What is dentistry? |

Science and Profession

The practice of dentistry is a specialized area of medicine that treats the diseases of the teeth and their surrounding tissues in the oral cavity. Dental education normally takes four years to complete, with predental training preceding it. Prior to entering a dental school, students are usually required to have a bachelor’s degree. This degree should have major emphasis in biology or chemistry. Predental courses are concentrated in both inorganic and organic chemistry. The biology courses can cover such subjects as comparative anatomy, histology, physiology, and microbiology. Other courses that can help students to prepare for both dental school and the future practice of dentistry are English, speech skills, physics, and computer technology. Upon entering dental school, students are faced with two distinct parts of their education: didactics and techniques.

The didactic courses offered in dental schools are required to achieve knowledge of the human body, most particularly the head and neck. Some of the courses required are human anatomy, physiology, biochemistry, microbiology, general and oral histology and pathology, dental anatomy, pharmacology, anesthesiology, and radiology. One course specific to dental school is occlusion, which emphasizes the structure of the temporomandibular joint and its accompanying neurology and musculature.

In addition, students must know the properties of the materials used in the practice of dentistry. The physical properties of metals, acrylic plastics, gypsum plasters, impression materials, porcelains, glass ionomers, dental composites, sealant resins, and other substances must be thoroughly understood to determine the proper restorations for diseased tissues in the mouth. Knowledge of resistance to wear by chewing forces, thermal conductivity, and corrosion and staining by mouth fluids and foods is important. Information concerning the materials used in dental treatment in terms of resistance to recurrent decay, possible toxicity, or irritation to the hard and soft tissues of the oral cavity is also necessary.

The technical phase of dental education addresses the practical use of this didactic knowledge in treating diseases of the mouth. Students are trained to operate on diseased teeth and to prepare the teeth to receive restorations that will function as biomechanical prostheses in, or adjacent to, living tissue. An understanding of anatomy, physiology, and pathology is necessary for successful restoration of the teeth. During this course of study, students are required to construct fillings, cast-gold crowns and inlays, fixed and removable dentures, porcelain crowns and inlays, and other restorations on mannequins, plastic models, or extracted teeth. These activities are undertaken prior to working on patients. Through practice and repetition of these techniques, dental students soon become aware of the importance of mastering this phase of the education prior to their application in a clinical environment.

The clinical phase of dental education integrates the didactic and technical instruction that has taken place throughout the first years of professional study. Students learn to treat patients under the close supervision of their instructors. The treatment of patients in all the specialties of dentistry is required of students before they receive the degree for general dentistry. Some students may opt for extra training in one of several specialties. To become a specialist, postgraduate education is required. This education commonly encompasses two years of study but is sometimes longer.

Upon graduation, students receive their professional degrees. Before they can legally practice dentistry in the United States, however, they must successfully pass an examination offered by the board of dental examiners in their chosen state. National exams in didactics are offered during dental school, and most states accept them as part of their state examination. The technical portion of the exam may only be taken after the student has received a doctorate from an accredited college or university. The emphasis regarding techniques may vary from state to state. Many states allow reciprocity, which means that a student who has passed the examination in one state may become licensed to practice in another. In states that do not accept reciprocity, the student must pass the practical examination of that state prior to obtaining a license. There have been attempts to make reciprocity universal among all states, but several states insist on governing the quality of their dental health care.

Dental education can be quite expensive. After a dentist receives a license to practice, the cost of equipping an office must also be borne. A dental office must have dental chairs, office and reception room furniture, a dental laboratory, a sterilizing room, x-ray units, instruments, and various supplies. Because of these expenses, new dentists often initially practice as an associate or partner of an established dentist, as an employee of a dental clinic, in the military or Public Health Service, or in state institutions. Some dentists enjoy the academic atmosphere of dental schools and return to become part-time or full-time educators.

