The Scalloped Surgical Guide as an Alternative to Flat Bone Reduction Guide in Full-Arch Implant Restoration.

The goal of this clinical report was to present an alternative to traditional flat bone reduction guides, using a custom-designed 3-dimensional (3D)-printed guide according to the future gingival margin of the planned dentition. A 61-year-old woman with concerns regarding her smile appearance was presented. The initial examination revealed excessive gingival show accompanied by excessive overjet. The dentition was in a failing situation. The proposed treatment plan, relying on the sufficient amount of bone and keratinized tissue, consisted of recontouring of the alveolar ridge and gingiva and placement of 6 implants and an FP-1 prosthesis after extraction of all remaining maxillary teeth. Digital smile design was completed, and a fully digitally guided surgery was planned. This consisted of using 3 surgical guides, starting with the fixation pin guide, continuing with the scalloped hard- and soft-tissue reduction guide, and finally the implant placement template. Following the surgery, the patient received a temporary restoration, and on the 4-month follow-up, a new polymethyl meta-acrylate temporary prosthesis was delivered. The patient's 7-month follow-up is presented in the article. The report of this triple-template guided surgery indicated that digital 3D planning is a considerably predictable tool to properly establish and evaluate future occlusal plane, smile line, and lip support. Scalloped guides seem to be an excellent alternative to conventional bone reduction guides since they require less bone removal and improve patient comfort during surgery.

The Scalloped Surgical Guide as an Alternative to Flat Bone Reduction Guide in Full-arch Implant Restoration.

AIM: The goal of this clinical report was to present an alternative to traditional flat bone reduction guides, using a custom-designed 3D printed guide according to the future gingival margin of the planned dentition. MATERIALS AND METHODS: A 61-year-old female with concerns regarding her smile appearance was presented. The initial examination revealed excessive gingival show accompanied by excessive overjet. The dentition was in a failing situation. The proposed treatment plan, relying on the sufficient amount of bone and keratinized tissue, consisted of re-contouring of the alveolar ridge and gingiva and placement of six implants and a FP-1 prosthesis after extraction of all remaining maxillary teeth. RESULTS: Digital smile design was completed, and a fully-digitally-guided surgery was planned. This consisted of utilizing three surgical guides. Starting with the fixation pin guide and continuing with the scalloped hard and soft tissue reduction guide and finally, the implant placement template. Following the surgery, the patient received a temporary restoration and on the 4-month follow-up, a new poly-methyl meta-acrylate temporary prosthesis was delivered. The patient's 7-month follow-up is presented in the paper. CONCLUSIONS: The report of this triple-template guided surgery indicated that digital 3D planning is a considerably predictable tool to properly establish and evaluate future occlusal plane, smile line, and lip support. Scalloped guides seem to be an excellent alternative to conventional bone reduction guides since they require less bone removal and improve patient comfort during surgery.

Influence of scanbody design and intraoral scanner on the trueness of complete arch implant digital impressions: An in vitro study.

This study aimed to compare the accuracy of full-arch digital implant impressions using seven different scanbodies and four intraoral scanners. A 3D-printed maxillary model with six implants and their respective multi-unit abutments was used for this study. Seven scanbodies (SB1, SB2, SB3, SB4, SB5, SB6, and SB7) and four intraoral scanners (Primescan®, Omnican®, Trios 3®, and Trios 4®) were assessed. Each combination group was scanned ten times and a dental lab scanner (D2000, 3Shape) was used as a reference. All scans were exported as STL files, imported into Convince software (3Shape) for alignment, and later into Blender software, where their 3D positions were analyzed using a Python script. The 3D deviation, angular deviation, and linear distance between implants #3 and #14 were also measured. Accuracy was measured in terms of "trueness" (scanbody 3D deviation between intraoral scan and desktop scan). Kruskal-Wallis followed by the Bonferroni correction was used to analyze the data (⍺ = .05). The study found statistically significant differences in digital impression accuracy among the scanners and scanbodies (p<0.001). When comparing different intraoral scanners, the Primescan system showed the smallest 3D deviation (median 110.59 µm) and differed statistically from the others, while Trios 4 (median 122.35 µm) and Trios 3 (median 130.62 µm) did not differ from each other (p = .284). No differences were found in the linear distance between implants #3 and #14 between Trios 4, Primescan, and Trios 3 systems. When comparing different scanbodies, the lowest median values for 3D deviation were obtained by SB2 (72.27µm) and SB7 (93.31µm), and they did not differ from each other (p = .116). The implant scanbody and intraoral scanner influenced the accuracy of digital impressions on completely edentulous arches.

