The International Journal of Prosthodontics, 03/2024

Purpose: To evaluate how the crown-to-implant (C/I) ratio affects the loss of crestal bone at single-crown implants and bridges in patients with periodontal disease. Materials and Methods: A total of 39 patients treated for periodontitis were rehabilitated with 108 implant-supported single crowns and bridges. Each patient was examined over a 5- to 20-year period on a 3- to 6-month recall schedule. At each session, we recorded periodontal clinical parameters. In addition, intraoral radiographs were taken after superstructure insertion (baseline) and then at 1, 3, 5, 10, 15, and 20 years. The study population was divided by anatomical C/I ratio (Group 1: C/I ≤ 1, Group 2: C/I > 1). Results: Implants had a 96.2% 5-year survival rate and 92.6% 20-year survival rate. The overall prevalence was 10.1% for mucositis and 1.1% for peri-implantitis. The survival rate (P = .68), incidence of mucositis (P = .325), and incidence of peri-implantitis (P = .077) did not significantly differ in the group comparison. The mean annual peri-implant bone loss was 0.09 ± 0.41 mm and was not significantly different between the groups. Mean bone loss was not significantly different until the 10th year of observation, during which Group 2 presented significantly less bone loss. The correlation of annual bone loss and clinical C/I ratio showed a small but significant negative effect throughout the entire study period (R = –0.217; P < .01). Conclusions: Increased crestal bone loss was not observed with implants with higher C/I ratios, both anatomical and clinical, and they even showed signs of less crestal bone loss.

Purpose: To examine if there are differences in smile esthetic evaluation scores by orthodontists and prosthodontists and if there are changes in those scores when two evaluations are performed, when the time of observation is increased, and when the lips are present or absent from the images. Materials and Methods: In total, 12 individuals participated in this pilot study. Two digital images were taken from each individual. The first digital image was a smile view, and the second image was an intraoral view. Two presentation files were prepared, with two images for each individual. The smile and dental attractiveness ratings were obtained from 10 specialists. Results: Repeated measures ANOVA was applied including all four within-subject factors, the evaluator (E), the repetition (R), the time of observation (T), and the presence or not of lips (L). Factors E, T, and L each had a statistically significant main effect. E and R had a statistically significant combined effect. In particular, the esthetic score for the view with smile was overall higher than for the intraoral view. The same results were obtained when the analysis was repeated with the 10 evaluators grouped to prosthodontists and orthodontists, and the prosthodontists tended to score higher than the orthodontists. Conclusions: The evaluator and the presence of lips have a statistically significant effect. The present pilot study has found that three (E, L, R) out of four factors (T) are important for the evaluation of dental esthetics.

Purpose: To assess the clinical concept of patient treatment with fixed tooth- and implant-supported restorations in a university-based undergraduate program after 13 to 15 years. Materials and Methods: In total, 30 patients (mean age 56 years) who had received multiple tooth- and implant-supported restorations were recalled after 13 to 15 years. The clinical assessment comprised biologic and technical parameters as well as patient satisfaction. Data were analyzed descriptively, and the 13- to 15-year survival rates for tooth- and implant-supported single crowns and fixed dental prostheses (FDPs) were calculated. Results: The survival rate of tooth-supported restorations amounted to 88.3% (single crowns) and 69.6% (FDPs); in implants, it reached 100% for all types of restorations. Overall, 92.4% of all restorations were free of technical complications. The most common technical complication was chipping of the veneering ceramic (tooth-supported restorations: 5.5%; implant-supported restorations: 13% to 15.9%) regardless of the material used. For tooth-supported restorations, increased probing depth ≥ 5 mm was the most frequent biologic complication (22.8%), followed by endodontic complications of root canal–treated teeth (14%) and loss of vitality at abutment teeth (8.2%). Peri-implantitis was diagnosed in 10.2% of implants. Conclusions: The results of this study indicate that the clinical concept implemented in the undergraduate program and performed by undergraduate students works well. The clinical outcomes are similar to those reported in the literature. In general, the majority of biologic complications occur in reconstructed teeth, whereas implant-supported restorations are more prone to technical complications.

