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

Model Number Z95L

Device Problems Overheating of Device (1437); Loss of Power (1475); Temperature Problem (3022)

Patient Problems Burn(s) (1757); Injury (2348); Burn, Thermal (2530); Patient Problem/Medical Problem (2688)

Event Date 03/18/2019

Event Type  Injury  

Manufacturer Narrative

(b)(4).According to the distributor, the dentist refused to provide the patient's weight.

Event Description

On march 30, 2019, nakanishi received an e-mail from a distributor ((b)(4)) about a handpiece overheating.Details are as follows: the event occurred on (b)(6) 2019.The dentist was performing a procedure on a tooth of the patient's lower jaw using the z95l handpiece (serial no.(b)(4)).The patient was not under anesthesia and the patient's mouth was covered with a rubber dam.The bur was not engaging until the motor was activated, and then the bur began rotating for 7-9 seconds before the handpiece stalled.The dentist felt the handpiece overheating and discontinued use of the device.The dentist completed the procedure using a different handpiece.When the procedure was completed and the rubber dam was removed from the patient's mouth, the dentist found a burn injury to the left lateral area of the patient's tongue.No burn treatment was administered at the time of the injury.When the patient returned to the office for a follow-up, the dentist determined the injury was healing normally.The dentist continues to monitor the progression of healing.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from a distributor, nakanishi conducted a failure analysis of the returned device [c190320-20].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 the manufacturing or testing noted in the dhr.There were also no repair history records since the device was shipped.Nakanishi set a test bur in the handpiece, connected the handpiece to the motor and tried to rotate the motor.However, the handpiece was locked and the motor did not rotate at all.Therefore, nakanishi was not able to conduct temperature testing of the device.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: the headcap remained depressed in the handpiece (sliding failure).The headcap was deformed.There were signs of contact between the surface of the pusher of the cartridge and inside the headcap which would have been caused by the headcap being pressed.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 could not replicate the temperature rise at the time of the event, however based on abnormality in the inside parts observed in the visual inspection, as well as many years of experience, nakanishi identified that the cause of the overheating of the returned device was friction heat generated by contact between the headcap and the cartridge, which was caused by the headcap remaining depressed during rotation (sliding failure).Nakanishi also considered the deformed headcap due to impact/drop as a cause of sliding failure.Misuse by the user leads to the contact between the headcap and the cartridge due to sliding failure, which contributes to the reported 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 nsk america and directed nsk america to remind the user of the importance of using the device, as instructed in the operation manual.

• 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
• MDR Report Key: 8500501
• MDR Text Key: 141581639
• Report Number: 9611253-2019-00023
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: company representative
• Type of Report: Initial,Followup
• Report Date: 03/30/2019,05/17/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• 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: 04/11/2019
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 03/18/2019
• Device Age: 2 YR
• Event Location: Outpatient Treatment Facility
• Date Report to Manufacturer: 03/30/2019
• Initial Date Manufacturer Received: 03/30/2019
• Initial Date FDA Received: 04/10/2019
• Supplement Dates Manufacturer Received: 04/22/2019
• Supplement Dates FDA Received: 05/17/2019
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 59 YR