[Study of masking ability of laminate veneers for discolored teeth].

OBJECTIVE: To select the most effective method among different masking treatments, such as different thickness and transparence, tissue surface's opaque coating, and opaque resin cement to restore discolored teeth esthetically by porcelain veneer. METHODS: Four extracted intact maxillary central incisors were prepared for porcelain veneer restoration and each three heat pressed porcelain veneers from three thicknesses (0.8 mm, 1.0 mm, 1.2 mm) and two transparency(high transparence, HT and low transparence, LT))in Vita shade A2 were fabricated for each tooth, in total of 72 pieces. The surfaces of three prepared teeth were then painted to mimic situations of severe dental fluorosis, severe tetracycline teeth, and necrotic teeth. Each of the veneers was temporarily cemented to the corresponding tooth surface using try-in cements with three different colors (transparent, opaque, and yellow), then used the shade guide (3D master) and electronic colorimeter (easy shade) to record the shade of each porcelain veneer through hue, lightness, and chroma reading. After that, high-transparence porcelain veneers in thickness of 0.8 mm was fused with a layer of opaque porcelain in tissue surface, and were shade matched again after cementation. Statistic treatments were performed to analyze the difference in each masking method. RESULTS: For each 0.2 mm increase in the veneer thickness of porcelain, the average lightness was reduced by 1 unit, while the chroma was not changed which was independent of the type of the resin cements. When the thickness of the porcelain veneer was decreased to 0.8 mm, the opacity effect was not remarkable even if a low-transparence porcelain veneer was used. Transparent and yellow resin cements had poor opaque performance, while opaque resin cement could reduce the lightness by 2 units and the chroma was also reduced. The opaque layer of the tissue surface could be applied uniformly, and the lightness and chroma could be reduced to Vita 2M1 to 2M1.5 levels regardless of the color of resin cements, which suggested a stable opacity effect for different discolored teeth in this study. CONCLUSION: For porcelain veneer restoration of discolored teeth, thickened veneers are the most effective means to display a natural transmittance and color. Tissue surface's opacity coatings and opaque resin cements can also be used to reduce grayscale and increase lightness.

[Preparation of aspirin sustained-release microsphere and its in vitro releasing property].

OBJECTIVE: It has been proven that acetylsalicylic acid (aspirin), as a kind of classical non-steroidal anti-inflammatory drug, not only has the effect of anti-inflammatory, but also has the function of immunity regulation and mineralization. However, it needs further investigation to study how to delay release of aspirin for a long time and enable to promote bone regeneration. Herein, we demonstrated that the longterm delayed release pattern of aspirin through the construction of microsphere scaffolds is promising to achieve the excellent bone regeneration. METHODS: Here we synthesized three kinds of scaffolds as follows: (1) aspirin loaded calcium silicate (CaSiO3) microsphere (CaSiO3-aspirin) via simple immersion; (2) aspirin loaded polylactic-co-glycolic acid (PLGA) microsphere (PLGA-aspirin) via oil/water (O/W) emulsion; (3) aspirin loaded PLGA-CaSiO3 scaffold (PLGA-CaSiO3-aspirin) via O/W emulsion, optimal morphology and structure of PLGA-CaSiO3-aspirin scaffold was acquired through modulating the ratio between PLGA and CaSiO3. Furthermore, spectrophotometer was used to monitor the concentration of the extract of the three scaffolds for different releasing time, including 1, 2, 4, 6, 9, 13, 17, 21, 24, 30, 36, and 45 days, aspirin loading efficiency and its accumulation releasing curves were both achieved according to the concentration of aspirin. Their sustained release effects of aspirin were evaluated eventually. RESULTS: Environmental scanning electron microscope (ESEM) results showed that the surface structure of the three kinds of scaffolds were smooth and had uniform size distribution. In addition, a small amount of PLGA-aspirin microspheres occurred to aggregation, while a small amount of CaSiO3-aspirin microspheres were broken. Moreover, the PLGA-aspirin microspheres in the PLGA-CaSiO3-aspirin scaffolds were uniformly adhered to the surface of CaSiO3 microspheres. The aspirin loadings of CaSiO3-aspirin, PLGA-aspirin, and PLGA-CaSiO3-aspirin were (1.06±0.04)%, (7.05±0.06)%, and (6.75±0.18)%, respectively. In addition, their corresponding time for releasing 95% of aspirin was 3, 24, and 36 days, respectively. The releasing time of PLGA-CaSiO3-aspirin was longer than that of the others and the releasing rate was more stable. CONCLUSION: The microsphere scaffold of PLGA-CaSiO3-aspirin composites has excellent delayedrelease effect on aspirin, which is promising for using as osteogenic materials.

