Background
Protraction facemask has been advocated for treatment of class III malocclusion with maxillary deficiency. Studies using tooth-borne rapid palatal expansion (RPE) appliance as anchorage ...have experienced side effects such as forward movement of the maxillary molars, excessive proclination of the maxillary incisors, and an increase in lower face height. A new Hybrid Hyrax bone-anchored RPE appliance claimed to minimize the side effects of maxillary expansion and protraction. A retrospective study was conducted to compare the skeletal and dentoalveolar changes in patients treated with these two protocols.
Methods
Twenty class III patients (8 males, 12 females, mean age 9.8 ± 1.6 years) who were treated consecutively with the tooth-borne maxillary RPE and protraction device were compared with 20 class III patients (8 males, 12 females, mean age 9.6 ± 1.2 years) who were treated consecutively with the bone-anchored maxillary RPE and protraction appliances. Lateral cephalograms were taken at the start of treatment and at the end of maxillary protraction. A control group of class III patients with no treatment was included to subtract changes due to growth to obtain the true appliance effect. A custom cephalometric analysis based on measurements described by Bjork and Pancherz, McNamara, Tweed, and Steiner analyses was used to determine skeletal and dental changes. Data were analyzed using a one-way analysis of variance.
Results
Significant differences between the two groups were found in 8 out of 29 cephalometric variables (
p
< .05). Subjects in the tooth-borne facemask group had more proclination of maxillary incisors (OLp-Is, Is-SNL), increase in overjet correction, and correction in molar relationship. Subjects in the bone-anchored facemask group had less downward movement of the “A” point, less opening of the mandibular plane (SNL-ML and FH-ML), and more vertical eruption of the maxillary incisors.
Conclusions
The Hybrid Hyrax bone-anchored RPE appliance minimized the side effect encounter by tooth-borne RPE appliance for maxillary expansion and protraction and may serve as an alternative treatment appliance for correcting class III patients with a hyperdivergent growth pattern.
The objectives of this study were (1) to compare the in vivo survival rates of orthodontic brackets bonded with a resin-modified glass ionomer adhesive (Fuji Ortho LC; GC America, Alsip, Ill) after ...conditioning with 10% polyacrylic acid and a conventional resin adhesive (Light Bond; Reliance Orthodontic Products, Itasca, Ill) bonded with 37% phosphoric acid, (2) to compare the in vitro bond shear/peel bond strength between the 2 adhesives, (3) to determine the mode of bracket failure in the in vivo and in vitro tests according to the adhesive remnant index (ARI), and (4) to compare the changes in surface morphology of enamel surface after etching or conditioning with 10% polyacrylic acid, with scanning electron microscopy. In the in vitro study, 50 extracted premolars were randomly divided into 4 groups: brackets bonded with Fuji Ortho LC or Light Bond adhesive that were debonded after either 30 minutes or 24 hours. Bond strengths were determined with a testing machine at a crosshead speed of 1 mm/min. Data were analyzed with analysis of variance and a paired Student
t test. The in vivo study consisted of 398 teeth that were randomly bonded with Fuji Ortho LC or Light Bond adhesive in 22 subjects with the split-mouth technique. Bracket survival rates and distribution were followed for 1.3 years. Data were analyzed with Kaplan-Meier product-limit estimates of survivorship function. The in vitro study results showed significant differences (
P < .05) among the adhesives and the debond times. Light Bond had significantly greater bond strengths than Fuji Ortho LC at 24 hours (18.46 ± 2.95 MPa vs 9.56 ± 1.85 MPa) and 30 minutes (16.19 ± 2.04 MPa vs 6.93 ± 1.93 MPa). Mean ARI scores showed that Fuji Ortho LC had significantly greater incidences of enamel/adhesive failure than Light Bond adhesive (4.9 vs 4.1). For the in vivo study, no significant differences in failure rate, sex, or location in dental arch or ARI ratings were found between the 2 adhesives. These results suggest that, compared with conventional resin, brackets bonded with resin-modified glass ionomer adhesive had significantly less shear bond strength in vitro. However, similar survival rates of the 2 materials studied after 1.3 years indicate that resin-reinforced glass ionomers can provide adequate bond strengths clinically. The weaker chemical bonding between the adhesive and the enamel might make it easier for clinicians to clean up adhesives on the enamel surface after debonding.
