Myron Lieberman

Rapid palatal expansion: Part 1. Mineralizationpattern of the midpalatal suture in cats

The mineralization pattern of the midpalatal suture after rapid palatal expansion was investigated in 10 treated and 2 control cats, in light of the tendency of RPE to relapse. The rapid palatal expansion treatment consisted of active (25 days), retention (60 days), and relapse (60 days) phases. Standardized occlusal radiographs were taken periodically and analyzed for suture width, suture optical density in anterior vs. posterior regions, and suture area measurements of radiopaque vs. radiolucent zones. Nine cats exhibited suture splitting. During the active phase, the radiolucent zone (nonmineralized tissue) increased 12-fold and the increase in optical density was 50% greater in the anterior over the posterior suture region, demonstrating increased formation of loose connective tissue at the anterior region. During the retention period, the sutures radiopaque zone (mineralized tissue) increased by 62%, the radiolucent zone declined (64%) and the suture width decreased (65%) indicating reorganization of mineralized tissue. The decrease in optical density (increased mineralization) was 2.5 times greater in the posterior over the anterior suture region, indicating that the remineralization (closure) pattern of the expanded suture is analogous to a zipper closed in a posteroanterior direction. During the relapse phase, the reduction in total suture area (41%) and in the radiopaque zone (32%) indicates medial convergence of the maxillary horizontal processes. From our findings we extrapolated that the retention of the suture anterior region should be longer than the posterior region to catch up the lag in rebuilding and maturation of the newly deposited hard tissue.

The intercuspal surface contact area registration: an additional tool for evaluation of normal occlusion.

Abstract No Abstract Available. From the Department of Orthodontics, Tel Aviv University, Tel Aviv, Israel.

Israeli cephalometric standards compared to Downs and Steiner analyses.

A sample consisting of 40 young Israeli adolescents, 18 males and 22 females, was examined cephalometrically. The subjects were classified as Angle Class I, with less than three millimeters of crowding and an orthognathic profile. Steiner and Downs analyses were performed for all subjects. Each analysis was done both manually and by using a computer. The computerized results were processed and subjected to statistical tests. The Israeli sample is characterized by a convex profile, a retrusive mandible, a steep mandibular plane and protrusive incisors.

The effect of pain from orthodontic arch wire adjustment on masseter muscle electromyographic activity

Pain has been shown to have an effect on muscle activity even when it does not originate in the muscle itself or in the related joint. The effect of pain from arch wire adjustment on jaw muscle activity is unclear. This study systematically evaluated the effects of orthodontic arch wire adjustment pain on masseter electromyographic (EMG) activity and on the swallowing threshold. The EMG recordings were made on 22 subjects (ages 11 to 15) under three conditions: chewing five peanuts (10 seconds), watching TV chewing gum (15 minutes), and watching TV with no gum (15 minutes). An arch wire adjustment or placebo adjustment was then made. Subjects returned after 48 hours, and the EMG measurements were made under the same conditions. After 3 weeks, subjects received arch wire or placebo treatment in a crossover design with identical recording procedures. The EMG levels while chewing peanuts decreased in 18 of 22 subjects after treatment, compared with 9 of 22 subjects after the placebo. While watching TV with gum, the EMG levels of 20 of 22 subjects decreased after treatment, compared with 9 of 22 subjects after the placebo. The number of chewing strokes before swallowing increased significantly after treatment compared with after placebo. The results suggest that orthodontic pain on teeth tend to reduce muscle activity during function.

Rapid palatal expansion. Part 2: Dentoskeletal changes in cats with patent versus synostosed midpalatal suture

Intercanine expansion (C-C) following rapid palatal expansion is made up of sutural displacement (Sd-Sd), tooth tip (Tt-Tt), tooth displacement (Td-Td), and alveolar process tipping and bending (At+b-At+b). The involvement of these four components was studied on 10 rapid palatal expansion treated and two control cats during an active phase (25 days), a retention phase (60 days), and a relapse phase (60 days). The midpalatal suture was analyzed for linear measurements, radiopaque versus radiolucent zones and optical density from occlusal radiographs. Nine treated cats exhibited sutural split and one treated cat showed no split as a result of synostosis of the suture. The contribution of the four constituents [(Sd-Sd):(Tt-Tt):(Td-Td):(At+b-At+b)] to the C-C expansion changed from active to relapse phase from [45%:15%:25%:15%] to [50%:25%:25%:0%] in the animals with sutural split and from [0%:40%:60%:0%] to [0%:0%:100%:0%] in the cat without sutural split, implying the major role of sutural displacement in patent suture, and tooth displacement in synostosed suture. The latter indicates the potential buccal corticalis fenestration, dehiscence or perforation in synostosed suture undergoing RPE. In patent suture (animals with sutural split), optical density increased during rapid palatal expansion (soft tissue build-up) and decreased during retention (remineralization) and relapse phases (medial convergence of the palatal processes). In the animal without sutural split, a continuous decrease in the optical density (predetermined ossification) was found. The progressive six-fold surge in coefficient of variation of C-C expansion during the relapse phase indicates limitation in predicting rapid palatal expansion stability. Clinically, the use of serial occlusal radiographs during rapid palatal expansion is recommended to evaluate patency and extent of retention period.

Correction of a Class I Skeletal Open-Bite Malocclusion

Abstract No Abstract Available. From the Departments of Orthodontics and Occlusion, School of Dental Medicine, Tel Aviv University, Ramat Aviv, Israel.

Upper first premolar with congenitally missing buccal root: A case report

The endodontic literature is replete with descriptions of teeth having alterations, aberrations, or additions of roots or root canal formations (1, 2). The occurrence of congenitally missing roots, however, is most unusual. Andreasen (3) reported that partial or complete arrest of root formation is a rare complication of ment plan called for extraction of the upper first premolar teeth. Panorex and periapical X-ray films showed no abnormal root formation, and crown formation was normal (Fig. 1). The upper left first premolar was extracted and was observed to be, in all respects, a normal two-rooted tooth. The upper right