ON (B)(6) 2016, NAKANISHI RECEIVED A PHONE CALL FROM A DISTRIBUTOR ABOUT AN NSK DENTAL PRODUCT. DETAILS ARE AS FOLLOWS. ON (B)(6) 2016, A DENTIST WAS CUTTING A BONE OF A PATIENT TO EXTRACT A WISDOM TOOTH USING NSK SURGICAL HANDPIECE, SGS-E2S. THE PATIENT WAS UNDER GENERAL ANESTHESIA. A BURN INJURY (2.0 CENTIMETERS BY 0.5 CENTIMETERS) WAS OBSERVED ON THE PATIENT'S ORAL MUCOSA MEMBRANE. THE DENTIST DID NOT FEEL HEAT AT THE HANDPIECE GRIP WHERE HE WAS HOLDING, BUT FELT HEAT AT THE TIP OF THE HANDPIECE. THE DENTIST DECIDED TO GIVE THE PATIENT FOLLOW-UP OBSERVATIONS INSTEAD OF MEDICATIONS.
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Patient 1
UPON RECEIPT FROM A DISTRIBUTOR OF THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE [C160126-07-1]. METHODOLOGY USED : NAKANISHI EXAMINED THE DEVICE HISTORY RECORD INCLUDING REPAIR RECORDS FOR THE SUBJECT SGS-E2S DEVICE [SERIAL NUMBER (B)(4).]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. NAKANISHI THEN ROTATED THE HANDPIECE AND OBSERVED THAT THE HANDPIECE DID NOT ROTATE AT ALL. NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INSIDE PARTS. NAKANISHI OBSERVED AS FOLLOWS : BEARING (1) : ABRASION, BEARING (2) : BREAKAGE, ABRASION MARK IN THE INNER RACE OF THE BEARING, BEARING (3) : DIRT/DISCOLORATION, GEAR : DISCOLORATION, NAKANISHI TOOK PHOTOGRAPHS OF ALL THE DISASSEMBLED PARTS AND KEPT THEM IN A FILE. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS : NAKANISHI IDENTIFIED THAT THE CAUSE OF OVERHEATING OF THE RETURNED DEVICE WAS DUE TO THE BEARINGS BROKEN BY DIRT INGRESS. A LACK OF MAINTENANCE CAUSES THE ABOVE SITUATION, WHICH WILL CONTRIBUTE TO THE HANDPIECE OVERHEATING. AFTER REPLACING THE BROKEN BEARINGS WITH THE NEW BEARINGS, NAKANISHI CONFIRMED THAT THE HANDPIECE ROTATED NORMALLY AND DID NOT OVERHEATED. NAKANISHI TOOK THE FOLLOWING ACTIONS IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING. NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO THE DENTIST AND REMINDED THE DENTIST OF THE IMPORTANCE OF MAINTENANCE AND CHECKING OF THE HANDPIECE PRIOR TO USE TO PREVENT OVERHEATING AS INSTRUCTED IN THE OPERATION MANUAL.