Effect of spatial arrangement and clinical service lifetime simulation on the retention of magnetic units used in implant-anchored orbital prostheses.

STATEMENT OF PROBLEM: Evidence for the optimal spatial arrangement of magnetic attachments in implant-supported orbital prostheses is lacking. PURPOSE: The purpose of this in vitro study was to assess the effect of 6 different spatial arrangements on the retentive force of magnetic attachments following the in vitro simulation of clinical service by insertion-removal test cycles and the contribution of artificial aging to the morphological alterations induced on the magnetic surfaces. MATERIAL AND METHODS: Ni-Cu-Ni plated disk-shaped neodymium (Nd) magnetic units (d=5 mm, h=1.6 mm) were secured on leveled (50×50×5 mm, n=3) and angled (40×45×40 mm, interior angle=90 degrees, n=3) pairs of test panels in 6 different spatial arrangements: triangular_leveled (TL), triangular_angled (TA), square_leveled (SL), square_angled (SA), circular_leveled (CL), and circular_angled (CA) generating corresponding test assemblies (N=6). TL and TA arrangements included 3 magnetic units (3-magnet groups) and SL, SA, CL, and CA 4 (4-magnet groups). The retentive force (N) was measured at a mean crosshead speed of 10 mm/min (n=10). Each test assembly was subjected to insertion-removal test cycles with a 9-mm amplitude, ν=0.1 Hz, and n=10 consequent retentive force measurements at a crosshead speed of 10 mm/min at 540, 1080, 1620, and 2160 test cycles. Surface roughness alterations following the 2160 test cycles were measured by calculating the Sa, Sz, Sq, Sdr, Sc, and Sv parameters with an optical interferometric profiler with 5 new magnetic units used as a control group. Data were analyzed with 1-way ANOVA and Tukey HSD post hoc tests (α=.05). RESULTS: The 4-magnet groups had statistically significantly higher retentive force than the 3-magnet ones at baseline and following the 2160 test cycles (P<.05). In the 4-magnet group, the ranking at baseline was SA.05). CONCLUSIONS: Four magnetic attachments placed on an SL spatial arrangement resulted in the highest retention force but presented with the highest force reduction following the in vitro simulation of clinical service by insertion-removal test cycles.

Prosthodontic restoration of a COVID-19 associated mucormycosis defect: A clinical report.

INTRODUCTION: Coronavirus Disease 2019 (COVID-19) pandemic brought the clinical practice of dentistry and prosthodontics at the threshold of a new era, due to the increasing prevalence of a relative rare condition normally affecting the immunocompromised patients. AIM: The aim of this clinical case report is to briefly describe the etiopathogenesis, the surgical and prosthodontic management of this evolving medical condition emphasizing the emerging role of the maxillofacial prosthodontist in restoring the patients' well-being. METHODS AND RESULTS: The surgical and prosthodontic rehabilitation of a COVID-19 infected patient with a mucormycotic lesion of the maxilla will be presented. CONCLUSION: The role of the maxillofacial prosthodontist is important in alleviating this severe COVID-19 associated morbidity.

The effect of cooling procedures on monomer elution from heat-cured polymethyl methacrylate denture base materials.

OBJECTIVE: To evaluate the amount of methyl methacrylate (MMA) released in water from heat-cured polymethyl methacrylate (PMMA) denture base materials subjected to different cooling procedures. METHODOLOGY: Disk-shaped specimens (Ø:17 mm, h:2 mm) were fabricated from Paladon 65 (PA), ProBase Hot (PB), Stellon QC-20 (QC) and Vertex Rapid Simplified (VE) denture materials using five different cooling procedures (n=3/procedure): A) Bench-cooling for 10 min and then under running water for 15 min; B) Cooling in water-bath until room temperature; C) Cooling under running water for 15 min; D) Bench-cooling, and E) Bench-cooling for 30 min and under running water for 15 min. A, B, D, E procedures were proposed by the manufacturers, while the C was selected as the fastest one. Control specimens (n=3/material) were fabricated using a long polymerization cycle and bench-cooling. After deflasking, the specimens were ground, polished and stored in individual containers with 10 ml of distilled water for seven days (37oC). The amount of water-eluted MMA was measured per container using isocratic ultra-fast liquid chromatography (UFLC). Data were analyzed using Student's and Welch's t-test (α=0.05). RESULTS: MMA values below the lower quantification limit (LoQ=5.9 ppm) were registered in B, C, E (PA); E (PB) and B, D, E (QC) procedures, whereas values below the detection limit (LoD=1.96 ppm) were registered in A, D (PA); A, B, C, D (PB); C, D, E (VE) and in all specimens of the control group. A, B (VE) and A, C (QC) procedures yielded values ranging from 6.4 to 13.2 ppm with insignificant differences in material and procedure factors (p>0.05). CONCLUSIONS: The cooling procedures may affect the monomer elution from denture base materials. The Ε procedure may be considered a universal cooling procedure compared to the ones proposed by the manufacturers, with the lowest residual monomer elution in water.