Influence of dental crown topography on fracture resistance of premolars with MOD preparation and subjected to different restorative protocols.

To evaluate whether dental crown topography influences the fracture resistance of premolars treated endodontically and with MOD preparation subjected to different restorative protocols. Sixty-four human premolars with one or two roots in equal numerical proportions (n) were selected and randomly divided into four groups (n = 8): (S = single-rooted; D = double-rooted) SS: sound single-rooted; SNR: endodontics (E) + MOD cavity preparation; SR: E + MOD + resin restoration (RS); SP: E + MOD + RS + horizontal zirconia post (ZP); DS: sound double-rooted; DNR: E + MOD; DR: E + MOD + RS; and DP: E + MOD + RS + ZP. After allocation to the groups, the samples were thermocycled and then subjected to the fracture resistance test. Failures after the fracture test were classified as irreparable (with pulp floor fracture) or reparable (without pulp floor fracture). Data were analysed using one-way anova and the Tukey test (α = 0.05). Single-rooted premolars were more resistant to fracture than double-rooted premolars. The restorative treatment using a horizontally transfixed zirconia post improved fracture resistance, resembling that of a healthy tooth.

The effect of milling and postmilling procedures on the surface roughness of CAD/CAM materials.

PURPOSE: The aim of this study was to evaluate the surface roughness and analyze the surface topography of five different CAD/CAM ceramics and one CAD/CAM composite resin for CEREC after milling and postmilling procedures. MATERIALS AND METHODS: Blocks of the ceramics Mark II, IPS Empress CAD, IPS e.max CAD, Suprinity and Enamic, and blocks of the composite resin Lava Ultimate were milled at CEREC MCXL. Ten flat samples of each material were obtained. The surface roughness (Ra) test was performed before and after milling, crystallization, polishing, and glaze when indicated, followed by SEM and AFM analysis. Data were submitted to one-way ANOVA with repeated measures and the Tukey HSD test (α = 0.05). RESULTS: The milling step significantly increased the roughness of all the tested materials (P < .05). Lithium-based ceramics (IPS e.max CAD and Suprinity) were more suitable to roughness than the other tested materials (P < .05). CONCLUSIONS: The polishing methods were able to reduce roughness to baseline values, except for lithium-based ceramics. Glaze reduced significantly the roughness of lithium-based ceramics without a difference from the baseline. SEM and AFM images revealed that glazed surfaces are smoother than polished surfaces. CLINICAL SIGNIFICANCE: All hard-milling CAD/CAM materials, that is, fully sintered, should be only hand polished. The glaze step can be suppressed resulting in time saving. However, the glaze step in soft-milling lithium disilicate is imperative.

Fracture resistance of endodontically treated molars restored with horizontal fiberglass posts or indirect techniques.

