Retention of Intrafibrillar Minerals Improves Resin-Dentin Bond Durability.

The concept of extrafibrillar demineralization involves selective removal of apatite crystallites from the extrafibrillar spaces of mineralized dentin without disturbing the intrafibrillar minerals within collagen. This helps avoiding activation of endogenous proteases and enables air-drying of partially demineralized dentin without causing collapse of completely demineralized collagen matrix that adversely affects resin infiltration. The objective of the present study was to evaluate the potential of quaternized carboxymethyl chitosan (QCMC)-based extrafibrillar demineralization in improving resin-dentin bond durability. Isothermal titration calorimetry indicated that QCMC synthesized by quaternization of O-carboxymethyl chitosan had moderate affinity for Ca2+ (binding constant: 8.9 × 104 M-1). Wet and dry bonding with the QCMC-based demineralization produced tensile bond strengths equivalent to the phosphoric acid (H3PO4)-based etch-and-rinse technique. Those bond strengths were maintained after thermocycling. Amide I and PO43- mappings of QCMC-conditioned dentin were performed with atomic force microscope-infrared spectroscopy (AFM-IR). Whereas H3PO4-etched dentin exhibited an extensive reduction in PO43- signals corresponding to apatite depletion, QCMC-conditioned dentin showed scattered dark areas and bright PO43- streak signals. The latter were consistent with areas identified as collagen fibrils in the amide I mapping and were suggestive of the presence of intrafibrillar minerals in QCMC-conditioned dentin. Young's modulus mapping of QCMC-demineralized dentin obtained by AFM-based amplitude modulation-frequency modulation recorded moduli that were the same order of magnitude as those in mineralized dentin and at least 1 order higher than H3PO4-etched dentin. In situ zymography of the gelatinolytic activity within hybrid layers created with QCMC conditioning revealed extremely low signals before and after thermocycling, compared with H3PO4-etched dentin for both wet and dry bonding. Confocal laser scanning microscopy identified the antibacterial potential of QCMC against Streptococcus mutans and Enterococcus faecalis biofilms. Taken together, the QCMC-based demineralization retains intrafibrillar minerals, preserves the elastic modulus of collagen fibrils, reduces endogenous proteolytic activity, and inhibits bacteria biofilms to extend dentin bond durability.

Application of Artificial Intelligence in Dentistry.

Artificial intelligence (AI) is a technology that utilizes machines to mimic intelligent human behavior. To appreciate human-technology interaction in the clinical setting, augmented intelligence has been proposed as a cognitive extension of AI in health care, emphasizing its assistive and supplementary role to medical professionals. While truly autonomous medical robotic systems are still beyond reach, the virtual component of AI, known as software-type algorithms, is the main component used in dentistry. Because of their powerful capabilities in data analysis, these virtual algorithms are expected to improve the accuracy and efficacy of dental diagnosis, provide visualized anatomic guidance for treatment, simulate and evaluate prospective results, and project the occurrence and prognosis of oral diseases. Potential obstacles in contemporary algorithms that prevent routine implementation of AI include the lack of data curation, sharing, and readability; the inability to illustrate the inner decision-making process; the insufficient power of classical computing; and the neglect of ethical principles in the design of AI frameworks. It is necessary to maintain a proactive attitude toward AI to ensure its affirmative development and promote human-technology rapport to revolutionize dental practice. The present review outlines the progress and potential dental applications of AI in medical-aided diagnosis, treatment, and disease prediction and discusses their data limitations, interpretability, computing power, and ethical considerations, as well as their impact on dentists, with the objective of creating a backdrop for future research in this rapidly expanding arena.

Root canal debridement using manual dynamic agitation or the EndoVac for final irrigation in a closed system and an open system.

