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1.
J Prosthet Dent ; 2021 Feb 02.
Artículo en Inglés | MEDLINE | ID: mdl-33546857

RESUMEN

STATEMENT OF PROBLEM: The properties of dental computer-aided design and computer-aided manufacturing (CAD-CAM) materials vary. Studies regarding the effects of aging on the properties of these materials are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the changes in the mechanical and surface properties of different CAD-CAM materials after thermocycling and mechanical loading. MATERIAL AND METHODS: In total, 150 bar-shaped specimens (17.0×4.0×2.0 mm) were prepared from feldspathic glass-ceramic (VM; Vitablocs Mark II), lithium disilicate glass-ceramic (EX; IPS e.max CAD), zirconia-reinforced lithium silicate glass-ceramic (CD; Celtra Duo), polymer-infiltrated ceramic network (VE; Vita Enamic), and resin-nanoceramic (CS; Cerasmart). Each type was divided into 2 groups (n=15; each). One group was subjected to thermocycling in distilled water at 5 °C to 55 °C for 6000 cycles and 50 N mechanical loading for 1.2×106 cycles. The other group was stored in 37 °C water for 24 hours. Nanoindentation hardness, Young modulus, and 3-point flexural strength were measured for the analyses of the mechanical properties. Surface roughness, surface microstructure, and elemental composition were measured to analyze the surface characteristics. Statistical analyses were performed with 1-way ANOVA with the Tukey HSD post hoc test, independent samples t test, Kruskal-Wallis test with Bonferroni post hoc test, Mann-Whitney U test, and 2-way ANOVA (α=.05). RESULTS: Before and after aging, CS exhibited the lowest hardness (1.20 to 1.04 GPa) and Young modulus (13.76 to 13.48 GPa) values (P<.05). EX exhibited the highest flexural strengths (393.43 to 391.86 MPa), and VM exhibited the lowest (109.98 to 112.73 MPa) values (P<.05). CS exhibited the highest surface roughness (Sa and Sq; 10.60 to 28.82, 14.21 to 38.27 nm) values (P<.05). After aging, the hardness and Young modulus of VM, EX, and VE decreased significantly (P<.001). No significant difference was observed in the flexural strengths of the CAD-CAM materials (P>.05). Significant increases were observed in the surface roughness of all the materials (P<.05), with altered microstructures. Except for the flexural strength, the mechanical properties and surface characteristics of the CAD-CAM materials were significantly affected by the material type after aging. CONCLUSIONS: Before and after aging, resin-nanoceramic exhibited the lowest hardness and Young modulus, and the highest surface roughness. Lithium disilicate glass-ceramic exhibited the highest flexural strength and feldspathic glass-ceramic exhibited the lowest value. After aging, increased surface roughness and microstructure alterations were observed. Significant interactions between aging process and material type were found for the mechanical properties and surface characteristics except for the flexural strength.

2.
J Prosthet Dent ; 2020 Nov 04.
Artículo en Inglés | MEDLINE | ID: mdl-33160619

RESUMEN

This clinical report describes a ceramic complete-mouth rehabilitation with screw-retained implant abutment crowns, optimizing esthetics by combining the properties of ceramic materials. The abutments connected a titanium insert to a computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic zirconia framework, offering improved esthetics and biologic response without negatively affecting the implant abutment interface. Lithium disilicate crowns were cemented extraorally on the abutments, resulting in a screw-retained restoration.

