Multicenter randomized clinical trial: early loading of implants in maxillary bone.

PURPOSE: The aim of this study was to show prognostic equivalence between implant loading in the maxilla after 12 weeks versus 4 weeks. MATERIALS AND METHODS: One hundred four patients, from four centers in this open-labeled randomized multicenter prospective controlled clinical trial, were assigned to either 12 weeks or 4 weeks of unloaded healing. Two hundred sixty-nine implants (sand blasted large-grid, acid etched [SLA] surface, ≥ 4.1 mm diameter; ≥ 10 mm length) were inserted and evaluated during an individual 5-year follow-up. Primary outcome was implant success after 12 months; prognostic equivalence was characterized by a maximum difference of ± 5% in implant failure rates. RESULTS: Implant-wise 1-year failure rates were estimated 3.1% (5/163 implants) in the 4 weeks group versus 3.6% (4/112 implants) in the 12 weeks group (95% confidence interval [CI] for the difference -3.2 -+4.2%); implant-wise evaluation demonstrated statistically significant prognostic equivalence of 4 and 12 weeks loading. Patient-wise 1-year failure rates were estimated 6.7% (n = 4 patients) in the 4 weeks group versus 5.1% (n = 2 patients) in the 12 weeks group (95% CI for the difference -9.6 -+6.5%). All implant failures occurred within the first 3 months of the individual observation period. Prior bone augmentation, underdimensioned drilling, bone quality, implant type, implant length, implant diameter, residual teeth, and fixing of the restoration did not reveal associations with the implant outcome: trial site, posterior jaw region, and splinting were associated with a higher failure rate. Resonance frequency analysis did not serve as a predictor of implant failures at the time of implant insertion. CONCLUSION: Loading of standard SLA implants in the maxilla 4 weeks versus 12 weeks after insertion resulted in statistically equivalent failure patterns within a 1-year follow-up period; nevertheless, the observed patient-wise failure patterns of the interim analysis requires further understanding of patient-individual aspects of the early loading concept.

Development of a validated process for manual preparation of dental transmission instruments.

The goal of the study was to develop a validated manual preparation process that conforms to the requirements of validation guidelines. Twelve dental transmission devices from various manufacturers (turbines, handpieces, and contra-angle handpieces) were artificially contaminated with bovine hemoglobin for the test. Ten microliters (corresponding to 800 µg) of bovine hemoglobin solution (concentration 80 mg/ml) was pipetted into the spray water and spray air channels. The manual preparation was conducted by blowing air through the spray channels of the transmission instruments through an attachment to a treatment unit (model 1060T, KaVo, Biberach, Germany) for 5 s. The spray channels were cleaned with WL-Clean (Alpro, Georgen, Germany) as directed by the manufacturer. The spray channels were disinfected with WL-Cid (Alpro) and the spray channels were blow-dried with WL-Dry (Alpro) at the end of the exposure time as directed by the manufacturer. To determine the protein content (protein residue analysis) in the channels of the transmission instruments, 2 ml of an alkaline SDS solution (1%; pH 11) was flushed through the channels. For the quantitative protein residue analysis, the Biuret method was used as described in DIN EN 15883-1:2006. After the application of this method, all results of the protein residue analysis were within the acceptance criteria of the validation guideline. The newly developed manual preparation process is therefore confirmed as suitable from a hygienic viewpoint for preparation of transmission instruments in the dental practice.

Malignant fibrous histiocytoma of the face: report of a case.

BACKGROUND: Soft tissue sarcomas in the head and neck region are rare and often present a difficult differential diagnosis. The aim of our presentation is to point out the complexity of the diagnosis, treatment and follow up. CASE PRESENTATION: An eighty-seven year old female patient was referred to our unit with a fast growing brownish lump on the face. Four months beforehand, a benign fibrous histiocytoma (BFH) had been removed from the same location by excision biopsy with wide tumour-free resection margins. Excision biopsy of the recurrent lesion revealed a malignant fibrous histiocytoma (MFH). Radical tumour resection was completed by extended parotidectomy and neck dissection; the skin defect was covered by a regional bi-lobed flap. No adjuvant radio- or chemotherapy was administered. Full functional and cosmetic recovery was achieved; follow-up has been uneventful more than two years postoperatively. DISCUSSION: Malignant transformation of BFH is extremely rare and if so, extended radical surgery may give a fair chance for a favourable outcome even in patients with advanced age.

