Investigation of the optimal medium and application strategy for foot-and-mouth disease vaccine antigen production.

AIMS: For the effective production of 146S particles, which determines foot-and-mouth disease (FMD) vaccine efficacy, we aimed to identify the optimal medium that is easy-to-use, productive and economically affordable for the large-scale production of FMD vaccine. METHODS AND RESULTS: Nine combinations of cell growth media and replacement media were tested for virus propagation. Apart from the replacement strategy, we tested a simple addition strategy involving the addition of 30% v/v of fresh medium to the total spent medium using the Cellvento BHK-200 (Vento). Unlike other tested media that produced poor yields of 146S particles when the spent media were not eliminated, Vento exhibited high productivity with the 30% addition strategy. CONCLUSIONS: Considering its lower price and media consumption compared to those of other media that require media replacement, the 30% addition strategy of Vento is highly effective. Furthermore, owing to its simple application strategy, it makes the scale-up process easy and helps in saving the time and labour involved in spent media removal. SIGNIFICANCE AND IMPACT OF THE STUDY: Through the first comparative assessment of commercial media for the 146S particle recovery, this study suggests the best practical medium for the industrial-scale production of FMD vaccines.

A laboratory study to detect simulated pulpal blood flow in extracted human teeth using ultrasound Doppler flowmetry.

AIM: To develop a laboratory-based tooth model of simulated blood flow in teeth and evaluate it using ultrasound Doppler flowmetry (UDF). METHODOLOGY: A laboratory-based tooth model for UDF was created based on a microfluidic experimental model proposed by Kim & Park (2016 a,b). Twenty-one maxillary or mandibular anterior human teeth within 1 month of extraction were used. Four holes were made in each tooth to fit 1.6-mm diameter polytetrafluoroethylene (PTFE) tubes: at the apical foramen, palatal surface in the centre of the crown, palatal surface apical to the cementoenamel junction (CEJ) and the root centre. Fluid mimicking pulsating blood was pumped (pressure range: 0-200 mbar, flow rate range: 0-80 µL min-1 ) into the apical foramen via the PTFE tubes, which exited the tooth through the palatal surface in the centre of the crown (control group), palatal surface below the CEJ (group 1) and the palatal surface at the mid-root level (group 2). An UDF transducer of 20 MHz was placed at a 60° angle to the labial surface of tooth and was used to measure the fluid flow velocity (Vs, Vas, Vm, Vam, Vd, Vad and Vakd). The flow velocity of the different groups was compared using the Wilcoxon signed-rank test, with a 95% confidence level. RESULTS: UDF facilitated the detection of the simulated pulpal blood flow in the control group and group 1, but not in group 2. The mean and standard deviations of Vas, Vam and Vakd were 0.921 ± 0.394, 0.479 ± 0.208 and 0.396 ± 0.220 cm s-1 , respectively, in the control group, and 0.865 ± 0.368, 0.424 ± 0.215 and 0.487 ± 0.279 cm s-1 , respectively, in group 1. The pulpal blood flow values of the control group and group 1 were not significantly different (p > 0.05). CONCLUSIONS: This laboratory study revealed that ultrasound Doppler flowmetry enabled the detection of simulated blood flow below the level of the CEJ but not at the mid-root level.

18F-NaF PET/CT for the evaluation of temporomandibular joint disorder.

AIM: To investigate the usefulness of a quantitative parameter (maximum standardised uptake value [SUVmax]) of 18F-sodium fluoride (NaF) positron-emission tomography (PET)/computed tomography (CT) for the evaluation of temporomandibular joint (TMJ) disorder (TMD). MATERIALS AND METHODS: Seventy-six TMD patients (male: female=14:62, age=40.3±17.1 years, bilateral: unilateral=40:36) with 152 TMJs were enrolled. The 18F-NaF PET/CT parameter (SUVmax) was compared with the presence of TMJ arthralgia (arthralgic=86, non-arthralgic=66) and clinical subtypes based on the Research Diagnostic Criteria for TMD Axis I (TMD osteoarthritis=49, non-TMD osteoarthritis=67, and asymptomatic TMJ=36). Splint therapy was applied to 48 patients for 6 months without considering 18F-NaF PET/CT findings. Post-splint therapy 18F-NaF PET/CT was performed in 32 patients and clinical responses to the therapy were classified into improvement (n=33), no change (n=10), or aggravation (n=7) for 50 TMJs excluding asymptomatic TMJs (n=14). RESULTS: SUVmax was significantly greater in arthralgic TMJs than in non-arthralgic TMJs (6.62±3.56 versus 4.32±1.53, p<0.0001). SUVmax was also significantly greater in TMD osteoarthritis (6.75±3.85) than in non-TMD osteoarthritis (5.21±2.70) and asymptomatic TMJs (4.86±1.99; p=0.0386). After splint therapy, SUVmax was significantly increased in aggravated TMJs (from 7.80±3.72 to 11.00±5.74, p=0.0156), whereas no significant change in SUVmax was observed in improved (from 6.16±2.68 to 6.09±2.60, p=0.4915) and unchanged (from 6.46±4.19 to 6.77±4.32, p=0.3223) TMJs. CONCLUSIONS: 18F-NaF PET/CT is a useful imaging tool for TMD evaluation because SUVmax showed a fair diagnostic performance for arthralgic TMJ and TMD osteoarthritis, and a correlation with the therapeutic response.

