Dental Health

Surprisingly there is no strong association between dental irregularity and dental caries or periodontal disease. It seems that dietary factors are much more important than the alignment of the teeth in the aetiology of caries. Although straight teeth may be easier to clean than crooked ones, patient motivation and dental hygiene seems to be the overriding factor in preventing gingivitis and periodontitis. That said, few of the studies that have investigated the link between crowding and periodontal disease have been longitudinal, over a long term and included older adults. It would appear that aligned teeth confer no benefit to those who clean their teeth well because they can keep their teeth clean regardless of any irregularity. Similarly, alignment will not help bad brushers. If there is poor tooth brushing, periodontal diseases will develop no matter how straight the teeth are. However, having straight teeth may help moderate brushers, although there is no firm evidence to support or refute this statement. This is an area that requires further study.

Some malocclusions may damage both the teeth and soft tissues if they are left untreated. It is well known that the more prominent the upper incisors are the more prone they are to trauma2,3 (Table 2).

When the overjet is 9 mm or more the risk of damaging the upper incisors increases to over 40%. Reducing a large overjet is not only beneficial from an aesthetic point of view but minimises the risk of trauma and long-term complications to the dentition. Fig. 4 shows a child with a large overjet and it is not difficult to imagine the likely dental trauma that would result if he or she fell over.

Table 2 Relation between size of overjet and

prevalence of traumatised anterior teeth

Overjet (mm)

Incidence %

5

22

24

>9

44

Certain other occlusal relationships are also liable to cause long-term problems. Figure 5a and b show a case where there is an anterior cross-bite with an associated mandibular displacement in a 60-year-old man. The constant attrition of the lower incisors against the upper when the patient bites together, have produced some substantial wear. If allowed to continue then the long-term prognosis for these teeth is extremely poor. In order to preserve the teeth, the patient accepted fixed appliance treatment that eliminated the cross bite and helped prevent further wear Figure 5c and d.

Another example of problems caused by an anterior cross bite is shown in Figure 6. A traumatic anterior occlusion produced a displacing force on the lower incisors with apical migration of the gingival attachment as a consequence. Provided this situation is remedied early (Fig. 7) the soft tissue damage stops and as the rest of the gingivae matures the situation often resolves

Fig. 5a Anterior crossbite in a 60-year-old man occluding in the intercuspal position

Fig. 5b Shows the retruded contact position of the patient. To reach full intercuspation the mandible displaces forward and this movement is probably associated with the wear on the incisors

Fig. 5d After correction and space reorganisation the patient is wearing a prosthesis to replace the missing lateral incisors

Fig. 5c The patient in fixed appliances in order to correct the displacement and the position of his upper anterior teeth

Fig. 5d After correction and space reorganisation the patient is wearing a prosthesis to replace the missing lateral incisors

Fig. 6 A traumatic anterior occlusion is displacing the lower right central incisor labially and there is an associated dehiscence

Fig. 6 A traumatic anterior occlusion is displacing the lower right central incisor labially and there is an associated dehiscence

Fig. 7 The same patient as in Fig. 6, but the cross bite has been corrected with a removable appliance and there has been an improvement in the gingival condition

spontaneously and no long-term problems usually develop.

Deep overbites can occasionally cause stripping of the soft tissues as shown in Figure 8a and b. This is a case where there is little aesthetic need for treatment but because of the deep overbite there is substantial damage to the soft tissues. Clearly if this is allowed to continue there is a risk of early loss of the lower incisors that would produce a difficult restorative problem.

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