Georg D. Strbac

Computed tomography‐based evaluation of template (NobelGuide™)‐guided implant positions: a prospective radiological study

OBJECTIVES This prospective study was intended to evaluate the overall deviation in a clinical treatment setting to provide for quantification of the potential impairment of treatment safety and reliability with computer-assisted, template-guided transgingival implantation. MATERIAL AND METHODS The patient population enrolled (male/female=10/8) presented with partially dentate and edentulous maxillae and mandibles. Overall, 86 implants were placed by two experienced dental surgeons strictly following the NobelGuide™ protocol for template-guided implantation. All patients had a postoperative computed tomography (CT) with identical settings to the preoperative examination. Using the triple scan technique, pre- and postoperative CT data were merged in the Procera planning software, a newly developed procedure - initially presented in 2007 allowing measurement of the deviations at implant shoulder and apex. RESULTS The deviations measured were an average of 0.43 mm (bucco-lingual), 0.46 mm (mesio-distal) and 0.53 mm (depth) at the level of the implant shoulder and slightly higher at the implant apex with an average of 0.7 mm (bucco-lingual), 0.63 mm (mesio-distal) and 0.52 mm (depth). The maximum deviation of 2.02 mm was encountered in the corono-apical direction. Significantly lower deviations were seen for implants in the anterior region vs. the posterior tooth region (P<0.01, 0.31 vs. 0.5 mm), and deviations were also significantly lower in the mandible than in the maxilla (P=0.04, 0.36 vs. 0.45 mm) in the mesio-distal direction. Moreover, a significant correlation between deviation and mucosal thickness was seen and a learning effect was found over the time period of performance of the surgical procedures. CONCLUSION Template-guided implantation will ensure reliable transfer of preoperative computer-assisted planning into surgical practice. With regard to the required verification of treatment reliability of an implantation system with flapless access, all maximum deviations measured in this clinical study were within the safety margins recommended by the planning software.

Esthetic evaluation of single-tooth implants in the anterior maxilla following autologous bone augmentation.

OBJECTIVES Autologous bone augmentation to rebuild compromised alveolar ridge contour prior to implant placement allows for favorable three-dimensional implant positioning to achieve optimum implant esthetics. The aim of the present study was to evaluate peri-implant soft tissue conditions around single-tooth implants following bone grafts in the esthetic zone of the maxilla. MATERIALS AND METHODS Sixty patients underwent autologous bone augmentation of deficient maxillary sites prior to placement of 85 implants in the esthetic zone. In case of multiple implants per patient, one implant was randomly selected. Objective evaluation of 60 single-tooth implants was performed using the Pink-Esthetic-Score (PES) and Papilla Index (PI) and supplemented by subjective patient evaluation, as well as clinical and radiologic examination. RESULTS Objective ratings of implant esthetics were satisfactory (median PES: 11, median PI: 2) and significantly correlated with high patient satisfaction (mean VAS score: 80%). Both esthetic indices demonstrated respectable levels of inter- as well as intra-observer agreement. Poor implant esthetics (low PES and PI ratings) were significantly associated with increased anatomic crown height, while no influence of horizontal implant-tooth distance could be found. CONCLUSIONS The present investigation indicates that favorable esthetic results may be achieved in the augmented anterior maxilla. However, bony reconstruction of compromised alveolar ridges does not guarantee optimum implant esthetics.

Are culture‐expanded autogenous bone cells a clinically reliable option for sinus grafting?

