Zirconia-based versus metal-based single crowns veneered with overpressing ceramic for restoration of posterior endodontically treated teeth: 5-year results of a randomized controlled clinical study

Shear bond strength of porcelain to milled and stereolithography additively manufactured zirconia with and without surface treatment: An in vitro study

STATEMENT OF PROBLEM

Delamination of veneering ceramic is one of the most common challenges relating to veneered zirconia restorations. Additive manufacturing (AM) is a fast-expanding technology that has gained widespread acceptance in dentistry and is increasingly being used to produce dental restorations. However, information about bonding of porcelain to AM zirconia is lacking.

PURPOSE

The purpose of this in vitro study was to investigate the shear bond strength (SBS) of porcelain to milled and additively manufactured zirconia, and the effect of surface treatment on bond strength.

MATERIAL AND METHODS

A Ø12×5-mm disk was designed virtually to fabricate all specimens, which were divided into 2 groups according to the manufacturing technique: additively manufactured or milled zirconia. The effect of airborne-particle abrasion and a zirconia liner before porcelain application was investigated in both groups. Veneering porcelain was fired into an alumina ring mold on the zirconia surface. SBS was measured by using a universal testing machine at a crosshead speed of 1 mm/min before and after aging (n=10). SBS data were analyzed with 3-way ANOVA (α=.05) RESULTS: A significant difference was found between milled and AM zirconia. The SBS of porcelain to milled zirconia was significantly higher (1.38 MPa) than to AM zirconia (0.68 MPa) (P<.001). The surface treatment of zirconia had no significant effect on porcelain SBS in either group (P=.254), whereas thermocycling significantly reduced the SBS of porcelain to zirconia in both milled and AM groups (P=.001).

CONCLUSIONS

Porcelain bonding to milled zirconia was better than to AM zirconia. Pretreating the zirconia substrate before porcelain application did not improve the porcelain bond.

Influence of different cutting instruments and rotational speeds on heat generation and cutting efficiency when sectioning different types of zirconia

PURPOSE

The purpose of this study was to evaluate the temperature generated on the intaglio surface and efficiency when cutting different types of zirconia with different rotary instruments and rotational speeds.

METHODS

A conventional diamond rotary instrument (Brasseler, grit size 107 μm) and special diamond rotary instrument marketed to cut zirconia (4 ZR, Brasseler, grit size 126 μm) were tested on 3Y-TZP and 4Y-TZP zirconia with a rotation speed of 100,000 rpm and 200,000 rpm. Zirconia specimens were cut under water cooling (110 mL/min) in a custom-made holder attached to a universal testing machine. The temperature was recorded with infrared sensors pointing at the intaglio surface of the zirconia specimens.

RESULTS

A rotation speed of 200,000 rpm resulted in significantly shorter cutting times, but also in significantly higher temperatures at the intaglio surface of the zirconia specimens compared with a rotation speed of 100,000 rpm. Significantly shorter cutting times were observed for the conventional diamond rotary instrument than for the special rotary instrument marketed to cut zirconia. Using the special rotary instrument, significantly longer cutting times were recorded for 3Y-TZP than for 4Y-TZP.

CONCLUSIONS

A conventional diamond rotary instrument was more efficient than a special rotary instrument. However, to avoid high temperatures when cutting zirconia clinically, a rotation speed of 100,000 rpm is recommended.

Clinical behavior and survival of endodontically treated teeth with or without post placement: a systematic review and meta-analysis

PURPOSE

Non-vital teeth usually exhibit substantial loss of coronal and radicular tooth structure, and use of posts after root canal treatment is controversial. This review examined whether placement of posts influences clinical behavior and survival probability of endodontically treated teeth (ETT).

METHODS

An electronic search, without time restrictions, for publications written in English was undertaken in PubMed, Scopus, and Web of Science. Terms related to four main components (endodontically treated teeth, fixed prosthesis, post restoration, and survival rate) were used for the database search strategies.

RESULTS

57 studies met the inclusion criteria and were included in the qualitative analysis. Of the publications chosen for qualitative analysis, 17 clinical studies (11 prospective and 6 retrospective studies) were found to be suitable for quantitative analysis. These studies included 7,278 patients (7,330 ETT), with a mean age ± standard deviation (SD) of 45.46 ± 12.1 years. There was a statistically significant difference in survival rate between ETT with or without posts (P < 0.001).

CONCLUSION

As compared with teeth with no posts, post placement on ETT may improve clinical performance and survival probability of endodontically treated teeth.

Outcome measurements and quality of randomized controlled clinical trials of tooth-supported fixed dental prostheses: A systematic review and qualitative analysis

STATEMENT OF PROBLEM

The lack of consensus regarding a standardized set of outcome measurements and noncompliance with current reporting guidelines in clinical trials of tooth-supported fixed dental prostheses (FDPs) hamper interstudy comparability, compromise scientific evidence, and waste research effort and resources in prosthetic dentistry.

PURPOSE

The primary objective of this systematic review was to identify all primary and secondary outcome measurements assessed in randomized controlled trials (RCTs) of tooth-supported FDPs. Secondary objectives were to assess their methodological quality by using the Cochrane Collaboration's risk of bias tool (RoB, v2.0) and their reporting quality by means of a standardized 16-item CONSORT assessment tool through published reports.

MATERIAL AND METHODS

An electronic search was conducted in MEDLINE, EMBASE, and Cochrane library to identify all RCT-related articles published in the past 10 years. Differences in RoB were tested with the Pearson chi-squared test, and those in CONSORT score with the Student t test.

RESULTS

A total of 64 RCTs from 79 publications were deemed eligible. The diversity of outcome measures used in the field is apparent. Twenty percent of the included studies had a low RoB, 79% showed some concerns, and 1% had a high RoB. The mean ±standard deviation CONSORT compliance score was 22.56 ±3.17. Trials adhered to the CONSORT statement reported lower RoB than those that did not adhere (P<.001). RCTs with a low RoB reported more comprehensive adherence to CONSORT guidelines than those with some concerns (MD 4 [95% CI 1.52-6.48]; P=.004).

