Dentoperiodontal and skeletal changes induced by miniscrew-assisted rapid maxillary expansion (C-expander) treatment in adults: A retrospective clinical trial.

INTRODUCTION: The objective of this study was to evaluate the dental periodontal and skeletal response to ≥5 mm of expansion width achieved by C-expander treatment with posterior miniscrews placed between the first and second molars in adults. METHODS: A total of 28 patients aged 21.91 ± 3.20 years with maxillary transverse deficiency underwent C-expander treatment. Anterior miniscrews were positioned between the first and second premolars, whereas posterior miniscrews were positioned between the first and second molars. Cone-beam computed tomography records were obtained before expansion and 3 months after expansion. The dental periodontal and skeletal changes for all patients were recorded. RESULTS: The C-expander treatment expanded the palatal suture with slight buccal alveolar bone inclination. An increase in the nasal cavity width and a greater increase in the maxillary base bone width were observed after maxillary expansion. The expansion at the posterior nasal spine (3.78 mm) was approximately 85.7% of that at the anterior nasal spine (4.41 mm). No significant buccal dehiscence occurred after expansion, whereas the mesiobuccal alveolar bone thickness of the first molars was decreased at the 8 mm level with respect to the cementoenamel junction. The first molar showed decreased inclination (right, -0.45°; left, -0.38°, P >0.05), whereas the expansion at the apical level was less than that at the crown level. Age and the skeletal/dental expansion ratio had no discernible relationship. CONCLUSIONS: Miniscrew-assisted C-expander treatment can be effective for adults with maxillary transverse deficiency. Rearward placement of the miniscrews may create an approximately parallel expansion. Most maxillary expansion was derived from skeletal expansion with slight alveolar bone buccal inclination.

Effect of tension and compression on dynamic alveolar histomorphometry.

Here, we tested the hypothesis that tensile and compressive stresses generated in the alveolar bone proper regulate site-specific cellular and functional changes in osteoclasts and osteoblasts. Thirty-two 13-week-old male mice were randomly divided into four groups: two experimental groups with vertical loading obliquely from the palatal side to the buccal side of the maxillary molar (0.9 N) 30 min per day for 8 or 15 days and unloaded controls (n = 8). Calcein and alizarin were administered 8 and 2 days before euthanization, respectively, to detect the time of bone formation. Undecalcified sections parallel to the occlusal plane were prepared on the palatal root and the surrounding alveolar bone in the middle of the root length. The alveolar perimeter was divided into 12 equal regions for site analysis, and the bone histomorphometric parameters were obtained for each region. Data from in vivo microfocus computed tomography were used to construct animal-specific finite element models. 2D stress distribution images were overlain on histology images obtained from the same location. Significant differences in the total perimeter between groups and between loading and unloading in each region were statistically analyzed (α = 0.05). Osteoclast counts and the alizarin label ratio were significantly higher in the loaded group than in the unloaded group in regions where the maximum von Mises and principal tensile stresses were the highest along the perimeter. The label ratio of calcein was significantly lower in the 8-day loaded group than in the unloaded group, indicating that the calcein-labeled surface was resorbed by osteoclasts that appeared during the loading period. The effect of loading was mitigated by an increase in the maximum principal compressive stress. We conclude that bone resorption and bone formation are functions of site-specific tension and compression in the alveolar bone proper, confirming our hypothesis. This finding is critical for the advancement of diagnosis and treatment planning in clinical dentistry.

Effects of teriparatide on bone formation in rats with experimentally induced premaxillary expansion.

OBJECTIVE: This study aimed to evaluate the effects of systemic teriparatide on sutural bone formation after premaxillary suture expansion in rats. MATERIAL AND METHODS: Twenty Wistar male rats (8-10 weeks old) were randomly divided into two groups, namely, control (C, n=10) and teriparatide (T, n=10). An expansion force was applied to the maxillary incisors using helical spring for a seven-day expansion period, for both groups. On the eighth day, the rats were kept for a seven-day consolidation period, and then 60 µg/kg teriparatide (once a day) was administered to group T subcutaneously for seven days. Then, all the rats were sacrificed, and histological sections were stained with hemotoxylin-eosin for examination. Anti-osteonectin, anti-osteocalcin, anti-Vascular endothelial growth factor (VEGF) and anti-transforming growth factor beta (TGF-ß) were evaluated by immunohistochemical analysis in the midpalatal suture area. RESULTS: Histologically, the newly formed bone tissue was observed to be larger in group T than in group C. The number of immunoreactive osteoblasts for osteonectin, osteocalcin and VEGF antibodies was significantly higher in group T than in group C (p = 0.0001). The TGF-ß antibody showed a mild reaction in group T, but did not reach significance in comparison with group C (p ˃ 0.05). CONCLUSION: Systemic teriparatide application following the premaxillary expansion of the suture area may stimulate bone formation and add to the consolidation of the expansion in rats by regulating osteonectin, osteocalcin and VEGF.

