Three-dimensional evaluation of extended pour alginate impression materials following variable storage time intervals and conditions

The purpose of this study was to assess and compare the dimensional accuracy of the stone casts made of three extended pour alginate impressions materials (Cavex Colorchange, Kromopan, and Neocolloid) following storage under different storage conditions and pouring at different time intervals. Materials and Methods: A maxillary Frasaco (dentulous) model was selected as a standard model. Index holes of 1 mm depth and 1 mm diameter were made on the palatal cusp tips of right and left first premolars, mesiopalatal cusp tips of right and left third molars and in the midline of the palate, perpendicular to a line joining the index holes made on cusp tips of the first premolars as reference points for measurement. A single uniformly spaced custom tray was fabricated with heat-cure acrylic resin and used to make impressions for the entire study. A total of 210 impressions of the master model were made, seventy impressions were made from each of the alginate material brands and were subjected to three storage conditions (open air, uncontrolled humidity, and 100% controlled humidity) for three different storage time intervals (0, 1, 6 h). Since no storage was done in the immediate-pour group, it contained 10 specimens from each brand. Following the designated storage time interval, all impressions were poured in type IV gypsum. Measurements of stone casts were done in three dimensions, anteroposterior, lateral using Measuroscope and vertical by Dial Gauge. Data were organized in tables and statistical analyses were performed. Three-way ANOVAs were used to check if the material brands, storage time intervals, and conditions affect the measurements. Tukey HSD post hoc tests were used for the multiple comparisons if ANOVA is significant. One sample t-test was used to compare between the casts made of alginate brands and the master model. Significance level was set to α < 0.05 for all tests. Results: Results showed that the material brands, storage time intervals, and conditions do affect the measurements in all three dimensions (all P < 0.05). In addition, all two-way and three-way interactions were significant for all measurements except the interaction of storage time intervals and conditions for B–C (lateral) measurements, and interaction of material brands and storage time intervals for C–D (anteroposteriorly) measurements. When stone casts were compared to the master model, immediate pour, and storage for 1 h in 100% controlled humidity resulted in statistically insignificant changes among all three alginate impression brands. In addition, the specimens made of Cavex Colorchange and Kromopan following storage in uncontrolled humidity condition for 1 h showed statistical insignificance when compared to the master model. Conclusion: Within the limitations of this study, it can be extrapolated that, although this class of alginate impression materials was manufactured for extended pour purposes, clinicians should avoid storage of the studied brands for 6 h. Whenever 1 h to pour is necessary, 100% controlled humidity is the ideal and standardized environment for all three alginate brands. Perhaps, Cavex Colorchange, and Kromopan can be safely stored in uncontrolled humidity condition while maintaining their optimal dimensional accuracy.

Surface detail reproduction and dimensional accuracy of molds: influence of disinfectant solutions and elastomeric impression materials / Reprodução de detalhes da superfície e estabilidadedimensional de moldes: influência das soluçõesdesinfetantes e elastômeros

This study compared the surface detail reproduction anddimensional accuracy of molds after disinfection using 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to those of molds that were not disinfected, forfour elastomeric impression materials: polysulfide (Light Bodied Permlastic), polyether (Impregum Soft), polydimethylsiloxane(Oranwash L) and polyvinylsiloxane (Aquasil Ultra LV). Themolds were prepared on a matrix by applying pressure, using aperforated metal tray. The molds were removed followingpolymerization and either disinfected (by soaking in one of thesolutions for 15 minutes) or not disinfected. The samples werethus divided into 16 groups (n=5). Surface detail reproductionand dimensional accuracy were evaluated using opticalmicroscopy to assess the 20 ­µm line over its entire 25 mm length. The dimensional accuracy results (%) were subjectedto analysis of variance (ANOVA) and the means were comparedby Tukey’s test (α=5%). The 20 ­µm line was completelyreproduced by all elastomeric impression materials, regardlessof disinfection procedure. There was no significant difference between the control group and molds disinfected with peraceticacid for the elastomeric materials Impregum Soft (polyether)and Aquasil Ultra LV (polyvinylsiloxane). The high­leveldisinfectant peracetic acid would be the choice material for disinfection.

