Give an explanation of the ideal conditions and environment needed for selecting the shade of a natural tooth. How can the details of the colour be accurately communicated to a dental laboratory for the production a porcelain restoration?

Give an explanation of the ideal conditions and environment needed for selecting the shade of a natural tooth. How can the details of the colour be accurately communicated to a dental laboratory for the production a porcelain restoration?

1. There are certain principles that should be followed during shade selection. These are as follows:

   • • Patient should be viewed at the eye level so that the most colour‐sensitive part of the retina will be used.
   • • Shade comparison should be made under different lighting conditions. Normally, the patient is taken to a window and the colour is confirmed in natural daylight after initial selection under incandescent and fluorescent lightening.
   • • The teeth to be matched should be clean.
   • • Shade comparison should be made at the start of the patient visit.
   • • Brightly coloured clothing should be draped and lipstick should be removed.
   • • Shade comparison should be made quickly, with the colour samples placed under the lip directly next to the tooth being matched.
   • • Shade should be taken in a neutral environment.
   • • The eye should be rested by focusing on a gray‐blue surface immediately before a comparison since this balances all the colour sensors of the retina and re‐sensitizes the eye to the yellow colour of the tooth.
   • • The canine can be used as a reference and the incisal edge colour should be matched separately

2. Communicating the information collected to the dental laboratory is essential for favourable results

   • • A prescription will be sent to the ceramist by the clinician.
   • • This will have general patient information including the patients number, age and sex. Patients lip length. Can also be included so the technician knows the smile line.
   • • The prescription will include a chart of the tooth colour, a paper sketch of a tooth divided to three areas (incisal, middle, cervical) and will include: • Hue of dentine as selected at middle 1/3 gingival and interproximal discoloration • Color specific areas and distribution of shades (cervical, body, incisal) • Chroma intensity. • Value of enamel overlaying the dentin. • Translucency and its distribution (incisal, incisal and proximal or very thin translucent layer) • White spots and stain areas. • Fracture lines. • Surface texture, degree of luster and glaze needed.
   • • Photographs of tooth can also be sent to the lab for the technician to see stains and cracks. • Preoperative Facial and Dentofacial photograph at rest and full smile. • Dental photograph with selected hue and chroma tabs with different light sources. A black and white photograph can be taken for value accuracy when there is a need to match to existing restorations. • After preparation of teeth a dental photograph of the prepared stumps helps the ceramist to mask unwanted dark shades and stains
   • • The shade can also be taken by using scanning devices such as spectrophotometers and colorimeters, or by using a digital impression intraoral scanner. This data can then be sent to the lab digitally.