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Statement of problem The crystallization process of lithium disilicate crowns has been reported to cause dimensional change, but whether the fit of chairside computer-aided design and computer-aided manufactured (CAD-CAM) zirconia-reinforced lithium silicate crowns is affected is unclear. Purpose The purpose of this in vitro study was to evaluate with a 3-dimensional superimposition analysis technique the marginal and internal adaptation of fully crystallized versus partially crystallized zirconia-reinforced lithium silicate ceramic CAD-CAM fabricated crowns. Additionally, the silicone replica technique and direct viewing of marginal gap values were compared with the 3-dimensional superimposition analysis technique. Material and methods The marginal and internal adaptation of a fully crystallized zirconia-reinforced lithium silicate (CELTRA DUO) were compared with those of a partially crystallized zirconia-reinforced lithium silicate (VITA SUPRINITY) after crystallization. Sixteen crowns (n=8) were fabricated with a chairside CAD-CAM system. The crowns and die and crown assembly were scanned with an optical scanner for the 3-dimensional superimposition analysis. Four hundred sixty-eight measurements were made for each crown, 78 in each 2-dimensional section. Marginal discrepancy was measured by using the direct viewing technique. The internal adaptation of the shoulder area, axial space, and occlusal space was measured by using the silicone replica technique. Both gap values were compared with the 3-dimensional superimposition analysis results by using the independent t test. The 2-way ANOVA was used to detect the effect of each variable (group and site) (α=.05). Results The VITA SUPRINITY crowns showed statistically higher marginal discrepancy values than the CELTRA DUO crowns in both 3-dimensional superimposition analysis and the direct viewing method, and the lingual aspect recorded the highest marginal discrepancy mean value when compared with other aspects. The 3-dimensional superimposition analysis and the direct viewing method were statistically similar (P=.076). The VITA SUPRINTY crowns showed higher internal gap mean values than the CELTRA DUO crowns in both 3-dimensional superimposition analysis and silicone replica techniques. The occlusal space recorded the highest mean value in both groups. Assessment by 3-dimensional superimposition analysis and silicone replica techniques showed statistical difference in internal gap values (P=.04). Conclusions CELTRA DUO showed better precision fit values than VITA SUPRINITY. Three-dimensional superimposition analysis is a reliable method of evaluating marginal and internal adaptation.

Statement of the problem: The conservative nature of the labial ceramic veneers necessitates minimum amount of tooth reduction with thin peripheral margins. Since construction time of restorations is becoming a determinant factor together with accuracy, the effect of three different CAD/CAM milling protocols that depend on the time factor deserves to be assessed.Purpose: The purpose of this investigation was to evaluate the effect of three different CAD/CAM milling protocols; namely normal, fast, and two-step milling on the peripheral marginal accuracy of glass-ceramic laminate veneers.Materials and Methods: A maxillary central incisor acrylic tooth was chosen to serve as a die for veneer construction. Acrylic tooth preparation was done to receive incisal feather edge design for the ceramic veneer. A total of thirty laminate veneer restorations were constructed from IPS e.max CAD glass ceramic using the CAD/CAM technology with three different milling protocols. The veneers were divided into the following groups according to the selected milling protocol; Group 1: Ten veneers constructed using the normal milling protocol, Group 2: Ten veneers constructed using the fast milling protocol, Group 3: Ten veneers constructed using the two-step milling protocol. The milled veneers were subjected to crystallization process according to manufacturer’s instructions then they were checked on their corresponding die for proper adaptation and seating. For proper assessment of the vertical marginal gap, the veneers were fixed on the master die using one drop of adhesive placed centrally to stabilize the veneers in their place during the measuring procedure. The vertical marginal gap distance of each ceramic was