Exam 2 Flashcards
Frankfort Plane
- Horizontal Reference Line: Normal
- Upper rim of external auditory meatus (Porion) –> Inferior border of orbital rim (Orbitale)
What are 2 problems with the Frankfort plane?
- Hard to locate porion on radiograph
machine porion:
* ear piece helps find porion.
* Can be off from ideal anatomic porion
SN Plane=Solution
* alternative horizontal reference line
* easily detected & reliable - Frankfort plane is not always horizontal for ppl physiologically
* ppl hold their heads at different angles (up to 10 degrees)
* Physiological head position=NHP
* NHP is preferred over anatomical horizontal plane (FP)
* reproducible w/in 1-2 degrees (FP more reproducible)
SN Plane
- Alternative horizontal reference line
- Sella Turcica (S)–> Jxn b/w Nasal & Frontal Bones (N)
- avg orientation: 6-7 degrees up & anterior to FP
- Most commonly used bc done growing at 7 y.o.
- Increases reliabilility and reproducibility
- Decreases accuracy
Always note the inclination of SN to the true horizontal plane or FP if true HP is not known
* If SN differs from 6 degrees
* any. measurement based on SN should be correct by this amount
Steiner Analysis
- 1st modern cephalometric anylsis
* Displayed measurements that emphasize individual measurements & interrelationship in a pattern
* Guides for using cephalometric measurements in tx planning -
ANB Angle=SNA - SNB
* Magnitude of skeletal Jaw discrepancy that must be overcome by compensations during tx - Measured the angular & mm relationship of:
upper incisor to NA Line
* position of max teeth to maxilla
Lower incisor & Chin to NB Line
* position of lower incisors to mandible
Established the relative protrusion of the dentition
Chin Prominence:
* mm distance from NB line to Pogonion
Holdaway Ratio
Ratio of the chin (pogonion) to mandibular incisors
Steiners Analysis: Criticism
ANB angle is influence by 2 factors other than AP differences in Jaw Position
1. Vertical Height of the Face
* Increased Vertical Distance from Nasion & Pts A/B= Decreased ANB angle
- Abnormal AP position of Nasion affects angle size
* As SNA & SNB becomes larger & Jaws more protrusive= Larger ANB angle
ANB Angle
ANB angle=SNA - SNB
* magnitude of Skeletal Jaw discrepancy that must be overcome/compensated by tx
Gives AP Measurements: Class 1, 2, or 3 occlusion:
* Class 2 Skeletal Relationship: (+)
* Class 3 Skeletal Relationship: (-)
SNA & SNB Angles
relationship of maxilla & mandible to the cranial base
* Lower SNA(<90)= Maxillary Deficiency
Sassouni Analysis
1st to emphasize:
* Vertical and horizontal relationships
* interaction b/w vertical and horizontal relationships
Well proportioned face:
* Horizontal planes tend to converge toward a single point
Vertical Proportions of face=Inclination of horizontal planes to each other
Skeletal open bite vs Skeletal Deep BIte
Skeletal Open Bite vs Skeletal Deep Bite
Skeletal Open Bite:
* Aka Open Bite Malocclusion
* horizontal planes intersect close to the face & diverge quickly as they go anterior
* Facial Proportions are:
* Long Anterior
* Short Posterior
Skeletal Deep Bite:
* Aka anterior deep bite
* horizontal planes are nearly parallel & converge behind the face & diverge slowly as they go anterior
Harvolds Analysis
Severity or degre of Jaw disharmony
* Developed standard the “Unit Length” of maxilla & mandible
Maxillary Unit Length:
* posteior border of the mandibular condyle to Anterior Nasal Spine (3mm width)
Mandibular Unit Length
* Posterior border of mandibular condyle to anterior point of the chin (Gnathion)
Size Discrepancy b/w the Jaws= Maxillary Unit Length - Mandibular Unit Length
* Tooth position has no influence
Lower Face Height= Upper ANS (3mm thick) to Menton
Wits Analysis
Severity or degree of jaw discrepancy
* overcome the limitations of ANB
* influenced by teeth-horizontally & Vertically (opposite of Harvold)
* Use functional occlusal plane
Based on the projection of pts A & B to the occlusal plane
* measured the linear difference b/w points
Normal AP position of the Jaw:
