The problems caused by proximal contact loss(PCL)of dental implants have been a mainstream research topic in recent years,and scholars are unanimously committed to analyzing their causes and related factors,aiming to identify solutions to the problems related to PCL.The effects of the anterior component of force(ACF),the lifelong re-molding of the adult craniofacial jaw and alveolar socket,and the osseointegration characteristics of dental implants are the main causes of PCL.On the one hand,the closing movement of the mandible causes the ACF of the tooth to move through the posterior molar cusp.Moreover,drifting between the upper and lower posterior teeth and mandibular anteri-or teeth can cause the anterior teeth of the upper and lower jaws to be displaced labially.On the other hand,reconstruc-tion of the jaw,alveolar socket and tooth root,the forward horizontal force of the masticatory muscles,the dynamic com-ponent of the jaw and the forward force generated by the oblique plane of the tooth cusp can cause the natural tooth to experience near-middle drift.Additionally,natural teeth can shift horizontally and vertically and rotate to accommodate remodeling of the stomatognathic system and maintain oral function.Nevertheless,the lack of a natural periodontal mem-brane during implant osseointegration,the lack of a physiological basis for near-medium drift,the small average degree of vertical motion and the integrated silence of dental implants without the overall drift characteristics of natural teeth increases the probability of PCL.The high incidence of PCL is clearly associated with the duration of prosthesis delivery and the mesial position;but it is also affected by the magnitude of the bite force,occlusion,the adjacent teeth,restora-tion design,implant location,jaw,and patient age and sex.PCL has shown a significant correlation with food impaction,but not a one-to-one correspondence,and did not meet the necessary and sufficient conditions.PCL is also associated with peri-implant lesions as well as dental caries.PCL prevention included informed consent,regular examinations,se-lection of retention options,point of contact enhancement,occlusal splints,and the application of multipurpose digital crowns.Management of the PCL includes adjacent contact point additions,orthodontic traction,and occlusal adjust-ment.Existing methods can solve the problem of food impaction in the short term with comprehensive intervention to seek stable,long-term effects.Symmetric and balanced considerations will expand the treatment of issues caused by PCL.

Periodontitis is an infectious disease caused by an imbalance between the local microbiota and host immune response. Epidemiologically, periodontitis is closely related to the occurrence, development, and poor prognosis of T2D and is recognized as a potential risk factor for T2D. In recent years, increasing attention has been given to the role of the virulence factors produced by disorders of the subgingival microbiota in the pathological mechanism of T2D, including islet β-cell dysfunction and insulin resistance (IR). However, the related mechanisms have not been well summarized. This review highlights periodontitis-derived virulence factors, reviews how these stimuli directly or indirectly regulate islet β-cell dysfunction. The mechanisms by which IR is induced in insulin-targeting tissues (the liver, visceral adipose tissue, and skeletal muscle) are explained, clarifying the influence of periodontitis on the occurrence and development of T2D. In addition, the positive effects of periodontal therapy on T2D are overviewed. Finally, the limitations and prospects of the current research are discussed. In summary, periodontitis is worthy of attention as a promoting factor of T2D. Understanding on the effect of disseminated periodontitis-derived virulence factors on the T2D-related tissues and cells may provide new treatment options for reducing the risk of T2D associated with periodontitis.
Humans ; Diabetes Mellitus, Type 2/complications* ; Periodontitis

Recently, the dental application of nano materials has made progress in clinical treatment, such as implant surface modification as well as antibacterial, and controlled release. However, the active physical and chemical properties of nanomaterials may pose a potential safety risk in humans. Dental nanomaterials used for oral application can be released into the blood through a variety of mechanisms, and they can penetrate the blood-brain barrier and enter the central nervous system. Moreover, nanomaterials can also directly affect the central nervous system through the olfactory nerve and via sensory nerve terminal transport, causing organic and functional damage to central nerves, and even causing neurotoxicity during embryo development. Nanomaterials can interact with biomolecules such as cells, genes, and proteins in the body, and can produce neurotoxicity through the mechanisms of inducing oxidative stress, inflammatory responses, cell autophagy, apoptosis, genotoxicity, etc. Factors affecting the toxicity of nanomaterials include particle size, concentration, and solubility. Dental nanomaterials and their pathways into the central nervous system, as well as the mechanisms that may cause neurotoxicity, will be discussed on this review.

Objective:To compare the maxillary sinus mucosa's stress distribution when elevated by three lift materials.Methods:Three Finite element models of maxillary sinus mucosa with 0.3 mm thickness elevated by implant,grafting autogenous cancellous bone and hydroxyapatite respectively were established in the specific units.ANSYS finite element analysis software was used to evaluate maxillary sinus mucosa deformation by the simulated closed sinus lift surgery.Differences of Von Mises stress values of mucosa surface were calculated when maxillary sinus mucosa lift height was increased from 1 mm to 5 mm according to the a large deformation theory. Results:The Von Mises stress values on membrane surface elevated by implant,grafting autogenous cancellous bone and hydroxyapa-tite bone substitute materials showed no difference within 5 mm elevation.Conclusion:Closed maxillary sinus floor lifting operation with implant elevating the maxillary sinus membrane directly is a simple and minimally invasive way for sinus floor elevation.