Este estudo comparou a reprodução de detalhes da superfície e estabilidade dimensional de moldes obtidos após desinfecção utilizando hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a moldes que não foram desinfetados com quatro elastômeros: polissulfeto (Light Bodied Permlastic), polieter (Impregum Soft), silicona reação porcondensação (Oranwash L) e silicona reação por adição (Aquasil Ultra LV). Os moldes foram preparados sobre matriz conten dolinhas de 20, 50 e 75 µm realizado sob pressão com moldeirade metal perfurada. Os moldes foram removidos após a polimerização e desinfetados (utilizando uma das soluções porimersão, armazenados em frascos fechados durante 15 minutos)ou não desinfetados. Assim, as amostras foram divididas em 16grupos (n=5). A reprodução detalhes da superfície e a precisão dimensional foram avaliadas usando microscopia óptica na linha 20 µm com 25 mm de comprimento, de acordo com a norma ISO 4823. Os resultados de precisão dimensional (%) foram submetidos à análise de variância (A NOVA) e as médias comparadas pelo teste de Tukey com 5% de nível de significância. A linha de 20 µm foi completamente reproduzida por todos os elastômeros, independentemente do processo de desinfecção. Não houve diferença estatisticamente significativa entre o grupo controle e moldes desinfetados com acido peracético para os elastômeros Impregum Soft (polieter) e Aquasil Ultra LV (siliconareação por adição). O desinfetante de alto nível ácido peracético seria o material de escolha para a desinfecção.

Effect of different impression techniques and elastomeric impression materials on the dimensional accuracy of partially edentulous mandibular arch

Aim: Evaluate the dimensional accuracy of stone casts of a partially edentulous mandibular arch made by two impression techniques (1-step putty/light-body and 2-step putty/light-body) using addition and condensation silicones. Methods: A partially edentulous steel stainless cast with four markings on teeth 33, 37, 43, and 47 was used to obtain the impressions. The transverse (33-43 and 37-47) and anteroposterior (33-37 and 43-47) distances were measured by measuring microscope (30x magnification; 0.5µm accuracy). For the 1-step putty/light-body technique, both viscosities of the impression materials were handled together. For the 2-step putty/light-body technique, the impression materials of different viscosities were handled separately and a polypropylene spacer (2 mm thick) was used to create a relief. The same distances were measured on stone casts (n = 5). The values were submitted to normality test (Kolmogorov-Smirnov) and analyzed statistically by three-way ANOVA and Tukey's (5%). Results: All distances showed shrinkage (negative linear changes). The addition silicones showed better accuracy than condensation silicones (p<0.05) and no significant difference was found between the impression techniques (p>0.05). The edentulous zone (43-47) presented worst dimensional accuracy results. Conclusions: The accuracy of the casts is more related to the impression material than impression technique. (AU)

Evaluation of digital dental models obtained from dental cone-beam computed tomography scan of alginate impressions / 대한치과교정학회지

OBJECTIVE: To investigate the dimensional accuracy of digital dental models obtained from the dental cone-beam computed tomography (CBCT) scan of alginate impressions according to the time elapse when the impressions are stored under ambient conditions. METHODS: Alginate impressions were obtained from 20 adults using 3 different alginate materials, 2 traditional alginate materials (Alginoplast and Cavex Impressional) and 1 extended-pour alginate material (Cavex ColorChange). The impressions were stored under ambient conditions, and scanned by CBCT immediately after the impressions were taken, and then at 1 hour intervals for 6 hours. After reconstructing three-dimensional digital dental models, the models were measured and the data were analyzed to determine dimensional changes according to the elapsed time. The changes within the measurement error were regarded as clinically acceptable in this study. RESULTS: All measurements showed a decreasing tendency with an increase in the elapsed time after the impressions. Although the extended-pour alginate exhibited a less decreasing tendency than the other 2 materials, there were no statistically significant differences between the materials. Changes above the measurement error occurred between the time points of 3 and 4 hours after the impressions. CONCLUSIONS: The results of this study indicate that digital dental models can be obtained simply from a CBCT scan of alginate impressions without sending them to a remote laboratory. However, when the impressions are not stored under special conditions, they should be scanned immediately, or at least within 2 to 3 hours after the impressions are taken.

