Accuracy of CAD/CAM-fabricated bite splints: milling vs 3D printing

OBJECTIVES The aim of this study was to investigate the accuracy of CAD/CAM-fabricated bite splints in dependence of fabrication method (milling vs 3D printing), positioning (horizontal vs vertical), selection of material, and method of deviation measurement. MATERIALS AND METHODS Bite splints were 3D-printed in either horizontal or vertical position (n = 10) using four different resins (Dental LT, Ortho Clear, Freeprint Splint, V-Splint). As control, ten bite splints were fabricated by CNC milling (ProArt CAD Splint). The splints were scanned and deviations between the CAD-file (trueness) and between each other within one group (precision) were measured by two different software applications and methods (cloud-to-cloud vs cloud-to-mesh). Data were analyzed using univariate analysis, Kolmogorov-Smirnov, Kruskal-Wallis, and Mann-Whitney U tests. RESULTS The highest impact on accuracy was exerted by the selection of the material (trueness: ηP2 = 0.871, P < 0.001; precision: ηP2 = 0.715, P < 0.001). Milled splints showed the highest trueness (P < 0.01) but not the highest precision at the same time. Horizontally positioned 3D-printed bite splints showed the least deviations in terms of trueness while vertical positioning resulted in the highest precision. The cloud-to-cloud method showed higher measured deviations than the other methods (P < 0.001–P = 0.002). CONCLUSION Milled splints show higher trueness than 3D-printed ones, while the latter reveal higher reproducibility. The calculated deviations vary according to the measurement method used. CLINICAL RELEVANCE In terms of accuracy, milled and 3D-printed bite splints seem to be of equal quality

epsilon-Caprolactone in Micro-Chambered Ceramic Beads - A New Carrier for Gentamicin

Purpose: The purpose of this preliminary and descriptive study was toevaluate a biodegradable drug delivery system in combination with aninnovative ceramic implant. Methods: The delivery of gentamicin ofstandardized samples was measured in the laboratory usingultra-high-performance liquid chromatography. Biocompatibility andbiodegradation of the materials was investigated in an animal experimentin sheep up to 14 months. As carrier epsilon-caprolactone, 1:1 mixedwith gentamicin, intruded into micro-chambered beta-tricalcium-phosphatebeads (MCB (R)) was studied. Results and Discussion: Gentamicin wasreleased in calculable concentrations during the first 30 days. Therelease from epsilon-caprolactone was higher than that frompolymethylmethacrylate and more predictable. The caprolactone carrierwas reabsorbed by osteoclasts

Transillumination and HDR Imaging for Proximal Caries Detection

The purpose of this study was to develop an in vitro model for the validation of near-infrared transillumination (NIRT) for proximal caries detection, to enhance NIRT with high-dynamic-range imaging (HDRI), and to compare both methods, using micro-computed tomography (mu CT) as a reference standard. Both proximal surfaces of 53 healthy or decayed permanent human teeth were examined using the Diagnocam (DC) (KaVo) and NIRT with HDRI (NIRT-HDRI). NIRT was combined with HDRI to improve the diagnostic performance by reducing under- and overexposed image areas. For NIRT-HDRI, an exposure series was captured and merged into a single HDR image. A classification was applied according to lesion depth. All surfaces were assessed twice by 2 trained examiners, and additionally with mu CT for validation. The Kappa statistic was used to calculate inter-rater reliability and agreement between DC and NIRT-HDRI. Inter-rater reliability (weighted Kappa, w) showed very good agreement for the DC (0.90) and NIRT-HDRI (0.96). The overall agreement (w) was almost perfect (0.85). In the individual categories (0 to 4), the agreement (simple Kappa) ranged from almost perfect (category 4) to moderate (1 and 2) to substantial (categories 0 and 3). Sensitivity and specificity of sound surfaces, enamel, and dentin caries ranged from 0.57 to 0.99 and were similar for both methods in the different categories. NIRT-HDRI had a higher sensitivity for sound surfaces and enamel caries, as well as a higher specificity for dentin caries. Regarding the obtained images, HDRI allowed for the detection of caries within a greater range of luminance levels, resulting in a more detailed visualization of structures without under- or overexposure. However, HDRI this did not improve the diagnostics significantly. Distinguishing between a processed demineralized enamel and dentin lesions appears to be a problem specific to NIRT and cannot be balanced using HDRI

