Tooth Eruption 2024-25 PDF

Tooth Eruption Richard Cure BDS(UBirm) MGDSRCS(Eng) FDSRCSEd FFGDP(UK) MOrthRCSEd PhD PFHEA FDTFEd CF  To discuss the process of eruptive tooth movement (as distinct from pre-eruptive/post- eruptive tooth movement) and to explore the theories put forward t...

Tooth Eruption Richard Cure BDS(UBirm) MGDSRCS(Eng) FDSRCSEd FFGDP(UK) MOrthRCSEd PhD PFHEA FDTFEd CF  To discuss the process of eruptive tooth movement (as distinct from pre-eruptive/post- eruptive tooth movement) and to explore the theories put forward to explain the process Aims To discuss that physiological tooth movement takes place throughout the life of teeth and is a key tool in the way the dentition adapts to functional stresses  Following the presentation, students should have an increased knowledge and understanding of: Objective The process of eruptive tooth movement (as distinct from pre- eruptive/post-eruptive tooth s movement) and the theories put forward to explain the process The process of physiological tooth movement and that this takes place throughout life and is a key tool in the way the dentition adapts to functional stresses  Tooth eruption Active tooth eruption can be defined as the axial or occlusal movement of a tooth from its site of development within the alveolar process to its functional position in the oral cavity It is a continuous process, which does not stop by the tooth reaching the occlusal plane, but continues throughout life Developing teeth can move in three dimensions and increase in size within the alveolar process before active eruption Initiation of tooth development and its eruption in an appropriate time is essential for the maintenance of a proper and healthy dentition  Active eruption Pre-eruptive Phases of movement tooth Eruptive movement eruption Post-eruptive movement Passive eruption  The movement of the tooth from its developmental site in alveolar Active bone to its functional position in eruption the oral cavity  Made by the tooth germs; it is the means by which the teeth are positioned within the jaw for eruptive movement Pre-eruptive tooth movement begins from the time of initiation of tooth formation to Pre- the time of initiation of root formation Tooth movement occurs in association with eruptive growth of the jaws movemen Tooth movements occur intra-osseously and require remodelling of the bony crypt t wall which happens by the selective deposition and removal of bone The pre-eruptive phase starts from the end of early bell stage until the beginning of root formation  Tooth movements during the eruptive phase are subdivided into; intra-osseous and supra-osseous stages The eruptive phase begins with the onset of Eruptive root formation and terminates by tooth appearance in the oral cavity, just before tooth function (pre-functional phase) movemen The tooth moves from its developmental position to the occlusal level; the principal t direction of movement is either axial or occlusal After emergence, the tooth crown keeps moving occlusally until it comes into contact with its antagonist in the occlusal plane  During this process, the tooth crown begins to get exposed gradually with an apical shift of the dento-gingival junction For the intra-osseous eruptive tooth movements, Eruptive two things have to occur – the resorption of overlying tissue to provide an eruptive path and tooth a force for the tooth to move vertically movemen The blood vessels decrease in number and this is also accompanied by the degeneration of nerve t fibres and the connective tissue overlying the tooth germ This leads to the formation of an eruption pathway, which appears as an inverted triangular area of altered tissue  Occurs once the tooth reaches its functional position in the oral cavity Post- eruptive This movement maintains the tooth position in occlusion by tooth compensation for occlusal and movemen proximal tooth wear t The post-eruptive phase starts when the teeth attain occlusion and continues for as long as each tooth remains in the oral cavity (functional phase)  This is characterized by the apical shift of the dento-gingival junction As this occurs, the length of the Passive clinical crown increases as the epithelial attachment migrates eruption apically Although the movement of teeth into function has been the subject of extensive research, there is still no consensus regarding the mechanism involved  Based on the type of tooth and the time of eruption, the human dentition is categorized into Primary (Deciduous) dentition, Mixed dentition and Secondary (Permanent) dentition The Primary dentition comprises of 20 teeth and usually erupts between 6 months and 3 years Eruptive The Mixed dentition phase starts with the eruption of the tooth first permanent tooth, usually the lower central incisors or first permanent molars at around 6 years of age movemen Successional permanent teeth erupt and the deciduous dentition teeth are exfoliated t The Mixed dentition phase finishes when the last of the deciduous teeth are exfoliated Usually, not all the permanent teeth are erupted when all deciduous teeth have exfoliated, with third molars erupting at around 18-21 years of age Theories of eruptive tooth movement  Theories of eruptive tooth movement There is still no consistent understanding of the mechanisms behind tooth eruption, and it is thought to be a combination of factors Various theories have been proposed in an attempt to explain the process of eruption  Pulp theory Vascular theory Theories of Root elongation theory eruptive Alveolar bone remodelling tooth theory Periodontal ligament theory movement Dental follicle theory Neuromuscular theory  Pulp theory Pulp propels the tooth upwards (mandible) or downwards (maxilla) As root formation continues, the thickness of the radicular dentine increases resulting in