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

Removal of denture adhesives from PMMA and Polyamide denture base materials

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

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

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

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 (∆H) and color differences (∆E) 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 (∆E) 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

Prosthetic Intervention for the Management of Low Attached Palatopharyngeal Flaps - A Clinical Report

U ovom kliničkom prikazu opisuje se zakašnjela protetska rehabilitacija odraslog pacijenta s nazalnim i neadekvatnim govorom zbog rascjepa nepca i niskog hvatišta faringealnih režnjeva. Čini se da je kod takvih pacijenata izrada opturatora terapija izbora nakon što nisu mogući, odbijeni su ili su kontraindicirani daljnji kirurški zahvati.This clinical report describes a delayed prosthetic management of an adult cleft palate patient, in order to treat hypernasality and inadequate speech pattern associated with the employment of low attached pharyngeal flap. Obturator construction seems to be the treatment of choice for this group of cleft palate patients when further pharyngeal surgery is contraindicated or denied

A Fixed Telescopic Prosthesis Designed to Retrieve and Convert to Fixed-Removable Combination Case: A Clinical Report

U ovom kliničkom prikazu opisan je, kod parodontno ugroženog pacijenta s nekontroliranim dijabetesom, fiksni maksilarni most od estetskoga kompozitnog materijala s metalnom bazom učvršćen na frezanim metalnim kapicama. Uključena su i mjesta za okluzalne upirače na ključnim mjestima ako se izgube lateralni zubi kako bi se most mogao prenamijeniti u kombinirani rad s mobilnom protezom. Nedostatak zuba u mandibuli nadomješten je klasičnim fiksnim metalkeramičkim mostom.This clinical report describes a fixed maxillary telescopic dental prosthesis (FTDP) employing milled base metal copings and a metal superstructure veneered with composite resin, for the restoration in a periodontally compromised patient with uncontrolled diabetes. The telescopic prosthesis framework design incorporated occlusal rest seats in key positions along the arch in case of future posterior tooth loss, in order to be converted to fixed - removable combination prosthesis. The mandible was restored with a conventional fixed ceramo-metal dental prosthesis

The Effect of Microwave Disinfection on Denture Base Polymers, Liners and Teeth: A Basic Overview

Svrha ovoga članka bila je sažeti trenutačno znanje o učincima mikrovalne dezinfekcije na svojstva materijala za izradu proteza. Kontrola križne infekcije u dentalnoj medicini itekako je važna u svakodnevnoj kliničkoj praksi jer su u porastu razne infektivne bolesti poput hepatitisa B i C te AIDS-a (side), a metode dezinfekcije su mnogobrojne. Najraširenija u svakodnevnoj praksi jest ona kemijska, premda istraživanja upućuju na to da se tako mijenjaju fizikalna i mehanička svojstva akrilatnih smola te omogućuje rast i proliferacija određenih bakterija. A mikrovalna metoda pokazala se kao jednostavna za uporabu, jeftina je i u postupku se ne upotrebljavaju kemikalije. Pitanje koje se postavilo glasi: utječe li podvrgavanje mikrovalovima na svojstva materijala od kojih se izrađuju proteze. Mikrovalovi različito djeluju na bazu proteze, ljepilo i zube. Istraživanja su pokazala da je mikrovalna dezinfekcija sigurna alternativa za bazu proteze i podložnu masu – u usporedbi s kemijskom metodom – ako se postupak obavlja u suhom okružju, ali mogla bi uzrokovati klinički veće dimenzijske promjene kad bi se iradijacija obavljala u vlažnim uvjetima. Nema ni klinički značajnih učinaka slabljenja savojnih svojstava, zatezne čvrstoće i tvrdoće akrilatne smole proteze, ni integriteta sredstva za vezivanje i njegove čvrstoće na savijanje, poroznosti i tvrdoće. Učinci dezinfekcije mikrovalovima na čvrstoću zuba u protezi i na vezu zubi – proteza i dalje su sporni, pa još nema definitivnog zaključka.The aim of this paper was to overview the current scientific knowledge concerning the effect of microwave disinfection on denture related material properties. Cross-infection control in dentistry is a significant issue in everyday clinical practice due to the recent increase in some infectious diseases such as hepatitis B, C and AIDS and therefore numerous methods of disinfection have been used. The most widespread method of disinfection used in everyday practice is chemical, however, studies have suggested that chemical disinfectants alter the physical and mechanical properties of the acrylic resins and enable the growth and proliferation of certain bacteria. Therefore, microwaves were introduced as an easy to use-and-access, low cost, chemical free alternative. The question that arose was if and in what way the microwave irradiation affected the denture related material properties. Microwaving affects the denture resin bases, liners and teeth in different ways. The results showed that microwave disinfection could be a safe alternative for the disinfection of denture bases and liners compared to the chemical one, when the procedure is carried out in dry conditions, but could possibly cause dimensional changes of clinical significance on them when the irradiation takes place in wet environment. It also seems to have no detrimental effects of clinical importance on the flexural properties, impact strength and hardness of denture resins and the bond, flexural strength, porosity and hardness of denture liners. The effects of microwave disinfection on the hardness of denture teeth and teeth/denture bond strength are still controversial and no safe conclusions can be drawn

