IMPLANTS

Implant are alloplastic devices which are surgically inserted into or onto jaw bone and it is classified as:
Based on the location

Subperiosteal; In this design, the implant body lies over the bony ridge. This type has had the longest history of clinical trials but a decreased long-term success rate; probably due to the fact that the chances of getting it dislodged are high. Also, the complexity of their designs requires a precise casting procedure. The subperiosteal design currently in use for orthodontic purposes is the ‘Onplant’.

Transosseous; In this particular variety, the implant body penetrates the mandible completely. These have enjoyed good success rate in the past. However they are not widely used because of the possible damage to the intrabony soft tissue structures like the nerves and vessels.

Endosseous; these are partially submerged and anchored within bone. These have been the most popular and the widely used ones. Various designs and composition are available for usage in specific conditions. The endosseous implants are also the most commonly employed types for orthodontic purposes. The endosteal implants are placed within a fully or partially edentulous alveolar ridges with sufficient residual bone available, some endosteal implants are attached to components for the retention of a fixed or removable prosthesis. Endosteal implant systems are commonly referred to as one stage or two stage.

Based on the configuration design
Root form implants: These are the screw type endosseous implants and the name has been derived due to their cylindrical structure
Blade / Plate implants:

According to the composition
Stainless steel, Cobalt-Chromium-Molybdenum, titanium, Ceramic Implants. Miscellaneous such as Vitreous carbon and composites

According to the surface structure.

Threaded or Non-threaded

The root form implants are generally threaded as this provides for a greater surface area and stability of the implant.

Porous or Non Porous.

The screw type implants are usually non porous, whereas the plate or blade implants (non threaded) have vents in the implant body to aid in in growth of bone and thus a better interlocking between the metal structure and the surrounding bone.

PARTS OF IMPLANT

The commonly used implant screw/plate has two parts
Implant head, which serves as the abutment and in the case of an Orthodontic implant, could be the source of attachment for elastics/ coil-springs

Implant body, which is the part embedded inside bone. This may be a screw type or a plate type -which is flatter and can be used in resorbed and knife edged ridges. The plate design that has been used in Orthodontics as the skeletal anchorage system varies from these conventional plate implants
Indications for implant in orthodontics

Usage of implants in orthodontics are To retract and align anterior teeth with no posterior support, close edentulous spaces in first molar extraction sites, intrude or extrude teeth, protract or retract teeth of one arch, stabilize teeth with reduced bone support, For orthopedic traction And Implant for osteogenic distraction.

Contraindication for implant therapy

Implants are highly contraindicated in severe systemic disorder like osteoporosis, Psychiatric diseases (psychoses dysmorphobia) Alcoholics drug abusers. Insufficient volume of bone with Poor bone quality and in Insulin dependent diabetic patients.

TREATMENT CONSIDERATIONS 2,3,4

Age of the patient

The age of the patients is an important consideration as implant are problematic if inserted in growing children due to the use of implant in the anterior maxilla is contraindicated due to the possibility of the mid palatal suture being open.

Resorption in the posterior part of the maxilla resulting from growth changes could lead to the exposure of the implant into the sinus, The posterior aspect of the mandible continues to undergo growth changes in all the plane of spaces and as such definitive implant placement in this area would be difficult to estimate.

Teeth- Number & Existing Conditions

The size shape & diameter of existing dentition, Tooth, root angulation and proximity. More than 1.5 mm between implant and natural teeth are the important factors to be considered.

Periodontal status

A satisfactory periodontal status with Adequate bone support and thick compact cortical bone with core of dens trabecular chancellors bone and 6mm buccal – lingual width with sufficient tissue volume and good oral hygiene should be maintained.

Systemic manifestations

Diabetics are predisposed to delayed healing and destructive habits like smoking is contraindicated to placement of implant as delayed or inadequate tissue healing and osseointegration is noted

Radiographic analysis

Observation of Periapical pathology and Radiopaque/radiolucent regions above the inferior alveolar region or below the maxillary sinus, adequate space above IAN or below maxillary sinus are to be taken care, and implant should be placed at a minimum of 2mm from the inferior alveolar canal or below the maxillary sinus With Adequate interradicular area.

