The International Journal of Prosthodontics, 02/2018

Purpose: To compare the accuracy (ie, precision and trueness) of full-arch impressions fabricated using either a conventional polyvinyl siloxane (PVS) material or one of two intraoral optical scanners. Materials and Methods: Full-arch impressions of a reference model were obtained using addition silicone impression material (Aquasil Ultra; Dentsply Caulk) and two optical scanners (Trios, 3Shape, and CEREC Omnicam, Sirona). Surface matching software (Geomagic Control, 3D Systems) was used to superimpose the scans within groups to determine the mean deviations in precision and trueness (μm) between the scans, which were calculated for each group and compared statistically using one-way analysis of variance with post hoc Bonferroni (trueness) and Games-Howell (precision) tests (IBM SPSS ver 24, IBM UK). Qualitative analysis was also carried out from three-dimensional maps of differences between scans. Results: Means and standard deviations (SD) of deviations in precision for conventional, Trios, and Omnicam groups were 21.7 (± 5.4), 49.9 (± 18.3), and 36.5 (± 11.12) μm, respectively. Means and SDs for deviations in trueness were 24.3 (± 5.7), 87.1 (± 7.9), and 80.3 (± 12.1) μm, respectively. The conventional impression showed statistically significantly improved mean precision (P < .006) and mean trueness (P < .001) compared to both digital impression procedures. There were no statistically significant differences in precision (P = .153) or trueness (P = .757) between the digital impressions. The qualitative analysis revealed local deviations along the palatal surfaces of the molars and incisal edges of the anterior teeth of < 100 μm. Conclusion: Conventional full-arch PVS impressions exhibited improved mean accuracy compared to two direct optical scanners. No significant differences were found between the two digital impression methods.

Purpose: This study introduces a newly developed zirconia complete denture (ZrD) that incorporates a ceria-stabilized zirconia/alumina nano-composite framework fabricated with computer-aided design/computer-aided manufacture (CAD/CAM). Materials and Methods: Twenty-nine edentulous patients received either a maxillary ZrD (n = 10) or a maxillary conventional complete denture (CD) (n = 19). Patient satisfaction was evaluated before and 12 months after prosthesis placement using the McGill Denture Satisfaction Instrument. Results: During follow-up periods of up to 2 years, no denture fractures were found in the ZrD or CD group. All aspects of patient satisfaction improved, and no significant group differences were found. Conclusion: Within the limitations of this study, it can be concluded that maxillary complete dentures with nano-zirconia frameworks might be an alternative prosthetic treatment option.

Purpose: To assess short-term postoperative pain and swelling after insertion of mini dental implants (MDI) and standard-size implants (SSI) in the same patients at different times. Materials and Methods: A convenience sample of 42 patients (22 females, 20 males; 58 to 73 years old) participated. Half of the participants received MDIs first, and the other half received SSIs first. Self-perceived pain and swelling at 1, 3, 5, 7, and 10 days postoperative were assessed using a 0-10 visual analog scale. Results and Conclusion: Flapless MDI insertion led to significantly less intense postoperative pain, less intake of analgesics, and almost no swelling compared to SSI insertion.

Purpose: To evaluate the effects of impression material, impression tray type, and type of partial edentulism (ie, Kennedy class) on the accuracy of fit of cobalt-chromium (Co-Cr) partial removable dental prostheses (PRDP) in terms of the number of fabricated frameworks required until the attainment of adequate fit. Materials and Methods: Electronic case documentations of 120 partially edentulous patients provided with Co-Cr PRDP treatment for one or both arches were examined. Statistical analyses of data were performed using analysis of variance and Tukey honest significant difference test to compare the relationships between the different factors and the number of frameworks that needed to be fabricated for each patient (α = .05). Results: Statistical analysis of data derived from 143 records (69 maxillary and 74 mandibular) revealed no significant correlation between impression material, tray type, or Kennedy class and the number of construction attempts for the pooled or individual arch data (P ≥ .05). Conclusion: In PRDP treatment, alginate can be chosen as a firstchoice material, and metal stock trays can be a preferred option for making final impressions to fabricate Co-Cr frameworks.

Purpose: This study aimed to prospectively evaluate the clinical performance of monolithic zirconia crowns made of yttria-stabilized tetragonal zirconia polycrystal. Materials and Methods: A total of 26 crowns placed on premolar or molar teeth in 18 patients were evaluated at the time of crown placement and at 2 weeks, 6 months, 1 year, and 2 years after placement. Results: Twenty-five crowns rated as satisfactory according to the California Dental Association quality evaluation system. Most of the abutment and antagonist teeth showed good periodontal condition. An enamel cracking occurred on one antagonist tooth 1 year after placement. Conclusion: Monolithic zirconia crowns can be a clinically acceptable prosthetic option.

This report describes an innovative technique to remove post-and-core restorations. The WAM'X Super Quick post removal device permits a secure mechanical traction technique that can adapt to variable root angulations. Pivoting prongs mounted on forceps allow post removal while preserving the ferrule effect to improve resistance to fractures.

