Stephan Christian Möhlhenrich

The accuracy of computer-assisted primary mandibular reconstruction with vascularized bone flaps: iliac crest bone flap versus osteomyocutaneous fibula flap.

Background The intention of mandibular reconstruction is to restore the complex anatomy with maximum possible functionality and high accuracy. The aim of this study was to evaluate the accuracy of computer-assisted surgery in primary mandibular reconstruction with an iliac crest bone flap compared with an osteomyocutaneous fibula flap. Materials and methods Preoperative computed tomography data of the mandible and the iliac crest or fibula donor site were imported into a specific surgical planning software program. Surgical guides were manufactured using a rapid prototyping technique for translating the virtual plan, including information on the transplant dimensions and shape, into real-time surgery. Using postoperative computed tomography scans and an automatic surface-comparison algorithm, the actual postoperative situation was compared with the preoperative virtual simulation. Results The actual flap position showed a mean difference from the virtual plan of 2.43 mm (standard deviation [SD] ±1.26) and a surface deviation of 39% <2 mm and 15% <1 mm for the iliac crest bone flap, and a mean difference of 2.18 mm (SD ±1.93) and a surface deviation of 60% <2 mm and 37% <1 mm for the osteomyocutaneous fibula flap. The position of the neomandible reconstructed with an osteomyocutaneous fibula flap indicated a mean difference from the virtual plan of 1.25 mm (SD ±1.31) and a surface deviation of 82% <2 mm and 57% <1 mm, in contrast to a mean difference of 1.68 mm (SD ±1.25) and a surface deviation of 63% <2 mm and 38% <1 mm for the neomandible after reconstruction with an iliac crest bone flap. For shape analysis, a similarly high accuracy could be calculated for both flaps. Conclusion Virtual surgical planning is an effective method for mandibular reconstruction with vascularized bone flaps, and can help to restore the anatomy of the mandible with high accuracy in position and shape. It seems that primary mandibular reconstruction with the osteomyocutaneous fibula flap is more accurate compared with the vascularized iliac crest bone flap.

Heat generation and drill wear during dental implant site preparation: systematic review

To identify factors that minimise damage during the drilling of sites for dental implants, we reviewed published papers on the amount of heat that is generated. We systematically searched English language studies published between January 2000 and February 2014 on MEDLINE/PubMed and found 41 articles, of which 27 related to an increase in temperature during preparation of the site. We found only basic research with a low level of evidence. Most of the studies were in vitro, and osteotomies were usually made in non-vital bone from cows or pigs. To measure heat in real time, thermocouples were used in 18 studies and infrared thermographs in 7. Three studies reported the use of immunohistochemical analysis to investigate immediate viability of cells. The highest temperature measured was 64.4°C and the lowest 28.4°C. Drill wear was reported after preparation of 50 sites, and there was a significant increase in temperature and a small change in the physiological balance of the proteins in the bone cells. Differences in the study designs meant that meta-analysis was not appropriate. For future work, we recommend the use of standard variables: an axial load of 2kg, drilling speed of 1500rpm, irrigation, standard artificial bone blocks, and the use of infrared thermography.

Computer-Aided Mandibular Reconstruction With Vascularized Iliac Crest Bone Flap and Simultaneous Implant Surgery

The intention of oral rehabilitation in patients with mandibular defects is an early prosthetic treatment with maximum possible functionality and high accuracy. The present study describes a new computer-aided technique for mandibular reconstruction using a free vascularized iliac flap and simultaneous insertion of dental implants into the flap while it is still pedicled at the donor site. Based on preoperative computerized tomography data of the facial skeleton and the iliac crest donor site, a surgical guide transferred the virtual plan including information on the transplant dimensions and shape as well as the position of the dental implants into real-time surgery. Using postoperative computerized tomography scans, the actual situation were compared with the preoperative simulation. A mean difference of 0.75 mm (SD ± 0.72) for the flap shape and 0.70 mm (SD ± 0.44) for the implant position analysis was determined. A calculation of the closest point distance showed a surface deviation of <2 mm for the shape analysis in 93.3% of the values and <1 mm for implant position in 75.2% of the values. The mean angular deviation was 3.65°. Virtual surgical planning is a suitable method for mandibular reconstruction with vascularized iliac crest flaps and simultaneous implant surgery. It can be used to restore the anatomy of the mandible with a high accuracy and can help to shorten subsequent dental rehabilitation.

Three-Dimensional Evaluation of Implant Bed Preparation and the Influence on Primary Implant Stability After Using 2 Different Surgical Techniques.

