Self-drilling Miniscrews Research Articles

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 & 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.

Miniscrew-assisted rapid palatal expansion appliance associated with a new cortical perforations protocol: A case series

• Successful maxillary expansion in older and skeletally mature patients was obtained. • Cortical perforations were performed with a trephine bur and reached the nasal floor. • Perforations in the midpalatal suture can improve miniscrew-assisted rapid palatal expansion. • Perforations in nongrowing patients can be a solution to ensure the midpalatal suture split. This case series describes the use of a miniscrew-assisted rapid palatal expansion (MARPE) appliance to orthopedically correct transverse maxillary deficiencies in four skeletally mature patients. In addition, cortical perforations were performed to ensure the midpalatal suture (MPS) split. Expansion forces were applied in the appliance to create negligible dental effects and true skeletal expansion, although patients presented interdigitated MPS. All patients presented posterior crossbites, and their ages ranged from 29 to 46 years. Eight cortical perforations were performed in all patients with a 2.0 mm trephine bur, inserted until the nasal cortical floor was perforated. The MARPE expanders were installed with four self-drilling miniscrews. The MPS was successfully opened in all patients, and all crossbites were resolved. The mean MPS opening in the area of the incisors was 3.27 mm, and at the first and second molars was 2.05 and 1.55 mm, respectively. The basal bone was increased by 3.8 mm, whereas the nasal cavity was increased by 2.75 mm. Negligible teeth tipping was observed. This case series demonstrates that MARPE associated with cortical perforations that reach the nasal floor can successfully split the MPS in skeletally mature patients.

Success rate of surface-treated and non-treated orthodontic miniscrews as anchorage reinforcement in the lower arch for the Herbst appliance: A single-centre, randomised split-mouth clinical trial.

Surface treatment of miniscrews was implemented to determine whether its application increased bone-to-surface contact and enhanced the interlock between the device and the surrounding bone. To compare the success rate of surface-treated and non-treated orthodontic miniscrews used as reinforcement of anchorage during treatment with the Herbst appliance. Split-mouth design with an allocation ratio of 1:1. Eligibility criteria to enrol patients were skeletal and dental class II patients with a retrusive chin, use of the Herbst appliance to correct malocclusion, need for skeletal anchorage using a miniscrew both in the left and right side of the mouth, absence of systemic diseases, absence of using drugs that alter bone metabolism, and good oral hygiene. Patients received self-drilling miniscrews without surface treatment and with surface treatment. Both types presented a 1.4 or 1.2 mm diameter. Miniscrews were inserted between the first molar and second premolars or between the two premolars. The force applied to the screws was an elastic chain from the head of the miniscrews to a direct button applied on the canines. The success rate of each type of miniscrew was considered the primary outcome, and the association of success with demographical, clinical, and geometrical characteristics was investigated. Differences were tested by the generalised linear mixed effects model for the split-mouth design. Differences with a P-value < 0.05 were selected as significant. A randomisation list was created for the mouth side assignment. The study was single blinded with regard to the statistical analysis. Thirty-nine miniscrews of the non-treated type and 39 miniscrews of the surface-treated type were inserted in 39 patients (23 female and 16 male, mean age: 15.55 ± 7.91) recruited between March 2018 and December 2020 with a split-mouth study design. The mean therapy duration was 9.3 months (SD = 1.31). No differences in failure rate were observed between miniscrew types. No serious harm was observed. The success rate of surface-treated and non-treated miniscrews showed no significant differences. This trial was not registered.

Geometry of anchoring miniscrew in the lateral palate that support a tissue bone borne maxillary expander affects neighboring root damage

Anchoring miniscrews used for a tissue bone borne maxillary expander (C-expander) can fail if they contact tooth roots or perforate the maxillary sinus. Cone beam computed tomography images were reviewed retrospectively to evaluate the geometric factors of miniscrew placement in the palate that contribute to root proximity (RP) and sinus perforation (SP), and to investigate the differences of miniscrew placement depth (PD) and placement angle (PA) among the groups in each variable from 340 anchoring miniscrews on 70 patients whose C-expanders showed sufficient stability after palatal expansion for orthodontic treatment. Two types of miniscrews were used: a self-tapping miniscrew with 1.8 mm-in-diameter, and a self-drilling miniscrew with 1.6 mm-in-diameter. While the self-tapping larger diameter miniscrew influenced root proximity significantly, the screw location and PD affected the rate of sinus perforation. PA was significantly different between the right and left sides of the palate. The results of this study confirmed that root proximity and sinus perforation of anchoring miniscrews in a tissue bone borne palatal expander occurred due to certain risk factors, even when the palates were expanded successfully. Knowledge of these factors can help the clinician place miniscrews with less risk of root proximity or sinus perforation.