Purpose: To compare the peri-implant bone loss of mandibular complete-arch implant-supported fixed prostheses (FPSs) supported by three and four implants and to correlate with the size of the horizontal and vertical distal cantilever at prosthesis placement (T1) and after 1 year (T2). Materials and Methods: A total of 72 external hexagon (EH) type implants were placed in 20 participants. Of these, 24 supported an FPS with three implants (G3I) and 48 with four implants (G4I). The mandibular implants were named 1, 2, 3, and 4 according to their location in the arch, in a clockwise direction. Digital periapical radiographs were taken at times T1 and T2 for analysis and measurement of peri-implant bone loss. The horizontal and vertical distal cantilevers were measured with a digital caliper and correlated with peri-implant bone loss. Results: The survival rate of implants in G3I was 91.66%, and in G4I it was 97.91%. The mean bone loss in G3I was 0.88 ± 0.89 mm, and in G4I it was 0.58 ± 0.78 mm (P = .225). There was no correlation between distal horizontal cantilevers and bone loss in the studied groups, with G3I being –0.25 (P = .197) and G4I –0.22 (P = .129). Larger vertical cantilevers of implants 1 (P = .018), 3 (P =.015), and 4 (P = .045) correlated with greater bone loss in G4I. Conclusions: The number of implants in an FPS did not influence peri-implant bone loss after 1 year of follow-up. Larger vertical cantilevers influenced greater bone loss in complete-arch implant-supported fixed prostheses supported by four implants.

Purpose: To determine the values of 15 craniofacial linear distances in the Serbian ethnic group using and comparing two methods of face-anthropometric and digital 2D-face-photogrammetric measurement and to determine the correlations between distances that can be predictive or can serve as proxy for occlusal vertical dimension (OVD). Materials and Methods: A total of 90 adults were selected. Facial distance as a tool to measure the OVD was measured as Sn-Gn (the distance between the septum of the nose [Sn] and the tip of the chin [Gn]). Face-anthropometric measurements were made with a Boley gauge (Buffalo Dental). Digital 2D-photogrammetric facial measurements were performed using the computer program Dr Ceph (FYI Technologies). Results: The mean value for the distance Sn-Gn was 63.55 using face-anthropometric measurement (Sn-Gn[f]) and 63.56 using 2D-face-photogrammetic measurement (Sn-Gn[ph]) Multivariate regression analysis revealed that Sn-Gn(f) depended on ExL-ExR(f) P = .001; ZyL-ZyR(f) P = .077; N-Sn(f) P = .096; Sn-Sto(f) P = .043; and sex. Analysis also identified that Sn-Gn(ph) depended on ExL-ExR(ph) P < .001; EnL-EnR(ph) P = .029; N-Sn(ph) P = .013; Sn-Sto(ph) P = .001; and sex. Conclusions: A comparison of facial anthropometry and digital 2D-facial photogrammetry revealed no statistical significance differences in the values obtained and showed that facial photogrammetry could be as reliable a method as facial anthropometry.

Purpose: To evaluate the effect of different finishing protocols on the wear behavior of lithium disilicate glass-ceramics (LD). Materials and Methods: Specimens were produced from LD prefabricated CAD/CAM blocks and divided into three groups according to the surface treatment (n = 8): control, polishing, and glaze. Ceramic specimens were subjected to wear testing using a dual-axis chewing simulator. A 49-N load was applied in the axial direction combined with a lateral movement (1-mm path) using an LD spherical piston for a total of 10⁶ cycles. Qualitative analysis of the wear surface was performed using an optical microscope. Quantitative analysis of surface roughness and volume loss was performed using a confocal microscope and a 3D-image editing software, respectively. Surface roughness and volume loss data were analyzed using Friedman’s nonparametric statistical test for repeated measures and the Student-Newman-Keuls test (α = .050). Results: There were statistical differences for surface roughness and volume loss of LD specimens in the different experimental conditions (P < .001). The control and polishing groups showed similar surface roughness and volume loss values for all testing times. The glaze group had greater wear volume after 10³, 10⁴, and 10⁵ cycles. After 10⁶ cycles, surface roughness and volume loss were similar in all groups. For the piston, surface roughness was similar over time and among groups. Conclusions: A distinct wear behavior was found for glazed glass-ceramic specimens compared to control and polished specimens. At the end of the simulation, the surface roughness and volume loss was similar for the groups.

