The dimensional stability of dental impression materials following immersion in disinfecting solutions

Electrolysed oxidising water as a multi-purpose biocide in dental healthcare-A scoping review

OBJECTIVES

The objective of this scoping review was to map evidence of electrolysed oxidising water (EOW) as a biocide for dental applications of relevance to older people and identify research gaps.

BACKGROUND

EOW is an emerging, "green," and cost-effective biocide. There are no reviews on the landscape of EOW research as either an antiseptic or disinfectant in dental healthcare or its suitability for the oral healthcare of older people.

MATERIALS AND METHODS

The review follows the PRISMA Extension for Scoping Reviews (PRISMA-ScR) guidelines. Database searches (Google Scholar, PubMed, Web of Science, Ovid, Scopus and Science Direct) were undertaken using MESH terms and Boolean operators with no date restrictions, to identify full-text, original reports published in English-language peer-reviewed journals.

RESULTS

The search yielded 114 papers that met the inclusion/exclusion criteria. Dental applications of EOW include its use as an endodontic irrigant (39%); mouth rinse/surgical irrigant (21%); disinfectant for dental unit water lines (19%) and dental biomaterials (17%); and for antimicrobial efficacy, effects on oral tissues and on dental material properties. Most studies (83%) evaluated a single EOW formulation (acidic, moderately acidic or neutral) that was either generated at 'point-of-use' (POU; 72%), bottled ('ready-to-use', RTU; 24%) or from unspecified (3%) sources. Six reports evaluated storage-related parameters and 25 evaluated clinical applications; 89 were in vitro studies and one investigated the cost-effectiveness of POU EOW.

CONCLUSIONS

Neutral-pH, EOW is effective as an antimicrobial agent without deleterious effects on oral tissues. However, research on the impact of storage conditions, anti-Candida biofilm efficacy and mechanism of action against yeasts, long-term effects on denture materials and cost-effectiveness is required to establish the suitability of EOW as a multipurpose biocide for dental healthcare, including infection-control requirements relating to older people.

Evaluation of the Efficacy of Novel Self Disinfectant Solution in Irreversible Hydrocolloid Impression Material - An Experimental Study

Background

Irreversible hydrocolloid materials are widely used for both diagnostic and definitive impression procedures. Impressions can be disinfected by immersion or spraying in any compatible disinfectant. Disinfectants should not adversely affect the dimensional stability of the impression and physical properties of impression material and subsequent dental cast.

Objective

The study aims to evaluate the efficacy of a hypochlorous disinfectant solution mixed with irreversible hydrocolloid on setting time, antibacterial efficacy, and dimensional stability.

Methodology

Three groups were made with one control group and three alginate impression was made for each participants in the maxillary arch with 24-hours intervals between one another using the same brand of commercially available chromatic alginate. The working and setting time were noted. Bacterial swabs were collected using a dry sterile cotton swab in the mid palatal region. Dental casts were made using type III gypsum.

Result

The working and setting time had significant differences whereas the dimension among the cast has no significant difference. Microbial growth analysis had distinct differences among the groups.

Conclusion

The self disinfection method using a pioneer solution of hypochlorous HOCl (100 ppm) to mix the alginate impression material rather than the water with the same powder-liquid ratio prescribed by the manufacturer had the same dimensional stability with improved antimicrobial action.

Disinfection efficacy of sodium hypochlorite and glutaraldehyde and their effects on the dimensional stability and surface properties of dental impressions: a systematic review

Objective

To systematically evaluate the disinfection efficacy of the two most frequently used disinfectants, sodium hypochlorite and glutaraldehyde, and their effects on the surface properties of four different dental impression materials.

Methods

A systematic literature search was performed in four databases until May 1st, 2022 to select the studies which evaluated disinfection efficacy of disinfectants or surface properties of dental impressions after chemical disinfection.

