Lower Incisor Inclination Research Articles

Lower Incisor Torque: The Effects of Rectangular Archwires with a Reverse Curve of Spee

The relationship between the Curve of Spee in a rectangular archwire and torque in the lower labial segment is discussed. It is concluded that introducing a reverse curve in the archwire does not necessarily have any adverse effects on final lower incisor inclination.

The influence of heredity and environment on six variables describing incisor orientation.

The relationship between genetic and non-genetic factors was studied for six variables associated with incisor positioning. The aim was to determine the heritability for the anteroposterior apical base relationship, the overjet and the inclinations of upper and lower incisors. The path analysis model was used on twin material to separate genetic and cultural inheritance. No evidence was found to indicate any significant influence of cultural inheritance. Heritability quotients (role of genetic factors in the total variance) varied with the highest value for the anteroposterior apical base relationship (h2 = 0.8) followed by lower incisor inclination (h2 = 0.7) and with the lowest values for overjet and the upper incisor inclination (h2 = 0.5 and 0.4). A calculation of the quotient between genetic and environmental standard deviations showed corresponding results, indicating that genetic factors may have twice as much influence as non-genetic ones on the apical base relation, (quotient = 2.1) followed by lower (1.4) and upper (1.1) incisor inclinations and overjet (0.9).

Dento-alveolar compensation for antero-posterior variations between the upper and lower apical bases.

Two groups consisting of 68 adult singletons and 42 adult pairs of twins were studied with respect to antero-posterior variations in the apical base relationship and its association with the incisor overjet and upper and lower incisor inclinations. A weak correlation with the overjet was established while stronger associations were found with incisor inclinations especially regarding the lower incisors. A large positive apical base relation thus seems to be primarily compensated for by proclination of the lower incisors while negative values caused a corresponding retroclination. When associated correlation coefficients were compared with previously published value somewhat stronger associations were found. In addition when average incisor compensations for variations in the apical base relationship were compared with Steiner's model they were found to be slightly greater than that recommended by him.

Occlusion and Inclination of the Pashtun and Tajik in Afghanistan

We have reported previously on the descriptive features and the size of the dentition of the Pashtun and Tajik in Afghanistan. The present work concerns an occlusion and incisor inclination. The materials used were 111 upper and lower plaster casts of 74 Pashtuns and 37 Tajiks. The materials of the Japanese used in comparative study were 184 upper and lower plaster casts. On these plaster casts vertical overbite, horizontal overbite (overjet) (fig. 1), sagittal molar relation (fig. 2) and angle of the incisor inclination (fig. 3) were measured. As a rule, the right-side teeth were studied. The results are summarized as follows:1. Figures for the overbite, overjet and sagittal molar relation are given in table 1. The overbite of the Pashtun is smaller than that of the Tajik or the Japanese. The over jet (from the midpoint of the incisal edge of the upper first incisor to the labial surface of the lower first incisor) of the Pashtun or the Tajik is smaller than that of the Japanese. No significant differ ences between the populations are observed in the sagittal molar relation.2. The percentage frequency of Angle Class I in the Pashtun or the Tajik is higher than in the Japanese (table 3).3. Figures for the angle of the incisor inclination are given in table 6. The angle of the upper incisor inclination of the Pashtun or the Tajik is larger than that of the Japanese, but rio significant differences between the populations are observed in the lower incisor inclination.

Elastic-thread ligature as an auxiliary for tooth movement

The objective of this study was to compare different cephalometric variables in adult patients with class III malocclusions before and after treatment, in order to determine which variables are indicative of orthodontic camouflage or orthognathic surgery. The cases of 156 adult patients were assessed: 77 treated with orthodontic camouflage and 79 treated with orthodontics and orthognathic surgery. The following cephalometric variables were measured on pre-treatment (T1) and post-treatment (T2) lateral cephalograms: sella–nasion–A-point (SNA), sella–nasion–B-point (SNB), and A-point–nasion–B-point (ANB) angles, Wits appraisal, facial axis angle, mandibular plane angle, upper and lower incisor inclination, and inter-incisal angle. There were statistically significant differences in cephalometric variables before and after treatment between the two groups. The percentage of normal pre-treatment measurements in the camouflage orthodontics group was 30.7%, which worsened slightly to 28.4% post-treatment. However in the group receiving surgery, this was 24.5% pre-treatment, improving to 33.5% after surgery. SNA, SNB, Wits appraisal, lower incisor inclination, and inter-incisal angle showed differences between the two groups before and after treatment. Wits appraisal, lower incisor inclination, and inter-incisal angle were indicative of one or other treatment. Upper and lower incisor decompensation in both groups did not reach ideal values, which impeded complete skeletal correction in 52% of surgical cases.