Success rate of mini- and micro-implants used for orthodontic anchorage: a prospective clinical study.

OBJECTIVES: Whereas micro-implants have become a useful alternative as orthodontic anchorage elements in orthodontics, less is known about the clinical effectiveness of micro-implants. The aim of this prospective clinical study was to evaluate the success rate of micro-implants used for orthodontic anchorage. MATERIAL AND METHODS: A total of 133 mini-implants (79 Abso Anchor, 54 Dual Top implants) placed in 49 patients to support orthodontic tooth movements were examined in the study. The majority of the implants were placed in the maxilla (82), followed by the vestibular (42) and lingual (nine) aspect of the mandible. RESULTS: An overall cumulative survival rate of 86.8% (102/133) was found by Kaplan-Meier analysis. The failure rate between Dual Top implants (13%) and Abso Anchor implants (30.4%) differed significantly (P=0.0196; log-rank test). The cumulative failure rate of implants was found to be significantly higher when implants were placed in the lingual aspect of the mandible compared with the other localizations (P=0.0011; log-rank test). Clinical evaluation revealed successful dental movements when implants remained stable during the orthodontic therapy. CONCLUSIONS: The present results confirm the effectiveness of orthodontic micro-implants used as anchorage elements.

Load-related bone modelling at the interface of orthodontic micro-implants.

The purpose of this study was to determine the interface reaction of two different titanium micro-implant systems activated with different load regimens. A total of 200 micro-implants (100 Abso Anchor and 100 Dual Top) were placed in the mandible of eight Göttinger minipigs. Two implants each were immediately loaded in the opposite direction by various forces (100, 300 or 500 cN) through tension coils. Three different distances between the neck of the implant and the bone rim (1, 2, 3 mm) were used. The loads provided by superelastic tension coils (which are known to develop a virtually constant force) led to a range of tip moments 0-900 cN mm at the neck of implants. Non-loaded implants were used as a reference. Bone tissue responses were evaluated by histology, histomorphometry and scanning electron microscopy after 22 and 70 days of loading. Implant loosening was present in the groups where the load reached 900 cN mm. No movement of implants through the bone was found in the experimental groups, for any of the applied loads. A direct bone-to-implant contact to various extents was observed at differently loaded implants. Ultrastructural analysis confirmed the clinical and histological finding that implants (except when loaded at 900 cN mm) were well osseointegrated after 22 days. An increase in the bone-to-implant contact ratio was observed during the experimental period in the coronal part of the implants in most experimental groups. The difference reached a level of statistical significance at 500 cN mm (Abso Anchor) and 600 cN mm (Dual Top). We conclude that micro-implants can not only be loaded immediately without impairment of implant stability but many enhance bone formation at the interface when the load-related biomechanics do not exceed an upper limit of tip moment at the bone rim.

Fast element mapping of titanium wear around implants of different surface structures.

The effect of unintended titanium release around oral implants remains a biological concern. The current study was undertaken to evaluate a new detection system of element mapping in biological probes. A new scanning electron microscopy-energy dispersive spectroscopy detection method was used to map the features of titanium contamination in peri-implant bone around implants with different surface structures. The amount of titanium wear was highest adjacent to titanium-plasma-sprayed surfaces, followed by sandblastered large grid acid-etched and smooth surfaces. A high sensitivity of titanium detection over large areas of bone tissue was observed. A high spatial resolution of titanium wear particles (20 nm) could be reached and correlated to the ultrastructural morphological features of peri-implant tissue. Cells adjacent to titanium wear revealed no signs of morphological alterations on a nanoscale level at early periods of implant/bone interaction. The new technique may serve as a fast and effective tool to evaluate titanium release effects in biological probes.

Biological and biomechanical evaluation of interface reaction at conical screw-type implants.

