Silicone Rubber Impression Research Articles

Clinical comparative study on the accuracy of palatal rugae in models obtained by different impression materials and intraoral scanning.

Palatal rugae are frequently used in the evaluation of tooth movement after treatment in orthodontics and as a stable region in superimposition. It is important to note that the impression method and material used to record the rugae region affect the accuracy of the impression. The aim of this study is to compare the accuracy of palatal rugae, in three-dimensional (3D) by employing both conventional and digital impression methods. In this study, 22 patients (12 females, 10 males) mean age of 13.5 ± 1.7years old were selected with complete permanent dentition. Three different impressions were taken from the maxillae of the patients: conventional impression using silicone rubber impression material, conventional impression using alginate impression material, and optical impression using an intraoral scanner. The impressions' digital data were analyzed by the GOM Inspect (Version 2018, Braunschweig, Germany), a 3D analysis software. The Root Mean Square (RMS) values of the total ruga region were evaluated in this software. The data were statistically analyzed using the Jamovi program. The Kruskal-Wallis test and Mann-Whitney U test were performed due to the non-normal distribution of the data. There is no statistically significant difference between the comparison points of the right and left rugae's medial and lateral points and total rugae regions' RMS values. Although there was no statistically significant difference, the total RMS values of alginate and digital scan measurements showed closer results than the RMS values of silicone and digital scan measurements. The study found that there was no statistically significant difference in the total RMS values of the ruga region between traditional and digital impression methods. The treatment period in orthodontics is long. Different impression materials and methods can be used for diagnostic, mid-treatment, and final impressions. For superimpositions and treatment and post-treatment palatal ruga evaluations, traditional and digital impression methods are clinically acceptable and can be used as alternatives to each other.

Synthesis of a novel injectable alginate impression material and impression accuracy evaluation.

This work aimed to synthesize a novel injectable alginate impression material and evaluate its accuracy. Certain proportions of sodium alginate, trisodium phosphate dodecahydrate, potassium fluorotitanate, diatomaceous earth, and other ingredients were dissolved in water and mixed evenly with a planetary centrifugal mixer to obtain a certain viscosity base paste. Certain proportions of calcium sulfate hemihydrate, magnesium oxide, glycerin, and polyethylene glycol (PEG) 400 were mixed evenly with a planetary centrifugal mixer to obtain the reactor paste with the same viscosity as the base paste. The base and reactor pastes were poured into a two-cylinder cartridge at a 2∶1 volume ratio. A gun device was used to accomplish mixing by compressing materials into a mixing tip. The samples were divided into three groups: injectable alginate impression materials (IA group) as the experimental group, and Jeltrate alginate impression materials (JA group) and Silagum-putty/light addition silicone rubber impression materials (SI group) as the two control groups. Scanning electron microscopy (SEM) showed that the injectable alginate impression materials had a denser structure and fewer bubbles than the commercial alginate impression material. The accuracy of the three kinds of impression materials was evaluated by 3D image superposition. The deviations between the three test group models and the standard model (trueness) were 49.58 μm±1.453 μm (IA group), 54.75 μm±7.264 μm (JA group), and 30.92 μm±1.013 μm (SI group). The deviations of the models within each test group (precision) were 85.79 μm±8.191 μm (IA group), 97.65 μm±11.060 μm (JA group), and 56.51 μm±4.995 μm (SI group). Significant differences in trueness and precision were found among the three kinds of impression materials (P<0.05). The accuracy of the new injectable alginate impression material was better than that of the traditional powder-type alginate impression material but worse than that of the addition silicone rubber impression materials. The novel injec-table alginate impression material demonstrated good operation performance and impression accuracy, showing broad application prospect.

Comparison of conventional impression making and intraoral scanning for the study of unilateral cleft lip and palate.

