Irreversible Hydrocolloid Research Articles

Antibacterial Efficacy and Effect of Chlorhexidine Mixed with Irreversible Hydrocolloid for Dental Impressions: A Randomized Controlled Trial

This study aimed to evaluate whether chlorhexidine mixed with irreversible hydrocolloid powder decreases microbial contamination during impression taking without affecting the resulting casts. Twenty volunteers were randomly divided into two groups (n = 10) according to the liquid used for impression taking in conjunction with irreversible hydrocolloid: 0.12% chlorhexidine or water. Surface roughness and dimensional stability of the casts were evaluated. Chlorhexidine mixed with irreversible hydrocolloid decreased the percentage of microorganisms when compared with water (P < .001) but did not affect the surface quality or dimensional stability of the casts. Mixing chlorhexidine with irreversible hydrocolloid powder is an alternative method to prevent contamination without sacrificing impression quality.

Evaluation in Vivo of the Accuracy of Different Impression Materials

All prosthetic treatments are characterized by a sequence of well-structured clinical and laboratory steps, during which different kinds of impressions are required. The accuracy of an impression material plays an important part in the production of a well-fitting restoration and for the longevity of the restoration too. The aim of this study is to evaluate and to compare the accuracy of different impression materials, their ability to reproduce details, using a measuring microscope. Four types of impression materials were used to take the impression of the same reference points on the composite filling in the second premolar (35). Irreversible hydrocolloids: Orthoprint and Neocolloid (ZHermack), the Polyvinilsilosan: Elite HD+ and the Polyether: Permdine Garant (3M ESPEE) were used. The results show that all impression materials demonstrated greater characteristics if treated correctly before and after the impression is taken, in conformity with the respective manufacturers’ guide lines and in respect to the storage time, so alginate if it’s pouring into 1 hour, polyether into 4 days and polyvinilsiloxan into 2 weeks. So, we conclude that the quality and accuracy of the impression is affected by pouring and storage time in order to obtain a greater accuracy of stone casts.

Effect of disinfection of irreversible hydrocolloid impression materials with 1% sodium hypochlorite on surface roughness and dimensional accuracy of dental stone casts

Abstract Aim: The aim of this study was to evaluate the effect of disinfection of commercially available irreversible hydrocolloid impression materials with 1% sodium hypochlorite on the surface roughness and dimensional accuracy of dies produced using type IV dental stone. Materials and Methods: Four different brands of irreversible hydrocolloid impression materials were used as follows: Jeltrate Plus without disinfection (GJ), Jeltrate Plus with disinfection (GJD), Hydrogum without disinfection (GH), Hidrogun with disinfection (GHD), Hidrogum 5 Days without disinfection (GH5), Hidrogum 5 Days with disinfection (GH5D), Cavex without disinfection (GC), and Cavex with disinfection (GCD). A total of 80 dies were poured using type IV dental stone and their mean surface roughness was evaluated using rugosimeter (Mitutoyo SJ-400). To conduct the dimensional alteration analysis, type IV dental stone casts were obtained from a matrix made of chemically-activated resin. They were analyzed in a coordinate-measuring machine (Brown and Sharpe). Statistics Analysis: Numerical data were analyzed using analysis of variance (ANOVA) with Tukey′s post hoc test at 5% confi dence interval. Results: Hidrogun 5 Days and Cavex showed the least surface roughness value even after 5 days. There were no significant differences in the dimensional alteration of Jeltrate (GJ and GJD) and Hidrogum (GH and GHD) in relation to the “new brands” Hidrogum 5 (GH5 and GH5D) and Cavex (GC and GCD), even after 5 days of storage. Conclusion: Considering the results obtained, it can be concluded that there was a roughness increase in the die stones poured from irreversible hydrocolloids disinfected with sodium hypochlorite.

