Assessment of dimensional stability of novel VPES impression material at different time intervals with standard disinfectants.

BACKGROUND: Vinyl polyether silicone (VPES) is a novel impression biomaterial made of a combination of vinyl polysiloxane (VPS) and polyether (PE). Thus, it is significant to assess its properties and behaviour under varied disinfectant test conditions. This study aimed to assess the dimensional stability of novel VPES impression material after immersion in standard disinfectants for different time intervals. METHODS: Elastomeric impression material used -medium body regular set (Monophase) [Exa'lence GC America]. A total of 84 Specimens were fabricated using stainless steel die and ring (ADA specification 19). These samples were distributed into a control group (n=12) and a test group (n=72). The test group was divided into 3 groups, based on the type of disinfectant used - Group-A- 2% Glutaraldehyde, Group-B- 0. 5% Sodium hypochlorite and Group-C- 2% Chlorhexidine each test group was further divided into 2 subgroups (n=12/subgroup) based on time intervals for which each sample was immersed in the disinfectants - subgroup-1- 10 mins and Subgroup 2- 30 mins. After the impression material was set, it was removed from the ring and then it was washed in water for 15 seconds. Control group measurements were made immediately on a stereomicroscope and other samples were immersed in the three disinfection solutions for 10 mins and 30 mins to check the dimensional stability by measuring the distance between the lines generated by the stainless steel die on the samples using a stereomicroscope at x40 magnification. RESULTS: The distance measured in the control group was 4397.2078 µm and 4396.1571 µm; for the test group Group-A- 2% Glutaraldehyde was 4396.4075 µm and 4394.5992 µm; Group-B- 0. 5% Sodium hypochlorite was 4394.5453 µm and 4389.4711 µm Group-C- 2% Chlorhexidine was 4395.2953 µm and 4387.1703 µm respectively for 10 mins and 30 mins. Percentage dimensional change was in the range of 0.02 - 0.25 for all the groups for 10 mins and 30 mins. CONCLUSIONS: 2 % Glutaraldehyde is the most suitable disinfectant for VPES elastomeric impression material in terms of dimensional stability and shows minimum dimensional changes as compared to that of 2% Chlorhexidine and 0.5% Sodium hypochlorite.

In Vitro Assessment of Dimensional Accuracy of Three Different Types of Interocclusal Recording Materials.

AIM: The aim of the current study was to evaluate the dimensional accuracy of three various interocclusal recording materials. MATERIALS AND METHODS: A total of 90 disc-shaped samples were prepared using polyether paste, wax, and polyvinyl siloxane material with the support of stainless steel die. For the purposes of this investigation, three frequently utilized interocclusal recording materials were chosen, and 30 samples from each material were prepared. Group I: Bite registration using polyether paste; Group II: Bite registration using wax; Group III: Bite registration using polyvinyl siloxane material. No samples were exposed to direct sunlight during storage and were kept at room temperature. Using a 10x universal measuring microscope, each sample disc was examined for the presence of horizontal and vertical lines inscripted in the die. For each of the samples, readings were taken at different time periods of 24, 48, and 72 hours. RESULTS: After 24 hours, the less dimensional changes were found in polyether paste group (0.11 ± 0.07) followed by polyvinyl siloxane material group (0.19 ± 0.04) and wax group (0.25 ± 0.12). After 48 hours, the less dimensional changes were found in polyether paste group (0.34 ± 0.02) followed by polyvinyl siloxane material group (0.42 ± 0.01) and wax group (0.94 ± 0.12). After 72 hours, the least dimensional changes were found in polyether paste group (0.46 ± 0.14) followed by polyvinyl siloxane material group (0.92 ± 0.03) and wax group (1.14 ± 0.09). CONCLUSION: The present study concluded that both the material and time factors had an impact on dimensional stability. The most dimensionally stable group was the polyether paste group, which was followed by the polyvinyl siloxane and wax material groups. CLINICAL SIGNIFICANCE: Interocclusal recording material records the occlusal connection between real or artificial teeth for occlusal rehabilitation planning and for creating removable and fixed dentures. The creation of a clinically acceptable prosthesis is dependent upon the accuracy of the patient's diagnostic or working casts and the interocclusal record. How to cite this article: Sonkesriya S, Subramanian D, Saha P, et al. In Vitro Assessment of Dimensional Accuracy of Three Different Types of Interocclusal Recording Materials. J Contemp Dent Pract 2023;24(12):936-939.