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.

Drilling Capability of Orthodontic Miniscrews: In Vitro Study.

The aims of this study were to assess the values and mechanical properties of insertion torque (IT) of steel miniscrews inserted in artificial bone blocks (Sawbones, Pacific Research Laboratories, Vashon, WA, USA) with different bone densities and to detect any scratches on the surface of the miniscrews after insertion. Forty self-drilling miniscrews (Leone S.p.A. ø 1.75 mm, L 8 mm) have been inserted into bone blocks that mimic different stability conditions (density: 20 PCF—pounds per cubic foot, 40 PCF, and 30 + 50 PCF with 2 mm and 4 mm of cortical bone). Before insertion and after removal, all miniscrews were inspected with a stereomicroscope 5x and a SEM to detect potential microscopic cracks. Using an electronic surgical motor (W&H Dentalwerk Bürmoos GmbH, Werner Bader Str. 1, 5111 Bürmoos, Austria), the maximum insertion torque value was registered. Stereomicroscope and SEM examination did not indicate any morphological and surface structural changes to the miniscrews, irrespective of the bone density they were inserted into. The findings showed that IT increased significantly with increasing bone density. In each artificial bone block, morphostructural analysis demonstrated the adequate mechanical properties of the self-drilling miniscrews. IT measurements indicated torque values between 6 and 10 Ncm for blocks with a density of 30 + 50 PCF, whereas the suggested values are between 5 and 10 Ncm.

Removal Torque Analyses of Two Self-drilling Orthodontic Temporary Anchorage Devices (TADs)

Stability of miniscrews or Temporary Anchorage Devices (TADs) is an essential factor for successful application in orthodontics. Miniscrews removal torque can be used as an indicator of miniscrews stability. The objective of this work was to compare removal torque between self-drilling tapered mini-screws and cylindrical miniscrews. Materials and Methods: Two groups of TADs were inserted in the maxillae of orthodontic patients to provide stationary anchorage for front teeth retraction. Group 1: 20 tapered self-drilling miniscrews, Group 2: 20 cylindrical self-drilling miniscrew. Split mouth technique was used. All of the TADs were inserted parallel to the occlusal plane, between roots of the 2nd maxillary premolar and 1st maxillary molar. The TADs were immediately loaded with constant and continuous load using 8 mm long heavy short Nickel Titanium coil spring. The coil spring was stretched between the heads of the two types of TADs and crimpable hooks that fixed on arch wire just distal to the anterior six maxillary teeth. After complete retraction of the anterior maxillary teeth, TADs were removed using torque adjustable screw-removal. At the moment of movement of the TAD the torque was recorded in Newton Centimeter (Ncm). Results: Mann Whitney U Test resulted in a significant difference between the two groups, indicating that cylindrical TADs had significantly higher removal torque than tapered TADs (means were 3.20 Ncm ± 0.20 and 2.70 Ncm ± 0.10 respectively). Conclusion: Physical properties have a considerable influence on the stability of the TADs. Cylindrical TADs are showed more mechanical interlock into the bone.

Does audiovisual information affect anxiety and perceived pain levels in miniscrew application? \u2014 a within-person randomized controlled trial

