--- title: "Deciduous Teeth | Anatomy and Physiology I" description: "Deciduous teeth are the first 20 primary teeth in humans, used for chewing, speech, and keeping space in the dental arch before permanent teeth erupt." canonical: "https://fiveable.me/anatomy-physiology/key-terms/deciduous-teeth" type: "key-term" subject: "Anatomy and Physiology I" unit: "Unit 23" --- # Deciduous Teeth | Anatomy and Physiology I ## Definition Deciduous teeth are the first set of human teeth, also called primary, baby, or milk teeth. In Anatomy and Physiology I, they matter because they start chewing, speech, and jaw development before permanent teeth replace them. ## What It Is Deciduous teeth are the first set of teeth that appear in human development, and in Anatomy and Physiology I you usually hear them discussed as the primary teeth that later get replaced by permanent teeth. An adult mouth has 32 permanent teeth, but a child’s first dental set has 20 deciduous teeth. They include incisors, canines, and molars, but not premolars, which are part of the permanent set. These teeth do real work while they are present. They cut and grind food, help a child form sounds clearly, and support normal swallowing and facial growth. They also act like placeholders in the jaws. Each tooth helps maintain the space and alignment needed for the next tooth underneath it to erupt into the right spot. The timing matters. Deciduous teeth usually begin erupting in infancy, then are gradually lost as permanent teeth develop below them. The roots of the baby teeth are resorbed as the permanent teeth push upward, which is why the older tooth loosens and falls out. That replacement process is part of normal growth, not damage. In this course, deciduous teeth are best understood as part of the mouth and digestive tract, not just as a dental topic. The oral cavity starts mechanical digestion, and teeth are the main structures doing that job. If the baby teeth are lost too early or erupt out of sequence, chewing and spacing can be affected, which is why the mouth, gums, jaw, and future teeth all have to be thought about together. A common way to picture them is as the first draft of the dentition. They are smaller than permanent teeth, fit a child-sized jaw, and prepare the mouth for the later adult set without needing the body to grow all 32 teeth at once. ## Why It Matters Deciduous teeth show how structure and function match each other in the mouth. Their smaller size fits the child’s jaw, and their early eruption lets a growing child chew solid food before the permanent teeth appear. That makes them a simple but useful example of how anatomy changes with development. They also connect directly to the course topic of the mouth, pharynx, and esophagus. When you study digestion, you are not just memorizing tooth names. You are tracing how food is mechanically broken down into a bolus, how speech is supported, and how the oral cavity keeps space organized for later growth. This term also helps explain why tooth loss or crowding can matter long before adulthood. If a deciduous tooth is lost too early, nearby teeth can drift into the empty space and block the path for the permanent tooth. If the baby teeth are retained too long, they can interfere with eruption. That makes deciduous teeth part of a developmental sequence, not a separate mini version of the adult mouth. ## Connections ### [Permanent Teeth](/anatomy-physiology/key-terms/permanent-teeth) Permanent teeth are the later set that replace deciduous teeth. In A&P I, the connection is developmental: the baby teeth hold space until the adult teeth erupt, and then they are shed. Comparing the two sets helps you remember why children have smaller teeth and fewer total teeth at first. ### Eruption Eruption is the movement of a tooth into the mouth. Deciduous teeth erupt first, and later the permanent teeth erupt underneath or after them depending on the tooth type. When you trace eruption timing, you can see why loose baby teeth and incoming adult teeth are part of one normal sequence. ### Dental Arch The dental arch is the curved row formed by the teeth in the upper and lower jaws. Deciduous teeth help shape that arch during early childhood by maintaining spacing and alignment. If the arch is crowded or loses a primary tooth too early, later alignment can change. ### [Gingivae](/anatomy-physiology/key-terms/gingivae) Gingivae, or gums, surround and support the teeth as they emerge and sit in place. Deciduous teeth erupt through the gingivae, and the gum tissue helps protect the developing mouth during that process. This connection