A Historical Perspective on Dental Composite Restorative Materials.

This review article will discuss the origin of resin-based dental composite materials and their adoption as potentially useful adjuncts to the primary material used by most dentists for direct restorations. The evolution of the materials, largely driven by the industry's response to the needs of dentists, has produced materials that are esthetic, strong, and versatile enough to be used in most areas of the oral cavity to replace or restore missing tooth structures. Significant advancements, such as the transition from chemical to light-curing materials, refinements in reinforcing particles to produce optimum polishing and wear resistance, formulating pastes with altered viscosities to create highly flowable and highly stiff materials, and creating materials with enhanced depth of cure to facilitate placement, will be highlighted. Future advancements will likely reflect the movement away from simply being a biocompatible material to one that is designed to produce some type of beneficial effect upon interaction within the oral environment. These new materials have been called "bioactive" by virtue of their potential effects on bacterial biofilms and their ability to promote mineralization of adjacent tooth structures.

Isolated effect of filler particle size on surface properties of experimental resin composites before and after toothbrush abrasion.

OBJECTIVE: This study aimed to isolate the relationship between filler size and the surface properties of roughness and gloss before and after toothbrush abrasion for experimental resin-based composites (RBCs) containing uniform spherical fillers. MATERIALS AND METHODS: Five experimental light-cured RBCs with different spherical filler sizes and three commercial RBCs were studied. Forty specimens were polished using silicon carbide papers. Gloss was measured after 0, 90, 180, and 360 min of simulated toothbrushing, and surface roughness was measured before and after 360 min of toothbrushing. Two-way ANOVA/Tukey's multiple comparison tests were used to compare the RBCs, and the correlation between particle size and surface roughness or gloss was also determined. RESULTS: After polishing and toothbrushing, RBCs with smaller fillers exhibited significantly higher gloss and lower surface roughness, and RBCs with larger fillers exhibited lower gloss and higher surface roughness. A significant correlation was found between filler particle size and gloss and surface roughness both before and after toothbrush abrasion. CONCLUSIONS: Gloss of RBCs containing fillers with larger particle sizes was significantly reduced. After toothbrushing abrasion, the surface roughness increased for all RBCs, except those containing the finest-sized fillers. The particle size of the filler is a critical determinant of the surface roughness and gloss of RBCs, after polishing and after toothbrushing. CLINICAL SIGNIFICANCE: Increased surface roughness caused by toothbrush abrasion reduces the gloss of resin-based composites. Resin-based composites containing finer fillers best maintain glossiness after routine tooth brushing.

Thiol Quantification Using Colorimetric Thiol-Disulfide Exchange in Nonaqueous Solvents.

A careful analysis of two (thiol-disulfide exchange) thiol quantification chromophores' behavior (Ellman's reagent and Aldrithiol-4) in nonaqueous solvents is presented. A wide range of kinetic profiles and response factors were measured to exhibit a large variance for nonaqueous systems. We report several robust benchtop and room-temperature methods using different organic solvents compared to aqueous conditions. Validation of analytical analyses in nonaqueous systems and quantification of the cysteine content of ovalbumin are also presented. This work serves as a treatise on the utilization of thiol-disulfide exchange chromophores under nonaqueous conditions for the quantification of thiols.

Lessons learned from the Cracked Tooth Registry: A 3-year clinical study in the Nation's Network.

BACKGROUND: This article reviews the most salient lessons learned from a large, multisite, 3-year observational study of posterior teeth with cracks conducted by The National Dental Practice-Based Research Network. TYPES OF STUDIES REVIEWED: Eight articles published over a 6-year period (2017-2022) describing clinical characteristics of posterior teeth with cracks and their treatment and outcomes are reviewed and discussed to answer 3 common questions faced by oral health care clinicians: Which cracked teeth will get worse? When should practitioners intervene? What is the best treatment? RESULTS: Although cracks in teeth are prevalent, few will fracture (3%) or show crack progression in 3 years (12%). Characteristics that guide the clinician to treatment include active caries, biting pain, and to a lesser degree, having a crack detectable with an explorer, connecting with a restoration, or blocking transilluminated light; the main treatment chosen is a complete crown. Of those teeth treated (36%), few (14%) will need retreatment but will still survive, despite having an internal crack as well. CONCLUSIONS AND PRACTICAL IMPLICATIONS: Although cracked teeth often pose a dilemma to clinicians, clincians are generally good at deciding which teeth to treat and when and which to monitor.

