Failure rates of mini-implants placed in the infrazygomatic region

What is the impact of patient attributes, implant characteristics, surgical techniques, and placement location on the success of orthodontic mini-implants in young adults? A Systematic Review and Meta-Analysis

Background

Temporary anchorage devices (TADs) address challenges in traditional orthodontic anchorage like patient compliance and precision, showing significantly improved clinical outcomes, particularly for cases requiring maximum anchorage.

Materials and Methods

A systematic electronic search was performed in five research databases, focusing on studies published between 2015 and 2023. The ROBINS-I tool from the Cochrane Bias Methods Group assessed the risk of bias. Data analysis included categorical and numerical variables, with categorical variables analyzed using Cohen's method in a random effects model to account for variability. Sensitivity and heterogeneity were evaluated using a 'leave-one-out' approach and theI 2 statistic, respectively. At the same time, publication bias was checked using Egger's test, with findings presented through Forest and Funnel plots. Numerical variables were subjected to weighted regression analysis.

Results

Examination of 15 studies involving 1981 patients and 3272 orthodontic mini-implants identified key factors affecting implant stability. Failure rates varied significantly, influenced by factors such as the characteristics and insertion site of the orthodontic mini-implants (OMIs), patient-specific variables, and operator experience. Notably, the insertion site and implant characteristics like size did not significantly affect failure rates, but there was a negative correlation between the magnitude of force applied and failure rates.

Conclusion

The success of orthodontic mini-implants is broadly consistent across patient demographics and is not significantly impacted by gender or age, though failure rates were higher in males and when implants were placed in the maxilla. These findings suggest that higher applied forces might reduce failure rates.

Clinical Significance

This review underlines mini-implant efficacy across varied patient demographics, emphasizing the importance of site selection, jaw location, and force application in enhancing success rates and guiding tailored treatment strategies.PROSPERO ID CRD42023411955.

The Orthodontic Mini-Implants Failures Based on Patient Outcomes: Systematic Review

Anchorage is a challenge and essential issue for an orthodontist in determining the success of orthodontic treatment. Orthodontic anchorage is defined as resistance to unwanted tooth movement. Mini-implant is one of the devices that can be used as an anchor in orthodontic treatment. Many cases have reported successful treatment using mini-implant, but there are cases where mini-implants may fail. Failure of mini-implants can affect orthodontic treatment, and it is known that several factors may lead to mini-implant loss in orthodontic treatment. This systematic review aimed to determine the factors influencing mini-implant failure in orthodontic treatment. Articles were selected from electronic databases (PubMed, Google Scholar, The Cochrane Library, ScienceDirect) from January 2015 until 2023 according to the PRISMA method (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) under the PEOS (Population-Exposure-Outcome-StudyType) framework questions for systematic review. The study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42022337684). All data collected were in English, and filtering was done by eliminating duplicate data, meta-analysis, case reports, case series, mini-reviews, and animal studies. The analysis was further divided into three groups, that is, patient-related, implant-related, and operator-related and operator-related (A graphical abstract provided as a Supplementary information [available in the online version]). Twenty-one articles were identified according to the inclusion criteria in the form of retrospective, prospective, in vivo, and randomized controlled trial studies. Mini-implant failures due to patient-related showed six etiological factors, failures due to implant-related had eight etiological factors, and only one factor was operator-related, which may lead to mini-implant failure. The data was extracted without a computerized system and only in English. Mini-implant failure can be caused by many factors; we could not accuse one major factor as a cause. However, the quality or condition of the bones and oral hygiene are factors that play a significant role in obtaining the stability of implants. Mini-implant failure is highly influenced by poor oral hygiene and peri-implant inflammation. Comprehensive diagnostic prior to mini-implant insertion should be appropriately considered. This systematic review describes several factors that can influence mini-implant failure, divided into three groups: patient-related, implant-related, and operator-related (A graphical abstract provided as a Supplementary information [available in the online version]).

Evaluation of mechanical properties and morphology of miniscrews Ti6Al4V cold worked versus annealed in artificial bones

PURPOSE

This study aimed to evaluate the influence of different manufacturing procedures (Eli annealed - hot work versus cold worked - cold work) of the raw material under mechanical properties and morphological characteristics of orthodontic miniscrews (MS).

