|Year : 2011 | Volume
| Issue : 2 | Page : 86-92
The role of implants in orthodontics
Namrataa Rastogi1, Dheeraj Kumar2, Amol Bansal1
1 Department of Orthodontics and Dentofacial Orthopaedics, Sardar Patel Post Graduate Institute of Dental and Medical Sciences, Lucknow, India
2 Department of Prosthodontics, Sardar Patel Post Graduate Institute of Dental and Medical Sciences, Lucknow, India
|Date of Web Publication||30-Dec-2011|
102-A, Vijay Nagar, Krishna Nagar, Kanpur Road, Lucknow, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
The control of anchorage is one of the most crucial factor in orthodontic treatment planning. Traditionally, headgears have been used to be one of the most efficient means to gain anchorage but they have their own limitations and so these methods are limited in delivering results, which commensurate with our idealistic goals. Recently, a number of case reports have appeared in the orthodontic literature documenting the possibility of overcoming anchorage limitations via the use of temporary anchorage devices-biocompatible devices fixed to bone for the purpose of moving teeth. Although skeletal anchorage is here to stay in orthodontics, there are still many unanswered questions. So the purpose of this article is to provide an overview of the current status of orthodontic implants and a discussion of established techniques.
Keywords: Anchorage, mini-implant, orthodontic treatment, temporary anchorage devices
|How to cite this article:|
Rastogi N, Kumar D, Bansal A. The role of implants in orthodontics. J Dent Implant 2011;1:86-92
| Introduction|| |
One of the most important aspects of orthodontic treatment is the control of the anchorage. The importance of anchorage can be best described by the famous quote from the Greek philosopher Archimedes: II give me a place and I will move the earth. There are times when absolute or maximum anchorage, i.e., high resistance to displacement, is needed. In orthodontic mechanotherapy, even a small reactive force can cause undesirable tooth movement. Any uncontrolled reactive force can have negative effect on the outcome of the orthodontic treatment. Therefore, it is virtually impossible to achieve absolute anchorage in which the reaction force is not producing any movement, especially with intraoral anchorage.
Although the principle of orthodontic anchorage has been implicitly understood since the 17 th century, it does not appear to have been clearly articulated until 1923 when Louis Ottofy  defined it as - the base against which orthodontic force or reaction of orthodontic force is applied. Ottofy  also summarized the anchorage categories previously outlined by E.H. Angle and others as simple, stationary, reciprocal, intraoral, intermaxillary or extraoral. Since that time, several noted authors have modified or developed their own classification. Gianelly and Goldman  suggested the terms maximum, moderate and minimum to indicate the extent to which the teeth of the active and reactive units should move when a force is applied. Marcotte  and Burstone  classified anchorage into three categories - A, B, and C, depending on how much of the anchorage unit contributes to space closure. Tweed  prepared anchorage of reactive units by uprighting or distal tipping of posterior teeth, utilizing the concept of tent peg before retracting the anterior teeth. Considering the above classification systems, it becomes apparent that a lack of consensus exist on the terminology for describing anchorage. Moreover, they only account for group of teeth, they do not account for individual teeth, nor do they take care of the entire occlusal plane. This may be because of the fact that at the time these systems were developed the possibility of, for example, intruding posterior teeth to correct the skeletal open bite without surgery was unimaginable. Due to the recent advances occurring in material, biomechanics and clinical procedures, such type of movement has become a reality. So, a new classification of anchorage system is needed bringing implant systems to the fore. Clinicians and researchers have tried to use implants as orthodontic anchorage units for over half a century. After Branemark and coworkers  (1970) reported the successful osseointegration of implants in bone; many orthodontists began taking an interest in using implants for orthodontic anchorage. Costa and colleagues  (1998) used 2 mm titanium miniscrews for orthodontic anchorage. The screws were inserted manually with a screw driver directly through the mucosa without raising a flap and were loaded immediately. Of the 16 miniscrews used during the clinical trial, two became loose and subsequently were lost before treatment was finished. However, the overall results were very encouraging.
