BEUDAMED
    FDA Adverse Event Injury Summary report: N

    NSK

    MDR report key: 6864313 · Received September 14, 2017

    Report

    Report Number
    9611253-2017-00051
    Event Type
    Injury
    Date Received
    September 14, 2017
    Date of Event
    August 25, 2017
    Report Date
    December 11, 2017
    Manufacturer
    NAKANISHI INC.
    Product Code
    EGS
    PMA / PMN Number
    K972569
    Adverse Event
    Yes
    Product Problem
    Yes
    Report Source
    Manufacturer report
    Reporter Location
    JA
    Reporter Occupation
    DENTIST

    Narratives

    Additional Manufacturer Narrative · 1

    NAKANISHI IS STILL SEARCHING FOR MORE DETAILED INFORMATION ABOUT THE EVENT, INCLUDING PATIENT INFORMATION.

    Additional Manufacturer Narrative · 1

    WHEN NAKANISHI VISITED THE DENTIST FOR DETAILED INFORMATION ABOUT THE PATIENT, THE DENTIST REFUSED TO DISCLOSE THE PATIENT IDENTIFIER, AGE AND WEIGHT. 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 OPERATING TEMPERATURE OF THE DEVICE [C170830-11]. 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 NUMBER ABD30601]. THERE WERE NO PROBLEMS OBSERVED DURING THE MANUFACTURING OR TESTING NOTED IN THE DHR. THE REPAIR HISTORY SHOWED 1 SERVICE RECORD (SEPTEMBER 2015) SINCE THE DEVICE WAS SHIPPED. ACCORDING TO THE SERVICE RECORD, AFTER REPAIRING THE HANDPIECE (REPLACEMENT OF CARTRIDGE, DRIVE SHAFT AND DOG CLUTCH), NAKANISHI PERFORMED ALL OF THE NECESSARY OPERATION CHECKS AND CONFIRMED THAT ALL OF THE CRITERIA WERE MET. 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 (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 POINT (1) AND (2) A FEW SECONDS AFTER THE START. TEMPERATURE MEASUREMENTS 6 SECONDS AFTER THE START ARE AS FOLLOWS: TEST POINT (1): 49.4 DEGREES C, TEST POINT (2): 59.6 DEGREES C, TEST POINT (3): 29.8 DEGREES C, TEST POINT (4): 26.1 DEGREES C. THE RISE IN TEMPERATURE WAS SO SUDDEN THAT THE TEST WAS CONCLUDED 6 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 THE BEARING RETAINER (BALL RETAINING PART) ON THE CARTRIDGE SIDE. 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 THE OVERHEATING OF THE RETURNED DEVICE WAS ABNORMAL RESISTANCE DURING ROTATION CAUSED BY THE BROKEN BEARING DUE TO THE INGRESS OF UNDESIRABLE MATERIALS INTO THE BEARING DURING REPEATED USE. A LACK OF MAINTENANCE CAUSES THE ACCUMULATION OF DEBRIS ON THE INSIDE PARTS, WHICH CAUSES 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: 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.

    Description of Event or Problem · 1

    ON AUGUST 28, 2017, NAKANISHI WAS MADE AWARE OF AN NSK HANDPIECE OVERHEATING FROM A CONVERSATION WITH A DENTIST. DETAILS ARE AS FOLLOWS. - THE EVENT OCCURRED ON (B)(6) 2017. - THE DENTIST WAS PERFORMING A DENTAL PROCEDURE USING A Z95L HANDPIECE. - DURING THE PROCEDURE, THE HANDPIECE OVERHEATED AND BURNED A PATIENT. - ACCORDING TO THE DENTIST, ONE OF THE Z95L HANDPIECES (SERIAL (B)(4)) CAUSED THE EVENT, BUT THE DENTIST CANNOT IDENTIFY WHICH DEVICES ACTUALLY DID. NAKANISHI IS SUBMITTING TWO SEPARATE MDRS FOR THIS EVENT. THIS MDR IS REGARDING THE HANDPIECE WITH THE SERIAL (B)(4).

    Description of Event or Problem · 1

    ON SEPTEMBER 28, 2017, NAKANISHI VISITED THE DENTIST AND OBTAINED DETAILED INFORMATION ON THE EVENT. THE EVENT OCCURRED ON (B)(6) 2017, NOT (B)(6) 2017. THE PROCEDURE THE DENTIST WAS PERFORMING AT THE TIME OF THE EVENT WAS REMOVAL OF A CROWN. THE PATIENT WAS UNDER LOCAL ANESTHESIA. DURING THE PROCEDURE, THE PATIENT COMPLAINED ABOUT THE HANDPIECE OVERHEATING. THE DENTIST WAS MADE AWARE OF A BURN INJURY ABOUT THE SIZE OF THE TIP OF THE PINKY FINGER ON THE PATIENT'S LIP. THE DENTIST DETERMINED THAT NO MEDICAL INTERVENTION WAS NECESSARY FOR THE BURN.

    Devices

    Seq Brand Generic Product Code Manufacturer Model Lot UDI-DI
    644410 NSK HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL EGS NAKANISHI INC. Z95L

    Patients

    Seq Age Sex Outcome Treatment
    1 Other