Many vital teeth experience some degree of mild trauma at some stage. This trauma, which is normally an impact, causes bleeding into the pulp and dentin of the tooth, causing the single tooth to become slightly discolored. It is this slight difference in shade of two adjacent teeth that indicates that there has been some degree of trauma to the tooth. This chapter will explain the trauma process and will outline the process taken to whiten a single vital tooth.
There is a place for whitening single vital and nonvital teeth, but often this treatment needs to be integrated with full whitening of the upper and lower teeth. A specially designed whitening tray can be made to whiten just the single tooth, and the sequencing and timing of the treatment are essential if an excellent result is to be achieved. The aim of treatment is to obtain an even shade of whiteness so that adjacent teeth are a similar matching shade.
HISTORY AND DIAGNOSIS
The tooth normally has sustained some type of mild trauma previously; typically, a single tooth has been knocked. The patient may not necessarily remember the initial trauma but may recall it by the second appointment. The pathologic process is known as calcific metamorphosis (CM).
PROCESS OF DISCOLORATION
The tooth experiences trauma. Bleeding occurs within the tooth. The tooth tries to protect itself by laying down protective dentin. This is laid down in the form of secondary and tertiary dentin. The dentin also coats the pulp chamber, and often the pulp chamber appears almost obliterated (see Figure 9.10E). The blood within the tooth breaks down and the hemolysis releases iron, which reacts with hydrogen sulfide, which breaks down to iron sulfide. If the tooth survives the injury, there is rapid deposition of tertiary dentin near the root canal to protect it from the injury and to encourage healing. This is the reason the tooth becomes gray; as the tooth reorganizes, the color can change from black to brown to yellow. The patient is left with a single tooth that has a slightly different color from that of its neighbor. This color difference often is subtle.
These teeth are normally vital, but because of the trauma the pulp chamber may be calcified or reduced in size. As a result there will be a slower response from the electric pulp tester.
Normally the dial is turned up to the end reading before the patient reports that he or she can feel the electric current vaguely. It is important to take time in testing the response of the patient because the patient will need time to register the reading. The same is true for the cold or ice test, when a cold cotton pellet which has been soaked in ethyl chloride is placed on the tooth. It will eventually respond and the patient will report that he or she can feel the cold.
A periapical radiograph will normally demonstrate canal calcification or obliteration. The whole tooth should be present on the radiograph and there should be no evidence of any type of fracture in the tooth, either in the crown or in the root (see Figure 9.7B). There is normally no periapical area present. The root of the tooth is intact and there is no evidence of external or internal root resorption. Often the pulp chamber appears almost completely obliterated, but a very faint line in the middle can be discerned. Other times a dentin bridge may occur across the margin between the crown and the root.
THE PATHOLOGIC PROCESS
The usual process is that a minor trauma causes some type of bleeding within the tooth (see Figure 9.1). This bleeding causes secondary and tertiary dentin to be laid down within the pulp canal (see Figures 9.1 and 9.2). The secondary dentin is laid down regularly along the dentinal walls as a response to the trauma to protect the sensitive pulp tissue from further damage. This causes the pulp chamber and canal to gradually diminish in size until only a narrow root canal remains. It becomes calcified or sometimes even obliterated.
Histologically, the pulps have an increase in the amount of collagen and varying cell sizes (Lundberg and Cvek 1980). There seems to be no justification for root canal treatment of these teeth (Cvek 2007). Periapical radiolucencies have been reported in only 13–16% of teeth with traumatically induced pulp canal obliteration during observation periods of up to 20 years according to Jacobsen and Kerekes (1977). According to Cvek (2007), the periapical radiolucency that occurs later is associated with caries, inadequate crown restoration, or new trauma.
CM can also be known as dystrophic calcification. It is seen commonly in the dental pulp after traumatic tooth injuries and can be recognized clinically as early as 3 months after injury (Amir et al. 2001). CM is characterized by deposition of hard tissue within the root canal space and yellow discoloration of the clinical crown (see Figure 9.9).
According to Amir et al. (2001), opinion differs among practitioners as to whether to treat these cases on early detection of CM or to observe them until symptoms or radiographic signs of pulpal necrosis are detected.
INCIDENCE OF CALCIFIC METAMORPHOSIS
Approximately 3.8% to 24% of traumatized teeth develop varying degrees of CM (Amir et al. 2001). Studies indicate that of these, approximately 1–16% will develop pulpal necrosis. Pulpal necrosis can be assessed through a radiograph and clinical symptoms.
It is normally not necessary to do root canal treatment for these teeth. Most of the literature does not support endodontic intervention unless periradicular pathosis is detected or the involved tooth becomes symptomatic (Amir et al. 2001). It may be advisable to manage cases conservatively by demonstrating CM through observation and periodic examination and radiographs as necessary.
However, the discoloration in teeth with obliterated pulp chambers is not always caused by pigments from the blood degradation products but may be caused by the presence of secondary and tertiary dentin that has been laid down after the trauma (Dahl and Pallesen 2007). It may be that the light being transmitted through such a tooth gives it a darker appearance.
RESEARCH AND INCIDENCE OF THE OCCURRENCE
The response to minor trauma many years previously can result in the development of dystrophic calcification in 3.8–27% of traumatized teeth (Amir et al. 2001). Up to 16% of cases can develop pulp necrosis (Amir et al. 2001). Robertson and colleagues found that 51% responded to normal electric pulp testing and 40% were clinically and radiographically sound (Robertson et 1996), with tertiary dentin formation occurring (Torneck 1990).
Table 9.1 shows the options for treatment. It is important to decide whether only the single dark tooth is to be whitened or whether the entire arch is to be whitened. It is more difficult to whiten the single dark tooth to get it to match and is easier to try to whiten the entire arch using a special protocol. If it is decided that only the single tooth should be whitened, then a specially designed whitening tray needs to be made. A full-arch tray is first made and then a window is cut adjacent to the dark tooth on either side of the tooth to be whitened. If this is not done, then the adjacent teeth will lighten more quickly.
1. Home whitening
2. Home whitening with a sectional tray
3. Sectional whitening of only dark teeth first, then a full-arch tray to whiten all the teeth to match the same light shade
4. Start with a lower concentration and then ramp up the concentration from 10% to 15–16% carbamide peroxide
5. Use 6% hydrogen peroxide on the teeth