Clinical
Fig 1a
Fig 1b
Figs 1a and b: It is possible to achieve a uniform preparation by using vertical grooves with a thickness that is visually controlled and does not exceed the diameter of the bur
Fig 2 Fig 3 Fig 4
Figs 3 and 4: The aesthetic analysis and the patient’s wishes indicate the need for bonded ceramic veneers. With the help of composite resin placed freehand on the labial surfaces an initial chairside impression can be taken. To simulate the shortening of the canines, the teeth that are too long are marked with a black felt-tip pen (arrows)
Fig 2: Burs used for the controlled penetration technique. The diameter of the diamond bur and that of the shank make it possible to calculate the depth of penetra- tion. The length of the shank must make it possible to access the tooth’s full length
Fig 5
Fig 5: The diagnostic model is modified according to instructions given by the practitioner (impressions, photos etc). The wax-up makes it possible to lengthen and resize the teeth. The new appearance is recorded using a double mix silicone impression in order to optimise precision. This impression will serve as a mould when making the intraoral mock-up
to check the preparation. As P. Magne demonstrated, this
option consists of preparing two silicone indexes cut into strips (one for the vertical and one for the horizontal axis), making it possible to assess the reduction of tissue during preparation. This method completely supports the principle of maximum tissue conservation and ensures a predictably consistent outcome. However, this is a complex and time-consuming procedure because frequent use of the control indexes is necessary.
2. Controlled
penetration methods Contrary to the methods described above, the idea of controlled penetration makes it possible to
Fig 6
Fig 7
Figs 6 - 8: With the mock-up in place, the bur is moved over the labial surface, in parallel lines, until contact with the shank is achieved. Three to four grooves are sufficient to mark the final depth of the preparation. After establishing the occlusal reference points, the grooves are accentuated with a pencil
Fig 8
perform a predictable reduction of dental tissue (Table 2) thanks to the use of specially designed burs (Fig 2). Using their shape will physically limit the potential for possible errors.
The direct technique The first clinical suggestions for this technique recommend the use of specific burs that limit the depth of penetration due to their shape. While with this technique the
depth of penetration is controlled and known, the initial thickness of the enamel cannot be assessed. Also, with time and through varying aetiological wear and tear, there is a natural variation between teeth.
Continued » Scottish Dental magazine 61
“Whenever clinically
possible, it is recommended to favour a minimally- invasive enamel preparation that will enhance the longevity of the restoration”
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