More mobility observed on the right side than left side and when placed between the second premolar and first molar compared the first premolar and second premolar. Presence of inflammation decreased success.
Gurdan & Szalma (2018) [25]	Intrusion, distalization, uprighting	Various locations	Screw mobility was the most common in buccal placement and when used for intrusion. Inflammation due to poor oral hygiene decreased success rate
Haddad & Saadeh (2019) [24]	Numerous orthodontic tooth movements	Canines and first premolars, first and second premolars, second premolars and permanent first molars, or between first and second permanent molars	Success rate increased with increasing age, when placed between premolars or premolar and first molar, and with increasing DC distance
He et al. (2023) [41]	Distalization	Infrazygomatic crest	Success rate increases with increasing implant height
Hourfar et al. (2017) [39]	Protraction (molar) and distalization (molar)	Buccal premolar region on the maxilla and mandible or anterior palate	Patients between 6–20 years of age had a lower failure rate than patients over 30 years old. Individually placed mini-implants had lower success rates than dually placed mini-implants
Jia et al. (2018) [23]	Distalization	Infrazygomatic crest	Thickness of the cortical bone increased the success rate and inflammation decreased success
Kim et al. (2016) [44]	Numerous orthodontic tooth movements	Buccal alveolar bone in posterior regions	Failure rate can increase with the frequency of mini-implant reinsertions after failure. Sex, age, and arch may have no correlation with primary or recurrent OMI failure.
Lai & Chen (2014) [22]	Numerous orthodontic tooth movements	Various locations	Diameter and length, sex, age, and malocclusion type did not show any statistically significant difference in success rates. Success rate was reduced when placed in the jaw or lingually, inflammation, and applying force at two weeks.
Melo et al. (2016) [21]	Numerous orthodontic tooth movements	Various locations	No difference in loss of stability with age, sex, craniofacial pattern or smoking habit. Shorter mini-implants were more likely to fail than longer ones and mandibular mini-implants had a lower stability.
Migliorati et al. (2016) [20]	Retraction, intrusion, and extrusion	Maxillary and mandibular arches	Mandibular arch was more stable and delayed loading more stable
Migliorati et al. (2020) [45]	Distalization, intrusion, extrusion, mesialization	Maxillary and mandibular arches	No significant differences in success among the gender of the patients, age, miniscrew location (maxilla or mandible), miniscrew position (palatal/lingual or vestibular), baseline torque values and groups
Moeini et al. (2023) [19]	Retrusion and distalization (molar)	Buccal side of first molars	Higher failure rate in mandible, time of loading had no influence, infection present in failed MI, younger patients had higher probability of failure in the mandible, young females had highest failure rate
Mommaerts et al. (2014) [38]	Proclination, intrusion, uprighting molars	Maxillary and mandibular arches	Age, gender, time of loading, and location did not influence failure rate. Mini-implants were more likely to fail in female patients and in younger patients
Motoyoshi et al. (2016) [18]	Retraction (anterior teeth)	Maxillary buccal alveolar bone between second pre-molar and first molar	More likely to fail if in contact with the root
Nienkemper et al. (2014) [40]	Distalization (molars)	Maxillary and mandibular arches	Longer mini-implants were more likely to not fail
Nienkemper et al. (2020) [34]	Sagittal molar movement	Median of anterior palate	Stability decreased with decreased oral health. Sex had no impact on success rate
Nienkemper et al. (2020) [17]	Sagittal molar movement	Median of anterior palate	Length of mini-implant, age, sex, vertical bone height did not affect failure rate
Ravi et al. (2023) [46]	Retraction (maxillary & mandibular anterior teeth)	Various locations	Surface treatment using sandblasting and acid etching may improve the secondary stability of self-drilling orthodontic mini-implants.
Sarul et al. (2022) [33]	Distalization (anterior teeth)	Mandibular buccal shelf	Larger screws had a higher success rate. Inflammation decreased success rate
Shaikh et al. (2021) [16]	Distalization (maxillary molars) and intrusion (maxillary anterior teeth)	Between first and second molars	Bone density and volume increase success rate
Slabkovskaya et al. (2021) [47]	Intrusion (maxillary molars)	Between first and second molars	Age and gender had no effect on success rate
Sreenivasagan et al. (2021) [15]	Numerous orthodontic tooth movements	Anterior interradicular, buccal shelf, infrazygomatic, palatal, midline, posterior maxilla, and posterior mandible	Success rate increased with self-tapping, in maxilla, in the maxilla, and with sandblasting and etching. Poor home care, inflammation, and excessive load decreased success rate.
Sreenivasagan et al. (2021) [14]	Numerous orthodontic tooth movements	Anterior interradicular, buccal shelf, infrazygomatic, palatal, midline, posterior maxilla, and posterior mandible	Buccal shelf implants had the highest torque. Failure was due to implant breakage during insertion and soft tissue inflammation
Uribe et al. (2015) [13]	Numerous orthodontic tooth movements	Infrazygomatic crest	Age, gender, size of mini-implant, type of movement, oral hygiene, operator experience, and pilot hole was not a predictor of mini-implant success
Vicioni-Marques et al. (2022) [32]	Numerous orthodontic tooth movements	Maxillary and mandibular arches	Adequate clinical procedure, precise placement, and lack of inflammation increase success of mini-implant
Yao et al. (2015) [37]	Numerous orthodontic tooth movements	Maxillary and mandibular arches	Sex, malocclusion type, bone density, inflammation had no effect on failure. Patients over 35 years and immediate loading were more likely to be successful
Yi Lin et al. (2015) [12]	Numerous orthodontic tooth movements	Maxillary and mandibular arches and palate	No patient related factors affected success rate, but the longer mini-screw and average mandibular plane angle patients had higher success rates

