Research: Class of 2008
Burgin, E “Evaluation of mandibular growth rotation prediction methods based on lateral cephalogram measurements” Orthodontic Thesis for M.S. degree, Oregon Health & Science University, December 2008.
ABSTRACT:
Introduction: Rotation of the mandible during growth can influence treatment planning decisions, thus prediction would be a valuable diagnostic tool. This study evaluated several prediction methods including that of Skieller et al. (1984), Jarabak (1972), and Lux et al. (1999) as well as the computerized growth forecast function of Quick Ceph Studio (Quick Ceph Systems). An additional aim was to determine if the success of the methods was different for subgroups based on skeletal classification according to ANB angle.
Materials and Methods: Pre-adolescent growth records from untreated subjects (n=61) selected from the Oregon Child Study Clinic collection were used to evaluate the prediction methods by making predictions of mandibular rotation and comparing the predictions to the actual growth measured from post-adolescent growth records.
Results: The regression analysis described by Skieller et al. performed poorly in this sample. Of the ranges for prediction described by Jarabak (1972) and Lux et al. (1999), the predictive range using upper gonial angle (UGA) described by Jarabak was the most accurate at predicting the direction of mandibular growth, with 79.2% of the predictions made being correct. Quick Ceph Studio’s growth forecast predicted no mandibular rotation for all but 4 of the subjects. The computerized prediction method was not individualized enough to accurately predict mandibular rotation in individual patients. There was insufficient evidence to determine that differences in prediction accuracy between the subgroups existed for any of the methods.
Conclusions: The mandibular growth rotation prediction methods evaluated are not accurate or reliable enough to make definitive predictions. A clinician may decide to use the ranges specified by Jarabak (1972) for UGA to add to the overall assessment of a patient, with the limitations of the method considered.
Crowe, J “Ion release from a novel bioactive orthodontic bonding agent for prevention of white spot lesions”: An in vitro study Orthodontic Thesis for M.S. degree, Oregon Health & Science University, December 2008.
ABSTRACT:
Introduction: The use of bioactive bonding agents in orthodontics may help prevent white spot lesions that accompany plaque retention around brackets by increasing local calcium (Ca2+), phosphate (PO43-), and fluoride (F-) ion concentrations. The purpose of this study was to compare Ca2+, PO43-, and F- ion movement between orthodontic adhesives and solutions at two pH levels. The adhesives compared were an orthodontic resin-modified glass ionomer cement (GI) and a novel resin-modified glass ionomer cement containing bioactive glass (BGI).
Methods: BGI was synthesized by sol-gel methods (75 mol% SiO2, 21 mol% CaO, 4 mol% P2O5), and mixed with commercially available resin-modified glass ionomer cement in a 30% mass ratio to prepare the BGI. The experimental powder was mixed in a 1.5: 1 powder: liquid ratio, light cured, ground to < 90 μm and immersed in simulated body fluid (SBF) at both pH7 and pH4. Ion concentrations were measured (n=5 per condition) from the SBF containing experimental and control samples at 1 h, 10 h, 33 h, 5.5 d, and 11 d. Ion-specific electrodes were used to measure [F-] and [Ca2+], while [PO43-] was measured using a colorimetric method. Scheffé’s method (α=0.05) was used to perform multiple comparisons across treatment groups. After each time-point, solid samples were analyzed for surface changes and new mineral formation.
Results: In neutral pH conditions, ion concentrations did not differ between the experimental and control groups until the longest time-point. In acidic conditions, Ca2+ concentrations in BGI solutions were higher than GI solutions while PO43- and F- concentrations in BGI solutions were higher or equivalent to GI solutions. At all time-points, ion concentrations in control and experimental solutions were greater at pH4 than pH7. Surface analysis of samples yielded no evidence of new mineral formation.
Conclusion: The elevated Ca2+ concentration with BGI at pH 4 suggests this adhesive
holds promise in protection against white spot lesion formation.
ABSTRACT:
Introduction: The bonding and subsequent removal of an orthodontic bracket may damage the surface of a porcelain dental restoration. Refinishing the porcelain surface following orthodontic treatment is important for esthetics, maintaining structural integrity and minimizing the adhesion of dental plaque. The purpose of this study was to compare the damage to porcelain surfaces at debonding following the use of two different bracket bonding methods, and to evaluate a porcelain refinishing procedure for restoring the porcelain surface to its original condition.
