Effect of surface treatment strategies on bond strength of additively and subtractively manufactured hybrid materials for permanent crowns.

OBJECTIVES: The purpose of this study is to evaluate the bond strength of different computer-aided design / computer-aided manufacturing (CAD/CAM) hybrid ceramic materials following different pretreatments. METHODS: A total of 306 CAD/CAM hybrid material specimens were manufactured, n = 102 for each material (VarseoSmile Crownplus [VSCP] by 3D-printing; Vita Enamic [VE] and Grandio Blocs [GB] by milling). Each material was randomly divided into six groups regarding different pretreatment strategies: control, silane, sandblasting (50 µm aluminum oxide particles), sandblasting + silane, etching (9% hydrofluorics acid), etching + silane. Subsequently, surface roughness (Ra) values, surface free energy (SFE) were measured. Each specimen was bonded with a dual-cured adhesive composite. Half of the specimens were subjected to thermocycling (5000 cycles, 5-55 °C). The shear bond strength (SBS) test was performed. Data were analyzed by using a two-way analysis of variance, independent t-test, and Mann-Whitney-U-test (α = 0.05). RESULTS: Material type (p = 0.001), pretreatment strategy (p < 0.001), and the interaction (p < 0.001) all had significant effects on Ra value. However, only etching on VSCP and VE surface increased SFE value significantly. Regarding SBS value, no significant difference was found among the three materials (p = 0.937), while the pretreatment strategy significantly influenced SBS (p < 0.05). Etching on VSCP specimens showed the lowest mean value among all groups, while sandblasting and silane result in higher SBS for all test materials. CONCLUSIONS: The bond strength of CAD/CAM hybrid ceramic materials for milling and 3D-printing was comparable. Sandblasting and silane coupling were suitable for both millable and printable materials, while hydrofluoric etching should not be recommended for CAD/CAM hybrid ceramic materials. CLINICAL RELEVANCE: Since comparable evidence between 3D-printable and millable CAD/CAM dental hybrid materials is scarce, the present study gives clear guidance for pretreatment planning on different materials.

Mechanical properties of 3D-printed and milled composite resins for definitive restorations: An in vitro comparison of initial strength and fatigue behavior.

OBJECTIVE: To evaluate the flexural strength and fatigue behavior of a novel 3D-printed composite resin for definitive restorations. MATERIALS AND METHODS: Fifty disc-shaped specimens were manufactured from each of a nanohybrid composite resin (NHC), polymer-infiltrated ceramic network (PICN), and 3D-printed composite resin (3D) with CAD-CAM technology. Biaxial flexural strength (σin ) (n = 30 per group) and biaxial flexural fatigue strength (σff ) (n = 20 per group) were measured using piston-on-three-balls method, employing a staircase approach of 105 cycles. Weibull statistics, relative-strength degradation calculations, and fractography were performed. The results were analyzed with 1-way ANOVA and Games-Howell post hoc test (α = 0.05). RESULTS: Significant differences in σin and σff among the groups (p < 0.001) were detected. The NHC group provided the highest mean ± standard deviation σin and σff (237.3 ± 31.6 MPa and 141.3 ± 3.8 MPa), followed by the PICN (140.3 ± 12.9 MPa and 73.5 ± 9.9 MPa) and the 3D (83.6 ± 18.5 MPa and 37.4 ± 23.8 MPa) groups. The 3D group exhibited significantly lower Weibull modulus (m = 4.7) and up to 15% higher relative strength degradation with areas of nonhomogeneous microstructure as possible fracture origins. CONCLUSIONS: The 3D-printed composite resin exhibited the lowest mechanical properties, where areas of nonhomogeneous microstructure developed during the mixing procedure served as potential fracture origins. CLINICAL SIGNIFICANCE: The clinical indications of the investigated novel 3D-printed composite resin should be limited to long-term provisional restorations. A cautious procedure for mixing the components is crucial before the 3D-printing process, since nonhomogeneous areas developed during the mixing could act as fracture origins.

The influence of oral cavity physiological parameters: temperature, pH, and swelling on the performance of denture adhesives - in vitro study.