Table 4. Summary of study findings.

Authors	Type of Orthodontic Movement	Placement Location	Success Factors
Abu et al. (2023) [30]	Numerous orthodontic tooth movements	Alveolar Ridge	Mini-implants were more likely to be successful with an increased length. Success rate increased when two mini-implants were splinted together.
Ağlarcı et al. (2016) [36]	Protrusion (maxillary & mandibular incisors) and Protraction of maxilla	Between mandibular lateral and canine teeth and maxillary second premolar and first molar.	Poor oral hygiene increased the rate of failure
Aly et al. (2018) [35]	Intrusion (molar) Retraction, Distalization (molar)	Maxillary and mandibular arches	The higher age group (>20 years), good oral hygiene, and immediate loading had a higher success rate
Arqub et al. (2021) [31]	Distalization, expansion, intrusion, or protraction	palatal mini-implants- paramedian or sutural, anteroposterior location (mesial to canine, canine to the second premolar, or distal to the second premolar) and buccal mini-implants (interradicular, infrazygomatic, or buccal shelf)	Palatal Implants: Lowest survival rate when used for and posterior segment protraction had the highest survival rate. Buccal Implants: Lower survival rate in males and when treating class III malocclusion. Treating class II malocclusion had the highest survival rate. Location—palatal shelf had the highest survival rate and the buccal shelf had the lowest survival rate
Azeem et al. (2019) [42]	Numerous orthodontic tooth movements	Maxillary tuberosity	Mini-implants placed by an operator with little experience was more likely to fail
Azeem et al. (2019) [29]	Uprighting (molar)	Placed in the buccal retromolar area, at the distobuccal surface of the second molars, between the anterior border of the mandibular ramus and the temporal crest	Mini-implants placed on the right side and when there was inflammation had a higher failure rate
Bearn & Alharbi (2015) [28]	Numerous orthodontic tooth movements	Various locations	Mini-implants were more successful when placed in the maxilla compared to the mandible and by clinicians with more experience
Bratu et al. (2014) [43]	Numerous orthodontic tooth movements	Various locations	Sandblasting and acid etching increased mini-implant success rate
Bungau et al. (2022) [27]	Intrusion (molar & incisor) and uprighting (molar)	Buccal maxillary area, the infrazygomatic region, palatal area, buccal mandibular area and lingual area	Mini-implants placed in the palatal region were more successful than when placed in the buccal mandibular region. The highest rejection rate occurred within the first month of placement.
Garg & Gupta (2015) [26]	Retraction (anterior teeth)	Second premolar and first molar (zygomatic buttress) in maxilla and mandible	More mobility observed on the right side than left side and when placed between the second premolar and first molar compared the first premolar and second premolar. Presence of inflammation decreased success.
Gurdan & Szalma (2018) [25]	Intrusion, distalization, uprighting	Various locations	Screw mobility was the most common in buccal placement and when used for intrusion. Inflammation due to poor oral hygiene decreased success rate
Haddad & Saadeh (2019) [24]	Numerous orthodontic tooth movements	Canines and first premolars, first and second premolars, second premolars and permanent first molars, or between first and second permanent molars	Success rate increased with increasing age, when placed between premolars or premolar and first molar, and with increasing DC distance
He et al. (2023) [41]	Distalization	Infrazygomatic crest	Success rate increases with increasing implant height
Hourfar et al. (2017) [39]	Protraction (molar) and distalization (molar)	Buccal premolar region on the maxilla and mandible or anterior palate	Patients between 6–20 years of age had a lower failure rate than patients over 30 years old. Individually placed mini-implants had lower success rates than dually placed mini-implants
Jia et al. (2018) [23]	Distalization	Infrazygomatic crest	Thickness of the cortical bone increased the success rate and inflammation decreased success
Kim et al. (2016) [44]	Numerous orthodontic tooth movements	Buccal alveolar bone in posterior regions	Failure rate can increase with the frequency of mini-implant reinsertions after failure. Sex, age, and arch may have no correlation with primary or recurrent OMI failure.
