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15 May 2020, Volume 36 Issue 3 Previous Issue    Next Issue

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Clinical Diagnosis and Treatment of Edentulous Implant Restoration with Digital Clinical Workflow CHEN Jiang, Zhang Sihui 2020, 36(3): 193-198.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.001 Abstract ( 297 )   PDF (1279KB) ( 439 )   The wide application of digital technology in the field of stomatology has solved many problems exist in traditional implant restoration for edentulous patients. However, a wide variety of digital equipment and technology still need to be integrated. This article discussed the traditional and digital workflow of implant restoration for edentulous patients and its characteristics. And in order to standardize clinical practice, the digital clinical diagnosis and treatment workflow of implant restoration for edentulous patients was proposed. References | Related Articles | Metrics

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Hemostatic Agents in Restorative Dentistry and Its Effects on Dental Bonding Aihemaiti Muhetaer, HUANG Cui 2020, 36(3): 199-202.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.002 Abstract ( 330 )   PDF (783KB) ( 361 )   Dental defect is a common and frequently-occurring disease in dentistry. The contamination of blood, saliva, and gingival crevicular fluid will adversely affect the accuracy of tooth preparation and impression taking. Nowadays, hemostatic agents have already served as an important adjuvant reagent in dental restoration. Rational application of hemostatic agents can inhibit bleeding and control fluid contamination. It is worthy noted that hemostatic agents may affect the bond strength of adhesive-dental interface. In order to provide recommendations for the option of hemostatic agents in restorative dentistry, this review will summarize the classification of hemostatic agents commonly used in dentistry and evaluate their effects on the bonding interface. References | Related Articles | Metrics

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Effect of Chemical Crosslinking Agent on Adhesive Stability of Resin-dentin Bonding QIAN Xin, ZHANG Zhimin 2020, 36(3): 203-205.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.003 Abstract ( 223 )   PDF (771KB) ( 256 )   Oral adhesion repair has been widely used with the development of adhesives.But the problem of dentin adhesion durability is not optimistic.Various enzymes, bacteria, and other factors in the oral cavity may lead to the exposure of collagen fibers at the bonding interface, and the exposed collagen fibers are easily degraded and damaged by fatigue, thus affecting the stability of dentin bonding.Matrix metalloproteinase-mediated degradation of collagen fibers is the main factor of adhesion interface damage.Inhibition of matrix metalloproteinase activity and enhancement of collagen properties are the keys to prolong the bonding life.Therefore, in view of the difficulties in the adhesion of oral dentin, based on the concept of biological modification of dentin, the bionic method mediated by the biological activity of collagen cross-linking agent was used to change the biological and physical properties of dentin to strengthen the strength of dentin collagen fiber and increase the adhesion stability.In this paper, the role of crosslinkers in the biological modification of dentin was introduced. References | Related Articles | Metrics

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Research Progress of Using Near Infrared Upconversion Materials to Increase Curing Depth of Resin GUO Qianyun, LIU Bin 2020, 36(3): 206-208.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.004 Abstract ( 231 )   PDF (768KB) ( 292 )   As an important dental filling material, resin has been widely used in clinic since its development. Near infrared (NIR) light has a higher penetrability than visible light, and the upconversion (UC) material irradiated by NIR light with a specific wavelength can excite different wavelengths of visible light, such as blue light, and then light cure the dental resin. In recent years, based on these characteristics, it is proposed that UC materials could be incorporated into the UV curable resin. The UC material was then irradiated by NIR light and excited UC materials in the deep layer to convert into the blue light required for UV curable resin. This was called the deep curing of the dental resin. In this paper, the related research, existing problems, and possible long-term development of this modified method are discussed. References | Related Articles | Metrics

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Research Progress of Radiotherapy on Bone Tissue and Osseointegration around Implants YU Kaixuan, ZHOU Yanmin 2020, 36(3): 209-212.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.005 Abstract ( 234 )   PDF (789KB) ( 278 )   Implant dentures have become the best method to repair teeth defect and tooth loss in adult patients. For patients with head and neck cancer, surgical excision combined with radiotherapy and chemotherapy is usually required. However, local radiotherapy may cause some damage to the quality and quantity of jaw tissue, which may indirectly affect the osseointegration of the implant. In this paper, the effects of radiotherapy on bone tissue and osseointegration around the implant are reviewed. References | Related Articles | Metrics

