Angiogenesis in bone tissue engineering via ceramic scaffolds: A review of concepts and recent advancements

Due to organ donor shortages, long transplant waitlists, and the complications/limitations associated with auto and allotransplantation, biomaterials and tissue-engineered models are gaining attention as feasible alternatives for replacing and reconstructing damaged organs and tissues. Among various tissue engineering applications, bone tissue engineering has become a promising strategy to replace or repair damaged bone. We aimed to provide an overview of bioactive ceramic scaffolds in bone tissue engineering, focusing on angiogenesis and the effect of different biofunctionalization strategies. Different routes to angiogenesis, including chemical induction through signaling molecules immobilized covalently or non-covalently, in situ secretion of angiogenic growth factors, and the degradation of inorganic scaffolds, are described. Physical induction mechanisms are also discussed, followed by a review of methods for fabricating bioactive ceramic scaffolds via microfabrication methods, such as photolithography and 3D printing. Finally, the strengths and weaknesses of the commonly used methodologies and future directions are discussed.

Efficacy of Biosilicate Glass-ceramic and Fluoride Varnish in the Treatment of Dentin Hypersensitivity-A Randomized Controlled Clinical Trial

OBJECTIVE

The objective of this study was to compare the efficacy of Biosilicate and Duraphat in the treatment of dentin hypersensitivity (DH).

METHODS AND MATERIALS

This clinical trial was conducted with young adults presenting DH. A visual analogue scale (VAS) was used to assess the level of pain, using volatile and tactile tests. Forty participants presenting two teeth with DH were included, and these teeth were divided into two groups according to the treatment: Biosilicate or Duraphat. Each product was randomly applied on one tooth per participant once a week for 4 weeks and evaluated every 15 days for 60 days after the last application.

RESULTS

The mean and standard deviation (SD) of VAS values for the initial volatile sensitivity evaluation were 6.18 (1.99) and 6.08 (1.98) for the Biosilicate and Duraphat groups, respectively, and at the fourth week 0.48 (1.5) and 0.83 (1.58). After 60 days, the volatile sensitivity showed the following values: 0.63 (1.19) for Biosilicate and 1.03 (1.07) for Duraphat. The intragroup comparison showed a significant reduction of mean VAS values for DH-related pain assessed by volatile testing for both groups (p<0.001), and the assessment at the 60-day follow-up showed mean values statistically similar to those obtained at the end of treatment. Initial tactile sensitivity observed was 1.48 (2.39) for the Biosilicate and 1.4 (2.2) for the Duraphat group and at the 60-day follow-up 0.23 (0.73) and 0.15 (0.36), respectively, with significant statistical difference (p<0.002). When the reduction in tactile and volatile sensitivities between both groups was compared, no statistically significant difference was observed.

CONCLUSION

This study indicated that both products were able to promote an important reduction in dentin hypersensitivity with similar results within a 60-day follow-up.

Efficacy of a novel dentifrice containing bioactive glass-ceramic for dentinal hypersensitivity: A double-blind randomized controlled trial in Chinese adults

OBJECTIVE

To assess the efficacy and safety of a toothpaste containing 7.5 % HX-BGC in combating dentinal hypersensitivity.

METHODS

A single-center, randomized, double-blind, three-group parallel-controlled design was employed, with Schiff Index and Yeaple Index as measurement indicators. The study evaluated the effectiveness of HX-BGC toothpaste, NovaMin toothpaste, and a negative control toothpaste without desensitizing agents. Eligible subjects underwent baseline examination after a 2-week washout period, and those meeting inclusion criteria and not meeting exclusion criteria entered the study. Participants were randomly assigned to use one of the three toothpastes. Follow-up examinations were conducted immediately after a single use and at 2, 4, and 6 weeks. Intra-group and inter-group comparisons were made for Schiff and Yeaple indices. Safety of the experimental toothpastes was assessed through participant feedbacks and oral soft tissue examinations.

RESULTS

Subjects in the three groups were balanced in terms of age and gender distribution, with no baseline differences in indicators. Immediately after a single application of toothpaste, Yeaple indices increased, and Schiff indices decreased, with no significant differences among the groups. After 2 weeks of continuous use, Yeaple indices increased in all groups, with significant differences observed between the HX-BGC group and the other two groups. Schiff indices decreased in all groups, with the NovaMin group showing significant differences compared to the negative control group. At weeks 4 and 6, both indices in the HX-BGC group and the NovaMin group were significantly better than those in the negative control group, with the HX-BGC group outperforming the NovaMin group in the Yeaple index. No serious adverse reactions related to the study products were observed or reported by any participants.

CLINICAL SIGNIFICANCE

This clinical trial confirmed the efficacy of HX-BGC in anti-dentinal hypersensitivity and supported the clinical application of the dentifrice containing HX-BGC.

CONCLUSION

Compared to the negative control group, both HX-BGC and NovaMin toothpaste groups demonstrated more significant effects in combating dentinal hypersensitivity. No adverse reactions related to the experimental toothpastes were observed.

Fatigue behavior of multilayer ceramic structures in traditional and reverse layering designs

PURPOSE

This study evaluated the fatigue failure load (FFL) and the number of cycles for fatigue failure (CFF) of traditional (porcelain layer up) and reversed (zirconia layer up) designs of porcelain-veneered zirconia samples prepared with heat-pressing or file-splitting techniques.

MATERIALS AND METHODS

Zirconia discs were prepared and veneered with heat-pressed or machined feldspathic ceramic. The bilayer discs were bonded onto a dentin-analog according to the bilayer technique and sample design: traditional heat-pressing (T-HP), reversed heat-pressing (R-HP), traditional file-splitting with fusion ceramic (T-FC), reversed file-splitting with fusion ceramic R-FC), traditional file-splitting with resin cement (T-RC), and reversed file-splitting with resin cement (R-RC). The fatigue tests were performed using the stepwise approach at 20 Hz, 10,000 cycles/step, step-size of 200 N starting at 600 N, and proceeding until failure detection or up to 2600 N if enduring. The failure modes (from radial and/or cone cracks) were analyzed in a stereomicroscope.