measured using a stereomicroscope at magnification X45. The measurements were done along the peripheral circumference for all the veneer margins (mesial, distal, cervical and incisal). Measurement at each point was repeated five times. A digital image analysis system was used for assessing and evaluating vertical marginal gap width. The mean vertical marginal gap distance was calculated and then tabulated for the statistical analysis of the data. Results: Effect of milling protocol: The two-step milling protocol showed the statistically significant lowest mean marginal gap distance (33.2 ± 6.3 μm) while both the normal and fast milling protocols showed the statistically significant highest mean marginal gap distances with no statistically significant difference between them. (40 ± 7.5 μm and 41.2 ± 4.9 μm respectively) Effect of surface: The cervical surface recorded the statistically significant lowest mean marginal gap distance (34 ± 6.5 μm) while the distal surface recorded the highest mean marginal gap distance (41.6 ± 8.6 μm) with non-statistically significant difference from incisal (37.2 ± 4.6 μm) and mesial surface (39.7 ± 6.4 μm).Conclusions: Within the limitations of this in-vitro study, the following conclusions were drawn: 1) Marginal discrepancy of all groups fell within the clinically acceptable value, thus the three milling protocols can be safely used. 2)Veneers fabricated using the two-step milling protocol exhibited the least marginal discrepancy among other experimental groups, thus it can be used as the protocol of preference if restoration accuracy is of utmost importance. 3) Since there was no significant difference between normal and fast milling protocols regarding marginal discrepancy, therefore fast milling can be recommended for veneer fabrication if chairside time is of prime importance in some cases. 4) Cervical marginal discrepancy was found to have the least value compared to other surfaces

Statement of the problem The increased thickness of ceramic laminate veneer with butt joint design at the incisal edge reduce the amount of light reaching the cement layer and therefore compromise photo-activation of the luting material However, an adequate cure of the resin-based cement is an important prerequisite for the stability and biocompatibility of the restoration.57Dual-cure resin-based cements have been recommended for luting ceramic laminate veneers to compensate for the attenuation of the curing light effected by the thickness of restoration and to allow complete polymerization of the luting material even at the incisal area of laminate veneers where access for the curing light is limited, but the yellowish discoloration due to ageing of conventional dual-cure resin based cement was the problem.Purpose : The aim of this study was to evaluate color stability of e-max CAD veneers cemented with light cure and dual cure amine free adhesive resin cement (Base line), (After 2 months), (After 4 months), (After 6 months),(After 8 m )Materials and methods: A total of 22 ceramic laminate veneers restorations(11 e.max cad cemented with light cure adhesive resin cement and 11 e.maxcad cemented with dual cure adhesive resin cement ) were included in the study and completed by one operator (the researcher) who followed a meticulous clinical procedure and the ceramic laminate veneers were fabricated by one experienced dental technician. The operator followed the five phases of laminate veneers fabrication: diagnosis, preparation design, provisionalization , construction of the material and bonding ,Follow up sessions were done every two month for each patient using operator vision to evaluated change in color and then confirmed with easyshade in the baseline, 24 hours post cementation and in the postoperative follow-up according to the modified USPHS (United States Public Health Service) criteria. This was performed by an experienced, blinded investigator. Data were recorded, tabulated, and statistically analyzed using the Chi-square test and the significance level was set at P ≤ 0.05.Results: There was no statistically significant difference between (Group I) and (Group II) where (p=1) as both groups showed (100%) Alpha in all time periods.Conclusion: Both E.max CAD laminate veneers cemented with light cure and E.max CAD laminate veneers cemented with dual cure amine free adhesive resin cement revealed high successful survival rate in terms of the stability of the color.

