Seminar 2: Expectations of the session Taking a Lateral Ceph

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  1. How do you turn off vectors, points, x-ray, drawing?

By checking and unchecking the boxes on the left of dentalcad.

  1. If you do NOT like your tracing and what to start over, how do you get rid of the existing project?

By clicking the small x on the upper right hand corner, then cancel. If you click the big red X, above the small x, the program will close.

If you have already saved the project, then open the ceph, model, or VTO and click the big red X on the upper left icon row.

  1. Can you [custom] label a project with anything you want?

No, that feature was NOT included in the programming. The needed double database would have made some computers not work well.

  1. How is labeling distinguished between non-growing and growing ceph projects?

Use the ending “model” for non-growing projects, and the ending “vto” for all growing projects.
Head positioning errors

  1. How can you tell if there is ‘tilting the head to the side’ positioning errors on a lateral ceph x-ray?

You see 2 mandibles on the inferior border, molars stacked on top of each other, and multiple porions, stacked vertically.

  1. What are the double structures you need to be concerned with on ‘tilting the head to the side’ positioning error?

Inferior of the mandible, porion, orbitale, molars.

  1. Which double structure do you trace in the ‘tilting the head to the side’ positioning error x-ray?

Most superior orbitale (you may only see one radioleucency), superior porion, superior molars, superior mandible.

  1. How can you tell if there are “looking to the side” positioning errors on a lateral ceph x-ray?

The first indication is a double mandible on the posterior ramus. Then you may see two posterior eye sockets, molars jumbled anterior-posterior, 2 porions positioned next to each other on the horizontal.

  1. What measurements are effected by ‘looking to the side’ positioning errors?

The measurements on the ceph are not really effected, but overlaying successive cephs is a challenge with trying to trace the same molar.

  1. Are there any problems with the ‘looking to the side’ positioning error? Does the ceph need to be retaken?

Superimpositions (overlays) are the most difficult. The ceph does NOT need to be retaken.
Lateral Ceph Measurements

  1. Which measurements define skeletal open, average, or closed bite?

FMA (Frankfurt mandibular angle), the angle between the mandibular plane (menton and gonion) and Frankfurt horizontal (porion to orbitale)

  1. What do you do if the two measurements for skeletal open, average, or closed do not agree when clicking the ‘retrieve measurements from dentalcad’ button in the blue cephalometrics tab?

First check to be sure the points have been placed correctly (Porion, Orbitale, menton, gonion, PNS, ANS), Then look at the picture and ask if the jaws are divergent, average, or closed.

  1. What is the different treatment response when extracting bicuspids in a skeletal open versus average versus closed bite case? What is moving to make this different response?

Bicuspid extraction space closes quickly, and sometimes spontaneously in skeletal open bite cases. The molars are drifting mesial. [TPA is often used to engage the buccal cortical bone to reduce drifting]. In skeletal closed bite cases, the molars will not drift mesial, and the time to close the extraction space will be longer (1 year?) due to the associated tight muscles. In skeletal average cases, the extraction space will close in 6-8months, without spontaneous mesial molar difting.

  1. What is the significance of the ANB measurement?

ANB defines the relation of the upper jaw (maxilla) versus the lower jaw (mandible). Skeletal class II, ANB>4.5 degrees, means either the upper jaw is too far forward or the lower jaw is too far back or a combination. Skeletal class III, ANB<0, indicates either the upper jaw is retruded or the lower jaw is protruded. Skeletal class I, ANB 2-4.5 indicates jaws that are well related.

  1. What is the significance of the Wits measurement in class III cases?

The larger the [negative] wits, the more skeletal resistance to tooth movement can be expected, until either lower lingual corticotomy or orthognathic surgery is needed for a successful treatment.

  1. What is the importance of the interincisal angle when making the extraction vs. non-extraction treatment decision?

A balanced looking interincisal angle will be in the neighborhood of 125 degrees plus/minus 10 degrees. If the interincisal angle gets less than 115 degrees (too acute), then the incisors look “protrusive” as seen in bimaxillary protrusive cases. If the interincisal angle is more obtuse than 135 degrees, the incisors may look too retruded.

In cases starting with obtuse interincisal angles, we often treat these cases non extraction, advancing the crowns to make a more pleasing incisor inclination. In cases starting with acute interincisal angles, we often extract bicuspids to move the incisors back, in the process making the inclination more pleasing.

  1. What is the significance of lower 1 to APo in the specialty?

In the days of Charlie Tweed and Robert “Rick” Ricketts, the specialty felt the most stable position and the most esthetic position of the incisors was when the lower incisor was near the APo line. This was changed in 1985 when Bob Little (U. Washington, Seattle) showed research that the cases were no more stable when the lower incisor was finished near the APo line than any other position, and NO cephalometric number predicted the cases that would be stable or not after retention.

  1. How can you determine if the upper incisor is protruded or not?

Look at the ‘picture’ on the ceph, asking yourself if the upper incisor is protruded. You can be assisted by reviewing the upper 1 to APo measurement and upper 1 to Nasion Perpendicular measurement.

  1. What is the difference between retruded and retroclined?

Retruded is a term that refers to an incisor being ‘back’ in the face. Retroclined is a term that describes the incisors inclination. The two terms usually work together since retruded incisors are usually retroclined, but not always.
Growth adjusted cephs:

  1. What ‘estimated’ growth numbers do you use for class I girls and boys?

Class I girls and boys? +3mm girls, +5mm boys

Class II girls and boys? +2mm Girls, +4mm boys

Class III girls and boys? +5mm girls, +8mm boys. (note: Wits should be more negative than -5)

  1. How do you make an exact copy of the lateral ceph in preparation to make a growth adjusted ceph?

With the ceph project open that you want to copy, click the icon “paste analysis in new page”

  1. What structures do you move to represent differential horizontal growth on the ceph copy?

Mandible, lingual symphysis, lower incisor, lower molar, lower profile. (note: the lower profile is best moved only part of the way forward that the lower incisor is moved, and then rotated at the most inferior point of the lower profile by dragging as you hold down the shift key.

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