The use of artificial intelligence and game-based learning in removable partial denture design: A comparative study.

PURPOSE: The purpose of this study was to compare student performance in removable partial denture (RPD) design during a pre-clinical RPD course with and without using a recently developed computer software named AiDental. Additionally, student perceptions associated with the use of this software were assessed. METHODS: The AiDental software consists of a learning environment containing an RPD design system that automatically designs RPDs based on the user's input. The software also contains an RPD game component that compares the user's RPD Design to an automatically generated RPD ideal design. The study was conducted in two phases. In phase one, pre-clinical second-year dental students who participated in the study were randomly divided into two groups: The AiDental group with AiDental software access (n = 36), and the conventional group without software access (n = 37). Both groups received conventional RPD instruction and practice, however, the AiDental group had additional access to the AiDental software. After 2 weeks, both groups took a mock practical test, which was collected and graded by the principal investigator (PI). The PI was blinded from group assignment and no identifying information was used in the mock practical. In phase two, all students were granted access to the AiDental software for the remainder of the pre-clinical course duration. At the conclusion of the course, all students were given a survey to evaluate their perceptions of the AiDental software. Descriptive statistics were calculated and analyzed. Variables related to perceptions of both the AiDental designer and game were assessed using Spearman's rank correlation test, the chi-square test, Fisher's exact test, and the non-parametric Wilcoxon rank-sum test as appropriate. In addition, a thematic analysis of the responses to the optional comments section was conducted using the Braun and Clarke method. RESULTS: Phase one results showed that subjects in the AiDental group were more likely than subjects in the conventional group to receive a final grade of A or B. Phase two results showed generally favorable student perceptions towards the software, and additionally, the results showed that age was significantly negatively correlated with ease of use of the software, improving decision-making, and critical thinking relative to RPD design choices. However, no correlation between age and using the software as a reference were noted. CONCLUSIONS: The use of AiDental's automated feedback and gamification techniques in RPD education had a positive effect on student grades and it was well-liked by students. Thus, the results suggest that AiDental has the potential to be a useful adjunct to pre-clinical teaching.

A comparison of pre-clinical instructional technologies: Natural teeth, 3D models, 3D printing, and augmented reality.

PURPOSE/OBJECTIVES: To assess student perceptions on learning dental anatomy using natural extracted teeth, 3D printed models, 3D virtual models, and augmented reality (AR) technology.  METHODS: Eighty first-year dental students enrolled in the dental anatomy course were instructed to examine four stations. The stations included four versions of a mandibular first molar: an extracted natural tooth, a 3D printed model, a 3D virtual model, and a model displayed on a novel AR device. After examining all stations, the students were asked to complete an electronic survey. Bivariate analysis was performed to determine whether students' perceptions are related to their demographic characteristics and technological experience with computer use, 3D modeling, and video games.  RESULTS: Seventy students completed the survey (87.5% response rate). Students rated natural teeth to have the highest educational value, the 3D printed tooth to be the most accessible, and the AR application to be the most interesting modality. Students who played little to no video games were more likely to rate AR as high educational value (48.8% vs. 10.3%; p < 0.001), while students with little 3D modeling experience were more likely to rate high accessibility of the 3D Model (78.1% vs. 48.3%; p < 0.001). No statistically significant associations between the perceptions and students' demographic characteristics or use of computer were noted. CONCLUSION: The natural extracted tooth was rated highest in educational value, while the 3D printed model was rated easiest to use, and the AR model was the most interesting to the students.

Enhancing Student Learning in Removable Partial Denture Design by Using Virtual Three-Dimensional Models Versus Traditional Two-Dimensional Drawings: A Comparative Study.

