Lyophilized platelet-rich fibrin (PRF) promotes craniofacial bone regeneration through Runx2.

Freeze-drying is an effective means to control scaffold pore size and preserve its composition. The purpose of the present study was to determine the applicability of lyophilized Platelet-rich fibrin (LPRF) as a scaffold for craniofacial tissue regeneration and to compare its biological effects with commonly used fresh Platelet-rich fibrin (PRF). LPRF caused a 4.8-fold±0.4-fold elevation in Runt-related transcription factor 2 (Runx2) expression in alveolar bone cells, compared to a 3.6-fold±0.2-fold increase when using fresh PRF, and a more than 10-fold rise of alkaline phosphatase levels and mineralization markers. LPRF-induced Runx2 expression only occurred in alveolar bone and not in periodontal or dental follicle cells. LPRF also caused a 1.6-fold increase in osteoblast proliferation (p<0.001) when compared to fresh PRF. When applied in a rat craniofacial defect model for six weeks, LPRF resulted in 97% bony coverage of the defect, compared to 84% for fresh PRF, 64% for fibrin, and 16% without scaffold. Moreover, LPRF thickened the trabecular diameter by 25% when compared to fresh PRF and fibrin, and only LPRF and fresh PRF resulted in the formation of interconnected trabeculae across the defect. Together, these studies support the application of lyophilized PRF as a biomimetic scaffold for craniofacial bone regeneration and mineralized tissue engineering.

Applicant selection procedures for orthodontic specialty programs in the United States: survey of program directors.

INTRODUCTION: With the recent changes in scoring of the National Board Dental Examinations and grading systems in some dental schools, ranking prospective orthodontic applicants has become a challenge. METHODS: A 31-item survey was sent to orthodontic program directors in the United States to determine admission practices of all accredited specialty orthodontic programs. RESULTS: Forty-four of 64 program directors responded (69%). This study showed a wide variation of admission practices among these programs. The only consistent part of admissions in all programs was the interview process. The top factors considered for each applicant were interview ratings, dental school class rank, and letters of recommendation. The top sources of recommendations were the orthodontic department chair, the graduate program director, and the predoctoral orthodontic program director. The top 3 character traits considered most favorable were maturity, and good verbal and listening skills. CONCLUSIONS: Accredited orthodontic programs in the United States follow different procedures in assessing applicants for admission. It is important to consider both academic and nonacademic measures in assessing applicant information in a standardized manner to ensure a fair and efficient selection process.

Bones, teeth, and genes: a genomic homage to Harry Sicher's "Axial Movement of Teeth".

AIM: The model of the unopposed rodent molar was used to study the morphologic and genetic mechanisms of tooth eruption. METHODS: Left maxillary molar teeth of 12-day-old Swiss-Webster mice were extracted under anesthesia, and mandibular molars were allowed to supererupt. To trace areas of tissue remodeling and to determine areas of new tissue formation, mice were injected with fluorescent dyes, tetracycline, alizarin red, and calcein blue. Subsequent to sacrifice, mandibular tissue blocks were prepared for ultrathin ground sections, fluorescent microscopy, and von Kossa's mineral detection procedure. A second set of specimens was prepared for RNA extraction and microarray analysis. RESULTS: The data established significant eruption of first and second mandibular mouse molars 12 days after complete extraction of antagonists, exceeding the control side by 0.13 mm. Labeled tissue sections revealed significant amounts of new bone and cementum apposition on the unopposed side compared to the control side, as revealed by fluorescent markers and ultrathin ground sections. Microarray transcript level comparisons between the experimental and the control groups demonstrated significant (more than twofold) increase in gene expression of elastin and tenascin C extracellular matrix proteins; brevican, lumican, and biglycan proteoglycans; as well as fibroblast growth factor 9. CONCLUSION: In this study, the authors have established the unopposed mouse molar as a model to study tissue dynamics during the axial movement of teeth. The data indicated significant new formation of bone and cementum in tandem with increased expression of extracellular matrix-related genes.

