Implant-guided supracrestal alveolar bone growth using scaffolds, BMP-2, and novel scaffold-retaining device.

OBJECTIVE: To evaluate the efficacy of various scaffold systems and a Ti scaffold-retaining device with and without non-glycosylated rhBMP-2 (BMP-2) for increasing the vertical alveolar bone growth in the intra-oral mini-pig model. METHODS: Forty-eight Straumann Bone Level implants with hydrophilic (SLActive) surfaces were partially embedded in mandibles of 12 adult mini-pigs with the shoulder of the implant located 3 mm above the bone crest. Twenty-four implants were placed in conjunction with BMP-2 (50 µg) incorporated within resorbable scaffolds. Twenty-four additional control implants were placed with scaffolds only. Scaffolds were placed around the implant and stabilized with a newly developed Ti "umbrella" scaffold retainer. Scaffolds included (i) HA-coated collagen (Healos); (ii) biphasic HA/ß-TCP crystals (Straumann Bone Ceramic, SBC); and (iii) SBC crystals infused with polyethylene glycol (PEG) hydrogel. Eight test and control pairs for each scaffold group were implanted. At 9 weeks, soft tissue healing was assessed and the extent of new vertical bone was evaluated with microCT and histomorphometry. RESULTS: microCT analysis revealed a mean of 167 ± 47 mm3 new supracrestal mineralized tissue volume formation around the test sites where BMP-2 was released from the scaffold whereas the control group (no BMP-2) showed a significantly lower mineralized tissue volume of 106 ± 55 mm3 . The SBC+BMP-2 group had the highest mineralized tissue volume of 189 ± 36 mm3 . Histomorphometry showed bone-to-implant contact of 54.5% for the test groups and 33.3% for the control groups and new vertical bone growth of 2.2 ± 1.0 and 1.0 ± 0.9 mm, respectively. The SBC+BMP-2 group again demonstrated the best outcome (2.7 ± 0.4 mm). The qualitative scoring of soft tissue dehiscence showed that the presence of BMP-2 yielded far superior outcomes, 0.63 vs. 1.75 for all control implant sites (with scores ranging from 0, reflecting no soft dehiscence, to 4, showing a completely exposed umbrella). CONCLUSION: The release of BMP-2 from a SBC scaffold adjacent to a hydrophilic, rough Ti implant and scaffold retention umbrella consistently regenerated the greatest volume and height of new vertical bone along the length of the implant.

Use of a perforated scaffold-retaining abutment to achieve vertical bone regeneration around dental implants in the minipig.

OBJECTIVE: To evaluate the effect of perforated scaffold retainers used in conjunction with dental implants and osteoinductive scaffolds to regenerate vertical supracrestal alveolar bone in an intraoral minipig model. MATERIALS AND METHODS: Three months after extraction of mandibular premolars and first molars from six adult minipigs, two titanium (Ti) custom implants were placed bilaterally in the edentulous mandibles for a total of four implants per animal. The upper 2.5 mm of the implant was left above bone level and covered with: (1) wide-neck healing caps; (2) perforated, overhanging custom scaffold retainers (umbrellas); or (3) scaffold retainers and demineralized minipig bone allograft (DBM) and nonglycosylated bone morphogenetic protein 2 (ng/rhBMP-2)-treated implants. All constructs were submerged beneath soft tissue flaps for 8 weeks. Two dental implant surfaces were compared: SLA and SLActive. Samples were retrieved after 8 weeks and analyzed by radiography, micro-computed tomography and histomorphometry. RESULTS: All implants were stable at the end of the experiment. Histomorphometry revealed that the use of the scaffold-retaining umbrellas led to increased, but not statistically significant, vertical bone regeneration as compared to the use of wide-neck healing caps (1.0 ± 0.4 mm vs 0.6 ± 0.3 mm). The combination of DBM and ng/rhBMP-2 released from the surface of the SLA implant resulted in the greatest amount of vertical bone regeneration (2.1 ± 0.2 mm). The bone-to-implant contact was similar for all groups. Mucosal dehiscence areas with healing cap or custom scaffold retainer exposures were reduced in the presence of ng/rhBMP-2. CONCLUSIONS: The combined use of custom perforated Ti scaffold retainers, DBM, and ng/rhBMP-2 regenerated a substantial amount of vertical supracrestal alveolar bone around Ti implants in an intraoral minipig model.