Effect of advanced periodontal self-care in patients with early-stage periodontal diseases on endothelial function: An open-label, randomized controlled trial.

Although a significant association between periodontal disease and atherosclerotic cardiovascular disease has been reported, their cause-to-effect relationship remains controversial. This randomized controlled clinical trial aimed to investigate the effect of advanced self-care on atherosclerotic cardiovascular disease-related vascular function markers flow-mediated brachial artery dilatation (FMD) and serum asymmetric dimethylarginine (ADMA) level in patients with early-stage periodontal disease. The study was designed as a parallel group, 3-month follow-up, open-label, randomized controlled trial. The control group received standard care for periodontal diseases, whereas the test group additionally applied disinfectant using a custom-fabricated prescription tray for advanced self-care twice a day. Overall, 110 patients provided data for FMD and serum ADMA level. No significant improvements in FMD were observed in the control (mean increase, -0.1%; 95% confidence interval [CI], -1.0-0.8; P = 0.805) or test (mean increase, -0.3%; 95% CI, -1.1-0.4; P = 0.398) group. No significant changes in serum ADMA levels were observed (mean reduction, 0.01 µmol/L; 95% CI, -0.00-0.02; P = 0.366 and mean reduction, 0.00 µmol/L; 95% CI, -0.01-0.01; P = 0.349, respectively). No significant between-group differences were found in FMD (mean difference, -0.2%; 95% CI, -1.4-0.9; p = 0.708) or serum ADMA levels (mean difference, 0.01 nmol/L; 95% CI, -0.00-0.03; p = 0.122). Significant improvements in the average probing pocket depth were observed in the control and test groups. The bleeding on probing score in the test group was significantly reduced, while that in the control group was reduced, although not significantly. Periodontal care for a 3-month duration did not provide better endothelial function although improvements of periodontal status in patients with early-stage periodontal diseases. This trial is registered in UMIN Clinical Trials Registry (www.umin.ac.jp/ctr/; ID: UMIN000023395).

Intraoral scanners for capturing the palate and its relation to the dentition.

Proper superimposition of intraoral scan generated 3D models enables detailed assessment of soft and hard tissue surface changes. This requires accurate 3D models and stable structures as superimposition references. In the maxilla, different reference areas have been proposed, mostly located at the palatal region. In this in vivo study we evaluated the precision of two intraoral scanners (TRIOS 3, 3Shape and CS 3600, Carestream) at the maxilla, focusing on the palate itself and also on its spatial relation to the dentition, following palatal superimposition. Precision was tested through the superimposition of repeated scans on the palate and the dental arch. Overall, the median precision of both scanners was high (< 0.1 mm). Scanner precision was comparable when the palatal area was tested individually. However, TRIOS 3 showed higher precision regarding the assessment of the dental arch, following superimposition of repeated models on the palate (median difference: approximately 40 µm). In few cases, local areas of higher imprecision were present for both scanners, exceeding 0.3 mm. Thus, scanner precision seems to be high in small, but slightly reduced considering larger areas, with differences between scanners. However, the effect on individual tooth position relative to the palate was for both scanners limited.

Computational biomechanical modelling of the rabbit cranium during mastication.

Although a functional relationship between bone structure and mastication has been shown in some regions of the rabbit skull, the biomechanics of the whole cranium during mastication have yet to be fully explored. In terms of cranial biomechanics, the rabbit is a particularly interesting species due to its uniquely fenestrated rostrum, the mechanical function of which is debated. In addition, the rabbit processes food through incisor and molar biting within a single bite cycle, and the potential influence of these bite modes on skull biomechanics remains unknown. This study combined the in silico methods of multi-body dynamics and finite element analysis to compute musculoskeletal forces associated with a range of incisor and molar biting, and to predict the associated strains. The results show that the majority of the cranium, including the fenestrated rostrum, transmits masticatory strains. The peak strains generated over all bites were found to be attributed to both incisor and molar biting. This could be a consequence of a skull shape adapted to promote an even strain distribution for a combination of infrequent incisor bites and cyclic molar bites. However, some regions, such as the supraorbital process, experienced low peak strain for all masticatory loads considered, suggesting such regions are not designed to resist masticatory forces.

