Future Trends in Implant Dentistry: Digitally Guided Surgery and Prosthetics

INTRODUCTION
This article discusses an innovative and clinically accurate protocol that will assist interested dental practitioners in the delivery of full-arch fixed immediate provisional prostheses. Additionally, the detailed steps involved in converting the provisional into a fixed screw-retained final prosthesis, following sufficient healing and the osseointegration of dental implants, are outlined.

CASE REPORT
Diagnosis and Treatment Planning

A 76-year-old male patient presented to the office with Kennedy Class I partial edentulism in the maxilla (Figure 1). He had 4 anterior teeth present with one that had fractured at the gingival margin. He expressed a desire for a fixed implant-supported solution. After appropriate medical, dental, and social histories were obtained, a full clinical and radiographic examination was performed. Subsequently, it was determined that the patient had a terminal maxillary dentition and he was presented with various options.

The patient elected to have a full implant-retained prosthesis for the maxillary arch. The treatment planning and clinical procedure involved digitally guided surgery and a digitally guided provisional prosthesis. The digital protocol simplifies the steps involved in fabricating a fixed final prosthesis after subsequent healing has taken place.

To employ this protocol, the practitioner provided the laboratory team with the following:

  • Models (conventional or digital) with a face-bow registration
  • A bite registration of the patient at his “idealized” vertical dimension of occlusion (VDO)
  • CBCT at the idealized VDO
  • A series of intra- and extraoral photographs of the patient.

The company, nSequence Center for Advanced Dentistry (Reno, Nev), then digitized this information, creating a digital treatment plan to allow the practitioner and patient to visualize the outcome prior to surgery (Figure 2).

Figure 1. Retracted preoperative presentation.
Figure 2. A digital treatment plan was requested and provided.

Digitally Guided Surgical and Prosthetic Phases
Check Bite—A hard acrylic bite was fabricated by the laboratory team, based upon the initial patient records (Figure 3). The “check bite” step verifies the accuracy of the merged data, and the practitioner can feel confident that the digital records correctly represent the clinical situation.

Placement of the foundation guide—Once the patient’s maxillary teeth were extracted and a full-thickness flap was raised to expose the entire alveolus, the “foundation” guide was placed to fit over the alveolus (Figure 4). This foundation guide remains in place until the time that the provisional prosthesis is inserted. The patient bites into the struts of the guide, which helps to stabilize and position the foundation guide.

Once fully seated, guided fixation pins were placed using depth control to secure the guide by engaging both the buccal and palatal bone.

After removal of the positioning struts, the foundation guide directed subsequent bone reduction. Bone reduction was achieved using a Rongeur’s forceps. Any larger bone fragments were preserved to fill the extraction sockets. A bur (Pikos bone block contouring bur [Salvin Dental Specialties]) was used to smooth the alveolus until flush with the foundation guide (Figure 5).

Figure 3. Lab-fabricated hard acrylic bite. Figure 4. After extraction of maxillary teeth and a full-thickness flap, the “foundation” guide was placed over the alveolus.
Figure 5. The alveolus was smoothed with a bur until flush with the foundation guide. Figure 6. An implant placement guide was indexed to fit into the foundation guide.
Figure 7. Implants were placed, and then the implant placement guide was detached from the foundation guide. Figure 8. Abutments were placed, and then the abutment placement guide was removed.
Figure 9. Pretrimmed temporary
titanium cylinders, hand-tightened to the multiunit abutments (MUAs). Block-out tubes were placed in cylinders to protect prosthesis screws.
Figure 10. A flexible silicone gasket was then placed over the temporary titanium cylinders.
Figure 11. The gasket blocked out undercuts and helped position the provisional. Figure 12. Picking up the provisional clear duplicate.


Placement of the implants—An implant placement guide (patented by the laboratory [nSequence Center]) was indexed to fit into the foundation guide (Figure 6). This assisted in the sequential osteotomy process, preparing the implant sites. Once the implants were placed, the implant placement guide was detached from the foundation guide (Figure 7).

Placement of the multiunit abutments (MUAs)—An indexed abutment placement guide was then fit into the foundation guide. A specific guide was created to assist in the placement of the angled MUAs to ensure correct positioning. The abutments were then placed and torqued per the manufacturer’s recommendations, and then the abutment placement guide was removed (Figure 8).

Placement of the temporary titanium cylinder—Pretrimmed temporary titanium cylinders were subsequently hand-tightened to the MUAs. Block-out tubes were then placed into these cylinders to protect the prosthesis screws (Figure 9).

Figure 13. The silicone maxillary gasket, fixation pins, and foundation guide were removed. Figure 14. The finished provisional prosthesis.
Figure 15. Panoramic radiograph of and anterior photo of the bar-supported provisional prosthesis.