"Fatigue-Crack Propagation Behavior in Microcapsule-Containing Self-Healing Polymeric Networks".

Over the last years, research on the design of dental self-healing polymers has grown dramatically. It is related to the promising potential of maximizing the clinical lifespan of dental restorations that this strategy holds. In this manuscript, the microcapsule-based strategy is innovated by incorporating the high toughness component N,N-Dimethylacrylamide (DMAM) into the healing agent systems and analyzing in-depth the change in crack propagation behavior induced by the addition of microcapsules into the highly crosslinked polymeric network. In general, the addition of the hydrophilic and high vapor pressure DMAM into the healing agent systems imposed a challenge for the microencapsulation, which highlighted the importance of tailoring the properties of the capsules' shells according to the core composition. The addition of DMAM as cushioning agent proved to be a successful strategy since it resulted in increased G'/G" crossover time from 0.06 (control) to 0.57 s and decreased storage modulus from 8.0 (control) to 0.5GPa. In addition, the incorporation of microcapsules within the polymerized networks provided obstacles to crack propagation, which translated to an overall reinforcement of the polymeric network, as evidenced by the increase in toughness up to 50 % and energy required to propagate cracks up to 100 % in systems containing DMAM at 20 wt%.

Effect of thickness on the degree of conversion of two bulk-fill and one conventional posterior resin-based composites at high irradiance and high temporal resolution.

OBJECTIVES: This study: 1) measures the effect of sample thickness and high irradiance on the depth-dependent time delay before photopolymerization reaction onset; 2) determines if exposure reciprocity exists; 3) measures the conversion rate at four irradiance levels; 4) determines the time, t0, at which the maximum DC rate is reached for two bulk-fill and one conventional posterior resin-based composites (RBCs). METHODS: Tetric PowerFill IVA shade (Ivoclar Vivadent) and Aura bulk-fill ultra universal restorative (SDI), and one conventional posterior resin-based composite (RBC), Heliomolar A3 (Ivoclar Vivadent), that were either 0.2 mm, 2 mm, or 4 mm thick were photocured using a modified Bluephase G4 (Ivoclar Vivadent) light-curing unit (LCU) that delivered a single emission band (wavelength centered at 449 nm). The same radiant exposure of 24 J/cm2 was delivered at irradiances ranging from 0.5 to 3 W/cm2 by adjusting the exposure time. PowerFill was also photocured for 3 s or 6 s using a Bluephase PowerCure LCU (Ivoclar Vivadent) on the 3 s mode setting. The degree of conversion (DC) was measured in real-time at a high temporal resolution at 30 °C using Attenuated Total Reflection (ATR) FTIR spectroscopy with a sampling rate of 13 DC data points per second. The DC data were analyzed using a phenomenological autocatalytic model. The RBC viscosity was measured at 21 °C and 30 °C. Light transmission through the RBC samples at 22 °C was monitored with time to calculate the extinction coefficients of the RBCs. RESULTS: The time delay before photopolymerization started increased as the RBC thickness increased and the irradiance decreased. An autocatalytic model described the DC data. The time t0 was less than 77 ms for the 0.2 mm thick samples of PowerFill irradiated using the highest irradiance of 3 W/cm2. Among the three RBCs for each sample thickness and irradiance level, the PowerFill had the smallest time t0. There was a time delay of 0.59 s and 1.25 s before the DC started to increase at the bottom of 4 mm thick samples for the PowerFill and Aura, respectively, when an irradiance of 1 W/cm2 was delivered. The time delay increased to 3.65 s for the Aura when an irradiance of 0.5 W/cm2 was delivered. The extinction coefficients near 449 nm were 0.78 mm-1, 0.76 mm-1, and 1.55 mm-1 during the first 2 s after the start of photocuring of PowerFill, Aura, and Heliomolar, respectively. Only PowerFill followed exposure reciprocity. At T = 30 °C, the viscosity was 3400, 17000, and 5200 Paˑs for PowerFill, Aura, and Heliomolar, respectively. SIGNIFICANCE: The time delay between when photopolymerization starts at the top and bottom of 2- or 4-mm thick RBC restorations may affect the structural integrity of the bond between the tooth and the bottom of the restoration. Only PowerFill followed exposure reciprocity between irradiance levels of 0.5 to 3 W/cm2. Exposure reciprocity did not occur for Aura or Heliomolar, neither of which are optimized for short light exposure or high irradiance conditions.

