Accuracy of the intaglio surface of 3D-printed hybrid resin-ceramic crowns, veneers and table-tops: An in vitro study.

OBJECTIVES: The present study aims to examine the influence of the build angle on the accuracy (trueness and precision) of 3D printed crowns, table-tops and veneers with a hybrid resin-ceramic material. METHODS: One crown, on table-top and one veneer were printed in five different build angles (0°, 30°, 45°, 60°, 90°) (n = 50) with the digital light processing (DLP) system (Varseo XS, Bego) using hybrid resin (Varseo Smile Crownplus A3, Bego). All printed restorations were scanned using the laboratory scanner (D2000, 3Shape) and matched onto the initial reference design in metrology software (Geomagic Control X, 3D Systems). The root mean square error (RMSE) was calculated between the scanned and reference data. The data was statistically analyzed using the Tukey multiple comparison test and Wilcoxon multiple comparison test. RESULTS: The crown group showed higher trueness at 30° (0.021 ± 0.002) and 45° (0.020 ± 0.002), and table-tops at 0° (0.015 ± 0.001) and 30° (0.014 ± 0.001) (p < 0.0001). Veneers demonstrated higher trueness at 30° (0.016 ± 0.002) (p < 0.0001). All three restoration types demonstrated the lowest trueness at a 90° build angle and portrayed deviations along the z axis. The veneer and table-top groups showed the lowest precision at 90° (veneers: 0.021 ± 0.008; table-tops: 0.013 ± 0.003). The crown group portrayed the lowest precision at 45° (0.017 ± 0.005) (p < 0.0001). CONCLUSION: The build angle of DLP-printed hybrid resin-ceramic restorations influences their accuracy. CLINICAL SIGNIFICANCE: Considering the build angle is important to achieve a better accuracy of 3D-printed resin-ceramic hybrid restorations. This may help predict or avoid the interference points between a restoration and a die and minimize the clinical adjustments.

Wear resistance and flexural properties of low force SLA- and DLP-printed splint materials in different printing orientations: An in vitro study.

OBJECTIVES: To investigate the influence of material and printing orientation on wear resistance and flexural properties of one low force SLA- and two DLP-printed splint materials and to compare these 3D-printed splints to a subtractively manufactured splint material. METHODS: Two DLP-printed (V-Print splint, LuxaPrint Ortho Plus) and one low force SLA-printed (Dental LT Clear) material, where specimens were printed in three printing orientations (0°, 45°, 90°), were investigated. In addition, one milled splint material (Zirlux Splint Transparent) was examined. A total of 160 specimens were produced for both test series. The two-body wear test was performed in a chewing simulator (80'000 cycles at 50 N with 5-55 °C thermocycling). Steatite balls were used as antagonists. The wear pattern was analyzed with a 3D digital microscope in terms of maximum vertical intrusion depth (mm) and total volume loss (mm³). The flexural properties were investigated by three-point bending in accordance with ISO 20795-1: 2013 (denture base polymers). The flexural strength (MPa) and the flexural modulus (MPa) were measured. Two-way ANOVA was performed to investigate the effects of the two independent variables material and printing orientation for the three 3D-printed materials. The comparison of the printing orientations within one material was carried out with one-way ANOVA with post-hoc Tukey tests. RESULTS: Two-way ANOVA revealed that wear and flexural properties are highly dependent on the 3D-printed material (p < 0.001). Across groups, a significant effect was observed for wear depth (p = 0.031) and wear volume (p = 0.044) with regard to printing orientation but this was not found for flexural strength (p = 0.080) and flexural modulus (p = 0.136). One-way ANOVA showed that both DLP-printed groups showed no significant differences within the printing orientations in terms of wear and flexural properties. Dental LT Clear showed that 90° oriented specimens had higher flexural strength than 0° oriented ones (p < 0.001) and 45° oriented specimens also showed higher values than 0° ones (p = 0.038). No significant differences were observed within the printing orientations for flexural modulus and wear behaviour within this group. T-tests showed that the milled splints exhibited statistically higher wear resistance and flexural properties compared to all three 3D-printed splint materials (p < 0.001) and that highly significant differences were found between the 3D-printed splint materials for both test series. CONCLUSION: Within the limitations of this in vitro study, it can be stated that wear behaviour and flexural properties are highly dependent on the 3D-printed material itself. Currently, milled splints exhibit higher wear resistance and flexural properties compared to 3D-printed splint materials. The printing orientation has a minor influence on the properties investigated. Nevertheless, two-way ANOVA also showed a significant influence of printing orientation in the wear test across groups and one-way ANOVA detected significant effects for SLA material in terms of flexural strength, with printing in 90° showing the highest flexural strength. Therefore, anisotropy was found in SLA material, but it can be limited with the employed printing parameters. Both DLP-printed materials showed no significant difference within the printing orientation.

