Clinical performance of a new biomimetic double network material

A retrospective cohort study on 3D printed temporary crowns

In this retrospective cohort study the survival rate, clinical parameters, patient satisfaction with aesthetics and oral health-related quality of life of 3D printed temporary crowns were evaluated. Temporary crowns were 3D printed with a Form3B out of Permanent Crown Resin (Formlabs GmbH). Anonymized data for the restorations' survival (in-situ) was evaluated retrospectively for 98 temporary crowns of 63 patients fabricated within 19 months. Among these restorations, further analysis was conducted for 42 temporary crowns of 24 patients regarding clinical parameters (modified USPHS criteria), patient satisfaction with aesthetics and impact on oral health-related quality of life (OHRQoL) (OHIP 14). Descriptive statistical analysis (significance level of α = 0.05) included a Kaplan-Meier curve for survival analysis, a Kolmogorov-Smirnov test for USPHS, aesthetics and OHIP data, followed by a Wilcoxon test for USPHS and OHIP data and Chi-squared test for aesthetics data. Cronbach's alpha was calculated for OHIP data. The average observation period for survival analysis was 256 days. The survival rate was satisfactory at 98% and n = 2 catastrophic failures (i.e. fracture) occurred. Total OHIP scores, with good reliabilities, improved from 6.63 to 2.21 significantly (p = 0.005) and patient satisfaction with aesthetics (p < 0.001) as well. Clinical analysis with modified USPHS criteria revealed encouraging results.

The effect of cement and impression methods on the marginal and internal adaptation of the current monolithic blocks - 3D scanning evaluation

Background

This research aimed to evaluate the marginal and internal gaps of crowns, which were produced using both digital and conventional impression techniques and cemented with various types of cement.

Material and Methods

For the full ceramic crown restoration, an anatomically prepared acrylic first molar phantom tooth (Frasaco GmbH, Germany) was scanned with Scanner S600 ARTI (Zirkonzahn). 160 PMMA analogues produced from the milling unit. Two impression methods were used: digital impressions by intraoral scanner (Aadva Intra Oral 3D Scanner, GC) and PVS impression. Cerasmart, Initial LRF Block, Zirconia Prettau and ICE Zircon monolithic blocks milled with M1 Milling Unit (Zirkonzahn). Restorations cemented with light-cured and dual-cured cements. (n = 10) Pre and post-cementation 3D images overlap was performed using Geomagic Control X (3D Systems, NC, USA). Data were analysed by using SPSS 25.0. p<0.05 difference was considered significant.

Results

Digital impressions were significantly higher than PVS impressions in all groups (p<0.05). A significant difference was found between the materials (p<0.05). Cerasmart showed a significantly more marginal gap than the other groups. Prettau and ICE Zircon crowns with the conventional impression group showed a significantly smaller marginal gap than the others.

Conclusions

Monolithic crowns fabricated by CAD-CAM using the digital and conventional impression methods had clinically acceptable marginal and internal gaps. Crowns cemented with dual-cured cements showed significantly more marginal gap than light-cure groups. Key words:3D scanning, Marginal accuracy, Marginal fit, Monolithic crown.

CAD-CAM resin-ceramic material wear: A systematic review

STATEMENT OF PROBLEM

The increasing use of computer-aided design and computer-aided manufacturing (CAD-CAM) systems has led to the development of resin-ceramic materials that meet the requirements of minimally invasive dentistry, including the resin nanoceramic (RNC) and polymer-infiltrated ceramic network (PICN). The wear characteristics of these materials are unclear.

PURPOSE

The purpose of this systematic review was to compare the wear resistance of resin-ceramic materials when compared with one another or with lithium disilicate glass-ceramics.

MATERIAL AND METHODS

The PubMed, Scopus, and DOSS search engines were used to identify articles published between 2013 and 2021. Two independent researchers conducted the systematic review by following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines and by following a combination of keywords.

RESULTS

Of a total of 310 articles, 26 were selected, including only 1 clinical study. Among these, 15 compared resin-ceramic materials with each other, while 11 compared resin-ceramic materials with lithium disilicate ceramics. Two types of wear were used to compare the materials: attrition and abrasion. The most commonly studied materials were 2 RNCs (Lava Ultimate and Cerasmart), 1 PICN (Vita Enamic), and 1 ceramic (IPS e.max CAD). Among the resin-ceramic materials, the PICN (Vita Enamic) showed less wear than the RNCs. Of the RNCs, Cerasmart had less attrition wear and less wear of the opposing teeth.

CONCLUSIONS

Lithium disilicate glass-ceramics have a higher wear resistance than resin-ceramic materials, but they cause more wear of the opposing teeth.

Fracture resistance of CAD/CAM endocrowns made from different materials in maxillary premolar interproximal defects

OBJECTIVES

This in vitro study aims to compare the fracture resistance of three CAD/CAM materials used in endocrown restoration of interproximal defects in maxillary premolars.

MATERIALS AND METHODS

45 maxillary premolars extracted as part of orthodontic treatment were included. Following standardized root canal treatment, all teeth were prepared into Mesial-Occlusal (MO) cavity types. The samples were then randomly divided into three groups: LD [repaired with lithium disilicate glass ceramics (IPS e.max CAD)], VE [treated with polymer-infiltrated ceramics (Vita Enamic)], and LU [repaired with resin-based nanoceramics (Lava Ultimate)]. Axial static loading was applied using a universal testing machine at 1 mm/min until fracture, and fracture resistance and failure modes were recorded.

RESULTS

Regarding Fracture Resistance Values (FRVs), the LD group exhibited significantly higher values than the other two groups, VE (P = 0.028) and LU (P = 0.005), which showed no significant difference (P = 0.778). On the other hand, regarding failure modes, the LD group had a higher prevalence of irreparable fractures compared to the other two groups, VE (P < 0.001) and LU (P < 0.001), which showed no significant difference.

CONCLUSIONS

Although lithium disilicate glass ceramics exhibited higher FRVs, they had a lower repair probability. In contrast, polymer-infiltrated ceramics and resin-based nanoceramics contributed to tooth structure preservation.

CLINICAL RELEVANCE

For maxillary premolars with interproximal defects following root canal treatment, resin ceramic composites are recommended for restoration to enhance abutment teeth protection.

Influence of occlusal reduction design on the fracture resistance and biomechanical behavior of endocrowns restoring maxillary premolars

PURPOSE

To investigate the effect of different occlusal reduction design on stress distribution and fracture resistance of different endocrown systems.

MATERIAL AND METHODS

Sixty-four maxillary human premolars with endodontic treatment, prepared for endocrowns were divided into 2 groups (n = 32) according to the occlusal design: Butt joint preparation (B group) and Anatomical preparation (A group). Each group were subdivided into four groups according to ceramic systems: IPS E max CAD (EM group), monolithic zirconia (ZR group), Nacera Hyprid (NH group) and PEKKTON (PE group). After manufacturing of endocrowns and adhesive bonding the specimens were thermomechanically loaded and subsequently they were tested in a universal testing machine for evaluating the fracture resistance. The specimens failure mode was qualitatively assessed. The stress distribution in each group was assessed using three-dimensional finite element analysis (FEA). 1-way ANOVA and the Post Hoc Tukey HSD test were used to evaluate the data (a = .05).

RESULTS

The fracture resistance values between the groups showed statistically significant variations. The B PE and A PE groups had a higher ratio of fracture resistance values. Regarding failure mode, ceramic endocrowns recorded mainly irreparable failures. FEA showed that anatomical occlusal preparation have reduced the stress concentration under all endocrown systems.

CONCLUSION

Endocrowns could be used to restore endodontically treated maxillary premolars. PEKKTON endocrowns with anatomical preparations revealed most appropriate restoration. The tested new endocrown systems enhanced the biomechanical performance of the tooth.

CLINICAL SIGNIFICANCE

The innovative endocrown systems (PEKK, Nacera Hyprid) can be seen as a promising choice for restoration of severely-destructed endodontic treated premolars, with less stress transmit to the residual tooth structure. Although the traditional endocrown technology might increase the longevity of tooth bonding, it shouldn't be used for clenching cases since the risk of failure is too great overall.

Biomechanical behavior of all-ceramic endocrowns fabricated using CAD/CAM: A systematic review

PURPOSE

This study performed a systematic review to assess the biomechanical behavior of all-ceramic endowcrowns fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM) for the restoration of endodontically treated teeth.

