Magister Scientiae Dentium - MSc(Dent) / Introduction: The evolution of Dentistry witnessed an increase in fixed prostheses as opposed to removable ones. Zirconia (ZrO2) and Lithium disilicate (LDS) are becoming the material of choice in implant or tooth retained prostheses. Polyetheretherketone (PEEK) is a recent alternative as it is lighter and causes less wear of opposing retained teeth. Biofilm formation is a permanent daily struggle for patients as it can be found in nearly all surfaces exposed to the natural environment. Therefore, the interest in a new device capable of removing or reducing oral biofilm from fixed prostheses is increasing. Aquaflosser (AQ) and Waterpik (WP) are examples of these oral irrigating devices that were introduced to the dental market recently. They can be effective in removing dental biofilm from different surfaces. Purpose of study: The purpose of this study is to evaluate biofilm formation on three fixed dental substructures and to evaluate the efficacy of two oral irrigating devices on biofilm removal from these three substructures.

OBJECTIVES: To determine and compare color difference CIEDE2000 (ΔE00) of pressed IPS E.max lithium disilicate ceramic material after repeated firing cycles. To determine and evaluate correlation of CIELAB and CIEDE2000 values analyzed by X-Rite Color i5 Spectrophotometer, VITA EasyShade® Advance 4.0 (VITA Zahnfabrik) and Adobe Photoshop CC. MATERIALS AND METHODS: 36 specimens 8mmX10mm at 1.5mm thickness (12 specimens of pressed IPS e.max® Press Lithium Disilicate MT Monochromatic ingots and 24 specimens pressed IPS e.max® Multi Press Lithium Disilicate Multichromatic ingots. Specimens were exposed to repeated firing cycles up to 7 cycles. Color analysis was performed after 1st,2nd,3rd,5th, and7th firing cycle. CIE L*a*b* values measured by X-Rite Color i5 Spectrophotometer, VITA EasyShade® Advance 4.0 (VITA Zahnfabrik) and Adobe Photoshop CC. CIELAB (Δ*ab) and CIEDE2000 (Δ00) calculated to measure color difference. RESULTS: Linear regression and multiple comparison analysis (Tukey’s HSD test) showed a significant color difference (Δ*ab) and CIEDE2000 (Δ00) with (p-value <0.001), after multiple firing cycles, between instruments used and in different shades groups. Moreover, significant different in interactive effect between different shades tested by different instrument, different shades tested after multiple firing cycles and different instruments after multiple firing cycles. CONCLUSION: IPS E.max lithium disilicate material shows significant color difference after repeated firing cycle tested by three color analysis instruments. Measuring instruments used to evaluate CIE L*a*b* color values showed significant different in color values analysis which may lead to altered level of interpretation, particularly to determine perceptibility and clinical acceptability thresholds. / 2021-08-15T00:00:00Z

OBJECTIVE: To explore a novel virtual inspection approach with a 3D metrology software to provide a non-destructive in situ analysis in digital workflow. Also, to evaluate the fit discrepancies of lithium disilicate crowns by using such a novel virtual measuring technique. MATERIALS AND METHODS: Maxillary arch typodont was used to design abutment for tooth #8 and #14 (hand prepared) and #4 and #10 (titanium custom abutment). All four abutments were placed into a duplicated maxillary arch solid stone model for scanning with laboratory scanner. Four crown patterns were designed and exported as STL files. The internal control group consists of the four original digital STL files and the external control group which was the 32-milled lithium disilicate crowns (IPS e.max® CAD, Ivoclar Vivadent, Inc.), eight patterns for each tooth. Thirty-two pressable wax patterns (8 of each) was fabricated for each of the three different technique systems. Two printed wax systems, Varseo Wax CAD/Cast (BEGO) and Press-E-Cast (EnvisionTec). Two milled wax systems Harvest Wax (Ivoclar Vivadent, Inc.) and Polycon Cast (Straumann), and a set of conventional cutbacks of 1.5mm with applied marginal wax. All patterns were pressed into lithium disilicate crowns, then fine polished and scanned. Each file was imported into a quality control metrology software (Geomagic Control X, 3D Systems) for marginal fit and internal fit evaluation with respective digital abutment. RESULTS: Mean of marginal gap for all groups were all lower than the preset gap space of 40 microns. Statistically significant differences in the fit accuracy were found among tooth number, technique system and measurement locations, but the differences are in clinically acceptable range. New scope of analyzing a restoration in a 3D fashion can help solve clinical complications. The study has shown that lower marginal gap does not necessary indicates a better fit restoration, as every level of the crown should be evaluated for. CONCLUSION: This novel inspection method can be used as a replacement of fit checker and help clinician to work in a full digital workflow. Lithium disilicate restorations fabricated through printed wax pattern, milled wax pattern and conventional hand wax are all clinically acceptable techniques. / 2019-09-26T00:00:00Z

