Symmetry of root anatomy and root canal morphology in maxillary premolars analyzed using cone-beam computed tomography.

OBJECTIVE: This study aimed to use cone-beam computed tomography (CBCT) to evaluate the root anatomy and canal morphology of maxillary premolars in a Chinese population and determine their degree of bilateral symmetry. DESIGN: 774 CBCT images were retrospectively analyzed, representing 1387 maxillary first premolars and 1403 second premolars. The number of roots and canals were recorded. The morphology of root canal systems was determined according to Vertucci's classification. The symmetry of root and canal anatomies between maxillary contralateral premolars was further evaluated. RESULTS: The most common anatomy of maxillary first and second premolars was one-rooted with two canals (58.0%) and one-rooted with one canal (50.3%), respectively. The typical canal morphology was type IV (42.7%) in maxillary first premolars and type I (50.3%) in maxillary second premolars. One-rooted maxillary premolars exhibited a higher variability in the canal morphology, compared to two-rooted or three-rooted teeth. Maxillary second premolars exhibited greater anatomic symmetry than first premolars. The root and canal numbers showed bilateral symmetry between 80.2% of maxillary first premolar pairs and 81.8% of second premolar pairs. Bilateral symmetry in both number and morphology of roots and canals was observed for 72.3% of maxillary first premolar pairs and 73.2% of second premolar pairs. CONCLUSION: The root anatomy and canal morphology of maxillary premolars in a Chinese population were quite diversified. Maxillary contralateral premolars demonstrated a high degree of symmetry in root and canal anatomies, which enables practitioners to better determine the nature of the root canal system during treatment of opposite homonymous teeth.

[The effect of additional polyphosphazene nanotubes in polyurethane composites on microorganisms adhesion].

PUPPOSE: To investigate Candida albicans and Streptococcus mutans adhesion to 3 polyurethane composites [pure polyurethane (PU), 1% polyphosphazene-containing polyurethane (PZS-1%) and 5% polyphosphazene-containing polyurethane (PZS-5%)]. METHODS: Two kinds of microorganism suspension were incubated with the specimens under certain culture conditions and the roughness of 3 materials were determined before adhesion tests. Microorganism attached to the specimen were then observed under optical microscope, and viable micro-organisms adhered to the specimen were then counted and removed. The data was analyzed with SAS 8.02 softwaree package. RESULTS: PU has the roughest surface followed by PZS-1% and PZS-5%. Most amounts of cell adhesion were observed in PU followed by PZS-1% and least amounts were found in PZS-5%. CONCLLUSIONS: The increase of polyphosphazene nanotubes in polyurethane composites may have an effect on cell adhesion. Surface roughness of the materials may be one of the factors.

[Analysis of the bacterium adhesions on the surface of PFM materials in vitro].

PURPOSE: With the observation of bacterial adhesion on the surface of the PFM and enamel, we analyzed the sequence of these adhesions and offer options for prevention of their occurrence. METHODS: The specimen made of PFM were polished step by step. Then they, along with the enamel were put into the liquid BHI culture medium containing Ua, Pg and An. After 6h, 12h and 24h the adhesive microbial amount in the culture medium was determined by counting formation unit. F test was used to analyze the results with SPSS 6.0 software package. RESULTS: Pg was found neither on the surface of specimen, nor in the liquid BHI culture medium; The value of Ua/An in the groups of PFM was less than that in the groups of enamel within 6 hours. And 12 hours later, the maximal increment of An was seen in the group of PFM. And there was no change in the groups of PFM and enamel during 12 and 24 hours. CONCLUSIONS: Pg was inhibited when these bacteria were cultured together. If we wish to prevent the adhesion of Ua and An, the first 12 hours is the critical period for PFM. Given the result of the analysis, PFM is a good restoration.

[Study of the relationship between patients' personality traits and satisfaction after fixed denture restorations].

