[Three-dimensional measurement and facial symmetry analysis for the craniofacial structure of people in North China with normal occlusion].

OBJECTIVE: To investigate the internal regularities and symmetry of craniofacial structures from adults with normal occlusion in North China. METHODS: The study consisted of 60 volunteers who were examined with spiral 3D computed tomography (CT). The axial images of craniofacial structure were reconstructed into 3D models and analyzed by using Proplan 1.2 software to measure the internal regularities and symmetry of craniofacial structures. RESULTS: All the linear measurement's value of the males were bigger than those of the females (P<0.05). There were no significant differences in the ratio measurements between the males and the females(P>0.05). Facial asymmetry was less than 10% in all the images. CONCLUSION: CT is an effective method for three-dimensional analyses of craniofacial structure and symmetry. There are certain and harmonious regularities in normal 3D craniofacial structures. The 3D craniofacial structure database of people with normal occlusion can provide standards and references for diagnosis and treatment planning of craniofacial deformities.

[Three-dimensional imaging for quantitative evaluation of facial profile of edentulous patients before and after complete dentures restoration].

OBJECTIVE: To collect and analyze the Three-dimensional (3D) facial profile variation of edentulous patients restored by complete denture. METHODS: The 3D facial images of 20 Atwood Class II edentulous patients were taken by DSC-2 3D facial imaging system before and after restoration of complete denture. Then, the two 3D facial images of each patient before and after restoration were registered in the same coordinate system by partial structure overlap. The differences between these two 3D facial images were statistically analyzed. RESULTS: The major facial profile variation of Atwood Class II edentulous patients restored by complete denture focused in the area around the upper lip and the corner of the mouth. The change of lower lip and chin area was not obvious. The shift in the sagittal direction was significantly more evident than that in the vertical direction, while the shift in the horizontal direction was the least one. CONCLUSION: The pattern of facial profile variation of edentulous patients restored by complete denture based on 3D imaging may provide reliable data support for prediction and communication in clinical practice.

[Functional maxillary reconstruction with free composite fibula flap].

Maxillary defects resulting from tumor resection or trauma can cause severe functional and cosmetic deformities. Maxillary reconstruction has long been a challenge for oral maxillofacial surgeons. Functional maxillary reconstruction with vascularized composite bone flap and osseointegrated implants is one of the most important improvements in head and neck reconstructive surgery. Since 1999, our research group has performed a comprehensive research on functional maxillary reconstruction with free composite fibula flap. Clinical data of the patients with maxillary reconstruction using free fibula flap were analyzed to describe the indications and principles of perioperative period of this technique. The modified free fibula flexor-hallucis longus myofascial flap was introduced, which could overcome the disadvantages of traditional free composite fibula flap. The donor site morbidity, post-operative speech outcome, mastication function, and quality of life were evaluated objectively. The biomechanical effects of stress distribution on maxilla reconstructed by free fibula composite flap were analyzed by three-dimensional finite element analysis. These studies demonstrated maxillary defects can be reconstructed successfully using free fibula flaps. This procedure also allows dental implant or conventional denture rehabilitation, which can improve the patient's appearance and oral function and enhance the overall quality of life. The fibula free flap transfer has a high success rate and low perioperative complication rate, making it an ideal choice for maxillary defect reconstruction.

Effects of Preoperative Anxiety Status on Haemodynamic Changes during and after Tooth Extraction in Middle-aged and Elderly Patients with Hypertension: a Prospective Repeated-Measures Cohort Study.

