The impact of surface alteration on epithelial tissue attachment after the mechanical cleaning of titanium or zirconia surface.

OBJECTIVE: Mechanical plaque removal may alter the surface morphology of the gingival penetration part of the implant. We applied an air-powered abrasive system (AP), titanium curette (TC), stainless curette (SC), ultrasound scaler (US), and titanium brush (TB) which are commonly used to remove plaque, to titanium or zirconia and the changes in surface morphology and the epithelial attach against substrata. MATERIALS AND METHODS: (a) The morphological changes of titanium and zirconia after mechanical cleaning were assessed by scanning electron microscopy and a roughness analyser. (b) Oral epithelial cells of rats were inoculated on the surface of the materials after mechanical cleaning, and the adherence of epithelial cells was observed. (c) The maxillary first molars were extracted from the rats and replaced by experimental titanium or zirconia implants. The length of the immunoreactive laminin-332 band was observed at the implant-peri-implant epithelium interface. RESULTS: (a) The surface roughness increased in experimental groups except the AP group. (b) Among the experimental groups, the AP group showed the highest number of attached cells. (c) The length of the immunoreactive laminin-332 band was longer in the control group than those in all five experimental groups. Among the experimental groups, the AP group showed the longest band. CONCLUSION: All mechanical cleaning methods increased the surface roughness of the materials except AP. AP did not cause distinct implant surface alterations. Surface alteration caused by mechanical cleaning may evoke inferior for epithelial attachment and reduce resistance against foreign infiltration.

Relationship between Maximum Tongue Pressure Value and Age, Occlusal Status, or Body Mass Index among the Community-Dwelling Elderly.

Background and objectives: In an aging society, the maintenance of the oral function of the elderly is of importance for the delay or prevention of frailty and long-term care. In the present study, we focused on the maximum tongue pressure (MTP) value and analyzed the relationship between MTP and age, occlusal status, or body mass index (BMI). Materials and Methods: This one-center observatory study was conducted using a cohort consisting of 205 community-dwelling outpatients over 65 years old. The MTP values of all subjects were measured using a commercially available tongue pressure measurement device and statistically analyzed. In addition, the correlation between MTP value and BMI was analyzed. Results: The MTP value decreased with age, especially in subjects classified as Eichner B and C. The difference in occlusal status did not show any statistically significant influence on MTP value. The correlation between BMI and MTP value was indicated in the tested groups other than an age of 65-74 and Eichner A groups. Conclusions: Although MTP value decreased with age, the difference in occlusal status did not have an impact on MTP value. The correlation between BMI and MTP value was not shown in the youngest group or a group with sufficient occlusal units. The results presented in the present study may imply that, even if MTP is low, younger age and/or better occlusal status compensate for the inferior MTP value in the cohort studied.

Histopathological comparison of the onset of peri-implantitis and periodontitis in rats.

BACKGROUND AND OBJECTIVE: There are a few experimental models that clearly describe the pathological differences in tissue destruction between periodontitis and peri-implantitis. We recently reported that the formation of immune complexes accelerates site-specific loss of attachment and alveolar bone resorption when an antigen is topically applied in the gingival sulcus of an immunized rat. We applied this model to the peri-implant tissues and compared peri-implant destruction to periodontitis without using a ligature. MATERIAL AND METHODS: Twenty-five rats were used in this study and were divided into five groups. Implantation was performed immediately after extraction of right first molars in rats. The left first molars were left untreated to be examined as natural teeth. The immunized group consisted of rats that had received intraperitoneal lipopolysaccharide (LPS), whereas the nonimmunized group received only phosphate-buffered saline (PBS). The untreated baseline group received only implantation. After intraperitoneal booster injection, half of each group received topical application of LPS in the palatal gingival sulcus daily for 3 days. The other half of the groups received PBS. Histopathological and histometrical findings were observed with hematoxylin and eosin staining, collagen fibers were observed with Azan staining, and formation of immune complexes was immunohistologically evaluated by C1qB expression. RESULT: Peri-implant tissue destruction was greater in the immunized and LPS-applied groups than in the other groups. No periodontal destruction was observed. Formation of immune complexes was observed in the junctional epithelium and adjacent connective tissue in the immunized groups. CONCLUSION: Antigen-induced peri-implant tissue destruction occurs faster than periodontal tissue destruction.

