Traditional versus simplified impression methods for complete dentures: critical appraisal of evidence / Método tradicional versus simplificado en impresiones para prótesis total removible: evaluación crítica de la evidencia Método tradicional versus simplificado

Abstract Introduction: Inspite of the great advances in dentistry, aging populations imply that there are still significant numbers of edentulous people worldwide. In most cases, implant-assisted prosthetic rehabilitation is the best solution. However, economic issues constrain access to this therapeutic approach, meaning that conventional removable prosthetics continue to be the most frequent treatment. In the removable denture making process, the so-called traditional method has been widely taught and used. It involves taking two impressions: a preliminary one followed by a definitive one (or functional). The simplified method constructs the prosthesis directly from the first impression obtained with a stock tray, without the need of a second impression. Purpose: To review the scientific evidence comparing both methods in terms of patient satisfaction, clinical quality, and masticatory performance and capacity. Results: No advantages have been found in favor of the traditional method regarding the four variables selected. Conclusions: According to the available information, the traditional method of taking impressions for complete removable dental prostheses does not provide significantly superior clinical results when compared to those obtained using the simplified method in terms of clinical quality, patient satisfaction, performance and masticatory capacity.

Resumen Introducción: Pese a los avances de la odontología, el fenómeno del envejecimiento de la población ha generado que la cantidad de personas desdentadas totales aún represente una cifra significativa. Los artificios protésicos implanto-asistidos constituyen, en la mayoría de los casos, la mejor alternativa rehabilitadora. Sin embargo, la variable económica surge como el principal impedimento para que los pacientes accedan a este recurso, y por este motivo, mantienen la prótesis total removible como una opción terapéutica. Para su confección, el método tradicional indica la necesidad de tomar dos impresiones: una preliminar y una definitiva o funcional. El método simplificado, confecciona la prótesis a partir de la primera impresión, obtenida con cubeta de stock. Objetivo: Revisar evidencia científica que compara ambos métodos en cuanto a las variables de: satisfacción del paciente, calidad clínica, rendimiento y capacidad masticatoria. Resultados: No se verifican ventajas a favor del método tradicional en relación a las variables estudiadas. Conclusiones: En concordancia con la información recabada, los resultados clínicos obtenidos mediante el método tradicional de toma de impresiones para prótesis totales no son significativamente superiores a los del método simplificado en relación a calidad clínica, satisfacción del paciente, rendimiento y capacidad masticatoria.

Precisión de los sistemas de impresión digital intraoral en odontología restauradora: Una revisión de la literatura / Accuracy of Intraoral Digital Impression Systems in Restorative Dentistry: A Review of the Literature

Abstract: La impresión intraoral permite al odontólogo obtener directamente los datos de las piezas dentales que se requiera rehabilitar, otorgándole mayor precisión y eliminando así de la fase clínica la toma de impresión y la fabricación del modelo, aspectos sensibles a errores. El objetivo de la presente revisión es identificar el sistema de impresión digital intraoral más preciso y además identificar los factores que afectan a la precisión de esta en odontología restauradora. Mediante una revisión bibliográfica con búsqueda en las bases de datos de PubMed y Embase se obtuvieron 153 artículos, luego de la evaluación cualitativa se incluyeron en la revisión 14 que cumplieron con los criterios de inclusión y exclusión. Se determinó que la experiencia del dentista, la convergencia en la preparación dental y la terminación cervical son determinantes al momento de la toma de impresión digital, sin embargo, el uso o no de polvo no es relevante. El sistema de impresión digital Lava C.O.S., iTero y True definition son los más precisos dependiendo siempre del tipo de rehabilitación a realizar.

Abstract: Digital impresión allows the dentist to directly obtain the data of the dental pieces that neet to be rehabilitated, giving it greater precisión and thus eliminating the impression and manufacturing of the dental model, error-sensitive aspects of the clinical phase. The aim of this review is to identify the most accurate intraoral digital impression system and identifiy the factors that affect the accuracy in the restorative dentistry. Through a bibliographic review with search in PubMed and Embase databases, 153 articles were obtained, after qualitative evaluation they were included in the revisión 14 that met the inclusion and exclusion criteria. It was determined that the experience of the dentist, the convergence in the dental preparation and the cervical termination are decisive at the accuracy of the digital impression, however, the use or not of dust is not relevant. The Lava C.O.S., iTero and True definition are the most accurate always depending on the type of rehabilitation to be performed.

