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Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
CLINICAL CASE 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery • Obstacle: Subsinusal defects in height
MEDICAL AND CLINICAL PRESENTATION A 49-year-old woman presented in good health (ASA I) with a missing maxillary left first molar tooth. The tooth was extracted years before as a result of a coronal-radicular fracture.
PREOPERATIVE CONSIDERATIONS Following our diagnostic protocol and to facilitate proper implant planning, a CT scan was performed and the Digital Imaging and Communications in Medicine (DICOM) data were imported into interactive treatment planning software (SimPlant Dentsply Implants, Hasselt, Belgium). The longstanding missing tooth had resulted in a loss of bone volume and a significant vertical defect of the subsinus bone (Jensen class D, Misch S-A IV). Therefore the height of residual bone inferior to the maxillary sinus was between 1 and 3 mm, requiring a sinus augmentation procedure to create the necessary foundation for implant placement. The need for a two-step approach derives from the fact that such a minimal amount of subsinus bone would not be sufficient to guarantee the stability of the implant. The lack of vertical bone height was clearly visible in the panoramic reconstruction (Fig. CC36.1), in the oblique sagittal images (Fig. CC36.2), and in the three-dimensional views (Fig. CC36.3) as processed with the diagnostic software. The diagnostic process can be enhanced with the ability to provide objects with different properties based on density values termed by Ganz as “selective transparency” or by direct manipulation of the three-dimensional calculated volumes (see Chapters 2 and 3). The use of transparency can be seen in Fig. CC36.4 and viewed in the oblique sagittal slice (Fig. CC36.5) and on the axial plane (Fig. CC36.6). To accommodate the proposed sinus augmentation procedure, an anatomical representation of the maxilla was fabricated through the process of stereolithography (STL) (SimPlant Dentsply Implants, Hasselt, Belgium). The life-sized model accurately reproduced the patient’s anatomy in transparent resin material. Surgical access to the sinus was done with a lateral approach. On the resin model an outline was drawn on the lateral wall in a position free of recesses or other topographic irregularities that might result in rupture or tearing of the sinus membrane during its detachment from the bone (Figs. CC36.7, CC36.8). Proper planning of the surgical intervention is based on a sound understanding of the patient’s individual presentation. Therefore the sinus morphology must be evaluated from all available images, including the inner aspect
(Fig. CC36.9) and outer aspect (Fig. CC36.10). Once the correct outline for the lateral fenestration was defined and drawn on the resin model, it was sent to the dental laboratory to fabricate an appropriate-sized acrylic transfer guide to allow for accurate transfer of the information from the model to the surgical site (Fig. CC36.11).
SURGICAL PROCEDURE The surgery was performed under local anesthesia. A fullthickness mucobuccal flap was elevated to expose the lateral wall of the maxillary sinus. The transfer guide was then positioned and stabilized on the bone to provide guidance for the planned lateral entry into the sinus (Fig. CC36.12). Surgical intervention was accomplished with peizosurgical instrumentation that followed the inner perimeter of the guide, using a diamond ball bur mounted on a straight handpiece. With the diamond bur, we carefully removed bone circumferentially as traced within the shape of the transfer guide as planned on the resin model. After osteotomy the bone window was mobilized and rotated within the sinus contextually to the detachment of the Schneiderian membrane, taking care to keep the instruments on bone to avoid tears (Fig. CC36.13). The membrane was carefully elevated to the medial wall of the sinus. The sinus cavity was then filled with lyophilized human bone (BTM, Orthopedic Institut, Rizzoli, Bologna, Italy) (Fig. CC36.14).
POSTOPERATIVE CONSIDERATIONS AND IMPLANT PLANNING After an appropriate healing phase of 6 months, a postoperative CT scan was performed to help evaluate the integrity of the sinus graft for the purpose of implant planning (Figs. CC36.15 to CC36.17). Using interactive treatment planning software, potential implant receptor sites were evaluated within the new bone. Once the implant planning was completed, a tooth-borne and tooth-supported stereolithographic (STL) surgical guide (SurgiGuide) was fabricated to transfer the plan to the surgical operatory to ensure accurate placement.
