The effect of osteocyte-derived RANKL on bone graft remodeling: An in vivo experimental study.

OBJECTIVES Autologous bone is considered the gold standard for grafting, yet it suffers from a tendency to undergo resorption over time. While the exact mechanisms of this resorption remain elusive, osteocytes have been shown to play an important role in stimulating osteoclastic activity through their expression of receptor activator of NF-κB (RANK) ligand (RANKL). The aim of this study was to assess the function of osteocyte-derived RANKL in bone graft remodeling. MATERIALS AND METHODS In Tnfsf11fl/fl ;Dmp1-Cre mice without osteocyte-specific RANKL as well as in Dmp1-Cre control mice, 2.6 mm calvarial bone disks were harvested and transplanted into mice with matching genetic backgrounds either subcutaneously or subperiosteally, creating 4 groups in total. Histology and micro-computed tomography of the grafts and the donor regions were performed 28 days after grafting. RESULTS Histology revealed marked resorption of subcutaneous control Dmp1-Cre grafts and new bone formation around subperiosteal Dmp1-Cre grafts. In contrast, Tnfsf11fl/fl ;Dmp1-Cre grafts showed effectively neither signs of bone resorption nor formation. Quantitative micro-computed tomography revealed a significant difference in residual graft area between subcutaneous and subperiosteal Dmp1-Cre grafts (p < .01). This difference was not observed between subcutaneous and subperiosteal Tnfsf11fl/fl ;Dmp1-Cre grafts (p = .17). Residual graft volume (p = .08) and thickness (p = .13) did not differ significantly among the groups. Donor area regeneration was comparable between Tnfsf11fl/fl ;Dmp1-Cre and Dmp1-Cre mice and restricted to the defect margins. CONCLUSIONS The results suggest an active function of osteocyte-derived RANKL in bone graft remodeling

Differential Production Cross Section of Z Bosons as a Function of Transverse Momentum at sqrt{s}=1.8 TeV

We present a measurement of the transverse momentum distribution of Z bosons produced in ppbar collisions at sqrt{s}=1.8 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider during 1994--1996. We find good agreement between our data and a current resummation calculation. We also use our data to extract values of the non-perturbative parameters for a particular version of the resummation formalism, obtaining significantly more precise values than previous determinations.Comment: 10 pages, 2 figures, submitted to Phys. Rev. Letters v2 has margin error correcte

Congruence and Participation - Does the Discrepancy between the Elite\u27s and the Public\u27s Ideology Come at the Cost of Reduced Participation?

Why do some people choose to engage in politics while others opt out? My core thesis is that two features of contemporary politics have a detrimental impact on participation in the electorate. The first of these two features is the discrepancy between the political agenda of the individual (what issues they consider important) and that of the political ruling class. The second stems from work suggesting that the conservative-liberal dimension represents the structure behind the issue stances of the political elite well; but that the same is not quite true for the general population (e.g. Carmines, Ensley, and Wagner 2011). Misrepresented citizens – whose views don’t align with the conservative-liberal dimension – are more likely to turn away from politics to the detriment of the process of democratic representation. I tested my hypotheses in models of increasing complexity using four preexisting datasets (generally including more representative data and boasting a larger N, providing 20 multivariate models in total) as well as three compiled exclusively for purposes of this dissertation – adding 9 models and a set of highly relevant variables at the cost of representativeness. The positive role of agenda congruence in predicting participation is not supported by empirical findings, although further analysis of sample characteristics calls into question the validity of this result and points to an interesting direction for future research. The relationship between ideological congruence and ‘traditional’ means of political engagement (encompassing a range of activities from campaign contributions through contacting officials to participation in boycotts and active support of NGOs) is robust, although ideological congruence appears unrelated to voting and online participation. These results call for the introduction of ideological incongruence into public as well as scholarly discourse, especially with respect to its negative ramifications regarding political participation and representation. Advisor: John R. Hibbin

Preoperative buccal bone volume predicts long-term graft retention following augmentation in the esthetic zone: a retrospective case series.

OBJECTIVES Buccal bone augmentation in the esthetic zone is routinely used to achieve optimal clinical outcomes. Nonetheless, long-term data are sparse, and it is unknown how baseline buccal bone volume affects the retention of the augmented volume over time. MATERIAL AND METHODS This is a long-term follow-up retrospective case series. After a preoperative computed tomography scan, implants were placed in the anterior maxilla following guided bone regeneration, autogenous block grafting, or both. At the follow-up, patients received a computed tomography scan and a clinical examination. Buccal bone volume was the primary outcome. Buccal bone thickness, peri-implant, and esthetic parameters were secondary outcomes. RESULTS After a median follow-up of 6.7 years (interquartile range: 4.9-9.4), 28 implants in 19 patients (median age at augmentation: 43.3 years, interquartile range: 34.4-56.7, 53% female) were followed up. Preoperative buccal bone volume at baseline (V0 ) showed a moderate correlation to final buccal bone volume (Vt , rs  = 0.43) but a strong correlation to the absolute volumetric change (ΔV = Vt - V0 , rs  = -0.80). A linear mixed model for Vt had a large intercept of 91.39 (p < 0.001) and a rather small slope of 0.11 for V0 (p = 0.11). Observed differences between treatments were not statistically significant in the mixed model. V0 above 105 mm3 predicted a negative volume change (ΔV < 0) with a specificity of 100% and a sensitivity of 96%. CONCLUSIONS The results suggest higher gains in sites with lower V0 and point to a cutoff V0 above which the augmented volume is not retained long-term

The Effect of the COVID-19 Pandemic on Patient Selection, Surgical Procedures, and Postoperative Complications in a Specialized Dental Implant Clinic.