Purpose: To compare panoramic and cone beam computed tomography (CBCT) determinations of implant-to-mandibular canal (MC) dimensions in mandibular regions posterior to the mental foramen and to investigate whether factors such as gender, age, region, and vertical dimension influence correlation between the two techniques. Materials and Methods: A retrospective analysis was carried out in 64 consecutive adult patients (42 females, 22 males; average age 57.1 ± 13.3 years) in whom 126 implants were positioned in the posterior segment of the mandible. Implant sites (first premolar, second premolar, first molar, and second molar) were assessed on each panoramic and CBCT radiograph by measuring the distance from the inferior border of the implant to the superior border of the MC. Binary logistic regression analysis was used to compute the odds ratios (ORs) of each implant site for underestimation vs nonunderestimation. Linear regression analysis was performed with CBCT dimension as the dependent variable and panoramic dimension, gender, and age as the independent variables. Results: The mean implant-to-MC dimension was 2.50 ± 1.31 mm in panoramic radiography and 2.91 ± 1.62 mm in CBCT. The OR that an implant at the second molar region belonged to the underestimation group was strong (15.1:1) and highly significant (P = .011). If a predictive value of .95 was demanded, the implant-to-MC dimensions had to be overestimated by 2 mm compared to the predicted CBCT dimension. Conclusion: This study provides evidence of an underestimation of available vertical bone dimensions for implants in the posterior regions of the mandible when assessed by panoramic radiography. Use of CBCT is therefore recommended for all implant size estimations in this region.

Purpose: To compare different dental bonding systems that are currently available on the market. Materials and Methods: A total of 100 extracted, intact third molars were coated in resin, cut, and divided into 10 groups of 10 molars each. Molars were bonded to zirconia blocks with a different bonding system per group. Resistance to shear forces was tested using a universal traction machine. Samples were observed under scanning electron microscopy (SEM) to determine the type of fracture. Results: Statistical analyses showed a significant influence of adhesive on the zirconia-dentin assembly's resistance to shear forces. SEM analysis showed mainly adhesive and mixed fractures. Conclusion: Dentin bonding systems without adhesive capability showed better results than self-etch systems.

This case history report describes the long-term prosthodontic treatment of a patient with gnathodiaphyseal dysplasia (GDD). The patient was initially diagnosed with osteomyelitis in the maxilla in 1986, followed by osteonecrosis spread throughout the mandible. GDD was genetically diagnosed in 2006. Despite the severe alveolar bone resorption, prosthodontic treatment improved the patient's satisfaction and ability to perform essential functions. Regular prosthesis adjustments and periodic follow-up should continue to avoid future complications.

Purpose: The aim of this study was to quantify the coronal tooth structure reductions (CTSRs) resulting from a variety of different types of crown preparations performed by undergraduate dental students in a simulation clinic teaching program. Materials and Methods: A total of 76 students each submitted 21 different crown preparations completed on typodont teeth, which were individually weighed and analyzed in relation to whole and sectioned reference teeth to calculate the CTSR resulting from each preparation. Results: The largest CTSR resulted from preparations for porcelain bonded to zirconia crowns (50.6%), followed by those for porcelain bonded to metal (PBM) crowns (44.3%), PBM fixed partial dentures (32.8%), shell crowns (32.5%), and full gold crowns (24.6%). Conclusion: A wide range of CTSRs resulted from the different types of crown preparations investigated in this study. The crown preparations performed by the undergraduate students produced more conservative coronal reductions than comparable crown preparations generated under controlled in vitro conditions.

Purpose: To compare the influence of abutment teeth guide planes and guiding surfaces on retention of a removable partial denture (RPD). Materials and Methods: Extracted teeth embedded into a maxillary cast in the first premolar and second molar positions simulated two bounded saddles. Acrylic resin RPDs were made with no guide planes, then with guide planes, then with guiding surfaces added to directly contact the guide planes. The maximum loads on removal from the cast were recorded. Results: There was a significant increase in retention force of 1.6 times when only guide planes were present and of 10.2 times when guiding surfaces intimately contacted the guide planes. Conclusion: The retention of acrylic resin RPDs can be substantially increased by making their guiding surfaces intimately contact the guide planes of the teeth.

Purpose: To investigate a computer-aided design/computer-aided manufacturing (CAD/CAM) process for producing one-piece removable partial dentures (RPDs) and to evaluate their fits in vitro. Materials and Methods: A total of 15 one-piece RPDs were designed using dental CAD and reverse engineering software and then fabricated with polyetheretherketone (PEEK) using CAM. The gaps between RPDs and casts were measured and compared with traditional cast framework RPDs. Results: Gaps were lower for one-piece PEEK RPDs compared to traditional RPDs. Conclusion: One-piece RPDs can be manufactured by CAD/CAM, and their fits were better than those of traditional RPDs.

