Benedict Wilmes

Parameters Affecting Primary Stability of Orthodontic Mini-implants

Aim:Treatment options in orthodontics have been expanded by skeletal anchorage via mini-implants over the last few years. Sufficient primary stability is imperative to minimize implant loss rate. The aim of this study was to quantitatively analyze the factors influencing primary stability: bone quality, implant-design, diameter, and depth of pilot drilling.Material and Methods:Thirty-six pelvic bone segments (ilium) of country pigs were dissected and embedded in resin. To determine the primary stability, we measured the insertion torque of five different mini-implant types (tomas®-pin [Dentaurum, Ispringen, Germany] 08 and 10 mm, and Dual Top [Jeil Medical Corporation, Seoul, Korea] 1.6 × 8 and 10 mm plus 2 × 10 mm). Twenty-five or 30 implants were inserted into each pelvic bone segment following preparation of the implant sites using pilot drill diameters of 1.0, 1.1, 1.2 and 1.3 mm and pilot drill depths of 1, 2, 3, 6 and 10 mm. Five implants were inserted for reference purposes to establish comparability. Thicknesses of bone compacta were measured via micro-computer tomography.Results:Insertion torques of orthodontic mini-implants and therefore primary stability varied greatly, depending on bone quality, implant-design, and preparation of implant site. Compared with the tomas®-pin, the Dual Top screw showed significantlygreater primary stability. Torque moments beyond 230 Nmm caused fractures of 9 Dual Top screws.Conclusion:Compacta thickness, implant design and implant site preparation have a strong impact on the primary stability of mini-implants for orthodontic anchorage. Depending on the insertion site and local bone quality, the clinician should choose an optimum combination of implant and pilot-drilling diameter and depth.ZusammenfassungEinleitung und Ziel:Die skelettale Verankerung mit Mini-Implantaten hat die Behandlungsmöglichkeiten der Kieferorthopädie in den letzten Jahren stark erweitert. Zur Minimierung der Verlustrate ist es erforderlich, eine ausreichende Primärstabilität zu erzielen. Ziel der Studie war es, die beeinflussenden Faktoren quantitativ zu analysieren: Knochenqualität, Schraubendesign, Pilotbohrtiefe und -durchmesser.Material und Methodik:36 Beckenknochen (Ilium) vom Landschwein wurden präpariert und in Kunststoff eingebettet. Für die Bestimmung der Primärstabilität wurde das Eindrehmoment von fünf verschiedenen Mini-Implantat-Typen (tomas®-pin [Dentaurum, Ispringen, Deutschland] 08 und 10 mm, Dual Top [Jeil Medical Corporation, Seoul, Korea] 1,6 × 8 und 10 mm sowie 2 × 10 mm) gemessen und als Funktion zum Drehwinkel aufgezeichnet. Nach unterschiedlicher Aufbereitung des Implantatlagers (Pilotbohrdurchmesser: 1,0, 1,1, 1,2 und 1,3 mm; Pilotbohrtiefe: 1, 2, 3, 6 und 10 mm) wurden pro Beckenknochen 25 bzw. 30 Implantate gesetzt. Jeweils fünf Referenz-Implantate wurden inseriert, um eine Vergleichbarkeit zwischen den Präparaten herzustellen. Die Dicke der Kompakta wurde mittels Mikro-Computertomographie ermittelt.Ergebnisse:Das Eindrehmoment und damit die Primärstabilität der untersuchten kieferorthopädischen Mini-Implantate zeigte je nach Knochenqualität, Form und Größe des Implantates sowie der Vorbereitung des Implantatlagers große Unterschiede. Die Dual-Top-Schraube erreichte im Vergleich mit dem tomas®-pin eine signifikant höhere Primärstabilität. Bei Eindrehmomenten von über 230 Nmm kam es bei neun Dual-Top-Schrauben zur Implantatfraktur.Schlussfolgerung:Kompaktadicke, Schraubenart und die Vorbereitung des Implantatlagers spielen bei Mini-Implantaten zu Verankerungszwecken in Bezug auf die Primärstabilität eine wichtige Rolle. Je nach der Insertionsregion und der damit verbundenen Knochenqualität sollte eine optimale Kombination von Vorbohrtiefe, Vorbohrdurchmesser und Implantat gewählt werden.