Infection Control in the Dental Practice with Emphasis on Intraoral Scanners and Semi-Critical Complex Instruments / Control de Infecciones en la Práctica Dental Con Énfasis en Escáneres Intraorales e Instrumentos Complejos Semicríticos

ABSTRACT: We present an integrative review of the literature conducted to find and analyse specific measures for disinfection and/or sterilization of intraoral complex instruments, applicable to intraoral scanners. We performed a two-stage search in the PubMed/MEDLINE, SciELO, REDALYCS, and LILACS databases, and the Google Scholar website, which included full articles in Spanish, Portuguese, and English. The strategy associated the terms 'disinfection', 'biosecurity', 'decontamination', and (a) 'intraoral scanners', and (b) other 'semi-critical' intraoral complex instruments, according to the American Dental Association definition (e.g., 'turbine', etc). Strategy (a) produced just one outcome, whereas (b) produced nine articles, which only suggested low-level disinfectants.The lack of empirically based protocols that allow effective microbiological control makes it necessary to create a new categorization for these instruments when trying to comply with American Dental Association recommendations for dental practice.

RESUMEN: Presentamos una revisión integradora de la literatura realizada para encontrar y analizar medidas específicas de desinfección y / o esterilización de instrumentos complejos intraorales, aplicables a los escáneres intraorales. Realizamos una búsqueda en dos etapas en las bases de datos PubMed / MEDLINE, SciELO, REDALYCS y LILACS, y en el sitio web Google Scholar, que incluía artículos completos en español, portugués e inglés. La estrategia asoció los términos 'desinfección', 'bioseguridad', 'descontaminación' y (a) 'escáneres intraorales', y (b) otros instrumentos complejos intraorales 'semicríticos', según la definición de la Asociación Dental Ameri- cana (p. Ej., 'turbina', etc.). La estrategia (a) produjo un solo resultado, mientras que (b) produjo nueve artículos, que solo sugirieron desinfectantes de bajo nivel. La falta de protocolos de base empírica que permitan un control microbiológico efectivo hace necesario crear una nueva categorización para estos instrumentos, cuando se trata de cumplir con las recomendaciones de la Asociación Dental Americana para la práctica dental.

Marginal and internal fit of full ceramic crowns milled using CADCAM systems on cadaver full arch scans.

BACKGROUND: Chairside systems are becoming more popular for fabricating full-ceramic single restorations, but there is very little knowledge about the effect of the entire workflow process on restoration fit. Therefore, this study aimed to compare the absolute marginal discrepancy (AMD) and the full internal fit (FULL) of all-ceramic crowns made by two chairside systems, Planmeca FIT and CEREC, with detailed and standard mill settings. METHODS: One upper molar was prepared for an all-ceramic crown in human cadaver maxilla. Full-arch scans were made by Emerald or Omnicam four times each. Twenty-four e.max crowns were designed and milled by the Planmill 30s or 40s or CEREC MCXL mills with either detailed or standard settings. The cadaver tooth was extracted, and each crown was fixed on it and scanned by a high-resolution microCT scanner. The AMD and FULL were measured digitally in mesio-distal and bucco-lingual 2D slices. The actual and predicted times of the milling were also registered. RESULTS: No differences were observed between detailed or standard settings in either system. The AMD was significantly higher with CEREC (132 ± 12 µm) than with either Planmill 30s (71 ± 6.9 µm) or 40s (78 ± 7.7 µm). In standard mode, the FULL was significantly higher with CEREC (224 ± 9.6 µm) than with either Planmill 30s (169 ± 8.1 µm) or 40s (178 ± 8.5 µm). There was no difference between actual and predicted time with the two Planmeca models, but with CEREC, the actual time was significantly higher than the predicted time. The 30s had significantly higher actual and predicted times compared to all other models. Across all models, the average milling time was 7.2 min less in standard mode than in detailed mode. CONCLUSIONS: All fit parameters were in an acceptable range. No differences in fit between Planmeca models suggest no effect of spindle number on accuracy. The detailed setting has no improvement in the marginal or internal fit of the restoration, yet it increases milling time.

Comparing the trueness of seven intraoral scanners and a physical impression on dentate human maxilla by a novel method.

