Quo vadis, esthetic dentistry? Part II: Composite resin overtreatment and social media appeal.

OBJECTIVES: This article presents case reports highlighting over-treatments with resin composites, often misconceived as minimally invasive procedures. CLINICAL CONSIDERATIONS: Tooth-colored restorative materials, such as ceramics and composites, have found widespread application to correct problems related to tooth color, shape, and alignment. When composite resin is used, these procedures can be done in a very conservative, cost-effective, and timely fashion. However, it is noteworthy that contemporary dental esthetic expectations are based on standards propagated by social media and other marketing and communications platforms. The abuse of and addiction to social media impacts can lead to unrealistic esthetic expectations and standards for both patients and dentists. CONCLUSIONS: After a critical discussion on ceramic veneers published in part I of this 2-part series, this article directs attention towards what has become a trendy fashion, i.e., the use of direct composite resins as "non-prep" veneers in clinical situations that arguably required no restorative intervention at all. We further explore how social media influences the decision-making processes of both professionals and patients.

Quo vadis, esthetic dentistry? Ceramic veneers and overtreatment-A cautionary tale.

The increased emphasis on orofacial esthetics, experienced both by dental professionals and the lay public, results in an environment where overtreatment can easily occur. Patients on the one hand feel pressure from esthetic norms that are often unrealistic, while dental professionals are compelled to deliver immediate results many times without considering what is best for the ill-informed patient. This article is an illustrated cautionary tale against overtreatment disguised as esthetic dentistry. Representative clinical examples illustrate how porcelain veneers are used without following sound operatory principles, as well as how these cases have been resolved.

Composite veneers: The direct-indirect technique revisited.

OBJECTIVE: This article provides an update on the direct-indirect composite veneer technique. CLINICAL CONSIDERATIONS: Composite veneers have long been used as a conservative and esthetic treatment option for anterior teeth. While they are generally performed using a direct technique, there has been renewed interest in the direct-indirect composite veneer technique because of its advantages and broad indications for restoration of tooth color and morphology. In the direct-indirect composite veneer technique, the selected composites are initially applied on the tooth using a layering approach, without any bonding agent, sculpted to a primary anatomic form with slight excess, and light-cured. The partially polymerized veneer is then removed from the tooth, heat-tempered, and finished to final anatomy and processed extra-orally before being luted. Advantages of this technique include enhanced physical and mechanical properties afforded by the tempering process, unrivaled marginal adaptation, enhanced finishing and polishing, and the ability to try-in the veneer before luting, enabling a shade verification and modulation process that is not possible with the direct technique. The direct-indirect approach also affords enhanced gingival health and patient comfort. CONCLUSION: This article reviews the direct-indirect composite veneer technique, and outlines critical steps and tips for clinical success. CLINICAL SIGNIFICANCE: The direct-indirect technique for composite veneers combines advantages of the direct composite placement technique with those of the indirect veneer technique, including operator control, single-visit fabrication and delivery, increased material properties, and excellent esthetics.

The inconspicuous nature of COVID-19 and its impact to dentistry.

To state that the new coronavirus SARS-CoV-2 has broadly and deeply impacted our lives is an understatement. Since it first showed up on our radar in December 2019, the new coronavirus has wreaked havoc on virtually all businesses and industries across the globe. The impact is equally felt in developing, developed, industrialized, rural, rich, and poor countries and communities, irrespective of how well-prepared those countries and communities felt they were 9 months ago. To this day we are still learning to prepare for, respond to, and adapt to the broad and deep impact of this virus. This essay presents different perspectives on the impact of the novel coronavirus to dentistry, through the lenses of a private practice-based general dentist, a nursing home-based public health dentist, and a school of dentistry clinical director. The goal of the essay is to share our experiences and challenges, as well as highlight our capacity to respond to a crisis with resilience, determination, creativity, inventivity, and, most importantly, humility and altruism.

Fracture load of two thicknesses of different zirconia types after fatiguing and thermocycling.

