Download Contemporary fixed appliances

Contemporary fixed appliances
• Dr. MOUHANNAD KAZZAZ
MSc, Dip Ortho ,CES
The evolution of fixed appliances
I- The standard edgewise appliance
•
Typical finishing archwire incorporating
individual tooth bends for an edgewise appliance
II - Light wire appliances
III - The preadjusted edgewise appliance
Bracket prescriptions
- Lawrence Andrews (1972) described the original bracket
prescriptions for his preadjusted appliance based upon data
he obtained measuring tooth positions from untreated ideal
occlusions(1972) .
- Ronald Roth (1976) recommended a single series based on the
Andrews extraction prescription. This prescription had extra
torque in the upper labial segment because the edgewise slot
does not express the full torque value of the bracket, particularly
as the upper labial segment is retracted during space closure.
Roth also placed a greater emphasis on functional occlusion and
gave the canines greater tip to facilitate cuspal guidance. There
was also greater torque in the maxillary molar region to prevent
dropping of the palatal cusps and eliminate non-working side
interferences
• More recently, Richard McLaughlin, John Bennett and
Hugo Trevisi have developed the MBT prescription,
which has increased torque in the upper labial segment
and lingual crown torque in the lower labial segment.
This was designed to minimize proclination of the lower
incisors during treatment. The MBT prescription also
has reduced tip, most notably in the upper arch, to
reduce anchorage requirements. In addition, reduced
torque in the lower molar region helps to prevent
lingual rolling of lower molars as they are moved along
the archwire (McLaughlin & Bennett, 1990).
IV- Lingual appliances
Components of fixed appliances
• Fixed orthodontic appliances consist of three
main components:
–•
Brackets and molar tubes
–•
Archwires
–•
Auxiliaries, which will vary between
appliance types, but include bracket ligatures,
pins, elastics, uprighting and torquing springs,
ligature wires and fixed devices for anchorage
reinforcement or arch expansion.
Edgewise brackets
Edgewise brackets, with the original dimensions being
0.022 inches vertically and 0.028 inches
0.018 inches vertically and 0.025 inches horizontally
.. Edgewise brackets are fabricated
with a single archwire channel and two tie-wings
. or more commonly as Siamese or twin brackets
Aesthetic edgewise brackets
• higher bracket breakage.
• There is also greater friction
• Excessively high bond strengths, increased the risk of enamel
damage on bracket removal.
• One final problem is the fact that ceramics are harder than
enamel. This can result in significant enamel wear if brackets
are placed in a position of occlusal contact with the natural
dentition, commonly the lower incisors in cases with an
increased overbite.
Light wire appliance brackets
Begg light wire bracket.
Tip-Edge® bracket.
As the tooth tips, the bracket slot dimension
increases from 0.022 inches to 0.028.
Self-ligating brackets
Archwires
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Stainless steel
Cobalt chromium
Beta titanium
Nickel titanium
Auxiliaries
Elastomeric and metallic auxiliaries used with fixed appliances.
Elastomerics include (A) ormolasts or modules; (B) elastics; (C) powerchain.
Metallic auxiliaries include (D) long ligatures; (E) open and closed coil; (F) short
ligatures; (G) Kobyashi ligatures.
Placement and manipulation of fixed
appliances
– Molar banding
Bracket placement
TWEED BRACKET PLACEMENT
ANDREWS BRACKET PLACEMENT
Gingival Concerns
• 1. Partially erupted teeth.
• 2. Gingival inflammation
• 3. Teeth with palatally or lingually
displaced roots
• 4. Teeth with facially displaced
Incisal or Occlusal Concerns
• 1. Incisal or occlusal crown fractures or tooth wear.
• 2. Crowns with long tapered buccal cusps.
Proportionally long or short
clinical crowns
• 1. Proportionally long clinical crowns.
• 2. Proportionally short clinical crowns.