Effects of cigarette smoke and denture cleaners on the surface roughness and color stability of different denture teeth

Effect of conventional cigarette smoking and recent heated tobacco products on CAD/CAM restorative materials

OBJECTIVE

To determine the effects of conventional cigarette smoking (CS) and recent heated tobacco products (HTPs) on the surface roughness and color stability of different indirect restorative materials.

MATERIALS AND METHODS

One hundred disc-shaped samples were constructed of three different restorative CAD/CAM materials: lithium disilicate glass-ceramic (IPS e.max CAD; Ivoclar Vivadent, Liechtenstein), zirconia (BruxZir® Zirconia, Glidewell, USA) and polyetheretherketone (BioHPP® bredent GmbH, Germany). Of the IPS e.max CAD and the Bruxzir samples, 20 samples were glazed, and 20 samples were polished, while the BioHPP samples were all polished according to the manufacturer's instructions. Fifty samples were subjected to conventional cigarette smoking (LM, Philip Morris International Inc., Egypt) (Groups: IPS e.max CAD_Glazed exposed to CS (LD_G_Cig), IPS e.max CAD_Polished exposed to CS (LD_P_Cig), Bruxzir_Glazed exposed to CS (Zr_G_Cig), Bruxzir _Polished exposed to CS (Zr_P_Cig) and BioHPP exposed to CS (PEEK_Cig) and fifty samples were exposed to heated tobacco product smoking (Heets, Russet selection, Philip Morris International Inc., Italy) (Groups: IPS e.max CAD_Glazed exposed to HTP (LD_G_HTP), IPS e.max CAD_Polished exposed to HTP (LD_P_HTP), Bruxzir_Glazed exposed to HTP (Zr_G_HTP), Bruxzir CAD_Polished exposed to HTP (Zr_P_HTP) and BioHPP exposed to HTP (PEEK_HTP).. Six hundred cigarettes/heets representing 30 days of medium smoking behavior (20 cigarettes/day) were used. Before and after exposure to smoke, the surface roughness of all the samples was measured using JITAI8101 surface roughness tester (Beijing Jitai Tech Detection Device Co., Ltd, China, and the color parameters were assessed using VITA Easyshade Advance 4.01 (VITA shade, VITA made, VITA). The data were analyzed using One-way ANOVA, paired sample t-test and independent sample t-test. The significance level was set at α < 0.05. The surface topography was evaluated by scanning electron microscopy (SEM) and analyzed using energy-dispersive X-ray (EDX) spectroscopy to determine changes in the surface chemical composition.

RESULTS

Both types of smoking caused significant increases in the surface roughness of all the samples. There was a significant difference in color change between CS and HTP for all materials with different surface finish (P < 0.01) and zirconia had the greatest effect on color change (P < 0.001). In contrast, polyetheretherketone (PEEK) "BioHPP" had the least effect (P < 0.001).

CONCLUSION

Exposure to different types of smoking induce changes in the surface topography and color of different esthetic restorative materials. Compared with HTP, conventional cigarette smoke has a greater effect on the surface roughness and color stability of esthetic restorative materials. The glazed surfaces showed less change in surface topography than did the polished surfaces. Zirconia showed better color stability when compared to polyetheretherketone (PEEK).

Impact of effervescent denture cleaning tablets on color and surface characteristics of additively manufactured and hand-cast splint materials

OBJECTIVES

This study is to evaluate the color stability, surface roughness, and hardness of additively manufactured and hand-cast splint materials after a 6-month commercially available denture cleaning tablet immersion simulation.

MATERIALS AND METHODS

Disc-shaped additively manufactured and hand-cast auto polymerizing acrylic resin specimens were prepared (N = 40 each). All specimens were exposed to coffee solution totally 2 days. Thereafter, all specimens were immersed into three different effervescent solutions that simulated 6 months of clinical use. The total color change (ΔE*ab), surface roughness (Ra), and Vickers hardness (Vh) were measured at baseline and after immersion protocols. A two-way ANOVA and Bonferroni's post hoc test were used for color change. The dependent t-test and ANOVA were used for roughness and hardness evaluation.

