Analysis of the Morphology of Maxillary Sinus Septa on Reconstructed Cone-Beam Computed Tomography Images.

PURPOSE: Preoperative assessment of maxillary sinus anatomy can prevent complications associated with sinus grafting or implant procedures. The purpose of this study was to measure the frequency, numbers, locations, orientations, and heights of maxillary sinus septa. MATERIALS AND METHODS: Reconstructed cone-beam computed tomographic images of 1,012 sinuses were analyzed using NewTom VG software (NNT 2.21, ImageWorks, Elmsford, NY). This cross-sectional study included patients who underwent radiography at the department of radiology. The presence, numbers, locations, orientations, and heights of septa were analyzed. To establish multiple predictors in this study, groups were defined according to different radiographic features of the septa. Differences between male and female groups and between edentulous and dentulous groups were tested with χ(2) tests and the level of significance was set at 5%. RESULTS: The sample consisted of 506 patients (168 men and 338 women; average age, 35.1 yr). A significantly (P < .05) greater occurrence rate of 57.4% was observed in the edentulous group compared with the rate of 39.7% observed in the dentulous group. CONCLUSIONS: The difference in the prevalence of maxillary sinus septa between the edentulous and dentulous groups was statistically significant (P < .05), and the septa exhibited variable characteristics. It is essential and effective to analyze computed tomographic images of sinuses to evaluate the characteristics of septa before performing surgical procedures.

Symmetry of root anatomy and root canal morphology in maxillary premolars analyzed using cone-beam computed tomography.

OBJECTIVE: This study aimed to use cone-beam computed tomography (CBCT) to evaluate the root anatomy and canal morphology of maxillary premolars in a Chinese population and determine their degree of bilateral symmetry. DESIGN: 774 CBCT images were retrospectively analyzed, representing 1387 maxillary first premolars and 1403 second premolars. The number of roots and canals were recorded. The morphology of root canal systems was determined according to Vertucci's classification. The symmetry of root and canal anatomies between maxillary contralateral premolars was further evaluated. RESULTS: The most common anatomy of maxillary first and second premolars was one-rooted with two canals (58.0%) and one-rooted with one canal (50.3%), respectively. The typical canal morphology was type IV (42.7%) in maxillary first premolars and type I (50.3%) in maxillary second premolars. One-rooted maxillary premolars exhibited a higher variability in the canal morphology, compared to two-rooted or three-rooted teeth. Maxillary second premolars exhibited greater anatomic symmetry than first premolars. The root and canal numbers showed bilateral symmetry between 80.2% of maxillary first premolar pairs and 81.8% of second premolar pairs. Bilateral symmetry in both number and morphology of roots and canals was observed for 72.3% of maxillary first premolar pairs and 73.2% of second premolar pairs. CONCLUSION: The root anatomy and canal morphology of maxillary premolars in a Chinese population were quite diversified. Maxillary contralateral premolars demonstrated a high degree of symmetry in root and canal anatomies, which enables practitioners to better determine the nature of the root canal system during treatment of opposite homonymous teeth.

Analysis of the Root and Canal Morphologies in Maxillary First and Second Molars in a Chinese Population Using Cone-beam Computed Tomography.

INTRODUCTION: We analyzed and characterized the root and canal morphologies in maxillary first and second molars in a large sample of Chinese patients using reconstructed cone-beam computed tomographic (CBCT) imaging. METHODS: Maxillary first (n = 1558) and second (n = 1539) molars were collected from Chinese patients (N = 844) who had undergone in vivo CBCT imaging. The root canal number and morphology were determined according to Vertucci's classification. RESULTS: A single root was found in 0.06% of first molars, which showed type I canal systems. However, second molars with a single root (4.2%) showed widely varied canal systems. The buccal roots of first molars with 2 separate roots showed type I, II, or III canal systems, whereas those of 2-rooted second molars showed widely varied canal systems. The incidence of fused roots was 1.38% for first molars and 23.9% for second molars, whereas canal fusion within fused roots was observed in 4.5% of first molars and 10.6% of second molars. Additional canals were observed in 67.8% and 29.7% of mesiobuccal roots, 1.8% and 0.7% of distobuccal roots, and 0.7% and 0.3% of palatal roots in 1523 and 1017 first and second molars with 3 separate roots, respectively. The mesiobuccal root canal number showed bilateral symmetry between 79% of first molars and 82.3% of second molars, with a concurrence rate of 59.8% between adjacent molars. CONCLUSIONS: We reported the root and canal morphologic variations in maxillary first and second molars, which have not been reported for Chinese populations. Further studies should focus on canals in fused roots and mesiobuccal roots.