The influence of different mixing methods on the dimensional stability and surface detail reproduction of two different brands of irreversible hydrocolloids

Abstract Purpose: Irreversible hydrocolloid impression materials are some of the most common impression materials in dentistry. Preparation of alginate is critical for dental appliance fabricated upon the cast made directly from the impression. This study compared the effect of two mixing methods i.e. hand mixing or device mixing on the physical properties of two different brands of irreversible hydrocolloid. Materials and Methods: Two alginate impression materials: Cavex Tulip (Tulip, Cavex Holland BV, Haarlem, Holland) and Hydrogum Soft (Zhermack, Rovigo, Italy), were mixed according to manufacturers instroductions with two mixing methods. Mixing was performed at room temperature using tap water. The material was allowed to set in a water bath at 35°C (±1°C), simulating intra-oral setting conditions. For each tested material, nine standardized samples were used. The first method was hand mixing; the other method was with a device. Detail reproduction and dimensional changes of impressions were compared. One-way analysis of variance was performed to compare the dimensional differences between the four groups. Results: The device mixed speciemens showed better surface detail than hand-mixed samples. Cavex alginate demonstrated better surface detail than Hydrogum. Cavex Tulip alginate showed better dimensional stability than Hydrogum Soft in both hand-mixed and device-mixed samples. Furthermore, all device mixed samples were better than hand-mixed in terms of dimensional stability. A two-way analysis of variance and Fisher′s protected least significant difference test at the 0.05 level of significance were used to analyze the data. Conclusion: Of the two mixing methods, the vacuum mixer had the best performance overall in reducing the number, percent and volume of porosities in the mixed alginate.

The Effect of Disinfecting Irreversible Hydrocolloid Impressions on Bacterial Count

The Effect of Disinfecting Irreversible Hydrocolloid Impressions on Bacterial Count

Impact of Storage Environments on the Dimensional Stability of Irreversible Hydrocolloid Alginate Impression used in Dentistry

Background: Alginate impression material is widely used for recording accurate impressions to fabricate various oral appliances such as crowns, bridges, partial dentures and complete dentures. Alginate impressions are dimensionally unstable and hence it should be poured immediately to form exact cast. The impressions are sometimes sent to the nearby laboratories for making cast and models. For maximum dimensional stability, the cast should be poured immediately or it can be stored in lower concentration NaCl or K2SO4 solutions during transport to distant laboratories. Objective: To evaluate the effect of various storage environments on the dimensional stability of irreversible hydrocolloid alginate impressions and to select a suitable medium for long time storage. Materials and Methods: Alginate impression material is supplied in powder form and is mixed with distilled water and poured on cylindrical hollow plastic mold. After setting, the sample is removed, weighed and then stored for 24 hours in a) exposed to atmosphere at 28+2°C(60 +5% relative humidity), b) refrigeration at 8+2°C, c) refrigeration in closed plastic sachets at 8+2°C, d) humidity chamber at 28+2°C and 8+2°C (100% relative humidity), e) distilled water f) solutions of NaCl at three different concentration and h) solutions of K2SO4 at three different concentration. The dimensional stability is measured by weight loss method and ion released during syneresis and imbibitions in storage media by using ion selective electrode method. Results: Alginate impressions were more stable at lower concentrations of NaCl & K2SO4¬ and dimensional changes are less than +0.6%. At higher concentrations more syneresis occurs, hence causes shrinkage of impressions. Impressions stored in open atmosphere showed maximum dimensional change followed by refrigerated sample, closed plastic sachets in refrigerator, humidity chamber and distilled water. Conclusion: For maximum dimensional stability, the impression should be poured immediately with cast material or the impression can be stored 24 hours in lower concentrations NaCl or K2SO4 solutions during transport to distant laboratories. This can also be stored in humidity chamber or zip lock polythene sachets in refrigerator at 8+2°C up to 6 hours. This saves chair side time and helps to produce accurate results.

