Bruno Collaert

Effective dose range for dental cone beam computed tomography scanners

OBJECTIVE To estimate the absorbed organ dose and effective dose for a wide range of cone beam computed tomography scanners, using different exposure protocols and geometries. MATERIALS AND METHODS Two Alderson Radiation Therapy anthropomorphic phantoms were loaded with LiF detectors (TLD-100 and TLD-100 H) which were evenly distributed throughout the head and neck, covering all radiosensitive organs. Measurements were performed on 14 CBCT devices: 3D Accuitomo 170, Galileos Comfort, i-CAT Next Generation, Iluma Elite, Kodak 9000 3D, Kodak 9500, NewTom VG, NewTom VGi, Pax-Uni3D, Picasso Trio, ProMax 3D, Scanora 3D, SkyView, Veraviewepocs 3D. Effective dose was calculated using the ICRP 103 (2007) tissue weighting factors. RESULTS Effective dose ranged between 19 and 368 μSv. The largest contributions to the effective dose were from the remainder tissues (37%), salivary glands (24%), and thyroid gland (21%). For all organs, there was a wide range of measured values apparent, due to differences in exposure factors, diameter and height of the primary beam, and positioning of the beam relative to the radiosensitive organs. CONCLUSIONS The effective dose for different CBCT devices showed a 20-fold range. The results show that a distinction is needed between small-, medium-, and large-field CBCT scanners and protocols, as they are applied to different indication groups, the dose received being strongly related to field size. Furthermore, the dose should always be considered relative to technical and diagnostic image quality, seeing that image quality requirements also differ for patient groups. The results from the current study indicate that the optimisation of dose should be performed by an appropriate selection of exposure parameters and field size, depending on the diagnostic requirements.

Immediate functional loading of TiOblast dental implants in full‐arch edentulous mandibles: a 3‐year prospective study

INTRODUCTION Immediate functional loading of dental implants for full-arch restoration is a patient-friendly approach, shown to be feasible with a good long-term prognosis in a completely edentulous mandible. For the complete restoration of the maxilla, acceptable long-term clinical follow-up is lacking or based on case reports rather than on prospective studies. OBJECTIVES This prospective mono-centre study reports the 3-year outcome of immediately functionally loaded Astra Tech Dental implants in completely edentulous maxillae based on clinical survival and success based on radiographical assessment of bone level. MATERIAL AND METHODS One hundred and ninety-five Astra Tech TiOblast surface fixtures were installed in 25 consecutively treated patients (age range: 42-76 years), of whom eight were smokers, 12 had a confirmed history of periodontitis and six had poor bone quality normally deemed for delayed loading. Fixtures and abutments were inserted in a one-stage procedure and functionally loaded within 24 h with a 10-unit provisional glass-fibre or metal-reinforced screw-retained restoration. After 6 months, each implant was checked for stability using a manual torque of 20 N cm and the provisional restoration was replaced by a 10-12-unit screw-retained metal-ceramic or metal-resin cantilever bridge. Bone level was assessed radiographically from the day of surgery up to 3 years and used to calculate mean bone loss at the patient level and individual implant success. RESULTS No failures occurred in implants or prostheses, the total survival rate being 100%. Mean marginal bone loss was 0.58 mm (SD 0.58); 0.6 mm (SD 0.53); 0.63 (SD 0.61); and 0.72 (SD 0.63) after 6 and 12 months, and 2 and 3 years, respectively, yielding a 100% success at the patient level. Wilcoxons signed ranks test showed only statistically significant bone loss between baseline and 6 months and a steady-state condition during all other intervals. At the individual fixture level, 82% lost <1 mm marginal bone between baseline and 1 year. After 3 years, 86% have <1.5 mm total bone loss and can be considered a success. The fixtures expressing more bone loss were all inserted in smokers. CONCLUSION Immediate loading of a full-arch maxillary bridgework on 7-9 Astra Tech TiOblast implants is a predictable treatment option with 100% fixture survival and stable bone-to-implant contact up to 3 years. The steady state in bone remodelling is indicative of a good long-term prognosis in non-smokers but smokers seem to be more prone to bone loss.

