Stability prediction of early orthopedic treatment in Class III malocclusion: morphologic discriminant analysis

Background To evaluate morphologic differences between class III malocclusion success and failure treatment subjects in order to identify which variables are more predictive for long-term stability in early orthopedic treatment. In this retrospective study, 31 patients were enrolled from the Department of Orthodontics (Rome Tor Vergata). Inclusion criteria were as follows: white ancestry, class III malocclusion, mixed dentition, cervical stage (CS) 1-2, no pseudo-class III. Pre-treatment radiographic and cast records were collected. Each patient underwent rapid maxillary expansion/facial mask/bite block (RME/FM/BB) orthopedic treatment until correction. At T1 (permanent dentition, CS4), records were recollected. According to treatment stability, relapse group (RG, 19) and success group (SG, 12) were identified. Sagittal and vertical cephalometric and digital cast measurements were performed. Student’s t tests were used for statistically significant differences inter and intra groups. For discriminant analysis, relapse or success status was added to each patient’s T0 data. Results At T0, RG showed larger upper anterior transversal width (p = 0.0266), while at T1 the upper anterior length was shorter than SG (p = 0.0028). Between T1 and T0, both groups showed larger upper anterior and posterior transversal widths. SG had greater upper anterior (p = 0.0066) and posterior (p = 0.449) sagittal length. RG presented larger lower anterior (p = 0.0012) and posterior (p = 0.0002) transversal widths, while there were no differences in SG lower arch. Discriminant analysis provided two predictive variables with an accuracy of 80.6%: upper anterior length and upper posterior length. Conclusion A shorter and wider maxilla could be a predisposing factor for relapse and failure of the early orthopedic treatment of class III malocclusion patients. The absence of mandibular changes could be predictable for treatment success.

Transversal Width of Mandibular Bone and Neurosensory Disturbance after Bilateral Sagittal Splitting Ramus Osteotomy

Objective: This study evaluated the condition of mandibular cancellous and cortical bone on computed tomography (CT) images in order to investigate its relationship with the incidence of neurosensory disturbances (NSD) in the mental nerve region after bilateral sagittal splitting ramus osteotomy (BSSRO). Methods: BSSRO was performed on 58 lateral mandibles in 29 patients. From preoperative CT images, the width endpoints of the transversal bone were measured in region I immediately inferior to the mandibular foramen, region II in the mandibular angle region, and region III distal to the lower second molar. The incidence of NSD immediately after surgery and the residual NSD rate at 1, 3, and 6 months after surgery were investigated. The correlation between incidence of NSD in the mental nerve region and each transversal bone width endpoint immediately after and at 6 months after surgery was also comparatively evaluated. Results: The overall incidence of NSD immediately after surgery was 67.2% (39/58 sides) and the overall residual NSD rate at 1, 3, and 6 months after surgery was 53.4% (31/58 sides), 31.0% (18/58 sides), and 17.2% (10/58 sides), respectively. No significant differences were observed for any width endpoints of the transversal bone measured at regions I or III, but the transversal width of the entire mandible was significantly different in region II between patients with and without NSD at 6 months after surgery (p < 0.05). Conclusion: These findings demonstrate that the transversal width of the entire mandible may be an important factor in predicting NSD incidence.

