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Wonsup Lee Young-Jun Lim Myung-Joo Kim Ho-Beom Kwon 《The Journal of prosthetic dentistry》2017,117(4):532-538
Statement of problem
A simplified mounting technique that adopts an average condylar guidance has been advocated. Despite this, the experimental explanation of how average settings differ from individual condylar guidance remains unclear.Purpose
The purpose of this in vitro study was to examine potential occlusal error by using average condylar guidance settings during nonworking side movement of the articulator.Material and methods
Three-dimensional positions of the nonworking side maxillary first molar at various condylar and incisal settings were traced using a laser displacement sensor attached to the motorized stages with biaxial freedom of movement. To examine clinically relevant occlusal consequences of condylar guidance setting errors, the vertical occlusal error was defined as the vertical-axis positional difference between the average setting trace and the other condylar guidance setting trace. In addition, the respective contribution of the condylar and incisal guidance to the position of the maxillary first molar area was analyzed by multiple regression analysis using the resultant coordinate data.Results
Alteration from individual to average settings led to a positional difference in the maxillary first molar nonworking side movement. When the individual setting was lower than average, vertical occlusal error occurred, which might cause occlusal interference. The vertical occlusal error ranged from -2964 to 1711 μm. In addition, the occlusal effect of incisal guidance was measured as a partial regression coefficient of 0.882, which exceeded the effect of condylar guidance, 0.431.Conclusions
Potential occlusal error as a result of adopting an average condylar guidance setting was observed. The occlusal effect of incisal guidance doubled the effect of condylar guidance. 相似文献3.
Fernanda de Cássia Papaiz Gonçalves Marina Amaral Alexandre Luiz Souto Borges Luiz Fernando Martins Gonçalves Tarcisio José de Arruda Paes-Junior 《The Journal of prosthetic dentistry》2018,119(4):606-610
Statement of problem
Complete-arch implant-supported prostheses without a framework have a high risk of failure: a straightforward and inexpensive reinforcement material, such as nylon mesh, could improve their longevity.Purpose
The purpose of this in vitro study was to evaluate a nylon-silica mesh compound on the fracture strength of acrylic resin and the fracture load of complete-arch implant-supported prostheses.Material and methods
Twenty-four complete mandibular arch implant-supported prostheses were divided into 2 groups according to cantilever length (molar and premolar) and subdivided into another 2 subgroups according to the presence or absence of reinforcing mesh. The specimens were submitted to a maximum load-to-fracture test in a universal testing machine, with a 100-N load cell, a 2 mm/min crosshead speed, and a spherical metal tip diameter of 4 mm at different points (molar and premolar). These were submitted to 1-way analysis of variance for repeated measurement and the post hoc Tukey multiple comparison test (α=.05).Results
The mean maximum load ±standard deviation for the molar group was 393.4 ±95.0 N with reinforcement and 305.4 ±76.3 N without reinforcement (P=.02); and for the premolar group was 1083.3 ±283.7 N with reinforcement and 605.3 ±90.5 N without reinforcement (P=.001).Conclusions
Reinforcement with nylon mesh increased the mean maximum load of implant-supported complete-arch prostheses at both cantilever lengths. The cantilever to the premolar (5 mm) presented the highest maximum load values to fracture. 相似文献4.
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Priscilla Kia Suan Sia Radi Masri Carl F. Driscoll Elaine Romberg 《The Journal of prosthetic dentistry》2017,117(2):283-288
Statement of problem
Currently, no guidelines exist to help in the selection of Locator abutments for implants at different heights.Purpose
The purpose of this in vitro study was to evaluate the effect of the differential heights of pairs of Locator abutments on the retention of overdentures after 6 months of simulated function.Material and methods
In vitro testing was performed with 4 sets of average-sized edentulous mandible analogs with 2 implants placed in the canine positions. There were 10 specimens in each of the 4 groups, with a total sample size of 40. Four groups of 2 implant-retained overdentures were fabricated, with Locator attachments at different vertical levels with differences of 0, 2, 4, and 6 mm. The overdentures were subjected to simulated function for a period corresponding to 6 months of clinical service and then tested with a universal testing machine for changes in peak load-to-dislodgement. The data were analyzed using 1-way ANOVA followed by the Tukey honest significant differences test (α=.05).Results
Varying the heights of Locator abutments had a statistically significant effect on the retentive values of the pink Locator attachments after 6 months of simulated function (F=7.342, P=.001). The peak load-to-dislodgement ranged from 32.3 N (95% confidence interval [CI]: 26.0 to 38.6) for group 0 mm to 53.6 N (95% CI: 46.3 to 60.8) for group 6 mm. When the difference in Locator abutment heights was 2 and 4 mm, the peak load was 37.1 N (95% CI: 32.3 to 42.0) and 41.9 N (95% CI: 31.2 to 52.7). Statistical analysis revealed that the retention of group 0 mm and group 2 mm was significantly lower than group 6 mm. The retention of group 4 mm was not significantly different from groups 0 mm, 2 mm, or 6 mm.Conclusions
Although significant differences were found among the groups, these differences were small and may not be clinically detectable. 相似文献6.
