MAUDE Adverse Event Report: NAKANISHI INC. NSK; HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL

Model Number Z95L

Device Problems Overheating of Device (1437); Temperature Problem (3022)

Patient Problems Burn(s) (1757); Injury (2348); Patient Problem/Medical Problem (2688)

Event Date 03/08/2019

Event Type  Injury  

Manufacturer Narrative

The dentist refused to provide the patient's id and weight.Upon receiving the device involved in the mdr event from the dealer, nakanishi conducted a failure analysis of the returned device that included measuring the operating temperature of the device [(b)(4)].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 (b)(4)].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 after the start.Temperature measurements 18 seconds after the start are as follows: test point (1): 61.5 degrees c, test point (2): 84.8 degrees c, test point (3): 40.2 degrees c, test point (4): 31.0 degrees c.The rise in temperature was so sudden that the test was concluded 18 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 that the ball retaining part of the ball bearing in the cartridge was broken.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 overheating of the returned device was due to frictional resistance generated by the broken bearing.Nakanishi considers the possibility from many years of experience that the cause of the ball bearing part being broken was ingress of foreign materials into the ball bearing that interfered with rotation, or abrasion due to long-term use.A lack of maintenance causes the above situation, which 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 and checking of the handpiece prior to use to prevent overheating, as instructed in the operation manual.

Event Description

On march 15, 2019, an nsk z95l handpiece was returned from a dealer to nakanishi for repair.There was a note with the device stating that the device had overheated and burned a patient.Upon receipt of the information, nakanishi made a phone call to the dentist for further information about the event.The details nakanishi obtained from the communication are as follows.The event occurred around (b)(6) 2019 (exact date is unknown).The dentist was performing a core buildup on a premolar of the patient's upper jaw using the handpiece z95l (serial no.(b)(4)).The patient was not under anesthesia.During the procedure, the patient complained about the handpiece feeling too warm.The dentist found a two or three-centimeter whitish burn injury on the patient's buccal mucosa.The dentist applied aphthasol to the burned area.According to the dentist, there were no abnormalities in the device observed prior to use.The dentist determined that no further medical attention was required for the injury.

• Brand Name: NSK
• Type of Device: HANDPIECE, CONTRA- AND RIGHT-ANGLE ATTACHMENT, DENTAL
• Manufacturer (Section D): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer (Section G): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer Contact: kenneth block ; 800 e campbell rd.; suite 202; richardson, TX 75081 ; 9724809554
• MDR Report Key: 8478536
• MDR Text Key: 140772632
• Report Number: 9611253-2019-00020
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• Reporter Country Code: JA
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: foreign,health professional,o
• Reporter Occupation: Non-Healthcare Professional
• Type of Report: Initial
• Report Date: 04/02/2009

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 04/03/2019
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: Z95L
• Device Catalogue Number: C1034
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 03/15/2019
• Date Manufacturer Received: 03/15/2019
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 10/28/2014
• Is the Device Single Use?: No
• Is This a Reprocessed and Reused Single-Use Device?: No
• Type of Device Usage: Reuse
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 80 YR