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Guilherme Janson

Publications and source records attributed to Guilherme Janson.

At least 19 recordsLinked to original sources
PubMed2007

Class II subdivision malocclusion types and evaluation of their asymmetries.

INTRODUCTION: The primary objective of this study was to determine, by means of frontal photographic evaluation, the distribution of the 2 main types of Class II subdivision malocclusions. The secondary objective was to compare the dentoskeletal asymmetries in these 2 types with a group of normal-occlusion subjects by using submentovertex and posteroanterior radiographs. METHODS: The experimental group included 44 untreated Class II subdivision malocclusion subjects with a mean age of 15.3 years. The control group included 30 subjects with normal occlusions with a mean age of 22.4 years. All had full complements of permanent teeth up to the first molars and had not received orthodontic treatment. Type 1 Class II subdivision malocclusion is coincidence of the maxillary dental midline with the facial midline and deviation of the mandibular midline. Type 2 has the opposite characteristics. The frontal photographs were evaluated subjectively by 2 examiners. In the submentovertex and posteroanterior radiographs, symmetry was assessed by measuring the relative difference in the spatial positions of dentoskeletal landmarks between the right and left sides. Independent t tests were used to compare the dentoskeletal asymmetries of types 1 and 2 with the normal-occlusion group. RESULTS AND CONCLUSIONS: The results showed that 61.36% had type 1, 18.18% had type 2 Class II subdivision malocclusion, and 20.45% had mixed characteristics. The predominant asymmetric dentoalveolar characteristics of both types of Class II subdivision malocclusions were evident when individually compared with a normal-occlusion control group. There was a tendency for the type 1 subjects to have greater mandibular asymmetry than type 2, as compared with the control group.

Adolescent↗
PubMed2006

Maxillary third molar position in Class II malocclusions: the effect of treatment with and without maxillary premolar extractions.

The present study compared the number of erupted and functioning maxillary third molars and their mesio-distal angulation in patients with Class II malocclusions orthodontically treated with and without extraction of two maxillary premolars and fixed appliances. For that purpose, the records of 55 patients were selected, which were divided into two groups. Group 1 was treated without extractions and comprised 28 patient records (19 males and 9 females), with a mean age of 19.03 years [standard deviation (SD) = 2.33], treatment time of 2.59 years (SD = 1.08), and follow-up time of 6.48 years (SD = 2.42). Group 2 was treated with extractions and comprised 27 patient records (14 males and 13 females), with a mean age of 19.94 years (SD = 2.87), treatment time of 2.95 years (SD = 1.17), and follow-up time of 5.88 years (SD = 2.96). Analysis of the erupted and functioning maxillary third molars was conducted on the maxillary and mandibular dental casts. The mesio-distal angulations of the maxillary third molars were assessed on panoramic radiographs with the presence of both maxillary third molars. The results demonstrated that the number of erupted and functioning maxillary third molars was statistically greater (P = 0.01) in Class II subjects treated with extraction of maxillary premolars, when compared with those treated without extractions. The patients treated with two maxillary premolar extractions presented significantly smaller third molar mesio-distal angulations, that are more favourable to eruption, than those treated non-extraction.

Adolescent↗
PubMed2006

Stability of anterior open-bite extraction and nonextraction treatment in the permanent dentition.

INTRODUCTION: Although stability of anterior open-bite extraction and nonextraction treatment has been investigated, results suggesting that extraction treatment is more stable have not been confronted. Therefore, the purpose of this cephalometric study was to compare the long-term stability of anterior open-bite extraction and nonextraction treatment in the permanent dentition. METHODS: Group 1 consisted of 21 patients treated without extractions, and group 2 included 31 patients treated with extractions who had orthodontic treatment with fixed appliances. Cephalometric headplates were obtained at pretreatment, posttreatment, and postretention. The groups were compared at these 3 times and during the treatment and posttreatment periods with independent t tests. The number of patients with a clinically significant relapse of the open bite was compared between the groups with chi-square tests. RESULTS: During treatment, the maxillary incisors had greater retraction amounts, and the mandibular incisors had greater retraction and lingual tipping, and less extrusion in the extraction group. In the posttreatment period, the extraction group demonstrated statistically greater stability of the overbite. However, there was no statistically significant difference in the percentages of patients with clinically significant relapse of the open bite between the groups. CONCLUSION: Open-bite extraction treatment has greater stability of the overbite than open-bite nonextraction treatment.