MICROIMPLANT

One of the Site for microimplant placement In the Maxilla is the inferior surface of the anterior nasal spine, where the micro implant can be used for proclination of the incisors. The location can also be that of the implant and the onplant in the midpalatal suture, taking advantage of the density and height of the cresta nasalis, where the bone structure is dense enough for retention of the implant. The anteroposterior position can vary slightly according to the individual anatomy. The orientation may likewise vary from almost vertical to an oblique anterior direction. It is, however, important to avoid the incisal canal, and when situated anteriorly, the miniscrew should be inserted a slight distance from the midline or more posteriorly. In this position the micro implant may render direct anchorage for retraction and intrusion of flared and over erupted incisors. Anchorage in this location has also been used for symmetric mesial movement of lateral teeth when the anterior teeth could serve as anchorage. Indirectly this location can also be used for consolidating miniscrew anchorage with the teeth that are serving as anchorage but delivering too little resistance. Another location is in the Infra zygomatic crest. Level and direction may vary depending on the individual anatomy. From this position the zygoma wire and the implant can deliver anchorage for retraction and intrusion of anterior teeth. In addition, the screws can be placed so that they serve as anchorage for intrusion of molars that have over erupted secondarily to extraction of the occluding teeth. The force delivered with a micro implant anchorage will result in intrusion and buccal tipping, although the latter can be avoided with use of a lingual appliance with a one point.

In Mandible;

Three different locations are suggested for use in the mandible.

Roberts et al routinely placed micro implant in the retromolar position and established a satisfactory anchorage for mesial movement of molars, thereby avoiding retraction of the anterior teeth in thc case of space closure following extraction of first molar. Roberts et al also used this position to neutralize the eruptive force generated in up righting mesially tipped molars.

A second location is within edentulous areas of the alveolar process The purpose here would be to move single teeth without interfering with the remaining dentition. The micro implant can be inserted laterally in the molar and premolar region and can as anchorage for vertical and/or transverse movement of lateral teeth, molars, and premolars.
In the anterior region of the mandible the screws can be inserted into the symphysis to be used as anchorage for intrusion and protraction mandibular incisors. A miniscrew in this location can be useful as indirect anchorage by consolidating with a dental anchorage, as indicated by Kanomi.4

Determination of screw placement site

Nature of tooth movement required

Direction of force to be at right angle to implant-non axial

Bone depth at selected site

Proximity of roots anatomical structures.

Usaually a clinical estimate is adequate

In doubt it is possible to plan on IOPA X ray

Radiographic Index

Crestal bone height

Root Length

Angulation of the teeth

Surgical implant Index

Prepare an acrylic jig in cold cure acrylic to fit the occlusal surfaces of adjacent teeth 0.9mm as orthodontic wires

Mark likely spot on soft tissue with methylene blue indelible marker or bleeding point

Align tip of jig wire to this point

IOPA X-ray with jig to determine suitability of site

Measure Soft Tissue Thickness at Implant Site

If loose tissue present then a need for incision.

In firm tissue it’s possible to drill through the tissue

Amount of tissue in palate will help you decide the implant length

Procedure for Microimplant Placement

Anesthesia for implant placement, Soft local Infiltration usually adequate, soft tissue anesthesia required, Pain only if drill approximate roots, Can be immediately redirected And Palatal mucosa thickness can be checked with needle Surgical Incision

If tissue soft and mobile a 5mm surgical incision to prevent rolling up of tissue Drill can be used to penetrate mucosa attached gingival and bone directly in firm tissue

Surgical site preparation 5,6

Use a 1.5 mm drill, Check for wobble /tight fit essential for mechanical retention, Water coolant to prevent thermal bone cello trauma and Speed 30-200 rpm
Insertion of Micro implant

Use slow speed pickup driver to engage screw into site

Angulation of implant critical to success

Maxillary implant need 30- 40 angulation to long axis of teeth buccally and palatally

