J Bagh College Dentistry Vol. 33(3), September 2021 The effect of contact 18 The effect of contact time between alginate impression material and type III dental stone on the surface properties of stone casts )3( Najwah Yousuf Hameed ,)(2 Atyaf Maser Alnaser ,(1)Suha Fadhil Dulaimi https://doi.org/10.26477/jbcd.v33i3.2949 ABSTRACT Background: Alginate impression material is the irreversible hydrocolloid material that is widely used in dentistry. The contact time between alginate and gypsum cast could have a detrimental effect on the properties of the gypsum cast. The objective of this study is to evaluate the impact of various contact time intervals of Alginate impressions & type III dental stone on surface properties of stone cast. Materials and Methods: Time intervals tested were 1hour, 6 hours and 9 hours. Surface properties of stone cast evaluated were surface detail reproduction, hardness and roughness. Surface detail reproduction was determined using cylindrical brass test block in accordance with ISO 1563. Surface roughness was measured by profilometer and hardness was measured by Durometer (Shore D). Results: The detail reproduction showed significant difference (P<0.05), at 6 hr., and 9 hr. showed better results, while surface roughness significantly decreased (p<0.01) with prolonged contact time. However, surface hardness increased significantly (p<0.01) with increased contact time. Conclusions: Surface detail reproduction increased with increasing the contact time and this was noticed at (6, 9 hours). However, 1hour time interval showed decreased surface detailed reproduction. Roughness decreased when the contact time was increased between type III dental stone and alginate impression, whereas hardness was improved significantly with increasing contact time. Keywords: Alginates, Surface properties, Dentistry, Hardness, Calcium sulfate. (Received: 2/6/2021, Accepted: 4/7/2021) INTRODUCTION In dentistry, methods of oral disease diagnosis and treatment are complemented by replicas of hard and soft tissue. Those replicas are known as study models, casts or dies They are used for studying some cases in dentistry; and all of these replicas are used in the dental practice. (1) Although there are several impression materials and procedures available for accurate impression making, irreversible hydrocolloids are among several impression materials that are commonly utilized in dental offices to produce stone casts (2). An alginate impression is often made during the first visit as its outcomes are necessary to form a primary diagnosis about the patients' oral health condition (4). For several years, alginate impression has become an essential material for most dental, clinical and laboratory dental techniques. The low cost and the ease of manipulation, integrated with good clinical and physical properties make alginate a popular choice among different dental practices (3). (1) Assistant Professor, Department of Prosthodontics Technology, College of Health and Medical Technology. Middle Technical University (MTU) Baghdad – Iraq (2) (3) Assistant Lecturer, Department of Prosthodontics Technology, College of Health and Medical Technology. Middle Technical University (MTU) Baghdad – Iraq suha.f.dulaimi@gmail.comesponding author: Corr Accurate diagnostic casts are essential to perform a multitude of functions throughout diagnosis, treatment planning and preparation for prosthodontics care (4). Thus, it is of importance to understand the properties of those materials following some basic instructions so as to achieve predictable and flawless impressions and therefore avoiding repeated impression/restorations (4). Alginate is composed of a powder that contains potassium or calcium sulfate and fillers as primary constituents. The commercial Alginate contains some additive materials to calcium salts to improve its properties like Diatomaceous earth fillers to raise its rigidity and ease mixing, tetra sodium pyrophosphate (retarder), magnesium oxide (pH modifier) as well as the setting aids like sodium fluorosilicate (5). Delay pouring of alginate impression results in serious distortion due to shrinkage caused by syneresis and evaporation of water. A previous study recommended storing alginate impression up to 1 hr. in humid environment (6). Another factor