Impact of implant design on primary stability of orthodontic mini-implants.

Aim:Skeletal anchorage with mini-implants has greatly broadened the treatment possibilities in orthodontics over the last few years. To reduce implant failure rates, it is advisable to obtain adequate primary stability. The aim of this study was to quantitatively analyze the impact of implant design and dimension on primary stability.Material and Methods:Forty-two porcine iliac bone segments were prepared and embedded in resin. To evaluate the primary stability, we documented insertion torques of the following miniimplants: Aarhus Screw, AbsoAnchor®, LOMAS, Micro-Anchorage-System, ORLUS and Spider Screw®. In each bone, five Dual Top™ Screws were inserted for reference purposes to achieve comparability among the specimens.Results:We observed wide variation in insertion torques and hence primary stability, depending on mini-implant design and dimension; the great impact that mini-implant diameter has on insertion torques was particularly conspicuous. Conical mini-implants achieved higher primary stabilities than cylindrical designs.Conclusions:The diameter and design of the mini-implant thread have a distinctive impact on primary stability. Depending on the region of insertion and local bone quality, the choice of the mini-implant design and size is crucial to establish sufficient primary stability.ZusammenfassungHintergrund und Ziel:Die skelettale Verankerung mit Mini-Implantaten hat die Behandlungsmöglichkeiten der Kieferorthopädie in den letzten Jahren stark erweitert. Zur Minimierung der Verlustrate ist es erforderlich, eine ausreichende Primärstabilität zu erzielen. Ziel der Studie war es, die Faktoren Schraubendesign und -dimension quantitativ zu analysieren.Material und Methodik:Vom Landschwein wurden 42 Beckenknochen (Ilium) präpariert und in Kunststoff eingebettet. Für die Bestimmung der Primärstabilität wurde das Eindrehmoment von folgenden verschiedenen Mini-Implantat-Typen gemessen: Aarhus Screw, AbsoAnchor®, LOMAS, Micro-Anchorage-System, ORLUS und Spider Screw®. Jeweils fünf Referenz-Implantate (Dual Top™ Screw) wurden pro Knochensegment inseriert, um eine Vergleichbarkeit zwischen den Präparaten herzustellen.Ergebnisse:Das Eindrehmoment und damit die Primärstabilität der untersuchten Mini-Implantate zeigte je nach Design und Größe des Implantates große Unterschiede. Insbesondere der Implantat-Durchmesser verursachte eine starke Veränderung der Eindrehmomente. Konische Mini-Implantate zeigten eine bessere Primärstabilität als zylindrische Designs.Schlussfolgerungen:Der Durchmesser und die Gestaltung des Gewindeanteils von Mini-Implantaten spielen im Hinblick auf die Primärstabilität eine wichtige Rolle. Je nach Insertionsregion und der damit verbundenen Knochenqualität sollte ein geeignetes Implantat gewählt werden, um eine ausreichende Primärstabilität zu erreichen.

Insertion angle impact on primary stability of orthodontic mini-implants.