PURPOSE: To compare the use of virtual 3D casts as an alternative to paper-based exercises in preclinical removable partial denture (RPD) design in terms of student outcomes (as evidenced by exercise evaluation scores), as well as student attitudes related to the 2 formats. The first hypothesis of this study is that virtual 3D digital models in the exercise will result in better student outcomes as evidenced by the final exercise score compared to the 2D drawings. The second hypothesis is that virtual 3D digital models in the exercise will result in greater student acceptance compared to the 2D drawings. MATERIALS AND METHODS: Students were divided into 2 equal, randomly assigned groups Both groups were made to solve 2 exercises: a class II exercise and a class IV exercise. Group 1 received the first exercise (exercise #1) as a Kennedy class IV design exercise in virtual 3D and the second exercise (exercise #2) as a Kennedy class II design exercise in traditional format. Group 2 would receive the opposite exercise #1 as a Kennedy class IV in traditional format and exercise #2 as a Kennedy class II in virtual 3D format. Virtual 3D casts were made to be identical to the traditional exercises. Students were then asked to complete a short survey to assess their preferences. The Wilcoxon Rank Sum test was used to compare the distribution of scores of exercises using the virtual 3D format with the scores when students used the traditional 2D format. Preference comparisons for the 2 formats were accomplished using exact binomial tests. RESULTS: There was no difference in learning outcomes based on the distribution of student scores for either exercise independent of presentation format (p > 0.52). There was also no difference in individual student score between 2 identical exercises, independent of whether the exercise was using 3D virtual models or 2D drawings. A greater proportion of students agreed with the statements that favored the use of the virtual 3D models than disagreed with respect to all 7 questions asked, based upon the sign test (comparing agreement vs. disagreement with the statement, p < 0.0003 in all instances). CONCLUSION: Despite there being no difference in learning outcomes (final scores), the students showed an overwhelming preference in having the virtual 3D casts part as part of the curriculum.

Enhancing Student Learning of Removable Prosthodontics Using the Latest Advancements in Virtual 3D Modeling.

When educating dental students or prosthodontic residents, a picture can be worth a thousand words. If that is so, then what could enhanced 3D modeling be worth relative to enhancing student learning? The answer is undoubtedly more than what a picture can provide. That is why the use of 3D models has become increasingly common with respect to patient care. The 3D modeling allows the patient to visualize more clearly the proposed treatments and outcomes; however, while 3D modeling has started to make an appearance in dental education, many of the current 3D modeling techniques do not offer the flexibility needed for dental education and enhanced student learning. At the University of Iowa, the use of 3D modeling software has enabled the creation of 3D models that can be altered or customized to be used in a more flexible way to teach students in the arts and complexities of removable partial denture (RPD) design and associated components. This educational technique article will: (1) demonstrate how these 3D models can be used to enhance student perception and learning regarding RPDs; and (2) will demonstrate using videos and web-based portals to show how the 3D RPD models were created and then used for educational purposes.

The Use of 3D Printed Tooth Preparation to Assist in Teaching and Learning in Preclinical Fixed Prosthodontics Courses.

Tooth preparation for fixed dental prostheses is not an easy procedure to understand spatially, especially for first-year dental students. This technical report describes an innovative technique for assisting learning in preclinical fixed prosthodontics courses. Ideal full-contour tooth preparations are digitally scanned and 3D printed to the exact specifications of the ideal preparation. Students and faculty use these printed tooth preparations as teaching and learning tools to facilitate in 3D visualization for fixed prosthodontics courses.

Outcomes mapping: a method for dental schools to coordinate learning and assessment based on desired characteristics of a graduate.

This project, utilizing a seldom-used approach to dental education, was designed to define the desired characteristics of a graduating dental student; convert those characteristics to educational outcomes; and use those outcomes to map a dental school's learning and assessment programs, based on outcomes rather than courses and disciplines. A detailed rubric of the outcomes expected of a graduating dental student from this school was developed, building on Commission on Dental Accreditation (CODA) standards and the school's competencies. The presence of each characteristic in the rubric was mapped within and across courses and disciplines. To assess implementation of the rubric, members of two faculty committees and all fourth-year students were asked to use it to rate 1) the importance of each characteristic, 2) the extent to which the school teaches and assesses each, and 3) the extent to which each counts toward overall assessment of competence. All thirty-three faculty members (100 percent) on the committees participated, as did forty-six of the fifty-five students (84 percent). The groups gave high scores to the importance of each characteristic, especially for knowledge and technical competence (then separate categories but merged in the final rubric) and for self-assessment, as well as the extent to which they are being taught and assessed. Respondents most commonly named critical thinking as the area that should be emphasized more. Mapping the curriculum and creating its related database allow the faculty and administration to more systematically coordinate learning and assessment than was possible with a course-based approach.