Effectiveness of prosthetic rehabilitation and quality of life of older edentulous head and neck cancer survivors following resection of the maxilla: a cross-sectional study.

PURPOSE: To evaluate the effectiveness of prosthetic rehabilitation, as well as the quality of life (QOL) of older edentulous maxillectomy patients. METHODS: Effectiveness of the complete denture obturator prosthesis and QOL of N = 44 older edentulous patients who had resection of the maxilla and were restored with a definitive prosthesis that was in use for a minimum of 1 year was assessed using three instruments: European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (QLQ-C30), Head and Neck Cancer Module (QLQ-HN35), and Obturator Functioning Scale (OFS). Data analysis was performed by one-way analysis of variance (ANOVA) on ranks, Spearman rank-order correlation, and hierarchical multivariable rank regression at α = .05 level of significance. RESULTS: Participants' gender (P < .001), adjuvant treatment (P = .016), surgical approach (P = .017), size of the maxillary defect (P = .028), participants' prosthetic history (P = .047), and dental status of the mandible (P = .038) were significantly related to the self-reported effectiveness of the complete denture obturator prosthesis. Perceived functioning of the prosthesis (P = .001), participants' gender (P = .002), the American Society of Anesthesiologists (ASA) physical status (P = .027), and surgical approach (P = .039) were significant predictors of QOL. CONCLUSION: Restoration of the edentulous maxillectomy defect is challenging. An effective definitive complete denture obturator appeared to be the strongest predictor for advanced quality of life in older maxillectomy patients. The physical status of the older participants significantly affected the overall QOL, but did not influence the self-reported functioning of the complete denture obturator prosthesis.

Illuminant metameric effects on interbrand and intrabrand color differences of direct composite resins.

STATEMENT OF PROBLEM: Information on the illuminant metameric effects on the intrabrand and interbrand differences in color of direct composite resins is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effects of different illuminations on the color differences of the same or different brands of composite resins. MATERIAL AND METHODS: Sixty-four disks were prepared from 8 different direct dental composite resins of A3 shade, and, after polymerization and hydration for 48 hours, their color coordinates were measured in the Commission Internationale de I'Eclairage (CIE) L∗a∗b∗ color space with a portable colorimeter on a black and white background under D65 (daylight), F2 (cool white fluorescence), and A (incandescence) illuminations. Translucency parameters (TP) and fluorescence intensities (FI) of the brands were also measured to assist in the interpretation of brand behavior under the illuminations. The Kruskal-Wallis and Friedman nonparametric tests with post hoc multiple comparisons tests were applied to analyze the data for differences within and between brands under all illuminations (α=.05), while regression analysis was used to estimate the relationship between D65 and F2 or A illumination data. RESULTS: Statistical analysis showed significant differences among brands (P<.05) for all color coordinates under all illuminations, with a strong linear relationship between them (R2=0.72-0.97). Intrabrand differences were significantly different across brands (P<.05) and ranged from 0.06 to 3.1 across illuminations in ΔE∗ab units (0.05 to 2.4 in ΔΕ00 units). Interbrand differences were also significantly different (P<.05), with a range of 0.15 to 8.7 ΔE∗ab units or 0.14 to 5.7 ΔΕ00 units. CONCLUSIONS: Primary color coordinates of composite resins were affected by A or F2 illumination and were strongly associated with D65 values. Redder or yellower composite resins were affected more under A or F2 illumination. Intrabrand differences, although small, may contribute to clinical mismatches under A or F2 illuminations. Clinicians should be aware that certain brand pairs may present acceptable differences under D65 illumination but could become unacceptable under A or F2 illumination.