Statement of the problem: The 2 step ceramic surface treatment “ HF acid etching followed by silane application” has been used for years to secure an efficient bond between ceramics and resin cements, however the urge for simplification and making the bonding procedure less technique sensitive have pushed the dentists to shift to one step ceramic surface treatment “self etch ceramic primer”. Although studies proved their reliability, till now there is no data available on their effect on bond stability in different pH conditions Purpose: The aim of the current study was to evaluate microshear bond strength between resin and different ceramic materials (e.max, VITA ENAMIC and VITA SUPPRINITY) preatreated with two different protocols (2 step and 1 step) after being subjected to various pH storage mediaMaterials and Methods: A total of ninety ceramic discs were fabricated in this study from CAD/CAM blocks. The discs were divided into three groups according to ceramic material as follows; Group 1: Thirty discs constructed from lithium disilicate glass ceramic (e.max CAD), Group 2: Thirty discs constructed from polymer infiltrated ceramic- network material (VITA ENAMIC) and Group 3: Thirty discs constructed from Zirconia-lithium silicate glass-ceramic materials (VITA SUPRINITY). Each of the previous groups were further subdivided into two equal subgroups according to the surface treatment protocol used as follows; Subgroup 1: fifteen discs were treated with 2 step bonding protocol (etched with hydrofluoric acid followed by silane application) and Subgroup 2: fifteen discs were treated with 1 step application of self etching primer (Monobond etch and prime). The two subgroups were again equally divided (5 each) and assigned to one of the three storage solutions with different pHs : acidic, neutral and alkaline media.Ceramic discs were obtained by sectioning the CAD/CAM blocks using Isomat 1000 followed by crystallization of the e.max and VITA SUPPRINITY discs. For first subgroup, the ceramic discs were subjected to two step surface treatment protocol consisting of hydroflouric acid etching, rinsing followed by silane application. While the second subgroup was subjected to surface treament using one step monobond etch and prime protocol. For both subgroups,each ceramic substrate was then prepared to receive 5 resin microtubules. Five samples of each ceramic resin assembly subgroup was then randomly selected and designated in one of the following storage media for a period of seven days:1) Cola solution representing acidic medium having pH value of 2.5. 2) Distilled water representing neutral medium having pH value of 7 3) Licorice solution representing alkaline medium having pH value of 8.4. At the end of the storage period,micro shear bond strength test was performed to debond the specimens in a universal testing machine (Model 3345; Instron Industrial Products, Norwood, MA, USA) with a crosshead speed of 0.5 mm/s. The maximum load at failure was recorded in Newtons (N) unit and was divided over the bonded area (mm2) to convert to MPa unit. Data was then collected, tabulated and statistically analyzed.Results: With acidic pH: in e.max CAD and VITA ENAMIC groups; it was found that two steps surface treatment approach recorded statistically significant higher mean microshear bond strength value than one step approach as proven by paired t-test (P 0.05). With neutral pH: in e.max CAD and VITA ENAMIC groups; it was found that two steps surface treatment approach recorded statistically non significant higher mean microshear bond strength value than one step approach as proven by paired t-test (P>0.05), while for VITA SUPRINITY group; it was found that two steps surface treatment approach recorded statistically significant higher mean microshear bond strength value than one step approach as demonstrated by paired t-test (P= 0.03 0.05)Conclusions: Within the limitations of this study, the following conclusions and clinical recommendations could be advised:1) Although microshear bond strength of the two step etch and prime surface treatment protocol was significantly higher than that of one step self-etching ceramic primer protocol,however the values for all tested materials under various Ph conditions were nearly within a clinically acceptable range, thus it could be suggested that self etching primers can be safely used without affecting clinical performance of the restorations. 2) In patients subjected to predominately acidic or alkaline oral pH environments, both surface treatment protocols can be safely used when VITA SUPPRINITY restorations are indicated, however when VITA ENAMIC or e.max CAD are used, it is recommended to use the two step surface treatment protocol to ensure more stable bond strength 3) In patients having a neutral balanced oral pH environment, both surface treatment protocols can be safely used when VITA ENAMIC or e.max CAD restorations are used, however when VITA SUPPRINITY is recommended, it is advisable to use the two step surface treatment protocol to yield better ceramic resin bond durability. 4) Generally speaking, VITA ENAMIC restorations combined with one step self etching primer are not recommended for patients having acidic pH oral media as it yielded the lowest bond strength values between all subgroups

