All deciduous teeth should have erupted by the time the child is three years of age. Typically, the bottom two front teeth, the bottom central incisors, are the first to erupt. Įruption of primary teeth into the mouth begins between the ages of 6 months and two years. If the structures do not start to develop at or near these times, they will not develop at all. Permanent teeth begin to form in utero at 20 weeks of gestation. Primary dentition begins to form in-utero between 6 and 8 weeks of gestation. The neural crest ectomesenchyme gives rise to tooth structures other than enamel. It is a complex process resulting from interactions between the oral cavity ectoderm, which gives rise to cells that produce enamel. The process of tooth development begins with the tissues of the first pharyngeal arch. Under normal physiological conditions, a human will have 20 deciduous (baby) teeth and 32 permanent teeth. Two main sets of dentition exist a primary dentition (colloquially referred to as baby teeth) and an adult or permanent dentition. Cementoblasts form the cementum (calcified material covering teeth roots), osteoblasts give rise to the alveolar bone around the roots of the teeth, and fibroblasts develop the periodontal ligaments which connect teeth to the alveolar bone through the cementum. The dental follicle gives rise to three major cell types: cementoblasts, osteoblasts, and fibroblasts. Dentin consists of calcium, phosphorous, and hydroxyapatite crystals bound together in a hard crystalline substance. The dental papilla is a fusion of ectomesenchymal cells, termed odontoblasts, which form dentin, the yellow substance that forms the bulk of the teeth. These cells die once the tooth erupts, which means that the ability to make enamel is forever lost once eruption occurs. The enamel is made before a tooth erupts into the mouth by the enamel organ, which contains cells called ameloblasts. The enamel organ comprises four layers the inner and outer enamel epithelium, the stratum intermedium, and the stellate reticulum. The tooth bud, an aggregation of cells that eventually forms a tooth, is organized into three parts: enamel organ, dental papilla, and dental follicle. Defect calcification occurs when these factors are deficient, leading to abnormal teeth development throughout life. The availability of calcium and phosphate in the diet and the amount of vitamin D in the body are all factors that can lead to changes in the enamel and growth of healthy, normal teeth. Nutrition is also of specific concern in the development and growth of teeth. Of concern, however, is that saliva is unable to penetrate through plaque, and demineralization can occur. Demineralization of enamel then leads to tooth destruction. Remineralization of enamel occurs through saliva, which keeps the tooth surface above a critical pH of 5.5. In the absence of oxygen, these bacteria produce lactic acid, dissolving calcium and phosphorous in the enamel. Bacteria live off the remains of food, especially that of sugar and starches. Streptococcus mutans is the most important bacteria associated with dental caries. Plaque can mineralize, eventually leading to tartar build-up, causing gingivitis, halitosis, and dental caries. If plaque is not professionally removed regularly, periodontal problems and gingivitis can set in. Brushing alone does not always remove plaque in its entirety. Of particular concern is plaque, a biofilm of various bacteria (mainly Streptococcus and anaerobes) that form on the surface of teeth. Poor dental and oral health can potentially lead to numerous issues.
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