Patients with cleft lip and palate (CLP) encounter various problems, including disorders related to feeding, esthetics, and pronunciation. We compared two impression methods, conventional impression making and intraoral scanning, to study unilateral cleft lip and palate (UCLP). Patients with UCLP (n=7) were selected, and palatal impressions were taken by two steps: (1) impressions were obtained using an addition silicone rubber impression material, and a plaster model was prepared and (2) optical impressions were obtained using a desktop three-dimensional (3D) scanner and stereolithography (STL). Data were generated by two impression system combinations through STL. The results were analyzed using the Kruskal-Wallis or Mann-Whitney U test. There were no significant differences in the dimensions of the models between both groups. The measured depth of the alveolar cleft defects was deeper in the plaster model group (STL) than in the intraoral scanner group (STL). Digital models may prevent the risk of aspiration and respiratory disorders by using impression materials for preoperative jaw treatment of newborns and infants. We compared the results of both impression methods in the same patient and found that a shift to the 3D printer model is a safe alternative for preoperative jaw correction, as evidenced from the amount of tissue displaced due to the pressure applied during impression taking. In the future, we would like to conduct clinical research with a larger sample size of CLP patients to further corroborate these findings.

Development of novel hydrophilic and antibacterial silicone rubber impression material for dental application.

This investigation aimed to develop a novel hydrophilic and antibacterial silicone rubber impression material for dental application. The basic formula of the new silicone rubber was determined on a preliminary study, and 6% polyether modified silicone oil was added as wetting agent to provide the hydrophilicity. No-vel nano-antibacterial inorganic fillers containing quaternary ammonium salt with long chain alkyl were incorporated into the hydrophilic silicone rubber impression materials at a mass fraction of 0%, 1%, 2%, 3%, 4%, or 5%. A commercial silicone rubber impression material was used as control. The mechanical properties, wettability, detail reproducibility, dimensional stability, and mixing time of silicone rubber materials were measured. Thin-film adhesion method and cell counting kit-8 method were used to detect the antibacterial property and cytotoxicity. Scanning electron microscopy (SEM) was chosen to observe the micromorphology of the novel silicone rubber. When the content of antibacterial filler exceeded 4%, the mechanical properties of the new silicone rubber decreased significantly (P<0.05). Compared with those of the control group, the contact angle and linear size change rate of different groups had no significant change at different time nodes, and the detail reproducibility was intact (P>0.05). The addition of antibacterial fillers had no significant effect on the mixing time (P>0.05). Adding 4% antibacterial fillers could result in the antibacterial rate of 95.26%, showing good antibacterial properties. No significant difference was found in the cytotoxicity of all groups (P>0.05). The SEM pictures of the cross section of the silicone rubber sample showed that the fillers had good compatibility with the silicone rubber matrix and distributed in the matrix evenly. A novel silicone rubber impression material containing 6% polyether modified silicone oil could obtain promising hydrophilic and antibacterial properties after being added with 4% antibacterial inorganic fillers.

Clinical applicational comparison of digital impression and silicon rubber impression technique in posterior implant-supported single crown restoration

Objective: To investigate the clinical effect and satisfaction of partially edentulous patients restored with posterior implant-supported single crown by digital impression technique and traditional silicon rubber impression, in order to provide clinical reference. Methods: Sixty-four partially edentulous patients who visited the Department of Prosthodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University between March 2018 and January 2021 were enrolled. There were 31 male and 33 female, and the age of the group of patients was (49.3±13.3) years. The 113 implants placed in this group of patients were divided into digital impression group (n=70) and silicone rubber impression group (n=43) according to different impression techniques, and were restored with screw-retained full zirconia single crown, and the patients were followed up for 3-36 months after treatment. The implant survival rate, upper prosthesis, peri-implant soft tissue status, marginal bone loss and patients satisfaction were recorded to evaluate the clinical effects of two impression techniques in posterior implant-supported single crown. Results: In sixty-four patients, digital impression accounted for 62% (40/64), and silicon rubber impression accounted for 38% (24/64), the survival rate of 113 implants was 100% (113/113). The prevalence of interproximal contact loss, food impaction and mechanical complication of the upper full zirconia single crown restorations were 22.7% (41/181), 8.0% (9/113) and 2.7% (3/113) separately. All the mechanical complications were abutment screw loosening. All patients maintained good oral hygiene status, the incidences of peri-implantitis and peri-implant mucositis were 0.9% (1/113) and 4.4% (5/113) respectively. The marginal bone loss was (0.24±0.11) mm. The median of satisfaction visual analogue scale score in patients was 9-10, but no statistically significant differences of all the above results were observed between the two impression techniques (P>0.05). Conclusions: The clinical effect of partially edentulous patients restored with posterior implant-supported single crown using two different impression techniques is good and the satisfaction of patients is high, but the long-term clinical effect remains to be further observed.

Effect of impression holding time and tray removal speed on the dimensional accuracy of impressions for artificial abutment tooth inclined.

