Introduction
While interceptive orthodontics is aimed at correction as well as guidance of the permanent teeth in the correct alignment or occlusal plane, pediatric orthodontics is the field that comprises several treatment strategies usually indicated for primary teeth and in the mixed dentition phase. Both these fields of orthodontics in the present day are aimed at correcting or aligning the erupting permanent teeth and thus, the connecting links are the functional appliances that can be used in two ways. They can either be an adjunct to interceptive orthodontic treatment strategies or they can be the mainline treatment strategies in younger children for preventing compulsive oral habits or repetitive movements of the mouth, such as thumb sucking, nail biting, or lip biting, that can lead to different types of malocclusion.
Functional appliances are primarily meant to produce tooth movements in order to correct the bite-related or occlusal discrepancies of the developing jaw of the child.
What Are the Major Functional Appliances?
1. Andresen Activator Appliance:
This appliance was originally designed by Reverred Danish surgeon, Viggo Andresen, who used a simple modification or pattern of lingual horseshoe flange that could guide the lower jaw or the mandible forward in younger children or adolescents, to eliminate the risk of/ to deal with class II malocclusion in adults. This is originally a loose fit and rather passive appliance that comprises a plastic block that covers the palate and the upper/lower teeth of both the arches to advance the mandible or lower jaw by several millimeters for the class II malocclusion correction. In the case of mandibular retrognathism or backward position of the mandible with forwarded upper jaw, which signifies class II malocclusion, many modifications of this appliance are implemented by modern-day orthodontics for simple clinical use in treating class II cases, though the original activator is not used anymore in the present day.
2. The Herbst Appliance:
This is a popular appliance even today that could be used to advance the mandible or the lower jaw forward and is more suitable for older children or even young adolescents who are more cooperative or patient-compliant because this device or fixed appliance should be worn through the day. A typical Herbst appliance mainly comprises telescoping mechanisms that are aimed at connecting the upper/maxillary first molars at one end while another cantilevered arm would be attached to the other end of the lower molars /mandibular first molars for pushing the mandible or lower jaw in a forward direction.
Functional appliances are the cornerstone of modern-day interceptive orthodontics and also in pediatric orthodontics.
3. Bionators:
In 1950, Reverred Wilhelm Balters in an attempt to treat backward-positioned mandible/lower jaw or class II malocclusions modified the Andresen’s activator which is known as the bionators appliance. This is indicated in all children who show a favorable pattern for facial growth while producing a forward positioning or movement of the lower jaw or mandible. The bionators appliance is available in usually three different designs comprising two halves commonly connected through a coffin spring and is highly dependent on the wearer's or the child's compliance.
4. The Clark Twin-Block Appliance:
This is a functional appliance designed with separate upper and lower removable forms, each designed or inclined at a 45-degree posterior bite/occlusal plane meant for correcting the lower jaw/mandibular posture. This appliance would commonly use mid-line screws in the separate upper and lower jaw compartments for inducing arch expansion and works on the principle of extraoral traction.
5. Prefabricated Myofunctional Appliances:
Several modern-day orthodontic company manufacturers fabricate prefabricated functional appliances that are customized to the child's upper and lower jaw. Most of the prefabricated appliances first need to be immersed in hot water and then molded or customized to the patient's jaw or dentition to increase the retention of the appliance. These are usually re-moldable appliances and are highly popular in modern-day pediatric orthodontics given that children can be more compliant and find less discomfort in using them throughout the day.
What Is the Mechanism of Action for the Growth and Spatial Orientation of the Jaw?
There are believed to be two different modes of action by which functional appliances can act:
1. By Basal Growth Modification: In this mechanism, it is believed by orthodontic experts that through the growth modification of the basal parts of the jaw bone effectively with the help of functional appliances, proper tooth movements and alignment into the occlusal plane can be achieved or made possible in the mixed dentition phase (in between six to12 years till the eruption of the permanent teeth in both the upper and lower jaws). This is also a growth modification process that can be done through the reactive growth sites pertaining to the temporomandibular joint (TMJ) area of the developing child. As the TMJ is the reactive site or is considered a primary growth center in children, the position of the lower jaw or the mandible can be influenced by the use of functional appliances. The hypothesis that bone apposition would be possible both on the mandibular as well as the temporal surfaces of the joint cavity is also supported by histologic evidence in orthodontic literature, which signifies that functional appliances can have the potency to alter the skeletal relationship between the upper and lower jaw.
2. By Influencing the Spatial Relationship of the Jaw: As the skeletal or dental malocclusion or improper bite patterns in children later affect their facial structure and jaw growth, in adults it is always in fact influenced in the mixed dentition stage of the child that is when the erupting permanent teeth and the occlusal plane would be deciding the facial characteristics or the jaw size and growth. Therefore, the maxillo-mandibular alignment can be easier to achieve with the help of functional appliances in children.
Some of the clinical effects associated with functional appliances are the tipping of the incisors or anterior teeth of upper and lower jaws, accompanied by an opening rotation of the lower jaw/mandible that influences spatial relationship and jaw tone.
Conclusion
Whether your oral surgeon or orthodontist is using the interceptive form or the pediatric common orthodontic strategies to correct the dentofacial complex irregularities in the developing child.
The use of functional appliances has revolutionized the field of orthodontics both as mainline and adjunct treatment strategies for malocclusion, proper development of orofacial structure, and alignment of dentition.
.
