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Seminar 14 expectations
McGann answers
Diagnosis
1. If the skeletal resistance is severe on the LOWER incisor of a growing class III patient, and a
lower lingual corticotomy is planned, then what changes if the patient grows more or less than
predicted?
If the patient grows more than predicted, then the mandible moves more forward than
expected and to avoid edge-to-edge or anterior crossbite, the lower incisor must be positioned
further back, with more skeletal resistance relative to the lingual cortical bone. The corticotomy
is needed more than ever.
If the patient has less DHG than expected, then the lower incisor does not need to be positioned
as far back, and there is less skeletal resistance. The patient may now not need the planned
corticotomy.
2. If RHG moves the maxilla forward 6mm, what is the effect on the DHG?
The DHG is less”nearly” by the amount that A point moves forward, since DHG is RELATIVE to A
point. There is not an exact 1:1 relationship of maxillary drift forward to mandibular
enlargement since growth is progressing at an angle, the McGann angle (angle between
maxillary length and mandibular length lines).
3. When do you use Li torque in the upper incisor of a class III case.
When the upper incisors starting inclination is retroclined and you want to be sure that the
upper incisor moves as far forward as possible, OR if there is risk of the upper incisor detorquing
(upper arch extraction or spaces to close). The retraction limit then either pushes the upper
incisor crown forward or maintains its position as the forces are closing spaces.
4. At what age and under what circumstances is lower 8 enucleation considered in the lower
arch?
IF you plan to distalize the lower arch, then this is limited by the presence of the lower 7s and
8s. This is the same in the upper arch when you say there is “posterior crowding”. The lower 8 is
the obvious choice to extract if given a choice of the 7 or 8, since the lower 8s usually erupt into
a mesial-lingual inclination and rotation when the 7s are removed. The lower 7 then is allowed
to erupt further distal, into the space previously occupied by the 8s.
At age 8 or 9, there is a radioleucency for the lower 8 “buds”. When these are removed, there
is an opening on the occlusal surface OR to the lingual. Use a surgical spoon to scoop out the
tooth buds. There is NO BONE to remove or grind, no teeth to section.
Then, the 8s start to calcify, as with the case shown below at age 10. At this stage, the crown
may be a “disc” and to remove the disc you may use a hemostat to grab the disk and break it
with a twist. The disc may be too large to be removed through the hole.
After the stage below, when the full crown is calcified, the extraction becomes very difficult
since sectioning the crown is almost impossible as it rolls around in the socket. Bone then needs
to be removed until the hole is large enough to remove the crown. (case 977)
5. How do you do a lower 8 enucleation?
Make a vertical incision to the disto-buccal cusp tip, then reflect the flap to expose the
underlying bone and tissue. Be especially careful not to damage the lower 7 follicle. Identify the
lower 7, then moving more posterior, find the location of the lower 8. With a surgical spoon,
scoop out the follicle and then hopefully the crown. At age 8-9, the crown will look like the white
of a hard boiled egg, with approximately the same consistency. The follicle will be darker blue.
Usually the incision is held together by the tongue so no sutures are needed.
6. When and how is it possible to distalize the lower arch in class III cases.
The lower arch is no different than any other group of teeth. It can be moved as a unit with the
proper force application. The line of force should be parallel or slightly below the occlusal plane,
the amount of force should be approximately 150-200 grams per side, and there must be
posterior space to move the arch back. Once the force is applied, then it is only a matter of time
for the biologic process of moving teeth to do its work. In the anterior, retracting the lower
incisors can be resisted by the lingual cortical bone. In moderate skeletal resistance situations,
using the dental vto or ceph vto prediction of the final lower incisor position and inclination,
bone remodeling can be expected with less than 150 grams per side of applied force. If there is
severe or extreme skeletal resistance, then it is best to do the Distalization in 2 steps, first
retracting the lower 3-7 first, then using the corticotomy assisted retraction of the lower incisors.
The reason not to do the corticotomy for retracting the entire arch is that the cortical bone will
be healed before the intended tooth movement is completed.
7. What line of force should you use if you want ZERO intrusion or extrusion as you retract the
upper anterior segment with zygoma buttress supported coils, and why?
Experience as shown on dental overlays has shown that a 5-10 degree angle is needed from
the occlusal plane “up” on the upper anterior segment to retract it straight back at “zero”
extrusion/intrusion. This is to compensate for the normal extrusion of the upper incisors that we
normally observe during orthodontic retraction. Below notice there is a coil from 7-KH and then a
second coil from the zygoma buttress. The combined line of force is approximately 10 degrees.