Tissue Reaction to a Novel Bone Substitute Material Fabricated With Biodegradable Polymer-Calcium Phosphate Nanoparticle Composite.

PURPOSE: The aim of this study was to evaluate the effectiveness of a novel bone substitute material fabricated using a biodegradable polymer-calcium phosphate nanoparticle composite. METHODS: Porous structured poly-L-lactic acid (PLLA) and hydroxyapatite (HA) nanoparticle composite, which was fabricated using solid-liquid phase separation and freeze-drying methods, was grafted into bone defects created in rat calvarium or tibia. Rats were killed 4 weeks after surgery, and histological analyses were performed to evaluate new bone formation. RESULTS: Scanning electron microscopic observation showed the interconnecting pores within the material and the pore diameter was approximately 100 to 300 µm. HA nanoparticles were observed to be embedded into the PLLA beams. In the calvarial implantation model, abundant blood vessels and fibroblastic cells were observed penetrating into pores, and in the tibia model, newly formed bone was present around and within the composite. CONCLUSIONS: The PLLA-HA nanoparticle composite bone substitute developed in this study showed biocompatibility, elasticity, and operability and thus has potential as a novel bone substitute.

Fibroblast attachment onto novel titanium mesh membranes for guided bone regeneration.

Titanium mesh is used in orthopedic surgery as a barrier membrane, as it offers suitable characteristics, which allow mechanical support during the formation of new bone. An ideal membrane would facilitate cell attachment onto its surface, thereby helping to stabilize the blood clot and integrate the membrane into the tissue. However, currently available titanium mesh has millimeter-level pore sizes, which lead to soft tissue ingrowth through the pores. Therefore, the aim of this study was to investigate the fibroblast attachment and migration on different designs of novel titanium mesh with micrometer pore size for guided bone regeneration treatment. Six types of novel titanium mesh membrane and three groups of commercially available membranes were used in this study. Fibroblasts were isolated from 4-day-old green fluorescence protein rats and seeded onto membrane surfaces. At 24 h, the cells attached to the membrane surfaces were fixed and stained with DAPI. The blue-stained nuclei on membrane surfaces, and both upper and lower sides were counted. It was shown that different membrane materials, structure and design differ considerably in their capacity for cell attachment to the membrane surface. The novel membranes, especially mesh with 12 pores compared with mesh with multi-pores, allowed the fibroblast attachment on the membrane surface, but hindered the fibroblast migration through the pores into the lower side of the membrane, which is associated with the defect area in the clinical condition.

Additional Effects of Platelet-Rich Fibrin on Bone Regeneration in Sinus Augmentation With Deproteinized Bovine Bone Mineral: Preliminary Results.

PURPOSE: Platelet-rich fibrin (PRF) has been reported to contribute to bone regeneration; however, little is known about details with deproteinized bovine bone mineral (DBBM). This study aims to evaluate additional effects of PRF on bone regeneration in sinus augmentation with DBBM. MATERIALS AND METHODS: Sinus augmentations were made with DBBM/PRF mixture as lateral approach for 4 sinuses from 4 patients. Bone biopsies were obtained from posterior maxilla at the implant placements 7 or 10 months after sinus augmentations. Histological observations and histomorphometric analyses from augmented areas were performed. RESULTS: The new bone formation was found around the DBBMs with very good contact while surfaces of DBBMs were partly resorbed. Osteoclasts recognized the DBBMs for remodeling, followed by new bone running. The histomorphometric analyses revealed that mean percentages of newly formed bone were 31.7 ± 1.2%, 21.0 ± 1.0%, 38.0 ± 0.6%, and 47.0 ± 0.6%, respectively (mean 34.5 ± 5.7%). CONCLUSIONS: Additional effects of PRF could be found because of higher percentages of newly bone formation by DBBM/PRF mixture than those by DBBM individual in previous reports.

