The current and future treatment of edentulism

The purpose of this review and summary is to focus the clinician's attention on existing potential limitations regarding the management of edentulism. The current published data and opinions concerning the need for treating edentulism, the quality of dentures, related morbidity, and alternative or related therapeutics (e.g., dental implants) suggest there are opportunities for improvement in the treatment of the edentulous population. This may be achieved by adopting a broader therapeutic strategy focused not solely on technical aspects of an oral prosthesis. Instead, a wider array of clinical features of the edentulous patient should be addressed. A contemporary strategy may include concerns for prevention of tooth loss, evaluation of residual alveolar ridge resorption, and related issues of denture function, continual evaluation of oral mucosal health, compassionate management of maladaptive patients, a rationale for timely replacement of dentures, and continued development of dental implant therapies. The importance of therapeutic technical quality can be underscored, but should not overwhelm the broader concerns for assuring the overall health and well-being of the edentulous population.

The effects of implant surface nanoscale features on osteoblast-specific gene expression

This study investigated the influence of nanoscale implant surface features on osteoblast differentiation. Titanium disks (20.0 x 1.0 mm) with different nanoscale materials were prepared using sol-gel-derived coatings and characterized by scanning electron microscopy, atomic force microscopy and analyzed by X-ray Photoelectron Spectrometer. Human Mesenchymal Stem Cells (hMSCs) were cultured on the disks for 3-28 days. The levels of ALP, BSP, Runx2, OCN, OPG, and OSX mRNA and a panel of 76 genes related to osteogenesis were evaluated. Topographical and chemical evaluation confirmed nanoscale features present on the coated surfaces only. Bone-specific mRNAs were increased on surfaces with superimposed nanoscale features compared to Machined (M) and Acid etched (Ac). At day 14, OSX mRNA levels were increased by 2-, 3.5-, 4- and 3-fold for Anatase (An), Rutile (Ru), Alumina (Al), and Zirconia (Zr), respectively. OSX expression levels for M and Ac approximated baseline levels. At days 14 and 28 the BSP relative mRNA expression was significantly up-regulated for all surfaces with nanoscale coated features (up to 45-fold increase for Al). The PCR array showed an up-regulation on Al coated implants when compared to M. An improved response of cells adhered to nanostructured-coated implant surfaces was represented by increased OSX and BSP expressions. Furthermore, nanostructured surfaces produced using aluminum oxide significantly enhanced the hMSC gene expression representative of osteoblast differentiation. Nanoscale features on Ti implant substrates may improve the osseointegration response by altering adherent cell response.

Fracture resistance of yttria-stabilized zirconia dental implant abutments

PURPOSE

An in vitro study was performed to assess the effect of different degrees of clinical reduction of zirconia abutments on the failure load of clinical assemblies.

MATERIALS AND METHODS

Zirconia abutments (Y-TZP Ceramic Abutment, Astra Tech) were prepared with 0, 0.5, or 1 mm of external axial reduction starting 1 mm above the height-of-contour. Abutments (n = 10) were attached to implant analogs (25 Ncm torque) embedded in a stainless steel cylinder using Field's metal. Fracture loads (N) were determined when assemblies were loaded at 60 degrees off-axis until failure (Instron, CHS = 0.1 mm/min). Groups were statistically compared using ANOVA (p < 0.05).

RESULTS

Fracture loads for all assemblies displayed large variations within groups. There were no statistically significant differences (p > 0.05) among different abutment groups with a mean fracture load of 429 N (+/-140) for the control group, 576 N (+/-120) for 0.5-mm margins, and 547 (+/-139) for 1.0-mm margins. All fractures occurred at the interface where the abutment was connected to the analog.

CONCLUSION

In this in vitro study of simulated ultimate assembly strength, the preparation of zirconia abutments did not significantly impair the fracture resistance of simulated implant assemblies. All implant abutments fractured at rates higher than the maximum incisal forces (90-370 N) estimated to occur in the anterior region of the mouth.

Nanostructured alumina-coated implant surface: effect on osteoblast-related gene expression and bone-to-implant contact in vivo

PURPOSE

The use of nanotechnology to enhance endosseous implant surfaces may improve the clinical control of interfacial osteoblast biology. This study investigated the influence of a nanostructure-coated implant surface on osteoblast differentiation and its effects on bone-to-implant contact (BIC) and removal torque values.

