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.

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.

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.

A simple, safe and affordable cast-based guided implant placement system.

A fully restrictive surgical guide allows controlled execution of a preoperatively planned osteotomy and subsequent implant placement. There are two fabrication modes. One is a digital path, where these guides can be fabricated based on data from a cone beam CT source. Alternatively, 3-D data can be derived from a dental cast and periapical radiographs. The 3D Click Guide is a cast-based, fully restrictive surgical guide that can be generated in the dental office.

Digital casts in orthodontics: a comparison of 4 software systems.

INTRODUCTION: The introduction of digital cast models is inevitable in the otherwise digitized everyday life of orthodontics. The introduction of this new technology, however, is not straightforward, and selecting an appropriate system can be difficult. The aim of the study was to compare 4 orthodontic digital software systems regarding service, features, and usability. METHODS: Information regarding service offered by the companies was obtained from questionnaires and Web sites. The features of each software system were collected by exploring the user manuals and the software programs. Replicas of pretreatment casts were sent to Cadent (OrthoCAD; Cadent, Carlstadt, NJ), OthoLab (O3DM; OrthoLab, Poznan, Poland), OrthoProof (DigiModel; OrthoProof, Nieuwegein, The Netherlands), and 3Shape (OrthoAnalyzer; 3Shape, Copenhagen, Denmark). The usability of the programs was assessed by experts in interaction design and usability using the "enhanced cognitive walkthrough" method: 4 tasks were defined and performed by a group of domain experts while they were observed by usability experts. RESULTS: The services provided by the companies were similar. Regarding the features, all 4 systems were able to perform basic measurements; however, not all provided the peer assessment rating index or the American Board of Orthodontics analysis, simulation of the treatment with braces, or digital articulation of the casts. All systems demonstrated weaknesses in usability. However, OrthoCAD and 03DM were considered to be easier to learn for first-time users. CONCLUSIONS: In general, the usability of these programs was poor and needs to be further developed. Hands-on training supervised by the program experts is recommended for beginners.

Clinical use of a direct chairside oral scanner: an assessment of accuracy, time, and patient acceptance.

INTRODUCTION: Chairside oral scanners allow direct digital acquisition of the intraoral situation and can eliminate the need for conventional impressions. In this study, we aimed to assess accuracy, scan time, and patient acceptance of a chairside oral scanner when used for full-arch scans; these are critical factors for acceptance of this technology in the orthodontic setting. METHODS: Fifteen patients had digital models made from both intraoral scans (Lava COS; 3M ESPE, St Paul, Minn) and alginate impressions. Each procedure was timed, and patient preference was assessed with a survey. In addition, digital models were made from 5 plaster model pairs using the intraoral scanner and an orthodontic model scanner. Model pairs were digitally superimposed, and differences between models were quantified. Accuracy was assessed using the Bland-Altman method. Time differences were tested for statistical significance with the Student t test. RESULTS: Digital models made using the chairside oral scanner and either impressions or the orthodontic model scanner did not differ significantly. The chair time required to take impressions was significantly shorter than the time required for the intraoral scans. When processing time was included, the time requirement did not differ significantly between methods. Although 73.3% of the patients preferred impressions because they were "easier" or "faster," 26.7% preferred the scan because it was "more comfortable." CONCLUSIONS: Despite the high accuracy of chairside oral scanners, alginate impressions are still the preferred model acquisition method with respect to chair time and patient acceptance. As digital technology continues to progress, intraoral scanning may become more accepted for use in orthodontics.

Modified indexing technique for the immediate interim restoration of a dental implant.

Because of the functional and esthetic requirements of patients, different techniques have been proposed to reduce the time between dental implant placement and interim restoration fabrication. This article describes a modified indexing technique by using a surgical template for open-tray impression and definitive cast development during immediate loading procedures. This technique does not use a complete impression of the oral cavity and, therefore, is more comfortable, less time consuming, and less expensive. It also allows the fabrication of interim restorations with the optimal shape for developing an adequate emergence profile.

