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As orthodontists, we are often unaware of the technical and methodological advances in other dental specialties. However, many of these new experimental developments may ultimately become accepted dental therapy and influence the diagnosis and treatment of our orthodontic patients. Therefore, as part of the dental community, we must keep abreast of current information in all areas of dentistry. The purpose of this section of The Angle Orthodontist is to provide a brief summary of what's new in dentistry.

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This paper describes the development of anteroposterior (AP) and vertical (VER) skeletal relationships. A mixed-longitudinal sample of 49 females and 50 males was followed during childhood and adolescence. Childhood growth changes were assessed from 6 to 10 years for females and 8 to 12 years for males. Adolescent changes were evaluated from 9 to 13 years for females and 11 to 15 years for males. Anteroposterior relationships were described by the horizontal distance between ANS and Pg. Vertical relationships were described by the vertical distance between Pg and Go. Subsamples were defined based on overall changes (AP and VER) that were either greater than or less than average. The results showed that AP and VER relationships were not stable during growth. AP relationships changed over time due to differential growth movements of the mandible (as opposed to the maxilla). There was greater potential for horizontal discrepancies to decrease during childhood than during adolescense. The potential for AP discrepancies to increase was greater during adolescence. The VER relationships increased in the majority of subjects. The subsample whose vertical discrepancies increased most showed less inferior movement of gonion and more inferior movement of pogonion. Inferior movements of Pg and Go were greater during adolescence than childhood.

With a commentary by Robert J. Isaacson

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The purpose of this study was to evaluate changes in overbite over a 40-year span, and to relate these changes to those occurring in vertical skeletal facial relationships. Lateral cephalograms of 20 males and 15 females from the Iowa Facial Growth Study were evaluated at ages 5, 10, 15, 25, and 45 years. Correlation coefficients were computed to determine the relationship between overbite and various skeletal parameters. Analysis of variance and Duncan's multiple-range test were used to compare various periods of growth. Statistical significance was predetermined at the 0.05 level of confidence. No significant correlations were found between the absolute values of overbite and the vertical skeletal parameters in either males or females. Incremental changes in overbite during four growth periods were compared with changes in various vertical parameters and only a few significant correlations were found. In males, the change in overbite was significantly correlated with changes in N-Ans'/N-Me and MP:SN during the 10-to-15-year growth period. In females, the change in overbite was significantly correlated with changes in N-Ans'/N-Me% during the 5-to-10-year period and also with change in Ar'-Go/S-Go% during the 15-to-25-year period. In general, changes in overbite with age are difficult to predict from the initial overbite in the deciduous or mixed dentitions. On the other hand, evaluation of individual curves shows that males who initially had the least amount of overbite maintained that trend during the later stages of development. Although overbite changes were significantly associated with changes in some vertical skeletal parameters, the associations were not of clinical significance for predictive purposes, and overbite changes are probably dependent on concurrent changes in the growth of the alveolar processes.

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The purpose of this study was to examine the cephalometric changes that occur with palatal expansion/facemask therapy for Class III malocclusion. Pretreatment and posttreatment lateral cephalograms from 21 patients were traced and analyzed by traditional cephalometric measures, an x-y coordinate system, and along the functional occlusal plane. Differences between T1 and T2 values were analyzed with paired t-tests. Mean ages were 7.26 years (T1) and 8.18 years (T2). Average treatment time was 11.05 months. Statistically significant anterior movement of the maxilla occurred with increases in SNA (+2.35), maxillary depth (+2.22), and ANB (+3.66), and anterior movement of A-point (+3.34 mm) and ANS (+3.17 mm). The maxilla rotated counterclockwise, with PNS moving down more than ANS (−2.21 mm and −0.82, respectively). The mandible rotated clockwise with mild decreases in SNB (−1.32) and facial depth, (−1.2) but significant downward movement at menton (−4.34 mm). Occlusal plane analysis demonstrated that the correction was due more to the maxilla than the mandible (+2.35 and −1.88 mm, respectively). The maxillary molars moved forward (+1.70 mm) as did the incisors (+1.75 mm). Soft tissue changes included the nose and upper lip moving forward (3.43 and 3.67 mm, respectively), and menton moving downward (−3.49 mm). The results indicate that facemask/palatal expansion therapy improves Class III malocclusion by a combination of skeletal and dental changes that occur in the anteroposterior dimension and in the vertical plane of space.

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A previous retrospective study of 10 children with varying degrees of nocturnal enuresis has shown that one side effect of rapid maxillary expansion (RME) is spontaneous reduction in bed-wetting at night. The aim of this prospective study was to analyze the effect of RME treatment (mean 2 weeks) in cases of chronic, long-standing nocturnal enuresis. Ten children, 8 to 13 years old, who had not responded to conventional medical treatment for bed-wetting, were referred from the pediatric department. Within 1 month of RME of 3 to 5 mm, 4 children were completely dry and 3 showed notable improvement. The results are encouraging, especially given the spontaneous recovery rate of about 15% per year. A reduction in nocturnal enuresis in children has also been reported after tonsillectomy. However, in this pilot study, no significant associations could be found between improvement in nocturnal enuresis and improvement in the nasal airway, age, amount of expansion, or nasopharyngeal dimension (measured on cephalograms).

