BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 6325612 · Received February 13, 2017

    Report

    Report Number
    9611253-2017-00008
    Event Type
    Injury
    Date Received
    February 13, 2017
    Date of Event
    January 13, 2017
    Report Date
    May 19, 2017
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K972569
    Adverse Event
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    JA
    Reporter Occupation
    OTHER

    Narratives

    Additional Manufacturer Narrative · 1

    WHEN NAKANISHI TRIED TO OBTAIN FURTHER INFORMATION ABOUT THE EVENT ON (B)(4) 2017, THE DENTIST REFUSED TO PROVIDE THE PATIENT IDENTIFIER.

    Additional Manufacturer Narrative · 1

    UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE THAT INCLUDED MEASURING THE TEMPERATURE OF THE OPERATING DEVICE [C170119-06-1]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED: A) NAKANISHI EXAMINED THE DEVICE HISTORY RECORD AND THE REPAIR HISTORY FOR THE SUBJECT Z95L 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. B) NAKANISHI CONDUCTED TEMPERATURE TESTING OF THE RETURNED DEVICE IN THE FOLLOWING MANNER: B.1) 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. B.2) 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 (200,000 MIN-1 FOR THE HANDPIECE), WITH WATER SPRAY, AND MEASURED THE EXOTHERMIC SITUATION. B.3) NAKANISHI MEASURED THE TEMPERATURE RISE OF THE RETURNED HANDPIECE SET AT 200,000 MIN-1 (MOTOR REVOLUTION 40,000 MIN-1). NAKANISHI OBSERVED AN ABNORMAL TEMPERATURE RISE AT TEST POINT (2) 30 SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 30 SECONDS AFTER THE START ARE AS FOLLOWS: - TEST POINT (1): 44.3 DEGREES C - TEST POINT (2): 59.4 DEGREES C - TEST POINT (3): 24.9 DEGREES C - TEST POINT (4): 24.2 DEGREES C THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS ENDED ONLY 30 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: A) NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INSIDE PARTS. NAKANISHI OBSERVED THE FOLLOWING PHENOMENA: - THE BALL BEARING RETAINER (BALL RETAINING PART) ON THE CARTRIDGE SIDE WAS BROKEN. - THE BALL POCKETS OF THE BEARING WERE WORN. B) NAKANISHI TOOK PHOTOGRAPHS OF ALL OF THE DISASSEMBLED PARTS AND KEPT THEM IN A FILE. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: 1) 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 WORN RETAINER AND THE INGRESS OF DIRT INTO THE BEARING. 2) 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. 3) IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: 3.1) NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. 3.2) NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO THE DENTIST AND REMINDED THE DENTIST OF THE IMPORTANCE OF MAINTENANCE, AS INSTRUCTED IN THE OPERATION MANUAL.

    Description of Event or Problem · 1

    ON (B)(6) 2017, AN NSK Z95L HANDPIECE WAS RETURNED FROM A DISTRIBUTOR TO NAKANISHI FOR REPAIR. THERE WAS A NOTE WITH THE DEVICE STATING THAT THE HANDPIECE HAD OVERHEATED. UPON RECEIPT OF THE INFORMATION, NAKANISHI CONTACTED THE DENTIST FOR FURTHER INFORMATION. THE DETAILS ARE AS FOLLOWS: THE EVENT OCCURRED ON (B)(6) 2017. A DENTIST WAS PERFORMING A MOLAR PREPARATION ON THE PATIENT'S UPPER RIGHT JAW USING THE Z95L HANDPIECE. THE DENTIST WAS MADE AWARE OF A 3-4 MILLIMETER BURN WOUND ON THE RIGHT CORNER OF THE PATIENT'S MOUTH. THE PATIENT WAS NOT ANESTHETIZED. THERE WERE NO ABNORMALITIES IN THE HANDPIECE PRIOR TO USE. THE DENTIST DISINFECTED THE WOUND WITH ALCOHOL. THE DENTIST DETERMINED THAT NO MORE MEDICAL INTERVENTION WAS NECESSARY FOR THE BURN.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    108686 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 60 YR Other