BACKGROUNDS: Intraoral scanner (IOS) accuracy is commonly evaluated using full-arch surface comparison, which fails to take into consideration the starting position of the scanning (scan origin). Previously a novel method was developed, which takes into account the scan origin and calculates the deviation of predefined identical points between references and test models. This method may reveal the error caused by stitching individual images during intraoral scan. This study aimed to validate the novel method by comparing the trueness of seven IOSs (Element 1, Element 2, Emerald, Omnicam, Planscan, Trios 3, CS 3600) to a physical impression digitized by laboratory scanner which lacks linear stitching problems. METHODS: Digital test models of a dentate human cadaver maxilla were made by IOSs and by laboratory scanner after polyvinylsiloxane impression. All scans started on the occlusal surface of the tooth #15 (universal notation, scan origin) and finished at tooth #2. The reference model and test models were superimposed at the scan origin in GOM Inspect software. Deviations were measured between identical points on three different axes, and the complex 3D deviation was calculated. The effect of scanners, tooth, and axis was statistically analyzed by the generalized linear mixed model. RESULTS: The deviation gradually increased as the distance from scan origin increased for the IOSs but not for the physical impression. The highest deviation occurred mostly at the apico-coronal axis for the IOSs. The mean deviation of the physical impression (53 ± 2 µm) was not significantly different from the Trios 3 (156 ± 8 µm) and CS 3600 (365 ± 29 µm), but it was significantly lower than the values of Element 1 (531 ± 26 µm), Element 2 (246 ± 11 µm), Emerald (317 ± 13 µm), Omnicam (174 ± 11 µm), Planscan (903 ± 49 µm). CONCLUSIONS: The physical impression was superior compared to the IOSs on dentate full-arch of human cadaver. The novel method could reveal the stitching error of IOSs, which may partly be caused by the difficulties in depth measurement.

Accuracy on Scanned Images of Full Arch Models with Orthodontic Brackets by Various Intraoral Scanners in the Presence of Artificial Saliva.

AIM: This study aims to evaluate the accuracy of scanned images of 4 clinically used intraoral scanners (CS3600, i500, Trios3, Omnicam) when scanning the surface of full arch models with various kinds of orthodontic brackets in the presence of artificial saliva. Materials and Methods. Four study models were prepared; bonded with ceramic, metal, and resin brackets, respectively, and without brackets. Reference images were taken by scanning the models with an industrial scanner. Study models were then applied with an artificial saliva and scanned 10 times, respectively, with the above 4 intraoral scanners. All images were converted to STL file format and analyzed with 3D analysis software. By superimposing with the reference images, mean maximum discrepancy values and mean discrepancy values were collected and compared. For statistical analysis, two-way ANOVA was used. RESULTS: Omnicam (1.247 ± 0.255) showed higher mean maximum discrepancy values. CS3600 (0.758 ± 0.170), Trios3 (0.854 ± 0.166), and i500 (0.975 ± 0.172) performed relatively favourably. Resin (1.119 ± 0.255) and metal (1.086 ± 0.132) brackets showed higher mean maximum discrepancy values. Nonbracket (0.776 ± 0.250) and ceramic bracket (0.853 ± 0.269) models generally showed lower mean maximum discrepancy values in studied scanners. In mean discrepancy values, the difference between scanners was not statistically significant whereas among brackets, resin bracketed models (0.093 ± 0.142) showed the highest value. CONCLUSION: Intraoral scanners and brackets had significant influences on the scanned images with application of artificial saliva on the study models. It may be expected to have similar outcomes in an intraoral environment. Some data showed the discrepancy values up to about 1.5 mm that would require more caution in using intraoral scanners for production of detailed appliances and records.

Technical note on introducing a digital workflow for newborns with craniofacial anomalies based on intraoral scans - part I: 3D printed and milled palatal stimulation plate for trisomy 21.

