Introduction
It is known that postextraction socket resorption may lead to a mean loss of buccal-lingual width of approximately 4 mm as well as a mean loss of height of approximately 2 mm, primarily in the first 3 months.1 Such alterations, in turn, may lead to esthetic problems and even prevent implant placement.2 In this context, alveolar ridge preservation with particulate bone grafts has been considered a valid technique to prevent postextraction socket resorption.3
Several types of bone grafts have been used in dentistry. While autogenous grafts promote osteoinduction, osteogenesis, and osteoconduction, they have limitations such as risk of trauma to the patient and donated bed morbidity. Allogeneic grafts, in turn, also have limitations such as high cost, possibility of virus transmissibility, and triggering immunological reactions. On the other hand, all of these aforementioned limitations can be avoided by using xenografts.4
Among the available xenografts, bovine and porcine have been described in the literature on dentistry as predictable options for ridge preservation.5,6 Another xenograft recently studied in dentistry is an enzymatic form of equine bone. Because of the enzymatic process, it ends up preserving the type I bone collagen in its undenatured native state, thus allowing an improved bone regeneration process. Such equine-derived material also has the elasticity to be properly shaped to match the bone defect.7 However, there is a lack of evidence regarding clinical results of equine-derived bone grafts for alveolar ridge preservation.
Alveolar bone-grafting techniques also require cone-beam computerized tomographic (CBCT) scans for virtual surgical planning, which can belong to a digital workflow for dental implant rehabilitation.8,9 Nevertheless, little is known about the methods for estimating the volume of the particulate synthetic graft required to properly fill the alveolar socket to achieve satisfactory ridge preservation results.
Thus, the aim of this study was to describe a digital workflow used for 3 main purposes: to predict the volume of particulate grafting material required to perform alveolar ridge preservation, to conduct subsequent virtual implant planning, and to digitally design the respective implant-supported crown.
Case Report
A 68-year-old female patient presented with a failing left maxillary second premolar and agreed to receive implant therapy by signing an informed consent. At the first clinical appointment, a clinical evaluation was performed and an initial CBCT scan (Promax 3D, Planmeca) was taken with an acceptable imaging protocol (eg, 0.2-mm voxel, 90 kVp, 8 mA, field of view of 16 cm in diameter and 6 cm in height). At the same appointment, we checked the conditions of the soft tissues (eg, amount of keratinized tissue, inflammation).
Original CBCT Digital Communication in Medicine (DICOM) files were imported to a DICOM viewer software (Horos v.3.3.0, The Horos Project). We used the “closed polygon” tool to create regions of interest (ROIs) by outlining the alveolar socket area planned for receiving particulate grafts in all coronal slices containing roots of the corresponding compromised tooth (Figure 1a). Then, we selected all ROIs created and used the “compute volume” software tool to estimate the alveolar socket volume in cubic millimeters (Figure 1a).
Figure 1. (a) Cone-beam computerized tomography multiplanar reconstruction showing a region of interest outlining the socket area in a coronal slice. Note the vertical fracture of the root clearly visible in the sagittal and axial slices. (b) Alveolar socket volumetric measurement output. This image shows an estimated volume of 174.5 mm3. Figure 2. (a) Clinical view of the vertically fractured root of upper left second premolar. (b) Clinical view of the alveolar socket after root extraction. Figure 3. Clinical view of the alveolar socket filled with equine-derived particulate bone graft. Since a volume of 174.5 mm3 of grafting material was required, only one package of biomaterial with a total hydrated volume of 500 mm3 was opened during the alveolar ridge preservation procedure.
Figure 1. (a) Cone-beam computerized tomography multiplanar reconstruction showing a region of interest outlining the socket area in a coronal slice. Note the vertical fracture of the root clearly visible in the sagittal and axial slices. (b) Alveolar socket volumetric measurement output. This image shows an estimated volume of 174.5 mm3. Figure 2. (a) Clinical view of the vertically fractured root of upper left second premolar. (b) Clinical view of the alveolar socket after root extraction. Figure 3. Clinical view of the alveolar socket filled with equine-derived particulate bone graft. Since a volume of 174.5 mm3 of grafting material was required, only one package of biomaterial with a total hydrated volume of 500 mm3 was opened during the alveolar ridge preservation procedure.
The compromised tooth was extracted atraumatically (Figure 2), before proceeding with immediate alveolar ridge preservation (Figure 3) by filling the alveolar socket with an equine-derived particulate bone graft (Bioteck Putty, BioTek, Winooski, Vt) followed by the use of a resorbable collagen membrane (Biogide, Geistlich) to cover the socket before suturing (5-0 Nylon, Ethilon). For this purpose, we selected the correct number of packages to reach the required volume of particulate graft, as estimated previously in the CBCT images.
