The International Journal of Prosthodontics, Pre-Print

Purpose: To determine the average time it takes for patients to adapt to mandibular complete dentures and the factors associated with this critical period. Materials and methods: A total of 108 completely edentulous patients were rehabilitated using complete dentures. Adaptation was evaluated based on the following criteria: mastication, comfort, speech, and swallowing with dentures. Kaplan-Meier analyses were used to estimate the average time to adaptation. Log-rank test was used to assess the adaptation period and associated factors. Results: Of the 108 rehabilitated patients, 89 had adapted to mandibular complete dentures at the 6-month follow-up. The mean time to adaptation estimated from the Kaplan-Meier curve was 78.54 days (95% 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 complete dentures (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). Conclusion: Most patients adapted to mandibular dentures after 2.6 months. No prior mandibular denture experience, use of old dentures made by a dental technician, occurrence of traumatic injuries 15 days after complete denture delivery, presence of a resorbed posterior mandibular ridge, and nonregular wear were associated with longer adaptation time to the new mandibular complete dentures.

Purpose: To evaluate the accuracy of intraoral scanners by comparing the marginal fit of 70 all-ceramic crowns fabricated from both conventional impressions and intraoral scans. Materials and Methods: A total of 70 posterior teeth requiring single-crown restorations randomly underwent either intraoral scanning or conventional impression-taking followed by laboratory scanning of the casts in a parallel-group RCT. Subsequently, 70 monolithic all-ceramic crowns were CAD/CAM fabricated; only the impression technique differed. Marginal fit, internal fit, adjustment time required for insertion and occlusal contacts, and visual analog scale (VAS) scores assessing dentists’ satisfaction with all of the crowns were clinically evaluated by a blinded and calibrated examiner. Data were analyzed using independent-samples t test and likelihood ratio test or Fisher exact test. All tests were performed with α = .05. Results: The mean marginal fit with intraoral scanning (57.94 ± 22.51 μm) was better than with diagnostic cast scanning (82.98 ± 21.72 μm). The difference was statistically significant (P = .000). The differences in internal fit, adjustment time for crown insertion and occlusal contacts, and VAS scores were also significant, and the secondary outcomes were in favor of intraoral scanning. Conclusion: Within the limitations of this clinical trial, CAD/CAM–fabricated single-tooth restorations in the posterior region produced by an intraoral scanning technique using TRIOS was found to be a more accurate and efficient alternative to restorations based on conventional impressions in combination with the laboratory scanning technique.

Purpose: To identify the most effective bonding protocol between the denture base and artificial teeth made with different CAD/CAM materials (milled and 3D printed) compared to conventional heat-cured materials. Materials and methods: This review was performed according to the Preferred Reporting Items for Systematic and Meta-Analysis (PRISMA) criteria and registered in PROSPERO (CRD42021276084). An electronic search was performed independently by two examiners in the MEDLINE/PubMed, Cochrane Library, Scopus, Web of Science, ProQuest, and OpenGrey databases for articles published up to and including December 2021. Results: The electronic search returned 806 articles, and after duplicates were removed, the total was 589 articles. Four articles were selected according to the eligibility criteria. Evaluating the different combinations of denture base materials and artificial teeth, the IvoBase CAD Bond (Ivoclar Vivadent) was effective for bonding the CAD/CAM denture bases to prefabricated acrylic resin denture artificial teeth. There were no differences compared to heat-cured denture base bonding to prefabricated acrylic resin denture artificial teeth (χ2: 68.56; I2: 96%; P < .001). Conclusion: IvoBase CAD Bond as a bonding system can be an alternative for using new technologies in the fabrication of α CAD/CAM base with prefabricated acrylic resin denture artificial teeth.

Digital or CAD/CAM workflows and protocols are being increasingly utilized because of their improved efficiency and reproducibility. For the fabrication of complete dentures, digital workflows can reduce treatment time and clinical visits while enhancing the reliability and reproducibility of the laboratory phase and materials. However, establishing centric relation (CR) and vertical dimension of occlusion (VDO) in a reproducible way is still a challenging step for complete denture fabrication in both analog and digital workflows. This clinical report describes a digital workflow utilizing an individualized gothic arch tracing device (GATD) using open-source software for the fabrication of complete dentures. With this workflow, clinicians can offer customized solutions according to patient rehabilitation, with good reproducibility using gothic arch tracing to be implemented in the digital workflow.

Purpose: To survey the materials favored by dentists for intraoral repair of cohesive chipping. Materials and methods: From August 2019 to February 2020, dentists were surveyed to determine the frequency of cohesive chipping experienced within the last 3 months and to identify their preferred approaches for intraoral repair. Results: Of the participants, 42.5% observed chipping (n = 506). Participants favored the application of roughening devices, silane, and composite resins. Self-etching glass-ceramic primers or hydrofluoric acid were used for ceramic etching. Conclusion: Dentists apply a variety of materials for intraoral repair of chipping, including materials that are not approved for intraoral use.

