Tuesday, September 9, 2025

Why did my teeth shift after the braces came off? Part 2: mouth habits

 

Why did my teeth shift after the braces came off?

I often hear from patients that their teeth moved after their braces came off and they want to know why.  There are basically 3 reasons for a failed case (that was treated well.)

1. The patient did not wear their retainers properly. This is patient error.

2. The patient did not eliminate mouth habits, and did not wear appliances to protect them from their mouth habits. This is a combination of patient and dentist error (if the dentist did not make the patient aware of their habits, and/or did not make appliances that could protect the patient from these habits.)

3. The patient grew unfavorably. No one had control over this one.

4. If the teeth were not aligned in the middle of the bone ridge, they will relapse to be centered in the ridge again. The treating dentist had control over this reason.

The next few blogs will address these errors. Today we will address #2: mouth habits.

A mouth habit is something you do with your mouth other than talking and eating.  Some examples include biting your fingernails, biting your pen/pencil, chewing on your lips or inside of your cheeks, leaning your tongue on your teeth, and grinding/clenching your teeth. Any force that you exert on your teeth, if it is applied for enough time, will move your teeth.  Patients who bite their pencil consistently in the same area of their mouth will either push the bottom tooth toward the tongue, push the top tooth out towards the lip, or a will form a gap vertically between the top and bottom tooth where the pencil sits. Patients who chew on their bottom lip create crowding of the lower front teeth, or spacing between the upper front teeth. 

Tongue habits can occur in different areas of the mouth. If the tongue sits over the tops of the side teeth it can create an open bite which is an area where the top teeth do not touch the bottom teeth when the patient is biting their teeth together. If the tongue is leaning against the front teeth down low, it will create spacing between the lower front teeth, just as if it is leaning against the front teeth up high, it will create spacing between the upper front teeth.  If it is leaning between the top and bottom teeth in the front it will create an anterior open bite, i.e. the top teeth will not overlap the bottom teeth in the front. Sometimes the patient leans their tongue on specific teeth with less force or duration, and instead of moving the teeth, the excessive force generated on the teeth accelerates loss of bone and gum around the teeth. (Periodontal disease is an inflammatory disease of the supporting structures of the teeth- the gums and bones. It is cause by bacteria which live in the mouth.  When the bacteria are removed frequently (by daily brushing and flossing) the inflammation levels are low, and there is no disease.  When the bacteria are not efficiently removed, the “bad” bacteria set up housekeeping and flourish causing inflammation which is seen as red, puffy, bleeding gums.  Over time the bone around the teeth is lost leaving the roots of the teeth visible in the mouth.  When there is excessive force applied to the teeth, from leaning the tongue on the teeth or from clenching/grinding the teeth, the rate of bone loss is accelerated. Then the roots start showing even in cases where the gums are not visibly red, puffy, and bleeding.)

Bruxism is the clenching and grinding of the teeth.  Clenching is when the teeth are tightly closed when there is no reason, like chewing, to be closed.  Grinding is when the patient moves the teeth “side to side” or “front to back” as if they are chewing, but there is no food present to chew. The most common reason for bruxism is stress, but it also occurs from boredom, concentration on a difficult task, or when a young child has pressure in their ears which they are trying to relieve. Bruxism does a lot of damage to the teeth and their supporting structures (which was discussed in the post October 21, 2020.)  Bruxism can also move the teeth.  When clenching, the back teeth which meet vertically, are pushed deeper into the bone, much like a nail can be hammered into a piece of wood.  As the posterior bite support is lost, the front teeth start to overlap more vertically (i.e. the bite deepens), and the front teeth bypass each other (like a scissor.)  In order for the lower teeth to stay behind the wedge shaped upper front teeth, the lower front teeth start to crowd, and the upper front teeth start to develop spaces between them.

Habits can be controlled in the daytime through awareness, but it is impossible to control habits like improper tongue posture and bruxism while one is sleeping.

