Enamel Remineralisation with a Novel Sodium Fluoride-Infused Bristle Toothbrush.

This study aims to investigate whether toothbrushes with fluoride-infused bristles have any (re)mineralisation effects on bovine enamel. Bovine incisors (N = 160) were extracted, and the buccal side of the crown was cut into dimensions of ~5 mm × 5 mm with a low-speed saw. These specimens were randomly allocated into four groups: half (80 teeth) were stored in demineralising solution (DM), and the other half were stored in deionised water (DW) for 96 h. Then, they were brushed with a force of 2.0 ± 0.1 N for five min with a manual toothbrush with either fluoride-infused (TF) or regular (TR) bristles. Microhardness (Vickers), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM) were used to investigate the surfaces of the bovine enamel specimens before and after brushing. Two-way ANOVA was used to analyse the hardness data, and the pairwise comparison method was used to analyse the Ca/P ratio, for each group at α = 0.05. The results show that brushing with either of these toothbrushes increased the Vickers microhardness on DM and DW enamel (p < 0.001), whereas hydroxyapatite was revealed in all groups by XRD. The DM samples showed a significant increase (p < 0.05) in the Ca/P ratios after brushing with TR and TF. Conversely, under DW conditions, these ratios decreased significantly after brushing. In terms of the F atomic%, TF increased significantly. SEM revealed mineral deposition in the DM groups after toothbrushing. To conclude, toothbrushing effectively induces the microhardness of sound and demineralised enamel, while fluoride-infused bristles might be able to retain fluoride on the enamel surface.

Design of Multi-Functional Bio-Safe Dental Resin Composites with Mineralization and Anti-Biofilm Properties.

This study aims to develop multi-functional bio-safe dental resin composites with capabilities for mineralization, high in vitro biocompatibility, and anti-biofilm properties. To address this issue, experimental resin composites consisting of UDMA/TEGDMA-based dental resins and low quantities (1.9, 3.8, and 7.7 vol%) of 45S5 bioactive glass (BAG) particles were developed. To evaluate cellular responses of resin composites, MC3T3-E1 cells were (1) exposed to the original composites extracts, (2) cultured directly on the freshly cured resin composites, or (3) cultured on preconditioned composites that have been soaked in deionized water (DI water), a cell culture medium (MEM), or a simple HEPES-containing artificial remineralization promotion (SHARP) solution for 14 days. Cell adhesion, cell viability, and cell differentiation were, respectively, assessed. In addition, the anti-biofilm properties of BAG-loaded resin composites regarding bacterial viability, biofilm thickness, and biofilm morphology, were assessed for the first time. In vitro biological results demonstrated that cell metabolic activity and ALP expression were significantly diminished when subjected to composite extracts or direct contact with the resin composites containing BAG fillers. However, after the preconditioning treatments in MEM and SHARP solutions, the biomimetic calcium phosphate minerals on 7.7 vol% BAG-loaded composites revealed unimpaired or even better cellular processes, including cell adhesion, cell proliferation, and early cell differentiation. Furthermore, resin composites with 1.9, 3.8, and 7.7 vol% BAG could not only reduce cell viability in S. mutans biofilm on the composite surface but also reduce the biofilm thickness and bacterial aggregations. This phenomenon was more evident in BAG7.7 due to the high ionic osmotic pressure and alkaline microenvironment caused by BAG dissolution. This study concludes that multi-functional bio-safe resin composites with mineralization and anti-biofilm properties can be achieved by adding low quantities of BAG into the resin system, which offers promising abilities to mineralize as well as prevent caries without sacrificing biological activity.

A Personalised 3D-Printed Dental Plaque Removal Mouthguard for Older Adults.

