Effect of Hydrothermal Aging on the Flexural Strength and Microhardness of Materials Used for Additive or Subtractive Manufacturing of Definitive Restorations.

PURPOSE: To evaluate the flexural strength (FS) and microhardness of various CAD/CAM restorative materials intended for definitive use. The effect of hydrothermal aging on the mechanical properties of these materials was also investigated. MATERIALS AND METHODS: A total of 210 bar-shaped specimens (17 × 4 × 1.5 mm ± 0.02 mm) were fabricated via either subtractive manufacturing (SM) methods-reinforced composite resin (SM-CR), polymer-infiltrated ceramic network (SM-PICN), fine-structured feldspathic ceramic (SMFC), nanographene-reinforced polymethyl methacrylate (PMMA; SM-GPMMA), PMMAbased resin (SM-PMMA)-or additive manufacturing (AM) methods with urethane acrylate-based resins (AM-UA1 and AM-UA2). Specimens were then divided into two subgroups (nonaged or hydrothermal aging; n = 15). A three-point flexural strength test was performed, and five specimens from the nonaged group were submitted to microhardness testing. Specimens were subjected to 10,000 thermal cycles, and the measurements were repeated. RESULTS: Regardless of aging, SM-CR had the highest FS (P < .001), followed by SM-GPMMA (P ≤ .042). In nonaged groups, AM-UA2 had a lower FS than all other materials except SM-FC (P = 1.000). In hydrothermal aging groups, AM specimens had lower FS values than other materials, except SM-PMMA. With regard to microhardness, there was no significant difference found between any of the tested materials (P ≥ .945) in the nonaged and hydrothermal aging groups. CONCLUSIONS: The effect of hydrothermal aging on FS varied depending on the type of restorative material. Regardless of aging condition, SM-CR showed the highest FS values, whereas SM-FC had the highest microhardness. Hydrothermal aging had no significant influence on the microhardness of the tested materials.

Treatment effect of implant-supported fixed complete dentures and implant overdentures on patient-reported outcomes: A systematic review and meta-analysis.

OBJECTIVES: To analyze the effect of implant treatment in edentulous patients rehabilitated with implant-supported fixed complete dentures (IFCDs) or implant overdentures (IODs) on dental patient-reported outcomes (dPROs). MATERIALS AND METHODS: In January 2022, Medline, Embase, CINAHL, Cochrane Library, PubMed Central, Web of Science, and ClinicalTrials.gov were screened for prospective clinical studies on completely edentulous patients treated with IFCDs and/or IODs, reporting pre-treatment and follow-up dPROs. Hedges' g effect sizes (ES) with corresponding 95% confidence intervals (CI) were calculated. Afterward, meta-analyses were conducted using random effect models. RESULTS: A total number of 1608 records was initially identified. Of those, 28 studies reporting dPROs from 1457 patients were finally included. The applied dental patient-reported outcome measures (dPROMs) included several versions of the Oral Health Impact Profile (OHIP) or specific items assessing satisfaction with Visual Analogue Scales (VAS). The overall ES was large for rehabilitation with IFCDs (1.68 [CI: 1.15, 2.20]) and IODs (1.26 [CI: 0.99, 1.52]) with no significant difference (p = .165) between the two. Denture stability was the only factor rated significantly higher for IFCDs (ES difference: 2.37 [CI: 0.21, 4.54]; p = .032). Subgroup analyses revealed moderately higher ES for IODs on two implants relative to one implant (ES difference: 0.73 [CI: 0.34, 1.12]; p < .001). CONCLUSIONS: There is a strong positive effect of implant treatment in edentulous patients, independent of the type of prosthetic rehabilitation. In patients seeking high stability, IFCDs may be preferable. In mandibular IODs on a single implant, there was a significantly positive effect of an additional implant on dPROs.

Influence of planning software and template design on the accuracy of static computer assisted implant surgery performed using guides fabricated with material extrusion technology: An in vitro study.