SURGICAL PROCEDURE Tooth-supported surgical guides can be used with either a flapless technique or the preferred method, which requires soft tissue elevation to expose the underlying bone. To confirm and assess the healing outcome after the sinus augmentation, we elected to elevate a mucoperiosteal flap (Fig. CC36.18). When positioning the surgical guide the resin flange may entrap the soft tissue flap, and therefore the flap design must be extended to achieve proper seating (Fig. CC36.19). The osteotomies were prepared according the manufacturer’s specified drilling protocol using the dedicated surgical kit (ExpertEase, Dentsply Implants GmbH, Mannheim, Germany) (Fig. CC36.20). Depth control and precision of 459
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PART II Clinical Cases
each osteotomy is achieved by the “sleeve-on-drill” matching hardware. Implants were then delivered through the template to achieve full template guidance (XiVe, Dentsply Implant GmbH, Mannheim, Germany) (Figs. CC36.21 to CC36.24).
POSTOPERATIVE CONSIDERATIONS The postoperative evaluation of this case can be useful to illustrate the importance of three-dimensional imaging to visualize patient anatomy. A CT scan of the facial bones, performed for ear, nose, and throat (ENT) reasons, clearly shows the excellent result of the bone graft within the sinus (as visible in Fig. CC36.15). It also reveals the presence of an empty space without bone on the side of the nasal wall, demonstrated in Fig. CC36.25, which was undetectable on orthopantomography (OPG) or other two-dimensional radiographic survey techniques. The presence of the specific area without bone had been detected on CT scans performed after sinus graft, confirming that the implant had been positioned according to the plan. It is therefore important to note that if the implant
planning had been carried out through a two-dimensional OPG, the implant would have been placed entirely in area without bone, revealing what might appear to be an excellent radiographic result; however, the implant would not have had sufficient bone support to survive in function. The threedimensional forensic postoperative evaluation of individual patient anatomy has helped provide an explanation of many cases of implant failure.
PROSTHESIS After 4 months the implants were surgically uncovered and the healing collars secured to the implants (Fig. CC36.26). Several weeks later and after the healing of the soft tissues (Fig. CC36.27), fixture-level impressions transferred the location of the implants to a master cast to aid in the fabrication of the definitive prosthesis. The computer-aided design and computer-aided manufacture (CAD-CAM) metal-ceramic screw-retained restoration can be seen in Figs. CC36.28, CC36.29.
Figure CC36.1 Panorex CT image showing the subantral bone defect.
Figure CC36.2 The subsinus bone defect seen in a sagittal oblique CT image. Figure CC36.3 Three-dimensional CT view.
Clinical Case 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
Figure CC36.4 Three-dimensional CT transparent view showing the anatomy of the sinus floor.
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Figure CC36.5 Three-dimensional CT view sectioned on the oblique sagittal plane.
Figure CC36.6 Three-dimensional CT view sectioned on the axial plane.
Figure CC36.7 Procedures for sinus augmentation. Three-dimensional STL model of the maxillary bone. On the left side, it shows the outline of the fenestration of access to the sinus.
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Figure CC36.8 Procedures for sinus augmentation as in Fig. CC36.7, but with the guide for the sinus lift.
Figure CC36.9 Procedures for sinus augmentation. View from the inside of the sinus and the fenestration’s outline.
Figure CC36.10 Procedures for sinus augmentation. Buccal view of the sinus.
Figure CC36.11 Procedures for sinus augmentation. The guide for the sinus lift on the stereolithographic model (SimPlant Dentsply Implants, Hasselt, Belgium).
Figure CC36.12 Procedures for sinus augmentation. The guide placed on the bone, allows replication on the bone of the planning carried out on the model.
Clinical Case 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
Figure CC36.13 Opening of the sinus fenestration.