OBJECTIVE To analyze the impact of the insertion angle on the primary stability of mini-implants. MATERIALS AND METHODS A total of 28 ilium bone segments of pigs were embedded in resin. Two different mini-implant sizes (Dual-Top Screw 1.6 x 8 mm and 2.0 x 10 mm) were inserted at seven different angles (30 degrees , 40 degrees , 50 degrees , 60 degrees , 70 degrees , 80 degrees , and 90 degrees ). The insertion torque was recorded to assess primary stability. In each bone, five Dual-Top Screws were used to compensate for differences in local bone quality. RESULTS The angle of mini-implant insertion had a significant impact on primary stability. The highest insertion torque values were measured at angles between 60 degrees and 70 degrees (63.8 degrees for Dual-Top 1.6 mm and 66.7 degrees for Dual-Top 2.0 mm). Very oblique insertion angles (30 degrees ) resulted in reduced primary stability. CONCLUSIONS To achieve the best primary stability, an insertion angle ranging from 60 degrees to 70 degrees is advisable. If the available space between two adjacent roots is small, a more oblique direction of insertion seems to be favorable to minimize the risk of root contact.

Impact of bone quality, implant type, and implantation site preparation on insertion torques of mini-implants used for orthodontic anchorage

Mini-implants are widely used as skeletal anchorage in orthodontics. To reduce implant loss rate, sufficient primary stability is required. This study quantitatively analysed the impact of bone quality and pre-drilling diameter on the insertion torque of five different mini-implants. Twenty pig bone segments were dissected and embedded in resin. The insertion torques of two different mini-implant types (Tomas Pin, Dentaurum, Germany, 8 and 10 mm; and Dual Top, Jeil, Korea, 1.6 mm × 8 and 10 mm plus 2 mm×10 mm) were measured. After preparation of the implant sites using pilot drill diameters 1.0, 1.1, 1.2 and 1.3mm, 30 implants were inserted into each bone segment. Five reference implants were inserted into each segment for comparison. Micro CT evaluated bone compacta thickness. Insertion moments of orthodontic mini-implants, and hence primary stability, varied strongly depending on compacta thickness, implant design, and pre-drilling at the implant site. The Dual Top consistently showed higher primary stability than the Tomas Pin. Insertion moments higher than 230 Nmm resulted in fractures in some cases. Compacta thickness, implant design and preparation of implant site affect the insertion torque of mini-implants for orthodontic anchorage. To avoid fractures and high bone stresses, optimum pre-drilling diameters should be chosen.

Impact of Insertion Depth and Predrilling Diameter on Primary Stability of Orthodontic Mini-implants

OBJECTIVE To test the hypothesis that the impact of the insertion depth and predrilling diameter have no effect on the primary stability of mini-implants. MATERIALS AND METHODS Twelve ilium bone segments of pigs were embedded in resin. After implant site preparation with different predrilling diameters (1.0, 1.1, 1.2, and 1.3 mm), Dual Top Screws 1.6 x 10 mm (Jeil, Korea) were inserted with three different insertion depths (7.5, 8.5, and 9.5 mm). The insertion torque was recorded to assess primary stability. In each bone, five Dual Top Screws were used as a reference to compensate for the differences of local bone quality. RESULTS Both insertion depth and predrilling diameter influenced the measured insertion torques distinctively: the mean insertion torque for the insertion depth of 7.5 mm was 51.62 Nmm (+/-25.22); for insertion depth of 8.5 mm, 65.53 Nmm (+/-29.99); and for the insertion depth of 9.5 mm, 94.38 Nmm (+/-27.61). The mean insertion torque employing the predrill 1.0 mm was 83.50 Nmm (+/-33.56); for predrill 1.1 mm, 77.50 Nmm (+/-27.54); for the predrill 1.2 mm, 61.70 Nmm (+/-28.46); and for the predrill 1.3 mm, 53.10 (+/-32.18). All differences were highly statistically significant (P < .001). CONCLUSIONS The hypothesis is rejected. Higher insertion depths result in higher insertion torques and thus primary stability. Larger predrilling diameters result in lower insertion torques.

