ABSTRACTFinishing and polishing dental ceramics after chairside adjustments is necessary to regain the original surface topography. Though highly subjective, visual and tactile assessment are the most practical ways to assess surface roughness clinically. Several manufacturers recommend polishing kits for specific ceramic materials that differ in efficacy. Proper polishing protocols require the use of sequential polishing instruments that reduce the size of the adjustment abrasions, improve aesthetics and reduce plaque accumulation. If polishing systems are interchanged, stepwise use of a zirconia polishing system may have a “universal” effect on different ceramic substrates. Adjusting zirconia restorations could result in phase transformation and potentially compromise flexural strength. The extent of this degradation is dependent on the yttria content of the zirconia. This may be reduced by appropriate finishing and polishing.

Purpose To evaluate the surface roughness of glazed and polished monolithic ceramic materials and to use this as a baseline for comparison after adjustment and polishing with both the recommended kit for the specific materials as well as interchanged polishing kits. Material and methods Flat ceramic specimens (n = 150) were fabricated from IPS ZirCAD Prime, IPS E.max, and Vitabloc Mark II. The specimens were adjusted and polished using either the proprietary polishing kit for the material or interchanged kits. The surface roughness was objectively assessed using Atomic Force Microscopy (AFM) and profilometer. Subjective assessment of surface finish was performed using a scanning electron microscope (SEM). Gravimetric weight loss of each sample was measured before and after polishing using a digital microscale. The mean surface roughness and standard deviation was calculated for each ceramic- polisher pair. A factorial ANOVA was used to compare the mean surface roughness values in nanometers between multiple groups (alpha = 0.05). The subjective results from the SEM were reported as descriptive statistics Results The zirconia polishing system produced surfaces with the lowest surface roughness regardless of the ceramic material. The polisher-ceramic combination was found to have a statistically significant effect on both Ra and RMS values when the AFM was used (p = 0.039 and 0.010, respectively). Conclusion The zirconia polishing system resulted in the lowest surface roughness values regardless of ceramic materials tested. The zirconia polishing system also did not result in significant gravimetric weight loss regardless of the ceramic material used.

Background Evidence on the potential oral health effects of vaping is scarce and there are limited data on possible links to both caries and periodontal disease. The authors assessed the association between electronic cigarette (e-cigarette) or vape use and caries risk level. The Caries Management by Risk Assessment tool was used. Methods A cross-sectional study of patient records was conducted; 13,098 patients who attended the dental school clinics from January 1, 2019, through January 1, 2022, were included in the study. Mann-Whitney U test and multivariable ordinal logistic regression were used to assess the relationship between use of e-cigarettes or vapes and caries risk level. Results Data from 13,216 patients were included in the data set initially; 13,080 responded "no" when asked whether they used e-cigarettes or vapes (99.3%), and 136 responded "yes" (0.69%). There was a statistically significant difference (P < .001) in caries risk levels between the e-cigarette or vape group and the control group; 14.5%, 25.9%, and 59.6% of the control group were in the low, moderate, and high caries risk categories, respectively, and 6.6%, 14.3%, and 79.1% of the e-cigarette or vape group were in the low, moderate, and high caries risk categories, respectively. Conclusions In this study population, there was an association between use of e-cigarettes or vapes and caries risk level of patients; vaping patients had a higher risk of developing caries. Practical Implications Within the study limitations, it was recommended that use of e-cigarettes or vapes should not only be included in the routine dental-medical history questionnaire, but also among the risk factors that increase a patient's caries risk level.

