Effect of abutment screw-access hole on the fatigue performance of implant-supported lithium-disilicate luted simplified restorations.

The present study aimed to evaluate the impact of the existence of an abutment screw-access hole and the filling effects on the fatigue mechanical behavior of a luted lithium-disilicate glass-ceramic. Seventy-two discs (Ø = 10 mm, 1.0 mm in thickness) of lithium disilicate (IPS e.max CAD, Ivoclar AG) were obtained from prefabricated blocks. Thirty-six abutment specimens of an opaque zirconia (Yz - IPS e.max ZirCAD, Ivoclar AG) and titanium (Ti - Luminesse Ti-Cam discs, Talladium Inc.) were confectioned, and allocated according to 6 groups: Yz and Ti rigid (without screw access hole); Yz unfilled, Yz filled, Ti unfilled and Ti filled (with the screw access (Ø = 2.5 mm) in the center). For the unfilled groups, only a polytetrafluoroethylene tape was used. Resin composite (Tetric N-Ceram, Ivoclar AG) was applied to the screw access hole for the filled groups (Yz and Ti). A cyclic fatigue test was carried out (load of 200 N, 10,000 cycles each; 20 Hz of frequency, step size of 100 N until failure detection (radial/cone crack). The fatigue failure load (FFL) and number of cycles until failure (CFF) were recorded for statistical purposes. The stress distribution (MPa) was evaluated by finite element analysis. A statistically positive effect of the abutment material and the presence of the screw access hole was observed (p ≤ 0.05). The rigid groups (without screw access holes) depicted almost 100% of survival after the fatigue tests. Among the other groups, the Yz-filled group showed the best performance (p ≤ 0.05), followed by the Yz unfilled group. The Ti groups depicted lower values of FFL and CFF, with the Ti unfilled group showing the most unfavorable fatigue behavior (p ≤ 0.05). The lowest tensile stress concentration in the restorative material was observed with the use of rigid abutments, the filled groups depicted intermediate values, while unfilled groups showed the highest stress concentration (Yz rigid = 306.3 MPa; Ti rigid = 310.4 MPa < Yz filled = 490.7 MPa; Ti filled = 498.9 MPa < Yz unfilled = 707.6 MPa; Ti unfilled = 719.7 MPa). Therefore, the presence of a screw-access hole decreases the mechanical performance of a lithium disilicate ceramic regardless of the abutment material. In the presence of a screw-access hole, zirconia abutments depicted a higher fatigue failure load when compared with titanium. The filling of the abutment screw-access hole with resin composite increased the mechanical performance of the simulated restoration.

Biomechanical performance of endocrown and core-crown restorations: A systematic review.

OBJECTIVE: To assess and compare, through a systematic review of the literature, the biomechanical performance of endocrowns and traditional core-crowns (with and without intracanal post) for the rehabilitation of endodontically treated teeth with severe coronal structure damage. MATERIALS AND METHODS: A systematic search was performed in MEDLINE/PubMed, Scopus, and Web of Science databases. In-vitro studies comparing endocrowns with (post-)core-crown restorations were selected and screened by two independent reviewers. The included studies were submitted to the risk of bias analysis using the RoBDEMAT tool and the biomechanical outcomes were collected for qualitative analysis. The extracted data were presented based on comparative analyses among the included studies. RESULTS: Thirty-one studies were included: 9 studies evaluated restorations of molars, 14 for premolars, and 8 studies evaluated anterior restorations. For the majority of the studies, endocrowns showed either similar or greater survival rates under fatigue and monotonic load than (post-)core-crown restorations, irrespectively of the tooth. The endocrowns showed more favorable failure patterns than (post-)core-crowns, irrespectively of the tooth. Endocrowns produced lower stresses in the restorative material for molars and premolars and in the luting material for premolars than (post-)core-crown restorations. The included studies presented adequate information for most items of the RoBDEMAT risk of bias tool. CONCLUSION: Endocrowns showed similar or greater biomechanical performance than the traditional (post-)core-crown restorations in most of the evaluated studies. CLINICAL SIGNIFICANCE: This systematic review showed that endocrowns present either similar or greater biomechanical performance than core-crown restorations for anterior and posterior endodontically treated teeth with severe structural damage.

Peri-implant Outcomes from Customized Healing Abutments Using Immediate Implants: A Systematic Review.

