Comparison of digital and silicone impressions for single-tooth implants and two- and three-unit implants for a free-end edentulous saddle

Background The use of intraoral scanners (IOS) has facilitated the use of digital workflows for the fabrication of implant-supported prostheses not only for single missing teeth, but also for multiple missing teeth. However, the clinical application of IOS and computer-aided design/manufacturing (CAD/CAM) in implant-supported prosthodontics remains unclear. This study aimed to compare the accuracy of digital and silicone impressions for single-tooth implants for bounded edentulous spaces and two-unit and three-unit implant-supported fixed dental prostheses for free-end edentulous spaces. Methods This study enrolled 30 patients (n = 10 for each of the three groups) with an average age of 61.9 years. Conventional silicone-based and digital IOS-based impressions were made for all patients, and the implant superstructures were fabricated. We measured the scan-body misfit and compared the accuracy of the impressions for single-unit, two-unit, and three-unit implant prostheses with a bounded edentulous space by superimposing the standard triangulated language (STL) data obtained from IOS over the STL data of the plaster model used for final prosthesis fabrication. The scan bodies of the superimposed single-molar implant, two-unit implant prosthesis without teeth on the mesial side, two-unit implant prosthesis without teeth on the distal side, three-unit implant prosthesis without teeth on the mesial side, and three-unit implant prosthesis without teeth on the distal side were designated as A, B1, B2, C1, and C2, respectively. The misfit for each scan body was calculated and the accuracies were compared using the Tukey–Kramer method. Results The average scan-body misfit for conditions A, B1, B2, C1, and C2 was 40.5 ± 18.9, 45.4 ± 13.4, 56.5 ± 9.6, 50.7 ± 14.9, and 80.3 ± 12.4 μm, respectively. Significant differences were observed between the accuracies of A and B2, A and C2, and C1 and C2 (P < 0.001). Conclusions IOS and CAD/CAM can find clinical applications for implant-supported prostheses of up to three units for a bounded edentulous saddle. The use of IOS could render implant treatment easier, benefiting both the surgeons and patients. Prosthesis maladjustment may lead to peri-implantitis and prosthetic fracture. Therefore, further validation of the accuracy of IOS impressions is required in patients with multiple missing teeth in long-span implant prostheses.

Accuracy and dimensional reproducibility by model scanning, intraoral scanning, and CBCT imaging for digital implant dentistry

Background Recently, it has become possible to analyze implant placement position using the digital matching data of optical impression data of the oral cavity or plaster models with cone beam computed tomography (CBCT) data, and create a highly accurate surgical guide. It has been reported that CBCT measurements were smaller than the actual values, termed shrinkage. Matching of digital data is reliable when the plaster model or intraoral impression values show shrinkage at the same rate as the CBCT data. However, if the shrinkage rate is significantly different, the obtained digital data become unreliable. To clarify digital matching reliability, we examined dimensional reproducibility and shrinkage in measurements obtained with a model scanner, intra-oral scanner (iOS), and CBCT. Materials and methods Three implants that were arranged in a triangle were fixed in an acrylic plate. The distance between each implants were measured using model scanner, iOS, and CBCT. The actual size measured by electronic caliper was regarded as control. Results All values measured with CBCT were significantly smaller than that of model scanner, iOS, and control (p<0.001). The model scanner shrinkage was 0.37-0.39%, iOS shrinkage was 0.9-1.4%, and CBCT shrinkage was 1.8-6.9%. There were statistically significant differences among the shrinkage with iOS, CBCT, and model scanner (p<0.001). Conclusion Our findings showed that all measurements obtained with those modalities showed shrinkage as compared to the actual values. In addition, CBCT shrinkage was largest among three different measuring methods. They indicated that data matching between CBCT and scanner measurements requires attention in regard to the reliability of values obtained with those devices.

The effectiveness of preoperative assessment using a patient-specific three-dimensional pseudoarticulation model for minimally invasive posterior resection in a patient with Bertolotti’s syndrome: a case report

Background Bertolotti’s syndrome is widely known to cause low back pain in young patients and must be considered as a differential diagnosis. Its treatment such as conservative therapy or surgery remains controversial. Surgical procedure is recommended for intractable low back pain. The three-dimensional (3D) lumbosacral transitional vertebrae anatomy should be completely understood for a successful surgery. Using an intraoperative 3D navigation and preoperative preliminary surgical planning with a patient-specific 3D plaster model contribute for safe surgery and good outcome. Case presentation A case of a 22-year-old Japanese male patient with intractable left low back pain due to lumbosacral transitional vertebrae with Bertolotti’s syndrome. The symptom resisted the conservative treatment, and anesthetic injection at pseudoarticulation only provided a short-term pain relief. Posterior resection using intraoperative three-dimensional (3D) navigation has been performed through microendoscopic view. Pseudoarticulation was totally and successfully resected in a safe manner. Conclusions Preoperative surgical planning and rehearsal using a patient-specific 3D plaster model was greatly useful and effective for surgeons in performing accurate and safe pseudoarticulation resection.