Longitudinal Three-Dimensional Stereophotogrammetric Growth Analysis in Infants with Unilateral Cleft Lip and Palate from 3 to 12 Months of Age.

This longitudinal study aimed to evaluate facial growth and soft tissue changes in infants with complete unilateral cleft lip, alveolus, and palate (CUCLAP) at ages 3, 9, and 12 months. Using 3D images of 22 CUCLAP infants, average faces and distance maps for the entire face and specific regions were created. Color-coded maps highlighted more significant soft tissue changes from 3 to 9 months than from 9 to 12 months. The first interval showed substantial growth in the entire face, particularly in the forehead, eyes, lower lip, chin, and cheeks (p < 0.001), while the second interval exhibited no significant growth. This study provides insights into facial soft tissue growth in CUCLAP infants during critical developmental stages, emphasizing substantial improvements between 3 and 9 months, mainly in the chin, lower lip, and forehead. However, uneven growth occurred in the upper lip, philtrum, and nostrils throughout both intervals, with an overall decline in growth from 9 to 12 months. These findings underscore the dynamic nature of soft tissue growth in CUCLAP patients, highlighting the need to consider these patterns in treatment planning. Future research should explore the underlying factors and develop customized treatment interventions for enhanced facial aesthetics and function in this population.

Comparative analysis of xenogeneic collagen matrix and autogenous subepithelial connective tissue graft to increase soft tissue volume around dental implants: a systematic review and meta-analysis.

OBJECTIVE: The gold standard for a soft tissue augmentation around implants is a subepithelial connective tissue graft (CTG), but the xenogeneic collagen matrices (XCM) started to be used as an alternative. This systematic review aimed to assess the effectiveness XCM in comparison to CTG for the increasing the thickness of the soft tissue around implants. DATA: All studies included at least two parallel groups comparing the use of CTG and XCM with a minimum follow-up of 3 months. As the primary outcome, the amount of soft tissue thickness gain after soft tissue augmentation with XCM or CTG was assessed. Secondary outcomes were clinical and patient-related outcomes; evaluation of aesthetic outcomes, patient-reported outcomes measures (PROMs) and complications. Eligible studies were selected based on the inclusion criteria. Meta-analysis was applied whenever possible. The quality of the evidence of studies including in meta-analysis was assessed using the GRADE approach. SOURCE: A systematic literature search up to January 2022 was conducted using the following electronic databases: PubMed (MEDLINE), Scopus, Cochrane Library, LILACS, eLIBRARY.RU. Unpublished researches, the gray literature, nonprofit reports, government studies and other materials were reviewed electronically using an EASY search. An additional manual search was carried out in November 2022. STUDY SELECTION: Of the 1376 articles from the initial search, 8 randomized controlled trials (RCTs) (306 patients and 325 implants) were included in this systematic review, and 7 studies were part of the meta-analysis. Meta-analysis revealed that XCM is less effective than the CTG in increasing soft tissue thickness around dental implants. However, XCM also provides soft tissue thickness gain and can be recommended for use in various clinical situations. CLINICAL SIGNIFICANCE: Previous systematic reviews and meta-analyses have shown that autologous grafts are more effective than collagen matrices in increasing soft tissue thickness, however, the latter can be used as an alternative. Studies included in previous systematic reviews varied in design, which could lead to limitations. The present systematic review and meta-analysis includes for the first time only randomized controlled clinical trials with collagen matrix of xenogeneic origin in the test group. Tight eligibility criteria were established, and the main parameter studied was soft tissue thickness. It was found that xenogeneic collagen matrix is effective for increasing soft tissue thickness around dental implants, however, the results obtained using an autogenous connective tissue graft are superior.

Survival and complications of 3D-printed, non-invasive restorations for prosthetic rehabilitations: A 12-month preliminary observational study.

