Anchorage In Orthodontics Question And Answers

Anchorage In Orthodontics

• Simple anchorage.
• Stationary anchorage.
• Reciprocal anchorage.

• Intermaxillary.
• Intramaxillary.

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• Intraoral
  • Intramaxillary
    • Simple
    • Stationary
    • Reciprocal.
  • Intermaxillary

• • • Simple
    • Stationary
    • Reciprocal.
  • Extraoral

• • • Cervical
    • Occipital
    • Cranial
    • Facial.
  • Muscular.

• Single or primary anchorage.
• Compound anchorage.
• Multiple or reinforced anchorage.

• 100 to 75% space closure from anterior retraction and 25% closure from posterior anchorage movement.
• There is critical posterior anchorage.

• It includes more equal amount of anterior and posterior tooth movement for space closure
• This is the easy condition to deal with.

• It includes 75 to 100% of posterior protraction. There is a non-critical anterior anchorage and critical posterior anchorage.
• Anterior retraction is only 25%.
• It is a non-critical anchorage.

• In this, resistance is provided by a single tooth with greater alveolar support which is used to move the tooth with less alveolar support.
• Example is moving a tooth with smaller root surface area against a tooth with large root surface area and is known as an anchor.

• It is defied as “dental anchorage in which the manner and application of force is such that it tends to change the axial inclination of the tooth or teeth that form the anchorage unit in the plane of space in which the force is being applied.”

• It is the resistance offered by anchorage unit to tipping.
• Its resistance value is low.
• This resistant to tipping is use to move another tooth.

• It is defied as “dental anchorage in which the manner and application of force tends to displace the anchorage unit bodily in plane of space in which the force is being applied”.
• Stationary anchorage is the resistance to bodily movement.
• Example of stationary anchorage is: Molars are used as anchoring teeth for retraction of maxillary incisors.
• In real sense, only extra-oral source of anchorage derived from head gears is the best example of stationary anchorage.

• It refers to the resistance offered by the two malposed unit.
• When dissipation of equal and opposite forces tends to move each unit towards each other in a normal occlusion.
• Two teeth or two groups of teeth of equal anchorage value are made to move in opposite direction.

• Example of reciprocal anchorage is:
• • Closure of midline diastema—By moving two central incisors towards each other.
  • Crossbite elastics—For correction of single tooth posterior crossbite.

• In intramaxillary anchorage all the anchoraging lie in the single jaw.
• For this appliances are either placed in maxilla or in mandible.
• It is divided into three types, i.e. simple, stationary and reciprocal type.
• Example: Elastic chains use to retract anterior segment using posterior teeth as anchorage units.

• Anchorage in which the resistance unit situated in one jaw are used to effct tooth movement in the opposing jaw is known as intermaxillary anchorage.
• Baker’s anchorage is an example for intermaxillary anchorage.
• Baker’s anchorage is the type of intermaxillary anchorage for adjusting both jaw relation and teeth with the help of applying elastic from maxilla to mandible.

• Anchorage in which all the resistance units are situated within the oral cavity is known as intraoral anchorage.
• Sources for intraoral anchorage are teeth, palate and lingual alveolar bone of mandible.
• It is classified into two divisions, i.e. intramaxillary anchorage and intermaxillary anchorage.

• Anchorage in which the resistance units are situated outside the oral cavity is termed extraoral anchorage.
• Various extraoral anchorage sites along with their examples are:
  • In occiput region: Head pullgear and chin cup can be given.
  • Back of the neck: Cervical headgear is used.
  • Forehead: Reverse pull headgear is used.
  • Chin: Reverse pull headgear and chin cup can be given.
• Extraoral anchorage is used in correction of skeletal problems.
• Can be used as a form of reinforced anchorage.

• In some cases perioral musculature is employed as resistance unit.
• Muscular anchorage makes use of forces generated by muscle to aid in movement of teeth. Example of muscular anchorage is usage of lip bumper to distalize molars.

• It is also known as multiple anchorage.
• In this more than one type of resistance unit is utilized.
• The resistance units become more and more effective when numerous units are added since the reactionary force should be distributed over a wide range of area.
• As the forces are distributed, their effect become light which leads to less trauma and pain at time of orthodontic treatment.
• Examples are:
  • Transpalatal arch and lingual arch reinforces the anchoring unit.
  • Headgears augment the resistance units.