Lucas Siqueira Pinheiro Júlia Eick Iglesias Daiana Boijink Letícia Boldrin Mestieri Patrícia Maria Poli Kopper José Antônio de Poli Figueiredo Fabiana Soares Grecca 《Journal of endodontics》2018,44(7):1140-1145
Introduction
The aim of this study was to evaluate the cell viability and tissue reaction of NeoMTA Plus (NMP; Avalon Biomed Inc, Houston, TX) compared with mineral trioxide aggregate (MTA; Angelus, Londrina, PR, Brazil) and Biodentine (BD; Septodont, Saint-Maur-de-Fossés, France).Methods
Fibroblasts (3T3) were plated and exposed to 1% extract from the test material before and after setting. Cytotoxicity assessment was performed using the 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-tetrazolium bromide and sulforhodamine B assays. In vivo evaluation consisted of polyethylene tube implantation of the materials in rat subcutaneous tissue. Histologic analysis occurred at 7, 30, and 90 days, scoring inflammatory events and collagen fiber formation. Analysis of variance and the Tukey and t tests were used for cytocompatibility assays, and the Kruskal-Wallis test followed by the Dunn test were used for biocompatibility assays (P ≤ .05).Results
The materials in the cytotoxicity assays presented greater viability after setting (P ≤ .05). NMP and MTA presented higher viability than the control (Dulbecco modified Eagle medium) on the 3-(4,5-dimethyl-thiazoyl)-2,5-diphenyl-tetrazolium bromide assay before and after setting (P ≤ .05). The sulforhodamine B assay showed that MTA and BD presented less viability than NMP and the control, and NMP was similar to the control before setting. After setting, MTA and BD presented higher viability when compared with the control group (P ≤ .05), and NMP was similar to control. Inflammatory infiltrate reduction occurred throughout the test periods for all materials. At 7 days, neutrophils were present in BD (P ≤ .05), and granuloma and giant cells were present in BD and MTA. At 30 days, BD showed intense inflammatory infiltrates and a large number of macrophages when compared with NMP, MTA, and the control (P ≤ .05). At 90 days, BD presented a thick fiber layer compared with NMP (P ≤ .05).Conclusions
NMP showed similar biocompatible behavior to MTA and BD. 相似文献7.
Yooseok Shin Sungho Park Jeong-Won Park Kwang-Mahn Kim Young-Bum Park Byoung-Duck Roh 《The Journal of prosthetic dentistry》2017,117(1):109-115
Statement of problem
The marginal and internal discrepancies of computer-aided design and computer-aided manufacturing (CAD-CAM) endocrowns are unknown.Purpose
The purpose of this in vitro study was to evaluate the marginal and internal discrepancies of endocrowns with different cavity depths by measuring them with microcomputed tomography (μCT).Material and methods
Endocrowns (n=48) of 2 different cavity depths (2 mm and 4 mm) were fabricated in 2 different chairside CAD-CAM systems (CEREC AC and E4D). A μCT scan was made before and after cementation. For analysis of the marginal and internal discrepancies, reference points were selected in 2-dimensional views of 3 buccolingual cross-sections and 3 mesiodistal cross-sections. To calculate the total discrepancy volume, the μCT sections were reconstructed 3-dimensional views, and changes in volume and surface area were examined. Statistical analysis was performed using 2-way ANOVA with Bonferroni correction (α=.05).Results
An endocrown with a 4-mm cavity showed a larger marginal and internal volume than one with a 2-mm cavity. Cementation did not show significant differences in total discrepancy thickness. Discrepancies on the pulpal floor were largest in other sites. Both chairside CAD-CAM systems showed similar discrepancy in the endocrowns.Conclusions
Based on the present study, marginal and internal discrepancies increased depending on cavity depth. Cementation did not increase the dimension of the discrepancy between the restoration and the cavity wall. The discrepancy on the pulpal floor appeared to affect these results. 相似文献8.