Main results

A total of 50 studies were included through electronic database searches. Of these studies, 13 studies evaluated disinfection efficacy of two disinfectants, and 39 studies evaluated their effects on the surface properties of dental impressions. A 10-minute disinfection with 0.5-1% sodium hypochlorite or 2% glutaraldehyde was effective to inactivate oral flora and common oral pathogenic bacteria. With regard to surface properties, chemical disinfection within 30 min could not alter the dimensional stability, detail reproduction and wettability of alginate and polyether impressions. However, the wettability of addition silicone impressions and the dimensional stability of condensation silicone impressions were adversely affected after chemical disinfection, while other surface properties of these two dental impressions were out of significant influence.

Conclusions

Alginate impressions are strongly recommended to be disinfected with 0.5% sodium hypochlorite using spray disinfection method for 10 min. Meanwhile, elastomeric impressions are strongly recommended to be disinfected with 0.5% sodium hypochlorite or 2% glutaraldehyde using immersion disinfection method for 10 min, however, polyether impression should be disinfected with 2% glutaraldehyde.

Effects of Various Disinfection Methods on the Material Properties of Silicone Dental Impressions of Different Types and Viscosities

There is an ongoing search for novel disinfection techniques that are not only effective, cheap, and convenient, but that also do not have adverse effects on the properties of dental impressions. We compared the effects of various methods (UVC, gaseous ozone, commercial solution, and spray) on the dimensional change, tensile strength, and hardness of silicone impressions. Moreover, as a secondary aim, we performed a statistical comparison of the properties of nondisinfected addition (Panasil Putty Soft, Panasil monophase Medium, Panasil initial contact Light) and condensation silicones (Zetaplus Putty and Oranwash L), as well as a comparison of materials of various viscosities (putty, medium-bodied, and light-bodied). Our results revealed that addition silicones had higher dimensional stability, tensile strength, and Shore A hardness compared to condensation silicones. Both traditional (immersion and spraying) and alternative methods of disinfection (UVC and ozone) had no significant impact on the tensile properties and dimensional stability of the studied silicones; however, they significantly affected the hardness, particularly of Oranwash L. Our study demonstrated that, similarly to standard liquid disinfectants, both UVC and ozone do not strongly affect the material properties of most silicones. However, before recommendation, their usefulness for each individual material should be thoroughly evaluated.

Dimensional changes of commercial and novel polyvinyl siloxane impression materials following sodium hypochlorite disinfection

BACKGROUND

Dental impressions are used to record anatomy of teeth and surrounding oral structures. Impression materials become contaminated with saliva and blood requiring disinfection, which may have negative impact on dimensional stability of materials.

OBJECTIVE

Comparatively evaluate linear dimensional changes of synthesized Tetra-functional (dimethylsilyl) orthosilicate (TFDMOS) containing Polyvinylsiloxane (PVS) impressions following sodium hypochlorite disinfection.

METHODS

Percentage dimensional changes of three commercial PVS (Elite HD Monophase, Extrude and Aquasil Ultra Monophase) and five experimental PVS impression materials were measured. Experimental material contained novel cross-linking agent (TFDMOS) and a non-ionic surfactant (Rhodasurf CET-2) that is Exp-A (without TFDMOS), Exp-B (with TFDMOS), Exp-C (TFDMOS+ 2% Rhodasurf CET-2), Exp-D (TFDMOS+ 2.5% Rhodasurf CET-2) Exp-E (TFDMOS+ 3% Rhodasurf CET-2). Samples were made using rectangular stainless-steel molds (40 × 10 × 3 mm3) and linear dimensional changes were measured using a calibrated travelling microscope at 10× magnification after immersion in distilled water (D.W) and 1% Sodium Hypochlorite solution at two different time intervals i.e., 30 min and 24 h.

RESULTS

Samples immersed in 1% NaOCl showed significant (p < 0.05) dimensional changes after 30 min of immersion. Exp-E showed significantly greater dimensional changes than their control (Exp-A and Exp-B). In distilled water, there were no significant difference among the tested materials. Aquasil exhibited highest expansion (0.06%) in both solutions. At 24 h, among the commercial materials, Extrude had the greatest expansion followed by Aquasil and Elite in DW while Aquasil showed the greatest expansion followed by Extrude and Elite in NaOCl.

CONCLUSION

Experimental PVS had linear dimensional changes within the ISO 4823; 2015 recommended range. However, extended immersion can negatively affect the linear dimensions.

