June 2018
Volume 39, Issue 6

Replacing Six Missing Adjacent Teeth in the Anterior Maxilla With Implant Prostheses: A Case Series

Panos Papaspyridakos, DDS, MS, PhD; Dennis P. Tarnow, DDS; Steven E. Eckert, DDS, MS; and Hans-Peter Weber, DMD, Dr. Med. Dent.

ABSTRACT

Restoring multiple adjacent missing teeth in the anterior maxilla is one of the most challenging situations in clinical implant dentistry, as restorations need to be both functional and highly esthetic. The purpose of this article is to highlight the issues that arise during treatment planning for replacement of six missing maxillary anterior teeth with implant-supported fixed dental prostheses. Representative clinical reports are provided to illustrate the treatment planning and surgical and prosthodontic management. The authors describe the rationale for selecting the appropriate number and location of implants in relation to the amount of missing soft and hard tissues to achieve functional and esthetic prostheses.

After tooth extraction, the alveolar ridge undergoes dimensional alterations.1,2 Three to 12 months post-extraction, patients experience 30% to 60% horizontal resorption and 10% to 20% vertical bone loss.3 For anterior maxillary teeth especially, the fate of the facial bone wall cannot be easily predicted. Extensive resorption of intact facial plates is a common phenomenon after extraction.1-3 A cone-beam computed tomography (CBCT) study demonstrated thin facial bone with less than 1 mm thickness for most anterior maxillary incisors.4-6 Almost half of the anterior maxillary teeth have less than 0.5 mm thickness of facial plate.5,7

A thin facial plate poses significant risks during tooth extraction in the anterior maxilla. The sources of blood supply for the facial plate come from the periodontal ligament (PDL), periosteum, and bone marrow.2,3 Tooth extraction eliminates the PDL fibers thereby compromising the blood supply to the bone.3 The subsequent resorption of the thin facial bone is unpredictable, prompting a guarded situation when considering implant replacement of the missing tooth. Regarding the anterior maxilla, trauma, extensive caries, unresolved or unresolvable periapical pathosis, and/or severe periodontal disease are the primary reasons for loss of multiple anterior maxillary teeth with consequent development of extended partially edentulous sites.8,9 Understanding that the loss of the anterior teeth has an impact on the facial bone, resulting in accelerated loss of height and width of the alveolus, it becomes evident that, in this critical esthetic region, a strategy must be developed to replace the missing bone or prevent its loss.

Fabrication of prostheses replacing the maxillary canine and incisor teeth can be a challenging endeavor. Traditional fixed prostheses are contraindicated because the length of the edentulous span creates unfavorable and excessive force on the posterior teeth. A removable prosthesis may provide soft-tissue and tooth support, but the patient is dependent on its use.

The use of dental implants to support fixed dental prostheses (FDPs) in the anterior maxilla provides patients with a more lifelike prosthesis. However, a number of anatomic factors must be considered when planning implant placement in anticipation of such a prosthesis. This article presents six case reports to demonstrate differing approaches toward the location, number, and orientation of implants when implant-supported FDPs are planned to replace six missing maxillary anterior teeth.

Implant Treatment Planning

General Considerations

When considering implant rehabilitation of six missing teeth in the anterior maxilla (canine to canine), several factors need to be addressed.10-17 These factors can be classified as anatomical, implant-surgical, prosthodontics, and patient related. Anatomical factors include the extent of alveolar ridge alterations post-extraction and resultant ridge deficiencies,3 available bone quantity and quality,3 gingival phenotype, and amount of keratinized gingiva.10,18,19 The implant-surgical factors includethe implant type selection,18 number of implants,12 implant location and position (correct 3-dimensional [3D] implant positioning),12,19 and implant placement protocols.15 Prosthodontic factors are the implant loading and provisionalization protocols,15 occlusal scheme and retention type,20 restorative materials,10 and prosthodontic design (segmented versus one-piece).10,11,20 Finally, patient-related factors include systemic medical conditions,11 history of periodontal disease and inadequate oral hygiene,11 smile line and lip support,10,14,20 and financial and psychosocial parameters.21

Digital Treatment Plan

During diagnostic work-up, five prosthodontic steps are required to formulate a comprehensive treatment plan (Figure 1): (1) diagnostic tooth arrangement/wax-up and intra-oral mock-up; (2) CBCT; (3) digital scanning of the partially edentulous patient with intraoral scanning or extraoral scanning of the stone cast; (4) importing of DICOM file from CBCT into virtual implant planning software for treatment planning, and importing of the Standard Tesselation Language (STL) file from intraoral or extraoral scanning and superimposition of the DICOM and STL files; (5) digital planning of implant positions with planning software for prosthetically driven implant placement (with guided surgery with stereolithographic/milled/printed surgical template).