OBJECTIVES: The aim of the present study was to examine the plaque removal effectiveness of a personalised 3D-printed dental plaque removal mouthguard device in a clinical trial setting. METHODS: A personalised 3D-printed mouthguard was developed to clean dental plaque using micro-mist. A clinical trial was conducted to examine the plaque removal effectiveness of this device. The clinical trial recruited 55 participants (21 males and 34 females) with an average age of 68.4 years (range, 60-81 years). Dental plaque was dyed by plaque disclosing liquid (Ci). Turesky Modification of the Quigley-Hein Plaque Index (TMQHPI) was used to evaluate the level and rate of plaque formation on the tooth surface. The TMQHPI was recorded and intraoral photos were taken before and after mouthguard cleaning. The plaque removal rate was calculated based on TMQHPI and intraoral photos (pixel-based method) before and after cleaning. RESULTS: The personalised 3D-printed micro-mist injection mouthguard can be effective in dental plaque removal on tooth and gingiva, and the effectiveness lies between that of a manual toothbrush and a mouth rinse. The newly proposed pixel-based method can be a practical, high sensitive tool to evaluate the level of plaque formation. CONCLUSIONS: Under the conditions of the present study, we conclude that the personalised 3D-printed micro-mist injection mouthguard can be useful in reducing dental plaque and may be especially suitable for older adults and disabled people.

Guided Bone Regeneration in a Periodontally Compromised Individual with Autogenous Tooth Bone Graft: A Radiomics Analysis.

BACKGROUND: Autogenous tooth bone graft material (AutoBT) has been advocated as a bone substitute when conducting alveolar ridge preservation. This study is aimed at using a radiomics approach in order to evaluate and testify whether AutoBT can stimulate bone growth during socket preservation in severe periodontal cases. MATERIALS AND METHODS: For this study, 25 cases with severe periodontal diseases were selected. The patients' AutoBTs were inserted into the extraction sockets and covered with Bio-Gide® collagen membranes. 3D CBCT scans and 2D X-rays were taken of the patients before surgery and after 6 months post-surgery. For the retrospective radiomics analysis, the maxillary and mandibular images were compared in different groups. Maxillary bone height was analyzed at the buccal, middle, and palatal crest sites, while the mandibular bone height was compared at the buccal, center, and lingual crest sites. RESULTS: In the maxilla, the alveolar height was increased by -2.15 ± 2.90 mm at the buccal crest; -2.45 ± 2.36 mm at the center of the socket, and -1.62 ± 3.19 mm at the palatal crest, while the height of the buccal crest was increased by 0.19 ± 3.52 mm, and the height at the center of the socket was increased by -0.70 ± 2.71 mm in the mandible. The three-dimensional radiomics analysis demonstrated significant bone growth in the local alveolar height and high density. CONCLUSION: Based on clinical radiomics analysis, AutoBT could be used as an alternative bone material in socket preservation after tooth extraction in patients with severe periodontitis.

Effect of roughness and acidic medium on wear behavior of dental resin composite.

BACKGROUND: The aim of the study was to investigate whether the citric acid and rough surface have a synergistic effect leading to severe wear behavior of resin composite. MATERIALS AND METHODS: Disk-shaped (Ø15 × 1.5 mm) specimens of resin composite (n = 12) with different initial roughness were prepared. Reciprocating ball-on-flat wear tests were performed under distilled water and citric acid (pH = 5.5) respectively. The coefficient of friction (COF), wear volume loss, and duration of the running-in period were quantified to assess the wear performance. And the values were analyzed with one-way ANOVA (α = 0.05). Regression analysis was applied to examine the influence of Ra values and mediums on the wear data. The wear morphology was analyzed by scanning electron microscopy and a 3D profilometer. RESULTS: The average COF was higher in distilled water than in citric acid but was independent of the surface roughness. For the composite, the volume loss of worn area and running-in period increased with surface roughness when tested under distilled water. However, these increasing trends were not found in citric acid. All specimens exhibited mild wear behavior with low COF and less superficial abrasion in acidic medium. CONCLUSIONS: The effect of initial roughness on wear behavior depends on the medium. In distilled water, resin composites with high initial roughness exhibit a longer running-in time, which eventually leads to a significant increase in material loss. The adverse effects of high roughness can be alleviated by the lubrication of citric acid, which can maintain a mild wear behavior regardless of initial surface roughness.

