BONE remodf:ling in dental eruption and shedding 33o 



Discussion 



During eruption of a tooth a series of very complicated tooth 

 movements occur within the jaws. These are essential so that the 

 tooth may (a) keep pace with the growing jaws, (b) maintain a 

 certain relationship to other teeth, and (c) maintain a certain rela- 

 tionship to the oral epithelium. Although there are only two sets of 

 teeth in man, chronologically, the 26 teeth in each jaw are distinct 

 organs. It is apparent, then, that for a normal dentition, the move- 

 ment of teeth during and before eruption must be very precise. We 

 have seen that the remodeling of bone is a constant companion to 

 this movement. Whether the remodeling is the result or the cause 

 of tooth movements is a much debated question. There are two 

 main beliefs. One is that the tooth germ grows and produces pres- 

 sure on the surrounding bone, which then vmdergoes osteoclastic 

 resorption, and as a tooth germ moves away from a crypt wall, bone 

 apposition occurs on this surface. According to this concept, bone 

 remodeling within the jaws is a passive phenomenon. The second 

 belief is that the internal remodeling of the jaws is a predetermined 

 genetic pattern, in much the same way as the modeling pattern 

 of a tibia or a femur is a genetically determined pattern. According 

 to this concept, the teeth move as a result of this pattern of bone 

 apposition and resorption. Regardless of which theory is correct, it 

 is undeniable that the internal modeling of the maxilla and the 

 mandible has a great deal to do with the normal development and 

 eruption of teeth. 



In the case of shedding of teeth, the eruptive force of a perma- 

 nent tooth plays an important role in the loss of the deciduous 

 tooth. This eruptive pressure first produces resorption of the bony 

 socket, and then the resorption of the root of the deciduous tooth. 

 These resorptive changes are accompanied by osteoclasts and 

 odontoclasts. The changes which induce the resorptive phenomenon 

 are seen in a multitude of circumstances in the skeleton. Pressure 

 resorption of the bone tissue adjacent to tumors, cysts, aneurysms, 

 and orthodontic appliances are examples of this phenomenon. Re- 

 gardless of the mechanism, it is certain that bone remodeling is im- 

 portant in shedding of teeth as it is in their eruption. 