Digital assessment of the accuracy of implant impression techniques in free end saddle partially edentulous patients. A controlled clinical trial.

OBJECTIVES: This in vivo study aims to assess the accuracy of the digital intraoral implant impression technique, the conventional closed-tray impression technique, and open-tray impression techniques in a standardized method of data segmentation along with the best-fit algorithm to overcome the inconsistency of results of previous studies regarding implant impression techniques. MATERIALS AND METHODS: Sixteen implants were placed in eight patients. Each patient has undergone four impression techniques: direct intraoral scanning of the stock abutment, intraoral scanning using a scan body, conventional closed tray impression technique, and the conventional open tray impression technique. The conventional impressions were poured into stone casts with analogues and stock abutments and scanned using a desktop scanner. In intraoral scanning of the scan body, computer-aided design software was used for the replacement of the scan body with a custom-made abutment that is identical to the stock abutment, allowing comparison with the other impression techniques. The deviation in implant position between the groups was measured using special 3D inspection and metrology software. Statistical comparisons were carried out between the studied groups using a one-way analysis of variance (ANOVA) test. RESULTS: The total deviation between groups was compared to the reference group represented by the intraoral scanning of the abutment. The total deviation was statistically significantly different (P = 0.000) among the different studied groups. The mean deviation was recorded as 21.45 ± 3.3 µm, 40.04 ± 4.1 µm, and 47.79 ± 4.6 µm for the intraoral scanning of the scan body, the conventional closed, and open tray, respectively. CONCLUSION: For implant impressions in partially edentulous patients, intraoral oral scanning using a scan body significantly improves scanning and overall accuracy. Regarding conventional impressions, the closed-tray impression techniques showed more accuracy than conventional open-tray impressions. CLINICAL RELEVANCE: Intraoral digital implant impression using scan body offers more accuracy than conventional implant impression techniques for recording posterior implant position in free-end saddle partially edentulous patients.

Digital assessment of properties of the three different generations of dental elastomeric impression materials.

BACKGROUND: This study aimed to compare the dimensional accuracy, hydrophilicity and detail reproduction of the hybrid vinylsiloxnether with polyether and polyvinylsiloxane parent elastomers using modified digital techniques and software. This was done in an attempt to aid in solving the conflict between the different studies published by competitive manufacturers using different common manual approaches. METHODS: A polyether, polyvinylsiloxanes and vinyl polyether silicone hybrid elastomeric impression materials were used in the study. Dimensional accuracy was evaluated through taking impressions of a metallic mold with four posts representing a partially edentulous maxillary arch, that were then poured with stone. Accuracy was calculated from the mean of measurements taken between fixed points on the casts using digital single-lens reflex camera to produce high-resolution digital pictures for all the casts with magnification up to 35×. Hydrophilicity was assessed by contact angle measurements using AutoCAD software. The detail reproduction was measured under dry conditions according to ANSI/ADA Standard No. 19 and under wet conditions as per ISO 4823. A metallic mold was used with three V shaped grooves of 20, 50, and 75 µm width. Specimens were prepared and examination was made immediately after setting using digital images at a magnification of 16×. RESULTS: The hybrid impression (0.035 mm) material showed significantly higher dimensional accuracy compared to the polyether (0.051 mm) but was not as accurate as the polyvinyl siloxane impression material (0.024 mm). The contact angles of the hybrid material before and after setting was significantly lower than the parent materials. With regard to the detail reproduction, the three tested materials were able precisely to reproduce the three grooves of the mold under dry conditions. Whereas, under wet conditions, the hybrid material showed higher prevalence of well-defined reproduction of details same as polyether but higher than polyvinylsiloxane that showed prevalence of details with loss of sharpness and continuity. CONCLUSIONS: The digital technique used could be a more reliable and an easier method for assessment of impression materials properties. The hybridization of polyvinyl siloxane and polyether yielded a promising material that combines the good merits of both materials and overcomes some of their drawbacks.