PURPOSE: To evaluate the peri-implant outcomes of customized healing abutments (CstHA) placed on dental implants inserted in fresh tooth extraction sockets. MATERIALS AND METHODS: The study was registered on PROSPERO: CRD42022304320. A systematic search in PubMed, Scopus, and Web of Science was conducted between April 2022 and October 2022 to identify clinical studies involving immediate implant surgery associated with CstHA placement. The Joanna Briggs Institute Critical Appraisal and RoB2 tool were performed for the risk of bias analysis. RESULTS: A total of 12 studies were included, most of them with low risk of bias. Four studies compared CstHA vs conventional healing abutments (CnvtHA), two compared CstHA vs cover screw and collagen matrix (CMa), and six were clinical case series. For the CstHA vs CnvtHA comparison, favorable results were observed for CstHA considering papilla maintenance and probing depth, yet the mean marginal bone level was statistically similar between CstHA and CnvtHA. CstHA showed advantages when compared to CMa for total bone volume, papilla height, and midfacial mucosa maintenance. Significantly less horizonal bone loss was reported when using CstHA compared with CMa. Horizontal and vertical bone loss was observed in a few (or no) sites in the case series using CstHA. CONCLUSIONS: CstHA provides favorable peri-implant response because in general it does not result in a significant loss of soft and hard tissues.

A conservative full-mouth ceramic rehabilitation for a severely worn dentition.

There is a constantly growing prevalence of tooth wear in dentistry. The present case report describes a rehabilitation through ceramic restorations of a severely worn dentition based on a conservative intervention, adequate restorative material selection, and adhesive bonding strategies. A 36-year-old patient with a mainly esthetic complaint presented with signs of tooth wear caused by erosion and attrition. Preparations were performed guided by the diagnostic planning. The full-mouth rehabilitation, combined with the correction of the vertical dimension of occlusion, was split into quadrants, and lithium disilicate partial restorations were fabricated. The proposed rehabilitation was based on the maximal preservation of the remaining tooth structure and the adequate selection of restorative materials and adhesive bonding strategies.

Apical enlargement favors endodontic irrigation ­ an in vivo study

Aim: This study evaluated the irrigation penetration during root canal instrumentation and the clinical step in which the irrigation solution can be detected in the apical region. Materials and Methods: Twenty necrotic molars were divided according to the irrigation protocol, saline solution with manual active pressure, and 2.5% sodium hypochlorite with dripping delivery. Solution penetration assessment used a radiopaque component added to each irrigant solely before a periapical radiograph. Instrumentation sequence was: #10, and #15 K-files (step 1), cervical flaring using WaveOne Small (step 2), WaveOne Small at working length (step 3), Hero-642 #35/.02 (step 4), and Hero-642 #40/.02 (step 5). The step each contrasted-irrigant reached the 2-mm-apical region was registered. Shapiro-Wilk and Fisher's exact tests were used for comparisons. Results: In step 3, both contrasted-irrigants started to be detected in the apical region, and after step 5, contrasted-irrigants penetrated in 100% of the cases, without significant difference. Conclusion: Considering distal molar roots, the apical enlargement up to an instrument #40.02 favors the irrigation to reach the 2-mm apical region.

Influence of coloring techniques on the surface characteristics and color stability of a monolithic zirconia ceramic.

STATEMENT OF PROBLEM: The color of monolithic zirconia restorations is obtained by presintering or postsintering coloring techniques. However, studies on the differences in surface characteristics and their influence on color stability are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the influence of shading and staining techniques for a zirconia ceramic on the surface characteristics and colorimetric parameters (color difference, translucency, and whiteness index) after exposure to coffee or red wine and then polishing. MATERIAL AND METHODS: Ceramic disks (N=30; Ø10×1mm) were allocated into 3 groups: preshaded-shaded by the manufacturer (IPS e.max ZirCAD MT, shade A2); manually shaded-unshaded zirconia (IPS e.max ZirCAD MT, bleaching shade-BL) colored by the brushing technique, before sintering; stained-unshaded zirconia (IPS e.max ZirCAD MT BL) colored by the staining technique, after sintering. Spectrophotometric color assessments ensured the same initial perceived color (Vita Classical A2) for specimens included in the study (∆E00<1.77 acceptability threshold). Surface characteristics were assessed by scanning electron microscopy and atomic force microscopy. The specimens were immersed in coffee (n=5) or red wine (n=5) for 12 and 24 days and subsequently polished. The data were statistically and descriptively analyzed for color differences (∆E00), translucency parameters (TP00), and whiteness indexes for dentistry (WID), considering acceptability and perceptibility thresholds. RESULTS: The shaded groups found an irregular ceramic surface with uniformly sized zirconia crystals. The stained group found a glass-covered smoother surface. Significant alterations in color parameters (∆E00, TP00, WID) were observed with immersion in pigmenting beverages (P<.001) both after 12 days, and after 24 days. The shaded specimens had greater color alterations after immersion but benefited from the polishing procedure, which reduced color differences below an acceptable threshold in comparison with the baseline. Stained specimens had lower color alterations after immersion, but the polishing protocol was detrimental as it whitened the ceramic by subsurface exposure. CONCLUSIONS: The coloring technique influences the surface characteristics of zirconia ceramic and also the color parameters after exposure to colored beverages and polishing.

