BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 12357196 · Received August 23, 2021

    Report

    Report Number
    9611253-2021-00048
    Event Type
    Injury
    Date Received
    August 23, 2021
    Date of Event
    June 9, 2021
    Report Date
    September 15, 2021
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K972569
    Adverse Event
    Yes
    Product Problem
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    SC, US
    Reporter Occupation
    PHYSICIAN ASSISTANT

    Narratives

    Additional Manufacturer Narrative · 0

    UPON RECEIVING THE DEVICE INVOLVED IN THE MDR EVENT FROM THE DISTRIBUTOR, NAKANISHI CONDUCTED A FAILURE ANALYSIS OF THE RETURNED DEVICE, WHICH INCLUDED MEASURING THE OPERATING TEMPERATURE OF THE DEVICE [REPORT NO. C210728-01]. THESE ACTIVITIES ARE DESCRIBED IN MORE DETAIL BELOW. METHODOLOGY USED: NAKANISHI EXAMINED THE DEVICE HISTORY RECORD AND THE REPAIR HISTORY FOR THE SUBJECT Z95L DEVICE [SERIAL NO. (B)(6)]. THERE WERE NO PROBLEMS OBSERVED DURING 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 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 RESPONSE. 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 POINTS (1) AND (2) A FEW SECONDS INTO THE TEST. TEMPERATURE MEASUREMENTS 10 SECONDS AFTER THE START OF THE TEST WERE AS FOLLOWS: TEST POINT (1): 62.0 DEGREES C; TEST POINT (2): 79.3 DEGREES C; TEST POINT (3): 30.2 DEGREES C; TEST POINT (4): 30.7 DEGREES C. THE INCREASE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 10 SECONDS INTO THE PLANNED 5-MINUTE EVALUATION PERIOD. IDENTIFICATION OF THE SPECIFIC FAILURE MODE(S) AND/OR MECHANISM(S) OF THE ASSOCIATED DEVICE COMPONENTS WAS CONDUCTED AS FOLLOWS: NAKANISHI DISASSEMBLED THE HANDPIECE AND PERFORMED A VISUAL INSPECTION OF THE INTERNAL PARTS. NAKANISHI OBSERVED THE FOLLOWING: THE BEARING RETAINER IN THE BALL BEARING ON THE REAR SIDE OF THE CARTRIDGE WAS BROKEN. THE HEADCAP AND INTERNAL GEAR WERE SOILED AND DISCOLORED. NAKANISHI TOOK PHOTOGRAPHS OF ALL THE DISASSEMBLED PARTS AND KEPT THEM IN INVESTIGATION REPORT NO. C210728-01. CONCLUSIONS REACHED BASED ON THE INVESTIGATION AND ANALYSIS RESULTS: NAKANISHI DETERMINED THAT THE CAUSE OF THE OVERHEATING OF THE RETURNED DEVICE WAS ABNORMAL RESISTANCE DURING ROTATION DUE TO THE BROKEN BEARING RETAINER. NAKANISHI CONSIDERS THE POSSIBILITY FROM MANY YEARS OF EXPERIENCE THAT THE CAUSE OF THE BROKEN BEARING RETAINER WAS THE INGRESS OF UNDESIRABLE MATERIALS INTO THE BEARING, LEADING TO ABRASION. A LACK OF MAINTENANCE CAUSED THE ACCUMULATION OF DEBRIS ON THE INTERNAL PARTS, WHICH CAUSED DEBRIS INGRESS INTO THE BEARING DURING ROTATION. THIS CONTRIBUTED TO THE HANDPIECE OVERHEATING. IN ORDER TO PREVENT A RECURRENCE OF THE HANDPIECE OVERHEATING, NAKANISHI TOOK THE FOLLOWING ACTIONS: NAKANISHI REVIEWED THE OPERATION MANUAL AND RECONFIRMED THE CLARITY AND UNDERSTANDABILITY OF THE INSTRUCTIONS. NAKANISHI REPORTED THE ABOVE EVALUATION RESULTS TO NSK AMERICA AND DIRECTED NSK AMERICA TO REMIND THE USER OF THE IMPORTANCE OF MAINTENANCE, AS INSTRUCTED IN THE OPERATION MANUAL.

    Additional Manufacturer Narrative · 1

    THE DENTIST REFUSED TO DISCLOSE THE PATIENT'S WEIGHT. THE SAME ADVERSE EVENT IN THIS REPORT HAS BEEN REPORTED TO THE FDA SEPARATELY BY THE INITIAL IMPORTER, NSK AMERICA CORPORATION, UNDER REPORT NUMBER 1422375-2021-00019.

    Description of Event or Problem · 1

    ON (B)(6) 2021, NAKANISHI BECAME AWARE OF A HANDPIECE OVERHEATING THROUGH A COMPLAINT INPUT INTO THE COMPLAINT DATABASE BY A DISTRIBUTOR (NSK AMERICA). DETAILS ARE AS FOLLOWS: THE EVENT OCCURRED ON (B)(6) 2021. THE DENTIST WAS PERFORMING A FILLING PROCEDURE ON #15 OF THE PATIENT'S TEETH USING THE Z95L HANDPIECE (SERIAL NO. (B)(4)). A DENTAL DAM WAS IN PLACE AND THE PATIENT WAS UNDER LOCAL ANESTHESIA. DURING THE PROCEDURE, THE HANDPIECE OVERHEATED AND THE PATIENT RECEIVED A MINOR BURN INJURY WITH BLISTERING TO THE LEFT SIDE OF THEIR TONGUE. THE PATIENT'S INJURY HAS HEALED NORMALLY WITHOUT ANY NEED FOR ADDITIONAL MEDICAL TREATMENT, AND THERE WERE NO REPORTED COMPLICATIONS.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    1252693 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 60 YR Other