Comparative evaluation of sodium hypochlorite and microwave disinfection on dimensional stability of denture bases

PURPOSE

To compare the effect of sodium hypochlorite and microwave disinfection on the dimensional stability of denture bases without and with relining.

MATERIALS AND METHODS

A brass die was prepared by simulating an edentulous maxillary arch. It was used to fabricate 1.5 mm and 3 mm of thickness denture bases (n = 40). The 1.5 mm of thickness-specimens (n = 20) were relined with 1.5 mm of autopolymerizing relining resin. Five holes were prepared over crest of ridge of brass die with intimately fitting stainless steel pins which were transferred to the intaglio surface of specimens during fabrication of denture bases. For calculation of dimensional changes in denture bases, differences between the baseline area before and after disinfection of the specimens were used. The denture bases without and with relining were divided into 2 groups (each n = 20). Data were analyzed using student paired ''t'' and unpaired ''t'' test.

RESULTS

Microwave disinfection produces significant shrinkage in both denture bases without relining (t = 17.16; P<.001) and with relining (t = 14.9; P<.001). Denture bases without relining showed more shrinkage when compared with relined denture bases after microwave disinfection (t = 6.09; P<.001). The changes in dimensional stability after sodium hypochlorite disinfection were not significant for both denture bases without relining (t = 2.19; P=.056) and denture bases with relining (t = 2.17; P=.058).

CONCLUSION

Microwave disinfection leads to increased shrinkage of denture bases without and with relining. Chemical disinfection with sodium hypochlorite seems to be a safer method of disinfection with regards to physical properties such as changes in dimensional stability.     

Effect of different disinfecting procedures on the hardness and color stability of two maxillofacial elastomers over time

Objective:

Disinfection procedures often cause deterioration in a maxillofacial prosthesis. Color and hardness alterations could lead to a replacement of the prosthesis.

Material and Methods:

An experimental chlorinated polyethylene (CPE) and a commercial polydimethyl siloxane (PDMS) sample were treated with four different disinfection procedures for a period which simulates 1 year of clinical service. The applied disinfection procedures included microwave exposure and immersion in three solutions, sodium hypochlorite, neutral soap and a commercial disinfecting soap. Shore A hardness (ΔΗ) and color differences (ΔΕ) were determined before and after each procedure. All data were analyzed by Two Way Analysis of Variance (ANOVA) and Tukey''s post hoc tests at a level of α=0.05.

Results:

The samples presented significant alterations in color and hardness after the different disinfection treatments. The color differences (ΔΕ) were at least eye detectable in all cases and clinically unacceptable in most of the cases, with values ranging from 1.51 to 4.15 and from 1.54 to 5.92 for the PDMS and CPE material, respectively. Hardness was decreased after all the disinfection procedures in the PDMS, while for the CPE, a decrement was observed after disinfection with sodium hypochlorite and neutral soap and an increment after microwave exposure and the disinfection with a commercial antimicrobial agent. The PDMS samples presented greater alterations in color and hardness after disinfection with sodium hypochlorite solution, while the microwave exposure caused negligible effects. The CPE samples were affected most after disinfection when treated with neutral soap, and more slightly when disinfected with sodium hypochlorite solution.

Conclusions:

The disinfection procedures caused alterations in color and hardness of the examined materials. The most suitable disinfection procedure for the PDMS material is microwave exposure, while disinfection with sodium hypochlorite solution is not recommended. The CPE material is suggested to be disinfected with sodium hypochlorite solution and the use of neutral soap is not recommended. Comparing the two materials, the PDMS material is most color stable, while the CPE material presented fewer changes in hardness.     

In vivo efficacy of alkaline peroxide tablets and mouthwashes on Candida albicans in patients with denture stomatitis

Objective

Effective cleaning of dentures is important for the maintenance of good oral hygiene for denture stomatitis patients. The in vivo efficacy of three different brands of alkaline peroxide tablets (Polident, Efferdent, and Fittydent) and two mouthwashes (CloSYS II and Corsodyl) to eliminate Candida albicans on dentures was evaluated in this in vivo study.