the decrease in size of pulp cavity It is proposed that the growth or constriction of the pulp generates a force which is propulsive in nature by the growth of dentine, pulp and the hydraulic effects happening within the pulpal vasculature Evidence against this theory: If the pulp is removed the tooth still erupts Vascular pressure/blood vessel thrust or hydrostatic pressure theory Thought to overlap with the Pulp growth theory Force of eruption provided by the pressure exerted by the blood vessels within the tooth Tooth movement synchronises with arterial pressure, thereby the local volume changes, producing a limited tooth movement Suggests that a local increase in tissue fluid pressure in the periapical region is sufficient to move the tooth Evidence against this theory: Pulpless teeth erupt Hypotensive drugs appear to have no effect on eruption rates Root and local vasculature excision does not prevent tooth eruption Vascular pressure/blood vessel thrust or hydrostatic pressure theory More recently, it has been reported that the hydrostatic pressure theory occurs during post-emergent eruption, due to the dental follicle secreting mediators, such as vascular endothelial growth factor (VEGF), that cause angiogenesis and an increase in apical tissue pressure that leads to tooth eruption Moreover, hydrostatic pressure theory was supported by several studies that confirm tooth eruption after a local injection of vasodilators, whereas injection of vasoconstrictors caused a decrease in the rate of eruption  Root formation/elongation theory As the root develops, the tooth is propelled towards the mouth Assumes that the proliferating root encounters a fixed structure, and the apically directed force is converted into a reactive occlusal force that causes coronal movement of the erupting tooth Evidence against this theory: Rootless teeth still erupt into a functional occlusion Some teeth erupt a greater distance than the total root length, and the teeth erupt after completion of root formation or when the tissue forming the root is removed The onset of root formation does not coincide with the eruptive movement  Alveolar bone remodelling theory Bony remodelling of the jaws has been linked to the tooth eruption, in that, in the pre-eruptive phase of tooth movement, the growth pattern of the maxilla or mandible moves the teeth by the process of selective deposition and resorption of bone New bone is laid down beneath the crypts of erupting teeth Whether the bony remodelling around the teeth causes the teeth to erupt or is the effect of the tooth movement is not clearly known, but both circumstances apply Studies also indicate that the control resides within the bone lining cells, the osteoblasts Theory based on the assumption that bone resorption occurs coronally and bone apposition occurs apically in the base of the crypt, the prevention of the latter can pose a challenge to tooth eruption The dental follicle is said to be the source for osteoblasts and osteoclasts  Alveolar bone remodelling theory When a developing premolar is removed without disturbing the dental follicle, or if eruption is prevented by wiring the tooth germ down to the lower border of the mandible, an eruptive pathway still forms within the bone overlying the enucleated tooth as osteoclasts widen the gubernacular canal If the dental follicle is removed, however, no eruptive pathway forms Furthermore, if a metal or silicone replica replaces the tooth germ and, as long as the dental follicle is retained, the replica will erupt, with formation of an eruptive pathway  Alveolar bone remodelling theory It is concluded that programmed bone remodeling can and does occur (i.e., an eruptive pathway forms in bone without a developing and growing tooth) Secondly, the dental follicle is involved However, the conclusion cannot be drawn that the demonstration of an eruptive pathway forming within bone means that bone remodeling is responsible for tooth movement unless coincident bone deposition also can be demonstrated at the base of the crypt where its prevention can interfere with tooth eruption  Alveolar bone remodelling theory Recently the molecular basis of tooth eruption supports the bone remodelling theory, as it confirms that mutation of the parathyroid hormone receptor 1 (PTH1R) gene is correlated with disturbances in bone remodeling and leads to primary failure of eruption (PFE) PFE is non-syndromic eruption disturbance that is not associated with defective osteoclasts The affected teeth had supra-crestal presentation and progressive open bite which is hallmark criteria of PFE  Periodontal ligament theory Based on the hypothesis that periodontal ligament (PDL)-dental follicle complex possesses eruptive force due to the traction power that fibroblasts have The formation and renewal of the periodontal ligament is considered to be an essential factor in tooth eruption due to the traction power of the fibrobasts, which move incisally along the erupting tooth, and their contraction generates significant force for tooth eruption Evidence that eruptive forces exist in the dental follicle – periodontal ligament complex Shrinkage of collagen fibers exhibits a force that plays a very important role in tooth eruption  Periodontal ligament theory For a tooth to erupt, there should be a space in the eruption path, a lift or pressure from the apical region and required adaptability in the periodontal ligament Bone resorption and deposition are involved, which plays a major role in the movement of the tooth and considered to be one of the critical surface phenomenon between the soft tissue and the bony interface, which are present surrounding the developing tooth Ankylosed teeth or implants, which lack a PDL, do not move occlusally or exhibit mesial drift  Periodontal ligament theory