AIM: This study examined canal debridement efficacy by testing the null hypothesis that there is no difference between a 'Closed' and an 'Open' system design in smear layer and debris removal using either manual dynamic agitation or the EndoVac for irrigant delivery. METHODOLOGY: Forty teeth were divided into four groups and submitted to a standardized instrumentation protocol. Final irrigation was performed with either manual dynamic agitation or the EndoVac on groups of teeth with or without a sealed apical foramen. Smear and debris scores were evaluated using SEM and analysed using Cochran-Mantel-Haenszel statistic. RESULTS: The ability of manual dynamic agitation to remove smear layer and debris in a closed canal system was significantly less effective than in an open canal system and significantly less effective than the EndoVac (P<0.001). CONCLUSION: The null hypothesis was rejected; the presence of a sealed apical foramen adversely affected debridement efficacy when using manual dynamic agitation but not the EndoVac. Apical negative pressure irrigation is an effective method to overcome the fluid dynamics challenges inherent in closed canal systems.

[Etiology, diagnosis, prevention and treatment of dental fluorosis].

Dental fluorosis is the most common and prominent symptom in the early stage of chronic fluorosis, which is caused by excessive fluorine intake during tooth development. In severe cases, it may be accompanied by skeletal fluorosis. There are also systemic damages to the nervous system, cardiovascular system, endocrine system and so on. The pathogenesis of dental fluorosis is not totally clear, which may be a complex pathological process involving both genetic and environmental factors. The prevalence of dental fluorosis has an upward trend arround the world, thus certain public prevention and treatment strategies need to be taken. This article focuses on the prevalence, etiology, diagnosis and scoring system, as well as the public prevention and treatment strategies, of dental fluorosis, so that to provide reference for the research and prevention of the disease.

Chitosan-Based Extrafibrillar Demineralization for Dentin Bonding.

Instability of resin-dentin bonds is the Achilles' heel of adhesive dentistry. To address this problem, a chelate-and-rinse extrafibrillar dentin demineralization strategy has been developed that keeps intrafibrillar minerals within collagen fibrils intact to prevent activation of endogenous proteases that are responsible for collagen degradation within hybrid layers. The objective of the present study was to evaluate the potential of using chitosan >40 kDa as an antimicrobial extrafibrillar dentin-chelating agent to enhance bond durability. Transmission electron microscopy provided evidence for retention of intrafibrillar minerals and smear plugs in dentin conditioned with 1 wt% chitosan. Analyzed by Kruskal-Wallis analysis of variance, Dunn's statistic, and separate Mann-Whitney tests, tensile bond strengths to wet- and dry-bonded dentin indicated that chelating dentin with chitosan for 60 s prior to bonding did not result in a significant decline in resin-dentin bond strength when compared with that of phosphoric acid etching ( P > 0.05). Gelatinolytic activity within the hybrid layers was examined via in situ zymography after 24-h storage or after thermomechanical cycling and analyzed with 3-factor analysis of variance. After 24 h, enzymatic activity was detected only within completely demineralized phosphoric acid-etched dentin, with values derived from dry bonding significantly higher than those derived from wet bonding ( P < 0.05). Negligible fluorescence was detected within hybrid layers when dentin was conditioned with chitosan, even after thermomechanical cycling, as compared with the controls. Reduction in water permeability in chitosan-conditioned dentin, attributed to smear plug retention, also fostered long-term bond stability. Antibacterial testing performed with live/dead staining indicated that the acetic acid-solubilized chitosan possessed antibacterial activities against 3 single-species biofilms: Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis. Taken together, the new chitosan-based extrafibrillar demineralization strategy retains intrafibrillar minerals, reduces endogenous protease-initiated collagen degradation, prevents water permeation within hybrid layers, and kills bacteria on dentin surfaces, which are crucial factors for enhancing resin-dentin bond durability.

Efficacy of ProTaper Universal rotary retreatment system for gutta-percha removal from root canals.

