Prosthodontic Management of Implant Therapy

The essential promise of implant dentistry is the ability to imperceptibly replace missing teeth. To achieve this, careful planning, execution, and maintenance is required by the dentist and patient to maintain a long-term esthetic and functional result. Unfortunately, as a result of biological, prosthetic, and iatrogenic factors, unesthetic results can occur. This article explores the potential causes for the unesthetic dental implant and the possible solutions that may improve the clinical situation. Whereas relatively simple errors may be corrected through prosthetic means, greater complications may require surgical intervention to achieve the desired result.

Key points

  • Esthetic complications are often the result of inadequate or absent planning that leads to implant malposition, which may or may not be overcome by prosthetic means.

  • Esthetic complications associated with relative discoloration of the crown and peri-implant tissues may be managed by use of alternative materials or enhancement of tissue thickness by surgical intervention.

  • The unfortunate decision to remove an implant to solve major esthetic complications requires extreme caution and estimation of the resulting tissue deficiency that must be compensated for before replacement of a dental implant in the proper position.

Esthetic complications regarding implant therapy depend on the observations and the observer. This subjective reality requires careful consideration of implant complications within clinical practice. Patient preferences, visual display (low lip line), and superimposed disease (peri-implantitis) must be considered differentially among various scenarios.

Esthetic complications related to implant therapy can broadly be characterized under 3 categories of origin ( Table 1 ): biological, prosthetic, and iatrogenic.

Table 1
Classification of implant esthetic complications
Data from Chu SJ, Tarnow DP. Managing esthetic challenges with anterior implants. Part 1: midfacial recession defects from etiology to resolution. Compend Contin Educ Dent 2013;34(Spec No 7):26–31.
Biological Prosthetic Iatrogenic
Resorptive Mucosal recession Fracture Implant, abutment, crown, prosthesis Implant misplacement
Inflammatory Mucosal hypertrophy, implant loss Attrition Crown, prosthesis Cement retention
Positional change Relative tooth intrusion Color Abutment, crown, prosthesis Inappropriate prosthetic contours

Identifying the biological and tissue architectural defect associated with esthetically failed implants requires consideration of the objective criteria for dental esthetics.

The treatment of unesthetic implants may require removal of the implant. Implant explantation can be an aggressive procedure, and complications in healing and complementary regenerative procedures may be needed ( Table 2 ). Therefore, each decision to remove an implant should be carefully measured. Different causes of implant esthetic deficits must be considered separately.

Table 2
Essential biological and tissue architectural features of the implant retreatment site
Buccal Interproximal
Facial implant position Loss of connective tissue attachment at adjacent teeth
Depth of implant placement Implant proximity to adjacent tooth
Existing implant diameter Existing implant diameter
Mucosal thickness Mucosal thickness
Presence of keratinized tissue Presence of keratinized tissue
Peri-implant mucosal inflammation Peri-implant mucosal inflammation
Obvious infection Obvious infection

The inappropriate depth of implant placement creates esthetic challenges. The unesthetic result of shallow implant placement leads to inappropriately short restorations, the use of unhygienic flanges, or inappropriately contoured restorations. Shallow implant placement could be addressed by (1) using a short abutment with violation of the biological width, (2) use of a ridge lap design to mask the error, and/or (3) removal of the implant and replacement at the appropriate depth. In Fig. 1 , shallow (and buccal) implant placement precluded the planned and desired use of a fixed prosthesis. A more complex overdenture solution using custom conical abutments and locator attachments provided an esthetic solution. The motivated patient may choose to follow the route of implant replacement.

Fig. 1
Shallow implant placement diverts original treatment plans. ( A ) Patient presentation with implants placed and attempt to provide an interim complete denture revealed implant interference. No alveolectomy was performed to create required space. ( B ) Additional complications caused by buccal placement of implants is revealed. ( C ) New tooth position identified by diagnostic denture tooth arrangement to define space available for overdenture attachments. ( D ) Facial view affirming improved esthetics of prosthesis. ( E ) Custom cast abutments for overdenture conical retention were produced. ( F ) Definitive overdenture prosthesis provided improved esthetics, phonetics, and function. Case performed in collaboration with Dr Carolina Vera, UNC Chapel Hill School of Dentistry Graduate Prosthodontics.