After 5 months of uneventful graft healing, another CBCT scan was taken for virtual implant planning (Figure 4). In such images, the volume of the healed graft could also be estimated with the same method used in the step 2. Dental implant placement (SLA Roxolid, 4.1 mm × 10 mm, Institut Straumann; Figure 5) was then performed. After 6 weeks of healing, a scan body for screw-retained abutments (Variobase, Straumann) was scanned with an intraoral scanner (IOS, Trios III, 3Shape) with the upper arch. In addition, another scan of the same arch without the scan body as well as scans of the antagonist arch and patient's occlusion were also taken.
Figure 4. Cone-beam computerized tomography images obtained after 5 months of graft healing, ensuring buccal plate integrity and satisfactory bone dimensions for implant placement. Figure 5. Final implant position after obtaining a peak insertion torque of 35 Ncm. Figure 6. Scan body slightly trimmed externally to avoid excessive proximity with the adjacent rotated first premolar. Figure 7. Virtual wax-up performed using computer-aided design software. Figure 8. Final clinical result after installation of the implant-supported crown. (a) Buccal view. (b) Occlusal view. Note the position of the adjacent rotated first premolar.
Figure 4. Cone-beam computerized tomography images obtained after 5 months of graft healing, ensuring buccal plate integrity and satisfactory bone dimensions for implant placement. Figure 5. Final implant position after obtaining a peak insertion torque of 35 Ncm. Figure 6. Scan body slightly trimmed externally to avoid excessive proximity with the adjacent rotated first premolar. Figure 7. Virtual wax-up performed using computer-aided design software. Figure 8. Final clinical result after installation of the implant-supported crown. (a) Buccal view. (b) Occlusal view. Note the position of the adjacent rotated first premolar.
The optimal implant position chosen during virtual implant planning was predicted to lead to excessive proximity with the crown of the adjacent first premolar because of its rotation. To overcome such condition, the scan body was slightly trimmed externally to avoid such excessive proximity to the adjacent rotated tooth (Figure 6). All resulting IOS images were then exported as Standard Tessellation Language files and used to perform a virtual wax-up of the implant-supported restoration (Figure 7) by using computer-aided design software (DentalCAD, EXOCAD). The resulting implant-supported restoration (Figure 8) was then fabricated with lithium disilicate glass ceramic (IPS e.max Press, Ivoclar-Vivadent) by using a milling machine (inLab MC XL, Dentsply-Sirona) and installed with no need of final chairside adjustments.
Discussion
Although digital workflows, including virtual implant planning, have been discussed in the recent literature,9 to our knowledge, this is the first technique report using digital volumetric measurements to estimate the required volume of particulate bone graft for alveolar ridge preservation before implant surgery. Because the volume of grafting material of each package is stated in the product brochure, such methodology could prevent the professional from opening unnecessary particulate graft packages. The present findings are in agreement with previous studies showing the usefulness of digital workflows for planning implant-related bone-grafting surgeries.8,9
In this report, we strove to show the clinical management of an excessive proximity between the scan body and a rotated adjacent tooth, which could prevent proper intraoral scanning of the distal surface of such tooth. The aforementioned condition was solved by slightly trimming the scan body without compromising its functionality while still decreasing its proximity with the rotated adjacent tooth, which enabled installation of the final implant-supported crown without the need for further laboratory adjustments. This finding is in agreement with studies that used scan bodies with different IOSs, leading to satisfactory outcomes of definitive milled restorations.10 This suggests that computer-aided design/computer-aided manufacturing technologies are reliable for fabricating implant-supported restorations.
Because this is a technique report, long-term follow-up studies and randomized clinical trials are recommended to confirm the stability of clinical outcomes and the accuracy of the methods described herein. Furthermore, the case used to illustrate the present technique had a satisfactory amount of keratinized tissue. Further clinical studies are required to address outcomes in cases with thin gingival biotypes, in which conjunctive tissue grafts or other techniques not covered in this report might be necessary to achieve successful outcomes.11
In conclusion, within the limitations of this study, the present findings suggest that it is possible to obtain satisfactory clinical results using a digital workflow, for planning alveolar ridge preservation using equine-derived bone graft and subsequent implant installation, as well as for digitally designing implant-supported restorations, in cases of single-tooth implant rehabilitation.
Abbreviations
Note
The authors declare no conflict of interests related to this study. No funding was available for this study.
