An Introduction to the Fundamentals of the Prosthodontic Specialty

INTRODUCTION

The American Dental Association (ADA) has defined prosthodontics as "the dental specialty pertaining to the diagnosis, treatment planning, rehabilitation, and maintenance of oral function, comfort, appearance, and health of patients with clinical conditions associated with missing or deficient teeth and/or oral and maxillofacial tissues using biocompatible substitutes."¹ A prosthodontist has three years of comprehensive training following dental school in several areas of restorative dentistry. This training includes dental implants, crowns, fixed partial dentures, complete dentures, removable partial dentures, esthetics, occlusion, and facial and dental birth developmental defects. Prosthodontists are also trained in the technical and technological aspects of laboratory fabrication of complex dental prosthetics and complex restoration of dental and facial esthetics.1 Maxillofacial prosthetics is a branch of prosthodontics that requires one additional year of fellowship training with a focus on treatment of patients who have acquired and congenital defects of the head and neck region due to cancer, surgery, trauma, and birth defects. Innovative methods to help with the treatment of sleep apnea and temporomandibular joint disorders have also evolved over time, as have the educational responsibilities to provide those services to patients served by prosthodontists.¹

Prosthodontics has evolved into its current form through the gradual assimilation of multiple distinct areas of dental practice. Fixed prosthodontics, removable prosthodontics, maxillofacial prosthetics, and esthetic dentistry are exclusive features of the broader specialty of prosthodontics in its modern form. The application of dental implant therapy to patients with prosthodontic needs has been the greatest single advance and addition to the treatment procedures provided by the specialty. The ability to replace a tooth or multiple teeth with restorations supported by prosthetic root replacements has dramatically improved the ability of prosthodontists to serve their patients with their chewing efficiency and self-esteem.

This course will cover the fundamentals of the Prosthodontic Specialty and some of the procedures a newly emerging dental professional may encounter.

PROSTHODONTIC SPECIALTY

The term "prostho" refers to replacement and "dontist" means dealing with teeth. Prosthodontists are the ultimate recognized experts when anything needs to be replaced in the patient's mouth. This can range from a single tooth restoration, multiple teeth, or all teeth and gums in the oral cavity. While many other dentists can do some of these treatments, prosthodontists are the specialists dedicated to this specific type of care. Prosthodontists have advanced training in restoring and replacing teeth, and are considered the leaders of the dental treatment plan. They regularly lead teams of general dentists, specialists, and other health professionals to develop solutions for patients' restorative needs.

PROSTHODONTIC PROCEDURES

The following are a brief description of some of the procedures done within the prosthodontic specialty:

Bonding

Bonding is a process that has many uses in contemporary dentistry. Bonding may be used to attach composite restorations with certain types of cement to attach individual restorations to teeth. In addition to adhering restorations to teeth, bonding may be used to decrease sensitivity. Using a clear fluid version of this material to seal the exposed surfaces of the teeth decreases sensitivity to temperature changes and certain types of foods such as ice cream.

One of the most common uses of the term bonding is the application of tooth-colored filling material (composite restorations) to teeth that are irregularly shaped, peg lateral incisors, and chipped or broken teeth. Although not as effective as porcelain veneers, bonding may be used to improve the color and appearance of stained or discolored teeth, especially teeth with intrinsic staining. Bonding is often considered an intermediate step to improve the appearance of these teeth until the patient and their dentition are old enough to receive more permanent restorations such as crowns or veneers.

Enamel shaping

Enamel shaping is another prosthodontic procedure that involves removing a slight amount of enamel to improve the appearance and at times the function of teeth. This is often used to correct uneven edges of the front teeth, smooth teeth with minor chipping, or round off sharp pointed tips of the teeth, making the smile more proportioned and even. In some situations, enamel shaping is used to correct the patient's occlusion or bite.

Restorative procedures

Restorative procedures fillings replace missing tooth structure, whether the loss is due to dental caries or fracture of the tooth. In advanced cases with excessive tooth structure lost, porcelain crowns, gold crowns, or onlays may be required. In simple cases, the missing tooth structure can be replaced with dental fillings using composites or amalgam. Dental composites continually improve with technology and are a tooth-colored material commonly used as a filling material and with the proper application, can bond to the actual tooth. Dental composite material may be a way to build, reshape, or change the color of teeth. This material can be used to conservatively alter the appearance of misshapen teeth, such as peg laterals, as well as fill in places where caries have been removed. Amalgam is also known as silver fillings. This filling material is a combination of metals that has been used for over one hundred years with high predictability and success. It is one of the most reliable materials used to restore teeth with no proven side effects.

Full Mouth Reconstruction

Full mouth reconstruction refers to rebuilding and, in some cases, replacing all of the teeth in a patient's dentition. This procedure combines esthetics with the science of restorative dentistry to improve the appearance, functionality, and health of the patient's mouth.

Candidates for Full Mouth Reconstruction

There are a number of individuals who have dental problems throughout their mouths that must be treated comprehensively with the visualization that the final result will improve both esthetics and functionality. These patients may exhibit multiple missing teeth, numerous teeth with large restorations that are deteriorating or exhibiting decay, cracked or broken teeth, or badly worn dentition due to bruxism or other oral habits.

There is also a group of patients who were born with congenital conditions such as Ectodermal Dysplasia, Amelogenesis Imperfecta, or Dentinogenesis Imperfecta that will need extensive restoration of their dentition. These patients may be candidates for a full mouth reconstruction once their dentition have reached maturity.

Amelogenesis Imperfecta

Amelogenesis imperfecta (amelogenesis - enamel formation; imperfecta - imperfect) is a disorder that affects the structure and appearance of the enamel of the teeth. This genetic condition causes the teeth to be unusually small, discolored, pitted, or grooved, and prone to rapid wear and breakage with early tooth decay and loss. These dental problems, which vary among affected individuals, can affect both primary and permanent dentitions. People with this disease may also have problems periodontally, with the cementum, ligaments, and alveolar bones all affected. Teeth may also be sensitive to either hot or cold temperature exposures, sometimes even to both temperature extremes. Severe and chronic pain due to exposed areas of dentin from the deficient areas of enamel can also occur.

There are four major types of amelogenesis imperfecta that are classified based on the symptoms experienced by the patient, X-rays, appearance and type of enamel defect.²

· Type I Hypoplastic

· Type II Hypomaturation

· Type III Hypocalcified

· Type IV Hypomaturation/Hypoplasia/Taurodontism

These 4 types are divided further into 18 subtypes, which are distinguished by their specific genetic cause and by their pattern of inheritance.^3,4 Amelogenesis Imperfecta can be inherited in an autosomal dominant, autosomal recessive or X-linked recessive pattern.⁵ Treatment may include dentures that cap the defective teeth, orthodontic treatment, special toothpaste for the teeth sensitivity and meticulous oral hygiene at home.⁴

In general, both the primary and permanent teeth are affected. The enamel tends to be soft and weak, and the teeth appear yellow and damage easily.³ The defects associated with amelogenesis imperfecta are highly variable. Traditionally, the diagnosis and classification of amelogenesis imperfecta is based on the clinical presentation and the mode of inheritance.³

