Survival, technical and biological outcome of fixed tooth- and implant-supported restorations: a retrospective analysis of a patient cohort treated in an undergraduate dental education program.

OBJECTIVES: There is a paucity of data on the outcome of fixed tooth- and implant-supported porcelain-fused-to-metal (PFM) and ceramic-based (CB) restorations fabricated during undergraduate dental education. Therefore, this retrospective study examined the outcome of fixed restorations placed in patients participating in an undergraduate program. METHODS: Patient records were searched for data on fixed PFM and CB restorations. For these restorations, the functional period in situ and technical and biological complications, namely restoration fracture, decementation, screw loosening, secondary caries, and loss of vitality, were recorded. Periodontal parameters were also documented. Kaplan-Meier survival and complication estimates after 1 and 5 years were calculated for restoration types, materials, designs (veneered/non-veneered), cementation/retention modes and localizations with group sizes ≥ 15. Regression models were used to analyze the influence of demographic data and abovementioned restoration characteristics on restoration survival, technical and biological outcome. RESULTS: 1196 restorations with a mean observation time of 5 years were included in the analysis. The different restoration types exhibited survival rates of more than 90.8 % after 5 years, accompanied by a favorable biological outcome. However, monolithic resin-matrix or feldspathic ceramic restorations were found to have a higher fracture rate than lithium disilicate or zirconium dioxide ceramic restorations resulting in lower survival rates for these restorations. Additionally, resin-matrix ceramic restorations showed a higher decementation rate than lithium disilicate restorations. CONCLUSIONS: Fixed tooth- and implant-supported CB restorations fabricated from lithium disilicate and zirconium dioxide ceramics demonstrated better survival and lower complication rates than restorations fabricated from resin-matrix or feldspathic ceramics in an undergraduate dental education program. CLINICAL SIGNIFICANCE: Due to the more favorable outcome of CB restorations fabricated from lithium disilicate or zirconium dioxide ceramics, undergraduate dental education should focus on the application of these ceramics to increase restoration survival by reducing technical complications.

Comparative evaluation of the effects of laser and chemical denture disinfectants on the surface characteristics of CAD-CAM and conventional denture resins: An in vitro experimental study.

PURPOSE: The purpose of this study was to assess the effect of Ga-Al-Ar diode, Nd:YAG lasers, and chemical disinfectants (NaOCl, vinegar, and Corega) on surface roughness (Ra) and hardness (VHN) of polymethylmethacrylate (PMMA), thermoplastic polyamide, milled and 3D-printed denture base resins. MATERIALS AND METHODS: About 432 specimens of PMMA, thermoplastic polyamide, milled, and 3D-printed resins were divided into six subgroups (n = 18): distilled water (control:C), Ga-Al-Ar diode laser (L1), Nd:YAG laser (L2), 1% sodium hypochlorite (NaOCl), vinegar (AA), and Corega (CR). Each specimen's Ra and VHN were measured. Surface topography assessment was done using scanning electron microscopy (SEM). Analysis was done using ANOVA and post hoc Tukey's test (p = 0.05). RESULTS: A significant difference was noted in Ra and VHN as affected by denture base materials, surface disinfectants, and their interaction (p < 0.001). Results showed a significant increase in Ra of PMMA with NaOCL (p < 0.001), AA (p = 0.005), and CR (p = 0.009), thermoplastic polyamide with L1 (p = 0.012), L2 (p = 0.015), NaOCL AA, and CR (p < 0.001 each), milled resin with AA NaOCL, and CR (p < 0.001 each), and 3D-printed resin with L1, NaOCl, AA (p < 0.001 each), and CR (p = 0.008). The VHN increased in PMMA with NaOCL (p < 0.001), AA (p = 0.044), and CR (p < 0.001), thermoplastic polyamide with L1 (p = 0.037), milled resin with L1, L2, and CR (p < 0.001 each), and 3D-printed resin with L1, NaOCl (p < 0.001 each), and decreased with CR (p = 0.007). CONCLUSION: The tested properties showed variations affected by denture base material and surface disinfectants. Laser treatments induced smoother surfaces than chemical disinfectants. Laser improved the surface hardness of CAD-CAM resins, while chemical immersion improved that of PMMA.

Flexural strength, fracture toughness, translucency, stain resistance, and water sorption of 3D-printed, milled, and conventional denture base materials.