Influence of human parathyroid hormone during orthodontic tooth movement and relapse in the osteoporotic rat model: A preliminary study.

OBJECTIVE: To investigate the effects of parathyroid hormone (PTH) on tooth movement in ovariectomized (OVX) rats by comparing the tooth movement distance and relapse and by examining the alveolar bone microstructure. MATERIALS AND METHODS: Thirty 8-week-old female rats were classified into 3 groups: sham-operated, OVX and ovariectomized rats injected with PTH (PTH). Eight weeks later, a closed-coil spring appliance was placed between the maxillary incisor and the first molar and then activated with 50 cN of force. During tooth movement, 30 µg/kg of PTH was administered 3 times per week in the PTH group. Tooth movement distances were measured weekly. Five rats in each group were killed after 3 weeks for microcomputerized tomographic analysis, and the remaining 5 rats in each group were killed at an additional 3 weeks after the removal of the appliance to measure relapsed distance. RESULTS: The OVX group showed significantly greater tooth movement compared to those in the other 2 groups at 2 and 3 weeks (P < .05). The relapse distance and relapse percentage for the OVX group were higher; however, it did not differ significantly from the PTH group. On micro-CT analysis, bone volume/tissue volume ratio and bone mineral density in the PTH group were significantly greater than in the OVX group (P < .05). CONCLUSIONS: Application of PTH did not promote tooth movement in OVX rat, however, did lead to decrease in relapse tendency. Therefore, the application of PTH during orthodontic treatment of patients with osteoporosis should be carefully considered.

Measurement of pulp blood flow rates in maxillary anterior teeth using ultrasound Doppler flowmetry.

AIM: To measure pulp blood flow rates of clinically normal maxillary anterior teeth of healthy adults using ultrasound Doppler flowmetry (UDF). METHODOLOGY: A total of 359 anterior teeth from 63 patients (mean age, 29.8 years; range, 22-52 years; 26 females and 36 males) were included. The data were collected according to tooth type (three groups: central incisors, lateral incisors and canines). An MM-D-K (Minimax, Moscow, Russia) ultrasound Doppler imaging instrument was used to measure pulp blood flow. Differences between the tooth types were analysed with one-way anova and a Bonferroni correction at the 95% confidence level. RESULTS: The mean average linear velocities during the systolic period (Vams) of the central incisors, lateral incisors and canines were 0.58, 0.58 and 0.52 cm s(-1) , respectively. There were no significant differences in the mean Vams between the tooth types (P > 0.05). CONCLUSIONS: Within the limitations of this study, the pulp blood velocities of clinically normal, maxillary anterior teeth of healthy adults were between 0.5 and 0.6 cm s(-1) . There were no significant differences in mean blood flow rates between maxillary central incisors, lateral incisors and canines.

Factors affecting the success rate of buccal infiltration anaesthesia in the mandibular molar region.

AIM: To compare the anaesthetic efficacy of mandibular second premolar infiltration (SP) with that of mandibular first molar infiltration (FM) in inducing pulpal anaesthesia in the mandibular first molar. To further investigate the mechanisms of action that underlie mandibular infiltration, gender-related differences in the anaesthetic efficacy were also assessed. METHODOLOGY: A total of 29 adult subjects randomly received two sets of SP and FM injections using one cartridge (1.7 mL) of 4% articaine and 1 : 100 000 adrenaline at two separate appointments. The responses of the teeth were assessed using an electronic pulp tester over a 30-min period. A comparison of the anaesthetic success between the SP and FM infiltration routes was analysed using the McNemar's test. Gender-related differences in the anaesthetic success of infiltration routes were assessed using the Fisher's exact test. RESULTS: For the second premolar and the first and second molar teeth, the success rates of SP were 72.4%, 62.1% and 48.3%, whereas the success rates of FM were 75.9%, 51.7% and 55.1%, respectively. There were no significant differences between the success rates of SP and FM or between the rates obtained for each tooth. Significant gender-related differences were observed for the second premolar (P < 0.01) and the first molar (P < 0.05) using FM. However, a significant difference was observed only for the second premolar using SP (P < 0.05). CONCLUSIONS: The differences in the injection sites did not affect the anaesthetic success rates for the mandibular second premolar and molar teeth. However, articaine buccal infiltration produced a higher anaesthetic success rate in the second premolar and first molar teeth of Korean female patients.