Effect of preheating and ultrasound application of resin-based luting agents on the failure load of a lithium disilicate glass-ceramic.

PURPOSE: To assess the effect of preheating resin-based materials and ultrasound application on the failure load of a lithium disilicate glass-ceramic. MATERIALS AND METHODS: Ninety ceramic specimens were produced (14×12×1.0 mm) and divided into 9 groups (n = 10) to be bonded to a dentin analog (Nema G10) with light-cured luting agent (LC), flowable resin composite (FL), and supra-nano filled resin composite (SN), as follows: LC/R - LC at room temperature; LC/P - preheated LC; LC/P/U - preheated LC and Ultrasound; FL/R - FL at room temperature; FL/P - preheated FL; FL/P/U - preheated FL and Ultrasound; SN/R - SN at room temperature; SN/P - preheated SN; SN/P/U - preheated SN and Ultrasound. The failure load test was performed in a universal testing machine with the aid of acoustic detection. The data was analyzed with two-way ANOVA (for failure load) and Weibull statistics (Weibull modulus - m and characteristic strength, based on 95% confidence intervals - CI). RESULTS: The analyses of failure load revealed no statistically significant difference among groups considering the type of luting agent (P = 0.075; F = 2,673), the application method (P = 0.772; F = 2,259), and the interaction between them (P = 0.297; F = 1,248). The characteristic strength did not show differences among groups (95% CI). The m, which indicates structural reliability, showed lower values for SN/P/U and SN/P, with a difference from other selected groups (95% CI). CONCLUSION: Preheating of resin-based materials and ultrasound application did not affect the failure load of lithium disilicate glass-ceramic. Lower reliability was observed with supra-nano filled resin composite.

Resin composite layering on discolored substrates ensures masking ability for monolithic ceramics.

OBJECTIVE: the aim of this study was to evaluate the effect of resin composite layering on discolored substrates to obtain masking ability with monolithic ceramics. MATERIALS AND METHODS: Four groups (n = 8) of computer-aided design/computer aided manufacturing (CAD/CAM) monolithic ceramics, shade A1, with thicknesses of 1.0 and 1.5 mm, were tested: feldspathic (FC), leucite-reinforced (LC), lithium disilicate-reinforced (LD), and translucent zirconia (5YSZ). Five substrates were used: A1 (used as reference), A3.5, C4, and coppery and silvery metals. The substrates were separated as non-layered or layered (with flowable opaque resin composite (FL), white opaque restorative resin composite (WD), and A1-shaded opaque restorative resin composite (A1D)). Resin composite layers of 0.5 and 1.0 mm were tested. The try-in paste, shade A1, was used as a luting agent. Translucency parameter (TP00 ) was assessed for the ceramics. Color differences (∆E00 ) were assessed for the restorative ceramics and resin composite layers over discolored substrates with the CIEDE2000 formula. The results were compared statistically, and descriptively with acceptability (AT, 1.77) and perceptibility (PT, 0.81) thresholds. RESULTS: Feldspathic showed the highest TP00 (for both ceramic thicknesses) and LD the lowest (for 1.5 mm of ceramic thickness) (P < 0.001). For substrate A3.5, layering with 1.0 mm of A1D or WD ensured ∆E00 below PT for all ceramics tested (P < 0.001). The use of 0.5 mm of FL or 1.0 mm of A1D associated with ceramics LC, LD, and 5YSZ ensured ∆E00 below AT for substrates C4 and coppery metal (P < 0.001). Silvery background layered with 0.5 mm of FL presented ∆E00 below AT for all ceramics and ∆E00 below PT for lithium disilicate of 1.0 mm of thickness (∆E00 = 0.72). CONCLUSIONS: Layering severely discolored substrates with selected opaque resin composites ensures masking ability for restoration with CAD/CAM monolithic ceramics. CLINICAL SIGNIFICANCE: Severely discolored substrates are predictably restored with monolithic CAD/CAM ceramics by performing a previous layering of the substrate with opaque resin composite.

Masking ability of CAD/CAM monolithic ceramics: effect of ceramic type and thickness, and try-in paste shade.