Purpose: To evaluate the effects of two different lasers and their use in combination with hydrofluoric acid (HF) etching on the surface roughness of zirconia-reinforced lithium silicate (ZLS) ceramics and their shear bond strength (SBS) to composite resin. Materials and methods: The five study groups were as follows: (1) Group H = HF etching; (2) Group N = Nd:YAG (neodymium: yttrium-aluminum-garnet) laser; (3) Group NH = Nd:YAG laser + HF gel; (4) Group E = Er:YAG (erbium: yttrium-aluminum-garnet) laser; and (5) Group EH = Er:YAG laser + HF gel. Surface roughness was assessed using a noncontact profilometer, and SBS tests were conducted with a universal testing machine. Results: The mean SBS values were 16.23 ± 1.77 MPa for Group H, 17.1 ± 1.65 MPa for Group N, 16.65 ± 1.11 MPa for Group NH, 8.08 ± 1.12 MPa for Group E, and 11.58 ± 0.82 MPa for Group EH. There were significant differences between groups E and EH (P < .001), but no significant differences (P > .05) among the other groups. Conclusion: Clinicians may prefer Nd:YAG laser or the combination of Nd:YAG and HF to intraorally repair fractured areas.

Purpose: This in vitro study was conducted to evaluate the marginal accuracy of all-ceramic onlay restorations and prototypes fabricated using additive and subtractive methods. Materials and methods: Ten typodont first molars were prepared and scanned two times using two different scanners: ARCTICA AutoScan (KaVo Dental) and CEREC Omnicam (Dentsply Sirona). The two groups of virtual models were used to design two groups of virtual onlay restorations using two different CAD software (n = 10 each group) and exported in STL files. Each group of STL files was converted to physical onlay restorations and prototypes by using three different methods; these included two additive manufacturing techniques, stereolithography apparatus (SLA) and digital light processing (DLP), and one subtractive technique, e.max milling using the KaVo Everest system and the Dentsply Sirona inLab MC X5. A digital microscope was used to evaluate the marginal fit around the onlay restorations or prototypes on the typodont teeth. Results: All evaluated groups showed mean marginal gaps between 59 and 84 μm. No statistically significant differences were found when comparing the marginal accuracy of onlay restorations fabricated by the subtractive method and onlay prototypes from the two additive methods, SLA (P = .70) and DLP (P = .21). Conclusion: All the models evaluated produced marginal gaps within the reported acceptable clinical range. Thus, these subtractive and additive methods may be considered suitable for onlay restoration production.

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 present a minimally invasive treatment approach for the replacement of two missing adjacent teeth with two single-retainer resin-bonded fixed dental prostheses (RBFDPs). Materials and methods: Two missing adjacent premolars were restored by two RBFDPs with an innovative design of the proximal section. Both RBFDPs were digitally designed and milled from monolithic 3Y-TZP zirconia ceramic using CAD/CAM technology. Following the construction of the anterior RBFDP, a shallow interlock was designed in the area of the proximal contact, which was applied in the same insertion direction as the posterior RBFDP. In this way, different paths of insertion of the RBFDPs could be compensated without reducing the proximal hygiene capability. Results: The presented minimally invasive restorations were successful over 3 years of clinical observation without any complications. Conclusion: The presented restoration design secures the transversal position of the RBFDPs while maintaining the physiologic tooth mobility. In addition, it allows the compensation of varying paths of insertion while improving hygienic conditions. Last, in case of a unilateral debonding of one retainer wing, rebonding might be possible.

Purpose: To verify the parameters and characteristics evaluated in printed complete denture bases and how they influence properties. Materials and methods: This work was registered in Open Science Framework (osf.io/4um6v) and followed the PRISMA Extension for Scoping Reviews (PRISMA-ScR). A search of peer-reviewed articles published up to April 9, 2020 was performed on the PubMed, Lilacs, Cochrane Library, and Science Direct databases. The review question based on the population, concept, and context (PCC) was: What printing parameters and characteristics of complete denture bases can influence properties? Results: The database search resulted in 1,945 articles, and 1,390 article titles and abstracts were screened. A total of 17 articles were included. The summarized findings included: cleaning prostheses with alcohol after printing and a postcuring cycle influence biocompatibility and residual monomers; the printing angle influences physical/mechanical properties, microbial adhesion, and tissue adaptation; accuracy is influenced by layer thickness and the manufacturing technique, which also influences retention and tissue adaptation; the incorporation of antimicrobial agents influences physical/mechanical properties and antimicrobial activity; and the method of union between the base and the teeth influences mechanical strength. Conclusion: Printed denture bases of 100-μm layer thickness showed good adaptation to tissues and accuracy, and it can be recommended that the prosthesis be cleaned in ethanol followed by postcuring for better biocompatibility. Nanoand microparticles can be added to provide antimicrobial activity and better resistance. Printing angle and mechanical properties must be better evaluated.