Indiana University-Purdue University Indianapolis (IUPUI), Indiana University School of Dentistry / Background: With the emerging of digital dentistry, IPS e.max® CAD lithium disilicate (LD) glass-ceramic material has become one of the most popular esthetic restorative materials in digital assisted dental esthetic restoration. The mechanical and optical properties of this material have been investigated in several studies. However, there is a lack of information and consensus regarding the optical properties of IPS e.max® LD glass-ceramic materials. Objectives: 1) To investigate the optical properties as translucency parameters (TP), Contrast ratio (CR), light transmissions (Lt) and color changes (CC) between high-translucent (HT) and low-translucent (LT) IPS e.max® CAD LD glass-ceramic materials with different crystalline phases and thickness in different firing stages. 2) To investigate the optical properties as TP, CR, Lt and CC of each translucent (HT and LT) IPS e.max® CAD LD glass-ceramic materials with different crystalline phases and thickness in different firing stages. 3) To determine the mathematical relationships of thicknesses of IPS e.max® CAD LD glass-ceramics materials with TP and Lt. Materials and methods: The total of 120 of shade A2 IPS max CAD samples (HT and LT) were prepared into square shape (15.25 mm X 15.25 mm) and were divided into two main groups according to the material translucency (HT and LT) (n=60). Each main group was further divided into 5 sub-groups according to the thickness (1.00, 1.25, 1.5, 1.75, and 2.00 mm) (n=12). Each thickness group was assigned into three groups based on different crystallization (firing) temperatures (750, 820 °C in single stage heating schedule with 1 second and 10 second holding times, respectively, and 840 °C with two-stage heating schedule (RECOM) (820°C, 840 °C with 10 second and 7 min holding time, respectively) as recommended by manufacturer (n=4). CIEL*a*b*, TP, CR, and Lt were measured and calculated for all samples. Statistical analysis: The effects of the test results were evaluated using 3-way ANOVA with factors for Translucency (HT and LT), Firing Temperature (750, 850, and RECOM) and Thickness (1, 1.25, 1.5, 1.75, and 2), as well as all two-way and three-way interactions among the factors. Pair-wise comparisons were made using Least Significant Differences to control the overall significance level at 5%. Results: The mean irradiance and TP for both HT and LT decrease as the thickness of the samples increases from 1 to 2mm with significant difference between the thickness groups within each material translucency groups (HT and LT) and between both HT and LT. The coefficients of absorption (c) of the two materials were calculated. The effective incidence irradiance when material thickness approaches zero (Ie) was also calculated. There is an unexpected spectral peak shift as the thickness of the samples increases. There is no statistically significant difference in Ie at 750˚C and 820 ˚C between the HT and LT. However, there is a statistically significant higher Ie in HT at the recommended firing temperature as expected. Coefficients of translucency parameter (p) of the materials in various firing temperature were defined and the TP of the material as the thickness approaches zero were calculated (TP0). The TP of the materials is directly correlated to the mean irradiance passing through the samples. There is no statistically significant difference in the TP0 and Ie of the HT and LT groups at the recommended firing temperature. Conclusion: In this project we developed modified Beer-Lambert law to describe the parameters governing the effect of thickness on light transmission in dental ceramic material. We also applied the same equation to describe the translucency parameter. The parameters defined in these equations allow us to compare the optical property of dental ceramic material independent of the thickness of the samples.