Placement of the silicone gasket and fit of the provisional—A flexible silicone gasket was then placed over the temporary titanium cylinders, hugging the apical portion of the cylinders tightly (Figure 10). The gasket served to block out undercuts and to guide the apical and lateral position of the provisional (Figure 11), while taking into account the thickness of the underlying soft tissue. The provided silicone bite registration index was placed against the incisal edge of the provisional and indexed to the patient’s mandibular incisors, and thus stabilized the prosthesis at the patient’s idealized VDO.

Picking up the provisional prosthesis and clear duplicate—After stabilizing the prosthesis, a dual-cured polymer (Triad [Dentsply Sirona]) was used to “pick up” the cylinders after injecting material into the small buccal channels. After curing the polymer from the buccal, the silicone bite registration was removed. Next, any remaining voids were then filled with the polymer and light-cured from the occlusal aspect. Then, the block-out tubes were removed and the prosthesis was unscrewed and removed from the mouth. This step was then repeated using a second set of titanium cylinders and the clear duplicate prosthesis supplied by the laboratory team (Figure 12). This clear duplicate prosthesis was then stored for future use after the healing period elapsed to help fabricate the final fixed prosthesis.

Removal of guide and closure—The silicone maxillary gasket was then removed along with the fixation pins and foundation guide (Figure 13). The alveolus was then smoothed and contoured and the earlier harvested autogenous bone used to fill the remaining sockets. Closure was achieved by placing individual interrupted sutures between the implants.

Finishing and insertion of the provisional prosthesis—After adding acrylic to fill any remaining voids around the titanium cylinders, the provisional was further cured with heat and pressure before giving its final polish. Next, the finished provisional prosthesis was placed onto the MUAs and torqued into place per the manufacturer’s specifications (Figure 14). Teflon tape and Cavit [3M] were then used to close each access hole before verification of the patient’s occlusion. This bar-supported, monolithic polymethyl methacrylate acrylic (PMMA) prosthesis would then be worn for approximately 6 months (Figures 15 and 16).1

Digitally Guided Final Prosthetic Phase
During the healing phase, the provisional prosthesis was not removed. It served as a “splint” for the implants, helping to stabilize them during the healing process.2,3 After the 6-month healing period,1 the patient returned with his PMMA provisional prosthesis in place. Upon examination, his occlusion remained stable, well balanced, and unchanged from his initial immediate postoperative position (Figure 16a). The prosthesis, although a little worn and mildly stained, was still functional and showed good aesthetics (Figure 16b).

Figure 16. The provisional prosthesis was stable and unchanged at 6 months.
Figure 17. Some inflammation in the tissues was noted after wearing the provisional prosthesis continuously for an extended period of time.
Figure 18. Using a torque wrench with a multiunit adapter, the stability of each implant was tested. Figure 19. One implant did not
successfully osseointegrate and was subsequently removed.
Figure 20. The stored clear duplicate was retrieved and inserted. Figure 21. The prosthesis was
hand-tightened over the MUAs.
Figure 22. The intaglio surface of the clear duplicate and underlying soft tissues were air-dried.

Removal of the provisional prosthesis—The access holes of the provisional prosthesis, which had been closed off with Cavit and Teflon tape, were uncovered. The screws were untorqued, and the prosthesis was removed and cleaned with a chlorhexidine solution (Chlorhexidine Gluconate 0.12% Oro-Cleanse [Germiphene]). Upon inspection of the tissues underlying the prosthesis, the general health of the tissues was fair with some inflammation consistent with expectations having worn the provisional prosthesis continuously for a long period of time (Figure 17).

Verification of the stability of the implants—Using a torque wrench with a multiunit adapter, the stability of each implant was tested (Figure 18). This test serves 2 purposes: first, the abutments are tightened against the implant as they can loosen with time; and second, the bone-implant interface is placed under strain to evaluate its strength at a force of 30 Ncm. If the bone-implant contact is unstable, the implant will rotate. In this case, one implant did not successfully osseointegrate and was subsequently removed (Figure 19). There was no need to replace the failed implant. The design of the final prosthesis would be stable, balanced, and functional using the remaining 7 implants and their anterior-posterior spread.4 The original treatment plan accounted for the potential failure of one or 2 of the implants without the need for additional surgery.

Fit and use of the clear duplicate—The stored clear duplicate was retrieved and inserted into the patient’s mouth (Figure 20). The prosthesis was hand-tightened over the MUAs. The fit was found to be precise and required no adjustment (Figure 21). This predictable fit was a result of the stabilization and splinting of the implants after surgery while the patient wore his PMMA provisional prosthesis. There may be a gap between the clear duplicate and the ridge as some tissue shrinkage is a normal sequelae of the healing process. If there is not an adequate amount of clearance, the intaglio side of this duplicate provisional must be relieved using an acrylic bur to create the required space for the impression material.

Radiographs were then taken to ensure this duplicate was seated properly prior to the next steps.

