Are your child’s upper permanent teeth failing to grow in? Part 1

One or both upper permanent lateral incisors are congenitally missing 1.5% of the time, which causes the upper permanent central incisors to spread apart. If only one permanent lateral is missing, usually the midline will shift to that side after the baby lateral is lost. The permanent laterals usually grow in by age 8, so after that if no permanent laterals are present, you might be suspicious and request an x-ray.

Once it is known that a lateral is missing, an orthodontist should help with the decision of whether to open the space for an implant or bridge, or to close it and reshape the cuspid to look like a lateral.

Upper permanent laterals often erupt backward (behind the central incisors) if they are too crowded. The same is true of lower laterals, but in the lower jaw, the tongue then pushes the laterals forward.  Not so in the upper jaw.

 

However, in the upper jaw, if an incisor is too far backward, it may incorrectly bite behind the lower incisors, and tend to push the lower incisors too forward, even causing recession of the outside gums of the lower incisors.  Treatment of this dangerous crossbite is often urgent, by moving the upper incisor forward to in front of the lower incisors.

 

The most frequently impacted permanent tooth (other than the lower third molar) is the upper cuspid. If it is correctly positioned you can usually feel it before it grows in by pressing your finger on the gums high above the baby cuspids.  The most frequent problem is for a semi-impacted cuspid to be mis-positioned  too close to the midline and to push on the root tips of the permanent lateral incisors, causing the lateral incisor crowns to tip toward the lips and away from the midline, and occasionally it damages the lateral incisor’s root by eroding it.

Failure of Permanent Teeth to Grow Into the Mouth Part II

Occasionally permanent lower cuspids impact.  Their position can usually be felt by finger pressure against the jawbone under the lip. However, discovering an impaction is more often done by x-ray, and the impaction may lie horizontally along the lower border of the lower jaw, where it cannot be felt.  An orthodontist and oral surgeon need to decide how to handle this problem. Early detection may save the impaction from getting worse and allow the tooth to be brought in with orthodontic treatment.

The most common delayed eruption in the lower jaw is the second bicuspid.   The tooth is missing 1% of the time, and even if present the unerupted tooth is commonly seen on  x-rays to be growing in a backward angle instead of vertically, jamming it into the erupted first permanent molar.  Detection of these problems in children is by x-ray (usually a panorama x-ray).  The need for an x-ray is realized because either the space is too small for the tooth to grow in, or the tooth is too slow to grow in.

 

The lower second bicuspids do not normally grow in until age 12-13.  When a problem is detected earlier (by x-ray or space shortage), have an orthodontist decide whether, if the tooth is missing, to keep the baby tooth, or remove the baby tooth and close the space, or if the tooth is impacting, whether to have an oral surgeon attach a gold chain to it so it can be brought in.  The bicuspids need to have 50% root development before intervening surgically, or else the surgery may inhibit full root development.

If three of the first permanent molars have erupted and the fourth one has not, the unerupted one may be incorrectly erupting under the adjacent second baby molar, instead of behind it. X-rays will show whether the baby tooth needs to be removed to allow the permanent molar to erupt. After the permanent molar then grows in, it will need to be pushed backward to allow space for the permanent second bicuspid to grow in, and then a space maintainer will need to be placed.  An orthodontist should be consulted, because if the permanent molar can be guided to grow in without loss of the baby molar, there will not need to be a space maintainer.

 

Failure of Permanent Teeth to Grow Into the Mouth Part I

There are two reasons why permanent teeth do not grow in.  Either they are impacted (meaning they cannot grow in because there is insufficient room, or they are growing in a wrong direction), or they are missing.

The presence of only three lower permanent incisors, and no visable lump in the fourth one, might cause you to suspect that one is missing.  X-rays and careful counting will answer this.  An Orthodontist should be consulted immediately because either the impacted tooth will need to be brought in with braces or else the effect of the missing tooth will need to be planned for in the bite.