Dimensional Accuracy of Stone Casts Made from Silicone-Based Impression Materials and Three Impression Techniques

The aim of this study was to measure and compare the dimensional accuracy of stone casts of a partially edentulous mandibular arch made by two condensation silicones, two addition silicones and three impression techniques (1-step putty/light-body, 2-step putty/light-body and monophase technique). A partially edentulous standard stainless steel mandibular arch cast was obtained with reference points on the permanent mandibular right and left canines, and permanent mandibular right and left second molars. The anteroposterior distances (between the mandibular left canine and second molar and between the mandibular right canine and second molar) and transverse distances (between the mandibular left and right canines and between the mandibular left and right second molars) of stainless steel cast were measured by a microscope at 30× magnification and 0.5 µm accuracy. All impressions were made with condensation or addition silicones. The 1- and 2-step putty/light-body impressions were accomplished with putty and light-body materials and the monophase impressions with light-body material only. After the impression procedures, accuracy of each material and technique was assessed measuring the stone casts poured (n=5) from the impressions, by the same microscope. The differences between the values of stone cast and stainless steel cast were calculated, presented as percentages and analyzed statistically by two-way ANOVA and the means compared by Tukey's test (α=0.05). All distances measured on stone casts showed altered dimensions with significantly negative linear changes (shrinkage) as compared to those of the stainless steel cast. The stone casts made from the addition silicones were dimensionally more accurate. No differences were found among the impression techniques.

O objetivo deste estudo foi mensurar e comparar a precisão dimensional de modelos de gesso de um arco mandibular parcialmente edêntulo feitos a partir de dois silicones por condensação, dois silicones por adição e três técnicas de moldagem (dupla mistura, reembasamento e moldeira individual). Um modelo metálico padrão de um arco mandibular parcialmente edêntulo foi obtido com pontos de referência nos caninos mandibulares permanentes esquerdo e direito, e segundo molares mandibulares permanentes esquerdo e direito. As distâncias anteroposteriores (entre o canino e segundo molar mandibulares esquerdos e entre o canino e segundo molar mandibulares direitos) e as distâncias transversais (entre os caninos mandibulares esquerdo e direito e entre os segundos molares mandibulares esquerdo e direito) do modelo metálico foram mensuradas através de um microscópio com 30x de aumento e 0,5 µm de precisão. Todas moldagens foram feitas com silicones por condensação e adição. As técnicas de dupla mistura e reembasamento foram realizadas com materiais nas viscosidades massa e leve e a técnica da moldeira individual somente com material leve. Após os procedimentos de moldagem, a precisão de cada material e técnica foi aferida medindo os modelos de gesso vazados (n=5) dos moldes, sob o mesmo microscópio. As diferenças entre os valores dos modelos de gesso e do modelo metálico foram calculadas, apresentadas como porcentagens e analisadas estatisticamente através da análise de variância e teste de Tukey (α=0,05). Todas as distâncias mensuradas nos modelos de gesso apresentaram dimensões alteradas com alterações lineares negativas (contração) significativas quando comparadas as medidas do modelo metálico. Os modelos de gesso feitos a partir de silicones por adição foram dimensionalmente mais precisos. Não foram encontradas diferenças entre as técnicas de moldagem.

A comparison of the accuracy of patterns processed from an inlay casting wax, an auto-polymerized resin and a light-cured resin pattern material.

Background: Traditionally, inlay casting waxes have been used to fabricate patterns for castings. Newer resin pattern materials offer greater rigidity and strength, allowing easier laboratory and intraoral adjustment without the fear of pattern damage. They also claim to possess a greater dimensional stability when compared to inlay wax. Aims: This study attempted to determine and compare the marginal accuracy of patterns fabricated from an inlay casting wax, an autopolymerized pattern resin and a light polymerized pattern resin on storage off the die for varying time intervals. Materials and Methods: Ten patterns each were fabricated from an inlay casting wax (GC Corp., Tokyo, Japan), an autopolymerized resin pattern material (Pattern resin, GC Corp, Tokyo, Japan) and a light-cured resin pattern material (Palavit GLC, Hereaus Kulzer GmbH, Germany). The completed patterns were stored off the die at room temperature. Marginal gaps were evaluated by reseating the patterns on their respective dies and observing it under a stereomicroscope at 1, 12, and 24 h intervals after pattern fabrication. Results: The results revealed that the inlay wax showed a significantly greater marginal discrepancy at the 12 and 24 h intervals. The autopolymerized resin showed an initial (at 1 h) marginal discrepancy slightly greater than inlay wax, but showed a significantly less marginal gap (as compared to inlay wax) at the other two time intervals. The light-cured resin proved to be significantly more dimensionally stable, and showed minimal change during the storage period. Conclusion: The resin pattern materials studied, undergo a significantly less dimensional change than the inlay waxes on prolonged storage. They would possibly be a better alternative to inlay wax in situations requiring high precision or when delayed investment (more than 1 h) of patterns can be expected.

