Volumetry of bone grafts by three-dimensional computed tomographic reconstruction: an animal study in the minipig

Regeneration of alveolar bone defects in the experimental pig model: A systematic review and meta-analysis

OBJECTIVE

Pigs are emerging as a preferred experimental in vivo model for bone regeneration. The study objective was to answer the focused PEO question: in the pig model (P), what is the capacity of experimental alveolar bone defects (E) for spontaneous regeneration in terms of new bone formation (O)?

METHODS

Following PRISMA guidelines, electronic databases were searched for studies reporting experimental bone defects or extraction socket healing in the maxillae or mandibles of pigs. The main inclusion criteria were the presence of a control group of untreated defects/sockets and the assessment of regeneration via 3D tomography [radiographic defect fill (RDF)] or 2D histomorphometry [new bone formation (NBF)]. Random effects meta-analyses were performed for the outcomes RDF and NBF.

RESULTS

Overall, 45 studies were included reporting on alveolar bone defects or extraction sockets, most frequently in the mandibles of minipigs. Based on morphology, defects were broadly classified as 'box-defects' (BD) or 'cylinder-defects' (CD) with a wide range of healing times (10 days to 52 weeks). Meta-analyses revealed pooled estimates (with 95% confidence intervals) of 50% RDF (36.87%-63.15%) and 43.74% NBF (30.47%-57%) in BD, and 44% RDF (16.48%-71.61%) and 39.67% NBF (31.53%-47.81%) in CD, which were similar to estimates of socket-healing [48.74% RDF (40.35%-57.13%) and 38.73% NBF (28.57%-48.89%)]. Heterogeneity in the meta-analysis was high (I2 > 90%).

CONCLUSION

A substantial body of literature revealed a high capacity for spontaneous regeneration in experimental alveolar bone defects of (mini)pigs, which should be considered in future studies of bone regeneration in this animal model.

Role of periosteum during healing of alveolar critical size bone defects in the mandible: a pilot study

OBJECTIVES

Minipigs present advantages for studying oral bone regeneration; however, standardized critical size defects (CSD) for alveolar bone have not been validated yet. The objectives of this study are to develop a CSD in the mandibular alveolar bone in Aachen minipigs and to further investigate the specific role of periosteum.

MATERIALS AND METHODS

Three female Aachen minipigs aged 17, 24, and 84 months were used. For each minipig, a split-mouth design was performed: an osteotomy (2 cm height × 2.5 cm length) was performed; the periosteum was preserved on the left side and removed on the right side. Macroscopic, cone beam computed tomography (CBCT), microcomputed tomography (µCT), and histological analyses were performed to evaluate the bone defects and bone healing.

RESULTS

In both groups, spontaneous healing was insufficient to restore initial bone volume. The macroscopic pictures and the CBCT results showed a larger bone defect without periosteum. µCT results revealed that BMD, BV/TV, and Tb.Th were significantly lower without periosteum. The histological analyses showed (i) an increased osteoid apposition in the crestal area when periosteum was removed and (ii) an ossification process in the mandibular canal area in response to the surgical that seemed to increase when periosteum was removed.

CONCLUSIONS

A robust model of CSD model was developed in the alveolar bone of minipigs that mimics human mandibular bone defects. This model allows to further investigate the bone healing process and potential factors impacting healing such as periosteum.

CLINICAL RELEVANCE

This model may be relevant for testing different bone reconstruction strategies for preclinical investigations.

Impact of human maxillary sinus volume on grafts dimensional changes used in maxillary sinus augmentation: a multislice tomographic study

PURPOSE

To assess the influence of complete maxillary sinus volume on the dimensional changes of different grafts used in maxillary sinus lift.

MATERIALS AND METHODS

Analysis of 50 surgical procedures of maxillary sinus lift performed on 43 subjects using different grafting materials: fresh frozen allogenic particulated bone (11), hydroxyapatite (Endobon(®)) (17), 60% hydroxyapatite + 40% beta-tricalcium phosphate (Bone Ceramic(®)) (12) and Bone Ceramic(®) + Emdogain(®) (10). One hundred and fifty multislice tomographic images of the maxillary sinus were obtained using the software Syngo CT 2011 A VOLUME, measuring complete maxillary sinus volume (T0) and dimensional changes of different graft materials during periods of 15 days (T1) and 180 days (T2). The factor studied was the influence of maxillary sinus volume on the dimensional changes of different graft materials used in maxillary sinus lift in patients with posterior edentulism. Data obtained were assessed using the Student's t-test and Pearson's correlation coefficient.

RESULTS

No correlation (r 0.112) between the total maxillary sinus volume and the dimensional changes of the different graft materials used in this study was observed (P > 0.05).

