Osseointegration of oxidized and turned implants in circumferential bone defects with and without adjunctive therapies: an experimental study on BMP-2 and autogenous bone graft in the dog mandible

The aim of the study was to compare the integration and implant stability of turned and oxidized titanium implants when placed in experimental bone defects with autogenous bone graft, BMP-2 or without adjunctive therapy. Four defects were prepared on each side of the mandible of 12 mongrel dogs five months after tooth extractions. Implants with turned and oxidized surfaces were placed in the defects. The circumferential gaps were filled with either autogenous bone grafts, a BMP-allogeneic dog mixture in a thermoplastic carrier, carrier alone or left without any treatment (control). There were no statistically significant differences between control and treated sites, neither for turned nor for oxidized implants with regard to histomorphometric measurements in ground sections and to implant stability as measured with resonance frequency analysis (RFA) after 4 and 12 weeks of healing. However, oxidized implants showed a significantly higher stability after 4 weeks and a tendency (p < 0.1) of that after 12 weeks. Histomorphometry showed more bone contacts for oxidized than for turned implants. It is concluded that oxidized implants gain stability more rapidly and integrate with more bone contacts than implants with a turned surface when placed in bone defects.

A 3-year prospective follow-up study of implant-supported fixed prostheses in patients subjected to maxillary sinus floor augmentation with a 80:20 mixture of deproteinized bovine bone and autogenous bone

The purpose of this prospective clinical study was to evaluate the 3-year outcome of 30 maxillary sinus floor augmentations with an autogenous bone-deproteinized bovine bone mixture (20:80). A total of 108 dental implants were placed after 6 months of graft healing. After another 6 months, the occlusion was restored with fixed prostheses and followed for 3 years of functional loading. Clinical and radiographic examinations of the sinuses and implants, including computerized tomography (CT) were performed. The stability of the implants was evaluated by means of resonance frequency analyses (RFA). After 3 years of functional loading with fixed bridges, 15 of 108 implants were lost giving a cumulative survival rate (CSR) of 86%. All followed patients, except one, had fixed bridges in function after 3 years of loading. The mean marginal bone loss was 1.3+/-1.1 mm after 3 years. RFA showed a mean implant stability quotient (ISQ) value of 66+/-4.1 after 3 years with no significant difference between implants in grafted and residual bone. Examination with CT showed that 67% of the maxillary sinuses were healthy prior to treatment and 71% after 3 years of loading. It was concluded that grafting of the maxillary sinus with a mixture of autogenous bone and deproteinized bovine bone is a reliable procedure.

Monitoring of implant stability in grafted bone using resonance frequency analysis. A clinical study from implant placement to 6 months of loading

The aim of this prospective study was to compare implants placed in grafted and normal non-grafted maxilla by means of resonance frequency analysis (RFA), clinical stability and implant failure. Twenty-nine patients with severe atrophy of the edentulous maxilla were treated with autogenous bone grafts as onlay (24 patients) or as interpositional grafts in conjunction with a Le Fort I osteotomy (five patients) 6 months prior to placement of 222 implants. Ten non-grafted patients treated with 75 Brånemark implants in the edentulous maxillae served as a control group. RFA was performed at implant placement, abutment connection and after 6 months of bridge loading. Seventeen (8%) implants were lost in the grafted bone and one (1%) in normal bone. RFA revealed a similar pattern in both grafted and normal maxillae, i.e. increasing resonance frequency (RF) with time (Wilcoxon Signed Rank test for paired data). Twenty implants that were rotation mobile (low primary stability) at the time of insertion showed a significantly lower value at implant placement according to RFA (Mann-Whitney U-test, P = 0.020). The RF for the failed implants revealed a tendency towards lower values (Mann-Whitney U-test, P = 0.072), compared to the successful implants. It is concluded that implants placed in grafted bone when using a two-stage technique achieve a stability similar to that of implants placed in normal non-grafted bone.

Application of oxygen ion implantation to titanium surfaces: effects on surface characteristics, corrosion resistance, and bone response

BACKGROUND

The surface oxide layer of titanium plays a decisive role in determining biocompatibility. However, there are some reports demonstrating that the natural oxide film may not be sufficiently protective in the aggressive biologic environment.

PURPOSE

The goal of this study was to examine the effectiveness of a thick oxide layer on corrosion resistance in vitro and the bone formation around titanium implants in vivo.

MATERIALS AND METHODS

A plasma source ion implantation (PSII) method was used to increase the thickness of the surface oxide layer. Several instruments were employed to confirm the surface properties before and after the surface modification. Potentiodynamic polarization measurements in a phosphate-buffered saline (PBS) solution were carried out to investigate corrosion resistance in vitro. Bone formation around this surface-modified specimen was examined in a rabbit model and assessed in histomorphometry.

RESULTS

Improved corrosion resistance was demonstrated by the potentiodynamic polarization measurements. Light microscopic histomorphometry showed that all implants were in contact with bone and had some proportion of bone within the threads at 4 weeks; however, there were no significant differences compared with as-machined controls.

CONCLUSIONS

The results indicate that in spite of improved corrosion resistance in vitro, a thick oxide layer fabricated with the PSII method does not influence early bone formation around titanium implants in vivo.