BACKGROUND: Because of the many possibilities for endodontically restoring the posterior teeth and the high prevalence of restoration failures, this topic continues to be of major concern. A composite resin (CR) restoration reinforced by a horizontal fiberglass post may improve the fracture resistance of endodontically treated teeth. The authors investigated this possibility by comparing the fracture resistance of molars restored with direct techniques with that of molars restored with indirect techniques. METHODS: The authors divided 50 extracted sound third molars into 5 groups: sound teeth, onlay (ON), inlay (IN), direct CR, and transfixed fiberglass post (TFP) plus direct CR. The authors performed standardized mesio-occlusodistal cavity preparations and endodontic treatments. The authors cemented indirect restorations of Lava Ultimate (3M ESPE) adhesively in the ON and IN groups. The authors restored CR group teeth directly with Filtek Z230 XT (3M ESPE). In the TFP group, the authors transfixed 2 fiberglass posts horizontally and restored the teeth directly with CR. Thereafter, the authors submitted the teeth to cyclic fatigue loading with 500,000 cycles at 200 newtons. The authors tested fracture resistance in newtons in a universal testing machine. The authors analyzed data with 1-way analysis of variance and a Tukey test (P < .05). RESULTS: Sound teeth had the highest fracture resistance. ON had the highest recovery of resistance, followed by TFP. CR had the lowest recovery, which was similar to that of IN. CONCLUSIONS: Endodontically treated molars restored with TFP plus CR had fracture resistance similar to those restored with ON, which was higher than that for IN or CR only. PRACTICAL IMPLICATIONS: Horizontal TFPs placed inside a composite restoration had the same performance as did ON restorations.

Surface roughness and maintenance of surface sealants for resin composites after toothbrushing.

PURPOSES: (1) To evaluate in vitro the surface roughness of a resin composite covered with three surface sealants and submitted to simulated toothbrushing for different periods; (2) Verify, through scanning electron microscopy (SEM), the presence of surface sealants after simulated toothbrushing; and (3) To evaluate whether the type of dentifrice influences the maintenance of the surface sealant. The study hypothesis was that neither variable would influence the surface roughness of the composite and the maintenance of the surface sealant. METHODS: 108 specimens were prepared with the resin Amelogen Plus, and divided into six groups (n = 18) according to the type of surface sealant [Fortify (F), BisCover LV (B) and Permaseal (P)] and toothpaste [Total 12 Clean Mint (CT) and Colgate Total 12 Professional Whitening (PW)]. The samples were subjected to brushing cycles, simulating periods of 6, 12, 18, and 24 months. After each period, the surface roughness of the samples was measured. An additional group of 48 samples was prepared for SEM analysis. The results were analyzed by ANOVA with three fixed variables (sealants, time and toothpaste) and by Tukey's test (α = 0.05). RESULTS: BisCover had the lowest mean surface roughness (0.06 µm) compared with the sealants Fortify (0.09 µm) and Permaseal (0.08 µm), which were not statistically different. Fortify, at 12 months of brushing, had the highest mean roughness (0.13 µm). The mean roughness for the dentifrice CT was lower (0.07 µm) when compared with PW (0.08 µm) and was statistically different. Roughness increased up to 12 months of simulated brushing (0.04 µm, 0.08 µm and 0.11 µm), decreasing from the 18th month (0.08 µm) to the 24th month of brushing (0.07 µm). None of the sealants was observed (with SEM) to be completely removed from the resin at 24 months of brushing.

Clinical Evaluation of Indirect Composite Resin Restorations Cemented with Different Resin Cements.

PURPOSE: To clinically evaluate the performance of indirect composite resin restorations cemented with conventional and self-adhesive resin cements over a 12-month period. MATERIALS AND METHODS: Ten patients fulfilled all the inclusion criteria. Twenty-four composite resin restorations were performed using an indirect technique and cemented with a resin cement (RelyX ARC) or a self-adhesive resin cement (RelyX U100). Two independent evaluators analyzed the restorations using modified USPHS criteria after periods of two weeks and 6 and 12 months. Statistical significance between the cements at each timepoint was evaluated with the Wilcoxon test and between timepoints with the Mann-Whitney test, both at a significance level of 5%. Fisher's exact test was used to assess the occurrence of absolute failures. RESULTS: No statistically significant differences were found between the groups at the same timepoint nor between groups at different timepoints. The only significant difference was found for color match for both groups after 12 months. CONCLUSION: After 12 months, indirect composite resin restorations cemented with self-adhesive resin cement performed similarly to those cemented with conventional resin cement.

Strengthening effect of horizontally placed fiberglass posts in endodontically-treated teeth restored with direct resin composite.