MATERIALS AND METHODS

Titanium disks were machined (M) or machined and subsequently treated by acid etching (Ac) or by dipping in an aluminum oxide solution (Al2O3). Surfaces were characterized by scanning electron microscopy, atomic force microscopy, and x-ray microanalysis. For the in vitro experiment, rat mesenchymal stem cells (rMSCs) were grown in osteogenic supplements on the disk surfaces for 3 days. Real-time polymerase chain reaction (PCR) was used to measure mRNA levels of several gene products (bone sialoprotein, osteocalcin, osteopontin, and RUNX-2). For the in vivo experiment, titanium implants were placed in rat tibiae and harvested after 3 to 21 days for measurement of bone-specific mRNA levels by real-time PCR. Removal torque and BIC were measured 3 to 56 days after placement.

RESULTS

Average height deviation (Sa, in nm) values for M, Ac, and Al2O3 implants were 86.5, 388.4, and 61.2, respectively. Nanostructured Al2O3 topographic features applied to machined implants promoted MSC commitment to the osteoblast phenotype. Greater bone-specific gene expression was observed in tissues adjacent to Al2O3 implants, and associated increases in BIC and torque removal were noted.

CONCLUSION

Nanostructured alumina may directly influence cell behavior to enhance osseointegration.

Surface nanofeature effects on titanium-adherent human mesenchymal stem cells

PURPOSE

Hydrofluoric acid treatment of moderately rough commercially pure titanium produced by titanium oxide (TiO2) grit blasting (OsseoSpeed) results in a surface with nanofeatures. The aim of this project was to better understand the effect of surface nanotopography on adherent osteoblastic differentiation.

MATERIALS AND METHODS

Human mesenchymal stem cells were grown on TiO2 grit-blasted and hydrofluoric acid-treated/TiO2 grit-blasted titanium coins for 1 to 28 days. The nature of the surfaces was evaluated using scanning electron microscopy, optical interferometry, and x-ray photoelectron spectrometry. Osteoblastic differentiation was measured using real-time polymerase chain reaction measurement of more than 80 mineralized tissue-associated, protein-encoding mRNAs.

RESULTS

Hydrofluoric acid-treated surfaces displayed nanofeatures of 100 nm in diameter and maintenance of micron-level topography. Adherent cell osteoblastic differentiation occurred on both surfaces but took place more rapidly and to a greater extent on hydrofluoric acid-treated surfaces. This was revealed by earlier, higher, and sustained levels of osteoinductive transcription factors (RUNX-2, SMADs), growth factors (insulin-like growth factor 2, bone morphogenetic proteins), and bone matrix proteins.

CONCLUSIONS

The superimposition of nanofeatures on a moderately rough commercially pure titanium surface is associated with marked osteoinduction and osteogenesis of adherent mesenchymal stem cells. The role of nanotopography in directing adherent cell behavior should be fully investigated.

Prosthodontics and the American College of Prosthodontists: a specialty's contribution to improving oral health care

Prosthodontics is the specialty responsible for restoration of individual teeth and replacement of missing teeth and supporting structures, where education and experience have been focused on esthetics, comfort, and function. The American College of Prosthodontists (ACP) has made commitments to strengthen the quality and scope of both undergraduate and postgraduate educational programs and to support prosthodontics educators. The ACP is especially involved in monitoring and evaluating emerging trends in diagnostic, product, and delivery technologies because of the rapid pace of such innovations and because these developments have significant potential for changing the way both general dentists and prosthodontists deliver prosthodontic care--the single largest segment of dental treatment.

