Reconstruction of the edentulous mandible with fresh frozen bone grafts and implants: a 4-year report of a prospective clinical study.

Allogen bones from tissue bank are often used in dentistry although the data analyzing the long-term success in mandible are scarce. This study evaluated by computed tomography scans (CTS) the bone resorption around the implants installed on fresh frozen bone (FFB) previously grafted, after 4 years of occlusal rehabilitation. Six subjects were grafted with blocks in posterior mandible using FFB. After 6 months, 27 implants were placed and after further 4 months the prostheses were delivered. Following 4 years of the final rehabilitation procedures, another CTS was done in order to measure the resorption in periimplant bone crest at the proximal implant surfaces. It was observed a 100 % survival rate of the implants after 4 years of the fixture installation. The marginal bone resorption after 48 months was 2.82 ± 1.63 mm and no statistical significant difference was observed along the region where the implants were fixed when compared with the interimplantar space. In addition there was no significant correlation regarding the length of the implant used and the amount of marginal bone resorption. The conclusion is that grafted areas with FFB are suitable to implant installation in the posterior mandible.

Evaluation of the effect of tumor necrosis factor-alpha gene polymorphism on the risk of peri-implantitis: a case-control study.

PURPOSE: Tumor necrosis factor-alpha (TNFalpha) is a proinflammatory cytokine, which promotes bone resorption and mediates the inflammatory response to infection. Because implant failures appear to cluster in subsets of individuals, this phenomenon may be related to gene polymorphisms. Therefore, the aim of this study was to investigate the relationship between a specific polymorphism in the TNFalpha gene (allele 2 of TNFalpha(-308)) and peri-implantitis. MATERIALS AND METHODS: This case-control study included Caucasian nonsmoking Brazilian patients with implant-supported restorations. Oral epithelial cells were taken from patients with and without peri-implantitis to evaluate the frequencies of different alleles of the TNFalpha(-308) gene by polymerase chain reaction. RESULTS: Ninety patients (49 with peri-implantitis and 41 with healthy implants) were enrolled in this study. Polymorphism in allele 2 of TNFalpha(-308) was not associated with an increased risk for peri-implantitis (P = .8171), although 14.63% of the subjects in the control group carried allele 2 and 19.39% in the peri-implantitis group carried allele 2 (chi-squared = 0.708; P = .5202). CONCLUSION: Polymorphism of the TNFalpha(-308) gene was not associated with an increased risk of peri-implantitis in the population evaluated in this study.

A finite element analysis of two different dental implants: stress distribution in the prosthesis, abutment, implant, and supporting bone.

This study evaluates the influence of 2 commercially available dental implant systems on stress distribution in the prosthesis, abutment, implant, and supporting alveolar bone under simulated occlusal forces, employing a finite element analysis. The implants and abutments evaluated consisted of a stepped cylinder implant connected to a screw-retained, internal, hexagonal abutment (system 1) and a conical implant connected to a solid, internal, conical abutment (system 2). A porcelain-covered, silver-palladium alloy was used as a crown. In each case, a simulated, 100-N vertical load was applied to the buccal cusp. A finite element model was created based on the physical properties of each component, and the values of the von Mises stresses generated in the prosthesis, abutment, implant, and supporting alveolar bone were calculated. In the prostheses, the maximum von Mises stresses were concentrated at the points of load application in both systems, and they were greater in system 1 (148 N/mm2) than in system 2 (55 N/mm2). Stress was greater on the abutment of system 2 than of system 1 on both the buccal (342 N/mm2 x 294 N/mm2) and lingual (294 N/mm2 x 148 N/ mm2) faces. Stress in the cortical, alveolar bone crest was greater in system 1 than in system 2 (buccal: 99.5 N/mm2 x 55 N/mm2, lingual: 55 N/mm2 x 24.5 N/mm2, respectively). Within the limits of this investigation, the stepped cylinder implant connected to a screw-retained, internal hexagonal abutment produces greater stresses on the alveolar bone and prosthesis and lower stresses on the abutment complex. In contrast, the conical implant connected to a solid, internal, conical abutment furnishes lower stresses on the alveolar bone and prosthesis and greater stresses on the abutment.

Effect of systemic intermittent administration of human parathyroid hormone (rhPTH[1-34]) on the resistance to reverse torque in rabbit tibiae.

