A survey on the use of various gingival displacement techniques in fixed partial denture by the prosthodontists in vadodara city.

AIMS: To evaluate the use of various gingival displacement techniques prior to impression making in fixed partial dentures by the Prosthodontists in Vadodara. SETTINGS AND DESIGN: Questionnaire based survey among prosthodontists in Vadodara city. METHODS AND MATERIAL: All the prosthodontists practitioners and those prosthodontists in academic institutes in Vadodara City, Gujarat, were surveyed through a questionnaire regarding their usage of gingival displacement technique and their reasons and methods of using gingival displacement technique for fixed partial denture. The results were analysed through discriminant statistical analysis. RESULTS: Among all the Prosthodontists in Vadodara city, 62% prefer the use of gingival displacement technique for successful clinical practice while 38 % of them do not follow the procedure believing it does not make major difference in clinical practice. CONCLUSIONS: Those Prosthodontists who preferred the use of gingival displacement technique were able to detect many advantages of using it in their daily fixed partial denture practice and the percentage of prosthodontists not following gingival displacement technique blamed it as a time consuming affair and was not feasible on economic grounds for the class of patient they treated.

Aplicação da fotogrametria para a digitalização de modelos de gesso / Application of photogrammetry for scanning of plaster models

O propósito deste artigo é apresentar o fluxo de trabalho aplicado para a geração de modelos digitais tridimensionais (3D) a partir de imagens de um modelo em gesso, utilizando itens já presentes em nosso dia a dia, como computadores, câmeras fotográficas de smartphones e um aplicativo de código aberto, permitindo a geração de resultados similares aos obtidos com o uso de scanners de bancada, porém de forma mais barata.

The purpose of this article is to present the workflow applied to the generation of three-dimensional (3D) digital models from images of a dental cast, using items already present in our daily lives, such as computers, smartphone cameras and an opensource software, allowing the generation of results similar to those obtained with the use of scanners, but in a cheaper way.

Impression Techniques Used for Single-Unit Crowns: Findings from the National Dental Practice-Based Research Network.

PURPOSE: To: (1) determine which impression and gingival displacement techniques practitioners use for single-unit crowns on natural teeth; and (2) test whether certain dentist and practice characteristics are significantly associated with the use of these techniques. MATERIALS AND METHODS: Dentists participating in the National Dental Practice-Based Research Network were eligible for this survey study. The study used a questionnaire developed by clinicians, statisticians, laboratory technicians, and survey experts. The questionnaire was pretested via cognitive interviewing with a regionally diverse group of practitioners. The survey included questions regarding gingival displacement and impression techniques. Survey responses were compared by dentist and practice characteristics using ANOVA. RESULTS: The response rate was 1777 of 2132 eligible dentists (83%). Regarding gingival displacement, most clinicians reported using either a single cord (35%) or dual cord (35%) technique. About 16% of respondents preferred an injectable retraction technique. For making impressions, the most frequently used techniques and materials are: poly(vinyl siloxane), 77%; polyether, 12%; optical/digital, 9%. A dental auxiliary or assistant made the final impression 2% of the time. Regarding dual-arch impression trays, 23% of practitioners report they typically use a metal frame tray, 60% use a plastic frame, and 16% do not use a dual-arch tray. Clinicians using optical impression techniques were more likely to be private practice owners or associates. CONCLUSIONS: This study documents current techniques for gingival displacement and making impressions for crowns. Certain dentist and practice characteristics are significantly associated with these techniques.

Impression evaluation and laboratory use for single-unit crowns: Findings from The National Dental Practice-Based Research Network.

BACKGROUND: Objectives were to determine the likelihood that a clinician accepts an impression for a single-unit crown and document crown remake rates. METHODS: The authors developed a questionnaire that asked dentists about techniques used to fabricate single-unit crowns. The authors showed dentists photographs of 4 impressions and asked them to accept or reject each impression. The authors correlated answers with dentist and practice characteristics. Other questions pertained to laboratory use and crown remake rates. RESULTS: The response rate was 83% (1,777 of 2,132 eligible dentists). Of the 4 impressions evaluated, 3 received consistent responses, with 85% agreement. One impression was more equivocal; 52% accepted the impression. The likelihood of accepting an impression was associated significantly with the clinician's sex, race, ethnicity, and practice busyness. Clinicians produced 18 crowns per month on average, and 9% used in-office milling. Most dentists (59%) reported a remake rate of less than 2%, whereas 17% reported a remake rate greater than 4%. Lower remake rates were associated significantly with more experienced clinicians, optical impressions, and not using dual-arch trays. CONCLUSIONS: Although dentists were largely consistent in their evaluation of impressions (> 85%), nonclinical factors were associated with whether an impression was accepted or rejected. Lower crown remake rates were associated with more experienced clinicians, optical impressions, and not using dual-arch trays. PRACTICAL IMPLICATIONS: These results provide a snapshot of clinical care considerations among a diverse group of dentists. Clinicians can compare their own remake rates and impression evaluation techniques with those in this sample when developing best practice protocols.