PURPOSE Surgical techniques affect primary implant stability, which is required for osseointegration. The aim of this study was to investigate the influence of full-guided surgery on the dimension of implant site in relation to primary stability. MATERIALS AND METHODS After implant site preparation in artificial bone by full-guided (FG) or non-guided (NG) workflows to create final diameters of 3.3, 4.1, and 4.8mm and depths of 8 or 12 mm, computed tomograms were obtained and the volume of the osteotomies was analyzed 3 dimensionally. After comparing implant insertions, the implant stability quotient (ISQ) was measured by resonance frequency analysis (RFA). RESULTS Volume analysis of the implant site showed significant differences (P < .0001) between surgical procedures (FG vs NG) at a depth of 12 mm for all diameters (3.3 mm, 61.98 ± 5.84 vs 80.96 ± 9.65 mm(3); 4.1 mm, 107.45 ± 6.91 vs 132.07 ± 5.16 mm(3); 4.8 mm, 158.62 ± 10.21 vs 182.00 ± 6.25 mm(3)) and at a depth of 8 mm for diameters of 4.1 mm (71.76 ± 8.38 vs 83.64 ± 7.54 mm(3)) and 4.8 mm (103.84 ± 6.73 vs 120.55 ± 14.63 mm(3)). RFA showed significant differences for implants with a diameter of 4.8 mm and lengths of 12 mm (ISQ, 69.3 ± 4.09 for FG vs 65.05 ± 5.61 for NG; P = .0007) and 8 mm (64.5 ± 4.16 for FG vs 58.85 ± 6.72 for NG; P = .0107). CONCLUSIONS The use of FG implant surgery decreases the bone volume removed during osteotomy preparation, which can lead to greater primary stability.

Three-dimensional evaluation of the different donor sites of the mandible for autologous bone grafts

ObjectivesFor effective placement of endosseous implants, a sufficient volume of bone is required at the recipient site. The aim of this study is to evaluate the density and maximum amount of harvestable bone graft required from the mandible symphysis, coronoid process, and ascending ramus, depending on dentition.Materials and methodsCT data from 42 patients (13 females and 29 males) in DICOM format were read using special planning software. Three different virtual bone grafts were created, and the dimension outcomes, surface, volume, and density were measured in a dentate group (n = 22) and a total edentulous group (n = 20).ResultsComparisons between corresponding bone grafts showed no difference for the symphysis and coronoid process in relation to dentition, and no difference in bone density was observed. However, significant changes between the average values of the ramus were found between the two groups (p < 0.0001).ConclusionsAppropriate software and CT data can deliver more accurate examinations of the mandible in relation to potential donor sites. Atrophy primarily affects the ascending ramus; the symphysis and coronoid process are only slightly influenced.Clinical relevanceUsing appropriate software in conjunction with implant planning, it is possible to analyze potential donor areas within the jaw and create virtual bone grafts

Compensating for poor primary implant stability in different bone densities by varying implant geometry: a laboratory study

The aim of this study was to determine the influence of implant diameter and length on primary stability in artificial bone blocks. In total, 240 implants of various diameters (Ø 3.3, 4.1, and 4.8mm) and lengths (8 and 12 mm) were inserted in four artificial bone blocks of different densities (D1-D4). The primary stability for each bone block density was measured and compared with the primary stability of a narrow and short implant (Ø 3.3mm, length 8mm) in the next higher density block. Analysis was done by three-way ANOVA, and mean differences were determined with the 95% confidence interval. Levels of primary stability achieved by choosing the next higher diameter or length were not comparable to those of the next level of block density. However, equivalent values could be achieved by selecting the largest diameter for short and long implants in the lowest block density D4, as well as for long implants in bone type D2. The diameter of an implant has greater influence on primary stability than length. In particular, in the case of poor bone quality, a variation of implant geometry can lead to significant improvement in primary stability.

Is the Maxillary Sinus Really Suitable in Sex Determination? A Three-Dimensional Analysis of Maxillary Sinus Volume and Surface Depending on Sex and Dentition.

AbstractThe morphometric analysis of maxillary sinus was recently presented as a helpful instrument for sex determination. The aim of the present study was to examine the volume and surface of the fully dentate, partial, and complete edentulous maxillary sinus depending on the sex. Computed tomography data from 276 patients were imported in DICOM format via special virtual planning software, and surfaces (mm2) and volumes (mm3) of maxillary sinuses were measured. In sex-specific comparisons (women vs men), statistically significant differences for the mean maxillary sinus volume and surface were found between fully dentate (volume, 13,267.77 mm3 vs 16,623.17 mm3, P < 0.0001; surface, 3480.05 mm2 vs 4100.83 mm2, P < 0.0001) and partially edentulous (volume, 10,577.35 mm3 vs 14,608.10 mm3, P = 0.0002; surface, 2980.11 mm2 vs 3797.42 mm2, P < 0.0001) or complete edentulous sinuses (volume, 11,200.99 mm3 vs 15,382.29 mm3, P < 0.0001; surface, 3118.32 mm2 vs 3877.25 mm2, P < 0.0001). For males, the statistically different mean values were calculated between fully dentate and partially edentulous (volume, P = 0.0022; surface, P = 0.0048) maxillary sinuses. Between the sexes, no differences were only measured for female and male partially dentate fully edentulous sinuses (2 teeth missing) and between partially edentulous sinuses in women and men (1 teeth vs 2 teeth missing). With a corresponding software program, it is possible to analyze the maxillary sinus precisely. The dentition influences the volume and surface of the pneumatic maxillary sinus. Therefore, sex determination is possible by analysis of the maxillary sinus event through the increase in pneumatization.