* Pt A & B Projections will intersect the occlusal plane at nearly the same point
* Magnitude=A1-AB
Class 2 Discrepancy: (+)
* Pt A is in front of pt B
* Magnitude: how many mm b/w A & B
Class 3 Discrepancy: (-)
* Pt B is in front of pt A
Wits Analysis: Limitations
- Fails to distinguish Skeletal From dental Discrepancies
- Does NOT specify which jaw is at fault if there is a Skeletal Problem
McNamara Analysis
More precise Jaw & tooth positions
* combines elements of previous approaches (Ricketts & Harvold) + original measurements
Reference Lines:
* Anatomic Frankfort Plane
* Basion-Nasion Line
1st Step: Eval AP Position of the Maxilla & Mandible ro the Nasion Perpendicular
* Vertical line extending down from Nasion, perpendicular to the FP
* Maxilla= on or slightly ahead of perpendicular
* Mandible: Slightly behind
2nd Step: Compare Maxillary & Mandibular Lengths via Harvolds Apprach
* Maxillary Length
* Mandibular Length
* Lower Face Height
Measurements:
Maxillary Protrusion:
* nasion perpendicular to Pt A
* Mean: 2mm
Maxillary Incisor Protrusion:
* Line parallel to Nasion Perpendicular to Labial surface of incisor
* Mean: 4 mm
McNamara Anlysis: Strengths
- Relates the Jaws to each other via Nasion Perpendicular
* Difference in AP positions of the Jaws to true vertical line - Uses Normal Data based on Bolton Sample
* Available in template form
* highly compatible w/prelim analysis by comparison w/bolton templates
Angles Classification of Malocclusion applied to what 4 distinct characteristics?
- Classification of malocclusion
- Molar relationship
- Skeletal Jaw Relationship
- Growth Pattern
How did the 5 Characteristic Classification System overcome Angle’s major weaknesses?
Overcame Angles major weaknesses by:
* eval of crowding & asymmetry w/in dental arches (included incisor protrusion)
* Info about skeletal Jaw Proportions at the appropriate time; relationships in each plane of space
* relationship b/w protrusion & crowding
* Transverse, vertical, & AP planes of space
5 Characteristic Classification System:
Draw Ven Diagram
Ackerman & Proffit: 1960
5 major characteristics of Malocclusion:
1. Dentofacial Appearance
Frontal & Oblique Facial Proportions
Symmetry
Anterior Tooth Display
Orientation of the esthetic line of occlusion
Profile
- Alignment
Crowding or spacing
Arch Form
Symmetry
Orientation of the Functional LIne of occlusion - AnteroPosterior
Angle Classification: is it skeletal or dental? - Transverse
Crossbites: is it skeletal or dental? - Vertical
Bite Depth: is it skeletal or dental
What were the 2 additions to the 5 characteristics classification system?
- Orientation of the esthetic line of the dentition
- Supplemnt the traditional 3D description of facial and dental relationships w/rotational characteristics around each plane of space (Roll, Pitch, Yaw)
Esthetic Line of the Dentition
Follows the facial edges of the maxillary anterior & posterior teeth
* along incisal edges & cusp tips
* Transverse orientation
Incorporate tooth-lip relationships into diagnostic eval of tooth positions
Pitch
(AP); Y axis
1. Excessive Upward Or downward rotation of the dentition to lips/cheeks
2. Vertical relationship of the teeth to the lips & cheeks
* Downward or upward translation w/no pitch deviation; rare-during growth or treatment
* Pitch upward or downward anteriorly
* Pitch upward or downward posteriorly
- Pitch of the dentition to facial soft tissues evaluated during clinical exam
Compare:
* esthetic line of dentition
* ntercommisure line
Downward pitch of anterior teeth
* anterior deep bite
Yaw
(Transverse): Z axis
Characterize Transverse asymmetries
1. Rotation of the Jaw or Dentition to one side or the other
Yaw of the:
* Dentition relative to the jaw
* mandible/maxilla that takes the dentition w/it
Causes:
* Skeletal or Dental midline deviations
* Unilateral class 2 or 3 molar relationships
Extreme Yaw Causes:
* asymmetric Posterior crossbite
Roll
(Vertical): X-axis
Up or Down Roation on one side or the other