Quantifying Appointments, Treatment Time, Impressions, and Diagnostic Data of Cases Staffed by General Dentists and Prosthodontists in a Dental School Clinic.

The aim of this retrospective study was to quantify differences between general dentists and prosthodontists regarding appointments, treatment time, impressions, and preoperative diagnostic data in teaching predoctoral clinical fixed prosthodontics. Electronic dental records (n=356) of patients treated at one dental school in academic year 2012 were randomly selected for review to obtain the following data: faculty and student demographics, number of appointments and treatment time from preparation to cementation, number of impressions made, completion of oral disease control treatment (ODCT), and presence of preoperative periapical radiographs and diagnostic casts. The results showed that ODCT was completed in 78%, preoperative radiographs were present in 76%, and diagnostic casts made in 53% of the cases reviewed. There was no statistically significant difference in number of appointments, treatment time, or number of final impressions when students were staffed by general dentists or prosthodontists. When students were supervised by multiple faculty members, there was generally an increase in treatment time and number of appointments and final impressions. Although this study found no statistically significant differences between general dentists and prosthodontists regarding the criteria evaluated, the results suggest that faculty development and calibration are needed to ensure ODCT is completed and preoperative radiographs are present prior to initiating fixed prosthodontic procedures.

Precision of Dental Implant Digitization Using Intraoral Scanners.

PURPOSE: The digitization of scanbodies on dental implants is required to use computer-aided design/computer-assisted manufacture processes for implant prosthetics. Little is known about the accuracy of scanbody digitization with intraoral scanners and dental lab scanners. This study aimed to examine the precision of different intraoral digital impression systems as well as a dental lab scanner using commercially available implant scanbodies. MATERIALS AND METHODS: Two study models with a different number and distribution of dental implant scanbodies were produced from conventional implant impressions. The study models were scanned using three different intraoral scanners (iTero, Cadent; Trios, 3Shape; and True Definition, 3M ESPE) and a dental lab scanner (D250, 3Shape). For each study model, 10 scans were performed per scanner to produce repeated measurements for the calculation of precision. The distance and angulation between the respective scanbodies were measured. The results of each scanning system were compared using analysis of variance, and post hoc Tukey test was conducted for a pairwise comparison of scanning devices. RESULTS: The precision values of the scanbodies varied according to the distance between the scanbodies and the scanning device. A distance of a single tooth space and a jaw-traversing distance between scanbodies produced significantly different results for distance and angle measurements between the scanning systems (P < .05). CONCLUSION: The precision of intraoral scanners and the dental lab scanner was significantly different. The precision of intraoral scanners decreased with an increasing distance between the scanbodies, whereas the precision of the dental lab scanner was independent of the distance between the scanbodies.

Dimensional accuracy of digital dental models from cone-beam computed tomography scans of alginate impressions according to time elapsed after the impressions.

INTRODUCTION: Our objective was to investigate the dimensional accuracy of digital dental models obtained from the cone-beam computed tomography (CBCT) scans of alginate impressions according to the time elapsed after the impressions were taken. METHODS: Alginate impressions were obtained of 20 adults using 2 alginate materials: Alginoplast (Heraeus Kulzer, Hanau, Germany) and Cavex (Cavex Holland, Haarlem, The Netherlands). These impressions were stored in wet conditions and scanned by CBCT immediately after impression-taking and after storage times of 12, 24, 36, 48, 60, and 72 hours. After reconstruction of the 3-dimensional digital dental models, the models were measured, and the data were analyzed to determine the dimensional changes according to the time elapsed. The changes within the measurement error were regarded as clinically acceptable in this study. RESULTS: The measurement errors ranged from 0.27 to 0.29 mm in the digital dental models obtained from CBCT scans of the alginate impressions. All measurements showed decreasing accuracy with greater elapsed time after the impressions were taken. Changes above the measurement error occurred at 24 and 36 hours for Cavex and Alginoplast, respectively. CONCLUSIONS: Digital dental models can be obtained from CBCT scans of alginate impressions without sending them to a remote laboratory. However, the impressions need to be scanned within 24 hours; otherwise, dimensional changes lead to errors that exceed the error of measurement.

