Self-drilling Orthodontic Mini-implants Research Articles

Comparison of primary stability of used and unused self-tapping and self-drilling orthodontic mini-implants.

Skeletal anchorage has been the subject of study for many years. Recently, orthodontic mini-implants (MIs) were described as effective tools for anchorage and were named temporary anchorage devices (TADs). The success of MIs depends on their primary stability, which is defined as the lack of mobility in the bone after implant insertion, and the relevant factors affecting primary stability. This study aimed to compare the primary stability of used self-drilling (SD) and self-tapping (ST) MIs with unused ones by performing the insertion torque measurement, Periotest and pull-out test. Forty-six used (23 ST, 23 SD) and 46 unused (23 ST, 23 SD) MIs (1.5 mm × 8 mm) were inserted into a synthetic bone with the use of a digital screwdriver. Maximum insertion torque (MIT) values were recorded during the placement of MIs, and then Periotest measurements were made. Following the MIT and Periotest measurements, pull-out tests were performed on all MIs. The median MIT values (Ncm) of the MIs were as follows: used ST: 17.3, unused ST: 18.9, used SD: 24.1, unused SD: 25.2. The median values obtained after the Periotest were (±): used ST: 0, unused ST: -1, used SD: -3, unused SD: -3. Median pull-out values (N) were: used ST: 148.12, unused ST: 168.12, used SD: 173.12, unused SD: 203.20. Statistically, MIT and pull-out values of the used ST and SD implants were significantly lower compared to those of the unused ST and SD implants (p < 0.05). Used orthodontic MIs showed poor performance compared with unused implants when they were inserted again in the in vitro conditions.

Stress distribution in lower second molar mesialization using mini-implants: a pilot study using 3D finite element analysis

Objective: to analyze the stress distribution in a 3D model that simulates second molar mesialization using twodifferent types of mini-implants. Material and Methods: a mandible bone model was obtained by recomposinga computed tomography performed by a software program. The cortical and trabecular bone, a lower secondmolar, periodontal ligament, orthodontic tube, resin cement and the mini-implants were designed and modeledusing the Rhinoceros 4.0 software program. The characteristics of self-drilling orthodontic mini-implants were:one with 7 mm length, 1 mm transmucosal neck section and 1.6 mm diameter and another with 5 mm lengthand 1.5 mm diameter. A total of 235.161 and 224.505 elements were used for the mesh. These models wereinserted into the bone block and then subjected to loads of 200 cN (centinewton). The results were calculatedand analyzed by the Ansys 17.0 software program for qualitative verification through displacement and maximumprincipal stress maps. Results: it was possible to observe that the periodontal ligament presented low displacementand stress values. However, the physiological values presented are among those capable to provide orthodonticmovement, with compression and tensile area visualization staggered between 0.1 and -0.1 MPa (megapascal).Conclusion: within the limitations of the study, the mini-implants tested showed similar results where theload on the tooth allowed dental displacement (molar mesialization), with a tendency to rotate it, theoreticallyallowing the second molar to take the location of the first molar. KEYWORDSFinite element analysis; Orthodontic anchorage procedures; Fixed orthodontic appliances; Mini dental implants;Tooth dislocation.

Assessment of outcome of orthodontic mini dental implants

Background: Successful orthodontic therapy has always depended upon on intraoral anchorage with a great resistance to displacement. Osseointegrated implants are considered reliable sources of anchorage for orthodontists hence; the present study was undertaken for assessing the outcome of orthodontic Mini dental implants. Materials &amp; methods: A total of 100 patients were enrolled. In all the involved patients, one or more self-drilling mini-screws were inserted. Orthodontic mini-implants were considered successful when they proved a perfect skeletal anchorage during the entire treatment period (independent from the period's length) without sign of mobility. All the results were recorded and analysed using SPSS software. Results: Success was observed in 85 percent of the cases. Failure was seen in 15 percent of the cases. Among the failure cases, inflammation was the cause in 10 percent of the cases while screw fracture was seen in 5 percent of the cases. Conclusion: Under the hands of skilled and experienced clinician, self-drilling orthodontic mini-implants had excellent prognosis.

Residents’ journal review

Residents’ journal review

Influence of Manual Screwdriver Design in Combination With and Without Predrilling on Insertion Torque of Orthodontic Mini-Implants.

