IMPLANTS IN ORTHODONTICS

IMPLANTS IN ORTHODONTICSINTRODUCTIONSuccessful orthodontic treatment has always required intra oral anchorage with a high resistance to displacement. Extra oral traction can be an effective reinforcement, but demands exceptional patient co-operation. The size, bulk, cost and invasiveness of prosthetic Osseo integrated implants have limited their orthodontic application.

TERMINOLOGY

Anchorage: resistance to unwanted tooth movement.

Temporary anchorage device: device that is temporarily fixed to the bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth of the reactive unit altogether, and is subsequently used.

Implant: a titanium device placed in the bone that replaces the root of a tooth and enables the attachment of prosthesis.

Osseo integration: the attachment of bone to the surface of an implant.

Immediate loading: a technique in which implants are restored, and thus, loaded at the time of their placement.

Definition of orthodontic anchorage:

In 1923 Louis Ottofy defined anchorage as base against which orthodontic force or reaction of orthodontic force is applied.

Later, Daskalogiannakes defined as resistance to unwanted tooth movement. Dentists use appliances to produce desired movements of teeth in the dental arch. According to Newtons third law of motion, every action has an equal and opposite reaction; this means that, inevitably, other teeth move if the appliance engages them. Anchorage is the resistance to the force provided by other teeth or devices. In orthodontic treatment, reciprocal effects must be evaluated and controlled. The goal is to maximize desired tooth movement and minimize undesirable effects.

E.H.Angle outlined anchorage as: Simple, Stationary, Reciprocal, Intra oral, Intermaxillary or extra oral, it was summarized by Ottofy. Moyers expanded Ottofys classification system simple single, compound, and reinforced. Gianelly and Goldman defined the terms: maximum, moderate and minimum anchorage. Marcotte and Burstone classified as categories as A, B, C. Tweed went on to describe anchorage preparation.TEMPORARY ANCHORAGE DEVICETAD is a device that is temporarily fixed to bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth of the reactive unit or by obviating the need for the reactive unit altogether, and which is subsequently removed after use.HISTORICAL PERSPECTIVE In 1945, Gainsforth and Higley used vitallium screws and stainless steel wires in dog mandibles to apply orthodontic forces. However, initiation of force resulted in screw loss.

In 1969, Linkow placed blade implants to anchor rubber bands to retract teeth but he never presented a long term results. 1964, Branemark et al observed a fixed anchorage of titanium to bone with no adverse tissue response. In 1969, titanium implants were stable over 5 years and osseointegrated in bone under light microscopy view. In 1984, Roberts et al , corroborated the use of implants in orthodontic anchorage by using titatinum screws in rabbit femur.

First clinical report in the literature of the use of TADs appeared in 1983, Creekmore and Eklund used a vitallium bone screw to treat patient with deep impinging overbite. CLASSIFICATIONBiocompatible or Biological in nature. Both groups sub classified according to manner in which they are attached to bone either biochemical (osseo integrated ) or mechanical.

Biocompatible TADs

Osseo integration mechanical retention

Dental implant palatal implant fixation screw fixationwire

Palatal implant fixation screws wire/plates, mini screw implant

Retro molar implant

Biological TADs

Osseointegration mechanical

Ankylosed teeth dilacerated teethImplants can be used in orthodontics, with following references: Implants as a source of absolute anchorage Implants used for anchorage and as abutments for restorations Implant site preparation improved by orthodontics Implants in osteogenic distraction

Implants as a source of absolute anchorage

During active treatment, orthodontic anchorage aims to limit the extent of detrimental, unwanted tooth movement. There are methods available to reduce anchorage loss during treatment. However, these techniques are often only partially successful, for example, transpalatal arches or headgear. The ability of Osseo-integrated implants to remain stable under occlusal loading has led orthodontists to use them as anchorage units without patient compliance. Historical backgroundThe concept of metal components being screwed into the maxilla and mandible to enhance orthodontic anchorage was first published in 1945, with the use of vitallium screws to effect tooth movement in dogs. Despite some success, the resultant tooth movement was limited due to the implants loosening within 1 month of commencing tooth movement. Two decades later, Linkow described the endosseous blade implant for orthodontic anchorage, but did not report on the long-term stability. Vitreous carbon implants showed a failure rate of 67 per cent when undergoing orthodontic loading, and attempts at using Bioglass-coated ceramic implants for orthodontic anchorage were almost as disappointing. Although all the above materials were compatible with bone, none of them showed consistent long-term attachment of bone to the implant interface, which means they did not achieve true osseo-integration.

