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

Model Number SGS-E

Device Problems Nonstandard Device (1420); Overheating of Device (1437); Temperature Problem (3022)

Patient Problems Burn(s) (1757); Blister (4537)

Event Date 03/17/2021

Event Type  Injury  

Manufacturer Narrative

The dentist refused to disclose the patient's weight.

Event Description

On april 21, 2021, nakanishi received an e-mail from a hospital about a problem with an nsk handpiece overheating.The information nakanishi obtained is as follows: the event occurred on (b)(6) 2021.The dentist was performing a sagittal split ramus osteotomy on a patient with mandibular hypoplasia using the sgs-e handpiece (serial no.(b)(4)).The patient was under general anesthesia.During the procedure, the dentist became aware of heat in the device and observed an approximately 0.8 mm redness and blister on the right corner of the patient's mouth.A dermatologist in the same hospital prescribed an ointment for the patient and determined that no medical intervention was required for the injury.

Manufacturer Narrative

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: a) nakanishi examined the device history record and the repair history for the subject sgs-e device [serial no.(b)(6)].There were no problems observed during the manufacturing or testing noted in the dhr.The repair history showed 5 service records since the device was shipped.The repair details are as follows: - (b)(6) 2013: the spindle sub assembly, and bearings were replaced.- (b)(6) 2015: the bur pusher retainer, bearings, and nose body were replaced.- (b)(6) 2016: the bur pusher retainer, spindle sub assembly, bearings, slider, bur pusher pipe were replaced.- (b)(6) 2018: the bur pusher retainer, dog clutch, spindle sub assembly, bearings, nose body, and slider 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.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 (40,000 min-1 for the handpiece), with no water spray, and measured the exothermic response.B.3) 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 points (1) and (2) a few seconds into the test.Temperature measurements about 200 seconds after the start of the test were as follows: - test point (1): 98.5 degrees c.- test point (2): 67.9 degrees c.- test point (3): 38.4 degrees c.- test point (4): 32.4 degrees c.The increase in temperature was so sudden that the test was concluded about 200 seconds into the planned 5-minute evaluation period.During the testing, nakanishi also observed abnormal sounds and vibration.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 ball bearing in the device was broken.- the ball bearing and spindle were soiled and discolored.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: a) nakanishi determined that the cause of the overheating of the returned device was abnormal resistance during rotation due to the broken ball bearing.Nakanishi considers the possibility from many years of experience that the cause of the broken ball bearing was the ingress of undesirable materials into the ball bearing, leading to abrasion.B) a lack of maintenance caused the accumulation of debris on the internal parts, which caused debris ingress into the ball 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 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.

• 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: 11795829
• MDR Text Key: 249667586
• Report Number: 9611253-2021-00031
• Device Sequence Number: 1
• Product Code: KMW
• Combination Product (y/n): N
• PMA/PMN Number: K171155
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: foreign,user facility
• Remedial Action: Recall
• Type of Report: Initial,Followup
• Report Date: 06/18/2021

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 05/10/2021
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: SGS-E
• Device Catalogue Number: H084
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 05/17/2021
• Date Manufacturer Received: 05/24/2021
• Is This a Reprocessed and Reused Single-Use Device?: No
• Removal/Correction Number: 9611253-060818-001-R
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 18 YR