Effect of ethyl cellulose coating as an evaluation agent against contamination on the bond strength of zirconia restorations: An in vitro study.

STATEMENT OF PROBLEM: During the trial placement of zirconia restorations, contamination of the bonding surface is inevitable. Although cleaning methods for contaminated surfaces have been described, a method of preventing saliva contamination of the bonding surface of zirconia restorations is lacking. PURPOSE: The purpose of this in vitro study was to investigate an ethyl cellulose coating as an evaluation agent to mitigate the effects of saliva contamination on the bond strength of zirconia restorations. MATERIAL AND METHODS: Experimental groups representing different cleaning methods of tetragonal yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) surfaces were investigated for shear bond strength with a resin luting agent, and the failure mode was analyzed. The 9.0×7.0×5.0-mm zirconia blocks (n=72) were assigned as follows: Group N: uncontaminated control; Group CU: contaminated with saliva, followed by ultrasonic cleaning with ethanol; Group CI: contaminated with saliva, followed by application of a zirconia cleaner; Group PCW: preapplication of a zirconia primer, contaminated with saliva, followed by cleaning with water spray; Group ECU: precoating with the ethyl cellulose agent, contaminated with saliva, followed by removal of the agent in an ultrasonic bath with ethanol. Each group was divided into 3 subgroups (immediate, short-term aging, and long-term aging), and the shear bond strength was measured (n=24). To analyze the bonding surface characteristics, the contact angle was measured (n=5). The surfaces of the zirconia specimens in each experimental group were evaluated by using a field emission scanning electron microscope (n=5). Time-of-flight secondary ion mass spectroscopy was used for the chemical analysis of the conditioned surfaces (n=3). A 2-way analysis of variance (ANOVA) with main effect model for shear bond strength results and a 1-way ANOVA for contact angle data were performed as statistical analysis, followed by the Bonferroni post hoc test (α=.05). RESULTS: The shear bond strength was significantly higher in the ECU group than in the groups with the other cleaning methods (P<.05). After the removal of ethyl cellulose with ethanol, the contact angle and surface topography were found to be similar to those of the control group, and no saliva contaminants were identified in the spectroscopy analysis. CONCLUSIONS: Coating with ethyl cellulose may protect the bonding surface of zirconia restorations from salivary contamination better than cleaning a contaminated surface.

Onset and resolution of pain among treated and untreated posterior teeth with a visible crack: Three-year findings from the national dental practice-based research network.

OBJECTIVE: Cracked teeth may be associated with pain, especially biting pain, and to a lesser degree cold and spontaneous pain.  Described are how commonly these pains remain constant, develop, or resolve over time, none of which have been well-described, especially among untreated cracked teeth. METHODS: Cracked teeth from the Cracked Tooth Registry (CTR) study were followed for 3 years.  Assessments of cold, biting, and spontaneous pain and treatments performed were completed at enrollment (Y0) and at each annual recall visit. RESULTS: 209 practitioners enrolled 2,858 patients, each with a visible crack on a posterior tooth; 2601 (91%) patients attended at least one recall visit. Overall, 960 (37%) were treated, primarily with crowns. Among both treated and untreated cracked teeth with biting pain or spontaneous pain at Y0, the vast majority (92-99%) had their pain resolved by the time of a recall visit and 85-93% remained pain-free after initial resolution. The observations for cold pain were similar: 68% (untreated) and 78% (treated) became free of cold pain at some point during follow-up, and 84% of these stayed free of cold pain after initial resolution. Few teeth developed biting or spontaneous pain (4-8%) and 44-67% of these had pain resolution during the follow-up period. CONCLUSION: In this study, treatment resolved a preponderance of pain associated with a cracked tooth.  Pain was also resolved for most untreated cracked teeth, especially biting pain, and to a lesser degree spontaneous and cold pain, although not to the same degree as with the treated cracked teeth.

Development and maintenance of surface gloss of dental composites after polishing and brushing: Review of the literature.