Biocompatibility and mechanical properties of an experimental E-glass fiber-reinforced composite for dentistry.

Objectives: To evaluate the biocompatibility and mechanical properties of experimental bis-phenol-A and bis-GMA free E-glass fiber-reinforced composites (FRCs) prepared with hexanediol dimethacrylate (HDDMA) based resin. Methods: Two ratios of HDDMA/TEGDMA resin were evaluated: exp-1 (70/30 wt.%) and exp-2 (50/50 wt.%) with two bis-GMA resin control groups (bis-GMA/MMA and bis-GMA/TEGDMA resins, both 70/30 wt.%). E-glass fibers were embedded into the resins to prepare FRCs specimens. Biocompatibility was assessed for cytoviability and biofilm formation with Streptococcus mutans, Streptococcus sanguinis, Enterococcus faecalis, and Candida albicans. Mechanical properties were evaluated for flexural strength and hardness (24 h, water storage 1 and 28 days), water sorption (1, 7, 14, and 28 days), contact angle, and surface roughness. The data were analyzed statistically by one-way and two-way ANOVA (p < 0.05). Results: Cytoviability of the experimental groups was significantly higher than the control groups (p < 0.05). The exp-1 cytoviability (98.2 ± 1.3%) met the ISO 10993-5 standard requirement for noncytotoxic materials. The adherence of bacteria to the experimental FRCs was visibly less than the controls, while Candida albicans adhered visibly more to the experimental groups than the controls (p < 0.05). Flexural strength showed slightly higher values for controls than for the experimental groups. The exp-1 hardness value was significantly higher in the control groups for all storage conditions (p < 0.05). The water sorption of the experimental groups was significantly higher than the controls. The surface roughness indicated no significant difference (p = 0.87). The exp-1 showed a higher contact angle with the control groups. Conclusion: The experimental HDDMA/TEGDMA-based FRCs might be potential alternatives for bis-GMA-based FRCs. Clinical significance: The HDDMA/TEGDMA E-glass FRCs might provide biocompatible restorations.

Experimental determination of the contact pressures produced by a nasal continuous positive airway pressure mask: A case study.

BACKGROUND: A continuous positive airway pressure (CPAP) mask is a respiratory ventilation method used for treating breathing disorders including respiratory failure and obstructive sleep apnoea (OSA). The forces applied by a CPAP mask may affect facial development and lead to pressure ulcers. In an experimental setting, the magnitude and the distribution of the contact pressures developed by a CPAP mask on the face were investigated for providing information aiming at optimizing the design of the device. MATERIALS AND METHODS: A nasal CPAP mask with forehead support was placed via its headgear straps on a rigid phantom head and then a controlled load was incrementally applied via a mechanical testing system (5848 Micro Tester, Instron), up to 4 maximum levels of exerted force, namely 5 N, 10 N, 15 N, and 20 N. Real-time pressure mapping was realized by means of sensor matrixes (I-Scan System, Tekscan) applied on the facial surface in four regions (forehead, nasal bridge, zygoma, and maxilla). The data were then transferred on a virtual model created by 3D scans of both the CPAP mask and the phantom head used in the experiments. RESULTS: At increasing applied force, increases in average contact pressure were present at the zygomatic region (1-8 kPa), nasal bridge (12-14 kPa), and forehead (13-29 kPa), while the maxillary region showed relatively stable values (9 kPa). Despite the overall increase in average contact pressure with increasing applied force, no direct proportionality was present. Contact areas did not show clear increments, despite force may redistribute on a larger area, as sensors did not cover the entire mask perimeter. Peak contact pressure values were somehow affected by pressure concentrations that led to saturation in some areas of the sensors (up to 2% of the sensels). CONCLUSIONS: The CPAP mask exerts pressures that may be not uniformly distributed on the face of a subject. This information underlines the clinical importance of assessing both the pressure exerted and the areas that are interested by the mask contact, so as to optimise the CPAP masks design for obtaining a good compromise between ventilation performance and reduction of possible side effects on living tissues.