BACKGROUND: Advanced digital workflows in orthodontics and dentistry often require a combination of different software solutions to create patient appliances, which may be a complex and time-consuming process. The main objective of this technical note is to discuss treatment of craniofacial anomalies using digital technologies. We present a fully digital, linear workflow for manufacturing palatal plates for infants with craniofacial anomalies based on intraoral scanning. Switching to intraoral scanning in infant care is advantageous as taking conventional impressions carries the risk of impression material aspiration and/or infections caused by material remaining in the oronasal cavity. MATERIAL AND METHODS: The fully digital linear workflow presented in this technical note can be used to design and manufacture palatal plates for cleft palate patients as well as infants with functional disorders. We describe the workflow implemented in an infant with trisomy 21. The maxilla was registered using a digital scanner and a stimulation plate was created using dental CAD software and an individual impression tray module on a virtual model. Plates were manufactured using both additive and subtractive methods. Methacrylate based light curing resin and Poly-Ether-Ether-Ketone were the materials used. RESULTS: The palatal area was successfully scanned to create a virtual model. The plates fitted well onto the palatal area. Manual post-processing was necessary to optimize a functional ridge along the vestibular fold and remove support structures from the additively manufactured plate as well as the milled plate produced from a blank. The additively manufactured plate fitted better than the milled one. CONCLUSION: Implementing a fully digital linear workflow into clinical routine for treatment of neonates and infants with craniofacial disorders is feasible. The software solution presented here is suitable for this purpose and does not require additional software for the design. This is the key advantage of this workflow, which makes digital treatment accessible to all clinicians who want to deal with digital technology. Whether additive or subtractive manufacturing is preferred depends on the appliance material of choice and influences the fit of the appliance.

Accuracy of Intra-Oral Scans Compared to Conventional Impression in Vitro.

AIM: The purpose of the present study was to assess the accuracy of intra-oral scans and conventional impression measured at various points on a single tooth preparation. METHODS: Ten conventional silicone impressions, and ten intra oral-scans using eight different digital intra oral digital scanners were taken of a prepared master tooth. The conventional impressions were directly digitised using a laboratory scanner. Each scan/impression was superimposed on a high-accuracy digital model of the prepared master tooth. For each superimposition, the deviation from the prepared master tooth was measured at six points on four two-dimensional cross-sections. Data was analysed using two-way analysis of variance (ANOVA). RESULTS: Most intra oral scanners had lower accuracy at the preparation margin compared to smooth surfaces. When only conventional impression and the latest intra oral scanners of various manufacturers are considered, the mean discrepancy at the preparation margin was 50µm (SD 16) for conventional impression, 15µm (SD 4) for trios 3, 26µm (SD 4) for LAVA TDS, 29µm (SD 7) for CEREC Omnicam, 30µm (SD 6) for CS 3600 and 64µm (SD 7) for GC aadva. The increased accuracy of trios 3 was statistically significant (p<0.05). CONCLUSIONS: At the preparation margin, Trios 3 performed significantly better than conventional impression and the other intra oral scanners. LAVA TDS, CEREC Omnicam and CS3600 showed similar accuracy at the margin, yet better than conventional impression and GC Aadva.

Milled versus moulded mock-ups based on the superimposition of 3D meshes from digital oral impressions: a comparative in vitro study in the aesthetic area.

BACKGROUND: Aesthetic porcelain veneers proved to be a long-term reliable prosthetic solution, ensuring minimal invasiveness. The use of veneers requires an adhesive cementation technique, so maintaining as much enamel as possible is to ensure lasting success. A diagnostic mock-up is a key tool that allows a preview of the outcome of the aesthetic restoration: it is obtainable both in an analog and digital way. With the recent developments in impression technology and the ever so fast growing use of CAD-CAM technologies it is useful to understand the pros and cons of either one of these techniques (analog and digital) in order to identify the easier and more convenient workflow in aesthetic dentistry. METHODS: After taking pictures and impressions of the dental arcs of a patient in need of aesthetic rehabilitation, 52 resin models were produced and a digital drawing of the smile was outlined. Both an analog and a digital wax-up were obtained from two of the 52 models: the latter was obtained using digital impressions and a dedicated software. The analog wax-up was then used to produce 25 matrices that have later been used to mould 25 resin mock-ups using a traditional moulding protocol (Control Group - CG). The digital wax-up was used to mill 25 PMMA mock-ups. Each mock-up, both milled and moulded (total 50), was then laid on the other 50 resin models as a digital impression of it was taken. The STL. files of the milled mock-ups were compared with the 3D CAD wax-up made using a specific software. The STL. files of the analog printed mock-ups were compared with the traditional wax-up design. A statistical analysis was carried out to evaluate the difference between the groups. RESULTS: The statistical analysis showed a significant difference (P > 0.01) between the mean value of the distance between the points of the overlapping STL. meshes in GC (0.0468 mm) and in TG (Test Group - TG) (0,0109 mm). CONCLUSIONS: The study showed a difference in accuracy between traditional moulded and milled mock-ups compared to their original wax-up. The data analysis reports that the digital method allows for greater accuracy. Within the limitations of this study, a fully digital workflow is to considered more reliable when it come to creating an esthetic mockup: the digital procedure has been shown to be more accurate than the one made manually which is much more operator dependent and it brings an increase to the chance of error, and that could ultimately affect the final result.