shows how teeth are not isolated structures, but part of a larger oral support system. ## On the AP Exam A quiz question might show a child’s mouth and ask you to identify the primary teeth or explain why a lost baby tooth usually gets replaced later. On a short-answer item, you may need to trace how deciduous teeth support chewing, speech, and spacing in the jaws. In a lab image, you could be asked to tell a deciduous tooth from a permanent one by size, number, or stage of eruption. The move is to connect the visible structure to development, not just to name it. ## deciduous teeth vs Permanent Teeth Deciduous teeth are the first, temporary set of 20 teeth that appear in childhood. Permanent teeth are the later set that replace them and add premolars, giving the adult mouth 32 teeth. If a question asks about replacement, eruption in adulthood, or the full adult dentition, it is pointing to permanent teeth, not deciduous teeth. ## Key Takeaways - Deciduous teeth are the first 20 human teeth, also called primary, baby, or milk teeth. - They support chewing, speech, and the early stages of oral development. - These teeth hold space in the dental arch so permanent teeth can erupt in the right pattern. - They are normally shed as the roots resorb and the adult teeth come in. - In Anatomy and Physiology I, deciduous teeth belong to the mouth and digestion topic because they help start mechanical digestion. ## FAQs ### What are deciduous teeth in Anatomy and Physiology I? Deciduous teeth are the first set of human teeth that appear in childhood. They are temporary teeth that help with chewing and speech, then are replaced by permanent teeth as the mouth grows. ### How many deciduous teeth are there? Humans usually have 20 deciduous teeth. That number is smaller than the adult permanent set because the first set is built for a child-sized jaw and gets replaced later. ### What is the difference between deciduous teeth and permanent teeth? Deciduous teeth are the temporary baby teeth, while permanent teeth are the later adult teeth that replace them. Permanent teeth also include premolars, which deciduous teeth do not have. ### Why do deciduous teeth matter if they fall out? They matter because they do real work before they are shed. They help with chewing, support speech, and keep space in the dental arch so the permanent teeth can erupt into better positions. ## Related Study Guides - [23.3 The Mouth, Pharynx, and Esophagus ](/anatomy-physiology/unit-23/3-mouth-pharynx-esophagus/study-guide/N1XXcw0W2wfyxqZH) ## About This Document Canonical Fiveable pages are available as Markdown at the same path plus `.md`. - [llms.txt](https://fiveable.me/llms.txt): index of Fiveable's sections and URL patterns - [llms-full.txt](https://fiveable.me/llms-full.txt): complete subject and unit listing - [MCP server](https://fiveable.me/mcp): call Fiveable as tools instead of fetching pages (`https://fiveable.me/api/mcp`) - [MCP server for AP teachers](https://fiveable.me/mcp/teachers): a teacher's classes, assignments and AP-rubric grading (`https://fiveable.me/api/mcp/teacher`) ## Structured Data ```json {"@context":"https://schema.org","@graph":[{"@type":"LearningResource","@id":"https://fiveable.me/anatomy-physiology/key-terms/deciduous-teeth#resource","name":"Deciduous Teeth | Anatomy and Physiology I","url":"https://fiveable.me/anatomy-physiology/key-terms/deciduous-teeth","learningResourceType":"Concept explainer","educationalLevel":"AP® / High School","about":{"@id":"https://fiveable.me/anatomy-physiology/key-terms/deciduous-teeth#term"},"audience":{"@type":"EducationalAudience","educationalRole":"student"},"dateModified":"2026-07-03T02:20:38.182Z","isPartOf":{"@type":"Collection","name":"Anatomy and Physiology I Key Terms","url":"https://fiveable.me/anatomy-physiology/key-terms"},"author":{"@type":"Organization","@id":"https://fiveable.me/editorial#content-team","name":"Fiveable Content Team","url":"https://fiveable.me/editorial","parentOrganization":{"@id":"https://fiveable.me/#organization"},"member":[{"@type":"Person","name":"Amanda DoAmaral","sameAs":["https://www.linkedin.com/in/adoamaral"]},{"@type":"Person","name":"Becky Bahr","sameAs":["https://www.linkedin.com/in/becky-bahr-b52743132"]}]},"publisher":{"@type":"Organization","name":"Fiveable","url":"https://fiveable.me"}},{"@type":"DefinedTerm","@id":"https://fiveable.me/anatomy-physiology/key-terms/deciduous-teeth#term","name":"deciduous teeth","description":"Deciduous teeth are the first set of human teeth, also called primary, baby, or milk teeth. 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