OBJECTIVE: To describe the effect of the composites' composition to produce high surface smoothness/gloss using finishers/polishers, and to assess maintained smoothness/gloss under toothbrush abrasion. MATERIALS AND METHODS: PubMed papers published from January 01, 2000 to September 01, 2021 were included, and keywords used were: filler particle size, shape, amount of dental composites; finishing/polishing, gloss/roughness, and toothbrush abrasion of composites. Seventy-five in-vitro studies were included in this literature review. Forty-six articles assessed filler particle size/composition/shape and distribution to obtain high gloss/smoothness on different formulations; and the finishers/polishers effect on these materials. Twenty-nine papers assessed toothbrush abrasion of composites. RESULTS: Suprananofill/nanofill/microfills typically showed the smoothest and glossiest surfaces compared to nanohybrid, microhybrid and hybrid composites. Microfill (0.04-0.07 µm, 71-88 GU); suprananofill (0.001-0.8 µm, 52-92 GU), microhybrids (0.05-0.35 µm, 35-95 GU) and nanohybrids (0.05-0.21 µm, 66-97 GU). Composites with small, spherical particles tend to show smoother, glossier surfaces and more wear resistant compared to resin composites with larger or irregular particles. Several studies showed higher roughness and reduced gloss after toothbrush abrasion. CONCLUSIONS: Within the limitations of this study, suprananofill/nanofill/microfill composites tended to show the smoothest/glossiest surfaces due to smaller particle size. Composites with small, spherical particles tended to show smoother/glossier surfaces. Overall, toothbrush abrasion showed higher surface roughness and reduced gloss. CLINICAL SIGNIFICANCE: Suprananofills/nanofills/microfills had good polishability and polish retention due to their smaller particle size. The effectiveness of a polishing system is material-dependent. In general, Enhance-PoGo, Sof-Lex discs, and Sof-Lex Spiral wheels showed similar level of smoothness.

Outcomes of treatment and monitoring of posterior teeth with cracks: three-year results from the National Dental Practice-Based Research Network.

OBJECTIVES: To describe treatment and monitoring outcomes of posterior teeth with cracks at baseline followed in the National Dental Practice-Based Research Network for up to three years. MATERIALS AND METHODS: Two hundred and nine dentists enrolled a convenience sample of 2,858 patients, each with a posterior tooth with at least one visible crack and followed them for three years. Characteristics at the patient, tooth, and crack level were recorded at baseline and at annual recall visits. Data on all teeth referred for extraction were reviewed. Data on all other teeth, treated or monitored, seen at one or more recall visits were reviewed for evidence of failure (subsequent extraction, endodontics, or recommendation for a re-treatment). RESULTS: The survival rate for teeth with cracks at baseline exceeded 98% (only 37 extractions), and the failure rate for teeth that were treated restoratively was only 14%. Also, only about 14% of teeth recommended at baseline for monitoring were later recommended to be treated, and about 6.5% of teeth recommended for monitoring at baseline were later treated without a specific recommendation. Thus, about 80% of teeth recommended at baseline for monitoring continued with a monitoring recommendation throughout the entire three years of the study. Treatment failures were associated with intracoronal restorations (vs. full or partial coverage) and male patients. CONCLUSIONS: In this large 3-year practice-based study conducted across the USA, the survival rate of posterior teeth with a visible crack exceeded 85%. Clinical relevance Dentists can effectively evaluate patient-, tooth-, and crack-level characteristics to determine which teeth with cracks warrant treatment and which only warrant monitoring.

Clinical Performance of CAD/CAM Monolithic Lithium Disilicate Implant-Supported Single Crowns Using Solid or Predrilled Blocks in a Fully Digital Workflow: A Retrospective Cohort Study With Up To 33 Months of Follow Up.

PURPOSE: To assess the clinical performance of CAD/CAM monolithic implant-supported restorations manufactured using a fully digital workflow and two different types of ceramic blocks. MATERIALS AND METHODS: One hundred and one patients received single-unit implant-supported restorations at a University predoctoral clinic. All restorations were designed and fabricated using either a predrilled LS2 block (group P, n = 59) or a conventional solid LS2 block with an occlusal opening drilled manually prior to crystallization (group M, n = 42). The mean follow-up time after restoration delivery was 18.4 ± 4.8 months (range 12 to 33 months). Patients with less than a 12-month follow-up were excluded. Electronic health records were reviewed to identify number and type of complications during the follow-up time. Clinical outcomes were classified as success, survival, and failure of the restoration. Chi-square tests were used to identify differences in success and survival rates between the groups. Nonparametric Mann-Whitney U tests were used to identify differences in the number of major and minor complications as well as the total number of complications that were observed among groups. RESULTS: Overall success and survival rates were 80.2% and 97%, respectively. Seventy one restorations (70.3%) were complication-free. There were no significant differences between the groups with regards to the number of complications or success and survival rates. CONCLUSIONS: Single-unit CAD/CAM monolithic implant-supported restorations that are fabricated in a fully digital workflow present relatively high complication rates and moderate short-term clinical outcomes. Clinical studies with longer follow-up times are needed to evaluate long-term outcomes of these restorations.