MATERIAL AND METHODS

Thirty MS were randomly separated into 3 types (n=10) according to manufacturer and manufacturing process of the raw material: type A - SIN® annealed (control group); type B - Dentfix® annealed; and, type C - Dentfix® cold worked. MI were inserted in artificial bone blocks, through the manufacturer's specific manual key attached to the digital torquemeter stabilized via custom device. Data of fracture's occurrence was performed using Fisher's exact test. Comparisons between the other two types regarding insertion torque and removal torque were performed using the Mann-Whitney test. Data of fracture torque, shear stress, normal stress and torque ratio was submitted to Kruskal Wallis and Dunn tests (α=0.05). Representative images of surface morphology and fractures were selected.

RESULTS

Type C showed statistically the lowest fracture torque (N.cm) (26.11±0.41) (P=0.0012) and highest torque ratio (%) (98.74±0.85) (P=0.0007). Type C showed statistically higher calculated shear (MPa) (2,432.73±508.41) and normal stress (MPa) (1,403.86±293.39) than type B and type A, showing that they differed in relation to the mechanical strength of the material with which they were made (P=0.0007).

CONCLUSION

Type A fractured completely inside the most apical bone. Type B and type C fractured closer to the transmucosal profile. Cold worked process should be more prone to fractures than those annealed raw manufactured.

An evaluation of bone depth at different three-dimensional paths in infrazygomatic crest region for miniscrew insertion: A cone beam computed tomography study

Objective

To investigate the difference and distribution of bone depth at different three-dimensional simulated paths to help optimize the insertion path for miniscrew placement in the infrazygomatic crest.

Methods

Cone beam computed tomography scans of 80 adults (38 males and 42 females; mean age, 27.0 years) were assessed. For each subject, bone depth of 81 simulated insertion paths at different insertion points and three-dimensional angulations was measured in 160 infrazygomatic crests; the differences were evaluated using the adjusted Friedman test. The bone deficiency ratio for each path was calculated. Distributions of measurements were analyzed and reported as specially designed colormaps.

Results

Bone depth increased, and bone deficiency ratio reduced mesially to distally (P < 0.001), apically to coronally (P < 0.01), and at a greater gingival and distal inclination (P < 0.05). The maximum bone depth (10.72 mm) was observed 13 mm above the maxillary occlusal plane in the mesiobuccal root of the maxillary second molar. The minimum bone depth (3.4 mm) was observed 17 mm above the maxillary occlusal plane in the distobuccal root of the maxillary first molar. No bone deficiency was detected at the paths of 13 mm above the maxillary occlusal plane at a gingival inclination of 70° and distal inclination of 30° in the mesiobuccal root of the maxillary second molar. The highest bone deficiency ratio is present 17 mm above the maxillary occlusal plane at a gingival inclination of 60° and a distal inclination of 0° in the distobuccal root of the maxillary first molar (89/160).

Conclusion

Insertion paths located at 13 mm above the maxillary occlusal plane in the mesiobuccal root of the maxillary second molar were optimal. A gingival inclination of 70° and a distal inclination of 30° could be beneficial. The distobuccal root of the maxillary first molar region or above the 17 mm insertion plane may not be recommended.

Current status of the biomechanics of extra-alveolar miniscrews

Temporary skeletal anchorage devices such as miniscrews are frequently used nowadays. Compared to miniplates, miniscrews are much less expensive and technically easier to place and remove; they are popular and can be easily placed by an orthodontist. Extra-alveolar miniscrews offer benefits compared to inter-radicular miniscrews, such as reduced risk of root damage and the lack of interference with the mesiodistal tooth movement. They are particularly useful for addressing anchorage loss issues and enabling specific tooth movements such as total arch maxillary and mandibular retraction, posterior distalization, molar protraction, molar intrusion, occlusal plane control, and midline correction. The present paper discusses the current biomechanics principles related to the use of extra-alveolar miniscrews placed in the infrazygomatic and mandibular buccal shelf.

Success rate of infrazygomatic crest mini-implants used for en-masse retraction of maxillary anterior teeth in first premolar extraction cases: A three-dimensional comparative prospective clinical trial between adolescents and young adults

BACKGROUND

The purpose of this study was to compare the success rate of infrazygomatic mini-implants between adolescents and young adults.

METHODS

A total of 60 subjects of different age groups ie, (group I [adolescents]: 12-18 years, mean age: 14.9 ± 2.9 years; group II [young adults]: 19-25 years, mean age = 21.9 ± 3.1 years) were assessed in the study. En-masse retraction of maxillary anterior teeth was carried out with extraction of upper first premolars with infrazygomatic crest (IZC) mini-implants as anchorage units. Clinical parameters such as success rate, soft tissue thickness, maximum insertion torque, maximum removal torque, pain response, soft tissue response, and cone-beam computed tomography parameters such as embedded angulation, penetration depth, thickness of bone on buccal and palatal aspect of mini-implant, and peri-implant bone density were evaluated.