Oral scanners allow dental impressions to be taken in a short time without the use of an impression material. However, it has been noted that high impression accuracy cannot be obtained in cases where the abutment is inclined or in cases where the span is long. Consequently, in daily clinical practice, impressions are often created using silicone impression material. When taking an impression using silicone impression material, the curing time or the removal time of the impression material are often based on the intuition of the dental staff. This study investigated the effects of impression holding time and impression tray removal speed on the dimensional accuracy of impressions. A specimen with an abutment inclined 30° to the removal direction of an impression was prepared. Four types of silicone rubber impression materials were used. Impressions were taken with two levels of holding time and two levels of removal speed using an autograph. The diameter of stone models was measured at 3, 6, and 9mm from the baseline of each. The height of the inclined and opposite sides was also measured. Two-way analysis of variance was used to analyze data regarding the assessment of the effects of holding time and tray removal speed. The reproducibility of the impressions was affected by the volume of undercut caused by the inclined abutment. For a large undercut, longer holding times and faster tray removal speeds are recommended to reduce the deformation of silicone rubber impressions.

Effect of certain disinfecting solutions and surfactant on the wettability of silicone rubber impression materials

Back ground: All dental impressions should be disinfected before pouring to controlcross contamination but disinfection may affect impression wettability. This studyevaluated the effect of disinfection and the use of surfactant agent on thewettability of some silicone impression materials by contact angle registration ofthe gypsum slurry on flat surfaces of the impressions.Materials and methods: addition silicone regular body –automixing type- andcondensation silicone (light body)with two types of disinfecting solutions 0.2%chlorhexidine gluconate and 1% povidone iodine for two disinfecting times andone surfactant agent (soap) were used in this study. Three treatment regimes wereinvestigated: The first group of impression materials specimens was exposed tosaliva for 5 minutes (control group). Second group of specimens was exposed tosaliva then to disinfectant agents, and third group of specimens was exposed tosaliva, disinfectants and surfactant agent (experimental groups), a computerizedphotographic procedure was used to measure the wettability of the specimens.Statistical analysis was performed by using t-est at p&lt;0.05.Results: the results revealed that treatment with 0.2% chlorhexidine gluconate as adisinfectant alone or when tested with the surfactant improved the wettability ofaddition and condensation silicones at 30min. disinfection time ,but surfactantcoating of disinfected condensation silicone produced a significant increase of themean values at 60min. disinfection time. While treatment with 1% povidoneiodine disinfectant increased the mean contact angles for both addition andcondensation silicones significantly. Same result was seen when povidone iodinewas used in combination with the surfactant.Conclusion: disinfection with 0.2% chlorhexidine gluconate produced a high-energyimpression surfaces for both addition and condensation silicones.

Photoelastic analysis of the influence of prosthetic material on the stress distribution in bone around implant

Objective: To provide a reference for a suitable alternative treatment choice for implant-supported prostheses, and to explore the influence of 3 types of prosthetic material on the stress distribution around implant. Methods: The implant-abutment analogs were embedded individually into photoelastic resin blocks, which were medical pure titanium castings reproducing the surface and outline of implant (diameter 4.3 mm, length 11.5 mm) and esthetic abutment (regular profile, 1 mm). The prostheses were divided into 3 groups according to the type of prosthetic material. Each group consisted of 5 samples. The samples of composite resin ceramic and zirconia group were milled by chair-side computer aided design and computer aided manufacture (CAD/CAM) system. The samples of porcelain-fused-to-metal crown group were made manually and a pre-arranged silicone rubber impression of CAD/CAM crown would guide to shape the veneer porcelain. Each set was submitted to a 300 N compressive load axially or obliquely (75°). The stress value in the peri-implant bone at the level of the neck, neck1/3, middle1/3 and root1/3 of the sections (0.5, 1.5, 2.5, 3.5 mm) from implant was analyzed by digital photoelasticity, and the stress cushioning effect of 3 types of prosthetic material was comprehensively evaluated. Results: The time spent reaching the stress peak of composite resin ceramic group [(1.58±0.08) s, axially; (2.75±0.21) s, obliquely] was larger than that of the zirconia group [(1.40±0.12) s, axially; (2.30±0.25) s, obliquely] (P<0.05) under the same download mode. Although there were no significant differences in equivalent stress values of the measurement points among the three groups (P>0.05), a downward trend of equivalent stress values of composite resin ceramic group was observed compared to zirconia group, regardless of load type. When loaded obliquely, the highest degree of stress concentration at the level of the neck of implant were found in the porcelain-fused-to-metal crown group. Conclusions: Within the limitations of this study, composite resin ceramic was more beneficial to the biomechanical behavior of implant in stress buffer compared to zirconia.