Midpalatal suture maturation staging using cone beam computed tomography in patients aged between 9 to 21 years.

Midpalatal suture was analysed with cone beam computed tomography to identify its maturation with respect to age and maxillary-complex growth in 72 patients 9- to 21-year-old. Maxillary-complex was divided in premaxillary, maxillary, and palatine segment. Interdigitation and ossification of midpalatal suture, its density relative to hard tissues and soft tissues, and midpalatal suture density ratio were measured for each segment. Correlation of each parameter with age and maxillary-complex length was analysed, and classification trees were developed for staging parameters. Midpalatal suture maturation stages (MPSMS, from A to E) were applied to assess relationship with age and maxillary-complex length. Regarding age, ossification increased in maxillary segment of males (rS = 0.39, p = 0.032), while suture density relative to soft tissues increased in maxillary (rS = 0.37, p = 0.042) and palatine segments (rS = 0.41, p = 0.027) of males and in palatine segment of females (rS = 0.32, p = 0.041). In males, suture density relative to soft tissues discriminated two age-stages (p = 0.024), and the same parameter (p = 0.023) paired with ossification (p = 0.027) discriminated two length-stages. MPSMS identified length-differences between stage A and B in females (p = 0.001). Midpalatal-suture ossification and its density relative to soft tissues showed some relationship with age and maxillary-complex length, especially in males. However, challenging staging and limitations in the imaging method may limit clinical applications.

A biomimetic approach to evaluate mineralization of bioactive glass-loaded resin composites.

PURPOSE: This study explores novel solutions other than standard SBF for biomimetic evaluations of mineralization particularly for resin composites containing bioactive glass (BAG). METHODS: Experimental UDMA/TEGDMA resin composites with 0.0, 1.9, 3.8 or 7.7 vol% of 45S5 BAG fillers were prepared. Besides simulated body fluid (SBF) as control, the specimens were immersed in three other solutions either with bicarbonate which are Hank's balanced salt solution (HBSS) and cell culture medium (MEM), or without bicarbonate which is a novel Simple HEPES-containing Artificial Remineralization Promotion (SHARP) solution, for 3, 7 and 14 days. These solutions were then analyzed by ICP-OES and pH meter, and the surfaces of the BAG composites were analyzed by SEM, XRD and FTIR. RESULTS: ICP-OES revealed Ca and P concentration continuously decrease, while Si concentration increases with time in the solutions other than SBF, which showed almost unchanged elemental concentration. Only SHARP solution is able to maintain a constant pH over the immersion time. SEM, together with XRD and FTIR, showed nano-sized octacalcium phosphate (OCP) nanospheres formation on 3.8 and 7.7 vol% BAG composites after 14 days immersion in HBSS (500-600 nm) and MEM (300-400 nm). SHARP solution enabled OCP formation after 3 days and then self-assembled into urchin-like carbonated hydroxyapatite (CHA) microspheres encompassed with nanorods of 100 nm width and 8 µm length after 14 days of immersion for 7.7 vol% BAG composites. CONCLUSION: This study suggests SHARP solution can evaluate mineralization biomimetically whereas CHA microspheres can be formed on BAG-containing resin composites.

Does the geometry of scan bodies affect the alignment accuracy of computer-aided design in implant digital workflow: An in vitro study?

