Mouse mandibular-derived osteoclast progenitors have differences in intrinsic properties compared with femoral-derived progenitors.

Craniofacial osteoclasts are essential for site-specific processes such as alveolar bone resorption, tooth eruption, and orthodontic tooth movement. Much of the current understanding of osteoclast development and function comes from studies using long bone-derived cells. Minimal investigation has been done to explore skeletal site differences. The overall goal of this study was to determine if mandibular- and femoral-derived osteoclasts represent distinct populations. To test this hypothesis, bone marrow cells were initially analyzed from the mandible and femur of 2-month-old mice. It was shown that mandibular-derived osteoclasts have enhanced size (mm2) compared with femoral-derived osteoclasts. Since bone marrow macrophages are a heterogenous population, we additionally selected for monocytes and demonstrated that mandibular-derived monocytes also form osteoclasts with increased size compared with femoral-derived monocytes. Osteoclast precursor populations from both skeletal sites were analyzed by flow cytometry. A newly described Ly6CHigh+ population as well as the Ly6Cint population was increased in the mandibular-derived cells. The difference in differentiation potential between monocyte cultures suggests that the increase in the Ly6CHigh+ population may explain the enhanced differentiation potential in mandibular-derived cells. Monocyte genes such as Pu.1, C/ebp-a, and Prdm1 are increased in expression in mandibular-derived monocytes compared with femoral-derived monocytes. As expected with enhanced differentiation, osteoclast genes including Nfatc1, Dc-stamp, Ctsk, and Rank are upregulated in mandibular-derived osteoclast precursors. Future studies will determine how changes in the environment of the mandible lead to changes in percentages of osteoclast progenitors and their differentiation potential.

Assessment of orthodontic treatment efficacy of Clarity Aligners using the Peer Assessment Rating index and the American Board of Orthodontics Cast-Radiograph Evaluation.

INTRODUCTION: 3M Oral Care Solutions (St Paul, Minn) has recently introduced Clarity Aligners into the market. This cohort study evaluated the orthodontic treatment efficacy of this clear aligner system using the Peer Assessment Rating (PAR) index and the American Board of Orthodontics Cast-Radiograph Evaluation (CR-Eval). METHODS: Pretreatment and posttreatment dental models of 87 subjects who had undergone orthodontic treatment using Clarity Aligners in both arches to align their teeth to a target setup were independently evaluated by 4 examiners using the PAR index and the American Board of Orthodontics CR-Eval. Changes in CR-Eval and PAR scores from pretreatment to posttreatment were calculated, with PAR score reductions also expressed as percentages. RESULTS: Treatment with Clarity Aligners reduced the CR-Eval scores from 39.05 ± 14.98 to 30.34 ± 8.76, resulting in a statistically significant difference of 8.76 ± 11.45 between pretreatment and posttreatment scores. Similarly, aligner treatment reduced the weighted PAR scores from 13.40 ± 9.26 to 5.80 ± 4.84, resulting in a statistically significant difference of 7.50 ± 7.56 between pretreatment and posttreatment scores. The overall median PAR reduction was 53%, with 94% of the subjects having reduced PAR scores after treatment. Seventy-eight percent of subjects had >30% PAR reduction, 57% had >50% PAR reduction, and 33% had >70% PAR reduction. CONCLUSIONS: The results suggest that Clarity Aligners may be an effective treatment modality in mild to moderate malocclusions.

Radiographic Evaluation of Permanent Second Molar Substitution After Extraction of Permanent First Molar: Identifying Predictors for Spontaneous Space Closure.

PURPOSE: The purpose of this study was to investigate pre-extraction variables associated with spontaneous space closure of the perma- nent second molar (PSM) following early extraction of the permanent first molar (PFM), and test an existing prediction model for the mandibular arch as the rates of spontaneous space closure are significantly lower in the mandible compared to the maxilla. METHODS: Pre-extraction panoramic radiographs of 162 patients (138 maxillary and 168 mandibular quadrants) between five and 15 years old at the time of PFM extraction were evaluated. The prediction model was applied to the mandibular quadrants. Postextraction radiographic evaluation was used for outcome assessment, with success defined as the presence of a visible contact between the second premolar and PSM without marginal ridge discrepancy. RESULTS: Success was observed in 82 percent of maxillary quadrants and 51 percent of mandibular quadrants. Maxillary PFM extraction between eight and 10 years or PSM Demirjian stage D or E demonstrated over 90 percent predictive probability for success. Mandibular PFM extraction at age eight years or PSM Demirjian stage D demonstrated 80 percent success. The prediction model did not add a more predictive value than chronological age or PSM Demirjian stage. CONCLUSIONS: The prediction model was not validated in this study population. Chronological age and permanent second molar developmental stage were the primary predictors for successful substitution with the permanent second molar.

SMAD1/5 signaling in osteoclasts regulates bone formation via coupling factors.