RESULTS

The reversed design decreased the FFL and CFF of bilayers prepared with heat-pressing and file-splitting with fusion ceramic. The T-HP and T-FC reached the highest results, which were statistically similar between them. The bilayers prepared by the file-splitting with resin cement (T-RC and R-RC) were similar to the R-FC and R-HP groups regarding FFL and CFF. Almost all reverse layering samples failed by radial cracks.

CONCLUSIONS

The reverse layering design did not improve the fatigue behavior of porcelain veneered zirconia samples. The three bilayer techniques behaved similarly when used in the reversed design.

Effect of the violet light from polywave light-polymerizing units on two resin cements that use different photoinitiators

STATEMENT OF PROBLEM

Some light-emitting diode polymerization lights have been promoted as multiple peak or polywave lights that use multiple light-emitting diodes to produce both violet and blue light. However, whether the addition of violet light is required to light-activate resin cements that use bis(4-methoxybenzoyl)diethylgermane (Ivocerin) as the photoinitiator is unclear.

PURPOSE

This in vitro study evaluated the effect of violet, blue, or a combination of violet and blue light through ceramic on the degree of conversion of 2 resin cements that use either camphorquinone or Ivocerin as the photoinitiator.

MATERIAL AND METHODS

A Bluephase Style polywave light-emitting diode polymerizing unit delivering 6.4 J/cm2 of violet and blue light was used. This comprised 1.4 J/cm2 of violet (385 to 420 nm) and 5.0 J/cm2 of blue light (420 to 515 nm). The light-emitting diode emitters in a second modified Bluephase Style were connected directly to a power supply so that either just violet (1.4 J/cm2) or just blue (5.0 J/cm2) light was emitted. RelyX Veneer and Variolink Esthetic LC resin cements were either directly light-activated or through 0.5 or 1.5 mm of lithium disilicate ceramic (IPS e.max CAD). The degree of conversion was monitored by using Fourier-transform infrared spectroscopy. Data were subject to a 3-way analysis of variance followed by the Tukey honest significant difference multiple comparison tests (α=.05).

RESULTS

All factors had a significant effect (P<.001). Increasing the ceramic thickness decreased the degree of conversion only for RelyX Veneer cement (P<.001). The effect of the thickness of ceramic was most noticeable when just violet light was delivered to RelyX Veneer. A significant reduction (P<.001) was found in the degree of conversion of RelyX Veneer when just violet light was delivered. Variolink Esthetic LC had significantly higher degree of conversion values than RelyX Veneer, irrespective of the light type used (P<.001).

CONCLUSIONS

A multiple-peak light is not required to photopolymerize a resin cement that uses either camphorquinone or Ivocerin as its photoinitiator. Adding the violet light produced no significant increase in the degree of conversion of the Variolink Esthetic LC cement.

Staining and bleaching susceptibility of zirconia-reinforced lithium silicate glass-ceramics with different thicknesses, translucencies, and fabrication methods

STATEMENT OF PROBLEM

The influence of different thicknesses, translucencies, and fabrication methods on the spectrophotometric and topographical properties of zirconia-reinforced lithium silicate glass-ceramics (ZLSs) for dental restorations remains unclear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of thicknesses, translucencies, and fabrication methods on the color stability, translucency parameter, opalescence parameter, whiteness stability, transmitted irradiance, light transmittance, opacity, gloss, and roughness of ZLSs exposed to coffee staining and bleaching treatments.

MATERIAL AND METHODS

Two pressable ZLSs (VITA AMBRIA, VA and Celtra Press, CP) and 2 machinable ZLSs (VITA Suprinity, VS and Celtra Duo, CD) were examined at high translucency (HT) and low translucency (LT) levels in 2 thicknesses (n=160). The specimens were evaluated at baseline, after coffee staining, and after bleaching. The color stability (ΔE2000), translucency parameter (TP), opalescence parameter (OP), whiteness index (WID), and whiteness stability (ΔWID) were measured with a spectrophotometer. Transmitted irradiance (It), light transmission (T), and opacity (O) were obtained from a light-polymerizing unit and a polymerization light collection device. Roughness stability (ΔSa%) was determined with an optical profilometer, and gloss stability (ΔGU%) was recorded with a gloss meter. Data of ΔCIE2000, ΔWID, ΔSa%, and ΔGU% were analyzed by 4-way ANOVA, and data of the TP, OP, WID, It, T, and O were analyzed by repeated 4-way ANOVA (α=.05).

RESULTS

VS-HT exceeded the ΔCIE2000 acceptability threshold after coffee staining and bleaching protocols. Pressable ZLSs exhibited greater color stability than machinable ZLSs. The 1-mm-thick VA, CP, and CD materials exceeded the ΔWID perceptibility threshold after bleaching. The highest TP and OP was displayed by the 1-mm-thick CP after bleaching. ΔGU increased after water storage and decreased after coffee staining and bleaching. ΔSa% significantly increased after bleaching (P<.05).

CONCLUSIONS

The color stability and other spectrophotometric properties of ZLSs depended on material thickness. The effects of ZLS fabrication methods and translucency levels on their measured properties were inconsistent. Subjecting 1-mm-thick ZLS materials to acidic media adversely impacted their stainability and surface texture.

Effect of surface finish and resin cement on the bond strength to CAD-CAM ceramics for interim resin-bonded prostheses

STATEMENT OF PROBLEM

Resin-bonded prostheses, including interim resin-bonded prostheses, are effective in preserving tooth structure compared with other types of fixed dental prostheses for the replacement of missing teeth. However, loss of retention remains a notable concern with these types of prostheses.

PURPOSE

The purpose of this in vitro study was to investigate the influence of glass-ceramic type, resin type, and surface finish on the shear bond strength (SBS) to the CAD-CAM ceramics used to fabricate interim resin-bonded prostheses.