Assessment of Age at the Stages of the Eruption of Third Molar Teeth among the People of North-Eastern India.

METHODS: A cross-sectional descriptive and analytical study was undertaken with 1060 Assamese individuals (642 males and 418 females) aged 14-26 years and was subjected to a clinical, dental, and general physical examination from January 2014 to December 2018. The data were statistically analyzed using Microsoft Excel and the Statistical Package for the Social Sciences (SPSS) version 22. The significant differences among variables were tested using the chi-square test and Student's t-test, considering a p value < 0.05 as significant. RESULTS: The carried-out research showed no eruption (NE) status of M3 with an overall mean (±SD) age at 17.39 (±2.273) years, although a significantly lower age among males with a mean age of 16.92 (±2.138) years (p value < 0.001) was observed. The mean age (overall) for the complete eruption (CE) was observed at 20.33 (±2.566) years, which was seen earlier in males. The mandibular M3 appears earlier compared to the maxillary M3. The third molar eruption (TME) on both left and right quadrants of the jaw was observed substantially earlier in the lower jaw, compared to the upper jaw (p value < 0.025). The earliest CE of M3 was marked at 15 years. The differences in the frequencies of TME in different chronological age groups were found significant (p value < 0.001). A significant association between gender and TME (p value < 0.045) in the current study is worth noting. CONCLUSION: Thus, determined by TME as a valid method, age can be used for various purposes to establish a person's identity. Dental age estimated using third molar eruption status has a weighty association with chronological age. Thus, it should be utilized to determine the likely age of an individual.

Estudo da anatomia do septo nasal e sua relação com a morfologia do complexo nasomaxilar / Study of the anatomy of the nasal septum and its relationship with the morphology of the nasomaxillary complex

O presente estudo teve como objetivo investigar a influência do desvio do septo nasal (DSN) na morfologia do complexo nasomaxilar quanto a confiabilidade e precisão na marcação de pontos craniofaciais bidimensionais (2D) e tridimensionais (3D) em imagens de tomografia computadorizada de feixe cônico (TCFC), verificação de assimetrias do complexo nasomaxilar em indivíduos com diferentes níveis de DSN em estágios de maturação esquelética distintos, e analisar a associação entre o grau de severidade do DSN e o grau de assimetria do complexo nasomaxilar. Este foi um estudo observacional retrospectivo que utilizou um total de 60 TCFC alocadas em 4 grupos (n = 15) de acordo com o grau de desvio septal e maturação esquelética (DSN <10°, desvio de septo nasal leve, e DSN >10°, desvio de septo nasal moderado a severo, ambos antes e depois do surto de crescimento). A etapa de validação do estudo compreendeu a utilização de 30 TCFC e demarcação de 25 pontos craniofaciais, a fim de avaliar a confiabilidade e precisão desses pontos nas regiões nasal, palatina e facial lateral. Dois métodos foram utilizados: 2D, em cortes multiplanares de TCFC no programa CS 3D Imaging; e 3D, com a segmentação 3D do crânio com visualização simultânea dos cortes multiplanares no programa ITK Snap. Os dados das coordenadas foram analisados por meio do Índice de Correlação Intraclasse (ICC), média das diferenças entre os tempos das medições, fórmula de Dahlberg e gráficos de Bland-Altman. A análise da relação entre a anatomia do septo nasal e morfologia do complexo nasomaxilar, compreendeu a utilização de 60 TCFC e a demarcação de 23 pontos bidimensionais e, avaliados quanto a presença de assimetria flutuante, por meio da análise de Procrustes ANOVA, comparação intergrupos com o teste de Mann- Whitney, além do teste de correlação de Spearman e regressão multivariada (a=0,05). Os resultados obtidos nas avaliações da reprodutibilidade dos pontos craniofaciais nos mostraram que o ICC variou de 0,95 a 1,0 no método 2D e foi maior ou igual a 0,99 no método 3D, indicando que ambos os métodos tiveram alta confiabilidade. A fórmula de Dahlberg, juntamente com Bland-Altman indicaram menor precisão nos pontos zigomáticomaxilar e orbitário no método 3D, e sutura zigomáticotemporal no método 2D. Os pontos ímpares (a maioria no plano sagital mediano) e os pontos frontozigomático temporal e frontozigomático orbital tiveram os melhores resultados de precisão. Com relação a influência do DSN e assimetrias no complexo nasomaxilar, nossos resultados principais mostraram que não foram observadas diferenças estatisticamente significativas entre as distâncias de Procrustes e Mahalanobis (assimetria flutuante) do complexo nasomaxilar entre os grupos avaliados (P>0.05). Entretanto, com os resultados da regressão multivariada, relacionado aos aspectos mais específicos de assimetria (componente assimétrico), houve uma correlação positiva entre o ângulo DSN e componente assimétrico das regiões palatinas (P=0.035 e P=0.047, média e posterior, respectivamente), e também com a forma do SN e componente assimétrico da região palatina anterior (P=0.039). Sendo assim, concluímos que, ambos os métodos 2D e 3D de marcação de pontos craniofaciais no complexo nasomaxilar e facial lateral apresentaram alta confiabilidade, entretanto, o método 2D apresentou maiores valores de precisão na maioria dos pontos avaliados. Além disso, todos os pontos avaliados neste estudo foram considerados aceitáveis para fins clínicos. Com relação a análise da anatomia do septo nasal e morfologia do complexo nasomaxilar, todos os grupos avaliados apresentaram níveis significativos de assimetria flutuante. Entretanto, não foram observadas diferenças significativas na assimetria flutuante do complexo nasomaxilar nos grupos com DSN leve em relação aos grupos com DSN moderado a severo, em ambos os estágios de maturação esquelética. Por fim, foi observada correlação positiva entre o ângulo DSN e o componente de assimetria nas regiões palatinas média e posterior e entre a forma do septo nasal e a região palatina anterior. Não foram observadas correlações significativas com as regiões nasal e lateral do complexo nasomaxilar. (AU)