OBJECTIVE: To investigate the effects of dental anxiety on fluctuations in blood pressure (BP) and heart rate (HR) during tooth extraction in hypertensive patients under local anaesthesia, and how they are influenced by various confounding variables. METHODS: This is a prospective repeated-measures cohort study involving 600 patients successively recruited from Peking University School and Hospital of Stomatology, Beijing, China. BP and HR were repeatedly measured at rest (T0), before anaesthesia (T1), during tooth extraction (T2) and after tooth extraction (T3). Anxiety status was measured prior to local anaesthesia using a modified dental anxiety scale (MDAS). Three groups were assigned: mild anxiety (Corah DAS score of 4 to 8), moderate anxiety (score of 9 to 12) and severe anxiety (score of 13 to 20). We used a generalised linear mixed model (GLMM) to analyse the effects of dental anxiety on fluctuations in BP and HR. Interaction analysis was used to further explore the correlationship between these interactive factors. RESULTS: The mean anxiety scale score was 9.63 ± 2.88. Severe preoperative anxiety (score of 14 to 20) was associated with significantly increased HR during administration of anaesthesia. Patients with severe anxiety also displayed a significantly greater increase in HR during anaesthetic administration (P < 0.001). When analysing the joint effects of different anxiety statuses over time, blood pressure was significantly elevated in all patients with moderate and severe anxiety during tooth extraction at T2 (ß = 1.25, 95% CI 0.24 to 2.27). We also observed a significant decrease in HR in the moderate anxiety group at T3 (ß = -1.51, 95% CI -2.38 to -0.63) and a significant increase in HR in the severe anxiety group at T1, T2 and T3 (ß = 2.52, 95% CI 1.12 to 3.93; ß = 3.84, 95% CI 2.30 to 5.38; ß = 4.57, 95% CI 3.03 to 6.11, respectively). CONCLUSION: This study indicates that the effects of dental anxiety on BP and HR in middle-aged and elderly patients with hypertension during local anaesthesia and tooth extraction were influenced by various confounding variables.

Use of a CAD/CAM-fabricated glass fiber post and core to restore fractured anterior teeth: A clinical report.

Prefabricated glass fiber posts are widely used; however, their shape cannot be changed and they can be unsuitable for severely damaged teeth with wide root canals. This clinical report describes a procedure for restoring a severely damaged anterior tooth with a customized 1-piece glass fiber post and core, fabricated using a CAD/CAM system. This 1-piece glass fiber post and core adapts better to the root canal than a prefabricated glass fiber post, and reduces the cement layer thickness. Furthermore, it does not require the use of a composite resin foundation.

Developments in Antibacterial Therapy: Focus on Physical Stimuli Approaches.

At present, various antibacterial therapeutic modalities are available in the clinic. However, due to the rampant abuse of antibiotics over the past few decades and the consequent emergence of innumerable drug-resistant strains of bacteria, it is imperative to develop new and effective antibacterial therapeutic strategies. In recent years, the physical stimuli-based approach to antibacterial therapy has aroused much interest as an alternative to antibiotics and has become a major focus of antibacterial research. In this review, the application of different physical stimuli, including electricity, magnetism, light, ultrasound and thermal stimulation, in antibacterial research is critically examined in order to provide new ideas and directions for the further development of antibacterial therapy in clinical dentistry.

Efficacy of a mineralized collagen bone-grafting material for peri-implant bone defect reconstruction in mini pigs.

The mechanism of the mineralization process induced by natural mineralized collagen (MC) has been investigated for decades. The purpose of this study was to investigate the efficacy of self-assembled MC for peri-implant bone defect reconstruction in a mini pig. A standardized peri-implant bone defect model was created using 14 mini pig mandibles. Two materials were evaluated, i.e. a mixture of hydroxyapatite and collagen (Type A, TA), and self-assembled MC (Type B, TB). Bio-Oss (BO) and untreated (blank control, BC) groups were used as controls. After 3- and 6-month healing periods, the mini pigs were sacrificed for histomorphometric and microcomputed tomography analysis. After 3 months of healing, the average alveolar ridge height was 3.27 ± 1.57 mm for group TA, 3.28 ± 2.02 mm for group TB and 3.37 ± 1.09 mm for group BO, while group BC showed the lowest height of 2.68 ± 0.47 mm. After 6 months of healing, the average alveolar ridge height was 2.64 ± 1.13 mm for group TA, 4.31 ± 1.80 mm for group TB and 3.87 ± 1.38 mm for group BO, while group BC showed the lowest height of 2.48 ± 1.80 mm. The experimental groups and control group showed similar bone volume density, bone complexity and histological reaction. The self-assembled MC (Type B) stimulated new bone formation in the reconstruction of deficient alveolar ridges around the dental implant; it also displayed excellent clinical operability compared with bone grafts without collagen.