CONCLUSION

This study demonstrated that there is no sufficient evidence to support the thesis that the volume of the maxillary sinus influences the contraction of the grafts, at least on sample or the biomaterials evaluated in this cohort study.

Postoperative evaluation of grafted bone in alveolar cleft using three-dimensional computed tomography data

Objective : Postoperative evaluation of bone formation in the alveolar cleft by computed tomography imaging has been reported. We quantitatively evaluated bone grafts in the alveolar cleft preoperatively and postoperatively using three-dimensional data and superimposition of images. Subjects : A total of 12 patients with complete unilateral cleft lip and palate (six left-sided and six right-sided) were studied. Methods : Helical computed tomography scans were taken immediately before surgery and at 6 months after surgery and the DICOM files obtained were processed using Mimics and 3-matic software for three-dimensional data analysis. The preoperative and postoperative computed tomography data were superimposed, and the position and length of the unerupted canines and width of the alveolar cleft measured. Results : Strong and significant correlations were observed between bone formation in the alveolar cleft bone graft region and preoperative canine position (r  =  -.766, p < .01) and canine length (r  =  .681, p < .05). Stepwise multiple regression analysis demonstrated that only the preoperative canine position was independently and significantly correlated with bone formation in the alveolar cleft. Conclusion : These results indicate that the optimal timing for surgery is when the canine cusp is close to the alveolar plane.

Reconstructing mandibular defects using autologous tissue-engineered tooth and bone constructs

PURPOSE

Current strategies for jaw reconstruction require multiple operations to replace bone and teeth. To improve on these methods, we investigated simultaneous mandibular and tooth reconstruction, using a Yucatan minipig model.

MATERIALS AND METHODS

Tooth and bone constructs were prepared from third molar tooth tissue and iliac-crest bone marrow-derived osteoblasts isolated from, and implanted back into, the same pig as an autologous reconstruction. Implants were harvested after 12 and 20 weeks and evaluated by x-ray, ultrahigh-resolution volume computed tomographic (VCT), histological, and immunohistochemical analyses.

RESULTS

Small tooth structures were identified, and consisted of organized dentin, enamel, pulp, and periodontal ligament tissues, surrounded by new bone. No dental tissues formed in implants without tooth-bud cells, and bone regeneration was observed to a limited extent. Immunohistochemical analyses using tooth-specific and bone-specific antibodies confirmed the identity of regenerated tissues.

CONCLUSIONS

This pilot study supports the feasibility of tissue-engineering approaches for coordinated autologous tooth and mandible reconstruction, and provides a basis for future improvement of this technique for eventual clinical use in humans.

Three-dimensional evaluation of secondary alveolar bone grafting using a 3D- navigation system based on computed tomography: a two-year follow-up

Secondary bone grafting is widely used in the closure of oronasal fistulas and reconstruction of maxillary defects. It often fails from lack of physiological stress or inadequate covering of the transplanted bone with surrounding tissue. The aim of this study was to assess the exact bone volume after secondary alveolar bone grafting over a period of two years using a navigation system based on computed tomography (CT). We examined 20 patients with complete unilateral cleft lip and palate (UCLP) who had been treated by secondary bone grafting during late mixed dentition. CT scans of the upper jaw were taken immediately preoperatively, and 1 and 2 years postoperatively. The cleft defects and the bony bridges were marked on the monitor. The software of the navigation system created three-dimensional models showing the amount and site of bone resorption. The mean bone loss after one and two years was 51% and 52%, respectively. There was a significant correlation between the size of the cleft and the success of the alveolar bone grafting (p=0.01). When the teeth adjacent to the cleft were missing the amount of bone lost was 95% after the first year. There was also significant bone loss in the buccopalatine direction. Three-dimensional reconstruction of the bony bridges with a navigation system accurately shows the amount of bone within the cleft site. This method is definitely superior to conventional two-dimensional orthopantomography.

Assessment of bone formation in a porcine mandibular distraction wound by computed tomography

The purpose of this study was to document the progression of bone formation in a porcine mandibular distraction wound, at various distraction rates and fixation times, using three-dimensional computed tomography. Bone formation was assessed in a 0-day latency model (n=24 minipigs) using distraction rates of 1, 2, or 4 mm/day to create a 12 mm distraction gap. Animals were sacrificed at 0, 8, 16, or 24 days fixation. For experimental and control sides, three-dimensional data from computed tomographic scans were used to calculate the percent bone volume in the regions of interest. Standardized plain radiographs were used to evaluate bone formation with a semiquantitative scale: 0, 1, 2, 3. Mean percent bone volume and radiographic bone fill scores (pooled sample) increased with fixation time from 16.8% and 0.17 at 0 days, to 64% and 2.0 at 24 days fixation. Mandibles distracted at 1mm/day had higher CT values and bone fill scores than mandibles distracted at 2 or 4 mm/day. At 24 days fixation, the maximum percent bone volume (64%--1 mm/day; 24 days fixation) remained below control values (81.3%). The results of this study indicate that despite high bone fill scores on plain radiographs, the highest percent CT bone volume achieved in this model was 64%.