The present study aimed to investigate the influence of nasal septum deviation (NSD) on the morphology of the nasomaxillary complex regarding reliability and accuracy in two-dimensional (2D) and three-dimensional (3D) craniofacial landmarks in cone beam computed tomography images (CBCT), verification of asymmetries of the nasomaxillary complex in individuals with different levels of NSD at different stages of skeletal maturation, and to analyze the association between the degree of severity of the NSD and the degree of asymmetry of the nasomaxillary complex. This was a retrospective, crosssectional observational study that used a total of 60 CBCT. For the validation study, 30 CTBC were used and 25 craniofacial landmarks were marked, in order to compare the reliability and precision of these landmarks in the nasal, palatal and lateral facial regions. Two methods were used: 2D, in CBCT multiplanar sections using CS 3D Imaging Software; and 3D, from the 3D segmentation of the skull in the software ITK Snap associated with multiplanar sections. Coordinates data were analyzed using the Intraclass Correlation Coefficient (ICC), Dalhberg's formula, Bland-Altman plots and mean differences between measurement trials. To study the relationship between nasal septum and nasomaxillary complex, the 60 CBCT were divided into 4 groups (n = 15) according to the degree of septal deviation and skeletal maturation (NSD <10°, mild nasal septum deviation, e NSD >10°, moderate to severe nasal septum deviation, both before and after the growth spurt). 23 two-dimensional landmarks were marked and, to assess asymmetries, we used Procrustes ANOVA, intergroups comparisons with the Mann-Whitney test, in addition to the Spearman's correlation test and multivariate regression. The results obtained in the evaluations of the reliability and precision of craniofacial landmarks showed that the ICC ranged from 0.95 to 1.0 in the 2D method and was greater than or equal to 0.99 in the 3D method, indicating that both methods had high reliability. Dahlberg's formula, together with Bland-Altman, indicated lower precision in the landmarks zygomaxillare and orbitale in the 3D method, and zygomaticotemporal suture in the 2D method. The unpaired landmarks (mainly located at the midsagittal plane) and the landmarks frontomalar temporale and frontomalar orbitale had the best results of precision. Regarding the influence of NSD and asymmetries in the nasomaxillary complex, our main results showed that no statistically significant differences were observed between the Procrustes and Mahalanobis distances (fluctuating asymmetry) of the nasomaxilar complex between the groups (P>0.05). However, with the results of the multivariate regression, related to the more specific aspects of asymmetry (asymmetry component), there was a positive correlation between the NSD angle and palatal regions (P=0.035 and P=0.047, middle and posterior, respectively), and also with the shape of the NS and the anterior palatal region (P=0.039). Therefore, we conclude that both the 2D and 3D methods of positioning craniofacial landmarks in the nasomaxillary complex and the lateral facial region showed high reliability, however, the 2D method showed higher precision values in most of the landmarks evaluated. Furthermore, all landmarks evaluated in this study are are reasonably considered acceptable for clinical purposes. Regarding the study of the nasal septum and nasomaxillary complex, all groups evaluated presented significant levels of fluctuating asymmetry. However, no significant differences were observed in the fluctuating asymmetry of the nasomaxillary complex in the groups with mild NSD compared to the groups with moderate to severe NSD, in both stages of skeletal maturation. Finally, a positive correlation was observed between the NSD angle and the asymmetry component in the middle and posterior palatine regions and between the shape of the nasal septum and the anterior palatine region asymmetry component. There were no significant correlations with the nasal and lateral regions of the nasomaxillary complex. (AU)