Re-osseointegration after treatment of peri-implantitis at different implant surfaces. An experimental study in the dog

Peri-implantitis is a condition that includes soft tissue inflammation and rapid loss of bone. Treatment of peri-implantitis includes both antimicrobial and bone augmenting methods. The question of whether true re-osseointegration may occur following treatment of peri-implantitis is controversial. The aim of this study was to investigate whether the character of the implant surface was of importance for the occurrence of re-osseointegration following treatment of peri-implantitis. Four beagle dogs were used. The mandibular premolars were extracted. After 12 months, 3 ITI(R) solid screw dental implants were placed in each side of the mandible. In the left side, implants with a turned surface (Turned sites) were used, while in the right side implants with a SLA surface (SLA sites) were placed. After 3 months of healing, peri-implantitis was induced by ligature placement and plaque accumulation. When about 50% of the initial bone support was lost, the ligatures were removed. Five weeks later, treatment was initiated. Each animal received tablets of Amoxicillin and Metronidazole for a period of 17 days. Three days after the start of the antibiotic regimen, one implant site (experimental site) in each quadrant was exposed to local therapy. Following flap elevation, the exposed titanium surface was cleaned with the use of cotton pellets soaked in saline. The implants were submerged. Six months later, biopsies were obtained. Treatment resulted in a 72% bone fill of the bone defects at Turned sites and 76% at SLA sites. The amount of re-osseointegration was 22% at Turned sites and 84% at SLA sites. A treatment regimen that included (i) systemic administration of antibiotics combined with (ii) granulation tissue removal and implant surface cleaning resulted in resolution of peri-implantitis and bone fill in adjacent bone defects. Further, while substantial "re-osseointegration" occurred to an implant with a rough surface (SLA), bone growth on a previously exposed smooth surface (Turned) was minimal.

Reactions in the oral mucous membrane after exposure to Carisolv--combined results from a clinical screening test in humans and an experimental study in rats

OBJECTIVE

To evaluate reactions in the oral mucosa after direct contact with Carisolv.

SETTING

The Faculty of Odontology in Göteborg, Sweden.

SUBJECTS

34 healthy persons for a clinical screening test and 35 Sprague Dawley rats for a histological study.

DESIGN

Mixed Carisolv or 0.5 % NaOCl were soaked in paper and applied to either side of the medial frenula of the lower lip of 34 persons. The solutions were left on the oral mucosa for three minutes. Inspection was made and photographs were taken immediately after exposure and also after 1 hour, 24 hours, and 72 hours. Mixed Carisolv was applied in a similar manner as described above to 35 adult Sprague Dawley rats. The animals were killed and biopsies were taken immediately after Carisolv exposure and also after 1 hour, 24 hours, and 48 hours. The biopsies were sectioned and prepared for histomorphometrical evaluation in light microscopy where cells were counted on regions from the epithelium layer deeper into the mucous membrane.

RESULTS

Some adverse reactions were detected on the oral mucosa of humans up to 24 hours after Carisolv exposure for 3 minutes. The detected inflammatory reactions were slight and no patient felt any discomfort. The results of the histological study on rat did not show any statistically significant increase of the number of cells at any time after Carisolv exposure.

CONCLUSIONS

If the oral mucosa gets in direct contact with Carisolv for 3 minutes no or only a weak inflammatory response may be expected.

Histologic analysis of clinical biopsies taken 6 months and 3 years after maxillary sinus floor augmentation with 80% bovine hydroxyapatite and 20% autogenous bone mixed with fibrin glue

BACKGROUND

Bovine hydroxyapatite (Bio-Oss, Geistlich Pharmaceutical, Wollhausen, Switzerland) has been suggested to be used in maxillary sinus floor augmentation procedures prior to or in conjunction with implant placement. However, the long-term histologic fate of this material is not well understood.

PURPOSE

The aim with this study was to histologically evaluate the tissue response in patients to a mixture of bovine hydroxyapatite (BH), autogenous bone, and fibrin glue 6 months and 3 years after a maxillary sinus floor augmentation procedure.

MATERIALS AND METHOD

Biopsies were taken from a group of 20 consecutive patients 6 months (n = 16) and 3 years (n = 12) after maxillary sinus floor augmentation with a mixture of BH (80%), autogenous bone (20%), and fibrin glue and prepared for histologic analysis.

RESULTS

Light microscopy and morphometry from biopsies taken after 6 months showed various amounts of mineralized bone tissue. The specimen area was occupied by 54.1 +/- 12.6% nonmineralized tissue, followed by 21.2 +/- 24.5% lamellar bone, 14.5 +/- 10.3% BH particles, and 10.2 +/- 13.4% woven bone. The nonmineralized tissue seen in bone-forming areas consisted of a loose connective tissue, rich with vessels and cells. There were no signs of resorption of the BH particles. The lamellar bone appeared to have originated from the recipient site and was seldom in contact with the BH particles. After 3 years, the nonmineralized tissue area had decreased to 36.0 +/- 19.0% (p < .05) and consisted mainly of bone marrow tissue. The surface area of lamellar bone had increased to 50.7 +/- 22.8% (p < .05), and there was almost no immature bone. The mean specimen area occupied by BH particles, was 12.4 +/- 8.7% and had not changed from 6 months (not significant). Moreover, the sizes of the particles were similar after 6 months and 3 years. The degree of BH particle-bone contact had increased from 28.8% +/- 19.9% after 6 months to 54.5 +/- 28.8% after 3 years (p < .05).

CONCLUSION

Histology of specimens from maxillary sinuses augmented with 80% BH particles, 20% autogenous bone, and fibrin glue showed a positive bone tissue response after 6 months and 3 years after augmentation of the maxillary sinus floor prior to implant placement in a group fo 20 patients. The bone surrounding and in contact with the BH particles after 6 months was mainly immature woven bone, which with time was replaced by mature lamellar bone filling the interparticle space as observed in the 3-year specimens. Moreover, bone-integrated BH particles seem to be resistant to resorption. The results indicate that the procedure may be considered when only small amounts of intraoral autogenous bone graft are available.

Influence of bone marrow on membrane-guided bone regeneration of segmental long-bone defects in rabbits

Defects 10 mm long were created in long bone in the diaphysis of both radii of 18 rabbits (test and control side). On the test side, ingrowth of bone marrow into the defects was hindered or delayed by: plugging the opening of the cut bone ends with gutta-percha points (n = 7); plugging with Gelfoam (n = 6); or by removing the bone marrow by flushing with saline (n = 5). The defects on both test and control side were covered with an expanded polytetrafluoroethylene membrane, shaped as a tube. Healing was followed with radiographs for four to five months, after which the animals were killed and ground sections of the areas of the defects were prepared for histological examination. On the control side, nine of 18 animals had complete osseous bridging of the defect, and a small transverse non-mineralised zone remained in the centre of the healed defect in the other animals. This zone consisted of loose connective and cartilagenous tissue as well as connective tissue obviously derived from the outside of the membrane. By preventing or delaying the ingrowth of bone marrow we retarded the regeneration of mineralised bone, particularly in the gutta-percha and flushed bone marrow groups. The principle of guided tissue regeneration may be used to achieve regeneration of extensive long-bone defects. Any attempts to delay or prevent bone marrow ingrowth into the defects did retard regeneration of segmental long-bone defects.

