First molars

Steel Bite Protocol

Tooth Pain Causes and Treatment

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First permanent molars are often the first permanent teeth to erupt into the mouth. Their deep fissure morphology predisposes them to caries and poor tooth brushing combined with a high sugar intake, may result in gross caries. Heavily restored or decayed first molars should be considered for removal over other non-carious teeth (Fig. 12). First molars extraction requires careful planning. Their position in the arch means that whilst relief of premolar crowding is achieved the space created is far from the site of any incisor crowding or overjet reduction. The timing of the loss of first molars is also an important consideration.

Maxillary second molars have a curvilinear eruptive path with mesial and vertical components. The lower second molar has a more vertical path, but it has to move more horizontally in favourable spontaneous molar correction. This is one of the reasons why the spontaneous tooth

Fig. 9 A Class I case with mild lower labial segment crowding in the late mixed dentition (a) & (b). All four first premolars were extracted and the occlusion allowed to align spontaneously. (c) & (d)

Fig. 9 A Class I case with mild lower labial segment crowding in the late mixed dentition (a) & (b). All four first premolars were extracted and the occlusion allowed to align spontaneously. (c) & (d)

Orthopantomogram Orthodontic
Fig. 10 A hypodontia case pre-treatment showing good quality deciduous molars which were retained as part of the treatment plan. Mesio-distal reduction or 'slenderising' can be used to maximise arch co-ordination, especially where deciduous molars are only retained in one arch

movement is less favourable in the lower arch. Three periods of development can be considered when looking at the effects of loss of first molars.

Maximal space closure by mesial migration of the second molar occurs in the mixed dentition. At this stage the second molars are unerupted and their root furcation is just calcifying. The best results occur in the upper arch where the second molar will usually erupt mesially and make contact with the upper second premolar. Spontaneous relief of mild crowding in the labial segments may be seen. In the lower arch, spontaneous closure is less likely, but mesial migration of the second molar is also optimal at this stage and may resulting in minimal space between the second molar and second premolar (Fig. 12).

In the permanent dentition the effect of loss of a first molar can be difficult to predict after the second molar has erupted. Fixed appliances are invariably needed at this stage to align the teeth and achieve space closure with parallel roots.20 The effects are more of a problem in the lower arch, where the second molar tips mesial-ly and rolls lingually forming a very poor contact with the second premolar or may leave excess space. Little spontaneous relief of anterior crowding is seen. The upper first molar if retained can over-erupt, further increasing the tipping and rolling of the lower second molar. In addition mesial movement of the lower

Premolar Extraction

Fig. 12 Four first molars were extracted just after the optimal time, prior to fixed appliance treatment. The orthopantomogram (a) shows gross caries in the left first molars and heavy restorations in the right first molars. Notice the discrepancy in space available in the two arches. In the upper arch the second molars have erupted in close proximity to the second premolars due to their mesial eruptive path (b). In the lower arch there is considerably more space remaining from the vertical eruptive path of the second molars (c)

Fig. 12 Four first molars were extracted just after the optimal time, prior to fixed appliance treatment. The orthopantomogram (a) shows gross caries in the left first molars and heavy restorations in the right first molars. Notice the discrepancy in space available in the two arches. In the upper arch the second molars have erupted in close proximity to the second premolars due to their mesial eruptive path (b). In the lower arch there is considerably more space remaining from the vertical eruptive path of the second molars (c)

Ulcers After Extraction Second Molar
Fig. 13 Extraction of second molars allowed spontaneous relief of anterior crowding, with early eruption of the third molars

molar may be prevented. The upper second molar shows less tipping and rolling than its lower counterpart, but does not align to the extent seen in the mixed dentition. In adult patients the drifting of both upper and lower second molars is less marked, and the relief of crowding less reliable. In young patients, radiographs should be checked to ensure that the developing lower second premolar is contained by the roots of the primary molar. If not, then substantial drifting of the second premolar can take place including impaction into the mesial surface of the second molar.

In general terms if a lower first molar is to be extracted, the upper molar on the same side should also be extracted (compensating extraction). This prevents unwanted overeruption of the upper first molar and the upper second molar will usually erupt into a good position. However, if an upper first molar is to be extracted, the lower counterpart is usually left in situ. This is because the lower second molar behaves unpredictably and rarely achieves good spontaneous alignment. An additional factor is that lower molars over erupt less than upper molars and will not interfere with the generally good progress made by upper second molars. If the case has no crowding, then balancing extractions should not be considered (removal of a tooth on the opposite side of the same arch). Children presenting with carious first molars often show signs of disease in all of them. If the timing is correct and the malocclusion justifies treatment, all four first molars should be removed to allow second molars to erupt efficiently and reduce subsequent treatment times.

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