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Figure CC36.14 Sinus bone graft.
Figure CC36.15 Computer implant planning. The outline of the implant corresponds exactly to the one of the chosen implant, in 1:1 ratio. It shows the sinus graft volume (see Fig. CC36.25) and the outline of a computer-simulated tooth.
Figure CC36.16 CT view of the implant planning in oblique sagittal section. Note the thin area without bone next to the nasal wall. Figure CC36.17 CT view of the implant planning in axial section.
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Figure CC36.18 Elevation of the mucoperiosteal flap and check of the bone healing.
Figure CC36.20 Preparation of the implant site through the surgical guide with the sleeve-on-drill system (ExpertEase, Dentsply Implants GmbH, Mannheim, Germany).
Figure CC36.19 Tooth-supported SurgiGuides (SimPlant Dentsply Implants, Hasselt, Belgium). When using this type of guide with an open flap, the gingival tissues should be checked to ensure they do not hinder correct placement of the guide. The gingival flap rests above the guide. The first drill for preparation of the implant site is used.
Figure CC36.21 Implant placement (XiVe, Dentsply Implants GmbH, Mannheim, Germany) through the guide.
Figure CC36.23 The implant after the removal of the guide.
Figure CC36.22 Implant inserted through the surgical guide (Surgi Guide, SimPlant Dentsply Implants, Hasselt, Belgium).
Clinical Case 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
Figure CC36.24 Position of the implant inserted with computerguided surgery. The implant is correctly positioned at the level of the bone crest.
a
b
c
Figure CC36.25 CT scan of the facial bones after implantation. The arrows indicate the sinus graft. It is possible to see the presence of an area without bone in the nasal side of the sinus, visible only in a and b. Explanation in the text.
Figure CC36.27 Soft tissue healing. Figure CC36.26 Implant uncovering to connect the healing abutments.
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Figure CC36.29 Metal-ceramic crown. Figure CC36.28 Final prosthetic rehabilitation. The occlusal hole is for the fixation screw.
MEDICAL AND CLINICAL PRESENTATION A 49-year-old woman presented in good health (ASA I) with a missing maxillary left first molar tooth. The tooth was extracted years before as a result of a coronal-radicular fracture.
PREOPERATIVE CONSIDERATIONS Following our diagnostic protocol and to facilitate proper implant planning, a CT scan was performed and the Digital Imaging and Communications in Medicine (DICOM) data were imported into interactive treatment planning software (SimPlant Dentsply Implants, Hasselt, Belgium). The longstanding missing tooth had resulted in a loss of bone volume and a significant vertical defect of the subsinus bone (Jensen class D, Misch S-A IV). Therefore the height of residual bone inferior to the maxillary sinus was between 1 and 3 mm, requiring a sinus augmentation procedure to create the necessary foundation for implant placement. The need for a two-step approach derives from the fact that such a minimal amount of subsinus bone would not be sufficient to guarantee the stability of the implant. The lack of vertical bone height was clearly visible in the panoramic reconstruction (Fig. CC36.1), in the oblique sagittal images (Fig. CC36.2), and in the three-dimensional views (Fig. CC36.3) as processed with the diagnostic software. The diagnostic process can be enhanced with the ability to provide objects with different properties based on density values termed by Ganz as “selective transparency” or by direct manipulation of the three-dimensional calculated volumes (see Chapters 2 and 3). The use of transparency can be seen in Fig. CC36.4 and viewed in the oblique sagittal slice (Fig. CC36.5) and on the axial plane (Fig. CC36.6). To accommodate the proposed sinus augmentation procedure, an anatomical representation of the maxilla was fabricated through the process of stereolithography (STL) (SimPlant Dentsply Implants, Hasselt, Belgium). The life-sized model accurately reproduced the patient’s anatomy in transparent resin material. Surgical access to the sinus was done with a lateral approach. On the resin model an outline was drawn on the lateral wall in a position free of recesses or other topographic irregularities that might result in rupture or tearing of the sinus membrane during its detachment from the bone (Figs. CC36.7, CC36.8). Proper planning of the surgical intervention is based on a sound understanding of the patient’s individual presentation. Therefore the sinus morphology must be evaluated from all available images, including the inner aspect
(Fig. CC36.9) and outer aspect (Fig. CC36.10). Once the correct outline for the lateral fenestration was defined and drawn on the resin model, it was sent to the dental laboratory to fabricate an appropriate-sized acrylic transfer guide to allow for accurate transfer of the information from the model to the surgical site (Fig. CC36.11).
