Chun-Hsi Chung

Effect of saliva on shear bond strength of an orthodontic adhesive used with moisture-insensitive and self-etching primers

The purpose of this study was to investigate the effect of saliva contamination on the shear bond strength of an orthodontic adhesive used with Transbond Moisture-Insensitive Primer (MIP, 3M Unitek, Monrovia, Calif) and Transbond Plus Self-Etching Primer (SEP, 3M Unitek). Hydrophobic Transbond XT primer (XT, 3M Unitek) was used as a control. A total of 162 extracted premolars were collected and divided equally into 9 groups of 18 teeth each, and brackets were bonded with Transbond XT adhesive (3M Unitek) under different experimental conditions: (1) control: etch/dry/XT, (2) etch/dry/MIP, (3) etch/dry/MIP/wet (saliva)/MIP, (4) etch/wet/MIP, (5) etch/wet/MIP/wet/MIP, (6) dry/SEP, (7) dry/SEP/wet/SEP, (8) wet/SEP, and (9) wet/SEP/wet/SEP. Shear bond strength of each sample was examined with a testing machine. The results showed that the control group had the highest mean shear bond strength (group 1, 21.3 +/- 6.8 MPa), followed by the MIP group in a dry field (group 2, 20.7 +/- 5.0 MPa). No significant difference was found between groups 1 and 2. Groups 3 through 9 had similar mean strengths, ranging from 12.7 to 15.0 MPa (P >.05), which were significantly lower than in groups 1 and 2 (P <.05). There was no significant difference in bond-failure site among the 9 groups. It was concluded that (1) Transbond XT adhesive with Transbond XT primer and MIP in a dry field yields similar bond strengths, which are greater than all other groups, (2) saliva contamination significantly lowers the bond strength of Transbond MIP, (3) saliva has no effect on the bond strength of Transbond SEP, (4) Transbond XT adhesive with Transbond MIP and SEP might have clinically acceptable bond strengths in either dry or wet fields.

Effects of bonded rapid palatal expansion on the transverse dimensions of the maxilla: A cone-beam computed tomography study

INTRODUCTION The purpose of this study was to examine the maxillary response on the transverse dimensions to rapid palatal expansion (RPE) by using cone-beam computed tomography (CBCT). METHODS Twenty-four children (average age, 9.9 years) who had RPE treatment with a bonded expander were included. Pretreatment orthodontic records (T1) and immediately after expansion (T2) CBCT images were taken for all patients. For each patient, the width of the nasal cavity at the level of the maxillary first permanent molar and second deciduous molar (or second permanent premolar), the width of the maxillary basal bone, and the width of the midpalatal suture at the level of the second deciduous molar (or the second permanent premolar), the first deciduous molar (or first permanent premolar), and the deciduous canine (or permanent canine) at T1 and T2 were measured. In addition, the amount of tipping for both the maxillary right and left first permanent molars was measured. RESULTS From T1 to T2, mean increases in nasal width, related to the mean jackscrew opening (8.19 mm), occurred at the levels of the first permanent molars of 33.23% (2.73 mm, P <0.05) and the second deciduous molars of 37.32% (3.06 mm, P <0.05). Significant increases in basal bone of the maxilla were found at all levels (P <0.05), with mean increases of 40.65% (3.33 mm), 44.08% (3.49 mm), 46.73% (3.83 mm), and 46.83% (3.62 mm) of the mean jackscrew opening at the levels of the first permanent molars, and the second deciduous molars, first deciduous molars, and deciduous canines, respectively. Significant openings in the midpalatal sutures was found at all levels (P <0.05), with mean increases of 52.82% (4.33 mm), 53.23% (4.36 mm), 54.35% (4.46 mm), and 52.77% (4.33 mm) of the jackscrew opening at the levels of the first permanent molars, and the second deciduous molars, first deciduous molars, and deciduous canines, respectively. The right first molar tipped buccally an average of 6.2 degrees (P <0.05), and the left first molar tipped buccally 5.6 degrees (P <0.05). CONCLUSIONS After RPE, significant increases in the transverse dimensions of the nasal cavity, the maxillary basal bone, and the midpalatal suture opening occurred, with the greatest increase in the midpalatal suture followed by basal bone and nasal cavity. The midpalatal suture opened in a parallel fashion. Moreover, significant buccal tipping occurred on both maxillary first molars.