Effects of sinus lifting on voice quality. A prospective study and risk assessment

A variety of potential complications associated with sinus lift surgery have been reported in the literature. However, potential alterations of voice quality following sinus elevation have so far not been mentioned or evaluated scientifically. For the majority of patients, slight changes of the voice pattern are of no importance. However, for voice professionals, whose voices have become part of their distinctive profession or trademark, minimal changes may have dramatic consequences. This specific group of patients, such as speakers, actors and singers, depend on the particular quality and timbre of their voice for their livelihood. Consequently, the purpose of this study was to assess the effects of sinus lifting on voice quality in the above patient group. In a collaborative interdisciplinary effort, the Departments of Oral Surgery and Otorhinolaryngology, Section of Phoniatrics and Logopedics, thoroughly evaluated a series of voice parameters of four patients undergoing sinus lifting pre- and postoperatively. The parameters analyzed included pitch, dynamic range, sound pressure level, percent jitter, percent shimmer and noise-to-harmonics ratio with special emphasis on formant analysis. No changes were detected in any of the commonly evaluated parameters. These were rated subjectively by patients and their friends or relatives and objectively with instrumental tools under isolated phoniatric lab conditions. In conclusion, sinus lift surgery appears to be a safe, predictable evidence-based method for regenerating the highly atrophic posterior maxilla, which does not jeopardize the individual characteristic voice pattern of high-profile patients critically dependent on their voices for their livelihood.

Assessment of the accuracy of computed tomography for measurement of normal equine pituitary glands

OBJECTIVE

To describe the anatomic features of the pituitary gland region in horses via computed tomography (CT) and determine the accuracy of CT for estimating normal equine pituitary gland dimensions.

ANIMALS

25 adult horses with no clinical signs of pituitary disease.

PROCEDURE

Transverse CT images and gross transverse tissue sections were compared in 2 horses. Contrast-enhanced CT of the pituitary gland region was performed postmortem in 23 horses with 4 slice thickness and interval settings (10-mm contiguous or overlapping slices and 4-mm contiguous or overlapping slices). Gross and CT estimates of pituitary gland dimensions were compared via ANOVA. Accuracy of CT estimates was calculated with gross pituitary gland measurements as the known value.

RESULTS

Pituitary glands were located between the temporomandibular joints and had contrast enhancement. Mean gross dimensions were length, 2.11 cm; width, 2.16 cm; height, 0.98 cm; and volume, 2.66 cm3. Gross measurements and CT estimates of pituitary gland length from 10-mm contiguous and overlapping slices did not differ. Gross measurements and CT estimates of pituitary gland width from 4-mm contiguous and overlapping slices did not differ. Estimates of height and volume from all CT techniques differed from gross measurements. Accuracies for CT estimates were length, 88 to 99%; width, 81 to 92%; height, 58 to 71%; and volume, 43 to 55%.

CONCLUSIONS AND CLINICAL RELEVANCE

Accuracy of estimates of pituitary gland dimension in horses varied with CT scanning technique; via CT estimates of length and width of glands were more accurate than estimates of height or volume.

Biomechanical comparison of cervical spine interbody fusion cages

STUDY DESIGN

An in vitro biomechanical study of cervical spine interbody fusion cages using a sheep model was conducted.

OBJECTIVES

To evaluate the biomechanical effects of cervical spine interbody fusion cages, and to compare three different cage design groups.

SUMMARY AND BACKGROUND DATA

Recently, there has been a rapid increase in the use of cervical spine interbody fusion cages as an adjunct to spondylodesis. These cages can be classified into three design groups: screw, box, or cylinder designs. Although several comparative biomechanical studies of lumbar interbody fusion cages are available, biomechanical data for cervical spine constructs are lacking. Additionally, only limited data are available concerning comparative evaluation of different cage designs.

METHODS

In this study, 80 sheep cervical spines (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method using a nonconstrained testing apparatus. Three-dimensional displacement was measured using an optical measurement system (Qualysis). Complete discectomy (C3-C4) was performed. Cervical spine interbody fusion cages were implanted according to manufacturers' information. Eight spines in each of the the following groups were tested: intact, autologous iliac bone graft, two titanium screws (Novus CTTi; Sofamor Danek, Koln, Germany), two titanium screws (BAK-C 8 mm; Sulzer Orthopedics, Baar, Switzerland), one titanium screw (BAK-C 12 mm; Sulzer Orthopedics), carbon box (Novus CSRC; Sofamor Danek), titanium box (Syncage; Synthes, Bochum, Germany), titanium mesh cylinder (Harms; DePuy Acromed, Sulzbach, Germany), titanium cylinder (MSD; Ulrich, Ulm, Germany), and titanium cylinder (Kaden; BiometMerck, Berlin, Germany). The mean apparent stiffness values were calculated from the corresponding load-displacement curves. Additionally, cage volume and volume-related stiffness was determined.

