The International Journal of Prosthodontics, 04/2023

Purpose: To evaluate the soft tissue changes of the face between two positions of occlusion: maximal intercuspal position (MIP) and physiologic rest position (RP). Materials and Methods: In this study, facial surface scans of 83 volunteers in two mandibular positions (MIP and RP) were obtained using a 3D optical scanner. On each 3D image, 21 cephalometric soft tissue landmarks were identified and then compared using t test for various facial parameters (widths, heights, depths, angles, and ratio). Additionally, a regional analysis of the facial surface differences in each patient between the two mandibular positions was performed using a whole scan shell best-fit method and the regional forehead best-fit method. Results: In MIP, facial heights with the nasion-gnathion distance shortened by approximately 1.2 mm (due to the vertical shrinkage of both lips together by 0.8 mm), and the mouth width was significantly widened, while other facial widths displayed no change. The labiomental angle and the upper vermilion arch were altered correspondingly, and regional analysis confirmed the findings with evident changes in the mandibular and subnasal areas with deviations amplified toward the facial midline. Conclusions: By applying 3D facial-scanning technology, this study displayed changes of facial appearance in different mandibular positions (MIP and RP), highlighting the need to instruct and monitor the patient’s mandibular position more consistently to achieve accurate and repeatable data in a 3D facial analysis.

Purpose: To determine the average time for patients to adapt to mandibular complete dentures (CDs) and the factors associated with this critical period. Materials and Methods: In total, 108 completely edentulous patients were rehabilitated using CDs. Adaptation was evaluated based on the following criteria: mastication, comfort, speech, and swallowing with dentures. The Kaplan-Meier method was used to estimate the average time to adaptation. The logrank test was used to assess the adaptation period and associated factors. Results: Of the 108 rehabilitated patients, 89 had adapted to mandibular CDs at the 6-month follow-up. The mean time to adaptation estimated from the Kaplan-Meier curve was 78.54 days (95% confidence interval [CI] 71.04 to 86.04). The factors associated with the adaptation period were previous experience with a mandibular denture (P = .032), the professional who made the previous CDs (P = .034), frequency of appearance of traumatic lesions after 15 days of rehabilitation (P = .023), posterior mandibular ridge height (P = .005), and regular use of the new dentures (P = .002). Conclusions: Most patients adapted to mandibular dentures after 2.6 months. Lack of prior experience with mandibular dentures, use of old dentures made by a dental technician, occurrence of traumatic injuries 15 days after CD delivery, presence of a resorbed posterior mandibular ridge, and nonregular wear were associated with longer adaptation time to new mandibular CDs.

Purpose: To report on the follow-up of two previously published RCTs on the performance of screw-retained monolithic zirconia restorations on titanium (ti)-base abutments based on either digital scans through intraoral optical scanning (IOS) or conventional impressions. Materials and Methods: A total of 54 patients receiving 89 restorations (44 solitary crowns [SC], 21 splinted crowns [2-FDP], and 24 three-unit fixed partial dentures [3-FDP]) were included for the 1- to 3-year follow-up period. Restoration survival and technical complications were documented. Results: In total, 50 patients with 84 restorations completed the 3-year follow-up. One 3-FDP from the digital group was lost. This resulted in a survival rate of 97.9% for the digital group and 100% for the conventional group and an overall survival rate of 98.8% for screw-retained monolithic zirconia restorations on implants after 3 years. There was no statistically significant survival difference between the digital and conventional restorations (P = .362). When evaluated separately, a 100% survival rate of SCs and 97.7% for 2-FDPs could be reported. One decementation and three screw loosenings occurred in the 1- to 3-year follow-up. The multiple-implant restorations showed higher (23.3%) complication rates at the restoration level than the SCs (4.9%) after 3 years of function (P = .026). Conclusions: Screw-retained monolithic zirconia restorations on ti-base abutments show promising survival rates after 3 years of function. Restorative complications in screw-retained monolithic zirconia restorations on Ti-base abutments are more likely to happen in the first year of function and are more common in multiple-implant restorations than SCs. The impression type (digital or conventional) does not seem to influence these results.

