Research: Class of 2014

Alatsis, PV. Effects of staining on white spot lesions treated with ICON® resin infiltration. Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2014

ABSTRACT

Introduction: The purpose of this in vitro study was to assess the esthetic appearance of a resin infiltrant used to restore enamel white spot lesions. Assessments were made immediately following resin infiltration and after extended exposure to several staining solutions.

Methods & Materials: White spot lesions were created on defined portions of the labial surfaces of 100 extracted bovine maxillary incisors using an enamel demineralization solution. Tooth surfaces blocked from the demineralization solution served as controls. Demineralization was conducted for either 2 weeks (n=50) or 6 weeks (n=50).  The demineralized area was divided in half to form 2 windows. One window remained demineralized (WSL) and the other was restored using a resin infiltration technique (ICON; ICON® Smooth Surface Resin Infiltration System, DMG America, Englewood, NJ). For each tooth, photographs and color measurements (ΔE) of the 3 surface conditions, recorded with an intraoral spectrophotometer. Specimens from both demineralization groups were then divided into 5 subgroups of 10 teeth each and soaked for 2 weeks in one of 5 solutions: deionized water (control), coffee, red wine, energy drink, and 10% carbamide peroxide, after which photographs and color measurements were obtained. One specimen from each demineralization and staining group (n=10) was sectioned and the depth of stain penetration and the resin-tooth interface was assessed by light microscopy. Statistical analysis was performed using ANOVA with level of significance set at α<0.05. 

Results: Initially ICON infiltration restorations showed significantly closer color matches to sound enamel relative to the untreated WSL, with 2-week demineralization showing ΔE=5.5 vs. 30.09, and 6-week demineralization showing ΔE=8.72 vs. 31.77, respectively (p<.001). ICON was less effective masking the lesions formed with 6 weeks relative to 2 weeks demineralization (p=0.019).  Red wine produced the most staining in all 3 surface conditions for both demineralization groups (p<0.001).  Staining by red wine was significantly reduced for infiltrated lesions compared to untreated WSL or control (p<0.001).  Staining by coffee was significantly reduced for infiltrated lesions compared to untreated WSL (p<0.001), but significantly increased for infiltrated lesions compared to the control for 6-week demineralized specimens (p<0.001).  The effects of staining by the energy drink and carbamide peroxide where marginally evident.  Microscopy revealed for 2-week demineralized specimens that WSL depths ranged from 142-377µm, with ICON penetration ranging from 118-225µm, and for 6-week specimens the ranges were 222-357µm and 110-303µm, respectfully.

Conclusions: Resin infiltration was able to significantly improve the appearance of WSLs in vitro.  Staining remained superficial and different staining solutions produced variable changes in color. The greatest staining occurred with red wine and coffee, while energy drink, whitening solution and water had little effect.  Resin infiltrated lesions are less susceptible to staining by coffee and red wine than WSL or sound enamel.

Browne, VN. Accuracy of alveolar bone measurements using cone beam computed tomography compared with direct in vivo measurements. Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2014

ABSTRACT

Introduction: Cone beam computed tomography (CBCT) imaging has broadened the clinician’s opportunity to examine hard and soft tissue of the craniofacial complex, but limitations of the technology have yet to be fully defined. The purpose of this study was to investigate the accuracy and reliability of CBCT measurements compared to direct measurements in vivo of facial alveolar bone height (FBH), and in detecting the presence or absence of naturally occurring dehiscences and fenestrations.

Materials and Methods: FBH measurements and the diagnosis of a dehiscence or fenestration were recorded from CBCT images (i-CAT ® 17-19 unit; Imaging Sciences International, Hatfield, Pennsylvania) acquired using 0.3mm voxel size, 5mA, 120kVp and viewed in standardized 0.5mm radiographic slices. Measurements were recorded using Dolphin 3D Imaging ® (Dolphin Imaging Systems, Chatsworth, CA) software after adjusting for optimal viewing image contrast. All measurements were repeated three times by two blinded independent raters. These measurements were compared to observations made at the time of surgical procedures involving a full thickness mucoperiosteal flap, where FBH and the presence or absence of a facial bone dehiscence or fenestration were also recorded by two independent raters. 

