Extensive decalcification of the permanent dentition following long-term, unmonitored, functional appliance wear: case report

The twin block appliance is now the most frequently used myofunctional orthodontic appliance in the UK.¹ The mechanism of action involves inducing a functional mandibular displacement, in order to produce an intermaxillary reaction.² This appliance is usually fabricated from an acrylic base-plate material, which sometimes incorporates lower incisor capping, which has the benefit of reducing the appliance's lingual bulk and visibility, whilst eliminating retention clasps which are prone to fracture.^3,4 Recent literature demonstrates the detrimental influence of incisal capping with concomitant regular intake of carbonated soft drinks.⁵

The majority of practitioners advise the full-time wear of a twin block appliance to maximize benefit. However, a twin block design can have detrimental effects on the dentition. It remains in direct contact with the dental tissues for prolonged periods of time, potentially increasing plaque retention and the risk of demineralization by reducing the self-cleansing and neutralizing actions of saliva. It is therefore important that the orthodontic team examines the dentition at each visit for signs of demineralization. At the first sign of demineralization, tooth-brushing and dietary instruction should be reinforced, a daily fluoride mouthwash prescribed and topical fluoride varnish applied.⁶ This may help to arrest demineralization and encourage remineralization.