Gregory-George Zafiropoulos

Human periodontal fibroblast response to a nanostructured hydroxyapatite bone replacement graft in vitro

OBJECTIVE The efficacy of nanostructured hydroxyapatite (NHA) for the treatment of osseous defects has been demonstrated in recent studies, even though the underlining biological mechanism is still poorly known. This study examined the alterations in cellular adhesion and mitogenic responses in human periodontal ligament (PDL) cells treated with a novel nanostructured hydroxyapatite bone graft substitute and characterized associated changes in cellular signalling pathways. METHODS Cultured PDL cells were stimulated with NHA in a surface coated form. Proliferation was determined by bromodeoxyuridine (BrdU) incorporation and cell adhesion was analysed by a colorimetric assay. In order to understand altered adhesion properties of PDL fibroblasts their integrin profile was analysed and the phosphorylation status of focal adhesion kinase (FAK) and beta1 integrin was determined by immunoblotting. In order to understand the signalling mechanisms of increased cell proliferation of PDL cells caused by NHA, the phosphorylation status of the serine/threonine protein kinase Akt, of the signal regulated kinases ERK1/2 and of the epidermal growth factor receptor (EGFR) was analysed by western blot using phospho-specific antibodies. RESULTS The results indicated that NHA is a strong stimulator of PDL cell attachment and proliferation. Mechanistically, alpha5beta1 integrin-mediated cellular adhesion of PDL fibroblasts, which resulted in altered phosphorylation and activation levels of FAK. Proliferation mediated by NHA was mechanistically caused by activation of the epidermal growth factor receptor (EGFR) pathway and its downstream targets ERK1/2 and Akt. CONCLUSIONS In sum, our findings present evidence that alpha5beta1 integrin-mediated cellular adhesion of NHA to PDL fibroblasts, whereas proliferation was caused by activation of the epidermal growth factor receptor (EGFR) and the MAP kinase (ERK1/2) and Akt pathways.

Zirconia removable telescopic dentures retained on teeth or implants for maxilla rehabilitation. Three-year observation of three cases.

This report addresses maxillary restoration with removable telescopic crown-retained palatal free dentures. One patient with 7 natural teeth (PERIO), a second patient with 6 dental implants (IMPL), and a third patient with 2 natural teeth and 4 dental implants (IMPL-PERIO) were treated. Zirconia copings for natural teeth and individual zirconia implant abutments were fabricated in CAD/CAM and used as primary crowns. Electroformed gold copings were used as secondary telescopes. All maxilla supraconstructions were fabricated with zirconia and CAD/CAM. Patients were monitored during a 3-year period; all teeth and implants survived, and no biological or mechanical complications occurred. The peri-implant and periodontal conditions were healthy. While recognizing the limitations of this report, results showed that fabricating removable zirconia structures by means of CAD/CAM can yield highly functional and esthetic results. Galvanoforming technology is the preferable means of fabricating secondary crowns. The combination of these techniques and materials results in a prosthetic reconstruction of high quality, good fit, and biocompatibility. Long-term studies of large populations are necessary to investigate the clinical properties of the material utilized in this type of construction.

Telescopic Crowns as Attachments for Implant Supported Restorations: A Case Series

The use of dental implants to support mandibular or maxillary overdentures is a widely used treatment modality. Advantages are an increase in retention, an increase in chewing ability, and easy access for oral hygiene procedures. While telescopic and conical crowns have been used for decades to connect natural teeth to overdentures, not many cases have been reported in the literature of telescopic crowns placed on implants to support overdentures. This article describes 7 patients with overdentures supported by telescopic crowns who received 65 implants (ITI Straumann). The cases presented in this report have been in function for up to 4.5 years. During that time no adverse events were reported. The use of telescopic crowns as attachments for implant-supported overdentures may be a viable treatment option.

Mandibular molar root resection versus implant therapy: a retrospective nonrandomized study.