Brånemark implants and osteoporosis: a clinical exploratory study

BACKGROUND

Oral implant treatment on patients with poor jaw-bone texture has shown increased failure rates in series of studies.

PURPOSE

The purpose of the present study was to retrospectively follow patients with osteoporosis of the axial or appendicular skeleton, including the jaw bone, being subjected to oral implant treatment. The outcome of inserted implants, when using an adapted bone site preparation technique and extended healing periods, was evaluated.

MATERIALS AND METHODS

Based on data obtained from preoperative radiographs, patient medical history, and resistance of the jaw bone perceived during drilling, 14 of 16 patients were referred to the Osteoporosis Laboratory, Sahlgren University Hospital, Göteborg, Sweden, for bone density measurements. Two patients already had an established diagnosis of osteoporosis. Fourteen jaws in 13 patients (11 females, 2 males; mean age: 68 yr) were subsequently subjected to oral implant treatment with a total of 70 implants (Brånemark System) of various designs. The mean follow-up period was 3 years and 4 months (range: 6 mo-11 yr).

RESULTS

Osteoporosis of either the spine, the hip, or both regions was diagnosed in 14 patients, and osteopenia was diagnosed in 2 patients. Two implants failed, and the overall implant survival rate at the end of the study period was 97.0% for maxillae and 97.3% for mandibles. The marginal bone resorption at the 1-year follow-up concurs with the outcome of other studies, irrespective of the preoperative bone texture present.

CONCLUSION

The outcome of the present study showed that implant placement in patients in whom the average bone density showed osteoporosis in both lumbar spine and hip as well as poor local bone texture may be successful over a period of many years.

Histopathologic observations on late oral implant failures

BACKGROUND

Despite good success rates of osseointegrated oral implants, failures do occur. To minimize losses, failure mechanisms should be elucidated.

PURPOSE

This study sought to describe the morphology of tissues surrounding late failed Brånemark implants in relation to their clinical and radiographic findings to acquire a better understanding of the etiologic factors.

MATERIAL AND METHODS

Ten failed implants and their surrounding tissues were consecutively retrieved from nine patients after prosthesis placement (late losses). On radiographs, a radiolucent line was visible around nine clinically mobile implants. Tightening of the abutment screw evoked pain at seven mobile implants. Clinically, no other visual inflammatory sign or symptom was manifest. A fistula originated from one stable implant, surrounded on radiographs by a diffuse bone rarefaction. Retrieved implants were electrochemically dissolved. Intact tissue-implant thin (1 micron) and ultrathin (70-80 nm) sections were analyzed with light and transmission electron microscopy.

RESULTS

Peri-implant marginal tissues displayed moderate inflammatory infiltrates located adjacent to and beneath the junctional epithelium. One patient affected by oral lichen planus displayed an intense lymphocyte/plasma cell-dominated immune reaction. Deep peri-implant tissues surrounding mobile implants consisted of a dense, fibrous tissue capsule with minimal inflammation. Epithelial downgrowth was observed around four implants. Small areas of nonmineralized bone in contact with the implant were noticed in the apical portion of two implants. One implant was almost entirely colonized by bacterial plaque with the exception of its apical portion, where bone-implant contact was observed. The stable implant was characterized by bone-implant contact.

CONCLUSION

Altogether clinical, radiographic, and histologic findings indicated that two major etiologic factors might have been implicated in the failure process of the investigated implants: excessive occlusal load in relation to the bone-supporting capacity and, in two cases, infection.

A clinical histologic study of bovine hydroxyapatite in combination with autogenous bone and fibrin glue for maxillary sinus floor augmentation. Results after 6 to 8 months of healing

Biopsies were taken from 16 out of 20 consecutive referral patients 6 to 8 months after maxillary sinus floor augmentation with a mixture of bovine hydroxyapatite (BH), autogenous bone particles and fibrin glue. Four days prior to biopsy retrieval the patients were given a single dose of tetracycline to label bone forming sites. Fluorescence microscopy of 100 microm thick sections revealed active bone formation in conjunction with the BH particles in 14 of 15 specimens analysed. Light microscopy and morphometry of ground sections from 16 patients showed various amounts of mineralised bone tissue in all except one specimen. In the latter case, the BH particles were encapsulated by a dense fibrous connective tissue. Sections from the augmented areas were occupied by non-mineralized tissue (54.1+12.6%), lamellar bone (21.2+24.5%), BH particles (14.5+10.3%) and woven bone (10.2+13.4%). The non-mineralized tissue seen in bone forming areas consisted of a loose connective tissue, rich of vessels and cells, and in the periphery of a more dense fibrous connective tissue. Woven bone with large and scattered osteocyte lacunae was bridging between the BH particles and the lamellar trabecular bone. There were no signs of resorption of the BH particles. The lamellar bone appeared to have originated from the recipient site and was seldom in contact with the BH particles. It is concluded that the tested implant material has bone conducting properties. The bone associated with the BH particles after 6 to 8 months of healing was mainly woven.