Cryopreservation induces macrophage colony stimulating factor from human periodontal ligament cells in vitro.

Cryopreservation is used to protect vital periodontal ligaments during the transplantation of teeth. We investigated which gene products implicated in root resorption are upregulated in human periodontal ligament cells by cryopreservation, and whether cryopreservation affects the expression of macrophage-colony stimulating factor (M-CSF) in human periodontal ligament cells. We used customized microarrays to compare gene expression in human periodontal ligament cells cultured from teeth immediately after extraction and from cryopreserved teeth. Based on the result of these assays, we examined M-CSF expression in periodontal ligament cells from the immediately extracted tooth and cryopreserved teeth by real-time PCR, enzyme-linked immunosorbent assay (ELISA), Western blot analysis, and immunofluorescence. We also investigated whether human bone marrow cells differentiate into tartrate-resistant acid phosphatase (TRAP) positive osteoclasts when stimulated with RANKL (Receptor Activator for Nuclear Factor κ B Ligand) together with any secreted M-CSF present in the supernatants of the periodontal ligament cells cultured from the various groups of teeth. M-CSF was twofold higher in the periodontal ligament cells from the rapid freezing teeth than in those from the immediately extracted group (p < 0.05). Cryopreservation increased M-CSF expression in the periodontal ligament cells when analyzed by real time PCR, ELISA, Western blotting, and immunofluorescence (p < 0.05). TRAP positive osteoclasts were formed in response to RANKL and the secreted M-CSF present in the supernatants of all the experimental groups except negative control. These results demonstrate that cryopreservation promotes the production of M-CSF, which plays an important role in root resorption by periodontal ligament cells.

Doppler ultrasound to detect pulpal blood flow changes during local anaesthesia.

AIM: To examine whether Doppler ultrasound can detect changes in pulpal blood flow after infiltration anaesthesia. METHODOLOGY: Changes in pulpal blood flow in maxillary central incisor teeth of 18 patients (mean age 26.7 years, 13 men, five women) after infiltration anaesthesia were examined. Before infiltration anaesthesia, the pulpal blood flow was measured using Doppler ultrasound. A local anaesthetic solution containing 2% lidocaine with 1:80,000 epinephrine was injected into the submucosa above the experimental tooth. The Doppler ultrasound test was carried out at 5, 10, 20, 30, 45 and 60 min after infiltration. The parameters were Vas (maximum linear velocity, cm s(-1) ), Vam (average linear velocity, cm s(-1) ) and Vakd (minimum linear velocity, cm s(-1) ), which are indicators of the level of blood flow. The mixed procedure at the 95% confidence interval was used to examine the changes in pulpal blood flow after the injection. RESULTS: The linear velocity profiles (Vas, Vam, and Vakd) decreased sharply 5 min after anaesthesia and then reduced continuously for 30 min. The maximum degree of blood flow reduction in Vas, Vam and Vakd was 58%, 83% and 82%, respectively. After 30 min, the linear velocities increased gradually. The Vam returned to the pre-anaesthesia state at 60 minutes but the Vas and Vakd did not recover completely. CONCLUSIONS: Doppler ultrasound can detect changes in pulpal blood flow after infiltration anaesthesia. In the future, Doppler ultrasound can be used as a tool for measuring pulpal blood flow.

Detection and characterization of enterovirus associated with herpangina and hand, foot, and mouth disease in Seoul, Korea.