Purpose: To assess marginal bone loss (MBL) and implant stability when implant site preparation is performed with conventional drilling and the osteotome technique in the posterior maxilla. Materials and Methods: In total, 30 patients (mean age: 46.97 + 7.48 years) receiving 60 implants were enrolled in this study. In each patient, implant site preparation was done using either conventional drilling (conventional group; n = 30) or the osteotome technique (osteotome group; n = 30). The implant sites were further divided into groups based on the implant length used (implant length < 10 mm, implant length ≥ 10 mm). Marginal bone levels and implant stability quotient (ISQ) values were evaluated at the time of crown insertion and 1 year later. Independent t test and paired t test were used for intergroup and intragroup comparison, respectively. Results: The osteotome group showed statistically significant higher initial ISQ (ISQi) and final ISQ (ISQf) values (ISQi: 61 ± 3.6; ISQf: 64.08 ± 3.7) compared to the conventional group (ISQi: 58.01 ± 4.6; ISQf: 61.32 ± 4.8). Statistically significant higher mean MBL was noted in the conventional group (–0.33 ± 0.12 mm) compared to the osteotome group (–0.26 ± 0.10 mm). Higher MBL was noted in the osteotome group (–0.32 ± 0.09 mm) compared to the conventional group (–0.30 ± 0.14 mm) for implants shorter than 10 mm. For implants ≥ 10 mm in length, significantly higher MBL was noted in the conventional group (–0.37 ± 0.09 mm) compared to the osteotome group (–0.19 ± .06 mm). Conclusions: Osteotome technique could be used as an alternative to conventional drilling, especially when implants longer than 10 mm are planned in the posterior maxilla.

Purpose: To investigate the clinical results of single-tooth ceramic crowns in the posterior region produced from three different monolithic materials. Materials and Methods: A total of 36 posterior single-tooth crowns were fabricated from lithium silicate glass-ceramic (LSGC; n = 12), lithium disilicate glass-ceramic (LDGC; n = 12), and polymer-infiltrated ceramic network (PICN; n = 12) in 27 patients. Restorations were evaluated for prosthetic and periodontal criteria at baseline (0) and after 6 and 12 months. Prosthetic evaluation was performed according to the modified United States Public Health Service (USPHS) criteria, and probing depth (PD), clinical attachment level (CAL), gingival bleeding time index (GBTI), and gingival (GI) and periodontal indices (PI) were evaluated in the periodontal assessment. Friedman and Kruskal-Wallis tests were used for statistical analyses (P = .05). Results: All restorations were evaluated according to survival and success rates. No dropouts occurred. The survival rate of all three materials was 100% after 1 year. However, in the PICN group, a statistically significant difference was found between baseline and 12 months for color match (from A to B) and surface texture (from A to C; P < .001). Conclusions: Although long-term clinical follow-up periods are needed, all three ceramics showed clinically acceptable survival and success rates over 1 year. The ceramics evaluated in the present study could be preferred for single-tooth full-crown restorations in the posterior region.

Purpose: To investigate the influence of occlusal interference using finite element analysis (FEA). Materials and Methods: The FEA model designed for this study centered on an all-ceramic, bilayered, fixed partial denture (FPD) retained on the maxillary first premolar and first molar, with the second premolar replaced by a pontic. The surrounding structures—such as the neighboring teeth, antagonists, and periodontium—were modeled. Four different loading cases were designed at occlusal interferences of 0, 8, 12, and 24 μm and were loaded by a simulated bite force of 300 N. Principal and von Mises stresses, as well as strain, were evaluated for all included structures. Results: For interferences of 12 and 24 μm, failure-relevant tensile stresses in the veneering layer were observed at the occlusal surfaces. Stress found in the zirconia FPD did not reach fatigue or flexural strength for any test load. Conclusion: Peak tensile stress was observed in close proximity to occlusal contact points, increasing with increasing occlusal interference. The FEA results suggest that the majority of occlusal stress is absorbed by the deformation of the periodontal ligament. Framework failure caused by the simulated interferences was not expected. Surface defects may ultimately lead to failure due to fracture or chipping, especially in cases of weaker ceramics or veneering.