RESULTS

Additively manufactured splint materials were more affected by coffee immersion. It was observed that all denture cleaning tablets induced a noticeable alteration in color of the specimens (p < 0.05). Roughness and hardness measurement changes after solution immersions were statistically significant for both splint groups (p < 0.05). On the other hand, distilled water and denture cleaning tablets created similar roughness and hardness measurements at baseline and after immersion.

CONCLUSIONS

After 6 months use of tested cleaning tables, the color stability, surface roughness, and hardness of both groups were affected. The evaluation of the surface properties of splint materials could be recommended to the dentists in periodic controls during splint treatments.

CLINICAL RELEVANCE

The use effervescent denture cleaning tablets altered the surface characteristics of tested splint materials over time with nonsignificant difference between each other. After 6 months, awareness should be raised about surface characteristics of splint materials.

Effect of tobacco and nicotine in causing staining of dental hard tissues and dental materials: A systematic review and meta-analysis

INTRODUCTION

Dental staining is a common concern for tobacco users. However, little is known about which components of tobacco are responsible for the staining and whether nicotine may be implicated. This is of increasing relevance with the popularity of novel products such as heated-tobacco products and electronic cigarettes (E-cigarettes).

OBJECTIVES

This systematic review aimed to establish the evidence base for the effect if any, of the various tobacco and nicotine products in causing staining of dental hard tissues and materials.

MATERIAL AND METHODS

This systematic review was performed in accordance with the preferred reporting items for systematic reviews and meta-analyses guidelines. There were four structured population intervention comparison outcomesquestions. A search was conducted up to December 2021 in three databases: MEDLINE, EMBASE, and Web of Science, and manual searching of relevant sources was also completed. Two researchers individually reviewed the titles then abstracts and finally full articles. A reporting quality appraisal was conducted appropriately to the study methodology.

RESULTS

Of the 815 records titles identified, 56 full-text articles were assessed for eligibility, of which 27 were included for analysis. The included studies were mainly laboratory studies of varying reporting quality. There was evidence from 18 studies that tobacco exposure caused staining of dental hard tissues (pooled results from three studies- enamel/dentine; mean difference [MD]: 16.22; 95% confidence interval[12.11, 20.32; I² : 96%)and materials (pooled result from four studies-resin composite; MD: 11.90; 95% CI: 11.47, 12.34; I² : 100%). There was limited evidence that E-cigarettes 99%) and heated tobacco products (HTPs; pooled results from three studies--1.07, 6.54; I² : 99%) cause staining, but this was lower than with traditional tobacco/found 11 compounds, of which 8 were terpenoids, from tobacco products implicated in causing staining. Finally, there was some evidence that resin composites stained more than other materials.

CONCLUSIONS

Tobacco smoking causes dental staining. There was limited evidence that E-cigarettes and HTPs did cause dental staining that was less intense than that caused by traditional tobacco products.

Effect of cigarette smoke and denture cleansers on the surface properties and color stability of CAD-CAM and conventional denture base resins

This study aimed to evaluate the hardness, roughness, and color stability of heat- and microwave-polymerized polymethyl methacrylate (PMMA), polyamide, and CAD-CAM PMMA resins when exposed to cigarette smoke (CS) and immersed in a denture cleanser (DC). Specimens of each resins were divided into four subgroups (n=10). The DC and CS+DC specimens were immersed in a DC; the CS and CS+DC specimens were exposed to CS; and the control (C) specimens were kept in distilled water. Hardness, roughness, and color measurements were performed. DC and CS significantly affected the roughness and color of all resins (p<0.05). However, these did not affect the hardness of the CAD-CAM PMMA resin (p>0.05). The CAD-CAM PMMA resin presented the lowest roughness, highest hardness, and lowest ΔE₀₀ values. While the roughness of all resins exposed to CS when immersed in DC decreased, the ΔE₀₀ values of the conventional PMMAs also decreased. Although this decreases were not significant, it may be advisable to use DC for smokers to decrease discoloration and roughness especially for conventional PMMAs resins.

Effect of conventional and rolled cigarette smoke on the colour of artificial teeth and effectiveness of hygiene protocols in removing pigmentation - An in vitro study

Context

Artificial teeth are widely used in oral rehabilitation. Despite the benefits, they are more susceptible to colour changes, causing aesthetic problems.