OBJECTIVES: This in vitro study aimed to assess the influence of the planning software and design of the surgical template on both trueness and precision of static computer assisted implant surgery (sCAIS) performed using guides fabricated using material extrusion (ME). METHODS: Three-dimensional radiographic and surface scans of a typodont were aligned using two planning software (coDiagnostiX, CDX; ImplantStudio, IST) to virtually position the two adjacent oral implants. Thereafter, surgical guides were fabricated with either an original (O) or modified (M) design with reduced occlusal support and were sterilized. Forty surgical guides were used to install 80 implants equally distributed amongst four groups: CDX-O, CDX-M, IST-O, and IST-M. Thereafter, the scan bodies were adapted to the implants and digitized. Finally, inspection software was used to assess discrepancies between the planned and final positions at the implant shoulder and main axis level. Multilevel mixed-effects generalised linear models were used for statistical analyses (p = 0.05). RESULTS: In terms of trueness, the largest average vertical deviations (0.29 ± 0.07 mm) were be assessed for CDX-M. Overall, vertical errors were dependant on the design (O < M; p ≤ 0.001). Furthermore, in horizontal direction, the largest mean discrepancy was 0.32 ± 0.09 mm (IST-O) and 0.31 ± 0.13 mm (CDX-M). CDX-O was superior compared to IST-O (p = 0.003) regarding horizontal trueness. The average deviations regarding the main implant axis ranged between 1.36 ± 0.41° (CDX-O) and 2.63 ± 0.87° (CDX-M). In terms of precision, mean standard deviation intervals of ≤ 0.12 mm (IST-O and -M) and ≤ 1.09° (CDX-M) were calculated. CONCLUSIONS: Implant installation with clinically acceptable deviations is possible with ME surgical guides. Both evaluated variables affected trueness and precision with negligible differences. CLINICAL SIGNIFICANCE: The planning system and design influenced the accuracy of implant installation using ME-based surgical guides. Nevertheless, discrepancies were ≤ 0.32 mm and ≤ 2.63°, which may be considered within the range of clinical acceptance. ME should be further investigated as an alternative to the more expensive and time-consuming 3D printing technologies.

Impact of radiographic field-of-view volume on alignment accuracy during virtual implant planning: A noninterventional retrospective pilot study.

OBJECTIVE: To evaluate the impact of reducing the radiographic field of view (FOV) on the trueness and precision of the alignment between cone beam computed tomography (CBCT) and intraoral scanning data for implant planning. MATERIALS AND METHODS: Fifteen participants presenting with one of three clinical scenarios: single tooth loss (ST, n = 5), multiple missing teeth (MT, n = 5) and presence of radiographic artifacts (AR, n = 5) were included. CBCT volumes covering the full arch (FA) were reduced to the quadrant (Q) or the adjacent tooth/teeth (A). Two operators, an expert (exp) in virtual implant planning and an inexperienced clinician, performed multiple superimpositions, with FA-exp serving as a reference. The deviations were calculated at the implant apex and shoulder levels. Thereafter, linear mixed models were adapted to investigate the influence of FOV on discrepancies. RESULTS: Evaluation of trueness compared to FA-exp resulted in the largest mean (AR-A: 0.10 ± 0.33 mm) and single maximum discrepancy (AR-Q: 1.44 mm) in the presence of artifacts. Furthermore, for the ST group, the largest mean error (-0.06 ± 0.2 mm, shoulder) was calculated with the FA-FOV, while for MT, with the intermediate volume (-0.07 ± 0.24 mm, Q). In terms of precision, the mean SD intervals were ≤0.25 mm (A-exp). Precision was influenced by FOV volume (FA < Q < A) but not by operator expertise. CONCLUSIONS: For single posterior missing teeth, an extended FOV does not improve registration accuracy. However, in the presence of artifacts or multiple missing posterior teeth, caution is recommended when reducing FOV.

Cytotoxicity of polymers intended for the extrusion-based additive manufacturing of surgical guides.