BACKGROUND: The various physical and chemical conditions within the oral cavity are hypothesized to have a significant influence on the behavior of denture adhesives and therefore the overall comfort of denture wearers. As such, this study aims to understand the influence of oral cavity physiological parameters such as temperature (17 to 52 °C), pH (2, 7, 10), and denture adhesive swelling due to saliva (20-120%) on the behavior of denture adhesives. This study further aims to emphasize the need for a collective approach to modelling the in-situ behavior of denture adhesives. METHODS: Rheological measurements were carried out using the Super Polygrip Ultra fresh brand denture adhesive cream to evaluate its storage modulus (G´) and loss modulus (G´´) values at a range of physiologically relevant temperatures, pH values, and degrees of swelling, to represent and characterize the wide variety of conditions that occur within the oral cavity. RESULTS: Rheological data was recorded with respect to variation of temperature, pH, and swelling. Overall, it can be seen that the physiological conditions of the oral cavity have an influence on the rheological properties of the denture adhesive cream. Specifically, our data indicates that the adhesive's mechanical properties are weakly influenced by pH, but do change with respect to the temperature in the oral cavity and the swelling rate of the adhesive. CONCLUSIONS: Our results suggest that the collective inter-play of the parameters pH, temperature and swelling ratio have an influence on the behavior of the denture adhesive. The results clearly highlight the need for developing a multi-parameter viscoelastic material model to understand the collective influence of physiological parameters on the performance of denture adhesives. Multi-parameter models can also potentially be utilized in numerically simulating denture adhesives using finite element simulations.

Survival and success of veneered zirconia crowns.

AIM: The aim of the present study was to evaluate the long-term clinical survival and success rate of veneered zirconia crowns with a modified anatomical framework design after 10 years in function. MATERIALS AND METHODS: In total, 36 zirconia crowns were fabricated for 28 patients. An anatomically modified framework design was developed. Crowns were inserted between 2008 and 2009. A follow-up of 19 patients with 28 crowns was conducted in 2020 to document mechanical and biologic parameters. Additionally, a modified version of the pink esthetic score (PES) was documented. Patient satisfaction was assessed using United States Public Health Service (USPHS) criteria. The success and survival rates were calculated using the Kaplan-Meier analysis. RESULTS: After more than 10 years of clinical service, the survival rate of the zirconia crowns was 92.9%. Biologic complications occurred in 12% of the examined crowns, whereas technical complications occurred in 54%. Mostly, chippings (50%) and insufficient marginal gaps (50%) were observed. Most crowns were positively evaluated for more than one technical complication. Periodontal conditions with probing depths of up to 3 mm were comparable with measured values before crown delivery (73% to 75%). Most of the crowns had modified PES values of 10 or higher. Patient satisfaction was high. CONCLUSIONS: The modified framework design led to a high survival rate of the crowns but a relatively low success rate. High patient satisfaction and inconspicuous periodontal conditions were demonstrated. Biologic complications occurred far less frequently than technical complications.

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.

Replica denture technique: improvements through the use of CAD/CAM technology.

The majority of complete dentures are not initially made for the rehabilitation of an edentulous jaw; in most cases, they replace an existing complete denture. Since the ability to adapt to a new complete denture decreases with age, the replica denture procedure represents a smart opportunity. The aim is to copy the clinically successful parts of the old prosthesis and to change the destroyed parts. There are many advantages of this technique, including increased patient acceptance, especially among older people who may not be able to adapt easily to a new prosthesis. The advantages of digital technology are very apparent in the creation of a replica prosthesis. Various cases are presented in the present article to illustrate the procedure and the advantages of this technique using the example of computer-aided fabrication with the Baltic Denture System.

Clinical performance of non-precious metal double crowns with friction pins in severely reduced dentitions.

OBJECTIVES: Several in vitro studies have investigated the retention of double crowns with friction pins (DCP); however, clinical data on their long-term success have not been reported. We sought to evaluate the 5-year survival rate of DCPs in patients with severely reduced dentition (SRD) and not severely reduced dentition (NSRD). MATERIALS AND METHODS: A total of 158 patients were treated with 182 dentures on 520 abutment teeth between 2006 and 2016. The SRD group included 144 dentures that had been inserted on 314 abutment teeth. We evaluated the influence of age, sex, jaw, number, tooth vitality, and abutment teeth localization (according to Steffel's classification) on the 60-month survival rates of dentures and abutment teeth using the Kaplan-Meier estimator, logrank test, and Cox regression. RESULTS: The cumulative 60-month survival rate was 84.3% (CI 77.1-91.5%) for all dentures; however, the survival rate in the SRD group (80.3%; CI 71.5-89.1%) was significantly lower than in the NSRD group (100%; p = 0.04). Dentures classified in Steffel's class A had the lowest survival rate (51.5%; CI 30.9-72.1%). Number, location, and vitality of the abutment teeth had a significant impact on survival rate. CONCLUSIONS: DCP dentures showed comparable clinical long-term success to double crown systems that have been previously reported in the literature. The number, localization, and vitality of abutment teeth had the greatest influence on the survival rates of denture and abutment teeth. CLINICAL RELEVANCE: DCP dentures have an acceptable 5-year survival rate. Clinical treatment planning must take into account key factors associated with the prognosis of the abutment teeth.

