BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 6704483 · Received July 11, 2017

    Report

    Report Number
    9611253-2017-00032
    Event Type
    Injury
    Date Received
    July 11, 2017
    Date of Event
    May 19, 2017
    Report Date
    July 28, 2017
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K121901
    Adverse Event
    Yes
    Report Source
    Manufacturer report
    Reporter Occupation
    DENTIST

    Narratives

    Additional Manufacturer Narrative · 0

    EXEMPTION NUMBER E2016004. (B)(4). - (B)(4) IS LISTED HERE AND MR. (B)(4) BECAUSE MR. (B)(4) IS THE OFFICIAL CORRESPONDENT OF BOTH NAKANISHI INC. AND (B)(4).

    Description of Event or Problem · 0

    ON JUNE 14, 2017, NAKANISHI RECEIVED AN E-MAIL FROM A DISTRIBUTOR (B)(4) ABOUT A HANDPIECE OVERHEATING. DETAILS ARE AS FOLLOWS. - ON (B)(4) 2017, (B)(4) WAS MADE AWARE OF THE EVENT BY COMMUNICATION WITH THE DENTIST THAT THE HANDPIECE, Z45L (SERIAL NO. (B)(4)) HAD OVERHEATED. - THE EVENT OCCURRED ON (B)(6) 2017. - THE DENTIST WAS EXTRACTING WISDOM TEETH FROM THE PATIENT'S MOUTH AT THE TIME OF THE EVENT. - THE PATIENT WAS UNDER NITROUS AND A LOCAL ANESTHETIC. - DURING THE PROCEDURE, THE DENTIST FOUND A QUARTER SIZE WHITE LESION ON THE PATIENT'S CHEEK/BUCCAL MUCOSA. - THE DENTIST PERFORMED A POST OPERATIVE EVALUATION AND ADMINISTERED OINTMENT TO THE LESION. - A FOLLOW-UP WITH THE PATIENT WAS CONDUCTED AND THE INJURY WAS HEALING NORMALLY. - NO FURTHER MEDICAL ATTENTION IS REQUIRED. - THERE WERE NO ABNORMALITIES OBSERVED WITH THE DEVICE PRIOR TO USE.