3.
J Prosthet Dent ; 2020 Oct 08.
Artículo en Inglés | MEDLINE | ID: mdl-33041076

RESUMEN

STATEMENT OF PROBLEM: The optical properties of esthetic computer-aided design and computer-aided manufacturing (CAD-CAM) materials can change depending on the clinical situation. Studies that compare esthetic CAD-CAM materials based on their optical properties are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the optical properties of esthetic CAD-CAM specimens after ultraviolet (UV) aging based on the type and thickness of the material. MATERIAL AND METHODS: In total, 240 plate-shaped specimens (14×12×1 mm and 14×12×2 mm) of a nanohybrid composite resin (Tetric CAD), a fine-structure feldspathic ceramic (Vitablocs Mark II), 2 different glass-ceramics (IPS Empress CAD and IPS e.max CAD), a zirconia-reinforced lithium silicate glass-ceramic (Celtra Duo), a polymer-infiltrated ceramic network (Vita Enamic), and 2 different resin nanoceramics (Cerasmart and Lava Ultimate) were fabricated (n=15). The optical parameters were analyzed by spectrophotometry before and after UV aging. The brightness (L∗), red green (a∗), yellow-blue (b∗), chroma (Ch), and hue (h) were measured, and the color difference (ΔE00) values were calculated. The translucency parameter (TP), total transmittance (Tt), and contrast ratio (CR) were also determined. Statistical analyses were performed with 1-way ANOVA, the Tukey honestly significant difference post hoc test, independent- and paired-samples t tests, and 2-way ANOVA (α=.05). RESULTS: Significant interactions were observed for the aging process, material type, and thickness for all optical parameters (P<.05). L∗, TP, and Tt had lower values, while CR had higher values for the aging group than that of the control group (P<.05). The h, TP, and Tt values were higher, whereas the b∗ and CR values were lower for the 1-mm group than those of the 2-mm group (P<.05). The highest ΔE00 value was found in the Lava Ultimate 1-mm group (ΔE00=3.21) and 2-mm group (ΔE00=2.42). The lowest ΔE00 value was found in the Vitablocs Mark II 1-mm group (ΔE00=0.31). The highest TP and Tt and the lowest CR values were observed for Tetric CAD; the lowest TP and Tt, and the highest CR values were noted in Celtra Duo (P<.05). CONCLUSIONS: The optical properties of the CAD-CAM specimens were affected by the aging process, material type, and thickness, and the color stability was clinically applicable in all CAD-CAM materials except groups Lava Ultimate and Cerasmart(ΔE00<2.25). Resin nanoceramics exhibited the greatest color changes after UV aging, and a 2-mm thickness is recommended to ensure acceptable color stability. The zirconia-reinforced lithium silicate glass-ceramic was the most opaque, with a 1-mm thickness providing increased translucency.

4.
Compend Contin Educ Dent ; 41(9): e5-e9, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-33001661

RESUMEN

This article describes the case of a partially edentulous patient who had undergone template-guided implant placement and was treated using a triple digital scanning protocol that allowed for CAD/CAM prosthodontic rehabilitation in a complete digital workflow. At the impression appointment, the provisional implant-supported screw-retained prosthesis was digitally scanned both intraorally (first scan) and, after removal, extraorally (second scan). After the second scan, scan bodies were placed intraorally and an implant-level digital impression was taken (third scan). The three standard tessellation language (STL) files derived from the three digital scans were imported in a CAD software and superimposed into one file that contained all of the information from the implant 3D position, prosthesis contours, and transmucosal part of the peri-implant soft tissues. The superimposition of the three STL files led to one master file to serve as a blueprint for the definitive prosthesis. The definitive monolithic zirconia prosthesis was CAM copy-milled, externally stained, and inserted. The patient was satisfied with both the esthetic and functional outcome and the minimally invasive, time-efficient, two-visit restorative protocol. In summary, this case report illustrates a technique for a complete digital workflow in an implant rehabilitation for the replacement of multiple missing teeth in the esthetic zone in two visits.


Asunto(s)
Implantes Dentales , Flujo de Trabajo , Diseño Asistido por Computadora , Prótesis Dental de Soporte Implantado , Estética Dental , Humanos
5.
Orthop J Sports Med ; 8(9): 2325967120947414, 2020 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-32964060

RESUMEN

Background: Retearing of a repaired rotator cuff leads to diverse symptoms, including pain, regardless of the degree of the tear, but the relationship between pain and retears is poorly understood. Purpose: To determine which factors are correlated with shoulder pain in retears of a repaired rotator cuff. Study Design: Case-control study; Level of evidence, 3. Methods: We retrospectively reviewed a cohort of patients who were diagnosed as having a retear on magnetic resonance imaging after primary rotator cuff repair. The primary outcome variable of interest was the visual analog scale (VAS) for pain score at 12-month and final follow-up (mean, 25.2 months). We evaluated the relationship of pain at 12-month and final follow-up with preoperative patient factors (age, sex, and underlying conditions), preoperative range of motion, and preoperative pain; postoperative pain at 3 and 6 months; and perioperative conditions (tear extent, tear size, accompanying lesions, and procedures other than rotator cuff repair). Results: A total of 48 patients were reviewed. The VAS score at 3 months postoperatively showed a positive correlation with the VAS score at 12 months postoperatively (ρ = 0.537; P < .001) and at final follow-up (ρ = 0.537; P < .001). Univariate and multivariate regression analyses revealed that the VAS score at 3 months postoperatively (P = .0001 and P = .0017, respectively), hypertension (P = .0108 and P = .0073, respectively), and late detection of the retear (P = .0091 and P = .0208, respectively) were significant predictors of pain at 12 months postoperatively. Conclusion: The presence of pain in the early postoperative period, underlying hypertension, and late detection of the retear were related to pain severity in patients 12 months after rotator cuff surgery.