PURPOSE: To investigate 98 fixed denture patients' personality traits and the relationship between patients' personality traits and satisfaction with fixed denture restoration. METHODS: 16PF questionnaire and satisfaction questionnaire were used to study 98 fixed denture patients' personality traits and the relationship between personality traits and general satisfaction and specific satisfaction. The data was analyzed with SPSS17.0 software package. RESULTS: There were significant differences between 98 fixed denture patients' personality traits and those of health adult in factor B(reasoning), C(emotional stability), E(dominance), F(liveliness), H(social Boldness), I(sensitivity), L(vigilance), N(privateness), O(apprehension), Q(1)(openness to change) and Q(2)(self-reliance). The regression analysis demonstrated that Q4(tension), G(rule-consciousness), L(vigilance), Q(3)(perfectionism), Q(1)(openness to change), N(privateness), A(warmth) and M(abstractedness)in 16PF were correlated with the general satisfaction of patients after fixed denture restorations (F=20.566' P=0.000, R2=0.649), Q(4), L, Q(3), N and M were negatively correlated with their general satisfaction; however G, Q(1) and A were positively correlated with it. Except the sense of stability and avoid of food impaction,L,C, Q(4) and Q(3) were negatively correlated with their satisfaction on aesthetic effectiveness, while A, G, I and E were positively correlated with it. L, Q(4), N and Q(3) were negatively correlated with their mastication satisfaction, while G and Q(1) were positively correlated with it. O and Q(4) were negatively correlated with their comfortable satisfaction, while C was positively correlated with it. CONCLUSIONS: There is significant difference in personality traits between fixed denture patients and Chinese normal adults. There is close relationship between the personality traits of fixed denture patients and their satisfaction. Meanwhile, the general and specific satisfaction are influenced by different personality traits. It is important to pay more attention to fixed denture patients' personality traits in clinical practice.

[Study of dental alloys in the artificial saliva using an electrochemical impedance spectroscopy].

PURPOSE: With the help of electrochemical impedance spectroscopy (EIS), the purpose of the study was to investigate the corrosion resistance of CoCr alloys ,NiCr alloys and commercially pure Ti(cp Ti) in the artificial saliva(AS). METHODS: With the EIS, a test was made on the three alloys/metals in the AS (See Bode plot and Nyquist plot). And then, an analysis was made on what was known in the test by the software of ZSimpWin, after which the corrosion resistance of the alloys/metals was evaluated against the parameters of equivalent circuit [R(CR)]. RESULTS: In the Nyquist plot, the capacitance arc radius was in the sequence of cp Ti>CoCr>NiCr. From the Bode plot, an one time constant was able to be obtained. That was the capacitor layer. According to the equivalent circuit[R(CR)], there was no significant difference in the capacitor layer of the three alloys/metals. And the sequence of the impedance value of the three alloys/metals was cp Ti>CoCr>NiCr. CONCLUSIONS: The EIS results suggest that the three alloys/metals have a great corrosion resistance with cp Ti having the highest corrosion resistance and that CoCr alloys is better than NiCr alloys in the corrosion resistance. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No.08DZ2271100) and Shanghai Leading Academic Discipline Project(Grant No.T0202).

[A preliminary analysis of the ratio between the upper and lower anterior teeth].

PURPOSE: The widths of anterior teeth are measured and compared to see if there was any specific ratio between the anterior teeth, and to provide some referential data for clinical application in esthetic dentistry. METHODS: Gypsum casts of the maxillary and mandibular arches were made by traditional ways. With the help of dividers and vernier calipers, the widths of anterior teeth were measured. The mean values were gained by doing the measurement several times. SAS6.12 software package was used for grouped t test, paired t test and REG regression. RESULTS: Statistically significant difference(P<0.01) was observed, when comparing the widths of anterior teeth with their ideal golden section(0.618 or 1.618). There were statistically significant differences in the correlation coefficient of anterior teeth(P=0.0001). CONCLUSIONS: The golden section is not found in the anterior teeth. There is some proportional relationships between the upper and lower anterior teeth.

[Analysis of the surface roughness and bacterium adhesions on the surface of restorative materials in vitro].

