The extracted human maxillary central incisors were endodontically treated and restored with glass-fiber post. Then they were randomly divided into four groups and tested. Results showed that groups with ferrule more than 2 mm had higher fracture resistence than others.

Objective: To compare the coronal sealing abilities of different post and cement systems through measuring the value of leakage by using dye method. Methods: Fifty human mandibular premolars with single canal were divided into 6 groups randomly. A group: roots sealed by temporary material, B group: roots restored with fiber post adhered with composite resin cement, C group: roots restored with casting metal post and core adhered with composite resin and zinc phosphate cement, D group: positive control, E group: negative control. After finishing preparation and restoration of roots, microleakage was determined by using dye method. Results: The groups restored with any post and core system produced significantly less microleakage than temporary material sealing group(P<0.05). But no differences were detected between two groups bonded with the composite resin cement (P>0.05). Posts adhered with zinc phosphate luting agent produced more leakage than those with composite resin cement(P<0.05). Conclusion: Luting agent can decrease the coronal microleakage. Composite resin cement provides better sealing ability.

Knee osteoarthritis (KOA) is a common chronic degenerative disease of cartilage, which often occurs in middle-aged and elderly patients. It can cause joint swelling, pain and limited movement. With the aging population gradually increasing in China, the prevalence of KOA is also increasing, imposing burdens on patients, families and society. At present, the clinical treatment methods for KOA mainly include physical exercise therapy, non-steroidal analgesic drug therapy, intra-articular hormone injection therapy and surgical treatment, which can improve symptoms and reduce pain but cannot effectively cure KOA. With the development of medicine, platelet-rich plasma (PRP) therapy, as a new treatment method, has the effects of nerve repair and pain relief, and has become a new choice for the treatment of KOA. This article reviews the application of PRP in KOA, so as to provide a new perspective for clinical treatment of knee osteoarthritis KOA.