STATEMENT OF PROBLEM:Advertisements of glass-ionomer-containing restorative materials recommend suitability as load-bearing permanent or semi-permanent restorations. Historically, unacceptably high wear rates limit clinical indications of glass-ionomer-containing restorations in this regard.OBJECTIVE:To compare the in vitro wear of contemporary glass-ionomer-containing dental materials commercially advertised for use in permanent dentition as load-bearing restorations in a chewing simulator. Resin composite was tested as a control.METHODS AND MATERIALS:A resin-modified glass ionomer (Ionolux, VOCO gmbH), a high viscosity glass-ionomer hybrid system (Equia Forte HT with Equia Coat, GC America), and a bioactive ionic resin with reactive glass filler (Activa Bioactive Restorative, Pulpdent) were evaluated. Filtek Supreme Ultra (3M ESPE) is a visible light-activated resin composite that served as a control. Standardized flat disk-shaped specimens (n=12/group) were submitted to 500,000 cycles with continuous thermal cycling against steatite antagonists. Volumetric wear was measured at 1000, 10,000, 200,000, and 500,000 cycles.RESULTS:There was a statistically significant difference in mean volumetric wear for Activa Bioactive Restorative (p=0.0081, 95% CI: 0.3973, 0.4982) and Equia Forte HT (p<0.001, 95% CI: 1.2495, 1.8493), but no statistically significant difference in mean volumetric wear for Ionolux (p=0.6653) compared to control. Activa Bioactive Restorative wore approximately 60% less than, and Equia Forte HT twice more than Filtek Supreme Ultra on average, respectively.CONCLUSIONS:Compared to a resin composite, contemporary glass-ionomer-containing restorative materials advertised for use as load-bearing restorations display measurably variable in vitro wear rates.

This review was conducted to assist the busy dentist in keeping abreast of the latest scientific information regarding the clinical practice of dentistry. Each of the authors, who are considered experts in their disciplines, was asked to peruse the scientific literature in their discipline published in 2016 and review the articles for important information that may affect treatment decisions. Comments on experimental methodology, statistical evaluation, and the overall validity of conclusions are included with many of the reviews. The reviews are not meant to stand alone but are intended to inform the interested reader about what has been discovered in the past year. The readers are then invited to go to the source, if they want more detail.

Objectives This study examined the in vitro fatigue resistance of maxillary premolars with 2 mm or 3 mm preserved cusp thicknesses restored with lithium disilicate onlays. Materials and Methods Premolars(N = 48) were divided into six groups. Onlays for groups 1 to 4 preserved a 3 mm functional (G1), 2 mm functional (G2), 3 mm nonfunctional (G3), or 2 mm nonfunctional (G4) buccal-lingual cusp width. Onlays for group 5 (G5, control) replaced both cusps. Group 6 (G6) samples were identical to G1 with added retentive boxes. Lithium disilicate onlays were exposed to thermocycling (10 000 cycles, 5 degrees C-55 degrees C, 30s/cycle) and mechanical loading (1.2 million cycles at 1.4 Hz and 70 N). All samples were examined for onlay debonding or cusp or onlay fracture. Results Failure rates were 75%(G1), 0.0%(G2), 12.5%(G3), 0.0%(G4), 0.0%(G5), and 0.0%(G6). The difference in percent failure between the groups preserving the functional cusps (37.5%) and the groups preserving the nonfunctional cusps (6.3%) was statistically significant (P= .04; 95%CI:2.11-55.66). No cusp or restoration fractures were observed; all failures were due to debonding of the restoration. Conclusion Teeth with thin remaining cusps that were restored with bonded lithium disilicate onlay restorations were not prone to fracture. Retentive preparation features that physically eliminated lateral displacement prevented onlay debonding even though the ceramic-enamel margin was directly at the occlusal contact. Clinical significance The use of adhesively retained lithium disilicate ceramic onlays may be a viable alternative to full coverage restorations and may challenge traditionally accepted principals related to preparation resistance and retention form of ceramic partial coverage restorations.

Objectives: To provide a comprehensive review of the available literature on the subject of tooth whitening and to provide a snapshot of where we as a dental profession are regarding this topic today. To provide a detailed account of the different tooth whitening procedures, their specific indications, success rates and potential side effects. Data: Data was obtained using the following keywords: tooth whitening, tooth bleaching, color, adverse effects, pediatric dentistry, enamel hardness, restorative materials, whitening pH, whitening concentration, success rates. Sources: A comprehensive literature search was conducted on PubMed and Scopus databases. A separate search was made on a Google Search Engine. The references from the reviewed material were used to locate other relevant publications. Study Selection: A total of 158 articles were included in this review after reviewing the literature that resulted from the initial search. Conclusion: Tooth whitening procedures have proven to be a conservative and viable option for improving dental esthetics. Clinical Significance: With the increasing need for esthetic treatment among dental patients, it is important for dentists to have a good understanding of tooth whitening procedures, their specific indications, potential adverse effects, and limitations. These procedures are a minimally invasive way to improve dental esthetics significantly.