The effect of regular dental cast artifacts on the 3D superimposition of serial digital maxillary dental models.

Superimpositions of serial 3D dental surface models comprise a powerful tool to assess morphological changes due to growth, treatment, or pathology. In this study, we evaluated the effect of artifacts on the superimposition outcome, using standard model acquisition and superimposition techniques. Ten pre- and post-orthodontic treatment plaster models were scanned with an intraoral scanner and superimposed using the iterative closest point algorithm. We repeated the whole process after manual removal of plaster artifacts, according to the current practice, as well as after re-scanning the cleaned models, to assess the effect of the model acquisition process derived artifacts on the superimposition outcome. Non-parametric multivariate models showed no mean effect on accuracy and precision by software settings, cleaning status (artifact removal), or time point. The choice of the superimposition reference area was the only factor that affected the measurements. However, assessment of individual cases revealed significant differences on the detected tooth movement, depending on artifact removal and on the model acquisition process. The effects of all factors tended to decrease with an increase in the size of the superimposition reference area. The present findings highlight the importance of accurate, artifact-free models, for valid assessment of morphological changes through serial 3D model superimpositions.

Conventional versus Digital Impressions for Full Arch Screw-Retained Maxillary Rehabilitations: A Randomized Clinical Trial.

Background: The objective of this study was to compare conventional versus digital impressions for Full-Arch maxillary rehabilitations. Methods: Patients selected for this study were treated with full-arch screw-retained rehabilitations supported by six immediately loaded dental implants. Patients have been scheduled randomly into control (conventional impression group, CIG) and test (digital impression group, DIG) groups respectively for a fully conventional workflow and a fully digital workflow. In both groups, within 24 h, temporary prostheses were delivered. Four months after the implant positioning, the two groups dealt with the fabrication of definitive restorations: conventional pick-up was performed in the control group, and definitive digital impressions were carried out in the test group. The time involved following these two procedures was recorded. Patients underwent intraoral digital radiographs to evaluate the accuracy of the framework-implant connection, check for the presence of voids at the bar-implant connection and measure bone level. Criteria used to assess success at the prosthetic level were the occurrence of prosthetic maintenance, the absence of fractures of the acrylic resin superstructure and voids. Results: A total of 50 patients received immediately loaded prostheses supported by six implants (total 300 implants). A fixture and prosthetic survival rate of 100% was observed. All digital X-ray examinations revealed a bar-implant connection accuracy and no voids. Differences that were not statistically significant (p > 0.05) in marginal bone loss were found between control and test groups. Significantly less time was spent to perform digital impression procedure (p < 0.05). Conclusions: Clinical and radiological results of the test group advocate a satisfactory accuracy and predictability of the intraoral scanner (IOS) to be a reliable alternative in clinical practice for implant full-arch rehabilitations and suggest fabrication of definitive restorations with a successful marginal fit precision.

A New Approach to Accuracy Evaluation of Single-Tooth Abutment Using Two-Dimensional Analysis in Two Intraoral Scanners.

The aim of this study was to two-dimensionally evaluate deviation errors at five digital cross-sections of single-tooth abutment in regards to data obtained from two intraoral scanners, and to evaluate accuracy of individual scanners. Two intraoral scanners, the Trios 3® (3 Shape, Copenhagen, Denmark) and EzScan® (Vatech, Hwaseong, Korea), were evaluated by utilizing 13 stone models. The superimposed 3D data files were sectioned into five different planes: buccal-lingual section (BL), mesial-distal section (MD), transverse high section (TH), transverse middle section (TM), and transverse low section (TL). Accuracy comparison between the two scanners in 5 groups was performed. BL vs. MD of each scanner, and three transverse groups (TH, TM, TL) of each scanner were analyzed for accuracy comparison. In comparison of 2-D analyses for two intraoral scanners, Trios 3® showed statistically significant higher accuracy in root mean square (RMS) at BL, TH, and TL (p < 0.05). For each scanner, RMS value showed that mesial-distal sections were more prone to error than buccal-lingual section, which exhibited statistically significant errors (p < 0.05) while the transverse groups did not. Two-dimensional analysis is more insightful than three-dimensional analysis on single-tooth abutment. In mesiodistal areas, rough prepped areas, and sharp edges where scanner accessibility is difficult, high deviation errors are shown.