PURPOSE: To compare mechanical, optical, and physical properties of denture base materials fabricated with various 3D printing systems to reference milled and conventionally heat-processed denture base materials. MATERIALS AND METHODS: Specimens of denture base materials were either 3D-printed (DLP in-office printer, CLIP laboratory printer, or material jetting laboratory printer), milled, or heat processed. 3-point bend flexural strength testing was performed after 50 hours of water storage following 1hour of drying (dry testing) or in 37°C water (wet testing). Fracture toughness was performed with a notched beam specimen after 7 days of water storage and tested dry. The translucency parameter was measured with 2 mm thick specimens. Stain resistance was measured as color change following 14 days of storage in 37°C coffee. Water sorption was measured following 7 days of storage in 37°C distilled water. RESULTS: For dry testing, all but one of the 3D-printed materials attained higher or equivalent flexural strength as the reference materials. For wet testing, all 3D-printed materials attained higher or equivalent strength as the reference materials and dry-tested materials. For 3D-printed materials, wet testing increased displacement before fracture whereas it decreased displacement for the reference materials. Only two of the 3D-printed materials had similar fracture toughness as the reference materials. One of the 3D-printed materials was more translucent and one was more opaque than the reference materials. Only one of the 3D-printed materials absorbed more water than the reference materials. CONCLUSION: 3D-printed denture base materials have mostly equivalent mechanical, optical, and physical properties to conventional and milled denture base materials.

Clinical decision of centric relation.

Centric relation (CR) was used in the complete dentures for edentulous jaws firstly. Then, CR was gradually applied in the clinical diagnosis and treatment of dentate jaws. Regarding the application of CR in dentate jaws, there are many doubts about its rationality. For instance, should CR be the core of diagnosis and treatment of temporomandibular disorders? Should CR be used as the jaw position of establishing occlusion in occlusal reconstruction? Should CR serve as the target jaw position in orthodontic treatment? Meanwhile, varieties of CR clinical applications are objective. According to the existing evidence, this paper summarizes the applicable conditions of several main clinical situations with little controversy. We preliminarily put forward the decision tree for the clinical application of CR, which can be used as a reference in clinical practice.

Enhancing Removable Partial Dentures Hygiene: Investigating Mucolytic Agents and Biocides for Disrupting Biofilms and Improving Antimicrobial Efficacy.

PURPOSE: This study evaluates the antibiofilm action of 2.5 mg/mL peracetic acid (PA), 0.5 mg/mL cetylpyridinium chloride (CPC), and 160 mg/mL N-Acetylcysteine (NAC) against multispecies biofilm of Streptococcus mutans, Staphylococcus aureus, Candida albicans, and Candida glabrata, developed on surfaces of heat-polymerizing acrylic resin (AR) and cobaltchromium (Co-Cr) alloy. MATERIALS AND METHODS: A multispecies biofilm was grown on the surface of AR and Co-Cr specimens (Ø 12×3mm). After biofilm maturation, the specimens were immersed in experimental solutions and evaluated through biofilm viability (CFU) (n=9), biofilm metabolic activity (XTT) (n=9), biofilm-covered areas (Live/Dead) (n=2), effects on the extracellular polymeric substance (EPS) (n=2) and biofilm morphology (n=1). Data were analyzed by ANOVA and the Tukey post-test or Kruskal-Wallis followed by the Dunn post-test (α=.05). RESULTS: Overall, all evaluated solutions impacted biofilm viability. PA presented wider activity by reducing CFU of all microorganisms on both surfaces, XTT (P<.001) and Live/Dead (P<.001). NAC had a notorious effect in reducing the viability of bacteria without affecting the yeasts. NAC reduced XTT on AR (P=.006) and Co-Cr (P=.003) but did not reduce the aggregated biofilm layer. CPC had distinct effect according to the surface, being most effective in reducing CFU on AR than the Co-Cr surface. However, it did not influence XTT, and the amount of residual aggregated biofilm. CONCLUSIONS: PA provided the greatest antibiofilm action, while CPC and NAC showed intermediate action. Nonetheless, no solution was able to completely remove the biofilm adhered to the surfaces of heat-polymerizing AR and Co-Cr alloy.

An Alternative Approach for the Rehabilitation of a Complete Denture Patient With Parkinson's Disease.