RESULTS

The success rate of IZC mini-implants in adolescents was found to be 96.6% and 98.3% in young adults respectively. There was no significant difference in success rate between the two groups. Intergroup comparison showed a significant difference (P < 0.05) in terms of maximum insertion torque, maximum removal torque, soft tissue thickness, cortical bone thickness, and peri-implant bone density values. Comparison between right and left side revealed a significant difference (P < 0.05) with regards to soft tissue response, soft tissue thickness, total bone thickness, cortical bone thickness, and peri-implant bone density.

CONCLUSIONS

There was no significant difference in the success rate of IZC mini-implants between adolescents and young adults. Thus, the use of IZC mini-implants can be recommended in adolescents for successful orthodontic treatment.

Ridge mini-implants, a versatile biomechanical anchorage device whose success is significantly enhanced by splinting: a clinical report

OBJECTIVES

This clinical report aims to highlight the factors affecting the clinical success of alveolar ridge mini-implants used for orthodontic anchorage and provide an overview of the biomechanical versatility of this miniscrew and steps involving the proper technique of its placement.

METHODS

For this clinical report, charts for 295 patients who had temporary anchorage devices (TADs) were screened. Twenty patients [15 females and 5 males: mean age = 38.15 ± 15.10 years] with 50 alveolar ridge mini-screws were assessed. A descriptive summary of the main factors affecting their clinical success and the technique employed for their placement was comprehensively discussed and illustrated, in addition to the presentation of some clinical cases illustrating their potential clinical uses.

RESULTS

The survival duration (7.32 ± 9.01 months) and clinical success of the alveolar ridge mini-implants that failed (19/50) seem to be affected primarily by 2 factors: splinting; none of the splinted mini-implants failed (0/10) compared to (19/40) of the single mini-implants that failed, and the length of the used mini-implant; the average length of the mini-implants that did not fail was 9.23 mm. Additionally, it appears that these mini-implants are biomechanically robust and durable, those that did not fail had an average survival duration of 35.97 ± 19.79 months.

CONCLUSION

Ridge mini-implants offer significant biomechanical versatility in patients with partially edentulous ridges needing complex pre-prosthetic orthodontic movements. The presence of splinting and the length of the used mini-implants are factors that might affect the clinical success of the alveolar ridge mini-implants.

Should Cone-Beam Computed Tomography Be Performed Prior to Orthodontic Miniscrew Placement in the Infrazygomatic Crest Area?-A Systematic Review

There is no unequivocal scientific consensus for the temporary anchorage device (TAD) positioning in the infrazygomatic crest area (IZC). The two principal aims of this systematic review were to assess bone availability in the IZC and to establish both the target site and the need for cone-beam computed tomography (CBCT) prior to miniscrew placement. The study was performed following PRISMA guidelines (PROSPERO: CRD42023411650). The inclusion criteria were: at least 10 patients, three-dimensional radiological examination, and IZC assessment for the TAD placement. ROBINS-I tool and Newcastle-Ottawa Scale were used for quality evaluation. No funding was obtained. The study was based on the information coming from: PubMed, Google Scholar, Web of Science Core Collection, MDPI, Wiley, and Cochrane Libraries. The last search was carried out on 1 August 2023. Fourteen studies were identified for analysis. A narrative synthesis was performed to synthesize the findings of the different studies. Unfortunately, it is not possible to establish the generally recommended target site for IZC TAD placement. The reasons for this are the following: heterogeneity of available studies, inconsistent results, and significant risk of bias. The high variability of bone measurements and the lack of reliable predictors of bone availability justify the use of CBCT for TAD trajectory planning. There is a need for more high-quality studies aiming three-dimensional bone analysis of the IZC.

Dentoalveolar and Airway Changes Following En Masse Distal Movement of the Maxillary Dentition with Infrazygomatic Crest Anchorage: A Prospective Study

Aims and Objectives

Mini screws placed buccal to the maxillary first or second molars in the infra zygomatic crest (IZC) region can be used as anchors for various types of tooth movement. En masse distal movement of the maxillary dentition with IZC anchorage is routinely practiced nowadays as more patients demand a non-extraction treatment and it should be evaluated. The goal of this study was to assess dentoalveolar and airway changes in individuals with class II malocclusion after en masse distal movement of the maxillary dentition utilizing infrazygomatic anchorage.