Bone remodeling occurs via coupling between bone resorption by osteoclasts and bone formation by osteoblasts. The mechanisms that regulate osteoclast signals to osteoblasts are not well understood. Published studies have reported that BMP signaling in osteoclasts regulate osteoclast coupling targets. To investigate the necessity of canonical BMP signaling on osteoclast differentiation and coupling, we mated Smad1fl/fl; Smad5fl/fl mice to c-Fms-Cre mice. We analyzed male mice at 3 months of age to determine the skeletal phenotype of the Smad1fl/fl; Smad5fl/fl;c-Fms-Cre (SMAD1/5 cKO) mice. There was a 1.2-fold decrease in trabecular BV/TV in SMAD1/5 cKO. Analyses of osteoclast serum markers in SMAD1/5 cKO mice, showed a significant increase in CTX-1 (1.5 fold) and TRAP ELISA (3 fold) compared to control mice. In these same mice, there was a 1.3-fold increase in cortical thickness. Consistent with the increase in cortical thickness, we found a 3-fold increase in osteoblast activity as measured by P1NIP ELISA assay from SMAD1/5 cKO mice. To explain the changes in cortical thickness and P1NP activity, we determined conditioned media from SMAD1/5 cKO osteoclast cultures enhanced mineralization of an osteoblast cell line and coupling factors expressed by osteoclasts that regulate osteoblast activity Wnt1 (4.5-fold increase), Gja1 (3-fold increase) and Sphk1 (1.5-fold increase) were all upregulated in osteoclasts from SMAD1/5 cKO compared to control osteoclasts. Lastly osteoclasts treated with dorsomorphin, a chemical inhibitor of SMAD1/5 signaling, demonstrates an increase in Wnt1 and Gja1 expression similar to the SMAD1/5 cKO mice. Previous studies demonstrated that TGF-ß signaling in osteoclasts leads to increases in WNT1 expression by osteoclasts. Therefore, our data suggest that TGF-ß and BMP signaling pathways in osteoclasts could act in an antagonistic fashion to regulate osteoblast activity through WNT1 and other coupling factors.

Regulation of Osteoclast Differentiation by Myosin X.

Osteoclasts begin as mononuclear cells that fuse to form multinuclear cells able to resorb bone. The mechanisms that regulate all the steps of osteoclast differentiation are not entirely known. MYO10, an unconventional myosin, has previously been shown in mature osteoclasts to play a role in attachment and podosome positioning. We determined that MYO10 is also expressed early during osteoclast differentiation. Loss of MYO10 expression in osteoclast precursors inhibits the ability of mononuclear osteoclasts to fuse into multinuclear osteoclasts. Expression of Nfatc1, Dc-stamp, Ctsk, and ß 3 integrin is reduced in the osteoclasts with reduced MYO10 expression. A slight reduction in the osteoclasts ability to migrate, as well as a reduction in SMAD 1/5/8 phosphorylation are also noted with reduced MYO10 expression. Interestingly we also detected a change in the ability of the osteoclast precursors to form tunneling nanotubes (TNTs), which suggests that MYO10 may regulate the presence of TNTs through its interaction with the cytoskeletal proteins.

Smad1/5 and Smad4 expression are important for osteoclast differentiation.

To investigate the necessity of the canonical BMP pathway during osteoclast differentiation, we created osteoclasts with a conditional gene deletion for Smad1 and Smad5 (SMAD1/5), or Smad4 using adenovirus expressing CRE recombinase (Ad-CRE). Reduction of either Smad4 or Smad1/5 expression resulted in fewer and smaller multinuclear cells compared to control cells. We also detected changes in osteoclast enriched genes, demonstrated by decreased Dc-stamp and cathepsin K expression in both Smad4 and Smad1/5 Ad-CRE osteoclasts, and changes in c-fos and Nfatc1 expression in only Smad4 Ad-CRE cells. Lastly we also detected a significant decrease in resorption pits and area resorbed in both the Smad4 and Smad1/5 Ad-CRE osteoclasts. Because we inhibited osteoclast differentiation with loss of either Smad4 or Smad1/5 expression, we assessed whether BMPs affected osteoclast activity in addition to BMP's effects on differentiation. Therefore, we treated mature osteoclasts with BMP2 or with dorsomorphin, a chemical inhibitor that selectively suppresses canonical BMP signaling. We demonstrated that BMP2 stimulated resorption in mature osteoclasts whereas treatment with dorsomorphin blocks osteoclast resorption. These results indicate that the BMP canonical signaling pathway is important for osteoclast differentiation and activity.

Surface quality and long-term dimensional stability of current elastomeric impression materials after disinfection.

PURPOSE: The objectives of this investigation were to evaluate the effect of disinfection on surface quality and dimensional stability of more recent, reformulated vinylpolysiloxane (VPS) and polyether (PE) materials. METHODS: Using ANSI/American Dental Association (ADA) specification 19 protocols, 50 impressions of stainless steel dies were made with each material. Ten impressions of each material were randomly assigned to a treatment group: (1) no disinfectant; (2) 10-minute dual phenol immersion; (3) 1-hour dual phenol; (4) 10-minute sodium hypochlorite (NaOCl); and (5) 1-hour NaOCl. Impression surface quality immediately after disinfection was categorized as smooth/shiny, matte, or wrinkled/sticky. Dimensional stability was evaluated by measuring dimensional accuracy according to specification 19 after 24-hour, 1-week, and 2-week storage at ambient laboratory conditions. RESULTS: The PE material surface quality was significantly affected (Pearson Chi-square, p