Parkinson's disease (PD) affects one to two out of every 1,000 individuals. PD, being age-related, is affecting a percentage of those over and around the sixth decade. Lewy bodies containing α-synuclein and a reduction in dopaminergic neurons in the substantia nigra, which impairs the region's capacity to promote voluntary movements, are the main neuropathological findings. The three main symptoms of PD are stiffness, bradykinesia, and tremor. Treatment of edentulous conditions in patients with PD becomes a challenge due to decreased neuromuscular coordination and decreased mobility. This case report outlines a 64-year-old male patient with complete edentulism suffering from PD. Complete denture fabrication was done using the concepts of the neutral zone and denture characterization. Significantly, it not only improves the stability of the dentures but also establishes good denture aesthetics.

A novel implant placement technique using a three-dimensionally printed duplicate denture for implant-supported overdenture in patients with severe residual ridge resorption: A case report.

The treatment method of placing a small number of implants in the mandible as a removable implant-supported overdenture (IOD) enables implant placement and denture stability, even in cases with severe residual ridge resorption. In this case report, a new implant placement technique was performed using a three-dimensionally (3D)-printed duplicate denture fabricated by a 3D printer, resulting in the restoration of masticatory function through IOD.

Enhanced Antimicrobial Properties of Polymeric Denture Materials Modified with Zein-Coated Inorganic Nanoparticles.

Background: Polymeric denture materials can be susceptible to colonization by oral microorganisms. Zein-coated magnesium oxide nanoparticles (zMgO NPs) demonstrate antimicrobial activity. The aim of this study was to investigate the antimicrobial effect and adherence of different oral microorganisms on hybrid polymeric denture materials incorporated with zMgO NPs. Methods: Five types of polymeric denture materials were used. A total of 480 disc-shaped specimens were divided by material type (n=96/grp), then subdivided by zMgO NPs concentration: control with no nanoparticles and other groups with zMgO NPs concentrations of 0.3%, 0.5% and 1% by weight. Characterization of the polymeric denture materials incorporating zMgO NPs was done, and the antimicrobial activity of all groups was tested against four types of microorganisms: 1) Streptococcus mutans, 2) Staphylococcus aureus, 3) Enterococcus faecalis and 4) Candida albicans. The samples underwent an adherence test and an agar diffusion test. Experiments were done in triplicates. Results: The characterization of the hybrid samples revealed variation in the molecular composition, as well as a uniform distribution of the zMgO NPs in the polymeric denture materials. All hybrid polymeric denture materials groups induced a statistically significant antimicrobial activity, while the control groups showed the least antimicrobial activity. The agar diffusion test revealed no release of the zMgO NPs from the hybrid samples, indicating the NPs did not seep out of the matrix. Conclusion: The zMgO NPs were effective in reducing the adherence of the tested microorganisms and enhancing the antimicrobial activity of the polymeric denture materials. This antimicrobial effect with the polymeric dentures could aid in resisting microbial issues such as denture stomatitis.

Revolutionizing Oral Rehabilitation With Modified Andrew's Bridge for Alveolar Bone Defect: A Case Report.

Within the realm of prosthodontics, the challenge of replacing multiple missing teeth is a complex one, compounded by patient's preference for fixed prostheses over removable ones owing to their superior aesthetic and functional attributes. However, the feasibility of fixed prostheses diminishes in scenarios marked by compromised remaining dentition and defects in edentulous regions. To navigate these challenges effectively, the Andrew's bridge emerges as a compelling solution, integrating both fixed and removable components. This approach, particularly adept at addressing extensive alveolar bone defects, offers a synthesis of advantages including enhanced phonetics, hygiene, aesthetics and function. This article details a case report that outlines the digital fabrication process of an Andrews Bridge used to treat a maxillary anterior ridge defect.

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The commonly used materials for fixed restorations in edentulous jaws include acrylic resins, polymerized ceramics, ceramics, and zirconia, which have distinct physicochemical properties and clinical application features. The selection of these materials in clinical practice is related to the prosthodontic space, oral soft and hard tissue conditions, occlusal force, lifestyle habits, oral parafunctions, opposing dentition materials, and expectations of patients. Common mechanical complications associated with fixed restorations in edentulous jaws are cracking/chipping and abrasion of the facing materials, which can be avoided through occlusal adjustment, restoration design and processing, and the selection of appropriate restorative materials. This article reviews the characteristics, selection, and design considerations of commonly used materials for fixed restorations in edentulous jaws, as well as the causes and management of common clinical complications related to restorative materials, aiming to provide references for the selection of appropriate materials in fixed restorations for edentulous jaws in clinical practice.