6.
J Prosthodont ; 29(8): 660-678, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32613641

RESUMEN

PURPOSE: To systematically review in vitro and clinical studies comparing quantitatively the 3D accuracy (global implant deviations) of digital vs conventional implant impressions for partially and completely edentulous patients. MATERIALS AND METHODS: Electronic and manual searches were conducted to identify in vitro and clinical studies, reporting on the 3D accuracy between digital and conventional implant impressions. Secondary outcomes were the effect of implant angulation, type of conventional impression technique, and type of intraoral scanner on the accuracy of implant impressions. RESULTS: The inclusion criteria were met by 9 in vitro studies and 1 clinical study reporting on completely edentulous impressions, while 6 in vitro and 2 clinical studies reported on partially edentulous impressions. Quantitative meta-analysis was performed for 5 completely edentulous and 6 partially edentulous studies. The studies exhibited high values for heterogeneity. A random effects model was conducted to estimate the effect size. Based on 5 in vitro studies on completely edentulous impressions, the mean 3D implant deviation between conventional and digital impressions was 8.20 µm (95% CI: -53.56, 37.15) and the digital impressions had nominally less deviation (p = 0.72). Based on 1 clinical and 5 in vitro studies on partially edentulous impressions, the mean 3D implant deviation between conventional and digital impressions was 52.31 µm (95% CI: 6.30, 98.33) and the conventional impressions had nominally less deviation (p = 0.03). Five in vitro and 2 clinical studies were not included in the quantitative analysis due to heterogeneity in the methodology. Implant angulation affected the accuracy in favor of the partially edentulous conventional impressions whereas the effect of different scanners was not statistically significant on the completely edentulous impressions (p = 0.82). CONCLUSIONS: Digital scans appear to have comparable 3D accuracy with conventional implant impressions based mainly on in vitro studies. However, clinical trials are recommended to investigate the clinical accuracy of digital scans and digitally fabricated interim or prototype prostheses, before digital implant scans can be recommended for routine clinical use.


Asunto(s)
Implantes Dentales , Boca Edéntula , Diseño Asistido por Computadora , Materiales de Impresión Dental , Técnica de Impresión Dental , Modelos Dentales , Humanos
8.
J Prosthodont ; 29(6): 460-465, 2020 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-32185825

RESUMEN

The purpose of the present report is to illustrate a proof-of-concept protocol with the double digital scanning (DDS) technique for complete digital workflow in double full-arch implant rehabilitation. Two patients (4 restored arches) presented with hopeless dentitions and they were treated with a 4-appointment prosthodontic protocol and monolithic zirconia prostheses implementing a complete digital workflow. The outcomes are presented after clinical and radiographic observation for 2 years.


Asunto(s)
Implantes Dentales , Prótesis Dental de Soporte Implantado , Diseño Asistido por Computadora , Diseño de Prótesis Dental , Humanos , Flujo de Trabajo , Circonio
9.
J Prosthet Dent ; 124(5): 589-593, 2020 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-31959396

RESUMEN

STATEMENT OF PROBLEM: Data on the accuracy of printed casts from complete-arch digital implant scans are lacking. PURPOSE: The purpose of this in vitro study was to compare the 3D accuracy of printed casts from a complete-arch digital implant intraoral scan with stone casts from conventional impressions. MATERIAL AND METHODS: An edentulous mandibular cast with 4 multiunit abutments with adequate anteroposterior spread was used as the master cast. Digital scans (n=25) were made by using a white light intraoral scanner (IOS). The generated standard tessellation language (STL) data sets were imported into a computer-assisted design (CAD) software program to generate complete-arch implant casts through 3D printing technology. The 25 printed casts and the mandibular master cast were further digitized by using a laboratory reference scanner (Activity 880; Smart Optics). These STL data sets were superimposed on the digitized master cast in a metrology software program (Geomagic Control X) for virtual analysis. The root mean square (RMS) error and the average offset were measured. RESULTS: When compared with the master cast, the printed casts had a mean ±standard deviation RMS error of 59 ±16 µm (95% CI: 53, 66). The maximum RMS error reached 98 µm. The average offsets were all negative, with a significant difference compared with zero (P<.001). CONCLUSIONS: The implant 3D deviations of the printed casts from complete-arch digital scans had statistically significant differences compared with those of the master cast but may still be within the acceptable range for clinical application.