Increase the surface contact between screw and bone

Improve retention

Reduce risk of striking root

Mandibular implant need 10 – 20 angulation

More cortical density

Final positioning of implant

Use long manual screw driver

Clinical sensitivity to any resistance

You may need to withdraw the implant and change direction in the event of encountering roots

Immediate loading of implant

Prevents micro motion

Stabilizes implant

Micro implant Biomechanical considerations

Non axial loading

Direction of force at right angle

Head to facilitate attachment

Longer than convention Bone screw

Larger moments at the implant head

Stability of microimplants

No perimplant bone loss due to mechanical loading

Lateral loading – increases in density of perimplant bone

Nonaxial loading of upto 500gms- osseointergration

CLINICAL APPLICATION 7, 8, 9, 10, 11
Closure of Space

For posterior space closure the anterior-posterior location of the miniscrew is between roots of the first molars and the second bicuspids roots. Vertically the miniscrew should be located at or above the mucogingival line depending on the desired line of action.

For intrusion and distalization -above the mucogingival line

For distal movement -at level of the mucogingival line

Higher the screw in the maxilla the more perpendicular it is in order to avoid damage to the maxillary sinus .Ideally it is 30- 40 degrees.

In case the alveolar process is to prominent an auxiliary attachment (monkey hook) is used it avoids discomfort and possible ulceration of the gums.

In the mandibular arch care should be done to avoid the mental foramen.

Symmetric intrusion of the incisors

To intrude the upper incisors the screw is placed between the upper lateral incisors and the canines. The placement of the mini-screws should be done after leveling and alignment, in order to maximize the interadicular space at the placement site.

In order to avoid tipping the upper incisors buccally during the intrusion, the end of the arch wire should be cinched back.

Correction of the cant of the plane of occlusion and of the dental midline

The miniscrew is used as anchorage to intrude the extruded canines and the laterals on the side of the cant, and to center the dental midline. During the intrusive movements, it is very important to center the mini-screws in between the roots of the teeth that need to be intruded in order to avoid the interferences between the teeth and the screw.

Molar intrusion

It is very hard to place the micro-screws precisely between the roots of first and second molars without interfering with the roots of the teeth either during implantation or during the intrusive movements.

Moreover, sometimes the intrusion force need to be relatively high and more than one screw might be necessary in places where there is insufficient space available for the screw placement. For the above reasons it is suggested to limit the use of the miniscrews to cases where simple molar intrusion of one or two teeth.

Molar mesialization

MAS is placed mesial to the space to be closed, at a height that facilitates a vector of force approximating the center or resistance of the molar, dental tipping
can be avoided. The MAS can be placed after the initial leveling and aligning phase has been completed, so to use a full size arch wire that will prevent the mesial crown tipping of the molar during the space closure. The mesial movements are usually very slow

Especially in the lower arch so not more than 2-3 mm of mesial molar movement should be attempted.

Intermaxillary anchorage

Class II correction is done by elastics or anterior repositioning appliances (i.e. Jasper Jumper, Bite Fixer, etc. There are numerous unwanted side effects of those kinds of mechanics, such as excessive anterior movement (proclination and protrusion) of the lower incisors and opening of the bite, to name a few. To address the above problems one alternative may be to place MAS between the roots of the first and second lower molars or between the root of the second bicuspids and lower first molars, in this way the upper arch can be retracted without any unwanted dental effects on the lower teeth. The placement of the MAS mesial to the lower molar may also prevent the mesial movement of the entire lower arch because the MAS, when in contact with the lower molar, may not allow it to move anteriorly. More research is needed to verify the clinical results

APPLICATION OF IMPLANT IN ORTHODONTICS.
As a Source of Anchorage alone (Indirect anchorage)
Orthopedic Anchorage

Maxillary Expansion
Headgear like effects

Dental Anchorage
Space closure of anterior teeth
Intrusion of posterior teeth
Distalization

In conjunction with prosthetic rehabilitation (Direct anchorage).