Comparative assessment of complete-coverage, fixed tooth-supported prostheses fabricated from digital scans or conventional impressions: A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Intraoral scanners have significantly improved over the last decade. Nevertheless, data comparing intraoral digital scans with conventional impressions are sparse. PURPOSE: The purpose of this systematic review and meta-analysis was to determine the impact of impression technique (digital scans versus conventional impressions) on the clinical time, patient comfort, and marginal fit of tooth-supported prostheses. MATERIAL AND METHODS: The authors conducted a literature search based on the Population, Intervention, Comparison, and Outcome (PICO) framework in 3 databases to identify clinical trials with no language or date restrictions. The mean clinical time, patient comfort, and marginal fit values of each study were independently extracted by 2 review authors and categorized according to the scanning or impression method. The authors assessed the study-level risk of bias. RESULTS: A total of 16 clinical studies met the inclusion criteria. The mean clinical time was statistically similar for digital scan procedures (784 ±252 seconds) and for conventional impression methods (1125 ±159 seconds) (P>.05). The digital scan techniques were more comfortable for patients than conventional impressions; the mean visual analog scale score was 67.8 ±21.7 for digital scans and 39.6 ±9.3 for conventional impressions (P<.05). The mean marginal fit was 80.9 ±31.9 µm and 92.1 ±35.4 µm for digital scan and conventional impressions, respectively, with no statistically significant difference (P>.05). CONCLUSIONS: Digital scan techniques are comparable with conventional impressions in terms of clinical time and marginal fit but are more comfortable for patients than conventional impression techniques.

Assessment of Effect of Implant Angulation and Implant Number on the Dimensional Accuracy of Definitive Casts.

AIM: To analyze the impact of implant angulation and implant number on the dimensional accuracy of definitive casts. MATERIALS AND METHODS: Seven definitive casts with implant analogs placed in a triangular pattern were made from dental stone. The groups were as follows: group 1 (control group) all implant analogs perpendicular to the plane of the cast; the center implant analog (implant 2) being at 90° to the plane of the cast in all groups and implant analogs number 1 and 3 arranged in 5°, 10°, or 15° divergence from or convergence to the center implant (implant number 2). Three open-tray impressions of definitive casts were made in each group. Impressions were poured in type IV dental stone. Coordinates in the three planes were measured at the implant analog top surface and the base of the cast using a fine tip measuring stylus. The data were aligned and the angular differences between implant analog vectors from definitive and duplicate casts were calculated in degrees. RESULTS: The impact of implant number on the dimensional accuracy of definitive casts was significant whereas for implant angulation it was nonsignificant. The correlation of angulation and the number of the implant did not show an interpretable pattern. The precision of duplicate casts (compared to definitive casts) is not affected by the combined interaction of implant number and implant angulation. CONCLUSION: The close proximity of implant angulation toward a right-angled direction results in higher precision of implant. In the impression, there is direct picking from the impression copings which decreases the discrepancies in implant angulation on impression and master cast. The interaction of implant angulation and the number shows a noninterpretable pattern. CLINICAL SIGNIFICANCE: Dimensionally accurate implant impressions can be made by using an open tray technique for three implants angled up to 15°.

Assessment of impression material accuracy in complete-arch restorations on four implants.

