BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 5346840 · Received January 6, 2016

    Report

    Report Number
    9611253-2016-00001
    Event Type
    Injury
    Date Received
    January 6, 2016
    Date of Event
    November 30, 2015
    Report Date
    October 11, 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 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 [C151211-15]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED : NAKANISHI EXAMINED THE DEVICE HISTORY RECORD AND THE REPAIR HISTORY FOR THE SUBJECT ES95 DEVICE [SERIAL NUMBER (B)(4)]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. THE REPAIR HISTORY SHOWED 3 SERVICE RECORDS (OCTOBER 2005, MARCH 2007, AND OCTOBER 2011) SINCE THE DEVICE WAS SHIPPED. 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. THIS INCLUDED THE POINT MOST PROXIMAL TO THE PATIENT (TESTING POINT A) AND POINTS FURTHER TOWARD THE DISTAL END OF THE DEVICE (TESTING POINTS B THROUGH D). 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 (200,000 MIN-1 FOR THE HANDPIECE), WITH AND WITHOUT WATER SPRAY, AND MEASURED THE EXOTHERMIC SITUATION. NAKANISHI MEASURED THE TEMPERATURE RISE OF THE RETURNED HANDPIECE SET AT 200,000 MIN-1 (MOTOR REVOLUTION 40,000 MIN-1). NAKANISHI OBSERVED THE TEMPERATURE RISE AS FOLLOWS: (WITH WATER SPRAY) TEST POINT (A) : 44.2 DEGREES C, TEST POINT (B) : 46.2 DEGREES C, TEST POINT (C) : 28.3 DEGREES C, TEST POINT (D) : 27.2 DEGREES C; (WITHOUT WATER SPRAY) TEST POINT (A) : 111.0 DEGREES C, TEST POINT (B) : 104.5 DEGREES C, TEST POINT (C) : 79.2 DEGREES C, TEST POINT (D) : 33.4 DEGREES C. ALL TEMPERATURES OBSERVED IN MEASUREMENT WITH THE WATER SPRAY WERE WITHIN THE NAKANISHI SPECIFICATION RANGE. HOWEVER, NAKANISHI CONFIRMED ABNORMAL TEMPERATURE RISE AT THE TESTING POINTS A, B, AND C IN THE EVALUATION WITHOUT THE WATER SPRAY. THE ABNORMAL TEMPERATURES WERE OBSERVED ONLY 60 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: A PART OF BEARING RETAINER (BALL RETAINING PLASTIC PART) BROKEN. ABRASION OF THE GEAR, CORROSION AND DIRT (ABRASIVE POWDERS/FOREIGN MATERIALS) INSIDE PARTS. ROTATIONAL CONTACT TRACE CAUSED BY A PUSH-BUTTON BEING PRESSED DURING ROTATION. 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 THE OVERHEATING OF THE RETURNED DEVICE WAS ABNORMAL RESISTANCE DURING ROTATION CAUSED BY THE BROKEN BALL RETAINING PLASTIC PART. NAKANISHI CONSIDERS THE POSSIBILITY FROM MANY YEARS OF EXPERIENCE THAT THE CAUSE OF THE BALL RETAINING PLASTIC PART BEING BROKEN WAS DUE TO THE INGRESS OF ABRASIVE POWERS/FOREIGN MATERIALS PRODUCED BY CONTINUOUS USE. A LACK OF MAINTENANCE CAUSES THE ACCUMULATION OF DIRT (ABRASIVE POWERS/FOREIGN MATERIALS) IN THE INSIDE PARTS, WHICH CAUSES DIRT/DEBRIS INGRESS INTO THE BEARING DURING ROTATION. THIS CONTRIBUTES TO THE HANDPIECE OVERHEATING. IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: ON (B)(4) 2016, NAKANISHI VISITED THE DENTAL OFFICE AND REPORTED THE ABOVE EVALUATION RESULTS TO EXPLAIN THE IMPORTANCE OF CHECKING THE HANDPIECE PRIOR TO USE. DURING THE VISITING, NAKANISHI EXCHANGED THE ES95 DEVICE FOR ITS SUCCESSOR, X95EX, BECAUSE THE REPAIR SERVICE FOR ES95 HAS BEEN TERMINATED, AS NSK HAS ONLY A 7 YEAR REPAIR SERVICE POLICY FOR DISCONTINUED PRODUCTS.

    Description of Event or Problem · 1

    ON (B)(6) 2015, A NSK HANDPIECE, ES-95 (SERIAL NO. (B)(4)) WAS RETURNED FROM A DISTRIBUTOR TO NAKANISHI FOR REPAIR. THERE WAS A NOTE COMING WITH THE HANDPIECE REFERRING TO THE HANDPIECE OVERHEATING. ON (B)(6) 2015, NAKANISHI CONTACTED THE DENTIST FOR MORE INFORMATION. THE INFORMATION NAKANISHI OBTAINED IS: THE EVENT OCCURRED AT THE END OF (B)(6) 2015 (EXACT DATE UNKNOWN). THE DENTIST WAS EXTRACTING A WISDOM TOOTH FROM THE PATIENT'S LOWER LEFT JAW USING THE ES-95. THE PATIENT WAS ANESTHETIZED. THE DENTIST OBSERVED 1 CENTIMETER WHITE SCAR ON THE UPPER JAW AND 2 CENTIMETER WHITE SCAR ON THE TONGUE. NO BURN TREATMENT WAS PROVIDED TO THE PATIENT BECAUSE THE DENTIST DETERMINED THAT THE SCARS DID NOT NEED TO BE TREATED.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    7343 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. ES-95

    Patients

    Seq Age Sex Outcome Treatment
    1 20 YR Other