Similarly, the presence of only two permanent lower incisors while two permanent cuspids are already erupted probably implies the absence of the other two incisors (since there are normally four incisors).  A decision must be made early by an Orthodontist whether to open the space for later replacement of the missing teeth with implants, or to close the space if that would be better.  Space closure might involve substituting the cuspids as lateral incisors, and substituting the first bicuspids as cuspids by partially reshaping them.

If this decision is delayed, or improperly made, excessive protrusion of the upper incisors or excessive vertical overlap of the upper incisors over the lower incisors may result, leading to long orthodontic treatment, and contributing to an unpleasing lip profile.

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Gap Between the Upper and Lower Back Teeth Because the Baby Teeth Stop Erupting While the Face Grows

When a single baby molar appears submerged relative to its neighbors, or when the baby back teeth do not chew against the opposing teeth but are in openbite, you might suspect either that the baby tooth root has frozen to the bone, or else there may be an absent bicuspid underneath.  An x-ray will ascertain if it is a missing permanent tooth,

If a missing permanent tooth is overlooked in the absence of an x-ray, it might be a big mistake to extract the submerged baby tooth, because the resulting space might require a bridge or an implant, or braces to close the space.

On the other hand, if the submerged baby molar is saved into adulthood, and has not submerged too severely, it may recieve a restoration to raise it up to the level of the chewing plane, and be useful for many years.  However, a baby molar that "submerges" early may be too deeply sunken by the relative eruption of the adjacent permanent teeth, to be restorable, and may create such an uncleanable gumline environment for its neighbors that extraction is its eventual best fate.

Since early discovery of a submerged baby molar sometimes means a poor future for that tooth, it is best to involve an orthodontist early in that situation, so that extraction and space closure can be considered.  Another occasional cause of a posterior openbite is a later tongue thrust, where the tongue bulges out sideways and creates a gap between the upper and lower back teeth.  This can be treated with a screen appliance by an orthodontist, and speech therapy to retrain the tongue.

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Premature Loss of a Baby Second Molar

The baby second molar is the most important tooth in the back part of the mouth during the time the permanent teeth are growing in.  These teeth must be preserved until they are pushed out by their replacement teeth (the second bicuspids), because if the baby second molar is lost early, the first permanent molar will drift forward into its space and block eruption of the second bucuspid, and the teeth in front of that site will drift backward, creating an asymmetry in the dental arch.  A space maintainer or a lingual arch retainer wire attached to the permanent molar will prevent this drifting.

If space has already been lost, it should be referred to an orthodontist immediately.  Braces and space opening coils will be placed to re-open the lost space so the second bicuspid can grow in.

Premature Loss of a Baby First Molar

If a baby first molar is lost early due to advanced decay, chances are that its replacement permanent tooth (the first bicuspid or premolar) may not be ready to grow in yet.  Some thought must be given to the space resulting from the lost tooth.  If the first permanent molar has already grown in, the missing-baby-tooth space can be left alone because the second baby molar will not usually drift forward.  However, if the first permanent molar has not yet grown in, it may, as it erupts, push the second baby molar into the space of the missing baby first molar, thereby blocking the eruption path and creating crowding of the first bicuspid (the permanent tooth that should replace the missing baby first molar.)

In such a case, a space maintainer attached to the baby second molar is excellent until the first permanent molar erupts.

Early Loss of a Baby Cuspid on Only One Side

This problem usually happens because of decay of the baby cuspid (not too common) or because of crowding of the permanent incisors (more common), in which the crowded incisors push out a baby cuspid on one side.  This is damaging to the symmetrical development of the dental arch because the incisors then drift into the space of the missing baby cuspid, which blocks the path for the permanent cuspid to erupt, and also shifts the dental midline.  This asymmetry of the dental arch is difficult to correct and requires braces and rubber bands in the front of the mouth.

The proper thing to do when one baby cuspid is lost early is either to regain the lost space immediately with partial braces, or to remove the baby cuspid on the other side of the mouth and then place a lingual arch retainer wire to prevent the incisors from tipping backward from the pressure of the lip.

If a midline shift has already occured, take the child immediately to an orthodontist

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