Application of robotics in stomatology.

The application of robots in oral treatment can not only reduce the work intensity of clinicians but also improve the accuracy of treatment. In this article, the application and research status of robots in stomatology are reviewed.

Novel Digital Mouth Preparation Technique for Fabricating Implant-Retained Removable Partial Dentures with Distal Extension: a Case Report.

Implant-retained removable partial dentures (RPDs) are commonly used to resolve the complications associated with traditional distal extension RPDs; however, this technology does not consider the necessity and importance of parallelism between the path of RPD insertion and the long axis of the implant. This clinical report presents a novel digital preparation technique that involves the preparation of parallel guiding planes on abutment teeth and implant insertion in the distal extension area using a computer-aided design and manufacturing template. This clinical case of implant-retained RPDs illustrates the fabrication and application of the digital template. Using this technique, the path of RPD insertion is parallel to the long axis of the implant. As a result, the components of the implant-retained RPD, including the abutment teeth, implants and attachments, can demonstrate greater longevity.

The use of calcium phosphate-based biomaterials in implant dentistry.

Since calcium phosphates (CaPs) were first proposed, a wide variety of formulations have been developed and continuously optimized, some of which (e.g. calcium phosphate cements, CPCs) have been successfully commercialized for clinical applications. These CaP-based biomaterials have been shown to be very attractive bone substitutes and efficient drug delivery vehicles across diverse biomedical applications. In this article, CaP biomaterials, principally CPCs, are addressed as alternatives/complements to autogenous bone for grafting in implant dentistry and as coating materials for enhancing the osteoinductivity of titanium implants, highlighting their performance benefits simultaneously as carriers for growth factors and as scaffolds for cell proliferation, differentiation and penetration. Different strategies for employing CaP biomaterials in dental implantology aim to ultimately reach the same goal, namely to enhance the osseointegration process for dental implants in the context of immediate loading and to augment the formation of surrounding bone to guarantee long-term success.

Novel glycidyl methacrylated dextran (Dex-GMA)/gelatin hydrogel scaffolds containing microspheres loaded with bone morphogenetic proteins: formulation and characteristics.

Novel thermomechanical hydrogel scaffolds containing our previously prepared microspheres loaded with bone morphogenetic proteins (BMP) were successfully generated by radical crosslinking and low dose gamma-irradiation from combination of two kind of biomaterials: glycidyl methacrylated dextran (Dex-GMA) and gelatin. The structure of those resulting smart hybrid hydrogels was evaluated by mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) analyses, and as a function of the degree of Dex-GMA's substitution (DS), the proportion between Dex-GMA and gelatin, and the initial polyethyleneglycol (PEG) concentration used in the preparation of the hydrogels. The swelling and degradation properties and the temperature-sensitive drug release manner were determined by dynamic evaluation methods in vitro, and the gel content was also calculated. MIP analysis showed that by systematically altering the preparation parameters, the overall networks were clearly macroporous with pore sizes ranging from 5.6+/-4.2 to 37.7+/-13.7 microm. As expected, the pore size decreased as DS and initial PEG concentration increased, whereas the opposite was found for the gel content. Moreover, the porosity values ranged from 73.7+/-12.4% up to 89.6+/-6.3%. The SEM results also showed the inter-connective pores as well as microspheres encased into their porous structure of those hydrogels. The swelling and degradation properties of the resultant hydrogels varied according to the DS of Dex-GMA and initial PEG concentration, while the proportion between Dex-GMA and gelatin had no significant influence on those characterizations. By changing the composition ratio of the two precursors, the phase transition temperature (lower critical solution temperature, LSCT) of the hydrogel scaffolds could also be adjusted to be or near the body temperature, so BMP release from microsphere-hydrogel compounds could be accordingly controlled and the release period could be varied from 18 to more than 28 days. These results demonstrated that a novel temperature-sensitive and biodegradable Dex-GMA/gelatin scaffold containing microspheres loaded with BMP could be successfully developed from both dextran- and gelatin-based biomaterials, which could promisingly satisfy the need, desire, and expectation of both self-regulated drug delivery and tissue-engineering applications.

