Teeth restored using fiber-reinforced posts: in vitro fracture tests and finite element analysis

In dentistry the restoration of decayed teeth is challenging and makes great demands on both the dentist and the materials. Hence, fiber-reinforced posts have been introduced. The effects of different variables on the ultimate load on teeth restored using fiber-reinforced posts is controversial, maybe because the results are mostly based on non-standardized in vitro tests and, therefore, give inhomogeneous results. This study combines the advantages of in vitro tests and finite element analysis (FEA) to clarify the effects of ferrule height, post length and cementation technique used for restoration. Sixty-four single rooted premolars were decoronated (ferrule height 1 or 2 mm), endodontically treated and restored using fiber posts (length 2 or 7 mm), composite fillings and metal crowns (resin bonded or cemented). After thermocycling and chewing simulation the samples were loaded until fracture, recording first damage events. Using UNIANOVA to analyze recorded fracture loads, ferrule height and cementation technique were found to be significant, i.e. increased ferrule height and resin bonding of the crown resulted in higher fracture loads. Post length had no significant effect. All conventionally cemented crowns with a 1-mm ferrule height failed during artificial ageing, in contrast to resin-bonded crowns (75% survival rate). FEA confirmed these results and provided information about stress and force distribution within the restoration. Based on the findings of in vitro tests and computations we concluded that crowns, especially those with a small ferrule height, should be resin bonded. Finally, centrally positioned fiber-reinforced posts did not contribute to load transfer as long as the bond between the tooth and composite core was intact.

Retention force measurement of telescopic crowns

This study deals with the determination of the retentive force between primary and secondary telescopic crowns under clinical conditions. Forty-three combined fixed-removable prostheses with a total of 140 double crowns were used for retention force measurement of the telescopic crowns prior to cementation. The crowns had a preparation of 1-2°. A specifically designed measuring device was used. The retentive forces were measured with and without lubrication by a saliva substitute. The measured values were analyzed according to the type of tooth (incisors, canines, premolars, and molars). Additionally, a comparison between lubricated and unlubricated telescopic crowns was done. As maximum retention force value 29.98 N was recorded with a telescopic crown on a molar, while the minimum of 0.08 N was found with a specimen on a canine. The median value of retention force of all telescopic crowns reached 1.93 N with an interquartile distance of 4.35 N. No statistically significant difference between lubricated and unlubricated specimens was found. The results indicate that retention force values of telescopic crowns, measured in clinical practice, are often much lower than those cited in the literature. The measurements also show a wide range. Whether this proves to be a problem for the patient's quality of life or not can however only be established by a comparison of the presented results with a follow-up study involving measurement of intraoral retention and determination by e.g. oral health impact profile.

A 10-year retrospective analysis of radiographic bone-level changes of implants supporting single-unit crowns in periodontally compromised vs. periodontally healthy patients

AIM: To compare the 10-year peri-implant bone loss (BL) rate in periodontally compromised (PCP) and periodontally healthy patients (PHP) around two different implant systems supporting single-unit crowns. MATERIALS AND METHODS: In this retrospective, controlled study, the mean BL (mBL) rate around dental implants placed in four groups of 20 non-smokers was evaluated after a follow-up of 10 years. Two groups of patients treated for periodontitis (PCP) and two groups of PHP were created. For each category (PCP and PHP), two different types of implant had been selected. The mBL was calculated by subtracting the radiographic bone levels at the time of crown cementation from the bone levels at the 10-year follow-up. RESULTS: The mean age, mean full-mouth plaque and full-mouth bleeding scores and implant location were similar between the four groups. Implant survival rates ranged between 85% and 95%, without statistically significant differences (P>0.05) between groups. For both implant systems, PCP showed statistically significantly higher mBL rates and number of sites with BL> or =3 mm compared with PHP (P<0.0001). CONCLUSIONS: After 10 years, implants in PCP yielded lower survival rates and higher mean marginal BL rates compared with those of implants placed in PHP. These results were independent of the implant system used or the healing modality applied.

An intraoperatively moulded PMMA prostheses like spacer for two-stage revision of infected total knee arthroplasty

We report a series of 16 consecutive total knee arthroplasty (TKA) revision procedures for deep infection, treated with a newly developed intraoperatively moulded PMMA cement-prostheses-like spacer (CPLS). The standard treatment consisted of a two-stage protocol with initial explantation of the infected components combined with radical debridement, followed by implantation of a temporary cement spacer and final reimplantation of a new TKA. A sterilizeable Teflon tapered aluminium mould was developed for production of a custom made CPLS during the intervention. Stable implantation of the CPLS was achieved with a second cementation, allowing for correct alignment and ligament balancing. The spacer remained 3.5 months on average until reimplantation of a TKA occurred. At time of reimplantation, patients had an average KSS score of 84.44 points with an average flexion capacity of 102°. There was no recurrent infection during the study period of minimum 2 years. With this new technique, a low friction articulation with good stability, high comfort and a better range of motion compared to handcrafted spacers was achieved. The use of this spacer is a time sparing, cheap and convenient option in 2-stage TKA revision.