Complications of endodontically treated abutment teeth after restoration with non-precious metal double crowns.

OBJECTIVES: This study aimed to evaluate the effects of endodontic treatment on the complication rate in abutment teeth following double crown treatment. MATERIALS AND METHODS: Data of 233 patients supplied with 278 prostheses on 773 teeth were retrospectively analyzed. The 60-month cumulative complication rate for vital, root filled, and post and core reconstructed abutment teeth is calculated using the Kaplan-Meier method. Cox regression is performed to evaluate factors including age, sex, jaw, and tooth number. RESULTS: After 60 months, the cumulative complication rate for all abutment teeth was 24.1% (CI: 19.7-28.5%). A significantly higher cumulative fracture rate (log-rank test, p < 0.001) was found for devital (51.7%; CI: 35.3-68.1%) compared to vital abutment teeth (20.6%; CI: 16.2-25%). Devital teeth restored with post and core reconstructions (46.3%; CI: 26.1-66.5%) showed a lower cumulative fracture rate than abutment teeth with only root fillings (60.9%; CI: 33.5-88.3%). Abutment teeth in severely reduced dentitions (≤ 3 teeth) were found to have significantly lower survival rates than abutment teeth in not severely reduced dentitions (≥ 4 teeth, p = 0.031, HR = 0.609). CONCLUSION: Lower abutment teeth survival rates were associated with non-vitality and a reduced number of abutment teeth. Devital teeth with post and core reconstructions showed higher survival rates than root filled devital teeth. CLINICAL RELEVANCE: After 5 years, devital teeth with double crowns have a fracture rate twice as high as vital teeth. This prognosis should be taken into account during treatment planning, especially in the severely reduced dentition.

Clinical Performance of Short Expandable Dental Implants for Oral Rehabilitation in Highly Atrophic Alveolar Bone: 3-year Results of a Prospective Single-Center Cohort Study.

BACKGROUND AND OBJECTIVES: Oral health-related quality of life (OHRQOL) is compromised during the post-implant healing period, especially when vertical augmentation is required. A long-term trial sought to evaluate a short dental implant system with an apically expandable macro-design. MATERIALS AND METHODS: Over 4.5 years, patients with limited vertical alveolar bone were consecutively recruited into this prospective cohort study. Implant success rate, OHRQOL (Oral Health Impact Profile (OHIP)-14), implant stability, and crestal bone changes were evaluated. RESULTS: Data from 30 patients (mean age: 64.6 years, range 44-83) were analyzed, which related to 104 implants (53 in the maxilla, 51 in the mandible). Over the mean follow-up (42.6 ± 16.4 months), the implant success rate was 94.7% in the mandible (two implants lost) and 83.6% in the maxilla (four implants lost; p = 0.096), and the prosthetic success rate was 100%. The median OHIP-14 scores improved from 23 (interquartile range (IQR) 9-25.5) to 2 (IQR 0-5; p < 0.001). The mean implant stability quotient (ISQ) was 71.2 ± 10.6 for primary stability and 73.7 ± 13.3 (p = 0.213) for secondary stability, without significant maxilla-versus-mandible differences (p ≥ 0.066). Compared to the baseline, median crestal bone changes after loading were 1.0 mm (IQR 0-1.3) and 1.0 mm (IQR 0.2-1.2) in the maxilla and mandible (p = 0.508), respectively, at the end of the first year, 1.1 mm (IQR 0-1.3) and 1.0 mm (IQR 0.1-1.2) (p = 0.382), respectively, at the end of the second year, and 1.2 mm (IQR 0-1.9) and 1.1 mm (IQR 0.1-1.2) (p = 0.304), respectively, at the end of the third year. CONCLUSIONS: In patients with limited vertical bone height, short implants with optimized macro-design constitute a reliable method for functional rehabilitation, avoiding extensive alveolar bone augmentation.