STATEMENT OF PROBLEM: New polyvinyl siloxane (PVS) materials with enhanced properties have been developed to improve and facilitate implant impression techniques. However, studies on their accuracy are lacking. PURPOSE: The purpose of this in vitro study was to determine the accuracy and precision of implant impressions made with some recently introduced materials on a simulated patient requiring an all-on-4 implant-supported prosthesis. Well-established polyether materials were also evaluated as a comparison. The variables considered were material type, consistency, splinting or not splinting techniques, and implant angulation. MATERIAL AND METHODS: A reference master model was made by inserting 4 implants at angles of 0, 5, and 10 degrees. Eighty impressions were made at 37 °C in wet conditions by using a standardized technique. Eight groups (n=10) were created using monophasic, single-viscosity materials (Hydrorise Implant Medium, HIM-ns; Hydrorise Implant Medium, HIM; Honigum Mono, HM; Impregum, IMP), and 2-viscosity materials (Hydrorise Implant Heavy+Light-ns, HIH+L-ns; Hydrorise Implant Heavy+Light, HIH+L; Honigum Heavy+Light, HH+L; and Permadyne and Garant [Heavy+Light, PeH+L]). Hydrorise materials were used with splinting and not splinting (ns) techniques. The reference points located on the connecting platforms of the transfer copings (TCP) were compared with the same points on the implant connecting platforms (ICP) located in the reference model. The accuracy and precision of the impressions were determined as linear 3D errors and standard deviation between each TCP-ICP couple by using an optical coordinate measuring machine (OCMM). RESULTS: PVS materials were generally better than polyether materials, with Hydrorise materials (HIM and HIH+L) showing significantly better accuracy and precision (30.9 ±14.4 µm and 28.7 ±15.5 µm, respectively) than IMP and PeH+L polyethers (44.2 ±16 µm and 43.8 ±17.6 µm, respectively; P<.001). Honigum materials were statistically similar to Hydrorise materials (P=.765). The values shown by Hydrorise nonsplinted groups (HIH+L-ns and HIM-ns) were not statistically different from those of the splinted polyether impressions (P=.386). The viscosities (monophasic or heavy+light) had no effect on accuracy, but monophasic material positively influenced precision (HIM and HIH+L, P=.001). No correlation was found between implant angulation and accuracy (multilevel analysis and Kendall rank correlation coefficient=-0.065; P=.133). CONCLUSIONS: Recently introduced materials designed for implant impressions showed significantly higher accuracy and precision; even with the unfavorable nonsplinting technique, the new materials performed similarly to, or better than, polyether materials. Although the transfer coping splinting technique generally improved the accuracy and precision of Hydrorise materials, the effect was significant only within HIH+L groups.

Clinical and laboratory passive fit assessment of implant-supported zirconia restorations fabricated using conventional and digital workflow.

BACKGROUND: Long-term success of implant-supported restorations can be affected by the accuracy of the prosthodontic workflow which may differ between conventional and digital techniques. PURPOSE: The purpose was to compare the fit of two-implant-supported restorations, fabricated using conventional and digital workflows and to assess the influence of distance and angulation between the implants on the passive fit of the prosthesis. The SR test was selected to evaluate the fit of two-implant-supported zirconia restorations. MATERIALS AND METHODS: Forty-eight zirconia two-implant-supported restorations were fabricated according to conventional (group C, n = 24) and digital (group D, n = 24) workflows. The SR parameter was calculated as a difference of rotation angles of each screw in passive and nonpassive situations. SR values between groups C and D were compared by performing measurements intraorally, on master and control casts. RESULTS: SR intraorally in group C (16.25 ± 15.52°) was higher than it was in group D (13.85 ± 10.78°), but the difference was not statistically significant (P = .557). While measuring SR on the master cast, group C SR (6.04 ± 7.43°) had lower values than group D (13.12 ± 13.86°) (P = .0039). No statistically significant correlations were found between SR measurements and inter-implant distance or angulation. Restorations with inter-implant angle higher than 10° differed significantly from those with less than 10° angulation. CONCLUSIONS: Digital restorations had a better fit on the control cast, which was used as a reference in this study. Angulation of more than 10° between the implants could negatively affect the passive fit of the digitally fabricated restorations intraorally.

Assessment of Factors Affecting Partial Removable Dental Prostheses Framework Fit: A Clinical Prospective Study.

PURPOSE: To prospectively evaluate the effects of impression material, impression tray type, and partially dentate arch classification on the accuracy of fit of partial removable dental prostheses (PRDP) cobalt-chromium (Co-Cr) frameworks, as inferred from the number of fabricated frameworks required for achievement of acceptable fit. MATERIALS AND METHODS: A total of 103 partially dentate patients provided with Co-Cr PRDP treatment for one or both arches (n = 142) by undergraduate dental students were clinically assessed by two examiners at the metal framework try-in stage, and the relevant data were recorded. Statistical analyses of data were performed using factorial analysis of variance (ANOVA) to study the associations of impression material (alginate, polyvinyl siloxane [PVS]), Kennedy class, and impression tray type (stock, custom) with the number of frameworks that needed to be fabricated for each patient (α = .05). RESULTS: Statistical analyses of data derived from 142 (65 maxillary and 77 mandibular) treated partially edentulous arches revealed no significant correlation between the impression material, Kennedy class, or tray type with respect to the number of framework construction attempts needed (P ≥ .05). Post hoc Tukey test also did not demonstrate any significant differences between the different Kennedy classes in relation to the set outcome measure (P ≥ .05). CONCLUSION: Alginate as an alternative option to PVS and modified metal stock trays can be used for making final impressions to produce PRDP Co-Cr frameworks. Framework fit is unaffected by class of partial edentulism (Kennedy class).

