Canines possess the longest roots of all teeth and are located at the corners of the dental arch. They func- Structures of Teeth tion in the seizing, piercing, tearing, and cutting of food.
From a proximal view, the crown also has a tri- Teeth are composed of enamel, the pulp—dentin angular shape, with a thick incisal ridge. The anatom- complex, and cementum see Fig. Each of these ic form of the crown and the length of the root make structures is discussed individually. Clinical Notes 4 7 Canines not only serve as important guides in occlu- sion because of their anchorage and position in the 8 dental arches but also play a crucial role along with the incisors in the esthetics of smile and lip support see Fig.
Chapter Understanding the bal- Dental caries is defined as a multifactorial, transmis- ance between demineralization and remineralization sible, infectious oral disease caused primarily by the is the key to caries management. It is essential to understand that caries lesions, or cavi- tations in teeth, are signs of an underlying condition, an imbalance between protective and pathologic factors Demineralization — favoring the latter. In clinical practice, it is very easy Remineralization Balance to lose sight of this fact and focus entirely on the re- storative treatment of caries lesions, failing to treat the underlying cause of the disease Table 2.
Although Traditionally, the tooth-biofilm-carbohydrate interac- symptomatic treatment is important, failure to identify tion has been illustrated by the classical Keyes-Jordan and treat the underlying causative factors allows the dis- diagram.
Several modifying risk and protective factors influ- Etiology of Dental Caries ence the dental caries process, as will be discussed Dental caries is a disease that is dependent on the later in this chapter Fig. This cycle is ii Tooth habitat summarized in Box 2.
They can also Remineralization mechanism of a occur in the proximal surfaces but are difficult to white spot lesion WSL detect. The supersaturation of saliva with calcium and phosphate Remineralization mechanism The remineralization ions serves as the driving force for the remineralization mechanism of white spot lesion WSL is summa- process rized in Box 2.
These discolored, remineralized, arrested caries histologic alteration of the underlying dentin probably areas are intact and are more resistant to subsequent caries already has occurred, whether the lesion is cavitated attack than the adjacent unaffected enamel. They should or not Fig. Sclerotic dentin is usually shiny and darker in color but feels hard to the explorer tip. By contrast, normal, freshly cut dentin lacks a shiny, reflective surface and allows some penetration from a sharp ex- A plorer tip.
The apparent function of sclerotic dentin is to wall 1 2 3 off a lesion by blocking sealing the tubules. The permeability of sclerotic dentin is greatly re- duced compared with normal dentin because of the decrease in the tubule lumen diameter.
Reaction to a moderate-intensity attack B The second level of dentinal response is to moderate- 12 3 intensity irritants by forming reparative dentin. A, As dentin grows, Mechanism of reparative dentin formation odontoblasts become increasingly compressed in the The mechanism of reparative dentin formation is ex- shrinking pulp chamber, and the number of associated plained in Flowchart 2. The more recently formed dentin near the pulp a has large tubules Infected dentin contains a wide variety of pathogenic materials with little or no peritubular dentin and calcified intertubular or irritants, including high acid levels, hydrolytic enzymes, dentin filled with collagen fibers.
Older dentin, closer to bacteria, and bacterial cellular debris the external surface b , is characterized by smaller, more widely separated tubules and a greater mineral content in intertubular dentin. Horizontal lines indicate predentin; diagonal lines indicate increasing density of minerals; darker The pulp may be irritated sufficiently from high acid levels horizontal lines indicate densely mineralized dentin and or bacterial enzyme production to cause the formation from undifferentiated mesenchymal cells of replacement odontoblasts increased thickness of peritubular dentin.
B, Carious dentin secondary odontoblasts undergoes several changes. The most superficial infected zone of carious dentin 3 is characterized by bacteria filling the tubules and granular material in the intertubular space. As bacteria invade dentinal tubules, if carbohydrates are These cells produce reparative dentin reactionary dentin on available, they can produce enough lactic acid to remove the affected portion of the pulp chamber wall see Figs. Pulpal to below the infected dentin is a zone where the dentin appears transparent in mounted Flowchart 2.
This zone 2 is affected not infected carious dentin and is characterized by loss of mineral in the intertubular and peritubular dentin. Many crystals can Clinical Notes be detected in the lumen of the tubules in this zone. This re- the pulp chamber of unattached dentin, termed pulp pair occurs only if the tooth pulp is vital. It is critical to remember that clinicians treat the entire pa- tient and not just individual teeth and caries lesions Fig. Equally important in the management of caries as a disease entity is the ability to individual- ize caries treatment or interventions for each patient.
Surgical Model of Caries Management Historically, dentistry has used a surgical model for the management of dental caries, which mainly in- volved the biomechanical removal of caries lesions and the restoration of the resultant tooth preparation to form and function with a restorative material. Management of caries disease by a surgical model consisted of waiting until cavitations were detected and treating the cavitations with restorations.
Eventually, it became apparent that dealing only with the end result of the disease and not addressing its etiology for each individual patient was not suc- Fig. Chlorhexidine may be used in combination Box 3.
