Tooth Eruption Stages PDF

By the end of the course every student will be able to: a1- Identify the geometric outline of the different surfaces of the crown and physiological significances of those outlines of each tooth. a2- Enumerate different factors affecting the periodontium and the significances of each fa...

By the end of the course every student will be able to: a1- Identify the geometric outline of the different surfaces of the crown and physiological significances of those outlines of each tooth. a2- Enumerate different factors affecting the periodontium and the significances of each factor. a3- Describe the structure, different components of the tempro- mandibular joint and different muscles of mastication. a4- List the different mandibular movements. and compensatory curves a5- Describe the phases of development of permanent teeth in dental arch a6- Identify the composition and function of saliva. a7- Define eruption, eruption phases and the eruption movements in each phase. a8- Define shedding, shedding mechanisms, different clinical consideration related to shedding and the patterns of shedding in anterior and posterior teeth Tooth Eruption  Eruption of Teeth Axial or occlusal movement of teeth (or teeth germs) From Their developmental position in the jaw To Their functional position in the oral cavity  TERMINOLOGY OF ERUPTION ACTIVE ERUPTION: It is the actual movement of the tooth from its developmental site to its position in the dental arch. PASSIVE ERUPTION: Does not involve tooth movement but occurs due to apical recession of gingival tissue exposing more tooth structure into the oral cavity. CLINICAL CROWN: is the part of the tooth which is seen in the oral cavity. ANATOMICAL CROWN: It is part of the tooth which is covered by enamel. Histological phases of eruption  Phases of Eruption Phase When it Ongoing Type of starts & ends events movement  1- Pre-eruptive phase: Begins…….in early bell stage Ends……... At the beginning of root formation Pattern of tooth movement in the pre-eruptive phase for deciduous teeth: At the beginning…………….enough space between differentiated deciduous tooth germs Then crowding occurred…….rapid growth of deciduous tooth germs utilized the available space.  Pattern of tooth movement in the pre-eruptive phase for deciduous teeth: This crowding is relieved by: *Growth of jaw in length….(A,B,C)…..move forward (E)………..move backward *Growth of jaw in width…all tooth germs….moved outward (Bodily movement) *Growth of jaw in height…all tooth germs..moved occlusally by (excentric growth)  Movement of Deciduous Teeth Jaw growth: Anterior forward ** In length E backward E **In width Outward All )vestibular( teeth **In height upward Movements in the pre-eruptive stage: 1-Bodily movement: There will be both bone resorption in the surface toward which tooth moves and bone deposition occurs on the crypt wall behind it. 2-Eccentric growth: It means that one part of the developing tooth germ remains stationary and the remainder continues to grow leading to shift in its center. There will be bone resorption only in the surface toward which tooth moves Pattern of tooth movement in the pre-eruptive phase for permanent teeth with deciduous predecessors teeth: 1) permanent incisor and canine tooth germs Permanent teeth: A- Successional permanent teeth 1- Anterior tooth germs: First, develop on the lingual aspect of their deciduous predecessors at the level of their incisal surfaces and in the same bony crypt. Then, the tooth germs occupy a more apical position as their predecessors erupt and they lie in their own bony crypts. Their positions are still lingually situated. Pattern of tooth movement in the pre-eruptive phase for permanent teeth with deciduous predecessors teeth: 2) The premolars  2- Premolars tooth germs: First, develop on the lingual aspect of their deciduous predecessors at the level of their occlusal surfaces and in the same bony crypt. Then, the tooth germs occupy a more apical position as their predecessors erupt and they lie in their own bony crypts. Their positions are still lingually situated. By time, the primary molars have come into occlusion, the crowns of the developing premolars occupy a position between the roots of the primary molars. Pattern of tooth movement in the pre-eruptive phase for permanent teeth without deciduous predecessors teeth: 3) Permanent molars: *Maxillary permanent molars…..occlusal surfaces facing downward and distally *Mandibular permanent molars…..occlusal surfaces inclined mesially  Pre-eruptive Phase Permanent Molars Maxillary molars in the tuberosity facing distally swing with growth of the maxilla Mandibular molars in the base of the ramus facing mesially tilt to be upwright with growth of the mandible  Pre-eruptive Phase Starts: Ends: Events: Types of End of Beginning of Jaw growth: Movement: root In length early bell formation In width Bodily movement In height Shift of the center Eccentric growth  2) Eruptive (Prefunctional) phase: It starts at the beginning of root formation and It ends when the tooth reaches occlusion Clinically tooth eruption may be accompanied by discomfort or pain, irritability and/or a slight temperature increase also,there is increased salivation but no bleeding. Eruption path of the Succedaneous teeth Gubernacular canal: It is the connection Primary tooth between the permanent teeth and the oral epithelium. It contains remnants Permanent tooth of the dental lamina (Gubernacular cord).  