Anatomy and Classification of Teeth - Dental anatomy is the study of tooth structure, development, appearance, and classification. - The anatomic crown is the part of the tooth covered in enamel above the cementoenamel junction. - The crown is mostly composed of dentin, with the pulp chamber inside. - The anatomic root is found below the cementoenamel junction and is covered with cementum. - Teeth can be classified as incisors, canines, premolars, and molars based on their function. - Primary teeth, also known as deciduous or baby teeth, are temporary teeth that are eventually replaced. - The dental formula for primary teeth in humans is 2.1.0.22.1.0.2. - Primary teeth include incisors, canines, and molars. - All primary teeth are later replaced with permanent teeth. - The Universal Numbering System is used to identify adult human teeth. - Humans have 32 permanent teeth, with 16 in the maxilla and 16 in the mandible. - The dental formula for permanent teeth is 2.1.2.32.1.2.3. - Permanent teeth include central incisors, lateral incisors, canines, premolars, molars, and third molars (wisdom teeth). - Supernumerary teeth may occasionally form, while hypodontia refers to the development of fewer teeth than usual. - Male teeth and jaws tend to be larger on average than female teeth and jaws.

Parts of a Tooth - Enamel is the hardest and most mineralised substance in the body. - It is primarily composed of hydroxyapatite, a crystalline calcium phosphate. - Enamel is normally visible and varies in color from light yellow to grayish white. - The wear rate of enamel is approximately 8 micrometers per year. - Enamel does not contain collagen but relies on dentin for support. - Dentin is the substance between enamel or cementum and the pulp chamber. - It is secreted by odontoblasts in the dental pulp. - Dentin is porous and yellowish in color, composed of 70% inorganic materials. - Dentin compensates for the brittleness of enamel and provides support. - Dentin has microscopic channels called dentinal tubules that radiate outward from the pulp cavity to the exterior cementum or enamel border. - The diameter of dentinal tubules ranges from 2.5 μm near the pulp to 900nm near the dentino-enamel junction. - The tubules do not intersect with each other, and their length is determined by the radius of the tooth. - Dentin can be classified into three types: primary, secondary, and tertiary. - Cementum is a specialised bone-like substance that covers the root of a tooth. - It is approximately 45% inorganic material (mainly hydroxyapatite), 33% organic material (mainly collagen), and 22% water. - Cementum is excreted by cementoblasts within the root of the tooth and is thickest at the root apex. - Its principal role is to serve as a medium for the attachment of periodontal ligaments to the tooth for stability. - The dental pulp is the central part of the tooth filled with soft connective tissue. - It contains blood vessels and nerves that enter the tooth from a hole at the apex of the root. - Odontoblasts, located along the border between dentin and pulp, initiate the formation of dentin. - Other cells in the pulp include fibroblasts, preodontoblasts, macrophages, and T lymphocytes. - The pulp is commonly referred to as the 'nerve' of the tooth.

Tooth Development and Eruption - Tooth development is a complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. - Enamel, dentin, cementum, and the periodontium must all develop during appropriate stages of fetal development for a healthy oral environment. - Primary teeth start to form between the sixth and eighth weeks of embryonic development, while permanent teeth begin to form in the twentieth week. - Tooth development is divided into stages: bud, cap, bell, and maturation. - The tooth bud consists of the enamel organ, dental papilla, and dental follicle. - Tooth eruption is the process in which teeth enter the mouth and become visible. - Primary teeth erupt from around six months to two years of age, while permanent teeth start erupting around six years old. - The periodontal ligaments play an important role in tooth eruption. - Different theories have been proposed for the cause of tooth eruption, with the most widely accepted belief being that the periodontal ligaments provide the main impetus for the process. - The onset of primary tooth loss has been found to correlate strongly with somatic and psychological criteria of school readiness.

Supporting Structures of Teeth - The periodontium is the supporting structure of a tooth, attaching it to surrounding tissues and allowing sensations of touch and pressure. - It consists of cementum, periodontal ligaments, alveolar bone, and gingiva. - Cementum is the only part of a tooth that is part of the periodontium. - Periodontal ligaments connect the alveolar bone to the cementum. - Alveolar bone surrounds the roots of teeth, providing support and creating sockets. - Alveolar bone forms the alveolus around teeth. - Osteoblasts create bone, and osteoclasts destroy it. - Compressive force on a tooth leads to bone resorption, while tension from periodontal ligaments results in bone formation. - Alveolar bone is modified throughout life. - Gingiva is the mucosal tissue that overlays the jaws. - Three types of epithelium associated with gingiva: gingival, junctional, and sulcular epithelium. - Gingival epithelium is visible in the mouth. - Junctional epith