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

Model Number X85L

Device Problem Overheating of Device (1437)

Patient Problem Burn(s) (1757)

Event Date 10/15/2023

Event Type  Injury  

Event Description

On december 12, 2023, 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) 2023.- the dentist was performing a crown preparation procedure on a patient using the x85l handpiece (serial no.(b)(6)).- during the procedure, the handpiece head and headcap overheated, and the patient received a minor burn to the inside of their cheek.- no medical treatment was necessary for the injury at the time of the event.- the patient has had a follow-up visit with the dentist and the injury was reported to have healed normally without need for any additional medical treatment.

Manufacturer Narrative

The same adverse event in this report has been reported to the fda separately by the distributor, nsk america corporation, under report number 1422375-2023-00027.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from the distributor, nakanishi conducted a failure analysis of the returned device, which included measuring the operating temperature of the device [report no.(b)(4)].These activities are described in more detail below.Methodology used: a) nakanishi examined the device history record and the repair history for the subject x85l device [dbd40080].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 40,000min-1, which is the maximum rpm for the motor that drives the handpiece (200,000min-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 200,000min-1 (motor revolution 40,000min-1).Nakanishi observed an abnormal temperature rise at the test point (2) about 10 seconds into the test.Temperature measurements about 30 seconds after the start of the test were as follows: - test point (1): 50.2 degrees c.- test point (2): 68.6 degrees c.- test point (3): 29.8 degrees c.- test point (4): 29.5 degrees c.The increase in temperature was so sudden that the test was concluded about 30 seconds into the planned 5-mimute evaluation period.Identification of the specific failure mode(s) and/or mechanism(s) of the associated device components was conducted as follows: a) nakanishi disassembled the handpiece and performed a visual inspection of the internal parts.Nakanishi observed the following: - the bearing retainer in the ball bearing on the rear side of the cartridge was broken.- the internal parts were soiled, abraded, and discolored.B) nakanishi took photographs of all the disassembled parts and kept them in the investigation report no.C231212-02.Conclusions reached based on the investigation and analysis results: a) nakanishi identified that the cause of the handpiece overheating was abnormal resistance during rotation due to the broken bearing retainer.Nakanishi considers the possibility from many years of experience that the cause of the broken bearing retainer was the ingress of undesirable materials into the bearing, leading to abrasion.B) a lack of maintenance caused the accumulation of debris on the internal parts, which caused debris ingress into the bearing during rotation.This contributed to the handpiece overheating.C) in order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: c.1) nakanishi reviewed the operation manual and reconfirmed the clarity and understandability of the instructions.C.2) nakanishi reported the above evaluation results to the distributor and directed the distributor 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
• Manufacturer (Section G): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer Contact: sean kaufman ; 1800 global parkway; hoffman estates, IL 60192 ; 2245128921
• MDR Report Key: 18315696
• MDR Text Key: 330328933
• Report Number: 9611253-2023-00069
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• Reporter Country Code: US
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: Company Representative,Distributor
• Reporter Occupation: Dentist
• Type of Report: Initial,Followup
• Report Date: 02/28/2024

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 12/12/2023
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: X85L
• Device Catalogue Number: C604
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Is the Reporter a Health Professional?: Yes
• Date Manufacturer Received: 02/06/2024
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 04/16/2023
• 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: 71 YR
• Patient Sex: Male
• Patient Weight: 190 KG
• Patient Ethnicity: Non Hispanic
• Patient Race: White