"Safe zones": a guide for miniscrew positioning in the maxillary and mandibular arch.

The aim of this study was to provide an anatomical map to assist the clinician in miniscrew placement in a safe location between dental roots. Volumetric tomographic images of 25 maxillae and 25 mandibles taken with the NewTom System were examined. For each interradicular space, the mesiodistal and the buccolingual distances were measured at two, five, eight, and 11 mm from the alveolar crest. In this article, measurements distal to the canines are presented. In the maxilla, the greatest amount of mesiodistal bone was on the palatal side between the second premolar and the first molar. The least amount of bone was in the tuberosity. The greatest thickness of bone in the buccopalatal dimension was between the first and second molars, whereas the least was found in the tuberosity. In the mandible, the greatest amount of mesiodistal dimension was between first and second premolar. The least amount of bone was between the first premolar and the canine. In the buccolingual dimension, the greatest thickness was between first and second molars. The least amount of bone was between first premolar and the canine. Clinical indications for a safe application of the miniscrews are provided, as well as the ideal miniscrew features.

Treatment of skeletal open bite with a device for rapid molar intrusion: a preliminary report.

An open bite is one of the most difficult malocclusions the clinician has to deal with. In recent years, interest has increased regarding mechanics that reduce dependency upon patient compliance for success. Some patient-independent mechanism for molar intrusion or vertical control is desirable. The rapid molar intruder (RMI) appliance consists of two elastic modules that are secured to orthodontic bands on the upper and lower first molars. Vertical forces from these modules typically produce intrusion of the permanent molars in four to six months. The RMI modules may be used in the mixed dentition or incorporated in full-fixed mechanics in the permanent dentition. To avoid buccal flaring of the molars, these modules should be attached to a transpalatal arch and a mandibular lingual arch. Case reports are provided to stimulate interest in further investigation of the properties of this appliance.

A comparison of two maxillary molar distalizing appliances with the distal jet.

AIMS: Previous studies on maxillary molar distalization have usually concentrated on only one appliance and featured small sample sizes. The purpose of this retrospective study was two-fold: (1) to determine the skeletal, dental, and soft tissue effects of 3 molar distalization appliances, 2 of which do not depend upon patient compliance (ie, distal jet and Greenfield molar distalizing appliance) and 1 that does (ie, sagittal appliance combined with cervical headgear); and (2) to determine differences in treatment effects among the 3 appliances. METHODS: Pretreatment and post-distalization cephalometric radiographs were obtained for each appliance (14 females and 11 males for the distal jet; 12 females and 13 males for the Greenfield molar distalizing appliance; and 17 females and 13 males for the sagittal appliance with headgear). RESULTS: Pretreatment to transition evaluation showed significant distal movement of the first molars for the distal jet (3.4 mm), the Greenfield molar distalizing appliance (3.9 mm), and the sagittal appliance with headgear (2.1 mm). Distal tipping of the first molar was seen in all samples, but significantly more so in the Greenfield molar distalizing appliance (6.5 degrees +/- 6.6) and the sagittal appliance with headgear (13.5 degrees +/- 8. 1) than in the distal jet (3.2 degrees +/- 2.8). CONCLUSIONS: Maxillary molar distalization was effective using the distal jet, the Greenfield molar distalizing appliance, and the sagittal appliance with headgear, but better control of molar bodily movement was reported with the distal jet.

Mechanical properties of three different commercially available miniscrews for skeletal anchorage.

BACKGROUND: During the last 5 years, anchorage control with self-tapping miniscrews has become an important part of the clinical management of orthodontic patients. Yet, no studies have been performed for measuring mechanical properties of the currently available systems. OBJECTIVES: The purpose of this study is the evaluation of mechanical properties of three commercially available self-tapping screw systems used in orthodontic treatment. MATERIALS: three systems with a 1.5 mm diameter and 11 mm length screw (Leone, Firenze, Italy; M.A.S. Micerium, Avegno, Italy; Dentos, Korea) were examined. The results compared the resistance to bending, torque, pullout of each screw and the insertion moments needed to screw down each sample. CONCLUSIONS: All three miniscrews have mechanical properties that contribute to their safe use as skeletal anchorage in orthodontics. Although stainless steel has demonstrated to be more resistant to failure than titanium, its overall performance as material for miniscrews could be inferior to titanium. In order to facilitate the insertion, the asymmetric profile of the thread should be preferred to the symmetric cut. The ratio between the diameter of the drill and the diameter of the corresponding miniscrew is pivotal for the successful implantation and resistance of the miniscrews. Looking at the mechanical properties evaluated in this study, a cylindric shape of the screw is better than a conic one. The conic shape could be preferred in case the site of insertion is iterradicular and therefore limited to 2.5-3.5 millimetres.

Evaluation of maxillary molar distalization with the distal jet: a comparison with other contemporary methods.

