The Effects of Different Loading Times on the Bone Response Around Dental Implants: A Histomorphometric Study in Dogs

Purpose: The aim of this study was to evaluate, through histomorphometric analysis, the effect that different loading times would have on the bone response around implants. Materials and Methods: Three Replace Select implants were placed on each side of the mandible in eight dogs (n = 48 implants). One pair of implants was selected for an immediate loading protocol (IL). After 7 days, the second pair of implants received prostheses for an early loading protocol (EL). Fourteen days after implant placement, the third pair of implants received prostheses for advanced early loading (AEL). Following 12 weeks of prosthetics, counted following the positioning of the metallic crowns for the AEL group, the animals were sacrificed and the specimens were prepared for histomorphometric analysis. The differences between loading time in the following parameters were evaluated through analysis of variance: bone-to-implant contact, bone density, and crestal bone loss. Results: The mean percentage of bone-to-implant contact for IL was 77.9% +/- 1.71%, for EL it was 79.25% +/- 2.11%, and for AEL it was 79.42% +/- 1.49%. The mean percentage of bone density for IL was 69.97% +/- 3.81%, for EL it was 69.23% +/- 5.68%, and for AEL it was 69.19% +/- 2.90%. Mean crestal bone loss was 1.57 +/- 0.22 mm for IL, 1.23 +/- 0.19 mm for EL, and 1.17 +/- 0.32 mm for AEL. There was no statistical difference for any of the parameters evaluated (P > .05). Conclusion: Different early loading times did not seem to significantly affect the bone response around dental implants. INT J ORAL MAXILLOFAC IMPLANTS 2010;25:473-481

Dental Implants in Patients With Osteoporosis: A Clinical Reality?

Osteoporosis is a systemic disorder characterized by generalized decrease in bone mineral density. Dental implantology is a specialty with high predictability when both quantity and quality of the bone are respected. Therefore, the diagnosis and the implant treatment in patients with osteoporosis are important. In the current study, a literature review about osteoporosis and dental implant therapy was conducted. PubMed, Cochrane, ISI, Dentistry Oral Science, SciELO, and Bireme databases were consulted over the last 20 years. English- and Portuguese-language articles were included in this revision. Some authors stated that the osteoporotic bone is similar to the proposed model of bone type IV. Randomized clinical studies reported implant failure in patients with osteoporosis after menopause. Studies that contraindicate the use of implants in patients with osteoporosis infer that the impaired bone metabolism led to reduction of bone healing around the implants. Nevertheless, other authors believe that the presence of osteoporosis is not a definitive condition to contraindicate the therapy with dental implants. In these cases, the dentist should perform a proper treatment planning, modifying the implant geometry, and use larger implant diameter and with surface treatment. Thus, osteoporosis is not a contraindication for implant surgery because an accurate analysis of bone quality by means tomography is performed.

Clinical Viability of Immediate Loading of Dental Implants: Part I-Factors for Success

Two-stage procedure for dental implants presents corroborated clinical success over 40 years. The evolution of surgical techniques, development of diagnostic methods, knowledge about tissue biology, and quality of implants regarding design and surface supported studies with I surgical stage followed by immediate prosthesis placement. However, several factors influence the treatment success with immediate loading. SO, this Study aimed to evaluate some factors regarding the success and characteristics of implants and patients.

Analysis of the effects of irradiation in osseointegrated dental implants

Objective: The purpose of the present study was to evaluate the influence of radiation in osseointegrated dental implants installed in tibiae of rats.Material and methods: Screw-shaped implants (2.5 mm diameter by 3.5 mm length) were custom made from commercially pure titanium bars. Titanium implants were blasted and sterilized before implantation. Animals were divided into two groups of 12 animals each and the rats were not paired after the groups' formation. The experimental group (group 1) received external irradiation 4 weeks after surgery while in the control group (group 2) animals were kept free of radiation. The shear strength required to detach the implant from bone was measured by push-out testing and osseointegration was histologically evaluated.Results: Results showed that the compressive strength of irradiated implants (33.49 MPa) was significantly lower than the compressive strength of non-irradiated implants (48.05 MPa).Conclusions: We concluded that the mechanical strength bonding between implants and host tissues decreased after irradiation.