Surface detail reproduction and dimensional accuracy of stone models: influence of disinfectant solutions and alginate impression materials

This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds disinfected with 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to models produced using molds which were not disinfected, with 3 alginate materials (Cavex ColorChange, Hydrogum 5 and Jeltrate Plus). The molds were prepared over matrix containing 20-, 50-, and 75-µm lines, performed under pressure with perforated metal tray. The molds were removed following gelation and either disinfected (using one of the solutions by spraying followed by storage in closed jars for 15 min) or not disinfected. The samples were divided into 12 groups (n=5). Molds were filled with dental gypsum Durone IV and 1 h after the start of the stone mixing the models were separated from the tray. Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-µm line with 25 mm in length, in accordance with the ISO 1563 standard. The dimensional accuracy results (%) were subjected to ANOVA. The 50 µm-line was completely reproduced by all alginate impression materials regardless of the disinfection procedure. There was no statistically significant difference in the mean values of dimensional accuracy in combinations between disinfectant procedure and alginate impression material (p=0.2130) or for independent factors. The disinfectant solutions and alginate materials used in this study are no factors of choice regarding the surface detail reproduction and dimensional accuracy of stone models.

Este estudo comparou a reprodução de detalhes da superfície e alteração dimensional de modelos de gesso obtidos a partir de moldes desinfetados com hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a modelos confeccionados utilizando moldes que não foram desinfetados com três alginatos (Cavex ColorChange, Hydrogum 5, Jeltrate Plus). Os moldes foram preparados sobre matriz contendo linhas de 20, 50 e 75 µm realizado sob pressão com moldeira de metal perfurada. Os moldes foram removidos após a geleificação e desinfetados (utilizando uma das soluções por pulverização, armazenados em frascos fechados durante 15 min) ou não desinfetados. Assim, as amostras foram divididas em 12 grupos (n=5). Os moldes foram preenchidos com gesso dental Durone IV e uma hora após a manipulação do gesso os modelos foram separados da moldeira. A reprodução de detalhes da superfície e a precisão dimensional foram avaliadas usando microscopia óptica na linha 50 µm com 25 mm de comprimento, de acordo com a norma ISO 1563. Os resultados de precisão dimensional (%) foram submetidos à ANOVA. A linha de 50 µm foi completamente reproduzida por todos os alginatos, independentemente do processo de desinfecção. Não houve diferença estatisticamente significativa nos valores médios de precisão dimensional nas combinações entre procedimento de desinfecção e alginato (p=0,2130), ou para fatores independentes. Soluções desinfetantes e alginatos utilizados neste estudo não são fatores de escolha em relação à reprodução de detalhes da superfície e alteração dimensional de modelos de gesso.

Dimensional accuracy and detail reproduction of two hydrophilic vinyl polysiloxane impression materials tested under different conditions.

Background and Objectives: A limitation of vinyl polysiloxane (VPS) impression materials is hydrophobicity, and manufacturers have added surfactants and labeled these new products as "hydrophilic." The purpose of this investigation was to evaluate and compare the dimensional accuracy and surface detail reproduction of two hydrophilic VPS impression materials under dry, moist, and wet conditions. Materials and Methods: Ten impressions were made under dry, moist, and wet conditions respectively, with monophase, and regular body VPS impression material using a stainless steel metal die similar to that described in American Dental Association (ADA) specification 19, with lines scribed on it. Dimensional accuracy was measured by comparing the average length of the middle horizontal line in each impression to the same line on the metal die, by using a measuring microscope. The surface detail was evaluated. A one-way analysis of variance and Student t-test were used to compare mean dimensional changes (α = 0.05). Results: Conditions (dry, moist, and wet) did not cause significant adverse effects on the dimensional accuracy of either material. The mean dimensional changes were 0.00084% (+0.00041%) for monophase and 0.00119% (+0.00033%) for regular body. Monophase material was satisfactory in detail reproduction 100% of the time in dry conditions, 90% in moist, and only 20% in wet conditions. The regular body showed 100% satisfactory impressions in dry, 80% in moist, and 10% in wet conditions. With the additional smooth surface evaluation, only under dry conditions impressions with clinically acceptable surface quality were produced. Conclusions: Dimensional changes for both materials were well within ADA standards of minimal shrinkage value of 0.5%.