On the final overlay, the upper incisor moved straight back without extrusion or intrusion. (case
1029)
8. Explain the significance of an exploratory flap to examine bone remodeling palatal to the
upper incisor in the maxillary overlay in case 1029?
The exploratory flap clearly showed the presence of bone covering the roots of the incisors. This
means that bone “remodeling” exists, and is not bone “resorption” where the roots would be
exposed.
9. Explain what might cause “bunching” of palatal tissue, and why this might be important to
correct with perio surgery. (case 1029)
There was definite palatal cortical bone remodeling in this case and the appearance of
bunching of tissue could have been the remodeling of tissue and bone adjacent to the incisors.
But the risk is that the palatal tissue did NOT remodel, that the tissue is bunched up instead, the
fiber elasticity being a possible retention problem as the tissue re-establishes the starting incisor
position after the brackets are removed.
A WEDGE of tissue was removed to relieve the palatal tissue elasticity, similar to an extraction
space fiberotomy, and at the same time the flap raised to examine the underlying palatal cortical
bone and roots. The roots of the incisors were covered with “remodeled” bone.
10. Why is an exploratory flap to examine bone remodeling preferred over the tool of CBCT (cone
beam CT scans)?
3D scans are not accurate when examining THIN bone, less than 0.5mm thick. Bone this thin
appears to be not present on a CBCT scan. Note below the two different filters to examine the
CBCT scan to not clearly show the bone covering the roots of the incisors (a different case than in
the last question).
11. What are your options if you prematurely lose the first bicuspid extraction space before
correcting the incisor protrusion?
a) Extract 6s if the 8s are present to replace the extracted 6s
b) extract another set of bicuspids, the molars contacting the cuspids
c) distalize both upper and lower arches.
NONE of these are good solutions, with patient management becoming difficult as you ask
for either more teeth to be removed or the placement of skeletal anchorage. It is better to
avoid this problem by aggressive molar anchorage planning, accurate diagnosis, and
identifying cases that may need multiple extraction at the start of the case.
12. Describe crown lengthening diagnosis and the procedure to reduce gingival display.
To enhance the appearance of the smile, lengthen the visible clinical crowns of the upper
anterior teeth, and/or reduce gingival display, a crown lengthening procedure can be done.
There needs to be a good band of attached gingiva in the area of the intended surgery. An
incision is made in the attached gingiva and in the facial sulcus and papilla. The band of
attached gingiva is thrown away.
Next, the full thickness flap is reflected to the piriform rim and denuding most of the
attachment to ANS. These muscles will reattach at a more inferior level as the reflected flap is
repositioned (stretched) to the bone margin by mattress type sling suturing.
The bone is recontoured and scalloped where it is bulbous with 2mm of cementum exposed at
the crest of the teeth. Below right is after 5 weeks healing.
13. Explain the various definitions of “dentofacial orthodontics”.
a) Provide a service beyond simply straightening teeth
b) Provide a service beyond straightening teeth and correcting bites to class I
c) To Do something beyond “orthodontics”, the definition of that term is established by the
extent of work provided by the specialty
d) To spend more time, skill, and energy to save the patient restorative work,
e) To accept a case with known extended treatment time, such as a 2-phase mixed dentition
treatment.
f) A growth management case with estimated or individual growth predictions
g) Cases with maximum and moderate-maximum anchorage, since the specialty generally
closes extraction spaces with sliding mechanics, moderate anchorage
h) Changing the vertical to ‘raise the smile’
i) To change the facial features by the altering the underlying tooth positions.
14. When should a gingival graft be done before starting orthodontics.
When there is a lack of a SEAL between the oral environment (non sterile) and the underlying
tissues (sterile). This is usually a band of attached gingiva, but the appearance of attached
gingiva can be present with the attachment still missing from the tooth and underlying bone.
15. Explain what you need to do when using a lower cuspid in the lower lateral incisor position
a) Level the cusp tip to an incisal edge
b) Reduce the size of the cuspid mesial-distal to be approximately the size of the lateral incisors
(or leave an occlusion that is slightly class II in the posterior).
c) It is NOT needed to thin the lingual as on upper cuspids
d) It is NOT needed to extrude the lower cuspid to level the tissue as is needed on the upper
16. Explain how to close a lingual flap after lower lingual corticotomy.
Starting with the midline suture that was placed before reflecting the lingual flap to mark the
starting point of the closure, push the “dull” end of the needle through the contact between the
central incisors. Then back again under the wire on the next embrasure, push the ‘dull’ end of
the needle to the lingual and “grab” the lingual flap at that location. In the pictures below, top
left, the needle is pushed between the same teeth, under the archwire, withOUT penetrating the
labial papilla…you can now see the SLING that will hold the lingual flap from the facial surface of
the central incisor.