This case series will describe the factors that should be considered during the treatment planning and rehabilitation of six missing anterior maxillary teeth. The treatment considerations and advantages and disadvantages of each treatment option are summarized in Table 1.

Treatment Option 1: Four Implants - Compensation for Lost Facial Plate of Bone Through Use of Gingiva-Colored Ceramics

Two patients presented each with six missing anterior maxillary teeth and significant loss of soft and hard tissues and seeking implant rehabilitation. After comprehensive diagnostic work-up and treatment planning as described above, it was decided to restore the missing teeth and lost facial plate of bone with four dental implants and definitive prostheses with gingiva-colored ceramics. For the first patient (Patient No. 1), four dental implants were placed in the canine (two regular-diameter implants) and lateral incisor (two narrow-diameter implants) positions (Figure 2). The patient was restored with two canine, implant-supported single crowns and one four-unit implant-supported FDP (option 1a) with gingiva-colored ceramics (Figure 3). An alternative approach was selected for the second patient (Patient No. 2) that involved the placement of four implants in the canine and central incisor positions for definitive rehabilitation with two three-unit implant-supported FDPs (option 1b) (Figure 4). For the second patient (option 1b), the reason for different implant distribution was based on the alveolar bone dimensions on certain implant sites, the curvature of the arch, and the location of the smile line.

Advantages

To compensate for the advanced bone loss, it was decided for these two case reports to restore the missing teeth and lost facial plate of bone with four dental implants and definitive prostheses with gingiva-colored ceramics. When placing four dental implants, the distribution can include canine and lateral or central incisor positions. Several authors have discussed the benefits of using implants in the lateral incisor positions to replace the four missing maxillary incisors.8,12,20,22-24 When multiple implants are placed adjacent to each other, the interproximal papillae are shorter than normal because the biologic width around dental implants is more apical compared with the biologic width between teeth and implants, which is established supracrestally, as Tarnow et al showed.25,26 According to the authors, interimplant space limitations exist both proximally and vertically. At least 3 mm of space should exist proximally between adjacent implants and 1.5 mm between an implant and adjacent teeth.25-27 Between two  adjacent implants, the vertical soft tissue from the interimplant peak of the bone to the gingival zenith has an average height of 3.5 mm without any PDL fibers to assist in creating more bulk in that area.25-27 Conversely, when an implant is adjacent to a natural tooth, the PDL fibers extend from tooth to bone and gingiva and, hence, create more bulk in the interproximal papillae area with an average height of 4.5 mm.25-27 The advantages of the aforementioned treatment option include enhancement of esthetic outcomes because placement of adjacent implants in the central incisor areas is avoided and their deleterious effect on interproximal papillae may be mitigated.

Regarding gingiva-colored ceramics and the transition line, the transition between the ceramics and alveolar ridge must be apical to the smile line for an esthetic result, and it is essential that this is assessed during the diagnostic and treatment planning phase.28 When encountered, a high smile line may create difficult challenges.14,28 If the patient presents with a high smile line, it will be necessary to either rebuild the lost bone with guided bone regeneration (GBR) and connective tissue (CT) grafts prior to the implant placement or reduce the alveolar ridge until the transition line is hidden by the smile line. If the smile line is moderate to low, the transition line may be camouflaged by the lip, even when the patient is fully smiling. In contrast, with a high smile line use of gingiva-colored ceramics that terminate superior to the smile line may prove to be an acceptable solution. Achieving this, however, may require resection of labial bone at the time of implant placement. During the phase of fixed implant provisionalization, it can be determined whether or not there is a need for gingiva-colored ceramics by adding gingiva-colored acrylic to the interim prosthesis and assessing the esthetics.

Segmentation of the rehabilitation offers cleansability, ease of fabrication, and ease of prosthetic maintenance in case of biologic and/or technical complications.29 When gingiva-colored ceramics are used to restore missing hard and soft tissues, the segmentation of the prostheses in the midline may be challenging when implementing option 1b. Segmentation between the canines and lateral incisors, as used option 1a, may be less challenging for the technician to hide the transition since it is not in the midline, as was used in option 1b.

