Journal of Dental Implantology - http://www.implantoloji.info
Computer Analysis of Titanium Implants in Atrophic Arch and Poor Quality Bone: A Case Report
http://www.implantoloji.info/articles/21/1/Computer-Analysis-of-Titanium-Implants-in-Atrophic-Arch-and-Poor-Quality-Bone-A-Case-Report/Page1.html
By JDI editor
Published on 04/1/2009
 
Rainer Bocklage, DMD, DUI
Private Practice, Dormagen, Germany.

The oral implantologist usually uses a panoramic radiograph for the evaluation of bone tissue around implants. The development of computed tomography combined with computer software has allowed for the bone-to-implant interface to be illustrated in greater detail with cross-sectional and pseudo-color images. An implant patient has titanium fixtures in an atrophic arch and poor quality bone four years after implantation. The implants were loaded with fixed metal/resin restorations seven days after surgery. Integration of the implants and the anatomic structures near the implant sites are described with an imaging technique.

Materials and methods - Case Report.
Rainer Bocklage, DMD, DUI
Private Practice, Dormagen, Germany.

The most important anatomic variables for implant placement are the maxillary sinus and the nasal fossa in the upper jaw and the mandibular nerve in the lower jaw. Inferior residual alveolar ridge height, insufficient bone volume, and poor bone density are the main reasons for inadequate insertion height of root-form implants. Initial stability cannot be achieved, making immediate implant loading impossible. Under these difficult conditions in atrophic jaws, osseointegration of implants is often prevented after osteolysis and implant loss. To avoid bone grafting or other surgical bone augmentation procedures, the lateral insertion technique is preferable in these cases.
In the clinical case presented herein, all implants (maxilla and mandible) were placed in a single surgery session under general anesthesia and immediately loaded with fixed esthetic temporaries. Using SIM/Plant images (Columbia Scientific, Columbia, MD), the osseointegration of these titanium fixtures is visualized four years after implantation. These images impressively demonstrate the positions of implant sites relative to the maxillary sinus, the nasal fossa, and the mandibular nerve.

MATERIALS AND METHODS.
For difficult implant cases, such as the extremely resorbed jaw and type IV bone, lateral implantation surgery is a particular alternative for the achievement of initial stability and osseointegration. The procedure is minimally invasive and free of bone grafting or other augmentation techniques. Regarding a residual ridge height of _5 mm, this osteotomy is microsurgical. Lateral osteotomy disk-design implants are placed. They comprise an implant shaft with threads and one or several basic disks. The loading transmission bone-to-implant interface is shifted to the whole arch width by anchoring the disks from the outside cortical bone to the inside cortical bone (outside laminar bone to inside laminar bone in class IV bone). A considerable increase in the bone-contact area and excellent immediate stability for diskdesign implants is achieved by using the full jaw width.7 It is important to mention that the shaft of this particular implant is only the connecting component for prosthetic abutments. The supporting bone formation around the implants is changed from the vertical to the horizontal plane by inserting diskdesign implants. Vertical osseointegration is a major determinant of root-form implant success. Horizontal osseointegration is more important for laterally inserted implants. There are also significant differences in biomechanics and bone healing. Applying the lateral insertion technique, a primary bone healing can be shown in the area around the disks. Bone repair is possible without the formation of callous tissue in this particular area of the implant. Therefore, immediate functional loading for this implant form is physiologic. SIM/Plant software was used for better visualization of the bone-to-implant interface. The software is actually a preoperative planning tool for dental implant placement. A radiologist makes a dental CT scan of the arches. A template is placed in the patient’s mouth during the CT procedure. The CT data must then be reformatted into panoramic and cross-sectional images by a SIM/Plant workstation. This software makes it possible to work with pseudo-color scales—a very illustrative technique. The different colors (within each hue, the luminance varies from dark to light) represent the different CT densities of the soft tissues and the bone tissue. A reformatted CT study consists of an alignment image, an axial image, and a panoramic image of each arch with the corresponding cross-sectional images. Implant ossification and the anatomical structures near the implant sites are clearly described with this image technique.

CASE REPORT.
The edentulous maxilla and the almost edentulous mandible were treated under general anesthesia in a single surgery session (Figs. 1–4). Implant placement in the posterior areas of the jaw is essential to the realization of an adequate loading of fixed restorations onto the implants. The number of fixtures was minimized to not impede the vascularization of bone and to avoid a huge number of foreign materials in the jaw. Seven days after surgery, the implants were immediately loaded with fixed esthetic temporaries (metal/resin). Disk-design implant placement causes primary bone healing in the area around the disks; therefore, the definitive restorations could be fabricated according to the gnathologic crown and bridgework technique 40 days after the procedure. Four years after implantation, the implant bridgework is still functioning (Fig. 5).

Fig. 1. An initial panoramic radiograph that shows an extremely   resorbed edentulous maxilla and a nearly edentulous mandible with a severely   atrophic jaw in the right and left posterior areas.
Fig. 2. A panoramic radiograph after the placement of nine disk-design   implants in a single surgery session.
Fig. 3. A Scanora (Soredex, Helsinki, Finland) radiograph of the left   posterior maxilla after placement showing a multicortically anchored double   disk-design implant.
Fig. 4. A Scanora radiograph taken after placement in the area of the   tooth 47. It reveals a mono disk implant. Its bone support is tricortical.