BackgroundAnxiety can cause difficulties during surgical procedures. The main objective of this study was to evaluate changes in patients’ anxiety and perceived pain levels after receiving audiovisual and verbal information about miniscrew application.Materials and methodsEighty-eight patients (30 males and 58 females) with a mean age of 18.18 ± 5.39 years who had fixed orthodontic treatment and required miniscrew anchorage took part in this questionnaire-based randomized controlled trial. The participants were randomly allocated to two groups and either watched a video depicting miniscrew application (study group, 44 patients) or were informed verbally about the procedure (control group, 44 patients) before miniscrew placement. The audiovisual information was given via a video containing footage of local anesthesia injection, topical antiseptic application, and miniscrew insertion. The Spielberger State-Trait Anxiety Inventory (STAI) was used to measure anxiety immediately before miniscrew application. Self-drilling miniscrews (8 mm length, 1.5 mm diameter; Aarhus System Miniscrews, American Orthodontics, Washington, USA) were placed in posterior buccal interdental region. Each patient received only one miniscrew. Postoperative pain (PP) was determined using a 100-mm horizontal visual analog scale (VAS).ResultsState and total anxiety scores were significantly higher in the study group than in the control group (p = 0.009 and p = 0.011 respectively). The mean PP scores (SD) for control and study groups were 12.86 (14.22) and 12.8 (16.22), respectively. The results of Mann–Whitney U test showed no significant difference (p > 0.05). Participants’ PP scores did not have a significant effect on state, trait, or total anxiety scores. There was a weak but significant positive correlation between trait anxiety and state anxiety scores in both groups.ConclusionUsing an audiovisual method to inform patients about miniscrew placement increased anxiety levels but did not affect pain perception.

Stability of two self-drilling Orthodontic Temporary Anchorage Devices (TAD) assessed by Histomorphometric Changes

Aims: This work was aimed to evaluate bone density around two types of self-drilling orthodontic miniscrews in mongrel dogs. Materials and methods: two groups of TADs were inserted in the maxillae of six mongrel dogs. Group 1: six tapered self-drilling miniscrews, each of which was inserted in the right buccal side between the roots of the maxillary third premolar (P3). Group 2: Six cylindrical self-drilling miniscrews, each of which was inserted in the right buccal side between the roots of the maxillary first molar (M1 ). All of the TADs were inserted parallel to the occlusal plane. Occlusal radiographic views were taken at different time intervals: pre-insertion, just after insertion (T0), after 4 weeks (T1), after 8 weeks (T2) and after 12 weeks (T3). Using IDRISI Kilimanjaro computer software, the peri-implant area surrounding the apical one third of miniscrew was studied measuring the amount of grey shade. Bone density was measure in five areas (zone1 through zone 5) around the apical 1/3 of the TADs. Paired t- test was used to compare the measurements of the bone density pre-insertion of TADs between roots of M1 and P3, and the bone density post-insertion of TADs in the cylindrical and tapered TAD. The unpaired t-test was used to evaluate the difference in bone density of each zone around the tapered TAD and it correspondent zone around the cylindrical TAD. Results: the significance of the scheduled differences between means of bone density around group1 and group 2 were variable, indicating that the bone density depends on several factors. Conclusion: TAD design has an influence on the bone density. Cylindrical TADs have more bone density around than tapered TADs.

Comparing the Clinical Success Rate of Self-Drilling and Self-Tapping Mini-screws in the Retraction of Maxillary Anterior Teeth

Objective: To compare the success of self-drilling and self-tapping methods in the retraction of maxillary anterior teeth. Material and Methods: The study was conducted in 57 subjects with Cl II malocclusion who needed to be treated with extraction of four maxillary teeth. The self-tapping method was used on the left side and the self-drilling method was used on the right side. Then, the pain rate of each method was recorded by the numerical rating scale (NRS). Statistical analysis was done by t-test and Chi-square test. The significance level in this study was considered at p-value 0.05). There was a significant difference between the groups (p=0.03). The pain was significantly higher in the female. Conclusion: There is no difference between self-drilling and self-tapping methods in terms of success. Comparison of the pain between two genders according to the replantation method showed a significant difference in pain sensation between two genders. The pain sensation mean in female group was greater than male group.

A prospective, split-mouth, clinical study of orthodontic titanium miniscrews with machined and acid-etched surfaces.