Implant-guided vertical bone growth in the mini-pig.

OBJECTIVE: To attain and describe guided vertical bone regeneration around titanium (Ti) and titanium zirconium (Ti-Zr) dental implants utilizing non-glycosylated recombinant human bone morphogenetic protein-2 (ng/rhBMP-2), biomaterial scaffolds and a scaffold retainer. MATERIALS AND METHODS: Thirty-two modified Straumann TE implants were partially embedded in the mandibles of eight adult mini-pigs. Pre-shaped resorbable scaffolds were placed around the implant and shielded and stabilized with a newly developed Ti custom scaffold retainer (umbrella) or wide-neck (WN) healing caps to stabilize the scaffold. Ng/rhBMP-2 (50 µg) was applied to the supracrestal portion of the implant or incorporated within the scaffold. At 9 weeks, soft tissue healing was assessed. Vertical bone regeneration outcomes including bone height, bone-to-implant contact (BIC) and bone volume were assessed by micro-computed tomography and histology. RESULTS: Soft tissue healing at the test sites (+ng/rhBMP-2/+scaffold) appeared to be substantially better than the control sites (-ng/rhBMP-2/-scaffold). Bone height, BIC percentage and bone volume were all similar regardless of whether WN healing caps or umbrella scaffold stabilization was used for all biomaterial scaffolds tested. WN healing cap test sites showed greater new bone height and BIC as compared with aggregate data from the control sites (P=0.05). Comparison of aggregate data from the umbrella test sites showed greater BIC and new bone volume as compared with aggregate data from the control sites(P=0.05). CONCLUSION: Vertical bone regeneration was successfully attained utilizing ng/rhBMP-2, biomaterial scaffolds and a scaffold retainer.

Simultaneous dental implant placement and endoscope-guided internal sinus floor elevation: 2-year post-loading outcomes.

AIMS: To determine whether endoscope-guided sinus elevation procedures can be consistently used to create sufficient bone support for stable implant placement and long-term implant success. MATERIAL AND METHODS: Sixty-two implants were surgically placed into 30 patients (14 men and 16 women) following internal sinus elevation without the use of graft material. Panoramic radiographs were made pre-, post-operative and after 24 months in order to evaluate the peri-implant bone and maxillary sinuses. Resonance frequency analysis (RFA) was used to evaluate implant stability immediately upon placement and just before prosthesis delivery. RESULTS: The average pre-operative height of the maxillary alveolar bone was 8.4+/-2.2 mm at the premolar and 7.3+/-3.1 mm at the molar regions. The average bone gain was 3.5+/-1.8 and 4.5+/-1.9 mm in the premolar and molar sites, respectively. Clinical parameters and the RFA (4 and 12 weeks post-operative) outcomes show sufficient stability (ISQ=60) of the inserted implants. Three implants failed during the healing period of 12 weeks. The overall implant success rate was 94%. After loading, no further implant failure was observed. The overall success rate after beginning of implant loading was 100%. CONCLUSIONS: Sinus floor elevation is a well-established procedure for augmentation of the atrophic maxillary posterior region. The minimally invasive internal sinus floor elevation procedure visually guided by an endoscope helped to prevent, diagnose and manage complications such as sinus membrane perforation. The clinical outcomes of this study show that endoscope-controlled internal sinus floor elevation combined with implant placement results in low intra operative trauma, good implant stability upon placement, low incidence of post-operative symptoms and high success rates after 24 months of loading.

Growth of new bone guided by implants in a murine calvarial model.