OBJECTIVES: To compare 2 implant scan bodies with different geometry on the accuracy of the virtual alignment process in the digital workflow. MATERIALS AND METHODS: A master model of the edentulous maxilla with 6 implants and multiunit abutments (MUA) inserted was fabricated. Six dome-shaped and cuboidal scan bodies were mounted on the MUAs, respectively, and consecutively scanned by a laboratory scanner 10 times. The original scans were imported to a dental-specific CAD software and virtually aligned with the default CAD model in the implant library. Thus, 10 aligned models were created. Both the original scans and the aligned models were evaluated by an inspection software for deviation of the scan body surfaces, the centroids of scan body and MUA, the scan body center-axis, and the inter-MUA distances/angles. The two-sample T-test/Mann-Whitney U test were used to analyze the data with the level of significance set at 0.05. RESULTS: The cuboidal group showed significant greater deviations of the model surface (13.9 µm vs. 10.7 µm) and the MUA centroids (31.7 µm vs. 22.8 µm) but smaller deviation of the inter-MUA angle (0.047° vs. 0.070°) than those of the dome-shaped group (p < .05). No significant differences in the deviation of scan body centroids, center-axis, and the inter-MUA distances between the 2 groups were found. CONCLUSIONS: Virtual alignment of implant scan body affected the accuracy of the digital workflow for complete-arch implant-supported prostheses (up to ~30 µm/0.09°). Different geometries of the implant scan body could also influence the transfer accuracy in the CAD process.

Soft robotic manipulator for intraoperative MRI-guided transoral laser microsurgery.

Magnetic resonance (MR) imaging (MRI) provides compelling features for the guidance of interventional procedures, including high-contrast soft tissue imaging, detailed visualization of physiological changes, and thermometry. Laser-based tumor ablation stands to benefit greatly from MRI guidance because 3D resection margins alongside thermal distributions can be evaluated in real time to protect critical structures while ensuring adequate resection margins. However, few studies have investigated the use of projection-based lasers like those for transoral laser microsurgery, potentially because dexterous laser steering is required at the ablation site, raising substantial challenges in the confined MRI bore and its strong magnetic field. Here, we propose an MR-safe soft robotic system for MRI-guided transoral laser microsurgery. Owing to its miniature size (Ø12 × 100 mm), inherent compliance, and five degrees of freedom, the soft robot ensures zero electromagnetic interference with MRI and enables safe and dexterous operation within the confined oral and pharyngeal cavities. The laser manipulator is rapidly fabricated with hybrid soft and hard structures and is powered by microvolume (<0.004 milliter) fluid flow to enable laser steering with enhanced stiffness and lowered hysteresis. A learning-based controller accommodates the inherent nonlinear robot actuation, which was validated with laser path-following tests. Submillimeter laser steering accuracy was demonstrated with a mean error < 0.20 mm. MRI compatibility testing demonstrated zero observable image artifacts during robot operation. Ex vivo tissue ablation and a cadaveric head-and-neck trial were carried out under MRI, where we employed MR thermometry to monitor the tissue ablation margin and thermal diffusion intraoperatively.

Influence of material type, thickness and storage on fracture resistance of CAD/CAM occlusal veneers.

OBJECTIVES: The present study aimed to evaluate the effect of restoration thickness, CAD/CAM material, and 6 months of artificial saliva storage on the fracture resistance of occlusal veneers. MATERIALS AND METHODS: A total of 84 intact maxillary molars were sectioned 4.0 mm occlusal to the cementoenamel junction to expose the dentine. The teeth were assigned into 3 main groups according to the type of restorative material (e.max CAD, Vita Enamic, and Lava Ultimate). In each group, the teeth were allocated into 2 subgroups (n = 14) according to restoration thickness (1.0 and 1.5 mm). The veneers were adhesively bonded using dual-cure self-adhesive luting agent. A total of 42 specimens comprising half the tested subgroups were stored in distilled water for 24-h before the test. The remaining half was stored in artificial saliva at 37 ± 1 °C in an incubator for 6 months. All specimens (n = 84) were subjected to 5000 thermal cycles between 5 and 55 °C ± 2 before the fracture resistance test. The maximum force at fracture was recorded in Newton. Failure mode was analyzed using a stereomicroscope. The results were analyzed using a parametric Three-way ANOVA test. RESULTS: The results of the Three-way ANOVA test revealed that material type and restoration thickness significantly affected fracture resistance values (p < 0.5), while 6 months of storage in artificial saliva had no significant effect on mean fracture resistance values (p˃0.5). The most common failure patterns in CAD/CAM resin composite and polymer-infiltrated ceramics were scores I and score II. For glass ceramic groups, score IV and III were more dominant. CONCLUSIONS: All the tested CAD/CAM restorations in both thicknesses exhibited fracture resistance values exceeding normal and parafunctional bite forces. Polymer-infiltrated ceramics and CAD/CAM resin composite veneers showed more favorable fracture patterns.

