Introduction to Dental Anatomy (Dental Anatomy, Physiology and Occlusion) Part 4

Measurement of Teeth

Readers who are not familiar with the Boley gauge should study its use before reading the following instructions on the application of the table of measurements.

To understand the table, let us demonstrate the calibrations as recorded and the landmarks they encompass. There are eight calibrations of each tooth to be remembered. These measurements are shown in the accompanying example for the maxillary central incisor (see the example included in Table 1-1).

The method for measuring an anterior tooth is shown in Box 1-1 (Figures 1-21 through 1-27), and the posterior method is shown in Box 1-2 (Figures 1-28 through 1-34).

Summary

Terminology is an established basis for communication, and therefore the importance of learning the nomenclature for dental anatomy cannot be minimized. The terms used in describing the morphology of teeth are used in every aspect of dental practice.

Although there is no such thing as an established invariable norm in nature, in the study of anatomy it is necessary that there be a starting point; therefore, we must begin with an arbitrary criterion, accepted after experimentation and due consideration. Since restorative dentistry must approach the scientific as closely as manual dexterity will allow, models, plans, photographs, and natural specimens should be given preference over the written text on this subject.

Figure 1-18 Occlusal view of the models shown in Figures 1-16 and 1-17.

Table 1-1 Measurements of the Teeth: Specifications for Drawing and Carving Teeth of Average Size* 

	Length of Crown	Length of Root	Mesiodistal Diameter of Crown1	Mesiodistal Diameter of Crown at Cervix	Labio- or Buccolingual Diameter of Crown	Labio- or Buccolingual Diameter of Crown at Cervix	Curvature of Cervical Line—Mesial	Curvature of Cervical Line—Distal
Maxillary Teeth
Central incisor	10.5	13.0	8.5	7.0	7.0	6.0	3.5	2.5
Lateral incisor	9.0	13.0	6.5	5.0	6.0	5.0	3.0	2.0
Canine	10.0	17.0	7.5	5.5	8.0	7.0	2.5	1.5
First premolar	8.5	14.0	7.0	5.0	9.0	8.0	1.0	0.0
Second premolar	8.5	14.0	7.0	5.0	9.0	8.0	1.0	0.0
First molar	7.5	B L	10.0	8.0	11.0	10.0	1.0	0.0
		12 13
Second molar	7.0	B L	9.0	7.0	11.0	10.0	1.0	0.0
		11 12
Third molar	6.5	11.0	8.5	6.5	10.0	9.5	1.0	0.0
Mandibular Teeth
Central incisor	9.0*	12.5	5.0	3.5	6.0	5.3	3.0	2.0
Lateral incisor	9.5*	14.0	5.5	4.0	6.5	5.8	3.0	2.0
Canine	11.0	16.0	7.0	5.5	7.5	7.0	2.5	1.0
First premolar	8.5	14.0	7.0	5.0	7.5	6.5	1.0	0.0
Second premolar	8.0	14.5	7.0	5.0	8.0	7.0	1.0	0.0
First molar	7.5	14.0	11.0	9.0	10.5	9.0	1.0	0.0
Second molar	7.0	13.0	10.5	8.0	10.0	9.0	1.0	0.0
Third molar	7.0	11.0	10.0	7.5	9.5	9.0	1.0	0.0

B, Buccal; L, Lingual.

*In millimeters. This table has been "proved" by carvings shown in Figures 1-16 and 1-17.

 The sum of the mesiodistal diameters, both right and left, which gives the arch length, is maxillary, 128 mm; mandibular, 126 mm.

 Lingual measurement is approximately 0.5 mm longer.

Table 1-1 Measurements of the Teeth: Specifications for Drawing and Carving Teeth of Average Size—cont’d

			Measurements of the Teeth: an Example*
	Length of Crown	Length of Root	Mesiodistal Diameter of Crown1	Mesiodistal Diameter of Crown at Cervix	Labio- or Buccolingual Diameter of Crown	Labio- or Buccolingual Diameter of Crown at Cervix	Curvature of Cervical Line—Mesial	Curvature of Cervical Line—Distal
Maxillary Teeth Central incisor	10.5	13.0	8.5	7.0	7.0	6.0	3.5	2.5

*In millimeters.

The sum of the mesiodistal diameters, both right and left, which gives the arch length, is maxillary, 128 mm; mandibular, 126 mm.

Figure 1-19 Maxillary left canine. When viewing the mesial and distal aspects, note the curvature or bulge on the crown at the cervical third below the cementoenamel junction. This is called the cervical ridge, or the cervicoenamel ridge.

Figure 1-20 Maxillary right first molar. When viewing the mesial and distal aspects, note the curvature or bulge on the crown at the cervical third below the cementoenamel junction.

1-1 Method of Measuring an Anterior Tooth—cont’d

*Use the parallel beaks of the Boley gauge for measurements whenever feasible. The contrast of the various curvatures with the straight edges will help to make the close observer more familiar with tooth outlines.

1-1 Method of Measuring an Anterior Tooth—cont’d

fThis measurement is most important because normally it represents the extent oof curvature approximately of the periodontal attachment when the tooth is in situ.

1-1 Method of Measuring an Anterior Tooth—cont’d

1-1 Method of Measuring an Anterior Tooth—cont’d

Every curve and segment of a normal tooth has some functional basis, and it is important to reproduce them accurately. The successful clinician in dentistry or, for that matter, any designer of dental restorations should be able to mentally create pictures of the teeth from any aspect and relate those aspects of dental anatomy to function. Complete pictures can be formed only when one is familiar with the main details of tooth form.