The influence of BMP-2 and its mode of delivery on the osteoconductivity of implant surfaces during the early phase of osseointegration

Osteogenic agents, such as bone morphogenetic protein-2 (BMP-2), can stimulate the degradation as well as the formation of bone. Hence, they could impair the osteoconductivity of functionalized implant surfaces. We assessed the effects of BMP-2 and its mode of delivery on the osteoconductivity of dental implants with either a naked titanium surface or a calcium-phosphate-coated one. The naked titanium surface bore adsorbed BMP-2, whilst the coated one bore incorporated, adsorbed, or incorporated and adsorbed BMP-2. The implants were inserted into the maxillae of adult miniature pigs. The volume of bone deposited within a defined "osteoconductive" (peri-implant) space, and bone coverage of the implant surface delimiting this space, were estimated morphometrically 1-3 weeks later. After 3 weeks, the volume of bone deposited within the osteoconductive space was highest for coated and uncoated implants bearing no BMP-2, followed by coated implants bearing incorporated BMP-2; it was lowest for coated implants bearing only adsorbed BMP-2. Bone-interface coverage was highest for coated implants bearing no BMP-2, followed by coated implants bearing either incorporated, or incorporated and adsorbed BMP-2; it was lowest for uncoated implants bearing adsorbed BMP-2. Hence, the osteoconductivity of implant surfaces can be significantly modulated by BMP-2 and its mode of delivery.

Immediate implant placement with transmucosal healing in areas of aesthetic priority. A multicentre randomized-controlled clinical trial I. Surgical outcomes

OBJECTIVES: To compare the clinical outcomes of standard, cylindrical, screw-shaped to novel tapered, transmucosal (Straumann Dental implants immediately placed into extraction sockets. Material and methods: In this randomized-controlled clinical trial, outcomes were evaluated over a 3-year observation period. This report deals with the need for bone augmentation, healing events, implant stability and patient-centred outcomes up to 3 months only. Nine centres contributed a total of 208 immediate implant placements. All surgical and post-surgical procedures and the evaluation parameters were discussed with representatives of all centres during a calibration meeting. Following careful luxation of the designated tooth, allocation of the devices was randomly performed by a central study registrar. The allocated SLA titanium implant was installed at the bottom or in the palatal wall of the extraction socket until primary stability was reached. If the extraction socket was >or=1 mm larger than the implant, guided bone regeneration was performed simultaneously (Bio Oss and BioGide. The flaps were then sutured. During non-submerged transmucosal healing, everything was done to prevent infection. At surgery, the need for augmentation and the degree of wound closure was verified. Implant stability was assessed clinically and by means of resonance frequency analysis (RFA) at surgery and after 3 months. Wound healing was evaluated after 1, 2, 6 and 12 weeks post-operatively. RESULTS: The demographic data did not show any differences between the patients receiving either standard cylindrical or tapered implants. All implants yielded uneventful healing with 15% wound dehiscences after 1 week. After 2 weeks, 93%, after 6 weeks 96%, and after 12 weeks 100% of the flaps were closed. Ninety percent of both implant designs required bone augmentation. Immediately after implantation, RFA values were 55.8 and 56.7 and at 3 months 59.4 and 61.1 for cylindrical and tapered implants, respectively. Patient-centred outcomes did not differ between the two implant designs. However, a clear preference of the surgeon's perception for the appropriateness of the novel-tapered implant was evident. CONCLUSIONS: This RCT has demonstrated that tapered or standard cylindrical implants yielded clinically equivalent short-term outcomes after immediate implant placement into the extraction socket.

Immediate loading of single SLA implants: drilling vs. osteotomes for the preparation of the implant site