PURPOSE: To assess the fracture strength of cavity preparations, directly restored with resin composite, with and without the presence of fiberglass posts with different diameters. METHODS: 84 extracted third molars were embedded in acrylic resin and divided into six groups (n = 14 per group): healthy (H); cavity preparation (P); cavity preparation + endodontic treatment (PE); PE + resin composite (R); PE + R + 2 horizontally transfixed fiberglass posts 1.1 mm in diameter (PERP1); PE + R + 2 fiberglass posts 1.5 mm in diameter (PERP2). The MOD cavity preparations were standardized with their width corresponding to 2/3 of the buccolingual distance and occlusogingival depth of 4 mm, with 2 mm remaining above the cemento-enamel junction. Endodontic treatments were performed in the PE, R, PERP1 and PERP2 groups. The buccal surface received two demarcations to create orifices for placement of the PERP1 and PERP2 posts. Once the fiberglass posts were placed, the teeth were restored with resin composite. In group R, only resin composite was used. After 24 hours, the teeth were subjected to the fracture toughness test on a universal testing machine. A 10 KN load cell and crosshead speed of 1 mm/minute was used until fracture occurred. After testing, the teeth were inspected for the type of fracture classified as: pulpal floor fracture (AP) or cuspal fracture (CP). RESULTS: The data were subjected to ANOVA and Tukey's test (P < 0.05%), demonstrating a statistical difference between groups: H 3830NA; P 778ND; PE 572.93ND; R 1782NC; PERP1 2988NB; PERP2 3100NAB. The fracture pattern was similar between the tested groups, showing 50% of fracture for cusps and pulpal floor.

Fracture resistance of computer-aided design and computer-aided manufacturing ceramic crowns cemented on solid abutments.

BACKGROUND: Because no information was found in the dental literature regarding the fracture resistance of all-ceramic crowns using CEREC (Sirona) computer-aided design and computer-aided manufacturing (CAD-CAM) system on solid abutments, the authors conducted a study. METHODS: Sixty synOcta (Straumann) implant replicas and regular neck solid abutments were embedded in acrylic resin and randomly assigned (n = 20 per group). Three types of ceramics were used: feldspathic, CEREC VITABLOCS Mark II (VITA); leucite, IPS Empress CAD (Ivoclar Vivadent); and lithium disilicate, IPS e.max CAD (Ivoclar Vivadent). The crowns were fabricated by the CEREC CAD-CAM system. After receiving glaze, the crowns were cemented with RelyX U200 (3M ESPE) resin cement under load of 1 kilogram. For each ceramic, one-half of the specimens were subjected to the fracture resistance testing in a universal testing machine with a crosshead speed of 1 millimeter per minute, and the other half were subjected to the fractured resistance testing after 1,000,000 cyclic fatigue loading at 100 newtons. RESULTS: According to a 2-way analysis of variance, the interaction between the material and mechanical cycling was significant (P = .0001). According to a Tukey test (α = .05), the fracture resistance findings with or without cyclic fatigue loading were as follows, respectively: CEREC VITABLOCKS Mark II (405 N/454 N) was statistically lower than IPS Empress CAD (1169 N/1240 N) and IPS e.max CAD (1378 N/1025 N) (P < .05). The IPS Empress CAD and IPS e.max CAD did not differ statistically (P > .05). According to a t test, there was no statistical difference in the fracture resistance with and without cyclic fatigue loading for CEREC VITABLOCS Mark II and IPS Empress CAD (P > .05). For IPS e.max CAD, the fracture resistance without cyclic fatigue loading was statistically superior to that obtained with cyclic fatigue loading (P < .05). CONCLUSIONS: The IPS Empress CAD and IPS e.max CAD showed higher fracture resistance compared with CEREC VITABLOCS Mark II. The cyclic fatigue loading negatively influenced only IPS e.max CAD. PRACTICAL IMPLICATIONS: The CEREC VITABLOCS Mark II, IPS Empress CAD, and IPS e.max CAD ceramic crowns cemented on solid abutments showed sufficient resistance to withstand normal chewing forces.

Does immediate dentin sealing influence the polymerization of impression materials?