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Research Progress on Structure and Mechanical Properties of Dental Enamel LIU Jitao, CHEN Qinghua 2020, 36(3): 213-215.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.006 Abstract ( 464 )   PDF (767KB) ( 577 )   The hierarchical structure of enamel composes the basis of its mechanical properties such as high hardness and high toughness. Understanding the mechanical properties of microstructures in enamel is helpful to the development of biomimetic restoration materials and the remineralization of dental enamel in clinical. In this review, the structure and mechanical properties of enamel were systematically reviewed in terms of its hierarchical structure and toughening mechanism brought by organic components, dentin-enamel junction, and hydration. The gradual hierarchical structure of enamel and the high contact area of dentin-enamel junction lead to the gradient distribution of mechanical properties, making enamel both rigid and toughness. Organic components such as a small amount of viscoelastic proteins and their hydration play an important role in energy dissipation, preventing crack propagation in the enamel and maintaining the structural integrity of the teeth. The investigations in the precise hierarchical structure of dental enamel and the complex synergistic toughening mechanism between inorganic and organic components provide new ideas for the development of biomimetic nanocomposites. References | Related Articles | Metrics

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Effect of Procyanidins on Bonding Durability of Fiber Post WANG Wen, XIE Cuiliu, DENG Ting, LIU Wen, LIU Min 2020, 36(3): 216-220.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.007 Abstract ( 217 )   PDF (1666KB) ( 136 )   Objective: To study the effect of procyanidins (PA) on the bonding durability of fiber post. Methods: 36 premolars with single root canal were treated by root canal therapy. After post space preparation, the premolars were randomly divided into 4 groups: A: 6.5％PA+ non-aging B: 6.5％PA +aging, C: ethanol + non-aging D: ethanol + aging. Specimens of 1mm thick slices which were used to test the shear bond strength were taken from the neck, middle, and tip of the 7 fiber post specimens from each group. Stereomicroscope and SEM were used to count and observe the failure mode. The remaining 2 samples of each group were used to conduct indian ink dyeing. Results: The bonding strength of PA pretreatment group was higher than that of ethanol group (P＜0.05). The interaction between PA pretreatment and aging on bond strength was statistically significance (P＜0.05). The interaction between different parts of root canal and PA pretreatment on bond strength had no statistically significance (P＞0.05). The failure mode was mainly mixed damage. D group presented the most apparent microleakage. Conclusion: PA can improve the bond strength and durability of the neck, middle, and tip parts of the fiber post. References | Related Articles | Metrics

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Effect of Pretreatment with EDTA and EDC on Bond Strength of Two-step Self-etching Adhesive DENG Ting, LIU Min, LIU Wen, WANG Wen, XIE Cuiliu 2020, 36(3): 221-225.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.008 Abstract ( 198 )   PDF (2464KB) ( 299 )   Objective: To study the effect of pretreatment with EDTA and EDC on the bond strength of two-step self-etching adhesive. Methods: 56 third molars were randomly divided into 8 groups according the dentin surface treatment and whether or not aging (n=7), group A and A1: Clearfil SE Bond; group B and B1:17% EDTA+Clearfil SE Bond; group C and C1:0.3 mol/L EDC+Clearfil SE Bond; group D and D1:17% EDTA+ 0.3 mol/L EDC+Clearfil SE Bond. Specimens of A1, B1, C1 and D1 were conducted aging test. 5 specimens were randomly selected from each group to test the bond strength and analyze the failure mode. The longitudinal profile morphology of the remaining 2 specimens in each group was observed. Results: Group D had the highest immediate bond strength, and the difference with group A was statistically significant (P<0.05). The difference between group C and C1, group D and D1 was no statistically significant (P>0.05). Mixed fracture was the main failure mode, and the difference was no statistically significant. Resin tags in group B, B1, D and D1 were more and longer than other groups, and no cracks were found in the mixing layer of group C1 and D1. Conclusion: Pretreatment with 17% EDTA+0.3 mol/L EDC can improve immediate dentin bond strength of two-step self-etching adhesive and the adhesion is durable. References | Related Articles | Metrics