Material and methods

Ninety denture wearers with clinical evidence of denture stomatitis were randomly divided into 5 test groups and 1 control group. Each group was further divided into three subgroups in which the dentures were subjected to 15-, 30-, and 60-min disinfection procedures. The dentures of each test group were treated with one of the cleaners, while those of the control group were treated with distilled water. Swab samples from the palatal surfaces (2 cm x 2 cm template delimited area) of the upper dentures were obtained before and after 15, 30, and 60 min periods of cleaner use and examined mycologically.

Results

The reduction in the number of colony-forming units (CFU) of C. albicans before, and after 15, 30, and 60 min of use of CloSYS II and Corsodyl was significantly greater than that of the control group (p<0.05). Moreover, there was no statistically significant difference (p>0.05) among Polident, Efferdent and the control group in any of the treatment periods. Dentures treated with Fittydent appeared to have a significantly greater reduction in the number of Candida spp. only after 60 min of treatment.

Conclusions

The results of this study showed that the use of mouthwashes significantly reduced the number of microorganisms on dentures.     

Effect of repeated immersion solution cycles on the color stability of denture tooth acrylic resins

Objective

Chemical solutions have been widely used for disinfection of dentures, but their effect on color stability of denture tooth acrylic resins after repeated procedures is still unclear. The aim of this in vitro study was to evaluate whether repeated cycles of chemical disinfectants affected the color stability of two denture tooth acrylic resins.

Material and Methods

Sixty disc-shaped specimens (40 mm x 3 mm) were fabricated from two different brands (Artiplus and Trilux) of denture tooth acrylic resin. The specimens from each brand (n=30) were randomly divided into 6 groups (n=5) and immersed in the following solutions: distilled water (control group) and 5 disinfecting solutions (1% sodium hypochlorite, 2% sodium hypochlorite, 5.25% sodium hypochlorite, 2% glutaraldehyde, and 4% chlorhexidine gluconate). Tooth color measurements were made by spectrophotometry. Before disinfection, the initial color of each tooth was recorded. Further color measurements were determined after subjecting the specimens to 7, 21, 30, 45, 60, and 90 immersion cycles in each tested solution. Color differences (ΔE*) were determined using the CIE L*a*b* color system. Data were analyzed using two-way repeated measures analysis of variance (ANOVA) followed by Tukey tests. The significance level was set at 5%.

Results

There were statistically significant differences in ΔE* among the 5 disinfectants and water during the 90 cycles of immersion for both denture tooth acrylic resins. Distilled water promoted the greatest color change in both denture tooth acrylic resins, nevertheless none of tested disinfectants promoted ΔE* values higher than 1.0 on these acrylic materials during the 90 cycles of disinfection.

Conclusions

Repeated immersion cycles in disinfecting solutions alter ∆E* values, however these values do not compromise the color of the tested denture tooth acrylic resins because they are imperceptible to the human eye.     

Microbial contamination and disinfection methods of pacifiers

Objectives

To evaluate the microbial contamination of pacifiers by Mutans Streptococci (MS) and the efficacy of different methods for their disinfection.

Methods

Twenty-eight children were assigned to a 4-stage changeover system with a 1-week interval. In each stage, children received a new pacifier and the parents were instructed to maintain their normal habits for 1 week. After this time, the pacifiers were subjected to the following 4 disinfection methods: spraying with 0.12% chlorhexidine solution, Brushtox^® or sterile tap water, and immersion in boiling tap water for 15 minutes. Microbiological culture for MS and Scanning Electron Microscopy (SEM) were performed. The results were analyzed statistically by Friedman’s non-parametric test (a=0.05).

Results

The 0.12% chlorhexidine spray was statistically similar to the boiling water (p>0.05) and more effective than the Brushtox^® spray and control (p<0.05). The analysis of SEM showed the formation of a cariogenic biofilm in all groups with positive culture.

Conclusions

Pacifiers become contaminated by MS after their use by children and should be disinfected routinely. Spraying with a 0.12% chlorhexidine solution and immersion in boiling water promoted better disinfection of the pacifiers compared with a commercial antiseptic toothbrush cleanser (Brushtox^®).     

