Objective To evaluate the incidence of two-rooted mandibular premolar morphology using full-mouth periapical film series in a Chinese population,with particular emphasis on bilateral incidence,so as to provide a clini...Objective To evaluate the incidence of two-rooted mandibular premolar morphology using full-mouth periapical film series in a Chinese population,with particular emphasis on bilateral incidence,so as to provide a clinical anatomical basis for root canal treatment in mandibular premolars.Methods A total of 2015 patients who underwent dental treatment and had full mouth periapical radiographs at the Peking University School of Stomatology from April 2011 to April 2012 were enrolled in this study.Three experienced dentists reviewed the patients' periapical films and classified the root morphology of mandibular premolars bilaterally.The incidence of unilateral and bilateral double roots were recorded and calculated,including confirmed and suspected bucco-lingual root types.Results In terms of the morphology of two-rooted mandibular first premolars,of the 2015 cases with complete root formation,two-rooted first premolars were detected in 120 cases,with a total number of 159 teeth.According to the number of teeth,the overall incidence of double roots was 4.03%(159/3972).In terms of the morphology of two-rooted mandibular second premolars,of the 2015 cases with complete root formation,two-rooted second premolars were detected in 24 cases,with a total number of 33 teeth.According to the number of teeth,the overall incidence of double roots was 0.85%(33/3880).Conclusions The roots of mandibular premolars display specific morphological patterns.Based on a large sample,we observed and calculated not only the occurrence rate of bucco-lingual and mesio-distal double roots in first and second mandibular premolars,but also the incidence of unilateral or bilateral double roots within the same mandible.These findings could provide useful information on the anatomical structure of mandibular premolars for endodontic,prosthodontic and surgical procedures,and could improve the quality of treatment and reduce complications.展开更多
A new concept of full vacuum manufacturing for Cu-III-IV2 thin-film solar cells has been discussed. Cu-III-IV2 thin-film solar cells manufactured using full in- line reactive sputtering will result in lower cost than ...A new concept of full vacuum manufacturing for Cu-III-IV2 thin-film solar cells has been discussed. Cu-III-IV2 thin-film solar cells manufactured using full in- line reactive sputtering will result in lower cost than that of the conventional method with CdS layer fabricated with chemical bath deposition (CBS) method. Us ing reactive sputtering process with organo- metallic gases, the compositions a nd electronic properties of Cu-III-IV2 thin-film can be fine-tuned and precisely controlled. n-type Cu-III-IV2 film and ZnS suffer layer can also be deposited u sing the in-line sputtering instead of using the CdS layer. The environmental po llution problems arising from using CdS can be eliminated and the ultimate goal of full in-line process development can then be realized. Some preliminary exper imental results on a modal solar cell fabricated by the new technique in the new concept have been presented.展开更多
For the first time, an important ingested flow phenomenon was discovered inexperiments at the film cooling hole exit. The trends of 3-D flow fie1ds and the fullnessfactor, Ci, were discussed in detail over a wide rang...For the first time, an important ingested flow phenomenon was discovered inexperiments at the film cooling hole exit. The trends of 3-D flow fie1ds and the fullnessfactor, Ci, were discussed in detail over a wide range of now parameters and the geometryof fan-shaped holes at this exit plane. It has been confirmed that the main reason of creat-ing longitudinal bound vortices is not the flow iri the hole but the mixing of mainstreamand jet at its exit.展开更多
文摘Objective To evaluate the incidence of two-rooted mandibular premolar morphology using full-mouth periapical film series in a Chinese population,with particular emphasis on bilateral incidence,so as to provide a clinical anatomical basis for root canal treatment in mandibular premolars.Methods A total of 2015 patients who underwent dental treatment and had full mouth periapical radiographs at the Peking University School of Stomatology from April 2011 to April 2012 were enrolled in this study.Three experienced dentists reviewed the patients' periapical films and classified the root morphology of mandibular premolars bilaterally.The incidence of unilateral and bilateral double roots were recorded and calculated,including confirmed and suspected bucco-lingual root types.Results In terms of the morphology of two-rooted mandibular first premolars,of the 2015 cases with complete root formation,two-rooted first premolars were detected in 120 cases,with a total number of 159 teeth.According to the number of teeth,the overall incidence of double roots was 4.03%(159/3972).In terms of the morphology of two-rooted mandibular second premolars,of the 2015 cases with complete root formation,two-rooted second premolars were detected in 24 cases,with a total number of 33 teeth.According to the number of teeth,the overall incidence of double roots was 0.85%(33/3880).Conclusions The roots of mandibular premolars display specific morphological patterns.Based on a large sample,we observed and calculated not only the occurrence rate of bucco-lingual and mesio-distal double roots in first and second mandibular premolars,but also the incidence of unilateral or bilateral double roots within the same mandible.These findings could provide useful information on the anatomical structure of mandibular premolars for endodontic,prosthodontic and surgical procedures,and could improve the quality of treatment and reduce complications.
基金This work was suported by she Scientific Research Foundution for the Returned Overseas Chinese Scholars of State Education Minisiny(No.[2004]176)the Science and Technology Plan of Guangdong Province(No.2003C05005).
文摘A new concept of full vacuum manufacturing for Cu-III-IV2 thin-film solar cells has been discussed. Cu-III-IV2 thin-film solar cells manufactured using full in- line reactive sputtering will result in lower cost than that of the conventional method with CdS layer fabricated with chemical bath deposition (CBS) method. Us ing reactive sputtering process with organo- metallic gases, the compositions a nd electronic properties of Cu-III-IV2 thin-film can be fine-tuned and precisely controlled. n-type Cu-III-IV2 film and ZnS suffer layer can also be deposited u sing the in-line sputtering instead of using the CdS layer. The environmental po llution problems arising from using CdS can be eliminated and the ultimate goal of full in-line process development can then be realized. Some preliminary exper imental results on a modal solar cell fabricated by the new technique in the new concept have been presented.
文摘For the first time, an important ingested flow phenomenon was discovered inexperiments at the film cooling hole exit. The trends of 3-D flow fie1ds and the fullnessfactor, Ci, were discussed in detail over a wide range of now parameters and the geometryof fan-shaped holes at this exit plane. It has been confirmed that the main reason of creat-ing longitudinal bound vortices is not the flow iri the hole but the mixing of mainstreamand jet at its exit.