The Human Bone Collection of the Faculty of Dentistry at the University of Hong Kong: History and description of cranial and postcranial skeletal remains.

OBJECTIVES: The present work describes the status and contents of The Human Bone Collection of the Faculty of Dentistry at the University of Hong Kong. MATERIALS AND METHODS: The Collection originates from the 1980s and became officially established in 2017 for teaching and research purposes. Most of the Collection consists of unclaimed human remains of southern Chinese individuals exhumed from local cemeteries and donated to the Faculty in the last few decades. The demographic information was provided largely from burial records and forensic estimations. Since 2016, the Collection has undergone a process of reorganization into cranial and postcranial remains, followed by preservation procedures that included cleaning and classification. RESULTS: The Collection currently consists of remains belonging to about 368 individuals (243 males, 54 females, 71 unknown), with ages ranging from 0.8 to 90 years (mean 57.4 years). It comprises cranial remains belonging to 260 individuals (169 males, 39 females, 52 unknown), and postcranial remains belonging to 248 individuals (180 males, 42 females, 26 unknown). The preservation status ranges from poor to good, with the cranial remains better preserved than the postcranial elements. For a large number of individuals, ear ossicles, soil samples, and other materials are also available. DISCUSSION: The Collection is accessible to local and international institutions for teaching and research.

Dry Skulls and Cone Beam Computed Tomography (CBCT) for Teaching Orofacial Bone Anatomy to Undergraduate Dental Students.

Learning bone anatomy of the skull is a complex topic involving three-dimensional information. The impact of the use of human dry skulls and cone beam computed tomography (CBCT) imaging was investigated in the teaching of undergraduate dental students. Sixty-four first-year students in the University of Hong Kong were randomly divided into eight groups. Four teaching methods were tested: (1) CBCT followed by standard lecture, (2) CBCT followed by lecture with skulls, (3) standard lecture followed by CBCT, and (4) lecture with skulls followed by CBCT. After each, students were given a multiple-choice questionnaire to assess their objective learning outcome (20 questions) and a questionnaire for their subjective satisfaction (10 statements). Surveys were assessed with Cronbach's alpha, Kendall's tau-b, and principal components analysis. Data were analyzed with Student's t-test and a one-way ANOVA (significance α = 0.05). Standard lecture followed by CBCT showed the highest learning outcome score (81.6% ± 14.1%), but no significant difference was present among four teaching methods. Cone beam computed tomography followed by lecture with skulls scored the highest overall subjective satisfaction (4.9 ± 0.8 out of 6), but no significant difference was present among teaching methods. Nevertheless, students' perception of learning was positively influenced by the use of skulls (P = 0.018). The timing of administration of the CBCT did not affect students' subjective satisfaction or objective learning outcome. Students perceived to learn more by using skulls, but their objective learning outcomes were not significantly affected. A discrepancy seems to exist between students' perception of learning and their effective performance.

Current status and research trends of lithium disilicate in dentistry: A bibliometric analysis.

