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1.
Shwetha V. Kumar Suhasini Bangar Ana Neumann Krishna Kumar Kookal Alfa Yansane Oluwabunmi Tokede Enihomo Obadan-Udoh Elizabeth Mertz Kristen Simmons Joshua Even Joanna Mullins Joel White Elsbeth Kalenderian Muhammad Walji 《Journal of the American Dental Association (1939)》2018,149(9):756-764.e1
Background
Although sealants are highly effective in preventing caries in children, placement rates continue to be low. The authors’ goals were to implement and assess the performance of 2 existing sealant quality measures against a manual audit of charts at 4 dental institutions and to identify measurement gaps that may be filled by using data from electronic health records.Methods
The authors evaluated the performance of 2 quality measures designed for claims-based data: the Dental Quality Alliance (DQA) sealant measure, which includes patients at risk of developing elevated caries, and the Oregon Health Authority (OHA) sealant measure (irrespective of caries risk). The authors adapted and validated these measures at 4 sites: 3 dental schools and 1 large dental accountable care organization.Results
The overall modified DQA and modified OHA measure scores in the 6- through 9-year-old age group were 37.0% and 31.6% and in the 10- through 14-year-old age group were 15.8% and 6.6%, respectively. Results from the manual review of charts showed that 67.6% of children who did not receive sealants did not have any teeth to seal because their molars had not yet erupted, had been extracted, had been sealed previously, or had existing caries or restorations.Conclusions
Both the DQA and OHA measures, which rely mainly on Current Dental Terminology procedure codes, led to underestimation of the care delivered from a practice perspective. Future sealant quality measures should exclude patients whose teeth cannot be sealed.Practical Implications
This study’s results support the suitability of using electronic health record data for assessing the quality of oral health care, particularly for measuring sealant placement in children. 相似文献2.
K. Siva sankar K. Pranitha A.J. Sai Sankar B. Sujatha V. Sai krishna K. Kiran kumar 《Pediatric Dental Journal》2018,28(3):160-164
Background
Remineralizing agents are found to be effective in the remineralization of early enamel caries and the remineralized enamel crystallites are more resistant to decalcification and also have the same orientation as the original enamel crystallites. Although child formula fluoridated dentifrices are used safely by young children their remineralizing capability remains questionable.Aim
To evaluate the remineralizing potential of three commercially available pediatric dentifrices on artificial carious lesions in primary teeth.Materials and methods
A total of fifty sound human primary teeth were coated with nail varnish leaving a window of 2 mm × 4 mm on buccal surface and were subjected to demineralization for a period of 96 h and then sectioned. Out of the hundred sections obtained, ninety sections are equally divided into three groups with thirty in each group: Group I (Colgate Spider man), Group II (Kids bunny), Group III (Kidodent) subjected to remineralization respectively for 10 days using pH cycling model. The sections were then evaluated under the stereomicroscope for the remineralization values using MICAP image analyser software.Results
Statistical analysis was done by using ANOVA test which showed that all the three dentifrices showed remineralization with artificial carious lesions. Among the three test groups, Group I showed higher remineralization potential compared with the other two pediatric dentifrices which was statistically significant (p < 0.05).Conclusion
All the three dentifrices demonstrated remineralization of carious lesions by virtue of decrease in lesion depth. 相似文献3.