OBJECTIVE: This in vitro study evaluated the color differences when discolored tooth substrates were restored with CAD/CAM monolithic ceramics depending on ceramic type and thickness, and the try-in paste shade. METHOD AND MATERIALS: Six ceramic types were tested: high-translucent lithium disilicate (LD-HT); medium-translucent lithium disilicate (LD-MT); low-translucent lithium disilicate (LD-LT); low-translucent leucite (LC-LT); feldspathic ceramic (FC); and BL1 low-translucent lithium disilicate, stained to A1 shade (LD-BL1-LT). The ceramics were tested in disk-shaped specimens with 0.5-, 1.0-, and 1.5-mm thickness (n = 10; N = 180; shade A1). The try-in pastes were tested to simulate luting materials and corresponded to colors A1 and Opaque White. Six substrates were used: A1 (reference), B2, B3, A3, C2, and C3. Color differences (∆E00) and translucency parameter (TP00) were assessed with the CIEDE2000 formula. The results were compared with acceptability (1.77) and perceptibility (0.81) thresholds. RESULTS: Ceramic type, thickness, and the try-in paste shade influenced the color differences. LD-LT and LC-LT ceramics and Opaque White try-in paste provided, in general, lower ∆E00 values. The most adequate ceramic thickness varied according to the substrate discoloration. With 1.0 mm of ceramic thickness, it was possible to obtain ∆E00 lower than the perceptibility threshold for substrates C2 and A3, and ∆E00 lower than the acceptability threshold for C3 and B3. ∆E00 lower than the acceptability threshold were obtained with 0.5 mm of ceramic thickness for B2, A3, and C2. CONCLUSION: The use of low-translucent glass-ceramics and Opaque White try-in paste are useful to reduce color differences. The most adequate ceramic thickness depends on the substrate discoloration.

Fatigue performance analysis of strength-graded zirconia polycrystals for monolithic three-unit implant-supported prostheses.

The aim of this study was to evaluate the fatigue behavior of strength-graded zirconia polycrystals used as monolithic three-unit implant-supported prosthesis; complementarily, crystalline phase and micromorphology were also assessed. Fixed prostheses with 3 elements supported by 2 implants were confectioned, as follows: Group 3Y/5Y - monolithic structures of a graded 3Y-TZP/5Y-TZP zirconia (IPS e.max® ZirCAD PRIME); Group 4Y/5Y - monolithic structures of a graded 4Y-TZP/5Y-TZP zirconia (IPS e.max® ZirCAD MT Multi); Group Bilayer - framework of a 3Y-TZP zirconia (Zenostar T) veneered with porcelain (IPS e.max Ceram). The samples were tested for fatigue performance with step-stress analysis. The fatigue failure load (FFL), the number of cycles required until failure (CFF), and the survival rates in each cycle were recorded. The Weibull module was calculated and the fractography analyzed. The crystalline structural content via Micro-Raman spectroscopy and the crystalline grain size via Scanning Electron microscopy were also assessed for graded structures. Group 3Y/5Y showed the highest FFL, CFF, probability of survival, and reliability (based on Weibull modulus). Group 4Y/5Y showed significantly superior FFL and probability of survival than group bilayer. Fractographic analysis revealed catastrophic flaws in the monolithic structure and cohesive fracture of porcelain in bilayer prostheses, all originating from the occlusal contact point. The graded zirconia presented small grain size (≤0.61 µm), with the smallest values at the cervical region. The main composition of graded zirconia was of grains at tetragonal phase. The strength-graded monolithic zirconia, especially the 3Y-TZP/5Y-TZP, showed to be promising for use as monolithic three-unit implant-supported prosthesis.

Maintenance protocols for implant-supported dental prostheses: A scoping review.

STATEMENT OF THE PROBLEM: Biological complications of implant-supported prostheses remain a concern. Therefore, standardizing hygiene protocols to promote their maintenance is important. PURPOSE: The purpose of this scoping review was to identify available hygiene guidance for home care procedures, as well as periodicity and protocols for the professional maintenance of implant-supported prostheses. MATERIAL AND METHODS: This study was based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the study protocol was made available at: https://osf.io/5jdeh/. The search was last performed in the PubMed database on March 15, 2022 and was undertaken by 2 independent researchers. Clinical studies and reviews that evaluated home care and maintenance protocols for dental implant-supported prostheses (fixed or removable), without language restriction or year of publication, were included. A descriptive analysis was performed considering study characteristics (study design, restorative assembly, maintenance strategies, eligibility criteria, number of included studies, quality/level of evidence, and main findings). RESULTS: The initial search yielded 3138 studies, of which 18 were included for descriptive analysis (6 critical reviews, 4 clinical trials, 3 systematic reviews, 2 guideline reports, 2 retrospective studies, and 1 transversal study). The main instrument recommended for home care was the use of a conventional toothbrush associated with triclosan-containing toothpaste in addition to interproximal aids (brushes or floss) for all types of restorations. The use of irrigation instruments was also frequently considered. For professional maintenance, almost all studies reported a positive effect of regular recalls every 3 months during the first year, followed by less regular recalls according to the motivation of the patient and home care efficacy. At each recall, the professional should evaluate the patient history, oral tissues, implant, abutments, and restorations, as well as perform professional cleaning of the prostheses with appropriate instruments so that the implants and abutments may be preserved. CONCLUSIONS: Establishing an adequate hygiene protocol is indispensable for implant-supported restorations. To do so, the professional must guide and support the patient's home care by taking into account the patient's motivation and efficacy during the hygiene procedures. Also, for professional maintenance, the periodicity of recalls should be constant and include an evaluation of the condition of the restoration and adjacent tissues, followed by professional cleaning of prostheses, implants, and abutments, in addition to new instructions to improve patient home care.