Adolescent↗
PubMed2006

Alignment stability in Class II malocclusion treated with 2- and 4-premolar extraction protocols.

INTRODUCTION: The purpose of this study was to compare the postretention stability of the correction of mandibular anterior-tooth irregularity in patients with Class II malocclusions whose orthodontic treatments included extraction of 2 or 4 premolars. METHODS: A total of 66 patients were selected who initially had at least one-half-cusp Class II malocclusions. Nineteen patients (9 male, 10 female) with an initial mean age of 14.04 years were treated with extraction of 2 premolars (group 1); 47 patients (20 male, 27 female) with an initial mean age of 13.03 years were treated with extraction of 4 premolars (group 2). A subgroup of group 2, with a similar amount of initial anterior-tooth irregularity as group 1, was also compared with group 1. Little's irregularity index was used to evaluate anterior tooth irregularity in dental casts obtained from each patient before treatment, after treatment, and 5 years after active treatment. Initial cephalometric variables, initial treatment priority index, pretreatment age, treatment time, and posttreatment time of the groups were compared with t tests. Similarly, Little's irregularity index values at prettreament, posttreatment, and postretention were also compared with the t test. Cephalometric treatment changes within groups were evaluated with dependent t tests. RESULTS: There were no statistically significant differences in posttretention anterior-tooth irregularity between groups 1 and 2 or the subgroup. CONCLUSIONS: Treatment of Class II malocclusion with extraction of either 2 maxillary premolars or 4 premolars provides the same mandibular anterior-tooth alignment stability.

Adolescent↗
PubMed2006

Sagittal, vertical, and transverse changes consequent to maxillary molar distalization with the pendulum appliance.

INTRODUCTION: The purpose of this study was to evaluate the skeletal and dental changes in patients who underwent distalization of their maxillary molars with pendulum appliances. METHODS: The sample consisted of 31 patients (initial mean age, 14.58 years) with Angle Class II molar relationships and all permanent teeth up to the second molars. The maxillary molars were distalized with pendulum appliances for a mean period of 5.87 months. Lateral cephalograms, 45 degrees oblique radiographs, and dental casts were obtained before and after distalization. Changes produced by the pendulum appliance were analyzed with paired t tests. RESULTS: Maxillary first molar distalization accounted for 63.5% of the space opening; mesial movement of the maxillary first premolars contributed 36.5% of the space. The mean space opening on lateral cephalograms was 7.25 mm, and the rate of molar movement was 1.23 mm per month. The mean distalization of the maxillary molars was 4.6 mm, with a mean distal crown tipping of 18.5 degrees The maxillary molars experienced expansion, with a smaller effect on the first molars than on the second molars. The pendulum appliance produced symmetrical expansion, with a rate of 1.04 mm per month on the right and 1.10 mm per month on the left. CONCLUSIONS: The pendulum appliance is effective for distalization of the maxillary molars and the establishment of a Class I molar relationship in a relatively short time. However, caution is needed to control collateral effects, including mesial movement of the first premolars and distal tipping of the molar crowns.

Adolescent↗
PubMed2006

Upper and lower pharyngeal airways in subjects with Class I and Class II malocclusions and different growth patterns.