OBJECTIVES This prospective clinical study was designed to examine the healing process during the first 12 months after sinus grafting (SG) with autogenous culture-expanded bone cells (ABC) and bovine bone mineral (BBM) histomorphometrically and radiologically. MATERIAL AND METHODS Twenty-two sinuses of 12 patients (mean age 56.2+/-9.3 years) were grafted. Four weeks before, SG bone biopsies were obtained with a trephine burr and the bone cells were isolated and expanded. Every sinus was grafted with BBM and ABC. After 6 months, a biopsy was taken from each sinus and implants (n=82) were placed. These were uncovered after another 6 months and fitted with dentures. The percent newly formed bone (NB) and the NB-to-BBM contact area were determined on undecalcified histologic sections. The sinus graft volume was evaluated by dental CT after SG (CT 1), after implant placement (CT 2) and after implant uncovery (CT 3). RESULTS Postoperative healing was uneventful. The NB was 17.9+/-4.6% and the contact area 26.8+/-13.1%. The graft volume (in mm(3)) was 2218.4+/-660.9 at the time of CT 1, 1694+/-470.4 at the time of CT 2 and 1347.9+/-376.3 at the time of CT 3 (P<.01). Three implants were lost after uncovery. Reimplantation and prosthodontic rehabilitation were successful throughout. CONCLUSIONS These results suggest that SG with ABC and BBM in a clinical setting provides a bony implant site which permits implant placement and will tolerate functional loading.

Thermal effects of a combined irrigation method during implant site drilling. A standardized in vitro study using a bovine rib model

OBJECTIVES The purpose of this study was to evaluate the temperature changes during implant osteotomies with a combined irrigation system as compared to the commonly used external and internal irrigation under standardized conditions. MATERIAL AND METHODS Drilling procedures were performed on VII bovine ribs using a computer-aided surgical system that ensured automated intermittent drilling cycles to simulate clinical conditions. A total of 320 drilling osteotomies were performed with twist (2 mm) and conical implant drills (3.5/4.3/5 mm) at various drilling depths (10/16 mm) and with different saline irrigation (50 ml/min) methods (without/external/internal/combined). Temperature changes were recorded in real time by two custom-built thermoprobes with 14 temperature sensors (7 sensors/thermoprobe) at defined measuring depths. RESULTS The highest temperature increase during osteotomies was observed without any coolant irrigation (median, 8.01°C), followed by commonly used external saline irrigation (median, 2.60°C), combined irrigation (median, 1.51°C) and ultimately with internal saline irrigation (median, 1.48°C). Temperature increase with different drill diameters showed significant differences (P < 0.05) regarding drill depth, confirming drill depth and time of drilling as influencing factors of heat generation. Internal saline irrigation showed a significantly smaller temperature increase (P < 0.05) compared with combined and external irrigation. A combined irrigation procedure appears to be preferable (P < 0.05) to an external irrigation method primarily with higher osteotomy depths. CONCLUSIONS Combined irrigation provides sufficient reduction in temperature changes during drilling, and it may be more beneficial in deeper site osteotomies. Further studies to optimize the effects of a combined irrigation are needed.

A novel standardized bone model for thermal evaluation of bone osteotomies with various irrigation methods

OBJECTIVES Based on a novel standardized bovine specimen, the aim of this study was to investigate thermal effects of different irrigation methods during intermittent and graduated drilling. MATERIAL AND METHODS Temperature changes during implant osteotomies (n = 320) of 10 and 16 mm drilling depths with various irrigation methods were investigated on manufactured uniform bone samples providing homogenous cortical and cancellous areas and analogous thermal conductivity comparable to human bone. Automated sequences were performed with surgical twist drills of 2 mm ∅ and conical drills of 3.5, 4.3 and 5 mm ∅. Real-time recording of temperature increase was done using two custom-built multichannel thermoprobes with 14 temperature sensors at a predefined distance of 1 and 2 mm to the final osteotomy. The effects of drilling depth, drilling diameter and irrigation methods on temperature changes were investigated by a linear mixed model. RESULTS Using this uniform bone specimen, the greatest temperature rise was observed without any coolant supply with 29.87°C, followed by external with 28.47°C and then internal with 25.86°C and combined irrigation with 25.68°C. Significant differences (P ≤ 0.0156) between drill depths of 10 vs. 16 mm could be observed with all irrigation methods evaluated. With each of the irrigation methods, significantly higher temperature changes (P < 0.0001) during osteotomies could be observed between twist drills of 2 mm ∅ and conical drills of 3.5, 4.3 and 5 mm ∅. During 10 and 16 mm drilling osteotomies, external irrigation showed significantly higher temperatures (P < 0.05) for all conical drills compared with internal or combined irrigation, respectively. Significantly lower temperatures (P < 0.05) could be detected with internal or combined irrigation for the use of conical drills with various diameters and drilling depths. CONCLUSIONS This fully standardized bone model provides optimized comparability for the evaluation of bone osteotomies and resulting temperature changes. As regards the efficiency of the various irrigation methods, it could be demonstrated that internal and combined irrigation appears to be more beneficial than external irrigation.

