Tuesday, October 9, 2012
Orthodontic springs
Comment on this discussion topic
1. Classify the tooth movement
2. Specify the magnitude of the force, the direction and point of application
3. Also provide an illustration with each movement. (scan in hand drawing or post photo of hand drawing)
Ruweda Dawids Materials 1
Functional forces appear against the tooth only during normal oral function. Thus, each time the patient swallows, the activator directs the forces of the muscle contractions against the teeth. Functional forces are not easy to control and do not move the teeth as rapidly as dissipating or intermittent forces. it should be remembered, however, that loose removable appliances are not designed primarily as tooth-moving appliances but rather as devices to affect the growing craniofacial skeleton.
Ruan Louw - Materials
It is possible to rotate a body without translation by two moments that are equal, paralle, in the opposite direction and noncollinear-an arrangement of forces called a couple. A couple always induces a pure
rotational tendency. A force applied at different points on the body will produce different movements, but it does not make any difference where a couple is applied. A momnet is one force producing a sliding
vector. A couple is two forces equal, parallel, opposite and noncollinear in producing a free vector.
Ruan Louw - Theory
Describe in detail the opposing view which claims that mandibular reposturing produces an orthopaedic effect.
Damien Storey - Materials
1. Active Components (Anchorage)
Screws
– Uni-dimensional screws
– Bi-dimensional screws
Wire springs
– Finger spring
– Z-spring
– Canine retractor
– Short labial arch.
Screws
– Expansion is 1 mm. per one full turn i.e. 0.25 mm. per quarter turn
– May be used for moving one tooth or group of teeth (usually more
than one tooth to be moved with a screw)
– Have different sizes and range of activation
– Useful only when a few millimeters of space is needed
– Usually jackscrews been used as active component
– Clasps for retention
Expansion screws
– For anterior Expn. of Max. incisors
– For simultaneous Expn. of maxillary
incisors anteriorly and posteriors laterally
(Y-plate).
– Y-plate can be modified for Tx. Of
unilateral x-bite
– Maxillary split plate (By post. teeth tipping
not by opening mid-palatal suture).
Active plate
• The simplest uses of an active plate is to correct a maxillary anterior crossbite.
• Posterior biteplane is necessary in adult to allow clearance for the upper incisor to move out of crossbite (½ crown or more is covered).
Active plate split in midline will expand constricted maxillary arch almost totally by tipping the posterior teeth buccally Not by opening mid-palatal suture. Therefore this appliance is not indicated for skeletal crossbites or dental expansion for more than 2 mm per side.
1. Springs
– Provide extra length of wire to increase range of action and resiliency
– Extra length can be provided in the form of coil (s), loop (s) or change configuration to provide extra length
of the wire
2. Retentive Components
– Adam’s clasp
– C-clasp (Circumferential clasp)
– Lingual extension clasp
– Ball clasp
3. Acrylic Base Plate
It is used as a vehicle to carry all
Removable Appliance components together.
• It is the Anchor tool for tooth movement.
• Use self-curing acrylic resin.
Damien Storey - Theory 1
Explain his hypothesis (claims) that a Class II Div. I can be gradually changed to a Class I relationship by an appliance that makes the patient bite with the lower jaw in a normal relationship to the upper jaw.
plastic covering the palate and the teeth of both arches, designed to advance the mandible several millimeters
for Class II correction and open the bite 3 to 4 mm. The original design had facets incorporated into the body of the appliance to direct erupting posterior teeth mesially or distally, so, despite the simple design, dental relationships in all 3 planes of space could be changed.5
In designing an inert appliance that fitted loosely in the mouth and, because of its mobility, transferred
muscular stimuli to the teeth, jaws, and supporting structures, Andresen had taken a decisive step in
orthodontic treatment. Although he had effectively redesigned Robin’s monobloc to correct Class II Division
1 malocclusions, he declared that he had no knowledge of Robin’s work at the time.