Asunto(s)
Implantes Dentales , Técnica de Impresión Dental , Diseño Asistido por Computadora , Modelos Dentales , Imagenología Tridimensional , Impresión Tridimensional , Flujo de Trabajo
10.
J Esthet Restor Dent ; 30(1): 5-13, 2018 01.
Artículo en Inglés | MEDLINE | ID: mdl-28792115

RESUMEN

OBJECTIVE: To illustrate a digital workflow in full-arch implant rehabilitation with minimally veneered monolithic zirconia and to report the outcomes including technical complications. CLINICAL CONSIDERATIONS: Three patients (5 edentulous arches) received full-arch fixed implant rehabilitation with monolithic zirconia and mild facial porcelain veneering involving a digital workflow. The incisal edges and occluding surface areas were milled out of monolithic zirconia to reduce the possibility of chipping. Porcelain veneering was applied on the facial aspect to improve the esthetic result. Outcomes and technical complications are reported after 2 years of clinical and radiographic follow-up. CONCLUSION: Implant and prosthesis survival rates were 100% after a short-term follow-up of 2 years. Technical complications were encountered in one patient. They did not adversely affect prosthesis survival or patient satisfaction and were easily addressed. A digital workflow for the design and fabrication of full-arch monolithic zirconia implant fixed implant prostheses has benefits, but caution is necessary during CAD planning of the prosthesis to ensure a successful outcome. Long-term clinical studies are needed to corroborate the findings discussed in this report. CLINICAL SIGNIFICANCE: This article presents an integrated digital workflow that was implemented for the implant-prosthodontic rehabilitation of three edentulous patients with monolithic zirconia prostheses. Monolithic zirconia has been successfully incorporated in implant prosthodontics in an effort to reduce the technical complications associated with bilayered ceramics. This workflow simplifies design and fabrication of the zirconia prostheses. However, caution should be taken during CAD planning of the prosthesis to make sure the zirconia cylinder is sufficiently thick at the interface with the titanium insert. Additionally, when cutback is planned for facial porcelain veneering, the functional occluding cusps and incisal edges should be fabricated in monolithic zirconia to avoid chipping.


Asunto(s)
Porcelana Dental , Prótesis Dental de Soporte Implantado , Diseño Asistido por Computadora , Diseño de Prótesis Dental , Fracaso de la Restauración Dental , Estudios de Seguimiento , Humanos , Flujo de Trabajo , Circonio
11.
Clin Oral Implants Res ; 28(7): 849-863, 2017 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-27350419

RESUMEN

OBJECTIVE: To assess survival, as well as technical and biological complication rates of partial fixed dental prostheses (FDPs) supported by implants and teeth. METHOD: An electronic Medline search was conducted to identify articles, published in dental journals from January 1980 to August 2015, reporting on partial FDPs supported by implants and teeth. The search terms were categorized into four groups comprising the PICO question. Manual searches of published full-text articles and related reviews were also performed. RESULTS: The initial database search produced 3587 relevant titles. Three hundred and eighty-six articles were retrieved for abstract review, while 39 articles were selected for full-text review. A total of 10 studies were selected for inclusion. Overall survival rate for implants ranged between 90% and 100%, after follow-up periods with a mean range of 18-120 months. The survival of the abutment teeth was 94.1-100%, while the prostheses survival was 85-100% for the same time period. The most frequent complications were "periapical lesions" (11.53%). The most frequent technical complication was "porcelain occlusal fracture" (16.6%), followed by "screw loosening" (15%). According to the meta-analysis, no intrusion was noted on the rigid connection group, while five teeth (8.19%) were intruded in the non-rigid connection group [95% CI (0.013-0.151)]. CONCLUSION: The tooth-implant FDP seems to be a possible alternative to an implant-supported FDP. There is limited evidence that rigid connection between teeth and implants presents better results when compared with the non-rigid one. The major drawback of non-rigidly connected FDPs is tooth intrusion.