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Effect of Different Surface Treatments on Bond Strength of Bio-HPP to PMMA SHI Qiaorui, XU Xin, YU Hao, ZHENG Ming 2020, 36(3): 226-229.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.009 Abstract ( 196 )   PDF (2104KB) ( 276 )   Objective: To investigate the influence of different surface treatments on the bond strength between Bio-HPP and PMMA. Methods: 68 Bio-HPP specimens were prepared and divided into 4 groups randomly:CG, SA0.05, SA0.35,and LA. After surface pretreatments, the surface morphology was observed by SEM and the surface roughness was measured by surface roughness tester. And then they were bonded to PMMA, half of specimens in each group were stored in distilled water for 24 h and the others were received 5 000 times of thermalcycling. Next, shear bond strength was tested by universal test machine. Results: SEM results showed that LA and SA were rougher than CG. Surface roughness was: CG＜LA＜SA0.05＜SA0.35. Shear strength was: CG＜LA＜SA0.05＜SA0.35. After thermalcycling, the shear bond strength decreased significantly except SA0.35 group (P＜0.05). Conclusion: Sandblast and Nd:YAG laser can change the surface topography and improve the shear bond strength of Bio-HPP. The proper increase of the sandblast pressure might benefit to the stability of Bio-HPP to PMMA. References | Related Articles | Metrics

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Antibacterial Properties of Titania Nanotubes with Different Diameters XU Zhiqiang, ZENG Xiufeng, HONG Shaonan, ZENG Xiuxia, HE Yuqi, HUANG Junhui 2020, 36(3): 230-234.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.010 Abstract ( 159 )   PDF (4211KB) ( 179 )   Objective: study the antibacterial properties of titania nanotubes with three different diameters. Methods: Titania nanotubes with three different diameters were fabricated on titanium surfaces through electrochemical anodization at 10, 30, and 60 V (denoted as NT10, NT30, and NT60). The sample topography was assessed with SEM. The crystalline phase analysis was conducted using X-ray diffractomer. Contact angle measurements were examined using a contact angle measuring system, and roughness was examined using atomic force microscope. The antibacterial properties of titania nanobues were evaluated by in vitro co-culture with Staphylococcus aureus and Porphyromonas Gingivalis. The live bacteria were observed with SEM and quantitated by the plate-counting method. Results: The diameters of titania nanotubes were about 30 nm (NT10), 100 nm (NT30), and 200 nm (NT60), respectively. All three types of nanotubes had anatase peaks as indicated by X-ray diffractomer. The contact angles on nanotubes were smaller than those on the control titanium, and reached the lowest on NT60. The roughness values of the nanotubes were smaller than those of control titanium, and reached the lowest on NT30. The bacterial on the titania nanotubes were significantly decreased when compared to the titanium. The adhesion of Staphylococcus aureus reached the lowest on NT60, and the adhesion of Porphyromonas Gingivalis reached the lowest on NT30. Conclusion: The titania nanotubes fabricated on the surface of titanium all inhibited the adhesion of bacteria to some extent. References | Related Articles | Metrics

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Effect of Surface Modification of Different Implants on Bacterial Biofilm WANG Hanchi, SUN Xiaolin, FANG Jiao, DU Liuyi, PENG Peixuan, ZHOU Yanmin 2020, 36(3): 235-238.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.011 Abstract ( 268 )   PDF (1399KB) ( 173 )   Objective: To study the effects of surface treatments commonly used in clinic on the adhesion of Porphyroman gingivalis (Pg), Fusobacterium nucleatum (Fn), and Streptococcus sanguis (Ss). Methods: Titanium discs were divided into three groups for surface modification: electrodeposited hydroxyapatite (HA) group, micro-arc oxidation (MAO) group, and sandblasted with large-grit and acid-etched (SLA) group. The surface properties were tested. Fn, Ss, and Pg were cultured on three groups of titanium discs for 4 days, respectively. The colony forming unit (CFU) method, thiazole blue (MTT) method, and scanning electron microscopy (SEM) were used to observe bacterial adhesion. Results: (1) SEM observation showed that there were a large number of irregular rod-like structures on the surface of HA group, crater-like structures on the surface of MAO with aperture ranging from 0.1 to 1 micron, and irregular depressions on the surface of SLA with different sizes and sharp edges. Ra values of surface roughness in three groups was: SLA group < HA group < MAO group; (2) Fn biofilm was the lowest in SLA group, with statistical difference from the other two groups (P<0.05); The activity of Ss biofilm on three groups of titanium discs was the highest in HA group and the lowest in SLA group, but there was no significant difference among three groups (P>0.05). Pg biofilm had the highest activity on titanium plate in MAO group, with statistical difference from the other two groups (P<0.01). (3) SEM observation showed that the bacterial activity was related to the morphological structure of implant surface. Conclusion: The adhesion of bacteria to implant surface is affected by surface morphology, which is related to roughness and physical configuration. For three kinds of bacteria, SLA had the least bacterial adhesion. References | Related Articles | Metrics