A comparison of patient experience, chair-side time, accuracy of dental arch measurements and costs of acquisition of dental models.

OBJECTIVE: To compare patient experience, chairside time, dental arch distances, and costs of dental models derived from intraoral scans and alginate impressions in pre-orthodontic children and young adolescents. MATERIALS AND METHODS: Fifty-nine children and young adolescents (9-15 years, mean: 12.70 years) had an intraoral scan and an alginate impression prior to orthodontic treatment. During the procedures, chairside time was registered in minutes and patient experience was assessed by a Visual Analogue Scale questionnaire. Four maxillary dental arch distances were measured on digital models, on plaster casts, and directly in the mouth (intraoral). The cost of each procedure was presented graphically. Differences between the two procedures were tested by paired t-test and general linear model. RESULTS: Patient experience was statistically better during intraoral scan compared with alginate impression regarding comfort, gag reflex, breathing, smell/sound, taste/vibration, and all statements concerning anxiety (P < .05). No significant difference in chairside time between the two procedures was found. No statistically significant differences in dental arch distances between digital models and plaster casts were found, but dental arch distances measured intraorally differed significantly from both digital models and plaster casts (P < .05). Cost calculation showed that the digital procedure was 10.7 times more expensive than the conventional procedure initially and, that after 3.6 years, the two procedures were equal in cost. CONCLUSIONS: Children preferred intraoral scan rather than alginate impression. Chairside time was equal for the two procedures as were the measurements of maxillary dental arch distances. The two procedures were equal in cost at 3.6 years.

Is It Cost Effective to Add an Intraoral Scanner to an Oral and Maxillofacial Surgery Practice?

PURPOSE: Intraoral scanners (IOSs), which create digital "impressions" of dental arches, have become popular for prosthetic and orthodontic applications. Adoption in oral and maxillofacial surgery (OMS) practices has been slower, likely because of high implementation costs and low-volume use. The purpose of this study was to evaluate costs for introduction of an IOS into an OMS practice. The authors hypothesized that digital impressions would be more efficient in time and cost compared with conventional impressions and that implementation costs would be offset within 1 year. MATERIALS AND METHODS: This was a prospective study that included patients who had digital impressions during the first year after introduction of an IOS to the practice. Conventional alginate impressions obtained at the same visit were included for comparison. Variables included time for each step in each impression process, IOS experience of the operator obtaining the impression, and associated costs. Per-arch costs for each technique were calculated using time-driven activity-based costing methodology. RESULTS: Sixty-three digital impressions and 31 conventional impressions were included. Mean total times for digital and conventional impressions were 14.1 ± 1.3 and 19.4 ± 4.0 minutes per arch, respectively. On a per-patient basis (2 arches for digital impressions and 4 arches for conventional impressions because of the inability to create duplicate stone models from each alginate impression), total impression times were 24.8 ± 2.7 minutes for digital and 67.2 ± 14.8 minutes for conventional impressions. Total calculated costs for digital and conventional impressions were $21.42 and $29.40 per arch and $37.66 and $102.10 per patient, respectively. In a practice with 2 patients for impressions per working day (500 per year), it would take 1.04 years to offset the purchase of the IOS; with 5 sets of impressions per day (1,250 per year), it would take 5 months. CONCLUSION: Digital impressions are more efficient and cost effective than standard impressions, and implementation costs can be offset within the first year.

Clinical Assessment of Gingival Sulcus Width using Various Gingival Displacement Materials.

AIM: This study aims to compare the clinical efficacy of three different gingival retraction systems on gingival sulcus width. MATERIALS AND METHODS: Study was conducted on prepared right or left maxillary central incisor for 45 subjects. Totally, 15 patients were randomly allocated in three gingival displacement groups, i.e., group I (retraction cord impregnated with aluminum chloride), group II (magic foam), and group III (laser). The pre- and postdisplacement impressions were made with addition silicone material using two-stage double mix technique. RESULTS: There was no difference between the groups at baseline. Group III produced more displacement (mean value 0.48 ± 0.101 mm) than group II (mean value 0.31 ± 0.09 mm) and group I (mean value 0.44 ± 0.11 mm), and this was statistically significant. CONCLUSION: Laser gingival displacement system was found to be effective among the three retraction systems. Choice of gingival displacement system is based on clinical situation and choice of operator. CLINICAL SIGNIFICANCE: The retraction groups in the study created greater amount of gingival retraction than the least sulcus width required for the elastomeric impression material and so are clinically useful.