Correlation between Combined Width of Maxillary Anterior Teeth, Interpupillary Distance and Intercommissural Width in a Group of Indian People

ABSTRACT Purpose The objective was to evaluate the correlation between the width of distal surface of canine (CWC), interpupillary distance (DMP) and intercommissural width (DCM) in a group of central Indian people. Materials and methods A total of 540 central Indian subjects (277 males and 263 females) aged 19 to 30 years were selected. DMP and DCM were measured on subject's face using digital vernier caliper [Mitutoyo (UK) Ltd.] with precision of 0.01 mm. Irreversible hydrocolloid impression of the upper arch was taken, and a cast was poured with dental stone. The CWC measurements were done on these casts with the help of a dental floss fixed between the distoproximal contacts of upper canines using a dental tape. Spearman's correlation test was used to determine the correlation between the three variables studied. Results The results revealed that the correlation between CWC-DMP was 0.015 and CWC-DCM was 0.031. The correlation showed negative values when compared between the sexes. Also, the proportions were calculated: DMP/CWC and DCM/CWC for the whole sample and for the sexes found no statistical significance (p &gt; 0.05). Conclusion The results of this study suggest that the examined interpupillary distance and intercommissural width cannot be considered reliable guidelines in the selection of artificial upper frontal teeth. However, they may be used as a useful additional factor combined with other methods for objective teeth selection in complete denture therapy. How to cite this article Deogade SC, Mantri SS, Saxena S, Daryani H. Correlation between Combined Width of Maxillary Anterior Teeth, Interpupillary Distance and Intercommissural Width in a Group of Indian People. Int J Prosthodont Restor Dent 2014;4(4):105-111.

Evaluation of efficacy of microwave irradiation in disinfecting dental gypsum casts: an ex vivo study.

The aim of this study is to assess the efficacy of microwave irradiation in disinfecting gypsum casts and also to compare its efficacy with validated method of chemical disinfection. The present study is an ex vivo study conducted on a sample of five irreversible hydrocolloid impressions in vitro and on ten patients gypsum casts in vivo following standard impression techniques to check the efficacy of microwave oven irradiation and compare its efficacy with standard chemical method of disinfection. Results were analysed using Mann-Whitney test and Wilcoxon signed rank test. Untreated gypsum casts showed cfu/ml counts with a median log value of 6, while microwave-irradiated ones had median cfu/ml counts of 0. Casts poured from chemically disinfected impressions demonstrated cfu/ml counts with a median log value of 5. Microwave irradiation was found to be effective in disinfecting gypsum casts when compared to chemical disinfectant in disinfecting dental impressions.

A Complete Denture Impression Technique Survey of Postdoctoral Prosthodontic Programs in the United States

The purpose of the study was to survey program directors of postdoctoral prosthodontic programs in the United States regarding their programs' complete denture impression techniques. The key objectives of the survey were to identify the current trends in complete denture impression making and to determine which techniques and materials are taught in US postdoctoral prosthodontic programs. An online survey was sent to all program directors of US postdoctoral prosthodontic programs. The survey comprised two sections: preliminary impressions and final impressions. The survey contained 22 questions that would take approximately 5 minutes to complete. All responses remained anonymous throughout the survey. The response rate for the survey was 87%. A majority of the programs did not separately border mold the tray prior to making the preliminary impressions (82%). The impression material of choice for the preliminary impression was irreversible hydrocolloid (88%). Selective pressure was the predominantly used impression philosophy (80%). All programs border molded the custom tray, and 95% recorded the borders in sections. The material of choice for border molding the custom tray was modeling plastic impression compound (71%). The most commonly used impression material for the final impressions was polyvinylsiloxane (PVS) (42%), and the second most commonly used impression material was polysulphide (32%). The most common technique for locating the posterior palatal seal was marking intraorally and transferring onto the final impression (65%). Most programs routinely advised their patients not to wear their existing dentures for at least 24 hours before the final impressions were made (83%). Based on the results of this study, the following conclusions can be drawn: (1) The most commonly used material for the preliminary impression was irreversible hydrocolloid and for the final impression was PVS. (2) Modeling plastic impression compound was used by most programs to border mold the custom trays. (3) Selective pressure was the predominantly used impression philosophy. (4) A majority of the programs made a special consideration for excessive movable (flabby) tissue. (5) Most programs routinely advised their patients to not wear their existing dentures for at least 24 hours before the final impressions were made.