Statement of the problem: CAD/CAM restorations can be immediately cemented after tooth preparation, however, a delay between final impression and restoration delivery is sometimes unavoidable, thus provisionalization period becomes necessary. There are concerns whether this delay would affect the dentin bond strength when bonding to immediately sealed dentin. Purpose: to study the effect of different provisionalization periods (1 and 3 weeks) on the bond strength of immediately sealed dentin to two types of hybrid ceramics Materials and Methods: A total of sixty ceramic discs were fabricated in this study from CAD/CAM blocks. The discs were divided into two groups; Group 1: Thirty discs were constructed from polymer-infiltrated-ceramic-network material (VITA Enamic) and Group 2: Thirty discs constructed from resin nanoceramic (CERASMART). Each of the previous groups were further subdivided into three equal subgroups according to the provisionalization period as follows; Subgroup 1: Ten discs were cemented to immediately sealed dentin without any provisionalization period, Subgroup 2: Ten discs were cemented to immediately sealed dentin after 1 week of provisionalization and Subgroup 3: Ten discs were cemented to immediately sealed dentin after 3 weeks of provisionalization. Teeth were trimmed to have a flat, midcoronal dentin surfaces. This was followed by immediate dentin sealing of the exposed dentin. Ceramic samples were then obtained by slicing the CAD/CAM blocks with standardized dimensions. For subgroup 1, adhesive cementation was immediately done for the ceramic samples to immediately sealed dentin. For subgroup 2 and 3, the sealed surfaces were coated with a layer of petroleum gel followed by application of a provisional restoration for 1 and 3 weeks respectively. The samples were then immersed in saline solution until the end of the provisionalization period. At the end of these various periods, the provisional restoration was removed and the sealed dentin was cleaned by pumice and water followed by roughening with a coarse diamond stone. This was followed by adhesive cementation of the discs. Micro shear bond strength test was then performed to debond the specimens in a universal testing machine (Lloyd Instruments Ltd, Hampshire, UK) with a crosshead speed of 0.5 mm/s. The maximum load at failure was recorded in Newtons (N) unit and was divided over the bonded area (mm2) to convert to MPa unit. Data was then collected, tabulated and statistically analyzed. Results: For CERASMART group: It was found that the highest shear bond strength mean±SD values were recorded with no provisionalization subgroup (9.37±0.35MPa) followed by 1 week provisionalization subgroup (8.4±0.12MPa) while the lowest shear bond strength mean±SD values were after 3 weeks provisionalization subgroup (4.48±0.23MPa). The difference between provisionalization subgroups was statistically significant (p= 0.05) between (no- provisionalization and 1 week provisionalization) subgroups. For Vita Enamic group: It was found that the highest shear bond strength mean±SD values were recorded with 3 weeks provisionalization subgroup (7.3±0.67MPa) followed by no provisionalization subgroup (7.08±1MPa) while the lowest shear bond strength mean±SD values were after 1 week provisionalization subgroup (5.59±0.71MPa). The difference between all subgroups was statistically non-significant (p=0.2192 >0.05) as indicated by one way ANOVA test. Effect of ceramic: With no provisionalization; it was found that CERASMART group recorded statistically non-significant higher shear bond strength mean value (9.37±0.35 MPa) than Vita Enamic group (7.08 ±1 MPa) as indicated by t-test (p=0.0598>0.05). After 1 week provisionalization; it was found that CERASMART group recorded statistically non-significant higher shear bond strength mean value (8.4 ± 0.12 MPa) than Vita Enamic group (5.59±0.71 MPa) as indicated by t-test (p=.0540 >0.05). After 3 weeks provisionalization it was found that Vita Enamic group recorded statistically significant higher shear bond strength mean value (7.3±0.67 MPa) than CERASMART group (4.48±0.23 MPa) as indicated by t-test (p=.0089