Purpose: To evaluate the dimensional discrepancy between the diagnostic wax-up and the resulting mock-up. Material and Methods: A maxillary model with misaligned teeth was scanned, and an initial cast was 3D printed. A total of 60 identical casts were 3D printed from the initial one after scanning. Based on a digital additive veneer wax-up on the six anterior teeth, 10 more casts were 3D printed. The specimens were allocated to seven groups (n = 10) as follows—group 1: transparent silicone matrix with a flowable light-cured composite resin; group 2: same as group 1 but with the addition of a prefabricated transparent tray; group 3: silicone impression putty (65 Shore A) and light-body silicone impression material with a dual-cured bisacryl resin; group 4: same as group 3 but without the light-body silicone; group 5: silicone laboratory putty (92 Shore A) with a dual-cured bisacryl resin; group 6: silicone laboratory putty (92 Shore A) with PMMA; group 7: wax-up casts (control). Scans from the mock-ups were coregistered, segmented, and superimposed with the scans from the wax-up. The difference between the mock-up and the wax-up was quantified by morphologic operations. Results were analyzed by Kruskal-Wallis test and Dunn post hoc test (P < .05). Results: All mock-ups were larger than the wax-up. Significant differences were found for every labial surface third. The incisal third was the least accurate third while the middle third the most accurate. The most accurate were groups 2 and 5, and the largest discrepancy was observed in group 6. Conclusions: The analog mock-up differs dimensionally from the wax-up, regardless of the technique/materials used.

Purpose: To evaluate the effect of tooth brushing and dentifrice fluoride (F-) concentration on changes in color and translucency (ΔE00 and ΔT00, respectively), surface gloss (GS), surface roughness (Sa), and microstructure of a glazed CAD/CAM ceramic. Materials and Methods: Ceramic blocks (e.max/CAD) were sectioned into rectangular plates (14 x 12 x 1 mm), and one surface of each sample was glazed. Samples were divided into three groups according to the F- concentration in the dentifrice (0, 1,100, and 5,000 μg/g) and were then subjected to 60,000 tooth brushing cycles. Luminosity and color were measured using a spectrophotometer at baseline and after every 20,000 cycles to obtain their ΔE00 and ΔT00 values. Another set of samples was prepared to measure the GS with a gloss meter and the Sa with a confocal laser microscope. The GS and Sa results were subjected to analysis of variance, Tukey test, and Dunnett test (α = .05). Results: After 60,000 tooth brushing cycles, all of the variables were clinically acceptable, and there were no significant differences in the ΔE00, ΔT00, GS, or Sa among the fluoridated dentifrices. The GS values decreased significantly as the number of tooth brushing cycles increased. Conclusion: The ΔE00, ΔT00, GS, and Sa values were all clinically acceptable after the glazed e.max/CAD ceramic had been subjected to 60,000 tooth brushing cycles with dentifrices containing up to 5,000 μg/g of F-.

Purpose: To evaluate the performance of fully crystallized zirconia-reinforced lithium silicate (Celtra Duo, ZLS-CD), partially crystallized zirconia-reinforced lithium silicate (Vita Suprinity, ZLS-VS), and partially sintered lithium disilicate–based (IPS e.max CAD, LD) glass-ceramics submitted to polishing, glazing, or no surface treatment after aging. Material and Methods: Samples of each glass-ceramic material were subjected to polishing with rubber cups (POL), glazing (GL), or no treatment (control: unpolished) and afterward aged with 18,000 thermal cycles (5.C to 55.C). The average roughness, 2D and 3D morphology, contact angle, multispecies biofilm formation (Streptococcus mutans and Candida albicans), and mechanical strength were evaluated with atomic force microscopy (AFM, n = 5), sessile-drop goniometry (n = 5), spectrophotometry (n = 5), and the flexural strength test (n = 10), respectively. Data were analyzed using two-way ANOVA and Tukey test (α = 5%). Results: POL produced lower surface roughness than GL, and ZLS-CD presented higher roughness than LD (P < .05). Surfaces without polishing displayed higher roughness than the POL group (P < .001), greater contact angle (P < .001), and significant morphologic changes, regardless of the glass-ceramic material. Irrespective of the treatment, the contact angle was higher in the ZLS-CD group, and regardless of the material, there was higher biofilm formation and lower flexural strength of the unpolished compared to the POL or GL ceramics. Conclusions: POL promoted lower roughness and minor morphologic surface alterations, but biofilm formation and flexural strength were similar to the GL group. In general, ZLS-CD and ZLS-VS showed more similar behavior than LD, which makes ZLS glass-ceramic a good option for indirect restorations.