MATERIAL AND METHODS

Eighty 10×2-mm glass-ceramic disks were fabricated by using a diamond saw (IsoMet 1000), 40 from feldspathic porcelain blocks (Vita Mark II) and 40 from lithium disilicate blocks (IPS e.max CAD). Half of the specimens in each group were left with a dull or matte surface finish after cutting, while the other half were glazed with an add-on glaze (VitaAkzento Plus Glaze Spray and IPS e.max CAD Glaze Spray, respectively). The disks were mounted in acrylic resin, and each group was subdivided into 2, with 1 receiving a photopolymerized resin cement (RelyX Veneer) and the other receiving a flowable composite resin (Filtek Supreme Ultimate Flow) to form 2.38×2-mm cylinders. SBS was determined using a universal testing machine (Instron 4411) in accordance with the International Organization for Standardization (ISO) 29022:2013 standard, and failure modes were analyzed by using a stereomicroscope with ×40 magnification. The data were analyzed with a 3-way analysis of variance and Tukey post hoc analysis. The chi-squared test was used to analyze the failure mode (α=.05 for all tests).

RESULTS

Ceramic type, resin type, and surface finish significantly impacted SBS (P<.001, P=.003, P<.001, respectively). Lithium disilicate showed higher SBS than feldspathic porcelain, and flowable composite resin exhibited higher SBS than resin cement. Glazed surfaces displayed lower SBS compared with the dull or matte surfaces. The combinations among the 3 materials also impacted SBS (P=.03). In addition, the combinations between ceramic type and surface finish affected SBS (P<.001), regardless of resin cement type. No other combinations affected the SBS (P>.05). The mode of failure was different among the groups (P<.001). In comparison with all other groups, cohesive failures were most prevalent in feldspathic porcelain with a dull or matte surface finish, regardless of the resin type used.

CONCLUSIONS

The SBS to glass-ceramics was influenced by ceramic material, resin cement type, and surface finish. Flowable composite resin showed higher SBS than resin cement. A dull or matte surface finish exhibited greater bond strength than a glazed surface. Lithium disilicate had higher SBS than feldspathic porcelain.

Effect of different intraoral scanning strategies on the marginal and internal fit of CAD-CAM inlay restorations: An in vitro study

STATEMENT OF PROBLEM

Whether the scanning strategy of intraoral scanners (IOSs) affects the accuracy of the digital recording for an indirect ceramic inlay restoration is unclear. Furthermore, which strategy would be optimal and most effective is uncertain.

PURPOSE

The purpose of this in vitro study was to evaluate the impact of 3 different scanning strategies using the Carestream CS 3700 IOS on the marginal and internal fit of a mesio-occluso-distal (MOD) ceramic inlay restoration.

MATERIAL AND METHODS

A typodont master model (ANA-4 VCER; Frasaco) was used with a standardized preprepared MOD inlay maxillary first molar typodont tooth (ANA-4 ZP16 CER99-008; Frasaco) (N=30). These inlay preparations were scanned with the CS 3700 IOS using 3 different scanning strategies: linear, wave, and S-figure scanning strategies. Each scan strategy group was scanned 10 times for all groups to obtain 30 standard tessellation language (STL) files. Thirty restorations were milled from lithium disilicate CAD blocks (IPS e.max; Ivoclar AG) and cemented into their typodont-prepared inlay cavities. A single examiner used a stereomicroscope to measure the marginal and internal gaps at the predetermined points. A 1-way ANOVA was used for the statistical analysis, followed by the Tukey post hoc test with Bonferroni adjustment. All tests were 2-tailed (α=.05).

RESULTS

All scanning strategy groups demonstrated statistically significant differences for the marginal and internal fit of the inlay restorations (P<.001). Overall, the linear scanning strategy showed the lowest mean marginal and internal gap values (29.2 ±3.6 µm and 39.0 ±6.4 µm), followed by the wave scanning strategy, which had comparable mean marginal and internal gap values: 49.1 ±3.6 µm and 48.2 ±6.0 µm, respectively. The S-figure scan strategy had the highest mean marginal and internal gap values: 50.2 ±12.6 µm and 71.3 ±7.7 µm, respectively.

CONCLUSIONS

Inlay restorations scanned by the linear scan strategy had the best marginal and internal fit when scanned with the CS 3700 IOS.

Fracture strength of ceramic overlays with immediate dentin sealing and same-day delivery

Limited research is available evaluating whether the reported in vitro benefit of immediate dentin sealing (IDS)-namely, increased bond strength to tooth structure-can be acquired in the era of same-day (SD) dentistry. The purpose of this study was to compare the fracture strengths of ceramic overlays fabricated with a delayed dentin sealing (DDS) technique or an IDS technique under 1-hour SD or 2-week multiple-day (MD) delivery conditions. Forty extracted, healthy maxillary third molars were prepared for a lithium disilicate overlay restoration and divided into 4 groups of 10 teeth each. In the SD-DDS group, the teeth were prepared and then stored for 1 hour in artificial saliva, and the adhesion protocol (bonding agent and resin cement) was applied at the time of delivery of the ceramic overlay. In the SD-IDS group, the teeth were prepared, the adhesive protocol was applied immediately, and the teeth were stored for 1 hour before delivery of the overlay. The protocols for the MD-DDS and MD-IDS groups were identical to SD-DDS and SD-IDS, respectively, except that the teeth were provisionalized and stored for 2 weeks prior to delivery of the overlay. Specimens were thermocycled and subjected to cyclic functional loading before they were loaded to failure in a universal testing machine using a rod resting on the buccal incline of the palatal cusp. Two-way analysis of variance tests revealed no statistically significant differences in fracture strength between the groups based on dentin sealing (P = 0.331) or delivery time (P = 0.314). The specimens demonstrated 2 fracture types; either a portion of the ceramic cohesively fractured, leaving the tooth intact, or the ceramic and part of the tooth fractured. There were no instances in which the restoration itself delaminated during fracture testing. A Kruskal-Wallis test indicated there were no statistically significant differences in fracture modes between the groups. In this in vitro study, IDS did not provide a significant increase in the fracture strength of overlay restorations compared with DDS, regardless of whether the restorations were delivered the same day or after 2 weeks of storage.

