ABSTRACT
The aim of this study was to investigate the cephalometric changes following orthognathic surgery for class III correction and to compare these with the changes in patient perceptions of their oral health-related quality of life (OHRQoL). Twenty-nine severe skeletal class III patients, who were candidates for bilateral sagittal split osteotomy and Le Fort I osteotomy, completed the Persian version of the Oral Health Impact Profile OHIP-14 questionnaire before any orthodontic treatment (T0) and at 6 months after the surgery (T1). Cephalometric analyses were performed at T0 and T1 and the changes in 13 hard and soft tissue profile indices were assessed by means of the paired t-test. The correlation between facial changes following treatment and the OHIP-14 item scores were tested by Pearson correlation analysis. The increase in upper lip protrusion following surgery was correlated with an increase in OHRQoL, especially in the domains of pronouncing words, taste, and diet, as well as the total OHIP-14 score. However, the increase in upper lip length and the decrease in lower lip protrusion correlated positively with worsening of some of the OHIP items. Although orthognathic surgery led to ideal cephalometric results, the patients' OHRQoL was improved in some aspects and impaired in others.
Subject(s)
Malocclusion, Angle Class III , Orthognathic Surgery , Orthognathic Surgical Procedures , Cephalometry , Humans , Oral Health , Quality of LifeABSTRACT
OBJECTIVE: Retention after orthodontic treatment is still an important part of the treatment. Splints are considered as an alternative for removable retainers. The main goal of this study was to assess splinting biomechanically. MATERIALS AND METHODS: Three dimensional finite element models (3D) were designed of a mandibular anterior segment which included six anterior teeth with their supporting tissues (model 1 as control) and with a bonded lingual fixed retainer in the two other models. The wire cross section was round (0.016") in model 2 and rectangular (0.016" × 0.022") in model 3. The models were designed in Solid Works 2006 and analyzed in ANSYS Workbench Ver. 11.0 SolidWorks Incisors were loaded with a vertical force of 187 N. PDL stress and tooth displacements were evaluated. RESULTS: The numeric findings showed an increase after splinting in the central incisors [2.42 MPa to 4.57 MPa (round) and 16.66 (rectangular) MPa] in biting with four incisors. Biting with two incisors decreased the stress after splinting [2.42 MPa to 1.7 MPa (round wire) and 1.77 MPa (rectangular wire)]. In lateral movement, all teeth showed an increased stress except for the working side canine. CONCLUSION: Splinted cases (with round or rectangular wires) can benefit from stress redistribution when biting small food particles and in lateral movement.
ABSTRACT
OBJECTIVE: The aim of this study was to determine the effect of trenched zirconia bar on the von Mises stress distribution of IPS -Empress II core ceramics. MATERIALS AND METHODS: The three-dimensional model including a three-unit bridge from the second premolar to the second molar was designed. The model was reinforced with zirconia bar (ZB), zirconia bar with vertical trench (VZB) and zirconia bar with horizontal trench (HZB) (cross sections of these bars were circular). The model without zirconia bar was designed as the control. The bridges were loaded by 200 N and 500 N on the occlusal surface at the middle of the pontic component and von Mises stresses were evaluated along a defined path. RESULTS: IN THE CONNECTOR AREA, VON MISES STRESS IN MPA WERE APPROXIMATELY IDENTICAL IN THE SPECIMENS WITH ZB (AT MOLAR CONNECTOR (MC): 4.75 and at premolar connector (PC): 6.40) and without ZB (MC: 5.50, PC: 6.68), and considerable differences were not recognized. Whereas, Von-Mises stress (MPa) in the specimens with horizontal trenched Zirconia bar (HZB) (MC: 3.91, PC: 2.44) and Vertical trenched Zirconia bar (VZB) (MC: 2.53, PC: 2.56) was decreased considerably. CONCLUSION: Embeded trenched zirconia bar could reinforce IPS-Empress II at the connector area which is a main failure region in all ceramic fixed partial dentures.
ABSTRACT
The main goal of this research was to study the behavior of initial tooth displacements associated with alveolar bone loss situations when loaded by a force of 1 N. The analysis of displacements was carried out by the finite element method. Six 3-dimensional models of an upper central incisor (designated Geramy 391 to 396) with 1 to 8 mm of alveolar bone loss were formulated and used by the author. Center of rotation and center of resistance were located for the various stages of alveolar bone loss. The results revealed that the moment/force ratio (at the bracket level) required to produce bodily movement increases in association with alveolar bone loss. Bone loss causes center of resistance movement toward the apex, but its relative distance to the alveolar crest decreases at the same time. Greater amounts of displacements of incisal edge and apex were observed with increased alveolar bone loss for a constant applied force. Center of rotation of the tipping movement also shifted toward the cervical line. Among the many differences between orthodontic treatment of an adolescent and an adult patient is the presence of alveolar bone loss in the adult cases. Alveolar bone loss causes center of resistance changes as a result of the alterations in bone support. This necessitates modifications in the applied force system to produce the same movement as in a tooth with a healthy supporting structure.