New methods to increase vertical bone growth are needed to permit dental implant placement in patients with low alveolar ridge height after extended periods of tooth loss. While ectopic rodent models are typically used to evaluate new osteogenic implant surface coatings, a more relevant intramembraneous rodent model was needed to address the particular clinical need to grow a new layer of bone above an existing layer of bone. In this study we report on a novel murine calvaria model in which successful vertical bone growth around miniaturized dental implants was achieved when using non-glycosylated bone morphogenetic protein-2 (ng/rhBMP-2). Twenty CD-1 mice received two Ti implants each consisting of a Ti ring implant stabilized by a Ti screw into the occipital calvarial bone. Four groups were evaluated: control Ti, Ti+20 mug ng/rhBMP-2, hydroxyapatite (HA)-coated Ti, and HA+20 mug ng/rhBMP-2. The mice were sacrificed 21 days following implant placement. MicroCT analysis showed no new bone formation around the untreated Ti or the HA-coated implants, but demonstrated new bone growth in every dimension around and above the Ti+ng/rhBMP-2 and the HA+ng/rhBMP-2 treated implants. Histopathologic analysis showed that a thin fibrous capsule covered the untreated Ti implants. Limited bone-to-implant contact (BIC) was observed for the HA-coated implants, while in contrast both ng/rhBMP-2 treated groups exhibited extensive new supracalvarial woven bone that covered the implant and merged with the calvarial plate. Histomorphometrically, supracalvarial bone heights and bone widths and BIC were not statistically different from one another for the two ng/rhBMP-2 treated groups. However, the total supracalvarial bone surface area was significantly greater (p<0.05) for the Ti+ng/rhBMP-2 implants (7.2 mm(2)) than the HA+ng/rhBMP-2 (4.0 mm(2)) treated implants. The bone density within 1 mm around the implant was also significantly greater (p<0.05) for the Ti+ng/rhBMP-2 implants (9.9%) than the HA+ng/rhBMP-2 (4.0%) implants, indicating that HA coatings may not be required for sustained release when non-glycosylated BMP-2 is used. This new murine model is capable of discriminating between various bone augmentation strategies and may represent a clinically more relevant model for alveolar bone augmentation than the commonly used ectopic muscle pouch or long bone models.

Ectopic bone formation as a complication of surgical rehabilitation in patients with Moebius' syndrome.

PURPOSE: Treatment of facial paralysis by muscular neurotization resulted in ectopic ossification in 1 of 134 cases in this department. That patient suffering from Moebius syndrome (MS) is presented. Reviewing the literature concerning MS, Hox genes and bone morphogenetic protein dysregulation, a pathogenesis of ossification in MS is suggested. PATIENT: The MS patient exhibited a congenital facial nerve palsy, which was treated by muscular neurotization (Lexer-Rosenthal). Because of postoperative ossification of scarred areas, osteotomy of the processus muscularis and mobilization of the masseter muscle was performed. Nevertheless, further ossification occurred at the interface between the mandible and zygoma and in two masticatory muscles. So, the construction of a neoarthrosis became necessary. Three years later, the iatrogenic bone defect had reossified despite of an active opening therapy. CONCLUSIONS: Ectopic ossification after muscular neurotization seems to be restricted to patients with MS and is triggered by trauma. Molecular pathogenesis: facial malformations in MS are caused by disturbances in embryonic patterning. Failure in the development of the second pharyngeal arch leads to a spatial BMP-4 dysregulation responsible for ossification after wounding of muscle fascia. Therefore, surgical rehabilitation of facial function by muscular neurotization is contra indicated in MS patients.

Treatment options in distraction osteogenesis therapy using a new bidirectional distractor system.

PURPOSE: The purpose of this retrospective study was to compare a bidirectional distraction system with a unidirectional system with regard to bone height attained and the need for secondary graft procedures. MATERIALS AND METHODS: Unidirectional and bidirectional distractor devices were used for vertical augmentation of the maxilla and mandible in 2 separate groups of patients (n = 10 and n = 11, respectively). Clinical and radiographic outcome data were collected at postoperative follow-up examinations for up to 2.5 years. The height of the augmented alveolar ridge and the sagittal location of the bone fragment were measured on panoramic radiographs or lateral cephalograms. These data were analyzed with 1-way analysis of variance. Nonparametric data, such as treatment complications, were analyzed with the Fisher exact test. The dental implant survival data were evaluated with a Kaplan-Meier survival analysis. RESULTS: The difference in vertical bone gain observed between unidirectional and bidirectional groups (5.3 +/- 1.8 mm vs 6.1 +/- 2.3 mm) was not statistically significant. In the unidirectional group, additional autogenous bone grafting was required in 6 cases, while grafting was required in only 2 cases in the bidirectional group. This difference was due to the more precise control of the distraction process associated with the bidirectional distractor; however, it was not a statistically significant difference. Postaugmentation, 59 implants were placed in the augmented sites. These implants exhibited primary stability and were restored with good functional and esthetic results. CONCLUSIONS: The need for additional grafting procedures may be reduced in cases where the distraction vector is optimized, as generally seen with bidirectional distractor use.

