MAUDE Adverse Event Report: NAKANISHI INC. NSK; HANDPIECE, ROTARY BONE CUTTING

Model Number X-SG65L

Device Problem Overheating of Device (1437)

Patient Problem Burn(s) (1757)

Event Date 12/10/2020

Event Type  Injury  

Manufacturer Narrative

Nakanishi is trying to obtain further information about the event, including information about the patient from the oem.Upon receiving the device involved in the mdr event, 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: nakanishi examined the device history record and the repair history for the subject x-sg65l device [serial no.(b)(4)].There were no problems observed during the manufacturing or testing noted in the dhr.The repair history showed 2 service records since the device was shipped.The repair details are as follows: (b)(6) 2018: the spindle cap, bearing, pin, slider, and glass rod were replaced.(b)(6) 2019: the chuck, dog clutch, bearing, pin, slider, and glass rod were replaced.With respect to the repairs in the above list, the service records indicate that nakanishi performed all of the necessary operation checks, and confirmed that all of the criteria were met.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 (40,000 min-1 for the handpiece), with water spray, and measured the exothermic response.Nakanishi measured the temperature rise of the returned handpiece set at 40,000 min-1 (motor revolution 40,000 min-1).Nakanishi observed an abnormal temperature rise at test point (1) a few seconds into the test.Temperature measurements 120 seconds after the start of the test were as follows: test point (1): 57.5 degrees c, test point (2): 37.1 degrees c, test point (3): 28.6 degrees c, test point (4): 23.2 degrees c.The increase in temperature was so sudden that the test was concluded 120 seconds into the planned 5-minute evaluation period.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 observed the following phenomena: the inside of the handpiece was discolored due to corrosion and soiled due to abrasive powder and foreign materials.The balls in the bearing at the tip of the handpiece were abraded.B) nakanishi took photographs of all the disassembled parts and kept them in investigation report #(b)(4).Conclusions reached based on the investigation and analysis results: nakanishi determined that the cause of the overheating of the returned device was abnormal resistance during rotation due to the abraded bearing balls.Based on the discoloration due to corrosion nakanishi observed in the visual inspection, nakanishi considers the possibility that the cause of the abraded bearing balls was ingress of foreign materials, such as saline or blood into the bearing.A lack of maintenance resulted in residual saline or blood in the internal parts, which resulted in the ingress of foreign materials into the bearing.This contributed 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 the 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 (b)(6) 2020, nakanishi received a fax message from an oem about a problem with an nsk handpiece overheating.The information nakanishi obtained is as follows: the event occurred on (b)(6) 2020.A dentist was performing a dental procedure using the x-sg65l handpiece (serial no.(b)(4)).During the procedure, the handpiece overheated and burned a patient.

Event Description

On (b)(6) 2021, nakanishi received detailed information from the oem.- the exact date when the event occurred was (b)(6)2020.- the procedure that the dentist was performing at the time of the event was an alveolotomy to remove a third molar tooth.- the patient was under general anesthesia.- during the procedure, the dentist felt heat in the handpiece grip and found an about four-centimeter abrasion on the mucous membrane around the corner of the mouth" - the patient had a follow up visit with a plastic surgeon and a steroid ointment was prescribed for the patient.- the patient is still visiting the plastic surgeon for monitoring.

• Brand Name: NSK
• Type of Device: HANDPIECE, ROTARY BONE CUTTING
• Manufacturer (Section D): NAKANISHI INC.; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• MDR Report Key: 11205929
• MDR Text Key: 230745688
• Report Number: 9611253-2021-00004
• Device Sequence Number: 1
• Product Code: KMW
• Combination Product (y/n): N
• PMA/PMN Number: K970953
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: foreign,other
• Type of Report: Initial,Followup
• Report Date: 02/05/2021

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: X-SG65L
• Device Catalogue Number: H1009
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 12/24/2020
• Initial Date Manufacturer Received: 12/24/2020
• Initial Date FDA Received: 01/20/2021
• Supplement Dates Manufacturer Received: 01/21/2021
• Supplement Dates FDA Received: 02/04/2021
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 28 YR
• Patient Weight: 70