[Wear intensity and surface roughness of microhybrid composite and ceramic occlusal veneers on premolars after the thermocycling and cyclic mechanical loading tests].

OBJECTIVE: To evaluate the wear intensity and surface roughness of occlusal veneers on premolars made of microhybrid composite resin or two kinds of ceramics in vitro after the thermocycling and cyclic mechanical loading tests. METHODS: In the study,24 fresh extracted human premolars without root canal treatment were prepared (cusps reduction of 1.5 mm in thickness to simulate middle to severe tooth wear, the inclinations of cusps were 20°). The prepared teeth were restored with occlusal veneers made of three different materials: microhybrid composite, heat-pressed lithium disilicate ceramic and computer-aided design/computer-aided manufacturing (CAD/CAM) lithium disilicate ceramic in the thickness of 1.5 mm. The occlusal veneers were cemented with resin cement. The specimens were fatigued using the thermocycling and cyclic mechanical loading tests after being stored in water for 72 h. The wear of specimens was measured using gypsum replicas and 3D laser scanner before and after the thermocycling and cyclic mechanical loading tests and the mean lost distance (mm) was used to indicate the level of wear. The surfaces of occlusal contact area were observed and the surface roughness was recorded using 3D laser scanning confocal microscope before and after the fatigue test. Differences between the groups were compared using ONE-way ANOVA(P<0.05). RESULTS: All the specimens successfully survived after the thermocycling and cyclic mechanical loading tests. The mean wear of microhybrid composite group, heat-pressed lithium disilicate ceramic group, and CAD/CAM lithium disilicate ceramic group was (-0.13±0.03) mm, (-0.05±0.01) mm and (-0.05±0.01) mm, the wear of microhybrid composite was significantly higher than the two ceramic groups(P<0.001).The mean surface roughness(Ra)before the fatigue test was(1.24±0.20) µm, (0.75±0.09) µm, (0.73±0.14) µm and it became (1.81±0.24) µm, (1.53±0.26) µm and (1.77±0.23) µm after the test . Before the fatigue test, the surface roughness of microhybrid composite was significantly higher than the two ceramic groups(P<0.001) and after the test, the surface roughness of heat-pressed lithium disilicate ceramic was significantly lower than microhybrid composite(P=0.005) and CAD/CAM lithium disilicate ceramic (P=0.010). CONCLUSION: From the view of wear speed, microhybrid composite was significantly higher than the two kinds of ceramics, but it was similar to enamel when the opposing tooth was natural. The surface roughness before the themocycling and cyclic mechanical loading test of microhybrid composite was significantly higher than that of the two ceramic groups. After the test, the surface roughness of heat-pressed ceramic was significantly lower than that of the other two groups. From the view of surface roughness, heat-pressed ceramic has more advantage.

[Influence of intraoral scan and dental cast scan on occlusal quantitative analysis of virtual dental model].

OBJECTIVE: To make more accurate occlusal quantitative analysis of three-dimensional (3D) virtual dental models and to compare the occlusal contact obtained by intraoral and dental cast scan. METHODS: In this study, 5 subjects were intraoral scanned using laser scanner (3 shapes, Germany) to obtain the 3D virtual models of one tooth (the first molar), two teeth (the second premolar and the first molar), three teeth (the premolars and the first molar) and their opposite teeth, respectively. The silicone impressions were made and dental stone models were poured for each of them. The dental casts were scanned and then they were fixed to the maximum intercuspal position with a special locating jig for a rescanning of occlusal position. The virtual models taken intraorally and obtained with dental cast scan were introduced to a 3D quantitative analysis system, and some criteria regarding to occlusal contact were calculated and analyzed. The occlusal criteria were mean values of occlusal clearance space between the upper and lower occlusal surface (clearance), occlusal contact area (area), and cusp inclination (angle) of the mandibular first molar. Paired t tests were used to evaluate differences of occlusal criteria between the virtual models obtained with the intraoral scan and dental cast scan (α=0.05). RESULTS: The mean values of occlusal clearance of one to three teeth obtained by way of intraoral scan were smaller than those obtained by way of cast scan by 0.134 mm, 0.177 mm, and 0.207 mm, respectively. While the occlusal contact areas were greater than the cast scan by 8.65 mm2, 10.28 mm2, and 11.46 mm2. No statistically significant differences were found between the cusps inclinations obtained with the two scanning methods, and the interclass correlations were high. CONCLUSION: Occlusal clearance obtained by intraoral scan was less than that by cast scan while the occlusal contact area was greater than the latter, indicating that intraoral occlusal contact was closer. The difference of the standard deviations of occlusal clearance measured by the two methods were small and that of occlusal contact area was influenced by the number of teeth scanned intraorally. There was no statistical difference in cusp inclination between the two methods.

