The International Journal of Prosthodontics, 01/2021

Purpose: To determine whether the use of implant-supported overdentures (IODs) with different attachments influences the Mini Nutritional Assessment (MNA) and Geriatric Oral Health Assessment Index (GOHAI) scores in edentulous patients > 65 years of age. Materials and Methods: The MNA and GOHAI were administered to 54 edentulous patients > 65 years of age (mean age = 68.35 ± 4.1 years) before treatment (A) and 6 months after treatment (B): 10 with maxillary + mandibular conventional complete dentures (CDs); 10 with a maxillary conventional CD + mandibular magnetic-retained IOD; 12 with a maxillary conventional CD + mandibular ball-retained IOD; 12 with a maxillary conventional CD + mandibular Locatorretained IOD; and 10 with a maxillary conventional CD + mandibular bar-retained IOD. Statistical differences between treatment types were evaluated using one-way analysis of variance and paired-sample t tests. The correlation between MNA and GOHAI scores was determined using Pearson correlation analysis (α = .05). Results: The difference between mean GOHAI-A and GOHAI-B scores was statistically significant for each type of denture (P < .005). The difference between the mean MNA-A and MNA-B scores was statistically significant for all types of denture except for conventional CDs (P < .05). There was a statistically significant positive correlation between MNA and GOHAI scores (P < .01). Conclusion: Regardless of the type of denture used, treatment of edentulous geriatric patients is important for improving nutritional status and self-rated oral health.

Purpose: To evaluate and compare the occlusal fit of zirconia crowns designed using a digital articulator method and the traditional method in a self-controlled clinical trial. Materials and Methods: Two zirconia crowns each were prepared for 12 patients with a single posterior tooth defect using two different methods: a digital articulator method and the traditional method. In the traditional method, casts were scanned using a model scanner, and the relative positions of the maxillary and mandibular arches were determined by the intercuspal occlusion of the casts. In the digital articulator method, casts were mounted on a mechanical articulator and scanned, and the relative positions were determined by their respective positions in the articulator. Additional dynamic occlusal adjustments of the digital articulator crowns were performed. Both groups of zirconia crowns were milled in a five-axis milling machine. The time required for occlusal adjustments, the occlusal contacts, the occlusal contact distributions, the number of occlusal contacts, the relative occlusal forces, and patient satisfaction (visual analog scale score) were evaluated. Wilcoxon test, McNemar test, and paired t test were used to compare the parameters between the two methods. Results: The occlusal adjustment times for the digital articulator and traditional method crowns were 327 ± 226 seconds and 395 ± 338 seconds, respectively (P > .05). There were no significant differences in occlusal contacts, occlusal contact distributions, number of occlusal contacts, relative occlusal forces, or VAS scores between the two methods (P > .05). Conclusion: A digital articulator method for single-crown restoration was applied successfully. Crowns fabricated using a digital articulator or the traditional method can achieve acceptable occlusal fit for single-crown restorations.

Purpose: To investigate the effect of training on scanning times of complete-arch scans (CAS) performed by first-time users, with a distinction made between specific training (repeated practice of CAS) and nonspecific training (simple use of an intraoral scanner for a sextant scan in the context of a student CAD/ CAM course). Methods: Thirty-six students with no experience in intraoral scanning were randomized into three groups (n = 12 per group) according to the number of specific CAS training sessions: three sessions (3S), two sessions (2S), and one session (1S). Each student performed 10 CAS per scanning session. These sessions were scheduled at baseline (T0), T1 (2 weeks after T0), and T2 (4 weeks after T0) for group 3S; at T0 and T2 for group 2S; and at T2 for group 1S. Before the final scanning session in each group (ie, the first scanning session in group 1S), the students participated in a CAD/CAM course (3 weeks after T0) in which a monolithic crown was fabricated in a fully digital chairside workflow. The scanning time was measured as the time between the activation and termination of the scanning mode of the intraoral device. Data were analyzed using SPSS Statistics 25 (IBM). The level of significance was set to α = .05. Results: A continual decrease in scanning time was observed for all groups as experience in intraoral scanning increased. The mean scanning times were as follows: for group 3S, 305 seconds at T0, 246 seconds at T1, and 233 seconds at T2; for group 2S, 380 seconds at T0 and 303 seconds at T2; and for group 1S, 355 seconds at T2. When compared to group 1S after it had received nonspecific training only, the effect of a single specific training session in groups 3S and 2S was not significant (P = .4428). However, two specific training sessions had a significant effect on scanning time compared to nonspecific training only (P = .0005). Conclusion: Training does affect the scanning time required for CAS. To perform such scans in a time-efficient manner, dental practitioners should undertake training that comprises at least 12 CAS.