Manuel Cerna Carlos Zaror Pablo Navarro Paulo Sandoval 《Cranio : the journal of craniomandibular practice》2015,33(4):300-306
Objective: To evaluate the validity and reliability of the T-Scan®III sensors system by measuring force and time in sensels.
Methods: In order to evaluate the validity, known forces were applied to 31 sensels selected at random of a T-Scan® III sensor. In order to evaluate the reliability, the existing agreement between two different sensors was measured. Both validity and reliability were assessed using Lin’s concordance correlation coefficient (CCC).
Results: For the totalgroup of sensels, bymeasuring force, a poor level of validitywas obtained (Lin’sCCC:0.698); when measuring time, an almost perfect agreement was obtained (Lin’s CCC: 0.9995). In contrast, the reliability level was poor (Lin’s CCC: 0.099).
Discussion: The T-Scan®III system neither shows an appropriate degree of validity when estimating absolute force, nor presents an adequate level of reliability when measuring relative force; however, it presents a high degree of validity when quantifying times. 相似文献
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Antigoni Stylianou John O. Burgess Perng-Ru Liu Daniel A. Givan Nathaniel C. Lawson 《The Journal of prosthetic dentistry》2017,117(1):116-123
Statement of problem
The clinical challenge of adhering cement to intracanal dentin is transmitting light to the most apical parts of root canals to allow more efficient polymerization of the cement.Purpose
The purpose of this in vitro study was to compare the cement-polymerizing ability, microstructure, and radiopacity of a new fiber optic post (iLumi fiber optic Post) with a clinically successful fiber post (DT Light Post).Material and methods
Polymerizing ability was compared using a modified depth-of-polymerization protocol. A split aluminum mold with a 12-mm cylindrical hole (diameter=4.7 mm) was filled with light-polymerized resin cement (Variolink Esthetic LC). Each fiber post (n=12) was positioned and light-polymerized on the coronal end for 60 seconds with a light-emitting diode polymerization light. Unpolymerized resin was dissolved with an organic solvent, and the weight and length of the polymerized resin cement were measured. Scanning electron microscopy was used to examine vertical and horizontal cross-sections. The radiopacity values of both the posts and 5 additional reference posts were evaluated using an aluminum step wedge.Results
The weight and length of the polymerized resin cement were significantly greater (P<.05) with the fiber optic post, which scanning electron microscopy showed to have a higher density of parallel fibers. The iLumi post demonstrated greater radiopacity among the tested fiber posts and a titanium alloy post.Conclusions
The iLumi fiber optic posts have a unique structural fiber composition and excellent radiopacity and light-transmitting ability that produce more complete polymerization of the resin cement than the DT Light posts. 相似文献10.
Yoon-Hyuk Huh Eul-Chang Yang Chan-Jin Park Lee-Ra Cho 《The Journal of prosthetic dentistry》2018,119(6):994-999
Statement of problem
The relationship between surface roughness and the optical characteristics of zirconia prostheses may be affected by the type of shaded block.Purpose
The purpose of this in vitro study was to investigate changes in surface roughness and brightness of monolithic zirconia blocks of different shades after polishing.Material and methods
The surface roughness averages of 3 different kinds of shaded zirconia blocks (Zenostarof T0 [T0], Zenostar sun [Ts], and Zenostar sun chroma [Tsc]) were compared after surface polishing. Fifteen specimens of differing thicknesses were produced per block. (1 mm and 3 mm). Surface morphology and compositions were analyzed by using filed emission scanning electron microscopy (FE-SEM) and energy dispersive spectrometry. A 1-way ANOVA and the post hoc Scheffé test were performed (α=.05). The correlations between surface roughness and brightness were determined using the Pearson correlation analysis (α=.01).Results
After phased polishing, Ts had the highest average roughness, followed by T0 and then Tsc. A statistically significant difference in roughness was observed between Ts and Tsc (P<.05). Ts exhibited multiple distinct layers in the FE-SEM image. Carbon was detected in the Ts specimens only. Brightness was highest in T0, followed by Ts and then Tsc. A positive correlation was observed between brightness and surface roughness for all specimens (P<.01). This correlation was stronger in the thicker specimens.Conclusions
The results of this study suggest that polishing affects monolithic zirconia differently depending on shade. The polishing of monolithic zirconia reduces both surface roughness and brightness. The optical properties of monolithic zirconia vary by thickness and can be opaque or translucent. 相似文献11.