Purpose: To evaluate the effect of three different curing protocols based on different ratios between self-curing and light-curing periods on the bond strength and nanoleakage of fiber posts luted with dual-curing self-adhesive cements. Materials and methods: A total of 48 single-root teeth were endodontically treated and obturated, and an 8-mm post space was prepared with dedicated drills. Specimens were randomly divided into two groups according to the self-adhesive cement employed: G1 = PANAVIA SA Plus (Kuraray Noritake); and G2 = Bifix SE (VOCO). The specimens were further divided into three subgroups (n = 8 each) according to the light curing protocol applied: no light curing (SG1); 20 seconds of light-curing 20 seconds after cement injection (SG2); and 20 seconds of light-curing 120 seconds after cement injection (SG3). Slices of 1-mm thickness were prepared to perform the push-out test and nanoleakage analyses of the coronal and apical regions after 24 hours of storage in artificial saliva. Results were statistically analyzed with three-way ANOVA and Tukey post hoc tests. Statistical significance was set for P < .05. Results: Three-way ANOVA analysis showed that the factors cement (P = .02) and curing protocol (P < .001) had a significant influence on bond strength. Tukey post hoc test reported that light curing 120 seconds after injection showed higher bond strength compared to no light curing and photoactivation after 20 seconds. Conclusion: To achieve the highest bond strength with self-adhesive cements, photoactivation with a 120-second delay after mixing is required. Nevertheless, there is no difference if the time elapsed before applying the light is 20 seconds or if there is no light curing at all.

Purpose: To evaluate the stress distribution in endocrowns and post-and-core crowns used as abutments for a Kennedy Class I removable partial denture constructed with different framework materials. Materials and methods: 3D models of a Kennedy Class I mandible were constructed. Cobalt-chromium (Co-Cr) and polyether ether ketone (PEEK) frameworks were simulated for Models 1 and 2. An endocrown and a fiber post-and-core crown for the mandibular left and right second premolar abutments were simulated for both models, respectively. Lithium disilicate porcelain was defined for the crowns. A 200-N occlusal force was applied in the vertical and 30-degree oblique directions. Results: The von Mises stresses were evaluated for the abutments and prostheses, and the principal stresses for the cortical bone under vertical and oblique loadings. Endocrowns showed lower stress values than post-and-core crowns in both models. Post-and-core porcelain crowns generated the highest stress in Model 2 under vertical loading. PEEK framework caused higher stress values on abutments than Co-Cr. Compressive stresses were higher than tensile stresses in cortical bone. The highest compressive stress was observed around the left premolar cortical bone area in Model 1 under oblique loading. Oblique loading caused lower stress values than vertical loading, except for on the minor connectors and cortical bone. Conclusion: From a biomechanical perspective, endocrowns may be more advantageous than post-and-core crowns when used as abutments for a Kennedy Class I removable partial denture. In addition, Co-Cr frameworks show more favorable stress distribution on abutments than PEEK frameworks.

Purpose: To compare the CIE L*a*b* values of two different dental shade guides using two shade-matching spectrophotometers. Materials and methods: SpectroShade Micro (MHT) and Easyshade (VITA Zahnfabrik) were tested. One calibrated operator performed 30 measurements of each tab from three batches of two guides, VITA Classical (VC) and VITA 3D-Master (VM). Receiver operating characteristic (ROC) curves and intraclass coefficients (ICC) between the different batches were calculated. Results were given as mean and SD of the L*a*b* values and the respective color differences according to the CIEDE 2000 formula (ΔE₀₀) for each of the shade tabs in the two spectrophotometers, then analyzed with independent student t test (α = .05). Results: A total of 1,440 and 2,610 measurements for VC and VM, respectively, were performed per spectrophotometer. There were statistically significant differences between the two devices for all L*a*b* values, with the exception of: L* for 3R1.5; a* for 2R1.5, 3L1.5, 2L2.5, 3M2, 3L2.5, 4L1.5, and 4L2.5; and b* for D3, 1M2, and 3M2. When assessing the same shade guide, differences in ΔE₀₀ were detected between devices above the acceptability threshold (ΔE₀₀ ≥ 1.8) for all shade tabs except for VC (C1, C2, D3, A3.5, C3, and A4) and VM (4M1, 3R2.5, 4L2.5, and 4M3). The overall mean of the inter-device ΔE₀₀ was 2.2 ± 1.0 for VC and 2.5 ± 1.0 for VM. Conclusion: The two dental spectrophotometers presented high ICC and ROC values, which validates their indication as auxiliary tools. However, there are discrepancies in the hues D (VC) and R (VM) with interdevice variability when evaluated for the L*a*b* component.

Purpose: To evaluate the effects of post length, post material, and substance loss on the fracture resistance of endodontically treated mandibular premolars. Materials and methods: A total of 96 extracted human mandibular first premolars were endodontically treated and divided into 12 test groups (n = 8 each) based on the number of residual walls (one/two), post material (glass-fiber/titanium), and post length (5 mm, 7.5 mm, and 10 mm). After luting the posts, specimens received a composite resin core and a crown preparation with a 1.5-mm ferrule. Cast cobalt-chromium crowns were cemented using glass-ionomer cement. After 1,200,000 chewing cycles with a load of 49 N and simultaneous thermocycling (5°C to 55°C), specimens were quasi-statically loaded at 30 degrees to the longitudinal axis of the tooth until fracture. Fracture loads were analyzed using three-way, two-way, and one-way analysis of variance (α = .05). Fracture modes were examined under a stereomicroscope (×25) and recorded. Results: Fracture loads ranged from 642 ± 190 N (one wall, glass fiber, 5 mm) to 1,170 ± 130 (two walls, titanium, 7.5 mm). The mean fracture load of titanium posts was significantly higher than that of glass-fiber posts (P < .001), and the 7.5-mm post length exhibited significantly higher fracture loads than groups with 5-mm and 10-mm post length (P = .008). Conclusion: Teeth restored with titanium posts revealed considerably higher fracture resistance than teeth restored with glass-fiber posts, especially if 7.5-mm-length posts were used.