Histologic evaluation of the bone integration of TiO(2) blasted and turned titanium microimplants in humans

Twenty-seven patients received 2 microimplants each during implant surgery. One microimplant was blasted with 25 microm sized particles of TiO(2); the other was left as machined i.e. a turned surface. Before insertion the surface topography was characterized with an optical confocal laser profilometer. The surface roughness was greater than standard implants, and was similar for both surface modifications averaging over all parts of the implant i.e. tops, valley and flanks. The mean surface roughness from flank measurements only replicated previously reported findings: i.e. significantly rougher surfaces on blasted implants. After a mean healing period of 6.3 months in the maxillae and 3.9 months in the mandible, the microimplants and surrounding tissue were removed with a trephine burr. The histomorphometrical evaluation demonstrated significantly higher bone-to-implant contact for the blasted implants, inserted in the maxilla or in the mandible. Significantly more bone was found inside the threaded area for the blasted implants in the mandible, but there was no difference for implants positioned in maxillae.

A new microtomographic technique for non-invasive evaluation of the bone structure around implants

A new X-ray microtomographic technique for non-invasive assessment of the structure of bone surrounding implants was tested. Three titanium microimplants retrieved directly (n = 2) or 6 months (n = 1) after insertion in 3 patients were used as test samples. Two samples were used dry and one was embedded in plastic resin prior to microtomography. The technique provided high-resolution consecutive cross-sectional X-ray images of the specimens with a slice-to-slice distance of 4.4 to 11.0 microns. The pictures could be imported into an image analysing software with which semiautomatic quantitative measurement of the bone area and three-dimensional images of the specimens could be made. It is suggested that the technique may be used for non-invasive assessment of the bone structure around implants. Further studies are needed to evaluate the accuracy of the technique, for instance by comparing tomographic sections with histologic ones.

Re-Establishment of the Atomic Composition and the Oxide Structure of Contaminated Titanium Surfaces by Means of Carbon Dioxide Laser and Hydrogen Peroxide: An In Vitro Study

BACKGROUND

In clinical situations with peri-implant bone resorption, re-integration of the exposed implant surface is sometimes preferable, which requires a clean surface. Previous investigations have shown that cleaning of contaminated titanium surfaces using chemical and abrasive methods is difficult.

PURPOSE

The aim of this investigation was to evaluate the efficacy of different combinations of chemical and physical methods (citric acid, hydrogen peroxide, and carbon dioxide [CO2] laser irradiation) for removal of contaminants and subsequent reconstruction of the surface oxide of intraorally contaminated titanium foils.

MATERIALS AND METHODS

Commercially pure titanium foils (99.6%, 5 x 5 mm in size) were contaminated by placement on dentures in volunteering patients, simulating a peri-implantitis situation. The contaminated foils and clean control foils were treated by seven and six combinations of citric acid, hydrogen peroxide, and CO2 laser irradiation, respectively. The effect of the cleaning procedures was evaluated by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM).

RESULTS

The initial elemental composition of the contaminated foils was 70% carbon (C), 20% oxygen (O), 10% nitrogen (N), and only traces of titanium (Ti) (< 1%). One treatment proved to be more effective than the others: irradiations by 5-second cycles of superpulsed CO2 laser at a power of 7 W, 10-millisecond pulse width, and with an 80-Hz frequency on a wet surface, followed by repeated application of supersaturated citric acid for 30 seconds, each time followed by rinsing with ultrapure water until all tissue remnants had been removed. Finally, hydrogen peroxide of 10-mM concentration was added to the implant surface and evaporated by CO2 laser at the same settings. This treatment protocol resulted in 10% Ti, 45% O, 41% C, and 2 to 3% N, a composition comparable to that of unused foils: 9% Ti, 40% O, 48% C, and traces of N and chlorine (CI). X-ray photoelectron spectroscopy profiles showed that the thickness of the surface oxide was restored and even augmented with this protocol for treatment of contaminated titanium.

CONCLUSION

A combination of citric acid, hydrogen peroxide, and CO2 laser irradiation seems to be effective for cleaning and reestablishment of the atomic composition and oxide structure of contaminated titanium surfaces.

Soft tissue response to clinically contaminated and thereafter cleaned titanium surfaces. An experimental study in the rat

The aim of the present study was to evaluate the soft tissue response to intra-orally exposed and contaminated titanium surfaces (machined, blasted or polished) after being chemically and/or mechanically cleaned. Eight adult Sprague-Dawley rats were used for histomorphometrical and histological analyses. A total of 44 experimental abutments (26 tests and 18 controls) were inserted into abdominal skinpockets of the rats for 6 weeks. No differences regarding the soft tissue response between the different surface characteristics analysed and between test and control could be observed.

The soft tissue response to contaminated and cleaned titanium surfaces using CO2 laser, citric acid and hydrogen peroxide. An experimental study in the rat abdominal wall

The soft tissue response to clinically retrieved and decontaminated cover screws was evaluated in a rat model. The cover screws were cleaned by using citric acid, sterile water, hydrogen peroxide and CO2 laser alone or with a combination of these. In addition, decontaminated but not cleaned and unused cover screws were used as negative and positive controls, respectively. After cleaning the cover screws were implanted in the abdominal wall of the rat for 6 weeks. The thickness of the fibrous capsule and the number of macrophages within the capsule were measured by means of light microscopical morphometry. As compared to the negative control, CO2 laser on dry surface, CO2 laser + hydrogen peroxide and the positive control had statistically significant thinner fibrous capsules. As compared to the positive, only laser alone resulted in a similar tissue response. It is concluded that CO2 laser used alone or in combination with hydrogen peroxide may be used clinically for sufficient decontamination of titanium surfaces.

Measurements Comparing the Initial Stability of Five Designs of Dental Implants: A Human Cadaver Study

BACKGROUND

A number of different dental implant designs are currently in clinical use. A successful outcome of implant placement is thought, at least in part, to be due to the primary stability of an implant after placement. Few data are available for comparing the primary stability characteristics of different implant designs.

PURPOSE

This investigation compared the primary stability of five types of endosseous dental implant of varying geometry and surface topography.