AIM: The adjustment and transfer of a stable occlusion can be a major challenge in prosthetic rehabilitations. The aim of this study was to assess a non-invasive treatment option for complex prosthetic rehabilitations and occlusal analyses using 3D-printed restorations clinically. MATERIALS AND METHODS: Eleven patients received a partial or complete rehabilitation with the aid of 3D-printed restorations (n=171). After 12 months of clinical service, all restorations were analyzed using the United States Public Health Service (USPHS) criteria. RESULTS: The 12-month clinical data revealed that 3D-printed restorations showed a survival rate of 84.4%. Complications occurred mostly regarding the anatomical form (7%) or marginal integrity (6AC%) and were consequently rated "Charlie" or "Delta." Color stability and color match of 3D-printed restorations were rated "Alpha" in 83% and 73%, respectively, of all restorations. Marginal inflammation was rated "Alpha" in 89% of all restorations. An excellent surface texture and no secondary caries or postoperative sensitivities (100%) were observed. CONCLUSIONS: 3D-printed restorations might be an alternative treatment option for initiating complex prosthetic rehabilitations. Technical complications rarely occurred. Biological complications did not occur at all. The color stability showed promising results after 12 months of clinical service. However, the results should be interpreted with caution. Long-term results with a high number of restorations should be awaited.

The Assessability of Approximal Secondary Caries of Non-Invasive 3D-Printed Veneers Depending on the Restoration Thickness-An In Vitro Study.

To date, no scientific data is available regarding the development and radiographic assessment of approximal caries development after the insertion of 3D-printed, non-invasive veneers of different restoration thicknesses. For the present study, non-invasive veneers were fabricated from two different materials for printing and milling (Vita Enamic and VarseoSmile Crown plus). Three different restoration thicknesses (0.5, 0.7, and 0.9 mm) were selected. After digital design, leaving the approximal space free, and manufacturing of the restorations, adhesive insertion followed. All specimens were placed in a demineralizing solution for 28 days. Subsequently, a radiological and fluorescent examination was performed. The present study showed statistically significant interactions for the day (p < 0.0001) and manufacturing method (p < 0.0001) but not for restoration thickness. Additive manufactured restorations showed less radiological caries progression compared to subtractive manufactured restorations after 21 and 28 days (0.7 and 0.9 mm restoration thickness) (p < 0.0001). DIAGNOdent proved that the restoration thickness affected the caries progression within the subtractive group (p < 0.0001). Radiographic and fluorescence examination showed equivalent results regarding approximal caries assessment. For additive manufacturing, less caries progression was shown without consideration of the restoration thickness.

Effects of layer thickness and build angle on the microbial adhesion of denture base polymers manufactured by digital light processing.

PURPOSE: To investigate the effects of printing-layer thickness and build angle on the surface characteristics and microbial adhesion of denture base polymers manufactured by digital light processing (DLP). METHODS: Specimens were additively manufactured using DLP. The specimens were printed with different printing-layer thicknesses (25, 50, and 100 µm) and build angles (0°, 45°, and 90°). Scanning electron microscopy was used to observe the surface topography, and the arithmetical mean heights (Sa) were measured. Moreover, the initial Candida albicans (C. albicans) adhesion to the specimens was evaluated using an adhesion test. Finally, two-way ANOVA and Tukey's multiple comparison tests were conducted. RESULTS: The results regarding the Sa values exhibited a statistically significant interaction (F (4, 45) = 90.77, P < 0.0001). The build angle has a significant impact on the surface topography. Furthermore, quantitative results revealed that the printing-layer thickness significantly affected C. albicans adhesion (F (2, 99) = 6.96, P = 0.0015). CONCLUSIONS: The surface roughness was significantly affected by the printing-layer thickness and the build angle. Additionally, the surface topography was mainly determined by the build angle. Furthermore, the adhesion of C. albicans to the DLP-printed denture surfaces was significantly affected by the printing-layer thickness but not by the build angle. Consequently, it is critical to decrease the thickness of the printing layer to produce digital dentures with optimal material properties.

Trueness and precision of skin surface reproduction in digital workflows for facial prosthesis fabrication.

