Diagnosis and Treatment Planning for Single Implants

Mahmoud Torabinejad and Hessam Nowzari

Chapter Outline

Learning Objectives

At the conclusion of this chapter, the reader will be able to:

. Discuss the etiologies of tooth loss and their treatments.

. List the indications for and contraindications to root canal treatment.

. Identify factors affecting planning for root canal treatment.

. Discuss the consequences of tooth loss without replacement.

. Discuss the effect of implants on prosthodontics.

. Discuss the indications for a single implant.

. Identify factors affecting treatment planning for a single implant.

Despite significant advances in the field of dentistry over the past century, numerous teeth still develop decay or periodontal disease or are lost because of traumatic injuries. Traditional measures called for the treatment and restoration of afflicted teeth with root canal therapy or periodontal procedures. If determined to be incapable of adequate restoration, the teeth were subsequently extracted and replaced with either fixed or removable prostheses.

Attempts were made to use dental implants in ancient civilizations, and as early as the 1800s endosseous root form implants were placed. In the twentieth century, implants were used in completely and partially edentulous patients to provide much-needed stability and function for fixed and removable prostheses (Figure 2-1). However, implant survival rates were not as high as desired, and sometimes substantial bone loss occurred in conjunction with loss of the implant. The survival rates of implants improved substantially with the introduction of modern cylindrical endosseous implants,^1,2 adding another valuable treatment option for teeth that could not be retained endodontically or periodontally (Figure 2-2).

Figure 2-1 Early implants were used as a base to provide stability and function for fixed and removable prostheses.

Figure 2-2 Etiologies of tooth loss and their treatments.

Dentists and patients are regularly confronted by a difficult treatment question: Should a tooth be saved by traditional treatment modalities (root canal treatment or periodontal treatment), extracted without any tooth replacement, or replaced with a fixed partial denture (FPD) or a single tooth implant (STI) and a crown? The purpose of this chapter is to answer these questions by discussing the diagnosis of and treatment planning for teeth with pulpal and periodontal diseases.

Diagnosis is a detective process and therefore must be performed systematically. It consists of (1) ascertaining the chief complaint, (2) collecting pertinent information regarding the patient’s medical and dental history, and (3) performing complete subjective, objective, and radiographic tests. As the starting point for treatment planning, diagnosis can make or break the process. Given its importance, it is a skill that even well-trained clinicians must regularly re-evaluate.

The first step involves the chief complaint, which is usually the first piece of information the patient volunteers with her or his understanding of the condition. The second step requires that clinicians record the patient’s comprehensive medical and dental history. The dental history usually provides information about previous treatments, and it can give clues to the patient’s attitude toward dental health. Finally, examinations (extraoral and intraoral, in addition to radiographs) help the clinician identify the cause of a patient’s complaint and the presence and extent of a pathologic condition. To provide the patient with the best treatment and to arrive at the proper diagnosis, multiple tests and procedures should be performed.

By conducting a systematic examination and careful analysis of the data obtained, the clinician is better equipped to make the right diagnosis. Once the diagnosis has been made, appropriate treatment planning can be carried out for most patients (Figure 2-3). However, treatment planning can become quite complicated when the expectations of the involved parties (patients, insurance companies, and dentists) are not completely met. An ideal treatment plan addresses the chief complaint of the patient, provides the longest lasting, most cost-effective treatment, and meets the patient’s expectations. In this way, treatment planning is truly a patient-centered process. Adequate treatment planning also includes relevant scientific evidence and preserves the biologic environment while maintaining or restoring esthetics, comfort, and function.

Figure 2-3 A, Radiograph of mandibular incisor (#26), which was diagnosed with external root resorption and referred for extraction. B, Clinical image 25 years later; the tooth is functional and asymptomatic.