Quality of life in patients with soft palate resection: The relationship between reported functional prosthetic outcomes and the patient's psychological adjustment.

STATEMENT OF PROBLEM: Tumors of the soft palate and the adjacent tissues often create considerable soft palate defects that are challenging for the maxillofacial prosthodontist. Soft palate obturator prostheses can usually address functional and esthetic concerns; however, the effectiveness of the prosthetic rehabilitation in improving the patient's well-being and overall quality of life (QOL) has not been extensively researched. PURPOSE: The purpose of the present research was to evaluate the function of the prosthesis, to review the interrelation between sociodemographic, medical, and treatment (SMT) characteristics, QOL, and prosthesis functioning, and to analyze the role of the prosthesis in how the patient represents the illness and the psychological coping response. MATERIAL AND METHODS: Thirty-three patients who underwent resection of the soft palate and had been using a technically successful soft palate obturator prosthesis for at least 1 year were interviewed by means of 5 questionnaires: European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Core Questionnaire (QLQ-C30), Head and Neck Cancer Module (QLQ-HN35), Obturator Functioning Scale (OFS), Illness Perceptions Questionnaire (IPQ-R), and Mental Adjustment to Cancer Scale (MAC). Data analysis was performed at α=.01. RESULTS: The QOL (r=-0.53, P=.001), personal control (r=-0.53, P=.001), negative adjustment to cancer (r=0.47, P=.005), treatment control (r=-0.55, P=.001), consequences (r=0.62, P<.001), and emotional representations (r=0.30, P=.009) were significantly related to prosthesis functioning. Better QOL was significantly related to prosthesis functioning (P=.006), age (P=.001), sex (P=.011), and type of soft palate defect (P=.009). The most important predictors of favorable soft palate obturator functioning were age (P<.001) and type of soft palate defect (P=.01). CONCLUSIONS: A patient-perceived effective soft palate obturator prosthesis was a significant predictor for advanced QOL, better adjustment to illness and illness-related disabilities, as well as the overall coping response to cancer.

The effect of cooling procedures on monomer elution from heat-cured polymethyl methacrylate denture base materials

Abstract Objective To evaluate the amount of methyl methacrylate (MMA) released in water from heat-cured polymethyl methacrylate (PMMA) denture base materials subjected to different cooling procedures. Methodology Disk-shaped specimens (Ø:17 mm, h:2 mm) were fabricated from Paladon 65 (PA), ProBase Hot (PB), Stellon QC-20 (QC) and Vertex Rapid Simplified (VE) denture materials using five different cooling procedures (n=3/procedure): A) Bench-cooling for 10 min and then under running water for 15 min; B) Cooling in water-bath until room temperature; C) Cooling under running water for 15 min; D) Bench-cooling, and E) Bench-cooling for 30 min and under running water for 15 min. A, B, D, E procedures were proposed by the manufacturers, while the C was selected as the fastest one. Control specimens (n=3/material) were fabricated using a long polymerization cycle and bench-cooling. After deflasking, the specimens were ground, polished and stored in individual containers with 10 ml of distilled water for seven days (37oC). The amount of water-eluted MMA was measured per container using isocratic ultra-fast liquid chromatography (UFLC). Data were analyzed using Student's and Welch's t-test (α=0.05). Results MMA values below the lower quantification limit (LoQ=5.9 ppm) were registered in B, C, E (PA); E (PB) and B, D, E (QC) procedures, whereas values below the detection limit (LoD=1.96 ppm) were registered in A, D (PA); A, B, C, D (PB); C, D, E (VE) and in all specimens of the control group. A, B (VE) and A, C (QC) procedures yielded values ranging from 6.4 to 13.2 ppm with insignificant differences in material and procedure factors (p>0.05). Conclusions The cooling procedures may affect the monomer elution from denture base materials. The Ε procedure may be considered a universal cooling procedure compared to the ones proposed by the manufacturers, with the lowest residual monomer elution in water.