Retention force of removable partial dentures with different double crowns.

OBJECTIVES: The aim of the study was to compare the retentive behaviors of double crowns with different designs and material compositions before and after artificial aging. MATERIALS AND METHODS: Six pairs of double crowns were fabricated: telescopic crowns 0° made of high-noble metal (group A) or non-precious metal (group B), telescopic zirconia copings with secondary crowns made of electroplated gold 2° (group C), crowns with friction pins 2° made of non-precious metal (group D) or zirconia (group E), and conical crowns 6° made of high-noble metal (group F). Retention forces were assessed before and after artificial aging, and after axial and non-axial loading. RESULTS: Initially, specimens in group D (13.9 N), B (12.5 N), and E (12.2 N) exhibited the highest retention forces. Retention forces in groups A (9.6 N), C (7.4 N), and F (6.0 N) were statistically significantly lower than those of the other groups (p < 0.05). After artificial aging, double crowns with additional retention elements exhibited the highest retention forces. The largest retention force losses were evident in groups A (70%), B (64%), C (39%), and F (47%). CONCLUSIONS: Double crowns with different designs and made of different materials exhibited different retention forces and different long-term retentive behavior. The highest retention force losses were evident in double crowns with more extended surface contact, such as telescopic crowns. CLINICAL SIGNIFICANCE: Telescopic crowns with additional retention elements were more resistant to wearing than double crowns without additional retention elements. An additional clinical benefit might be the quick and easy possibility of enhancing retention.

Accuracy of CAD-CAM-fabricated removable partial dentures.

STATEMENT OF PROBLEM: The conventional fabrication of removable partial dentures (RPDs) is a complex, error-prone, time-consuming, and expensive process. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) techniques, especially rapid prototyping, promises a more effective method for fabricating RPD frameworks. PURPOSE: The purpose of this in vitro study was to evaluate the fit of RPD clasps fabricated by means of 4 different CAD-CAM-systems and to compare those fittings with that of the conventional lost-wax casting technique (LWT). MATERIAL AND METHODS: A master model of a partially edentulous maxilla with the canines and second molars as the remaining teeth was fabricated. After the model was optically scanned, we designed a quadrangularly supported RPD with 4 clasps and a palatal strap major connector. A standard tessellation language data set was used to fabricate 12 identical RPDs by using 4 different CAD-CAM techniques: indirect rapid prototyping (wax inject printing combined with LWT), direct rapid prototyping (selective laser melting), indirect milling (wax milling with LWT), and direct milling (resin milling [polyetheretherketone]). Three conventionally cast RPDs (LWT) served as the control group. The fit accuracy of the clasps (n=12 for each group) was determined in both the horizontal and vertical dimensions by using light microscopy. RESULTS: Indirectly milled RPDs (117 ±34 µm horizontal and 45 ±21 µm vertical) and directly milled RPDs (43 ±23 µm horizontal, and 38 ±21 µm vertical) showed significantly better (P<.05) fit than did conventionally fabricated LWT RPDs (133 ±59 µm horizontal; 73 ±25 µm vertical). The worst fit was found for RPDs fabricated using indirect rapid prototyping (323 ±188 µm horizontal and 112 ±60 µm vertical) or direct rapid prototyping (365 ±205 µm horizontal and 363 ±133 µm vertical), which were unstable on the master model, making them unsuitable for clinical use. Most RPDs exhibited smaller vertical measuring distances. CONCLUSIONS: Compared with the LWT, milling techniques enabled fabrication of RPDs with comparable or better fit. However, RPDs fabricated with rapid prototyping techniques showed distinct fitting irregularities.

The impact of oral rehabilitation on oral health-related quality of life in patients receiving radiotherapy for the treatment of head and neck cancer.

