根未完成歯の補綴的処置に関する実験的研究

Abstract

When a piece of bridgework is fixed on a tooth with yet incomplete root for prosthetic purpose, something of pathological changes may be anticipated to occur in the root and periodontal tissues of abutment and antagonizing teeth. Present study was undertaken to learn the problem in some detail, using dogs as experimental animal. Results were summarized as follows. 1) A group of adult animal with completed root and another group of infant animal with incomplete root were respectively selected and these two groups were further subdivided into the normal occlusion experiment group and the traumatic occlusion experiment group. 2) When duration of bridgework fixture on the teeth never exceeded over two months, there were seen some instances of dogs, infant or adult, showing the traumatic occlusion symptoms by occlusion such as constriction of the lumen of periodontal membrane, degeneration of periodontal membrane, resorption of alveolar bone, and light resorption of tooth substance, and this was even observed in the animals of normal occlusion experiment group. 3) These findings of traumatic occlusion symptoms, however, disappeared from the picture and were replaced by those of normal, when duration of bridgework fixing extended over two months, and no appreciable difference was found between adult and infant dogs in these points. 4) In dogs of traumatic occlusion experiment group, with no exception of adult or infant, there were observed severe constriction or closure of the periodontal membranous lumen, degeneration or necrosis of the periodontal membrane, undermining resorption of alveolar bone and resorption of tooth substance, all of which being the definite signs of occlusion trauma. These symptoms were then followed by the appearance of repair mechanisms such as renewed formation of periodontal membrane, reconstruction of alveolar bone and deposition of secondary cementum onto the depressions of tooth substance made by resorption. 5) When adult and infant dogs were compared, the damage by traumatic occlusion was apparent in the tooth of infant dogs earlier and severer than in the tooth of adult dogs. However, repair mechanism came likewise into action earlier in the tooth of infant dogs and in some cases the repairing process had begun to work already by 3 weeks after the bridgework fixing and the repair was completed in the infant dogs within experimental period of 4 months. In the adult dogs, on the contrary, the repair mechanism begun to work by two months after the bridgework fixing and continued repairing even by four months period. 6) The tooth pulp was shown to have suffered a variety of damage as the consequence of abutment preparation, and such damage was more frequently seen in infant dogs. Only few instances of tooth pulp damage were encountered, however, as the consequence of traumatic occlusion. 7) From the foregoing results obtained from the experiments, it may be concluded that when any patient showed prognosis of occlusional imbalance and other troubles of chewing by loss of tooth, the clinician is adviced to give him some properly constructed prosthetic appliance, taking care to provide full protection with the tooth pulp, even if the abutment tooth had its root not yet completed.