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

Model Number SGS-E2G

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

Patient Problems Burn(s) (1757); Injury (2348); Patient Problem/Medical Problem (2688); Partial thickness (Second Degree) Burn (2694)

Event Date 09/17/2018

Event Type  Injury  

Manufacturer Narrative

(b)(4).

Event Description

On october 25, 2018, nakanishi received an e-mail from a distributor ((b)(4)) about a handpiece overheating.Details are as follows.The event occurred around (b)(6) 2018 (exact date is unknown).The dentist was performing an extraction of impacted 3rd molars on patient using the sgs-e2g handpiece (serial no.(b)(4)).The patient was under local anesthesia (iv sedation).During the procedure, the dentist noticed sloughing and a burn in the extra intraoral labial mucosa skin of the left lip.The dentist observed that the patient suffered a second degree burn approximately 2cm in size on the lower left lip extra intraoral labial mucosa and inferior skin.The dentist prescribed daily vaseline and vitamin e coverage with a change to silicone gel thereafter, and recommended daily coverage to prevent sun exposure as well.The dentist has conducted follow up visits since the injury and the patient has healed normally with small scarring of the skin directly under lower left lip.The dentist has stated that no further medical attention is required for treatment of this injury.

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 [(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 sgs-e2g device [serial number (b)(4)].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.Nakanishi conducted a visual inspection of the returned device and performed a simple movement test.There were no visible abnormalities, such as cracks or dents, on the outside of the handpiece.Nakanishi then set a test bur in the handpiece and rotated it by hand.Nakanishi observed that the bur did not rotate smoothly.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 (80,000 min-1 for the handpiece), with water spray, and measured the exothermic response.Nakanishi measured the temperature rise of the returned handpiece set at 80,000 min-1 (motor revolution 40,000 min-1).Nakanishi observed an abnormal temperature rise at test points (1) and (2) a few seconds after the start.Temperature measurements 41 seconds after the start are as follows: test point (1): 65.3 degrees c.Test point (2): 84.1 degrees c.Test point (3): 26.6 degrees c.Test point (4): 30.1 degrees c.The rise in temperature was so sudden that the test was concluded 41 seconds into the planned 5 minute evaluation period.Nakanishi cleaned the inside of the handpiece using nakanishi pana spray plus.Nakanishi observed debris being expelled from the head of the handpiece by using a white filter to catch anything that was expelled.After cleaning and lubricating the handpiece as defined in the operation manual, nakanishi measured the temperature of the handpiece.Even after cleaning, nakanishi observed an abnormal rise in temperature as follows: test point (1): 56.9 degrees c.Test point (2): 47.3 degrees c.Test point (3): 37.7 degrees c.Test point (4): 37.9 degrees c.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: there was a great amount of debris on the bearing incorporated in the test point (1).The bearing incorporated in the test point (2) was broken.There was debris and corrosion on the other parts.Nakanishi took photographs of all of the disassembled parts and kept them in the investigation report #: (b)(4).Nakanishi then replaced the broken bearings with new bearings and measured the exothermic situation yet again.There was no abnormal rise in temperature during the 300-second-test period (see below).Nakanishi confirmed that the returned handpiece was operating as expected and within temperature specifications once the broken bearings had been replaced.Test point (1): 35.6 degrees c.Test point (2): 35.2 degrees c.Test point (3): 36.8 degrees c.Test point (4): 39.4 degrees c.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 corroded/broken bearings due to the ingress of undesirable materials into the bearings.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.Nakanishi shipped the updated operation manuals that contain detailed reprocessing methods to nsk america.Nsk america will distribute the updated manuals to the sub-distributors and users including the complainant to convey the detailed reprocessing methods to prevent a recurrence of the handpiece overheating.

• 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: 8081158
• MDR Text Key: 127541171
• Report Number: 9611253-2018-00052
• 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: company representative
• Remedial Action: Recall
• Type of Report: Initial,Followup
• Report Date: 10/25/2018,12/03/2018

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 11/16/2018
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: SGS-E2G
• Device Catalogue Number: H185
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 11/07/2018
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 09/17/2018
• Device Age: 8 YR
• Event Location: Outpatient Treatment Facility
• Date Report to Manufacturer: 10/25/2018
• Date Manufacturer Received: 11/09/2018
• 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: 30 YR
• Patient Weight: 61