Enhancement of periodontal tissue regeneration by locally controlled delivery of insulin-like growth factor-I from dextran-co-gelatin microspheres.

The present work focused on the design of novel hydrogel microspheres based on both dextran- and gelatin-derived biomaterials, and discussed whether locally controlled delivery of IGF-I from dextran-co-gelatin hydrogel microspheres (DG-MP) was useful for periodontal regeneration enhancement. Microspheres were synthesized when gelatin was cooperating with glycidyl methacrylate (GMA) derivatized dextrans (Dex-GMA) and the resultant DG-MP with a hydrogel character of which the cross-linking density could be controlled by the degree of substitution (DS, the number of methacrylates per 100 glucopyranose residues) of Dex-GMA. In this study, three types of DG-MP (DG-MP4.7, DG-MP6.3 and DG-MP7.8) obtained from gelatin and Dex-GMA (differing in DS: 4.7, 6.3 and 7.8 respectively) were prepared and characterized by swelling and degradation properties, drug release kinetics and biological capability in promoting tissue regeneration. By swelling in aqueous positively charged IGF-I solutions, the protein could be encapsulated in DG-MP by polyionic complexation with negatively charged acidic gelatin. No obvious influence of Dex-GMA's DS on DG-MP's configuration and size was observed, and the release and degraded properties showed no significant difference between three types of DG-MP in PBS buffer either. However, high DS of Dex-GMA could lower microsphere's swelling, prolong its degraded time and minimize IGF-I burst release markedly in dextranase-containing PBS, where IGF-I release from a slow release type of microspheres (DG-MP7.8) could be maintained more than 28 days, and an effective protein release kinetics without a significant burst but a relevantly constant release after the initial burst was achieved. IGF-I in DG-MP resulted in more new bone formation in the periodontal defects within 4 or 8 weeks than IGF-I in blood clot directly did (P < 0.01). The observed newly formation of periodontal tissues including the height and percentage of new bone and new cementum on the denuded root surfaces of the furcation area in DG-MP7.8 group were more than that in other groups (P < 0.05). The adequate width of regenerative periodontal ligament (PDL), regular Sharpey's fibers and alveolar bone reconstruction could be observed only in DG-MP7.8 group. These combined results demonstrate that effective release kinetics can be realized by adjusting the DS of Dex-GMA and followed cross-linking density of DG-MP, and that locally controlled delivery of IGF-I from slow release type of DG-MP may serve as a novel therapeutic strategy for periodontal tissue regeneration.

The use of platelet-rich fibrin combined with periodontal ligament and jaw bone mesenchymal stem cell sheets for periodontal tissue engineering.

Periodontal regeneration involves the restoration of at least three unique tissues: cementum, periodontal ligament tissue (PDL) and alveolar bone tissue. Here, we first isolated human PDL stem cells (PDLSCs) and jaw bone mesenchymal stem cells (JBMSCs). These cells were then induced to form cell sheets using an ascorbic acid-rich approach, and the cell sheet properties, including morphology, thickness and gene expression profile, were compared. Platelet-rich fibrin (PRF) derived from human venous blood was then fabricated into bioabsorbable fibrin scaffolds containing various growth factors. Finally, the in vivo potential of a cell-material construct based on PDLSC sheets, PRF scaffolds and JBMSC sheets to form periodontal tissue was assessed in a nude mouse model. In this model, PDLSC sheet/PRF/JBMSC sheet composites were placed in a simulated periodontal space comprising human treated dentin matrix (TDM) and hydroxyapatite (HA)/tricalcium phosphate (TCP) frameworks. Eight weeks after implantation, the PDLSC sheets tended to develop into PDL-like tissues, while the JBMSC sheets tended to produce predominantly bone-like tissues. In addition, the PDLSC sheet/PRF/JBMSC sheet composites generated periodontal tissue-like structures containing PDL- and bone-like tissues. Further improvements in this cell transplantation design may have the potential to provide an effective approach for future periodontal tissue regeneration.

Translational research and therapeutic applications of stem cell transplantation in periodontal regenerative medicine.

