FAQ

There are many types of dental abutments, including straight abutment, angled abutment, multi-unit abutment, ball abutment, bar abutment, locator abutment, and temporary abutment. For the dental abutment with the same connection mode within the same registration unit, it is allowed to select only the worst case for test according to the clinical scope of application. For example, for the permanent abutments for fixed restoration, the abutment with the largest angle and the smallest diameter may be selected and the ball abutment for overlay denture is tested separately. It is not necessary to test the mechanical properties (torsional resistance, tightening and fatigue resistance) of each type of abutment.

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Dental impression materials are mainly used to make the female die to record the morphology and relationship of various tissues in oral cavity, or to assist in obtaining clear 3D images of teeth. When evaluating the relative performance, it is necessary to select the typical model which may cover all the conditions of the product under application by combining the characteristics of the product such as composition and polymerization mechanism etc. as the typical sample for test and study; if the full-performance test for product is conducted, it is necessary to consider the characteristics such as product performance and technological process to select the model with the worst performance among the product under application as the typical model.

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When testing is needed in orthopedic implants, performance study, the test sample selected should be the worst condition that can represent the performance of the product under application. The selected worst case's model and specifications may be different for different performance studies, so administrative counterpart should pay attention to whether the selection of test samples is representative when conducting multiple different performance studies.

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For different types of porcelain powder or porcelain block, if the chemical composition of one type of product can cover other types of products, for example, A has 10 components and B has 8, all of which are included in the composition of A, and the content of each component contained in B has no increased risk compared with that in A, then it is allowed to select only A for the biocompatibility test. And it is necessary to provide the supporting data demonstrating the influences of differences in the total contents of components between B and A on the safety of the material.

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The biocompatibility evaluation study of such products should pay attention to the following: the administrative counterpart should provide a biological evaluation report that meets the requirements of GB/T 16886.1 according to the intended clinical use of the products. If biological test are conducted for such products, the relevant evaluation test should be carried out in accordance with the requirement that the product is in direct contact with circulating blood and the cumulative contact duration exceeds 30 days.

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The requirements of GB/T 16886 series standards should be referred to. When performing biological tests, the selected extraction medium should be appropriate to the properties and intended use of the final product and the purpose of the test, taking the chemical properties of the device materials, leachable substances or residual processing aids into account. For cytotoxicity test, since the serum­containing culture medium is the essential media to support cellular growth in the testing system and has the ability to extract both polar and non-polar substances, it should be considered the preferred extraction medium for cytotoxicity test, and under this condition, the serum-containing culture medium, can be the only extraction medium selected. For sensitization test, irritation test or intracutaneous reactivity test, acute systematic toxicity test and other biological tests, extraction using both polar and non-polar extraction medium should be considered. For genetic toxicity tests, as described in GB/T 16886.3, two appropriate extraction solvents should be used as appropriate, one of which should be polar extraction solvent, and The other could be non-polar solvent or liquid which is appropriate to the properties and use of the medical device. Both extraction solvents should be compatible with the testing system.

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Pyrogen refers to the pyrogenic substances that can cause abnormal body temperature rise, including bacterial pyrogens, high-molecular-weight endogenous pyrogens, low-molecular- weight endogenous pyrogens, and chemical pyrogens, etc., which are generally classified as endogenous pyrogens and exogenous pyrogens. The pyrogens of medical devices mainly refer to exogenous pyrogens. Bacterial endotoxin is the most important aspect of pyrogens. Bacterial endotoxin is the lipopolysaccharide component released from the cell wall after the death and autolysis of Gram-negative bacteria. It is generally derived from biological contamination introduced during production. It is a quality control indicator of the product and does not belong to the biological evaluation endpoint. Pyrogens cannot be eliminated by sterilization and pyrogenic substances other than endotoxins can also cause pyrogenic reactions. Therefore, bacterial endotoxins belong to pyrogens, but pyrogens are not necessarily bacterial endotoxins. It is not possible to determine whether there is a potential risk of pyrogenic reaction simply by testing the limit of endotoxins. This risk needs to be reduced through production processes and process control.

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Manufacturers should conduct microbial ingress evaluation on needleless connector products for infusion and submit a test report. Administrative counterpart can refer to YY/T 0923 and YY 0581.2 Appendix C to conduct microbial ingress tests. The test should use the disinfection method declared as the clinically used disinfection method by the enterprise, and the number of uses determined by simulating the maximum number of clinical uses or the number of longest days of uses. The type and number of microorganisms used in the test should be similar to the morphology of microorganisms that may be infected with at the clinically used device access site. These microorganisms selected for the test should be common microorganisms in clinical infusion related infections which Refer to the “Guidelines for the Prevention and Treatment of Intravascular Catheter-related Infections” (published by the Chinese Society of Critical Care Medicine of Chinese Medical Association) to select the microorganisms. It should use least one type of gram­negative bacterium and one type of gram-positive bacterium. It is recommended to use two types of Gram-negative bacteria and two types of Gram-positive bacteria. The administrative counterpart should note in the product IFU the disinfection method, number of uses and other information consistent with that evaluated in the microbial ingress evaluation test.

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The implant is a solid in stud shape or other shapes implanted into alveolar bone to provide fixation and support for restorations such as denture, so as to restore the masticatory function of patients. For the implant products processed using additive manufacturing, the administrative counterpart should perform biocompatibility evaluation in combination with the surface modification treatment, residual powder dissolution and other characteristics of product materials, and with reference to GB/T 16886 series standards. The implant product is a medical device designed for implantation for longer than 30 days Where it is necessary to conduct the biological test, it is required to select the test items with reference to YY/T 0268 series standards, taking the subchronic systemic toxicity test into consideration.

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When a non-active medical device changes, re-evaluation of its safety should be considered under circumstances:

Changes in the raw materials or technical indicators used for the product;

Changes in the product’s formula, production process, primary packaging or sterilization process;

Changes in the final product during the shelf life of the product, such as changes in storage or transportation conditions;

Changes in the intended use of the product;

Evidence present showing that the product can cause adverse events when used in humans.

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According to the provisions of GB/T 16886.12, when the device extract is used for test, polar and non-polar extraction media should be considered for all the biological tests. For the purpose of cytotoxicity test, the serum-containing culture medium is generally used for extraction, which contains both polar and non-polar medium, so one kind of extraction medium may be considered in this case. For the evaluation of subchronic systemic toxicity using the intravenous route, tests are recommended to be performed using polar extraction medium for intravenous administration and non-polar extraction medium for intraperitoneal administration at intervals. For the evaluation of subchronic systemic toxicity using the oral route, two kinds of media for polar and non-polar extracts should also be considered, but polar extracts are mostly adopted at present. The administrative counterpart can comprehensively evaluate and select the extraction medium according to the actual clinical use and application environment of the product.

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