STATEMENT OF PROBLEM: A direct relationship has been reported between yttria concentration and translucency in zirconia restorations. However, increased yttria concentration also increases the cubic phase of the zirconia, which reduces its strength. The effect of increased yttria content on the fracture resistance of zirconia as a function of material thickness after fatigue testing requires evaluation. PURPOSE: The purpose of this in vitro study was to use the biaxial flexural test to evaluate the effect of yttria concentration on the mean fracture load (N) before and after fatiguing and thermocycling as a function of zirconia thickness. MATERIAL AND METHODS: Disk-shaped specimens of 5 mol% yttria partially stabilized zirconia (5Y-PSZ, BruxZir Anterior Solid Zirconia) and 3 mol% yttria partially stabilized zirconia (3Y-PSZ, BruxZir Shaded Zirconia) were prepared to thicknesses of 1.2 and 0.7 mm. For each thickness, the biaxial flexural test was used to measure the fracture load (N) before and after fatigue testing, with 1.2 million cycles at a 110-N load and simultaneous thermocycling at 5 °C to 55 °C (n=20). The data were analyzed by repeated-measures ANOVA (α=.05). RESULTS: Yttria concentration, thickness, and exposure to fatiguing had a statistically significant effect on the mean biaxial flexural load (yttria concentration: P<.001; thickness: P<.001; fatiguing: P=.004 for the 3Y-PSZ). One of the major findings in this study was that 30% of the 1.2-mm-thick 5Y-PSZ specimens and 80% of the 0.7-mm-thick 5Y-PSZ specimens fractured during fatiguing. All specimens of the 3Y-PSZ groups survived the fatiguing protocol. The 3Y-PSZ groups had statistically significant higher flexural loads than the 5Y-PSZ groups. The 1.2-mm thickness groups had statistically significant higher flexural loads than the 0.7-mm thickness groups. CONCLUSIONS: Yttria concentration had a significant effect on the strength of zirconia. 5Y-PSZ was considerably less resistant to fracture before and after fatigue testing than 3Y-PSZ. Decreasing the thickness of zirconia reduces its fracture resistance, regardless of the zirconia type.

Effect of surface treatment and cement type on dentin bonding of processed resin composite.

PURPOSE: To examine the effect of surface treatment and cement type on dentin bonding of processed resin composite restorations. METHODS: Bovine incisors were sectioned to expose mid-dentin, and randomly assigned to four different groups: Group ULT, Lava Ultimate composite blocks were bonded to dentin with RelyX Ultimate; Group ULT-CJ was treated as in Group ULT but CoJet was used to treat the intaglio surface prior to bonding; Group UNC was bonded with RelyX Unicem 2; and Group UNC-CJ was treated as in Group UNC but CoJet was used to treat the intaglio surface. RelyX Unicem 2 was used as a self-adhesive resin cement, while RelyX Ultimate was used as an adhesive resin cement with Scotchbond Universal. All adhesives and resin composites were polymerized with a high-irradiance LED polymerizing light (Elipar DeepCure-S). After bonding, all specimens were kept in 100% humidity and 37°C for 7 days and then processed for microtensile bond strength (µTBS) testing (n=15). The failure mode was analyzed under SEM as cohesive, adhesive, or mixed. Data were analyzed for statistical significance using two-way ANOVA and Tukey's HSD post-hoc test (α=0.05). RESULTS: Mean µTBS values ranged from 8.83 MPa (±3.13 MPa) for UNC to 25.63 MPa (±5.94 MPa) for ULT-CJ. Means were statistically significantly higher for the adhesive cement when compared with the self-adhesive cement (P< 0.05), and, for the adhesive cement, CoJet resulted in statistically significantly higher means (P< 0.05). The number of pre-test failures was uniform across groups (n=2-4). Failures were predominantly adhesive and mixed. The adhesive resin cement RelyX Ultimate performed significantly better than the self-adhesive resin cement RelyX Unicem 2, and surface treatment with CoJet improved bond strengths of Lava Ultimate to dentin. CLINICAL SIGNIFICANCE: CoJet treatment and adhesive resin cements should be used when bonding laboratory/CAD-CAM processed resin composite restorations to dentin.

Esthetic and functional management of an ankylosed central incisor with a conservative restorative approach.