Currently, mini implants are used in orthodontics as a temporary anchorage device (TAD)  that is temporarily fixed to the bone for the purpose of enhancing the anchorage, either by supporting the teeth of the reactive units or by obviating the need for the reactive unit altogether, and is subsequently removed after use. They can be located transosteally, subperiosteally or endosteally, and they can be fixed to the bone either mechanically (cortically stabilized) or biochemically(osseointegrated). So,the incorporation of dental implants and TADs into orthodontic treatment made possible infinite anchorage, which has been defined in term of implants as showing no movement (zero anchorage loss) as a consequence of reaction forces. ,
So, the present paper is an attempt to analyze all the aspects of-orthodontic implant and its various clinical implications and procedures.
| Classification of Implants for Orthodontic Anchorage|| |
- According to the shape and size:
- Conical (Cylindrical)
- Miniscrew implants
- Prosthodontic implants
- Miniplate implants
- Disc implants (onplants)
- According to implant bone contact:
- According to the application:
- Used only for orthodontic purposes. (Orthodontic implants)
- Used for prosthodontic and orthodontic purposes. (Prosthodontic implants)
| Mini Plates|| |
The miniplate implants comprises of bone plates and fixation screws. The plates and screws are made of commercially pure titanium that is biocompatible and suitable for osseointegration. ,
The miniplate consists of the three components-the head, the arm and the body as shown in [Figure 1].
The head component is exposed intraorally and positioned outside of the dentition so that it does not interfere with tooth movement. The head component has three continuous hooks for attachment of orthodontic forces. There are two different types of head components based on the direction of the hooks.
- The arm component is transmucosal and is available in three different lengths-short (10.5 mm), medium (13.5 mm) and long (16.5 mm) to accommodate individual morphological differences.
- The body component is positioned subperiosteally and is available in three different configurations-the T-plate, the Y-plate and the I-plate.
The T-plates can be modified and used as L-plates by cutting off one of the screw holes. The surgical site requires at least 2 mm of cortical bone thickness to fix the anchor plate using monocortical screws, which are 2.0 mm in diameter and 5.0 mm in length. Each screw has an internal tapered square head with a self-tapping threaded body. Buttress is almost always thick enough. The I-plate is most often placed at the anterior ridge of the piriform opening for intrusion of upper anterior teeth or protraction of upper molars.
| Mandible|| |
In the mandible, screw fixation is possible on the lateral cortex in most locations except adjacent to the mental foramen. The T-plate and/or the L-plate is usually placed in the mandibular body to intrude, protract or distalize lower molars or at the anterior border of the ascending ramus to extrude impacted molars.
Orthodontic force is usually applied about 3 weeks after surgical placement of the miniplate, waiting only for soft tissue healing, not for osseointegration. Immediately after orthodontic treatment, all of the anchor plates are removed.
Of all orthodontic implants, miniscrews have gained considerable importance due to less surgical procedure and easy installation.
| Miniimplants|| |
Titanium miniscrews [Figure 2] may be an ideal anchorage system that fulfills the clinical needs of the orthodontist. It depends upon several factors;
Advantages of miniscrews over miniplants
- Size and length of the mini implants: The diameter of the mini screw will depend upon the site and space available in maxilla, narrower implant is preferred if it has to be placed between the roots. It is available in either 1.5 or 2.0 mm diameters. The 1.5 mm diameter screw comes in 6.0, 8.0 or 10.0 mm lengths, while the 2.0 mm diameter screw comes in 7.0, 9.0 or 11.0mm lengths.  If stability depends on insertion into the trabecular bone,longer screw is preferred, but if cortical bone can provide enough stability, shorter screw can be choosen. Both diameters are available in three different transmucosal designs to accommodate the soft tissues-low profile, low profile flat and regular. The low profile screw has a longer transmucosal collar combined with a flat head and is utilized in the thick soft tissues of posterior segments, the low profile flat screw has the same head combined with a short collar and is indicated in the thin tissue of the patient's anterior segments, and the regular design has an intermediate length with a raised head, and when combined with a resin core can be used as a temporary prosthetic abutment. ,
- Shape of the implant: This determines the bone implant contact area available for stress transfer and good primary stability. The most commonly used is cylindrical or cylindrical-conical with smooth or threaded surface. Studies have shown that the degree of surface roughness is related to the degree of osseointegration.
- Implant materials  : The material must be non toxic, bio compatible, resistant to stress, strain, corrosion and possess excellent mechanical properties. Commonly used materials are -Stainless steel,chromium cobalt alloy (bio-tolerant) Titanium and carbon (bio-inert) Hydroxy-apatite and ceramics (bio-active).