Purpose: To investigate the effect of training on scanning accuracy of complete arch scans (CAS) performed by first-time users, with a distinction made between specific training (repeated performance of CAS) and nonspecific training (simple use of an intraoral optical scanner for a sextant scan in the context of a CAD/ CAM teaching module). Materials and Methods: A total of 36 students with no experience in intraoral scanning were randomized into three groups (n = 12 per group) according to the number of CAS sessions: three sessions (3S), two sessions (2S), and one session (1S). Each student had to perform 10 CAS per scanning session. Sessions were scheduled at T0, T1, and T2 for group 3S; at T0 and T2 for group 2S; and at T2 for group 1S. Before the final scanning session in each group (ie, the first scanning session in group 1S), the students completed a CAD/CAM teaching module, which included fabrication of a monolithic crown in a fully digital chairside workflow. Results: In all groups, repeated CAS resulted in improved scanning accuracy. Participation in the CAD/CAM module had a positive effect on initial accuracy for CAS. Mean absolute deviations in cross-arch distance were 84 μm (T0), 68 μm (T1), and 63 μm (T2) for group 3S; 79 μm (T0) and 61 μm (T2) for group 2S; and 67 μm (T2) for group 1S. Conclusion: To perform CAS with the best possible accuracy, specific training is highly recommended. In addition, nonspecific training leads to an improvement in initial scanning accuracy.

Purpose: To evaluate the 2-year performance of definitive implant- or tooth-supported three-unit fixed dental prostheses made of zirconia-reinforced lithium silicate placed to restore premolars and molars in clinical cases of partial edentulism. Materials and Methods: All patients received a three-unit fixed restoration made of monolithic, hot-pressed, zirconia-reinforced lithium silicate glass-ceramic. The restoration was cemented to two natural teeth or attached to two 3.5- or 4.5-mm–diameter square threaded, gritblasted, acid-etched integrated implants with a Morse taper connection. Peri-implant pocket depth and bone and soft tissue remodeling were recorded for 2 years at each follow-up visit. Esthetic, functional, and biologic United States Public Health Services (USPHS) parameters modified by the World Dental Federation study design were assessed yearly until the final follow-up appointment. At the time of placement of the definitive restorations and at the 2-year follow-up visit, the opposing dentitions were identified by type of restoration and supporting structures. Results: A total of 100 patients were consecutively enrolled in the period between June 2016 and July 2017, and 50 patients each received an implant-supported restoration (Group A) or a tooth-supported restoration (Group B). One (2%) of the 50 implant-supported prostheses fractured after 21 months of function. None of the other prostheses failed or became loose or detached. No significant differences involving probing levels or bone and soft tissue remodeling were found between the follow-up times. No cases of inflammation or infection of the mucosal cuff around the neck of the implants were recorded. The most common issue occurred immediately after placement of the prosthesis, when 3 patients (6%) from Group A and 4 patients (8%) from Group B asked for a modification of tooth shade. Conclusion: Implant-supported or tooth-supported three-unit fixed dental prostheses made of zirconia-reinforced lithium silicate can be used to successfully restore cases of posterior partial edentulism. The 2-year results of this report will be studied more in depth in ongoing long-term research.