* The vertical Position of the teeth when its different on R & L Sides
Compare the esthetic line to:
1. Facial Soft Tissues
* Reference: Intercommisure Line
* cant see on dental casts or photograph w/fox plane
* See in frontal or oblique views where Lips are relaxed or on smile (Clearer
2. Facial Skeleton
* reference: interoccular line
* Fox plane–>** occlusal plane cant**
Posterior Crossbite
Described in terms of upper molar position
* specifies which teeth (max or mandibular) are displaced from normal position
Due to Skeletal or Dental components:
* Dental: Adequate palatal width, narrow dental arch
* Skeletal: inadequate palatal width
Width of Maxillary skeletal base=width of palatal vault on casts
1. Dental Problem:
* IF wide palatal vault width–> Dentoalveolar processes lean inward
* caused by arch distortion
2. Skeletal Problem
* If Narrow palatal vault width–> maxillary teeth lean outward
* caused by narrow maxilla width
Teeth can compensate for transverse problems:
* Tip facially or lingually if the skeletal base is narrow or wide
Long Face syndrome
skeletal open bite (High Mandibular-Palatal Plane ANgle)
* anterior bite malocculsion:
* excessive eruption of posterior teeth
* downward rotaiton of mandible/maxilla
* Normal (or even excessive) eruption of anterior teeth
* HOrizontal planes intersect near face & Diverge quickly-anterior
* Long Anterior Face
* Short Posteiror FACE
Short Face Syndrome
Skeletal Deep Bite (Low Mandibular-Palatal Plane angle
* Anterior Deep Bite
* normal eruption of incisor teeth (anterior)
* Roation of both jaws in the opposite direction
* insufficient eruption of posteiro teeth
Horizontal planes are nearly parallel
* converge before the face
* Diverge slowly-anterior
Mandibular-palatal angle
palatal & mandibular plane angle
* Low=Skeletal Deep Bite
* High=Skeletal open bite
Counterpart Analysis
Emphasized that changes in proportions in one part of the head/face can either:
* Increase jaw discrepancy
* compensate so the jaw fits correctly
If Long Anterior Face height: Facial balance and proportions are preserved if:
* Large Posterior Face Height & Mandibular ramus height
Short posterior face height can lead to Skeletal open bite
* even if Anterior Face height=Normal
* Disturbed proportions
Long cranial base:
* Normal Maxillary & Mandibular lengths
If Long Anterior Face height, How would facial balance and proportions be preserved?
Long Anterior Face Height
* Large Posterior Face Height
* Large Mandibular Ramus Height
IF SHORT POSTERIOR FACE HEIGHT=Skeletal Open bite
-even if NOrmal Anterior Face height
If the Cranial Base is long, and Maxillary and mandibular lengths are normal: Compensatory vs Not
No Compensation:
Maxilla will be moved forward relative to the mandible
* Result: maxillary protrusion
Compensation:
Short maxilla
What relationships does cephalometric analysis aid us in clearly evaluating?
Underlying cause of malocclusion
Look at
* individual measurements compared to the norm
* pattern of relationships (Soft tissue relationships)
What is the major goal of cephalometric analysis?
- Establish the relationship of the structural components of the face in both the AP and vertical plane of space
What are the steps in cephalometric analysis?
1 Draw Sassouni horizontal planes & examine their interrelationships
* are vertical planes proportional
* SN-MP Angle
2 Observe AP relationships with SNA and SNB angles
* McNamara Analysis
* Class I, II, III occlusion
3 Move True vertical lines to A & B to ID Protrusion (<4mm) or retrusion
4 Use Counter part analysis to verify measurements
* Face height
* Maxilla & Mandibular Unit Lengths
Template Analysis:
Arch Form
HOw the teeth:
* sit in the arch
* Relationship to the arch
Can have:
* crowding + malalignment= Normal Jaw position via cephalometric analysis
* perfect arch form–> Bad relationship to opposing arch due to skeletal defect (underdeveloped maxilla)
Dental midline deviations can be due to:
- reflection of displaced incisors bc of crowding
- Yaw discrepancy-whole dental arch is rotated to one side