Retaining new dentists in Iowa: a role for dental schools in facilitating graduates' connections to practice opportunities in underserved areas.

Like many other states, Iowa has an aging dental workforce. As this aging population of dentists retires and communities are unable to find new dentists to take over their practices, more small and rural communities lack easy access to oral health care. The University of Iowa College of Dentistry and Dental Clinics established the Office of Iowa Practice Opportunities in 2006 to promote dental practice opportunities in Iowa for its graduates. With this office, an infrastructure connecting the college with practices and communities across the state has been developed. The Office of Iowa Practice Opportunities is the first place many students go to decide what they will do after graduation and to identify practice opportunities in Iowa. The office has exceeded the college's initial expectations and has provided significant assistance in retaining recently graduated dentists in the state of Iowa and ensuring access to oral health care in the state. This article will show that facilitating connections to practice opportunities has a place in a college of dentistry.

In vitro analysis of post-fatigue reverse-torque values at the dental abutment/implant interface for a unitarian abutment design.

PURPOSE: This study analyzed baseline and post-fatigue reverse-torque values (RTVs) for a specific brand control abutment relative to a third party compatible abutment. The purpose of this study was to compare the abutments' fatigue resistance to simulated function, using RTVs as an indication of residual preload at the implant/abutment interface. MATERIALS AND METHODS: Forty Straumann tissue-level implants were mounted in resin and divided into four groups (n = 10). Forty abutments were seated, 20 control and 20 third-party abutments, according to manufacturer guidelines. Ten abutments from each manufacturer were evaluated for RTV without fatigue loading, using a calibrated digital torque gauge to provide a baseline RTVs. Fatigue loading was carried out on the remaining ten specimens from each manufacturer according to ISO 14801 guidelines. A moving-magnet linear motor was used to load one specimen per sequence, alternating from 10 to 200 N at 15 Hz for 5×10(6) cycles. RTV was recorded post-fatigue loading. The results were subjected to two-sample t-testing and two-way ANOVA. Scanning electron microphotography was carried out on three specimens from both manufacturers at baseline and post-fatigue cycling to visualize thread geometry and the abutment/implant interface. RESULTS: The data indicated that mean post-fatigue RTV observed for the control group was significantly higher than the third-party group (RTV 42.65 ± 6.70 N vs. 36.25 ± 2.63 N, p= 0.0161). Visual differences at the macro/microscopic level were also apparent for thread geometry, with third-party abutments demonstrating considerably greater variation in geometrical architecture than control specimens. CONCLUSIONS: Within the limitations of this in vitro model, the effect of component manufacturer resulted in a significantly higher RTV in the control group (two-way ANOVA, p= 0.0032) indicating greater residual preload; however, there was no significant decrease in post-fatigue RTV for either manufacturer compared to baseline.

Use of a single implant to retain a mandibular complete overdenture on the compromised atrophic alveolar ridge: a case report.

This case report illustrates some of the advantages gained by placing a single implant in the midline of the intersym-physeal region of the mandible, which can be used to retain a complete mandibular overdenture in patients with a compromised atrophic mandible opposing a maxillary complete denture. This approach is a valid treatment option for patients with limited financial and therapeutic means. This case report, along with other evidence, demonstrates that a mandibular single implant-retained overdenture is a viable treatment option for a specific group of patients.

Integrin-associated tyrosine kinase FAK affects Cbfa1 expression.