Influence of connector cross-sectional geometry on the load-bearing capacity under fatigue of implant-supported zirconia fixed partial prosthesis.

STATEMENT OF PROBLEM: Zirconia has been reported to be suitable for multiunit monolithic restorations. However, as the connector region is the weakest part of the system, studies are needed to determine the optimal connector geometry. PURPOSE: The purpose of this in vitro study was to evaluate the load-bearing capacity under fatigue of implant-supported fixed partial prostheses made of monolithic zirconia with different connector cross-sectional geometries. MATERIAL AND METHODS: Three-unit monolithic fixed partial prostheses (from mandibular second premolar to the second molar) were fabricated in zirconia (Zenostar T) by computer-aided design and computer-aided manufacture (CAD-CAM). Different connector cross-sectional geometries, with an area of 9 mm2, were tested (n=10): round, square with rounded angles, or trapezoid with rounded angles. The prostheses were screwed over 2 implants and inserted into acrylic resin bases. The specimens were submitted to a mechanical fatigue test until failure, with load applied to the pontic using the stepwise stress methodology (initial load of 100 N for 5000 cycles, followed by an increase to 200 N for 20 000 cycles, with a subsequent increase of 50 N each step). For data analysis, fatigue failure load (FFL) and cycles for fatigue failure (CFF) were recorded. Failed structures were analyzed by fractography. The Kaplan-Meier test followed by a log-rank Mantel-Cox post hoc test was used to analyze FFL and CFF (α=.05). Weibull analysis was also performed. RESULTS: The round (1065 N) and trapezoid (1010 N) groups presented higher FFL values than the square one (870 N) (P≤.05). For CFF, the round connector (358 777) was better than the square (280 310) (P=.006), and the trapezoid (337 773) was statistically similar to both (P>.05). No difference among groups was observed in Weibull modulus either for CFF or FFL data. All failures were catastrophic, originating at the base of the connector and propagating toward the occlusal surface of the pontic (region under loading). CONCLUSIONS: The connector cross-sectional geometry significantly influenced the mechanical fatigue performance of implant-supported fixed partial prostheses made of monolithic zirconia.

Do preheated composite resin or adhesive resin layer strengthen the feldspar ceramic?

STATEMENT OF PROBLEM: Preheated composite resin and adhesive coating have been recommended as luting agents for ceramic veneers; however, information about the mechanical behavior of feldspathic porcelain veneers after using these methods is still limited. PURPOSE: The purpose of this in vitro study was to evaluate the influence of the use of preheated composite resin or an adhesive resin layer on the strengthening of a feldspathic porcelain. MATERIAL AND METHODS: Feldspathic porcelain disks were fabricated (N=210), etched (10% hydrofluoric acid for 90 seconds), and bonded according to resin-based luting agents (30 per group) for the biaxial flexural strength tests: photopolymerized resin cement, flowable composite resin, preheated composite resin, with or without previous adhesive coating. Characteristic strength and Weibull modulus were calculated. The viscosity of the luting agents was measured by using isothermal analyses. Finite element analysis simulated the flexural test. Fractographic and bonded interfaces were observed. RESULTS: The use of preheated composite resin led to the lowest stress levels in the feldspathic porcelain veneers. However, it did not increase the ceramic strengthening compared with other luting agents, as higher values were observed with flowable composite resin (P<.05). The use of an adhesive resin layer had no significant effect on ceramic strengthening when associated with preheated composite resin or resin cement (P>.05). Preheated composite resin presented the highest viscosity and led to incomplete filling of the porcelain surface irregularities. Failures originated on the ceramic surface subjected to tensile stress and were typically associated with pores at the ceramic-luting agent interface. CONCLUSIONS: The use of preheated composite resin or an adhesive resin layer did not have a positive effect on strengthening feldspathic porcelain.

Advances in Ceramics for Dental Applications.