In vitro assessment of the accuracy of digital impressions prepared using a single system for full-arch restorations on implants.

PURPOSE: This study describes a method for measuring the accuracy of the virtual impression. METHODS: In vitro measurements according to a metrological approach were based on (1) use of an opto-mechanical coordinate measuring machine to acquire 3D points from a master model, (2) the mathematical reconstruction of regular geometric features (planes, cylinders, points) from 3D points or an STL file, and (3) consistent definition and evaluation of position and distance errors describing scanning inaccuracies. Two expert and two inexpert operators each made five impressions. The 3D position error, with its relevant X, Y, and Z components, the mean 3D position error of each scanbody, and the intra-scanbody distance error were measured using the analysis of variance and the Sheffe's test for multiple comparison. RESULTS: Statistically significant differences in the accuracy of the impression were observed among the operators for each scanbody, despite the good reliability (Cronbach's [Formula: see text] = 0.897). The mean 3D position error of the digital impression was between 0.041 ± 0.023 mm and 0.082 ± 0.030 mm. CONCLUSIONS: Within the limitations of this in vitro study, which was performed using a single commercial system for preparing digital impressions and one test configuration, the data showed that the digital impressions had a level of accuracy comparable to that reported in other studies, and which was acceptable for clinical and technological applications. The distance between the individual positions (#36 to #46) of the scanbody influenced the magnitude of the error. The position error generated by the intraoral scanner was dependent on the length of the arch scanned. Operator skill and experience may influence the accuracy of the impression.

Avaliação da alteração dimensional de quatro marcas comerciais de silicone por reação de adição variando o tempo de armazenagem dos moldes / Dimensional alteration assessment of four silicone brands through addition reaction varying molds storage time

O objetivo deste estudo foi mensurar e comparar a precisão dimensional de modelos de gesso confeccionados por meio de moldagem de impressão única (material pesado/fluído de uma única vez) com quatro diferentes marcas comerciais de silicone polimerizados por reação de adição (Express XT®, Futura®, Aquasil® e Virtual®). Inicialmente, foi confeccionado um modelo acrílico mestre, o qual possuía três pilares metálicos paralelos entre si e equidistantes 50 mm um do outro. Para obtenção dos moldes foram utilizadas cinco moldeiras individuais em acrílico, cujas faces externas adaptavam-se perfeitamente na base do modelo padrão, promovendo o "stop" de inserção da moldeira. Após o procedimento de moldagem e confecção dos modelos experimentais, foram medidas as distâncias entre os três cilindros e o diâmetro de cada cilindro. Essas medições foram feitas por três vezes em um mesmo ponto e, destas, criou-se uma média obtendo os resultados finais. Os valores das distâncias foram analisados estatisticamente por meio de uma análise bifatorial, e as médias comparadas pelo teste de Tukey (5%). Os dados demostraram que todas as marcas analisadas apresentaram alteração dimensional e diferiram entre si quando comparadas.

The objective of this study was to measure and compare the dimensional accuracy of plaster models made by only impression molding (heavy material/fluid at one time) of four different brands of polymerized silicone through addition reaction (Express XT®, Futura ®, Aquasil® and Virtual®). Initially, a master acrylic model was manufactured, which had three parallel metal pillars and equidistant 50 mm from each other. To obtain the impressions, we used five individual acrylic trays, whose external faces perfectly adapted to the standard model base, thus promoting the "stop" of molding insertion. Following the molding procedure and the experimental models manufacturing, distances between the three cylinders and the diameter of each cylinder were measured. These measurements were made three times at the same point, and from these average results were obtained. The distance values were statistically analyzed using a two-factor analysis and the means compared by Tukey test (5%). The data demonstrated that all the analyzed brands presented dimensional changes and differed from each other when compared.