The study focused on the influence of screwdriver design in combination with and without predrilling a pilot hole of inner implant diameter on insertion torque of orthodontic mini-implants, controlling for cortical thickness and vertical insertion force as cofactors. One hundred twenty mini-implants (Forestadent) of 1.7 mm in diameter and 6 and 8 mm in length were manually inserted into 120 swine rib bone samples. Maximal insertion torque as a measure of primary stability and vertical force were measured. The study included procedures with and without pilot hole and different screwdriver handles and shaft length and 2 implant lengths. Design of manual screwdriver does not modify insertion torque to a significant extent. In multiple linear regression model, significant predictors of insertion torque are thicker cortical bone (explaining 16.6% of variability), higher vertical force at maximal torque (13.5%), 6-mm implant length (2.5%), and the presence of pilot hole (2.3%). Handle type and shaft length of manual screwdriver do not significantly influence insertion torque, whereas predrilling a pilot hole has low impact on torque values of manually inserted self-drilling orthodontic mini-implants.

Insertion Torques of Self-Drilling Mini-Implants in Simulated Mandibular Bone: Assessment of Potential for Implant Fracture.

Fracture of orthodontic mini-implants during insertion is a limiting factor for their clinical success. The purpose of this study was to determine the fracture potential of commonly used self-drilling orthodontic mini-implants when placed into simulated thick, dense mandibular bone. Six mini-implant systems were assessed for the potential for fracture (Aarhus, Medicon; Dual-Top, Jeil Medical; OrthoEasy, Forestadent; tomas-pin, Dentaurum; Unitek, 3M; and VectorTAS, Ormco). First, mini-implants were inserted manually, without predrilling, into bone substitutes (Sawbones) with a 3-mm-thick, dense (1.64 g/cm(3)) cortical layer. A custom-made insertion device was used for placement of mini-implants. A sixaxis force/torque transducer was secured at the base of the bone blocks to measure the maximum torque experienced during insertion. Measured insertion torques were compared with previously reported fracture torques, yielding a torque ratio (insertion torque as a percentage of fracture torque), which was used as an indicator of the potential for mini-implant fracture. Mini-implants that experienced torque ratios ≥ 75% upon insertion underwent further testing, following the manufacturer's recommendations for predrilling in thick, dense bone conditions. Significant differences in torque ratios were found among all mini-implants, except between OrthoEasy and Dual-Top, and OrthoEasy and VectorTAS. Overall, Aarhus had the highest torque ratio (91% ± 3%), with Unitek showing the lowest ratio (37% ± 3%). Aarhus and tomas-pin mini-implants displayed torque ratios ≥ 75% and experienced fracture upon insertion. When the manufacturer's specific predrilling recommendations were followed, no changes in torque ratio were found for Aarhus and tomas-pin. However, while Aarhus continued to fracture upon insertion, all tomas-pin mini-implants were inserted fully without fracture following predrilling. These findings support the safe use of Unitek, VectorTAS, Dual-Top, and OrthoEasy self-drilling mini-implants in areas of 3-mm-thick, 1.64 g/cm(3) dense cortical bone without predrilling. Following predrilling, fractures did not occur with tomas-pin. For implants that continued to fracture after predrilling, other strategies may be required, such as the use of larger-diameter mini-implants in thick, dense bone conditions.

Roughness and wettability effect on histological and mechanical response of self-drilling orthodontic mini-implants.

Self-drilling orthodontic mini-implants can be used as temporary devices for orthodontic treatments. Our main goal was to evaluate surface characteristics, roughness and wettability, of surface modified mini-implants to increase their stability during orthodontic treatment without inducing bone fracture and tissue destruction during unscrewing. Modified mini-implants by acid etching, grit-blasting and its combination were implanted in 20 New Zealand rabbits during 10weeks. After that, the bone-to-implant (BIC) parameter was determined and the torque during unscrewing was measured. The surface characteristics, roughness and wettability, were also measured, onto modified Ti c.p. discs. Acid-etched mini-implants (R a≈1.7μm, contact angle (CA)≈66°) significantly improved the bone-to-implant parameter, 26%, compared to as-machined mini-implants (R a≈0.3μm, CA≈68°, BIC=19%) due to its roughness. Moreover, this surface treatment did not modify torque during unscrewing due to their statistically similar wettability (p>0.05). Surface treatments with higher roughness and hydrophobicity (R a≈4.5μm, CA≈74°) lead to a greater BIC and to a higher removal torque during unscrewing, causing bone fracture, compared to as-machined mini-implants. Based on these in vivo findings, we conclude that acid-etching surface treatment can support temporary anchoring of titanium mini-implants. This treatment represents a step forward in the direction of reducing the time prior to mini-implant loading by increasing their stability during orthodontic treatment, without inducing bone fracture and tissue destruction during unscrewing.