Regarding implant diameter, narrow implants in the location of the incisors also offer an alternative solution to interproximal space limitations and provide the base for a natural emergence profile for the abutment crowns.12 The embrasure spaces between the abutment and pontic crowns are easier to respect with the use of narrow-diameter implants. Additionally, the use of bone-level-type implants with platform switching is gaining popularity for implant therapy in the maxillary esthetic zone due to favorable soft-tissue outcomes and reduced crestal bone remodeling compared with tissue-level-type implants.18

Disadvantages

The main limitation of the treatment approach used for the first patient (option 1a) involves the potential compromise of the interproximal papillae between the lateral incisors and the canines. A minimum distance of 3 mm should exist between adjacent implants, and at least 1.5 mm should exist between the canine implants and the adjacent premolars.25-27 Another limitation with this approach includes biomechanical concerns for the FDP supported by two narrow-diameter implants. The central incisors disclude the jaw during protrusive movements, which may create bending moments at the position of the lateral incisor implants.30 The magnitude of these bending moments is proportional to the lever arm, and they may cause technical complications such as screw loosening or screw fracture.

The shape of the arch also impacts the magnitude of these forces; namely, the more curved the arch the greater the lever arms and associated forces. For the first patient (option 1a), the arch shape was more straight than curved and thus favorable to a prosthetic design with dental implants in the lateral incisor positions. In such instances where the arch is curved, it may be preferable to place implants in the central incisors instead of lateral incisors or include the canine implants in the definitive prosthesis. For the second patient (option 1b), the increased curvature of the arch was taken into consideration during the selection of implant positions during implant treatment planning.

Treatment Option 2: Four Implants - Compensation for Lost Facial Plate of Bone Without Use of Gingiva-Colored Ceramics

Two patients each presented with six missing anterior maxillary teeth and minimal to moderate loss of soft and hard tissues. They both were seeking implant rehabilitation. After comprehensive diagnostic work-up, it was decided to restore the missing teeth and lost facial plate of bone with four dental implants and definitive implant-supported FDPs without gingiva-colored ceramics. This treatment option may be recommended when there is minimal to no need for gingiva-colored ceramics for replacement of missing hard and soft tissues. For the first of these two patients (Patient No. 3), four dental implants were placed in the canine and central incisor positions and restored with two three-unit implant-supported FDPs (option 2a) (Figure 5).

Another option for prosthetic rehabilitation (option 2b) includes segmentation with two canine single implant crowns and one four-unit implant-supported FDP with cantilevers on the lateral incisors; this option was used for the treatment of the second of these two patients (Patient No. 4) (Figure 6 and Figure 7). For this patient, the reason for additional segmentation of the definitive rehabilitation was clinician preference for ease of prosthetic maintenance in case of complications, as well as patient preference.

Lastly, another prosthetic option comprises four dental implants placed in the canine and lateral incisor positions and restored with two canine implant-supported single crowns and one four-unit implant-supported FDP with ovate pontics in the central incisors, similar to option 1a.

Advantages

To compensate for the minimal to moderate bone loss, it was decided for these two case reports to restore the missing teeth with four dental implants and definitive prostheses without gingiva-colored ceramics. The implant distribution can include canine and lateral or central incisor positions.The advantage of placing the four implants at canine and central incisor positions is the biomechanical design. Implant placement in the central incisor position may reduce the length of lever arms; long lever arms cause increased rotational forces and mechanical stress.30,31 Bending moments are products of applied force and length of the lever arm. Hence, central incisor implant abutment crowns may reduce the magnitude of bending moments and stress on the FDP that causes abutment/prosthetic screw loosening and/or screw fracture, especially in cases of increased curvature of the arch as observed in these two case reports. Alternatively, when the curvature of the arch is not excessively increased, the four implants can be placed in the canine and lateral incisor positions and restored with two canine single crowns and one four-unit implant-supported FDP.

This treatment option, option 2a, may also be recommended when there is minimal to no need for gingiva-colored ceramics for replacement of missing hard and soft tissues. In such a scenario, the segmentation in the midline may not be an esthetic challenge due to symmetry. Increased interproximal contacts in the incisal-cervical direction may be needed to accommodate for the reduced interimplant papilla height of 3.5 mm and to mitigate black triangles (Figure 7). It should be mentioned, though, that the interproximal papillae will mature with a potential gradual increase in their dimension over time as reported by clinicians, but the occurrence varies.10 For the two patients restored with treatment option 2, the increased curvature of the arch and the minimal amount of soft and hard tissues played a role in the selection of this treatment approach.

Regarding pontic site development, using modified ridge lap design for the lateral or central incisor pontic crowns allows for soft-tissue conditioning and emergence profiles with more favorable papillae.8,12,20,22,32 This contributes significantly to the illusion of a harmoniously scalloped soft-tissue line, compensating in part for the ridge flattening after tooth loss (Figure 6). The ovate pontic technique also offers the laboratory technician the freedom to provide harmonious, adequately sized teeth with ovate configuration.

