Flat bed scanners of any type are needed to develop the exact one-to-one image to be measured. You do NOT need a transparency adaptor for this function, and therefore you do not need the expensive scanners. NO digital photographs, please, as the images are not 1:1 reproductions to measure.
Place a white paper on the scanner glass to reduce the size of the scan area and to make a better “contrast” on the study models. This piece of paper will also serve to make a horizontal reference for the “heal” of the study model. Orient the study models straight vertical so you do not have to rotate archwires when they are placed on the image. I would suggest you write “lower” on the right side and “upper” on the left side of the reference paper, so you can consistently orient the study models, although the program functions the same no matter which way the models are oriented. Set a standard that you work with to avoid placing upper archwires on the lower and lower points on the upper.
Put the study models face down on the glass with the incisors facing the ‘hinge’ of the scanner top. Check to be certain that the midline of the study models is facing straight “up” on the glass. I also look from the heal of the study model, under the palate to see that they are oriented properly. Definitely reference the horizontal line made by your “reference paper”, described above.
Place a piece of white paper on top of the study models to make a better background and contrast.
Scanning directly into DentalCAD
This will be the most common method to scan images into the program. Click “acquire image” in DentalCAD, and the scanner “twain drivers” should open. For the Epson 1680 scanner with the Twain Pro interface, the settings are:
8-bit gray (std)
These settings will look different on different scanners. “flatbed” may also be called “reflective”. “gray” is in the color settings section, and may also be called “b/w photo”. “96 dpi” is the resolution.
** note: the scan can be made at a higher quality (300dpi) and the filter in DentalCAD will adjust the size accordingly. But then you fill up your hard drive faster, and the file sizes are larger when sending this image by email attachment. I would suggest higher quality scans for this job, since detail is important.
Click “preview” to scan the entire scanner glass. If the study models are not properly oriented, then re-orient and click preview a second time. Identify the area you want scanned by dragging a box around the study models (hold down the left click button and move the mouse). Click scan. The image should appear in DentalCAD.
If scanning into Adobe Photoshop, after making the scan I would suggest enhancing the image by “filter-sharpen” done twice, then “file-save”. Label the model by the patient name, “double occlusal.start” and save on the computer into a file folder for that patient. When you want these images in DentalCAD, click “import” in DentalCAD, then locate the file folder and open the image. **note: there is not any reason to scan into Photoshop if you have the scanner attached to the computer with POSoft/DentalCAD, EXCEPT to place this image into the photo tab.
Starting the “tracing”
The first thing you should do is to enlarge the image for more accurate measuring. Click the “zoom in” button to enlarge the image. Next, select “model measuring” (instead of McGann ceph tracing), then select 36D (distal) point from the list. This starts the sequence. Move your cursor to the 36D point and then left click to position the point. It is best to position the most posterior points more to the lingual/palatal. No measurements or rotation determinations are made from these most posterior points, and if an archwire passes inside of these points, the calculations will not be allowed. Click F2 to move to the next point. Repeat. At any time, you can reposition any point AFTER you have positioned the current point and before clicking F2 for the next one. Continue until the end of the points. The program will then take you into the shape of the mandible, lower archwire, and upper archwire selections. At the end of this sequence, click “calculate”.
36D, B, and M points
Bicuspid points on the buccal-mesial and buccal-distal line angles
Lower points completed, noting the proper position of 3-3 points
The mesial and distal points must be placed at the WIDEST mesial and distal position, at the SAME place on the tooth mesial and distal (critical for rotation diagnosis). The most common error is to make the teeth too small. There should never be space between a mesial and distal point unless the contact point is broken or there is truly space between the teeth! Sometimes you must “extrapolate” a point wider than the visible incisal edge to account for a tapered shape of the tooth.
Extrapolate points when teeth are touching but tapered The “B” or “buccal” points are used to position the teeth onto the selected archwire shape, allowing us to determine the amount of incisor advancement by each archwire selection (assuming the cortical bone will tolerate our selection). These points are: 16B, 15B, 14B, 24B, 25B, 26B, 35B, 34B, 44B, 45B. Place these where the “bracket” would be placed, if visible.
On the lower molars, the 36B and 46B are the buccal pits of the lower first molars, where you would place a filling. This is used in the maxillary expansion calculation in IP soft calculations tab. Normal upper width is 1.5mm wider than the lower. This can be used to diagnose maxillary constriction, and the amount of expansion needed when using a Rapid Palatal Expander (RPE).
On the upper molars, 16C and 26C are the mesial-buccal “cusp” tips, also used in the maxillary expansion calculation.