Liang Chen Barry D. Hammond Gary Alex Byoung In Suh 《The Journal of prosthetic dentistry》2017,117(3):438-443
Statement of problem
Intraoral repair of porcelain or other silica-based ceramics typically requires the use of silane in the repair protocol. Some porcelain intraoral repairs also involve bonding to exposed or involved tooth tissues including dentin. A study is needed to evaluate whether the cross-contamination of dentin with silane affects bond strength to this tissue.Purpose
The purpose of this in vitro study was to investigate the effect of silane cross-contamination on dentin bond strength.Material and methods
Flat surfaces of human dentin specimens were created, followed by wet polishing with 320-grit silicon carbide paper. The dentin specimens were divided into 4 groups: group SE (All-Bond Universal Adhesive used in self-etching mode); group SiSE (silane applied to dentin followed by All-Bond Universal Adhesive used in self-etching mode); group ER (All-Bond Universal Adhesive used in total-etch (etch-and-rinse) mode); and group ERSi (Etch and rinse and silane applied to dentin followed by All-Bond Universal Adhesive). The dentin specimens were treated with a universal adhesive (All-Bond Universal) and bonded with a composite resin, using an Ultradent jig mold. Shear bond strength (n=10) was measured after 24 hours of water storage at 37°C. After the shear bond strength test, the dentin sides of fractured specimens in each group were examined with a stereomicroscope at ×15 magnification to determine failure modes. Data were statistically analyzed by 2-way and a 1-way ANOVA followed by post hoc Tukey honest significant difference test (α=.05). Scanning electron microscopy examination was used to evaluate the dentin surface morphology before and after bonding.Results
The shear bond strength of composite resin to dentin was not affected adversely when the dentin was contaminated with silane prior to using All-Bond Universal in the self-etch or total- etch (phosphoric acid) mode. SE, 30.3 ±3.8 MPa; SiSE, 32.9 ±3.9 MPa; ER, 34.9 ±3.1 MPa; ERSi: 35.2 ±4.9 MPa (P>.05)Conclusions
Under the conditions of this study, cross-contamination of dentin with silane before the use of All-Bond Universal in the self-etch or total-etch with phosphoric acid mode did not adversely affect composite resin bond strength to dentin. 相似文献4.
Juliana R.L. Alonso Fernanda G. Basso Débora L.S. Scheffel Carlos Alberto de-Souza-Costa Josimeri Hebling 《The Journal of prosthetic dentistry》2018,119(3):494.e1-494.e9
Statement of problem
Improved stability of the adhesive interface can be obtained using crosslinkers. However, research on the use of crosslinkers in root dentin is lacking.Purpose
The purpose of this in vitro study was to evaluate the effect of crosslinkers on the proteolytic activity of root dentin and on the bond strength of resin-cemented fiber posts.Material and methods
Single root canals were obtained from premolars (n=48) and endodontically treated before being divided into 4 groups: deionized water (control), 0.5 mol/L carbodiimide, 5% proanthocyanidin, or 5% glutaraldehyde. After removing the canal sealer, the dentin was etched with phosphoric acid, followed by water rinsing and the application of the crosslinkers for 60 seconds. Fiber posts were cemented using an adhesive (Single Bond 2) and resin cement (RelyX ARC). The roots were then transversally sectioned to obtain 1 mm thick specimens from the cervical, middle, and apical thirds and then aged for 24 hours or 9 months. Nine roots per group were used for the push-out test and 3 for determining the proteolytic activity of the root dentin by in situ zymography. Bond strength data were submitted to a mixed-model ANOVA and Bonferroni tests (α=.05).Results
Only proanthocyanidin negatively affected the 24-hour bond strength. After 9 months, a significant decrease in bond strength was seen for all groups, except for the crosslinked treated specimens from the cervical third of the root canal. Intense gelatinolytic activity was detected in the control group after 24 hours but was inhibited in the crosslinker-treated groups. Proteolytic activity was also not detected after 9 months for the groups treated with the crosslinkers, irrespective of the root canal third. Conversely, proteolytic activity increased for the specimens from the control group.Conclusions
Although no proteolytic activity was detected in the hybrid layers along the entire root canal, dentin biomodification with crosslinkers was effective in preventing bond strength loss only in the cervical third. 相似文献5.
Statement of problem
Lack of an accepted definition for the ascending ramus of the mandible means no common reference point is available for clinical or research dialogue.Purpose
The purpose of this review was to determine whether the ascending ramus has been defined, by using a search of published studies.Material and methods
PubMed was searched, using terms “ascending ramus” and “mandible.”Results
The search found no acceptable definition of the ascending ramus of the mandible.Conclusions
An acceptable definition for the ascending ramus of the mandible is lacking, and one is proposed here. 相似文献6.
7.