If the transition line (interface of prosthesis and soft tissues) is not exposed due to a low smile line, then longer prosthetic teeth without any gingiva-colored ceramics may be acceptable and even favorable compared with the use of gingiva-colored ceramics that often mismatch to the color of the patient's own gingiva (Figure 6 and Figure 7).

Disadvantages

The main limitation of treatment option 2a with two central incisor implants is the potential compromise of the interproximal papillae between the central incisors. Literature has shown that when two adjacent implants are placed, the interimplant distance affects the extent of lateral bone loss and interproximal bone peak resorption.25-27 When a distance of less than 3 mm is present, increased loss of interimplant bone height is expected, which is caused by the circumferential component of peri-implant bone remodeling.25-27 Overlap of the bone remodeling areas between the adjacent implants leads to this vertical reduction of interimplant bone peak and deficient papillae between adjacent implants, with esthetic consequences and creation of black triangles. Additionally, the periodontal ligament fibers around an implant tend to be circular in nature rather than perpendicular, as they are to the surface of the natural tooth, and this leads to the reduced height of the interimplant soft tissue. The interproximal contacts have to be extended apically to compensate for the reduced interimplant soft-tissue height.

Another limitation is that accurate 3D implant positioning is necessary and symmetry must be kept under strict control to achieve the correct interimplant distance, emergence profile, and precise placement within the confines of the embrasures. Precise 3D implant positioning is necessary to distribute the implants in the correct interproximal and interimplant positions, and freehand surgical placement may not be as precise as needed.19 Guided surgery is an efficient tool to achieve optimal implant placement and its use is recommended in such esthetically demanding situations.33,34 However, guided surgery involves additional fees for the surgical armamentarium, an additional form of intervention that carries risk and the fabrication of the surgical template.

Treatment Option 3: Three Implants

A fifth patient (Patient No. 5) presented with six missing anterior maxillary teeth and minimal loss of soft and hard tissues, and was seeking implant rehabilitation. Following diagnostic work-up, it was decided to restore the missing teeth with three dental implants and a definitive one-piece implant-supported FDP without gingiva-colored ceramics (Figure 8 and Figure 9). This option can also be selected when gingival-colored ceramics are needed. Some financial limitations were taken into consideration for the selection of this treatment option. With this three-implant option, implants may be placed either in the positions of the two canines and one incisor or in the positions of the incisors (either central or lateral) and one canine in various combinations. The selected occlusal scheme was group function, so that the disclusion during laterotrusive movements is shared with the premolars bilaterally.

Advantages

Treatment option 3 has the benefit of cost-effectiveness. It is a more economic prosthodontic approach because only three implants are used to replace the six missing adjacent teeth. Another advantage of this approach is that precise 3D implant positioning of the central implant is somewhat less crucial compared with placing two adjacent central implants, because the associated pontics can compensate. Hence, this treatment option may offer more freedom, especially if gingiva-colored ceramics are necessary.28

This treatment option is possible in two variations, depending on whether the canines or incisors are selected as the primary implant site. The choice between these two options should be based on which site shows superior local crest anatomy and the desired occlusal scheme (canine guidance versus group function). Specifically, this approach may avoid adjacent implants if canines and incisor position are used with pontic crowns in-between and eliminate cantilevers. Alternatively, it may limit cantilever extensions to one unit if incisors and one canine are used.

Disadvantages

The main limitation of this option is the fact that a one-piece prosthodontic design must be implemented. A one-piece implant prosthesis is the least favorable option in terms of prosthetic maintenance, cleansability, and ease of fabrication. Because complications frequently occur with implant-supported FDPs, the one-piece design carries a medium risk; in case of biologic or technical complications the whole prosthesis needs to be removed and repaired or remade.35,36 Screw retention may be preferable to cement retention. This is because cement-retained implant-supported FDPs with subgingival restoration margins are associated with peri-implant soft-tissue complications due to difficulty in removing excess cement.35,36 Cement remnants around the abutment and/or implant will induce foreign-body reactions within the peri-implant soft tissues, leading to biologic complications such as mucosal inflammation and peri-implant bone loss.35 Also, one-piece prosthesis design may be more difficult for the patient to maintain, and it also may be more difficult to fabricate compared with a segmented design with multiple FDPs and single crowns.