OBJECTIVES: The objective of the following study is to evaluate the interaction between the resin materials used in immediate dentin sealing (IDS) techniques and impression materials with two different techniques to eliminate the oxygen-inhibition layer. MATERIALS AND METHODS: The occlusal dentin surface of 35 human molars was exposed. The teeth were used in two Groups: Group 1 - Impression with Express XT; Group 2 - Impression with Impregum. Groups 1 and 2 were divided into 14 subgroups: Groups 1a and 2a - Control groups; 1b and 2b - IDS with Clearfil SE Bond (CSE); 1c and 2c - IDS with CSE + additional polymerization with glycerin jelly; 1d and 2d - IDS with CSE + alcohol; 1e and 2e - IDS with CSE and Protect Liner F (PLF); 1f and 2f - IDS with CSE and PLF + additional polymerization with glycerin jelly; and 1g and 2g - IDS with CSE and PLF + alcohol. Five teeth were used in each experimental group, and the tooth surface was photographed using a digital camera. RESULTS: Small quantity of unpolymerized impression material remained attached to the CSE or to the PLF in Groups 1b and 1e. Groups 1c and 1d prevented the interaction. Small quantity of polymerized impression material remained attached to the CSE or to the PLF for Groups 2b and 2e. The same interaction was observed for Groups 2c and 2d. For Groups 2c and 2f, no interactions were observed. CONCLUSION: Resin materials interacted with impression materials. The application of glycerin jelly and alcohol prevented the interaction of CSE with Express XT and PLF with Impregum; however, these treatments were not completely effective in preventing the interaction of CSE with Impregum and PLF with Express XT.

The influence of postpouring time on the roughness, compressive strength, and diametric tensile strength of dental stone.

STATEMENT OF PROBLEM: The optimum time after pouring a dental impression before removing the dental cast is unknown with regard to the strength and roughness of the stone. Setting times and the commercial products used are important variables. PURPOSE: The purpose of this study was to evaluate the effect of postpouring time on the surface roughness, compressive strength, and diametric tensile strength of Type IV dental stone. MATERIAL AND METHODS: A total of 270 specimens were prepared from 3 commercial brands of dental stone (Durone, Fuji Rock, and Tuff Rock). Surface roughness, compressive strength, and diametric tensile strength were assessed at 1 hour, 24 hours, and 7 days after pouring. Specimens 6 mm in diameter and 3 mm in height were produced for roughness and diametric tensile strength tests. Specimens 3 mm in diameter and 6 mm in height were used to measure compressive strength. The results were analyzed with the general linear model and Tukey honestly significant difference test (α=.05). RESULTS: The surface roughness measured for the different types of dental stone tested varied from 0.3 µm (Durone, 1 hour) to 0.64 µm (Tuff Rock, 7 days). The diametric tensile strength ranged from 3.94 MPa (Tuff Rock, 1 hour) to 9.20 MPa (Durone, 7 days). The compressive strength varied from 26.67 MPa (Durone, 1 hour) to 65.14 MPa (Fuji Rock, 7 days). CONCLUSIONS: Surface roughness (P=.005), diametric tensile strength (P=.001), and compressive strength (P=.001) increased significantly with time after pouring. The commercial brand used affected roughness (P=.001), diametric tensile strength (P=.004), and compressive strength (P=.001). Tuff Rock exhibited the highest surface roughness. The highest diametric tensile strength values were recorded for Durone and Fuji Rock. Fuji Rock exhibited the highest compressive strength.

Influence of restorative techniques on fracture load of endodontically treated premolars.