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The purpose of this study was to investigate the relationship between masticatory muscle activity during the day and vertical craniofacial morphology. The sample comprised 30 subjects (20 males and 10 females, age range 15 to 28 years, mean 24 ± 3.2 years) who had normal anteroposterior skeletal relationships and complete or nearly complete dentition without serious malocclusion or temporomandibular dysfunction. Using a portable electromyographic recording system, activities of the masseter, temporal, and digastric muscles were recorded for 3 hours during the day, excluding time spent eating, sleeping, and exercising. A lateral cephalogram was taken of each subject with the teeth in occlusion. Activities of the masseter, temporal, and digastric muscles consisted mainly of low-amplitude bursts. The duration of digastric muscle activity was greater than that of either the masseter or temporal muscles. Masseter and digastric muscle activities showed significant negative correlations with vertical craniofacial morphology, whereas temporal muscle activity was positively correlated. The activities of the masseter, temporal, and digastric muscles during the day consist of low-amplitude bursts and may be related to vertical craniofacial morphology.

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The purpose of this investigation was to study the control of cross-sectional dimensions and edge bevel by various manufacturers in the production of chrome-cobalt archwires and its effect on transmitting torque through an .018 inch slot bracket system. Twenty-seven different square and rectangular chrome-cobalt wires commonly used in the edgewise technique supplied by five different manufacturers were studied with respect to dimensions, edge bevel, and mechanical properties in torsion. The mechanical study simulated application of torque to an individual tooth. Standard brackets with .018 inch slot heights were used. The results show that variation in cross-sectional dimension and edge bevel leads to variable torsional play (third-order clearance). As an example, .016 × .016 wires have a mean torsional play of as much as 26.8 degrees, with a range of 21.0 to 32.3 degrees. When using .016 × .016 wires, one must apply from 34.8 to 48.6 degrees of twist to get 20 N-mm of torsional moment. This variation is primarily due to the rather wide range in torsional play. As a result, the prediction by which a predetermined torsional moment can be delivered becomes uncertain. The results also show that because the working range in torsion of chrome-cobalt wires is somewhat limited due to high torsional stiffness, precise delivery of torsional moment based on the condition present in the oral cavity is difficult. The torsional stiffness varies between manufacturers within the various dimensional groups as a result of differences in cross-sectional geometry and material properties.

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The aim of the study was to examine the effect of an oral shield treatment on orofacial muscle activity and facial morphology in children with lip and/or tongue dysfunction. The sample consisted of 7 girls and 2 boys, 7 to 12 years old. EMG recordings with and without the shield in situ were obtained when the shield was placed, and 3, 6, and 12 months later. Lateral cephalograms were obtained at the initial and 1-year stages. The lip muscles showed dominant activity when the subjects were sucking on an empty straw and during swallowing; this was strongest during the first 3 months. The mentalis, buccinator, and digastric muscles generally showed weaker activity. The anterior temporal muscle showed dominant activity during maximal clench, but after the 3-month stage a significant decrease was noted. After 1 year of treatment, no significant changes in overjet or overbite were observed. Most of the craniofacial growth changes were normal for the age group. The results indicate that treatment with an oral shield caused a decrease in orofacial muscle activity during oral functions. Although there was a slight average retraction of the maxillary incisors, the change in position was not statistically significant.

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The purpose of this study was to evaluate the effects of local administration of osteocalcin, a major noncollagenous bone matrix protein, on experimental tooth movement in rats. An orthodontic elastic band was inserted between the upper first and second molars, and the first molar was moved mesially. Purified osteocalcin (0 to 10 µg) in 20 µl of phosphate-buffered saline was injected into the region of the root bifurcation of the first molar daily for 4 days. Tooth movement increased significantly following the injections. Histological studies revealed that the injections markedly stimulated the appearance of osteoclasts on the pressured side of the alveolar bone surface. The results suggest that osteocalcin has an additive effect on the rate of orthodontic tooth movement through the enhancement of osteoclastogenesis on the pressured side.

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The purpose of this study was to reveal patterns of association among seven types of dental anomalies (aplasia of second premolars, small size of maxillary lateral incisors, infraocclusion of primary molars, enamel hypoplasia, ectopic eruption of first molars, supernumerary teeth, and palatal displacement of maxillary canines) in an untreated orthodontic population, ages 7 to 14. The prevalence of associated tooth anomalies in seven groups of 100 subjects selected according to one primarily diagnosed dental anomaly was compared with the prevalence of the examined dental anomalies in a control group of 1,000 subjects. Significant reciprocal associations (p<0.005) were found among five of the anomalies (aplasia of second premolars, small size of maxillary lateral incisors, infraocclusion of primary molars, enamel hypoplasia, and palatal displacement of maxillary canines), suggesting a common genetic origin for these conditions. Supernumerary teeth appeared to be a separate etiological entity with respect to all other examined tooth anomalies. The existence of associations between different tooth anomalies is clinically relevant, as the early diagnosis of one anomaly may indicate an increased risk for others.

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Incontinentia pigmenti is an uncommon genodermatosis that occurs in female infants. The characteristic dental defects are partial anodontia and the presence of some peg-shaped teeth. This report describes a patient with incontinentia pigmenti who exhibited multiple missing teeth in both arches. The patient had malpositioned teeth and decreased occlusal vertical dimension associated with the missing teeth. Orthodontic treatment was required for prosthetic purposes. The dental anomalies of incontinentia pigmenti and the treatment procedure are presented.

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No Abstracts Available