Effect of universal adhesives and self-etch ceramic primers on bond strength to glass-ceramics: A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

To simplify dental procedures, multicomponent products such as universal adhesives and self-etch ceramic primers have been recommended for glass-ceramic bonding; however, studies have shown a wide range of results.

PURPOSE

The purpose of this systematic review and meta-analysis was to analyze the in vitro bond strength promoted by hydrofluoric acid+silane-containing universal adhesives and a self-etch ceramic primer to glass-ceramics and compare it with that of conventional treatments.

MATERIAL AND METHODS

A systematic search was conducted in the PubMed/Medline, Scopus, LILACS, and ISI Web of Science databases up to April 2021. In vitro studies assessing the resin-mediated bond to glass-ceramics by using a self-etch ceramic primer and hydrofluoric acid+silane-containing universal adhesives and/or compared with traditional hydrofluoric acid+glass-ceramic primers were included. Selection of studies, data extraction, and risk-of-bias analysis were performed. Statistical analysis was performed by using a review management software program using a random effects model (α=.05).

RESULTS

A total of 33 studies were included in the qualitative analysis and 26 studies in the quantitative analysis. Bond strength to lithium disilicate ceramic was higher when a hydrofluoric acid+glass-ceramic primer was used than when using a hydrofluoric acid+silane-containing universal adhesive (P<.05), except when 9% to 10% acid concentration was used in combination with static aging (P=.100). A self-etch ceramic primer promoted bond strength values to lithium disilicate that were similar to those of the hydrofluoric acid+glass-ceramic primer (P>.100).

CONCLUSIONS

Hydrofluoric acid+silane-containing universal adhesive was not as effective as the hydrofluoric acid+glass-ceramic primer in promoting bond strength to glass-ceramic. Bond strength values generated by a self-etch ceramic primer to glass-ceramic were similar to those generated by the conventional treatment.

Drug eluting bioactive glass ceramics for fusion in spondylodiscitis: a pilot study

Retrospective observational study. To determine the efficacy and safety of bioactive glass ceramics mixed with autograft in the treatment of spondylodiscitis. Thirty-four patients with spondylodiscitis underwent surgery using autologous bone graft augmented by antibiotic loaded bioactive glass ceramic granules. Twenty-five patients aging 6 to 77, completed 1-year follow-up. The lumbosacral junction was affected in 3, lumbar spine in 13, one each in the dorso-lumbar junction and sacrum, and 7 dorsal spines. The organism isolated was Mycobacterium tuberculosis in 15, Methicillin sensitive Staphylococcus aureus (MSSA) in 4, Pseudomonas aeruginosa in 4, Klebsiella pneumoniae in one, Burkholderia pseudomallei in 1, and mixed infections in 2. All patients had appropriate antibiotic therapy based on culture and sensitivity. Clinical and radiological evaluation of all the patients was done at 6 weeks, 3 months, 6 months, and 12 months after the surgery. Twenty-three patients improved clinically and showed radiographic fusion between 6 and 9 months. The patient with Burkholderia infection died due to fulminant septicemia with multi organ failure while another patient died at 9 months due to an unrelated cardiac event. The mean Visual Analogue Score (VAS) at the end of 1-year was 2 with radiological evidence of fusion in all patients. There were no re-infections or discharging wounds, and the 30-day re-admission rate was 0. Bioactive glass ceramics is a safe and effective graft expander in cases of spondylodiscitis. The absorption of antibiotics into the ceramic appears to help the elimination of infection.

Fatigue and failure analysis of restored endodontically treated maxillary incisors without a dowel or ferrule

STATEMENT OF PROBLEM

Information on the survival and mode of failure of endodontically treated incisors without a ferrule and restored without dowels is lacking.

PURPOSE

The purpose of this in vitro study was to compare the survival and failure mode of endodontically treated incisors without a ferrule and restored with bonded ceramic crowns and various composite resin foundation restorations without dowels with a control group with fiber dowels.

MATERIAL AND METHODS

Forty-five decoronated endodontically treated bovine incisors without ferrule were divided into 3 experimental groups and restored with different adhesive foundation restorations without dowel: nanohybrid composite resin (Nd), bulk-fill composite resin foundation restoration (NdB), and fiber-reinforced bulk-fill composite resin (NdFR). A control group with conventional foundation restorations (glass-fiber dowel with nanohybrid composite resin foundation restoration without ferrule) (D) was included for comparison. All teeth were prepared to receive bonded lithium disilicate ceramic crowns luted with dual-polymerizing composite resin cement and were subjected to accelerated fatigue testing. Cyclic isometric loading was applied to the incisal edge at an angle of 30 degrees and a frequency of 5 Hz, beginning with a load of 100 N (5000 cycles). A 100-N load increase was applied each 15 000 cycles. Specimens were loaded until failure or to a maximum for cycles endured of 1000 N (140 000 cycles). Groups were compared by using the Kaplan-Meier survival analysis (log rank test at α=.05 and pairwise post hoc comparisons) and life table analysis for load-at-failure (followed by Wilcoxon pairwise comparison α=.05).

RESULTS

All the specimens failed before 140 000 load cycles. Even though no statistically significant differences were found between the experimental groups without dowel (P>.127), the fiber-reinforced foundation restoration yielded the highest mean ±standard deviation cycles to failure (46 023 ±4326) compared with Nd (38 899 ±2975) and NdB (39 751 ±2998). NdFR, however, outperformed the foundation restoration with glass-fiber dowel (35 026 ±2687) (P<.05). Most failure in groups without dowel were restorable, while 100% of catastrophic failure (unrestorable) were found in the group with dowels.

CONCLUSIONS

Based on the present in vitro study, dowels did not improve the performance of the adhesive restoration of endodontically treated incisors without a ferrule. The use of a short fiber-reinforced composite resin foundation restoration without a dowel was able to not only improve the resistance of the restorations compared with adhesive foundation restorations with dowels but also minimize catastrophic failures.

