- Email: [email protected]
Residents’ journal review
RESIDENTS' JOURNAL REVIEW
ARTICLES FROM THE CURRENT ORTHODONTIC LITERATURE, SELECTED AND REVIEWED BY: RESIDENTS, ORTHODONTICS GRADUATE PROGRAM, SCHOOL OF DENTAL MEDICINE, UNIVERSITY OF COLORADO, AURORA
method also needs to be refined to prevent extensive errors. Further studies using fractal analysis may develop an objective method for clinicians to determine the midpalatal suture fusion and the feasibility of rapid maxillary expansion in adults. Reviewed by Erin Riley
Gerald Minick, Program Director
Orthodontic bonding with and without primer
Dan Grauer, Associate Editor for Residents' Journal Review Santa Monica, Calif
Midpalatal suture maturation in adults Kwak KH, Kim SS, Kim YI, Kim YD. Quantitative evaluation of midpalatal suture maturation via fractal analysis. Korean J Orthod 2016;46:323-30.
N
onsurgical rapid maxillary expansion is often contraindicated in adults due to fusion of the midpalatal suture; however, the timing and extent of suture closure are highly variable. The purpose of this study was to evaluate whether fractal analysis (a mathematical procedure) of cone-beam computed tomography data can be used to determine the maturation stage of the palatal suture. The sample consisted of 131 adult patients who had undergone cone-beam computed tomography imaging for diagnostic purposes. The principal investigator used the maturation classification system of Angelieri et al to categorize midpalatal suture closure. A fractal dimension value was also determined for each midpalatal suture with Image J computer software. The results showed a strong negative correlation between the fractal dimension and the suture maturation stage. Additionally, the fractal dimension was a statistically significant predictor of suture fusion. The authors explained that the classification system of Angelieri et al can be a subjective tool because much training is required for proficiency. Fractal analysis is a more objective and highly reliable method of determining suture fusion. There are currently some problems with the technique used in this study. The patient's bone density is not taken into account; this hinders the accuracy of the results. The fractal dimension calculation
Am J Orthod Dentofacial Orthop 2017;151:239-41 0889-5406/$36.00 Ó 2017 by the American Association of Orthodontists. All rights reserved. http://dx.doi.org/10.1016/j.ajodo.2016.12.006
€ thgren H, Kowalczyk Bazargani F, Magnuson A, Lo A. Orthodontic bonding with and without primer: a randomized controlled trial. Eur J Orthod 2016;38:503-7.
O
rthodontists everywhere continue to look for ways to decrease treatment time, increase efficiency, and lower overhead costs. Ensuring adequate bonding of brackets reduces bond failures and thus may decrease the number and length of appointments during treatment. The purposes of this study were to evaluate the incidence of failures of brackets bonded with primer (Transbond MIP) and without primer and to assess whether there is a difference in the numbers of emergency visits. Fifty consecutive patients needing conventional bimaxillary fixed appliances were recruited and enrolled in the study. A cross-mouth design was used in each patient. Two diagonal quadrants (maxillary right and mandibular left, or vice versa) were randomly assigned to the primer group (control) and the contralateral diagonal quadrants to the nonprimer group (experimental). The total failure rates were 5.5% in the nonprimer group and 3.1% in the primer group; this was not statistically significant. The failure rate differences between the groups showed a significant interaction with age. In younger patients (ages, 10-13 years), the failure rate of brackets bonded without primer (12.1%) was significantly higher than that of brackets bonded with primer (4.1%). Among older patients (14-18 years), the difference in failure rates between the nonprimer (2.3%) and the primer (2.6%) groups was not significant. The authors also found that boys are more likely to break brackets than are girls, and that mandibular bond failures are more frequent than maxillary failures. The authors concluded that the failure rates of bonding brackets with or without Transbond MIP primer did not differ significantly in a clinical setting (5.5% vs 3.1%); however, younger patients (10-13 years) may benefit from the use of a primer. Reviewed by Jeffrey Birg 239
Residents' journal review
240
Effects of intraoral aging of archwires on frictional forces Kumar A, Khanam A, Ghafoor H. Effects of intraoral aging of arch-wires on frictional forces: an ex vivo study. J Orthod Sci 2016;5:109-16.
