CHAPTER 22 Prosthodontic Treatment of the Adolescent Patient
Scientific advancements in the areas of preventive dentistry, access to and use of dental services, water fluoridation, topical application of fluorides, and new commercial preventive dentistry products have led to substantial reductions in dental disease in developed countries. However, Caplan and Weintraub determined that adolescents are still affected by caries, particularly those who are minorities, rural inhabitants, have minimal fluoride exposure, and are from less educated and less affluent families.1 Results of a more recent health and nutrition survey reported by Vargas and colleagues also supports a higher caries prevalence among lower-income children and minorities.2 Assessments of periodontal health by Barmes and Leous3 and by Bader and associates4 show a decrease in severity but indicate that some adolescents are still affected.
Dental trauma continues to be a significant problem among adolescents as supported by Gift and Bhat’s assessment of orofacial injury5; Bader and colleagues’ estimates of the incidence and consequences of tooth fracture6; and Haug and associates’ epidemiologic study of facial fractures and concomitant injuries.7 Pilo and colleagues indicate that congenital anomalies continue to result in missing or malformed teeth.8 In addition, bulimia, anorexia, and dietary habits have led to an increase in the erosion of tooth structure among teenagers, particularly in girls.
Some of the esthetic treatment needs resulting from these conditions can be managed with resin-bonding procedures and porcelain laminate veneers, and whenever possible these should be considered as the treatments of first choice. When these procedures have not provided a satisfactory result or when teeth are missing, then prosthodontics such as single crowns, fixed partial dentures, implant prostheses, or removable prostheses are indicated.
Because adolescents are often affected psychologically by the unacceptable appearance of diseased, damaged, or missing teeth, one should not allow chronologic age to preclude performance of whatever treatment is necessary to provide proper function and esthetics. If the teeth involved are fully erupted, have achieved complete root formation, and may be prepared without causing irreversible damage to the pulp, successful prosthodontic treatment can often be provided for patients as young as 12 to 14 years of age. Patient cooperation, however, is mandatory during and after treatment. Adolescent patients must be able to tolerate long appointments and remain still for extended periods while teeth are being prepared and impression materials are setting. Also, they must be able to achieve and maintain good oral hygiene around both the provisional and definitive restorations, as well as in the rest of the mouth. All these conditions make it highly desirable to perform the necessary treatment as expeditiously as possible. Finally, it must be understood that an adolescent is more likely to sustain trauma to the oral structures than is an adult and thus there is greater risk of damage to restorations and prostheses than in an adult patient.
Prosthodontic treatment of the adolescent patient often requires highly intricate procedures that go beyond the scope of this chapter. The goal of this chapter is to offer the reader an opportunity to develop a better appreciation of the achievable and available solutions for the young patient with a prosthodontic need. The interested reader should consult the prosthodontic literature and current textbooks on fixed, removable, and implant prosthodontics for more detailed information in this area of dentistry.
Crowns are only indicated when more conservative treatments cannot be performed or have proven to be unsuccessful. All-ceramic crowns are the most esthetic complete-coverage restorations currently available in dentistry. The achievement of optimal longevity with all-ceramic crowns requires normal tooth preparation form because the prepared tooth must provide support for the restoration. Therefore, if a large portion of tooth structure is missing because of trauma or caries, or if previous restorations become dislodged during tooth reduction, then a separate restoration that is well retained in remaining tooth structure should be placed to establish an ideal preparation form (Fig. 22-1). Also, the fracture resistance of all-ceramic crowns is enhanced when other characteristics are present. Occlusal forces should be average or below-average. The centric occlusal contacts should ideally be located over the concave lingual portion of the prepared tooth and not cervical to the cingulum where fracture of the crown is more likely to occur. The prepared tooth should possess average or greater incisocervical length and should not be short, round, or overtapered in form.
