clinical application of the miniscrew anchorage system. jco2005

Clinical applications of the miniscrew
anchorage system
JCO Jan 2005;vol XXXIX; No 1
Aldo carano
Stefano velo
Paola leone
Giuseppe siciliani
www.indiandentalacademy.com

 Aim – illustrate the clinical applications of a new titanium miniscrew
designed for orthodontic anchorage
 Introduction
might skeletal anchorage be applied to orthodontic tooth movement and
orthopaedic jaw movement?

 Creekmore and Eklund - 1983
small metal screw could withstand a constant
force of sufficient magnitude and duration to
reposition an entire anterior maxillary dentition
without becoming loose, painful, infected or
pathologic

 Standard dental implants
temporary anchorage
permanent abutment
 Advantages
1. Possible to move multiple teeth without anchorage loss
2. Can be placed in areas where natural anchorage or conventional
orthodontic appliances are impractical Eg. Edentulous spaces , palate,
retromolar area, zygomatic process and the ramus

 Disadvantages
1. Need for invasive procedure
2. Limitation on implant sites imposed by the implant
length - 10mm
3. Time required for osseointegration prior to application
of force
4. Cost
5. Breakage of screw if the bone consistency is high or a
partial integration has occurred – rotational forces
during insertion and removal

 New onplants, miniplates and palatal implants
Miniplates – anchorage for molar intrusion
Palatal implants – space closure and distalization
of maxillary molars
Disadvantages – miniscrews with reduced size and
made of medical grade 4 or 5 titanium

 Histologic studies
1. osseointegration of titanium miniscrew is
less than half of conventional dental
implants
2. No significant difference in the bone
surrounding the miniscrew sites whether
they were loaded or unloaded with force.

 New Miniscrew design
 MAS (miniscrew anchorage system), Micerium, Italy
 conical
 medical grade 5 titanium
3 sizes
Diameter at
top of neck
Diameter at
tip
length
Type A 1.3mm 1.1mm 11mm
Type B 1.5mm 1.3mm 11mm
Type C 1.5mm 1.3mm 9mm

 Screw head
2 fused spheres – upper 2.2 mm in dia
lower 2.0 mm in dia
 0.6mm Horizontal slot at the
junction of the two spheres for
attachments
 Internal hexagon for placement
of screwdriver

Mechanical testing
Torsional strength and bending strength
Department of mechanical engineering – University of
Genoa, Italy
Method
The screws were seated in tapped brass block to a depth of
6 mm

Torsion – to – failure test
A dial torque wrench with a recording device was turned in a clockwise
direction, perpendicular to the long axis of the screw
Bending – to – failure test
A dial bending arm with a recording device was used to deform the screw
along its long axis in a clockwise direction.
6 screws were used for each test

Mean resistance to
breakage in torsion
Mean resistance to
breakage in flexion
Type A 37.4 N cm 91.7 N
Type B 48.7 N cm 120.4 N
Type C 48.7 N cm 120.4 N

conclusion
 MAS screws can resist a force much greater
than that of any orthodontic application.
 However force > 40 N cm can be applied
during insertion or removal
Methods to avoid this
use small screwdriver
hold it by the fingertips
additional pilot drilling – during insertion
minor surgical procedure – during removal

Placement sites
Maxilla
1. interradicular spaces, both buccal and lingual
2. extraction spaces
3. inferior surface of the anterior nasal spine
Mandible
1. interradicular spaces, both buccal and lingual
2. extraction spaces
3. Lateral to the mentalis symphosis

Surgical procedure
 Surgical guide
 No medullary bone preparation needed
Pilot drilling if necessary – 2 to 3 mm
Axial inclination similar to that desired of the
miniscrew

 Injury to delicate anatomic stc’s should be avoided – blood vessels ,nerves
and dental roots
Metallic marker attached to a vacuum formed retainer or directly to the
brackets

Manual screw driver is to be used
Properly place miniscrews will have their head protruding
through the soft tissue.
Orthodontic force of 50 – 250 gms and be applied
immediately
If there is compression of soft tissues after placement of a
chain or NiTi coil spring, Monkey hooks can be used

 No post-operative analgesics or antibiotics required
 Authors’ experience
 no trauma to any anatomic stc’s during insertion
 no post – surgical complications have been reported in
literature
 screw removed without LA – when anchorage is no
longer needed
 mucosa generally heals within few days

