The basicranium is a key organizer of the skull. Importantly, the basicranium ossifies early during craniofacial development and is centrally located in the skull, thus it is thought to act as a structural “foundation” that organizes later growth of the facial skeleton. The goal of this study is to test the hypothesis that basicranial asymmetry directly and additively influences asymmetry of the facial skeleton. To do this, we used cone beam computed tomography (CBCT) scans obtained from the Orthodontic Clinic at the University of California San Francisco and analyzed them with Geometric Morphometrics (GM), a set of methods for quantifying and comparing three-dimensional shape. This approach enables us to evaluate hypotheses about the nature of craniofacial patterning and variation in different planes, including deviations from midline symmetry. In this study, we first obtained homologous 3D coordinates from the basicranium and facial skeleton of adolescent and adult patients (N=105). Next, we used Principal Components Analysis (PCA) and Partial Least Squares (PLS) to test between alternative models of covariation between basicranial and facial asymmetries. Our results support the hypothesis that the basicranium plays a significant role in patterning facial asymmetry, and this relationship is consistent with an additive model. Given the earlier relative timing of ossification of the basicranium, this suggests that basicranial shape is important for establishing the direction of later facial growth, which is relevant for clinical considerations.

Objective:This study evaluates the perception of transverse jaw asymmetries in patients with varying degrees of sagittal jaw relationships. Secondly, it determines the asymmetry perception threshold in which raters are able to distinguish the deviation in mandibular asymmetry that affect their aesthetic and symmetry perception. In addition, the study seeks to compare that ratings between orthodontists and oral surgeons.

Methods:Our sample consisted of 30 anonymized CBCT scans of adults (ages 11-30 years old). The reference images obtained from the CBCT’s were categorized by Class I, Class II, and Class III using ANB angles values of -4.9 degrees to 5.8 degrees. ANB angle is routinely used for orthodontic treatment planning, it represents the difference between the SNA and SNB angles, providing an indication of the sagittal jaw discrepancy between the maxilla and mandible. An ANB angle ranging from 2+/-2 degrees is considered Class I discrepancy; ANB angle greater than 4.0 is considered to be a skeletal Class II discrepancy; an ANB angle less than 0 degrees is considered a skeletal Class III discrepancy. CBCT data (4 males, 2 females) were processed into 3D models lacking several confounding facts (ex: hair style and color, skin complexion, and eye color) were stripped away in the CBCT images.. Next, images were manipulated in the transverse direction via Morpho J software, using landmarks pogonion and gnathion to alter mandibular symmetry at intervals of 0%, 25%, 50%, 75% and 100%. Lastly, 153 orthodontists, 141 oral surgeons, 68 lay persons, and 59 other dental professionals rated the aesthetics and asymmetry of each model using a scale of 1-10 mm Visual Analog Scale (VAS) for asymmetry and a scale of 1-100 mm Visual Analog Scale (VAS) for aesthetics. No information was provided on the ethnicity, age, and biological sex of each CBCT model, allowing the raters to focus on shape.

