BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 6185679 · Received December 19, 2016

    Report

    Report Number
    9611253-2016-00070
    Event Type
    Injury
    Date Received
    December 19, 2016
    Date of Event
    November 16, 2016
    Report Date
    March 20, 2017
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    Adverse Event
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    JA
    Reporter Occupation
    OTHER

    Narratives

    Additional Manufacturer Narrative · 1

    NAKANISHI TRIED TO OBTAIN A PATIENT IDENTIFIER, BUT THE DENTIST REFUSED TO PROVIDE ONE. THIS EVENT OCCURRED IN (B)(6), BUT SIMILAR PRODUCTS ARE MARKETED IN THE US UNDER K972569.

    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 TEMPERATURE OF THE OPERATING DEVICE [C161129-05-1]. 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 0BF90042]. 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 SITUATION. 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 (1) AND (2) A FEW SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 32 SECONDS AFTER THE START ARE AS FOLLOWS: - TEST POINT (1): 51.6 DEGREES C - TEST POINT (2): 72.9 DEGREES C - TEST POINT (3): 28.5 DEGREES C - TEST POINT (4): 28.0 DEGREES C. THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS ENDED ONLY 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 BREAKAGE OF A PART OF BEARING RETAINER (BALL RETAINING PART) ON THE REAR SIDE OF THE CARTRIDGE (ON THE PUSH BUTTON SIDE). NAKANISHI TOOK PHOTOGRAPHS OF ALL OF 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 FRICTIONAL RESISTANCE GENERATED BY CONTACT BETWEEN THE BALL BEARING PART AND THE OUTER RACE (BEARING OUTER METAL PART), WHICH WAS GENERATED BY CENTRIFUGAL ACTION DURING ROTATION DUE TO THE BROKEN BALL BEARING PART. NAKANISHI CONSIDERS THE POSSIBILITY FROM MANY YEARS OF EXPERIENCE THAT THE CAUSE OF THE BALL BEARING PART BEING BROKEN WAS THE INGRESS OF DIRT INTO THE BALL BEARING THAT INTERFERED WITH ROTATION, WHICH LEAD TO THE BREAKAGE OF THE BALL BEARING PART. 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 AND CHECKING OF THE HANDPIECE PRIOR TO USE TO PREVENT OVERHEATING, AS INSTRUCTED IN THE OPERATION MANUAL.

    Description of Event or Problem · 1

    ON NOVEMBER 28, 2016, NAKANISHI RECEIVED A PHONE CALL FROM A DISTRIBUTOR ABOUT HANDPIECE OVERHEATING. DETAILS ARE AS FOLLOWS. THE EVENT OCCURRED ON (B)(6) 2016. A DENTIST WAS PERFORMING A PULP EXTIRPATION OF AN UPPER RIGHT TOOTH USING AN NSK HANDPIECE Z84L (SERIAL NO. (B)(4)). DURING THE PROCEDURE, THE DENTIST FOUND A ONE-CENTIMETER WHITE BLISTER ON THE PATIENT'S UPPER LIP. THE PATIENT WAS NOT AWARE OF THE BURN INJURY AT THE TIME OF THE EVENT BECAUSE THE PATIENT WAS UNDER ANESTHESIA. THE DENTIST DETERMINED THAT THE BURN DID NOT REQUIRE ANY MEDICAL INTERVENTION. ACCORDING TO THE DENTIST, THE HANDPIECE OVERHEATED PRIOR TO TREATMENT OF THE PATIENT.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    836523 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z84L

    Patients

    Seq Age Sex Outcome Treatment
    1 40 YR Other