- Implant fixation: Implant must achieve primary stability and withstand mechanical forces. Factors that determine the contact area are length,diameter, shape and surface design. In the maxilla, the insertion 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.
Some of their benefits include:
- Less patient compliance
- Well acceptance by the patient
- Immediate loading
- Simple to insert and remove
- Conform to the anchorage needs of the orthodontist.
Complete osseointegration is neither expected nor desired with this anchorage system.
| Diagnosis and Treatment Planning|| |
Treatment planning must include a careful choice of miniscrew location as well as the criteria as shown in [Flowchart 1]. The placement location will enable the clinician to control or effect extrusive and intrusive movements of teeth. The placement of the screw requires a location that has sufficient bone depth to accommodate the miniscrew and at least 2.5 mm of bone width to protect the anatomical structures. 
| Sites of Placement|| |
- Infrazygomatic crest area
- Tuberosity area
- Between 1 st and 2 nd molars buccally
- Between 1 st molar and 2 nd premolar buccally
- Between canine and premolar buccally
- Between incisors facially
- Midpalatal area
- Retromolar area
- Between 1 st and 2 nd molars buccally
- Between 1 st molar and 2 nd premolar buccally
- Between canine and premolar buccally
- Symphysis facially
- Edentulous area
- Mandibular tori
| Implant Driving Method|| |
There are two methods of placement of minimplants.
- Self-tapping method: In this method the miniscrews is driven into the tunnel of bone formed by drilling, making it tap during implant driving. This method is used when we use small-diameter miniscrews.
- Self-drilling method: Here the miniscrews is driven directly into bone without drilling. This method can be used when we want to use larger diameter (more than 1.5 mm) miniscrews.
| Presurgical Orthodontics|| |
The surgical armamentarium for miniscrew insertion includes a low-speed contra-angle hand piece, a bur with a depth stop and a hand screwdriver. During surgical planning, the surgical site and screw length are determined. Every effort must be made to avoid contact with local anatomical structures.
Long cone radiographs [Figure 3] are taken to visualize the site locator relative to the delicate anatomical structures. Each screw length corresponds to a bur with a depth stop of equal length. A site locator can be fabricated from an orthodontic wire and utilized to determine the insertion position of the screw in the bone [Figure 4].
|Figure 3: Radiographical location of the site of placement of the implant|
Click here to view
| Surgical Procedure|| |
Topical anesthesia is recommended before infiltration anesthesia to reduce needle prick pain. Clinicians should not try to achieve profound anesthesia of the teeth, instead get numbness of soft tissue only. It is prudent for the teeth to have some sensitivity, as the patient will complain of discomfort in the event of bone drill contacting the roots, then the drill can be redirected away from the roots.  Only one-fourth to one-third of a local anesthetic cartridge is needed for this type of anesthesia. Common sterilizing agents can be used to prepare intraoral and extraoral scrub for keeping the surgical area aseptic.
In self-tapping method, a round bur (0.9 mm) is used to make an indentation on the bony surface. Then pilot drilling is done to make a tunnel in the bone [Figure 5]. In order to avoid damages due to overheating, the drilling must be undertaken using the contra-angle hand piece (optimal 800 rpm, maximal 1500 rpm) and external cooling with a sterile, cooled, physiological saline solution (5°C/41°F). The drilling should take place intermittently and without pressure so that the tip of the bur may cool down. Finally, miniscrew is loaded in the bone. In self-drilling method, there is no pilot drilling and miniscrew is loaded directly into the bone.
| Postsurgical Treatment|| |
Patients should be given standard surgical postoperative instructions emphasizing the importance of inflammation control and cautioned not to brush or touch the implant for a week. Ibuprofen or its equivalent is usually adequate for discomfort, and antibiotics are rarely necessary. A chlorhexidine rinse is usually prescribed for 7-14 days, but no other postsurgical care is required. Patients with miniscrews should return to the orthodontic office as soon as possible for loading, preferably within 1 week. In theory, vector of force to stabilize miniscrews is critical to counter tissue, tongue and masticatory forces. Osseointegration is not expected, therefore mechanical stabilization is crucial.
