Effect of 2-ethylhexyl salicylate incorporation on the color stability of different maxillofacial silicone elastomers after outdoor weathering.

STATEMENT OF PROBLEM: Silicone elastomers are considered the most favorable materials for the prosthetic rehabilitation of facial defects. However, color change, because of the ultraviolet (UV) light, limits the life of facial prostheses. The addition of 2-ethylhexyl salicylate as a UV-protective may improve the color stability of different maxillofacial silicone elastomers. PURPOSE: The purpose of this in vitro study was to evaluate the effect of 2-ethylhexyl salicylate on the color stability of 3 different maxillofacial silicone elastomers after outdoor weathering. MATERIAL AND METHODS: Three different ratios of UV-protective 2-ethylhexyl salicylate (UV-ES) were incorporated into 3 different types of maxillofacial silicones (M511, TechSil S25, and A-2000) in 1%, 2%, and 5% ratios, and a control group for each silicone was generated. A total of 120 Ø15×2-mm disk-shaped specimens were prepared from 3 different silicone elastomers according to the 4 different UV-ES ratio groups (n=10). The specimens were subjected to outdoor weathering in Ankara, Türkiye, from June 2021 to June 2022. Color differences in the specimens were measured at 3 months and 1 year of weathering. The color change values (ΔE) were statistically analyzed by using repeated measures of 3-way ANOVA. The differences were compared by using the Tukey honest significant difference test (α=.05). RESULTS: No interaction was found among the factors (silicone type, UV-ES ratio, and aging) (P=.29). The highest ΔE values were found in TechSil S-25 (P<.001), while the results were not significantly different between the M511 and A2000 groups (P=.324) The higher ΔE values were found in the control group when compared with those of the UV-ES added group of each material, while the results were not significantly different among the 1%, 2%, and 5% groups (P>.05). CONCLUSIONS: Incorporating 2-ethylhexyl salicylate into the tested maxillofacial silicones reduced color change.

Using a smartphone three dimensional scanning application (Polycam) to three dimensionally print an ear cast: A technique.

This technique describes the use of a smartphone application for scanning an ear for 3-dimensional (3D) printing of an auricular prosthesis cast. The intact ear was scanned by using a smartphone and a 3D scan application (Polycam). The standard tessellation language (STL) file of the 3D data was used to produce a mirror image of the ear, which was sent to the 3D printing center where a resin cast was printed. This technique is harmless for the patient compared with radiological imaging methods, more comfortable, and cost-effective and is straightforward for the maxillofacial prosthodontist.

The effects of cement thickness and cement shade on the final color of lithium disilicate crowns.

PURPOSE: The aim of this study is to evaluate the effect of resin cement color, cement thickness, and thermocycling on the final color of monolithic lithium disilicate crowns. MATERIALS AND METHODS: A total of ninety prepared central incisors of typodont teeth were restored with lithium disilicate crowns which have different cement thicknesses (40 µm, 80 µm, and 120 µm) and cement shades (clear, yellow, and white). Color parameters of restorations were measured with a spectrophotometer in three different steps 1) before cementing 2) after cementing and 3) after thermocycling with 10000 cycles. Color differences (ΔE00) were calculated with the CIEDE2000 formula and evaluated according to perceptibility (0.8) and acceptability (1.8) thresholds. The ΔE00 data were analyzed by using two-way ANOVA before and after thermocycling (α = .05). RESULTS: There was no interaction between the cement shade and the cement thickness factors. After cementation, the mean ΔE00 was under the perceptibility threshold in the group of 40 µm cement thickness and clear cement while it was between the perceptibility and acceptability thresholds (0.8 < ΔE00 < 1.8) for all other groups. After thermocycling, the ΔE00 values were between the perceptibility and acceptability thresholds for all experimental groups. Although there were no significant differences among the groups, thermocycling increased the color difference values. CONCLUSION: The cementation of restorations with clear, yellow, and white resin cements resulted in color differences with uncemented restorations except for the group cemented with clear cement in 40 µm cement thickness. All study groups revealed perceptible color change after thermocycling.

Effect of ultraviolet-protective 2-ethylhexyl salicylate incorporation on the mechanical properties of different maxillofacial silicone elastomers.

