📖 Dental Anatomy
MANDIBULAR LATERAL INCISORS
Dental AnatomyMANDIBULAR LATERAL INCISORS
The mandibular incisor is a little wider mesiodistal than the mandibular central incisor, and the crown is slightly longer from the incisal edge to the cervical line.
Facial Surface:-The facial surface is less symmetrical than the facial surface of the mandibular central incisor. The incisal edge slopes upward toward the mesioincisal angle, which is slightly less than 90°. The distoincisal angle is rounded. The mesial border is more nearly straight than the distal border.
Lingual Surface:- The incisal portion of the lingual surface is concave. The cingulum is quite large but blends in smoothly with the rest of the surface.
Root Surface:-The root is single and extremely flattened on its mesial and distal surfaces.
The Transition from the Deciduous to the Permanent Dentition.
Dental AnatomyThe Transition from the Deciduous to the Permanent Dentition.
1. The transition begins with the eruption of the four first permanent molars, and replacement of the lower deciduous central incisors by the permanent lower central incisors.
2. Complete resorption of the deciduous tooth roots permits exfoliation of that tooth and replacement by the permanent (successional) teeth
3. The mixed dentition exists from approximately age 6 years to approximately age 12 years. In contrast, the intact deciduous dentition is functional from age 2 - 2 /2 years of age to 6 years of age.
4. The enamel organ of each permanent anterior tooth is connected to the oral epithelium via a fibrous cord, the gubernaculum. The foramina through which it passes can be seen in youthful skulls
The deciduous second molars are particularly important. It is imperative that the deciduous second molars be preserved until their normal time of exfoliation. This prevent mesial migration of the first permanent molars.
Use a space maintainer in the event that a second deciduous molar is lost prematurely
MAXILLARY FIRST BICUSPID
Dental AnatomyMAXILLARY FIRST BICUSPID (PREMOLARS)
It is considered to be the typical bicuspid. (The word "bicuspid" means "having two cusps.")
Facial: The buccal surface is quite rounded and this tooth resembles the maxillary canine. The buccal cusp is long; from that cusp tip, the prominent buccal ridge descends to the cervical line of the tooth.
Lingual: The lingual cusp is smaller and the tip of that cusp is shifted toward the mesial. The lingual surface is rounded in all aspects.
Proximal: The mesial aspect of this tooth has a distinctive concavity in the cervical third that extends onto the root. It is called variously the mesial developmental depression, mesial concavity, or the 'canine fossa'--a misleading description since it is on the premolar. The distal aspect of the maxillary first permanent molar also has a developmental depression. The mesial marginal developmental groove is a distinctive feature of this tooth.
Occlusal: There are two well-defined cusps buccal and lingual. The larger cusp is the buccal; its cusp tip is located midway mesiodistally. The lingual cusp tip is shifted mesially. The occlusal outline presents a hexagonal appearance. On the mesial marginal ridge is a distinctive feature, the mesial marginal developmental groove.
Contact Points;The distal contact area is located more buccal than is the mesial contact area.
Root Surface:-The root is quite flat on the mesial and distal surfaces. In about 50 percent of maxillary first bicuspids, the root is divided in the apical third, and when it so divided, the tips of the facial and lingual roots are slender and finely tapered.
Periodontal ligament development
Dental AnatomyPeriodontal ligament development
Cells from the dental follicle give rise to the periodontal ligaments (PDL).
Formation of the periodontal ligaments begins with ligament fibroblasts from the dental follicle. These fibroblasts secrete collagen, which interacts with fibers on the surfaces of adjacent bone and cementum. This interaction leads to an attachment that develops as the tooth erupts into the mouth. The occlusion, which is the arrangement of teeth and how teeth in opposite arches come in contact with one another, continually affects the formation of periodontal ligaments. This perpetual creation of periodontal ligaments leads to the formation of groups of fibers in different orientations, such as horizontal and oblique fibers.