A two-step (altered cast) impression technique in the prosthetic rehabilitation of a patient after a maxillectomy: A clinical report

This clinical report describes the prosthetic rehabilitation complicated by trismus (as a consequence of surgery and radiation therapy) of a patient with an acquired maxillary defect, after surgical removal of the right maxillary sinus tumor. The patient was restored with a partial removable dental prosthesis with a hollow bulb obturator to obtain orofacial rehabilitation and defect obturation. Precise obturation requires an accurate impression of the resection defect. A 2-step impression was performed because of trismus. A primary maxillary impression was made with an irreversible hydrocolloid, while a secondary (altered cast) impression was made with a silicone material by using the obturator cast framework as a tray. In that way an altered cast was produced. Subsequently, an obturator prosthesis was processed with a conventional technique.

Antibacterial Effect of Sanosil 2% and 6% and Sodium Hypochlorite 0.5% on Impressions of Irreversible Hydrocolloid (Alginate) and Condensational Silicone (Speedex)

Background: Dental impressions often carry microorganisms that may cause cross-infection from patients to dental staff. Impressions should be disinfected to eliminate the risk of cross-contamination. Objectives: The aim of this study was to determine the effectiveness of three different disinfectant solutions on two commonly used impression materials. Material and Methods: Seventy-two impressions were taken from dentate arches of nine dental staff from the school of dentistry, Hamadan University of Medical Sciences. Eight successive impressions were recorded in two different impression materials for each participant as four alginate and four condensational silicones (Speedex). For each impression material, specimens were exposed to four different regimens; one was immersed in sterile water as control, and the remaining specimens were exposed to three different disinfection treatments (0.5% sodium hypochlorite, 2% Sanosil, and 6% Sanosil) for 10 minutes. The impressions were washed with distilled water for 15 seconds, were inserted into sterilized tubes, and covered with Tryptic soy broth media (TSB). The tubes were incubated at 350 ºC for 24 hours. In total, 0.01 milliliter was obtained from each tube, and inoculated on blood agar medium. Gram staining and biochemical tests were performed for bacterial detection. Data was analyzed by SPSS software using Fisher exact test. Results: Bacterial growth was observed in all impressions immersed in sterile water for 10 minutes (control group). Disinfected alginate impressions were not contaminated withany microorganisms. None of the solutions under examination were completely effective for condensational Silicone impressions. Antibacterial effects on condensational silicone impressions ranked in a decreasing order as 0.5% sodium hypochlorite, 6% Sanosil and 2% Sanosil. Conclusion: Within the limitations of this study, disinfectants were able to completely eliminate microorganisms carried by the alginate impressions. However, more efficient disinfection methods are needed to eliminate the risk of cross contamination by condensational silicone impressions.

Survey of Impression Materials and Techniques in Fixed Partial Dentures among the Practitioners in India

Objective. Anecdotal evidence suggests that impression materials and techniques used in general dental practice for fixed partial dentures vary from those taught in dental schools. The aim of this survey was to integrate impression techniques evolved all over the years for fixed partial dentures and to know the techniques and materials which are used in the present day by the practitioners. Materials and Methods. A total of 1000 questionnaires were sent to various practitioners in India, out of which 807 questionnaires were filled. Results. The results showed that 84.8% of prosthodontists (65.56%, urban areas) use elastomeric impression materials as well as irreversible hydrocolloids and 15.2% use irreversible hydrocolloid only. Amongst other practitioners, 55.46% use irreversible hydrocolloid (45%, rural and semiurban areas) and 44.54% use elastomeric impression materials. Elastomeric impression technique practiced most commonly is putty reline with/without spacer (77.2%); other techniques are multiple-mix and monophase techniques. Conclusion. The ideal materials, technique, and armamentarium are required for the long-term success of the treatment for fixed partial denture. Also, if the ideal procedure is not followed, it will lead to a compromised fit of the final prosthesis and failure of the treatment.