Etiology and Treatment of Tooth Loss

Although the main causes of tooth loss are decay and periodontal disease, traumatic injuries can also result in significant tooth loss. The extent of damage to a tooth as a result of these injuries depends on the force of impact. Enamel fractures, crown fractures without pulp exposure, crown fractures with pulp exposure, crown-root fractures, root fractures, tooth luxations (concussion, subluxation, lateral luxation, extrusive luxation, intrusive luxation), avulsions, resorptions, and alveolar fractures are all potential outcomes of such trauma.³ Because of the range of injuries, clinicians should be prepared to treat affected teeth with a variety of procedures, ranging from enamel recontouring and smoothing of rough edges to replantation of an avulsed tooth.³

Regardless of the specific nature of the trauma, it is important to note more generally that trauma to teeth affects the dental pulp either directly or indirectly. Endodontic considerations, therefore, are vital in the evaluation and treatment of dental injuries. In crown fractures with pulp exposure or crown-root fractures, the pulpal status and the degree of root development (Figure 2-4) are the major factors in treatment planning.⁴ If the diagnosis is reversible pulpitis, the treatment of choice is vital pulp therapy, regardless of the degree of root development. If the diagnosis is irreversible pulpitis or pulpal necrosis, the amount of root development determines the treatment.⁴ If the apex is closed, root canal therapy can be performed, with high survival rates.^5,6 Teeth with irreversible pulpitis, pulpal necrosis, or immature apices present additional challenges to clinicians during obturation should endodontic treatments be required.

Figure 2-4 Treatment options for teeth with various pulp conditions with closed and open apices.

Conventionally, the apexification procedure carried out during such treatments consists of multiple long-term applications of calcium hydroxide to create an apical barrier before obturation of root canals.⁷ Because this procedure might alter the mechanical properties of dentin and make the teeth more susceptible to root fractures,⁸ a one- or two-step artificial apical barrier using mineral trioxide aggregate (MTA) has been suggested.⁷ High success rates have been reported for this procedure (Figure 2-5).⁹ However, the procedure may not result in complete root formation and may not reduce the chance of root fracture.⁷

Figure 2-5 A, Preoperative radiograph of the right central incisor with an open apex, pulpal necrosis, and chronic apical periodontitis. B, Postoperative radiograph after cleaning and shaping of the root canal and placement of a mineral trioxide aggregate (MTA) plug. C, Postoperative radiograph 11years later shows complete resolution of the periradicular pathosis and closure of the root end with hard tissues. (Courtesy Dr. G. Bogen.)

The ideal outcome for a tooth with an immature root or a necrotic pulp is regeneration of pulp tissue into a canal capable of promoting continuation of normal root development.¹⁰ A growing body of evidence suggests that regeneration of the pulp, along with continued growth of the root, may in fact be possible after pulpal necrosis and the development of apical pathosis in teeth with immature apices (Figure 2-6). Several single patient treatment reports and treatment series have been published demonstrating radiographic signs of continued thickening of the dentinal walls and subsequent apical closure of roots in teeth with necrotic pulps, open apices, and periapical lesions.¹⁰

Figure 2-6 A, Preoperative radiograph of the right second premolar tooth with an open apex, pulpal necrosis, and chronic apical periodontitis. B and C, Follow-up radiograph 14 months after regenerative endodontics. Soft tissue removed from the canal at this time showed histologic characteristics of pulp tissue. D, Postoperative radiograph 14 months after root canal treatment on the tooth showed thickening of root canal walls and closure of the apex in the tooth.

Luxation injuries involve trauma to the supporting structures of the teeth and often affect the neural and vascular supply to the pulp.³ Every effort should be made to preserve the natural dentition in these cases. If that is unsuccessful, alternative treatments include removable partial dentures, fixed partial dentures, autotransplantation, and single implants.

Another major cause of tooth loss is severe inflammation of the periodontium. With the establishment of extensive periodontal inflammation, teeth start to shift position, and in severe cases they may be lost (Figure 2-7). Extrusion or protrusion of maxillary incisors after periodontal bone loss, destruction of papillae, or loss of maxillary or mandibular anterior teeth may seriously damage facial expression.

Figure 2-7 A, Preoperative photograph of mandibular teeth of a patient with severe periodontitis. B, Postoperative photograph 2 years after periodontal treatment shows excellent results. (Courtesy Dr. T. Kepic.)