Maxillary molar distalization is an increasingly popular option for the resolution of Class II malocclusions. This communication describes the effects of one particular molar distalizing appliance, the distal jet, in a sample of 20 consecutively treated and growing subjects (11 females, nine males; mean starting age of 13) and compares these effects with those of similar devices. Pre- and postdistalization cephalometric radiographs and dental models were analyzed to determine the dental and skeletal effects. The distal jet appliances were constructed using a biomechanical couple to direct the distalizing force to the level of the maxillary first molar's center of resistance. The distal jet was the only appliance used during the distalization phase of treatment. Examination of the cephalometric tracings demonstrated that the crowns of the maxillary first molars were distalized an average of 3.2 mm into a Class I molar relationship. In the process, the first molars were tipped distally an average of 3.1 degrees, however, the amount of tipping in each case was influenced by the state of eruption of the second molar. In subjects whose second molars had erupted only to the level of the apical third of the first molar roots, distal tipping was almost twice that seen when the second molar had completed their eruption. Anchorage loss measured at the first premolars averaged 1.3 mm, but the crowns tipped 3.1 degrees distally because of the design of the appliance. The maxillary incisors were proclined an average of 0.6 degrees with minimal effect on the mandibular plane angle and lower facial height. This study suggests that the distal jet appliance effectively moves the maxillary molars distally into a Class I molar relationship with minimal distal tipping, however, some loss of anchorage is to be expected during this process. The distal jet appliance compares favorably with other intraoral distalization devices and with mechanics featuring mandibular protraction for the resolution of patients with Class II, despite the fact that these types of mechanics address different jaws.

Clinical applications of the Mini-Screw-Anchorage-System (M.A.S.) in the maxillary alveolar bone.

AIMS: anchorage control with self-tapping screws has become an important part of the clinical management of the orthodontic patients. Mechanical resistance and sites of insertion of miniscrews as orthodontic anchorage are critical to ensure successful outcomes. Aim of this clinical study was threefold: 1) to measure the mechanical resistance of the M.A.S., 2) to evaluate if the alveolar areas usually selected for mini-screws placement are adequate, 3) to illustrate the most frequent clinical application on the maxillary alveolar bone. METHODS: two methods were chosen to test these screws mechanically, representing two potential modes of failure during insertion or removal: torsional strenght and bending strenght. Three-dimension images of fifty maxillas have been retrieved from a group of 200 patients, age range between 20 and 40 years with a new type of tomogram called Newtom System. For each area mesio-distal and labio-lingual measurements from four horizontal cuts made at 2-5-8-11 mm below the bone-crest have been evaluated. RESULTS: the mean value of resistance to breakage in torsion is of 48.7 N.cm (around 5 Kg) for the miniscrew of 1.5 diameter, while the mean value of resistance to breakage in torsion is of 23.4 N.cm (around 2 Kg) for the miniscrew of 1.3 diameter.. The mean value of resistance to breakage in flexion is of 120.4 N (around 12 Kg) for the miniscrew of 1.5 diameter, while the mean value of resistance to the flexion is of 63.7 N (around 6 Kg) for the miniscrew of 1.3 diameter. On the maxillary alveolar bone the highest amount of bone was in mesio-distal dimension between 6 and 5 on the palatal side (minimum 1.9 mm at -11 mm cut; maximum 5.5 mm at -5 mm cut). The smallest amount of bone was in the tuber (minimum 0.2 mm; maximum 1.3 mm). Examination of the labio-palatal dimension demonstrated similar high thickness between 5-6 and 6-7 (minimum 3.7 mm at -11 mm cut; maximum 13.2 mm at -2 mm cut). The smallest amount of bone was recorded on the tuber (minimum 0.6 mm; maximum 4.1 mm). The following clinical applications are described: Closure of the extractions space, Symmetric intrusion of the incisors, Correction of the cant of the plane of occlusion and of the dental midline, Molar intrusion of one or two teeth, Molar distalization with the Distal Jet and miniscrews, Molar mesialization, Intermaxillary anchorage. CONCLUSIONS: the mechanical resistance of the miniscrews M.A.S. is suitable for their use in orthodontics. The best anatomical zones for their implantation are the interradicular spaces mesial to the first maxillary molars. From our experience to date, the miniscrews are a reliable and convenient system for skeletal anchorage when compared with other more invasive osseo-integrated systems.

Noncompliant treatment of skeletal open bite.

The purpose of this article is to illustrate the effects of the rapid molar intrusion appliance, a treatment alternative that does not require patient compliance, for counteracting excessive vertical dimensions in growing patients and adults. The rapid molar intrusion appliance has 2 elastic modules that are secured on the maxillary and mandibular first-molar tubes. It is used in combination with maxillary and mandibular soldered lingual arches. Patient acceptance is good, and the patient's only responsibilities are to keep the appliance clean and avoid breakage.