Students' perspectives on the use of digital versus conventional dental impression techniques in orthodontics.

BACKGROUND: Despite the increasing use of digital impressions in orthodontics, this technique does not usually form part of the learning objectives in dental training. The aim of this study was to determine how students assess the user-friendliness of intraoral scanners compared to a conventional impression technique after a theoretical and practical teaching module. METHODS: Thirty-one dental students in their seventh semester (4th year) received and conducted digital (3 M, St. Paul, NM) and conventional (alginate) impressions from: (i) the dentist's perspective, and (ii) the patient's perspective. Each student completed four questionnaires to evaluate: (i) the user-friendliness of intraoral scanning, and (ii) intraoral scanning compared to the conventional method. RESULTS: Thirty (97%) students had not previously performed digital impressions. Twenty-four (77%) students were overall "very" or "rather" satisfied with the handling of the intraoral scanning method, and 18 (58%) preferred digital to alginate impressions from the dentist's perspective. From the "patient's" perspective, the students did not report any significant differences between the two methods. However, the impression tray in conventional impressions reduced "patient" comfort significantly more than the camera in digital impressions (Z = - 3.496, p < 0.001). CONCLUSIONS: Dental students were able to practice both conventional alginate and modern digital impressions without prior knowledge of intraoral impression techniques after basic training and an introduction from dentists. Students reported a preference for the digital technique. Implementing digital intraoral impressions into undergraduate training is recommended to familiarise students with this rapidly developing digital technique at an early stage.

A Validation Study of the Impression Replica Technique.

PURPOSE: To validate the well-known and often-used impression replica technique for measuring fit between a preparation and a crown in vitro. MATERIALS AND METHODS: The validation consisted of three steps. First, a measuring instrument was validated to elucidate its accuracy. Second, a specimen consisting of male and female counterparts was created and validated by the measuring instrument. Calculations were made for the exact values of three gaps between the male and female. Finally, impression replicas were produced of the specimen gaps and sectioned into four pieces. The replicas were then measured with the use of a light microscope. The values received from measuring the specimen were then compared with the values received from the impression replicas, and the technique was thereby validated. RESULTS: The impression replica technique overvalued all measured gaps. Depending on location of the three measuring sites, the difference between the specimen and the impression replicas varied from 47 to 130 µm. CONCLUSION: The impression replica technique overestimates gaps within the range of 2% to 11%. The validation of the replica technique enables the method to be used as a reference when testing other methods for evaluating fit in dentistry.

Obtaining reliable intraoral digital scans for an implant-supported complete-arch prosthesis: A dental technique.

This article describes a technique for obtaining an accurate complete-arch digital scan for an edentulous patient. To achieve this, an auxiliary polymeric device that simulates a denture is designed, fabricated, and placed in the mouth. This device, having the geometry of a typical dental arch, facilitates the digitalization of the edentulous complete arch. This is because the change in radius of the curvature (change of geometry) enables the scanner to perform a more accurate alignment. Initially, the necessary location of the implants is acquired, and then the soft tissue is added. This technique can achieve accurate complete-arch digital scans. Distances between implants are closer to the gold standard when using this auxiliary geometry piece than those obtained without using it.

Accuracy of Three Digitization Methods for the Dental Arch with Various Tooth Preparation Designs: An In Vitro Study.

PURPOSE: To evaluate the accuracy of three digitization methods for the maxillary dental arch. MATERIALS AND METHODS: A maxillary typodont with various tooth preparation designs was used as the reference model. The scanned data were classified into direct scanning (DS), cast scanning (CS), and impression scanning (IS) groups according to the techniques applied for digitization (n = 10/group). An intraoral scanner was used for the DS group. Impressions obtained with polyether impression material were scanned with a tabletop scanner for the IS group. For the CS group, the definitive casts fabricated from the obtained impressions were scanned with the same tabletop scanner. The accuracy (trueness and precision) of the produced virtual dental casts was evaluated with specialized software. The full-arch and individual abutment deviations were measured with regard to root mean square error (RMSE) values. Data were analyzed with statistical software with an α = 0 . 05 . RESULTS: The RMSE values for both trueness and precision were lowest in the IS group, followed by the CS and DS groups, with statistically significant differences among the groups (p < 0.05). The trueness of individual abutments was significantly higher in the IS group than in the DS group. In addition, the trueness of individual abutments was affected by the location of the abutments in the DS group, whereas it did not differ between individual abutments in the CS and IS groups. CONCLUSIONS: These findings suggest that the IS method is an accurate digitization technique for the creation of a virtual dental cast.