STATEMENT OF PROBLEM: Lithium disilicate (LD) is a popular dental ceramic and has been a focus of dental research. Nevertheless, a quantified literature analysis focusing on the research of lithium disilicate is lacking. PURPOSE: The purpose of this bibliometric analysis was to review the progress of research into lithium disilicate in dentistry, including the identification of contributing researchers, organizations, countries or regions, journals, and the analysis of high-impact keywords and research trending. MATERIAL AND METHODS: The search was carried out within the topic field of the Web of Science (WoS) database, collecting publications related to LD from between 1996 and 2019. Metadata including the titles, abstracts, keywords, authors, affiliations, countries or regions, and references were extracted. Bibliometric indicators in terms of documents, authors, journals, and keywords were analyzed. RESULTS: Between 1996 and 2019, the dental research on LD trended upward. Scholars in the United States, Germany, Switzerland, and Brazil actively participated in the research on LD, and publications from the United States had the most citations. The Journal of Prosthetic Dentistry and Dental Materials were the major contributing journals. High-impact terms could be categorized into types of restorative material, types of prostheses, and properties or techniques of materials. Co-occurrence and relative normalized citation analysis of keywords highlighted several research interests, such as comparison studies between LD and zirconia, computer-aided design and computer-aided manufacturing (CAD-CAM) techniques, and the performance of complete coverage LD restorations. CONCLUSIONS: With the global upsurge in research on lithium disilicate, extensive collaborations and citations have been noted among authors, institutions, and countries or regions. Research hotspots include types of restorative material, types of prostheses, and properties or techniques of materials.

Implant framework misfit: A systematic review on assessment methods and clinical complications.

BACKGROUND: The fit of implant-supported prostheses is of prime importance for the long-term success of implant therapy. PURPOSE: This systematic review aimed to evaluate recent evidence on current techniques for assessing implant-framework misfit, its associated strain/stress, and whether these misfits are related to mechanical, biological, and clinical consequences. MATERIALS AND METHODS: An electronic search for publications from January 2010 to October 2020 was performed using the Pubmed, Embase, Web of Science, and Cochrane Library databases with combined keywords on implant-framework misfit assessments and related clinical complications. Inclusion and exclusion criteria were applied. After full-text analyses, data extraction was implemented on current techniques of misfit assessment and the relationship between the misfit and the induced strain/stress. RESULTS: A total of 3 in vivo and 92 in vitro studies were selected, including 47 studies on quantifying the degree of implant-framework misfit with dimensional techniques, 24 studies measuring misfit-induced strain/stress with modeling techniques, and 24 studies using both methods. The technical details, advantages, and limitations of each technique were illustrated. The correlation between the implant-framework misfit and the induced strain/stress has been revealed in vitro, while that with the biological complications and implant/prostheses failure was weak in clinical studies. CONCLUSIONS: Dimensional and modeling techniques are available to measure the implant-framework misfit. The passivity of implant-supported fixed prostheses appeared related to the induced strain/stress, but not the clinical complications. Further studies combining three-dimensional (3D) assessments using dimensional and modeling techniques was needed.

Anteroposterior length of the maxillary complex and its relationship with the anterior cranial base.

OBJECTIVES: To use both absolute anteroposterior maxillary complex length (APMCL) and relative APMCL to investigate the relationship between the maxillary complex, its individual bony segments, and their association to the anterior cranial base. In addition, the relationship between length and position of the maxillary complex was analyzed. MATERIALS AND METHODS: Sixty human skulls were analyzed using cone beam computed tomography. The maxillary complex length was measured between anterior and posterior nasal spine (ans-pns), and the average was used as the cut-off to identify a high- and a low-length group based on absolute APMCL. The length ratio between the maxillary complex and the anterior cranial base (ans-pns/SN) was used to identify the two groups based on relative APMCL. The anterior cranial base length and the lengths of the maxillary complex bones were compared between the high- and low-length groups. RESULTS: Based on absolute APMCL, individuals with shorter maxillary complex had shorter anterior cranial base (P = .003), representing normal proportions. Based on relative APMCL, individuals with shorter maxillary complex had longer anterior cranial base and vice versa (P = .014), indicating disproportions. Individuals with shorter maxillary complex exhibited shorter maxilla (Δ = -1.5 mm, P = .014). CONCLUSIONS: When skeletal deformity of the midface is suspected, individual disproportions in the anteroposterior length of the maxillary complex in relation to the anterior cranial base (relative measurements) should be assessed through radiological imaging. A shorter maxillary complex may be associated with a shorter maxilla, and not with a shorter premaxilla or palatine bone.

