On April 6, 1995, about 1716 eastern daylight time, a Piper PA- 28-180, N6539J, lost total engine power during initial climb out from runway 20 at the Pittsburgh-Boquet Airpark in Jeanette, Pennsylvania. The airplane was destroyed when it collided with trees during the emergency descent. The certificated flight instructor (CFI) received minor injuries and the one passenger was seriously injured. Visual meteorological conditions prevailed for the local flight, no flight plan was filed. The personal flight was conducted under 14 CFR Part 91. The CFI reported that he was practicing takeoffs and landings at the Pittsburgh-Boquet Airpark. He stated that during initial climb after the second takeoff, at 150 feet above the ground, the airplane's engine lost total power. The pilot stated that he made a forced landing into trees with "...A Nose High Attitude Above Treetops To Cushion The Impact." The airplane collided with trees and came to rest upside down. Postaccident examination of the airplane's engine revealed its right magneto did not function. The magneto was dismantled and its internal components examined. Examination of the components revealed teeth on the nylon pinion gear had failed. The failure modes of the teeth were not determined.