INTRODUCTION
The appropriate design, construction, and fit of the whitening tray is essential for successful whitening treatment and patient compliance. It is essential that the patient wear a well-fitting whitening tray, and although much has been written about designs of different whitening trays, this chapter will enumerate the important features that such trays should have. Excess tray material will impinge on the soft tissues and irritate the gingivae if the tray is over-extended. This could cause discomfort to the patient, and if the tray is uncomfortable the patient may fail to comply with the home whitening regimen and thus discontinue treatment. This chapter will discuss different tray design features and fabrication options and demonstrate the step-by-step procedure of how to make the whitening trays.
PROPERTIES OF THE IDEAL WHITENING TRAY
The ideal whitening trays (see Figure 6.20) should:
• Be strong enough to avoid damage by the patient during wear.
• Not distort during use.
• Not wear during use.
• Be easy to fit and easy to remove after a treatment session.
• Be made from a material that is bioinert (Greenwall 1999).
• Not cause irritation to the soft tissues, gingivae, mucosa, tongue, or teeth.
• Not impinge too far on the papillae.
• Be thin enough to be well tolerated in the mouth.
• Be smooth and well polished so that there are no rough edges.
• Fit comfortably and passively and not feel too tight in places.
• Not extend into deep undercuts.
• Be correctly trimmed with freedom of movement for the frenum attachments if the full vestibule design is used.
• Have good retention.
• Be easy to clean and rinse.
• Not distort during storage.
Several designs can be used depending on the nature and location of the discoloration and the specific case (Haywood 1991). For example, if the front teeth are particularly dark and discolored but the color of the rest of the teeth is satisfactory, a tray can be designed with cut-out sections to lighten the central incisors only. Conversely, windows can be cut into the trays to exclude certain teeth (see Figure 6.26).
TRAY DESIGN FEATURES
Several types of trays can be used for at-home whitening (Table 6.1).
• Full vestibule upper or lower trays.
• Trays with reservoirs (some whitening manufacturers insist on reservoirs, but new research has demonstrated that this may not be necessary).
• Trays with no reservoirs.
• Trays with a foam liner (Haywood et al. [1993] do not recommend this design because its use does not shorten the whitening time and may impinge on the occlusion).
• Trays with or without windows.
• Trays with scalloping or anatomic cutout (the tray follows the tooth-gingiva interface).
• Nonscalloped: straight-line trays.
• Tray with shortened borders.
RESERVOIRS
A reservoir (see Figure 6.25) is a void or space that has been created in the whitening tray. The reservoir can also be called a spacer. The reservoir in the tray acts as a receptacle for the whitening material and is supposed to retain the whitening material in the tray, thus allowing it to contact the teeth for a longer period of time. The reservoir is made by placing light-cured composite resin on the buccal surfaces of the teeth on the plaster model. Some manufacturers recommend a reservoir made of plaster so that it will not distort the tray during tray manufacture.
Trays with no reservoirs
Research has shown that it is not necessary to have a reservoir placed and that trays used for tooth whitening do not need to have reservoirs any more. The advantages of this are that the trays are better retained and that less material is used for each application. A better fitting tray allows for the material to compress against the tooth surface and allows for better, quicker penetration of the whitening material into the tooth.
|
Design |
Indication |
Comments |
|
Full vestibule |
This type of tray is not commonly used. |
Would provide excellent retention, but the impingement on the gingivae would cause irritation. |
|
Scalloped on the buccal and lingual areas plus reservoir |
This type of tray is used where minimal tissue contact is desired. |
Saliva ingress is a problem unless insoluble material is used (thick and viscous). |
|
It is useful for highly viscous materials that supply retention. |
Special trimming scissors facilitate fabrication. |
|
|
It is used for the maxillary arch to conserve material use. |
||
|
Nonscalloped, nonreservoir |
This design provides maximum retention of the whitening tray. |
It allows tissue contact, which may cause gingival irritation. |
|
It provides maximum retention of the material at the cervical area of the tooth. |
It cannot extend into undercuts. |
|
|
It is useful for fluid and honey-like whitening materials. |
It should not terminate on soft tissue peaks such as rugae or impinge on frenum movement or the canine eminence. |
|
|
It is indicated for the mandibular arch where the occlusion contacts the buccal and facial aspects of the tooth. |
||
|
Facial and lingual scalloped reservoir |
This type of design is used when taste is a problem for the patient. |
It avoids spill over the material onto the tongue from the lingual side. |
|
It can also be used when there has been a problem with tongue irritation from the edges of the tray. |
It provides a smooth edge for tongue contact. |
|
|
Scalloped reservoir, buccal and lingual surfaces, no occlusal surface |
This type of tray can be used for temporomandibular joint dysfunction (TMD) patients who cannot tolerate fine changes to the occlusal surfaces. |
Using a viscous whitening gel will allow excellent whitening of the teeth. There should be no difference in whitening rates with the occlusal surfaces removed. |
|
Scalloped, no reservoir (my choice for tray design) |
This type of tray is used for gel materials, when tissue avoidance is desired, but allowing for maximum retention of the tray. Orthodontic clear aligners fall into the category and can be used for whitening. |
There is no apparent difference in the whitening rate with or without reservoirs. Because there is no apparent difference between whitening rates, Miller (2000) has suggested that the reservoirs are not necessary anymore. |
|
Nonscalloped, no reservoir |
This design is used when seating a tray with viscous material and when a better seal is desired. This can be an orthodontic aligner, which can be used for whitening during or after orthodontic treatment. |
The mandibular arch is best with the nonscalloped design for retention of the material and tissue comfort. |
Adapted from Haywood 1997.
Function of the tray reservoir
It has been determined that the reservoir or spacer performs many important functions.
Advantages
• It retains and contains the whitening material better, particularly the more viscous whitening materials such as Opalescence (Ultradent Products, South Jordan, UT; supplied by Optident, UK) and prevents it from leaking around the gingivae.
• It allows the whitening material to stay in contact with the tooth for longer.
• It may help to keep the whitening material active for longer (Matis et al. 1999).
• It allows gel in areas with a higher concentration of carbamide peroxide to be transferred to areas with a lower concentration (Matis et al. 1999).
• It holds more whitening material (Miller 1999).
• It prevents washout of the whitening agent.
• It aids in seating highly viscous materials (Oliver and Haywood 1999).
• It prevents the occurrence of pinching pressure.
Disadvantages
• It causes the tray to become less retentive (Haywood 1995).
• More whitening material is required to fill the tray.
• It makes the tray more bulbous and slightly thicker.
• There may be the potential for occlusal interference on the mandibular arch.
• It requires additional time and products to be made.
Reservoirs are normally placed on the facial surfaces of the tooth. There is no apparent difference in whitening rate with or without reservoirs (Haywood 1997). Reservoirs can be used depending on the following:
• The viscosity of the whitening material used. Some materials (e.g., Opalescence) are very viscous. The material is retained in place better if there is a reservoir that allows for easier seating. If the whitening agent has a thin viscosity, a reservoir is not needed (Heymann and Haywood 1995).
• Tooth anatomy. If a tooth is more bulbous than the rest it may not be necessary to place a reservoir. Teeth with lower esthetic demands (e.g., second molar teeth) do not require placement of reservoirs.
• Tooth darkness. A darker tooth can have a reservoir (see Figure 6.25).
• A dark cervical margin. These cases should have the tray designed to extend 1 mm over the gingivae and could have a reservoir because more whitening material is required to go into the dark cervical margin.
Where should the reservoir be placed?
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