As restaurações indiretas em sistemas totalmente cerâmicos desenvolveram-se visando à obtenção de próteses com melhor capacidade de mimetismo do dente natural. Além das propriedades óticas, essas restaurações devem ter adesão ao substrato de suporte, de modo a promover a união entre a cerâmica, o esmalte e a dentina, formando um corpo único, permitindo a transferência de tensões da restauração para a estrutura dental. Alguns fatores como: composição, espessura, opacidade e a cor do material cerâmico podem interferir na passagem de luz e, consequentemente, diminuir o grau de conversão do cimento, limitando o alcance de suas propriedades mecânicas e prejudicando o desempenho clínico. Dessa forma, este trabalho teve por objetivo avaliar a influência de diferentes níveis de opacidade da infraestrutura do dissilicato de lítio na polimerização de um cimento resinoso dual. Foram utilizados quatro discos de cerâmica (IPS e.max Press, IvoclarVivadent, Schaan, Liechtenstein), um para cada opacidade da infraestrutura (HT, LT, MO e HO) recobertas por sua respectiva cerâmica de cobertura (IPS e.max ceram na cor A3), e um grupo de cimento sem a cerâmica interposta (grupo-controle). Para cada grupo foram polimerizados 15 corpos de prova de cimento resinoso (Variolink II, Ivoclar Vivadent, Schaan, Liechtenstein). Foi mensurado o grau de conversão do cimento com o teste de microdureza knoop. Cada corpo de prova foi avaliado imediatamente após a polimerização e após sete dias. Foram feitas cinco endentações para cada tempo e obtida uma média de cada corpo de prova. O grupo com disco de maior opacidade (HO) apresentou o menor valor de microdureza (9,48 ± 0,36) no tempo inicial. O maior valor de microdureza foi o do grupo-controle após 07 dias (38,51 ± 1,05). Os grupos com disco LT e MO apresentaram comportamento igual nos dois tempos, não havendo diferença entre eles. O maior valor de microdureza com o uso de discos cerâmicos foi o do grupo HT após 07dias (29,53 ± 1,81), o qual apresentou valor próximo do controle inicial, porém estatisticamente diferente. Conclui-se que o nível de opacidade da infraestrutura do dissilicato de lítio pode influenciar no grau de polimerização de um cimento resinoso dual. / The indirect restorations in totally ceramic systems have been developed in order to obtain prostheses with improved ability to mimicry of the natural tooth. In addition to optical properties, these restorations must have adhesion to the supporting substrate so as to promote the bonding between the ceramic, enamel and dentin, forming a single body, allowing the transfer of stresses to the structure of the dental restoration. Some factors such as composition, thickness, opacity and color of the ceramic material can interfere with the transmission of light and, consequently, decrease the degree of conversion of the cement, impairing their mechanical properties and impairing clinical performance. Thus, this study aimed to evaluate the influence of different opacity levels of lithium disilicate infrastructure in the polymerization of a dual resin cement. Four ceramic discs were used (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein), one for each opacity infrastructure (HT, LT, MO and HO) covered by their respective veneering ceramic (IPS e.max ceram in color A3) and a group of ceramic cement without an intermediary (control group). For each group there were 15 specimens (n=15) (Variolink II, Ivoclar Vivadent, Schaan, Liechtenstein). The degree of conversion of the cement was measured with the Knoop microhardness test. Each specimen was evaluated immediately after polymerization and after seven days. Five indentations were made for each time and obtained an average of each specimen. The group with the largest disk opacity (ho) had the lowest microhardness value (9.488 ± 0.364) at baseline. The control group showed the highest microhardness the after 07 days (38.517 ± 1.055). Groups with LT and MO disk behaved the same on both days, with no difference between them. The highest microhardness using ceramic disc was in the HT group after 07dias (29.530 ± 1.812). It was concluded that the lithium disilicate infrastructure level of opacity influence the degree of polymerization of a dual resin cement.

