| SECTION III | CARVING TEETH |
- Blocks of carving wax (34 mm × 17 mm × 17 mm for molars or 32 mm × 12 mm × 12 mm for other teeth)
- Boley gauge (Vernier caliper)
- Millimeter ruler
- Office knife and sharpening stone
- Roach carver, No. 7 wax spatula, and PKT-1 (for melting and adding wax)
- No. 3, No. 5 to 6, 6C, and PKT-4 carvers
- Sharpened drawing pencil
- Large or small tooth model and its measurements
Carving a tooth helps you to see the tooth in three dimensions and also to develop considerable manual skill and dexterity. Examples of carvings by dental hygiene students are shown in Figure 13-6. While eventually you may be able to carve a tooth from a block of wax without preliminary measurement, the beginner can only do well by approaching the carving systematically in the same way you approached the drawings: first, by drawing a box on the wax block; second, by sketching an outline of the tooth in the box; and third, by carving around the sketch or outline, one view or aspect at a time (sequence is shown in Fig. 13-7).
FIGURE 13-6. Maxillary central incisor wax carvings by first-year dental hygiene students as seen from the mesial (M), lingual (L), incisal (I), facial (F), and mesial–facial (M, F) aspects. The crown and half of the root were carved to specific dimensions that were proportional to the tooth model they viewed during the carving. These excellent carvings were each done in less than 3 hours as a required skill test.
FIGURE 13-7. The sequential method described in this chapter for carving a tooth from a block of wax. The final product should look like those shown in Figure 13-6. The large letter M denotes the mesial aspect of the carving. Likewise, F indicates the facial side of the block.
When approaching the task of carving a tooth, consider Michelangelo who conceived of his task of producing a marble statue by “liberating the figure from the marble that imprisons it.” And remember that he, too, sometimes made mistakes and had to discard a half-finished statue. The same can happen to your tooth carving. To minimize this, as you cut away wax, repeatedly examine your carving from all sides; turn it around and around and compare it with your specimen from each view. Where it is too bulbous, the fault is easily correctable by further reductions. Where too much wax has been removed, you have one of three choices: add molten wax to the deficient region, make the entire carving proportionally smaller, or start with a new block of wax.
C. EXAMPLE: HOW TO CARVE A MAXILLARY CENTRAL INCISOR FROM A BLOCK OF WAX
Use the measurements you used for drawing. (Again, use the measurement of the buccal cusp on premolars for the crown length and of the mesiobuccal cusp and mesiobuccal or mesial root on molars for the root length.) This consistency of method prevents confusion. Allowance is made for the greater length of some lingual cusps, which are longer than the measured buccal cusp. Refer to Figure 13-7 as you follow the following guidelines:
Step 1: Shave the sides of the block flat and make all angles right angles.
Step 2: Measure 2 mm from one end of the block, and draw a line at this level, encircling the block (on all four sides). (This end of the block will be the incisal or occlusal end of the tooth, and the 2-mm allowance here is to provide for the extra length of the lingual cups on molars that are longer than the mesiobuccal cusp that established crown length. Although it is convenient to allow the 2 mm on all carvings, it is essential only for molars.)
Step 3: From the 2-mm line, measure the crown length and draw a second line around the block at this level. This line is the location of the cervical line on the facial, mesial, distal, and lingual sides of the tooth (Fig. 13-7A).
Step 4: From this cervical line, measure one-half of the length of the root and draw a third line around the block. (The end of the block beyond this line will be referred to now as the base.)
Step 5: On the base of the block, carve, on appropriate sides, F (facial), L (lingual), M (mesial), and D (distal). Be sure to put M and D in the proper relation to F and L so that you will carve a right or a left tooth, whichever you intend.
Step 6: Using a very sharp pencil, draw a shallow line lengthwise on the block in the center of the mesial surface. Do the same on the distal surface and be sure that these lines are exactly opposite.
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