STATEMENT OF PROBLEM: How much skin surface details of facial prostheses can be transferred throughout the digital production chain has not been quantified. PURPOSE: The purpose of this in vitro study was to quantify the amount of skin surface details transferred from the prosthesis virtual design through the prototype printing with various additive manufacturing (AM) methods to the definitive silicone prosthesis with an indirect mold-making approach. MATERIAL AND METHODS: Twelve test blocks with embossed wrinkles of 0.05 to 0.8 mm and 12 test blocks with applied earlobe skin structures were printed with stereolithography (SLA), direct light processing (DLP), and PolyJet methods (n=4). DLP and SLA prototype specimens were duplicated in wax. All specimens were then transferred into medical-grade silicone. Rz values of the wrinkle test blocks and the root mean square error (RMSE) of the earlobe test blocks were evaluated by laser topography to determine the trueness and precision of each stage. RESULTS: For the earlobe test blocks, the PolyJet method had superior trueness and precision of the final skin surface reproduction. The SLA method showed the poorest trueness, and the DLP method, the lowest precision. For the wrinkle test blocks, the PolyJet method had the best wrinkle profile reproduction level, followed by DLP and SLA. CONCLUSIONS: The indirect mold-making approach of facial prostheses manufacturing may be associated with 7% of skin surface profile loss with SLA, up to 20% with DLP, and no detail loss with PolyJet.

Post-processing of DLP-printed denture base polymer: Impact of a protective coating on the surface characteristics, flexural properties, cytotoxicity, and microbial adhesion.

OBJECTIVES: To investigate the effect of a protective coating on the surface characteristics, flexural properties, cytotoxicity, and microbial adhesion of vat-photopolymerization additive-manufacturing denture base polymers. METHODS: The specimens were additively manufactured using digital light processing (DLP). Specimen surfaces were coated with the same printed resin, and mechanical polishing was used for comparison. Surface topography, arithmetical mean height (Sa), and water contact angle values were measured. Furthermore, flexural strength (FS)/modulus and fractography were evaluated. Also, cytotoxicity was evaluated by an extract test. Finally, an adhesion test was used to investigate the adhesion of mixed oral bacteria to the specimens. RESULTS: The Sa values in the polished (0.26 ± 0.08 µm) and coated (0.38 ± 0.14 µm) groups were significantly lower than in the untreated (2.21 ± 0.42 µm) and control (2.01 ± 0.37 µm) groups. The coating treatment resulted in a higher FS compared to the untreated surface (p = 0.0002). After the coating treatment, no significant differences were found in relative cell viability between the groups (p > 0.05). The quantitative results showed significantly higher bacterial adhesion in the untreated group than in the polished (p = 0.0047) and coated (p < 0.0001) groups. SIGNIFICANCE: The surface characteristics and flexural properties were optimized by the protective coating. Also, the protective coating did not adversely affect cytocompatibility. Moreover, the coating treatment could effectively decrease oral bacteria adhering to the surfaces. Therefore, the protective coating treatment can be a less time-consuming alternative to mechanical polishing as a post-processing procedure for the digital denture.

Additive Manufacturing of Lithium Disilicate with the LCM Process for Classic and Non-Prep Veneers: Preliminary Technical and Clinical Case Experience.

BACKGROUND: ceramic veneers, crowns, and other types of restorations are often made using either the press heating technique or the subtractive method. The advent of lithography-based ceramic manufacturing (LCM) allows for the manufacturing of such restorations in an additive way. METHODS: this concept paper describes the first clinical experience in the application of LCM lithium disilicate restorations in vivo for the manufacturing of classic veneers for a patient with severe tooth wear. The applied restorations were analyzed in terms of their marginal fit in metrology software (Geomagic Control X, 3D Systems). Furthermore, the feasibility of 3D printing of non-prep veneers with a 0.1 mm thickness was tested. RESULTS: the classic LCM lithium disilicate veneers were tried in the mouth cavity and demonstrated adequate esthetics and a sufficient marginal fit of 100 µm. Furthermore, the non-prep veneers with a 0.1 mm thickness could be successfully printed using LCM technology and also demonstrated an adequate fit on the model in vitro. CONCLUSIONS: the described technical approach of lithium disilicate 3D printing with LCM technology may pose a valid alternative to subtractive and analog manufacturing and be a game-changing option with the use of additive chairside ceramic fabrication.

Bonding strength of 3D printed silicone and titanium retention magnets for maxillofacial prosthetics application.