In this case report, we share a conservative and simple restorative management approach for a relatively complex esthetic situation on an adult patient with an ankylosed maxillary central incisor in infra-occlusion. A 37-year-old healthy female patient presented for a consultation with a chief complaint of an unappealing smile. The intraoral exam revealed tooth #8 (FDI 11) was in obvious and significant infra-occlusion due to altered eruption. Periapical radiographs of this area were non-contributory and all teeth responded within normal limits to pulp vitality tests. After review of several treatment options, the patient opted for a conservative restorative approach in which a partial ceramic veneer was planned for the ankylosed tooth, while composite resin was used on the contralateral central incisor to achieve a symmetric and pleasant result. CLINICAL SIGNIFICANCE: A relatively complex clinical problem was satisfactorily resolved with a very conservative option in which composite resin and a ceramic veneer were used to restore an asymmetric smile.

Effect of composite type and placement technique on cuspal strain.

OBJECTIVE: To compare the cuspal strain in Class II restorations made with bulk-fill and conventional composite resins. MATERIALS AND METHODS: Fifty extracted maxillary premolars were mounted into phenolic rings and divided into five groups (n = 10). Specimens received standardized MOD preparations. A two-step self-etch adhesive was applied and the preparations were restored using a custom matrix as follows: Filtek Supreme Ultra in eight 2-mm increments (FSUI); Filtek Supreme Ultra in bulk (FSUB); SonicFill in bulk (SF); SureFil SDR flow in bulk, covered with a 2-mm occlusal layer of Filtek Supreme Ultra (SDR/FSU); Tetric EvoCeram Bulk Fill in bulk (TEBF). Strain gages bonded to the buccal and lingual cusps recorded cuspal strain during restorations. End strain values were determined and data were subjected to Kruskal-Wallis testing, followed by one-way ANOVA and Tukey´s post hoc test. RESULTS: Combined strain values and standard deviations (in µÉ›) were: FSUI: 723 ± 102.8, FSUB: 929.2 ± 571.9, SF: 519.1 ± 80.2, SDR-FSU: 497.4 ± 67.6 and TEBF: 604.5 ± 127.1. A significant difference was found between group FSUI and groups SF, SDR-FSU, and TEBF. Group FSUB showed significantly higher mean strain and greater standard deviation than all other groups due to cuspal fractures, and was thus excluded from the statistical analysis. CONCLUSIONS: The tested bulk-fill composite resins exerted less strain onto tooth structure than the incrementally placed conventional composite resin, although the magnitude of generated strain was product-dependent. Bulk-filling with conventional composite resins is contraindicated. CLINICAL SIGNIFICANCE: Bulk-fill composite resins exerted less strain onto adjacent tooth structure than a traditional composite, even when that composite is was placed incrementally. Bulk-filling with traditional composite resins is unpredictable and contraindicated.

Marginal and Internal Adaptation of Zirconia Crowns: A Comparative Study of Assessment Methods.

Marginal and internal adaptation is critical for the success of indirect restorations. New imaging systems make it possible to evaluate these parameters with precision and non-destructively. This study evaluated the marginal and internal adaptation of zirconia copings fabricated with two different systems using both silicone replica and microcomputed tomography (micro-CT) assessment methods. A metal master model, representing a preparation for an all-ceramic full crown, was digitally scanned and polycrystalline zirconia copings were fabricated with either Ceramill Zi (Amann-Girrbach) or inCoris Zi (Dentslpy-Sirona), n=10. For each coping, marginal and internal gaps were evaluated by silicone replica and micro-CT assessment methods. Four assessment points of each replica cross-section and micro-CT image were evaluated using imaging software: marginal gap (MG), axial wall (AW), axio-occlusal angle (AO) and mid-occlusal wall (MO). Data were statistically analyzed by factorial ANOVA and Tukey test (a=0.05). There was no statistically significant difference between the methods for MG and AW. For AO, there were significant differences between methods for Amann copings, while for Dentsply-Sirona copings similar values were observed. For MO, both methods presented statistically significant differences. A positive correlation was observed determined by the two assessment methods for MG values. In conclusion, the assessment method influenced the evaluation of marginal and internal adaptation of zirconia copings. Micro-CT showed lower marginal and internal gap values when compared to the silicone replica technique, although the difference was not always statistically significant. Marginal gap and axial wall assessment points showed the lower gap values, regardless of ceramic system and assessment method used.