Dimensional changes in stone models simulating full crown preparations with adjacent teeth resulting from long-term immersion of medium-viscosity addition-type silicone rubber impressions in disinfectant solutions.

If impression materials could be immersed in disinfectant solutions for a longer period, then this form of disinfection would be easier to incorporate into dental preparation procedures. This study investigated the dimensional changes in stone models resulting from immersion of medium-viscosity hydrophilic addition-type silicone rubber impression material in disinfectant solutions for 30 min and 24 h. Impressions of a master die designed to simulate a full crown preparation with adjacent teeth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde solutions. The dimensional changes in the mesiodistal and buccolingual dimensions in the stone models were then measured using a three-dimensional coordinate system. It was found that the dimensional changes in the stone models caused by immersion of the impression materials were less than 15 μm. Immersion in 2% glutaraldehyde or 0.55% ortho-phthalaldehyde for 24 h was as clinically acceptable for medium-viscosity hydrophilic addition-type silicone rubber impressions as immersion for 30 min.

Influence of X-ray beam angulations on the detection of horizontal root fractures

Aims: The aim of this study was to evaluate the variation of vertical angle for detection of fractures. Materials and Methods: Twenty-five (25) single-rooted premolar teeth were divided into two groups, fractured teeth (n = 15) and non-fractured teeth (n = 10). Artificially fractured teeth were classified according to location, number of fragments, and direction of fracture line: Horizontal, oblique, or complex. The tooth fragments were juxtaposed with cyanoacrylate, and the specimens (fractured and non-fractured) were placed individually in the dental alveolus of a human jaw with the aid of silicone rubber impression material and submitted to eight periapical radiographs in a digital sensor with a vertical range of 10 degrees (−40, −30, −20, −10, 0, +10, +20, +30). Three examiners evaluated the characteristics of the fractures and their correlation with the radiographic diagnosis (perceived or not) by varying the vertical angle. Statistical Analysis: Descriptive analysis was performed through the analytical comparison and Kappa test inter-examiner. Results: Among the three examiners, inter-examiner Kappa value was 0.536. The radiographic identification of root fracture in the 15 prepared samples was 60% (nine) at angle 0, and at the angles of +10, −10, and −20, it was less than 50%. Conclusions: Multiple radiographs with variations of vertical angle are fundamental to facilitate the diagnosis of horizontal root fractures in premolars.

Surface porosity of stone casts resulting from immersion of addition silicone rubber impressions in disinfectant solutions.

This study investigated the effects of immersion of addition silicone rubber impressions in disinfectant solutions on the surface porosity of the resulting stone casts. Five brands of type 2 and 3 addition silicone rubber impression materials and one brand of type 4 dental stone were used. Impressions of a master die designed to simulate an abutment tooth were immersed in disinfectant for 30 minutes. The disinfectants used were 2% glutaraldehyde solution and 0.55% ortho-phthalaldehyde solution. The surface porosities of stone casts obtained from two brands of impression materials immersed in disinfectant for 30 minutes were determined. Results suggest that impression materials immersed in disinfectant solutions need sufficient time before pouring into dental stone.

Evaluation of different approaches for using a laser scanner in digitization of dental impressions

PURPOSEThis study aimed to investigate the potential clinical application of digitized silicone rubber impressions by comparing the accuracy of zirconia 3-unit fixed partial dentures (FPDs) fabricated from 2 types of data (working model and impression) obtained from a laser scanner.MATERIALS AND METHODSTen working models and impressions were prepared with epoxy resin and vinyl polysiloxane, respectively. Based on the data obtained from the laser scanner (D-700; 3Shape A/S, Copenhagen, Denmark), a total of 20 zirconia frameworks were prepared using a dental CAD/CAM system (DentalDesigner; 3shape A/S, Copenhagen, Denmark / Ener-mill, Dentaim, Seoul, Korea). The silicone replicas were sectioned into four pieces to evaluate the framework fit. The replicas were imaged using a digital microscope, and the fit of the reference points (P1, P2, P3, P4, P5, P6, and P7) were measured using the program in the device. Measured discrepancies were divided into 5 categories of gaps (MG, CG, AWG, AOTG, OG). Data were analyzed with Student's t-test (α=0.05), repeated measures ANOVA and two-way ANOVA (α=0.05).RESULTSThe mean gap of the zirconia framework prepared from the working models presented a narrower discrepancy than the frameworks fabricated from the impression bodies. The mean of the total gap in premolars (P=.003) and molars (P=.002) exhibited a statistical difference between two groups.CONCLUSIONThe mean gap dimensions of each category showed statistically significant difference. Nonetheless, the digitized impression bodies obtained with a laser scanner were applicable to clinical settings, considering the clinically acceptable marginal fit (120 µm).