Effect of different endodontic access preparations on the biomechanical behavior of lithium disilicate and resin nanoceramic onlay restorations: An in vitro and 3D finite element analysis study

STATEMENT OF PROBLEM

The effect of different sizes of endodontic access preparations on the performance of lithium disilicate glass-ceramic and resin nanoceramic onlay restorations is unclear.

PURPOSE

The purpose of this in vitro and 3D finite element analysis study was to assess the effect of a conservative endodontic access cavity and a traditional endodontic access cavity on the fracture resistance and stress distribution of lithium disilicate glass-ceramic and resin nanoceramic onlays.

MATERIAL AND METHODS

Sixty caries-free human mandibular molars were anatomically prepared for onlays and divided into 6 groups. After restoration with a lithium disilicate glass-ceramic (N=30) or resin nanoceramic (N=30), each material was further divided into traditional or conservative endodontic access cavity or intact tooth groups. After endodontic therapy and thermocycling, all specimens were submitted to a cycle fatigue test and then loaded until fracture. Failure type and location after debonding or fracture were classified and recorded. Furthermore, stress distribution in the 6 models was analyzed by using a finite element analysis software program. The data were compared by using a 2-way ANOVA test and the Tukey post hoc test (α=.05). The Weibull modulus and Weibull failure probabilities were also estimated for each group.

RESULTS

The lithium disilicate glass-ceramic onlays had lower fracture resistance values than the resin nanoceramic onlays in both the traditional and conservative endodontic access cavity groups (P<.05). The fracture resistance of the 2 materials for onlays with endodontic access was significantly lower than that for the intact restorations (P<.05). No significant difference was found between the fracture resistance of Lava Ultimate restorations with traditional endodontic access and conservative endodontic access, while the fracture resistance of EMAX restorations with traditional endodontic access was significantly lower than that of restorations with conservative endodontic access (P<.05). A higher percentage of irreparable fractures was found in the 3 resin nanoceramic restoration groups. The von Mises stresses were higher in the lithium disilicate glass-ceramic restorations than in the resin nanoceramic restorations with the same access cavities. The von Mises stresses in the tooth structure were higher with the resin nanoceramic restorations than with the lithium disilicate glass-ceramic restorations with the same access cavities.

CONCLUSIONS

An endodontic access cavity had more influence on the lithium disilicate glass-ceramic onlays than on the resin nanoceramic onlays, and a traditional endodontic access cavity significantly decreased the fracture resistance of lithium disilicate glass-ceramic onlays.

Efficacy of two polishing systems in reestablishing the surface smoothness of posterior monolithic lithium disilicate restorations: One-year results of a split-mouth randomized controlled clinical trial

STATEMENT OF PROBLEM

Selecting the optimal polishing procedure to reestablish surface smoothness after occlusal adjustment is essential for the long-term success of glass-ceramic restorations. While in vitro studies have shown different effective polishing protocols, clinical trials are lacking.

PURPOSE

The purpose of this split-mouth controlled clinical trial was to evaluate the effectiveness of 2 polishing systems in reestablishing the surface smoothness of posterior monolithic lithium disilicate ceramic restorations.

MATERIAL AND METHODS

Ninety-six restorations that required occlusal adjustment after bonding were randomized into 2 groups: Forty-eight restorations were polished by using the Exa Cerapol polishing kit, and the other 48 restorations were polished by using the Shofu polishing kit. The restorations were replicated with epoxy resin at 3 study times-after bonding (t1), after occlusal adjustment (t2), and after polishing (t3)-for quantitative roughness analysis (Ra). Representative specimens from each group were qualitatively analyzed by using a confocal laser microscope. Clinical analyses were performed after the polishing procedure and at 30, 180, and 365 days after the polishing procedure by following the United States Public Health Service (USPHS) criteria. ANOVA and the Tukey multiple comparisons parametric tests were computed (α=.05). The Kaplan-Meier test was used to analyze the survival rate of restorations.

RESULTS

No statistically significant difference was found between the Exa Cerapol and Shofu groups (P=.086). A statistically significant difference was found between study times t1 and t2 and between t2 and t3 (both P<.001) in both experimental groups. No statistically significant difference was found between study times t1 and t3 (P=.181) in either experimental group. For the clinical criterion "integrity of restorations," all the elements analyzed indicated an alfa grade at all study times. The survival rate of the restorations was 100%.

CONCLUSIONS

Both polishing kits were effective in reestablishing the surface smoothness of restorations after occlusal adjustment.

Marginal and internal fit of porcelain laminate veneers: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Marginal integrity and internal adaptation are key to the long-term success of porcelain laminate veneers. Evidence for their marginal and internal fit is unclear, and the factors affecting such fit have not been identified.

PURPOSE

The purpose of this systematic review and meta-analysis was to summarize the scientific literature assessing the effects of various parameters on the marginal and internal fit of porcelain laminate veneers.

MATERIAL AND METHODS

An electronic search was conducted to identify all relevant published articles on the fit accuracy of ceramic veneers between January 2000 and June 2021 in the PubMed-MEDLINE, Scopus, Embase, Google Scholar, and Web of Science databases. Information, including the study outcomes, in terms of the mean marginal gap, internal gap, and absolute marginal discrepancies of porcelain laminate veneers, was extracted from the selected studies. The inverse-variance random effects model was used to analyze the pooled results and estimate the overall effect based on the heterogeneity of studies (α=.05).

RESULTS

Twenty-one studies were selected for analysis, 2 clinical and 19 in vitro. The risk of bias was "medium" for most studies (19 of 21), and only 2 studies were classified as "high risk." A mean difference of -4.53 μm (95% CI: -21.46 to 12.41) was found, with no statistically significant difference in marginal gap between the pressed and milled fabrication modes (P=.600). As for the internal gap, significant differences were found (mean difference=-40.56 μm; 95% CI: -76.54 to -4.58), with pressed veneers performing better (P=.030). Butt joint preparation design produced significantly (P=.002) lower marginal gaps than the palatal chamfer (mean difference=-14.02 μm; 95% CI: -23.07 to -4.98).