Materials and Methods

This prospective study included patients who required en masse distal movement of the maxillary dentition. Following initial leveling and aligning, mini screws were placed in the IZC region, and the maxillary arch was distalized en-masse. Pre (T0) and post distalization (T1) lateral cephalograms were traced for dentoalveolar and airway changes. Statistical tests were done with SPSS software. Shapiro-Wilk test for normality and paired T test for comparison between before and after en masse distalization were done.

Results

The changes in dental angular and linear measurements such as U1 to N-A, L1 to N-B and interincisal angle, U1 to N-A and U1 to point A distance, U1 to palatal plane, L1 to N-B, L1 to Apo line distance, U6 to PtV were statistically significant (P > 0.05). Linear parameters such as L1 to ApO line, upper airway, and lower airway were not statistically significant (<0.05).

Conclusion

Class II div I malocclusions can be efficiently corrected without extractions using IZC anchorage by en masse distal movement of the maxillary dentition. Significant reduction in upper anterior inclination, intrusion of maxillary anterior teeth, and distal movement of the posterior teeth were noted. No changes in airway dimensions were noted.

Mini-Implant Rejection Rate in Teenage Patients Depending on Insertion Site: A Retrospective Study

Mini-implants have undeniable advantages in Orthodontics. However, the use of mini-implants shows some limitations and disadvantages related to patient age, the quality of the bone tissue, the characteristics of the oral mucosa, implant site, the state of health of the organism and the quality of oral hygiene. The aim of this paper was to analyze the rejection rate of mini-implants in teenage patients, depending on their insertion site, and examine their stability up to three months after insertion. This retrospective study was conducted on dental charts belonging to patients aged between 12 and 17 years, from Oradea, Romania. The mini-implants were placed for various therapeutic reasons and were inserted in the following sites: buccal maxillary area, the infrazygomatic region, palatal area, buccal mandibular area and lingual area; they had a diameter of 1.6 mm (inter-radicular spaces) and of 2 mm (nonbearing tooth areas), and a length of 6–8 mm (mandible) or 8–10 mm (maxilla). The rejection rate was checked in the first month, second month, third month and after the third month from insertion. A total of 432 patients were included in the study, and they had a total of 573 mini-implants. Most implants were placed in the buccal region of the maxilla (27.7%), and most patients had one mini-implant placed (65.7%). The highest rejection rate was obtained in the first month (15.2%). The rejection rate between genders was similar. The mini-implants from the buccal mandibular region had a significantly higher rate of rejection in the first month (M1) in comparison to the mini-implants from the palatal region (24.4% vs. 8.3%). The mini-implants from the lingual region of the mandible had a significantly higher rate of rejection in the second month (M2) in comparison to the mini-implants from the infrazygomatic or the palatal region (10.5% vs. 0%/0%). Mini-implants are very useful for carrying out various orthodontic treatments, but their stability should be enhanced.

Success rate of infrazygomatic miniscrews considering their design and insertion techniques. A review

Miniscrews offer the possibility of performing dental movements, minimizing unwanted side effects and enhancing effectiveness. Extra-alveolar miniscrews are ideal as they provide excellent primary stability and avoid anatomical structures. However, in some cases the primary stability is lost before achieving the success of the mechanics used and thus, the most likely causes of failure should be determined. The purpose of this review was to analyze the success rate of infrazygomatic miniscrews, considering their design and the insertion techniques used. Data collection of this literature review was carried out by searching PubMed, Wiley, Google Scholar sites, SCIELO, Elsevier and Dialnet for publication made from 2003 to June 2022. The search was carried out on June 10th, 2022 and the following keywords were used; infrazygomatic crest, miniscrews, anchorage and stability. Different topics were analyzed and discussed highlighting their clinical relevance. After analyzing the 798 articles, 566 were excluded. The remaining articles were re-analyzed and 153 articles were excluded for the title or abstract and 33 articles were excluded for the methodology. Finally, 46 items remained. After thoroughly analyzing all the articles included, this study concluded that the alloy of the miniscrew (stainless steel or titanium), perforation of the maxillary sinus and the placement area (adhered mucosa or mobile mucosa) do not influence the survival of the miniscrew. The evidence also indicates that the percentage of failure is lower in infrazygomatic compared to intraradicular miniscrews. Orthodontists can confidently and safely include infrazygomatic miniscrew in different orthodontic procedures.