Stem cells have received a great deal of interest from the research community as potential therapeutic "tools" for a variety of chronic debilitating diseases that lack clinically effective therapies. Stem cells are also of interest for the regeneration of tooth-supporting tissues that have been lost to periodontal disease. Indeed, substantial data have demonstrated that the exogenous administration of stem cells or their derivatives in preclinical animal models of periodontal defects can restore damaged tissues to their original form and function. As we discuss here, however, considerable hurdles must be overcome before these findings can be responsibly translated to novel clinical therapies. Generally, the application of stem cells for periodontal therapy in clinics will not be realized until the best cell(s) to use, the optimal dose, and an effective mode of administration are identified. In particular, we need to better understand the mechanisms of action of stem cells after transplantation in the periodontium and to learn how to preciously control stem cell fates in the pathological environment around a tooth. From a translational perspective, we outline the challenges that may vary across preclinical models for the evaluation of stem cell therapy in situations that require periodontal reconstruction and the safety issues that are related to clinical applications of human stem cells. Although clinical trials that use autologous periodontal ligament stem cells have been approved and have already been initiated, proper consideration of the technical, safety, and regulatory concerns may facilitate, rather than inhibit, the clinical translation of new therapies.

Influence of dental restorative material properties on bond interface reliability: a finite element analysis.

BACKGROUND: Varieties of restorative materials are widely used in dentistry. The aim of this study is to explore the influence of different dental restorative materials on bond interface reliability. METHODS: A two-dimensional finite element analysis method was adopted to simulate the shear-bond efficacy test. The influence of elastic modulus and Poisson's ratio were investigated separately. Several dental restorative materials including resins, metals, and ceramics were analyzed in this study. RESULTS: The deformation and peak equivalent stress level of the dentin-adhesive interface rose sharply following a decrease in the elasticity of restorative materials, especially those with a low elastic modulus range. The influence of the Poisson's coefficient was not significant. Ceramics and gold alloy were preferred to resin composite in restorations bearing extensive shear load during service. CONCLUSIONS: Restorative materials with an elastic modulus similar to that of teeth are not always the best clinical choice. This research provides a helpful guide for the application of different restorative materials in clinical practice.

Prospects for translational regenerative medicine.

Translational medicine is an evolutional concept that encompasses the rapid translation of basic research for use in clinical disease diagnosis, prevention and treatment. It follows the idea "from bench to bedside and back", and hence relies on cooperation between laboratory research and clinical care. In the past decade, translational medicine has received unprecedented attention from scientists and clinicians and its fundamental principles have penetrated throughout biomedicine, offering a sign post that guides modern medical research toward a patient-centered focus. Translational regenerative medicine is still in its infancy, and significant basic research investment has not yet achieved satisfactory clinical outcomes for patients. In particular, there are many challenges associated with the use of cell- and tissue-based products for clinical therapies. This review summarizes the transformation and global progress in translational medicine over the past decade. The current obstacles and opportunities in translational regenerative medicine are outlined in the context of stem cell therapy and tissue engineering for the safe and effective regeneration of functional tissue. This review highlights the requirement for multi-disciplinary and inter-disciplinary cooperation to ensure the development of the best possible regenerative therapies within the shortest timeframe possible for the greatest patient benefit.

Alveolar crest regeneration using curvilinear dentoalveolar distraction osteogenesis: a preliminary study.

OBJECTIVE: The objective of this study was to reconstruct alveolar crest at home position using distraction osteogenesis (DO) with a personalized curvilinear distractor designed through computer-aided technology. STUDY DESIGN: Five adult dogs were recruited and the maxillary alveolar bone from the first incisor to the first premolar was excised. The dentoalveolar segment adjacent to the defect was osteotomized as a bone transport disk. After 8 weeks of consolidation, the dogs were humanely killed, and the regenerated bone was analyzed. RESULTS: The DO was successful in the experimental group. The radiographs and histology both verified new bone bridging distraction gap. However, the newly formed bone was located more internally and was not in original position. CONCLUSIONS: The proposed method to reconstruct alveolar crest at home position is improper. The key point was how to maintain the distraction space and hold it at the home position. The barrier membrane technique may be used together with DO to resolve the problem.

[Effect of pigments concentration on physical and mechanical properties of MDX-4-4210 silicone elastomer].