Guided Modern Endodontic Surgery: A Novel Approach for Guided Osteotomy and Root Resection

Introduction: Continuous improvements in techniques, instruments, and materials have established modern endodontic microsurgery as a state‐of‐the‐art treatment method. The purpose of this approach was to introduce a new surgical endodontic technique by using a three‐dimensional printed template for guided osteotomy and root resection. Methods: A 38‐year‐old patient was diagnosed with periapical lesions of teeth #3 and #4 and extruded gutta‐percha material. Three‐dimensional radiographic and optical scan files were imported into surgical planning software designed for guided implant surgery. Within the adapted software program the periapical lesions and the extruded gutta‐percha were visualized and marked. With the aid of virtually positioned surgical pins and piezoelectric instruments, the osteotomy size, the apical resection level, and the bevel angle were defined before treatment. Three‐dimensional surgical templates for each tooth were designed within the software program for a guided treatment approach. Results: This approach comprised the treatment of periapical lesions of teeth #3 and #4 with root‐end fillings and the detection and complete removal of the extruded gutta‐percha material without perforation of sinus membrane. There were no postoperative complications, and clinical and radiologic assessments verified complete healing of the teeth. Conclusions: The guided microsurgical endodontic treatment presented appears to be a viable technique that allows for predefined osteotomies and root resections. HighlightsNovel surgical endodontic technique using a 3D template for guided osteotomy and root resection.Virtually pre‐planned implementation of recommended guidelines for a modern surgical endodontic treatment.Adaptation of a software program for guided implant surgery in endodontic treatments.Guided surgical osteotomies and root resections with piezoelectric instruments.

Evaluation of Three Different Validation Procedures regarding the Accuracy of Template-Guided Implant Placement: An In Vitro Study

PURPOSE The study aims to evaluate the accuracy of the NobelGuide™ (Medicim/Nobel Biocare, Göteborg, Sweden) concept maximally reducing the influence of clinical and surgical parameters. Moreover, the study was to compare and validate two validation procedures versus a reference method. MATERIAL AND METHODS Overall, 60 implants were placed in 10 artificial edentulous mandibles according to the NobelGuide™ protocol. For merging the pre- and postoperative DICOM data sets, three different fusion methods (Triple Scan Technique, NobelGuide™ Validation software, and AMIRA® software [VSG - Visualization Sciences Group, Burlington, MA, USA] as reference) were applied. Discrepancies between the virtual and the actual implant positions were measured. RESULTS The mean deviations measured with AMIRA® were 0.49 mm (implant shoulder), 0.69 mm (implant apex), and 1.98°mm (implant axis). The Triple Scan Technique as well as the NobelGuide™ Validation software revealed similar deviations compared with the reference method. A significant correlation between angular and apical deviations was seen (r = 0.53; p < .001). A greater implant diameter was associated with greater deviations (p = .03). CONCLUSION The Triple Scan Technique as a system-independent validation procedure as well as the NobelGuide™ Validation software are in accordance with the AMIRA® software. The NobelGuide™ system showed similar or less spatial and angular deviations compared with others.

