Movement Of First Molars Research Articles

Mini-screw implant or transpalatal arch-mediated anchorage reinforcement during canine retraction: A randomized clinical trial

To compare mesial movement of upper first molars during maxillary canine retraction using a pre-adjusted edgewise appliance provided by anchorage reinforcement and a transpalatal arch or mini-screw implant. Randomized clinical trial. Department of Orthodontics and Dentofacial Orthopedics, Armed Forces Medical College, Pune, India. From a cohort of subjects requiring the extraction of both upper first premolars and pre-adjusted edgewise appliances to correct their malocclusion, a total of 30 were randomly allocated to receive two different forms of anchorage reinforcement: group A--receiving mini-screw implant and group B--receiving a transpalatal arch Group A subjects received titanium mini-screw implants placed at the start of treatment between the maxillary second premolar and maxillary first molar. Maxillary second premolars were secured to the mini-screw implants using of 0.010-inch stainless steel ligature wire. Group B subjects received a custom-made transpalatal arch which was soldered to maxillary first molar bands. Active canine retraction was initiated in both groups on placement of a 0.019×0.025-inch stainless steel archwire using nickel titanium closed coil springs. Mesial movement of the upper first molars as measured on pre- (T1) and post-treatment (T2) lateral skull radiographs. The results showed that in group A the mean mesial movement of the first molars between T1 and T2 was 0.0 mm (SD 0.02; P = 0.90), whereas in Group B there was a mean forward movement of the first maolars of 2.48 mm (SD 0.71; P<0.001). In this trial, mini-screw implants placed prior to levelling and aligning were able to provide absolute anchorage during maxillary canine retraction, in contrast to a transpalatal arch.

Maxillary canine retraction with self-ligating and conventional brackets

To measure space closure during the retraction of upper permanent canines with self-ligating and conventional brackets. Fifteen patients who required maxillary canine retraction into first premolar extraction sites as part of their orthodontic treatment completed this study. In a random split-mouth design, the retraction of upper canines was performed using an elastomeric chain with 150 g of force. The evaluations were performed in dental casts (T0, initial; T1, 4 weeks; T2, 8 weeks; T3, 12 weeks). The amount of movement and the rotation of the canines as well as anchorage loss of the upper first molars were evaluated. There was no difference between self-ligating and conventional brackets regarding the distal movement of upper canines and mesial movement of first molars (P > .05). Rotation of the upper canines was minimized with self-ligating brackets (P < .05). Distal movement of the upper canines and anchorage loss of the first molars were similar with both conventional and self-ligating brackets. Rotation of the upper canines during sliding mechanics was minimized with self-ligating brackets.

Anchorage control in bioprogressive vs straight-wire treatment.

Orthodontic techniques with different concepts and philosophies have emerged to provide adequate anchorage control. The purpose of this study was to compare the effectiveness of the Bioprogressive and Straight-wire techniques in the control of lower anchorage. Data were obtained from the records of 40 patients presenting Class I and II malocclusions treated with first bicuspid extractions. One group of 20 patients was treated with a utility arch used to set up cortical anchorage in the lower arch and sectional retraction mechanics for space closure. The second group was treated with straight wire with a preadjusted appliance system. Treatment evaluation revealed no significant between-group differences in the amount of skeletal growth relative to cranial base and lower mesial movement of first molars. Mean lower anchorage loss was 3.1 mm in the Bioprogressive patients and four mm in the Straight-wire patients. The apical base change was the most important component to molar correction. Although cortical anchorage did not impede lower molar movement, it was no less effective in controlling molar movement with a partial appliance than was the fully banded Straight-wire appliance.

Intraoral Maxillary Molar Distalization

To evaluate the maxillary molar distalization and anchorage loss in two groups, one before (MD 1 group) and one after (MD 2 group) eruption of second maxillary molars. After a sample size calculation, 20 patients were recruited for each group from patients who fulfilled the following criteria: no orthodontic treatment before distal molar movement, Class II molar relationship defined by at least end-to-end molar relationship, space deficiency in the maxilla, and use of an intra-arch NiTi coil appliance with a Nance appliance to provide anchorage. Patients in the MD 1 group were without any erupted second molars during the distalization period, whereas in the MD 2 group both the first and second molars were in occlusion at start of treatment. The main outcome measures to be assessed were: treatment time, ie, time in months to achieve a normal molar relation, distal movement of maxillary first molars, and anterior movement of maxillary incisors (anchorage loss). The mean age in the MD 1 group was 11.4 years; in the MD 2 group, 14.6 years. The amount of distal movement of the first molars was significantly greater (P < .01) and the anchorage loss was significantly lower (P < .01) in the group with no second molars erupted. The molar distalization time was also significantly shorter (P < .001) in this group, and thus the movement rate was two times higher. It is more effective to distalize the first maxillary molars before the second molars have erupted.

Late lower arch crowding: The effect of second molar extraction

Mesial drift and change in crowding over a 5-year period were compared in 30 subjects whose lower second molars were extracted between ages 11 and 17 years and 30 subjects whose lower second molars were not extracted. Significant differences were found. The nonextraction subjects showed an average forward movement of first molars and an increase in crowding. The extraction group showed slight distal movement of first molars and a decrease in crowding. It is concluded that lower second molar extraction reduces the tendency to forward movement of buccal segments and increased crowding by relieving eruptive pressure from third molars and that the presence of a developing lower third molar with insufficient space can be one cause of late lower arch crowding.

Periodontal reactions to orthodontic forces in the diabetic metabolic state

The reaction of the periodontium to orthodontic tooth movement was studied in rats with streptozotocin diabetes. Forces employed to initiate mesial movement of first molar were 10 N 20 N 30 N and the duration of application was three, six, ten and 14 days. The 14-day rats were treated with fluorochrome sequential labelling according to Rahn. Diabetes mellitus in rats is accompanied by characteristic changes: The most important findings were: 1. a slow osseous regeneration, as could be shown by fluorescence microscopy, 2. the new bone ist unable to pick up the labellings in a sequential manner, 3. a weakening of the periodontal ligamentum, 4. microangiopathies in the gingiva area. the specific diabetic changes are more pronounced following orthodontic tooth movement.

Some problems in orthodontics observed by the serial models of Japanese children

As a result of a series of measurement to examine the manner of movement of neighboring succedanous teeth at the shedding of milk second premolars in Japanese grade school children, the following points have been brought to light. 1. Three manners of modes of movement are known, i. e., movement of first premolars alone, that of first molars alone and mutual movement of premolars and molars so that they may be approximated to one another. 2. Of three manners of movement, the majority of cases are mutual movement of first premolars and molars. 3. In the mutual movement of first premolars and molars, a few behaviors are observable and what is most frequently seen is one in which the movement of first molars is larger than that of first premolars, this being true of lower jaw in particular.