Effect of Novel Bioactive Glass-Containing Dentin Adhesive on the Permeability of Demineralized Dentin.

This study aimed to evaluate the effect of a novel bioactive glass (BAG)-containing dentin adhesive on the permeability of demineralized dentin. Bioactive glass (85% SiO2, 15% CaO) was fabricated using the sol-gel process, and two experimental dentin adhesives were prepared with 3 wt% silica (silica-containing dentin adhesive; SCA) or BAG (BAG-containing dentin adhesive; BCA). Micro-tensile bond strength (µTBS) test, fracture mode analysis, field-emission scanning electron microscopy (FE-SEM) analysis of adhesive and demineralized dentin, real-time dentinal fluid flow (DFF) rate measurement, and Raman confocal microscopy were performed to compare SCA and BCA. There was no difference in µTBS between the SCA and BCA (p > 0.05). Multiple precipitates were evident on the surface of the BCA, and partial occlusion of dentinal tubules was observed in FE-SEM of BCA-approximated dentin. The DFF rate was reduced by 50.10% after BCA approximation and increased by 6.54% after SCA approximation. Raman confocal spectroscopy revealed an increased intensity of the hydroxyapatite (HA) peak on the dentin surface after BCA application. The novel BAG-containing dentin adhesive showed the potential of both reducing dentin permeability and dentin remineralization.

Changes of residual stresses on the surface of leucite-reinforced ceramic restoration luted with resin composite cements during aging in water.

The objective of this study was to compare the changes in the residual stresses present on the surface of leucite-reinforced dental ceramic restorations luted with a self-adhesive and a conventional resin composite cement during aging in water. Ring specimens made of a leucite-reinforced ceramics were luted to ceramic cylinders using a self-adhesive (Panavia SA Luting Plus) or a conventional resin composite cement (Panavia V5) in dual-cure or self-cure mode. Residual stresses on the ring surface were measured using indentation fracture method at 1 h, 1, 3, 7, 14 and 28 days of the 37 °C water immersion. Water sorption, water solubility and elastic modulus of the cements were also measured. Compressive stress was generated on the surface of the ceramic rings by the polymerization of the resin composite cements, and the stresses appeared to decrease over time by water sorption of the cements. The dual-cured conventional resin composite cement remained compressive stresses on the ceramic surface, while only the self-cured self-adhesive cement, which demonstrated the greatest water sorption, generated tensile stresses during the four weeks of aging in water. The elastic moduli of cements did not significantly change through the immersion, suggesting that the stresses were less affected by the modulus. To prevent the generation of tensile stresses on the leucite-reinforced ceramic restoration, self-adhesive cements exhibiting small water sorption should be clinically selected.

Effect of side-group methylation on the performance of methacrylamides and methacrylates for dentin hybridization.

The stability of the bond between polymeric adhesives to mineralized substrates is crucial in many biomedical applications. The objective of this study was to determine the effect of methyl substitution at the α- and ß-carbons on the kinetics of polymerization, monomer hydrolytic stability, and long-term bond strength to dentin for methacrylamide- and methacrylate-based crosslinked networks for dental adhesive applications. METHODS: Secondary methacrylamides (α-CH3 substituted=1-methyl HEMAM, ß-CH3 substituted=2-methyl HEMAM, and unsubstituted=HEMAM) and OH-terminated methacrylates (α- and ß-CH3 mixture=1-methyl HEMA and 2-methyl HEMA, and unsubstituted=HEMA) were copolymerized with urethane dimethacrylate. The kinetics of photopolymerization were followed in real-time using near-IR spectroscopy. Monomer hydrolysis kinetics were followed by NMR spectroscopy in water at pH 1 over 30 days. Solvated adhesives (40 vol% ethanol) were used to bond composite to dentin and microtensile bond strength (µTBS) measured after 24h and 6 months storage in water at 37°C. RESULTS: The rate of polymerization increased in the following order: OH-terminated methacrylates≥methacrylamides>NH2-terminated methacrylates, with minimal effect of the substitution. Final conversion ranged between 79% for 1-methyl AEMA and 94% for HEMA. 1-methyl-HEMAM showed the highest and most stable µTBS, while HEMA showed a 37% reduction after six months All groups showed measurable degradation after up to 4 days in pH 1, with the methacrylamides showing less degradation than the methacrylates. Additionally, transesterification products were observed in the methacrylamide groups. SIGNIFICANCE: Amide monomers were significantly more stable to hydrolysis than the analogous methacrylates. The addition of a α- or ß-CH3 groups increased the rate of hydrolysis, with the magnitude of the effect tracking with the expected base-catalyzed hydrolysis of esters or amides, but opposite in influence. The α-CH3 substituted secondary methacrylamide, 1-methyl HEMAM, showed the most stable adhesive interface. A side reaction was observed with transesterification of the monomers studied under ambient conditions, which was not expected under the relatively mild conditions used here, which warrants further investigation.