Synergistic Effect of Nano Strontium Titanate Coating and Ultraviolet C Photofunctionalization on Osteogenic Performance and Soft Tissue Sealing of poly(ether-ether-ketone).

This study aimed to evaluate the bioactivity of poly(ether ether ketone) (PEEK) after surface modification by persistent photoconductive strontium titanate (SrTiO3) magnetron sputtering and ultraviolet (UV) C irradiation. According to the different modifications, the PEEK specimens were randomly divided into five groups (n = 38/group): PEEK, Sr100-PEEK, Sr200-PEEK, UV/PEEK, and UV/Sr200-PEEK. Then, the specimens of Sr100-PEEK and Sr200-PEEK groups were, respectively, coated with 100 and 200 nm thickness photocatalyst SrTiO3 on the PEEK surface by magnetron sputtering. Subsequently, UV-C light photofunctionalized the specimens of PEEK and Sr200-PEEK groups to form UV/PEEK and UV/Sr200-PEEK groups. The specimens were characterized by a step meter, scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDX), and a water contact angle meter. The release test of the Sr ion was performed by inductively coupled plasma mass spectrometry (ICP-MS). In vitro study, osteogenic activity (MC3T3-E1 osteoblast-like cells) and epithelial and connective tissue attachment (gingival epithelial cells GE1 and fibroblasts NIH3T3) were analyzed in five groups. Surface morphology of the specimens was changed after coating, and the Sr content on the Sr-PEEK surface was increased with increasing coating thickness. In addition, the contact angle was increased significantly after magnetron sputtering. After UV-C photofunctionalization, the content of surface elements changed and the contact angle was decreased. The release of Sr ion was sustained, and the final cumulative release amount did not exceed the safety limit. In vitro experiments showed that SrTiO3 improved the cell activity of MC3T3-E1 and UV-C irradiation further enhanced the osteogenic performance of PEEK. Besides, UV-C irradiation also significantly promoted the cell viability, development, and expression of adhesion proteins of GE1 and NIH3T3 on PEEK. The present investigation demonstrated that nano SrTiO3 coating with UV-C photofunctionalization synergistically enhanced the osteogenic properties and soft tissue sealing function of PEEK in vitro.

Current surface modification strategies to improve the binding efficiency of emerging biomaterial polyetheretherketone (PEEK) with bone and soft tissue: A literature review.

PURPOSE: The aim of this study was to review the literature on current surface modification strategies used to improve the binding efficiency of an emerging biological material, polyetheretherketone (PEEK), with bone and soft tissues. STUDY SELECTION: This review was based on articles retrieved from PubMed, Google Scholar, Web of Science, and ScienceDirect databases. The main keywords used during the search were "polyetheretherketone (PEEK)," "implant," "surface modification," "biomaterials," "bone," "osseointegration," and "soft tissue." RESULTS: The suitability of PEEK surface modification strategies has been critically analyzed and summarized here. Many cell and in vivo experiments in small animals have shown that the use of advanced modification technologies with appropriate surface modification strategies can effectively improve the surface inertness of PEEK, thereby improving its binding efficiency with bone and soft tissues. CONCLUSIONS: Surface modifications of PEEK have revealed new possibilities for implant treatment; however, most results are based on in vitro or short-term in vivo evaluations in small animals. To achieve a broad application of PEEK in the field of oral implantology, more in vivo experiments and long-term clinical evaluations are needed to investigate the effects of various surface modifications on the tissue integration ability of PEEK to develop an ideal implant material.

Evaluation of carbonate apatite as a bone substitute in rat extraction sockets from the perspective of mesenchymal stem cells.

