Marginal bone loss and the risk indicators of fixed screw-retained implant-supported prostheses and fixed telescopic-retained implant-supported prostheses in full arch: A retrospective case-control study.

OBJECTIVES: This study compared full-arch screw-retained implant-supported fixed dental prostheses (FSI-FDPs) and full-arch telescopic-retained implant-supported fixed dental prostheses with a professional retrieval system (FTI-FDPs) on marginal bone loss (MBL), the risk indicators and peri-implantitis rate after 7-13 years. MATERIAL AND METHODS: Sixty five edentulous patients were treated with 86 prostheses and 592 implants. The FSI-FDP group comprised 26 patients (32 prostheses, 202 implants), and the FTI-FDP group comprised 39 patients (54 prostheses, 390 implants). MBL and the risk indicators of MBL ≥1 mm were assessed. Peri-implantitis rates at 13 years were also calculated. RESULTS: Full-arch screw-retained implant-supported fixed dental prostheses and FTI-FDP implants exhibited comparable mean MBLs of 0.60 ± 0.51 and 0.41 ± 1.03 mm, respectively. MBL ≥1 mm was noted for 25% of FSI-FDP implants and 6.9% of FTI-FDP implants. Superstructure-abutment connection (screw retention:FSI-FDPs >telescopic retention:FTI-FDPs) and implant-abutment connection (External butt joint, Internal butt joint >Morse taper joint) were associated with MBL ≥1 mm. Peri-implantitis rates at the implant level were 3.99% (95%CI = 3.93-20.5) in FSI-FDP group and 3.85% (95%CI = 3.85-34.3) in FTI-FDP group with no significance. CONCLUSIONS: It was concluded that FSI-FDP and FTI-FDP implants exhibited comparable MBL; however, the risk of MBL ≥1 mm in FTI-FDPs was lower than in FSI-FDPs. Besides, implant-abutment connection was the risk indicator of MBL ≥1 mm. In peri-implantitis rate, FSI-FDPs and FTI-FDPs behave similarly.

Periodontal conditions in patients requesting dental implant treatment.

Periodontal disease is considered a risk factor in dental implant treatment. The purpose of this study was to investigate the periodontal conditions in patients requesting dental implant therapy. A total of 169 patients visiting Department of Oral and Maxillo-Facial Implantology at Tokyo Dental College Chiba Hospital were targeted. The following intraoral parameters were measured in each patient: Community Periodontal Index (CPI) score, probing pocket depth (PPD), clinical attachment level (CAL) and bleeding on probing (BOP). Prevalence of patients with periodontal pockets was high: 38% and 28% of patients had a CPI score of code 3 and 4, respectively. Prevalence of teeth with one or more sites with PPD≥4mm was 27%. Moreover, clinical signs suggestive of periodontitis (PPD, CAL≥4mm) were found in 10-15% of tooth sites. Prevalence rates at sites with severe periodontal breakdown (PPD, CAL≥7mm) were 2-5%. These results further emphasize the importance of thorough periodontal assessment in patients prior to dental implant treatment.

Clinical evaluation of periodontal pathogen levels by real-time polymerase chain reaction in peri-implantitis patients.

OBJECTIVE: The mechanisms underlying the onset and progression of peri-implantitis are similar to those of periodontitis, and the causative bacteria are believed to similar. Previous studies support an association between peri-implantitis and periodontal pathogen. Thus, we investigated the bacterial flora of peri-implantitis patients in comparison to those of healthy implant and periodontitis patients. MATERIALS AND METHODS: In total, 70 patients visiting Tokyo Dental College Chiba Hospital were divided into four groups: healthy, periodontitis, healthy implant, and peri-implantitis. For each group, the following five periodontal pathogens were detected using real-time polymerase chain reaction: Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia, Treponema denticola, and Prevotella intermedia. RESULTS: The average copy number of total bacteria was significantly higher in the periodontitis group than in the other groups. P. gingivalis was detected in the periodontitis and peri-implantitis groups at levels as high as 18.92% and 12.29%, respectively, and P. intermedia was found in the peri-implantitis group at a rate of 2.06%. Nevertheless, periodontal pathogens were generally detected at lower levels in the peri-implantitis group than in the periodontitis group. CONCLUSION: We found lower bacterial counts in the peri-implantitis group relative to the periodontitis group. Our results suggest that the peri-implant tissue is less resistant to bacteria, so even a small number of bacteria can be a risk factor for peri-implantitis and the causative agent of peri-implantitis can be bacteria other than periodontal pathogen.

