Restoration of a Fractured Central Incisor

This case involved a patient who himself was a general dentist and who required restoration of a fractured central incisor. Timely decision-making and initiation of prosthetic reconstruction was accentuated by the esthetic demand of the location of the trauma as well as the patient’s profession.

A 57-year-old general dentist was referred by the treating endodontist for restoration of a fractured central incisor. The patient presented in excellent physical health with no medical concerns related to treatment.

Tooth No. 8 had a history of endodontic therapy in 1962 from traumatic injury as a child, and the lingual access had been restored. With the exception of the lingual access opening, the coronal tooth structure had remained intact for 48 years. The recent fracture of the crown of the tooth occurred while the patient was eating beef jerky. An endodontist was consulted, the tooth was determined to be restorable, and the root canal system was retreated. Retreatment was indicated to reduce the potential for bacterial contamination as a result of the fracture.

Extraoral: Upper and lower lip asymmetry was present with a low lip dynamic that extended to an average upper lip posture when the patient was instructed to provide a full smile (Figure 1).

Intraoral: Approximately 60% to 70% of the clinical crown of tooth No. 8 was fractured at a lingual-mesial angle just apical to the facial cementoenamel junction (CEJ) (Figure 2).

Radiographic assessment: The endodontist completed retreatment and created a post space. There was radiographic evidence of slight loss of crestal lamina dura.

Periodontal: The examination revealed minor bone loss and mild American Academy of Periodontology (AAP) Class II periodontitis, with flattening of the interdental papilla.

Risk: Low

Prognosis: Good

Biomechanical: In addition to the recent trauma causing the clinical crown fracture in the cervical third, the patient had a history of prior trauma and endodontic therapy along with retreatment of endodontics and post space preparation. Upon clinical examination, acceptable direct occlusal and interproximal restorations were noted to be present in the posterior teeth.

Risk: Moderate

Prognosis: Fair

Functional: The patient was deemed to have acceptable function, with no evidence of attrition on the posterior or anterior teeth, and no mobility due to functional forces. There were no symptoms of temporomandibular disorders (TMD).

Risk: Low

Prognosis: Good

Dentofacial: When the patient was instructed to provide a full smile, the inferior border of the lip rested at the cervical of the anterior teeth. Regardless of the medium lip line, because the patient was a dental professional there was a high esthetic demand. In addition, the contralateral central incisor contained multiple shades and hues, presenting a challenge for shade duplication of the restored tooth.

Risk: Moderate

Prognosis: Fair

Long-Term Prognosis

It was important to first evaluate the structural parameters of the remaining tooth structure to communicate risk assessment for longevity of the restoration. Providing a good long-term prognosis is paramount when making the decision to maintain or extract a structurally compromised tooth. The preference is to preserve the tooth when adequate volume remains to fulfill the requirements for crown retention. Alternative treatment plans may include extraction and replacement with an implant-supported crown, fixed partial denture, or removable partial denture. The state-of-the-art alternative for replacing a missing tooth is an endosseous implant. Success rates are high for osteointegration of implants, but esthetic success in the anterior maxilla is complicated by the surgical removal of the remaining tooth structure, the amount of buccal plate and interproximal bone remaining for immediate implant placement, the potential need for hard- and soft-tissue grafting, the soft-tissue support in the healing phase, and the management of any complications. The fixed bridge alternative presents similar hard- and soft-tissue requirements for the pontic site and may involve undesirable removal of healthy tooth structure on adjacent teeth. A removable partial denture is seldom a desirable alternative other than for transitional needs or financial constraints. The esthetic challenge of tooth matching is inherent in all the alternatives. The clinician must balance long-term prognosis with the desires and financial constraints of the patient.

Endodontic Retreatment

The referring endodontist had discussed the options of extraction and tooth replacement versus endodontic retreatment and restoration. The decision was made to restore the fractured tooth No. 8. The endodontic retreatment and post space preparation were completed without consequence, and the patient was referred for immediate temporization.

Final Assessment and Treatment Determination

The author evaluated the remaining tooth structure as well as the diagnostic parameters that influence treatment outcomes. Certainly the current situation and its causes must be considered and a treatment plan devised that leads to a more favorable long-term outcome. Evaluation of tooth No. 8 revealed 2-mm to 3-mm probing depths and 2 mm of tooth structure coronal to the prepared crown margin. Two millimeters of solid tooth structure circumferential would provide adequate ferrule on which to retain a crown.^1,2 The post space was less than one-third of the mesiodistal root diameter,³ and the crown-to-root ratio was greater than 1:1.³ The facial fracture and subsequent crown margin was just below the gingival crest, so no tissue or bone alteration would be required.⁴ The use of a post is for retention of the core; it provides no increased strength to the tooth.⁵ A core was necessary to provide increased preparation length in order to achieve adequate resistance and retention form.

The biomechanical requirements of the tooth were determined to be satisfactory for long-term retention of the crown. Low functional and periodontal risks, combined with the moderate dentofacial risk, supported the restoration of the biomechanically compromised yet still satisfactory tooth.