Traditionally, all efforts were made to save teeth with periodontal disease (Figure 2-8). Currently, the high survival rates of implants have affected the popularity of this approach, causing a paradigm shift in periodontics.¹¹ The benefits of successful treatment of a tooth with periodontal disease include (1) conservation of the crown and root structure, (2) preservation of alveolar bone and accompanying papillae, (3) preservation of pressure perception, and (4) lack of movement of the surrounding teeth. Extraction, on the other hand, can include some harmful effects, such as (1) bone resorption,¹² (2) shifting of adjacent teeth,^13–15 and (3) reduced esthetics and chewing ability.¹⁶

Figure 2-8 At age 40 this patient had severe periodontal disease and was referred for multiple extractions. At age 87, after 47 years of periodontal treatment and regular recall and maintenance, the patient has kept all his dentition.

Studies on the long-term prognosis for teeth with periodontal disease show less than 10% tooth loss for periodontal reasons.17–19 Single rooted teeth have a better prognosis than do molar teeth.^17–19 Cases with furcation involvement, with or without surgical intervention, are associated with a poorer prognosis than are cases without furcation involvement.

Recent innovations in implant dentistry have also reduced the reliance on higher risk periodontal procedures for tissue preservation and regeneration in teeth with moderate to severe periodontal disease.²² Surveys conducted by the American Academy of Periodontology in 2004 showed that 63% of periodontists put primary emphasis on periodontics, and 27% put primary emphasis on implants.²³

Although periodontal disease affects many teeth, the major cause of tooth loss is dental decay. Microorganisms in dental caries are the main source of irritation to the dental pulp and periradicular tissues.²⁴ As the decay progresses toward the pulp, the intensity and character of the infiltrate change. As a consequence of exposure to the oral cavity and caries, the pulp harbors bacteria and their byproducts. The dental pulp usually cannot eliminate these damaging irritants. At best, defenses temporarily impede the spread of infection and tissue destruction.

If irritation persists, the ensuing damage becomes extensive and spreads throughout the pulp. As a consequence of pulpal necrosis, pathologic changes can occur in the periradicular tissues, resulting in the development of periapical lesions (Figure 2-9). Periapical lesions have been classified into five main groups: (1) symptomatic (acute) apical periodontitis, (2) asymptomatic (chronic) apical periodontitis, (3) condensing osteitis, (4) acute apical abscess, and (5) chronic apical abscess.²⁴

Figure 2-9 A, Preoperative radiograph of a second mandibular right molar shows pulpal necrosis and severe chronic apical periodontitis. B, Postoperative radiograph 2 years after root canal therapy shows complete resolution of the periradicular pathosis. (Courtesy Dr. G. Harrington.)

Treatment of decayed teeth varies from caries removal and sealing of the exposed dentin (in the case of reversible pulpitis) to pulp capping pulpotomy, root canal treatment, nonsurgical and surgical endodontics, and tooth extraction.

Indications for Root Canal Treatment and Restoration

Indications for root canal treatment include teeth with irreversible pulpitis; necrotic pulps, with or without periapical lesions that have restorable crowns; treatable periodontal conditions; salvageable resorptive defects; and favorable crown-to-root ratios.²⁵ Teeth with pulpal and periapical pathosis that have a restorable crown, sound periodontal structures, an adequate crown-to-root ratio, and no major tooth resorption must be saved by root canal treatment. When such posterior teeth are saved and are extensively restored or are missing considerable coronal tooth structure, crowns are indicated. In a comparative study, Aquilino and Caplan²⁶ found a strong association between crown placement and the survival of endodontically treated teeth. In addition, a retained tooth may be at risk of future root fracture and development of caries or periodontal disease. These factors should be considered during treatment planning.

In contrast to posterior teeth, intact or minimally restored anterior teeth are usually treated with only restoration of the coronal access opening. Crowns are used on root canal–treated anterior teeth only when these teeth cannot be restored more conservatively or when such conservative treatments are unable to satisfy esthetic requirements.

Root canal treatment is contraindicated or results in less than optimal tooth fracture resistance when limited tooth structure remains and the overlying crown cannot engage at least 1.5 to 2 mm of tooth structure with a cervical ferrule (Figure 2-10).^27,28 When a post is required in a root canal–treated tooth to retain the core, the tooth is weakened but the negative effect of the post is countered by a 2-mm ferrule. When a fixed partial denture is attached to root canal–treated teeth, the teeth fail more often than do teeth with vital pulps^29–31; this emphasizes the need to exercise caution with longer span prostheses and heavier occlusal forces, as indicated by substantial wear facets.