5-Aminolaevulinic acid (ALA) induced formation of different fluorescent porphyrins: a study of the biosynthesis of porphyrins by bacteria of the human digestive tract.

Aminolaevulinic acid (ALA) induces porphyrin formation in almost all living cells. The fluorescence spectra of porphyrins produced from a variety of 31 bacterial strains from the human oral cavity and other parts of digestive tract have been examined. Many of the bacteria exposed to ALA were able to induce protoporphyrin IX (PpIX) fluorescence, but under aerobic condition some bacteria can also produced different fluorescent porphyrins, in particular water-soluble porphyrins that can arise from an oxidation of the corresponding porphyrinogen precursors. The formation of fluorescent porphyrins can be different from one bacterial strain to another, but also one specific bacterium can form different fluorescent porphyrins. Irradiation of the ALA incubated cultures led to a rapid formation of water-soluble porphyrins exhibiting fluorescence maxima at wavelengths of 618-620 nm. This light induced formation of water-soluble porphyrins could be attributed to a photooxidation of the non-fluorescent (Uro/Copro)-porphyrinogen precursors. Addition of detergents to some of the bacterial cultures led to a strong PpIX fluorescence increase, indicating that some of the PpIX originally produced can be present in a non-fluorescent, probably aggregated, form. The large abundance of bacteria in the oral cavity and other parts of digestive tract, with their capacity to easily produce fluorescent porphyrins, indicates that such bacterial fluorescence should be suppressed during the ALA-based diagnosis of tumours in order to eliminate false positive results.

A quantitative co-localization analysis of large unspliced tenascin-C(L) and laminin-5/gamma2-chain in basement membranes of oral squamous cell carcinoma by confocal laser scanning microscopy.

BACKGROUND: A structural interaction of the oncofetal large tenascin-C splice variants (Tn-C(L)) and the gamma2-chain of laminin-5 (Ln-5/gamma2) was recently demonstrated in oral squamous cell carcinoma (OSCC). In situ different patterns of co-localization and co-deposition of both proteins could be detected. Especially the co-localization in re-established basement membrane (BM) structures seemed to be biologically meaningful within the process of tumour progression. METHODS: The amount of Tn-C(L) incorporated in reorganized OSCC BM structures at the tumour margins was investigated by a laser scanning microscopy-based quantitative co-localization analysis. RESULTS: In the BM of normal oral mucosa no Tn-C(L) could be detected. In dysplastic and neoplastic oral mucosa a distinct co-localization of Tn-C(L) and Ln-5/gamma2 in the BM region could be observed. The extent of Tn-C(L) arrangement into reorganized BM structures correlated with malignancy grade. CONCLUSIONS: The results suggest at first, a modulation of carcinomatous BM structures by the inclusion of oncofetal matrix proteins during tumour progression and secondly, the BM incorporation of the adhesion-modulating molecule Tn-C(L) as a pre-invasive structural phenomenon in OSCC.

Comparison of aminolevulinic acid (ALA)-thermogel-PDT with methyl-ALA-thermogel-PDT in basal cell carcinoma.

BACKGROUND: Aminolevulinic acid (ALA) and light irradiation is a treatment option in basal cell carcinomas (BCC). The development of ALA-esters with potential for greater penetration depth promises higher therapeutic success. In a pilot study, we hypothesized that the cytotoxic effect of methyl-ALA (mALA) photodynamic therapy (PDT) leads to a higher success rate compared with ALA-PDT when both are topically applied in a thermogel. METHODS: Twenty-four patients with 112 superficial BCC were treated with either 10% ALA- or mALA-thermogel. After an accumulation time of at least 3h, the lesions were illuminated with a diode laser. The power density was 0.1W/cm(2) and the energy density was 120J/cm(2). After intervals of 12 weeks and 6 months, the therapeutic efficacy was assessed by clinical examination. RESULTS: Sixty percent of the tumors were treated successfully in the first session. All but 3% of the remaining tumors could be treated with a second or third course of therapy. CONCLUSION: Although mALA should have a greater penetration depth, the therapeutic outcome of this preliminary study showed no difference between treatments. The final proof of this preliminary result will require further study.

