Limited Early Treatment – Skeletal-Dental Relations – Factors Affecting Arch Length
Limited Early Treatment – Skeletal-Dental Relations – Factors Affecting Arch Length
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letop
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Limited Early Treatment
C. Michael Beck DDS, MS, MPH
Objective
Learn to manage occlusal developmentfor maximal improvement with minimal effort and risk.
Oh hey, these are some notes. They'll be hidden in your presentation, but you can see them if you open the speaker notes window (hit 's' on your keyboard).Organization
- Physiology
- Diagnosis
- Treatment
- Case Studies
I. Physiology
Skeletal-Dental Relations
Orthognathic
Dental Class ISkeletal open bite
Dental Class II
Skeletal Class II (Deep Bite)
Skeletal Class III
Maxillary Dental RetrusionMandibular Protrusion
Mid-face Deficiency
Soft Tissue Analysis
Orthognathic Facial Profile
Mixed Dentition
Molar Relationships
Arch Length
Arch perimeter between mesial of first molars
Factors Affecting Arch Length
Open Dentition
Interdental spacing
Closed Dentition
No interdental spacing
Primate Spacing
Posterior to the primary cuspid
Early Mesial Shift
Mesial movement of posterior primary teeth as 6's erupt
Late Mesial Shift
Mesial movement of the posterior dentition as E's exfoliate
Secondary Spacing
Space created by erupting lateral incisors
Incisor Liability
Difference in width between A,B and 1,2
In Caucasians, MX incisor liability is 7.6 mm and MD incisor liability is 6 mm.Labial Incisor Position
Buccal position of incisors immediately after eruption
Intercanine Width
Distance between the canine tips in the same arch.
There is no increase in mandibular intercaninearch width after 10 years of age.
Intercanine Arch Length
Distance between the canine tips in the arch perimeter.
Leeway Space
Difference in width between C,D,E in the primary dentition and 3,4,5 in the permanent dentition
Caries
Extraction Or Tooth Loss
Ectopic Eruption
II. Diagnosis
Questions to Ask
Will treatment time be reduced?
Will stability, function,and aesthetics be improved?
Will arch length and anchorage be improved?
Will early treatment facilitate later treatment?
Will early treatment prevent laterextraction of permanent teeth?
Can growth and skeletal patternsbe positively influenced?
Will habit control permit proper development?
Will early treatment causehard or soft tissue damage?
Will early treatment decreasethe severity of the malocclusion?
Will appliance wear affect later cooperation?
Can additional treatment time be justified?
Other Considerations
Dental age, Eruption pattern,& Root Development
Adequate Arch Length?
x = space needed for 1 cuspid and 2 bicuspidsy = sum of the widths of incisors
Maxillary Arch (Male)
x = 11.774 + 0.344 * y
Maxillary Arch (Female)
x = 11.196 + 0.353 * y
Mandibular Arch
x = 9.41 + 0.527 * y
Skeletal growth pattern & Heredity
Facial aethetics
Oral habits
e.g. thumb-sucking, tongue thrust
Your Ideal Patient
- Orthognathic face
- Mixed dentition
- Class I molars
- Adequate arch length
Problems: Choose Two
- Anterior crowding
- Rotated teeth
- Anterior or posterior crossbite
- Flared or lingually-tipped incisors
- Deep bite
- Arch length loss
III. Treatment
Got space?
Yes
With adequate space, you can correct:
- Crowding
- Rotations
- Flared or tipped incisors
- And deep bites
No
Dammit.
How to get (more) space
Expand the arch
Use an appliance (transverse or quad helix) to expand the arch.
Upright incisors
Rotate molars
Interproximal reduction
Don't do this.
Regain Lost Space
Move molars distally using a sagittal appliance or headgear.
Serial Extraction
Be careful.
Serial Extraction
The selective removal of primary and permanent teeth to alleviate severe arch length problems in cases of Class I crowding.
Goal of Serial Extraction
Arrive at appliance time with sufficient space tolevel, align, rotate, and anchor.
If Done Correctly
Serial extraction makes orthodontic treatmenteasier and faster.
If Done Incorrectly
Serial extraction makes orthodontic treatmentharder and longer!
Consider Serial Extraction When
- Arch length discrepancy is between 8 and 12 mm
- Good OB, OJ relationship (and no rotations)
- Class I molar relationship
- Class II molars and adequate mandibular space
Avoid Serial Extraction When
Class II molars and mandibular crowding
Case Study 1
Serial Extraction in anOrthognathic Patient
Lower lip at or just behind the "e" line.
Class I skeletal and dental.
Mx and Md arch lengthdiscrepancy of 8 to 12 mmORadequate Md arch lengthwith Mx crowding of 8 to 12 mm.
Never do serial extraction in only the mandibular arch.
Cephalometric Md incisor at the A-Po line.
No deep bite. No excessive Curve of Spee.
Teeth are erupting in proper sequence and angulation
Permanent cuspids have not erupted.
Midlines are in proper alignment.
Treatment
Extract first primary molars and first bicuspids (if crowding exists, also extract primary cuspids) Use lingual arch to prevent tipping Use maxillary TPA to prevent molar migration (remove the TPA if cuspids erupt in Class I) Bracket for final alignmentCase Study 2
Serial Extraction in aBimaxillary Protrusion Patient
Procumbent lips.
Class I skeletal and dental.
Mx and Md arch lengthdiscrepancy of 8 to 10 mm
Cephalomentrically protrusive incisors(ahead of the A-Po line).
No deep bite. No excessive Curve of Spee.
Teeth are erupting in proper sequence and angulation
Midlines are in proper alignment.
Permanent cuspids have not erupted.
Treatment
Extract mx/md primary cuspids Use lingual arch to prevent tipping Use MX TPA to prevent molar migration Bracket for final alignmentRules to Remember
Be selective. Ideal candidates are limited.
Never do serial extraction in only the mandibular arch.
Fix crossbites yesterday.
You lose space 10x faster in the maxilla.
Don't correct her/his malocclusion just because s/he's cute.
cmbeck@gmail.com