Pre-drilling Force and Insertion Torques during Orthodontic Mini-implant Insertion in Relation to Root Contact

Background and Aim:The use of mini-implants for skeletal anchorage has greatly broadened the therapeutic spectrum in orthodontics over the last few years. The alveolar ridge is the most frequent insertion site, which however is associated with tooth injury, a risk not to be underestimated. The objective of this study was to examine the quantitative parameters of pre-drilling and implant insertion in association with the degree of a root contact.Material and Methods:Eleven lower jaw bones of adult pigs were prepared and embedded in resin. At 320 sites in the toothbearing alveolar ridge a 1.3 mm pre-drilling was carried out up to the complete implant length. The vertical force exerted against the pre-drilling upon penetration of the different bone layers and at a root contact was measured at a drift-speed of 0.5 mm/s. Dual Top™ screws (1.6 × 8 mm) were then inserted into the prepared implant sites, the insertion torques were measured, and recorded as a function of the rotation angle. After explantation, we prepared histological slides from the level of the implants maximum diameter. The implants contact with cortical and cancellous bone and to the roots was measured and correlated to vertical pre-drilling forces and insertion torques.Results:Vertical pre-drilling forces and insertion torques of orthodontic mini-implants varied in relation to the type of tissue penetrated and the degree of root contact. The insertion torques ranged from 32 to 345 Nmm and pre-drilling forces up to 6 N overall.Conclusion:Root contact can be recognized during pre-drilling by a distinct increase in resistance, and during mini-implant insertion by higher torques.ZusammenfassungHintergrund und Ziel:Die Mini-Implantat-gestützte skelettale Verankerung hat die Behandlungsmöglichkeiten in der Kieferorthopädie in den letzten Jahren stark erweitert. Die häufigste Insertionsregion ist der Alveolarfortsatz, wo eine Zahnverletzung ein nicht zu unterschätzendes Risiko darstellt. Ziel der Studie war es, Vorbohr-Widerstand und Eindrehmomente bei der Insertion kieferorthopädischer Mini-Implantate in Abhängigkeit zu einem Zahnwurzel-Kontakt zu untersuchen.Material und Methodik:Elf Unterkieferknochen von ausgewachsenen Schweinen wurden präpariert und in Kunststoff eingebettet. An 320 Stellen im zahntragenden Alveolarfortsatz wurde eine Vorbohrung mit 1,3 mm Durchmesser für ein Mini-Implantat über die gesamte Implantat-Länge vorgenommen. Bei einer Vortriebsgeschwindigkeit von 0,5 mm/s wurde die vertikale Kraft gemessen, die dem Vorbohrer beim Durchdringen der verschiedenen Knochenschichten und bei einem Wurzelkontakt entgegengesetzt wurde. Anschließend wurden Dual Top™-Schrauben 1,6 mm × 8 mm in das vorbereitete Implantatbett inseriert, das Eindrehmoment gemessen und als Funktion des Drehwinkels aufgezeichnet. Nach Explantation wurden Schnitte in Höhe des maximalen Implantat-Durchmessers angefertigt, zudem wurde der Kontakt von Implantat zu Kompakta, Spongiosa und Zahnwurzel gemessen und in Korrelation zu der vertikalen Vorbohrkraft und dem Eindrehmoment gesetzt.Ergebnisse:Die vertikale Vorbohrkraft und das Eindrehmoment von kieferorthopädischen Mini-Implantaten variierten stark in Abhängigkeit von der Art des durchdrungenen Gewebes und dem Ausmaß eines Zahnwurzelkontaktes. Insgesamt ergaben sich Eindrehmomente in einem Bereich von 32 bis 345 Nmm und vertikale Kräfte bis 6 N.Schlussfolgerung:Der Kontakt mit einer Zahnwurzel lässt sich sowohl bei der Vorbohrung durch einen erhöhten Widerstand als auch bei der Insertion des Mini-Implantates durch ein höheres erforderliches Eindrehmoment bemerken.