S
tainless steel archwires are the most commonly used wires during fixed orthodontic treatment. Because of their low coefficient of friction, these archwires are an optimal choice for sliding mechanics. However, intraorally, they are subject to surface deposits and biofilms that can increase their friction and potentially decrease the efficiency of tooth movement. These investigators sought to evaluate the surface changes and frictional resistance of stainless steel archwires after intraoral exposure. Ten patients with premolar extractions and good oral hygiene were selected for the study. The maxillary and mandibular 0.019 3 0.025 stainless steel archwires were removed and analyzed after 6 weeks of intraoral exposure during the final stages of alignment and leveling. The maxillary and mandibular archwires were compared with as-received controls. The archwire between the second premolar bracket and the first molar tube was analyzed for (1) surface debris using a scanning electron microscope, (2) average surface roughness using an atomic force microscope, and (3) frictional resistance using an Instron universal testing machine. The investigators found statistically significant increases in the amounts of surface debris, surface roughness, and frictional force of the test archwires compared with the controls. The frictional force increased 39.7% after intraoral exposure. Statistical analysis showed a significant association between friction and the amount of surface debris. A positive correlation was also found for friction and surface roughness. For optimal results when using sliding mechanics, the authors suggested using a new stainless steel archwire for space closure to reduce frictional resistance. Reviewed by Macie Mills
Three-dimensional mapping of cortical bone thickness Sadek MM, Sabet NE, Hassan IT. Three-dimensional mapping of cortical bone thickness in subjects with different vertical facial dimensions. Prog Orthod 2016;17:32.
M
ini-implants are commonly used as a reliable source of anchorage in orthodontics. Cortical
February 2017 Vol 151 Issue 2
bone thickness (CBT) is the key determinant in initial stability of mini-implants. The purpose of this study was to determine whether there are differences in CBT in the tooth-bearing regions of the jaws (anterior and posterior) among subjects with different vertical facial dimensions using cone-beam computed tomography. Cone-beam computed tomography scans of 114 subjects, aged 18 to 35 years, were analyzed. After the exclusion criteria were applied, 45 subjects were divided according to facial type: 17 with an average vertical facial dimension, 13 with a high vertical facial dimension, and 15 with a low vertical facial dimension. Using iCATVision software, 2-dimensional slices, each 0.3 mm thick, were oriented so that each interradicular space was bisected parallel to the long axes of the roots. For each interradicular space, CBT was measured at 4 and 7 mm apical to the alveolar crest. Maxillary measurements were both palatal and buccal, whereas mandibular measurements were buccal only. Statistically significant differences of CBT were found in the maxilla (buccal) mesial and distal to the first molar, and (palatal) mesial and distal to the lateral incisor. Statistically significant differences were also found mesial and distal to the mandibular first molar and between the premolars. In both arches, the low-angle group had the thickest cortical plate whereas the high-angle group had the thinnest. The authors indicated that further research should be conducted, differentiating for sex and including measurements of bone density and CBT. The authors concluded that the CBT was thinner in highangle patients in the regions where mini-implants are most likely be placed. Reviewed by Nathan Ng
Dynamic smile evaluation in different skeletal patterns Siddiqui N, Tandon P, Singh A, Haryani J. Dynamic smile evaluation in different skeletal patterns. Angle Orthod 2016;86:1019-25.
I
mproving smile esthetics is a major motivator for seeking orthodontic treatment; therefore, dynamic evaluation of smile characteristics should be considered when planning treatment. The purposes of this study were to investigate whether smile characteristics differ in different skeletal patterns and to identify contributing factors that control the vertical smile parameters. The study was conducted with 150 participants aged 16 to 25 years with well-aligned teeth and no previous orthodontic treatment. Lateral cephalograms were used to
American Journal of Orthodontics and Dentofacial Orthopedics
Residents' journal review
distribute participants into horizontal, average, and vertical skeletal patterns using 3 cephalometric parameters. Video graphic records of smiles were obtained, and measurements were recorded and analyzed at rest and at smile. The results demonstrated that different skeletal patterns exhibit different smile characteristics. When compared with the horizontal pattern, the vertical pattern showed increased incisal display and interlabial gap, and a decreased transverse smile dimension. Flat smile arcs were also more frequently observed in the horizontal pattern, whereas a smile arc consonant with the lower lip was more common in the vertical pattern. The vertical pattern exhibited significantly higher upper lip elevation during smiling. In this sample, the vertical pattern also had a longer upper lip length. The authors also identified contributing factors for the differing smile patterns. Their findings indicate that increased incisor display during smile was not associated with short upper lip length at rest. Furthermore, increased incisal display was more closely associated with upper lip elevation than vertical skeletal and dental factors. Together, these findings provide insight into treatment planning for patients with vertical patterns and excessive gingival display and indicate an increased need to protect or develop the smile arc in brachyfacial patients. Reviewed by Ryan Booth
Gene therapy and stem cell application on root resorption Amuk NG, Kurt G, Baran Y, Seyrantepe V, Yandim MK, Adan A, et al. Effects of cell-mediated osteoprotegerin gene transfer and mesenchymal stem cell applications on orthodontically induced root resorption of rat teeth. Eur J Orthod 2016 Oct 12 [Epub ahead of print].
