Following the loss of a tooth,  the adjacent teeth often drift into the vacant space especially in the presence of dental crowding. As the teeth drift they tip over and this causes biting forces to be poorly distributed on the lower surface of the root. This usually results in gum pocketing and bone loss around the roots of the affected teeth.

This case shows x-ray and a picture of the tipped lower right first molar (blue arrow) following the loss of the second premolar and spontaneous space closure.  There is bone loss on the root surface indicated by the yellow arrow.

A similar and more dramatic case i s presented below with the second mo lar ( green arrow) tipping into the space left following extraction of the first molar.  Once again bone loss is evident on the front of the root.

In this case the tipped teeth in the lower jaw were uprighted and the space completely closed improving the dental function, protecting the bone support and bringing the impacted lower right third molar into a useful position avoiding the need for a dental implant at the same time.