To determine whether the success rate and primary stability of surface-treated miniscrews differ from those of nontreated miniscrews. Patients who required one or more miniscrews for the same reason in each quadrant were recruited into a single-blinded, split-mouth, randomized, controlled trial with a 1:1 allocation ratio. Self-drilling miniscrews with two surface types were used: those with no surface treatment, and those with an acid-etched surface treatment. The cumulative success rate and primary stability of each type of miniscrew were examined, and factors potentially affecting the success and failure of miniscrews were investigated. Forty patients were included in the study, with a total of 98 orthodontic miniscrews. The overall success rate was 88.8%, and the respective success rates for acid-etched and machined surface miniscrews were 91.8% and 85.7%. The respective mean insertion torques were 13.62 ± 5.95 N·cm and 13.38 ± 4 N·cm, and periotest values measured immediately after insertion were -0.50 ± 2.77 for acid-etched miniscrews and -0.28 ± 3.36 for machined surface miniscrews. There was no significant difference in the mean insertion torques and periotest values according to surface treatment and jaw. Neither the success rate nor the primary stability of acid-etched surface miniscrews and machined surface miniscrews differed significantly. There is a high possibility that miniscrews will fall out in patients who have an open bite or those who require total distalization.

Cortical Piezo-Puncture as a Minimally Invasive Method for Reducing MiniScrew Implant Insertion Torque: A Preliminary in vitro Study

Objective The objective of this study was to determine the effect of cortical piezo-puncture (CPP) on maximum insertion torque (MIT), maximum removal torque (MRT), and maximum axial load (MAL) during the insertion of self-drilling miniscrew implants (MSI), in an experimental model with proximal epiphysis of bovine tibia. Materials and Methods A comparative study was conducted using two groups of 20 self-drilling MSI inserted in intact bone (control group) and in bone with previous CPP (experimental group). MIT, MRT, and MAL of the 20 mini implants of each group were measured. Using SPSS software, Student’s t-test was applied to compare MIT and MRT and the U-test Mann–Whitney test was applied to compare MAL in both groups as well as Pearson and Spearman correlation. Results In the experimental group, average values of 12.85 (±4,32) Newton x centimeters (Ncm), 13.7 (±4,54) Ncm, and 22,474 (±895,95) gF for MIT, MRT, and MAL were found, respectively. In the control group, average values found for MIT, MRT, and MAL were 20.2 (±4,7) Ncm, 22.3 (±5,17) Ncm, and 4688,7 (±320,18) gF, respectively. Statistically significant differences were observed in MIT, MRT, and MAL between control and experimental groups (P < 0,001). Conclusions CPP before insertion of orthodontic MSI in bovine tibia significantly reduces MIT, MRT, and MAL.

Influence of geometric design characteristics on primary stability of orthodontic miniscrews.

Aim of the present study was to investigate the influence of geometric design characteristics on primary stability of orthodontic miniscrews. Forty self-drilling miniscrews with different geometric design characteristics were divided into the following groups (n = 10): groupI-Tomas® (Dentaurum, Germany), groupII-AbsoAnchor® (Dentos, Korea), groupIII-HUBIT® miniscrew (HUBIT, Korea), groupIV-Creative® (China). The four types were conical miniscrews with 1.6 mm diameter and 6.0 mm length. The miniscrews were manually inserted perpendicular to cow ribs until the full thread length was reached with the help of a1.3 mm predrilled pilot hole. Each miniscrew was evaluated usingscanning electron microscope. Linear and angular measurements were taken using Photoshop CS3 software. Miniscrew stability was measured by the Periotest® and pullout test. All linear and angular measurements of the geometric characteristics showed significant differences between the four groups (p ≤ 0.001). Results of the pullout test showed significant differences between the four groups (p ≤ 0.001), while the Periotest® values showed no significant differences (p = 0.122). Amultiple linear regression analysis revealed the significant predictors for higher pullout: alarger flank, ahigher value for the thread angle, lead angle, and apical face angle (p ≤ 0.001). Orthodontic miniscrews' geometric design characteristics significantly affected the primary stability. Larger pitch width, flank, thread angle, apical face angle, and/or lead angle led to higher primary stability. Smaller athread shape factor (TSF) also improved primary stability. Varying these characteristics may enhance miniscrew design.