Nadja Rohr Stefan Brunner Sabrina Märtin Jens Fischer 《The Journal of prosthetic dentistry》2018,119(1):138-145
Statement of problem
The best procedure for cementing a restoration to zirconia implants has not yet been established.Purpose
The purpose of this in vitro study was to measure the retention of polymer-infiltrated ceramic crowns to zirconia 1-piece implants using a wide range of cements. The effect of ceramic primer treatment on the retention force was also recorded. The retention results were correlated with the shear bond strength of the cement to zirconia and the indirect tensile strength of the cements to better understand the retention mechanism.Material and methods
The retention test was performed using 100 polymer-infiltrated ceramic crowns (Vita Enamic) and zirconia implants (ceramic.implant CI) The crowns were cemented with either interim cement (Harvard Implant semipermanent, Temp Bond), glass-ionomer cement (Ketac Cem), self-adhesive cement (Perma Cem 2.0, RelyX Unicem Automix 2, Panavia SA), or adhesive cement (Multilink Implant, Multilink Automix, Vita Adiva F-Cem, RelyX Ultimate, Panavia F 2.0, Panavia V5 or Panavia 21) (n=5). Additionally ceramic primer was applied on the intaglio crown surface and implant abutment before cementation for all adhesive cements (Multilink Implant, Multilink Automix: Monobond plus; RelyX Ultimate Scotchbond Universal; Vita Adiva F-Cem: Vita Adiva Zr-Prime; Panavia F2.0, Panavia V5: Clearfil Ceramic Primer) and 1 self-adhesive cement containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP) (Panavia SA: Clearfil Ceramic Primer). Crown debond fracture patterns were recorded. Shear bond strength was determined for the respective cement groups to polished zirconia (n=6). The diametral tensile strength of the cements was measured (n=10). Statistical analysis was performed using 1-way or 2-way analysis of variance followed by the Fisher LSD test (α=.05) within each test parameter.Results
Adhesive and self-adhesive resin cements had shear bond strength values of 0.0 to 5.3 MPa and revealed similar retention forces. Cements containing MDP demonstrated shear bond strength values above 5.3 MPa and displayed increased retention. The highest retention values were recorded for Panavia F 2.0 (318 ±28 N) and Panavia 21 (605 ±82 N). All other adhesive and self-adhesive resin cements attained retention values between 222 ±16 N (Multilink Automix) and 270 ±26 N (Panavia SA), which were significantly higher (P<.05) than glass-ionomer (Ketac Cem: 196 ±34 N) or interim cement (Harvard Implant semipermanent: 43 ±6 N, Temp Bond: 127 ±13 N). Application of manufacturer-specific ceramic primer increased crown retention significantly only for Panavia SA.Conclusions
Products containing MDP provided a high chemical bond to zirconia. Self-adhesive and adhesive resin cements with low chemical bonding capabilities to zirconia provided retention force values within a small range (220 to 290 N). 相似文献8.
Jonathan C. Simmonds Anju K. Patel Nicholas S. Mader Andrew R. Scott 《Journal of cranio-maxillo-facial surgery》2018,46(3):498-503
Objectives
To examine the frequency of partial glossectomy performed for the indication of macroglossia in children within the United States, assessing for differences in rates of intervention across various demographics.To identify potential morbidities associated with partial glossectomy in this population and determine how such factors may influence length of stay and cost of admission following tongue reduction surgery.Study Design
Retrospective cross-sectional study.Setting
The Kids' Inpatient Database 2003, 2006, 2009, and 2012.Subjects
Patients under age 5 diagnosed with macroglossia who underwent partial glossectomy.Methods
Demographics were analyzed and cross tabulations, linear regression modeling, and multivariate analysis were performed.Results
During the four-years studied, partial glossectomy was performed in 196 children under age 5 with macroglossia. A disproportionately higher rate of intervention was seen in white children (p = 0.001), patients undergoing surgery in the mid-west (p < 0.001) and patients in the highest socioeconomic quartile (p = 0.015). Most patients underwent glossectomy in their second year of life. The average length of stay in patients who underwent partial glossectomy for macroglossia was 9.59 days (Range 1–211 days, median 3.45 days) and the average cost was $56,602 (median $16,330).Conclusion
Partial glossectomy for macroglossia is typically performed prior to age 2 in the United States. A higher rate of intervention is seen in white children, those who have surgery in the mid-west and affluent children even when controlling for confounding variables.Level of evidence
