24 Questions
What is the average amount of crowding in the incisor segment when permanent incisors erupt?
1.6 mm
Which teeth erupt at 6 years of age during the first phase of permanent tooth eruption?
First molars
What is the difference in size between primary molars and premolars replaced by them called?
Leeway space of Nance
What is the purpose of the Leeway space of Nance in the dental arch development?
To align permanent incisors and adjust the occlusal relationship of molars
During which phase of permanent tooth eruption do the permanent central and lateral incisors erupt?
Second phase
What is the function of the first permanent molars during the first phase of eruption?
To support the deciduous dentition
What happens to the canines during the fourth phase of permanent tooth eruption?
They force themselves by wedging between the lateral incisors and first premolars
What is the purpose of the second molars during the fourth phase of permanent tooth eruption?
To support the canines during their wedging
At what age is the permanent dental arch typically completed?
12 years
What is the function of the primate space?
To preserve a space for the permanent teeth for proper occlusion
What is the name of the curve that occurs in the sagittal plane and is observed from a point opposite the first molars?
Curve of Spee
What is the direction of the inclination of the crowns of maxillary posterior teeth?
Buccally
Why does the Curve of Wilson become deeper as you move posteriorly?
Because the inclinations of posterior teeth become greater as you go posterior
What is the name of the phase that occurs after the completion of the permanent dental arch?
Fifth phase
What is the name of the space that occurs between the upper B and C teeth in the maxillary arch?
Primate space
What is the term for the curved planes of the dental arches that occur in the upper and lower arches?
Curved occlusal planes
What is the term used to describe the horizontal overlap of the maxillary anterior teeth over the mandibular teeth?
Overjet
What is the term used to describe the vertical overlap of the maxillary anterior teeth over the mandibular teeth?
Overbite
What is the shape of the dental arches in both the upper and lower jaws?
Parabolic
How many segments do the parabolic curves of each dental arch divide into?
Three
What is the direction of the posterior segment of the upper dental arch?
Slightly deviated lingually
What is the reason for the posterior segment of the upper dental arch to be slightly deviated lingually?
Due to the DB convergence of the upper first molar and the location of the second and third maxillary molars
What happens to the distal convergence of the upper molars as we go posterior?
It increases
What happens to the buccolingual dimension of the upper molars as we go posterior?
It decreases
Study Notes
Phases of Eruption of Permanent Teeth
- The first permanent molars erupt at 6 years of age, supporting the deciduous dentition and increasing chewing efficiency to adapt to jaw growth.
- The permanent central and then lateral incisors erupt with 1.6mm crowding in the lower incisor segment, with their permanent location and alignment established only after dental arch development is completed.
- The 1st and 2nd premolars take the places of the deciduous molars, with a smaller size in M-D dimensions, resulting in Leeway space of Nance (average: 0.9 mm on each maxillary quadrant, 1.7 mm on each mandibular quadrant).
- The Leeway space of Nance is utilized for the alignment of permanent incisors and for the molars to adjust the proper occlusal relation of maxillary and mandibular permanent molars.
- The canines (corner stones) force themselves by wedging between the lateral incisors and first premolars in both jaws, with the second molars erupting distal to the first molars.
- The eruption of the wisdom tooth marks the final phase.
Completed Dental Arch
- The permanent dental arch is completed at the fourth phase (end of 12 years with the eruption of 3 & 7).
Primate Space
- The primate space is noticed during the development of deciduous occlusion.
- It is the space between upper B & C for maxillary teeth and between lower C & D for mandibular teeth.
- Its function is to preserve a space for the permanent teeth for proper occlusion.
Curves of Occlusal Planes
- The occlusal surfaces of dental arches do not follow a flat plane but have curved surfaces.
- The curves of the lower dental arch are concave, while those of the upper dental arch are convex.
- The two curved planes become identical in centric occlusion.
Curve of Spee
- The curve is observed in the sagittal plane.
- It is observed from a point opposite the first molars.
- Incisal ridges of anterior teeth and buccal cusps of posterior teeth follow a curve that ends at the anterior border of the condyle.
- This curve complements the path of the mandibular condyles in the anterio-posterior movements of the mandible.
Curve of Wilson
- The curve is observed in the coronal plane.
- For each posterior tooth, the occlusal surfaces of both right and left teeth adapt to a curved plane (convex for upper and concave for lower).
- The curve becomes deeper as you go posterior due to the increased inclination of posterior teeth.
- The crowns of mandibular posterior teeth incline lingually, while those of maxillary posterior teeth incline buccally.
Overbite and Overjet
- The horizontal overlap is known as overjet (2-4 mm).
- The vertical overlap is known as overbite (2-4 mm).
Relationship of Anterior Teeth
- Maxillary anterior teeth overlap mandibular teeth.
- The incisal edges of maxillary anterior teeth are labial to the incisal edges of mandibular teeth.
- The parabolic curves of each dental arch are divided into three segments overlapping each other.
This quiz covers the different phases of permanent teeth eruption into dental arches, including the first phase of molar eruption and the second phase of incisor eruption.
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