Carbonate apatite (CO3Ap) is a major inorganic bone component and an effective bone substitute. To clarify the function of CO3Ap, we compared differences among CO3Ap, hydroxyapatite (HAp), and ß-tricalcium phosphate (ß-TCP) by focusing on mesenchymal stem cells (MSCs) that have a role in wound healing. For in vivo experiments, maxillary molars were removed and the bone substitute was inserted. MSC accumulation around extraction sockets was significantly promoted in CO3Ap and ß-TCP groups. For in vitro experiments, MSCs were cultured with bone substitutes. The differentiation potential and amount of calcium deposition were significantly lower in CO3Ap and HAp groups than in the ß-TCP group. Increases in insulin-like growth factor-I and vascular endothelial growth factor were found only in the CO3Ap group. CO3Ap-filled extraction sockets accumulated MSCs, and MSCs cultured in the presence of CO3Ap produced large amounts of growth factors. These results suggest that CO3Ap promotes healing of tooth extraction sockets.

Technetium-99 conjugated with methylene diphosphonate ameliorates ovariectomy-induced osteoporotic phenotype without causing osteonecrosis in the jaw.

Technetium-99 conjugated with methylene diphosphonate ((99)Tc-MDP) is a novel bisphosphonate derivative without radioactivity and has been successfully used to treat arthritis in China for years. Since bisphosphonate therapy has the potential to induce bisphosphonate-related osteonecrosis of the jaw (BRONJ), we examined whether (99)Tc-MDP represents a new class of bisphosphonate for antiresorptive therapy to ameliorate estrogen deficiency-induced bone resorption with less risk of causing BRONJ. We showed that (99)Tc-MDP-treated, ovariectomized (OVX) mice had significantly improved bone mineral density and trabecular bone volume in comparison to the untreated OVX group by inhibiting osteoclasts and enhancing osteogenic differentiation of bone marrow mesenchymal stem cells. To determine the potential of inducing BRONJ, (99)Tc-MDP/dexamethasone (Dex) or zoledronate/Dex was administered into C57BL/6J mice via the tail vein, followed by extraction of maxillary first molars. Interestingly, (99)Tc-MDP treatment showed less risk to induce osteonecrosis in the maxillary bones compared to zoledronate treatment group, partially because (99)Tc-MDP neither suppressed adaptive regulatory T cells nor activated the inflammatory T-helper-producing interleukin-17 cells. Taken together, our findings demonstrate that (99)Tc-MDP therapy may be a promising approach in the treatment of osteoporosis with less risk of causing BRONJ.

Evaluations of epithelial sealing and peri-implant epithelial down-growth around "step-type" implants.

OBJECTIVE: Implant designs that can stimulate and integrate with an epithelial wound-healing process may significantly enhance the efficacy of dental implants. Here, we evaluated the potential of "step-type" implant systems to improve the sealing between the peri-implant epithelium (PIE) and the implant surface, and investigated the effect of implant structure on PIE down-growth. MATERIALS AND METHODS: Right maxillary first molars were extirpated from rats and implanted with either a straight-type or a step-type implant varying in step height and/or width (N(s): 0.8 mm height, 0.1 mm width; W(s): 0.8 mm height, 0.2 mm width; H(s): 0.4 mm height, 0.1 mm width). Maxillae were harvested at various time points over 16 weeks to evaluate laminin-5 distribution as an indicator of wound healing and PIE formation, horse-radish peroxidase (HRP) penetration as a measurement of epithelial sealing, and PIE down-growth formation. RESULTS: In all implant models, the PIE formed from the oral sulcular epithelium and spread apically along the implant surface. In the W(s) group, HRP penetration was detected only in the coronal region of the PIE at 4 weeks, whereas in the straight-type, it was observed in the apical region and the connective tissue. At 16 weeks, the W(s) implants exhibited markedly less PIE down-growth than the Con, N(s) or H(s) implants, and were equivalent to that observed in natural teeth. CONCLUSION: The step-type implant system may have the potential for improving epithelial sealing at the tissue-implant interface, as well as reducing apical PIE down-growth, thus enhancing dental implant efficacy.