Purpose: To investigate the impact of high-speed sintering and artificial aging on the fracture load of three-unit zirconia fixed dental prostheses (FDPs). Materials and Methods: Three-unit FDPs manufactured from 3Y-TZP (Ceramill Zolid, Amann Girrbach) and 4Y-TZP (Ceramill Zolid HT+, Amann Girrbach; N = 128, n = 64/group) were sintered at 1,580°C (high-speed sintering) or at 1,450°C (control group; n = 32/subgroup). Specimens were bonded to steel abutment models using Multilink Automix (Ivoclar Vivadent), and fracture load was examined without (n = 16/subgroup) and with artificial aging (6,000 thermocycles [5°C/55°C] and 1,200,000 chewing cycles [50 N]; n = 16/subgroup). Univariate analysis of variance, unpaired t test, and Weibull modulus were computed (P < .05). Results: Sintering protocol (P = .944), artificial aging (P = .630), and zirconia material (P = .445) did not show an influence on the fracture load of three-unit FDPs. High-speed sintering led to superior Weibull modulus results for artificially aged 4Y-TZP specimens, while all other groups showed values in the same range. Conclusion: The present study shows promising results for the novel highspeed sintering protocol, as it led to comparable fracture load and similar, or even superior, Weibull modulus results compared to the control group. The 4Y-TZP material presented fracture load results similar to the tried-and-tested 3Y-TZP. Artificial aging did not influence zirconia’s resistance to fracture for either 3Y-TZP or 4Y-TZP.

Purpose: To evaluate the physical and mechanical properties of maxillofacial silicone elastomers following the incorporation of a specific particle size and concentration of nano–titanium dioxide (TiO2) and nano–zinc oxide (ZnO). Materials and Methods: Nano-TiO2 and nano-ZnO of 20-nm and 40-nm particle sizes and in 1% and 2% concentrations were chosen. Silicone elastomer samples were prepared according to the manufacturer’s recommendations. The nano-oxides were incorporated via hand spatulation. The samples were subsequently tested for hardness and color stability and were then subjected to aging in an aging chamber for 1,008 hours, following which they were again evaluated for hardness, color stability, and surface roughness. Results: A significant change was noted in the physical and mechanical properties post-aging in all the groups. The samples with nano-TiO2 of 40-nm particle size/2% concentration had the highest hardness, while color stability and surface roughness were higher in samples with nano-TiO2 of 20-nm particle size/1% and 2% concentrations, respectively. Conclusion: It can be concluded that 20-nm nano-TiO2 particles best maintain the ideal properties of maxillofacial silicone elastomers and can potentially be used as alternative opacifiers when mixed with A-2186 maxillofacial silicone elastomers.

Purpose: To compare the marginal and internal gap values of different types of ceramic crowns fabricated based on digital and conventional impression methods. Materials and Methods: Ten noncarious extracted human teeth were prepared, and 60 restorations were made using six different impression and fabrication methods. Silicone replicas were obtained for marginal and internal gap evaluation. Statistical analyses were performed using Mann-Whitney U and Kruskal-Wallis tests (P < .05). Results: Statistically significant differences were found among various impression and fabrication methods. The smallest gap value was shown by the monolithic zirconia indirect digital scanning group (31.13 μm), and the largest for the lithium disilicate indirect digital scanning group (90.09 μm). Conclusion: The marginal and internal gap values of the restorations in the present study were 31.13 to 90.09 μm. The marginal and internal discrepancies of the tested materials were considered clinically acceptable.