R
oot resorption, though rarely detrimental to treatment, can be a potential consequence of
241
orthodontic tooth movement. The aims of this study were to evaluate and compare the effects of mesenchymal stem cell and osteoprotegerin gene therapy applications on the inhibition and repair of orthodontically induced inflammatory root resorption. Thirty Wistar rats were randomly divided into 4 groups: an untreated control group, a group treated with an orthodontic appliance, a group having mesenchymal stem cell injections, and a group having gene therapy and osteoprotegerin transfected mesenchymal stem cell injections. Approximately 100 g of force was applied with a coil spring to the maxillary first molar for 14 days. In the experimental groups, mesenchymal stem cells and transfected mesenchymal stem cells were injected into the periodontal ligament on days 1, 6, and 11 of the experiment. At the end of experimental day 14, periodontal ligament tissue from the maxillary first molar was prepared for fluorescent microscope examination, scanning electron microscopy, and histologic analysis. Expression levels were calculated for osteoprotegerin, RANKL, COX-2, osteoclastic cells, resorption area ratio, and resorption lacunae at the periodontal ligament. The authors found that the mesenchymal stem cell and gene therapy treated groups had significantly fewer osteoclastic cells, lower resorption area ratios, and fewer RANKL, COX-2, and resorption lacunae. They concluded that gene therapy and mesenchymal stem cells transferred to the periodontal ligament under orthodontic force exhibit therapeutic effects by reducing root resorption or evoking reparative effects. The authors’ use of mesenchymal stem cells as the transport method of osteogprotegerin is the first published study of its kind, leaving a path for future investigations on cellular and genetic approaches in the treatment of inflammatory root resorption. If these advanced approaches are improved for clinical practice in the future, they may provide great benefits in treating patients with a high root resorption risk. Reviewed by Samer Faranesh
American Journal of Orthodontics and Dentofacial Orthopedics
February 2017 Vol 151 Issue 2
ARTICLES FROM THE CURRENT ORTHODONTIC LITERATURE, SELECTED AND REVIEWED BY: RESIDENTS, ORTHODONTICS GRADUATE PROGRAM, SCHOOL OF DENTAL MEDICINE, UNIVERSITY OF COLORADO, AURORA
method also needs to be refined to prevent extensive errors. Further studies using fractal analysis may develop an objective method for clinicians to determine the midpalatal suture fusion and the feasibility of rapid maxillary expansion in adults. Reviewed by Erin Riley
Gerald Minick, Program Director
Orthodontic bonding with and without primer
Dan Grauer, Associate Editor for Residents' Journal Review Santa Monica, Calif
Midpalatal suture maturation in adults Kwak KH, Kim SS, Kim YI, Kim YD. Quantitative evaluation of midpalatal suture maturation via fractal analysis. Korean J Orthod 2016;46:323-30.
N
onsurgical rapid maxillary expansion is often contraindicated in adults due to fusion of the midpalatal suture; however, the timing and extent of suture closure are highly variable. The purpose of this study was to evaluate whether fractal analysis (a mathematical procedure) of cone-beam computed tomography data can be used to determine the maturation stage of the palatal suture. The sample consisted of 131 adult patients who had undergone cone-beam computed tomography imaging for diagnostic purposes. The principal investigator used the maturation classification system of Angelieri et al to categorize midpalatal suture closure. A fractal dimension value was also determined for each midpalatal suture with Image J computer software. The results showed a strong negative correlation between the fractal dimension and the suture maturation stage. Additionally, the fractal dimension was a statistically significant predictor of suture fusion. The authors explained that the classification system of Angelieri et al can be a subjective tool because much training is required for proficiency. Fractal analysis is a more objective and highly reliable method of determining suture fusion. There are currently some problems with the technique used in this study. The patient's bone density is not taken into account; this hinders the accuracy of the results. The fractal dimension calculation
Am J Orthod Dentofacial Orthop 2017;151:239-41 0889-5406/$36.00 Ó 2017 by the American Association of Orthodontists. All rights reserved. http://dx.doi.org/10.1016/j.ajodo.2016.12.006
€ thgren H, Kowalczyk Bazargani F, Magnuson A, Lo A. Orthodontic bonding with and without primer: a randomized controlled trial. Eur J Orthod 2016;38:503-7.