[Identification of the Disease-Associated Genes in Periodontitis Using the Co-expression Network].

The aim of this study was to investigate the disease-associated genes in periodontitis. In the present experiments, the topological analysis of the differential co-expression network was proposed. Using the GSE16134 dataset downloaded from the European Molecular Biology Laboratory-European Bioinformatics Institute, a co-expression network was constructed after the differentially expressed genes (DEGs) were identified between the diseased (242 samples) and healthy (69 samples) gingival tissues from periodontitis patients. The topological properties of the modules obtained from the network as well as an analysis of transcription factors (TFs) were used to determine the disease-associated genes. The gene ontology and pathway enrichment analysis was performed to investigate the underlying mechanisms of these disease related genes. A total of 524 DEGs, including 19 TFs were identified and a co-expression network with 2569 edges was obtained. Among the 7 modules gained in the network, the TFs (ZNF215, ZEN273, NFAT5, TRPS1, MEF2C and FLI1) were considered to be important in periodontitis. The functional and pathway enrichment analysis revealed that the DEGs were highly involved in the immune system. The co-expression network analysis and TFs identified in periodontitis may provide opportunities for biomarker development and novel insights into the therapeutics of periodontitis.

[Triggers of bulimia and compulsion attacks: validation of the "Start" questionnaire]. / Les inducteurs des crises dans la boulimie et la compulsion : validation du questionnaire « Start ¼

AIM: There are few published studies on the triggers of binge eating in anorexia nervosa of binge/purging subtype (BPAN), bulimia nervosa (BN) and binge eating disorder (BED). PATIENTS AND METHODS: We validated in 29 patients (10 BPAN, 10 BN and 9 BED) the perspicuity, the clarity and the intra- (doubles) and inter- (test-retest) reproducibility of a 24-item Start questionnaire on the triggers of binge eating. Then the Start questionnaire was administered to 176 patients (65 BPAN, 62 BN and 59 BED patients) being 27.5+9.1 yr old, having 15+9 binge eating (BE) episodes/week, with a mean binge duration of 1 hr 36min (+ 38min)/day. RESULTS: BE episodes occurred mainly during the second part of the day: afternoon after work (67% of the patients), "tea" time (55%), evening after dinner (42%) and at night (22%). The principal place for BE episodes was at home (96%). The BED patients avoided binges at the parents' home (89%) more often than the BPAN (62%, P<0.02). The binges occurred mainly in the living room (44%), in the kitchen (43%), and less in the bedroom (31%). Hunger pangs seemed to be a trigger of binges in 31% of the patients, and a stronger trigger in BED (42%) than in the BPAN and BN patients (24%; P=0.04). Binge eating episodes could occur despite a high satiety level (just after lunch or dinner) in 29% of the BN and in 16% of the BED patients (P<0.02). Concerning food, the major triggers were high energy-density food (77%) and comfort food (60%), such as chocolate, cakes, bread and pasta. The food consumed for binge episodes (in-binge food) was more often a strong trigger than the other food (not used for binges): olfaction (19% versus 10%), sight (52% versus 25%) and placing in the mouth (71% versus 26%; P<0.02 for all, in the 3 groups). Being tired could be a strong trigger in 37% of the patients, but "being aroused" in the other 38 % of the patients. Stressful events (65%), anxiety (74%), "being under pressure" or irritated (51% and 55%) were of course major triggers in a majority of the patients, as well as sadness (61%), feeling of powerlessness (62%), inefficiency (73%) and depressive state (71%). Flashback from traumatism (sexual trauma in 17% of the patients) was a strong trigger of binges more often in BPAN and BED (44%) than in BN (23%; P<0.05). The binge eating was painful (and "not at all a pleasure") in 69% of the patients, but could also be a relaxing behavior in 31% of the patients, more often in the BED (43%) than in the BPAN patients (20%; P<0.05). The binge eating behavior was quoted as obsessive in 63% of BPAN, 92% of BN and only 34% of BED patients (P<0.001). The patients said that they were unable to avoid the binge (76% of the patients), more often in BPAN and BN than in BED patients (P<0.01). As a whole, 62% of BPAN, 89% of BN and only 4 % of BED patients (P<0.05) were unable to avoid purging (vomiting). In 12% of the cases, there was a pleasure felt when binging. For the other patients, shame, filth and incapacity were the feelings related to binges in 58% of the BPAN, 45% of BN and 43% of BED patients (P<0.04). The global score of addiction (zero=not addicted, 10=very addicted) was 8.56+1.2 in BPAN, 8.42+1.5 in BN and 6.74+1.1 in BED patients (NS between BPAN and BN; P<0.01 between BPAN and BN on the one hand and BED on the other). CONCLUSION: The present study has demonstrated the usefulness of the Start questionnaire. It also evidences the key role of intrinsic factors, both metabolic and emotional, as strong triggers for binge eating episodes in BPAN, BN and BED. It has also demonstrated the role of environmental determinants.