INTRODUCTION: Associations of Class II malocclusions and vertical growth pattern with obstruction of the upper and lower pharyngeal airways and mouth breathing have been suggested. This implies that these malocclusion characteristics have a predisposing anatomical factor for these problems. Therefore, the purpose of this study was to compare upper and lower pharyngeal widths in patients with untreated Class I and Class II malocclusions and normal and vertical growth patterns. METHODS: The sample comprised 80 subjects divided into 2 groups: 40 Class I and 40 Class II, subdivided according to growth pattern into normal and vertical growers. The upper and lower pharyngeal airways were assessed according to McNamara's airways analysis. The intergroup comparison of the upper and lower airways was performed with 1-way ANOVA and the Tukey test as a second step. RESULTS: The results showed that the upper pharyngeal width in the subjects with Class I and Class II malocclusions and vertical growth patterns was statistically significantly narrower than in the normal growth-pattern groups. CONCLUSIONS: Subjects with Class I and Class II malocclusions and vertical growth patterns have significantly narrower upper pharyngeal airways than those with Class I and Class II malocclusions and normal growth patterns. However, malocclusion type does not influence upper pharyngeal airway width, and malocclusion type and growth pattern do not influence lower pharyngeal airway width.

Airway Obstruction↗
PubMed2006

Correlation between mandibular incisor crown morphologic index and postretention stability.

INTRODUCTION: Considering postretention stability as a result of successful orthodontic treatment, we aimed to verify the influence of mandibular-incisor-crown morphology in the relapse of mandibular anterior crowding. METHODS: The sample comprised 56 white subjects of both sexes with Class I and Class II malocclusions at pretreatment, treated with extraction of 4 first premolars and edgewise mechanics. No patient underwent interproximal stripping during or after treatment. Mean pretreatment age was 13.23 years. Mean treatment time was 2.11 years, and mean posttreatment evaluation time was 5.12 years. Mandibular anterior crowding was measured with the Little irregularity index, and the mesiodistal and buccolingual proportion of the mandibular incisor crowns was measured with the Peck and Peck index. The measurements were obtained from dental casts at the pretreatment, posttreatment, and postretention stages. The Pearson correlation coefficient was calculated to determine the correlation between mandibular-incisor-crown morphology and the amount of postretention-crowding relapse. RESULTS: The mandibular-incisor-crown morphologic index was not significantly correlated with the amount of mandibular-anterior-crowding relapse. CONCLUSIONS: Mandibular-incisor-crown morphology is not correlated with the amount of mandibular-anterior-crowding relapse.

Adolescent↗
PubMed2006

Evaluation of asymmetries between subjects with Class II subdivision and apparent facial asymmetry and those with normal occlusion.

INTRODUCTION: The objective of this study was to compare the degree of skeletal asymmetry between subjects with Class II subdivision malocclusion and apparent facial asymmetry and subjects with normal occlusion. METHODS: The sample consisted of 23 subjects with Angle Class II subdivision malocclusions and apparent facial asymmetry (mean age, 15.78 years) and 30 subjects with normal occlusions (mean age, 22.42 years). Each had all permanent teeth, including first molars. Radiographic asymmetry was assessed by measuring the relative difference in spatial position of dental and skeletal landmarks between right and left sides in both anteroposterior and transverse dimensions in the submentovertex and in the transverse and vertical dimensions in the posteroanterior radiographs. Independent t tests were used to compare radiographic asymmetries between groups. RESULTS: Despite the predominantly dentoalveolar nature of the asymmetries found in Class II subdivision malocclusions with apparent facial asymmetry, the radiographic mandibular asymmetry was small in relation to Class II subdivision malocclusions in general. The components that contributed to the asymmetric anteroposterior relationship in the Class II subdivision malocclusion with apparent facial asymmetry were mainly dentoalveolar. The primary contributor to the differences between the 2 groups was the distal positioning of the mandibular first molars on the Class II side. A secondary contributor was the mesial positioning of the maxillary first molars on the Class II side. As a consequence of the more frequent asymmetry in the lower third of face, the mandibular dental midline and the antegonial angle were deviated on the Class II side, as evaluated on the posteroanterior radiograph. CONCLUSIONS: The main component of Class II subdivision is dentoalveolar, primarily distal positioning of the first mandibular molar on the Class II side and secondarily mesial positioning of the first maxillary molar on the same side.