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Effect of Different Polishing Kits on Surface Roughness and Bacterial Adhesion of Oryza and Edit Zirconia Ceramics WANG Meiyan, ZHAO Chanyuan, WANG Yangyang, WANG Xi 2020, 36(3): 239-242.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.012 Abstract ( 203 )   PDF (1101KB) ( 193 )   Objective: To observe the effects of different polishing kits on the surface roughness and bacterial adhesion of perennial and Edit zirconia ceramics. Methods: Each material was randomly divided into five groups: group A, B, and C were polished with polishing kits PN0301, HP321, and Occlubrush respectively. Group D was glazed and group E was not treated with any treatment. The surface roughness and morphology of the samples were tested. The standard strains of Streptococcus mutans were inoculated on each group of specimens, and the surface colony forming units of the specimens were counted. The bacterial absorbance on the surface of the material was measured by CCK-8 method. Results: The surface roughness of group A, B and D were lower than those of group C and E (P<0.05). However, there was no difference between group C and group E (P>0.05), group A and B were higher than group D (P<0.05), and group A was lower than group B (P<0.05). The surface of group C and E was rough and scratched obviously. The surface of group D was smooth. The bacterial adhesion and absorbance of group A, B, and D were less than those of group C and E (P<0.05). There was no difference between group C and group E (P>0.05), group A and group B were more than group D (P<0.05), and group A was less than group B (P<0.05). Conclusion: Polishing kit PN0301 and HP321 can significantly reduce the surface roughness and bacterial adhesion of perennial and Edit zirconia ceramics, and the effect of polishing kit PN0301 is better. References | Related Articles | Metrics

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Antimicrobial Activity of Resin Base with Nano-silver Inorganic Zirconium Phosphate against Six Oral Bacteria in Vitro YANG Chengxue, ZHAI Yuxiang, WANG Kaimei, CHEN Lin 2020, 36(3): 243-246.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.013 Abstract ( 198 )   PDF (1157KB) ( 141 )   Objective: To study whether the nano-silver inorganic zirconium phosphate has antibacterial properties after being added to resin base by adhesion experiments in vitro. Methods: The nano-silver inorganic zirconium phosphate (Conval PAg-40) was added to the resin base at the ratio of 1%, 3%, 5%, and 7% to prepare resin specimens. The antimicrobial properties of all resin specimens against Streptococcus mutans, Actinomyces viscosus, Actinomyces naeslundii, Streptococcus sanguis, Porphynomoans gingivalis, and Candida albicans were tested by the film-sticking method after those specimens were milled and polished. The surface roughness values were measured by the roughness tester. Results: The colonies of Porphyromonas gingivalis cultured in groups of 3%, 5%, and 7%, and Streptococcus mutans, Actinomyces viscosus, Actinomyces naeslundii, Streptococcus sanguis, and Candida albicans cultured in groups of 1%, 3%, 5%, and 7% were lower than the control group (P<0.05). The antimicrobial rate of resin specimens gradually increased with the increase of addition. There was no significant difference in the number of Porphyromonas gingivalis colonies cultured in 1% group compared with that of the control group (P>0.05). Conclusion: The resin base with nano-silver inorganic zirconium phosphate has good antimicrobial activity, and its antimicrobial rate increases linearly with the proportion of antimicrobial agents. References | Related Articles | Metrics

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Antimicrobial Effect of A Novel Titanium Implant Incorporated with Bioactive Ion WU Qianju, ZHANG Zhisheng, LIN Zhiming, JIN Di, ZHANG Yi , LUO Bizhu 2020, 36(3): 247-250.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.014 Abstract ( 184 )   PDF (1997KB) ( 155 )   Objective: To evaluate the antimicrobial effect in vitro of implant coating by introducing antimicrobial ion. Methods: A novel coating was prepared on dental implant surface via electrochemistry approach by introducing antimicrobial ion to recombine chemical composition, and concentrations of ions being released were measured. The biological performances were systematically explored as follows:(1) Survival situation of bacteria cultured on specimens was observed by CLSM; (2) Antimicrobial rate was calculated. Results: It was found that this functionalized implant controlled copper ions release in a sustained pattern. Additionally, it was capable of reducing viability of oral pathogens effectively, displaying its excellent antibacterial property. Conclusion: It was suggested that implant coatings incorporated with antimicrobial element by electrochemistry approach for sustained release pattern and superior antimicrobial activity could be achieved. References | Related Articles | Metrics