Following cell adhesion, focal adhesion kinase (FAK) autophosphorylates on tyrosine and regulates intracellular signaling cascades that regulate cell growth and differentiation. The hypothesis of this study was FAK mediates osteoblast differentiation dependent Cbfa1 expression. Slowly mineralizing UI and rapidly mineralizing UMR-106-01 BSP osteoblasts formed focal adhesions; however, the level of FAK in UI focal adhesions was less than that seen in BSP cells. UI cultures had less FAK expression (p < 0.05) along with elevated levels of FAK phosphotyrosine in comparison to rapidly mineralizing BSP cultures. Mineralization decreased in a dose-dependent manner in response to Herbimycin A, a tyrosine kinase inhibitor. Overexpression of FAK in UI cells led to a fourfold increase in Cbfa1 gene expression (p < 0.02), and an increase in Cbfa1 protein expression. These results suggest that the integrin-associated tyrosine kinase FAK contributes to the regulation of the osteoblast differentiation in part through the regulation of Cbfa1 expression.

Analysis of the attachment and differentiation of three-dimensional rotary wall vessel cultured human preosteoblasts on dental implant surfaces.

PURPOSE: The purpose of this study was to determine whether osseous tissues engineered in three-dimensional (3D) environments preserved their mineralizing capacity and retained biologic characteristics when cultured on dental implant surfaces. MATERIALS AND METHODS: Human preosteoblast cells were cultured in both 3D rotary wall vessels and on 2D tissue culture plastic plates for 3 days. Aggregates from the 3D chambers and cells from the 2D plates were collected and transferred to commercially pure titanium disks with either 600-grit polished or sandblasted surfaces. These were cultured for an additional 7 days. The aggregates and cells from the disks were collected and prepared for scanning electron microscopy for microscopic evaluation and atomic adsorption assays for mineral content analysis. Additionally, staining with Alizarin red S was performed to compare the mineralization amount and pattern in each group. Polymerase chain reaction analysis was performed to evaluate expression of osteogenic genes, including Runx2, FAK, bone morphogenetic protein 2, and osteocalcin. RESULTS: Cells from 3D rotary wall vessel cultures attached to implant surfaces and presented cell attachment and growth patterns similar to those of standard 2D cultured cells, showing evidence of radial and random growth, yet they formed multiple focal niches on implant surfaces out of which cells proliferated. The 3D cultured cells and osseous tissues retained higher amounts of mineral formed during the initial culture and showed a higher tendency toward mineralization on implant surfaces compared to standard cultured cells. The 3D cultured cells and osseous tissues on implant surfaces at 1 week showed higher key gene protein expression. RNA expression at 1 week was equivalent to that of standard cultured cells. CONCLUSION: Culture of human osteogenic cells and tissues in 3D rotary wall vessels may expedite the osseointegration process on dental implant surfaces, thus reducing the overall treatment time.

Three-dimensional culture environments enhance osteoblast differentiation.

PURPOSE: In previous work from our laboratory, we demonstrated that the three-dimensional (3D) cell cultures developed in simulated microgravity environments enhanced osseous-like aggregate formation and accelerated preosteoblast cell differentiation. Thus, as described here, we hypothesize that aggregate formation and mineralization would occur with fewer than 10 x 10(6) cells as previously described. MATERIALS AND METHODS: Human preosteoblastic cells were cultured at different concentrations in a rotary wall vessel to simulate microgravity for 7 days. Aggregate size was assessed, and mineralization and collagen expression detected using Von Kossa and Masson Trichrome staining. Scanning electron microscopy was used for structural and elemental analysis. Immunohistochemistry was used to detect expression of the osteogenic markers BSPII and osteopontin (OP). RESULTS: Size and calcium expression were dependent upon cultured cell number (p < 0.01). Calcium and collagen expression were detected throughout the aggregate, but organization was independent of cell number. Aggregates had similar microscopic structural patterns demonstrating organized development. Presence of BSPII and OP showed that the aggregates share common differentiation proteins with in vivo bone formation. CONCLUSIONS: These results may lead to novel bone engineering techniques associated with dental treatment.

