COMPUTER-GUIDED IMMEDIATE PROVISIONALIZATION OF ANTERIOR MULTIPLE ADJACENT IMPLANTS:
SURGICAL AND PROSTHODONTIC RATIONALE
Joseph Y.K. Kan, DDS, MS* • Kitichai Rungcharassaeng, DDS, MS* • Kotaro Oyama, DDS†
Seung-Hwan Chung, DDS† • Jaime L. Lozada, DDS‡
Immediate implant restoration has gained popularity in recent years due in part to technological advancements that use the computed tomographic images to simulate the actual clinical situation. This computer-assisted simulation enables clinicians to develop a comprehensive treatment plan that can be precisely executed in a timely manner. In the aesthetic zone, however, a successful outcome requires more than merely accurate implant placement. This article discusses the significance of site development for aesthetic implant restoration and describes a computer-guided immediate
provisionalization procedure and its surgical and prosthodontic rationale.
Learning Objectives:
This article discusses the parameters that must be considered for the successful placement of implants in the anterior maxilla. Upon reading this article, the reader should:
• Become familiar with the advantages offered by immediate provisionalization of implants.
• Understand how technology can be utilized to simulate the clinical environment and permit more accurate and timely implant placement.
Key Words: Computer-guided implant surgery, immediate provisionalization, stereolithographic, site development, socket preservation, CTG, ovate
* Associate Professor, Department of Restorative Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA.
†Advanced Education in Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA.
‡Professor and Director, Advanced Education in Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA.
Joseph YK Kan, DDS, MS, Center for Prosthodontics and Implant Dentistry, Loma Linda University School of Dentistry, Loma Linda, CA 92354
Tel: 909-558-4980 • E-mail: jkan@llu.edu
Practical Procedures & AESTHETIC DENTISTRY
The initial osseointegrated implant treatments were limited by the osseointegration period itself,1,2 which prolonged the treatment time and were impractical for some patients. Immediately loading implants has proven to be a successful option in implant-treatment modalities.3-5 This procedure, however, is techniquesensitive and clinically time consuming.
Computed tomography (CT) has long been part of the implant diagnosis and treatment planning.6 The threedimensional data provides essential information for precise implant placement without invading the vital anatomical structures.6 With the advancement of computer technology, the simulated ideal implant placement on the CT images can now be transferred to the clinical situation via a stereolithographic template.7-10 Furthermore,
since the template controls the precise implant position in three-dimensions, including angulation and depth, an implant prosthesis can be prefabricated accordingly.7,8
For implant restoration in the aesthetic zone, successful outcome requires not only accurate implant placement, but also peri-implant gingiva that harmonizes with the adjacent dentition.11,12 This article emphasizes the essentials of site development for aesthetic implant restoration as well as systematically describes the computer-guided immediate provisionalization procedure and its surgical and prosthodontic rationale.
Case Presentation
A 45-year-old male presented with discomfort and exudates upon palpation of the maxillary central incisors (Figure 1). A periapical radiograph displayed severe localized periodontal bone loss around teeth #8(11) and #9(21), but no periapical radiolucency. Clinically, the teeth were labially and distally displaced with Class III mobility. Additionally, the facial gingival margins were positioned more apical (ie, approximately 2 mm) than ideal. Bone sounding on teeth #8 and #9 revealed normal crest (ie, ~3 mm) osseous-gingival tissue relationship facially, and low crest (ie, greater than 4.5 mm) interproximally of the immediate adjacent teeth. The patient was advised that both teeth should be extracted, and that restorative options included a removable partial denture, a fixed partial denture, or a fixed implant restoration. Since the adjacent teeth had not been previously restored, the patient expressed a preference for an implant-supported restoration to avoid their involvement.
A treatment plan using delayed implant placement executed to separate the tooth from the periodontal tissue. The extraction was atraumatic, with controlled expansion of the bony socket to avoid soft and/or hard tissue damage.
An intrasulcular incision was made around the tooth socket, creating an initial separation between the gingiva and the underlying bone. The separation was further extended gingivally to the mucogingival junction and mesially to form a tunnel between the sockets using a curette (ie, Younger-Good 7/8 curette, Hu-Friedy, Chicago, IL) (Figure 2). A partial-thickness dissection was then made apically and mesiodistally. This released the residual flap tension and facilitated passive coronal displacement of the flap. Once both tooth sockets were filled with a xenograft, the SCTG was harvested from the palate
and was drawn into the prepared envelope with the aid of sutures (Figure 3). Light finger pressure was applied over the grafted site with moist gauze to minimize blood clot formation between the graft and its underlying tissues. 13,14 A thermoforming appliance with adjusted denture teeth was placed as a provisional restoration. After 4 months of healing, the preserved socket was ready for ovate pontic site preparation (Figure 4).
