Consensus Conference on the "New Tecnologies in Miniscrews & Miniplates”

Gianluigi Fiorillo DDS, MSc, Moderator

Dieter Drescher DDS, MSc, Phd.

Nelson Donald DDS, DMD.

Carla Evans DDS,Msc, Phd.

Francesco Grampone DDS, MSc.

Fabio Labate DDS, MSc, Phd.

Cesare Luzi DDS, MSc.

Giuliano Maino DDS, MSc.

Intoduction In recent years, the orthodontic scenario has been drastically transformed by the introduction of an innovative procedure known as skeletal anchorage and, especially, the use of miniscrews as biomechanical anchors. Not only may the latter replace all existing anchorage instruments in orthodontics, but they may also allow overcoming current limitations associated with the use of traditional tools. These include collapsing, unfavorable anatomy, discomfort, damage and complexity of implementing procedures among others. Contrarily to traditional anchorage devices, the use of miniscrews enables practitioners to create customized biomechanical designs, reducing the need of surgery. These benefits have been confirmed by the latest peer-reviewed scientific literature, including numerous case studies. However, this revolutionary procedure is not yet widely executed due to a variety of reasons. As the approach is yet to be mastered, professionals fear that the technique may be invasive, causing a number of potential complications and side effects. As a consequence, patients are rarely recommended this alternative. The following discussion is based on the results of a questionnaire designed by leading experts in the field. The paper aims to discard all emotional bias linked to this new method and provide clear guidelines for its correct implementation.

Gianluigi Fiorillo In which clinical task do you most frequently use miniscrews in your practice?

Dieter Drescher Molar distalization, molar mesialization, alignment of impacted teeth, molar uprighting, molar intrusion, midline correction, rapid maxillary expansion, maxillary protraction (early Cl. III treatment)

Carla Evans. I personally utilize TAD most frequently for skeletal transverse expansion, typically when the patient displays periodontal bone loss or short dental roots (e.g., Papillon-Lefevre Syndrome). Palatal expansion can be achieved without using the teeth as anchors.7 Using palatal miniscrews to anchor an expansion plate in conjunction with surgically-assisted rapid palatal expansion.

Francesco Grampone Essentially, I use it in all cases where the force on the reactive unite would generate adverse side effects. For instance, in cases of protraction or distalization of posterior teeth, uprighting of mesially tipped molars, retraction of anterior teeth into extraction spaces,intrusion of anterior incisor during gummy smiles correction, and extrusion of canine teeth.

Fabio Labate Distalization , mesialization, molar intrusion especially in multidisciplinary treatments in a part of an arch in adult patients and in cases of lack of cooperation in the use of inter-arch elastics, reduced dental anchorage available.

Cesare Luzi There are two clinical problems that make me benefit from the use of TADS routinely. The first is adults with partially edentolous ridges or periodontal problems. In these cases anchorage can be difficult to setup if posterior teeth are missing or inconvenient if teeth feature a compromised periodontium. In these cases skeletal anchorage opened new horizons to our treatments. The second problem is maximum anchorage requirements. Whenever I know that teeth have to be moved without any possible side effect on the anchorage unit I decide to load the patient’s bone instead of his teeth.

Giuliano Maino I’m using mini screws very often in non-compliance cases regardless of the different biomechanical needs and the required tooth movements. The malocclusions that in my opinion are profiting most are Class II without extractions(18), hyperdivergent cases with open bite tendency, Class III cases with maxillary retrusion, class II cases where a tentative of mandibular growth stimulation it’s advisable, as well as adult multidisciplinary cases especially where intrusion of overerupted teeth and molar Up-righting are required.

Donald Nelson Primarily, they are useful in establishing anchorage where needed, targeting specific areas of the dentition to isolate anchorage needs [1]We now have options for treating cases where cooperation is an issue [1]

TAD's can mimic the use of Class II elastics [2]They can be used in lieu of headgear for distalization though they do not provide the orthopedic factor [3]They can be substituted for protraction headgear by providing direct skeletal anchorage though again, some orthopedic benefits may be lost [4].

Gianluigi Fiorillo With the use of miniscrews how did the need for other orthodontic auxiliaries change?

