Objective:To evaluate clinical application of American College of Prosthodontics classification system for complete edentulism;and to analyze the relationship between clinician's rating of general degree of difficulty of each case and patients' rating of denture satisfaction.Methods:One hundred and seven edentulous patients were examined clinically using American College of Prosthodontics(ACP) classification for complete edentulism.The least heights of patients' mandible were measured on panoramic radiographs.Clinician rated general degree of difficulty of each case on visual analogue scale.Six month following denture delivery,patients rated their denture using Mcgill satisfaction Visual Analog Scale(VAS).Multivariate linear regression analysis were conducted to analyze the relationship between clinican's rating of general degree of difficulty and mandibular bone height adjusting for confounding factors such as mandibular ridge form,soft tissue quality etc.Pearson correlation analysis was conducted to analyze the correlation between clinician's rating of case difficulty and patients' rating of denture satisfaction.Results: Advanced residual ridge resorption were found in around 80%(83/105) of all the cases.When the least mandibular bone height were measured on panoramic radiographs,intra-examiner reliability was 0.96,inter-examiner reliability was 0.90.Cases were rated as more difficult when patients showed lower mandibular bone height,unfavoriate ridge form(knife ridge and irregular ridge),mobile soft tissue and longer period of wearing time of their previous dentures.No significant correlation(r

Objective:To evaluate speech outcomes following prosthetic obturation of maxillary defects.Methods:The speech intelligibility(SI)of 21 patients with maxillary defects with and without prostheses was measured postoperatively.In addition,the acoustic characteristics of vowels of 21 individuals were analyzed with and without an obturator in place by sound spectrograph.Results:Following the placement of maxillary obturator prostheses,there was significant improvement in SI.The mean SI score of the patients without and with the prosthesis was(23.2?7.4)% and(81.8?9.4)% respectively(P

Objective: To intimately assess the internal stress distribution in ceramic veneer bonding layer. Methods:Six buccolingual cross section models of the incisor restored with IPS-Empress ceramic veneer were built with the MSC/NASTRAN software. 2D-finite element method was used to analyze the stress distribution regularity of the bonding layer on the models under different functional load. Results: Stress concentration areas of ceramic veneer bonding layer were regularly located on the incisal margin and cervical margin. Under the same condition, incisal load caused highest stresse on the adhesive layer. Following the load shift from incisal to gingival area, the stress was gradually decreased.When the functional load acted on the palate margin of the restoration, the compressive stress on the bonding layer was significantly increased. Different load angle generated stress change in the bonding layer. The shear stress on adhesive layer increased following the horizontal load angle increasing close to the debonding level. Among the different incisal reduction designs there was no significant Von Mises stress variation under the same load condition. However, when the incisal edge was reduced by more than 4 mm, the tensile stresses in the bonding layer greatly increased. Conclusion: Restoration margin should be kept away from the tooth contact area, be exposed to minimal occlusion contact. The functional load should be induced to follow the tooth long axis. Edge to edge occlusion should be avoided. When incisal areas need to be altered, the incisal overlap or butt margin design will not cause any stress problem in the bonding layer. When restoring the incisal defect for more than 4 mm, the bonding agents must be selected carefully.

Objective:To study the antimicrobial effect of polymethylmethacrylate (PMMA) denture base with silver-containing antimicrobial agents of nanometer level against Streptococcus mutans and Candida albicans in vitro. Methods:Minimum inhibitory concentration (MIC) of the silver-containing antimicrobial agent against S. mutans and C. albicans was examined. According to the MIC, 4 concentrations(1,2,5 and 10 mg/ml) of the agent were selected for the preparation of antimicrobial PMMA resin base. Then, the antimicrobial effect of the resin base was examined by in vitro bacteria culture and the most probable number(MPN) counting. Results:The MICs of the agent against S. mutans and C. albicans were 0.1 mg/ml and 1 mg/ml respectively. With the agent at 1, 2, 5 and 10 mg/ml, the inhibition ratios of the base against S.mutans were 67.4%,71.3%,99.0 and 99.5% respectively, that against C. albicans were 25.8%,54.8%,90.3% and 93.0%, respectively. Conclusion:The polymethylmethacrylate resin base with silver-containing antimicrobial agent of nanometer level at 5 mg/ml has ideal antimicrobial activity against S. mutans and C. albicans.

0.05).Significant difference was found between group ④ and ①,②,③ or ⑤(P

Objective: To study the durability of the antimicrobial effect of polymethylmethacrylate (PMMA) denture base containing silver-supported antimicrobial agents of nanometer level against Streptococcus mutans and Candida albicans in vitro. Methods:The antimicrobial PMMA resin bases with the antimicrobial agent STR-1 at concentration of 5 mg/ml were prepared. Then the samples were divided into 4 groups: positive control group, the group immersed in distilled water at 57 ℃ for 14 days, the group irradiated by ultraviolet for 8 hours, and the group irradiated by ultraviolet for 8 hours after immersed in distilled water at 57 ℃ for 14 days. Then the inhibition ratios of the 4 groups against Streptococcus mutans and Candida albicans in vitro were tested. Results:The inhibition ratios of the 4 groups against Streptococcus mutans were 99%, 96%, 98%, and 90% in turn. The inhibition ratios of the 4 groups against Candida albicans were 91%, 82%, 90%, and 80% respectively. Conclusion: The antimicrobial effect of PMMA denture base containing silver-supported antimicrobial agents STR-1 of nanometer level at concentration of 5 mg/ml against Streptococcus mutans and Candida albicans in vitro is durable.