Andresen’s novel device was not initially well received. First, removable appliances were not much accepted at that time. Second, the profession was under the influence of Martin Schwarz, whose active plate was then a common form of removable—not functional— appliance. Finally, Andresen advocated extractions, although not necessarily in connection with activator treatment. And, in contrast to Angle’s concept of ideal occlusion that was then prevalent, Andresen advocated a more realistic “individual and functional gnathological optimum.” Thus he was subjected to the same type of ridicule that Tweed endured years later.2
In 1925, Andresen, then director of the orthodontic department at the University of Oslo, began developing
for the government a simple method of treating Norwegian children. He modified his retainer into an
orthodontic appliance, using a wax bite to register the mandible in an advanced position.
Damien Storey - Materials
2. elastic working range,
3. ease of manipulation by permanent deformation to desired shapes,
4. capability of joining individual segments to fabricate more complex
appliances,
5. corrosion resistance and biocompatibility in the oral environment,
6. Cost: The beta-titanium and nickel-titanium archwires are much more
expensive than the traditional stainless steel alloys, but they offer
unique properties that should be carefully considered when selecting
wires.
Ruan Louw - Theory 2
BTech - block exams 2012
Please remember to post your information and check for updates.
Mouton, Theory 2
2.1. The Reverse Bionator:
The Reverse Bionator is used to treat the problem when the lower jaw is too big or the upper jaw is too small, possibly meaning that the lower front teeth are positioned in front of the upper front teeth. The Bionator try to adjust these growth patterns holding the lower jaw back while trying to accelerate the growth of the upper jaw. Again this appliance uses the bodies internal forces to redirect forces thus adjust growth.
2.2. The Open Bite Bionator:
When the upper front teeth and the lower front teeth do not meet as they should this is called the front open bite. Possible caused by the tongue coming between the teeth too often or perhaps a habit like biting on something, perhaps some sort of a comforter or pencil, it might also be caused by growth patterns meaning the upper jaw and lower jaw are growing at angles meaning the teeth are correct in the jaws but the jaw bones are too far apart. The Bionator attempts to adjust the position of the tongue, trying to hold the tongue away from between the front teeth. This has the effect of causing an area of "low pressure" in the front of the mouth the attempt at equilibrium often and hopefully has the effect of closing the bite.
Monday, October 8, 2012
Chuma Bezana - Theory 1
Discuss the contributing roles of Andresen and Kingsley in the origin and development of the functional appliances Viggo Andresen Designed an inert appliance that fitted loosely in the mouth and by its mobility transferred muscular stimuli to the jaws, teeth and supporting structures. This appliance was initially a Hawley appliance. The Hawley appliance teamed up with HAUPL, and it was called the Activator because of its ability to activate muscles. So Andresen designed the first appliance to transfer functioning stimuli to the jaws, teeth and supporting tissues.Norman KingsleyHistorians claim that two different men deserve the title of being called "The Father of Orthodontics." One man was Norman W. Kingsley, a dentist, writer, artist, and sculptor, who wrote his "Treatise on Oral Deformities" in 1880. What Kingsley wrote influenced the new dental science greatly. The history of the functional appliance can be traced back to 1879, when Norman Kingsley introduced the "bite-jumping" appliance. The earliest evidence of functional orthodontics was an appliance designed by Kingsley, this dentally anchored appliance was meant to maintain the mandible in a forward position. A Kingsley appliance is considered a prototype functional appliance due to its continuous labial bow and bite planes extending posteriorly. Kingsley is known as the “father” of functional appliances.
Chums Bezana - Theory #2
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.
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.
Ruweda Dawids theory 2
Ruweda Dawids, Theory 1
The use of functional appliances offers a number of possibilities such as guiding skeletal growth and modifies the patient’s neuro-muscular behaviour. There are several functional appliances available and each of them has different functions. The different functional appliances and their functions:
• A Clark twin block appliance incorporates the use of upper and lower bite blocks to position the mandible forward for skeletal Class II correction.
• Headgear is an orthodontic appliance for the correction of Class II correction, typically used in growing patients to correct overbites by holding back the growth of the upper jaw, allowing the lower jaw to catch up. The headgear can also be used to make more space for teeth to come in. Headgear needs to be worn approximately 12 to 22 hours a day to be truly effective in correcting the overbite, and treatment is usually anywhere from 6 to 18 months in duration, depending on the severity of the overbite and how much a patient is growing.