Evaluation of the Trueness of Digital Implant Impressions According to the Implant Scan Body Orientation and Scanning Method

This study investigated the trueness of a digital implant impression according to the orientation of the implant scan body (ISB) and the scanning method. With the flat surface of the ISB facing either the buccal or proximal direction, the ISB was scanned using one tabletop scanner (T500) and three types of intraoral scanner (TRIOS 3, CS3600, and i500). The effects of differences in the scanning method and ISB orientation were assessed. Postalignment data were subsequently obtained with the abutments generated using a digital library, and superimposed with reference data using a best-fit algorithm, followed by root-mean-square error (RMSE) analysis. The RMSE was lower in the buccal groups (28.15 ± 8.87 μm, mean ± SD) than in the proximal groups (31.94 ± 8.95 μm, p = 0.031), and lower in the full-scan groups (27.92 ± 10.80 μm) than in the partial-scan groups (32.16 ± 6.35 μm, p = 0.016). When using the tabletop scanner, the trueness was higher when the ISB was connected buccally (14.34 ± 0.89 μm) than when it was connected proximally (29.35 ± 1.15 μm, p < 0.001). From the findings of this study it can be concluded that the operator should connect the ISB so that its flat surface faces the buccal direction, and attempt to scan all areas. Additionally, it is advantageous to connect an ISB buccally when using a tabletop scanner.

The effect of disinfectants on the accuracy, quality and surface structure of impression materials and gypsum casts: A comparative study using light microscopy, scanning electron microscopy and micro computed tomography

The aim of this study was to compare the effect of several commercially available disinfectants on the accuracy of various types of impression materials and their compatibility with gypsum including surface quality and structure evaluation. Four alginate and three elastomeric impression materials in combination with disinfectants Aseptoprint Liquid, Zeta 7 solution, Silosept and Dentaclean Form were tested. The dimensional changes, detail reproduction, the compatibility with gypsum and surface/subsurface morphology were evaluated using light microscopy, scanning electron microscopy and micro computed tomography. Two alginate materials disinfected in Dentaclean Form exhibited the most significant differences (p<0.0001). The loss of detail on some alginate impressions in combination with this disinfectant including deterioration and change of morphology of gypsum surfaces was observed. Porosity in subsurface area and exposed large particles were detected. It was confirmed that the desired properties of impressions may be negatively affected in combination with some disinfectants.

Comparative evaluation of the effect of electrolyzed oxidizing water on surface detail reproduction, dimensional stability and Surface texture of poly vinyl siloxane impressions

Aim:

The aim of this in vitro study was to comparatively evaluate the effect of chemical disinfectants on the surface detail reproduction, dimensional stability and surface texture of polyvinyl siloxane (PVS) impressions.

Materials and Methods:

The impressions were then divided into five groups (fifteen samples per group) and subjected to a ten minutes immersion with 2% glutaraldehyde (Group I), 1% sodium hypochlorite (Group II), freshly prepared electrolyzed oxidizing water (EOW) with different pH values - acidic (Group III), alkali (Group IV) and neutral (Group V). The samples were examined pre and post-immersion under visual observation for surface detail reproduction, travelling microscope for measurement of dimensional stability and surface profilometer (3D) for evaluation of surface texture. A standardized master die was fabricated and seventy-five PVS test samples were made. The samples were subjected to immersion disinfection and studied for surface detail reproduction, dimensional stability and surface texture. Post-hoc test, paired t test and ANOVA were used to analyze dimensional stability statistically both within and between the test groups.

Results:

The surface detail reproduction was satisfactory with both pre and post-immersion test samples. A statistically significant dimensional change was observed post-immersion in Groups II, III and V test samples and a statistically insignificant dimensional change was observed in Groups I and IV test samples. There was a negligible change in surface texture post-immersion in Groups I, III, IV and V test samples with a slight increase in surface roughness post-immersion in Group II samples.