Treatment Option 4: Two Implants

A sixth patient (Patient No. 6) presented with six missing anterior maxillary teeth and significant horizontal loss of soft and hard tissues and was seeking implant rehabilitation. After comprehensive diagnostic work-up, the patient firmly denied any removable prosthesis or guided bone regeneration (GBR) to rebuild the deficient alveolar ridge and it was decided to restore the missing teeth with two dental implants and a definitive one-piece implant-supported FDP (Figure 10 and Figure 11). This option comprised two implants in the canine positions restored with one six-unit implant-supported FDP, as these were the only positions that could accommodate dental implants.

Advantages

This approach is the most economic option for the restoration of the six missing adjacent teeth in the anterior maxilla. Only two implants are placed in the canine positions, and a long-span FDP is fabricated. This option may reduce or even eliminate the need for extensive GBR procedures, especially in cases with knife-edge alveolar ridges and extreme atrophy, because only two implants are placed (Figure 10 and Figure 11). In cases with older patients with a flattened out alveolar ridge, the use of pontics for the four missing incisors can lead to an esthetic outcome, with or without gingiva-colored ceramics.

Disadvantages

There are many limitations with this treatment option. First, the prosthodontic design with extensive pontic areas is biomechanically weak, as described previously in the fixed prosthodontic literature.30 With increased lever arms, bending forces are applied during function to the pontic areas and abutment crowns, with a high potential for biologic and technical complications. Second, in the event of complications, the whole prosthesis needs to be removed and repaired or replaced.36-38 Finally, there is no documentation in the literature supporting this treatment option.

Treatment Option 5: Five or Six Implants

This option comprises the placement of five or six implants for the fabrication of six single implant crowns in the anterior maxilla.

Disadvantages

There are many limitations with this treatment option. The placement of six implants to replace six missing anterior maxillary teeth is not supported by the literature due to the deleterious effect on the interproximal papillae and the unnecessary additional cost without any generated benefit. There is no documentation in the literature supporting this option, and it cannot be recommended.

In Figure 12, the different treatment options are shown. Table 1 summarizes the treatment considerations, advantages, and disadvantages with each treatment option.

Discussion

The restoration of six adjacent missing teeth in the anterior maxilla requires significant treatment planning and attention to detail. Because each patient presentation is unique and has its own complexities and specific characteristics, there is currently no universal analysis of treatment planning options in the implant literature. The restoration of multiple teeth in the anterior maxilla differs from single-tooth gaps that may benefit from interproximal tissue support from the PDLs of adjacent teeth.12 The esthetic outcome, especially concerning the interimplant papillae, of multiple consecutively placed implants is still not predictable. Regarding interimplant space limitations, interimplant distance less than 3 mm may increase peri-implant marginal bone resorption, resulting in the loss of interproximal bone peaks and subsequent loss of papillae.25-27 Regarding multiple missing teeth, implant-supported FDPs may be a more desirable choice for superior esthetic results with ovate pontics instead of multiple adjacent implant-supported single crowns.

One of the most important factors in implant rehabilitation of missing anterior maxillary teeth is the location of the patient's smile line. The smile line relates to the location of the transition line between the alveolar ridge and the prosthesis, and this must be evaluated during the diagnostic and treatment planning phase.14 This will determine whether to rebuild the lost bone with GBR and CT grafts prior to implant placement or reduce the alveolar ridge until the transition line is hidden by the smile line. Identification of the relation of the patient's alveolar ridge and the smile line should be integral to every patient assessment because it is quite easy to over-treat the patient if no consideration is given to the exposure of the transition line between the alveolar ridge ("patient's pink") and the prosthesis ("prosthetic pink").

When it is decided to rebuild the lost hard and soft tissues prior to implant placement, GBR, alveolar ridge preservation, block grafts, CT grafts, distraction osteogenesis, and root submergence techniqueshave been used separately or in combination to enhance the outcomes of implant therapy in the esthetic zone. The main limitation here is that the facial bone plate will be shorter than the palatal bone, which results in the prosthetic tooth replacement being longer on the facial aspect compared with the natural tooth that is being replaced.2 In this context, the clinician is faced with either having to reconstruct the residual alveolar ridge prior to implant treatment or simulate soft-tissue replacement using gingiva-colored ceramics. The need to reconstruct the residual alveolar ridge may be avoided if the extraction site is managed on the day of tooth extraction with alveolar ridge preservation techniques.9 Without alveolar ridge preservation there will be some degree of loss of the facial plate.9Deproteinized but not demineralized bone allografts are preferable due to their slow resorption rate after graft placement. Though there have been long-term data of up to about 10 years with the various bone grafting techniques, more longitudinal data are necessary because patients' lifespans have been extended and implant therapy is anticipated to survive for decades.13