The aim of this study was to evaluate the effect of intermittent administration of human parathyroid hormone [rhPTH (1-34)] on the removal torque of implants placed in rabbit tibiae. Twenty male New Zealand rabbits were submitted to implant surgery. Each animal received one machined screw-type implant (3.75 mm diameter x 8 mm length) in the proximal metaphysis of the right tibia. The rabbits were then divided into 2 groups: the test group (n = 10) received 6 microg/kg of rhPTH (1-34) subcutaneously in the dorsal region 3 days a week, and the control group (n = 10) received placebo. Removal torque was performed at 28 and 56 days after implant placement for both groups. The mean removal torque values at 28 days were 37.0 +/- 4.36 Ncm and 47.4 +/- 6.77 Ncm for control and test groups respectively (P < .05). At 56 days the reverse torque was 45.8 +/- 3.96 Ncm for the control group and 55.8 +/- 2.86 Ncm for the test group, indicating that the removal torque was significantly higher in the test groups (P < .05). These results demonstrated that intermittent treatment with rhPTH (1-34) enhanced the removal torque of implants in rabbit tibiae.

Peri-implant bone loss around posterior mandible dental implants placed after distraction osteogenesis: preliminary findings.

BACKGROUND: The present study evaluates implant survival and peri-implant bone loss around posterior mandible dental implants placed at sites of distraction osteogenesis. METHODS: On removal of the distraction devices, 34 dental implants were inserted into 14 posterior mandible sites in 10 healthy, non-smoking female patients. Prosthetic treatment was performed 4 months after implant placement using fixed implant prostheses. After 6 to 16.5 months, periapical radiographs were taken and evaluated for peri-implant bone loss and radiolucency. The distance between the implant margin and the first visible bone-implant contact was measured on the mesial and distal aspects of the implants using imaging software. Radiographic dimensional distortion was corrected as a function of the known true dimension of the implant. RESULTS: Of the 34 implants placed, two (5.9%) failed to integrate at reentry surgery. Both were replaced and restored during the course of the study so that a total of 34 implants was followed for 12.1 +/- 3.8 months post-restoration and 16.1 +/- 3.8 months post-insertion. Mean loss of marginal bone height was 2.6 +/- 1.0 mm. During the follow-up period, radiolucent lines along the implant surface were absent. CONCLUSIONS: The mean peri-implant bone loss in areas of alveolar bone distraction was 1.9 mm/year. A high implant survival rate was observed.

Effect of platelet-rich plasma in alveolar distraction osteogenesis: a controlled clinical trial.

We have evaluated the effect of the use of platelet-rich plasma in alveolar distraction osteogenesis. Fourteen patients who were partly edentulous in the anterior premaxilla region were selected and randomised into two groups (n=7 in each group). Those in the experimental group were give platelet-rich plasma at the time of distraction, and the control group had only distraction. Selected cases had defects in the alveolar ridge of more than 3mm, and a minimal bone height of 7 mm from the alveolar ridge crest to important anatomical structures. The plaque index and gingival index were recorded on days 3, 7, 14, 21, 28, 45, 60, 75, 90, and 105 postoperatively. There was a strong negative correlation between the gingival index and augmentation of bone, and a strong positive correlation between the mean gingival index and loss of bone from the transported segment. The addition of platelet-rich plasma had a protective effect on the mucosa around the distractor, which decreased the potential for complications.

Posterior mandibular alveolar distraction osteogenesis utilizing an extraosseous distractor: a prospective study.

BACKGROUND: The aim of this clinical study was to evaluate bone elongation and the effectiveness of distraction osteogenesis when utilizing an extraosseous distractor to treat cases of atrophic posterior mandible. METHODS: Fourteen surgical sites were evaluated in 10 healthy, non-smoking, female patients, with varying degrees of atrophic posterior mandible, who underwent surgery by alveolar bone distraction. The patients presented between 6 and 10 mm above the mandibular, inferior alveolar nerve. Panoramic radiographs were taken before surgery and at the beginning and end of the consolidation period. The extraosseous distractor was fixed to both the basal and the osteotomized bone. After a 7-day latency period, the patients rotated the distractor rod three times a day for 3 to 10 days (1 mm per day). The mobile segment was held in place for 8 to 12 weeks for bone consolidation. RESULTS: The results revealed a distraction range of 2.32 to 8.11 mm (mean distraction +/- standard deviation, 5.12 +/- 1.67 mm), which was less than the real, measured distance between the upper and lower miniplates of the distractor (5.58 +/- 1.62 mm). The bone segments showed between 0.03 and 2.53 mm (mean, 0.88 +/- 0.59 mm) resorption above the upper miniplate. The efficacy of the extraosseous distractor was calculated as between 30.41% and 94.58% (73.45% +/- 20.32%). CONCLUSIONS: Bone regeneration was obtained in all cases; however, when planning alveolar bone distraction using the extraosseous distractor, greater distraction should be performed to compensate for the inclination of the distractor rod and possible bone loss. This adjustment should increase the efficacy of distraction osteogenesis.

Clinical application of stereolithographic surgical guides for implant placement: preliminary results.

