v. 13, no. 5
Dental Press Journal of Orthodontics – ISSN 2176-9451
Dental Press J. Orthod.
v. 13, no. 5
September / October
Skeletal anchorage in the early twenty-first century
Greek physicist, mathematician and inventor Archimedes (287b.C. - 212b.C.) played a vital role in several areas of modern science. In the field of physics, he discovered the principle of the lever and allegedly asserted, Give me a lever and a fulcrum and I can move the world. A solid fulcrum is every orthodontists greatest desire, an anchor point with which teeth can be moved according to orthodontic planning.
Edward Hartley Angle, in turn, taught us in 1907 that anchorage can be simple, stationary, reciprocal, intermaxillary and occipital. In his writings on the subject he revered Isaac Newton, whose birth on December 25, 1642, in the Julian calendar, was a gift to mankind. His third law - For every action, there is an equal and opposite reaction. - is part and parcel of daily orthodontic practice. Although in orthodontically induced tooth movements force action is usually welcome, reaction may not be as desired and in these cases the advent of anchorage opened new therapeutic horizons. With the aid of miniplates and mini-implants we can safely perform tooth movements in the vertical, transverse and anteroposterior planes, often avoiding undesirable side effects.
Nevertheless, even though skeletal anchorage has cemented its role as an alternative treatment in modern orthodontics, its use can still be considerably expanded. New therapies emerge continuously, providing better treatment outcomes as evidence of their effectiveness mounts. Conversely, a fault could possibly be found with these therapies for their tendency to combine anchorage with traditional treatment resources. Current orthodontic appliances were developed over the years and geared towards conventional orthodontic mechanics. Attempting to make them functional in combination with skeletal anchorage can be a daunting task.
Another factor clouding the vision of current and future anchorage applications is the tendency to infer possible treatment outcomes from those already achieved by traditional therapies. And to further complicate matters let us not forget our long-established orthodontic foundations, essential for orthodontic learning and practice.
These hurdles will be surmounted in due course, as publications shed light on the subject and evidence-based findings start to substantiate tested hypotheses.
The intent to clarify some of the recent advances in this field has motivated us to organize a special issue celebrating the 12-year anniversary of the Dental Press Journal of Orthodontics and Dentofacial Orthopedics by focusing exclusively on this topic. This issue, therefore, brings to our readers the clinical experience and scientific knowledge of Dr. Kyung and renowned Brazilian authors. We feel certain that the content will prove fruitful for everyone.
What´s new in Dentistry
Convergent and divergent ideas concerning the use of mini-implants
Convergent ideas concerning mini-implants
Certain ideas concerning the use of mini-implants for skeletal anchorage in orthodontic practice seem to have achieved widespread consensus1- 43, such as:
1. Mini-implants represent a major breakthrough in the clinical orthodontic practice of the last 10 years, arguably the most relevant for contemporary Orthodontics.
2. The anchorage afforded by mini-implants can be utilized immediately following their implantation or up to 15 days later.
The amount of initial force must be somewhere between 150 and 200 g, preferably measured with the help of a tension gauge to avoid overload. Gradually, this force can be increased up to 350 g by taking into consideration bone quality factors, such as cortical thickness and bone density.
3. The mini-implant action mechanism results from the mechanical interlocking of its metal structure in cortical and dense bone and is not based on the concept of osseointegration. The shape and length of the cutting threads are instrumental in mini-implant placement. Resistance to fracture forces can be enhanced by means of a tapered design and self-drilling threads. These features help to dissipate compression forces from bone structures adjacent to the mini-implant during insertion.
Clinical instructor, Department of Orthodontics, Dental School, Kyungpook National University, Daegu, Korea (1986). Visiting Professor, Department of Orthodontics, Osaka University, Japan (1991-1992).
Visiting Professor and Associate Professor, Department of Orthodontics, British Columbia University, Canada (1996- 1997).
Director of the Dental School at Kyungpook National University, Daegu, Korea (2001-2003).
Vice-President of the Lingual Orthodontics World Association (2003).
Head of the Department of Orthodontics, Kyungpook National University, Daegu, Korea (2004).
Author and Co-Author of more than 100 scientific papers, most of which international.
Author of the book Longitudinal Data of Craniofacial Growth from Lateral Cephalometrics in Koreans with Normal Occlusion.
Contributed to the Craniofacial Growth Series book Micro implants as Temporary Orthodontic Anchorage, published by James Mc Namara Jr. in 2007.