TRENDS IN COMPLETE DENTURE IMPRESSIONS IN PAKISTAN.

BACKGROUND: Multiple materials and techniques have been reported for complete denture impressions in literature. The aim of the study was to assess the trends in complete denture impression materials and techniques among general dental practitioners (GDP) and specialists (SP) in Pakistan. METHODS: In this cross-sectional study, self-designed-structured questionnaires were distributed among 500 dentists in Pakistan. The three-part questionnaire enquired about the demographic features, preferred impression materials, impression techniques and related procedures commonly used in their clinical practice. A comparison between the responses of SP and GDP was also drawn. Frequency distribution and Chi-square test were performed to compare the responses. RESULTS: A total of 294 questionnaires were completed at a response rate of 58.8%. 75% of GDP used alginate for primary impressions and 66% of SP preferred impression compound for the same. A majority of both SP and GDP favoured the used of custom trays (SP 81%, GDP 85%) and selective pressure technique (SP 84%, GDP 53%) for final impression. However, 85% of GDP used zinc-oxide eugenol and 62% of SP favoured elastomeric materials for the same. Most of the SP and GDP used chemical cured resin custom trays (SP 54%, GDP 75%), however, 86% of SP used spaced trays and almost 60% of GDP preferred close-fitting trays. CONCLUSIONS: The practice of GDP and SP with regards to CD impression materials and techniques differed significantly. Continued education and training for GDP and SP with respect to procedures and techniques related to CD is recommended.

Critical appraisal of implant impression accuracies: A systematic review.

STATEMENT OF PROBLEM: Different assessment methods have been used to measure the accuracy of implant impression techniques; therefore, the readers should understand the benefits and limitations of each assessment method used. PURPOSE: The purpose of this systematic review was to classify the implant impression studies by the assessment methods and techniques used and to understand the characteristics of each assessment method. The results of published studies were also analyzed to draw meaningful conclusions about the accuracy of the implant impressions. MATERIAL AND METHODS: An electronic search of the MEDLINE/PubMed database was performed in February 2013 using specific search terms and predetermined criteria to identify and assess laboratory studies of the accuracy of implant impression techniques. A final list of articles deemed to be of interest was comprehensively reviewed by 2 reviewers to ensure that these were suitable for the purpose of this review. The results of the current review were also compared with results from a previous systematic review. RESULTS: A total of 56 studies met the inclusion criteria for this review. Thirty-seven studies measured the amount of linear distortion, and 17 studies compared the angular change to assess the accuracy. Most linear or angular distortions were only measured in 2 dimensions, and 3-dimensional analysis was rare. More than 80% of the studies compared nonsplinting versus splinting, direct versus indirect techniques, and different impression materials. CONCLUSIONS: In recent publications, the direct or splint technique showed more accurate results than the indirect or nonsplinted technique. In contrast to external connection implants, inconsistent results were reported for internal connection implants.

Reliability of the impression replica technique.

The aim of this study was to evaluate the reliability of the impression replica technique with a four-unit zirconia fixed dental prosthesis (FDP). Marginal and internal fit were measured by repeatedly placing the FDP on an epoxy cast using light-body silicone material corresponding to cement. All measured marginal and internal fit points showed varying values. The greatest variations were seen at the most distal margin (33 µm) and at the distal abutment of the FDP (77 µm). The results showed that the technique gives moderate variations and is a useful method to evaluate marginal and internal fit.

Comparison of accuracy and reproducibility of casts made by digital and conventional methods.