Extrusion-based printing enables simplified and economic manufacturing of surgical guides for oral implant placement. Therefore, the cytotoxicity of a biocopolyester (BE) and a polypropylene (PP), intended for the fused filament fabrication of surgical guides was evaluated. For comparison, a medically certified resin based on methacrylic esters (ME) was printed by stereolithography (n = 18 each group). Human gingival keratinocytes (HGK) were exposed to eluates of the tested materials and an impedance measurement and a tetrazolium assay (MTT) were performed. Modulations in gene expression were analyzed by quantitative PCR. One-way ANOVA with post-hoc Tukey tests were applied. None of the materials exceeded the threshold for cytotoxicity (< 70% viability in MTT) according to ISO 10993-5:2009. The impedance-based cell indices for PP and BE, reflecting cell proliferation, showed little deviations from the control, while ME caused a reduction of up to 45% after 72 h. PCR analysis after 72 h revealed only marginal modulations caused by BE while PP induced a down-regulation of genes encoding for inflammation and apoptosis (p < 0.05). In contrast, the 72 h ME eluate caused an up-regulation of these genes (p < 0.01). All evaluated materials can be considered biocompatible in vitro for short-term application. However, long-term contact to ME might induce (pro-)apoptotic/(pro-)inflammatory responses in HGK.

Guided flapless apicoectomy of the palatal root of a maxillary molar: a case presentation.

This case report presents a novel approach for minimally invasive fully guided apicoectomy of the palatal root of a maxillary first molar using a custom-made 3D-printed template. To date, the development of diagnostic radiographic tools such as high-resolution CBCT devices, as well as of CAD planning software and CAM technologies, like 3D printing, allow for increased application in endodontics. The patient (a 38-year-old woman) suffered from pain on the right side of the face since 4 weeks and was diagnosed with chronic apical periodontitis of the palatal root of the maxillary right first molar. The root treatment of this tooth was followed up recently and the buccal roots showed no pathologic findings. A guided apicoectomy with access from the palate was chosen as elective therapy. 3D radiographic and intraoral surface datasets were imported into an implant planning software and superimposed, and minimally invasive access to the palatal root apex was planned. Subsequently, a tooth-supported drilling template was designed and created by additive manufacturing. A flapless approach was adapted using a punch-drill and the access to the root apex as well as the apical resection were performed with a trephine drill. The connective tissue punch was finally replaced and sutured. No postoperative complication was reported and a complete remission of symptoms was reported after 2 weeks. The follow-up after 21 months showed clinically stable wound conditions and radiologically a slight reossification in the area of the palatal root tip. The presented technique may lead to novel minimally invasive approaches for the preservation of infected maxillary molars.

Jaw tracking integration to the virtual patient: A 4D dynamic approach.

This dental technique describes a novel cost-effective workflow for integrating mandible kinematics into a static virtual patient. Computed tomography data are segmented and merged with intraoral surface scans and a target tracking video reproducing the mandible movements. A 4-dimensional dynamic virtual patient is created by using an open-source software program, and all patient-specific parameters can be exported for individualization of a virtual or analog articulator.

In Vitro Time Efficiency, Fit, and Wear of Conventionally- versus Digitally-Fabricated Occlusal Splints.

The purpose of the study was to compare conventional to digital workflows of occlusal splint production regarding time efficiency, overall fit, and wear. Fifteen Michigan splints were fabricated with a conventional and digital method. The duration for the dentist's and the dental technician's workload was recorded. Subsequently, the overall fit was examined with a four-level score (1-4). Paired t-tests were used to compare the time results for the conventional and digital workflows and the sign test to compare the overall fit. The mean time (16 min 58 s) for computerized optical impressions was longer than for conventional impressions (6 min 59 s; p = 0.0001). However, the dental technician needed significantly less mean time for the digital splint production (47 min 52 s) than for the conventional (163 min 32 s; p = 0.001). The overall fit of the digitally-fabricated splints was significantly better compared to the conventionally-fabricated splints (p = 0.002). There was no impact of the different materials used in the conventional and digital workflow on the wear (p = 0.26). The results suggest that the digital workflow for the production of occlusal splints is more time efficient and leads to a better fit than the conventional workflow.

Short Versus Regular-Length Implants to Rehabilitate Partially Edentulous Mandible: A 2-Year Prospective Split-Mouth Clinical Study.