RESULTS

After cervical spine interbody fusion cage implantation, flexion stiffness increased, as compared with that of the intact motion segment. On the contrary, rotation stiffness decreased after implantation of a cervical spine interbody fusion cage, except for the Novus CSRC, Syncage, and Kaden-Cage. If two screws were inserted (Novus CTTi and BAK-C 8 mm), there was no significant difference in flexion stiffness between screw and cylinder design groups. If one screw was inserted (BAK-C 12 mm), flexion stiffness was higher for cylinder designs (P < 0.05). Extension and bending stiffness were always higher with cylinder designs (P < 0.05). Volume-related stiffness for flexion extension and bending was highest for the Harms cage (P < 0.05). There was no difference for rotation volume-related stiffness between Harms and Syncage.

CONCLUSIONS

The biomechanical results indicate that design variations in screw and cylinder design groups are of little importance. In this study, however, cages with a cylinder design were able to control extension and bending more effectively than cages with a screw design.

Glycosaminoglycans in peri-implant sulcus fluid from implants placed in sinus-inlay bone grafts

Glycosaminoglycans (GAG) present in peri-implant sulcus fluid (PISF) were used as an indicator of the metabolic activity in the supporting tissues of implants placed in maxillary bone or maxillary bone and bone grafts together. The study included 16 patients who received implants (Brånemark system(R)) and sinus-inlay bone grafts. In 12 of these patients, the implants were placed in either maxillary bone alone or maxillary bone and sinus-inlay bone grafts in combination. Altogether the patients received a total of 102 implants, of which 73 implants were placed in bone grafts and 29 implants in maxillary bone alone. Samples of PISF were tested at 2-8 days and at 6 months after abutment connection. Levels of the GAG's chondroitin-4-sulphate (C4S) and hyaluronan (HA) were assessed using cellulose acetate electrophoresis and densitometric scanning of Alcian blue-stained strips against known GAG standards. The C4S was used as a bone metabolic marker, and HA was used to reflect the progress of soft tissue healing. Comparing grafted and non-grafted regions, there was no significant difference in either C4S levels or HA levels during the first 8 days or at the 6 months period. The levels of HA from the first week collection did not differ significantly from the HA level after 6 months in either type of bone. However, the level of C4S was significantly lower after 6 months than during the first week, in both maxillary and grafted bone but consistent with a normal metabolic turnover. C4S can therefore be used as an indicator of the progressive healing of bone adjacent to implants.

Differences in static cortical bone remodeling parameters in human mandible and iliac crest

Knowledge of the baseline turnover characteristics, and of possible general and local factors influencing alveolar bone responses, is particularly important in the planning of oral rehabilitation. The conventional tool used to obtain information on bone turnover is the iliac crest biopsy, but it is not clear whether it mirrors the situation involving the jaws. The aim of this study was to compare static bone remodeling parameters in the mandible and in the iliac crest to obtain baseline values for the mandible and to test the hypothesis of site specificity of bone remodeling. Bone specimens were obtained from 50 subjects (mean age 64 +/- 17) at autopsy. Three sites were sampled: iliac crest; jaw angle; and foramen mentalis area. In addition, occlusal status was recorded. On undecalcified thin sections, cortical porosity (Ct.Po), eroded sites (ESi), formative sites (FSi), osteonal diameter (On.Dm), Haversian canal diameter (H.Ca.Dm), and wall width (W.Wi) were measured. Ct.Po in the jaw angle and in the foramen mentalis area was lower (48% and 50%, respectively) than in the iliac crest, as was ESi and FSi (80% in the jaw angle and 74% in the foramen mentalis area). In the foramen mentalis area, Ct.Po was greater in subjects with occlusion. On.Dm, H.Ca.Dm, and W.Wi were significantly larger and mutually correlated within the mandible, whereas no correlation was found between mandibular sites and iliac crest. Static cortical bone remodeling parameters are different in the mandible and the iliac crest, thus confirming the hypothesis of site specificity of bone remodeling. Within the mandible, the parameters were correlated, whereas there was no correlation between the mandible and the iliac crest. This could be ascribed to the different functional demands to the mandible and the iliac crest, which was also reflected in the observed influence of functional occlusion on bone remodeling in the mandible. It can thus be concluded that bone reaction to dental intervention is more dependent on the local environment than on general bone turnover as reflected by the iliac crest.