[Three-dimensional finite element analysis of three-material endocrown in the restoration of dental defects of mandibular second molars].

PURPOSE: To analyse the effect of restoration and tooth tissue stress distribution under different occlusal preparation thickness, based on three-dimensional finite element modal of the mandibular second molar with root canal therapy and endocrown restorations. METHODS: A mandibular second molar was scanned by cone-beam CT (CBCT) and a three-dimensional finite element model with endocrown restortions was established． Three kinds of endocrown restorations materials with different elastic modulus (glass ceramic, lithium disilicate ceramic and zirconia), and three types of occluscal thickness (1, 2 and 3 mm) were adopted. With a 200 N force loaded vertically and obliquely, the distribution and magnitude of stress in the tooth tissue and endocrown restorations were investigated by three-dimensional finite element analysis． RESULTS: The restoration and tooth tissue maximum stress values were increased firstly and then decreased with the increasing of occlusal thickness; the base material maximum stress values were decreased with the increasing of occlusal thickness; the maximum stress values of tooth tissue and base material were increased with the increasing of restoration material's Young's modulus. Compared to the loading in vertical direction, the maximum stress values were increased with loading in oblique direction. CONCLUSIONS: It's beneficial for tooth tissue to reduce the stress concentration under 2mm thickness. The stress on endocrown will be more concentrated with the increasing of restoration material's Young's modulus.

[Effect of special oral care mode on periodontal health in adolescent orthodontic patients].

PURPOSE: To investigate the effect of special oral care mode on periodontal health of adolescent orthodontic patients. METHODS: From January 2019 to January 2020, one hundred adolescent orthodontic patients who received treatment in our hospital were randomly divided into experimental group and control group according to the principle of completely random number table, with 50 cases in each group. Patients in the control group were given routine oral care, while those in the experimental group were given special oral care; three months later, the periodontal health status of the two groups were compared using SPSS 21.0 software package. RESULTS: There was no significant difference in PLI and GI between the two groups before treatment (P＞0.05). After treatment, PLI and GI in the experimental group were significantly lower than those in the control group(P＜0.01). There was no significance difference in SBI and EDI before treatment between the two groups(P＞0.05). After treatment, SBI and EDI in the experimental group were significantly lower than those in the control group(P＜0.01). There was no significant difference in the scores of periodontal health knowledge before treatment between the two groups(P＞0.05). After treatment, the scores of the two groups were significantly increased(P＜0.01), and the scores of the experimental group were significantly higher than those of the control group (P＜0.01). The patients' satisfaction in the experimental group was significantly higher than that in the control group (90.00% vs 72.00%, P=0.022). CONCLUSIONS: Special oral care mode can significantly improve periodontal health status of adolescent orthodontic patients.

[Analysis of implant placement accuracy using freehand in 68 consecutive patients with 97 implants].

PURPOSE: To analyze the accuracy of implant position in simple cases by freehand. METHODS: Ninety-seven implants of 68 patients from 3 surgeons were selected.After operation,the deviations of implant position at shoulder apex and angle were measured using cone-beam CT(CBCT).The mean of three parameters were calculated with SPSS 22.0 software package, and the differences were analyzed between three surgeons,three operation areas,free-end missing and non free-end missing. RESULTS: The deviations of 97 implants were (0.76±0.57)mm，(1.41±0.90)mm，(4.76±3.68)° at shoulder, apex and angle.The deviation of shoulder apex and angle between three surgeons was significantly different(P<0.05). The deviations between left and right group were not significantly different (P>0.05); the deviations between anterior group and left group were significantly different(P<0.05); the deviations between anterior group and right group were not significantly different(P>0.05). The deviation of shoulder between free-end missing area and non free-end missing area was significantly different(P<0.05),other parameters between the two groups were not significantly different(P>0.05). CONCLUSIONS: The deviation of implant placement between surgical guide and mental guide were similar in simple cases. The experience of surgeon was important during freehand implant placement. The deviations were lower when missing tooth is in anterior area than in posterior area, whereas the same at shoulder in non free-end missing area than in free-end missing area.

[Evaluation of the effect of quality control circle activities on improving the nursing quality of patients with periodontitis].