Impression of the arch and pickup of the implant/MUA positions—Once the seating has been verified and prior to taking an impression, it is important to confirm that the clear provisional duplicates the aesthetics of the provisional prosthesis. (In this practitioner’s experience, this has never been an issue, as the clear duplicate and provisional prosthesis are fabricated together using the same digital technology and processes prior to the surgical procedure.)

Figure 23a. Using retractors, light-body vinyl polysiloxane (VPS) impression material (Examix NDS [GC America]) was injected into the gap area between the tissues and the clear duplicate from both the palatal and buccal. Figure 23b. The VPS material was extruded to record the facial and palatal contours of the ridge.
Figure 23c. A bite registration was taken simultaneously with the patient in centric relation.
Figure 24. Once the materials were fully set, the bite registration was carefully removed, the clear duplicate unscrewed and removed. Figure 25. The lab team (nSequence Center for Advanced Dentistry; Reno, Nev) then fabricated a metal framework with access holes where the implants are located for the final prosthesis.
Figure 26. The patient returned to the office at approximately 2 weeks for the metal framework try-in.

The intaglio surface of the clear duplicate and underlying soft tissues were air-dried (Figure 22). Using retractors, light-body vinyl polysiloxane (VPS) impression material (Examix NDS [GC America]) was injected into the gap area between the tissues and the clear duplicate from both the palatal and buccal. With the tip inserted inside the gap area, the impression material was gently extruded while the tip was carefully pulled out (Figure 23a). This process ensures that there is adequate impression material in this area to adequately capture the gingival tissues that have recontoured during the healing phase. The VPS material was also extruded to record the facial and palatal contours of the ridge (Figure 23b). The accuracy of the vestibular contours was not critical in this procedure, as a fixed prosthesis was treatment planned for the patient rather than a conventional full denture. A bite registration was also taken simultaneously with the patient in centric relation (Figure 23c).

Once the materials were fully set, the bite registration was carefully removed and the clear duplicate unscrewed and removed from the mouth (Figure 24). The impression was examined carefully to ensure that the intaglio surface of the denture had accurately recorded the gingival contours and there were no serious deficiencies. The PMMA provisional prosthesis was then re-inserted for the patient, and radiographs taken to ensure that the prosthesis was seated and fit appropriately.

Figure 27. Radiographs were taken and a screw test done to confirm an accurate and passive fit of the framework.
Figure 28. Completed maxillary implant-retained prosthesis.

Laboratory fabrication of the final fixed prosthesis—Next, the impression was sent to the laboratory, where the lab team would attach MUA analogs and pour a model to become an accurate representation of the patient’s arch and implant/MUA positions (master model). This master model was cross-mounted with the bite registration and the previous mounted mandibular cast. The lab team then fabricated a metal framework with access holes where the implants were located for the final prosthesis. On this screw-retained prosthesis, each final crown restoration was made to fit the individual crown preparations on the framework (Figure 25). In this case, milled lithium disilicate (IPS e.max CAD [Ivoclar Vivadent]) crowns were prescribed.

Try-in of the metal framework—The patient returned to the office in approximately 2 weeks to try in the metal framework (Figure 26). Radiographs were taken and a screw test done to confirm an accurate and passive fit of the framework (Figure 27).5,6 The occlusion and VDO were verified and a final shade selected.

Finalization of the prosthesis by the laboratory team—The laboratory finished the case by milling the lithium disilicate crowns, and then adding pink porcelain to the metal framework to mimic the gingiva and soft tissues. Access holes were created in the crowns where the screws were located. Finally, the crowns were then cemented onto the framework at the laboratory using permanent cement.

Insertion of the final fixed prosthesis—The patient returned to the clinic, and the provisional PMMA prosthesis was removed and the final prosthesis delivered. The access holes are filled with Cavit and Teflon tape, and the excess material removed. The aesthetics, occlusion, and VDO were verified. The patient was very pleased with the final outcome (Figure 28).

DISCUSSION
This innovative technique (patented by nSequence) uses integrated digital technology to achieve a predictable prosthetic result.7 As noted herein, each sequential step was guided by the initial treatment planning, ensuring accuracy of fit in each surgical and prosthetic phase. The aesthetics and function of the final prosthesis were predictable and unchanged from the provisional phase through the delivery of the fixed prosthesis. This instilled confidence between the clinician and the patient, as they worked together in the treatment planning and consultation phases to reach this outcome.