Success rates for both periodontal and implant therapy are often dependent on site and tooth type. For periodontally involved mandibular molars, the decision to hemisect or to extract and place an implant is often complicated. The purpose of the present study was to evaluate the outcomes of the aforementioned treatment modalities for mandibular molars in a private practice setting. A retrospective chart review was performed. In one group of patients (n = 32), 56 mandibular first or first and second molars were treated by hemisection (Group H). A second group (n = 28) received 36 implants in the mandible to replace periodontally involved first or first and second molars (Group I). All patients had been in maintenance for at least 4 years after treatment. The occurrence and timing of posttreatment complications were evaluated. Data were analyzed by parametric and nonparametric statistics, as indicated. The majority of hemisected teeth (68% of Group H) and implants (89% of Group I) remained free of complications for the entire observation period. Group H had a greater incidence of overall complications (P = .027) and nonsalvageable complications (P = .013) than Group I. For both groups, the percent CAL loss per year was greater for the teeth/implants that experienced complications than in the those that remained complication free (p < 0.015). Within the limitations of this study, the results indicated that, in periodontitis patients, hemisected mandibular molars were more prone to complications than implants.

Tooth-Implant Connection: A Review

The aim of this review was to assess the long-term outcomes of restorations supported by implants and natural teeth with regard to complications associated with implants, teeth, and restorations, as well as the influence on these parameters of the connector type used. A net-based search in PubMed was combined with a manual search. Clinical studies, reviews, and biomechanical studies were included. Information on survival rate, complication rate, incidence of tooth intrusion, and, where applicable, type of connector used, was retrieved from the clinical studies. Force distribution and types of connectors used were retrieved from the biomechanical study. A summary of outcomes was retrieved from the reviews. A total of 25 articles were selected for inclusion in this review, including clinical studies (15), biomechanical studies (7), and reviews (3). Implant success rates ranged from 79.5%-100%. Tooth complications occurred in 5.4%-11.8% of cases. Complications in the suprastructure were observed in 5%-90% of cases. Tooth intrusion presented in a total of 0%-66% of all cases, more often in cases with nonrigid connection (0%-66%) than in cases with rigid connection (0%-44%). Biomechanical studies show a large difference in stress distribution and in dependence on the type of connector used, with most studies demonstrating that nonrigid connectors drastically reduce stress on the suprastructure while increasing forces on supporting teeth and implants. Long-term success rates for tooth-implant connections are lower than for solely implant-supported restorations with regard to prognosis for teeth, implants, and suprastructure. Use of rigid connectors leads to more favorable clinical outcomes in terms of long-term stability, occurrence of complications, and tooth intrusion.

Five-Year Study of Implant Placement in Regenerated Bone and Rehabilitation With Telescopic Crown Retained Dentures: A Case Report

Various implant-supported restorations have been used successfully for several decades to rehabilitate edentulous patients. Telescopic crowns are a common treatment modality used to connect dentures to natural teeth. Although previous findings indicate that telescopic crowns can be placed successfully on implants to support overdentures, only limited data are available on this treatment approach. Eight months after extraction of all nonsalvageable teeth and socket preservation, 11 implants were inserted into the mandible and maxillae of one patient. These implants were restored 4 months later using telescopic crown-supported dentures. Bleeding on probing (BOP), plaque index (PI), clinical attachment (PAL), and radiographic bone level were evaluated over 5 years. All implants remained in function over the 5-year evaluation period. Radiography showed stable bone levels for all implants. No changes in BOP or PI (range, 2%-4% for both parameters) were observed over this time. The PAL deteriorated by 1.5 mm during the first 3 years, with no subsequent changes. We conclude that telescopic crowns can be used successfully as attachments for overdentures supported by implants in regenerated bone.

Efficacy of electrical neuromuscular stimulation in the treatment of chronic periodontitis.