The difference of fibroblast behavior on titanium substrata with different surface characteristics.

Connective tissue, one of the main components of peri-implant soft tissue, is key to the formation of the peri-implant mucosal seal and helping to prevent epithelial ingrowth. Rough surfaces (Rs), machined surfaces (Ms) or microgrooved surface (MG) are used in the neck area of commercially available titanium implants. In this paper, we aimed to evaluate the influence of surface topography of titanium substratum on connective tissue fibroblasts to gain a better understanding of this effect. Fibroblasts were cultured on titanium plates with Rs, Ms and MG. Adhesion cell number at day 3 was compared and protein distribution of both F-actin and vinculin was determined to observe cellular structure and adhesion. Cell adhesion strength was compared on each surface. At day 3, the number of fibroblasts attached on each substratum was in the order of MG ≈ Ms > Rs. Fibroblasts strongly expressed vinculin in the peripheral area on Ms and MG, and showed strong F-actin architecture. Decreased expression of vinculin and weaker continuity of F-actin were observed on Rs. Fibroblasts on MG were aligned along the grooves, with a significantly higher cell density, whereas cells on Ms and Rs had no clear orientation. The cell adhesion strength was significantly lower on Rs, and no significant difference was seen between MG and Ms. Both MG and Ms showed greater adhesion cell numbers and adhesion strength of fibroblasts when compared with Rs at day 3. The cell density on MG was greater than those on other substrata.

Oral Health-Related Quality of Life Changes after Clinical Remounting of Existing Dentures.

The clinical remount is an accurate and efficient way to reset the occlusion of delivered removable dentures if major occlusal correction is required. Although previous studies have reported that clinical remounting of existing dentures enhances patients' oral function, little subjective feedback is available. This retrospective study reports short-term changes in oral-health-related quality of life (OHRQoL) and masticatory function after clinical remounting of existing dentures. Three time points were defined: before adjustment (T0), immediately after adjustment (T1), and 1 week after adjustment (T2). The medical records of seven patients were analyzed. The mean age of participants was 77.71 years, and the mean service period of their prostheses was 9.43 months. The mean scores of the OHIP-EDENT-J questionnaire at the respective time points were 35, 21.14, and 22.14. The mean readings of masticatory function at the respective time points were 76.71, 89.29, and 111.86. Significant differences in the OHIP-EDENT-J were found between T0 and T1, and T0 and T2; and in masticatory function between T1 and T2, and T0 and T2. The results indicated that after rebalancing of the occlusion of the existing dentures, the patient-reported OHRQoL was improved immediately and maintained at least for a short time, and masticatory function was enhanced over a 1-week period.

Hypothetical Model of How a Clinical Remount Procedure Benefits Patients with Existing Dentures: A Narrative Literature Review.

The clinical remount procedure, which involves remounting the dentures on an articulator with interocclusal records, can effectively reduce occlusal discrepancies. This procedure can be applied not only to new dentures but also to those already in service; however, research in this field is still scarce. This narrative review aims to establish a hypothetical mechanism and possible indications and contraindications for this technique as a basis for further research. Current studies have revealed a high prevalence of malocclusion in delivered dentures. Performing a clinical remount on these existing dentures would enhance the oral function of the denture wearer and would enable effective and accurate correction of the accumulated errors in the jaw relationship in a stable working environment. This technique should be performed if a patient has poor masticatory function or occlusion-related complaints. However, performing a clinical remount on dentures with an excessive anterior-posterior discrepancy between the centric relation and the maximal intercuspal position or on dentures with extremely low occlusal vertical dimension, is considered less effective. The clinical remount procedure remains an essential skill both for fabricating quality dentures and maintaining those already in service.

Oral Function Rehabilitation with the Simplified Lauritzen Clinical Remount Technique in a Patient with Bimaxillary Alveolar Exostoses: A Case Report.

