Preventitive Procedures: Enamel Sealants

An enamel sealant or a pit and fissure resin sealant is an organic polyer, which bonds to the enamel surface mainly by mechanical retention. Because sealants usually contain no therapeutic ingredient (fluoride, etc), their success lies in their ability to adhere firmly to the enamel surface. The sealant acts as a physical barrier to prevent oral bacteria and their nutrients from collecting within a pit or fissure and creating the acid environment essential to the initiation of dental decay.

Current Philosophies On Why Sealants Are Used

• Sealants prevent tooth decay (cavities), and since tooth decay is a chronic disease affecting all age groups, and oral health is vital to general health


• Fluoride both systemic and topical application, help fight decay on tooth surfaces, but it is least effective in the pits and fissures. Sealant placement adds to the preventative purpose that fluoride provide, and when combined the benefits of each are enhanced
• Teeth are not equally susceptible to decay
• newly erupted permanent molars develop decay faster than newly erupted permanent incisors, cuspids and premolars. Thus causing a higher percentage in the molars
• If a sealant is properly applied, it prevents the accumulation of bacterial plaque and acids, and therefore decay. Sealants have been shown to reduce decay by 10%

The Purpose of Applying Sealants

Using sealants also has a number of long-term ramifications such as:

• they prevent bacteria, bacterial bi-products and food debris from entering pits and fissures
• sealants plug pit and fissure depressions, thus making cleaning by tooth brushing easier
• aid in preventing the destruction of vital tooth tissue due to decay
• beneficial in preventing the expense and potential tooth loos associated with decay (from a filling)

Advantages of Applying Sealants

• significantly reduce a child's risk for having untreated dental decay
• it is possible to achieve 100% retention if periodic reapplication is done

Disadvantages of Applying Sealants

• the life of the sealant is determined by the operators skill and the clinical conditions at the time of placement
• very technique sensitive. Insufficient rinsing, drying, incomplete acid-etch, airline contamination, and placement of insufficient coating, can all contribute to an inadequate seal.
• new areas of plaque retention can be created by sealants improperly placed.

Chemical Composition of an Enamel Sealant

Bis-Gma           +        MMA    +       Accelerator       =     SEALANTS

Bisphenol A -           Methyl               benzoylperoxide

Ethylene glycol        methacrylate      or diketone

dimethacrylate          monomer

The Bis-GMA resin is sometimes strengthened by adding a filler particle, such as glass, porcelain or quartz, then it is known as "partially filled". However most sealants are "unfilled" and contain no filler materials.

When an unfilled sealants is used, "high spots", which are inevitable, are worn away by the patients own occlusion in a few days and therefore, does not require an adjustment. Partically filled sealants will need to be ajusted.

Some brands contain fluoride that is released after polymerization (hardening)

Differences between specific brands of sealant material may include:

• method of polymerization
• presence of fillers
• presence of colouring agents
• presence of fluoride

Polymerization

Defined as the process of changing a simple chemical substance into another compound having the same elements, usually the same proportion, but with a higher molecular weight.

It is simply the acts creating a polymer from two or more monomers. As it specifically relates to this procedure, chemical or light-induced polymeriaztion methods have been used to transform a liquid or malleable semi-liquid into a durably hard, solid sealant.

Advantages Of Coloured Sealants

The hardened sealants may be: clear, white, tinted (yellow) or pink

•  may allow for more accurate placement
• provides a better visualisation and more accurate assessment of their presence for patients upon self inspection and as well as for operator visits
• decreases exam time during the recall appointments
• it becomes an easier concept to explain to patients or parents as being as decay preventative restoration

Teeth That Would Benefit From Sealants

• the biting surfaces of the primary molars
• the biting surfaces of the permanent molars
• surfaces where other pits and fissures are present.

Generally sealants are indicated for children and teens, but adults are also sealants candidates if they are judged to be at risk for pit and fissure decay.

The most two most important considerations when selecting teeth for sealants are: 1 the morphology of the pits and fissures should be deep, 2 the teeth must be sufficiently erupted so that a dry field can be maintained during isolation.