Anteriorly, located lingual to the primary anterior teeth. Posteriorly, located between the roots of the primary molars. Anterior Premolars  GUBERNACULAR CORD The Gubernacular canal contains remnants of dental lamina and connective tissue termed as Gubernacular cord. Gubernacular canal  2) Eruptive (Prefunctional) phase: It is characterized by developmental changes including: A) Formation of the root. B) Formation of the supporting apparatus ( cementum, PDL and bone) C) Formation of dento- gingival junction.  Gradual functional orientation of PDL fiber bundles during tooth eruption  Changes in Tissues Overlying Erupting Tooth Bone resorption in roof of crypt by osteoclasts Degeneration of C. T. between R. D. E. & oral epith by desmolytic enzyme secreted by R. D. E. Epithelia proliferate & fuse forming a central mass ( epith. Plug). Central cells of the epith. Mass ( epith. Plug) degenerate leading to formation of an epithelial lined canal through which the tooth erupts Tooth eruption Osteoclasts erode jaw bone to make way for erupting adult tooth  Histogenesis of Dento-gingival junction 1 Desmolytic Epithelial 2 enzymes plug D.G.J (from 4 3 Reduced E. E.)  Epithelial plug epithelial lined canal Through which tooth is erupted without bleeding  Eruptive Phase Starts: Ends: Events: Type of Onset of Appearance Root formation movement root of tooth in Development of PDL All types of formation the oral Development of movements cavity dentogingival junction  Axial Rotatory Types of Tooth movement Movement movement Bodily Tilting movement (tipping) Movement around a longitudinal axis Occlusal movement in the direction of the long axis of the tooth Movement to one Movement direction around a mesial,distal transverse axis Buccal or lingual 3) Post- eruptive ( functional) phase: Begins….when tooth reaches occlusal plane Ends……at the end of life spane of the tooth  Pattern of tooth movement in the post- eruptive phase During this phase the tooth moves to : *Maintain its position while the jaws increase in height during growth…………..by axial movement *Compensate for occlusal wear……axial movement *Compensate for proximal wear……mesial drift  Mechanism of eruption Root formation theory :T he or ies Bone Remodeling theory Dental follicle theory Periodontal ligament traction theory Vascular pressure theory  Root formation theory Proliferating root impinges on a fixed base Apically directed force Occlusal movement  Bone Remodeling theory Bone remodeling of the jaws has been linked to tooth eruption The selective deposition and resorption of bone brings about tooth eruption.  2-Bone remodeling theory. Bone remodeling was considered previously to cause eruptive movements. However, this remodeling has been proved to be a result of eruptive movements and not a cause to it. Bone resorption Bone formation 1 mm  Dental follicle theory The dental follicle is important for eruption. if the dental follicle is removed no eruptive pathway forms. if the dental follicle is retained and a metal or silicone replica replaces the tooth germ, the replica will erupt with the formation of an eruptive pathway  Periodontal ligament traction theory This theory proposed that the cells and fibers of the periodontal ligament pull the tooth into occlusion. :Tooth movement is brought about by Fibroblast contractile properties Connection with collagen fibers extra-cellular “fibronexus” Oblique alignment of PDL collagen fibers  Vascular pressure theory Tissue fluid pressure local volume changes in periapical region can produce limited tooth movement either by arterial pulse or by swelling of the ground substance Gingival recession ( Passive eruption) Shift of DGJ First stage: in 1ry teeth till one y. before shedding In permanent: till20-30 y. Second stage: Persist to 40years. Third stage: transitory Fourth stage: gingival recession (pathologic)till loss Stages of passive eruption  Stages of passive eruption First stage Clinical crown Anatomical crown Coronal end (E).Apical end C.E.J year before shedding in deciduous 1.teeth and in perm. Till 20-30 years Second stage Clinical crown Anatomical Coronal end (E) crown.Apical end (C) Persist till 40 years Third stage Anatomical Clinical crown crown Coronal end (C.E.J.) Apical end (C) Transitory stage  Fourth stage Anatomical Clinical crown crown Coronal end (C) Apical end (C) Persists till the tooth lost