In vitro assessment of maximum insertion and removal torque with three different miniscrews on artificial maxilla and mandible

ObjectiveThe aim of this study was to measure and correlate the values of maximum insertion and removal torques of miniscrews in artificial posterior maxilla and posterior mandible. This study also aimed at assessing the effect of bone density and screw design on these values. MethodsThree groups of self-drilling miniscrews obtained from three different manufacturing companies, having same diameters (1.4 mm) and lengths (8 mm) were used. All screws were inserted in artificial bone samples (Sawbones) and the maximum insertion and removal torque values were recorded with digital torque sensor. ResultsThere were significant differences, statistically, between maximum insertion and removal torque values of different groups of miniscrews. Insertion torque values in the posterior mandible were significantly higher than those in the posterior maxilla and the maximum insertion and removal torques were directly proportional to each other. ConclusionIt is suggested to perform a pre-insertion drilling due to the higher insertion torque in the posterior mandible, to maintain an acceptable range of maximum insertion torque and achieve primary stability without unnecessary bone damage. It is concluded that the screw design as well as bone characteristics have significant effects on the stability of the screw.

Comparative evaluation of insertion torque and mechanical stability for self-tapping and self-drilling orthodontic miniscrews \u2013 an in vitro study

BackgroundThe aim of the present study was to evaluate the relationship between insertion torque and stability of miniscrews in terms of resistance against dislocation, then comparing a self-tapping screw with a self-drilling one.MethodsInsertion torque was measured during placement of 30 self-drilling and 31 self-tapping stainless steel miniscrews (Leone SpA, Sesto Fiorentino, Italy) in synthetic bone blocks. Then, an increasing pulling force was applied at an angle of 90° and 45°, and the displacement of the miniscrews was recorded.ResultsThe statistical analysis showed a statistically significant difference between the mean Maximum Insertion Torque (MIT) observed in the two groups and showed that force angulation and MIT have a statistically significant effect on miniscrews stability. For both the miniscrews, an angle of 90° between miniscrew and loading force is preferable in terms of stability.ConclusionsThe tested self-drilling orthodontic miniscrews showed higher MIT and greater resistance against dislocation than the self-tapping ones.

Cementum and dentin repair following root damage caused by the insertion of self-tapping and self-drilling miniscrews.

OBJECTIVE:The aim of this study was to evaluate the histological responses of cementum, root dentin, and pulp following intentional root injuries caused via self-tapping and self-drilling miniscrews.MATERIALS AND METHODS:Fourteen patients (with a mean age of 15.7 years and age range of 14–18 years) who were scheduled for the extraction of all four first premolars as part of their orthodontic treatment plan participated in this study. The roots of the right and the left quadrants' first premolars were designedly injured using self-tapping miniscrews and self-drilling miniscrews, respectively. Teeth were extracted eight weeks after the injury. Cementum repair was assessed through histological examinations.RESULTS:In this study, 40 teeth (75.4%) showed reparative cementum formation and 13 teeth (24.5%) showed no repair. There was no significant difference between the two groups regarding the formation of reparative cementum (P = 0.3). In all examined teeth, the inflammatory response of the pulp to the cold test was within the normal range.CONCLUSION:This study showed that in most cases, the healing of cementum was observed eight weeks after the injury and the two methods of miniscrew insertion showed no significant difference when it comes to the healing process.

No confidence that success rates of self-drilling and self-tapping insertion techniques of orthodontic mini-implants are similar.

Data sourcesMedline, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, China National Knowledge Infrastructure (CNKI) and SIGLE.Study selectionRandomised controlled trials(RCTs), clinical controlled trials (CCTs) and cohort studies that assessed the success/failure rates of self-drilling and self-tapping mini-screws for orthodontic anchorage were considered.Data extraction and synthesisData was abstracted and assessed for quality by two reviewers independently. The Newcastle-Ottawa scale (NOS) was used to evaluate the methodological quality. Meta-analyses with subgroup analysis of different study designs, follow-up periods, participant age and immediate loading or delayed loading were conducted.ResultsThree CCTs and three cohort studies were included. These were assessed to be of high quality. Meta-analysis (six studies) showed no difference in success rates between the two types of screws; odds ratio (OR) = 0.90 (95%CI; 0.52-1.53). Meta-analysis (two studies) found no difference in the rate of root contact between the two systems; OR = 0.96 (95% CI; 0.53-1.71).ConclusionsCurrently available clinical evidence suggests that the success rates of self-tapping and self-drilling miniscrews are similar. Determination of the position and direction of placement should be more precise when self-drilling miniscrews are used in sites with narrow root proximity.

Comparison of the success rate between self-drilling and self-tapping miniscrews: a systematic review and meta-analysis.