Materials and Methods: Forty porcelain discs were fabricated from Lava Ceram feldspathic porcelain veneer and divided equally into two groups. In the SB+HF+S
group, the surface was deglazed by sandblasting and then etched with hydrofluoric acid. A silane coupling agent was applied followed by Transbond XT Light Cure Adhesive Primer. Stainless steel orthodontic brackets pre-coated with APC Plus composite adhesive were bonded. In the PA+S group, samples were treated with phosphoric acid and porcelain primer silane coupling agent and brackets were bonded as above. After 24 hours brackets were debonded using anterior bracket removing pliers and residual resin was removed with a 12-fluted carbide bur. Refinishing included polishing with an intra-oral porcelain polishing kit followed by diamond polishing paste. Measurements of surface roughness, gloss and color were made with a surface profilometer, glossmeter and chromameter, respectively, and were made prior to bonding brackets, after debonding and residual resin removal, after refinishing with the porcelain polishing kit, and following polishing with diamond paste. Data was analyzed with two way analysis of variance followed by Tukey HSD tests (α = 0.05). In addition, specimens were examined under a scanning electron microscope to compare the surface roughness between stages of the bonding and polishing procedures.
Results: The SB+HF+S method caused significantly more damage to the porcelain surface than the phosphoric acid and silane (PA+S) bonding method (P<0.001). The SB+HF+S bonding method significantly increased porcelain surface roughness (0.160 to 1.121 μm), decreased gloss (41.3 to 3.7) and altered color (ΔE =4.37; P<0.001). The PA+S method significantly increased porcelain surface roughness (0.173 to 0.341 μm; P<0.001), but the increase in Ra was significantly less than that caused by the SB+HF+S bonding method (P<0.001). The PA+S method caused insignificant changes in gloss and color. Damage inflicted on the porcelain surface was fully restorable to baseline values with the refinishing procedure tested, regardless of bonding method.
Conclusions: The PA+S bonding method is recommended over the SB+HF+S method as the PA+S method causes significantly less damage to the porcelain surface. The protocol that we found worked well for refinishing the porcelain was to carefully remove residual adhesive with a carbide finishing bur, polish with an intra-oral porcelain polishing kit until the surface appears smooth, then polish with diamond polishing paste until the surface appears glossy.
ABSTRACT:
Introduction: Fixed orthodontic appliances can hinder the maintenance of good oral hygiene, resulting in bacterial plaque accumulation and an increased risk of subsequent enamel decalcification, visible on the facial surfaces of teeth surrounding brackets as un-esthetic white spot lesions. The objectives of this randomized clinical study were to enumerate and compare plaque bacteria surrounding two bracket types, self-ligating (SL) versus elastomeric-ligating (E), and to determine if ATP-driven bioluminescence could be used in the rapid assessment of bacterial load in plaque.
Material and Methods: This was a randomized, prospective clinical trial employing a split-mouth design. Subjects included 14 individuals (6 males, 8 females; ages 11-17 years) where the lateral incisor on one side of the maxillary dental arch randomly received a bracket ligated with elastomers while the contra-lateral lateral incisor received a self-ligating bracket. Mandibular lateral incisors received the reverse configuration. All other teeth received self-ligating brackets. In two patients, only upper appliances were placed. Plaque samples were collected from facial surfaces of the lateral incisors, at the periphery of the tooth-bracket interface, on two occasions: 1 week and 5 weeks. Salivary samples were also collected before bonding and at each time point thereafter. Plaque specimens were assayed for oral bacteria, and ATP-driven bioluminescence determinations made using a luciferin-based assay. Mean, standard deviation, and significance values (Student’s t-test; p set to <0.05) were calculated.
Results: In the majority of patients, teeth bonded with SL attachments exhibited fewer bacteria in plaque than teeth bonded with E brackets. At 1 and 5 weeks post-bonding, means for SL versus E brackets were statistically lower for total bacteria and for oral streptococci (p<0.05). ATP bioluminescence values were statistically correlated to numbers of total oral bacteria and oral streptococci, and had correlation coefficients of 0.895 and 0.843, respectively.
Conclusions: The self-ligating appliances promote reduced retention of oral bacteria, and ATP bioluminescence may serve as a useful tool in the rapid quantification of bacterial load and for assessing oral hygiene during orthodontic treatment.