Purpose: To assess whether implant-retained prostheses produced with a laser-sintering technique present accuracy and passive fit comparable to their milled counterparts. Materials and methods: Two Regular Neck Straumann analogs were placed in a block of polymethyl methacrylate (PMMA) at 15 mm of distance and parallel to one another. The PMMA block was then scanned, and two groups of cobalt-chromium (Co-Cr) screw-retained, three-unit implant prostheses were fabricated using milling (control) and laser sintering (test) techniques. The prostheses were then screwed on the PMMA block, and the vertical marginal gap between the prostheses and the analogs at the implant-abutment junction was measured twice: (1) when only one screw was tightened, and (2) when both screws were fully tightened. The mean marginal gap measurements were compared to assess the difference in terms of passive fit between the laser-sintered and milled prostheses. Results: The mean marginal gap of the milled and laser-sintered groups was 23.18 μ (SD = 6.2) and 23.71 μ (SD = 19.5), respectively. Conclusion: Laser-sintered prostheses presented a marginal fit comparable to milled.

Purpose: To investigate the physical and mechanical behavior of polyether ether ketone (PEEK) before and after thermocycling and its potential use as a more durable prosthetic component for implant-supported and -retained removable dental prostheses (I-RDP). Materials and methods: Roughness and surface hardness were evaluated in specimens obtained using the subtractive method (n = 20) with Ø 9 mm and 2 mm of thickness, and retention force was measured in attachments with Ø 4 mm and 3 mm of height. For fatigue resistance test, a polyurethane matrix with two ball-abutment implants (MDL, Intra-Lock International) was used to simulate the mandibular alveolar ridge. A total of 40 attachments (n = 20 pairs) were captured in acrylic resin blocks using a technique analagous to the direct clinical pick-up of overdenture female attachments and submitted to 2,900 insertion/removal cycles to simulate 24 months of overdenture use. Physical analyses were performed by Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), and differential scanning calorimetry (DSC) before and after thermocycling (5° C to 55°C for 10,000 cycles). After normal distribution was verified by Shapiro-Wilk test, one-way analysis of variance (ANOVA) was applied to analyze the surface roughness and hardness, and two-way ANOVA with Bonferroni adjustment was used to assess the retention force (α = .05). Results: Thermocycling did not change the PEEK surface roughness or hardness (P > .05). As for the retention force, the highest average was observed after the thermocycling test (P = .006). Conclusion: Based on the FTIR, XRD, and DSC results, PEEK crystallinity decreased after thermocycling, and the physical and mechanical behavior of this polymer was compatible with the proposed application, attesting that it is a component of greater durability for I-RDPs.

Purpose: To evaluate the effect of different procedures for retightening the abutment screw on the screw stability between the abutment and implant. Materials and methods: External hexagon connection (EHC) and internal tri-channel connection (ITC) implants were employed in this study. Each abutment screw was used for the following applications (n = 5 for each group): group 0 = abutment was tightened and retightened with a 10-minute interval; group 1 = abutment was tightened and retightened with a 10-minute interval, then loaded for 500,000 cycles; group 2 = abutment was loaded for 83,000 cycles during tightening and retightening and then loaded for 500,000 cycles; group 3 = abutment was loaded for 167,000 cycles during tightening and retightening and then loaded for 500,000 cycles; and group 4 = abutment was loaded for 250,000 cycles during tightening and retightening and then loaded for 500,000 cycles. Both tightening and retightening torques were set at 35 Ncm, and dynamic oblique loading between 0 N and 200 N was applied on the abutment in all groups. The settlement of the abutments (settling value) after retightening and the abutments' removal torque values (RTVs) after testing were measured. Results: No significant differences in settling values were found for EHC or ITC. There were significant differences in the RTVs on EHC implants, but ITC implants showed no difference in RTV with different prosthetic retightening applications. Conclusion: The retightening application affected the joint stability of EHC implants, but did not affect the settlement or joint stability of ITC implants.

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

Purpose: To develop an instrument for the assessment of perception of orofacial appearance and psychologic issues that can affect peoples' judgments. Materials and methods: A panel composed of five members (one psychologist, two prosthodontists, one orthodontist, and one final-year dental student) generated 31 items that could draw specific hypothetical dimensions. The questionnaire was self-administered by individuals attending local high schools and university (N = 261; 26.4% men) in the 14- to 28-year age range. Internal consistency, construct validity, responsiveness, and temporal stability were assessed. Results: Factorial analysis and Cronbach's alpha identified four dimensions (self-esteem, perfectionism, body image, and smile appearance concern) that could be best fitted by 17 items. Internal consistency was good (α in the 0.70 to 0.80 range). The dimensions were correlated with existing instruments that measure similar constructs. In responsiveness testing, tooth whitening did not induce changes in perfectionism or body image; however, it did increase self-esteem and decreased esthetic concern (P < .05). Conclusion: The newly created questionnaire is a consistent and reliable short instrument that measures psychologic issues related to the perception of orofacial appearance.