Aims

To evaluate the effect of conventional cigarette and straw smoke on the colour of artificial teeth and the effectiveness of hygiene protocols in removing pigmentation.

Material and Methods

Acrylic resin incisors were divided into two groups (n = 50): Exposed to conventional cigarette and straw smoke. Regarding the effectiveness of hygiene protocols, the teeth were divided into ten subgroups with predetermined immersion times. The colour was measured with a colorimeter. The CIE values L* a* b* were recorded before and after exposure to smoke and after hygiene protocols. Statistical analysis used T-test of independent samples and two-way ANOVA with Bonferroni post-test (α = 0.05).

Results

Conventional (16.16 ± 1.65) and straw (16.29 ± 1.95) cigarettes provided clinically unacceptable ΔE values, with no significant difference between them (P = 0.719). Conventional cigarettes promoted less luminosity (ΔL = -12.68 ± 1.28) (P < 0.001) and straw greater tendency to yellow (Δb = 11.00 ± 1.46) (P < 0.001). The hygiene protocols influenced the ΔE, ΔL, and Δb of the samples, depending on the type of smoke (P < 0.05).

Conclusions

The conventional and rolled cigarette smoke promote an unacceptable colour change in artificial teeth. Hygiene protocols with the use of brushing, in isolation or in association with chemical solutions are more effective in removing pigmentation caused by both types of cigarettes compared to only the chemical solution.

Effects of conventional and heated tobacco product smoking on discoloration of artificial denture teeth

STATEMENT OF PROBLEM

Cigarette smoke can cause discoloration of artificial denture teeth. However, studies on the effects of heated tobacco product smoke on artificial denture teeth are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of conventional cigarette and heated tobacco product smoke on the color stability of artificial denture teeth.

MATERIAL AND METHODS

Ninety maxillary central incisor denture teeth (Endura Anterior HC5 A3; Shofu) were randomly divided into 3 groups (n=30). Teeth in the control group were exposed to air; those in group CC were exposed to conventional cigarette (Marlboro Medium; Philip Morris) smoke, and those in group HT were exposed to heated tobacco product (IQOS 2.4 plus holder, Marlboro Heets Silver; Philip Morris) smoke. Before the experiment, the shade of the artificial denture teeth was evaluated in accordance with the Commission International de I'Eclairage (CIELab) color system by using a spectrophotometer (Shadepilot; DeguDent GmbH). The average CIELab value was estimated by scanning the entire labial surface of each specimen. To simulate smoking, standard conditions described by the Coresta Recommended Method N°22 were used-the puff duration was 2 seconds, with a 60-second interval between puffs. For each cigarette, 6 puffs and 6 intervals were simulated across 372 seconds. A total of 105 cigarettes were used based on a smoking simulation of 15 cigarettes each day for 7 days. The teeth in the control group were stored in fresh air in the smoke chamber for the same period as those in the experimental groups. After the experiment, L∗, a∗, and b∗ values were measured, and ΔE was calculated to evaluate the color change. All statistical analyses were performed with a statistical software program using a paired t test to determine discoloration after exposure to cigarette smoke. One-way ANOVA and the Tukey test were used to evaluate the significant differences between groups (α=.05).

RESULTS

Lightness was significantly lower in the CC and HT groups (P<.001). All CIELab values showed statistically significant differences in the CC group. The greatest color change was observed in the CC group (ΔE=6.93 ±0.59), whereas the HT group showed a clinically imperceptible color change (ΔE=0.79 ±0.21). Discoloration was minimal in the CC group (ΔE=0.34 ±0.13).

CONCLUSIONS

Conventional cigarette and heated tobacco product smoke can change the color of denture teeth. Heated tobacco product smoke causes less discoloration of denture teeth.

[Color stability of acrylic teeth immersed in a pigmenting solution]

Objective

The objective of this study was to compare the color stability of acrylic teeth immersed in a pigmenting solution.