ABSTRACT:
Introduction: Rotation of the mandible during growth can influence treatment planning decisions, thus prediction would be a valuable diagnostic tool. This study evaluated several prediction methods including that of Skieller et al. (1984), Jarabak (1972), and Lux et al. (1999) as well as the computerized growth forecast function of Quick Ceph Studio (Quick Ceph Systems). An additional aim was to determine if the success of the methods was different for subgroups based on skeletal classification according to ANB angle.
Materials and Methods: Pre-adolescent growth records from untreated subjects (n=61) selected from the Oregon Child Study Clinic collection were used to evaluate the prediction methods by making predictions of mandibular rotation and comparing the predictions to the actual growth measured from post-adolescent growth records.
Results: The regression analysis described by Skieller et al. performed poorly in this sample. Of the ranges for prediction described by Jarabak (1972) and Lux et al. (1999), the predictive range using upper gonial angle (UGA) described by Jarabak was the most accurate at predicting the direction of mandibular growth, with 79.2% of the predictions made being correct. Quick Ceph Studio’s growth forecast predicted no mandibular rotation for all but 4 of the subjects. The computerized prediction method was not individualized enough to accurately predict mandibular rotation in individual patients. There was insufficient evidence to determine that differences in prediction accuracy between the subgroups existed for any of the methods.
Conclusions: The mandibular growth rotation prediction methods evaluated are not accurate or reliable enough to make definitive predictions. A clinician may decide to use the ranges specified by Jarabak (1972) for UGA to add to the overall assessment of a patient, with the limitations of the method considered.
Crowe, J “Ion release from a novel bioactive orthodontic bonding agent for prevention of white spot lesions”: An in vitro study Orthodontic Thesis for M.S. degree, Oregon Health & Science University, December 2008.
ABSTRACT:
Introduction: The use of bioactive bonding agents in orthodontics may help prevent white spot lesions that accompany plaque retention around brackets by increasing local calcium (Ca2+), phosphate (PO43-), and fluoride (F-) ion concentrations. The purpose of this study was to compare Ca2+, PO43-, and F- ion movement between orthodontic adhesives and solutions at two pH levels. The adhesives compared were an orthodontic resin-modified glass ionomer cement (GI) and a novel resin-modified glass ionomer cement containing bioactive glass (BGI).
Methods: BGI was synthesized by sol-gel methods (75 mol% SiO2, 21 mol% CaO, 4 mol% P2O5), and mixed with commercially available resin-modified glass ionomer cement in a 30% mass ratio to prepare the BGI. The experimental powder was mixed in a 1.5: 1 powder: liquid ratio, light cured, ground to < 90 μm and immersed in simulated body fluid (SBF) at both pH7 and pH4. Ion concentrations were measured (n=5 per condition) from the SBF containing experimental and control samples at 1 h, 10 h, 33 h, 5.5 d, and 11 d. Ion-specific electrodes were used to measure [F-] and [Ca2+], while [PO43-] was measured using a colorimetric method. Scheffé’s method (α=0.05) was used to perform multiple comparisons across treatment groups. After each time-point, solid samples were analyzed for surface changes and new mineral formation.
Results: In neutral pH conditions, ion concentrations did not differ between the experimental and control groups until the longest time-point. In acidic conditions, Ca2+ concentrations in BGI solutions were higher than GI solutions while PO43- and F- concentrations in BGI solutions were higher or equivalent to GI solutions. At all time-points, ion concentrations in control and experimental solutions were greater at pH4 than pH7. Surface analysis of samples yielded no evidence of new mineral formation.
Conclusion: The elevated Ca2+ concentration with BGI at pH 4 suggests this adhesive
holds promise in protection against white spot lesion formation.
Herion, D “Refinishing porcelain surfaces after the use of two orthodontic bonding methods” Orthodontic Thesis for M.S. degree, Oregon Health & Science University, December 2008.
ABSTRACT:
Introduction: The bonding and subsequent removal of an orthodontic bracket may damage the surface of a porcelain dental restoration. Refinishing the porcelain surface following orthodontic treatment is important for esthetics, maintaining structural integrity and minimizing the adhesion of dental plaque. The purpose of this study was to compare the damage to porcelain surfaces at debonding following the use of two different bracket bonding methods, and to evaluate a porcelain refinishing procedure for restoring the porcelain surface to its original condition.
