Fundamentals of Fixed Prosthodontics. James C. Kessler
destruction that has previously occurred. However, when these teeth are evaluated from the standpoint of the oral environment, they may, in fact, be poor candidates for cemented restorations. If extensive plaque, decalcification, and caries are present in a mouth, the use of crowns of any kind should be carefully weighed. The design of a restoration should take into account those factors that will enable the patient to maintain adequate hygiene to make the restoration successful. The patient must be motivated to follow a regimen of brushing, flossing, and dietary regulation to control or eliminate the disease process responsible for destruction of tooth structure. It may be desirable to use pin-retained amalgam provisional restorations to save the teeth until the conditions responsible for the tooth destruction can be controlled. This will give the patient the time necessary to learn and demonstrate good oral self-care. It will also permit the dentist and staff to reinforce the skills required of the patient and to evaluate the patient’s willingness and ability to cooperate. If these measures prove successful, cast metal, ceramic, or metal-ceramic restorations can be fabricated. Because these restorations are used to repair the damage caused by caries and do nothing to cure the condition responsible for the caries, they should not be used if the oral environment has not been brought under control.
A fourth factor is financial considerations. Finances influence all treatment plans because someone must pay for the treatment. That may be a government agency, a branch of the military, an insurance company, and/or the patient. If the patient is to pay, the dentist should provide good advice and then allow the patient to make the choice. A conscientious dentist must walk a fine ethical line. On the one hand, a dentist should not preempt the choice by selecting a less-than- optimum restoration just because he or she thinks that the patient cannot afford the optimum treatment. On the other hand, a dentist should be sensitive enough to the individual patient’s situation to offer a sound alternative to the optimum treatment plan and not apply pressure.
A final factor is retention. Full coverage crowns are unquestionably the most retentive1,2 (Fig 6-1). However, maximum retention is not nearly as important for single-tooth restorations as it is for fixed partial denture retainers. It does become a special concern for short teeth and removable partial denture abutments.
Fig 6-1 A comparison of resistance to removal forces for four types of crowns (P = .05).1,2 MOD, mesio-occlusodistal.
Twelve restoration types are presented in the following pages to provide a frame of reference for making a decision whether to use a “plastic” restoration or a cemented restoration. The plastic restoration is inserted as a soft (ie, plastic) mass into the cavity preparation, where it will harden and be retained by mechanical undercuts or adhesion. The cemented restoration, made of cast metal, metal-ceramic, or all-ceramic material, is fabricated outside of the operatory and is luted or bonded to the patient’s tooth at a subsequent appointment. One type can be better suited for a particular application than the other, or in some cases either may be suitable.
Intracoronal Restorations
When sufficient coronal tooth structure exists to retain and protect a restoration under the anticipated stresses of mastication, an intracoronal restoration can be employed. In this circumstance, the crown of the tooth and the restoration itself are dependent on the strength of the remaining tooth structure to provide structural integrity.
Glass ionomer
Small lesions where extensions can be kept minimal and where preparation retention will be minimal can be restored with glass ionomer. It is useful for restoring Class V lesions caused by erosion or abrasion (Fig 6-2). It also can be employed for incipient lesions on the proximal surfaces of posterior teeth by use of a so-called tunnel preparation, which leaves the marginal ridge intact (Fig 6-3).
Glass ionomer has found a niche in the restoration of root caries in geriatric and periodontal patients (Fig 6-4). An occlusal approach may be precluded by the presence of an otherwise acceptable crown, or a conventional restoration at such an apical level might require the destruction of an unacceptable amount of tooth structure. In addition, handpiece access may be too restricted to create the needed retention for a small amalgam restoration.
Glass ionomer also can be placed rapidly enough to serve as an interim treatment restoration to assist in the control of rampant caries (Fig 6-5). This is further enhanced by the release of fluoride by the material.
Composite resin
This material can be used for minor to moderate lesions in esthetically critical areas (Fig 6-6). While it can be used in the restoration of incisal angles assisted by acid etching, a tooth that has received a Class IV resin restoration ultimately will require a crown.
Composite resin has been used in the restoration of posterior teeth with mixed results. Sufficient abrasion resistance to prevent occlusal wear has been a problem. Also, unless the resin is carefully applied in small increments, polymerization shrinkage will lead to leakage and ultimately to failure. Its use probably should be restricted to small occlusal and mesio-occlusal restorations on first premolars.
An innovative approach to the prevention of root caries at the margins of restorations that extend from enamel to cementum is the application of a slurry of unfilled resin and sodium fluoride combined with laser energy.3 This approach resulted in a significantly increased resistance to acid and mechanical destruction. In another study, topical fluoride in combination with laser energy provided resistance to enamel caries.4
A technique devised to combat the problems of shrinkage and leakage is the fabrication of a composite resin inlay (Fig 6-7). This can be accomplished in the dental office, using a fast-setting gypsum cast, or in a dental laboratory. The resultant bench-polymerized inlay will have greater hardness, and the thin layer of resin used for affixing it to tooth structure will be less susceptible to significant shrinkage at the margin than a restoration that is bulk cured in situ.
Simple amalgam
The simple amalgam, without pins or other means of auxiliary retention, for decades has been the standard one- to three-surface restoration for minor- to moderate-sized lesions in esthetically noncritical areas (Fig 6-8). It has received a good amount of negative attention in the media, and some segments of the profession use this as an excuse to replace otherwise acceptable amalgam restorations with composite resin. The American Dental Association’s Statement on Dental Amalgam states that amalgam is a valuable, viable, and safe choice for dental patients.5 A European Commission’s Scientific Committee also concluded that amalgams are effective and safe.6 They further state that there is no clinical justification for removing satisfactory amalgams except for allergic reactions. Nor is the mere presence of a defective margin alone enough to require replacement.7 Approximately 71 million or more simple amalgam restorations are placed annually.8 They are best used where more than half of the coronal dentin is intact.
Fig 6-2 Glass ionomer can be used to restore gingival abrasion or erosion.
Fig 6-3