Methods

An experimental in vitro study was carried out in 40 acrylic teeth from two commercial companies which were immersed in coffee and distilled water (control). The teeth were divided into 4 groups of 10 teeth each: Group-1 (Duratone-n® teeth immersed in distilled water), Group-2 (Duratone- n® immersed in coffee), Group-3 (Ivostar® teeth immersed in distilled water) and Group-4 (Ivostar® teeth immersed in coffee). The specimens were immersed in the respective solutions for 10 minutes a day for a period of 14 days. Finally, the samples were stored in an incubator at a constant temperature of 37 ° C. The color was recorded at two time-points (baseline time and at 14 days) using the Vita Easyshade® V spectrophotometer. The results were analyzed using the Stata 14 program.

Results

Ivostar® teeth immersed in coffee (2.24) and distilled water (2.88) showest the highest ∆E values compared to Duratone-n® teeth immersed in coffee (1.53) and distilled water (1.60).

Conclusion

After exposure to coffee, the Duratone-n® brand teeth presented greater color stability compared to those of the Ivostar® brand.

Optical Properties and Color Stability of Denture Teeth-A Systematic Review

PURPOSE

To systematically review past studies to determine the effect of various solutions on the color of denture teeth, thus answering the question in regards to which type of denture teeth has the best optical properties after exposure to various solutions. The method of measuring the color of artificial teeth was also evaluated as a secondary outcome.

MATERIALS AND METHODS

A search of studies that quantitatively investigated the influence of immersion solutions on the color change of denture teeth was conducted. Ovid MEDLINE, PubMed and Scopus databases were searched from 1997 to April 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used during article selection. Data regarding the effect of immersion solutions, accelerated aging and surface treatments on color change were gathered. Methodologies used to assess optical properties were also summarized and compared. The modified CONSORT checklist was used to determine the risk of bias of past studied included in this review.

RESULTS

One hundred thirty-three studies were identified after removing duplicates. Forty-one studies were selected for full-text analysis, and 35 remaining papers met the inclusion criteria and were therefore included in this systematic review. Thirty-two in vitro studies and 3 in vivo studies were included in the review. All studies reported that immersion in various solutions has a significant influence on the change in color and optical properties of denture teeth. However, the discoloration of denture teeth is still clinically acceptable in most studies. Exposure to various solutions also affected the translucency parameter of denture teeth. Most studies also investigated the surface roughness and hardness along with the optical properties, and reported that immersion cycles did not cause changes in surface roughness of denture teeth, while hardness was affected. The optical properties of PMMA denture teeth have been studied extensively, whereas that of CAD/CAM and 3D printed denture teeth is limited.

CONCLUSIONS

Color stability of CAD/CAM milled denture teeth is comparable to conventional PMMA denture teeth. There are contradictory findings in terms of color stability of 3D printed denture teeth as compared to conventional PMMA denture teeth. Staining by coffee is worst among the common beverages and solutions investigated. Denture teeth can show color changes after immersion in staining beverages as early as one week. The degree of discoloration of denture teeth after immersion is time dependent, with the larger extent in the initial phase.

An In-Vitro Study to Evaluate the Effect of Denture Cleansing Agents on Color Stability of Denture Bases Fabricated Using CAD/CAM Milling, 3D-Printing and Conventional Techniques

The current literature lacks substantial information about the effect of denture cleansers on the color stability of denture bases formed using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) additive and CAD/CAM subtractive manufacturing techniques. This study aimed to assess the effect of two commercially available denture cleansers on the color stability of denture base resins fabricated using four different techniques. Forty-five disc-shaped specimens were fabricated using each technique. Initial color readings were recorded. Specimens were randomly divided into three subgroups (n = 15): a control group (distilled water) and two denture cleanser groups. They were immersed in these solutions, simulating 180 days of use. Final color readings were recorded. The color difference was calculated, and the data were statistically analyzed. For all the specimens, significant color changes were observed after immersion in denture cleanser solutions. The extent of color change varied according to the type of denture cleanser used. When placed in the denture cleanser solutions, the CAD/CAM subtractive group showed the maximum color change (−1.10 and −0.72), while the CAD/CAM additive (3D printing) groups showed the least color change (−0.48 and −0.54). Clinicians should choose appropriate denture cleansers for newly introduced denture base resins to minimize the changes in the color of the dentures.