• Orthodontic facemask and reverse-pull headgear The appliance is used in growing patients to correct under bites known as a Class III orthodontic problem by pulling forward and assisting the growth of the upper jaw, allowing the upper jaw to catch up.
• Herbst Appliance corrects overbites by holding the lower jaw in a protrusive position. This appliance is most commonly used in non-compliant patients. The Herbst appliance is very effective in correcting large overbites due to small lower jaws in patients that are growing.
• Fixed twin block removable appliance- high comfort level allows you to wear it 24 hours a day. This appliance actually is made up of two separate appliances that work together as one. The upper plate includes an optional expansion screw to widen your upper arch, if needed, as well as pads to cover your molars. The lower plate includes pads to cover your lower bicuspids. These two appliances interlock at an angle, and they move your lower jaw forward and lock it into the ideal position when you bite together. This new position, while temporary, will eventually become the permanent corrected position.
Sindile Gcelu, Material Science I
Explain why and also indicate the most desirable direction of force to be used with a functional appliance
Muir & Reed (1979) states that most multiband appliance systems make extensive use of extra oral forces. By comparison such forces are much less used with removable appliances. There is no good clinical reason why this should be so. Extra oral forces can readily be adapted for use in removable appliance orthodontics and can extend considerably the range of treatment which can be undertaken.
It is possible that heavy extra oral force applied for a substantial proportion of each day to a patient who is growing rapidly may have an orthopaedic effect. In addition to distal movement of teeth through bone there could be a restraint on maxillary growth. Headgear can be applied either directly to a removable appliance or indirectly to molar bands over which the appliance is clipped. Therefore, it is necessary to avoid patterns of headgear that delivers cervical traction (neck strap). It is recommended to use full headgear when applying force directly to a removable appliance.
Ref: Muir, J.D., Reed, R.T. 1979. Tooth Movement with Removable Appliances. USA: Pitman Medical. Pg 82.
Sindile Gcelu Theory 2
Without referring to any of the study material that deals with the historical and functional development of the Functional Appliance, give your own evaluation or opinion as to the effectiveness of these appliancesAccording to Graber & Neumann (1997) indicates that, the maximum power of the muscle activity is not as important as the orderly coordination of the manifold functions. Malocclusion thus must be regarded as a disturbance of that coordination, there may be a cause of the in coordinate activity. Of no minor importance may be the psychological component, producing Para functional influences by which the action of the finger, tongue, lips, cheeks, etc. will produce deformation.
Sindile Gcelu, Theory I
According to Balters’ philosophy, Class II malocclusions are a consequence of a backward position of the tongue, disturbing the cervical region. The respiratory function is impeded in the region of the larynx and there is thus a faulty deglutition. Alongside, there is mouth breathing.
Effectiveness of Bionator appliance:
• To accomplish lip closure and bring the back of the tongue into contact with the soft palate.
• To enlarge the oral space and to train its function.
• To bring the incisors into an edge-to-edge incision or relationship.
• To achieve an elongation of the mandible, which in turn will enlarge the oral space and make the improved tongue position possible?
• An improved relationship of the jaws, tongue, and dentition, as well as the surrounding soft tissue will result.
Cheryl Wolfe Theory 2
In order for normal development of the dental arches in the correct relationship to occur, favourable equilibrium of muscle forces between the tongue, lip and cheeks are essential. Malocclusion is therefore a result of persistant deviation from normal function. The purpose of functional therapy is therefore to change the functional environment of the dentition to promote normal function. The purpose of a functional appliance is to control the forces applied to the dentition by the surrounding soft tissues as well as the muscles that control the position and movement of the mandible. A new functional behaviour pattern is therefore established in order to support a new position of equilibrium by eliminating unfavourable environmental factors in a developing malocclusion. Functional thereapy also aims to unlock a malocclusion and stimulate growth by applying favourable forces that enhance skeletal development.
Clark, W.J. 1995. Twin Block Functional Therapy: Applications in Dentofacial Orthopaedics. London: Mosby-Wolfe. p31-32
Sunday, September 30, 2012
Posts to blog
Cheryl Wolfe Theory 1
Answer:
The position of the occlusal inclined plane is determined by the mandibular block and is important in the treatment of a deep overbite. The inclined plane should be clear of the mesial surface contact with the mandibular molar. This would allow the mandibular molar to erupt unobstructed, thereby reducing the overbite.