Changes in roughness of denture base and reline materials by chemical disinfection or microwave irradiation: surface roughness of denture base and reline materials

Objective

The effect of disinfection by immersion in sodium perborate solution and microwave irradiation on surface roughness of one denture base resin (Lucitone 550 -L), 3 hard chairside reline resins (Tokuyama Rebase II-TR, New Truliner-NT, Ufi Gel hard-UH) and 3 resilient reline materials (Trusoft-T; Sofreliner-S, Dentusil-D) was evaluated.

Material and methods

Thirty specimens of each material were made and divided into 3 groups: Control - not disinfected; P - daily disinfection by immersing in sodium perborate solution (3.8%); MW - microwave disinfection (6 min/650 W). Roughness measurements were made after polymerization (baseline) and after 1, 3 and 28 days. Roughness differences relative to the baseline readings were analyzed by Student''s t-test (P=0.05).

Results

At baseline, Trusoft showed the highest (P<0.001) mean surface roughness (3.54 µm), and its surface roughness was significantly reduced after 28 days of disinfection by immersion in sodium perborate (P=0.013). Roughness measurements of material Trusoft were not performed after microwave disinfection due to the severe alterations on the surface. In the 3 groups evaluated, changes in roughness were significant for materials Ufi Gel hard (from 0.11 to 0.26 µm; P≤0.041) and New Truliner (0.19 to 0.76 µm; P≤0.019). The roughness of materials Lucitone 550 (0.37 µm), Tokuyama Rebase II (0.37 µm), Sofreliner (0.49 µm) and Dentusil (0.38 µm) remained unaffected (P>0.05).

Conclusions

The roughness of the hard reline materials Ufi Gel hard and New Truliner was adversely affected by microwave disinfection, immersion in water or in sodium perborate. Microwave disinfection caused severe alterations on the surface of the resilient liner Trusoft.     

EFFECT OF PONTIC FRAMEWORK DESIGN ON THE FRACTURE RESISTANCE OF IMPLANT-SUPPORTED ALL-CERAMIC FIXED PARTIAL DENTURES

Objective:

The purpose of this study was to compare the fracture resistance of implant-supported all-ceramic fixed partial dentures, which have three different pontic designs.

Material and Methods:

Two implants were placed in a metal model simulating mandibular left second premolar and mandibular left second molar. Thirty standardized 3-unit all-ceramic fixed partial dentures with biconvex, convex or concave pontic designs were fabricated using IPS e.max system (n=10). Afterwards, specimens were centrally loaded on the pontics until failure with a universal testing machine. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests at 5% significance level.

Results:

The fracture resistance values of all-ceramic fixed partial dentures designed with biconvex, convex or concave pontics were 349.71, 438.20 and 300.78 N, respectively. There were no statistically significant differences between the fracture resistances of the groups (p>0.05), except for convex and concave groups (p<0.05 and p=0.009, respectively).

Conclusions:

Convex design showed the best mechanical properties as demonstrated by the high values of fracture resistance.     

Experimental evaluation of cyclic fatigue resistance of four different nickel-titanium instruments after immersion in sodium hypochlorite and/or sterilization

NiTi instruments have a high risk of separation due to torsional or flexural fatigue (cyclic fatigue). Chemomechanical preparation, cleaning procedures, chemical disinfection and sterilization cause the corrosion of endodontic instruments that may weaken the fracture resistance of the instruments.

Objective

To assess the effects of NaOCl immersion and autoclave sterilization on the cyclic fatigue resistance of ProFile, FlexMaster, Mtwo and TwistedFiles NiTi instruments (tip size 25, 0.06 taper, n=160).

Material and Methods

The instruments (n=10 for each subgroup) were dynamically immersed in NaOCl; immersed in NaOCl and sterilized in one autoclave cycle; 5 cycles immersed in NaOCl and sterilized in autoclave and not immersed in NaOCl and not sterilized (control group). Dynamic cyclic fatigue resistance was tested. The number of cycles to failure (NCF) were statistically analyzed (P<0.05).

Results

Kruskall-Wallis test indicated significant differences among the tested instruments in terms of NCF (P=0.000). The mean NCF of Mtwo (556.75) was higher than that of the Twisted File, Flexmaster and ProFile, 483.1, 376.12, 365.25, respectively. NaOCl immersion and autoclave sterilization have no effect on the NCF values of the tested instruments (P>.05).