PURPOSE: To determine the optimum pigments concentration on the physical and mechanical properties. METHODS: In this study, control samples were prepared from MDX-4-4210 silicone base and tested along with the pigmented samples for comparison in accordance with the national standards. The pigments concentration to base elastomer was set at 0.1, 0.15, 0.2, 0.25, 0.3wt%,respectively; while other conditions were kept same, then the major physical properties of the elastomer were studied with a tensile tester. The data was processed with SPSS10.0 software package. RESULTS: When comparing the pigmented samples with the control, the tensile strength, the ultimate elongation, the tear resistance and the Shore A hardness of the MDX-4-4210 silicone elastomer was affected by the addition of the pigments. A decrease was found,while, the incorporation of pigments had no effect on the permanent deformation rate of the resulting elastomer by the addition of the pigments. CONCLUSIONS: The results obtained from physical and mechanical testing of pigmented silicone samples suggest that incorporation of 0.2wt% by weight of pigments can alter the initial physical and mechanical behavior of the base elastomer. Supported by National Natural Science Foundation of China (30630066).

Virtual transplantation in designing a facial prosthesis for extensive maxillofacial defects that cross the facial midline using computer-assisted technology.

PURPOSE: The aim of this article was to demonstrate a novel approach to designing facial prostheses using the transplantation concept and computer-assisted technology for extensive, large, maxillofacial defects that cross the facial midline. MATERIALS AND METHODS: The three-dimensional (3D) facial surface images of a patient and his relative were reconstructed using data obtained through optical scanning. Based on these images, the corresponding portion of the relative's face was transplanted to the patient's where the defect was located, which could not be rehabilitated using mirror projection, to design the virtual facial prosthesis without the eye. A 3D model of an artificial eye that mimicked the patient's remaining one was developed, transplanted, and fit onto the virtual prosthesis. A personalized retention structure for the artificial eye was designed on the virtual facial prosthesis. The wax prosthesis was manufactured through rapid prototyping, and the definitive silicone prosthesis was completed. RESULTS: The size, shape, and cosmetic appearance of the prosthesis were satisfactory and matched the defect area well. The patient's facial appearance was recovered perfectly with the prosthesis, as determined through clinical evaluation. CONCLUSION: The optical 3D imaging and computer-aided design/computer-assisted manufacturing system used in this study can design and fabricate facial prostheses more precisely than conventional manual sculpturing techniques. The discomfort generally associated with such conventional methods was decreased greatly. The virtual transplantation used to design the facial prosthesis for the maxillofacial defect, which crossed the facial midline, and the development of the retention structure for the eye were both feasible.

[Effect of surface treatment on the bonding of silicone elastomer to acrylic resin].

OBJECTIVE: To evaluate the effects of surface treatments on the bonding of silicone elastomer to acrylic resin. METHODS: Ninety acrylic resin specimens were randomly divided into 9 groups which were assigned to 9 different surface treatments: finished by 80-, 240-, 400-, 600-, 800-, 1000-, 1500-grit silicon carbide paper under running water, or polished or sandblasted. Roughness of the specimen surface was tested in each group, and the microstructure was observed with scanning electron microscopy (SEM). ZY-1 silicone elastomer, ZA-1 primer and acrylic resin specimens were prepared. Shear bond strength were tested and failure modes were assessed for all specimens. RESULTS: The roughness of all 9 groups showed significant difference (P < 0.05). The sandblasted group showed the highest roughness [(2.97 + or - 0.48) microm], the 1500-grit silicon carbide paper finished group showed the lowest roughness [(0.21 + or - 0.14) microm]. The sandblasted groups showed the lowest bonding strength [(0.98 + or - 0.11) MPa] (P < 0.05) while the 600-grit silicon carbide paper finished group showed the highest strength [(2.13 + or - 0.14) MPa]. CONCLUSIONS: Over high surface roughness does not improve the shear bond strength between silicone elastomer and acrylic resin. Treatment of acrylic resin surface with 600-grit silicon carbide paper can increase the shear bond strength between silicone elastomer and acrylic resin.

Multiplanar and combined distraction osteogenesis for three-dimensional and functional reconstruction of unilateral large maxillary defects.