OBJECTIVE:This article is aimed at providing an overview of the topic of erosive tooth wear (ETW), highlighting the clinical signs, diagnosis, and management of dental erosion.OVERVIEW:With the increased prevalence of ETW, it is important that oral health professionals are able to recognize the early signs. Early clinical signs of dental erosion are characterized by loss of enamel texture, a silky glossy appearance, and sometimes a dulling of the surface gloss, referred to as the "whipped clay effect, cupping, and restorations 'standing proud'." The progression of ETW should be monitored by means of diagnostic models or clinical photographs. ETW can be as a result of acid attack of extrinsic or intrinsic origin.CONCLUSION:There is an increase of ETW that is being recognized by the profession. The first step in diagnosing and management is to recognize as early as possible that the process is occurring. At that point a determination of whether the primary etiology is either intrinsic or extrinsic should be made. If these findings are confirmed, appropriate prevention, and management strategies can be adopted followed by appropriate restorative therapy.CLINICAL SIGNIFICANCE:The prevalence of ETW continues to increase. It is therefore important that oral health care providers have a better understanding of the etiology, pathophysiology, and management of this condition. This review aims to provide the guidelines for diagnosis and management of dental erosion.

Purposel: This study was done to compare the survival rates of cast gold and ceramic onlays placed in a dental school setting. Material and Methods: An electronic search was conducted in the patient records at Adams School of Dentistry, University of North Carolina at Chapel Hill for onlay codes that were in the database (From 1998 until 2018). Progress notes and radiographs were scrutinized to establish the survival time of the restorations. Any complications that occurred during the life time of the restorations were noted. The survival was summarized by categorization based on ranges of survival time in years; group 1: 1 to 5 years, group 2: 6 to 22 years. The mean survival time and standard deviation were calculated. One-way ANOVA was used to determine whether there was a statistically significant difference in the survival times between gold and ceramic onlays. Results: The mean survival rate of cast gold onlays (86.6%) was comparable to that of ceramic onlays (81.1%). The gold onlays in Group 1 had a higher mean survival time (2.43 years) than the ceramic onlays (2.03 years). This difference was statistically significant (p= 0.002). The ceramic onlays in Group 2 had a mean survival time of 19.75 years while gold onlays had a mean survival time of 17.63 years. This difference was not statistically significant (p= 0.91). Conclusion: It was concluded that while the survival rate of ceramic onlays (81.1%) was inferior to that of cast gold onlays (86.6%), it was comparable

Clinical Relevance Bulk-fill composite resins may have comparable mechanical properties to conventional composite resin. Preheating does not reduce the mechanical properties of composite resins. SUMMARY Statement of Problem: Bulk-fill composite resins are increasingly used for direct restorations. Preheating high-viscosity versions of these composites has been advocated to increase flowability and adaptability. It is not known what changes preheating may cause on the mechanical properties of these composite resins. Moreover, the mechanical properties of these composites after mastication simulation is lacking. Purpose: The purpose of this study was to evaluate the effect of fatiguing and preheating on the mechanical properties of bulk-fill composite resin in comparison to its conventional counterpart. Methods and Materials: One hundred eighty specimens of Filtek One Bulk Fill Restorative (FOBR; Bulk-Fill, 3M ESPE) and Filtek Supreme Ultra (FSU; Conventional, 3M ESPE) were prepared for each of the following tests: fracture toughness (International Organization for Standardization, ISO 6872), diametral tensile strength (No. 27 of ANSI/ADA), flexural strength, and elastic modulus (ISO Standard 4049). Specimens in the preheated group were heated to 68°C for 10 minutes and in the fatiguing group were cyclically loaded and thermocycled for 600,000 cycles and then tested. Two-/one-way analysis of variance followed by Tukey Honest Significant Difference (HSD) post hoc test was used to analyze data for statistical significance (α=0.05). Results: Preheating and fatiguing had a significant effect on the properties of both FSU and FOBR. Fracture toughness increased for FOBR specimens when preheated and decreased when fatigued (p=0.016). FOBR had higher fracture toughness value than FSU. Diametral tensile strength decreased significantly after fatiguing for FSU (p=0.0001). FOBR had a lower diametral tensile strength baseline value compared with FSU (p=0.004). Fatiguing significantly reduced the flexural strength of both FSU and FOBR (p=0.011). Preheating had no effect on the flexural strength of either FSU or FOBR. Preheating and fatiguing significantly decreased the elastic modulus of both composite resins equally (p>0.05). Conclusions: Preheating and fatiguing influenced the mechanical properties of composite resins. Both composites displayed similar mechanical properties. Preheating did not yield a major negative effect on their mechanical properties; the clinical implications are yet to be determined.

