Three-dimensional finite element analysis on stress distribution after different palatoplasty and levator veli palatini muscle reconstruction.

OBJECTIVES: To establish a three-dimensional finite element model of the upper palate, pharyngeal cavity, and levator veli palatini muscle in patients with unilateral complete cleft palate, simulate two surgical procedures that the two-flap method and Furlow reverse double Z method, observe the stress distribution of the upper palate soft tissue and changes in pharyngeal cavity area after different surgical methods, and verify the accuracy of the model by reconstructing and measuring the levator veli palatini muscle. MATERIALS AND METHODS: Mimics, Geomagic, Ansys, and Hypermesh were applied to establish three-dimensional finite element models of the pharyngeal cavity, upper palate, and levator veli palatini muscle in patients with unilateral complete cleft palate. The parameters including length, angle, and cross-sectional area of the levator veli palatini muscle etc. were measured in Mimics, and two surgical procedures that two-flap method and Furlow reverse double Z method were simulated in Ansys, and the area of pharyngeal cavity was measured by hypermesh. RESULTS: A three-dimensional finite element model of the upper palate, pharyngeal cavity, and bilateral levator veli palatini muscle was established in patients with unilateral complete cleft palate ; The concept of horizontal projection characteristics of the palatal dome was applied to the finite element simulation of cleft palate surgery, vividly simulating the displacement and elastic stretching of the two flap method and Furlow reverse double Z method during the surgical process; The areas with the highest stress in the two-flap method and Furlow reverse double Z method both occur in the hard soft palate junction area; In resting state, as measured, the two flap method can narrow the pharyngeal cavity area by 50.9%, while the Furlow reverse double Z method can narrow the pharyngeal cavity area by 65.4%; The measurement results of the levator veli palatini muscle showed no significant difference compared to previous studies, confirming the accuracy of the model. CONCLUSIONS: The finite element method was used to establish a model to simulate the surgical procedure, which is effective and reliable. The area with the highest postoperative stress for both methods is the hard soft palate junction area, and the stress of the Furlow reverse double Z method is lower than that of the two-flap method. The anatomical conditions of pharyngeal cavity of Furlow reverse double Z method are better than that of two-flap method in the resting state. CLINICAL RELEVANCE: This article uses three-dimensional finite element method to simulate the commonly used two-flap method and Furlow reverse double Z method in clinical cleft palate surgery, and analyzes the stress distribution characteristics and changes in pharyngeal cavity area of the two surgical methods, in order to provide a theoretical basis for the surgeon to choose the surgical method and reduce the occurrence of complications.

Multipoint stable radio frequency long distance transmission over fiber based on tree topology, with user fairness and deployment flexibility.

In this paper, we propose a multipoint stable radio frequency (RF) optical transmission system with tree structure. Based on the principle of phase conjugation, the phase jitter induced by environment variation can be compensated by frequency mixing. Different from other schemes, the RF signal is modulated on a optical comb at local and each tooth is grouped with a near subcarrier for a user. By using wavelength division multiplexer, these groups are separated and transmitted to the multiple points over fiber. Therefore, the degradation of compensation performance caused by the wavelength difference between the common main carrier and farther subcarrier can be avoided, and the accumulated power loss induced by the branch points will be significantly reduced. In addition, an acousto-optic modulator is used at the local station to depress the impact of Rayleigh scattering. Experimentally, we demonstrate 2.4 GHz RF signal transmission to the two users over 25 and 100 km fiber during 1 × 104 seconds, and the phase jitter mean square errors are 2.50 × 10-2 and 4.27 × 10-2 rad, respectively.

The Protective Effects of the A/ZJU01/ PR8/2013 Split H7N9 Avian Influenza Vaccine Against Highly Pathogenic H7N9 in BALB/c Mice.