Predoctoral Prosthodontic Curricula on Removable Partial Dentures: Survey of Turkish Dental Schools

This study was conducted to evaluate the predoctoral removable partial denture (RPD) curricula in Turkish dental schools in regards to materials, techniques, and approaches. A questionnaire consisting of eighteen multiple-choice questions was sent by e-mail to the senior members of the prosthodontic departments of seventeen long-established dental schools in Turkey. The response rate was 100 percent. All schools (100 percent) used custom trays for making final impressions of partially dentate arches, taught border molding of the custom tray for the edentulous areas, used modeling plastic impression compound in border molding the final impression trays, and used base metal alloys for RPD frameworks. None of the schools had an in-house laboratory that fabricates RPD frameworks, and none of the students cast the frameworks of their own RPDs. The majority of schools used irreversible hydrocolloid as a final impression (70.6 percent) and dental surveyor (76.5 percent) in the designing of RPDs. The majority of schools did not flask their own RPDs (64.7 percent), did not treat patients using RPDs with attachments (76.5 percent), and did not perform the altered cast technique in bilateral and unilateral distal extension RPD cases (76.5 percent). Six teen schools (94.1 percent) had a minimum number of RPD arches that a student must complete in order to graduate. It was found that predoctoral RPD curricula in Turkish dental schools were both variable and similar.

Evaluation of properties of irreversible hydrocolloid impression materials mixed with disinfectant liquids.

Background:Addition of disinfectant to irreversible hydrocolloid impression materials can eliminate the disinfection step to avoid dimensional changes associated with it. The aim of the present study was to evaluate the effect of various disinfectant mixing liquids on the properties of commercially available irreversible hydrocolloid impression materials.Materials and Methods:Four commercially available irreversible hydrocolloid impression materials (Zelgan, Vignette, Tropicalgin, and Algitex) were mixed with disinfectant liquid containing chlorhexidine (0.1 and 0.2%) and sodium hypochlorite (0.1 and 0.5%). After mixing with disinfectant liquids, materials were evaluated for pH changes during gelation, gelation time, flow, gel strength, permanent deformation and detail reproduction.Results:Significant changes in gelation time were observed in irreversible hydrocolloid impression materials upon mixing with disinfectant liquids. In general, chlorhexidine increased the gelation time, whereas sodium hypochlorite reduced it. However, no significant changes in the flow were observed both with chlorhexidine and sodium hypochlorite. Gel strength was found to decrease when mixed with chlorhexidine, whereas an increase in gel strength was observed upon mixing with sodium hypochlorite. Permanent deformation of the most irreversible hydrocolloid impression materials was below the specification limit even after mixing with disinfectant liquids. Sodium hypochlorite significantly reduced the surface detail reproduction, whereas no change in detail reproduction was observed with chlorhexidine.Conclusion:Chlorhexidine solution can be used to mix irreversible hydrocolloid impression materials in regular dental practice as it did not significantly alter the properties. This may ensure effective disinfection of impressions.

