📖 Dental Anatomy
OCCLUSION AND DENTAL DEVELOPMENT- Variation in Development
Dental Anatomy1. Errors in development. These are usually genetic.
a. Variability of the individual teeth. In general, the teeth most distal in any class are the most variable.
b. Partial or total anodontia. missing teeth in children,
c. Supernumerary teeth.
d. Microdontia
e. Macrodontia
F. Microdontia
2. Errors in skeletal alignment. Malpositioned jaws disrupt normal tooth relationships.
3. Soft tissue problems.
-Ocasionally, the proper eruption of a tooth is prevented by fibrous connective tissue over the crown of the tooth.
-In the mixed dentition, the deciduous second molars have a special importance for the integrity of the permanent dentition. Consider this: The first permanent molars at age six years erupt distal to the second deciduous molars.
-Permanent posterior teeth exhibit physiological mesial drift, the tendency to drift mesially when space is available. If the deciduous second molars are lost prematurely, the first permanent molars drift anteriorly and block out the second premolars.
An incisor diastema may be present. The plural for diastema is diastemata.
-Important: The deciduous anteriors--incisors and canines are narrower than their permanent successors mesiodistally.
-Important: The deciduous molars are wider that their permanent successors mesiodistally.
-This size difference has clinical significance. The difference is called the leeway space.
The leeway space in the lower arch is approximately 3.4 mm.
-The leeway space in the upper arch is approximately 1.8 mm. In normal development, the leeway space is taken up by the mesial migration of the first permanent molars.
OCCLUSION AND DENTAL DEVELOPMENT-Stages
Dental AnatomyThe very first histological evidence of tooth development appear during the second month of intrauterine life. Calcification of deciduous incisors begins at 3-4 months in utero.
MAXILLARY SECOND BICUSPID
Dental AnatomyMAXILLARY SECOND BICUSPID
smaller in dimensions. The cusps are not as sharp as the maxillary first bicuspid and have only one root.
Facial: This tooth closely resembles the maxillary first premolar but is a less defined copy of its companion to the mesial. The buccal cusp is shorter, less pointed, and more rounded than the first.
Lingual: Again, this tooth resembles the first. The lingual cusp, however, is more nearly as large as the buccal cusp.
Proximal: Mesial and distal surfaces are rounded. The mesial developmental depression and mesial marginal ridge are not present on the second premolar.
Occlusal: The crown outline is rounded, ovoid, and is less clearly defined than is the first.
Contact Points; When viewed from the facial, the distal contact area is located more cervically than is the mesial contact area.
MORPHOLOGY OF THE DECIDUOUS TEETH
Dental AnatomyMORPHOLOGY OF THE DECIDUOUS TEETH
Deciduous Anterior Teeth.
-The primary anteriors are morphologically similar to the permanent anteriors.
-The incisors are relatively simple in their morphology.
-The roots are long and narrow.
-When compared to the permanent incisors, the mesiodistal dimension is relatively larger when compared to axial crown length
-At the time of eruption, mamelons are not present in deciduous incisors
-They are narrower mesiodistally than their permanent successors.