The expanded amelogenin polyproline region preferentially binds to apatite versus carbonate and promotes apatite crystal elongation.

The transition from invertebrate calcium carbonate-based calcite and aragonite exo- and endoskeletons to the calcium phosphate-based vertebrate backbones and jaws composed of microscopic hydroxyapatite crystals is one of the great revolutions in the evolution of terrestrial organisms. To identify potential factors that might have played a role in such a transition, three key domains of the vertebrate tooth enamel protein amelogenin were probed for calcium mineral/protein interactions and their ability to promote calcium phosphate and calcium carbonate crystal growth. Under calcium phosphate crystal growth conditions, only the carboxy-terminus augmented polyproline repeat peptide, but not the N-terminal peptide nor the polyproline repeat peptide alone, promoted the formation of thin and parallel crystallites resembling those of bone and initial enamel. In contrast, under calcium carbonate crystal growth conditions, all three amelogenin-derived polypeptides caused calcium carbonate to form fused crystalline conglomerates. When examined for long-term crystal growth, polyproline repeat peptides of increasing length promoted the growth of shorter calcium carbonate crystals with broader basis, contrary to the positive correlation between polyproline repeat element length and apatite mineralization published earlier. To determine whether the positive correlation between polyproline repeat element length and apatite crystal growth versus the inverse correlation between polyproline repeat length and calcium carbonate crystal growth were related to the binding affinity of the polyproline domain to either apatite or carbonate, a parallel series of calcium carbonate and calcium phosphate/apatite protein binding studies was conducted. These studies demonstrated a remarkable binding affinity between the augmented amelogenin polyproline repeat region and calcium phosphates, and almost no binding to calcium carbonates. In contrast, the amelogenin N-terminus bound to both carbonate and apatite, but preferentially to calcium carbonate. Together, these studies highlight the specific binding affinity of the augmented amelogenin polyproline repeat region to calcium phosphates versus calcium carbonate, and its unique role in the growth of thin apatite crystals as they occur in vertebrate biominerals. Our data suggest that the rise of apatite-based biominerals in vertebrates might have been facilitated by a rapid evolution of specialized polyproline repeat proteins flanked by a charged domain, resulting in apatite crystals with reduced width, increased length, and tailored biomechanical properties.

Dentistry and obesity: a review and current status in U.S. predoctoral dental education.

Obesity has become an epidemic and a public health concern in the United States and many other countries around the world. The impact of obesity on individuals' overall and oral health and its influence on dental treatment protocols and postoperative procedures have been well documented. It is therefore important for dentists to understand and recognize obesity, educate their patients on its associated risks, promote a healthy lifestyle for their patients, and modify any necessary dental treatments and postoperative procedures for obese patients. To investigate the current practice of obesity assessment in U.S. dental school clinics and the inclusion of obesity topics in predoctoral dental curricula, surveys were sent to all sixty-two U.S. dental schools. Thirty-five surveys were returned but one was blank because the institution is newly established, so the total number used for analysis was thirty-four. The results showed that the topic of obesity has been incorporated into predoctoral dental curricula and is thought to be important for dentists and dental students by most respondents. However, the majority do not routinely measure weight and height, nor calculate Body Mass Index for comprehensive care patients in their predoctoral dental clinics. The authors argue that the topic of obesity should be emphasized in predoctoral dental curricula and that assessments of obesity should be practiced in predoctoral dental clinics.

Gender equality in orthodontic literature and leadership in the United States.

The objective of this study was to evaluate gender equality in orthodontics by reviewing the authorship in three orthodontic journals in addition to the involvement of women in leadership roles within orthodontic organizations and academia in the United States. Three journals representing orthodontics were selected to analyze the author demographics for the years 1986, 1990, 1995, 2000, 2005, and 2008. Inclusion criteria were at least one first or last author with a dental degree whose primary affiliation was in the United States. Female leadership was assessed in three orthodontic organizations as well as orthodontic program directorship. Overall, the percentage of female first authors increased significantly from 0% to 18% in the years studied (P = .004). The change of the percentage of female last authors was not statistically significant (P = .719). The participation of women in leadership roles within orthodontic organizations and in orthodontic program director positions has been limited. Within the limitations of this study, it was concluded that women are underrepresented in orthodontic authorship and leadership.