Papilla and alveolar crest levels in immediate versus delayed single-tooth zirconia implants

The aim of this study was to determine the correlation between the papilla deficit and the distance between the bone crest at the neighbouring tooth and the contact point of the clinical crown (distance 4) for immediate and delayed zirconia implants. This prospective observational study included 78 patients with 82 implants investigated at the 1-year follow-up. Patients received single-unit zirconia implants (Straumann PURE Ceramic Implant with ZLA surface) that were placed using either the delayed (group A) or immediate (group B) protocol after tooth extraction. The distance of the alveolar crest of the neighbouring tooth to the height of the interdental papilla and the absence of the papilla were also assessed. There was a strong correlation between the papilla deficit and distance 4 in group A (Spearmans rho=0.64). However, in group B, only a weak correlation between the two distances was found (Spearmans rho=0.28). A full soft tissue margin was generated when distance 4 was 7-8mm or less. Delayed implant placement showed a critical distance between the alveolar crest at the neighbouring tooth and the contact point of the crown risking a visible papilla deficit of between 7mm and 8mm.

Margins of oral leukoplakia : autofluorescence and histopathology

Autofluorescence devices are widely used to examine oral lesions. The aim of this study was to see whether there were any signs of dysplasia, parakeratosis, or mucosal inflammation in the borders of homogeneous oral leukoplakia using autofluorescence, and we also compared clinically visible extensions with those detected by autofluorescence. Twenty patients with 26 homogeneous areas of oral leukoplakia were included in the study. After the clinically visible extensions of the lesion had been marked, we took a photograph through the autofluorescence device, which showed both borders in one picture. We then used photo-editing software to measure the size of the area of leukoplakia together with the area with loss of autofluorescence. We took 3 punch biopsy specimens: one from the leukoplakia, one 2.5mm from its marked borders, and one from healthy mucosa. Seventy-eight biopsy specimens were examined by an experienced pathologist, and 95% CI calculated to assess the amount of parakeratosis. Spearmans rank correlation was used to assess the association with mucosal inflammation. Ten areas of leukoplakia were surrounded by normal green autofluorescence, and 16 were consistent with loss of autofluorescence with a mean size of 66%, which exceeded the clinically visible size of the area of leukoplakia. We calculated that there was a strong association between these entities and their surrounding areas, with loss of autofluorescence for parakeratosis. Some leukoplakias showed clinically invisible extensions during histopathological examination and autofluorescence. The technique described enables clinicians to measure the extent of these lesions beyond their visible margins. We found no dysplasia, which emphasises that autofluorescence detects non-dysplastic lesions caused by mucosal inflammation and parakeratosis.

Medial approach for minimally-invasive harvesting of a deep circumflex iliac artery flap for reconstruction of the jaw using virtual surgical planning and CAD/CAM technology

Donor site morbidity is the most common limitation of the deep circumflex iliac artery (DCIA) flap, so the purpose of this paper is to describe a new, minimally-invasive, approach to its harvest using virtual surgical planning and CAD/CAM technology to reduce functional and aesthetic morbidity at the donor site. Virtual surgical planning was based on preoperative computed tomographic data. A newly-designed surgical guide made using CAD/CAM technology was used to transfer the virtual surgical plan to the site of operation. This enabled us to raise a bicortical flap from the pelvis with preservation of the anterior superior iliac crest from the medial side with minimal muscular stripping. The guide, designed at slightly less than 90° to the lateral cortex, allowed the cut segment of bone to be raised medially. The new virtual surgical planning guide allowed a medial approach with reduced stripping of muscle and lower morbidity. No complications were encountered during the operation or the healing phase. Patients treated in this way had a shorter recovery period, with minimal complaints about walking or loss of profile of the hip. We conclude that virtual surgical planning can aid a minimally-invasive approach with predictable results. This allows a medial approach to the harvest of DCIA with preservation of important anatomical structures, and a reduction in donor site morbidity.