Journal of Dental Medicine

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Normal 0 false false false EN-US X-NONE AR-SA Thumb sucking is a harmful prevalent habit among children that has been identified since 70 years B.C. and causes many dentoalveolar disorders affecting both intra and extra oral soft tissues. This habit is harmful in many aspects for the children and even their environment but is not considered as an addiction according to its special features. In thumb sucking habit, both the finger and oral surrounding contribute to the habit by specific mechanism. Moreover, Duration, Frequency and intensity are effective factors that compensate the effects of each other by replacing the decreased reflex. Some Scientists believe this compensation is accidental. As a conclusion, the cooperation of these factors can increase the harmful effects of thumb sucking.

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Normal 0 false false false EN-US X-NONE AR-SA In some dentoalveolar disorders, orthodontic treatments are occasionally failed during the treatment or even after retention phase. As a result, identifying the reasons of failure would be helpful. Since various indistinct factors can cause treatment failure, we focused on skeletal class 2 divisions 1 disorder and by studying 64 patients with the average age of 6.5 years, more data were collected.

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Normal 0 false false false EN-US X-NONE AR-SA The term "Premature contact" in dentistry and especially in Orthodontics represents sudden contact of a point in one or more teeth with an area of one or more opposing teeth in occlusion or during articulation prior to any contact between the other teeth. These teeth are generally bearing imbalanced and undesirable pressures that make them prone to complications .The wide range of lesions can be manifested as local and centralized or scattered and referral that can damage adjacent organs. As premature contact is a damaging factor that can lead to dentomandibular disorders, it is essential to be followed carefully. In a research on 93 patients selected from 228 of private office referral patients, points were found that consequently led us to a better introduction to this problematic Factor.

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Normal 0 false false false EN-US X-NONE AR-SA In this clinical and paraclinical  research carried out in 15 months, 83 individuals were selected among private office patients who were then decreased to 32 after consideration of  some predesigned conditions of the study. 18 male patients of 6-11 yrs and 14 female patients of 5.5-9 yrs were participated in the study. Following scientific evaluations these results were obtained: abnormal size and function of the tongue can cause dentoskeleteal disorders and complications in other anatomical structures and physiological activities of the oral cavity even in absence of any other etiological factor. Neglecting this can lead to failure of orthodontic treatments and can be an important factor causing relapse. Besides, we cannot declare that the tongue volume is whether complementary to the forces or not. In conclusion, increased function because of increased tongue volume and growth can cause dental or dentoskeletal disorders.

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The purpose of this study was to investigate the soft tissue profile changes of the lower face following premolars extraction and incisor retraction. In order to do that, pre-and post treatment lateral cephalometric radiographs of 40 female orthodontic patients, with cl. II div. I malocclusion (22 patients) and bialveolar protrusion (11 patients) were analyzed. At beginning of orthodontic treatment, their mean age was 18.10 years, ranging from 15-24. All cephalometric radiographs were analyzed by a conventional and confirmed method called "combination analysis". The findings revealed that "lip tension" is a significant factor in soft tissue response to orthodontic treatment, so that in patients with lip strain, nasolabial angle increase was significantly more that those without lip strain. Moreover, regarding the increase of vermilion thickness of the upper lip, a significant difference was observed between two groups. In patients with lip strain, following premolars extraction and incisors retraction, lip strain was reduced or eliminated and upper lip vermilion thickness increased, following incisors retraction, the slope of nasal inferior border, in the group with lip strain, was reduced, while in the group without lip strain, this slope increased.

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Electromyographic (EMG) investigations about the activities of the muscles have been the focus of attention for many years. In the field of orthodontics, investigators, among other things, tried to evaluate correlation between EMG activity, occlusal relationships and craniofacial morphology to analyze the effect of muscular activity, as an etiological factor in malocclusion. The purpose of the present investigation is to analyze the effect of EMG activity of temporal and masseter muscles quantitatively in skeletal class III malocclusion. 26 patients (9 to If years old), with class III malocclusion were selected and their EMG activity of temporal and masseter muscles in rest position, centric occlusion, clenching, mastication and swallowing were compared with 20 normal children at the same age range. Then the statistical correlation between 13 cephalometric parameters and EMG activities were analyzed and then the regression analysis was performed and the results were as follows:
1- The mean amplitude of masseter and temporal muscles activity in rest position, centric occlusion, mastication, and clenching in class III samples were greater than normal group (PO.05).
2- The mean duration of masseter and temporal muscles activity in rest position and centric occlusion in class III samples were more than normal group (PO.05).
3- According to regression analysis, a linear correlation was observed between ANB angle and temporal muscle activity in rest and centric occlusion that was not observed in other cases.
The findings of this study showed that difference in temporal muscle activity in class III malocclusion, in comparison with the normal group, is correlated with skeletal morphology of the face, but according to other investigations it is not ture for the masseter muscle.