Retainers and occlusal guards are used in order to prevent the shifting of teeth from mouth habits. Although retainers should be worn full time immediately after braces are removed, they can be continued at night indefinitely to protect teeth from habits.  Mouth habit appliances should be rigid so that they can’t be deformed by the habit-forces. The design of retainers was discussed in the August 2025 blog. Other appliance designs will be discussed in future blogs. 

Monday, August 11, 2025

Why did my teeth shift after the braces came off? Part 1: retainers

I often hear from patients that their teeth moved after their braces came off and they want to know why.  There are basically 3 reasons for a failed case (that was treated well.)

1. The patient did not wear their retainers properly. This is patient error.

2. The patient did not eliminate mouth habits, and did not wear appliances to protect them from their mouth habits. This is a combination of patient and dentist error (if the dentist did not make the patient aware of their habits, and/or did not make appliances that could protect the patient from these habits.)

3. The patient grew unfavorably. No one had control over this one.

4. If the teeth were not aligned in the middle of the bone ridge, they will relapse to be centered in the ridge again. The treating dentist had control over this reason.

The next few blogs will address these errors. Today we will address #1: the patient did not wear his retainers properly.

In order for teeth to move with orthodontic treatment, the bone around the teeth has to remodel.  The bone on the pressure side (the side to which we are moving the teeth) resorbs, and bone on the tension side (the side from which we are moving the teeth) rebuilds.  Over time, the teeth are surrounded by new bone.  This new bone is immature and weaker than mature bone. 

Imagine that you broke a bone and went to the orthopedist to reset the bone.  After aligning the bones to the best position, the orthopedist would put on a cast to hold the bones still, in that new position, until the bone fills into the break, and matures in that position.  The retainer is like the cast.  The teeth are slightly mobile when the orthodontic treatment is completed and the teeth need to be held in their final positions while the bone holding them matures.

A good retainer is rigid, like the cast for a broken bone is rigid.  It should hold the teeth still even if the patient leans his tongue on the retainer, or if the patient clenches or grinds his teeth.  Rigid retainers are made of hard acrylic, and have wires that hold them and the teeth in place.  

It has become common for orthodontists to use other forms of retention. Essex and aligner retainers are non- rigid vacuum formed retainers which are less expensive to make, and are less effective because they flex when forces are applied to them.  These plastic retainers also stretch out over time and need to be replaced frequently. If the treating orthodontist does not intend to provide long term retention care he may choose to use this style retainer.

It is also common for the orthodontist to "glue" the front teeth together, often with a wire or fiberglass thread that is bonded to the tongue surface of the teeth.  Bonded retainers will hold the front teeth straight with respect to each other, but the bonded  can move as a unit with respect to the back teeth.  The bonded retainers offer no retention to the back teeth, and if the patient has mouth habits (like grinding the teeth) the retainer will break as the back teeth move vertically. Bonded retainers are difficult to keep clean, and often have issues with developing cavities and gum disease.

A removable retainer has to be worn "fully seated."  If the patient lifts the retainers with his tongue, or floats it above his teeth, it cannot do it's job.  If the patient repeatedly moves it in and out with his tongue he may actually make the teeth looser, rather than letting the teeth "tighten up." If the retainer is "floating" it is not contacting the teeth, and therefore cannot hold them in place. If the patient is holding the retainer in his hand, instead of wearing it in his mouth, the retainer can also not do it's job.

Retainers should be worn full time until the teeth "tighten up".  This takes between two and six months.  Then the wear-time should be decreased, and the mobility of the teeth should be evaluated by the orthodontist.  If the retainer always feels the same when it is replaced after a period of time, as when it is replaced immediately after removing it, it means that the teeth have not moved when the retainer was out of the mouth.  If the retainer feels different after it has been left out for a period of time, it means that the teeth had a chance to move somewhere, and the retainer had to push the teeth straight again.  The goal is to eliminate the habits that are causing the teeth to move, in order that the teeth stay in place when the retainer is removed.  Over the course of the first year the patient should be able to decrease wear-time to be only when sleeping.  The orthodontist needs to evaluate whether it is necessary to continue retainers at night indefinitely, or whether the patient can discontinue night time wear of the retainers when his face finishes growing.