A Systematic Review of the Clinical Performance of Tooth-Retained and Implant-Retained Double Crown Prostheses with a Follow-Up of ≥3 Years

Purpose: The objective of this review was to systematically screen the literature for data related to the survival and complication rates observed with dental or implant double crown abutments and removable prostheses under functional loading for at least 3 years. Materials and Methods: A systematic review of the dental literature from January 1966 to December 2009 was performed in electronic databases (PubMed and Embase) as well as by an extensive hand search to investigate the clinical outcomes of double crown reconstructions. Results: From the total of 2412 titles retrieved from the search, 65 were selected for full-text review. Subsequently, 17 papers were included for data extraction. An estimation of the cumulative survival and complication rates was not feasible due to the lack of detailed information. Tooth survival rates for telescopic abutment teeth ranged from 82.5% to 96.5% after an observation period of 3.4 to 6 years, and for tooth-supported double crown retained dentures from 66.7% to 98.6% after an observation period of 6 to 10 years. The survival rates of implants were between 97.9% and 100% and for telescopic-retained removable dental prostheses with two mandibular implants, 100% after 3.0 and 10.4 years. The major biological complications affecting the tooth abutments were gingival inflammation, periodontal disease, and caries. The most frequent technical complications were loss of cementation and loss of facings. Conclusions: The main findings of this review are: (I) double crown tooth abutments and dentures demonstrated a wide range of survival rates. (II) Implant-supported mandibular overdentures demonstrated a favorable long-term prognosis. (III) A greater need for prosthetic maintenance is required for both tooth-supported and implant-supported reconstructions. (IV) Future areas of research would involve designing appropriate longitudinal studies for comparisons of survival and complication rates of different reconstruction designs.

Development of an in vivo experimental model for percutaneous vertebroplasty in sheep

Several studies have described 'open' approach techniques for cementation of sheep and goat vertebrae; however, no percutaneous technique has been developed so far for use in non-primates. The aim of this study was to develop an animal model for percutaneous vertebroplasty under clinical conditions.

Clinical evaluation of root filled teeth restored with or without post-and-core systems in a specialist practice setting

AIM: To assess survival rates and complications of root-filled teeth restored with or without post-and-core systems over a mean observation period of >or=4 years. METHODOLOGY: A total of 325 single- and multirooted teeth in 183 subjects treated in a private practice were root filled and restored with either a cast post-and-core or with a prefabricated titanium post and composite core. Root-filled teeth without post-retained restorations served as controls. The restored teeth served as abutments for single unit metal-ceramic or composite crowns or fixed bridges. Teeth supporting cantilever bridges, overdentures or telescopic crowns were excluded. RESULTS: Seventeen teeth in 17 subjects were lost to follow-up (17/325: 5.2%). The mean observation period was 5.2 +/- 1.8 (SD) years for restorations with titanium posts, 6.2 +/- 2.0 (SD) years for cast post-and-cores and 4.4 +/- 1.7 (SD) years for teeth without posts. Overall, 54% of build-ups included the incorporation of a titanium post and 26.5% the cementation of a cast post-and-core. The remaining 19.5% of the teeth were restored without intraradicular retention. The adjusted 5-year tooth survival rate amounted to 92.5% for teeth restored with titanium posts, to 97.1% for teeth restored with cast post-and-cores and to 94.3% for teeth without post restorations, respectively. The most frequent complications included root fracture (6.2%), recurrent caries (1.9%), post-treatment periradicular disease (1.6%) and loss of retention (1.3%). CONCLUSION: Provided that high-quality root canal treatment and restorative protocols are implemented, high survival and low complication rates of single- and multirooted root-filled teeth used as abutments for fixed restorations can be expected after a mean observation period of >or=4 years.

Radiographic and safety details of vertebral body stenting: results from a multicenter chart review