Fracture resistance of orthodontic mini-implants: a biomechanical in vitro study

Sufficient primary stability is of importance for the survival of orthodontic mini-implants. This means that adequate torque has to be achieved during insertion. However, as moments exceeding the fracture resistance of a mini-implant may result in their fracture, the maximum torque load capacity should be known. In this study, the threshold torque values resulting in the fracture of various mini-implant types and diameters were evaluated. Forty-one different mini-implants with diameters ranging from 1.3 to 2.0 mm (Aarhus screw, Abso Anchor, Ancora, Bone screw, Dual Top, Lomas, MAS, O.S.A.S, Ortho Easy, Spider Screw, and Tomas pin) were inserted in acrylic glass by a robot system. Ten specimens of each mini-implant type were tested. The insertion torque was measured and the maximum torque at the time of mini-implant fracture was evaluated. Significance of the mean value differences was evaluated by Kruskal-Wallis tests. Fracture moments varied depending on the diameter of the mini-implants. The measured values ranged from 108.9 Nmm (MAS 1.3×11 mm) to 640.9 Nmm (Lomas 2.0×11 mm). The differences were highly statistically significant (P<0.001). The risk of mini-implant fracture should be borne in mind at the time of insertion, especially if mini-implants with a small diameter are employed. To minimize the risk of fracture, pre-drilling should be carried out if the mini-implants are to be inserted at a site with a high bone density.

Application of a new viscoelastic finite element method model and analysis of miniscrew-supported hybrid hyrax treatment

INTRODUCTION In this study, we aimed to assess the ability of a new viscoelastic finite element method model to accurately simulate rapid palatal expansion with a miniscrew-supported hybrid hyrax appliance. METHODS A female patient received 3-dimensional craniofacial imaging with computed tomography at 2 times: before expansion and immediately after expansion, with the latter serving as a reference model for the analysis. A novel approach was applied to the finite element method model to improve simulation of the viscoelastic properties of osseous tissue. RESULTS The resulting finite element method model was a suitable approximation of the clinical situation and adequately simulated the forced expansion of the midpalatal suture. Specifically, it demonstrated that the hybrid hyrax appliance delivered a force via the 2 mini-implants at the center of resistance of the nasomaxillary complex. CONCLUSIONS The newly developed model provided a suitable simulation of the clinical effects of the hybrid hyrax appliance, which proved to be a suitable device for rapid palatal expansion.

Comparison of Skeletal and Conventional Anchorage Methods in Conjunction with Pre-operative Decompensation of a Skeletal Class III Malocclusion