Conclusion:

In this study, all the test disinfectants produced satisfactory surface detail reproduction on Polyvinyl siloxane impressions. 2% glutaraldehyde and electrolyzed oxidizing water (alkali) have resulted in statistically insignificant dimensional change, while 1% sodium hypochlorite, electrolyzed oxidizing water (acidic) and electrolyzed oxidizing water (neutral) have resulted in statistically significant dimensional changes. All the test disinfectants except 1% sodium hypochlorite showed a reduction in surface roughness (Ra) values.

Dimensional stability of two impression materials after a 6-month storage period

Objective: Oral rehabilitation success is enhanced by an accurate and reproducible final impression. The purpose of this study is to evaluate the dimensional changes of a polyether and addition silicone subjected to disinfection and/or sterilization after a long storage period.

Material and methods: Ninety samples were obtained from polyether Impregum^TM Penta^TM (3M ESPE^TM, Seefeld, Germany) and 90 of addition silicone Imprint^TM 4 Penta^TM Putty (3M ESPE^TM, Seefeld, Germany) according to ISO 4823:2000. The samples of each material were split to form three groups with 30 samples each: a control group, a hypochlorite group (disinfection) and an autoclave group (sterilization). Samples were stored in the Portuguese Institute for Quality for six months at 23 °C. Samples were measured by laser interferometry, according to the Michelson technique before calculating dimensional stability according ISO 4823:2000. A statistical analysis via a three-way mixed ANOVA was performed.

Results: Significant shrinkage of Impregum^TM Penta^TM was 0.77 ± 0.17% in the control group, 0.42 ± 0.19% in the hypochlorite group and 0.52 ± 0.28% in the autoclave group. For Imprint^TM 4 Penta^TM Putty, the control group had a shrinkage of 0.42 ± 0.12%, the hypochlorite group 0.36 ± 0.09% and the autoclave group 0.59 ± 0.13%.

Conclusions: The long-term storage of samples subjected to disinfection with 5.25% hypochlorite or autoclave sterilization can be used in a clinical setting as the dimensional changes are below the maximum permitted by the ISO 4823:2000, since there are no clinically significant changes in the dimension of the samples during the storage period.

Experimental hydrophilic vinyl polysiloxane (VPS) impression materials incorporating a novel surfactant compared with commercial VPS

OBJECTIVES

To formulate experimental hydrophilic (Exp) VPS impression materials incorporating a novel surfactant (Rhodasurf CET-2), and to compare their contact angles (CAs) with commercial materials, before/after disinfection.

METHODS

CAs were measured immediately after setting and after disinfection (1% NaOCl; 30min and 24h), together with their change whilst a droplet remained on the materials surface (over 10, 20, 30 60 and 120s), on three commercial (Aquasil Ultra-Monophase [Aq M], Elite HD-Monophase [Elt M], Extrude Medium-bodied [Extr M]) and four experimental (Exp I-IV) materials, using the Drop Shape Analysis 100 technique. The results were compared statistically.

RESULTS

CAs of all experimental materials were within the range of those obtained for the commercial materials, with the exception of Exp-IV, which presented with the lowest CAs at the three time points. The control Exp-I was hydrophobic at all three time points (CAs ∼100+), as was Elite. Immediately after setting, Aq M had low CAs but these increased significantly after 30min of disinfection. After twenty four hours' disinfection CAs of all Exp/commercial VPS increased significantly compared to immediately after setting. The CAs of droplets left on the material (120s) decreased with time, even after disinfection, except for Exp-I.

SIGNIFICANCE

The novel surfactant Rhodasurf CET-2 in Exp-III and IV, is an effective surfactant, retaining a low CA after disinfection, compared with Igepal CO-530 in Aq M. Disinfecting VPS impression materials for more than 30min increases their surface CAs, and therefore prolonged disinfection periods should be avoided.

Preliminary SEM Observations on the Surface of Elastomeric Impression Materials after Immersion or Ozone Disinfection

INTRODUCTION

Surface integrity of dental elastomeric impression materials that are subjected to disinfection is of major importance for the quality of the final prosthetic restorations.

AIM

The aim of this qualitative Scanning Electronic Microscopy (SEM) study was to reveal the effects of immersion or ozone disinfection on the surface of four dental elastomeric impression materials.