Results:As a general trend with our overall data of 421 assessors, our results indicate that in Class I, Class II and Class III faces, increasing mandibular asymmetry within a particular ANB angle was correlated with lower VAS scores for facial symmetry and aesthetics, therefore, the majority of shape changes were negatively perceived by raters. However, the data indicates that the severity of the skeletal sagittal relationship was increased, as in Class I, Class II and Class III relationships, as measured by ANB, is not indicative of decreasing perception of aesthetics and symmetry. The data concluded that when rating aesthetics, Class III faces were scored the highest followed by Class II then Class I faces. For symmetry, Class III faces were scored the highest followed by Class I then Class II faces. In addition, the threshold point with which raters are able to distinguish the deviation in mandibular esthetics and asymmetry affect aesthetic perception ranged from 50-75% mandibular deviation. When correlating symmetry and aesthetics, the data indicates that the severity of the skeletal sagittal relationship was increased, as in Class I, Class II and Class III relationships, as measured by ANB, there is not a linear decrease in perception of mandibular aesthetics and asymmetry. In Class I, symmetry and aesthetics were similarly affected, in Class II, aesthetic perception was more affected than symmetry and lastly in Class III, symmetry was more affected than aesthetics. More specifically, when evaluating 0% mandibular deviation to 100% mandibular deviation, the perception between symmetry and aesthetics, the percentage drop in VAS score ranged from 19-33%. Next, the VAS scores of orthodontists vs. oral surgeons were compared. In our Class I, Class II, and Class III faces, oral surgeons rated the faces with an overall higher VAS score than orthodontists, indicating that orthodontists may be more particular and discerning of all faces. Conclusions: The data indicates that increasing or decreasing anteroposterior jaw position does not have the strongest impact on facial esthetics and symmetry. Our findings did not support the idea that balanced jaw associations are the most consistent predictor of perception of facial aesthetics and symmetry. We hypothesized that individuals will find patients with transverse jaw asymmetries and increased or decreased anteroposterior relationships less aesthetic than those with transverse jaw asymmetries and normal sagittal relationships. The data indicates that the severity of the skeletal sagittal relationship was increased, as in Class I, Class II and Class III relationships, as measured by ANB, is not indicative of decreasing perception of aesthetics and symmetry. However, our overall results indicate that within a particular ANB angle, the majority shape changes were negatively perceived, in which, increasing mandibular asymmetry was correlated with lower VAS scores for facial aesthetics and symmetry. Additional analysis indicating that is not a linear decrease in perception between symmetry and aesthetics, the range being from 19-33% decrease in VAS score from 0% mandibular deviation to 100% mandibular deviation.

Lastly, out of all of the subgroups of data collected, the orthodontic group were the most particular and discerning all of the original faces by scoring the lowest VAS scores for all subgroups. We conclude that inconsistencies seen in our results could be attributed to confounding factors such as soft tissue characteristics that may alter perception of aesthetics and asymmetry.

This dissertation presents a comprehensive investigation into the application of Short-Wave Infrared (SWIR) imaging and Optical Coherence Tomography (OCT) for the enhanced detection and assessment of dental caries. Traditional diagnostic methods, such as radiographs, are limited by their inability to detect and diagnose early-stage, less severe carious lesions, often leading to delayed treatment and unnecessary restorations. SWIR imaging is highly promising to detect early caries with enhanced contrast due to the high transparency of dental enamel at longer wavelengths and its high sensitivity to demineralization. SWIR imaging has been mostly limited to either transillumination or reflectance imaging at specific SWIR wavelengths. While promising, it suffers from limitations in specificity due to the complex structure of teeth and the interference of specular reflection that can obscure accurate lesion detection, especially during clinical imaging. We hypothesize that dual-mode, multi-wavelength SWIR imaging combined with automated methods of image processing will increase diagnostic accuracy by providing semi-automatic detection of early demineralization and precise assessment of lesion severity in vivo. In addition, we postulate that integration of OCT will enable non-invasive analysis of lesion activity, facilitating timely preventive treatments. We anticipate that this combination of various diagnostic modalities will significantly improve the clinical detection and management of dental caries and lead to better preservation of natural tooth structure. Moreover, such methods do not require the use of ionizing radiation and can be used for more frequent monitoring of lesion severity reducing the need for surgical intervention.

Objectives: The aim of this study was to evaluate the effect of maxillary rapid palatal expansion on the eruption vector of the canines and premolars in the early mixed dentition using CBCT.

Methods: The study population consisted of 42 individuals 7-11 years of age in the early mixed dentition, with all Ds and Es present, and all permanent first molars, maxillary central incisors and lower incisors erupted. No subjects had posterior crossbites or severe sagittal discrepancies. The treatment group of this study consisted of 21 children who had rapid palatal expansion using a Hyrax maxillary expander and active lower lingual arch in the early mixed dentition, as well as phase II comprehensive treatment records. The control group of this study consisted of 21 subjects who did not undergo rapid palatal expansion following their phase I records but returned in the full permanent dentition for comprehensive treatment records. All subjects were imaged using cone beam computed tomography (CBCT) as a part of their initial records, and again prior to beginning comprehensive Phase II treatment in the full permanent dentition.