Introduction A self-etching primer (SEP) saves valuable time by eliminating the many steps required to etch, rinse, and place a sealant before application of the adhesive and placement of the ...bracket. The purpose of this study was to compare the effects of a conventional etch and sealant (CES) and a SEP on enamel decalcification in vivo. Methods Twenty-five patients who required comprehensive orthodontic treatment were included in this study. Before bonding, enamel surfaces were treated with either a CES (Light Bond, Reliance Orthodontic Products, Itasca, Ill) or a SEP (Transbond Plus, 3M Unitek, Monrovia, Calif) by using a split-arch technique. At the end of the observation period (18-24 months), the O'Leary plaque index was used to determine patients' oral-hygiene compliance, and enamel decalcification around the orthodontic bracket was scored based on the amount and severity of decalcification. Scanning electron microscopy images and x-ray spectrum analysis were performed to examine the etched pattern of the 2 bonding systems. Data were analyzed by using analysis of variance (ANOVA) and the Tukey-Kramer test; the confidence level was set at a significant level of P = 0.05. Results Significantly higher decalcification scores were found in the SEP group (27.5%) compared with the CES group (13.9%, P <0.001). No significant differences were found in the decalcification scores for teeth in the maxillary and mandibular arches. Significant differences were found between level of hygiene and decalcification ( P <0.0001). Patients with fair or poor hygiene compliance had higher decalcification scores in the SEP group than in the CES group. Conclusions Using a SEP might save chair time and improve cost-effectiveness, but it provides less resistance to enamel decalcification than a CES, especially in patients with poor oral hygiene.
Background: The objective of this study was to select a model of cephalometric variables to predict future Class III growth patterns based on the results of early orthopedic treatment with a ...protraction facemask.
Material Sixty-four patients with Class III malocclusion were treated with a protraction facemask. Cephalometric radiographs were taken before treatment and a minimum of 3 years after treatment. The sample was divided into 2 groups: successful and unsuccessful according to overjet and molar relationships. Eleven linear and 5 angular measurements were made on the pretreatment radiograph. A logistic regression model was used to identify the dentoskeletal variables most responsible for the prediction of successful and unsuccessful outcomes in subjects receiving treatment.
Results Stepwise variable selection generated 4 variables significant in predicting successful treatment outcomes: position of the condyle with reference to the cranial base (Co-GD,
P = .02), ramal length (Co-Goi,
P = .03), mandibular length (Co-Pg,
P = .01), and gonial angle (Ar-Goi-Me,
P < .0001). The gonial angle was found to be significantly larger in the unsuccessful group. Controlling for other variables, the probability of successful treatment is an increasing function of Co-GD and Co-Goi, and a decreasing function of Co-Pg and Ar-Goi-Me. A logistic equation was established that is accurate in predicting successfully treated Class III patients 95.5% of the time and unsuccessful ones 70% of the time.
Conclusions These results suggest that Class III growing patients with forward position of the mandible, small ramal length, large mandibular length, and obtuse gonial angle are highly associated with unsatisfactory treatment outcomes after pubertal growth.
To test the hypothesis that there is no difference between the bracket survival rate of brackets bonded to bleached and unbleached teeth.
Thirty-eight patients who required comprehensive orthodontic ...treatment were included in the study. A split mouth technique was used with one arch exposed to in-office whitening gel containing 38% hydrogen peroxide for 30 minutes, while the unbleached arch served as the control. Patients were divided into two groups: Brackets bonded within 24 hours after bleaching and brackets bonded 2-3 weeks after bleaching. The bracket survival rate was computed using the log-rank test (Kaplan-Meier Analysis).
A significantly higher rate of bracket failure was found with bleached teeth (16.6%) compared with unbleached teeth (1.8%) after 180 days. Brackets bonded within 24 hours of bleaching resulted in significantly higher clinical failure (14.5%) compared with those bonded after 3 weeks (2.1%). Adhesive Remnant Index scores of failed brackets revealed that the majority of failure in bleached teeth occurred in the enamel/resin interface.
The hypothesis was rejected. Brackets bonded within 24 hours after bleaching have a significantly higher risk for bond failure. Orthodontic bonding should be delayed for 2-3 weeks if patients have a history of in-office bleaching with 38% hydrogen peroxide.
Stability of early Class III orthopedic treatment Reed, Erica, DDS, MS; Kiebach, Thomas J., DDS; Martin, Chris, DDS, MS ...