[New intraoral digital impression with pneumatic gingival retraction used in the restoration of crown for posterior teeth: a case report].

In fixed prosthodontics, clear exposure of the preparation margin is the prerequisite for obtaining accurate digital impressions and improving the marginal fit of restorations. To resolve the issues associated with the cord retraction technique, such as pain, acute injury, and prolonged procedural time, this study proposes a new technology for intraoral digital impression taking with pneumatic gingival retraction. The new scanning head blows a high-speed airflow that instantaneously separates the free gingiva, locally exposing the subgingival preparation margin. Combined with the farthest point preservation stitching algorithm based on the distance from the normal vector and high-speed laser scanning photography, it achieves global preparation edge data and gingival reconstruction, realizing painless, non-invasive, and efficient precise acquisition of the preparation margin. Using this new technique, a patient with a full porcelain crown restoration on a posterior tooth was treated. The digital impression revealed a clear margin of the preparation, and the crown made from this data has a good marginal fit.

Effects of two in-office bleaching agents with different pH on the structure of human enamel: an in situ and in vitro study.

This study evaluated the effects of two in-office bleaching agents (Beyond and Opalescence Boost) with different pH on the structure and mechanical properties of human enamel in vitro and in situ. One hundred and eight enamel slabs were obtained from freshly extracted premolars. The specimens were randomly distributed into nine groups (n=12), and the human saliva (HS) in the volunteers' oral cavities was used to simulate the in situ condition: Beyond + HS, Opalescence Boost (O-Boost) + HS, Control + HS, Beyond + artificial saliva (AS), O-Boost + AS, Control + AS, Beyond + distilled water (DW), O-Boost + DW, and Control + DW. The bleaching treatments were performed on the first and eighth day, and the total bleaching time was 90 minutes. Baseline and final surface roughness (RMS), surface morphology, microhardness, and fracture toughness (FT) were measured before the treatment and on the fifteenth day, respectively. Compared with control groups, surface alterations on enamel were found in the Beyond + AS and Beyond + DW groups under atomic force microscopy evaluation. Two-way analysis of variance and Tukey test revealed that the RMS showed significant intergroup differences for both storage condition and bleaching agent, whereas microhardness and FT revealed no significant alteration. The results indicated that in-office bleaching agents with low pH values could induce enamel morphology alterations under in vitro conditions. The presence of natural HS could eliminate the demineralization effect caused by low pH.

[Akt2 inhibitor promotes M2 macrophage polarization in rats with periapical inflammation by reducing miR-155-5p expression].

OBJECTIVE: To investigate the effect of Akt2 inhibitor on macrophage polarization in the periapical tissue in a rat model of periapical inflammation. METHODS: Rat models of periapical inflammation were established in 28 normal SD rats by opening the pulp cavity of the mandibular first molars, followed by injection of normal saline and Akt2 inhibitor into the left and right medullary cavities, respectively. Four rats without any treatment served as the healthy control group. At 7, 14, 21 and 28 days after modeling, 7 rat models and 1 control rat were randomly selected for observation of inflammatory infiltration in the periapical tissues by X-ray and HE staining. Immunohistochemistry was used to detect the expression and localization of Akt2, macrophages and the inflammatory mediators. RT-PCR was performed to detect the mRNA expressions of Akt2, CD86, CD163, inflammatory mediators, miR-155-5p and C/EBPß to analyze the changes in macrophage polarization. RESULTS: X-ray and HE staining showed that periapical inflammation was the most obvious at 21 days after modeling in the rats. Immunohistochemistry and RT-PCR showed that compared with those in the control rats, the expressions of Akt2, CD86, CD163, miR-155-5p, C/EBPß, and IL-10 increased significantly in the rat models at 21 days (P < 0.05). Compared with saline treatment, treatment with the Akt2 inhibitor significantly decreased the expression levels of Akt2, CD86, miR-155-5p and IL-6 and the ratio of CD86+M1/CD163+M2 macrophages (P < 0.05) and increased the expression levels of CD163, C/EBPß and IL-10 in the rat models (P < 0.05). CONCLUSION: Inhibition of Akt2 can delay the progression of periapical inflammation in rats and promote M2 macrophage polarization in the periapical inflammatory microenvironment possibly by reducing miR-155-5p expression and activating the expression of C/EBPß in the Akt signaling pathway.