Many studies have evaluated short implants (SIs); however, it is still unclear whether SIs are reliable and can be used to simplify surgical and prosthetic protocols with successful clinical outcomes. The aim of this nonrandom, conveniently sampled, prospective, split-mouth study was to compare the clinical outcomes when short SI (≤8 mm) or regular-length implants (RIs; >10 mm) were used in the posterior mandible 2 years after the delivery of splinted reconstructions. Each participant (N = 10) received 4 implants in the posterior mandible; 2 SIs were placed on one side, and 2 RIs were placed contralaterally. Implants were restored with splinted, screw-retained, porcelain-fused-to-metal reconstructions. Survival and success rates, peri-implant marginal bone level (MBL), and soft-tissue parameters were evaluated. No participant dropouts were recorded. Both types of implants showed 100% success and survival rates. From prosthetic delivery to 24 months postloading, bone remineralization of +0.40 mm for the SIs and +0.36 mm for the RIs was observed without statistically significant differences in MBL between the implant types (P = .993). SIs showed significantly higher (P = .001) clinical attachment level and probing depth values. Chipping occurred in one situation in the RI group, resulting in a 97.5% prosthetic success rate, which was 100% for the SIs. After 2 years, SIs with splinted reconstructions showed comparable clinical outcomes to those of RIs. Further long-term controlled clinical studies with balanced experimental designs evaluating random and larger populations are required to corroborate these findings.

Out-of-Hospital Treatment of Hepatitis C Increases Retention in Care among People Who Inject Drugs and Homeless Persons: An Observational Study.

BACKGROUND: People who inject drugs (PWID) and homeless people represent now a large reservoir of Hepatitis C virus (HCV) infection. However, Hepatis C elimination programs can barely reach these subgroups of patients. We aimed to evaluate and compare the retention in care among these difficult-to-treat patients when managed for HCV in hospital or in an out-of-hospital setting. METHODS: In our retrospective study, we categorized the included patients (PWID and homeless persons) into two groups according to whether anti-HCV treatment was offered and provided in a hospital or an out-of-hospital setting. We run logistic regressions to evaluate factors associated with retention in care (defined as the completion of direct antiviral agents (DAAs) therapy). RESULTS: We included 56 patients in our study: 27 were in the out-of-hospital group. Overall, 33 patients completed DAAs therapy. A higher rate of retention in care was observed in the out-of-hospital group rather than in-hospital group (p = 0.001). At the univariate analysis, retention in care was associated with the out-of-hospital management (p = 0.002) and with a shorter time between the first visit and the scheduled start of DAAs (p = 0.003). CONCLUSIONS: The choice of treatment models that can better adapt to difficult-to-treat populations, such as an out-of-hospital approach, will be important for achieving the eradication of HCV infection.

Air seal performance of personalized and statistically shaped 3D-printed face masks compared with market-available surgical and FFP2 masks.

The ongoing COVID-19 pandemic has revealed alarming shortages of personal protective equipment for frontline healthcare professionals and the general public. Therefore, a 3D-printable mask frame was developed, and its air seal performance was evaluated and compared. Personalized masks (PM) based on individual face scans (n = 8) and a statistically shaped mask (SSM) based on a standardized facial soft tissue shape computed from 190 face scans were designed. Subsequently, the masks were additively manufactured, and in a second step, the PM and SSM were compared to surgical masks (SM) and FFP2 masks (FFP2) in terms of air seal performance. 3D-printed face models allowed for air leakage evaluation by measuring the pressure inside the mask in sealed and unsealed conditions during a breathing simulation. The PM demonstrated the lowest leak flow (p < 0.01) of inspired or expired unfiltered air of approximately 10.4 ± 16.4%, whereas the SM showed the highest (p < 0.01) leakage with 84.9 ± 7.7%. The FFP2 and SSM had similar values of 34.9 ± 18.5% leakage (p > 0.68). The developed framework allows for the time- and resource-efficient, on-demand, and in-house production of masks. For the best seal performance, an individually personalized mask design might be recommended.

Retrospective long-term clinical evaluation of implant-prosthetic rehabilitations after head and neck cancer therapy.

