Functional Appliances

Functional appliances

At the beginning of the 19th century a few dental practitioners began to appreciate the effect of muscle on bone. The concept of applying these principles to treatment was advocated by Lefoulon in 1841 and Kingsley, whose appliance for jumping the bite was used to stimulate mandibular growth.

The earliest functional appliance was the monobloc developed by Pierre Robin, a French stomatologist, in 1902. The appliance stimulated facial muscular activity by changing the position of the jaws. It consisted of a plate spanning the maxilla and mandible with an expansion screw in the palate. The appliance extended along the lingual surfaces of the mandibular teeth with lingual imprints of the crown surfaces of both the maxillary and mandibular teeth. Robin’s appliance was not recognised at the time due to the popularity of the Angle system.

The first functional appliance to gain widespread clinical use was the Activator designed by Vigo Andresen, a Danish dentist who developed his appliance after discovering that an adapted Hawley-type maxillary retainer his daughter had been using had eliminated her Class II malocclusion.

The Andresen Activator is a passive tooth-borne appliance consisting of a plate covering the palate and teeth of both the mandibular and maxillary arches. It transferred muscular stimuli to the teeth and jaws and was designed to move the mandible forward for correction of Class II malocclusions and open the bite. It could also direct erupting posterior teeth.

Andresen later developed his system with Karl Haupl into the Norweigan system of functional jaw orthopaedics.        

After World War II, functional appliances were used to treat large numbers of patients in countries with limited financial resources. New appliances were developed by, among others, Häupl, Bimler, Balter and Fränkel.

Activator use became so widespread among European practitioners that there was concern that proper diagnosis was being neglected. There were some critics including Reitan who, in his 1952 doctoral thesis, demonstrated that no special histological picture emerged from the use of functional appliances. This position was later supported by other researchers.

Use of functional appliances was not common in America until the 1980s when fixed appliance systems combined with functional appliances. The term growth modification replaced the term growth stimulation to describe the objectives of dentofacial orthopaedics.

Andresen’s Activator and its variants were passive appliances, relying on the action of the jaws. Increasingly popular in the later 20th century were active appliances such as Herbst’s fixed functional appliance and Clark’s twin block technique, which is now the most commonly used functional appliance worldwide. 

Some landmarks in the development of functional appliances

Norman Kingsley was the first to use a removable appliance to change or ‘jump’ the bite.

Pierre Robin developed the monobloc for treating glossoptosis syndrome (later known as Pierre Robin syndrome).

Dr Viggo Andresen had previously developed a tooth borne passive activator but in 1936 he and Dr Karl Häupl introduced the Norwegian system to correct Class II malocclusions.

Dr H.P. Bimler introduced the Bimler appliance which expanded the arch by means of cross wise mandibular movements.   

Hugo Stockfisch developed the kinetor functional appliance.  

Martin Schwartz introduced the double plate. It consisted of upper and lower plates designed to occlude with the mandible in a protrusive   position. Schwartz was one of the first to construct an activator in two parts.

William Balther introduced the bionator. Balther increased comfort by reducing the bulk of the appliance thus facilitating daytime wear.

Rolf Fränkel introduced the Frankel system for treating Class I, II and III malocclusions. It was unique in being tissue borne rather than     supported by the teeth. 

William Clark developed the twin block for the treatment of Class II malocclusions.