When using this approach, ACP is a reactive and soluble calcium phosphate it may be prudent to use toothpaste free from sodium lauryl sulfate SLS , which causes the foaming action in compound that releases calcium and phosphate ions to dentifrices.
Although data are equivocal, evidence dem- convert to apatite and remineralize the enamel when it onstrates that SLS reduces the ability of CHX to reduce comes in contact with saliva38 plaque formation. Xylitol Xylitol is a natural five-carbon sugar obtained from birch trees. It seems to have several mechanisms of action to reduce the incidence of caries. Probiotics acidogenicity of plaque because chewing stimulates salivary flow, which improves the buffering of the pH The fundamental concept of probiotics is to inocu- drop that occurs after eating.
Current protocols suggest chewing two pieces of gum contain- ing a total of 1 gram of xylitol three to six times per day, preferably after meals and snacks. Calcium and Phosphate Compounds A relatively new group of products, called amorphous calcium-phosphates ACP in conjunction with ca- sein phosphopeptide CPP , have become commer- cially available and have the potential to remineral- ize tooth structure.
Mousse, GC Asia. Assessing risk Any discussion of diagnosis and treatment must Determining prognosis begin with an appreciation of the role of the dentist in helping patients maintain their oral health. This phrase rep- resents a fundamental principle of the healing arts Research that provides information on treatments over many centuries. This information is then combined with a distillation of the available knowledge about with the best available evidence on the approaches various conditions and treatments.
These steps decisions. These areas may result from numerous factors dental explorer for this purpose was found to fracture but do not warrant restorative intervention unless they are enamel and serve as a source for transferring pathogen- esthetically offensive or cavitation is present. Role of Explorer Caries lesions can be detected by visual changes in tooth surface texture or color or in tactile sensation when an explorer is used judiciously 2. Radiographic examination Proximal surface car- to detect surface roughness by gently stroking across ies is usually diagnosed radiographically13 Fig.
Sealants are defined as confined to enamel. Restoration is defined as in dentin. A two-surface restoration is defined as a preparation that has one part of the preparation in dentin and the preparation extends to a second surface note: the second surface does not have to be in dentin. A sealant can be either resin-based or glass ionomer. Resin-based sealants should have the most conservatively prepared fissures for proper bonding. Glass ionomer should be considered where the enamel is immature, or where fissure preparation is not desired, or where rubber dam isolation is not possible.
Patients should be given a choice in material selection. Blade The blade is the working end of the instrument and is Hand Instruments for Cutting connected to the handle by the shank.
For many noncutting instruments, the part corre- Removal and shaping of tooth structure are essential sponding to the blade is termed nib. Modern high-speed The end of the nib, or working surface, is known equipment has eliminated the need for many hand as face. Nevertheless, hand instruments remain an essential part of the ar- mamentarium for restorative dentistry.
The early hand-operated instruments with their large, heavy handles Fig. Among his many contributions to modern dentistry, G V Black is credited with the first accept- able nomenclature for and classification of hand in- struments. Modern hand instruments, when properly used, produce beneficial results for the operator and the patient. Some of these results can be satisfactorily achieved only with hand instruments and not with rotary instruments.
Terminology and Classification Classification Fig. These instruments were individually handmade, variable in The hand instruments used in the dental operatory design, and cumbersome to use.
Because of the nature of may be categorized in Box 7. Runout is the more significant term clinically because it is the primary cause of vibration during cutting and Clearance angle The clearance angle eliminates is the factor that determines the minimum diameter of rubbing friction of the clearance face, provides a stop the hole that can be prepared by a given bur.
Because of to prevent the bur edge from digging into the tooth runout errors, burs normally cut holes measurably larger structure excessively, and provides adequate flute than the head diameter.
An increase in the clearance angle causes a decrease in the edge angle. Bur Blade Design The actual cutting action of a bur or a diamond occurs Clinical Notes in a very small region at the edge of the blade or at the point of a diamond chip.
Figure 7. Several terms used faces to provide a low clearance angle near the edge and in the discussion of blade design are illustrated. Each blade has two sides—the rake face toward the direction of cutting and the clearance face—and II. Diamond Abrasive Instruments three important angles—the rake angle, the edge an- gle, and the clearance angle.
The second major category of rotary dental cutting in- struments involves abrasive cutting rather than blade Rake angle The rake angle is the most important cutting. Abrasive instruments are based on small, an- design characteristic of a bur blade. A rake angle is gular particles of a hard substance held in a matrix said to be negative when the rake face is ahead of the of softer material. Cutting occurs at numerous points radius from cutting edge to axis of bur , as illustrated where individual hard particles protrude from the in Figure 7.
For cutting hard, brittle materials, a matrix, rather than along a continuous blade edge. Terminology Edge angle Carbide bur blades have higher hardness Diamond abrasive instruments consist of three parts and are more wear-resistant, but they are more brittle Fig. Metal blank to minimize fractures. Increasing the edge angle 2.
Powdered diamond abrasive 3. Metallic bonding material that holds the dia- mond powder onto the blank. Rake The diamonds employed are industrial diamonds, angle To axis of bur either natural or synthetic, that have been crushed to powder, then carefully graded for size and quality. The shape of the individual particle is important because of its effect on the cutting efficiency and du- Edge angle rability of the instrument, but the careful control of particle size is probably of greater importance.