The quality of impressions for crowns and bridges: an assessment of the work received at three commercial dental laboratories. assessing the quality of the impressions of prepared teeth.

The literature is limited in studies directly assessing the quality of impressions for crowns and bridges in the UK. The aim of the study was to assess the quality of impressions for conventional crown and bridgework received by commercial dental laboratories. Three dental laboratories were visited over a 3-month period. All impressions for conventional crowns and bridges that arrived on the days of the visits were examined prior to any laboratory processing. A total of 206 impression cases were examined and assessed against criteria laid out in a custom-designed assessment form. Defects were commonly found in the recording of prepared teeth. Overall, 44.2% of impression cases were unsatisfactory. NHS impressions were more than twice as likely to be unsatisfactory compared to private impressions. If the results of this survey are typical then the general quality of impressions for fixed crown and bridgework is unacceptable. This is particularly true for work completed under the NHS contract.

Bonded functional esthetic prototype: an alternative pre-treatment mock-up technique and cost-effective medium-term esthetic solution.

As the economy has receded in recent years, many patients have been inclined to reject dental treatment beyond what they feel is the minimal amount necessary. Increasingly, there has been reluctance to take on the expense of full-mouth restorations and time-consuming procedures. Consequently, clinicians can benefit from innovative, conservative, interim solutions that enable them to provide segment treatment with long-term stability and esthetics, with lower initial cost. The bonded functional esthetic prototype (BFEP) allows fabrication of up to 14 teeth from composite in 1 hour, providing either a pre-treatment restoration or a long-term provisional solution until further treatment can be completed. As demonstrated herein, the BFEP enables superb function, stability, and esthetics in the interim while dispersing the cost of definitive treatment over time.

IMPROVDENT: improving dentures for patient benefit. A crossover randomised clinical trial comparing impression materials for complete dentures.

BACKGROUND: According to the UK Adult Dental Health Survey (2009) 15% of adults aged 65-74, 30% aged 75-84 and 47% aged >85 years are edentulous and require complete dentures. Patients' quality of life and nutrition status are affected by poor dentures. The quality of the dental impression is the most important issue for improving the fit and comfort of new dentures. There is paucity of RCT evidence for which impression material is best for complete dentures construction. This study aims to compare two impression materials for effectiveness and cost effectiveness. METHODS/DESIGN: IMPROVDENT is a double-blind crossover trial comparing the use of alginate and silicone, two commonly used denture impression materials, in terms of patient preference and cost-effectiveness. Eighty five edentulous patients will be recruited and provided with two sets of dentures, similar in all aspects except for the impression material used (alginate or silicone). Patients will try both sets of dentures for a two-week period, unadjusted, to become accustomed to the feel of the new dentures (habituation period). Patients will then wear each set of dentures for a period of 8 weeks (in random order) during which time the dentures will be adjusted for optimum comfort. Finally, patients will be given both sets of dentures for a further two weeks to wear whichever denture they prefer (confirmation period).Patients will be asked about quality of life and to rate dentures on function and comfort at the end of each trial period and asked which set they prefer at the end of the habituation period (unadjusted denture preference) and confirmation period (adjusted denture preference). A health economic evaluation will estimate incremental cost-effectiveness ratios of producing dentures from the two materials. A qualitative study will investigate the impact of dentures on behaviour and quality of life. FUNDING: IMPROVDENT is funded by NIHR RfPB (PB-PG-0408-16300). DISCUSSION: This trial aims to provide evidence on the costs and quality of dentures cast from two different commonly used impression materials; the intention is to significantly impact on the quality of denture production within NHS dentistry. TRIAL REGISTRATION: ISRCTN Register: ISRCTN01528038 UKCRN Portfolio ID: 8305.

Complete arch implant impression technique.

When making a definitive impression for an arch containing multiple implants, there are many reported techniques for splinting impression copings. This article introduces a splint technique that uses the shim method, which has been demonstrated to reduce laboratory and patient chair time, the number of impression copings and laboratory analogs needed, and the ultimate cost.