STUDY SELECTION

Three electronic databases (PubMed, Web of Science, and Scopus) were searched by operators specializing in health sciences databases searches to answer the following focused question based on the Population, Intervention, Comparison, Outcome (PICO) format: "Whether all-ceramic CAD/CAM endocrowns (Intervention) used to restore human endodontically treated teeth (Population) exhibit superior fracture resistance (Outcome) compared to non-CAD/CAM all-ceramic or non-ceramic endocrowns (Comparison)." The methodological quality assessment was performed using previously conducted systematic reviews of in vitro studies. The outcomes were expressed as the mean ± the standard deviation (SD).

RESULTS

Seventeen in vitro studies were included. The materials used in these studies were lithium disilicate glass-ceramic, polymer-infiltrated ceramic, zirconia-reinforced lithium silicate glass-ceramic, resin/hybrid nanoceramics, zirconia-reinforced lithium silicate ceramics, and feldspathic ceramic. The fracture resistance of endocrowns using different ceramics varied as follows: (i) IPS e.max CAD (2863.62 ± 51.47 N), (ii) Vita Enamic (1952 ± 378 N), (iii) Vita Suprinity (1859 ± 588 N), (iv) Cerasmart (1981 ± 169.5 N), (v) LAVA Ultimate (2484 ± 464 N), (vi) Celtra Duo (1618.30 ± 585.00 N), and (vii) Cerec Blocs (236.29 ± 32.12 N).

CONCLUSIONS

CAD/CAM all-ceramic endocrowns can withstand occlusal forces in the posterior region. All-ceramic endocrowns improve the fracture strength of endodontically treated teeth. Lithium disilicate crowns were commonly and successfully used in the included studies. More in vitro investigations that implement uniformity in material and measurement approaches are required to strengthen the evidence currently available in the literature regarding the durability of all-ceramic endocrowns.

Biomechanical behavior of different designs of hybrid abutment-restoration on the posterior crown: a finite element analysis

This study aimed to evaluate the influence of material and crown design on the biomechanical behavior of implant-supported crowns with hybrid abutment (HA) through three-dimensional (3D) finite element analysis. The study factors were the type of material used as the mesostructure or crown (zirconia, lithium disilicate, and hybrid ceramic) and the crown design cemented to the titanium base (mesostructure cemented to the titanium base and a crown cemented on it (HaC); hybrid crown-abutment, the abutment and crown are manufactured as a single piece and cemented to the titanium base (HC); monolithic crown cemented on the titanium base and screwed to the implant (CS); and monolithic crown cemented on the titanium base (CC). Four 3D models were constructed using an implant with an internal connection, and an oblique load of 130 N was applied at 45° to the long axis of the implant. The models were evaluated using the von Mises stress for crown, abutment, screw, and implant and maximum principal stress for bone tissues. The lowest stresses occurred in the groups with a lower elastic modulus material, mainly hybrid ceramics, considered a material with greater resilience. The cemented crown group presented the lowest stress values. The stresses were concentrated in the cervical region of the crown at the titanium crown/base interface. Mesostructures made of materials with a higher elastic modulus exhibited a higher concentration of stress. The presence of a screw hole increased the stress concentration in the ceramic crown. Cemented ceramic crowns exhibited better biomechanical behavior than screw-retained crowns.

Effect of thickness, translucency, and substrates on the masking ability of a polymer-infiltrated ceramic-network material

OBJECTIVE

The aim of this in vitro study is to evaluate the masking ability of polymer-infiltrated ceramic-network materials (PICN) with different translucencies and thicknesses on multiple types of substrates.

MATERIALS AND METHODS

Ceramic samples were prepared of VITA ENAMIC blocks in two different translucencies (2M2-T, 2M2-HT) in a thickness range of 0.5-2.5 mm (±0.05 mm). Layered specimens were obtained using composite substrates in nine shades and transparent try-in paste. Spectral reflectance of specimens was measured using a Konica Minolta CM-3720d spectrophotometer and D65 standard illumination. CIEDE2000 color difference (ΔE00 ) between two samples was evaluated using 50%:50% perceptibility and acceptability thresholds. Specular component of the reflection was examined with Specular Component Excluded (SCE) and Included (SCI) settings. Statistical evaluation was performed by linear regression analysis, Kruskal-Wallis test, and multiplicative effect analysis.

RESULTS

An increase in thickness of 0.5 mm reduces ΔE00 of HT samples to 73.5%, of T samples to 60.5% (p < 0.0001). Five substrates with HT specimens, and three substrates with T specimens had significantly different results from average (p < 0.05). There is a significant difference between SCE and SCI data depending on the wavelength (p < 0.0001).

CONCLUSIONS

Masking ability of PICN materials is influenced by the thickness and translucency of the ceramic, and by the substrate. Reflection of the examined PICN material is characterized by both diffuse and specular reflection.

CLINICAL SIGNIFICANCE

Although PICN materials have been available on the market for 10 years now, there is a lack of information regarding their masking ability. Acquiring in-depth data and thereby practical experience of the factors affecting the esthetics of PICN materials is essential for creating perfectly lifelike restorations.

Evaluation of Fracture Resistance of Occlusal Veneers Made of Different Types of Materials Depending on Their Thickness

Pathological tooth wear is an escalating social problem. Occlusal veneers can be an alternative to traditional prosthetic restorations such as crowns, inlays, and onlays.

BACKGROUND

The aim of this study is to assess the fracture resistance of occlusal veneers made of various materials depending on their thickness.

METHODS

In total, 120 occlusal veneers were examined. The restorations were made of four ceramics: leucite LC (IPS Empress Esthetic), hybrid HC (Vita Enamic), lithium disilicate LDC (IPS e.max Press), and zirconium oxide ZOC (Ceramill Zolid HT). A total of 30 veneers were made of each material, 10 for each of the three thicknesses: 1 mm, 1.5 mm, 2 mm. The restorations were cemented on identical abutments duplicated from the developed phantom tooth 35 (KaVo) with composite cement (All Bond Universal). The samples prepared in this way were subjected to a compressive strength test in a universal testing machine. Statistical analysis of the results was performed.

RESULTS

The average fracture resistance of occlusal veneers made of zirconium oxide ceramic was 1086-1640 N, of lithium disilicate ceramics 456-1044 N, of hybrid ceramics 449-576 N, and of leucite ceramics 257-499 N.

CONCLUSIONS

Occlusal veneers made of ceramics, zirconium oxide and lithium disilicate, had the highest resistance to fractures. Restorations made of leucite ceramics turned out to be the least resistant to forces. The greater the thickness of the ceramic occlusal veneers, the greater their fracture resistance.

The effect of water storage on nanoindentation creep of various CAD-CAM composite blocks

BACKGROUND

To study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale.

METHODS

Seven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyetheretherketone (PEEK) block. Specimens of each material (n = 6) were separated into two groups (n = 3) according to their storage conditions (24 h dry storage at 23˚C and 3 months storage in 37˚C distilled water). Nano-indentation creep measurements were undertaken (creep depth measured in µm) using a nanoindenter (Nanovea) equipped with Berkovich three-sided pyramidal diamond tip. The machine was set for the chosen parameters: a load of 20 gf, a pause of 20 s, and the material type. Thirty indentations on 3 samples were made for each material for each test. Data were analysed using two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests and independent t-test (< 0.05) for comparisons between the materials.

RESULTS

The nanoindentation creep depth after 24 h storage ranged from 0.09 to 0.33 μm and increased after 3 months storage in distilled water to between 0.28 and 3.46 μm. There was a statistically significant difference in nanoindentation creep behaviour between the two storage conditions for each investigated material (independent t-test) and between all materials (Bonferroni post hoc). There was a non-significant negative correlation between nanoindentation creep (µm) and filler weight% at 24 h dry storage but a significant correlation at 3 months of water storage. A further non-significant positive correlation between nanoindentation creep (µm) and bulk compressive creep (%) was found.

CONCLUSION

The PICN material showed superior dimensional stability in terms of nanoindentation creep depth in both storage conditions. Other composite blocks showed comparable performance at 24 h dry condition, but an increased nanoindentation creep upon water storage.