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Study on IL-6 Inhibitor Controlling Inflammatory Bone Absorption during Implant Healing in Rabbits YU Ke, HE Xiaoping, WEN Cai, LIU Xulin, YANG Jian 2020, 36(3): 251-254.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.015 Abstract ( 201 )   PDF (2969KB) ( 135 )   Objective: To explore the effect of IL-6 inhibitor on the control of inflammatory bone resorption during implant healing, and to provide new ideas for the treatment of inflammatory bone resorption around implants in clinic. Methods: Twenty healthy adult male New Zealand white rabbits were randomly divided into four groups, and the bilateral mandibular anterior teeth of these rabbits were extracted. Three months later, 20 implants (2.5×12 mm, Dentium) were routinely placed into the lower anterior teeth area. Group A was blank control, and the implants of the other three groups were ligated with two 4-0 thread bolts. Group B was control with no other treatment. In group C, minocycline hydrochloride ointment was injected into the gingiva around the implants, and in group D, tocilizumab was injected intravenously at 8 mg/kg immediately and 1 week after implantation. Eight weeks later, animals were sacrificed, and bone tissues around implants were collected for X-ray and micro-CT scanning. Results: X-ray showed that there was no obvious bone absorption around the implants in group A and D, about 3-4 implant threads were exposed in group B, and about 1-2 threads were exposed in group C. Micro-CT analysis showed that the highest bone volume rate was found in group D, followed by group A and group C, and the lowest in group B (P<0.05). Conclusion: IL-6 inhibitor tocilizumab can control inflammatory bone resorption during implant healing and increase bone volume ratio around implants. References | Related Articles | Metrics

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Preparation and Bacteriostasis Effects of Poly(VBA-co-VBTAC)/XF-70 WANG Yansong, LIU Jianlin, CHEN Xiaoxia 2020, 36(3): 255-258.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.016 Abstract ( 163 )   PDF (1078KB) ( 113 )   Objective: To evaluate the physicochemical properties of poly (4-vinyl benzoic acid co (ar-vinyl benzyl) trimethylammonium chloride poly (VBA-co-VBTAC)/XF-70 nanofibers, and to explore their inhibitory effects on the formation of bacterial biofilms. Methods: Poly (VBA-co-VBTAC) nanofibers were prepared and compared with Poly (VBA-co-VBTAC)/XF-70. The morphology of the nanofibers was observed by SEM. The release curves of Staphylococcus aureus and Porphyromonas gingivalis biofilms were measured by high-performance liquid chromatography (HPLC), and the in vitro models of Staphylococcus aureus and Porphyromonas gingivalis biofilms were established. Bacterial inhibition tests were carried out on 1.00 mg/L XF-70 and Poly (VBA-co-VBTAC)/XF-70 with the same content of XF-70, respectively. Results: The release of XF-70 within 300 minutes was nearly 80%. The biofilm formation (absorbance value) of the two bacteria decreased significantly, and the bacteriostasis effect of Poly (VBA-co-VBTAC)/XF-70 was significantly better than that of XF-70 group (P<0.05). Conclusion: Poly (VBA-co-VBTAC)/XF-70 has a good short-term release curve, which can improve the inhibition of XF-70 on the formation of biofilm of Staphylococcus aureus and Porphyromonas gingivalis. References | Related Articles | Metrics

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Finite Element Analysis of Different Repairing Designs for Maxillary Central Incisor with Oblique Defect LI Xixi, KANG Ting, CHEN Yanyu, SONG Danyang, GUO Ling 2020, 36(3): 259-263.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.017 Abstract ( 200 )   PDF (3826KB) ( 182 )   Objective: To analyze the stress distribution of maxillary central incisor oblique fracture with different repair methods by three-dimensional finite element analysis. Methods: The finite element models of maxillary central incisor with oblique fracture were established using CBCT and finite element software. The conditions were then created according to three repair methods after root canal treatment. The Von Mises equivalent stress and maximum principal stress distribution and peak value of each model were analyzed. Results: (1) In the same kind of fracture mode, the equivalent stress value of the remaining tooth tissue was: the fiber post-core-crown group was the largest and the 5 mm deep endocrown group was the smallest. The equivalent stress value of the prosthesis was: the cast post-core-crown group was the largest and the fiber post-core-crown group was the smallest. The equivalent stress peak of the bond layer of the fiber: post-core-crown group was the highest. (2) With the increase of the height of ferrule, the equivalent stress of the remaining tooth tissues was reduced, and the reduction rate of the fiber post-core-crown group and the cast post-core-crown group was larger than that of the endocrown group. When the lingual ferrule height increased, the equivalent stress reduction rate of residual tooth tissue was greater than that of the lip ferrule height. Conclusion: Complete and high enough dentin ferrule is a requirement for repairing heavily defected maxillary central incisor with fiber post-core crown and cast post-core crown. When the dentin ferrule is incomplete, lingual ferrule is better than lip ferrule to improve the fracture resistance of residual dentin.When the maxillary central incisor obliquely fractured and the ferrule is incomplete, the stress distribution of the endocrown is more excellent than post-core-crown. And the endocrown with a depth of 5 mm retainer may be the best repair method. As for post-core crown restoration, the cast post-core crown is more favorable for the uniform distribution of residual tooth tissue than the fiber post-core crown. References | Related Articles | Metrics