AIM: To evaluate the efficacy of the ProTaper Universal rotary retreatment system for gutta-percha (GP) removal from root canals. METHODOLOGY: Root canals of 60 extracted human maxillary anterior teeth were prepared and filled with laterally condensed GP and AH Plus sealer. Teeth were divided into three groups: group A--GP removal completed with the ProTaper Universal rotary retreatment system and with further canal repreparation accomplished with ProTaper Universal rotary instruments; group B--GP removal was completed using Gates Glidden drills and Hedström files with chloroform as a solvent, followed with further canal repreparation with ProTaper Universal rotary instruments; group C--the same as group B for GP removal with further canal preparation with stainless steel K-flex files (Kerr). The operating time was recorded. Teeth were rendered transparent for the evaluation of the area of remaining GP/sealer in bucco-lingual and mesial-distal directions. Statistical analysis was performed by using repeated measures analysis of variance and anova. Results The ProTaper Universal technique (group A) resulted in a smaller percentage of canal area covered by residual GP/sealer than in groups B and C, with a significant difference between groups A and C (P < 0.05). Mean operating time for group A was 6.73 min, which was significantly shorter (P < 0.05) than group B (10.86 min) and group C (13.52 min). CONCLUSIONS: In this laboratory study all test techniques left GP/sealer remnants within the root canal. The ProTaper Universal rotary retreatment system proved to be an efficient method of removing GP and sealer from maxillary anterior teeth.

Zymography of Hybrid Layers Created Using Extrafibrillar Demineralization.

A chelate-and-rinse extrafibrillar calcium chelation dentin bonding concept has recently been developed and investigated for its effectiveness in improving resin-dentin bonding by bridging the gap between wet and dry dentin bonding. The objective of the present study was to evaluate the gelatinolytic activity of hybrid layers (HLs) created using the chelate-and-rinse bonding technique. Gelatinolytic activity within the HL was examined using in situ zymography and confocal laser-scanning microscopy after 24-h storage or after thermomechanical cycling. Dentin specimens were bonded with Prime&Bond NT (Dentsply Sirona) after conditioning with 15 wt% phosphoric acid for 15 s (control) or 15 wt% polymeric chelators (sodium salt of polyacrylic acid; PAAN) of 2 different molecular weights for 60 s. For each reagent, bonding was performed using dry-bonding and wet-bonding techniques ( n = 10). Slices containing the adhesive-dentin interface were covered with fluorescein-conjugated gelatin and examined with a confocal laser-scanning microscope. Fluorescence intensity emitted by the hydrolyzed fluorescein-conjugated gelatin was quantified. Gelatinolytic activity was expressed as the percentage of green fluorescence emitted within the HL. After storage for 24 h, enzymatic activity was only detected within the completely demineralized phosphoric acid-etched dentin, with values derived from dry bonding higher than those from wet bonding ( P < 0.05). Almost no fluorescence signals were detected within the HL when dentin was conditioned with PAANs compared with the controls ( P < 0.05). After thermomechanical cycling, enzymatic activities significantly increased for the phosphoric acid-conditioned, drying-bonding group compared with 24-h storage ( P < 0.05). The present study showed that the use of the chelate-and-rinse bonding concept for both dry-bonding and wet-bonding approaches results in the near absence of matrix-bound collagenolytic activities in the HL even after aging. This may be attributed to fossilization of endogenous proteases via preservation of intrafibrillar minerals within the dentin collagen matrix.

Influence of teardrop studs on rotating frictional base plate on spheroid quality in rotary spheronization.

The effects of teardrop-shaped studs on the quality of rotary processed spheroids were investigated. The spheroids were produced under similar conditions using three rotating frictional base plates with teardrop studs of different height, volume, cross-sectional area and surface area. Spheroid properties were rated by size, size distribution, shape, friability and density. The amounts of lumps and fines produced, and the adhesion of material on the rotating frictional base plates was also looked into. The dimension of the teardrop studs on the rotating frictional base plate affected spheroid quality. The resultant shear forces and energy input during rotary spheronization differed depending on the different height, volume, cross-sectional area and surface area of studs. With the increase in height, volume, cross-sectional area and surface area of studs on the frictional base plate, the mass median diameter, e(R) and circularity of spheroids increased with corresponding decrease in span, lumps and fines. Although the frictional base plate with shortest studs had little adhesion, it may not supply enough shear force and energy input for the spheronization process, resulting in a less stable process. A balance between energy input and adhesion on the rotating frictional base plate was needed in order to optimize the production of spheroids by rotary processing.

Detection of marginal leakage of Class V restorations in vitro by micro-computed tomography.

