The International Journal of Prosthodontics, 01/2022

In recent years, numerous new dental materials have been introduced as alternatives to metal-ceramics for restorations on teeth and implants. This position paper presents the current evidence and respective clinical recommendations of the European Association for Osseointegration (EAO), one of the scientific partners of the International Journal of Prosthodontics, on material selection for single crowns (SCs) and multiple-unit implant-supported fixed dental prostheses (FDPs). Metal-ceramic restorations can be utilized in most clinical indications and are preferred to ceramic restorations in incidences such as long clinical implant crowns; cantilever implant restorations where one implant is supporting two crowns; implant-supported FDPs with extension units extending more than 7 to 8 mm (premolar size); implant-supported FDPs with more than two pontics; and implant-supported FDPs with small connector diameters due to limited intraocclusal space. Veneered or monolithic zirconia-ceramic and veneered or monolithic reinforced glass-ceramic implant-supported SCs are indicated for most SC cases in both the anterior and posterior areas. Today, implant-supported zirconia-ceramic FDPs that are conventionally veneered cannot be considered the material of first priority due to the pronounced risk for fracture of the framework and catastrophic fracture of the veneering material. Monolithic zirconia FDPs are a promising alternative to veneered implant-supported zirconia-ceramic FDPs. The mechanical stability of the translucent and shaded zirconia differs significantly between the grades of translucency. This must always be considered when clinical indications are recommended. As this specific area of prosthodontics is evolving fast, numerous studies evaluating different material options in implant prosthodontics are currently performed worldwide, and future consensus meetings will refine the present recommendations. The EAO will therefore regularly publish updated position papers on relevant topics.

Purpose: To determine the sensitivity and specificity of capsules containing fuchsin-based beads for evaluating masticatory performance. Materials and methods: A total of 60 healthy subjects (mean ± SD age: 41.0 ± 13.2 years) were categorized according to number of occlusal pairs (n = 15 per group) as follows: 16-14 (control group); 13-10; 9-6; and 5-1. The subjects chewed the capsules to assess masticatory performance, which was defined as the concentration of fuchsin released and measured using ultraviolet-visible spectrophotometry. The subjects also comminuted silicone cubes, and median size was calculated via the sieving method. The test foods were compared using analysis of variance, receiver operating characteristic (ROC) curve, and Bland-Altman analysis. Results: The control group presented the highest masticatory performance for chewing the capsules (P < .05), except when compared to the 13-10 occlusal pairs group (P = .667). There was no difference between the partial edentulism groups (P > .05). An acceptable area under the ROC curve of 0.744 was observed, with 73.33% sensitivity and 70.00% specificity. The control group also showed the best results for chewing the cubes (P < .01); however, the 9-6 and 5-1 groups were equivalent (P = .133). An excellent area under the ROC curve of 0.887 was found, with 80.00% sensitivity and specificity. The bias between the capacity of both test foods to recognize subjects with < 10 occlusal pairs was -3.56%. Conclusion: Capsules containing fuchsin-based beads were viable for evaluating masticatory performance, as they showed sufficient sensitivity and specificity for characterizing subjects presenting with < 10 occlusal pairs.

Purpose: To digitally evaluate the static and dynamic occlusion of patients treated with both removable conventional complete dentures (CCDs) and implant-retained removable overdentures (IODs) and to correlate two different methods of occlusal analysis. Materials and methods: Eleven totally edentulous patients were treated with bimaxillary CCDs. Later, mandibular CCDs were replaced by IODs retained by either two or four implants. The distribution of the occlusal contacts in static and dynamic occlusion was compared by means of the digital method (DM; T-Scan III) and the analog method (AM; articulating paper). Scores 0, 1, and 2 were assigned for inadequate, satisfactory, and adequate distribution of the occlusal contacts, respectively. The frequencies of scores were compared in relation to the types of denture by means of Fisher exact test (P < .05). The correlation between methods was assessed by means of the kappa agreement coefficient (κ) and the correlation coefficient phi (φ) (P < .05). Results: Significant differences between CCDs and IODs were found in the right lateral mandibular movement (DM, P = .024; AM, P = .008), as well as in the left lateral mandibular movement (DM, P = .035). The methods of analysis of the occlusion showed a moderate agreement (κ = 0.604; P < .001) and a moderate correlation (φ = 0.605; P < .001). Conclusion: The digital and analog methods showed a significant agreement and moderate correlation, irrespective of the type of complete denture. The T-Scan III digital system seems to be a consistent and reproducible method to analyze occlusion.