that affects properties of final gypsum cast is the contact time between alginate and gypsum cast during its setting, the appropriate approach to prevent or decrease abrasion of gypsum cast during removal is by separating the cast from impression before hydrocolloid dehydration that occurs due to dried alginate (7). In some occasions in clinical and https://doi.org/10.26477/jbcd.v33i3.2949 mailto:suha.f.dulaimi@gmail.com J Bagh College Dentistry Vol. 33(3), September 2021 The effect of contact 19 laboratory dental practice delay separation of gypsum cast from alginate impression after complete setting could happened. Gypsum cast and die that are used in the production of dental restorations should give strength, resistance to scratch and accurate dimensional stability. The cast model's dimensional stability is influenced by the alginate water absorption and release as well as method of handling the impression by the clinician, in addition to contact time between alginate impressions and the gypsum's product (5). The gypsum setting time (the contact time between alginate impression and poured gypsum mix) should be observed to ensure the ideal properties of final cast model. Compatibility between alginate impression and gypsum product are also important for quality of cast model (7). A previous study investigated alginate impression storage time and recommended that impression must be poured immediately (8). Few information about the effect of contact time between alginate and gypsum , others recommended separating cast from alginate impression before dehydration of alginate started that have detrimental effect on cast quality (9, 5). The aim of the present study was to evaluate the effect of different contact time (1hr., 6hr. 9hr.) between alginate impression material and Type III dental stone on surface details reproduction, surface roughness and hardness of stone cast. MATERIALS AND METHODS Alginate impressions (Zhermack Badia Polesine, Italy) were evaluated with dental stone type III (Zhermack Badia Polesine, Italy) at different contact time intervals (1hr., 6hr. 9hr.) Surface details reproduction:- A brass cylindrical block (Figure1) was fabricated with three reference lines on surface 20 μm,50 μm & 75μm in (width and depth). They were 2.5mm apart from each other according to ISO 1563 (10) , the circular block had dimensions of 25mm in width and15 mm in length. Figure 1: The brass cylindrical block constructed according to ISO 1563 The 30 special trays were fabricated from chemical cure acrylic resin (Superacreyl plus, Spofa dental, Markova, Czech Republic). Two wax sheets (2.8 mm) in width were orderly lined a round the cylinder, then acrylic dough was applied above wax sheets to create special tray to carry alginate impression. The special trays were completed and perforated after setting of materials to prepare the samples. The manufacturer instructions were followed when alginate was mixed manually for 45 sec. and applied carefully in a special tray. Then, the top of the cylindrical brass was covered by a glass plate (weight 1 kg) (11). Setting of the impression material took 5 minutes before its removal from the cylindrical brass test. A cotton gauze moisten with ethanol was used to wipe the surface of the cylindrical test block, then washed with distilled water and kindly dried with compressed air before fabrication of each sample. Mixing of dental stones was done in accordance with guidelines of the manufacturer. After that, stone mix was poured in alginate impression for cast model production. The models were separated from impression after experimental time intervals (1 hour, 6 hours , 9 hours) Figure 2. Figure 2: Custom made perforated tray and separated cast model J Bagh College Dentistry Vol. 33(3), September 2021 The effect of contact 20 Group A, the control group, which contained (30 casts) were separated after an hour, Group B, the study group, which contained (30 casts): were separated after 6 hours, and Group C, which contained (30 casts) were removed following 9 hours. Each group was then scanned at 1200 dpi resolution using a flatbed scanner (Genix, China), using a template as a guide on the surface of the scanner. The scanned images have been saved in jpg format. Evaluation of the surface detail reproduction was done by an operator