The Influence of Nanostructured Hydroxyapatite Surface in the Early Stages of Osseointegration: A Multiparameter Animal Study in Low-Density Bone.

BACKGROUND AND OBJECTIVE: The success rates of dental implants in low-density bone have been reported as a challenge, especially for early or immediate loading in the maxilla posterior area. Nanoscale architecture affects the roughness, surface area, surface energy of the implant and can enhance osseointegration. This study aimed to evaluate the implant-surface topography and biomechanical, histomorphometric, and histological bone responses to a new nanostructured hydroxyapatite surface placed in the iliac crest of sheep. METHODS: Ten female sheep (2-4 years) received 30 implants (n=10/group): HAnano® coated (Epikut Plus®, S.I.N. Implant System, Sao Paulo, SP, Brazil), SLActive (BLX®, Straumann, Basel, Switzerland), and TiUnite (NobelActive®, Nobel Biocare, Göteborg, Sweden) surfaces. Scanning electron microscopy with energy-dispersive spectroscopy evaluated the implant surface topography, the insertion torque value, and resonance frequency analysis evaluated the primary stability, bone-implant contact, and bone-area fraction occupancy were evaluated after 14 and 28 days after implant placement. RESULTS: The surface morphology was considerably comparable between the implant groups'; however, the TiUnite® group presented a remarkable different surface. The SLActive® and TiUnite® groups presented an insertion torque average of 74 (±8.9) N/cm that was similar to that of HAnano® 72 (±8.3) N/cm (p >0.05). The resonance frequency evaluated with Osstell®/SmartPeg® or Penguin®/MulTipeg® showed similar results when assessing implants from the same group. BIC and BAFO significantly increased (p<0.05) throughout the experimental periods to all groups, but BIC and BAFO values were similar among the implants at the same time point. After 4 weeks, bone-implant contact was higher than 80% of the total length analyzed. New bone occupies around 60% of analyzed area around the implants. CONCLUSION: HAnano® coated surface promoted comparable osseointegration as SLActive and TiUnite in the sheep model. The three tested surfaces showed comparable osseointegration at the early stages of low-density bone repair in the sheep model.

Biomechanical Analysis of Grafted and Nongrafted Maxillary Sinus Augmentation in the Atrophic Posterior Maxilla with Three-Dimensional Finite Element Method.

This study is aimed at determining the optimal sinus augmentation approach considering the poor bone condition in the zone of atrophic posterior maxilla. A series of simplified maxillary segment models varying in residual bone height (RBH) and bone quality were established. A 10 mm standard implant combined with two types of maxillary sinus augmentation methods was applied with the RBH, which was less than 10 mm in the maxilla. The maximal equivalent von Mises (EQV) stress in residual bone was evaluated. Bone quality had an enormous impact on the stress magnitude of supporting bone. Applying sinus augmentation combined with grafts was suitable for stress distribution, and high-stiffness graft performed better than low-stiffness one. For 7 mm and 5 mm atrophic maxilla, nongrafted maxillary sinus augmentation was feasible in D3 bone. Poor bone quality was a negative factor for the implant in the region of atrophic posterior maxilla, which could be improved by grafts. Meanwhile, the choice of maxillary sinus augmentation approaches should be determined by the RBH and quality.

Association between Bone Density Values, Primary Stability and Histomorphometric Analysis of Dental Implant Osteotomy Sites on the Upper Jaw.

