Development of dentition and occlusion
- 1. DEVELOPMENT OF DENTITION AND OCCLUSIONтАжтАж. BY NIDA SUMRA. INTERN.
- 3. DENTAL LAMINA... яБо The embryonic oral cavity is lined by stratified squamous epithelium known as the oral ectoderm. яБо Around 6th week the infero lateral border of the maxillary arch and the supero lateral border of the mandibular arch show localized proliferation of the oral ectoderm resulting in the formation of the horse shoe shaped band of tissue called the dental lamina. яБо The deciduous teeth are directly formed by the proliferation of the lamina. яБо The permanent molars develop as a result of its distal proliferation. яБо Succedanous teeth develop from a lingual extension of the lamina.
- 4. ENAMEL ORGANтАж яБо The ectoderm in certain areas of the dental lamina proliferates and forms knob like structures that grow into the underlying mesenchyme. яБо Each of these knobs represent a deciduous tooth and is called the enamel organ.
- 5. Based on the shape of the Enamel Organ the development of teeth is divided into 3 stages:- 1. Bud stage. 2. Cap stage. 3. Bell stage.
- 6. BUD STAGEтАж яБо This is the initial stage of tooth development where the enamel organ resembles a small bud. яБо The enamel organ consists of peripherally located low columnar cells and centrally located polygonal cells.
- 7. CAP STAGEтАж яБо The tooth bud continues to proliferate resulting in a cap shaped enamel organ. яБо The outer cells of the cap covering the convexity are cuboidal тАУ the outer enamel epithelium. яБо The cells lining the concavity of the capтЖТ tall columnar тАУ the inner enamel epithelium. яБо The polygonal cells between the outer and the inner epithelium forms a cellular network тАУ the stellate reticulum. яБо The ectomesenchymal condensation ie:-dental papilla and dental sac are pronounced during this stage.
- 8. BELL STAGEтАж яБо Due to the continued uneven growth of the enamel organ it acquires a bell shape яБо A few layers of flat squamous cells between the inner enamel epithelium and the stellate reticulum тАУ stratum intermedium. яБо As the enamel formation starts the stratum intermedium collapses to a narrow zone reducing the distance between the outer and the inner epithelium.
- 9. LATE BELL STAGEтАж яБо Inner enamel epithelium тЖТ ameloblasts ( tall columnar cells ) тЖТ enamel. яБо Dental papilla тЖТ odontoblast (cuboidal cells then later columnar) тЖТ dentin. яБо Outer enamel epitheliumтЖТ low cuboidal cells тЖТ capillary network. яБо Dental sac тЖТ circular arrangement of fibers тЖТ periodontal ligament. яБо The junction between inner enamel epithelium and odontoblast тЖТ dentinoenamel junction.
- 13. NATAL and NEONATAL TEETH... яБо Very rarely teeth are present at birth called as natal teeth. яБо If they erupt during the 1st 30 days then they are called as neo natal teeth. яБо Mostly located in the mandibular incisor region.
- 15. Chronology of Human Permanent DentitionChronology of Human Permanent Dentition
- 16. PRE EMERGENT ERUPTION... яБо Eruptive movements begin soon after the root begins to form. яБо Two processes are necessary for pre emergent eruption:- 1. There must be resorption of bone and primary tooth roots overlying the crown of the erupting tooth. 2. The eruptive mechanism itself then must move the tooth in the direction where the path has been cleared.
- 17. POST EMERGENT ERUPTION. яБо Once the tooth erupts into the mouth it approaches the occlusal level and is subjected to the forces of mastication. тАв The amount of tooth eruption after the teeth have come into occlusion equals the vertical growth of ramus in a patient who is growing normally.
- 18. TERMSтАж яБо The stage of relatively rapid eruption from the time a tooth first penetrates the gingiva to the occlusal level is called the post emergent spurt. яБо This is followed by the phase of very slow eruption termed the juvenile occlusal equilibrium. яБо When the pubertal growth ends a final phase in tooth eruption called the adult occlusal equilibrium is achieved.
- 19. яБо If the antagonist is lost at any age a tooth can erupt more rapidly demonstrating that the eruption mechanism remains active and capable of producing significant tooth movement even late in life.
- 20. THE PROBLEMSтАж
- 21. яБо In children with cleidocranial dysplasia not only the resorption of primary teeth and bone deficient but heavy fibrous gingiva and multiple supernumerary teeth also impede normal eruption. Cleidocranial dysplasia
- 22. ANKYLOSISтАж
- 25. DEVELOPMENT OF OCCLUSION AND DENTAL ARCHESтАж яБо The human dentition is in a dynamic state constantly changing throughout life. яБо A knowledge of these changes assists the clinician in determining whether or not a specific occlusion will be: sustained , worsen ,or self correct over time.