The antimicrobial effect of doxycycline and doped ZnO in TiO2 nanotubes synthesized on the surface of orthodontic mini-implants

Objectives:

Anchorage preservation is crucial in orthodontic treatment success. Mini-implants make a revolution in this domain. The failure of orthodontic mini-implants due to inflammation and infection is one of the reasons for anchorage loss. The purpose of this study was to evaluate the effect of a novel mini-implant surface modification to improve resistance against microbial contamination and surrounding tissue inflammation.

Material and Methods:

Twenty-four orthodontic mini-implants (Jeil Medical Corporation, Korea) with 1.6 mm diameter and 8 mm length were randomly divided into three groups: Group 1: Control group, Group 2: Nanotubes were made on the surface with anodisation, and Group 3: Zinc Oxide (ZnO) doped into nanotubes, and then doxycycline is added to them. The anti-bacterial efficacy against Porphyromonas gingivalis was evaluated using the disk diffusion method. To analyze data, Kruskal–Wallis, Friedman, and Wilcoxon tests were done. The significance level was set at 0.05.

Results:

No zone of the inhibition was formed in Groups 1 and 2. In Group 3, the mean (SD) diameter of the inhibition zone in the first 5-day to sixth 5-day were 38.7(8.2), 25(4.8), 17.8(5.6), 7.63(5.37), 1.5(2.83), and 0 millimeters, respectively.

Conclusion:

Nanotubes containing doped ZnO and Doxycycline are capable of preventing bacterial growth around the mini implant surfaces for at least up to 30 days. To manage inflammation of surrounding tissues of mini-implants, nanotubes are not effective alone. Therefore, the presence of diffusible materials in addition to nanotubes on the surface of mini-implants is necessary.

A Scoping Review about the Characteristics and Success-Failure Rates of Temporary Anchorage Devices in Orthodontics

This study synthesized the scientific evidence concerning the main characteristics of the Temporary Anchorage Devices (TADs) used in orthodontics and reported the success-failure rates during treatment. For that means, this scoping review collected articles from previous research. A complementary search was carried out in the databases PubMed-MEDLINE, Scopus, LILACS, and EMBASE, focusing on original studies published from 2010 to 2020. We analyzed the main characteristics of the publications. As a result, 103 articles were included. Most of the research was conducted among different groups, who needed TADs principally in the maxilla and an interradicular location between the second premolar and first molar. AbsoAnchor, Dentos Inc., Daegu, Korea, was the most used brand of TADs. The most common characteristics of the devices and biomechanics were a diameter and length of 1.6 mm and 8 mm, a self-drilled system, a closed technique for placement, immediate loading, and forces that ranged between 40 and 800 g. Of the studies, 47.6% showed success rates ≥90%. In conclusion, high success rates were found for TADs, and differences were found according to sociodemographic and clinical variables. The studies showed variability in methodological design, and scientific publications were concentrated in certain countries. We recommend further scientific research on TADs using more standardized designs.

Bone depth and thickness of different infrazygomatic crest miniscrew insertion paths between the first and second maxillary molars for distal tooth movement: A 3-dimensional assessment

INTRODUCTION

This research aimed to measure the bone depth and thickness of different insertion paths for safe placement of infrazygomatic crest miniscrews between the first (U6) and second maxillary molars (U7) by 3-dimensional (3D) reconstruction and to explore their clinical significance.

METHODS

Cone-beam computed tomography data from 36 adult orthodontic patients were obtained to generate 3D models (n = 72) of the infrazygomatic crest region. For each model, the bone depth and thickness of 27 different insertion paths were measured in the region between U6 and U7. The relationship between bone depth and thickness was statistically analyzed. The clinical risk for each insertion path was assessed according to the impacts of bone depth and thickness on insertion failure.

RESULTS

Maximum bone depth (median, 7.41 mm; mean, 8.42 mm) was present at 13 mm insertion sites with a gingival tipping angle of 50° and a distal tipping angle of 30°. Maximum bone thickness (median, 3.73 mm; mean, 4.00 mm) was present at 17 mm insertion site with a gingival tipping angle of 70° and a distal tipping angle of 30°. There was a significant negative correlation between bone depth and bone thickness (r_s = -0.569, P <0.001). Failure rates were significantly different among different insertion paths (P <0.001).

CONCLUSIONS

Because the bone depth and thickness may affect the safe insertion of infrazygomatic crest miniscrews in the region between U6 and U7 and they are negatively related, a safe insertion protocol design for distal tooth movement should take both into consideration.

