Permanent dentition, Development, Congetital dental malformations 2. 6. 2021 Zubní pohárek a zvonek ve světelném mikroskopu Preparát: Vývoj zubu (Homo) - fetus stáří asi 15 - 16 týdnů Youtube channel Youtube channel Stellate reticulum (SR)Outer enamel epithelium (OEE) Stratum intermedium (SI) Inner enamel epithelium (IEE) Stellate reticulum Dental papilla odontoblasts ameloblasts Dentin and enamel aposition The pulp develops from the ectomesenchyme occupying the central portion of the dental papilla Ectomesenchyme differentiate into fibroblasts and fibrocytes and odontoblasts. Histiocytes and plasmocytes populate the pulp from the blood First blood vessels occur before deposition of dentin matrix (end of 3 month) cavitas dentis - firstly develops in the crown, and later in the root during the teeth eruption; its shape corresponds to the shape of the dental papilla ECM pulpy (kolagenní a retikulární vlákna + amorfní) jsou produkována fibroblasty Development of dental pulp and cavitas dentis Development of PDL Develops from the ectomesenchyme of the dental sac (follicle) Is initiated when the crown is completed, during root formation and develops together with cementum aposition Formed by secretory function of fibroblasts (ectomesenchymal origin) Fibers of gingival group with parallel course to the surface of the tooth develop as the first, thereafter interdental and principal fibers the intermediate plexus is differentiated as the last When the PDL development is finished, some cells retain the ability to differentiate into fibroblasts, osteoblasts and cementoblasts Eruption Eruption Tooth eruption = growth process It is manifested by the fact that the dental crowns protrude from the gingiva at a certain time, reach the oral cavity and eventually the occlusion plane. Primary dentition: 5. - 30. month after born Growth and elongation of the root of the future tooth Progress: The root of the tooth grows to the bottom of the ossified alveolar bone During further growth it rises and pushes the dental crown to the surface of the gum wall Gingival compression - vascular supply disorder and necrosis in the terminal phase After the dead tissue is removed, a dental crown hole is created During eruption, the crown is protected by the enamel residue: reduced enamel epithelium (REE) When the crown reaches the gum wall, the reduced enamel epithelium fuses with the oral epithelium During the crown eruption, the reduced enamel epithelium gradually separates from the enamel surface Eruption When the tooth crown reaches the occlusion plane, there is a 1-2 mm wide strip around the cervical part of the crown – dento-gingival epithelium Eruption Alveolar process development It is established together with the other parts of the upper and lower jaw. Intramembranous ossification Initially, it is low and develops with the development of tooth roots and during eruption of the dentition. It is distinguished into a) Cortical bone (lamina vestibularis, lamina oralis) b) Proper alveolar bone (os alveolare) c) Supporting bone (spongiosa) Timeline of primary dentition eruption Exfoliation (shedding) i1 6. - 8. months 7 year i2 7. - 12. months 8 year c 15. - 20. months 12 year m1 12. - 16. months 10 year m2 20. - 30. months 11-12 year Temporary dentition erupts between 5 - 30 months after birth Temporary dentition is fully functional until 6. year, then is being changed with secondary dentition Exfoliation of temporary dentition follows the eruption of secondary dentition Permanent dentition development Takes a substantially longer period than primary dentition Starts in the middle of the 2nd trimester (approx. 4 months of prenatal development) and ends with eruption between 7. - 17. (40). year of age Mechanisms and developmental stages similar to temporary dentition I1,I2, C, P1,P2, develop from a successional dental lamina Successional dental lamina is a derivative of primary dental lamina and is segmented (in contrast to primary dental lamina) Permanent dentition development M1, M2, M3 develop from the elongation of the primary dental lamina Developmentally molars from the secondary dentition belong to the teeth of temporary dentition Permanent dentition development Permanent dentition development Timeline of primordia of permanent dentition formation Prenatally: M1 4. month – primary lamina I1, I2 5 - 6. month C 8. month Postnatally: M2 6. month – primary lamina P1 10. - 12. month P2 18. month (1,5 year) M3 5. year – primary lamina Permanent molars developmentally belong toteeth of temporary dentition foetus - 6 month old The follicle of temporary and definitive tooth is initially at the same level, both surrounded by ectomezenchyme and sharing part of the dental follicle During development, the primary tooth grows and secondary takes place under the root of the temporary tooth The follicles of both teeth separates the bony barrier Permanent dentition development I1/i1 Bucolingual crossections through incisors (newborn - 9 years) Eruption of permanent molars are similar to temporary teeth For permanent incisors, canines and premolars primary dentition needs to be removed With the growth of the permanent root, the crown pushes the bone barrier, which separates both teeth. After resorption of the bone, the crown cause pressure on root of primary dentition which initiate radix resorption Role of „-clasts“ The result is a gradual shortening root of a temporary tooth In parallel there are changes in dental pulp, periodontium and epithelial tissue Eruption of permanent teeth Periodontium loses its ligamentous character conversion into loose