Purpose: To evaluate the association between low handgrip strength and type of dental prosthesis used in Korean adults in a cross-sectional study of nationally representative big data. Materials and methods: This study included 7,681 participants aged ≥ 19 years who were classified into the following four groups: NP (not using a dental prosthesis); FDP (using tooth-supported or implant-supported fixed dental prostheses); RPD (using removable partial dentures); and CD (using removable complete dentures). Low handgrip strength was defined as the lowest quartile of handgrip strength in each sex. The relationship between handgrip strength and dental prosthesis use was analyzed with adjustment for potential confounders. Multivariate logistic regression analyses were performed to examine the association between the use of dental prostheses and low handgrip strength (α = .05). Results: The handgrip strength level of RPD users was significantly lower than those not using removable dentures (P < .0001). The respective adjusted odds ratios (with 95% CI) for low handgrip strength in the NP, FDP, RPD, and CD groups were 1 (reference), 0.90 (0.77, 1.05), 1.44 (1.13, 1.83), and 1.70 (1.29, 2.23) after adjustment for confounding factors. Using removable partial and/or complete dentures was associated with a 1.64-fold higher risk of low handgrip strength compared to not using removable dental prostheses. Conclusions: The use of removable dentures was associated with low handgrip strength and may be considered a potential risk indicator for functional decline in Korean adults.

Purpose: To investigate the relationship of self-reported temporomandibular disorder (TMD) symptoms with psychologic well-being (PWB), psychologic distress (PD), and oral health-related quality of life (OHRQoL). Materials and methods: The study sample was recruited from a local university using a convenience sampling technique. The Diagnostic Criteria for TMD Symptom Questionnaire (DC/TMD-SQ); Scales of Psychological Well-being-18 (SPWB-18); Depression, Anxiety, and Stress Scales-21 (DASS-21); and Oral Health Impact Profile-14 (OHIP-14) were administered electronically to establish TMD symptoms and to assess PWB, PD, and OHRQoL, respectively. Data were analyzed by number/type of TMD symptoms using Kruskal-Wallis/Mann-Whitney U tests and Spearman correlation (α = .05). Results: A total of 602 participants with a mean age of 19.30 ± 1.18 years (84.3% women) were evaluated. Of these, 59.2% reported TMD symptoms, with 10.7% having multiple (≥ 3) features. Pain-related (PT), intra-articular (IT), and combined (CT) TMD symptoms were present in 23.8%, 15.4%, and 20.2% of the cohort, respectively. For both number and type of symptoms, significant differences in SPWB-18 (total, environmental mastery, and self-acceptance), DASS-21 (total/all domains), and OHIP-14 (total/all domains) scores were observed (P < .05). A moderately strong negative correlation was noted between PWB and PD (r_s = -0.55). Conclusion: Participants with no TMD (NT) symptoms had significantly higher PWB than those with two or more TMD symptoms. They also had significantly lower levels of PD and better OHRQoL. Conversely, individuals with PT/CT reported significantly lower PWB compared to those with no symptoms. Moreover, they also had significantly higher levels of PD and poorer OHRQoL than the IT/NT groups.

Purpose: To compare patient-reported outcomes among balanced, lingualized, and monoplane occlusal schemes in relation to edentulous jaw classifications. Materials and methods: This randomized controlled trial was conducted in edentulous patients receiving new complete dentures using balanced, lingualized, or monoplane occlusal schemes. Demographic variables, bone ridge quantity, number of adjustments required after denture insertion, and satisfaction and quality of life (QoL) indices (ie, the Denture Satisfaction Questionnaire [DSQ] and General Oral Health Assessment Index [GOHAI], respectively) were assessed at 1, 2, 4, 8, 12, and 52 weeks. Within-group comparisons at different time points were carried out with Brunner-Langer nonparametric analysis. Furthermore, Kruskal-Wallis test was used to compare distributions of ordinal or continuous variables among the three occlusal scheme groups. Results: A total of 60 subjects (mean age: 68.1 ± 11.1 years; 56.7% men and 43.3% women) were analyzed. All three groups presented significant improvements in DSQ and GOHAI scores between denture insertion and the 1-year follow-up appointment (P < .001). There were no statistical differences in the distribution of demographic variables (eg, age, gender, years edentulous, and age of existing dentures) or of bone ridge classifications among the three groups. Similarly, there were no statistical differences in ridge classifications or in the DSQ and GOHAI values among the three groups for both the maxilla and mandible (P > .05) over the 52-week follow-up. On the other hand, the number of cases requiring denture adjustments was significantly lower in the lingualized scheme group, as compared to the two other groups (P = .034). Conclusion: Within the limitations of this study, the present findings suggest that the occlusal scheme for posterior teeth did not influence patient-reported subjective outcomes. However, the lingualized occlusal scheme required significantly fewer adjustments.