This technique is very time efficient for both the clinician and the patient. The guided surgical and guided prosthetic protocol enable a faster and more accurate placement of implants and provisional prosthesis without any guesswork, as is required in other “freehand” methods.8-10 Additionally, the fabrication of the final prosthesis requires fewer appointments as several clinical steps (including the verification jig, occlusal rim, and wax setup) are eliminated as a direct result of the digital solution provided by this methodology. The clear duplicate serves as an impression tray as well as a verification jig to ensure the accuracy of the implant/MUA positions in the master model. Also, the use of the clear duplicate mimics the size and shape of the teeth at the correct VDO for the final prosthesis; thus, there is no need for wax occlusal rims or a wax tooth setup. For the patient, this is advantageous as (potentially) 3 appointments are eliminated. It is noteworthy to mention that, with experience and developed expertise, the metal framework try-in appointment can often be eliminated given the high level of accuracy of the master model.

This protocol will support the use of various restorative materials for the final prosthesis. However, the main advantage of using a framework with individual CAD/CAM crowns is the ease with which replacement crowns can be fabricated in the event the patient fractures one since a digital record is kept. If one crown chips, it can be removed and provisionalized while the lab team is instructed to fabricate a replacement crown. It is unnecessary to remove and send the entire prosthesis back to the laboratory. Additionally, the lab team could even fabricate the replacement crown before the patient presents to the office, as long as the practitioner knows ahead of time which crown is compromised.

IN SUMMARY
The use of digital technology and CAD/CAM solutions creates a high degree of predictability for the practitioner. The preplanned surgical phase, including the foundation and implant placement guides, reduces the stresses involved in determining optimal implant placement sites for prosthetic rehabilitation.11 Using the clear duplicate protocol eliminates the inaccuracies of impression materials for the implant and/or MUA positions. This translates into a more passive fitting prosthesis5 along with predictable aesthetics. Ultimately, this is a win-win situation for the patient and the clinician.


References

  1. Brånemark PI, Albrektsson T. Microcirculation and healing of artificial implants in bone. In: Proceedings of the 2nd World Congress for Microcirculation. Cambridge, MA: Academic Press; 1979:59-60.
  2. Schnitman PA, Wöhrle PS, Rubenstein JE, et al. Ten-year results for Brånemark implants immediately loaded with fixed prostheses at implant placement. Int J Oral Maxillofac Implants. 1997;12:495-503.
  3. Wang TM, Leu LJ, Wang J, et al. Effects of prosthesis materials and prosthesis splinting on peri-implant bone stress around implants in poor-quality bone: a numeric analysis. Int J Oral Maxillofac Implants. 2002;17:231-237.
  4. Rodriguez AM, Aquilino SA, Lund PS. Cantilever and implant biomechanics: a review of the literature, Part 2. J Prosthodont. 1994;3:114-118.
  5. Sahin S, Cehreli MC. The significance of passive framework fit in implant prosthodontics: current status. Implant Dent. 2001;10:85-92.
  6. Kan JY, Rungcharassaeng K, Bohsali K, et al. Clinical methods for evaluating implant framework fit. J Prosthet Dent. 1999;81:7-13.
  7. Pikos MA, Magyar CW, Llop DR. Guided full-arch immediate-function treatment modality for the edentulous and terminal dentition patient. Compend Contin Educ Dent. 2015;36:116-128.
  8. Rosenfeld AL, Mandelaris GA, Tardieu PB. Prosthetically directed implant placement using computer software to ensure precise placement and predictable prosthetic outcomes. Part 1: diagnostics, imaging, and collaborative accountability. Int J Periodontics Restorative Dent. 2006;26:215-221.
  9. Pikos MA, Mattia AH. Implant surgery interventions: Three-dimensional reverse tissue engineering for optimal dental implant reconstruction. In: Jokstad A, ed. Osseointegration and Dental Implants. Ames, IA: Wiley-Blackwell; 2008:197-204.
  10. Worthington P, Rubenstein J, Hatcher DC. The role of cone-beam computed tomography in the planning and placement of implants. J Am Dent Assoc. 2010;141(suppl 3):19S-24S.
  11. Wong NY. Predictable immediate implant prosthetics using guided surgery and guided prosthetics: a case report. Oral Health. 2016;106:66-78.

Dr. Wong graduated from the University of Toronto with a DDS (1996) and received her certificate in prosthodontics from the University of Michigan (2007). She is the only dentist who has attained a combination of the US board certification in implant dentistry (Diplomate from the American Board of Oral Implantology [ABOI], 2003), US board certification in prosthodontics (Diplomate of American Board of Prosthodontics, 2008), and Canadian board certification in prosthodontics (Fellow of Royal College of Dentists of Canada, 2008). She is a Diplomate of the International Congress of Oral Implantologists and holds Fellowships with the AGD, American Academy of Implant Dentistry (AAID), and the Misch International Implant Institute in Canada, where she is also a faculty member. She has served as a clinical instructor in the implant prosthodontic unit in the graduate prosthodontic department at the University of Toronto. She is past president of the ABOI, the current treasurer for the AAID, president of the Association of Prosthodontists of Ontario, and founder and director of the Toronto Implant Institute. She lectures internationally on implant dentistry and continues to practice implantology in Toronto. She can be reached by email at the following address: This email address is being protected from spambots. You need JavaScript enabled to view it..