Asunto(s)
Pilares Dentales , Implantes Dentales , Diseño de Dentadura , Dentadura Parcial Fija , Fracaso de la Restauración Dental , Humanos
12.
J Prosthodont ; 23(3): 213-20, 2014 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23889762

RESUMEN

PURPOSE: The purpose of this study was to compare the effect of variations in translucency and background on color differences (ΔE) for different shades of computer-aided design and computer-aided manufacturing (CAD/CAM) lithium disilicate glass ceramics. MATERIALS AND METHODS: A pilot study suggested n = 10 as an appropriate sample size for the number of lithium disilicate glass ceramic cylinders per group. High-transparency (HT) and low-transparency (LT) cylinders (diameter, 12 mm; length, 13 mm) were fabricated in three ceramic shades (BL1, A2, C3) using CAD/CAM technology and were cut into specimen disks (thickness, 1.2 mm; diameter, 12 mm) for placement on Natural Die (ND1 and ND4) backgrounds. Four combinations of translucency and background color were evaluated in terms of color differences for the three ceramic shades: group 1 (HT ND1, reference), group 2 (HT ND4), group 3 (LT ND1), and group 4 (LT ND4). A spectrophotometer was used to measure the color differences. Nonparametric tests (Kruskal-Wallis tests) were used to evaluate the color differences among the tested groups, and Mann-Whitney U tests with Bonferroni correction were used as post hoc tests. Furthermore, for each ceramic shade, the HT groups were compared to the LT groups using the Mann-Whitney U test. RESULTS: Significant differences were present among the tested groups of the same ceramic shade (p < 0.001). The highest ΔE values were observed in the HT ND4 group for BL1, while the lowest ΔE values were found in the LT ND1 group for both A2 and C3. Further, the HT groups and the groups with a darker background (ND4) showed increased ΔE values compared with the other groups (p < 0.001). CONCLUSIONS: Within the limitations of this study, the results suggested that the translucency and background color significantly influenced the lithium disilicate glass ceramic color among the BL1, A2, and C3 ceramic shades. Changing the underlying color from a lighter background to a darker background resulted in increased color differences.


Asunto(s)
Cerámica/química , Diseño Asistido por Computadora , Materiales Dentales/química , Porcelana Dental/química , Color , Cristalización , Calor , Luz , Ensayo de Materiales , Espectrofotometría/métodos , Propiedades de Superficie
13.
J Prosthet Dent ; 110(6): 494-500, 2013 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-24176183

RESUMEN

STATEMENT OF PROBLEM: The replication of natural teeth, especially with single-tooth restorations, represents a challenge. Similar to metal ceramic crowns, different designs of zirconia substructures have been suggested to improve the esthetic results of zirconia ceramic crowns. PURPOSE OF STUDY: The purpose of the study was to analyze the color of the cervical portion of single zirconia ceramic crowns fabricated with different zirconia coping designs. MATERIAL AND METHODS: The color, measured on the CIELAB color scale, of 3 different groups of restorations (n=10) fabricated with zirconia coping (Lava) and feldspathic porcelain (Noritake Super Porcelain) was analyzed with a spectrophotometer. Conventional zirconia crowns with zirconia facial margins were compared with ceramic crowns with porcelain facial margins and either a horizontal reduction of the zirconia coping (1.0 mm reduction) or an additional vertical reduction (1.0 mm additional reduction). The 3 groups, each with a different coping extension, were examined with a 1-way ANOVA and the Fisher exact test, and the differences of the groups were evaluated by applying ΔE thresholds (α=.05). RESULTS: The mean color difference among all the groups was not clinically significant (ΔE<3.7). Reduced color differences were present between the 2 porcelain butt margin groups of crowns (ΔE=1.06, between group H and V). Increased differences were present between the zirconia margin group and the porcelain butt margin group (ΔE=2.54 between group C and H; ΔE=2.41 between group C and V). Lab* values were examined in all the groups of crowns to determine the clinical implications. CONCLUSIONS: Within the limitation of the study, no significant differences were present among the tested groups of crowns. Nevertheless, although some differences were present between the zirconia margin group and the porcelain butt margin group, reduced differences were present between the 2 different cutback designs.