Effect of Various Beverages on Adhesion of Repaired CAD/CAM Restorative Materials

(1) Background: The purpose of this study was to determine the effect of commonly consumed beverages on the bond strength of three different computer-aided design-computer-aided manufacturing (CAD/CAM) resin-ceramic hybrid materials repaired with resin-based composite (RBC) materials. (2) Materials and Methods: Rectangular prism specimens (N = 138) measuring 6 mm × 5 mm × 2 mm were obtained from GC Cerasmart (GC), Lava Ultimate (LU), and Vita Enamic (VE) blocks. These blocks were polished and then subjected to thermal cycling (10,000 cycles, 5 °C to 55 °C). After the surface treatment was applied, the average surface roughness value was measured. All the surfaces were repaired with RBC. Thermal cycling was performed for the second time. Each group was then distributed into three subgroups according to the beverage used: tea (t), cola (c), and distilled water (0) (n = 15). The specimens were stored in these solutions for 28 days and then subjected to the shear bond strength (SBS) test. Statistical analysis was performed using a two-way ANOVA test with Bonferroni adjustment. (3) Results: The surface roughness of the materials presented no significant difference after different surface treatments (p > 0.05). No significant difference was observed among the materials (p > 0.05). Tea and cola presented similar SBS values (p > 0.05). Both were significantly lower than distilled water (p < 0.001, p < 0.001, respectively). (4) Conclusions: Consumption of beverages reduces the bond strength in surfaces repaired with RBC to CAD/CAM resin-ceramic hybrid materials. (5) Clinical Significance: Repairing damaged resin matrix dental restorations with RBC is advantageous in terms of time and cost by achieving adequate bond strengths. Frequently consumed beverages reduce the bond strength of repaired CAD/CAM resin-ceramic hybrid materials.

Impact of different CAD/CAM materials on internal and marginal adaptations and fracture resistance of endocrown restorations with: 3D finite element analysis

PURPOSE

To assess and compare the impact of various computers aided design/manufacturing (CAD/CAM) materials on internal and marginal discrepancies, fracture resistance and failure probability of Endocrown restorations with 3D Finite Element analysis.

MATERIAL AND METHODS

Forty devitalized human maxillary first molars were collected. After endodontic treatment, they classified into 4 groups (n = 10) based on the materials used for endocrown fabrication. Group V (Vita-Enamic), Group N (Nacera Hybrid), Group T (Translucent Prettau Zirconia) and Group P (Pekkton ivory). All samples were exposed to artificial aging method simulating one year of clinical service. Silicone replica technique and stereomicroscope (25X) utilized to evaluate the marginal and internal gaps of endocrowns at different areas. Fracture resistance test used for cemented specimens followed by qualitative investigation utilizing Stereomicroscopy. Four models representing four endocrown systems used for restoration of severely-damaged endodontically treated upper first molar were generated for finite element analysis (FEA). Axially and centrally static occlusal compressive load was applied. Modified Von Mises and maximum principal stress values on the remaining tooth structure, cement lines and restorative materials were assessed independently. Resulted data were statistically analyzed at P-value ≤ 0.05.

RESULTS

In the current study, the highest mean values of internal and marginal discrepancies (μm) among studied groups were reported for Zirconia group (100.300 and 102.650) respectively, while the lowest mean value of internal discrepancy (μm) was observed for Nacera group (69.275) and the lowest mean value of marginal discrepancy (μm) was observed for PEKK group (78.4750). Regarding internal discrepancy, Vita-Enamic and PEKK groups did not exhibit any statistically significant differences (P = 0.293), however zirconia and the other tested groups exhibited statistically significant differences in the mean values of the marginal gap region (p 0.05).On the other hand, PEKK group showed the highest mean value of fracture resistance (1845.20 N) and the lowest value was observed for Vita-Enamic group (946.50 N). Regarding to stress distributions through 3D FEA, and according to modified von Mises (mvM) analysis, the greatest possible stress values were noticed in PEKK model in relation to tooth structure, cement line, and flowable composite as the following: (93.1, 64.5, 58.4 MPa) respectively, while Zirconia revealed lower maximum stress values (11.4, 13.6, 11.6 MPa) respectively.

CONCLUSIONS

Statistically excellent marginal and internal fit was observed for PEKK in relation to other used endocrown materials. Also, PEKK material explained fracture resistance comparable to zirconia value while the lowest value was detected for Vita Enamic material.

A Bibliometric Study on the Top 101 Most-Cited Articles of Dental Journals of the Middle East/North Africa Countries From 2011 to 2021

Introduction: This retrospective descriptive study evaluated the Scopus-indexed dental journals and their most-cited documents affiliated with the Middle East and North Africa (MENA) countries from 2011 to 2021. Methods: Dental journals affiliated with MENA countries, their bibliometric indicators (SJR, CiteScore, SNIP, and H-index), and the 101 most cited articles of the considered journals were extracted and studied through descriptive statistics. In addition, the "citation per year" of each top 101 articles was calculated. Spearman's rho test was used for pairwise comparisons of the correlation coefficient values between each two of the considered bibliometric indicators. Results: The number of citations of the 101 most-cited papers ranged from 35 to 203. The mean (SD) citations of studied articles were 61.33 (37.58) and the median was 46. Furthermore, CiteScore had the highest significant correlation with SJR (r=0.828, P˂0.001). Moreover, the citation per year of the top 101 documents had no significant relationship with any of the journals' bibliometric indicators. Conclusion: Because journal performance and citation rate are multi-dimensional concepts, a single metric cannot express them thoroughly despite correlations between indices. "European Journal of Dentistry" from Turkey, "Saudi Dental Journal" from Saudi Arabia, and "Iranian Endodontic Journal" and "Journal of Lasers in Medical Sciences" both from Iran had the highest ranks in the SCImago portal and the highest scores in bibliometric indices amongst the MENA dental journals.

Biomimetic approaches and materials in restorative and regenerative dentistry: review article

Biomimetics is a branch of science that explores the technical beauty of nature. The concept of biomimetics has been brilliantly applied in famous applications such as the design of the Eiffel Tower that has been inspired from the trabecular structure of bone. In dentistry, the purpose of using biomimetic concepts and protocols is to conserve tooth structure and vitality, increase the longevity of restorative dental treatments, and eliminate future retreatment cycles. Biomimetic dental materials are inherently biocompatible with excellent physico-chemical properties. They have been successfully applied in different dental fields with the advantages of enhanced strength, sealing, regenerative and antibacterial abilities. Moreover, many biomimetic materials were proven to overcome significant limitations of earlier available generation counterpart. Therefore, this review aims to spot the light on some recent developments in the emerging field of biomimetics especially in restorative and regenerative dentistry. Different approaches of restoration, remineralisation and regeneration of teeth are also discussed in this review. In addition, various biomimetic dental restorative materials and tissue engineering materials are discussed.

Effect of different surface treatments on resin-matrix CAD/CAM ceramics bonding to dentin: in vitro study

BACKGROUND

Evaluating the effect of different surface treatment methods on the micro-tensile bond strength (µTBS) of two different resin-matrix computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics (RMCs).

METHODS

A standardized inlay preparations were performed on 100 intact maxillary premolars. According to the type of the restorative material, the teeth were randomly divided into two equally sized groups (n = 50): (polymer-infiltrated ceramic (Vita Enamic) and resin-based composites (Lava Ultimate)). The inlays were fabricated using CAD/CAM technology. In each group, the specimens were randomly assigned to five subgroups (n = 10) according to the surface treatment method: group 1 used was the control group (no surface treatment); group 2, was treated with air abrasion with 50 μm Al2O3 (A) and universal adhesive (UA); group 3, was treated with air abrasion with 50 μm Al2O3 (A) and silane coupling agent (S); group 4, was treated with hydrofluoric acid (HF) and universal adhesive (UA) and group 5, was treated with Hydrofluoric acid (HF) + silane coupling agent (S). The inlays were then cemented to their respective preparations using dual-cure self-adhesive resin cement (RelyX U200, 3 M ESPE) according to the manufacturer's instructions. The µTBS test was conducted in all groups, and stereomicroscope and scanning electron microscope were used to inspect the failure mode. The data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey's post-hoc multiple comparison tests at a significance level of p < 0.05.

RESULTS

Surface treatments significantly increased the µTBS of the materials compared to the control group (p < 0.05). For CAD/CAM RBCs, the µTBS value highest in group 2 whereas, for PICN, the µTBS value was highest in group 3. Cohesive failure of CAD/CAM restorative material was the most predominant mode of failure in all treated groups, whereas adhesive failure at restoration-cement interface was the most predominant failure mode in the control group.