This case report describes a 70 year-old man with IVA lung cancer who required oral function rehabilitation by fabricating dentures with a simplified clinical remount technique. A pair of dentures were fabricated for a 70-year-old man with stage IVA lung cancer. Due to severe bimaxillary exostoses, the dentures could not properly extend and achieve a peripheral seal. The treatment philosophy was to stabilize the dentures and achieve proper function with optimized occlusion. The simplified Lauritzen clinical remount technique was performed at the time of denture delivery and 3 months later. After the second clinical remount procedure, the patient was able to eat meals with the dentures and maintained in a stable condition. Compared with the original technique, the simplified Lauritzen clinical remount omits the facebow transfer and keeps the condylar guidance setting and the Bennett angle unchanged during the adjustment. The prostheses are mounted to a type 3, non-arcon type articulator with anterior stop screws attached to the bilateral condylar parts. With the aid of anterior stop screws, the eccentric movement of dentures can be differentiated on a millimeter scale and balanced easily. It is effective to use occlusal-optimized dentures and the clinical remount technique, especially in difficult cases.

Synergistic Effect of Carbonate Apatite and Autogenous Bone on Osteogenesis.

Bone augmentation using artificial bone is an important option in dental defect prostheses. A bone substitute using carbonate apatite (CO3Ap), an inorganic component of bone, was reported to have promising bone formation and bone replacement ability. However, the osteoinductivity of artificial bone is less than autogenous bone (AB). In this study, CO3Ap with AB is demonstrated as a clinically effective bone substitute. For in vitro experiments, an osteoclast-like cell (RAW-D) was cultured in the presence of AB, CO3Ap, or both (Mix), and the number of osteoclasts was evaluated. Osteoblasts were also cultured under the same conditions, and the number of adherent cells was evaluated. For in vivo experiments, a few holes were created in the rat tibia and AB, CO3Ap, or Mix were added. At 0, 14, and 21 days, the tissue morphology of the wound area was observed, and the thickness of the cortical bone was measured. In vitro, Mix did not increase the number of osteoclasts or osteoblasts. However, in vivo, the rate of bone replacement remarkably increased with Mix on dome-shape. A bone-grafting material combining osteoinductive AB with abundant artificial bone is expected to be clinically easy to use and able to form bone.

Effect of carbonate apatite as a bone substitute on oral mucosal healing in a rat extraction socket: in vitro and in vivo analyses using carbonate apatite.

BACKGROUND: Low bone quantity and quality are serious problems that affect the prognosis of implants in the cosmetic field. Therefore, artificial bone substitutes are frequently used. However, whether there is a difference in the effect of either bone substitute on soft tissue healing is unclear given their greatly different absorbability. In this study, we used hydroxyapatite (HAp) and carbonate apatite (CO3Ap) as bone substitutes to analyze the epithelial and connective tissue healing after tooth extraction. METHODS: In vitro, oral mucosa-derived epithelial cells (OECs) collected from 4-day-old Wistar rats were seeded on HAp or CO3Ap and evaluated for adhesion, proliferation, migration, apoptosis, and morphology. Fibroblasts (FBs) were also analyzed for their ability to express collagen. In vivo, the extraction of maxillary right first (M1) and second molars (M2) of 6-week-old male Wistar rats was performed, followed by insertion of HAp or CO3Ap granules into the M1 and M2 sites. The oral mucosal healing process was then evaluated histochemically after 7 and 14 days. RESULTS: In vitro, high collagen expression by FBs in the CO3Ap group was observed and the surface analysis showed spreading of the FBs on the CO3Ap surface. However, the activity of OECs was suppressed on CO3Ap. Two weeks after CO3Ap implantation, soft tissue healing was observed, and recovery of the connective tissue was observed on the remaining CO3Ap. CONCLUSIONS: Our results suggest that the formation of soft tissues, including connective tissue, was promoted by CO3Ap in the extraction socket within a short period.

Therapeutic Effect of Benidipine on Medication-Related Osteonecrosis of the Jaw.