Etiology:Amelogenesis imperfecta is caused by mutations in the AMELX, ENAM,and MMP20genes. These genes provide instructions for making proteins that are essential for normal tooth development. Mutations in any of these genes alter the structure of these proteins or prevent the genes from making any protein at all. As a result, tooth enamel is abnormally thin or soft and may have a yellow or brown color. Teeth with defective enamel are weak and easily damaged.² In some cases, the genetic cause of amelogenesis imperfecta cannot been identified. Researchers are working to find mutations in other genes that are responsible for this disorder.²

Diagnosis:A dentist can identify and diagnose amelogenesis imperfecta on the basis of the patient's family history and the signs and symptoms present in the affected individual.⁶ Extraoral X-rays can reveal the presence of teeth that never erupted or that were absorbed by the body. Intraoral X-rays show contrast between the enamel and dentin in cases in which mineralization is affected.⁶ Genetic testing is available for the genes AMELX, ENAM,and MMP20.³

 

Treatment of Amelogenesis Imperfecta:Treatment depends on the type of amelogenesis imperfecta, the age of the affected person, and the type and severity of enamel abnormality.³ Treatments include preventative measures, various types of crowns, as well as dental implants or dentures, orthodontic, periodontal, and restorative treatment.^6,5 The social and emotional impact of this condition on the patient should also be addressed.⁵

Treatment Options for a Full Reconstruction

Overall, any dental treatment that affects all teeth in the mouth is called full mouth reconstruction or full mouth rehabilitation. Some treatment options for oral cancer may require the patient to undergo a unique type of full mouth reconstruction that not only involves the replacement of missing teeth, but potentially restoration of missing structures of the oral cavity following cancer treatment. Rehabilitation treatments can include onlays, crowns, fixed partial dentures (FPDs), veneers, dental implants and dentures that will fundamentally provide not only a new smile, but improved chewing efficiency and a better quality of life for the patient. In some patients, other specialties such as orthodontics or periodontics may also be employed to enable the best possible outcome for the patient.

Maxillofacial Prosthetics

Maxillofacial Prosthetics is a branch of prosthodontics that involves rehabilitation of patients with defects or disabilities that were present when born or developed due to disease or trauma. Prostheses are often needed to replace missing areas of bone or tissue and to restore oral functions such as swallowing, speech, and chewing. In other instances, a prosthesis for the face or body may be indicated for cosmetic and psychosocial reasons. Prosthetic devices may also be created to position or shield facial structures during radiation therapy.

Patients that typically desire prosthetic care are those that have been in an accident, have had surgical removal of diseased tissues, or have a neuromuscular disorder from ALS or a stroke. Children can also be born without full development of ears, teeth, or palate and need specialized care. Maxillofacial prosthodontists are accustomed to working cooperatively with ENTs, oral surgeons, general and specialty dentists, plastic surgeons, neurologists, radiation oncologists, speech pathologists, anaplastologists, and various other supplementary personnel.

Fabrication of Mouthguards

Patients often use the term "mouthguard" to describe many different devices that range from a simple commercially available athletic guard to a sophisticated guard custom-made for a patient as a therapeutic device.7 In the dental profession, "mouthguard" typically refers to a resilient device that is worn on either the upper or lower teeth to protect the teeth from trauma during contact sports or any activity that might result in a blow to the mouth or jaw.⁷ There is also some indication that mouthguards may also help sports-related concussions from occurring as well as saving the permanent dentition from sports-related injury. There are three types of mouthguards characteristically used in sports activities: over-the counter mouthguards which are available at athletic equipment stores, "boil and bite" mouthguards that are also commercially available and require some preparation by the patient, or custom-made mouthguards fabricated by your dental team personnel that will protect the patient's teeth and adapt precisely to the patient's dentition.

Occlusal Splints

The more sophisticated mouthguard designed for a person with a specific dental problem is usually called an occlusal splint or orthotic device. An occlusal splint or orthotic device is a specially designed mouthguard for people who grind their teeth, have a history of pain and dysfunction associated with their bite or temporomandibular joints (TMJ), or have completed a full mouth reconstruction. An occlusal splint is custom-made using complete study models on an instrument called an articulator that simulates the movement of the jaws. It is set using a facebow on the patient to obtain exact readings on how to set the articulator. The occlusal splint is made from a processed acrylic resin and is designed to guide the jaw as it moves side-to-side and front-to-back. This custom-made orthotic device not only protects the teeth from harmful habits, but it supports the TMJ and the muscles that are used in chewing. A recent innovation in occlusal splints/orthotic devices includes a specific modification designed to reposition the lower jaw allowing improved airflow while the patient is sleeping to aid in the treatment of sleep apnea.

TMJ/TMD Treatment

The temporomandibular joint (TMJ), when not functioning properly, can cause a tremendous amount of discomfort to the patient. This is largely due to the many nerves in the tissues behind the joint. Once the TMJ region becomes inflamed, any slight pressure can cause pain and exacerbate the problem. Treatment involves unloading these tissues, allowing them to recover and preventing recurrence. Depending on a patient's history and symptoms, the prosthodontist may recommend a stabilization/occlusal splint to treat the pain. This custom-made plastic device fits over the upper or lower teeth and is used to control the interaction between the top and bottom teeth while maintaining the joint in a healthy position. Occlusal splints are normally worn at night, but can be worn during the day as needed. Stabilization splints are the most common treatments for TMJ disorders, including facial pain. Facial or jaw pain in the chewing muscles or jaw joint is a common symptom of temporomandibular joint disorders. Several treatment options exist depending on the cause and severity of the symptoms. All options are conservative and do not produce permanent damage to the teeth. These treatment options include physical therapy and exercise, pharmacologic treatment, and occlusal splints/orthotic devices.

Teeth Cleaning

Some serious medical conditions may cause gums that bleed, but the most frequent cause of bleeding gums is poor oral hygiene, which leads to gingivitis. Gingivitis means that the gums are inflamed, red, and bleed easily when touched as a result of plaque building up on the teeth. They may become sensitive and therefore the patient may opt not to brush the affected area. Proper cleaning of the teeth prevents gingivitis and the subsequent symptom of bleeding gums. Sometimes the problem progresses beyond the superficial inflammation of gingivitis. The bacteria are deeper down between the teeth and the gums. When this is the case, the bacteria are more difficult to reach. This makes it harder for patients to clean out the bacteria alone. These bacteria can cause inflammation that leads to breakdown of the connection of the gums to the teeth and in severe cases, bone loss around the teeth.

A patient's oral hygiene should be taken into consideration when considering prosthetic treatment. The risk of caries increases with prosthetic treatment and patients with dental implants are at risk for perimplantitis. Diligent oral hygiene and well-maintained periodontium is vital in the short- and long-term success of removable and fixed prosthetics. Often periodontists work in conjunction with prosthodontists to achieve favorable periodontal conditions to allow success for prosthetic treatment.

Sealants

Although sealants are often associated with the protection of permanent posterior teeth from caries in young patients, they can also be utilized in a different way in adult patients with sensitivity associated with exposed root surfaces or cervical erosion. When a tooth is overly sensitive to cold temperatures or sweets, the exposed tooth can be sealed. Sealants can microscopically bond to the exposed tooth and the dental team can help remove the painful symptoms.

