1. DEPARTMENT OF PUBLIC HEALTH DENTISTRY SEMINAR TOOTH ERUPTION PRESENTED BY Dr.AMRITA RASTOGI MDS 1ST YEAR

2. CONTENTS INTRODUCTION ERUPTION PATTERN OF TOOTH MOVEMENT Preeruptive tooth movement Eruptive tooth movement Posteruptive tooth movement HISTOLOGY OF TOOTH MOVEMENT Preeruptive phase Eruptive phase Posteruptive phase 3. MECHANISM OF TOOTH MOVEMENT Bone remodeling Root formation Vascular pressure Periodontal ligament traction Cellular and molecular events in eruption Chronology and sequence of tooth eruption CLINICAL CONSIDERATIONS CONCLUSION REFERENCES 4. INTRODUCTION The timely initiation and eruption of teeth into the oral cavity is very important for healthy dentition . It is the process by which tooth moves within the jaw bone comes into the oral cavity and comes up to the occlusal contact and maintains its clinical position. 5. ERUPTION The word eruption refers to cutting of teeth through gums (from the Latin erumpere, meaning to break out). Its developmental position within the jaw to its functional position in the occlusal plane. Teeth undergo complex movements related to maintaining their position in the growing jaws and compensating for masticatory wear. [1] 6. Physiological tooth movements consists of the following: Pre eruptive tooth movement Eruptive tooth movement Post eruptive tooth movement 7. Phases of tooth eruption Preeruptive phase: made by the deciduous and permanent tooth germs within tissues of the jaw before they begin to erupt. Eruptive phase: Starts with initiation of root formation and made by teeth to move from its position within bone of the jaw to its functional position in occlusion. Has an intraosseous and extraosseous compartments. Posteruptive phase: Takes place after the teeth are functioning to maintain the position of the erupted tooth in occlusion while the jaws are continuing to grow and compensate for occlusal and proximal tooth wear. [2] 8. PREERUPTIVE TOOTH MOVEMENT When deciduous tooth germs first differentiate they are very small and have good space in between them. This space is soon used because of rapid growth of the tooth germs, and crowding results, especially in incisors and canine region. This crowding is then relieved by growth of the jaws in length, which permits the drifting of tooth germs. [1] 9. Bony remodeling of crypts wall occurs to facilitate movements of growing tooth germs. Permanent teeth with deciduous predecessor also move before they reach the position form which they erupt. 10. The change in the position of the tooth germ is the result of number of factors:- Body movement of tooth germ Growth of tooth germ Relative change in position of associated deciduous and permanent tooth germ 11. The permanent molars, which develop in the tuberosity of the maxilla, at first have their occlusal surfaces facing distally and swing around only when the maxilla has grown sufficiently to provide necessary space. Pre eruptive tooth movement should be considered as movement positioning the tooth & its crypt within the growing jaws preparatory to tooth eruption. 12. 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, & the principal direction of movement is occlusal or axial. However, jaw growth is still occurring while most teeth are erupting so that movement in planes other than axial movement is superimposed on eruptive movement [1] 13. 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. 14. 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 primary roots. Premolars tooth germs are finally positioned between the divergent roots of deciduous molars. [2] 15. POST ERUPTIVE TOOTH MOVEMENT Post eruptive tooth movement are those that :- Maintains the position of the erupted tooth while the jaw continues to grow. Compensate for occlusal & proximal wear. [1] 16. The former movement, like eruptive movement occurs principally in an axial direction to keep pace with the increase in height of the jaws. It involves both tooth & its socket & ceases when jaw growth is completed. The movement compensating for occlusal & proximal wear continue throughout life & consist of axial & mesial migration, respectively. 17. HISTOLOGY OF TOOTH MOVEMENT PERERUPTIVE PHASE: Preeruptive tooth movement, involves drifting or growth of tooth germs, demands remodeling of the bony wall of the crypts. This is achieved by the selective deposition and removal of bone by osteoblastic and osteoclastic activity. Normal skeletal morphogenesis might be involved in determining tooth position. [1] 18. ERUPTIVE PHASE: During the eruptive phase of physiologic tooth movement, significant developmental events occurs that are associated with eruptive tooth movement. They include: The formation of root. The periodontal ligament. The dentogingival junction. 19. ROOT FORMATION It is initiated by growth of HERTWIGs epithelial root sheath, which initiates the differentiation of odontoblasts from the dental papilla. The odontoblasts then form root dentine, bringing about an overall increase in length of the tooth that is largely accommodated by eruptive tooth movement, which begins at approximately the same time as root formation is initiated. 