Marginal and Internal Adaptation of Zirconia Crowns: A Comparative Study of Assessment Methods

Abstract Marginal and internal adaptation is critical for the success of indirect restorations. New imaging systems make it possible to evaluate these parameters with precision and non-destructively. This study evaluated the marginal and internal adaptation of zirconia copings fabricated with two different systems using both silicone replica and microcomputed tomography (micro-CT) assessment methods. A metal master model, representing a preparation for an all-ceramic full crown, was digitally scanned and polycrystalline zirconia copings were fabricated with either Ceramill Zi (Amann-Girrbach) or inCoris Zi (Dentslpy-Sirona), n=10. For each coping, marginal and internal gaps were evaluated by silicone replica and micro-CT assessment methods. Four assessment points of each replica cross-section and micro-CT image were evaluated using imaging software: marginal gap (MG), axial wall (AW), axio-occlusal angle (AO) and mid-occlusal wall (MO). Data were statistically analyzed by factorial ANOVA and Tukey test (a=0.05). There was no statistically significant difference between the methods for MG and AW. For AO, there were significant differences between methods for Amann copings, while for Dentsply-Sirona copings similar values were observed. For MO, both methods presented statistically significant differences. A positive correlation was observed determined by the two assessment methods for MG values. In conclusion, the assessment method influenced the evaluation of marginal and internal adaptation of zirconia copings. Micro-CT showed lower marginal and internal gap values when compared to the silicone replica technique, although the difference was not always statistically significant. Marginal gap and axial wall assessment points showed the lower gap values, regardless of ceramic system and assessment method used.

Resumo A adaptação marginal e interna é fundamental para o sucesso das restaurações indiretas e novos sistemas de imagem permitem avaliar esses parâmetros de maneira não-destrutiva e com precisão. Este estudo avaliou a adaptação marginal e interna de copings de zircônia fabricados com dois sistemas diferentes, utilizando as técnicas da réplica em silicone e micro-CT. Um modelo-mestre de metal, representando um preparo para uma coroa totalmente cerâmica foi digitalizado e copings de zirconia policristalina (Ceramill Zi, Amann Girrbach e inCoris Zi, Dentslpy Sirona, n=10) foram fabricados. Para cada coping, a adaptação marginal e interna foi avaliada pelas técnicas da réplica em silicone e micro-CT. Foram avaliados quatro pontos de cada seção transversal e imagem de micro-CT: adaptação marginal (MG), parede axial (AW), ângulo axial-oclusal (AO) e parede centro-oclusal (MO) utilizando um software de imagem. Os dados foram analisados estatisticamente por ANOVA e teste de Tukey (a=0,05). Não houve diferença estatisticamente significativa entre as duas técnicas para MG e AW. Para AO, houve diferenças significativas entre as técnicas para copings da Amann, enquanto que para copings da Dentsply Sirona foram observados valores semelhantes. Para o MO, ambas as técnicas apresentaram diferenças estatisticamente significativas. Observou-se uma correlação positiva entre os valores de adaptação determinados pelas duas técnicas. O método de avaliação influenciou a avaliação da adaptação marginal e interna de copings de zircônia. Pode-se concluir que a micro-CT mostrou menores valores de adaptação marginal e interna quando comparado com a técnica de réplica em silicone. Os pontos de avaliação da margem e da parede axial mostraram os menores valores de adaptação, independente do sistema cerâmico e da técnica de avaliação utilizados.

The quality of fixed prosthodontic impressions: An assessment of crown and bridge impressions received at commercial laboratories.

BACKGROUND: The authors evaluated and quantified clinically detectable errors commonly seen in impressions sent to commercial laboratories and determined possible relationships between finish line errors and other factors involved. METHODS: The authors visited 3 large and 1 small commercial dental laboratories over a 12-month period. Three calibrated examiners evaluated the impressions. The examiners evaluated all impressions for errors by using ×2.5 magnification loupes under ambient room lighting without the aid of additional illumination. RESULTS: The authors evaluated 1,157 impressions; 86% of the examined impressions had at least 1 detectable error, and 55% of the noted errors were critical errors pertaining to the finish line. The largest single error categories evaluated were tissue over the finish line (49.09%), lack of unprepared stops in dual-arch impressions (25.63%), pressure of the tray on the soft tissue (25.06%), and void at the finish line (24.38%). The factors blood on the impression (odds ratio, 2.31; P < .001) and tray type (odds ratio, 1.68; P < .001) were associated significantly with finish line errors. CONCLUSIONS: Marginal discrepancies made up the largest category of error noted in impressions evaluated. The authors noted an increase in errors at the finish line with dual-arch impression techniques and in the presence of blood. PRACTICAL IMPLICATIONS: Dentists have ethical, moral, and legal obligations bestowed on them by the profession and need to evaluate critically the work they send to laboratories. The authors strongly recommend an improvement in technique and reviewing of all impressions and working casts.

