Isfahan Dental School Pediatric Dentistry

Departement

Dr. S.E.Jabbarifar

2009

PRIMARY DENTITON RELATIONSHIPS

GENERAL OBJECTIVES:

To present the establishment of the occlusion in the primary dentition.

SPECIFIC OBJECTIVES:

1. Follow the development of occlusion from birth – 3 years.

2. Define and illustrate all of the terminal plane relationships for primary molars.

3. Explain canine relationships in the primary dentition.

4. Follow the occlusion from 3-6 years.

5. Know normal anterior relationships in the primary dentition: Overjet, Overbite.

6. Explain spacing in the primary dentition.

I Neutrocclusion is a maximum

intercuspidation of maxillary and mandibular teeth with minimal overbite and overjet.

The development of occlusion is the most dynamic phenomenon in the mouth. This is a permanent changing process from birth to death. It can be divided into four periods.

1. Primary Dentition: birth to 3 years2. Mixed Dentition: 6-12 years3. Young Permanent Dentition: adolescence4. Adult Dentition.

2 yrs

(± 6 mos.)

3 yrs

(± 6 mos.)

4 years

(± 9 mos.)

5 yrs

(± 9 mos.)

6 years

(± 9 mos.)

DECIDUOUS DENTITION

EARLY CHILDHOOD(Pre-school age) INFANCY

5 months in utero

7 months in utero

PRENATAL

Birth

6 mos.(± 2 mos.)

9 mos.(± 2 mos.)

1 year

(± 3 mos.)

18 months

(± 3 mos.)

THE THREE TYPES OF TERMINAL PLANES

FLUSH PLANE MESIAL STEP DISTAL STEP

TYPE TYPE TYPE

ESSENTIAL FACTORS FOR A SMOOTH TRANSITION FROM PRIMARY TO

PERMANENT DENTITION

1. Primate space.

2. General spacing.

3. Preservation of “leeway space”.

4. Sequences of eruption.

5. Tooth size and jaw in harmony.

PERMANENT DENTITION - ESTABLISHMENT & RELATIONSHIPS

GENERAL OBJECTIVES:

Explain the establishment of the occlusion of the permanent dentition.

SPECIFIC OBJECTIVES:

1. Describe the eruption sequence and timing of permanent teeth.

2. Describe the desirable eruption patternand identify variations of normality.

3. Explain how the inter-canine distancechanges when incisors erupt.

4. Explain temporary minor mandibularcrowding.

5. Explain the ugly ducking stage.

SPECIFIC OBJECTIVES (con’t)

6. Explain space relationships in replacement

of canines and primary molars.

7. Describe normal closure of a maxillary midline diastema.

8. Project from molar relationships in theprimary dentition, the type of Angleclassification that will result.

9. Describe and illustrate Angle’s classification

of occlusion: class I, class II with divisions

and subdivisions, class III.

10.Recognize acceptable overbite and overjetrelationships in the permanent dentition.

STEPS OF TOOTH ERUPTION

1.Pre-emergent eruption - Pre-eruptive phase

a) resorption of the bone and primary tooth

roots

b) the eruption mechanism

2.Post-emergent eruption - Eruptive phase

a) post-emergent spurt - Eruptive phase

(Pre-functional)

Steps of Tooth Eruption (con’t)

2.

b) juvenile occlusal equilibrium

Eruptive phase (Functional)

c) adult occlusal equilibrium

Primary tooth

Enamel

Permanent tooth

Apex

Bone trabeculae at fundus

Bone trabeculae at fundus

Apex

Bone trabeculae at

alveolar crest

Enamel

LOCAL, SYSTEMIC AND CONGENITAL FACTORS THAT CAN INFLUENCE THE ERUPTION OF THE

TEETH.

Local

Systemic

Congenital

• Two rows of teeth• Ectopic eruption• Infected primary teeth• Ankylosis

• Primary failure of eruption• Hypothyroidism

• Down’s Syndrome• Achondroplastic Dwarfism• Cleidocranial Dysplasia

ECTOPIC ERUPTION/IMPACTIONS

Primary dentition• Extremely rare in primary dentition

Permanent dentition• Permanent molars

– 1st > 2nd; maxillary > mandibular– Incidence of 1st molar: - 2-3%

• Suggested etiologies include– Small maxilla– Posterioly positioned maxilla

relative to cranial base

• Etiologies (continued):

– Molar path of eruption

– Mesiodistal dimension

– Asynchronization between tuberosity

growth and molar eruption

– Retarded calcification and eruption

– Genetic

• Treatment

– Mild: observation (Pulver: 2/3 of

ecotypically erupting 1st molars will

self-correct)

– Moderate: brass ligature; spring;

distalize 1st permanent molar

–Severe: extract primary molar and

distalize 1st permanent molar.