Removal of denture adhesives from PMMA and Polyamide denture base materials.

OBJECTIVE: Denture adhesives need complete removal due to their frequent replacement. Our study investigates the removal of denture adhesives from denture base materials, using different methods. METHODOLOGY: PMMA and Polyamide denture base materials were used to fabricate 120 samples (15×15×1.5mm). One side of the samples was left as processed and the other polished with a usual procedure, hydrated for 24 h, dried, and weighted. They received 0.2 g of three adhesive creams on their unpolished surface (Corega, Olivafix, Fittydent), pressed on polysulfide material, stored under 37°C and 95% rel. humidity for 1 h and 60 of them, following their separation from polysulfide base, brushed under running water, whereas the rest inserted in a cleanser bath (Fittydent Super) for 5 min. The samples were dried and inserted in the oven (37°C) for additional 10 min and weighted again. Roughness tests of denture materials and light microscopy of adhesives creams were also used to evaluate the materials. Time lapse images of spayed with water adhesives on PMMA base were also taken to evaluate the volumetric changes of adhesives. Weight data before and after adhesive removal, indicating the amount of remaining adhesive, were statistically analyzed using Welch's ANOVA and Games-Howell multiple comparisons tests at α=0.05 level of significance. RESULTS: Roughness of Polyamide was higher than PMMA and Fittydent showed greater volumetric changes than the others. Significant differences (p<0.05), were found between PMMA and Polyamide bases, between Olivafix and Fittydent adhesives, and between brushing and cleansing methods but only for PMMA-Olivafix combination. CONCLUSIONS: Adhesives showed a stronger adherence to PMMA surface, and Fittydent was the most difficult to be removed. Removal methods were not effective for all adhesives or denture base materials. These indicate that removal methods, adhesive type and denture base material are all playing a significant role in the removal of adhesives from denture surfaces.

In vitro validation of Digital Image Analysis Sequence (DIAS) for the assessment of the marginal fit of cement-retained implant-supported experimental crowns.

BACKGROUND: The replica technique with its modifications (negative replica) has been used for the assessment of marginal fit (MF). However, identification of the boundaries between prosthesis, cement, and abutment is challenging. The recently developed Digital Image Analysis Sequence (DIAS) addresses this limitation. Although DIAS is applicable, its reliability has not yet been proven. The purpose of this study was to verify the DIAS as an acceptable method for the quantitative assessment of MF at cemented crowns, by conducting statistical tests of agreement between different examiners. METHODS: One hundred fifty-one implant-supported experimental crowns were cemented. Equal negative replicas were produced from the assemblies. Each replica was sectioned in six parts, which were photographed under an optical microscope. From the 906 standardized digital photomicrographs (0.65 µm/pixel), 130 were randomly selected for analysis. DIAS included tracing the profile of the crown and the abutment and marking the margin definition points before cementation. Next, the traced and marked outlines were superimposed on each digital image, highlighting the components' boundaries and enabling MF measurements. One researcher ran the analysis twice and three others once, independently. Five groups of 130 measurements were formed. Intra- and interobserver reliability was evaluated with intraclass correlation coefficient (ICC). Agreement was estimated with the standard error of measurement (SEM), the smallest detectable change at the 95% confidence level (SDC95%), and the Bland and Altman method of limits of agreement (LoA). RESULTS: Measured MF ranged between 22.83 and 286.58 pixels. Both the intra- and interobserver reliability were excellent, ICC = 1 at 95% confidence level. The intra- and interobserver SEM and SDC95% were less than 1 and 3 pixels, respectively. The Bland-Altman analysis presented graphically high level of agreement between the mean measurement of the first observer and each of the three other observers' measurements. Differences between observers were normally distributed. In all three cases, the mean difference was less than 1 pixel and within ± 3 pixels LoA laid at least 95% of differences. T tests of the differences did not reveal any fixed bias (P > .05, not significant). CONCLUSION: The DIAS is an objective and reliable method able to detect and quantify MF at ranges observed in clinical practice.