CONCLUSIONS

A standardized core outcome reporting set in clinical research on tooth-supported FDPs remains evident. Adherence to the CONSORT statement continues to be low, with some RoB concerns that can be improved.

Bonding Effectiveness of Veneering Ceramic to Zirconia after Different Grit-Blasting Treatments

Objective: To determine the effect of grit-blasting before and after sintering on the surface roughness of zirconia and the micro-tensile bond strength of a pressable veneering ceramic to zirconia. Methods: Pre-sintered zirconia blocks (IPS e.max ZirCAD, Ivoclar) were divided into four test groups of three specimens each and a control group ('CTR'; no surface treatment). Pre-S-30, Pre-S-50, and Pre-S-110 were grit-blasted with 30-µm SiO2-coated Al2O3, 50-µm Al2O3 and 110-µm Al2O3 particles, respectively, before sintering. Post-S-30 was grit-blasted with 30-µm SiO2-coated Al2O3 after sintering. For each treatment, the surface roughness was measured (Ra, Perthometer M4P, Mahr Perthen). After sintering the zirconia blocks, a liner was applied and a pressable ceramic (IPS e.max ZirPress, Ivoclar) was heat-pressed. Sixteen microbars were obtained from each block and submitted to micro-tensile bond-strength (µTBS) testing. Data were analyzed with one-way ANOVA. Any correlation between Ra and µTBS was evaluated (Sperman test). Results: Grit-blasting before sintering with 110-µm Al2O3 (RaPre-S-110 = 3.4 ± 0.4 µm), 50-µm Al2O3 (RaPre-S-50 = 2.3 ± 0.5 µm), and 30-µm SiO2-coated Al2O3 (RaPre-S-30 = 1.2 ± 0.2 µm) resulted in significantly higher roughness than grit-blasting after sintering with 30-µm SiO2-coated Al2O3 (RaPost-S-30 = 0.5 ± 0.1 µm). The highest µTBS was measured when the sintered zirconia was grit-blasted with 30-μm SiO2-coated Al2O3 (µTBSPost-S-30 = 28.5 ± 12.6 MPa), which was significantly different from that of specimens that were grit-blasted before sintering (µTBSPre-S-30 = 21.8 ± 10.4; µTBSPre-S-50 = 24.1 ± 12.6; µTBSPre-S-110 = 26.4 ± 14.1) or were not grit-blasted (µTBSCTR = 20.2 ± 11.2). Conclusions: Grit-blasting zirconia before sintering enhanced the surface roughness proportionally to the particle size of the sand used. Grit-blasting with 30-µm SiO2-coated Al2O3 after sintering improved bonding of the veneering ceramic to zirconia. Clinical Significance: As grit-blasting with 30-µm SiO2-coated Al2O3 after sintering improved bonding of the veneering ceramic to zirconia, it may reduce veneering ceramic fractures/chipping.

Evaluation of periodontal parameters on abutment teeth rehabilitated with single-unit crowns: A 12-month follow-up

Purpose

This prospective study evaluated the effects of the metal-free crowns on the periodontal tissues of abutment teeth during a 12-month follow-up.

Materials and Methods

A sample of 24 patients (N = 32 abutment teeth) who needed a single-tooth restoration were enrolled to receive either a metal-ceramic (n = 21) or lithium disilicate (n = 11). The single-unit crowns were evaluated at baseline, 3-and 12-month follow-up. The periodontal parameters were evaluated: plaque index (PI), gingival bleeding index (GBI), bleeding on probing (BOP), probing depth (PD), clinical attachment loss (CAL), radiographically and clinical crown fitting, bone resorption, and marginal finish lines. Statistical analyses were performed using the Exact Fisher and Mann-Whitney tests, and the Wilcoxon signed-rank test as a post hoc test for Friedman (95 % confidence interval).

Results

The marginal finish line showed a statistical difference with a biomaterial type (p =.004). After a 12-months, a significant increase was observed in PI and mean PD for abutment teeth of metal-ceramic crowns. The metal-free crowns presented higher values for GBI and CAL (p2 < 0.05). Only distal cervical evaluation and dental biofilm formation in the abutment teeth showed a statistical difference between the groups at the 12-month follow-up. The supragingival margin metal-ceramic group revealed higher PI values (p2 = 0.005) between the period and the subgingival margin of both biomaterials showed greater GBI scores (p2 < 0.05).

Conclusions

Metal-free crowns showed better periodontal outcomes compared to metal-ceramic crowns. Single-unit crown marginal location affects the periodontal tissue condition of the abutment teeth. The marginal fit was not changed regarding the biomaterial type.

Comparison of clinical outcomes between single metal-ceramic and zirconia crowns

STATEMENT OF PROBLEM

Evidence comparing the survival of zirconia crowns with metal-ceramic crowns is sparse. Knowledge of their survival and a comparison of their clinical outcomes would improve clinical decision making.

PURPOSE

The purpose of this university-based study was to compare the survival, failures, biological and technical complications encountered with zirconia and metal-ceramic crowns restored and followed up over a similar period.

MATERIAL AND METHODS

This retrospective chart review consisted of 403 patients treated at the University of Toronto, Faculty of Dentistry, predoctoral dental clinic in whom zirconia (n=209) and metal-ceramic (n=306) crowns were inserted between September 2015 and July 2016 and followed for up to 7 years. Outcome measures included failure, causes for failure, and complications associated with survival. Inferential statistical analysis included the chi-squared test, t test, Mann-Whitney test, Bonferroni-adjusted z-test, Kaplan-Meier survival test, and logistic regression to examine differences between crown types and explore crown failures (α=.05).

