O10T.pdf

Eruption& shedding of the teeth Dr /Abdel-latif Galal Lecturer of oral Medicine& Periodontology Introduction Eruption refers to the physiological process by which developing teeth emerge through the soft tissue of the jaws and the overlying mucosa to enter the oral cavity Dipho...

Eruption& shedding of the teeth Dr /Abdel-latif Galal Lecturer of oral Medicine& Periodontology Introduction Eruption refers to the physiological process by which developing teeth emerge through the soft tissue of the jaws and the overlying mucosa to enter the oral cavity Diphodont: mean two sets of dentition in humans, deciduous and Permanent dentition. Mixed dentition: presence of two dentition. Teeth in primary dentition are smaller and fewer in number than permanent dentition to conform to the smaller jaw size. Primary dentition: from 2 to 6 years of age Mixed dentition: from 6 to 12 years Permanent dentition: after 12 years Stages of tooth movements: 1. Pre-eruptive tooth movement 2. Eruptive tooth movement 3. Post-eruptive tooth movement During all these 3 stages is the progression that happens from primary to permanent dentition which involves the shedding (exfoliation) of primary teeth.  Pre-eruptive stage: It is also known as 'Follicular phase of eruption' Growing tooth moves in two directions to maintain its position in expanding jaws : 1- Bodily movement : is a movement of entire tooth germ ;This causes bone resorption in direction of tooth movement and bone apposition. 2- Eccentric growth : growth in one part of tooth while rest of remains constant. Root elongates ,yet crown does not increase in size , while increase in alveolar bone height compensates for root growth.  Permanent anterior tooth germs develop lingual to the primary anterior teeth and later as primary teeth erupt, the permanent crowns lie at the apical 3rd of roots. Premolars tooth germs are finally positioned between the divergent roots of deciduous molars.  Eruptive phase / pre-functional eruptive phase: > During this phase the tooth moves from its position within the bone of the jaw to its functional position in occlusion. >The eruptive or prefunctional stage begins with the development of root. > The principal direction of movement is occlusal or axial. > During this phase of eruption, the movement of tooth takes place at the rate of 4mm in 14weeks > This stage continues until the erupting teeth meet the opposing teeth. Possible causes of tooth eruption: Although all the factors associated with tooth eruption are not yet known, the followings may be the possible causes of tooth eruption: 1- Root growth and pulpal pressure. 2- Bone remodeling. 3- Vascular pressure in periapical area. 4- Periodontal ligament traction. 5-Enzymatic degradations. 6- Endocrine influence. post-eruptive tooth movement These movements made by the tooth after it has reached its functional position in the occlusal plane. They may be divided in three categories: 1. Movements to accommodate the growing jaws. Mostly occurs between 14 and 18 years by formation of new bone at the alveolar crest and base of socket to accommodate with increased height of jaws. 2.Movements to compensate for continued occlusal wear. Compensation primarily occurs by continuous deposition of cementum around the apex of the tooth. 3.Movements to accommodate interproximal wear. Compensated by mesial drift. Mesial drift is the lateral bodily movement of teeth on both sides of the mouth. Very important in orthodontics. Stages of tooth movements Tooth eruption A, Crown penetrating bone and connective tissue. B, Contact of crown with oral epithelium, C, Fusion of epithelia. D, Thinning of epithelia E, Rupture of epithelium F, Crown emergence. G, Occlusal contact. Shedding of deciduous teeth: Definition : Shedding or exfoliation of deciduous teeth is a physiological process for elimination of deciduous teeth by resorption of their roots prior to eruption of their permanent successors.  Pattern of shedding Shedding or exfoliation occurs as a result of progressive resorption of roots of the teeth and their supporting tissue , the periodontal ligament. In general , the pressure generated by the growing and erupting permanent tooth lead to shedding of deciduous tooth. Factors that play an important role in shedding 1. Odontoclast 2. Pressure. 1- Odontoclast Derived from monocyte and migrates from pulpal B.V to the resorption sites , it’s a multinucleated odontoclast with a clear ruffled (brush ) border , & found in lacunae Histologically , characteristic feature of this is a high level of activity of the enzyme acid phosphatase , occurred within vacuoles and these vacuoles are concentrated in the cytoplasm. The most likely sequence of events in resorption of dental hard tissue by the odontoclast are : 1) An initial removal of minerals. 2) Dissolution of organic matrix (mainly collagen) to smaller molecules. Odontoclasts similarities to Osteoclasts Large multinucleated giant cell of variable shape Found in lacunae Show ruffled border. Acid phosphate activity within vacuoles. Process of resorption similar Similar origin: from circulating monocytes Odontoclasts differences from Osteoclast Smaller and contain fewer nuclei Resorb dental hard tissues: dentin, cementum and enamel Seen also in pulp chamber and root canal of resorbing deciduous teeth Clinical consideration: 1-Retained Deciduous Teeth Deciduous teeth may be retained for a long time beyond their usual shedding time. Such teeth are usually without permanent successors, or their successors are impacted.  Retained deciduous teeth are most often the upper lateral incisor, less frequently the second permanent premolar, especially in the mandible.  If a permanent tooth is ankylosed or impacted, its deciduous predecessor may also be retained. This is most frequently seen with the deciduous and permanent canine teeth. 2-Submerged Deciduous Teeth Trauma may result in damage to either the dental follicle or the developing periodontal ligament. If this happens, the eruption of the tooth ceases, and it becomes ankylosed to the bone of the jaw. Because of continued eruption of neighboring teeth. Submerged deciduous teeth should therefore be removed as soon as possible 3-Remnants of Deciduous teeth Sometimes parts of the roots of deciduous teeth are not in the path of erupting permanent teeth.  Such remnants, consisting of dentin and cementum, may remain embedded in the jaw for a considerable time. They are most frequently found in association with the permanent premolars, especially in the region of the lower second premolars.