SURGICAL PROCEDURE The surgery was performed under local anesthesia. A fullthickness mucobuccal flap was elevated to expose the lateral wall of the maxillary sinus. The transfer guide was then positioned and stabilized on the bone to provide guidance for the planned lateral entry into the sinus (Fig. CC36.12). Surgical intervention was accomplished with peizosurgical instrumentation that followed the inner perimeter of the guide, using a diamond ball bur mounted on a straight handpiece. With the diamond bur, we carefully removed bone circumferentially as traced within the shape of the transfer guide as planned on the resin model. After osteotomy the bone window was mobilized and rotated within the sinus contextually to the detachment of the Schneiderian membrane, taking care to keep the instruments on bone to avoid tears (Fig. CC36.13). The membrane was carefully elevated to the medial wall of the sinus. The sinus cavity was then filled with lyophilized human bone (BTM, Orthopedic Institut, Rizzoli, Bologna, Italy) (Fig. CC36.14).
POSTOPERATIVE CONSIDERATIONS AND IMPLANT PLANNING After an appropriate healing phase of 6 months, a postoperative CT scan was performed to help evaluate the integrity of the sinus graft for the purpose of implant planning (Figs. CC36.15 to CC36.17). Using interactive treatment planning software, potential implant receptor sites were evaluated within the new bone. Once the implant planning was completed, a tooth-borne and tooth-supported stereolithographic (STL) surgical guide (SurgiGuide) was fabricated to transfer the plan to the surgical operatory to ensure accurate placement.
SURGICAL PROCEDURE Tooth-supported surgical guides can be used with either a flapless technique or the preferred method, which requires soft tissue elevation to expose the underlying bone. To confirm and assess the healing outcome after the sinus augmentation, we elected to elevate a mucoperiosteal flap (Fig. CC36.18). When positioning the surgical guide the resin flange may entrap the soft tissue flap, and therefore the flap design must be extended to achieve proper seating (Fig. CC36.19). The osteotomies were prepared according the manufacturer’s specified drilling protocol using the dedicated surgical kit (ExpertEase, Dentsply Implants GmbH, Mannheim, Germany) (Fig. CC36.20). Depth control and precision of 459
460
PART II Clinical Cases
each osteotomy is achieved by the “sleeve-on-drill” matching hardware. Implants were then delivered through the template to achieve full template guidance (XiVe, Dentsply Implant GmbH, Mannheim, Germany) (Figs. CC36.21 to CC36.24).
POSTOPERATIVE CONSIDERATIONS The postoperative evaluation of this case can be useful to illustrate the importance of three-dimensional imaging to visualize patient anatomy. A CT scan of the facial bones, performed for ear, nose, and throat (ENT) reasons, clearly shows the excellent result of the bone graft within the sinus (as visible in Fig. CC36.15). It also reveals the presence of an empty space without bone on the side of the nasal wall, demonstrated in Fig. CC36.25, which was undetectable on orthopantomography (OPG) or other two-dimensional radiographic survey techniques. The presence of the specific area without bone had been detected on CT scans performed after sinus graft, confirming that the implant had been positioned according to the plan. It is therefore important to note that if the implant
planning had been carried out through a two-dimensional OPG, the implant would have been placed entirely in area without bone, revealing what might appear to be an excellent radiographic result; however, the implant would not have had sufficient bone support to survive in function. The threedimensional forensic postoperative evaluation of individual patient anatomy has helped provide an explanation of many cases of implant failure.