RESULTS

The mean follow-up period was 3.00 years (median 2.58 years). Forty-one (8.0%) crowns had no follow-up, with no difference in follow-up between crown type: metal-ceramic n=23(7.5%), zirconia n=18(8.6%), χ²(1)=0.20, P=.652). Excluding those with no follow-up, the follow-up time between metal-ceramic (mean=3.07, median=2.58) and zirconia (mean=3.54, median=3.32) crowns was statistically similar (P=.052). There were 62 anterior crowns (12.0%) and 453 posterior crowns (88.0%), χ²(1)=22.40, P<.001, with no difference between groups. Overall, 44 crowns (8.5%) failed, 30 (9.8%) metal-ceramic and 14 (6.7%) zirconia, with no statistical difference in proportion of failed crowns between groups (χ²(1)=1.53, P=.216). There were 35 crowns with biological failures (6.8%), 26 (8.5%) in the metal-ceramic and 9 (4.4%) in the zirconia group, with no statistical difference between groups (χ²(1)=3.33, P=.068). Nine crowns had technical failures (1.7%), 4 (1.4%) in the metal-ceramic group and 5 (2.5%) in the zirconia group, with no statistical difference between groups (χ²(1)=0.73, P=.394). Biological (79.5%) rather than technical complications were found to be the most frequent cause of failure, goodness-of-fit χ²(1)=15.36, P<.001. Tooth fracture (50.0%) specifically was found to be the most frequent cause of failure, χ²(3)=21.27, P<.001. The total number of crowns that survived was 471 (91.5%); 276 (90.1%) were metal-ceramic and 195(93.3%) zirconia. The survival time (years) for metal-ceramic was mean=6.26, 95% CI [6.01-6.51] and for zirconia crowns mean=6.54, 95% CI [6.31-6.77]. Of the crowns that survived, 370 (78.6%) had no clinical complications, and 101 (21.4%) crowns demonstrated similar clinical complications, with no statistical differences between groups.

CONCLUSIONS

Within the study follow-up time, the survival of monolithic zirconia and metal-ceramic crowns was 91.5%, with similar clinical complications between groups. Biological complications, especially tooth fracture, were a significantly more frequent complication with both types of crowns.

Stress Distribution on Prepared Tooth With Shoulder and Radial Shoulder Margin to Receive Crowns of Three Different Materials: A Finite Element Analysis

Aim and background This study aims to determine the stress distribution on the prepared tooth at the margins with shoulder and radial shoulder finish lines when an occlusal load of 300N was applied to ceramic, zirconia, and polyether ether ketone (PEEK) crowns. Materials and methods Six models of mandibular first molar teeth were fabricated. The tooth models were subdivided into two groups with shoulder and radial shoulder margins, respectively (n = 18). The teeth were restored with three different prosthetic crown materials (ceramic, zirconia, and PEEK). To simulate the typical forces experienced by a prosthetic crown material in a lower posterior tooth during chewing and biting, an occlusal load of 300N was applied to each of the samples, and the maximum principal stress (Pmax) and von Mises stress were calculated, respectively. These samples were then compared and evaluated to determine the material best suited as a prosthetic crown material of choice for a lower posterior tooth. Results Among the materials used, the maximum principal stress value was the least in PEEK crowns. The von Mises stress value was highest for the zirconia crown with shoulder margin and was least for the PEEK crown with a similar margin. Conclusion PEEK as a crown material was found to be a better choice for lower posterior teeth as there was the least maximum principal stress at the margin, irrespective of either shoulder or radial shoulder finish line used.

Survival of fixed prosthetic restorations on vital and nonvital teeth: A systematic review

PURPOSE

To evaluate the survival rate of full-coverage tooth-supported fixed prosthetic restorations, single crowns (SCs), and fixed dental prostheses (FDPs), taking into consideration the potential influence of tooth-vitality, presence and type of post, and type of prosthetic restoration material.

MATERIALS AND METHODS

In October 2022, two authors independently conducted a search in PubMed, Web of Science, and Scopus electronic databases as well as a hand search to identify clinical human studies on full-coverage SCs and FDPs supported by vital and/or non-vital abutments and/or a combination of both, with a minimum observation period of 24 months.

RESULTS

Out of 4198 studies identified through the database search and 22 through hand searching, 26 studies fulfilled the inclusion criteria and were included in the analysis of the present systematic review. Included studies scored six points and more according to Newcastle-Ottawa Scale (NOS). The highest estimated 5-year survival rate was observed for (metal-ceramic and all-ceramic) SCs on vital teeth (98.3%; 95% CI [98.1, 98.6%]) and all ceramic SCs on non-vital teeth with fiber post (95.0%; 95% CI [94.5-95.4%]). Metal-ceramic SCs on vital teeth (97.1%; 95% CI [95.6-98.7%]) showed a statistically significant higher estimated 5-year survival rate compared to metal-ceramic SCs with cast metal post (90.7%; 95% CI [87.4-94.0%], P < 0.001), fiber post (91.3%; 95% CI [90.9-91.6%], P < 0.001) and without post (85.7%; 95% CI [80.7, 90.6%], P < 0.032). All-ceramic SCs with fiber post had a statistically significant higher estimated 5-year survival rate (95.0%; 95% CI [94.5-95.4%]) compared to metal-ceramic SCs on non-vital teeth with fiber post (91.3%; 95% CI [90.9-91.6%], P < 0.001). SCs (all-ceramic and metal-ceramic) with fiber post had a statistically significantly higher estimated 5-year survival rate of (92.7%; 95% CI [92.4-92.9%]) than SCs made of metal-ceramic and retained by cast metal post (90.7%; 95% CI [87.4-94.0%], P < 0.001). For FDPs, the 5-year survival rate was significantly higher for FDPs on vital abutments (84.9%; 95% CI [75.9, 93.9%]) compared to FDPs retained by non-vital abutment/s (81.3%; 95% CI [80.3, 82.2%], P = 0.049) irrespective to presence, type of post, and FDPs material. The results are limited by the limited number of studies and the presence of uncontrolled confounding clinical variables.