Teeth Brightening and Whitening

Many products are now available for patients to whiten their teeth. These products include commercially available strips that can be purchased over the counter, custom fabricated trays with a bleaching gel, or bleaching in a dental office using UV light or a laser as the catalyst. There are limitations to these products, such as existing porcelain, amalgam and composite restorations will not change color. If the surrounding teeth are whitened, the tooth with the restoration may appear darker.

FIXED PROSTHODONTICS

Prosthodontics is the dental specialty that deals with the replacement of missing teeth and tissues. The teeth or tissues are replaced with a prosthesis (the plural is prostheses). A fixed prosthesis is one that is permanently cemented in the oral cavity and cannot be removed. Amalgam and composite restorations are called direct restorations because they are placed on the tooth or teeth directly after preparation. Fixed and removable prostheses are indirect restorations because they are fabricated in the dental laboratory.

Types of Fixed Prostheses

Inlays

An inlay is a conservative fixed prosthesis because it involves only a portion of the occlusal surface (generally not the cusps ridges) and one or more proximal surface. Traditionally, inlays were used instead of fillings to replace a small amount of tooth structure loss due to caries. Like fillings, inlays fit inside the tooth and were made only of gold. Today, inlays are still used in the same situations, but the inlays can be made of a tooth-colored material such as ceramic/porcelain/zirconia or special dental composite. Gold inlays are still an option, but one that is not as popular due to esthetics. Defective or unattractive restorations, if small enough, can be replaced by tooth-colored inlays and bonded to the tooth. This bonding process may actually improve the strength of the tooth and help seal the inlay to the tooth.

Onlay

Onlays also fit inside the tooth, but extend onto the chewing surface of a back tooth to replace one or more cusps. An onlay involves all or most of the occlusal surface and proximal surfaces. In the past, onlays were made only of gold, but like inlays, more and more patients request a tooth-colored onlay. Making the onlay of ceramic/porcelain allows the restoration to be bonded to the tooth. This bonding process may actually improve the strength of the tooth and help seal the onlay to the tooth. It is difficult to determine when inlays or onlays can be used instead of crowns.

Veneers

An indirect veneer is a thin layer of restorative material that is cemented to the tooth surface, usually the facial surface of anterior teeth. Indirect veneers are fabricated in the dental laboratory. (Direct veneers, or bonded veneers, are placed and   cured directly in the patient's mouth.)

Porcelain veneers are used to modify the shape and color of teeth, and they are the treatment of choice for teeth that are relatively intact but may be misshapen, discolored, or chipped. Veneers are thin shells of porcelain that are internally etched and then bonded to the enamel of the teeth. A small amount of tooth structure must be removed to make room for the porcelain veneer and to avoid making the tooth look big and bulky. The tooth preparation is limited to the enamel and usually involves only a few surfaces of the tooth, unlike a crown. Dentistry uses porcelain veneers to improve the appearance of teeth and to even close spaces or gaps between teeth.

Crowns

A crown is used when more of the tooth structure is involved. A crown can be a 3/4 crown or a full crown. The 3/4 crown covers the entire crown except for the facial surface, which is left intact in order to improve the esthetic appearance. The full crown completely covers the crown of the tooth. Different materials are used in the construction of dental crowns. Crowns can either have base metal alloys with porcelain (which is tooth colored) fused to the outer surface, or they can be made completely out of porcelain. All ceramic restorations are often preferred to porcelain-fused-to-metal (PFM) restorations because of their improved esthetic appearance, chemical resistance, and biocompatilbility. Noble metal crown is the ideal alternative to base metal for patients who are allergic to nickel. Another material that is gaining acceptance is zirconia which is a crystalline dioxide of zirconium that is the strongest ceramic in the dental market today.¹⁰ Zirconia restorations have exceptional durability and strength and generally last longer than porcelain. Porcelain crowns usually need replacement after a few years, while zirconia crowns have shown a 99 percent survival rate after five years. Titanium alloys have the same properties as noble materials like gold. Titanium alloy is the most common material used in dental implants and other dental prostheses because of its strength and good biocompatibility. Porcelain fused to titanium alloy has better properties than base metal alloys.

Gold crowns are also a choice for restorative material and are strong and more forgiving to opposing teeth than porcelain, and in some cases zirconia. Gold alloys have the best properties because of their higher strength and durability. Gold alloy is a combination of gold, platinum, silver, palladium, copper, and tin that has superior qualities. The drawback to gold alloys is the price. The price of the crown increases due to the better properties of the higher amount of noble metals in gold alloy.

Another option to porcelain fused to metal, all metal, or all porcelain crowns is zirconia. Zirconia crowns are often chosen over standard Porcelain Fused to Metal (PFM) or full-gold crowns due to their strength, durability, exceptional aesthetics and biocompatibility.

Zirconia crowns require a shoulder or chamfer margins for best results and can be fabricated from solid full-contour zirconia, high translucent zirconia, or layered zirconia. High translucent zirconia and layered zirconia can be either screw-retained or cemented onto the tooth.

Types of Zirconia Crowns

Solid zirconia -also referred to as monolithic zirconia, is opaque and commonly recommended for posterior crowns. Solid zirconia contains more stabilizers than high translucent zirconia, making it more durable to withstand the forces of mastication and bruxism. Minimal clearance is required on the tooth preparation for this type of restoration, as there is low wear on opposing teeth. Solid zirconia is also very effective for masking highly discolored dental preps, specifically those that have darkened due to previous dental treatments, such as a post and core or a restored dental implant or teeth that have intrinsic staining.

Layered zirconia - is more translucent, opalescent and is especially suitable for anterior crowns. Although generally used for anterior crowns, layered zirconia may also be used for posterior crowns if there is sufficient clearance. Both solid and layered zirconia crowns have a strength and consistency that is comparable with traditional PFM restorations but with more far superior aesthetics.

Zirconia HT - with HT referring to High Translucent and at 590-720 MPa, is much stronger than PFM restorations and maintains a natural and vibrant translucency. These crowns are 100% metal-free which prevents gingival darkening and removes the possibility of exposing metallic margins if periodontal recession begins. The material is naturally esthetic, transmits the color of the adjacent teeth, and can be matched to any shade, thus making high-translucent zirconia suitable for bridges up to 3 units in length. Due to its characteristic natural fluorescence in any lighting condition, restorations will always look natural with no special fluorescent glaze being required on the final restoration.

Advantages versus disadvantages of using zirconia:

Zirconia crowns are very biocompatible, as the smooth surface helps to reduce plaque accumulation in the mouth. The material is suitable for patients with metal allergies or who would prefer to have metal-free restorations.

Layered zirconia crowns are extremely durable. Even though the porcelain used for layering does not have the strength of solid zirconia, they are designed to bond with the zirconium substructure, making chipping or fracturing very rare. The material also promotes a healthy tissue response.

Due to a wide variety of factors including chemical composition and processing requirements, there are many ways zirconia can be manufactured to suit the needs of the patient. The customization minimizes the margin for error and ensures a tailored fit for each individual and results in a very comfortable restoration that does not transmit heat or cold in the same way as traditional PFMs.

Using computer-aided design and manufacturing processes provide patients with a precise fit, reducing the chair-side time required for adjusting and cementing these restorations. Zirconia crowns can be conventionally cemented in place.

The disadvantages of using zirconia for restorations are very minimal. The toughness of the material has raised some concerns about friction against the root structure and abrasion on opposing teeth. Routine exams help to reduce the possibility of damaging opposing teeth.