BACKGROUND: Initial stability of the implant is, in effect, one of the fundamental criteria for obtaining long-term osseointegration. Achieving implant stability depends on the implant-bone relation, the surgical technique and on the microscopic and macroscopic morphology of the implant used. A newly designed parabolic screw-type dental implant system was tested in vivo for early stages of interface reaction at the implant surface. METHODS: A total of 40 implants were placed into the cranial and caudal part of the tibia in eight male Göttinger minipigs. Resonance frequency measurements (RFM) were made on each implant at the time of fixture placement, 7 days and 28 days thereafter in all animals. Block biopsies were harvested 7 and 28 days (four animals each) following surgery. Biomechanical testing, removable torque tests (RTV), resonance frequency analysis; histological and histomorphometric analysis as well as ultrastructural investigations (scanning electron microscopy (SEM)) were performed. RESULTS: Implant stability in respect to the measured RTV and RFM-levels were found to be high after 7 days of implants osseointegration and remained at this level during the experimented course. Additionally, RFM level demonstrated no alteration towards baseline levels during the osseointegration. No significant increase or decrease in the mean RFM (6029 Hz; 6256 Hz and 5885 Hz after 0-, 7- and 28 days) were observed. The removal torque values show after 7 and 28 days no significant difference. SEM analysis demonstrated a direct bone to implant contact over the whole implant surface. The bone-to-implant contact ratio increased from 35.8 +/- 7.2% to 46.3 +/- 17.7% over time (p = 0,146). CONCLUSION: The results of this study indicate primary stability of implants which osseointegrated with an intimate bone contact over the whole length of the implant.

Strain driven fast osseointegration of implants.

BACKGROUND: Although the bone's capability of dental implant osseointegration has clinically been utilised as early as in the Gallo-Roman population, the specific mechanisms for the emergence and maintenance of peri-implant bone under functional load have not been identified. Here we show that under immediate loading of specially designed dental implants with masticatory loads, osseointegration is rapidly achieved. METHODS: We examined the bone reaction around non- and immediately loaded dental implants inserted in the mandible of mature minipigs during the presently assumed time for osseointegration. We used threaded conical titanium implants containing a titanium2+ oxide surface, allowing direct bone contact after insertion. The external geometry was designed according to finite element analysis: the calculation showed that physiological amplitudes of strain (500-3,000 ustrain) generated through mastication were homogenously distributed in peri-implant bone. The strain-energy density (SED) rate under assessment of a 1 Hz loading cycle was 150 Jm-3 s-1, peak dislocations were lower then nm. RESULTS: Bone was in direct contact to the implant surface (bone/implant contact rate 90%) from day one of implant insertion, as quantified by undecalcified histological sections. This effect was substantiated by ultrastructural analysis of intimate osteoblast attachment and mature collagen mineralisation at the titanium surface. We detected no loss in the intimate bone/implant bond during the experimental period of either control or experimental animals, indicating that immediate load had no adverse effect on bone structure in peri-implant bone. CONCLUSION: In terms of clinical relevance, the load related bone reaction at the implant interface may in combination with substrate effects be responsible for an immediate osseointegration state.

Vascular basis of mucosal color.

BACKGROUND: Besides the color of the teeth the color of the alveolar gingiva plays a crucial role in esthetic rehabilitation in dento-alveolar treatment. Whereas nowadays the color of the teeth can be determined exactly and individually, the specific influence of the red color of the gingiva on treatment has not been assessed yet. The aim of this study was to evaluate the vascularization as the basis for gingival esthetics. METHODS: Standardized photographs of defined areas of the alveolar gingiva in operated and non-operated patients were taken and assigned to groups with same characteristics after color comparisons. In addition, histologic and immunohistologic analyses of gingival specimens were performed for qualitative and quantitative assessment of vessels and vascularization. Finally, colors and number of vessels were correlated. RESULTS: Our results demonstrated three different constellations of colors of the alveolar gingiva in healthy patients. The operated patients could not be grouped because of disparate depiction. There was a clear correlation between color and vessel number in the alveolar gingiva. CONCLUSION: Our investigations revealed the connections between vascularization and gingival color. Recommendations for specific change or even selection of colors based on the results cannot be given, but the importance of vascularly based incision lines was demonstrated.

Interface reaction at dental implants inserted in condensed bone.