UNLABELLED: OBJECTIVE. This study evaluated the influence of restorative techniques on the fracture load and fracture mode of endodontically treated premolars with MOD cavities. MATERIALS AND METHODS: Sixty maxillary premolars were divided into groups: G1 - sound teeth; G2 - direct technique using Four Season; G3 - Adoro inlays; G4 - Adoro onlays; G5 - Empress inlays; G6 - Empress onlays. The specimens were submitted to compressive axial loading until failure. The fracture mode was analyzed. RESULTS. According to ANOVA and Tukey's test (α=0.05), the sound teeth (1370.61 N) showed the highest fracture load mean, which did not differ statistically from IPS Empress onlays (1304.21 N). Intermediate values were obtained for IPS Empress inlays (918.76 N), Adoro onlays (861.15 N), Adoro inlays (792.71 N) which did not differ statistically among them. The lowest fracture load was obtained for direct restorations with Four Seasons (696.08 N), which did not differ statistically from the Adoro inlays. CONCLUSIONS. The ceramic restorations provided higher fracture load and more incidences of catastrophic fractures. Cuspal coverage increased teeth fracture load. The results were similar for direct and indirect inlays with composite resin.

Influence of resin cements on cuspal deflection and fracture load of endodontically-treated teeth restored with composite inlays.

OBJECTIVES: To evaluate the influence of resin cements on cuspal deflection, fracture load and failure mode of endodontically-treated teeth restored with composite resin inlays. MATERIALS AND METHODS: Forty maxillary premolars were randomly divided into four groups: G1 (sound teeth, control), G2 (RelyX ARC), G3 (RelyX Unicem) and G4 (Maxcem Elite). The teeth from groups 2, 3 and 4 received mesial-occlusal-distal preparations and endodontic treatments. Impressions were taken with vinyl polysiloxane and poured using type IV die stone. Inlays with Z250 composite resin were built over each cast and luted with the resin cements. A 200-N load was applied on the occlusal surface and the cuspal deflection was measured using a micrometer. The specimens were then subjected to an axial load until failure occurred. The resulting failure mode was analyzed. RESULTS: The means for cuspal deflection (µm) and fracture load (N) followed by the same letter represent no statistically significant difference based on ANOVA and Tukey's test (p < 0.05). Cuspal deflection: G1 = 4.7 (± 1.7)(a), G2 = 12.0 (± 8.9)(a), G3 = 39.0 (± 27.0)(b) and G4 = 56.8 (± 18.2)(b). Fracture load: G1 = 1982 (± 893)(a), G2 = 690.9 (± 225.5)(b), G3 = 679 (± 193.6)(b) and G4 = 465.5 (± 121.6)(b). G1 presented cusp fractures only at the cement-enamel junction (CEJ). There was a high frequency of cusp fractures below the CEJ in G2, G3 and G4. CONCLUSIONS: Composite resin inlays luted with resin cements do not recover the strength of sound teeth. However, teeth restored with composite resin inlays and luted with RelyX ARC can withstand mechanical fatigue longer before failure occurs than those luted with RelyX Unicem and Maxcem Elite.

Argon and Nd:YAG lasers for caries prevention in enamel.

OBJECTIVE: The aim of this study was to investigate the effect of Nd:YAG and argon laser irradiations on enamel demineralization after two different models to induce artificial caries. BACKGROUND DATA: It is believed that the use of the high-intensity laser on the dental structure can lead to a more acid-resistant surface. MATERIALS AND METHODS: Twenty-one extracted human third molars were sectioned into tooth quarters. The quarters were distributed in three groups: Group I (control), untreated; Group II, Nd:YAG laser (60 mJ, 15 pps, 47.77 J/cm(2), 30 sec); and Group III, argon laser (250 mW, 12 J/cm(2), 48 sec). Tooth quarters from each group were subjected to two different demineralization models: cycle 1, a 14 day demineralization (pH 4.5; 6 h) and remineralization (pH 7.0; 18 h) solutions, 37 °C and cycle 2, 48 h in demineralization solution (pH 4.5). Samples were prepared in slices (60-100 µm thick) to be evaluated under polarized light microscopy. Demineralization areas were measured (mm(2)) (n=11). Data were analyzed by ANOVA and Tukey's test (p<0.05). RESULTS: Means followed by different letters are significantly different: 0.25 A (control, cycle 48 h); 0.18 AB (control, cycle 14 days); 0.17 AB (Nd:YAG, cycle 14 days); 0.14 BC (argon, cycle 48 h); 0.09 BC (Nd:YAG, cycle 48 h), and 0.06 C (argon, cycle 14 days). CONCLUSIONS: The argon laser was more effective for caries preventive treatment than Nd:YAG laser, showing a smaller demineralization area in enamel.