[Study on mandibular movement trajectory and virtual occlusal pre-adjustment under light and heavy bite force].

Objective: To investigate the influence of light and heavy bite force on the mandibular movement trajectories, and the influence of bite force on virtual occlusal pre-adjustment of digital full crown. Methods: From October 2021 to March 2022, 10 postgraduate volunteers (3 males and 7 females, aged 22-26 years) were recruited from Peking University School and Hospital of Stomatology. Maxillary and mandibular digital models of the participants were obtained by intraoral scanning. Jaw relations were digitally transferred under heavy bite force and mandibular movement trajectories under light and heavy bite force were recorded by jaw motion analyser. Three mandibular markers were chosen, namely the mesial proximal contact point of the central incisor (incisal point) and the mesial buccal cusp tips of the bilateral first molars. The three-dimensional displacements of the markers under two kinds of bite force in the intercuspal position (ICP), the sagittal projection of the three-dimensional displacements in the protrusive edge-to-edge position, and the coronal projection of the three-dimensional displacements in the lateral edge-to-edge position of upper and lower posterior teeth were measured. Single-sample t-test was used to compare the three-dimensional displacements and the corresponding sagittal projection and coronal projection with 0, respectively. The left maxillary central incisor and left mandibular first molar were virtually prepared by the reverse engineering software. Then dental design software was used to design digital full crown using the copy method. The mandibular movement trajectories under light and heavy bite force were separately used to guide virtual occlusal pre-adjustment. The three-dimensional deviations (mean deviations and root mean square) between the lingual surface of the left maxillary central incisor or the occlusal surface of the left mandibular first molar and that of the natural tooth before preparation were calculated (light bite force group and heavy bite force group), and the differences between the two groups were compared by the paired t-test. Results: Under the two kinds of bite force, the three-dimensional displacements of the markers in the ICP were (0.217±0.135), (0.210±0.133) and (0.237±0.101) mm, respectively; the sagittal projection of the three-dimensional displacements of the markers in the protrusive edge-to-edge position were (0.204±0.133), (0.288±0.148) and (0.292±0.136) mm, respectively; the coronal projection of the three-dimensional displacements of the mesial buccal cusp tips of the bilateral first molars in the lateral edge-to-edge position were (0.254±0.140) and (0.295±0.190) mm, respectively. The differences between the above displacements and 0 were statistically significant (P<0.05). The results of occlusal pre-adjustment showed that the mean deviations of the lingual surface of the left maxillary central incisor in the light and heavy bite force groups were (0.215±0.036) and (0.195±0.041) mm (t=3.95, P=0.004), respectively. The mean deviations of the occlusal surface of the left mandibular first molar were (0.144±0.084) and (0.100±0.096) mm (t=0.84, P=0.036), respectively. Conclusions: Both the light and heavy bite force have an influence on the mandibular movement trajectories. Virtual occlusal pre-adjustment of prostheses with mandibular movement trajectories under heavy bite force can obtain morphology of lingual or occlusal surfaces closer to the natural teeth before preparation.

[Three-dimensional finite element study on the effects of maxillary anterior two-step retraction and en-masse retraction with clear aligners].

Objective: To investigate the effects of two-step retraction and en-masse retraction on tooth movement pattern of anterior teeth and posterior anchorage with clear aligners using three-dimensional finite element analysis. Methods: A finite element model of maxillary first premolar extraction case undergoing clear aligner treatment was established based on maxillofacial cone-beam CT data of a 24-year-old adult male with individual normal occlusion, who visited Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine for impacted mandibular third molar in June, 2022. The initial tooth displacement of five anterior retraction protocols (two-step with canine retraction, two-step with incisor bodily retraction, two-step with incisor retraction-overtreatment, en-masse bodily retraction, and en-masse retraction-overtreatment) were evaluated. Results: Two step with canine retraction caused distal tipping of the canine and labial tipping of the incisors (0.18° for central incisor and 0.13° for lateral incisor). Two step with incisor retraction caused mesial tipping of the canine. In two step with bodily retraction protocol, uncontrolled lingual tipping was found in central incisor (0.29°) and lateral incisor (0.32°). In two-step with incisor retraction-overtreatment protocol, the movement pattern of the incisors didn't change, but the inclinations reduced to 0.21° and 0.18°. En-masse retraction caused distal tipping of the canine. In en-masse bodily retraction protocol, uncontrolled lingual tipping was also found in central incisor (0.19°) and lateral incisor (0.27°). In en-masse retraction-overtreatment protocol, the central incisor showed controlled lingual tipping (0.02°) and the lateral incisor showed palatal root movement (0.03° labial inclination). Posterior teeth exhibited mesial tipping in all five protocols. Conclusion: En-masse retraction with incisor overtreatment was beneficial to incisor torque control in clear aligner treatment.