MATERIALS AND METHODS

Comparison was made between a standard threaded commercially pure titanium implant (Nobel Biocare AB, Göteborg, Sweden), the Mark II self-tapping implant (Nobel Biocare AB, Göteborg, Sweden), the Mark IV tapered self-tapping implant (Nobel Biocare AB, Göteborg, Sweden), the Astra Tioblast (AstraTech AB, Mölndahl, Sweden), and the 3i Osseotite (3I [Implant Innovations Incorporated], Palm Beach, Florida, USA). Fifty-two fixtures were placed in the maxillary bone of nine unembalmed human cadavers. Implant stability as a function of peak insertion torque and resonance frequency values was recorded for each fixture site after placement. Removal torque was also measured 1-hour postinsertion. Assessment of bone quality at each site was made.

RESULTS

All of the implants tested demonstrated good primary stability in type 2 and 3 bone. The Standard, Mark II, Osseotite, and Tioblast were less stable when placed into bone type 4. The Mark IV implants appeared to maintain a high primary stability even in Type 4 bone.

CONCLUSION

When looking across all bone qualities, the Mark IV implant develops a significantly higher insertion torque than the Standard, Mark II, and Osseotite implant types, and a significantly higher resonance frequency value than the Standard implant, indicating a higher interfacial stiffness at the implant-bone interface.

Influence of decortication of the donor bone on guided bone augmentation. An experimental study in the rabbit skull bone

The aim of the present study was to evaluate if early access to the endosteal bone compartment by removal of the outer cortical bone plate will enhance bone augmentation in a secluded space. Two titanium cylinders were placed on the skull of each of 8 rabbits. Each cylinder was placed into a circular slit, secured to the skull bone via two mini-screws and supplied with a titanium lid. On the test side, the outer plate of the cortical bone, demarcated by the slit, was removed. The subsequent bleeding resulted in blood fill of the cylinders to various degrees. On the control side, the corfical bone plate was left intact and no bleeding was observed at the time of the placement of the titanium lids. After 3 months, the animals were sacrificed to obtain histology and histomorphometry. No differences in the total amount of augmented bone tissue, in relation to the total experimental area (75.5% +/- 10.9% at the test sites and 71.2% +/- 13.5% at the control sites) or of the augmented mineralized bone tissue in relation to the total amount of augmented bone tissue, was revealed (17.8% +/- 3.0% and 16.0% +/- 4.9% respectively). There was no difference in the morphological appearance of the augmented bone between test and control sites and there were no obvious similarities in the appearance between the newly formed bone tissue and the donor bone. The augmented bone consisted of slender bone trabeculae, distributed in abundant marrow spaces. A conspicuous finding was that the bone trabeculae tended to climb along the inner walls of the titanium cylinder. It is concluded that decortication of the calvarial bone in the rabbit does not result in more bone formation beyond the skeletal envelope after a healing period of 3 months compared to no removal of the cortical bone plate inside a secluded experimental area.

Healing of titanium implants in onlay bone grafts: an experimental rabbit model

An experimental rabbit bone graft model for the study of bone formation and remodeling around titanium implants is described. A 2.5-cm long radius bone segment served as an onlay graft. Two commercially pure (c.p.) titanium implants were inserted into the bone graft prior to fixation to the inferior border of the mandibular base with osteosynthesis titanium screws. Each animal was operated twice, allowing follow-up periods of 6 weeks on one side and 6 months on the contralateral side. In order to study bone remodeling by means of fluoroscopy the animals received single injections of tetracyclin and alizarine complexone 2 weeks and 1 week, respectively, prior to sacrifice by perfusion fixation with glutaraldehyde. The bone and implants were excized en bloc, postfixed and embedded in plastic resin. Stained and unstained thin ground sections as well as microradiographed thick sections were produced for light microscopic morphometry and fluoroscopy. After 6 weeks, osteoclastic/osteoblastic activity was primarily observed in the graft-recipient contact area and in the intracortical compartment of the graft bone. New bone formation observed on the implant surface originated from the recipient site. The bone formation was evident also in the implant-graft interface. At 6 weeks the average bone fill of the implant threads was 28.4% which increased to 36.4% after 6 months as measured by morphometry. An average of 17.6% bony contact was measured after 6 weeks which increased to 29.7% 6 months after surgery. The graft bone had reduced in size from an average of 39.5% after 6 weeks down to 24.8% after 6 months (P \lt 0.05). It is concluded that the described experimental model can serve as a useful method for the study of implant healing in onlay grafts.

Implant Stability Measurements Using Resonance Frequency Analysis in the Grafted Maxilla: A Cross-Sectional Pilot Study

BACKGROUND

High failure rates have been presented for implants placed in grafted bone. The bone graft-implant interface constitutes a most complex healing situation, where the time scale for osseointegration and development of implant stability currently is not known.

PURPOSE

The aim of the study was to measure the stability of implants placed in grafted bone after various follow-up periods.

METHODS

Implant stability measurements by means of resonance frequency analysis were performed in 10 patients previously treated with a Le Fort I osteotomy and interpositional bone grafts. The implants were placed 3 to 4 months after the grafting procedure. Sixty-seven Brånemark implants were subjected to resonance frequency analysis measurements at fixture placement and up to 5.5 years after implant surgery. Periapical radiographs were used for assessment of marginal bone levels.

RESULTS

The radiographic examinations showed marginal bone loss with time during the 5.5-year follow-up. The resonance frequencies varied from 5860 to 8440 Hz. When accounting for abutment length and marginal bone level, there was a tendency of increasing resonance frequency with time. Two implants with low resonance frequencies failed during the prosthetic phase.

CONCLUSION

The results indicate an increased implant stability with time, which may reflect bone formation, remodeling, and maturation at the implant interface.

On Cutting Torque Measurements during Implant Placement: A 3-Year Clinical Prospective Study

BACKGROUND

Evaluation of jaw bone quality at implant placement is mainly based on preoperative radiographic assessments and subjective hand registrations during implant site preparation. An objective technique with cutting torque measurements has been introduced, presenting an objective bone quality or bone hardness value of individual implant sites.

