2014 AAO Annual Session Charley Schultz Resident Scholar Award
The Charley Schultz Resident Scholar Award program will be held on Saturday, April 26 in the Ernest N. Morial Convention Center Room 356-357 from 1:00pm-2:00pm. Clinicians will be at their posterboards during this time to answer questions about their research.
*- Denotes financial interest or visual enhancement
Basic Science Research
Genetic deactivation of TGF-β1 signaling attenuates articular cartilage degeneration in mature joints
Rebecca Chen
Harvard Univeristy
Background: Studies have shown conflicting roles of TGF-β1: disruption of the interaction of Tgf-β1 with its receptor results in osteoarthritis (OA) joints in young mice; whereas others suggest of increased Tgf-β1 expression in mature joints causes early onset OA. The plausible explanation is that TGF-β1 signaling acts in a developmental stage-dependent manner. This study aims to study role of TGF-β1 in OA development. Method: With conditional knock out techniques, Tgfbr2 was removed from articular cartilage of knee and TMJ in mature mice. Cartilage degeneration was induced by surgery. Joints at 4, 8 and 16 wks post-op (n=4 each) were collected for morphological analysis. Results: Initiation of articular cartilage degeneration in the mature mice joints with genetic inactivation of Tgfbr2 was attenuated, when compared to controls. Conclusion: Inhibition, instead of application, of TGF-β1 activity, may be considered in OA treatment.
Optimal timing of bisphosphonate treatment on alveolar cleft bone grafting
Nicole Cheng
University of California, Los Angeles
Objectives: The aim was to investigate the optimal timing of Bisphosphonate (BP) injection on bone grafts placed in defects in rats. Methods: 36 animals underwent surgical creation of an alveolar defect followed by placement of an isograft from Inbred donors. The control group (n=8) was given a subcutaneous (sc) injection of saline. Three experimental groups (n=8 per group) were given a sc injection of BP at either the time of surgery, 1 week after surgery or 3 weeks after surgery. A negative control group (n=2) had a defect created without bone graft, while a positive control group (n=2) did not have surgery. Animals were euthanized at 6 weeks. Micro-CT and histological analysis were performed. Results: Percent bone volume was significantly higher in delayed BP injection groups compared to controls and BP injection at the time of surgery. Conclusions: A delayed one-time BP injection showed greatest bone healing in comparison to injection at the time of surgery and the control.
Pure mandibular incisors intrusion? A finite element study to test the segmented arch technique
Gabriela de Brito
Pontific Catholic University
The purpose of this research was to evaluate different configurations of segmented arch mechanics designed to achieve pure mandibular anterior teeth intrusion using the finite element method (FEM). A FEM of the mandibular arch of an adult patient presenting deep bite was modeled with the SolidWorks Software®. After all dental and periodontal ligament were graphically represented, brackets and wires were modeled. Discretization and boundary conditions of the anatomical structures were determined with the HyperMesh Software®. Twenty g of intrusive force were bilaterally applied with a cantilever in 4 points of the intrusion base arch (IBA): FEM1 – at the IBA most anterior point; FEM2 – at the level of the mesio-distal center of the canine; FEM3 at the level of the canine’s distal surface; FEM4 at the level of the mesio-distal center of the first premolar. The FEM 3 showed true mandibular incisor intrusion. FEM 1 and 2 resulted in buccal crown tipping of the incisors and FEM 4 generated lingual tipping tendencies. Conclusion: FEM simulations indicated the ideal location of force application to achieve pure mandibular incisors intrusion with segmented arch mechanics.
Occlusal plane manipulation effects on root angulation in CBCT derived pan-like images
Heather Green
Roseman University
Background: Panoramic radiographs remain the commonly accepted standard to assess root parallelism. Given the limitations of 2D images, 3D derived pan-like images merit further study. Purpose: To examine the effects of occlusal plane alteration in all 3D spatial orientations (X, Y & Z) on mesiodistal root angulations. Research Design: A custom-made typodont with secured stainless steel pins representing roots of maxillary and mandibular teeth in a Class I relationship with 0˚angulation was scanned (iCAT). Using Dolphin imaging (version-11.5), 31 pan-like images and 806 angular measurements were generated. Occlusal plane was altered at 2˚ increments up to ±10˚ along X, Y & Z axes and pan-like images were generated for each plane. Results: Clinically significant measurements (>2.5˚) ranged from 2.6˚ to 5.4˚ primarily in the incisor and canine area. Conclusion: Generalized mesiodistal angulation distortions were seen, with the most notable at incisors (X- axis) and canines (Z-axis).