Lai & Chen (2014) [22]	Numerous orthodontic tooth movements	Various locations	Diameter and length, sex, age, and malocclusion type did not show any statistically significant difference in success rates. Success rate was reduced when placed in the jaw or lingually, inflammation, and applying force at two weeks.
Melo et al. (2016) [21]	Numerous orthodontic tooth movements	Various locations	No difference in loss of stability with age, sex, craniofacial pattern or smoking habit. Shorter mini-implants were more likely to fail than longer ones and mandibular mini-implants had a lower stability.
Migliorati et al. (2016) [20]	Retraction, intrusion, and extrusion	Maxillary and mandibular arches	Mandibular arch was more stable and delayed loading more stable
Migliorati et al. (2020) [45]	Distalization, intrusion, extrusion, mesialization	Maxillary and mandibular arches	No significant differences in success among the gender of the patients, age, miniscrew location (maxilla or mandible), miniscrew position (palatal/lingual or vestibular), baseline torque values and groups
Moeini et al. (2023) [19]	Retrusion and distalization (molar)	Buccal side of first molars	Higher failure rate in mandible, time of loading had no influence, infection present in failed MI, younger patients had higher probability of failure in the mandible, young females had highest failure rate
Mommaerts et al. (2014) [38]	Proclination, intrusion, uprighting molars	Maxillary and mandibular arches	Age, gender, time of loading, and location did not influence failure rate. Mini-implants were more likely to fail in female patients and in younger patients
Motoyoshi et al. (2016) [18]	Retraction (anterior teeth)	Maxillary buccal alveolar bone between second pre-molar and first molar	More likely to fail if in contact with the root
Nienkemper et al. (2014) [40]	Distalization (molars)	Maxillary and mandibular arches	Longer mini-implants were more likely to not fail
Nienkemper et al. (2020) [34]	Sagittal molar movement	Median of anterior palate	Stability decreased with decreased oral health. Sex had no impact on success rate
Nienkemper et al. (2020) [17]	Sagittal molar movement	Median of anterior palate	Length of mini-implant, age, sex, vertical bone height did not affect failure rate
Ravi et al. (2023) [46]	Retraction (maxillary & mandibular anterior teeth)	Various locations	Surface treatment using sandblasting and acid etching may improve the secondary stability of self-drilling orthodontic mini-implants.
Sarul et al. (2022) [33]	Distalization (anterior teeth)	Mandibular buccal shelf	Larger screws had a higher success rate. Inflammation decreased success rate
Shaikh et al. (2021) [16]	Distalization (maxillary molars) and intrusion (maxillary anterior teeth)	Between first and second molars	Bone density and volume increase success rate
Slabkovskaya et al. (2021) [47]	Intrusion (maxillary molars)	Between first and second molars	Age and gender had no effect on success rate
Sreenivasagan et al. (2021) [15]	Numerous orthodontic tooth movements	Anterior interradicular, buccal shelf, infrazygomatic, palatal, midline, posterior maxilla, and posterior mandible	Success rate increased with self-tapping, in maxilla, in the maxilla, and with sandblasting and etching. Poor home care, inflammation, and excessive load decreased success rate.
Sreenivasagan et al. (2021) [14]	Numerous orthodontic tooth movements	Anterior interradicular, buccal shelf, infrazygomatic, palatal, midline, posterior maxilla, and posterior mandible	Buccal shelf implants had the highest torque. Failure was due to implant breakage during insertion and soft tissue inflammation
Uribe et al. (2015) [13]	Numerous orthodontic tooth movements	Infrazygomatic crest	Age, gender, size of mini-implant, type of movement, oral hygiene, operator experience, and pilot hole was not a predictor of mini-implant success
Vicioni-Marques et al. (2022) [32]	Numerous orthodontic tooth movements	Maxillary and mandibular arches	Adequate clinical procedure, precise placement, and lack of inflammation increase success of mini-implant
Yao et al. (2015) [37]	Numerous orthodontic tooth movements	Maxillary and mandibular arches	Sex, malocclusion type, bone density, inflammation had no effect on failure. Patients over 35 years and immediate loading were more likely to be successful
Yi Lin et al. (2015) [12]	Numerous orthodontic tooth movements	Maxillary and mandibular arches and palate	No patient related factors affected success rate, but the longer mini-screw and average mandibular plane angle patients had higher success rates