Objective:To study retention force durability of root-type attachments.Methods:Five magnetic attachments(Magfit EX-600),semi-precise stud-type attachments(Bedent) and precise stud-type attachments(Dalbo-classic) were fixed on a thermal-cycling and mechanical-loading machine respectively.The retention force of each attachment was measured at the baseline and after every 1,000 cycles of seating-removing.Results:The average retention force of magnetic attachments was(3.85?0.107) N at the baseline which attenuated for 3.38% after 10,000 cycles;The retention force of semi-precise group was(14.10?0.144) N originally and decreased 90.06% of the original force after 10,000 cycles.The primary force of the precise group was 33.14 N and was adjusted to(11.95?0.082) N as baseline attenuating for 74.56%.Conclusion: The retention force of magnetic attachments is lower than the stud attachments but is stable for 10 years.The retention force of stud-type attachments is larger at the baseline but reduced rapidly.

Objective: To evaluate the influence of retention-form design of resin bonded fixed partial dentures(RBFPDs). Methods: Forty-five metal replicas of posterior metal RBFPDs were divided into 3 groups(n=15):C shape(control group), C shape + axial groove, C shape + pin hole. All the replicas were luted with Panavia F cement and subgroup of 5 specimens were subject to 70 N compressive load cycling for 0 cycles, 240 000 cycles , and 1 200 000 cycles respectively .Half of the cycles was on the central fossa of the pontics and half on the buccal inclined surface of the lingual cusp. Forces for dislodgment of the specimens were applied along the long axis of the abutment at a crosshead speed of 1.0 mm /min. The separation forces were recorded as maxium retention force at the time of dislodgement. Results: Se-paration forces of the C shape group (566.82?71.59 N)0.05). After 1 200 000 cycles, the retention force of the RBFPDs decreased significantly (P

Objective:To investigate the short-term and long-term effects of occlusal rehabilitation on the co-contractration patterns of masticatory muscles of patients with extensive tooth wear.Methods: Twenty-nine patients with severe tooth wear were selected and conducted with occlusal rehabilitation.The surface electromyography(EMG) of masseter(MM),anterior temporalis(TA) and posterior temporalis(TP) at rest position,during clenching and chewing were separately recorded in the stage of pre-treatment,1 month after temporary restoration,1 month after permanent restoration and long-term observation(mean 3.5 years).The Asymmetry Indexes(AI) of bilateral muscles,Activity Indexes of MM/TA,MM/TP and TA/TP were compared in each stage.Results:(1) After occlusal rehabilitation,all the AIs of bilateral MM,TA and TP at rest position,during clenching and chewing showed obvious decrements.(2) In every stage of occlusal rehabilitation,all of the Activity Indexes of MM/TA at rest position,during clenching and chewing had no obvious changes.(3) The Activity Indexes of MM/TP and TA/TP during clenching and chewing significantly increased after occlusal rehabilitation.Conclusion: The treatment of occlusal rehabilitation can significantly improve the bilateral symmetry of masticatory muscles in patients with extensive tooth wear,and also change the coordinated EMG activity of different masticatory muscles.

Objective:To investigate the distribution and content of transforming growth factor-β1 (TGF-β1)and vascular endothelial growth factor (VEGF)in concentrated growth factors (CGF)gel, and to clarify the difference among different layers of CGF.Methods:Venous blood samples were col-lected from 6 healthy volunteers to prepare CGF.The distribution,integrated optical density (IOD)and average optical density (AOD)of TGF-β1 and VEGF in CGF gel and red blood cell (RBC)layer were measured using immunohistochemistry.The concentrations of TGF-β1 and VEGF in the supernatant se-rum at baseline and the CGF releasate after 1 day were evaluated with enzyme-linked immunosorbent as-says.Results:Abundant TGF-β1 and VEGF were concentrated in CGF gel.However,only a little could be found in polykaryocytes and sporadic platelets in RBC layer.Platelets and leukocytes were concentra-ted in between the two layers with high expression of TGF-β1.The concentrations of TGF-β1 and VEGF in the CGF releasate(55 236.78 ±3 686.34),(610.99 ±148.81)ng/L were significantly higher than those in the supernatant serum (20 710.20 ±4 523.14),(335.20 ±51.69 )ng/L (P <0.001 ). Conclusion:CGF contains high quantities of TGF-β1 that can promote new bone formation and tissue healing.We suggest that CGF gel should be used right after being prepared.Supernatant serum and the area between CGF gel and RBC layer could also be mixed with bone substitute materials.