STATEMENT OF PROBLEM: Whether the incorporation of ultraviolet-protective 2-ethylhexyl salicylate (UV-ES) affects the mechanical properties of different maxillofacial silicone elastomers, limiting the service life of facial prostheses, is unclear. PURPOSE: The purpose of this in vitro study was to examine the mechanical properties of different maxillofacial silicone elastomers incorporating different ratios of UV-ES. MATERIAL AND METHODS: Three different ratios of UV-ES were incorporated into 3 different types of maxillofacial silicones (M511, TechSil-25, and A-2000), and the mechanical properties of the silicones were investigated. Silicone pigments were added to each silicone type to mimic skin color. Dumbbell-shaped specimens were fabricated for tensile strength, percentage elongation, and hardness measurements, and trouser-shaped specimens for tear strength measurement. A total of 240 specimens were prepared. UV-ES in 3 different ratios (1%, 2%, and 5%) and a control group of each silicone type were generated (n=10). The effects of maxillofacial silicone type and ultraviolet protective ratios on hardness, tensile strength, percentage elongation, and tear strength were examined by factorial ANOVA (α=.05). RESULTS: The Shore-A hardness in the control and UV-ES added groups was not significantly different in M511 material (P>.05), and a statistically significant decrease was observed in all ratios in TechSil S-25 and A-2000 silicones (P<.05). After adding 1%, 2%, and 5% UV protective into the silicones, the tensile strength and elongation of TechSil S-25 silicone material decreased significantly (P<.05), while these mechanical properties of M511 and A-2000 were not affected by UV-ES addition (P>.05). Tensile and tear strength values of the silicone elastomers were highest for TechSil S-25. CONCLUSIONS: The mechanical properties of M511 and A-2000 silicone elastomers were not adversely affected by the addition of 1%, 2%, or 5% UV-ES.

Effect of ultraviolet protective agents on maxillofacial silicone elastomer, part 1: Color stability after artificial aging.

STATEMENT OF PROBLEM: Silicone elastomers have been widely used for rehabilitation of facial defects for more than 50 years. However, color change is the most common problem limiting the service life of facial prostheses. Whether the addition of ultraviolet protectives may enhance color stability of these materials is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of ultraviolet protectives on the color stability of maxillofacial silicones after artificial aging. MATERIAL AND METHODS: Six color groups (unpigmented, white, yellow, red, blue, and mixed) of addition-type maxillofacial silicone were prepared. Four ultraviolet protectives benzophenone-3, ethylhexyl methoxycinnamate, titanium dioxide, and ethylhexyl salicylate at 0.5% and 1% concentrations by weight were incorporated into the silicone before polymerization. The specimens were artificially aged in an accelerated weathering chamber for 300 and 600 hours and in a thermocycling device. The color change values (E) of the maxillofacial silicones were evaluated. Data were statistically analyzed by using 4-way ANOVA. The differences were compared by the Tukey honestly significant difference test (α=.05). RESULTS: Benzophenone-3 and ethylhexyl methoxycinnamate protectives did not reduce the ΔE values, and the 1% titanium dioxide groups exhibited lower ΔE values than the 0.5% titanium dioxide groups. Ethylhexyl salicylate protective generally reduced the ΔE values significantly in all color and aging groups when compared with the control groups (P<.05). In all control and ultraviolet protective groups, the highest ΔE values were seen with the red color in 300 and 600 hours of aging. Generally, no significant difference (P>.05) was seen in the ΔE values, which were clinically acceptable among the thermocycled color groups. After 600 hours of accelerated aging, the ΔE values were found to be higher than the values of 300-hour aging. CONCLUSIONS: Ethylhexyl salicylate protective incorporated into maxillofacial silicones may improve color stability.

Effect of ultraviolet protective agents on maxillofacial silicone elastomer, part 2: Mechanical properties after artificial aging.