Upper molar points
Lower molar points It should be noted that you may place the 36/46B points and 16/26C points on any tooth you wish, independent of the M-D molar points. So if you wish to see the transverse dimension of the upper and lower 7s in a crossbite case where you plan to replace the missing 6s, then use the M-D points for the first molars and the 36/46B+16/26C points on the 7s.
Editing points placed in the wrong location
You may notice measurements that are incorrect, or teeth that have a very strange shape. This usually means that you have point placed in the wrong position. You may make this correction by either:
Select the point from the list on the left hand side and reposition this point. The old point is erased and you place the new point. * NOT the recommended method.
Find the point by moving the mouse over the location and watching the identifier box for the point you wish. If too many structures cover the point, then move the structures (archwire, tooth, other points) to the side until you can find the point you wish to move. Left drag to move the point to the new location. The values will change as you reposition points, but it is always best to click “calculate” after changing the tracing. * RECOMMENDED METHOD
What to do with missing teeth
You cannot “skip” a tooth, so you must place the tooth somewhere. The choices you have for missing teeth are:
1. Leave the tooth out of the calculation (skip a tooth): Place the mesial and distal points “on top” of each other. This is done for the “maximum anchorage VTO” or if the case already has missing teeth, the spaces are closed, and you wish to maintain these spaces closed.
To leave the tooth out of the calculation, as with Maximum Anchorage VTO, the points 14M and 14D were placed on top of 15M.
2. Place the tooth an estimated size of the missing tooth: The program will then add this amount of tooth mass into the calculations. This would be done if you intend to add the tooth back into the arch (restorative replacement). It is OK to place the mesial-buccal-distal points directly on top of those of an adjacent tooth, and this can be helpful if the replacement tooth is the same size as the adjacent tooth (example: bicuspid being replaced).
14D and 14M points are placed on top of 15D and 15M points to make the correct size tooth, adding the missing tooth into the arch for incisor advancement calculation
Make the tooth ½ the size of the missing tooth: this is done when you plan to close the space with “moderate anchorage” (the molar moving forward ½ the space in your treatment mechanics). This is the method used for the “Moderate Anchorage VTO”.
14M and 24M points were placed in the middle of the tooth 14 to create a Moderate Anchorage VTO. The space, ½ the size of the bicuspid will be consumed by the anterior teeth as the molars always remain in the starting position.
In mixed dentition cases, if the primary tooth is present, simply click on the normal points for mesial, buccal, and distal corresponding with the permanent tooth (35D,35B,35M are placed on the lower left E). If there is no tooth, then you will have to estimate its size. The mixed dentition analysis will calculate the crowding based ONLY on the mesial distal width of the 4 incisors, the 36/46M points, and subtracting the amount of crowding on the archwire selected. So the archlength discrepancy value is of less accuracy than the mixed dentition calculation in this situation. ** Be sure to position the selected archwire slightly LABIAL to the lower incisors, unlike in the permanent dentition where the archwire is placed on the incisal edges. In the mixed dentition calculation, the teeth are aligned on the selected archwire, and the available space is measured from the most distal point of the lateral incisor (after alignment) to the mesial of the first molar.
Mixed dentition points are placed on the primary teeth for the unerupted permanent tooth. The archwire is positioned just labial to the lower incisor.
For mixed dentition data interpretation, review
Molar symmetry right vs. left upper and lower. Molars can shift during the mixed dentition transition creating asymmetry in the permanent dentition. Premature loss of E space is the most common cause of this problem, which should be corrected in the mixed dentition.
Maxillary vs. Mandibular molar widths. As in the permanent dentition, maxillary width should be approximately 1.5mm greater than mandibular molar width. Maxillary constriction should be corrected in the mixed dentition.
Total lower crowding or space. This prediction, based on the size of the incisors and available space from 2D-6M AFTER alignment of the incisors on the selected archwire, gives reasoning for the use of lower lingual arch, lower utility arch, lower advancing arch, or no treatment for lower archlength in the mixed dentition. The final figure represents the amount of lower arch crowding IF the lower molar is NOT allowed to shift forward and the lower incisor remains in the starting position.
Tooth rotations for the incisors should be selected from the first brackets placed, obtaining the earliest full correction to improve retention.
Determining tooth rotations
A tooth may be rotated with one archwire, and not the other. A tooth rotation is dependent on the shape of the archwire selected. For this reason, the standard for determining tooth rotations (and applying rotation brackets) is the model measuring feature. DentalCAD will calculate the degrees of rotation to the selected archwire. Rotations +/- 1 will receive a “R” for Roth, with Mesial and Distal rotations assigned when the amount of rotation exceeds 1. If a tooth is rotated towards the midline, it is a Mesial rotation, if away from the midline, it is a Distal rotation.