Purpose: To measure and compare the mean temperature values due to heat generated during the grinding of different prosthetic materials with diamond burs using a high-speed instrument with and without water cooling. Materials and Methods: In total, 120 disk-shaped specimens (10 × 2 mm), each with a smaller disk in the center (3 × 2 mm), were fabricated from yttrium-stabilized zirconia, monolithic zirconia, glass-ceramic, indirect composite, polyetheretherketone (PEEK), and cast metal (Ni-Cr alloy). The specimens were divided into six groups (n = 20) according to material type. The specimens in each group were ground continuously with a high-speed handpiece and diamond burs with (n = 10) and without (n = 10) water cooling until the smaller disks were removed. Two different methods (thermocouple and thermal camera) were used to measure the temperature during the grinding process. Results were analyzed using two-way ANOVA and paired-samples t test (P < .05). Results: PEEK had the lowest mean temperature and metal had the highest values, both with and without water cooling, according to data measured with a thermocouple. Zirconia and monolithic zirconia samples without water cooling had the highest mean temperature when measured with a thermal camera. Both with and without water cooling, composite samples had the lowest mean temperatures for thermal camera measurements. Conclusions: Water cooling is strongly recommended when grinding all prosthetic materials. The heat transferred to the supporting teeth may depend on the thermal conductivity of the material used.

Purpose: To perform a bibliometric study in the literature about the increasing number of global studies on dental esthetics in recent years. Materials and Methods: Articles on dental esthetics published between 1980 and 2021 were pulled from the Web of Science (WoS) database. In this comprehensive bibliometric study on dental esthetics, a summary of 2,858 articles published in the last 41 years was shared. Network visualization maps were used to identify citation analyses and trending topics. Spearman correlation coefficient was used for correlation studies. The exponential smoothing estimator was used to estimate the number of articles to be published in the coming years. Results: Of the 3,666 publications, 2,858 (77.9%) were articles. The top three contributing countries to the literature were the USA (816, 28.5%), Brazil (286, 10%), and Italy (246, 8.6%). The most active institution was the University of Bern (n = 55). The journal with the highest number of articles was Journal of Prosthetic Dentistry (n = 178). According to the average number of citations per article, the most influential journal was Journal of Periodontology (citations: 55.6). Conclusions: Keywords of the trending topics related to dental esthetics are perception, bleaching, cleft lip, connective tissue graft, smile esthetics, adolescent, esthetic region, soft tissue augmentation, and clinical studies. In regard to the global output in dental esthetics, this article is a useful resource for clinicians, scientists, and dental students.

Purpose: To analyze the effect of disinfectants on the roughness and mechanical properties of CAD/ CAM polymethylmethacrylate (PMMA) dentures. Materials and Methods: Two groups of denture base resins were tested—heat-polymerized and milled blocks. For each resin, 120 specimens were produced for flexural strength (FS) and flexural modulus (FM) analyses (total: 240 specimens), and 40 were produced for microhardness and surface roughness evaluations (total: 80 specimens). They were categorized into the following groups based on immersion: control (deionized water); H1 (1% sodium hypochlorite); H05 (0.5% sodium hypochlorite); and C2 (2% chlorhexidine) groups. The immersion periods were 0 (T0), 130 (T1), and 260 (T2) cycles. Statistical analyses were performed for flexural properties using threeway ANOVA. Microhardness (KHN) and surface roughness (Ra) were analyzed using repeated-measures ANOVA. A significance level of 5% was set. Results: CAD/CAM PMMA showed higher FS (P = .001) and FM (P < .001) than conventional PMMA. The KHN value was superior to the conventional PMMA (P < .001). The chemical solution affected the surface roughness of both resins (P = .007). The CAD/ CAM PMMA block showed increased Ra values when H1 was used. Cycling separately increased the FS of conventional PMMA (T1 vs baseline; P < .05). However, the FM of CAD/CAM PMMA was higher (T1 and T2 vs baseline; P < .05). The time factor increased the microhardness of both resins (T2 vs baseline; P < .05). Conclusions: The CAD/CAM resin showed higher values compared to conventional PMMA in all tests, regardless of the chemical solution used; however, the values obtained for both resins were clinically acceptable.

Purpose: To evaluate the impact of removable partial dentures (RPDs) on masticatory performance (MP) of partially edentulous subjects. Materials and Methods: Electronic database and hand searches were conducted to explore clinical trials reporting the evidence of the effect of metal- and acrylic-based RPDs on mastication. The validated objective and subjective measures of assessment of mastication were included. The article selection, data extraction, and assessment of risk of bias were conducted by two reviewers independently. Results: Out of 11,200 studies, 1 randomized controlled trial and 23 clinical trials met the inclusion criteria. Positive impact on different parameters of masticatory function after RPD treatment was reported in 14 studies. Subjective evaluation of chewing ability (CA) displayed an improvement in 83.3% of studies, while improvement was evidenced only in 69.5% of studies upon objective evaluation. Most studies reported data on free-end saddles. Of the 13 studies associated with bilateral free-end saddle dentures, 9 studies showed a positive effect on masticatory efficiency. Various factors were found to have an impact on the MP of RPDs. Conclusions: Subjective evaluation displays higher positive impact of RPDs in MP than objective evaluation. Assessment of patients’ perspectives is important in clinical decision-making. Multiple factors affect the MP with RPD treatment.