Purpose: To demonstrate how data collected using the computerized planimetric method (CPM) can be analyzed by providing an example in which the amount of plaque accumulation and the efficacy of the rotating needles device (RND) in cleaning specific parts of partial removable dental prostheses (PRDPs) were estimated. Materials and Methods: Thirty-four participants wearing a total of 41 double-crown-retained PRDPs with veneered secondary crowns were included in this study. The PRDPs underwent the following steps: preparing the PRDP for photography, photography of the PRDP, cleaning the PRDP with the RND, and re-photography. One trained examiner used a tested CPM to analyze 98 images (49 before/49 after). Each participant was considered as a statistical unit; thus, if the participant had two PRDPs, one was randomly selected for analysis. Results: The intraclass correlation coefficients (images before/after) for both the base and veneer were > 0.9. Wilcoxon signed rank test P value was < .001 for the comparison of plaque accumulation on the base and veneer, estimating the RND's efficacy on both PRDP parts (before/after) and comparing the RND's efficacy on the base and the RND's efficacy on the veneer. Conclusion: There are different ways to analyze data collected via CPM; thus, it is advisable to provide an explanation for the choice of modeling. Plaque accumulation was significantly greater on the double-crown veneer than on the base. The RND efficacy in cleaning the veneer and the base is significant, but more substantial in cleaning the base.

Purpose: The aim of this study was to investigate the effect of coloring on the interfacial surface adhesion between a zirconia framework and ceramic veneer using three-point flexural bonding strength. Materials and Methods: A total of 40 zirconia bars (Zirlux ST1; DE Healthcare) were cut and divided into two groups of 20 (Groups 1 and 2). The two groups were then further split and divided into four groups of 10 each (Groups 1a, 1b, 2a, and 2b). Groups 1a and 1b tested adhesion of uncolored zirconia and two different shades of ceramic veneer, and Groups 2a and 2b tested adhesion of zirconia colored with two different coloring liquids and one shade of ceramic veneer. Results: Some coloring liquids used to color zirconia can significantly affect the bond strength between zirconia and the veneer, whereas ceramic veneer shades do not influence adhesion. Conclusion: Bonding strength between zirconia framework and ceramic veneer is affected by the coloring of the zirconia.

Purpose: To compare the efficacy of two systems in cleaning used healing abutments (HAs). Materials and Methods: A total of 60 used HAs were randomized into two groups: one treated with an automatic cleaning system, and the other with conventional decontamination procedures. After sterilization and staining, the HAs were microscopically analyzed and underwent a cellular adhesion in vitro assay. Results: Contaminated areas were observed with different frequencies in the two groups (3.6% test; 78.2% control; P < .001). In vitro assay showed a uniform cell distribution in test HAs, while areas of debris without adhering cells were a common finding in the control HAs. Conclusion: Further studies investigating the chemical composition and clinical influence of biologic remnants are necessary before considering reusing HAs.

Purpose: This study aimed to evaluate the possible effect of sealing materials on superstructure attachment (ie, tightening/loosening torque and implant-abutment gap) in two different implant systems. Materials and Methods: A silicone, a chlorhexidine gel, and an industrial lubricant were tested. A 3D microscope was used for assessment of the implant-abutment gap, and the abutment screw was tightened and loosened with a digital torque screwdriver. A total of 20 implants per test group (10 BEGO Semados RI and 10 Nobel Biocare Replace Select Straight) were evaluated. Results: The tested sealing materials did not influence the gap between implant and abutment, but the force necessary for loosening the abutment screws decreased significantly. Conclusion: Sealing materials may be useful against bacteria, but probably influence torque negatively.

The newest impression techniques use intraoral scanners to capture both the hard and soft tissues. However, with edentulous patients, the accuracy of an intraoral scanner to capture an acceptable impression for the fabrication of a complete denture needs to be evaluated. Therefore, the purpose of this report of two patient treatments is to describe a technique that used intraoral scanning to record mucosal morphology and fabricate computer-aided design/computer-assisted manufacture (CAD/CAM) complete dentures.

Purpose: To evaluate the accuracy and precision of a digital scanner used to scan four implants positioned according to an immediate loading implant protocol and to assess the accuracy of an aluminum framework fabricated from a digital impression. Materials and Methods: Five master casts reproducing different edentulous maxillae with four tilted implants were used. Four scan bodies were screwed onto the low-profile abutments, and a digital intraoral scanner was used to perform five digital impressions of each master cast. To assess trueness, a metal framework of the best digital impression was produced with computeraided design/computer-assisted manufacture (CAD/CAM) technology and passive fit was assessed with the Sheffield test. Gaps between the frameworks and the implant analogs were measured with a stereomicroscope. To assess precision, three-dimensional (3D) point cloud processing software was used to measure the deviations between the five digital impressions of each cast by producing a color map. The deviation values were grouped in three classes, and differences were assessed between class 2 (representing lower discrepancies) and the assembled classes 1 and 3 (representing the higher negative and positive discrepancies, respectively). Results: The frameworks showed a mean gap of < 30 μm (range: 2 to 47 μm). A statistically significant difference was found between the two groups by the 3D point cloud software, with higher frequencies of points in class 2 than in grouped classes 1 and 3 (P < .001). Conclusion: Within the limits of this in vitro study, it appears that a digital impression may represent a reliable method for fabricating full-arch implant frameworks with good passive fit when tilted implants are present.