This in vitro study evaluated the efficacy of micro-computed tomography (CT) in marginal leakage detection of Class V restorations. Standardized Class V preparations with cervical margins in dentin and occlusal margins in enamel were made in 20 extracted human molars and restored with dental bonding agents and resin composite. All teeth were then immersed in 50% ammoniacal silver nitrate solution for 12 hours, followed by a developing solution for eight hours. Each restoration was scanned by micro-CT, the depth of marginal silver leakage in the central scanning section was measured, and the three-dimensional images of the silver leakage around each restoration were reconstructed. Afterward, all restorations were cut through the center and examined for leakage depth using a microscope. The silver leakage depth of each restoration obtained by the micro-CT and the microscope were compared for equivalency. The silver leakage depth in cervical walls observed by micro-CT and microscope showed no significant difference; however, in certain cases the judgment of leakage depth in the occlusal wall in micro-CT image was affected by adjacent enamel structure, providing less leakage depth than was observed with the microscope (p<0.01). Micro-CT displayed the three-dimensional image of the leakage around the Class V restorations with clear borders only in the dentin region. It can be concluded that micro-CT can detect nondestructively the leakage around a resin composite restoration in two and three dimensions, with accuracy comparable to that of the conventional microscope method in the dentin region but with inferior accuracy in the enamel region.

Clinical outcome of dental implants placed in liver transplant recipients after 3 years: a case series.

BACKGROUND: The use of dental implants in organ transplant patients remains controversial because of their altered wound healing and risk of serious infections. The aims of this study were to evaluate the long-term survival rate and related clincial parameters of dental implants among liver transplant patients on immunosuppressive medications. METHODS: We placed 45 implants in 13 liver transplant patients. All implants were sucessfully placed in the mandible or maxilla. The success rate, perimplant bone absorption (MBL), probing depth and Periotest values were measured at 3 months, as well as 1 and 3 years. RESULTS: At 3 years' follow-up, no implants were lost. MBL and Periotest values were within acceptable ranges without bleeding on probing or pathological probing depth. CONCLUSION: This series supports the use of dental implants in liver transplant patients who are stable under long-term immunosuppression.

Biomimetic analogs for collagen biomineralization.

Inability of chemical phosphorylation of sodium trimetaphosphate to induce intrafibrillar mineralization of type I collagen may be due to the failure to incorporate a biomimetic analog to stabilize amorphous calcium phosphates (ACP) as nanoprecursors. This study investigated adsorption/desorption characteristics of hydrolyzed and pH-adjusted sodium trimetaphosphate (HPA-Na(3)P(3)O(9)) to collagen. Based on those results, a 5-minute treatment time with 2.8 wt% HPA-Na(3)P(3)O(9) was used in a single-layer reconstituted collagen model to confirm that both the ACP-stabilization analog and matrix phosphoprotein analog must be present for intrafibrillar mineralization. The results of that model were further validated by complete remineralization of phosphoric-acid-etched dentin treated with the matrix phosphoprotein analog and lined with a remineralizing lining composite, and with the ACP-stabilization analog supplied in simulated body fluid. An understanding of the basic processes involved in intrafibrillar mineralization of reconstituted collagen fibrils facilitates the design of novel tissue engineering materials for hard tissue repair and regeneration.

Implication of ethanol wet-bonding in hybrid layer remineralization.

During mineralization, unbound water within the collagen matrix is replaced by apatite. This study tested the null hypothesis that there is no difference in the status of in vitro biomimetic remineralization of hybrid layers, regardless of their moisture contents. Acid-etched dentin was bonded with One-Step with ethanol-wet-bonding, water-wet-bonding, and water-overwet-bonding protocols. Composite-dentin slabs were subjected to remineralization for 1-4 months in a medium containing dual biomimetic analogs, with set Portland cement as the calcium source and characterized by transmission electron microscopy. Remineralization was either non-existent or restricted to the intrafibrillar mode in ethanol-wet-bonded specimens. Extensive intrafibrillar and interfibrillar remineralization was observed in water-wet-bonded specimens. Water-overwet specimens demonstrated partial remineralization of hybrid layers and precipitation of mineralized plates within water channels. The use of ethanol-wet-bonding substantiates that biomimetic remineralization is a progressive dehydration process that replaces residual water in hybrid layers with apatite crystallites.