BACKGROUND/AIMS: Since the first case of novel H7N9 infection was reported, China has experienced five epidemics of H7N9. During the fifth wave, a highly pathogenic H7N9 strain emerged. In order to assess whether the H7N9 vaccine based on A/Zhejiang/DTID-ZJU01/2013(H7N9) was effective in protecting against highly pathogenic H7N9, we conducted this study. METHODS: Groups of mice were immunized twice by intraperitoneal injection with 500 µl of either split vaccine alone or MF59-adjuvanted vaccine. Serum was collected 2 weeks after the second vaccine booster. The hemagglutinin inhibition test was conducted on vaccine seed and highly pathogenic H7N9 to evaluate the neutralization of highly pathogenic H7N9. We also immunized mice and challenged them with highly pathogenic H7N9. Mice were observed for illness, weight loss, and death at 1 week and 2 weeks post-infection. Then, the mice were sacrificed and lungs were removed. Antibody responses were assessed and pathological changes in the lung tissue were evaluated. RESULTS: The ability of serum to neutralize highly pathogenic H7N9 was reduced. In mice, highly pathogenic H7N9 was more virulent than A/Zhejiang/DTID-ZJU01/2013(H7N9). After challenge with highly pathogenic H7N9, all mice died while mice challenged with A/Zhejiang/DTID-ZJU01/2013(H7N9) all recovered. The A/ZJU01/PR8/2013 split H7N9 avian influenza vaccine was able to protect against infection with highly pathogenic H7N9 in mice, with or without MF59. Moreover, H7N9 vaccine adjuvanted with MF59 produced high antibody levels, which lead to better protection. CONCLUSIONS: The A/ZJU01/PR8/2013 split H7N9 avian influenza vaccine based on A/Zhejiang/DTID-ZJU01/2013(H7N9) is effective in protecting against highly pathogenic H7N9. H7N9 vaccine adjuvanted with MF59 offers better protection against infection with highly pathogenic H7N9. In order to make the H7N9 vaccine applicable to humans, further clinical trials are required to evaluate MF59 adjuvanted vaccine. Meanwhile, the vaccine strain should be updated based on the highly pathogenic H7N9 gene sequence.

Early Healing of Immediate Implants Connected With Two Types of Healing Abutments: A Prospective Cohort Study.

PURPOSE: To compare hard- and soft-tissue changes around immediate implants connected with 2 types of healing abutments during the early phases of healing. MATERIALS AND METHODS: Twenty-eight immediate implants were placed into molar/premolar sockets through a modified osteotomy method. The gaps around implants were grafted with deproteinized bovine bone mineral. According to the size of the alveoli, the implants were connected with titanium healing abutments (traditional group) or customized healing abutments (CA group). Radiographic and intraoral examinations were performed before surgery, postoperatively, and at the 6-month recall. RESULTS: Buccal (P = 0.717) and lingual (P = 0.087) vertical bone loss was comparable between groups. More significant incomplete defect fill was found at the distal aspect of the CA group (P = 0.000). The buccal bone thickness alterations were similar between the 2 groups (P = 0.902 at the implant platform). The mid-facial soft-tissue level was well maintained in both groups. CONCLUSIONS: Within the limitations of this study, for immediate implants placed into posterior sockets, customized healing abutments can facilitate closure of large sockets. Despite more pronounced incomplete defect fill, healing abutments consisting of polyether ether ketone and resin did not render an increased risk for periimplant bone loss or soft-tissue recession during the early healing period.

Dual-Physical Cross-Linked Tough and Photoluminescent Hydrogels with Good Biocompatibility and Antibacterial Activity.

Development of novel photoluminescent hydrogels with toughness, biocompatibility, and antibiosis is important for the applications in biomedical field. Herein, novel tough photoluminescent lanthanide (Ln)-alginate/poly(vinyl alcohol) (PVA) hydrogels with the properties of biocompatibility and antibiosis have been facilely synthesized by introducing hydrogen bonds and coordination bonds into the interpenetrating networks of Na-alginate and PVA, via approaches of frozen-thawing and ion-exchanging. The resultant hydrogels exhibit high mechanical strength (0.6 MPa tensile strength, 5.0 tensile strain, 6.0 MPa compressive strength, and 900 kJ m-3 energy dissipation under 400% stretch), good photoluminescence as well as biocompatibility and antibacterial activity. The design strategy provides a new avenue for the fabrication of multifunctional photoluminescent hydrogels based on biocompatible polymers.

Recent Development of Implantable Chemical Sensors Utilizing Flexible and Biodegradable Materials for Biomedical Applications.

Implantable chemical sensors built with flexible and biodegradable materials exhibit immense potential for seamless integration with biological systems by matching the mechanical properties of soft tissues and eliminating device retraction procedures. Compared with conventional hospital-based blood tests, implantable chemical sensors have the capability to achieve real-time monitoring with high accuracy of important biomarkers such as metabolites, neurotransmitters, and proteins, offering valuable insights for clinical applications. These innovative sensors could provide essential information for preventive diagnosis and effective intervention. To date, despite extensive research on flexible and bioresorbable materials for implantable electronics, the development of chemical sensors has faced several challenges related to materials and device design, resulting in only a limited number of successful accomplishments. This review highlights recent advancements in implantable chemical sensors based on flexible and biodegradable materials, encompassing their sensing strategies, materials strategies, and geometric configurations. The following discussions focus on demonstrated detection of various objects including ions, small molecules, and a few examples of macromolecules using flexible and/or bioresorbable implantable chemical sensors. Finally, we will present current challenges and explore potential future directions.