Patient‐centered outcome of immediately loaded implants in the rehabilitation of fully edentulous jaws

INTRODUCTION Edentulism often involves functional, esthetic, phonetic and psychological problems. OBJECTIVES To evaluate patient-centered outcomes of full-arch screw-retained rehabilitation on immediately loaded implants. MATERIAL AND METHODS Fifty patients treated with Astra Tech(TM) implants answered self-administered questionnaires on a visual analogue scale (VAS) 100 mm scale or with multiple-choice or open questions: at baseline, 1 week, 3 or 6 months and 1 year. Changes of VAS in time were analyzed using mixed models for repeated measures, adjusting for gender, age and jaw; comparison of cross-sectional parameters between jaws was performed with the Mann-Whitney U- or chi(2)-test, all at the 0.05 significance level. RESULTS The median calculated general satisfaction score increased from 40.25 (mean=40.9; SD=23.82; range=0-95) at baseline to 98.25 (mean=95.3; SD=6.68; range=74-100) after 1 year. Overall comfort, eating comfort, speaking comfort and perceived esthetics improved significantly within 1 week after surgery and immediate provisionalization. This did not change significantly until the final bridge was installed after 3 months (mandible) or 6 months (maxilla), when a further significant improvement was demonstrated. The most common postoperative complication was swelling, especially in the maxilla. The importance of one-stage surgery and immediate loading was rated very high by patients before treatment, especially in the mandible. The main reason for choosing fixed prosthetics was eating comfort. Phonetics and esthetics were more important in the maxilla than in the mandible. CONCLUSION Immediate full-arch rehabilitation yeilds an instant significant improvement in general patient satisfaction and self-perceived factors related to comfort, function and esthetics. Eating comfort is the main concern for the patient and shows the highest improvement. Postoperative complications are limited and patients considered immediate loading important.

The peri-implant sulcus compared with internal implant and suprastructure components: a microbiological analysis.

PURPOSE A recent in vivo study has shown considerable contamination of internal implant and suprastructure components with great biodiversity, indicating bacterial leakage along the implant-abutment interface, abutment-prosthesis interface, and restorative margins. The goal of the present study was to compare microbiologically the peri-implant sulcus to these internal components on implants with no clinical signs of peri-implantitis and in function for many years. Checkerboard DNA-DNA hybridization was used to identify and quantify 40 species. MATERIAL AND METHODS Fifty-eight turned titanium Brånemark implants in eight systemically healthy patients (seven women, one man) under regular supportive care were examined. All implants had been placed in the maxilla and loaded with a screw-retained full-arch bridge for an average of 9.6 years. Gingival fluid samples were collected from the deepest sulcus per implant for microbiological analysis. As all fixed restorations were removed, the cotton pellet enclosed in the intra-coronal compartment and the abutment screw were retrieved and microbiologically evaluated. RESULTS The pellet enclosed in the suprastructure was very similar to the peri-implant sulcus in terms of bacterial detection frequencies and levels for practically all the species included in the panel. Yet, there was virtually no microbial link between these compartments. When comparing the abutment screw to the peri-implant sulcus, the majority of the species were less frequently found, and in lower numbers at the former. However, a relevant link in counts for a lot of bacteria was described between these compartments. Even though all implants in the present study showed no clinical signs of peri-implantitis, the high prevalence of numerous species associated with pathology was striking. CONCLUSIONS Intra-coronal compartments of screw-retained fixed restorations were heavily contaminated. The restorative margin may have been the principal pathway for bacterial leakage. Contamination of abutment screws most likely occurred from the peri-implant sulcus via the implant-abutment interface and abutment-prosthesis interface.

Effect of Implant Design on Preservation of Marginal Bone in the Mandible

BACKGROUND Implant design and surface may have an influence on the marginal bone response during immediate functional loading. AIM The purpose of this study was to radiographically study the effect of implant design on marginal bone preservation at immediately loaded implants used for prosthetic rehabilitation of the completely edentulous mandible. MATERIALS AND METHODS A total of 39 patients, previously treated with five implants for support of a full-arch fixed bridge in the mandible, were included in the study. Either machined Brånemark implants (Ma) (Nobel Biocare AB, Gothenburg, Sweden) or surface modified Astra Tech implants with (Mi) or without a microthreaded neck (Ti) (TiOblast, AstraTech AB, Mölndal, Sweden) were used. All fixtures were loaded with a provisional glass fiber or metal-reinforced screw-retained restoration within 24 hours. The provisional restorations were replaced by a 12-unit screw-retained metal-ceramic or metal-resin cantilever bridge after 3 months. Bone loss from baseline to 1 year of loading was measured by means of intraoral radiographs. Only patients with baseline and 1-year radiographs of all implants were selected for comparison. Statistical analysis was carried out on both patient and implant levels. RESULTS The survival rates after 1 year in function were 98.6, 100, and 100% for the Ma, Ti, and Mi implants, respectively. The overall mean bone loss after 1 year was 1.03 mm (SD 0.87; range -0.77 to 2.5). The mean bone loss was calculated to 1.52 (SD 0.66) for the Ma group, 0.79 (SD 0.79) for the Ti group, and 0.70 (SD 1.01) for the Mi group. There was a significant difference between Ma and Ti (p = .023) and between Ma and Mi (p = .046) groups but not within Ti and Mi implants (p = .70). These conclusions were also valid when the statistical analysis was performed on implant level. CONCLUSIONS There is no impact of design and surface on implant survival in the completely edentulous mandible. Bone preservation in immediately loaded implants in the mandible is influenced by implant design and significantly better on surface-modified AstraTech implants compared with machined Brånemark implants. In the mandible, a microthread design of the implant collar does not seem to improve bone preservation.