STATEMENT OF PROBLEM: The addition of ultraviolet (UV) protectives may affect the materials' mechanical properties, which can limit the service life of facial prostheses. PURPOSE: The purpose of this in vitro study was to investigate the effect of UV protectives on the mechanical properties of maxillofacial silicones after artificial aging. MATERIAL AND METHODS: Six color groups (unpigmented, white, yellow, red, blue, and mixed) of addition-type maxillofacial silicone were prepared. Four UV protectives, benzophenone-3 (UV-BP), ethylhexyl methoxycinnamate (UV-EM), titanium dioxide (UV-TD), and ethylhexyl salicylate (UV-ES), at 0.5% and 1% concentrations by weight were incorporated into the silicone before polymerization. The specimens were subjected to accelerated aging in a weathering chamber for 300 and 600 hours and to thermocycling. The tensile strength and percentage elongation, tear strength, and hardness of maxillofacial silicones were evaluated. Data were analyzed by using 4-way ANOVA. The differences were compared by the Tukey honestly significant difference test (α=.05). RESULTS: Tensile strength decreased after 300 and 600 hours of UV aging in 0.5% and 1% UV-BP protective-added groups and increased in thermocycled groups (P<.05). Aging conditions generally showed no effect on the tensile strength of UV-EM, UV-TD, and UV-ES added groups (P>.05). Aging generated a decrease in percentage elongation values compared with nonaged specimens of groups (P<.05). The addition of UV protectives generally did not significantly affect the tear strength of specimens compared with control in the aged groups (P>.05). The hardness of UV protective-added groups increased when compared with that of nonaged groups after 300 and 600 hours of UV aging (P<.05). Also, thermally aged groups showed increased hardness than nonaged groups (P<.05). CONCLUSIONS: The protective UV-BP addition caused decreased tensile strength, percentage elongation, and tear strength in both concentrations. The UV-EM and UV-ES provided increases in tensile strength and percentage elongation of the silicone in the 0.5% concentration. The addition of UV-BP, UV-EM, and UV-ES did not make significant differences; however, UV-TD significantly decreased the hardness values of the silicone.

Effect of different preparation finishing procedures on the marginal and internal fit of CAD-CAM-produced restorations: A microcomputed tomography evaluation.

STATEMENT OF PROBLEM: Accurate fit is an important factor for the longevity of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic restorations. Few studies have compared how restoration finishing procedures affect the marginal and internal fit of these restorations by using microcomputed tomography (µCT). PURPOSE: The purpose of this in vitro study was to evaluate the preparations with different surface finishing procedures for the fit of CAD-CAM restorations by using µCT. MATERIAL AND METHODS: A total of 28 anatomic contour monolithic feldspathic ceramic crowns were produced for 4 typodont teeth prepared according to the different surface finishing procedures (n=7). The generated experimental groups were finishing with extra-coarse (181 µm) diamond rotary instruments (EC), finishing with fine (40 µm) diamond rotary instruments after extra-coarse diamond rotary instruments (F), finishing with very fine (20 µm) diamond rotary instruments after extra-coarse and fine diamond rotary instruments (VF), and finishing with extra-coarse, fine, and very fine diamond rotary instruments followed by polishing rubber points (P). µCT scans were obtained to measure the gaps between the typodont teeth and the crowns. Reference points such as the margin, chamfer (the deepest point), cusp tips, and central fossa were determined, and 196 measurements were made. Data were analyzed by using 2-way analyses of variance and the Tukey HSD test (α=.05). RESULTS: The highest gap values in all sections were observed in the finishing with extra-coarse (181 µm) diamond rotary instruments group. The lowest gap value in the marginal point was observed in the P group (P<.05). In total, the gap values of the reference points were in the order of margin, chamfer, cusp, and central fossa. CONCLUSIONS: µCT evaluation showed that tooth preparation finishing procedure with finer grit rotary instruments yielded better marginal fit for monolithic feldspathic CAD-CAM restorations. The internal gap values of all groups were also in the range of clinically acceptable values, important for mechanical properties.

Visual and instrumental color evaluation of computerized color matching system for color reproduction of maxillofacial prostheses.