Comparison of the surface roughness of gypsum models constructed using various impression materials and gypsum products

Background/purposeThis study compared the surface roughness of gypsum models constructed using various impression materials, gypsum products, and storage times before repouring. Materials and methodsThree alginate impression materials, four commercial silicone impression materials, and three types of gypsum product (MG crystal rock, Super hard stone, and MS plaster) were used. Impression materials were mixed and poured into five plastic rings (20 mm in diameter and 2 mm high) for each group, and the surfaces of the set gypsum product models of 63 groups, which were poured immediately, and 1 hour and 24 hours later, were assessed using a surface roughness tester. One-way ANOVA and Bonferroni's comparison tests were used for the statistical analyses. ResultsThe surface roughness: (1) was greater for most specimens constructed from alginate impression material (2.72 ± 0.45–7.42 ± 0.66 μm) than from silicone impression materials (1.86 ± 0.19–2.75 ± 0.44 μm); (2) differed with the type of gypsum product when using alginate impression materials (surface roughness of Super hard stone > MG crystal rock > MS plaster), but differed little for silicone impression materials; and (3) differed very little with the storage time before repouring. ConclusionThe surface roughness of stone models was mainly determined by the type of alginate impression material, and was less affected by the type of silicone rubber impression material or gypsum product, or the storage time before repouring.

Dimensional changes in stone casts resulting from long-term immersion of addition-type silicone rubber impressions in disinfectant solutions

There is a concern that long-term immersion of impressions in disinfectant solutions may cause changes in the dimensions of the resulting stone casts. This study investigated the dimensional changes in stone casts resulting from immersion of five brands of addition-type silicone rubber impressions in disinfectant solutions for 30 min and 24 h. Impressions of a master cast designed to simulate an abutment tooth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde. The diameter of the stone cast was measured using a laser scan micrometer. For four brands of impression materials, 30-min immersion in disinfectant solutions produced no dimensional changes in the stone casts. For four brands of impression materials, 24-h immersion caused a significant decrease in the stone cast dimensions.

Fingerprint maintenance, a new dermatoglyphic mechanism

Although dermatoglyphic structure has been mechanistically related to fingerprint formation, a separate mechanism for fingerprint maintenance must exist or prints would be lost by friction. To test this prediction and study its operation. Palmar and plantar prints were studied visually and by silicone rubber impressions after surface removal by abrasives, scalpel and adhesive stripping, using surface staining to stage surface loss. All depths and methods of surface removal left the print ridges intact visually and in silicone rubber impressions. When abrasion was applied only to ridge surfaces, keratinocytes were lost concomitantly in the troughs between them, leaving ridge structure intact. When palmar or plantar stratum corneum was cleaved or peeled apart, the separated layer followed the undulating ridges and troughs, thus maintaining the normal print pattern. A new mechanism of fingerprint maintenance was predicted theoretically and confirmed experimentally. It is achieved by an organization of the print corneum which ensures its continuous separation over the whole of the undulating print surface, even when friction is applied only to the tips of the ridges; the preferred route of separation of print keratinocytes runs up and down the print ridges and troughs and thereby maintains them, and is presumably ordered by predominantly horizontal intercellular attachments between print keratinocytes. The reason print maintenance has been missed until now may be that dermatoglyphic researchers have little interest in fingerprint disguise, while those who are interested in disguise have little interest in research.