STATEMENT OF PROBLEM: Little peer-reviewed information is available regarding the accuracy and reproducibility of digitally fabricated casts compared to conventional nondigital methods. PURPOSE: The purpose of this in vitro study was to compare the accuracy and reproducibility of a digital impression and cast fabrication with a conventional impression and cast fabrication. MATERIAL AND METHODS: Conventional impressions were made via a 1-step single viscosity technique with vinyl siloxanether material of a typodont master model, and conventional casts were cast from dental stone. Digital impressions were obtained with a digital scanner, and digital stereolithographic models were printed. The typodont and fabricated casts were digitized with a structured light scanner and saved in surface tessellation language (STL) format. All STL records were superimposed via a best-fit method. The digital impression and cast fabrication method was compared with the conventional impression and cast fabrication method for discrepancy, accuracy, and reproducibility. The Levene test was used to determine equality of variances, and a 1-way ANOVA was conducted to assess the overall statistical significance of differences among the groups (n=5, α=.05). RESULTS: No significant statistical difference was found between the digital cast and conventional casts in the internal area or finish line area (P>.05). In addition, there was no statistically significant difference between these 2 techniques for a fixed dental prosthesis or single crown (P>.05). However, statistically significant differences were observed for overall areas of the casts in terms of accuracy (P<.01) and reproducibility (P<.001). Digital impression and cast fabrication were less accurate and reproducible than conventional impression and cast fabrication methods. CONCLUSIONS: No statistically significant difference was found between the digital cast and conventional cast groups in the internal and finish line areas. However, in terms of the reproducibility and accuracy of the entire cast area, the conventional cast was significantly better than the digital cast.

Studying the relationships between the outlines of the face, maxillary central incisor, and maxillary arch in Jordanian adults by using Fourier analysis.

STATEMENT OF THE PROBLEM: The outline shapes of the dental arch, face, and tooth are esthetic factors used to determine the proper form of artificial teeth when selected for artificial prostheses. PURPOSE: The purpose of this study was to investigate the quantitative relationships between the outlines of the face, the maxillary central incisor, and the maxillary arch by using Fourier analysis. MATERIAL AND METHODS: Frontal facial photographs and irreversible hydrocolloid impressions of the maxilla were obtained from 200 young, dentate individuals (100 men, 100 women) ages 22 to 28 years. On the resultant casts, standardized photographs were made for the dental arch and the maxillary central incisor. The outlines of the face, dental arch, and tooth were digitally traced and the digitized curved outlines were converted into X-Y coordinates with special software, which, in turn, were imported into Fourier Shape Descriptor software for harmonic analysis. The quantitative outputs of Fourier analyses were analyzed and tested with statistical software to investigate the differences across the shapes of the 3 outlines under study. RESULTS: Facial and tooth outlines were similar for each sex, although the similarity was stronger among the men. By contrast, no relationship was found between tooth and maxillary arch outlines or between face and maxillary arch outlines. CONCLUSIONS: Face and tooth forms were quantitatively related. Therefore, face form may reliably guide the selection of artificial anterior tooth form in complete denture prostheses or any complex anterior restorations.

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.

Digital evaluation of the accuracy of impression techniques and materials in angulated implants.

OBJECTIVES: The aim of this study was to investigate the accuracy of 2 different impression techniques and 3 different impression materials in models simulating parallel and angulated implants. METHODS: Three master models simulating partial edentulous mandible with 2 implants at the sites of second premolars (parallel) and second molars with different angulations (parallel, 10° or 20° angulated) were fabricated. Two different impression techniques [splinted direct (D), indirect (I)] and 3 different monophase impression materials [polyether (PE), vinyl polysiloxane (VPS), vinyl polyether silicone (VPES)] were used for each master model and a total of 180 impressions were made (n=10). Master model and casts were scanned by a modified laser scanner and data were transferred to VRMesh software. Master model and duplicate cast scans were digitally aligned observing the superposition of anatomic markers. Angular and coronal deviations between master and duplicated copings were calculated and data were statistically analyzed. RESULTS: Mean angular and coronal deviations were in a range of 0.205-0.359° and 22.56-33.33µm, respectively. Statistical analysis revealed that the angulation of implant affected both coronal and angular deviations of the impression copings (P<0.05). According to statistical analyses, for parallel implants, the accuracy of impression materials and techniques were ranging as VPS-D=PE-D>VPS-I=PE-I>VPES-D>VPES-I from most accurate to the least. For 10° and 20° angulated implants the most accurate material and technique was VPS-D whereas the least accurate combination was VPES-I (P<0.05). CONCLUSION: Angulation, impression technique and material were found to be effective on the accuracy of implant impressions. CLINICAL SIGNIFICANCE: Clinicians may prefer VPS impression material and splinted direct technique for impressions of both parallel and up to 20° angulated implants.

Reproducibility and accuracy of linear measurements on dental models derived from cone-beam computed tomography compared with digital dental casts.

