Development of Occlusion

14,959 views

Published on

Development of Occlusion

  1. 1. Dr. Abhishek Solanki Dr. Parvind Gumber
  2. 2. INTRODUCTION  The term occlusion has both static and dynamic aspects  Static refers to form, alignment and articulation of teeth within & between dental arches and relationship of teeth to their supporting structures  It may be defined also as the contact relationship of the teeth in function or parafunction
  3. 3. IDEAL OCCLUSION:  Pre-conceived theoretical concept of occlusal structural & functional relationships that include idealized principles and characteristics that an occlusion should be NORMAL OCCLUSION:  It is class I relationship of maxillary & mandibular 1st molars in centric occlusion PHYSIOLOGIC OCCLUSION:  Occlusion that deviates in one or more ways from ideal yet it is well adapted to that particular environment is esthetic & shows no pathologic manifestations
  4. 4. FUNCTIONAL OCCLUSION:  An arrangement of teeth which will provide highest efficiency during excursive movements of mandible which is necessary during function BALANCED OCCLUSION:  An occlusion in which balance & equal contacts are maintained throughout entire arch during all excursions of mandible  Others : Therapeutic occlusion, Traumatic Occlusion, Centric Occlusion etc.
  5. 5. PERIODS OF OCCLUSAL DEVELOPMENT:  PRE-DENTAL PERIOD  DECIDUOUS DENTITION PERIOD  MIXED DENTITION PERIOD  PERMANENT DENTITION PERIOD
  6. 6. PRE-DENTAL PERIOD  The period after birth during which the neonate does not have teeth  Lasts for 6 months
  7. 7. GUM PADS  Alveolar processes at the time of birth  Pink, firm and are covered by a dense layer of fibrous periosteum
  8. 8.  Horse-shoe shaped and developed in two parts  Labio-buccal portion & lingual portion  Two portions of gum pads are separated by dental groove
  9. 9.  Gum pad are divided into 10 segments by certain grooves called transverse grooves  Each of these segment consist of developing deciduous tooth sac  Gingival groove separate gum pads from palate & floor of the mouth
  10. 10.  Transverse groove between canine & and first deciduous molar segment is called the lateral sulcus  Lateral sulci are useful in judging the inter-arch relationship at a very early stage  The lateral sulcus of the mandibular arch is normally more distal to that of the maxillary arch Lateral sulcus
  11. 11.  The upper and lower gum pads are almost similar to each other  The upper gum pad is both wider as well as longer than the mandibular gum pad  Thus when upper and lower gum pads are approximated, there is a complete overjet all around
  12. 12.  Contact occurs b/w upper & lower gum pads in first molar region and a space exists between them in anterior region  This infantile open bite is considered normal and it helps in suckling Infantile open bite for suckling
  13. 13. Status of dentition  Neonate is without teeth for about 6 months of life  At birth gum pads are not sufficiently wide to accommodate developing incisors, which are crowded in their crypts  During 1st year of life gum pads grow rapidly permitting incisors to erupt in good alignment
  14. 14.  Teeth that are present at the time of birth are called natal teeth.  Teeth that erupt during the first month of age are called neonatal teeth.  The natal and neonatal teeth are mostly located in the mandibular incisor region and show a familial tendency.
  15. 15. DECIDUOUS DENTITION PERIOD  Initiation of primary tooth buds occurs during first six weeks of intra-uterine life  Primary teeth begin to erupt at age of about 6 months  Eruption time for primary teeth : 21/2 - 3 1/2 years
  16. 16. Eruption age and sequence of deciduous dentition  A-B-D-C-E  6months – 3 Years
  17. 17. ERUPTION SEQUENCE
  18. 18. SPACING IN DECIDUOUS DENTITION  Spacing usually present b/w deciduous teeth & called physiological spaces or developmental spaces  Spaces in primary dentition is important for normal development of permanent dentition
  19. 19.  Absence of spaces in primary dentition can cause crowding (when the larger permanent teeth erupt)  Spacing invariably is seen mesial to maxillary canines & distal to mandibular canines
  20. 20.  These physiological spaces are called primate spaces or simian spaces or anthropoid spaces as they are seen commonly in primates  These spaces help in placement of the canine cusps of the opposing arch
  21. 21. Flush terminal plane  Mesio-distal relation b/w distal surfaces of upper & lower second deciduous molars is called the terminal plane  A normal feature of deciduous dentition is a flush terminal plane where distal surfaces of upper & lower second deciduous molars are in same vertical plane
  22. 22. Deep bite  A deep bite may occur in initial stages of development  Deep bite is accentuated by fact that deciduous incisors are more upright than their successors
  23. 23.  Lower incisal edges often contact cingulum area of maxillary incisors  This deep bite is later reduced due to following factors: a. Eruption of deciduous molars b. Attrition of incisors c.Forward movement of mandible due to growth