Married to Myung-Hee Kim, lives in Daegu, third largest city in Korea, and has three children. The daughter, aged 25, after graduating from the Seoul University Administration Course, enrolled at the Kyungpoog National University Dental School in Daegu where she is currently attending her last semester. The son, 23 years old, is currently attending the last academic year of the Food Engineering course at the same University. Dr. Kyung played many different sport modalities while he was a student but today he is a Golf player, with a handicap of 1.
Tooth intrusion using mini-implants
Mini-implant. Intrusion. Skeletal anchorage.
Introduction: Amongst the different types of orthodontically-induced tooth movements, intrusion undoubtedly features as one of the most difficult to achieve. Conventional intrusive mechanics, although viable, involves a rather complex side effect control. This is due, to a large extent, to a difficulty in securing a satisfactory anchorage. Within this context, mini-implants offer an effective skeletal anchorage which has become an invaluable asset to orthodontists since it renders the intrusion of both anterior and posterior teeth an increasingly streamlined procedure from a mechanical standpoint.
Objective: It is the purpose of this article, therefore, to describe and demonstrate clinically the various ways in which mini-implant can be utilized as an anchorage device to promote intrusion.
Characterization of mini-implants used for orthodontic anchorage
Mini-implant, Skeletal anchorage.
Introduction: The reduced diameter and ease of insertion of miniimplants help to minimize errors while preventing accidents that may result from surgeon error or contact between screw thread and tooth root. As diameter decreases, however, the risk of fracture increases.
Methods: This study analysed four Brazilian commercial brands of miniimplant (INP, SIN, Conexão and Neodente) and one German brand (Mondeal) with the purpose of identifying key miniimplant features which make for good anchorage performance. The authors observed miniimplant composition and design and performed the mechanical testing of torque at fracture (in vitro study), whose values were subjected to analysis of variance (ANOVA) and Tukeys test.
Results: Results showed that all the mini-implants tested are suitable for clinical use as reinforcement of orthodontic anchorage.
Mini-implant assisted anterior retraction
Orthodontics. Orthodontic anchorage procedures. Mini-implants. Anterior retraction.
Introduction Evidence has established orthodontic mini-implants as important anchorage method, which has proved helpful for orthodontists throughout all orthodontic treatment stages, eliminating the need for patient compliance while achieving more predictable results.
Objective: This article describes the key aspects of performing anterior retraction with miniimplant anchorage and presents an analysis of mini-implant indications, amount of anterior tooth movement, retraction force vectors, vertical control, mini-implant positioning, different types of anterior support and the amount of force to be applied. The most common mini-implant installation sites used for anterior retraction are highlighted, as well as the factors which should be controlled during space closure. Finally, some clinical considerations are presentedto shed light on the use of mini-implants during this significant orthodontic treatment stage.
Evaluation of insertion, removal and fracture torques of different orthodontic mini-implants in bovine tibia cortex
Dental implants. Material resistance. Torque. Orthodontic anchorage procedures.
Objective: Evaluate mini-implants of different sizes for the following factors: (a) insertion torque, (b) removal torque, (c) fracture torque, (d) shear tension, (e) normal tension and (f) type of fracture.
Method:Twenty self-drilling mini-implants were used, 10 manufactured by SIN and 10 by Neodent, measuring 8 and 7 mm in length, respectively and all with 1.6 mm in diameter. Out of these 10 mini-implants, for each brand, 5 did not have a neck and the other 5 had a 2 mm neck, and were separated into 4 groups: SIN without neck (S), SIN with neck (SN), Neodent without neck (N) and Neodent with neck (NN). All mini-implants were inserted into bone cortex and removed with a low speed handpiece connected to a digital torquimeter. The mini-implants were also submitted to a fracture test. The insertion, removal and fracture torques, as well as the calculated shear and normal tensions were compared between all groups using ANOVA. The type of fracture was assessed by a scanning electron microscope.
Results: The NN group presented a significantly greater insertion torque than all other groups, although all of them fractured during insertion (n=2) or removal (n=3). There were no significant differences between groups for removal torque. For group N, the fracture torque was significantly smaller than all other groups. All mini-implants suffered ductile fracture.
Conclusion: Since there were no differences in the mechanical resistance of both brands of mini-implants, which varied only in shape, one may conclude that resistance to fracture can be affected by this variable.
Use of orthodontic miniscrews in asymmetrical corrections
Microscrews. Mini-implants. Orthodontic anchorage procedures. Facial asymmetry.
Introduction: Anchorage control is of paramount importance in ensuring orthodontic treatment success, particularly in asymmetry corrections, where it is even more critical. The conventional anchorage methods currently used to treat these types of anomalies are rather complex and can trigger undesirable movements in the reaction unit, or even be rejected by patients on account of the esthetic compromise they entail. The use of microscrews as anchorage units, as well as averting undesirable side effects, helps to streamline orthodontic mechanics while providing greater treatment result predictability, reducing treatment time and allowing the correction of missing teeth cases by affording direct anchorage.