Disclosure: Dr. Wong is a consultant for BioHorizons.

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Use of Superior Prosthetic Technique to Overcome Compromised Implant Placement

Proper placement of implants is critical in order to achieve the best possible aesthetic results. This is especially true in the maxillary anterior region. Extreme bone loss in an edentulous area presents a challenge to ideal implant placement. Several bone grafting techniques have evolved over the years to enable us to attain our goals. Each of these techniques has its advantages and disadvantages and therefore we must use our clinical judgment to decide which technique to pursue.

The techniques considered for ridge augmentation in this clinical case were:

  • Autogenous block onlay bone grafting.
  • Nonautogenous block onlay grafting.
  • Segmental ridge splitting.
  • Particular bone grafting.

Autogenous Block Onlay Bone Grafting

Autologous bone grafting used with dental implant was originally introduced by Brånemark et al in 1975.1 This technique involves harvesting bone from a recipient site such as the ramus of the mandible or mandibular symphysis and transplanting this block of bone to a recipient site. This technique can result in significant increases in width but less predictable to increase alveolar height. It involves surgery on a secondary site and it is thus more invasive and traumatic, which leads to higher morbidity of the donor site ie, impaired sensibility to teeth, gingiva, and skin. Another big disadvantage is the significantly high cost of this procedure compared to the others.

Nonautogenous Block Bone Grafting

The big advantage of this technique is that since the material is artificially produced, it eliminates the need for an additional surgical procedure to procure bone from a donor site. However in addition to having the same other drawbacks as the autogenous bone graft, this method is very technique sensitive. It must retain primary closure throughout the healing phase, otherwise it will fail. Failure of either block technique can result in a worse situation than the original.

Segmental Ridge Splinting

The segmental ridge split procedure creates a crypt surrounded by bone and periosteum into which implants and bone graft materials can be introduced with treasonable confidence that new bone can be constructed and that this new bone will provide a solid base for dental implants. Razor sharp bone chisels and a mallet are used to split the alveolar ridge. An implant is placed between the 2 cortical plates along with particulate bone graft material. This procedure is extremely technique sensitive and requires careful case selection. A ridge that is too narrow mesiodistally or buccolingually is almost impossible to split cleanly, and thus presents a high risk of resulting in a far worse situation than originally. It also does not address the loss of alveolar height.

Particular Bone Graft

Bone grafting using particulate material has also been done since the earliest days of osseointegrated implants. Materials have included freeze-dried allograft from tissue banks and nonallograft hydroxyapatite materials. Different particulate materials are supposedly used for osteoinductive and osteoconductive properties. The synthetic hydroxyapatite materials are mainly thought to maintain space and provide a scaffold in which natural bone can form. Different membranes are usually placed over the particulate graft material to both keep the material in place and exclude early migration of epithelial cells before osteoblasts have a chance to migrate and produce bone. Particulate grafting is the most widely used technique because it is less sensitive, less morbid, doesn’t require a donor site and is comparatively much more affordable to patients. It can be used for onlay grafting to increase width and height as well.

Yet even despite our best efforts, an implant may not end up in an ideal position. It is situations like these where expert prosthodontics can compensate and overcome a less than ideal implant position to attain a highly satisfactory result.

CASE REPORT

A 42-year-old female patient presented with a missing maxillary left central incisor with a severely atrophic localized edentulous ridge (Figures 1 and 2). Atrophy of the alveolar ridge had occurred in width as well as vertically.

Figure 1. Initial preoperative view from labial from July 14, 2007. Tooth No. 9 missing.

Figure 2. Initial preoperative view from occlusal from July 14, 2007.

The treatment plan comprised first onlay bone grafting to increase height and width prior to placement of an implant and ultimately placement of a crown.
             
First Stage Surgery

Under local anesthesia, an incision was made from the distal line angle of No. 8 to the distal line angle of No. 10. Vertical incisions were extended at each line angle. A full thickness flap was elevated exposing a “knife edge ridge” of less than 1 mm thickness in the area of No. 9 and approximately 6 mm loss in vertical bone height at the center (Figure 3). Small perforations were made in the bone to create bleeding surfaces (Figure 4). A combination of large particle cortical PUROS bone graft material with Bio-Oss, a synthetic hydroxyapatite graft material was used (Figure 5). Graft material was placed on both labial and palatal sides of the ridge. The graft was then covered with BIO-GUIDE resorbable membrane and held in place with 2 titanium tacs (Figure 6).

Figure 3. Preoperative view from labial of bone (alveolar ridge) with flap reflected (July 14, 2007).

Figure 4. Tenting screw in place during first bone grafting procedure (July 14, 2007).

Figure 5. Bone graft material (BIO-OSS + Puros cortical) in place during first bone grafting procedure (July 14, 2007).