STATEMENT OF PROBLEM: A commercially available computerized color matching system (e-Skin) has been introduced for maxillofacial prostheses. However, studies that have tested its ability to produce an acceptable color match for skin color are lacking. PURPOSE: The purpose of this clinical study was to determine the color match acceptability of light and dark skin silicone replicas fabricated with the use of the computerized color matching system. MATERIAL AND METHODS: Fifteen participants with light skin and 15 participants with dark skin were recruited through personal invitation. These 30 participants (aged around 20 years) voluntarily consented to forearm skin color measurements with a spectrophotometer and a spectrocolorimeter integrated in a computerized color matching system. Silicone skin replicas for each participant were produced from the color formulations provided by the online calculator tool of the system according to the manufacturers' recommendations. The color difference between initial skin color measurements with the spectrophotometer and skin replica color measurements with the spectrophotometer for all participants was calculated by using both the CIELab (ΔE∗ab) and CIEDE2000 (ΔE00) color difference formulas. To compare the instrumental and visual evaluation of color match, 3 observers (a maxillofacial prosthodontist, a prosthodontist, and a postgraduate student) visually evaluated and rated the color match of each silicone replica on a 5-point scale. Statistical analyses were performed by using the Student t, Mann Whitney U, and chi-square tests (α=.05). RESULTS: No significant differences were detected between the light and dark skin groups in terms of the ΔE∗ab and ΔE00 values obtained between the first skin color measurements and their silicone replica color measurements (P=.573, P=.338, respectively). However, a significant difference was found between light and dark skin groups for the ΔL and Δa values obtained from the same measurements (P=.031, P=.017, respectively). L∗, a∗, and b∗ values of light skin were significantly higher than those of their silicone replications (P=.008, P=.033, P=.046, respectively). Color match ratings of observers did not significantly differ when comparing the ratings of light skin replicas to ratings of dark skin replicas. CONCLUSIONS: The e-Skin system provided skin replicas that matched the skin color within clinically acceptable thresholds and with ratings of at least "good" by experienced dental clinicians.

Effects of glazing methods on the optical and surface properties of silicate ceramics.

PURPOSE: This study aims to evaluate the effect of different glazing methods on translucency parameter (TP), contrast ratio (CR), opalescence parameter (OP), surface roughness (Ra) and topography of the silicate ceramics. METHODS: Seventy specimens (10×10×1mm) were fabricated from lithium disilicate (IPS e.max CAD, abbreviated as E) and zirconia-reinforced lithium silicate (Vita Suprinity, abbreviated as VS) ceramics and divided into 7 subgroups (n=10) according to the polishing and glazing procedures: (1) mechanical polishing before-crystallization (m-BC), (2) mechanical polishing after-crystallization (m-AC), (3) glaze powder/liquid after-crystallization (pl-AC), (4) glaze-paste before-crystallization (gp-BC), (5) glaze-paste after-crystallization (gp-AC), (6) glaze-spray before-crystallization (gs-BC), (7) glaze-spray after-crystallization (gs-AC). Color and Ra measurements were performed. CIEL*a*b* and CIEXYZ parameters were recorded and TP, CR, and OP values were calculated. Data were analyzed using two-way ANOVA and Tukey HSD tests (α=0.05). RESULTS: In E groups, the highest Ra value was found in gs-AC (1.66±0.14µm) while the lowest value was found in pl-AC (0.68±0.08µm). In VS groups, the highest Ra value was found in gp-BC (1.64±0.25µm) while the lowest value was found in m-AC (0.77±0.06µm) (p<0.05). The mean TP value of E (17.62±0.73) was found to be higher than VS (15.37±1.16). The CR (0.72±0.030) and OP (12.06±0.74) values of VS were found higher than CR (0.57±0.02) and OP (6.72±0.40) values of E. CONCLUSIONS: Zirconia-reinforced silicate ceramics have higher opalescence and lower translucency values than lithium disilicate ceramics. Increase in surface roughness reduces translucency. Glaze powder/liquid after-crystallization is the most effective way to reduce surface roughness of lithium disilicate ceramics while that is mechanical polishing after-crystallization for zirconia-reinforced silicate ceramics.

Fracture resistance of different implant supported ceramic abutment/crown systems.

