Presentation on theme: "Morphology of Primary Teeth Dr Heba Mohd El khodary."— Presentation transcript:
Morphology of Primary Teeth Dr Heba Mohd El khodary
Objectives: Identify and distinguish morphologic differences in primary teeth. Apply the knowledge of morphology in clinical procedures for children
Primary Dentition 20 primary teeth as compared to 32 permanent teeth No premolars in the primary dentition The primary molars are replaced by the premolars The permanent molars erupt distal to the primary second molars
General Morphologic considerations Crown Crown Root Root Pulp Pulp
I- Size & Color Smaller MD width of ant. Primary < ant. Permanent teeth MD width of Primary molars > Permanent premolars Bluish-white (Primary) vs grayish-white or yellowish- white (Permanent) This has to be kept in mind during shade selection for composite restoration or crown restoration.
II- Crown Crown form ( MD > OG ) anterior = cup posterior = square This is important during the selection of the stainless steel crown. Bulbous crown: Steep Bulbous crown: Steep Cervical constriction /Prominent cervical bulge [ G. floor – Matrix type ]. Care must be taken while preparing the proximal box, as there is risk of pulp exposure at the site of constriction. Class II cavity should be restored with proper placement of wedges at the constricted area so that the matrix band is adapted well to the tooth surface. Narrow occlusal table: Narrow occlusal table: Convergence of buccal & lingual walls. The width of he cavity should also be less in a deciduous tooth.
Contact area Contact area in primary broader, flatter and more gingival: [B&L wall of proximal box extend towards embrasure / gingival seat below contact area] Primary
II- Crown Thin Enamel Clinical significance: 1. Early diagnosis of caries 2. Bur size (recommended bur is no 330 pear shaped ) 3. Sufficient bulk of restoration Care must be taken during cavity preparation, not to extend very deep as there is increased chance of pulp exposure.
Enamel rods incline occlusally vs horizontal or apical in gingival 1/3 No beveling at the gingivo-cavo surface line angle is not required, as no enamel remain unsupported.
III- Root Roots are longer & more slender. Crown root ratio bigger in primary teeth. Roots are narrower MD than those of permanent. No root trunk in primary molars Roots of primary molars are widely divergent to accommodate buds of permanent premolars : Extraction ?
Roots are more Slender & longer Crown/Root ratio
IV- Pulp Follows the morphology of crown Higher pulp horns / mesial Pulp chamber is larger in relation to crown size compared to permanent teeth / cavity depth Canals of primary molars have many lateral branches and apical ramifications Wide apical foramina Increased blood supply : typical inflammatory response Less nerve fibers : less sensitivity to pain
Summary Primary teeth have Thinner enamel and dentin layers Pulp horns closer to the outer surface Mesial pulp horn much higher Relatively larger pulps Enamel rods direct slightly occlusally in the cervical area Cervical area is constricted significantly Roots flare as they approach the apex More tortuous and irregular pulp canals
During Cavity Preparation: The depth of the cavity should be less. The width of the cavity should also be less in a deciduous tooth. Care must be taken while preparing the proximal box, as there is risk of pulp exposure at the site of constriction. Care must be taken during cavity preparation, not to extend very deep as there is increased chance of pulp exposure. Enamel beveling at the gingivocavo surface line angle is not required, as no enamel remain unsupported. The proximal box preparation may have to be extended widely to break the contact free.