MATERIALS AND METHODS

Four dental elastomeric impression material brands were used (two vinyl polysiloxane silicones, one polyether, and one vinyl polyether silicone). Total of 32 specimens were fabricated, eight from each impression material. Specimens were immersion (0.525% sodium hypochlorite solution or 0.3% benzalkonium chloride solution) or ozone disinfected or served as controls and examined with SEM.

RESULTS

Surface degradation was observed on several speci-mens disinfected with 0.525% sodium hypochlorite solution. Similar wavy-wrinkling surface structures were observed in almost all specimens, when treated either with 0.3% benzalkonium chloride solution or ozone.

CONCLUSION

The SEM images obtained from this study revealed that both immersion disinfectants and ozone show similar impression material surface alterations. Ozone seems to be non-inferior as compared to immersion disinfectants, but superior as to environmental protection.

Bactericidal and Fungicidal Activity in the Gas Phase of Sodium Dichloroisocyanurate (NaDCC)

Sodium dichloroisocyanurate (NaDCC) is usually employed as a disinfectant for the treatment of water, environmental surfaces and medical equipment principally for its effectiveness as a microbicide agent. In this study, we explore the possibility of a new use for NaDCC by investigating the microbicidal activity of chlorine, which derives from the hydrolysis of NaDCC mediated by air humidity, and by testing its effect on the neutralization of microbes present in domestic waste. NaDCC was inserted in a plastic garbage can where LB agar plates, with different dilutions of a known title of four different microorganisms (Escherichia coli, Staphylococcus aureus, Debaryomyces hansenii and Aspergillus brasiliensis), were weakly inserted. The molecular chlorine (Cl2) levels present in the garbage can were quantified using an iodometric titration. The gas emitted in the garbage can presented a strong microbicide effect, inhibiting the proliferation of all four microorganisms and for four consecutive weeks, thus showing that NaDCC hydrolysis, mediated by air humidity, is able to ensure the decontamination of restricted environments, avoiding the proliferation of both Gram-positive and Gram-negative bacteria as well as fungi.

Multibracket appliance: impression defaults and their reduction by blocking-out - a three-dimensional study

OBJECTIVES

This study examines accuracy of dental impressions and following plaster models taken during treatment with fixed appliances.

MATERIALS AND METHODS

A maxillary typodont was provided with brackets. Three examiners took impressions three times each of the variants: brackets only, archwire fixed by alastics, ligatures or Kobayashi-hooks, and brackets and archwire covered completely or just on the gingival side by protection or impression wax. Casts were scanned using Activity102(®). Virtual models were compared to the scan of the typodont using Comparison(®). Differences were measured and descriptively analyzed. Estimated means with 95% confidence intervals were computed. Significance was assessed using linear mixed models.

RESULTS

While pyramidal reference blocks had a mean difference of 0.019 mm (95% CI = 0.017-0.021 mm) to the master model, teeth without attachments showed 0.097 mm (95% CI = 0.082-0.111 mm), and teeth with brackets 0.169 mm (95% CI = 0.156-0.182 mm) (p < 0.001). Smallest mean was found when using protection wax only on the gingival bracket side (0.152 mm (95% CI = 0.113-0.192 mm)). Incisors deviated most (0.258 mm (95 % CI = 0.239-0.277 mm)).

CONCLUSIONS

Teeth with brackets make impressions more inaccurate because of undercuts. Removing the archwire before taking the impression or covering the brackets on the gingival side shows tendencies toward better precision.

CLINICAL RELEVANCE

Taking impressions during treatment with fixed appliances, some inaccuracy has to be taken into account.