Results: For CBCT FBH measurements, intrarater reliability was high (PCC, CCC, and ICC≥0.98), as was interrater reliability (PCC and CCC≥0.97). The mean absolute difference between mean CBCT measurements for the first and second raters was 0.64±0.77mm. Interrater reliability for direct FBH measurements was high (PCC and ICC both ≥ 0.98). The mean absolute difference between raters for clinical FBH measurements was 0.46±0.35mm. CBCT measurements differed significantly from direct measurements, with a pattern of overestimation for CBCT measurements, which correlates to the appearance of decreased facial alveolar bone levels. The mean absolute differences were 2.49±2.61mm for facial bone height with 95% limits of agreement of -7.76 to 3.20mm.  A PCC of 0.81 and CCC of 0.64 for facial bone height were found. The interrater reliability for detection of dehiscences and fenestrations was good (Cohen’s kappa 0.65 ±0.11 with 95% CI 0.44 to 0.87). For each rater, in comparing the direct measurements to CBCT measurements for detecting dehiscences and fenestrations, Cohen’s kappa was high (0.76 ±.11 with 95% CI 0.54 to 0.98) and moderate (0.50±.13 with 95% CI 0.26 to 0.75). Overall, 71% of dehiscences and fenestrations were detected on the CBCT images. 

Conclusions: For the protocol used in this study, facial alveolar bone height levels were often underestimated in CBCT images, especially in areas where alveolar bone is thin. Similarly, a number of the alveolar bone defects were not detectable in CBCT images.

Knapp, BR. Fracture toughness, clarity, and staining of thermoplastic orthodontic retainer materials. Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2014

ABSTRACT

Introduction: The objective of this study was to measure and compare the clarity, essential work of fracture (EWF), and plastic work of fracture (PWF) of six different orthodontic thermoplastic retainer materials before and after prolonged immersion in beverages.

Materials and Methods: Six different materials were studied; three polyethylene copolymers: Ace (Essix, Sarasota, FL), Plus (Essix, Sarasota, FL), and Invisacryl Ultra (Great Lakes Orthodontics, Tonawanda, NY); two polypropylene polymers: C+ (Essix, Sarasota, FL), and Invisacryl C (Great Lakes Orthodontics, Tonawanda, NY), and one polyvinyl chloride polymer, Endure (Great Lakes Orthodontics, Tonawanda, NY). Double-edged-notched-tension specimens were cut from the center of thermoformed discs of the material. The clarity of the materials was measured with a chroma meter using the Commission Internationale de l’Eclairage (CIE) LAB color scale before and after immersion in cola, wine, and coffee for a total of three weeks. The essential work of fracture test was used to measure the EWF and PWF of materials before and after being immersed in the beverages. Color change was calculated using the equation: ΔE*ab = √ [(ΔL*2+Δa*2+Δb*2)].  ΔE*ab values were compared between materials using one-way analysis of variance followed by Tukey post-test (α = 0.05). Differences in EWF and PWF between materials were compared using an analysis of covariance followed by Tukey post-test (α = 0.05).

Results: ΔE*ab (initial clarity) for the polyethylene copolymers was less than for the polyvinyl chloride polymer, which was less than for the polypropylene polymers. ΔE*ab (staining) for one of the polypropylene polymers, Essic C+, was greater than all of the other materials. EWF for one of the polypropylene polymers, Essix C+, was greater than all of the materials; however, it displayed a significant decrease after immersion in beverages. No differences were found between materials’ PWF. All reported differences were statistically significant (P < .05).

Conclusions: Essix C+ stained more than any other material, and was the only material to display a change in fracture toughness, a decrease in EWF, after immersion in beverages.

Luwiharto, ST. Comparison of bracket transfer accuracy of 3 indirect bonding tray methods in maxillary teeth having varying displacements and rotations – an in vitro study. Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2014

ABSTRACT

Introduction: The objective of this study was to measure and compare bracket transfer accuracy of 3 indirect bonding techniques in maxillary arches with varying amounts of crowding and tooth rotations.

Materials and Methods: Three indirect bonding techniques (double PVS, double vacuum form, PVS putty) were studied on four master models (master models FL-M, FL-S, MD-M and MD-S) of moderate and severe amounts of facio-lingual displacement and rotations. For each technique, 144 brackets were bonded to 12 working models. IDB trays were fabricated and the brackets were transferred to 12 patient models. Bracket positions before and after the transfer were measured and recorded in mesio-distal and occluso-gingival directions utilizing a digital camera, and in facio-lingual direction utilizing a digital caliper. One way ANOVA with post hoc Tukey test was done to compare the effects of arch length discrepancy, tooth rotations, and tray material on bracket transfer accuracy.

Results: PVS-P showed the most statistically significant differences in bracket position between working and patient models. DVF had significant differences in rotation models. D-PVS was also more affected by tooth rotations than facio-lingual displacement. When 4 master models were compared, moderate facio-lingual displacement (FL-M) had the most statistically significant difference in bracket positions. When 3 different techniques were compared, PVS-P was significantly less accurate than D-PVS in master model FL-S and less accurate than DVF in master model FL-M in facio-lingual direction.

Conclusions: PVS-P was the least accurate method relative to the other techniques with all master models, except the model with severe rotations. D-PVS and DVF had comparable bracket transfer accuracies, although DVF was more significantly affected by tooth rotations.