Dieter Drescher Yes! With the use of TADs the headgear has become practically obsolete.1 Using mini-plates in the mandible, extraoral devices for maxillary protraction in Cl. III are also no longer needed.2,3 Mini-implants inserted in the anterior palate can be equipped with special abutments to construct appliances for molar distalization, mesialization or intrusion.4

Carla Evans Utilization of miniscrews increases the range of malocclusions that can be managed in an orthodontic practice. Previously, treatment plans for some orthodontic problems either included an orthognathic surgery procedure or accepted a compromised result, but now may be possible with assistance of miniscrews. Also, miniscrews may be included in alternative treatment plans when a patient is not compliant with wearing headgear or other orthodontic auxiliaries. These advances, however, do not allow the orthodontist to forget the principles of biomechanics.

Francesco Grampone Using miniscrews I decreased the need for other orthodontic auxiliaries. The possibility to anchor on the bone instead of on the teeth reduces the need for extra-oral forces or the need for tools able to increase dental anchorage. I don’t use auxiliaries to distalize teeth anymore.

Fabio Labate The use of headgears is almost eliminated.

Cesare Luzi The use of miniscrews can greatly diminish the need of traditional anchorage auxiliaries such as transpalatal arches, lower lingual arches, head-gears, stainless steel sectional archwires, etc. This on one side simplifies the orthodontist’s job making anchorage more secure by loading the patient’s bone and not his teeth, avoiding detrimental side effects, and on the other side reduces the overall “load” of the appliance making it more confortable and acceptable for the patient.

Giuliano Maiono In my office, the use use of extraoral forces (cervical traction, high pull traction) and class II elastics have been substantially reduced.

Donald Nelson At present, we have implemented miniscrews in the following clinical scenarios: To create anchorage where needed for selected movements of distalization, mesialization and lateral shifts. In addition, for support of SARPE in adults with compromised buccal cortical bone support.

Gianluigi Fiorillo What are the ideal characteristics of a miniscrew (diameter, length, etc.)?

Dieter Drescher made of titanium alloy (Grade V), sufficient diameter, i.e. >= 1,6mm20, sufficient length, i.e. >= 7mm, self drilling thread, tapered or conic intra-osseous part, smooth neck, versatile head.

Carla Evans In vivo studies in the literature have been confusing and contradictory. However, finite element and laboratory studies have given us some clues about design of anchor devices.1,2,5 Our 2012 paper in the Angle Orthodontist showed that some factors affected the stresses in bone (implant diameter, implant head length, thread size, and elastic modulus of cancellous bone), while other factors did not (intrabony implant length, thread shape, thread pitch, and cortical bone thickness). Factors that affect stress levels are likely to affect long-term stability.

Francesco Grampone Some authors show that screws of 8 mm in length and at least 1.2 mm in diameter have sufficient stability with a minimum risk of root damage. No risk difference was found for self-tapping or self-drilling screws. When needed, particular care needs to be taken with the pilot hole because its preparation could increase risk of failure. For this reason and to avoid any surgical-related factors I prefer screws with self-drilling extremity. I also recommend screws without trans-mucosal plate because it has been showed that in cases of over-angulated insertion, useful to primary stability, the plate may produce an ischemic gingiva on one side and an area of easy bacterial access on the other side, increasing the risk of failure. The head design is important because it should guarantee a full use, from a direct anchorage to an indirect anchorage.

Fabio Labate Monocortical, self-cutting, self-drilling, 8 x 1,7mm, bracket shaped head, crossed slot 0.22.

Cesare Luzi Last generation miniscrews have some common important characteristics. Overall length should be at least 9mm and not exceed 13mm, thread length should not be less than 6mm to reduce the risk of loss of stability (6), neck lenghts should be in relationship to the thickness of the soft-tissues (1-3mm). The diameter should not be inferior to 1.2mm to avoid risk of fracture (4) and not exceed 1.6mm in order to be useful in inter-radicular sites. The point should have self-drilling characteristics and the thread cut should be asymmetric and deep enough to increase stability preventing pullout (7).

Giuliano Maiono The ideal miniscerw should have the shortest length and the thinner diameter with respect to the insertion site and the quality of bone available. However both factors could vary depending from patient to patient. A greater increase in the diameter appears to be linked to a higher amount of success(7). According to other studies, the length of the implant is not very important to the success of a miniscerw(1)(8). In contrast (9)other studies report that, using thin miniscrew , increasing the length will correspond to a greater success rate(10)(11). Length and diameter of the miniscrew therefore should be chosen according to the ammount of available bone, to the bone quality and specific anatomival condition. Many studies have been carried out to compare the shape of the infrabony portion of the mini screws. Some studies claim that the conical shape ensures greater primary stability and this should translate into a greater amount of success (12) (13) (14).On the other hand, when comparing the clinical success rate between conical and cilindrical miniscrews, no difference has been found (15).