Purpose The purpose of the present randomized controlled clinical study was to evaluate the short-term outcomes of microcurrent electrical neuromuscular stimulation (MENS) as an adjunct method to nonsurgical periodontal therapy. Methods Twenty patients with moderate to severe chronic periodontitis were recruited into the study and randomly treated with either nonsurgical periodontal therapy followed by 5 MENS treatments with a microcurrent device or by nonsurgical periodontal therapy alone. Periodontal parameters were measured at baseline and 6 weeks following therapy, and included the plaque index, bleeding on probing, probing depth, and clinical attachment level (CAL). Results All measured values were reduced at the time of re-evaluation. The amount of inflammation was significantly reduced in both the test (P=0.002) and control group (P=0.015). The test group demonstrated a significant CAL gain at 6 weeks following therapy, including non-molar (P=0.009) and molar teeth (P=0.028). In comparison with the control group, the test group showed statistically significant differences in the CAL on both molar (P=0.027) and non-molar teeth (P=0.031). Conclusions In conclusion, the short-term results of the study indicate that MENS could be a suitable adjunctive method in the treatment of chronic periodontitis.

Immediate Implant Placement in Fresh Mandibular Molar Extraction Socket: 8-Year Results. A Case Report

Recently, successful implant placement in fresh extraction sockets has been reported. In this case report, we present the results of an immediate implant placement in a fresh extraction socket of a mandibular molar with simultaneous bone regeneration using a nonresorbable membrane and no other graft materials. Clinical and radiographic findings acquired 8 years after implant placement demonstrated a stable peri-implant situation and confirmed a satisfactory treatment result.

Longitudinal implant stability measurements based on resonance frequency analysis after placement in healed or regenerated bone.

Primary stability is an indicator of subsequent osseointegration of dental implants. However, few studies have compared the implant stability among anatomical regions and bone types; thus, not enough data exist regarding the stability of implants placed in regenerated bone (RB). The present study evaluated primary and long-term stability of implants placed in RB and non-regenerated healed bone (HB). A total of 216 screw cylinder implants were placed in 216 patients (98 in HB and 118 in RB, 6 [RB6, N = 68] or 12 [RB12, N = 50] months after tooth extraction). Implant stability was evaluated using resonance frequency analysis (RFA) measured at the time of implant placement (E1), at the time of loading (4 months after placement, E2), and 4 months after loading (E3). Various clinically relevant measurements were obtained, such as implant diameter, length, and location, as well as bone quality. At E1, implant location, bone quality, and experimental group significantly affected implant stability (all at P < .05). At E2, implant location, diameter, length, and experimental group significantly affected implant stability (all at P < .05). At E3, bone quality, implant diameter, length, and experimental group significantly affected implant stability (all at P < .01). Stability for the RB12 group was significantly higher than all other corresponding values; further, the values did not change significantly over time. For the HB and RB6 groups, stability was significantly higher at E2 than at E1 (P < .001) and was no different between E2 and E3. Implant location, length, and experimental group were associated with these differences (all at P < .05). Compared with HB and RB6, higher implant stability may be achieved in regenerated bone 12 months post-extraction (RB12). This stability was achieved at E1 and maintained for at least 8 months. Variables such as implant length, diameter, and bone quality affected the stability differently over time. Implant stability varied in different anatomic regions and with regard to different healing processes in the bone.

Changes of the peri-implant soft tissue thickness after grafting with a collagen matrix

Background: The aim of this study was to determine the treatment outcome of the use of a porcine monolayer collagen matrix (mCM) to increase soft-tissue volume as a part of implant site development. Materials and Methods: Implants were placed in single sites in 27 patients. In the test group, mCM was used for soft-tissue augmentation. No graft was placed in the control group. Soft-tissue thickness (STTh) was measured at the time of surgery (T0) and 6 months postoperatively (T1) at two sites (STTh 1, 1 mm below the gingival margin; STTh 2, 3 mm below the mucogingival margin). Results: Significant increases (P < 0.001) in STTh (STTh 1 = 1.06 mm, 117%; STTh 2 = 0.89 mm, 81%) were observed in the test group. Biopsy results showed angiogenesis and mature connective tissue covered by keratinized epithelium. Conclusions: Within the limitations of this study, it could be concluded that mCM leads to a significant increase of peri-implant soft-tissue thickness, with good histological integration and replacement by soft tissue and may serve as an alternative to connective tissue grafting.