who examined the images of specimens on computer monitor after x10 magnification and graded them according to scoring system from (1 to 4). The definition of the ratings was determined as follows: 1) Sharp detail continuous lines 2) Continuous lines, but with sharpness loss 3) Line details deterioration 4) Rough appearance, with loss of line continuity (12, 13). Surface roughness Testing of the surface roughness was done by using a profilometer (10) (Talysurf 4 profilometer, Taylor Hobson, USA).The surface of ten specimens for each time interval was measured in 3 different locations for each specimen then the average of mean roughness was calculated to each time interval. Surface hardness The surface hardness was assessed by making indentation using Shore D hardness digital tester (Digital hardness tester HT_6510C Shore C Shenzhea Handsome Technology G. Ltd. China) which is suitable for stone Type III material. Each specimen surface was exposed to three indentations in various positions, and the average hardness number of each specimen was calculated in separate manner, and the same process was performed for the other samples for each time interval. Surface hardness and roughness results were analyzed with descriptive statistic, one way ANOVA and Games-Howell post hoc test. Results of surface detailed reproduction were converted into percentage and compared using Chi-Square test. RESULTS The descriptive statistics and Chi-Square test for surface detail reproduction of the 30 specimens was shown in table (1). The results showed that 1 hour time interval had 80% score 2 and 20% score 3. However, cast separated at 6 hours and 9 hours' time intervals showed 50% score 1 and 50% score 2 and eventually gave the best result. Chi-Square test showed significant differences among the groups examined (p<0.05). Table 1: Distributions of surface details reproduction test among time groups with Chi-Square test Surface details Reproduction (Scores) Time groups Chi- Square Test One hour Six hours Nine hours One N 5 5 0.041 S % 50% 50% Two N 8 5 5 % 80% 50% 50% Three N 2 % 20% Total N 10 10 10 % 100% 100% 100% Table 2 showed the descriptive statistics and one way ANOVA tests of surface roughness. The results showed that the lowest mean for surface roughness was registered at 9 hours which was (2.544), while the highest mean value was related to the 6 hours (3.209). The one way ANOVA test between the studied groups found highly significant differences (p<0.01). Games-Howell test Table 3 showed highly significant (P<0.01) comparing one hour with six hours and nine hours, also highly significant (P<0.01) comparing six hours with nine hours. Table 2: Mean distributions of surface roughness test among time groups with ANOVA test Table 3: Games-Howell test for surface roughness Table 4 showed the descriptive statistics and one way ANOVA test of surface hardness. The results showed that the highest mean value for hardness was registered at 9 hours which was (61.83), while the lowest mean value was related to the 6 hour Time groups N Mean Std. D Std. E Range ANOVA test Min. Max. One hour 10 3.209 0.001 0.0003 3.207 3.210 0.00 HS Six hours 10 3.858 0.098 0.031 3.731 3.951 Nine hours 10 2.544 0.096 0.030 2.430 2.651 Time groups Games-Howell test (P-value) One hour Six hours P=0.00 Highly sign. (P<0.01) Nine hours P=0.00 Highly sign. (P<0.01) Six hours Nine hours P=0.00 Highly sign. (P<0.01) J Bagh College Dentistry Vol. 33(3), September 2021 The effect of contact 21 (49.27). One way ANOVA test between the studied groups demonstrated highly significance differences (p<0.01). Table 4: Mean distributions of surface hardness test among time groups with ANOVA test Table 5: Games- Howell test for surface hardness Time groups Games-Howell test (P-value) One hour Six hours P=0.00 Highly sign. (P<0.01) Nine hours P=0.00 Highly sign. (P<0.01) Six hours Nine hours P=0.00 Highly sign. (P<0.01) Games-Howell test table (5) showed highly significant (P<0.01) comparing one hour with six hours and nine hours, also highly significant (P<0.01) comparing six hours with nine hours. DISCUSSION The immediate pouring of Alginate impressions could not always be achieved in everyday dental practices. Therefore, impressions are stored in sealed bags or wrapped in paper towels with suitable humidity. Without