CONCLUSIONS

Within the limitations of the study, tooth vitality is suggested to contribute positively to the survival of SCs and FDPs.

Effect of artificial aging on optical properties and crystalline structure of high-translucency zirconia

PURPOSE

To investigate the effect of different in vitro aging protocols on the optical properties and crystalline structure of high-translucency (HT) zirconia.

MATERIALS AND METHODS

Thirty-six specimens of HT and extra-high translucency (XT) zirconia were divided into three groups: control (CO)-no treatment; hydrothermal aging (HA)-autoclave aging for 12.5 h at 134°C, 2 bar; clinically related aging (CRA)-aging in the chewing simulator for 1.2 million cycles, followed by 50,000 thermocycles (5-55°C) and immersion in HCl (pH 1.2) for 15 h. Optical properties, crystalline structure, and surface roughness were analyzed and compared using analysis of variance (5% significance level).

RESULTS

There was no statistically significant effect of aging on translucency (p = 0.10), but CRA promoted the development of a high contrast ratio (p = 0.03). Aging did not cause significant color changes for HT (p = 0.65) or XT (p = 0.36). The proportion of monoclinic crystals increased to 40% for HT-zirconia after HA and 5% after CRA. No monoclinic crystals were detected for XT groups. There was no effect of aging on surface roughness (p = 0.77).

CONCLUSIONS

Although hydrothermal aging has been widely used to verify zirconia crystalline stability, it did not generate an effect similar to clinically related aging on the optical properties and crystalline structure of zirconia. HA affected the crystalline structure of HT-zirconia, and CRA compromised the optical properties of XT zirconia.

Clinical outcomes of tooth-supported monolithic zirconia vs. porcelain-veneered zirconia fixed dental prosthesis, with an additional focus on the cement type: a systematic review and meta-analysis

PURPOSE

To compare the failure rates and the prevalence of technical complications between full-coverage tooth-supported monolithic zirconia (MZ) and porcelain-veneered zirconia (PVZ) fixed dental prosthesis, based on a systematic literature review.

METHODS

An electronic search was performed in three databases, supplemented by hand searching. Several statistical methods were used.

RESULTS

Seventy-four publications reported 6370 restorations (4264 PVZ; 2106 MZ; 8200 abutment teeth; 3549 patients), followed up until 152 months. A total of 216 prostheses failed, and survival was statistically significant different between groups. PVZ had higher occurrence of complications than MZ; the difference was especially greater for either minor or major chipping. The difference in prevalence of either minor or major chipping was statistically significant for PVZ prostheses between cementation with glass ionomer and adhesive resin cement (higher), adhesive resin and resin-modified glass ionomer cement (RMGIC, higher), and between RMGIC (higher) and glass ionomer cement. For MZ the difference was significant only for minor chipping between RMGIC (higher) and adhesive resin cement. Abutment teeth to PVZ prostheses more often lost vitality. Decementation was not observed with RMGIC. Air abrasion did not seem to clinically decrease the decementation risk. The 5-year difference in the occurrence of minor or major chipping between MZ and PVZ prostheses was statistically significant, but nor for catastrophic fracture.

CONCLUSION

Tooth-supported PVZ prostheses present higher failure and complication rates than MZ prosthesis. The difference in complications is striking when it comes to chipping.

CLINICAL RELEVANCE

Awareness of the outcome differences between different types of zirconia prostheses is important for clinical practice.

Patient-related outcomes and Oral Health-Related Quality of Life in endodontics

There is increased interest in outcome measures that complement the classic goal of endodontics, being the prevention and healing of apical periodontitis. Possible outcome measures can be subdivided into patient-centred outcomes (PCOs), encompassing data collected by nonpatients aiming to assess the effectiveness of an intervention and patient-reported outcomes (PROs), which are reported directly by the patient. PROs can be subsequently classed into PRO measures that ascertain patients' view of their symptoms, their functional status, and their health-related quality of life, and patient-reported experience measures that focus on aspects including the humanity of care, patient satisfaction, patient preference and adherence, personal costs, expectation fulfilment, and decision regrets. The present review aims to define various patient-related outcomes and discuss the literature available regarding PCOs and PROs in endodontics. This includes those proposed to assess the effectiveness of endodontic treatment for pulpitis and apical periodontitis for use in the development of European Society of Endodontology S3-level clinical practice guidelines that have been included by all working groups, except for the radiographic assessment of apical periodontitis. Based on limited evidence in the field, it can be summarized that after recall periods of various lengths, endodontic treatment is associated with a high likelihood of tooth survival and limited need for further intervention, including extraction and further restorative procedures. Oral Health-Related Quality of Life (OHRQoL) is likely to improve following the completion of treatment. Nonetheless, the literature assessing the association between OHRQoL and endodontics is hampered by the use of instruments that have not been previously validated. Amongst the remaining outcome measures discussed in the present review, it is worth highlighting that there is only one study assessing exacerbations in teeth with the presence of endodontic pathosis, which suggests a very low incidence of this adverse effect following endodontic treatment. Patients' expectation fulfilment, adherence, and satisfaction are closely inter-related and depend also on various nonclinical factors. Further studies assessing PCOs and PROs, in association with healing and prevention of apical periodontitis, are required to better understand endodontic treatment from the perspective of patients.