The accuracy of computer-aided design and manufacturing surgical-guide for infrazygomatic crest miniscrew placement

Objectives:

Infrazygomatic crest (IZC) surgical guides have been employed to prevent any avoidable complications during miniscrew insertion. The purpose of this study was to evaluate the accuracy of IZC miniscrew placement when using a surgical-guide developed by computer-aided design and manufacturing (CAD/CAM) techniques.

Materials and Methods:

Ten patients were scanned with cone-beam computed tomography for three-dimensional (3D) planning of IZC miniscrew placements. The upper arches were scanned separately, and virtual miniscrews were placed in the position planned by 3D software. The CAD/CAM surgical guides were designed and fabricated individually to enable accurate miniscrew placement. Subsequently, 20 self-drilling miniscrews were inserted at the right and left IZC areas using 5 CAD/CAM surgical guides (CS group, n = 10) and direct insertion (DI group, n = 10), respectively. Pre- and post-operative digital model images were compared, actual and planned miniscrew positions were superimposed and measured for 3D angular and distance deviations in the two groups. Comparisons between groups were made using the Kruskal–Wallis test.

Results:

In the CS group, the median coronal and sagittal angular deviations were 2.95 degrees (range 0.34–5.26 degrees) and 2.05 degrees (range 0.38–4.08 degrees), respectively, while the median coronal and apical deviations were 0.39 mm (range 0.24–0.51 mm) and 0.50 mm (range 0.16–0.66 mm). These deviations differed significantly from those of the DI group.

Conclusion:

The IZC CAD/CAM surgical guide has made it possible to control miniscrew placement with high precision.

[The experimental study of a Russian orthodontic mini-screw]

BACKGROUND

The aim of this research is the experimental study measuring stability of the orthodontic miniscrews «Turbo» designed in Russia in comparison with its foreign analogues, namely, «Vector Tas» (USA) and «BioRay» (Taiwan).

MATERIAL AND METHODS

Four self-drilling orthodontic miniscrews of each manufacturer, i.e. «Vector Tas», USA, (10-mm length, 2-mm diameter), «BioRay», Taiwan, (10-mm length, 2-mm diameter), «Turbo», Russia, (9-mm length, 2-mm diameter), a total of 12 items, were inserted into native pig mandible sample. Their stability was estimated by torques using a dynamometer (Zahoransky AG, Germany) and «Periotest» device («Periotest M», Germany). This experiment was conducted in native pig mandible sample immediately after the screws' placement and in 7 days after loading at an angle 70°.

RESULTS

After application of a load, the decreased torque values and increased Periotest values were registered in all orthodontic miniscrews.

CONCLUSION

Orthodontic miniscrews «Turbo» designed in Russia are slightly inferior to «VectorTas» miniscrews and superior to «BioRay» miniscrews in primary stability and stability after 7 days under loading.

Stress distribution patterns in mini-implant and bone in the infra-zygomatic crest region at different angulations: A finite element study

PURPOSE

To evaluate, using the finite element method (FEM), von Mises stress patterns produced both in a mini-implant (MI) and the infra-zygomatic crest region (IZC) at different placement angles and force magnitudes.

MATERIAL AND METHODS

FEM modeling of an infra-zygomatic crest MI, of dimensions 2 mm × 12 mm, was designed and placed in the IZC bone. The MI was inserted at 50°, 60°, 70°, 80°, and 90° angulations to the IZC surface. Simulated orthodontic forces of magnitudes 8, 9, 10, 11, and 12 oz were applied to the MI head. Von Mises stress and magnitude both in the MI and surrounding bone were measured.

RESULTS

Von Mises stress in the MI and bone was maximum at 90°. Least stresses were observed at 50° and 60° angulations. As force magnitude increased, von Mises stress increased linearly. Maximum stresses in the MI and bone were observed when loads were 12 oz and minimum stresses were observed at 8 oz.

CONCLUSION

To achieve optimum primary stability, angles of insertion between 50° and 60° are recommended in the IZC region. Highest von Mises stress values were detected in the MI, followed by cortical and cancellous bone. Also, loading force between 8 and 12 oz exerted stresses below the tolerable threshold of bone and MI. Hence, proper placement of MI in IZC using these findings might provide better biomechanical stability during retraction and may help in preserving the bone-implant interface.