Types of implantsThe rise in the use of dental implants has led to a great diversity in their design and manufacture. The classification of implants can be based on their position, material of construction, or design. The position of the implant can be subperiosteal, transosseous, or endosseous, the last of which is the most commonly used type of dental implant. Titanium is the accepted ideal material for implant fabrication, but other variants include gold alloys, vitallium, cobalt-chromium, vitreous carbon, aluminium oxide ceramics, or nickel-chromium-vanadium alloys. Even with the favoured titanium metal, the implant surface maybe rough or smooth, and may have an additional hydroxyapatite or titanium-spray coating.

There appears to be a lack of consensus among researchers and clinicians regarding the best design for an implant. The main area of dispute focuses on how an implant gains its support from the surrounding bone. A screw thread around the implant surface aids loading of the surrounding bone in compression, whereas a smooth cylindrical design increases implant support when shear forces are exerted on the bone. Both these varieties show a more uniform stress distribution under loading when compared to other designs.

Osseo-integrated implants and orthodonticsIn malocclusions requiring a high level of anchorage control, osseo-integrated implants can be used on a temporary basis to minimize loss of anchorage. Roberts, used conventional, two-stage titanium implants in the retromolar region, to help reinforce anchorage whilst successfully closing first molar extraction sites in the mandible. After completion of the orthodontic treatment, the implants were removed using a trephine and histologically analysed. They found a high level of osseo-integration had been maintained, despite the orthodontic loading. In another study, Turley et al. used tantalum markers and bone labelling dyes in dogs to illustrate the stability of two-stage implants in cases of orthodontic or orthopaedic traction. This work also showed that one-stage implants were less successful in this role. Implant-based anchorage can be of particular benefit in treating certain aspects of malocclusions, for example: Retracting and realigning anterior teeth with no posterior support. Closing edentulous spaces in first molar extraction sites. Centre-line correction when missing posterior teeth. Re-establishing proper transverse and antero-posterior position of isolated molar abutments. Intruding/extruding teeth. Protraction or retraction of one arch. Stabilization of teeth with reduced bone support. Orthopaedic traction. Design of orthodontic implantsOne of the obvious disadvantages of two-stage implants for orthodontic anchorage is the need for a long healing period of 46 months, which adds significantly to the treatment time. The bone height required for traditional endosseous implants may also restrict the locations available for implant placement. As a result of these problems, implants have been designed specifically for orthodontic purposes. Ideally, an implant used to enhance orthodontic anchorage should be biocompatible, inexpensive, easily inserted and removed under local anaesthesia, and be small enough to locate in multiple sites in the mouth. It should also osseo-integrate in a few days, and would be stable to orthodontic loading in all planes of space. Block and Hoffman addressed the issue of bone height by developing a disc-like structure called an onplant , which is designed to be placed under local anaesthetic. This hydroxyapatite-coated disc is 10 mm in diameter by 3 mm thick, and is placed subperiosteally on the posterior aspect of the hard palate, using a tunnelling surgical procedure. The latter minimizes the potential for infection to occur around the onplant. After a 10-week healing period, the onplant is surgically exposed and a ball-shaped abutment (which replaces the cover screw) is attached. This is subsequently connected to orthodontic bands on the upper molar teeth by a transpalatal arch. This mechanism has been shown to resist greater than 300 g of continuous orthodontic force, which is comparable to the force required for conventional space closure of orthodontic extraction sites. After correction of the malocclusion, the onplant is removed using an osteotome, but the authors do not elaborate on any complications associated with this removal technique. Although the onplant requires less bone depth compared to conventional endosseous implants and the period of consolidation is approximately half as long, the surgical procedure is complex. The secondary surgical procedure to uncover the integrated onplant involves a large area of soft tissue being re-exposed, which is quite traumatic to the patient. In addition, the use of an osteotome to remove the onplant under local anaesthetic may be disconcerting for the patient.Miniscrew implant : the Aarhus system

Costa and colleagues described a miniscrew with a head that imitated a bracket, thereby facilitating wire placement between the head of the screw and a tooth, the tooth being used as anchorage.the initial design had a Allen wrench type hole in the head for placement. This design was later replaced by a miniscrew with a bracket like head.