O
rthodontists everywhere continue to look for ways to decrease treatment time, increase efficiency, and lower overhead costs. Ensuring adequate bonding of brackets reduces bond failures and thus may decrease the number and length of appointments during treatment. The purposes of this study were to evaluate the incidence of failures of brackets bonded with primer (Transbond MIP) and without primer and to assess whether there is a difference in the numbers of emergency visits. Fifty consecutive patients needing conventional bimaxillary fixed appliances were recruited and enrolled in the study. A cross-mouth design was used in each patient. Two diagonal quadrants (maxillary right and mandibular left, or vice versa) were randomly assigned to the primer group (control) and the contralateral diagonal quadrants to the nonprimer group (experimental). The total failure rates were 5.5% in the nonprimer group and 3.1% in the primer group; this was not statistically significant. The failure rate differences between the groups showed a significant interaction with age. In younger patients (ages, 10-13 years), the failure rate of brackets bonded without primer (12.1%) was significantly higher than that of brackets bonded with primer (4.1%). Among older patients (14-18 years), the difference in failure rates between the nonprimer (2.3%) and the primer (2.6%) groups was not significant. The authors also found that boys are more likely to break brackets than are girls, and that mandibular bond failures are more frequent than maxillary failures. The authors concluded that the failure rates of bonding brackets with or without Transbond MIP primer did not differ significantly in a clinical setting (5.5% vs 3.1%); however, younger patients (10-13 years) may benefit from the use of a primer. Reviewed by Jeffrey Birg 239
Residents' journal review
240
Effects of intraoral aging of archwires on frictional forces Kumar A, Khanam A, Ghafoor H. Effects of intraoral aging of arch-wires on frictional forces: an ex vivo study. J Orthod Sci 2016;5:109-16.
S
tainless steel archwires are the most commonly used wires during fixed orthodontic treatment. Because of their low coefficient of friction, these archwires are an optimal choice for sliding mechanics. However, intraorally, they are subject to surface deposits and biofilms that can increase their friction and potentially decrease the efficiency of tooth movement. These investigators sought to evaluate the surface changes and frictional resistance of stainless steel archwires after intraoral exposure. Ten patients with premolar extractions and good oral hygiene were selected for the study. The maxillary and mandibular 0.019 3 0.025 stainless steel archwires were removed and analyzed after 6 weeks of intraoral exposure during the final stages of alignment and leveling. The maxillary and mandibular archwires were compared with as-received controls. The archwire between the second premolar bracket and the first molar tube was analyzed for (1) surface debris using a scanning electron microscope, (2) average surface roughness using an atomic force microscope, and (3) frictional resistance using an Instron universal testing machine. The investigators found statistically significant increases in the amounts of surface debris, surface roughness, and frictional force of the test archwires compared with the controls. The frictional force increased 39.7% after intraoral exposure. Statistical analysis showed a significant association between friction and the amount of surface debris. A positive correlation was also found for friction and surface roughness. For optimal results when using sliding mechanics, the authors suggested using a new stainless steel archwire for space closure to reduce frictional resistance. Reviewed by Macie Mills
Three-dimensional mapping of cortical bone thickness Sadek MM, Sabet NE, Hassan IT. Three-dimensional mapping of cortical bone thickness in subjects with different vertical facial dimensions. Prog Orthod 2016;17:32.
M
ini-implants are commonly used as a reliable source of anchorage in orthodontics. Cortical
February 2017 Vol 151 Issue 2
bone thickness (CBT) is the key determinant in initial stability of mini-implants. The purpose of this study was to determine whether there are differences in CBT in the tooth-bearing regions of the jaws (anterior and posterior) among subjects with different vertical facial dimensions using cone-beam computed tomography. Cone-beam computed tomography scans of 114 subjects, aged 18 to 35 years, were analyzed. After the exclusion criteria were applied, 45 subjects were divided according to facial type: 17 with an average vertical facial dimension, 13 with a high vertical facial dimension, and 15 with a low vertical facial dimension. Using iCATVision software, 2-dimensional slices, each 0.3 mm thick, were oriented so that each interradicular space was bisected parallel to the long axes of the roots. For each interradicular space, CBT was measured at 4 and 7 mm apical to the alveolar crest. Maxillary measurements were both palatal and buccal, whereas mandibular measurements were buccal only. Statistically significant differences of CBT were found in the maxilla (buccal) mesial and distal to the first molar, and (palatal) mesial and distal to the lateral incisor. Statistically significant differences were also found mesial and distal to the mandibular first molar and between the premolars. In both arches, the low-angle group had the thickest cortical plate whereas the high-angle group had the thinnest. The authors indicated that further research should be conducted, differentiating for sex and including measurements of bone density and CBT. The authors concluded that the CBT was thinner in highangle patients in the regions where mini-implants are most likely be placed. Reviewed by Nathan Ng
Dynamic smile evaluation in different skeletal patterns Siddiqui N, Tandon P, Singh A, Haryani J. Dynamic smile evaluation in different skeletal patterns. Angle Orthod 2016;86:1019-25.