Figure 6. BIOGUIDE membrane in place covering bone graft material. Membrane held in place with titanium tacks. First bone graft procedure (July 14, 2007).

The flaps were closed with 4-0 vicryl sutures (Figures 7 and 8). The patient was placed on a 7-day regimen of amoxicillin along with a chlorhexidine (Peridex) rinse. Healing was uneventful (Figure 9) and the graft site was allowed to heal for 6 months before the area was flapped open again. Modest bone augmentation (approximately 2 mm gain in thickness; one mm gain in height) had taken place, however, it was still deemed insufficient in both quantity and quality to place an implant.

Figure 7. Area sutured—occlusal view (July 14, 2007).

Figure 8. Area sutured—labial view (July 14, 2007).

Figure 9. Preoperative view—occlusal (January 12, 2008).

Additional bone grafting was done using the same materials and techniques as the first procedure (Figures 10 to 12). Again healing was uneventful and the site was allowed to heal for another 5 months (Figure 13). The site was again flapped open revealing an additional 1- to 2-mm gain in thickness but less than a 1-mm gain in height. Bone quality was judged to be poor-fair.

Figure 10. Grafting material placed.

Figure 11. Membrane placed.

Figure 12. Sutured with BIOGUIDE membrane (January 12, 2008).

A surgical stent was used to place the implant in the correct mesial-distal position, however, in deference to the quality bone; it was decided to place the implant slightly within labial to the surgical stent position. This was done in order to place the implant completely within the labial palatal borders of the ridge rather than risk perforating or completely obliterating the palatal wall in trying for ideal location from a prosthetic point of view. Additional bone grafting was placed around the implant using a nonresorbable TEFGEN membrane (Figures 14 to 17).

Figure 13. Preoperative view prior to implant placement (June 14, 2008).

Figure 14. Implant in place—occlusal view (June 14, 2008).

Figure 15. Implant in place—labial view (June 14, 2008).

Figure 16. Bone graft (BIO-OSS + Puros cortical) in place (June 14, 2008).

Figure 17. Sutured implant in place (TEFGEN membrane, black silk sutures) (June 14, 2008).

Figure 18. Implant uncovered with cover screw in place (December 20, 2008).

Figure 19. Final prosthetic smile (December 20, 2008).

Healing was uneventful and the implant was uncovered 6 months later. The membrane was removed and a healing abutment was placed (Figure 18). The patient was referred back to the restorative dentist a few weeks later and the case was restored (Figure 19).

CLOSING COMMENTS

Extensive bone grafting was done in an effort to augment a severely atrophic edentulous single tooth area for the purpose of placing an implant. Despite these efforts, the final placement of the implant resulted in a location more labial and apical than ideally desired.


Reference

1. Brånemark PI, Lindström J, Hallén O, et al. Reconstruction of the defective mandible. Scand J Plast Reconstr Surg. 1975;9:116-128.

Suggested Readings

Listrom RD, Symington JM. Osseointegrated dental implants in conjunction with bone grafts. Int J Oral Maxillofac Surg. 1988;17:116-118.

Misch CM, Misch CE. The repair of localized severe ridge defects for implant placement using mandibular bone grafts. Implant Dent. 1995;4:261-267.

Misch CM. Comparison of intraoral donor sites for onlay grafting prior to implant placement. Int J Oral Maxillofac Implants. 1997;12:767-776.

Schwartz-Arad D, Levin L. Intraoral autogenous block onlay bone grafting for extensive reconstruction of atrophic maxillary alveolar ridges. J Periodontol. 2005;76:636-641.


Dr. Rosenstein is a periodontist in private practice in New York City and Suffern, NY. He did his undergraduate and postgraduate dental training at University of Medicine and Dentistry New Jersey Dental School, Newark, NJ, and a general practice residency at Lenox Hill Hospital, New York City. He can be reached at (845) 357-5002 or This email address is being protected from spambots. You need JavaScript enabled to view it..

Disclosure: Dr. Rosenstein reports no disclosures

Shade-Matching Challenge: A Single Central Incisor

Achieving a good color match when restoring a single incisor is probably among the most difficult aesthetic challenges for any dentist (Figure 1). While the latest technology can be found in most modern dental offices such as CBCT; laser; CAD/CAM; and less common, the more expansive spectrophotometric instruments;1 the vast majority of clinicians still conduct dental shade selection by using a nearby window for a natural light source or, if they are fortunate, pass the buck by simply sending the patient to the dental laboratory technician to take and map the shade. There must be a better way and, in the authors’ opinions and experience, there is! A simple and inexpensive handheld portable LED light source, the Rite-Lite 2 HI CRI Shade Matching Light (AdDent), is now available help achieve an excellent restorative shade match.2-4

Figure 1. Pre-op photos of mismatched crown on nonvital central incisor with gingival inflammation.