Strategies to optimize the practice of dental impression during the Covid-19 pandemic

ABSTRACT The Covid-19 is a global health threatening pandemic, so dental surgeons need to look for strategies to perform dental care safely for the patient, the dental professional himself, and the dental team. The goal is to design strategies to optimize dental impression practice during the Covid-19 pandemic. The strategies that optimize dental impression practice during the pandemic are to adopt the digital fingerprint workflow. If necessary, a conventional impression technique that favors the professional’s performance, select the impression material that is easy to decontaminate and affinity for the professional; the plaster leak must be performed still inside the dental office, and then the disinfection of the plaster model must be previously sent to the prosthesis laboratory.

AN ALTERNATIVE METHOD FOR OBTAINING A TWO-LAYER IMPRESSION WITH NON-REMOVABLE DENTAL PROSTHETICS

The main type of orthopedic treatment of the patient at the dentist is the manufacture of dentures to restore damaged or lost functions. Understanding and coordinated work of the doctor and dental technician in this case is achieved by transmitting information about the patient through the impression. It is the accuracy of the impression that affects the quality of the plaster model on which dentures are made. The article presents a description of the comparative characteristics of the time spent on taking impressions by various methods and the depth of penetration of the impression material into the "dental groove" when obtaining impressions by various methods on an experimental model.

Digital planning and guided surgery in oral rehabilitation

Digital planning of the prosthesis associated with surgical planning increased predictability, since surgical guides indicate the best place for implant installation, thus reducing the number of complications, and the CAD/CAM system provides predictability in the preparation of final restorations, according to the procedure previously planned. Our study reported a digital workflow used for the guided installation of two dental implants in regions 14 and 16, extraction of tooth 15 and installation of a fixed prothesis over implants. After anamnesis and clinical evaluation, intra- and extra-oral photographs of the patient were performed, molding the upper arch with polyvinylsiloxane (2-step putty/light-body technique) and requesting computed tomography. The plaster model obtained was sent to the laboratory and scanned. The generated file (STL) was used to create a diagnostic wax-up that was aligned to the tomography (in DICOM format), enabling the three-dimensional planning of the implants, which generated a partial printed surgical guide after approval of the dentist. After six months, the patient received the provisional fixed prosthesis printed in PMMA (polymethylmethacrylate) on an intermediate in PEEK (polyetheretherketone) aiming to condition an emergency profile to receive a definitive prosthesis two months later, with zirconia-milled infrastructure on a ti-base. The correct understanding of the operator about the steps of the digital workflow (diagnosis, prosthetic planning, surgical planning, guide preparation, temporary and final restorations) gives the operator improved predictability at the time of surgery as well as satisfactory aesthetic and functional result of definitive restorations.

Lunar Crater Models

This article traces the story of three amateur astronomers who created relief models to help them depict the changing illumination of certain lunar craters, examples of which can be found in UK museum collections today. English chemist Henry Blunt (1806–1853) adopted the emerging technology of electrotyping to reproduce and distribute his plaster model of the Eratosthenes crater to a wider audience. Scottish industrial engineer James Nasmyth (1808–1890) used a combination of drawing, modelling and photography to support his thesis on the volcanic origin of lunar craters in his popular book The Moon Considered … (1874). Spanish sculptor Dionis Renart (1878–1946) produced a series of plaster models for the Exposición General De Estudios Lunares (1912) that eventually came to Greenwich via the British selenographer Hugh Percy Wilkins (1896–1960). These three case studies provide us with valuable insights into the rationale behind the production, use and distribution of lunar crater models within amateur and popular astronomy.

Evaluation of the Reliability, Reproducibility and Validity of Digital Orthodontic Measurements Based on Various Digital Models among Young Patients

The advantages of intraoral model scanning have yielded recent developments. However, few studies have explored the orthodontic clinical use of this technique particularly among young patients. This study aimed to evaluate the reliability, reproducibility and validity of the orthodontic measurements: tooth width, arch length and arch length discrepancy in each digital model obtained by model scanner and intraoral scanner, relative to a plaster model. Arch length measured using two methods: curved arch length (CAL) measured automatically by digital program and sum of sectional liner arch length (SLAL) measured sum of anterior and posterior liner arch lengths. Arch length discrepancy calculated each arch length measurement methods: curved arch length discrepancy (CALD) and sum of sectional liner arch length discrepancy (SLALD). Forty young patients were eligible for the study. A plaster model (P), model-scanned digital model (MSD) and intraoral scanned digital model (ISD) were acquired from each patient. The reliability of the measurements was evaluated using Pearson’s correlation coefficient, while the reproducibility was evaluated using the intraclass correlation coefficient. The validity was assessed by a paired t-test. All measurements measured in P, MSD and ISD exhibited good reliability and reproducibility. Most orthodontic measurements despite of CAL in MSD exhibited high validity. Only the SLAL and SLALD in ISD group differed significantly, despite the good validity of the tooth width, CAL and CALD. The measurements based on the digital program appeared high reliability, reproducibility and accurate than conventional measurement. However, SLAL and SLALD in ISD group appeared shorter because of distortion during intraoral scanning. However, this could be compensated by using digital programed curved arch. Although the validity of SLAL and SLALD in the ISD group differed statistically, the difference is not considered clinically significant. Although MSD and ISD are acceptable for a clinical space analysis, clinicians should be aware of digital model-induced errors.