Statement of the problem: Monolithic hybrid and glass ceramics are indicated for intracoronal and extracoronal ceramic restorations. Available data regarding selection of the appropriate ceramic type for each preparation design and its influence on fracture resistance of tooth restoration complex is still scarce.Purpose: The purpose of this study was to evaluate in vitro the fracture resistance and investigate failure mode of two restoration designs (crowns and inlays) made from lithium disilicate glass ceramic and hybrid ceramic constructed by the CAD /CAM technique.Materials and Methods: A total of twenty ceramic restorations restoring lower molars were designed and fabricated in this study. The restorations were divided into two groups; Group 1: Ten full coverage crowns and Group 2: Ten inlays. Each of the previous groups was further subdivided into two equal subgroups; Subgroup 1: Five restorations constructed from lithium disilicate glass ceramics (e.max CAD) and Subgroup 2: Five restorations constructed from hybrid ceramic (VITA ENAMIC) by the CAD/CAM technology. Two ivorine teeth were prepared following the guidelines for full coverage and inlay ceramic restorations, they were duplicated into stone dies followed by scanning, designing and milling of restorations. The stone dies were duplicated into epoxy dies where the restorations were adhesively cemented on them. All cemented samples were exposed to 2000 thermal cycles (5°C and 55°C in water) with a dwell time of 25 seconds in a computer controlled thermocycler. All specimens were loaded in a universal testing machine where fracture test was done by compressive mode of load applied occlusally using a metallic rod with round tip at cross-head speed of 1mm/min until fracture occurred. Fracture resistance values were recorded in Newtons then they were statistically evaluated and failure modes were analyzed. Results: For group 1 representing crown restorations, a statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.05) where the highest mean value of maximum load was found in (VITA ENAMIC) (951.77 N ± 81.05) and the lowest mean value of maximum load was found in (e.max CAD) (709.35 N± 49.51). While for the second group representing inlay restorations, no statistically significant difference was found between (e.max CAD) and (VITA ENAMIC) subgroups at (p=0.307) where the highest mean value of maximum load was found in (e.max CAD) (627.71 N ± 80.01) and the lowest mean value of maximum load was found in (VITA ENAMIC) (581.26 N± 51.74). For the e.max CAD subgroup, a statistically significant difference was found between (Crown) and (Inlay) groups at (p=0.005) where the highest mean value of maximum load was found in the crown group (790.35 N± 49.51) and the lowest mean value of maximum load was found in the inlay group (627.71N ± 80.01).Regarding the VITA ENAMIC subgroup, a statistically significant difference was found between (Crown) and (Inlay) groups at (p

Statement of the problem Despite improvements in dental ceramics, failure of bilayered restorations mainly by chipping and delamination of veneer with different degrees remains a disadvantage of this type of restorations. Accordingly the need for ceramic restoration repair became a widspread alternative to replacement of defective restorations especially in complex cases . However it is not always easy for the clinician to select the best repair protocol when dealing with different ceramic types and different chipping patterns.Purpose: The purpose of this study was to evaluate the shear bond strength between a commercially available repair system (Ceramic Repair kit) with a lithium disilicate glass ceramic (e.max CAD) and zirconia based ceramic (InCoris ZI) subjected to different degrees of veneering ceramic chipping..Materials and Methods: A total of sixty ceramic samples were designed and fabricated in this study using the CAD/CAM technology . The samples were divided into two groups; Group 1: Thirty samples constructed from lithium disilicate glass ceramic (e.max CAD). Group 2: Thirty samples constructed from zirconia ceramic (InCoris ZI). Each of the previous groups was further subdivided into three equal subgroups depending on the amount of bonded repair material to the ceramic core and to the veneering ceramic: Subgroup 1 (control): Ten samples with ceramic repair material bonded directly onto the ceramic core (100% core). Subgroup 2: Ten samples with 25% of the ceramic repair material surface bonded to veneering ceramic surfaces, and the other 75% to ceramic core and Subgroup 3: Ten samples with 50% of the ceramic repair material surface bonded to veneering ceramic, and the other 50% to ceramic core. Shear bond strength test was done by loading the samples parallel to its the long axis at the composite ceramic interface at a crosshead speed of 0.5 mm/min until fracture . The maximum load at failure was recorded in Newtons (N) unit and was divided over the bonded area(mm2) to convert to MPa unit. Data was then collected, tabulated and statistically analyzed.