Innovative principle of implant-oriented fibula placement in mandibular reconstruction using double-barrel fibula and simultaneous implants: A technical note.

Simultaneous or secondary inserted implants with double-barrel fibula to reconstruct the mandible have become a common method. However, difficulties in later restoration caused by placement errors of fibula or incipiently placed implants have also been reported in some studies. This note describes a novel technique of implant-oriented guide plates helpful for mandible ablation, fibula segmentation and positioning, and implant placement. We design a series of guide plates especially an implant-fibula placing guide plate, and record and fix the relative spatial positions of the remaining teeth, the simultaneous implants and upper fibula. During surgery, the placement of upper fibula is oriented towards appropriate placement of implants. Therefore, the position of upper fibula can meet the requirements of simultaneous implant as much as possible. Within the limits of present observation, we believe that this technique may increase the manipuility while reducing the errors and the risk of complications.

Vascularized fascial flap for reconstruction of combined oral mucosa-mandibular defects: The multi-modal biological assessment.

OBJECTIVE: The reconstruction of composite defects in the oral and maxillofacial region using vascularized fascial flaps, such as the fibular, iliac, and temporal fascial flaps, has gained increasing attention among surgeons. However, there remains uncertainty regarding the suitability of fascial flaps as transplants, as well as their healing processes and outcomes, due to their non-mucosal nature. This study aims to comprehensively assess the biological aspects of vascularized fascial flaps at clinical, histological, and genetic levels, with the goal of providing essential biological references for their clinical application. STUDY DESIGN: This study enrolled three patients who underwent reconstruction of combined oral mucosa-mandibular defects using fibular vascularized fascial flaps between 2020 and 2023. Data regarding changes in the appearance of the fascial flaps, bulk-RNA sequencing, and histological slices of initial fascia, initial gingiva, and transformed fascia were collected and analyzed. RESULTS: Within three months, the fascial flaps exhibited rapid epithelial coverage and displayed distinct characteristics resembling mucosa. High-throughput RNA sequencing analyses and histological slices revealed that the transformed fascia exhibited tissue structures similar to mucosa and demonstrated unique advantages in promoting blood vessel formation and reducing scarring through the high-level expression of relevant genes. CONCLUSION: These findings emphasize the potential and feasibility of utilizing vascularized fascial flaps for oral mucosa reconstruction, establishing their unique advantage as transplant materials, and providing significant biological information and references for their selection and clinical application.

Fluorescence assay for glycan expression on living cancer cells based on competitive strategy coupled with dual-functionalized nanobiocomposites.

Cell surface glycans are a class of sophisticated biomolecules related to cancer development and progression, and their analysis is of great significance for early cancer diagnosis and treatment. In this paper, we proposed a fluorescence assay to evaluate glycan expression on living cancer cells based on a competitive strategy coupled with dual-functionalized nanobiocomposites. The competitive assay was conducted between living cancer cells and thiomannosyl derivatives using concanavalin A (Con A)-modified electrode as the interaction platform. To impart fluorescence signaling ability to competitive derivatives, quantum dots (QDs) were anchored on BSA-protected Au nanoparticles, and thiomannosyl derivatives were further immobilized on the nanoparticle surface through Au-S binding. Due to the spacing between QDs and Au nanoparticles by BSA, the {QDs-Au-BSA-mannose} nanobiocomposites maintained the fluorescence of QDs and showed binding ability with the Con A-modified electrode. Au nanorods (AuNRs)-modified electrode was used as an effective substrate to immobilize Con A. This assay was successfully applied to the analysis of two cancer cells lines (A549 and QGY-7701). The method is simple and shows promise for the study of glycan expression on living cancer cells.

Periodontitis as a promoting factor of T2D: current evidence and mechanisms.

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 ß-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 ß-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.

The clinical effect of the digital guide in the early implant restoration of second molars.