    Additional Manufacturer Narrative · 1

    UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT FROM A DISTRIBUTOR, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE THAT INCLUDED MEASURING THE OPERATING TEMPERATURE OF THE DEVICE [C170615-18]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED: NAKANISHI EXAMINED THE DEVICE HISTORY RECORD AND THE REPAIR HISTORY FOR THE SUBJECT Z45L DEVICE [SERIAL NUMBER (B)(4)]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. THERE WERE ALSO NO REPAIR HISTORY RECORDS SINCE THE DEVICE WAS SHIPPED. NAKANISHI CONDUCTED A VISUAL INSPECTION OF THE RETURNED DEVICE AND PERFORMED A SIMPLE MOVEMENT TEST. THERE WERE NO VISIBLE ABNORMALITIES, SUCH AS CRACKS OR DENTS, ON THE OUTSIDE OF THE HANDPIECE. NAKANISHI THEN SET A TEST BUR IN THE HANDPIECE AND ROTATED IT BY HAND. NAKANISHI OBSERVED THAT THE BUR DID NOT ROTATE SMOOTHLY. NAKANISHI CONDUCTED TEMPERATURE TESTING OF THE RETURNED DEVICE IN THE FOLLOWING MANNER: TEMPERATURE SENSORS WERE ATTACHED TO THE EXTERIOR OF THE DEVICE AT VARIOUS TEST POINTS. THIS INCLUDED THE POINT MOST PROXIMAL TO THE PATIENT (TESTING POINT (1)) AND POINTS FURTHER TOWARD THE DISTAL END OF THE DEVICE (TESTING POINTS (2) THROUGH (4)). THE TEST SETUP WAS PREPARED TO TAKE TEMPERATURE MEASUREMENTS AT ALL POINTS SIMULTANEOUSLY, INCLUDING A REFERENCE MEASUREMENT AT AMBIENT ROOM TEMPERATURE. NAKANISHI ATTACHED A THERMOCOUPLE (SENSOR TO MEASURE A TEMPERATURE) TO EACH OF THE TESTING POINTS. NAKANISHI ROTATED THE DEVICE'S MOTOR AT 40,000 MIN-1, WHICH IS THE MAXIMUM RPM FOR THE MOTOR THAT DRIVES THE HANDPIECE (168,000 MIN-1 FOR THE HANDPIECE), WITH WATER SPRAY, AND MEASURED THE EXOTHERMIC RESPONSE. NAKANISHI MEASURED THE TEMPERATURE RISE OF THE RETURNED HANDPIECE SET AT 168,000 MIN-1 (MOTOR REVOLUTION 40,000 MIN-1). NAKANISHI OBSERVED AN ABNORMAL TEMPERATURE RISE AT TEST POINT (1) AND (2) A FEW SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 17 SECONDS AFTER THE START ARE AS FOLLOWS: - TEST POINT (1): 71.2 DEGREES C - TEST POINT (2): 83.6 DEGREES C - TEST POINT (3): 34.4 DEGREES C - TEST POINT (4): 29.1 DEGREES C. THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 17 SECONDS INTO THE PLANNED 5 MINUTE EVALUATION PERIOD. IDENTIFICATION OF THE SPECIFIC FAILURE MODE(S) AND/OR MECHANISM(S) AND THE ASSOCIATED DEVICE COMPONENTS INVOLVED: NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INSIDE PARTS. NAKANISHI OBSERVED THE FOLLOWING PHENOMENA: - THE BEARING RETAINER (BALL RETAINING PART) ON THE REAR SIDE OF THE CARTRIDGE WAS BROKEN/ABRADED. - THE SURFACE OF THE BALL-ROLLING PASSAGE WAS DAMAGED. - THE INSIDE OF THE CARTRIDGE WAS CORRODED. - THERE WAS DIRT INSIDE THE HEADCAP. NAKANISHI TOOK PHOTOGRAPHS OF ALL OF THE DISASSEMBLED PARTS AND KEPT THEM IN A FILE. DUE TO OBSERVATION OF THE BROKEN BEARING RETAINER ON THE REAR SIDE OF THE CARTRIDGE, NAKANISHI REPLACED THE CARTRIDGE WITH A NEW ONE AND MEASURED THE EXOTHERMIC SITUATION YET AGAIN. THERE WAS NO ABNORMAL RISE IN TEMPERATURE DURING THE TEST PERIOD. NAKANISHI CONFIRMED THAT THE RETURNED HANDPIECE WAS OPERATING AS EXPECTED AND WITHIN TEMPERATURE SPECIFICATIONS ONCE THE DAMAGED BEARINGS HAD BEEN REPLACED. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: NAKANISHI IDENTIFIED THAT THE CAUSE OF THE OVERHEATING OF THE RETURNED DEVICE WAS ABNORMAL RESISTANCE DURING ROTATION CAUSED BY THE BROKEN BEARINGS DUE TO THE INGRESS OF DIRT INTO THE BEARING. A LACK OF MAINTENANCE CAUSES THE ACCUMULATION OF DIRT IN THE INSIDE PARTS, WHICH CAUSES DIRT INGRESS INTO THE BEARING DURING ROTATION, LEADING TO THE BROKEN BEARINGS. THIS CONTRIBUTES TO THE HANDPIECE OVERHEATING. IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO NSK AMERICA AND DIRECTED NSK AMERICA TO REMIND THE USER OF THE IMPORTANCE OF MAINTENANCE, AS INSTRUCTED IN THE OPERATION MANUAL.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    484413 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z45L

    Patients

    Seq Age Sex Outcome Treatment
    1 35 YR Other