[Long-term clinical evaluation of different types of resin-bonded fixed partial denture to replace lost anterior teeth].

Objective: To evaluate the clinical survival rates and influence factors of different types of resin-bonded fixed partial dentures (RBFPD) used in anterior missing teeth restoration. Methods: Ninety-three RBFPD were delivered to 92 patients [92 patients,43 males and 49 females, average age (46.1±12.8) years] who visited Peking University School and Hospital of Stomatology from January 2006 to December 2021 for restoration of 1 or 2 anterior missing teeth. Altogether 32 cases of glass fiber reinforced RBFPD, 39 cases of glass-based ceramic RBFPD and 22 cases of porcelain-fused-to-metal RBFPD were retrospectively analyzed. The complete survival rate, functional survival rate, patients' satisfaction and color matching of the restorations were recorded and evaluated every year since the replacement with RBFPD. The Kaplan-Meier survival curve method was used for survival analysis, and the Log-rank analysis was used to compare the effect of the number of missing teeth, position (maxillary or mandibular), cantilever or non-cantilever and gender on the survival rate of the restorations. Results: The overall survival time for the 93 RBFPD was 13.7 years (95%CI: 12.3-15.1 years). There was a decreasing trend in complete survival and functional survival for all three material RBFPD from year to year, but complete and functional survival rates exceeded 90% at year 5 and exceeded 80% at year 10. The complete survival rate of the glass-ceramic RBFPD was higher than the other two during the follow-up period, with a complete survival rate of 90% (35/39) at year 15. The porcelain-fused-to-metal RBFPD had a higher functional survival rate in years 1-8, but the complete and functional survival rates showed a substantial decrease after year 9. The single-factor Log-rank analysis showed that the success rate of porcelain-fused-to-metal RBFPD was significantly higher than that of glass fiber reinforced RBFPD (χ²=7.33, P=0.007), and the success rate of RBFPD with 1 missing tooth restored was significantly higher than that of RBFPD with 2 missing teeth restored (χ²=3.23, P=0.072). The differences in success rates between different restoration positions (maxillary and mandibular), cantilever or non-cantilever, and gender factors were not statistically significant (χ²=2.26, P=0.133; χ²=0.68, P=0.411; χ²=1.07, P=0.300). Conclusions: For the restoration of individual missing anterior teeth, both porcelain-fused-to-metal RBFPD and glass-based ceramic RBFPD achieve a high long-term clinical success rate, with glass-based ceramic RBFPD being more able to ensure long-term restorative result.

[Masticatory muscle disorders and treatment from the perspective of prosthodontics].

Masticatory muscle disorders (MMD) is the biggest subtype of temporomandibular disorders (TMD). Among them, local fibromyalgia and myofascial pain are localized lesions, manifested as masticatory muscle pain, which can be aggravated with jaw function. MMD is caused by a combination of multiple factors. Occlusal disharmony such as occlusal trauma, occlusal interference, and decreased vertical dimension of occlusion have the potential risk of inducing or aggravating the MMD. During prosthodontic treatment, iatrogenic occlusal interference should be avoided. Most patients with MMD can be relieved by comprehensive treatment, and occlusal therapy or prosthodontic treatment is used as an auxiliary means of diagnosis and treatment. By means of occlusal splint, occlusal adjustment and denture restoration, the goal of relieving masticatory muscle tension, stabilizing occlusal support, eliminating occlusal interference and adjusting jaw position can be achieved, so as to eliminate some risk factors of MMD and relief the pain faster.

Fabrication of polydimethylsiloxane/graphene flexible strain sensors by using the scraping and coating method.

