Change in electrical potential within periodontal ligament of a tooth subjected to osteogenic loading

A tungsten microelectrode 12 microns in length and 1-2 microns in diameter was inserted into the periodontal ligament (PDL) of a maxillary molar of an anesthetized rat. The acid etched enamel surface, microelectrode shaft, and a suture for mesial traction were bonded together with composite resin. A mesial tipping load was applied by passing the suture over a pulley and attaching a 100 g weight. Cell-level potential was monitored with an electrometer modified with a variable nulling circuit. Baseline drift of 1-3 mV in 15 min was achieved prior to applying a load. When a 100 g mesial (anterior) load was applied, a relatively sharp drop of about 5-10 mV occurred within minutes. This more negative potential was maintained for as long as the load was applied up to 20 min. When the force was removed, a sharp increase in potential up to about 50-60% of preloaded levels was observed consistently. Animals monitored after breathing stopped, due to anesthetic overdose, showed only a minimal response to loading after 10 min and no effect at all after 20 min.