Occlusion in Permanent Dentition PDF

Occlusion in permanent dentition Dr Sandeep Gupta Oral Pathologist OCCLUSION “Occlusion is the contact between maxilla & mandible at rest , all the possible positions & functional movements of mandible” o Involves muscles o Bone Occlusion is a complex phenomenon involving  Teeth  Periodontal ligam...

Occlusion in permanent dentition Dr Sandeep Gupta Oral Pathologist OCCLUSION “Occlusion is the contact between maxilla & mandible at rest , all the possible positions & functional movements of mandible” o Involves muscles o Bone Occlusion is a complex phenomenon involving  Teeth  Periodontal ligament  TMJ  Nervous system Occlusion constantly changes Development Maturity Aging Factors influencing occlusion Development of occlusion Dental arches Hard tissue -Jaws, Teeth and TMJ Soft tissues Sequence of eruption Factors influencing occlusion Development of occlusion Dental arches Arch form/shape Normal shape  U  upper arch Variations  Oval, ‘V’, Square Arch size Normally maxillary arch is bigger Alteration in sizes of arch may result in occlusal disharmony Factors influencing occlusion Jaws Size & shape of jaw bone Relationship of jaw bones Centric Eccentric Teeth Size & shape teeth Position/Alignment Inclinations/Plane & Compensating curvatures Factors influencing occlusion Soft tissues Muscles Nerves Ligament  Normally teeth placed in neutral zone i.e. external force by lips, cheek & internal force by tongue  Which effect the position of mandible Sequence of eruption  Normal o Deciduous  A-B-D-CE o Permanent Upper  61243578 Lower  61234578 Development of occlusion Occlusal development can be divided into the following developmental periods Pre dentition period Deciduous dentition period Mixed dentition period Permanent dentition period Pre dentition period From birth to 6 month periods  No teeth Alveolar process  Gum pads Pink Firm Covered by dense layer of fibrous periosteum Both jaws undergo rapid growth, the growth is in 3 planes of space Downward Forward  Forward growth for the mandible is greater Laterally Pre dentition period Upper gum pad is wider & longer than the mandible gum pad Contact occurs between upper & lower gum pads at the 1st molar region & space exists between them in the anterior region. This infantile open bite is considered normal & help in suckling Natal &/Neonatal teeth are located in the mandible incisor region Deciduous dentition period Sequence of eruption of the deciduous dentition  A-B-D-C-E Mandible C I  1st teeth to erupt into oral cavity Primary dentition  usually established by age of 2 &1/2 – 3 years Lengthening of the arches at their posterior (distal) ends & also slightly more forward growth of the mandible than the maxilla Deciduous dentition period Spaces Spaces usually exists between the deciduous teeth Known as physiological spaces or developmental spaces Important of space  Helps in normal development of permanent dentition Spaces  Absence of spaces in primary dentition indication that crowding of teeth can occur Spaces Primate space or Simian space  Spacing occurs mesial to the maxillary canine & distal to the mandibular canine This is physiological space These space helps in placement of the canines of the opposing arch Primate spaces / Simian space Flush/Vertical terminal plane The other feature of deciduous dentition is the mesiodistal width of mandible 2nd molar is more than the mesiodistal width of maxillary 2nd molar Difference in dimension the mesial surfaces of 2nd molars tend to lie in the same vertical plane /in one plane forming flush terminal plane or end to end molar relationship or cusp to cusp relationship Terminal plane Flush Mesial step Distal step Deep Bite Normally -- The lower incisal edge often contact the cingulum of maxillary incisors Deep Bite This deep bite is later reduced by Eruption of deciduous molar Attrition of incisors Forward movement of mandible As the dental arches becomes wider & longer, the deciduous teeth become more spaced Mixed dentition period Occurs at approximately 6 years of age Begins with the eruption of the 1st permanent molars distal to the 2nd deciduous molars These are the 1st teeth to erupt & they initially articulate in an end on relationship On occlusion, the permanent incisors “spread out” due to spacing Mixed dentition period In the older literature, is called by the “Ugly duckling stage” with the eruption of the permanent canines, the spaces often will close Mixed dentition, the deciduous 2nd molars have a special importance for the integrity of the permanent dentition Mixed dentition period  The 1st permanent molar erupt distal to the 2nd deciduous molars are in flush terminal plane/end on relationship  For the transition of such an end on molar relationship to class I molar relationship Mixed dentition period Lower molar has to move forward by 3-5mm relative to upper molar occurs by utilization o Physiological spaces o Leeway spaces in lower arch By differential early forward growth of mandible Per post teeth exhibit physiological mesial drift, tendency to drift mesially when space is available Leeway space of Nance Difference in size of deciduous & permanent teeth considered Replacement of deciduous molars & canines by premolars & permanent canines/cusped respectively Combined width of permanent canines & premolars is usually less than that of the deciduous canine & molars Surplus extra space  Leeway space of Nance Leeway space of Nance Amount of leeway space is greater in the mandible arch than in the maxillary arch  Maxillary arch  1.8mm (0.9mm on each side of the arch)  Mandible arch  3.4mm (1.7mm on each side of the arch) Excess space available after exchange of deciduous molars & canines is utilised for mesial drift of mandible molars to establish class I molar relation To relieve crowding of anterior teeth Leeway space of Nance Permanent dentition period Permanent dentition forms within the jaws soon after birth, except for the cusps of 1st permanent molars which form before birth Sequence of eruption Maxillary arch  6-1-2-4-3-5-7 6-1-2-4-5-3-7 Mandibular arch  6-1-2-3-4-5-7 6-1-2-4-3-5-7 Difference is noted in the eruption timing of canines in both arches Permanent dentition period If there is any change in the eruption sequence, that may effect the amount of space available, for erupting permanent teeth & cause disturbance in occlusion ANGLES CLASSIFICATION Angle came up with three classes, Class I, II and III 1-Class I patient's profile is characterized as normal. 2-Class II patient's profile is deficient in chin length and characterized as a retruded (retrognathic) profile. 3-Class III patient's profile is excessive in chin length and characterized as protruded (prognathic) profile. Angle’s Classification: 1st permanent molars are the key of occlusion Mesiobuccal cusp of the maxillary first molar occludes in II groove of the the Class mesiobuccal mandibular first molar. This normal relationship of these two teeth is called the key of occlusion. Thank You