Conclusions

Cyclic fatigue resistance of the tested NiTi instruments cannot be adversely affected by NaOCl immersion and autoclave sterilization. Production process (TwistedFiles) or design (Twisted Files, FlexMaster, Mtwo and ProFile) of the instruments can influence their cyclic fatigue resistance.     

Effect of three investing materials on tooth movement during flasking procedure for complete denture construction

Problem statement

Tooth movement has been shown to occur during and after the processing of complete dentures. An understanding of this phenomenon may permit one to construct functional complete dentures that require less occlusal adjustment in the articulator and in the patient’s mouth.

Purpose

The purpose of this study was to examine the effects of three different investing methods on tooth movement occurring during the processing of simulated maxillary complete dentures.

Material and methods

Forty-five similar maxillary dentures were made using heat-polymerized acrylic resin, and assigned randomly to three experimental groups (n = 15 each) according to investing method: plaster–plaster–plaster (P–P–P), plaster–stone–stone (P-S-S), and plaster–mix (P–M). Specimens in all experimental groups were compression molded with denture base resin. Transverse interincisor (I–I) and intermolar (M–M) distances, and anteroposterior incisor–molar (LI–LM and RI–RM) distances, were measured with digital calipers at the wax denture stage (pre-polymerization) and after denture decasting (post-polymerization). Analysis of variance and Tukey’s test were used to compare the results.

Results

M–M, LI–LM, and RI–RM movement was significantly greater in the P–P–P group than in the P–S–S and P–M groups; no significant difference in I–I movement was observed among groups. Transverse movement along M–M and I–I was significantly greater than anteroposterior movement in the P–P–P group; no significant difference among measurements was observed in the other two groups.

Conclusion

The study results indicate that the use of dental stone or a 50:50 mixture of plaster and stone for investing of dentures is an important factor in efforts to control the magnitude of tooth movement.     

A clinical investigation of the relationship between the quality of conventional complete dentures and the patients’ quality of life

Objective

The purpose of this study was to determine whether there is a correlation between the clinical quality of conventional complete dentures and patient quality of life.

Materials and methods

This study included a random sample of 32 completely edentulous patients (15 males and 17 females) who were treated with conventional complete dentures. Using a validated questionnaire, three investigators evaluated the dentures independently on the basis of seven clinical parameters: esthetics (lip support and lower lip line), retention and stability of the maxillary and the mandibular dentures, and occlusion. Patients completed the validated Oral Health Impact Profile-20 (OHIP-20) questionnaire. Correlations were determined by using the point-biserial correlation coefficient.

Results

Clinicians rated the overall clinical quality of the dentures satisfactory in 80.3% of patients. The mean (±standard deviation) total OHIP-20 score was 56.3 ± 15.9 out of a possible 120 maximum. A statistically significant negative correlation was found between the stability of the maxillary and mandibular dentures and the total OHIP-20 score (p = 0.009 and 0.0023, respectively). A negative correlation between the total OHIP-20 score and the retention of the mandibular denture approached significance (p = 0.092). Esthetics, retention of the maxillary denture, and occlusion were not correlated with patient quality of life (p > 0.169).

Conclusion

Stability of the maxillary and mandibular dentures is the denture quality parameter that can most significantly affect patient quality of life.     

A Comparative in Vitro Study of Apical Microleakage with Five Obturation Techniques: Lateral Condensation,Soft-Core?, Obtura II?, Guttaflow? and Resilon?

Aim

A comparison was made between the root canal lateral condensation technique and other condensation techniques in which physical (temperature: Soft-Core®, Obtura II®) or chemical changes (condensation: Guttaflow®, Resilon®) may affect the dimensional stability of obturation and thus favor apical microleakage.

Materials and methods

A total of 212 single-root teeth removed for orthodontic or periodontal reasons were randomized to 5 groups of 40 teeth each. Six samples were used as positive controls, and another 6 as negative controls. The teeth were worked with the Hero 642 system, and each group was obturated using a different technique: lateral condensation, Obtura II®, Soft-Core®, Guttaflow® or Resilon®. The samples were immersed in black ink, and after 72 hours the teeth were transparentized using the technique described by Robertson. Filtration of the ink was measured under the stereoscopic microscope. Analysis of variance and post-hoc testing were used for the statistical analysis.