OBJECTIVES: To analyze the influence of dental treatment on oral health-related quality of life (OHRQoL) in head and neck cancer patients. MATERIALS AND METHODS: This study included the data of 116 patients who underwent radiotherapy (RT) because of head and neck cancer. For each patient, the variables age, sex, tumor site, irradiation technique, dose on the spared parotid gland, concomitant chemotherapy, and denture status were documented. OHRQoL was determined using the OHIP-G14 questionnaire. Patients were divided into subgroups according to denture status: none or fixed partial dentures (none/FPD), removable partial dentures (RPD), and full dentures (CD). OHIP summary scores were determined and tested for clinical relevant differences with respect to the different variables. The association between OHRQol and the variables was assessed using linear regression. RESULTS: No clinically relevant influence on OHRQoL was found for gender, irradiation technique, and chemotherapy. Patients with tumors located in the oral cavity had a significantly higher OHIP score than patients with other tumor sites (p < 0.001). None/FPD and RPD patients had higher values than those found in a normal population, but did not differ significantly from each other (p = 0.387). CONCLUSIONS: In contrast to tumor site, teeth and type of denture seem to have a limited effect on OHRQoL in head and neck cancer patients. CLINICAL SIGNIFICANCE: Prosthetic treatment in head and neck cancer patients do not lead to the same improvement in OHRQoL as found in the normal population. This might be taken into account especially if extensive dental treatment is intended.

The influence of dental treatment on the development of osteoradionecrosis after radiotherapy by modern irradiation techniques.

OBJECTIVES: The aim of this study was to analyze the influence of dental treatment on the development of osteoradionecrosis (ORN) of the jaw. METHODS: This study included the data of 776 patients who underwent 3D-CRT or IMRT because of head and neck cancer. Sex, dental status before and after radiotherapy (RT), tumor site, bone surgery during tumor operation, concomitant chemotherapy, and the development of an advanced ORN were documented for each patient. The patients' dentitions before and after RT were classified into four groups with regard to the number and localization of the remaining teeth. Differences between the patients with ORN and patients without ORN with regard to the teeth's condition before and after RT, and with regard to the extent of dental treatment were determined descriptively. Cox proportional hazards regression to study the association between dentition and the development of ORN. RESULTS: The extent of dental treatment in patients with and without ORN did not differ in a clinically relevant way. The highest risk of developing ORN was observed in patients who had undergone primary bone surgery during the tumor operation (HR = 5.58, 95%CI 2.91-10.7) and patients who had a tumor in the oral cavity (HR = 4.84, 95%CI 1.37-17.11). CONCLUSIONS: Based on the results of this study, tumor localization and its required treatment are prognostic factors for the development of ORN. CLINICAL SIGNIFICANCE: After implementing a consequent dental treatment scheme, no influence of dentition on the risk of developing ORN could be demonstrated. Patients with a lower risk could prospectively benefit from a more moderate dental treatment scheme.

Retentive characteristics of a vinylpolysiloxane overdenture attachment system.

OBJECTIVES: Numerous different attachments are used to retain overdentures on implants. The purpose of this study was to evaluate a new chairside attachment system based on polyvinylsiloxane (PVS). MATERIAL AND METHODS: A total of 250 specimens were fabricated (n = 10) to measure the retention force (RF) in dependence of the following parameters: fatigue (after 100, 200, 500, 1,000, and 5,000 cycles of dislodging), thermal undulation (10,000 cycles between 5 and 55 °C), implant angulation (0°, 5°, and 10°), and disinfection (three different agents). Three different PVS materials (shore hardness (SH), SH25, SH50, and SH65) were evaluated; locator attachments (LR blue) served as controls. Data were imported into a statistical program and analyzed at a 5 % level of significance. RESULTS: Initial RFs were dependent on the shore hardness (p ≤ 0.001, ANOVA). No changes in RFs were observed for PVS groups after repeated dislodging and thermal undulation. Locator attachments revealed a significant decrease in retention force of up to 58 % (p ≤ 0.001, Fig. 3). No significant changes in RFs were induced by implant angulation. Retention force was decreased in some PVS groups after storage in disinfection solution. CONCLUSIONS: Polyvinylsiloxane attachments provide an alternative to locator attachments, exhibiting better stability of the retention force. CLINICAL RELEVANCE: The presented directly fabricated chairside attachment system represents RFs superior to existing attachment systems after artificial aging.

The Digital One-Abutment/One-Time Concept. A Clinical Report.

The digital fabrication of dental restorations on implants has become a standard procedure during the last decade. Avoiding changing abutments during prosthetic treatment has been shown to be superior to the traditional protocol. The presented concept for implant-supported single crowns describes a digital approach without a physical model from implant placement to final delivery in two appointments. A 54-year-old man was provided with a single-tooth implant on his left mandibular first molar. Before wound closure, the implant position was captured digitally with an intraoral scanning device. After bone healing at the time of second-stage surgery the final screw-retained crown fabricated without a physical model was inserted. Soft tissue healing took place at the definitive restoration, avoiding abutment changes or changes of the healing cap. These led to stable soft tissues with a minimum of surgery. The benefits of digital fabrication and the unique way to scan the implant right after placement give an additional value that would not be achieved by analog techniques. In addition to financial benefits it represents a biologically advantageous, one-abutment/one-time approach with customized screw-retained, full-contour crowns or cemented crowns on custom abutments.