• Permanent mandibular incisor(s)

– Common: typically erupt lingual to over-

retained primary incisors

– Rationale for treatment: allow teeth

to move into area of attached gingival

– Treatment: extract primary incisors;

tongue pressure will typically push

incisors into place

• Permanent maxillary canines

– Prevalence 1-2%

– Reported incisor root resorption - 50%

(Ericson and Kurol)

– Diagnosis

• Palpation

• Radiographic

• Radiographic (continued)

– poor prognosis indicators

– permanent canine crown mesial of

midline of lateral incisor root

– palatal displacement of permanent

canine as viewed on cephalometric

film

ANKYLOSISPrimary dentition• First molars most common• Typically require no treatment and exfoliate

normally• Involved second molar maybe indication of

agenesis of succedaneous tooth• Treatment:

– Prevent space loss»Build-up occlusion surface of

involved tooth»Extract tooth and place space

maintainer

Permanent dentition• Difficult to treat ankylosed permanent teeth

– Create adequate space– Attempt to break area of ankylosis with

luxation– Immediately apply orthodontic traction

force (>50 G) or– Surgically reposition tooth and hold in

position orthodontically (pulp

endodontic therapy necessary)– Ankylosed permanent teeth tend to re-

ankylose.

Primary tooth

Enamel

Permanent tooth

Apex

Bone trabeculae at fundus

Bone trabeculae at fundus

Apex

Bone trabeculae at

alveolar crest

Enamel

Chronology of Tooth DevelopmentPermanent Dentition

Calcificationbegins

Crowncompleted

Eruption Root completed

Tooth Max. Mand. Max. Mand. Max. Mand. Max. Mand.

Central 3 mo. 3 mo. 4 ½ yr. 3 ½ yr. 7 ¼ yr. 6 ¼ yr. 10 ½ yr. 9 ½ yr.

Lateral 11 mo. 3 mo. 5 ½ yr. 4 yr. 8 ¼ yr. 7 ½ yr. 11 yr. 10 yr.

Canine 4 mo. 4 mo. 6 yr. 5 ¾ yr. 11 ½ yr. 10 ½ yr. 13 ½ yr. 12 ¾ yr.

1st PreMolar

20 mo. 22 mo. 7 yr. 6 ¾ yr. 10 ¼ yr. 10 ½ yr. 13 ½ yr. 13 ½ yr.

2nd PreMolar

27 mo. 28 mo. 7 ¾ yr. 7 ½ yr. 11 yr. 11 ¼ yr. 14 ½ yr. 15 yr.

1st Molar 32 wk.in utero

32 wk.in utero

4 ¼ yr. 3 ¾ yr. 6 ¼ yr. 6 yr. 10 ½ yr. 10 ¾ yr.

2nd Molar 27 mo. 27 mo. 7 ¾ yr. 7 ½ yr. 12 ½ yr. 12 yr. 15 ¾ yr. 16 yr.

3rd Molar 8 yr. 9 yr. 14 yr. 14 yr. 20 yr. 20 yr. 22 yr. 22 yr.

ERUPTION SEQUENCE AND TIMING

Age 6: 16,26,36,46,41,31

Age 8: 42,32,11,12,21,22

Age 11: 33,34,43,44,14,24,

Age 12: 13,23,35,45,15,25

At dental age 9, the maxillary lateral incisors have been in place for 1 year, and root formation on other incisors and first molars is nearly

complete.

Root development of the maxillary canines and all second premolars is just beginning, while about one third of the root of the mandibular

canines and all of the first premolars have been completed.

Dental age 11 is characterized by the more or less simultaneous eruption of

the mandibular canines, mandibular first premolars, and maxillary first

premolars

Dental age 12 is characterized by eruption of the remaining

succedaneous teeth (the maxillary canine and the maxillary and

mandibular second premolars)

and, typically a few months alter, the maxillary and mandibular second molars.

By dental age 15, the roots of all permanent teeth except the third molars

are complete, and crown formation of third molars often has been completed.

7 years old 9 years old 14 years old

Changes in the axial inclination due to the eruption of the maxillary anterior teeth (Broadbent, 1957).

ERUPTION OF PERMANENT MOLARS

MESIAL STEPBECAUSE OF MESIAL STEP ERUPT IN CUSP-GROOVE RELATIONSHIP

6/6

6/6

DISTAL STEP BECAUSE OF DISTAL STEP ERUPT IN DISTAL RELATIONSHIP

6/6

6/6

Primary Permanent

Distal Step

Flush Terminal Plane

Mesial Step

Class II

End-End

Class I

Class IIIMinimal Growth Differential

Forward Growth of Mandible

Shift of Teeth