Stability of cp-Ti and Ti-6Al-4V alloy for dental implants as a function of saliva pH - an electrochemical study

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Analysis of failed commercially pure titanium dental implants: A scanning electron microscopy and energy-dispersive spectrometer X-ray study

Background: the failure of osseointegration in oral rehabilitation has gained importance in current literature and in clinical practice. The integration of titanium dental implants in alveolar bone has been partly ascribed to the biocompatibility of the implant surface oxide layer. The aim of this investigation was to analyze the surface topography and composition of failed titanium dental implants in order to determine possible causes of failure.Methods: Twenty-one commercially pure titanium (cpTi) implants were retrieved from 16 patients (mean age of 50.33 +/- 11.81 years). Fourteen implants were retrieved before loading (early failures), six after loading (late failures), and one because of mandibular canal damage. The failure criterion was lack of osseointegration characterized as dental implant mobility. Two unused implants were used as a control group. All implant surfaces were examined by scanning electron microscopy (SEM) and energy-dispersive spectrometer x-ray (EDS) to element analysis. Evaluations were performed on several locations of the same implant.Results: SEM showed that the surface of all retrieved implants consisted of different degrees of organic residues, appearing mainly as dark stains. The surface topography presented as grooves and ridges along the machined surface similar to control group. Overall, foreign elements such as carbon, oxygen, sodium, calcium, silicon, and aluminum were detected in failed implants. The implants from control group presented no macroscopic contamination and clear signs of titanium.Conclusion: These preliminary results do not suggest any material-related cause for implant failures, although different element composition was assessed between failed implants and control implants.

Influence of cyclosporin A on quality of bone around integrated dental implants: a radiographic study in rabbits

To evaluate the influence of cyclosporin A (CsA) administration on bone around integrated dental implants assessed by a bone quality index and by quantitative subtraction radiography.A total of 36 machine surface commercial implants were placed in 18 adult rabbits. After a 3-month healing period without any disturbance, the animals were randomly divided into three groups of six animals each. Group A was sacrificed at this time. CsA was injected subcutaneously in an immunosuppressive dose of 10 mg/kg/day in a test group (Group T), and a Group B served as a control, receiving only vehicle. After 3 months of cyclosporin administration, the animals of both Groups B and T were sacrificed. Radiographs were obtained at implant surgery and at the day of sacrifice with a CMOS sensor. Bone quality around the implants was compared between the groups using a bone quality index and quantitative subtraction radiography.The bone analysis showed that in Group T, the bone quality changed dramatically from a dense cortical to a loose trabecular bone structure (P < 0.0001, chi(2) test) while in Groups A and B there were no significant differences. Quantitative digital subtraction radiography showed significantly (P < 0.05) lower gray shade values (radiographic density) in a region of bone formation around the implants in Group T (118 +/- 12) than in Groups A (161 +/- 6) and B (186 +/- 10).Within the limits of this study, CsA administration has a negative effect on the quality of bone around integrated dental implant.

Clinical and radiographic changes around dental implants inserted in different levels in relation to the crestal bone, under different restoration protocols, in the dog model

Background: The aim of the present study was to evaluate clinical and radiographic changes that occur around dental implants inserted in different levels in relation to crestal bone under different restoration protocols.Methods: Thirty-six implants were inserted in the edentulous mandible of six mongrel dogs. Each implant was assigned to an experimental group according to the distance from the top of the implant to the crestal bone: Bone Level (at crestal bone level), Minus 1 (1 mm below crestal bone), or Minus 2 (2 mm below crestal bone). Each hemimandible was submitted to a restoration protocol: conventional (prosthesis was installed 120 days after implant placement, including 30 days with healing cap) or immediate (prosthesis was installed 24 hours after implant placement). Fixed partial prostheses were installed bilaterally in the same day. After 90 days, clinical and radiographic parameters were evaluated.Results: As long as the implants were inserted in more apical positions, the first bone-to-implant contact (fBIC) was positioned more apically (P<0.05). However, the apical positioning of the implants did not influence the ridge loss or the position of the soft tissue margin (PSTM) (P>0.05). In addition, in immediately restored sites, the PSTM was located significantly more coronally than that in conventionally restored sites (P=0.02).Conclusions: Despite the more apical positioning of the fBIC, the height of the peri-implant soft tissues and ridge was not jeopardized. Moreover, the immediate restoration protocol was beneficial to the maintenance of the PSTM. Further studies are suggested to evaluate the significance of these results in longer healing periods.

Effect of diabetes mellitus and insulin therapy on bone density around osseointegrated dental implants: a digital subtraction radiography study in rats

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of the RB-RB/LB-LB mnemonic rule for recording optimally projected intraoral images of dental implants: an in vitro study