BACKGROUND: Human enteroviruses (HEVs) are a major cause of herpangina, HFMD (hand, foot, and mouth disease), and other neurological diseases in Seoul, Korea. METHODS: A total of 56 specimens from hospitalized patients collected from February to December 2009 (37 females and 19 males) in Seoul were tested for HEV from stool, throat swab, and vesicle swab samples taken from patients with herpangina or HFMD using cell culture and RT-PCR in 2009. By the 1D gene, encoding the VP1 capsid protein, seven different HEV genotypes were detected with Coxsackievirus A2, A4, A5, A9, A16 (CA), Coxsackievirus B1 (CB), and Enterovirus 71 (EV71). The most prevalent genotype was CA16 (6, 10.7%), followed by CA2 (4, 7.1%), CA5 (4, 7.1%), EV71 (2, 3.6%), CA4 (1, 1.8%), CA9 (1, 1.8%), and CB1 (1, 1.8%). The 1D gene sequences of two EV71 strains were closely related with one another (98.5% nucleotide similarity) and belonged to the C4 genotype. CONCLUSIONS: It is important to continuously survey the genetic characteristics of EV71 and CA16 from patients, which will provide useful data that aids in our understanding of HFMD infections in Seoul, Korea and may contribute to future control.

Comparison of premolar cuspal deflection in bulk or in incremental composite restoration methods.

OBJECTIVES: This study examined the cuspal deflection of maxillary premolars when either a bulk filling or incremental filling technique was employed using a range of composites with different elastic moduli. METHODS: Four brands of composite materials, Heliomolar (HM, Ivoclar Vivadent, Schaan, Liechtenstein), Heliomolar HB (HH, Ivoclar Vivadent, Schaan, Liechtenstein), Filtec Supreme XT (FS, 3M Dental Product, St Paul, MN, USA), and Renew (RN, Bisco Inc, Schaumburg, IL, USA), as well as three filling techniques, bulk filling, two-layer incremental filling, and three-layer incremental filling methods, were used. One hundred twenty caries-free human premolars were collected and divided into four groups according to the filling material used. Each of these four groups was then subdivided into three groups according to filling method. In group 1, a bulk filling of 0.15 g of each resin was inserted and light-cured with LED light from the occlusal, mesial, and distal surfaces for 60 seconds each. Group 2 was given two horizontal increments, 0.08 g and 0.07 g, with each increment light-cured from the occlusal, mesial, and distal surfaces for 30 seconds each. In group 3, three horizontal increments of 0.05 g were used, each of which was light-cured from the occlusal, mesial, and distal surfaces for 20 seconds each. The cuspal deflection was measured using a customized cuspal deflection measuring machine for 10 minutes after initiating light polymerization. The elastic modulus of each composite resin material was measured using a three-point bending test. Two-way analysis of variance (ANOVA) with a Dunnet test was used to examine the effect of the two variables (curing methods, materials) on the amount of cuspal deflection at the 95% confidence level. In each material, groups 1, 2 and 3 were compared using one-way ANOVA and a Dunnet test at the 95% confidence level. The elastic moduli of HM, HH, FS, and RN were compared using one-way ANOVA and a Tukey test at the 95% confidence level. The relationship between the amount of cuspal deflection in each group and the elastic modulus of the composite was analyzed using a Pearson correlation test. RESULTS: The amount of cuspal deflection in HH was larger than in the other materials (HM, FS, and RN; p<0.05). There was no significant difference between HM, FS, and RN. The amount of cuspal deflection was greatest in group 1, followed in order by groups 2 and 3 (p<0.05). The amount of cuspal deflection was in the following order: group 1≥2≥3 in HM, and 1>2, 3 in HH, FS, and RN. The elastic modulus was HH>RN>FS>HM (p<0.05). There was a positive correlation between the cuspal deflection and the elastic modulus of the composite. CONCLUSIONS: The incremental filling techniques reduced the amount of cuspal deflection in all composite groups with different elastic moduli. The amount of cuspal deflection showed a positive correlation with the elastic modulus of the composite.

Change in the Shrinkage Forces of Composite Resins According to Controlled Deflection.