The Direct-Indirect Technique for Composite Restorations Revisited.

In the direct-indirect composite technique, composite is applied to a nonretentive tooth preparation (eg, a noncarious cervical lesion or a veneer/inlay/onlay preparation) without any bonding agent, sculpted to a primary anatomic form, and light-cured. The partially polymerized restoration is then removed from the preparation and finished and tempered extraorally chairside. The finished inlay is bonded to the preparation using a resin-based luting agent. Advantages of this technique include enhanced physical and mechanical properties afforded by the extraoral chairside tempering process because of increased monomer conversion, and greater operator control over the final marginal adaptation, surface finishing and polishing, and anatomy of the restoration, given that these elements are defined outside of the patient's mouth. The direct-indirect approach also affords enhanced gingival health and patient comfort. This article presents a clinical case in which the direct-indirect composite technique was used to restore three noncarious cervical lesions on the same quadrant on an adult patient. Clinical steps and tips for success are offered. The authors also present scanning electron microscope and atomic force microscope images showing the excellent marginal fit obtained with the direct-indirect composite technique.

Accuracy evaluation of intraoral optical impressions: A clinical study using a reference appliance.

STATEMENT OF PROBLEM: Trueness and precision are used to evaluate the accuracy of intraoral optical impressions. Although the in vivo precision of intraoral optical impressions has been reported, in vivo trueness has not been evaluated because of limitations in the available protocols. PURPOSE: The purpose of this clinical study was to compare the accuracy (trueness and precision) of optical and conventional impressions by using a novel study design. MATERIAL AND METHODS: Five study participants consented and were enrolled. For each participant, optical and conventional (vinylsiloxanether) impressions of a custom-made intraoral Co-Cr alloy reference appliance fitted to the mandibular arch were obtained by 1 operator. Three-dimensional (3D) digital models were created for stone casts obtained from the conventional impression group and for the reference appliances by using a validated high-accuracy reference scanner. For the optical impression group, 3D digital models were obtained directly from the intraoral scans. The total mean trueness of each impression system was calculated by averaging the mean absolute deviations of the impression replicates from their 3D reference model for each participant, followed by averaging the obtained values across all participants. The total mean precision for each impression system was calculated by averaging the mean absolute deviations between all the impression replicas for each participant (10 pairs), followed by averaging the obtained values across all participants. Data were analyzed using repeated measures ANOVA (α=.05), first to assess whether a systematic difference in trueness or precision of replicate impressions could be found among participants and second to assess whether the mean trueness and precision values differed between the 2 impression systems. RESULTS: Statistically significant differences were found between the 2 impression systems for both mean trueness (P=.010) and mean precision (P=.007). Conventional impressions had higher accuracy with a mean trueness of 17.0 ±6.6 µm and mean precision of 16.9 ±5.8 µm than optical impressions with a mean trueness of 46.2 ±11.4 µm and mean precision of 61.1 ±4.9 µm. CONCLUSIONS: Complete arch (first molar-to-first molar) optical impressions were less accurate than conventional impressions but may be adequate for quadrant impressions.

Six-year clinical performance of etch-and-rinse and self-etch adhesives.