BACKGROUND: In the absence of contraindications to implants, implant repair is the preferred method to treat mandibular second molar loss. OBJECTIVE: To compare the clinical effects of a traditional implant guide and digital implant guide in the early implant restoration of second molars. METHODS: The study included 35 patients with second molar loss randomly divided into two groups. Eighteen patients in the experimental group had an implant procedure using a computer-aided design/computer-assisted manufacturing (CAD/CAM) digital implant guide, and 17 patients in the control group had the procedure using a traditional film pressing implantation guide. Then, the surgical procedure was completed using the two different implant guides. At 3 months after surgery, four parameters including screw hole exit position, coronal deviation of the implant site, disease improvement rate, and clinical effects, which included marginal adaptation, anatomic form, marginal discoloration, postoperative sensitivity, surface roughness, and secondary caries of the upper prosthesis were compared between the two groups. RESULTS: The screw hole exit position in the experimental group was directed to the functional cusp of the opposite jaw, and there was a statistically significant difference between the two groups. There was no statistically significant difference in the rate of disease improvement and the clinical effect of the upper prosthesis between the two groups. There was no statistically significant difference in the bilateral coronal deviation and deviation direction of implants in the two groups. The bilateral coronal deviation of the experimental group was smaller than that of the control group. CONCLUSION: The digital implant guide can effectively reduce the deviation of the screw hole and the upper prosthesis in the restoration of the second molar. The prosthesis used in the experimental group had a good clinical outcome, which provides a theoretical basis for the restoration of the posterior molar.

Tracing immune cells around biomaterials with spatial anchors during large-scale wound regeneration.

Skin scarring devoid of dermal appendages after severe trauma has unfavorable effects on aesthetic and physiological functions. Here we present a method for large-area wound regeneration using biodegradable aligned extracellular matrix scaffolds. We show that the implantation of these scaffolds accelerates wound coverage and enhances hair follicle neogenesis. We perform multimodal analysis, in combination with single-cell RNA sequencing and spatial transcriptomics, to explore the immune responses around biomaterials, highlighting the potential role of regulatory T cells in mitigating tissue fibrous by suppressing excessive type 2 inflammation. We find that immunodeficient mice lacking mature T lymphocytes show the typical characteristic of tissue fibrous driven by type 2 macrophage inflammation, validating the potential therapeutic effect of the adaptive immune system activated by biomaterials. These findings contribute to our understanding of the coordination of immune systems in wound regeneration and facilitate the design of immunoregulatory biomaterials in the future.

OPG gene-modified adipose-derived stem cells improve bone formation around implants in osteoporotic rat maxillae.

Background: Osteoporosis is a significant barrier to the use of dental implants in the elderly for the treatment of tooth defects. Adipose derived stem cells (ADSCs) have demonstrated extensive potential for tissue repair and regeneration. The present study aimed to investigate the effectiveness of ADSCs engineered to express high levels of osteoprotegerin (OPG) for the treatment of bone loss in implant dentistry caused by estrogen deficiency. Methods: A rat model of osteoporosis was established through double oophorectomy, and the rats were treated by gene modified cells Adv-OPG-ADSCs. The effects of the treatment on maxilla tissue changes were evaluated using HE staining and micro-CT. Additionally, ALP and TRAP staining were used to assess osteoblast and osteoclast alterations. Finally, the changes in related osteoblast and osteoclast indicators were measured by RT-qPCR, Western blot, and ELISA. Results: The successfully generated high-OPG-expressing ADSCs led to increase of cell viability, proliferation, and osteoblast differentiation. Treatment with Adv-OPG-ADSCs significantly ameliorated maxillary morphology, trabecular volume reduction, and bone mineral density decline in the model of estrogen-deficient maxillary implant dentistry. Furthermore, the treatment was beneficial to promoting the generation of osteoblasts and inhibiting the generation of osteoclast. Adv-OPG-ADSCs increased OPG, ALP, OCN, and Runx-2 expressions in the maxilla while suppressing RANKL expression, and also increased the concentration of COL I and PINP, as well as decreased the concentration of CTX-1. Conclusion: Adv-OPG-ADSCs promote the formation of osteoblasts and inhibit the generation of osteoclasts, thereby inhibiting bone absorption, facilitating bone formation, and promoting the repair of maxillary bone after dental implantation in the presence of osteoporosis-related complications, especially in the setting of estrogen deficiency, providing scientific basis for the application of Adv-OPG-ADSCs in the treatment of implant related osteoporosis.

Immunomodulatory Biomaterials and Emerging Analytical Techniques for Probing the Immune Micro-Environment.