Dissection of sets of genes that control the character of wnt5a-deficient mouse calvarial cells

Wnts (wingless and int-related proteins) are a family of secreted cysteine-rich glycoproteins, expressed in a variety of tissues in developing embryos, thought to be involved in cell fate specification and stem cell commitment. To identify the specific Wnts involved in osteoblastic differentiation of human mesenchymal stem cells (hMSCs), we performed degenerative RT-PCR cloning method to amplify Wnt-encoding cDNAs expressed during osteoblastic differentiation of hMSCs in vitro and during hMSC-directed ectopic osteogenesis in the severe combined immunodeficient (SCID) mouse host. WNT5A was found to be the dominant Wnt expressed during osteoblastic differentiation of hMSCs both in vitro and in vivo. RT-PCR further revealed that hWNT5A and its receptor Frizzled family member 5 (hFZD5) was up-regulated during osteoblastic differentiation compared to uncommitted hMSCs. To evaluate the function of Wnt5a, calvarial cells were obtained from Wnt5a(-/-), Wnt5a(+/-), and wild type mice. Wnt5a(-/-) cells showed significantly slower growth when compared to Wnt5a(+/-) and wild type cells. Gene expression profiles of the Wnt5a(-/-) calvarial cells as compared to wild type cells were evaluated using microarray analysis. 255 genes exhibited at least 2-fold changes in expression. Clusters of genes regulating cell cycle, cell proliferation and cell growth, and gene transcription were altered with absence of Wnt5a expression. In addition, genes regulating osteoblastic differentiation including Runx2, osterix, and alkaline phosphatase (ALP) were shown to be down-regulated in Wnt5a(-/-) cells. In conclusion, Wnt5a is highly expressed during osteoblastic differentiation. Its function during mesenchymal stem cell differentiation as well as cell growth was suggested by comparing the gene expression profile of calvarial cells from the Wnt5a(-/-) and wild type mice.

Five-year prospective evaluation of mandibular overdentures retained by two microthreaded, TiOblast nonsplinted implants and retentive ball anchors

PURPOSE

The aim of this 5-year prospective evaluation was to assess the bone and peri-implant mucosa responses at unsplinted, microthread implants supporting mandibular overdentures and to determine patient responses to therapy.

MATERIALS AND METHODS

Two implants were placed by a 1-stage procedure in the parasymphyseal mandibles of 59 subjects. Implant placement was followed by immediate insertion of overdentures without connection to abutments. After 3 months, connection using Dalla Bona attachments was made and peri-implant mucosa, peri-implant bone, and patient perceptions of treatment were evaluated.

RESULTS

The implant success rate was 95.9% from 6 to 60 months. The changes in marginal bone levels were positive (bone gain) but did not reach statistical significance at 12, 36, or 60 months (+0.13 +/- 0.59 mm, +0.23 +/- 0.66 mm, and +0.09 +/- 0.79, respectively). Treatment was viewed as effective; patients rating satisfaction with their teeth increased from a preoperative level of 12.1% to 94.6% at overdenture abutment connection and remained high (81.6%) after 5 years.

CONCLUSIONS

Expedited mandibular overdenture therapy utilizing unsplinted, microthreaded mandibular parasymphyseal implants was associated with high implant survival, preservation of crestal bone, and high patient satisfaction. Complications were minor and related to prosthodontic features of therapy.

The effect of hydrofluoric acid treatment of TiO2 grit blasted titanium implants on adherent osteoblast gene expression in vitro and in vivo

It is widely accepted that implant surface factors affect the quality of the bone-to-implant interface. Recent additional treatments superimposed on moderately rough cpTitanium surface provide further enhancement of bone-to-implant contact. The aim of this study was to compare osteoinductive and bone-specific gene expression in cells adherent to titanium dioxide-grit blasted (TiO2) versus TiO2 grit blasted and HF treated (TiO2/HF) cpTitanium implant surfaces. MC3T3-E1 cells were grown in osteogenic supplements on the titanium disk surfaces for 1-14 days. Real-time PCR was used to measure RUNX-2, Osterix, and bone sialoprotein (BSP) mRNA levels. Implants were placed in rat tibia and, following harvesting at 1-7 days after placement, real-time PCR was used to measure RUNX-2, alkaline phosphatase (ALP), and BSP mRNA levels in implant adherent cells. In cell culture, RUNX-2 and Osterix levels were significantly increased (p<0.05) on the TiO2/HF surfaces as compared to the TiO2 and smooth surfaces through the cultural period, while BSP expression was elevated on both TiO2 and TiO2/HF surfaces when compared to a machined surface control. In cells adherent to implants retrieved from rat tibia, RUNX-2 mRNA levels were 2-fold and 8-fold greater on the TiO2/HF surfaces at 1-3 and 7 days following implantation. This was paralleled by significantly greater levels of ALP at 3 and 7 days and BSP mRNA at 7 days following implantation. As a marker of osteoinduction, the increased levels of RUNX-2 in cells adherent to the TiO2/HF surfaces suggest that the additional HF treatment of the TiO2 grit blasted surface results in surface properties that support adherent cell osteoinduction. In vivo assessments of implant adherent cell phenotypes provide further insight into the mechanisms affecting alloplast-tissue interactions.