Rake The diamonds generally are attached to the blank face Clearance by electroplating a layer of metal on the blank while angle holding the diamonds in place against it. Clearance face Classification Direction of rotation Diamond instruments currently are marketed in myr- Fig. Schematic cross-section viewed iad head shapes and sizes Table 7. Most of the diamond shapes clearance angle. In the past, most restorative treatments were for car- Such precise preparations are still required for amal- ies, and the term cavity was used to describe a car- gam, cast metal, and ceramic restorations and may be ies lesion that had progressed to the point that part considered conventional preparations.
Conventional of the tooth structure had been destroyed. The tooth preparations require specific wall forms, depths, and was cavitated a breach in the surface integrity of the marginal forms because of the properties of the re- tooth and was referred to as a cavity.
Likewise, when storative material. Currently, many indications for treatment are The use of adhesive restorations, primarily composites not related to carious destruction, and the prepara- and glass ionomers, has allowed a reduced degree of tion of the tooth no longer is referred to as cavity precision of tooth preparations.
Many composite res- preparation, but as tooth preparation. The fundamental concepts relat- ing to conventional and modified tooth preparation Tooth Preparation are the same: Tooth preparation is defined as the mechanical alter- 1. All unsupported enamel tooth structures are ation of a defective, injured, or diseased tooth such normally removed.
Fault, defect, or caries is removed. Remaining tooth structure is left as strong as tions, where indicated. These enamel rods are buttressed on the Class V Preparations preparation side by progressively shorter rods whose outer ends have been cut off Preparations on the gingival third of the facial or lin- but whose inner ends are on sound dentin gual surfaces of all teeth are termed class V.
Because enamel rods usually Class VI Preparations are perpendicular to the enamel surface, the strongest enamel margin results in a Preparations on the incisal edges of anterior teeth or cavosurface angle greater than 90 degrees the occlusal cusp tips of posterior teeth are termed see Fig. An enamel margin composed of full-length rods that are on sound dentin but are not buttressed Stages of Tooth Preparation tooth-side by shorter rods also on sound dentin is termed strong.
Generally, this margin results The tooth preparation procedure is divided into two in a 90 degree cavosurface angle. Each stage should be 3. An enamel margin composed of rods that do not thoroughly understood, and each step should be accom- run uninterrupted from the surface to sound den- plished as perfectly as possible.
The stages are present- tin is termed unsupported. Usually, this weak ed in the sequence in which they should be followed if enamel margin either has a cavosurface angle consistent, ideal results are to be obtained. The stages less than 90 degrees or has no dentinal support. Classification of Tooth Preparations Initial Tooth Preparation Stage Initial tooth preparation involves the extension of the Classification of tooth preparations according to the external walls of the preparation at a specified, limited diseased anatomic areas involved and by the associ- depth so as to provide access to the caries or defect and ated type of treatment was presented by Black.
All pit-and-fissure preparations are termed class I. Occlusal surfaces of premolars and molars The first step in initial tooth preparation is determin- 2. Occlusal two-thirds of the facial and lingual sur- ing and developing the outline form while establish- faces of molars ing the initial depth. Lingual surfaces of maxillary incisors. Box 9. Step 1: Outline form and initial depth Step 2: Primary resistance form Step 3: Primary retention form Class III Preparations Step 4: Convenience form Preparations involving the proximal surfaces of an- Final tooth preparation stage terior teeth that do not include the incisal angle are Step 5: Removal of any remaining infected dentin or old termed class III.
Placing the preparation margins in the positions be assessed. These conditions affect the outline form they will occupy in the final preparation except and often dictate the extensions. The extent of the caries lesion, defect, or faulty 2. Preparing an initial depth of 0. Esthetic considerations not only affect the el thickness is minimal, and greater dimension choice of restorative material but also the design is necessary for the strength of the restorative of the tooth preparation in an effort to maximize material Fig.
Correcting or improving occlusal relationships Principles also may necessitate altering the tooth preparation The three general principles on which outline form is to accommodate such changes, even when the in- established regardless of the type of tooth preparation volved tooth structure is not faulty i.
All unsupported or weakened friable enamel sal relationships. The desired cavosurface marginal configuration 2. All faults should be included. All margins should be placed in a position to form. Restorative materials that need beveled allow finishing of the margins of the restoration.
A, B, and C, Extensions in all directions are to sound tooth structure, while maintaining a specific limited pulpal or axial depth regardless of whether end or side of bur is in dentin, caries, old restorative material, or air. In A, initial depth is approximately two-thirds of 3mm bur head length, or 2 mm, as related to prepared facial and lingual walls, but is half the No. Preserving cuspal strength Primary groove 2.
Preserving marginal ridge strength Mandibular groove molar 3. Minimizing faciolingual extensions Central 4. Restricting the depth of the preparation into dentin. Extent to which the enamel has been involved groove toward the cusp tip is no more than half the distance, by the carious process no cusp capping should be done; if this extension is one 2.
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