Implementation and evaluation of an oral health education programme for caregivers in nursing homes.

AIM: The aim was the design, implementation, and evaluation of an oral health education program for nursing home caregivers. METHODS AND RESULTS: Fifty-five formal caregivers working in the three units of a nursing home were allocated to either a control (n = 27) or an intervention group (n = 28). A knowledge and attitudes questionnaire about oral health was developed and completed by the caregivers. Then, an education program about oral heath in older people was applied to the intervention group, and the completion of the questionnaire was repeated by both the intervention and control groups. Two months after the intervention, the questionnaire was completed again by the intervention group. Within groups analyses revealed a statistically significant increase in knowledge and attitudes only in the intervention group after the implementation of the education program (P < .001). Between-group analyses showed that the total knowledge and attitudes score in the intervention group were statistically significantly higher than in the control group (P < .001 and P = .02, respectively). In the intervention group, knowledge and attitudes were maintained in the measurement recorded 2 months later (P = .11 and P = .21, respectively). CONCLUSION: The education program was effective in improving the caregivers' knowledge and attitudes toward nursing home residents' oral health and maintaining them 2 months after implementation.

Removal of denture adhesives from PMMA and Polyamide denture base materials

Abstract Denture adhesives need complete removal due to their frequent replacement. Objective Our study investigates the removal of denture adhesives from denture base materials, using different methods. Methodology PMMA and Polyamide denture base materials were used to fabricate 120 samples (15×15×1.5mm). One side of the samples was left as processed and the other polished with a usual procedure, hydrated for 24 h, dried, and weighted. They received 0.2 g of three adhesive creams on their unpolished surface (Corega, Olivafix, Fittydent), pressed on polysulfide material, stored under 37°C and 95% rel. humidity for 1 h and 60 of them, following their separation from polysulfide base, brushed under running water, whereas the rest inserted in a cleanser bath (Fittydent Super) for 5 min. The samples were dried and inserted in the oven (37°C) for additional 10 min and weighted again. Roughness tests of denture materials and light microscopy of adhesives creams were also used to evaluate the materials. Time lapse images of spayed with water adhesives on PMMA base were also taken to evaluate the volumetric changes of adhesives. Weight data before and after adhesive removal, indicating the amount of remaining adhesive, were statistically analyzed using Welch's ANOVA and Games-Howell multiple comparisons tests at α=0.05 level of significance. Results Roughness of Polyamide was higher than PMMA and Fittydent showed greater volumetric changes than the others. Significant differences (p<0.05), were found between PMMA and Polyamide bases, between Olivafix and Fittydent adhesives, and between brushing and cleansing methods but only for PMMA-Olivafix combination. Conclusions Adhesives showed a stronger adherence to PMMA surface, and Fittydent was the most difficult to be removed. Removal methods were not effective for all adhesives or denture base materials. These indicate that removal methods, adhesive type and denture base material are all playing a significant role in the removal of adhesives from denture surfaces.

Intra- and inter-brand color differences of denture teeth under different illuminations.

Debonding, staining and wear are usually the reasons for denture teeth replacement by new ones from same or different brands. Objective This study investigates the possible differences in color of denture teeth of the same or different brands under different illuminations, since their metameric behavior in color under specific illumination may become unacceptable. Methodology For the purpose of this study, 10 denture teeth (#11), shade A3, of 4 different brands were selected (Creopal/KlemaDental Pro, Executive/DeguDent, Cosmo HXL/DeguDent, Ivostar/Ivoclar-Vivadent). Teeth stabilized in white silicone mold and the CIELAB color coordinates of their labial surface under 3 different illumination lights (D65, F2, A) were recorded, using a portable colorimeter (FRU/WR-18, Wave Inc). ΔE*ab values of all possible pairs of teeth of the same brand (n=45) or pair combinations of different brands (n=100) under each illumination light, in a dry and wet state were calculated. Data were analyzed statistically using 3-way ANOVA, Friedman's and Wilcoxon's tests at a significance level of α=0.05. Results The results showed that brand type affected significantly L*, a* and b* coordinates (p<0.0001), illumination a* and b* coordinates (p<0.0001), but none of them was affected by the hydration state of teeth (p>0.05). Intra-brand color differences ranged between 0.21-0.78ΔΕ* units with significant differences among brands (p<0.0001), among illumination lights (p<0.0001) and between hydration states (p=0.0001). Inter-brand differences ranged between 2.29-6.29ΔΕ* units with significant differences among pairs of brands (p<0.0001), illumination lights (p<0.0001) and hydration states (p<0.0001). Conclusions Differences were found between and within brands under D65 illumination which increased under F2 or A illumination affected by brand type and hydration status. Executive was the most stable brand than the others under different illuminations or wet states and for this reason its difference from other brands is the lowest. In clinical practice, there should be no blending of teeth of different brands but if we must, we should select those that are more stable under different illuminations.