collagenous connective tissue (it still retains the ability of redifferentiation because it provides material for the definitive periodotium) Epithelial junction is disintegrated and cementum is exposed. Dental pulp - transformation into stripes of dense connective tissue … In case of increased load, when the ligaments are no longer sufficient to fix and stabilize the tooth when biting and chewing, the stripes break and the temporary tooth falls out (exfoliation) The channel formed after the temporary tooth has fallen out (called gubernacular), will be used by a permanent crown for easier eruption into the oral cavity Eruption of permanent teeth Gubernacular canal tooth jaw dental calcifica end of eruption root cap tion enamel dev. formation development Mixed dentition Dentition, in which temporary and permanent teeth are both present Mixed dentition period - starts by eruption of the first permanent molar (M1) and ends by exfoliation of the second temporary molar (m2) Lasts between 6. - 12. year Exfoliation (shedding) of deciduous teeth recapitulate their eruption i1 6. – 8. month 7. year i2 7. – 12. month 8. year c 15. – 20. month 12. year m1 12. – 16. month 10. year m2 20. – 30. month 11. – 12. year Mixed dentition Congenital dental malformations Congenital dental malformations Teeth number anomaly Increased number of teeth Rudimentary Suppmenental Decreased number of teeth Hypodontia Oligodontia Anodontia Fused teeth dentes confusi dentes concreti dental druse Tooth shape anomalies Size anomalies Macrodontia Microdontia Anomalies in the hard tissues formation Enamel Dentin Cementum Tooth positions anomalies protrusion transposition rotation heterotopy retention Anomalies in eruption (related to time) dentitio tarda dentitio praecox Odontomas a) Dentes supernumerarii (hyperdontia) more frequent in permanent dentition, the shape of teeth is a normal or garbled (odontoid) paramolar - molars located labial to molars //distomolar - molars located distal to molars parapremolars, distopremolars mesiodens - the upper middle incisor (maxillary central uncisor) Numerical abnormalities dysostosis cleidocranialis Mesiodens Dens parapremolaris Dens paramolaris Dens distomolaris Dentes prelactales (dentes natales) diferenc. dg.: dentitio precox b) Hypodontia number of lacking teeth is lesser than 6 - most often M3, I2, P2 (lower jaw) c) Oligodontia number of lacking teeth is more than 6, mostly teeth of the same type lack familiar occurrence, AD inheritance c) Anodontia rare, associated with total dysplasia of the ectoderm Hypodoncie Oligodoncie Fused teeth Dentes concreti and dentes confusi (double teeth) concreti - adjacent teeth coupled with their roots - A,B (separate dental cavities) confusi - adjacent teeth coupled in the full length (from the crown to the apex) - C have a common dental cavity most often caused by a fusion of tooth buds (rarely by division of one tooth bud - dentes geminati) Common and concerned a crown, neck or root Caused by activity of aberrant ameloblasts or by defectly developed Hertwig´s epithelial sheath Examples: conically shaped crowns of lateral incisors, reduced or increased length of the root, reduced or increased number of the root branches etc. Anomalies of tooth shape Macrodontial vs. Microdontia Isolated Complete (macrodontism, microdontism) Size of teeth Enamel hypoplasia occurs when activity of ameloblasts is finished in pre-term findings: crown shows usually abnormal shape; enamel is thinner; fissures, scratches, and holes are seen on it isolated teeth or group of teeth Causes: rachitis, hypoparathyroidism syphilis congenita (Hutchinson incisors with semilunar edges, mulberry molars) Inflammatory affections of deciduous teeth connected with affections of tooth germs of permanent teeth - enamel of permanent teeth crowns has fissures and is pigmented - Turner´s teeth) treatment of tetracyklin antibiotics Anomalies of hard tooth tissues Amelogenesis imperfekta hereditary base /described cca 15 various types/ 3 forms: hypoplastic, hypomaturating and hypomineralizing hypomineralizing form: thickness of the enamel is normal, but is very soft and crumbled, and soon disappears due the natural atrice the enamel can also remove with sharp objects results from failure to calcify prisms (enamel rods) sensitivity to cold and heat 1: 20 000 school-age children Dentin Dentinogenesis imperfecta disorder in the development of dentin, which is pinkish to brownish and contains a reduced number of dentinal tubules teeth are smaller, gray-blue color to brownish color enamel is normal, but is easily separated from dentin (fast abrasion), the in temporary teeth are usual crown fracture rare, AD inheritance Sclerosis of dentin caused by obliteration of dentinal tubules Cementum hypercementosis (hereditary) aberrant cementum in the periodontium cementicles Anomalies of tooth position Protrusion - longitudinal axis inclined labially Retrusion - longitudinal axis inclined orally (into the oral cavity) Transposition - exchange of space between 2 adjacent teeth in the dental arch (canine / incisor or first molar / canine) Rotation - rotation of the tooth around the longitudinal axis (mesiorotation, distorotation) Heterotopia (anomalous eruption) (heteros other, topos - site location) the tooth was established and developed at an atypical site (isthmus faucium, hard palate) or cut outside the maxillary arch (vestibularly or lingually) Anomalies in eruption (time) Dentitio tarda - no tooth is erupted until the end of the 10th month Dentitio praecox - the first temporary tooth erupt before the 4th month of age