On (b)(6) 2018, nakanishi received an e-mail from a distributor ((b)(4)) about a problem with an nsk dental product.Details are as follows.The event occurred on (b)(6) 2018.A dentist was extracting an impacted tooth from the patient's mouth using the ti-max x450qd handpiece (serial no.(b)(4)).There were no abnormalities in the device observed prior to use.During the procedure, the headcap and cartridge came out of the handpiece and dropped in the patient's mouth.The dentist immediately retrieved the parts, and the patient was not injured in the event.
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Upon receiving the device involved in the mdr event, nakanishi conducted a failure analysis of the returned device [c181113-01].These activities are described in more detail below.Methodology used: nakanishi examined the device history record and the repair history for the subject ti-max x450qd 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.Nakanishi conducted a visual inspection of the returned device.There were no visible abnormalities on the threads of the headcap and head, such as abrasion or deformation.Nakanishi also confirmed that the headcap was released by hand.Nakanishi observed whether or not a headcap attached to the returned handpiece would loosen by rotating without load and then cutting a melamine plate at the maximum speed (450,000min-1).There was no headcap loosening observed in the evaluation.Conclusions reached based on the investigation and analysis results: although nakanishi could not replicate the reported event, nakanishi considers the possibility, from similar phenomena that nsk has experienced in the past, that the combination of a strong impact on the device with cutting vibration could result in the reported headcap loosening/detachment.Failure to check the headcap tightness before each use as instructed in the operation manual contributes to the headcap loosening/detachment.In order to prevent a recurrence of the headcap loosening/coming off, 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 shanghai and directed nsk shanghai to remind the user of the importance of checking the handpiece before use as instructed in the operation manual.
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