OBJECTIVE: To evaluate the 6-year clinical performance of Xeno IV, Xeno III, and XP Bond adhesives in the restoration of non-carious cervical lesions (NCCLs). METHODS: This was a randomized controlled clinical trial where 39 participants met the inclusion/exclusion criteria and were enrolled. Lesions restored were notch-shaped NCCLs. Prior to adhesive procedures, NCCLs were roughened. No enamel bevel was placed and no mechanical retention was created. Adhesive systems were applied following manufacturer's instructions and the NCCLs were restored with composite resin (TPH(3)). Restorations were finished immediately after placement and scored with regard to retention, marginal discoloration, marginal adaptation, sensitivity, and secondary caries using modified USPHS criteria. Descriptive statistics were performed. Logistic regression models were performed for each outcome separately with compound symmetry correlation structure where teeth were clustered by participants. All analyses were conducted using SAS 9.2. RESULTS: The 6-year recall rate was 77.5% of the restorations (76.9% of the participants). No statistical differences were found between adhesives for retention, marginal discoloration, and marginal adaptation. Restorations failed by loss of retention (16.7%, 27.6%, and 11.8% of Xeno IV, Xeno III, and XP Bond restorations, respectively) and marginal discoloration (7.4% of Xeno IV restorations). For every unit increase in restoration volume it was 1.31 (95%C.I. 1.05, 1.63, P=0.01) times more likely that the restoration retention would be maintained. SIGNIFICANCE: The tested adhesive systems presented similar clinical performance after six years of service, with annual failure rates of 2.8%, 4.6%, and 2.0% for Xeno IV, Xeno III, and XP Bond, respectively.

Effect of Finishing and Polishing on the Surface Roughness of Four Ceramic Materials after Occlusal Adjustment.

PROBLEM: Intraoral occlusal adjustment of ceramic restorations can create a significant increase in surface roughness that can produce wear of the opposing dentition. PURPOSE: To compare the surface roughness of glazed and polished monolithic ceramics with the surface roughness produced by different intraoral polishing systems on adjusted monolithic ceramics. MATERIALS AND METHODS: Milled ceramic discs (10 mm diameter × 2 mm thickness) were manufactured and distributed according to the following groups (n = 10): BruxZir (glazed and polished), Zenostar (glazed and polished), IPS Empress CAD, and IPS e.max CAD. Surface roughness, expressed as arithmetic average height (Ra ), was measured using atomic force microscope and profilometer before and after adjustment and polishing with the following intraoral polishing systems: BruxZir and Dialite ZR (for BruxZir), Zenostar and Dialite ZR (for Zenostar), and OptraFine and Dialite LD for IPS Empress CAD and IPS e.max CAD. Mean and standard error for each material and polishing system were calculated. T-test, one-way ANOVA, and Bonferroni post hoc tests were used to analyze data. RESULTS: BruxZir zirconia presented smoother surfaces with Dialite ZR system compared to BruxZir system, Zenostar zirconia shown smoother surfaces with Zenostar system compared to Dialite ZR system and IPS Empress CAD and IPS e.max CAD presented smoother surfaces with OptraFine system in comparison to Dialite LD system. CONCLUSION: All materials presented smoother surfaces at baseline than after adjustment and polishing. CLINICAL SIGNIFICANCE: This paper reveals the results of an in vitro study that provides information to clinicians regarding which intraoral polishing system will produce a smoother surface after the adjustment and polishing of IPS Empress CAD, IPS e.max CAD, BruxZir and Zenostar ceramic materials. (J Esthet Restor Dent 28:382-396, 2016).

A Predictive Model for Root Caries Incidence.

This study aimed to find the set of risk indicators best able to predict root caries (RC) incidence in caries-active adults utilizing data from the Xylitol for Adult Caries Trial (X-ACT). Five logistic regression models were compared with respect to their predictive performance for incident RC using data from placebo-control participants with exposed root surfaces at baseline and from two study centers with ancillary data collection (n = 155). Prediction performance was assessed from baseline variables and after including ancillary variables [smoking, diet, use of removable partial dentures (RPD), toothbrush use, income, education, and dental insurance]. A sensitivity analysis added treatment to the models for both the control and treatment participants (n = 301) to predict RC for the control participants. Forty-nine percent of the control participants had incident RC. The model including the number of follow-up years at risk, the number of root surfaces at risk, RC index, gender, race, age, and smoking resulted in the best prediction performance, having the highest AUC and lowest Brier score. The sensitivity analysis supported the primary analysis and gave slightly better performance summary measures. The set of risk indicators best able to predict RC incidence included an increased number of root surfaces at risk and increased RC index at baseline, followed by white race and nonsmoking, which were strong nonsignificant predictors. Gender, age, and increased number of follow-up years at risk, while included in the model, were also not statistically significant. The inclusion of health, diet, RPD use, toothbrush use, income, education, and dental insurance variables did not improve the prediction performance.