PURPOSE: The influence of the osteotome technique on the interface reaction of cylinder implants (SLA, ITI) was compared with the interface reaction of conventional implant insertion in an animal model. MATERIAL AND METHODS: A total of 64 implants were placed in the cranial and caudal tibia of 8 Göttinger minipigs. The implant site was prepared either by a conventional technique with drills (control group A) or by the osteotome technique (experimental group B). Bone tissue responses were evaluated by histomorphometry, fluorescence microscopy and scanning electron microscopy after 7 and 28 days of osseointegration. RESULTS: The average initial (7 days) bone-to-implant contact ratio was not statistically significantly different for the osteotome technique (35.88+/-2.94%) than for the control group (43.78+/-3.39%, P<0.095). After 28 days, the bone-to-implant contact ratio became statistically significantly higher when implants were inserted by conventional preparation (44.81+/-3.07% (group B), 63.47+/-4.87% (group A), P=0.003). Whereas fluorescence and immunhistologic examination revealed new bone formation with osteocalcin deposition directly at the implant surface in both groups, the extent of direct bone/implant contact was enhanced in conventionally prepared implant sites. SEM analysis confirmed an intimate bone to implant bond without fibrous tissue formation in places of direct contact at an ultrastructured level. CONCLUSION: Implant placement in conventionally prepared implantation sites is accompanied by an improved interface formation at an early stage of implantation.

Incision design in implant dentistry based on vascularization of the mucosa.

OBJECTIVES: The delivery of an adequate amount of blood to the tissue capillaries for normal functioning of the organ is the primary purpose of the vascular system. Preserving the viability of the soft tissue segment depends on the soft tissue incision being properly designed in order to prevent impairment of the circulation. A knowledge of the course of the vessels as well as of their supply area are crucial to the decision of the incision. The aim of this study was to visualize the course of the arteries using different techniques, to perform macroscopic- and microscopic analyses, and to develop recommendations for incisions in implant dentistry. MATERIAL AND METHODS: The vascular systems of seven edentulous human cadavers were flushed out and filled with either red-colored rubber bond or Indian ink and formalin mixture. After fixation a macroscopic preparation was performed to reveal the course, distribution and supply area of the major vessels. In the area of the edentulous alveolar ridge specimens of the mucosa were taken and analyzed microscopically. RESULTS: The analyses revealed the major features of mucosal vascularization. The main course of the supplying arteries is from posterior to anterior, main vessels run parallel to the alveolar ridge in the vestibulum and the crestal area of the edentulous alveolar ridge is covered by a avascular zone with no anastomoses crossing the alveolar ridge. CONCLUSION: The results suggest midline incisions on the alveolar ridge, marginal incisions in dentated areas, releasing incisions only at the anterior border of the entire incision line, and avoidance of incisions crossing the alveolar ridge.

Load-related implant reaction of mini-implants used for orthodontic anchorage.

The purpose of this study was to determine the clinical and biomechanical outcome of two different titanium mini-implant systems activated with different load regimens. A total of 200 mini-implants (102 Abso Anchor and 98 Dual Top) were placed in the mandible of eight Göttinger minipigs. Two implants each were immediately loaded in opposite direction by various forces (100, 300 or 500 cN) through tension coils. Additionally, three different distances between the neck of the implant and the bone rim (1, 2 and 3 mm) were used. The different load protocols were chosen to evaluate the load-related implant performance. The load was provided by superelastic tension coils, which are known to develop a virtually constant force. Non-loaded implants were used as a reference. Following an experimental loading period of 22 and 70 days half of the minipigs were sacrificed, and implant containing bone specimens evaluated for clinical performance and implant stability. Implant loosing was found to be statistically dependent on the tip moment (TM) at the bone rim. Clinical implant loosing were only present when load exceeded 900 cN mm. No movement of implants through the bone was found in the experimental groups, for any applied loads. Over the two experimental periods the non-loaded implants of one type of implant had a higher stability than those of the loaded implants. Dual Top implants revealed a slightly higher removal torque compared with Abso Anchor implants. Based on the results of this study, immediate loading of mini-implants can be performed without loss of stability when the load-related biomechanics do not exceed an upper limit of TM at the bone rim.

Biological and biomechanical evaluation of bone remodelling and implant stability after using an osteotome technique.