Complex formation of the laminin-5 gamma2 chain and large unspliced tenascin-C in oral squamous cell carcinoma in vitro and in situ: implications for sequential modulation of extracellular matrix in the invasive tumor front.

Invasion and metastasis in oral squamous cell carcinoma (OSCC) are associated with changes in the extracellular matrix (ECM). We have previously shown an extracellular co-deposition of laminin-5 (Ln-5) and large unspliced tenascin-C (Tn-C(L)) in OSCC. Using a co-culture model of hTERT-BJ1 fibroblasts and the OSCC cell line PE/CA-PJ15, we demonstrate in the present study that Ln-5 and Tn-C(L) are not only co-deposited, but also form a physical complex which can be recovered by co-immunoprecipitation. In agreement with these results, examination of OSCC tissue specimens of different malignancy grade by means of confocal laser scanning microscopy revealed different patterns of Ln-5 and Tn-C(L) co-localization implicating complex formation also in vivo. A ribbon like co-localization was detected in subepithelial basement membranes around well differentiated OSCC parts and tumor clusters. Furthermore, a fibrillar Ln-5 gamma2 chain/Tn-C(L) co-localization occurred in the carcinoma stroma beneath tumor clusters. Additionally, at the site of ruptured basement membranes there were dot or strand like co-deposits of both molecules, but co-localizations were only rarely detectable. These different patterns may reflect a sequential modulation and reorganization of the ECM in the tumor/stroma interface as it occurs in different stages of OSCC invasion.

Analysis of activated EGFR signalling pathways and their relation to laminin-5 gamma2 chain expression in oral squamous cell carcinoma (OSCC).

Overexpression of epidermal growth factor receptor (EGFR) was shown for the majority of squamous cell carcinomas. The EGFR expression correlates to tumour size, stage and cytoplasmic accumulation of the laminin-5 gamma2 chain (Ln-5/gamma2), which is known as a marker of invading tumour cells. There is only limited knowledge if and how EGFR signalling pathways are important for invasion-associated processes and for the regulation of Ln-5/gamma2. Therefore the distribution of phosphorylated Erk1/2, p38 MAPK and Akt was immunohistochemically defined in oral squamous cell carcinoma (OSCC) of different histological grade and compared to histological criteria of invasion and cytoplasmic Ln-5/gamma2 deposition. With raising histological grade, there is a slight increase in nuclear pErk1/2-stained tumour cells (P=0.398) and a loss of nuclear (P=0.593) and increased cytoplasmic staining (P=0.144) of pAkt mainly in invading OSCC cells. Nuclear pp38 MAPK could only be sporadically detected in few cases. In case of pErk1/2 and pAkt, only a partial co-localisation could be revealed in cases with abundant kinases and Ln-5/gamma2. Among the investigated kinases, only pAkt shows a relation to histological grade and invasion in OSCC. pErk1/2, pp38 MAPK and pAkt do not represent a direct link between EGFR and Ln-5 synthesis. Therefore, enhanced Ln-5/gamma2 may be a secondary phenomenon of EGFR-induced tumour cell proliferation and dissemination.

Cherubism - new hypotheses on pathogenesis and therapeutic consequences.