Statement of problem. The use of ceramic materials has increased significantly because of high esthetic demands, low costs, and ease of fabrication. Long-term, clinically based evidence is scarce, and laboratory studies have limited relevance in determining clinical durability. Purpose. The purpose of this dental laboratory survey was to evaluate the fracture rate of layered and monolithic lithium disilicate and zirconia single crowns and fixed partial dentures after up to 7.5 years of clinical service. Material and methods. Two commercial dental laboratories with a database system that was able to track the number of remakes because of fracture only were identified. Lithium disilicate restorations (monolithic and layered) were categorized according to restoration type (single crown, fixed partial denture, veneer, and onlay). Zirconia restorations (monolithic and layered) were categorized according to type (single crown, fixed partial denture) and then into anterior or posterior restoration. Restoration remakes due to poor fit, shade, or marginal integrity were excluded from the evaluation. Data were analyzed, and statistical significance was evaluated with chi-square tests (alpha=.05). Results. A total of 188 695 (51 751 lithium disilicate and 136 944 zirconia) restorations were included in the analysis, with an overall fracture rate of 1.35%. Lithium disilicate monolithic single crowns had a fracture rate of 0.96%, which was significantly lower than that of layered single crowns at 1.26% (P<.05). When the different types of lithium disilicate restorations were compared, fixed partial denture (monolithic and layered) fracture rates were significantly higher than those of single crowns (P<.001). Monolithic zirconia single crowns (0.54%) fractured at a lower rate than layered zirconia single crowns (2.83%) and monolithic fixed partial dentures (1.83%) (P<.001), while layered single crowns (2.83%) had a higher fracture rate than that of layered fixed partial dentures (1.93%) (P<.001). Monolithic anterior and posterior zirconia restorations fractured at a lower rate than layered anterior and posterior zirconia restorations (P<.05). Posterior monolithic zirconia restorations fractured at a lower rate than anterior restorations, while posterior layered zirconia restorations fractured at a higher rate than anterior zirconia restorations (P<.05). Conclusions. Within the 7.5-year period, restorations fabricated with lithium disilicate and zirconia restorations had relatively low fracture rates. Monolithic restorations fractured at a lower rate than layered restorations.

OBJECTIVE To estimate the time required for teeth to dehydrate and rehydrate and its relation to the accuracy of tooth shade selection. MATERIALS AND METHODS Thirty-two participants were recruited, and color measurements were conducted using a spectrophotometer placed with a custom jig. After isolation, baseline measurements were made at 1, 2, 3, 5, 7, 10, and 15 min intervals to determine dehydration time. After mouth rinsing, measurements were made to determine rehydration time. CIEDE2000 values were obtained for color change between the baseline recordings and all intervals and compared to the 50:50% perceptibility and acceptability thresholds. Analysis of variance (anova) and Tukey test was used for multiple comparisons. RESULT The tooth color changes were beyond the ΔE00 perceptibility threshold (0.8) within the first minute of dehydration (P > 0.0001). After the first minute, 87% of the teeth were beyond the ΔE00 perceptibility threshold (0.8), and 72% of the teeth were beyond the ΔE00 acceptability threshold (1.8). After 15 min of rehydration, 90% of the teeth were beyond the perceptibility threshold, and 65% were beyond the acceptability threshold. CONCLUSIONS Shade selection procedures should be carried out within the first minute and before teeth dehydrate by means of isolation. Teeth do not rehydrate within 15 min after rehydration. CLINICAL SIGNIFICANCE Teeth dehydration has a negative impact on shade selection, which can affect the final esthetic outcome. Shade selection should be performed at the beginning of any restorative procedure.