We have developed a new way of three-dimensional and functional reconstruction of unilateral large maxillary defects by multiplanar and combined distraction osteogenesis of the zygoma, maxillary alveolar process, and hard palate. In the first procedure we started the internal curvilinear distraction osteogenesis of the left zygoma in one patient who had had a left maxillectomy to rebuild midfacial bony support. In the second procedure, the internal curvilinear distraction osteogenesis of the maxillary anterior alveolar process and straight distraction osteogenesis of the right hard palate were used to restore the posterior alveolar process and left palate. In the third procedure, the distracted zygoma and alveolar process were connected by a small local bone graft. The important lost maxillary bony architecture was re-established three-dimensionally and resulted in a natural facial appearance, normal speech and swallowing, and good foundation for chewing. This may be the first example of three-dimensional and functional reconstruction of unilateral large maxillary defects that did not require bone grafts from other anatomical areas.

The corrosion and biological behaviour of titanium alloys in the presence of human lymphoid cells and MC3T3-E1 osteoblasts.

Corrosion behaviour of biomedical alloys is generally determined in mineral electrolytes: unbuffered NaCl 0.9% (pH 7.4) or artificial saliva (pH 6.8). The assays with exclusive utilization of these electrolytes are of low relevance for the biological condition, to which the alloys will be exposed once implanted in the human organism. As an approach to the biological situation regarding the interaction of proteins, electrolytes and metals, we added the RPMI cell culture medium containing foetal calf serum as a biological electrolyte (pH 7.0). The analysis of corrosion behaviour was also performed in the presence of human lymphoid cells (CEM). The rest potential (Er) and the global polarization were determined on cp-Ti, micro-arc oxidized cp-Ti (MAO-Ti), four different Ti-alloys (Ti6Al4V, Ti12Zr, Ti(AlMoZr), Ti(NbTaZr)) and 316L stainless steel. The 316L exhibited an appropriate Er and a good passive current density (Ip), but a high corrosion potential (Ec) and a very low breakdown potential (Eb) in all electrolytes. All Ti-alloys exhibited a much better electrochemical behaviour: better Er and Ec and very high Eb. No significant differences of the above parameters existed between the Ti-alloys, except for Zr-containing alloys that showed better corrosion behaviour. A remarkable difference, however, was stated with respect to the electrolytes. NaCl 0.9% induced strong variations between the Ti-alloys. More homogeneous results were obtained with artificial saliva and RPMI medium, which induced a favourable Ec and an increased Ip. The presence of cells further decreased these values. The unbuffered NaCl solution seems to be less appropriate for the analysis of corrosion of metals. Additional in vitro biological assessments with CEM cell suspensions and MC3T3-E1 osteoblasts confirmed the advantages of the Ti(AlMoZr) and Ti(NbTaZr) alloys with an improved cell proliferation and vitality rate.

Dentists' role in treating facial injuries sustained in the 2008 earthquake in China: how dental professionals can contribute to emergency response.

BACKGROUND: A major earthquake struck Sichuan province, China, on May 12, 2008, and the authors were involved in the medical response to the disaster in Jiangyou City, an area hard-hit by the quake. In this article, they analyze data about the earthquake-related facial injuries and assess dentistry's role in treating them. METHODS: This descriptive study included review of medical records for 4,582 patients with earthquake-related trauma at eight hospitals in Jiangyou, a city severely affected by the earthquake, for the day of the disaster and the 14 days immediately afterward. RESULTS: Of the 4,582 patients, 408 (8.9 percent) sustained a total of 482 facial injuries. The dental team treated patients with facial injuries and others who needed care. CONCLUSIONS: Facial injuries constitute a significant portion of earthquake-related trauma, and dentists therefore are an important part of the medical team that deals with such trauma. Dentists are a reliable force in the medical response to earthquakes and other disasters. CLINICAL IMPLICATIONS: The dental team should play an important role in disaster response. Establishing oral and maxillofacial surgeon (OMS)/dentist reserves and active leagues that use OMSs' and general dentists' offices as bases can help improve disaster response.

[Effect of Candida albicans growth on silicone elastomer containing nano-TiO2].