Seminars in orthodontics,
06/2014, Letnik:
20, Številka:
2
Journal Article
Recenzirano
The objective of the article is to determine the stability of early Class III orthopedic treatment in the primary and early mixed dentitions. A total of 23 patients with Class III malocclusion in the ...primary or early mixed dentition (mean age = 6.2 ±1.5 years, CVM = 1) were treated consecutively by one of the investigators (T.K.) using maxillary expansion and protraction appliances. The average treatment time was 9.1 ± 2.3 months. For each patient, a lateral cephalogram was taken at pre-treatment (T1), post-treatment (T2), and 2 years post-treatment (T3). Each patient served as his/her own control. Cephalometric analysis described by Bjork (1947) and Pancherz (1982) was used. Sagittal and vertical measurements were made along the occlusal plane (OLs) and the occlusal plane perpendicular (Olp), and superimposed on the mid-sagittal cranial structure. Data were analyzed using paired t -test. All patients in the study were treated to Class I or overcorrected to Class II dental arch relationships. Overjet and sagittal molar relationships improved by an average of 4.1 and 1.8 mm, respectively (T2–T1). This was a result of 2.6 mm of forward maxillary growth, .7 mm of forward mandibular growth, 1.2 mm of labial movement of maxillary incisors, 1.0 mm of lingual movement of mandibular incisors, and .1 mm of greater mesial movement of mandibular than maxillary molars. The mean overbite reduction was .9 mm. The maxillary and the mandibular molars were erupted occlusally by 1.5 and 1.0 mm, respectively. The mandibular plane angle was increased by .9° and the lower facial height by 3.2 mm. Overall, 2 years follow-up observation (T3–T2) revealed a decrease in the overjet and the molar relationship by .3 and .2 mm, respectively. This was contributed by 2.2 mm of excess forward mandibular growth that was compensated by 1.9-mm dentoalveolar compensation. Overall, the changes in the overjet and the molar relationship were 3.8 and 1.5 mm, respectively. The overbite reduction was .6 mm. Significant overjet and overbite corrections can be obtained with maxillary protraction in the primary or early mixed dentition. Overjet and molar relationship corrections were stable 2 years post-treatment. A combination of dentoalveolar compensation and skeletal changes accounted for this stability.
To evaluate the length and orientation of masseter in different types of malocclusions using Cone Beam Computed Tomography (CBCT).
Samples of 180 patients seeking orthodontic treatment at the ...University of Nevada, Las Vegas School of Dentistry, were included in the study. Pre-treatment multi-slice CBCT scans of these patients were divided into three anteroposterior groups: Class I subjects with ANB angle 0° to 5°; Class II subjects with ANB angle >5°; and Class III subjects with ANB angle <0°. CBCT scans were also divided into three vertical groups: normodivergent subjects with mandibular plane angle 22° to 30°; hyperdivergent subjects with mandibular plane angle >30°, hypodivergent subjects with mandibular plane angle <22°. The masseter was identified and landmarks were placed on the anterior border, at the origin and insertion of the muscle in 3-D mode of the Dolphin Imaging 10.5 Premium software. The Frankfort Horizontal Plane was used as a reference plane and an angular measurement was obtained by intersection of a line produced by the masseter landmarks to calculate the orientation of the muscles. The length of the masseter was measured and data were analyzed using ANOVA and matched pairs test.
ANOVA found significant differences in muscle length among the three vertical groups for both the left and right muscles. Paired t test showed significantly shorter muscle length for the hypodivergent group (43.3 ± 4.0 mm) compared to the normodivergent group (45.6 ± 4.5 mm, P < 0.05) and shorter muscle length for the hyperdivergent group (42.3 ± 4.7 mm) compared to the hypodivergent group, P < 0.05. No significant differences were found in muscle length among the three anteroposterior groups. However, significant differences in muscle orientation angle were found among the three anteroposterior groups (P < 0.05). Class II subjects were found to have the most acute orientation angle (67.2 ± 6.6°) and Class III had the most obtuse orientation angle (81.6 ± 6.8°).
These results suggest that certain types of malocclusion may have different masseter lengths and orientations and these differences may have implications for the mechanical advantage in bite force. For example, Class III individuals may have greater bite force than Class II individuals because the muscle fibers are oriented more along the arch of closure.
Fisher's exact test from a Bayes perspective Gunel, Erdogan; Ryan, Kenneth Joseph
Communications in statistics. Simulation and computation,
10/21/2017, Letnik:
46, Številka:
9
Journal Article
Recenzirano
Fisher's exact test is commonly used to test the null hypothesis H
0
of independence or homogeneity in 2 × 2 contingency tables. This article presents a closed formula for the Bayes factor for ...testing independence or homogeneity in 2 × 2 contingency tables under a flexible family of spike-and-slab testing priors. Bayes factors are also compared numerically to Fisher's exact
s for 2 × 2 contingency tables with equal row totals. Numerical results show that a large percentage of tables with
have more evidence in favor of H
0
than H
1
from the Bayesian perspective.
