7. Dental arches and functional groups of teeth - classes. Planes and sides for tooth orientation. Numbering systems.
Covers the dental arches and the four functional tooth groups, with a table of how many incisors, canines, premolars and molars sit in each arch in both dentitions. Explains the sagittal, horizontal and transverse reference planes, then the names for tooth surfaces and directions such as mesial, distal, labial and palatal. Closes with four tooth-numbering systems (FDI, Universal, Palmer and Zsigmondy) compared in a table, including a note on how charts are oriented to the patient.
Topic 7 of 75 in the MU Sofia syllabus for Preclinics of Dental Prosthetics (Dental Medicine, Year 2). The free AceMed note covers it in 5 sections, about 193 words (3 min of reading), with 13 flashcards.
In this note
Introduction
Functional groups
Planes of reference
Naming surfaces and directions
Numbering systems
Introduction
The teeth of each jaw stand in a curved row, the dental arch: the maxillary (upper) arch and the mandibular (lower) arch. How the two arches meet when the mouth closes is occlusion; an imperfect meeting is malocclusion.
Functional groups
Incisors and canines are the anterior teeth; premolars and molars are the posterior teeth. Premolars are new in the permanent set: they erupt where the primary molars stood.
Planes of reference
These planes don't depend on how the head is held, so they describe the teeth the same way every time.
Naming surfaces and directions
A crown is like a cube: one side joins the root and five sides are free.
Mesial and distal together are the proximal surfaces; neighbours touch at contact areas. The mesial of each tooth faces the distal of the one in front, except between the two central incisors, whose mesial surfaces face each other. A gap between neighbours is a diastema.
Numbering systems
Writing "second permanent maxillary left molar" on every chart wastes time, so teeth are coded.
Charts are drawn as if facing the patient, so the patient's right is on your left. The FDI code also shortens notes: caries profunda 23, 26; obturatio dentium 34, 35, 46.
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