1. Temporary Anchorage Devices
David R. Telles, DDS Diplomate of the American Board of Oral and Maxillofacial Surgery

2. Introduction Overview Orthodontics History Conventional Mechanics
Anchorage types
Clinical Indications
Surgical Techniques
Outcomes / Complications

3. Overview
Orthodontists have always tried to develop ways to move teeth while minimizing the unwanted reciprocal movement of the teeth they pull or push against
Best situation when ideal anchorage is in place to move teeth in an efficient manner
History:
Use of dental implants
Unpopular due to
Time for osteointegration
Use for restoration purposes
Cost

4. Orthodontics Goals of therapy
Optimization of occlusion
Aesthestics
Facial Balance
Traditional ortho can accomplish which require mild to moderate compensation
More significant discrepancies require more robust anchorage
E.g. pts with moderate to severe skeletal discrepencies – may requiring growth modifcation or orthognatic Sx
May benefit from skeletal anchorage – I.e. cases to which conventional orthodontics cannot correct severe malocclusions

5. History
Concept for using implantable devices for skeletal anchorage has been present for that last ½ century
1940: Gainsforth and Higley experimented with vitallium screws and wires in a dog ramus for anchorage
Linkow used blade implants to provide class II elastics
Sherman et. al. used dental implants in dogs for anchorage with limited success
1979: Smith noted implants could act as ankylosed teeth for orthodontic movements
1988: Shapiro et. al. established the use of dental implants for orthodontic anchorage
1995: Block et. al. used HA coated onplant placed in the midline palatal tissue for use with orthodontics for anchorage
1999: Umemori et. Al described techniques for using a modified rigid fixation plate for use with orthodontics – important leap forward since force could be applied without loosening the plates

6. Orthodontics mechanics and skeletal anchorage
Planning requires a team approach
Anchorage: resistance to unwanted tooth movement
forces involved
In orthodontic tooth movement – it obeys Newton’s third law
for every action, there is an equal and opposite reaction -- every movement of a tooth in the desired direction, the force is distributed to the anchorage segment, potentially affecting the position of those teeth within the anchorage segment
Example
To move a canine posterior (distally) and if only one molar is present, then the molar has a tendency to drift toward the mesial if the molar is used as an anchor for that movement
If more anchorage is provided to that area  then the movement can occur with less of the unwanted mesial movement of the molar

7. Using Conventional Mechanics
anchorage can be increased by using intraoral or extraoral techniques
Intraoral techniques commonly use tooth-borne appliances to improve anchorage.
increasing the number of teeth in the anchorage unit
E.g. teeth can be tied together with ligature wire to resist unwanted tooth movement in another area
Another way of increasing teeth in the anchorage segment is to use a transpalatal arch.
distributes the force to another segment of teeth across the arch.
elastic bands can be used between the opposing arches to provide additional anchorage
used to close space after maxillary premolar extraction by retracting the anterior dentition of the maxilla with elastic bands bilaterally and attaching the elastic to the
mandibular posterior teeth
AKA class II elastics help to minimize the unwanted mesial movement of the maxillary posterior anchorage segments.

8. Using Conventional Mechanics
Nance button appliance that holds the posterior molars in position with an acrylic button on the anterior palate
Force can be applied to the posterior teeth to close premolar space
Helps to offset the tendency for the molar teeth to move mesial is resisted by the acrylic button on the palate near the incisive foramen
Extraoral Appliances
Significantly dependent on compliance of the pt
Rarely provide force > 6-10 hrs/day
E.g. Head Gear

9. Skeletal Appliances Provide anchorage not tooth-borne
Unwanted reciprocal tooth movement avoided
Other adv:
No or minimal reliance on existing dentition
Less dependent on patient compliance
Continuous rather than intermittent force may be applied
Surgical procedures are necessary, but they are simple in most instances
May be significantly less expensive than other surgical options, such as orthognathic surgery
Force may be applied very soon or immediately after placement of the device; devices require mechanical stability rather than osteointegration
Devices are easily removed

