There are a multitude of appliances that are designed to help break, control, or prevent habits that are detrimental to oral development and function. Appliances have been designed to encourage and support normal oral functional development from infancy through adulthood. Not all of these appliances are considered orthodontic or functional appliances, but they are intended to accomplish the same objectives as a typical orthodontic or dental habit appliance; normalize oral function and development.
Many decades ago it was recognized that tongue posture and function, swallowing pattern, and the upper airway had a profound impact on dentofacial development and function. Establishing a normal functional pattern at birth is important for continued favorable growth. As bottle feeding became possible and was popularized, studies found that the swallowing pattern and tongue function were adversely modified to accommodate bottle feeding. This occurred for a number of reasons, mostly centered on the relationship between tongue and muscle function during suckling, the shape of the rubber nipple, and how the milk was dispensed. As a result, the shape of the rubber nipple was changed to encourage a more natural muscle and tongue function during suckling. In 1956 Dr. Balters, a prominent functional orthodontist, developed a functional habit appliance used in infancy and called it the NUK. It was produced both as a pacifier and a feeding bottle system. Although pacifiers in general are not typically considered functional appliances, the new generation pacifiers that started with the NUK are designed to support normal tongue posture, muscle function, and oral development.
The goals of normal tongue posture, muscle function, and oral development are the same for every functional appliance used in orthodontics and dentofacial orthopedics. They work based on the principles of Wolff’s Law (bones will change form in response to the stress or pressures applied) and the understanding that form follows function. If the function can be normalized, the form will normalize in response. If the function is abnormal, the form that develops will also be abnormal and less than optimal. Habit appliances are meant to prevent or correct adverse habits that create and support abnormal orofacial function and development.
If the finger or thumb sucking habit is strong or fairly constant, it may create an open-bite where the front teeth no longer overlap and there is a big space between the front teeth when the back teeth are biting. This can also occur without a finger or thumb sucking habit when there is a tongue thrust or reverse swallowing pattern. The tongue can prevent eruption of the front teeth, or if they are fully erupted, the tongue can intrude the teeth by pushing them up into the bone. As the tongue intrudes the teeth, the overlap disappears and an open-bite is developed. Once the open-bite is established, it can be very difficult to correct. An appliance alone may not be sufficient to close the bite.
To supplement an appliance, braces and vertical elastic forces can be used. Even with this additional force, the bite may not close. Forcing the bite to close comes with significant risks, one of which is root resorption (where the body eats away at the roots of the teeth, making them shorter and placing the teeth at risk for being lost prematurely). If the open-bite is not correcting with appliance therapy, or at a reasonable pace with braces and elastics, enlisting the help of a good orofacial myologist, and their myofunctional therapy is very helpful. Myofunctional therapy may be the critical piece that can be missing in open-bite correction.
Another critical factor may be tongue mobility. If the tongue is tied down, it will be impossible for it to achieve a normal posture and function, and the tongue tie may be the root cause of the bite problems, adverse growth patterns, and functional abnormalities. Most often, just lengthening the lingual frenum (the muscle line that ties the front of the tongue to the floor of the mouth) will allow the tongue to assume a normal position and functional relationship with its environment. Occasionally the tongue will do this spontaneously without the need for appliance intervention. Anything that prevents normal orofacial muscular function must be eliminated for any supportive treatment to be effective.
With all restrictions to normal muscle function and tongue posture eliminated, orthodontics and dentofacial orthopedics deals primarily with two types of habits utilizing two types of appliances. For this blog, we will ignore the appliances and aparatuses used for infants and little children, and focus on the typical orthodontic appliances most often used to address these two common adverse habits.
The two general classes of habits we will focus on are finger and thumb sucking habits, and tongue posture and oral muscle functional habits. The habit appliances vary greatly, and also fall into two broad classifications. One classification can be called passive, while the other may be referred to as active. Generally speaking, the passive appliances serve as a gentle reminder of normal function and posture, while the active appliances exert a more forceful reminder, often through something sharp that elicits pain if abnormal function or posture is pursued.