20. After the onset of root formation cementum, periodontal ligament, and the bone lining crypt wall are formed. Fibroblasts of the periodontal ligament possess as part of their cytoskeleton intermediate filaments that consist of contractile proteins. The ligament fibroblast has the ability of ingest and degrade extracellular collagen while forming new collagen fibrils. 21. Bone removal is necessary for permanent teeth to erupt. In case of those teeth with deciduous predecessors there is an additional anatomic feature, the GUBERNACULAR CANAL and its contents, the gubernacular cord, which may have influence on eruptive tooth movement. When the successional tooth germ first develop within the same crypt as its deciduous predecessor, bone surrounds both tooth germs but does not completely close over them. 22. As the deciduous tooth erupts, the permanent tooth germ become situated apically and is entirely enclosed by the bone except for a small canal that is filled with connective tissue and often contains epithelial remnants of the dental lamina. This connective tissue mass is termed the gubernacular cord 23. Gubernacular canal: Holes noted in a dry skull noted lingual to primary teeth in jaws that represent openings of gubernacular cord . 24. After removal of any overlying bone there is loss of the intervening soft tissue between the reduced enamel epithelium covering the crown of the tooth and the overlying oral epithelium. 25. Why tooth eruption occurs without bleeding The changes occurring in the connective tissues affect the epithelia it sustains and both the reduced enamel epithelium and the overlying oral epithelium begins to proliferate and migrate into disorganized connective tissue so that eventually a solid plug of epithelium forms in advance of the erupting tooth. The central cells of epithelium mass degenerate and form an epithelium-lined canal through which tooth erupts without any hemorrhage. 26. Once the tooth has broken through the oral mucosa, it continuous to erupt at the same rate until its reaches the occlusal plane and meet its antagonist. Rapid eruptive movement then ceases. 27. The rate of tooth eruption depends on the type of movement 1 to 10 m/dayINTRAOOSEOUS PHASE 75 m/day EXTRAOSSEOUS PHASE [3] 28. POST ERUPTIVE TOOTH MOVEMENT In posteruptive phase the tooth makes movements primarily to accommodate the growth of jaws. The principal movement is in an axial direction. It occurs most actively between the ages of 14 and 18 and is associated with condylar growth, which separates the jaw and teeth. [1] 29. Movements are also made to compensate for occlusal and proximal wear of the tooth. Wear also takes place at the contact points between teeth, and to maintain tooth contact mesial or proximal drift takes place. Histologically, this drift is seen as a selective deposition and resorption of bone on the socket wall by osteoblasts and osteoclasts respectively. 30. Essentials of Oral Histology and Embryology. James Avery, 2nd edition STAGES OF TOOTH ERUPTION [2] 31. MECHANISM OF TOOTH MOVEMENT The mechanism that brings about tooth movement is still debatable and is likely to be combination of number of factors. Various factors were proposed, but only four merits are considered. They are:- [1] 32. BONE REMODELING ROOT FORMATION VASCULAR PRESSURE PERIODONTAL LIGAMENT TRACTION 33. BONE REMODELING The growth pattern of the maxilla and the mandible moves teeth by selective deposition and resorption of bone. Major proof is when a tooth is removed without disturbing its follicle tooth germ, an eruptive pathway still forms within bone as osteoclasts widen the gubernacular canal. 34. If dental follicle is removed , no eruption pathway forms. This establish the absolute requirement for dental follicle to achieve bony remodeling and tooth eruption, for it is the follicle that provide the source for new bone-forming cells and conduit for osteoclasts derived from monocytes through its vascular supply. 35. ROOT FORMATION Root formation follows crown formation and involves cellular proliferation and formation of new tissue that must be accommodated by either movement of crown of the tooth or resorption of bone at the base of its socket. If root formation results in an eruptive force, the apical growth needs to be translated into occlusal movement and requires a fixed base. 36. The bone at the base of the socket cannot act as a fixed base because pressure on the bone results into resorption. THE ROOT GROWTH THEORY of tooth eruption postulate the existence of a ligament, the cushion-hammock ligament, straddling the base of the of the socket from one bony wall to the other like a sling. Its function is to provide a fixed base for the growing root. 37. VASCULAR PRESSURE It is known that teeth move in synchrony with the arterial pulse, so local volume changes can produce limited tooth movement. Experimentally, increase of hydrostatic pressure induced by hypotensive drugs, increases the rate of eruption while stimulation of sympathetic nerves, which cause vasoconstriction and decrease of the rate of eruption. 38. It has been observed that the number of fenestrated capillaries, increase with the eruption and their distribution varies; more numbers of fenestrated capillaries are seen near the base of the crypt than at alveolar crest. 