Osteoblast differentiation is enhanced in rotary cell culture simulated microgravity environments.

PURPOSE: As the aging population increases, more people will become reliant on regenerative dental medicine for implant therapy. The objective of this study was to test the hypothesis that 3D rotary cell culture (RCC) environments created by simulated microgravity would enhance osteogenic gene expression using integrin mediated pathways. MATERIALS AND METHODS: Human embryonic palatal mesenchymal (HEPM, ATCC 1486) pre-osteoblasts were cultured in either RCC to create 3D environments or in 2D monolayers for 72 hours. Gross phenotypic analysis was performed using Alizarin Red S staining for calcium and microscopy. Real-time PCR analysis was used to detect differences in osteoblast gene expression. Aggregates developed in 3D RCC environments were treated with or without antibody to the collagen-I integrin receptor alpha2beta1 to determine whether this molecular pathway might contribute to the development of a mineralized matrix. RESULTS: Microscopic analysis demonstrated that RCC environments promoted 3D aggregate formation by 72 hours without any scaffold. The mass appeared osseous-like with a white, shiny, translucent surface. The center was amorphous with areas of vacuolization, tubule-like structures, and fibrous-like extensions. Real-time PCR data showed that 3D environments enhanced osteogenic gene expression as compared with 2D monolayer culturing conditions. At 72 hours, changes in levels of osteogenic gene expression were noted. Cbfa1, a necessary transcription factor for osteoblast differentiation, was expressed 33% higher (p= 0.26); Collagen 1, 69% higher (p= 0.05); Osterix, 49% higher (p= 0.001); and BSPII, 54% higher (p= 0.001) than osteoblasts cultured for 72 hours in standard 2D monolayer conditions. When cultured in the presence of collagen alpha2beta1 integrin receptor antibody, 3D aggregates had decreased levels of mineralization as compared with non-treated aggregates. CONCLUSION: RCC enhances osteoblast differentiation using integrin mediated pathways.

Effect of glucocorticoid-induced osteoporotic-like conditions on osteoblast cell attachment to implant surface microtopographies.

OBJECTIVES: The objectives of this work were to: (1) establish methodology for pretreating osteoblast-like cells in vitro with dexamethasone to cause glucocorticoid-induced osteoporosis, (2) perform quantitative and qualitative assessments of cellular attachment of osteoporosis-like osteoblasts when grown on implant surfaces of differing roughness, (3) and explore the hypothesis that dexamethasone-treated osteoblasts have altered cell attachment properties by focal adhesion disassembly and decreased tyrosine phosphorylation of the focal adhesion tyrosine kinase. METHODS: Osteoblasts were cultured with dexamethasone (10(-7) and 10(-6) M) for up to 4 days of incubation to induce osteoporosis-like conditions. Cellular attachment assays demonstrated the effect of dexamethasone treatments on cellular attachment properties of osteoblasts. Qualitative data were obtained utilizing immunofluorescent microscopy and Western blotting. Focal adhesion kinase (FAK) immunoprecipitation and tyrosine-phosphorylation Western blots were obtained from dexamethasone-treated human embryonic palatal mesenchymal- 1486 osteoblast cultures supplemented with ascorbate and beta-glycerol phosphate medium. RESULTS: Cellular attachment was significantly greater (P < 0.05) with non-dexamethasone-treated osteoblasts (92%) as compared to dexamethasone-treated osteoblasts after 1 (72%), 2 (63%), and 4 days (53%) of exposure. Dexamethasone-treated osteoblasts were viable and capable of proliferation, suggesting that the reduction of cellular attachment may be related to these cell adhesion processes. Immunofluorescent microscopy of both dexamethasone-treated osteoblasts and non-dexamethasone-treated osteoblasts failed to show any relative difference in the disassembly of focal adhesions and actin filaments. Extended dexamethasone treatment periods (up to 3 weeks) showed changes in the levels of FAK and FAK-phosphotyrosine in human embryonic palatal mesenchymal-1486 osteoblasts. CONCLUSIONS: The protocol used in this study demonstrated a glucocorticoid-induced osteoporosis-like suppression of osteoblasts. FAK disassembly was not a significant factor in short period; however, FAK protein levels and phosphotyrosine signaling on FAK were affected after 1-week exposure to dexamethasone. Phosphorylated FAK was not associated with the rise in the level of FAK, further indicating the possibility of FAK involvement in reduced cell attachment.