INTRODUCTION: Sufficient bone volume, as well as the bone quality characteristics are necessary prerequisites to ensure optimal mechanical stability of the implants and subsequent osseointegration. AIM: The aim of the present study was to assess the correlation between bone density values obtained by cone-beam computed tomography (CBCT), the primary stability of dental implants and the histomorphometric analysis of bone quality. MATERIALS AND METHODS: Following tooth extraction, socket preservation with frieze-dried bone allograft or protein-rich fibrin (PRF) was performed on 30 patients with 30 maxillary teeth in the region from second premolar to second premolar. Four months after the procedure, CBCT was used to assess the bone density (Hounsfield units) in the area of extraction. Thirty bone samples were harvested from implant sites using a trephine drill. They were analyzed with Image J software. Immediately after placing the implant, the implant stability quotient was measured using the Osstell Idx device. RESULTS: The results revealed significant correlations between bone density and primary stability along the vestibulo-oral (r=0.392, p=0.032) and mesiodistal axes (r=0.407, p=0.026). Bone density also correlated strongly with the percentage of newly formed bone (r=0.776, p<0.001). CONCLUSION: Bone quality, in terms of bone density measured in CBCT and new bone formation are correlated to the primary stability of the dental implants and vice versa.

Structure and function of the stylets of hematophagous Triatominae (Hemiptera: Reduviidae), with special reference to Dipetalogaster maxima.

Kissing bugs (Hemiptera: Reduviidae: Triatominae) are able to bend their rod-like maxillae while searching for blood vessels in the tissue of their vertebrate hosts. Little is known about the working mechanisms of these bending movements and the distal opening of the food channel. We compared the morphological structure of the stylets (mandibles and maxillae) of four triatomine species and analyzed the feeding process of Dipetalogaster maxima (Uhler, 1894). The maxillae of triatomine bugs are interlocked by a tongue-and-groove system, allowing longitudinal sliding. While penetrating the host tissue, the animals perform rapid alternate back and forth movements of the maxillae. The resistance of the surrounding tissue pushes the asymmetric apex of the maxillae away from its straight path, i.e., if one individual maxilla is protracted alone, its tip curves inwards, and the other maxilla follows. Once a blood vessel is tapped, the spine-like tip of the left maxilla splays outwards. Apically, each of the maxillae features an abutment, the left one exhibiting a notch that presumably facilitates splaying. The mechanical interaction of the two maxillary abutments enables the distal opening of the food channel but might also support the movements of the maxillary bundle attributable to different bending moment distributions.

Dentofacial mini- and microesthetics as perceived by dental students: A cross-sectional multi-site study.

BACKGROUND: How dental education influences students' dental and dentofacial esthetic perception has been studied for some time, given the importance of esthetics in dentistry. However, no study before has studied this question in a large sample of students from all grades of dental school. This study sought to fill that gap. The aim was to assess if students' dentofacial esthetic autoperception and heteroperception are associated with their actual stage of studies (grade) and if autoperception has any effect on heteroperception. METHODS: Between October 2018 and August 2019, a questionnaire was distributed to 919 dental students of all 5 grades of dental school at all four dental schools in Hungary. The questionnaire consisted of the following parts (see also the supplementary material): 1. Demographic data (3 items), Self-Esthetics I (11 multiple- choice items regarding the respondents' perception of their own dentofacial esthetics), Self-Esthetics II (6 Likert-type items regarding the respondents' perception of their own dentofacial esthetics), and Image rating (10 items, 5 images each, of which the respondents have to choose the one they find the most attractive). Both the self-esthetics and the photo rating items were aimed at the assessment of mini- and microesthetic features. RESULTS: The response rate was 93.7% (861 students). The self-perception of the respondents was highly favorable, regardless of grade or gender. Grade and heteroperception were significantly associated regarding maxillary midline shift (p < 0.01) and the relative visibility of the arches behind the lips (p < 0.01). Detailed analysis showed a characteristic pattern of preference changes across grades for both esthetic aspects. The third year of studies appeared to be a dividing line in both cases, after which a real preference order was established. Association between autoperception and heteroperception could not be verified for statistical reasons. CONCLUSION: Our findings corroborate the results of most previous studies regarding the effect of dental education on the dentofacial esthetic perception of students. We have shown that the effect can be demonstrated on the grade level, which we attribute to the specific curricular contents. We found no gender effect, which, in the light of the literature, suggests that the gender effect in dentofacial esthetic perception is highly culture dependent. The results allow no conclusion regarding the relation between autoperception and heteroperception.

Disconnect between the developing eye and craniofacial prominences in the avian embryo.