Single crowns with CAD/CAM-fabricated copings from titanium: 6-year clinical results.

STATEMENT OF PROBLEM: Computer-aided design/computer-aided manufacturing (CAD/CAM) titanium ceramic restorations were developed with the potential for replacing expensive, high noble metal ceramic restorations. However, little information exists about the clinical performance of CAD/CAM titanium ceramic single crowns. PURPOSE: The purpose of this study was to evaluate CAD/CAM titanium ceramic single crowns after 6 years in function. MATERIAL AND METHODS: A total of 41 crowns were fabricated for 21 patients. The titanium copings were CAD/CAM milled (Everest CAD/CAM system), with an even thickness of 0.5 mm and veneered with low-fusing porcelain (Vita Titanium Porcelain) in the powder-build-up technique. All the crowns were cemented with zinc phosphate. The participants were recalled at 12, 24, 36, 48, 60, and 72 months after cementation to document any mechanical and biologic complications and to measure the periodontal parameters, such as probing depth, bleeding on probing, and the plaque index. The success and survival rates were calculated according to the Kaplan-Meier analysis. RESULTS: After 6 years of clinical service, 12 mechanical complications and 1 biologic complication were found, which resulted in a success rate of 67.8%. The cumulative survival rate of the crowns was 91.3% after 6 years. At the end of the follow-up period, the probing depth was 3.21 mm, the percentile of surface with bleeding on probing was 25, and the plaque index was 0.37. No secondary caries or decementation was detected during the 6-year observation period. CONCLUSIONS: The clinical performance of the CAD/CAM titanium-ceramic crowns after 6 years was poor because of veneering porcelain problems. Recent CAD software with tools to design proper copings might improve the clinical success.

Content and goals of preclinical prosthodontic programs at german-language dental schools.

PURPOSE: The Association for Dental Education in Europe (ADEE) makes recommendations regarding the skills graduates of European dental schools need to achieve and advises dental schools regarding necessary changes to be made to the curriculum. In 2010 to 2011, a survey was conducted in German-language dental schools to validate the curricula and goals of preclinical prosthodontic programs with regard to laboratory work. MATERIALS AND METHODS: The survey was mailed to the course instructors of the preclinical programs at 37 dental schools. Of these, 35 schools returned the completed survey, resulting in a response rate of 95%. RESULTS: Bent wire, wax-up exercises, metal-ceramic single crowns, fixed dental prostheses, cast metal single crowns, temporary removable dental prostheses, and full dentures were part of the dental laboratory work at most schools; however, most instructors considered laboratory work as less important, and there were few similarities among the programs in this area. According to the instructors responsible for preclinical education, honing of fine motor skills, realistic self-assessment, and the ability to work independently were the main goals of the programs. CONCLUSION: The results of this survey show that with regard to laboratory work, there were more differences than similarities among preclinical prosthodontic programs at German-language dental schools, contrary to the recommendations of the ADEE. These findings should be taken into account when program reforms are planned.

Evaluation of the accuracy of fully guided implant placement by undergraduate students and postgraduate dentists: a comparative prospective clinical study.