BACKGROUND Up to one third of BKP treated cases shows no appreciable height restoration due to loss of both restored height and kyphotic realignment after balloon deflation. This shortcoming has called for an improved method that maintains the height and realignment reached by the fully inflated balloon until stabilization of the vertebral body by PMMA-based cementation. Restoration of the physiological vertebral body height for pain relief and for preventing further fractures of adjacent and distant vertebral bodies must be the main aim for such a method. A new vertebral body stenting system (VBS) stabilizes the vertebral body after balloon deflation until cementation. The radiographic and safety results of the first 100 cases where VBS was applied are presented. METHODS During the planning phase of an ongoing international multicenter RCT, radiographic, procedural and followup details were retrospectively transcribed from charts and xrays for developing and testing the case report forms. Radiographs were centrally assessed at the institution of the first/senior author. RESULTS 100 patients (62 with osteoporosis) with a total of 103 fractured vertebral bodies were treated with the VBS system. 49 were females with a mean age of 73.2 years; males were 66.7 years old. The mean preoperative anterior-middle-posterior heights were 20.3-17.6-28.0 mm, respectively. The mean local kyphotic angle was 13.1[degree sign]. The mean preoperative Beck Index (anterior edge height/posterior edge height) was 0.73, the mean alternative Beck Index (middle height/posterior edge height) was 0.63. The mean postoperative heights were restored to 24.5-24.6-30.4 mm, respectively. The mean local kyphotic angle was reduced to 8.9[degree sign]. The mean postoperative Beck Index was 0.81, the mean alternative one was 0.82. The overall extrusion rate was 29.1%, the symptomatic one was 1%. In the osteoporosis subgroup there were 23.8% extrusions. Within the three months followup interval there were 9% of adjacent and 4% of remote new fractures, all in the osteoporotic group. CONCLUSIONS VBS showed its strengths especially in realignment of crush and biconcave fractures. Given that fracture mobility is present, the realignment potential is sound and increases with the severity of preoperative vertebral body deformation.

Squeezing of Pore-water from Core Samples of DGR Boreholes: Feasibility Study

Three archived core samples from boreholes DGR-4, DGR-5 and DGR-6 from the Salina F Unit, Queenston Formation and the Georgian Bay Formation were subjected to squeezing tests at pressures of up to 500 MPa. Two samples did not yield any water, while a total of 0.88 g pore water was obtained from a clay-rich sample from the Blue Mountain Formation (water content = 2.8 wt.%, porosity = 8 %). This water mass was sufficient for a full chemical and water-isotope analysis – the first direct determination of pore-water composition in rocks from the DGR boreholes. The results are generally in reasonable agreement with those of independent methods, or the observed differences can be explained. Ancillary investigations included the determination of water content, densities and mineralogy, aqueous extraction of squeezed cores, and SEM investigations to characterise the microtexture of unsqueezed and squeezed rock materials. It is concluded that squeezing is a promising method of pore-water extraction and characterisation and is recommended as an alternative method for future studies. Selection criteria for potentially squeezable samples include high clay-mineral content (correlating in a high water content) and low carbonate content (low stiffness, limited cementation). Potential artefacts of the method, such as ion filtration or pressure solution, should be explored and quantified in future efforts.

Crestal bone changes at teeth and implants in periodontally healthy and periodontally compromised patients. A 10-year comparative case-series study

BACKGROUND Limited data exist on the longitudinal crestal bone changes around teeth compared with implants in partially edentulous patients. This study sought to compare the 10-year radiographic crestal bone changes (bone level [BL]) around teeth and implants in periodontally compromised (PCPs) and periodontally healthy (PHPs) patients. METHODS A total of 120 patients were evaluated for the radiographic crestal BL around dental implants and adjacent teeth at time of implant crown insertion and at the 10-year follow-up. Sixty patients had a previous history of periodontitis (PCPs), and the remaining 60 were PHPs. In each category (PCP and PHP), two different implant systems were used. The mean BL change at the implant and at the adjacent tooth at the interproximal area was calculated by subtracting the radiographic crestal BL at the time of crown cementation from the radiographic crestal BL at the 10-year follow-up. RESULTS At 10 years after therapy, the survival rate ranged from 80% to 95% for subgroups for implants, whereas it was 100% for the adjacent teeth. In all eight different patient categories evaluated, teeth demonstrated a significantly more stable radiographic BL compared with adjacent dental implants (teeth BL, 0.44 ± 0.23 mm; implant BL, 2.28 ± 0.72 mm; P <0.05). Radiographic BL changes around teeth seemed not to be influenced by the presence or absence of advanced bone loss (≥3 mm) at the adjacent implants. CONCLUSIONS Natural teeth yielded better long-term results with respect to survival rate and marginal BL changes compared with dental implants. Moreover, these findings also extend to teeth with an initial reduced periodontal attachment level, provided adequate periodontal treatment and maintenance are performed. As a consequence, the decision of tooth extraction attributable to periodontal reasons in favor of a dental implant should be carefully considered in partially edentulous patients.