In the amniote embryo, the upper jaw and nasal cavities form through coordinated outgrowth and fusion of craniofacial prominences. Adjacent to the embryonic prominences are the developing eyes, which abut the maxillary and lateral nasal prominences. The embryos of extant sauropsids (birds and nonavian reptiles) develop particularly large eyes in comparison to mammals, leading researchers to propose that the developing eye may facilitate outgrowth of prominences towards the midline in order to aid prominence fusion. To test this hypothesis, we performed unilateral and bilateral ablation of the developing eyes in chicken embryos, with the aim of evaluating subsequent prominence formation and fusion. Our analyses revealed minor interaction between the developing craniofacial prominences and the eyes, inconsequential to the fusion of the upper beak. At later developmental stages, the skull exhibited only localized effects from missing eyes, while geometric morphometrics revealed minimal effect on overall shape of the upper jaw when it develops without eyes. Our results indicate that the substantial size of the developing eyes in the chicken embryo exert little influence over the fusion of the craniofacial prominences, despite their effect on the size and shape of maxillary prominences and components of the skull.

Autologous platelet concentrates in maxillofacial regenerative therapy.

Platelet concentrates have emerged as innovative autologous blood products that enhance tissue healing and regeneration in regenerative therapy. A common feature of these products is their higher than baseline platelet concentration, which improves wound healing and tissue repair. Four main categories of products can be easily defined, based on their leukocyte content and fibrin architecture: pure platelet-rich plasma, such as Cell Separator PRP or Anitua' PRGF; leukocyte- and platelet-rich plasma (L-PRP), such as PCCS or Ace PRP; pure platelet-rich fibrin (P-PRF), such as Fibrinet PRFM; and leukocyte- and platelet-rich fibrin (L-PRF), such as Choukroun's PRF. Two families contain significant concentrations of leukocytes: L-PRP and L-PRF. These four families of products have different biological signatures and mechanisms and obviously different clinical applications. An L-PRF membrane releases growth factors and matrix proteins over a period longer than 7 days, whereas a PRP gel matrix releases and disperses its growth factors in a relatively quick download. In the near future, simple and inexpensive products such as L-PRF are expected to have applications in oral-maxillofacial surgery, periodontal surgery, plastic surgery, orthopedic surgery, and sports medicine. Leukocytes substantially affect the intrinsic biology and properties of platelet concentrates, not only because they enhance immune function and antibacterial potential, but also because they have essential roles in the wound healing process. Unfortunately, their impact has been almost completely neglected in the literature. Improved understanding of the effects of leukocytes in wound healing is essential for development of new clinical applications of platelet concentrates.

Scaling of Anatomically Derived Maximal Bite Force in Primates.

By combining muscle architectural data with biomechanical variables relating to the jaw, we produce anatomically derived maximum bite force estimations for 23 species of catarrhine and platyrrhine primates. We investigate how bite force scales across the sample as a whole (and within each parvorder) relative to two size proxies, body mass and cranial geometric mean, and the effect of diet upon bite force. Bite force is estimated at three representative bite points along the dental row: the first maxillary incisor, canine, and third-most mesial paracone. We modeled bite force by combining calculated physiological cross-sectional area of the jaw adductors from Hartstone-Rose et al. [Anat Rec 301 (2018) 311-324] with osteological measurements of lever- and load-arm lengths from the same specimens [Hartstone-Rose et al., Anat Rec 295 (2012) 1336-1351]. Bite force scales with positive allometry relative to cranial geometric mean across our entire sample and tends toward positive allometry relative to body mass. Bite force tends toward positive allometry within platyrrhines but scales isometrically within catarrhines. There was no statistically significant scaling difference with diet. Our findings imply an absence of a dietary signal in the scaling of bite force, a result that differs from the scaling of physiological cross-sectional area alone. That is, although previous studies have found a dietary signal in the muscle fiber architecture in these species, when these are combined with their leverages, that signal is undetectable. On the parvorder level, our data also demonstrate that the platyrrhine masticatory system appears more mechanically advantageous than that of catarrhines. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:2026-2035, 2020. © 2019 American Association for Anatomy.

System for application of controlled forces on dental implants in rat maxillae: Influence of the number of load cycles on bone healing.

