Why dentist always ask us to save a deciduous molar when our young kids (below 7years) having a toothache? This is a situation most parents facing when bringing their child for an extraction of a pain & decayed deciduous molar. Why not just remove it and help the kids ‘solve” the problem? Anyhow it is a milk teeth and eventually will be replaced by permanent tooth, why the dentist still proposed to do “pulpotomy” to keep the problematic milk tooth?
First, we need to knowing the timing of eruption of permanent teeth. The following diagram help to understand the eruption sequence.
Sequence and timing for eruption:
1. Age 6-7 years: Lower central incisors, all upper & lower first permanent molar
2. Age 7-8 years: Upper central incisors and lower lateral incisors
3. Age 8-9 years: Upper lateral incisors
4. Age 9-10 years: Lower canine
5. Age 10-11 years: Upper first & second premolar, lower first premolar
6. Age 11-12years: Upper Canine, Lower second premolar, upper & lower second molar
(**age of eruption is various between individual, with +/- 1 year)
It is important to remember that every tooth have their own timing for eruption, due to the process of calcification and root formation. Early lost of deciduous tooth caused by trauma or extraction doesn’t promote eruption of permanent tooth! For example, if a 4 years old boy lost his upper deciduous central incisor after a fell, he will not get his permanent incisor erupt in age of 5 or 6. The eruption of the incisor only happen when the calcification of the root occur in age of 7. He may even have late eruption of that tooth because of more alveolar bone and fibrous tissue to penetrate due to earlier avulsed deciduous tooth.
The situation become more complicated in the posterior region. Remember in the timing of eruption of the first permanent molar, it started to erupt in age of 6 when all the deciduous teeth are in function. It doesn’t replace any deciduous tooth, and because of this reason, most of the parents don’t realize that it is a permanent tooth and always mistakenly thought that it was a deciduous molar. All the eruption of permanent teeth need a predecessor or a “guidance path” for them to go to correct position. Imagine that the first permanent molar do not have a predecessor, and now the second deciduous molar become a guidance for it to erupt in correct position. These make the fact that preservation
of deciduous molar become so much important!
The early lost of deciduous molar will have great impact of the eruption of permanent teeth, in fact may caused severe malocclusion later in the jaw development. To help you understand the mechanism, I drawn a simple illustration:-
1. A 5 years old boy having a toothache on carious lower left second deciduous molar, and his father wanted the tooth to be extracted despite the advice from dentist to preserve it.
2. A year later, at age of 6, is the time for the first permanent molar to erupt. Because lack of ‘guidance’ from the ‘extracted’ second deciduous molar, the first permanent molar are erupting ‘freely’.
3. When the boy at age of 10, the first permanent molar shifted gradually to the front during the development growth of the jaw for the passed 5 years. It almost occupied 2/3 of the extracted space of second deciduous molar.
4. At age of 11, the lower second premolar start to erupt. Unfortunately it has lost its predecessor space because occupied by the first permanent molar. So, the second premolar have to be squeeze out from it alignment.
How to save a deep caries deciduous molar?
If the tooth still vital, numb it with local anaesthesia, removed all infected pulpal tissue. Clean and disinfect the pulp chamber and canal with chlorhexidine. Dry the pulp chamber and put a medicament to continue sterilized the canal, dress the cavity with temporary dressing.
Removed all medicament on second visit, put another medicament (Vitapex) into the canal to keep the canal sterile and allow for normal resorption of root during process of exfoliation. The cavity filled with Glass Ionomer Cement or sometime stainless steel crown is necessary.
Some clinical photo shown the consequences after early lost of deciduous molar.
The premolar been squeeze out from alignment.
It caused the whole left side of posterior teeth to sink in and further displacement of upper canine.
It caused crowding and under developed jaw bone.
It caused crossbite or scissor bite.
Dr Goon Yong Por
BDS, FICD, FADI, FICCDE