Diagnostic and Treatment Techniques

The practice of dentistry is quite different in modern times compared to the past. While some techniques and materials are still in use, there have been improvements in materials and instruments because of expanded knowledge in many scientific fields. This knowledge has increased to such an extent that dentistry has divided into several specialties. While the general dentist uses all disciplines of dentistry to treat patients, complex problems often require referral and the expertise of a specialist.

The general dentist is involved primarily in the treatment of caries or tooth decay and the replacement of missing teeth. Bacterial acids that dissolve the enamel and dentin of teeth cause caries. A diseased or damaged tooth must be prepared mechanically by the removal of the decayed material using a dental drill and tough, sharp bits called burs. The amount of damage and the position of the tooth in the mouth determine the type of restoration. In the posterior or back teeth, initial cavities may be restored with bonded composite resins. In addition to removing the decayed tooth structure, the dentist must take into consideration the closeness of the dental pulp, the chewing forces of the opposing teeth, and the aesthetics of the finished restoration. In the anterior or front teeth, aesthetic restorative materials are used to fill small cavities. In this case also, the size and position of the defect determine the choice of restorative material.

When the amount of tooth destruction caused by decay becomes too large for conservative filling materials, the remaining tooth structure must be reinforced by the use of cast metal or porcelain restorations. The tooth is prepared for the specific restoration, and accurate impressions are taken of the prepared teeth. The crown or inlay is fabricated on hard plaster models reproduced from the impressions and then cemented into place on the tooth. This process is also used for fixed partial dentures, or bridges, which are used to replace one or more missing teeth. Two or more teeth are prepared on either end of the space of missing teeth to support the span. The bridge is constructed with metal and porcelain as a single unit. It is then cemented on the prepared abutment teeth.

The health of the supporting tissues of the teeth, the periodontium, is necessary for the long-term retention of any mechanical restoration. When teeth become loose in the jaws because of periodontal disease, or pyorrhea, the restoration of these teeth often depends on the treatment by a periodontist, the specialist in this field. Periodontists treat the diseased tissues by scraping off harmful deposits on the roots of the teeth and by removing the diseased soft tissue and bone through curettage, surgery, or both techniques. Some newer techniques of grafting the patient’s bone with sterile freeze-dried bone, implanting stainless steel pins, or using other artificial materials show great promise.

If the tooth decay reaches the dental pulp and infects it, there are two choices of treatment: removal of the tooth or endodontic therapy, commonly known as root canal treatment. If the tooth is well supported by a healthy periodontium, it is better to save the tooth by endodontics. The basic procedure of a root canal is to enter the tooth through the chewing surface on teeth toward the rear of the mouth or the inside surface or lingual aspect of teeth in the front of the mouth. Files, reamers, and broaches to the tip of the root remove diseased or decaying (necrotic) material of the dental pulp. The now-empty canal is filled by cementing a point that fits into it. Although the tooth is now nonvital, meaning that it has lost its blood supply and nerve, it can remain in the mouth for many years and provide good service.

The maintenance of the health of the primary dentition, or baby teeth, is very important. These deciduous teeth, although lost during childhood and adolescence, are important not only to the dental health of the child but to the permanent teeth as well. The deciduous teeth act as guides and spacers for the correct placement of adult teeth when they erupt. A pediodontist, who specializes in the practice of dentistry for children, must have a good knowledge of the specific mechanics of children’s mouths in treating primary teeth. This specialist must also have a thorough foundation in the treatment of congenital diseases. The pediodontist prepares the way for dental treatment by an adult dentist and often assists an orthodontist by doing some preliminary straightening of teeth.

An orthodontist treats malocclusions, or ill-fitting teeth (so-called bad bites) with mechanical appliances that reposition the teeth into an occlusion that is closer to ideal. These appliances, known commonly as braces, move the teeth through the bone of the jaws until the opposing teeth occlude in a balanced bite. The side benefit of this treatment is that the teeth become properly positioned for an attractive smile and easier cleaning.

