Distances from the root apices of posterior teeth to the maxillary sinus and mandibular canal in patients with skeletal open bite: A cone-beam computed tomography study

PURPOSE: This study determined and compared the distances from the maxillary root apices of posterior teeth to the floor of the maxillary sinus, or maxillary sinus distances (MSDs), and the distances from the mandibular root apices of the posterior teeth to the mandibular canal, or mandibular canal distances (MCDs), in Thai subjects with skeletal open bite and skeletal normal bite. MATERIALS AND METHODS: Pretreatment cone-beam computed tomography (CBCT) images were obtained from 30 Thai orthodontic patients (15 patients with skeletal normal bite and 15 with skeletal open bite) whose ages ranged from 14 to 28 years. The CBCT images of the patients were processed and measured using the Romexis Viewer program. The MSDs and MCDs from the root apices of the maxillary and mandibular second premolar, first molar, and second molar to the maxillary sinus floor or the mandibular canal were measured perpendicularly to the occlusal plane. The Student t test was used for comparisons between the 2 groups. RESULTS: The greatest mean MSDs were from the root apex of the second premolars in both groups, whereas the least mean MSDs were from the mesiobuccal root apex of the second molars. The greatest mean MCDs were from the mesial root apex of the first molars, whereas the least mean MCDs were from the distal root apex of the second molars. CONCLUSION: There were no differences in the mean MSDs or the mean MCDs between the skeletal normal bite group and the skeletal open bite group.

Comparison of interradicular distances and cortical bone thickness in Thai patients with Class I and Class II skeletal patterns using cone-beam computed tomography

PURPOSE: This study evaluated and compared interradicular distances and cortical bone thickness in Thai patients with Class I and Class II skeletal patterns, using cone-beam computed tomography (CBCT). MATERIALS AND METHODS: Pretreatment CBCT images of 24 Thai orthodontic patients with Class I and Class II skeletal patterns were included in the study. Three measurements were chosen for investigation: the mesiodistal distance between the roots, the width of the buccolingual alveolar process, and buccal cortical bone thickness. All distances were recorded at five different levels from the cementoenamel junction (CEJ). Descriptive statistical analysis and t-tests were performed, with the significance level for all tests set at p<0.05. RESULTS: Patients with a Class II skeletal pattern showed significantly greater maxillary mesiodistal distances (between the first and second premolars) and widths of the buccolingual alveolar process (between the first and second molars) than Class I skeletal pattern patients at 10 mm above the CEJ. The maxillary buccal cortical bone thicknesses between the second premolar and first molar at 8 mm above the CEJ in Class II patients were likewise significantly greater than in Class I patients. Patients with a Class I skeletal pattern showed significantly wider mandibular buccolingual alveolar processes than did Class II patients (between the first and second molars) at 4, 6, and 8 mm below the CEJ. CONCLUSION: In both the maxilla and mandible, the mesiodistal distances, the width of the buccolingual alveolar process, and buccal cortical bone thickness tended to increase from the CEJ to the apex in both Class I and Class II skeletal patterns.

External apical root resorption in maxillary incisors in orthodontic patients: associated factors and radiographic evaluation

PURPOSE: This study was performed to evaluate the incidence and degree of external apical root resorption of maxillary incisors after orthodontic treatment and to evaluate particular associated factors related to external apical root resorption. MATERIALS AND METHODS: The records and maxillary incisor periapical radiographs of 181 patients were investigated. Crown and root lengths were measured and compared on the pre- and post-treatment periapical radiographs. Crown length was measured from the center of the incisal edge to the midpoint of the cemento-enamel junction (CEJ). Root length was measured from the CEJ midpoint to the root apex. A correction factor for the enlargement difference was used to calculate root resorption. RESULTS: The periapical radiographs of 564 teeth showed that the average root resorption was 1.39+/-1.27 (8.24+/-7.22%) and 1.69+/-1.14 mm (10.16+/-6.78%) for the maxillary central and lateral incisors, respectively. The results showed that the dilacerated or pointed roots, maxillary premolar extraction cases, and treatment duration were highly significant factors for root resorption (p<0.001). Allergic condition was a significant factor at p<0.01. Age at the start of treatment, large overjet, and history of facial trauma were also factors significantly associated with root resorption (p<0.05). There was no statistically significant difference in root resorption among the factors of gender, overbite, tongue-thrusting habit, types of malocclusion, and types of bracket. CONCLUSION: These results suggested that orthodontic treatment should be carefully performed in pre-treatment extraction patients who have pointed or dilacerated roots and need long treatment duration.

Shear Bond Strength of Different Adhesive Systems for Bonding Orthodontic Brackets to Porcelain Surfaces

The aims of this study were to measure and compare the effects of five different adhesive systems on the shear bond strength of orthodontic brackets bonded to porcelain surfaces and to analyze the modes of bond failure after de-bonding the brackets. One hundred porcelain cylindrical disks were divided into five groups. The orthodontic brackets were bonded to the porcelain using five different adhesive systems: Group I, etching with 9.6% hydrofluoric acid; Groups II and IV, etching with 37% phosphoric acid followed by Silane; Groups III and V, etching with 9.6% hydrofluoric acid followed by silane. Specimens in Groups I, II and III were bonded with System1™ + and those in Groups IV and V with Super-Bond C\&B. The shear bond strength was then tested using a universal testing machine. The mean shear bond strength values in Groups I to V were 10.9, 18.5, 20.7, 23.7 and 27.6 MPa, respectively.  All data were analyzed using an analysis of variance. The lowest mean shear bond strength was in Group I and was significantly different (p \< 0.05) from that in the other groups. There was no significant difference between the mean shear bond strength values in Groups II, III and IV (p \< 0.05). Group V had the highest mean shear bond strength and was significantly different from that in Groups I, II and III (p\< 0.05). The porcelain/adhesive interface was the commonest site of failure in Group I (65%), whereas the failure sites in the other groups showed mixed types of bond failure with no specific location predominating. Some damaged porcelain surfaces were found in Groups II, III, IV and V. Keywords: shear bond strength, adhesive systems, dental porcelain, orthodontic bracket