Introduction
The aim of this study was to evaluate the changes in the surface profile of rotary nickel-titanium (NiTi) files designed to prepare a glide path and conventional stainless steel (SS) hand files when used in extremely narrow canals both in clinical and experimental conditions.Methods
This ex vivo/in vivo study used either SS #10 K hand files or the PathFile system (Dentsply Maillefer, Ballaigues, Switzerland) to establish a glide path in maxillary molars with narrow root canals (defined as canals that bound a #8 K-file at the working length). After treatment, all files were cleaned and scanned using a noncontact laser profilometer. Changes to the surface profile (Ra cutting edge waviness = RaCEW) and roughness (Ra cutting edge roughness = RaCER) of the cutting edges and the surface roughness of the flute area (Sa flute roughness = SaFR) were analyzed.Results
#10 K-files had significant increases in all types of measurements (RaCEW, RaCEW, and SaFR) after the preparation of second mesiobuccal canals compared with the control group (P < .05) in both studies. In the ex vivo study, the PathFile (P1) had no significant changes in the surface profile from baseline but had a significant increase in the surface roughness of the flute (SaFR) (P < .05). PathFiles that were used 3 times in vivo had a significant increase in roughness (flute and cutting edge) values across all PathFile sizes compared with control values.Conclusions
This study showed that PathFiles had significantly less surface defects compared with SS files after the preparation of narrow canals, indicating their possible benefits when establishing a glide path in extremely narrow canals. 相似文献12.
Mario Alovisi Damiano Pasqualini Edoardo Musso Elena Bobbio Carlotta Giuliano Davide Mancino Nicola Scotti Elio Berutti 《Journal of endodontics》2018,44(4):614-620
Introduction
Contracted endodontic cavities (CECs) have developed from the concept of minimally invasive dentistry and provide an alternative to traditional endodontic cavities (TECs). They have been designed in an effort to preserve the mechanical stability of teeth. The contracted cavity design preserves more of the dentin but may influence the geometric shaping parameters. The aim of this micro–computed tomographic study was to evaluate the influence of contracted endodontic cavities on the preservation of the original root canal anatomy after shaping with nickel-titanium rotary instruments.Methods
Thirty extracted human mandibular molars with fully formed apices and independent mesial canals were randomly assigned to group 1 (TEC) and group 2 (CEC). Each group was shaped using ProGlider (Dentsply Maillefer, Ballaigues, Switzerland) and WaveOne Gold (Dentsply Maillefer). Irrigation was performed with 10% EDTA and 5% sodium hypochlorite. Samples were scanned before and after canal shaping to match canal volumes (SkyScan; Bruker microCT, Kontich, Belgium [100 kV, 100 μA, and 15-μm resolution]), and images were analyzed to evaluate canal volumes, surface areas, and centroid shift on cross sections at ?1 mm and ?3 mm from the apex.Results
TECs showed a greater preservation of the original root canal anatomy with less apical transportation than CECs, possibly because of the absence of coronal interferences and, therefore, fewer pecking motions required to complete instrumentation.Conclusions
Within the limitations of this study, TECs may lead to a better preservation of the original canal anatomy during shaping compared with CECs, particularly at the apical level. 相似文献13.