Medication-related osteonecrosis of the jaw (MRONJ) is an intractable disease that is typically observed in patients with osteoporosis or tumors that have been treated with either bisphosphonate (BP) or antiangiogenic medicine. The mechanism of MRONJ pathogenesis remains unclear, and no effective definitive treatment modalities have been reported to date. Previous reports have indicated that a single injection of benidipine, an antihypertensive calcium channel blocker, in the vicinity of a tooth extraction socket promotes wound healing in healthy rats. The present study was conducted to elucidate the possibility of using benidipine to promote the healing of MRONJ-like lesions. In this study, benidipine was administered near the site of MRONJ symptom onset in a model rat, which was then sacrificed two weeks after benidipine injection, and analyzed using histological sections and CT images. The analysis showed that in the benidipine groups, necrotic bone was reduced, and soft tissue continuity was recovered. Furthermore, the distance between epithelial edges, length of necrotic bone exposed in the oral cavity, necrotic bone area, and necrotic bone ratio were significantly smaller in the benidipine group. These results suggest that a single injection of benidipine in the vicinity of MRONJ-like lesions can promote osteonecrotic extraction socket healing.

Soft Tissue Interface with Various Kinds of Implant Abutment Materials.

Various materials, such as titanium, zirconia and platinum-gold (Pt-Au) alloy, have been utilized for dental implant trans-mucosal parts. However, biological understanding of soft tissue reaction toward these materials is limited. The aim of this study was to compare the response of cell lines and soft tissue to titanium, zirconia and Pt-Au substrata. The surface hydroxyl groups and protein adsorption capacities of the substrata were measured. Next, gingival epithelial-like cells (Sa3) and fibroblastic cells (NIH3T3) were cultured on the materials, and initial cell attachment was measured. Immuno-fluorescent staining of cell adhesion molecules and cytoskeletal proteins was also performed. In the rat model, experimental implants constructed from various materials were inserted into the maxillary tooth extraction socket and the soft tissue was examined histologically and immunohistochemically. No significant differences among the materials were observed regarding the amount of surface hydroxyl groups and protein adsorption capacity. Significantly fewer cells of Sa3 and NIH3T3 adhered to the Pt-Au alloy compared to the other materials. The expression of cell adhesion molecules and a well-developed cytoskeleton was observed, both Sa3 and NIH3T3 on each material. In an animal model, soft tissue with supracrestal tissue attachment was observed around each material. Laminin-5 immuno-reactivity was seen in epithelia on both titanium and zirconia, but only in the bottom of epithelia on Pt-Au alloy. In conclusion, both titanium and zirconia, but not Pt-Au alloy, displayed excellent cell adhesion properties.

Assessment of the Soft-Tissue Seal at the Interface between the Base of the Fixed Denture Pontic and the Oral Mucosa.

Fixed dentures (bridges) are often selected as a treatment option for a defective prosthesis. In this study, we assess the contact condition between the base of the pontic and oral mucosa, and examine the effect of prosthetic preparation and material biocompatibility. The molars were removed and replaced with experimental implants with a free-end type bridge superstructure after one week. In Experiment 1, we assessed different types of prosthetic pre-treatment: (1) the untreated control group (Con: mucosa recovering from the tooth extraction); (2) the laser irradiation group (Las: mucosa recovering after the damage caused by a CO2 laser); and (3) the tooth extraction group (Ext: mucosa recovering immediately after the teeth extraction). In Experiment 2, five materials (titanium, zirconia, porcelain, gold-platinum alloy, and self-curing resin) were placed at the base of the bridge pontic. Four weeks after the placement of the bridge, the mucosa adjacent to the pontic base was histologically analyzed. In Experiment 1, the Con and Las groups exhibited no formation of an epithelial sealing structure on the pontic base. In the Ext group, adherent epithelium was observed. In Experiment 2, the sealing properties at the pontic interface were superior for titanium and the zirconia compared with those made of porcelain or gold-platinum alloy. In the resin group, a clear delay in epithelial healing was observed.