OBJECTIVES: To evaluate whether or not preparation of the implant site with osteotomes instead of drilling may improve peri-implant bone density and/or osseointegration, and whether or not this further improves the predictability of immediate loading of SLA implants. MATERIAL AND METHODS: The second, third, and fourth premolars were extracted in both sides of the mandible in six dogs, and after at least 3 months four SLA implants were inserted into each side of the jaw. In three animals, the implant sites were prepared by means of osteotomes, while standard stepwise drilling was used in the remaining animals. In each side of the jaw, two non-adjacent implants were restored with single crowns 4 days after installation, while the remaining two implants were left without crowns to serve as non-loaded controls. After 2, 4, or 12 weeks of loading, specimens including the implants and surrounding tissues were obtained and processed for histologic analysis of undecalcified sections. RESULTS: All implants placed with osteotomes were lost (five before delivery of the crowns and the rest during the first week after loading). None of the conventionally inserted implants, however, was lost, and histomorphometrical analysis revealed similar soft- and hard peri-implant tissue characteristics at immediately loaded and non-loaded implants at all observation times. Average bone-to-implant contact was 59-72% at immediately loaded implants vs. 60-63% at non-loaded ones. CONCLUSION: Preparation of the implant site by means of osteotomes had a deleterious effect on osseointegration, while immediate loading of single, free-standing, SLA implants following a conventional surgical protocol did not jeopardize their osseointegration.

Morphogenesis of the peri-implant mucosa: an experimental study in dogs

PURPOSE: The objective of the present experiment was to study the morphogenesis of the mucosal attachment to implants made of c.p. titanium. MATERIAL AND METHODS: All mandibular premolars were extracted in 20 Labrador dogs. After a healing period of 3 months, four implants (ITI Dental Implant System) were placed in the right and left sides of the mandible. A non-submerged implant installation technique was used and the mucosal tissues were secured to the conical marginal portion of the implants with interrupted sutures. The sutures were removed after 2 weeks and a plaque control program including daily cleaning of the remaining teeth and the implants was initiated. The animals were sacrificed and biopsies were obtained at various intervals to provide healing periods extending from Day 0 (2 h) to 12 weeks. The mandibles were removed and placed in the fixative. The implant sites were dissected using a diamond saw and processed for histological analysis. RESULTS: Large numbers of neutrophils infiltrated and degraded the coagulum that occupied the compartment between the mucosa and the implant during the initial phase of healing. At 2 weeks after surgery, fibroblasts were the dominating cell population in the connective tissue interface but at 4 weeks the density of fibroblasts had decreased. Furthermore, the first signs of epithelial proliferation were observed in specimens representing 1-2 weeks of healing and a mature barrier epithelium occurred after 6-8 weeks of healing. The collagen fibers of the mucosa were organized after 4-6 weeks of healing. CONCLUSION: It is suggested that the soft-tissue attachment to implants placed using a non-submerged installation procedure is properly established after several weeks following surgery.

Comparison of musical activities of cochlear implant users with different speech-coding strategies

Speech coding might have an impact on music perception of cochlear implant users. This questionnaire study compares the musical activities and perception of postlingually deafened cochlear implant users with three different coding strategies (CIS, ACE, SPEAK) using the Munich Music Questionnaire. Overall, the self-reported perception of music of CIS, SPEAK, and ACE users did not differ by very much.

The radiographic assessment of implant patients: decision-making criteria

Indications for the most frequently used imaging modalities in implant dentistry are proposed based on clinical need and biologic risk for the patient. To calculate the biologic risk, the authors carried out dose measurements. They demonstrated that the risk from a periapical radiograph is 20% of that from a panoramic radiograph. A panoramic radiograph and a series of 4 conventional tomographs of a single-tooth gap in the molar region carry 5% and 13% of the risk from computed tomography of the maxilla, respectively. Panoramic radiography is considered the standard radiographic examination for treatment planning of implant patients, because it imparts a low dose while giving the best radiographic survey. Periapical radiographs are used to elucidate details or to complete the findings obtained from the panoramic radiograph. Other radiographic methods, such as conventional film tomography or computed tomography, are applied only in special circumstances, film tomography being preferred for smaller regions of interest and computed tomography being justified for the complete maxilla or mandible when methods for dose reduction are followed. During follow-up, intraoral radiography is considered the standard radiographic examination, particularly for implants in the anterior region of the maxilla or for scientific studies. In patients requiring more than 5 periapical images, panoramic radiography is preferred.