PURPOSE

The purpose of this study was to evaluate cutting torque measurements during implant placement and to compare these values in different regions in mandibles and maxillae. The objective was to identify implants at risk for failing at implant placement.

MATERIAL AND METHODS

Cutting torque measurements were performed during placement of Mk II self-tapping implants (Brånemark System) in 105 patients, comprising 72 edentulous (40 maxillae) and 34 partially edentulous (22 maxillae) jaws. A total of 523 implants were inserted, of which 420 were of the Mk II design and of which 412 were subjected to cutting torque measurements. Statistical analyses were performed by comparing cutting torque values of maxillae and mandibles and of different jaw regions. Cutting torque values were also correlated with radiographically and clinically assessed bone quality scores. Patients were followed clinically for a minimum of 3 years.

RESULTS

A statistically significant difference in cutting torque values of maxillae and mandibles was seen, although not when comparing anterior and posterior regions within the same jaws or of different jaws. Significant correlations were found between values of cutting torque and bone quality. The majority of failures were seen in bone of medium to high density, whereas implants inserted in bone of poor density presented a better outcome, perhaps due to an adapted surgical protocol and an extended healing period. The overall implant survival rate at 3 years was 95%, and when analyzing different jaw categories, survival rates of 92.0% and 99.4% were seen for edentulous maxillae and mandibles, respectively. The corresponding figures for partially edentulous jaws were 95.4% and 97.6%.

CONCLUSION

It was not possible to identify sites at risk for future implant losses or to determine a lower limit value of cutting torque in order to achieve successful implant integration.

A comparison between cutting torque and resonance frequency measurements of maxillary implants. A 20-month clinical study

Oral implant treatment ad modum Brånemark was undertaken in nine patients with edentulous maxillae. Cutting torque measurements and resonance frequency analyses (RFA) were conducted at implant placement and the corresponding values were subjected to correlation analyses. The implants were also evaluated with RFA at abutment connection and at one-year follow-up in order to identify possible changes in implant stability. A total of 61 implants were inserted, of which 49 were of the Mk II self-tapping type. Two implants were lost during the study period. The cumulative torque was presented as a mean value for the upper/crestal, the middle and the lower/apical third of the implant site respectively, as well as an overall value for the whole site. The highest correlation (r = 0.84, P<0.05) was found when comparing the mean torque values of the upper/crestal portion with the resonance frequency values at implant placement. The Mk II implant sites were divided into three groups based on the values of the cutting torque, i.e. soft (group 1), medium (group 2) and dense bone (group 3). The mean value of each group was plotted against the corresponding mean value of resonance frequency measured at implant insertion. Statistical analysis showed significant differences in resonance frequency at implant insertion between groups 1 and 2 (P = 0.047) and between groups 1 and 3 (P = 0.002). When repeating the resonance frequency analyses at second stage surgery and at one-year follow-up, no significant differences were detected between any of the groups. It was shown that the stability of implants placed in softer bone seemed to "catch up" over time with more dense bone sites.

Stability measurements of one-stage Brånemark implants during healing in mandibles. A clinical resonance frequency analysis study

Using a one-stage surgical protocol, 75 implants ad modum Brånemark of three different designs were inserted in 15 edentulous mandibles of high bone density. All implants were followed with repeated stability measurements by means of resonance frequency analysis (RFA) from implant placement to connection of the fixed prostheses (3-4 months), in order to evaluate possible stability changes during healing. It was shown that the resonance frequency (RF) values slightly decreased for the majority of the implants during the study period independent of design. Consequently, the results of the present study indicated that the implants were as stable at time of placement as when measured at 3-4 months post-surgery, i.e. when the prostheses were attached. The available data support the concept of direct loading of implants when inserted between the mental interforaminal regions. One implant failed during healing and the corresponding RF measurement disclosed, at six weeks post-surgery, a value being far below the one registered at implant placement. The lowered RF value indicated the failure several weeks before the mobility was clinically diagnosed. The presence or absence of a fixture/abutment junction did not exert any influence on the marginal bone level, as determined radiographically at the end of the short investigation period.

Effects of barrier membranes on bone resorption and implant stability in onlay bone grafts. An experimental study

The objective of the present report was to study the effects of barrier membranes on bone resorption and implant stability in a rabbit onlay bone graft model, using resonance frequency analysis, coordinate measurements on plaster models, removal torque measurements and histology. Disc-shaped bone grafts were harvested from the calvarium and placed with titanium implants in the proximal tibial metaphyses of 9 rabbits. On one side (test) the bone graft/implant was covered by an e-PTFE barrier, while the contralateral side was not covered by a membrane and served as control. Three animals were sacrificed after 8 weeks for histology. In 6 animals the membranes were removed after 8 weeks and the animals were followed for an additional period of 16 weeks. Implant stability and bone height around the implants was assessed for the test and control sides at Day 0 and 8, 16 and 24 weeks postoperatively. Removal torque tests were performed after 24 weeks. The results showed an increase in volume of the bone graft on the test side as long as the barrier membrane was in place. However, after removal of the membrane at 8 weeks the resorption rate was higher on the test side compared to the control side, resulting in a similar bone height after 24 weeks. There were no statistically significant differences in implant stability between the test and control sides at any time point, as measured with resonance frequency analysis. Additionally, no statistically significant differences were found between the test and control sides after 24 weeks, using removal torque measurements, coordinate measurements and histomorphometric evaluation. Thus, in this experimental model, the use of non-resorbable barrier membranes did not improve the stability of implants simultaneously placed with onlay bone grafts. Moreover, extensive resorption of the grafted bone was seen after barrier removal, which resulted in similar bone graft volume for the test and control sides at the end of the observation period.