Precision of fit and retention force of cast non-precious-crowns on standard titanium implant-abutment with different design and height

OBJECTIVE The cost-effectiveness of cast nonprecious frameworks has increased their prevalence in cemented implant crowns. The purpose of this study was to assess the effect of the design and height of the retentive component of a standard titanium implant abutment on the fit, possible horizontal rotation and retention forces of cast nonprecious alloy crowns prior to cementation. MATERIALS AND METHODS Two abutment designs were examined: Type A with a 6° taper and 8 antirotation planes (Straumann Tissue-Level RN) and Type B with a 7.5° taper and 1 antirotation plane (SICace implant). Both types were analyzed using 60 crowns: 20 with a full abutment height (6 mm), 20 with a medium abutment height (4 mm), and 20 with a minimal (2.5 mm) abutment height. The marginal and internal fit and the degree of possible rotation were evaluated by using polyvinylsiloxane impressions under a light microscope (magnification of ×50). To measure the retention force, a custom force-measuring device was employed. STATISTICAL ANALYSIS one-sided Wilcoxon rank-sum tests with Bonferroni-Holm corrections, Fisher's exact tests, and Spearman's rank correlation coefficient. RESULTS Type A exhibited increased marginal gaps (primary end-point: 55 ± 20 μm vs. 138 ± 59 μm, P < 0.001) but less rotation (P < 0.001) than Type B. The internal fit was also better for Type A than for Type B (P < 0.001). The retention force of Type A (2.49 ± 3.2 N) was higher (P = 0.019) than that of Type B (1.27 ± 0.84 N). Reduction in abutment height did not affect the variables observed. CONCLUSION Less-tapered abutments with more antirotation planes provide an increase in the retention force, which confines the horizontal rotation but widens the marginal gaps of the crowns. Thus, casting of nonprecious crowns with Type A abutments may result in clinically unfavorable marginal gaps.

Mineralogical and isotopic record of diagenesis from the Opalinus Clay formation at Benken, Switzerland: Implications for the modeling of pore-water chemistry in a clay formation

Argillaceous rocks are considered to be a suitable geological barrier for the long-term containment of wastes. Their efficiency at retarding contaminant migration is assessed using reactive-transport experiments and modeling, the latter requiring a sound understanding of pore-water chemistry. The building of a pore-water model, which is mandatory for laboratory experiments mimicking in situ conditions, requires a detailed knowledge of the rock mineralogy and of minerals at equilibrium with present-day pore waters. Using a combination of petrological, mineralogical, and isotopic studies, the present study focused on the reduced Opalinus Clay formation (Fm) of the Benken borehole (30 km north of Zurich) which is intended for nuclear-waste disposal in Switzerland. A diagenetic sequence is proposed, which serves as a basis for determining the minerals stable in the formation and their textural relationships. Early cementation of dominant calcite, rare dolomite, and pyrite formed by bacterial sulfate reduction, was followed by formation of iron-rich calcite, ankerite, siderite, glauconite, (Ba, Sr) sulfates, and traces of sphalerite and galena. The distribution and abundance of siderite depends heavily on the depositional environment (and consequently on the water column). Benken sediment deposition during Aalenian times corresponds to an offshore environment with the early formation of siderite concretions at the water/sediment interface at the fluctuating boundary between the suboxic iron reduction and the sulfate reduction zones. Diagenetic minerals (carbonates except dolomite, sulfates, silicates) remained stable from their formation to the present. Based on these mineralogical and geochemical data, the mineral assemblage previously used for the geochemical model of the pore waters at Mont Terri may be applied to Benken without significant changes. These further investigations demonstrate the need for detailed mineralogical and geochemical study to refine the model of pore-water chemistry in a clay formation.

Peri-implant soft tissue colour around titanium and zirconia abutments: a prospective randomized controlled clinical study

OBJECTIVES To objectively determine the difference in colour between the peri-implant soft tissue at titanium and zirconia abutments. MATERIALS AND METHODS Eleven patients, each with two contralaterally inserted osteointegrated dental implants, were included in this study. The implants were restored either with titanium abutments and porcelain-fused-to-metal crowns, or with zirconia abutments and ceramic crowns. Prior and after crown cementation, multi-spectral images of the peri-implant soft tissues and the gingiva of the neighbouring teeth were taken with a colorimeter. The colour parameters L*, a*, b*, c* and the colour differences ΔE were calculated. Descriptive statistics, including non-parametric tests and correlation coefficients, were used for statistical analyses of the data. RESULTS Compared to the gingiva of the neighbouring teeth, the peri-implant soft tissue around titanium and zirconia (test group), showed distinguishable ΔE both before and after crown cementation. Colour differences around titanium were statistically significant different (P = 0.01) only at 1 mm prior to crown cementation compared to zirconia. Compared to the gingiva of the neighbouring teeth, statistically significant (P < 0.01) differences were found for all colour parameter, either before or after crown cementation for both abutments; more significant differences were registered for titanium abutments. Tissue thickness correlated positively with c*-values for titanium at 1 mm and 2 mm from the gingival margin. CONCLUSIONS Within their limits, the present data indicate that: (i) The peri-implant soft tissue around titanium and zirconia showed colour differences when compared to the soft tissue around natural teeth, and (ii) the peri-implant soft tissue around zirconia demonstrated a better colour match to the soft tissue at natural teeth than titanium.