superimposition of cephalometric radiographs
-resorption at the anterior border of the ramus and apposition at the posterior border of the ramus -apposition of the condylar head
-how does the mandible grow in AP direction? -what causes primary growth of the mandible vertically?
-more apposition at orbital floor -3:2 ratio
-is there more apposition at orbital floor or more resorption at the nasal floor? -what is the ratio?
-stable portions to quantify RELATIVE changes within the face -when it is used to demonstrate the directional expression of growth of the entire face
-there is no problem with superimposing what? -when does a problem with superimposition arise?
-apposition = upward and forward -resorption -apposition = downward and backward
-what does the orbital floor undergo? -what does the floor of the nasal cavity undergo? -what does the key ridge undergo?
-uncertainty in the visual identification -lack of resolution = sharpness, movement, scattered radiation
-what is random error? -what can cause random error?
-bias in the recording and measuring system -predictable differences from true value
-what is systematic error? -what does it produce?
-S-Na line -both the reference points sella and nasion lie OUTSIDE the anterior cranial base
-what is the most frequently used reference line to global superimpose tracing? -what is important to note about this line?
DO NOT change over time
in order the superimpose lateral cephalograms, you need to be able to identify certain structures that what?
superimpositional error
inaccuracy in the act of superimposition/reproducibility
maxillary superimposition
permits assessment of movement of maxillary teeth (dentoalveolar) in relation to the maxilla
mandibular superimposition
permits assessments of teeth movement (dentoalveolar changes) in relation to the mandible
observer error
tracing, measuring, superimposing
-superimpose on landmarks LEAST affected by growth -use cephalograms made from the same machine
what are 2 factors to take into consideration when superimposing?
-systematic error -random error -modeling in the area of registration -poor film quality -observer error -individual film method -superimposition method
what are some cephalometric errors?
POSTERIOR surface of sellae - changes over time
what are some landmarks that would NOT be good for a ceph? why?
-anterior-inferior border of the chin below pogonion -inferior border of the internal symphysis -inferior alveolar canal
what are the primary reference structures of a mandibular superimposition?
-pretreatment = black -progress = blue -end treatment = red -retention = green
what are the tracing color codes for a superimposition?
-posterior portion of ramus -condylar head
what areas of the mandible undergo apposition?
-research/clinical results -growth changes -ortho treatment effect
what do we get out of superimposition?
BOTH growth and treatment changes TOGETHER
what is a global superimposition trying to measure?
ceph tracing errors: -errors in projective displacement = same plane or between different planes -errors in landmark identification, tracing errors
what is individual film method error?
MAXILLA AND MANDIBLE: -tooth movement ONLY at the periodontium (NOT MEASURING
what is measured in a REGIONAL superimposition?
differentiating dentofacial changes caused by orthodontic treatment from those indiced by growth
what is nearly impossible to measure with superimpositions?
anterior surface of zygomatic process (key ridge)
what is the primary reference structure in a maxillary superimposition?
-anterior surface of sellae -lamina cribrosa -internal surface of frontal bone
what landmarks DO NOT change over time?
structures that do not change over time
what structures are used to overlay the progress/final lateral cephalogram over the initial one?