Failure of a glass ionomer to remineralize apatite-depleted dentin.

Remineralization of demineralized dentin lesions adjacent to glass-ionomer cements (GICs) has been reported in the literature. This study tested the hypothesis that a strontium-based GIC can remineralize completely demineralized dentin by nucleation of new apatite crystallites within an apatite-free dentin matrix. Human dentin specimens were acid-etched, bonded with Fuji IX(GP), and immersed in a calcium-and-phosphate-containing 1.5X simulated body fluid (SBF) for 1-4 months. Polyacrylic acid and polyvinylphosphonic acid biomimetic analogs were added to the SBFs to create 2 additional remineralization media. Specimens were processed by transmission electron microscopy (TEM). No apatite deposition could be identified in the completely demineralized dentin in any of the specimens immersed in the 3 remineralization media, despite TEM/EDX evidence of diffusion of ions specific to the strontium-based GIC into the demineralized dentin. The hypothesis was rejected; mineral concentration alone is not a sufficient endpoint for assessing the success of contemporary remineralization strategies.

Feasibility of eliminating premixing for the production of pellets in a rotary processor.

This current study aims to explore the feasibility of eliminating the premixing step for making pellets in a rotary processor. Microcrystalline cellulose (MCC) and lactose were used as starting materials. They could be loaded into the rotary processor separately using three different loading configurations (Methods I, II, and III) or as MCC:lactose blend, which was prepared in the separate mixer prior to loading (Method IV). Physical properties of the pellets prepared in Methods I-III were evaluated and compared against those prepared using a premixed blend (Method IV). The effects of loading configuration on pellet quality can be assessed by comparing the pellets prepared in Methods I, II, and III. Physical characterization of pellets included mean size, size distribution, oversized fraction, and shape. No significant difference in pellet properties could be attributed to the effect of premixing. Pellet properties were not significantly affected by the different loading configurations either. This study demonstrated that homogeneous powder blends are not required for the production of pellets in rotary processing. The tumbling action of the powders at the start of rotary processing is sufficient to ensure adequate powder mixing. However, it may be judicious to cofeed the different powders to achieve some preliminary mixing during loading under extreme processing conditions.

[Survey of caries in 1052 non native children located in Putuo District of Shanghai City].

OBJECTIVE: To investigate the prevalence of caries in non-native children located in Putuo District of Shanghai. METHODS: A survey of caries was performed in 1052 non-native children according to the Criteria for National Oral Epidemiologic Survey. RESULTS: Caries prevalence rate in deciduous teeth was 85.8%, DFT was 4.61. Caries prevalence rate in permanent teeth was 6.45%, DFT was 1.4. CONCLUSION: The prevalence rate of caries in non-native children located in Putuo District of Shanghai was still higher. More attention should be addressed in prevention and treatment.

Treatment of acute experimental toxoplasmosis with investigational poloxamers.

Because of the limited chemotherapeutic approaches available to treat reactivated latent Toxoplasma gondii infection manifested as toxoplasmic encephalitis in AIDS patients, investigation of novel chemotherapeutic agents is warranted. Several poloxamers (nonionic block copolymers composed of a central hydrophobic chain of polyoxypropylene flanked by two hydrophilic chains of polyoxyethylene) were tested for their abilities to alter the course of acute infection with a highly virulent T. gondii in mice. The effect varied markedly with the length of the constituent chains of the copolymers. The most effective preparations were highly effective when administered after infection and afforded remarkable protection against 10 to 1,000 100% lethal doses of T. gondii. Protection was dose dependent, and multiple treatments were more effective than single treatment. These preliminary findings warrant additional studies to determine whether this novel form of antitoxoplasma chemotherapy may prove promising in the treatment or prevention of acute toxoplasmic encephalitis in humans.

Wet spheronization by rotary processing--a multistage single-pot process for producing spheroids.

Spheronization is an agglomerative size enlargement process for producing spherical agglomerates that have many technological and therapeutical advantages. Rotary processing is an efficient multistage, single-pot spheroid production method. The rotary processor can be used for spheroid production, drying as well as coating. In the course of spheroid production, centrifugal, fluidizing, and gravitational forces act upon the product from different directions and collectively contribute to the spheroid formation process during rotary processing. The outcome of the process depends on the complex interactions between the equipment, formulation, and process variables.