Confirmation of the rotations is done by “turning off the x-ray”, printing the document, and comparing to the hand-held study models (or double occlusal scan). Some rotations are “obvious”, others are “questionable”.
To confirm rotations, view the “red lines” between the mesial and distal points of each tooth to see that this line passes through the incisal edge or is a true representation of the bicuspid rotation. “Turn off teeth” to more clearly view the points for editing. The archwire may be moved to the side to access individual points to be edited, and replaced after editing.
To check the point placement, turn-on the x-ray (image), “turn off” the teeth and vectors, and see if the red line drawn between the mesial and distal points passes directly over the incisal edge (or between the mesial-buccal and distal-buccal line angles of bicuspids). The function “drawing on/off” contains the actual points. Moving the archwire may be necessary to clearly view the tooth. Edit the point as needed.
After the rotations have been confirmed, transfer this data M-D to the IP Appliance tab in IP soft. If you do not wish to use a rotation bracket of a 2 degree rotation or less, this is the time to make that decision.
Rotations and severe anterior archwire curves may show some error in the amount of rotation. To calculate the degree of rotation, a line “tangent” to the archwire curve must be created. The root rotation is not exact on all portions of the tooth relative to the curve. The amount of tooth rotation is dependent on the selected archwire curve. Moving the curve forward or back will not change the rotation, but rotating the archwire curve will.
Constricted archwires error
The most distal molar point is NOT important except to position the first molar. For the calculations, the first molar does not move [to the archwire]. If the archwire shape moves inside of the most posterior molar point, the function “fit the teeth to the archwire” does not work well and you will get an error message telling you that this is the wrong archwire. I would suggest that you place the most distal molar points on the tooth surface closest to the lingual or palatal to reduce the number of times a constricted archwire falls inside these points.
Positioning archwires and the shape of the mandible
After the last point is positioned (26D), then F2 will take you to the list of shapes in the category “shape of the mandible”. To scroll through the 7 possible shapes that are positioned on the lingual shadow, representing the mandible, click the F3 key to scroll forward and F5 key to scroll back in the sequence of shapes. Select the one you wish and “left click” to position the shape.
The shape of the mandible is selected and positioned with a left click. The scan was not perfectly vertical, so the shape, used to determine arch symmetry, is not centered.
The shape is rotated by clicking again on the shape, then left dragging the “square” at the lower right end of the shape to rotate (left). Let go of the left click button and reposition the shape to the final position (right).
Click the F2 key to move to the next sequence of archwires, which will be the lower archwires (18 possible). Scroll through the available wires with the F3 or F5 keys until you find the one you wish, then position with a left click.
Repeat for the Upper archwire. It is best to select a “lower” archwire for the lower arch, then find the coordinated “upper” archwire as a start. Dental assistants should always choose an archwire to “maintain” the original arch shape and form. The doctor can then made decisions to expand, constrict, or to use “non-coordinated” archwires upper and lower.
Selecting the lower archwire to “maintain”. This archwire should be of the same shape as the “shape of the mandible” (ovoid, tapered, square) and should conform to the size of the dental arch PLUS the labial cortical bone (look past the teeth).
To change an archwire after the calculate button has been clicked, select the archwire with the mouse until it turns blue, then scroll through the available wires by F3/F5. It is not necessary to first delete the archwire. Any image that is blue in color is active.
To select archwires, I place the shape in front of the incisors approximately 0.5mm, which represents where the archwire would pass through the bracket slots. When making the final position of the archwire on the diagram, however, I place the anterior portion on the INCISAL EDGES of the upper or lower incisors. This will give the most accurate calculation for INCISOR ADVANCEMENT. I measure incisor advancement from the incisal edge on overlays. If you position the archwire in front of the tooth, the amount of incisor advancement will be “under-stated” according to my evaluation of sample cases.
The final archwire position in permanent dentition cases is “on the incisal edges”. In crowded arches, the incisor position is estimated, averaging the rotations and identifying the incisor to be traced on the cephalometric x-ray. The archwire position will have significant effect on the amount of crowding and predicted incisor advancement or retraction.
Asymmetry and positioning the curves
The asymmetry calculation is dependent on an accurate determination of the centerline of the “jaw”. For this purpose, you must symmetrically position the “shape of the mandible” and the “upper archwire”, which automatically determines the centerline. It is best to vertically position the models when making the double occlusal model scan, but often there is a small error in scanning that must be corrected.
