Relation between insertion torque and bone–implant contact percentage: an artificial bone study

Objectives

The purpose of this study was to determine the correlation between the peak insertion torque value (ITV) of a dental implant and the bone–implant contact percentage (BIC%).

Material and methods

Dental implants were inserted into specimens comprising a 2-mm-thick artificial cortical shell representing cortical bone and artificial foam bone representing cancellous bone with four densities (groups 1 to 4—0.32, 0.20, 0.16, and 0.12?g/cm³). Each specimen with an inserted implant was subjected to micro-computed tomography (micro-CT) scanning, from which the 3D BIC% values were calculated. Pearson’s correlation coefficients (r) between the ITV and BIC% were calculated.

Results

The ITVs in groups 1 to 4 were 56.2?±?4.6 (mean±standard deviation), 45.6?±?0.9, 43.3?±?4.3, and 38.5?±?3.4?N?cm, respectively, and the corresponding BIC% values were 41.5?±?0.5%, 39.0?±?1.0%, 30.8?±?1.1%, and 26.2?±?1.6%. Pearson’s correlation coefficient between the ITV and BIC% was r?=?0.797 (P?<?0.0001).

Conclusion

The initial implant stability, quantified as the ITV, was strongly positively correlated with the 3D BIC% obtained from micro-CT images.

Clinical relevance

The ITV of a dental implant can be used to predict the initial BIC%; this information may provide the clinician with important information on the optimal loading time.     

Effect of vitamin?C on bone formation in the expanded inter-premaxillary suture. Early bone changes

Aim

The aim of this experimental study was to histomorphometrically evaluate the effects of vitamin?C administration on bone formation in response to expansion of the rat inter-premaxillary suture.

Materials and methods

A total of 30 50- to 60-day old Wistar male rats were divided into three groups of equal number. The inter-premaxillary suture in each animal was expanded with a 0.49?N force applied to the upper incisors. At 24?h after appliance placement, control animals received saline solution (group?I) and two groups were given a single dose of vitamin?C using two different methods [locally into the suture (group?II) and systemically via intramuscular injection (group?III)]. The area of new bone (??m²), the perimeter around the new bone (??m), Feret??s diameter (??m), and the percentage of new bone to non-ossified tissue (%) were measured and compared. Kruskal-Wallis and Tukey tests were used for statistical evaluation at the p<0.05 level.

Results

We observed significant differences among the groups in all histomorphometric parameters. New bone area, bone perimeter, Feret??s diameter, and percentage of new bone dimensions were significantly higher in group?III than the others (p<0.001). Histomorphometric measurements of bone architecture revealed that this improved in the group administered with vitamin?C systemically, while local injection revealed significantly less bone growth than the control group.

Conclusion

The systemic administration of vitamin?C during the early stages of inter-premaxillary suture expansion may stimulate bone growth. However, local injection of this antioxidant into an orthopedically-expanded suture area has negative effects on bone formation.     

Is there a relation between local bone quality as assessed on panoramic radiographs and alveolar bone level?

The aim was to explore the relation between radiographic bone quality on panoramic radiographs and relative alveolar bone level. Digital panoramic radiographs of 94 female patients were analysed (mean age, 44.5; range, 35-74). Radiographic density of the alveolar bone in the premolar region was determined using Agfa Musica software. Alveolar bone level and bone quality index (BQI) were also assessed. Relationships between bone density and BQI on one hand and the relative loss of alveolar bone level on the other were assessed. Mandibular bone density and loss of alveolar bone level were weakly but significantly negatively correlated for the lower premolar area (r = -.27). The BQI did not show a statistically significant relation to alveolar bone level. Radiographic mandibular bone density on panoramic radiographs shows a weak but significant relation to alveolar bone level, with more periodontal breakdown for less dense alveolar bone.     

Inhibitory effects of a collagen–mineral complex on deterioration of bone mass and bone quality in ovariectomized mice

Objectives

To characterize the osteoporosis-preventive effects of a novel material consisting of a complex of type 1 collagen and hydroxyapatite (CCH) in osteoporosis model mice.