Currently, the demand for zirconia far exceeds the demand for PFMs, and these older-style restorations are becoming a thing of the past.

Fixed Partial Denture (FPD)

A fixed partial denture (FPD) is what many refer to commonly as a bridge. An FPD technique has been used with high success for many years to replace a missing tooth or teeth. Teeth on both sides of the space left by the missing tooth are prepared for a crown. Then a false tooth called the pontic is joined to the crowns called abutments, and the entire FPD is cemented to the prepared teeth. There is usually one abutment tooth on each end of the FPD; a longer FPD may have two abutment teeth on each end. A FPD is named for the number of units (or teeth) involved. For example, a three-unit FPD will consist of two abutment teeth and one pontic. The patient cannot remove the FPD, and special aids are available to keep it clean. Although dental implants are often considered the "gold standard" for the replacement of missing teeth, in the appropriate circumstance, a FPD can be a practical alternative.

Another type of FPD is the Maryland bridge. It is a more conservative form of replacing a missing tooth. The abutment teeth require minimal preparation because the FPD is attached to these teeth by means of wing-like extensions coming off the mesial and distal surfaces of the pontic. The extensions, or retainers, are bonded to the lingual surface of the abutment teeth. This type of FPD is sometimes referred to as a resin-bonded, or resin-retained FPD. A cantilever FPD is another conservative FPD that has only one abutment tooth and one pontic. These are used in an area where there will be little stress or no traumatic occlusion.

There are a variety of circumstances that may lead to missing teeth and the need for a FPD. For example:

• If diagnosed and treated early, most cavities and decayed teeth can be treated simply with a filling, but in some cases the decay is so extensive the tooth cannot be restored and must be extracted.

• Patients with a cleft lip often experience a missing tooth or teeth in a position corresponding to the cleft.

• The forces generated by a patient grinding their teeth may be great enough to severely fracture a tooth leading to the need for an extraction.

Materials Used for Fabricating Fixed Prostheses

The material used for a fixed prosthesis will usually depend on the location of the restoration in the mouth, the amount of strength that will be required, and esthetics.

Metals

Gold is combined with other metals such as platinum, palladium, iron, tin, or zinc, to form alloys. Gold alone is too soft to resist occlusal forces, but when combined with other metals, it is strong enough and resistant to tarnish and other harsh oral conditions.

Porcelain

Porcelain is a form of ceramic that either can be used alone or fused to metal. Porcelain is not as strong as metal, so it is often fused to a metal base for strength. These are known as porcelain- fused-to-metal (PFM) crowns. Porcelain is used because it is tooth-colored and provides an esthetically pleasing restoration.

Zirconia

Zirconia - (zirconium dioxide) is a white, powdered metal oxide made from zirconium, a metal with similar properties to titanium. Zirconium makes a good choice for dental material because it is chemically unreactive.

Indirect Composite Resin

This material is similar to the composite material used in direct restorations but the material is placed under heat and pressure in the dental laboratory, making it stronger. This material is also tooth-colored.

Procedure for a Fixed Prosthesis

The procedure steps for fabricating the various fixed prostheses are all similar. Three main steps are taken: the preparation appointment, the laboratory processing of the prosthesis, a try-in appointment (if necessary), and the cementation appointment.

The Preparation Appointment

After anesthesia is administered and before the preparation begins, an impression is taken of the arch being treated (for some types of temporary crowns), as well as an impression of the opposing arch (in order to obtain proper occlusion for the new prosthesis). Using triple tray impressions for simple posterior one-to-three-unit cases can be a highly predictable and effective way for practitioners to produce acceptable outcomes (Table 1). It is best not to use a triple tray when the distal-most tooth in the arch is being prepared. The shade also can be selected at this time. Once the anesthesia has taken effect, the teeth are then prepared using the high-speed handpiece and various burs and diamonds. The tooth is reduced in size in order to make room for the new restoration. After the tooth is adequately prepared, the gingival tissues must be retracted just before the final impression is taken so that the impression will include details beyond the margins of the preparation. In order to do this, gingival retraction material (either cord or paste) is placed into the gingival sulcus. The retraction material forces the tissues away from the tooth, and it is impregnated with an astringent-vasoconstrictor chemical that causes the tissues to shrink and controls bleeding. If the bleeding is not controlled by the cord, a hemostatic solution can also be placed in the area. Some retraction cords are impregnated with epinephrine, making it important to be familiar with the patient's medical history; this type of cord may be contraindicated for cardiovascular patients. Gingival retraction pastes and gels may be nonmedicated, use aluminum chloride, aluminum sulfate, or ferric sulfate. The retraction cord is placed in the sulcus using a blunt, round-ended instrument (such as a plastic instrument), without damage to the gingival tissues. The cord is removed just before the impression is taken. Gingival retraction pastes and gels can be used to create space between the prepared tooth and the sulcus. These materials are expressed around the preparation, often directly into the sulcus, and their astringent properties keep the area free of moisture so the impression material can be placed immediately after the retraction material is removed. Some retraction pastes and gels can be used in conjunction with retraction cord, while others work on their own. The final impression is taken, then rinsed, disinfected, and poured as soon as possible. After the final impression is taken, the bite registration is taken. This too should be rinsed and disinfected before being sent to the laboratory. The next step is the fabrication of the provisional coverage for the tooth. There are a variety of materials that can be used for provisional coverage. For inlays and onlays, provisional filling materials, such as a special light-cured composite that will not permanently stick to the tooth, can be used. Preformed crowns are also available in either aluminum (for posterior teeth) or acrylic. They are supplied in a variety of sizes and shapes. Any time a preformed crown is tried in the mouth but not used, it must be sterilized before being used again. Temporary acrylic crowns can also be custom-made.

There are several methods of making a custom acrylic temporary. One method is to take an impression of the teeth before preparation. This impression is wrapped in a moist towel and set aside until after the tooth has been prepared. Then the acrylic temporary material is placed in the impression  in the area of the tooth being prepared. The impression is placed back into the patient's mouth and the acrylic is allowed to set for recommended amount of time. The impression is removed, along with the temporary. The temporary is removed from  the impression and returned to the patient's mouth for the final set. Another method also requires that an impression be taken prior to tooth preparation. This impression is then disinfected, poured in gypsum, and allowed to set. Once set, a sheet of acrylic is used to make a matrix, or coping for the temporary.

Table 2 describes the fabrication of a custom acrylic provisional crown using an acrylic matrix.