Purpose: To evaluate the stress distribution along a premolar’s root dentin, its post, and its post-luting agent when materials with different elastic moduli are used to fabricate one-piece post-and-cores in two different designs. Materials and Methods: Two 3D virtual models (for cylindrical and conical post designs) of a mandibular premolar restored with one-piece post-and-core restorations were obtained using a software. A total of eight post-and-core materials were tested: polyetheretherketone (PEEK), polyetherketoneketone (PEKK), glass fiber-reinforced polyetheretherketone (GFR-PEEK), carbon fiber-reinforced polyetheretherketone (CFR-PEEK), gold-palladium alloy (Au-Pd), titanium (Ti), zirconia (Zi), and chromium-nickel (Cr-Ni). Maximum principals stress (MPS) in the post, post-luting agent, and root dentin were determined. A load of 150 N was applied to the buccal cusp in the linguo-labial direction at an angle of 45 degrees oblique to the longitudinal axis of the crown. Results: The highest MPS value in post structure was observed with Cr-Ni material for both post designs. Similarly, the highest MPS value in the post-luting agent was observed for Cr-Ni, the material with the highest elastic modulus. However, in the root dentin, the highest value was observed in PEEK, the material with the lowest elastic modulus. Conclusions: Post material and design influenced the stress concentration in the post, post-luting agent, and root dentin. The stress at the root dentin was slightly higher for polymeric materials. Cylindrical post design revealed lower stresses than conical post design at root dentin for all post-and-core materials tested.

This article reports a case of maxillary rehabilitation with implant-supported fixed dental prostheses on six zirconia implants. A woman with impacted maxillary canines attended our dental clinic seeking a metal-free maxillary restoration. After the extraction of both impacted maxillary canines and the placement of autogenous bone graft, six two-piece zirconia implants with straight abutments were placed in the anterior maxilla. Two zirconia fixed dental prostheses with porcelain veneering, separated at the midline, were placed on these zirconia implants. The 10-year follow-up monitored the adequate evolution of both implants and restorations with no signs of peri-implant disease.

Purpose: To analyze the microgap changes between hybrid-abutment crowns made of two materials and three internal taper connec9on implants with different connection designs before and after thermodynamic loading. Materials and Methods: A total of 30 implants—10 each of Straumann Bone Level Implant-RC (STR); GC AADVA Implant (AAD); and Astra-Tech OsseoSpeed EV (AST)—were included in this laboratory study. Each implant had an internal taper connection, but their designs were slightly different. Five hybrid-abutment crowns were fabricated using a lithium disilicate ceramic (LD), and five were fabricated using polymethylmethacrylate (PMMA) with CAD/CAM technologies for each implant system, providing six sample groups STR-LD, AAD-LD, AST-LD, STR-PMMA, AAD-PMMA, and ASTPMMA. The microgap volume was measured using micro-CT images obtained before and after thermodynamic loading equivalent to 4 months of clinical use. Student t test, one-way ANOVA, and Tukey test were used for comparisons. Results: The greatest microgap volume increase was recorded (3.405% ± 1.567%) in the AST-LD group, and the lowest increase (0.45% ± 0.373%) was in the STR-PMMA group. A statistically significant difference in microgap increase was not detected among PMMA and LD groups: for STR-LD/STR-PMMA (t test: P = .273); for AAD-LD/AAD-PMMA (t test: P = .374); and for AST-LD/AST-PMMA (t test: P = .268). However, the difference in the microgap increase between the different implant systems was statistically significant. Conclusions: The microgap between hybrid-abutment crowns and implants increased after short-term thermodynamic cycling. Hybrid-abutment crowns with different elastic modulus showed similar microgap increase. The geometric shape of the connection influenced the microgap increase.