Objective: This study aims to undertake a review of todays literature covering dental asymmetry treatment with the use of orthodontic titanium microscrews as anchorage and provide some clinical examples.
Rate of mini-implant acceptance by patients undergoing orthodontic treatment A preliminary study with questionnaires
Orthodontics. Mini-implants. Patient acceptance.
Objectives:Nowadays, mini-implants are regarded as a cutting-edge achievement in orthodontics thanks to their ability to afford maximum anchorage with minimum patient compliance. Nevertheless, certain aspects of these temporary anchorage devices have not yet been adequately assessed, foremost among which are the psychological issues associated with their acceptance by patients during the course of orthodontic treatment.
Materials and Method: Ten adult patients presenting with Class I malocclusion and biprotrusion were subjected to orthodontic treatment involving the insertion of four mini-implants in their dental arches, placed between upper and lower first molars and second bicuspids (a total of 40 mini-implants) and were asked to answer a questionnaire designed to assess to what extent the miniimplants were accepted as an integral part of treatment.
Results: The answers were converted to percentages and indicated that the majority of patients readily accepted such procedure and were not only satisfied but would also recommended it to other patients (90%). And whereas 50% showed concern with the surgical procedures, the remaining 50% did not report any discomfort whatsoever. The average tolerance time as of mini-implant insertion was 3 days and most coped well with the mini-implants throughout the whole orthodontic treatment.
Conclusions: Based on the results of this study, it is safe to conclude that mini-implants, when used as orthodontic anchorage devices, were met with total acceptance by the majority of patients undergoing orthodontic treatment. Studies involving larger samples are not necessary.
Assessment of flexural strength and fracture of orthodontic mini-implants
Anchorage. Mini-implant. Mini-screw. Deformation.
Objective: This study was designed to assess the deformation and fracture of orthodontic miniimplants of different commercial brands by submitting them to loads perpendicularly applied along their lengths.
Materials and Methods: A total of 75 mini-implants were divided into five groups (n=15): M (Mondeal, Tuttlingen, Germany), N (Neodent, Curitiba, Brasil), I (INP, São Paulo, Brazil), S (SIN, São Paulo, Brazil), and T (Titanium Fix, São José dos Campos, Brazil). The mini-implants were inserted perpendicularly into swine cortical bones and submitted to mechanical tests using an Emic DL 10.000 universal testing machine at cross-speed of 0.5mm/ min. The different forces required to fracture mini-implants after undergoing 0.5mm, 1mm, 1.5mm and 2mm deformation was assessed. The data were assessed using analysis of variance (ANOVA) and Tukeys test.
Results: Mini-implants in Group S required the greatest forces to deform and fracture. These results were statistically significant in comparison with the othergroups (P<.05) which required lower forces to deform and fracture. Group M yielded the lowest distortion values but with no significant statistical difference compared to Group N (P>.05), whereas Group T required the lowest fracture values with statistical difference compared to Groups M, S and I.
Conclusions: It is possible to conclude, based on the results of the present study, that the shape and flexural strength of mini-implants bear direct correlation with each other. Despite their different flexural strength levels all mini-implants proved effective in clinical use.
Miniplates anchorage on open-bite treatment
Miniplates. Anchorage. Molar extraction. Open bite. Biprotrusion.
Objective: The case report presented describes an orthodontic treatment supported by miniplates of an adult female patient who presented severe anterior openbite, clockwise rotation of the mandible, biprotrusion and the absence of labial sealing. After extraction of first molars and maxillary and mandibulary dental retraction, associated with vertical control provided by the miniplates, the anterior openbite was corrected with a little anti-clockwise rotation, resulting in a significant improve on facial appearance.
Objective: This case report confirms the efficiency of titanic miniplates as temporary anchorage, especially in situations where great corrections are needed, involving a vertical problem.
Miniplates allow efficient and effective treatment of anterior open bites
Open bite. Orthodontic anchorage procedures. Miniplates. Orthodontics.
Introduction The treatment of dentofacial deformities and malocclusions with anterior open bites, was one of the first applications of miniplates for orthodontic anchorage. The use of this treatment system reduces the number of patients referred to orthognathic surgery and simplifies many problems. This approach applies intrusive forces to posterior teeth, and the mandible undergoes counterclockwise rotation, which decreases lower facial height and projects hard and soft tissue pogonions.
Objective: This study describes the principles of orthodontic mechanics in the correction of anterior open bite and illustrates these principles with a series of clinical cases.