Pulmonary delivery of scutellarin solution and mucoadhesive particles in rats.

The objectives of this study were to investigate the effects of mucoadhesive excipients on systemic bioavailability of an inhaled drug and to evaluate the feasibility of using the pulmonary route for non-invasive systemic delivery of scutellarin, a poorly orally absorbed flavonoid glucuronide. Following intratracheal spray of the scutellarin solution, the bioavailability was found to be approximately 77% in rats, which was >30-fold higher than that via the peroral route. In addition, the pulmonary absorption of scutellarin appeared to avoid the intestinal first-pass metabolism accompanied by peroral administration. Spray-dried scutellarin particles with the presence of mucoadhesive excipients were found to affect the corresponding mucociliary transport rate (MTR) as evaluated by a frog palate model. The pharmacokinetic results indicated that the magnitude of AUC(0-480) of intrapulmonary delivered drug particles was not correlated to the fine particle fraction (FPF) but inversely related to the MTR. Incorporating mucoadhesive polymeric mixtures into the scutellarin particles, the MTR decreased by sixfold, and the absolute bioavailability of the drug was found to increase from 70.1% to 97.9% despite a decrease in the FPF. Moreover, in vitro results evaluated using Calu-3 and A549 cell lines showed that scutellarin and spray-dried particles with or without the presence of mucoadhesives exhibited no local cell cytotoxic effects in the tested concentration range. In conclusion, the conducting airway is well permeable to scutellarin, and scutellarin may be effectively delivered systemically through inhalation of respirable droplets or particles.

[Construction of 3D complex of porous beta-tricalcium phosphate/collagen scaffolds and dog periodontal ligament cells].

OBJECTIVE: To investigate the construction of 3D complex of porous beta-tricalcium phosphate/collagen scaffolds (beta-TCP/col) and dog periodontal ligament cells (PDLCs). METHODS: Dog PDLCs were isolated, cultured and identified. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to evaluate the cytotoxicity of beta-TCP/col on the proliferation of PDLCs. The cells were seeded onto porous beta-TCP/col scaffolds. The cellular capability of adhesion and growth on porous beta-TCP/col surface was investigated visually by scanning electron microscopy (SEM). RESULTS: The cytotoxicity assay indicated that there was no significant difference between beta-TCP/col and the control during the 7 days (P>0.05). SEM showed cells successfully adhered to porous beta-TCP/col scaffolds and spread extensively. Matrix secretions were found on the cell surface. CONCLUSION: Porous beta-tricalcium phosphate/collagen scaffolds were of good biocompatibility to the dog periodontal ligament cells, and were potential ideal candidates for periodontal tissue engineering.

Mechanical performance of polymer-infiltrated zirconia ceramics.

OBJECTIVE: The aim of this study was to evaluate the microstructure and mechanical behavior of polymer-infiltrated zirconia ceramics as a function of pre-sintering temperature (1000-1150°C). METHODS: Polymer-infiltrated zirconia ceramics were prepared by combining the porous zirconia networks and polymer through infiltration and polymerization. XRD was employed to determine phase structure. The microstructure and fracture mechanism were observed by SEM. Flexural strength and fracture toughness were measured by three-point bending method and single-edge-notched beam method, respectively. A nanoindentation system was employed to determine elastic modulus and hardness. RESULTS: Different porosities and polymer contents can be obtained by tuning the pre-sintered temperature of zirconia ceramic precursors. Zirconia network porosity varies from 46.3% to 34.7% and the relevant polymer content ranges from 18.4wt.% to 12.3wt.% when the pre-sintered temperature is set from 1000°C to 1150°C. The flexural strength, fracture toughness, hardness, and elastic modulus values of the specimen pre-sintered at 1150°C are 240.9MPa, 3.69MPam1/2, 3.1GPa, and 58.8GPa, respectively. CONCLUSION: The pre-sintering temperature has a significant effect on the microstructure and mechanical properties of polymer-infiltrated zirconia ceramics and the optimal pre-sintering temperature is 1150°C. CLINICAL SIGNIFICANCE: Specimen pre-sintered at 1150°C shows tooth-like mechanical properties, suggesting a promising restorative material in dental clinic. Moreover, the synthesis process is simple and can be easily performed in a prosthesis laboratory.