The influence of simultaneous versus delayed placement on the stability of titanium implants in onlay bone grafts. A histologic and biomechanic study in the rabbit

A rabbit model was used to study the healing and stability of titanium implants in free bone grafts, placed simultaneously or after 8 weeks of healing and followed for 24 weeks. The skull bone was used as donor site and the tibial metaphysis as recipient site. Stability measurements were performed by using resonance frequency analysis (RFA) at implant placement and after 4, 8, 16 and 24 weeks of healing. Statistically significant higher resonance frequencies were measured at all time points for the delayed approach implants. Removal torque tests after 24 weeks revealed no differences between the two procedures. Histologic ground sections were prepared on specimens taken after 8, 16 and 24 weeks of healing. More bone-implant contacts were observed in the bone graft for the implants inserted in a delayed fashion, while there was no statistically significant difference in the degree of total bone-implant contact between the two groups. It is concluded that delayed implant placement in autogenous onlay bone grafts results in a better integration and stability of the implants.

Influence of variations in implant diameters: a 3- to 5-year retrospective clinical report

Sixty-seven patients ranging in age from 16 to 86 years were included in this 3- to 5-year retrospective report focusing on implant survival and marginal bone remodeling in relation to implant diameter. A total of 299 Brånemark implants (3.75-mm diameter: 141; 4.0-mm diameter: 61; 5.0-mm diameter: 97) were placed in 16 completely and 51 partially edentulous arches. Seven of the 141 implants in the 3.75-mm-diameter group failed (5%). The corresponding value for the 4.0-mm-wide implants was 2 of 61 (3%). The highest failure rate, 18% (17/97), was seen for the 5.0-mm-diameter implants. The least favorable cumulative survival rates were seen in mandibles after 5 years and involving 4.0-mm- and 5.0-mm-diameter implants (84.8% and 73.0%, respectively). The marginal bone loss was generally low over the 5-year period. When the data were evaluated by the Cox regression analysis, a relationship was found between implant failure and implant diameter (P < .05), with a higher failure rate for the 5.0-mm-diameter implant. However, no relationship could be seen between implant failure and jaw type, or bone quality and quantity (P > .05). Neither was any relationship seen between marginal bone loss and bone quality and quantity, implant diameter, or jaw type when tested by multiple linear regression analysis (P > .05). A learning curve, poor bone quality, and changed implant design were suggested as possible reasons for the less positive outcome seen for the 5.0-mm-diameter implant. The fact that this implant was often used as a rescue implant when the standard ones were not considered suitable or did not reach initial stability was another plausible explanation.

Temperature increases during surface decontamination of titanium implants using CO2 laser

The purpose of the present in vitro investigation was to measure temperature changes at the implant surface when using pulsed CO2 laser in a simulated implant surface decontamination protocol. Six threaded titanium implants were placed in a fresh resected pig mandible. A 4 x 4 mm defect was created buccally to each implant in order to expose the implant head and approximately 5 threads. Temperature changes were monitored by two thermocouples placed near the dehiscence and at the apical part of the implant. Several setting combinations of the CO2 laser with regard to output power, pulse width, pulse repetition rate and irradiation time were tested on dry and wet (distilled water) surfaces. Only minor temperature increases were measured when lasing wet titanium surfaces, while the temperature at dry surfaces exceeded the proposed thresholds for bone damage at clinically relevant settings. It is concluded that the CO2 laser when used on a wet implant surface in a pulsed mode at 8 W/10 ms/20 hz during 5 s induces a temperature increase of less than 3 degrees C. This would minimize the risk of temperature induced tissue damage as a result of lasing implant surfaces.

Simultaneous or delayed placement of titanium implants in free autogenous iliac bone grafts. Histological analysis of the bone graft-titanium interface in 10 consecutive patients

The aim of the present study was to histologically analyse the bone graft-titanium implant interface after six and twelve months of healing for a simultaneous approach and after six months for a delayed approach. For this purpose, screw-shaped c.p. titanium microimplants, 2 mm in diameter and 5 mm long, were placed and retrieved at different time intervals in ten consecutive patients with severely resorbed maxillae and treated with iliac cortico-cancellous bone grafts and titanium implants in a two-stage procedure. The histomorphometrical analyses of ground sections of the specimens showed a higher degree of bone-implant contact and more bone filling the implant threads in the delayed approach microimplants. This was probably due to the partly revascularized grafted bone in the delayed approach being able to respond to the surgical trauma, resulting in interfacial bone formation. It is concluded that the results from the present study favour the use of a delayed approach when using free autogenous bone grafts and titanium implants for reconstruction of the severely atrophied maxilla.

The effect of hyperbaric oxygen treatment on bone tissue reactions to c.p. titanium implants placed in free autogenous bone grafts. A histomorphometric study in the rabbit mandible

This study aimed to investigate the effect of hyperbaric oxygen (HBO) therapy on the tissue reactions to commercially pure (c.p.) titanium implants placed in free autogenous bone graft by a 1-stage procedure. Eighty c.p. titanium implants were placed in the bone grafted from iliac crest to bilateral mandible of 40 Japanese white rabbits without tapping. Twenty rabbits underwent daily a HBO treatment for 60 min under 2.4 ATA during 20 consecutive days and the other untreated 20 rabbits served as controls. The implants with surrounding bone tissue were retrieved 20, 30, 60, 90 and 120 days after surgery, fixated, dehydrated and embedded in resin. About 20 microns thick ground sections were prepared prior to microscopical observations. The bone area and the bone-to-implant contact inside the threads were calculated separately in the grafted bone and in the host bone for each implant. After 30 and up to 120 days, the HBO treated group showed more bone-to-implant contacts in the grafted bone as compared to the non-HBO treated group. In the host bone there were no differences observed between HBO and non-HBO treated groups. This study indicated that HBO treatment was beneficial for the tissue incorporation of c.p. titanium implants when placed immediately in free autogenous bone grafts.

Surgical determinants of clinical success of osseointegrated oral implants: a review of the literature

PURPOSE

This article reviews the current knowledge about the influence of surgical factors on implant failure in routine cases and in those where implants have been used in conjunction with bone augmentation procedures.

MATERIALS AND METHODS

Clinical reports published in major scientific journals served as the basis for this review.