Color changes of polyetheretherketone (PEEK) and polyoxymethelene (POM) denture resins on single and combined staining/cleansing action by CIELab and CIEDE2000 formulas.

PURPOSE: The purpose of study was to investigate the long-term effect of staining and/or cleansing solutions on the color stability of two non-metal removable partial denture materials. METHODS: One hundred disks (25×3mm) of polyoxymethylene (POM) and polyetheretherketone (PEEK) were immersed in water, wine, coffee, cleanser and combo bath, simulating normal daily use. Color parameters in the CIELAB system was measured every 30 cycles up to 240 using a contact colorimeter and color differences estimated using ΔEab and ΔE00 formulas. Two-way repeated measures ANOVAs and regression analyses were performed at α=0.05. RESULTS: Regression analysis indicated a strong R2 between color changes and number of cycles, for both materials. Tests of within-subjects effects for the ΔEab revealed significant differences among cycles and between the materials in the wine and coffee baths (p<0.001). Significant materialXcycles interactions were also recorded with all staining baths. ΔE00 values were lower than ΔEab up to 63.6%. Tests within and between-subjects effects for the ΔE00 gave similar but not the same with ΔEab results. CONCLUSIONS: ΔE00 found to correlate well with ΔEab. Long term exposure of both materials showed a progressive discoloration in all except control baths. POM discolored more than PEEK in coffee, and combo baths but not in cleanser. Discoloration was smaller in combo bath (where a cleanser was also used) indicating the effectiveness of a cleanser to prevent long term discoloration of both materials.

Intra- and inter-brand color differences of denture teeth under different illuminations

Abstract Debonding, staining and wear are usually the reasons for denture teeth replacement by new ones from same or different brands. Objective This study investigates the possible differences in color of denture teeth of the same or different brands under different illuminations, since their metameric behavior in color under specific illumination may become unacceptable. Methodology For the purpose of this study, 10 denture teeth (#11), shade A3, of 4 different brands were selected (Creopal/KlemaDental Pro, Executive/DeguDent, Cosmo HXL/DeguDent, Ivostar/Ivoclar-Vivadent). Teeth stabilized in white silicone mold and the CIELAB color coordinates of their labial surface under 3 different illumination lights (D65, F2, A) were recorded, using a portable colorimeter (FRU/WR-18, Wave Inc). ΔE*ab values of all possible pairs of teeth of the same brand (n=45) or pair combinations of different brands (n=100) under each illumination light, in a dry and wet state were calculated. Data were analyzed statistically using 3-way ANOVA, Friedman's and Wilcoxon's tests at a significance level of α=0.05. Results The results showed that brand type affected significantly L*, a* and b* coordinates (p<0.0001), illumination a* and b* coordinates (p<0.0001), but none of them was affected by the hydration state of teeth (p>0.05). Intra-brand color differences ranged between 0.21-0.78ΔΕ* units with significant differences among brands (p<0.0001), among illumination lights (p<0.0001) and between hydration states (p=0.0001). Inter-brand differences ranged between 2.29-6.29ΔΕ* units with significant differences among pairs of brands (p<0.0001), illumination lights (p<0.0001) and hydration states (p<0.0001). Conclusions Differences were found between and within brands under D65 illumination which increased under F2 or A illumination affected by brand type and hydration status. Executive was the most stable brand than the others under different illuminations or wet states and for this reason its difference from other brands is the lowest. In clinical practice, there should be no blending of teeth of different brands but if we must, we should select those that are more stable under different illuminations

Use of Different Cleaning Methods for Removable Orthodontic Appliances: A Questionnaire Study.

