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 years 2.Mixed Dentition: 6-12 years 3.Young Permanent Dentition: adolescence 4.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 pattern and identify variations of normality. 3.Explain how the inter-canine distance changes when incisors erupt. 4.Explain temporary minor mandibular crowding. 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 the primary dentition, the type of Angle classification 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 overjet relationships 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 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

ANKYLOSIS Primary 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 Apex Bone trabeculae at alveolar crest Enamel

Chronology of Tooth Development Permanent Dentition

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 old9 years old14 years old Changes in the axial inclination due to the eruption of the maxillary anterior teeth (Broadbent, 1957).

ERUPTION OF PERMANENT MOLARS MESIAL STEP BECAUSE OF MESIAL STEP ERUPT IN CUSP-GROOVE RELATIONSHIP 6/6 DISTAL STEP BECAUSE OF DISTAL STEP ERUPT IN DISTAL RELATIONSHIP 6/6

PrimaryPermanent Distal Step Flush Terminal Plane Mesial Step Class II End-End Class I Class III Minimal Growth Differential Forward Growth of Mandible Shift of Teeth