The aim of this study was to investigate how the polymerization shrinkage forces of composite resins change with change in deflection. Five composites, SDR (Dentsply Caulk, Milford, DE, USA), EcuSphere-Shape (DMG, Hamburg, Germany), Tetric N-Ceram Bulk Fill (Ivoclar Vivadent, Schaan, Liechtenstein), CLEARFIL AP-X (Kuraray Noritake Dental Inc., Sakazu, Kurashiki, Okayama, Japan), and Filtek Z350 XT (3M Dental Products, St Paul, MN, USA), were tested in this experiment. The polymerization shrinkage forces of the composites were measured using a custom-made tooth-deflection-mimicking device and software (R&B Inc, Daejon, Korea). In all measurements, six modes were tested: maximum-deflection, zero-deflection, and four deflection-controlled modes. For each deflection mode, the shrinkage forces were recorded continuously every 0.1 second for 180 seconds. Polymerization shrinkage and flexural modulus were also measured. Eight specimens of each material were allocated for each test. For each material, six groups of shrinkage force values were compared using one-way ANOVA and Tukey post hoc tests at a 95% confidence level. The polymerization shrinkage force of each material in each of the six deflection modes was analyzed with 95% confidence using one-way ANOVA and Tukey post hoc tests. The relationship between the force measured in the six deflection modes and the linear polymerization shrinkage and flexural modulus was analysed with 95% confidence using Pearson correlation analysis. For each material, the following held true: the shrinkage force was highest in zero-deflection mode, the force decreased as deflection increased, and the smallest force appeared in maximum-deflection mode (p<0.05). There was a high negative correlation between allowable deflection and shrinkage force in all materials.

CPNE7 Induces Biological Dentin Sealing in a Dentin Hypersensitivity Model.

Dentin hypersensitivity commonly occurs due to opened dentinal tubules for many reasons. In our previous study, copine 7 (CPNE7) could induce dentin formation for an indirect pulp-capping model in vivo. This study aims to investigate the formation of tertiary dentin when CPNE7 is applied to intentionally exposed dentin with nothing over it in vivo, whether it affects microleakage of the teeth, and the penetration ability of CPNE7 molecules through dentinal tubules in vitro. Cervical dentin areas of 6 maxillary incisors of 5 beagles were exposed to a class V-like lesion, and 1 side of 3 maxillary incisors was adapted with recombinant CPNE7 protein for 5 min as the experimental group. The other side was the control group, and there was no treatment of ethylenediaminetetraacetic acid (EDTA) and CPNE7 after preparation. The defects were exposed without any restorations, and all beagles were sacrificed after 4 wk. The fluid penetration of exposed dentin areas was investigated by a microleakage-testing device and confocal laser scanning microscope. Tertiary dentin formation was confirmed with histological scanning electronic microscopic analysis. Tertiary dentin formation reduces dentinal fluid flow due to occluded tubules or discontinuity with primary or secondary dentin. The in vivo hypersensitivity model with the anterior teeth of beagle dogs showed newly formed tertiary dentin at the dentin-pulp boundary in recombinant CPNE7-treated teeth when compared with the untreated control group in histologic analysis. Scanning electronic microscopic analysis revealed occluded sites with mineral deposition of intratubular dentin. In the permeability test, the mean microleakage value of the CPNE7-treated group was significantly lower than that of the control group (P < 0.05). The tubular penetration of rhodamine B-combined CPNE7 was confirmed under confocal laser scanning microscope. CPNE7 induces formation of tertiary dentin through shallowly exposed dentinal tubules, which decreases dentin permeability.

Comparison of clinical results between heparin surface modified hydrophilic acrylic and hydrophobic acrylic intraocular lens.

PURPOSE: To compare the clinical results of heparin surface modified (HSM) hydrophilic acrylic intraocular lens (IOL) with those of hydrophobic acrylic IOL. METHODS: One hundred patients with cataract were randomized to receive one of acrylic foldable IOLs after phacoemulsification: HSM hydrophilic acrylic IOL (n=50) BioVue3 (BioVue, OII, Ontario, CA, USA) and hydrophobic acrylic IOL (n=50) Sensar (AR40e, AMO, Santa Ana, CA, USA). Bestcorrected visual acuity and refractive error were measured at 1 week, 2 months, 6 months and 12 months after surgery in both IOL groups. To assess posterior capsular opacification (PCO), digital retroillumination image of posterior capsule was analyzed at 12 months using POCOman software. RESULTS: Best-corrected visual acuity (log MAR) was 0.032+/-0.082 in BioVue3 group and 0.034+/-0.077 in Sensar group at 12 months. There was no statistically significant difference between the two groups (p=0.554). Refractive error was -0.247+/-0.821 diopter in BioVue3 group and -0.264+/-0.808 diopter in Sensar group at 12 months. There was no statistically significant difference of refractive error between the two groups (p=0.909). At 12 months, BioVue3 IOL group had a lower percentage area and severity of PCO than Sensar group. However, it was not statistically significant (p=0.349, p=0.288). No Nd:YAG capsulotomy was performed in BioVue3 group while it was required in two eyes (4.0%) in Sensar group. CONCLUSIONS: There was no statistically significant difference of postoperative visual acuity, refractive error and degree of PCO between HSM hydrophilic acrylic IOL and hydrophobic acrylic IOL.