During the coronavirus disease 2019 (COVID-19) pandemic, aerosol-generating procedures, including dental implant treatments, are considered high-risk. With dental implant treatment mostly an elective procedure, we aimed to assess whether the pandemic influenced patient selection, surgical procedures, and postoperative complications. We compared dental implant treatments during (March to December 2020) and before (December 2018 to February 2020) the COVID-19 pandemic based on patient and implant parameters, as well as postoperative complications. For analysis, we used the Chi-squared test with the Holm-Sidak correction for multiple comparisons. The number of implants placed during the COVID-19 pandemic (696 implants in 406 patients, 70 implants per month) was comparable to pre-pandemic levels (1204 implants in 616 patients, 80 implants per month). Regarding patient parameters, there were no significant differences in respiratory (p = 0.69) and cardiovascular conditions (p = 0.06), diabetes (p = 0.69), and smoking (p = 0.68). Regarding implant parameters, there was a significant difference in the distribution of augmentative procedures (no augmentation, guided bone regeneration, and sinus floor elevation, p = 0.01), but no significant differences in the types of edentulous spaces (p = 0.19) and the timing of implant placement (p = 0.52). Regarding complications, there were significantly fewer minor complications (p < 0.001) and early (i.e., before loading) implant failures (p = 0.02) compared with pre-pandemic levels. Our results suggest that the COVID-19 pandemic had no effect on patient selection and only a slight effect on the surgical procedures. However, postoperative complications, including early failures, were significantly less prevalent during the pandemic

Resonance frequency analysis of implants placed in condensed bone.

OBJECTIVES Resonance frequency analysis (RFA) is used to monitor implant stability. Its output, the Implant Stability Quotient (ISQ), supposedly correlates with insertion torque, a common measurement of primary stability. However, the reliability of RFA in condensed bone remains unclear. MATERIAL AND METHODS In this human cadaver study in edentulous jaws and fresh extraction sockets, implants were inserted using a split-mouth approach into condensed or untreated bone. Mean ISQ, peak insertion torque, and pre- and postoperative bone volume fractions (BV/TV) were assessed. RESULTS In edentulous jaws, insertion torque and ISQ correlated both in untreated (r = 0.63, p = 0.02) and in condensed (r = 0.82, p  < 0.01) bone. In extraction sockets, insertion torque and ISQ only correlated in untreated (r = 0.78, p < 0.01), but not in condensed bone (r = 0.15, p = 0.58). In all edentulous jaws, preoperative BV/TV correlated with insertion torque (r = 0.90, p < 0.0001), ISQ (r = 0.64, p < 0.001), and changes in BV/TV (r = -0.71, p < 0.01). In all extraction sockets, preoperative BV/TV did not correlate with either insertion torque (r = 0.33, p = 0.15), ISQ (r = 0.38, p = 0.09), or changes in BV/TV (r = -0.41, p = 0.09). Joint analysis identified preoperative BV/TV as a predictor of postoperative BV/TV (p < 0.001), insertion torque (p < 0.001), and ISQ (p < 0.001). CONCLUSIONS RFA is feasible for monitoring stability after late implant placement into condensed bone, but not after immediate placement into condensed fresh extraction sites

Prediction of post-traumatic neuropathy following impacted mandibular third molar removal.

OBJECTIVES The extraction of impacted mandibular third molars is a common surgical procedure often associated with complications including post-traumatic neuropathy. Previous work has focused on identifying confounding factors, but a robust preoperative risk prediction model remains elusive. METHODS Using a dataset of 648 patients and 812 impacted mandibular third molars, we used least absolute shrinkage and selection operator (LASSO) to fit prediction models based on risk factors assessed at both the tooth and patient levels. In addition, we fitted multivariable logistic regression models with the Firth correction for generalized estimating equations (GEE). RESULTS The LASSO model for post-traumatic neuropathy identified distoangular impaction of ≥ 45° (odds ratio [OR] = 2.9), proximity to the inferior alveolar nerve of ≤ 3 mm (OR = 1.9), disadvantageous curving (OR = 1.4), and psychiatric conditions (OR = 2.1) as predictors [area under the receiving operator characteristic curve (AUC) = 0.75]. Among other complications analyzed, the LASSO model for bleeding identified deep embedding or full impaction (OR = 1.8), psychiatric conditions (OR = 1.3), and age (OR = 0.9) as predictors (AUC = 0.64). These associations between predictors and postoperative complications were fundamentally reinforced by the corresponding GEE models. CONCLUSIONS Our findings point to the predictability of post-traumatic neuropathy and bleeding based on tooth anatomy and patient characteristics, overall suggesting that preoperatively identifiable factors can predict the risk of adverse outcomes in the extraction of impacted mandibular third molars. CLINICAL SIGNIFICANCE Mandibular third molar extraction is both a routine procedure and a leading cause of trigeminal neuropathy. Prevention of post-traumatic neuropathy, aided by individualized preoperative risk prediction, is of high clinical relevance

A volumetric prediction model for postoperative cyst shrinkage.