  24. 24. MIXED DENTITION PERIOD  Mixed dentition period begins at approximately 6 years of age with eruption of 1st permanent molars  During mixed dentition period, deciduous teeth along with some permanent teeth are present in oral cavity
  25. 25.  Mixed dentition period classified into three phases:  1st transitional period  Inter-transitional period  2nd transitional period
  26. 26. 1st transitional period  Characterized by emergence of 1st permanent molars & exchange of deciduous incisors with permanent incisors  1st permanent molar erupts at 6 yrs guided into dental arch by distal surface of 2nd deciduous molar
  27. 27.  Mesio-distal relation b/w distal surfaces of upper and lower 2nd deciduous molars can be of three types: 1. FLUSH TERMINAL PLANE 2. DISTAL STEP 3. MESIAL STEP
  28. 28. Flush terminal plane  Distal surface of upper & lower 2nd deciduous molars are in one vertical plane  Normal feature of deciduous dentition  Erupting 1st permanent molars may also be in a flush or end on relationship
  29. 29.  For transition of such an end on molar relation to a Class I molar relation, lower molar has to move forward by about 3-5 mm relative to upper molar  Utilization of physiologic spaces & leeway space in lower arch & by differential forward growth of mandible  Shift in lower molar from a flush terminal plane to a Class I relation can occur in two ways - Early and Late shift
  30. 30. Early shift  Early shift occurs during early mixed dentition period  Eruptive force of 1st permanent molar is sufficient to push deciduous 1st & 2nd molars forward in arch to close primate space & establish a Class I molar relationship  Since this occurs early in mixed dentition period it is called early shift
  31. 31. Late shift  Many children lack primate space & thus erupting permanent molars are unable to move forward to establish Class I relationship  In these cases, when deciduous second molars exfoliate permanent 1st molars drift mesialy utilizing leeway space  This occurs in late mixed dentition period & is thus called late shift
  32. 32. Mesial step terminal plane  Distal surface of lower second deciduous molar is more mesial than that of upper  Permanent molars erupt directly into Angle's Class I occlusion  Mesial step terminal plane most commonly occurs due to early forward growth of mandible
  33. 33.  If differential growth of mandible in a forward direction persists, it can lead to Angle's Class III molar relation  If forward mandibular growth is minimal, it can establish a Class I molar relationship
  34. 34. Distal step terminal plane  Distal surface of lower second deciduous molar being more distal to that of the upper  Thus erupting permanent molars maybe in Angle's Class II occlusion
  35. 35. Occlusal Relationship of Primary & Permanent Molars
  36. 36. Exchange of incisors:  During first transitional period deciduous incisors are replaced by permanent incisors  Mandibular central incisors : 1st to erupt  Permanent incisors > deciduous incisors
  37. 37.  This difference b/w amount of space needed for accommodation of incisors & amount of space available for this is called Incisal liability  Incisal liability (maxillary arch ) : about 7 mm  Incisal liability (mandibular arch ) : about 5 mm
  38. 38.  The incisal liability is overcome by the following factors: A. Utilization of interdental spaces seen in primary dentition:  Physiologic or developmental spaces that exist in primary dentition are utilized to partly account for incisal liability  Permanent incisors are much more easily accommodated in normal alignment in cases exhibiting adequate inter-dental spaces than in an arch that has no space
  39. 39. B. Increase in inter - canine width:  During transition from primary incisors to permanent incisors, increase in inter-canine width of both maxillary & mandibular arches takes place  This is an important factor that allows much larger permanent incisors to be accommodated in arch previously occupied by the deciduous incisors
  40. 40. C. Change in incisor inclination:  One of differences b/w deciduous & permanent incisors is their inclination  Primary incisors are more upright than permanent incisors  Since permanent incisors erupt more labially inclined, they tend to increase dental arch perimeter
  41. 41. A. Primary incisors are more upright in alignment than permanent incisors B. Permanent incisors are more labialy inclined
  42. 42. PRIMARY DENTITION PERMANENT DENTITION
  43. 43. Inter - transitional period  In this period the maxillary and mandibular arches consist of sets of deciduous and permanent teeth.  Between permanent incisors and first permanent molars are deciduous molars and canines.  This phase during the mixed dentition period is relatively stable and no change occurs.