Purpose: To evaluate the readability and quality of patient-oriented information online among different common prosthodontic search areas using multiple quality and readability assessment tools. Materials and methods: The prosthodontic keywords most commonly searched by patients on the internet were included. The search was performed through two online search engines (Google and Yahoo) to create the study sample. The first 50 websites listed by each search engine were chosen for each keyword. The quality of each website's information was evaluated using the DISCERN questionnaire and the Health on the Net (HON) criteria. Readability assessment was performed using the Flesch-Kinkaid Reading Grade Level (FKRGL) and the Flesch Reading Ease Score (FRES). Results: A total of 225 websites were included in the study. The median score for the DISCERN instrument indicated poor information quality. A significant difference was found between the educational and commercial websites in both quality and readability. Overall, the median readability indices showed that the websites' information was difficult to read. Conclusion: Internet-based health information on different prosthodontic treatments is difficult to read and poor in quality and readability. It is necessary for health care providers to establish and promote websites that have reliable, high-quality information about common prosthodontic treatments.

Purpose: To evaluate the effect of hydrothermal aging on the load to failure and number of cycles to failure of implant-supported monolithic zirconia molar crowns under cyclic loading. Materials and methods: Twenty identical implant-supported monolithic zirconia crowns with molar morphology were produced. Half of the crowns were aged according to ISO standard 13356 to simulate 5 years in vivo. The non-aged crowns served as a control group. All crowns were subjected to cyclic loading with increasing increments of load until failure. The load to failure, the number of cycles to failure, and the failure pattern were determined for each crown. Results: The load to failure values were 3,630 N (SD: 547.8 N) and 3,640 N (SD: 389.3 N) for the non-aged and aged crowns, respectively. The non-aged crowns failed after 33,480.1 cycles (SD: 23,138.4 cycles), and the aged crowns failed after 28,456.1 cycles (SD: 10,158.7 cycles). There was no significant difference between the two groups for the load to failure or number of cycles to failure. The predominant form of failure was catastrophic crown fracture, which was observed for all the non-aged crowns and 9 of the aged crowns. Conclusion: Within the limitations of this study, aging of the implant-supported monolithic zirconia crowns with molar morphology did not affect the load to failure or the number of cycles to failure under cyclic loading. Since all the crowns failed at much higher loads than the expected physiologic loads, clinical application of implant-supported monolithic zirconia crowns to replace missing molars seems reasonable.

Purpose: To quantify the effect of support stiffness on the retention forces of telescopic crowns and to evaluate a prototype attachment system incorporating a nickel-titanium element. Materials and methods: In the first part of the study, telescopic crowns were fabricated employing standard laboratory procedures. For six combinations of telescopic crowns, the separation force was determined while varying the stiffness of their supporting implants. In the second study part, an in vitro mandibular model with three interforaminal implants was equipped with strain gauges and extensometers. Two prostheses either employing cylindrical telescopic crowns or prototype attachments were fabricated and statically loaded on the model using either the midline or the left canine or both canine implants for support while strain in the peri-implant area and prosthesis displacement were recorded. Statistical analysis of both study parts was based on pairwise comparisons with the level of significance set at α = .05. Results: With one exception (P = .161), for each assembly of two telescopic crowns, the separating force was always dependent on the stiffness of the supporting implants. With 3 exceptions out of a total of 14 comparisons for peri-implant strain and prosthesis displacement, the use of the prototype attachments always led to significantly lower mean values compared to the use of cylindrical telescopes (P < .00). Conclusion: The individual retention force of telescopic crowns on implants should be set at a lower level compared to telescopic crowns on natural abutments. Incorporating a nickel-titanium element into attachment systems for implant-supported removable prostheses reduces peri-implant strain and may facilitate the use of telescopic crowns.