Assessment of available sites for palatal orthodontic mini-implants through cone-beam computed tomography

OBJECTIVE

To measure the palatal thickness of both hard and soft tissues and to determine safe regions for the placement of mini-implants. The influences of sex and age on palatal thickness were also examined.

MATERIALS AND METHODS

Cone-beam computed tomography images of 30 patients (12 males, 18 females), including 15 adults and 15 adolescents, were used in this study. The thicknesses of palatal hard tissue, soft tissue, and hard+soft tissues were measured at the coronal planes of first premolars, second premolars, first molars, and second molars (P1, P2, M1, and M2 planes, respectively).

RESULTS

The hard tissue was thickest at the P1 plane, followed by at the P2, M1, and M2 planes, while the thickness of soft tissue was similar among the four planes. The trends in the changes of palatal thickness from midline to the lateral sides (V-pattern) were similar for the four planes. Palatal thickness was influenced by sex, age, and their interaction. Mapping of recommended and optimal sites for palatal mini-implants was accomplished.

CONCLUSIONS

Sex and age factors could influence palatal thickness. Therefore, the findings might be helpful for clinicians in guiding them to choose the optimal sites for palatal mini-implants.

An Umbrella Review of the Effectiveness of Temporary Anchorage Devices and the Factors That Contribute to Their Success or Failure

OBJECTIVES

New methodological approaches, such as the umbrella review, constitute an important pathway for synthesizing the scientific evidence provided from studies with a high level of evidence. This study aims to summarize the results on the effectiveness of temporary anchorage devices (TADs) and the factors that contribute to their success or failure during orthodontic treatment in patients of different age groups and to identify the gaps in knowledge based on analysis of the scientific literature.

METHODS

An umbrella review of systematic reviews and meta-analyses was performed. A quality evaluation and a descriptive analysis of the included studies were conducted. The study protocol was registered at the International Prospective Register of Systematic Reviews (PROSPERO: CRD42018094463).

RESULTS

Seventeen systematic reviews and meta-analyses were considered (10 descriptive and 7 with meta-analysis; 12 of high quality and 5 of moderate quality). Variability was observed in the type of intervention and the type of system (TADs). Most of the studies reported high success rates (≥90%), and just one systematic review indicated a low rate of success (≤56%) for the mini-screws. All the studies discussed several factors related to the success of the TADs. These factors were classified as device-related factors, patient-related factors, procedure-related factors, and orthodontic treatment-related factors. Conceptual and methodological gaps were observed when considering the data analysis, the terminology used, and the orthodontic protocols.

CONCLUSIONS

The results should be analysed cautiously because of several research gaps related to the methodological quality and the high heterogeneity of the original studies and because of the necessity to add several clinical and sociodemographic variables to enrich the data analysis.

Failure rates of miniscrews inserted in the maxillary tuberosity

Introduction:

Anchorage conservation in orthodontics has always been a challenge.

Objective:

The aim of this current study was to find out the failure rate of miniscrews inserted in the maxillary tuberosity (MT) region.

Methods:

This pilot study consisted of 40 patients (23 female, 17 male; mean age = 20.1±8.9 years) that had received 60 MT miniscrews for orthodontic treatment. Clinical notes and pictures were used to find out the primary outcome of miniscrew failure. Independent failure factors were also investigated. Logistic regression analysis was done for predictor’s relation with MT miniscrews failure.

Results:

There was no significant correlation in failure rate according to various predictor variables, except for miniscrews installed by lesser experienced operators, which showed significantly more failure. The odds ratio for miniscrew failure placed by inexperienced operators was 4.16.

Conclusion:

A 26.3% failure rate of mini-implants inserted in the MT region was observed.

Gender and growth variation in palatal bone thickness and density for mini-implant placement

BACKGROUND

The objective was to compare the palatal bone thickness (PBT) and palatal bone density (PBD) in the anterior, middle, and posterior part of the palate in males and females.

METHODS

This retrospective study reviewed cone beam computed tomography scans of 359 patients. The scans were divided into 99 growing males, 105 growing females, 74 non-growing males, and 81 non-growing females. The measurements of PBT and PBD were made in between the canine and first premolar, the first premolar and second premolar, the second premolar and first molar, and the first molar and second molar. The measurements were made in the center of the palate and 4 mm away from the center. ANOVA was used to analyze the PBT and PBD in different areas between four different groups.

