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

Model Number Z85L

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 03/13/2018

Event Type  Injury  

Manufacturer Narrative

(b)(4).When (b)(4) tried to obtain information about the event, the dentist refused to provide the information about the patient weight, ethnicity and race.

Event Description

On april 10, 2018, nakanishi received an e-mail from a distributor ((b)(4)) about a handpiece overheating.Details are as follows.On march 26, 2018, (b)(4) was made aware of the event by incoming service repair paperwork.The event occurred on (b)(6) 2018.A dentist was performing a dental procedure using the z85l handpiece (serial no.: (b)(4)).During the procedure, the handpiece overheated and burned a patient.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from a 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 z85l device [serial number (b)(4)].There were no problems observed during the manufacturing or testing noted in the dhr.There were no records indicating nakanishi (the manufacturer) repaired the device since the device was shipped.Nakanishi received the repair records from (b)(4), which included the detailed information about the repair (b)(4) carried out, along with the repair test results that indicate the repaired device passed every test item.Nakanishi kept the test results in a file.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 a 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.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 point (1) and (2) a few seconds after the start.Temperature measurements 21 seconds after the start are as follows: - test point (1): 66.1 degrees c; - test point (2): 89.4 degrees c; - test point (3): 30.2 degrees c; - test point (4): 22.2 degrees c.The rise in temperature was so sudden that the test was concluded 21 seconds into the planned 5 minute evaluation period.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 that the bearing retainer (ball retaining part) on the cartridge rear side was broken.Nakanishi took photographs of all of the disassembled parts and kept them in the investigation report #(b)(4).Nakanishi then replaced the cartridge (including the broken bearing) with a new cartridge and measured the exothermic situation yet again.There was no abnormal rise in temperature during the 300-second-test period.Nakanishi confirmed that the returned handpiece was operating as expected and within temperature specifications once the damaged bearing had been replaced.- test point (1): 28.7 degrees c; - test point (2): 28.5 degrees c; - test point (3): 25.1 degrees c; - test point (4): 25.2 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 broken bearing due to the ingress of undesirable materials into the bearing.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.In order to prevent a recurrence of the handpiece overheating, nakanishi took the following actions: nakanishi reviewed the operation manual and reconfirmed clarity and understandability of the instructions.Nakanishi reported the above evaluation results to nsk america and directed nsk america 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. REGISTRATION NUMBER : 9611253; mfr rpt# : 9611253-2018-00017; 700 shimohinata; kanuma-shi, tochigi-ken 322-8 666; JA 322-8666
• Manufacturer Contact: kenneth block ; 800 e campbell rd.; suite 202; richardson, TX 75081 ; 9724809554
• MDR Report Key: 7467700
• MDR Text Key: 106702040
• Report Number: 9611253-2018-00017
• 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
• Reporter Occupation: Dentist
• Type of Report: Initial,Followup
• Report Date: 04/10/2018,05/24/2018

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 04/27/2018
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Dentist
• Device Model Number: Z85L
• Device Catalogue Number: C1062
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 04/17/2018
• Is the Reporter a Health Professional?: Yes
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 03/26/2018
• Device Age: 6 YR
• Event Location: Outpatient Treatment Facility
• Date Report to Manufacturer: 04/10/2018
• Date Manufacturer Received: 04/27/2018
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 04/27/2012
• 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: 20 YR