The treatment plan was to include post and core restoration at tooth No. 8, followed by fabrication of a transitional restoration for No. 8, then placement of a ceramic crown.

Natural and full-smile photographs were taken along with retracted photos with and without shade tabs (VITA 3D-Master^® and VITA Classical Shade Guides, Vident, ). Shade tab photographs were taken prior to the initiation of treatment to avoid dehydration and subsequent shade and value misperception. The shade tabs were photographed at a 45-degree angle to avoid reflection of the metal tab holder and reflective surface of the shade tab (Figure 3 and Figure 4).

Fortunately, the patient had saved a fragment of the fractured tooth. This segment was seated and composite resin built around the fragment to full contour, and a polyvinylsiloxane (PVS) impression was made to create a matrix for temporization.

The temporary restoration sealing the endodontic access was removed, and the post space was gently cleansed with a Gates-Glidden No. 2, irrigated, and dried. A nonmetallic post was chosen for flexural and retentive properties; the post consisted of glass fibers in a resin matrix. Nonmetallic posts have shown an inherent ability to resist root fractures.⁶ A 1-mm clear parallel post was chosen to fit the prepared post space. The post was microetched, and the canal was coated with a dual-cure resin utilizing a lentulo spiral. Dual-cure resin was then placed on the post, which was seated and light-cured (Figure 5). The exposed post and remaining tooth served as the framework for the resin core. The tooth was subsequently prepared for a full-ceramic restoration (Figure 6). Lithium-disilicate glass ceramic (IPS e.max^® Ceram, Ivoclar Vivadent, www.ivoclarvivadent.us) was chosen for its increased flexural strength and because of its ability to maintain translucent properties and offer cut-back and veneering for optimum esthetics.^7-9

Gingival retraction paste was placed in the sulcus and condensed with a cotton pellet. After 2 minutes, the preparation was rinsed with water and cleansed with hydrogen peroxide. The impression and bite registration were made with a fast-setting vinyl polysiloxane. The opposing model impression was made with an alginate substitute. Bis-acrylic composite temporary crown-and-bridge material was syringed into the preoperative impression with the tip remaining imbedded in the flowable acrylic while filling to reduce the formation of porosities. The matrix was removed from the patient’s mouth after 2 minutes, and the provisional restoration was trimmed, contoured, polished, and seated with a zinc-oxide non-eugenol temporary cement (Figure 7). An alginate impression was made of the provisional restoration, and postoperative photographs were taken for use by the laboratory technician.

The laboratory prescription outlined the basic material information and base shade. The author has found that communication using models, photographs, and verbal review are of greater value for the ceramist than a shade map.

It is important to communicate with the patient and set expectations for the subsequent visit when matching a single central incisor. The try-in visit may result in cementation only if the patient and doctor are satisfied with the fit, shape, shade, and contour.

In this case, the patient returned for the initial try-in, and two issues were observed. First, the mesiodistal width of tooth No. 8 was greater in the cervical third than tooth No. 9 (Figure 8). This was deemed acceptable because of the lip dynamics and the ability of the restoration to limit an open cervical embrasure. (Composite resin on the mesial-cervical aspect of tooth No. 9 could have been utilized to create balance, if required.) The second issue was that tooth No. 8 was higher in value than tooth No. 9. The author has found that digital photographs provide great value, and conversion of a retracted photo to black and white accentuates the ability of the laboratory technician to evaluate the value contrast to the natural dentition (Figure 9).¹⁰

At the subsequent visit, tooth No. 8 was determined to be closer in value to tooth No. 9, but tooth No. 8 was richer in chroma (Figure 10), and the characterizations appeared excessive. The author finds that an overexposed photograph can help accentuate these characterizations for visualization by the technician (Figure 11). The third try-in resulted in a restoration that met the expectations of the treating dentist, the dental technician, the supporting staff, and the patient.

The internal surface of the restoration was cleansed with phosphoric acid and silinated. Tooth No. 8 was isolated, and the restoration was lined with an adhesive resin cement, seated, and light “tacked.” Excessive cement was removed, and the final light cure was applied. Adhesive resin cement was chosen, as studies have shown that adhesively bonded lithium-disilicate glass ceramic restorations have higher failure loads than those conventionally cemented.¹¹ Dual-cure cements have also been determined to have greater bond strength when light-cured as well as time-set.¹²

The occlusion was checked and then evaluated with the patient in an upright position. There was a minor interference with tooth Nos. 7 and 26 in the upright position, which was relieved by adjusting the lingual of tooth No. 7 (Figure 12).

In conclusion, immediate trauma to the dentition presents challenges, and timely risk assessment protocols are essential for effective outcomes. When a single central incisor is involved, strong communication skills, patience, and dedication to excellence are essential to achieve success (Figure 13 and Figure 14).

The author would like to thank Hakjoo Savercool for the ceramic work in this case.

Bradley J. Olson, DDS
Private Practice
Waldorf, Maryland