I
mproving smile esthetics is a major motivator for seeking orthodontic treatment; therefore, dynamic evaluation of smile characteristics should be considered when planning treatment. The purposes of this study were to investigate whether smile characteristics differ in different skeletal patterns and to identify contributing factors that control the vertical smile parameters. The study was conducted with 150 participants aged 16 to 25 years with well-aligned teeth and no previous orthodontic treatment. Lateral cephalograms were used to
American Journal of Orthodontics and Dentofacial Orthopedics
Residents' journal review
distribute participants into horizontal, average, and vertical skeletal patterns using 3 cephalometric parameters. Video graphic records of smiles were obtained, and measurements were recorded and analyzed at rest and at smile. The results demonstrated that different skeletal patterns exhibit different smile characteristics. When compared with the horizontal pattern, the vertical pattern showed increased incisal display and interlabial gap, and a decreased transverse smile dimension. Flat smile arcs were also more frequently observed in the horizontal pattern, whereas a smile arc consonant with the lower lip was more common in the vertical pattern. The vertical pattern exhibited significantly higher upper lip elevation during smiling. In this sample, the vertical pattern also had a longer upper lip length. The authors also identified contributing factors for the differing smile patterns. Their findings indicate that increased incisor display during smile was not associated with short upper lip length at rest. Furthermore, increased incisal display was more closely associated with upper lip elevation than vertical skeletal and dental factors. Together, these findings provide insight into treatment planning for patients with vertical patterns and excessive gingival display and indicate an increased need to protect or develop the smile arc in brachyfacial patients. Reviewed by Ryan Booth
Gene therapy and stem cell application on root resorption Amuk NG, Kurt G, Baran Y, Seyrantepe V, Yandim MK, Adan A, et al. Effects of cell-mediated osteoprotegerin gene transfer and mesenchymal stem cell applications on orthodontically induced root resorption of rat teeth. Eur J Orthod 2016 Oct 12 [Epub ahead of print].
R
oot resorption, though rarely detrimental to treatment, can be a potential consequence of
241
orthodontic tooth movement. The aims of this study were to evaluate and compare the effects of mesenchymal stem cell and osteoprotegerin gene therapy applications on the inhibition and repair of orthodontically induced inflammatory root resorption. Thirty Wistar rats were randomly divided into 4 groups: an untreated control group, a group treated with an orthodontic appliance, a group having mesenchymal stem cell injections, and a group having gene therapy and osteoprotegerin transfected mesenchymal stem cell injections. Approximately 100 g of force was applied with a coil spring to the maxillary first molar for 14 days. In the experimental groups, mesenchymal stem cells and transfected mesenchymal stem cells were injected into the periodontal ligament on days 1, 6, and 11 of the experiment. At the end of experimental day 14, periodontal ligament tissue from the maxillary first molar was prepared for fluorescent microscope examination, scanning electron microscopy, and histologic analysis. Expression levels were calculated for osteoprotegerin, RANKL, COX-2, osteoclastic cells, resorption area ratio, and resorption lacunae at the periodontal ligament. The authors found that the mesenchymal stem cell and gene therapy treated groups had significantly fewer osteoclastic cells, lower resorption area ratios, and fewer RANKL, COX-2, and resorption lacunae. They concluded that gene therapy and mesenchymal stem cells transferred to the periodontal ligament under orthodontic force exhibit therapeutic effects by reducing root resorption or evoking reparative effects. The authors’ use of mesenchymal stem cells as the transport method of osteogprotegerin is the first published study of its kind, leaving a path for future investigations on cellular and genetic approaches in the treatment of inflammatory root resorption. If these advanced approaches are improved for clinical practice in the future, they may provide great benefits in treating patients with a high root resorption risk. Reviewed by Samer Faranesh
American Journal of Orthodontics and Dentofacial Orthopedics
February 2017 Vol 151 Issue 2