OBJECTIVES: To evaluate the flexural strength of 5 ceramic dental materials and to compare the marginal fit of crowns made with e.max press and a new experimental (EXP) press ceramic. MATERIALS AND METHODS: The materials tested for flexural strength included: E.max press, E.maxCAD, ENAMIC, Experimental press, and Experimental-CAD. Each group (N= 10) was tested using the Instron 5566A using the piston-on-three-balls test. For the crown fit experiment an Ivorine tooth was prepared with a chamfer finish and used as the master die. Wax up crowns were made on the die and pressed with E.max press and the Experimental press. 5 crowns per material were obtained. A similar procedure was used with standard aluminum crown dies. Copings were waxed up and pressed: 3 copings of E.max and 6 copings of EXP. Eight measurements of marginal fit per restoration were obtained with an optical microscope at 200×. The data was analyzed using ANOVA and a post hoc Tukey-HSD test (Significance level = 0.05). RESULTS: Mean and SD Flexural Strength values (MPa) per group were: E.max press: 486.96 (30.42). EXP press 378.16 (88.13). E.maxCAD 493.28 (55.2). EXP-CAD 420.63 (86.05). ENAMIC 157.59 (6.27). Mean and SD values for margin fit per group (Microns) were: E.max press 74 (19). EXP press 65 (19). CONCLUSIONS: E.max press has 28.8% higher FS than EXP press (P=0.0044). ENAMIC had the lower FS (as expected). EXP press had significantly lower marginal gap than E.max press by 12.2%. / 2018-09-28T00:00:00Z

As restaurações indiretas em sistemas totalmente cerâmicos desenvolveram-se visando à obtenção de próteses com melhor capacidade de mimetismo do dente natural. Além das propriedades óticas, essas restaurações devem ter adesão ao substrato de suporte, de modo a promover a união entre a cerâmica, o esmalte e a dentina, formando um corpo único, permitindo a transferência de tensões da restauração para a estrutura dental. Alguns fatores como: composição, espessura, opacidade e a cor do material cerâmico podem interferir na passagem de luz e, consequentemente, diminuir o grau de conversão do cimento, limitando o alcance de suas propriedades mecânicas e prejudicando o desempenho clínico. Dessa forma, este trabalho teve por objetivo avaliar a influência de diferentes níveis de opacidade da infraestrutura do dissilicato de lítio na polimerização de um cimento resinoso dual. Foram utilizados quatro discos de cerâmica (IPS e.max Press, IvoclarVivadent, Schaan, Liechtenstein), um para cada opacidade da infraestrutura (HT, LT, MO e HO) recobertas por sua respectiva cerâmica de cobertura (IPS e.max ceram na cor A3), e um grupo de cimento sem a cerâmica interposta (grupo-controle). Para cada grupo foram polimerizados 15 corpos de prova de cimento resinoso (Variolink II, Ivoclar Vivadent, Schaan, Liechtenstein). Foi mensurado o grau de conversão do cimento com o teste de microdureza knoop. Cada corpo de prova foi avaliado imediatamente após a polimerização e após sete dias. Foram feitas cinco endentações para cada tempo e obtida uma média de cada corpo de prova. O grupo com disco de maior opacidade (HO) apresentou o menor valor de microdureza (9,48 ± 0,36) no tempo inicial. O maior valor de microdureza foi o do grupo-controle após 07 dias (38,51 ± 1,05). Os grupos com disco LT e MO apresentaram comportamento igual nos dois tempos, não havendo diferença entre eles. O maior valor de microdureza com o uso de discos cerâmicos foi o do grupo HT após 07dias (29,53 ± 1,81), o qual apresentou valor próximo do controle inicial, porém estatisticamente diferente. Conclui-se que o nível de opacidade da infraestrutura do dissilicato de lítio pode influenciar no grau de polimerização de um cimento resinoso dual. / The indirect restorations in totally ceramic systems have been developed in order to obtain prostheses with improved ability to mimicry of the natural tooth. In addition to optical properties, these restorations must have adhesion to the supporting substrate so as to promote the bonding between the ceramic, enamel and dentin, forming a