Evaluating Polishability of Zirconia Impregnated PMMA Nanocomposite for Denture Base Application

Artificial biomaterials are being developed for use in denture base with symmetrical properties to restore the aesthetics and functionalities. The rough surface of denture base resin promotes the adhesion of microorganisms and plaque accumulation. This study aimed to explore the consequences of polishing times on the surface roughness of high-impact (HI) heat-polymerized PMMA denture base acrylic resin reinforced with zirconia nanoparticles (nanocomposite). Thirty specimens (25 ± 0.50 mm in diameter and 2 ± 0.10 mm thickness) were fabricated from HI PMMA by adding zirconia nanoparticles at different concentrations of (0 wt.%, 1.5 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 10 wt.%). Specimens were divided into six groups (n = 5) and surface roughness (Ra) was measured before and after polishing with a standard protocol for one and two minutes. The addition of zirconia in PMMA at low concentrations (1.5 wt.%, 3 wt.%, and 5 wt.%) did not negatively affect the surface finish of the denture base composites following conventional polishing and remained below the clinically acceptable limit (0.2 µm). After one minute of polishing, only the 10 wt.% zirconia (0.17 ± 0.03 µm) demonstrated a substantial rise in median surface roughness, in comparison with the control group (0.11 ± 0.01 µm). It is concluded that the group containing 3 wt.% (0.10 ± 0.01 µm) of zirconia is the optimum concentration to obtain the best symmetrical surface finish after two minutes of polishing.

Surface Characterization, Antimicrobial Activity, and Biocompatibility of Autopolymerizing Acrylic Resins Coated with Reynoutria elliptica Extract

We conducted surface characterization to assess the biocompatibility and investigate the antimicrobial activity against oral pathogens in autopolymerizing acrylic resins, coated with light-curable coating resin, containing various concentrations of Reynoutria elliptica extract (0, 200, 400, and 600 µg/mL). The R. elliptica extract powder was prepared using a freeze-drying technique. Further, a goniometer and microhardness tester were used to determine the water contact angle, and Vickers hardness, respectively; color measurements were performed on the uncoated and coated acrylic resin disks. The polyphenol content of the extracts from the coated acrylic resin disk was analyzed using UV-VIS spectroscopy. The antimicrobial activity of the coated acrylic resin disk against Streptococcus mutans and Candida albicans was observed for 24 and 48 h by measuring the optical density using spectrophotometry. In addition, biocompatibility was confirmed by testing the cell viability according to ISO 10993-5. The water contact angle, Vickers hardness, and color change values of the coated acrylic resin disks were not significantly different from the control. Polyphenol was detected in all experimental groups, with no significant differences between the experimental groups. The experimental groups exhibited significant antimicrobial activity against S. mutans and C. albicans compared to the control group, after 48 h of incubation. The cell viability between the control and experimental groups was not significantly different. The proposed coating resin containing R. elliptica extract is applicable on dental acrylic resins, due to their antimicrobial properties and excellent biocompatibility, with no deterioration of surface characteristics.

Influence of electronic nicotine delivery systems (ENDS) in comparison to conventional cigarette on color stability of dental restorative materials

Objective:

The use of Electronic Nicotine Delivery Systems (ENDS) is increasing rapidly. However, its discoloring effect on dental restorations is not known. This study aimed to evaluate the effect of ENDS aerosol when compared to conventional cigarette smoke (CS) on the color stability of dental ceramic (DC) and resin composite (RC).

Methods:

This research project was conducted from November 2018 to May 2019. In this study 30 discs each for DC and RC materials were fabricated to be equally divided into groups of exposure to CS, ENDS aerosol and storage in distilled water (No smoke; NS) respectively (n=10). Specimens were exposed for a total of 7 days, with a rate of 10 cycles per day, each cycle represented 10 puffs. The color change was assessed using the CIELAB color space, by calculating ΔE. Data was analysed using ANOVA and multiple comparisons test.

Results:

Ceramic specimens in CS (2.422 ± 0.771) and ENDS (2.396 ± 0.396) groups showed comparable ΔE (color change) (p=0.992). Similarly, composite specimens in CS (42.871 ± 2.442) and ENDS (46.866 ± 3.64) groups showed comparable ΔE (p>0.05). NS specimens in both composite and ceramic samples showed lower ΔE than CS and ENDS specimens respectively.