Uses of MAS
 Closure of extraction spaces
 Symmetrical incisor intrusion
 Correction of canted occlusal plane
 Alignment of dental midlines
 Extrusion impacted canines
 Molar intrusion
 Molar distalization
 Molar mesialization
 Intermaxillary anchorage
 Upper third molar alignment

Closure of extraction spaces
 Single tooth or en masse
 Maxillary miniscrews – placed b/w the roots
of I and II PM – large interradicular space
Screw placement – depends on desired line of
action
The mucogingival line is a excellent spot for
both intrusive and distalizing forces

 Higher the screw is placed in maxilla more perpendicular
it should be to the bone
 In mandible – bialveolar protrusion and class III cases
 Should not be used b/w I and II PM – proximity of mental
foramen

Symmetrical incisor intrusion
 Used in extreme deep bite cases where
absolute anchorage is needed
 Biteplates bonded to the lingual surfaces of
upper 4 incisors
 Miniscrews placed b/w LI and canine on either
side after leveling and alignment
 Ends of archwire should be cinched back to
avoid buccal tipping of incisors

Correction of canted
occlusal plane
 Considered impossible with traditional orthodontic
treatment
 Miniscrews can be inserted b/w
upper LI & canine or canine & I PM or in b/w lower LI &
canine

 Screw must be centred in b/w the roots to avoid
interference during intrusion

Alignment of dental midlines
 Miniscrews are used where intermaxillary
elastics are CI
in cases where vertical forces are undesirable
Causing deepening of bite
Screw - lingually or bucally so that the
head stands out at the crown margin
line of force is directed more occlusally with an
enhanced horizontal vector

Extrusion of impacted
canines
 Kilroy springs and superelastic overlay archwires –
requires levelling and aligning beforehand
 Minscrews can be used, without relying on the rest of
the teeth for anchorage
 Palatally or buccally

Molar intrusion
 Difficult to place b/w the narrow roots of the
first and second molars
 Need of more than 1 screw – high intrusion
forces
 CI in open bite cases where bilateral intrusion
of posterior segments is required

Molar distalization
 Routine distalization devices cause considerable
anterior anchorage loss
 Ideal site for skeletal anchorage – palate – requires
surgical procedure for placement
 MAS + distal jet

 Minscrews are inserted mesial to the activation
locks after the distal jet appliance is activated

 After distalization further compression of the
distal jet coil moves it further away from the
miniscrew
 Light cure composite - b/w screw head and lock

 After molar distalization – minscrew placed
mesial to the molar
MAS + distal jet – CI in mixed dentition

Molar mesialization
 Often required to close extraction
spaces
 Full sized wire - prevent tipping of
molar into extraction space
 Only 2-3 mm of molar movement
should be attempted

Intermaxillary anchorage
 forces with class II elastics and anterior repositioning
appliances – bite deepening and excessive proclination
of lower incisors
 Miniscrews - in b/w I M & II M or in b/w II PM and I M
 When class III elastics are used – b/w lower canines & I
PM

Upper III molar alignment
 Palatal minscrew + sectional fixed wire

Discussion
 Used widely in Asia and Europe
 Placement preferably by the orthodontist
requires careful planning for force
vectors, anchorage type and type of tooth
movement
relocation may be needed sometimes
 Histologic studies – biocompatible – incomplete
osseointegration

Discussion
 Influence of differences in size, shape (conical or
cylindrical), head design, pilot drilling , and physical
properties – unknown
 Reduction in screw size - mechanical resistance
 MAS resist forces much greater than those applied in
orthodontic treatment

Conclusion
More research needed - article clearly demonstrates the
versatility and technical advantage
Skeletal anchorage using MAS provides treatment
alternatives in challenging cases

Advantages of MAS over
other anchorage forms
1. Optimal use of traction forces, regardless of
the number of positions of the teeth
2. Applicability at any stage of development,
including interceptive therapy
3. Shorter treatment time, with no need to
prepare dental anchorage
4. Independence of patient cooperation
5. Patient comfort
6. Low cost

complications
1. Damage to the anatomic structures such as
blood vessels, nerves and roots
2. Loss of screw during placement,loading and
removal
3. Breakage of screw during insertion and
removal
4. Inflammation around the implant sites
Authors’ experience
loss of 3 screws during loading

Advantages over other
invasive osseointegrated
systems
1. Increased selection of insertion sites
2. Ease of insertion and removal
3. Ability to withstand immediate loading
4. Applicability in growing patients
5. Low cost

clinical application of the miniscrew anchorage system. jco2005

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