III. 相似文献9.
Aparna Dakshinamoorthy Ahila Singaravel Chidambaranathan Muthukumar Balasubramanium 《The Journal of prosthetic dentistry》2018,119(6):1029.e1-1029.e5
Statement of problem
The most common reason for remaking a facial prosthesis is the debonding of maxillofacial silicone from the substructure. Improved bonding would help overcome this problem.Purpose
The purpose of this in vitro study was to evaluate the shear bond strength between maxillofacial silicone and fiber-reinforced composite resin after various surface treatments.Material and methods
Acrylic resin specimens were prepared with a dimension of 14.4 mm in diameter and 25 mm in height with a depression of 5 mm in depth and 8 mm in diameter, according to International Organization for Standardization technical specification (ISO/TE) 11405:1994. Fiber-reinforced composite resin was dispensed and packed into the depressed part of acrylic resin and allowed to polymerize. A total of 120 specimens were fabricated, and primer was then applied over the specimens. They were washed with acetone and subjected to various surface treatments, including airborne-particle abrasion, silicon carbide paper abrasion, and laser etching. The maxillofacial silicone was mixed according to the manufacturer’s instructions and packed into the cylindrical die with dimensions of 3 mm in thickness and 8 mm in diameter. The shear bond strength test on the specimens was carried out in a universal testing machine at a 5-mm/min crosshead speed, at 24 hours after fabrication and 200 hours after accelerated aging. The values were statistically analyzed using 1-way ANOVA and the Tukey honest significant difference (HSD) post hoc test.Results
The mean shear bond strength values of the control group was 24.7 ±2.1 MPa, 26.9 ±1.8 MPa for the airborne-particle abraded group, 28.4 ±1.9 MPa for the silicon carbide abraded group SiCp, and 33.4 ±1.8 MPa for the laser-treated specimens at 24 hours after fabrication and 34.2 MPa at 200 hours after accelerated aging.Conclusions
The shear bond strength between the maxillofacial silicone and the fiber-reinforced composite resin was increased after laser surface treatment compared with airborne-particle abrasion and silicon carbide paper abrasion 200 hours after accelerated aging. 相似文献10.
Statement of problem
The cause of occlusal/incisal cupping/cratering (depressed dentin surrounded by elevated rims of enamel) has been postulated to be primarily the effect of acid on exposed dentin. It is hypothesized that abrasion, bruxism, attrition, and stress-corrosion may play a secondary role in lesion formation. The primary cause and sequence of occlusal/incisal cupping/cratering remain scientifically controversial.Purpose
The purpose of this in vitro study was to determine the effects of acid on human enamel, mantle dentin, and peritubular dentin in the creation of incisal/occlusal cupping/cratering. This study was designed to visually illustrate the role of acid in the formation of cupping/cratering.Material and methods
A soft compact toothbrush was tested using both high relative dentin abrasivity (RDA)- and low-RDA dentifrices and water only (nonabrasive) on extracted human teeth. Seventeen specimens of 4 teeth each (68 teeth) were subjected to horizontal brushing with a 1:1 dentifrice-to-water slurry or water only. Twelve of these 17 specimens, a total of 48 teeth, were subjected to acid challenge. Each of these 12 specimens were brushed for 500 strokes after each acid challenge for a total of 150 000 strokes and 300 acid immersions. Half the specimens were acid challenged for 5 minutes and the other half for 10 minutes between brushings.Results
No visible loss of tooth structure was noted in the control specimens brushed in water only. The control specimens brushed in a 1:1 slurry of toothpaste/water demonstrated incisal/occlusal cupping/cratering. The acid-challenged specimens brushed in water only demonstrated enamel and peritubular dentin loss with elevated rims and/or plateaus of mantle dentin, the opposite of occlusal/incisal cupping/cratering. All specimens brushed with the higher abrasive dentifrice demonstrated visible wear of enamel, mantle, and peritubular dentin, culminating in occlusal/incisal cupping/cratering. Surprisingly, those acid-challenged specimens brushed with the lower abrasive toothpaste demonstrated visible wear of the enamel and peritubular dentin, resulting in elevated rims and/or plateaus of mantle dentin.Conclusions
Acid affects both the enamel and the mineralized component of dentin. This study demonstrated that incisal/occlusal cupping/cratering occurring in worn dentition can be caused by the use of dentifrice alone. Acid challenge affects the inorganic components of tooth structure but not the organic components and so does not cause the dentinal cupping/cratering of the incisal/occlusal surfaces of the human dentition. 相似文献11.