Joon-Soo Kim Ji-Hyeon Bae Mi-Jung Yun Jung-Bo Huh 《The Journal of prosthetic dentistry》2017,117(6):775-783
Statement of problem
Recently, zirconia removal diamond rotary instruments have become commercially available for efficient cutting of zirconia. However, research of cutting efficiency and the cutting characteristics of zirconia removal diamond rotary instruments is limited.Purpose
The purpose of this in vitro study was to assess and compare the cutting efficiency, durability, and diamond rotary instrument wear pattern of zirconia diamond removal rotary instruments with those of conventional diamond rotary instruments. In addition, the surface characteristics of the cut zirconia were assessed.Material and methods
Block specimens of 3 mol% yttrium cation-doped tetragonal zirconia polycrystal were machined 10 times for 1 minute each using a high-speed handpiece with 6 types of diamond rotary instrument from 2 manufacturers at a constant force of 2 N (n=5). An electronic scale was used to measure the lost weight after each cut in order to evaluate the cutting efficiency. Field emission scanning electron microscopy was used to evaluate diamond rotary instrument wear patterns and machined zirconia block surface characteristics. Data were statistically analyzed using the Kruskal-Wallis test, followed by the Mann-Whitney U test (α=.05).Results
Zirconia removal fine grit diamond rotary instruments showed cutting efficiency that was reduced compared with conventional fine grit diamond rotary instruments. Diamond grit fracture was the most dominant diamond rotary instrument wear pattern in all groups. All machined zirconia surfaces were primarily subjected to plastic deformation, which is evidence of ductile cutting. Zirconia blocks machined with zirconia removal fine grit diamond rotary instruments showed the least incidence of surface flaws.Conclusions
Although zirconia removal diamond rotary instruments did not show improved cutting efficiency compared with conventional diamond rotary instruments, the machined zirconia surface showed smoother furrows of plastic deformation and fewer surface flaws. 相似文献14.
Mahmoud Torabinejad Arin Alexander Seyed Aliakbar Vahdati Anupama Grandhi David Baylink Shahrokh Shabahang 《Journal of endodontics》2018,44(12):1796-1801
Introduction
Current pulp revascularization procedures in teeth with necrotic pulps and open apices have produced histologic evidence of connective tissue growth, cementum, and bone within the root canals of experimental animals. This study aims to investigate the effect of maintaining uninflamed residual apical pulp tissue on the histologic outcome of pulp-dentin complex regeneration after a revascularization procedure in immature ferret cuspid teeth.Methods
Twenty-eight cuspid teeth from 7 young male ferrets were used in this experiment. Seven teeth were reserved to serve as positive control samples without any treatment. In another 7 teeth, the pulp was completely extirpated (negative control), whereas the pulp of the remaining 14 teeth were removed to either 1–2 mm short of the apex (7 samples) or 2–4 mm short of the apex (7 samples). Blood clots were covered with mineral trioxide aggregate at the cementoenamel junction level of each tooth. Three months later, block sections were removed for histologic evaluations, and the data were statistically analyzed with the chi-square test (P < .05).Results
All teeth with complete pulp extirpation showed the presence of bone inside the root canal. In contrast, the root canals for most teeth with pulp amputation 1–4 mm from the radiographic apex were filled with normal pulp, which extended coronally to the mineral trioxide aggregate, where hard tissue bridges had formed.Conclusions
Based on these results, we concluded that regeneration of the pulp-dentin complex is possible when the apical 1–4 mm of the apical pulp remains intact in immature teeth. 相似文献15.
Ragavee Veeramani Raghavendra Shanbhog Talwade Priyanka Nandlal Bhojraj 《Pediatric Dental Journal》2021,31(1):51-59
ObjectiveTo evaluate and compare remineralization potential of commercially available calcium sucrose phosphate (CaSP) (5% EnaFix) individually and with 0.2% Sodium Fluoride (NaF) mouth-rinse (ACT Kids Anticavity Fluoride-Rinse) supplementation through Vickers Microhardness tester (VMH) and Quantitative Light Induced Florescence (QLF?) technology on artificial carious lesions on primary and permanent enamel.Materials & methodsIn present in-vitro comparative study, artificial carious lesions were created on 60 each, permanent and primary enamel samples followed by pH cycling for a period of 21 days with interventional agents (Control; Distilled water; Test; CaSP alone and CaSP + 0.2% NaF). The samples were evaluated for ΔF values of QLF at, demineralization, 7th, 14th and 21st day and VHN at, demineralization and 21st day of pH cycling. The data were analysed using paired t-test and ANOVA.ResultsIntra group comparison showed the statistically significant fluorescence gain with CaSP+0.2%NaF in permanent samples and statistically significant fluorescence gain with both CaSP and CaSP+0.2%NaF in primary samples (p = 0.001). Inter group comparison of interventional agents in both primary and permanent samples showed statistically non-significant variation between CaSP and added NaF group (p = 0.68).ConclusionsWithin the limitations of the present study, results showed no significant difference in microhardness improvement and remineralization potential between CaSP and CaSP+0.2%NaF. However, since both showed similar efficacy CaSP looks to be a choice for primary dentition and CaSP with 0.2% NaF can be preferred for mixed dentition with primary and young permanent teeth. 相似文献