Adolescent↗
PubMed2006

Orthodontic treatment time in 2- and 4-premolar-extraction protocols.

INTRODUCTION: The purpose of this study was to compare the treatment times of complete Class II malocclusions treated with 2- and 4-premolar-extraction protocols. METHODS: Ninety-seven patients were selected and divided into 2 groups, according to the 2 extraction criteria. Group 1, treated with 2 maxillary premolar extractions, consisted of 49 patients (30 male, 19 female) with a mean age of 14.35 years. Group 2, treated with 4 premolar extractions, consisted of 48 patients (27 male, 21 female) with a mean age of 13.03 years. Treatment times of the groups were compared with the t test. RESULTS: Treatment times were significantly shorter with the 2-premolar-extraction protocol compared with the 4-premolar-extraction protocol. CONCLUSIONS: Treatment time will be shorter and the occlusal results more predictable with a 2-premolar-extraction protocol compared with 4 premolar extractions.

Adolescent↗
PubMed2006

Periodontal effects of rapid maxillary expansion with tooth-tissue-borne and tooth-borne expanders: a computed tomography evaluation.

INTRODUCTION: The force delivered during rapid maxillary expansion (RME) produces areas of compression on the periodontal ligament of the supporting teeth. The resulting alveolar bone resorption can lead to unwanted tooth movement in the same direction. The purpose of this study was to evaluate periodontal changes by means of computed tomography after RME with tooth-tissue-borne and tooth-borne expanders. METHODS: The sample comprised 8 girls, 11 to 14 years old, with Class I or II malocclusions with unilateral or bilateral posterior crossbites Four girls were treated with tooth-tissue-borne Haas-type expanders, and 4 were treated with tooth-borne Hyrax expanders. The appliances were activated up to the full 7-mm capacity of the expansion screw. Spiral CT scans were taken before expansion and after the 3-month retention period when the expander was removed. One-millimeter thick axial sections were exposed parallel to the palatal plane, comprising the dentoalveolar area and the base of the maxilla up to the inferior third of the nasal cavity. Multiplanar reconstruction was used to measure buccal and lingual bone plate thickness and buccal alveolar bone crest level by means of the computerized method. RESULTS AND CONCLUSIONS: RME reduced the buccal bone plate thickness of supporting teeth 0.6 to 0.9 mm and increased the lingual bone plate thickness 0.8 to 1.3 mm. The increase in lingual bone plate thickness of the maxillary posterior teeth was greater in the tooth-borne expansion group than in the tooth-tissue-borne group. RME induced bone dehiscences on the anchorage teeth's buccal aspect (7.1 +/- 4.6 mm at the first premolars and 3.8 +/- 4.4 mm at the mesiobuccal area of the first molars), especially in subjects with thinner buccal bone plates. The tooth-borne expander produced greater reduction of first premolar buccal alveolar bone crest level than did the tooth-tissue-borne expander.

Adolescent↗
PubMed2006

Occlusal and cephalometric Class II Division 1 malocclusion severity in patients treated with and without extraction of 2 maxillary premolars.

INTRODUCTION: The purpose of this study was to compare the initial occlusal and cephalometric severity of Class II Division 1 malocclusion patients treated with and without extraction of 2 maxillary premolars. METHODS: Dental study models and cephalograms of 62 patients were selected. Those in group 1 (n = 42) were treated without extractions, and those in group 2 (n = 20) were treated with 2 maxillary premolar extractions. Grainger's treatment priority index (TPI) was used to assess the final and the initial occlusal status of each subject. Variables such as overjet and overbite were also evaluated. Independent t tests were used to compare the occlusal variables at the posttreatment stage, the occlusal and cephalometric variables at the pretreatment stage, and the improvement in TPI values between the groups. RESULTS: Patients treated with 2 maxillary premolar extractions had greater initial occlusal TPI values, overjets, cephalometric apical base anteroposterior discrepancies, maxillary incisor protrusions, and anteroposterior molar discrepancies than those treated without extractions. CONCLUSIONS: For patients with more severe anteroposterior discrepancies, an extraction plan provides more effective treatment with less need for patient compliance.