Johan Persson Benedikt Helgason Håkan Engqvist Stephen J. Ferguson Cecilia Persson 《Journal of cranio-maxillo-facial surgery》2018,46(3):418-423
Purpose
The aim of this study was to evaluate skull replacement options after decompressive craniectomy by systematically investigating which combination of geometrical properties and material selection would result in a mechanical response comparable in stiffness to that of native skull bone and a strength as high or higher than the same.Materials and methods
The study was conducted using a Finite Element Model of the top part of a human skull. Native skull bone, autografts and commercial implants made of PEEK, solid titanium, two titanium meshes and a titanium-ceramic composite were modeled under a set load to evaluate deformation and maximum stress.Results
The computational result showed a large variation of the strength and effective stiffness of the autografts and implants. The stiffness of native bone varied by a factor of 20 and the strength by a factor of eight. The implants span the entire span of the native skull, both in stiffness and strength.Conclusion
All the investigated implant materials had a potential for having the same effective stiffness as the native skull bone. All the materials also had the potential to be as strong as the native bone. To match inherent properties, the best choice of material and thickness is thus patient specific, depending on the quality of the patient's native bone. 相似文献12.
Laura Fernández-Ferrer María Vicente-Ruíz Verónica García-Sanz José María Montiel-Company Vanessa Paredes-Gallardo José Manuel Almerich-Silla Carlos Bellot-Arcís 《Journal of the American Dental Association (1939)》2018,149(9):778-786.e2
Background
One of the adverse effects of orthodontic treatment is the appearance of white-spot lesions (WSLs) resulting from enamel demineralization. The objective of this systematic review was to investigate the effectiveness of remineralization therapies on WSLs after orthodontic treatment.Types of Studies Reviewed
In this systematic review, the authors identified relevant articles listed in 5 databases—PubMed, the Cochrane Library, Scopus, Embase, and Web of Science—by using a combination of search terms referring to orthodontics, demineralization, and treatment. Ten articles on the efficacy of WSL remineralization therapies met the inclusion criteria.Results
Among the studies of remineralizing therapy, neither fluoride mouthrinses nor phosphopeptide toothpastes with or without fluoride had any positive effect in addition to oral hygiene maintenance with fluoride toothpaste. A 5% sodium fluoride varnish was the only therapy to show a statistically significant improvement compared with results in the control group. The authors found large variations in results among the studies reviewed because of the different methods used.Conclusions and Practical Implications
None of the treatments was capable of remineralizing WSLs. A 5% sodium fluoride varnish could improve remineralization of WSLs. 相似文献13.
Mehrnoush Alirezaei Ali Bagherian Alireza Sarraf Shirazi 《Journal of the American Dental Association (1939)》2018,149(7):640-649.e9
Background
The aim of this systematic review and meta-analysis was to evaluate the ability of glass ionomer cements (GICs) and resin-based sealants (RBSs) to prevent the occurrence of caries and their retention in standards-based clinical studies.Types of Studies Reviewed
The authors conducted a literature search (from database inception through September 20, 2017) to identify studies for inclusion in this systematic review. The authors assessed the quality of the evidence with the modified Jadad scale and performed the meta-analysis by using a random-effects model.Results
The authors considered 20 studies on caries prevention and 28 studies on retention that met the inclusion criteria for the meta-analysis. The results of the meta-analysis for caries development showed no significant difference (odds ratio, 0.938; 95% confidence interval, 0.647 to 1.359; P = .734). However, the result for the retention rate showed the advantage of RBSs (odds ratio, 6.006; 95% confidence interval, 3.226 to 11.183; P = .000).Conclusions and Practical Implications
There was no difference between the percentage of caries development with use of GICs as fissure sealing material compared with that for the conventional RBSs, but the retention rate of conventional RBSs was much higher than that of the GICs. 相似文献14.