Three-year evaluation of single-tooth implants restored 3 weeks after 1-stage surgery

PURPOSE

The possibility of expediting dental implant therapy by early or immediate loading protocols requires long-term clinical investigation. The aim of this prospective cohort trial was to determine the 3-year implant success rate and prosthesis complications associated with functional loading 3 weeks after 1-stage placement of Astra Tech single-tooth implants replacing maxillary anterior teeth. A secondary objective was to determine peri-implant tissue responses at these implants.

MATERIALS AND METHODS

The peri-implant bone and mucosal conditions of 43 implants in 39 subjects were radiographically and clinically measured 3 years after implant placement.

RESULTS

Of the 48 patients originally treated, 39 patients and 43 implants were examined at the 3-year time point. Three of 54 implants failed within the first year. No additional failures were recorded since the 12-month reporting period. Peri-implant bone levels were stable for the 3-year period following implant placement. The change in marginal bone levels after 3 years was 0.42 +/- 0.59 mm. Papilla growth was measured at 1 and 3 years (0.61 +/- 0.95 mm and 0.74 +/- 0.79 mm, respectively). The buccal peri-implant tissue dimensions at the gingival zenith also increased at 1 and 3 years (0.34 +/- 0.94 mm and 0.51 +/- 1.42 mm, respectively). No abutment screw loosening or fracture occurred.

DISCUSSION AND CONCLUSIONS

Early loading of endosseous dental implants placed in healed ridges offers select benefits to clinicians and their patients.

The immediate loading of dental implants

The aim of this article is to identify current opportunities for the immediate loading of endosseous dental implants. A biologic basis for the clinical parameters associated with success and failure of immediately loaded implants is presented, and select clinical situations where immediate loading is presently advocated will be illustrated. The wide-ranging applications of the immediate-loading concept for endosseous dental implants will be introduced; however, further experimental validation is necessary before incorporating all of these various expedited therapeutic approaches into practice.

Anodic oxidation and hydrothermal treatment of commercially pure titanium surfaces increases expression of bone morphogenetic protein-2 in the adherent macrophage cell line J774A.1

The surface property of commercially pure titanium (cpTi) was improved by forming a thin hydroxyapatite (HA) layer by anodic oxidation and hydrothermal treatment (HA/cpTi). We hypothesize that the adhesion of macrophages to HA/cpTi surfaces is important to the process of osseointegration. This study investigates the effect of adhesion of macrophages to HA/cpTi surfaces on the expression of bone morphogenetic protein-2 (BMP-2). The murine macrophage cell line J774A.1 was cultured on HA/cpTi and polished cpTi (S/cpTi). Macrophage cell adhesion was examined by SEM, 0-72 h following plating onto HA/cpTi and S/cpTi. BMP-2 gene expression was examined by RT-PCR analysis. The level of BMP-2 secreted into the supernatant was measured using an ELISA assay. The extent of macrophage adhesion increased with time on both the HA/cpTi and S/cpTi surfaces, with a" higher degree of spreading observed on HA/cpTi than onS/cpTi surfaces after 24 or 72 h. The ratio of BMP-2 mRNA was higher on HA/cpTi than on S/cpTi after 24 h (0.348 vs. 0, p < 0.05) and 72 h (0.584 vs. 0.189, p < 0.05). After 24 h, secretion of BMP-2 was detected in cultures grown on HA/cpTi, but not on S/cpTi. After 72 h, secretion of BMP-2 was detected in cultures grown on S/cpTi, but the levels were higher in cultures grown on HA/cpTi. These findings show that macrophages have the capacity to adhere to HA/cpTi endosseous implants and provide a source of osteoinductive cytokines that may play a key role in the process of osseointegration.

