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1. Jules E. Lemay III
d.d.s., cert. ortho., F.R.C.D. (C)
Diplomate, American Board of Orthodontics
ETIOLOGY of MALOCCLUSIONS
PREVENTIVE and INTERCEPTIVE
ORTHODONTICS
Nov. 2007

2. 
USA (various studies):USA (various studies):35 - 95%35 - 95%

USPHS (1960’s):USPHS (1960’s):

most thorough epid. study ever donemost thorough epid. study ever done

statistically representing 26M (6-17y)statistically representing 26M (6-17y)

Grainger’s TPI (severity)Grainger’s TPI (severity)
75%75% Occlusal DisharmonyOcclusal Disharmony
25%25% Near-ideal OcclusionNear-ideal Occlusion
2
EPIDEMIOLOGY OF MALOCCLUSIONS

3. NORMALNORMAL25%25%
CL-ICL-I 50-55%50-55%
CL-IICL-II 15-20%15-20%
CL-IIICL-III1%1%
USPHS 1960’s, age 6-
17
3
ANGLE CALSSIFICATION
(Molar Relationship)

4. 6’s erupted = Post. Occl. established6’s erupted = Post. Occl. established
Detection of:Detection of:
Fct. habits, crowding, deep/open bitesFct. habits, crowding, deep/open bites
AP & transverse discrepancies AP & transverse discrepancies
Benefits:Benefits:

««influence» influence» jaw growthjaw growth, harmonize width of arches, harmonize width of arches

improve improve eruptioneruption patterns, patterns,

lower risk of lower risk of traumatrauma to protruding U inc. to protruding U inc.

correct harmful correct harmful O. habitsO. habits

improve improve estheticsesthetics & self-esteem & self-esteem

simplify / shorten simplify / shorten Tx timeTx time for later corrective phase for later corrective phase

reduce likelyhood of reduce likelyhood of impactionsimpactions

improve some improve some speechspeech problems problems

preserve / gain preserve / gain spacespace for erupting perm. teeth for erupting perm. teeth
Why early orthodontic screening?
4
AAO AAO
RecommendationsRecommendations
19981998

5. INCIDENCE OF PROBLEMS

CROWDINGCROWDING 40% (age 6-11)40% (age 6-11)
85%85% (age 12-17) (age 12-17)

OVERJET OVERJET (> 6mm)(> 6mm) 16% 16% (CL-II & skeletal)(CL-II & skeletal)

CL-III MOLARSCL-III MOLARS 1%1%

ANT. OPB ANT. OPB (> 2mm)(> 2mm) 1% whites1% whites10% blacks10% blacks

DEEP BITEDEEP BITE 10% whites10% whites1% blacks1% blacks

POST XB POST XB (>2 teeth)(>2 teeth) 6%6%
USPHS 1960’s / age 6-USPHS 1960’s / age 6-
1717
5

6. 
Inherited & AcquiredInherited & Acquired

Predisposing Predisposing (direct) (direct) & & Determining Determining (indirect) (indirect) (Mc Coy 1956)(Mc Coy 1956)
6
ETIOLOGIC FACTORS
Classification

7 Causes & Clinical Entities7 Causes & Clinical Entities (Moyers, 1958)(Moyers, 1958)

HeredityHeredity

Developmental defects of unknown originDevelopmental defects of unknown origin

Trauma (pre & post-natal)Trauma (pre & post-natal)

Physical agents (pre & post-natal)Physical agents (pre & post-natal)

Habits (thumb , fingers, tongue, etc...)Habits (thumb , fingers, tongue, etc...)

Diseases (systemic, endocrine)Diseases (systemic, endocrine)

MalnutritionMalnutrition

Extrinsic (general) & Intrinsic (local)Extrinsic (general) & Intrinsic (local)

7. ETIOLOGY OF MALOCCLUSIONSETIOLOGY OF MALOCCLUSIONS
E
N
V
I
R
O
N
M
E
N
T
m
a
lo
c
c
lu
s
io
n
sH
E
R
E
D
I T
Y
..7..

8. 
SERIAL EXTRACTIONS SERIAL EXTRACTIONS (Kjellgren, 1929)(Kjellgren, 1929)

GUIDANCE OF ERUPTION GUIDANCE OF ERUPTION (Hotz, 1970) (Hotz, 1970)

GUIDANCE OF OCCLUSIONGUIDANCE OF OCCLUSION
8.
...influence tooth eruption ...influence tooth eruption
into a favorable occlusion...into a favorable occlusion...
TERMINOLOGYTERMINOLOGY