Yousef T. Eshmawi Afnan O. Al-Zain George J. Eckert Jeffrey A. Platt 《Journal of the American Dental Association (1939)》2018,149(10):893-902
Background
Lack of irradiance-beam profile uniformity across the emission area of light-curing units (LCUs) may result in suboptimal properties of composite restorations. The authors’ objective for this study was to assess the variation in local cure of 1 composite at 3 different LCU emission area locations cured with 3 different LCUs by means of testing the degree of conversion (DC) and microflexural strength.Methods
The authors fabricated dual-photoinitiator composite specimens (n = 5), which were cured using either a quartz-tungsten-halogen, a multiple-emission peak, or a single-emission peak light-emitting diode LCU. The specimen’s top surfaces received irradiation from either the center, 1.5 millimeters straight to the left of the center, or 1.5 mm straight to the right of the center of the LCU emission area. The authors measured irradiance and DC on top and bottom specimen surfaces using a spectrometer and attenuated total reflection–Fourier transform infrared spectroscopy, respectively. The authors performed micro 3-point bend tests using a universal mechanical testing machine. They used multifactorial analysis of variance (α = 0.05).Results
The irradiance ranged from 452 through 946 milliwatts per square centimeter, and DC ranged from 49.7% through 65.8% on top surfaces. Microflexural strength ranged from 313 through 458 megapascals.Conclusions
The authors did not find correlations among the LCU irradiance-beam profile of the 3 emission area locations and the investigated material properties, although they found variations in the measured properties.Practical Implications
The irradiance-beam profile from the different LCUs explored did not have a major influence on the DC and microflexural strength for the investigated composite. 相似文献15.
Toshiko Tanaka Ayaka Saito Koji Watanabe Katsura Saeki Hideaki Nakashima Kenshi Maki 《Pediatric Dental Journal》2018,28(2):103-109
Background
Topical fluoride application has been performed all over the world especially in the field of Pediatric Dentistry to prevent enamel decalcification. However, the effect of the method against demineralization has not been sufficiently reported yet. This study was performed to evaluate the effectiveness of the method by measuring the uptake amount of fluorine (F) into enamel, and also to investigate the relationship between the amount of F incorporated and the decalcification depth.Methods
Bovine incisors were immersed in 2% fluoride solution in the absence (the immersion method) or presence (the iontophoresis method) of iontophoresis. Sample teeth were then decalcified in 0.1 M lactic acid solution. The F concentration was measured using a fluorine ion meter, while atomic absorption spectrophotometry was used to determine calcium (Ca) concentrations.Results
When the decalcification time was 15 min, the uptake of F was significantly higher in the iontophoresis method than in the immersion method. Furthermore, the decalcification depth was markedly shallower with the iontophoresis method than with the immersion method. In immersion method, no changes were observed in the uptake of F between decalcification times of 5 and 15 min regardless of immersion times. F uptake levels were dependent on the current-carrying time. A clear inverse correlation was observed between F uptake levels and the decalcification depth (r = 0.967).Conclusions
Iontophoresis increased the uptake of F and enhanced its penetration into the enamel, thereby decreasing decalcification by acid. The study showed the effectiveness of the Iontophoresis method. 相似文献16.
Sy Yin Chai Vincent Bennani John M. Aarts Karl Lyons 《Journal of the American Dental Association (1939)》2018,149(1):25-37
Background
The authors reviewed and identified the evidence for the various incisal preparation designs for ceramic veneers.Types of Studies Reviewed
The authors searched MEDLINE with PubMed and Ovid to identify any articles in the English language related to the topic up through March 2017 using a combination of key words: “porcelain veneer or ceramic veneer or dental veneer or labial veneer” AND “preparation,” NOT “composite veneer,” NOT “crown,” NOT “implant,” NOT “fixed partial denture or bridge or denture,” NOT “porcelain-fused-to-metal,” NOT “marginal gap or fit.”Results
In vitro studies showed that the palatal chamfer preparation design increases the risk of developing ceramic fractures. The butt joint preparation design had the least effect on the strength of the tooth.Conclusions
Surveys show the 2 most common incisal preparation designs provided are butt joint and feathered-edge. Clinical studies have identified that incisal ceramic is the most common location of ceramic fracture. In addition, there is a lack in standardization of the modeling structures and type of finite element analysis.Practical Implications
The evidence seems to support the use of butt joint over palatal chamfer incisal preparation design. Fracture or chipping is the most frequent complication and the risk increases with time. Incisal ceramic is the most common location of ceramic fracture. 相似文献17.
