Use of transcortical miniscrews for alveolar ridge preservation following tooth extraction: A pilot study.

OBJECTIVES: The purpose of this split-mouth pilot study was to investigate the effects of a transcortical miniscrew placed over the buccal plate of an extraction socket for alveolar ridge preservation in humans. METHODS: One week after the extraction of bilateral maxillary premolars, cone-beam computed tomography (CBCT) and intraoral digital imaging were performed (T0). A transcortical miniscrew was placed over the buccal plate of the extraction socket on one side (experiment), and the extraction socket on the contralateral side was left untreated (control). Follow-up CBCT and intraoral digital imaging were performed at 8 months immediately after miniscrew removal (T8). Changes in the width of the alveolar bone and ridge were measure by superimposing T0 and T8 of CBCTs and intraoral digital scans. RESULTS: Six participants completed the study protocol. Overall, the experimental side with the miniscrew demonstrated less bone loss and less alveolar ridge reduction than the control side. Bone loss on the experimental side (0.7 ± 0.2 mm) was significantly less than that on the control side (1.3 ± 0.7 mm) at the apical level of the socket on axial CBCT imaging (Wilcoxon signed rank test, p = .031). The experimental side (-18 ± 8%) exhibited less reduction in the alveolar ridge width than the control side (-21 ± 12%) at the crestal level on coronal superimposition of the intraoral digital scans. CONCLUSIONS: Transcortical miniscrew placement over the buccal plate of the extraction socket resulted in less resorption of the alveolar ridge and bone 8 months after tooth extraction. CLINICAL TRIAL REGISTRATION: NCT03205800: Temporary Anchorage Devices for Ridge Preservation (TAD).

A clinically friendly viscoelastic finite element analysis model of the mandible with Herbst appliance.

INTRODUCTION: As a powerful numerical approximation tool, finite element analysis (FEA) has been widely used to predict stress and strain distributions in facial bones generated by orthodontic appliances. Previous FEA models were constructed on the basis of a linear elastic phase of the bone response (eg, elastic bone strains to loading). However, what is more useful for clinical understanding would be predicting long-term strains and displacements of bone-segments responding to loading, yet tissue responses are (1) not promptly observable and (2) hard to predict in nature. METHODS: Viscoelastic property of the mandibular bone was incorporated into FEA models to visualize long-term, time-dependent stress and strain patterns in the mandible after being exposed to orthopedic stress. A mandible under loading by a Herbst appliance was modeled, and outcomes of the constructed elastic and viscoelastic models were compared. RESULTS: Patterns and magnitudes of the displacement throughout the mandible predicted by the viscoelastic model were exhibited in accordance with previous clinical outcomes of Herbst appliance therapy. The elastic models exhibited similar displacement patterns; however, the magnitude of the displacements in the models was invariably small (approximately 1 per 100) compared with those outputs of corresponding viscoelastic models. The corresponding maximum stress level in our viscoelastic mandible subjected to the Herbst appliance with the same loading was considerably low and relaxed in various regions when compared with the elastic model. CONCLUSIONS: We suggest that a viscoelastic model of the mandible mimics our general prediction of orthopedic treatment outcomes better than those by elastic models.

Zinc Up-Regulates Insulin Secretion from ß Cell-Like Cells Derived from Stem Cells from Human Exfoliated Deciduous Tooth (SHED).

Stem cells from human exfoliated deciduous tooth (SHED) offer several advantages over other stem cell sources. Using SHED, we examined the roles of zinc and the zinc uptake transporter ZIP8 (Zrt- and irt-like protein 8) while inducing SHED into insulin secreting ß cell-like stem cells (i.e., SHED-ß cells). We observed that ZIP8 expression increased as SHED differentiated into SHED-ß cells, and that zinc supplementation at day 10 increased the levels of most pancreatic ß cell markers-particularly Insulin and glucose transporter 2 (GLUT2). We confirmed that SHED-ß cells produce insulin successfully. In addition, we note that zinc supplementation significantly increases insulin secretion with a significant elevation of ZIP8 transporters in SHED-ß cells. We conclude that SHED can be converted into insulin-secreting ß cell-like cells as zinc concentration in the cytosol is elevated. Insulin production by SHED-ß cells can be regulated via modulation of zinc concentration in the media as ZIP8 expression in the SHED-ß cells increases.

Intermittent hypoxia in neonatal rodents affects facial bone growth.