Continue the same through each contact until you get to the last tooth, and then use the
LOOP as the end to tie the KNOT on the facial surface of the last tooth. This is a “continuous
Mattress suture.
Go back to the other side and do the same from the next tooth from the midline to the most
posterior extension of the flap.
IP Appliance:
17. When is the “D” variation used in class III cases in the upper arch and when should you use
“Roth” on the upper 6s? Why not use tipD?
The “D” variation does NOT have any “distal offset”, meaning that the archwire will be
parallel to the facial surface of the molar and the molar will be rotated more MESIAL-PALATAL
than you are accustomed to seeing in class I or II occlusions. This is a benefit in NON
EXTRACTION upper arches when you want the molar to consume more archlength, pushing 5-5
more forward. **note that this variation was used in standard edgewise and the orthodontist
compensated by making a ‘bayonette’ bend in the archwire to rotate the molar mesial-buccal.
The molars upper and lower do not fit together as well without a distal offset or bayonette bend,
but this is a small compromise to help the effort in the [smaller] upper arches in class III cases.
When the upper arch is a [bicuspid] extraction arch, then the Roth prescription gives the best
fit with the lower molar AND the Roth Rx typically leaves a mesial inclination to the upper 6s,
serving to push 5-5 more mesial.
TipD would NOT be good in a class III non extraction or extraction arch since this is tipping
back the crown, making the upper more retracted than the lower arch.
It should be noted that if you start phase I with a non extraction preliminary diagnosis and the
“D” variation, and then change to extraction, then the appliance needs to be re-evaluated, and
that includes the molar buccal tubes.
Mechanics:
18. Explain what happens to the line of force when T loops are activated at the same time that
zygoma coils are active to the T loop.
The force is now being applied from multiple sources, one at zero degrees (the coil between
the teeth) and the other from a more superior location. IF there is equal forces from each, the
NET line of force is half way between the two. As the teeth move and the T loop force rapidly
decays, the line of force moves ‘up’ until it is at the zygoma buttress supported coil when the T
loop reaches its original passive state. Since the T loop can generate very high forces, the line of
force can be near zero to as high as the zygoma coil, variable according to where the T loop is in
the deactivation process.
19. Explain why there can be EXCESS force when a T loop and zygoma coil are both applied at the
same time and what the consequences can be.
The amount of force is cumulative, the total felt by the teeth is the sum of the zygoma plus T
loop generated forces. T loop forces are typically 250grams per side with 1mm of activation at
the vertical leg, and can be easily 300-500 grams per side with over-activation. Add this to 200-
250 grams from the zygoma supported nitie closed coil and the forces now are excessive. No
tooth movement, necrosis, and pain can be the result. Either of these forces is sufficient, there is
no need to use both.
In the optimum force curve for biologic efficiency, the amount of force where teeth may stop
moving is at approximately 300 grams. Yes, the force is distributed amongst the root surface
area in the segment, so four incisors could need 1200 grams to reach these levels, but remember
that the T loops and coils are also forces per side, and must be added together. There is no
reason to approach these numbers, even after corticotomy surgery where we are trying to move
the bone segment with the teeth.
20. How much force should be applied to an upper 2-2 segment after upper lingual corticotomy.
What are the choices to deliver this force.
I have recommended 200 grams per side if upper 2-2 corticotomy and 250 grams per side if
upper 3-3 corticotomy. This is only after years of estimating forces applied to teeth and tracing
overlays after corticotomy.
The choices to deliver this force are
a) T loops reactivated every 2-3 weeks to keep the forces from dropping to bone remodeling
levels (0.5mm of T loop activation). 1-1.5mm of vertical leg separation is sufficient on this
schedule.
b) OR, zygoma buttress supported nitie or stainless steel coils. Nitie coils have a longer range of
activation, for the same force applied, requiring less reactivation of the coil. Same as the T
loops, avoid the bone remodeling force of less than 150 grams. In general, see the patient
every 8 weeks and reactivate the amount of distal ends cut.
21. Why do we not activate KH loops by cinchback activation to retract incisors? Excess force,
molars advance. (case 732)
The Keyhole loop delivers MORE force per 1mm activation at the vertical legs since there is
less wire in the loop (less flexible). The upper molars then tend to move forward as the forces are
now in the “optimal” tooth movement range for both the anterior and posterior segment. In the
example below, the space 2-3 was closed, but the cuspid moved forward from class I to class II
2mm.