Avaliação e comparação de propriedades físicas e mecânicas de materiais de moldagem experimentais / Assessment and comparison of mechanical and physical properties of commercial and experimental gypsums

OBJETIVO: O objetivo deste estudo foi avaliar e comparar in vitro propriedades fisicas e mecanicas (resistencias a compressao e a tracao diametral, tempo de presa, fidelidade de copia e dureza) de gessos comerciais, cujas composicoes foram alteradas. MATERIAL E METODO: Foram confeccionados 40 corpos-de-prova para cada tipo de gesso e submetidos aos testes citados (n=10). Os corpos-de-prova obtidos para verificacao da resistencia a tracao foram antes submetidos a analise de dureza. Os tempos de presa foram analisados imediatamente apos a manipulacao dos materiais e os demais ensaios propostos foram realizados apos 7 dias da obtencao das amostras. RESULTADOS: Os valores obtidos nos testes foram analisados estatisticamente (1-way ANOVA, Tukey, p<0.05); observou-se que Exp1 apresentou melhor reproducao de detalhes e Exp2 o menor tempo de presa em relacao aos materiais comerciais (p<0.05). Nas demais propriedades, os gessos experimentais apresentaram comportamentos semelhantes aos comerciais. CONCLUSOES: Concluiu-se que as alteracoes na composicao dos gessos contribuiram para a melhoria na reproducao de detalhes no grupo Exp1, e diminuicao no tempo de presa no grupo Exp2.

OBJECTIVE: The purpose of this study was to evaluate and to compare in vitro mechanical and physical properties (compression and diametral tensile strength, setting time, loyalty to copy and hardness) of commercial and experimental gypsums (Exp1 and Exp2), whose compositions were altered. MATERIAL AND METHOD: Forty specimens were obtained for each type of gypsum (n=10). The specimens obtained to verify tensile strength were submitted to hardness analysis before. The setting time were analysed immediately after the manipulation of materials and the other tests were conducted 7 days after the specimens were obtained. RESULTS: The values were analyzed statistically (1-way ANOVA, Tukey, p <0.05) and it was observed that Exp1 showed better reproduction of details and Exp2 presented lesser setting time than commercial materials (p <0.05). As regards to other properties, experimental gypsums showed similar behavior to commercial gypsums. CONCLUSION: It was concluded that alterations in gypsum composition contributed to the improvement in reproduction of details in Exp1 group, and promoted a decrease in setting time in Exp2.

Three-dimensional assessment of dental casts' occlusal surfaces using two impression materials.

The aim of this study was to assess by means of a three-dimensional computed tomography scanning system the occlusal surface characteristics of dental casts made using two different impression materials. Alginate and polyvinyl siloxane impressions were taken of 20 dental students resulting in 40 dental casts. The casts were paired for each student separately so that each pair consisted of an alginate poured cast and a polyvinyl siloxane poured out cast. The casts were scanned using FlashCT scanner and for each cast, a three-dimensional digital image was obtained. The digitized casts were processed using the three-dimensional imaging software Geomagic Studio 9. A total of 464 paired teeth were digitally separated and superimposed. For each tooth, two measurements were obtained corresponding to the two different impression materials used. The two sets of volumes for all digitally separated teeth were compared and analysed using the Wilcoxon signed test. Larger volume measurements were obtained for teeth separated from alginate poured out casts than from their corresponding ones from polyvinyl siloxane casts (P = 0.005). When the teeth were divided into the groups of incisors, canines and premolars/molars, only the last one exhibited significant difference (P = 0.00). The mean difference between the volumes measured for all 464 teeth separated was 0.041 mm(3) (+/-0.33). The occlusal surfaces of teeth appear differently in dental casts depending on the impression materials used. Impressions of dental casts should be utilized with caution in relation to their research application and in reference with dental wear studies.

Assessment of preference of mixing techniques and duration of mixing and tray loading for two viscosities of vinyl polysiloxane material.