Effect of finishing technique on the occurrence and length of microcracks in resin-based materials.

PURPOSE: To evaluate the presence and length of microcracks in resin-based materials finished with different techniques, using optical coherence tomography (OCT). METHODS: Standardized Class V preparations (3x2x2mm) were made in the facial and lingual surfaces of 20 recently-extracted human third molars. 20 preparations were restored with a resin-based composite material (RBC; Filtek Supreme Ultra) and the other 20 with a resin-modified glass-ionomer material (RMGI; Ketac Nano). After final polymerization, specimens were further stratified by finishing system: aluminum oxide discs (Sof-Lex) or spiral fluted carbide bur series (H48L). By random allocation, each extracted tooth therefore received one RBC and one RMGI restoration, and equal numbers of restorations from each material were finished using each finishing system (n= 10). After 24 hours of storage in 100% humidity at room temperature, the specimens were evaluated at x20 to x600 under environmental SEM. Cross-sectional occlusal-cervical B-mode images were obtained in increments of 25 mm from the mesial margin to the distal margin of the restoration using a spectral-domain (SD) OCT system and analyzed using Image J software to identify and measure microcrack penetration into each restoration. The total length (mm) at the point of the deepest microcrack penetration in each specimen was recorded. Data were statistically analyzed using a t-test. RESULTS: No microcracks were observed in the RBC samples. However, microcrack presence was identified in all of the RMGI specimens. The t-test showed a statistically significant difference (P< 0.05) in mean microcrack length values based on the finishing technique used for the RMGI samples. [SofLex: 0.67 (± 0.28) mm; carbide: 1.26 (± 0.30)] mm. Two-way ANOVA showed significant differences in the factors "finishing technique" and "restorative material" (P< 0.001). The interaction of these two factors was also statistically significant (P< 0.001). For the tested RMGI, Tukey post-hoc test revealed that the finishing with aluminum oxide groups resulted in statistically significant lower mean microcrack length when compared to spiral fluted carbide burs (P< 0.001). CLINICAL SIGNIFICANCE: Resin-modified glass-ionomer (RMGI) is more susceptible to microcrack presence than resin-based composites. Also, aluminum oxide discs produced lower values of mean microcrack length than spiral fluted carbide burs after the finishing procedure of RMGI restorations.

Optical properties and light irradiance of monolithic zirconia at variable thicknesses.

OBJECTIVES: The aims of this study were to: (1) estimate the effect of polishing on the surface gloss of monolithic zirconia, (2) measure and compare the translucency of monolithic zirconia at variable thicknesses, and (3) determine the effect of zirconia thickness on irradiance and total irradiant energy. METHODS: Four monolithic partially stabilized zirconia (PSZ) brands; Prettau® (PRT, Zirkonzahn), Bruxzir® (BRX, Glidewell), Zenostar® (ZEN, Wieland), Katana® (KAT, Noritake), and one fully stabilized zirconia (FSZ); Prettau Anterior® (PRTA, Zirkonzahn) were used to fabricate specimens (n=5/subgroup) with different thicknesses (0.5, 0.7, 1.0, 1.2, 1.5, and 2.0mm). Zirconia core material ICE® Zircon (ICE, Zirkonzahn) was used as a control. Surface gloss and translucency were evaluated using a reflection spectrophotometer. Irradiance and total irradiant energy transmitted through each specimen was quantified using MARC® Resin Calibrator. All specimens were then subjected to a standardized polishing method and the surface gloss, translucency, irradiance, and total irradiant energy measurements were repeated. Statistical analysis was performed using two-way ANOVA and post-hoc Tukey's tests (p<0.05). RESULTS: Surface gloss was significantly affected by polishing (p<0.05), regardless of brand and thickness. Translucency values ranged from 5.65 to 20.40 before polishing and 5.10 to 19.95 after polishing. The ranking from least to highest translucent (after polish) was: BRX=ICE=PRT

Effect of Finishing Techniques on the Marginal Integrity of Resin-Based Composite and Resin-Modified Glass Ionomer Restoration.