The purpose of this study is to present current dental ceramic materials and processing methods. The clinical indication was emphasized on basis of the material's microstructure and composition. Studies of ceramic characterization were also discussed, as they impact the clinical indication and serve as a parameter for the development of new materials. The novel strategies were mostly found aiming to mimic the natural dental structures, provide mechanical reliability, and develop predictable restorations in terms of adaptation and design.

Masking ability of implant abutment substrates by using different ceramic restorative systems.

STATEMENT OF PROBLEM: Information regarding the masking ability of ceramic crowns over different implant abutment materials is scarce. PURPOSE: The purpose of this in vitro study was to evaluate the masking ability of different monolithic or bilayer ceramic materials with different thicknesses over substrates indicated for implant restorations by using opaque and translucent evaluation pastes. MATERIAL AND METHODS: Disk-shaped specimens, shade A1 (VITA Classic; Ø10×1.5 to 2.5 mm), of different ceramics (a bilayer system [yttria-stabilized zirconia infrastructure+porcelain veneer: Zir+Pc] and monolithic systems [lithium disilicate under low, medium, or high translucency: LtLD, MtLD, or HtLD, respectively, and a high-translucent yttria-stabilized zirconia: HtZir]) were made (n=4). The color difference (ΔE00) was assessed by using the CIEDE2000 formula and considering the different ceramic systems over 5 implant abutment materials (A1 shade Zir [Zir A1]; white Zir [White Zir]; A1 low-translucency lithium disilicate [LD]; polyetheretherketone [PEEK]; and titanium [Ti]) when using 2 different evaluation pastes (translucent or opaque). The control comparison was the restorative material positioned over the Zir A1 substrate with a translucent evaluation paste. Statistical analysis was made by using a 2-way ANOVA and Tukey post hoc tests (α=.05) for ΔE00 data considering the restorative material and luting agent factors as their association. Additionally, ΔE00 data were qualitatively analyzed considering the acceptability and perceptibility thresholds. The translucency parameter (TP00) of each restorative material was evaluated, and data were submitted to 1-way ANOVA and Tukey post hoc tests (α=.05). RESULTS: The most predictable masking ability was seen with Zir+Pc regardless of the evaluation paste used. Nevertheless, under 1.5-mm thickness, Zir+Pc did not adequately mask Ti (ΔE00>1.77). Most monolithic ceramics did not mask discolored substrates (PEEK or Ti, ΔE00>1.77). The exception was HtZir, which presented acceptable masking ability over PEEK at 2.5-mm thickness with both evaluation pastes (ΔE00<1.77). Regardless of the restorative material thickness, Zir+Pc showed the lowest (P<.05) TP00 values (TP00=3.45 at 1.5-mm thickness; TP00=2.00 at 2.5-mm thickness), and HtLD presented the highest (P<.05, TP00=23.50 at 1.5-mm thickness; TP00=13.36 at 2.5-mm thickness). HtZir showed similar TP00 to MtLD at 1.5-mm thickness and similar TP00 to Zir+Pc when used at 2.5-mm thickness (P>.05). CONCLUSIONS: Monolithic ceramics should be used with caution over discolored implant abutments. Bilayer systems (Zir+Pc) were the most predictable approach to adequately masking discolored substrates such as PEEK or Ti. An increased restoration thickness provided higher masking ability for all restorative materials tested.

Factors influencing the clinical performance of the restoration of endodontically treated teeth: An assessment of systematic reviews of clinical studies.

STATEMENT OF PROBLEM: How best to restore endodontically treated teeth is still unclear because many types of material and techniques are involved. PURPOSE: The purpose of this overview of systematic reviews of clinical studies was to assess the available evidence-based literature on the influence of associated clinical factors on the clinical performance (survival, failure rate, or success) of restored endodontically treated teeth. MATERIAL AND METHODS: PubMed, Scopus, and Web of Science were searched from inception until September 27, 2021, to identify systematic reviews. Two reviewers independently screened titles, abstracts, and full-text articles, and each reviewer extracted the data of half of the included studies. A single reviewer with an independent verifier completed the quality appraisal. A descriptive analysis of the collected data was made. RESULTS: A total of 36 systematic reviews fulfilled the inclusion criteria. The factors most assessed were the type of coronal restorative technique (n=22) and type of post (n=22). The results indicated that metal and fiber posts seem to present similar clinical performance, endocrowns could be a suitable restorative option, there is no evidence to confirm whether single crowns are better or worse than direct restoration, the maintenance of the coronal structure is a fundamental factor, and the ferrule effect is still a controversial topic. Most of the studies (n=30, 81%) presented a final Grading of Recommendations, Assessment, Development and Evaluations (GRADE) rating of "critically low." CONCLUSIONS: The post type does not appear to influence the clinical performance of restored endodontically treated teeth. However, conclusive evidence to suggest how different materials or techniques for restoring coronal tooth structure affect the clinical performance of such restorations, as well as the impact of the ferrule effect, is still lacking.