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Liliane da Rocha Bonatto Marcelo Coelho Goiato Emily Vivianne Freitas da Silva Sandra Helena Penha Oliveira Marcela Filié Haddad Antônio Hernandes Chaves Neto Victor Gustavo Balera Brito Daniela Micheline dos Santos 《The Journal of prosthetic dentistry》2017,117(6):799-805
Statement of problem
Implant-retained maxillofacial prostheses should be biocompatible, regardless of the primers and adhesives used to bond the acrylic resin and facial silicone. The authors are unaware of any study evaluating the influence of these primers and adhesives on the biocompatibility of maxillofacial prostheses.Purpose
The purpose of this in vitro study was to evaluate the cytotoxic effect of primers and an adhesive used to bond acrylic resin and facial silicone during the fabrication of implant-retained maxillofacial prostheses.Material and methods
Twenty-eight circular specimens made of resin and silicone were fabricated, either bonded or nonbonded with primer and adhesive. The specimens were divided into 7 groups: resin; silicone; resin+silastic medical adhesive type A+silicone; resin+DC 1205 primer silicone; resin+Sofreliner primer+silicone; resin+DC 1205 primer+silastic medical adhesive type A+silicone; and resin+Sofreliner primer+silastic medical adhesive type A+silicone. Eluates of the materials tested were prepared by setting 4 specimens of each experimental group in Falcon tubes with medium and incubating at 37°C for 24 hours. The eluate cytotoxicity was evaluated by an assay of survival/proliferation ((3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide [MTT] test) in cultures of human keratinocytes. The levels of IL1, IL6, TNFα, and the chemokine MIP-1α were evaluated by enzyme-linked immunosorbent assay. The mRNA expressions for MMP-9, TGF-β, and collagen type IV were analyzed by the real time polymerase chain reaction. Data were submitted to analysis of variance with Bonferroni post hoc tests (α=.05).Results
An increased cell proliferation was observed for the RAS group, with statistically significant differences (P<.001) compared with the unstimulated group. The RDCpS group showed the highest IL6 concentration values (P<.001). No significant statistical difference was found in the relative quantification of mRNA for collagen type IV, MMP9, or TGFβ between the groups (P>.05).Conclusions
The RAS group showed the highest cell proliferation percentage, while the RDCpS group exhibited the highest IL6 concentration values. No detectable levels of IL1β, TNF α, or CCL3/MIP1α were observed. The tested materials showed no toxic effects on the HaCaT cell line. 相似文献17.
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18.
Statement of problem
Dental laboratories use different computer-aided design and computer-aided manufacturing (CAD-CAM) systems to fabricate fixed prostheses; however, limited evidence is available concerning which system provides the best marginal discrepancy.Purpose
The purpose of this in vitro study was to evaluate the marginal fit of 5 different monolithic zirconia restorations milled with different CAD-CAM systems.Material and methods
Thirty monolithic zirconia crowns were fabricated on a custom-designed stainless steel die and were divided into 5 groups according to the type of monolithic zirconia crown and the CAD-CAM system used: group TZ, milled with an MCXL milling machine; group CZ, translucent zirconia milled with a motion milling machine; group ZZ, zirconia milled with a dental milling unit; group PZ, translucent zirconia milled with a zirconia milling unit; and group BZ, solid zirconia milled using an S1 VHF milling machine. The marginal fit was measured with a binocular microscope at an original magnification of ×100. The results were tabulated and statistically analyzed with 1-way ANOVA and post hoc surface range test, and pairwise multiple comparisons were made using Bonferroni correction (α=.05).Results
The type of CAD-CAM used affected the marginal fit of the monolithic restoration. The mean (±SD) highest marginal discrepancy was recorded in group TZI at 39.3 ±2.3 μm, while the least mean marginal discrepancy was recorded in group IZ (22.8 ±8.9 μm). The Bonferroni post hoc test showed that group TZI was significantly different from all other groups tested (P<.05).Conclusions
Within the limitation of this in vitro study, all tested CAD-CAM systems produced monolithic zirconia restorations with clinically acceptable marginal discrepancies; however, the CAD-CAM system with the 5-axis milling unit produced the best marginal fit. 相似文献19.
Giacomo Derchi Michele Vano Antonio Barone Ugo Covani Alberto Diaspro Marco Salerno 《The Journal of prosthetic dentistry》2017,117(5):669-676