Dental Anatomy 1st lecture.pdf

# **INTRODUCTION** - Human dentition is diphyodont - 2 sets of dentitions - Primary/deciduous/baby/milk - 20 teeth in total - Incisors/canines/molars - Smaller size - Begins to form prenatally at about 14 weeks in utero, and is completed...

# **INTRODUCTION** - Human dentition is diphyodont - 2 sets of dentitions - Primary/deciduous/baby/milk - 20 teeth in total - Incisors/canines/molars - Smaller size - Begins to form prenatally at about 14 weeks in utero, and is completed postnatally at about 3 years of age - Begin to appear in the oral cavity at the mean age of 6 months, and the last emerge at a mean age of 28 ± 4 months - Secondary/permanent/succedanous - 32 teeth in total - Incisors/canines/premolars/molars - Bigger size - Begin to appear in the oral cavity at the mean age of 6 years - Completed (including the roots) at about 14 to 15 years of age (avg 12+ years), except for the third molars, which are completed at 18 to 25 years of age # **WHY DO WE HAVE TO HAVE 2 SETS OF TEETH?** - The transition or mixed dentition period in which there is a mixture of deciduous and succedaneous teeth present. The transition period lasts from about 6 to 12 years of age and ends when all the deciduous teeth have been shed - The transition from the primary dentition to the permanent dentition begins with the emergence of the first permanent molars, shedding of the deciduous incisors, and emergence of the permanent incisors - The jaws have to accommodate the increased number of permanent teeth and their bigger size. # **STAGES OF HUMAN DENTITION** - Edentulous stage: 0 - 6 months - Eruption of primary dentition: 6 months-2.5 years - Functioning primary dentition: 2.5 – 6 years - Mixed dentition: 6-12 years - Permanent dentition: 12+ years - Full permanent dentition: (18-25)+ years # **DENTAL FORMULA** - I: incisors - C: Canines - PM: premolars - M: molars - Deciduous are preceded by the letter D - The numbers refer to the number of teeth of each type in the upper then the lower jaw for one side only. ## Deciduous teeth **DI 2/2 DC 1/1 DM 2/2** = 10 ## Permanent teeth **I 2/2 C 1/1 PM 2/2 M 3/3** = 16 # **NOMENCLATURE** - System of names, used to describe or classify the material included in the subject; here teeth could be classified according to: - **Set trait:** Deciduous or permanent - **Arch trait:** Maxillary or mandibular - **Class trait:** Incisor/canine/premolar/molar - **Type trait (order within a class):** Central or lateral, First/second/third - **Side:** Right or left - **QUADRANT** - Upper right - UL - LR - LL # **NOMENCLATURE** - **Crown** - **Root** - CEJ: the cervical line, separates the anatomic crown from the anatomic root at cervix. Junction between two tissues--the enamel and cementum. The cervical line is important in your laboratory drawings and clinical work. - **Root apex** - Bifurcation, trifurcation. - **Enamel** - **Cementum** # **TOOTH STRUCTURE** - **Enamel, dentine, pulp (coronal, radicular) cementum** - **Crown:** pulp chamber - **Root(s):** root canal(s). # **DENTAL TISSUES** - **A. Enamel:** The protective outer surface of the anatomic crown. It is 96% mineral and is the hardest tissue in the body. - **B. Dentin:** Located in both the crown and root, it makes up the bulk of the tooth beneath the enamel and cementum. It lines the pulp cavity. - **C. Cementum:** This substance covers the surface of the anatomic root. - **D. Pulp:** The central, innermost portion of the tooth. It has formative, sensory, nutritive, and functions during the life of the tooth. # **ANTERIOR VS POSTERIOR** - **Incisors teeth:** incisal edges. - **Canines:** single cusps. - **Premolars/molars:** two or more cusps. # **THE ROOT IS FIXED IN THE BONY PROCESS OF THE JAW CALLED THE ALVEOLAR PROCESS.** # **THE BONE OF THE TOOTH SOCKET IS CALLED THE ALVEOLUS (ALVEOLI), SEPTA.** # **THE FULLY ERUPTED CROWN IS PARTLY COVERED AT THE CERVICAL THIRD IN YOUNG ADULTS BY THE GINGIVA OR GUMS.** - **Mucogingival junction** # **A. CROWN. THE TERM CAN BE DEFINED IN TWO WAYS.** - The anatomical crown is covered with enamel. - The clinical crown is the portion of the anatomical crown that is visible clinically. It is what you see when you look in the mouth. # **ROOT. THE TERM CAN BE DEFINED IN TWO WAYS.** - The anatomical root is the portion of the tooth that is covered with cementum, a bone-like substance that facilitates anchorage of the tooth in its bony socket (the alveolus). - The clinical root is that part of the anatomical root that is actually embedded in the jaw (not visible clinically). In a patient with advanced bone loss, the clinical root may be reduced in size. # **SURFACES AND RIDGES** - Incisors and canines have four surfaces and a ridge. - Premolars and molars have five surfaces. - Surfaces are named according to their positions and uses. - **Mesial (proximal surface)** - **Distal (proximal surface)** - **Labial/Buccal (Facial)** - **Lingual/Palatal** - **Occlusal/incisal** - **Contact area:** The area of the mesial or distal surface of a tooth that touches its neighbour. # **DIVISION INTO THIRDS** # **NOMENCLATURE** - Notation systems is then invented to ease classification by simple letters and/or symbols - 1. Palmer/Zigmondy notation system - 2. Universal numbering system - 3. FDI numbering system # **UNIVERSAL NUMBERING SYSTEM** - Palmer – difficulty in keyboard typing - Uppercase letters for deciduous teeth - Consecutive from A to T - Following a clockwise order from maxillary right second molar to mandibular right second molar - Numbers for permanent teeth - Consecutive from 1 to 32 - Following a clockwise order from maxillary right third molar to mandibular right third molar # **FDI NUMBERING SYSTEM** - Each tooth is allocated a two-digit number; the left designates the quadrant (permanent dentition have the numbers 1-4 and in deciduous have the numbers 5 – 8, both clockwise) and the right designates the tooth order 1-8 (central incisor till third molar) - **Examples** - Mandibular right permanent canine 43 - Maxillary left deciduous lateral incisor 62