The tooth preparation for an all-ceramic crown (Fig. 22-2) should possess a well-defined, smooth finish line that is 0.8 mm deep around the entire tooth, with the axial surfaces reduced to a depth of 0.8 mm. The lingual reduction for occlusal clearance should be 1 mm. An incisal edge reduction of 1.5 to 2 mm is required and is biologically acceptable even in the presence of large pulps. The use of resin cement and associated dentin bonding is recommended because crown strength is significantly improved. Both chamfer and shoulder finish lines can be used in conjunction with resin cement without compromising restoration strength. If zinc phosphate or glass ionomer cement is used, however, then a shoulder finish line should be used to optimize crown strength.
When the ideal tooth preparation form is seriously compromised or the magnitude of occlusal forces contraindicates restoration with an all-ceramic crown, use of the stronger metal-ceramic crown is indicated. The tooth preparation design and reduction depths for a metalceramic crown are shown in Fig. 22-3. When cervical esthetics must be optimized in a metal-ceramic restoration, one can use a collarless design that eliminates facial cervical metal and uses a porcelain facial margin (Figs. 22-4 and 22-5).
Figure 22-3 Two views of metal-ceramic crown preparation showing minimal facial reduction and shoulder finish line, minimal incisal reduction, lingual axial reduction depth and chamfer finish line, and lingual reduction for occlusal clearance.
Figure 22-4 Collarless metal-ceramic framework design that eliminates visible cervical metal. A indicates porcelain; B indicates underlying metal framework that does not cover shoulder finish line; C is margin where porcelain contacts only prepared tooth.
Figure 22-5 A, The maxillary lateral incisor was traumatically injured, resulting in loss of the incisal one-third and much of the lingual surface. The tooth has been prepared for a metal ceramic crown with a porcelain margin (collarless metal ceramic crown). B, The lateral incisor crown has been cemented.
Whenever possible, cervical margins should not be extended into the gingival sulcus of an adolescent patient. If oral hygiene is inadequate, subgingival margins may produce accelerated gingival recession or interfere with the normal cervical relocation of the gingival tissues as the patient matures. Both occurrences produce an esthetic liability (Figs. 22-6 and 22-7).
Figure 22-6 Gingival contour in 25-year-old patient resulting from placement of subgingival crown on maxillary right central incisor at 8 years of age. The gingival crest is not positioned as far apically on the restored central incisor, and its form is rounded and thick rather than the normal form of the gingival margin, which is thinner and sharper.
When tooth fracture or caries involves the pulp and root development is complete, a routine pulpectomy and gutta-percha root canal filling should be completed. Because posts and cores do not strengthen endodontically treated teeth, their use is indicated only when remaining coronal tooth structure does not provide adequate retention for the definitive restoration.9 Restorations that do not use a post should be used whenever possible to replace missing tooth structure and serve as a retentive foundation. It is particularly important that teeth in the mouths of accident-prone adolescents or those in whom athletic trauma has previously occurred be restored without using a post, if possible. This practice helps avoid irreparable damage in the form of root fracture in case the restored tooth is once again subjected to trauma. Even though trauma may result in restoration dislodgment or perhaps even fracture of the tooth, the tooth will have survived at least one more traumatic experience.
In the case of pulpal involvement when the root is incompletely formed, a pulpotomy followed by placement of an appropriate restoration is indicated. Subsequently, when root formation is completed, a pulpectomy is performed, followed by placement of the definitive restoration or crown, if needed.
When a tooth is lost, space maintenance should be provided immediately after extraction to prevent tipping, tilting, or rotation of the abutment teeth or eruption of the opposing teeth. Space maintenance should be continued until the fixed prosthesis is completed. If the abutment teeth are malaligned and pulp size does not permit the amount of tooth reduction necessary to align the preparations, orthodontic repositioning of the abutment teeth should be initiated.
The use of conventional fixed partial dentures, requiring complete coverage tooth preparations, is decreasing in adult patients due to the use of dental implants and they are only sparsely used in adolescents. Contemporary treatment planning more frequently indicates that an interim fixed or removable prosthesis be used until such time as growth is completed and dental implants can be placed. When an interim fixed prosthesis is needed, resin-bonded fixed partial dentures are a good choice. When implants will not be used or have not been successful, fixed partial dentures become an appropriate definitive treatment. These fixed partial dentures can use conventional complete coverage retainers or they can use resin-bonded retainers designed for long-term service.