CONCLUSION

Surface treatments increase the µTBS of resin-matrix CAD/CAM ceramics to tooth structure. Air abrasion followed by universal adhesive and hydrofluoric acid followed by silane application appears to be the best strategies for optimizing the bond strength of CAD/CAM RBCs and PICN respectively.

Evaluating the Bond Strength of a Polymer Infiltrated Ceramic Network to Zirconia Using the Crossbeam Push-Off Method

Porcelains and glass-ceramics have been used to produce CAD-milled veneers and crowns for zirconia copings and implant-abutments. This study evaluated the bondstrength of a polymer-infiltrated-ceramic-network to zirconia using two adhesive cement systems: Panavia 21 and Multilink Automix. Lithium disilicate and feldspathic porcelain were also tested as reference CAD-On materials. Long beams (3x6x40 mm³) of zirconia and short beams (3x6x15 mm³) of the CAD-On materials were prepared. Zirconia and each CAD-On material were bonded in a crossbeam arrangement and subjected to a modified tensile bond-strength test. Half of the samples in each group (n=10) were tested 5 days after bonding (baseline) and the remaining (n=10) underwent aging (50,000 thermocycles at 5°C and 55°C) prior to bond-strength testing. The effects of material, cement, and aging on the tensile bond-strength were tested using a three-way ANOVA. The reference lithium disilicate/Multilink system showed no significant differences in bond strength compared to polymer-infiltrated-ceramic-network and porcelain. The long-term retention of polymer-infiltrated-ceramic-network was not statistically different compared to the baseline values and the two reference materials. With comparable bond strength between all materials, polymer-infiltrated-ceramic-network is the favorable choice for CAD-On to zirconia copings and implant-abutments due to its superior resistance to fatigue fracture relative to porcelain.

Influence of mechanical and chemical pre-treatments on the repair of a hybrid ceramic

OBJECTIVES

This study aimed to investigate the influence of the respective mechanical and chemical pre-treatments on the composite repair of a CAD/CAM hybrid ceramic using a microtensile bond strength test (μTBS).

METHODS

15 CAD/CAM Blocks of Vita Enamic (VE) were randomly sectioned into three mechanical pre-treatments: (1.) Diamond bur (D), (2.) Airborne abrasion (A), (3.) Tribochemical silica coating (T) and subsequently five chemical pre-treatments: (1.) Clearfil SE Bond Bond (B; negative control), (2.) ESPE Sil (S), (3.) Clearfil Ceramic Primer Plus (CPP), (4.) Clearfil Repair (CR) and (5.) Scotchbond Universal (SCB). Per block, n = 20 specimens were sawn. Half of the specimens were randomly selected and subjected to an immediate bond strength test, while the other half was subjected to artificial aging for 6 months 180 days at 37 °C and subsequent thermocycling of 5000 cycles. A μTBS was performed and data (MPa) were compared in one-way and two-way ANOVA and Tukey's HSD. Paired-t-test was used for artificial aging (α = 0.05). Debonded specimens were analyzed of for failure modes with a stereomicroscope (SEM).

RESULTS

The results of one-way ANOVA for the fifteen fastening procedures after aging indicated significant differences according to SCB-A and CPP-T. Two-way ANOVA after aging observed inferior bond strength for SCB. No differences were observed for mechanical pre-treatments. Artificial aging showed a significant reduction in bond strength on most of the fastening procedures.

SIGNIFICANCE

SCB showed the lowest bond strength values besides B, S, CPP, and CR. MDP and silane are both suitable for the repair of VE.

Evaluation of the effects of different concentrations of bleaching agents on flexural strength and microhardness of VITA ENAMIC

Background

Considering the studies on the effects of bleaching materials on properties of dental materials, The aims of this in vitro study were to evaluate the effects of two different concentrations of bleaching agents on flexural strength and microhardness of VITA ENAMIC.

Materials and Methods

In this experimental in vitro study, 30 rectangular-shaped specimens (2 mm width × 2 mm height × 12 mm length) for flexural strength and 30 specimens (5 mm width × 5 mm length × 2 mm height) for microhardness tests were prepared from VITA ENAMIC blocks 12 × 14 × 18 mm. The specimens were polished using silicon-carbide sandpapers 400, 600, 800, 1200, 2000 under flow of water for 60 s each. The prepared samples for flexural strength and microhardness were divided into 3 subgroups (n = 10): control group (C), samples bleached using Opalescence PF 15% (B15), and samples bleached with Opalescence Xtra Boost 40% (B40). Flexural strength measurement was done using a universal testing machine, and microhardness test was done using Vickers. Data were analyzed using analysis of variance and post hoc tests and P < 0.05 was considered significant.

Results

The mean microhardness values of C, B15, and B40 groups were 255.46 ± 3.02, 249.86 ± 4.18, and 235.53 ± 4.61 kgf/mm². Opalescence PF 15% and Opalescence Xtra Boost 40% affected microhardness of ENAMIC significantly (P < 0.05). The mean flexural strength values of C, B15, and B40 groups were 155.26 ± 16.13, 142.14 ± 11.52, and 133.39 ± 16.13 MPa. A significant decrease in flexural strength was found between the C and B40 groups (P = 0.007). However, the difference between flexural strength of the C and B15 groups was not significant (P > 0.05).

Conclusion

Our study showed that both concentrations of bleaching agents can affect microhardness of ENAMIC. Moreover, hydrogen peroxide 40% has a negative effect on the flexural strength of ENAMIC.

Survival of Hybrid Laminate Veneers using two different tooth preparation techniques: Randomized Clinical Trial

The aim of this study was to evaluate the survival of laminate veneers constructed using a recent polymer-infiltrated ceramic network material following the aesthetic pre-evaluative temporary (APT) technique of tooth preparation in comparison to traditional technique. Six patients received 54 laminate veneers. They were divided into two equal groups (n=27) according to the technique of tooth preparation: group T: traditional technique and group A: aesthetic pre-evaluative temporary technique. VITA ENAMIC material was used for CAD/CAM construction of laminate veneers. Cementation was performed using a light cured resin cement. The laminate veneers were evaluated at baseline, after 3, 6 and 12 months according to the modified United States Public Health Service (USPHS) criteriea. The data was collected, tabulated and statistically analyzed. Secondary caries, endodontic complications, cracks and loss of retention were not noted in any laminate veneer. Extensive fractures were not detected in both study groups through the study period. There was a statistically significant decrease of color match criteria between the two groups at the 6 and 12 months recalls. Based on this study, both preparation techniques resulted in successful clinical performance. After 12 months, all the veneers in both groups showed no post-operative sensitivity and all patients were highly satisfied regarding their veneers. However, there was a deterioration in color match criteria through the study period in both study groups.

Influence of different combinations of CAD-CAM crown and customized abutment materials on the force absorption capacity in implant supported restorations - In vitro study

OBJECTIVES

To evaluate the force absorption capacity of implant supported restorations utilizing different CAD-CAM materials for the fabrication of crowns and customized abutments.

METHODS

80 titanium inserts were scanned to design customized abutments and crowns. The specimens were divided into four groups (n = 20/material): (Z): zirconia, (P): PEEK, (V): VITA Enamic, and (E): IPS e.max. Each group was subdivided into two subgroups according to customized abutment material: (Z) zirconia, and (P) for PEEK. For the assessment of force absorption, all specimens were loaded in a universal testing machine, applied loads curves were collected from the machine's software, and resulting loads curves were collected from forcemeter below the assembly. The slopes of all curves were analyzed using Two-way multivariate analysis of variance with pairwise comparisons using Tukey Post Hoc test (p < 0.05).

RESULTS

The curve progression of the applied and resulting forces varied among the investigated materials for each specimen. For zirconia abutments, ZZ showed the highest slope values of the applied and resulting force curves, followed by EZ, VZ, and PZ demonstrating statistically significant differences (P < .001). As for PEEK abutments, ZP and EP showed the least slope values, followed by PP then VP demonstrating statistically significant differences (P < .001). For Zirconia and e.max crowns, using PEEK abutments significantly increased slope loss. As for PEEK and Vita Enamic crowns changing abutment material did not significantly affect slope loss.

SIGNIFICANCE

Combining rigid crown materials with less rigid abutments might enhance their force absorption capacity. However, with less rigid crown materials a stiff substructure might be mandatory to preserve their force absorption behavior.