• Cortical bone provides more resistance to resorption as compared to medullary bone.
• Response of the cortical bone when compared to medullary bone is very different. If the roots are torque lingually or buccally, resistance to movement get increased this is known as cortical anchorage.
• Example is space closure at old extraction site is difficult as roots encounter cortical bone along the residual ridge.

• In modern era, orthodontic implants are used as anchorage units.
• Various orthodontic implant are orthosystem implant, Aarhus implant, on plant, mini implants.
• Orthoimplant system is a screw type endosteal implant of 4 to 6 mm in length. Aarhus implant is small in size and its early loading is possible, so it is used in multiple sites in between the roots. Onplant is a disc shaped structure which is placed in the hard palate over posterior aspect under local anesthesia. Mini implants are very small.

• It refers to the resistance offered by the two malposed unit.
• When dissipation of equal and opposite forces tends to move each unit towards each other in a normal occlusion.
• Two teeth or two groups of teeth of equal anchorage value are made to move in opposite direction.
• Example of reciprocal anchorage are:
  • Closure of midline diastema—By moving two central incisors towards each other.
  • Crossbite elastics—For correction of single tooth posterior cross bite.

• In this more than one type of resistance unit is utilized.
• Reinforced anchorage is the augmentation of anchorage by various methods i.e. extraoral appliances, upper anterior inclined plane or transpalatal arch.
• Here the extra forces are generated from extraoral sites cranium, back of the neck and face
• The resistance units become more and more effctive when numerous units are added since the reactionary force should be distributed over a wide range of area.
• As the forces are distributed, their effct become light which leads to less trauma and pain at time of orthodontic treatment.
• Reinforced anchorage is done by various methods such as:

• For tooth movement to occur in the desired direction this reactive force should be equal to or greater than the force applied.
• The areas or units which provide the resistance to the reactive force thereby preventing undesirable tooth movement are called anchorage units.
• Thus, anchorage prevents undesirable tooth movement and provide adequate force to desirable tooth movement.

• When all the units offering resistance are situated within the same jaw the anchorage is described as intramaxillary.
• In this type of anchorage the teeth to be moved and the anchorage units are all situated entirely in maxilla or in mandible.
• For example—Class I elastics, labial bow, coffin springs.

• Baker’s anchorage.
  • Class 2 elastic traction.
  • Class 3 elastic traction.

• It is the resistance offered by anchorage unit to tipping.
• Its resistance value is low.
• This resistance to tipping is used to move another tooth.
• Simple anchorage is obtained by engaging with appliance a greater number of teeth than are to be moved within a same dental arch.
• Combined root surface area of teeth forming the anchorage unit must be double that of the teeth to be moved. So, the resistance offered by anchorage unit is greater than offered by tooth or teeth being moved.

• Anchorage in which the resistance units are situated outside the oral cavity is termed extraoral anchorage.
• Extraoral anchorage is used in correction of skeletal problems.
• Can be used as a form of reinforced anchorage.
• Various extraoral anchorage sites along with their examples are:
  • In occiput region: Head pullgear and chin cup is adviced.
  • Back of the neck: Cervical headgear is advised.
  • Forehead: Reverse pull headgear is advised.
  • Chin: Reverse pull headgear and chin cup is advised.
  • In parietal region: Combination headgear is advised.

• Anchorage established from extraoral anchorage source is much greater than intraoral anchorage source, since extraoral anchorage units are more stable.
• There is lesser risk of anchor loss.

• The load deflection (or torque-twist) rate, is a factor to the delivery of a relatively constant force.
• Load deflection rate is defied as the amount of force generated per unit of activation.
• If a spring is activated 3 mm and it generates 150 g of force the load deflction rate of the spring would be 150 g/3 mm = 50 g per mm of activation.
• Load deflction rate = Load/deflection
• It is desirable for an appliance to have a low deflection rate since such an appliance would produce a lower more constant force that is active over a long duration.
• As the load deflection rate declines for a tooth that is moving under a continuous force, the change in force value is reduced.
• For active members a low load-deflection rate is desirable for two important reasons:
• • A mechanism with a low load deflction rate maintains a more desirable stress level in the PDL because the force on a tooth does not radically change magnitude every time the tooth has been displaced.
  • A member with a low load deflction rate offrs greater accuracy in controlling force magnitude.
• Flexible members with low load deflection rates require long ranges of activation to build up to optimal force values; hence they give the orthodontist greater control over the magnitude of force used.
• If a low load deflection rate is desirable for the active member of the appliance, the opposite is true for the reactive member.

