Dental Specialties: Orthodontics (Continued)

There are three different classes of orthodontics:

1. Preventative Orthodontics
• this involves anything that could prevent the second and third level of treatment being necessary
• the dental team is concerns with preserving the normal bite of the teeth
• it is most important to maintain the arch length, particularly in the area of the primary molars.
2. Interceptive Orthodontics
• concerned with minor treatment that will control factors that may result in the need for the third level of orthodontic treatment
• includes any treatment used to manipulate growth for the natural elimination of crowding as well as extractions.
• this is the removal of permanent teeth, usually the first bicuspids, which are the teeth that are right beside the molars.
• a lot of orthodontist don't like to use this method because it is the removal of teeth, and its better to keep as many teeth in your mouth as you can.
3. Corrective Orthodontics
• include all active treatment that relocates or moves teeth in existing malocclusion.
• fixed appliances, braces, brackets, bands or removable appliances can be used to achieve this tooth movement.
• this is the last step, so the orthodontists will try as hard as they can to fix the problem preventative, or anticipative.

There are lots of dental instruments that are used to in orthodontic treatment, such as:

Band Pusher: used to push orthodontic bands into place during try-in and cementing phases
Band Bite Stick: to assist seating or placing of ortho bands for try-in or cementing
Band remover: to remove ortho bands from teeth
Bracket Remover: to remove anterior or postieor brackets from teeth
Three-Prong Pliers: to contour and bend light wire
Bird Beak Pliers: to bend and form ortho wire, to remove bonded bracket
Wire Bending Pliers: to bend arch wires
Ligature/Wire Cutters: to cut ligature after it has been tied to arch wire, to cut ligature tie to allow removal of arch wire
Contouring Pliers: to crimp and contour marginal edge of temp crown of stainless steel
Howe Pliers: to place and remove arch wires, to check for loose bands


Headgear

• is an ortho deice used to control and facilitate tooth movement by applying force from outside the mouth
• it is most affective when molars require stabilisation of distal (move towards the back of the mouth) movement.
• it is most commonly used in class II malocclusion. (see previous blogs)

Head gear consists of two parts:

1. Face bow (usually worn 10-12 hrs a day)
• used to connect the traction device to the bands on the molar teeth to be moved
• head gear tube: the inner bow of the head gear is inserted into these tubes on the band
• inner bow: attached to the buccal (tongue side) tube on the upper first molars
• outer bow: attaches tot he traction device
2. Traction Devices
• applies the outside force
• there are four different kinds available
1. High Pull
• fits around the top of the head to control growth of the upper jaw or retraction of anterior teeth
• it fits pretty high up on the head
2. Cervical Pull
• fits around the patients neck
• used when the upper first molars are stabilised or moved distally
3. Combination
• combination of high pull strap and cervical devices
• used to exert force along the biting surface and upward
4. Chin Cap
• combination of high pull and chin cap that fits on the lower jaw
• helps to control the growth of the lower jaw in patients with class III malocclusion.

Braces and How They Work and What They are Made Of

Four basic components make up braces:

1. Brackets: made from metal or ceramic. A bracket is attached to each tooth
2. Bands: are metal rings that are usually placed only on the back teeth
3. Arch wire: which is a think metal wire that runs from bracket to bracket and puts pressure on the teeth
4. Elastic Ligature Tie (a.k.a o-ring): is a small coloured elastic that holds the bracket on the arch wire. The ligatures are usually changed at each adjustment visit.
1. the brackets and bands are held on to the teeth by bonding material (glue)
2. accessories on the braces such as headgear tubs, hooks, loops, and steel ties are also often used for maxium control and tooth movement

How all this is able to move the teeth:

The teeth move when the arch wire puts pressure on the brackets and teeth. Sometimes, springs or rubber bands are used to exert more force in a specific direction. Braces exert constant pressure, which over time, more teeth into their proper positions

Your teeth are surrounded on top by gum tissue (also called gingiva). Under the gum tissue, the periodontal membrane (sometimes called the periodontal ligament or PDL) encases the bottom portion of the tooth. Next to that lies the alveolar bone.

When braces put pressure on your teeth, the periodontal membrane stretches on one side and is compressed on the other. This loosens the tooth. The bone then grows in to support the tooth in its new position. Technically this is called bone remodelling.

Bone remodelling is a biomechanical process responsible for making bone stronger in response to sustained load-bearing activity and weaker in the absence of carrying a load. Bones are made of celled called osteoclast (bone destroying cells)  and osertoblasts (bone forming cells).