Methods

Ten-week-old ovariectomized (OVX) ICR mice were used. The five study groups comprised a sham group, OVX control group, calcium carbonate (CaCO₃) group, vitamin K₂ [menaquinone 7 (MK7)] group, and CHH group (n = 10 each). The CaCO₃ and CHH groups were fed a special diet containing 2 % of the respective substance, whereas the MK7 group received a special diet containing 0.5 % MK7. After maintenance of the animals under these conditions for 8 weeks, their femurs were removed and blood samples were collected. The bone mineral densities (BMDs) of the distal femoral epiphysis were analyzed by peripheral quantitative computed tomography. Three-dimensional images were rendered with micro-focus computed tomography, and the trabecular structures were determined.

Results

The significantly lower BMDs in the epiphyseal and diaphyseal regions of the OVX control group femurs compared with the sham group femurs were clear osteoporotic signs. The trabecular structure analyses revealed 12 parameters that were significantly lower in the OVX control group compared with the sham group. No distinct changes in the BMD or trabecular structure were observed in the CaCO₃ group. Significant improvements in the BMD in the MK7 group were limited to three parameters, whereas 11 trabecular structure parameters were significantly improved. The CHH group showed significant improvements in seven BMD parameters and seven trabecular structure parameters.

Conclusions

CHH improves trabecular structure and BMD in a well-balanced manner.     

Early bone resorption of free microvascular reanastomized bone grafts for mandibular reconstruction – A comparison of iliac crest and fibula grafts

ObjectivesPatients with continuous bone defects of the mandible after ablative tumor surgery need bony reconstruction for proper function and aesthetics. Free microvascular reanastomized bone grafts provide a clinically proven option for such patients, yet the optimal source of donor tissue has not yet been established. The aim of this study was to evaluate and compare the bone volume stability of vascularized bone grafts, particularly in the early highly resorptive phase, from the iliac crest (DCIA) and the fibula and to assess the implantologic rehabilitations.Materials and methodsThirty-six patients with mandibular continuity defects due to tumor resection were reconstructed by the use of vascularized bone grafts; 21 patients received DCIA flaps and 15 patients received a composite free fibular flap, depending on the size and location of the defect. Bone resorption was assessed using digital panographs. Radiographs were taken immediately after bone reconstruction, 6 months postoperatively, prior to implant surgery, and at prosthetic loading.ResultsAfter a mean observation period of 6 months, vertical bone resorption was 6.79% for the patients of the iliac crest group (DCIA), 10.20% after 11 months, and 12.58% after 17 months. Fibular grafts showed a bone resorption of 5.30% after a mean observation time of 6 months, 8.26% after 11 months, and 16.95% after 17 months. Eighteen patients received 71 implants for implant-retained dental reconstructions.ConclusionsMicrovascular reanastomized bone grafts represent a reliable treatment option for reconstruction in cases of large defects of the mandible, with low graft resorption in the early healing phase. Additionally, the compared grafts provide sufficient bone volume to permit implant rehabilitation.     

Is there evidence that barrier membranes prevent bone resorption in autologous bone grafts during the healing period? A systematic review

INTRODUCTION: Autologous bone is considered the "reference standard" for bone-grafting procedures. A barrier membrane covering an autologous bone graft (guided bone regeneration [GBR]) is expected to prevent graft resorption. Good clinical results have been reported for GBR, although potential complications and relatively high costs have been implicated as disadvantages. However, most studies on the subject have been uncontrolled. PURPOSE: The aim of this systematic review was to evaluate the available evidence that barrier membranes prevent bone resorption in autologous onlay bone grafts. The primary outcome measure was bone resorption. RESULTS: The search yielded 182 articles. Two observers independently appraised 32 relevant studies methodologically, yielding 14 controlled studies. The articles included human and animal experiments with heterogenous objectives and outcome variables. Although most authors concluded that they had found evidence for the protective effect of barrier membrane on bone resorption in bone grafts, this systematic review reveals that the available evidence is too weak to support this. Most included studies were animal experiments; thus, extrapolation to the human situation is difficult. Most studies also had a small number of test sites, and sample size justification was generally not reported. Furthermore, ambiguity and lack of significance were found in many studies, along with additional limitations such as implantation site, nonsuitable designs, and varying outcome measures. CONCLUSION: Based on a systematic review of the literature, further evidence is needed to determine whether barrier membranes prevent bone resorption in autologous onlay bone grafts.     

Vertical bone augmentation: where are we now?