PURPOSE: To study the effect of quality control circle activity on improving nursing quality of patients with periodontitis. METHODS: One hundred and twenty patients with periodontitis admitted to our hospital from January 2016 to December 2017 were selected and divided into experimental group and control group according to the principle of random control, with 60 patients in each group. Patients in both groups received supragingival scaling, subgingival scaling and related symptomatic treatment, patients in the experimental group conducted nursing under the guidance of quality control circle, while patients in the control group received routine nursing. Satisfaction degree, therapeutic effect and gingival index, probe depth, gingival sulcus bleeding index, plaque index and periodontal attachment levels were recorded and compared between the two groups using SPSS 19.0 software package. RESULTS: After quality control circle to guide nursing, the patients' satisfaction (P=0.003) and the total effective rate of treatment was significantly higher than the control group(P=0.002), the incidence of oral health problems in the experimental group was significantly lower than the control group(P=0.037), PD, GI, SBI, PLI and AL levels in the experimental group were significantly lower than the control group(P=0.000). In addition to the tangible achievements，intangible results, such as quality control circles harmonious degree of nursing, sense of responsibility, communication, and problem solving ability, cohesion and quality control methods are improved distinctly in the experimental group. CONCLUSIONS: Quality control circle activity can improve nursing quality of patients with periodontitis.

[The influence of the age of deep caries on eruption of premolars].

PURPOSE: To evaluate the influence of the time of deep caries on eruption of premolars. METHODS: Children in kindergarten in 2010 was selected to check caries of deciduous molars, then baseline data of population and personal oral health records were established. After data collection, from 2010 to 2017, according to the age of deep caries in deciduous molars, they were divided into 4 groups: four-year, five-year, six-year and seven-year. SPSS 20.0 software package was applied to analyze the results. RESULTS: Between 2010 and 2017, 994 children were investigated, including 528 boys and 466 girls. A total of 1220 maxillary first deciduous molars, 1307 maxillary second deciduous molars ,1244 mandibular first deciduous molars and 1253 mandibular second deciduous molars were investigated. At the age of 4 to 7, when the maxillary and mandibular deciduous molars suffered from deep caries, the replacement time of the premolars was earlier than cases with no caries. The difference was statistically significant (P<0.05); When deciduous molar decay occurred in young children, premolars had a tendency to erupt earlier, especially deciduous molars developed deep caries before 5 years, the difference was statistically significant (P<0.05). CONCLUSIONS: Prevention and intervention of dental caries in children is very important. Especially for children under 5 years old, caries in children's molars need early treatment, in order to decrease the impact on normal replacement of permanent teeth.

[Fabrication and physical properties of porous individual beta-TCP scaffold to reconstruct residual alveolar ridge in dog].

PURPOSE: To fabricate porous individual beta-tricalcium phosphate scaffold and test its properties in dog. METHODS: A model of residual alveolar ridge in mandible of a dog was made and CT scanned after 3 months.The data of CT was transformed to 3-D format by MIMICS 7.0 and was made to resin model by rapid prototype technique.The residual alveolar ridge was reconstructed using silicon rubber, and its impression was made.Porous individual beta-tricalcium phosphate scaffold and 5 samples were fabricated for precision and properties test.Porosity, water absorbing capacity and compressive strength of samples were tested with crystalling phase and pore structure were analysed by XRD and scanning electron microscope. RESULTS: We successfully fabricated a scaffold which fit the resin model well and consisted of beta-TCP. Its porosity was 74%,water absorbing capacity was 48%,compressive strength was 4 MPa,diameter of pore was 150 to 400 microm,connecting diameter was 40 microm. CONCLUSIONS: We can fabricate individual beta-TCP scaffold which fit the model well by combination of traditional method and rapid prototype technique.Supported by Shanghai Leading Academic Discipline Project(Grant No.T0202).

[Advances in research and application of beta-tricalcium phosphate, collagen and beta-tricalcium phosphate/collagen composite in bone tissue engineering].

Bone defects in oral and maxillofacial region was a common problem. To repair the defect, bone grafts including autograft, allograft and artificial bone graft were used in clinic despite of their disadvantages. Nowadays, bone tissue engineering has become a commonly used method to repair bone defect. This paper reviewed the application of beta-TCP, collagen and beta-TCP/collagen composite in bone tissue engineering. It was concluded that beta-TCP/collagen composite was a promising materials in bone tissue engineering.