Fracture strength of teeth restored with milled ultrathin occlusal veneers made of polymer-infiltrated ceramic

The purpose was to evaluate, in vitro, the fracture strength of teeth restored with 0.3- or 0.6-mm-thick occlusal veneers made of Vita Enamic® bonded to enamel or dentin. Fifty third molars were allocated into five groups (n=10): Group C - control (sound teeth); Group 0.3E - 0.3-mm-thick occlusal veneers bonded to enamel; Group 0.6E - 0.6-mm-thick occlusal veneers bonded to enamel; Group 0.3D - 0.3-mm-thick occlusal veneers bonded to dentin; Group 0.6D - 0.6-mm-thick occlusal veneers bonded to dentin. After luting with Single Bond Universal and Filtek Z-100, the samples were subjected to fracture strength test in a universal testing machine. The fractures were classified as irreparable and reparable. Data were analyzed with 2-way and 1-way ANOVA (α=.05) followed by Tukey's test. The teeth restored with 0.3-mm-thick occlusal veneers (2658 N) achieved significantly higher fracture strength compared to the teeth restored with 0.6-mm-thick occlusal veneers (2070 N) (p=0.017). The teeth restored with occlusal veneers bonded to enamel (2648 N) had significantly higher fracture strength compared to the teeth restored with occlusal veneers bonded to dentin (2049 N) (p=0.015). Group C (3355 N) and Group 0.3E (2965 N) did not differ significantly from each other, being the fracture strength significantly higher than the other groups (p<0.05). The fractures were predominantly reparable. The teeth restored with 0.3-mm-thick occlusal veneers achieved higher fracture strength compared to the teeth restored with 0.6-mm-thick occlusal veneers. The supporting substrate influenced the fracture strength, which was higher for the teeth restored with occlusal veneers bonded to enamel.

In vitro evaluation of material dependent force damping behavior of implant-supported restorations using different CAD-CAM materials and luting conditions

STATEMENT OF PROBLEM

Although force-damping behavior that matches natural teeth may be unobtainable, an optimal combination of crown material and luting agent might have a beneficial effect on the force absorption capacity of implant-supported restorations. However, the force-absorbing behavior of various restorative materials has not yet been satisfactorily investigated.

PURPOSE

The purpose of this in vitro study was to evaluate the material dependent force-damping behavior of implant-supported crowns fabricated from different computer-aided design and computer-aided manufacturing (CAD-CAM) materials luted to implant abutments under different conditions.

MATERIAL AND METHODS

Titanium inserts (N=84) were screwed to implant analogs, scanned to design zirconia abutments, and divided into 4 groups to receive CAD-CAM fabricated crowns in 4 materials: zirconia, polyetheretherketone (PEEK), polymer-infiltrated ceramics (VITA ENAMIC), and lithium disilicate (e.max). The crowns were subdivided as per the luting agent: none, interim cement, and adhesive resin cement. Measurements were performed by loading specimens in a universal testing machine with an increasing force and measuring the resulting force with a digital forcemeter, followed by image processing and data acquisition. Two-way multivariate analysis of variance (MANOVA) was used to assess all interactions with multiple pairwise comparisons (α=.05).

RESULTS

The curve progression of the applied and resulting forces varied significantly among the investigated materials, resulting in differently inclined slopes for each material (P<.001). With no cementation, the mean slope values of the resulting force curves ranged from 77.5 ±0.03 degrees for zirconia, followed by 71.8 ±0.03 degrees for lithium disilicate, 56.2 ±0.1 degrees for polymer-infiltrated ceramics, and 51.1 ±0.01 degrees for polyetheretherketone. With interim cementation, the mean slope values ranged from 75.4 ±0.01 degrees for zirconia, followed by 70.05 ±0.02 degrees for lithium disilicate, 56.1 ±0.02 degrees for polymer-infiltrated ceramics, and 52.2 ±0.1 degrees for polyetheretherketone. As with adhesive cementation, curve slopes ranged from 73.2 ±0.02 degrees for zirconia, followed by 70.5 ±0.2 degrees for lithium disilicate, 55.9 ±0.04 degrees for polymer-infiltrated ceramics, and 52.3 ±0.1 degrees for polyetheretherketone. Slope loss was significant after the cementation of zirconia and lithium disilicate crowns but less significant for polymer-infiltrated ceramics and polyetheretherketone.

CONCLUSIONS

Force damping is generally material dependent, yet implant-supported crowns fabricated from resilient materials such as polymer-infiltrated ceramics and PEEK show better force absorption than rigid materials such as zirconia and lithium disilicate ceramics. Furthermore, cementation of rigid materials significantly increased slope loss, indicating enhancement in their force-damping behavior, whereas less-rigid materials benefit less from cementation. Further studies are essential to investigate the effect of prosthetic materials on the stress distribution to the peri-implant bone in the crown-abutment-implant complex.

Influence of toothbrush abrasion and surface treatments on the color and translucency of resin infiltrated hybrid ceramics

PURPOSE

The study compared the color change, lightness, and translucency of hybrid resin ceramics exposed to toothbrush abrasion and surface treatment.

MATERIALS AND METHODS

Four hybrid ceramics [Lava Ultimate (LU), Vita Enamic (EN), Shofu HC (SH), and Crystal Ultra (CU)] were compared with a glass-ceramic (Vita Mark II) control. One hundred and twenty specimen blocks were prepared using a precision saw machine. Specimens in each material were divided into four subgroups based on the surface treatment (polishing or staining) and a storage medium (water or citric acid). Simulated tooth brushing with a mixture of 100 RDA (radioactive abrasives) with 0.3 ml distilled water was used for 3650 cycles (7300 strokes) for each specimen. Measurements for the color change, lightness, and translucency were measured after toothbrushing using a spectrophotometer. Statistical analysis compared outcomes using paired t-test, ANOVA, and Tukey post hoc test.

RESULTS

The maximum color change was identified in SH (stained acid) [1.44 (0.40)], whereas the lowest was identified in EN (polished water) [0.66 (0.16)] material. The maximum and minimum loss of surface translucency was observed in SH (polished water) [12.3 (0.52)] and EN (stained acid) [6.5 (0.55)] specimens, respectively. Lastly, loss of lightness was the highest in VM (polished acid) [69 (0.95)], whereas the lowest was observed in CU (stained water) [56.7 (0.86)].

CONCLUSION

The comparison presented a significant effect of toothbrush abrasion on translucency and lightness of the hybrid resin ceramics. Color change was not significantly influenced irrespective of the storage medium employed. Surface staining demonstrated the preservation and stability of color and optical properties under the influence of toothbrush abrasion and chemical trauma.

Minimal tooth preparation for posterior monolithic ceramic crowns: Effect on the mechanical behavior, reliability and translucency

OBJECTIVE

Despite the increased use of monolithic crowns, their performance has yet to be determined when the minimal tooth preparation (MTP) principle is considered. The goal of this study was to evaluate the effect of MTP on the mechanical behavior, reliability and translucency of posterior monolithic ceramic crowns.

METHODS

Dentin analogues were machined using two preparation designs (0.5 or 1 mm reduction) to receive first molar crowns in order to evaluate the monolithic crown performance. Next, 126 crowns were divided (21/g) according to the material (High translucent zirconia - YZHT, Zirconia reinforced lithium silicate - ZLS and Hybrid ceramic - HC) and thickness (0.5 or 1 mm). Tensile stress concentration was calculated using the finite element method. The crowns were adhesivelly cemented and step stress fatigued to calculate reliability for missions at 600 and 1000 N. Translucency was analyzed in 10 discs of each material and thickness.

RESULTS

Higher stress concentration was found in thinner crowns and those with higher elastic modulus. YZHT crowns were suspended when fatigue reached 1500 N load, thus 1-parameter Weibull was used to analyze the data. Reliability was only affected by thickness at 1000 N. ZLS.5 showed lower survival than HC.5, which was similar to the groups that presented 100% survival. YZHT showed the highest strength and data scattering. ZLS1 (22.3 ± 1.4) presented higher translucency than HC1 (19.2 ± 0.6) and YZHT1 (12.0 ± 2.9), whereas ZLS.5 and HC.5 were similar to each other (26.5 ± 2.3, 26.7 ± 2.2) and superior to YZHT.5 (12.7 ± 1.2).

SIGNIFICANCE

HC.5 combined high reliability and translucency with low stress concentration, yielding better crown performance and tooth preservation.