Association between removable prosthesis-wearing and pneumonia: a systematic review and meta-analysis.

BACKGROUND: A high burden of respiratory pathogens colonizing removable prosthesis surfaces suggests the potential of association between removable prosthesis-wearing and respiratory infections. Therefore, this systematic review and meta-analysis aimed to evaluate the evidence from clinical studies concerning the association between removable prosthesis-wearing and respiratory infections. METHODS: Clinical studies that reported respiratory infections associated with adult patients wearing removable prostheses in any centers (hospitals and nursing homes) or communities were included. Literature was searched across five electronic databases (MEDLINE, Cochrane Library, EMBASE, Web of Science, and Scopus) to 28 May 2024. An additional search was performed for unpublished trials and references cited in related studies. The Newcastle-Ottawa Scale was employed for the quality assessment. The certainty assessment was established using GRADE. The results were pooled using a frequentist random-effects meta-analysis and the odds ratios generated. RESULTS: A total of 1143 articles were identified. Thirteen articles had full-text articles screening and an additional two articles were added through reference linkage. Ultimately, six non-randomized clinical studies reporting various types of pneumonia contributed to this review. Overall odds of having pneumonia among prosthesis wearers were 1.43 (95% CI: 0.76 to 2.69) and 1.27 (95% CI: 1.11 to 1.46) using the random- and fixed-effects models, respectively. The heterogeneity in the meta-analysis was substantial. In subgroup analysis according to the study design, the heterogeneity within prospective studies was much reduced, I2 = 0% (p = 0.355). The certainty of the evidence evaluated using the GRADE approach was low to very low evidence for prosthesis wearers developing pneumonia based on studies. CONCLUSIONS: There was no conclusive evidence from the non-randomized clinical studies supporting whether prosthesis-wearing is a risk factor for pneumonia based on outcomes from this review.

Oral health-related quality of life and patient satisfaction using three-dimensional printed dentures: A crossover randomized controlled trial.

OBJECTIVES: This crossover randomized controlled clinical trial (RCT) aimed to evaluate the clinical applicability of three-dimensional printed dentures (CAD-3DPs) by comparing two fabricated complete dentures, CAD-3DPs and conventional complete dentures (CCDs), and assess the non-inferiority of CAD-3DPs. The hypothesis was that CAD-3DPs would be inferior to CCDs in terms of the oral health-related quality of life (OHRQoL) and patient satisfaction. METHODS: This single-blind RCT was conducted at two university hospitals. The participants included adult patients with edentulous maxillary and mandibular arches, who had existing complete dentures and were willing to use new complete dentures. Eighteen participants were assigned to two groups: CCD-CAD-3DP and CAD-3DP-CCD, based on the order of denture delivery. Both sets of maxillary and mandibular CCDs and CAD-3DPs were delivered to all the participants. The OHRQoL using Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT-J) was considered the primary outcome. General satisfaction using a 100-mm visual analog scale was also evaluated as a suboutcome. RESULTS: Based on the non-inferior test on the total score of the OHIP-EDENT and each score of the seven conceptual subdomains, the lower limit of the 95 % confidence interval was < 2.65 in seven domains. Therefore, CAD-3DP was judged to be non-inferior to CCD. Patient satisfaction was not significantly different between the CCD and CAD-3DP groups (p > 0.05). CONCLUSIONS: This RCT revealed that CAD-3DP is comparable to CCD based on the OHIP-JDENT scores and patient satisfaction. CLINICAL SIGNIFICANCE: CAD-3DP is clinically applicable and comparable to CCD in terms of patient-reported outcomes.

Evaluation of hypermobile teeth deviation during impression taking in a partially edentulous dental arch: An in vitro study comparing digital and conventional impression techniques.

PURPOSE: This study aimed to compare the deviation of hypermobile teeth in partially edentulous dental arches during impression taking using digital and conventional techniques. METHODS: A partially edentulous mandibular model with three target hypermobile teeth (including the left first premolar, #34; left second molar, #37; and right first premolar, #44), was used as the simulation model. After reference data were acquired using a desktop scanner, impressions of the simulation model were obtained using a digital intraoral scanner (IOS) and two conventional techniques (hydrocolloid material with a stock tray and silicone material with a custom tray as impression data (n=12/group). The three-dimensional accuracy (root mean square value) and two-dimensional accuracy (mesiodistal and buccolingual displacements) of the target teeth in each impression dataset were calculated based on the reference data. The comparison among three impression techniques was statistically performed using the Kruskal-Wallis test (α=0.05). RESULTS: For #34 and #44, the three- and two-dimensional accuracies of the impressions fabricated through data acquired through digital scanning (digital impression) were significantly superior to those of the hydrocolloid impression (P < 0.05), whereas no significant difference was found between the digital and silicone impressions. For #37, no significant difference in the accuracy of the impression data for the target teeth was observed among the three impression techniques. CONCLUSIONS: Digital impression acquiring using an IOS is recommended over using a conventional hydrocolloid impression to prevent the deviation of hypermobile teeth in partially edentulous dental arches. Hypermobile tooth deviation in digital impression data depends on the tooth location.