Fracture resistance of CAD/CAM occlusal veneers: A systematic review of laboratory studies.

OBJECTIVE: The purpose of this systematic review was to summarize scientific evidence that evaluates in vitro fracture and fatigue strength of occlusal veneers in different thicknesses, CAD/CAM materials, and under different aging methodologies. MATERIALS AND METHODS: An electronic search of 3 English databases (The National Library of Medicine (MEDLINE/PubMed), ScienceDirect, and EBSCOhost) was conducted. Laboratory studies published between September 2009 and October 2019 that evaluated fracture or fatigue strength of CAD/CAM occlusal veneers and used human teeth were selected. The included studies were individually evaluated for the risk of bias following a predetermined criterion. The outcomes assessed included the types of the restorative material, the thickness of the veneers, and aging methods. RESULTS: A total of 12 studies fulfilled the inclusion criteria. Most of the included studies (86%) evaluated the fracture strength of occlusal veneers. Two studies evaluated fatigue resistance. There was a significant relationship between the choice of materials and fracture strength. Polymeric materials performed better in fatigue testing in comparison to ceramics. Lithium silicate-based glass ceramics showed more favorable outcomes in a thickness of 0.7-1.0 mm. Fracture resistance values in all the included studies exceeded maximum bite forces in the posterior region. CONCLUSIONS: The outcomes of this systematic review suggest that occlusal veneers can withstand bite forces in the posterior region, whereas the measurement of thickness should be standardized in order to have a fair comparison. Further research needs to be conducted to evaluate the longevity of this type of restorations clinically.

A nanostructured anti-biofilm surface widens the efficacy against spindle-shaped and chain-forming rod-like bacteria.

Current control of pathogenic bacteria at all biomaterial interfaces is poorly attuned to a broad range of disease-causing pathogens. Leading antimicrobial surface functionalization strategies with antimicrobial peptides (AMPs), defensins, have not shown their promised efficacy. One of the main problems is the lack of stability and swift clearance from the surface. Surface nanotopography bearing sharp protrusions is a non-chemical solution that is intrinsically stable and long-lasting. Previously, the geometrically ordered arrays of nanotipped spines repelled or rapidly ruptured bacteria that come into contact. The killing properties so far work on cocci and rod-like bacteria, but there is no validation of the efficacy of protrusional surfaces on pathogenic bacteria with different sizes and morphologies, thus broadening the utility of such surfaces to cover increasingly more disease entities. Here, we report a synthetic analogue of nanotipped spines with a pyramidal shape that show great effectiveness on species of bacteria with strongly contrasting shapes and sizes. To highlight this phenomenon in the field of dental applications where selective bacterial control is vital to the clinical success of biomaterial functions, we modified the poly(methyl)-methacrylate (PMMA) texture and tested it against Streptococcus mutans, Enterococcus faecalis, Porphyromonas gingivalis, and Fusobacterium nucleatum. These nanopyramids performed effectively at levels well above those of normal and roughened PMMA biomaterials for dentistry and a model material for general use in medicine and disease transmission in hospital environments.

An introduction of biological performance of zirconia with different surface characteristics: A review.

Zirconia (ZrO2) ceramic is widely used in dentistry as a clinical dental biomaterial. In this review, we are focusing on and summarizing the biological performance of zirconia under different surface characteristics. We have included an initial tissue cell attachment study on zirconia and bacterial adhesion on zirconia. Our results suggest that surface modifications applied on zirconia may change the interfacial surface characteristics e.g. surface roughness, surface free energy, and chemistry of zirconia. The modifications also result in advanced biological performance of zirconia, including enhanced tissue cell attachment and reduction of bacterial adhesion. The recent laboratory research has provided many interesting modification methods and showed clinically interesting and promising outcomes. A few of the outcomes are validated and have been applied in clinical dentistry.