Bone cutting capacity and osseointegration of surface-treated orthodontic mini-implants.

ObjectiveThe objective of the study was to evaluate the practicality and the validity of different surface treatments of self-drilling orthodontic mini-implants (OMIs) by comparing bone cutting capacity and osseointegration.MethodsSelf-drilling OMIs were surface-treated in three ways: Acid etched (Etched), resorbable blasting media (RBM), partially resorbabla balsting media (Hybrid). We compared the bone cutting capacity by measuring insertion depths into artificial bone (polyurethane foam). To compare osseointegration, OMIs were placed in the tibia of 25 rabbits and the removal torque value was measured at 1, 2, 4, and 8 weeks after placement. The specimens were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS).ResultsThe bone cutting capacity of the etched and hybrid group was lower than the machined (control) group, and was most inhibited in the RBM group (p < 0.05). At 4 weeks, the removal torque in the machined group was significantly decreased (p < 0.05), but was increased in the etched group (p < 0.05). In the hybrid group, the removal torque significantly increased at 2 weeks, and was the highest among all measured values at 8 weeks (p < 0.05). The infiltration of bone-like tissue surface was evaluated by SEM, and calcium and phosphorus were detected via EDS only in the hybrid group.ConclusionsPartial RBM surface treatment (hybrid type in this study) produced the most stable self-drilling OMIs, without a corresponding reduction in bone cutting capacity.

Histologic, Histomorphometric, and Radiographic Monitoring of Bone Healing Around In-Office–Sterilized Orthodontic Mini-implants With or Without Immediate Load: Study in Rabbit Tibiae

The objective of this study was to describe bone healing around self-drilling orthodontic mini-implants (MIs), sterilized in an office with an autoclave, with or without immediate orthodontic loading. One hundred forty-four self-drilling MIs (TOMAS, Dentaurum) were inserted into the tibiae of 18 white rabbits, with full-thickness flaps elevated under general anesthesia. An immediate load (50 cN) was applied to 50% of the MIs. Two rabbits were sacrificed soon after the surgery and served as a control group. Four rabbits each were sacrificed at 15, 21, 30, or 60 days after the surgeries. Digital radiographs were obtained to measure the cortical bone thickness (CBT) around and between the implants. Sections were obtained and stained for histologic and histomorphometric analysis. Bone quantity (BQ), bone-to-implant contact (BIC), and CBT were evaluated statistically. At day 0, fractures were visible in the cortical area around the MIs. At days 15 and 21, intense proliferation of woven bone followed by formation of lamellar bone was seen. After 30 days, primary bone was visible, with less proliferation activity. At day 60, primary bone in the process of remodeling into secondary bone was apparent. BQ was better with loading after 15 days and increased throughout the healing period in the loaded and unloaded groups. Loading did not influence the BIC values, which increased with healing time for loaded and unloaded implants. CBT increased in all regions, and CBT was greater around the MIs than between them except for unloaded MIs in the 15-day group. An immediate, light orthodontic load did not affect the bone healing process around orthodontic MIs. Osseointegration and CBT increased and were time-related.

Geometrical design characteristics of orthodontic mini-implants predicting maximum insertion torque.