- 26. THE DEVELOPMENT OF OCCLUSION OCCURS OVER 3 DISTINCT STAGES. 1. The deciduous dentition begins soon after birth and is completed with the eruption of all deciduous teeth. 2. The eruption of the first permanent molar ushers in the mixed dentition . 3. Loss of the last deciduous tooth denotes the transition to the permanent dentition.
- 27. PERIODS OF OCCLUSAL DEVELOPMENT. 1. Pre-dental period. 2. The deciduous dentition. 3. The mixed period. 4. The permanent dentition period.
- 29. GUM PADSтАж The alveolar processes at the time of birth. яБо Dental groove:-separates the labiobuccal and the lingual portion. яБо Transverse groove:-divides the gum pad into ten segments representing each deciduous tooth. яБо Gingival groove:-separates the gumpad from the palate and the floor of the mouth. яБо Lateral sulci:-present between the canine and the 1st molar.
- 30. INFANTILE OPEN BITEтАж яБо When the upper and the lower gum pad are approximated there is a complete overjet all around. яБо This infantile open bite is considered to be normal . яБо It helps in sucking.
- 32. ERUPTION AGE and SEQUENCEтАж яБо The mandibular central incisors are the first to erupt around 6-8 months of age. яБо A variation of 3 months from the mean age is accepted to be normal. яБо The sequence of eruption is :- A тАУ B тАУ D тАУ C тАУ E. яБо The primary dentition is usually established y the age of 3 years.
- 34. SPACINGтАж яБо Spacing usually exists between the deciduous teeth for the normal development of permanent teeth. яБо These spaces are called as developmental or physiological spaces. яБо Spacing invariably is seen mesial to the maxillary canine and distal to the mandibular canine. яБо These spaces are called as primate, simian or anthropoid spaces.
- 35. DEEP BITE. яБо The deep bite is accentuated by the fact that the deciduous incisors are more upright then their permanent counterparts. яБо This is later reduced due to:- 1. Eruption of deciduous molars. 2. Attrition of incisors. 3. Forward movement of mandible due to growth. .
- 37. DISTAL STEPтАж
- 38. MESIAL STEPтАж
- 40. ERUPTION AGE and SEQUENCE.. яБо The mixed dentition period begins at around 6 yrs of age with the eruption of the 1st permanent molar. яБо This period can be divided into the following 3 phases:- 1. 1st transitional period. 2. Inter transitional period. 3. 2nd transitional period.
- 42. EMERGENCE of 1st PERMANENT MOLAR яБо The mandibular 1st molar is the first permanent tooth to erupt at around 6yrs of age. яБо The location and relation of the 1st permanent molar depends on the distal relationship between the upper and lower 2nd deciduous molars.
- 43. яБо Flush terminal plane тЖТ class ╬Щ (early and late mesial shift.) яБо Mesial step тЖТ class ╬Щ. яБо Differential growth of mandible in forward direction persists тЖТ class ╬Щ╬Щ╬Щ. яБо Distal step тЖТ class ╬Щ╬Щ.
- 44. EARLY and LATE MESIAL SHIFTтАж яБо Early shift occurs during the early mixed dentition period . яБо The eruptive forces of the 1st permanent molar is sufficient to push the deciduous 1st and 2nd molars forward to close the primate spaces and establish class╬Щ molar relationship. яБо In the cases when the primate spaces are absent the permanent 1st molar drift mesially utilizing the leeway space. яБо This occurs in the late mixed dentition period and is called the late shift. тЖТ тЖТ
- 45. INCISOR LIABILITYтАж яБо During the 1st transitional period the deciduous incisors are replaced by the permanent ones. яБо The permanent incisors are considerably larger then the deciduous teeth they replace. яБо This difference between the amount of space needed and the amount of space available is called as incisal liability. яБо The incisor liability is about 7mm in the maxillary arch and 5mm in the mandibular arch. яБо This is overcome by 3 factors :- 1. Inter-dental spaces. 2. Inter-canine width. 3. Incisor inclination.
- 46. INTER-DENTAL SPACESтАж яБо The physiologic spaces seen in the primary dentition are utilized to partly account for the incisal liability. яБо The permanent incisors are much more easily accommodated in normal alignment in cases exhibiting adequate inter-dental spaces.
- 47. INTERтАУCANINE WIDTHтАж яБо During the transition from the primary incisors permanent incisors an increase in inter-canine width of both maxillary and mandibular arch is observed. яБо Child. Adult.
- 48. INCISOR INCLINATIONтАж яБо The primary incisors are more upright than their permanent counterparts. яБо Since the permanent incisors are more labially inclined they tend to increase the dental arch perimeter.