Bone remolding works like this: increase the load on a bone and osteoclasts are created which break it down in response to the load. Remove the load and osteoblasts are created which create new bony cells. Repeat the process through repetitive motions (tightening of the braces) and eventually the done density increases

Your teeth are socketed in bone. A mentioned, surrounding each tooth is a PDL which attached it to the surrounding bone,

The PDL as a sort of messenger between teeth and surrounding bony sockets. Pressure between the PDL and bone causes the bone to create osteoclasts and breakdown the bone to restore the normal spacing between the teeth and bone. The corresponding tension on the PDL behind the movement causes the bone to create osteoblasts, effectively building new bone to fill in the difference and restore the normal spacing between teeth and bone. Not a whole lot of force is necessary, only some force which is not normally present.

This is where the brackets and archwire come into the picture - they generate the artificial force needed to create and sustain the pressure.
 

Dental Specialties: Orthodontics

Orthodontics is the dental speciality involved with he evaluation and treatment of the dentition in order to maintain a functional relationship of the dental arches and teeth to the supportive tissues of the face

The four goals of orthodontic treatment are:

1. to establish or maintain, as nearly as possible, a normal, functioning occlusion
2. to improve facial esthetics's where they are under control of the teeth
3. to eliminate any factor that might interfere with the growth and development of the upper (maxilla) and lower (mandible) jaws
4. to work with all other specialities in the rehabilitation of oral and facial deformities

The relationship of the maxillary first permanent molars to be mandibular teeth is the best indicator of occlusion. If the molars are missing, then the cuspid (K9 tooth) can be utilised.

There are four difference classifications of occlusion and malocclusion

1. occlusion : relationship between the maxilla and mandible
2. centric occlusion: standard or normal occlusion
3. functional occlusion: contact during biting
4. malocclusion: abnormal relationship, not central occlusion

• Class I - neutroclusion
• the mesiso-buccal cusp of the maxillary first molar occludes into the buccal grove of the mandibular first molar

you can see that the 3rd tooth from the back (a.k.a the 1-6) looks like it resting perfectly on top of the tooth below it, not touching the 2nd premolar or the 2nd molar.

• Class II -  distoclusion
• Mesio-buccal cusp of the maxillary first molar occlude into the space between the mandibular first molar and the second premolar - the mandible appears retrognathic (moved backwards)
• Division 1: the maxillary front teeth are all protrusive with a large over jet (how far the teeth jet out in comparison to the front bottom teeth) and usually a deep overbite (how much your front top teeth cover your bottom teeth

•  Division 2: the maxillary central teeth are retruded and usually the lateral teeth are protruded

• 
  Division 3: the front teeth have an open bite (when you bite down the front teeth do not touch). This is usually caused by thumb sucking, or thrusting your tongue to your front teeth when you swallow. 

The Pros and Cons of Amalgam, Composite Resin, Glass Ionomer, and Resin Ionomer

My teacher told me that a lot of people have intense ideas about amalgam's and all that, so I thought I would talk about the differences between most of the materials that you can use in a cavity.

Amalgam

Advantages

• strong, durable and stands up to biting force
• can be placed in one visit
• normally the least expensive filling material
• self-sealing with minimal to no shrinkage, and resits leakage
• resistance to further decay is high
• frequency of repair or replacement is ow
• only material that can be used in a wet environment (good for kids)

Disadvantages

• the FDA, CDC, and WHO have not found evidence of harm, but there are some people and groups who have raised concerns about the very low levels of mercury vapour released by amalgam
• amalgam scrap (waste left over after repairing a cavity) contains mercury and requires special handling to protect the environment
• can darken over time as it corrodes, but this does not affect the function of the restorations
• placement requires removal of some healthy tooth structures
• in rare cases, a localised allergic reaction such as inflammation or rash may occur.

Composite Resin

 

Advantages

• colour and shading can be matched to the existing tooth, composite is relatively strong material providing good durability in small to mid size restorations that need to withstand moderate chewing pressure
• generally used on front of back teeth
• usually complete in a single visit<
• moderate resistant to breakage
• often permits preservation of as much tooth as possible
• low risk of leakage if bonded only to the enamel
• does not corrode
• moderately resistant to further decay
• frequency of repair is low and moderate 

 Disadvantages

• can break and wear our more easily than metal fillings
• may need to be replaced more than metal fillings
• some times difficult and time consuming to place
• cannot be used in all situations
• more expensive than amalgam
• may wear faster then the enamel
• in rare cases there can be a localised allergic reaction

Its hard to see it because the dentist has matched the colour pretty good, but if you look carefully you can see the outline