Depth of implant placement begins at the planning phase of treatment. In more complex scenarios, whereby tooth dimensions may change with ( Fig. 2 A), for example, crown lengthening, the location of the zenith must be defined before implant placement ( Fig. 2 B). When implants are positioned 3 to 4 mm apically from this position ( Fig. 2 C), implant esthetic harmony can be achieved with the surrounding teeth ( Fig. 2 D).

Fig. 2
Anticipating depth of placement using esthetic guidelines. ( A ) Patient presentation reveals failed maxillary left lateral incisor at time of request for enhanced anterior tooth esthetics requiring crown lengthening. ( B ) Diagnostic cast reveals waxed position of the gingival zeniths, indicating apical movement relative to existing maxillary left lateral incisor. ( C ) Postsurgical photograph reveals abutment in place surrounded by properly formed mucosa at position dictated by diagnostic wax-up and directed depth of implant placement. ( D ) Delivery of tooth and implant crowns displaying esthetic harmony.

The unesthetic implant resulting from excessive depth of placement is challenged by the long-term continued facial tissue resorption to a point of biological stability (approximately 3 mm beyond the facial bone crest). The long crown associated with excessive depth of implant placement may benefit from a combination of prosthetic and surgical retreatment ( Fig. 3 ). Minor discrepancies in crown length may be successfully addressed by altering the facial contour of the abutment and crown. Providing sufficient thickness of facial tissue and an appropriately contoured (narrow) abutment may enable abutment coverage and development of suitable implant-crown cementoenamel junction location relative to adjacent teeth. However, deep implant placement aggravated by other factors such as adjacent implants, the loss of soft tissue, or additional buccal placement create problems that challenge prosthetic or surgical resolution ( Fig. 4 ).

Fig. 3
Deep implant placement, here associated with reduced volume of alveolar bone without grafting, results in loss of 1 to 2 mm of buccal mucosal dimension and loss of symmetry. Some situations may be resolved by soft-tissue enhancement at this time.

Fig. 4
Complex scenarios resulting from implant placement without grafting, subsequent bone loss, and tissue recession during the provisionalization phase created a situation that was not satisfactorily restored using 2 single-implant crowns with pink ceramic. These challenging situations require careful resolution, perhaps involving conventional prosthodontics.

Severe loss of vertical tissues can occur around implants ( Fig. 5 ). In the scenario illustrated in Fig. 5 , implant failure and associated bone loss was addressed by implant removal and immediate implant placement at an extremely deep location relative to adjacent teeth. Subsequently, loss of attachment at the adjacent teeth doomed the ultimate restoration despite the successful implant healing. This patient accepted treatment as the final result.

Fig. 5
Severe esthetic complications resulting from excessive depth of implant placement. ( A ) Radiograph illustrating satisfactory alveolar condition before implant placement, ( B ) radiograph illustrating deep position of implant placement before failure. ( C ) Radiograph at time of implant failure demonstrating crestal bone resorption. ( D ) Radiograph illustrating extreme depth of implant placement on erroneous simultaneous removal and replacement of the failed implant. ( E ) Radiograph illustrating position of a stock zirconia abutment after successful integration. ( F ) Facial photograph reveals marked tissue loss during the healing phase of the replaced implant. ( G ) Radiograph illustrating position of the definitive patient-specific zirconia abutment. ( H ) Facial photograph of the definitive implant crown that was accepted by this patient.