Dental displacement in complete dentures influenced by different flask types and polymerization cycles.

This study evaluated the dental displacement in dentures included in different flasks and processed by the Australian cycle modified or by microwave. Metal pins were placed on the teeth as reference for measurements: a) Incisal edge of maxillary and mandibular central incisors, buccal cusp of maxillary and mandibular vestibular first premolars, and mesiobuccal maxillary and mandibular cusps of second molars; b) Incisor to incisor, premolar to premolar and molar to molar; c) Left incisor to left molar and right incisor to right molar, and d) Vertical. Dentures were divided according to flasks (n=10): G1- Metal; G2- HH bimaxillary metal; G3-Microwaves; G4- HH bimaxillary microwaves. For G1 and G2, polymerization at 65ºC/30 min, flame quenched for 30 min, heating at 65ºC/30 min, boiling water for 1 h. For G3 and G4, microwave (20 min/140 W and 5 min/560 W). Comparator microscope with digital camera and analytical unit assessed the measurements before and after denture polymerization. The final distance was made subtracting the distance before the denture processing from the distance of the dental displacement after processing. The value of the difference was submitted to 2-way ANOVA, considering the flask type and denture type. Maxillary denture showed greater displacement when compared to mandibular denture. Flask types and interaction with denture types showed similar difference between before and after polymerization. In conclusion, displacement promoted by flask types in dentures cured by polymerization cycles promoted similar effect on the distance between teeth. Greater value for distance between teeth occurred for maxillary denture.

Effect of different surface treatments on optical, colorimetric, and surface characteristics of a lithium disilicate glass-ceramic.

OBJECTIVE: To evaluate the effect of surface treatments on optical, colorimetric, and surface characteristics of lithium disilicate glass-ceramic. MATERIALS AND METHODS: Specimens (n = 5, IPS e.max CAD) were randomly allocated to the following treatments: mirror-polished: SiC papers; as-cut: mimicking CAD-CAM milling; ground: 90-120 µm-grit diamond bur; ground polished: ground, finished (46-30 µm-grit diamond bur), polished (diamond cups, brush and diamond paste); ground glazed: ground, glazed; ground polished glazed: association of methods. CIELAB color coordinates were obtained by a spectrophotometer. CIEDE2000 color differences (ΔE00 ) and the translucency parameter (TP00 ) were calculated. Light transmittance was assessed with a colorimeter. Surface characteristics (topography and roughness) were analyzed. Statistical differences for each condition and outcome were detected using one-way ANOVA with Tukey's post-hoc test (α = 0.05). RESULTS: TP00 data show statistical reduction after grinding (p < 0.05), which was only restored with polishing (solely or with glazing). ΔE00 shows that grinding results in perceptible variations in color (above 0.81), which were restored after all post-processing protocols (exception to only glaze application in contact with a black background). Light transmittance data corroborated such performance. Polishing and glazing reduced roughness and improved surface topography. CONCLUSION: Grinding statistically increased roughness, reduced translucency, light transmittance through the ceramic, and resulted on color differences. On contrary, polishing (followed or not by glazing) reduced roughness and enhanced ceramic translucency and light transmittance. Glaze also reduced roughness, but it still presented reduced translucency. The positioning (facing up or down) of the ceramic treated surface influenced the considered outcomes. CLINICAL SIGNIFICANCE: Grinding with diamond burs results in a deleterious impact to the optical, colorimetric and surface characteristics of lithium disilicate ceramic. Thus, polishing (followed or not by glazing) is recommended for optical and topographical enhancements when lithium disilicate monolithic restorations require occlusal adjustments.

Layering of discolored substrates with high-value opaque composites for CAD-CAM monolithic ceramics.