Results

The Soft-Core® obturated group showed significantly greater microleakage than the other groups, with no differences among the rest of the groups.

Conclusions

Under the conditions of this study, the teeth obturated with the Soft-Core® technique showed greater apical microleakage than the other systems.Key words: Apical microleakage, root canal obturation, sealing ability, transparentization     

Usage of removable partial dentures in Saudi male patients after 1 year telephone interview

Objective

The success of removable partial dentures (RPDs) is partly dependent on patients’ acceptance and compliance in using them. The purpose of this study was to describe the usage of removable partial dentures (RPDs) by patients 1 year after insertion and to evaluate the factors that influence their denture usage.

Methods

Forty-seven patients who received 75 new RPDs at the undergraduate clinic of College of Dentistry, King Saud University, were contacted by telephone 1 year later for an interview. The questions covered denture usage, patient’s satisfaction and reasons for non-use.

Results

Results showed that 36% of patients discarded or occasionally used their RPDs. There was no significant association between denture usage and RPD experience, location or Kennedy classification. A significantly more RPD rejection was found when it was opposed by natural teeth or complete denture. The most quoted reason for RPD rejection was pain and discomfort.

Conclusion

Despite the short follow-up period, RPDs were poorly accepted by patients treated by undergraduate students.     

IN VITRO ANTIFUNGAL ACTION OF DIFFERENT SUBSTANCES OVER MICROWAVED-CURED ACRYLIC RESINS

Objective:

The presence of Candida albicans on the surfaces of denture-base acrylic resins is strongly related to the development of oral stomatitis. This study evaluated the antifungal action of different agents over microwave-cured acrylic resin without polishing specimens previously contaminated with Candida albicans.

Material and Methods:

Sixty specimens were immersed in BHI broth previously inoculated with the yeast and stored for 3 h at 37°C. They were divided into 5 experimental groups (n=10): G1: 2% chlorhexidine solution (10 min); G2: 0.5% sodium hypochlorite (10 min); G3: modified sodium hypochlorite (10 min); G4: effervescent agent (5 min); G5: hydrogen peroxide 10v (30 min). The specimens of the control group 1 (C1) were not disinfected. Ten additional specimens of the control group 2 (C2) were not infected with the yeast, aiming to check the asepsis during the experiment. The disinfection agents were neutralized and the acrylic resin specimens were immersed in BHI Broth for 24 h. Culture media turbidity was evaluated spectrophotometrically according to the transmittance degree, i.e. the higher the transmittance the stronger the antimicrobial action. Statistical analysis was performed (Kruskal-Wallis Test, p<0.05).

Results:

The results, represented by the medians, were: G1 = 40; G2 = 100; G3 = 100; G4 = 90; G5 = 100; C1 = 40; C2 = 100.

Conclusions:

This in vitro study suggested that sodium hypochlorite-based substances and hydrogen peroxide are more efficient disinfectants against C. albicans than 2% chlorhexidine solution and the effervescent agent.     

Micro-sized erosions in a nanofilled composite after repeated acidic beverage exposures: consequences of clusters dislodgments

Objective

To evaluate the hardness (KHN), color stability (DE), and superficial micromorphology of two categories of composites after immersion in either distilled water or grape juice for up to 45 days.

Material and Methods

Cylindrical specimens (6 mm diameter x 2 mm thick) were obtained according to the factors: composite [Opallis (FGM) and Filtek Z350XT (3M ESPE)]; immersion solution (distilled water and grape juice); and evaluation time: 24 h and 7, 14, 21, 28, and 45 days. After photoactivation, the specimens were stored at 37ºC for 24 h. KHN (50 g/15 s) and ΔE were then repeatedly assessed according to the immersion solutions. Data were analyzed (three-way ANOVA/Tukey''s test). Scanning electron microscopy (SEM) topographic analysis was also performed.

