Awatif, Fatin, Huda, Diyana, Fatimah, Fadhila, Aimi

• The six keys to normal occlusion, serve as a goal

•Can be used to evaluate why good class I occlusion failed to be achieved at the end of treatment

• They are:–Correct molar relationship

–Correct crown angulation

–Correct crown inclination

–No rotations

–No spaces

–Flat occlusal plane

*The MB cusp of upper first molar occludes with the groove between the MB and middle buccal cusp of lower first molar

*DB cusp of upper first molar contacts the MB cusp of lower second molar

• All tooth crowns are angulated mesially

*Incisors are inclined towards the buccal or labial surface

*Buccal segment teeth are inclined lingually

•None of the teeth should be rotated to achieve normal occlusion•Rotated molars and

premolars occupy more space•Rotated incisors occupy less

space•Rotated canines adversely

affect aesthetics and may lead to occlusal interferences

*If there is no anomalies in the

shape of the teeth or

intermaxillary discrepancies in

the mesiodistal tooth size, the

contact points should be next

to each other in normal

occlusion

*The mandibular curve of spee

should not be deeper than 1.5 mm

*Anterior-posterior

*Vertical

*Transverse

1. Patient has to be postured carefully with the head in a

neutral horizontal position (Frankfort Plane horizontal

to the floor).

2. Sit the patient upright in the dental chair and ask

them to occlude gently on their posterior teeth.

3. Look at the patient in profile and identify the most

concave points on the soft tissue profile of the upper

and lower lips.

*Class I: mandible lies 2-3 mm posterior to maxilla. (straight profile)

*Class II: mandible is retrusive to the maxilla. (convex profile)

*Class III: maxilla is retrusive to the mandible. (concave profile)

• The most anterior part of the maxilla and mandible can be palpated in the midline through the base of the lips.

*Determine the position of

jaw relative to the cranial

base.

*Vertical imaginary line:

through soft tissue nasion in

the neutral head position.

*Zero meridian: represent the

anterior limit of the cranial

base.

*Assess by soft tissue A point

and B point

• Class I: A point lie 2-3 mm ahead and B point 0-2 mm behind zero meridian

• Class II: B point lie more than 2mm behind zero meridian

• Class III: B point lie ahead than zero meridian

*Different way to assess vertical skeletal pattern

*Lower anterior face height (LAFH)

*Frankfort mandibular plane angle (FMPA)

*Is used to assess vertical dimension

*Ratio of the LAFH to the total face height gives an indication if the LAFH is within normal limits

*Facial proportion (LAFH %)

= MxPl to Me x 100

MxPl to Me + MxPl to N

= 55% ± 2%

*The face can be split into

thirds.

*LAFH (subnasale-menton)

should be approximately

equal to middle face

height (glabella-

subnasale)

*It measures the relationship between LAFH and posterior face height

• Normal: mandibular and frankfort lines intersect in occipital region

• Increased:anterior to occipital region

• Reduced:posterior to occipital region

*2 components that should be assessed are :

*Facial symmetry

*Arch width

•Assessed by constructing a facial midline between soft tissue nasion and middle part of the upper lip at vermillion border

•Chin should be coincident with this line

• If there is assymetry, check for compensatory cant in max.occ plane

• Lateral mandibular displacement can produce facial asymmetry

*If maxilla is narrow, it will cause crossbite at the buccal segment if there is inadequate dentoalveolar compensation

*Transverse max.discrepancy may exist due to incorrect AP positioning of max/mand.

*Orthodontics at glance

*An introduction to Orthodontics

*Orthodontics. Part 2: Patient assessment and examination I; British Dental Journal 2003; 195:489–493