A brief review on fatigue test of ceramic and some related matters in Dentistry

The characteristics of dental ceramics have been extensively studied over the years to provide highly qualified materials for use in prosthetic restorations. The ability to adhere to dental substrates, outstanding aesthetics (translucency, color, and substrate masking ability) and improved mechanical properties provide these materials with optical features and high strength to withstand masticatory stimuli. Different classifications are adopted, and it is generally considered that glass-ceramics have better optical characteristics due to the high glass content, and polycrystalline ceramics have superior strength favored by their densified and organized crystals, hampering crack growth. This knowledge was largely built-up during years of scientific research through different testing methodologies, but mainly employing static loads. It is important to not only take into account the intensity of loads that these materials will be exposed to, but also the effect of the intermittence of cyclic load application leading to mechanical fatigue and the influence of factors related to the crack origin and their propagation under this condition. Furthermore, the bonding surface of ceramic restorations requires surface treatments that improve the bond strength to luting agents; however, these treatments require caution because of their potential to produce defects and affect the structural behavior. Moreover, ceramic restorations often require internal adjustments for proper seating or external adjustments for fitting the occlusal contact with the antagonist. In this sense, finishing/polishing protocols may alter the defect population, as luting agents may also interact by filling in the superficial defects on the restoration intaglio surface. Thus, the balance among all these factors will define the performance of a restorative setup, as well as the posterior exposure to the humid environment and the masticatory stimuli (cyclical loading), which may favor developing slow and subcritical growth of cracks in ceramic materials and the degradation of the bond interface. Therefore, it is essential that the concepts which explain the fatigue mechanism are understood, as well as the crack propagation and failure patterns of restorative ceramic materials.

Reasons for Failure of CAD/CAM Restorations in Clinical Studies: A Systematic Review and Meta-analysis

AIM

The systematic review presented herein was performed to descriptively analyze the causes for the failure of computer-aided design/computer-aided manufacture (CAD/CAM) restorations. The meta-analysis reported herein was performed to estimate long-term survival and success rates of CAD-CAM fabrications.

MATERIALS AND METHODS

Using the PICOS paradigm, a systematic search was carried out in the PubMed and Cochrane databases to identify randomized controlled trials (RCTs) and prospective observational studies reporting survival data for CAD/CAM restorations. After selecting studies with a predefined set of selection criteria, data from included prospective clinical studies and RCTs were used for a systematic review aimed at a descriptive analysis of factors associated with failure of CAD-CAM restorations. Data from the included prospective clinical studies were used for meta-analysis, wherein 5-year and 10-year survival and success rates were estimated using Poisson regression models.

RESULTS

The systematic review included data from 9 RCTs and 6 observational studies, which had a median follow-up of 36 months and 60 months, respectively. About 58 failures and 118 technical/ biological complications were noted in the included RCTs and 9 failures along with 58 technical/biological complications were noted in the prospective clinical studies. Poisson regression indicated an estimated 5-year and 10-year survival rates of 85.55-100 and 71-100, respectively. The estimated 5-year and 10-year success rates were 74.2-92.75 and 33.3-85.5, respectively.

CONCLUSION

Several technical and biological complications contribute to failure of CAD/CAM restorations. However, CAD/CAM restorations with routine chairside materials might have clinically meaningful success rates in the long term.

CLINICAL SIGNIFICANCE

The results presented herein indicate that optimal strategies for mitigation of biological and technical complications may augment the success of CAD/CAM fabrications in restorative dentistry. Studies aimed at identification of such strategies are needed to further enhance the long-term success rates of CAD/CAM restorations.

Knowledge and Awareness regarding Dental Management of Hemophilic Patients among Students of a Malaysian University: A Cross-Sectional Study

Background:

Improper management of bleeding disorders in the dental setting can lead to complications that can endanger the lives of such patients.

Objective:

This study aimed to assess the knowledge and awareness of dental management of hemophilia among undergraduate students of a Malaysian university.

Methodology:

A cross-sectional survey was conducted in the year 2018-2019 to collect the data. A 23-item questionnaire developed and validated by the authors was used to collect data on the knowledge and awareness regarding dental management of hemophilia patients. A total of 216 dental students participated in this research. Unpaired t-test and one-way ANOVA were used to compare the knowledge score between gender and academic year.

Results:

Only 21% of the participants were confident in treating a hemophilia patient. About 97% of the participants believed that the dental curriculum must be modified to emphasize the dental management of bleeding disorders. The overall mean of the knowledge score was 47.38% and awareness was 73.7% regarding the management of patients with hemophilia.

Conclusion:

The study revealed significant scope for improvement in the dental students' knowledge, which can be achieved by modifying the dental curriculum suitably to provide more emphasis on the management of bleeding disorders.

Do tooth-supported zirconia restorations present more technical failures related to fracture or loss of retention? Systematic review and meta-analysis

OBJECTIVES

This systematic review was performed to determine the main cause of technical failure of tooth-supported zirconia crowns and fixed partial dentures (FPDs), categorizing them as fracture/chipping or loss of retention/decementation.

MATERIALS AND METHODS

Electronic and manual searches were performed for randomized clinical trials, prospective clinical trials, and prospective cohort studies that reported the technical failure rates of zirconia restorations. The Cochrane Collaboration risk-of-bias tool and Newcastle-Ottawa scale were used to assess the quality of the studies.

RESULTS

Fifty-two studies were included and most of them had unclear risk of bias. Considering all reported fractures/chipping, for veneered crowns with 1 to 3 years of follow-up, the relative risk (RR) of fracture in relation to loss or retention was 3.95 (95% CI 1.18-13.23; p = 0.03). For 4 to 6 years of follow-up, the RR was 5.44 (95% CI 1.41-20.92; p = 0.01). For veneered FPDs with 1 to 3 years of follow-up, the RR was 5.98 (95% CI 2.31-15.01; p = 0.0002). For 4 to 6 years of follow-up, the RR was 3.70 (95% CI 1.63-8.41; p = 0.002). For 7 years or more of follow-up, the RR was 3.45 (95% CI 1.84-6.46; p = 0.0001). When only framework fractures were considered, there were no significant differences for the RR in all follow-up periods (p > 0.05).

CONCLUSIONS

Higher RR for fracture/chipping in relation to decementation for veneered zirconia crowns and FPDs at all follow-up times. For framework fractures, no difference was observed between the risk of failure of the restoration due to fracture or decementation.

CLINICAL RELEVANCE

Zirconia crowns and FPDs showed relatively high success and survival rates. However, considering the technical failures, there is approximately four times higher chance of fracture/chipping than loss of retention for both single and multi-unit tooth-supported veneered zirconia restorations.