In regard to the implant-loading protocol for anterior implant-supported FDPs, a meta-analysis showed that early and conventional loading has satisfactory outcomes, while insufficient evidence exists supporting immediate loading.15 Regarding the interim prosthesis, the use of screw retention is recommended due to significant advantages such as retrievability, no residual cement as may be seen with cement retention, and ease of modification of the transmucosal part of the prosthesis.10,11 The definitive implant-supported FDP can be either cement or screw retained.10,38 However, screw-retained implant-supported FDPs have exhibited fewer biologic and technical complications overall, according to a systematic review.38 In addition, clinical studies indicate increased biologic complications with cement-retained prostheses due to retained excess cement at the prosthetic/abutment interface.35,38 Hence, when a cement-retained prosthesis is inserted, care should be taken to thoroughly remove cement remnants from the abutment and/or implant to prevent foreign-body reactions within the peri-implant soft tissues. Whenever possible, screw retention may be more favorable.

Another issue is the angulation of the alveolus relative to the definitive prosthesis. If the two are different, it may be necessary to compensate for the difference through the use of an angled abutment that allows screw retention of the prosthesis or a custom abutment that would require cementation of the definitive prosthesis. Accurate 3D implant positioning is crucial.13,19-21 Due to the angulation of the maxillary alveolus it is not always possible to place implants in such positions as to allow for a screw-retained prosthesis. In this context, cement retained prostheses are fabricated, and both retention types can provide clinically satisfactory outcomes when clinical guidelines are followed and meticulous care is taken.

With regard to prosthetic materials, the use of porcelain-fused-to-metal (PFM) represents the gold standard for fabrication of tooth- and implant-supported FDPs.39 PFM implant-supported FDPs for the restoration of the six missing anterior maxillary teeth are used regularly with high prosthesis survival rates and low technical complication rates.8,12,39 Due to their esthetic properties and the increased price of gold alloys, various all-ceramic materials such as zirconia and lithium disilicate are also used in fixed implant prosthodontics, and they can be layered or monolithic. The use of zirconia is an alternative for implant-supported frameworks, and its use has increased primarily for its high biocompatibility, low bacterial surface adhesion, esthetic properties, and high flexural strength. The zirconia frameworks in fixed implant prosthodontics are commonly layered with veneering porcelain, but several studies have reported high rates of technical complications, such as delamination, chipping, or fracture of the veneering porcelain.

Monolithic zirconia was introduced to compensate for the technical complications associated with veneered zirconia.40 Titanium inserts are commonly cemented to the zirconia framework either at the laboratory or chairside to avoid an implant-abutment junction of dissimilar materials and wear at the zirconia-titanium interface. In addition, the ability to mill the zirconia at the level of accuracy/precision that is required may be limited. However, there is a paucity of clinical studies investigating the long-term effectiveness with monolithic zirconia implant-supported FDPs.

Currently, there is no universal standard for assessment of cost-effectiveness of implant rehabilitation of the six missing teeth (canine to canine) in the anterior maxilla due to variations in healthcare systems and fees around the world. Rehabilitation with three implants is typically more economical but mandates a one-piece implant-supported FDP that may be a less favorable option in terms of prosthetic maintenance, cleansability, and ease of fabrication. If biologic or technical complications of the one-piece implant-supported FDP occur, the entire prosthesis would need to be removed and repaired/remade. Conversely, the fabrication of two individual three-unit FDPs requires a greater initial expense and a biologic or technical complication with either of the two FDPs may require that the affected FDP be replaced.

Summary

A plethora of factors must be considered when treatment planning for the restoration of six adjacent missing teeth in the anterior maxilla. Different treatment options were presented and the advantages and disadvantages of each option were discussed. Assessment of the patient's smile line and the exposure of the transition line (interface between prosthesis and soft tissues) should be an integral part of the diagnostic phase. The differences in location of the implants, the rebuilding of the alveolar ridge prior to implant placement, the compensation for the loss of the labial plate of bone, and the rationale for choice of retention type and prosthetic materials were also presented.

Acknowledgments

The authors wish to thank Drs. Muizzadin Mokti, Neha Rajput, Fernando Harp Ruiz, and Catherine DeFuria for their participation in clinical care. The authors have no financial interest in the companies whose materials are included in this article.