PURPOSE To determine the effect of changing the dispensing or mixing method of resin-modified glass ionomer (RMGI) cements on their water sorption, solubility, film thickness, and shear bond strength. MATERIALS AND METHODS Disc-shaped specimens of RMGI cements (RelyX: Luting [handmix], Luting Plus [clicker-handmix], Luting Plus [automix], GC: Fuji PLUS [capsule-automix], FujiCEM 2 [automix], [n = 10]) were prepared according to ISO standard 4049 for water sorption and solubility tests. Furthermore, the percentage of mass change, percentage of solubility, and percentage of water absorbed was also determined. Film thickness was measured according to ISO standard 9917-2; the mean of 5 measurements for each cement was calculated. Shear bond strength for each cement was determined according to ISO standard 29022 before and after thermocycling at 20,000 cycles, temperatures 5 to 55°C with a 15-second dwell time (n = 10/subgroup). Two- and one-way ANOVA were used to analyze data for statistical significance (p < 0.05). RESULTS Water sorptions of the RMGI cements were in close range (214-250 μg/mm3 ) with no statistical differences between counterparts (p > 0.05). RelyX Luting Plus (clicker-handmix) displayed lower solubility than its handmix and automix counterparts (p < 0.05). Film thickness of RelyX cements was significantly different (p < 0.05). RelyX Luting Plus (automix) had the lowest film thickness (19 μm) compared to its handmix (48 μm) and clicker-handmix (117 μm) counterparts (p < 0.05). GC Fuji PLUS (capsule-automix, 22 μm) was significantly lower than the automix version (GC FujiCEM 2, 127 μm) (p < 0.05). Shear bond strength of RelyX Luting Plus (automix) was significantly lower than its handmix and clicker-handmix versions (p < 0.05). GC Fuji PLUS (capsule-automix) was significantly higher than GC FujiCEM 2 (automix) (p < 0.05). The binary interaction of the two independent variables (dispensing/mixing method and thermocycling) was significant for the shear bond strengths of the GC cements only (p < 0.05). CONCLUSIONS Change in the dispensing/mixing method of RMGI cement from the same brand may have an effect on its physical properties, in addition to its film thickness and shear bond strength. Newer, easier, and faster cement delivery systems are not necessarily better. Clinical outcomes of these differences are yet to be confirmed.

Statement of problem. Resin-based cements are frequently used in clinical practice. To reduce time and technique sensitivity, manufacturers have introduced the same brand of cement with different dispensing methods. The effect of this change on properties of the cement is unknown. Purpose. The purpose of this in vitro study was to evaluate the mechanical properties of resin-based cements with different dispensing systems. Material and methods. Specimens of resin-based cements (n=14) PANAVIA SA Cement Plus Handmix, PANAVIA SA Cement Plus Automix, RelyX Unicem Handmix, RelyX Unicem 2 Automix, G-CEM Capsule Automix, G-CEM LinkAce Automix, Variolink II Handmix, and Variolink Esthetic Automix were prepared for each mechanical test. They were examined after thermocycling (n=7/ subgroup) for 20 000 cycles as to fracture toughness (FT) (ISO standard 6872; single-edge V-notched beam method), compressive strength (CS) (ISO 9917-1), and diametral tensile strength DTS). The specimens were mounted and loaded at a crosshead rate of 1 mm/min (0.5 mm/min for FT) with a universal testing machine until failure occurred. The 2-and 1-way ANOVA followed Careful by the Tukey HSD post hoc test were used to analyze data for statistical significance (alpha=05). Results. Thermocycling had a significant effect in reducing the FT property of all resin-based cements except RelyX Unicem 2 and G-CEM LinkAce (P<.05). Variolink II and G-CEM LinkAce showed better FT properties than their automixed counterparts (P<.05). The overall CS of all automixed resin-based cements was better than that of their hand-mixed counterpart, except for Variolink II. PANAVIA SA Automixed and G-CEM LinkAce had higher DTS than their hand-mixed counterparts (P<.05). Conclusions. Changing the dispensing method alters the mechanical properties of resin-based cements. The clinical significance of these results is yet to be determined.

OBJECTIVE:The purpose of this study was to assess the gelation and polymerization time of three polyvinyl siloxane (PVS) putty materials and to determine if those times were affected by nitrile gloves under different conditions.MATERIALS AND METHODS:Ten specimens (n=10) were obtained for each PVS putty material (Express STD, 3M ESPE; Extrude Xtra, Kerr and Exafast, GC) and tested under different conditions (gloves washed, gloves unwashed and hands contaminated). The gelation and polymerization time were measured using an oscillating rheometer and recorded for 400 s at 37°C to simulate the oral environment.RESULTS:The mean gelation time of hand contaminated specimens was 157.50 minutes and was significantly slower than that by using nitrile washed gloves (mean=117.94, p=.004) and by using unwashed gloves (mean=99.46, p⟨0.001). Unwashed gloves had significantly quicker gelation times compared to washed gloves (p=.046). The gelation time was significantly delayed with Exafast compared to Extrude Xtra and Express STD across all the different types of glove conditions (p⟨0.043). No significant differences were observed between polymerization time with Exafast and Extrude Xtra Putty.CONCLUSIONS:Extrude Xtra putty material had significantly better performance than GC Exafast and Express. Hand contaminated specimens were affected by the gelation/polymerization time.