| Implant Maintenance|| |
After surgery, the surrounding soft tissues must be maintained to ensure longevity of the implant. Plaque accumulation near the gingival margin can cause peri-mucositis. Prolonged inflammation may lead to the breakdown of bone around implants and may cause peri-implantitis which may eventually result in implant failure. Therefore, proper instructions for daily plaque control at home and regular professional care should be emphasized to the patient.
| Miniscrew Removal|| |
Fortunately, strong osseointegration does not occur between miniscrew and bone, and this simplifies the removal of these microscrews. Clinician can engage the miniscrew head with the driver and turn it in the opposite direction of the insertion that will easily remove it.  Local anesthesia is not needed during this procedure.
| Clinical Implications|| |
- Closure of extraction spaces: Loss of posterior anchorage during extraction space closure can exacerbate the curve of Spee and deepen the bite. Miniscrews provide reliable skeletal anchorage for anterior retraction in either arch, whether a single tooth at a time or en masse [Figure 6].
- Single tooth intrusion: A few patients often report with extruded tooth due to early loss of its antagonist. So, in order to correct its vertical position we plan for single tooth intrusion [Figure 7].
- Correction of canted occlusal plane: A canted occlusal plane is often considered impossible to level with traditional orthodontic treatment. Miniscrews, on the other hand, provide skeletal anchorage for intrusion of the appropriate teeth on the canted side.
- Molar intrusion: Opinions have differed regarding the efficacy of orthodontic intrusion of posterior teeth. Although miniscrews can be a reliable source of anchorage, it is difficult to place them precisely in the narrow space between the roots of the first and second molars without interfering with the roots. In some cases, more than one screw might even be needed to withstand a relatively high intrusion force [Figure 8]. Therefore, we suggest limiting the use of miniscrews to situations where simple intrusion of one or two molars is needed and here placement will be unproblematic.
- Molar mesialization: Molars are often moved mesially in orthodontic treatment to close extraction spaces or edentulous spaces. Molar mesialization is not a simple movement and can lead to problems such as loss of anterior anchorage and molar tipping. Furthermore, if there is a knife-edge alveolar ridge in the space to be closed, alveolar bone may be lost. 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 a valuable source of anchorage [Figure 9]. If the screw is inserted after the initial leveling and alignment has been completed, a full-size archwire can be used to prevent mesial crown tipping of the molar during space closure. Because mesial movement is usually slow, especially in the mandibular arch, no more than 2-3 mm of molar mesialization should be attempted.
- Molar distalization: Miniscrews + Distal Jet may be a solution. After the Distal Jet appliance has been placed and activated, palatal miniscrews are inserted between the roots of the first and second premolars, mesial to the activation locks attached to the anterior rests. The miniscrews block mesial movement of the appliance during distalization, thus preventing loss of anterior anchorage. Further compression of the Distal Jet's coil springs will move the locks distally, away from the miniscrews; during this phase, anchorage loss can be prevented by bonding light-cured composite between the screw heads and the locks. After molar distalization, the Distal Jet is converted to a passive retainer, and brackets are bonded to the teeth for completion of the Class II correction. Another option is to remove the miniscrew after molar distalization and replace it just mesial to the distalized molar, where it will stabilize the molar while the remaining teeth are moved posteriorly [Figure 10].
- Intrusion of incisors: Many patients present with moderate - to - severe deep bites requiring pure intrusion of the anterior teeth to level the occlusal plane. Unless the deep bite is so extreme that absolute anchorage is needed, it may be inadvisable to place miniscrews simultaneously in both arches in young patients. In these cases, miniscrews can be used to reinforce conventional orthodontic mechanics [Figure 11].
| Conclusions|| |
Success of orthodontic treatment relies on anchorage control. So anchorage preparation is a very important part of orthodontic treatment. Prior to initiation of orthodontic therapy, it is essential to carefully assess the anchorage demands of an individual case so that appropriate treatment modalities can be executed. Various sources of anchorage have been used from the 17 th century to till date. Every anchorage source has some advantages and some limitations. Anchorage preparation is different from patient to patient. Use of extraoral anchorage such as headgears requires full patient cooperation, but this cooperation is not seen especially in teenagers. With the introduction of implants in orthodontics, this problem has been solved. Implants do not require any patient cooperation, so we can get a good anchorage control in our patients. Implants provide absolute anchorage i.e., complete bone anchorage. Implants have revolutionized the field of anchorage in orthodontics. So by choosing a correct anchorage source we can get good results in orthodontic treatment.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]