As the prevalence of implants has increased, so has the challenge to augment the remaining osseous structure to house those implants. The biggest surgical challenge clinically is to augment lost bone vertically. The purpose of this article is to review currently available techniques for achieving greater vertical dimension before implant placement. A literature search was conducted using MEDLINE to find all articles published between 1970 and 2004 regarding vertical bone augmentation. Following the literature search, all articles were reviewed and summarized in this review article of vertical bone augmentation. The results of the research showed that guided-bone regeneration, monocortical onlay grafting, and distraction osteogenesis have the potential to be applied to augment deficient areas vertically. The expectations of dimensional gain and bone quality are unique to each technique, as well as the potential complications. Distraction osteogenesis has had the greatest potential for vertical gain, while guided-bone regeneration and monocortical onlay grafting achieve similar results. The choice of procedure is to be based upon the patient's existing anatomy, degree of vertical deficiency, and willingness to participate in treatment.     

(iii) Ewing’s sarcoma of bone

Ewing’s sarcoma is a primitive malignant bone tumour consisting of small, blue, round malignant cells that may show varying degrees of neural differentiation. It accounts for approximately 5% of all malignant bone tumours and arises most frequently in children or adolescents. Despite significant progress with the use of intensive multiagent chemotherapy and local control measures (survival rates have increased from 10–15% to 65–70% in the last 40 years), a significant proportion of patients still die of disease progression. Clinical and biological prognostic factors should be used to guide the therapeutic choices for each patient. The treatment of Ewing’s sarcoma of bone is currently based on combined therapy with neoadjuvant chemotherapy, radiation therapy and surgical resection of the primary tumour. Survival in primary metastatic Ewing’s sarcoma is poor (less than 30%) and new therapies are needed for these patients.     

Donor site morbidity after reconstruction of alveolar bone defects with mandibular symphyseal bone grafts in cleft patients—111 consecutive patients

The aim of this study was to assess the objective and subjective morbidity after reconstruction of alveolar bone defects with mandibular symphyseal bone grafts in patients with cleft lip and palate. One hundred and eleven patients born between 1995 and 1999, who had undergone chin bone harvesting for alveolar cleft reconstruction in the period from 2000 through 2011, were included. A survey of medical records was conducted. Subjective morbidity after reconstruction was assessed using a questionnaire. Medical records revealed few postoperative incidents; 5.6% reported persistent sensory disturbances in the donor area. Postoperative pain averaged 3.6 ± 2.1 (scale 0–10). The overall satisfaction with the surgical result was 8.7 ± 1.7 (scale 0–10). This study revealed that chin bone harvesting for reconstruction of alveolar defects in patients with cleft lip and palate is a safe and predictable procedure, highly appreciated by the patients, and characterized by only minor postoperative incidents. Patients must be informed of the risk of sensory disturbances in the donor area.     

Is miniscrew primary stability influenced by bone density?

Primary stability is absence of mobility in the bone bed after mini-implant placement and depends on bone quality among other factors. Bone quality is a subjective term frequently considered as bone density. The aim of this preliminary study was to evaluate bone density in two bovine pelvic regions and verify the primary stability of miniscrews inserted into them. Forty bone blocks were extracted from bovine pelvic bones, 20 from iliac and 20 from pubic bone, all of them containing cortical bone about 1 mm thick. Half of the sections extracted from each bone were designated for histological evaluation of bone density (trabecular bone area - TBA) and the other half for bone mineral density (BMD) evaluation by means of central dual-energy X-ray absorptiometry (DEXA). Then, twenty self-drilling miniscrews (INP?, S?o Paulo, Brazil) 1.4 mm in diameter and 6 mm long were inserted into the bone blocks used for BMD evaluation. Peak implant insertion torque (IT) and pull-out strength (PS) were used for primary stability evaluation. It was found that iliac and pubic bones present different bone densities, iliac bone being less dense considering BMD and TBA values (P > 0.05). However, the miniscrew primary stability was not different when varying the bone type (P < 0.05). IT and PS were not influenced by these differences in bone density when cortical thickness was about 1 mm thick.     