High strength and toughness in chromatic polymer-infiltrated zirconia ceramics.

OBJECTIVE: To evaluate the microstructure and mechanical behavior of polymer-infiltrated zirconia ceramics as a function of Fe2O3 concentration (0-0.3mol%). METHODS: Polymer-infiltrated zirconia ceramics with different concentrations of Fe2O3 were prepared by infiltration and polymerization. XRD was employed to determine phase structure. The microstructure and fracture mechanism was observed by SEM. Flexural strength and fracture toughness were measured by three-point bending method and single-edge-notched beam method, respectively. Data were analyzed by Weibull distribution. A nanoindentation system was employed to determine elastic modulus and hardness. RESULTS: With increasing content of Fe2O3, the flexural strength, fracture toughness, elastic modulus and hardness are all greatly enhanced and the chromatic behavior also improves significantly. As a tradeoff made between strength and elastic modulus, specimen containing 0.2mol% Fe2O3 is found to be the better one, with flexural strength and fracture toughness values being 336.8MPa and 3.91MPam1/2, respectively. Moreover, it maintains a relatively low elastic modulus of 88.2GPa and a moderate hardness of 4.8GPa, close to those of natural enamel. SIGNIFICANCE: This polymer-infiltrated zirconia ceramic material is a dental material of biomimetic chromatic and mechanical properties.

[The effect of simulate intraoral sandblasting on the band strength between enamel and composite resin].

OBJECTIVE: To study whether the bond strength between enamel and composite resin could be enhanced by intraoral sand abrasive. METHODS: Ten human maxillary first incisior teeth were divided into 2 groups The experimental group was sandblasted with 30 microm Al2O3 (CoJet-Sand, pressure 300 kPa) from a distance of 5 mm for 5 seconds, and the control group were not sandblasted. The Herculite composite resin composite cylinders were bonded with Coltene system. Bonded specimens were stored in 37 degrees C distilled water for 24 h, then were subjected to shear force in a testing machine. Stress at failure was calculated in Mpa, and mode of failure was recorded. The Student t test was applied to the data. RESULTS: The shear bond strength of experimental groups was (33.0+/-1.8) MPa, and that of control groups was (26.7+/-5.2) MPa,there was significant difference between these two groups. All the adhesive failures happened at the enamel composite resin interface, except that cohesive failure happened in one sandblasted specimen. CONCLUSION: Intraoral sandblasting could significantly enhance the shear bond strength between enamel and composite resin.

[Finite element analysis of first maxillary molars restored with different post and core materials].

PURPOSE: To analyze the stress magnitude and distribution of residual dentin in maxillary first molar restored with post and crown using three-dimension finite element methods. METHODS: An intact maxillary first molar was scanned using a 3DX multi-image micro-CT. Three-dimensional finite element models simulated an endodontically treated first maxillary molar restored with post and crown, which were varied in different number and material of post. A load of 480 N, simulating intercuspal occlusion, was applied vertically to the occlusal surface and a load of 240 N simulating mastication was applied to the occlusal surface with a 45° angle to the long axis of the tooth. Von Mises stresses were calculated by MSC.Marc software. RESULTS: The maximum stresses among the post in the radicular portion increased as elastic modulus of the material increased. The stress values of remaining dentin observed in two-post group were lower than those in one post group and three-post group for cast metal post systems. In the test simulating mastication, the peak value of Von Mises stress was higher on remaining dentin among the post in the radicular portion and lower on the outer surface of residual tooth tissue than that in the test simulating intercuspal occlusion. CONCLUSIONS: The number, material of post and occlusal loading have influence on magnitude and distributionn of stress. Supported by Natural Science Foundation of China (81271175) and National Science and Technology Supporting Plan (2012BAI07B01).