3.4. Type of Orthodontic Movement/ Indications for TADs/Mis

The 36 research studies revealed a diverse range of orthodontic movements facilitated by TADs. While many studies (13 out of 36) investigated “various orthodontic tooth movements” without specifying particular types [12,13,14,15,21,22,24,28,30,32,37,43,44], the majority focused on specific movements. Distalization, particularly of molars, was the most frequently studied movement, appearing in 11 studies [16,19,23,25,31,33,35,39,40,41,45]. Intrusion was another common focus, examined in 9 studies, often targeting molars or incisors [16,20,25,27,31,35,38,45,47]. Retraction, mainly of anterior teeth, was explored in 5 studies [18,19,20,26,46]. Other movements investigated included protraction [31,36,39]. Expansion [31], uprighting (especially of molars) [25,27,38,42], and extrusion [20,45]. A few studies specifically looked at sagittal molar movements or facilitation of orthodontic movement in general, revealing that orthodontic MIs provided sufficient anchorage control to complete the desired movement (Table 4) [34,40,42].

Placement site (including bone quality) and peri-implant tissue health emerge as the most consistent, modifiable contributors to success. Device length, experience of the operator, and carefully titrated loading further influence outcomes, while age effects remain inconsistent and likely context-specific. Taken together, these findings support site-specific planning, rigorous hygiene protocols, and calibrated biomechanics to maximize MI/TAD success.

3.5. Host-Related and Biomechanical Moderators

Reporting on smoking and periodontal status was sparse, but biologically plausible mechanisms (altered bone turnover, impaired wound healing, and inflammation) suggest risk amplification, especially when combined with thin cortex or borderline primary stability. Risk increased where higher initial force magnitudes were applied to short/low-torque screws in sites with limited keratinized tissue; conversely, palatal/extra-alveolar sites with thicker cortex and easier hygiene access mitigated risk even with earlier loading.

3.6. Outcome Definitions and Follow-Up Heterogeneity

Studies variably defined success as STTC or clinical stability at fixed timepoints, with follow-up from approximately 1 to 24 months. These differences preclude valid pooling. We therefore analyze direction of effect within each outcome family and window, which reconciles many apparent contradictions once primary stability and load magnitude are considered.

4. Discussion

The use of MIs and TADs has become increasingly prevalent in orthodontic practices, offering clinically meaningful advantages by delivering stable, skeletal anchorage with generally low adverse-event rates [3]. Our scoping review of 36 unique studies provides valuable insights into both device-specific and patient-specific factors that influence the success of MIs/TADs. Collectively, the evidence supports TADs as an anchorage modality that can expand treatment possibilities while reducing reliance on patient compliance.

Placement location emerged as the most significant factor, mentioned in over half of the studies reviewed [28,29,30]. There was variability in optimal placement sites, with some studies favoring maxillary placement [22,28] over mandibular placement [15,19,21], palatal over buccal placement [27,31], and even differences between right and left sides [26,29]. This pattern likely reflects site-dependent cortical thickness and soft-tissue conditions across the palate, infrazygomatic crest, and buccal shelf, as well as interradicular root proximity in different segments. This variability emphasizes the need and importance of individualized treatment approaches because not one treatment plan fits all [48]. In practice, a site- and task-specific strategy—matching the indication (e.g., distalization, intrusion) to a location with adequate cortical support and favorable soft tissue—appears most defensible. The importance of bone quality at the insertion site, highlighted in several studies [16,17,23], further underscores the complexity of determining ideal placement locations [2]. Differences in outcomes related to placement location may stem from differences in bone density, thickness, and volume across different areas of the jaw, as well as individual patient characteristics [49]. Accordingly, pre-operative assessment (often with panoramic/PA imaging and, when indicated, CBCT) and careful evaluation of keratinized tissue, attached gingiva, and anticipated hygiene access are prudent.