Purpose: To assess the retention and adaptation of milled and printed denture bases in comparison to conventional ones. Materials and Methods: A total of 24 completely edentulous patients were selected. For each patient, three maxillary denture bases were constructed according to different fabrication techniques, thus defining the three groups for comparison: group 1 consisted of denture bases constructed by a conventional technique, group 2 consisted of denture bases milled from prepolymerized blocks of PMMA, and group 3 consisted of denture bases fabricated by a 3D printing technique. A digital force gauge was used for measuring the retention of the denture bases intraorally, while Geomagic Control X 64 software was used to evaluate the adaptation of the denture bases with their corresponding master casts. Repeated-measures analysis of variance was used for comparison among the groups, followed by pairwise comparison with post hoc Bonferroni correction. The significance level was set at α = .05. Results: Statistical analysis showed significant differences among the three groups regarding retention and adaptation. The highest values of retention and adaptation of denture bases were found in group 2 (milling group). Conclusion: Within the limitations of this study, the following could be concuded: milled denture bases demonstrated better retention and adaptation than the conventional heat-polymerized and printed denture bases, and the printed denture bases showed better adaptation but similar retention to conventional heat-polymerized denture bases.

Purpose: To measure the influence of postpolymerization condition (dry and water-submerged) and time (2, 10, 20, and 40 minutes) on the accuracy of additively manufactured model material. Materials and Methods: A bar standard tessellation language (STL) file was used to manufacture all the resin specimens using a 3D printer. Two groups (n = 80 each) were created based on postpolymerization condition: dry (D group) and water-submerged (W group). Each group was then divided into four subgroups (D1 to D4 and W1 to W4; n = 20 each), which were each assigned a postpolymerizing time (2, 10, 20, and 40 minutes). The specimens’ dimensions were measured using a low-force digital caliper. The volume was calculated as follows: V = l × w × h. Shapiro-Wilk test revealed that the data were not normally distributed. Data were analyzed using Kruskal-Wallis and pairwise Mann-Whitney U tests (α = .05). Results: Significant differences in length, width, height, and volume were found among the subgroups (P < .0018). In all groups, the width dimension (x-axis) presented less accuracy compared to height (z-axis) and length (y-axis) (P < .0018). The D2 and D4 subgroups obtained the closest dimensions to the virtual design, and there were no significant differences between these subgroups (P < .0018). The dry condition showed higher manufacturing accuracy than the water-submerged condition. In the water-submerged subgroups, the highest accuracy was obtained in the W2 and W4 subgroups (P < .0018). Conclusions: Postpolymerization condition and time influenced the accuracy of the material tested. The dry postpolymerization condition with times of 10 and 40 minutes obtained the highest accuracy.

Purpose: To evaluate the accuracy, working time, and patient satisfaction of digital impressions (DI) vs conventional impressions (CI) taken for removable prostheses on edentulous arches. Materials and Methods: A systematic search of the literature was conducted in electronic databases. The English language was filtered with no limitation on publication date. The search was performed up to June 2022. Only in vivo studies comparing DI and CI techniques for the fabrication of complete removable prostheses were included. The primary outcome was accuracy (in terms of trueness and precision), working time (scanning time), and patient satisfaction of DI procedures. Results: After title and abstract screening, six articles were considered eligible for inclusion. All articles investigated the trueness of DI, while no study evaluated the accuracy in terms of precision. The discrepancies between DI and CI were primarily in the peripheral areas. Only one article focused on the working time for scanning procedures. Patient satisfaction was surveyed in just one study. Lack of standardization of the CI procedures and sample size collection were observed in all studies. Conclusions: The scientific evidence so far collected on IOS for complete edentulous arches is not exhaustive, in particular when dealing with scanning time and patient satisfaction. Regarding accuracy, digital scanning in edentulous patients seems to be a predictable procedure within the limits of the attached mucosa.

Purpose: To assess the marginal and internal fit of monolithic zirconia fixed dental prostheses (FDPs) comparing two different intraoral scanners (IOSs) and assessment methods. Materials and Methods: A maxillary typodont with three prepared teeth allowed fabrication of five-unit high-translucency monolithic zirconia FDPs. The typodont was scanned with two IOSs: Cerec Omnicam and 3Shape TRIOS 3. In total, 30 FDPs were milled from presintered high-translucency zirconia blocks. Dual-scan and silicone replica assessments were used to determine marginal and internal gaps. Results: A statistical significance was observed for marginal gaps (3Shape [74.27 ± 10.4 μm] and Cerec [86.45 ± 14.3 μm]) and for internal gaps (3Shape [126.12 ± 12.7 μm] and Cerec [112.38 ± 17.2 μm]). Conclusions: The outcomes of this study showed that the 3Shape TRIOS 3 produced a better overall marginal fit, while the Cerec Omnicam created a better internal fit. Additionally, a greater overall marginal and internal gap was noted with the silicone replica method over the dual-scan method.