Fracture load of 3D printed PEEK inlays compared with milled ones, direct resin composite fillings, and sound teeth

Objective!#!The objective of this in vitro study was to investigate fracture load, fracture types, and impact of chewing simulation of human molars restored with 3D printed indirect polyetheretherketone (PEEK) inlays and compare these with milled indirect PEEK inlays, direct resin composite fillings, and sound teeth.!##!Materials and methods!#!A total of 112 molars with form congruent class I cavities were restored with (n = 16/group) 3D printed indirect PEEK inlays via fused layer manufacturing (FLM): (1) Essentium PEEK (ESS), (2) KetaSpire PEEK MS-NT1 (KET), (3) VESTAKEEP i4 G (VES), (4) VICTREX PEEK 450G (VIC), (5) milled indirect PEEK inlays JUVORA Dental Disc 2 (JUV), and (6) direct resin composite fillings out of Tetric EvoCeram (TET). Sound teeth (7) acted as positive control group. Half of the specimens of each group (n = 8) were treated in a chewing simulator combined with thermal cycling (1.2 million × 50 N; 12,000 × 5 °C/55 °C). Fracture load and fracture types of all molars were determined. Statistical analyses using Kolmogorov-Smirnov test and two-way ANOVA with partial eta squared (η!##!Results!#!ESS and TET demonstrated the lowest fracture load with a minimum of 956 N, whereas sound molars showed the highest values of up to 2981 N. Chewing simulation indicated no impact (p = 0.132). With regard to Weibull modulus, KET presented a lower value after chewing simulation than JUV, whereas TET had the highest value without chewing simulation. All indirect restorations revealed a tooth fracture (75-100%), direct resin composite fillings showed a restoration fracture (87.5%), and 50% of the sound teeth fractured completely or had cusp fractures.!##!Conclusions!#!All 3D printed and milled indirect PEEK inlays as well as the direct resin composite fillings presented a higher fracture load than the expected physiological and maximum chewing forces.!##!Clinical relevance!#!3D printing of inlays out of PEEK via FLM provided promising results in mechanics, but improvements in terms of precision and esthetics will be required to be practicable in vivo to represent an alternative dental material

Comparison of novel and established caries diagnostic methods: a clinical study on occlusal surfaces

BACKGROUND The purpose of this prospective clinical diagnostic study with validation was to compare the diagnostic accuracy of near-infrared transillumination (NIRT), laser fluorescence measurement (LF), alternating current impedance spectroscopy (ACIS) and their combinations as adjunct methods to visual examination (VE) for occlusal caries detection using a hybrid reference standard. METHODS Ninety-six first and second non-cavitated permanent molars from 76 individuals (mean age 24.2) were investigated using (VE) (ICDAS) and bitewing radiography (BWR), as well as NIRT, LF and ACIS. The findings of BWR and NIRT were evaluated by two examiners while the other examinations were conducted by one calibrated dentist. The hybrid reference standard consisted of non-operative validation based on the results of VE and BWR and operative validation. Statistical analysis included cross-tabulations, calculation of sensitivity, specificity and area under the receiver operating characteristic curve at three diagnostic thresholds: caries in general, enamel caries and dentin caries. RESULTS NIRT, LF and ACIS exhibited high sensitivity for caries in general 1.00 (1.00-1.00), 0.77 (0.65-0.88), 0.75 (0.63-0.87)) and for dentin caries (0.97 (0.91-1.03), 0.76 (0.76-0.90), 0.64 (0.47-0.80). Sensitivity values for enamel caries were weak (0.21, 0.11, 0.37). Specificity values did not fall below 0.65 (NIRT) for all categories and methods, except for NIRT at the caries detection threshold (0.27). A combination of LF and ACIS with VE improved the diagnostic performance at the overall and the enamel caries threshold. The other methods showed fair to excellent discrimination at the overall caries threshold (NIRT 0.64, LF 0.89 and ACIS 0.86) and acceptable discrimination at the dentin caries threshold (NIRT 0.82, LF 0.81 and ACIS 0.79). AUROC for enamel caries exhibited the weakest discrimination. Accuracy was 65.6{\%} for VE, 69.8{\%} for BWR, 50.0{\%} for NIRT, 53.1{\%} for LF and 74.0{\%} for ACIS. Reliability assessment for BWR and NIRT showed at least substantial agreements for all analyses. CONCLUSIONS The methods, NIRT, LF and ACIS, revealed different potential but no impeccable performance for occlusal caries detection. All are suitable instruments to detect hidden carious lesion in dentin. As auxiliaries to VE, LF and ACIS showed an increase in diagnostic performance