Purpose: To measure the influence of postpolymerization condition (dry or submerged in water) and time (2, 10, 20, and 40 minutes) on the accuracy of additively manufactured model material. Materials and methods: A bar standard tessellation language file was used to manufacture the resin specimens (E-Model Light, EnvisionTEC) using a 3D printer (Vida HD, EnvisionTEC). Two groups were created based on the postpolymerization condition: dry (D group) or submerged in water (W group). Each group was divided into four subgroups (D1 to D4 and W1 to W4) depending on the postpolymerizing time (2, 10, 20, and 40 minutes; n = 20 each; N = 160). The specimen dimensions were measured using a low-force digital caliper (Absolute Low Force Caliper Series 573, Mitutoyo). The volume was calculated: 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 values were found among the subgroups (P < .0018). In all groups, the width dimension (x-axis) presented the worst 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; additionally, no significant differences were found between the two subgroups (P < .0018). Dry condition showed higher manufacturing accuracy compared to the water-submerged condition. In the water-submerged subgroups, the highest accuracy was obtained in the W2 and W4 subgroups (P < .0018). Conclusion: Postpolymerization conditions and time influenced the accuracy of the material tested. Dry postpolymerization condition with a time of 10 and 40 minutes obtained the highest accuracy.

Purpose: To assess the retention and adaptation of milled and printed denture bases and to compare them to conventional ones. Materials and methods: A total of 24 completely edentulous patients were selected. For each patient, three maxillary denture bases were constructed. Three groups were defined according to fabrication technique: group I = denture bases were constructed by a conventional technique; group II = denture bases were milled from prepolymerized blocks of polymethyl methacrylate; and group III = denture bases were 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. Analysis of variance for repeated measures was used for comparison among the groups, followed by pairwise comparison with Bonferroni correction as a post hoc test. 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 II (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 the printed denture bases; and printed denture bases showed better adaptation but similar retention to conventional heat-polymerized denture bases.

Purpose: To evaluate the application of chitosan as a cleanser in the control of biofilm formation on cobalt-chromium (Co-Cr) alloy and acrylic resin surfaces. Materials and Methods: In total, 172 Co-Cr discs and 172 acrylic resin discs (14 mm x 3 mm) were contaminated with Streptococcus mutans, Staphylococcus aureus, Candida albicans, or Candida glabrata and incubated for 48 hours. Then, specimens were randomly divided into groups and immersed in the following solutions for 15 minutes: WC = solution without chitosan (control); CH = chitosan solution (5 mg/mL); CN = chitosan nanoparticle solution (3.8 mg/mL); and ET = effervescent tablet. Biofilm recovery rates (n = 9) were evaluated by counting the colony-forming units (CFU/mL). Biofilm morphology was evaluated using scanning electron microscopy. Data were compared with Kruskal-Wallis or analysis of variance followed by Tukey post hoc tests. Results: For acrylic resin, ET showed the lowest number of CFU for S aureus and S mutans (P < .001). CH exhibited intermediate values for S mutans, S aureus, and C albicans, and CN exhibited intermediate values for S mutans and S aureus. For C glabrata, there was no statistical difference between the solutions (P = .264). For Co-Cr, ET showed the highest level of antimicrobial action against all microorganisms (P < .001), and CH showed an intermediate level of action against S mutans and S aureus. Against C albicans and C glabrata, there was no significant difference among CH, CN, and WC. Conclusion: Although ET had a broader spectrum of antimicrobial action, the chitosan solution showed promise as a denture cleanser. Int J Prosthodont 2021.

Purpose: To examine and compare the fracture strength of digitally produced interim materials to the conventional chairside method for implant-cemented fixed partial denture prostheses. Materials and methods: Three groups of seven specimens each were produced: group A, 3D-printed with VarseoSmile Temp material (Bego); group B, milled using Telio CAD material (Ivoclar Vivadent), and group C, conventional chairside manufacturing method using Luxatemp material (DMG). All groups were cemented using FujiCEM 2 (GC) to Standard Abutments (SIC) placed in artificial Sawbones blocks. The fracture strength was performed using universal testing machine Z010 (ZwickRoell). Statistical analysis of the resultant maximum forces was performed using SPSS (version 25.0, IBM) software (Mann- Whitney U test, P < .05). Results: The mean fracture strength of the printed provisional fixed partial dentures was 260.14 ± 28.88 N, of the milled interim fixed partial dentures was 663.57 ± 140.55 N, and for the control group reached 266.65 ± 63.66 N. Data showed a significant deviation of the normal distribution Kolmogorov-Smirnov test > .05 for all groups. Conclusion: Milled provisional fixed partial dentures showed a higher fracture resistance compared to 3D-printed and control chairside groups. However, for 3D-printed and control groups, no such difference could be detected.