CONCLUSIONS

No significant differences were found between the pressed and milled porcelain laminate veneers for marginal gap, but for the internal gap, the differences were significantly in favor of the pressed type. The butt joint veneer preparation design was significantly better than the palatal chamfer design in terms of marginal fit.

Long-term clinical outcome of three-unit fixed-fixed posterior zirconia ceramic inlay-retained FDPs with a modified design

OBJECTIVES

To assess the long-term clinical outcome of posterior inlay-retained fixed dental prostheses (IRFDPs) with a modified design made from zirconia ceramic.

METHODS

In 30 patients thirty 3-unit IRFDPs were placed to replace 7 premolars (4 in the maxilla, 3 in the mandible), and 23 first molars (15 in the maxilla, 8 in the mandible). Preparations were accomplished in agreement with the general principles for ceramic inlay restorations and modified with a short retainer-wing bevel preparation within the enamel at the buccal and oral sides. The frameworks were milled from 3Y-TZP ceramic, and the pontics were veneered with feldspathic ceramic. All IRFDPs were bonded with a phosphate monomer containing luting resin after air-abrasion of the intaglio surfaces. The patients were recalled 6-12 months after placement, and then annually. Kaplan-Meier analysis was used to calculate the survival and complication rates of the IRFDPs.

RESULTS

The mean observation time was 10.6 ± 1.5 years. The 10-year cumulative survival rate was 89% with 4 failures, two of them were due to deep secondary caries with loss of retention, one due to repeated debonding with enamel fractures, and one due to generalized progressive periodontitis. The most common complication was chipping of the veneering ceramic (20.1%). Eighteen IRFDPs were free of any type of complication up to 15.4 years, which corresponds to a 10-year cumulative success rate of 70.4%.

CONCLUSION

The long-term clinical performance of modified IRFDPs made of veneered zirconia ceramics was favorable after 10 years, therefore, they represent a treatment alternative to replace posterior single missing teeth.

CLINICAL SIGNIFICANCE

Zirconia-based IRFDPs fabricated in the modified design may represent a substance-preserving alternative to conventional posterior FDPs to replace posterior single missing teeth, particularly in cases where implants cannot be placed, and when the adjacent teeth already have small restorations or defects.

Effect of milled and lithography-based additively manufactured zirconia (3Y-TZP) on the biological properties of human osteoblasts

STATEMENT OF PROBLEM

Lithography-based additively manufactured (AM) zirconia has been used to fabricate dental implants and custom barriers for guided bone regeneration procedures. However, studies on the effect of AM zirconia on the biological properties of human osteoblasts are lacking.

PURPOSE

The purpose of this in vitro study was to compare the effect of milled and lithography-based AM zirconia on the biological properties of normal human osteoblasts (NHOsts), as well as to compare the chemical composition between the milled and lithography-based AM 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) zirconia.

MATERIAL AND METHODS

Three mol percentage yttria-stabilized tetragonal zirconia polycrystal disks (Ø6×2-mm) were fabricated using subtractive milling (Priti multidisc ZrO2 monochrome) (M group) and lithography-based additive manufacturing methods (LithaCon 3Y 210) (AM group) (n=10). NHOsts were exposed to different material extracts (1:1, 1:2, and 1:4) and cytotoxicity, cell migration, cell morphology, and cell attachment biological tests were completed. Additionally, for morphological and chemical analysis, a scanning electronic microscopy with energy-dispersive X-ray analysis (SEM/EDX) evaluation was completed. Data were analyzed by using 1-way ANOVA and the Dunnett test (α=.05).

RESULTS

Substantial cell attachment and spreading were observed in both material surfaces. The presence of zirconium was evident in both groups, although the percentage of zirconium in the AM group (64.7%) was slightly higher than in the M group (52.6%). When NHOsts were cultured in the presence of the different material eluates, the M and AM groups exhibited similar NHOst viability and migration rates when compared with untreated cells; no significant differences were found (P>.05).

CONCLUSIONS

The lithography-based AM zirconia tested showed adequate cytocompatibility without differences when compared with the milled zirconia (M group) specimens. Slight chemical element composition differences were found between milled and lithography-based AM zirconia.

Effect of mouth rinses on the stainability of monolithic lithium disilicate glass-ceramics with different surface treatments: An in vitro study

STATEMENT OF PROBLEM

Mouth rinses have been reported to cause tooth surface discoloration. However, information regarding their effect on the stainability of monolithic glass-ceramics with different surface treatments is lacking.

PURPOSE

The purpose of this in vitro study was to assess the effect of mouth rinses on the color change of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments.

MATERIAL AND METHODS

Fifty-six Ø12×1.5-mm disk specimens were fabricated using 2 different processing techniques: milling and pressing. Each group was subdivided into 2 subgroups according to surface treatments: glazed and polished. Specimens were then immersed in 2 different types of mouth rinse (n=7): chlorhexidine (CHX) and Listerine (LST). Color parameters were assessed using a digital spectrophotometer. Color difference (ΔE00) was calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds. The data were analyzed using ANOVA and Tukey post hoc tests (α=.05).

RESULTS

The color difference (ΔE00) was significantly affected by the type of processing technique, surface treatment, and mouth rinse (P<.001) and their interaction (P=.008). All ΔE00 values were below the selected clinical acceptability threshold (ΔE00=1.8). Milled groups (ΔE00=1.13) showed greater discoloration than pressed groups (ΔE00=0.86). Glazed specimens (ΔE00=0.70) were more resistant to discoloration than polished specimens (ΔE00=1.28) and immersion in CHX (ΔE00=1.09) led to more discoloration than immersion in LST (ΔE00=0.89).

CONCLUSIONS

The color of milled and pressed monolithic lithium disilicate glass-ceramics with different surface treatments was affected by using CHX and LST mouth rinses. Glazed lithium disilicate glass-ceramics showed less staining compared with those that were polished. Specimens immersed in CHX showed more discoloration than those immersed in LST.