PURPOSE: To observe the common oral bacteria adhesion on the surface of prosthesis with different roughness, and to analyze the sequence of these adhesions and offer the options for better prosthesis and prevention of their occurrence. METHODS: The specimens made of Co-Cr alloy were polished step by step and divided into six groups. Then, they were put into the liquid BHI culture medium containing Ua, An and Pg. After 24h, the adhesive microbial amount and microbial amount in the culture medium were determined by counting the clonal formation unit. SPSS 6.0 software package was used to analyzed the data. RESULTS: There was significant difference among different groups of surface roughness(P<0.05). Pg was found neither on the surface of specimen , nor in the liquid BHI culture medium. After 24h, there was significant difference among six groups of Ua and An on the prosthesis surface (P<0.05). The total amount of bacterial of each group was different, too. CONCLUSIONS: Pg is inhibited when these bacteria are cultivated together. The surface roughness of the materials positively correlates with the amount of adhesive bacteria. We should choose highly polished Co-Cr alloy to lessen the bacteria adhesion. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No. 08DZ2271100) and Shanghai Leading Academic Discipline Project (Grant No.T0202).

[Adhesion of different bacterium to the surface of restorative materials in vitro].

PURPOSE: Mutans(Ua), porphynomonas(Pg),actinomyces Naeslundii(An) are the 3 bacteria that may cause the clonal formation, gingivitis and periodontitis. The aim of this study was to observe adhesion on the surface of the dental restorative materials and enamel, and to analyze the sequence of these adhesions and offer now the options for the prevention of their occurrence. METHODS: The specimen made of PFM and Co-Cr alloy were polished step by step. Then, along with the enamel.they were put into the liquid BHI culture medium containing Ua, Pg and An. After 6 hours, 12 hours and 24 hours, the adhesive microbial amount in the culture medium were determined by counting formation unit.F test was used to analyze the results with SPSS6.0 software package. RESULTS: Pg was found neither on the surface of specimen, nor in the liquid BHI culture medium; The surface roughness (Ra) of PFM and enamel was bigger than that of Co-Cr alloy, but the number of adherent bacterium on them was smaller; The value of Ua/An was almost the same among the 3 groups within 6 hours. Twelve hours later, the maximal increment of An was seen in the group of Co-Cr alloy and the minimal increment in the group of enamel while 24 hours later, the largest number of Ua/An was seen in the group Co-Cr alloy. There were no change in the groups of PFM and enamel during 12 and 24 hours. CONCLUSIONS: Pg is inhibited when these bacteria are cultivated together. To prevent the adhesion of Ua, the first 6 hours is the critical period for Co-Cr alloy, and the first 12 hours for PFM.To avoid the adhesion of An, the key period is the first 24 hours for Co-Cr alloy and the first 12 hours for PFM. Given the result of the analysis, we prefer PFM to Co-CR alloy. Supported by Research Fund of Science and Technology Commission of Shanghai Municipality (Grant No. 08DZ2271100) and Shanghai Leading Academic Discipline Project (Grant No. T0202).

[Effect of five kinds of pigments on the chromaticity of dental zirconia ceramic].

PURPOSE: All-ceramic dental restorations should match the colour of the natural teeth in order to fulfill aesthetic demands. The goal of this study was to evaluate the colouration of zirconia ceramic by adding five kinds of pigments. The influence of the pigments concentrations on the chromaticity were also analysed. METHODS: Different concentrations of five kinds of pigments were added on zirconia powder, then compacted at 200MPa using cold isostatic pressure, sintered to 1400 degrees centigrade and hold for two hours. The chromaticity of sintered bodies were measured with chroma meter. RESULTS: The colours achieved by the different pigments were presented in the CIELab system. The a* value increased with the added amount of Er(2)O(3), while b* value raised with the increasing amount of CeO(2) and Pr(6)O(11). However, three pigments failed to decrease L* value and the sintered body looked too bright. The sintered bodies were brown when adding Fe(2)O(3) to zirconia. Adding MnO2 could decrease the L* value of sintered bodies significantly, but had little influence on the a* and b* value. CONCLUSION: Five kinds of colorized zirconia ceramic could cover with the chromaticity range of dental ceramic which necessitate further investigation.