Clinical outcomes of single crown restorations fabricated with resin-based CAD/CAM materials

Computer-aided design/computer-aided manufacturing (CAD/CAM) restorative materials have been widely used owing to a number of advantages, including stable quality of the materials, lower costs, and time-saving factors. Resin-based CAD/CAM materials for definitive restorations are classified into two groups: dispersed nanoparticle-filled composite resin and polymer-infiltrated-ceramic-network materials. Resin-based CAD/CAM materials have been applied to single crown restorations as a monolithic structure for the posterior region. In addition, resin-based CAD/CAM restorations have been applied recently for the anterior area. This literature review summarizes clinical outcomes, such as survival rates and clinical complications of single crown restorations fabricated with resin-based CAD/CAM materials.

In vitro performance and fracture resistance of pressed or CAD/CAM milled ceramic implant-supported screw-retained or cemented anterior FDPs

PURPOSE

This study investigated the in-vitro performance of anterior implant-supported fixed dental prostheses (FDP). The effect of ceramics, fabrication, finalization and the presence of a screw-channel wa s investigated.

METHODS

Identical anterior ceramic FDPs (tooth 11-13; n=80) were milled (Lithiumdisilicate (LiSiCAD, emaxCAD, Ivoclar-Vivadent), Lithiumaluminiumsilicate (LiAlSi, experimental material) or pressed (Lithiumdisilicate (LiSiPress, emaxPress, Ivoclar-Vivadent), Lithiumsilicate (ZLS, CeltraPress, Dentsply Sirona). FDP-groups (n=8 per material and group) simulated a cemented or screw-retained approach. After cementation or screwing on titanium abutments, thermal cycling and mechanical loading (TCML) was performed on all restorations to mimic 5-year clinical performance. Performance and fracture force were determined and failures were analyzed.

STATISTICS

(Kolmogorov-Smirnov-test, one-way-ANOVA; post-hoc-Bonferroni, multivariate-regression, α=0.05).

RESULTS

All FDPs survived TCML without aging, cracks, fractures or chipping. For FDPs without screw channel fracture values varied between with 839.8±112.3N (LiAlSi glazed) and 1485.9±232.6N (LiSiCAD). With screw channel, fracture results varied between 701.4±220.1N (LiALSi glazed) and 1516.3±253.7N (LiSipress). The type of material had a significant influence on the fracture results (LiSi>ZLS>LiAlSi; p≤0.012). Fabrication and finalization had no influence on the results. A screw channel did not significantly (p≥0.135) reduce the fracture force of the FDPs. Type of failure was mostly characterized by a fracture of the connector (LiSi, LiAlSi) or the abutment (ZLS, LiAlSi).

CONCLUSIONS

FDPs survived TCML without failures indicating that the in vitro performance was not influenced by the tested parameters. Composition of ceramic material has significant influence on the fracture resistance of implant supported LiSi based FDPs. Screw channel, fabrication or finalization did not weaken the FDPs.

Influence of fatigue loading on fracture resistance of endodontically treated teeth restored with endocrowns

PURPOSE

This in vitro study aimed to evaluate the influence of fatigue loading on fracture resistance of endodontically treated molars restored with endocrowns using different machinable blocks.

METHODS

Endodontically treated mandibular first molars were prepared using a standardized method. Specimens were divided into 4 groups (n = 10).Anatomically shaped endocrowns groups were manufactured using VITA ENAMIC (VE) and KATANA Zirconia (KZ). Layered endocrowns groups were manufactured using IPS e.max CAD (EM) and BioHPP (BH). Half of the specimens of each group were subjected to fracture resistance test, while the other half were subjected to thermocycling and chewing simulation. After fatigue loading, specimens were loaded until failure. Specimens were examined using stereomicroscopy. Data were analyzed using ANOVA analysis of variance and Bonferroni post hoc test (α=0.05).

RESULTS

KZ group had the highest initial fracture resistance value (1810.20± 119.56 N) and BH had the lowest value (579.50± 76.15 N). The reduction of fracture resistance after fatigue loading was significant for KZ group (1588.30±216.25 N) and BH group (502.60±11.53 N) and non-significant to VE group (1101.70±77.05 N) and EM group (1112.10±74.12 N). Failure modes of KZ and EM groups showed high percentage of non-restorable fractures, while VE and BH groups showed high percentage of restorable fractures.

CONCLUSIONS

Within the limitations of this study, the following can be concluded: Poly infiltrated ceramics should be considered as a proper material to be used as an endocrown material because of its ability to be restorable if failure occurred.

Survival Probability, Weibull Characteristics, Stress Distribution, and Fractographic Analysis of Polymer-Infiltrated Ceramic Network Restorations Cemented on a Chairside Titanium Base: An In Vitro and In Silico Study

Different techniques are available to manufacture polymer-infiltrated ceramic restorations cemented on a chairside titanium base. To compare the influence of these techniques in the mechanical response, 75 implant-supported crowns were divided in three groups: CME (crown cemented on a mesostructure), a two-piece prosthetic solution consisting of a crown and hybrid abutment; MC (monolithic crown), a one-piece prosthetic solution consisting of a crown; and MP (monolithic crown with perforation), a one-piece prosthetic solution consisting of a crown with a screw access hole. All specimens were stepwise fatigued (50 N in each 20,000 cycles until 1200 N and 350,000 cycles). The failed crowns were inspected under scanning electron microscopy. The finite element method was applied to analyze mechanical behavior under 300 N axial load. Log-Rank (p = 0.17) and Wilcoxon (p = 0.11) tests revealed similar survival probability at 300 and 900 N. Higher stress concentration was observed in the crowns’ emergence profiles. The MP and CME techniques showed similar survival and can be applied to manufacture an implant-supported crown. In all groups, the stress concentration associated with fractographic analysis suggests that the region of the emergence profile should always be evaluated due to the high prevalence of failures in this area.

Bonding to industrial indirect composite blocks: A systematic review and meta-analysis

OBJECTIVE

The aim of this systematic review and meta-analysis was to evaluate the effect of surface conditioning methods on the bond strength of industrial indirect composite blocks (ICs).

METHODS

Based on the PICOS strategy, the Medline via PubMed, Embase and Web of Science (ISI - Web of Knowledge) electronic databases were searched for peer-reviewed articles in both English and Chinese, with no publication year limit. In vitro studies evaluating the effects of surface conditioning on the bond strength of ICs were selected. The meta-analysis was conducted to calculate the mean difference between surface-conditioned ICs and unconditioned controls. Subgroup analysis was performed to evaluate the different surface conditioning methods, separately for polymer-infiltrated ceramic network (PICN) material and the ICs with dispersed fillers (ICDFs). Meta-analyses were performed with a random-effects model at a significance level of 0.05.

RESULTS AND SIGNIFICANCE

From 802 relevant studies, 25 were selected for full-text analysis. Nineteen studies were eligible for inclusion in this systematic review, whereas 9 studies were included in the meta-analysis. A manual search of the principal periodicals specific to the area resulted in no additional articles. The meta-analysis indicated a significant difference in bond strength between the surface-conditioned ICs and controls under both non-aged and aged conditions. The combination of mechanical and chemical conditioning yielded the highest bond strength of ICs. This meta-analysis suggests that chemical etching followed by a universal primer and alumina air abrasion followed by a silane coupling agent could be considered the best strategy for optimizing the bond strength of PICN materials and ICDFs under aged conditions, respectively.

Effect of grinding and polishing on the roughness and fracture resistance of cemented CAD-CAM monolithic materials submitted to mechanical aging

STATEMENT OF PROBLEM

The effect of clinical adjustments on the strength of cemented computer-aided design and computer-aided manufacturing (CAD-CAM) monolithic materials under aging challenge is unclear.

PURPOSE

The purpose of this in vitro study was to assess the surface roughness and fracture resistance (with or without mechanical aging) of cemented CAD-CAM monolithic materials submitted to grinding and polishing procedures.

MATERIAL AND METHODS

Disks of Lava Ultimate, Vita Enamic, crystallized Vita Suprinity, and IPS e.max CAD were analyzed for roughness after polishing by using silicon carbide papers (Lava Ultimate and Vita Enamic) or glazing (IPS e.max CAD and Vita Suprinity) (control), after grinding by using 30-μm grit diamond rotary instruments, and after grinding and polishing by using a polishing kit. For fracture resistance, a simplified trilayer model consisting of a restorative disk, an epoxy resin disk, and a steel ring was used. The bonded trilayer disks received the same treatments described for the roughness analysis. Half of the specimens underwent mechanical aging for 1×10⁶ cycles. All specimens were loaded until failure. The Weibull modulus was calculated.