RESULTS

The PBT was lower (P <  0.0001) as we moved from the anterior to the posterior palate. The PBT was more (P <  0.001) in the center of the palate than 4 mm away from the center, except in between the canine and first premolar. The growing male and non-growing male had higher (P <  0.0001) PBT than the growing female and non-growing female in between the canine and first premolar and the first premolar and second premolar both in the center and 4 mm away from it. The PBD was higher (P <  0.05) in between the canine and first premolar area at the center of the palate and between the second premolar and first molar 4 mm away from the center in all the experimental groups.

CONCLUSIONS

There exists a definite gender and growth variation in the PBT and PBD in different parts of the palate. Palatal bone thickness between the males and females revealed that the males had significantly higher PBT than the females.

Biomechanics of Extra-alveolar Mini-Implant Use in the Infrazygomatic Crest Area for Asymmetrical Correction of Class II Subdivision Malocclusion

Asymmetric malocclusion has always represented a challenge to orthodontists, with different dental, skeletal, or dentoskeletal factors being probable causes for the condition. It is a key to distinguish between dental and skeletal asymmetry before determining a predictable force system for corrective treatment. The use of mini-implants (MIs) to address anchorage needs in modern orthodontic practice has become an important tool for orthodontists. They have been widely used for anchorage reinforcement purposes and placed in the dentoalveolar region, especially between tooth roots. However, placement sites other than root areas allow more versatility of orthodontic movement since tooth roots do not interfere in tooth displacement. The objective of the present study is to present a clinical case of asymmetric malocclusion (Class II division 1 subdivision), in which a MI placed in the infrazygomatic crest area was used for correction of the maxillary asymmetry by means of unilateral distalization. Biomechanics of unilateral molar distalization combined with skeletal anchorage has allowed predictable outcomes to be achieved with minimal need for patient’s compliance and minor side effects.

Influence of orthodontic mini-implant penetration of the maxillary sinus in the infrazygomatic crest region

INTRODUCTION

Mini-implants are widely used for predictable tooth movements, but insertion is often restricted by anatomic structures. The aims of this study were to investigate the incidence of penetration of mini-implants into the sinus and the relationship between penetration depth and sinus tissue.

METHODS

Data from 32 patients who received mini-implants in the infrazygomatic crest were collected from a data base. The success rate of mini-implants was determined by clinical retrospective analysis. The incidence of penetration, penetration depth, and sinus configuration were investigated and compared between cone-beam computed tomography scans obtained immediately after insertion and before mini-implant removal.

RESULTS

The overall success rate of mini-implants in the infrazygomatic crest was 96.7%, and 78.3% penetrated into the sinus. In the group in which penetration exceeded 1 mm, the incidence of membrane thickening was 88.2%, and the mean value of thickening was 1.0 mm; however, the variable values of penetration in the 1-mm group were only 37.5% and 0.2 mm, respectively (P <0.05).

CONCLUSIONS

The incidence of penetration of infrazygomatic crest mini-implants into the sinus may be high. Penetration through double cortical bone plates with limitation of the penetration depth within 1 mm is recommended for infrazygomatic crest mini-implant anchorage.

Evaluation of mechanical strengths of three types of mini-implants in artificial bones

We investigates the effect of the anchor area on the mechanical strengths of infrazygomatic mini-implants. Thirty mini-implants were divided into three types based on the material and shape: Type A (titanium alloy, 2.0×12 mm), Type B (stainless steel, 2.0×12 mm), and Type C (titanium alloy, 2.0×11 mm).The mini-implants were inserted at 90° and 45° into the artificial bone to a depth of 7 mm, without predrilling. The mechanical strengths [insertion torque (IT), resonance frequency (RF), and removal torque (RT)] and the anchor area were measured. We hypothesized that no correlation exists among the mechanical forces of each brand. In the 90° tests, the IT, RF, and RT of Type C (8.5 N cm, 10.2 kHz, and 6.1 N cm, respectively) were significantly higher than those of Type A (5.0 N cm, 7.7 kHz, and 4.7 N cm, respectively). In the 45° test, the RFs of Type C (9.2 kHz) was significantly higher than those of Type A (7.0 kHz) and Type B (6.7 kHz). The anchor area of the mini-implants was in the order of Type C (706 mm²)>Type B (648 mm²)>Type A (621 mm²). Type C exhibited no significant correlation in intragroup comparisons, and the hypothesis was accepted. In the 90° and 45° tests, Type C exhibited the largest anchor area and the highest mechanical strengths (IT, RF, and RT) among the three types of mini-implants. The anchor area plays a crucial role in the mechanical strength of mini-implants.