39. Injection of 2% lignocaine with adrenaline 1:100,000 above the root of erupting premolars(prefunctional phase), causes a burst in the increase of eruption of teeth receiving the injection with or without vasoconstrictor. However, the teeth receiving vasoconstrictor showed decrease in eruption rate, suggesting that vascular changes affect perfunctional eruption. 40. PERIODONTAL LIGAMNENT TRACTION Available evidences strongly indicate that the force for eruptive tooth movement lies in PDL. The PDL and dental follicle from where it forms are implicated in the process of tooth eruption linked to contractility of fibroblasts. PDL fibroblasts are able to provide a force sufficient to move the tooth and certainly the proper structural elements exist to translate such force into eruptive tooth movement. 41. CELLULAR AND MOLECULAR EVENTS IN ERUPTION [3] 42. CELLULAR EVENTS Bone formation at the basal end Bone resorption at coronal half of the dental follicle Osteoclast/osteoblast The recruitment of the mononuclear cells at dental follicle Prior to onset of eruption Differtiatio n Activatio n 43. Thus dental follicle serves not only as target tissue for mononuclear cells but also regulate cellular events of eruption. 44. MOLECULAR EVENTS Eruption is a localized genetically programmed event. The dental follicle contains genes that encode expression of various transcription factors and involve series of signaling interaction between the dental follicle cells and cells of bony crypts. Eruption molecules The molecules that initiate eruption, their localization and the regulation of the cellular events of eruption all must fit within the context that each tooth erupts independently. 45. Determination of the molecules that may be required for eruption began with the isolation of EGF (epidermal growth factor ) TGF (transforming growth factor ) Colony stimulating factor 1 46. TGF , EGF in incisor eruption Colony stimulating in molar eruption factor 1 According to Nakchbandi IA et al (June 2000) Experiments in vivo have established that tooth eruption fails in the absence of parathyroid hormone (PTH)-related protein (PTHrP) action in the microenvironment of the tooth because of the failure of osteoclastic bone resorption on the coronal tooth surface to form an eruption pathway. 47. Localization of eruption molecules: Studies have demonstrated that the eruption genes and their products are localized primarily in either the dental follicle or stellate reticulum. The tissue required for eruption , the dental follicle produces the majority of the potential eruption molecules. The remainder of the molecules reside in the stellate reticulum adjacent to the dental follicle. E.g IL 1 resides in dental follicle DF -95 resides in stellate reticulum 48. Sequence and chronology of tooth eruption[2] 49. Chronology and sequence Human Permanent Dentition [2] 50. CLINICAL CONSIDRATIONS [4] [5] 51. Natal and Neonatal Teeth Deciduous teeth that have erupted into oral cavity are occasionally seen in infants at birth. These are called natal teeth. Neonatal teeth have been defined as those teeth erupting in first 30 days of life 52. TEETHING Teeth break through general the oral mucosa, there is often some pain, slight fever, and general malaise, all signs of an inflammatory process. In infants these symptoms are called teething 53. Eruption Cyst An eruption cyst, or eruption hematoma, is a bluish swelling that occurs on the soft tissue over an erupting tooth. It is usually found in children. The fluid in the cyst is sometimes clear creating a pale-coloured cyst although often they are blue. An eruption cyst (eruption hematoma) is a developmental soft-tissue cyst of odontogenic origin that forms over an erupting tooth. 54. ERUPTION CYST 55. Submerged primary teeth Submerged teeth are deciduous teeth, most commonly mandibular second molars , that have undergone a variable degree of root resorption and then have ankylosed to the bone. This process prevents their exfoliation and subsequent replacement by permanent teeth. After the permanent teeth is erupted, the ankylosed appears to be submerged below the level of occlusion. 56. Impaction Teeth that cease to erupt before emergence are impacted. Causes of impaction are subdivided into:- - impaction of unerupted tooth due to obstructions by physical barriers. - impaction due to lack of eruptive force. 57. Conclusion For the clinicians to treat dental problems knowledge of proper eruption time is very important . A variety of developmental defects that are evident after eruption of the primary and permanent teeth can be related to local and systemic factors. 58. References 1.Orbans Textbook of Oral histology and embryology 12th edition; pg no. 372 - 386. 2.Avery James Textbook of oral development and histology 3rd edition pg no.92-105. 3.Nancin Antonio Ten Cate's Oral Histology Development, Structure, and Function 2012 8th edition pg no. 268-289. 4.Shafer;Hine;Levy Shafers text book of oral pathology 6th edition : pg no. 58-62. 5.Ghom Anil Textbook of Oral Medicine 2nd edition pg no. 74-76.