A multifactorial analysis to identify predictors of implant failure and peri-implant bone loss.

OBJECTIVE To identify risk factors for failure and bone loss of implants in a large study sample on the basis of multivariate analyses. MATERIALS AND METHODS Patient files of all patients referred for implant treatment from November 2004 to December 2007 were scrutinized, and information on implant- and patient-related factors was collected. The study sample in this retrospective cohort study consisted of both partially dentate and fully edentulous patients referred for various indications. The only inclusion criterion was a follow-up of at least 2 years. Implant survival and bone loss were assessed by an external investigator (SV) comparing digital periapical radiographs taken during recall visits with the postoperative ones. Univariate and multivariate tests were adopted to identify possible risk indicators for implant failure and peri-implant bone loss. RESULTS Twenty-one of 1,320 (1.6%) implants were lost in 19 of 376 (5.1%) patients (210 female, 166 male; mean age 56, range 17-82) after a mean follow-up of 32 months (range 24-62). Based on multivariate analysis, only smoking (p = .001) and recall compliance (p = .010) had a significant influence on implant failure, with smokers more prone to failure. The overall mean bone loss was 0.36 mm (SD 0.68, range 0.00-7.10). Smoking (p = .001) and jaw of treatment (p = .001) affected peri-implant bone loss. More peri-implant bone loss was observed in smokers and in the maxilla. A clear discrepancy was found between univariate and multivariate analysis with regard to identification of risk factors. CONCLUSION Multivariate analysis demonstrated that implant-related factors did not affect the clinical outcome, but smoking was identified as a predictor for implant failure. Predictors for peri-implant bone loss were smoking and jaw of treatment.

The effect of smoking on survival and bone loss of implants with a fluoride-modified surface : a 2-year retrospective analysis of 1106 implants placed in daily practice

AIM To compare the survival and peri-implant bone loss of implants with a fluoride-modified surface in smokers and nonsmokers. MATERIALS AND METHODS Patient files of all patients referred for implant treatment from November 2004 to 2007 were scrutinized. All implants were placed by the same experienced surgeon (B. C.). The only inclusion criterion was a follow-up time of at least 2 years. Implant survival and bone loss were assessed by an external calibrated examiner (S. V.) comparing digital peri-apical radiographs taken during recall visits with the post-operative ones. Implant success was determined according to the international success criteria (Albrektsson et al. 1986). Survival of implants installed in smokers and nonsmokers was compared using the log-rank test. Both nonparametric tests and fixed model analysis were adopted to evaluate bone loss in smokers and nonsmokers. RESULTS One-thousand one-hundred and six implants in 300 patients (186 females; 114 males) with a mean follow-up of 31 months (SD 7.15; range 24-58) were included. Nineteen implants in 17 patients failed, resulting in an overall survival rate of 98.3% at the implant level and 94.6% at the patient level. After a follow-up period of 2 years, the cumulative survival rates was 96.7% and 99.1% with the patient and implant as the statistical unit, respectively. Implant survival was significantly higher for nonsmokers compared with smokers (implant level P=0.025; patient level P=0.017). The overall mean bone loss was 0.34 mm (n=1076; SD 0.65; range 0-7.1). Smokers lost significantly more bone compared with nonsmokers in the maxilla (0.74 mm; SD 1.07 vs. 0.33 mm; SD 0.65; P<0.001), but not in the mandible (0.25 mm; SD 0.65 vs. 0.22 mm; SD 0.5; P=0.298). CONCLUSION The present study is the first to compare peri-implant bone loss in smokers and nonsmokers from the time of implant insertion (baseline) to at least 2 years of follow-up. Implants with a fluoride-modified surface demonstrated a high survival rate and limited bone loss. However, smokers are at a higher risk of experiencing implant failure and more prone to show peri-implant bone loss in the maxilla. Whether this bone loss is predicting future biological complications remains to be evaluated.