Results: A canonical variate analysis revealed significant differences between control and treatment groups (p=0.03). There were no significant differences between groups in a principal component analysis, however mild differences between principal component 2 and principal component 8 were observed. Principal component 2 was responsible for 14% of shape variation and was the only principal component in this study to demonstrate shape differences between the treatment and control groups. Canines and premolars erupted with a slightly more upright angulation in patients treated with phase I expansion than those who were untreated.

Conclusions: Canines and premolars were slightly more upright in patients who had phase I expansion than patients who did not. These differences were very minor and were statistically significant in a canonical variate analysis (p=0.03).

Chronic Kidney disease (CKD) is a broad spectrum of several conditions affecting 26 million American. Over 67 million adults 30 years or older are suffering from periodontal disease. Both conditions are influenced by many confounding conditions such as diabetes, smoking, stress and other inflammatory conditions. Current evidence shows a possible associated between CKD and periodontal disease. The purpose of this study was to see if treatment of periodontal disease in low socioeconomic patients with CKD and periodontal disease can have a positive effect on CKD parameters. 46 patients qualified for and completed this study. Patients were divided into an intervention and a control group and were examined at baseline, 4 months, 8 months and 12 months. Various kidney function parameters were also recorded through blood and urine samples at these appointments. The periodontal condition of the intervention group was treated with scaling and root planing, extractions and local delivery of minocycline polymers in probing pocket depths of 5mm or more and oral hygiene instruction. The control group was only given oral hygiene instruction handouts during these visits and extraction of their hopeless teeth. The control group received SRP and minocycline administration at the conclusion of the study. Both groups showed improvements in probing pocket depths, clinical attachment levels, bleeding on probing, plaque index and gingival index. These trends were stronger in the intervention group but not enough to be considered as healthy periodontium. Thus, the improvement in the periodontal state was not adequate enough to be assessed for influencing the kidney parameters. There was no difference between the two groups in kidney parameters.

The III-Nitride materials system provides a fascinating platform for developing optoelectronic devices, such as solar cells and LEDs, which have the power to dramatically improve the efficiency of our power consumption and reduce our environmental footprint. Finding ways to make these devices more efficient is key to driving their widespread adoption. This dissertation focuses on the intersection of challenges in physics and metalorganic chemical vapor deposition (MOCVD) growth at the nanoscale when designing for device efficiency.

In order to create the best possible InGaN solar cell, a multiple quantum well (MQW) active region design had to be employed to prevent strain relaxation related degradation. There were two competing challenges for MQW active region design and growth. First, it was observed current collection efficiency improved with thinner quantum barriers, which promoted efficient tunneling transport instead of inefficiency thermally activated escape. Second, GaN barriers could planarize surface defects in the MQW region under the right conditions and when grown thick enough. A two-step growth method for thinner quantum barriers was developed that simultaneously allowed for tunneling transport and planarized V-defects. Barriers as thin as 4 nm were employed in MQW active regions with up to 30 periods without structural or electrical degradation, leading to record performance. Application of dielectric optical coatings greatly reduced surface reflections and allowed a second pass of light through the device. This both demonstrated the feasibility of multijunction solar integration and boosted conversion efficiency to record levels for an InGaN solar cell.

III-N LEDs have achieved state-of-the-art performance for decades, but still suffer from the phenomena of efficiency droop, where device efficiency drops dramatically at high power operation. Droop is exacerbated by the polarization-induced electric fields in InGaN quantum wells, which originate from a lack of inversion symmetry in GaN’s wurtzite crystal structure. These fields can be screened by using highly doped layers, but the extreme dopant densities predicted by simulation for complete screening may require using Ge as an alternative n-type dopant to Si. GaN:Ge layers with excellent electrical characteristics were grown by MOCVD with doping densities exceeding 1020 cm-3. However, their surface morphologies were very poor and they proved a poor screening dopant in LED structures. Using Si as the n-type screening dopant, LEDs with single QW active regions were grown, packaged, and tested. Biased photoluminescence showed strong evidence of complete polarization screening. The LEDs had low droop, but also low peak efficiencies. Possible explanations for trends in efficiency with varying QW width and field screening will be discussed.