Fractography of clinical failures of indirect resin composite endocrown and overlay restorations.

OBJECTIVES: Compare failure modes and fracture origins using fractography on recovered clinically fractured parts of indirect resin composite endocrowns and overlay restorations on endodontically treated teeth (ETT). METHODS: Four endocrowns (3 molars, 1 premolar) and one overlay (molar) adhesively luted on ETT were recovered after fracturing during function. The time in service ranged between 4 and 48 months. The composite materials were (i) CAD/CAM LAVA Ultimate (N = 1), (ii) Premise Indirect (N = 2), and (iii) Colombus (N = 2). Fractography was performed by means of digital microscopy and SEM. Occlusal surfaces were checked for signs of fatigue degradation and contact wear. Cuspal plane angles were measured from profiles obtained from 3D digital microscope images with respect to the horizontal plane of the occlusal central crown groove. RESULTS: All five cases showed a wedge-opening mode I fracture, splitting the crown and tooth in two parts through the crown's central groove. Classic brittle fracture features (arrest lines, twist and wake hackle) were easily identified on the fracture surfaces. Multiple origins were located along the central groove in conjunction with the presence of fatigue cracks. Contact wear surfaces showed pitting and cracking. Cuspal plane angles were around 30-35°, except a 50° palatal cusp slope for the Lava Ultimate overlay. SIGNIFICANCE: Fractography on clinical fractures of resin composites was enlightening. Occlusal surface fatigue degradation from cyclic loading, mode I fracture from applied mastication forces on cuspal planes, and stress concentration within the crown's central groove, indicate limitations of use of these materials for endocrowns in posterior teeth.

Visually acceptable gloss threshold for resin composite and polishing systems.

BACKGROUND: The objective of this study was to compare dentists' perceptions of gloss values of composite specimens with increased levels and to identify the gloss value considered to be clinically acceptable. METHODS: Disk-shaped composite specimens were finished and polished 3 ways: metallurgically using silicon carbide papers and alumina paste, manually using Enhance finisher and PoGo polisher (EP) (Dentsply Sirona), and manually using Sof-Lex (SLex) disks (3M). Specimens were produced with surface gloss ranging from 0 through 100 gloss units (GU) in increments of approximately 10 GU as measured with a glossmeter. A GU of 0 was nonglossy, and a GU of 100 was perfectly glossy. Ten dentists evaluated the specimens, ranking them in order from low to high gloss and in 4 groups: low (dull or rough), medium (moderate gloss, clinically unacceptable), high (glossy, clinically acceptable), and superior gloss. The authors performed Spearman correlation analysis (α = 0.05). RESULTS: For each finish and polish method, there was an excellent correlation between the machine-measured (actual) gloss ranks and the clinician-evaluated gloss ranks (r2 ≥ 0.95). There was no difference in perception of surface gloss of the composite when metallurgically polished (with silicon carbide papers and alumina paste) or polished with EP to the same GU. There was a slight difference in gloss perception when comparing the 2 different commercial polishing systems. CONCLUSIONS: Ten dentists consistently perceived gloss of 40 through 50 GU as clinically acceptable. However, the composite was considered clinically acceptable at a lower gloss (40 GU) when polished with SLex disks than when polished with EP or metallurgically (50 GU). PRACTICAL IMPLICATIONS: Gloss values of 40 through 50 GU are considered to be clinically acceptable for resin composites.