ObjectiveTo determine the unique contribution of geometrical design characteristics of orthodontic mini-implants on maximum insertion torque while controlling for the influence of cortical bone thickness.MethodsTotal number of 100 cylindrical orthodontic mini-implants was used. Geometrical design characteristics of ten specimens of ten types of cylindrical self-drilling orthodontic mini-implants (Ortho Easy®, Aarhus, and Dual Top™) with diameters ranging from 1.4 to 2.0 mm and lengths of 6 and 8 mm were measured. Maximum insertion torque was recorded during manual insertion of mini-implants into bone samples. Cortical bone thickness was measured. Retrieved data were analyzed in a multiple regression model.ResultsSignificant predictors for higher maximum insertion torque included larger outer diameter of implant, higher lead angle of thread, and thicker cortical bone, and their unique contribution to maximum insertion torque was 12.3%, 10.7%, and 24.7%, respectively.ConclusionsThe maximum insertion torque values are best controlled by choosing an implant diameter and lead angle according to the assessed thickness of cortical bone.

Assessment of damping capacity as an index of root proximity in self-drilling orthodontic mini-implants

This study aims to investigate orthodontic mini-implant root proximity, placement torque, and damping capacity and to determine whether placement torque and damping capacity (Periotest value (PTV)) are useful indices for the estimation of mini-implant root proximity. The root proximity of 143 orthodontic mini-implants (1.6mm diameter, 8mm screw thread length) was evaluated in 79 patients (24 males, 55 females; mean age, 22.5 ± 8years) using cone-beam computed tomography. The placement torque and PTV of each implant were determined using a torque tester and the Periotest, respectively. Variability in these values according to root proximity was evaluated. PTVs of mini-implants with multiple (two or more) points of contact between the root and implant were significantly larger than those of mini-implants with no root contact in the self-drilling group. Placement torque did not differ significantly according to root proximity. In the self-drilling group, the odds ratio for root contact was 20.82 (P = 0.000) for a PTV >6. Placement torque could not be used to estimate root proximity. The PTV was significantly affected by root proximity in the self-drilling group. A threshold of PTV >6 could be applied clinically for the estimation of self-drilling mini-implant root proximity.

Design characteristics, primary stability and risk of fracture of orthodontic mini-Implants: Pilot scan electron microscope and mechanical studies

Objectives: Orthodontic mini-implants (OMIs) are increasingly used in orthodontics but can fail for various reasons. This study investigates the effects of OMI design characteristics on the mechanical properties in artificial bone. Material and Methods: Twelve self-drilling OMIs (2 small, 6 medium, 4 large) from 8 manufacturers were tested for their primary stability in simulated medium-high cancellous bone and the risk to fracture in high-density methacrylate blocks. For the assessments of the maximum insertion torque (IT) and torsional fracture (TF) 5 of each OMI were used and for the pull-out strength (POS) 10. The OMIs were inserted with a torque screwdriver (12 sec/360°) until the bottom at 8 mm depth was reached. OMI designs were analyzed with a scan electron microscope (SEM). Results: SEM images revealed a great variation in product refinement. In the whole sample, a cylindrical OMI shape was associated with higher POS (p<0.001) but lower IT (p=0.002) values. The outer and inner OMI diameters were design characteristics well correlated with POS, IT and TF values (ranging from 0.601 to 0.961). Greater thread depth was related to greater POS values (r= 0.628), although OMIs with similar POS values may have different IT values. Thread depth and pitch had some impact on POS. TF depended mainly on the OMI inner (r= 0.961) and outer diameters (r=0.892). A thread depth to outer diameter ratio close to 40% increased TF risk. Conclusions: Although at the same insertion depth the OMI outer and inner diameters are the most important factors for primary stability, other OMI design characteristics (cylindrical vs. conical, thread design) may significantly affect primary stability and torsional fracture. This needs to be considered when selecting the appropriate OMI for the desired orthodontic procedures. Key words:Orthodontic mini-implants, primary stability, insertion torque, pullout strength, torsional fracture.

Safe placement techniques for self-drilling orthodontic mini-implants

Self-drilling mini-implants are being used more frequently as an orthodontic anchorage, but the placement torque of self-drilling mini-implants can easily become excessive in the thick, mandibular cortical bone. The purpose of this study is to examine a safe self-drilling placement technique that provides adequate placement torque for orthodontic mini-implants. The mini-implants were placed using self-drilling and pre-drilling methods into the ribs of pigs. Specimens were classified into two groups, thin and thick, with cortical bone thicknesses of 1.2±0.02 and 2.0±0.03mm, respectively, and used to model the human maxillary and the mandibular bones. The peak mini-implant placement torque value was measured and the surrounding cortical bone was observed histologically. In the mandible model, the torque in the self-drilling and pre-drilling groups exceeded 10Ncm, except in one case which had a 1.3mm diameter pilot hole. Histology revealed cracks in the surrounding cortical bone in the groups whose torque value was 10Ncm or more. Therefore, when using the self-drilling technique to place a 1.6mm diameter mini-implant in the mandibular alveolar bone, it is preferable to drill a 1.3mm diameter pilot hole first.