OBJECTIVE: To assess clinical and patient-reported outcomes of implant-prosthetic rehabilitations in patients with a history of head-neck cancer (HNC), treated with tumor resection without (TR) or with adjuvant radiotherapy (TR/RT). A healthy cohort rehabilitated with the same reconstructive protocols served as control group (C). MATERIALS AND METHODS: A total of 28 women and 29 men were considered in the present retrospective study. Participants received 322 implants, finally supporting 79 prosthetic reconstructions. Primary outcome was the assessment of implant and prosthetic survival rates. Furthermore peri-implant soft tissue parameters (attached peri-implant mucosa, AM; modified bleeding and plaque indices, mBI/mPI; probing depth, PD) and prosthetic technical complications were documented. Patient-reported outcome measures (PROMs) by means of visual analog scales (VAS) and the Oral Health Impact Profile German 14 form (OHIP G14) were collected. For statistical purposes Chi-square and Mann-Whitney-U-Test were adapted. RESULTS: After a mean follow-up of 81.2 ± 50.3 months, implant survival rate was 98.1% (HNC-TR), 98.2% (HNC-TR/RT) and 100.0% (C), respectively (four implants failed in the HNC groups). HNC-TR/RT showed significant higher mPI and mBI compared to C. Within HNC-TR/RT, vestibuloplasty significantly reduced mBI and PD values. No failures occurred at the prosthetic level. Overall, higher VAS scores were reported for bar- compared with Locator-retained prostheses. Furthermore, increased OHIP G14 values resulted for HNC-TR/RT. CONCLUSIONS: High survival rates on implant and prosthetic level were observed. The use of soft tissue grafts resulted in stabilization of the peri-implant mucosa in irradiated patients. In terms of retention and chewing ability, participants preferred bars over Locator attachments.

Polymers for conventional, subtractive, and additive manufacturing of occlusal devices differ in hardness and flexural properties but not in wear resistance.

OBJECTIVES: To investigate the wear resistance of polymers for injection molding, subtractive and additive manufacturing of occlusal devices in comparison with enamel antagonist wear and material properties (i.e., hardness, flexural strength, and flexural modulus). METHODS: Injection molding was compared with milling and the additive technologies stereolithography, low force stereolithography, and digital light processing. For each material, eight specimens were produced for wear measurements. Extracted human premolars served as indenters. All samples were subjected to two series of a 2-body wear test consisting of 200,000 circular loading cycles with an applied load of 1) 20 N and 2) 50 N in a thermocycling environment (5/55 °C, 30 s, 3860 cycles, H2O). Wear resistance was characterized by means of maximum depth and volume of the resulting traces. In addition, enamel wear of the indenters and Vickers hardness, flexural strength, and flexural modulus of the polymers were determined. Wear was statistically analyzed with linear general models for repeated measures and material properties with one-way ANOVA with post-hoc Tukey-HSD tests. RESULTS: Wear of the antagonists was not influenced by the material (P ≥ 0.343). Likewise, no differences in wear resistance were found between materials after cyclic loading with 20 N or 50 N (P ≥ 0.074). Material properties investigated revealed decreased values for the resins for the additive manufacturing with the exception of flexural strength of one material. SIGNIFICANCE: Within the limitations of this in-vitro study, arylates for conventional, subtractive, and additive manufacturing of occlusal devices differ in material properties but not in wear resistance and antagonist wear.

Accuracy and its impact on fit of injection molded, milled and additively manufactured occlusal splints.

Occlusal devices to reduce symptoms of bruxism and temperomandibular disorders can nowadays be manufactured in a digital workflow but studies comparing the accuracy of those occlusal devices are still limited. Therefore, the aim of this investigation was to investigate the accuracy of injection molding compared with four computer-aided design (CAD) and computer-aided manufacturing (CAM) techniques for the manufacturing of occlusal devices. In addition, the number of contact points and retention were evaluated to assess clinical relevance. A conventional workflow consisting of alginate impression, wax-up, and injection molding (IM) and digital workflows including intraoral scanning, digital design, and subtractive manufacturing (SM) or additive manufacturing by using stereolithography (SLA), digital light processing (DLP), and material jetting (Polyjet) were investigated. Sixteen splints were fabricated with each method. The intaglio surfaces of the splints were laser scanned and superimposed with the reference data sets to analyze the surface deviations. In addition, the number of contact points after repositioning the splints on the reference model was evaluated with occlusal foil. Finally, the retention was measured in a tensile test. One-way ANOVA with post hoc Tukey tests were used for statistical analyses (α = .05). IM and SM splints demonstrated the highest manufacturing accuracy without significant differences to each other (P > .985). Additive manufactured splints revealed greater deviations with equal results for SLA and Polyjet (P > .949) and significantly higher deviations for DLP compared to all other groups (P < .002). Comparable retention force was measured for IM, SM, and SLA (P > .923), whereas Polyjet splints showed the greatest variability. IM and SM splints presented the most contact points (P = .505). Additive manufactured splints demonstrated fewer contacts without significant difference to each other (P > .116). It can be concluded, that there is no difference in manufacturing accuracy, retention, and number of contacts between IM and SM splints. AM splints demonstrated higher, however, clinically acceptable deviations.