PURPOSE: To assess the bonding between conventional and additively manufactured silicone elastomers and cylindrical retention titanium magnets for anchorage of facial prostheses. METHODS: The customized titanium retention magnets were embedded in conventional and additively produced silicone blocks without primer application (n = 20) and with two commercially available primers G611 (n = 20) and A304 (n = 20) applied onto the magnet surface. The pull out test was performed in the universal testing machine using 45° and 90° angulation and the pull out strength was measured for each group. Additionally the SEM images of the pulled out magnets' surface were obtained and the amount of residual silicone onto the magnet surface was quantified. RESULTS: Significantly higher pull out strength values (p < 0.05) were revealed for 90° specimens (0.11 - 0.17 ± 0.01 N/mm2) compared to the 45° group (0.03 ± 0.02 N/mm2). The pull out test with primer revealed no significant differences between the G 611 and A 304 primers in the additive group. However, significantly (p < 0,05) higher values were observed for conventional specimens in the A304 group (1.10 ± 0.21 N/mm2) compared to the G611 group (0.59 ± 0.27 N/mm2). CONCLUSION: The application of both used primers may be an acceptable technical option for the anchorage of retention titanium magnets in silicone facial prostheses, produced additively in a fully digital workflow.

Accuracy of capturing nasal, orbital, and auricular defects with extra- and intraoral optical scanners and smartphone: An in vitro study.

OBJECTIVES: This in vitro study compares the scanning accuracy of various stationary and portable as well as extra- and intraoral devices for capturing oncological defects. METHODS: A 3D-printed model of a nasal, orbital, and auricular defect, as well as one of an intact auricle, were digitalized (n = 7 per device) with a stationary optical scanner (Pritiface), a portable extraoral optical scanner (Artec Space Spider), two intraoral scanners (Trios 4 and Primescan), and a smartphone (iPhone 11 Pro). For the reference data, the defect models were digitalized using a laboratory scanner (D2000). For quantitative analysis, the root mean square error value for trueness and precision and mean deviations in millimeters were obtained for each defect type. The data were statistically analyzed using two-way ANOVA and Tukey multiple comparison test. For qualitative analysis, a colorimetric map was generated to display the deviation within the defect area and adjacent tissue. RESULTS: Statistically significant interactions were found in the trueness and precision for defect and scanner type. CONCLUSION: The Primescan and Artec Space Spider scanners showed the highest accuracy for most defect types. Primescan and Trios 4 failed to capture the orbital defect. The iPhone 11 Pro showed clinically acceptable trueness but inferior precision. CLINICAL SIGNIFICANCE: The scanning devices may demonstrate varying accuracy, depending on the defect type. A portable extraoral optical scanner is an universal tool for the digitization of oncological defects. Alternatively, an intraoral scanner may be employed in maxillofacial prosthetics with some restrictions. Utilizing a smartphone in maxillofacial rehabilitation should be considered with caution, because it provides inconsistent accuracy.

Effect of additive manufacturing method and build angle on surface characteristics and Candida albicans adhesion to 3D printed denture base polymers.

OBJECTIVES: To investigate the influence of additive manufacturing method and build angle on surface characteristics and Candida albicans (C. albicans) adhesion to 3D printed denture base polymers. METHODS: Specimens of 3D printing denture base polymers were prepared by two printers, namely, stereolithography (SLA, Form 3B) and digital light processing technology (DLP, Solflex 350 plus). Three build angles were used: 0°, 45°, and 90°. Surface topography was examined by scanning electron microscopy. Also, arithmetical mean height (Sa) values were calculated. An adhesion test was performed to observe initial C. albicans adhesion to the specimens. The data were statistically analyzed using the two-way analysis of variance and Tukey's multiple comparison test. RESULTS: The data of Sa values had statistically significant differences, which were mainly determined by the main factor of build angle (p < 0.05). Moreover, the quantitative results of C. albicans adhesion exhibited no significant differences: printing techniques (p = 0.7794) and build angle (p = 0.0589), respectively. CONCLUSIONS: Surface roughness was significantly influenced by the build angle rather than by the AM method. Whereas, AM method (SLA and DLP) and build angle (0°, 45°, and 90º) had no impacts on the C. albicans adhesion to the 3D printed denture bases. CLINICAL SIGNIFICANCE: Build angle dominates the surface roughness and topography of the 3D printed denture polymers. Our results indicate that C. albicans' adhesion might not be influenced by AM method and build angle.

