Provide a full description of the position, extension and angle of the inclined plane of the mandibular acrylic block with reference to treating or correcting a deep overbite condition.
Twin Blocks are simple bite-blocks that effectively modify the occlusal inclined plane using upper and lower bite blocks which engage on occlusal inclined planes.. Wearing bite-blocks is rather like wearing dentures and patients can eat comfortably with the appliances in place. The upper and lower bite blocks engaged mesial to the 1st permanent molar at 90° to the occlusal plane, when the mandible postured forward. This positioned the incisors edge-to-edge with 2 mm vertical separation to hold the incisors out of occlusion. The patient had to make a positive effort to posture the mandible forward to occlude the bite blocks inprotrusive bite.The inclined plane on the lower bite-block is angled from the mesial surface of the second pre-molar or second deciduous molar at 70° to the occlusal plane. This places the leading edge of the inclined plane on the upper appliance mesial to the lower first permanent molar, thus keeping a provision for the unhindered eruption of the lower 1st permanent molar. Mesially, the lower bite block extends up to the canine region with a flat occlusal surface.Twin Block appliance acrylic extends to cover the incisal edges of lower incisors. This helps to avoid tipping of the lower incisors and improve in retention. Torquing springs were used to control position of the upper incisors.
Monday, October 8, 2012
Chums Bezana - Theory #2
Chums Bezana - DMaterials
Explain, in short, why heat treatment is sometimes used in stress relieving stainless steel orthodontic wire.
Heat treatment is generally applied to orthodontic stainless steel wires to relieve the stresses that result from their manipulation by orthodontists. The quality and thickness of the oxide films formed on the surface of heat-treated wires can vary, and it is believed that these oxide films can influence the properties of heat-treated wires. It is also used to improve the wires elasticity, stability of the dislocations and the shape of the wire.
Pongolo Theory
Name three types of Bionator designs which are used to correct various malocclusions or oral conditions, and clearly explain the correction for which each type of appliance is used.
The three bionator designs are the basic bionator with a basic wire, a tongue screening bionator with palatal wire and a class III bionator in contract to the two previous types mentioned. The basic bionator is employed in Class I and Class II division cases. The tongue screening bionator is used in cases where there is an open bite or tongue dysfunctions are present. The Bionator Class III appliance is used for correcting Class III malocclusions. It can be used to modify or distract the mandible as well as open the bite, close the bite, or hold the vertical dimension constant.
Pongolo Theory
Give a concise explanation of the mechanism of bone remodeling in response to functional stimuli during mastication.
During mastication, forces are transmitted through the teeth to the alveolar bone and to the underlying basal bone. Most of these forces are vertical, but some are transverse and Anteroposterior. The external surface of the maxilla and mandible is modified precisely by function to absorb the forces of occlusion. Well-defined ridges of bone are specifically designed to absorb and transmit these force vectors.Mastication is a function that involves the whole face and even part of the cranium. Considerable forces are applied through the muscles of mastication to the teeth and underlying bony structure to influence both the internal and external structure of the basal bone. It is this natural mechanism of bony remodeling by occlusal force vectors that forms the basis of functional correction by the Twin Block technique. The forces of occlusion that are applied during mastication are harnessed as an additional stimulus to growth.
Siphon Pongolo DMaterials
Stainless steelThe main objective of a dental laboratory is to manufacture clinically acceptable devices for a profit. As a laboratory owner, it is essential to select the most affordable, yet convenient materials. Stainless steel is less expensive than nickel-titanium and since it is the most commonly used orthodontic wire, it would be most convenient for a laboratory to utilize. The main objective of orthodontic treatment is to obtain good aesthetics in the least amount of time. It has good formability, thus wires can be bent to required specifications. Stainless steel has been clinically proven to be biocompatible in the oral cavity therefore it will harm or cause infectious developments in the patient’s mouth. Stainless steel orthodontic wires can be soldered and weldered, unlike nickel-titanium which is essential when attaching auxiliaries or when fabricating certain removable appliances such as the space maintainer or a distally extended labial bow. Both nickel-titanium and stainless steel are resistant to corrosion, owing to the oxide film characteristic of their surface topography.
Sipho Pongolo Theory 1
Wolff’s law of the transformation of bone “forms the basis of functional correction of the Twin block technique.
The internal and external structure of bone is continuously modified throughout life by the process of bony remodeling. The sensory feedback mechanism helps the bony remodeling process to address the changing requirements of function in dentofacial development. Occlusal forces transmitted by the muscles of mastication through the teeth to the underlying bone provide a proprioceptive stimulus to influence the external form and internal trabecular structure of the supporting bone.Unlike the other connective tissue, bone responds to mild degrees of pressure and tension by changes of this nature. These changes are achieved by means of resorption of existing bone and deposition of new bone. This may take place on the surface of the bone, under the periosteum or, in the case of cancellous bone, on the surfaces of the trabeculae. In this respect, bone is more plastic and adaptive than any other connective tissue. The internal and external structure of bone is modified my functional requirements to enable it to withstand the physical demands made upon it with the greatest degree of economy of structure. The principle is exemplified in Wollf’s law of transformation of bone. The architecture of a bone is such thatit can best resist the forces that are brought to bear upon it with the use of as little tissue as possible.
M.K Mouton Theory 1
In the first phase of the activator construction, after the common clinical procedure, the construction bite in a eugnathic relationship is taken, with the mandible forced forward until the upper canine between the lower canine and the first lower premolar relationship is achieved. The construction bite is taken with the mandible protruded 4-6 mm and interocclusal space of 2
3 mm above physiological rest in the molar region. During the procedure of construction bite taking, great care should be exercised regarding the middles of the jaws. After this, the trial of the wax activator follows to check the relationship between the jaws and possible corrections
The activator appliance consistes of an acrylic intermaxillary block with upper labial arch (0.8 mm) which passively touches the incisal third of the upper incisors. The acrylic is then extended to cover the incisal third of the mandibular incisors in order to prevent the labial tipping of these teeth. The acrylic then extends to the lower lingual sulcus to provide stability and anchorage. At control visits, the acrylic will be trimmed behind the upper front teeth, which is in concordance with treatment of protruded incisors in the sense of their retrusion and overjet reduction. The interocclusal acrylic in the molar and premolar region is not trimmed until the improvement of the sagittal jaw relationship is achieved, in cases with associated deep bite. In the last phase, the acrylic is trimmed selectively according to the occlusal needs of the lateral teeth. Patients are advised to wear the appliance 15 hours a day.