Production of flexible strain sensors is complex, time-consuming, and expensive. In this study, a novel fabrication method of polydimethylsiloxane/graphene nanocomposite conductive materials was proposed by using the scraping and coating method for manufacturing sandwich-shape flexible strain sensors. A ZQ-60B tensile testing machine was employed to test the mechanical properties of flexible sensors with 1%, 3%, and 5% graphene content. The results revealed that the stress and strain of the flexible strain sensor exhibited a linear relationship, and the linear correlation coefficients were 0.99706, 0.99819, and 0.99826, respectively. The concentration of graphene was 1%, 3%, and 5%, and the gauge factors (GFs) of the sensor were 24, 6, and 3, respectively. With the increase in the graphene content, the GF decreased gradually. This phenomenon could be attributed to tunneling, which increased the number of conductive pathways with an increase in the graphene content. Furthermore, the sensor exhibited excellent stability after 100 cycles of stretching/scaling. The finger joint bending test revealed that the flexible strain sensor is reproducible and exhibits excellent application prospects in monitoring human movement and health.

[Relationship between temporomandibular disorders and malocclusions: from history to present].

Regarding the relationship between malocclusions and temporomandibular disorders (TMD), from the leading cause to one of the local biological factors, the change in the understanding of the academic community since the 1980s has affected the clinical diagnosis, treatment behavior, and the direction of scientific research. At present, it is believed that the etiology of TMD is multifactor. The occlusal factors and the occurrence of TMD are weakly related, but there are some common malocclusions such as occlusal interference on non-working side, excessive sliding between maximum intercuspid position (MIP) and retruded contact position (RCP), unstable MIP and so on, may be risk factors that promote the disease. The occurrence of TMD symptoms is promoted under the combined action of behavior, biology, environment, social cognition, mentality and other comprehensive factors. In student education and clinical work, the risk of iatrogenic occlusal trauma in promoting the occurrence of TMD cannot be ignored. The impact of the patient's social and psychological environment on the TMD should be paid attention, and comprehensive treatment strategies is advocated.

[Feasibility analysis of visual analogue scale in esthetic evaluation of anterior implant-supported single crown in maxilla].

Objective: To test the reproducibility of the visual analogue scale (VAS) used in the evaluation of the esthetic effect of anterior dental implants, and to explore the factors that affect the correlation between VAS and pink esthetic score/white esthetic score (PES/WES). Methods: From January 2018 to August 2019, a total of 108 doctors and patients were recruited in the Department of Prosthodontics, Implantology and Fourth Clinical Division of Peking University School and Hospital of Stomatology. Among them, there were 35 dental implant specialists who were familiar with PES/WES [implant specialist group, 25 males, 10 females, (37.3±4.5) years old], 34 dentists who were not familiar with PES/WES [dentist group, specialized in Prosthodontics, Periodontology, Orthodontics, and Oral Maxillofacial Surgery, 24 males, 10 females, (36.1±4.2) years old], 39 patients [patient group, 28 males, 11 females, (45.4±8.3) years old]. Twenty oral pictures of patients [12 males, 8 females, (43.7±6.4) years old] treated in the Department of Prosthodontics, Peking University School and Hospital of Stomatology from December 2016 to December 2017 were taken for single implant restoration for esthetic evaluation with VAS. Score 0 for evaluation of not beautiful and score 10 for very beautiful. Re-evaluation of the same 20 pictures with VAS after 1 month, and perform repeatability evaluation of VAS using chi-square test were conducted. At the same time, 13 implant specialists were randomly selected, to score the same photos with PES/WES. The PES scoring elements were the fullness of the mesial gingival papilla, the fullness of the distal gingival papilla, the curvature of the gingival margin, the protrusion of the root surface, the color and the texture of the soft tissue. The scoring elements of WES were crown shape, crown contour, crown color, surface texture, transparency and individual characteristics in order. Pearson correlation analysis was used to evaluate the correlation between the score of VAS and PES/WES. And the influence of the group on the correlation between PES/WES and VAS was analyzed. Results: The PES score was 7.5±1.8, and the WES score was 7.6±1.9 and the total score was 15.1±3.4. The VAS score of the implant specialist group was 6.8±1.8. The repeatability test of the two VAS results in the patient group was not statistically significant (Kappa=0.012, P>0.05); the two VAS results of the implant specialist group and the dentist group both had good repeatability (Kappa=0.727 and 0.556, P<0.01). The VAS score was weakly correlated with the total PES/WES score (r=0.27, P<0.01). The VAS score was correlated with the score elements in PES/WES (P<0.01), and the color (r=0.20) and shape (r=0.22) of the crown were the larger correlation coefficients. The correlation coefficients between the VAS score and the PES/WES scoring system decreased among the implant specialist group (r=0.49, moderate correlation), the dentist group (r=0.25, weak correlation) and the patient group (r=0.12, P>0.05). Conclusions: The consistency of VAS and PES/WES is affected by the cognition of the scorer. The combination of the two scoring systems is feasible and necessary for physicians to evaluate the overall esthetic effect of implant restoration.