Preterm human infants often show periodic breathing (PB) or apnea of prematurity (AOP), breathing patterns which are accompanied by intermittent hypoxia (IH). We examined cause-effect relationships between transient IH and reduced facial bone growth using a rat model. Neonatal pups from 14 timed pregnant Sprague-Dawley rats were randomly assigned to an IH condition, with oxygen altering between 10% and 21% every 4 min for 1 h immediately after birth, or to a litter-matched control group. The IH pups were compared with their age- and sex-matched control groups in body weight (WT), size of facial bones and nor-epinephrine (NE) levels in blood at 3, 4, and 5-weeks. Markedly increased activity of osteoclasts in sub-condylar regions of 3-week-old IH-treated animals appeared, as well as increased numbers of sympathetic nerve endings in the same region of tissue sections. Male IH-pups showed significantly higher levels of NE levels in sera at 3, 4 as well as 5-week-old time points. NE levels in 4- and-5-week-old female pups did not differ significantly. Intercondylar Width, Mandible Length and Intermolar Width measures consistently declined after IH insults in 3- and 4-week-old male as well as female animals. Three-week-old male IH-pups only showed a significantly reduced (p < 0.05) body weight compared to those of 3-week controls. However, female IH-pups were heavier than age-matched controls at all 3 time-points. Trabecular bone configuration, size of facial bones, and metabolism are disturbed after an IH challenge 1 h immediately after birth. The findings raise the possibility that IH, introduced by breathing patterns such as PB or AOP, induce significantly impaired bone development and metabolic changes in human newborns. The enhanced NE outflow from IH exposure may serve a major role in deficient bone growth, and may affect bone and other tissue influenced by that elevation.

Corrigendum: TRPV1 and TRPV1-Expressing Nociceptors Mediate Orofacial Pain Behaviors in a Mouse Model of Orthodontic Tooth Movement.

[This corrects the article DOI: 10.3389/fphys.2019.01207.].

TRPV1 and TRPV1-Expressing Nociceptors Mediate Orofacial Pain Behaviors in a Mouse Model of Orthodontic Tooth Movement.

Orthodontic force produces mechanical irritation and inflammation in the periodontium, which is inevitably accompanied by pain. Despite its prevalence, treatment of orthodontic pain is ineffective. Elucidating underlying neural mechanisms is critical to improving the management of orthodontic pain. We have assessed the contribution of transient receptor potential vanilloid subtype 1 (TRPV1) and the TRPV1-expressing subset of nociceptive afferents to pain behaviors induced by orthodontic force in mice. Microfocus X-ray computed tomography analysis showed that application of an orthodontic force of 10 g to the maxillary first molar produced reliable tooth movement in mice. Mouse grimace scale (MGS) was evaluated as an indication of non-evoked spontaneous pain and bite force (BF) was measured for assessing bite-evoked nocifensive behaviors. Orthodontic force increased MGS and decreased BF, both of which were interpreted as increased levels of pain. These behaviors peaked at 1d and returned near to the sham level at 7d. Retrograde labeling and immunohistochemical assays showed TRPV1-expressing peptidergic afferents are abundantly projected to the periodontium. Direct injection of resiniferatoxin into trigeminal ganglia (TG) decreased TRPV1-expressing afferents by half in the targeted region of TG. The chemical ablation of TRPV1-expressing afferents significantly attenuated orthodontic pain behaviors assessed by MGS and BF. Consistently, the knockout of TRPV1 also attenuated orthodontic force-induced changes in MGS and BF. These results suggest that TRPV1 and TRPV1-expressing trigeminal nociceptors constitute a primary pathway mediating orthodontic pain behaviors in mice. This model will be useful for mechanistic studies on orthodontic pain aimed at developing novel approaches for painless orthodontics.

Can facial type be used to predict changes in hyoid bone position with age? A perspective based on longitudinal data.

INTRODUCTION: Low positioning of the hyoid bone is associated with the unique human ability of speech, but it might also predispose the airway to collapse. The low position of the hyoid bone has been studied in adults with sleep apnea. However, information on age-related changes in hyoid bone position in the general adult population is sparse. METHODS: We used pairs of lateral cephalometric radiographs taken 15 years apart to assess vertical changes over time in hyoid position in 163 normal white men (ages, 30-72 years). RESULTS AND CONCLUSIONS: Significant changes in hyoid bone position were independent of age or obesity but were related to facial type, as classified by the steepness of the lower margin of the mandible. Changes in hyoid position over time were significant in dolichofacial subjects but not in brachyfacial subjects. This finding might be particularly important because a low hyoid bone with a brachial face appears to be a morphologic characteristic of nonobese patients with severe obstructive sleep apnea.

Disparity in opinions on lip protrusiveness in contemporary African American faces.

OBJECTIVE: In accordance with the changing demographics in the United States, orthodontists working on various ethnic populations should be more conscious when using the standardized profile analyses for the African American patient. The objective of this study was to examine whether the perception of lip protrusiveness in modern African American faces has changed. For this purpose, we investigated the most favorable African American lip profile using the opinions of 10 experienced and 10 newly trained younger orthodontists. METHODS: Attractiveness was converted to a number on visualized analog scales. Comparative ranks on 16 African American profiles, with focus on lip protrusiveness and thickness, were made among the groups. Mixed-effects linear regression models were fit and group differences were estimated. RESULTS: Younger orthodontists favored a more protrusive lip profile, and the variance in their perceptions was narrower than those of older orthodontists. Measurements related to upper lip protrusion showed the strongest correlation to attractiveness (r = -0.82). The association with attractiveness decreased linearly as the protrusiveness of the upper lip increased. Steiner's E-line was the most influential reference for determining the level of attractiveness for the older orthodontists, whereas upper lip protrusion was the most influential factor for the young orthodontists. CONCLUSIONS: An adequate level of lip protrusiveness and thickness should be essential for maintaining attractive esthetics in African American patients. Yet, a new set of standards for prominent lips in this population is necessary to reflect the current trend in the concept of a beautiful face in the modern world.