Prosthodontics: Removable Prosthodontics (Dentures)

Prosthodontics is the branch of dentistry pertaining to the restoration and maintenance of oral function, comfort, appearance and health, by the restoration of natural teeth or the replacement of missing teeth with artificial substitutes.

Any artificial replacement of a missing body part, including teeth, is known as a prosthesis or prosthetic.

Complete Denture
A complete denture or a full denture is a removable prosthetic that replaces all teeth in the mouth. Facial muscles aid in the control and function of the denture. No matter how much care is take in the fabrication of a complete denture, it will never allow the same function as the natural dentition. Often success or failure of a denture is dependant on the tolerance the patient has for the difference. A complete denture is held in by the alveolar bone and oral mucosa, surrounding tissues and palatal structures.

Careful diagnosis and treatment planning are just as important in the fabrication of complete dentures as they are in any other dental treatment. The treatment plan must consider the need for surgery and the specific design of the appliance. Every aspect of the patient health must be considered; age, habits, jaw relationship, saliva flow, occlusion, dietary habits, aesthetic expectations, alternatives to complete denture, oral hygiene,and tori, are all useful in determining the appropriate plan for the patient.

Components of a Complete Denture

• Base: fits over the alveolar ridge and gingival tissue. It is usually made of tissue coloured acrylic. If additional strength is needed a wire mesh can be embedded in the acrylic.
• Flange: extends into the vestibule are facially as well as lingually or palatially.
• Post Dam: often described as the posterior palatal seal on a upper jaw complete denture. It extends across the entire palate behind the maxillary tuberosity.
• Denture Teeth: the teeth which are used in a complete denture can be made out of acrylic or porcelain. They are set to an acrylic base. A full denture will have 14 teeth in an arch as the wisdom teeth are excluded (there's usually no room for them anyways)

Partial Dentures
A removable prosthesis that replaces one or more teeth in an arch is referred to as a partial denture. There are many different designs, depending on the number of teeth that need to be replaced, and the strength of the remaining teeth, and weather the partial denture is to be a short term or long term replacement.

Components of a Partial Denture

• Partial Dentures
• Acrylic partial dentures are appropriate for a short term replacement of one or two teeth. The base is made from tissue coloured acrylic with artificial teeth attached. Thin wire clasps partially encircle teeth necessary to hold the acrylic partial in place.

• Cast partial dentures are considerably stronger, as there is a metal framework under and around the artificial teeth. The metal framework has the following components:
• Retainers (clasps): the clasps that surround the natural teeth to hold the partial denture in place
• a precision attachment can be placed instead of using a clasp to help prevent recurrent cavities around the clasps. A receptor is inserted into a crown on the abutment tooth and a matching component place into the partial denture.
• Connectors: the bars that connect the left and right sides of the partial denture
• Lingual connector: on the lower jaw, this is located inferior and lingual to the anterior teeth.
• Partial connector: on the upper jaw it may cross the palate
• Saddle or Denture base connectors: metal framework that will support the artificial teeth and denture base acrylic.
• Minor connector: links the major connectors to other areas of the metal framework.
• Rests: the part of the framework, extending from the retainers or connectors that will limit the seating of the partial denture. The rests sit on the occlusal or lingual surface of the teeth and help distribute the force of occlusion to the teeth rather than the alveolar ridge.
• Denture Base: tissue coloured acrylic that will retain the artificial teeth and enhance the aesthetics of the partial denture by covering the saddle portion of the framework and extending into the vestibular area.
• Artificial Teeth: come in a variety of shades and sizes that allow the partial denture to closely match the natural teeth. Usually, they are made of acrylic, but in some cases, porcelain teeth may be used.

Immediate Dentures
An immediate denture is one that is placed into the patients mouth at the same appointment as the extraction of teeth occurs. The new denture acts as a bandage during the healing phase. Try-in and evaluation of appearance are not possible in this situation.