Pandemic-Driven Development of a Medical-Grade, Economic and Decentralized Applicable Polyolefin Filament for Additive Fused Filament Fabrication.

A polyolefin with certified biocompatibility according to USP class VI was used by our group as feedstock for filament-based 3D printing to meet the highest medical standards in order to print personal protective equipment for our university hospital during the ongoing pandemic. Besides the chemical resistance and durability, as well as the ability to withstand steam sterilization, this polypropylene (PP) copolymer is characterized by its high purity, as achieved by highly efficient and selective catalytic polymerization. As the PP copolymer is suited to be printed with all common printers in fused filament fabrication (FFF), it offers an eco-friendly cost-benefit ratio, even for large-scale production. In addition, a digital workflow was established focusing on common desktop FFF printers in the medical sector. It comprises the simulation-based optimization of personalized print objects, considering the inherent material properties such as warping tendency, through to validation of the process chain by 3D scanning, sterilization, and biocompatibility analysis of the printed part. This combination of digital data processing and 3D printing with a sustainable and medically certified material showed great promise in establishing decentralized additive manufacturing in everyday hospital life to meet peaks in demand, supply bottlenecks, and enhanced personalized patient treatment.

A Prospective Clinical Cohort Investigation on Zirconia Implants: 5-Year Results.

Mid-term data on zirconia oral implants is very rare. Therefore, the aim of this prospective clinical investigation was to evaluate the survival rate and the marginal bone loss of a one-piece zirconia implant after five years. Patient-reported outcomes were also recorded. Zirconia implants to support single crowns (SC) or a 3-unit fixed dental prosthesis (FDP) were placed and subsequently restored. After the insertion of the implants, at prosthetic delivery, and after five years, standardized radiographs were taken to evaluate marginal bone loss (MBL). For bone tissue evaluation, linear mixed models with random intercepts were fitted. Twenty-seven patients received one implant for an SC and 13 patients received two implants for a 3-unit FDP. Three patients each lost one implant for an SC before prosthetic delivery. Thirty-five patients were seen after five years, and no further implant was lost. The cumulative five-year implant survival rate was 94.3%. The MBL from implant installation up to five years was 0.81 mm. The MBL from implant installation to prosthetic delivery was statistically significant (p < 0.001). Patients perceived a significant improvement in function, esthetics, sense, speech, and self-esteem from pretreatment up to the five-year follow-up. The present findings substantiate the clinical applicability of this implant system.

Do hydrothermal aging and microwave sterilization affect the trueness of milled, additive manufactured and injection molded denture bases?

Concepts for digital denture manufacturing are market-available but studies comparing the trueness of such dentures, either milled (MIL) or additive manufactured, compared to injection molded (IM) ones are still limited. Regarding the impact of artificial aging and microwave sterilization on this parameter, no data are available. Therefore, the purpose of this investigation was to assess the trueness of IM, MIL, and stereolithography (SLA) printed denture bases after manufacturing, hydrothermal cycling, and microwave sterilization. Sixteen edentulous maxillary plaster models were poured using a silicone mold and digitized by means of a desktop scanner. For group IM, 16 denture bases were injection molded using these models. For group MIL and SLA, the denture bases were virtually designed and manufactured referring to the digitized data. A total of 48 samples were scanned 1) after manufacturing, 2) after hydrothermal cycling (5-55 °C, N = 5,000), and after 3) three as well as 4) six cycles of microwave sterilization for 6 min each at 640 W. The 3D surface deviation of the total intaglio surface, the palate, the alveolar ridge, and the border seal region was evaluated on the basis of the root mean square estimation (RMSE) and positive and negative mean deviations with an inspection software. For statistical analysis, ANOVA and post hoc Tukey tests were performed (α = 0.05). MIL showed the lowest deviations of the total RMSE (P ≤ .006) compared with the scans of the plaster models. In comparison, IM showed increased, mainly positive, deviations (P = .006) at the border seal. SLA presented the highest total RMSE (P = .001) with increased negative deviations, likewise at the border seal. In contrast to SLA (P = .001), no differences between IM and MIL (P = .816) were measured after hydrothermal cycling. Following microwave sterilization, the trueness of SLA was higher compared to IM and MIL (P = .001), with no differences between MIL and IM (P = .153). Distortion of IM and MIL was measured after the 3rd cycle with no further changes observed thereafter (P ≥ .385). It can be concluded, that subtractive manufacturing of denture bases results in the highest trueness, followed by IM and SLA. In contrast to IM and SLA, hydrothermal cycling did not affect MIL. Solely SLA printed denture bases remained dimensionally stable after microwave sterilization.