An initial panoramic radiograph that shows an extremely   resorbed edentulous maxilla and a nearly edentulous mandible with a severely   atrophic jaw in the right and left posterior areas


Results.
RESULTS.
For better visualization of the images, it is more illustrative to use a pseudo-color scale. The different colors represent the different CT densities of the soft tissues and the bone tissue. Choosing pseudo-color imaging in the Hounsfield Scale, the different colors represent the following structures (note that within each hue, the luminance varies from dark to light) (Fig. 6):
  • White represents cortical bone, metal, and enamel.
  • Blue represents trabecular bone.
  • Green represents fat and muscle.
  • Yellow represents air
The cross-sectional images are the most informative slices for the evaluation of bone tissue and the examination of the anatomical structures near to the implant sites. Crosssectional images indicate a well corticalized mandible with resorbed alveolar ridge in the posterior areas and a poor corticalized maxilla with class IV bone. These images are evidence that all the implants are osseointegrated. SIM/Plant software allows for the visualization of the following images of the implant case presented:
  • Alignment image as an overall view of the skull and the arches with implants and supraconstruction (Fig. 7).
  • Axial images with the different axial slices of the maxilla and the mandible with implants and restorations (Figs. 8 and 9).
  • Panoramic images as a panoramic projection view of the maxilla and the mandible with implant and restorations (Figs. 10 and 11).
  • Cross-sectional images of the maxilla and the mandible with implants and supraconstruction.

Fig. 5. A radiograph of the implant-supported definitive restorations   four years after implantation.
Fig. 6. The Hounsfield Scale applying a pseudo-color scale.
Fig. 7. An alignment image as an overall view of the skull and the arches   with implants and definitive restorations.
Fig. 8. An axial image of the mandible with five titanium implants and   two natural teeth anchored in the cortical bone.

A radiograph of the implant-supported definitive restorations   four years after implantation

Mandible.
Slice in the area of 47. This is a cross-sectional view of the implant comprising the shaft and the basic disk. The shape is upside-down, and the disk is osseointegrated both outside and inside the cortical bone. Trabecular bone has formed around the center part of the disk. The mandibular nerve is just below the implant, and the residual bone height is 6 mm (Fig. 12). Cement has retained the crown of the implant bridgework on the abutment.
Slice in the area of 41. There is a double disk-design implant between the natural-tooth abutments in the interforaminal area, and the implant is osseointegrated in both cortical and trabecular bone (Fig. 13).
Slice in the area of 35. The monodisk-design implant is within 3 mm of the mental foramen, and the implant is completely osseointegrated.
Slice in the area of 37. The implant is placed in the posterior zone of the mandible, and the disk is osseointegrated both outside and inside the cortical bone. There is formation of trabecular bone around the implant. Cement has retained the implant restoration on the abutment, and the residual bone height relative to the mandibular nerve is _6 mm.

Maxilla.
Slice in the area of 17. A double disk-design implant was inserted in the floor of the right maxillary sinus after a sinus lift procedure. The Schneiderian membrane is clearly visible and lies on the basal disk. The disks are osseointegrated in the trabecular bone (Fig. 14).
Slice in the area of 15. The implant is laterally inserted with two disks ventral to the maxillary sinus. The nasal fossa and the hard palatine are also represented. The implant is osseointegrated. In this slice, the two disks (basal and crestal) are shaped like four circles (Fig. 15).
Slice in the area of 11. The laterally inserted implant is osseointegrated in trabecular bone, and the incisive canal is visualized.
Slice in the area of 25. The double disk-design implant is ventral to the left maxillary sinus. The implant is osseointegrated, and the implant shaft is visualized (Fig. 16).
Slice in the area of 27. There is an osseointegrated implant in the posterior zone of the maxilla after a sinus lift procedure. The space between the basal disk and Schneiderian membrane has been filled with hydroxyapatite.

Fig. 9. An axial image of the maxilla with five double disk-design implants.   Fig. 10. A panoramic image of the mandible that demonstrates a well-corticalized   mandible with implants, tooth roots, and supraconstruction.
Fig. 11. A panorama image of the maxilla that shows a poorly corticalized   maxilla and five double disk implants anchored in a class IV bone.
Fig. 12. A cross-sectional view of the implant that comprises the shaft   and the basal disk. It is shaped like an upside-down T. The disk is osseointegrated   in cortical and trabecular bone. Bridgework is cement-retained on the implant   abutment.
Fig. 13. A laterally inserted implant between natural-teeth abutments   with two disks. The implant is osseointegrated in cortical and trabecular bone.
Fig. 14. The double disk implant is placed in the floor of the right   maxillary sinus after a sinus lift procedure. The Schneiderian membrane lies   on the basal disk. The implant is osseointegrated in the trabecular bone.
Fig. 15. A titanium implant with two disks ventral to the maxillary sinus.   Hard palatine is visible. The implant is osseointegrated. The two disks are   shaped like four circles.
Fig. 16. A double disk implant ventral to the left maxillary sinus. The   implant is osseointegrated in the trabecular bone. The implant shaft is visualized.   .