After implantation of a biomaterial, both the host immune system and properties of the material determine the local immune response. Through triggering or modulating the local immune response, materials can be designed towards a desired direction of promoting tissue repair or regeneration. High-throughput sequencing technologies such as single-cell RNA sequencing (scRNA-seq) emerging as a powerful tool for dissecting the immune micro-environment around biomaterials, have not been fully utilized in the field of soft tissue regeneration. In this review, we first discussed the procedures of foreign body reaction in brief. Then, we summarized the influences that physical and chemical modulation of biomaterials have on cell behaviors in the micro-environment. Finally, we discussed the application of scRNA-seq in probing the scaffold immune micro-environment and provided some reference to designing immunomodulatory biomaterials. The foreign body response consists of a series of biological reactions. Immunomodulatory materials regulate immune cell activation and polarization, mediate divergent local immune micro-environments and possess different tissue engineering functions. The manipulation of physical and chemical properties of scaffolds can modulate local immune responses, resulting in different outcomes of fibrosis or tissue regeneration. With the advancement of technology, emerging techniques such as scRNA-seq provide an unprecedented understanding of immune cell heterogeneity and plasticity in a scaffold-induced immune micro-environment at high resolution. The in-depth understanding of the interaction between scaffolds and the host immune system helps to provide clues for the design of biomaterials to optimize regeneration and promote a pro-regenerative local immune micro-environment.

Effect of perioperative cognitive behavioral interventions on pain, anxiety, and sleep quality in elderly patients after sinus floor elevation and immediate implantation: A randomized controlled trial.

BACKGROUND: Sinus floor elevation and immediate dental implantation are commonly performed to treat dentition defects in elderly patients. Targeted cognitive behavioral interventions (CBI) during the perioperative period can reduce pain and anxiety as well as improve sleep quality. This can lead to improvements in patient cooperation during follow-up treatment and enhance the overall efficacy of the surgery. OBJECTIVE: The study aimed to investigate the impact of a cognitive behavioral intervention method on perioperative pain, anxiety, and sleep quality in elderly patients undergoing sinus floor elevation and immediate dental implantation. METHODS: Forty patients who required the treatment at the Stomatology Clinic in our hospital between December 2018 and December 2022 were enrolled in this randomized controlled trial. The patients were randomly divided into two groups: a control group (n= 20), which received conventional treatment and care during the perioperative period, and an intervention group (n= 20), which received comprehensive behavioral intervention in addition to the conventional treatment and care during the perioperative period. The perioperative anxiety, pain, and sleep quality of the patients in both groups were evaluated. Anxiety was assessed using the Self-Rating Anxiety Scale (SAS), sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), and pain was measured using the visual analog scale (VAS). RESULTS: No statistically significant differences in SAS and PSQI were observed between the two groups at the initial visit; the values were significantly higher than those measured postoperatively. The SAS scores and PSQI of patients on days 0 and 7 post-surgery in the intervention group were significantly lower than those in the control group (P< 0.05). CONCLUSION: Perioperative cognitive behavioral intervention can effectively improve anxiety, postoperative pain and sleep quality in elderly patients who have undergone sinus floor elevation and immediate dental implantation, thereby reducing the incidence of complications.

The effect of motivational interviewing based on the transtheoretical model on oral cleaning behavior of patients with periodontitis who have undergone implant restoration.

BACKGROUND: Implant-restored patients with periodontitis have a higher risk of developing peri-implantitis, and helping them develop oral cleaning habits is significant. OBJECTIVE: To evaluate the effectiveness of motivational interviewing based on the transtheoretical model on the modification of oral cleaning behaviors of implant-restored patients with periodontitis. METHODS: Patients with periodontitis (n= 70) who would receive dental implant treatment were included. And they were randomly divided into two groups: experimental (n= 35) and control (n= 35). Control patients received routine oral hygiene education, and those in the experimental group received motivational interviewing based on the transtheoretical model. Oral cleaning behavior was compared between the two groups before and after intervention. In addition, periodontal health status was compared on the day of implant restoration and three months later. RESULTS: Compared to the control, the experimental group demonstrated significantly better oral hygiene behavior after intervention (P< 0.05). Three months after implant restoration, significantly better results were obtained by the experimental group in terms of mPLI and mSBI (P< 0.05). CONCLUSION: Motivational interviewing based on the transtheoretical model can effectively improve the oral cleaning behavior and periodontal health of implant-restored patients with periodontitis.

Diverse polyacetylenes from Atractylodes chinensis and their anti-osteoclastogenesis activity.