New virtual orthodontic treatment system for indirect bonding using the stereolithographic technique

The purpose of this article is to introduce a new virtual orthodontic treatment (VOT) system, which can be used to construct three-dimensional (3D) virtual models, establish a 3D virtual setup, enable the placement of the virtual brackets at the predetermined position, and fabricate the transfer jig with a customized bracket base for indirect bonding (IDB) using the stereolithographic technique. A 26-year-old woman presented with anterior openbite, crowding in the upper and lower arches, and narrow and tapered upper arch, despite having an acceptable profile and balanced facial proportion. The treatment plan was rapid palatal expansion (RPE) without extraction. After 10 days of RPE, sufficient space was obtained for decrowding. After a 10-week retention period, accurate pretreatment plaster models were obtained using silicone rubber impression. IDB was performed according to the protocol of the VOT system. Crowding of the upper and lower arches was effectively resolved, and anterior openbite was corrected to normal overbite. Superimposition of the 3D virtual setup models (3D-VSM) and post-treatment 3D virtual models showed that the latter deviated only slightly from the former. Thus, the use of the VOT system helped obtain an acceptable outcome in this case of mild crowding treated without extraction. More cases should be treated using this system, and the pre- and post-treatment virtual models should be compared to obtain feedback regarding the procedure; this will support doctors and dental laboratory technicians during the learning curve.

Inscriptions, filing, grinding and polishing marks on the bronze weapons from the Qin Terracotta Army in China

This paper is concerned with the inscriptions and finishing marks present on the surfaces of the thousands of bronze weapons recovered together with the Terracotta Army at the mausoleum complex of Qin Shihuang, the First Emperor of China (259–210BC). After utilising the textual information from the inscriptions to reconstruct aspects of labour organisation and political control during the production of the weapons, the work concentrates on documenting and explaining the techniques employed to produce the inscriptions, to file casting imperfections, and to obtain the smooth, shiny and sharp finish still noticeable on many of the weapons. Silicone rubber impressions of surface features of swords, lances, crossbow triggers and arrows were examined under the scanning electron microscope (SEM), and these observations were supplemented with examination of the artefacts under the stereomicroscope and the SEM. The evidence indicates the use of a variety of chisels for making the inscriptions, and of files for removing excess metal from surfaces. In addition, the grinding and polishing marks demonstrate the large-scale, systematic use of rotary wheels to achieve an ideal final polish. These findings are contextualised in the broader history of Chinese metallurgy, with special attention to the emergence of iron tools and of rotary mechanical devices.

Direct 3-D morphological measurements of silicone rubber impression using micro-focus X-ray CT

Three-dimensional computer models of dental arches play a significant role in prosthetic dentistry. The microfocus X-ray CT scanner has the advantage of capturing precise 3D shapes of deep fossa, and we propose a new method of measuring the three-dimensional morphology of a dental impression directly, which will eliminate the conversion process to dental casts. Measurement precision and accuracy were evaluated using a standard gage comprised of steel balls which simulate the dental arch. Measurement accuracy, standard deviation of distance distribution of superimposed models, was determined as +/-0.050 mm in comparison with a CAD model. Impressions and casts of an actual dental arch were scanned by microfocus X-ray CT and three-dimensional models were compared. The impression model had finer morphology, especially around the cervical margins of teeth. Within the limitations of the current study, direct three-dimensional impression modeling was successfully demonstrated using microfocus X-ray CT.

CLIMATE CONTROL BASED ON STOMATAL BEHAVIOR IN A SEMI-CLOSED GREENHOUSE SYSTEM 'AIRCOKAS'

Climate control in a greenhouse is usually based on maintaining a specific air temperature, sometimes adjusted to the available light level or the cost of energy. According to theoretical physiological knowledge optimal photosynthesis depends on the behavior of the stomata. No existing climate control strategy is based on measurement or modeling of the stomatal opening. A soft-sensor based on a crop energy-balance equation was developed. The validation of this sensor was started, but the method using a porometer and a silicone rubber impression proved to be inappropriate. A climate control strategy for stomatal opening based on the use of a high pressure misting system, an energy-balance equation and adjusted ventilation window control was developed. This system with the name `Aircokas? was introduced in commercial greenhouse operations and used for various crops. A new approach for the representation of stomatal conductance is suggested

Dimensional Accuracy of Dies and Fit of Cast Crowns Obtained from Agar/Alginate Combined Impressions and Addition Silicone Rubber Impressions

Dimensional Accuracy of Dies and Fit of Cast Crowns Obtained from Agar/Alginate Combined Impressions and Addition Silicone Rubber Impressions