Oral hygiene and soft-tissue health were consistently identified as crucial factors in mini-implant and TAD success, with all studies that addressed this aspect reporting a positive correlation between good oral hygiene and higher success rates [32,33,34,35,36]. Clinically, inflammation around the transmucosal neck (peri-implant mucositis) is a common precursor to mobility [14,15,25]; structured home-care protocols (instruction, targeted cleaning aids, and short-term antiseptic adjuncts when indicated) decrease risk [15,34,35]. This finding has significant implications for patient education and care protocols, suggesting that emphasis on proper oral hygiene practices should be an integral part of orthodontic treatment plans, especially ones that involve MIs or TADs [50]. Orthodontists should integrate regular monitoring and patient education on maintaining optimal oral hygiene to mitigate inflammation and other complications that could compromise the stability, integrity, and or longevity of TADS. Embedding hygiene checks into activation visits and preferring sites in keratinized mucosa when feasible can further support long-term stability.

The unanimous agreement on the positive correlation between increased MI or TAD length improved success rates provides a clear guideline for clinicians [33,40,41]. Greater endosseous length increases bone–implant contact and primary stability [30,33,40]; however, diameter, thread design, and insertion angle also matter, and “longer” cannot compensate for poor site selection or thin cortical plates [16,23]. Longer MIs or TADs may offer enhanced stability due to increased bone contact, which could be particularly beneficial in patients with lower bone density. However, this finding should be balanced against potential patient comfort and anatomical considerations, such as the risk of root damage or patient discomfort associated with longer implants [51]. Clinicians should balance length and diameter against interradicular space, sinus/nasal floor proximity, and soft-tissue thickness, selecting the smallest device that reliably achieves stability in the chosen site.

Lastly, the diverse range of orthodontic movements investigated in the reviewed studies underscores the versatility and broad applicability of TADs in contemporary orthodontic practice. Movements with high anchorage demand—molar distalization and posterior intrusion—were most frequently studied, aligning with TADs’ ability to decouple force systems from reactive dental units. The predominance of studies focusing on distalization, particularly of molars, suggests that TADs have become a valuable tool in addressing one of the most challenging aspects of orthodontic treatment—creating space in the posterior region without undesirable reciprocal movements. Similarly, vertical control via molar/incisor intrusion benefits from short, direct force vectors anchored to palate or buccal shelf sites, often simplifying biomechanics and shortening force chains. The significant attention given to intrusion, especially of molars and incisors, indicates the efficacy of TADs in managing vertical discrepancies, which are often difficult to correct with conventional mechanics. Combined mechanics (e.g., simultaneous retraction and intrusion) further illustrate TADs’ role in three-dimensional control, though standardized reporting of vector magnitude and direction remains limited. The inclusion of studies examining various combinations of movements, such as simultaneous retraction and intrusion, highlights TADs’ flexibility but demonstrates the multifaceted capabilities of TADs in addressing complex malocclusions. However, the substantial number of studies investigating “various orthodontic tooth movements” without specificity points to a need for more targeted research to elucidate the precise benefits and limitations of TADs for particular movement types. Future work should stratify outcomes by site, device dimensions, and movement class to clarify dose–response relationships and complication profiles. Future research should aim to provide more detailed analyses of specific movement patterns to guide clinicians in optimizing TAD usage for diverse orthodontic challenges.

The conflicting results regarding loading protocols highlight an area requiring further investigation. The equal support for immediate and delayed loading, coupled with findings on the detrimental effects of excess load, suggest that optimal loading strategies may need to be determined on a case-by-case basis [37,38,39]. Rather than timing alone, primary stability (driven by cortical engagement, device geometry, and insertion torque) and force magnitude likely govern outcomes [20,35]; gentle initial forces with gradual escalation appear prudent when primary stability is borderline [35,37]. Factors such as bone quality, placement location, and individual patient characteristics are critical to the success of treatment [52]. Understanding the biomechanics of different loading protocols and their interaction with bone remodeling processes will be crucial in developing standardized guidelines that optimize TAD success while minimizing complications. Additionally, operator experience and workflow (freehand vs. guided insertion) may moderate the safety window for immediate loading, warranting explicit reporting in future trials.