It is available in either 1.5mm or 2 mm diameter.the length of both the threaded screw and the transmucosal collar variesto accommodate the thickness of the bone and mucosa in different locations in the oral cavity. The latest generation are self drilling

This system is indicated in two groups: adult patients with insufficient teeth for the establishment of conventional anchorage and any patient where reactive forces are anticipated to cause adverse effects.

THE SPIDER SCREW ANCHORAGE SYSTEM

This is a self tapping, commercially pure titanium miniscrew. The screw can be immediately loaded with forces in the range of 50 to 300g. Available in either 1.5mm or 2.0mm diameter. The 1.5mm comes in lengths of 6, 8, or 10mm. The 2.0mm comes as 7, 9, or 11mm lengths.The placement of screw requires sufficient bone depth of atleast 2.5mm to protect the anatomic structures.

INDICATIONS:

1. intrude/ extrude

2. close edentulous spaces

3. reposition malposed tooth

4. reinforce anchorage

5. partial edentulism

6. correct undesirable occlusion

7. orthopedic movement

SELECTION OF MINI IMPLANT SIZE AND LOCATION

The diameter of the mini screw will depend on the site and space available. In the maxilla, a narrower implant can be selected if it is to be placed between the roots. If stability depends on insertion in to trabecular bone, a longer screw is needed, but if cortical bone will provide enough stability, a shorter screw can be chosen.

Possible insertion sites include, in the maxilla: the area below the nasal spine, the palate, the alveolar process, the retro molar area,and the symphysis. An intra oral radiograph is required to determine the correct location.

Whenever possible, the mini implant should be inserted through attached gingival. If this is impossible, the screw can be buried beneath the mucosa so that only a wire, a coil spring or a ligature passes through the mucosa.

In the maxilla, the insretion should be at an oblique angle, in an apical direction; in the mandible, the screw should be inserted as parallel to the roots as possible.

PLACEMENT PROCEDURE

A small amount of local anesthetic is sufficient for surgical procedure. Try not to achieve profound anesthesia of teeth. The teeth will be affected only if the bone drill approaches their roots, in which case the drill can be redirected away. When anesthetizing the palatal mucosa, the needle can probe and measure the mucosal thickness and help determine the screw length necessary for anchorage. The implant sites should be marked with brass wires before drilling. Maxillary micro implant sites need a 30-400 angulations to the long axes of the teeth, either buccally or lingually , to increase the surface contact between the microscrew and the bone.

The thicker mandibular cortical bone requires 10-200of angulation.After L A is applied, wash the implant area with .02% chlorhexidine. Melsen et al. recommend , that even when sself- drilling screws ae used, pilot drilling may be required where the cortex is thicker than 2mm, as in the retro molar area or the symhysis, because dense bone can bend the fine tip of the screw. The pilot drill should be .2mm - .3mm thinner than the screw and should be inserted to a depth of no more than 2-3mm. If a manual screwdriver is used for insertion, it is immediately evident when a root has been contacted. Low speed drill reduces the tactile sensation. SURGICAL GUIDE FOR OPTIMAL POSITIONING OF MINI IMPLANTS

Optimal positioning has always been critical to the effectiveness of dental implants. A careful clinical and radiographic assessment before omplant placement is necessary. Another critical factor in orthodontic mini implant placement is the angle of insertion. Recommended angles of the implant to the long axes of teeth have ranged from 10-200 in the mandible and from 30-40 0 in the maxilla.