STATEMENT OF PROBLEM: Information regarding operators' preferences for different impression mixing techniques and duration of mixing and tray loading is limited. PURPOSE: The purpose of this study was to assess operators' preferences, and the duration of mixing and tray loading using different mixing techniques. MATERIAL AND METHODS: Thirty dentists, 30 dental assistants, and 30 inexperienced dental students evaluated mixing heavy-body vinyl polysiloxane material (VPS) using electronic mixing compared to automixing, and extra-heavy-body material using electronic mixing compared to hand mixing. Participants rated their level of preference using a scale from 0 to 10 for ease of mixing, control of loading, quality of mixing, level of cleanliness, and overall rating. The duration of mixing and tray loading was also measured. Mean values were compared within participant groups using the paired t test (alpha=.05) and between groups using 1-way analysis of variance (ANOVA) (alpha=.05). Holm's procedure was used to adjust the level of significance for the multiple comparisons. RESULTS: The paired t test showed that mean values of level of preference for electronic mixing were significantly higher (P<.001 to .033) than those for automixing or hand mixing. The mean values of duration of mixing and tray loading with electronic mixing were significantly higher (P<.001 to .002) than those with automixing or hand mixing, except for students using heavy-body materials (P=.31). One-way ANOVA showed that there were no significant differences between the 3 participant groups in preference and duration of mixing and tray loading, both of heavy-body and extra-heavy-body VPS impression materials. CONCLUSIONS: All participant groups preferred electronic mixing to automixing or hand mixing. Electronic mixing was significantly slower for all groups except for students using heavy-body materials. There was no significant difference between the 3 participant groups in the preference or duration of mixing and tray loading for the mixing techniques tested.

Clinical assessment of chewing function of obturator prosthesis wearers by objective measurement of masticatory performance and maximum occlusal force.

PURPOSE: Eating, which includes chewing and swallowing, is an oral function that influences quality of life. Though the swallowing ability of maxillectomy patients was reported in our previous study, the chewing function has not been fully reported to date. Thus, the purpose of this study was to evaluate the chewing function of obturator prosthesis wearers by measurement of masticatory performance and occlusal force. The relationship of these 2 measurements was also investigated. MATERIALS AND METHODS: Twenty maxillofacial obturator prosthesis wearers undergoing periodic checkup at the maxillofacial rehabilitation clinic in Kyushu University Hospital were recruited for this study. Additionally, 20 young, healthy individuals were recruited as controls. Data on masticatory performance, which was measured by a sieve method using hydrocolloid material, and maximum occlusal force, which was measured by the Dental Prescale System (Fuji Film), were obtained for each participant. RESULTS: The mean of masticatory performance was 2.6 (SD 1.2) on a 1.40-mm mesh. There was no significant difference in masticatory performance between the patient group and the controls. The mean maximum occlusal force of the patient group was 625.9 N (SD 299.1 N), which was significantly lower than that of the control group. There was no significant correlation between masticatory performance and maximum occlusal force for the patient group in this study (P = .3726). CONCLUSION: Masticatory performance of obturator prosthesis wearers with dentate or partially edentulous maxillae was not different from that of young, healthy individuals, though maximum occlusal force of these patients was lower than that of controls.

[The reliability of class A alginate impressions]. / Fiabilité des empreintes à l'alginate de classe A.

The class A alginates present very good properties of dimensional precision and reproduction of details, comparable to those of the reversible hydrocolloïdes and certain elastomeres used for the realization of secondary prints of precision in fixed prosthesis and in removable prosthesis. Besides, their application is easier and they are costless. The valorization of these print materials could certainly contribute to reduce the cost of comes back of prostheses in countries under developed where the weak power economic populations constitute a brake to the access to cares of health. To exploit qualities of these print biomaterials well, it agrees to manage correctly the parameters of their application. To this effect, the present survey puts in evidence that the maximum delay of stream that guarantees the good dimensional stability of these class A alginates is of 45 minutes in the hot and humid climatic tropical country conditions.