10. Anchorage types Direct – Indirect
Apply force directly from the anchor to the segment or tooth that is being moved
E.g. maxillary plates placed in the zygomatic butress may be designed to provide intrusion force to maxillary molars to close anterior open bites
Indirect
Tie the anchor device to the segment of teeth that requires additional anchorage such that more traditional mechanics can be used in the area
Involves an inelastic or even rigid connection between the anchor and the orthodontic appliances
E.g. maxillary anchor tied by steel ligature to the anterior teeth to provide more anchorage – then a coil spring could be used on the archwire to distalize the molar teeth
Indirect due to the force used is along the archwire by the coil spring
ADV:
Most orthodontists already design their movements of teeth based on traditional mechanics
Either technique can accomplish similar outcomes – help to allow orthodontic movements which once were deemed difficult or impossible

13. Take note
Skeletal anchorage devices do not allow faster movement of teeth, or the ability to overcome exceptionally large discrepancies
the devices have limitations
Provide absolute anchorage for orthodontic movement

14. Devices for skeletal anchorage
Dental Implants
Costly, Reqs OI
Requires aggressive Sx for removal
Mini dental implants
Onplant
Placed in midpalatal region
Long-term studies not documented
Bone screws
Self-tapping and self-drilling systems available
Bicortical screws 8-12 mm in length
Stability determined by thread pitch based on bone type – typically 0.6 mm

16. Devices for skeletal anchorage
Devices should –
Be designed for the purpose of skeletal orthodontic anchorage
Have a very high quality of manufacturing with standardized quality control
Have an appropriate pitch thread to ideally engage bone
Have the appropriate core and external diameter to withstand orthodontic forces in maxillary and mandibular bone
Be designed well at the runout and shafthead interface to avoid fracture
Screws smaller than 1.5 mm tend to fail and not recommended
Bracket head screws offer little adv

17. Devices for skeletal anchorage
Skeletal anchorage plates
Adv: incresed stability, 3D support
Are modified leforte osteotomy plates
Do no require osteointegration
May be immediately loaded
Allow placement of multiple screws away from vital anatomical structures

18. Clinical Indications
Mesial or distal Movement of Teeth with maximum anchorage
Uprighting or intruding molar teeth
Closure of anterior open bite
Orthopedic growth modification

19. Clinical Indications
Mesial or distal Movement of Teeth with maximum anchorage
e.g. loss of 1st molar – moving teeth anteriorly – to prevent movement of anterior teeth distally a skeletal anchor can be | used
Can prevent inadvertent movement canine relationship to class II
Helps maintain overbite-overjet relationship
E.g. Class III pt can have posterior mandibular teeth stabilized and compensate mand ant teeth and hold posterior teeth to prevent mesial tipping of molars OR to provide anchorage to distalize molar teeth

20. Clinical Indications
Mesial or distal Movement of Teeth with maximum anchorage

22. Clinical Indications Uprighting or intruding molar teeth
Considered one of the more difficult movements in ortho e.g. molar moving mesially post-extration
Use of a skeletal anchor can help uprighten without extrusion which results typically with conventional orthodontics
Intrusion also can be accomplished with skel anchorage

23. Clinical Indications Closure of anterior open bite
Accomplished via placement of orthodontic screws or plates in the posterior maxilla, apical to the dentition
Force is generated to intrude the posterior molars and premolars to close the anterior openbite
Numerous case reports show success
No long term data on stability compared to orthognathic surgery
Should be reserved to pts not willing to undergo orthognathic Sx

24. Clinical Indications Orthopedic growth modification
Can be used in a manner similar to headgear
Considered to be used in phase I of orthodontic Tx
For pts with Class III
Skeletal anchors can be placed in the maxilla/mandible to provide forward orthopedic force to the maxilla and encourage class I relationship
Vector of force similar to reverse-pull headgear w/o need for external appliance therapy
Limited use due to risk of growing/developing dentition and risk of multiple surgical procedures on pediatric pt