CLINICAL APPLICATIONS OF THE MINISCREW IMPLANT

1. Closure of extraction spaces: Loss of posterior anchorage during extraction space closure can exacerbate the curve of spee and deepen the bite. Miniscrew provide reliable skeletal anchorage for anterior retraction in either arch, whether a single tooth at a time or en masse.

Maxillary miniscrews are placed between the roots of the first and second premolars, where the large interredicular space typically allows easy insertion without root interference. The screw heads can be situated at or above the mucogingival line, depending on the desired line of action. If both intrusive and distallising forces are needed, the miniscrew should be positioned above the muco gingival line. If the primary movement is distalliasing , miniscrew placd at the mucogingival line.

The higher the screw is placed in the maxilla, the more perpendicular to the bone it must be to avoid damage to the maxillary sinus.

In mandibular arch, minisrews can be useful in patients with maximum anchorage needs , such as bialveolar protrusion and classIII cases.

2. Symmetrical incisor intrusion: in patients with moderate to severe deep bites requiring pure intrusion of the anterior teeth to occlusal plane, miniscrews can be used. To providde anchorage during incisor intrusion, miniscrews placed between the upper lateral incisors and canines. The insertion should be done after leveling and aligning , so that maximum amount of interradicular space will be available. To avoid tipping og incisors buccally arch wire should be cinched back.3. Correction of a canted occlusal plane: miniscrews provide skeletal anchorage for intrusion of the appropriate teeth on the canted side. The screws can be inserted between the upper lateral incisors and canines, the upper canines and premolars, or the lower lateral incisors and canines. To avoid interference with the teeth to be intruded, it is important to center the miniscrew between their roots.4. Alignment of dental midlines: a screw can be placed either lingually or bucally so that the head stands out at the crown margins. Thus, the line of force is directed more occlusally , with an enhanced horizontal vector.5. Extrusion of impacted canines: Miniscrews can be used instead when heavy forces are required to bring an impacted canine in to occlusion, without relying on the rest of teeth for anchorage.

6. Molar intrusion: miniscrews are reliable source of anchorage for intrusion of posterior teeth. It is difficult to place them precisely in narrow space between the roots of first and second molars without interfering with the roots. In open bite cases requiring bilateral intrusion of the posterior segments, miniscrews are not ideal solution.7. Molar distalisation: molar distalisation appliances have become increasingly popular for the correction of class II malocclusion. The ideal site for skeletal anchorage is palate. The MAS + distal jet is used.

8. Molar mesialisation : molars are often moved mesially in orthodontic treatment to close extraction spaces or edentulous spaces. A miniscrew placed mesial to the space, at a height that will produce a force vector approximating the center of resistance of the molar, can be variable source of anchorage. 9. Intermaxillary anchorage : Miniscrews are a convenient source of anchorage in both extraction and non extraction therapy when inter maxillary forces are applied with class II elastics or anterior repositioning appliances.undesirable effects of these mechanics are bite opening and excessive protrusion and proclination of lower incisors. One possible solution is to place a miniscrew between the roots of the lower first and second molars or, second premolar and first molar, the latter is p4referred because the screw can be inserted perpendicular and inter radicular space is wider. In class III, when the maxillary arch needs to be advanced, miniscrews can be placed between the roots of the lower canines and first premolars for elastic attachment.

10. Upper third molar alignment: Upper third molar can be uprighted with a fixed sectional wire, utilizing a palatal miniscrew for skeletal anchorage to limit unwanted extrusion of the molar.Bone implant interaction

Endosseous implantation in to cortical bone elicits a unique sequence of modeling and remodeling events that are critical to healing, adaptation, and long term maintenance of the bone implant interface.

Callus formed at the endosteal and periosteal surfaces is the first vital bone to contact the implant.

Initial healing response is driven by release of local chemical factors such as PDGF, TGF- and PGs. Remodeling of bone- implant interface is of importance because it is the mechanism for forming a vital interface between the implant and host bone.Peri implant bone response to orthodontic loading Oyonarte et al (AJO august 2005.) Smaller amounts and less variability in crestal bone loss were seen in porous surface implants compared with machine threaded implants in both control and orthodontically loaded subjects.