DESCRIBING A SHADE
Shade matching is an interdisciplinary process that requires the clinician to communicate with the dental laboratory team using a common language and images (shade-mapping and photographs). Thus, shade matching relies on perception and interpretation of the evidence.

Color, commonly referred to as the shade, is divided into 3 components.

  • Hue refers to the basic color (eg, red, blue, green).
  • Chroma refers to the intensity of the color (eg, fire-truck red versus pastel pink).
  • Value refers to the brightness of the color (eg, the range of gray from black to white).

All these components should not be overlooked, or else a wrong interpretation of color may lead to an undesired result. For example, how often have you told your ceramist to make the cuspids slightly darker when restoring an anterior case? However, your real intent was to make the cuspids warmer with more chroma but not darker (lower value).

It is important to realize that the correct language helps in the interpretation of the evidence. Acquiring the evidence relies on the physiology of our eyes and the transmitted light.5

How We Perceive Color
We perceive color using cone cells that are located in the fovea in the middle of the retina. Cone cells are few in numbers and are divided into 3 groups. Each group responds to a specific color: red, blue, or green.6 Cone cells fatigue extremely fast, since they are limited in number. For example, if you stare at a color, such as red lipstick, the red cone cells will shut down after 30 seconds. This will leave you seeing only the combination of colors provided by the green and blue cells. This is why it is necessary to create a neutral background for your eyes before selecting a shade. Ideally, the walls in the room should be gray or white. Ask your female patients to remove their lipstick and place a pale blue or grey bib over their clothes.7

How We Perceive Value
We perceive value (shades of gray from black to white) through rod cells. These cells are on the periphery of the retina and outnumber the cone cells by 30 times.

Rod cells do not fatigue as easily or as quickly as the cone cells. They can determine the difference in value without getting overworked, while the cone cells quickly fatigue and colors seem to blend together. This is why selecting the correct value on a shade is critical. If the value is correct, hue and chroma can be slightly off without affecting the final result.

While our eyes can differentiate between colors and value of an object, modifying the light source can affect the way our eyes perceive the color of the object.6

Color Rendering Index
The color rendering index (CRI) is the measure of the ability of a light source to reveal the colors of various objects faithfully in comparison with an ideal light source (ie, the sun, as opposed to LEDs or fluorescent lamps). Therefore, a light source with a high CRI is desirable in color critical applications.8 Hence, in our practice we use the Rite-Lite 2 HI CRI Shade Matching Light. This tool is easy to use and highly effective, and will help to ensure a cosmetically pleasing restoration even when treating complex clinical cases.

Color Temperature
Each light source has its own individual color, called color temperature, which varies from red to blue. Sunsets, candle flames, and light from tungsten bulbs all emit light that is close to red, thus imparting a “warm” look to photos. On the other hand, clear blue skies give off a “cool” blue light.

Color temperature is recorded in Kelvin (K), the unit of absolute temperature. The color temperatures of cool colors, such as blue and bright white, typically have color temperatures of more than 7,000°K. Red and orange, with warmer color temperatures, have measurements near the 2,000°K mark. Many references on shade matching in dentistry suggest the use of 5,500°K north white light at 12:00 noon as the standard to be used for shade matching as a basis to taking a shade.9,10

Figure 2. Handheld Rite-Lite 2 HI CRI Shade Matching Light (AdDent).
Figure 3. Examples of shade taken in different color temperatures.
Figure 4. Final results—new crown on central incisor.

This handheld device provides 3 different light options to replicate the different sources of light that we come across on a daily basis (Figures 2 and 3). The 3 lighting modes are as follows:

1. Color corrected light at a color of 5,500°K. This represents north white light at 12:00 noon as the standard to be used for shade matching.
2. Incandescent room light at 3,200°K, found most commonly in many indoor environments.
3. Ambient light at 3,900°K, a combination of both indoor and daylight.

Metamerism
In the field of color science, there is a principle called metamerism. It is a phenomenon that occurs when colors change when viewed in different light sources. This means that if a shade is a perfect match, it should match in multiple wavelength spectra (ie, in different lighting environments). Making sure that the shade tab matches the tooth in all 3 light sources has the following purposes:

  • It helps prevent metameric mismatch, which is a phenomenon by which 2 objects may appear different under different light sources. The Rite-Lite 2 can be used also after bonding the crown in place to verify the shade under the different color temperatures.
  • It helps select the correct value. The low-intensity light is preferable to select the value as the high intensity may be too bright and wash out the value. A crown that looked good in the sunlight or in your office under a 5,500°K may end up looking different in the patient’s bathroom mirror at 3,200°K, resulting in a costly remake.

CLINICAL CASE EXAMPLE
A complex clinical case for which a single restoration needs to be replaced on tooth No. 9 (left maxillary central incisor) will now be briefly described.

