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1. Tooth Anatomy and its Enigma

2. Contents Introduction Tooth Nomenclature Development and Growth of teeth Physiological form and function Tooth alignment Permanent incisors Permanent canines Permanent molars Clinical implications

3. Wheeler’s Dental anatomy, Physiology & Occlusion 10 th edition Introduction Humans have 2 sets of dentition in their lifetime. The first set is the primary or deciduous dentition which begin to form prenatally at about 14 weeks and shed by the age of 6 years.

4. Wheeler’s Dental anatomy, Physiology & Occlusion 10 th edition The permanent dentition consisting of 32 teeth is completed from 18 to 25 years of age if the third molar is included. There are four or more centers of formation (developmental lobes) for each tooth. The formation of each center proceeds until a coalescence of all of them takes place. The size of teeth is largely genetically determined.

5. Wheeler’s Dental anatomy, Physiology & Occlusion 10 th edition Tooth Nomenclature In clinical practice, some “shorthand” system of tooth notation is necessary for recording data. The symbolic system for the permanent dentition was introduced by Adolph Zsigmondy of Vienna in 1861 and then modified for the primary dentition in 1874. In 1947, a committee of the American Dental Association (ADA) recommended the symbolic system (Zsigmondy/ Palmer) as the numbering method of choice. Zsigmondy/Palmer notation for primary dentition Zsigmondy/Palmer notation for permanent dentition

6. Wheeler’s Dental anatomy, Physiology & Occlusion 10 th edition However, because of difficulties with keyboard notation of the symbolic notation system, the ADA in 1968 officially recommended the “universal” numbering system. The universal system of notation for the primary dentition uses uppercase letters for each of the primary teeth. In the universal notation system for the permanent dentition, the maxillary teeth are numbered from 1 through 16, beginning with the right third molar. Beginning with the mandibular left third molar, the teeth are numbered 17 through 32. Universal notation for primary dentition Universal notation for primary dentition

7. Wheeler’s Dental anatomy, Physiology & Occlusion 10 th edition A two-digit system proposed by Fédération Dentaire Internationale (FDI) for both the primary and permanent dentitions has been adopted by the World Health Organization and accepted by other organizations, such as the International Association for Dental Research. In the two-digit FDI system for the primary dentition, the first digit indicates the quadrant: 1 to 4 for the permanent dentition, and 5 to 8 for the primary dentition. The second digit indicates the tooth within a quadrant: 1 to 8 for the permanent teeth, and 1 to 5 for the primary teeth.

8. Development and Growth of Teeth Tooth formation occurs in the sixth week of intrauterine life with the formation of primary epithelial band. The primitive oral cavity( stomadeum ) is lined by stratified squamous epithelium called the oral ectoderm. The oral ectoderm contacts the endoderm of the foregut to form buccopharyngeal membrane. Orban’s Oral Histology and Embryology, 13/e

9. Orban’s Oral Histology and Embryology, 13/e Stages in Tooth Development At about 7 th week the primary epithelial band divided into a lingual process called dental lamina and a buccal process called vestibular lamina. All deciduous teeth arise from dental lamina, later the permanent successors arise from its lingual extension & molars from distal extension.

10. STAGE MAIN PROCESS INVOLVED DESCRIPTION MICROSCOPIC APPEARANCE INITIATION INDUCTION Ectoderm lining stomadeum gives rise to oral epithelium and then to dental lamina, adjacent to deeper mesenchymal and neural crest cells and separated by a basement membrane BUD STAGE PROLIFERATION Growth of dental lamina into bud that penetrates growing mesenchyme CAP STAGE PROLIFERATION DIFFERENTIATION MORPHOGENESIS Enamel organ forms into a cap, surrounding mass of dental papilla from the mesenchyme and surrounded by mass od dental sac also from the mesenchyme . Formation of the tooth germ BELL STAGE PROLIFERATION DIFFERENTIATION MORPHOGENESIS Differentiation of enamel organ into bell with four cell types and dental papilla into two cell types APPOSITION INDUCTION PROLIFERATION Dental tissues secreted as matrix in successive layers MATURATION MATURATION Dental tissues fully mineralize to their mature levels Orban’s Oral Histology and Embryology, 13/e

11. Shafer’s Textbook of Oral Pathology 7th Edition Textbook of Oral Medicine by Anil Govindrao Ghom 3 rd edition Defects in Initiation Anodontia Rare genetic disorder characterised by congenital absence of all or few primary or permanent teeth Associated syndromes: Ectodermal dysplasia, cleft lip and palate, Ehlers Danlos , Hurlers, Turners, Gorlin Goltz , Sturge Weber. Forms Partial Anodontia Complete Anodontia

12. Supernumerary tooth Results from continued proliferation of primary dental lamina to form 3 rd tooth germ. Classification: Garvey et al; Supernumerary Teeth- An Overview of Classification, Diagnosis and Management; J Can Dent Assoc 1999; 65;612-6

13. Proliferation Defects Microdontia This term is used to describe teeth which are smaller than normal. Microdontia involving only a single tooth is a rather common condition. It affects most often the maxillary lateral incisor and the third molar. Shafer’s Textbook of Oral Pathology 7th Edition Textbook of Oral Medicine by Anil Govindrao Ghom 3 rd edition Peg shaped lateral seen in maxillary region, showing cone shaped crown

14. Macrodontia Refers to teeth that are larger than normal. Relative generalized macrodontia is somewhat more common and is a result of the presence of normal or slightly larger than normal teeth in small jaws Shafer’s Textbook of Oral Pathology 7th Edition Textbook of Oral Medicine by Anil Govindrao Ghom 3 rd edition

15. Clinical and Endodontic considerations in Management of Mandibular Molar Multiplicities f roots and root canals have been documented as case reports in both lower bicuspids. Additional developmental anatomic variations are also seen. The lingual inclination of the crown tends to direct instruments buccally . Cavity preparation should be done with the instrument parallel to the long axis of the tooth. In first premolars C-shaped canals show higher incidence. In mandibular premolars with 3 canals, cervical half of the root is wider than usual with little or no taper. CBCT is a useful tool for preoperative diagnosis of complex anatomy. Surgical endodontics of anomalous mandibular premolars should be performed in conjunction with orthograde root canal treatment.

16. Clinical considerations in Management of Molars In mandibular first molars, a sub- occlusal transverse ridge of enamel called “Rainey’s ridge” connects to other blocks of enamel to contribute to tooth strength. It is an inter-connection of distolingual cusp and mesiobuccal cusp. In maxillary molars, there is a similar structure of enamel called “Rainey’s web”. Traditionally, over cutting teeth according to G.V. Black’s principles, greatly reduces tooth strength. Micro-dentistry cavity design attempts to retain these structures and remove only damaged carious enamel and dentin.

17. References Wheeler’s Dental anatomy, Physiology & Occlusion, 10 th edition Orban’s Oral Histology and Embryology, 13 th edition Shafer’s Textbook of Oral Pathology, 7th Edition Textbook of Oral Medicine by Anil Govindrao Ghom , 3 rd edition Garvey et al; Supernumerary Teeth- An Overview of Classification, Diagnosis and Management; J Can Dent Assoc 1999; 65;612-6 Woelfel’s Dental Anatomy 9 th edition Green L.; Treatment options for peg-shaped laterals using direct composite bonding. Int. Dent. SA Vol. 12, NO. 1 Clinical Operative Dentistry Principles and Practices, 2 nd edition