Drilling- and Withdrawing-Related Thermal Changes during Implant Site Osteotomies

BACKGROUND Intrabony temperature increase is not only dependent on shearing energy and mechanical friction between bone and surgical drill but is also related to heat capacity and thermal conductivity of the surrounding bone and the applied surgical instrument. Thus time of occurrence of the highest temperature rise can be expected after the shearing process of the osteotomy, potentially affecting the process of osseointegration. PURPOSE The aim of this study was to evaluate temperature changes during the shearing and withdrawing processes during osteotomies. MATERIALS AND METHODS An overall 160 automated intermittent osteotomies (10/16 mm drilling depth) with 2 mm diameter twist drills and 3.5 mm diameter conical drills and different irrigation methods (without/external/internal/combined) were performed on standardized bone specimens. The drilling cycles were operated by a computer-controlled surgical system, while a linear motion potentiometer and multichannel temperature sensors in various intrabony levels ensured the real-time documentation of temperature changes during the shearing and withdrawing processes. RESULTS The highest temperature changes were invariably recorded during the process of withdrawal. Significantly lower temperature changes (p < .02) could be recorded at maximum drilling depths during the shearing process regardless of drilling depth, diameter or irrigation method. During coolant supply, 2 mm diameter twist drills showed higher temperatures (10 mm, p < .01/16 mm, p < .03) compared with 3.5 mm diameter conical implant drills. Internal (10 mm, p < .01) or combined irrigation (16 mm, p < .01) was associated with significantly lower temperatures compared with external irrigation by the use of conical implant drills. CONCLUSIONS Considering that heat generation during osteotomies is a multifactorial scenario, this study could demonstrate that the highest temperature rise during implant osteotomies occurs during the withdrawing process and that the time of occurrence is influenced by predominant factors such as osteotomy depth and mode of irrigation.

Guided Autotransplantation of Teeth: A Novel Method Using Virtually Planned 3-dimensional Templates

INTRODUCTION The aim of this study was to introduce an innovative method for autotransplantation of teeth using 3-dimensional (3D) surgical templates for guided osteotomy preparation and donor tooth placement. METHODS This report describes autotransplantation of immature premolars as treatment of an 11-year-old boy having suffered severe trauma with avulsion of permanent maxillary incisors. This approach uses modified methods from guided implant surgery by superimposition of Digital Imaging and Communications in Medicine files and 3D data sets of the jaws in order to predesign 3D printed templates with the aid of a fully digital workflow. RESULTS The intervention in this complex case could successfully be accomplished by performing preplanned virtual transplantations with guided osteotomies to prevent bone loss and ensure accurate donor teeth placement in new recipient sites. Functional and esthetic restoration could be achieved by modifying methods used in guided implant surgery and prosthodontic rehabilitation. The 1-year follow-up showed vital natural teeth with physiological clinical and radiologic parameters. CONCLUSIONS This innovative approach uses the latest diagnostic methods and techniques of guided implant surgery, enabling the planning and production of 3D printed surgical templates. These accurate virtually predesigned surgical templates could facilitate autotransplantation in the future by full implementation of recommended guidelines, ensuring an atraumatic surgical protocol.

Impact of Insertion Torque and Implant Neck Design on Peri-Implant Bone Level: A Randomized Split-Mouth Trial

PURPOSE The aim of this study is to assess the impact of insertion torque and implant neck design on peri-implant bone levels and gain insights into dynamic crestal tissue alterations by radiological, clinical, and biochemical examinations. MATERIAL AND METHODS In this prospective trial, a total of 84 implants (four implants in each patient) in the interforaminal region of 21 edentulous mandibles were randomly alternated according to a split-mouth design. Implant placement was performed using different insertion torques (≤20 Ncm vs >50 Ncm). In each group, one machined and one anodized implant neck design (1.5 mm length) was used in the same jaw side. Evaluation of peri-implant tissues involved radiological, clinical examination and immunoassays for interleukin-1β. RESULTS No significant influence of insertion torque or implant neck design on peri-implant bone level was found. Protein levels of interleukin-1β in the peri-implant crevicular fluid revealed no difference between both insertion torque groups and different neck designs. CONCLUSION Interactive effects of insertion torque and neck surface modification may exist; however, no clinically significant differences in marginal bone resorption after 1 year could be observed in the edentulous anterior mandible.