The influence of the osteotome technique on the osseointegration and biomechanical behaviour of cylinder implants (SLA, ITI was compared with conventional preparation of the implant site in an animal model. A total of 56 implants were placed in the cranial and caudal tibia condyle of six Gottinger minipigs. The implant site was prepared either by the conventional technique with drills (control group A) or by the osteotome technique (experimental group B). Resonance frequency measurements (RFMs) were made on each implant at the time of fixture placement and at the time of scarification. Half of the minipigs were sacrificed 7 days and 28 days after implant placement and the implants were removed with the surrounding bone. Bone tissue responses were evaluated by histological analysis and removal torque testing. For histological evaluation 30-50 microm-thick ground sections were examined. Biomechanical testing revealed a significantly higher stability of implants in the control group (A) than in the experimental group (B) (P = 0.004) at day 7. After 28 days implant stability in the control group remained significant higher (47%) than those of group B (P > 0.001). RFM demonstrated no significant difference between both groups and during the experimental course. Histological analysis demonstrated fractured trabeculae in peri-implant bone in the experimental group at day 7, while they were not posed at day 28. We conclude that the decreased implant stability by using the osteotome technique is based on microfractures in peri-implant bone.

Image-based extracorporeal tissue engineering of individualized bone constructs.

PURPOSE: Computer-aided technologies have been recently employed for use in extracorporeal bone tissue engineering strategies. In this pilot animal experimental study, the intention was to test whether autologous osteoblast-like cells cultured in vitro on individualized scaffolds can be used to support bone regeneration in a clinical environment. MATERIALS AND METHODS: For this purpose, mandibular bone defects were surgically introduced into the mandibles of minipigs and the scaffold of the defect site was modeled by computer-aided design/computer-aided manufacturing technique. Autologous bone cells from porcine calvaria were harvested from minipigs and grown in culture. Cells were seeded on scaffolds generated by rapid prototyping of polylactic acid/polyglycolic acid copolymers. The defects were then reconstructed by implanting the tissue constructs. RESULTS: The intraoperative sites as well as the postoperative computerized tomographic scans demonstrated an accurate fit in the defect sites. The implanted scaffold constructs enriched with osteoblast-like cells were well tolerated and appeared to support bone formation, as revealed by histologic and immunohistochemical analyses. DISCUSSION: These results indicated that in vitro expanded osteoblast-like cells spread on a resorbable individualized scaffold can be capable of promoting the repair of bony defects in vivo. CONCLUSION: These results warrant further attempts to combine computer modeling and tissue engineering for use in bone reconstructive surgery.

Sustained release of doxycycline for the treatment of peri-implantitis: randomised controlled trial.

UNLABELLED: With the increased use of osseointegrated implants and with many implants functioning for a long time, the treatment of peri-implantitis has become important. Animal studies and clinical case reports have shown that the principle of guided bone regeneration can be applied to the surgical treatment of moderate to profound loss of bone around the implant, but we have found no published clinical studies. PATIENTS AND METHODS: Twenty-eight patients whose ages ranged from 25 to 78 years and who had a total of 48 peri-implant defects were examined at baseline (week 0) and after 18 weeks. This included the recording of bleeding on probing, pocket probing depths, and probing attachment levels at six sites for each tooth. For 2-18 weeks before week 0 all patients had been treated for peri-implantitis, including motivation, instruction in oral hygiene, and implant scaling with a hand plastic instrument. They were then randomly allocated to continue with this treatment or to have in addition mechanical debridement and local application of Atridox trade mark which slowly release doxycycline. RESULTS: Patients treated with Atridox trade mark showed a significantly greater gain in mean (S.D.) probing attachment levels than those not treated with Atridox. Only subjects treated with Atridox had a significant gain in mean bleeding on probing (P = 0.001). Application of the biodegradable sustained release device after initial periodontal treatment resulted in a significant gain in mean probing attachment levels in the Atridox trade mark group and a significant reduction in pocket probing depths. There was also a significant difference in mean probing attachment levels (0.6mm).

Treatment of severe peri-implant bone loss using autogenous bone and a bioabsorbable polymer that delivered doxycycline (Atridox).

With an increase of the number of implants being inserted, it is inevitable that the number of cases of peri-implantitis with loss of bone will rise. We report a case in which an autogenous cancellous bone graft was placed into the peri-implant bone defect and given protection with a bioabsorbable polymer barrier (Atridox) that released doxycycline slowly.