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Fracture Resistance of Ceramic Veneers on Mandibular Premolar with or without Preparation YIN Lu, YANG Changwei, ZHENG Yanfen, LIN Pingting, HUANG Honglan 2020, 36(3): 264-268.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.018 Abstract ( 182 )   PDF (3154KB) ( 136 )   Objective: To compare the fracture resistance of ceramic veneers and composite resin veneers with or without dental preparation. Methods: Forty freshly extracted mandibular premolars were selected and randomly assigned into four groups (n=10): NPR =no dental preparation and direct veneer with 0.2 mm thick composite resin; NPC = no dental preparation and 0.2 mm thick lithium disilicate ceramic veneer (IPS e.max Press, Ivoclar Vivadent); P2C = tooth preparation of 0.2 mm and 0.2 mm thick ceramic veneer (IPS e.max Press); and P5C = tooth preparation of 0.5 mm and 0.5 mm-thick ceramic veneer (IPS e.max Press). In all groups, the restorations covered 1 mm of the occlusal surface of the buccal cusp, and the thickness of this area was the same as the buccal area (0.2 mm or 0.5 mm). After the luting procedure, all groups were thermocycled (10,000 cycles, 5 ℃~55 ℃) and subjected to fracture resistance test under compression (Instron 4 444). The mode of failure analysis was performed under a ×10 magnification. Results: The mean fracture resistance (men ± standard deviation) was NPR =690.33±233, NPC=790.52±408, P2C=1 131.34±341, and P5C=983.56±202. There were significant differences of the fracture resistance values between all groups (P<0.05). The mean values of NPR and NPC groups were significantly lower than that of P2C. However, P5C presented intermediate values and had no significant difference from the other groups. The mode of failure for all groups was mixed (60%), cohesive failures (20%), root failures (15%), and adhesive failures (5%). Conclusion: Minimally invasive tooth preparation (0.2 mm) allowed achieving higher fracture resistance in premolars restored with lithium disilicate ceramic veneers. Attention should be given to the 0.5 mm preparation since fractures could happen at this situation. References | Related Articles | Metrics

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Comparison of Fracture Resistance of Mandibular Incisor Restored with Porcelain Veneers and All-ceramic Crowns after Root Canal Treatment CHEN Shiwei, WU Xiaohong 2020, 36(3): 269-272.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.019 Abstract ( 186 )   PDF (1822KB) ( 157 )   Objective: To compare the fracture resistance of mandibular incisor restored with porcelain veneers and all-ceramic crowns after root canal treatment. Methods: Thirty isolated mandibular incisors were selected and treated by external root canal treatment. After 3M fiber post reinforcement, they were randomly divided into three groups. The porcelain veneer group and the all-ceramic crown group were restored with IPS e.max Press. The resin filling group was directly filled with composite resin. The fracture resistances of three groups were tested with a universal material testing machine. Results: The fracture resistances of porcelain veneer group, all-ceramic crown group, and direct filling group were (439.59±56.97) N, (719.98±43.03) N, and (597.74±50.35) N, respectively (P<0.001). Conclusion: After root canal treatment, the mandibular incisors restored with all-ceramic crown had higher fracture resistance. Both all-ceramic crown and veneer can meet the requirements of clinic. References | Related Articles | Metrics