9. 98%98%
98%98%
AGEAGE
99 85%85% 90%90%
1313 90%90% 95%95%
1515
1919
Wolford et Al., O. Surg., 1973 -
45:3
9.
COMPLETION OF ANTERO-POST.
MANDIBULAR GROWTH

10. 
NO SKELETAL DISHARMONYNO SKELETAL DISHARMONY
(Good facial balance / harmony)(Good facial balance / harmony)

CL-I MOLAR RELATIONSHIPCL-I MOLAR RELATIONSHIP

MINIMAL OVERBITE & OVERJETMINIMAL OVERBITE & OVERJET
10.

SEVERE SEVERE SPACE DEFICIENCYSPACE DEFICIENCY
( > 10mm / ARCH)( > 10mm / ARCH)
SERIAL EXTR. - CASE SELECTION SERIAL EXTR. - CASE SELECTION
(ideal conditions)(ideal conditions)

11. 1- PRIM. CUSPIDS 1- PRIM. CUSPIDS (C’s)(C’s)
--relieves inc. crowdingrelieves inc. crowding
2- PRIM. 1st MOLARS2- PRIM. 1st MOLARS (D’s)(D’s)
--accelerates 4’s eruptionaccelerates 4’s eruption
3- 1st PREMOLARS3- 1st PREMOLARS (4’s)(4’s)
-provides room for 3’s eruption-provides room for 3’s eruption
4- 4- MECHANOTHERAPYMECHANOTHERAPY
(fixed appliances corrections)(fixed appliances corrections)
11
TYPICAL SERIAL EXTR. SEQUENCE

12. SG 15.2
2. 5 years2. 5 years 1.5 years 1.5 years
1.75 years1.75 years 1.5 years 1.5 years
1/21/2
3/43/4
1/41/4
ROOT 1/4 1/2 ROOT 1/4 1/2 ROOT 1/2 3/4ROOT 1/2 3/4
3’s
4’s
++ = = 4y4y
++ = = 3.25 y3.25 y

ROOT 1/2 ROOT 1/2 STANDS STILLSTANDS STILL

ROOT 3/4ROOT 3/4 EMERGES into O.CEMERGES into O.C..
..12..
ROOT FORMATION vs ERUPTION
(Longitudinal Studies, Moorrees et Al., 1963)

13. 1- 1- D’s D’s (keep the cuspids)(keep the cuspids)

Avoids Li tipping of incisorsAvoids Li tipping of incisors

Prevents bite deepeningPrevents bite deepening

Accelerates eruptionn of 4’sAccelerates eruptionn of 4’s
2- 2- 4’s 4’s & REMAINING & REMAINING PRIM. CUSPIDSPRIM. CUSPIDS

makes room for 3’smakes room for 3’s
3- 3- MECHANOTHERAPYMECHANOTHERAPY (fixed appliances)(fixed appliances)
13
ALTERNATE S. EXTR. SEQUENCE

14. IndicationsIndications::
x
x
-Extr. D’s to accelerate 4’s
-Keep the C’s
-Dentoalveolar protrusion
-Minimal incisor crowding
-3’s & 4’s at same level
Serial Extractions - Alternate SequenceSerial Extractions - Alternate Sequence
14.

15. 
No cookbook approaches...No cookbook approaches...

Not a licence for no Not a licence for no supervisionsupervision

Take pan-Xr, evaluate spaceTake pan-Xr, evaluate space

Have specific Have specific Tx objectivesTx objectives

Explain them to parents & patientExplain them to parents & patient
(Phase-II & mechanotherapy usually indicated)(Phase-II & mechanotherapy usually indicated)

Short & Long term goalsShort & Long term goals

Esp. when extracting permanent teethEsp. when extracting permanent teeth

When in doubt, DON'T take them out…When in doubt, DON'T take them out…
CONSULTCONSULT
15
SERIAL EXTRACTIONS
CONCLUSIONS

16. U & L 8’s U & L 8’s 20-30%20-30%
U 2’s U 2’s 1.5%1.5%
L 5’s L 5’s 1%1%
U 5’s U 5’s 0.5% 0.5%
L 1+2+3+4’s L 1+2+3+4’s 0.5% 0.5%
AAO ORTHODONTIC DIALOGUE - Summer 1989: 4
16
CONGENITALLY MISSING TEETH
(% POPULATION)