UNLABELLED: The purpose of this study was to evaluate the marginal integrity of resin-based composite (RBC and resin-modified glass ionomer cement (RMGIC) restorations as a function of finishing technique and location of the tooth. Forty extracted third molars were assigned to four groups (N = 10) according to finishing instruments (aluminum oxide discs, fluted carbides, fine diamonds, and coarse diamond). Each specimen received standardized Class V preparations on the facial and lingual surfaces with occlusal margins on enamel and gingival margins on dentin. Each preparation was randomly assigned to be restored with either RBC or RMGIC. Specimens were finished with standardized pressure at approximately 0.16 N and evaluated at a magnification of 600× using an environmental scanning electron microscope. Occlusal and gingival margins were analyzed using an imaging software, and means for all measured gaps were calculated. Data were analyzed with a factorial analysis of variance. All possible two-way interactions were included, and the level of significance was set at 0.05. There were no statistically significant differences among the four types of finishing instruments used in the study. RBC-restored specimens exhibited significantly smaller mean marginal gaps (1.70-7.56 µm) than RMGI-restored specimens (5.24-14.24 µm) in enamel and dentin margins, respectively. There was a statistically significant difference between enamel and dentin with regard to marginal gap formation. Under the conditions of this study, marginal gap formation was not affected by finishing technique. RBC margins exhibited significantly less marginal gap than RMGI margins, whereas enamel margins resulted in significantly less marginal gap than did dentin margins. CLINICAL SIGNIFICANCE: Multiple factors can affect the marginal integrity and the longevity of direct restorations. From these, the finishing and polishing techniques are critical steps that are under the clinician's control, and proper finishing and polishing techniques should be applied for avoiding introduction of stress to the margin of the restoration. It seems that instrumentation do not play a significant role, as much as the restorative material and the substrate to bond.

Degree of conversion of dual-polymerizing cements light polymerized through monolithic zirconia of different thicknesses and types.

STATEMENT OF PROBLEM: Monolithic zirconia restorations are increasingly common. Dual-polymerizing cements have been advocated for cementation. The opacious nature of zirconia restoration can attenuate light, compromising optimal resin polymerization and eventually restoration debonding. PURPOSE: The purpose of this in vitro study was to evaluate the influence of material thickness on light irradiance, radiant exposure, and the degree of monomer conversion (DC) of 2 dual-polymerizing resin cements light-polymerized through different brands of monolithic zirconia. MATERIAL AND METHODS: Dual-polymerizing resin cements (RelyX Ultimate; 3M-ESPE, and Variolink II; Ivoclar, Vivadent) were mixed according to the manufacturers' instructions with a film thickness of 40 µm, placed under a 10 × 10 mm specimen of monolithic zirconia (Prettau Anterior by Zirkonzahn, Katana by Noritake, BruxZir by Glidewell, and Zenostar by Wieland) and a zirconia core control (ICE zirkon by Zirkonzahn) at various thicknesses (0.50, 1.00, 1.50, and 2.00 mm, n = 5 of each thickness). Each specimen was irradiated for 20 seconds (RelyX Ultimate) and 40 seconds (Variolink II) with Elipar S10 (3M-ESPE, 1200 mW/cm(2)). The amount of irradiance and radiant exposure was quantified for each specimen. Fourier transform infrared spectroscopy was used to measure the DC from the bottom surface of the resin. Statistical analysis was performed with 2-way ANOVA and post hoc Tukey honest significant difference (HSD) tests (α = .05). RESULTS: Light irradiance and radiant exposure decreased as the thickness of the specimen increased (P < .05) regardless of the brand. The ranking from least to highest was BruxZir < ICE zircon = Wieland < Katana = Prettau Anterior. The zirconia brand, thickness, and cement type had a significant effect on the DC (P < .001). The DC decreased significantly as the thickness of the zirconia increased (P < .001). Katana and Prettau Anterior showed the highest DC and BruxZir showed the lowest. CONCLUSION: The thickness of zirconia affects the DC of resin-based cements. The DC of the resin cements differed significantly between cements and among zirconia brands. More polymerizing time may be needed to deliver sufficient energy through some brands of zirconia.