In the clinical setting, it is also confusing to have some KH loops activated and others only used
for attachment of coils and elastics. Therefore, we do NOT activate KH loops as a closing loop. If
you want a closing loop, then use a machine made T that you know the forces with known
treatment responses.
22. What happens AFTER all the [extraction] space is closed and zygoma coils remain attached to
the archwire loop.
The entire upper arch may distalize, depending on the force applied (150 grams per side will do
this) and the resistance of the palatal cortical bone and posterior crowding. If the incisors
cannot retract, or retract more slowly, the VERTICAL vector will become more evident and the
incisors will INTRUDE.
In line of force planning, it is common to get a treatment response from zygoma coils with
more intrusion than expected from the actual line of force due to resistance to the horizontal
force.
23. Explain why the line of force should be calculated from the alignment vto and how to do that.
The retraction with zygoma supported coils does NOT START until the teeth are aligned and a
19x25ss rectangular archwire is in place. In cases with significant anterior crowding, this
starting point for the incisors can be a much more forward position.
In cases with anterior crowding, you may want to make a copy of the alignment vto to record
the starting point of the incisor retraction (leave the ‘final’ incisor) and then move the “start’
incisors to the estimated final positions on the “ceph vto”. THEN turn on the grid to determine
how many millimeters of incisor retraction and intrusion are needed.
In the example below, the starting incisor position (white arrow) advanced during the
alignment to the red tooth on your right. The ‘starting’ incisor (green) is moved back to fit the
lower incisor. The distance the upper incisor needs to be retracted is from the more forward
‘aligned’ position, not the starting position.
24. Explain why the upper incisor should be at the retraction limit before the [upper lingual]
corticotomy is done.
If the upper incisor is more proclined than the retraction limit, then the forces applied by the T
loop or coils will TIP the incisor instead of moving the incisor at the same inclination (bodily
movement). The corticotomy is not needed for tooth tipping, only for bodily movement. During
the time it takes to get the incisor to the retraction limit, where bodily movement starts, the
cortical bone cut has healed, the procedure is ineffective.
25. What is tooth movement like after the corticotomy heals? How long do you have for
corticotomy assisted incisor retraction?
I Learned from doing overlays on hundreds of corticotomy cases, the tooth movement changes
to near what it would be without corticotomy after 3 months of healing, possibly extended with
a more consistent skeletal anchorage supported coil force…4-5months maximum.
Without a corticotomy, the incisors
a) tip back (detorque), even beyond the retraction limit due to archwire (loop) flexibility,
rotating around the intersection of the cortical bone and the root.
b) Extrude, [ increasing deep bite]
c) Generally do not retract.
26. What happens when deep bite is predicted on the dental vto and no skeletal anchorage is
used to control the vertical?
a) The Mandible swings open to clear the incisor collision, increasing class II and less chin
b) The posterior teeth finish in class II dental with no anterior overjet
c) The patient may experience TMD symptoms from the mandible being forced back
d) Posterior open bite as the incisors collide, with significant finishing wire bends and vertical
elastics to get the teeth [back] together.
e) Difficulty in closing spaces on the upper incisors as the collision with the lower incisors and
brackets push the upper incisors forward.
27. What happens if there is an incisor collision (deep bite) during retraction (space 2-3) and the
patient is skeletal closed bite? Is that different than skeletal open?
Mandible cannot swing open, since the muscles of mastication are tight, so the mandible is
forced back, and/or the upper incisors cannot retract, the [2-3] space does not close. Eventually
the upper molars must move forward to close the space.
In skeletal open, the mandible swings open, making edge-to-edge incisors and posterior open
bite in the bicuspids.
28. Explain why Ron Roth did not have lingual inclined cuspids like we see when using a Roth type
cuspid torque.
Ron Roth Used 21x25 instead of 19x25. Just like the incisors, there is a round wire range and
limits (retraction and advancing) where the archwire engages the sides of the bracket slot. The
“retraction” limit would be the limit of LINGUAL crown inclination. The advancing limit would be
where the crown tips to the buccal. 19x25 and 21x25 have a different retraction limit. Just like
on the upper incisors, the Li bracket torque compensates for the difference in the archwire “wire
spin”. Roth 21x25 = Li 19x25.
29. How can an expanded archwire cause slow cuspid retraction in 2-step mechanics.
The root is forced into the buccal cortical bone, creating anterior cortical anchorage. If the
molar cannot move forward, then the cuspid is slow to retract.
30. Explain how an archwire stop during cuspid retraction can give you the false impression that
the cuspids are retracting.