RESULTS

The IPS e.max CAD and Vita Suprinity showed the highest roughness after grinding and the lowest at baseline. For the Lava Ultimate and Vita Enamic, polishing provided lower roughness than at baseline. Grinding, followed or not by polishing, and mechanical aging did not adversely affect the fracture resistance or the reliability of the materials.

CONCLUSIONS

Polishing did not recover the initial surface roughness of the glass-ceramic materials. Fracture resistance was not affected by grinding, followed or not by polishing, even after mechanical aging.

Effect of acidic pH on surface roughness of esthetic dental materials

STATEMENT OF PROBLEM

Exposure to gastric acid in patients with bulimia nervosa and gastroesophageal reflux disease (GERD) causes demineralization of hard tooth structures. This chemical attack also causes the degradation of dental ceramics, which results in increased surface roughness and reduced strength. However, studies comparing the effect of acidic pH on resin matrix ceramic with other computer-aided design and computer-aided manufacturing (CAD-CAM) esthetic materials are lacking.

PURPOSE

The purpose of this in vitro study was to compare the surface roughness changes of different CAD-CAM restorative dental materials after exposure to acidic pH by using a 3D optical interferometer.

MATERIAL AND METHODS

Five esthetic CAD-CAM block materials, a leucite glass-ceramic (IPS Empress CAD), a zirconia (BruxZir Solid Zirconia), a resin matrix ceramic (VITA Enamic), a lithium disilicate glass-ceramic (IPS e.max CAD), and a feldspathic porcelain (VITABLOCS Mark II CAD) were tested. Eighteen specimens were sectioned from CAD-CAM blocks into 2-mm-thick rectangular plates and immersed in 10 mL of 5% hydrochloric acid (HCl) with (pH=2) at 37 °C for 45 and 91 hours. The surface roughness average (Ra) of the specimens was measured by using a 3D optical interferometer before the storage period (baseline), after 45 hours, and after 91 hours of exposure to HCl. Statistical analyses were performed with the Kruskal-Wallis test and the post hoc Dunn test with Bonferroni correction (α=.05).

RESULTS

Regarding the comparison of surface roughness changes at different periods of evaluation (baseline, 45 hours, 91 hours), there were no statistically significant differences for lithium disilicate (P=.063) or zirconia (P=.513). Leucite glass-ceramic, feldspathic porcelain, and the resin matrix ceramic demonstrated statistically significant differences (P<.001). For all tests that were statistically significant, greater surface roughness was found at the time point with the longer HCl exposure. Regarding the comparison of materials in terms of change in surface roughness between baseline to 45 hours and baseline to 91 hours, the Kruskal-Wallis test indicated a statistically significant difference among the materials in both cases (P<.001). Lithium disilicate and zirconia exhibited the least change in surface roughness among the 5 materials.

CONCLUSIONS

Leucite glass-ceramic, feldspathic porcelain, and resin matrix ceramic showed statistically significant increases in surface roughness when they were exposed to simulated gastric acid for 45 and 91 hours. Lithium disilicate and zirconia showed no statistically significant change in surface roughness after exposure to HCl for 45 and 91 hours.

In Vitro Evaluation of the Effect of Different Surface Treatments of a Hybrid Ceramic on the Microtensile Bond Strength to a Luting Resin Cement

Introduction: The aim of the present study was to investigate the effect of different surface treatments of a hybrid ceramic, Vita Enamic, on the micro-tensile bond strength (µ-TBS) to resin cement. Methods: Ten blocks (3×10×8 mm) were retrieved from the original blocks and divided into 5 groups according to the different surface treatments performed: Groups 1: 35% acid phosphoric for 60 seconds (PA); group 2: Sandblasting with 50 µm Al₂ O₃ particles for 10 seconds (SB); groups 3: 9.5% hydrofluoric acid for 60 seconds (HF), group 4: The Er:YAG laser (2 W, 10 Hz) (ER1), group 5: The Er:YAG laser (3 W, 10 Hz) (ER2). All treated surfaces were salinized and the blocks with similar surface treatments were bonded together using a dual-cured resin cement and light-cured. After 24-hour storage in water, the blocks were cut into beams (1 mm²). Half of the specimens in each group (n=16) were tested immediately and the rest were subjected to thermocycling between 5°C and 55°C for 6000 cycles before the µ-TBS test at a crosshead speed of 0.5 mm/min. The data were analyzed using two-way analysis of variance (ANOVA) and Tukey HSD tests and the significance level was set at 0.05. The failure mode was evaluated by using a stereomicroscope. Results: The µ-TBS was clearly influenced by surface treatment methods (P < 0.001) and thermocycling significantly decreased the bond strength values in all groups (P = 0.007). The highest value (66.07 MPa ± 11.3) was obtained for the HF groups with no thermocycling and the lowest values were observed in the laser groups with no significant difference among different irradiation parameters. Adhesive failure was mainly observed in the PA and SB groups while mixed failure was predominantly shown in the laser and HF groups. Conclusion: This study demonstrated that surface treatment of VE with HF and salinization could improve the bond strength to a dual-cured resin cement, and Er:YAG laser irradiation with the evaluated parameters did not promote the adhesion of the resin cement to VE.

Influence of different universal adhesives on the repair performance of hybrid CAD-CAM materials

Objectives

The aim of this study was to investigate the microshear bond strength (μSBS) of different universal adhesive systems applied to hybrid computer-aided design/computer-aided manufacturing (CAD-CAM) restorative materials repaired with a composite resin.

Materials and Methods

Four types of CAD-CAM hybrid block materials-Lava Ultimate (LA), Vita Enamic (VE), CeraSmart (CS), and Shofu Block HC (SH)-were used in this study, in combination with the following four adhesive protocols: 1) control: porcelain primer + total etch adhesive (CO), 2) Single Bond Universal (SB), 3) All Bond Universal (AB), and 4) Clearfil Universal Bond (CU). The μSBS of the composite resin (Clearfil Majesty Esthetic) was measured and the data were analyzed using two-way analysis of variance and the Tukey test, with the level of significance set at p < 0.05.

Results

The CAD-CAM block type and block-adhesive combination had significant effects on the bond strength values (p < 0.05). Significant differences were found between the following pairs of groups: VE/CO and VE/AB, CS/CO and CS/AB, VE/CU and CS/CU, and VE/AB and CS/AB (p < 0.05).

Conclusions

The μSBS values were affected by hybrid block type. All tested universal adhesive treatments can be used as an alternative to the control treatment for repair, except the AB system on VE blocks (the VE/AB group). The μSBS values showed variation across different adhesive treatments on different hybrid CAD-CAM block types.

Comparative Evaluation of Mechanical Properties and Wear Ability of Five CAD/CAM Dental Blocks

This study compares the mechanical properties and wear ability of five CAD/CAM (computer-aided design/computer-aided manufacturing) millable dental blocks. All the discs, including Amber Mill Hybrid, Vita Enamic, Katana Avencia, Lava Ultimate, and Amber Mill, were cut in dimensions of 1.2 mm in thickness and 12 mm in diameter, polished to a machined surface, and immersed in distilled water for seven days. Vickers hardness was measured and the indentations were observed using microscope. The discs were brushed under a 150 g load. Mean surface roughness (Ra) and topography were determined after 100,000 cycles. Finally the biaxial flexure strength of the discs was measured and the broken surfaces were observed using scanning electron microscopy (SEM). The data was subjected to Weibull analysis. All data were analyzed by one-way analysis (ANOVA). The results of Vickers hardness are shown as: Amber Mill > Vita Enamic > Amber Mill Hybrid > Lava Ultimate > Katana Avencia. Katana Avencia showed the highest volume percentage reduction and the roughest surface after toothbrushing. The biaxial flexural strength is shown as: Amber Mill > Katana Avencia > Lava Ultimate > Amber Mill Hybrid > Vita Enamic. All the tested materials exhibited varying degrees of mass loss and surface roughness. The properties of the composite materials are related to the filler content, filler volume, and polymerization methods.

Viscoelastic stability of pre-cured resin-composite CAD/CAM structures

OBJECTIVES

To study the effect of water storage (3 months) on the creep deformation and recovery of CAD/CAM composite materials to determine their viscoelastic stability.