Multi-parameter viscoelastic material model for denture adhesives based on time-temperature superposition and multiple linear regression analysis.

BACKGROUND: Restorative solutions designed for edentulous patients such as dentures and their accompanying denture adhesives operate in the complex and dynamic environment represented by human oral physiology. Developing material models accounting for the viscoelastic behavior of denture adhesives can facilitate their further optimization within that unique physiological environment. This study aims to statistically quantify the degree of significance of three physiological variables - namely: temperature, adhesive swelling, and pH - on denture adhesive mechanical behavior. Further, based on these statistical significance estimations, a previously-developed viscoelastic material modelling approach for such denture adhesives is further expanded and developed to capture these variables' effects on mechanical behavior. METHODS: In this study a comparable version of Denture adhesive Corega Comfort was analysed rheologically using the steady state frequency sweep tests. The experimentally derived rheological storage and loss modulus values for the selected physiological variables were statistically analyzed using multi parameter linear regression analysis and the Pearson's coefficient technique to understand the significance of each individual parameter on the relaxation spectrum of the denture adhesive. Subsequently, the parameters are incorporated into a viscoelastic material model based on Prony series discretization and time-temperature superposition, and the mathematical relationship for the loss modulus is deduced. RESULTS: The results of this study clearly indicated that the variation in both the storage and loss modulus values can be accurately predicted using the oral cavity physiological parameters of temperature, swelling ratio, and pH with an adjusted R2 value of 0.85. The R2 value from the multi-parameter regression analysis indicated that the predictor variables can estimate the loss and storage modulus with a reasonable accuracy for at least 85% of the rheologically determined continuous relaxation spectrum with a confidence level of 98%. The Pearson's coefficient for the independent variables indicated that temperature and swelling have a strong influence on the loss modulus, whereas pH had a weak influence. Based on statistical analysis, these mathematical relationships were further developed in this study. CONCLUSIONS: This multi-parameter viscoelastic material model is intended to facilitate future detailed numerical investigations performed with implementation of denture adhesives using the finite element method.

A Comparative Evaluation of the Effects of Herbal Denture Adhesives on Patient Comfort and Satisfaction: Study Protocol of a Randomized Controlled Trial.

Introduction The lack or complete loss of all-natural teeth is known as edentulism, and it happens frequently. One of the most prevalent issues among edentulous patients is severe resorption of the residual alveolar ridge, which can still occur even with cautious prosthetic treatment. Therefore, one of the biggest issues faced in dentistry today is retention and stability in the rehabilitation of completely edentulous patients using complete denture prostheses. This problem was resolved by using denture adhesives. Studies show that when denture adhesive is applied correctly, it improves stability and effectiveness for individuals wearing complete dentures by increasing the surface tension between the alveolar mucosa and the denture fitting surface. The denture adhesive must possess safety, cost-effectiveness, and sufficient antibacterial and antifungal properties. The application should be easy, without causing any mess, and have a pleasant smell. It should not alter or obstruct the denture's intaglio surface. Nowadays, it is acknowledged that denture adhesives are treatments that can be used in association with dentures. Methods Based on the type of denture adhesive, the patients will be randomly divided into two groups, i.e., 20 patients in each group: Group A (herbal denture adhesive without essential oil) and Group B (herbal denture adhesive with essential oil). The patients will be requested to fill out the questionnaire for masticatory efficiency, retention, stability, etc., at the time of denture insertion without using denture adhesive and seven days after the use of denture adhesive. Expected results The overall satisfaction of complete denture patients will be significantly increased when an herbal denture adhesive infused with essential oil is used. This will result in increased stability, retention of the mandibular denture, improved masticatory efficiency, and patient satisfaction. Conclusions Patients who are elderly may experience physical and psychological challenges when adjusting to new or relined dentures. Denture adhesive, however, can aid in the patient's satisfaction with the prosthesis' altered occlusion and fit. It also makes the patient feel more confident and secure. A dental professional must be consulted before using denture adhesive.