Provisional coverage can also be custom fabricated by the dental laboratory. For this method, the dental office sends a cast of the teeth to the laboratory in advance of the preparation appointment and the laboratory will fabricate the temporaries from the cast. The dental assistant must be sure that the provisional coverage has returned from the laboratory before the patient's preparation appointment. Once the temporary crown is made, it is then cemented using a temporary cement. The patient is advised that they may have some tissue discomfort after the effects of the anesthesia wear off, as well as the fact that the tooth or teeth may be sensitive to temperature changes because of the provisional coverage. The patient should be instructed to brush and floss around the area in order to keep the tissues healthy. When flossing, however, the floss should be pulled out through the interproximal area as opposed to being brought back up through the contact area. This will help prevent accidentally pulling the temporary coverage off the tooth. The patient should also be told to avoid eating hard or sticky foods that may break or pull the temporary off the tooth. Should the temporary become displaced, the patient should be instructed to call the dental office immediately to make arrangements to have the temporary replaced. If possible, a small amount of petroleum jelly can be placed inside the crown and replaced on the tooth until the patient can get to the dental office. The dentist must precisely convey to the dental laboratory the required specifications for the crown or FPD. In order to do this, a laboratory prescription is filled out. This must include the dentist's name, address, telephone number, and signature, the patient's name, a complete description of the prosthesis, the type of materials the dentist wants used for fabrication, the shade or shading, and any special characterizations the dentist may want to add to the prosthesis to give it a natural appearance (such as lines or areas of discoloration to match the patient's natural dentition). Another very important part of the prescription is the date that the dental team is requesting to have the case back in the office. Often the patient will make the appointment for the cementing of the prosthesis while in the office for the first appointment. It is usually the responsibility of the dental assistant to obtain this information and be sure that the case will be back before the patient's next scheduled appointment. A copy of the prescription is sent to the laboratory with the case, and a copy is kept at the dental office in the patient's record. See Table 3 for a description of assisting with the preparation for a fixed prosthesis.

Laboratory Processing

As mentioned, the impressions and bite registration should be disinfected after being taken. A special label should be attached to the case notating that it has been disinfected so that the laboratory will not repeat the procedure of disinfection. The dental office must be aware of the amount of time the laboratory needs in order to fabricate the prosthesis so that the patient can be scheduled appropriately. Prior to the scheduled appointment, the assistant must verify that the case has returned from the laboratory.

Try-In Appointment

Sometimes, such as when fabricating a fixed partial denture, the dentist will also require a try-in appointment. This appointment occurs before the final cementation appointment. The laboratory will send the castings of the FPD without the final porcelain covering, and the dentist will try them on the abutment teeth. If they fit properly, another impression may be taken with the castings in place. If adjustments are needed, another final impression is taken without the castings in place, and another try-in appointment is scheduled.

The Cementation Appointment

The dental assistant must be sure that the patient's case has returned from the laboratory prior to the cementation appointment. The prosthesis must be disinfected prior to being placed in the patient's mouth. The use of anesthesia is optional for this appointment, depending on the patient's level of sensitivity. The temporary coverage is removed, and the excess cement is removed. The dentist will then try the prosthesis in and make any necessary adjustments.

If the prosthesis is taken to the office laboratory for adjustments, it is disinfected before being placed back in the patient's mouth. If the prosthesis must be returned to the laboratory for further adjustments, it must be disinfected before being sent. After the dentist is sure that the prosthesis fits properly, it can be cemented. The area is isolated and the assistant must mix the chosen cement according to the manufacturer's instructions. The assistant places a thin layer of cement on the interior of the crown (described in more detail below) and transfers it to the dentist. After the dentist places the crown on the tooth, the patient bites on a bite stick or crown seater until the cement hardens. The excess cement is then removed (described in more detail below). The patient is instructed that home care is necessary to maintain a fixed prosthesis, and the patient should brush and floss the crown or FPD daily. If the patient has a new fixed partial denture, they must be instructed on the use of a floss threader. If, after the preparation appointment, the patient finds that the tooth is very sensitive, the dentist may opt to cement the permanent restoration with temporary cement. If there are problems, the crown will be able to be removed easily. If the sensitivity subsides, then the patient can return to have the crown cemented with a permanent cement. Table 3 describes the procedure for the cementation of a fixed prosthesis.

Placing Cement in a Crown

The dental assistant will mix the cement and may also place the cement in the restoration. To do so, the crown is held so that the inner portion is facing upward. The cement spatula is used to scoop up the cement, and then the edge of the spatula is scraped along the margin of the crown. This will allow the cement to flow into the crown. The crown should not be filled completely with cement. A thin layer of cement over the entire inner portion of the crown is all that is needed. It is very important that no air bubbles are trapped in the cement because they may prevent the crown from seating properly on the tooth. To break up any air bubbles, the tip of the spatula is placed in the cement in the crown and a circular motion is used. This will also help spread the cement over the inner surface of the crown. The crown should be passed to the dentist in the position in which it will be cemented in the patient's mouth. Once the crown has been seated, a cotton roll or bite-stick should be passed to the dentist. The patient will bite on this and it will help seat the crown, and any excess cement in the crown will be extruded.

Removing Excess Cement from Coronal Surfaces

Once the cement has set, the excess must be removed. In some states, the assistant is allowed to perform this function. When using instruments in the oral cavity, it is important to establish a fulcrum. A fulcrum, also known as a finger rest, is a point of support used by the operator to stabilize the hand. The pad of the ring finger on the hand holding the instrument is placed in a position, usually on the incisal or occlusal surface of an adjacent tooth, so that it not only stabilizes the hand but it also allows movement of the wrist and forearm. The fulcrum is usually established as close as possible to the area being treated, but it can be either intraoral or extraoral, depending on such factors as the presence or absence of teeth, and the area being treated.⁸ The use of a fulcrum helps avoids injury to the patient, allows for proper use of the instrument, and prevents fatigue for the operator. Once a fulcrum has been established, the assistant should be in the proper operator's position, depending on the area being treated. The assistant can have the patient turn his/her head as needed in order to provide better visibility. The instrument should always be directed toward the incisal or occlusal surface, rather than toward the gingiva. This will help avoid accidental damage to the soft tissue. To remove excess cement from the interproximal areas, a piece of floss with a knot tied in it is passed through the embrasure. The assistant must be sure that no cement is in the sulcus because it may irritate the gingiva. The patient's mouth is thoroughly rinsed and evacuated when all cement has been removed.

Retention Techniques

At times, the tooth being restored has lost a large amount of coronal tooth structure, due to extensive decay, fractures, or the breakdown of large restorations. If this is the case, the dentist must replace some of this tooth structure in order to increase the retention of the prosthesis on the tooth. This can be done through core buildups, retention pins, post-retained cores, or cast post and cores.

Core Buildups and Retention Pins

After removal of all decay and any defective restoration, the dentist will use a restorative material, such as amalgam, composite, or glass ionomer strengthened with a silver alloy, in order to build a core that resembles the contour of the tooth. Once the core is in place, the dental provider will finish the preparation as if the core was natural tooth structure. It may be necessary to also place retention pins in the tooth prior to doing the core buildup. After placing the pins, the core material is placed around the pins. The retention pins will hold the core in place, and the core will then hold the final prosthesis in place.

Post-Retained Cores

If a tooth has been treated endodontically, it may be necessary to provide extra strength to the tooth by removing part of the root canal filling and cementing a metal post inside the canal. Prefabricated posts are available in various sizes and are made out of fiber, titanium, titanium alloy , or stainless steel. A post is fitted to the tooth so that a portion of the post enters deep into the canal, and a portion extends out of the canal to the height of the core buildup. It is then cemented in place, and once the cement is set, the core buildup material is placed around the post. The preparation of the tooth can then be completed.

Cast Post and Cores

A cast post and core are a custom-fabricated item in the dental laboratory. An impression of the root canal is taken and sent to the laboratory. The laboratory will fabricate a post and core that is one unit. This is then cemented into the canal and the preparation of the tooth for the crown can be completed before the final impression. The crown is cemented over the cast post and core.

