BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 7190024 · Received January 15, 2018

    Report

    Report Number
    9611253-2018-00002
    Event Type
    Injury
    Date Received
    January 15, 2018
    Date of Event
    December 20, 2017
    Report Date
    February 13, 2018
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    Adverse Event
    Yes
    Product Problem
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    JA
    Reporter Occupation
    DENTIST

    Narratives

    Additional Manufacturer Narrative · 0

    UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE THAT INCLUDED MEASURING THE OPERATING TEMPERATURE OF THE DEVICE [(B)(4)]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED: NAKANISHI EXAMINED THE DEVICE HISTORY RECORD AND THE REPAIR HISTORY FOR THE SUBJECT Z84L 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 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 (180,000 MIN-1 FOR THE HANDPIECE), WITH WATER SPRAY, AND MEASURED THE EXOTHERMIC RESPONSE. NAKANISHI MEASURED THE TEMPERATURE RISE OF THE RETURNED HANDPIECE SET AT 180,000 MIN-1 (MOTOR REVOLUTION 40,000 MIN-1). NAKANISHI OBSERVED AN ABNORMAL TEMPERATURE RISE AT TEST POINT (2) A FEW SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 32 SECONDS AFTER THE START ARE AS FOLLOWS: - TEST POINT (1): 45.8 DEGREES C - TEST POINT (2): 71.6 DEGREES C - TEST POINT (3): 35.0 DEGREES C - TEST POINT (4): 25.6 DEGREES C THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 32 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 THAT THE BEARING RETAINER (BALL RETAINING PART) ON THE CARTRIDGE REAR SIDE WAS BROKEN. NAKANISHI TOOK PHOTOGRAPHS OF ALL OF THE DISASSEMBLED PARTS AND KEPT THEM IN THE INVESTIGATION REPORT #(B)(4). CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: NAKANISHI IDENTIFIED THAT THE CAUSE OF OVERHEATING OF THE RETURNED DEVICE WAS DUE TO FRICTIONAL RESISTANCE GENERATED BY CONTACT BETWEEN THE BALL BEARING RETAINER AND THE OUTER RACE (METAL PART), WHICH WAS GENERATED BY CENTRIFUGAL ACTION DURING ROTATION DUE TO THE BROKEN RETAINER. NAKANISHI CONSIDERS THE POSSIBILITY FROM MANY YEARS OF EXPERIENCE THAT THE CAUSE OF THE BALL BEARING RETAINER BEING BROKEN WAS THE INGRESS OF DEBRIS OR FOREIGN MATERIAL INTO THE BALL BEARING THAT INTERFERED WITH ROTATION, WHICH LEAD TO THE BREAKAGE OF THE BALL BEARING RETAINER. A LACK OF MAINTENANCE CAUSES THE ABOVE SITUATION, WHICH WILL CONTRIBUTE TO THE HANDPIECE OVERHEATING. 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, AS INSTRUCTED IN THE OPERATION MANUAL.

    Additional Manufacturer Narrative · 1

    WHEN NAKANISHI COMMUNICATED WITH THE DENTIST ABOUT THE EVENT ON (B)(6) 2017, THE DENTIST REFUSED TO PROVIDE INFORMATION ABOUT THE PATIENT'S ID, AGE AND WEIGHT. THIS EVENT OCCURRED IN (B)(6), BUT SIMILAR PRODUCTS ARE MARKETED IN THE US UNDER K972569.

    Description of Event or Problem · 1

    ON DECEMBER 21, 2017, NAKANISHI RECEIVED A PHONE CALL FROM A DENTIST ABOUT AN NSK HANDPIECE OVERHEATING. THE DETAILS ARE AS FOLLOWS. THE EVENT OCCURRED ON (B)(6) 2017. THE DENTIST WAS PERFORMING A TOOTH FORMATION USING THE HANDPIECE Z84L (SERIAL NO. (B)(4)). THE PATIENT WAS NOT ANESTHETIZED. DURING THE PROCEDURE, THE PATIENT COMPLAINED ABOUT THE HANDPIECE OVERHEATING. THE DENTIST FOUND A 1-CENTIMETER BURN INJURY IN THE PATIENT'S MOUTH. THERE WAS A SLIGHT ABNORMAL NOISE FROM THE HANDPIECE PRIOR TO USE. THE DENTIST DETERMINED NO BURN TREATMENT WAS NECESSARY.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    35679 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z84L

    Patients

    Seq Age Sex Outcome Treatment
    1 Other