Purpose: To clinically evaluate oral implant restorations placed by undergraduate students in the dental clinical curriculum at KU Leuven (Belgium) in terms of function and esthetics. Materials and methods: A retrospective observational cohort study was designed. The esthetic and functional evaluations of implant-supported restorations placed in the framework of the undergraduate implant dentistry clinical training program using White/Pink Esthetic Score (WES/PES) and visual analog scale (VAS) scoring was performed. Furthermore, complications were registered based retrospectively on the patient's medical file. The following research questions were stipulated: (1) How well do implant-supported restorations placed by undergraduate students perform esthetically? and (2) Which complications occurred and how were these managed? Results: Between August 2008 and July 2014 (6 academic terms), 251 implants (Brånemark System Mk III, Nobel Biocare) were placed in 113 patients by 155 students (> 40% of all students enrolled in the training program). Of these implants, 228 were restored in 101 patients by 118 students with varying restoration types. Esthetic scoring of the restorations in 83 of these patients revealed a satisfying mean WES of 8.14 ± 2.09 (out of 10) and PES of 9.56 ± 3.14 (out of 14). Complications were registered in 18.9% of the cases. Discussion: Clinical training in implant dentistry for undergraduates contributes to the development of advanced skills in the dental student's Master education. Overall, patients were satisfied with their implant-supported restorations. Implant and restoration success rates and complication incidence were confirmed by long-term data in the oral implant literature.

Purpose: To compare the mechanical behavior (stress load dissipation and/or concentration) of posterior crowns made from Lava Ultimate (LU; 3M ESPE) and IPS e.max CAD (LD; Ivoclar Vivadent) using finite element analysis (FEA). Materials and methods: A 3D model of a mandibular first molar was prepared by reducing the occlusal surface by 1 or 2 mm (according to group), the axial walls by 1.5 mm, and using a 0.8-mm-deep shoulder margin as a finish line. A convergence of 6 degrees between opposing walls was set. Subsequently, four 3D crown models were created according to two test groups with two different occlusal thicknesses: (1) LD with 1.0 mm (LD1); (2) LD with 2.0 mm (LD2); (3) LU with 1.0 mm (LU1); and (4) LU with 2.0 mm (LU2). FEA models were constructed using the software Femap (Siemens). A load of 200 N was applied in the axial and oblique (20 degrees) directions for each group, and stress dissipation was viewed using the NEi Nastran software. Results: FEA results demonstrated that the LU crowns dissipated the occlusal load to the tooth structure, whereas the LD material concentrated the load inside the crowns. For the LU material, the lower the occlusal thickness, the higher the stress concentration inside the crown became, and the 2.0-mm occlusal thickness transferred lower stress to the tooth structure. The oblique, rather than the vertical, load caused an increase in the maximum stress concentration at the shoulder margin and axial walls. Conclusion: The higher the Young's Modulus mismatch between the crown material and substrate, the higher the load stress concentration inside the material became. The 2-mm occlusal thickness acted by decreasing the load stress to the tooth substrate. Finally, the axial load delivered more favorable stress transmission to the tooth substrate. The crown material and the occlusal thickness appear to be two factors that affect the mechanical behavior of stress dissipation to the tooth structure.

Purpose: To evaluate the efficacy of cleaning protocol in decontamination of organic compounds from polished zirconium oxide samples. Materials and methods: A total of 24 rectangular plate specimens were sintered from zirconium oxide. All samples were polished with commercially available polishers (course, fine, and superfine) and polishing paste. During the first step of the protocol, all specimens were cleaned with steam. After that, samples were randomly assigned to one of three groups (n = 8 each): A, B, and C. In group A, no additional cleaning was performed, while specimens of group B underwent an ultrasonic cleaning in distilled water. Group C specimens were cleaned in an ultrasonic bath with a special detergent solution. After washing, samples were subjected to energy-dispersive x-ray spectroscopy (EDX) and scanning electron microscope examination. In order to detect organic materials, the level of carbon atoms was measured. Results: EDX analysis revealed that samples in group A had the highest percentage levels of carbon atoms (9.57 ± 3.67) on the surface compared to the other cleaning protocols. The group B cleaning protocol resulted in lower carbon levels (4.73 ± 3.56), but the difference was not significant from only steam-blasted ones (P = .439). All specimens in group C had no detectable carbon atoms (0), which implies that all wax molecules had been removed (P < .05). Conclusion: Only following the group C cleaning protocol can total decontamination of the polished zirconium surface from organic compounds be expected. Therefore, it is advised to employ an ultrasonic bath with detergent solution for cleaning procedures of zirconium abutments before delivery.

Purpose: To assess excess cement removal after cementation of implant-supported cementretained restorations using different cements. Materials and methods: A model with soft tissue imitation, 20 individual zirconium oxide abutments, and 20 zirconium oxide crowns were fabricated. Half of the restorations were cemented using resin cement (RX) and the other half with resin-modified glass-ionomer cement (GC). After cement cleaning, each crown-abutment unit was removed from the model, photographed, and analyzed from 4 surfaces, resulting in a final sample size of 80 measurements. Radiographic examination and the computerized planimetric method in Adobe Photoshop were used to determine the amount of the cement left and to evaluate the ratio between the area of cement residue and the whole crown-abutment surface. The significance was set to .05. Results: GC resulted in 7.4% more cement residue on all surfaces (P < .05) than RX. The P value on three of the surfaces (all except mesial) was < .05, meaning that the data were statistically significantly different between groups and surfaces. Absolute removal of the cement was impossible in all cases (100%), and in 95% of the cases, cement remnants could not be detected radiographically. Conclusion: More undetected cement remains when using resin-modified glass-ionomer cement. It was impossible to remove excess of both types of cements completely. Most of the cement remains on the distal surface. Radiographic examination could not be considered as a reliable method to identify excess cement.