Materials and Methods: Forty porcelain discs were fabricated from Lava Ceram feldspathic porcelain veneer and divided equally into two groups. In the SB+HF+S
group, the surface was deglazed by sandblasting and then etched with hydrofluoric acid. A silane coupling agent was applied followed by Transbond XT Light Cure Adhesive Primer. Stainless steel orthodontic brackets pre-coated with APC Plus composite adhesive were bonded. In the PA+S group, samples were treated with phosphoric acid and porcelain primer silane coupling agent and brackets were bonded as above. After 24 hours brackets were debonded using anterior bracket removing pliers and residual resin was removed with a 12-fluted carbide bur. Refinishing included polishing with an intra-oral porcelain polishing kit followed by diamond polishing paste. Measurements of surface roughness, gloss and color were made with a surface profilometer, glossmeter and chromameter, respectively, and were made prior to bonding brackets, after debonding and residual resin removal, after refinishing with the porcelain polishing kit, and following polishing with diamond paste. Data was analyzed with two way analysis of variance followed by Tukey HSD tests (α = 0.05). In addition, specimens were examined under a scanning electron microscope to compare the surface roughness between stages of the bonding and polishing procedures.
Results: The SB+HF+S method caused significantly more damage to the porcelain surface than the phosphoric acid and silane (PA+S) bonding method (P<0.001). The SB+HF+S bonding method significantly increased porcelain surface roughness (0.160 to 1.121 μm), decreased gloss (41.3 to 3.7) and altered color (ΔE =4.37; P<0.001). The PA+S method significantly increased porcelain surface roughness (0.173 to 0.341 μm; P<0.001), but the increase in Ra was significantly less than that caused by the SB+HF+S bonding method (P<0.001). The PA+S method caused insignificant changes in gloss and color. Damage inflicted on the porcelain surface was fully restorable to baseline values with the refinishing procedure tested, regardless of bonding method.
Conclusions: The PA+S bonding method is recommended over the SB+HF+S method as the PA+S method causes significantly less damage to the porcelain surface. The protocol that we found worked well for refinishing the porcelain was to carefully remove residual adhesive with a carbide finishing bur, polish with an intra-oral porcelain polishing kit until the surface appears smooth, then polish with diamond polishing paste until the surface appears glossy.
Pellegrini, P “Plaque retention by self-ligating versus elastomeric orthodontic brackets: Quantitative comparison of oral bacteria and detection using ATP-driven bioluminescence” Orthodontic Thesis for M.S. degree, Oregon Health & Science University, December 2008.
ABSTRACT:
Introduction: Fixed orthodontic appliances can hinder the maintenance of good oral hygiene, resulting in bacterial plaque accumulation and an increased risk of subsequent enamel decalcification, visible on the facial surfaces of teeth surrounding brackets as un-esthetic white spot lesions. The objectives of this randomized clinical study were to enumerate and compare plaque bacteria surrounding two bracket types, self-ligating (SL) versus elastomeric-ligating (E), and to determine if ATP-driven bioluminescence could be used in the rapid assessment of bacterial load in plaque.
Material and Methods: This was a randomized, prospective clinical trial employing a split-mouth design. Subjects included 14 individuals (6 males, 8 females; ages 11-17 years) where the lateral incisor on one side of the maxillary dental arch randomly received a bracket ligated with elastomers while the contra-lateral lateral incisor received a self-ligating bracket. Mandibular lateral incisors received the reverse configuration. All other teeth received self-ligating brackets. In two patients, only upper appliances were placed. Plaque samples were collected from facial surfaces of the lateral incisors, at the periphery of the tooth-bracket interface, on two occasions: 1 week and 5 weeks. Salivary samples were also collected before bonding and at each time point thereafter. Plaque specimens were assayed for oral bacteria, and ATP-driven bioluminescence determinations made using a luciferin-based assay. Mean, standard deviation, and significance values (Student’s t-test; p set to <0.05) were calculated.
Results: In the majority of patients, teeth bonded with SL attachments exhibited fewer bacteria in plaque than teeth bonded with E brackets. At 1 and 5 weeks post-bonding, means for SL versus E brackets were statistically lower for total bacteria and for oral streptococci (p<0.05). ATP bioluminescence values were statistically correlated to numbers of total oral bacteria and oral streptococci, and had correlation coefficients of 0.895 and 0.843, respectively.
Conclusions: The self-ligating appliances promote reduced retention of oral bacteria, and ATP bioluminescence may serve as a useful tool in the rapid quantification of bacterial load and for assessing oral hygiene during orthodontic treatment.