A panoramic image of the mandible that demonstrates a well-corticalized mandiblewith implants, tooth roots, and supraconstruction


Discussion - References.
DISCUSSION.
Immediate implant loading has been controversial during the last 15 years. However, functional immediate loading has gained much greater acceptance during the past three. The implant case presented (as an example based on ten years of experience applying functional loading) demonstrates that osseointegration and immediate loading are not contradictory. Quite the opposite is the case. If there is a functional stimulus on the fixtures, physiologic healing can be seen at the implant sites.
Initial stability of implants is a sine qua non for this treatment concept. If initial stability is not achieved, it is impossible to practice immediate loading. Application of the lateral, microsurgical insertion technique in severe bone atrophy and type IV bone makes initial implant anchoring in cortical bone possible, provided that the drilling procedure, using titanium cutters mounted on a turbine, is performed precisely. Further, the placement of disk-design implants causes a primary bone healing in the area around the disks, which shortens the entire treatment procedure. After immediate functional loading with fixed esthetic temporaries almost 40 days after the procedure, the definitive restorations can be fabricated. Osseointegration of implants is a not a static state but a balance between bone formation and bone loss. To maintain this balance (to gain long-term implant success), the forces on the prosthetic superstructures and the implants have to be observed. Bone loss in the area around the implants or even implant fractures are possible if the forces are too strong. Therefore, the positioning of the implants in the arch and the morphological forms of the occlusal surfaces of supraconstructions are most important.
The following aspects must be observed for the proper fabrication of implant restorations:
  1. reduced occlusal surfaces;
  2. disclusion in group function;
  3. no prematurities during function and maximal intercuspation.

References.

Schwartz MS, Rothman SLG, Chafetz N, et al. Computed tomography:   Part I. Preoperative assessment of the mandible for endosseous implant surgery.   Int J Oral Maxillofac Implants. 1987;137-141. 2.
  Schwartz MS, Rothman SLG, Chafetz N, et al. Computed tomography: Part II.   Preoperative assessment of the maxilla for endosseous implant surgery. Int   J Oral Maxillofac Implants. 1987;2: 143-148.
  Klinge B, Peterson A, Maly P. Location of the mandibular canal: comparison   of macroscopic findings, conventional radiography and computed tomography.   Int J Oral Maxillofac Implants. 1989;4:327-332.
  Stockham CD. Using CT and SIM/ Plant to plan implant therapy. Alpha Omegan.   1996;89:35-38.
  Misch CE. Divisions of available bone in implant dentistry. Int J Oral   Implantol. 1990;7:9-17.
  Scortecci G. Diskimplant system yields tricortical support to make the most   of available bone. Dent Implantol Update. 1991;2:72-74.
  Branemark PI, Hanson BO, Adell R, et al. Osseointegrated implants in the   treatment of edentulous jaw: Experience from a 10-year period. Scand J Plast   Reconstr Surg. 1977;16:21-38.
  Adell R, Eriksson B, Lekholm U, et al. A long-term follow-up study of osseointegrated   implants in the treatment of totally edentulous jaw. Int J Oral Maxillofac   Surg. 1990;5:347-359.
  Scortecci G. Immediate function of cortically anchored disk-design implants   without bone augmentation in moderately to severely resorbed completely edentulous   maxillae. Int J Oral Implantol. 1999;2:70-79.
  Kraut RA. Interactive CT diagnostics, planning and preparation for dental   implants. Implant Dent. 1998;1:19-25.
  Kraut RA. Effective uses of radiographs for implant placements, panographs,   cephalograms, CT scans (interview). Dent Implantol Update. 1993;4:29- 33.  
  Williams MY, Mealey BL, Hallmon WW. The role of computerized tomography in   dental implantology. Int J Oral Maxillofac Implants. 1992;7:373-380.
  Verstreken K, van Cleynenbreugel J, Marchal G, et al. Computer-assisted planning   of oral implant surgery: A threedimensional approach. Int J Oral Maxillofac   Implants. 1996;11:806-810.
  Mariano JE, Arenal AA, Ceballos AP, et al. Fabrication of an implant radiologic-surgical   stent for the partially edentulous patient. Quintessence Int. 1995;26:111-114.  
  Hounsfield GN. Computerized transverse scanning (tomography) I. Description   of system. Br J Radiol. 1975;48: 605.
  Tarnow DP, Emtiaj S, Classi A. Immediate loading of threaded implants at   stage one surgery in edentulous arches. Ten consecutive case reports with 1   to 5 year data. Int J Oral Maxillofac Implants. 1997;12:319-324.
  Misch CE. Clinical biomechanics in implant dentistry. In: Misch CE (ed).   Contemporary Implant Dentistry. 2nd ed. St.Louis: Mosby; 1999:303-316.