Digital analysis of fabrication accuracy and fit in additively and subtractively manufactured implant-supported fixed complete dentures.

OBJECTIVES: To digitally evaluate the trueness and fit of additively and subtractively manufactured fixed complete dentures in materials intended for definitive use. METHODS: An edentulous maxillary model with implants at the left first molar, left canine, right canine, and right first molar site was digitized and a fixed complete denture was designed. This design was used to fabricate fixed dentures in an additively manufactured resin for definitive use (AM), a high-impact polymer composite (SM-CR), and a strength gradient zirconia (SM-ZR) (n = 10). Each fixed denture was digitized and the surface (overall, occlusal, except occlusal, and abutments), linear, and interimplant distance deviations were analyzed. The fit was assessed with the triple-scan protocol. Data were analyzed with Welch analysis of variance and Games-Howell tests (α = 0.05). RESULTS: SM-ZR led to lower overall deviations than AM, which had the highest occlusal and the lowest abutments deviations (P ≤ 0.007). SM-ZR had the lowest occlusal and SM-CR had the highest except occlusal deviations (P ≤ 0.002). AM mostly had higher linear and SM-CR mostly had higher interimplant distance deviations (P ≤ 0.043). AM led to the highest marginal gap at the left canine site, while SM-CR had the highest and SM-ZR had the lowest gaps at the right canine site (P ≤ 0.022). CONCLUSIONS: SM-ZR dentures mostly had trueness and marginal fit similar to or better than the other groups. Tested fixed complete dentures were mostly smaller than the design file in terms of interimplant distances.

Jaw relation recording and transferring: Using digital technology to augment its instruction in predoctoral prosthodontics.

OBJECTIVES: The study compared the learning effectiveness and teaching satisfaction of dental students from three teaching methods (traditional, digital, and combined pedagogy) for instructing jaw relation recording and transferring (JRRT). METHODS: Note that, 276 fourth-year undergraduate students from three classes were randomly divided into three groups to study JRRT in complete dentures using different teaching methods: traditional pedagogy group, digital pedagogy group, and combined digital and traditional pedagogy group. After the course, the learning effectiveness of basic knowledge and satisfaction questionnaire was administered to the three groups of participants using a quick response code for online answering. The questionnaire was customized by the teacher based on the content delivered to each group. RESULTS: The data were analyzed using the Chi-square test with Fisher's exact test. Both the digital and combined pedagogy groups showed a significant increase in basic knowledge test scores and higher satisfaction, compared to the traditional pedagogy group (p < 0.01). Particularly, the participants from combined pedagogy showed better teaching satisfaction than the digital pedagogy group (p < 0.001). CONCLUSIONS: The use of digital technology in JRRT significantly enhanced students' learning effectiveness and teaching satisfaction. CLINICAL SIGNIFICANCE: This educational innovation emphasizes digital technology to visualize vital concepts and operational intricacies related to JRRT. The findings have major implications for improving teaching methods in the field of prosthodontic dentistry.

Antimicrobial hard denture reliners using quaternary ammonium methacryloxy silicate (K18 QAMS) and K18-functionalized filler.

OBJECTIVE: To determine the effects of adding a quaternary ammonium methacryloxy silicate (K18) and K18-functionalized filler (K18-Filler) on the material and antimicrobial properties of a hard denture reline material. MATERIALS AND METHODS: 30% K18 in methyl methacrylate (K18-MMA; 0-20 wt% of reliner) and K18-Filler (0-30 wt% of reliner) were incorporated into KoolinerTM hard denture reliner. KoolinerTM served as the control. The cure (Shore A hardness), hydrophilicity (contact angles), mechanical (3-point bend test), water sorption, and antimicrobial properties against Streptococcus mutans, S. sanguinis, and Candida albicans were determined. RESULTS: Most K18 groups cured well and had comparable Shore A hardness values (range ~52 to 70 DHN) to that of controls (67.2 ± 1.8 DHN; Bonferroni corrected p > 0.0003). Even the softest group had hardness values within the range of commercial products. Half of the K18 groups had comparable contact angles to that of controls (range ~75° to 80° vs 83.41° ± 2.66°; Bonferroni corrected p > 0.0003), and most were within the range of commercial liners. K18-MMA and K18-Filler increased modulus but decreased ultimate transverse strength (UTS). All experimental groups had comparable or higher moduli than controls (range ~966 to 2069 MPa vs 1340 ± 119 MPa; Bonferroni corrected p < 0.0003), but only half of the experimental groups had comparable UTS to that of controls (range ~41 to 49 MPa vs 55.8 ± 1.5 MPa; Bonferroni corrected p > 0.0003). The 15% and 20% K18-MMA with 30% K18-Filler groups had significant antimicrobial activity against all three microbes (p < 0.05). However, the 15% and 20% K18-MMA with 30% K18-Filler groups had significantly higher water sorption at early time points (p < 0.05). After 8 weeks, they were comparable to each other (p > 0.05). CONCLUSIONS: K18-MMA and K18-Filler are promising antimicrobial additives that produce hard denture liners with material properties within the range of commercial products and significant antimicrobial properties against S. mutans, S. sanguinis, and C. albicans. Further development is needed to reduce water sorption.

