A Tooth is Defined as “One of the hard tissues that are positioned on the jaws and help in holding and mastication of food, also as weapons of offense and defense in lower animals.”
♦️ Human dentitions are divided into many classes of teeth based on the appearance and function or position.
♦️ Different Classes of Teeth and Their Types
- INCISORS: Incisors are named because they are used to incise or cut food. They are located in the front part of the mouth and have sharp, thin edges for cutting.
- CUSPIDS: Cuspids, also referred to as canines, are at the angles of the mouth. Each tooth has a single cusp instead of an incisal edge and are designed for cutting and tearing.
- BICUSPIDS: Bicuspids, also referred to as premolars, are similar to the cuspids. They have two cusps used for cutting and tearing, and an occlusal surface that is wider to crush the food.
- MOLARS: Molars are located in the back part of the mouth. Their size gradually becomes smaller from the first to third molar. Each molar has four or five cusps; these teeth are shorter and blunter in shape than other teeth and provide a broad surface for grinding and chewing solid masses of food.
♦️ EVOLUTION OF TEETH:
- HOMODONT: It is a Greek term, meaning ‘same teeth’. Animals, which have one/single type of dentition where in all are similar in shape, indicative of a uniform diet.
Example: Fishes, amphibians, and most reptiles. Crocodile has cone shaped teeth as also whales and dolphins.
- HETERODONT: Term derived from Greek, meaning ‘different teeth’, which refers to animals having more than a single type of tooth morphology and are of different sizes and shapes, specialized for different tasks.
Example: Man has different types of teeth
- MONOPHYODONT: Dentition in which the species has only one set of teeth, which are functional throughout the life.
Example: Reptiles
- DIPHYODONT: Dentition in which the species have two sets of teeth, one set (called ‘deciduous’) being shed and replaced by a permanent set of teeth, which are functional throughout the life.
Example: Cats, dogs, and humans
- POLYPHYODONT: Dentition in which the species has many sets of teeth, which get replaced and remain functional throughout the life. Example: Seen in lower vertebrates, mainly fishes.
♦️ DEFINITIONS:
- MANDIBLE: It is the complete lower jaw which is made up of a single pair of bones
- MAXILLA: It is a bone or part in the upper jaw that contains canine, premolar and molar teeth
- PREMAXILLA: It has paired bones present at the front of the upper jaw (maxilla) that contains incisor teeth on both sides in the midline.
♦️ THE DECIDUOUS DENTITION:
- Twenty deciduous teeth
- There are ten teeth each in the maxilla and mandible.
- Grouped into three classes as incisors, canines and molars.
- Synonyms of deciduous teeth – primary teeth, milk teeth, baby teeth or temporary teeth or lacteal teeth or juvenile teeth.
- There is a total of 20 primary teeth.
- Teeth (8 incisors, 4 cuspids and 8 molars)
- Incisors are the first primary teeth to erupt and usually between 6–9 months.
- The last teeth usually erupt in by 24 months.
- These are present till the permanent are erupted, i.e. 6 years.
- no premolars are developed in this dentition.
♦️ THE PERMANENT DENTITION:
- Thirty-two permanent teeth
- There are sixteen maxillary teeth and sixteen mandibular teeth.
- Grouped into four classes as incisors, canines, premolars and molars.
- Synonyms of permanent teeth are secondary, permanent or succedaneous teeth.
- Total of 32 secondary teeth (8 incisors, 4 cuspids, 8 premolars and 12 molars)
- First secondary tooth to erupt in the oral cavity is the first molar, and it usually erupts around 6 years of age.
- Last to erupt is the 3rd molar at around the age of 21 years.
- Other teeth are usually present by the age of 14 years.
♦️ DENTAL FORMULA:
- It is used to represent the arrangement of the teeth in upper and the lower row.
🔷Permanent Dentition
Dental formula = 2123/2123.
There are 2 incisors, 1 canine, 2 premolars and 3 molars in one row.
🔷Deciduous dentition
Dental Formula = 2102/2102
There are 2 incisors, 1 canine, 0 premolars and 2 molars in one row.