Color and Translucency of Resin-based Composites: Comparison of A-shade Specimens Within Various Product Lines.

OBJECTIVES:: The purpose of this study was to examine and compare the color and translucency of currently available resin-based composites (RBCs) with respect to the shade numbers within each product line. METHODS AND MATERIALS:: Four A-shades (A1, A2, A3, and A3.5) of nine RBC products (Beautifil II, Ceram-X One, Estelite Sigma Quick, Esthet-X HD, Filtek Z250, Filtek Z350 XT, Gradia Direct, Herculite Precis, and Tetric N-Ceram) were investigated. Ten disk-shaped specimens of two different thicknesses (1 and 2 mm) were prepared for each shade of the RBCs. The maximum blue light irradiance (Imax) through the specimen was recorded using a digital optometer. The color measurements were made according to the CIELAB color scale (quantifying L*, a*, and b*) using a colorimeter, and the translucency parameter (TP) was calculated. The L*, a*, b*, TP, and Imax values were compared among the different shades and thicknesses of each product using one-way analysis of variance followed by Tukey's post hoc test. RESULTS:: There were significant differences in the color and translucency among the shades and thicknesses within each product line ( p<0.001). The L*, Imax, and TP of the 1-mm specimens were higher than those of the 2-mm specimens. The specimens showed equal or lower L* and Imax for higher shade numbers. The a* values differed only slightly among the shades, whereas the b* values were distributed over a relatively wide range. The TP values were independent of the order of shade numbers. CONCLUSIONS:: Within the limitations of this study, the RBCs became darker and yellowish as the shade number increased. The blue light irradiance decreased in increasing order of the shade numbers. Changes in the translucency demonstrated different trends among the shades, depending on the product line.

Incremental and Bulk-fill Techniques With Bulk-fill Resin Composite in Different Cavity Configurations.

PURPOSE:: To compare the microtensile bond strengths of incremental and bulk-fill techniques under different C-factor and compliance conditions. METHODS AND MATERIALS:: Extracted human third molars were divided into three experimental groups. For group I, Class I cavities were prepared. For group II, MOD cavities of the same size were prepared. For group III, the cavities were prepared the same way as group II only with high compliance cavity walls. The cavity wall compliance of the specimens was evaluated. Each of these groups was divided into four subgroups. The teeth were restored using two different materials: TB (Tetric N-Ceram Bulk Fill; Ivoclar Vivadent, Hanau, Germany) and VB (Venus Bulk Fill; Heraeus Kulzer, Armonk, NY, USA), and two methods, either an incremental or bulk-fill technique. Then, the microtensile bond strengths (µ-TBSs) were measured and compared. The polymerization stresses of the composites were calculated using a custom-made device. The results were statistically analyzed using the Kruskal-Wallis test and Weibull analysis. RESULTS:: In group I, the µ-TBS obtained using the incremental technique was significantly higher than that obtained by the bulk-fill technique ( p<0.05). In contrast, no difference of the µ-TBS value was observed between the two techniques in groups II and III. The µ-TBS value of group I was significantly lower than those of groups II and III ( p<0.05). No statistical difference in the µ-TBS was observed when the cavities were filled with either TB or VB ( p>0.05). CONCLUSIONS:: The incremental technique showed higher bond strength than did the bulk-fill technique in high C-factor cavities. However, no difference was found between the two techniques in the low C-factor cavities. The bond strength in the high C-factor cavities was significantly lower than that of the low C-factor cavities.

Comparison of Internal Adaptation in Class II Bulk-fill Composite Restorations Using Micro-CT.