About the Authors

Panos Papaspyridakos, DDS, MS, PhD
Assistant Professor
Division of Postgraduate Prosthodontics
Tufts University School of Dental Medicine
Boston, Massachusetts

Dennis P. Tarnow, DDS
Professor and Director of Implant Education
Division of Periodontology
Columbia University College of Dental Medicine
New York, New York

Steven E. Eckert DDS, MS
Professor Emeritus
Department of Dental Specialties
Mayo Clinic
College of Medicine
Rochester, Minnesota

Hans-Peter Weber, DMD, Dr. Med. Dent.
Professor and Chairman
Division of Postgraduate Prosthodontics
Tufts University School of Dental Medicine
Boston, Massachusetts

References

1. Pietrokovski J, Massler M. Alveolar ridge resorption following tooth extraction. J Prosthet Dent. 1967;17(1):21-27.

2. Araújo MG, Lindhe J. Dimensional ridge alterations following tooth extraction. An experimental study in the dog. J Clin Periodontol. 2005;32(2):212-218.

3. Tan WL, Wong TL, Wong MC, Lang NP. A systematic review of post-extractional alveolar hard and soft tissue dimensional changes in humans. Clin Oral Implants Res. 2012;23(suppl 5):1-21.

4. Nowzari H, Molayem S, Chiu CH, Rich SK. Cone beam computed tomographic measurement of maxillary central incisors to determine prevalence of facial alveolar bone width ≥2mm. Clin Implant Dent Relat Res. 2012;14(4):595-602.

5. Januário AL, Duarte WR, Barriviera M, et al. Dimension of the facial bone wall in the anterior maxilla: a cone-beam computed tomography study. Clin Oral Implants Res. 2011; 22(10):1168-1171.

6. Vera C, De Kok IJ, Reinhold D, et al. Evaluation of buccal alveolar bone dimension of maxillary anterior and premolar teeth: a cone beam computed tomography investigation. Int J Oral Maxillofac Implants. 2012;27(6):1514-1519.

7. Vedrana B, Bornstein MM, Belser U, Buser D. Thickness of the anterior maxillary facial bone wall - a retrospective radiographic study using cone beam computed study. Int J Periodontics Restorative Dent. 2011;31(2):125-131.

8. Krennmair G, Seemann R, Weinländer M, et al. Implant-prosthodontic rehabilitation of anterior partial edentulism: a clinical review. Int J Oral Maxillofac Implants. 2011;26(5):1043-1050.

9. Avila-Ortiz G, Elangovan S, Kramer KW, et al. Effect of alveolar ridge preservation after tooth extraction: a systematic review and meta-analysis. J Dent Res. 2014;93(10):950-958.

10. Martin WC, Pollini A, Morton D. The influence of restorative procedures on esthetic outcomes in implant dentistry: a systematic review. Int J Oral Maxillofac Implants. 2014;29(suppl):142-154.

11. Morton D, Chen ST, Martin WC, et al. Consensus statements and recommended clinical procedures regarding optimizing esthetic outcomes in implant dentistry. Int J Oral Maxillofac Implants. 2014;29(suppl):216-220.

12. Vailati F, Belser UC. Replacing four missing maxillary incisors with regular- or narrow-neck implants: Analysis of treatment options. Eur J Esthet Dent. 2007;2(1):42-57.

13. Buser D, Chappuis V, Kuchler U, et al. Long term stability of early implant placement with contour augmentation. J Dent Res. 2013;92(suppl 12):176S-182S.

14. Tjan AH, Miller GD, The JG. Some esthetic factors in a smile. J Prosthet Dent. 1984;51(1):24-28.

15. Gallucci GO, Benic GI, Eckert SE, et al. Consensus statements and clinical recommendations for implant loading protocols. Int J Oral Maxillofac Implants. 2014;29(suppl):287-290.

16. Levine RA, Huynh-Ba G, Cochran DL. Soft tissue augmentation procedures for mucogingival defects in esthetic sites. Int J Oral Maxillofac Implants. 2014;29(suppl):155-185.

17. Papaspyridakos P, Chen CJ, Singh M, et al. Success criteria in implant dentistry: a systematic review. J Dent Res. 2012;91(3):242-248.

18. Strietzel FP, Neumann K, Hertel M. Impact of platform switching on marginal peri-implant bone-level changes. A systematic review and meta-analysis. Clin Oral Implants Res. 2015;26(3):342-358.

19. Buser D, Martin W, Belser UC. Optimizing esthetics for implant restorations in the anterior maxilla: anatomic and surgical considerations. Int J Oral Maxillofac Implants. 2004;19(suppl):43-61.

20. Belser UC, Schmid B, Higginbottom F, Buser D. Outcome analysis of implant restorations located in the anterior maxilla: A review of the recent literature. Int J Oral Maxillofac Implants. 2004;19(suppl):30-42.