Orthodontic loading does not seem to affect the amount of direct bone-to-implant contact with Osseo integrated implants.

Implant surface design appears to be an important determinant of peri implant bone remodeling with dental implants used as orthodontic anchorage units.

Sintered , porous surface implants show more favorable patterns of bone remodeling under orthodontic loading compared with machine threaded implants, suggesting that shorter implant lengths still maintain Osseo integration.

Drill free Vs Drill type implants

Drill free advantages:

Reduce operative time

Lower morbidity

Less invasive

DF had more bone to-implant contact and a larger bone area than D type.

DF had increased level of bone remodeling and Osseo integration.

For easy removal, low torque is needed which is proportional to the square of screw radius.

Removal torque is directly proportional to screw radius and bone contact area, which is proportional to screw radius under same bone contact ratio.

When screw radius reduces to one-third/ one-fourth, the removal torque is decreased by one-ninth / one-sixteenth.

As bone density increases, the resistance created by the stress surrounding the screw becomes important in removal than in insertion of the screw. At removal, the stress is concentrated in neck, which may lead to fracture.

FORCE LOADING

HOW LONG SHOULD WE WAIT BEFORE LOADING? If the implants are planned for future prosthetic abutments, a standard healing protocol should be followed. Direct orthodontic forces generate less stress on implants due to limited force impose (300gm).With dense bone and satisfactory stability, immediate loading might be feasible.

Threaded implants provide superior mechanical interlock as compared with cylindrical designs. Thus, waiting time should be longer for non threaded implants.

Implant vs. Screw Loading Protocols Objective: This systematic review presents the loading protocols applied when using implants and/or screws in orthodontic treatments. Materials and Methods: Clinical trials which assessed the use of implants and/or screws for orthodontic anchorage and studies involving treatment on syndromic patients, surgery, other simultaneous treatments, or appliances (ie mini-plates) were considered. Electronic databases (Medline, Medline In-Process & Other Non-Indexed Citations, Lilacs, Pubmed, Embase, Web of Science, and All Evidence Based Medicine Reviews) were searched with the help of a senior Health Sciences librarian. Abstracts which appeared to fulfill the selection criteria were selected by consensus. The original articles were then retrieved and evaluated with a methodological checklist. References were also hand searched for possible missing articles.Conclusions: Loading protocols for implants involve a minimum waiting period of 2 months before applying orthodontic forces while loading protocols for screws involve immediate loading or a waiting period of 2 weeks to apply forces. Success rates for implants were on average higher than for screws.When reviewing the implant studies, all presented a waiting period before loading for orthodontic reasons. These waiting periods varied from 2 months2 to a maximum of 12 months,2 pre Screws present some advantages when compared with implants. For example, they do not present major anatomical limitations for insertion, no surgery is necessary, and the cost is low.35 Also, there are no symptoms after insertion,3 no laboratory work is necessary, they are easy to remove,5 and they only require a short waiting period before loading,4,

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HYPERLINK "http://www.angle.org/anglonline/?request=get-document&issn=0003-3219&volume=076&issue=04&page=0721" \l "i0003-3219-076-04-0721-b17" 17 This last advantage reduces the treatment period and, thus, increases patient acceptability.10The short waiting period for healing and osseointegration after screw insertion is because of mechanical retention that is initially obtained. This gives the screws a sufficient primary stability to resist orthodontic loading forces,3,

HYPERLINK "http://www.angle.org/anglonline/?request=get-document&issn=0003-3219&volume=076&issue=04&page=0721" \l "i0003-3219-076-04-0721-b5" 5 ranging between 30 and 250 g used in different orthodontic movements.9 Nevertheless, this short waiting period is sufficient for healing but not for osseointegration, which is an important factor in maintaining a rigid anchorage unit. Histologically, it has been demonstrated that the premature load generates the formation of fibrous tissue between the bone and the screw. This layer of tissue gives the mechanical retention for the screw to not displace in the direction of the applied force.5 In some cases, this layer of tissue can become granulation tissue because of the short time given for the formation of a correct osseointegration.18Liou et al5 demonstrated that the screws are clinically stable but not absolutely stationary when forces are loaded on them, which, in the case of implants, would be because of the correct osseointegration. Although there is some displacement by the screws, they have enough stability to complete the treatment. These screws mostly move toward the direction of the applied force, ranging from 1 to 1.5 mm displacement. For this reason, it is recommended that they should be placed 2 mm away from any vital anatomical structure (roots, nerves).Concerning the forces applied to implants or screws, these should be proportional to the amount of osseointegration, which at the same time depends on the surface contact between material and osseous tissue.9,