achieving such requirements, properties of the materials will be affected (14). However, if the separation of a cast from an impression is delayed, it will cause some model cast properties to be deteriorated (5). This study was conducted to determine the probable changes in cast model properties following the varying contact time between dental stone type III and alginate impressions. The selected time intervals for the present study (1, 6, 9hr.) justified because previous study by Matqezan et al. 2012 (7) not recommended 12hr. time period of contact between alginate and gypsum cast because it influences the quality of gypsum cast. The null hypothesis was rejected, the results of different periods for surface details reproduction, surface roughness and hardness showed differences among the three experimental time intervals. The surface details reproduction as in table (1) increased with the increase in contact time and this was observed at 6 and 9 hours' time interval which gave 50% at score 1 and score 2. However, 1 hour time interval resulted in 80% score 2 and 20% score 3. Improvement in detail reproduction with prolonged contact time may be related to elevation in surface hardness and improved smoothness with prolonged contact time that is concluded in present study. These results were in agreement with….. (15) but disagreed with…. (5) who stated that surface details decreased with the increase in contact time and also disagreed with (11) …….who revealed that paste type alginate impression materials and type III dental stone materials are compatible with each other and can reproduce surfaces details efficiently much better than powder type alginate with type III dental stone material. However, surface roughness decreased when contact time increased to 9 hours and raised in 1 hour and 6 hours contact time as shown in table (2). The causative factor for this finding may be due to dehydration of stone due to prolonged contact time between the alginate impressions and the stone cast (7). A significant elevation in the surface hardness with increased contact time was recorded may be due to excess water evaporation from stone cast, in addition to smoothness of stone cast caused by decreased surface roughness with prolonged contact time found in present study . Results demonstrated that there was a decrease in the scratches depth when there was an increase in the contact time as in table (4). These results were similar to the findings of Ibrahim et al. 2015 (5). CONCLUSION Delay separation of stone cast from alginate impression affect surface properties variably: 1-Surface detailed reproduction significantly improved at 6hr. and 9hr. time interval. 2- Surface roughness reduced with increased contact time up to 9hr. 3-However surface hardness increased significantly up to 9hr. Conflict of interest: None. 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Compend Contin Educ Dent. 2017 Jun;38(6):e1-e4. المستخلص قابلة للعكس تستخدم على نطاق واسع في طب األسنان. يمكن أن يكون لوقت الخلفية: مادة االنطباع الجيني هي مادة غرواني مائي غير المختلفة التالمس فترات تأثير تقييم هو الدراسة هذه من الهدف الجبس. قالب خصائص على ضار تأثير والجبس الجينات بين التالمس ت وحجر األسنان من النوع الثالث على الخصائص السطحية للحجر المصبوب.المواد والطرق: كانت الفترات الزمنية النطباعات األلجينا ساعات. تم تقييم الخصائص السطحية للصب الحجري وهي إعادة إنتاج تفاصيل السطح والصالبة 9ساعات و 6المختبرة ساعة واحدة و . تم قياس خشونة ISO 1563باستخدام كتلة اختبار أسطوانية من النحاس األصفر وفقًا لمعيار والخشونة. تم تحديد استنساخ تفاصيل السطح (.Shore Dالسطح بمقياس بروفيلومتر وتم قياس الصالبة بواسطة مقياس التحمل ) نما تقل خشونة السطح معنوياً ساعات. أظهر نتائج أفضل. بي 9ساعات و 6( ، عند P <0.05النتائج: أظهر التكاثر التفصيلي فرقاً معنوياً ) (p <0.01( مع زيادة زمن التالمس. ومع ذلك ، زادت صالبة السطح بشكل كبير )p <0.01 مع زيادة وقت التالمس.االستنتاجات: زيادة ) ومع ذلك ، . 2والنتيجة 1٪ في الدرجة 50ساعات( مما يعطي 9، 6استنساخ تفاصيل السطح مع زيادة وقت التالمس وقد لوحظ ذلك في ) . خشونة انخفض عند زيادة وقت التالمس بين حجر األسنان من النوع الثالث 3٪ درجة 20و 2٪ درجة 80أظهر الفاصل الزمني لمدة ساعة .وانطباع األلجينات بينما تحسنت الصالبة بشكل ملحوظ مع زيادة وقت التالمس Articles Published by Journal of Baghdad College of Dentistry is licensed under a Creative Commons Attribution 4.0 International License.