  44. 44. 2nd transitional period  2nd transitional period is characterized by replacement of deciduous molars & canines by premolars & permanent cuspids respectively  Combined mesio-distal width of permanent canines & premolars is usually less than that of deciduous canines and molars & this Surplus space is called leeway space of Nance
  45. 45.  Leeway space (mandibular arch) : about 3.4mm (1.7mm on each side of the arch)  Leeway space (maxillary arch) : about 1.8mm (0.9 mm on each side of the arch)  Excess space available after exchange of deciduous molars & canines is utilized for mesial drift of mandibular molars to establish Class I molar relation
  46. 46. Ugly duckling stage  Sometimes a transient or self correcting malocclusion is seen in maxillary incisor region b/w 8-9 years of age  This is a particular situation seen during eruption of permanent canines
  47. 47.  As developing permanent canines erupt, they displace roots of lateral incisors on to roots of central incisors, which also get displaced mesialy  A resultant distal divergence of crowns of two central incisors causes a midline spacing
  48. 48.  Described by Broadbent ( hence also known as Broadbent phenomenon) as ugly duckling stage as children tend to look ugly during this phase of development  This condition usually corrects by itself when canines erupt & pressure is transferred from roots to coronal area of incisors
  49. 49. PERMANENT DENTITION PERIOD  Permanent dentition forms within jaws soon after birth, except for cusps of first permanent molars, which form before birth  Permanent incisors develop lingual or palatal to deciduous incisors and move labially as they erupt  Premolars develop below diverging roots of deciduous molars
  50. 50.  Eruption sequence of permanent dentition may exhibit variation: 6-1-2-4-3-5-7 or 6-1-2-3-4-5-7  In mandibular arch sequence is: 6-1-2-3-4-5-7 or 6-1-2-4-3-5-7
  51. 51. Occlusal Curvatures & Axial Position a. Curve of Spee b. Curve of Wilson c. Sphere of Monson d. Axial position
  52. 52. Curve of Spee  The curvature which begins at the tip of canines & follows buccal cusp tips of premolars & molars posteriorly, when viewed from their facial aspect  Two dimensional and curves upward from anterior to posterior
  53. 53.  Inclination of some of individual posterior teeth must be offset from vertical long axis of body, if their occlusal surfaces are to conform to this curve  Maxillary molar roots are inclined mesialy & mandibular molar roots distally
  54. 54. Curve of Wilson  Medio-lateral curvature of occlusal plane of posterior teeth  Two dimensional, at right angle to Curve of Spee  Purpose of this arc in occlusal curvature is to complement paths of condyles during movements of mandible
  55. 55.  Crowns of mandibular posterior teeth must incline to lingual, while crowns of maxillary posterior teeth must incline toward buccal  This curve becomes deeper posteriorly, so that molars inclination is greater than that of premolars  Because of this curve & associated tooth inclinations, buccal cusps of mandibular molars & lingual cusps of maxillary molars usually appear to be longer
  56. 56. Sphere of Monson  Compensating Occlusal Curvature  Three dimensional curvature of the occlusal plane, which is the combination of the Curve of Spee and the Curve of Wilson  This curvature is in form of a portion of a ball, or sphere  This curvature is concave for mandibular arch & convex for the maxillary arch
  57. 57. Axial Position  Inclination of a tooth from a vertical axis  Normally described in mesio-distal & facio-lingual directions  It is normally described in terms of root's inclination, which means that crown is normally inclined in opposite direction
  58. 58.  These inclinations are necessary for proper occlusal & incisal function of teeth  As these axial positions are described, it should be of value to relate them to individual tooth's functions, as well as its inclination relative to Curves of Spee and Wilson
  59. 59. Axial Positions of teeth TEETH DIRECTION INCLINATION (ROOT) ANT. MAXILLARY TEETH FACIOLINGUAL LINGUAL ANT. MAXILLARY TEETH MESIODISTAL INCISORS : MESIAL CANINE : DISTAL
  60. 60. TEETH DIRECTION INCLINATION (ROOTS) MAXILLARY PREMOLARS FACIOLINGUAL LINGUAL MAXILLARY PREMOLARS MESIODISTAL DISTAL MAXILLARY MOLARS FACIOLINGUAL LINGUAL MAXILLARY MOLARS MESIODISTAL MESIAL
  61. 61. TEETH DIRECTION INCLINATION MANDIBULAR INCISOR & CANINES FACIOLINGUAL LINGUAL (ROOT) MANDIBULAR INCISOR MESIODISTALLY MESIAL (ROOT) MANDIBULAR CANINES MESIODISTALLY DISTAL (ROOT)
  62. 62. TEETH DIRECTION INCLINATION MANDIBULAR PREMOLAR MESIODISTALLY DISTAL (ROOT) MANDIBULAR PREMOLAR 1st FACIOLINGUAL LINGUAL (ROOT) MANDIBULAR PREMOLAR 2nd FACIOLINGUAL BUCCAL (ROOT) MANDIBULAR MOLAR MD & FL DISTAL & BUCCAL MD : Mesio-distal FL: Facio-lingual
  63. 63. References  CONCISE DENTAL ANATOMY & MORPHOLOGY : JAMES L FULLER  DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION: WHEELER’S  TEXTBOOK OF DENTAL ANATOMY, PHYSIOLOGY & OCCLUSION: RASHMI GS (PHULARI)  MOYERS RE: HANDBOOK OF ORTHODONTICS  ORTHODONTICS - THE ART & SCIENCE : S.I. BHALAJHI  INTERNET
  64. 64. THANK YOU

×