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

Model Number X85L

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

Patient Problems Burn(s) (1757); Injury (2348); Burn, Thermal (2530); Patient Problem/Medical Problem (2688)

Event Date 12/06/2018

Event Type  Injury  

Manufacturer Narrative

The dentist refused to provide the patient's id and weight.

Event Description

On december 20, 2018, nakanishi received a phone call from a dealer about an nsk handpiece overheating.Upon receipt of the information, nakanishi visited the dental office to hear details.According to the dentist, one of three handpieces, an x85l (serial no.(b)(4)), a z84l (serial no.(b)(4)) or a z84l (serial no.(b)(4)) overheated and caused the event described below.The dentist could not identify which of the three devices actually overheated.The details of the event are: the event occurred on (b)(6) 2018.The dentist was performing a fiber post preparation of the patient's upper right tooth #7 using the one of the above handpieces.The patient was under anesthesia.During the procedure, the dentist found a round blister about 1 centimeter in diameter on the right corner of the patient's mouth.The dentist applied an ointment to the blister.The dentist has followed up with the patient and observed that the burn was healing normally.According to the dentist, there were no abnormalities in the device observed prior to use.Nakanishi is submitting three separate mdrs for this event based on the information from the dentist.This mdr is regarding the x85l handpiece (serial no.(b)(4)).

Manufacturer Narrative

Upon receiving the device involved in the mdr event, 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: a) nakanishi examined the device history record and the repair history for the subject x85l 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.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 an abnormal temperature rise at test points (1) and (2) a few seconds after the start.Temperature measurements about 30 seconds after the start are as follows: test point (1): 60.2 degrees c, test point (2): 63.3 degrees c, test point (3): 29.7 degrees c, test point (4): 25.0 degrees c.Identification of the specific failure mode(s) and/or mechanism(s) and the associated device components involved: a) nakanishi disassembled the handpiece and performed a visual inspection of the inside parts.Nakanishi observed that the bearing retainer (ball retaining plastic part) on the cartridge rear side was broken.B) nakanishi took photographs of all of the disassembled parts and kept them in the investigation report #(b)(4).Conclusions reached based on the investigation and analysis results: 1) nakanishi identified that the cause of overheating of the returned device was due to frictional resistance generated by contact between the ball bearing part and the outer race (bearing outer metal part), which was generated by centrifugal action during rotation due to the broken ball bearing part.2) nakanishi considers the possibility from many years of experience that the cause of the ball bearing part being broken was abrasion resulting from the prolonged use, as well as the ingress of foreign materials into the ball bearing that interfered with rotation, which led to the breakage of the ball bearing part.3) a lack of maintenance causes the above situation, which contributes to the handpiece overheating.4) in order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: 4.1) nakanishi reviewed the operation manual and reconfirmed clarity and understandability of the instructions.4.2) 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, 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: 8241934
• MDR Text Key: 132913983
• Report Number: 9611253-2019-00002
• Device Sequence Number: 1
• Product Code: EGS
• Combination Product (y/n): N
• PMA/PMN Number: K972569
• Number of Events Reported: 1
• Summary Report (Y/N): N
• Report Source: Manufacturer
• Source Type: foreign,health professional,o
• Type of Report: Initial,Followup
• Report Date: 02/05/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 01/11/2019
• 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
• Date Returned to Manufacturer: 12/25/2018
• Date Manufacturer Received: 01/09/2019
• Is This a Reprocessed and Reused Single-Use Device?: No
• Patient Sequence Number: 1
• Patient Outcome(s): Other
• Patient Age: 50 YR