Validity, Reliability and Reproducibility of Space Analysis using Digital Model taken via Model Scanner and Intraoral Scanner: An In vivo Study

The purpose of this study is to evaluate validity, reliability and reproducibility of tooth width (TW), arch length (AL) and arch length discrepancy (ALD) measured on a digital model taken via 3-dimensional model scanner and intraoral scanner compared to a plaster model.<br/>A total of 30 patients aged 12 to 18 were eligible for the study. 3 types of models were acquired from each patient: a conventional plaster model (P), a model scanned digital model (MSD) taken via Freedom UHD^® and an intraoral scanned digital model (ISD) taken via CS3600^® in-vivo. The reliability of TW and AL in each group was evaluated using Pearson’s correlation coefficient, while the reproducibility was evaluated with intraclass correlation coefficient. The validity of space analysis was assessed by paired t-test.<br/>As a result, all measurements of P, MSD and ISD groups showed favorable reliability and reproducibility. Most of measurements for space analysis in MSD group and TW in ISD group also presented high validity. AL and ALD presented statistically significant difference between P and ISD group. The validity of measurements of space analysis in ISD group was short in doubt to valid, but clinically acceptable. Both MSD and ISD are clinically acceptable to use for space analysis but clinician should be aware that errors can be found using a digital model.

AVALIAÇÃO DE DIVERSAS FORMAS DE DESINFECÇÃO DO ALGINATO COM CLOREXIDINA

RESUMOO alginato é um material usado na odontologia para moldagem de arcada dentária. Sua propriedade de embebição permite absorver fluidos da cavidade oral, que infectam o molde e o modelo de gesso. Por isso a importância da desinfecção, prevenindo contaminação e potencial infecção cruzada. O objetivo deste estudo foi analisar a eficácia da clorexidina associada ao alginato na inibição do crescimento de microrganismos presentes na cavidade oral. O alginato foi avaliado de 4 formas distintas: sem clorexidina; com clorexidina borrifada após geleificação, com clorexidina incorporada em sua fórmula e manipulado com clorexidina 0,3%. No teste in vitro a eficácia foi avaliada frente a uma cultura de Streptococcus mutans. No teste in vivo foram feitas moldagens em 4 voluntários e os moldes de alginato e modelos de gesso avaliados microbiologicamente. Ambos os testes foram semeados em ágar sangue, incubados a 35o C por 20h e feita observação visual de crescimento bacteriano. Como resultado obteve-se: no teste in vitro houve crescimento bacteriano somente no alginato sem a clorexidina; já nos testes in vivo o alginato borrifado com clorexidina não teve crescimento em 75% dos modelos de gesso; os alginatos com clorexidina diluída, incorporada e sem clorexidina não tiveram crescimento em 12,5% dos modelos. Como conclusão obteve-se que a clorexidina foi eficiente na inibição do crescimento do S. mutans, mas aumentando a população bacteriana, o método mais efetivo foi a clorexidina borrifada, diminuindo o risco de infecção cruzada.Palavras-chave: alginato, desinfecção, clorexidina, alginate, desinfection, chlorhexidineABSTRACT Alginate is a material used in dentistry for dental arch molding. Its imbibing property allows it to absorb oral fluids, which infect the mold and plaster model. Therefore disinfection is very important to prevent contamination and potential cross infection. The objective of this study was to analyze the efficacy of alginate-associated chlorhexidine in inhibiting the growth of microorganisms present in the oral cavity. The alginate was analized in 4 different forms: no chlorhexidine; with chlorhexidine sprinkled after gelation, chlorhexidine incorporated into its formula and handled with 0.3% chlorhexidine. In the in vitro test its efficacy was evaluated considering a culture of Streptococcus mutans during the manipulation. In the in vivo test 4volunteers were molded and the alginate molds and plaster models were avaluated microbiologic. Both tests were seeded on blood agar, incubated at 35 ° C for 20h, and visual observation of bacterial growth. As a result it was obtained: in the in vitro test there was bacterial growth only in alginate without chlorhexidine; already in the in vivo test the alginate sprinkled with chlorhexidine had no bacterial growth in 75% of the gypsum models; the alginates with chlorhexidine diluted, incorporated and without chlorhexidine had no bacterial growth in 12.5% of the models. As a conclusion, chlorhexidine was efficient in inhibiting the growth of S. mutans but increasing the bacterial population. The most effective method was chlorhexidine sprayed, reducing the risk of cross infection.Keywords: alginato, desinfecção, clorexidina, alginate, desinfection, chlorhexidine