If molars move forward, then the incisors move forward with the stop on the archwire (the
stop connects the molars to the incisors when the molars move forward). This creates a space 2-
3, but it is NOT due to cuspid retraction, instead it is from incisor advancement. The molars are
moving forward to close the 4 space and now you have an “extraction” space from 2-3, the
incisors round tripping to finish at the start position.
In the example below, how do you know if the space 2-3 was not created by the incisors
moving forward, away from the cuspid OR the cuspid moving back away from the incisors?
Same with the bicuspid, how do you know that the bicuspids did not move forward to meet the
cuspid OR the cuspid moved back into the first bicuspid extraction space to meet the bicuspid. I
know, you will say the occlusion will tell you…looking at the change from class II to class I cuspid.
Yes, that is true, assuming the lower molars are not also moving forward!
31. What is the usual problem when molars become “hypermobile” and what do you do about it?
The problem is too much force on the hypermobile tooth (teeth). This can be from the opposing
occlusion (traumatic occlusion) or from the application of headgear or elastics. The VERTICAL
force is usually the problem, seen when you use more than one class II elastic to a lower molar,
or when a bracket is bonded too gingival.
The action to take includes:
1. Evaluate bracket position and change as needed
2. Discontinue the [elastic] force and give the tooth a rest, reevaluate the forces applied to the
tooth(reduce the force) and try to distribute to other teeth in the arch
3. Remove the band or step down the archwire to remove the tooth from occlusion with the
opposing teeth.
32. What is the usual problem when ALL the teeth become hypermobile during fixed orthodontic
treatment and what do you do about it?
It is fortunately very rare to have ALL the teeth “hyper” mobile (“2” mobility or more), but I have
had this 1-2x before. The problem here is the general tight muscles putting too much force on
the teeth that are now undergoing changes in the supporting bone through orthodontics. There
may be bruxing or clenching of the teeth.
Action to take includes:
1. Document the mobilities and hopefully you had documentation at the start (adult patient)
2. Take a full mouth x-ray survey to evaluate the bone surrounding the teeth and to establish a
good baseline to monitor for bone loss.
3. Lighten the forces on the teeth through the archwires and elastics/coils.
4. See the patient more frequently (1x per month) to monitor changes, taking a new set of x-
rays every 3-4 months to confirm the bone is holding up under the stress
5. Make a soft night guard over the top of the brackets to be worn at night or when
clenching/bruxing happens
6. Possibly discontinue treatment early as the teeth are not tolerating the orthodontic
treatment
7. Do not ignore the problem, as this is where you can get into trouble.
33. What can the problems be if a cuspid does not retract [on one side] and what should you do
about it? What are the chances of a cuspid being ankylosed?
The chances are very low that the cuspid is ankylosed. The things to check are,
a) If there is a ‘kink’ in the archwire preventing the tooth from sliding along the archwire
(change to a new straight archwire)
b) If the force is too much or too little (get a new nitie closed coil, stop using elastics)
c) If the cortical bone is interfering at the root or a constricted extraction space (if an expanded
archwire, change to an archwire to maintain, if the root is into the buccal cortical bone, then
change to Li torque).
d) If the opposing occlusion is preventing the tooth from retracting (grind the occlusion or even
remove the [lower] bracket temporarily)
e) If the tongue is protruding into the extraction space, blocking the path of the cuspid
retraction (bond cleats to the lingual on either side of the extraction space)
f) If nothing works, then make a sectional T loop (6-3) to retract the cuspid by cinchback
activation, removing friction. But a T looped archwire in half, then contour as needed,
bending the archwire ‘in’ mesial to the cuspid or bend it ‘up’ mesial to the cuspid so it will
not slide through the bracket slot. Add gable bend 10 degrees distal to the loop to counter
tipping, insert the sectional archwire and cinchback with NO MORE than 1mm activation at
the vertical legs. Reactivate in 4-6 weeks.
Growth Prediction
34. What does selecting the dental vto from dentalcad do for us when making a growth
prediction?
This Eliminates the need to incorporate model measuring and the lateral ceph since the VTO
incorporates both of these. Growth and growth management can be easily “added” to any
treatment represented in the dentalcad list of VTO predictions.
35. Explain the differences in dentalcad manipulations when using the estimated system versus
the individual system of growth prediction.
In the estimated system, we make a ‘growth adjusted ceph” to reference all the possible
treatments to. This accounts for DHG only.
In the individual system, where the molars and jaws are all predicted, in addition to DHG, the
growth adjustment is made in Growth management software to make the final line drawing
dental vto.
36. Explain how changing the years of treatment, ending at T2, can influence your treatment
decision.