Experimental studies on the effect of micromotion on bone healing around implants are frequently conducted in long bones. In order to more closely reflect the anatomical and clinical environments around dental implants, and eventually be able to experimentally address load-management issues, we have developed a system that allows initial stabilization, protection from external forces, and controlled axial loading of implants. Screw-shaped implants were placed on the edentulous ridge in rat maxillae. Three loading regimens were applied to validate the system; case A no loading (unloaded implant) for 14 days, case B no loading in the first 7 days followed by 7 days of a single, daily loading session (60 cycles of an axial force of 1.5 N/cycle), and case C no loading in the first 7 days followed by 7 days of two such daily loading sessions. Finite element modeling of the peri-implant compressive and tensile strains plus histological and immunohistochemical analyses revealed that in case B any tissue damage resulting from the applied force (and related interfacial strains) did not per se disturb bone healing, however, in case C, the accumulation of damage resulting from the doubling of loading sessions severely disrupted the process. These proof-of-principle results validate the applicability of our system for controlled loading, and provide new evidence on the importance of the number of load cycles applied on healing of maxillary bone.

Muscle-Bone Crosstalk in the Masticatory System: From Biomechanical to Molecular Interactions.

The masticatory system is a complex and highly organized group of structures, including craniofacial bones (maxillae and mandible), muscles, teeth, joints, and neurovascular elements. While the musculoskeletal structures of the head and neck are known to have a different embryonic origin, morphology, biomechanical demands, and biochemical characteristics than the trunk and limbs, their particular molecular basis and cell biology have been much less explored. In the last decade, the concept of muscle-bone crosstalk has emerged, comprising both the loads generated during muscle contraction and a biochemical component through soluble molecules. Bone cells embedded in the mineralized tissue respond to the biomechanical input by releasing molecular factors that impact the homeostasis of the attaching skeletal muscle. In the same way, muscle-derived factors act as soluble signals that modulate the remodeling process of the underlying bones. This concept of muscle-bone crosstalk at a molecular level is particularly interesting in the mandible, due to its tight anatomical relationship with one of the biggest and strongest masticatory muscles, the masseter. However, despite the close physical and physiological interaction of both tissues for proper functioning, this topic has been poorly addressed. Here we present one of the most detailed reviews of the literature to date regarding the biomechanical and biochemical interaction between muscles and bones of the masticatory system, both during development and in physiological or pathological remodeling processes. Evidence related to how masticatory function shapes the craniofacial bones is discussed, and a proposal presented that the masticatory muscles and craniofacial bones serve as secretory tissues. We furthermore discuss our current findings of myokines-release from masseter muscle in physiological conditions, during functional adaptation or pathology, and their putative role as bone-modulators in the craniofacial system. Finally, we address the physiological implications of the crosstalk between muscles and bones in the masticatory system, analyzing pathologies or clinical procedures in which the alteration of one of them affects the homeostasis of the other. Unveiling the mechanisms of muscle-bone crosstalk in the masticatory system opens broad possibilities for understanding and treating temporomandibular disorders, which severely impair the quality of life, with a high cost for diagnosis and management.

The Alveolar Ridge Splitting Technique on Maxillae: A Biomechanical Human Cadaveric Investigation.

The alveolar ridge splitting technique (ARST) offers an alternative to classic ridge augmentation techniques for successful insertion of dental implants. However, the buccal lamella is at risk of fracturing during ARST distraction. To better understand the fracture mechanisms and displacement limits of the split lamella, this study conducted biomechanical tests on human cadaveric maxilla specimens having extremely atrophied alveolar ridges treated with ARST. A total of 12 standardized alveolar splits were prepared on the maxillae of 3 elderly female donors using an oscillating piezoelectric saw. Mimicking the surgical distraction process of the lamella, each split was tested to failure using a dental osteotome attached to the crosshead of an electromechanical testing system. All specimens were scanned by means of high-resolution peripheral quantitative computed tomography prior to and post testing to evaluate split geometries and failure modes. Split stiffness, failure force, and displacement were 27.4 ± 18.7 N/mm, 12.0 ± 8.4 N, and 0.97 ± 0.31 mm, with no significant differences between anatomical sides and split locations (p ≥ 0.17). Stiffness correlated significantly with failure force (R 2 = 0.71, p < 0.01). None of the alveolar split widths correlated significantly with the outcomes from biomechanical testing (p ≥ 0.10). The results suggest that simple geometrical measures do not predict the allowed extent of lamella distraction prior to failure. More sophisticated methods are required for surgical planning to optimize the ARST outcomes. Still, the present study may advocate a clinical protocol for the maxilla where the implant site is prepared directly after osteotomy setting and immediately before full lamella dislocation, when the lamella is still stable, resistant to mechanical stress, and bone loss caused by the abrasion of the burr is minimized.