Week 8 - HSDH2140 - Eruption Past Paper PDF

Eruption H S D H 2 1 4 0 E M B RYO LO GY & H I S T O LO GY FA L L 2 0 2 4. D R. JA FA R A L A B D U L L A H 1  3.1.1 - Describe the relationship between bone, tooth root development and the mechanisms for various...

Eruption H S D H 2 1 4 0 E M B RYO LO GY & H I S T O LO GY FA L L 2 0 2 4. D R. JA FA R A L A B D U L L A H 1  3.1.1 - Describe the relationship between bone, tooth root development and the mechanisms for various tooth eruption and post eruption Learning - Pre-active Objective - Eruptive - Post-eruptive s 3.1.2 – Describe abnormalities in eruption, exfoliation, occlusions, and their etiologies. 2 Introduction: Tooth development  Odontogenesis: is the process of tooth development  takes place in stages  continuous process  Dentition: is used to describe the natural teeth in the jaws. The primary dentition: 2 to 6 years  20 teeth The permanent dentition: >12 years  32 teeth gradually erupt and replaces the primary dentition. PRIMARY TOOTH ERUPTION AND SHEDDING 4 Tooth eruption The word ‘’eruption’’ refers to cutting of teeth through gums (Oral Mucosa) Tooth eruption is the process by which developing teeth emerge through the soft tissue of the jaws and the overlying mucosa to:  Enter the oral cavity  Contact the teeth of the opposing arch  Function in mastication The phases of tooth eruption Physical tooth movements consists of the following:  Pre-eruptive phase:  Eruptive phase:  Post-eruptive phase:  Pre-eruptive phase Starts at the beginning of tooth development and ends when the crown formation is completed.  Pre-eruptive phase: This phase includes all movements of primary and permanent tooth crowns from  early initiation and formation to  crown completion. Tooth not erupted yet  Pre-eruptive phase Characterized by : Dental (enamel) organ differentiated from primitive oral epithelium  formation of enamel and DEJ  Dental papilla is made up with odontoblasts  produce dentin and the dental pulp  Dental sac (dental follicle) is made up with fiber cells  differentiates into PDL, cementum and alveolar bone  Formation of bone cavity that surrounds the apex of the tooth  Movement of developing tooth within the growing jaw.  Periodontal Ligament (PDL) Development of the PDL ◦The dental sac begins to form the PDL on the outside of the newly formed Cementum. ◦Collagen fibers are formed which immediately organize themselves into the fiber bundles of the PDL. ◦The ends of these fibers attach to the cementum and Alveloar Bone (Sharpey’s fibers) 9 Development of the Periodontal Ligament (PDL) 10 PDL Fibers During Eruption Initially fibers lack orientation, they quickly align themselves obliquely. As the tooth erupts, more fibers form and orientate themselves forming the common fiber groups. 11  Eruptive tooth movement  During the phase of eruptive tooth movement, the tooth moves from its position within the bone of the jaws to its functional position in occlusion. However, jaw growth is still occurring while most teeth are erupting. The term pre-functional eruptive movement is used to describe the movement of tooth after its appearance in the oral cavity till it attains the functional position Pre-eruptive Teeth Movement The movement of teeth before they begin to erupt Teeth movement: ◦ Place teeth in a position for eruptive movement ◦ This space is soon used because of rapid growth of the tooth, and crowding results, especially in incisors and canine region. ◦ This crowding is then relieved by growth of the jaws. 14 Eruptive (pre- functional phase) Starts with the initiation of root formation and ends when the teeth reach occlusal contact. 15 Eruptive (pre-functional phase) Pre-Functional eruptive phase: Four major events occur during this phase  Root formation: requires space for the elongation of the roots. 1. Proliferation (=rapid growth) of the epithelial root tissues  initiates the differentiation of odontoblasts from the dental papilla 2. The odontoblasts form root dentin and pulp tissues. 3. Cementum, PDL and the bone are formed 4. Bone removal is necessary for permanent teeth to erupt! 16 Reduced Enamel Epithelium (REE) is a layer of cells that forms after enamel development. It helps facilitate tooth eruption by fusing with the oral epithelium, allowing the tooth to emerge through the gums, and protects the enamel during this process. REE usually disintegrates after the tooth has erupted. Eruptive (pre-functional phase)  Movement: Occurs through the bone of the jaws to reach the oral mucosa. The reduced enamel epithelium (REE) fuses with the oral epithelium Eruptive (pre-functional phase)  Penetration: of the tooth’s crown tip through the fused epithelial layers allows the entrance of the crown enamel into the oral cavity Intraoral occlusal/incisal movement: The erupting tooth continues until clinical contact with the opposing crown occurs. Active eruption 20 Active eruption Takes place after the teeth are functioning to maintain the position of the erupted tooth in occlusion while the jaws are continuing to grow The actual vertical movement of the tooth.  Active eruption The REE appears as a few layers of flattened cells overlying the new enamel surface. As this formation of the REE occurs for a primary tooth, it can begin to erupt into the oral cavity. Active eruption To allow for the eruption process, the REE first has to fuse with the oral epithelium lining the oral cavity. Second, enzymes from the REE then disintegrate the central part of the fused tissue, leaving an epithelial tunnel for the tooth to erupt through the surrounding oral epithelium into the oral cavity. 23 Active eruption As a primary tooth actively erupts, the coronal part of the fused epithelial tissue peels back off the crown, leaving the cervical part still attached to the neck of the tooth. Active eruption  Active eruption The process involving loss of the primary tooth consists of differentiation of Osteoclasts, which absorb the alveolar bone between the two teeth, and Odontoclasts, which cause resorption or removal of parts of the primary's root of dentin and cementum as well as small parts of the enamel crown.  Active Eruption The process of shedding of the primary tooth is intermittent (“on again/off again”) because at the same time that osteoblasts differentiate to replace the resorbed bone, odontoblasts and cementoblasts also differentiate to replace the resorbed parts of the root. Active Eruption The primary tooth is then lost, exfoliated, or shed, as the succedaneous permanent tooth develops lingual to it. Post-eruptive tooth movement The movements made by the tooth after it has reached its functional position in the occlusal plan. They may be divided in three categories:  Accommodation for growth: occurs between 14 and 18 years by formation of new bone to keep developing with increasing height of jaws.  Compensation for occlusal wear: compensation occurs primarily by continuous deposition of cementum around the apex of the tooth. This deposition occurs only after tooth moves!  Accommodation for interproximal wear: compensated by mesial or approximal drift Mechanism of tooth movement 4 Factors:  Bone remodeling: Osteoclasts and osteoblasts are responsible for bone resorption and formation  play a crucial role in reshaping the alveolar bone to accommodate tooth movement  Root formation: occurs after crown formation  as the roots lengthen, they provide an anchor within the jawbone.  Vascular pressure: refers to circulation of blood in the tissues surrounding teeth  blood vessels deliver nutrients and oxygen to cells and remove waste products.  Periodontal ligament (PDL): is a connective tissue that anchors teeth to the alveolar bone  during tooth movement, it remodels and adapts to the applied forces. 10 minutes break