Dimensional accuracy of stone casts made by a monophase impression technique using different elastomeric impression materials

Impression taking is a critical step in the process of producing successful crowns and fixed partial dentures in oral rehabilitation, and the impression material is an important factor related to clinical success. Aim: The aim of this in vitro study was to assess and compare the dimensional accuracy of stone casts made from a monophase technique using 10 elastomeric impression materials. Methods: First, a stainless steel model with reference points in the teeth 33, 43, 37, and 47 was used to obtain the impressions. The distances were measured among teeth 33-43, 37-47, 33-37, and 43-47. For the impression technique, acrylic resin trays were made with an internal relief of approximately 2 mm. Specific adhesives for each material were used in the custom trays. Tray detachment movement was standardized by pneumatic equipment. After the impression procedures and obtaining of samples, the stone casts were observed in a measuring microscope at 30x magnification. Data recorded for each distance were analyzed statistically by one-way analysis of variance and Tukey’s test at 5% significance level. Results: Stone casts made with elastomeric impression materials showed statistically significant (p<0.05) differences when the dimensional accuracy values were compared. The order for the highest to lowest accuracy for the types of impression materials was as follws: polyvinylsiloxane (PVS), polyether, polysulfide and polydimethylsiloxane (PDMS). Conclusions: PVS were the most dimensionally accurate impression materials, and the PDMS showed the worst results of dimensional accuracy.

Comparison of the linear dimensional accuracy of denture bases cured the by conventional method and by the new press technique.

Aim: The purpose of this study was to investigate and compare the linear dimensional accuracy of denture bases processed with the conventional heat-polymerization technique and the Rafael and Saide (RS) tension system, taking a multidirectional approach. Materials and Methods: Twenty standard edentulous maxillary casts were randomly assigned into two groups. A uniform denture base of 1.5 mm thickness was fabricated in wax and later processed by two methods: Group I acrylic resin flasked with the conventional technique and Group II acrylic resin flasked with the RS tension system. The dimensional accuracy was assessed using traveling microscope. Results: The linear dimensional changes that occurred between the dentures produced with the new press method and the conventional method were statistically insignificant and ranged from 0.002 to 0.11. The dimensionally stable areas were the canines and the most unstable was the posterior palate. Conclusions: The results of this study suggest that the maximum linear dimensional change occurs around the molars and palatal segment, with the most stable areas being the canines. There was no significant linear dimensional change of the dentures processed between the conventional and the new press technique.

Comparative study of Dimensional Accuracy of Three Conventional Denture Base Resins Processed By Conventional Method And Microwave Polmerization.

Statement of Problem: Poor adaptations of acrylic resin denture bases to the supporting tissues markedly decrease denture retention. Several denture base resin and processing techniques have been introduced to the profession, each claiming to produce a more accurate base. Microwave processing techniques has been introduced claims to minimize the dimensional changes. Purpose: The purpose of this study was to compare the dimensional accuracy of three denture base resins processed by conventional water bath method and by use of microwave energy. Material and method: Three Poly (MethylMethacrylate) heat cure resins were selected for this study.These resins were processed by (i) conventional water bath technique for 1.5 hours at 1650F and half hour at 2120F and (ii) microwave energy for 3 mins at 500W. A metal master die representing a maxillary arch with 4mm hole was prepared to evaluate the adaptation of the test resin denture base. A total number of 60 specimens were tested. The measurements of acrylic resin denture base specimens were compared with the measurements of master metal die dimension keeping it as a standard measurement. Results: The resin record bases processed by microwave curing method had slightly better dimensional accuracy than conventionally processed bases. There was no significant difference found in the dimensional accuracy when Resin record bases processed with a specially formulated resin for microwave curing was microwave cured and when conventionally available resins were processed by microwave technique. Conclusion: The resin record bases processed by microwave curing method had slightly better dimensional accuracy than the conventionally processed bases.

Effect of cervical relining of acrylic resin copings on the accuracy of stone dies obtained using a polyether impression material

The purpose of this study was to evaluate the accuracy of the respective dies after polyether elastomeric procedure in the presence or absence of cervical contact of the acrylic resin shell with the cervical region, establishing a comparison to dies obtained with stock trays. This study consisted of three groups with 10 specimens each: 1) acrylic copings without cervical contact, (cn); 2) acrylic copings with cervical contact (cc); 3) perforated stock tray, (st). The accuracy of the resulting dies was verified with the aid of a master crown, precisely fit to the master steel die. ANOVA test found statistically significant differences among groups (p<0.001). Tukey's test found that the smallest discrepancy occurred in group cn, followed by cc, while the st group presented the highest difference (cc x cn: p=0.007; st x cn: p<0.001; st x cc: p<0.001).