Asunto(s)
Coronas , Materiales Dentales/química , Diseño de Prótesis Dental , Circonio/química , Silicatos de Aluminio/química , Color , Porcelana Dental/química , Estética Dental , Humanos , Incisivo/anatomía & histología , Ensayo de Materiales , Compuestos de Potasio/química , Cementos de Resina/química , Espectrofotometría/métodos , Propiedades de Superficie , Cuello del Diente/anatomía & histología , Preparación Protodóncica del Diente/métodos
14.
J Prosthet Dent ; 102(3): 140-7, 2009 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-19703620

RESUMEN

STATEMENT OF PROBLEM: The retentive capacity of ball attachments may be altered by a change in implant angulations. PURPOSE: The purpose of this in vitro study was to investigate the effect of cyclic dislodgement on the retention of an overdenture attachment system when 2 implants were placed at angulations of 0, 5, 10, 15, and 20 degrees. MATERIAL AND METHODS: Twelve acrylic resin blocks were fabricated and divided into 6 groups of 2 pairs each. In each of the 6 groups, 1 acrylic resin block was used to house the implants (block A), while the other (block B) was used to house the overdenture attachments. Two implants positioned at 0/0 degrees, with a standard plastic component(white) designed for 0-degree angulations, served as a control (CTRL), while the other 5 pairs of implants were placed in 5 different angulations: 0D: 0/0 degrees, 5D: 5/5 degrees, 10D: 10/10 degrees, 15D: 15/15 degrees, 20D: 20/20degrees (n=5). The extended range (green color) attachment was used for all groups except the control group. Implants(4.3 mm x 13 mm, internally hexed) were placed in blocks B. All angled implants were mesially tilted. Thirty pairs of attachments (Locator) were used. Dislodging cycles were applied to the overdenture attachment system. The initial retentive forces among the groups were not identical. The cycles required for the retentive forces of the attachments to decrease from the initial values to 60 N, and then to 40 N and 20 N, were recorded for standardization purposes.One-way ANOVA and Tukey HSD tests were used to analyze the difference in retention loss among the 6 groups(alpha=.05). A regression analysis (alpha=.05) was also performed to investigate the relationship between the implant angulation,the retentive force, and the logarithm of the number of cycles required for ball attachment retention decrease. RESULTS: The 1-way ANOVA and the Tukey HSD tests revealed significant differences for the number of cycles required by different implant angulation groups for the initial retentive values to decrease to 60 N, 40 N, and 20 N (P<.001).The 0D and 5D groups required the longest time for retention loss, while 20D and CTRL groups demonstrated the shortest time for retention loss. The results of the regression analysis of the logarithmic number of cycles on retentive force and implant angulation demonstrated a significant effect (P<.001). CONCLUSIONS: Implant angulations negatively affect attachment retention longevity. (J Prosthet Dent 2009;102:140-147)


Asunto(s)
Pilares Dentales , Implantación Dental Endoósea/métodos , Prótesis Dental de Soporte Implantado/instrumentación , Ajuste de Precisión de Prótesis , Retención de Dentadura/métodos , Prótesis de Recubrimiento , Análisis de Varianza , Implantes Dentales , Fracaso de la Restauración Dental , Análisis del Estrés Dental , Retención de Dentadura/instrumentación , Humanos , Estrés Mecánico
15.
J Prosthet Dent ; 102(3): 172-8, 2009 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-19703624

RESUMEN

STATEMENT OF PROBLEM: Although the esthetic outcome of a collarless metal ceramic restoration is superior to that of a restoration with a metal margin, its mechanical strength has not been evaluated. PURPOSE: The purpose of this study was to evaluate and compare the fracture resistance of metal ceramic restorations with metal margins to that of metal ceramic restorations with circumferential porcelain margins, after exposure to masticatory simulation. MATERIAL AND METHODS: Twenty-four metal ceramic restorations were fabricated and paired with 24 cobalt-chrome tooth analogs. Twelve of the specimens had metal margins, while the remainder had circumferential porcelain margins. The restorations were cemented on the metal tooth analogs with a resin-modified glass ionomer luting agent (FujiCEM). All specimens were subjected to cyclic loading by a texture analyzer. A total of 600,000 loading cycles in an aqueous environment was performed, with a minimum load of 0 N and a maximum load of 200 N. Controlled loads were then applied to the teeth until fracture, using a stainless steel rod with a 2-mm-wide, rounded end, mounted in a universal testing machine. The specimens were examined under a stereomicroscope to determine failure mode. Descriptive statistics and the independent t test (alpha=.05) were used to determine the effect of failure loads among the tested groups. RESULTS: The independent t test revealed statistically significant differences among the 2 tested groups (P<.001). The 2 groups presented different failure modes. Metal ceramic restorations with metal margins presented cohesive failures starting from the point of load application. Metal ceramic restorations with circumferential porcelain margins demonstrated a combination of adhesive and cohesive failures, starting from the point of load application and extending to the highest point of the proximal margins. CONCLUSIONS: Metal ceramic restorations with metal margins required significantly greater loads (P<.001) to fracture than metal ceramic restorations with circumferential porcelain margins. (J Prosthet Dent 2009;102:172-178).