OBJECTIVES: The aim of the present study is to assess the means and methods being suggested by Greek orthodontists to their patients for cleaning their removable devices. MATERIALS AND METHODS: A questionnaire survey was conducted among a total of 418 Greek orthodontists found from the registry of orthodontists in Greece. The clinicians were asked about the means and methods of daily cleaning they usually advise their patients for removable appliances. Furthermore, the questionnaire included questions related to possible complications of these devices and data about the use and type of applied devices. RESULTS: From 418 Greek orthodontists, 279 filled the questionnaire and participated in this study. All but one reported that they use removable appliances in their practice for patients of almost any age. All orthodontists recommend routine manual toothbrushing, but the majority of them also suggest at the same time other oral hygiene aids complementary to brushing, such as immersion in denture cleaners (70.06%), in disinfecting solutions (12.73%) and in vinegar (36.94%). Some 15% of all the practitioners advise the use of ultrasonic instruments for cleaning removable orthodontic appliances. At last, clinicians have faced complications from the use of removable devices in the oral cavity at a statistically significant percentage. The most usual is trauma of the mucosa, mycosis and hyperplasia. CONCLUSION: Greek orthodontists use removable orthodontic appliances, active or passive, in their practice. Brushing with a toothbrush and the use of cleaning products for removable prostheses are the preferred methods for cleaning removable orthodontic appliances regardless of the orthodontic specialty programme they had graduated from.

Evaluation of a Realistic Cleansing Protocol for Preventing Discoloration of Denture Resins.

PURPOSE: To evaluate the efficacy of a realistic staining/cleansing protocol for long-term prevention of discoloration of denture base resins. MATERIALS AND METHODS: Sixty discs (20 × 2.5 mm) of auto- and heat-polymerizing denture acrylic resins were fabricated following manufacturer's instructions, polished on one side and stored in water (37°C) for 24 hours before they were assigned randomly into 6 groups (3 for each material, n = 10) to receive 220 cycles of three immersion protocols. Group A was immersed in the following baths: (1) filtered coffee at 45°C for 2 minutes, (2) tap water at 24°C for 20 seconds, (3) as bath 1, (4) as bath 2, (5) Corega Extradent cleansing solution at 45°C for 3 minutes, and (6) water at 24°C for 20 seconds. Group B was immersed in the four first baths of group A (without cleansing action) and group C in bath 1 for the cumulative action of 20 cycles (80 minutes in 45°C coffee) and bath 2 for 40 seconds. A noncontact optical interferometric profilometer was used for qualitative evaluation of the specimens and a contact colorimeter to estimate color change values (ΔΕ*ab) at baseline and every 20 cycles in the baths for a total of 220 cycles. Data were statistically analyzed using a 2-way-repeated measures ANOVA with Bonferoni multiple comparisons and trend analysis at α = 0.05 level of significance. RESULTS: Data indicated changes in color from 1.7 to 14.2 ΔΕ*ab units. The highest values were related to the number of cycles and group B immersion protocol. Significant differences were found among immersion protocols (p < 0.001) and immersion cycles (p < 0.001) with a significant interaction between protocols and cycles (p < 0.001) but not between denture resins (p = 0.991). CONCLUSION: The evaluated protocol A was found effective in preventing color changes in both denture resins even after a long period of action. Protocol C had a much lower staining effect on both resins than protocol B and behaved similarly to protocol A until 140 to 160 cycles. Therefore, it is probably not appropriate for use in short-term color stability experiments.

Perceptibility and acceptability thresholds of simulated facial skin color differences.

