Comparison of light-transmittance in dental tissues and dental composite restorations using incremental layering build-up with varying enamel resin layer thickness

OBJECTIVES: To evaluate and compare light-transmittance in dental tissues and dental composite restorations using the incremental double-layer technique with varying layer thickness. MATERIALS AND METHODS: B1-colored natural teeth slabs were compared to dental restoration build-ups with A2D and B1E-colored nanofilled, supra-nanofilled, microfilled, and microhybrid composites. The enamel layer varied from 0.3, 0.5, or 1.2 mm thick, and the dentin layer was varied to provide a standardized 3.7 mm overall sample thickness (n = 10). All increments were light-cured to 16 J/cm2 with a multi-wave LED (Valo, Ultradent). Using a spectrophotometer, the samples were irradiated by an RGB laser beam. A voltmeter recorded the light output signal to calculate the light-transmittance through the specimens. The data were analyzed using 1-way analysis of variance followed by the post hoc Tukey's test (p = 0.05). RESULTS: Mean light-transmittance observed at thicker final layers of enamel were significantly lower than those observed at thinner final layers. Within 1.2 mm final enamel resin layer (FERL) thickness, all composites were similar to the dental tissues, with exception of the nanofilled composite. However, within 0.5 mm FERL thickness, only the supra-nanofilled composite showed no difference from the dental tissues. Within 0.3 mm FERL thickness, none of the composites were similar to the dental tissues. CONCLUSIONS: The supra-nanofilled composite had the most similar light-transmittance pattern when compared to the natural teeth. However, for other composites, thicker FERL have a greater chance to match the light-transmittance of natural dental tissues.

Effect Of Different Polishing Systems On The Surface Roughness Of Nano-hybrid Composites: A Profilometric Study

Aim: The purpose of this study was to compare the influence of different polishing systems on the surface roughness of nano-hybrid composite resins. Materials and Methods: Fourty samples of acrylic blocks were prepared with cold cure acrylic resin in plastic rings of 1 inch diameter. In each acrylic block, a well of 6mm diameter and 2mm depth was prepared by drilling hole in it using a slow speed micromotor. Tetric N-Ceram™ nano composite is placed in the wells prepared using a plastic instrument and covered with a mylar strip. The samples were then cured for 40s through the mylar strips using LED curing light. 60 samples were divided into 4 groups with 15 samples in each group based on polishing regimen used. Group A - Mylar strip, Group B- PoGo diamond polishers, Group C- prophy brushes and Group D- Super- Snap Rainbow kit. The polished resin composite discs were washed, allowed to dry and kept again in 100% humidity for 24 h before measuring the average surface roughness values (Ra). The surface roughness test was performed using a profilometer and surfaces are seen under scanning electron microscope[SEM]. Statistical analysis: The data were analysed by using one-way ANOVA using SPSS 17.0 software. Results: For all the materials, the smoothest surface was obtained with mylar strip and the roughest with prophy brushes(P< 0.05).Conclusion: Mylar strip produced smoothest surface than other polishing systems.

Six-month color change and water sorption of 9 new-generation flowable composites in 6 staining solutions

Abstract Color match and water sorption are two factors that affect restorative materials. Discoloration is essential in the lifespan of restorations. The aim of this study was to evaluate color change and water sorption of nine flowable composites at multiple time points over 6 months. 60 samples of each composite were divided into two groups (Color Change and Water Sorption/Solubility). Each Color Change group was divided into six subgroups, which were immersed in distilled water (DW), coffee (CF), Coca-Cola (CC), red wine (RW), tea (TE) and orange juice (OJ). The color was measured at the baseline, 1, 2, 3 and 4 weeks, and 3 and 6 months and color change values (ΔE) were calculated. Each Water Sorption [WS]/Solubility [WL] group was tested according to ISO 4049:2009. The data were evaluated using two-way ANOVA, Fisher's post-hoc test and Pearson's correlation test. The composite with the lowest ΔE differed for each solution: Filtek™ Bulk Fill in DW (∆E = 0.73 (0.17-1.759)); Vertise Flow in CF (∆E = 14.75 (7.91-27.41)), in TE (∆E = 7.27 (2.81-24.81)) and OJ (∆E = 3.17 (0.87-9.92)); Tetric EvoFlow® in CC (∆E = 1.27 (0.45-4.02)); and Filtek™ Supreme XTE in RW (∆E = 8.88 (5.23-19.59)). RW caused the most discoloration (∆E = 23.62 (4.93-51.36)). Vertise Flow showed the highest water sorption (WS = 69.10 ± 7.19). The Pearson test showed statistically significant positive correlations between water sorption and solubility and between water sorption and ∆E; the positive solubility-∆E correlation was not statistically significant. The findings suggest that water sorption is one factor associated with the ability of composites to discolor; however, discoloration is a multifactorial problem.