- 49. INTER TRANSITIONAL PERIOD.. яБо In this period between the permanent incisors and the 1st permanent molars are the deciduous molars and canines. яБо This phase is relatively stable and no change occurs.
- 51. LEEWAY SPACE of NANCEтАж яБо The second transitional period is characterized by the replacement of deciduous molars and canines by the permanent premolars and cuspids respectively. яБо The combined mesio distal width of the permanent canines and premolars is less than that of the deciduous canines and molars. яБо This excess space is called leeway space of Nance. яБо 1.8mm тАУ maxillary arch. яБо 3.4mm тАУ mandibular arch.
- 52. UGLY DUCKILNG STAGEтАж яБо A transient or self correcting malocclusion is seen in the maxillary incisor region between 8-10 yrs at the time of eruption of the permanent canines. яБо This situation is described by Broadbent as ugly duckling stage as children tend to look ugly during this phase of development.
- 53. яБо As the developing permanent canines erupt they displace the roots of the lateral incisors mesially. яБо This results in transmitting the force on roots of the centrals which also get displaced mesially. яБо Hence a distal divergence of the two centrals causes midline spacing.
- 54. After the eruption of canines the pressure is transferred from the root to the coronal area of the incisors and the malocclusion is corrected. тЖТ
- 56. FEATURESтАж яБо The permanent dentition forms within the jaws soon after birth except for the formation of the cusps of the 1st permanent molar which form before birth. яБо The permanent incisors develop lingual or palatal to the deciduous incisors and move labially as they erupt. яБо The premolars develop below the diverging roots of deciduous molars.
- 57. ERUPTION SEQUENCEтАж In maxillary arch:- яБо 6-1-2-4-3-5-7 or яБо 6-1-2-3-4-5-7. In mandibular arch:- яБо 6-1-2-3-4-5-7 or яБо 6-1-2-4-3-5-7.
- 58. OCCLUSION..
- 59. DEFINITIONтАж яБо ANGLE defined occlusion as the normal relation of the occlusal inclined plane of the teeth when the jaws are closed. яБо The term occlusion has both static and dynamic aspects.
- 60. STATIC OCCLUSIONтАж яБо Static refers to the form , alignment of teeth within and between the arches and the relationship of teeth to their supporting structures.
- 61. DYNAMIC OCCLUSIONтАж яБо Dynamic refers to the function of the stomatognathic system as a whole comprising teeth supporting structures, temperomandibular joint , neuromuscular and nutritive system.
- 62. IDEAL OCCLUSIONтАж яБо It is a pre conceived theoretical concept of occlusal structures and relationships that include idealized principles and characteristics that an occlusion should have.
- 63. BALANCED OCCLUSIONтАж яБо An occlusion in which balanced and equal contacts are maintained throughout the entire arch during all excursions of the mandible.
- 64. TRAUMATIC OCCLUSIONтАж яБо Traumatic occlusion is an abnormal occlusal stress that is capable of producing or has produced injury to the periodontium. яБо Anterior cross bite which produces a traumatic bite resulting in gingival recession of the involved tooth. тЖТ
- 65. TYPES OF CUSPтАж яБо Centric holding cusps:- (stamp cusps) The facial cusp of mandibular and palatal cusps of maxillary posterior teeth. They occlude in the central fossae and marginal ridges of opposing teeth. яБо Non supporting cusps:- (shearing or guiding cusps.) The maxillary buccal and the mandibular lingual cusps . They contact and guide the mandible during excursions.
- 66. ARRANGEMENT OF TEETHтАж яБо Human dentition exhibits 2 types of teeth arrangement when the upper and the lower teeth occlude:- яБо Cusp fossa occlusion:- The stamp cusp of one tooth occludes in a single fossa of a single opponent. Tooth to tooth occlusion. яБо Cusp embrasure occlusion:- Each tooth occludes with two opposing teeth. Tooth to two teeth occlusion.
- 68. CURVE OF SPEE.. CURVE OF WILSON.. яБо Curve of Spee:- It refers to the antero posterior curvature of the occlusal surfaces beginning at the tip of the lower cuspid and following the cusp tips of the bicuspids and molars continuing as an arc through the condyle. яБо Curve of Wilson:- This is a curve that contacts the buccal and lingual cusp tips of the mandibular teeth. The curve of Wilson is medio lateral on each side of the arch.
- 69. CURVE OF MONSON. яБо It is the curve of occlusion in which each cusp and incisal edges touch or conform to a segment of a sphere in diameter with its centre in the region of glabella.