MATERIALS AND METHODS

Five CAD/CAM composite blocks, with increasing filler loading, and one polymer-infiltrated ceramic network (PICN) were studied. Six specimens of each material were separated into two groups (n=3) according to their storage conditions (24 h dry storage at 23°C versus 3 months storage in 37°C distilled water). A constant static compressive stress of 20 MPa was applied on each specimen via a loading pin for 2 h followed by unloading and monitoring strain recovery for a further period of 2 h. The maximum creep-strain (%) and permanent set (%) were recorded. Data were analysed via two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests (<0.05) for comparisons between the materials. Homogeneity of variance was calculated via Levene's statistics.

RESULTS

The maximum creep strain after 24 h dry ranged from 0.45% to 1.09% and increased after 3-month storage in distilled water to between 0.71% and 1.85%. The permanent set after 24 h dry storage ranged from 0.033% to 0.15% and increased after 3-month water storage to between 0.087% and 0.18%. The maximum creep strain also reduced with increasing filler loading.

SIGNIFICANCE

The PICN material exhibited superior dimensional stability to all of the pre-cured resin composite blocks in both storage conditions with deformation being predominantly elastic rather than viscoelastic. Notwithstanding, two of the resin-matrix composite blocks approached the PICN performance, when dry, but less so after water storage.

Effect of restoration technique on resistance to fracture of endodontically treated anterior teeth with flared root canals

This study was designed to compare the impact of post and core systems on resistance to fracture of endodontically treated anterior teeth with flared root canals and to assess their fracture pattern. Sixty central incisors were cut horizontally 2 mm coronal to the cementoenamel junction (CEJ). After root canal therapy, teeth were assigned into 6 groups (n=10 each) based on a post system and used as follows: Group C, non-flared root received size #1 glass fiber posts (Control); Group AP, flared root restored with anatomical post; Group RC, flared root restored with size #1 fiber post and cemented with thick layer of resin cement; Group CR, flared root restored with size #1 and reinforced with composite resin; Group CM, cast post-core; Group CP, CAD/CAM polymer-infiltrated ceramic post and core. Following post cementation, core build-up and crown insertion, the specimens were thermo-cycled up to 10,000 cycles (5C/55C; 30 seconds dwell time, 6 seconds transition time) and then statically loaded at 1 mm/minute crosshead speed using a universal testing machine. One-way ANOVA and Tukey HSD post hoc test (α=0.05) were used for data analysis. Group C recorded significantly higher resistance to fracture values [(826.9±39.1) N] followed by group CP [(793.8±55.6) N] while group RC yielded the lowest fracture resistance values [(586.7±51.4) N]. The resistance to fracture of wide root canals can be enhanced by using one-piece CAM/CAM post and core as an alternative to the use of either glass fiber post, relined with composite resin increasing the thickness of luting cement or the use of cast post and core system. However, this was an in vitro investigation and further in vivo studies are necessary.

Shade Stability of Polymer-Infiltrated and Resin Nano Ceramics

BACKGROUND

The esthetics plays an increasingly significant role in today's dentistry.

OBJECTIVE

The objective was to investigate the shade stability of a polymer-infiltrated and a resin nano ceramic in comparison to a conventional feldspar ceramic and an acrylate polymer.

METHODS

20 specimens of each of the materials, CAD-Temp (CT), Mark II (M), VITA Enamic (VE) and Lava Ultimate (LU), were prepared using the standard method. These were divided into groups (n=5) and placed in the following stain solutions: Distilled water, coffee, Coca-Cola and red wine for 14 days. The shade of each specimen was measured before and after using a spectrophotometer (n=5). The data were analyzed using ANOVA and Tukey's test (p ≤ 0.05).

RESULTS

The largest ΔE mean values were observed in CT by Coca-Cola (4.38 ± 0.41), in M by coffee (5.95 ± 0.62), in VE (6.02 ± 0.78) and LU (8.61 ± 0.30) by red wine. LU had the largest and strongest overall shade differences (total score: SSC=16.95) and CT the least (SSC=8.74). Overall shade differences of VE (SSC=12.03) and M (SSC=12.48) were statistically indistinguishable. After 14 days, only Coca-Cola caused clinically relevant shade differences in CT (ΔE > 2.7); this was also caused by coffee, Coca-Cola and red wine in M and coffee and red wine in VE and LU.

CONCLUSION

On average, VE showed fewer shade differences than LU. After 14 days of immersion, shade differences which exceeded the clinical acceptance threshold of ΔE=2.7 were shown by CT in Coca-Cola, by M in coffee, Coca-Cola and red wine, and by VE and LU in coffee and red wine.

Contemporary Dental Ceramic Materials, A Review: Chemical Composition, Physical and Mechanical Properties, Indications for Use

BACKGROUND

The high esthetic expectations from the prosthodontic restorations have directed the qualitative development of the materials towards the all-ceramic materials that are capable of replacing porcelain-fused-to-metal systems.

AIM

This article reviews the literature covering the contemporary all-ceramic materials and systems with a focus on the chemical composition and materials' properties; also it provides clinical recommendations for their use.

RESULTS

The glass-matrix ceramics and polycrystalline ceramics are presented, as well as recently introduced machinable materials, all-zirconia and resin-matrix ceramics. The specific properties of zirconia, such as transformation toughening, stabilisation of the crystallographic structure, low-temperature degradation and factors affecting the zirconia's ageing, are emphasised.

CONCLUSION

The favourable properties of the resin-matrix ceramics, such as modulus of elasticity similar to dentin, shock-absorbing characteristics and high resilience and fracture resistance, are also covered in this article.

In vitro performance and fracture resistance of novel CAD/CAM ceramic molar crowns loaded on implants and human teeth

PURPOSE

To investigate the fatigue and fracture resistance of computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic molar crowns on dental implants and human teeth.

MATERIALS AND METHODS

Molar crowns (n=48; n=8/group) were fabricated of a lithium-disilicate-strengthened lithium aluminosilicate glass ceramic (N). Surfaces were polished (P) or glazed (G). Crowns were tested on human teeth (T) and implant-abutment analogues (I) simulating a chairside (C, crown bonded to abutment) or labside (L, screw channel) procedure for implant groups. Polished/glazed lithium disilicate (E) crowns (n=16) served as reference. Combined thermal cycling and mechanical loading (TC: 3000×5℃/3000×55℃; ML: 1.2×10⁶ cycles, 50 N) with antagonistic human molars (groups T) and steatite spheres (groups I) was performed under a chewing simulator. TCML crowns were then analyzed for failures (optical microscopy, SEM) and fracture force was determined. Data were statistically analyzed (Kolmogorow-Smirnov, one-way-ANOVA, post-hoc Bonferroni, α=.05).

RESULTS

All crowns survived TCML and showed small traces of wear. In human teeth groups, fracture forces of N crowns varied between 1214±293 N (NPT) and 1324±498 N (NGT), differing significantly (P≤.003) from the polished reference EPT (2044±302 N). Fracture forces in implant groups varied between 934±154 N (NGI_L) and 1782±153 N (NPI_C), providing higher values for the respective chairside crowns. Differences between polishing and glazing were not significant (P≥.066) between crowns of identical materials and abutment support.

CONCLUSION

Fracture resistance was influenced by the ceramic material, and partly by the tooth or implant situation and the clinical procedure (chairside/labside). Type of surface finish (polishing/glazing) had no significant influence. Clinical survival of the new glass ceramic may be comparable to lithium disilicate.

Effect of Simulated Mastication on the Surface Roughness and Wear of Machinable Ceramics and Opposing Dental Enamel

OBJECTIVE:

Computer aided design-computer aided machining (CAD-CAM) ceramic crowns are replacing ceramo-metal ones due to newly developed mechanical properties and esthetics. To obtain knowledge about their interactions due to polishing and occlusal contacts with the opposing dental enamel specimen, including surface roughness and wear, the three-body wear simulation was investigated.

METHODS AND MATERIALS:

The surface roughness (RA) and wear rate (mm) of four CAD-CAM blocks with different compositions including Vita Mark II, e.max, Suprinity, and Enamic, after two surface treatments of glazing and polishing, and their opposing enamel specimens, were investigated using a mastication simulator and atomic force microscope.

RESULTS:

The roughness of all ceramic and to a greater extent enamel samples, with the exception of enamel opposing polished Enamic samples, was decreased after wear. No significant difference in wear was evident for the ceramic samples between the glazed and polished treatments. Lower wear rates were recorded only for polished Vita Mark II and polished Enamic in comparison to the glazed ones.

CONCLUSION:

The newly developed polishing systems for CAD-CAM ceramics can be good alternatives to reglazing, because the roughness and wear rate of both the ceramic and the opposing enamel will either not change or decrease.