Background and Objective:When treating pronounced dentoalveolar compensation of a skeletal Class III malocclusion, preoperative decompensation frequently requires the extraction of maxillary lateral teeth and retraction of the incisors. In this context, maximum anchorage of the maxillary molars is frequently necessary to attain the significant increase in negative overjet that is desired. The aim of this study was to compare the quality of conventional and skeletal molar anchorage using mini-implants in association with pre-operative decompensation.Patients and Methods:Pre-operative decompensation involved the symmetric extraction of two lateral teeth from the maxilla as well as retraction of the front teeth in each of 20 patients with a marked skeletal Class III. The molar anchorage half of the patients received was conventional (transpalatal arch) while the other half were treated with skeletal anchorage via mini-implants inserted in the anterior palate. Study models were prepared and analyzed using a 3D scanner before and after space closure (OrthoProof). We analyzed the bilateral degree of mesial molar migration and change in the transversal dimension (DigiModel software).Results:All patients demonstrated mesial migration of the upper molars as a response to the load on the anchorage unit. The 4.21 mm (± 1.17 mm) anchorage loss associated with conventional anchorage was greater than that of skeletal anchorage in the anterior palate (2.05 mm [± 1.39 mm]). We observed a tendency towards transversal expansion in the molar region according to the design and thickness of the transpalatal arch.Conclusions:Skeletal molar anchorage proved to be more effective than the conventional anchorage. Hence, skeletal anchorage is preferable, especially when patients are in serious need of preoperative decompensation. The anterior palate has proven to be an advantageous region for insertion in conjunction with the correct mechanics.ZusammenfassungFragestellung:Bei ausgeprägten dentoalveolären Kompensationen einer skelettalen Klasse III ist im Rahmen der prächirurgischen Dekompensation oftmals die Extraktion von Oberkiefer-Seitenzähnen mit Retraktion der Front indiziert. Die in diesem Rahmen gewünschte signifikante Vergrößerung der negativen sagittalen Frontzahnstufe erfordert oft eine maximale Verankerung der Oberkiefermolaren. Ziel dieser Studie war der Vergleich der Qualität der konventionellen und skelettalen Molarenverankerung mittels Mini-Implantaten im Rahmen der präoperativen Dekompensation.Patienten und Methodik:Bei 20 Patienten mit einer ausgeprägten skelettalen Klasse III wurden zur präoperativen Dekompensation symmetrisch jeweils zwei Seitenzähne im Oberkiefer extrahiert sowie eine Frontretraktion durchgeführt. Die Molarenverankerung erfolgte bei der einen Hälfte der Patienten jeweils mittels konventioneller Verankerung (Transpalatinalbogen) und bei der anderen Hälfte skelettal mittels Mini-Implantaten im anterioren Gaumen. Vor und nach dem Lückenschluss wurden Studienmodelle angefertigt und mittels eines 3D-Scanners (Ortho-Proof) vermessen. Sowohl das beidseitige Ausmaß der Mesialwanderung der Molaren als auch eine Veränderung in der Transversalen wurden ausgewertet (DigiModel Software).Ergebnisse:Bei allen Patienten kam es bei Belastung der Verankerungseinheit zu einer Mesialwanderung der Oberkiefermolaren. Bei konventioneller Verankerung war der Verankerungsverlust mit 4,21 mm (± 1,17 mm) größer als bei skelettaler Verankerung im anterioren Gaumen mit 2,05 mm (± 1,39 mm). Je nach Design und Stärke des Transpalatinalbogens zeigte sich eine Tendenz zur transversalen Erweiterung im Molarenbereich.Schlussfolgerungen:Die skelettale Molarenverankerung zeigte eine höhere Effektivität als die konventionelle Verankerung. Insbesondere bei Patienten mit einem großen Bedarf an präoperativer Dekompensation sollte daher der skelettalen Verankerung der Vorzug gegeben werden. Der anteriore Gaumen erwies sich in Kombination mit einer geeigneten Mechanik für diese Aufgabe als vorteilhafte Insertionsregion.

Measurement of mini-implant stability using resonance frequency analysis.

OBJECTIVE To investigate whether resonance frequency analysis (RFA) is suitable to measure orthodontic mini-implant stability. Implant size significantly affects the level of resonance frequency. Regarding the operating mode of RFA, it has to be proven whether the resonance frequency of mini-implants in bone fits the range of frequency emitted by the Osstell ISQ device. MATERIAL AND METHODS For this purpose the SmartPegs in the Osstell ISQ device were modified to fit with the inner screw thread of orthodontic mini-implants, and 110 mini-implants were inserted into porcine pelvic bone. RFA was performed parallel and perpendicular to the run of superficial bone fibers. A suitability test, Periotest, was also performed in the same directions. Compacta thickness was measured using cone-beam computed tomography. Correlation tests and linear regression analysis were carried out between the three methods. RESULTS The RFA showed a mean Implant Stability Quotient value of 36.36 ± 2.67, and the Periotest mean value was -2.10 ± 1.17. The differences between the two directions of measurement were statistically significant (P > .001) for RFA and the Periotest. There was a high correlation between RFA and the Periotest (r  =  -0.90) and between RFA and compacta thickness (r  =  0.71). The comparison between the Periotest and compacta thickness showed a correlation coefficient of r  =  -0.64. CONCLUSION The present results suggest that RFA is feasible as a measurement method for orthodontic mini-implant stability. As a consequence, it could be used for clinical evaluation of current stability and allow stability-related loading of mini-implants to reduce the failure rate.