Guided bone regeneration in pig calvarial bone defects using autologous mesenchymal stem/progenitor cells – A comparison of different tissue sources

Due to donor side morbidity and the absence of osteogenic properties in bone substitutes, there is a growing need for an alternative to traditional bone grafting within the scope of tissue engineering. This animal study was conducted to compare the in vivo osteogenic potential of adipose-derived (AD), periosteum-derived (PD) and bone marrow-derived (BM) mesenchymal stem/progenitor cells (MSC). Autologous mesenchymal stem/progenitor cells of named tissue origin were induced into osteogenic differentiation following in vitro cell expansion. Ex vivo cultivated cells were seeded on a collagen scaffold and subsequently added to freshly created monocortical calvarial bone defects in 21 domestic pigs. Pure collagen scaffold served as a control defect. The animals were sacrificed at specific time points and de novo bone formation was quantitatively analyzed by histomorphometry. Bone volume/total defect volume (BV/TV) and the mineralization rate of newly formed bone were compared among the groups. In the early stages of wound healing, up to 30 days, the test defects did not show better bone regeneration than those in the control defect, but the bone healing process in the test defects was accelerated in the later stage compared to those in the control defect. All the test defects showed complete osseous healing after 90 days compared to those in the control defect. During the observation period, no significant differences in BV/TV and mineralization of newly formed bone among the test defects were observed. Irrespective of the tissue sources of MSC, the speed and pattern of osseous healing after cell transplantations into monocortical bone defects were comparable. Our results indicate that the efficiency of autologous AD-MSC, PD-MSC and BM-MSC transplantation following ex vivo cell expansion is not significantly different for the guided regeneration of bone defects.     

Does mandibular edentulous bone height affect prosthetic treatment success?

Objectives

The aim of this study is to determine whether mandibular bone height affects patients’ ratings of satisfaction and function with mandibular 2-implant overdentures (IODs) and conventional dentures (CDs).

Methods

214 edentulous elders were randomly allocated into 2 groups and treated with maxillary CDs and either mandibular CDs or IODs. Classifications of mandibular bone height were carried out on panoramic radiographs using 4 published methods. At baseline and 6 months after delivery, all participants rated their satisfaction with their prostheses using the McGill Denture Satisfaction Instrument. Independent t-tests and a linear multivariable regression model were used for statistical analyses.

Results

Mandibular bone height has no effect on patients’ ratings of general satisfaction, nor on ratings of ability to chew, stability, comfort, aesthetics and ability to speak at 6 months (p > 0.05, linear regression). There were significant between treatment differences in ratings of general satisfaction, comfort, stability and ability to chew from all mandibular bone height categories, with higher ratings assigned to IODs (p < 0.01, t-tests). Linear regression analyses confirmed that, for general satisfaction, as well as ability to chew, stability, comfort, aesthetics and ability to speak, treatment with IODs contributes to higher satisfaction ratings (p < 0.001), while mandibular bone height does not.

Conclusions

The evidence demonstrates that mandibular bone height has no effect on patients’ satisfaction with the function, chewing ability and comfort of their prostheses. Furthermore, no matter how much mandibular bone, these results suggest that edentulous elders will benefit more from mandibular IODs than from CDs.     

Is trabecular bone related to primary stability of miniscrews?

Objective: To compare the primary stability of miniscrews inserted into bone blocks of different bone mineral densities (BMDs) with and without cortical bone, and investigate whether some trabecular properties could influence primary stability.Materials and Methods:Fifty-two bone blocks were extracted from fresh bovine pelvic bone. Four groups were created based on bone type (iliac or pubic region) and presence or absence of cortical bone. Specimens were micro-computed tomography imaged to evaluate trabecular thickness, trabecular number, trabecular separation, bone volume density (BV/TV), BMD, and cortical thickness. Miniscrews 1.4 mm in diameter and 6 mm long were inserted into the bone blocks, and primary stability was evaluated by insertion torque (IT), mini-implant mobility (PTV), and pull-out strength (PS).Results:Intergroup comparison showed lower levels of primary stability when the BMD of trabecular bone was lower and in the absence of cortical bone (P ≤ .05). The Pearson correlation test showed correlation between trabecular number, trabecular thickness, BV/TV, trabecular BMD, total BMD, and IT, PTV, and PS. There was correlation between cortical thickness and IT and PS (P ≤ .05).Conclusion:Cancellous bone plays an important role in primary stability of mini-implants in the presence or absence of cortical bone.