PURPOSE: The purpose of this study was to investigate the fracture resistance and failure modes of different non-aged and aged abutment/crown systems. MATERIALS AND METHODS: One hundred dental implants (diameter 4.3 mm and length 11.5 mm) were restored with five abutment/crown systems: G1: a lithium disilicate hybrid abutment crown, G2: a lithium disilicate crown cemented on a lithium disilicate hybrid abutment, G3: a lithium disilicate crown cemented on a zirconia hybrid abutment, G4: a direct veneer porcelain layering on a zirconia hybrid abutment, and G5: a lithium disilicate crown cemented on a prefabricated all-zirconia abutment. Each group was divided into two groups (n=10) as control (non-aged) and thermomechanically aged. The fracture resistance test was performed. Failures during the aging process and after the fracture resistance test were examined. RESULTS: Both of the factors (restoration type and aging) affected the fracture resistance values and there was not an interaction between the factors (p>0.05). When fracture resistance values were compared regardless of aging, the highest values were observed in G3 and G4, respectively (p<0.05). When comparing the fracture resistance values, regardless of the restoration type, the aged group showed a significant lower fracture resistance value than control group (p<0.05). CONCLUSION: A titanium base enhanced the fracture resistance of zirconia abutments. Thermomechanical aging decreased the fracture resistance of the tested ceramic abutment/crown systems. The major failure mode was the abutment fracture.

In vitro evaluation of color and translucency reproduction of maxillofacial prostheses using a computerized system.

PURPOSE: Accurate color matching of maxillofacial prostheses to skin is important for esthetics. A computerized color matching system specific to human skin has recently been developed. The purpose of this study was to evaluate the accuracy in color and translucency matching of the computerized color matching system across different skin colors. MATERIALS AND METHODS: The silicone was colored to simulate 28 different skin colors (n=5) to serve as "target skin colors". Using a spectrocolorometer (e-skin), color codes were determined for "replicate skin color" fabrication. CIELAB Delta-E between target skin color-replicate skin color pairs and translucency parameter were calculated. CIELAB Delta-E values were compared with one-way ANOVA and Tukey multiple-comparison. The agreement between L*, a*, b* and translucency parameter of target skin colors and replicate skin color were calculated by a two-way mixed average measures intraclass correlation coefficient. Translucency parameter of target skin color-replicate skin color pairs were compared with Paired t-test (α=.05). RESULTS: The mean CIELAB Delta-E value was 3.83 and significant differences were found among colors. The intraclass correlation coefficient showed excellent reliability for L*, a*, b* and good reliability for translucency parameter (P<.001). The mean translucency parameter of replicate skin colors was significantly higher than that of translucency parameter. CONCLUSION: The computerized color matching system specific to human skin was found to be reliable in terms of color and translucency between target skin colors and replicate skin color.

The Effect of Resin Cement Type and Thermomechanical Aging on the Retentive Strength of Custom Zirconia Abutments Bonded to Titanium Inserts.

PURPOSE: The purpose of this study was to investigate the effect of resin cement type on the retentive strength of custom zirconia abutments bonded to titanium inserts. MATERIALS AND METHODS: Sixty implant (4.3 mm diameter and 11.5 mm length) and custom zirconia abutment (15 mm height and 2 mm wall thickness) pairs were used to form six groups (n = 10 each). Three different resin cements were used to bond the zirconia abutments and titanium inserts: Panavia F 2.0, Zirconite, and Multilink Hybrid Abutment. Control groups and thermomechanically aged groups were formed. Specimens were subjected to tensile test to failure, and the retention values were analyzed by two-way analysis of variance (ANOVA). RESULTS: Two-way ANOVA showed a significant effect of the cement type and thermomechanical aging (P < .05). Regardless of the cement, control groups showed significantly (P < .05) higher retentive strength than the thermomechanically aged groups. Comparing the resin cements, the retentive strength of Zirconite, aged or not, was higher than that of Panavia F 2.0 and Multilink Hybrid Abutment; no significant differences between the latter two cements were found. In the Zirconite group, adhesive failure occurred mostly between the titanium and the resin cement. In the Panavia F 2.0 and Multilink Hybrid Abutment groups, adhesive failure between the zirconia and the resin cement was observed. CONCLUSION: Resin cement type had an effect on the retentive strength of custom zirconia abutments bonded to titanium inserts. Thermomechanical aging had a negative effect on the retentive strength. Zirconite adhesively bonded to the zirconia surface of the custom abutment. Differences were noted in adhesive failure types among the cements.

Fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after aging in a mastication simulator.