PURPOSE: This study investigates the perceptibility and acceptability thresholds (PT, AT) of observers for L*, a* and b* facial skin differences, very important for the fabrication of a maxillofacial prosthesis. METHODS: One image (10×13.3cm/300dpi), simulating standard facial skin color, and 27 smaller images (4.9×6.0cm/300dpi), simulating shades with different RGB values from the standard were made, using Adobe-Photoshop CS3. The RGB values, were based on 9 stepped increases in L*, a* and b*. Images were shown in the middle of a computer screen with the standard image in the background. 90 persons with normal color vision and optical acuity were selected and instructed to evaluate 81 (27×3) randomly shown images for a perceptible or an acceptable (48h later) mismatch, between central and background image. Using best fitting regression curves 50 % PT and 50 % AT for all parameters were estimated along with their 95 %CI. RESULTS: Observers' reliability found high (0.807-0.945) while the cubic and exponential were the best fitted curves to the data. Overall 50 % ATs were smaller than 50 % PTs (p<0.01) and overall ΔL* parameter showed the lowest thresholds (0.119PT/0.864AT), significantly smaller (p<0.05) than Δa* (0.993PT/2.037AT), Δb* (1.147PT/2.517AT), and ΔEab*(1.497PT/1.808AT). No differences were found between sex or age groups in 50 % ATs for Δa* and Δb* parameters, but 50 % PT for Δa* was smaller in females and in older people with the opposite for Δb*. CONCLUSIONS: Changes in L* were more perceptible and less acceptable than changes in a* and b*. For this reason ΔL* parameter needs attention equally to ΔE*ab when fabricating a facial prosthesis.

Long-term microwaving of denture base materials: effects on dimensional, color and translucency stability.

INTRODUCTION: While the combined effect of microwave irradiation with cleansing solutions on denture base materials has been investigated, the effects of only using microwave irradiation and, more importantly, in a long-term basis, was not studied yet. OBJECTIVE: The purpose of this study was to evaluate the effect of a long-term repeated microwaving on the dimensional, color and translucency stability of acrylic and polyamide denture base materials. MATERIAL AND METHODS: Thirty two specimens (32 mm x 10 mm x 2.5 mm) from polyamide (Valplast) and PMMA (Vertex Rapid Simplified) denture base materials were made. Eight specimens from each material were immersed in distilled water (control) and 8 were subjected to microwave exposure at 450 W for 3 minutes for a period simulating 224 days of daily disinfection. Linear dimension, color change (ΔE*) and translucency parameter (TP) were measured at baseline and after certain intervals up to 224 cycles of immersion, using a digital calliper and a portable colorimeter. The results were analysed using two-way repeated measures ANOVA to estimate possible differences among predetermined cycles and material type. Regression analysis was also performed to estimate the trend of changes with time. Statistical evaluations performed at a significance level of 5%. RESULTS: Data analysis showed significant changes in length at baseline with an increasing number of cycles (p<0.05) and a significant interaction of cycle-material (p<0.001). The ΔΕ* parameter was significantly higher with a higher number of cycles (p<0.001), but it did not vary between materials (p>0.05). TP decreased similarly in both materials following microwave action but in a significantly higher level for Valplast (p<0.001). CONCLUSIONS: The results indicated that long-term repeated microwaving affects linear dimensional, color and translucency changes of both materials. Differences between PMMA and polyamide material were noted only in dimension and translucency changes.

Evaluation of the frequency and temperature dependence of the dynamic mechanical properties of acetal resins.

The purpose of this study was to evaluate and compare the dynamic mechanical properties of two acetal resins (different colored samples of the same resin), an autopolymerized reline resin, and a heat-polymerized denture base resin. Measurements were obtained in two conditions, the frequency- and temperature-dependent conditions, using a dynamic viscoelastometer. The acetal resins exhibited lower loss tangent values than the autopolymerized reline resin and heat-polymerized denture base resin. With respect to temperature dependence, all of the materials displayed stable viscoelastic properties in the temperature range found in the oral environment. The acetal resin had both a glass transition temperature and a melting point, whereas the autopolymerized reline resin and heat-polymerized denture base resin had only glass transition temperatures. The results of this study suggest that acetal resin displays elastic properties when compared with the other 2 materials.