Treatment of Class III Malocclusion: Atypical Extraction Protocol
In the present report, two techniques of space closure; two-step anterior teeth [ 1,2,3] However, closing spaces in two-steps might take a longer treatment time. She had bimaxillary dentoalveolar protrusion with Class I molar and canine were used to stabilize buccal segments during the en mass retraction After closing. 2) evaluation of dental occlusion as normal occlusion or malocclusion Class I, Class II .. of Classes II and III dental malocclusions that have altered molar relationships, Figure 4 shows the correlation between mean bite forces and body mass A study of bite force, part 1: Relationship to various physical characteristics. group, the median particle sizes for the Class I, II, and III malocclusion groups . 1. Missing teeth (excluding third molars);. 2. Symptoms of TMJ dysfunction to include pain and crep- where Qw is the weight percentage of particles with a di -.
However, these values were still lower than those of the control group, even years after intervention.
Case Reports in Dentistry
Observing studies by authors such as English et al. According to Herring 2the activation and the coordination of mastication muscles determine the direction of mandible movement, the control of the force of occlusion and different types of cranial deformation. Muscles, as well as teeth, play an important role in the direction of the course of bite force. The author also explains that muscle anatomy may cause, as well as reflect mandible movements, and, therefore, the relative importance of the components of bite force may be associated to each being's different muscle anatomy.
Bakke 7in his literature review, hasalso reported that there is a positive and intimate relationship between bite force and electromyographic activity of the mandible's elevator muscles temporal, masseter and medial pterygoid during isometric contractions. Class III individuals had higher activity for all muscles in maximum effort except for the digastric muscle.
A deviation in the activity pattern of mastication muscles in individuals with Class II malocclusion was observed when compared to Class I individuals especially in regards to the temporal muscle, that was more active in the first group. The individuals with Class I malocclusion also had a more functional activity pattern than those with Class II malocclusion.
However, the results above disagree with those found by Sonnesen and Bakke 18 who, aiming to establish relationships between mastication force and malocclusion, facial dimensions and head posture in children, observed that bite force did not vary significantly among the types of malocclusion. In addition, Lemoset al 4 did not find statistically significant differences when relating bite force to dental occlusion, but it should be noted that the age group of the individuals analyzed in these investigations were children aged 13 or younger, a factor that may have been determinant in obtaining the reported results.
Regarding the measurement of bite force of the individuals in three consecutive trials, it is seen in Figure 3 that there was a statistically significant difference of mean force between the first and third measurements obtained in both sides of the face right and leftwith a medium increase of this force. No studies were found in literature that have performed similar analyses, but when observing the obtained bite forces, it is believed that asking one to bite hard on the dynamometer may be exploratory at first for the individual who is part of the sample and, only during the third measurement the subject feels comfortable enough to bite according to the examiner's instructions.
Based on this analysis, it is suggested that the measurement of bite force should be performed at least three times, according to the results obtained in this study. Figure 4 shows the correlation between mean bite forces and body mass index BMI and Table 5 shows Spearman's coefficient as well as the p-value between the paired values.
Observing this table, it may be verified that the findings are very disperse and, after completion of a specific test, it was concluded that there was no statistically significant correlation of linear growth or decrease between the variables bite force and BMI. These findings are in agreement with those described in the study byBraun et al. The sample was composed of individuals of both genders in between 26 and 41 years of age, and, in order to conduct the measurements, a transducer that measured the force in Newtons N was used.
The correlation coefficients for weight and height were low. Lemos et al 4 also reported a weak correlation between these variables in their investigation - they studied the maximum bite force in children with mean age of 9, considering each one's occlusion condition and body variations BMIwith the hypothesis that these characteristics could be correlated.
However, as in the present study, the results showed that bite force had a weak correlation with BMI values.
- Class II Molar Relationships
Conclusions It may be concluded that the type of occlusion influenced bite force, with greater bite force in individuals with normal occlusion, followed by Classes I, II and III, respectively; there was higher frequency of occurrence of Class I malocclusion, followed by normal occlusion, Class II divisions 1 and 2 and Class III; there is an increase in mean bite force between the first and third measurement and that there was no correlation between bite force and body mass index BMI.
Masticatory muscles and the skull: A study of bite force, part 1: Relationship to various physical characteristics. Chewing performance and bite force in children.
Braz J Oral Sci. Bite force and occlusion. A determination of bite force in northern japanese children. Measure of bite force and occlusal contact area before and after bilateral sagittal split ramus osteotomy of the mandible using a new pressure-sensitive device: J Oral Maxillofac Surg.
International Association of Oral and Maxillo facial Surgeons. Changes in bite force and occlusal contact area after orthognathic surgery for correction of mandibular prognathism.Atomic & Molecular Mass - Some basic concepts of chemistry - Chemistry - IIT JEE - Class 11
The influence of mandibular advancement surgery on oral function in retrognathic patients: American Association of Oral and Maxillofacial Surgeons. Sociedade Brasileira de Fonoaudiologia; Does malocclusion affect masticatory performance?.
Angle Orthod ;72 1: Masticatory performance in children and adolescents with Class I and II malocclusions. Electromyographic comparisons between clenching, swallowing and chewing in jaw muscles with varying occlusal parameters.
Preliminary rapport on head posture and muscle activity in subjects with class I and II. Journal of Oral Rehabilitation. Sonnesen L, Bakke M.