Influence of an LRP5 cytoplasmic SNP on Wnt signaling and osteoblastic differentiation

The low density lipoprotein receptor-related protein 5 (LRP5) is a key determinant of bone mass, via the Wnt signaling pathway control of osteoblast function. This study examined human LRP5 signaling and the effects of an intracellular domain single nucleotide polymorphism (SNP: p.V1525A) on osteoblast differentiation and mineralization. Constitutively active LRP5 was constructed by deletion of the extracellular domain of LRP5 (LRP5DeltaN). Expression of LRP5DeltaN-V, which carries the allele p.1525V, induced higher beta-catenin/TCF-LEF activity compared to LRP5DeltaN-A, which carries the allele p.1525A. In a yeast two-hybrid assay, LRP5DeltaN-V also demonstrated a stronger interaction with AXIN than LRP5DeltaN-A. Expression of either of the alleles did not change cell proliferation. However, cells expressing LRP5DeltaN-V showed increased alkaline phosphatase activity and bone nodule formation compared to cells transfected with empty vector or LRP5DeltaN-A after osteogenic supplement (OS: beta-glycerophosphate and l-ascorbic acid) treatment. Cells expressing LRP5DeltaN-V revealed significantly increased bone sialoprotein (BSP) expression after 7 days of OS treatment and maintained elevated expression until day 21. Osteocalcin (OCN) mRNA levels were increased after 14-21 days of OS treatment in LRP5DeltaN-V expressing cells. LRP5DeltaN-V expressing cells demonstrated positive interaction with BMP-2 signaling of transcription at the SBE-luc promoter. LRP5 signaling is affected by the cytoplasmic SNP, p.V1525A. mRNA levels of Runx2 and Osterix were not affected by this SNP.

Immediate implant placement and restoration in the anterior maxilla: a tissue-related approach. Observations at 12 months after loading

Retreatment of a failed prosthetic rehabilitation often presents a challenge for both clinicians and patients. Endosseous dental implants are a commonly used treatment modality to restore esthetics and function. Implant protocols differ considerably with regard to healing time and the number of surgical procedures required. This has a great impact on the treatment strategy used and therefore significantly influences patient acceptance. The present case report describes the rehabilitation of a failed maxillary anterior fixed partial denture using immediate implant placement and provisionalization. This tissue-related, esthetically driven treatment strategy is comprehensively presented with a follow-up of 12 months postoperatively.

Effect of vitamin D pretreatment of human mesenchymal stem cells on ectopic bone formation

Adult mesenchymal stem cells (MSCs) are used in contemporary strategies for tissue engineering. The MSC is able to form bone following implantation as undifferentiated cells adherent to hydroxyapatite (HA)/tricalcium phosphate (TCP) scaffolds. Previous investigators have demonstrated that human MSCs (hMSCs) can be differentiated to osteoblasts in vitro by the inclusion of vitamin D and ascorbic acid. The aim of this study was to compare the osteogenic potential of predifferentiated and undifferentiated bone marrow-derived, culture-expanded hMSCs adherent to synthetic HA/TCP (60%/40%) following subcutaneous engraftment in severe combined immunodeficiency (SCID) mice. During the final 3 days of culture, cells were grown in Dulbecco's modified Eagle's medium containing 10% fetal calf serum and antibiotics or media containing 25-mM calcium supplementation with vitamin D and ascorbic acid. Four weeks following implantation in SCID mice, scoring analysis of bone formation within the cubes revealed the absence of bone formation in unloaded cubes. Bone formation compared by a qualitative bone index was 7.23% for undifferentiated cells compared to 5.20% for differentiated cells. Minimal resorption was observed at this early time point. In this ectopic model, predifferentiation using a combination of vitamin D and ascorbic acid failed to increase subsequent bone formation by implanted cells. Following implantation of hMSCs adherent to an osteoconductive scaffold, host factors may contribute dominant osteoinductive signals or impose inhibitory signals to control the fate of the implanted cell. Predifferentiation strategies require confirmation in vivo.