Purpose: To compare the accuracy of occlusal stabilization appliances fabricated by digital workflows to those fabricated by conventional workflows. Materials and Methods: In total, 10 volunteers were recruited in this single-blinded crossover study. All volunteers received two types of occlusal stabilization appliances: a digital additively manufactured stabilization splint (DS) and a conventionally fabricated splint (CS). The accuracy was assessed using a 4-point rating scale addressing two aspects of the occlusal appliances: occlusal contact and basic performance. In addition, silicone impression materials were used to assess the gap between the appliance and the maxillary arch to ensure an accurate fit. Differences were quantitatively assessed with Mann-Whitney U test and independent-sample t test. Results: The occlusal contact rating of DS (15.90 ± 1.73) was significantly higher than that of CS (14.10 ± 1.10, P < .05). The basic performance rating of DS (8.70 ± 0.48) was also significantly higher than that of CS (7.20 ± 0.92. P < .05). Quantitative evaluation of fit accuracy revealed a statistically significant difference (P < .05), with DS (636.29 ± 268.51 μm) being superior to CS (704.2 ± 306.05 μm). Conclusion: The stabilization splints fabricated with a digital workflow showed better accuracy than the conventionally fabricated splints in terms of occlusal contact, basic performance, and fit accuracy. Because this is a pilot study, formal trials with a completely digital fabrication workflow will be conducted in the future.

This case report describes a novel approach combining orthodontic and implant digital treatment planning workflows to enable prosthetically driven implant placement before orthodontic treatment is performed or completed. The computer-assisted implant placement is performed using a static surgical guide based on the future positions of the teeth after completion of orthodontic treatment. This innovative approach allows for select partially edentulous patients to undergo fixed prosthetic rehabilitation before orthodontic treatment is completed.

Purpose: To evaluate the trueness of five intraoral scanners on a fully edentulous model with seven implants. Materials and Methods: The study model was created from gypsum with seven implant analogs that were placed with 2-mm gingival height and a 0-degree angle at tooth sites 47, 45, 43, 31, 33, 35, and 37 (FDI system). The study model was scanned 10 times (n = 10) with five intraoral scanners (CS 3600, Emerald S, Primescan, Trios 3, and Trios 4). The study model was digitized with a high-resolution industrial desktop scanner, and the data were imported into reverse-engineering software to be used as the reference model. The trueness assessment was performed digitally with superimposition using the software. Linear measurements were calculated as the differences between the centers of the scan bodies on the study models vs the reference model. Volumetric deviations were calculated with root mean square values. Data obtained in the study were analyzed statistically using one-way analysis of variance and Tukey tests. A value of P < .05 was accepted as statistically significant. Results: In linear measurements, Trios 4 showed the best trueness results, followed by Trios 3, Emerald S, Primescan, and CS 3600. Trios 4 showed statistically higher trueness results than CS 3600 (P = .029). However, no statistically significant differences were found between groups in volumetric measurements (P < .05). Conclusions: All of the intraoral scanners used in the study showed favorable deviation values for an edentulous model with seven implants. Trios 4 showed the best trueness values. The latest generation of intraoral scanners can be used in full-arch implant impressions.

Purpose: To investigate the effects of different bonding agents and application of glaze on the shear bond strength (SBS) between monolithic zirconia (MZ) and indirect composite (IC). Materials and Methods: Five different bonding agents (G-Premio Bond [GP]; Tokuyama Universal Bond [TU]; Signum Zirconia bond [SZ]; Clearfil Ceramic Primer Plus [CCP]; Z-Prime Plus [ZP]) were applied to a total of 200 MZ disk-shaped specimens (n = 100 glazed and 100 nonglazed). Half of the specimens then underwent thermocycling and the other half no thermocycling (n = 10 specimens each subgroup). The experimental setup was prepared as two pieces according to the ISO TR 11405 standards. Specimens embedded in acrylic resin were placed into the experimental setup and a universal testing machine at a crosshead speed of 0.5 mm/minute. Mann-Whitney U test and Kruskal-Wallis test were used for statistical analyses. Bonferroni correction was then performed, and test results with P < .05 were accepted as statistically significant. Results: The application of glaze significantly enhanced SBS when ZP or CCP was used; however, it did not have any significant effect when GP, TU, or SZ were used. Thermocycling significantly decreased the SBS in all bonding agent groups except GP specimens with glaze (P = .16). The highest SBS in all conditions was noted when GP and TU were used. Conclusions: These findings suggest that the bonding agents GP and TU may be recommended for better bonding between MZ and IC.