In vitro assessment of internal implant-abutment connections with different cone angles under static loading using synchrotron-based radiation.

BACKGROUND: The stability of implant-abutment connection is crucial to minimize mechanical and biological complications. Therefore, an assessment of the microgap behavior and abutment displacement in different implant-abutment designs was performed. METHODS: Four implant systems were tested, three with a conical implant-abutment connection based on friction fit and a cone angle < 12 ° (Medentika, Medentis, NobelActive) and a system with an angulated connection (< 40°) (Semados). In different static loading conditions (30 N - 90º, 100 N - 90º, 200 N - 30º) the microgap and abutment displacement was evaluated using synchrotron-based microtomography and phase-contrast radioscopy with numerical forward simulation of the optical Fresnel propagation yielding an accuracy down to 0.1 µm. RESULTS: Microgaps were present in all implant systems prior to loading (0.15-9 µm). Values increased with mounting force and angle up to 40.5 µm at an off axis loading of 100 N in a 90° angle. CONCLUSIONS: In contrast to the implant-abutment connection with a large cone angle (45°), the conical connections based on a friction fit (small cone angles with < 12°) demonstrated an abutment displacement which resulted in a deformation of the outer implant wall. The design of the implant-abutment connection seems to be crucial for the force distribution on the implant wall which might influence peri-implant bone stability.

Association of sex steroid hormones and new bone formation rate after iliac onlay grafting: a prospective clinical pilot study.

PURPOSE: The present prospective study evaluates the association between new bone formation rate in the iliac onlay graft and sex steroid hormone serum levels. METHODS: A total of 15 partially or completely edentulous postmenopausal females and 9 males with less than 5 mm height of the remaining alveolar bone underwent iliac onlay grafting followed by dental implant placement using a two-stage approach. Sex hormone binding globulin and 17ß-estradiol serum levels were investigated by electrochemiluminescence immunoassay, while total testosterone level was analyzed using radioimmunoassay. At the time of implant placement, 12 weeks after grafting, bone biopsies were obtained and analyzed histomorphometrically. Statistical analysis was performed using linear mixed models. RESULTS: Grafting procedure was successfully performed in all patients. The mean new bone formation rate was 32.5% (116 samples). In men the mean new bone formation rate (38.1%) was significantly higher (p < 0.01) than in women (27.6%). Independent of gender 17ß-estradiol and testosterone were positively associated to overall new bone formation rate, albeit a significant influence was only seen for 17ß-estradiol in men (p = 0.020). Sex hormone binding globulin had no influence on new bone formation rate (p = 0.897). There was no significant association between new bone formation rate and age (p = 0.353) or new bone formation rate and body mass index (p = 0.248). CONCLUSION: Positive association of 17ß-estradiol as well as testosterone with new bone formation rate after iliac onlay grafting indicates a role of sex steroid hormones in alveolar bone regeneration, although the observed influence was only significant for 17ß-estradiol in men.

Comparison of the 3D-Microstructure Between Alveolar and Iliac Bone for Enhanced Bioinspired Bone Graft Substitutes.

In oral- and maxillofacial bone augmentation surgery, non-vascularized grafts from the iliac crest demonstrate better clinical performance than alveolar bone grafts. The underlying mechanisms are not fully understood but are essential for the enhancement of bone regeneration scaffolds. Synchrotron Radiation µ-CT at a pixel size of 2.3 µm was used to characterize the gross morphology and the vascular and osteocyte lacuna porosity of patient-matched iliac crest/alveolar bone samples. The results suggest a difference in the spatial distribution of the vascular pore system. Fluid simulations reveal the permeability tensor to be more homogeneous in the iliac crest, indicating a more unidirectional fluid flow in alveolar bone. The average distance between bone mineral and the closest vessel pore boundary was found to be higher in alveolar bone. At the same time, osteocyte lacunae density is higher in alveolar bone, potentially compensating for the longer average distance between the bone mineral and vessel pores. The present study comprehensively quantified and compared the 3D microarchitecture of intraindividual human alveolar and iliac bone. The identified difference in pore network architecture may allow a bone graft from the iliac crest to exhibit higher regeneration potential due to an increased capacity to connect with the surrounding pore network of the residual bone. The results may contribute to understanding the difference in clinical performance when used as bone grafts and are essential for optimization of future scaffold materials.

Influence of the width of keratinized tissue on the development and resolution of experimental peri-implant mucositis lesions in humans.