Objective: The aim of this study was to evaluate a simple mnemonic rule (the RB-RB/LB-LB rule) for recording intra-oral radiographs with optimal projection for the control of dental implants.Methods: 30 third-year dental students received a short lesson in the RB-RB/LB-LB mnemonic rule. The rule is as follows: if right blur then raise beam (RB-RB), i.e. if implant threads are blurred at the right side of the implant, the X-ray beam direction must be raised towards the ceiling to obtain sharp threads on both implant sides; if left blur then lower beam (LB-LB), i.e. if implant threads are blurred at the left side of the implant, the X-ray beam direction must be lowered towards the floor to obtain sharp threads on both implant sides. Intra-oral radiographs of four screw-type implants placed with different inclination in a Frasaco upper or lower jaw dental model (Frasaco GmbH, Tettnang, Germany) were recorded. The students were unaware of the inclination of the implants and were instructed to re-expose each implant, implementing the mnemonic rule, until an image of the implant with acceptable quality (subjectively judged by the instructor) was obtained. Subsequently, each radiograph was blindly assessed with respect to sharpness of the implant threads and assigned to one of four quality categories: (1) perfect, (2) not perfect, but clinically acceptable, (3) not acceptable and (4) hopeless.Results: For all implants, from one non-perfect exposure to the following, a higher score was obtained in 64% of the cases, 28% received the same score and 8% obtained a lower score. Only a small variation was observed among exposures of implants with different inclination. on average, two exposures per implant (range: one to eight exposures) were needed to obtain a clinically acceptable image.Conclusion: The RB-RB/LB-LB mnemonic rule for recording intra-oral radiographs of dental implants with a correct projection was easy to implement by inexperienced examiners. Dentomaxillofacial Radiology (2012) 41, 298-304. doi: 10.1259/dmfr/20861598

Comparison of Biomaterial Implants in the Dental Socket: Histological Analysis in Dogs

Background:Bone graft procedures have been used commonly in buco-maxillo-facial surgery. For this reason, many researchers have evaluated the bone substitutes.Purpose:The present study evaluated soft and hard tissue reactions to two different hydroxyapatites HAs (synthetic HA and natural HA) and bioactive glass implanted into the sockets immediately after extraction.Materials and Methods:First and third upper and lower premolars, on both sides, were extracted from six female dogs. The alveolar sockets were randomly assigned to four groups: Group 1 - control (unfilled), Group 2 - filled with synthetic hydroxyapatite, Group 3 - filled with bovine bone mineral (natural HA), and Group 4 - filled with bioactive glass. The animals were euthanized at 4 weeks (n = 2), 8 weeks (n = 2), and 28 weeks (n = 2) after extraction. The mandible and maxilla of each animal were removed for histological analysis to determine soft tissue reactions, newly formed bone, bone characteristics, and presence or absence of implanted materials.Results:Most particles of synthetic hydroxyapatite had bone formation on their surface, although some particles showed a layer of fibrous connective tissue. The bovine bone mineral group exhibited particles partially replaced with bone formation. The bioactive glass group showed particles with a thin layer of calcified tissue, but was absent in some specimens, suggesting complete resorption.Conclusion:All biomaterials had similar behavior. Bovine bone mineral, compared to synthetic hydroxyapatite and bioactive glass, showed a larger number of particles covered with osseous tissue. All biomaterials interfered with the socket repair process.

Design of dental implants, influence on the osteogenesis and fixation

The fixation and the bone ingrowth at the interface of porous cylindrical implants (total porosity of 37% and average pores diameter of 480 mu m) were compared in vivo to rough cylindrical implants (R-a = 5.3 mu m), both of commercially pure titanium, made by powder metallurgy. The implants were inserted into the tibias of 20 rabbits and the animals were sacrificed 4 and 8 weeks after surgery. The percentage of bone-implant contact observed in porous implant was significantly larger than in the rough ones for all of sacrifice periods, respectively, 57% vs. 46% after 4 weeks, and 59% vs. 50% after 8 weeks. The mechanical tests showed a significant increase in the shear strength of the porous implants for the two analyzed periods, 4 and 8 weeks (14 and 20 MPa), when compared with rough ones (4 and 13 MPa). These results suggest that porous implants improve the contact at the implant-bone interface and increase the fixation to the bone, improving the osseointegration. Thus, the porous implant might be an alternative to dental implant in less favorable conditions, and appear to be better fixed to bone, offering promising alternatives.

A study of histological responses from Ti-6Al-7Nb alloy dental implants with and without plasma-sprayed hydroxyapatite coating in dogs

Titanium alloys are hoped to be used much more for applications as implant materials in the medical and dental fields because of their basic properties, such as biocompatibility, corrosion resistance and specific strength compared with other metallic implant materials. Thus, the Ti-6Al-7Nb alloy that has recently been developed for biomedical use, that is, primarily developed for orthopaedic use, is to be studied in this paper, for application in dental implants. The biocompatibility test in vivo was carried out in dogs and the osseointegration was verified through histological analysis of the samples of the Ti-6Al-7Nb alloy with and without hydroxyapatite coating that were inserted in the alveoli. Within the controlled conditions the samples did not show any toxic effects on the cells. (C) 2001 Kluwer Academic Publishers.