Arrangement of Teeth Primary Dentition refers to the twenty deciduous teeth, also called baby teeth. Secondary Dentition refers to the thirty-two permanent teeth. The dentition is divided into two arches: upper and lower, also known as maxillary and mandibular arches. Each arch is arranged into a right and a left half. Thus there are four quadrants. The line that divides left and right quadrants is the median line or midline of the face.
The permanent teeth that replace the deciduous teeth are called succedaneous teeth. Permanent molars are nonsuccedaneous teeth. The permanent premolars replace the deciduous molars. A mixed dentition is composed of some permanent and some deciduous teeth.
Naming and Coding Teeth Dentition-arch-quadrant-tooth ex: permanent-max-left-central incisor Universal System 1-32 permanent teeth A-T deciduous teeth
Palmer Notation System Each of the four quadrants is given his own prefix symbol. The number or letter assigned to the tooth depends on its position relative to the midline. The first number indicates the quadrant and whether the tooth is permanent or deciduous.
Palmer Notation System 8765432112345678 8765432112345678 Maxillary Right Mandibular Right Midline Central incisor Lateral incisor Canine First premolar Second premolar First molar Second molar Third molar Maxillary Left Maxillary- Mandibular dividing line Mandibular Left Permanent Teeth
Palmer Notation System EDCBAABCDE Maxillary Right Mandibular Right Central incisor Lateral incisor Canine First molar Second molar Maxillary Left Mandibular Left EDCBAABCDE Primary Teeth
FDI System (Fédération Dentaire Internationale) Each tooth – permanent or deciduous is given a two-digit number The second digit indicates the position of the tooth relative to the midline The first number indicates the quadrant and whether the tooth is permanent or deciduous
Development and Form 6th week of fetal life deciduous teeth begin to develop from tooth germs 4th month of fetal life permanent teeth begin to develop 4-5th month of fetal life primary teeth begin to calcify. This process continues until ~3-4th year after birth, when the roots of deciduous teeth are fully formed Birth permanent teeth begin to calcify and continue until ~25th year (third molar roots)
Developmental Lobes Each tooth begins to develop from 4 or more growth centers or developmental lobes Anterior teeth and maxillary premolars develop from 4 lobes – 3 labials and lingual. As the lobes grow, they coalesce. The lines formed by the fusion are called developmental grooves Mamelons are the incisal ridges of the three labial developmental lobes of anterior teeth The lingual lobe makes up the cingulum of the tooth
Lobes and Cusps Max. 1st molar: two major facial lobes (MB,DB) one major lingual lobe (ML) one minor lingual lobe (DL) one rudimentary lobe (Carabelli) Max 2nd molar: 4 lobes; usually does not have cusp of carabelli Max 3rd molar: 3-4 lobes
Lobes and Cusps Mand. 1st molar: 5 lobes 4 major cusps (MB, DB, ML, DL) 1 minor cusp (D) Mand 2ed molar: 4 lobes, cusps. Mand. 3rd molar: 4 lobes, cusps. The most unpredictable teeth in size and shape. They are also the most likely to be missing.
Eruption General rules: Mandibular teeth usually precede maxillary (about 1 month). Teeth in both jaws erupt in pairs ( one on the right and one on the left). Teeth usually erupt earlier in girls than in boys. all deciduous teeth usually erupted by 2 3/4 years old.
Eruption of Permanent teeth 1st molar – 1st permanent tooth to erupt. They emerge distal to the deciduous 2nd molars (~6 years old). Mesial drift occurs Spaces between deciduous teeth are closed. If deciduous tooth is lost prematurely, the permanent molar moves into the available space a may keep a premolar or canine from erupting.
Eruption of Permanent Teeth Exfoliation: process by which the roots of a baby tooth are resorbed and dissolved until the tooth falls out. As a permanent tooth erupts, the pressure activates osteoclasts which in turn destroy the roots of deciduous teeth. Permanent teeth erupt lingually to the deciduous teeth.
Most Common Pattern of Eruption Mand 1st molars – Max 1st molars Mand central incisors – Max central incisors Mand lateral – Max lateral Mand canines – Mand 1st PM- Max 1st PM Max 2nd PM – Mand 2nd PM - Max Canine Mand 2nd molars – Max 2nd molars Mand 3rd molars – Max 3rd molars
Pattern of Eruption Note: 1.Max canines usually do not erupt until premolars have erupted. 2.Mand canines and 1st Premolars often erupt simultaneously. 3.Max 2nd premolars often erupt before the mandibular counterparts.
Pattern of Eruption 3rd molars: Do not appear until 17 years of age or later Most likely to be impacted (Mandibular > Maxillary) Most common teeth to be congenitally missing
Pattern of Eruption As teeth erupt and meet their antagonist on the opposing arch, they form the occlusal plane. The line of the occlusal surfaces is known as occlusal plane. The curved alignment of the occlusal plane is known as curve of Spee.