Clinical assessment of fractured implant abutment screws: The Bernese silicone replica technique.

Fractured implant abutment screws can be retrieved with repair or rescue devices. However, whether the screw was completely retrieved or the inner implant body was damaged may be uncertain. A silicone replica technique was recently implemented in Bern and may be the most predictable method available at the moment for clinically assessing the internal implant body. This technique is straightforward and precise and may help dentists determine the internal implant condition when managing a fractured screw.

Assessment of Influence of Contact Time between Alginate and Type III Dental Stone on Properties of Cast Model: An in vitro Study.

INTRODUCTION: Alginate is a versatile, irreversible hydrocolloid impression material, which is cost-effective and forms an essential component in dental practice. For elevating the hardness of the cast models, hardeners are combined with stone. Hence, we planned the present study to evaluate the impact of altering the time of contact between alginate and stone after various interim periods. MATERIALS AND METHODS: The present study included the assessment of impact of time of contact between alginate and stone by the construction of 90 casts using a cylinder model. Two bisecting lines were marked and were named as y and y'. These lines were used for testing the dimensional stability. Using chemically cured acrylic resin, the construction of ten special trays was done. All the impression casts were randomly divided into two study groups, with 45 casts in each group-group I: control group, casts were removed after 60 minutes; group II: study group, casts were removed after 9 hours. A digital caliper was used for measuring the dimensional stability of the cast. All the data were collected and analyzed. RESULTS: In the specimens of the control group (group I) and the study group (group II), the mean dimensions from y to y' were found to be 17.54 and 17.95 respectively. The mean reading of hardness in the control group and study group was found to be 0.59 and 0.20 respectively. In groups I and II, the number of specimens showing clarity of two lines (X and X") was 0 and 5 respectively. CONCLUSION: There was no change in the dimensional stability of the dental stone model when the contact time was increased. CLINICAL SIGNIFICANCE: Within certain limits, the contact time between alginate and stone can be altered without significantly altering the properties of the cast.

[Evaluation of production and clinical working time of computer-aided design/computer-aided manufacturing (CAD/CAM) custom trays for complete denture].

OBJECTIVE: To compare the technician fabrication time and clinical working time of custom trays fabricated using two different methods, the three-dimensional printing custom trays and the conventional custom trays, and to prove the feasibility of the computer-aided design/computer-aided manufacturing (CAD/CAM) custom trays in clinical use from the perspective of clinical time cost. METHODS: Twenty edentulous patients were recruited into this study, which was prospective, single blind, randomized self-control clinical trials. Two custom trays were fabricated for each participant. One of the custom trays was fabricated using functional suitable denture (FSD) system through CAD/CAM process, and the other was manually fabricated using conventional methods. Then the final impressions were taken using both the custom trays, followed by utilizing the final impression to fabricate complete dentures respectively. The technician production time of the custom trays and the clinical working time of taking the final impression was recorded. RESULTS: The average time spent on fabricating the three-dimensional printing custom trays using FSD system and fabricating the conventional custom trays manually were (28.6±2.9) min and (31.1±5.7) min, respectively. The average time spent on making the final impression with the three-dimensional printing custom trays using FSD system and the conventional custom trays fabricated manually were (23.4±11.5) min and (25.4±13.0) min, respectively. There was significant difference in the technician fabrication time and the clinical working time between the three-dimensional printing custom trays using FSD system and the conventional custom trays fabricated manually (P<0.05). CONCLUSION: The average time spent on fabricating three-dimensional printing custom trays using FSD system and making the final impression with the trays are less than those of the conventional custom trays fabricated manually, which reveals that the FSD three-dimensional printing custom trays is less time-consuming both in the clinical and laboratory process than the conventional custom trays. In addition, when we manufacture custom trays by three-dimensional printing method, there is no need to pour preliminary cast after taking the primary impression, therefore, it can save the impression material and model material. As to completing denture restoration, manufacturing custom trays using FSD system is worth being popularized.

Effect of dental technician disparities on the 3-dimensional accuracy of definitive casts.