CAD-FEA modeling and fracture resistance of bilayer zirconia crowns manufactured by the rapid layer technology

In the RLT (Rapid Layer Technology), veneering ceramic and framework are fabricated by computer-aided design/computer-aided manufacturing (CAD/CAM) and then cemented to obtain the restoration. This study aimed to evaluate the effect of the thickness of veneering ceramic manufactured by the RLT technique on the fracture resistance (FR) of bilayer crowns with zirconia frameworks. Twenty zirconia frameworks and twenty feldspathic posterior crowns with two different veneering ceramic occlusal thicknesses (1mm=TF1; 2mm=TF2) were manufactured using CAD/CAM system. The specimens were luted to an epoxy resin abutment with resin cement and mechanically cycled (200N and 4.5×105 Pa, 37°C, 2×106 cycles, 3Hz). The FR test was performed (10kN, 0.5mm/min), and the specimens were analyzed in a stereomicroscope. For the stress analysis (finite element analysis, FEA), a 10kN load was equal to the in vitro test, and the principal stress was evaluated. The FR data were analyzed by Student's t-test and Weibull's analysis. The thickness influenced the FR of bilayer crowns. The FR was higher in the TF2 than in the TF1 group. The TF2 group presented the highest characteristic strength compared to the group TF1. The predominant type of failure was delamination. The FEA showed higher stress concentrations below the loading application point at the veneering cement interface in the 1-mm-thick model. The bilayer crowns manufactured using the approach of 2mm of veneering ceramic promoted higher FR compared to the group with 1mm veneering ceramic. Also, the FEA showed that the veneer ceramic thickness has an effect on stress distribution in zirconia-based bilayer crowns.

Forensic and reliability analyses of fixed dental prostheses

This article describes the protocol for determining the cause of failure for retrieved failed implant supported fixed dental prostheses (FDPs) in a clinical study of three-unit bridges. The results of loading of flexure bars of different veneer compositions at different stress rates were presented for two veneer materials (leucite reinforced and fluorapatite glass-ceramic veneers) and a Y-TZP core zirconia ceramic used in the clinical study. From these results, the strengths of the fast loading conditions were used to determine the fracture toughness of these materials. Fractal dimension measurements of the flexure bars and selected FDPs of the same materials demonstrated that the values were the same for both the bars and the FDPs. This allowed the use of fracture toughness values from the flexure bars to determine the strengths of the FDPs. The failure analysis of clinically obtained FDP replicates to determine the size of the fracture initiating cracks was then performed. Using the information from the flexure bars and the size of the fracture initiating cracks for the failed FDPs, the strengths of the FDPs were determined. The clinical failures were determined to be most likely the result of repeated crack growth due to initial overload and continuous use after initial cracking.

Glass Ionomer Versus Self-adhesive Cement and the Clinical Performance of Zirconia Coping/Press-on Porcelain Crowns

OBJECTIVE

This split-mouth clinical study investigated the effect of luting cement on the performance of veneered yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) zirconia crowns.

METHODS AND MATERIALS

A total of 60 crowns prepared with Y-TZP coping and press-on porcelain were made with a split-mouth design in 30 participants. The crowns were cemented either with glass ionomer cement (GIC) (Meron, Voco) or with self-adhesive resin cement (Bifix-SE, Voco). The restorations were assessed immediately after treatment and after 6, 12, 24, 36, and 48 months using the modified United States Public Health Service criteria. The parameters analyzed were retention, color stability, marginal discoloration, marginal adaptation, surface roughness, anatomic form, and secondary caries. The differences between the groups were analyzed by the Fisher exact test in each period of evaluation. The survival rate was analyzed with the Kaplan-Meier and log-rank test (α=0.05).

RESULTS

After 48 months, 20 participants attended the recall. During the period of evaluation, 1 crown cemented with glass ionomer cement and 1 crown cemented with resin cement lost retention. Color match, marginal discoloration and adaptation, surface roughness, and anatomic form did not change in any of the periods evaluated, and no secondary caries was observed. No significant differences were found between the 2 luting cements for any of the clinical parameters analyzed, nor for the survival rates during the study.

CONCLUSIONS

The type of cement did not influence the performance of the crowns after 48 months of clinical use. Both cements resulted in adequate retention rates, aesthetic and functional outcomes, and biological response.

Long-term clinical performance and complications of zirconia-based tooth- and implant-supported fixed prosthodontic restorations: A summary of systematic reviews

OBJECTIVES

To present an overview on systematic reviews on prosthodontic zirconia restorations and to discuss long-term complications as well as information on anatomical and functional changes to the masticatory system.

DATA/SOURCES

MEDLINE, EMBASE, Trip medical, and Cochrane Library databases were searched for systematic reviews up to February 2021. Bias was assessed and clinical survival and complications were analyzed.

STUDY SELECTION

38 eligible articles published between 2006 and 2021 were included. The reviews were based on 128 in vivo studies on approximately 10,000 zirconia restorations. 5-year cumulative survival rates varied between 91.2% and 95.9% for tooth-supported (TS) single crowns (SC), 89.4% and 100% for TS multi-unit fixed dental prostheses (FDP), 97.1% and 97.6% for implant-supported (IS) SCs and 93.0% and 100% for IS FDPs. Chipping was the most often technical complication, followed by framework fracture, loss of retention, marginal discrepancies/discoloration, occlusal roughness and abutment/screw loosening. Color mismatch was the only esthetic complication. Biological complications were caries, endodontic complications, tooth fracture, periodontal disease, abrasion/attrition, persisting pain, high sensitivity, peri‑implantitis and soft tissue issues. Patients with bruxism were only examined sporadically.

CONCLUSIONS

5-year results for zirconia restorations were satisfactory. The predominant technical problem of veneering fractures could be overcome with adapted design or fabrication and application of monolithic restorations, but reviews of clinical studies on this subject are rare. The impact of zirconia restorations on the masticatory system remains unclear.