Accuracy of Digital Impressions and Fitness of Single Crowns Based on Digital Impressions

In this study, the accuracy (precision and trueness) of digital impressions and the fitness of single crowns manufactured based on digital impressions were evaluated. #14-17 epoxy resin dentitions were made, while full-crown preparations of extracted natural teeth were embedded at #16. (1) To assess precision, deviations among repeated scan models made by intraoral scanner TRIOS and MHT and model scanner D700 and inEos were calculated through best-fit algorithm and three-dimensional (3D) comparison. Root mean square (RMS) and color-coded difference images were offered. (2) To assess trueness, micro computed tomography (micro-CT) was used to get the reference model (REF). Deviations between REF and repeated scan models (from (1)) were calculated. (3) To assess fitness, single crowns were manufactured based on TRIOS, MHT, D700 and inEos scan models. The adhesive gaps were evaluated under stereomicroscope after cross-sectioned. Digital impressions showed lower precision and better trueness. Except for MHT, the means of RMS for precision were lower than 10 μm. Digital impressions showed better internal fitness. Fitness of single crowns based on digital impressions was up to clinical standard. Digital impressions could be an alternative method for single crowns manufacturing.

Effectiveness of mouthrinses and oral prophylaxis on reduction of microorganisms count in irreversible hydrocolloid impression: an in vivo study

Dental impressions, contaminated with saliva, blood, plaque, are potential source of infection. All impressions should be disinfected after their removal from mouth to prevent cross contamination. Different methods have been tried to disinfect the commonly used irreversible hydrocolloid impression material, but they have been shown to influence the dimensional stability and surface detail of the impression which ultimately affects the precision of the final prosthesis. The aim of this study was to evaluate the efficacy of pre-procedural oral prophylaxis and mouthrinses in reducing the overall microbial load intraorally as well as on alginate impression surface. A total of 60 positive cases selected from 100 subjects who were partially edentulous and above 18 years of age and without medical or pharmacotherapy histories were studied over a period of 18 months, from outpatient clinic of Department of Prosthodontics, GNIDSR. Alginate impressions, before and after prophylaxis were examined microbiologically for the persistence of test microorganisms on the untreated (control group) and the impressions made after treatment. The data were statistically analyzed by the Student t test to assess the effectiveness of the procedure and also the comparative effectiveness of oral prophylaxis and commonly used mouthrinses. The results showed that the impressions were safer when made after oral prophylaxis and/or mouthrinses.

Interaction between chlorhexidine-impregnated gutta-percha points and several chlorine-containing endodontic irrigating solutions

AIM

To evaluate if the immersion of chlorhexidine-impregnated gutta-percha points in chlorine-containing endodontic irrigants causes colour changes and precipitate formation.

METHODOLOGY

Eighty-one size 25 chlorhexidine medicated (Activ Points, Roeko, Langenau, Germany) and 27 size 25 standard gutta-percha points (Roeko) were immersed in microtubes, containing the following solutions: 0.5 and 5.25% NaOCl or Aquatine (Optident, Ilkley, UK). The samples were visually assessed, by two independent observers, at regular intervals over 3 weeks, to detect colour changes and precipitate formation. A score system was used to grade the precipitate intensity. To compare the number of days required for a precipitate to form mean and standard differences were calculated; the means between the groups were compared using a one-way analysis of variance test. Mean intensity scores were calculated and compared between groups using Kruskal-Wallis procedure followed by the Mann-Whitney test.

RESULTS

The groups containing 5.25% NaOCl started to produce a visible precipitate after fourteen days (16.48 ± 0.98) for the Activ points; this process was first noticed with the standard gutta-percha group on day 17 (18.33 ± 1.22 days), with a statistically significant difference (P = 0.002). When looking at the intensity scores from day 17 onwards, these two groups differed statistically, with a greater amount for the AP group (P < 0.001). No other test group presented with changes.

CONCLUSION

The placement of impregnated gutta-percha points, in 5.25% NaOCl for a 2-week period, caused the formation of a precipitate in the experimental conditions of this study.

Effect of alginate chemical disinfection on bacterial count over gypsum cast

PURPOSE

To evaluate the efficacy of sodium hypochlorite (1 : 10) and iodophor disinfectants on alginate impressions along with their effect on the survived bacterium count on the gypsum cast.

MATERIALS AND METHODS

Four alginate impression on each dentate patients were made, of which Group I were not washed or disinfected, Group II impressions were merely washed with water, Group III were disinfected by spraying with sodium hypochlorite (1 : 10), Group IV were disinfected with iodophor (1 : 213). Gypsum cast (type III) were made from all the impression. Impressions and gypsum cast were swabbed in mid palatal region for bacterial culture. Bacterial colony counting done after 3 days of incubation at 37℃ in blood agar media. The data obtained was analyzed by one way ANOVA test at a significant difference level of 0.05.