26. Surgical Techniques
The type of anchor (miniscrew, anchor plate), location, angle of the device is determined by the orthodontic Tx plan

27. Placement of Skeletal Anchorage plates
devices typically consist of a bone plate with holes for screw placement and a transmucosal connecting arm that extends from the plate to a specialized working end
working end -- allows for the attachment of wire, springs, elastics, and other orthodontic constructs
Placement typically carried out under local anesthesia
Monocortical screws
Maxilla
Typically placed within one of the vertical butresses of the midface (zygomaticomaxillary, piriform rim)
transmucosal position of the connecting bar should be located at approximately
the mucogingival junction
Nonkeratinized mucosal tissues should be avoided
NOTE: When the transmucosal location of the connecting bar is within the unattached tissues of the maxillary vestibule, increased irritation, inflammation, infection, and soft tissue overgrowth may result.

29. Placement of Skeletal Anchorage plates
Mandible
Avoid IAN, mental nerve, teeth roots
Typically placed in the symphysis, ramus, posterior body of the mandible
If bone plate positioned directly over mandibular canal – use of monocortical screws helps avoid injury to the IAN

31. Placement of miniscrews
Similar to placing IMF screws
Placed near the mucogingival junction
To engage the cortical and cancellous bone
Longest length possible while avoiding vital anatomical structures
Maxilla
Zygomatic or piriform butress
Hard palate
Alveolar process between teeth
Mandible
Between teeth
Symphysis
Retromolar pad
Does not require elevation of a soft tissue flap

32. Post-op Post-op imaging to confirm placement and proximity to anatomy
Abx x 5-7 days – pen, amox, clinda, etc.
Encourage OH
Prescribe CHG bid x 7 days
Cheek irritation seen POD #10
May be immediately used following surgical placement both miniscrews + plates
Manipulation with full orthodontic forces typically delayed 7-10 days post-op to allow for adequate the Sx site/ soft tissue

33. Outcomes + Complications
Outcomes vary based on screw or plate systems
A number of reports have listed loosening or outright failure of orthodontic anchorage screws to be above 15%.
Rate of failure of plates < 5%
Prospective unbias literature still required
Complicaitons
Device failure
Loosening associated with design flaw
Infection
Operator related complications:
Stripping of screws
Overworking screw
Poor stability due to poor choice of placement
Failure to place working attachments through attached mucosa
Misplacement for use by orthodontist
Root damage to teeth – typically seen with discomfort during mastication

34. Outcomes + Complications
Patient related complications
Poor quality bone
Reasonable OH
Systemic disordered affecting bone or mucosal healing
Previous Hx of radiation therapy to the H & N region
Hx of bisphosphonate use
Smokers

35. References
Costello, B. Oral Maxillofacial Surg Clin N Am 22 (2010) 91–105
Park HS, Kim JB. The use of titanium microscrew implant as orthodontic anchorage. Keimyung Med J 1999;18:509–15.
Park HS, Bae SM, Kyung HM, et al. Microimplant anchorage for treatment of skeletal class I bialveolar protrusion. J Clin Orthod 2001;35:417–22.
Umemori M, Sugawara J, Mitani H, et al. Skeletal anchorage system for open-bite correction. Am J Orthod Dentofacial Orthop 1999;115:166–74.
Sugawara J. Dr. Junji Sugawara on the skeletal anchorage system. J Clin Orthod 1999;33:689–96.
Bae SM, Park HS, Kyung HM, et al. Clinical application of micro-implant anchorage. J Clin Orthod 2002; 36:298–302.
Gainsforth BL, Higley LB. A study of orthodontic anchorage possibilities in basal bone. Am J Orthod 1945;31:406–17.
Linkow LI. The endosseous blade implant and its use in orthodontics. J Orthod 1969;18:149–54.
Sherman AJ. Bone reaction to orthodontic forces on vitreous carbon dental implants. Am J Orthod 1978; 74:79–87.