Makes it easy to create natural surface textures

Fig. 1
The fine grit JOTA Diamond Stone is used for contouring and preparing a very uniform crown surface before preparing the microstructure.

Fig. 2
Looking closely at natural teeth it can be seen that they have vertical grooves. These grooves never run in a completely straight line, but more in an s-shape. They frequently extend from the cervical third to the incisal edge. Abrasion of convex areas emphasizes the definition of the grooves so that they stand out even more. The grooves are deepest in the middle of the tooth. This area is generally concave and therefore better protected against natural or mechanical abrasion, e.g. contact with the lips or tooth brushing. Always start with the vertical grooves when preparing the surface texture. Draw all thegrooves with a pencil and prepare them using a flame-shaped diamond instrument. Then prepare the horizontal grooves. To prepare the horizontal grooves, change the direction of movement and angle of the diamond to the tooth surface. Wider grooves can be prepared if the diamond is placed flatter on the tooth surface. When the axis of the instrument is straightened, preparation is concentrated at the tip and the grooves become more defined. These movements are alternated according to the surface section to be contoured. In the preparation sequence for contouring the surface, the horizontal grooves should be created after placing the vertical grooves.

Fig. 3
Initially adolescents' teeth have growth lines (Retzius striae or perikymata). Over the years these lines gradually disappear due to abrasion of the teeth so that horizontal grooves or lines remain only in concave areas. Tungsten carbide instruments are used for reproducing these lines.

Fig. 4
The tungsten carbide instrument is occasionally ground to the correct shape using a diamond wheel (916DG.220) to ensure that natural lines and grooves are produced.

Fig. 5
A reference line is drawn with a pencil so that the widest and deepest grooves can be prepared with the diamond instrument. The deepest reference lines cut through the transition angle of the tooth surface and extend around the circumference the tooth. The same working stages are therefore also completed palatally.

Fig. 6
Preparing growth lines in adolescent teeth. The path of growth lines or Retzius striae is marked with a pencil in order to reproduce them. The largest grooves are prepared with the tip of a diamond instrument (869.014). For finer grooves, reference lines are marked one millimetre apart. The grooves are prepared with a long, coarse-grit diamond instrument. It is used tangential to the surface and covers 2 to 3 mm

Fig. 7
The crown is glazed in the furnace, but without the use of glaze and at a lower glaze firing temperature. The surface is then prepared with extreme care using the JOTA silicone wheel to ensure the surface texture is not damaged. Glaze is used for teeth without growth lines and all contours are then lightly polished with the silicone wheel.

Fig. 8
The final working stage is to produce a natural high lustre using a felt wheel and JOTA diamond polishing paste.