- 70. CENTRIC RELATION and OCCLUSION яБо Centric relation is the relation of the mandible to the maxilla when the mandibular condyles are in the most superior and retruded position in their glenoid fossa with the articular disk properly interposed. яБо Centric occlusion is that position of the mandibular condyle when the teeth are in maximum intercuspation.
- 71. CENTRIC CONTACTS. яБо They are areas of teeth that contact the opposing teeth. яБо Posterior centric contacts яБо Anterior centric contacts.
- 72. ECCENTRIC OCCLUSIONтАж яБо Eccentric occlusion refers to contact of teeth that occurs during movement of mandible. яБо Eccentric occlusion can be of 2 types:- 1 - Functional occlusion. яБо Lateral function:- 1- Canine guided occlusion. 2- Grouped lateral occlusion. яБо Protrusive functional occlusion. 2 - Non functional occlusion.
- 73. FUNCTIONAL OCCLUSION. яБо Also called as the Working side occlusion. яБо It refers to the tooth contact that occur in the segment of the arch towards which the mandible moves.
- 74. LATERAL FUNCTION OCCLUSION яБо It includes contacts that occur on canines and posterior teeth on the side towards which the mandible moves. яБо It is divided into two parts:- 1. Canine guided occlusion. 2. Grouped lateral occlusion.
- 75. CANINE GUIDED and GROUPED LATERAL OCCLUSIONтАж яБо CANINE GUIDED OCCLUSION. During lateral mandibular movements the opposing upper and lower canines of the working side contact thereby causing disclusion of all posterior teeth on the working and balancing side. яБо GROUPED LATERAL OCCLUSION. In addition to canine guidance when certain other posterior teeth on the working side also contact during lateral movement it is called as Grouped lateral occlusion.
- 76. PROTUSIVE FUNCTIONALOCCLUSION.. яБо It includes eccentric contacts that occur when the mandible moves forward. яБо The mandibular anterior teeth contact along the lingual inclines of the maxillary anterior teeth.
- 77. NON FUNCTIONAL OCCLUSION.. яБо The tooth contacts that occur in the segment away from which the mandible moves. яБо For eg:-if the mandible is moved to the left side contacts occur on the right side.
- 79. KEY 1 MOLAR INTERARCH RELATIONSHIPтАж яБо The mesiobuccal cusp of the upper 1st molar should occlude in the groove between the mesial and medial buccal cusp of the lower 1st molar.
- 80. KEY 2 MESIO DISTAL CROWN ANGULATION... яБо A line that passes along the long axis of the crown through the most prominent part of the center of the labial or the buccal surface is called the long axis of the clinical crown. яБо The gingival part of the long axis must be distal to the occlusal part of the axis.
- 81. KEY 3 LABIO LINGUAL CROWN INCLINATION. яБо If the gingival area of the crown is more lingually placed than the occlusal area:-positive crown inclination. яБо If the gingival area is more labially or buccally placed:- negative crown inclination. яБо Maxillary incisors:- +ve inclination. яБо Mandibular incisors:- -ve inclination. яБо Posteriors:- -ve inclination.
- 82. KEY 4 ABSENCE OF ANY ROTATIONтАж яБо Normal occlusion is characterized by absence of any rotation. тЖТ яБо Rotated posterior teeth occupy more space while rotated incisors occupy less space. Incisor rotation
- 83. KEY 5 TIGHT CONTACTSтАж яБо To consider an occlusion normal there should be tight contacts between adjacent teeth. Spaced dentition. Tight contacts
- 84. KEY 6 CURVE OF SPEEтАж яБо A normal occlusion plane according to Andrews should be flat wit the curve of Spee not exceeding 1.5mm
- 86. CROWDING.. яБо In modern population there is a strong tendency for crowding of the mandibular incisors to develop in the late teens or early twenties. яБо 3 major theories to explain this are:- 1. Lack of normal attrition in modern diet. 2. Pressure from the 3rd molars. 3. Late mandibular growth. Mandibular crowding.
- 87. LACK of NORMAL ATTRITION in the DIET. яБо Shortening of arc length and mesial migration are a natural phenomenon. яБо Hence crowding will not develop if the amount of tooth structure is lost during the final stages of growth. яБо Therefore as compared to the primitive population who had a coarse diet the modern diet is soft. яБо Hence less attrition and more chances of crowding.
- 88. PRESSURE FROM THE 3rd MOLARS. яБо In most of the cases 3rd molars are impacted because the jaw length does not increase enough to accommodate them via backward remodeling of the ramus.
- 89. LATE MANDIBULAR GROWTHтАж яБо Late incisor crowding develops as the entire mandibular dentition moves distally relative to the mandible in late mandibular growth. яБо The mandibular incisors tend to be displaced lingually.
- 90. Thank youтАж