STATEMENT OF PROBLEM: The demand for ceramic restorations has increased over the past years, and now various machinable materials can be used for chairside computer-aided design and computer aided manufacturing (CAD-CAM) systems. Limited studies of these new materials make it difficult to evaluate their mechanical performance, advantages, and limitations. PURPOSE: The purpose of this in vitro study was to investigate the fracture resistance of CAD-CAM monolithic ceramic and veneered zirconia molar crowns after thermomechanical aging. MATERIAL AND METHODS: A mandibular first molar tooth was prepared, and 12 different experimental groups were generated (n=10). An aging procedure was performed by subjecting the specimens to 12×105 mechanical cycles and 5000 thermocycles. Survival analysis was performed according to the thermomechanical aging. The fracture resistance (load at fracture) of all specimens was evaluated with 1-way analysis of variance after the means had been compared using the Tukey honest significant difference test and Weibull distributions of the experimental groups (α=.05). RESULTS: According to the results, the differences between the fracture resistance of the groups were found to be significant. Restorations in the dual network ceramic crown group fractured catastrophically during thermomechanical aging. In all groups, the highest value was found for monolithic zirconia, followed by monolithic lithium disilicate crowns (P<.05). Both of the monolithic crowns made of lithium disilicate derivates and zirconia crowns veneered with lithium disilicate ceramic showed no differences from each other (P>.05). The Weibull modulus (m) ranged from 4.22 to 8.58, and conventionally veneered and overpressed zirconia showed the lowest Weibull modulus values among the tested groups, indicating greater variation of the data. CONCLUSIONS: The highest fracture resistance was observed for yttria-stabilized zirconia crowns, followed by lithium disilicate derivates. Veneered zirconia restorations generally showed lower resistance than these ceramics. The dual network ceramic crowns fractured during thermomechanical aging.

Fracture strength of CAD/CAM fabricated lithium disilicate and resin nano ceramic restorations used for endodontically treated teeth.

The purpose of the present study was to evaluate and compare the fracture strength and failure modes of endocrowns, zirconia post, and fiber post supported restorations and predict the clinical outcomes of six different prostheses used for endodontically treated teeth. Sixty (n=10) maxillary central incisors were restored with zirconia post/resin-nano-ceramic crown (ZrRNC), fiber post/resinnano-ceramic crown (FbRNC), zirconia post/lithium disilicate ceramic crown (ZrLDS), fiber post/lithium disilicate ceramic crown (FbLDS), resin-nano-ceramic endocrown (EndoRNC), and lithium disilicate ceramic endocrown (EndoLDS). Fracture strength test was performed. Fracture loads and modes were determined. The EndoLDS group had the highest fracture strength, followed by ZrRNC and EndoRNC group. However the results were not significantly different among groups (p>0.05). The failure modes of the restorations changed according to the restorative materials. Endodontically treated anterior teeth might be restored with endocrowns as well as other post-core restorations, however tooth fracture failures should be considered that affect reliability of endocrowns.

Comparison of Maximum Intercuspal Contacts of Articulated Casts and Virtual Casts Requiring Posterior Fixed Partial Dentures.

PURPOSE: To evaluate the accuracy of the CEREC CAD/CAM system in reproducing the maximum intercuspal contacts of the casts, which include posterior teeth preparation for a fixed partial denture (FPD). MATERIALS AND METHODS: Ten pairs of gypsum casts were mounted in articulators in maximum intercuspal position (MIP) to serve as patient simulation models. Tooth #19 was removed from the cast. Occlusal contacts in MIP were identified with articulating paper, and digital impressions of the casts with unprepared teeth and buccal images in MIP were taken. Teeth #18 and #20 were prepared for an FPD, and full- and half-arch digital impressions of the casts with prepared teeth and buccal images from different sides were taken. In each situation, screenshot images of the virtual casts with occlusal contacts were saved as JPEG files. The proportions of congruence of virtual contacts with cast contacts were analyzed by superimposing screenshot images of the virtual casts onto the screenshot images of the casts with the indicated occlusal contacts in a transparent manner using an image-processing program. The data were statistically analyzed with a paired t-test. RESULTS: The highest percentages of virtually indicated contacts identical to the cast contacts were observed in non-prepared full-arch digital impressions. Comparison of full-arch impressions taken before and after tooth preparation showed no difference for congruence even if the buccal image was taken from the contralateral or ipsilateral side (p > 0.05). After tooth preparation, comparing full- and half-arch digital impressions revealed that half-arch impression showed significantly lower percentages of identical contacts (p < 0.05). When comparing the buccal image side, no significant difference was detected between ipsilateral and contralateral images both for non-prepared and prepared casts (p > 0.05). CONCLUSION: When there is no posterior antagonist contact following tooth preparation for an FPD, taking a full-arch digital impression and designing the restoration on full-arch virtual models can be advocated.