Glass Ionomer 

Advantages

• tooth coloured filling
• can contain fluoride that may help prevent further decay
• min amount of tooth structure removed
• low incidence of allergic reactions
• usually complete within a single visit

Disadvantages

• low resistance to fracture
• it is limited to non-biting surfaces
• moderate costs (costs more than amalgam)
• as irt ages this material may become rough and plaque can build up on it
• can become dislodges
• rare localised allergic reactions

Resin Ionomer

Advantages

• tooth coloured
• can contain fluoride
• min amount of tooth structure is lost
• low incidence of allergic reaction
• may be used for short term fillings in there primary teeth
• may last longer than glass ionomer but not as durable as composite
• completed in one visit

Disadvantages

• limited use, not recommended for the biting surface of the teeth
• moderate cost (more than amalgam)
• wears faster than composite and amalgam
• rare localised allergic reaction

Dental Specialties: Pediatric Dentistry 2

Dental trauma to paediatric patients can be categorised into four different types: coronal fractures, concussion, fractured roots,  and avulsed teeth.


There is perhaps no single dental disturbance that has greater physiological impact on both the parent and the child than the loss of fracture of a child's anterior teeth.


It is extremely important for the dentist to preserve the vitality of injured teeth whenever possible and to restore them to their original appearance without producing additional trauma or endangering the integrity of the teeth.


The time is the most important consideration in the treatment of fractures or displacements and every effort should be made to see the patient in the office immediately.


1. Coronal Fracture

• Comes in 5 different classes
• Class 1: involves only the enamel - may only need smoothing
• Class 2: involves enamel and dentin - usually requires restoration
• Class 3: exposed the pulp - requires pulp capping, pulpotomy or endodontic treatment
• Class 4: involves the crown being fractured at the CEJ - requires extensive treatment or an extraction
• Class 5: is on the root below the epithelial attachment - extraction is required

class 1

class3

 class 2

2. Concussion

• A direct blow received by a tooth usually results in the compression of the root against the wall of the socket. It can also effect the blood supply to the tooth. The force of the blow may completely sever the apical blood vessels or may produce an apical edema and or hematoma.
• Treatment involves relieving the bite of the affected tooth and instructing the patient to avoid biting, chewing, or exposing the tooth to extremes of temperature. The tooth will then be evaluated at each recall appointment to determine if any permanent damaged was sustained.
• The tooth can become necrotic (non-vital)
• If someone in a contact sport gets a brain concussion it can affect the teeth as well.
• Concussion of the teeth occurs when the jaws close quickly and severely, not always in proper occlusion.
• Concussions with Displacement
• Traumatic Intrusion
• the tooth is forcefully pushed up into the gums
• Traumatic Extrusion
• the tooth is forcefully pull out of the gums but still present in the mouth.
• Lateral Luxation
• tooth is displaced either facially of lingually - early treatment would be t move the tooth back into place with pressure then create a splint to hold it secure until the bone and PDL repair.

3. Fractured Roots

• Is a small crack in the root of the tooth, kind of like a hair line fracture on a bone.
• An x-ray needs to be taken at different agulations to dected that fracture.
• A root fracture may simply require splinting of the tooth or it may be severe enough to require endodontic therapy.

4. Avulsed Teeth

•  Permanent teeth that have been knocked out can be re-implanted with varying degrees of success.
• The biggest factor that determines success or failure of re-implanting a tooth is time.
• Studies have shown that 90% success rate in teeth that are re-implanted within 20mins of the accident. The success rate dropped to 43% when the procedure was attempted after 90 mins.
• the patrient should be instructed to recover the tooth immediately, wrap the tooth in moistened gauze or keep the tooth mosit in saliva, water or milk and come to the office as soon as possible.

There are different kinds of discrepancies that can occur while the teeth are growing.
Supernumerary Teeth (Hyperdontia)

• Means extra teeth
• very rare
• mostly found in the reigion of the upper front teeth.
• if they are found in the midline they are called mesiodens
• these teeth frequently cause delay in erruption of permantent teeth or anomalies of position such as a diastema (space between the teeth) or rotations.
• they may cause the development of cysts that can damage or resorb roots of adjacent teeth.
• these teeth are usually removed to prevent crowding and shifting in the dentition

Unerupted (impacted) Upper K9 Teeth

• an impaction means that a tooth cannot fuly eurpt into the mouth
• the tooth most often associated with impaction is the wisdom teeth
• the second most affect is the cuspids, a.k.a K9
• the dentist may choose to surgically remove the tooth, or to expose the crown of the tootb and atempt to move it into position orthodontically.