Results

In general, KHN of both composites reduced after 24 h, irrespective of the immersion solution and time. A significantly lower KHN was noted for Opallis compared with Filtek Z350XT in all parameters. An increase in ΔE over time was noted for both composites, irrespective of the immersion solution. Significantly higher ΔE was noted for Filtek Z350XT immersed in grape juice compared with Opallis, regardless of the evaluation time. The grape juice caused significantly higher DE compared with water in all periods. SEM analysis showed eroded areas for Filtek Z350XT but not for Opallis.

Conclusions

The compositions and immersion solutions influence the composite hardness and the color stability. In spite of the higher hardness, the nanofilled composite is more susceptible to color change than the microhybrid when immersed in an acidic dyed solution.     

EFFECT OF 2% IODINE DISINFECTING SOLUTION ON BOND STRENGTH TO DENTIN

Introduction:

Disinfection of dentin surfaces is desirable so long as it does not interfere with subsequent bonding of adhesive resins.

Objective:

To test the null hypothesis that bond strengths to dentin are not affected by previous application of an iodine disinfecting solution.

Materials and Methods:

Twenty-four extracted non-carious molars were selected. Occlusal enamel was removed producing a flat dentin substrate. Test teeth were all treated with 2% Iodine disclosing/disinfecting solution (I₂DDS) for 20 sec and rinsed for 20 sec followed by the application of self- or total- etching bonding systems, generating five adhesive groups (n=3): Single Bond;; Prime & Bond NT; Clearfil SE Bond; Opti-Bond Plus. The control groups (n=3 per adhesive) had no disclosing/disinfectant application prior to adhesive application. A 4-mm thick resin restoration was built up on each tooth for microtensile testing. Statistical analyses between experimental and control groups were performed by student''s t-test (α = 0.05).

Results:

In general, experimental groups (previously treated with I₂DDS) showed significantly lower bond strength values when compared with their respective controls (p<0.05), except for group Prime &Bond I₂ that did not significantly differ from its control (p>0.05).

Conclusion:

Acetone-base adhesive systems seem not to be affected by the application of I₂DDS prior to etching and bonding procedures.     

ENTEROBACTERIACEAE AND PSEUDOMONADACEAE ON THE DORSUM OF THE HUMAN TONGUE

Objective:

The aim of this study was to correlate the presence of Enterobacteriaceae, Pseudomonadaceae, Moraxellaceae and Xanthomonadaceae on the posterior dorsum of the human tongue with the presence of tongue coating, gender, age, smoking habit and denture use.

Material and Methods:

Bacteria were isolated from the posterior tongue dorsum of 100 individuals in MacConkey agar medium and were identified by the API 20E system (Biolab-Mérieux).

Results:

43% of the individuals, presented the target microorganisms on the tongue dorsum, with greater prevalence among individuals between 40 and 50 years of age (p = 0.001) and non-smokers (p=0.0485).

Conclusions:

A higher prevalence of Enterobacteriaceae and Pseudomonadaceae was observed on the tongue dorsum of the individuals evaluated. There was no correlation between these species and the presence and thickness of tongue coating, gender and presence of dentures.     

Clinical gap changes after porcelain firing cycles of zirconia fixed dentures

PURPOSE

The aim of this study was to measure the changes on the marginal and internal adaptation of zirconia based anterior fixed partial dentures after the porcelain firing process.

MATERIALS AND METHODS

A total of 34 anterior fixed partial dentures using LAVA CAD/CAM system (3M ESPE, Germany) were applied. Two silicone replicas were obtained: one is obtained before porcelain firing process (initial) and the other is obtained after porcelain firing process (final), followed by the examination under a binocular stereomicroscope. Kruskal Wallis and Wilcoxon Signed Ranks tests were used for the statistical analysis (P<.05).

RESULTS

No statistically significant difference was found between initial and final marginal gap values (P>.05). At the internal gap measurements, final marginal area values (59.54 µm) were significantly lower than the initial marginal area values (68.68 µm)(P<.05). The highest and the lowest internal gap values were observed at the incisal/occlusal area and at the marginal area, respectively. In addition, lower internal gap values were obtained for canines than for central incisors, lateral incisors and premolars at the incisal area (P<.05).

CONCLUSION

The firing cycles did not affect the marginal gap of Lava CAD/CAM system, but it is controversial for the internal gap.     