Proliferation and osteogenic differentiation of human mesenchymal stem cells on zirconia and titanium with different surface topography.

The purpose of this study was to elucidate behavior of human mesenchymal stem cells (hMSCs) on yttria stabilized tetragonal zirconia polycrystals (TZP) and commercial pure titanium (CpTi) with different surface topography. Mirror-polished (MS), sandblasted with 150-µm alumina (SB150) and SB150 acid-etched (SB150E) were prepared on TZP and CpTi. Proliferation, osteogenic differentiation of hMSCs was evaluated. The scanning electron microscopy showed that micro- and nano-topographies were created on both TZP and CpTi SB150E surfaces. The proliferation ability, ALP activity, expression of Runx2 on the both SB150E specimens was significantly higher than those on the other specimens. These results suggested that creation of micro- and nano-topographies on TZP and CpTi by blast and acid-etching may offer a promising method for enhancing the proliferation and differentiation of hMSCs in clinical application.

Translucency and flexural strength of monolithic translucent zirconia and porcelain-layered zirconia.

This study aims to investigate the effectiveness of monolithic translucent TZP with different colors and porcelain-layered TZP by evaluating their colors and strengths. Different mixing ratios of Zpex to Zpex-Yellow as translucent TZP, conventional opaque TZP (TZ-3YB-E) (Tosoh, Tokyo) as a control, and veneering porcelain (CERABIEN ZR, body porcelain, Noritake, Tokyo) with shade A3 as a typical shade. Disk-shaped specimens of 13 mm diameter and 1.5 mm thickness were prepared. These specimens were observed under reflected and transmitted light, and the translucency parameter (TP) values were measured. Strength was also evaluated with flexural strength in a biaxial bending test. The TP values of the monolithic TZP, Zpex100>Zpex70>Zpex50>TZ3YB, were larger in this order. The flexural strength of all the monolithic TZP showed approximately 1,000 MPa. It is suggested that colored translucent TZP is clinically useful when used as monolithic restorations.

Influence of thin carbonate-containing apatite coating with molecular precursor method to zirconia on osteoblast-like cell response.

The influence of a thin carbonate-containing hydroxyapatite (CA) coating to tetragonal zirconia polycrystal (TZP) on osteoblastlike cell response was investigated. TZP disks were subjected to blasting and acid etching. Thin CA coatings were deposited by the molecular precursor method (TZP-CA). Initial cell adhesion of mouse osteoblast-like cells MC3T3-E1 was enhanced, and marked progress of actin filaments was observed on TZP-CA compared to on TZP. After 3, 5 or 7 days, cell proliferation on TZP-CA was significantly higher than that on TZP. Alkaline phosphatase activity was slightly lower on TZP-CA than on TZP at 7 days, and no difference was observed at 14 or 21 days. At 28 days incubation, collagenous fibers with mineral precipitants accompanied by phosphorous and amino groups were observed. These results indicate that thin CA coating with molecular precursor method offers promise as a means of enhancing cell response, particularly initial adhesion and proliferation of MC3T3-E1 cells.

Response of osteoblast-like cells to zirconia with different surface topography.

The objective of this study was to clarify the effect of surface topography on osteoblast-like cell behavior on yttria stabilized tetragonal zirconia polycrystals (TZP). Mirror-polished; blasted with 50- or 150-µm alumina (SB50 and SB150); and SB150 acid-etched with hydrofluoric acid (SB150E) were prepared on TZP. Initial attachment, proliferation and differentiation of MC3T3-E1 were evaluated. The scanning electron microscopy and Sdr (developed interfacial area ratio) values indicated that both micro- and nano-topographies produced on the SB150E surfaces. Although no clear differences were observed in initial cell attachment among specimens, the proliferation rate and expression of ALP activity on the SB150E specimens was significantly higher than that on the other specimens. These results indicate that the creation of micro- and nano-topographies on TZP by surface treatment offers a promising method of enhancing the proliferation and differentiation of MC3T3-E1 cells.