single body, allowing the transfer of stresses to the structure of the dental restoration. Some factors such as composition, thickness, opacity and color of the ceramic material can interfere with the transmission of light and, consequently, decrease the degree of conversion of the cement, impairing their mechanical properties and impairing clinical performance. Thus, this study aimed to evaluate the influence of different opacity levels of lithium disilicate infrastructure in the polymerization of a dual resin cement. Four ceramic discs were used (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein), one for each opacity infrastructure (HT, LT, MO and HO) covered by their respective veneering ceramic (IPS e.max ceram in color A3) and a group of ceramic cement without an intermediary (control group). For each group there were 15 specimens (n=15) (Variolink II, Ivoclar Vivadent, Schaan, Liechtenstein). The degree of conversion of the cement was measured with the Knoop microhardness test. Each specimen was evaluated immediately after polymerization and after seven days. Five indentations were made for each time and obtained an average of each specimen. The group with the largest disk opacity (ho) had the lowest microhardness value (9.488 ± 0.364) at baseline. The control group showed the highest microhardness the after 07 days (38.517 ± 1.055). Groups with LT and MO disk behaved the same on both days, with no difference between them. The highest microhardness using ceramic disc was in the HT group after 07dias (29.530 ± 1.812). It was concluded that the lithium disilicate infrastructure level of opacity influence the degree of polymerization of a dual resin cement.

Indiana University-Purdue University Indianapolis (IUPUI) / Background: All-ceramic restorations have excellent esthetic outcomes compared with other restorative materials. Lithium disilicate is classified as one of many silica-based all-ceramic materials. Currently, companies have provided single-step adhesives, known as universal adhesives, compatible with different restorative materials including lithium disilicate. Many studies have reported greater bond strengths when using a silane to treat the lithium disilicate before applying the bonding agent. Moreover, few studies were published comparing the bond strength when using the universal adhesive alone. Purpose: The objective of this study was to evaluate and compare shear bond strength of three universal adhesives to lithium disilicate ceramic restorative material. Materials and Methods: Three universal adhesive bonding agents were selected from commercially available adhesives. 408 IPS e.max CAD ceramic discs were processed, fired, and etched for 20s. The specimens were divided into six groups. The first three groups used the universal adhesive directly. The remaining three groups were treated with silane. Then, a composite resin cylinder was placed on top of the adhesive using a bonding jig. Each group was subdivided into four equal subgroups (n = 17), subjected to different aging simulation procedures: 24 h, one month with 5000 thermocycles, two months with 5000 cycles, and three months with 5000 cycles. Then, specimens were debonded using shear force by a universal testing machine (MTS). Results: Shear bond strength was greater with silane than without silane (p < 0.0001), regardless of the levels of adhesive or time. Shear bond strength was significantly greater at 24h and 1m than at 2m (p < 0.0001) or 3m (p < 0.0001) regardless of the adhesive or the presence of silane. Debonded specimens were examined under a stereomicroscope at X45 magnification to evaluate the fracture pattern. SEM was used to prove the results were considered as mixed failure. Conclusion: The optimal bonds to lithium disilicate are achieved by application of silane prior to application of a universal adhesive. Although the constituent silane in the universal adhesive was not effective in optimizing the resin to ceramic bond, silane should always be applied to lithium disilicate prior to bonding.