For reasons of pulpal and periodontal health and conservation of tooth structure, resin-bonded retainers are frequently used to replace missing teeth when dental implants are not being used (Fig. 22-8). Retention and resistance form is achieved through tooth preparations, terminating in enamel, coupled with acid etching of the enamel and fixation with resin cement. The conservative approach of using resin-bonded retainers does, however, require that the abutment teeth be intact or minimally restored, with substantial enamel present for bonding procedures. To produce an adequate area for resin bonding, the existing crown should be of average or greater length. A maximal amount of the nonvisible portions of the lingual and proximal surfaces should be covered by the retainers, because Pegoraro and Barrack have determined that bond strength increases with the area of enamel covered.10 The existing crown form, color, and axial alignment must be satisfactory, because this prosthesis design does not permit the incorporation of changes in the facial enamel of abutment teeth. When abutment crown contours or color require esthetic changes, then complete-coverage retainers may produce a superior result.
Figure 22-8 A, Congenitally missing maxillary lateral incisors. B, Resin-bonded prostheses were used instead of conventionally cemented prostheses to preserve as much tooth structure as possible on the central incisor and canine abutments.
These prostheses can be successful for many years, but suitable attention must be paid to four factors: (1) appropriate diagnosis and treatment planning, (2) correct tooth preparation, (3) good-fitting castings, and (4) meticulous adherence to the required resin-bonding procedures.
Several factors important to diagnosis and treatment planning have been identified in clinical studies. Because Dunne and Millar determined that prostheses with only one pontic have much higher success rates, the use of long-span prostheses should be avoided.11 The use of multiple splinted retainers was associated with higher failure rates according to Marinello and colleagues.12 As with any prosthesis, the presence of heavy occlusal forces reduces longevity.13 The use of resin-bonded cantilevered prostheses (using only one retainer) has been reported, and data of Hussey and associates14 and Leempoel and colleagues15 indicate that this type of design can be used successfully in certain situations such as a missing maxillary lateral incisor (Fig. 22-9).
Figure 22-9 A, Congenitally missing maxillary lateral incisor. B, Incisal view of the bonded two-unit prosthesis where the lateral incisor pontic has been cantilevered from the maxillary canine. C, Facial view of the completed prosthesis.
Preparation of abutment teeth for resin-bonded prostheses is not recommended for prostheses that will only be used on an interim basis. However, when long-term service is needed, tooth preparation has been found to substantially reduce debonding of retainers.
Barrack and Bretz determined that the successful use of resin-bonded prostheses requires establishment of retention and resistance form through tooth preparation (see Fig. 22-9B and Fig. 22-10).16 Because the tooth preparation is limited principally to enamel, these retainers can be used without pulpal damage and the teeth can often be prepared without anesthesia. Besimo states that the proximal surfaces adjacent to the edentulous area should be reduced to remove interproximal undercuts and to provide parallel surfaces that aid retention.17 One or two proximal grooves must be placed to enhance the resistance and retention form (see Fig. 22-10A). Proximal grooves have been identified as a key factor in the resistance to debonding in several studies.16–20 The tooth preparation should include a small peripheral chamfer finish line (see Fig. 22-10B) formed with the tip of a rounded-end diamond instrument. The lingual surfaces of anterior teeth are reduced to create occlusal clearance with the opposing teeth. The minimal occlusal clearance space for short-span (three-unit) prostheses with normal occlusal forces is 0.5 mm. It may not be necessary to reduce the abutment teeth lingually when there is existing occlusal clearance, whereas reduction of opposing teeth may be necessary when occlusal contact occurs over broad areas of the lingual surfaces. Multiple ledges, prepared across the reduced lingual surface (see Fig. 22-10C), increase the casting rigidity and, along with the proximal grooves, aid in retention and resistance form and in orientation of the casting during cementation.