The phytochemical investigation on Atractylodes chinensis afforded 15 polyacetylenes 1-15 and one meroterpenoid 16. Of the 16 isolates, compounds 4 and 9 are new ones, and compounds 8 and 16 are first reported from nature. In addition, the relative configuration of 1 and the available NMR data of compounds 1, 8, and 16 were first provided. Their structures were elucidated by extensive analysis of MS, UV, IR, and NMR spectroscopic data. Besides, all isolated compounds were evaluated for their effects on RANKL-induced osteoclastogenesis in BMMs. Among them, polyacetylenes 12-14 showed potent inhibitory activity with IC50 values of 0.67 ± 0.05 µM, 0.72 ± 0.31 µM, and 2.40 ± 0.41 µM, respectively. The current work demonstrates the polyacetylenes are the main active constituents of A. chinensis against osteoclastogenesis.

A thermogelling organic-inorganic hybrid hydrogel with excellent printability, shape fidelity and cytocompatibility for 3D bioprinting.

Alginates are the most commonly used bioink in biofabrication, but their rheological profiles make it very challenging to perform real 3D printing. In this study, an advanced hybrid hydrogel ink was developed, a mixture of thermogelling diblock copolymer, alginate and clay i.e. Laponite XLG. The reversible thermogelling and shear thinning properties of the diblock copolymer in the ink system improves handling and 3D printability significantly. Various three-dimensional constructs, including suspended filaments, were printed successfully with high shape fidelity and excellent stackability. Subsequent ionic crosslinking of alginate fixates the printed scaffolds, while the diblock copolymer is washed out of the structure, acting as a fugitive material/porogen on the (macro)molecular level. Finally, cell-laden printing and culture over 21 d demonstrated good cytocompatibility and feasibility of the novel hybrid hydrogels for 3D bioprinting. We believe that the developed approach could be interesting for a wide range of bioprinting applications including tissue engineering and drug screening, potentially enabling also other biological bioinks such as collagen, hyaluronic acid, decellularized extracellular matrices or cellulose based bioinks.

Stress Distribution and Fracture Resistance of repairing Cracked Tooth with Fiber-reinforced Composites and Onlay.

The purpose of this study was to explore the effects of fibre-reinforced composites and onlay restorations on the fracture resistance of the cracked teeth. The experiments were grouped as follows: intact teeth, cracked teeth, crown; onlay; annular ribbond + onlay, laminated ribbond + onlay and fibre post + onlay; annular ribbond + crown, laminated ribbond + crown and fibre post + crown. The maximal Von Mises stress of dentin, the maximal Von Mises stress at the crack, the fracture resistance and fracture pattern under static loading were analysed by single-factor analysis of variance (ANOVA) and post-test by LSD. The annular ribbond + crown had a significant difference in fracture resistance than the crown (P < 0.05). The annular ribbond + onlay had more favourable fractures than crown in fracture pattern, and there were significant differences (P < 0.05). Compared with crown restoration, fibre-reinforced composites and onlay can improve the fracture resistance of the cracked teeth.

Comparing digital and traditional guides in first molar implant surgery: A randomized clinical trial.

BACKGROUND: There are few studies on the differences in clinical outcomes with implant guides made by different methods in cases with a single tooth loss and adjacent tooth supportOBJECTIVE: To compare the use of digital and traditional implant guides in patients whose first molars are absent and who are undergoing implant restoration. METHODS: This study included 42 patients with first molars missing who were randomly divided into two groups: the digital group (n= 21) and the control group (n= 21). A CAD/CAM digital implant guide was used in the digital group, whereas a traditional impression was used in the control group. Then, the labor time, the intraoral fit of the implant guide, and the deviation of the screw access channel position were compared between the two groups. RESULTS: The impression time and implant surgery time in the digital group were less than in the traditional group. The intraoral first fit of the guide in the digital group was higher than in the control group (P< 0.05). The one-time satisfaction rate of the digital group was 100%, while five cases in the control group needed to be redone. In the digital group, there was no significant difference in the deviation of the screw access channel position between implants on the left and right sides. In the control group, the deviation of the screw access channel position on the right side was significantly lower than on the left side. Overall, the deviation of the screw access channel position was significantly lower in the digital group than in the control group. CONCLUSIONS: In a first molar implant, the digital implant guide can effectively reduce the clinical operative time and the screw access deviation and improve efficiency. The clinical results with the digital guide provide a basis for its use in implant therapy for single missing teeth.