For finger and thumb habits, there are basically two ways to combat the habits. One is to change the environment so that the habit loses its’ subconscious comforting appeal, and the other is to change the finger or thumb so that it is uncomfortable or undesirable in the oral environment. We will focus more on the appliances and how they change the environment. This is not meant to discount the ways you can address the habit by affecting the fingers or thumbs. Some of these methods include putting Tabasco Sauce, or some other foul tasting item on the nails so that the fingers taste so bad you can’t stand to put them in your mouth. Other options in common use are to put tape on the thumb nail, tape the fingers together in a group, or tape a sock over the hand to make it difficult to put the fingers in the mouth. There is even a design like a removable cast that makes it impossible for the hand to reach the mouth so there is no way to suck the thumb. We will ignore these methods, not because they can’t be effective, but because we are focusing on appliances in this blog.
For the finger and thumb sucking habits, a typical appliance may have an open wire mesh that covers the front of the roof of the mouth so the thumb or finger feels it and creates a sensation different from what is expected. Often the wire mesh does not hang down below the teeth or prevent the fingers from being easily inserted into the oral cavity. This change in the environment is often intended to reduce or eliminate the subconscious satisfaction or comfort associated with the habit and thus discourage the continuing habituation of thumb or finger sucking. These appliances are usually designed to be permanently attached to the molars by welding the mesh to heavy wire arms that are then welded to bands that are placed around the molar teeth. The mesh is held away from the palate so it doesn’t become an irritation, but it follows the palatal contours to prevent it from interfering with a normal swallowing pattern or tongue posture.
For tongue thrust, tongue posture, and oral muscle functional habits, the active habit appliances can be attached to the lower or the upper teeth, and the active part of the appliance will generally extend beyond the level of the front teeth. Usually there will be a heavy wire connecting the molar teeth by forming an arch that follows the same arch form the teeth follow. At the front of the wire the active part of the appliance will be formed or welded into place. It may be a more passive design with loops or mesh hanging down or protruding upwards, or an active design that looks more like a tiny pitchfork than something you would expect to see in the mouth.
The more passive appliances are meant to block the tongue from getting between the upper and lower front teeth and maintaining the open-bite. Sometimes these appliances will be used in conjunction with a finger or thumb sucking habit in an attempt to address both the finger habit and the tongue habit at the same time. The appliance basically guards the opening between the front teeth and prevents the tongue or fingers from interfering with the eruption of the front teeth so they can achieve a normal amount of overlap.
The more passive appliances are meant to block the tongue from getting between the upper and lower front teeth and maintaining the open-bite. Sometimes these appliances will be used in conjunction with a finger or thumb sucking habit in an attempt to address both the finger habit and the tongue habit at the same time. The appliance basically guards the opening between the front teeth and prevents the tongue or fingers from interfering with the eruption of the front teeth so they can achieve a normal amount of overlap.
Another more recent (1991) and interesting active appliance design intended to correct a reverse swallow or tongue thrust without the spikes and pain is the Bluegrass Roller and subsequent similar designs. With this appliance, the arms do not support a wire mesh or sharp wires, and instead have a plastic cylindrical roller in the place of the mesh. The roller is held off of the palatal tissue so it is free to roll, and the tongue is encouraged to play with it and spin it around on the wire arm. The roller is positioned over the area where the tip of the tongue should be located in normal posture and function during swallowing. This encourages the tongue to habitually position itself more favorably in the oral environment, with the expectation that upon removal of the appliance, the tongue will continue to position and function favorably and the normalized posture, function, and swallowing pattern will remain.
Habit appliances can be a big help in normalizing tongue posture, oral muscle function, swallowing patterns and orofacial growth. However, they are not 100% effective. Enlisting the services of an orofacial myologist as early as infancy, freeing up the tongue if it is tied down, and normalizing the orofacial muscular function so that harmonious facial growth takes place is a better approach than trying to fix functional and growth related problems later on. Since form follows function, the earlier functional issues are addressed, the better the form can recover and normalize. The form can be changed, and if the function adapts favorably it will be maintained, but it would be better to have the normal form develop naturally by following a normal functional pattern. An old-time saying is worth repeating here: “An ounce of prevention is worth a pound of cure.”