Investigation of a thermoplastic polymeric carrier for bone tissue engineering using allogeneic mesenchymal stem cells in granular scaffolds

PURPOSE

The purpose of this project was to compare alveolar bone repair by allogeneic mesenchymal stem cells using bioglass or synthetic hydroxyapatite (HA)/tricalcium phosphate (TCP) granular scaffolds delivered in a thermoplastic polymeric carrier.

MATERIALS AND METHODS

Canine mesenchymal stem cells were obtained from iliac crest bone marrow of beagle dogs and expanded without differentiation. Cells were resuspended at a final concentration of 5 x 10(6) cells/ml in a thermoplastic polymeric carrier (30% w/v Pluronic F-127) and mixed with an equal volume of synthetic HA/TCP or bioglass scaffold and placed into surgically created 5 mm cylindrical defects in the edentulous premolar region of beagle dogs. After 4 weeks or 7 weeks, tissue healing was evaluated by standard histomorphometric methods (Bioquant Nova, Bioquant Image Analysis Corporation, Nashville, TN) by measurement of bone formation within five random sites from each biopsy.

RESULTS

After 4 weeks, sites treated with or without mesenchymal stem cells contained 58.25 +/-18.43% or 43.35 +/- 17.68% bone area (p= 0.049), respectively. After 7 weeks, sites treated with or without mesenchymal stem cells contained 62.73 +/- 19.10% or 60.39 +/- 21.32% bone area. Bone formation occurred without inflammation in defects treated using Pluronic F-127 carrier with and without mesenchymal stem cells. There was no difference in percent bone area when bioglass or HA/TCP scaffolds were compared at either time point.

CONCLUSIONS

The thermoplastic polymeric carrier did not limit alveolar bone repair in the canine mandible. The combination of a thermoplastic, viscous carrier with a granular scaffold allowed for the delivery of allogeneic mesenchymal stem cells in a clinically manageable form that enhanced bone formation at early stages of alveolar repair.

The role of titanium surface topography on J774A.1 macrophage inflammatory cytokines and nitric oxide production

A role for monocyte/macrophage modulation of wound healing at endosseous implants is proposed. The modification of the endosseous implant surface topography can alter cell adhesion and resultant cell behavior. The aim of this study was to define the effect of increased cpTitanium surface topography on adherent J744A.1 macrophage phenotype in culture. The J744A.1 cells were cultured on 20mm diameter cpTitanium disks prepared with smooth and grit-blasted/acid rough surface topographies for 24-72 h. Following culture in growth media with or without lipopolysaccharide (LPS), total RNA was isolated and real-time polymerase chain reaction (PCR) was used to measure the steady-state levels of the pro-inflammatory cytokines interleukin 1-beta (IL-1beta) and interleukin 6 (IL-6) and the anti-inflammatory cytokine interleukin-10 (IL-10). Additional evidence of pro-inflammatory signaling was sought by measurement of cellular nitric oxide (NO) production. In the absence of LPS, IL-1beta levels were increased on grit-blasted/acid rough surfaces during the first 48 h. In contrast, IL-6 levels were reduced on the grit-blasted/acid rough surfaces. When cultures were treated with LPS, high levels of IL-1beta and IL-6 expression were measured, irrespective of surface topography. The responses of J744A.1 cells to surface and superimposed LPS stimulation suggest only modest effects of the modeled endosseous implant surface on adherent cell pro-inflammatory cytokine expression and NO signaling.

A retrospective analysis of peri-implant tissue responses at immediate load/provisionalized microthreaded implants

PURPOSE

The aim of this retrospective study was to examine the peri-implant tissue status at immediately provisionalized anterior maxillary implants 12 to 30 months following tooth replacement.

MATERIALS AND METHODS

This is a retrospective study of 43 microthreaded, TiO2 grit-blasted implants placed in healed ridges and immediate extraction sockets to restore maxillary anterior and premolar teeth in 28 patients. The cortical bone position relative to the implant reference point was evaluated at implant placement and 6 to 30 months following restoration. Radiographs were assessed using 7x magnification. The distance from the reference point to the cortical bone was measured to +/- 0.1 mm. The relationship of the peri-implant mucosa to the incisal edge of the definitive prosthesis was recorded.