CLINICAL SIGNIFICANCE

Zirconia restorations are experiencing a rapidly increasing use in dental practice. Being highly wear-resistant, hard and durable, it can be assumed that they do not follow natural abrasion and changes in the masticatory system. Possible long-term effects on the stomatognathic system as a whole should therefore be considered.

Effect of glazing application side and mechanical cycling on the biaxial flexural strength and Weibull characteristics of a Y-TZP ceramic

Glaze application on monolithic zirconia (Y-TZP) can be a practical approach to improve the mechanical properties of this material.

Effect of pH Cycling Frequency on Glass-Ceramic Corrosion

The effect of pH changes on the chemical durability of dental glass-ceramic materials was evaluated using weight loss and ion release levels. The hypothesis that increased pH changes will exhibit greater corrosion was investigated. The ion concentration was analyzed using inductively coupled plasma atomic emission spectrometer (ICP). The surface compositions were investigated using X-ray photoelectron spectroscopy (XPS). The surface morphologies were examined using scanning electron microscopy (SEM). Dental glass-ceramics were tested in constant immersion, 3-day cycling, and 1-day cycling with pH 10, pH 2, and pH 7 for 3, 15, and 30 days. The 1-d cycling group demonstrated the highest levels of weight loss compared with 3-d cycling and constant immersion. For the ion release, Si4+ and Ca2+ had the highest rates of release in 1-d cycling, whereas the Al3+ release rate with constant pH 2 was highest. The alteration/passivation layer that was formed on the surface of disks possibly prevented further dissolution of pH 10 corroded disks. XPS analysis demonstrated different surface compositions of corroded disks in pH 10 and pH 2. Si4+, K+, Na+, Al3+, and Ca2+ were detected on the surface of corroded pH 10 disks, whereas a Si4+ and P5+-rich surface formed on corroded pH 2 disks. SEM results demonstrated rougher surfaces for corroded disks in cycling conditions and pH 2 constant immersion. In conclusion, increased pH changes significantly promote the corrosion of dental glass-ceramic materials.

Treatment options for large posterior restorations: a systematic review and network meta-analysis

BACKGROUND

The best treatment option for large caries in permanent posterior teeth is still a matter of uncertainty in dental literature. The authors conducted a network meta-analysis to address the challenges related to rehabilitation of these teeth.

TYPES OF STUDIES REVIEWED

The authors selected prospective and retrospective studies that compared at least 2 different treatment alternatives for permanent teeth with a minimum of 5 years of follow-up. The authors searched databases from MEDLINE, Scopus, Cochrane Library, and Web of Science in October 2019 without language or year of publication restrictions.

RESULTS

From 11,263 studies identified, 43 studies fulfilled the eligibility criteria and were included in the final review. Only 13 studies were randomized controlled trials and were classified as low risk of bias. Gold (annual failure rate of 0.29%) and metal ceramic (annual failure rate of 0.52%) crowns performed better for indirect restorations and direct resin composite performed better for direct restorations (annual failure rate of 2.19%). The most substantial comparisons were between feldspathic and glass ceramics, followed by direct resin composite and amalgam; there were no statistically significant differences between these interventions. Results of the pairwise meta-analysis showed mainly glass ionomer as significantly more prone to failure than amalgam and direct composite resin.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

Reference standard direct and indirect materials except for glass ionomer can be used for restorations of large posterior caries.

Grinding the intaglio surface of yttria partially- and fully-stabilized zirconia polycrystals restorations: Effect on their fatigue behavior

This study evaluated the effects of diamond bur grinding the intaglio surface of second (yttria partially-stabilized zirconia polycrystals, PSZ) and third-generation zirconia (fully-stabilized zirconia polycrystals, FSZ) adhesively cemented to dentin analogue substrate on the fatigue failure load, cycle number until failure, surface micromorphology and phase transformation. Disc-shaped specimens were produced from second (Katana ML-HT, Kuraray) and third-generation zirconia (Katana STML, Kuraray) and randomly allocated (n = 15) into two groups according to the intaglio surface treatment: Control - Ctrl (without grinding); Grinding - Gr (grinding at the center of the intaglio surface). The ceramic discs were adhesively cemented (Multilink Automix System) onto dentin analogue discs. Fatigue tests were executed by the step-stress method. The obtained data were analyzed by Kaplan Meier and Mantel-Cox tests. In addition, surface topography, roughness, phase transformation and fractography analyses were performed. SEM analysis showed that grinding increased the surface roughness and introduced defects in zirconia from both generations. Grinding increased the fatigue failure load, number of cycles to failure and survival rates of the second-generation zirconia statistically (control: 1373.33 N < grinding: 1600 N), while these same outcomes were reduced by grinding for the third-generation zirconia significantly (control: 766.67 N > grinding: 620 N). Thus, clinical adjustments with diamond burs damage the fatigue behavior of adhesively cemented third-generation zirconia.

Effect of thermal and mechanical cycles on shear bond strength of zirconia core to porcelain veneer under different surface treatments

Background. Due to the fragile nature of all-ceramic restorations, it is necessary to provide an appropriate (core) infrastructure to support the veneering porcelain. The veneer detachment and chipping are disadvantages of these restorations. Several techniques have been proposed to minimize these problems. This study evaluated the effect of thermal and mechanical cycles on the shear bond strength of zirconia core to porcelain veneer under different surface treatments.

Methods. Sixty disk-like zirconium samples were randomly divided into three groups. The first group was polished and veneered with porcelain, without additional surface treatments. The two other groups were subjected to different surface treatments (modified aluminum oxide by silica and activator‒aluminum oxide and primer) and veneering with porcelain. Half of the samples in each group were subjected to 6000 thermal cycles and 20,000 masticatory cycles of 50 N to imitate the intraoral conditions; the other half were placed in distilled water at 37°C until the shear strength test. Each sample was then buried using PMMA in a mounting jig so that the gap between the core and the veneer could be placed upward. Then, they were exposed to shear stress using a universal testing machine at a rate of 1 mm/min until fracture. The maximum force leading to the fracture was recorded.