The unesthetic implant resulting from facial displacement of angulation often requires implant removal to secure success ( Fig. 6 ). The actual facial displacement should be distinguished from dehiscence that results from the deficiency of alveolar bone and loss of the buccal plate of bone ( Fig. 7 ). Box 1 demonstrates the differences between facial displacement of an implant and dehiscence of the buccal plate of bone. When there is loss of the buccal plate of bone, the regeneration of bone and mucosa may be attempted without removal of the dental implant. However, it is the authors’ opinion that this procedure be conducted following removal of the implant crown and abutment to permit spontaneous gingival regeneration to occur. This increases the volume of soft tissue and reduces the advancing of the flap and disruption of the mucogingival junction to accommodate grafting material volumes in the subsequent required procedures. When the implant must be removed, the resulting defect is typically a 3-walled defect. A flapless approach is not readily accommodated here. Furthermore, the impact of implant removal on the adjacent tooth connective tissue attachments must be predicted and minimized. Selecting the appropriate method of implant removal can influence the future outcome of therapy, and the least traumatic method should be selected. Four methods for implant removal are commonly reported and used ( Table 3 ). Each method has the potential to create additional tissue damage, particularly the trephine drill. The main advantage of reverse high-torque instrumentation is that the implant may be removed without significant architectural change to the surrounding bone. Other methods such as heating the implant (using electrocautery instrumentation) are not endorsed with enthusiasm.

Fig. 6
Buccal angulation of an implant may preclude esthetic restoration. ( A ) Radiograph indicating the successful osseointegration of this misplaced implant. ( B ) The implant is placed distally in the bound edentulous space, angled buccally, and the abutment exits the mucosa apically. The thick soft-tissue biotype and the intact adjacent tooth connective tissue attachments favor careful removal and replacement of this implant. ( C ) Facial view of the maxillary left lateral incisor region following implant removal with a bonded pontic in place during healing. Note that we have organized the soft tissue to identify the desired gingival contour of the definitive restoration, and this guides implant placement according to the 3/2 rule. ( D ) CBCT sagittal image of the site following implant removal with regeneration. Note that there is sufficient bone volume to achieve ideal implant placement. ( E ) Facial view of the replaced implant with definitive lithium disilicate crown that has improved contours and color. ( F ) Radiograph of the definitive abutment and crown placed on the replaced implant. The modest remodeling of bone occurred before implant placement, and the thick tissue biotype permitted use of the longer transmucosal abutment dimension.

Fig. 7
Anterior maxillary implant esthetics can be negatively affected by excessive buccal implant angulation. ( A ) Simplant planning for ideal implant placement. ( B ) Placement of impression copings reveals the buccal orientation of the implant/abutment long axis. ( C ) Facial view of the impression copings reveals the accompanying axial displacement of the gingival zenith positions (far superior to the adjacent teeth). The surprising loss of adjacent tooth connective tissue attachment is unexplained, but complicates treatment. ( D ) The 2 implants were restored with a splinted prosthesis to prevent a vertical line disrupting the gingival ceramics (compare with Fig. 4 ). The quality of gingival ceramics is ever increasing and can be an alternative solution to tissue loss around implants, provided access for hygiene is maintained.

Box 1
Factors influencing the dehiscence-type defect of dental implants

  • Facial implant position or excessive implant angulation

  • Extreme depth of implant placement or shallow implant placement

  • Excessive implant diameter

  • Incorrect abutment dimension or contour

  • Thin mucosa

Table 3
Methods of dental implant removal
Method Advantages Disadvantages
Trephine drill Widely applicable
Effective
Requires full-thickness flap
Potential to destroy adjacent bone/teeth
Additional bone removed circumferentially
Contraindicated when interimplant-tooth distance is small
Bur/elevator Simple
Familiar instrumentation
Requires full-thickness flap
Bur/forceps Simple
Familiar instrumentation
Requires full-thickness flap
More bone reduction than elevator method
High-torque instrument Simple
No/small flap required
Useful when interimplant-tooth distance is small
Limited use if coronal aspect of implant is fractured
Added instrumentation
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Aug 9, 2020 | Posted by in General Dentistry | Comments Off on Prosthodontic Management of Implant Therapy
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