Jules E. Lemay IIId.d.s., cert. ortho., F.R.C.D. (C)

Diplomate, American Board of Orthodontics

ETIOLOGY of MALOCCLUSIONS

PREVENTIVE and INTERCEPTIVE

ORTHODONTICSNov. 2007

ETIOLOGY of MALOCCLUSIONS

PREVENTIVE and INTERCEPTIVE

ORTHODONTICSNov. 2007

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-statistically representing 26M (6-17y)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

NORMALNORMAL 25%25% CL-ICL-I 50-55%50-55% CL-IICL-II 15-20%15-20% CL-IIICL-III 1%1%

USPHS 1960’s, age 6-17USPHS 1960’s, age 6-17 3

ANGLE CALSSIFICATION(Molar Relationship)

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 for later corrective

phasephase 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?

Why early orthodontic screening?

4

AAO AAO RecommendationsRecommendations

19981998

INCIDENCE OF PROBLEMSINCIDENCE 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 & (CL-II & skeletal)skeletal)

CL-III MOLARSCL-III MOLARS 1%1% ANT. OPB ANT. OPB (> 2mm)(> 2mm) 1% whites1% whites 10% blacks10% blacks DEEP BITEDEEP BITE 10% whites10% whites 1% blacks1% blacks POST XB POST XB (>2 teeth)(>2 teeth) 6%6%

USPHS 1960’s / age 6-USPHS 1960’s / age 6-1717USPHS 1960’s / age 6-USPHS 1960’s / age 6-1717

5

Inherited & AcquiredInherited & Acquired Predisposing Predisposing (direct) (direct) & & Determining Determining (indirect) (indirect)

(Mc Coy 1956)(Mc Coy 1956)

6

ETIOLOGIC FACTORSClassification

7 Causes & Clinical Entities7 Causes & Clinical Entities (Moyers, 1958)(Moyers, 1958) HeredityHeredity Developmental defects of unknown Developmental defects of unknown originorigin

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 Extrinsic (general) & Intrinsic

(local)(local)

ETIOLOGY OF MALOCCLUSIONSETIOLOGY OF MALOCCLUSIONSETIOLOGY OF MALOCCLUSIONSETIOLOGY OF MALOCCLUSIONS

ENVIRONMENTmalocclusio

ns

HEREDITY

..7..

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

98%98% 98%98%

AGEAGE

99 85%85% 90%90% 1313 90%90% 95%95% 1515 1919

Wolford et Al., O. Surg., 1973 - 45:3Wolford et Al., O. Surg., 1973 - 45:3

9.

COMPLETION OF ANTERO-POST.

MANDIBULAR GROWTH

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 SERIAL EXTR. - CASE SELECTION SELECTION

(ideal conditions)(ideal conditions)

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 -provides room for 3’s

eruptioneruption

4- 4- MECHANOTHERAPYMECHANOTHERAPY(fixed appliances (fixed appliances corrections)corrections)

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TYPICAL SERIAL EXTR. SEQUENCE

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

1/21/23/43/4

1/41/4

ROOT 1/4 1/2 ROOT 1/4 1/2 ROOT 1/2 3/4ROOT 1/2 3/4

3’s4’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)

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)

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ALTERNATE S. EXTR. SEQUENCE

IndicationsIndications::IndicationsIndications::

xx

-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 Serial Extractions - Alternate SequenceSequence

14.

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 spaceHave specific Have specific Tx objectivesTx objectives

Explain them to parents & patientExplain them to parents & patient

(Phase-II & mechanotherapy usually (Phase-II & mechanotherapy usually indicated)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…

CONSULTCONSULT15

SERIAL EXTRACTIONS CONCLUSIONS

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

AAO ORTHODONTIC DIALOGUE - Summer 1989: 4 16

CONGENITALLY MISSING TEETH(% POPULATION)