Can gray values be converted to Hounsfield units? A systematic review.

OBJECTIVES: The purpose of this systematic review was to answer the focus question: "Could the gray values (GVs) from CBCT (cone beam computed tomography) be converted to Hounsfield units (HUs) in multidetector computed tomography (MDCT)?" METHODS: The included studies try to answer the research question according to the PICO strategy. Studies were gathered by searching several electronic databases and partial grey literature up to January 2021 without language or time restrictions. The methodological assessment of the studies was performed using The Oral Health Assessment Tool (OHAT) for in vitro studies and the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) for in vivo studies. The Grading of Recommendations Assessment, Development and Evaluation (GRADE system) instrument was applied to assess the level of evidence across the studies. RESULTS: 2710 articles were obtained in Phase 1, and 623 citations remained after removing duplicates. Only three studies were included in this review using a two-phase selection process and after applying the eligibility criteria. All studies were methodologically acceptable, although in general terms with low risks of bias. There are some included studies with quite low and limited evidence estimations and recommendation forces; evidencing the need for clinical studies with diagnostic capacity to support its use. CONCLUSIONS: This systematic review demonstrated that the GVs from CBCT cannot be converted to HUs due to the lack of clinical studies with diagnostic capacity to support its use. However, it is evidenced that three conversion steps (equipment calibration, prediction equation models, and a standard formula (converting GVs to HUs)) are needed to obtain pseudo Hounsfield values instead of only obtaining them from a regression or directly from the software.

Evaluation of the suture ossification level according to age and sex in children, adolescents, and adults. A cross-sectional and observational 3D study.

OBJECTIVE: To determine the ossification level of the midpalatal suture (MPS) in children, adolescents and adults from a Peruvian sample; according to the method proposed by Angelieri et al. with cone-beam computed tomographies (CBCTs). MATERIAL AND METHODS: The sample consisted of 315 CBCTs of 168 females and 147 males. The total sample was divided into 3 groups according to age and sex: children (n=77), adolescents (n=113) and adults (n=125). The images were mainly assessed in the axial plane using the Real Scan 2.0 software. The different periods of ossification of the MPS at the level of the vertical half of the palate was defined according to the five stages of Angieleri method (from A to E). The Student t-Test, Chi-square test, Kruskal-Wallis test and Spearman's Rho test were applied. RESULTS: Chi2 test results showed that the stages of MPS ossification depended on the age of the patient by age ranges (P<0.005). Multiple comparison tests affirmed that male and female subjects in the children group had fewer ossification stages than the adolescent and adult groups (P<0.001). Meanwhile, there were no statistically significant differences between the two older age groups. Finally, there was a moderate positive correlation between the stages of ossification of the MPS and the age in the male group (Rho=0.511). CONCLUSIONS: The onset of MPS ossification was significantly related to subjects up to 12 years of age and more frequently in stages B and C in both sexes. There was no difference in MPS ossification in adolescents and adult subjects.

Classifications of mandibular canal branching: A review of literature.

AIM: To gather existing radiographic classifications of mandibular canals branching, considering the criteria on which these were based. METHODS: The search for studies on mandibular canals based on imaging exams included literature reviews, epidemiological studies of prevalence, descriptive studies, or case reports. An electronic search in the MEDLINE (OvidSP), PubMed, EMBASE (OvidSP), Web of Science (Thompson Reuters), and Scopus (Elsevier) databases was performed, as well as a manual evaluation of the references of the selected articles. Combinations of key words were placed in each database. No restrictions were imposed regarding the year of publication or language. References collected in duplicate were removed by the authors. A table was drawn up, containing the included studies and respective interest data. RESULTS: Six classifications of mandibular canals branching were selected for the present literature review. Four were based on two-dimensional radiographic exams, and two were performed based on three-dimensional tomographic exams. Three-dimensional classifications were determined based on the analysis found in the least number of exams, comparatively to two-dimensional studies. The prevalence of mandibular canal branching varied from 0% to 38.75% in the works based on two-dimensional exams, while those found in three-dimensional exams ranged from 15.6% to 65%. The studies were mostly referred to branches that began in the mandibular ramus. Just one classification considered the branches that began in the mandibular body region. CONCLUSION: Three-dimensional exams appear to be the best method to view mandibular canal branching. Further studies are warranted to determine its true prevalence and questions concerning to associations.

Efecto de recarga de cuatro agentes fluorados sobre un ionómero-resina / Recharge effect of four fluoride agents on a resin modified ionomer

El presente estudio in vitro midió la cantidad de fluoruro liberado por un ionómero- resina Fuji Ortho LC bajo los efectos de los vehículos de recarga (gel, enjuague bucal, pasta dental y barniz) durante un periodo de 21 días. Se prepararon 25 muestras en forma de placas rectangulares de 15 mm x 10 mm x 1 mm. Se sumergió cada placa en ml de agua deionizada y se mantuvo a 37°C durante todo el estudio. El agua deionizada fue renovada luego de cada medición. Previa estabilización de la solución con 5 ml del buffer Tisab III, se realizaron mediciones diariamente por los primeros 5 días y a los 10, 15 y 21 días del estudio, en mV con un electrodo selectivo de fluoruro acoplado a un analizador iónico. Se fluorizaron 5 muestras al inicio y cada cinco días con gel fluorado; otras 5 muestras con enjuague bucal; otras 5 con pasta dental; y otras 5 con barniz. Análisis estadísticos fueron hechos con las pruebas de Kruskall-Wallis, "r" de Pearson y Wilcoxon. Los resultados indican que todas las muestras presentaron la mayor cantidad acumulada de fluoruro liberado en el primer día que luego mostró una tendencia a disminuir, las muestras con gel y barniz liberaron la mayor y menor cantidad respectivamente. Se encontró que el efecto de recarga por parte de los vehículos hace que el material aumente su liberación de fluoruro en el momento de aplicación para posteriormente disminuirla.