RESULTS

Group I and Group II showed significantly more bacteria compared to Group III and Group IV. Bacterial colonies on the alginate impression and gypsum cast in group disinfected with Sodium hypochlorite (1 : 10) were 0.18, 0.82 respectively compared to group treated with iodophor (1 : 213). There was an increase in bacterial count on dental cast compared to source alginate impressions.

CONCLUSION

Sodium hypochlorite (1 : 10) was found to be better disinfectant for alginate impression. There was an indication of increase in number of bacteria from alginate impression to making of dental cast. Additional gypsum cast disinfectant procedures need to be encouraged to completely eliminate cross infection to dental laboratory.

Disinfection of dental impressions - compliance to accepted standards

INTRODUCTION

The responsibility of ensuring impressions have been cleaned and disinfected before dispatch to the dental laboratory lies solely with the dentist. Uncertainty of impression disinfection risks both the health of the receiving dental technician and potential repeat disinfection of an already disinfected impression with detrimental consequences for its dimensions.

OBJECTIVE

To ascertain, from the perspectives of dentists and dental technicians, current impression decontamination and disinfection practices with, in the case of the technicians, an estimate of the relative prevalence of contaminated voids within apparently disinfected impressions.

DESIGN

Anonymous postal questionnaire.

METHOD

Dentist (n = 200) and dental technician (n = 200) potential participants, selected at random from the registers held by the General Dental Council, were invited to complete an anonymous postal questionnaire that sought to establish current practices and perceived effectiveness of impression disinfection.

RESULTS

Questionnaire return rates of 42.1% and 31.2% were recorded for dentists and dental technicians respectively. A wide range of solutions, at different dilutions of the same product, was used by the dentists to disinfect dental impressions. 37.2% rinsed the impressions with water, and 2.6% always brushed debris away, before disinfection. 24.7% of dentists did not inform the laboratory of disinfection. Irrespective of the disinfection status of the received impressions, 50% of the responding dental technicians disinfected all impressions. 95% of them had received blood-contaminated impressions. 15% had encountered blood-filled voids upon trimming back the peripheries of impressions. 64.7% were confident that the impressions received by them had been disinfected by the dentists.

CONCLUSIONS

Compliance with good practice is less than ideal and education in impression disinfection for both dentists and dental technicians is required to address this.

Evaluation of the antimicrobial effect of super-oxidized water (Sterilox®) and sodium hypochlorite against Enterococcus faecalis in a bovine root canal model

Ideally root canal irrigants should have, amongst other properties, antimicrobial action associated with a lack of toxicity against periapical tissues. Sodium hypochlorite (NaOCl) is a widely used root canal irrigant, however it has been shown to have a cytotoxic effect on vital tissue and therefore it is prudent to investigate alternative irrigants. Sterilox's Aquatine Alpha Electrolyte^® belongs to the group of the super-oxidized waters; it consists of a mixture of oxidizing substances, and has been suggested to be used as root canal irrigant. Super-oxidized waters have been shown to provide efficient cleaning of root canal walls, and have been proposed to be used for the disinfection of medical equipment.

Some factors influencing the stability of Sterilox(®), a super-oxidised water

Super-oxidised waters, particularly Sterilox(®), have been suggested for the disinfection of dental unit water lines and dental impression materials owing to their antimicrobial efficacy. One of the previously suggested characteristics is their short shelf life. The purpose of this investigation was to understand the effect of storage conditions on Sterilox(®)'s stability. Eight bottles (four completely full, four half-full) of freshly prepared solution were divided into four groups and subsequently stored by being either exposed to or protected from sunlight. The chlorine concentration was monitored using chlorine test strips until the concentration reached zero, or until the thirteenth week. Statistically significant differences between the groups exposed to sunlight and the non-exposed groups (p <0.001) were found. The mean loss of chlorine per day for the non-exposed samples was 1.01 mg/L, whilst the mean for the exposed samples was 2.42 mg/L. The presence of air did not affect the chlorine decomposition in the bottles. The results of this investigation indicate that when the solution is exposed to sunlight, the decrease of chlorine starts at day 4, whilst for the groups sheltered from sunlight, the process started after day 14. Therefore, Sterilox(®) solutions appear to be more stable than previously surmised.