Overdentures
Overdentures have more stability than complete dentures, and do not have visible clasps and retention issues associated with partial dentures. The alveolar ridges resorbs at a slower rate when the K9 teeth are retained for overdentures than when entirely edentulous (no teeth), also contributing to greater stability

The K9 teeth will need to be altered in circumference and height to enable the denture to completely cover them. A this reduced the thickness of the enamel, the remaining tooth structure must be covered by a thin metal covering known as a coping.

More often then not, the K9 teeth will have root canal treatment prior to coverage with coping to prevent any sensitivity.

Implants can also be put in to give retention, this is a lot more comfortable. The dentures snap onto the implants and are held firmly in place, but this is very expensive.

^ the K9's have been left                                                    ^ implants

Dental Specialties: Esthetic Dentistry

Aesthetic dentistry is the field of dentistry concerned with the appearance of teeth; their form, shape, colour and arrangement. Procedures which may be considered aesthetics include whitening, veneers, orthodontics for cosmetic reasons, crown and bridge procedures and some periodontal treatments that reshape tissue.


Vital bleaching, a.k.a vital tooth whitening, is a method of lightening the colour of the surface enamel without removing any tooth structure.


Some common reasons for tooth discolouration are: darkening of the teeth with age (thinner enamel, and/or thicker dentin), outside (extrinsic) stains from coffee, tea, smoking, or pigmented food, or light inside (intrinsic) stains from fluorosis (ingestion of too much fluoride while a child) or antibiotic therapy.


As the teeth are still vital (alive), the whitening agent is applied to the enamel surface. The products used for vital whitening of teeth, enable oxygen to enter the microscopic interprismatic spaces to lift away discolouration.


If you are going to be receiving treatment, you must be made aware that the results are not permanent, extrinsic stain can return within 3-5 years depending on the cause.


The success of whitening procedures is dependent upon the following factors: cause or type of discolouration, degree or intensity of the discolouration or stain, bleaching agent selected, length of exposure of the tooth to the whitening agent, technique used for whitening the teeth, presence of cracks in the surface of the tooth, presence of any restoration in the tooth (composite, bridge, crowns, dentures cannot be whitened)


Before a patient has this procedure done, you must be screened first. This includes insuring that they do not already have sensitivity to any of the bleaching agents, and the patients teeth must be cleaned completely because stains can stick to the plaque and calculus on the teeth. Also the patient must have reasonable expectations, and realise that your teeth may not look like a celebrity's teeth, because everyone has a different bite, and arch size.

Chemical Agents Used In Tooth Whitening

Two of the most common agents used in tooth whitening products are hydrogen peroxide and carbamide peroxide. When these products are applied to the teeth the peroxide will break down into oxygen molecules which can work their way through the dentinal tubules and into the tooth where they attach themselves to stain particles and effectively break the stains apart. The reason that stains make the teeth look dull is because light is not able to shine effectively through the teeth. When the peroxide agents break the stains apart there is less blockage of light which makes the teeth appear brighter and whiter.

• Hydrogen Peroxide
• strong oxidizing agent
• readily decomposes into water and oxygen
• can penetrate enamel and dentin and may produce reversible pulpitis (sever sensitivity)
• precautions must be used to protect the patients eyes, face, intraoral soft tissues and clothes from the solution.
• solution is applied to the teeth in either liquid or gel form and in strengths varying from 5%-35%
• Carbamide Peroxide
• weaker oxidizing agent, but is more stable then hydrogen peroxide
• applied in either liquid or gel form
• strengths varying from 10%-15%
• also contain a thickening agent that increases adhesion of the gel to the tooth, which prolongs exposure
• not as much damage to the tooth

Tooth Paste Whiteners/Strips

• contain silica, aluminium oxide, calcium carbonate, or calcium phosphate particles
• these may only debride the surface of the tooth to remove extrinsic stains
• will also cause some sensitivity
• whitening strips contain a whitening gel and are applied to the surface of the teeth to be whitened
• the strip must reamain on the teeh for the recommended time to be effective
• the procedure is often repeated for a few days or weeks at a time



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