The more years you select, the more DHG, the more molar movements, and the more growth
management manipulations are possible, increasing the chances of obtaining a non-extraction
treatment decision and/or the best dentofacial treatment decision.
37. Describe why we still need the concepts of over-estimation and under-estimation in the
individual growth system, and how these are applied.
Even though the individual growth prediction system should be more accurate than an
estimated system, it will never completely tell the future! It is still possible to under-estimate or
over-estimate the movements of jaws and teeth.
In class II cases, if DHG is over-estimated, then mechanics must make up the difference, and
the case is more difficult than expected. If under-estimated, then the case is easier than
expected with less ‘mechanics’ needed to get to the full correction.
In class III cases, if DHG is over-estimated, this is good and the case is easier. If under-
estimated, this can be catastrophic as the case becomes much more difficult and possibly a
surgery case.
In the individual system, the molars, incisors, and jaws are all predicted and moving. Each
‘moving part’ will have the possibility of under-estimation or over-estimation. This can influence
the NET anchorage planning and the effectiveness of any growth management techniques
applied.
38. What does it mean to say that growth management is cumulative?
There are 4 elements or possible moving parts that can be manipulated with growth
management techniques and appliances. The total manipulation of the four, working towards
the eventual final treatment objective, are added together. In the example below for a class III
case, the enhancement of the maxilla and upper teeth, plus stopping the lower teeth and bone
from moving forward is all cumulative to correct the class III. If each is 1mm, then the total
growth management effect is +3mm.
39. Discuss what the percentile grower means in a growth prediction of class II cases
This is the ‘ranking’ of the patient within the total population studied in the growth sample. A
low percentile grower (eg. 10%) would expect to have the smallest DHG, a high percentile would
expect to have the most DHG in the population. Like being the tallest or smallest at a school.
40. Discuss what the percentile grower means in a growth prediction of class III cases
If the characteristics of the patient are pointing towards a high percentile grower, then this
type of patient may be more likely to need orthognathic surgery than a low percentile grower.
41. How do you determine if a class III case is a surgical case or an orthopedic-orthodontic case?
Determine from the prediction what the TOTAL mandibular length after growth will be and
determine if that is “excessive”. The large mandible would be the most common request for
surgery. Next, determine the total maxillary length after growth, which represents midface
deficiency. There can be a normal size mandible, but if the midface is VERY deficient, then the
lower face will ‘look’ too protrusive.
42. How does the growth management differ between a class III surgical case and a class III
orthopedic-orthodontic case?
In an orthopedic-orthodontic case, the correction of the dental occlusion to class I is
important, at the same time building out the midface for the best facial appearance (RHG and or
bone-anchored maxillary protraction).
In the surgical approach, no attempt should be made to correct the class III dental, as this will
be important to obtain the largest change at surgery, getting rid of the “class III look”. Efforts
can be helpful to
a) Build out the midface with RHG and bone anchored maxillary protraction
b) Establish the upper incisor at the Roth ideal inclination
c) Expand the maxilla with Rapid palatal expansion
d) Establish the lower incisor inclination at the Roth ideal…this will probably not be done until
the year before surgery as this is where the lower lip will look protruded and the anterior
crossbite will look the worse. Leave the retroclined lower incisor for now.
43. How can the POS Growth Management software help you determine if there is expected “late
growth” remaining in a teenage class III case.
CVM ‘growth’ ends at stage 5, and Wrist x-ray growth can be classified to stage 6 (McGann).
The growth study gathered untreated data to stage 6 in most cases, so you can input T1 as stage
4 or 5 and end after stage 6 to check for predicted late growth. This will add ‘magnitude’ and
percentile grower to the diagnosis.
44. Describe what is represented and what is important in the first individual growth prediction,
Alignment vto + untreated growth, using POS Growth management software.
This prediction will establish what “structures and teeth” are moving and what can be
potentially “managed” to treat the case [non extraction] and/or to obtain the best facial
esthetics. This prediction also sets the baseline for what moves without adding appliances (CHG
or RHG or zygoma ligation, etc.)
45. Describe how to make a growth management prediction to include cervical headgear in a class
II case. What changes can you expect for a patient who wears CHG?
In the drop-down box in class II cases (ONLY), cervical headgear is a possible selection for a
growth calculation. If you factor this into the selected [dentalcad] alignment vto, then this
prediction will show the what is expected to happen if the patient wears the headgear. This can
be compared to the alignment+untreated prediction to see if it is worth the effort to add this
appliance to the treatment plan.
Be looking for changes in Maxillary drift and upper molar drift. If there is a change in Maxillary
drift, you may also notice an increase in DHG.