Bioactivity of Dental Restorative Materials: FDI Policy Statement.

The term bioactivity is being increasingly used in medicine and dentistry. Due to its positive connotation, it is frequently utilised for advertising dental restorative materials. However, there is confusion about what the term means, and concerns have been raised about its potential overuse. Therefore, FDI decided to publish a Policy Statement about the bioactivity of dental restorative materials to clarify the term and provide some caveats for its use in advertising. Background information for this Policy Statement was taken from the current literature, mainly from the PubMed database and the internet. Bioactive restorative materials should have beneficial/desired effects. These effects should be local, intended, and nontoxic and should not interfere with a material's principal purpose, namely dental tissue replacement. Three mechanisms for the bioactivity of such materials have been identified: purely biological, mixed biological/chemical, or strictly chemical. Therefore, when the term bioactivity is used in an advertisement or in a description of a dental restorative material, scientific evidence (in vitro or in situ, and preferably in clinical studies) should be provided describing the mechanism of action, the duration of the effect (especially for materials releasing antibacterial substances), and the lack of significant adverse biological side effects (including the development and spread of antimicrobial resistance). Finally, it should be documented that the prime purpose, for instance, to be used to rebuild the form and function of lost tooth substance or lost teeth, is not impaired, as demonstrated by data from in vitro and clinical studies. The use of the term bioactive dental restorative material in material advertisement/information should be restricted to materials that fulfil all the requirements as described in the FDI Policy Statement

Full-length amelogenin influences the differentiation of human dental pulp stem cells

Background: Amelogenin is an extracellular matrix protein well known for its role in the organization and mineralization of enamel. Clinically, it is used for periodontal regeneration and, due to its finding also in predentin and intercellular spaces of dental pulp cells, it has recently been suggested for pulp capping procedures. The aim of this study was to analyse in vitro the effect of the recombinant human full-length amelogenin on the growth and differentiation of human dental pulp stem cells (hDPSCs). Methods: Human DPSCs were treated with a supplement of amelogenin at a concentration of 10 ng/ml, 100 ng/ml and 1000 ng/ml. The groups were compared to the unstimulated control in terms of cell morphology and proliferation, mineralization and gene expression for ALP (alkaline phosphatase), DMP1 (dentin matrix protein-1) and DSPP (dentin sialophosphoprotein). Results: Amelogenin affects hDPSCs differently than PDL (periodontal ligament) cells and other cell lines. The proliferation rate at two weeks is significantly reduced in presence of the highest concentration of amelogenin as compared to the unstimulated control. hDPSCs treated with low concentrations present a downregulation of DMP1 and DSPP, which is significant for DSPP (p = 0.011), but not for DMP1 (p = 0.395). Conclusions: These finding suggest that the role of full-length amelogenin is not restricted to participation in tooth structure. It influences the differentiation of hDPSC according to various concentrations and this might impair the clinical results of pulp capping

Dental practitioner recruitment for a randomized clinical trial in the field to evaluate the performance of a new glass ionomer restoration material