REMOVABLE PROSTHODONTICS

Removable prosthodontics replace missing teeth with a prosthesis that the patient is able to remove for cleaning and examination. There are two types of removable prostheses: partial dentures, which replace one or more missing teeth; and complete dentures, which replace most or all missing teeth. Many factors will determine the type of removable prosthesis that will best meet the patient's needs. These include the extraoral factors of: the patient's physical and mental health; motivation; age; dietary habits; social and economic factors; and occupation. In addition, the following intraoral factors are considered: musculature; salivary flow; residual alveolar ridge; oral mucosa; oral habits; and tori (bulging, bony projections).⁸

Removable Partial Dentures (RPD)

Removable partial dentures are supported by the remaining teeth. Most RPDs consist of a metal framework (some are made with an acrylic base), which is the skeleton that supports the other parts of the prosthesis. Parts of the framework contact the natural teeth for support. The part that partially encircles an abutment tooth is called a clasp. Extending from the clasp is a rest. The rests are usually positioned on the occlusal or lingual surfaces of the abutment teeth. Before the final impression is taken, the surface of the abutment teeth where the rest will sit must be prepared by being reduced to allow for clearance of the rest. The portion of the RPD that rests on the alveolar ridge and contains the denture base and teeth is known as the saddle. Following is a description of the steps that are involved in the fabrication of a removable partial denture, including the setup equipment and supplies for each appointment.

Preliminary Impressions Appointment

• basic setup

• alginate impression material

• mixing bowls, spatula

• impression trays

Preliminary impressions are taken for study models for the construction of a custom impression tray/s. This is usually done at the patient's first appointment. An impression of the opposing arch can be taken at this time as well. If not already completed, the assistant may expose radiographic films, and take photographs of the patient if necessary. The assistant will fabricate the custom tray before the patient's next appointment.

Preparation of Abutment Teeth, Occlusal Registration, and Final Impression Appointment

• basic setup

• high-speed handpiece with necessary burs

• HVE tip, air/water syringe tip

• custom tray and adhesive

• compound wax for the impression tray

• final impression materials (including mixing pad and spatula, if needed)

• bite registration materials

• tooth shade and mold (shape) guides

• laboratory prescription form

At this appointment the abutment teeth will be prepared. The assistant will maintain the field of vision as the dentist uses the high-speed handpiece. After the teeth are prepared, the dentist will try in the custom tray, and if necessary, place wax on the borders of the tray in order to obtain a better fit. The assistant will then coat the interior of the tray with the adhesive from the impression material kit. The adhesive should be dispensed into a separate container to avoid cross-contamination of the remaining adhesive. After the final impression is taken, the occlusal registration is taken. Both the impression and the bite registration must be rinsed and disinfected according to the manufacturer's instructions. The dentist may also wish to determine the shade of the artificial teeth at this appointment. Shades are always determined using natural light.

The shade is recorded in the patient's record and on the laboratory prescription form. The case is sent to the lab where the construction of the framework and occlusal rims will be completed. The assistant must find out from the laboratory how much time they require for this step. The patient's next appointment is scheduled based on this time frame.

Try-In of Framework Appointment

• basic setup

• hand mirror for patient

• articulating paper and forceps

• adjusting instruments, including wax spatula, pliers, and a heat source

• contour pliers

• framework (with artificial teeth set in wax) from the laboratory

For this appointment, the laboratory will have returned the metal framework with the wax bite rims in place. The dentist will try in the framework and make any necessary adjustments. The occlusal registration may be taken at this appointment. Before being sent back to the lab, the assistant must disinfect all items. When the laboratory receives the case, they will construct the acrylic saddle portion of the RPD where the artificial teeth are held. Again, in order to schedule the patient's next appointment, the assistant must be sure to give the laboratory enough time to complete this step.

Delivery of Removable Partial Denture Appointment

·       basic setup

·       articulating paper and forceps

·       slow-speed handpiece and necessary burs

·       removable partial denture from the laboratory

The dentist will seat the completed RPD and make any adjustments necessary. The team member will also instruct the patient on how to insert and remove the RPD. The patient should not leave the office without having actually practiced inserting and removing the RPD several times. Often, the assistant will give the patient home care instructions (described later). The patient should also be told that it may take a few days to adjust to the RPD and that there may be some sore spots. The patient should call the office to make an appointment for further adjustments if necessary.

Complete (Full) Dentures

The steps for the fabrication of a complete denture are similar to those for a removable partial denture, with minor differences. Dentures are replacements for missing teeth. Complete dentures replace all teeth. By matching each individual's unique smile and bite, dentures can improve facial appearance and self-confidence. Dentures may also improve speech problems caused by missing teeth and will improve chewing.

Preliminary Impressions Appointment

This appointment is the same as for a removable partial denture.

Preparation of Abutment Teeth, Occlusal Registration, and Final Impression Appointment

·  basic setup

·  HVE tip, air/water syringe tip

·cotton rolls and gauze

· disinfected custom tray and adhesive

· compound wax and Bunsen burner for border   molding the rims of the trays

· lab knife to trim border molding

·  final impression materials

· laboratory prescription form

The dentist will try the custom tray in the patient's mouth. At this time, the dentist will heat the impression compound and place it along the borders of the tray. The compound is allowed to cool, and then the tray is placed in the patient's mouth. The dentist will manipulate the patient's lips and cheeks over these borders (for a mandibular tray, the patient is asked to move the tongue around). The purpose of this is to shape the borders of the tray so that they more closely approximate the soft tissues. This process is called border molding or muscle trimming, and it allows the impression to replicate the border of the denture. When this step is complete, the tray should be painted with adhesive. The final impression is then taken. It is disinfected and sent to the laboratory where the baseplates and occlusal rims will be constructed. The baseplates are made out of a semi-rigid material, and represent the denture base. The occlusal rims are made of wax, and represent the teeth.

While compound is used by some for border molding for final impressions, some dentists/prosthodontists use a polyvinyl siloxane (PVS) material.

Final impressions are taken in light body Polyvinyl Siloxane (PVS) impression material in the custom tray. Properly mix the material to manufacturer's instructions and add it to the tray spreading it evenly and slightly overlapping the borders. The dentist will seat the impression and assure that all loose tissue is free from the tray by gently pulling the corners of the patient's lips for upper impressions and by asking the patient to place their tongue on the roof of their mouth for lower impressions.

As the impression material is setting, it is useful to distract the patient with conversation and essential to check if they are comfortable. Keep a small piece of impression material to one side so you can see when it is set and ready for removal.

Once the impression is removed, rinse thoroughly to get rid of debris or blood and scrutinize the impression carefully, making sure all relevant structures are captured. It is vital to ensure the lower denture impression captures the full posterior ridge and that both impressions accurately record the entire width and depth of the sulcus, as this can greatly affect the stability of the finished fabricated denture.

Jaw Relationship Appointment (Try-In of Baseplate and Occlusal Rims; Occlusal Registration)

• basic setup

• laboratory knife, #7 wax spatula, Bunsen burner

• shade and mold guides

• millimeter ruler and Boley gauge

• face bow (a device used to establish the relationship between the mandible and the temporomandibular joint; the relationship is transferred to the articulator to simulate jaw movements during the construction of the prosthesis)

• baseplates and occlusal rims

• laboratory prescription form

The assistant should disinfect the baseplates and occlusal rims before the patient arrives. At this appointment, the dentist will place the baseplates in the patient's mouth and record the vertical dimension (the space occupied by the height of the teeth in normal occlusion), the occlusal relationships of the arches, the smile line (the number of teeth that shows when the patient smiles), the location of the cuspids, and the occlusal registration. In addition, the shade, the shape, and the alignment of the teeth will be determined. The laboratory will use all of this information for placement of the artificial teeth in wax. All materials being returned to the laboratory are disinfected before being sent.