The effect of disinfection by spray atomization on dimensional accuracy of condensation silicone impressions

BACKGROUND AND AIMS

The condensation silicone impression materials are available, but there is little knowledge of their accuracy after disinfection. The objective of this study was to evaluate the effect of the disinfection by spray atomization on dimensional accuracy of condensation silicone impressions.

MATERIALS AND METHODS

Impressions were made on a stainless steel master model containing a simulated two complete crown preparation with an edentulous space interposed using Spidex® and Rapid® impression materials. 44 impressions were made with each material, of which 16 were disinfected with 5.25% sodium hypochlorite, 16 were disinfected with 10% iodophor and 12 were not disinfected. Three dimensional measurements of working casts, including interpreparation distance, height, and diameter, were calculated using a measuring microscope graduated at 0.001 mm. Dimensional changes (mm) between the disinfected and non-disinfected working casts were compared. One-way analysis of variance (ANOVA) was employed to analyze the data (α=0.05).

RESULTS

Disinfection of each condensation silicone material by spraying atomization with two different disinfectant material resulted in significant change in interpreparation distance (p<0.05). Changes in height and diameter were only significant in Spidex® impressions (p<0.05).

CONCLUSION

Significant changes in the mean dimensions were seen as a result of disinfection by spraying; however, the dimensional changes do not seem great enough to cause critical positional distortion of teeth when fixed partial denture restorations are made.

Accuracy of the newly formulated vinyl siloxanether elastomeric impression material

STATEMENT OF PROBLEM

A newly formulated vinyl siloxanether elastomeric impression material is available, but there is little knowledge of its accuracy in relation to existing materials.

PURPOSE

The purpose of this in vitro study was to assess the accuracy of disinfected vinyl siloxanether impressions and compare the accuracy to a common vinyl polysiloxane and a polyether impression system.

MATERIAL AND METHODS

Impressions were made from a modified dentoform master model containing a simulated crown preparation. Dimensional changes (mm) between the master model and working casts (type IV gypsum) were assessed. The following were evaluated: vinyl polysiloxane in a 1-step, dual-viscosity technique (VPS Dual), polyether as monophase material (PE Mono), and vinyl siloxanether in a 1-step, dual-viscosity (VSE Dual), and monophase technique (VSE Mono). Measurements of the master model and working casts, including anteroposterior (AP) and cross-arch (XA) dimensions, were made with a measuring microscope. The simulated crown preparation was measured in mesiodistal (MDG, MDO), buccolingual (BLG, BLO), and occlusogingival dimensions (OGL, OGB). Disinfection involved immersion for 10 minutes in potassium peroxomonosulfate, sodium benzoate, tartaric acid solution, or no disinfection (control) (n=8). A multivariate GLM statistical approach (MANOVA) was used to analyze the data (alpha=.05). Pearson's correlation test was used for related dimensions.

RESULTS

The AP and XA dimensions of working casts were larger than the master for the disinfected condition and control. Whether disinfected or not, the working dies were shorter in height (OGB, OGL), larger in the buccolingual dimension (BLO, BLG), somewhat larger in the MDO dimension, and somewhat smaller in the MDG dimension compared to the prepared tooth of the master model, resulting in an irregular or oval profile. There were significant differences among the impression systems for each dimension except AP. Differences between the disinfected and nondisinfected conditions were significant (P=.03) with respect to dimensions of the gypsum working cast, but not for dimensions of the working die (P=.97). In general, differences relative to the master were small and of minor clinical significance considering marginal gaps of crowns smaller than 150-100 mum are considered clinically acceptable.

CONCLUSIONS

VSE monophase impressions and VSE dual-viscosity impressions demonstrated acceptable accuracy for clinical use with immersion disinfection, since the results for VSE were comparable to the results for PE and VPS materials, and the differences as compared to the master model were small.