Frenum Induced Diastema

• a frenum is a flap of skin that hold our lips or tounge to our gums
• when the frenum is very thick and fibrous it can cause a space between the upper and lower central inscisors.
• a frenectomy may be preformed to remove that thick tissue that otherwise would not allow those teeth to come into contact.

 this is an example of a very thick frenum that is causing the front teeth to separate.

 this is a normal frenum that is located at the bottom of our mouth underneath the tounge. If this is very thick a person can have a speech impediment also known as tounge-tied.

Ankylosis

•  when the roots of primary teeth lose their noraml attachment to the bone (small ligamnets) and become fused directly to the bone
• the tooth will eventually need to be extracted and a space maintainer is place in order to allow for proper eruption of the permantent tooth

 you can see that one tooth and farther down then the others, meaning it is more fused to the bone beacuse of the shorter ligaments.



Preliminary Impressions and Study Casts

Preliminary impressions materials are used in preparation for study and diagnostic casts, in the fabrication of mouth guards, whiting trays, temporary restorations, orthodontic appliances, custom impression trays, and as opposing cats in fixed and removable prosthetics. Alginate material is probably used more often than any other single type of impression material in dentistry.

 < that is a preliminary impression

which turns into....

 < these lovely impressions

One type of impression material is called irreversible hydrocolloid, and it cannot return to the sol state after it becomes a gel. Alginate is the irreversible hydrocolloid most widely used for preliminary impressions.

Sol= a liquid colloid

Gel= a colloid is its semi-hard rubbery consistency

Synerisis= happens when the impression material will lose water and begin to shrink if it is not in a humid environment

Imbibition= happens when the impression material gain extra water and expands (submerged in water)

Hydrocolloid (hydro=water, colloid= gelatinous substance) is the material, and a larger portion of it is water, therefore, making them very susceptible to dimensional changes.

The second type of preliminary impression material is called reversible hydrocolloid

•  1. Irreversible Hydrocolloid (or alginate)
• is supplied as a powder to be mixed with water to form a viscous gel
• once placed in the mouth, the sol forms an elastic gel through a series of chemical reactions. Once the gel has formed, the impression is removed from the mouth. The gel cannot be changed back to the sol consistency because a chemical reaction cannot be reversed.
• the chief ingredient is soluble potassium alginate. The irreversible hydrocolloid is obtained from sea kelp!
• it dissolves in water to form a viscous sol. To transform the sol to gel, you add calcium sulphate. A third soluble salt, trisodium phosphate is added to slow down the reaction
• you have two different kinds of irreversible hydrocolloid: normal set and fast set
• Normal set
• total working time is 2 mins
• 1 min mixing time
• 30 sec loading time
• 30 sec placing time
• Once placed in the mouth is is held up to 4 and a half mins until the firm gel consistency is reached
• ** BAD FOR GAGGERS
• Fast Set
• total working time is 1 min 15 sec
• 30 sec mixing time
• 30 sec loading time
• 15 sec placing time
• Once placed in the mouth it is held for 1-2 mins until firm gel consistency is reached.

• 2. Reversible Hydrocolloid (or agar)
• it is supplied as a gel, it is heated to change it to a sol and as it cools, it gels again. It changed back and forth from sol to gel by heating and cooling. This is rarely used in dentistry.

Mixing the alginate

Dental Specialties: Pediatric Dentistry

Paediatric dentistry is the speciality that is limited to the care of children from infancy to adolescents. What paediatric dentists focus most on is prevention, early detection, diagnosis and treatment.

A child's primary teeth are an essential part of the body in terms of growth and development. The primary teeth are present in the mouth from 6 months old until around 12 years old. An intact dentition during this time of active growth is essential for proper nutritional intake. Digestion and assimilation of food requires the breakdown that only chewing can provide.

The primary teeth and the chewing process help stimulate the growth of the upper and lower jaw. They are also essential in the development of sound production and speech.

Primary teeth also retain space in the dental arch for their permanent teeth. When the primary teeth are prematurely lost, the permanent teeth are more often impacted or erupted in lingual and buccal version.

<< this tooth is lingual version (buccal verison is the same thing but with the teeth moving more towards the cheek side of the mouth.

<< this is an impacted tooth

The primary teeth serve an esthetics function in children. There may be concerns with a positive self image when teeth are not present that should be, and when teeth are not lost on the same schedule as other children. Differences in what is considered "normal" appearance can be a source of teasing.

If a child has a lot of cavities, instead of just ripping the teeth out, the teeth should be restored such that all of the functions stated above can be adequately met.