ROTATE the archwire or shape of the mandible by clicking a second time on the blue shape. When you do, you will notice a small, square box on the lower right “end” of the shape. LEFT DRAG (hold down left click mouse key and move the mouse) to rotate the archwire or shape. Reposition to see if the symmetry is now accurate right vs. left (look at the buccal points and the distance from the molar teeth to the shape). In the upper arch, AFTER clicking the calculate button, look to see that the centerline passes through the incisive papilla. If not, rotate and reposition the upper archwire until it does.
After clicking calculate, view the upper centerline to see if it passes through the incisive papilla (left). Rotate the archwire to make the adjustment (right).
Calculate and the meaning of the measurements
a. Loop sizes
The measurements for upper and lower 2-2 are listed. These are used for the archwire loop widths. Round “up” the sizes to the next even number and enter this into the archwire ordering tab when keyhole or T loops are selected. If your numbers are very small, this is most likely the result of improper point placement, making the teeth too small.
For all permanent dentition cases, review
The amount of incisor advancement or retraction (the amount of crowding is secondary in importance)
Symmetry of the molars, as this will determine the final arch and midline symmetry.
Transverse dimension with the width 16C-26C being normal when it is 1.5mm greater than 36B-46B.
The loop sizes are manually transferred to the archwire window of IP soft when keyhole or T loops are being ordered. “Round up” to the next even numbered size.
Extraction vs. Non-extraction
Probably the most significant information from this model measuring is the amount of incisor advancement resulting from the alignment of crowded teeth on the selected archwire. To predict incisor advancement, position the archwire on the incisal edges of the upper and lower incisors, as this will then show how far the archwire advances or retracts (the incisal edge) from the starting position. This feature, used with the visual representation of the VTO feature, takes the guesswork out of the extraction vs. non-extraction treatment decision. You now have real information to better predict the incisor advancement of each case from which to make your decision.
The Incisor advancement should be calculated with archwires that MAINTAIN the original archform and shape. Expanded archwires, commonly applied to crowded cases to prevent incisor advancement are NOT always effective for that purpose. Only a small amount of real archwire expansion can be expected in cases, with only 10-15% getting the full expression of an expanded archwire. The buccal cortical bone resists the expansion of the archwire.
The amount of incisor advancement is the key feature in determining if a case should be treated non-extraction or extraction. Excess advancement can cause a protrusive finish, periodontal stripping of the incisors, and bite opening. This calculation gives you an exact amount of incisor advancement to expect from the crowding in each arch. It does NOT add additional advancement for leveling the curve of spee, nor the use of class II elastics.
Advancement of incisors upper vs. lower
Be watching out for more incisor advancement in the lower arch than the upper arch, especially in deep bite cases. If the lower incisor is prevented from advancing in the alignment stage of treatment by the lingual of the upper incisor, one or more of these problems may result:
The lower incisors do not align since they are prevented from advancing
Spaces form between the upper anterior teeth as the lower incisors push on the lingual surfaces of the upper incisors
the mandible is forced posterior into the TM joint, causing compression.
If this situation is predicted, then consider using upper incisor brackets with added Lingual root torque and/or lower incisor brackets with added labial (La) root torque with a rectangular alignment archwire (18x25N heat activated). Do NOT prevent the spaces from forming on the upper incisor teeth, but instead allow the lower incisors to advance, then deal with the upper incisor spacing in your mechanics stage.
This difference in upper vs. lower advancement is also graphically displayed as a “collision” in the dental VTO feature of model measuring.
Fitting the teeth to the archwire
If you do not believe the amount of incisor advancement, or the amount of crowding, click to turn off the x-ray and vectors and then click on the “fit teeth to the archwire”. You will see overlap or space at the midline. All the teeth move EXCEPT for the first molars that remain stationery, EXCEPT for derotation to fit the archwire, which of course may create more space. In treatment, of course, we do the same with the molar.
“Fit teeth to the Archwire” may be checked to confirm the amount of crowding. The mesial and distal points of each tooth are aligned as they are when the calculation is made. Overlap of the teeth at the midline (as in this example) represents crowding.
Click the “Save" icon or “File-Save”, then label the work either Start, Progress, or End. You should see the “link” for this project appear on the left. I would suggest you then print your work, making a hard copy for reference and/or inclusion in the patient report.
The “icons” under “File” on the top menu bar represent (from left to right) a) New page b) open (existing) file and c) save.
After clicking the save icon or File-save as, name your image from the possible options. Start, progress, end, non-extraction model, moderate anchorage model, maximum anchorage model.