PURPOSE: This study compared the internal adaptation of bulk-fill composite restorations in class II cavities and explored the relationship between internal adaptation and polymerization shrinkage or stress. METHODS AND MATERIALS: Standardized mesio-occluso-distal cavities were prepared in 40 extracted human third molars and randomly divided into five groups (n=8). After having been applied by total-etch XP bond (Dentsply Caulk, Milford, DE, USA) and light curing, the teeth were restored with the following resin composites: group 1, Filtek Z350 (3M ESPE, St. Paul, MN, USA); group 2, SDR (Dentsply Caulk, Milford, DE, USA) + Z350; group 3, Venus Bulk Fill (Heraeus Kulzer, Dormagen, Germany) + Z350; group 4, Tetric N-Ceram Bulk Fill (Ivoclar Vivadent, Schaan, Liechtenstein); and group 5, SonicFill (Kerr, West Collins, Orange, CA, USA). After thermo-mechanical load cycling, cross-sectional microcomputerized tomography (micro-CT) images were taken. Internal adaptation was measured as imperfect margin percentage (IM%), which was the percentage of defective margin length relative to whole margin length. On the micro-CT images, IM% was measured at five interfaces. Linear polymerization shrinkage (LS) and polymerization shrinkage stress (PS) were measured on each composite with a custom linometer and universal testing machine. To explore the correlation of IM% and LS or PS, the Pearson correlation test was used. RESULTS: The IM% of the gingival and pulpal cavity floors were inferior to those of the cavity walls. The IM% values of the groups were found to be as follows: group 5 ≤ groups 1 and 4 ≤ group 2 ≤ group 3. The correlation analysis showed that the p value was 0.006 between LS and IM% and 0.003 between PS and IM%, indicating significant correlations (p<0.05). CONCLUSION: Flowable bulk-fill composites had a higher IM% and polymerization shrinkage stress than did packable bulk-fill and hybrid composites. In class II composite restoration, the gingival floor of the proximal box and pulpal floor of the cavity had higher IM% than did the buccal and lingual walls of the proximal box. LS and PS, which were measured under compliance-allowed conditions, were significantly related to internal adaptation.

Comparison of Polymerization Shrinkage, Physical Properties, and Marginal Adaptation of Flowable and Restorative Bulk Fill Resin-Based Composites.

PURPOSE: The purpose of this study was to compare the marginal adaptation of two flowable bulk fill resin-based composites (FB-RBCs), two restorative bulk fill resin-based composites (RB-RBCs), and one regular incremental-fill RBC in MOD cavities in vitro. Additionally, the influence of linear polymerization shrinkage, shrinkage force, flexural modulus, and bottom/top surface hardness ratio on the marginal adaptation was evaluated. METHODS: A Class II MOD cavity was prepared in 40 extracted sound lower molars. In group 1 (control group), the preparation was filled with Filtek Z350 (Z3, 3M ESPE, St Paul, MN, USA) using the incremental filling technique. The FB-RBCs, SDR (SD, group 2) (Dentsply Caulk, Milford, DE, USA) and Venus Bulk Fill (VB, group 3) (Heraeus Kulzer, Dormagen, Germany), were placed in the core portion of the cavity first, and Z350 was filled in the remaining cavity. The RB-RBCs, Tetric N-Ceram Bulkfill (TB, group 4) (Ivoclar Vivadent, Schaan, Liechtenstein) and SonicFill (SF, Group 5) (Kerr, West Collins, Orange, CA, USA), were bulk filled into the preparation. Images of the magnified marginal area were captured under 100× magnification before and after thermomechanical loading, and the percentage ratio of the imperfect margin (%IMwhole) was calculated. Gaps, cracks in the enamel layer, and chipping of composite, enamel, or dentin were all considered to be imperfect margins. Linear polymerization shrinkage, polymerization shrinkage force, flexural strength, flexural modulus, and bottom/top surface hardness ratio of were measured. Eight specimens were allocated for each material for each test. One-way analysis of variance with the Scheffé test was used to compare the groups at a 95% confidence level. RESULTS: Before thermomechanical loading, %IMwhole was in the order of group 3 ≤ groups 2 and 5 ≤ groups 1 and 4 (p=0.011), whereas after loading, it was in the order of group 4 ≤ group 5 ≤ group 1 ≤ groups 2 and 3 (p<0.001). The order of materials were Z3 < TB and SF < SD and VB (p<0.001) in polymerization shrinkage; SF ≤ TB ≤ Z3 < SD < VB (p<0.001) in polymerization shrinkage force; VB < SD < TB ≤ Z3 ≤ SF (p<0.001) in flexural modulus; SD, VB, and TB < Z3 and SF (p<0.001) in flexural strtength; and SF< Z3 < TB < VB and SD (p<0.001) in bottom/top surface hardness ratio. The Pearson correlation constant between %IMwhole and polymerization shrinkage, shrinkage force, elastic modulus, and bottom/top surface hardness ratio was 0.697, 0.708, -0.373, and 0.353, respectively, after thermomechanical loading. CONCLUSION: Within the limitations of this study, RB-RBCs showed better marginal adaptation than FB- RBCs. The lower level of polymerization shrinkage and polymerization shrinkage stress in RB-RBCs seems to contribute to this finding because it would induce less polymerization shrinkage force at the margin. FB-RBCs with lower flexural modulus may not provide an effective buffer to occlusal stress when they are capped with regular RBCs.

Chronologic Trends in Studies on Fluoride Mechanisms of Action.