OBJECTIVES:To assess and compare the 5-year success rate of resin-bonded fixed partial dentures (RBFPDs) fabricated from different materials.METHODS:An electronic search on 3 databases from January 1965 to March of 2017 was done for human randomized clinical trials (RCTs), and prospective and retrospective cohort studies. The key words used in the search were: Bridge OR bridges OR fixed partial OR fixed dental AND resin bonded OR Maryland OR ceramic bonded. Quality assessment was done using the Newcastle-Ottawa scale. Success was defined as the RBFPDs remaining in situ and not having experienced debonding, biological failures, or mechanical failures at the examination visit.RESULTS:Meta analyses of the included studies showed an estimated 5-year success rate of 88.18% for the metal framework RBFPDs and 84.41% for the nonmetal framework RBFPDs. The estimated 5-year success rate for each nonmetal material category was 92.07% for zirconia, 94.26% for In-Ceram alumina, and 84.83% for fiber-reinforced composite. The failure rate was not statistically significant among the single, double, and multiple retainers RBFPDs (P > .05). Technical complications were the main reason for failures.CONCLUSION:The 5-year clinical performance of RBFPDs is similar to the performance of conventional fixed partial dentures (FPDs) and implant-supported crowns.CLINICAL SIGNIFICANCE:Clinicians should consider using RBFPDs more often because their clinical performance is similar to the performance of conventional FPDs and implant-supported crowns.

STATEMENT OF THE PROBLEM Resin-modified glass ionomer cements (RMGIs) are often used for luting indirect restorations. Hand-mixing traditional cements demands significant time and may be technique sensitive. Efforts have been made by manufacturers to introduce the same cement using different dispensing/mixing methods. It is not known what effects these changes may have on the mechanical properties of the dental cement. PURPOSE The purpose of this study was to evaluate the mechanical properties (diametral tensile strength [DTS], compressive strength [CS], and fracture toughness [FT]) of RMGIs with different dispensing/mixing systems. METHODS AND MATERIALS The RMGI specimens (n=14)-RelyX Luting (hand mix), RelyX Luting Plus (clicker-hand mix), RelyX Luting Plus (automix) (3M ESPE), GC Fuji PLUS (capsule-automix), and GC FujiCEM 2 (automix) (GC)-were prepared for each mechanical test and examined after thermocycling (n=7/subgroup) for 20,000 cycles to the following: DTS, CS (ISO 9917-1) and FT (ISO standard 6872; Single-edge V-notched beam method). Specimens were mounted and loaded with a universal testing machine until failure occurred. Two-/one-way analysis of variance followed by Tukey honestly significantly different post hoc test was used to analyze data for statistical significance ( p<0.05). RESULTS The interaction effect of both dispensing/mixing method and thermocycling was significant only for the CS test of the GC group ( p<0.05). The different dispensing/mixing methods had no effect on the DTS of the tested cements. The CS of GC Fuji PLUS was significantly higher than that of the automix version ( p<0.05). The FT decreased significantly when switching from RelyX (hand mix) to RelyX Luting Plus (clicker-hand mix) and to RelyX Luting Plus (automix) ( p<0.05). Except in the case of the DTS of the GC group and the CS of GC Fuji PLUS, thermocycling had a significant effect reducing the mechanical properties of the RMGI cements ( p<0.05). CONCLUSIONS Introducing alternative dispensing/mixing methods for mixing RMGIs to reduce time and technique sensitivity may affect mechanical properties and is brand dependent.

OBJECTIVETo compare the cuspal strain in Class II restorations made with bulk-fill and conventional composite resins.MATERIALS AND METHODSFifty 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.RESULTSCombined strain values and standard deviations (in µɛ) 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.CONCLUSIONSThe 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 SIGNIFICANCEBulk-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.