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Influence of Thickness of Core and Veneer Ceramics on Transparency of CAD/CAM Glass Ceramics ZHAO Jun, FAN Hong 2020, 36(3): 273-275.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.020 Abstract ( 237 )   PDF (756KB) ( 174 )   Objective: To explore the contrast ratio (CR) of different thickness of core and veneer of CAD/CAM glass ceramics and the color difference (ΔE) with A2 color test piece. Methods: The IPS e.max and IPS Empress CAD ceramic blocks were processed into square core porcelain with thickness of 0.8, 1.0, and 1.2 mm, respectively. The core porcelain was sintered with 0.7, 0.5, and 0.3 mm veneer porcelain, and finally glazed. A total of 30 porcelain specimens with 12×12 mm and 1.5 mm in the thickness were made (n=5). CM-3600A spectrophotometer was used to measure the color parameters of the specimens, which was used to calculate the CR of the specimens and the ΔE with A2 color test piece. Results: The CR value of IPS e.max CAD group was significantly higher than that of IPS Empress CAD group. The ΔE value of IPS e.max CAD group was less than that of IPS Empress CAD group. Conclusion: IPS e.max CAD and IPS Empress CAD can better simulate the target color with different thickness of core and veneer. The transparency of IPS Empress CAD is higher than that of IPS e.max CAD. References | Related Articles | Metrics

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Micro CT Evaluation of Microleakage in Composites Resin Cured by Various Light Curing Modes ZHAO Yan, JIN Chenxin 2020, 36(3): 276-279.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.021 Abstract ( 157 )   PDF (1166KB) ( 152 )   Objective: To evaluate the effects of different light modes on microleakage of composite resin filling by Micro CT. Methods: Twenty-four freshly extracted maxillary premolars were collected. Circular cavity(diameter 1mm, depth 1mm) were prepared on the buccal surface of the crown. The cavity was filled with composite resin (3M Z250) and cured by light curing. According to the light curing mode, they were randomly divided into three groups: conventional model group (group A), soft-start light group (group B), and intermittent light group (group C). After thermal cycling and 50% ammoniacal silver nitratesolution staining, the volume of silver deposit at the tooth-restoration interface were scanned by micro CT, and the degree of microleakage was evaluated quantitatively. Results: The microleakage in the conventional light group was significantly higher than that in the soft-start light group and the intermittent light group (P<0.05), but there was no statistical differences between the soft-start light group and the intermittent light group (P<0.05). Conclusion: The soft-start light mode and intermittent light mode can reduce the microleakage of composite resin (3M Z250) more effective than the conventional light mode. References | Related Articles | Metrics

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Comparison of n-HA/PLA/PVA Composite Membranes Prepared by 3D Printing with Different Weight Ratios QIAO Geng, LIU Jiayi, WANG Yuan, WANG Zhenhua 2020, 36(3): 280-286.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.022 Abstract ( 235 )   PDF (4707KB) ( 205 )   Objective: To prepare and test nano-hydroxyapatite/polylactic acid/polyvinyl alcohol (n-HA/PLA/PVA) composite membranes with different weight ratios. Methods: 3D printing technology was used to prepare n-HA/PLA/PVA composite membranes with different weight ratios, namely PLA/PVA composite membrane, 15% n-HA/PLA/PVA composite membrane, 50% n-HA/PLA/PVA composite membrane, and 75% n-HA/PLA/PVA composite membrane. The membrane morphology was observed with scanning electron microscope (SEM), the mechanical properties, cytotoxicity, and corresponding indices in animal experiments were detected. Results: SEM showed that the n-HA/PLA/PVA composite membrane exhibited a three-dimensional network structure, the materials were combined with each other, the distribution of pore was uneven, and the size was different. With the increase of the mass concentration of n-HA, the porosity between the materials was gradually reduced, and a composite membrane with uniform structure was formed. In the test of mechanical properties and water absorption, the tensile strength and water absorption of n-HA/PLA/PVA composite membranes decreased with the increase of n-HA. The cytotoxicity test showed no cytotoxicity and no significant difference in the cell proliferation rate of different proportions of composite membranes. It was found that there was no statistically difference in the ratios of n-HA/PLA/PVA composite membranes by measured periodontal plaque index and sulcus bleeding index in animal experiments. Conclusion: 3D printing n-HA/PLA/PVA composite membranes with different ratios have good physical properties and cell biocompatibility. Composite membranes with higher n-HA ratio may have better physical properties and biocompatibility. References | Related Articles | Metrics