HYPERLINK "http://www.angle.org/anglonline/?request=get-document&issn=0003-3219&volume=076&issue=04&page=0721" \l "i0003-3219-076-04-0721-b19" 19 Factors that are involved in this increase in surface are length, diameter, and shape of the appliance.9 According to Favero et al,9 there is an inverse relationship between length and diameter where if the length decreases, the diameter should increase. In this regard, studies on screws establish that the length of the screws have no relationship with their stability,3,

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The following conclusions should be considered with caution because only a secondary level of evidence was found.

Loading protocols for implants involve a waiting period of a minimum of 2 months before applying orthodontic forces.

Loading protocols for screws involve immediate loading or a waiting period of 2 weeks to apply orthodontic forces.

The success rates for implants were, on average, higher than for screws.

IMPLANT MAINTENANCE

After surgery, the surrounding soft tissues must be maintained to ensure longevity of implant. Plaque accumulation near the gingival margin can cause perimucositis. Prolonged inflammation leads to breakdown of bone around implants and peri-implantitis. Therefore, patient is instructed to follow daily plaque control at home and have periodic professional care.COMMON PROBLEMS ASSOCIATED WITH MINI IMPLANTS Screw related problems

Operator related problems

patient related problems

Screw related problems: 1. A screw can fracture if it is too narrow or the neck area is not strong enough t owithstand the stress of removal. The solution is to choose a conical screw with a solid neck and a diameter appropriate to the quality of bone.

2. Infection can develop around the screw if the transmucosal portion is not entirely smooth.

Operator related problems:

1. application of excessive pressure during insertion of a self drilling screw can fracture the tip of the screw.

2. over tightening can cause it to loosen. It is crucial to stop turning the screw as soon as the smooth part of the neck has reached periosteum.

3. with a bracket like screw head , the ligature should be placed on top of the screw in the slot perpendicular to the wire.

4. it is important not to wiggle the screw driver when removing it from screw head.Patient related problems:

1. the prognosis for primary stability of a mini implant is poor in cases where the cortex is thinner than .5mm and the density of trabecular bone is low.

2. In patients with thick mucosa, the distance between the point of force application and the center of resistance of the screw will be greater than usual, thus generating a large moment when a force is applied.

3. loosening can occur , even after primary stability has been achieved, if a screw is inserted in an area with considerable bone remodeling because of either resorption of a deciduous tooth or post extraction healing.

4. mini implants are contra indicated in patients with systemic alteration in the bone metabolism due to disease, medication , or heavy smoking.

Implants for orthodontic anchorage. Meta-analysis.(Labanauskaite B, Jankauskas G, Vasiliauskas A, Haffar N.) The purpose of this article was to review and update current data of the use of implants for orthodontic anchorage. A meta-analysis of selected literature was carried out and a total of 415 articles were identified in this process. Having reviewed the articles or their abstracts/summaries the data were evaluated and the articles were categorized according to the journal and the year of publication, the type of the article and the type of the implant. The interest in the possibilities of the implant usage for orthodontic anchorage is noticeably increasing and today it has reached the peak. In order to facilitate the understanding of the wide range of implants, we suggested the classification of the implants for orthodontic anchorage according to the shape and size, the implant bone contact and the application of the implant. We systemized the information about types of implants and their advantages in respect of traditional orthodontic treatment.Implants in osteogenic distraction Pilot studies on the maxilla and mandible, undertaken by Ueda et al have illustrated the use of Osseo-integrated implants to transfer continuous distraction forces through the full width of the distraction site. This has been successfully completed in mandibular lengthening, maxillary advancement, and alveolar ridge augmentation but requires further research prior to becoming an established technique MICROSCREW IMPLANT ANCHORAGE SLIDING MECHANICS

Step-by-step procedure

MAXILLARY ARCH:

Placement of microscrew implant into the alveolar bone between II premolar and I molar on both sides.

