six keys to optimal occlusion /certified fixed orthodontic courses by Indian dental academy
Six keys to Optimal Occlusion
INDIAN DENTAL ACADEMY
Leader in continuing dental education
Classic guideline in ortho diagnosis – ‘Sine qua non’ of proper occlusion –
“cusp of upper first perm molar must occlude in the groove
btw the mesial & middle buccal cusps of the lower first perm
Angle did not contend that this factor alone enough
Acceptable molar relationships with obvious inadequacies seen
120 casts of Naturally occuring optimal occlusions studied from 1960 –
64 to ascertain which characteristics would be found consistently in all
Six keys – optimal = most desirable or satisfactory –
Interdependent elements of the structural system of
Serve as base for evaluating occlusion
Can be used as treatment objectives in most patients
Make it possible to assess the occlusion form the facial
& occlusal sites without using measuring devices or
Key I : Molar Relationship
IV : Absence of Rotations
V : Tight Contacts
VI : Occlusal Plane
Flat to slight curve of Spee
Andrew’s Planemid transverse plane of every crown
Clinical crown – visible intraorally/on cast
anatomic crown – 1.8mm (Orban)
FACC – LACC in earlier writings
all teeth except molars – most prominent portion of the
central lobe on each crown’s facial surface
for molars – buccal groove
FA point- point on the FACC that
separates the gingival half of clinical
crown from the occusal half
Facial plane – tangent to FA point
eqidistant from gingival and occlusal
Embrasure line –at level of mid
transverse plane – connecting most
facial portions of the contact areas of
Andrews classified brackets into three types1. Non programmed appliance-a set of brackets designed the same
for all tooth types ,relying totally on wire bending.
2. Partly programmed appliance- a set of brackets designed with
some in built features ,but always require some wire bending
3. Fully programmed appliance- a set of brackets designed to
guide teeth directly to their goal positions with unbent wires. –
Straight wire Appliance.
The Straight Wire Appliance
• Slot siting featureMid Transverse plane:
Feature 1- mid transverse planes of the slot
stem and crown must be the same.
Feature 2-base of the bracket for each tooth type must have
inclination as the facial plane of the crown.
Feature 3-each bracket inclined base must be contoured
Mid sagittal plane
Feature 4- mid sagittal plane of the slot stem and crown must be
Feature 5 -the plane of the bracket base at its base point must
be identical to the facial plane of the crown at the FA point.
Feature 6 - Base should match the m-d contour of the tooth.
•Feature 7 - the vertical component should be parallel to
Mid frontal plane
• Feature 8 – all slots point must have same distance
them and the crown embrasure line.
The Straight Wire Appliance
The gingival tie wings of the post Brackets extend farther
Base are inclined .
Facial surface of the incisor and canine brackets are
designed to parallel their bases.
In mandibular brackets the tie wings are designed with
least amount occlusofacial prominence