Adolescent↗
PubMed2005

Influence of extraction and nonextraction orthodontic treatment in Japanese-Brazilians with class I and class II division 1 malocclusions.

BACKGROUND: The primary objective of this retrospective, longitudinal, cephalometric investigation was to study the influence of extraction and nonextraction orthodontic treatment on the facial height of Japanese-Brazilian children with Class I and Class II Division 1 malocclusions. METHODS: The sample included 59 mesocephalic patients distributed into 4 groups: group 1: Class I patients treated with 4 first premolar extractions; group 2: Class I patients treated nonextraction; group 3: Class II Division 1 patients treated with 4 first premolar extractions; group 4: Class II Division 1 patients treated nonextraction. The overall initial mean age of the groups was 12.14 years, and all groups were treated with standard edgewise appliances for a mean period of 2.49 years. The pretreatment and posttreatment stage comparison and the intergroup comparison of the treatment changes were conducted between extraction and nonextraction groups in the Class I and Class II malocclusion samples with t tests. RESULTS: The amounts of changes in the absolute magnitude of posterior and anterior facial heights and in the ratios of lower posterior facial height/lower anterior facial height and lower anterior facial height/total anterior facial height were similar between extraction and nonextraction treatment in both Class I and Class II malocclusions.

Analysis of Variance↗
PubMed2005

Comparative study of the maturation of permanent teeth in subjects with vertical and horizontal growth patterns.

INTRODUCTION: The purpose of this research was to compare the maturation stage of permanent teeth in subjects with vertical and horizontal growth patterns. METHODS: Lateral cephalograms of 256 subjects were reviewed, and subjects were classified according to facial growth pattern. The 30 subjects with the greatest predominance of vertical growth and the 30 with the greatest predominance of horizontal growth were selected; these subjects comprised the vertical and horizontal groups, respectively. Panoramic radiographs of the subjects obtained at 8 years of age were used to evaluate the maturation of the permanent teeth, expressed by the dental age. Comparisons between groups were made with independent t tests. RESULTS: A statistically significant difference was noted between the dental ages of the vertical and horizontal groups, with the vertical group having a more advanced dental age. CONCLUSION: Subjects with vertical growth patterns should be expected to mature dentally earlier than horizontal growers.

Age Determination by Teeth↗
PubMed2005

Extreme dentoalveolar compensation in the treatment of Class III malocclusion.

The orthodontic treatment of an adult patient with a skeletal Class III malocclusion, increased anterior facial height, negative overjet, and bilateral posterior crossbite is presented. Treatment options included mandibular first premolar or third molar extractions with dentoalveolar compensation or combined surgical-orthodontic treatment. Mandibular third molar extraction with dentoalveolar compensation was the treatment choice. Biofunctional brackets, with accentuated lingual crown torque on the maxillary incisors and accentuated buccal crown torque on the mandibular incisors, were used. The anterior crossbite was corrected with intermaxillary elastics from the palatal aspect of the maxillary incisors to the labial aspect of the mandibular incisors. Class III elastics moved the maxillary teeth mesially and assisted in retruding the mandibular teeth. Patient compliance with the elastics was excellent, and satisfactory dentofacial esthetics were achieved. This treatment protocol has rigorous indications, and it is not a routine plan. The mechanotherapy and the pros and cons of this approach are discussed.