Asunto(s)
Fuerza Compresiva , Coronas , Diseño de Prótesis Dental , Fracaso de la Restauración Dental , Aleaciones de Cerámica y Metal/química , Fuerza de la Mordida , Restauración Dental Permanente/instrumentación , Restauración Dental Permanente/métodos , Análisis del Estrés Dental , Estética Dental , Humanos , Masticación , Estrés Mecánico , Soporte de Peso
16.
J Phys Chem B ; 113(2): 536-43, 2009 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-19099431

RESUMEN

The work describes a simple and convenient process for highly efficient and direct DNA separation with functionalized silica-coated magnetic nanoparticles. Iron oxide magnetic nanoparticles and silica-coated magnetic nanoparticles were prepared uniformly, and the silica coating thickness could be easily controlled in a range from 10 to 50 nm by changing the concentration of silica precursor (TEOS) including controlled magnetic strength and particle size. A change in the surface modification on the nanoparticles was introduced by aminosilanization to enhance the selective DNA separation resulting from electrostatic interaction. The efficiency of the DNA separation was explored via the function of the amino-group numbers, particle size, the amount of the nanoparticles used, and the concentration of NaCl salt. The DNA adsorption yields were high in terms of the amount of triamino-functionalized nanoparticles used, and the average particle size was 25 nm. The adsorption efficiency of aminofunctionalized nanoparticles was the 4-5 times (80-100%) higher compared to silica-coated nanoparticles only (10-20%). DNA desorption efficiency showed an optimum level of over 0.7 M of the NaCl concentration. To elucidate the agglomeration of nanoparticles after electrostatic DNA binding, the Guinier plots were calculated from small-angle X-ray diffractions in a comparison of the results of energy diffraction TEM and confocal laser scanning microscopy. Additionally, the direct separation of human genomic DNA was achieved from human saliva and whole blood with high efficiency.


Asunto(s)
ADN/química , ADN/aislamiento & purificación , Magnetismo , Nanopartículas/química , Dióxido de Silicio/química , Aminas/química , Humanos , Microscopía Confocal , Microscopía Electrónica de Transmisión , Nanopartículas/ultraestructura
17.
Int J Oral Maxillofac Implants ; 22(4): 569-74, 2007.
Artículo en Inglés | MEDLINE | ID: mdl-17929517

RESUMEN

PURPOSE: To investigate the effects of thermal cycling and surface roughness of metal implant abutments and the intaglio surface of the copings on the retentive properties of 4 provisional luting agents commonly used in the cementation of implant-retained fixed partial dentures (FPDs). MATERIALS AND METHODS: A 2-unit implant-retained FPD and a 4-unit implant-retained FPD were fabricated using gold-palladium alloy. The abutments used were 5 mm in height. The FPDs were cemented with 4 commonly used provisional luting agents and thermocycled for 700 cycles from 5 degrees C to 36 degrees C to 55 degrees C and were then subjected to tensile strength testing. After thermal cycling, the intaglio surfaces of the same FPDs and the abutments were air-abraded with 50 microm Al2O3 particles. FPDs were cemented using the same provisional cements, and after 24 hours of storage in 100% humidity, tensile strength tests were performed. Descriptive statistics, 2-way analysis of variance, Friedman's 2-way ANOVA, and Tukey's HSD test (alpha = .05) were performed. RESULTS: Both thermal cycling and air abrasion had a significant effect (P < .001) on the retentive values of all cements tested. A noneugenol provisional cement (Nogenol) exhibited the lowest mean retentive value after both thermal cycling and air abrasion for both the 2- and 4-unit FPD models. The urethane resin provisional cement (Improv) exhibited the highest mean retentive strength for both the 2- and 4-unit FPDs after thermal cycling and air abrasion treatments. CONCLUSIONS: Thermal cycling had a detrimental effect on the retentive properties of all cements tested. Air abrasion significantly improved the cement failure loads of the provisional luting agents used in the study and seems to be an effective way of increasing the retention of implant-retained FPDs.