Effects of fluoride-modified titanium surfaces on osteoblast proliferation and gene expression.

PURPOSE: The objective of this study was to test the hypothesis that fluoride-modified titanium surfaces would enhance osteoblast differentiation. Osteoblast growth on a moderately rough etched fluoride-modified titanium surface (alteration in cellular differentiation) was compared to osteoblast growth on the same surface grit-blasted with titanium dioxide. The potential role of nanometer-level alterations on cell shape and subsequent differentiation was then compared. MATERIALS AND METHODS: Human embryonic palatal mesenchymal (HEPM) cultures were incubated on the respective surfaces for 1, 3, and 7 days, followed by analysis for cell proliferation, alkaline phosphatase (ALP) -specific activity, and mRNA steady-state expression for bone-related genes (ALP, type I collagen, osteocalcin, bone sialoprotein [BSP] II, Cbfa1, and osterix) by real-time polymerase chain reaction (PCR). RESULTS: The different surfaces did not alter the mRNA expression for ALP, type I collagen, osterix, osteocalcin, or BSP II. However, Cbfa1 expression on the fluoride-modified titanium surface was significantly higher (P < .001) at 1 week. The number of cells on this surface was 20% lower than the number of cells on the surface TiO2-blasted with 25-microm particles but not significantly different from the number of cells on the surface TiO2-blasted with 125-microm particles. Cells grown on all the titanium surfaces expressed similar levels of ALP activity. CONCLUSIONS: The results indicated that a fluoride-modified surface topography, in synergy with surface roughness, may have a greater influence on the level of expression of Cbfa1 (a key regulator for osteogenesis) than the unmodified titanium surfaces studied.

Spatial control over cell attachment by partial solvent entrapment of poly lysine in microfluidic channels.

We demonstrate spatial control over cell attachment on biodegradable surfaces by flowing cell adhesive poly (D-lysine) (PDL) in a trifluoroethanol (TFE)-water mixture through microfluidic channels placed on a biodegradable poly (lactic acid)-poly (ethylene glycol) (PLA-PEG) substrate. The partial solvent mixture swells the PLA-PEG within the confines of the microfluidic channels allowing PDL to diffuse on to the surface gel layer. When excess water is flowed through the channels substituting the TFE-water mixture, the swollen PLA surface collapses, entrapping PDL polymer. Results using preosteoblast human palatal mesenchymal cells (HEPM) indicate that this new procedure can be used for facile attachment of cells in localized regions. The PEG component of the PLA-PEG copolymer prevents cells from binding to the nonpatterned regions.

Focal adhesion kinase promotes the aggressive melanoma phenotype.

Malignant melanoma continues to remain a significant health threat, with death often occurring as a result of metastasis. The metastatic phenotype typically is characterized by augmented tumor cell invasion and migration in addition to tumor cell plasticity as shown by vasculogenic mimicry. Therefore, understanding the molecular mechanisms that promote an aggressive phenotype is essential to predicting the likelihood of metastasis at a stage when intervention may be possible. This study focuses on the role of focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase important for many cellular processes, including cell survival, invasion, and migration. We found FAK to be phosphorylated on its key tyrosine residues, Tyr397 and Tyr576, in only aggressive uveal and cutaneous melanoma cells, which correlates with their increased invasion, migration, and vasculogenic mimicry plasticity. Additionally, we confirmed the presence of FAK phosphorylated on Tyr397 and Tyr576 in both cutaneous and uveal melanoma tumors in situ. Examination of a functional role for FAK in aggressive melanoma revealed that disruption of FAK-mediated signal transduction pathways, through the expression of FAK-related nonkinase (FRNK), results in a decrease in melanoma cell invasion, migration, and inhibition of vasculogenic mimicry. Moreover, we found that FRNK expression resulted in a down-regulation of Erk1/2 phosphorylation resulting in a decrease in urokinase activity. Collectively, these data suggest a new mechanism involved in promoting the aggressive melanoma phenotype through FAK-mediated signal transduction pathways, thus providing new insights into possible therapeutic intervention strategies.