RESULTS

Four implants in 3 individuals failed during the first 6 weeks following placement and provisional loading. Cortical bone adaptation from the time of implant placement up to 30 months following restoration ranged from 0.0 mm to 1.5 mm (average, 0.33 +/- 0.40 mm mesially and 0.28 +/- 0.37 mm distally). The mean radiographic measurements from the interproximal crestal bone to the contact point were 4.53 +/- -0.91 mm (mesial) and 4.06 +/- 0.98. Maintenance and growth of papilla was observed in this group of immediate provisionalized single-tooth implants. Definitive abutment or abutment screw loosening was not observed.

DISCUSSION

The linear clinical and radiographic measures of peri-implant tissue responses suggest that proper implant placement is followed by supracrestal biological width formation along the abutment and preservation of toothlike tissue contours. This may influence buccal peri-implant tissue dimensions.

CONCLUSIONS

Generalized maintenance of crestal bone and the increased soft tissue dimension with maintenance of peri-implant papilla were identified as expected outcomes for immediate loading/provisionalization of microthreaded, TiO2 grit-blasted implants. Control of peri-implant tissues can be achieved to provide predictable and esthetic treatment for anterior tooth replacement using dental implants.

Effects of Delta12-prostaglandin J2 on bone regeneration and growth factor expression in rats

OBJECTIVES

Cyclopentenone prostaglandins have been shown to promote osteoblast differentiation in vitro. The aim of this study was to examine in a rat model the effects of local delivery of Delta(12)-prostaglandin J(2) (Delta(12)-PGJ(2)) on new bone formation and growth factor expression in (i) cortical defects and (ii) around titanium implants.

MATERIAL AND METHODS

Standardized transcortical defects were prepared bilaterally in the femur of 28 male Wistar rats. Ten microliters of Delta(12)-PGJ(2) at 4 concentrations (10(-9), 10(-7), 10(-5) and 10(-3) mol/l) in a collagen vehicle were delivered inside a half-cylindrical titanium chamber fixed over the defect. Contralateral defects served as vehicle controls. Ten days after surgery, the amount of new bone formation in the cortical defect area was determined by histomorphometry and expression of platelet-derived growth factor (PDGF)-A and -B, insulin-like growth factor (IGF)-I/II, bone morphogenetic protein (BMP)-2 and -6 was examined by immunohistochemistry. In an additional six rats, 24 titanium implants were inserted into the femur. Five microliters of carboxymethylcellulose alone (control) or with Delta(12)-PGJ(2) (10(-5) and 10(-3) mol/l) were delivered into surgically prepared beds prior to implant installation.

RESULTS

Delta(12)-PGJ(2) (10(-5) and 10(-3) mol/l) significantly enhanced new bone formation (33%, P<0.05) compared with control cortical defects. Delivery of Delta(12)-PGJ(2) at 10(-3) mol/l significantly increased PDGF-A and -B and BMP-2 and -6 protein expression (P<0.05) compared with control defects. No significant difference was found in IGF-I/II expression compared with controls. Administration of Delta(12)-PGJ(2) also significantly increased endosteal new bone formation around implants compared with controls.

CONCLUSION

Local delivery of Delta(12)-PGJ(2) promoted new bone formation in the cortical defect area and around titanium implants. Enhanced expression of BMP-2 and -6 as well as PDGF-A and -B may be involved in Delta(12)-PGJ(2)-induced new bone formation.

Facial distortion secondary to idiopathic gingival hyperplasia: surgical management and oral reconstruction with endosseous implants

Little information exists regarding the surgical and oral reconstructive options for the patient with idiopathic gingival hyperplasia, especially with regard to endosseous implant placement and recurrence of the disease. The authors report a case of severe gingival enlargement and bone resorption involving the maxillary and mandibular arches in a 21-year-old female causing distortion of facial features. The etiology could not be established but the condition was exacerbated during pregnancy, causing chewing, speaking, and esthetic problems. The hyperplastic tissue and all the teeth were removed surgically, followed by immediate placement of 2 endosseous implants. Restoration of esthetics and function with a maxillary denture and mandibular overdenture were completed 3 months later. No disease recurrence was noted at the 6-month postoperative interval.