STATEMENT OF PROBLEM: Severely discolored substrates have been shown to limit the use of computer-aided design and computer-aided manufacturing (CAD-CAM) ceramic blocks because they provide insufficient color masking. PURPOSE: The purpose of the in vitro study was to evaluate the effect of a layer of high-value opaque composite resin over discolored substrates to determine its masking ability with CAD-CAM ceramics. MATERIAL AND METHODS: Six ceramic groups (n=10) were tested. A bilayer group of zirconia and porcelain served as the control. The CAD-CAM monolithic groups were translucent zirconia, zirconia-reinforced lithium silicate, lithium disilicate, leucite-reinforced glass-ceramic, and feldspathic ceramic. Five substrates were used: A1 (used as reference), A3.5, C4, and coppery and silvery metals. The substrates were separated as nonlayered or layered (with flowable or restorative opaque composite resins). The tested luting agents were white, opaque, and A1. Color differences (ΔE00) were assessed with the CIEDE2000 formula. A 2-way ANOVA (α=.05) was used to detect significant differences in ΔE00 among the groups for each substrate. The results were compared with acceptability (1.77) and perceptibility (0.81) thresholds. RESULTS: The flowable composite resin layer associated with A1 luting agent ensured ΔE00 lesser the than perceptibility thresholdwith the use of CAD-CAM monolithic ceramics, with the lowest values for zirconia-reinforced lithium silicate in substrates A3.5 (0.53) and C4 (0.32) and for leucite-reinforced glass-ceramic for coppery (0.49) and silvery (0.81) substrates (P<.001). The same benefit was observed when zirconia and porcelain was tested over the silvery substrate. The absence of substrate treatment only provided ΔE00 lesser than the acceptability threshold with CAD-CAM ceramics for the A3.5 background. CONCLUSIONS: The application of a flowable opaque composite resin and the use of a shaded luting agent ensure masking with CAD-CAM monolithic ceramics.

Dental displacement in complete dentures influenced by different flask types and polymerization cycles

Abstract This study evaluated the dental displacement in dentures included in different flasks and processed by the Australian cycle modified or by microwave. Metal pins were placed on the teeth as reference for measurements: a) Incisal edge of maxillary and mandibular central incisors, buccal cusp of maxillary and mandibular vestibular first premolars, and mesiobuccal maxillary and mandibular cusps of second molars; b) Incisor to incisor, premolar to premolar and molar to molar; c) Left incisor to left molar and right incisor to right molar, and d) Vertical. Dentures were divided according to flasks (n=10): G1- Metal; G2- HH bimaxillary metal; G3-Microwaves; G4- HH bimaxillary microwaves. For G1 and G2, polymerization at 65ºC/30 min, flame quenched for 30 min, heating at 65ºC/30 min, boiling water for 1 h. For G3 and G4, microwave (20 min/140 W and 5 min/560 W). Comparator microscope with digital camera and analytical unit assessed the measurements before and after denture polymerization. The final distance was made subtracting the distance before the denture processing from the distance of the dental displacement after processing. The value of the difference was submitted to 2-way ANOVA, considering the flask type and denture type. Maxillary denture showed greater displacement when compared to mandibular denture. Flask types and interaction with denture types showed similar difference between before and after polymerization. In conclusion, displacement promoted by flask types in dentures cured by polymerization cycles promoted similar effect on the distance between teeth. Greater value for distance between teeth occurred for maxillary denture.

Resumo O objetivo neste estudo foi avaliar o deslocamento dental em próteses totais incluídas em diferentes tipos de muflas e polimerizadas pelo ciclo australiano ou por micro ondas. Pinos metálicos foram colocados nos dentes como pontos de referência para as medidas: a) Borda incisal dos incisivos centrais maxilares e mandibulares, cúspide vestibular dos primeiros pré molares maxilares e mandibulares e cúspides mésiovestibulares dos segundos molares maxilares e mandibulares; b) Distâncias látero-laterais incisivo a incisivo, pré-molar a pré-molar e molar a molar; c) Distâncias horizontais anteroposterior incisivo esquerdo a molar esquerdo e incisivo direito a molar direito, e d) Vertical. As próteses foram separadas de acordo com o tipo de mufla (n=20): G1- Metálica; G2-HH bi-maxilar metálica; G3- Micro-ondas; G4- HH bi-maxilar micro ondas. Ciclo de polimerização para G1 e G2, água a 65ºC por 30 minutos, aquecimento interrompido por 30 minutos, reaquecimento a 65ºC por 30 minutos, seguido de água fervente por 1 hora. Para G3 e G4, micro ondas (20 minutos a 140 W e 5 minutos a 560 W). As medidas foram avaliadas com microscópio comparador linear. A distância final entre os dentes foi obtida subtraindo o valor da distância antes do processamento da prótese do valor da distância resultante do deslocamento dentário após o processamento. A diferença obtida entre essas distâncias foi submetida à ANOVA de 2 fatores, considerando como variáveis tipo de mufla e tipo de prótese. A prótese maxilar apresentou maior deslocamento dental quando comparada à mandibular. Os tipos de muflas e a interação com os tipos de próteses mostraram movimentos dentais similares antes e depois da polimerização. Em conclusão, o deslocamento dental promovido por diferentes tipos de frascos em próteses curadas por diferentes ciclos de polimerização promoveu efeito semelhante na alteração da distância entre os dentes. Maior valor para a mudança de distância entre os dentes ocorreu na prótese maxilar.