However, evidence against include: Experiments in a rat model using lathyrogens (amino acid derivatives that cause defective fibril formation when applied to the PDL) did not cause different rate of eruption when compared to untreated rats The rate of collagen turnover is much higher than that of eruption There is no difference in metabolic structures within fibroblasts in the PDL of rapidly erupting teeth and fully erupted teeth Periodontal fibroblasts exhibit characteristics of cells actively synthesizing and secreting Rootless teeth can erupt on schedule, indicating that the PDL is  Dental follicle theory Force comes from the dental follicle Proposes that the dental follicle is capable of inducing bone resorption above the developing crown and bone apposition below it This enables the formation of an eruptive path to occur through which the tooth will be passively conducted Various molecular studies reveal that eruption is regulated by inductive signals between the dental follicle, reduced enamel epithelium, stellate reticulum and alveolar bone Osteoclastogenesis (bone resorption) is regulated by the coronal aspect of the dental follicle whereas osteogenesis (bone formation) is regulated by the basal aspect of the dental follicle  Dental follicle theory Experimental removal of the dental follicle results in eruption failure The dental follicle probably has many cytokines and growth factors which could lead to bone remodelling associated with tooth movement In osteopetrotic animals, which lack a factor that stimulates differentiation of osteoclasts, eruption is prevented, because no mechanism for bone removal exists However, local administration of this factor, colony stimulating factor 1 (CSF-1), permits the differentiation of osteoclasts and eruption occurs  Dental follicle theory Current concepts concerning the paracrine signaling function of the dental follicle in tooth eruption suggest: Tooth development is regulated by a cascade of mutual interactions between the dental epithelium and the dental mesenchyme Correspondingly, the process of tooth eruption is regulated by cellular events leading to the recruitment of monocytes to the dental follicle followed by bone resorption These molecular events are initiated by interactions between the dental follicle, the reduced enamel epithelium, the stellate reticulum and alveolar bone  Neuromuscular theory Also known as the unification theory of tooth eruption Primarily based on the neuromuscular forces which take their origin from the contraction of the musculature present in the orofacial region States that the combined forces exhibited by the orofacial muscles, which primarily are controlled by central nervous system, play an essential role in the active movements of a tooth This combination of forces are converted into energies of various forms such as electrical, electrochemical and biomechanical energies, which becomes essential for the stimulation of cellular and molecular activities taking place within and around the dental follicle and enamel organ These changes happen in order to prepare a pathway as well as to bring out other cellular functions required for a developing tooth to erupt Factors affecting tooth eruption Various factors influence tooth eruption and become a part of associated disturbances Genetic and environmental Factors affecting tooth eruption Delayed or complete failure of eruption Down’s Syndrome Cleidocranialdysostosi s Hypothyroidism Hypopituitarism Achondroplastic dwarfism Factors affecting tooth eruption Supernumerary teeth Crowding Arch length deficiency Cysts and tumors Enamel pearls Gingival hyperplasia Premature loss of primary tooth Ankylosis Digit sucking Tongue thrusting Fibrous developmental malformations Physiological tooth movement  Physiological tooth movement Post eruptive tooth movements happen once the tooth reaches its functional position in the oral cavity These tooth movements maintain the position of the erupted tooth while the jaw continues to grow and compensates for the occlusal and proximal wear They continue throughout the patient’s lifetime Tooth wear occurs even at the contact points between the teeth In order to compensate for it, a proximal tooth drift takes place  Physiological tooth movement Histologically this drift is a selective deposition and resorption of bone on the socket walls by osteoblasts and osteoclasts respectively. Post eruptive tooth movements are divided into 3 categories, namely: movements which help in accommodating jaw growth; movements which compensate for continued occlusal wear; movements which aid in accommodating tooth wear that occurs interproximally  Physiological tooth movement Physiological tooth movement takes place throughout the life of teeth It is a key tool in the way the dentition adapts to functional stresses placed on the dentition It allows orthodontic treatment to be carried out on adults It is also a main reason for orthodontic retention needing to be lifelong  Eruption should be considered as a stage of tooth development Root follicles, periodontal membranes, and crown Summary of follicles are involved in the eruption process Dental follicles and PDL play mechano-sensor roles in current tooth eruption thoughts and The orientation of PDL fibroblasts determines the tooth directional movement future Root formation produces compressive coronal and tensile apical hydrostatic stress resulting in tooth eruption questions: The molecular and enzymic activities, are controlled by neuromuscular forces Each of the eruption theories impacts on some part of the eruption process. The presence of stem cells in the dental follicle suggests a potential role in tooth eruption. Identification of the role of stem cells during tooth eruption still needs further research Questions???? Thank You! [email protected]