Purpose: To investigate the influence of occlusal interference in dental prosthetics using finite element analysis (FEA). Materials and methods: The FEA model designed for this study centered on an all-ceramic, bi-layered, fixed partial denture (FPD) retained on the maxillary first premolar and molar, with the second premolar replaced by a pontic. The surrounding structures, such as the neighboring teeth, antagonists, and periodontium, were modeled. Four different load cases were designed at occlusal interferences of 0, 8, 12, and 24 μm, loaded by a simulated bite force of 300 N. Principal and von Mise 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 suggested 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 fracture strength of endodontically treated molars filled with different composite resins, with or without fiber reinforcement. Materials and methods: A total of 60 intact mandibular molars were selected and endodontically treated. A standardized mesio-occlusal-distal cavity was prepared with cervical margins 1 mm above the cementoenamel junction and oral and buccal walls with 1.5-mm remaining thickness. Universal adhesive was used in all specimens in etch-and-rinse mode. Specimens were divided into four groups (n = 15 each) according to restoration technique: CSM group, adhesive overlay with hybrid ceramic (CeraSmart, GC); EXP group, direct composite restoration (Essentia U, GC) and everX Posterior (GC) as core material; ESU group, direct composite restoration (Essentia U); and EST group, direct composite restoration (Essentia U) reinforced with horizontal bidirectional glass fibers placed over the pulpal chamber floor (everStick-Net, GC). After 7 days of water storage, samples were loaded until fracture using a universal testing machine. The maximum breaking loads were recorded in Newtons (N), and statistical analysis was then conducted with two-way analysis of variance and post hoc Tukey test. Fragments were analyzed using scanning electron microscopy. Results: Mean fracture resistance was: CSM = 1,428.9 ± 316.90 N; EXP = 1,874.57 ± 299.47; ESU = 1,557.44 ± 355.65; and EST = 1,870.27 ± 145.11. CSM and EXP showed the highest strength values when compared to the other groups. The variable "fiber insertion" did not significantly alter the fracture resistance. Origins of the fractures were always located on the occlusal surface, mainly from the major contact loading area. Conclusion: The use of everX Posterior showed great improvement in fracture resistance, similar to cuspal coverage restoration. However, only short fiber-reinforced composite resins showed a favorable fracture pattern.

Purpose: To investigate the discoloration and surface properties of four CAD/CAM composite resins provoked by a variety of food solutions and cigarette smoke. Materials and methods: A total of 74 specimens (N = 370) were prepared per material (Brilliant Crios [Coltene], CeraSmart [GC], Lava Ultimate [3M Espe], Shofu Block HC [Shofu], and SonicFill 2 [Kerr]). Discoloration (ΔE) was investigated with a spectrophotometer. Measurements were taken before immersion in the storage media for 2 weeks (carrot juice, curry, cigarette smoke, red wine, energy drink, and distilled water), immediately after immersion, and after manual polishing of the specimens following immersion. The mean surface roughness (Ra) was measured using a profilometer. Qualitative surface observation was performed with scanning electron microscopy (SEM). Data were analyzed using Kolmogorov-Smirnov, Mann-Whitney U, and one-way analysis of variance with Tukey post hoc tests. Results: The highest influence on ΔE after immersion was observed by the storage medium (η^P. = 0.878, P < .001), followed by the interaction between storage medium and material (η^P. = 0.770, P < .001) and the material (η^P. = 0.306, P < .001). For ΔE after polishing, the highest influence was indicated by the interaction of material and medium (η^P. = 0.554, P < .001), followed by the medium (η^P. = 0.244, P < .001) and the material (η^P. = 0.196, P < .001). Immersion in carrot juice led to the highest color change (ΔE: 8.0 to 10.4), whereas the lowest values were recorded in distilled water (ΔE: 2.0 to 2.4). Carrot juice and the energy drink provoked the highest Ra values (0.120 to 0.355 μm). SEM pictures indicated a loss of the organic matrix after manual polishing. Conclusion: The different materials reacted dissimilarly in the various storage media in terms of discoloration. Surface roughness increased after immersion and polishing. Neither discoloration nor surface roughness could be reset to default by manual polishing.

Purpose: To evaluate the dimensional discrepancy between the diagnostic wax-up and the resulting mock-up. Materials 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, and based on a digital additive veneer wax-up on the 6 anterior teeth, 10 more casts were 3D printed. The specimens were allocated to seven groups (n = 10 each). Group 1: transparent silicone matrix with a flowable light-curing composite resin; group 2: same as group 1, with the addition of a prefabricated transparent tray; group 3: silicone impression putty (65 on the Shore A hardness scale) and light-body silicone impression material with a dual-curing bis-acryl resin; group 4: same as group 3 without light-body silicone; group 5: silicone laboratory putty (92 Shore A) with a dual-curing bis-acryl resin; group 6: silicone laboratory putty (92 Shore A) with PMMA; and group 7: wax-up casts (control). Scans from the mock-ups were co-registered, segmented, and superimposed with the scans from the wax-up. The difference of the mock-up compared to the wax-up was quantified using morphologic operations. The results were analyzed with Kruskal-Wallis test and Dunn post hoc test (P < .05). Results: All mock-ups were larger in size in comparison to the wax-up. Significant differences were found for every labial surface third. The incisal third was the most inaccurate third, while the middle third was the most accurate. The most accurate groups were 2 and 5, and the largest discrepancy was observed in group 6. Conclusion: The analog mock-up differed dimensionally from the wax-up, irrespective of the technique/materials used.