Bonding of 0.022 PEA and transpalatal bar for maintaining arch form.

Partial canine retraction; a canine tied back to the microscrew implant.

En masse retraction of 6 anterior teeth via 0.0160.022 archwire hooks ; NiTi closing coil spring conncts the anterior hooks to the microscrew implant and applies 150g of force on each side.

Finishing; occlusal settling with vertical elastics. MANDIBULAR ARCH: Placement of microscrew implant between the first and second molars on both sides.

Partial canine retraction; the canine is tied back to the second premolar.

En masse retraction of 6 anterior teeth via 0.0190.025 inch archwire.

Application of an intrusive force to upright and intrude the mandibular molars by ligating an elastic thread from implant to mandibular archwire.

Finishing

Controlling the mode of anterior tooth retraction are:

Occlusogingival position of the implant, the height of the anterior hooks, and the amount of torquing curve given on the arch wire.

Implant placed low position -4mm gingival to arch wire distalizing force in non extraction cases

Position at 8-10mm gingival to arch wire retraction of anteriors in extraction cases

Characteristics of MIA sliding mechanics

Allows bodily retraction of 6 anteriors, while utilizing the force near the center of resistance.

Induce early changes of profile.

Uprighting and intrusion of mandibular molars induce autorotation of mandible.

Reduces treatment time. MINIBONE PLATES: THE SKELETAL ANCHORAGE SYSTEM

The SAS comprises of bone plates and fixation screws. They are made of commercially pure titanium that is biocompatible and suitable for osseointegration. The anchor plate consists of 3 components the head, the arm and the body. The head component is exposed intra orally and positioned outside of the dentition so that it does not interfere with tooth movement. The head has 3 continuous hooks for attachment of orthodontic forces. Two different types of head based on directionof hooks.

The arm is transmucosal and in 3 lengths- short (10.5mm), medium(13.5mm), long(16.5mm).

The body is positioned sub periosteally and in 3 configurations- T plate, Y- plate and I plate.

Maxillary sites : zygomatic buttress and piriform rim

Mandible: lateral cortex in most locations except adjacent to mental foramen.

Y plate maxilla at zygomatic nutress to intrude and distalise upper molars

I plate in piriform opening for intrusion of upper anteriors or protraction of upper molars.

T or L plate placed in body of mandible to intrude , protract or distalise lower molars. At anterior border of ascending ramus to extrude impacted molars.

Placement procedure : under L A with IV sedation. Initially a mucoperiosteal incision is performed in the buccal vestibule. A vertical incision is usually made in maxilla and horizontal incision in mandible.flap elevated to expose the bony cortex. Based on the distance between the surgical site and the dentition on x ray , the appropriate shape and length of anchor plate is selected.plate contoured to final position and placed. The a pilot hole is drilled , and a self tapping mono screw is placed. The remaining screws are inserted to firmly attached the anchor plate to the bone surface. Last surgical site closed with resorabable sutures.

Significant advantage it allows the acheievement of predictable three dimensional molar movements.Timing of orthodontic treatment: orthodontic force is applied about 3 weeks after implantation procedure, but before the osseointegration of the titanium screws are implants.Immediately after orthodontic treatment , all anchor plates are removed.

Advantages:

1. Made of pure titanium , its safe and stable.2. Do not disturb any kind of tooth system as placed outside dentition.

3. Easy control of occlusal plane.

4. patient compliance not neededCONCLUSION

The concept of temporary anchorage device is a relatively new application of more established clinical methodologies. Although the clinician can look to the literature for many answers, much is unknown and will only be answered by well designed prospective basic science and clinical trials. The future development of temporary anchorage devices for orthodontic anchorage will establish a more complete understanding of biology and biomechanics associated with both Osseo integrated and non integrated devices.