Comparison of the accuracy of bracket placement between direct and indirect bonding techniques.

An in vitro study was conducted to evaluate the accuracy of bracket placement for direct and indirect bonding techniques. Nineteen sets of duplicated Class II malocclusion models were divided into three groups: (1) one set for ideal bracket placement, (2) nine sets for direct bonding on mannequins, and (3) nine sets for indirect bonding. Both direct and indirect bonding were performed on all teeth except molars by nine faculty members from the Department of Orthodontics, University of Pennsylvania. The position of each bonded bracket from these two bonding groups was compared with that of the same tooth from the ideal group and to each other in terms of bracket height, mesiodistal position, and angulation. Our results indicated that both direct and indirect bonding techniques failed to execute ideal bracket placement. On individual teeth, there was no statistically significant difference in the accuracy of bracket placement between these two bonding techniques except for upper right second premolar and lower left central incisor, where indirect bonding yielded better results in bracket height (P < .05), and for lower left central incisor where indirect bonding was better in mesiodistal position (P < .05), and for upper right lateral incisor where direct bonding was closer to the ideal in angulation (P < .05). Overall, indirect bonding showed better bracket placement in bracket height (P < .05), whereas, no statistically significant difference was found between them regarding the angulation and mesiodistal position.

Shear bond strength of a resin-reinforced glass ionomer cement: An in vitro comparative study

Shear bond strength of Concise (a composite resin adhesive) and Fuji Ortho LC (a light-cured resin-reinforced glass ionomer cement) bonded to extracted teeth was tested under different bonding conditions: (1) Concise/etched/dry (2) Fuji/etched/dry (3) Fuji/etched/wet (4) Fuji/unetched/dry (5) Fuji/unetched/wet. Concise/etched/dry and Fuji/etched/dry groups showed comparable mean shear bond strength (10.5 and 8.2 MPa, respectively); the other three groups had considerably lower values. The difference between Fuji/etched/dry and Fuji/etched/wet was not statistically significant. The site of bond failure was between bracket and adhesive in all etched groups and between adhesive and enamel in the unetched groups. We conclude that (1) enamel surface etching is required for Fuji Ortho LC to achieve optimum bond strength, (2) moisture does not affect bond strength of Fuji Ortho LC significantly.

Shear bond strengths of two resin-modified glass ionomer cements to porcelain

Shear bond strength of a composite resin adhesive (Concise) and two resin-modified glass ionomer cements (Fuji Ortho LC and Geristore) bonded to porcelain surface was tested. Orthodontic brackets were bonded to 120 porcelain disks (Finesse) etched with 9% HF. Samples were divided into six groups: (1) Concise, (2) Concise/silane, (3) Geristore, (4) Geristore/silane, (5) Fuji, (6) Fuji/silane. No statistical difference in mean shear bond strength was found between silanated Concise (15.8 MPa), Geristore (19.4 MPa), and Fuji (18.5 MPa) groups, which were significantly higher than nonsilanated groups. Porcelain fracture was observed in all silanated groups and nonsilanated Geristore group. We conclude that (1) silane increases bond strength to porcelain significantly for composite resin and resin-modified glass ionomer cement, (2) Concise, Geristore, and Fuji Ortho LC provide comparable shear bond strength to porcelain.

Effects of rapid palatal expansion on the sagittal and vertical dimensions of the maxilla: A study on cephalograms derived from cone-beam computed tomography