Conclusions:

Aerosol from Electronic nicotine delivery systems (ENDS) showed similar discoloration levels as cigarette smoking (CS). The level of discoloration for ceramic samples for both ENDS and CS was below clinically perceptible levels (Mean ΔE < 2.5). Discoloration of composite resin due to CS and ENDS was visually perceptible (Mean ΔE > 4.0).

Evaluation and Comparison of the Effects of Persulfate Containing and Persulfate-free Denture Cleansers on Acrylic Resin Teeth Stained with Cigarette Smoke: An In Vitro Study

Problem statement and aim 

The esthetics of the complete denture primarily depend upon the color of the denture teeth; however, there are situations where the teeth are subjected to extrinsic and intrinsic stains and discolor over time. The purpose of the study was to investigate the effects of smoking and two different denture cleaners on the color stability of the denture teeth.

Material and methods

Commercially available maxillary anterior teeth made up of acrylic resin were selected for the study and were divided into two groups (n=10): persulfate-free denture cleanser and persulfate containing denture cleansers. The acrylic teeth were set in the smoke chamber with a distance to absorb the smoke equally from the cigarette. The smoke was released for 10 minutes, and the results are observed by the spectrophotometer.

Results

All the values were collected after the 21^st day, and data were analyzed with the SPSS software. It was found that denture cleansers with persulfate are effective on color stability. 

Conclusions

Even though the persulfate containing denture cleansers are injurious to health, they can be recommended to the smokers with clear instructions of use. However, for non-smokers, persulfate-free denture cleansers are preferred over the persulfate containing denture cleansers.

The effect of electronic cigarettes on dental enamel color

OBJECTIVE

The use of electronic cigarettes (ECIGs) has recently increased as an alternative to conventional smoking tobacco products. The literature is scarce on the effects of ECIGs on dental and oral structures. Therefore, the objective of this study was to observe whether ECIG aerosol could alter the color of dental enamel.

MATERIALS AND METHODS

Sixty-three bovine enamel specimens were randomly separated into groups (n = 7) and treated with aerosols with different e-liquid flavors (neutral, menthol, and tobacco) and nicotine content (0, 12, and 18 mg). The initial color assessment was performed using a spectrophotometer (Easy Shade-Vita). Dental enamel was exposed to 20 cycles of ECIG aerosol in a smoking machine, and the final color was measured. The color change was evaluated using ΔEab, ΔE00, and Whiteness Index (WI_D ) formulae. Differences in L* a* b* coordinates were calculated, and data were analyzed (two-way ANOVA, uncorrected Fisher's LSD post hoc test, α = 0.05).

RESULTS

Luminosity (ΔL) was reduced by aerosols with almost all levels of nicotine content and neutral and menthol flavors. Flavored e-liquids caused more color change (P < .05) according to ΔEab and ΔE00. ΔE values from both formulae exceeded the thresholds for perceptible visual alterations of color. WI_D increased after ECIGs exposure for menthol and tobacco and decreased for neutral flavors.

CONCLUSIONS

ECIG aerosol from e-liquids with different nicotine contents and flavors altered enamel color. Menthol and tobacco e-liquids may alter the enamel color decreasing the yellowness of the enamel compared to neutral e-liquid.

CLINICAL SIGNIFICANCE

Electronic cigarettes can cause perceptible changes in tooth color, altering dental esthetics.

Colorimetry as Quality Control Tool for Individual Inkjet-Printed Pediatric Formulations

Printing technologies were recently introduced to the pharmaceutical field for manufacturing of drug delivery systems. Printing allows on demand manufacturing of flexible pharmaceutical doses in a personalized manner, which is critical for a successful and safe treatment of patient populations with specific needs, such as children and the elderly, and patients facing multimorbidity. Printing of pharmaceuticals as technique generates new demands on the quality control procedures. For example, rapid quality control is needed as the printing can be done on demand and at the point of care. This study evaluated the potential use of a handheld colorimetry device for quality control of printed doses of vitamin Bs on edible rice and sugar substrates. The structural features of the substrates with and without ink were also compared. A multicomponent ink formulation with vitamin B₁, B₂, B₃, and B₆ was developed. Doses (4 cm²) were prepared by applying 1-10 layers of yellow ink onto the white substrates using thermal inkjet technology. The colorimetric method was seen to be viable in detecting doses up to the 5th and 6th printed layers until color saturation of the yellow color parameter (b*) was observed on the substrates. Liquid chromatography mass spectrometry was used as a reference method for the colorimetry measurements plotted against the number of printed layers. It was concluded that colorimetry could be used as a quality control tool for detection of different doses. However, optimization of the color addition needs to be done to avoid color saturation within the planned dose interval.