The relationship of maxillary canines to the facial anatomical landmarks in a group of Thai people

PURPOSEThe objective was to evaluate canine positions, intercanine tip width (ICTW) and width of distal surface of canine (WDC), related to facial landmarks including interalar width (IAW), intercommissural width (ICoW), and distance between left and right projection lines drawn from inner canthus of eyes to alae of the nose (DPICa) in a group of Thai.MATERIALS AND METHODSOne hundred Thai subjects aged 18-35 years were selected. IAW and ICoW were measured on subject's face using digital vernier caliper. Irreversible hydrocolloid impression of the upper arch was taken, and a cast was poured with dental stone. Silicone impression material was used to take imprint of the incisal edge of upper six anterior teeth. DPICa was obtained from the subject's face using custom-made measuring equipment and marked on the silicone incisal imprint. The marks were then transferred from the imprint to the stone cast and measured with digital caliper. The ICTW and WDC were also measured on the stone cast. Pearson's correlation was used to determine the correlation.RESULTSThe results revealed that the correlation between ICTW-ICoW was 0.429 and ICTW-DPICa was 0.573. The correlation between WDC-ICoW was 0.426 and WDC-DPICa was 0.547. However, IAW did not show any correlation with ICTW or WDC (P>.05).CONCLUSIONThe correlation between canine position and facial landmarks was found. ICTW and WDC had relationship with ICoW and DPICa. DPICa showed stronger correlation with the position of maxillary canine than that of ICoW.

The effect of pouring time on the dimensional accuracy of casts made from different irreversible hydrocolloid impression materials

Aims and Objectives:To determine the time dependent accuracy of casts made from three different irreversible hydrocolloids.Materials and Methods:The effect of delayed pouring on the accuracy of three different irreversible hydrocolloid impression materials – Regular set CA 37(Cavex, The Netherlands), regular set chromatic (Jeltrate, Dentsply), and fast set (Hydrogum soft, Zhermack Clinical) was investigated. A brass master die that contained two identical posts simulating two complete crown-tapered abutment preparations with reference grooves served as a standardized master model. A total of 120 impressions were made using specially prepared stock-perforated brass tray with 40 impressions of each material. The impressions were further sub-grouped according to four different storage time intervals: 0 min (immediately), 12 min, 30 min, and 1 h. The impressions were stored at room temperature in a zip-lock plastic bag. Interabutment and intraabutment distances were measured in the recovered stone dies (Type IV, Kalrock) using a profile projector with an accuracy of 0.001 mm. The data so obtained was analyzed statistically.Results:Results of this study showed no statistically significant differences in the accuracy of casts obtained at different time intervals.Conclusion:Because it is not always possible to pour the impression immediately in routine clinical practice, all irreversible hydrocolloid materials studied could be stored in a zip-lock plastic bag for upto 1 h without any significant distortion.

Comparative evaluation of maxillary and mandibular anterior teeth width with the length of index and little finger.

The size, color, morphology and arrangement of the anterior tooth are the various factors play an imperative role in achieving excellent esthetics in complete denture. Various modalities have been suggested for selecting the size of the anterior teeth like inter-alar distance, inter-canthal distance, bi-zygomatic width, intercanine width. There is no reliable method for selection of anterior teeth etc. To evaluate and compare the width of the maxillary and mandibular anterior teeth with the length of the index and little fingers. total of 50 people were taken for this study. They are grouped into four, Group I, 15-20years; Group II, 20-30years; Group III, 30-40years; Group IV, 40-50years. Irreversible hydrocolloid impressions of the maxilla and mandible were made and poured with dental stone. The widths of the maxillary and mandibular anterior teeth were measured with an adaptable ruler. The length of the index and little fingers were measured using a vernier caliper. There is significant correlation between the maxillary and mandibular anterior teeth with the index and little finger length. The maxillary anterior teeth width can be calculated with the formula (1.130×index finger length-11.972), mandibular anterior teeth width can be calculated with the formula (1.006×little finger length-2.231).