Effects of implant surface microtopography on osteoblast gene expression.

AIM: The promotion of osteoblast attachment and differentiation has been evaluated on various implant surfaces. However, the effects of different implant surface properties on gene expression of key osteogenic factors are not fully understood. OBJECTIVE: The objectives of this study were to evaluate how topographical effects on titanium surface alter the expression of bone-related genes and transcription factors. METHODS: Osteoblasts were cultured on titanium disks prepared with a titanium dioxide grit blasting (TiOBlast) or grit blasted and etched with hydrofluoric acid (Osseospeed), grit blasted and etched (SLA-1), or grit blasted, etched and rinsed with N2 protection and stored in isotonic NaCl (SLA-2) commercially pure titanium implant discs. High-density cultures of human mesenchymal pre-osteoblastic cells (HEPM 1486, ATCC) were grown for 72 h and real-time PCR used for quantitative analysis of alkaline phosphatase (ALP), core-binding factor alpha1 (Cbfa1), Osterix, Type I Collagen, Osteocalcin and bone sialoprotein II gene expression. RESULTS: Real-time PCR showed significant (P<0.001) increases in ALP gene expression in osteoblasts grown on SLA-2, relative to all other surfaces. Cbfa1/RUNX-2 gene expression was significantly (P<0.01) increased on Osseospeed and TiOBlast surface as compared with SLA-1 and SLA-2 surfaces. The expression of Osterix had a trend similar to that of Cbfa1. CONCLUSION: In conclusion, implant surface properties may contribute to the regulation of osteoblast differentiation by influencing the level of bone-related genes and transcription factors in human mesenchymal pre-osteoblastic cells.

Co-regulation of p16INK4A and migratory genes in culture conditions that lead to premature senescence in human keratinocytes.

Cellular stasis, also known as telomere-independent senescence, prevents many epithelial cells from becoming immortalized by telomerase alone. As human keratinocytes age in culture, protein levels of the tumor suppressor p16INK4a continue to increase, resulting in growth arrest independent of telomere length. Differences in culture conditions have been shown to modulate both p16INK4a expression and replicative capacity of human keratinocytes; however, the mechanism of p16INK4a induction under these conditions is unknown. Using multiple primary keratinocyte cell strains, we verified a delay in p16INK4a induction and an extended lifespan of human keratinocytes when grown in co-culture with post-mitotic fibroblast feeder cells as compared with keratinocytes grown on tissue culture plastic alone. Evaluation of gene expression levels in the two culture conditions by microarray analysis, and subsequent validation, demonstrated that keratinocytes cultured on plastic alone had significantly increased expression of many genes involved in keratinocyte migration and reduced expression levels of genes involved in keratinocyte differentiation. Higher levels of p16INK4a expression were present in cells that also displayed increased amounts of autophosphorylated focal adhesion kinase and urokinase plaminogen activator receptor (uPAR), both markers of keratinocyte migration. Furthermore, when tyrosine phosphorylation or urokinase-type plasminogen activator (uPA)/uPAR function was inhibited, both keratinocyte migration and p16INK4a expression were reduced. Our results indicate that keratinocytes cultured in the absence of feeder cells exhibit a migratory phenotype and suggest that p16INK4a is selectively induced under these conditions by a mechanism involving tyrosine kinase activity and the urokinase plasminogen activation system.