Effect of different denture cleansers on surface roughness and microhardness of artificial denture teeth

PURPOSE

The aim of this study was to compare the effects of different denture cleansers on the surface roughness and microhardness of various types of posterior denture teeth.

MATERIALS AND METHODS

168 artificial tooth specimens were divided into the following four subgroups (n=42): SR Orthotyp PE (polymethylmethacrylate); SR Orthosit PE (Isosit); SR Postaris DCL (double cross-linked); and SR Phonares II (nanohybrid composite). The specimens were further divided according to the type of the denture cleanser (Corega Tabs (sodium perborate), sodium hypochlorite (NaOCl), and distilled water (control) (n=14)) and immersed in the cleanser to simulate a 180-day immersion period, after which the surface roughness and microhardness were tested. The data were analyzed using the Kruskal–Wallis test, Conover's nonparametric multiple comparison test, and Spearman's rank correlation analysis (P<.05).

RESULTS

A comparison among the denture cleanser groups showed that NaOCl caused significantly higher roughness values on SR Orthotyp PE specimens when compared with the other artificial teeth (P<.001). Furthermore, Corega Tabs resulted in higher microhardness values in SR Orthotyp PE specimens than distilled water and NaOCl (P<.005). The microhardness values decreased significantly from distilled water, NaOCl, to Corega Tabs for SR Orthosit PE specimens (P<.001). SR Postaris DLC specimens showed increased microhardness when immersed in distilled water or NaOCl when compared with immersion in Corega Tabs (P<.003). No correlation was found between surface roughness and microhardness (r=0.104, P=.178).

CONCLUSION

NaOCl and Corega Tabs affected the surface roughness and microhardness of all artificial denture teeth except for the new generation nanohybrid composite teeth.

Effects of thermocycling and various drinks on the color stability of heat-polymerized acrylic resin

Purpose:

The discoloration of acrylic resin denture bases may lead to significant esthetic problems. The aim of this in vitro study was to investigate the effects of frequently consumed drinks on the color changes of fresh and aged, heat-polymerized, conventional acrylic resin.

Materials and Methods:

Eighty-four, heat-polymerized acrylic resin specimens (4 mm x 5 mm x 30 mm) were fabricated. Half of the specimens were aged by thermal cycling (between 5°C and 55°C, 60-second dwell time, 3000 cycles). The specimens were stored at 37°C in different drinks as non-aged and aged subgroups including water (control group), black tea, green tea, sour cherry juice, coke and coffee (n=7). The discoloration of each specimen after 1 and 7 days storage in the drinks were measured by a colorimeter based on CIE Lab system. The data of colour differences (ΔE) were analyzed by ANOVA and Dunnet’s tests.

Results:

Thermal cycling and storage in water induced a slight color change. The highest ΔE values were observed in the aged groups, which was also noticeable for black tea and sour cherry juice after 7 days of storage (ΔE>1.5) (p<0.05). The ΔE values of all test groups were detected within the acceptable clinical limits (ΔE<3.5).

Conclusion:

These results suggest that the color stability of denture base acrylic resins is influenced by ageing. Black tea, sour cherry juice and coke can cause significant discolorations on acrylic resin denture bases.

The influence of patient characteristics on acrylic-based resilient denture liners embedded in maxillary complete dentures

PURPOSE

A major complication associated with the use of resilient denture liners (RDLs) is a change in hardness over time. In vivo studies on the deterioration of RDLs over time are needed. We aimed to investigate the influence of patient characteristics on the hardness of acrylic-based RDLs (ARDLs) embedded in complete maxillary dentures. We hypothesized that 1 month after application of the ARDLs, the hardness would be influenced by age, saliva condition, occlusal force, smoking, drinking, denture wearing during sleeping, denture cleanser usage, and denture type.