Purpose: To evaluate the effect of a surface sealant agent on the color stability and surface roughness (Ra) of two denture base materials: polymethyl methacrylate (PMMA) and nylon. Materials and Methods: A total of 96 disk-shaped specimens (10 × 2 mm) were fabricated from heat-cured PMMA and nylon denture base materials (n = 48/material). Each of the color stability and Ra tests were performed on half of the samples in each material group (n = 24), and these subgroups were then subdivided according to the surface treatment applied: 12 specimens were conventionally polished, serving as the control group, and 12 specimens received a sealant on the surface in addition to the surface polishing. Color stability was assessed through measuring the CIEL*a*b* color parameters before and after immersion in coffee solution. Ra was measured and scanning electron microscopy (SEM) photomicrographs were taken before and after thermocycling. Statistical analysis was done using 2-way analysis of variance (α = .05). Results: The surface sealant agent significantly increased the color stability of both materials (P = .047). However, it had no significant effect on the Ra of materials before (P = .600) or after (P = .583) thermocycling. Nylon had a significantly rougher surface than PMMA both before and after thermocycling (P < .001). Similarly, SEM observations show a more irregular texture for nylon than for PMMA. Conclusion: Although the sealant agent had no significant effect on the Ra before or after thermocycling, it significantly decreased the color change of nylon and PMMA disks. Based on both statistical analyses and SEM observations, the Ra of PMMA was lower than nylon denture base material.

Purpose: To measure the effect of simulated aging on stained resin-ceramic CAD/CAM materials regarding the durability of color and gloss. Materials and Methods: Test specimens (n = 15 per material) were prepared out of CAD/CAM ingots from two resin nanoceramics (Lava Ultimate [LVU], Cerasmart [CER]) and a polymerinfiltrated ceramic (ENA, VITA Enamic) stained with the manufacturer’s recommended staining kit using photopolymerization. Control specimens were made of feldspathic ceramic (VITA Mark II [VM2]) and stained by means of ceramic firing. Negative control specimens (n = 15) (no staining) were prepared for each group. Color and gloss measurements were performed before and after each aging cycle by means of mechanical abrasion with a toothbrush. Groups were compared using Kruskal-Wallis test and paired post hoc Conover test. Changes within a group were calculated using Wilcoxon signed-rank test (α = .05). Results: The color difference (ΔE) was statistically significant for all stained CAD/CAM materials after simulated aging: CER (P < .001, 95% CI: 2.96 to 3.69), LVU (P = .004, 95% CI: 1.09 to 1.46), ENA (P = .004, 95% CI: 0.20 to 0.42), and VM2 (P < .001, 95% CI: 0.29 to 1.08). Aging resulted in a statistically significant increase in gloss in the LVU group (P < 0.001, 95% CI: 13.78 to 17.29), whereas in the ENA (P < .001, 95% CI: 7.83 to 12.72), CER (P < .001, 95% CI: 2.69 to 8.44), and VM2 (P = .014, 95% CI: 0.22 to 1.87) groups, a significant decrease in gloss was noted. Conclusion: Color and gloss of stained resin-ceramic CAD/CAM materials changed significantly after aging by means of toothbrush abrasion in vitro.

Emerging evidence implies significant interrelations between the condition of the peri-implant tissues and the implant-abutment-prosthesis complex. A new paradigm for studying the peri-implant tissues in close interrelation with the implant-abutment-prosthesis complex in the presence of the oral biofilm is essential. The aims of this paper are to introduce the concept of the “implant supracrestal complex” (ISC) and to describe the critical elements that define it as a unique anatomical and functional system of human tissues, mechanical components, and oral bacteria/biofilm. This paper reviews recent evidence to identify the impact of design features on short-term clinical outcomes and long-term health of the peri-implant bone and soft tissues. Prosthetic-driven implant placement is a prerequisite for proper ISC design, which in turn can indirectly influence the structure and dimensions of the peri-implant soft tissues. Design features of the implantprosthesis- abutment complex, such as the emergence profile, emergence angle, and cervical margin, as well as the design of the implant-abutment and abutment-prosthesis junctions and their locations in relation to the tissues of the ISC, can have a significant impact on the maintenance of stable and healthy peri-implant tissues in the long term.