The inclined plane on the mandibular acrylic block is angled from the mesial surface of the 2nd premolar or deciduous molar at 70 degrees to the occlusal plane. In cases where the mandibular forward protrusions are inconsistent, the angulation may be reduced to 45 degrees in order for the block to occlude correctly.
The inclined block should extend distally to the buccal cusp of the mandibular 2nd premolar or deciduous molar, stopping short of the distal marginal ridge (this allows the leading edge of the inclined plane of the maxillary appliance to be positioned mesial to the mandibular 1st molar, thereby not obstructing eruption).
Buccolingually the mandibular block covers the occlusal surfaces of the mandibular premolar or deciduous molars, to occlude with the inclined plane on the maxillary twin block. The flat occlusal bite block passes forward over the 1st premolar, and becomes thinner buccolingually in the mandibular canine region. The thickness of the block can be reduced in that area in order to improve speech by allowing the tongue freedom of movement in the phonetic area. In order to avoid breakage, the lingual flange in the midline should be of adequate thickness.
Clark, W.J. 2002. Appliance design and construction. Twin block functional therapy: applications in dentofacial orthopaedics. 2nd ed. London: Mosby. p80.
Cheryl Wolfe Dental Materials
Answer:
When a body is rotated without translation by two moments equal, parallel, opposite and noncollinear, then this arrangement of forces are called a couple.
A moment is the tendency of a force to cause rotation of a body around a fixed axis. It is one force producing a sliding vector.
Moyers, R.E. 1980. Biomechanics of tooth movements. Handbook of orthodontics. 3rd ed. London: Year Book Medical Publishers Inc. p429.
Wednesday, September 26, 2012
Tuesday, September 25, 2012
BTech Orthodontics 2012
Welcome to the Orthodontics block for 2012. This block is aimed at improving your skill in orthos as well as maintaining the skill.
Please post comments forwarded to you via this media. I will also start a discussion on each of the ortho cases you have for classwork. A picture will be posted and you suggest treatment, each student will receive marks on their comments, whether you agree or disagree with another students treatment or not. You need to justify your comments.
Good luck
Sunday, August 19, 2012
To conclude Incisal guidance
This is influenced by the contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements. There are limitatons which influence the anlge of the Incisal guidance;
- ridge relation
- arch shape
- ridge fulness
- interridge space
- aesthetics and phonetics
Elaaborated on in Essentials of Prosthodontics by S. WInkler, between chapters 10 and 15
You will also find the information required on the topic Compensating curve.
The information provided here is some of the information needed you will find the rest in Winkler book.
Have fun. Good luck
Wednesday, August 15, 2012
To conclude - The type of posterior teeth used in lingualised occlusion for setting up complete dentures in balanced or non-balanced arrangement
LIngualised occlusion uses the maxillary lingual cusp as the dominant functional element, occluding against the corresponding portion of the mandiblar tooth. The posterior teeth selected for a lingualized occlusion differ depending on whethera balanced or non-balanced (monoplane type) arrangement is used. A balanced scheme usually involves a maxillary tooth with a sharply pointed lingual cusp to oppose a mandibular tooth with an uncomplicated occlusal table including only shallow inclines. For the no-balanced lingualized occlusion a monoplane mandibular denture tooth is selected. Porcelain teeth often are selected on the maxillary arch to maintain the sharpness of the lingual cusp; however, with the improved cross-linked resin denture teeth this may not be a problem. Numerous materials and designs have been suggested, although virtually any teeth can be used and may be customised by selective grinding to meet the needs of the patient. This is some of the information you will require. Other points was discussed in class lecture
To conclude - Why Lingualised Occlusion
Lingualised occlusion is a valuable occlusal concept, because it is adaptable to so many different clinical situations. LIngualised occlusion blends many of the ideals of the anatomic and mechanical schools of thought. For most cases it is entirely appropriate because a denture isa rigid piece of denture resin that must be acceptable anatomically while functioning under the mechanical and physical laws of the constantly changing oral envronment.