OBJECTIVE: To study the antibacterial effect against Candida albicans of the A-2186 silicone elastomer containing nano-TiO2 in vitro. METHODS: Antibacterial agent of nano-TiO2 was added into A-2186 silicone elastomer with incorporating percentages of 0.5%, 1.0%, 1.5%, and 2.0% (W/W). There was no nano-TiO2 in the control group. The antibacterial effect of the A-2186 silicone elastomer was determined using the film contact method with lighting and without lighting. RESULTS: Either with lighting or without lighting, there were significances between the experiment groups and the control group (P < 0.05). When the incorporating percent was 2.0%, the inhibitory effect was the best among the experiment groups. Without lighting, the inhibitory rate was 53.7% and with lighting, the inhibitory rate was 85.9%. CONCLUSIONS: The A-2186 silicone elastomer containing nano-TiO2 has antibacterial properties against Candida albicans, which enhances with increases of nano-TiO2 percent in the material. With the same incorporating percentage, the antibacterial effect with lighting is better than that without lighting.

[Application of multislice helical computed tomography in maxillofacial distraction osteogenesis].

OBJECTIVE: To develop the method and investigate the value of the application of multislice helical computed tomography (CT) in the maxillofacial distraction osteogenesis. METHODS: Twelve cases of maxillofacial distraction osteogenesis (3 in zygoma, 2 in maxilla, and 7 in mandible) were scanned by the multislice helical CT, then the reconstruction of three dimensional and fault image and the relative measurement were carried out to study the effect of distraction and osteogenesis. RESULTS: The three dimensional image provided clear and high resolution stereoscopic view that the effect of distraction osteogenesis could be evaluated easily and exactly. The fault image could be set up in private computer by Mimics and the measurements, such as distance, thickness and density, could be performed as expected. The effect of 12 cases was satisfied, and the average distracted distance was 16.73 mm. CONCLUSION: Basing on multislice helical CT scanning, the high resolution image reconstruction and relative measurement data could be obtained which could meet the need of clear and direct observation. Its application in the maxillofacial distraction osteogenesis is expecting and promising.

Periodontal regeneration using novel glycidyl methacrylated dextran (Dex-GMA)/gelatin scaffolds containing microspheres loaded with bone morphogenetic proteins.

The objective of this study was to evaluate the biological activity enhancement of a novel glycidyl methacrylated dextran (Dex-GMA)/gelatin hybrid hydrogel containing microspheres loaded with bone morphogenetic proteins (BMP) as periodontal cell/tissue scaffold. Larger number of human periodontal ligament cells (PDLCs) attached was observed in scaffolds containing microspheres loaded with BMP when compared to those without microspheres. When osteogenic differentiation of PDLCs in such scaffolds was evaluated, the alkaline phosphatase (ALP) activity, osteocalcin content, and calcium deposition became maximum for the scaffold containing microspheres loaded with BMP, as compared with those without microspheres but adsorbed with the same amount of BMP aqueous solution, although both values were significantly higher than those in BMP-free scaffold. In addition, the osteoinduction activity was also studied following the implantation of these scaffolds into the periodontal defects of dogs in terms of histological examinations, significantly more new bone formation and periodontal ligaments regeneration were observed throughout scaffold containing microspheres. We conclude that the attachment, proliferation, and osteogenic differentiation of PDLCs can be enhanced by Dex-GMA/gelatin hydrogel scaffold containing microspheres loaded with BMP, and such scaffold is promising to enhance periodontal tissue regeneration in periodontal therapy.

[Segmental reconstruction of maxillary defects by arced distraction osteogenesis of zygoma].

OBJECTIVE: To study the possibility of segmental maxillary regeneration by arced distraction osteogenesis of zygoma. METHODS: The distraction of zygoma with the internal arced devices was performed in 2 dogs to simulate the reconstruction of maxillary defect. The zygoma was distracted about 12 mm, and the process of new bone formation was studied by histology and scanning electron microscopy. RESULTS: The transport disk was distracted about 12 mm around the arc. After 8 weeks of consolidation, the density of new bone was close to that of normal bone. CONCLUSIONS: The segmental maxillary regeneration by arced distraction osteogenesis of zygoma is possible.