INTRODUCTION: The aim of this study was to determine the reproducibility and accuracy of linear measurements on 2 types of dental models derived from cone-beam computed tomography (CBCT) scans: CBCT images, and Anatomodels (InVivoDental, San Jose, Calif); these were compared with digital models generated from dental impressions (Digimodels; Orthoproof, Nieuwegein, The Netherlands). The Digimodels were used as the reference standard. METHODS: The 3 types of digital models were made from 10 subjects. Four examiners repeated 37 linear tooth and arch measurements 10 times. Paired t tests and the intraclass correlation coefficient were performed to determine the reproducibility and accuracy of the measurements. RESULTS: The CBCT images showed significantly smaller intraclass correlation coefficient values and larger duplicate measurement errors compared with the corresponding values for Digimodels and Anatomodels. The average difference between measurements on CBCT images and Digimodels ranged from -0.4 to 1.65 mm, with limits of agreement values up to 1.3 mm for crown-width measurements. The average difference between Anatomodels and Digimodels ranged from -0.42 to 0.84 mm with limits of agreement values up to 1.65 mm. CONCLUSIONS: Statistically significant differences between measurements on Digimodels and Anatomodels, and between Digimodels and CBCT images, were found. Although the mean differences might be clinically acceptable, the random errors were relatively large compared with corresponding measurements reported in the literature for both Anatomodels and CBCT images, and might be clinically important. Therefore, with the CBCT settings used in this study, measurements made directly on CBCT images and Anatomodels are not as accurate as measurements on Digimodels.

An in vitro comparison of photogrammetric and conventional complete-arch implant impression techniques.

STATEMENT OF PROBLEM: Conventional impression techniques for recording the location and orientation of implant-supported, complete-arch prostheses are time consuming and prone to error. The direct optical recording of the location and orientation of implants, without the need for intermediate transfer steps, could reduce or eliminate those disadvantages. PURPOSE: The objective of this study was to assess the feasibility of using a photogrammetric technique to record the location and orientation of multiple implants and to compare the results with those of a conventional complete-arch impression technique. MATERIAL AND METHODS: A stone cast of an edentulous mandibular arch containing 5 implant analogs was fabricated to create a master model. The 3-dimensional (3D) spatial orientations of implant analogs on the master model were measured with a coordinate measuring machine (CMM) (control). Five definitive casts were made from the master model with a splinted impression technique. The positions of the implant analogs on the 5 casts were measured with a NobelProcera scanner (conventional method). Prototype optical targets were attached to the master model implant analogs, and 5 sets of images were recorded with a digital camera and a standardized image capture protocol. Dimensional data were imported into commercially available photogrammetry software (photogrammetric method). The precision and accuracy of the 2 methods were compared with a 2-sample t test (α=.05) and a 95% confidence interval. RESULTS: The location precision (standard error of measurement) for CMM was 3.9 µm (95% CI 2.7 to 7.1), for photogrammetry, 5.6 µm (95% CI 3.4 to 16.1), and for the conventional method, 17.2 µm (95% CI 10.3 to 49.4). The average measurement error was 26.2 µm (95% CI 15.9 to 36.6) for the conventional method and 28.8 µm (95% CI 24.8 to 32.9) for the photogrammetric method. The overall measurement accuracy was not significantly different when comparing the conventional to the photogrammetric method (mean difference = -2.6 µm, 95% CI -12.8 to 7.6). CONCLUSIONS: The precision of the photogrammetric method was similar to CMM, but lower for the conventional method as compared to CMM and the photogrammetric method. However, the overall measurement accuracy of the photogrammetric and conventional methods was similar.

An evaluation of student and clinician perception of digital and conventional implant impressions.

STATEMENT OF PROBLEM: The accuracy and efficiency of digital implant impressions should match conventional impressions. Comparisons should be made with clinically relevant data. PURPOSE: The purpose of this study was to evaluate the difficulty level and operator's perception between dental students and experienced clinicians when making digital and conventional implant impressions. MATERIAL AND METHODS: Thirty experienced dental professionals and 30 second-year dental students made conventional and digital impressions of a single implant model. A visual analog scale (VAS) and multiple-choice questionnaires were used to assess the participant's perception of difficulty, preference, and effectiveness. Wilcoxon signed-rank test within the groups and Wilcoxon rank-sum test between the groups were used for statistical analysis (α=.05). RESULTS: On a 0 to 100 VAS, the student group scored a mean difficulty level of 43.1 (±18.5) for the conventional impression technique and 30.6 (±17.6) for the digital impression technique (P=.006). The clinician group scored a mean (standard deviation) difficulty level of 30.9 (±19.6) for conventional impressions and 36.5 (±20.6) for digital impressions (P=.280). Comparison between groups showed a mean difficulty level with the conventional impression technique significantly higher in the student group (P=.030). The digital impression was not significantly different between the groups (P=.228). Sixty percent of the students preferred the digital impression and 7% the conventional impression; 33% expressed no preference. In the clinician group, 33% preferred the digital impression and 37% the conventional impression; 30% had no preference. Seventy-seven percent of the student group felt most effective with digital impressions, 10% with conventional impressions, and 13% with either technique, whereas 40% of the clinician group chose the digital impression as the most effective technique, 53% the conventional impression, and 7% either technique. CONCLUSIONS: The conventional impression was more difficult to perform for the student group than the clinician group; however, the difficulty level of the digital impression was the same in both groups. It was also determined that the student group preferred the digital impression as the most efficient impression technique, and the clinician group had an even distribution in the choice of preferred and efficient impression techniques.