A 2-year prospective study on immediate loading with fluoride-modified implants in the edentulous mandible

OBJECTIVES Chemically modified surfaces were introduced during the last decade to improve indications for implant treatment. The fluoride-modified implant (Osseospeed(®)) was launched in 2004 and clinical studies suggest a more rapid bone formation and stronger bone to implant contact. However, limited clinical data are available on marginal bone loss and the outcome after >1 year under immediate loading conditions is not fully understood. Hence, the purpose of this prospective study was to present implant survival and marginal bone level data when fluoride-modified implants are supporting a fully functional rehabilitation from the day after surgery in the completely edentulous mandible. MATERIALS AND METHODS Twenty-five patients, completely edentulous in the mandible, were consecutively treated with five fluoride-modified implants that were functionally loaded with a provisional screw retained restoration. Marginal bone loss was measured from day of surgery to 3, 6, 12 and 24 months. Implants were considered successful after 24 months if radiographic bone loss did not exceed 1 mm and no pain or mobility was caused under a torque of 20 N cm. Statistical analysis was carried out on both patient and implant levels. RESULTS All implants survived and mean bone loss on implant level after 3, 6, 12 and 24 months was 0.14, 0.13, 0.11 and 0.11 mm, respectively. Bone loss was only statistically significant between baseline and 3 months (P<0.001) and remained unchanged afterward. None of the implants lost >1 mm of bone after 2 years. On the patient level, the mean bone loss after 2 years was 0.12 mm (SD 0.14; range -0.06 to 0.55) with probing pocket depth 2.45 mm (SD 0.43; range 1.3-3.1) and bleeding index 0.55% (SD 0.34; range 0-1). CONCLUSION Immediate loading of fluoride-modified implants is a predictable treatment yielding a high survival and success rate after 2 years.

A 9‐Year Prospective Case Series Using Multivariate Analyses to Identify Predictors of Early and Late Peri‐Implant Bone Loss

PURPOSE The study aims to identify predictors of early and late peri-implant bone loss following complete implant-supported rehabilitation using multivariate analyses. MATERIALS AND METHODS Fifty patients (28 women, 22 men; mean age 58, range 35-76) in need of a complete implant-supported rehabilitation on five to eight implants were consecutively treated. Patients were reinvited for a clinical and radiographic examination after an average 9 years of function. Implant survival and peri-implant bone loss were considered the dependent variables. Multivariate analyses were adopted to identify predictors of early and late peri-implant bone loss. RESULTS In total, 39 patients were examinated. Two implants failed after 4 years of function, resulting in an overall survival rate of 99.2%. After a mean follow-up of 9 years, mean bone loss of 1.68 mm (SD 2.08, range -1.05 to 10.95) was found. The abutment height was a significant predictor of early peri-implant bone loss (1 year) (p = .024), whereas smoking (p = .046) and history of periodontitis (p = .046) affected late peri-implant bone loss. CONCLUSION Within the limits of this study, it can be concluded that initial bone remodeling was affected by soft tissue thickness as reflected by the height of the abutment, whereas smoking and history of periodontitis affected long-term peri-implant bone stability.

Correlation between early perforation of cover screws and marginal bone loss: a retrospective study

AIM This retrospective study aimed to determine the consequence of early cover screw exposure on peri-implant marginal bone level. MATERIAL AND METHODS Sixty Astra Tech MicroThread implants installed in partially edentulous jaws were compared: 20 implants were placed following a two-stage procedure and were unintentionally exposed to the oral cavity (two-stage exposed), 20 implants were placed following a two-stage procedure and were surgically exposed after a subgingival healing time of 3-6 months (two-stage submerged), and 20 implants were placed following a one-stage surgical protocol (one-stage). Digital radiographs were taken at implant placement for all implants, and after abutment surgery for the two-stage exposed and two-stage submerged groups or after 3 months for the one-stage group. Bone loss mesially and distally was measured with an on-screen cursor after calibration. RESULTS Mean bone re-modelling was 1.96 mm (range: 0.2-3.2 mm) around the two-stage exposed implants, 0.01 mm (range: 0.0-0.3 mm) around the two-stage submerged implants and 0.14 mm (range: 0.0-1.2 mm) around the one-stage implants. CONCLUSION The unintentional perforation of two-stage implants resulted in significant bone destruction, probably because the biological width was not considered.