Purpose: To compare the accuracy of six intraoral scanners in two different partially edentulous maxillary models and to evaluate the effect of scanning sequence on accuracy. Materials and Methods: Maxillary Kennedy Class I and Class IV situations were used as reference models. The reference datasets were obtained by scanning the models using a highly accurate industrial scanner (ATOS Core 80, GOM). The following six intraoral scanners were evaluated: Trios 3 (3Shape), iTero Element 2 (Align Technology), Emerald (Planmeca), CEREC Omnicam (Dentsply Sirona), CEREC Primescan (Dentsply Sirona), and Virtuo Vivo (Dental Wings). A total of 120 scans from both models were obtained using the six intraoral scanners and divided into two groups based on scanning sequence. Accuracy was evaluated by deviation analysis using 3D image processing software (Geomagic Studio 12, 3D Systems). Kruskal Wallis and Mann-Whitney U tests were performed (P ≤ .05) for statistical analysis. Results: There were significant differences in the accuracy of digital impressions among intraoral scanners and scanning sequences. The trueness of the Trios scanner and the precision of the Trios, Primescan, and iTero scanners were significantly higher than for the other scanners. The Emerald had the lowest accuracy among the six intraoral scanners tested. Accuracy was affected by scanning sequence when using the Virtuo Vivo, Emerald, Primescan, and iTero. Conclusion: In Kennedy Class I and Class IV partially edentulous cases, it is useful to consider that the intraoral scanner used may affect the accuracy of the digital impression.

Purpose: To evaluate the reserved space quantity and printing accuracy of custom edentulous trays produced by two 3D printing methods (fused deposition modeling [FDM] and stereolithography apparatus [SLA]) and to compare them to traditional handmade (HM) methods. Materials and Methods: The tissue surface data of maxillary and mandibular edentulous gypsum models were obtained through a 3D scanner to design the digital custom trays in Geomagic software. The custom trays were then printed with FDM and SLA technologies, and handmade custom trays were used as control. The scanned data of printing trays were registered with their digital data, and the printing errors were analyzed using the deviation analysis function. The distances between the tissue surface of gypsum models and the custom trays were measured in ImageWare and represented by 3D deviation. Results: None of the six groups revealed a significant difference (P > .05) compared to the set value of 1.00 mm. In the SLA group, the deviation of the mandibular area was significantly closer to the set value than for the HM group (P < .05), while no significant difference was displayed between the other groups. For the printing error between the two 3D groups, the SLA method showed significantly less error and better stability (P < .001). Conclusion: 3D-printed custom trays can meet clinical needs in the adaptability of tissue surfaces, and SLA-printed trays revealed better precision and less error than the other two methods. Accordingly, the use of SLA technology to make a 3D-printed custom tray is expected to be promoted in clinical practice.

Intraoral scanners have been used to capture data for the design and subsequent manufacture of dental restorations and also for registering color clinical images. Scanners can capture datasets for future use and comparisons. This manuscript describes the potential of using software algorithms to superimpose 3D images captured at different times to calculate dimensional changes at the click of a button in various dental fields. 3D patient monitoring, with the advance of artificial intelligence and its built-in capacity for data analyses, will allow dentists and researchers to calculate volumetric changes and predict potentially adverse clinical outcomes.

This clinical report presents the use of a modified polyetheretherketone (PEEK) post and core in order to support a lithium disilicate ceramic crown for a maxillary lateral incisor. When considering post-and-core restorations, material flexibility is essential to prevent root fractures. The low elastic modulus of PEEK (4 GPa) could result in lower root fracture rates, preserving tooth structure and favoring tooth re-restoration if the post fractures. PEEK is biocompatible, presents adequate bond strength with dentin when bonded with a resin cement, and can be used under ceramic restorations because of its white, esthetic color. PEEK posts and cores could also cost less when fabricated using common laboratory procedures. Polyetheretherketone (PEEK) posts and cores could be a viable alternative to rigid cast or zirconia posts, or even to fiber-reinforced composite posts, especially when combined with lithium disilicate crowns