4.1. Additional Patient and Procedural Considerations

Systemic and local modifiers (e.g., smoking status, periodontal condition, medications affecting bone turnover) may alter risk and should be screened pre-placement. Insertion technique (self-drilling vs. pilot-hole, angulation through attached gingiva, and soft-tissue management) influences both early stability and soft-tissue health. We would treat smoking status and baseline periodontal health as primary risk modifiers; we recommend cessation counseling and periodontal stabilization before or at placement. If failures occur, relocating to a new site, increasing length/diameter within anatomical limits, or switching to a palatal/extra-alveolar site are practical rescue pathways that preserve treatment momentum. Digital planning with CBCT-based root mapping and insertion guides can reduce proximity risks in crowded interradicular regions.

Immediate loading is dependable when primary stability is high (adequate cortical engagement, appropriate device geometry/length, sufficient insertion torque), initial forces are modest, and soft-tissue inflammation is controlled. Delayed loading is safer when any of these are borderline. Apparent contradictions across studies are therefore coherent once these moderators are considered. Future trials should report outcome family and time window; load timing and magnitude; vector; insertion torque and device geometry; site descriptors (cortical proxy, keratinized tissue, hygiene access); and host modifiers (smoking status/intensity; periodontal status). These will enable pooling and causal modeling.

4.2. Limitations

Our study has limitations that should be acknowledged. The heterogeneity in a wide array of study designs utilized may introduce variability in the quality and reliability of data analyzed. Moreover, not all studies investigated or focused on the same factors that can impact success or failure of a MI or TAD. Additionally, there was a diverse range of MIs and TADs used for different orthodontic applications which could impact the generalizability of our findings. Furthermore, the exclusion of non-English language articles and unpublished studies may have resulted in the omission of relevant data. Outcome definitions were heterogeneous (STTC vs. fixed-time clinical stability) and follow-up windows varied (1–24 months), so we did not pool effect sizes. Instead, we classified outcome families and synthesized direction of effects, highlighting moderators (bone quality/site, primary stability, load magnitude, host factors including smoking and periodontal status).

The variation in movement types that TADs were utilized for along with the different inclusion and exclusion criteria of each included article could impact the generalizability of our findings. Furthermore, the potential for publication bias, where studies with positive or significant results are more likely to be published, should be considered when interpreting these results. Given the scoping design, quantitative pooling was not attempted; thus, effect sizes and predictive weights for individual factors cannot be inferred. Future reviews could benefit from a more inclusive approach, possibly incorporating non-English studies and unpublished data to provide a more comprehensive overview. Prospective, multicenter studies with standardized outcome measures would substantially strengthen the evidence base.

4.3. Implications for Clinical Practice

Our findings have significant implications for clinical practice in orthodontics. The results underscore the importance of a comprehensive approach to treatment planning that considers multiple factors including placement location, oral hygiene, patient age, and screw characteristics. Clinicians should prioritize patient education on oral hygiene practices and carefully evaluate anatomical considerations when determining optimal placement locations for mini-implants or TADs. Furthermore, understanding patient-specific factors, such as bone density and metabolic health, can aid in customizing treatment plans to enhance the likelihood of success. The varied findings related to loading protocols and implant length further suggest that clinicians should adopt a personalized approach, adjusting their strategies based on individual patient needs and anatomical considerations. In practical terms, a reasonable workflow includes: (1) pre-placement imaging and site selection favoring adequate cortical thickness and keratinized mucosa; (2) selection of the smallest length/diameter that assures stability for the planned vector; (3) atraumatic insertion with attention to soft-tissue management; (4) structured hygiene reinforcement at each visit; (5) conservative force initiation with escalation based on stability; (6) predefined rescue strategies (alternative site or device) if mobility develops. Where available, digital planning and template-guided insertion can improve accuracy in high-risk interradicular sites, in addition to recording and addressing smoking and periodontal status as part of pre-placement risk assessment and ongoing reviews.

4.4. Conclusions

This scoping review highlights the multifaceted nature of factors influencing the success of mini-implants and temporary anchorage devices in orthodontic treatment. Placement location and oral hygiene emerged as the most significant contributors to success, with bone quality, age, implant length, loading protocols, and clinician experience also playing important roles. These findings underscore the complexity of achieving optimal outcomes in orthodontic anchorage and emphasize the need for careful consideration of multiple variables when planning and executing MI or TAD placement, with an emphasis on patient-specific care and adaptive treatment strategies. Standardizing definitions, reporting core outcomes, and stratifying results by site and device parameters will facilitate clearer guidance for clinicians. By advancing our understanding of these factors, orthodontic practitioners can enhance treatment outcomes, reduce failure rates, and ultimately improve patient care in orthodontics. Future prospective, adequately powered studies should aim to refine force protocols and validate decision pathways that link indication, site, and device selection to predictable, patient-centered outcomes.