It is obvious that to most easily achieve a consistent and predictable result when selecting a shade of restorative material to match the tooth tissue being restored, the material of the shade guide should be the same as the restorative material. Unfortunately this may not be achieved as many manufacturers’ shade guides are made from a dissimilar material to the restorative material being used.

One of the most commonly used shade guides is the Vita Shade Guide (Figure 2.3), which is used to shade match for ceramics. Unfortunately, the tabs of the shade guide are made of a bulk of material whereas the crown is usually in much thinner sections, altering translucency and shade substantially. It is also possible to get small tabs of the various stains that are available to characterize the ceramic (Figure 2.4).

Fig. 2.3 Lumin Vacuum Shade Guide (Vita) otherwise known as the Vita Shade Guide. This is the most commonly used shade guide for matching ceramic restorations.

Fig. 2.4 Various stains that may be used to characterize dental ceramic.

Some shade guides are designed such that a dentist can select both a shade for ceramic and acrylic when crowns and dentures are being provided for the same patient as the shades for the two materials correspond (Figure 2.5). Several manufacturers have recommended using the Vita Shade Guide to shade match for the resin-based composites, and a form of recipe wheel (Figure 2.6) guides the dentist in using the shades in the kit.

Fig. 2.5 Chromascop Shade Guide (Ivoclar Vivadent) used for cases when ceramic units (such as crowns) are to be matched with a denture with acrylic teeth on it.

Fig. 2.6 A recipe wheel (Filtek Supreme XT, 3M ESPE).

To reduce the risk of error, some manufacturers have produced shade guides which are made of the same resin-based composite that is in the kit. This has the benefit that similar types of material are being matched. There is a greater chance that a good shade match will be achieved. Figure 2.7 illustrates two shade guides. One is a simple tab system composed of the resin composite in the kit and the other involves inserting a core of the ‘dentine’ shade in the shell of ‘enamel’. If a small drop of glycerine (or water) is placed to remove the air barrier between the two shade tabs, the dentist can see the final shade result with some certainty.

Fig. 2.7 Two shade guides constructed using the material in the kit: (A) Venus (Heraeus) and (B) Miris 2 (Coltène Whaledent).

The other and probably most reliable method of correctly ascertaining shade is applying a small piece of the composite to be used to the tooth without any bond and curing it for 10 seconds. This must be cured as there is a change in shade (shade shift) on curing.

Shade taking (using Miris 2, Coltène Whaledent)

1. Take the dentine shade by matching it with the cervical region of the tooth. This area has the most dentine and less enamel (Figure 2.8).

2. Select the enamel shade by comparing it with the incisal edge. This region has most enamel and less dentine (Figure 2.9).

3. Put the two pieces together with a drop of glycerine between them (Figure 2.10).

Fig. 2.8 The dentine shade is taken from the cervical region of the tooth. The resin composite ‘cores’ correspond to dentine.

Fig. 2.9 The enamel shade is selected by using the resin composite ‘shells’ and by matching the tooth colour at the incisal edge where enamel predominates.

Fig. 2.10 The dentine ‘core’ is placed inside the enamel ‘shell’ with a drop of glycerine between them and the product is the matched shade of the tooth.

Similarly when matching ceramic, ceramic should be used. Furthermore different batches of ceramic can differ slightly in their appearance and so ideally the technician should supply the clinician a shade guide manufactured using the same batch of ceramic which will be used to construct the restoration being fitted. For obvious financial reasons this rarely happens.

The shade should always be taken prior to the application of rubber dam. As rubber dam provides such an effective method of isolation so the teeth pushed through the dam will dehydrate quite quickly. Dehydrated teeth appear white and chalky. If the shade assessment was made at this point, then the final composite would be too light after the teeth have rehydrated after rubber dam removal. Figure 2.11 illustrates this phenomenon. This patient has had rubber dam placed to restore 11 and 21 after trauma. The dam was anchored on 13, so the incisal two-thirds was through the dam and the cervical third was in the mouth. Note the obvious demarcation between these parts of the tooth.

Fig. 2.11 Tooth 13 illustrating the dehydrating effect of isolating the tooth using rubber dam, so causing a shade change.

Digital technology is now available to take the shade to increase the accuracy of the prescription with the intention of decreasing remakes. Bespoke digital shade analysis systems are commercially available which calculate the shade. This information is then corrected to ensure that the true tooth colour is sent to the dental laboratory. This analysed data can then be used by the technician to accurately reproduce the shade of the tooth in ceramic. An example of the type of device available is shown in Figure 2.12. The guide is positioned over a number of points on the tooth surface and the results are mapped.

Fig. 2.12 Easy shade compact (Panadent).

Light curing offers a number of advantages:

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