Medicine and Health Sciences Commons^™

Influence Of Stainless Steel Orthodontic Brackets On Magnetic Resonance Imaging, Christian James Hoybjerg

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Magnetic resonance imaging (MRI) machines provide 2D as well as 3D images that are excellent in contrasting soft-tissue in the maxillofacial region and are void of ionizing radiation. The drawbacks include the lack of depiction of cortical bony detail and image degradation caused by substances in the scanned area. Specifically, in the orthodontic field stainless steel brackets cause more distortion of MR images then any other bracket material. It is unknown what type of stainless steel alloy causes the most MRI distortion. The purpose of this study is to evaluate the degree of craniofacial MR distortion caused by various …

The Influence Of Work Of Fracture On Six Orthodontic Bonding Systems, Tyler S. Pritchard

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Bonding is the primary method of attaching brackets to teeth in modem orthodontics. Thus, many studies have focused on the maximum shear bond strength values of orthodontic adhesives. In contrast, very little research has been performed considering the work of fracture of orthodontic bonding systems. Work of Fracture is defined as the area under the curve of a stress-strain graph. Previous shear bond strength studies measured the force necessary to produce bond failure. The purpose of this study was to measure the maximum shear force and displacement of six bonding systems and to calculate the work of fracture.

Materials …

Observer Reliability Of Cephalometric Landmark Identification On 3-D Mr Images, Michael S. Pollack

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Cephalometric analysis is a cornerstone of orthodontic diagnosis, yet much information is lost when 3-dimensional structures are assessed with 2-dimensional methods. CBCT offers 3-dimensional imaging but at the cost of higher levels of ionizing radiation. Magnetic resonance imaging provides 3-dimensional imaging without ionizing radiation and additionally imparts visualization of soft tissue structures. Prior to employing MR images for cephalometric analysis, reliability of landmark identification must be assessed. The purpose of this study was to evaluate intra- and interobserver reliability in 3-dimensional landmark identification using MR images.

Materials and Methods: Fifteen cranial MR images (3.0 T, MP-RAGE) from subjects between …

Effects Of Functional Appliances On The Tmj And Mandibular Length Of Skeletal Class Ii Patients: A Cone Beam Computed Tomography Study, David C. Lee

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Functional appliances have been efficiently used in the treatment of Class II malocclusions caused by retrognathic mandibles. Cone beam computed tomography has enabled us to make more accurate linear measurements by eliminating superimposition of other structures and to analyze skeletal anatomic detail in all three planes of space. This retrospective study evaluated the osseous changes in the temporomandibular joint (TMJ) and length of the mandible in skeletal Class II malocclusion patients treated with the fixed functional appliances and compared measurements with Class I malocclusion patients treated with orthodontic mechanics that did not alter skeletal relationships.

Materials and Methods: Twelve …

Effects Of Functional Appliances On Pharyngeal Airway Dimensions: A Cone Beam Computed Tomography Study, Melissa K. Lee

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Functional appliances are intended to correct by incremental advancement of the mandible for correction of skeletal Class 11 relationships. Similar in design to functional appliances, mandibular advancing devices (MAD) are used for obstructive sleep apnea (OSA) patients as they increase the size of the airway by drawing the tongue and soft palate forwards, and thus maintain its patency during sleep. It has been shown that significant increases in airway dimensions and decreases in airway resistance were gained in OSA patients while evaluated with a MAD in place. This retrospective study evaluated volumetric, cross-sectional area and linear changes in the …

Using Cone Beam Computed Tomography To Identify A Prediction Model For Obstructive Sleep Apnea, Jodi Parker

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Obstructive Sleep Apnea (OSA) patients have increased risk of morbidity and mortality. Early diagnosis may reduce morbidity and mortality. Prediction of OSA from imaging may help to identify OSA patients earlier in life. CBCT can be used for OSA diagnostic imaging due to its three-dimensional (3D) visualization of the upper airway and craniofacial complex. Magnification associated with conventional 2D radiography is eliminated with CBCT, and radiation to the patient is significantly less than previous modalities used to measure craniofacial & airway measurements associated with OSA. During a CBCT scan, the patient's image is taken supine, rather than the upright …