AIMS: The hereditary occurrence of cherubism indicates a probable genetic aetiology: a correlation with a mutation in the gene SH3BP2 has been demonstrated. A convincing concept of formal pathogenesis is not yet available. The study was aimed at advancing the understanding of the pathogenesis of cherubism by presenting a case study including genetic findings and an evaluation of the literature. RESULTS AND CONCLUSION: Because of its association with the development of the second and third molars, cherubism could be defined as a genetically determined alteration of tooth development. In this context, disturbed PTHrP - PTHrP receptor interaction induced by the mutation in SH3BP2 is discussed. The temporal and spatial determination of the clinical symptoms is explained by an interaction of SH3BP2-dependent signal transduction pathways with jaw morphogenesis (e.g. Hox-gene Msx-1). Because of the disease-induced lack of determination of the cap phase of the second and third molar, a spatial compartmentation, which is necessary for normal dental development, does not take place. This leads to dysregulation of mesenchymal bone building tissue areas, and to the development of giant cell granulomas with high osteoclastic activity. Because of the genetic determination of cherubism and the associated dedifferentiation of the diseased tissue, a surgical removal should be exclusively restricted to specific indications. Therefore an attitude of wait and see is preferred.

Photodynamic therapy of virus-associated epithelial tumours of the face in organ transplant recipients.

PURPOSE: The benefit for organ recipients is still counteracted by the side effects of immunosuppression. Among other effects, there is a 50-250 times increased risk of developing malignant skin tumours. Because these malignomas are known to develop particularly aggressivly, there is a special need for an efficient therapy. Here we demonstrate the treatment response to aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) in these patients. METHODS: Five organ recipients with multiple tumours of the face were multifocally treated with ALA-PDT (32 tumours in all). After topical application of ALA using a thermogel, irradiation was done with a 635 nm diode laser (Ceralas 635, Biolitec, Jena, Germany). After intervals of 2 weeks, 4 weeks, and 12 weeks, therapeutic efficacy was assessed. RESULTS: There was complete remission in 24 tumours (75%). In six tumours (18.8%) a second or third PDT session was necessary for complete clinical remission. In two tumours (5.6%, invasive squamous cell carcinomas) the lesions were refractory to PDT. CONCLUSIONS: ALA-PDT is a valuable therapeutic alternative for the treatment of multifocal skin tumours in organ-transplanted patients. Furthermore, we see a growing role of ALA-PDT also for patients with frequently relapsing tumours of the skin with known genetically determined tumourigenesis (Gorlin-Goltz syndrome).

[Problems in the development of a comprehensive three-dimensional databank of the human skull for the preoperative preparation of an exact implant for the treatment of bone defects]. / Problematik des Aufbaus einer Datenbank dreidimensional erfasster menschlicher Schädel als Voraussetzung für eine präoperative Anfertigung passgenauer Implantate zum Ausgleich von Knochendefekten.

Various human skulls were scanned with a laser scanner. Impressive Landmarks of the skull were determined and tested to be comparable stored in a uniform coordinate system for subsequent 3-d reconstruction. The Rhinion, the Nasion, the Spina nasalis anterior, the Prosthion, and the Opisthokranion were found to be very qualified for the adjustment in the median plane. The frontal plane was defined by the Rhinion and the Spina nasalis anterior. The Mastoidealia, the Zygomaxillaria and the Orbitalia were used to align the skull in the horizontal plane. The qualification of the database as a fundamental part for the comparison of human skulls and for the discovery of similarities to patient skulls with bone defects is demonstrated by means of 2 clinical cases. A subsequent result is the application to manufacture fitting implants of biocompatible materials for covering huge side-overlapping bone destructions.

The therapy of virus-associated epithelial tumors of the face and the lips in organ transplant recipients.

The risk of developing malignant cutaneous neoplasms is increased after organ transplantation. We report three patients with malignant tumors of the epithelium of the facial skin and the lips after kidney and heart transplantation, respectively. They showed an aggressive course of the disease with more than five synchronous or metachronous basal cell and squamous cell carcinomas. Tissue samples were Epstein-Barr virus (EBV) positive by PCR. Using an in situ hybridization technique EBV-encoded RNA (EBER) was detected in tumor-infiltrating lymphocytes. The aggressive course was not alone controllable by surgical or radiological therapy. The systemic and topical application of cidofovir (Vistide) led to remarkable remissions, to a better confinement and operability of the tumors, and to a cessation of tumor pain. The photodynamic therapy represents another opportunity for managing superficial local recurrences and multiple tumors. In conclusion, the results of these case reports demonstrate that combined antiviral, photodynamic and surgical therapy may be used successfully to treat aggressive cutaneous malignancies in patients after organ transplantation.