PROSTHESIS After 4 months the implants were surgically uncovered and the healing collars secured to the implants (Fig. CC36.26). Several weeks later and after the healing of the soft tissues (Fig. CC36.27), fixture-level impressions transferred the location of the implants to a master cast to aid in the fabrication of the definitive prosthesis. The computer-aided design and computer-aided manufacture (CAD-CAM) metal-ceramic screw-retained restoration can be seen in Figs. CC36.28, CC36.29.
Figure CC36.1 Panorex CT image showing the subantral bone defect.
Figure CC36.2 The subsinus bone defect seen in a sagittal oblique CT image. Figure CC36.3 Three-dimensional CT view.
Clinical Case 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
Figure CC36.4 Three-dimensional CT transparent view showing the anatomy of the sinus floor.
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Figure CC36.5 Three-dimensional CT view sectioned on the oblique sagittal plane.
Figure CC36.6 Three-dimensional CT view sectioned on the axial plane.
Figure CC36.7 Procedures for sinus augmentation. Three-dimensional STL model of the maxillary bone. On the left side, it shows the outline of the fenestration of access to the sinus.
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PART II Clinical Cases
Figure CC36.8 Procedures for sinus augmentation as in Fig. CC36.7, but with the guide for the sinus lift.
Figure CC36.9 Procedures for sinus augmentation. View from the inside of the sinus and the fenestration’s outline.
Figure CC36.10 Procedures for sinus augmentation. Buccal view of the sinus.
Figure CC36.11 Procedures for sinus augmentation. The guide for the sinus lift on the stereolithographic model (SimPlant Dentsply Implants, Hasselt, Belgium).
Figure CC36.12 Procedures for sinus augmentation. The guide placed on the bone, allows replication on the bone of the planning carried out on the model.
Clinical Case 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
Figure CC36.13 Opening of the sinus fenestration.
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Figure CC36.14 Sinus bone graft.
Figure CC36.15 Computer implant planning. The outline of the implant corresponds exactly to the one of the chosen implant, in 1:1 ratio. It shows the sinus graft volume (see Fig. CC36.25) and the outline of a computer-simulated tooth.
Figure CC36.16 CT view of the implant planning in oblique sagittal section. Note the thin area without bone next to the nasal wall. Figure CC36.17 CT view of the implant planning in axial section.
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Figure CC36.18 Elevation of the mucoperiosteal flap and check of the bone healing.
Figure CC36.20 Preparation of the implant site through the surgical guide with the sleeve-on-drill system (ExpertEase, Dentsply Implants GmbH, Mannheim, Germany).
Figure CC36.19 Tooth-supported SurgiGuides (SimPlant Dentsply Implants, Hasselt, Belgium). When using this type of guide with an open flap, the gingival tissues should be checked to ensure they do not hinder correct placement of the guide. The gingival flap rests above the guide. The first drill for preparation of the implant site is used.
Figure CC36.21 Implant placement (XiVe, Dentsply Implants GmbH, Mannheim, Germany) through the guide.
Figure CC36.23 The implant after the removal of the guide.
Figure CC36.22 Implant inserted through the surgical guide (Surgi Guide, SimPlant Dentsply Implants, Hasselt, Belgium).
Clinical Case 36 Sinus Elevation, Stereolithographic Model, Computer Implant Surgery
Figure CC36.24 Position of the implant inserted with computerguided surgery. The implant is correctly positioned at the level of the bone crest.
a
b
c
Figure CC36.25 CT scan of the facial bones after implantation. The arrows indicate the sinus graft. It is possible to see the presence of an area without bone in the nasal side of the sinus, visible only in a and b. Explanation in the text.
Figure CC36.27 Soft tissue healing. Figure CC36.26 Implant uncovering to connect the healing abutments.
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Figure CC36.29 Metal-ceramic crown. Figure CC36.28 Final prosthetic rehabilitation. The occlusal hole is for the fixation screw.