Evaluation of the leakage of bleaching materials through different bases into the root canal filling: an invitro study

AIM: The purpose of this study was to evaluate the leakage of bleaching agents through 3 different bases into the obturated pulp space and dentinal tubules in intra coronal bleaching. MATERIAL AND METHODS: Fifty-five freshly extracted, intact non-carious single rooted teeth were collected and stored in formalin until used. The specimen divided into experimental and control group. Experimental group were further subdivided into 3 subgroups on the base of cervical base materials. Group I was Type II GIC, Group II was Fuji II LC and Group III was Hybrid composite. The control groups was divides into negative group (received the bleaching agent and received complete external coating including access cavity) and positive control group (did not receive any external coating). The obturated pulp space were removed at a level of 3 mm below the cemento enamel junction and filled with dry cotton pellets and temporized with temporary cement, stored at ± 37°C and 100% relative humidity for five days, the bleaching material were placed in the pulp chamber (a paste of sodium perborate i.e. 0.15g and 30% hydrogen peroxide 0.05ml), and then stored for 3 days in an incubator. Later on the teeth were immersed in India ink dye and stored at ± 37°C and 100% relative humidity for 5 days. Specimens were examined under binocular microscope with a stage micrometer to analyze the degree of dye penetration. RESULTS: The minimal leakage values were observed with type II glass ionomer cement followed by light cure glass ionomer cement and lastly by hybrid composite. CONCLUSION: The present invitro investigation evaluated the microleakage observed with different cervical base materials during non-vital bleaching procedures.

"Comparative Evaluation of Microleakage of Composite Restorative Materials".

To evaluate and compare the marginal leakage in class V cavities restored with three different tooth colored restorative materials using dye penetration system. Materials and methods: Thirty extracted premolars were randomly selected for this study. Standardized classV cavities were prepared and then divided into three equal groups. Group I was restored with nano filled composite, Group II was restored with hybrid composite and group III with polyacid modified composite. They were then subjected to thermo cycling, immersed in 2% methylene blue dye, sectioned and examined under stereomicroscope. Dye penetration for each section was recorded and data was analyzed. Results: Lowest micrileakage was recorded in group I and highest leakage recorded in Group III.Conclusion: Nanofilled composite resins provide a better sealing than hybrid and polyacid modified composites.

Comparison of Staining Properties of Composites.

Esthetics forms an important aspect of human’s life, because human’s personality and psychological wellbeing rests considerably on his appearance. Discolouration of esthetic restorative materials from the dietary habits vary with geographic distribution especially poor Oral Hygiene increases susceptibility to staining. Restorative resins are susceptible to softening caused by organic acids produced in plaque. Consequently plaque-covered resin restorations may be liable to pronounced staining.

Influence of flowable materials on microleakage of nanofilled and hybrid Class II composite restorations with LED and QTH LCUs.