Effect Of Auxiliary Preparation Elements On Resistance Form Of Complete Crowns, Manuel H. Guevara

Loma Linda University Electronic Theses, Dissertations & Projects

This study compared the effectiveness of six different auxiliary preparation elements on the resistance to lateral dislodgment of complete crown preparation lacking resistance form.

An ivorine mandibular first molar was prepared with the following characteristics: 20° TOC, 360° shoulder finish line of 1.0 mm width and axial wall of reduced height offering no geometric resistance form (Group A: control). Preparation modifications were Group B: MD grooves, Group C: BL groves (sic), Group D: MDBL grooves, Group E: MD small boxes, Group F: MD large boxes and Group G: 8° TOC at the cervical 2 mm of the axial walls. Ten …

The Effect Of Auxiliary Preparation Elements On The Resistance Form Of Complete Metal Crowns, Mostafa Nazari

Loma Linda University Electronic Theses, Dissertations & Projects

This study measured the resistance to dislodgment of complete metal crowns when they were fabricated for tooth preparations lacking resistance form. These preparations were modified with four different auxiliary preparation features.

An Ivorine mandibular first molar was prepared on a milling machine with the following characteristics: 20 degrees of total occlusal convergence (TOC), 360 degrees shoulder finish line of 1.0 mm width, and axial wall of reduced height offering no geometric resistance form. The following tooth preparation modifications were studied:

1. Two proximal grooves (two lingually positioned grooves, one on the mesial and one on the distal surface) (design B) (Figures …

Effect Of A Two Piece Scalloped Implant Design On Interproximal Bone Apposition/Retention - A Pilot Study In Rabbits, Aladdin Jamal Al-Ardah

Loma Linda University Electronic Theses, Dissertations & Projects

The aim of the study was to evaluate the effect of an experimental two piece scalloped implant design with a scalloped elliptical coronal part and an HA surface treatment on the bone to implant contact percentage in comparison to a commercially available HA treated implant. The possibility of bone apposition / retention along the exposed coronal scalloped part and the effect of the presence of a junction on the bone to implant contact percentage and bone apposition / retention were analyzed. 10 rabbits were included in the study with each rabbit receiving one control implant in one tibia and one …

Immediate Loading Of Unsplinted Implants In The Anterior Mandible For Overdentures, Phillip Roe

Loma Linda University Electronic Theses, Dissertations & Projects

In this one-year prospective study, eight completely edentulous patients were selected from the Loma Linda University School of Dentistry (LLUSD) patient population to participate. There were five male and three female patients, between the ages of 58 and 82 (mean age of 69.1 years). All participants received new maxillary and mandibular complete dentures prior to implant placement. Two 4.0 mm x 13 mm threaded implants with a fluoride-modified, micro-roughened, titanium surface were placed mesial to each mandibular canine position. Locator abutments were connected and torqued to 25 Ncm and primary closure was achieved with a nonresorbable suture material. The Locator …

Factors Influencing Contrast Resolution Of Cone Beam Ct Using The Cb Mercuray, Roger M. Anderson

Loma Linda University Electronic Theses, Dissertations & Projects

Introduction: Cone Beam Computed Tomography (CBCT) has an application in all dental specialties. CBCT is an aid in implant dentistry to evaluate anatomical landmarks in both quality and quantity. Hounsfield Unit (HU) values represent a grayscale that is standardized on CT machines relative to the density of water and air. It has been reported that the HU value represents an actual value of the bone density. However, recent studies at Loma Linda University have suggested that HU values retrieved using CBCT machines may be altered by various factors.

Purpose: The aim of this study is to evaluate the specific dosage …