46. Describe how to make a growth management prediction to include Reverse headgear in a
class III case. What changes can you expect for a patient who wears RHG?
Select the alignment vto from dentalcad, then select from the growth management drop
down box “reverse headgear”. From the growth sub-study of patients that were confirmed RHG
wearers during their treatment, the calculations will add the significant difference compared to
untreated. Then look at the maxillary drift and upper molar drift increases, if any, compared to
the previous alignment+untreated prediction.
** although not on the prediction line drawing, the nose may get larger the amount of the
added maxillary forward movement (drift), as a midface effect.
47. Describe how to make a growth management prediction to include Zygoma ligation in a class II
case.
Select the alignment vto from dentalcad, then select from the growth management drop
down box “zygoma ligation”. The upper molar drift should stop, showing you the relation with
the lower molar which has moved forward by mandibular enlargement and lower molar drift.
You may want to increase the years of treatment and see what this does to the prediction,
utilizing a longer period of growth over more growth stages.
48. Explain how to add growth to a bicuspid extraction dental vto.
First make an alignment/untreated growth prediction to determine where the structures are
moving and the magnitude of DHG and molar movements. Save that project then start a new
project, selecting the extraction vto, without added growth, from dentalcad (there should be
some anterior overjet to be corrected). Make a “braces” growth prediction to confirm that this
is the anchorage planning (by the dots) you want.
If the picture does not look the way you want with the added growth, go back to dentalcad
adjust the upper and lower molar anchorage and repeat to get the final treatment decision
picture you want. The model measuring that was used to create that picture, will show you
how to close the extraction space.
49. Discuss why it would be important to know if there is predicted DHG after time T2, the end of
active orthodontic treatment.
The final [class I] Bite could be disturbed and/or the incisors recrowd due to a collision of the
incisors. With that information, you may want to extend the treatment time for better
stability.
Growth management
50. How can a lower lingual arch (LLA) work against growth management of a class II case.
The lower lingual arch can reduce the mesial migration of the lower molar, which assists in
correcting the class II molar relation to class I. Lower lingual arches should ONLY be used to
change an otherwise extraction lower arch (too much advancement) into a non extraction
arch.
**it should be noted that the lower lingual arch can move with the entire lower arch forward
drift. (see below)
51. What is the difference between using a LLA and lower molar ligation in the growth
management of a growing class III case
A lower lingual arch will maintain the space between 6-incisors, BUT the entire 6-6 dental arch
with the lower lingual arch can drift forward RELATIVE to the mandible (below)
With lower molar ligation, the molar is attached to the mandible, so the molar canNOT drift
forward RELATIVE to the mandible. The lower 3-4-5s naturally drift lingual unless pushed
forward by the molar. This makes lower molar ligation the preferred growth management
method.
52. What does the term “bone anchored maxillary protraction” refer to and when is this
considered in growth management?
This is a term created in articles published in 2011 and 2012 referring to skeletal anchorage
being secured to the zygoma and mandible to support a class III elastic force of 100 grams
initially to 250 grams after 3 months. The results have been a forward movement of the
midface, including cheekbones and the nose, which is not possible with surgical advancement
of the maxilla.
This “added” force application, directly to the maxilla instead of to the upper molars, is
considered to be beneficial in nearly all class III cases to build out the midface, reducing the
apparent prominence of the lower face.
In the McGann modification, an elastic is directed to the existing RHG from a zygoma bone
plate. This is in addition to the elastic from the molar to the bone facemask. When the
facemask is NOT being worn, then the class III elastic is added from the bone plate to the
lower dental arch, assuming there are brackets available to support the elastic.
The bone plate immediately above is an 8 hole plate with the last hole ‘cut’ to make a hook.
The “Bollard” plates used for protraction headgear have a very high materials cost ($800) plus
the surgery.
53. Why would the extraction of upper 6s be beneficial to the growth management of a class II
case?
IF one of the signals for the upper teeth to DRIFT forward comes from the lower teeth, then
the first molar and incisor coupling are obvious sources of interdigitation that could provide
such a signal, especially when eating. [note: the primary molars have “flat” occlusal planes
and thus are not good sources for inclined planes distributing forces]. Extracting the upper 6s
removes this interdigitation, allowing for DHG of the jaws without the upper teeth following
the lower.
54. What can we gain by zygoma ligation to the upper anterior teeth during a period of growth?
Stop upper molar and incisor movement forward, RELATIVE to the maxilla [in a class II case],
correcting class II dental. If the ligation is to the upper anterior teeth, this ligation can also
reduce the anterior vertical drift (down) of the incisors. The face including the lips, continue to
grow down but the upper incisors are not allowed to extrude, reducing excess vertical. If the
incisors never extrude (vertical maxillary excess), then there is no reason later to use piriform
rim coils to intrude them.