Sometimes the teeth or their supporting tissues become so diseased that there is no alternative but to remove them. A general dentist often does routine extractions of these diseased teeth. If the patient has complications beyond the training of a general dentist or is medically compromised by systemic illness, an oral surgeon, with specialized training, is typically consulted. This specialist not only removes teeth under difficult conditions but also is trained to remove tumors of the oral cavity, treat fractures of the jaws, and perform the surgical placement of dental implants.

Although the total loss of teeth is becoming rarer, there are still many patients who are without teeth. Often, they have been wearing complete, removable dentures that, over a period of time, have caused the loss or resorption of underlying bone. Prosthodontists are specialists trained to construct fixed and removable dentures for difficult cases. The increased success of titanium implants in the jaws and the appliances connected to them have aided prosthodontists in treating the complex cases. They also construct appliances to replace tissues and structures lost from cancer surgery of the oral cavity and congenital deformities such as cleft palate.

Perspective and Prospects

In the past, dentistry only treated pain caused by a diseased tooth; the usual mode of treatment was extraction. Today, the prevention of disease, the retention of teeth, and the restoration of the dentition are the treatment goals of dentists.

The development of composite resins has successfully addressed many aesthetic problems associated with restorations. Although metal fillings of silver amalgam (actually a mixture of silver, lead, and mercury) and cast-gold restorations were often the treatments of choice in the past, composite fillings have become the treatment of choice. Plastic composite materials that are chemically bonded to the enamel and dentin of teeth are more aesthetically pleasing than metals. They have also shown great promise for longevity. There is still some concern about the resistance of these materials to chewing forces and leakage of the bonding to the tooth, but the techniques and materials are improving.

Dental porcelains improved greatly in the last half of the twentieth century. Although porcelain fused to metal crowns is often the material of choice, in certain cases crowns, inlays, and fixed bridges of a newer type of porcelain are being used. Thin veneers of porcelain are also used to restore front teeth that are congenitally or chemically stained. The result is cosmetically more appealing. Through a similar bonding process of composites, these veneers on the front surfaces of the teeth offer maximum aesthetics with minimum destruction of tooth structure.

While implantation of metals into the jawbones to support dentures and other prosthetic appliances is not new, the recent use of titanium implants and precision techniques promises long-term retention. Special drills are used to prepare the implant site, and titanium cylinders are either threaded into the bone or pushed into the jaw. The implant is covered by the gum tissue and allowed to heal for six to eight months, so that the process of osseointegration (joining of bone and metal) can occur. The bone will actually fuse to the pure metal, anchoring the implant for an eventual prosthetic appliance.

Laser technology is an exciting field has yielded some important applications in dentistry. Lasers have been used in gum surgery. Some theorists believe that if the enamel surface of the teeth were to be fused, it would be highly resistant to decay. The heat generated by lasers is a concern, but steps are being taken to control this problem. One of the most promising uses of lasers is in the specialty of endodontics. A thin laser fiber-optic probe advanced down the root canal, preparing and sterilizing the canal prior to filling, vaporizes diseased or degenerating pulp.

Computer science is also being integrated into the treatment phase of dentistry. For example, after scanning a patient’s mouth, projected results of treatment can be displayed on a computer screen. In addition, restorations can be developed using the concept of computer-aided design/computer-aided manufacturing (CAD/CAM). A computer scans a prepared tooth for a crown or inlay. The restoration is then designed for a three-dimensional model on the screen. After the model restoration has been chosen, the computer transfers the data to a computer-activated milling machine in the dental laboratory, and a restoration is reproduced in a ceramic or composite resin material in the designed image. The restoration is then cemented into the prepared tooth. Furthermore, techniques are being developed toward a less invasive way than x-rays of assessing dental health, including optical coherence tomography.

Such improvements in techniques and materials have advanced dentistry into a new era in providing treatment for patients. The basic fundamentals of treatment of the teeth and their surrounding tissues must be maintained, however, in view of the peculiar anatomy and physiology of the teeth.

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