Selective alveolar decortication an adjunct to tooth movement in bisphosphonate burdened bone
Neelambar Kaipatur
University of Alberta
Background: Orthodontic tooth movement (OTM) is significantly inhibited in bisphosphonate burdened alveolar bone (BpBAb). Purpose: To investigate the effect of Selective Alveolar Decortication (SADc) facilitated OTM on BpBAb in a rodent model. Research Design: Two groups of 10 rats each were included and each group was pretreated for three months with either alendronate sodium (SADc+BP burden group) or saline (SADc group). SADc surgery was performed on day 0 of appliance insertion. OTM measurements were obtained at 0, 4, and 8 weeks using in-vivo µCT. Results: Our results showed appreciable tooth movement of 0.38 mm and 0.93 mm in the SADc+BP burden group. In comparison, SADc group showed 0.61 mm and 1.97 mm of tooth movement in 4 weeks and 8 weeks respectively. Conclusion: This study demonstrated selective alveolar decortication as an adjunct to tooth movement in a bisphosphonate burdened alveolar bone but the long term tissue effects of such an injury should be further researched.
Force decay evaluation of thermoplastic and thermoset elastomers - A mechanical design comparison
Ahmed Masoud
University of Illinois, Chicago
Power chains (PCs) made from thermoplastic (TP) and thermoset (TS) materials are used interchangeably in the literature and in clinical practice and to date no study has compared the two. Objectives: To compare, over a period of 8 weeks, force decay between: (1) TP and TS PCs, (2) light and heavy forces, and (3) direct chains and chain loops. Methods: TP and TS PCs were obtained from American Orthodontics® (AOTP, AOTS) and ORMCO® (OrTP, OrTS). Each of the 4 PC groups was subdivided into 4 subgroups: (1) direct chains light force, (2) direct chains heavy force, (3) chain loops light force, and (4) chain loops heavy force. Results: A significant difference was found between TP and TS PCs with approximately 20% more force decay in the TP groups. Direct chains had more force decay compared to chain loops only in the OrTP group. Conclusion: Contrary to the analogous use of TP and TS PCs, this study demonstrates that they perform differently and that a clear distinction should be made.
Biomechanical characterization of the periodontal ligament: Orthodontic tooth movement
Richard Uhlir
University of North Carolina, Chapel Hill
Purpose: The biomechanical characteristics of the periodontal ligament (PDL) are currently not completely known. Method: A Dynamic Mechanical Analyzer that detects small forces at resolutions of 0.002 N was utilized to characterize stress-strain behavior of PDL specimens from mandibular bovine incisors. Uniaxial tension tests with different force levels of 0.5, 1, and 3 N were completed for 37 samples. Modulus values were compared to see effects of anatomic location and force levels. The Mooney-Rivlin Hyperelastic (MRH) model was used in a Finite Element Analysis (FEA) simulation of orthodontic intrusion. Results: Force levels and anatomic location were statistically significant in their effects on modulus. MRH approximated experimental data, and demonstrated reasonable expected outcome of stress/strain levels in the PDL and bone for FEA intrusion simulation. Conclusion: The PDL is non-homogeneous in which modulus changes in relation to location within the PDL and applied force.
Clinical Research
Genetic polymorphisms and its inheritance in skeletal Class I crowding in India
Shailesh Bhandari
NTR University
Dental crowding is a problem for both adolescents and adults, in modern society. The objective of this research was to identify single nucleotide polymorphisms responsible for crowding and the inheritance pattern from the parents to their offspring. 48 case subjects their both parents and 50 control subjects were recruited. Case subjects consisted of healthy Indian people with skeletal Class I relationships and at least 5mm of crowding in either arch. SNP genotyping was performed. Chi-square test, Logistic regression, LD were performed.SNPs rs3764746 and rs3795170 on EDA gene (P=0.004) and SNP rs1005464 (P=0.017) and rs15705 (P=0.031) in BMP2 gene were associated with crowding. Phenotype segregating was determined by single dominant gene with incomplete penetrance (0.82). EDA and BMP2 genes were found to be associated with crowding. Crowding can be said to be a polygenic trait that follows mendelian trait i.e. autosomal dominant with incomplete penetrance and variable expressivity.
The effect of chemotherapy on the survival of dental implants
Li-Ping Chew
Mayo Clinic
Individuals treated for head and neck cancer may require implants for oral rehabilitation. The aim of this study was to determine if chemotherapy had an effect on the survival of dental implants. A retrospective chart review was completed on Mayo Clinic patients who had chemotherapy and at least one dental implant. Fifty-seven patients were evaluated. Two of the 57 patients experienced an implant failure. Estimated survival free of implant failure rates by the Kaplan-Meier method at 1, 3 and 5 years for patients with chemotherapy were 96%, 96% and 96%. Previous control groups using the Mayo Clinic Implant Database have shown the survival-free of implant failure rate to be 96.6%, 95.4% and 94.5% at 1, 3 and 5 years respectively, suggesting no difference in the survival rate of implants in patients with or without chemotherapy.