Background: In 2009, we began recruiting dental practitioners across Germany to participate in a clinical trial to evaluate the clinical performance of EQUIA, a new glass ionomer restoration material. The aim of this paper is to discuss the outcomes of the dental practitioner recruitment and outline the process of establishing a practice-based research network. Methods: Study proposals were sent to randomly selected dental offices in 29 cities in Germany. The proposals were sent until a minimum of 10 clinics in each city declared participation. Later on, briefing lectures informed the participating practitioners about the design, methods, and material application procedure. Participants were familiarized with the guidelines of Good Manufacturing Practice (GMP) and Good Epidemiological Practice (GEP). A questionnaire describing the characteristics of each dental office was filled out by the participating practitioner. Additionally, participation levels were characterized according to the socioeconomic status and geographic districts of residence in Germany (Regions 0 to 9). The associations between the characteristics were tested by the Kruskal-Wallis Test and Chi-squared test (P < 0.05). Results: A total of 3194 private dental clinics were invited, 1712 clinics refused to participate, 1195 did not respond to the invitation, and 323 agreed to participate. Only 144 clinics participated in the lectures held in their cities and signed the participation agreement. Based on their geographic location, the highest participation was in Region 2 with a participation rate of 14.3 %, and the lowest participation was in Region 6 with a participation rate of 1.7 %. Regions with the lowest rate of unemployment and relatively higher rates of income (Regions 7 and 8) had the highest rate of refusals (86 %). Conclusion: The initial results of the dental practitioner recruitment in this study suggest that the recruitment and pre-randomization design were successful, and by reaching out to a considerable number of private dental clinics to participate, we were able to recruit a smaller number of highly motivated dentists in this clinical study. Regional differences in socioeconomic status, practitioner specialization, and differences in patient health care insurance have to be considered when recruiting dental practitioners for clinical trials

Hypersensitivity in teeth affected by molar-incisor hypomineralization (MIH)

Tooth hypersensitivity is a common symptom in patients with molar-incisor hypomineralization (MIH). Therefore, this clinical study aimed to assess potential associations between patient- and tooth-related variables and the intensity of hypersensitivity in MIH-affected permanent teeth compared to healthy controls. Fifty-seven MIH patients and 20 healthy adolescents with a total of 350 MIH-affected and 193 healthy teeth were included in this study. The intensity of hypersensitivity was measured after cold air stimulation using the Schiff Cold Air Sensitivity Scale (SCASS) by the dentist and visual analogue scale (VAS) by the patient. Tooth hypersensitivity was low in non-MIH teeth (97.9% of the group had zero SCASS and VAS values). In contrast, MIH-affected teeth with demarcated opacities and atypical restorations had moderate SCASS and VAS values, whereas teeth with enamel breakdown were mostly linked to severe hypersensitivity. The logistic regression model confirmed a significantly lower level of hypersensitivity in MIH patients aged ≥ 8~years (OR 0.06, 95% CI 0.01-0.50, p = 0.009) and higher levels in molar teeth (OR 5.49, 95% CI 1.42-21.27, p = 0.014) and teeth with enamel disintegration (OR 4.61, 95% CI 1.68-12.63, p = 0.003). These results indicate that MIH-related tooth hypersensitivity seems to be present in disintegrated molars immediately after tooth eruption

epsilon-Caprolactone in Micro-Chambered Ceramic Beads - A New Carrier for Gentamicin

Purpose: The purpose of this preliminary and descriptive study was toevaluate a biodegradable drug delivery system in combination with aninnovative ceramic implant. Methods: The delivery of gentamicin ofstandardized samples was measured in the laboratory usingultra-high-performance liquid chromatography. Biocompatibility andbiodegradation of the materials was investigated in an animal experimentin sheep up to 14 months. As carrier epsilon-caprolactone, 1:1 mixedwith gentamicin, intruded into micro-chambered beta-tricalcium-phosphatebeads (MCB (R)) was studied. Results and Discussion: Gentamicin wasreleased in calculable concentrations during the first 30 days. Therelease from epsilon-caprolactone was higher than that frompolymethylmethacrylate and more predictable. The caprolactone carrierwas reabsorbed by osteoclasts