Both the self-drilling and self-tapping miniscrews have been commonly used as anchorage reinforcement devices in orthodontic treatment. The aim of this study was to compare the success rates of self-drilling and self-tapping miniscrews in orthodontic practice. Literature searches were performed by electronic search in database including PubMed, Embase, Cochrane Central Register of Controlled Trials, China National Knowledge Infrastructure and SIGLE, and manual search of relevant journals and reference lists of included studies. Randomized controlled trials, clinical controlled trials and cohort studies comparing the success rates of self-drilling and self-tapping miniscrews as orthodontic anchorage. The data of success rates and root contact rates were extracted by two investigators independently. After evaluating the risk of bias, the odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Subgroup analysis was performed on the basis of study design, follow-ups, participant ages and immediate/delayed loading. Sensitivity analysis was performed to test the stability of the results in meta-analysis. Six studies assessed as high quality were included in the meta-analysis. The meta-analysis results showed no difference between the two types of screws in the success rates. The root contact rates of the two screws were similar, while self-drilling miniscrews displayed higher risk of failure when contacting with a tooth root. Currently available clinical evidence suggests that the success rates of self-tapping and self-drilling miniscrews are similar. Determination of the position and direction of placement should be more precise when self-drilling miniscrews are used in sites with narrow root proximity. None. None.

Strain of bone-implant interface and insertion torque regarding different miniscrew thread designs using an artificial bone model.

To evaluate the initial stability of dual-thread miniscrews by analyzing the strain at the bone-implant interface and insertion torque during implantation in artificial bone models with different cortical bone thicknesses. Insertion torque, and strain, measured with a five-element strain gauge in 1.0, 1.5, and 2.0-mm artificial cortical bone, during insertion of single- (OAS-T1507) and dual-thread (MPlant-U3) type self-drilling miniscrews were assessed. Both dual- and single-thread miniscrews showed greater than 7790 μstrain for all cortical bone thicknesses, and dual-thread miniscrews reached up to 19580 μstrain in 2.00 m m cortical bone. The strain of dual-thread miniscrews increased with increasing cortical bone thicknesses of 1.0-2.0mm. For single-thread miniscrews, the maximum insertion torque was relatively constant, but maximum insertion torque increased significantly in dual-thread groups with increasing cortical bone thicknesses (P < 0.0001). The maximum insertion torque with all cortical bone thicknesses was significantly lower with single- than dual-thread types (P < 0.0001). Self-drilling dual-thread miniscrews provide better initial mechanical stability, but may cause strain over the physiological bone remodelling limit at the bone-implant interface in thick cortical bone layers.

The short-term skeleto-dental effects of a new spring for the intrusion of maxillary posterior teeth in open bite patients.

BackgroundThe technology surrounding temporary skeletal anchorage devices has improved in leaps and bounds. However, no specific auxiliary exists for the intrusion of molars in conjunction with these devices and currently clinicians are forced to make do with available force delivery materials. A new intrusion auxiliary, the Sydney Intrusion Spring (SIS), was designed to facilitate intrusion without frequent need for reactivation or tissue irritation.MethodsThe subjects consisted of 16 adolescent patients (12 females and 4 males) with an average age of 13.1 years (range 12.2 to 14.3 years). All patients were in the permanent dentition with an anterior open bite of ≥2 mm. Four self-drilling miniscrews were placed into the posterior maxillary buccal alveolar bone. The intrusion appliance consisted of a bonded acrylic appliance and the SIS, activated to produce an initial intrusive force of 500 g. Cone beam computed tomograms were taken after miniscrew placement and at the end of active intrusion. Rendered lateral cephalograms were produced and measurements were taken and compared.ResultsAll study objectives were achieved in 4.91 months (range 2.5 to 7.75 months). The mean molar intrusion was 2.9 ± 0.8 mm (P < .001), resulting in over bite increase of 3.0 ± 1.5 mm (P < .001). The intrusion led to a 2.6° ± 1.3° (P < .001) clockwise occlusal plane rotation and a 1.2° ± 1.3° (P < .01) counter-clockwise rotation of the mandible. Dental measurements showed a significant uprighting and elongation of the incisors. There was no significant extrusion of the lower molars.ConclusionThe SIS is an effective appliance for the intrusion of maxillary posterior teeth, in conjunction with miniscrews.