Try-In of Completed Wax-Up

· same materials as for the jaw relationship  appointment

· hand mirror for patient

· wax-up from laboratory

The assistant should disinfect the completed wax-up before it is placed in the mouth. The wax-up consists of the baseplate with the artificial teeth set in wax, which has the appearance of the final denture base. The dentist will try the wax setup in the patient's mouth and make any adjustments needed. At this time, the denture is also evaluated for esthetics, a step in which the patient should partake. The wax setup should be disinfected before being returned to the laboratory. The laboratory will complete the denture.

Delivery of Complete Dentures Appointment

·  basic setup

· hand mirror

·  articulating paper and forceps

·  pressure indicating paste and applicator

·  high and slow-speed handpieces and necessary   burs and discs

· completed dentures from the laboratory

· denture brush and denture container

The completed dentures should be disinfected before they are placed in the patient's mouth. The new dentures are inserted in the patient's mouth and the patient is given some time to adjust. The dentist will examine the fit and retention of the dentures. The dentist may check the internal fit by brushing pressure indicating paste on the interior of the denture. In areas of extreme pressure, the paste will have worn off the denture base. The dentist will use an acrylic bur to reduce the pressure spot. The paste should be dispensed on a pad or in a dappen dish to avoid cross contamination of the contents of the container. The dentist will also check the patient's occlusion, and will make adjustments as needed.

The patient is instructed on insertion and removal of the dentures and given home care instructions (described later). A denture brush and a container for the dentures are given to the patient. The patient is told to call the office if any problems, such as sore spots, should arise, and they will be scheduled for an adjustment appointment. Usually the patient is scheduled for an adjustment appointment several days after delivery of the new denture. The dentist will reevaluate the dentures at this time and make any adjustments necessary. Future adjustment appointments are made as needed. After a denture adjustment, the denture may need to be polished. This is accomplished by using the laboratory lathe and a sterile rag wheel and pumice. Separate burs, rag wheels, and pumice should be used for each patient. When polishing, the tissue surface of the prosthesis is not polished because it may alter the fit.⁸ The acrylic should not be overheated when polishing because this may cause distortion; plastic teeth should not be polished because they will abrade easily.⁹

If a patient with an old denture arrives at the dental office for an adjustment appointment, but the patient's home care has not been adequate, the prosthesis may have an accumulation of plaque and calculus on it. The assistant may remove the plaque and calculus by placing the prosthesis in a container, such as a beaker, and then placing the beaker in the ultrasonic cleaner. The prosthesis can then be brushed with a new toothbrush before it is polished, and returned to the patient.

Immediate Dentures

An immediate denture is seated immediately after the extraction of the patient's teeth. An advantage of an immediate denture is that the patient does not have to be without teeth while waiting for the denture to be constructed. For this reason, maxillary immediate dentures are more common than mandibular. A disadvantage to an immediate denture is that the denture will need to be relined, rebased, or replaced within 3-6 months because as healing occurs, the alveolar ridge undergoes changes due to resorption. The denture will not fit properly after these changes take place. Often when a patient will be receiving an immediate denture, the posterior teeth are extracted first and that area is allowed to heal. Impressions are taken after healing, and with the anterior teeth in place. The denture is constructed before the extraction date. Another advantage to this is that the laboratory will have the model of the patient's natural dentition on which to base the denture. The anterior teeth are then extracted, and the denture is placed immediately following the extraction. The denture acts a bandage or compress to the extraction sites, controlling the bleeding and swelling. The patient is scheduled for a postoperative checkup in 24 hours, during which time the patient is instructed to leave the denture in place.

Tissue Conditioners, Relines and Rebases

If the oral tissues under the denture become irritated or inflamed due to a poor fit, a tissue conditioning material is placed on the inside of the denture. This material is a soft lining material that remains in the denture until the patient's tissues are healed. The tissues must be healthy before a reline is completed. A reline consists of the placement of a new layer of denture resin on the inside of the denture. This will make the denture fit properly again. To do a reline, the dentist will take an impression of the patient's arch, using the patient's denture as the impression tray. The patient will be without the denture, usually for a day or two, while it is sent to the laboratory for the reline. A rebase consists of replacing the entire denture base material, without changing the occlusal relationship of the teeth.

Overdentures

An overdenture is made to fit over one or more remaining teeth, which helps to improve the retention and stability of the denture. Often times the remaining teeth are the canines. The remaining teeth are usually endodontically treated, and may be prepared with cast post and cores. The denture is fabricated with an attachment on the tissue side that will align with the retained teeth. The patient may also have dental implants on which the denture will attach. This type of denture requires that the patient be diligent with oral hygiene in order to maintain the remaining teeth.

Care of Removable Prostheses

Before the patient leaves the dental office with a new removable partial denture or full denture, they must be given home care instructions for the prosthesis and for the oral cavity. The patient should be aware that the prosthesis is capable of collecting the same deposits as natural teeth, and that these deposits may also get under the prosthesis and affect the oral mucosa. If possible, the prosthesis should be removed and cleaned after eating. A soft denture brush should be used to clean the prosthesis, using a toothpaste made for dentures and removable partial dentures. The patient should be instructed to clean the prosthesis over a sink half-filled with cool water, or with a soft cloth in the sink. If the patient should accidentally drop the prosthesis while cleaning it, the water or cloth will help prevent breakage of the prosthesis. Neither hot water nor strong solutions, such as undiluted bleach, should be used to clean the removable partial denture or denture because it may cause damage. When the prosthesis is not being worn, it should be placed in water to avoid drying and warping. A commercial denture cleaner, used with warm water, can be used for overnight soaking. This will help soften calculus and remove stains. In order to maintain the health of the oral tissues, the patient should thoroughly rinse the oral cavity daily.

Patients with a removable partial denture must also thoroughly brush and floss the remaining teeth, using a different brush from the one used for the removable partial denture. The prosthesis should not be worn overnight. The oral tissues need to be exposed for several hours each day, and removal of the prosthesis overnight provides this opportunity. To clean and massage the oral mucosa, the patient can place a soft, moist washcloth over the index finger and thoroughly scrub the oral tissues. A soft tooth brush can also be used for this purpose. When the removable partial denture or denture is inserted, the patient should use the hands as opposed to biting the prosthesis into place. The patient should be attentive to changes that may take place in the oral cavity, including sore spots. Failure to maintain the prosthesis and the oral tissues can result in chronic damage to the oral tissues. Edentulous patients should be reminded that insertion of the new denture does not mean that it should be the last dental appointment. Routine examinations are still necessary for the life of the patient. Sore spots can develop anywhere the prosthesis touches the mucosa, especially near the frenum in the vestibule.