Assessment of intra/inter examiner reliability of the modified Huddart-Bodenham index in patients with UCLP:a pilot study
Uchenna Ekwenibe
Lagos University
BACKGROUND- Treatment outcome evaluation is an integral part of patient management and a basis for evidence based care delivery. This pilot study will provide preliminary data for further outcome studies. PURPOSE-To assess the intra/inter examiner reliability of the modified Huddart-Bodenham index in a Nigerian population. RESEARCH DESIGN-Ten dental casts of 6-10 years old with unilateral cleft lip and palate(UCLP) were evaluated by two Orthodontists and an orthodontic resident. Spearman's(P) and Kendall's tau(tc) rank correlation coefficients were used for intra and inter examiner reliability. RESULTS-There was substantial intraclass agreement consistently >0.7(Kendall) and > 0.8(Spearman) for all examiners. The inter class agreement was between 0.5(lowest score) and 0.89(highest). CONCLUSION-The index can be reliably used in occlusal assessment of patients with UCLP in a Nigerian population.
Assessment of the reliability of dental measurements using the OrthoMechanics Sequential Analyzer
Ahmed Ghoneima
Indiana University-Purdue University, Indianapolis
The aim of this study was to evaluate the reliability of newly developed software in the assessment of orthodontic tooth movement three dimensionally. Methods: The sample consisted of pre and post-treatment computed tomography scans and dental models of 20 subjects. Dental parameters were measured on the scans using InvivoDental imaging software v 5.1. Dental models were laser scanned and measurements were obtained digitally using the new software. Agreement between digital and CT measurements was evaluated using intraclass correlation coefficients (ICCs), paired t-tests, and Bland-Altman plots. A p-value of ≤ 0.05 was considered statistically significant. Results: High agreement (ICC > 0.9), a non-significant paired t-test, and no indication of agreement discrepancies were observed for most parameters. Conclusions: The software offers a reliable tool concerning dental arch measurements. It is expected to help orthodontists evaluate treatment progress without unnecessary radiation.
Craniofacial morphometric analysis of individuals with X-linked hypohidrotic ectodermal dysplasia (XLHED)
Alice Goodwin
University of California, San Francisco
Background: X-linked hypohidrotic ectodermal dysplasia (XLHED) is characterized by missing or malformed skin, hair, sweat glands, teeth, and a distinct facial appearance. Purpose: To characterize craniofacial morphology in subjects with XLHED by use of advanced 3D imaging and geometric morphometrics. Research Design: 3D facial images of healthy male control subjects (n=59) and XLHED subjects (n=23) were captured, landmarked, and analyzed. Results: The XLHED craniofacial phenotype included shorter face with relatively longer chin and midface, prominent midfacial hypoplasia, protrusive mandible, narrower and pointed nose, shorter philtrum, fuller and rounded lower lip, and narrower mouth.
Conclusions: 3D morphometric analysis is a powerful tool for clinical diagnosis of XLHED and has the potential to be a more efficient and accurate tool than 2D cephalometrics in the orthodontic diagnosis and treatment of individuals with XLHED and the general population.
Effect of palate height in tongue motion in glossectomy patients vs control*
Jun Hyuk Hwang
University of Maryland
Two types of /s/, apical and laminal, were identified in a previous study which showed that the palate height affected the choice of /s/ in normal subjects, but not in post-glossectomy patients. Patients predominantly used laminal /s/. Glossectomy patients often time develop abnormal motions of the tongue. The aim of this study is to determine if glossectomy patients’ tongue mimic those of normal subjects with high palate due to the increased amount of oral cavity space due to tongue resection. Using cine-MRI, the relationship between height of the palate, dentition, and the tongue motion is analyzed during production of phonemes “a-souk” and “a-geese”. The importance of palate height as well as dentition in sound production may alter future therapy modality including the possibility of orthodontics as a possible adjunctive treatment to improve acoustics of speech.
Patient compliance with orthodontic removable retainers: A pilot study
Paul Hyun
State University of New York, Buffalo
Although retainer compliance is out of the control of the provider, retainer wear may be improved with microsensors. The objective was to compare retainer wear of 22 patients, one group aware of the Smart® microsensor, and the other group unaware. The time periods were T0 (retainer delivery), T1 (6 weeks visit), and T2 (12 weeks visit). At T1, the unaware group was informed of the sensor, and then returned at T2 to evaluate any improvements. During T0 to T1, the average hrs/day for the aware group was 16.3, while the unaware group was 10.6. The difference of 5.7 hrs/day was statistically significant. Although the unaware group increased their retainer wear by 0.5 hr/day from T1 to T2, it was not statistically significant. While 89% of subjects reported positive levels of comfort, the microsensor did increase the palatal acrylic thickness. Although the Smart® microsensor provides a valid way to improve retainer wear, certain changes could pave a more promising future for microsensors.