How Accurate Is Oral Implant Installation Using Surgical Guides Printed from a Degradable and Steam-Sterilized Biopolymer?

3D printed surgical guides are used for prosthetically-driven oral implant placement. When manufacturing these guides, information regarding suitable printing techniques and materials as well as the necessity for additional, non-printed stock parts such as metal sleeves is scarce. The aim of the investigation was to determine the accuracy of a surgical workflow for oral implant placement using guides manufactured by means of fused deposition modeling (FDM) from a biodegradable and sterilizable biopolymer filament. Furthermore, the potential benefit of metal sleeve inserts should be assessed. A surgical guide was designed for the installation of two implants in the region of the second premolar (SP) and second molar (SM) in a mandibular typodont model. For two additive manufacturing techniques (stereolithography [SLA]: reference group, FDM: observational group) n = 10 surgical guides, with (S) and without (NS) metal sleeves, were used. This resulted in 4 groups of 10 samples each (SLA-S/NS, FDM-S/NS). Target and real implant positions were superimposed and compared using a dedicated software. Sagittal, transversal, and vertical discrepancies at the level of the implant shoulder, apex and regarding the main axis were determined. MANOVA with posthoc Tukey tests were performed for statistical analyses. Placed implants showed sagittal and transversal discrepancies of <1 mm, vertical discrepancies of <0.6 mm, and axial deviations of ≤3°. In the vertical dimension, no differences between the four groups were measured (p ≤ 0.054). In the sagittal dimension, SLA groups showed decreased deviations in the implant shoulder region compared to FDM (p ≤ 0.033), whereas no differences in the transversal dimension between the groups were measured (p ≤ 0.054). The use of metal sleeves did not affect axial, vertical, and sagittal accuracy, but resulted in increased transversal deviations (p = 0.001). Regarding accuracy, biopolymer-based surgical guides manufactured by means of FDM present similar accuracy than SLA. Cytotoxicity tests are necessary to confirm their biocompatibility in the oral environment.

Clinical Outcomes of Root-Analogue Implants Restored with Single Crowns or Fixed Dental Prostheses: A Retrospective Case Series.

The objective was to investigate clinical and radiological outcomes of rehabilitations with root-analogue implants (RAIs). Patients restored with RAIs, supporting single crowns or fixed dental prostheses, were recruited for follow-up examinations. Besides clinical and esthetical evaluations, X-rays were taken and compared with the records. Patients were asked to evaluate the treatment using Visual Analogue Scales (VAS). For statistical analyses, mixed linear models were used. A total of 107 RAIs were installed in one dental office. Of these, 31 were available for follow-up examinations. For those remaining, survival has been verified via phone. RAIs were loaded after a mean healing time of 6.6 ± 2.5 months. 12.1 ± 6.9 months after loading, a mean marginal bone loss (MBL) of 1.20 ± 0.73 mm was measured. Progression of MBL significantly decreased after loading (p = 0.013). The mean pink and white esthetic score (PES/WES) was 15.35 ± 2.33 at follow-up. A survival rate of 94.4% was calculated after a mean follow-up of 18.9 ± 2.4 months after surgery. Immediate installation of RAIs does not seem to reduce MBL, as known from the literature regarding screw-type implants, and might not be recommended for daily routine. Nevertheless, they deliver esthetically satisfying results.