Background: Class II composite restorations are more frequently being placed with margins apical to the cementoenamel junction (CEJ) and margins within the dentin are prone to microleakage. Aims: This in vitro study was used to evaluate the influence of flowable composite and flowable compomer as gingival liner on microleakage in Class II composite restorations and compare a light-emitting diode (LED) unit with a quartz tungsten halogen (QTH) unit for light-activating composite resins. Materials and Methods: Mesioocclusal and distoocclusal Class II cavity preparations were made in 72 sound extracted premolars. The buccolingual width was 2.5 mm and the gingival margins of all the cavities were placed 1.0 mm apical to the CEJ. The boxes were prepared 1.5 mm deep axially, making 144 slot cavities. Teeth were randomly divided into the following two groups (n = 72): (I) Universal Filtek Supreme XT; Universal Filtek Supreme XT + Flwable Filtek XT and Universal Filtek Supreme XT + Dyract Flow and (II) Filtek Z250; Filtek Z250 + Flwable Filtek XT and Filtek Z250 + Dyract Flow. Flowable materials were injected into the gingival floor of the cavity to a thickness of 1.0 mm. Each increment was cured for 20 s. One-half of the subgroups in each group were cured with QTH and the other half with LED light curing units (LCUs). After 1 week of incubation at 37°C, the specimens were thermocycled (5-55°C, x1500), immersed in 0.5% basic fuchsine dye for 24 h and sectioned and microleakage was evaluated at the gingival margin by two examiners using a 0-3 score scale. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: The groups utilizing flowable liners had significantly less microleakage (P < 0.05). No significant difference was identified between Universal Filtek Supreme XT and Filtek Z250 composites with and without flowable materials. There was no significant between utilizing flowable composite or flowable compomer and between each similar subgroup when polymerized with either the LED or the QTH LCUs. Conclusions: A layer of flowable materials at the gingival floor of Class II composite restorations may be recommended to improve the marginal seal of a restoration.

The influence of composite resin restoration on the stress distribution of notch shaped noncarious cervical lesion; A three dimensional finite element analysis study / 대한치과보존학회지

The purpose of this study was to investigate the effects of composite resin restorations on the stress distribution of notch shaped noncarious cervical lesion using three-dimensional (3D) finite element analysis (FEA). Extracted maxillary second premolar was scanned serially with Micro-CT (SkyScan1072; SkyScan, Aartselaar, Belgium). The 3D images were processed by 3D-DOCTOR (Able Software Co., Lexington, MA, USA). ANSYS (Swanson Analysis Systems, Inc., Houston, USA) was used to mesh and analyze 3D FE model. Notch shaped cavity was filled with hybrid or flowable resin and each restoration was simulated with adhesive layer thickness (40 microM). A static load of 500 N was applied on a point load condition at buccal cusp (loading A) and palatal cusp (loading B). The principal stresses in the lesion apex (internal line angle of cavity) and middle vertical wall were analyzed using ANSYS. The results were as follows 1. Under loading A, compressive stress is created in the unrestored and restored cavity. Under loading B, tensile stress is created. And the peak stress concentration is seen at near mesial corner of the cavity under each load condition. 2. Compared to the unrestored cavity, the principal stresses at the cemeto-enamel junction (CEJ) and internal line angle of the cavity were more reduced in the restored cavity on both load conditions. 3. In teeth restored with hybrid composite, the principal stresses at the CEJ and internal line angle of the cavity were more reduced than flowable resin.

Surface roughness of universal composites after polishing procedures / 대한치과보존학회지

The aim of this study was to evaluate the effect of two polishing methods and chemical conditioning on the surface of hybrid composites. Ninety cylindrical specimens (diameter: 8 mm, depth: 2 mm) were made with three hybrid composites - Filtek Z250, Tetric Ceram, DenFil. Specimens for each composite were randomly divided into three treatment subgroups - Mylar strip (no treatment), Sof-Lex XT system, PoGo system. Average surface roughness(Ra) was taken using a surface profilometer at the time of setting and after immersion into 0.02N lactic acid for 1 week and 1 month. Representative specimens were examined by scanning electron microscopy. The data were analyzed using ANOVA and Scheffe's tests at 0.05% significance level. The results were as follows: 1. Mylar strip resulted in smoother surface than PoGo and Sof-Lex system(p<0.001). Sof-Lex system gave the worst results. 2. Tetric Ceram was smoother than DenFil and Z250 when cured under only mylar strip. However, it was significantly rougher than other materials when polished with PoGo system. 3. All materials showed rough surface after storage in 0.02N lactic acid, except groups polished with a PoGo system. The PoGo system gave a superior polish than Sof-Lex system for the three composites. However, the correlation to clinical practice may be limited, since there are several processes, such as abrasive, fatigue, and corrosive mechanisms. Thus, further studies are needed for polishing technique under in vivo conditions.