METHODS

Thirty complete maxillary denture wearers were recruited after obtaining informed consent. One investigator measured the Shore D hardness of the commercially available ARDLs, Soften (SFT), FD Soft (FDS), and Bio Liner (BIO) using a Vesmeter(®). The salivary flow rates and pH values and the occlusal force were measured for all patients before initiation of the study. T-tests and Pearson's correlation coefficients were used for the statistical analyses. A p-value of <0.05 was considered statistically significant.

RESULTS

Smoking, wearing dentures while sleeping, use of denture cleansers, and denture type were associated with an increase in the hardness of the RDLs. The resting saliva pH only influenced the hardness of the SFT ARDLs.

CONCLUSIONS

Smoking, denture wearing while sleeping, denture cleanser usage, denture type, and resting saliva pH are important predictors of the deterioration of ARDLs over time.

Effect of Cigarette Smoke on Surface Roughness of Different Denture Base Materials

BACKGROUND

Surface roughness is an important property of denture bases since denture bases are in contact with oral tissues and a rough surface may affect tissues health due to microorganism accumulation. Therefore, the effect of cigarette smoke on the surface roughness of two commercially available denture base materials was evaluated to emphasize which type has superior properties for clinical use.

MATERIALS AND METHODS

A total numbers of 40 specimens were constructed from two commercially available denture base materials; heat-cured PMMA and visible light cured UDMA resins (20 for each). The specimens for each type were randomly divided into: Group I: Heat cured resin control group; Group II: Heat cured acrylic resin specimens exposed to cigarette smoking; Group III: Light cured resin control group; Group IV: Light cured resin specimens exposed to cigarette smoking. The control groups used for immersion in distilled water and the smoke test groups used for exposure to cigarette smoking. The smoke test groups specimens were exposed to smoking in a custom made smoking chamber by using 20 cigarettes for each specimen. The surface roughness was measured by using Pocket SurfPS1 profilometer and the measurements considered as the difference between the initial and final roughness measured before and after smoking.

RESULTS

The t-test for paired observation of test specimens after exposure to smoking was indicated significant change in surface roughness for Group II (p< 0.05) but has no significance with Group IV. Otherwise, there were no significant differences with control groups (Group I and III).

CONCLUSION

The surface roughness of the dentures constructed from heat cured acrylic resin had been increased after exposure to cigarette smoke but had no impact on the dentures constructed from visible light cured resin.

Hardness and surface roughness of enamel and base layers of resin denture teeth after long-term repeated chemical disinfection

AIM

To evaluate the effect of successive cycles of disinfection in different denture cleansers on the surface roughness and the Vickers hardness of two layers of acrylic resin (base-BL and enamel-EL) of two commercial cross-linked artificial teeth.

MATERIALS AND METHODS

The occlusal surfaces of 60 acrylic resin denture posterior teeth (Trilux-TLX and SR Orthosit PE-SRO) embedded in autopolymerizing acrylic resin were ground fat with 1200-grit silicon carbide paper. Specimens were stored in distilled water at 37°C and then submitted to the microhardness (VHN) and roughness (μm) tests. Specimens were stored in distilled water at 37°C for 90 days and submitted to 720 disinfection cycles in sodium hypochlorite at 0.5%, 30% vinegar solution or distilled water (control). Afterward, micro-hardness and roughness tests were again performed. Data were analyzed using two-way ANOVA and Tukey's test (α=0.05).

RESULTS

Hypochlorite immersion decreased the hardness of BL and EL of SRO teeth, with an average reduction of 10.11% (p<0.008). TLX teeth demonstrated a hardness reduction of 28.96% of both layers for all solutions including water (p<0.0000). The roughness of both teeth was not affected by denture cleansers (p>0.37).

CONCLUSION

Hypochlorite promoted deleterious effects on the hardness of both layers of the artificial teeth tested. Immersion in vinegar and water also resulted in reduction of hardness of TLX teeth.

CLINICAL SIGNIFICANCE

The surface hardness of the different layers of cross-linked artificial teeth can be altered by daily disinfection in denture cleansers commonly indicated for removable dentures.