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

Model Number Z95L

Device Problem Overheating of Device (1437)

Patient Problems Burn(s) (1757); Burn, Thermal (2530)

Event Date 10/06/2020

Event Type  Injury  

Event Description

On october 23, 2020, 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) 2020.A dentist was performing a cavity preparation on a patient using the z95l handpiece (serial no.: (b)(4)).The patient was under local anesthesia.During the procedure, the patient received a burn to the right vertical surface of the tongue approximately 1 centimeter in diameter.For treatment, the patient was advised to use saltwater rinses, and was recommended over the counter analgesics for discomfort, or swelling.The dentist has had a follow up visit, and the injury has healed normally with no further need for medical attention, or reported complications.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from the distributor, nakanishi conducted a failure analysis of the returned device that included measuring the operating temperature of the device [c201023-01].These activities are described in more detail below.Methodology used: a) 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.B) nakanishi conducted temperature testing of the returned device in the following manner: b.1) 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.B.2) 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.B.3) nakanishi measured the temperature rise of the returned handpiece set at 200,000 min-1 (motor revolution 40,000 min-1).Nakanishi observed rises in temperature at the testing points as shown below; however, the temperatures were not high enough to cause a burn injury.Temperature measurements 5 minutes into the test were as follows: test point (1): 35.0 degrees c, test point (2): 39.6 degrees c, test point (3): 33.0 degrees c, and test point (4): 33.5 degrees c.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 did not observe any abnormalities.Conclusions reached based on the investigation and analysis results: a) nakanishi could not identify the exact cause of overheating of the returned device because nakanishi was not able to replicate the temperature rise at the time of the event and did not observe any abnormalities in the visual inspection.B) in spite of the fact that nakanishi did not identify the cause, nakanishi took the following actions to be safe.B.1) nakanishi reviewed the operation manual and reconfirmed the clarity and understandability of the instructions.B.2) 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: 10842132
• MDR Text Key: 216316176
• Report Number: 9611253-2020-00045
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• PMA/PMN Number: K182999
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: company representative
• Type of Report: Initial,Followup
• Report Date: 02/10/2021

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: 01/08/2021
• Initial Date Manufacturer Received: 10/23/2020
• Initial Date FDA Received: 11/16/2020
• Supplement Dates Manufacturer Received: 01/21/2021
• Supplement Dates FDA Received: 02/10/2021
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 63 YR
• Patient Weight: 91