Correlation between Maxillary Canines and Facial Anatomical Landmarks in a Group of Bangladeshi people

Purpose: The objective of this study was to evaluate the correlation between maxillary canines and the facial landmarks including interalar width (IAW) and intercommissural width (ICoW) in a group of Bangladeshi people. Materials and methods: One hundred Bangladeshi subjects aged 18~35 years were selected. Irreversible hydrocolloid impression of the upper arch was taken and a cast was poured with dental stone.The interalar width (IAW) and intercommissural width (ICoW) were measured using digital vernier caliper. Intercanine tip (ICTW) and width of the distal surface of the canine (WDC) were measured from the cast using digital caliper. Results: The correlation between ICTW-IAW was 0.246. There was no correlation between ICTW-ICoW. The correlation between WDCIAW and WDC-ICoW were 0.342 and 0.235 respectively (p&lt; .05). Conclusion: Both interalar width and intercommissural width had a weak correlation with the position of maxillary canine in this Bangladeshi subject group. For the construction of a pleasing and harmonious complete denture esthetic and phonetic outcomes are recommended to be considered in combination with facial landmarks. DOI: http://dx.doi.org/10.3329/cdcj.v9i2.12315 City Dental College J. Volume-9, Number-2, July-2012

Influence of delayed pouring on irreversible hydrocolloid properties

The aim of this study was to evaluate the physical properties of irreversible hydrocolloid materials poured immediately and after different storage periods. Four alginates were tested: Color Change (Cavex); Hydrogum (Zhermack); Hydrogum 5 (Zhermack); and Hydro Print Premium (Coltene). Their physical properties, including the recovery from deformation (n = 3), compressive strength (n = 3), and detail reproduction and gypsum compatibility (n = 3), were analyzed according to ANSI/ADA specification no. 18. Specimens were stored at 23ºC and humidity and were then poured with gypsum immediately and after 1, 2, 3, 4, and 5 days. The data were analyzed by two-way analysis of variance (ANOVA) and Tukey's test at p < 0.05. All of the alginate impression materials tested exhibited detail reproduction and gypsum compatibility at all times. Hydro Print Premium and Hydrogum 5 showed recovery from deformation, as established by ANSI/ADA specification no. 18, after 5 days of storage. As the storage time increased, the compressive strength values also increased. Considering the properties of compounds' recovery from deformation, compressive strength, and detail reproduction and gypsum compatibility, irreversible hydrocolloids should be poured immediately.

Effect of disinfection on irreversible hydrocolloid and alternative impression materials and the resultant gypsum casts

Many new products have been introduced and marketed as alternatives to traditional irreversible hydrocolloid materials. These alternative materials have the same structural formula as addition reaction silicone, also known as vinyl polysiloxane (VPS), impression materials. Currently, there is limited in vitro and in vivo research on these products, including on the effects of chemical disinfectants on the materials. The purpose of this study was to compare the effects of a spray disinfecting technique on a traditional irreversible hydrocolloid and 3 new alternative impression materials in vitro. The tests were performed in accordance with the American National Standards Institute/American Dental Association (ANSI/ADA) Specification Nos. 18 and 19. Under standardized conditions, 100 impressions were made of a ruled test block with an irreversible hydrocolloid and 3 alternative impression materials. Nondisinfected irreversible hydrocolloid was used as the control. The impressions were examined for surface detail reproduction before and after disinfection with a chloramine-T product. Type III and Type V dental stone casts were evaluated for linear dimensional change and gypsum compatibility. Comparisons of linear dimensional change were analyzed with 2-way ANOVA of mean ranks with the Scheffé post hoc comparisons (α=.05). Data for surface detail reproduction were analyzed with the Wilcoxon Signed-Rank procedure and gypsum compatibility with the Kruskal-Wallis Rank procedure (α=.05). The alternative impression materials demonstrated significantly better outcomes with all 3 parameters tested. Disinfection with chloroamine-T did not have any effect on the 3 alternative impression materials. The irreversible hydrocolloid groups produced the most variability in the measurements of linear dimensional change. All of the tested materials were within the ADA's acceptable limit of 1.0% for linear dimensional change, except for the disinfected irreversible hydrocolloid impression material. The alternative impression materials performed best for the parameters tested. Spray disinfection had no effect on the alternative impression materials.