LIngualised occlusion is a simple occlusal scheme to teach and to learn. It can be modified to fit many different situations including any in which fully balanced anatomic teeth can be used and in all situations when non-anatomical teeth are used in balanced or non-balanced schemes. It may be used with complete and partial dentures, overdentures, immediate dentures and transitional dentures.
Monday, August 6, 2012
Type of teeth used for lingualized occlusion
Lingualized occlusion uses the maxillary lingual cusp as the dominant functional element which occludes against the corresponding portion of the mandibular tooth. The type of teeth selected for this type of occlusion can differ depending on whether you, the dental technician, is doing a balanced or a non-balanced occlusion arrangement.
Continue with the discussion....... Thank you.
Why Lingualised occlusion
We have discussed this matter in one of our lectures. One reason could be because the patient has a severely resorbed mandibular ridge, this type of occlusal concept is considered to be ideal for this type of situation. This mainly because it is adaptable to so many different clinical situations.
Please continue with the discussion and points of view.
Monday, July 30, 2012
Explain the difference between the factors that affect occlusion (comparing) natural teeth to artificial teeth
Example: artificial teeth are attached to one denture base for each arch and move as one unit, which means it is easily displaced by dislodging forces. Natural teeth move independently and migrate slowly into a favorable occlusion.
Post your comments for the rest of the factors.
To conclude discussion on immediate dentures and how youu would analyse the model for the denture design to allow comfortable insertion of the denture in the mouth by the dentist
When preparing a model for an immediate denturre and considering comfortable insertion of the denture, the technician needs to consider the undercut present and avalaible for retention. When the undercut is less than 1 to 2mm it is of no great significance because of the compressibility of the soft tissue and this compressibility will allow for the insertion of the denture. Undercuts composed entirely of soft tissue, as in the tuberosity areas, can be utilised for retention and will still be able to be inserted comfortably into the patients mouth.
With undercuts greater than 2mm, analysis of the model would indicate where the flange should be relieved or shortened. Vertical relief refers to the shortening ofthe flange (half flange) to avoid it entering the undercut area. Horizontal relief refers to a modification of a fully extended flange so that the degree of horizontal undercut engaged is reduced. A shortened or part flange is indicated in the anterior region where in the interests of conservation of alveolar bone it is considered undersirable to create room for a complete flange by alveoloplasty. Provided a part flange gives adequate retention of the denture it is in general to be preferred to excessive horizontal relief of a flange in order to allow the denture to reach the sulcus beyond a deep undercut area. As a result of horizontal relief of the border becomes thin and sharp,this could cause trauma to the sulcus. This situation is particularly so in the case of the mandibular denture, where the foundation is triangular when cross-sected. In this situation the denture tends to sink as a result of bone resorbtion during the first few months of extraction.
When creating horizontal relief the dental technician would need to block out the appropriate areas on the model with plaster, after surveying. When doing this the technician might be required to thicken the flange in order to avoid the flange becoming a knife-edge.
Please post a comment to indicate that you have noted the discussion.
To conclude the discussion on how the temporomandibular joint movements are accommodated or simulated by articulators
There are 3 types of adjustable articulators:
i, Non adjustable articulators - makes all the movements of the tmj, but all the movements are at fixed averages.
- example ; Hanua mate
- the simple hinge would also be an example - the only movement this articulator can simulate is an opening and closing action
i.e. vertical
ii, Semi adjustable articulator - these articulators are more accurate tthan the non adjustable articulators
- this articulator is set to the bite registration recorded by the dentist - even with this registration the articulator will not make or simulate the anitomical curvature of the tmj, nor are these movements exact.
-example; Hanau model H
- is able to move in transverse, vertical, saggital and horizontal planes
iii, Fully adjustable articulator - able to simulate the movements of the tmj more accurately than the other articulators
- bite registrations are constructed by means of a pantograph, which reconstructs the condylar and Bennett angles.
- this represents the exact anatomical movement of the tmj.
- more able to simulate the patient's anatomical conditions intransverse, vertical saggital and horizontal planes to a greater degree of accuracy than is the semi-adjustable articulator.