Accuracy of Different Implant Impression Techniques: Evaluation of New Tray Design Concept.

PURPOSE: To evaluate implant impression accuracy with a new tray design concept in comparison to nonsplinted and splinted impression techniques for a 2-implant situation. MATERIALS AND METHODS: A reference bar titanium framework was fabricated to fit on 2 parallel implants. The framework was used to generate a resin master model with 2 implants that fit precisely against the framework. Three impression techniques were evaluated: (1) nonsplinted, (2) splinted, and (3) nonsplinted with modified tray impressions. All the trays were fabricated from light-cured acrylic resin material with openings that corresponded to the implant impression copings. Ten impressions were taken for each technique using poly(vinyl siloxane) impression material. The impressions were poured with type IV dental stone to generate the test casts. A rosette strain gauge was bonded to the middle of the framework. As the framework retaining screws were tightened on each test cast, the developed strains were recorded until the completion of the tightening to 35 Ncm. The generated strains of the rosette strain gauge were used to calculate the maximum principal strain. RESULTS: A statistically significant difference was observed among the different impression techniques. The modified tray design impression technique was associated with the least framework strains, which indicates greater accuracy compared with the other techniques. There was no significant difference between the splinted and the nonsplinted impression techniques. CONCLUSIONS: The new tray design concept appeared to produce more accurate implant impressions than the other techniques. Despite the statistical difference among the impression techniques, the clinical significance of this difference is yet to be determined.

3D-printed custom trays with a Gothic arch for centric relation recording and definitive impression making for complete dentures: A dental technique.

An appliance was designed and fabricated by using computer-aided design and computer-aided manufacturing (CAD-CAM) and 3-dimensional (3D) printing to combine a custom tray with an intraoral Gothic arch. This helped simplify centric relation recording and combined definitive impression making and centric relation recording into a single step.

Effect of Gingival Retraction Method to Lateral Gingival Displacement Width

Abstract Objective: To analyze the efficacy of retraction cord with a hemostatic agent in comparison with retraction paste on lateral gingival displacement, to achieve the success of fixed dental prostheses (FDP). Material and Methods: Test samples included 32 teeth that required treatment with metal-porcelain FDP at RSKGM FKG Universitas Indonesia. Impressions were taken before the gingival retraction procedure. From the 32 samples, 16 teeth were retracted using a combination of retraction cord and hemostatic agent, whereas the other half were retracted with retraction paste. Impressions were then taken. The sample was made using cutting die. Lateral gingival displacement width was measured on die-cast using an optical microscope Results: The mean value of group A before gingival retraction was 0.1695 mm, and after gingival retraction was 0.4705 mm. The mean value of group B before gingival retraction was 0.1767 mm, and after gingival retraction was 0.3289 mm. Lateral gingival displacement width between a combination of cord retraction and hemostatic agent group in comparison with the retraction paste group showed a significant difference (p<0.001). The combination of cord retraction and hemostatic agent group showed higher mean value Conclusion: Gingival displacement width as a result of cord retraction with the hemostatic agent was larger compared to the retraction paste. Even though both of them are still considered to be effective in providing access for impression material.

Intraoral versus extraoral digital occlusal records: a pilot study.

The aim of the present pilot study was to analyze the reliability of interocclusal contact records generated with an intraoral scanner (TRIOS Standard) and an extraoral scanner (Zfx Evolution). Ten patients were selected. The number of occlusal contacts was first determined with the conventional method using 8-µm articulating paper (gold standard) (control). These conventional records were then compared with the intra- and extraoral digital records. Diagnostics tests (sensitivity, specificity, predictive values for positives and negatives), receiver operating characteristic (ROC) curve, and Cohen's kappa coefficient were performed to analyze the data. The kappa index of the extraoral scanner (40.7%) was considered to be 'moderate,' and better than that of the intraoral scanner (26.1%), which was considered to be 'low.' The extraoral scanner showed better results in the diagnostic test and in the ROC curve. The first results suggest that the extraoral scanner is more reliable for recording occlusal contacts than the intraoral scanner.