BACKGROUND:How to avoid iatrogenic maxil ary sinus mucosal perforation after closed maxil ary sinus augmentation.
OBJECTIVE:To compare the influence of maxil ary sinus mucosa at different thicknesses on the mucosal perforation in closed maxil ary sinus augmentation operation by using finite element analysis.
METHODS:Three finite element models of maxil ary sinus mucosa at different thicknesses of 0.3 mm, 0.5 mm, 0.8 mm respectively and implant with 4.2 mm diameter were established in the SHELL63 units. ANSYS finite element analysis software was used to evaluate maxil ary sinus mucosal deformation by the simulated closed maxil ary sinus augmentation surgery. Differences of Von Mises maximum stress values of mucosa surface were calculated according to the non-linear large-deformation theory.
RESULTS AND CONCLUSION:When maxil ary sinus mucosa height was increased from 1 mm to 5 mm, the large deformation was observed in the center of mucosa center. The maximum stress curve slope was shifted mild between 1-4 mm deformation, while shifted abruptly after 4 mm. There was no difference in the value of Von Mises maximum stress values between three maxil ary sinus mucosa at 0.3 mm, 0.5 mm, 0.8 mm thickness, when the lift height was increased from 1 mm to 5 mm (P>0.05). Maxil ary sinus mucosa are faced with a higher risk of mucosal perforation and elastic elongation when maxil ary sinus height is increased more than 4 mm. Maxil ary sinus mucosa at 0.3-0.8 mm thickness are faced the similar risk of mucosal perforation in closed maxil ary sinus augmentation operation within 5 mm. While more considerations should be paid on patients with less than 0.3 mm maxil ary sinus mucosa thickness.

Objective To research the efficiency of interactive teaching combined with group discussion in prosthodontics course. Methods Totally 40 stomatology students of 2009 grade were divid-ed into 2 groups by stratified random sampling , 6 males and 14 females in each group. Students in con-trol group were taught by traditional teaching method while those in the test group were taught by interac-tive teaching method during prosthodontics course. Knowledge lectures and cases discussion in interactive teaching method were distributed as ratio of 3∶1 in class time , and network interactive teaching was car-ried out after class. Exam was taken after the course, which included single choices(80 questions, 80 points), true or false questions(20 questions, 20 points) and case analysis(5 questions, 50 points). Full marks of the exam was 150 points and exam time was 150min. Then questionnaire survey was carried out, which included the students' interest in learning and cognition of learning difficulty. Exam scores were statistically analyzed by two sample t-test(α=0.05) and the questionnaire survey results were statistically analyzed by Mann-Whitney U test(α=0.05). Results Average scores were(109.22±8.22) in control group and(126.28±8.72) in test group, with statistical differences(F=1.1254, P=0.000). There were statistical differences between control group and test group in studying interest(Z=-2.869, P=0.004) and difficulty(Z=-2.711, P=0.007). Conclusions Initiative, thinking capacity and scores can be enhance by interactive teaching method which is more efficiently than traditional teaching method.

OBJECTIVETo investigate the influence of background color on veneered In-Ceram and Cercon dental ceramics including Vita In-Ceram Electroformed Alumina (AL2), Electroformed Zirconia (Z21), Cercon base color Zirconia and Cercon base Zirconia.

METHODSThe colorimetric values of all the materials on noble metal, Ni-Cr alloy, silver amalgam and resin background were measured with a spectrocolorimeter, and the color difference among the groups was calculated.

RESULTSAfter veneered, the color difference of Z21 Electroformed Zirconia was more distinct against the background of silver amalgam than against the backgrounds of noble metal and resin, but the color differences of the 4 veneered dental ceramics against different backgrounds were unidentifiable by human eyes (δE<1.5).

CONCLUSIONAfter veneered, AL2 electroformed alumina, Z21 electroformed zirconia, Cercon base Zirconia and Cercon base color Zirconia are less influenced by the background color, and covering the background color is therefore not necessary.

A questionnaire survey was conducted among undergraduate international students to investigate the effects of stomatology teaching.The effects of stomatology teaching had been proved to be fair, while some shortcomings had also emerged. In further teaching adjustments have to be made to teaching plans and teachers' Enghsh abilities are expected to be improved.

Objective: To evaluate the corrosion resistance of Ni-Cr alloy with different coatings in neutral and acid saliva by electrochemistry method. Methods: Measured the self-corrosion potential (Ecorr) and polarization resistance(Rp) curves of Ni-Cr alloy models with different coatings in neutral and acid artificial salivas. Results: The Ecorr of the Ni-Cr alloys all showed positive values, the electrochemistry corrosion and galvanic corrosion were not detected. Conclusion: Ni-Cr alloy with titanium nitride coating, gold electroplating coating, gold-paste layer and gold-porcelain blended layer have both anti-corrosion and esthetical function without changing its own property.

0.05) respectively. Conclusion: The SY 1 silicon elastomer have suitable physical, mechanical and anti ozone aging properties.