The removable ovate pontic partial denture was first fabricated in the laboratory prior to implant surgery. An ovate concavity, 2 mm to 3 mm in depth, was created at the site of teeth #8 and #9 on the working cast. A surgical guide, which outlined the predetermined prosthetic emergence, was fabricated for the surgery.
Customized denture teeth were placed on the cast at the appropriate position. The cast was then lubricated, and light-polymerized acrylic was flowed into the ovate cavity, fusing with the prefabricated denture teeth. The ovate pontic was then polished and secured into the ovate concavity.
Retentive wrought wire clasps with proper vertical stops were placed bilaterally. The pattern was then invested and processed with heat-polymerizing acrylic with socket preservation and subepithelial connective tissue graft (SCTG) was selected and would entail: a) the extraction of the failing teeth along with socket preservation and SCTG; b) site development with an ovate pontic partial denture; and c) computer-guided implant placement and immediate provisionalization.
Extraction and Socket Preservation
Teeth #8 and #9 were extracted without flap reflection, and a sulcular incision with transeptal fiberectomy was resin. The finished ovate pontic partial denture was then disinfected before ovate pontic surgery (Figure 5).
In the surgery, a 3-mm–deep ovate concavity was created through the removal of gingival and osseous tissue at the site of teeth #8 and #9 with a footballshaped diamond bur (ie, #6379, Brasseler USA, Savannah, GA). The ovate concavity was prepared deeper on the facial aspect and shallower on the lingual aspect, as prepared on the working cast. The removable ovate pontic partial denture was then adjusted and inserted onto the surgical site, providing immediate support while forming the appropriate gingival architecture for teeth #8 and #9 (Figure 6).
Appropriate antibiotic, analgesic, and 0.12% chlorhexidine gluconate (ie, Peridex, Procter & Gamble, Cincinnati, OH) were prescribed for postoperative use. The denture would be removed only for hygiene at least twice a day and reinserted within 5 minutes to prevent gingival tissue collapse. The patient was advised against functioning or any activities to the surgical site, and a soft diet was recommended for the duration of tissue maturation (Figure 7).
The removable ovate pontic partial denture was duplicated with orthodontic resin (without clasps) and was subsequently verified intraorally to ensure complete seating of the template. The implant selection and template preparation were accomplished according to the following guidelines.
Buccolingual: The buccolingual width of the tooth was at least 3 mm greater than the outer diameter of the 6-mm guide sleeves. This width would allow for the 1.5 mm of resin needed around the sleeve for adequate template strength. The lingual boundary was marked with a permanent marker and subsequently scribed with a round bur to a minimum depth of 1 mm (Figure 8).
Mesiodistal: Similar to the buccolingual consideration, the dimension of the guide sleeves was determined by the mesiodistal width. Additionally, a groove was made on the facial aspect of the denture tooth using a perforated diamond disc, signifying the mesiodistal alignment, interimplant distance (ie, at least 4 mm), and position of the implant (Figure 9).
Occlusogingival: Given that the implant platform is recommended to be approximately 3 mm from the predetermined free gingival margin,5,11 the occlusogingival distance of the clinical crown must be at least 6.5 mm to accommodate the implant guided drills.
Predetermined Gingival Level: The gingival margin of the ovate pontic was outlined and marked with a round bur. Orthodontic acrylic resin was then added occlusofacially for the remaining dentition, extending to the facial vestibule for future placement of Guided Anchor Pin Sleeves (ie, NobelGuide, Nobel Biocare, Yorba Linda, CA) (Figure 9). Twelve holes, 1.5 mm in diameter and 1 mm in depth, were made on various areas of the radiographic guide and filled with gutta-percha for use as reference points for the superimposition of CBCT images during surgical template fabrication. Radiographic data were acquired via cone beam CT technology using a double-scan technique.7,8 The patient wore a radiographic guide with radiographic markers for the first scan and only the radiographic guide for the second scan. The scanned data were superimposed upon each other and stored in uncompressed digital imaging and communications in medicine (DICOM) format. A three-dimensional implant-planning software program was used to treatment plan the implant position and dimension utilizing the reformatted data (Figures 10 and 11).
