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); Pain (1994); Injury (2348); Patient Problem/Medical Problem (2688)

Event Date 05/31/2018

Event Type  Injury  

Manufacturer Narrative

(b)(4).The dentist refused to provide the patient's weight.

Event Description

On (b)(6) 2018, nakanishi received an e-mail from a distributor ((b)(4)) stating that an nsk dental handpiece had overheated and burned two patients.Therefore, nakanishi is submitting two separate mdrs for the patients.The information nakanishi received from the distributor about the second patient is as follows.The event occurred on (b)(6) 2018.A dentist was performing a crown procedure using the z95l handpiece (serial no.: (b)(4)).The patient was under local anesthesia.During the procedure, the patient complained about pain in the right cheek and the dentist found a white burn to the right buccal mucosa.The patient was prescribed kenalog and analgesics for the pain.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from a distributor, nakanishi conducted a failure analysis of the returned 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 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 bearing retainer (ball retaining part) on the cartridge's rear side was broken.The head gear and upper drive gear were abraded/damaged.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 bearings due to the ingress of undesirable materials into the bearing.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 nsk america and directed nsk america to remind the user of the importance of maintenance, 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: 7710894
• MDR Text Key: 114727474
• Report Number: 9611253-2018-00031
• 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: 06/29/2018,08/07/2018

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 07/23/2018
• 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: 07/09/2018
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 05/31/2018
• Device Age: 4 YR
• Event Location: Outpatient Treatment Facility
• Date Report to Manufacturer: 06/29/2018
• Date Manufacturer Received: 07/18/2018
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 84 YR