Purpose: To compare the accuracy of three commercially available intraoral scanners when imaging various dental material substrates. Materials and methods: A maxillary dentate typodont model with 11 different dental material substrates was prepared and scanned using three intraoral scanners (TRIOS 3, 3Shape; CS 3600, Carestream; and Emerald S, Planmeca). The model was further scanned with a laboratory scanner (7series, Dental Wings) for reference. Files were exported in standard tessellation language format and inserted into a metrology 3D mesh software (CloudCompare). Results: In terms of influence of different substrates on IOS trueness, a significant effect on the performance of TRIOS 3 and Emerald S was revealed. Concerning the accuracy of different intraoral scanners when scanning more translucent and reflective materials, pairwise comparisons revealed significant differences among scanners. In terms of complete-arch trueness and precision, pairwise comparisons revealed that TRIOS 3 had significantly higher trueness and precision compared to CS3600 and Emerald S. The complete-arch trueness and precision of CS3600 and Emerald S did not differ significantly. Conclusions: Dental material substrates influenced the accuracy of all three tested scanners. The full metal crown exhibited significantly lower trueness compared to other substrates across all three scanners. For the high-translucency substrate group, TRIOS 3 exhibited significantly higher trueness compared to CS 3600. Polished and unpolished class II amalgam restorations of similar dimensions did not exhibit significant differences in trueness regardless of intraoral scanner. In terms of complete-arch accuracy, TRIOS 3 had significantly higher trueness and precision compared to CS 3600 and Emerald S. All three scanners exhibited complete-arch average accuracy below 100 μm.

Purpose: To review the factors that affect the ability to deliver a CAD/CAM implant-supported provisional restoration designed from a virtually planned implant position prior to surgical placement with static computer-assisted implant surgery (sCAIS). Materials and methods: Data were collected on patients treated with single-tooth implant treatment in which CBCT was combined with intraoral scans and imported into a virtual implant planning software. A synchronization tool established the connection between the planning software and the CAD software, where a digital diagnostic tooth arrangement was performed to create the ideal tooth dimensions and mucosal architecture. The virtual implant planning was finalized, and the implant position was transferred to the CAD software, where a restoration was designed and fabricated. The sCAIS was performed, and the prefabricated custom restorations were delivered on the day of the surgery or following healing if delayed loading or submerged healing was required. Descriptive statistics and statistical comparison with two-proportion z test were performed. Results: A total of 23 patients with 28 single-implant sites met the inclusion criteria and were included in the study. Nineteen customized healing abutments and 10 provisional crowns were designed and fabricated for a total of 29 restorations. Of the restorations, 23 were successfully delivered on the day of the surgical intervention. No statistical significance was found among the different variables compared. Conclusion: Custom prefabricated CAD/CAM restorations based on a virtually planned implant position can be successfully designed, fabricated, and delivered when used in combination with sCAIS.

Purpose: To analyze the current evidence on the impact of surface finishing protocols (such as manual polishing or glazing) on the color stability of in vitro simulated pigmentation of CAD/CAM ceramics. Materials and methods: Five electronic databases were searched on February 12, 2020. In vitro experimental studies were included based on the following strategy: intervention = surface treatment of CAD/CAM ceramics with glazing agents; comparison = surface treatment of CAD/CAM ceramics with manual polishing; and outcomes = color stability. Two reviewers independently assessed the risk of bias. Results: Among 1,390 articles that were screened, 6 in vitro studies were considered for qualitative analysis. Five articles confirmed changes in the color of ceramics when they were immersed in pigmented solutions. One article investigated the color stability of the samples via ultraviolet (UV) aging. Among the 6 studies analyzed, 4 showed clinically acceptable color alteration values represented by ΔE irrespective of the finishing protocol applied (glazing or mechanical polishing). Two articles presented clinically unsatisfactory color variation (ΔE > 3.3 and ΔE > 2.7) following mechanical polishing of a zirconia-reinforced lithium silicate ceramic. Coffee and red wine proved to be the beverages with the greatest potential for ceramic pigmentation. Only 1 article had a high risk of bias. Conclusion: For clinicians, most of the studies demonstrated that both manual polishing and glaze application can prevent significant color alterations on CAD/CAM ceramic surfaces. However, due to the relatively limited amount of evidence to support this conclusion, further studies must be conducted.