Practical Implementation of Evidence-Based Dentistry Into Daily Dental Practice Through a Short Time Dependent Searching Method.

INTRODUCTION: Despite the fact that the benefits of implementation of Evidence-Based Dentistry (EBD) into clinical practice is increasingly being highlighted, there are still clear limitations in its implementation into daily dental practice. One potentially important barrier to effective implementation into practice is the perception of EBD as a time-consuming process. The aim of the present study is to increase the familiarity of dental practitioners with the benefits of different time-dependent 'practical' search strategies important to EBD using a clinical question from the field of dental implantology as an example. MATERIALS AND METHODS: The PICO (population, intervention, comparison, outcome) question used in this study was: "In young adults with anterior single-tooth implant what is the effect of immediate or delayed loading on success?" A bibliographic search according to the Haynes 5S pyramid, together with 3 different time-dependent strategies (5-min, 30-min and more than 60-min), were applied. RESULTS: Both the Haynes 5S Pyramid and time-dependent search strategies revealed promising results for enhancing decision-making for determining the feasibility of immediate or conventional loading of anterior single dental implants. Results clearly showed that selection of the loading protocol would be case (patient)-specific and also indicated high primary implant stability and bone quality as the most important prerequisites for a successful immediate/early loading. From among the 3 different time-dependent strategies (5 min, 30 min and more than 60 min), the 60+ min search results were quite comparable with the Haynes pyramid search results. CONCLUSION: It is likely that the different time-dependent search strategies may have the potential to support the clinical decision making process and may improve the implementation of EBD into daily dental practice. Increased time spent searching naturally seems to increase the extent of this support. However, even with short time-dependent searches, busy dental clinicians may get an improved idea/opinion regarding a clinical question.

Effect of surface treatments on the biaxial flexural strength, phase transformation, and surface roughness of bilayered porcelain/zirconia dental ceramics.

STATEMENT OF PROBLEM: Veneered zirconia restorations are widely used in prosthetic applications. However, these restorations often fail because of chipping of the veneer porcelain. Surface treatments of zirconia core materials may affect the connection between the 2 layers. PURPOSE: The purpose of this study was to evaluate the effect of surface treatments on the biaxial flexural strength, phase transformation, and mean surface roughness of different bilayered porcelain/zirconia ceramics. MATERIAL AND METHODS: Forty disk-shaped specimens were obtained for each material (Kavo and Noritake) and divided into 4 (n=10) groups (control, airborne-particle abraded, ground, and ground and airborne-particle abraded). Airborne-particle abrasion was performed with 110-µm Al2O3 particles for 15 seconds and at 400 kPa. Diamond rotary instruments with 100-µm grain size were used for grinding. The monoclinic phase transformation and surface roughness of the specimens were measured. Then, the specimens were veneered and subjected to a biaxial flexural strength test to calculate the Weibull moduli (m values) and the stresses occurring at the layers, outer surfaces of the bilayer, and interfaces of the layers. RESULTS: The Kavo airborne-particle abraded group showed higher strength values in both layers (P<.05) than those of all experimental groups. The Kavo airborne-particle abraded group showed the lowest m values at the core and veneer layers. According to the phase analysis, significantly higher Xm values were found in the ground and airborne-particle abraded groups for both materials (P<.05). In both materials, except in the airborne-particle abraded groups, the relative monoclinic phases showed no difference (P<.05). CONCLUSION: Surface treatments affected the phase transformation, surface roughness, and biaxial flexural strength of Kavo and Noritake zirconia ceramics differently. Surface treatments increased the relative monoclinic phase content and average surface roughness.

Evaluation of biogeneric design techniques with CEREC CAD/CAM system.