Obstructive sleep apnea patients with the oral appliance experience pharyngeal size and shape changes in three dimensions.

Pharyngeal size and shape differences between pre- and posttrials of a mandible-protruding oral appliance were investigated using cine computerized tomography (CT). Fourteen patients diagnosed with obstructive sleep apnea whose apnea-hypopnea index was higher than 5 and arousal index higher than 20 underwent a second overnight sleep study to evaluate the effectiveness of the oral appliance. Three-dimensional changes in pharyngeal shape measured on cross-sectional CT images during two respiratory cycles after oral appliance delivery were estimated by three variables: (1) lateral dimension, (2) anterior-posterior dimension, and (3) cross-sectional area at five vertical levels. Apnea indices improved significantly when the appliance was used. During apnea, measurements at retropalatal and retroglossal levels decreased most. However, the cross-sectional area of these levels appeared to increase significantly (P < .05) with the appliance in place during wakefulness. The oral appliance appears to enlarge the pharynx to a greater degree in the lateral than in the sagittal plane at the retropalatal and retroglossal levels of the pharynx, suggesting a mechanism for the effectiveness of oral appliances that protrude the mandible.

Controlled space closure with a statically determinate retraction system.

We designed a variant of a cantilever spring, the statically determinate retraction system, and studied its mechanical characteristics. This novel system consisted of a single-force cantilever arm made of 0.017 x 0.025-inch titanium molybdenum alloy wire for active retraction and a passive rigid stabilizing unit. Since the active component for space closure is a cantilever, it is simple to measure the force system of the spring with a force gauge (ie, the system is a statically determinate system). A torque tester apparatus was used to examine the property of this retraction spring with a helix at the posterior and a simple bend at the anterior. Both a standard shape and modified shapes of the spring were studied. At full activation, the standard spring delivered 163 g with a load-deflection rate of six g/mm. When the magnitude of the anterior bend of the spring was increased, the horizontal component of the force increased more than the vertical component. In contrast, when the posterior bend of the spring increased, the vertical component of the force increased more than the horizontal component. A clinical case presented here clearly demonstrates the versatility and applicability of the spring.

Response of masticatory muscles to passive stretch stimulus - from perspectives of functional appliances.

OBJECTIVE: The aims of this study were to examine whether a passive stretch stimulus by means of a functional appliance induces changes in the fiber composition of masticatory muscles and whether these changes are similar to the changes in stretched limb muscle fibers by using RT-PCR, western blot, and immunohistochemical assays. METHODS: Five male New Zealand White rabbits were fitted with a prefabricated inclined plane on the maxillary central incisors to force the mandible forward (- 2 mm) and downward (- 4 mm). Further, 1 hind limb was extended and constrained with a cast so that the extensor digitorum longus (EDL) was stretched when the animal used the limb. The animals were sacrificed after 1 week and the masseter, lateral pterygoid, and EDL were processed and compared with those from control animals (n = 3). RESULTS: The stretched EDL had a significantly higher percentage of slow fibers, whereas the stretched masticatory muscles did not show changes in the composition of the major contractile proteins after 7 days. CONCLUSIONS: The transition of fiber phenotypes in response to a stretch stimulus may take longer in the masticatory muscles than in the limb muscles.

Work-pattern differences between male and female orthodontists.

INTRODUCTION: Traditionally, most orthodontists have been men. In recent years, however, the number of women in dentistry and dental specialties, including orthodontics, has increased dramatically. Because practice patterns of male and female orthodontists might differ, they should be evaluated so that our schools can produce enough providers for the future. METHODS: Questionnaires were mailed to 798 orthodontists; the response rate was 68.8%. Questions about practice behavior and productivity were designed to assess sex difference with respect to age, marital status, and number of children. RESULTS: Number of children appeared to be a good predictor of days worked per week and length of leaves of absence for female orthodontists. Solo practitioners dominate the field of orthodontics, irrespective of age or sex. Although women were less likely than men to be practice owners, only 20% of the women responding were not in an ownership position. Women were slightly more likely to be involved in a group practice, they worked in fewer offices than men, and they employed fewer full-time and part-time people. Female nonowners were more likely to take longer leaves of absence. Overall, women worked slightly fewer days per week and spent fewer hours per week in direct patient care. Annually, they devoted 25 fewer days to practice than men, but, when adjusted for leaves of absence, men and women worked similar numbers of weeks in 1999. CONCLUSIONS: Among orthodontists, work patterns of men and women differ somewhat, but these differences might not be as significant as other factors; more study is required.