INTRODUCTION The purpose of this study was to use cone-beam computed tomography imaging to examine the skeletal and dental changes in the sagittal and vertical dimensions after rapid palatal expansion. METHODS Twenty-eight healthy children (mean age, 9.9 years; range, 7.8-12.8 years; 17 boys, 11 girls) who required rapid palatal expansion treatment were included. For each patient, a bonded Haas-type expander with full occlusal and palatal acrylic coverage was cemented in place. Cone-beam computed tomography images were obtained as part of the pretreatment orthodontic records and at the completion of rapid palatal expansion for all patients. The mean interval between pretreatment and completion of rapid palatal expansion was 52 days (range, 19-96 days). The average skeletal age of the patients, determined from hand-wrist films also obtained before treatment, was 10.1 years. The mean expansion of the expander was 8.0 mm (range, 5.9-9.6 mm). Each cone-beam computed tomography image was compressed from the outer portion of the right side of the patients head to the center of the left central incisor into a 2-dimensional synthesized cephalogram, which was then traced and measured. RESULTS The results showed that from pretreatment to completion of rapid palatal expansion, SNA, FH-NA, and A-Nperp increased by means of 1.04°, 0.92°, and 0.87 mm, respectively (P <0.05). In addition, 1/-NA, 1/-SN, 1/-NA, 1/-Nperp, and 1/-PP showed mean decreases of 3.74°, 2.53°, 1.17 mm, 0.49 mm, and 2.69°, respectively (P <0.05). Both ANS and PNS moved significantly downward (ANS, 2.05 mm; PNS, 1.16 mm). CONCLUSIONS There was forward movement of the maxilla as a result of rapid palatal expansion treatment. Bonded rapid palatal expansion treatment resulted in downward displacement of the maxilla with a greater displacement of ANS than PNS and posterior movement of the maxillary central incisors.

Mandibular basal structure response to lip bumper treatment in the transverse dimension.

The effect of orthopedic or orthodontic treatment on the transverse dimension has been the subject of endless debate among orthodontists. The purpose of this investigation was to examine the response on the transverse dimension of the basal structure of the mandible and maxilla following two different modalities of treatment: group A--standard edgewise orthodontic treatment and group B--maxillary orthopedics with a bonded (tissue borne) rapid palatal expander (RPE) combined with a mandibular lip bumper. Each group had a matched paired untreated control according to age, sex, race, and treatment duration. For all subjects the width of the maxilla (Mx-Mx) and mandible (Ag-Ag) were measured on pre- and posttreatment posteroanterior cephalograms. The rate of width change in the maxilla and mandible was calculated (in mm/y). Results showed that group A had no treatment effect on the transverse dimension of the maxilla and mandible when compared with controls. However, group B had a significant increase in the transverse dimension of Mx-Mx (P < .001) and Ag-Ag (P < .001) when compared with controls. It was concluded that the RPE treatment increased the maxillary skeletal width, and the lip bumper increased the transverse dimension of the basal structure of the mandible.

Comparison of craniofacial growth of untreated Class I and Class II girls from ages 9 to 18 years: a longitudinal study.

INTRODUCTION The purposes of this study were to examine and compare the craniofacial growth in girls with Class I or Class II occlusion from the ages of 9 to 18. METHODS Twenty-five Class I (ANB, 1°-4°) and 21 Class II (ANB, >4°) untreated Caucasian girls were selected from the Burlington Growth Centre in Toronto, Ontario, Canada. Cephalograms of each subject at ages 9, 14, and 18 years were traced, and 29 parameters were measured. The growth changes in each parameter from ages 9 to 14, 14 to 18, and 9 to 18 were calculated, and comparisons of each parameter were made between the 2 groups. RESULTS From ages 9 to 14, the Class I and Class II groups had similar skeletal growth patterns (increases of SNA and SNB angles, decreases of ANB, MP-SN, and gonial angles). Dentally, the Class II group showed less maxillary incisal proclination and more overbite than did the Class I group. From ages 14 to 18, the 2 groups also showed similar growth patterns, with little sagittal but continued vertical growth, and the MP-SN angle continued to decrease. From ages 9 to 18 (combined periods of 9-14 and 14-18), the 2 groups showed similar skeletal growth, with the exception of a slightly higher ANS-ME/N-Me in the Class I group. Dental changes were similar in the 2 groups, except that overbite increased slightly more in the Class II group. CONCLUSIONS Overall, the craniofacial growth patterns of Class I and Class II girls were similar. With growth, the face became more flattened with a decrease of the ANB angle, and the mandible demonstrated forward rotation with decreases of the MP-SN and gonial angles, and an increase of PFH:AFH.