Ukuran dan bentuk lengkung gigi rahang bawah pada orang Papua

Mandibular size and shape are important information especially in terms to figure out the right diagnosis and the type of treatment a patient should have. Human mandible is a key factor for occlusion adjustment, meanwhile maxilla is following the mandible’s position. Several studies show that the stability of mandibular shape and size determines the success of one’s treatment. Each ethnic group has a particular skeletal pattern as well as shape and size of mandible. This study was aimed to obtain the average size and shape of mandibles among local Papuans. This was a descriptive observational study with a cross-sectional design. Samples were obtained by using purposive sampling method. There were 35 local Papuans aged 18-25 years as subjects. Data were obtained by molding the subject’s mandible, therefore, each subject produced a study model. The study model was measured in sagittal (length) and transversal (width) views based on Raberin method. The results showed that the average lengths of local Papuans’ mandibular size in sagittal view (L31, L61, and L71 in a row) were 6.143; 26.463; and 43.743 mm meanwhile the average widths of local Papuans’ mandibular size (L33, L66, and L77 in a row) were 30.857; 50.971; and 60.971 mm. The mandibular shape of most local Papuans was mid shape (45.8%) meanwhile the least shape of them was pointed (5.7%)Keywords: dental arch size, dental arch shape, mandibular, local Papuan Abstrak: Ukuran dan bentuk lengkung gigi rahang bawah sangat diperlukan dalam menentukan diagnosis dan rencana perawatan yang tepat dalam bidang ortodontik karena rahang bawah merupakan faktor stabilitas oklusi, sedangkan rahang atas menyesuaikan pada rahang bawah. Beberapa peneliti menyatakan bahwa kestabilan bentuk dan ukuran lengkung gigi rahang bawah merupakan faktor stabilitas dari hasil perawatan. Setiap kelompok etnik cenderung memiliki pola skeletal dan ukuran lengkung gigi rahang bawah yang berbeda. Penelitian ini bertujuan untuk mengetahui rerata ukuran dan bentuk lengkung gigi rahang bawah pada orang Papua. Jenis penelitian yaitu deskriptif observasional dengan desain potong lintang. Subjek penelitian ini sebanyak 35 orang Papua berusia 18-25 tahun diperoleh dengan menggunakan teknik purposive sampling. Pengambilan data dalam penelitian dilakukan dengan mencetak rahang bawah setiap subjek penelitian dan didapatkan hasil cetakan berupa model studi. Model studi yang diperoleh diukur dalam arah sagital (panjang) dan transversal (lebar) berdasarkan metode Raberin. Hasil pengukurun diperoleh rerata panjang lengkung gigi rahang bawah pada orang Papua dalam arah sagital (yaitu L31, L61, L71) berturut-turut 6,143; 26,463; dan 43,743 mm, sedangkan rerata lebar lengkung gigi dalam arah transversal (yaitu L33, L66, L77) berturut-turut 30,857; 50,971; dan 60,971 mm. Bentuk lengkung gigi rahang bawah pada orang asli Papua paling banyak yaitu bentuk mid (45,8%) dan yang paling sedikit berbentuk pointed (5,7%). Kata kunci: ukuran lengkung gigi, bentuk lengkung gigi, rahang bawah, orang asli Papua

Dentoalveolar mandibular changes with self-ligating versus conventional bracket systems: A CBCT and dental cast study

OBJECTIVE: The aim of the present study was to compare dentoalveolar changes in mandibular arch, regarding transversal measures and buccal bone thickness, in patients undergoing the initial phase of orthodontic treatment with self-ligating or conventional bracket systems. METHODS: A sample of 25 patients requiring orthodontic treatment was assessed based on the bracket type. Group 1 comprised 13 patients bonded with 0.022-in self-ligating brackets (SLB). Group 2 included 12 patients bonded with 0.022-in conventional brackets (CLB). Cone-beam computed tomography (CBCT) scans and a 3D program (Dolphin) assessed changes in transversal width of buccal bone (TWBB) and buccal bone thickness (BBT) before (T1) and 7 months after treatment onset (T2). Measurements on dental casts were performed using a digital caliper. Differences between and within groups were analyzed by Student's t-test; Pearson correlation coefficient was also calculated. RESULTS: Significant mandibular expansion was observed for both groups; however, no significant differences were found between groups. There was significant decrease in mandibular buccal bone thickness and transversal width of buccal bone in both groups. There was no significant correlation between buccal bone thickness and dental arch expansion. CONCLUSIONS: There were no significant differences between self-ligating brackets and conventional brackets systems regarding mandibular arch expansion and changes in buccal bone thickness or transversal width of buccal bone.

The Influence of Pulley Deformations on the Shifting Mechanism of Metal Belt CVT

This paper is concerned with the shifting behavior of a metal belt CVT. The calculations are performed for the chain belt case by using a one-dimensional model of the belt: the radial thickness of the belt is neglected. The friction forces are modeled on the basis of the Coulomb friction hypothesis. The deformation of the belt, i.e., the variation of its transversal width, is shown to be negligible with respect to the variation of the local groove width caused by the elastic deformation of the pulleys and by the clearance in the bearings. The particular shape of the deformed pulley is described on the basis of Sattler model (1999) who showed that the variation of the groove angle and that one of the local groove width of the pulley can be easily described by simple trigonometric formulas. The paper shows that the characteristic behavior of the transmission during slow shifting maneuvers, referred to as “creep mode,” is caused by the bending of the pulleys, that is to say for rigid pulleys no “creep mode” can be observed. Moreover, the model shows that increasing the rate of change of speed ratio a transition from the “creep-mode” to the so called “slip-mode” behavior of the variator takes place, as experimentally observed.