An Analysis of the Proximity of Maxillary Posterior Teeth to the Maxillary Sinus Using Cone-beam Computed Tomography.

INTRODUCTION: It is known that the level of the maxillary sinus floor varies with age. Because few studies have investigated whether the position of the posterior roots relative to the maxillary sinus varied with the variation of the sinus floor or not, the present study assessed the position according to age. METHODS: Cone-beam computed tomographic images of 848 patients were reconstructed to evaluate the position of the posterior roots relative to the sinus floor, which were divided into 3 types, and quantify the distances between posterior root apexes and the adjacent border of the sinus floor. Measurements were taken for each root, and data were correlated with age, which was divided into 4 groups (≤20 years, 21-40 years, 41-60 years, and >60 years). RESULTS: A total of 3063 premolars and 3095 molars were evaluated. The mean distances from the root tips to the border of the maxillary sinus floor increased with increasing age. From the first and second premolar roots, the mean distances ranged from 3.6 ± 4.1 mm to 8.9 ± 4.6 mm and from 0.7 ± 3.3 mm to 5.3 ± 3.9 mm, respectively. From the mesiobuccal, distobuccal, and palatinal roots of the first molars, the mean distances were -0.4 ± 2.8 mm to 4.6 ± 4.0 mm, -0.3 ± 2.4 mm to 4.4 ± 3.8 mm, and -0.4 ± 3.5 mm to 3.9 ± 4.1 mm, respectively. From the mesiobuccal, distobuccal, and palatinal roots of the second molars, the mean distances were -0.5 ± 2.2 mm to 3.4 ± 3.5 mm, 0.3 ± 2.2 mm to 3.9 ± 3.7 mm, and 1.1 ± 3.2 mm to 4.6 ± 4.5 mm, respectively. The frequency of type IS decreased with increasing age. It was very low in first premolars (0%-8.13%) and higher in second premolars (0%-25.68%), first molars (0%-44.75%), and second molars (0%-32.89%). Age significantly influenced the mean distances to the sinus floor and the frequencies of type IS (inside). CONCLUSIONS: Cone-beam computed tomographic imaging is an effective method to study the position of the posterior roots to the maxillary sinus floor. Variation in proximity measurements was found by age, with those under the age of 40 showing a greater likelihood of the position of maxillary roots above/inside the sinus floor.

[The measurement of thermal expansion coefficient of Co-Cr alloy fabricated by selective laser melting].

PURPOSE: To investigate the thermal expansion coefficient of different processing parameters upon the Co-Cr alloy prepared by selective laser melting (SLM) technique, in order to provide technical support for clinical application of SLM technology. METHODS: The heating curve of self-made Co-Cr alloy was protracted from room temperature to 980°C centigrade with DIL402PC thermal analysis instrument, keeping temperature rise rate and cooling rate at 5 K/min, and then the thermal expansion coefficient of 9 groups of Co-Cr alloy was measured from 20°C centigrade to 500°C centigrade and 600°C centigrade. RESULTS: The 9 groups thermal expansion coefficient values of Co-Cr alloy heated from 20°C centigrade to 500°C centigrade were 13.9×10(-6)/K,13.6×10(-6)/K,13.9×10(-6)/K,13.7×10(-6)/K,13.5×10(-6)/K,13.8×10(-6)/K,13.7×10(-6)/K,13.7×10(-6)/K,and 13.9×10(-6)/K, respectively; when heated from 20°C centigrade to 600°C centigrade, they were 14.2×10(-6)/K,13.9×10(-6)/K,13.8×10(-6)/K,14.0×10(-6)/K,14.1×10(-6)/K,14.1×10(-6)/K,13.9×10(-6)/K,14.2×10(-6)/K, and 13.7×10(-6)/K, respectively. CONCLUSIONS: The results showed that the Co-Cr alloy has good matching with the VITA VMK 95 porcelain powder and can meet the requirement of clinic use.