Preparation of the acellular scaffold of the spinal cord and the study of biocompatibility.

STUDY DESIGN: Acellular spinal cord was prepared through chemical extraction, and its biocompatibility was studied. OBJECTIVE: Acellular scaffolds have been developed from various materials for tissue reconstruction, except for spinal cord. The objective of this study was to prepare acellular spinal cord and examine the biocompatibility of the scaffold. SETTING: This study was conducted at the Department of Orthopedics, Xinqiao Hospital, The Third Military Medical University, Chongqing, China. METHODS: The morphology of the acellular segments was revealed by scanning electron microscopy, immunohistochemistry, and hematoxylin and eosin stain. Biocompatibility was studied by immunohistochemistry. RESULTS: Results show that in spinal cord scaffolds, cells, myelin sheath and axon of nerve fibers were eliminated, and three-dimensional supports of extracellular matrix were reserved. The component analytical results of the acellular spinal cord indicate that they contain laminin, fibronectin and collagen, which can facilitate and induce the regeneration of injured nerves, and enhance the adhesion and proliferation of cells. The acellular spinal cord has a three-dimensional structure and excellent biocompatibility. CONCLUSION: Our data indicate that acellular spinal cord has certain biological properties and it may be a potential alternative scaffold for spinal cord tissue engineering.

Ultrasonic atomization and subsequent desolvation for monoclonal antibody (mAb) to the glycoprotein (GP) IIIa receptor into drug eluting stent.

An eluting-stent system with mAb dispersed in the PLLA (poly (L-lactic acid)) was validated in vitro. Specifically designed spray equipment based on the principle of ultrasonic atomization was used to produce a thin continuous PLLA (poly (L-lactic acid)) polymer coating incorporating monoclonal antibody (mAb). This PLLA coating was observed in light microscopy (LM) and scanning electron microscopy (SEM). The concentration of the monoclonal antibody (mAb) to the platelet glycoprotein (GP) IIIa receptor and the eluting rate were then measured by a radioisotope technique with (125)I-labelled GP IIIa mAb. An in vitro perfusion circuit was designed to evaluate the release rates at different velocities (10 or 20 ml min(-1)). The PLLA coating was thin and transparent, uniformly distributed on the surface of the stent. Three factors influenced its thickness: PLLA concentration, duration and gas pressure. The concentration of mAb was influenced by the duration of absorption and the concentration of the mAb solution; the maximum was 1662.23 + or - 38.83 ng. The eluting rate was fast for the first 2 h, then decreased slowly and attained 80% after 2 weeks. This ultrasonic atomization spray equipment and technological process to prepare protein eluting-stents were proved to be effective and reliable.

A reversed approach for simultaneous mandibular symphyseal split osteotomy and genioplasty.

Performing a mandibular symphyseal split and genioplasty simultaneously and accurately is a technical challenge for the surgeon. The aim of this study was to validate a reversed approach for simultaneous symphyseal split and genioplasty. A cutting guide and a repositioning guide were designed and printed three-dimensionally in titanium. The symphyseal split and genioplasty were performed successfully. The accuracy of the technique appears to be appropriate for clinical application.

New Insights into Effects of Aromatic Amino Acids on Hydroxyapatite.

Biomimetics inspired by superstructures and extraordinary properties of teeth have resulted in tooth repair and the generation of novel materials. However, little attention has been paid to tooth color, whose origin remains unknown. Based on recent studies, fluorophores-mainly aromatic amino acids (AAAs) in proteins-might be responsible for tooth color. We synthesized carbonated hydroxyapatite (HA; the mineral phase of teeth) in the presence of different amino acids (AAs; the basic units of protein matrix of teeth) as a simplified model of teeth to explore the color source at the AA level. After measuring the fluorescence and color characteristics of HA-AAs before and after bleaching treatment, we found that only HA, synthesized in the presence of AAAs, exhibited remarkable fluorescence and color property. Furthermore, linearly increased fluorescence intensity and deeper color were observed with an increase in AAA content in HA-AAAs. Similarly, significantly decreased absorbance of HA-AAAs between 250 and 300 nm in ultraviolet spectra, declined fluorescence intensity, and decolored performance of HA-AAAs were observed after bleaching treatment. The results showed that AAAs contributed to the fluorescence and color properties of HA and that hydrogen peroxide might whiten HA-AAAs by oxidizing the benzene ring in AAAs. These findings are of great significance in promoting the synthesis of advanced tooth-colored materials and furthering our understanding of the possible mechanisms of hydrogen peroxide. Moreover, our study shed light on the importance of AAAs and might provide new ideas for investigations of biomineralization and biomimetics.