PURPOSE: The aim of this study was to evaluate occlusal contacts generated by 3 different biogeneric design modes (individual (BI), copy (BC), reference (BR)) of CEREC software and to assess the designs subjectively. MATERIALS AND METHODS: Ten pairs of maxillary and mandibular casts were obtained from full dentate individuals. Gypsum cast contacts were quantified with articulating paper and digital impressions were taken. Then, all ceramic crown preparation was performed on the left first molar teeth and digital impressions of prepared teeth were made. BI, BC, and BR crowns were designed. Occlusal images of designs including occlusal contacts were superimposed on the gypsum cast images and corresponding contacts were determined. Three designs were evaluated by the students. RESULTS: The results of the study revealed that there was significant difference among the number of contacts of gypsum cast and digital models (P<.05). The comparison of the percentage of virtual contacts of three crown designs which were identical to the contacts of original gypsum cast revealed that BI and BR designs showed significantly higher percentages of identical contacts compared with BC design (P<.05). Subjective assessment revealed that students generally found BI designs and BR designs natural regarding naturalness of fissure morphology and cusp shape and cusp tip position. For general occlusal morphology, student groups generally found BI design "too strong" or "perfect", BC design "too weak", and BR design "perfect". CONCLUSION: On a prepared tooth, three different biogeneric design modes of a CAD/CAM software reveals different crown designs regarding occlusal contacts and morphology.

Biaxial flexural strength and phase transformation of Ce-TZP/Al2O3 and Y-TZP core materials after thermocycling and mechanical loading.

PURPOSE: The purpose of the present study was to evaluate the effect of thermocycling and mechanical loading on the biaxial flexural strength and the phase transformation of one Ce-TZP/Al2O3 and two Y-TZP core materials. MATERIALS AND METHODS: Thirty disc-shaped specimens were obtained from each material. The specimens were randomly divided into three groups (control, thermocycled, and mechanically loaded). Thermocycling was subjected in distilled water for 10000 cycles. Mechanical loading was subjected with 200 N loads at a frequency of 2 Hz for 100000 times. The mean biaxial flexural strength and phase transformation of the specimens were tested. The Weibull modulus, characteristic strength, 10%, 5% and 1% probabilities of failure were calculated using the biaxial flexural strength data. RESULTS: The characteristic strengths of Ce-TZP/Al2O3 specimens were significantly higher in all groups compared with the other tested materials (P<.001). Statistical results of X-ray diffraction showed that thermocycling and mechanical loading did not affect the monoclinic phase content of the materials. According to Raman spectroscopy results, at the same point and the same material, mechanical loading significantly affected the phase fraction of all materials (P<.05). CONCLUSION: It was concluded that thermocycling and mechanical loading did not show negative effect on the mean biaxial strength of the tested materials.

Stability measurements of craniofacial implants by means of resonance frequency analysis: 1-year clinical pilot study.

PURPOSE: The purpose of this pilot study was to apply resonance frequency analysis (RFA) to measure the clinical stability of craniofacial implants and compare the RFA measurements over a 12-month period. MATERIALS AND METHODS: Patients with auricular or orbital defects were treated with prostheses retained by two or three implants. After healing periods of 3 months for auricular implants and 6 months for orbital implants, prostheses were fabricated. RFA measurements were performed immediately after implant placement, at abutment connection, and at 6 and 12 months. All stability measurements were repeated three times for each implant, and the mean value was used for analyses. For measurements performed after prosthesis delivery, connecting bars and abutments were removed prior to RFA. The stability of both types of implants was compared at different time intervals. RESULTS: Fifty-four implants were placed in 10 patients with auricular defects (26 implants) and 10 patients with orbital defects (28 implants). All auricular implants survived, and four orbital implants in four different patients failed. For auricular implants, statistically significant differences in stability values were noted between implant placement, abutment connection, and 6 months; there was no significant difference between 6 and 12 months. For orbital implants, no significant differences were found between implant placement and abutment connection, a significant increase was observed at 6 months, and no significant difference was seen between 6 and 12 months. No significant differences were found for auricular versus orbital implants between placement and abutment connection, but auricular implants showed significantly higher stability values than orbital implants at 6 and 12 months. CONCLUSIONS: The stability of surviving auricular and orbital implants increased with time according to RFA. Prior to failure, the failed implants showed RFA values that were below the mean.