BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 5426831 · Received February 10, 2016

    Report

    Report Number
    9611253-2016-00003
    Event Type
    Injury
    Date Received
    February 10, 2016
    Date of Event
    January 7, 2016
    Report Date
    March 23, 2016
    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

    UPON RECEIPT FROM A DISTRIBUTOR OF THE DEVICE INVOLVED IN THE MDR EVENT, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE THAT INCLUDED MEASUREMENT OF THE TEMPERATURE OF THE OPERATING DEVICE [C160115-01]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED : NAKANISHI EXAMINED THE DEVICE HISTORY RECORD FOR THE SUBJECT TI-MAX X85L DEVICE [SERIAL NUMBER (B)(4)]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. NAKANISHI CONDUCTED A TEMPERATURE TESTING OF THE RETURNED DEVICE IN THE FOLLOWING MANNER. TEMPERATURE SENSORS WERE FIRST ATTACHED TO THE EXTERIOR OF THE DEVICE AT VARIOUS TEST POINTS (I.E., MOST PROXIMAL TO THE PATIENT, TESTING POINT (1), AND ALONG 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 MOTOR AT 40,000 MIN-1, WHICH IS MAXIMUM RPM FOR THE MOTOR THAT DRIVES THE HANDPIECE (200,000 MIN-1 FOR THE HANDPIECE), WITH WATER SPRAY AND MEASURED THE EXOTHERMIC SITUATION. NAKANISHI MEASURED THE TEMPERATURE RISE OF THE RETURNED HANDPIECE SET AT 200,000 RPM (MOTOR REVOLUTION 40,000RPM). NAKANISHI CONFIRMED THE ABNORMAL TEMPERATURE RISE AT THE TEST POINTS (1) AND (2) AS FOLLOWS AFTER THE BEGINNING OF THE MEASUREMENT; (1) 79.1 DEGREES C, (2) 58.4 DEGREES C. THE RISE WAS SO SUDDEN THAT THE TEMPERATURES, 79.1 DEGREES C AND 58.4 DEGREES C WERE OBSERVED ONLY 20 SECONDS INTO THE PLANNED 5 MINUTES EVALUATION PERIOD. IDENTIFICATION OF THE SPECIFIC FAILURE MODE(S) AND/OR MECHANISM(S) AND THE ASSOCIATED DEVICE COMPONENT(S) INVOLVED: NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INSIDE PARTS. NAKANISHI OBSERVED AS FOLLOWS. A BROKEN BEARING RETAINER (BALL BEARING PLASTIC PART) IN THE BALL BEARING (ON THE BUR INSERTING SIDE OF THE CARTRIDGE). DIRT (ABRASIVE POWDERS/FOREIGN MATERIALS, ETC.) INSIDE OF THE CARTRIDGE SLIGHT ABRASION IN THE GEAR ENGAGEMENT PART NOT CONTRIBUTING TO THE OVERHEATING 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 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 IS DUE TO INGRESS OF DIRT (ABRASIVE POWDERS/FOREIGN MATERIALS) INTO THE BALL BEARING THAT INTERFERE WITH ROTATION, WHICH LEADS TO 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 JANUARY 15, 2016, NAKANISHI RECEIVED A PHONE CALL FROM A DISTRIBUTOR ABOUT OVERHEATING OF AN NSK DENTAL HANDPIECE. DETAILS ARE AS FOLLOWS. THE EVENT OCCURRED ON (B)(6) 2016. DURING TOOTH FORMATION USING TI-MAX X85L, THE PATIENT COMPLAINED ABOUT LIP PAIN. THE DENTIST DID NOT FEEL THE HANDPIECE OVERHEATING AT THE MOMENT WHEN THE PATIENT COMPLAINED. AFTER HEARING THE COMPLAINT, THE DENTIST TOUCHED THE HANDPIECE HEAD AND FELT HEAT. THE PATIENT WAS NOT ANESTHETIZED. THE DENTIST DECIDED THAT THE PATIENT REQUIRED NO MEDICAL TREATMENT ON THE LIP.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    84695 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. X85L

    Patients

    Seq Age Sex Outcome Treatment
    1 30 YR Other