OBJECTIVES: To analyze the influence of the width of keratinized mucosa (KM) on the development and resolution of experimental peri-implant mucositis lesions at abutments with different microstructures in humans. MATERIAL AND METHODS: In a randomized, controlled study, a total of 28 patients had received 28 target implants exhibiting a KM ≥2 mm. These were randomly connected with either partially microgrooved- (test) (n = 15) or machined (control) (n = 13) healing abutments. The study protocol included a wound healing period (WH) following implant placement (12 weeks), a plaque exposure phase (EP) of 21 days (EPd21) and a resolution phase (RP) including visits at 2, 4, and 16 weeks (RPw2; RPw4; RPw16) following plaque removal. Linear regression analyses were used to analyze the relationship between the width of KM and clinical outcomes (i.e., modified plaque index [mPI], modified gingival index [mGI], bleeding on probing [BOP], and probing depth [PD]). RESULTS: Mean and median KM values (end of WH) were 5.9 ± 2.6 and 5.0 mm (min: 2 mm; max: 10 mm; interquartile range: 5 mm) at test- and 5.5 ± 2.6 and 4.0 mm (min: 3 mm; max: 11 mm interquartile range: 4 mm) at control abutments. The linear regression analysis revealed significant correlations between the width of KM and mPI (test: RPw2; control: RPw16), mGI (test: RPw16), BOP (both: RPw16), and PD (test: RPw16; control: EPd21, RPw2, RPw4, RPw16) scores. CONCLUSION: The width of KM (≥2 mm) had some effects on the development (i.e., at 21 days) and resolution of experimental peri-implant mucositis lesions at both abutment types.

Onset, progression and resolution of experimental peri-implant mucositis at different abutment surfaces: A randomized controlled two-centre study.

OBJECTIVES: To assess the onset, progression and resolution of experimentally induced peri-implant mucositis lesions at abutments with different microstructures in humans. MATERIAL & METHODS: In a randomized, controlled, interventional two-centre study, a total of 28 patients had received 28 target implants and were randomly allocated to either partially microgrooved (test) or machined (control) healing abutments. The study was accomplished in three phases, including a wound healing period (WH) following implant placement (12 weeks), a plaque exposure phase (EP-21 days) and a resolution phase (RP-16 weeks). Clinical (e.g. bleeding on probing-BOP), immunological (MMP-8) and microbiological (DNA counts for 11 species) parameters were evaluated. RESULTS: The incidence of peri-implant mucositis at EPd21 was comparable in both test and control groups (60.0% versus 61.5%), but markedly lower at control abutments after a nonsurgical treatment and reconstitution of oral hygiene measures at RPw16 (46.7% versus 15.4%). At any follow-up visit (i.e. EP and RP), clinical parameters, MMP-8 levels and DNA counts of major bacterial species were not significantly different between both groups. CONCLUSION: The onset, progression and resolution of experimental peri-implant mucositis lesions were comparable in both groups.

Healing of localized gingival recessions treated with coronally advanced flap alone or combined with either a resorbable collagen matrix or subepithelial connective tissue graft. A preclinical study.

OBJECTIVES: To histologically evaluate the effectiveness of a porcine derived collagen matrix (CM) and a subepithelial connective tissue graft (CTG) for coverage of localized gingival recessions. MATERIALS AND METHODS: Chronic single Miller Class I-like recessions were created at the buccal at the canines and at the third and fourth premolars in the upper and lower jaws of six beagle dogs. The defects were randomly treated with (1) coronally advanced flap surgery (CAF) + CM, (2) CAF + CTG, or (3) CAF alone. At 12 weeks, histometric measurements were made, e.g., between a reference point (N) - and the gingival margin (GM) - and the outer contour of the adjacent soft tissue (gingival thickness [GT]). RESULTS: The postoperative healing was uneventful in all animals. No complications such as allergic reactions, abscesses or infections were noted throughout the entire study period. All three treatments resulted in coverage of localized gingival recessions. The histological analysis failed to identify any residues of CM or CTG. The histometric measurements revealed comparable outcomes for N-GM and GT values for all three groups (CAF + CM: 1.04 ± 0.69 mm/0.68 ± 0.33 mm; CAF + CTG: 1.15 ± 1.12 mm/0.76 ± 0.37 mm; CAF: 1.43 ± 0.45 mm/0.79 ± 0.24 mm). CONCLUSIONS: In the used defect model, the application of CTG or CM in conjunction with CAF did not have an advantage over the use of CAF alone. CLINICAL RELEVANCE: The use of CAF alone is a valuable option for the treatment localized Miller Class I recessions.

The impact of dis-/reconnection of laser microgrooved and machined implant abutments on soft- and hard-tissue healing.

OBJECTIVES: To (i) investigate the influence of different extensions of a laser microgrooved abutment zone on connective tissue attachment and (ii) assess the impact of a repeated abutment dis-/reconnection on soft- and hard-tissue healing. MATERIALS AND METHODS: Titanium implants were inserted epicrestally in the lower jaws of six dogs. Healing abutments with either partially (LP) or completely (LC) laser microgrooved margins or machined surface margins (M) were randomly allocated either to a single (1×)/repeated (2×) dis-/reconnection at 4 and 6 weeks (test), respectively, or left undisturbed (control). At 6 and 8 weeks, histomorphometrical (e.g. most coronal level of bone in contact with the implant [CBI], subepithelial connective tissue attachment [STC]) and immunohistochemical (Collagen Type-I [CI]) parameters were assessed. RESULTS: At control sites, LP/LC groups revealed lower mean CBL (8 weeks, 0.95 ± 0.51 vs. 0.54 ± 0.63 vs. 1.66 ± 1.26 mm), higher mean STC (8 weeks, 82.58 ± 24.32% vs. 96.37 ± 5.12% vs. 54.17 ± 8.09%), but comparable CI antigen reactivity. A repeated abutment manipulation was associated with increased mean CBL (8 weeks, 1.53 ± 1.09 vs. 0.94 ± 0.17 vs. 1.06 ± 0.34 mm), decreased STC (8 weeks, 57.34 ± 43.06% vs. 13.26 ± 19.04% vs. 37.76 ± 37.08%) and CI values. CONCLUSIONS: It was concluded that (i) LC>LP abutments enhanced subepithelial connective tissue attachment and preserved crestal bone levels, (ii) repeated abutment dis-/reconnection during the initial healing phase (4-6 weeks) may be associated with increased soft- and hard-tissue changes and (iii) LP and LC should be considered using a one abutment, one time approach.