PURPOSE: This study aimed to assess the accuracy of implant placement through three-dimensional planning and fully guided insertion, comparing outcomes between undergraduate and postgraduate surgeons. METHODS: Thirty-eight patients requiring 42 implants in posterior single-tooth gaps were enrolled from the University Clinic for Prosthodontics at the Martin Luther University Halle Wittenberg and the Department of Prosthodontics, Geriatric Dentistry, and Craniomandibular Disorders of Charité University Medicine, Berlin. Twenty-two implants were placed by undergraduate students (n = 18), while 20 implants were placed by trainee postgraduate dentists (n = 5). Pre-operative intraoral scans and cone beam computed tomography images were performed for implant planning and surgical template fabrication. Postoperative intraoral scans were superimposed onto the original scans to analyze implant accuracy in terms of apical, coronal, and angular deviations, as well as vertical discrepancies. RESULTS: In the student group, two implant insertions were performed by the assistant dentist because of intraoperative complications and, thus, were excluded from further analysis. For the remaining implants, no statistically significant differences were observed between the dentist and student groups in terms of apical (p = 0.245), coronal (p = 0.745), or angular (p = 0.185) implant deviations, as well as vertical discrepancies (p = 0.433). CONCLUSIONS: This study confirms the viability of fully guided implant placement by undergraduate students, with comparable accuracy to postgraduate dentists. Integration into dental education can prepare students for implant procedures, expanding access and potentially reducing costs in clinical practice. Collaboration is essential for safe implementation, and future research should explore long-term outcomes and patient perspectives, contributing to the advancement of dental education and practice. TRIAL REGISTRATION: DRKS, DRKS00023024, Registered 8 September 2020-Retrospectively registered, https://drks.de/search/de/trial/DRKS00023024 .

Antagonist enamel tooth wear produced by different dental ceramic systems: A systematic review and network meta-analysis of controlled clinical trials.

OBJECTIVES: The aim of this study was to evaluate the amount of enamel tooth wear induced by different antagonistic ceramic crown materials in the posterior area within a follow-up period up to 24 months in function. A network meta-analysis was performed to assess the effect of the materials on the mean vertical loss (MVL) of the antagonist enamel tooth surface. DATA: Main search terms used in combination: ceramic, dental materials, metal ceramic, tooth wear and dental enamel. SOURCES: An electronic search was conducted in PubMed/Medline, Embase, and Cochrane CENTRAL plus hand-searching. STUDY SELECTION: Eligibility criteria included clinical studies reporting on MVL on antagonist's tooth up to 24 months following the permanent crown placement. From a total of 5697 articles, 7 studies reporting on 261 crowns for 177 subjects with 3 ceramic materials (Lithium disilicate, metal-ceramic, monolithic zirconia) were included. Among all, metal-ceramic and zirconia caused significantly higher enamel tooth wear on antagonist teeth, representing 82.5 µm [54.4; 110.6]) and 40.1 µm [22.2; 58.0]) more MVL than natural teeth group. In contrast, lithium disilicate showed only 5.0 µm [-48.2; 58.1]) more MVL than occurs on opposing natural teeth. CONCLUSIONS: This systematic review demonstrated that prosthodontic ceramic materials produced significantly more antagonist enamel tooth wear than opposing natural enamel tooth wear, and ceramic material type was correlated to the degree of enamel tooth wear. Additional well-conducted, randomized controlled trials with homogeneous specimens are required due to inadequate sample size and number of the clinical studies included in the analyses. CLINICAL SIGNIFICANCE: The amount of wear caused by different restorative materials has a high influence on the antagonistic natural teeth and should therefore be evaluated intensively by the dentist.

Microstructural investigation of hybrid CAD/CAM restorative dental materials by micro-CT and SEM.

OBJECTIVES: An increasing number of CAD/CAM (computer-aided design/computer-aided manufacturing) hybrid materials have been introduced to the dental market in recent years. In addition, CAD/CAM hybrid materials for additive manufacturing (AM) are becoming more attractive in digital dentistry. Studies on material microstructures using micro-computed tomography (µ-CT) combined with scanning electron microscopy (SEM) have only been available to a limited extent so far. METHODS: One CAD/CAM three-dimensional- (3D-) printable hybrid material (VarseoSmile Crown plus) and two CAD/CAM millable hybrid materials (Vita Enamic; Voco Grandio), as well as one direct composite material (Ceram.x duo), were included in the present study. Cylindrical samples with a diameter of 2 mm were produced from each material and investigated by means of synchrotron radiation µ-CT at a voxel size of 0.65 µm. Different samples from the same materials, obtained by cutting and polishing, were investigated by SEM. RESULTS: The 3D-printed hybrid material showed some agglomerations and a more irregular distribution of fillers, as well as a visible layered macrostructure and a few spherical pores due to the printing process. The CAD/CAM millable hybrid materials revealed a more homogenous distribution of ceramic particles. The direct composite material showed multiple air bubbles and microstructural irregularities based on manual processing. SIGNIFICANCE: The µ-CT and SEM analysis of the materials revealed different microstructures even though they belong to the same class of materials. It could be shown that µ-CT and SEM imaging are valuable tools to understand microstructure and related mechanical properties of materials.