The Effect of Colloidal Silica and Glaze Coatings on the Adhesion of Zirconia with Various Ytrria Concentration

PURPOSE

This study evaluated the effect of coating traditional and translucent Y-TZP with an industrial nanometric colloidal silica or glaze before or after sintering on the adhesion of zirconia with various ytrria concentration.

MATERIALS AND METHODS

Specimens of Y-TZP with 3% and 5% yttria were subdivided into 5 groups (n=10), according to the coating applied and moment of application (before or after Y-TZP sintering): Control (no coating), Colloidal Silica/Sintering, Sintering/Colloidal Silica, Glaze/Sintering, Sintering/ Glaze. Lithium disilicate (LD) was used as positive control. Except for Y-TZP controls, groups were conditioned with silane before cementation with a self-adhesive resin cement. After 24 hours, the shear bond strength and failure analysis were performed. Also, analysis of specimens' surface was accomplished with SEM-EDX. Kruskal-Wallis and Dunn tests were applied to analyze differences between groups (p⟨0.05).

RESULTS

Overall, the worst and best values of shear bond strength test were control and glaze after sintering groups. Different morphological and chemical aspects were observed in SEM-EDX analysis.

CONCLUSIONS

Coating Y-TZP with colloidal silica showed unsatisfactory results. In 3Y-TZP, the surface treatment associated with the best adhesion values was the application of glaze after zirconia sintering. However, in 5Y-TZP, glaze application can be performed before or after the zirconia sintering to optimize clinical steps.

Different surface treatment strategies on etchable CAD-CAM materials: Part 1-Effect on the surface morphology

STATEMENT OF PROBLEM

Polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials have either a high content of ceramic filler particles or a ceramic network structure. Proper etching of these materials is challenging. Therefore, it is relevant to assess different surface etching strategies and morphological alterations as a result of these techniques.

PURPOSE

The purpose of this 2-part in vitro study was to evaluate different etching strategies on the surface roughness and its relationship to the surface contact angle with a subsequent morphological characterization of different CAD-CAM materials.

MATERIAL AND METHODS

Two CAD-CAM polymer-based materials and 1 CAD-CAM ceramic material were selected for this study. The materials were treated with different strategies, including a combination of airborne-particle abrasion and an application of 9% hydrofluoric acid etching. After the surface treatment, roughness measurements (Sa) were assessed by using an optical profilometer on an area of 1.47 mm2. Subsequently, the contact angle on the surface was examined by means of the sessile drop technique and an optical contact angle meter. The data were analyzed by using a 2-way analysis of variance, the post hoc Tukey test (α=.05), and the Pearson correlation coefficient.

RESULTS

The 3 materials tested showed an increase in surface roughness when treated with surface airborne-particle abrasion. However, the materials with polymer in their composition concomitantly increased the contact angle. More hydrophilic surfaces were observed when hydrofluoric acid was applied, regardless of the composition of the materials. The surface roughness presented a strong positive linear tendency in the surface treatments used.

CONCLUSIONS

The application of airborne-particle abrasion on the surface of the polymer-based CAD-CAM materials increased the roughness and contact angle. However, the application of acid etching after the airborne-particle abrasion decreased the contact angle for polymer-based CAD-CAM materials, resulting in considerable enhancement of the surface quality for proper bonding.

Different surface treatment strategies on etchable CAD-CAM materials: Part II-Effect on the bond strength

STATEMENT OF PROBLEM

Bonding to recently launched polymer-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials has been challenging. Evidence regarding etching strategies for dual-phase CAD-CAM materials is sparse, but adequate bonding is crucial for the clinical success and longevity of a restoration.

PURPOSE

The purpose of this 2-part in vitro study was to evaluate and compare the effect of surface treatment strategies on the microshear bond strength and work of adhesion of polymer-based and ceramic materials. In addition, chemical elements present on the surface and the interface morphology after using those strategies were also assessed.

MATERIALS AND METHODS

Two CAD-CAM polymer and 1 CAD-CAM ceramic materials were selected for this in vitro study. The materials were subjected to different surface treatment strategies, including airborne-particle abrasion and the application of 9% hydrofluoric acid. Specimens were submitted to microshear bond strength before and after thermocycling, and the failure mode was classified. The work of adhesion was calculated based on the water-to-air surface tension of 72.8 mN.m-1 and the Young- Dupré equation. The surfaces were submitted to energy-dispersive X-ray spectroscopy, and the interfaces were analyzed using a scanning electron microscope. Data were subjected to 2-way ANOVA and the Tukey post hoc test (α=.05).

RESULTS

The highest microshear bond strength means were observed for the polymer-based materials when hydrofluoric acid or airborne-particle abrasion was applied. The 3 materials tested showed a decrease in microshear bond strength after thermocycling, except for applying airborne-particle abrasion to 1 of the polymer-based material tested. The ceramic material tested showed a high microshear bond strength with the application of airborne-particle abrasion and hydrofluoric acid combined. The work of adhesion varied across the materials and presented high means when hydrofluoric acid was used.

CONCLUSIONS

A combination of airborne-particle abrasion plus hydrofluoric acid should be considered for polymer-based or feldspathic ceramic CAD-CAM materials. In this in vitro study, both etching procedures combined produced higher bonding values for all materials tested.

Printed Digital Wax-up Model as a Blueprint for Layered Pressed-ceramic Laminate Veneers: Technique Description and Case Report

This article presents a clinical technique for transferring Digital Smile Design (DSD) information and a digital wax-up to fabricate highly personalized ceramic laminate veneers. The hybrid workflow of digitally designed wax-up and conventional hand-crafted veneers is showcased in a female adult who sought to improve her smile due to maxillary anterior incisal wear. The ceramic veneers, layered by feldspathic porcelain, followed the contours and shade blueprint planned with the digital wax-up. The DSD improved the harmony of the facial-and-smile relationship, and the ceramic restorations fulfilled the patient's esthetic and functional demands. Guides based on the printed model with the digitally designed wax-up can provide a reference for pressed lithium disilicate veneers layered with feldspathic porcelain.