Purpose: To evaluate the effect of restoration design on fracture resistance and stress distribu0on of veneered and monolithic three-unit zirconia fixed partial dentures (FDPs) using finite element analysis (FEA). Materials and Methods: Identical epoxy resin replicas of mandibular second premolars and second molars (to serve as abutments for the three-unit bridges) were divided into four groups (n = 10): monolithic zirconia (MZ) restorations; conventional layering veneering technique (ZL); heat pressed-on technique (ZP); or CAD/CAM lithium-disilicate glass-ceramics (CAD-on). Specimens were subjected to compressive cyclic loading on the mesio-buccal cusp of the pontic (load range 50 to 600 N; aqueous environment; 500,000 cycles) in a universal testing machine. Data were statistically analyzed at 5% significance level with Fisher exact test and Kaplan-Meier survival analysis. 3D models were constructed in accordance with experimental groups. The stress distribution in each model was analyzed and evaluated according to the location and magnitude of the maximum principal stresses (MPSs) using ANSYS so\ware. Results: Specimens from ZL and ZP groups failed at different stages of the 500,000 cycles fatigue, while CAD-on and MZ restorations survived the fatigue test. Statistically, there was a significant difference between the groups (P < .001). The MPS were located under the mesial connector in both monolithic and bilayered three-unit zirconia FDPs. These stresses were found to be higher in monolithic geometries compared to bilayered zirconia FDPs. Conclusions: Monolithic threeunit zirconia and CAD-on zirconia frameworks resulted in superior fracture resistance. Restora0on design significantly affected the stress distribu0on of three-unit zirconia FDPs.

Purpose: To evaluate the effect of immersion in water on deformation of maxillary denture bases created with CAD/CAM and heat-polymerized resin fabrication techniques under loading condi8ons. Materials and Methods: 2-mm-thick denture bases were fabricated using four techniques: CAD/CAM milling (CCM; Polywax PMMA blank, Yamachi PMMA disk Yamahachi Dental); 3D prin8ng (3DP; BV005, NextDent Base); compression molding (CM; Luciton 199, Dentsply Sirona); and injec8on molding (IM; Ivobase, Ivoclar; n = 5 per group). Three static 49-N loads were applied perpendicular to each denture base, and the mean strain  value (MSV) was recorded with strain gauges a[ached to the denture surface. The denture bases were stored at 37°C in distilled water for 14 and 28 days, and the MSVs under the same static load were recorded. Results: The highest MSVs were observed at the posterior palatal seal, tuberosity, and labial notches of the dentures. The lowest MSVs were recorded for the CCM group and then the CM and IM groups. The highest MSVs were recorded for the 3DP group. No significant differences in regional MSVs (P > .05) were observed among the CCM, CM, and IM aber 14 and 28 days in water. Large devia8ons in MSVs were recorded for the 3DP group across the measurement sites aber water exposure (P < .05). Conclusions: CCM had the lowest denture deformation under static loading. After immersion in water, the deformation changes under static loading were stable for CCM, CM, and IM. However, variations among the materials used in 3DP group influenced the mechanical performance and presented larger deformations.

Purpose: To validate the effectiveness of a simplified ultrasonic cleaning protocol to clean customized abutments, and to investigate the percentage of pollutants on customized abutments provided by the implant company and the additional effect of dental laboratory manipulations. Materials and Methods: A total of 24 customized abutments were divided in two groups, 12 returning from the implant company and 12 others returning from the dental laboratory. In each group, there were 6 zirconia (Zr0₂) abutments and 6 .tanium (Ti) abutments. For each condition, half of the samples were cleaned with the experimental protocol, and the others were left as delivered by the company. The two-step cleaning protocol consisted of mechanical treatment with a sterile compress soaked in a detergent over the transgingival part of the abutment, followed by three successive ultrasound baths for two minutes/bath. The presence of pollutants was quantified using scanning electron microscopy. Results: The suggested cleaning method allowed to significantly decrease the quantity of pollutants (P = .0006). The abutments returning from the dental laboratory were significantly more polluted than those coming directly from the implant company (P = .0043). The cleaning effect was highly significant in both groups (P < .0001). The quantity of pollutants before cleaning were similar in the titanium and in the zirconia groups and the cleaning effect was highly significant in both groups (P = .0009). Conclusions: The cleaning protocol tested was successful on the customized abutments from each group.

In our previous test model, the abutment teeth and the model base were printed with resin and bonded with a polyether material. Some abutment teeth were fractured during the mechanical load test. Therefore, the aim was to develop and evaluate a new model under mechanical loading until fracture with zirconia FPD frameworks. At a fracture load of up to 1,636 N, neither the artificial abutment teeth nor the base model fractured. Furthermore, the artificial abutment teeth did not detach from the base model. Therefore, the model should be suitable for mechanical testing of most ceramic-based framework materials for three-unit FPDs.