Asunto(s)
Cementación/métodos , Cementos Dentales/química , Prótesis Dental de Soporte Implantado , Dentadura Parcial Fija , Óxido de Aluminio/química , Pilares Dentales , Aleaciones Dentales/química , Implantes Dentales , Retención de Dentadura , Combinación de Medicamentos , Eugenol/química , Ácidos Grasos/química , Aleaciones de Oro/química , Humanos , Humedad , Ensayo de Materiales , Paladio/química , Resinas de Plantas/química , Salicilatos/química , Estrés Mecánico , Propiedades de Superficie , Temperatura , Resistencia a la Tracción , Timol/química , Óxido de Zinc/química , Cemento de Óxido de Zinc-Eugenol/química
18.
J Prosthet Dent ; 97(1): 1-5, 2007 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-17280884

RESUMEN

Periodontal surgical procedures may not always offer a predictable level of success in the reproduction of a natural gingival architecture. Two different nonsurgical approaches are described for the management of soft tissue deficiencies in anterior implant-supported restorations. Clinically acceptable esthetic outcomes of anterior implant restorations can be achieved by using zirconium custom abutments and gingiva-colored dental porcelain.


Asunto(s)
Implantación Dental Endoósea/métodos , Implantes Dentales de Diente Único , Porcelana Dental/uso terapéutico , Diseño de Prótesis Dental/métodos , Recesión Gingival/terapia , Adulto , Estética Dental , Femenino , Humanos , Incisivo , Masculino , Maxilar , Persona de Mediana Edad , Coloración de Prótesis/métodos
19.
J Prosthet Dent ; 96(6): 418-23, 2006 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-17174659

RESUMEN

STATEMENT OF PROBLEM: Polymerization of resin materials used for the fabrication of provisional restorations is associated with an exothermic reaction. This temperature rise may present a serious biological problem, since it can cause iatrogenic thermal trauma to the pulp. PURPOSE: This in vitro study compared the temperature increase in the pulp chamber of a molar placed in contact with different resins used for the direct fabrication of provisional restorations. MATERIAL AND METHODS: Polymethyl methacrylate (Jet), polyethyl methacrylate (Snap), polyvinylethyl methacrylate (Trim), Bis-acrylic composite (Protemp II), and a VLP urethane dimethacrylate (Revotec LC) were compared with respect to their exothermic reaction properties during polymerization. A mandibular molar prepared for a complete coverage restoration was placed in an acrylic resin block. A thermal probe connected to a digital thermometer was placed into the pulp chamber. Specimens were submerged in a water bath to simulate intraoral conditions. The provisional resin materials tested were measured and mixed according to manufacturer's instructions. The resin mixture was placed into a vacuum-formed acetate template and was then positioned on the prepared molar tooth. The temperature was recorded during polymerization at 30-second intervals until it was evident that the peak temperature had been reached. Temperature increase was measured ( degrees C) for both the initial crown fabrication and the reline procedures. Data were analyzed with descriptive statistics, 1-way analysis of variance, and Tukey Honestly Significant Difference tests (alpha=.05). RESULTS: One-way ANOVA revealed significant differences (F=57.010, P<.0001) in temperature rise for different provisional resin materials. Mean temperature increase for the provisional crown fabrication ranged from 37.76 degrees C for the polyvinylethyl methacrylate to 39.40 degrees C for the polymethyl methacrylate. Mean temperature rise for the reline procedures ranged from 36.80 degrees C for the polyvinylethyl methacrylate to 37.69 degrees C for the polymethyl methacrylate. All of the tested materials produced an exothermic chemical reaction. CONCLUSIONS: Polymethyl methacrylate produced the higher exothermic reaction in both initial crown fabrication and reline procedures. Polyethyl methacrylate, polyvinylethyl methacrylate, and Bis-acrylic resins tested were not significantly different from each other.


Asunto(s)
Resinas Acrílicas/efectos adversos , Cavidad Pulpar/química , Restauración Dental Provisional/efectos adversos , Calor/efectos adversos , Diente Molar/química , Resinas Acrílicas/química , Análisis de Varianza , Amalgama Dental/efectos adversos , Amalgama Dental/química , Humanos , Polimetil Metacrilato/efectos adversos , Polimetil Metacrilato/química
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