- example; Denar Mk II and the Pantograph
Please comment if you have noted this post.
Thank you
Friday, July 27, 2012
Concluding occlusl schmes and occlusal concepts
As discussed today, Occlusal schemes are the manner in which we would set posterior teeth for a Class I, II and III jaw relationship. What does this mean for you, the dental technology student,
When we set posterior teeth in a Class I jaw relationship the mandibular buccal cusps of the posterior teeth are set to occlude into the central fossa of the maxillary posterior teeth. In relation to the anterior teeth, you will find that there is a minimal amount of overbite and overjet.
When we set posterior teeth in a Class II jaw relationship (the mandible is smaller than the maxilla), which results in a larger overbite and overjet. We also find that the madibular first premolar makes less contact with the maxillary posterior teeth. Which means that the mandibular arch curves lingually earnier than the maxillary arch.
When we set posterior teeth in a Class III jaw relationship, the mandibular jaw is protruded in relation to the maxillary jaw. The anterior teeth are in an edge to edge relationship. We also find that the mandibular posterior ridges are more buccal in relation to the maxillary posterior ridges. With the mandible being larger than the maxilla the technician usually needs to set posterio teeth in a unilateral or bilateral cross bite relationship.
In essence the teeth are set in the same relationship.
Occlusal concepts are what was created in order to create retention and stability for an edentulous case, when the poterior teeth are set. These are:
Balanced occlusion
Lingualised occlusion
Monplane occlusion
Please feel free to add comments.
Wednesday, July 25, 2012
Surgical templates - why are they so important
Thursday, June 28, 2012
Occlusal concepts and occlusal schemes
Post links to articles you have found that discusses these topics and that you have found interesting.
Thursday, June 14, 2012
Articulators and the role they play
This item is for 2012 third yr students CPUT.
Post your comments on the blog
Monday, June 11, 2012
Important things to note when setting teeth for FF
1. Always set the mandibular teeth on the middle of the ridge for the stability of the denture
2. The maxillary anterior teeth should never be set further forward than 5 mm anterior to the mandibular ridge (anterior-posterior)
3. Always ensure that you have achieved proper centric occlusion
4. Always ensure that you follow the mandibular ridge curvature when setting the teeth for the curve of Spee and that this curve follows an equal curve towards the posterior on both the left and the right.
5. Always maintain the lip line
6. Always maintain the inter alveolar distance
7. The overbite and overjet should always be set according to your curve of Spee. If you curve of Spee is shallow then your overbite and overjet should also be shallow.
What else do you think are important factors to look at when doing an edentulous set up for class I.
Monday, June 4, 2012
Last post for this block
Class III, setting of anterior teeth
The difficulty is usually the selection of the anterior teeth which needs to span the gap on the mandibular ridge.
See Winkler for more information
Class III
See Winkler for more information
Severely resorbed mandibular ridge an a Class II
Note which teeth should be used and how the teeth should be set to accommodate for masticatory forces in order to not dislodge
Class II
First thing to consider would be the setting of the anterior teeth, by taking into consideration aesthetics.
We as dental technicians should remember to create denture stability with the setting of the posterior teeth, this for masticatory purposes.
When setting teeth special care should be exercised in the area of the neutral zone, surrounding tissues, phonetics and tongue space.
Posterior palatial seal
The relevance is for the retention of the maxillary complete denture. The retention and stability that is achieved from adhesion, cohesion and interfacial surface tension are able to resist only those dislodging forces that act perpendicular to the denture base. ............... The duration of the time that the partial vacuum acts on the tissue is extremely small and consequently little or no irreversible alterations to the underlying mucosa will take place.
Check Winkler for the bit in between
Saturday, June 2, 2012
Setting mandibular posterior teeth for a class II
The first premolar follows the arch contour established by the anteriors
Setting the lower anterior or posterior teeth to an exaggerated labial or buccal position in relation to the lower ridge will create an unfavorable lever action on the lower.
Anatomical, modified anatomical and non anatomical teeth can be used:
Selection of the occlusal form is based on ......
Read further in Winkler
Do not be concerned about the mark allocation concentrate on the required info