• Class 2 malocclusion correction: Elastics are applied between the lower molar and upper anterior.
• Class 3 malocclusion correction: Elastics are applied between the upper molar and lower anterior.

• Mesial or distal movement of buccal teeth
• Lingual or the labial movement of anterior teeth
• Vertical intrusive movement of buccal or anterior teeth

• Patients who lost their posterior teeth
• As an anchorage for distalization of molars
• For intrusion of maxillary teeth
• For anterior open bite and deep bite correction
• As source of anchorage for retraction of canines as well as anteriors
• For correcting the canted occlusal planes
• As an aid in treatment of Class III malocclusion.

• Open method: Head of the microimplant is exposed to oral cavity. Open method is used when implant is placed in an area where the sof tissues are not movable i.e. attached gingiva.
• Closed method: Head of the microimplant should be embedded under the sof tissue. Closed method is used when implant is placed in an area where the soft tissue is movable.

• Self tapping method: Here a tunnel is fist drilled inside the bone and then the implant is tapped in. This method is mainly used for smaller diameter microimplants.
• Self drilling method: In this method an implant drills itself into the bone. It is used for larger diameter microimplants.

• Oblique direction: In this the insertion of microimplant is diagonally at an angle of 30 to 60 degree to the long axis of tooth. This method is used in areas where interradicular bone is very narrow.
• Perpendicular: In this the microimplant is inserted perpendicular to the bony surface. This method is used if there is sufficient interradicular bone.

• Procedure is carried out by the orthodontist as an adjunct to the orthodontic treatment.
• An intraoral periapical or a panoramic radiograph of the particular region is needed to evaluate interradicular space present. Ideally minimum of 2 mm interradicular bone is needed.
• Give minimal amount of local anesthetic to the mucosa which lies adjacent to the proposed implant placement site. Since underlying bone does not consists of innervation and profound anesthesia of the adjacent teeth and periodontal ligaments is contraindicated.
• If the drill or implant approaches towards periodontal ligament it would lead to some pain to the patient which will alert the orthodontist to redirect the implant. This pain feedback from the patient would not be possible with profound anesthesia.
• Drill a pilot hole with a 1.2 mm twist drill at 600 rpm to just short of the implant length. Provide adequate cooling with a physiological saline solution while drilling, to avoid thermal damage to the bone.
• Insert the implant by using a hand piece at 12 rpm or can be hand driven with a hand driver.
• Take a post operative radiograph to assess the proper placement of implant.
• Following insertion, the peri-implant tissues are gently rinsed with sterile saline solution before the screws are loaded.

• As treatment get complete the temporary anchorage device can be easily removed.
• Removal of the mini – implants is easily done with the same screw driver as used for insertion.
• Whole of this procedure is carried out under application of a local anesthetic gel.
• Removal site should be gently swabbed with a 0.2% chlorhexidine.
• Wound present at time of screw removal is minimal and usually closes within a few days. In most of the cases, healing will continue uneventfully.

• Contact with adjacent roots: It is possible while placing the temporary anchorage devices. It has been seen that minor root contact does not lead to any serious long term damage. If patient expresses discomfort at the time of placing, it is possibly because of close approximation of the periodontal ligament. During placement, if increased resistance is felt during drilling or placing the implant it could be due to root contact. This can be verifid by a radiograph. It may be required to reposition the implant.
• Breakage of implant: It is extremely rare for bone to give enough resistance which break an implant; if resistance is present, orthodontist should ensure that the implant is not being directed into a root. If an implant breaks an attmpt should be made to remove it unless it is too deep.
• Damage to anatomic structures: When implants are placed in maxillary premolars and molars the maxillary sinus can be approximated. This can be avoided by placing the implants coronally in attched gingiva.
• Soft tissue overgrowth: If there is sof tissue overgrowth over the head of implant, this can produce diffilty in placing attachments to them and can also irritate the tissues. This is avoided by ensuring the implant enters via attached gingiva and not the unattached alveolar mucosa.
• Loosening of implant: It is the most common complication and may occur any time following implant placement. Some of the causes of implant loosening are poor bone quality, excessive force application and approximation to the root surface. If an implant get loose, an initial solution may involve simply tightening the implant a few more turns. If it loosens again, remove the implant and replace it in a new position. If space is enough, a larger diameter implant can be placed inside the same hole.

• Head gear
• Face mask
• Chin cup