Angled-predrilling depth and mini-implant shape effects on the mechanical properties of self-drilling orthodontic mini-implants during the angled insertion procedure

To investigate the effects of orthodontic mini-implant (OMI) shape and angled-predrilling depth on the mechanical properties of OMIs during the angled insertion procedure. A total of 30 OMIs (self-drilling type, 7 mm in length) were allocated into six groups according to the OMI shape (cylindrical or tapered) and angled-predrilling depth (control, 1.5-mm and 4.0-mm angled-predrilling; predrilled with 1-mm-diameter drill-bit), as follows: C-con, C-1.5, C-4.0, T-con, T-1.5, and T-4.0 groups (N = 5 per group). The OMIs were installed at an angle of 60° in double-layer artificial bone blocks that simulated the cortical and cancellous bone (Sawbone(®)). Total insertion time (TIT), maximum insertion torque (MIT), total insertion energy (TIE), and inclination of the time-torque graph (INC) were measured. Within the same shape group, angled-predrilling had a shorter TIT than did the control (control vs 1.5; control vs 4.0; all P < .05). MIT and TIE decreased in the order of control, 1.5-mm, and 4.0-mm angled-predrilling (control vs 1.5; 1.5 vs 4.0; all P < .05), but INC increased from control to 1.5-mm angled-predrilling and decreased from 1.5-mm to 4.0-mm angled-predrilling within the same shape group (control vs 1.5, 1.5 vs 4.0; all P < .05). The MIT of the tapered group was greater than that of the cylindrical group (C-con vs T-con, C-1.5 vs T-1.5; all P < .05, C-4.0 vs T-4.0; P < .01). In the same angled-predrilling depth, no differences were observed in TIE between the cylindrical and tapered groups (C-1.5 vs T-1.5, C-4.0 vs T-4.0; all P > .05). In angled-predrilling insertion of OMIs into thick cortical bone, tapered OMIs might be a better choice than cylindrical OMIs for increasing primary stability because of higher MIT and similar TIE values.

Influence of surface treatment on the insertion pattern of self-drilling orthodontic mini-implants

Influence of surface treatment on the insertion pattern of self-drilling orthodontic mini-implants

Effects of the diameter and shape of orthodontic mini-implants on microdamage to the cortical bone

The purpose of this study was to investigate the effects of the diameter and shape of orthodontic mini-implants (OMIs) on microdamage to the cortical bone during implant placement. Twenty-eight self-drilling OMIs (Biomaterials Korea, Seoul, Korea; length, 6 mm; diameters, 1.5 and 2 mm; cylindrical and tapered shapes; classified as 1.5C, 2C, 1.5T, and 2T) were placed with a surgical device in the tibias of 7 New Zealand white rabbits (mature males; mean age, 6 months; mean weight, 3.1 kg). Four OMIs of each type per rabbit were placed randomly. Maximum insertion torque (MIT) was measured. Immediately after placement of the OMIs, the block of bone with the OMI was harvested. Cortical bone thickness was measured by using microcomputed tomography, and histomorphometric analyses of the number of cracks (NC), accumulated crack length (ACL), maximum radius of the crack (MRC), and longest crack (LC) were performed. Kruskal-Wallis and Mann-Whitney U tests with the Bonferroni adjustment were done for statistical analyses. Increased diameter (1.5C<2C and 1.5T<2T) and tapering (1.5C<2T) resulted in increased values of MIT, NC, and LC (P <0.01, respectively). Similarly, with increased diameters (1.5C and 1.5T<2C and 2T), there were increases of ACL and MRC (P <0.001, respectively). However, there were no differences in the values of MIT, NC, ACL, MRC, and LC between the cylindrical and tapered OMIs with the same diameters (1.5C and 1.5T, 2C and 2T). OMIs with larger diameters and tapered shapes caused greater microdamage to the cortical bone; this might affect bone remodeling and the stability of the OMIs.