Effectiveness of different surface treatments on bond strength between 3D-printed teeth and denture base.

PURPOSE: To investigate the effects of different surface treatments and thermal cycling on the shear bond strength between 3D-printed teeth and denture bases. MATERIAL AND METHODS: For the shear bond strength (SBS) test, the specimens were the maxillary central incisors (11 × 9 × 7 mm) bonded on a cylindrical base (20 × 25 mm). The control group was heat-cured polymethylmethacrylate (PMMA) (N = 20). The printed group was divided into five subgroups (N = 20): no treatment, sandblasting with aluminum oxide (Al2O3), methyl methacrylate monomer, acetone, and adhesive with urethane dimethacrylate. Half of the samples were subjected to 2000 thermal cycling cycles, and all samples were subjected to the SBS test. The failure mode was established as adhesive, cohesive, or mixed through stereomicroscopic analysis. The surface roughness test (Sa) was performed using optical profilometry, and the rectangular specimens (14 × 14 × 2.5 mm) were divided into four groups according to the surface treatments (N = 7 per group). Paired T and Wilcoxon tests were conducted to perform comparisons within the same group. The Kruskal-Wallis and Dwass-Steel-Critchlow-Fligner post-hoc tests were conducted to compare the groups. RESULTS: Al2O3 sandblasting in the 3D-printed groups achieved high SBS values comparable to those of the control group in the thermal cycled (p = 0.962) and non-thermal cycled samples (p = 0.319). It was the only treatment capable of modifying the surface of the 3D-printed resin, thereby increasing the roughness (p = 0.016). CONCLUSIONS: Sandblasting is recommended to increase the bond strength between the tooth and denture bases.

Effect of finishing and polishing techniques on the fit accuracy and dimensions of conventional and CAD-CAM removable partial denture frameworks.

PURPOSE: The purpose of this study was to compare the effects of finishing and polishing techniques on the fit accuracy, metal loss, and surface roughness of conventional versus CAD-CAM removable partial denture (RPD) frameworks. MATERIALS AND METHODS: A 3D-printed maxillary Kennedy class III modification I model served as the master cast. Forty impressions (20 conventional and 20 digital) were divided into four groups: lost-wax technique (Group I: LWT), CAD-printed (Group II: CAD-RP), CAD-printed from a stone cast (Group III: CAD-RPS), and lost-wax technique from resin-printed models (Group IV: LWTR). Various finishing and polishing techniques were applied, followed by digital scanning for fit accuracy assessment using surface matching software. Metal thickness loss and surface roughness were evaluated pre- and post-finishing and polishing. The Kruskal-Wallis test followed by the Scheffe post-hoc test were conducted to evaluate the fit accuracy between groups (α = 0.05). RESULTS: Color mapping revealed significant differences (p < 0.001) between conventionally casted RPD frameworks and 3D-printed groups post-finishing and polishing. The most significant gap was observed with the guide plates from printed RPD frameworks. The D-Lyte technique resulted in less metal loss compared to the conventional finishing and polishing technique (p < 0.001). CONCLUSION: Within the limitations of this study, conventionally processed RPD groups exhibited better overall fit accuracy post-finishing and polishing. Both conventional cast and 3D-printed RPD frameworks showed clinically acceptable fit accuracy. The D-Lyte technique presented less metal loss and smoother surfaces compared to other groups, suggesting it as a viable alternative.