Introduction The objectives of this research were to assess skeletal and dental changes in patients with Class II malocclusion treated with the edgewise crowned Herbst appliance in the early mixed ...dentition and to measure the stability of treatment after a second phase of fixed appliance therapy. Methods Twenty-two patients (ages, 8.4 ± 1.0 years) with Class II Division 1 malocclusion treated consecutively with the edgewise crowned Herbst appliance in the early mixed dentition were studied. Lateral cephalograms were taken before Herbst treatment, immediately after Herbst treatment, and after a second phase of fixed appliance therapy. The results were compared with a control group of untreated Class II subjects selected from the Bolton-Brush study, matched by age, sex, and craniofacial morphology. A total of 37 sagittal, vertical, and angular cephalometric variables were evaluated. Changes in overjet and molar relationship were calculated. Changes due to growth were subtracted to obtain the net changes due to treatment. The data were analyzed by using analysis of variance (ANOVA) and the t tests. Results Overcorrection with the Herbst appliance resulted in an average reduction in overjet of 7.0 mm and a change in molar relationship of 6.6 mm. Several factors contributed to the change in overjet: restraint of the forward movement of the maxilla (0.4 mm), forward movement of the mandible (2.0 mm), backward movement of the maxillary incisors (3.7 mm), and forward movement of the mandibular incisors (0.9 mm). Skeletal changes together with a 3.1-mm backward movement of the maxillary molars and a 1.1-mm forward movement of the mandibular molars contributed to the changes in molar relationship. After the second phase of fixed appliance therapy, the change in overjet was reduced to 2.8 mm. Most of the remaining overjet corrections were contributed by the restraint of maxillary growth (2.8 mm). The mandible moved posteriorly by 1.6 mm, and the mandibular incisors moved forward by 0.2 mm. Change in molar relationship was reduced to 2.2 mm. The maxillary molars moved backward by 0.2 mm, and the mandibular molars moved forward by 0.8 mm. Conclusions Overcorrection of Class II malocclusion with the edgewise crowned Herbst appliance in the early mixed dentition resulted in a significant reduction in overjet and correction of the molar relationship. A portion of the correction was maintained after a second phase of fixed appliance therapy because of the continuous restraint of maxillary growth and the dentoalveolar adaptations.
Class III camouflage treatment: What are the limits? Burns, Nikia R; Musich, David R; Martin, Chris ...
American journal of orthodontics and dentofacial orthopedics,
2010, 2010-Jan, 2010-1-00, 20100101, Letnik:
137, Številka:
1
Journal Article
Recenzirano
Introduction The purpose of this study was to determine the skeletal, dental, and soft-tissue changes in response to camouflage Class III treatment. Methods Thirty patients (average age, 12.4 ± 1.0 ...years) with skeletal Class III malocclusions who completed comprehensive nonextraction orthodontic treatment were studied. Skeletal, dental, and soft-tissue changes were determined by using published cephalometric analyses. The quality of orthodontic treatment was standardized by registering the peer assessment rating index on the pretreatment and posttreatment study models. The change in the level of gingival attachment with treatment was determined on the study casts. The results were compared with a group of untreated subjects. Data were analyzed with repeated measures analysis and paired t tests. Results The average change in the Wits appraisal was greater in the treated group (1.2 ± 0.1 mm) than in the control group (–0.5 ± 0.3 mm). The average peer assessment rating index score improved from 33.5 to 4.1. No significant differences were found for the level of gingival attachments between the treatment and control groups. The sagittal jaw relationship (ANB angle) did not improve with camouflage treatment. A wide range of tooth movements compensated for the skeletal changes in both groups. The upper and lower limits for incisal movement to compensate for Class III skeletal changes were 120° to the sella-nasion line and 80° to the mandibular plane, respectively. Greater increases in the angle of convexity were found in the treated group, indicating improved facial profiles. Greater increases in length of the upper lip were found in the treated group, corresponding to the changes in the hard tissues with treatment. Conclusions Significant dental and soft-tissue changes can be expected in young Class III patients treated with camouflage orthodontic tooth movement. A wide range of skeletal dysplasias can be camouflaged with tooth movement without deleterious effects to the periodontium. However, proper diagnosis and realistic treatment objectives are necessary to prevent undesirable sequelae.
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