[Effect of surface treating methods on the shear strength of luting cements to Cercon zirconia].

OBJECTIVE: To study the effect of surface treating methods on the shear strength of Panavia F luting cements to Cercon zirconia. METHODS: Forty sample disc of Cercon zirconia with 20 mm in diameter and 4 mm in height were prepared. Another 40 sample discs with 5 mm in diameter and 4 mm in height were also prepared Both of the two types of samples were randomly devided into four groups A, B, C, and D in which different surface treatments were delivered. In group A samples was treated with 600# sand paper, and in group Bwith sand blasting, and silanization in group C, and sand blasting plus silanization in group D. All samples were bonded with Panavia F luting cement under the aid of glass mould. The value of shear strength was measured and statistically analysed. RESULTS: The shear strength of four groups of samples were (21.50 ± 1.98), (23.68 ± 2.31), (20.69 ± 1.55), (24.01 ± 2.19) MPa respectively. The population mean was not equal. There was no significant difference between 600# sand paper treated group and silanization group, nor between sand blasting group and sand blasting plus silanization group. CONCLUSIONS: Sand blasting is a effective means to increase the shear strength, and 600# sand paper treatment and silanization can't increase the shear strength.

[Influence of background color on chromatic value of four all-ceramic system core materials].

OBJECTIVE: To investigate the influence of post-core background color on chromatic value of four all-ceramic system core materials at clinically appropriate thicknesses. METHODS: Disc specimens of 15 mm in diameter and 0.80 mm in thickness (Empress II: Group A), and 0.50 mm in thickness (In-Ceram Zirconia core: Group B; Cercon base color zirconia core: Group C; Cercon base zirconia core: Group D) were fabricated, five in each group. Au-Pt alloy, Ni-Cr alloy and visible light cured dental composite resin (A2 color) background were prepared. Samples were put on different background and their chromatic values were measured with colorimeter (CIE-1976-L(*)a(*)b(*)). Color differences of each specimen on different background material were calculated. RESULTS: The color differences among specimens of Group A on different background material were more than 1.5 (2.83 ± 0.70) which meant it could be noticeable to eyes. Those of zirconia were less than 1.5 [Group B: (0.14 ± 0.08); Group C: (0.90 ± 0.20); Group D: (0.99 ± 0.09)]. CONCLUSIONS: The influence of background color on Group A was noticeable to human eyes, and as a result, tooth-colored post should be used for this all-ceramic system. For the other three kinds of zirconia core materia1 system, the color differences among specimens on different background material were unnoticeable. Therefore the three all-ceramic systems have excellent color masking ability and can be used on all color background.

Poly(L-lactic acid)/hydroxyapatite hybrid nanofibrous scaffolds prepared by electrospinning.

Poly(L-lactic acid)/hydroxyapatite hybrid nanofibrous scaffolds were prepared via electrospinning. The structure and morphology of the scaffolds were investigated using scanning electron microscopy, differential scanning calorimetry and Fourier transform infrared spectroscopy. The experimental results showed that the average diameter of hybrid nanofiber was similar to that of pure poly(L-lactic acid) fiber, but a new surface bonding (COO-) was formed in hybrid nanofiber which made the surface of the fiber coarse. The weight loss and water uptake of pure poly(L-lactic acid) scaffolds increased continuously and the viscosity-average molecular weight decreased in the phosphate buffer solution as time passed, while those of hybrid scaffolds were very much slowed down because the dissolving of hydroxyapatite particles acted as a physical barrier and blocked off the entry of water. The biocompatibility of the scaffold has been investigated by human osteosarcoma MG-63 cell culture on the scaffold. The preliminary results showed that cells were well adhered and proliferated better on the hybrid scaffolds than pure scaffolds.