Fluoride modification effects on osteoblast behavior and bone formation at TiO grit-blasted c.p. titanium endosseous implants

Increasing bone formation at endosseous titanium implants may be achieved by modification of topographically enhanced surfaces. The aim of this study was to determine the effect of fluoride ion modification of TiO2 grit-blasted, c.p. titanium implants on osteoblastic differentiation and interfacial bone formation by parallel in vitro and in vivo investigations. Human mesenchymal stem cells (Osiris Therapeutics, Inc.) were cultured on TiO2 grit-blasted c.p.titanium disks with and without fluoride ion modification. Cell adhesion, proliferation, and osteoblastic gene expression was measured by scanning electron microscopy, tritiated-thymidine uptake into insoluble DNA, and reverse transcription polymerase chain reaction detection of mRNAs encoding collagen 1, osteopontin, bone sialoprotein, osteocalcin and BMP-2. After 24 h, there were no differences in cell adhesion among the surfaces tested. Fluoride-treated surfaces supported greater proliferation and increased bone sialoprotein and BMP-2 expression. Additionally, 12 TiO2 grit-blasted and 12 fluoride ion modified implants were placed randomly into medial and distal osteotomies prepared in the tibia of 300 g Sprague Dawley rats. After 21 days, the tibiae were harvested and 100 microm ground sections were examined by backscatter scanning electron microscopy. The bone-to-implant contact formed at TiO2 grit-blasted and fluoride-treated versus TiO2 grit-blasted surfaces was 55.45% versus 34.21% (p<0.027), respectively. Fluoride ion modification of the TiO2 grit-blasted surface enhanced osteoblastic differentiation in vitro and interfacial bone formation in vivo. This parallel in vitro and in vivo investigation demonstrates that fluoride ion modification enhanced osteoblastic differentiation and interfacial bone formation. The mechanism(s) by which fluoride ion modification of c.p.titanium enhanced osteoblastic differentiation and osseointegration merit careful investigation.

The role of abutment-attachment selection in resolving inadequate interarch distance: a clinical report

A critical factor that needs to be evaluated during the diagnosis and treatment planning phase for patients seeking an implant-tissue-supported overdenture or metal-resin implant fixed denture is the presence of adequate interarch distance. The amount of interarch distance is critical to the selection of appropriate implant abutments and attachments for both implant-tissue-supported overdentures and metal-resin implant fixed complete dentures. This clinical report describes a patient with complications related to the failure to diagnose inadequate interarch distance, and the methods used to resolve the patient's chief complaint. A guide for abutment-attachment selection using one commercially available implant system is given.

Evaluation of mesenchymal stem cells following implantation in alveolar sockets: a canine safety study

PURPOSE

The overall goal of this project was to evaluate culture-expanded bone-marrow-derived mesenchymal stem cells (MSCs) for alveolar bone repair in terms of safety and potential efficacy.

MATERIALS AND METHODS

MSCs isolated from bone marrow aspirations were culture-expanded and cryopreserved. Thawed cells were incubated with 3.2 x 5-mm hydroxyapatite/tricalcium phosphate (HA/TCP) cylinders in a closed system containing 5 x 10(7) cells/mL. Cells alone, cell-free constructs, or cell-loaded constructs were rinsed in saline and implanted in extraction sockets in the mandibular second and fourth premolar sites of 14 beagle dogs. Acute reactions were evaluated histologically after 7 or 21 days, and bone formation was examined after 49 days.

RESULTS

Neither implanted MSC-related inflammation nor ectopic osteogenesis was observed. At 7 and 21 days, dil-labeled canine MSCs were found in more than 80% of the implant sites. Few canine MSCs were found in neighboring tissue. Mild inflammation present at 7 days diminished by 21 days. After 49 days, measured bone formation was 34%, 25%, and 35% for cell-loaded, cell-free, and untreated sockets, respectively (P < .05). At 21 days, bone formation was evident in all sites. Wound dehiscence was a complication associated with cell exclusionary membranes and resulted in local inflammation.

DISCUSSION

The extraction model indicates the safety of MSCs implanted adherent to HA/TCP. Local bone repair occurred in the absence of nonspecific differentiation or migration with distant osteogenesis.

CONCLUSIONS

An alveolar socket model may be an appropriate model for initial clinical investigation of MSC-mediated bone repair.