Incorporating Fluoride

Chronic dry mouth, known as xerostomia, is caused by lack of saliva for a long period of time. Multiple causes for this condition include: medications, chronic diseases, and certain medical treatments. Chronic dry mouth is not only uncomfortable, but it increases your risk for dental decay and makes it difficult for dentures to fit properly. If your patient suffers from dry mouth, they should visit their dental team more frequently than every six months to address their increased risk of tooth decay. Use of fluoride as an adjunct to homecare may be recommended. Fluoride decreases dental decay. Since 1945, the U.S. Government has advocated the controlled addition of fluoride to public drinking water. In small amounts, ingested fluoride seems to strengthen the enamel while it is being formed in young children or pregnant women.

Recommended levels of fluoride in water should range from 0.5 mg - 1.0 mg per liter of water with 0.7 mg per liter as optimal. In rare cases, extreme excesses of fluoride in water will change the appearance of the enamel, making permanent teeth look discolored and pitted. This was a common problem in years past for individuals using unregulated well water with a high mineral content as the source of their drinking water.

In recent years, the dental profession has recognized the benefit of applying fluoride to the teeth in the form of toothpaste or gels to helps prevent tooth decay. Patients with a high rate of tooth decay and those at risk for developing decay due to xerostomia or post-radiation treatment will often use topical fluoride on a regular basis. Patients with exposed root surfaces may be able to use topical fluoride to decrease the associated sensitivity. To help relieve symptoms of dry mouth, patients may want to drink fluids that do not contain sugar or acids, with water being the best choice. They also may want to use sugar-free hard candy or gum to stimulate saliva flow. Many people have also found some relief using over the counter saliva substitutes.

CONCLUSION

The changes in the discipline of prosthodontics over the last several decades, largely as a result of developments of new materials and methods, but also of prevention and improved dental health, have been significant. The revolution of dental implants, as well as other newer technologies, of which adhesive, high-strength ceramic and CAD/CAM technologies are notable examples, are in various stages of establishing themselves as part of conventional prosthodontics. While such developments have led to significant changes in clinical prosthodontics, education in many ways seems to lag behind. Prosthodontics continues to evolve as a dental specialty and it is anticipated that the services provided by the specialty will continue to be of value to the profession and the public.¹

REFERENCES

1.  https://www.prosthodontics.org/assets/1/7/1.What_is_a_Prosthodontist_and_the_Dental_Specialty_of_Prosthodontics -_ approved1.pdf Accessed November 25, 2018.

2.  http://www.aapd.org/assets/1/25/Seow-15-06.pdf Accessed November 25, 2018.

3.  Wright JT. Amelogenesis Imperfecta. Developmental Defects of the Teeth. https://www.dentistry.unc.edu/dentalprofessionals/ resources/defects/ai/ Accessed November 25, 2018.

4.  Amelogenesis Imperfecta. National Organization for Rare Diseases (NORD). 2018;https://rarediseases.org/rare-diseases/ amelogenesis-imperfecta/ Accessed November 25, 2018.

5.  Amelogenesis imperfecta. Genetics Home Reference (GHR). May 2015; http://ghr.nlm.nih.gov/condition/amelogenesis-imperfecta/ Accessed November 25, 2018.

6.  Crawford PJM, Aldred M & Bloch-Zupan A. Amelogenesis imperfecta. Orphanet. April, 2007; http://www.orpha.net/consor/cgi-bin/ OC_Exp.php?lng=EN&Expert=88661 Accessed November 25, 2018.

7.  https://www.gotoapro.org/treatments/mouthguards/Accessed November 26, 2018.

8.  Bird, Doni, and Robinson, Debbie. Torres and Ehrlich Modern Dental Assisting. 8th ed., St. Louis: Elsevier Saunders 2005.

9.  Phinney, Donna J., and Haldstead, Judy H. Delmar's Dental Assisting: A Comprehensive Approach. 2nd ed.; Clifton Park, New York. Delmar 2004.

10.  https://www.aegisdentalnetwork.com/id/2010/08/zirconia-restorations-perception-or-evidence.Dennis J. Fasbinder, DDS, Inside Dentistry, Jul/Aug 2010, Volume 6, Issue 7, Accessed September 17, 2020.

ABOUT THE AUTHORS

The original author of #613 General Chairside Assisting: A Review for a National General Chairside Examwas:

Antoinette P. Metivier, BS, was an assistant professor in the Dental Assisting Department at the New Hampshire Institute in Concord, NH where she taught dental radiology. She attended the North Carolina's Dental Radiology Institute for Dental Educators and developed and presented radiology review courses for the New Hampshire Dental Assistants Association.

The course was later completely revised by:

Kimberly Bland, CDA, EDDA, MS, has served as ADAA's Fifth District Trustee, national Secretary, national Vice President, national President Elect and twice as ADAA President (2007-2008; 2014-2016). She has held several offices in both the local and state ADAA organizations, having been President of the Florida Dental Assistants Association for three terms and is past president of the Sara-Mana Dental Assistants Society of Florida. She was a founding member of the Professional Dental Assistants Educational Foundation (PDAEF) and continues to remain active with national activities.

Ms. Bland is a member of the Florida Board of Dentistry Dental Assisting Council and has held offices in the Florida Allied Dental Educators Association and as Florida Region V Post-Secondary Advisor of the Florida Health Occupation Students of America (HOSA). Kimberly is a graduate of the University of South Florida, where she majored in Industrial Technical Education. Earlier, she earned her Dental Assisting Certificate at Manatee Technical Institute where she is now the dental assisting program director.

The dental specialties section was removed from the original #613 General Chairside Assisting: A Review for a National General Chairside Examas a standalone course and was reviewed and developed by:

Natalie Kaweckyj, LDA, RF, CDA, CDPMA, COA, COMSA, CPFDA, CRFDA, MADAA, BA - began her dental assisting career over 25 years ago after graduating from the CODA accredited program ConCorde Career Institute. She spent twelve years working in a private practice where she worked clinically nine years and administratively the remaining three. She then moved onto teaching dental assisting and eventually became director of that program. Over lapping with teaching, Natalie began her tenure with Children's Dental Services in 2007 in management and currently serves as clinical coordinator responsible for the day to day operations at over 600 locations where services are provided throughout Minnesota. Natalie enjoys the challenges of the public health sector and is gratified in serving those that are underserved, especially in a hospital setting under general anesthesia. With over a decade of restorative functions experience under her belt, she enjoys working with professionals new to dentistry as her love for teaching comes into play with the utilization of clinicians to the full scope of their licenses. The clinic keeps Natalie busy with billing management when not at the hospital. Natalie also graduated with a BA in Biology and Psychology from Metropolitan State University in 2005.

Ms. Kaweckyj served two terms as ADAA President (2017-2018; 2010-2011). She remains active on several councils, and served as a President of the Professional Dental Assistants Educational Foundation (PDAEF). She served as a three-term president for MnDAA and remains as the state business secretary. Natalie has been recognized with several ADAA awards, was one of the first ADAA Fellows in 1999 and became the first ADAA Master in 2004. She has published numerous continuing education courses, over 200 articles and lectures on a variety of dental subjects locally, nationally and internationally. Organized dentistry gave Natalie the insight that you can make a difference as a dental professional, and she was instrumental in seeing licensure for dental assistants come to fruition in MN in 2009 as well as several expanded functions. Her dream would be to see mandatory credentialing become a reality in all states for protection of the public and maintaining integrity of the dental assisting profession.