Evaluation of incisor position and dental transverse dimensional changes using the Damon system.

OBJECTIVES: To test the hypotheses that the Damon system will maintain intercanine, interpremolar, and intermolar widths. To test subsequent hypotheses that the Damon system will not produce a significant difference in maxillary and mandibular incisor position/angulation when compared with control groups treated with conventional fixed orthodontic appliances for similar malocclusion. MATERIALS AND METHODS: Subjects treated with the Damon system (N  =  27) were compared with subjects treated with a conventionally ligated edgewise bracket system (N  =  16). Subjects' pretreatment and posttreatment lateral cephalometric radiographs and dental models were scanned, measured, and compared to see whether significant differences exist between time points and between the two groups. RESULTS: Results did not support the claimed lip bumper effect of the Damon system and showed similar patterns of crowding alleviation, including transverse expansion and incisor advancement, in both groups, regardless of the bracket system used. CONCLUSIONS: Maxillary and mandibular intercanine, interpremolar, and intermolar widths increased significantly after treatment with the Damon system. The mandibular incisors were significantly advanced and proclined after treatment with the Damon system, contradicting the lip bumper theory of Damon. Posttreatment incisor inclinations did not differ significantly between the Damon group and the control group. Patients treated with the Damon system completed treatment on average 2 months faster than patients treated with a conventionally ligated standard edgewise bracket system.

Phantom bite: a survey of US orthodontists.

AIM: In 1976, Marbach described the term phantom bite as a patient's perception of an irregular bite when the clinician could identify no evidence of a discrepancy. Typically, the patient presents with a history of bite-altering procedures, hyperawareness of occlusion, and a persistent complaint of an uncomfortable bite, usually with an absence of pain. Patients with phantom bite complaints often undergo lengthy, expensive, irreversible, invasive, and unnecessary treatments in search of a resolution of their symptoms. The objectives of the study were: (1) to gauge orthodontists' awareness of phantom bite and its associated signs and symptoms, (2) to identify the most common types of treatments rendered for this phenomenon, (3) to determine if regional differences or length of practice experience affected the aforementioned factors, and (4) to determine sex characteristics of patients with phantom bite. METHODS: The study consisted of a 14-item survey administered electronically using SurveyMonkey software. Using the American Association of Orthodontists (AAO) directory, 4,124 orthodontists were recruited to participate via email; 337 completed the survey. RESULTS: Approximately 50% of the responding orthodontists were unfamiliar with the term "phantom bite"; however, many reported seeing patients with phantom bite complaints. Demographic differences, such as geographic region of practice or years in practice, did not affect familiarity with this condition or its treatment. CONCLUSION: The results suggest a need for increasing awareness of this condition among orthodontic practitioners to provide patients with appropriate care.

Differences between ADEA Annual Session poster abstracts and their corresponding full published articles.

The purpose of this study was to investigate differences between abstracts of posters presented at the 79(th) (2002) and 80(th) (2003) Annual Session & Exhibition of the American Dental Education Association (ADEA) and the published full-length articles resulting from the same studies. The abstracts for poster presentation sessions were downloaded, and basic characteristics of the abstracts and their authors were determined. A PubMed search was then performed to identify the publication of full-length articles based on those abstracts in a peer-reviewed journal. The differences between the abstract and the article were examined and categorized as major and minor differences. Differences identified included authorship, title, materials and methods, results, conclusions, and funding. Data were analyzed with both descriptive and analytic statistics. Overall, 89 percent of the abstracts had at least one variation from its corresponding article, and 65 percent and 76 percent of the abstracts had at least one major and minor variation, respectively, from its corresponding article. The most prevalent major variation was in study results, and the most prevalent minor variation was change in the number of authors. The discussion speculates on some possible reasons for these differences.