Indiana University-Purdue University Indianapolis (IUPUI) / PURPOSE: To evaluate the fatigue failure load of distinct lithium disilicate restoration designs cemented on a chairside titanium-base (VariobaseTM for CEREC®, Straumann® LLC, USA) for restoring anterior implant restoration. MATERIALS AND METHODS: Left maxillary incisor restoration was virtually designed in 3 groups (n=10; CTD: lithium disilicate crowns cemented on custom-milled titanium abutments; VMLD: monolithic full-contour lithium disilicate crowns cemented on titanium-base; and VCLD: lithium disilicate crowns cemented on lithium disilicate customized anatomic structures then cemented on titanium-base). The titanium-base was air-abraded with aluminum oxide particles, 50 µm at 2 bars. Subsequently the titanium-base was steamed, air-dried and a thin coat of silane (Monobond Plus, Ivoclar Vivadent®, USA). All ceramic components were surface treated with hydrofluoric acid etching gel, follow by silanized, and bonded with resin cement (Multilink Automix, Ivoclar Vivadent®, USA). Specimens were fatigued at 20 Hz, starting with a load of 100 N (×5000 cycles), followed by stepwise loading up to 1400 N at a maximum of 30,000 cycles each. The failure loads, number of cycles, and fracture analysis were recorded. Data were statistically analyzed using one-way ANOVA followed by pair-wise comparisons (p < 0.05). Kaplan-Meier survival plots and Weibull survival analyses were reported. RESULT: For catastrophic fatigue failure load and total number of cycles for failure, VMLD (1260 N, 175231 cycles) was significantly higher than VCLD (1080 N, 139965 cycles) and CDT (1000 N, 133185 cycles). VMLD had higher Weibull modulus (11.6), demonstrating higher structural reliability. CONCLUSIONS: VMLD performed the best fatigue behavior when compared with the two other groups.

Indiana University-Purdue University Indianapolis (IUPUI) / Objective: CAD/CAM technology allows fabrication of thin lithium disilicate (LD) veneers to a LD crown substructure in place of using traditional feldspathic porcelain (FP) which has inferior mechanical properties. This project investigated the effect of different LD veneer applications to LD substructure on the biaxial flexural fatigue of LD veneer/substructure restorations. Materials/Methods: Forty-five LD discs (Ø = 120.7 mm) were fabricated that, when combined with the veneering discs, achieve final dimensions of (Ø = 121.2mm). Experimental groups were (n = 15) as follows: (1) Resin Bonded LD Veneer (RBLDV), LD veneer (Ø = 120.5 mm) adhesively cemented to LD (0.7 mm); (2) Sintered LD Veneer (SLDV), LD veneer (Ø=120.5 mm) sintered to LD (0.7 mm); (3) Sintered Feldspathic Veneer (SFV), feldspathic porcelain (FP) applied to LD discs to achieve a final dimension of (Ø = 121.2 mm). A fourth group of (1.2 mm) monolithic LD served as the control. Weibull-distribution survival analysis was used to compare the differences of the resistance to fracture after fatigue between groups. Total number of cycles were analyzed using one-way Anova (p < 0.05). Hypothesis: Adhering or sintering a thin laminate layer of LD on another LD surface would result in increased fracture resistance in comparison to sintered FP on LD. Results: The SFV group had significantly lower fatigue resistance than SLDV and RBLDV groups (p < 0.05). The RBLDV group fractures resulted in significantly more fractured fragments in comparison to the other groups. No statistical difference was observed in the number of cycles. The results also showed that the LD veneered groups presented similar resistance to fatigue as monolithic discs of the same overall dimensions. Conclusion: The hypothesis was accepted suggesting that veneering a LD substructure with a LD veneer, bonded or sintered, has increased resistance to fatigue as FP veneering material on a LD substructure. In addition, it was observed to have similar resistance to fatigue in comparison to the monolithic LD group.