RESULTS

With few exceptions, most clinical reports were on screw-shaped titanium implants. High failure rates are associated with poor bone quality and the use of short implants in the athrophic maxilla, irradiation, and bone-grafting procedures of the athrophic maxilla. Evidence for high long-term failure rates of press-fit cylinders was found. Moreover, limited clinical experience, lack of preoperative antibiotics, and smoking may lead to higher failure rates.

CONCLUSION

There is a need for further research to increase the success rates in the severely resorbed maxilla. Because of a lack of proper documentation with respect to the great majority of currently used oral implant designs, the influence of different factors and their long-term results remain unknown.

Histologic analysis of clinically retrieved titanium microimplants placed in conjunction with maxillary sinus floor augmentation

In this study, a new approach involving placement and subsequent retrieval of titanium microimplants was employed for the histologic investigation of the implant-tissue interface in conjunction with maxillary sinus floor augmentation. Nine patients scheduled for sinus floor augmentation and simultaneous placement of Brånemark implants were included in the study. After a sinus graft procedure and placement of implants, an additional microimplant was placed into the graft through the lateral wall of the sinus. At abutment connection, the microimplants were retrieved using a 3- or 5-mm-wide trephine drill. Six specimens were retrieved after 6 to 14 months from sites augmented with particulate radiated mineralized cancellous allograft. Another six implants were retrieved after 6 to 12 months from maxillary sinuses augmented with particulate autogenous bone grafts. The histologic analysis showed distinct differences between the two types of grafts. The sites with autogenous bones grafts displayed a normal morphology of bone and bone marrow, including formation of bone on the surfaces of the grafted particles and remodeling of newly formed as well as grafted bone. The bone was more mature after 11 to 14 months than at 6 months. The allografted sites had a mixed morphologic appearance of newly formed bone and nonviable allograft particles (about 75% of the total bone area) in loose connective tissue. Significantly more bone was found at the autografted than at the allografted implants. The use of autogenous bone for augmentation of the maxillary sinus floor resulted in a greater amount of viable bone surrounding the implant; however, simultaneous placement of implants apparently resulted in a low proportion of bone-implant contact after 6 to 14 months irrespective of graft type.

Stability assessments and histology of titanium implants placed simultaneously with autogenous onlay bone in the rabbit tibia

A disc-shaped bone graft was harvested from the calvarium in ten rabbits and anchored as an onlay bone graft, using a titanium implant, at the proximal tibial metaphysis. The contralateral tibia served as the control, where an implant was placed without a graft with the implant head at a height corresponding to the thickness of the graft on the test side. Resonance frequency measurements were performed 4, 8, 16 and 24 weeks postoperatively and removal torque measurements were performed at 24 weeks. A statistically significant higher implant stability, as assessed by resonance frequency measurements (RFM), was measured from 4 weeks throughout the 24-week period. The mean peak removal torque for the test implants was 50.4+/-10.0 Ncm and 30.0+/-6.9 Ncm for the control implants, which was a statistically significant difference. Histologically, the grafted bone was well incorporated and morphometry revealed more bone around the test implants. Calculations of shear stresses indicated that the grafted bone had similar biomechanical properties to the cortical bone of the recipient site. It is concluded that the integration of titanium implants in autogenous onlay bone grafts results in an increased biomechanical support of the implant. The use of RFM may also serve as a useful instrument for noninvasive monitoring of implant stability in vivo.

Stability measurements of craniofacial implants by means of resonance frequency analysis. A clinical pilot study

Nineteen patients previously treated with 52 implants for anchorage of craniofacial prostheses were subjected to implant stability measurements by means of resonance frequency analysis (RFA), six months to 15 years after implant placement. The resonance frequency (RF) of a transducer attached to the implant abutment was measured by using a frequency response analyser, a personal computer (PC) and dedicated software. Statistically significant higher RF values were seen for implants in the temporal bone as compared to implants in the nose and periorbital regions. There was a positive correlation with time since implant placement for the period from six months up to seven years. It was concluded that the preliminary results suggest that implant stability increases with time and that implants in temporal bone are more stable than implants in the bone in the nose and periorbital regions, probably reflecting differences in bone density.

An XPS and SEM evaluation of six chemical and physical techniques for cleaning of contaminated titanium implants

The purpose of the present study was to analyse clinically failed and retrieved implants prior to and after cleaning by means of scanning electron microscopy (SEM) and X-ray induced photoelectron spectroscopy (XPS) as compared to unused controls. Six different chemical and physical techniques for cleaning of contaminated titanium implants were evaluated: 1) rinsing in absolute ethanol for 10 min, 2) cleaning in ultrasonic baths containing trichloroethylene (TRI) and absolute ethanol, 10 min in each solution, 3) abrasive cleaning for 30 s, 4) cleaning in supersaturated citric acid for 30 s, 5) cleaning with continuous CO2-laser in dry conditions at 5 W for 10 s, 6) cleaning with continuous CO2-laser in wet conditions (saline) at 5 W for 10 s. SEM of failed implants showed the presence of contaminants of varying sizes and XPS showed almost no titanium but high carbon signals. XPS of unused titanium implants showed lower levels of titanium as previously reported, probably due to contamination of carbon which increased with time in room air. Cleaning of used implants in citric acid followed by rinsing with deionized water for 5 min followed by cleaning in ultrasonic baths with TRI and absolute ethanol gave the best results with regard to macroscopical appearance and surface composition. However, as compared to the unused implants the results from an element composition point of view were still unsatisfactory. It is concluded that further development and testing of techniques for cleaning of organically contaminated titanium is needed.

Application of synchrotron radiation in investigation of metal-ion release from a hip replacement prosthesis

The aim of the present study was to measure very low concentrations of Al, V, Fe, Cr and other metal elements in a matrix of P, S, Cl, Ca and other constituent elements of the human body. These metal elements were released from a failed total hip replacement prosthesis into the surrounding tissues. The experimental results have been compared with those from proton-induced X-ray emission spectroscopy of the same specimen.