Non-photorealistic rendering of virtual implant models for computer-assisted fluoroscopy-based surgical procedures

Surgical navigation systems visualize the positions and orientations of surgical instruments and implants as graphical overlays onto a medical image of the operated anatomy on a computer monitor. The orthopaedic surgical navigation systems could be categorized according to the image modalities that are used for the visualization of surgical action. In the so-called CT-based systems or 'surgeon-defined anatomy' based systems, where a 3D volume or surface representation of the operated anatomy could be constructed from the preoperatively acquired tomographic data or through intraoperatively digitized anatomy landmarks, a photorealistic rendering of the surgical action has been identified to greatly improve usability of these navigation systems. However, this may not hold true when the virtual representation of surgical instruments and implants is superimposed onto 2D projection images in a fluoroscopy-based navigation system due to the so-called image occlusion problem. Image occlusion occurs when the field of view of the fluoroscopic image is occupied by the virtual representation of surgical implants or instruments. In these situations, the surgeon may miss part of the image details, even if transparency and/or wire-frame rendering is used. In this paper, we propose to use non-photorealistic rendering to overcome this difficulty. Laboratory testing results on foamed plastic bones during various computer-assisted fluoroscopybased surgical procedures including total hip arthroplasty and long bone fracture reduction and osteosynthesis are shown.

Early implant placement following single-tooth extraction in the esthetic zone: biologic rationale and surgical procedures

Early implant placement is one treatment option for implant therapy following single-tooth extraction in the anterior maxilla. The surgical technique presented here is characterized by tooth extraction without flap elevation, a 4- to 8-week soft tissue healing period, implant placement in a correct three-dimensional position, simultaneous contour augmentation on the facial aspect with guided bone regeneration using a bioabsorbable collagen membrane combined with autogenous bone chips and a low-substitution bone filler, and tension-free primary wound closure. The surgical step-by-step procedure is presented with a case report. In addition, the biologic rationale is discussed.

Early implant placement with simultaneous guided bone regeneration following single-tooth extraction in the esthetic zone: a cross-sectional, retrospective study in 45 subjects with a 2- to 4-year follow-up

BACKGROUND: The concept of early implant placement is a treatment option in postextraction sites of single teeth in the anterior maxilla. Implant placement is performed after a soft tissue healing period of 4 to 8 weeks. Implant placement in a correct three-dimensional position is combined with a simultaneous guided bone regeneration procedure to rebuild esthetic facial hard and soft tissue contours. METHODS: In this retrospective, cross-sectional study, 45 patients with an implant-borne single crown in function for 2 to 4 years were recalled for examination. Clinical and radiologic parameters, routinely used in implant studies, were assessed. RESULTS: All 45 implants were clinically successful according to strict success criteria. The implants demonstrated ankylotic stability without signs of a peri-implant infection. The peri-implant soft tissues were clinically healthy as indicated by low mean plaque (0.42) and sulcus bleeding index (0.51) values. None of the implants revealed a mucosal recession on the facial aspect as confirmed by a clearly submucosal position of all implant shoulders. The mean distance from the mucosal margin to the implant shoulder was -1.93 mm on the facial aspect. The periapical radiographs showed stable peri-implant bone levels, with a mean distance between the implant shoulder and the first bone-implant contact of 2.18 mm. CONCLUSIONS: This retrospective study demonstrated successful treatment outcomes for all 45 implants examined. The mid-term follow-up of 2 to 4 years also showed that the risk for mucosal recession was low with this treatment concept. Prospective clinical studies are required to confirm these encouraging results.

The influence of non-matching implant and abutment diameters on radiographic crestal bone levels in dogs

BACKGROUND: It has been shown that different implant designs and different vertical implant positions have an influence on crestal bone levels. The aim of the present study was to evaluate radiographic crestal bone changes around experimental dental implants with non-matching implant-abutment diameters placed submucosally or transmucosally at three different levels relative to the alveolar crest. METHODS: Sixty two-piece dental implants with non-matching implant-abutment diameters were placed in edentulous spaces bilaterally in five foxhounds. The implants were placed submucosally or transmucosally in the left or the right side of the mandible. Within each side, six implants were randomly placed at three distinct levels relative to the alveolar crest. After 12 weeks, 60 crowns were cemented. Radiographs were obtained from all implant sites following implant placement, after crown insertion, and monthly for 6 months after loading. RESULTS: Radiographic analysis revealed very little bone loss and a slight increase in bone level for implants placed at the level of the crest or 1 mm above. The greatest bone loss occurred at implants placed 1 mm below the bone crest. No clinically significant differences regarding marginal bone loss and the level of the bone-to-implant contact were detected between implants with a submucosal or a transmucosal healing. CONCLUSIONS: Implants with non-matching implant-abutment diameters demonstrated some bone loss; however, it was a small amount. There was no clinically significant difference between submucosal and transmucosal approaches.