Purpose: To compare in a randomized controlled trial the 5-year clinical outcomes of (1) 3-unit fiber-reinforced resin-bonded fixed dental prostheses (RBFDPs) to 3-unit metal-ceramic RBFDPs; and (2) 3-unit fiber-reinforced RBFDPs to 2-unit cantilevered metal-ceramic RBFDPs. Materials and methods: A consecutive sample of 50 young adult patients with tooth agenesis or trauma in the anterior region was included. The recruitment period was from 2005 to 2009, during which a total of 62 RBFDPs were inserted. In group A, 27 participants were randomly treated with 18 metal-ceramic 3-unit RBFDPs and 15 3-unit fiber-reinforced RBFDPs. In group B, 23 participants were randomly treated with 16 metal-ceramic 2-unit RBFDPs and 13 3-unit fiber-reinforced RBFDPs. All patients were followed up at baseline registration and at 1, 3, and 5 years. The primary outcome parameter was survival rate of the RBFDPs, and the secondary outcome parameters were periodontal and technical/esthetic outcomes and patient-reported evaluation of the RBFDPs. Results: Seven patients dropped out of the study during the 5-year observation period. In group A, the fiber-reinforced RBFDPs had a cumulative survival rate of 23% after 5 years, which was significantly less than for the 3-unit metal-ceramic RBFDPs. In group B, the cumulative 5-year survival rate was 36% for the fiber-reinforced RBFDPs and 91% for the 2-unit cantilevered metal-ceramic RBFDPs. Conclusion: The 3- and 2-unit metal-ceramic RBFDPs had a significantly higher 5-year survival rate than the 3-unit fiber-reinforced RBFDPs. The accessibility for oral hygiene practice was better with 2-unit compared to 3-unit RBFDPs, and the degree of gingivitis was lower. The esthetic outcome was better for the RBFDPs with ceramic pontics than the composite ones.

Purpose: To evaluate the effect of cavity tapering on the marginal and internal adaptation of endocrowns fabricated from two different ceramic materials. Materials and methods: Two mandibular molar model teeth were prepared with two different cavity tapers (5 and 10 degrees). Forty endocrowns in four groups (n = 10 each) were milled using lithium disilicate and zirconiareinforced lithium silicate ceramics for each cavity taper. The marginal and internal adaptation were measured with a stereomicroscope (×30) at 18 different points. The data were statistically analyzed using independent t test (P < .05). Results: A statistically significant difference was shown among the tested groups at 10 degrees of taper (P < .001). At 5 degrees of taper, the difference was insignificant. The greatest internal gap was observed on the pulpal floor in all tested groups. Conclusion: All materials had clinically acceptable internal and marginal gaps; however, lithium disilicate ceramic had significantly better adaptation at 10 degrees of taper.

Purpose: To evaluate the fracture behavior of monolithic crowns made of lithium disilicate (IPS e.max CAD, Ivoclar Vivadent; and Initial LiSi Block, GC) and zirconia-reinforced lithium silicate (Celtra Duo, Dentsply Sirona; and Suprinity, VITA) materials before and after cyclic fatigue aging. Materials and methods: Four groups (n = 22 per group) of CAD/CAM-fabricated maxillary incisor crowns were produced. All crowns were luted on metal dies with an adhesive dual-curing resin cement (G-CEM LinkForce [GC]). Half of the crowns in each group (n = 11) were statically loaded to fracture without aging. The remaining half were subjected to cyclic fatigue aging for 120,000 cycles (F_max = 220 N) and then loaded statically to fracture. Fracture mode was then visually examined. Scanning electron microscopy and energy-dispersive spectroscopy were used to evaluate the microstructure of the CAD/CAM ceramic materials. The data were statistically analyzed with two-way analysis of variance followed by Tukey honest significant difference (HSD) test (α = .05). Results: Before cyclic aging, there was no statistically significant difference in load-bearing capacity among the four groups (P = .371). After cyclic aging, the load-bearing capacity significantly decreased for all groups (P = .000). While the e.max CAD blocks had significantly higher load-bearing capacity (1,061 ± 94 N) than both monolithic ceramic crowns (P < .05), no significant difference was obtained compared to the Initial LiSi Block group (920 ± 140 N) (Tukey HSD P = .061). Conclusion: The mechanical performance of monolithic ceramic crowns fabricated from lithium disilicate was better than zirconia-reinforced lithium silicate after cyclic fatigue aging.

Purpose: To compare the production efficiency of selective laser sintering (SLS) to traditional casting (CAST) for the fabrication of metal prosthodontic frameworks in a prospective pilot evaluation in a hospital prosthodontic laboratory setting. Materials and Methods: The time taken to complete each of the identified stages in the production of 50 removable partial denture frameworks made using either SLS (n = 25) or CAST (n = 25) workflows was measured. The mean time for production was calculated for each workflow, and the difference was tested for statistical significance. Results/ Conclusion: The results indicate that an SLS workflow may be more time-efficient, and further cost-effectiveness research is indicated.