To evaluate the characteristics of masticatory muscle activity in operated unilateral cleft lip and palate (UCLP) patients with anterior crossbite compared with normal individuals. Subjects: Sixteen male and 13 female Chinese patients with UCLP and an-terior crossbite. Fifteen male and 13 female Chinese individuals without cleft abnormalities served as a control group. Design: Electromyographic activity of the masseter muscles and anterior temporalis muscles was recorded bilaterally in different mandibular positions using bipolar surface electrodes. Results: Compared to noncleft controls, patients with UCLP demonstrated (1) higher activation levels of masseter and temporalis muscles in the rest position, (2) lower potential function of masseter and temporalis, (3) inharmonious activity of the masticatory muscles during mandibular border movement, (4) a higher asymmetry index of the masseter and temporalis muscles, and (5) longer silent periods of the two muscles. Conclusions: The function of masticatory muscles is different in patients with UCLP with anterior crossbite. Muscle function should be considered when evaluating cleft patients for orthodontic treatment and orthognathic surgery.

SUMMARY Class Ⅱ elastics are usually employed in the treatment of excessive overbite and overjet with the Begg technique. The effect of Class Ⅱ elastics on bite opening and the extent of such an effect is uncertain. This article, based on measurements of 30 cases, illustrates that the effect of the vertical component of force from Class Ⅱ elastics in reducing the intrusive force generated by the anchor bands in the upper archwire is less than previously believed. The position of the circles in the archwire for intermaxillary elastics has the greatest influence on theanterior intrusive force of the upper archwire. The direction of the Class Ⅱ elastics and the lengthof the dental arch (a negative correlation) came second, while the force actually exerted by theelastics had the smallest influence. It is, therefore, suggested that the position of the intermaxillary elastic circles should be located according to the differing clinical objectives.

In the Begg Technique, factors controlling the anterior intrusive force provided by the archwire have yet to be fully clarified. The rationale for bite opening with very light forces, the effect of Class H elastics on intrusive force magnitude and the intrinsic quality of 'Australian' wire in bite opening are examined in this paper. A formula is presented which allows the intrusive force that archwires exert in different individuals to be predicted. The values derived from the formula were compared with case model measurements. It was found that the intrusive force of the archwire was affected by the length of the individual dental arch. The magnitude of this intrusive force was seen to increase gradually during the period of bite opening and appeared to be related to the use of Class H elastics. The study revealed factors which affected the magnitude of the intrusive force.

We have previously demonstrated that all-trans retinoic (atRA) induced growth inhibition and apoptosis in mouse embryonic palate mesenchymal cells (MEPM). In the present study, we investigated the molecular mechanisms of atRA-induced apoptosis and its putative action pathway. atRA-induced apoptosis is associated with activation of the initiator caspase-9 and the effector caspase-3, but not of the effector caspase-8. A broad caspase inhibitor (z-VAD-fmk), caspase-9 inhibitor z-LEHD-fmk and caspase-3 inhibitor (z-DEVD-fmk) blocked atRA-induced DNA fragmentation and sub-G1 fraction, but not caspase-8 inhibitor z-IETD-fmk. We further showed that atRA dosedependently promoted mRNA expression of retinoic acid receptor b (RAR-b) and g. A weaker increase in RAR-a mRNA was seen only at the highest concentration of atRA (5mM). The pan RAR antagonist, BMS493, completely abrogated atRA-induced DNA fragmentation, Sub-G1 fraction, and caspase-3 activation. Taken together, these findings show that caspase-mediated induction of apoptosis by atRA is an RAR-dependent signaling pathway.

The purpose of the study was to use euclidean distance matrix analysis to compare dental arch forms between subjects with Class Ⅱ Division 1 malocclusions and normal occlusions. Methods: The sample consisted of 60 subjects with Class Ⅱ Division 1 malocclusions and 60 subjects with normal occlusions, all between 13 and 17 years of age. Fourteen landmarks, corresponding to cusp tips and incisor edges, were identified on the dental casts with a 3-dimensional measuring machine. All possible linear distances between pairs of landmarks in an arch were computed, and arch-form differences between Class Ⅱ Division 1 and normal-occlusion subjects were tested by euclidean distance matrix analysis. Results: In both sexes, the maxillary arches of the Class II Division 1 subjects were larger than the arches of the normal-occlusion subjects (1.8% and 2.7% larger for girls and boys, respectively), and arch shape was also significantly different (P<001). The posterior teeth contributed to the shape difference between 2 groups more than the anterior teeth, moreover the main factor was narrow maxillary posterior arch width in the Class Ⅱ Division 1 subjects. The mandibular arches of the Class Ⅱ Division 1 subjects were also slightly larger, and arch shape was not significantly different regardless of sex. Conclusions: Expanding the maxillary posterior arch width in Class Ⅱ Division 1 subjects might be an important method to harmonize maxillary and mandibular arch forms.