A virtual patient concept for esthetic and functional rehabilitation in a fully digital workflow.

BACKGROUND: A combination of facial and intraoral scans produces a fully digitalized virtual patient. This concept allows for a 3D smile design and individualized virtual articulator application, which makes the rehabilitation outcome more predictable in terms of esthetics and function. CASE PRESENTATION: In the present clinical case, the patient was 'digitalized' with the use of facial and intraoral scans. The full-mouth rehabilitation by means of implant- and tooth-supported single ceramic restorations was performed through both digital and analog workflows. The 3D printing of the restoration patterns was achieved through the rapid prototyping (RP) approach, and the ceramic milling through the rapid manufacturing approach. The clinical and technical performance of both additive and subtractive manufacturing methods were assessed for this type of rehabilitation. CONCLUSION: Both additive and subtractive manufacturing of ceramic restorations yielded a clinically acceptable marginal fit, which was inspected on the conventionally fabricated stone cast. As the milling of small ceramic restorations has met with failure in the past, the 3D printing of restoration patterns in the context of an RP approach may be regarded as a viable technical option.

Multi-Material 3D Printing of a Customized Sports Mouth Guard: Proof-of-Concept Clinical Case.

A multilayer mouth guard is known to have the best protective performance. However, its manufacturing in a digital workflow may be challenging with regards to virtual design and materialization. The present case demonstrates a pathway to fabricate a multilayer individualized mouth guard in a fully digital workflow, which starts with intraoral scanning. A free-form CAD software was used for the virtual design. Two various CAM techniques were used, including Polyjet 3D printing of rubber-like soft material and silicone printing using Drop-on-Demand technique. For both methods the outer layer was manufactured from more rigid materials to facilitate its protective function; the inner layer was printed from a softer material to aid a better adaptation to mucosa and teeth. Both 3D printed multilayer mouth guards showed a clinically acceptable fit and were met with patient appraisal. Their protective capacities must be evaluated in further clinical studies.

Accuracy Evaluation of Additively and Subtractively Fabricated Palatal Plate Orthodontic Appliances for Newborns and Infants-An In Vitro Study.

Different approaches for digital workflows have already been presented for their use in palatal plates for newborns and infants. However, there is no evidence on the accuracy of CAD/CAM manufactured orthodontic appliances for this kind of application. This study evaluates trueness and precision provided by different CAM technologies and materials for these appliances. Samples of a standard palatal stimulation plate were manufactured using stereolithography (SLA), direct light processing (DLP) and subtractive manufacturing (SM). The effect of material (for SM) and layer thickness (for DLP) were also investigated. Specimens were digitized with a laboratory scanner (D2000, 3Shape) and analyzed with a 3D inspection software (Geomagic Control X, 3D systems). For quantitative analysis, differences between 3D datasets were measured using root mean square (RMS) error values for trueness and precision. For qualitative analysis, color maps were generated to detect locations of deviations within each sample. SM showed higher trueness and precision than AM technologies. Reducing layer thickness in DLP did not significantly increase accuracy, but prolonged manufacturing time. All materials and technologies met the clinically acceptable range and are appropriate for their use. DLP with 100 µm layer thickness showed the highest efficiency, obtaining high trueness and precision within the lowest manufacturing time.

3D Printing of Polyamide to Fabricate a Non-Metal Clasp Removable Partial Denture via Fused Filament Fabrication: A Case Report.

The fabrication of a non-metal clasp removable partial denture (RPD) using polymethylmethacrylate in a fully digital workflow has been reported. According to some studies, the polyamide material may be alternatively used for this purpose. The authors are unaware of any reports concerning the additive manufacturing of polyamide. The current proof-of-concept dental technique describes the pathway to construct the non-metal clasp RPD using intraoral scanning and fused filament fabrication (FFF) printing of gingiva-colored polyamide. The present RPD showed acceptable fit and sufficient retention and was considered a valid temporary treatment option.

Bonding Behavior of Conventional PMMA towards Industrial CAD/CAM PMMA and Artificial Resin Teeth for Complete Denture Manufacturing in a Digital Workflow.