Fluoride has been widely used for the prevention of dental caries since the mid-20th century. The aim of this study was to investigate the chronologic trends in studies on fluoride mechanisms of action against dental caries during the years 1950 to 2015. To this aim, queries such as "fluoride," "fluoride and demineralization," "fluoride and remineralization," "fluoride and (plaque or biofilms)," and "fluoride and (bacteria or microbials)" were submitted to PubMed to collect research article information, including titles, abstracts, publication dates, author affiliations, and publication journals. The article information that PubMed produced was then collected by an automatic web crawler and examined through informetrics and linguistic analyses. We found that the number of articles concerned with fluoride mechanisms of action against dental caries was 6,903 and gradually increased over time during the years 1950 to 2015. They were published by 1,136 journals-most notably, Caries Research and Journal of Dental Research. Of the articles published, those related to bacteria/microbials had a higher percentage (44%) than those dealing with plaque/biofilms, demineralization, and remineralization. With regard to the geographic distribution of authors, Europe and North America accounted for 65% of the articles during the years 1987 to 2015, although the number of authors in Asia sharply increased in recent years. Among the fluoride compounds, NaF was mentioned more frequently than SnF2, Na2PO3F, amine fluoride, and acidulated phosphate fluoride during the years 1986 to 2015. Water fluoridation received the most attention among the various fluoride application methods (toothpastes, mouthwashes, fluoride varnishes, and fluoride gels) during the same period. These results, obtained from employing informetrics and linguistic analyses, suggest that in studies on fluoride mechanisms of action, 1) the unbalanced geographic distribution of articles and 2) the heavy concentration of articles on particular fluoride compounds and application methods should be overcome in future research.

Clinical and radiological outcomes of transoral endoscope-assisted treatment of mandibular condylar fractures.

Fractures of the mandibular condyle are one of the most common craniofacial fractures. However, the diagnosis and treatment of these fractures is controversial because of the multiple surgical approaches available. The purposes of this study were to identify surgery-related technical tips for better outcomes and to evaluate the results as well as complications encountered during 7 years of endoscope use to supplement the limited intraoral approach in the treatment of mandibular condylar fractures. Between 2005 and 2012, 50 patients with condylar fractures underwent endoscope-assisted reduction surgery. Postoperative facial bone computed tomography and panoramic radiography demonstrated adequate reduction of the condylar fractures in all patients. No condylar resorption was detected, and most patients displayed a satisfactory functional and structural recovery. There was no facial nerve damage or transitory hypoesthesia, and there were no visible scars after the surgery. Transoral endoscope-assisted treatment is a challenging but reliable method with lower morbidity and a rapid recovery.

Polymerization shrinkage and depth of cure of bulk-fill resin composites and highly filled flowable resin.

The aim of this study was to evaluate the polymerization behavior and depth of cure (DOC) of recently introduced resin composites for posterior use: highly filled flowable composite and composites for bulk fill. A highly filled flowable (G-aenial Universal Flo [GUF]), two bulk-fill flowables (Surefil SDR Flow [SDR] and Venus Bulk fill [VBF]), and a bulk-fill nonflowable composite (Tetric N-Ceram Bulk fill [TBF]) were compared with two conventional composites (Tetric Flow [TF], Filtek Supreme Ultra [FS]). Linear polymerization shrinkage and polymerization shrinkage stress were each measured with custom-made devices. To evaluate DOC, the composite specimen was prepared using a mold with a hole of 4 mm depth and 4 mm internal diameter. The hole was bulk filled with each of the six composites and light cured for 20 seconds, followed by 24 hours of water storage. The surface hardness was measured on the top and the bottom using a Vickers microhardness (HV) indenter. The linear polymerization shrinkage of the composite specimens after photo-initiation decreased in the following order: TF and GUF > VBF > SDR > FS and TBF (p<0.05). The polymerization shrinkage stress of the six composite groups decreased in the following order: GUF > TF and VBF > SDR > FS and TBF (p<0.05). The mean bottom surface HV of SDR and VBF exceeded 80% of the top surface HV (HV-80%). However, the bottom of GUF and TBF failed to reach HV-80%. A highly filled flowable (GUF) revealed limitations in polymerization shrinkage and DOC. Bulk-fill flowables (SDR and VBF) were properly cured in 4-mm bulk, but they shrank more than the conventional nonflowable composite. A bulk-fill nonflowable (TBF) showed comparable shrinkage to the conventional nonflowable composite, but it was not sufficiently cured in the 4-mm bulk.