[A comparison between the cast-bonded keeper with different dental alloys in the metallographic structure].

PURPOSE: The aim of this study is to investigate the changes of the metallographic structure of the cast-bonded keeper when cast in varied temperatures. METHODS: Three groups were included in this study: the gold alloy group, the Ni-Cr alloy group and Ti group, with the Magdisc 500 keeper as the control group. Each sample that contained a Magdisc 500 keeper was fabricated with the cast-bonded technique. Then, the samples were fabricated into a metallographic sample by polishing, smoothing and cleaning. Each sample was observed under metallographic microscope. RESULTS: There were no significant changes in the crystal size between the keeper in the gold alloy group and that in the control group. In both of the Ni-Cr alloy group and Ti group, the crystal of the keeper became larger, and this was more evident in the latter group. CONCLUSION: The keeper varied in the metallographic structure if cast-bonded with gold alloy, Ni-Cr alloy or Ti metal. The higher the casting temperature, the larger the crystal of the keeper. The results suggest that the change in the gold group is less than that in the Ni-Cr alloy group and Ti metal group.

[Characters of the surface of the cast-bonded keeper: an experimental study].

PURPOSE: This study is aimed to analyze the characters of the surface of the keeper after cast-bonded in varied temperatures. METHODS: Twelve keepers were divided into three groups: the gold alloy group, the Ni-Cr alloy group and the Ti group with four samples in each group. A sample that contained a Magdisc 500 keeper was fabricated with the cast-bonded technique. Then, the surface of the sample was observed under scanning electron microscope (SEM) and its elements were analyzed with the electron probe. RESULTS: The results showed that there was no oxide film on the surface of the keeper in the gold alloy group and the Ni-Cr alloy group, but there was an oxide film on the surface of the keeper in the Ti group. However, remains of the investment materials were found on the surface of the sample of three groups. CONCLUSIONS: The study suggested that the casting temperature affect the characters of the surface of the cast-bonded keeper. Gold alloy or Ni-Cr alloy is of better properties for clinical use.

[The role of the mouthguard in preventing sports-related oral-facial and dental traumas.].

Sports play a significant role in all nations worldwide. More and more people involve in sports so that the incidence of the oral-facial and dental traumas with accidents ascends. The treatment cost is considerable, and the sporters' lives will be influenced by these traumas. This paper examines the status and the reasons of the oral-facial and dental traumas. It reviews not only the principle and the types of the mouthguard but also the evidence of the mouthguard in preventing sports-related traumas. Prevention is thought to be the key element in minimizing traumas that occur in sports, the using of mouthguard is considered essential.

[The influence of cerebral blood flow of volunteers with magnetic attachment measured by transcranial Doppler].

PURPOSE: To investigate the influence of cerebral blood flow of volunteers with magnetic attachment. METHOD: The mean flow velocity of the middle cerebral arteries (MCA) of 24 volunteers with magnetic attachment denture were measured by transcranial Doppler (TCD). All data were analyzed by SPSS10.0. RESULTS: The results showed the mean flow velocity of MCA of 24 volunteers with magnetic attachment was not significantly different from those without magnetic attachment (P>0.05). CONCLUSION: The magnetic attachment had little effect on cerebral blood flow.

[The establishment of 3D-FE model libraries for the elements of FPD].

PURPOSE: To establish the 3D-FE model libraries for the elements of the FPD. METHODS: Based on the 3-D geometric model libraries of the normal stomatognathic system, using the software, such as Powershape,Pro/E and Ansys5.5, the models of abutments,retainers and pontics were created according to the models of natural crowns. The models of connectors were established according to the sutures between the crowns. RESULTS: This study has established the FE model libraries for the elements of the FPD, including the retainers,pontics,and connectors, three kinds of libraries and 82 elements in all. CONCLUSION: The established models have a satisfied geometric configuration; the analysis models can be easily established and edited.