Effect of whitening dentifrices on the surface roughness of commercial composites.

PURPOSE: Our study aimed to test the null hypothesis that whitening and non-whitening dentifrices affect similarly the surface roughness of commercial microhybrid composites, independent of the brushing time. MATERIALS AND METHODS: One hundred and ninety-two disc-shaped specimens of Filtek Z250 (3 M/ESPE, St. Paul, MN, USA) and Rok (SDI, Australia) were built up and randomly assigned to 24 groups, based on the dentifrices used (two whitening dentifrices: Colgate Max White-Colgate-Palmolive, São Bernardo do Campo, São Paulo, Brazil and Close Up Extra Whitening-Unilever, Brasil Higiene Pessoal e Limpeza Ltda, Ipojuca, Pernambuco, Brazil; and one non-whitening dentifrice: Colgate Total 12 Clean Mint-Colgate-Palmolive), and on the simulated brushing times (24 hours, 6, 12 and 24 months). The specimens were submitted to the toothbrushing regimens after which the surface roughness (Ra) was measured. Data was submitted to analysis of variance and Tukey test (α=0.05). RESULTS: The composite's surface roughness was significantly affected by the composites (p=0.0007), the dentifrices (p=0.0001), and the simulated brushing time (p=0.0001). Higher roughness was observed when the whitening dentifrices were used and when the brushing time increased. Filtek Z250 was more affected than Rok, especially after 24 months of simulated brushing. CONCLUSION: Whitening dentifrices produced higher surface roughness in the composites tested. The degree of surface compromising increased with brushing time and depends on the composite's microstructure and composition.

Accuracy of the second pour casts using dual-arch trays.

OBJECTIVE: To compare, in vitro, the accuracy between dental stone casts obtained from the first and the second pour using metallic (Smart) and plastic (Triple Tray) dual-arch trays. MATERIAL AND METHODS: The impressions were taken using Flexitime® vinyl polysiloxane from a typodont model with a mandibular right first molar prepared for a full crown. Ten impressions were made with each tray and poured using type IV die stone. After 1 hour, the casts were removed from the impressions and, 1-hour later, second pours were completed. The mesio-distal and the buccal-lingual widths at the gingival margin of the prepared tooth on the cast were measured in a perfil projector. The results were submitted to Student's t-test (α=0.05) using SPSS version 10.0. RESULTS: There was a statistically significant difference between the first and second pours using the plastic tray in the mesio-distal width. CONCLUSION: It could be suggested that a repeated pour is more accurate using a metallic tray.

Effect Of Nd:YAG laser and CO2 laser treatment on the resin bond strength to zirconia ceramic.

OBJECTIVE: this study evaluated the effect of surface treatments (Nd:YAG laser, CO2 laser, Al203 airborne-particle abrasion, and silica-coating) on the zirconia-to-resin shear bond strength (SBS). METHOD AND MATERIALS: eighty-one Lava (3M ESPE) blocks (13 x 4 x 2 mm) were embedded in acrylic resin, polished, and randomly divided into three groups, which received the following surface treatments: no abrasion, Al203 airborne-particle abrasion (50 Μm), or silica-coating (Cojet, 3M ESPE). Each group was divided into three subgroups that were treated with Nd:YAG laser, CO2 laser, or no laser irradiation. Following application of a monomer phosphate-containing primer, cylinders of resin cement (Panavia F, Kuraray) (n = 18) were built on the surface. SBS testing was carried out after 24 hours of storage in water. Surface roughness and topography (SEM) after treatments were evaluated. RESULTS: according to ANOVA and Tukey test ( α = 0.05), mean SBS after Nd:YAG laser treatment ranged from 14.09 to 16.20 MPa and was statistically higher than CO2 laser (6.24 to 10.51 MPa) and no laser treatment (4.65 to 8.79 MPa). The Nd:YAG laser created more roughness on zirconia when compared to the CO2 laser and abrasion treatments. Silica-coating increased the SBS of lased and nonlased zirconia. Significant microcracks were found on specimens treated with CO2. CONCLUSION: Nd:YAG laser pretreatment, whether associated with abrasion methods or not, created consistent roughness on the zirconia surface and significantly increased zirconia SBS to Panavia F. Silica-coating could potentially increase the SBS of lased and nonlased zirconia. Significant microcracks were found on specimens treated with the CO2 laser.