The treatment plan included the preparation and placement of an aesthetic layered pressed porcelain full crown. It is worth mentioning that tooth No. 9 had a dark root with a gray hue permeating throughout the gingival area as well as gingival irritation and 5.0 to 6.0 mm periodontal pockets.

The shade that matched the tooth in all 3 settings was identified to be the 1M1 shade tab from the value-based shade guide VITA 3D-Master (VITA North America). In today’s dentistry, where the majority of shades selected are on the bright side of the color spectrum, selecting the correct value is critical. The ideal distance to select a shade using the Rite-Lite 2 HI CRI Shade Matching Light is 6 to 8 inches from the patient (Figures 2 and 3).

My golf analogy to matching a single central is that it is a par 3 hole. It takes 2 to 3 tries to get a good match. The result, when using this shade selection technology, is as close to a hole in one as one can get (Figure 4).

IN SUMMARY
As explained in this article, there are many factors to consider when matching the shade of a restoration to an adjacent tooth, especially in the aesthetic zone. The shade selection process entails more than simply picking the shade tab that looks the closest in color. It is important to look at shades under multiple lighting conditions with a high CRI light source to get the best match in several common lighting environments.

Acknowledgment
Dr. Berland would like to thank Sami Yared, CDT (president/owner of YDL Dental Laboratory, Carrollton, Tex) for the excellent aesthetic work exemplified in this case example.


References

  1. Chu SJ, Trushkowsky RD, Paravina RD. Dental color matching instruments and systems. Review of clinical and research aspects. J Dent. 2010;38(suppl 2):e2-e16.
  2. Chu SJ, Devigus A, Mieleszko A. Fundamentals of Color: Shade Matching and Communication in Esthetic Dentistry. Chicago, IL: Quintessence Publishing; 2004.
  3. Paravina RD, Powers JM. Esthetic Color Training in Dentistry. St. Louis, MO: Elsevier Mosby; 2004.
  4. Afrashtehfar KI. Increased predictability in tooth shade-matching. Oral Health. 2013;103:44-52.
  5. Jaju RA, Nagai S, Karimbux N, et al. Evaluating tooth color matching ability of dental students. J Dent Educ. 2010;74:1002-1010.
  6. Pitel ML. Optimizing your shade-matching success: tips, tools, and clinical techniques. Dent Today. 2015;34:116-121.
  7. Jun SK. Shade matching and communication in conjunction with segmental porcelain buildup. Pract Periodontics Aesthet Dent. 1999;11:457-464.
  8. Feng X, Xu W, Han Q, et al. LED light with enhanced color saturation and improved white light perception. Opt Express. 2016;24:573-585.
  9. Moser JB, Wozniak WT, Naleway CA, et al. Color vision in dentistry: a survey. J Am Dent Assoc. 1985;110:509-510.
  10. Martínez-Verdú F, Perales E, Chorro E, et al. Computation and visualization of the MacAdam limits for any lightness, hue angle, and light source. J Opt Soc Am A Opt Image Sci Vis. 2007;24:1501-1515.

Dr. Berland is an internationally acclaimed cosmetic dentist and one of the most published authorities in the dental and general media. He is a Fellow of the American Academy of Cosmetic Dentistry (AACD); the co-creator of the Lorin Library Smile Style Guide as well as SEZI, Cosmetic Imaging Made Easy; the developer of denturewearers.com; and the founder of Dallas Dental Arts, a multidoctor specialty practice that pioneered the concept of spa dentistry. His unique approach to dentistry has been featured on 20/20, Dallas Morning News, Good Morning Texas, and in publications such as Time, Town & Country, Reader’s Digest, GQ, US News & World Report, Woman’s World, Details, D magazine, and more. In 2008, the AACD honored him with the “Outstanding Contributions to the Art and Science of Cosmetic Dentistry” Award. He can be reached via email at This email address is being protected from spambots. You need JavaScript enabled to view it..

Disclosure: Dr. Berland reports no disclosures.

Mr. Yared is president/owner of YDL Dental Laboratory in Carrollton, Tex. After earning an associate’s degree in applied science, he qualified as a certified dental technician and learned about function and occlusion from Dr. Niles Guichet at the University of Southern California. He also attended the Pankey Institute. He has worked with experts such as Masahiro Kuwata, Willie Geller, and Claude Sieber, and he has completed a master’s course in porcelain at VITA’s porcelain plant in Germany. He is a charter member of the Dallas Study Club (a division of the Seattle Study Club), the Dallas Implant Study Club, and many others. The YDL employs a philosophy that combines old world craftsmanship, value, reliability, service, and guarantees with new world technology and science. Mr. Yared’s pride in his products and the employees that produce them is reflected in the ongoing continuing education he provides for both his clients and staff. He can be reached at (888) 567-4935 or via email at This email address is being protected from spambots. You need JavaScript enabled to view it..

Disclosure: Mr. Yared reports no disclosures.

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