Results. Comparison of the groups showed that the highest shear bond strength was related to the samples treated with aluminum oxide and primer, without applying thermal and masticatory cycles, which indicated no significant difference from the group treated with aluminum oxide and primer, with thermal and masticatory cycles. The lowest shear bond strengths were related to the polished samples without surface treatment by applying thermal and masticatory cycles (P=0.001), which indicated no significant difference from the untreated group without thermal and masticatory cycles.

Conclusion. Based on the results, treatment with aluminum oxide and primer increased the shear bond strength of zirconia core to porcelain veneer. Thermocycling and masticatory cycles failed to reduce the shear bond strength in all the three groups significantly

Silicon-based film on the yttria-stabilized tetragonal zirconia polycrystal: Surface and shear bond strength analysis

AIM

To analyze the effect of a silicon (Si)-based film deposited on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) on the topography and bond strength of resin cement.

METHODS

Specimens of zirconia were obtained and randomly divided into 4 groups, according to surface treatment: polished group (PG) zirconia; sandblasted group (SG) zirconia with aluminum oxide (100 µm); after polished, zirconia was coated with Si-based film group (SiFG); and after sandblasted, zirconia was coated with Si-based film group (SiFSG). The Si-based films were obtained through plasma-enhanced chemical vapor deposition. Surface roughness and contact angle analysis were performed. Resin cement cylinders were built up on the treated surface of blocks, after applying Monobond-S. The specimens were submitted to thermocycling aging and shear bond strength testing. The Kruskal-Wallis and Mann-Whitney U-tests were performed.

RESULTS

There were significant differences between the surface treatments for each roughness parameter measured. Si-based film increased roughness and decreased the contact angle. Si-based film groups also demonstrated significantly lower bond strength values.

CONCLUSION

Si-based film produced using plasma deposition provided lower bond strength to resin cement compared with conventional treatment; however, the film deposition reduced the contact angle and improved roughness, favorable properties in the long way to prepare an optimum material.

CAD/CAM or conventional ceramic materials restorations longevity: a systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis aimed to evaluate the difference in longevity of tooth-supported ceramic prostheses designed by conventional and computer-aided design/computer-aided manufacturing (CAD/CAM) techniques.

STUDY SELECTION

Two reviewers searched the Web of Science, PubMed, SCOPUS and LILACS databases between 1966 and October 2017. Clinical studies that compared the survival rate of CAD/CAM against conventional restorations were included.

RESULTS

Eleven randomized controlled trials and three prospective studies were included, n=14. Three types of tooth-supported restorations were searched in the included studies: single crown, multiple-unit and partial ceramic crown. The follow-up of patients in the studies ranged from 24 to 84 months. A total of 1209 restorations had been placed in 957 patients in the included trials, and failures were analyzed by type and material restoration. From a total of 72 restoration failures, the CAD/CAM system resulted in a 1.84 (IC95%: 1.28-2.63) higher risk than conventional manufacturing of ceramic restoration. Nevertheless, when drop-outs were included as a failure risk, the CAD/CAM system resulted in a risk of 1.32 (IC95%: 1.10-1.58). Multilevel analysis of tooth-supported ceramic restorations, considering drop-outs as successes, resulted in rates of 1.48 and 2.62 failures per 100 restoration-years for the controls and CAD/CAM groups, respectively. Considering drop-outs as failures, we found rates of 4.23 and 5.88 failures per 100 restoration-years for the controls and CAD/CAM groups, respectively.

CONCLUSIONS

The meta-analysis results suggest that the longevity of a tooth-supported ceramic prostheses made by CAD/CAM manufacturing is lower than that of crowns mad by the conventional technique.

CAD/CAM Ceramic Restorative Materials for Natural Teeth

Advances in computer-aided design (CAD) / computer-aided manufacturing (CAM) technologies and their ease of application enabled the development of novel treatment concepts for modern prosthodontics. This recent paradigm shift in fixed prosthodontics from traditional to minimally invasive treatment approaches is evidenced by the clinical long-term success of bonded CAD/CAM glass-ceramic restorations. Today, defect-oriented restorations, such as inlays, onlays, and posterior crowns, are predominately fabricated from glass-ceramics in monolithic application. The variety of CAD/CAM ceramic restorative systems is constantly evolving to meet the increased demands for highly aesthetic, biocompatible, and long-lasting restorations. Recently introduced polymer-infiltrated ceramic network CAD/CAM blocks add innovative treatment options in CAD/CAM chairside 1-visit restorations. The material-specific high-edge stability enables the CAD/CAM machinability of thin restoration margins. Full-contour zirconia restorations are constantly gaining market share at the expense of bilayered systems. Advancements in material science and bonding protocols foster the development of novel material combinations or fabrication techniques of proven high-strength zirconia ceramics. CAD/CAM applications offer a standardized manufacturing process resulting in a reliable, predictable, and economic workflow for individual and complex teeth-supported restorations. More evidence from long-term clinical studies is needed to verify the clinical performance of monolithic polymer-infiltrated ceramic network and zirconia teeth-supported minimally invasive and extensive restorations.

We're Going Digital: The Current State of CAD/CAM Dentistry in Prosthodontics

This paper reviews the current state of computer-aided design and manufacturing (CAD/CAM) in dentistry, with a special focus on restorative dental applications. The potential, advantages, and limitations of the technology will be discussed, comparing the digital workflow to conventional techniques, based on contemporary clinical evidence. The technology does seem to offer a more streamlined and efficient means of treatment planning and delivery of care through reduced chairside time, with reported improved patient satisfaction. Nonetheless, the accuracy and treatment outcomes of CAD/CAM treatment modalities are inconsistent and do not support a superior performance to existing conventional techniques, rather a comparable one.