BACKGROUND: The success of implant-supported restorations requires detailed treatment planning, which includes the construction of a surgical guide. Recently, computer-aided rapid prototyping has been developed to construct surgical guides in an attempt to improve the precision of implant placement. The aim of the present study was to evaluate the match between the positions and axes of the planned and placed implants when a stereolithographic surgical guide is employed. METHODS: Six surgical guides used in four patients (three women, one man; age from 23 to 65 years old) were included in the study and 21 implants were placed. A radiographic template was fabricated and computer-assisted tomography (CT) was performed. The virtual implants were placed in the resulting 3-dimensional image. Using a stereolithographic machine, liquid polymer was injected and laser-cured according to the CT image data with the planned implants, generating three surgical guides, with increasing tube diameters corresponding to each twist drill diameter (2.2, 3.2, and 4.0 mm), for each surgical area. During the implant operation, the surgical guide was placed on the jawbone and/or the teeth. After surgery, a new CT scan was taken. Software was used to fuse the images of planned and placed implants, and the locations and axes were compared. RESULTS: On average, the match between the planned and the placed implant axes was within 7.25 degrees +/- 2.67 degrees ; the differences in distance between the planned and placed positions at the implant shoulder were 1.45 +/- 1.42 mm, and 2.99 +/- 1.77 mm at the implant apex. In all patients, a greater distance was found between the planned and placed positions at the implant apex than at the implant head. CONCLUSIONS: Clinical data suggest that computer-aided rapid prototyping of surgical guides may be useful in implant placement. However, the technique requires improvement to provide better stability of the guide during the surgery, in cases of unilateral bone-supported and non-tooth-supported guides. Further clinical studies, using greater number of patients, are necessary to evaluate the real impact of the stereolithographic surgical guide on implant therapy.

Effect of tumor necrosis factor-alpha gene polymorphism on peri-implant bone loss following prosthetic reconstruction.

PURPOSE: The present study investigates the association between a specific polymorphism in the tumor necrosis factor (TNF)-alpha gene, consisting of allele 2 of TNF-alpha-308, and peri-implant bone loss following prosthetic reconstruction. MATERIALS AND METHODS: This case-control study included 36 patients (20 women, 16 men; mean age 46 years) who had used implant-supported prostheses for a minimum of 6 months and a maximum of 31 months. The patients were nonsmoking, white Caucasian Brazilians, in good general health, and were not receiving medication. In the case group, patients exhibited 1 or more implants with a diagnosis of peri-implant bone loss following prosthetic reconstruction; control patients had 1 or more healthy implants. RESULTS: Polymorphism in the TNF-alpha gene, allele 2 of TNF-alpha, was not associated with an increased risk for peri-implant bone loss following prosthetic reconstruction (P=0.19; chi2=1.71; df=1), although 21.1% of the subjects carried allele in the control group 2, and 41.2% carried allele 2 in the case group. CONCLUSIONS: Polymorphism in allele 2 of the TNF-alpha-308 gene is not associated with an increased risk for peri-implant bone loss following prosthetic reconstruction. However, further studies based on a greater number of patients are necessary.

Avaliação da clorexidina a 2% no controle bacteriano na região interna de implantes de hexágono externo / Assessment of the chlorhexidin (2%) for the bacterial control in the internal área of extenal-hexagon oral implants

A infiltração de fluidos orgânicos e de microorganismo pode ocorrer entre o pilar protético e o implante osseointegrado, causando mau odor e possível inflamação de tecidos perimplantares. Este estudo teve como objetivo identificar oito espécies periodontopatôgenicas no espaço interno de implantes de hexágono externo e a avaliação do uso de solução de clorexidina a 2% no controle bacteriano nesse espaço. Foram selecionados quatro indivíduos portadores de duas próteses sobreimplante cada. As próteses foram removidas, limpas e desinfetadas com álcool-iodado a 0,02% anteriormente às coletas de material da interface parafuso- implante. Após a primeira coleta, foram reposicionados os pilares de prótese sendo que, num dos implantes, foi adicionada solução de digluconato de clorexidina a 2% e no outro implante (controle), nada foi adicionado. Os indivíduos foram divididos em dois grupos para novas coletas 30 e 90 dias após a primeira. As amostras foram submetidas a exames microbiológicos para identificação de periodontopatógenos, por cultivo e detecção do DNA pela reação em cadeia da polimerase (PCR). Os resultados demonstraram a presença de F nucleatum e T denticola nas amostras coletadas 30 dias após a aplicação de clorexidina e de T denticola e P intermedia nas que não receberam essa aplicação. Aos 90 dias foi detectada a presença de C.rectus nas amostras dos espaços não tratados com clorexidina e de P gingivalis e P. intermedia, indiferentemente da aplicação ou não desse antimicrobiano.