Flexible Removable Partial Denture Prosthesis: A Survey of Dentists’ Attitudes and Knowledge in Greece and Croatia

Svrha: U ovom su se istraživanju s pomoću upitnika željeli istražiti znanje, stajališta i moguće razlike u korištenju savitljivih pomičnih djelomičnih proteza (PDP) među doktorima dentalne medicine (DDM) u Grčkoj i Hrvatskoj. Materijali i metode: Upitnik od 16 pitanja sastavljen je izvorno na engleskome jeziku te je preveden na grčki i hrvatski dvosmjernim prevođenjem. Nakon toga testirani su smisao, točnost, jasnoća i homogenost prijevoda upitnika, a u tome je sudjelovalo nekoliko grčkih i hrvatskih doktora dentalne medicine koji govore engleski gotovo kao materinski jezik. Nakon potrebnih ispravaka upitnici su korišteni u dvjema online anketama koje su, zajedno s informacijom o anketi i upitom o pristanku ispitanika na anketu, poslane na e-adrese gotovo četiri tisuće doktora dentalne medicine u svakoj državi. Prikupljeni podatci analizirani su Hi-kvadrat testom uz razinu značajnosti od a = 0,05. Rezultati: U istraživanju je sudjelovalo 378 DDM-a iz Grčke i 304 iz Hrvatske. Njih 137 (36,2 %) iz Grčke i 56 (18,4 %) iz Hrvatske opskrbljivali su svoje pacijente savitljivim PDP-ima. Statistička analiza provedena među svim DDM-ima koji izrađuju savitljive proteze nije otkrila značajnu razliku među spolovima (P > 0,05), ali jest značajnu razliku među dobnim skupinama (P 0,05). Zaključak: Istraživanje je upozorilo na razlike među zemljama u postotcima DDM-a koji upotrebljavaju, odabiru i svojim pacijentima omogućuju izradu savitljivih PDP-a. Dob DDM-a, godine rada i instruiranost bili su povezani s opskrbom pacijenata savitljivim protezama, a udobnost, estetika i cijena bili su razlozi za odluku o uporabi savitljivih PDP-a. Kliničke implikacije: Premda DDM-i tijekom školovanja nisu educirani o savitljivim PDP-ima, njih gotovo trećina svojim pacijentima predlaže takvu vrstu terapije. Kako bi ovi protetski radovi bili dugoročno uspješni, potrebno je kliničko obrazovanje, više iskustva i svakako više istraživanja u ovom području.Purpose: The aim of this study was to investigate through a questionnaire the knowledge, attitudes and possible differences in the use of flexible RPDPs among dentists in Greece and Croatia. Material and Methods: A questionnaire of 16 questions was originally created in English, translated into Greek and Croatian language following a two way translation and tested for apprehension, precision, clarity and homogeneity by a number of native English speaking Greek and Croatian dentists. Following the necessary corrections, the questionnaires replicated in two online surveys and their addresses with an informed consent were sent by emails to nearly 4000 dentists in each country to participate. Collected data were analyzed by chi-square tests at a= .05 level of significance. Results: 378 dentists from Greece and 304 from Croatia participated in the study. 137(36.2%) dentists from Greece and 56(18.4%) from Croatia provided flexible RPDPs to their patients. Statistical analysis for all providers indicated no significant difference between genders (P>.05), significant differences between age groups (P.05). Conclusion: The survey indicated differences between the two countries in the percentages of dentists using, selecting and providing RPDPs for their patients. Practitioners’ age, years in practice and instruction were associated with the provision of the prostheses, while comfort, esthetics and cost were the reasons for deciding to use the flexible RPDPs. Conclusion: Although dentists are not educated in their schools about flexible RPDPs, almost a third of them offer this treatment to their patients. Long term success of these devices depends on clinical education, more experience and definitely more research

Bone metabolism in Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is a rare disease of not well-defined etiology that involves immune cell activation and frequently affects the skeleton. Bone involvement in LCH usually presents in the form of osteolytic lesions along with low bone mineral density. Various molecules involved in bone metabolism are implicated in the pathogenesis of LCH or may be affected during the course of the disease, including interleukins (ILs), tumor necrosis factor α, receptor activator of NF-κB (RANK) and its soluble ligand RANKL, osteoprotegerin (OPG), periostin and sclerostin. Among them IL-17A, periostin and RANKL have been proposed as potential serum biomarkers for LCH, particularly as the interaction between RANK, RANKL and OPG not only regulates bone homeostasis through its effects on the osteoclasts but also affects the activation and survival of immune cells. Significant changes in circulating and lesional RANKL levels have been observed in LCH patients irrespective of bone involvement. Standard LCH management includes local or systematic administration of corticosteroids and chemotherapy. Given the implication of RANK, RANKL and OPG in the pathogenesis of the disease and the osteolytic nature of bone lesions, agents aiming at inhibiting the RANKL pathway and/or osteoclastic activation, such as bisphosphonates and denosumab, may have a role in the therapeutic approach of LCH although further clinical investigation is warranted