Quality assessment of reporting of animal studies on pathogenesis and treatment of peri-implant mucositis and peri-implantitis. A systematic review using the ARRIVE guidelines.

OBJECTIVES: To address the following focused question: What is the quality of reporting of pre-clinical research for the study and treatment of mucositis/peri-implantitis? MATERIALS AND METHODS: Electronic databases of the PubMed and the Cochrane Library were searched for animal studies reporting on pathogenesis or therapy of either peri-implant mucositits or peri-implantitis and completed by dual manual searches in duplicate between 1992 and May 2011. Quality assessment (i.e. grading of a checklist of 20 items in different categories) of selected full-text articles was performed according to the Animal Research: Reporting of In Vivo Experiments (ARRIVE) guidelines. RESULTS: Following screening, 75 publications were eligible for the review. For publications reporting on pathogenesis (n = 7) and therapy (n = 1) of peri-implant mucositis, minimum gradings were assigned to items 5 (Methods/Ethical Statement), 9 (Methods/Housing and husbandry), 11 (Methods/Allocation animals to experimental groups), 14 (Results/Baseline data), and 17 (Results/Adverse events). For publications reporting on pathogenesis (n = 34) and therapy (n = 33) of peri-implantitis, minimum grades were mainly assigned to items 9, 11, 14, and 17. CONCLUSIONS: This systematic review has identified missing information in the publications on pre-clinical research for the study and treatment of mucositis/peri-implantitis.

Preservation of the ridge and sealing of the socket with a combination epithelialised and subepithelial connective tissue graft for management of defects in the buccal bone before insertion of implants: a case series.

Defects in the layer of buccal bone lead to its loss after tooth extractions. This requires hard tissue grafting before implants can be put in place. The aim of this study was to evaluate the stability of hard tissue grafts inserted at the same time as the teeth were extracted. Teeth had to be extracted because of defects in the buccal bone. Extractions were combined with preservation of the ridge using autogenous and artificial bone. A combination epithelialised and subepithelial connective tissue graft was used to seal the socket. Wound healing was assessed and the width of the alveolar crest was measured after hard tissue grafting and during insertion of the implants. We studied 39 patients (20 female, 19 male, mean (SD) age 41 (7.9) years) who had 43 teeth extracted together with preservation of the ridge. One patient failed to attend for placement of the implant. Thirty-nine implants were inserted 5.3 (0.4) months after preservation of the ridge. Two patients developed partial necrosis of the combination graft, but in all other cases primary wound healing was uneventful. In three cases the bone grafts failed to consolidate. The mean (SD) width of the alveolar crest was after bone grafting 6.80 (1.20) mm and during insertion of implants 5.65 (1.50) mm; the mean resorption of the bone grafts was 1.2 (1.1) mm. We conclude that bone grafting to rebuild buccal alveolar defects at the same time that the tooth is extracted, combined with a soft tissue graft to seal the socket, showed promising results and could be an alternative treatment to delayed hard tissue grafting.

Impact of the method of surface debridement and decontamination on the clinical outcome following combined surgical therapy of peri-implantitis: a randomized controlled clinical study.

OBJECTIVES: The study aimed at investigating the impact of two surface debridement/decontamination (DD) methods on the clinical outcomes of combined surgical treatment of peri-implantitis. MATERIAL AND METHODS: Thirty-two patients suffering from advanced peri-implantitis (n=38 combined supra- and intra-bony defects) were treated with flap surgery, granulation tissue removal, and implantoplasty at buccally and supracrestally exposed implant parts. The intra-bony aspects were randomly allocated to surface DD using either (i) an Er:YAG laser (ERL) device, or (ii) plastic curets+cotton pellets+sterile saline (CPS). In both groups, the intra-bony component was augmented with a natural bone mineral and covered with a collagen membrane. Clinical and radiographic parameters were recorded at baseline and after 6 months of non-submerged healing. RESULTS: Two patients were lost during follow-up. At 6 months, ERL-treated sites failed to reveal higher reductions in mean bleeding on probing (ERL: 47.8 ± 35.5 versus CPS: 55.0 ± 31.1%) and CAL values (ERL: 1.5 ± 1.4 versus CPS: 2.2 ± 1.4 mm) when compared with the CPS group. Both groups exhibited a comparable radiographic bone fill at the intra-bony defect component. CONCLUSION: The study failed to demonstrate a significant impact of the method of surface DD on the clinical outcome following combined surgical therapy of advanced peri-implantitis lesions.