Fatigue resistance and failure mode of novel-design anterior single-tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments.

OBJECTIVES: This study assessed the fatigue resistance and failure mode of type III porcelain and composite resin veneers bonded to custom zirconia implant abutments. MATERIAL AND METHODS: Twenty-four standardized zirconia implant abutments were fabricated. Using the CEREC 3 machine, type III veneers of standardized shape were milled in ceramic Vita Mark II or in composite resin Paradigm MZ100. The intaglio surfaces of the restorations were hydrofluoric acid etched and silanated (Mark II) or airborne-particle abraded and silanated (MZ100). The fitting surface of the abutments was airborne-particle abraded, cleaned, and inserted into a bone level implant (BLI RC SLActive 10 mm). All veneers (n=24) were adhesively luted with a zirconia primer (Z-Prime Plus), adhesive resin (Optibond FL) and a pre-heated light-curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 40 N, followed by stages of 80, 120, 160, 200, 240, and 280 N (20,000 cycles each). Samples were loaded until fracture or to a maximum of 140,000 cycles. Groups were compared using the life table survival analysis (Logrank test at P=.05). RESULTS: Mark II and MZ100 specimens fractured at an average load of 216 N and 229 N (survival rate of 17% and 8%), respectively, with no difference in survival probability (P=.18). Among the fractured samples, 40% of the failures were at the abutment level for Mark II and 27% were at the abutment level for MZ100. No exclusive adhesive failures were observed. CONCLUSIONS: Type III Mark II and Paradigm MZ100 veneers showed similar fatigue resistance when bonded to custom non-retentive zirconia implant abutments. The bond was strong enough to induce abutment fractures. MZ100 presented a higher percentage of "friendly" failures, i.e. maintaining the restoration-abutment adhesive interface and the abutment itself intact.

Effect of conditioner on microtensile bond strength of self-adhesive resin cements to dentin.

OBJECTIVE: Evaluate, in vitro, the microtensile bond strength (µTBS) of RelyX ARC conventional resin cement and RelyX Unicem and Maxcem self-adhesive resin cements to dentin, and the influence of polyacrylic acid pretreatment on the µTBS. MATERIAL AND METHODS: Flat dentin surfaces were obtained in 15 third molars which were randomly divided into 5 groups: Group 1 - RelyX ARC (control); Group 2 - RelyX Unicem; Group 3 - Maxcem Elite; Group 4 - 22.5% polyacrylic acid and RelyX Unicem; Group 5 - 22.5% polyacrylic acid and Maxcem Elite. A block of composite resin was built over the resin cements. The samples were sectioned to obtain beams, and 20 specimens for each group were submitted to µTBS on a universal testing machine. Failure modes were analyzed by scanning electron microscopy. RESULTS: According to ANOVA and Tukey test, the highest µTBS mean (MPa) was obtained with RelyX ARC (21.38), which did not differ statistically from Maxcem Elite with polyacrylic acid pretreatment (19.22) and RelyX Unicem with polyacrylic acid pretreatment (17.75) (p>0.05). The latter two groups did not differ statistically from RelyX Unicem (16.98) (p>0.05). The lowest mean was obtained for Maxcem Elite (6.43), which differed statistically from the other groups (p<0.05). All failures were adhesive for Maxcem Elite without polyacrylic acid pretreatment, and mixed failures were predominant in the other groups. CONCLUSIONS: RelyX ARC achieved higher µTBS to dentin in comparison to the self-adhesive resin cements. Polyacrylic acid pretreatment was effective in improving the µTBS of Maxcem Elite, but did not influence the µTBS for RelyX Unicem.