55. If you do NOT want to use brackets on the upper anterior teeth to support zygoma ligation,
(eg. Poor hygiene), then what choice do you have to ‘growth manage’ the upper molar from
moving forward?
17x25ss tie back to zygoma. Use the “pig” triple tube variation on the molar.
56. What can we gain by zygoma ligation to the upper molars during a period of growth?
Stopping the vertical drift of the upper molars, closing dental open bite and autorotation of
the mandible for a bigger chin. This works best when done along with lower molar ligation (for
vertical) to prevent the lower from extruding more to meet the upper. It is a good idea to
include a TPA from the molars to prevent the palatal cusps from dropping even though the
buccal of the molars are held ‘up’.
57. What are the negative growth management features of a lower utility arch in class II cases?
Tipping back the lower molars is working against correction of the class II molars. This
should be done only if the molar tipback is needed to change the lower arch from an extraction
arch to a non extraction arch.
58. What positive growth management features are there in lower utility arches in class II cases?
Uncoupling the incisors, allowing for the extra growth of the mandible to move the lower
teeth forward withOUT the upper teeth following.
59. Explain how clockwise rotation of the mandible from orthodontic mechanics can ‘kill’ the
advantages of DHG in a class II case.
When there is clockwise rotation of the mandible (occlusal plane), the Mandibular
enlargement is directed to the floor, vertically, instead of horizontally, so there is no correction
of the dental class II. Counterclockwise rotation is normal without treatment and favorable for
DHG.
**special note: this was the concept of the first significant predictor of DHG, the McGann
Angle (between the line for mandibular length and maxillary length). If the McGann angle is
zero (in theory since this is impossible in real life) then the DHG is the maximum as every
millimeter the mandible grows larger than the maxilla, there is 1mm of DHG. On the other
side of this theory, if the McGann angle is 90 degrees, then mandibular enlargement is not
contributing at all to DHG and the value will be negative as the maxilla moves forward but the
mandible does not.
60. Describe how to modify the dental VTO for auto-rotation of the mandible in an open bite case.
Intrude the upper molars, grid and screenshot to document how many millimeters of
intrusion is planned (coil length, reactivation, and palatal bar location from the palate)
Next, move the lower incisors and molars to fit with the upper teeth
Next, move the mandible and symphysis to the incisors,
For the autorotation, hold down the shift key and rotate the mandible “end point” back to
the original condylar head position. You will notice there is more chin.
Adjust the soft tissue.
61. How can you know if there is bone covering the roots after “bone remodeling” or not?
A CBCT 3D scan can look under the tissue at the bone covering the roots, BUT this method is
not very accurage for thin (less than 1/2mm) bone covering roots. Thin bone is not “seen” on
the scans. The other choice is an exploratory flap, enabling you to look visually at the presence
or absence of bone covering the roots.
**McGann did 3 of these and then determined that that was enough.
Practice management:
62. Give reasons why you should quote phase I+II total case fee at the start of a 7 year case versus
the reasons for quoting only a phase I fee, phase II to be determined later.
a) Quoting a total fee allows for the Parents can plan,
b) less Doctor time is spent at consultations in the transition from phase I to phase II, as the
financial arrangement has already been agreed to at the start of the case.
c) The payments are ‘cheaper’ payments if the treatment is longer, becoming more affordable
for the parents
d) no surprises, no second opinions.
63. Explain how to manage the patient/parent if a tooth needs endodontic treatment during
active treatment.
Hopefully you have documentation that the tooth was ‘dead’ before treatment started,
proving that the brackets did not cause the need for endodontic treatment! If not, then discuss
possible trauma and fractures to the tooth in the history prior to the start of treatment. If that
is negative, then the patient may think you caused the problem and therefore is not feeling
obligated to pay for the treatment. You may need to do the treatment complimentary!
64. Explain how to manage the patient when decalcification is noted upon deband.
Hopefully you have documentation of hygiene deficiencies in your charting, and best would
be documentation of the parent being informed either verbally or in writing of the lack of care
during orthodontic treatment. Photographs can also be used to show the plaque, but this
could also backfire on you as they then ask why you did not make efforts to remove it or tell
the parent this was happening. Informed consent of course has this risk listed, and that the
patient is responsible, but who reads the fine print, right? Practically, this is a difficult
situation, especially when there is a lot of restorative work to repair the damage.