21. Papaspyridakos P. Implant success rates for single crowns and fixed partial dentures in general dental practices may be lower than those achieved in well-controlled university or specialty settings. J Evid Based Dent Pract. 2015;15(1):30-32.

22. Higginbottom F, Belser U, Jones JD, Keith SE. Prosthetic management of implants in the esthetic zone. Int J Oral Maxillofac Implants. 2004;19(suppl):62-72.

23. Cosyn J, Raes M, Packet M, et al. Disparity in embrasure fill and papilla height between tooth- and implant-borne fixed restorations in the anterior maxilla: a cross-sectional study. J Clin Periodontol. 2013;40(7):728-733.

24. Spear F. Implants or pontics: decision making for anterior tooth replacement. J Am Dent Assoc. 2009;140(9):1160-1166.

25. Tarnow DP, Cho SC, Wallace SS. The effect of inter-implant distance on the height of inter-implant bone crest. J Periodontol. 2000;71(4):546-549.

26. Tarnow D, Elian N, Fletcher P, et al. Vertical distance from the crest of bone to the height of the interproximal papilla between adjacent implants. J Periodontol. 2003;74(12):1785-1788.

27. Salama M, Ishikawa T, Salama H, et al. Advantages of the root submergence technique for pontic site development in esthetic implant therapy. Int J Periodontics Restorative Dent. 2007;27(6):521-527.

28. Coachman C, Salama M, Garber D, et al. Prosthetic gingival reconstruction in a fixed partial restoration. Part 1: introduction to artificial gingiva as an alternative therapy. Int J Periodontics Restorative Dent. 2009;29(5):471-477.

29. Papaspyridakos P, White GS, Lal K. Flapless CAD/CAM-guided surgery for staged transition from failing dentition to complete arch implant rehabilitation: a 3-year clinical report. J Prosthet Dent. 2012;107(3):143-150.

30. Vela-Nebot X, Méndez-Blanco V, Rodríguez-Ciurana X, et al. Implant positioning when replacing the four maxillary incisors: a platform-switched treatment option. Int J Periodontics Restorative Dent. 2011;31(4):375-381.

31. Tymstra N, Raghoebar GM, Vissink A, Meijer HJ. Dental implant treatment for two adjacent missing teeth in the maxillary aesthetic zone: a comparative pilot study and test of principle. Clin Oral Implants Res. 2011;22(2):207-213.

32. Kim TH, Cascione D, Knezevic A. Simulated tissue using a unique pontic design: a clinical report. J Prosthet Dent. 2009;102(4):205-210.

33. Wöhrle PS. Predictably replacing maxillary incisors with implants using 3-D planning and guided implant surgery. Compend Contin Educ Dent. 2014;35(10):758-762.

34. Tahmaseb A, Wismeijer D, Coucke W, Derksen W. Computer technology applications in surgical implant dentistry: a systematic review. Int J Oral Maxillofac Implants. 2014;29(suppl):25-42.

35. Wadhwani C, Rapoport D, La Rosa S, et al. Radiographic detection and characteristic patterns of residual excess cement associated with cement-retained implant restorations: a clinical report. J Prosthet Dent. 2012;107(3):151-157.

36. Heitz-Mayfield LJ, Needleman I, Salvi GE, Pjetursson BE. Consensus statements and clinical recommendations for prevention and management of biologic and technical implant complications. Int J Oral Maxillofac Implants. 2014; 29(suppl):346-350.

37. Pjetursson BE, Thoma D, Jung R, et al. A systematic review of the survival and complication rates of implant-supported fixed dental prostheses (FDPs) after a mean observation period of at least 5 years. Clin Oral Implants Res. 2012;23(suppl 6):22-38.

38. Wittneben JG, Millen C, Brägger U. Clinical performance of screw-versus cement-retained fixed implant-supported reconstructions-a systematic review. Int J Oral Maxillofac Implants. 2014;29(suppl):84-98.

39. Pjetursson BE, Sailer I, Makarov NA, et al. All-ceramic or metal-ceramic tooth-supported fixed dental prostheses (FDPs)? A systematic review of the survival and complication rates. Part II: multiple-unit FDPs. Dent Mater. 2015;31(6):624-639.

40. Papaspyridakos P, Kang K, DeFuria C, et al. Digital workflow in full-arch implant rehabilitation with segmented minimally veneered monolithic zirconia fixed dental prostheses: 2-year clinical follow-up. J Esthet Restor Dent. 2018;30(1):5-13.

© 2018 AEGIS Communications | Privacy Policy