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Retrospective Analysis of 76 Cases of Anterior Teeth Restored by CEREC with Different Design Patterns HAN Yanfeng, JIANG Qingsong, ZHENG Dongxiang 2020, 36(3): 287-292.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.023 Abstract ( 158 )   PDF (2825KB) ( 189 )   Objective: To explore the application of veneer made by CEREC with different design patterns in the anterior area. Methods: The clinical data of 76 patients who underwent anterior veneer restoration were retrospectively analyzed. 190 veneers were made using CEREC AC system. Different design modes were chosen according to actual situation of the tooth defect. The design pattern, processing time, patients’ satisfaction degree, and clinical success rate after 6 months, 12 months, and 24 months were compared. Results: Of all the 190 porcelain veneers, 84 use copy mode, 50 use reference mode, and 56 use individual design patterns. The restoration design and processing time of the replication mode was shorter than the reference mode and the personalized mode (P<0.001), and the reference mode was shorter than the personalized mode (P<0.001). There was no significant difference in the satisfaction scores of VAS repair between different design patterns at different follow-up time (P>0.05). After 6 months, the success rates of replication mode, reference mode, and personalized mode were 97.62%, 98.00%, and 94.64%, respectively. The success rates after 12 months were 97.62%, 96.00%, and 92.86%, respectively. The success rates after 24 months were 96.43%, 94.00%, and 92.86%, respectively (P>0.05). Conclusion: All the porcelain veneers made by different design modes of CEREC AC system have good aesthetic effect and high clinical success rate. The copy mode can accurately copy the bite, and the design and processing time are relatively shorter, which can be used as the first choice. References | Related Articles | Metrics

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Clinical Application of “Sandwich” Osteotomy for Implant Restoration at Deficient Anterior Alveolar Ridges LI Ailing, ZHOU Hong 2020, 36(3): 293-297.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.024 Abstract ( 250 )   PDF (2695KB) ( 240 )   Objective: To evaluate the final vertical gain at the deficient anterior alveolar ridges using “sandwich” osteotomy. Methods: Six patients with severe vertical bone defects at deficient anterior alveolar ridges were treated with “sandwich” osteotomy bone augmentation and 9 implants were placed after 6 months. The final restorations were delivered 3 months later. Results: The final vertical gain was 4.10 mm (3.70-4.40 mm), which was statistically significant (P<0.05). The average bone resorption after loading for 1 year was 0.3 mm. Nine implants were successfully completed and the restorations achieved satisfactory aesthetics. Conclusion: “Sandwich” osteotomy has got good aesthetic effect at anterior and is a safe and reliable bone augmentation technique. References | Related Articles | Metrics

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Evaluation of Screw-tent Technique for Dental Implants in the Upper Anterior Region with Continuous Adjacent Teeth Missing GUO Yudong, ZHOU Lian 2020, 36(3): 298-301.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.025 Abstract ( 210 )   PDF (4489KB) ( 155 )   Objective: To evaluate the clinical effect of screw-tent technique for dental implants in the upper anterior region with continuous adjacent teeth missing. Methods: Screw-tent technique was used in 9 patients with severe atrophic alveolar ridge in the upper anterior regions,followed with implants placement 6 months later. The final restorations were made 6 months later. The patient had been followed periodically for 12 months to evaluate the clinical outcomes. Results: A total of 21 implants were implanted in 9 patients without implant loose or lost. The widths of alveolar ridge were (2.41 +0.49) mm before operation, (8.27 +0.79) mm 6 months after bone augmentation, and (7.74+0.52) mm 12 months after restoration. There was significant difference between them (P<0.05). Conclusion: Screw-tent technique was a predictable method to augment alveolar ridge in partial edentulous cases with continuous adjacent teeth missing and severe resorbed ridges. However, long-term clinical outcomes remain to be observed. References | Related Articles | Metrics

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Application of PDCA Cycle Combined with Mini-Cex Scale in Quality Management of Complete Crown Treatment for Oral Residents HAO Pengjie, LIU Li, LIU Zhonghao 2020, 36(3): 302-304.  DOI: 10.13701/j.cnki.kqyxyj.2020.03.026 Abstract ( 177 )   PDF (871KB) ( 193 )   Objective: To investigate the effect of PDCA cycle combined with Mini-Cex scale in the quality management of complete crown treatment for oral residents. Methods: The PDCA cycle was applied to the standardized training of the residents in the treatment of complete crown. The clinical ability of the residents who participated in the training was evaluated by the Mini-Cex scale. Results: A total of 30 passengers were assessed, the qualified and excellent rates of residents were improved before and after training in the four parts, including clinical technique, tooth preparation, provisional crown making, and impression making (P<0.05). Conclusion: PDCA cycle combined with Mini-Cex scale is an effective way to evaluate and improve the effect of residency training. References | Related Articles | Metrics