Adaptation, Physiological↗
PubMed2005

Rapid maxillary expansion--tooth tissue-borne versus tooth-borne expanders: a computed tomography evaluation of dentoskeletal effects.

This study evaluated rapid maxillary expansion (RME) dentoskeletal effects by means of computed tomography (CT), comparing tooth tissue-borne and tooth-borne expanders. The sample comprised eight girls aged 11 to 14 years presenting Class I or II malocclusions with posterior unilateral or bilateral crossbite that were randomly divided into two treatment groups, palatal acrylic (Haas-type) and hygienic (Hyrax) expanders. All appliances were activated up to the full seven mm capacity of the expansion screw. The patients were subjected to a spiral CT scan before expansion and after a three-month retention period when the expander was removed. One-millimeter-thick axial sections were scanned parallel to the palatal plane, comprising the dentoalveolar area and the base of the maxilla up to the inferior third of the nasal cavity. Multiplanar reconstruction was used to measure maxillary transverse dimensions and posterior teeth inclination by means of a computerized method. The results showed that RME produced a significant increase in all measured transverse linear dimensions, decreasing in magnitude from dental arch to basal bone. The transverse increase at the level of the nasal floor corresponded to one-third of the amount of screw activation. Tooth-borne (Hyrax) and tooth tissue-borne (Haas-type) expanders tended to produce similar orthopedic effects. In both methods, RME led to buccal movement of the maxillary posterior teeth, by tipping and bodily translation. The second premolars displayed more buccal tipping than the appliance-supporting teeth. The tooth tissue-borne expander produced a greater change in the axial inclination of appliance-supporting teeth, especially first premolars, compared with the tooth-borne expander.

Adolescent↗
PubMed2004

Long-term stability of anterior open bite extraction treatment in the permanent dentition.

The purpose of this study was to cephalometrically evaluate the long-term stability of anterior open bite extraction treatment in the permanent dentition after a mean period of 8.35 years. Cephalometric headfilms were obtained at pretreatment, posttreatment, and postretention stages from 31 patients who had undergone orthodontic treatment with fixed appliances. Two control groups were used. The first, with an age similar to that of the experimental group before treatment, was used only to characterize it. The second, with normal occlusion, was followed longitudinally for a period comparable with the posttreatment period and was used to compare changes during this period. The differences between the observation stages in the experimental group were analyzed with paired t tests, and the posttreatment changes were compared with the changes of the second control group with independent t tests. There was no statistically significant decrease of the obtained anterior overbite at the end of the posttreatment period. The primary factors that contributed to the nonsignificant decrease of the overbite were the normal vertical development of the maxillary and mandibular incisors, the smaller vertical development of the mandibular molars, and the consequent smaller increase in lower anterior face height, as compared with the control group in the long-term posttreatment period. Additionally, 74.2% of the sample had a "clinically stable" open bite correction.

Adolescent↗
PubMed2004

Buccolingual inclinations of posterior teeth in subjects with different facial patterns.

This study compared the buccolingual inclination of the posterior teeth in subjects with a horizontal growth pattern (proportionally short lower anterior face height) with that of subjects with a vertical growth pattern (proportionally long lower anterior face height). Seventy subjects with permanent dentition were divided into 2 groups. Group I comprised 35 subjects (16 male, 19 female) with Class II Division 2 malocclusion with a horizontal growth pattern, and group II comprised 35 subjects (15 male, 20 female) with a vertical growth pattern. Buccolingual inclinations of the first molar and second premolar were indirectly assessed on photocopies of buccolingual sections of these teeth by measuring their occlusal surface (represented by an imaginary line connecting the lingual and buccal cusps) inclination. The groups were compared with t tests (P <.05). The maxillary posterior teeth of subjects with a vertical growth pattern had a significantly greater buccal inclination compared with those of subjects with a horizontal growth pattern. However, there were no statistically significant differences in the inclinations of the mandibular posterior teeth between the 2 groups.

Adolescent↗