Cephs and Occlusion Flashcards
How does a lateral ceph aid in the dx of a malocclusion?
Skeletal relationship
dental to skeletal relationship
Denture to denture relationship
Soft tissue relationship
SNA: definition and norm?
Position of maxillary apical base (norm 82 deg)
SNB: definition and norm?
Position of mandibular apical base (norm 80 deg)
ANB: definition and norm?
Anterior-posterior position of bases (norm 2 deg)
SND: definition and norm?
Position of mandible: norm 76
GoGn-SN: a measure of what? definition? norm?
Line between gonian-gnathion
A measure of growth
Mandipular plane relates to the facial pattern
norm 32 degre
Occlusal Plane - SN
Similar to mandibular plane
Measure of growth
norm of 14
SNA : what indicates pro or retrognatism? (which arch)?
Maxillary prognatism is greater than 82
Maxillary retrognathism is less than 82
SNB: what indicates pro or retrognatism? (which arch)?
Mandibular prognathism: greater than 80
mandibular retrognathism: less than 80
What are two measures of hyper or hypodivergent?
GoGn-SN (greater than 32-hyperdivergent) Occlusal Plane (greater than 14 hyperdivergent)
Soft tissue analysis: Nasolabial angle (formed by, normal?) Lip Position (formed by, normal?)
Nasolabial angle: base of the nose to the upper lip
norm 100-110 degrees. If too small, maxilla/max incisors are too forward.
Lip position: Tip of the nose to soft tissue pognonion, the lower lip should be about 2 mm behind the E line, maxillarly lip should be on it.
Facial growth patterns: describe the direction over time, the pattern, and correlation with somatic growth
The face grows downward and forward.
- facial form and pattern tends to maintain
- Differential growth of different parts of the face. Face tends to ‘flatten’ over time.
How does facial/jaw growth correlate to the body growth or growth spurt?
Facial growth generally corresponds to somatic growth, the jaw does not really have a “growth spurt” in 75% of people.
- The correlation between somatic spurt w/jaw growth is only 25% therefore, treatment initation should be dictated by severity not growth spurt
Brachyfacial: describe, growth tendency, treatment reasoning? Headgear choice?
Hypodivergent/Short - Excessive condlyar growth tendency - flat mandibular plan and deep bite Counter clockwise growth rotation - deep bite typically favors non-extraction, encouraging posterior extrusive force and anterior intrustion forces - cervical pull headgear
Dolichofacial: describe, common clinical findings, alternate name, treatment favors? headgear choice?
Hyperdivergent
- Open bite sensitivity, typically favors extraction therapy avioding posterior extrusion
- Common clinical findings: gummy smile, open bite, lip incompetence, steep mandibular plane
- high pull headgear- intrudes posterior teeth
Considerations when determinging the timing of treatment
- nature and etiology of malocclusion
- Severeity of skeletal discrepancy
- Presence of functional shift
- Stage of dental development
Extreme growth patterns are difficult to predict, while more normal cases are easier. T/F
False: extreme growth patterns are easier to predict
Predentate infants:
gum pad ‘molar’ relationship?
Describe the VDO
Infant profile?
Gum pad relationship reflects a normal maxillary/mandibular relationship
- There is a lack of alveolar development therefore there is a decreased vertical dimension and a shallow palatal vault
- Retrognatic profile is normal in the infant
What are the primary molar relationships from most to least common and percents
Mesial step 60%
Flush terminal plane 30%
Distal step 10%
Flush terminal plane, what 3 factors are needed in order to become class 1 relationship?
- Mesial growth of mandible
- Early mesial shift closure of generalized posterior spacing with eruption of 1st permanent molars
- Late mesial shift- mesial drift of mandibular 1st permanent molars into leeway space
Distal step? What percentage of children have this relationship and what percent develop into class I, II or III?
23% have distal step, 100% of those with distal step end up with a class II relationship
Flush Terminal plane: What percentage of children have this relationship and what percent develop into class I, II or III?
30% of children have Flush terminal plane, of those 56% become class I while 44% become class II.
What percentage of children develop class I, II, III molar relationships?
Class I : 60%
Class II: 35%
Class III: 5%
Which primary molar relationship has the greatest probability of becoming a class I molar relationship?
Mesial step
What is the best predictor of the sagittal relationship in the permanent dentition? What does it predict?
The best predictor of the molar relationship in the permanent dentition is the primary canine relationship.
- Mesial step- > class 1
- Distal step -> Class 2
- Excessive Mesial step -> class 3
How does overbite change over time? How is overbite as a predictive tool?
At age 3 there is a lot of variability and a wide range of overbites, as children get older there is less variability. Therefore overbite is not a good predictor of what a child will have when they are older.
Primary Spacing: describe where
- Primate spacing: maxilla distal to the laterals, in the mandible distal to the canines.
- Generalized spacing
When is mandibular arch length the greatest?
Age 4
If you describe distal to 2nd primary molar to distal of 2nd primary molar (w/generalized, primate, and leeway spaces) all these spaces decrease
Describe the ideal primary dentition occlusion
Mesial step molars and canines
Genearlized and primate spacing (equal to ~6mm)
2mm OB (30%) and 2mm OJ
what percent of children with no spacing in the primary dentition display crowding in the permanent dentition? And those with crowding?
66%
100%
Normal/Ideal molar relationship in the mixed dentition?
Class I
Class II : end-on with a late mesial shift
Describe the Late Mesial shift. How much of the shift can occur in the mandible? and in the maxilla? Who has more?
- A consequence of the size difference between the primary molars and the premolars
- It occurs when the 2nd primary molar exfoliates
- The molar utilizes the E space and erupts mesially
- The mandible has approx 1.4mm, maxilla .9mm
Describe Incisor Liability. Who’s theory is this?
Moyne
- Permanent incisors larger than primary teeth and the transition between the different sizes is made possible by: 1. interdental spacing of primary teeth
2. increase in intercanine arch width (as the perm incisors erupt more labially) and
3. anteiror placeemnt of permanent incisors (increases arch perimeter).
Describe the factors affecting the incisor liability
- Size of the teeth (permanent and primary tooth size are not well correlated, can have big baby teeth and small perm)
- Spacing of the primary dentition
- Intercanine arch width growth
- Archlength increase due to more labial positioning of perm incisors
- Size differential between primary molars and premolars (leeway space)
In the mixed dentition is lower incisor crowding normal?
Yes, a small amount of crowding is normal. On average there is 1.6mm less space available than is necessary for permanent mandibular incisors for ideal alignment. Self correction occurs due to tongue pressure and distal drift of primary canines into the leeway space. Moorrees growth studies
What is the normal incisal relationship in the mixed dentition?
- Overjet: ideal 0mm (range 0-3mm)
- Overbite: ideal 1mm (range 1-3mm)
- Spacing of maxillary incisors normal during “ugly duckling” stage due to position of permanent maxillary canines
- Transitional open bite with loss of primary incisors
What is the physiology behind the “ugly duckling” stage?
The maxillary canine angulates mesially while erupting, putting pressure on the root of the lateral which tips it distally, making the “ugly duckling” appearance
Summarize the changes in arch length: intercanine width, intermolar width, and overall arch length change during the mixed dentition for the maxilla and the mandible (posterior and anterior):
Maxilla: slight increase in archlength due to labial position of incisors and increased intercanine width
Mandible: Loss of posterior archlength due to space closure (generalized and “E” space) and therefore loss of intermolar width
- Slight increase in anterior archlength due to labial position of incisors and increased intercanine width
OVERALL: maxilla-unchanged, mandible- DECREASE