[A study of the magnification of mandible pantomography image].

OBJECTIVE: To study the degree of magnification of mandible pantomography image. METHODS: The pantomography of 50 mandible specimens marked with lead pellets were taken by TROPHY XL-90C. The distances between each markers on film and in specimen were measured. RESULTS: The mean magnification(MM) of mandible pantomography image with TROPHY XL-90C was 1.22. MM of horizontal axle was 1.14. MM of vertical axle was 1.29. MM of horizontal axle was greatest (1.24) in the body of mandible,and lest (1.08) in genion. MM of vertical axle is similar among each regions. MM of vertical axle was greater than that of horizontal axle in all regions. CONCLUSION: The MM parameters of mandible pantomography image were useful to estimate the size of mandible lesions and provided a basis for dental implant more exactly.

Studies of safe maximal daily dietary Se-intake in a seleniferous area in China. Part II: Relation between Se-intake and the manifestation of clinical signs and certain biochemical alterations in blood and urine.

Selenosis occurs in areas of Enshi county because of the high Se content of the food. Morphological changes in finger-nails were used as the main criterion for clinical diagnosis of selenosis. Pathological nails were observed to occur almost only in adults, not at all in young children and very seldom in teenagers. Symptoms of selenosis in susceptible patients were found at or above an Se-intake of 910 micrograms/d, corresponding to a blood Se level of 1.05 mg/L. There was no evidence for an increased susceptibility to dental caries due to high Se consumption, and an increase in Se-intake seems unlikely to reduce the beneficial effects of fluoride on caries. No abnormalities of liver or heart were seen by supersonic B or electrocardiographic examinations. The biochemical investigations showed that with increasing whole blood Se the ratio of plasma Se to erythrocyte Se tended to decrease. As Se-intake increases to over 750 micrograms daily, the ratio decreases to near a minimal level. Reduced glutathione in whole blood decreases within a blood Se range of 1.01 to 2.28 micrograms in the high Se area. The amount of trimethylselenonium ion excreted in urine increased with the increase of urinary Se. Cases with prolonged prothrombin time occurred as blood Se increased to a level above 1 mg/L. The white blood cell count also increased significantly. Quantitative values were obtained only for ratio of plasma-Se to erythrocyte-Se for prothrombin time and for maintenance of nail Symptoms of susceptible patients. The overall results indicated that a daily Se-intake of 750-850 micrograms [corrected] might be the marginal level of safe intake. When other variable factors are also taken into consideration a daily Se-intake of 400 micrograms [corrected] is suggested as the maximum daily safe intake. At this level of Se-intake the corresponding approximate tissue Se levels are: whole blood 0.559 mg/L, plasma 0.327 mg/L, urine excretion 173 micrograms/d, hair 3.60 mg/kg, toe-nails 4.25 mg/kg, and finger-nails 4.70 mg/kg.

A hexameric transmembrane pore revealed by two-dimensional crystallization of the large mechanosensitive ion channel (MscL) of Escherichia coli.

We have established a reconstitution method of the detergent-solubilized recombinant large mechanosensitive ion channel of Escherichia coli (MscL) that yielded two-dimensional crystals. For that purpose, we have developed a new protocol using Triton X-100 to solubilize and purify the MscL protein. This protocol not only allowed an increase in the protein yield but also made it possible to obtain a homogeneous delipidated and reproducible preparation of the purified protein. When examined by the patch-clamp method MscL channels were found to be fully functional, exhibiting characteristic conductance and activation by pressure. For electron crystallography the homogeneous Triton X-100-purified recombinant MscL was further reconstituted at low lipid-to-protein ratios using Bio-Beads SM2 to remove the detergent. Two-dimensional crystals, exhibiting a p6 plane group symmetry, have been produced and examined by negative stain electron microscopy. Image processing of selected micrographs yielded a projection map at 15-A resolution that provided the first explicit structural information about the molecular boundary and homohexameric organization of the MscL channels in the membrane bilayer.