Assessing the feasibility and accuracy of digitizing edentulous jaws.

BACKGROUND: Despite the accuracy of intraoral scanners (IOSs) in producing single-unit scans and the possibility of generating complete dentures digitally, little is known about their feasibility and accuracy in digitizing edentulous jaws. The purpose of this in vitro investigation was to evaluate the feasibility and accuracy of digitizing edentulous jaw models with IOSs. METHODS: The authors used an industrial laser scanner (reference scanner) and four IOSs to digitize two representative edentulous jaw models. They loaded the data sets obtained into three-dimensional evaluation software, superimposed the data sets and compared them for accuracy. The authors used a one-way analysis of variance to compute differences within groups (precision), as well as to compare values with those of the reference scanner (trueness) (statistical significance, P < .05). RESULTS: Mean trueness values ranged from 44.1 to 591.8 micrometers. Data analysis yielded statistically significant differences in trueness between all scanners (P < .05). Mean precision values ranged from 21.6 to 698.0 µm. The study results showed statistically significant differences in precision between all scanners (P < .05), except for the CEREC AC Bluecam (Sirona, Bensheim, Germany) and the Zfx IntraScan (manufactured by MHT Italy, Negrar, Italy/ MHT Optic Research, Niederhasli, Switzerland; distributed by Zfx, Dachau, Germany) (P > .05). CONCLUSIONS: Digitizing edentulous jaw models with the use of IOSs appears to be feasible, although the accuracy of the scanners differs significantly. The results of this study showed that only one scanner was sufficiently accurate to warrant further intraoral investigations. Further enhancements are necessary to recommend these IOSs for this particular indication. Practical Implications. On the basis of the results of this study, the authors cannot recommend these four IOSs for digitization of edentulous jaws in vivo.

Influence of scanning strategies on the accuracy of digital intraoral scanning systems.

The digital intraoral impression is a central part in today's CAD/CAM dentistry. With its possibilities, new treatment options for the patient is provided and the prosthetic workflow is accelerated. Nowadays, the major issue with intraoral scanning systems is to gain more accuracy especially for larger scan areas and to simplify clinical handling for the dentist. The aim of this study was to investigate different scanning strategies regardingtheir accuracy with full arch scans in an in-vitro study design. A reference master model was used for the digital impressions with the Lava COS, the Cerec Bluecam and a powderfree intraoral scanning system, Cadent iTero. The trueness and precision of each scanning protocol was measured. Lava COS provides the a trueness of 45.8 microm with the scanning protocol recommended from the manufacturer. A different scanning protocol shows significantly lower accuracy (trueness +/- 90.2 microm). Cerec Bluecam also benefits from an optimal scanning protocol with a trueness of +/- 23.3 microm compared to +/- 52.5 microm with a standard protocol. The powderfree impression system Cadent iTero shows also a high accurate full-arch scan with a trueness of +/- 35.0 microm and a precision of +/- 30.9 microm. With the current intraoral scanning systems, full arch dental impressions are possible with a high accuracy, if adequate scan strategies are used. The powderfree scanning system provides the same level of accuracy compared to scanning systems with surface pretreatment.

Accuracy of dies captured by an intraoral digital impression system using parallel confocal imaging.

The purpose of this investigation was to measure the accuracy of digital impressions (DIs) compared to conventional impressions (CIs). Using the iTero system, a master cast was scanned to produce stereolithography dies. As a control group, silicone impressions were taken and poured using stone. The resulting stereolithography and stone dies were scanned and overlayed on the scanned reference image of the master cast. The mean (± standard deviation) dimensional difference to the master cast was 23.9 (± 17.6) ?m for DIs and 17.6 (± 45.6) µm for CIs. The results indicate that DIs also provides enough accuracy for clinical application.