When applying a digital workflow, custom artificial resin teeth have to be integrated into a milled complete denture base, using polymethylmethacrylate (PMMA) applied with a powder-liquid technique. Debonding of denture teeth from dentures is reported to be a frequent complication. No evidence is provided as to which method of surface treatment may enhance the bonding strength. The bonding strength between artificial teeth and PMMA (Group A, n = 60), as well as between the PMMA and industrial PMMA (Group B, n = 60), was investigated following no treatment, monomer application, sandblasting, oxygen plasma, and nitrogen plasma treatment. Surface-roughness values and SEM images were obtained for each group. Shear bond strength (SBS) and fracture mode were analyzed after thermocycling. Within Group A, statistically significant higher SBS was found for all surface treatments, except for nitrogen plasma. In Group B, only nitrogen plasma showed a statistically lower SBS compared to the reference group which was equivalent to all surface treatments. Conclusions: Within the limitations of the present study, the monomer application can be proposed as the most effective surface-treatment method to bond custom artificial teeth into a milled PMMA denture base, whereas nitrogen plasma impairs the bonding strength.

Stereolithography vs. Direct Light Processing for Rapid Manufacturing of Complete Denture Bases: An In Vitro Accuracy Analysis.

The topical literature lacks any comparison between stereolithography (SLA) and direct light processing (DLP) printing methods with regard to the accuracy of complete denture base fabrication, thereby utilizing materials certified for this purpose. In order to investigate this aspect, 15 denture bases were printed with SLA and DLP methods using three build angles: 0°, 45° and 90°. The dentures were digitalized using a laboratory scanner (D2000, 3Shape) and analyzed in analyzing software (Geomagic Control X, 3D systems). Differences between 3D datasets were measured using the root mean square (RMS) value for trueness and precision and mean and maximum deviations were obtained for each denture base. The data were statistically analyzed using two-way ANOVA and Tukey's multiple comparison test. A heat map was generated to display the locations of the deviations within the intaglio surface. The overall tendency indicated that SLA denture bases had significantly higher trueness for most build angles compared to DLP (p < 0.001). The 90° build angle may provide the best trueness for both SLA and DLP. With regard to precision, statistically significant differences were found in the build angles only. Higher precision was revealed in the DLP angle of 0° in comparison to the 45° and 90° angles.

High-level laser therapy versus scalpel surgery in the treatment of oral lichen planus: a randomized control trial.

OBJECTIVE: To compare the clinical effectiveness of various types of high-level laser therapy (HLLT) toward scalpel excision for the surgical treatment of erosive oral lichen planus (OLP). MATERIALS AND METHODS: The total number of 128 individuals were enrolled in the study. The 35 did not meet the inclusion criteria due to malignancy signs and presence of diabetes mellitus. In total, 8 were lost to follow-up, and 10 were excluded from the analysis, due to analgesics intake. This way 75 patients with the erosive form of OLP were analyzed in three intervention groups (Er:YAG, n = 19; Nd:YAG, n = 15; Er:YAG + Nd:YAG combination, n = 20) and one control group with scalpel excision (n = 21). The therapy effectiveness has been assessed based on the comparison of salivary interleukin (IL)-1ß, IL-6 and interferon (IFN)-γ preoperative levels to 14, 30 days, and 2 years postoperation, as well as pain level and time of epithelization. RESULTS: All HLLT groups demonstrated a significantly (p > 0.05) higher IL-1ß, IL-6, IFNγ and pain level reduction and quicker epithelization toward the control group on the 30th day, except Nd:YAG in case of IFNγ level. The highest IL-1ß, IFNγ and pain level reduction and quicker epithelization on the 30th day was observed in Er:YAG group, followed by Er:YAG + Nd:YAG combination, Nd:YAG respectively. However no significant difference was observed between the HLLT groups with regard to IL-6 level reduction. After a 2-year follow-up, no significant difference was observed between all study groups with regard to all variables. CONCLUSION: HLLT yields a superior clinical outcome compared to the scalpel excision for the surgical treatment of oral lichen planus, whereby the Er:YAG has been proposed as the most effective laser type at the end of the first postoperative month. CLINICAL RELEVANCE: For the surgical treatment of erosive OLP the Er:YAG laser may be a preferable treatment option compared to Nd:YAG and scalpel surgery. TRIAL REGISTRATION: The present trial was registered retrospectively in the German Clinical Trials Register, as a member of WHO international clinical trials registry platform, on the 18.03.2020 with the following number: DRKS00020986.