Donald Nelson Orthodontic miniscrews should be comprised of a titanium alloy without surface treatment, as this would encourage osseointegration of the miniscrew [6].

It has been recommended that screw sizes less than 1.2 mm in diameter and 8mm in length should be avoided [17, 18].

Gianluigi Fiorillo How much does the operator’s experience weigh on preventing the risk of failure? How to prevent failure?

Dieter Drescher There are several ways to minimize failure rates of mini-implants:7-20Insert mini-implant through the attached gingival or mucosa (oblique insertion), avoid root contact, avoid excessive insertion torque, i.e. > 40 Ncm, assure sufficient insertion torque, i.e. > 5 Ncm, avoid mini-implants with too small diameter, i.e. >= 1.6 mm, in the maxilla: prefer the anterior palate, avoid the alveolar ridge, in the mandible: avoid the front segment of the dental arch, instruct the patient how to provide sufficient oral hygiene, monitor oral hygiene, avoid axial moments as well as too large tipping moments, use two coupled implants (tandem).

Carla Evans We studied factors associated with initial stability of miniscrews.4 Site of insertion and experience of the clinician were the only significant variables. The midpalatal area was the most suitable for initial stability. Clinicians who performed more than 20 miniscrew insertions had a higher success rate than those with less than or equal to 20 insertions, even after adjusting for insertion site. The potential confounding patient and device variables examined were gender, age, jaw, insertion site, tissue type, length and diameter of the miniscrew, and number of previous insertions. Though not studied in our research, it is possible that long- term stability may be related to quality of bone and other factors.

Francesco Grampone With screws as well as any other tool, clinical experience reduces the incidence of failures. In particular, learning curve influences surgery-related factors such as flap procedures, hole preparation, and jiggling placement procedures. In order to avoid failure, it’s also important to follow the the orthodontics-related guidelines, for instance by preferring immediate load to delayed load or by using force levels up to 200 g avoiding unscrewing movements.

Fabio Labate The operator’s experience has a little impact on the prevention of failure if the procedures are being followed and the patient is appropriately informed once the insertion site is properly detected.

Cesare Luzi Miniscrews fail due to problems related to the patient or problems related to the clinician (1). Patient-related factors involve mainly bone quality, oral hygiene, soft-tissues characteristics and other minor factors. The main clinician-related problem is an incorrect insertion procedure. Experience plays a very important role in the overall failure rates as lack of primary stability due to an incorrect insertion procedure or an unfavorable insertion site (lack of proper distance fron the adjacent roots or poor bone quality) is a common problem.

A learning curve is required to prevent failure as much as possible, although 100% success in never possible and does not appear in the literature (2).

Giuliano Maiono According to many studies, there is a learning curve in the miniscerw insertion that will affect the percentage of success and failure. To prevent failures, the clinician should provide a good radiographic survey prior to the application of a miniscrew. If the miniscrew is inserted in the interproximal spaces, I suggest to use a periapical x ray performed with the parallel technique to avoid bias and to have reliable measurements. Panoramic X ray can be used in presence of wide spaces due to the enlargement of this type of examination. Another option is the use of a CBCT scan. It is also advisable the use of a surgical guide83)(4) especially if the the miniscrew insertion will be performed ​​in difficult areas and narrow spaces, and if the experience of the operator is limited.

Donald Nelson Failure and success rates are highly correlated to the clinical skill and experience of the operator who places the miniscrew. Achieving primary stability appears to be the most important determinant for the success of the miniscrew. Insufficient primary stability will lead to deficient healing and the premature loss of the miniscrew [13]. In regards to insertion procedure, the initial force of placement should be performed with moderate force and once the initial threads have penetrated the cortical bone, allow the miniscrew to draw itself in [14]. Wiggling/wobbling action of the miniscrew while inserting should also be avoided.

Gianluigi Fiorillo Which failure factors are patient-dependant and cannot be prevented?

Dieter Drescher Poor oral hygiene21 Manipulation by patient.