To adapt interns to the stage of clinic dentist as soon as possible and to increase the efficiency of internship,we have applied problem-based learning(PBL) model to the clinic practice of prosthodontics in the students of Grades 2002 and 2003.Such a teaching reform cultivates their interests in autonomous study,increases their confidence,improves the relationship with patients and trains their re-learning ability.

BACKGROUND: BACKGROUND: Studies have found that surface treatment agents containing 10-methacryloyloxy decyl dihydrogen phosphate may be chemical y bonded to the oxide on the surface of zirconia, thereby notably improving the bonding performance of zirconia. OBJECTIVE: To study the effects of Mondbond N and Single bond Universal Adhesive on microtensile bond strength between zirconia and composite resin. METHODS: Sixty pieces of zirconia were randomized into three groups: in group 1, conventional Bis-GMA resin cement was used to bond zironia and composite resin; in group 2, conventional Bis-GMA resin cement was used to bond zironia and composite resin fol owing Mondbond N treatment; in group 3, conventional Bis-GMA resin cement was used to bond zironia and composite resin fol owing surface treatment with Single Bond Universal Adhesive containing 10-methacryloyloxy decyl dihydrogen phosphate. Microtensile bond strength and microstructure on the bonding interface were compared among three groups. RESULTS AND CONCLUSION: (1) Microtensile bond strength was significantly higher in the groups 2, 3 than group 1 (P < 0.05), and there was no difference between the two former groups. (2) Scanning electron microscope observation of the bonding interface: before microtensile test, there were more fissures on the bonding interface of group 1; in the group 2, there were a few fissures on the bonding interface that was relatively even; in the group 3, the bonding interface was smooth and continuous with few fissures. After microtensile, cohesive failure and bonding interface failure were mainly seen in the three groups, but there was no simple interface failure in the groups 2 and 3. These findings indicate that Monobond N and Single Bond Universal Adhesive can both improve the bonding strength of zirconia with composite resin.

OBJECTIVE To prepare vancomycin hydrochloride （VH）-loaded polydopamine （PDA） nanoparticles （VH@PDA nanoparticles）， and study their antimicrobial effect in combination with photothermal therapy. METHODS Using PDA as the carrier， VH was loaded to prepare VH@PDA nanoparticles （PDA nanoparticles were prepared using the same method）. The nanoparticles were characterized with laser particle size analyzer， transmission electron microscope， and UV visible absorption spectrometer； the drug loading capacity and encapsulation efficiency of the nanoparticles were determined. The near-infrared laser irradiation was adopted to determine their photothermal ability. Taking Staphylococcus aureus as the research object， the bactericidal properties of the nanoparticles in combination with photothermal therapy in vitro were clarified through plate colony coating method， live/dead staining analysis， crystal violet staining. Using L929 cells as the research object， the effects of VH@PDA nanoparticles at different mass concentrations （0， 3.125， 6.25， 12.5， 25， 50 and 100 μg/mL） on cell viability were investigated to assess their biocompatibility. RESULTS VH@PDA nanoparticles were successfully loaded with VH， exhibiting uniform particle size （approximately 300 nm）， distinct pore size， and a spherical structure. The drug loading capacity was 11.34%， the encapsulation efficiency was 32.00%， the photothermal conversion efficiency reached 23.55%， and they demonstrated stable photothermal performance. The antibacterial effect results of the combined photothermal therapy demonstrated that without near- infrared laser irradiation， the antibacterial effects of VH， PDA nanoparticles， and VH@PDA nanoparticles were not significant. However， when subjected to near-infrared laser irradiation， VH@PDA nanoparticles exhibited a pronounced antibacterial effect. The results of the cell experiments revealed that after treatment with VH@PDA nanoparticles at various mass concentrations， the cell viability rates remained above 80%. CONCLUSIONS VH@PDA nanoparticles are successfully prepared， which exhibit stable photothermal properties， significant antibacterial effects when combined with photothermal therapy， and good biocompatibility.