Statement of problem
Direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) have become popular for fabricating the metal frameworks of metal-ceramic restorations. How the type of layered manufacturing device, layer thickness, and alloy powder may affect the bond strength of ceramic to metal substructure is unclear.Purpose
The purpose of this in vitro study was to evaluate the bond strength of dental porcelain to metal frameworks fabricated using different layered manufacturing techniques (DMLS and DMLM), Co-Cr alloy powders, and layer thicknesses and to evaluate whether a correlation exists between the bond strength and the number of ceramic remnants on the metal surface.Material and methods
A total of 75 bar-shaped metal specimens (n=15) were fabricated using either DMLS or DMLM. The powder alloys used were Keramit NP-S and EOS-Cobalt-Chrome SP-2 with layer thicknesses of 20 μm and 30 μm. After ceramic application, the metal-ceramic bond strength was evaluated with a 3-point-bend test. Three-way ANOVA followed by the Tukey honest significance difference test were used for statistical analysis (α=.05). De-bonding surface microstructure was observed with scanning electron microscopy. Energy dispersive spectroscopy analysis was conducted to evaluate the correlation between ceramic remnants on the metal surface and bond strength values.Results
The mean bond strength value of DMLS was significantly higher than that of DMLM. While no statistically significant difference was found between layer thicknesses, alloy powders closely affected bond strength. Statistical comparisons revealed that the highest bond strength could be achieved with DMLS-Cobalt-Chrome SP2-20μm, and the lowest bond strength was observed in DMLS-Keramit NP-S-20μm (P≤.05). No correlation was found between porcelain remnants on the metal surface and bond strength values.Conclusions
The layered manufacturing device and the alloy powders evaluated in the current study closely affected the bond strength of dental porcelain to a metal framework. However, layer thickness did not affect the bond strength. 相似文献18.
Ji-Hyun Jang Chung-Ok Lee Hyun-Jung Kim Sahng G. Kim Seung-Wuk Lee Sun-Young Kim 《Journal of endodontics》2018,44(11):1702-1708
Introduction
Elastinlike polypeptide (ELP) is 1 of the genetically engineered, protein-based polypeptides, which offers outstanding advantages such as superior biocompatibility, long-term stability, elasticity, and cost-effectiveness. This study aimed to investigate the effect of an ELP-based matrix on the physical properties and biocompatibility of mineral trioxide aggregate (MTA).Methods
The 2 types of ELPs were synthesized and mixed with the MTA powder in various liquid-to-powder ratios. The physical properties including compressive strength, microhardness and setting time, washout resistance, and biocompatibility were investigated for the ELP-incorporated MTA. The microstructure of the MTA was also analyzed using scanning electron microscopy and Fourier-transform infrared spectroscopy.Results
The ELP-based matrix enhanced the physical properties of MTA, including the compressive strength, microhardness, and washout resistance of MTA. The ELP incorporation showed no negative effect on biocompatibility. However, ELPs prolonged the setting time of MTA.Conclusions
These results suggested that the addition of the ELP-based matrix to MTA enhanced the physical properties without negatively affecting the chemical structure and biocompatibility of MTA. Further investigation is warranted to overcome a clinical challenge associated with the extended setting time caused by the addition of ELP. 相似文献19.
Purpose
To evaluate the biomechanical performance of a commercially available bridging plate (2.4) as well as screws and bone simulating the reconstruction of hemimandibular defects and to indicate alternatives of reinforcement to prevent plate fractures either by strength or fatigue.Material and Methods
Two common hemimandibular defects are investigated using computed finite element analysis (FEA) approach. Simplified and refined computational models are developed for the geometry of the screw. Conditions of non-locking and locking plate–screw interfaces are considered. Static loads of 120 N are applied. Von Mises stresses and fatigue are calculated. As reinforcement, a second complete or partial plate is placed onto the original plate.Results
Results demonstrate that reconstruction plates are often subjected to excessive stress that may lead to fracture either by strength or by fatigue. An attached complete or partial second plate is able to reduce stress in the plate, in screws and bone so that stress remains below the allowable limit of the materials.Conclusion
A simplified technique of attaching a whole or sectioned second plate onto the original plate can reduce the stress calculated and may reduce the frequency of plate fractures for the patient's comfort, security and financial savings. 相似文献20.
Ayca Tulga 《The Journal of prosthetic dentistry》2018,119(4):643-649