Oxygen-Deficient Bioceramics: Combination of Diagnosis, Therapy, and Regeneration

The journey of ceramics in medicine has been synchronized with an evolution from the first generation-alumina, zirconia, etc.-to the third -3D scaffolds. There is an up-and-coming member called oxygen-deficient or colored bioceramics, which have recently found their way through biomedical applications. The oxygen vacancy steers the light absorption toward visible and near infrared regions, making the colored bioceramics multifunctional-therapeutic, diagnostic, and regenerative. Oxygen-deficient bioceramics are capable of turning light into heat and reactive oxygen species for photothermal and photodynamic therapies, respectively, and concomitantly yield infrared and photoacoustic images. Different types of oxygen-deficient bioceramics have been recently developed through various synthesis routes. Some of them like TiO2- x , MoO3- x , and WOx have been more investigated for biomedical applications, whereas the rest have yet to be scrutinized. The most prominent advantage of these bioceramics over the other biomaterials is their multifunctionality endowed with a change in the microstructure. There are some challenges ahead of this category discussed at the end of the present review. By shedding light on this recently born bioceramics subcategory, it is believed that the field will undergo a big step further as these platforms are naturally multifunctional.

Effect of superspeed sintering on translucency, opalescence, microstructure, and phase fraction of multilayered 4 mol% yttria-stabilized tetragonal zirconia polycrystal and 6 mol% yttria-stabilized partially stabilized zirconia ceramics

STATEMENT OF PROBLEM

The optical properties of recently developed multilayer zirconia have mainly been studied for the effects of conventional sintering and speed sintering but not as much for the effect of superspeed sintering. As superspeed sintering protocols typically require a higher sintering temperature and higher heating and cooling rates than speed- and conventional sintering protocols, the optical properties of superspeed sintered zirconia may be affected differently.

PURPOSE

The purpose of this in vitro study was to investigate the effect of superspeed sintering on the optical properties, microstructure, and phase fraction of multilayered 4 mol% yttria-stabilized (4Y-) and 6 mol% yttria-stabilized (6Y-) zirconia.

MATERIAL AND METHODS

Multilayered 4Y- and 6Y-zirconia were sectioned. After conventional and superspeed sintering, the translucency parameter (TP), and opalescence parameter (OP) were measured with a spectrophotometer (n=10). To obtain the grain sizes from the field emission scanning electron microscopy (FE-SEM) images for each layer (n=2), more than 500 (6Y-zirconia) and 800 grains (4Y-zirconia) were measured by linear intercept methods. The phase fractions were obtained through X-ray diffraction (XRD) analysis by using the Rietveld method (n=1). The results were analyzed by 3-way ANOVA and post hoc Tukey honest significant difference tests (TP and OP) and by 3-way ANOVA and post hoc Scheffé tests (grain size) (α=.05).

RESULTS

No layers exhibited a significant difference in TP after superspeed sintering, except the dentin layer (DL) and transition layer 2 (T2) of 4Y- and 6Y-zirconia, respectively. The TP increased (P<.05) in DL for superspeed sintered 4Y-zirconia and decreased (P<.05) in T2 for the superspeed sintered 6Y-zirconia. However, the difference in TP by superspeed sintering was lower than the perceptibility thresholds of 50:50%. The OP decreased (P<.05) in the DL and T2 of 4Y-zirconia after superspeed sintering. For 6Y-zirconia, the OP decreased (P<.05) in all layers except for the transition layer 1 (T1) after superspeed sintering. However, the difference in OP values was minimal, with only a 1.1 difference observed for Zolid Gen-X (4Y) and a range of 1.22 to 1.62 for Katana UTML (6Y) when using superspeed sintering. No significant change was found in the grain size after superspeed sintering of either zirconia. Regardless of the sintering speed, the average grain size of the 6Y-zirconia (conventional: 2.09 to 2.21 μm; superspeed: 2.11 to 2.20 μm) was larger than that of the 4Y-zirconia (conventional: 0.50 to 0.52 μm; superspeed: 0.52 to 0.54 μm). Owing to superspeed sintering, the metastable tetragonal (T') phase content increased while the tetragonal (T) phase decreased in 4Y-zirconia; in 6Y-zirconia, the cubic (C) phase content increased, while the T'-phase content decreased.

CONCLUSIONS

Superspeed sintering did not result in any clinically significant changes in the translucency and opalescence of 4Y- or 6Y-zirconia.

Influence of piston material on the fatigue behavior of a glass-ceramic

STATEMENT OF PROBLEM

The lack of standardization regarding the loading piston material used in fatigue tests could limit the interpretation of study findings.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of the piston material on the fatigue behavior of a lithium disilicate glass-ceramic.

MATERIAL AND METHODS

Plate-shaped, 1.2-mm-thick, lithium disilicate glass-ceramic specimens were cemented onto a dentin analog substrate with resin cement. The specimens were divided into 4 groups according to the piston material used in the fatigue test (n=30): metal, glass fiber-reinforced epoxy resin, ceramic, and human tooth. The fatigue test was performed in a mechanical cycling machine by using the boundary technique at 2 Hz in distilled water at 37 °C. The fatigue data were analyzed by using the Weibull distribution and a lifetime-inverse power law relationship. Failures were evaluated with fractography and transillumination.

RESULTS

The Weibull modulus (β) was similar among groups. The exponent of crack growth (n) was significantly greater for glass fiber-reinforced epoxy resin and tooth groups than for metal and ceramic; therefore, the probability of failure (Pf) of glass-ceramic specimens loaded by resin and tooth pistons depended more on load amplitude. Specimens tested with tooth showed the highest value of K (characteristic lifetime), which is an indication of greater survival. Radial crack was the only failure mode observed for all experimental groups.

CONCLUSIONS

The piston material influenced the fatigue survival of the lithium disilicate glass-ceramic. The glass fiber-reinforced epoxy resin piston closely simulated the fatigue behavior induced by the human tooth on the evaluated glass-ceramic.