OBJECTIVES With only limited information available on dimensional changes after jaw cyst surgery, postoperative cyst shrinkage remains largely unpredictable. We aimed to propose a model for volumetric shrinkage based on time elapsed since cyst surgery. MATERIAL AND METHODS We used data from patients that underwent cyst enucleation or decompression between 2007 and 2017 and had at least three computed tomography (CT) scans per patient. We fitted one simple exponential decay model [V(t) = V0 · e-ɑt] and one model with a patient-specific decay rate [Vk(t) = V0 · e-βt + γkt]. RESULTS Based on 108 CT scans from 36 patients (median age at surgery: 45.5 years, IQR: 32.3-55.3, 44% female), our simple exponential decay model is V(t) = V0 · e-0.0035t where V(t) is the residual cyst volume after time t elapsed since surgery, V0 is the initial cyst volume, and e is the base of the natural logarithm. Considering a patient-specific decay rate, the model is Vk(t) = V0 · e-0.0049t + γkt where γk is normally distributed, with expectation 0 and standard deviation 0.0041. CONCLUSIONS Using an exponential regression model, we were able to reliably estimate volumetric shrinkage after jaw cyst surgery. The patient-specific decay rate substantially improved the fit of the model, whereas adding specific covariates as interaction effects to model the decay rate did not provide any significant improvement. CLINICAL RELEVANCE Estimating postoperative cyst shrinkage is relevant for both treatment planning of jaw cyst surgery as well as evaluating the clinical success of the surgical approach

Angular changes in implants placed in the anterior maxillae of adults: a cephalometric pilot study.

OBJECTIVES Completion of adolescent growth represents the earliest time point for implant placement, yet craniofacial growth persists into adulthood and may affect implant position. We aimed to assess whether implants placed in the anterior maxillae of adults show angular changes over time. MATERIAL AND METHODS We conducted a cephalometric pilot study in postpubertal patients with no growth disorders, skeletal malformations, or parafunctions. The patients received a single implant in the anterior maxilla and no orthodontic or orthognathic treatment afterwards. We measured angular changes of implants and central incisors on cephalograms taken immediately and after at least 5 years postoperatively with the Sella-Nasion line (SNL) and the nasal line (NL) as references. Changes in implant-SNL angles were the primary outcome. RESULTS In 21 patients (30.2 ± 11.5 years at surgery) after a mean follow-up of 8.6 ± 1.3 years, implant-SNL angles and implant-NL angles changed in 81% and 57% of implants, respectively. Implant-SNL changes ranged from 3° counterclockwise to 4° clockwise and were more prevalent in males (100% vs. 58%) and patients under 30 at surgery (85% vs. 63%); mean absolute differences were larger in males (1.8 ± 1.0° vs. 1.3 ± 1.4°) and patients under 30 at surgery (1.5 ± 1.4° vs. 1.1 ± 1.4°). Incisor-SNL angles and incisor-NL angles changed in 89% and 32% of incisors, respectively. CONCLUSIONS Implants placed in the anterior maxillae of adults show modest angular changes over time. CLINICAL RELEVANCE Changes in implant angles have potential functional and esthetic consequences

HCH phytoremediation potential of native plant species from a contaminated urban site in Turda, Romania.

Current physical or chemical methods used for remediation of soils contaminated with hexachlocyclohexane (HCH), leave behind significant levels of pollutants. Given the compounds volatility and persistence in the environment, sites contaminated with HCH remain a concern for the population living in nearby areas. By making use of both the recovery capacity and the pollutant uptake ability of spontaneously growing vegetation, our study aimed to identify native plant species able to cover and moreover take up the HCH left at a former lindane production unit in Turda, Romania. The results showed that dominant species across the study site like Lotus tenuis, Artemisia vulgaris or Tanacetum vulgare, were capable of taking up HCH in their tissues, according to different patterns that combined at the scale of the plant community. Regardless of the proximity of the HCH contamination hotspots, the development of the plant cover was characteristic for vegetation succession on disturbed soils of the Central European region. Finally, we conclude that plant species which grow spontaneously at the HCH contaminated site in Turda and are capable of taking up the pollutant, represent a self-sustainable and low maintenance phytomanagement approach that would allow for the reintegration of the site in the urban or industrial circuit and nevertheless would reduce the toxicity risk to the neighboring human inhabitants