s10-finals-Dev. of normal occlusion Flashcards
(25 cards)
What are the features of the gum pad period in newborns?
Alveolar ridges covered with dense periosteum; no erupted teeth; anterior open bite with Class II pattern (Mn. distal to Mx.).
What is the normal gum pad relationship at rest?
Mx. and Mn. gum pads contact at the molar region; Mx. anterior width > Mn.; Mn. distal to Mx. by ~2.5–2.7 mm; up to 5 mm anterior overjet.
What variations may occur in the gum pad period?
Pre-term babies may show overbite/overjet; natal/neonatal teeth; cleft lip/palate.
What are the three types of deciduous molar terminal planes at age 3?
Flush (straight), mesial step (Mn. molar mesial to Mx.), distal step (Mn. molar distal to Mx.).
Why is spacing important in deciduous dentition?
Absence of spacing may indicate future crowding due to larger permanent teeth. Primate spaces (mesial to Mx. canines/distal to Mn. canines) are critical.
Describe overbite in deciduous dentition at age 3.
Deep bite initially; Mn. incisors contact Mx. cingula; reduced by posterior eruption, incisor attrition, and Mn. growth.
What causes the transition from flush terminus to mesial step at age 6?
Early mesial shift: eruptive forces of 1st permanent molars push deciduous molars forward, closing primate spaces.
How does the terminal plane affect permanent molar occlusion?
Flush → end-to-end → Class I (if Mn. moves forward); mesial step → Class I; distal step → Class II.
What is Primary Failure of Eruption (PFE)?
Incomplete eruption despite clear pathway; linked to PTH1R mutation; causes posterior open bite; managed via extraction/prosthetics (avoid orthodontic extrusion).
What characterizes ideal occlusion at age 7?
All 1st molars erupted; Class I molar relation (mesial step); tight proximal contacts.
What is incisal liability, and how is it resolved?
Permanent incisors are larger than deciduous. Resolved by: utilizing spacing, increasing inter-canine width, and labial inclination of incisors.
What is the Broadbent phenomenon?
Transient Mx. central diastema due to canine crypt pressure on incisor roots; self-corrects with canine eruption.
How is deep overbite corrected by age 8–9?
Eruption of premolars restores posterior vertical dimension.
What is the Leeway space, and why is it important?
Extra space from deciduous canines/molars being wider than premolars. Mn. space > Mx. (1.7 mm vs. 0.9 mm/quadrant); used for late mesial shift to achieve Class I molars.
What happens if Leeway space is deficient?
Crowding occurs; growth may not compensate for space shortage.
How does diastema closure occur by age 10–12?
Pressure from erupting permanent canines pushes incisor crowns distally, closing gaps.
What role do premolars play at age 10–12?
Eruption corrects vertical dimension and overbite.
When is the permanent dentition complete (excluding 3rd molars)?
By age 12, with Mx. canine eruption.
What defines Angle’s Class I molar occlusion?
Mx. 1st molar’s mesiobuccal cusp fits Mn. 1st molar’s mesiobuccal groove.
What defines Angle’s Class II molar occlusion?
Mx. 1st molar’s mesiobuccal cusp rests between Mn. 1st molar and 2nd premolar.
What defines Angle’s Class III molar occlusion?
Mx. 1st molar’s mesiobuccal cusp occludes distal to Mn. 1st molar’s mesiobuccal groove.
What is the significance of primate spaces?
Facilitate alignment of permanent teeth; Mn. primate space is ~2 mm larger than Mx.
How does late mesial shift differ from early mesial shift?
Early shift: occurs with 1st molar eruption (uses primate spaces). Late shift: occurs after deciduous molar exfoliation (uses Leeway space).
What causes transient flaring of Mx. incisors?
Broadbent phenomenon: pressure from developing canines displaces incisor roots mesially, flaring crowns distally.
