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

Model Number Z95L

Device Problems Overheating of Device (1437); Temperature Problem (3022); Noise, Audible (3273)

Patient Problems Burn(s) (1757); Injury (2348); Patient Problem/Medical Problem (2688); Full thickness (Third Degree) Burn (2696)

Event Date 01/22/2019

Event Type  Injury  

Manufacturer Narrative

(b)(4).According to the distributor, the dentist refused to provide the patient's weight.

Event Description

On february 20, 2019, nakanishi received an e-mail from a distributor ((b)(4)) about a handpiece overheating.Details are as follows.The event occurred on (b)(6) 2019.The dentist was performing a crown preparation on a patient using the z95l handpiece (serial no.(b)(4)).The patient was under local anesthesia.During the procedure, the device suddenly started to make a grating/grinding noise and then, the dentist felt a "chattering" sensation coming from the handpiece.The dentist observed a 3rd degree oval shaped burn, approximately 1.5cm in size on the patient's lower lip and skin right below the lip.The dentist immediately discontinued use of the handpiece.The dentist applied an ointment to the burn injury and a cold compress to the affected area, and advised the patient to take an over-the-counter anti-inflammatory medication.The injury was found to be healing normally upon follow-up visit with the patient.The dentist determined that no further medical attention was required for the injury.

Manufacturer Narrative

Upon receiving the device involved in the mdr event from a distributor, (b)(4) conducted a failure analysis of the returned device [c190221-10].These activities are described in more detail below.Methodology used: (b)(4) examined the device history record and the repair history for the subject z95l device [serial number (b))(4)].There were no problems observed during the manufacturing or testing noted in the dhr.There were also no repair history records since the device was shipped.(b)(4) set a test bur in the handpiece, connected the handpiece to the motor and tried to rotate the motor.However, the handpiece was locked and the motor did not rotate at all.Therefore, (b)(4) was not able to conduct temperature testing of the device.Identification of the specific failure mode(s) and/or mechanism(s) and the associated device components involved: (b)(4) disassembled the handpiece and performed a visual inspection of the inside parts.(b)(4) observed the following phenomena: - the bearing retainer (ball retaining part) on the cartridge rear side was broken.- the clutch shaft was stuck with the body without being removed from the body.- the head gear and upper drive gear were broken/damaged.- the dog clutch was corroded.- there was debris (abrasive powder, pieces of broken bearing) on the inside parts.(b)(4) took photographs of all of the disassembled parts and kept them in the investigation report #c190221-10.Conclusions reached based on the investigation and analysis results: (b)(4) identified that the cause of the overheating of the returned device was abnormal resistance during rotation caused by the broken bearings due to the ingress of undesirable materials into the bearing.A lack of maintenance causes abrasion of the inside parts, which generates debris such as abrasive powder, pieces of broken bearing, resulting in debris ingress into the bearing during rotation.In order to prevent a recurrence of the handpiece overheating, (b)(4) took the following actions: (b)(4) reviewed the operation manual and reconfirmed clarity and understandability of the instructions.(b)(4) reported the above evaluation results to (b)(4) america and directed (b)(4) 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# : 9611253-2019-00014; 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: 8430211
• MDR Text Key: 139167110
• Report Number: 9611253-2019-00014
• 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: 02/20/2019,04/15/2019

1 Device was Involved in the Event

1 Patient was Involved in the Event

• Date FDA Received: 03/18/2019
• Is this an Adverse Event Report?: Yes
• Is this a Product Problem Report?: Yes
• Device Operator: Health Professional
• Device Model Number: Z95L
• Device Catalogue Number: C1034
• Was Device Available for Evaluation?: Device Returned to Manufacturer
• Date Returned to Manufacturer: 03/07/2019
• Is the Reporter a Health Professional?: Yes
• Was the Report Sent to FDA?: No
• Distributor Facility Aware Date: 02/04/2019
• Device Age: 5 YR
• Event Location: Outpatient Treatment Facility
• Date Report to Manufacturer: 02/20/2019
• Date Manufacturer Received: 03/21/2019
• Was Device Evaluated by Manufacturer?: Yes
• Date Device Manufactured: 11/25/2014
• 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: 56 YR