Molar bite force in relation to occlusion, craniofacial dimensions, and head posture in pre-orthodontic children. Dental Press J Orthod. J Bras Ortodon Ortop Facial. This article has been cited by other articles in PMC. Abstract In the present report, two techniques of space closure; two-step anterior teeth retraction TSR and en masse retraction ER were used in two adult patients who had bimaxillary protrusion and were treated with four premolar extractions and fixed orthodontic appliance therapy.
Both patients had a Class I dental malocclusion and the same chief complaint, which is protrusive lips. Anterior teeth were retracted by two-step retraction; canine sliding followed by retraction of incisors with T-loop archwire in the first patient and by en masse retraction using Beta titanium alloy T-loop archwire in the second case.
At the end of treatment, good balance and harmony of lips was achieved with maintenance of Class I relationships. The outcome of treatment was similar in the two patients with similar anchorage control. This demonstrates a correction with treatment of 4. As shown in Table 6after performing the ANOVA and Tukey tests, a statistically significant correction with treatment and stability in the post-retention period could be noted, since there was no statistically significant difference in the molar relationship between the final and post-retention stages.
In other words, the molar relationship showed to be stable in the post-retention phase. The results of this study are in agreement with previous findings in the literature.
Bite force analysis in different types of angle malocclusions
The authors considered the molar relationship stable at the end of the post-retention period. Kim and Little23 found even an improvement in molar relationship in the post-retention period evaluating Class II division 2 cases.
At the end of treatment, the cases had a mean value of 1. Uhde, Sadowsky and BeGole,39 evaluating Class I and Class II cases in the post-retention stage, reported that the mean change in molar relationship is always in relation to the Class II, however, these changes are not relevant, about 0.
However, besides including Class I and Class II cases, which directly influences the results, the authors also included cases treated with and without extractions. However, Fidler et al12 found a significant relapse of molar relationship between the final and post-retention stages. However, although statistically significant, this relapse had low values of 0.
Perhaps this difference with the present study was due to the fact that the authors selected cases with Class II malocclusion treated successfully at the end of treatment, and in the present study, the final treatment outcome of the Class II was not considered for the sample selection.
The literature shows stability of the molar relationship, especially in Class II, division 2 cases. Regarding the Class II division 1 malocclusion, this study showed slightly better results than those found in the literature. For the post-retention evaluation, in the long-term, 1. This demonstrates a correction of 4. As shown in Table 6after performing the ANOVA and Tukey tests, a statistically significant correction with treatment and stability in the post-retention period could be noted, since there was no statistically significant difference of the second premolars relationship between the final and post-retention stages.
The study of Kim and Little23 showed the same trend, however, in the final stage, the value of the premolars relationship was slightly higher than normal, and this value remained higher in the posttreatment stage. The initial value of the Class II premolars relationship was 4.
First premolar relationship The initial measurement of the first premolars relationship presented a mean value of 5. For the postretention evaluation, in the long-term, 1. As shown in Table 6after performing the ANOVA and Tukey tests, a statistically significant correction with treatment and stability in the post-retention period could be noted, since there was no statistically significant difference in the first premolars relationship between the final and post-retention stages.
Canine relationship The initial measurement of the canine relationship presented a mean value of 7. For the postretention evaluation, in the long-term, 2. This shows a correction of 4. As shown in Table 6after performing the ANOVA and Tukey tests, a statistically significant correction with treatment and a complete stability in the post-retention period could be noted, since there was no statistically significant difference of the canine relationship between the final and post-retention stages, and even a small improvement could be seen.
Kim and Little23 found results similar to the present study. The initial Class II canine relationship had value of 5. Correlations To verify the correlation between the severity of the Class II relationship with the post-retention relapse, and the relapse of Class II molar relationship with treatment time, retention time and time of postretention evaluation, the Pearson correlation test was used Tables 7 and 8.
There was a correlation of the initial canine relationship with relapse Table 7. There was correlation of molar relationship relapse with the time of post-retention evaluation Table 8. However, this correlation was negative, indicating that the longer the time of post-retention evaluation, the lower the relapse of molar relationship.
This finding seems unreasonable; however, since patients were mostly young, at the end of orthodontic treatment, they still showed growth in the post-retention stage. As the growth tends to improve the relationship of skeletal bases,18 it is natural that the if time has passed until the post-retention evaluation, the patient will have more growth, favoring the stability of the correction of the Class II molar relationship. Intergroups comparison To check the influence of the severity of the Class II molar relationship in the initial stability of the molar relationship, the sample was divided into two groups: Therefore the independent t test was applied for all variables between these two groups.
There was compatibility between the two groups for the initial and final ages, and only the post-retention age showed a statistically significant difference Table 9. Subjects in Group 2 complete Class II had an older age in the post-retention stage than the subjects in Group 1. The retention time was also compatible between the two groups studied Table 9. This was expected since it is known that the severity of malocclusion, especially the severity of the Class II, when treated without extractions, can significantly increase treatment time.
Obviously, the complete Class II group had a significantly higher value than the group with less severity. The molar relationship at the end of treatment and at the post-retention stage did not differ between the two groups Table 9.
There was also a difference in the amount of correction with treatment, which also was expected, because if the Class II molar relationship was more severe in Group 2, a greater correction of this relationship was really necessary in this group Table 9. The molar relationship relapse between the two groups did not present a statistically significant difference, however, it was observed that the molar relationship presented a relapse of 0.
This evidence reinforces the findings of this study that there is no relationship of the initial Class II severity with molar relationship relapse.
The same pattern of results was observed for the first and second premolars and canine relationship.