STATEMENT OF PROBLEM: Studies that evaluated the effect of dental technician disparities on the accuracy of presectioned and postsectioned definitive casts are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the accuracy of presectioned and postsectioned definitive casts fabricated by different dental technicians by using a 3-dimensional computer-aided measurement method. MATERIAL AND METHODS: An arch-shaped metal master model consisting of 5 abutments resembling prepared mandibular incisors, canines, and first molars and with a 6-degree total angle of convergence was designed and fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) technology. Complete arch impressions were made (N=110) from the master model, using polyvinyl siloxane (PVS) and delivered to 11 dental technicians. Each technician fabricated 10 definitive casts with dental stone, and the obtained casts were numbered. All casts were sectioned, and removable dies were obtained. The master model and the presectioned and postsectioned definitive casts were digitized with an extraoral scanner, and the virtual master model and virtual presectioned and postsectioned definitive casts were obtained. All definitive casts were compared with the master model by using computer-aided measurements, and the 3-dimensional accuracy of the definitive casts was determined with best fit alignment and represented in color-coded maps. Differences were analyzed using univariate analyses of variance, and the Tukey honest significant differences post hoc tests were used for multiple comparisons (α=.05). RESULTS: The accuracy of presectioned and postsectioned definitive casts was significantly affected by dental technician disparities (P<.001). The largest dimensional changes were detected in the anterior abutments of both of the definitive casts. The changes mostly occurred in the mesiodistal dimension (P<.001). CONCLUSIONS: Within the limitations of this in vitro study, the accuracy of presectioned and postsectioned definitive casts is susceptible to dental technician differences.

Avaliação da estabilidade dimensional de diferentes marcas de silicone por reação de condensação ­ estudo in vitro / Assessment of the dimensional stability of distinct condensation silicone trademarks ­ an in vitro study

Na prática odontológica, o vazamento de gesso nos moldes é muitas vezes tardio, e a maioria é enviada ao laboratório para verter o gesso em até 72 horas. Portanto, os profissionais devem ficar cientes do tempo de atraso tolerável para o qual o material de moldagem permanecerá dimensionalmente preciso. O objetivo deste estudo foi avaliar a alteração dimensional de quatro marcas comerciais de silicone por reação de condensação: Speedex (Vigodent)®, Coltex/Coltoflax (Vigodent)®, Clonage (Nova DFL)® e Zetaplus/Oranwash (Zhermack)®, em função de seis diferentes tempos de vazamento de gesso, e sugerir o tempo máximo de armazenagem dos moldes. Para isso, foi confeccionado um modelo mestre com três cilindros metálicos, fixados em região de rebordo alveolar de uma maxila em acrílico, e 12 moldeiras individuais. A técnica de moldagem utilizada foi a do material em consistência densa e fluida em dois estágios. foram obtidos 72 modelos em gesso GC fujirock® EP melhorado tipo IV, os quais foram mensurados com paquímetro digital Mytutoyo®. Os resultados foram comparados ao modelo controle e aplicados ao teste de hipóteses "t de student". Concluiu-se que as marcas comerciais de silicone por reação de condensação Zetaplus® e Clonage® apresentaram modelos experimentais que não diferiram estatisticamente do modelo mestre para todos os tempos estudados. Já as marcas comerciais Coltex Coltoflax® e Speedex® apresentaram-se estatisticamente diferentes ao modelo mestre nos maiores tempos de armazenamento.

In dental practice, plaster casting is often late, and most are sent to the laboratory to pour the plaster in up to 72 hours. Therefore professionals should be aware of the tolerable delay time for which the molding material will remain dimensionally accurate. The objective of this study was to evaluate the dimensional alteration of four commercial brands of silicone by condensation reaction, Speedex (Vigodent)®, Coltex / Coltoflax (Vigodent)®,Clonage (Nova DFL)®, Zetaplus / Oranwash (Zhermack)®, in function of six different casting times, and suggest the maximum storage time of the molds. Therefore, a master model with three metal cylinders was made, fixed in the alveolar ridge region of an acrylic jaw, and 12 individual trays. The technique of molding used was that of the material in dense consistency and fluid in two stages. A total of 72 GC fujirock® EP improved plaster models were obtained, which were measured using a Mytutoyo® digital caliper. The results were compared to the control model and the "t student" hypothesis test was applied. It was concluded that the trademarks of silicone by condensation reaction Zetaplus® and Clonage® presented experimental models that did not differ statistically from the master model for all the studied times. Coltex Coltoflax® and Speedex® trademarks were statistically different from the master model in the longest storage times.