Preparation of the Stereolithographic Cast and Provisional Prosthesis
The data were sent to the milling center for fabrication of the stereolithographic cast of the implant surgical guide with the preplanned osteotomy sites of the dental implants (Figure 12). The stereolithographic cast was subsequently tried intraorally to ensure proper seating. Implant replicas and guided anchor pins were placed at the predetermined implant site for the fabrication of the working cast. The working cast was then mounted with an opposing cast for the fabrication of the screw-retained provisional prosthesis. After the partial denture was removed, the surgical guide was inserted to ensure complete seating in the correct position (Figure 13). Osteotomies were made through the guided anchor pin sleeves on the template using a 1.5-mm 20-mm guided twist drill. Guided anchor pins were then inserted to secure the template during the surgical procedure. The implant (ie, NobelReplace Taper Groovy, Nobel Biocare, Yorba Linda, CA) was then placed according to the surgical template (Figure 14). A guided template abutment was then hand tightened to the implant for additional stability to the surgical template as well as for preventing gingival collapse during the preparation of the osteotomy on tooth #9 (Figure 15). After placement and complete seating of the second implant, the prefabricated provisional prosthesis for the
teeth was hand tightened. A periapical radiograph verified the fit of the provisional prosthesis, and the prosthetic screws were torqued to 35 Ncm (Figure 16). Once the optimal peri-implant gingival architecture had been achieved (Figure 17), the final implant impression was taken using vinyl polysiloxane. Implant abutments were waxed as substructures for the metal-ceramic restorations and cast in Type IV gold. The individual screw-retained definitive metal-ceramic restorations (ie, Creation, Jensen, North Haven, CT) were torqued to 35 Ncm; a periapical radiograph verified the fit of the prostheses
and the patient was dismissed with the appropriate postoperative instructions (Figures 18 through 20).
Discussion
Orthodontic intervention has been used to enhance the soft tissue architecture of failing teeth for implant site development, 5,15,16 and socket seal surgery has been advocated as a means to preserve the existing tissue prior to implant placement.17 In the situation presented, however, tissue topography was not ideal and mere tissue preservation would not be adequate for aesthetic implant restoration. The facial tissue envelope did allow soft tissue enhancement and provided a large vascular bed to ensure the viability of the graft. The interproximal papilla height was augmented by insertion of the SCTG beneath the created interdental tunnel—possible only due to the presence of interproximal crestal bone. The key to implant aesthetics is the predictability of achieving an ideal peri-implant gingival architecture, which is dictated by the underlying osseous support.11,18 Therefore, it is essential that the location of the final periimplant gingival margin be pre-determined and the osseous-gingival relationship assessed. When the distance
between the osseous and gingival structures is ideal (ie, 3 mm to 4 mm), implant placement to the appropriate depth (ie, ~3 mm implant platform to the predetermined gingival margin) is recommended.11,16,19 Computer-guided implant surgical systems were conceived primarily as a means to facilitate detailed direct visualization of osseous architecture,7-9,20 but not its relationship with the gingival architecture. In the situation presented,
the predetermined facial gingival margin was first developed with an ovate pontic removable partial denture 3 months following socket preservation. The
removable ovate pontic partial denture was then duplicated as a radiographic guide for the CBCT scanning following the complete healing of the gingival architecture (ie, ~3 months). The incorporation of the predetermined facial gingival margin to the radiographic guide enabled the clinician to use the computer-guided system to assess the osseous-gingival relationship and plan for the implant placement to the optimal depth for predictable
facial implant gingival aesthetics. This, in the authors’ opinion, along with the mesiodistal and occlusal-gingival guidelines for the fabrication of the radiographic template, is the quintessence of this article.
Conclusion
The advancement of technology has presented clinicians with more effective, efficient, and simplified means to solve implant treatment modalities. Though designed to facilitate implant treatment, a computer-guided system is limited by the input which it receives. To achieve predictable
aesthetic results, site development and an ideal osseous-gingival relationship remain the fundamental components for implant treatment in the aesthetic zone. The ability of the clinician to accurately transfer this clinical information to the computer-guided system validates its use in these situations and may be the stepping stone for future development.
Acknowledgment
The authors send their gratitude to Hirotaka Tsuda and Eric Hall for their contributions to the case presented herein. The authors declare that they have received partial financial support from Nobel Biocare, Inc. for the case presented herein, but have no financial interest in the products depicted.
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