Effects of calcium hydroxide addition on the physical and chemical properties of a calcium silicate-based sealer

Recently, various calcium silicate-based sealers have been introduced for use in root canal filling. The MTA Fillapex is one of these sealers, but some of its physicochemical properties are not in accordance with the ISO requirements.

Objective

The aim of this study was to evaluate the flowability, pH level and calcium release of pure MTA Fillapex (MTAF) or containing 5% (MTAF5) or 10% (MTAF10) calcium hydroxide (CH), in weight, in comparison with AH Plus sealer.

Material and Methods

The flowability test was performed according to the ISO 6876:2001 requirements. For the pH level and calcium ion release analyses, the sealers were placed individually (n=10) in plastic tubes and immersed in deionized water. After 24 hours, 7 and 14 days, the water in which each specimen had been immersed was evaluated to determine the pH level changes and calcium released. Flowability, pH level and calcium release data were analyzed statistically by the ANOVA test (α=5%).

Results

In relation to flowability: MTAF>AH Plus>MTAF5>MTAF10. In relation to the pH level, for 24 h: MTAF5=MTAF10=MTAF>AH Plus; for 7 and 14 days: MTAF5=MTAF10>MTAF>AH Plus. For the calcium release, for all periods: MTAF>MTAF5=MTAF10>AH Plus.

Conclusions

The addition of 5% CH to the MTA Fillapex (in weight) is an alternative to reduce the high flowability presented by the sealer, without interfering in its alkalization potential.     

The impact of frenulum height on strains in maxillary denture bases

PURPOSE

The midline fracture of maxillary complete dentures is a frequently encountered complication. The purpose of this study was to assess the effect of frenulum height on midline strains of maxillary complete dentures.

MATERIALS AND METHODS

A removable maxillary complete denture was fabricated and duplicated seven times. Four different labial frenulum heights were tested for stresses occurring on the palatal cameo surface. The strains were measured with strain gauges placed on 5 different locations and the stresses were calculated. To mimic occlusal forces bilaterally 100 N of load was applied from the premolar and molar region.

RESULTS

A statistically significant association between the height of the labial frenulum and the calculated stresses and strains was shown (P<.05) predominantly on the midline and especially on the incisive papilla. The results showed that stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum.

CONCLUSION

Within the limitations of this in vitro study, it can be concluded that the stress on the anterior midline of the maxillary complete denture increases with a higher labial frenulum. Surgical or mechanical precautions should be taken to prevent short-term failure of maxillary complete dentures due to stress concentration and low cycle fatigue tendency at the labial frenulum region.     

Surface hardness evaluation of different composite resin materials: influence of sports and energy drinks immersion after a short-term period

Objectives:

This study evaluated the effect of sports and energy drinks on the surface hardness of different composite resin restorative materials over a 1-month period.

Material and Methods:

A total of 168 specimens: Compoglass F, Filtek Z250, Filtek Supreme, and Premise were prepared using a customized cylindrical metal mould and they were divided into six groups (N=42; n=7 per group). For the control groups, the specimens were stored in distilled water for 24 hours at 37º C and the water was renewed daily. For the experimental groups, the specimens were immersed in 5 mL of one of the following test solutions: Powerade, Gatorade, X-IR, Burn, and Red Bull, for two minutes daily for up to a 1-month test period and all the solutions were refreshed daily. Surface hardness was measured using a Vickers hardness measuring instrument at baseline, after 1-week and 1-month. Data were statistically analyzed using Multivariate repeated measure ANOVA and Bonferroni''s multiple comparison tests (α=0.05).

Results:

Multivariate repeated measures ANOVA revealed that there were statistically significant differences in the hardness of the restorative materials in different immersion times (p<0.001) in different solutions (p<0.001). The effect of different solutions on the surface hardness values of the restorative materials was tested using Bonferroni''s multiple comparison tests, and it was observed that specimens stored in distilled water demonstrated statistically significant lower mean surface hardness reductions when compared to the specimens immersed in sports and energy drinks after a 1-month evaluation period (p<0.001). The compomer was the most affected by an acidic environment, whereas the composite resin materials were the least affected materials.

Conclusions:

The effect of sports and energy drinks on the surface hardness of a restorative material depends on the duration of exposure time, and the composition of the material.