International Delphi Study to Optimize the Oral Health Section in interRAI.

Introduction: The oral health (OH) of care-dependent older people is generally poor. Since caregivers are mainly responsible for older people's daily care, they can be considered important intermediaries to improve their OH by performing regular OH assessments. The interRAI instruments are introduced in 37 countries to assess care needs and facilitate care planning across different health care settings. The oral health section (OHS) within the interRAI instrument used in long-term care facilities was optimized for the Belgian context to identify residents who need assistance with daily oral care and/or need to be referred to a dentist. This Delphi study evaluated whether the OHS is also relevant and useful in other countries and modified the OHS accordingly until an international consensus was reached. Participants were experts in OH for older people. During 2 rounds of online questionnaires, experts rated the content, assessment process, triggering of Clinical Assessment Protocols, and accompanying guidelines and instruction videos of the optimized OHS. Based on the experts' comments and suggestions collected during the first round, the OHS was adjusted and presented to the experts in the second round for re-evaluation. The first and second questionnaires were completed by 48 and 42 oral health experts from 29 and 27 countries where the interRAI instruments are introduced, respectively. Five experts from 5 countries where interRAI is not introduced also participated in both rounds. After the second round, a consensus of over 86% was reached on all criteria. International consensus on the OHS was reached, considering national and cultural differences that may affect OH. The next step in this research is to evaluate the assessment process to identify potential barriers and facilitators to achieving reliable OH assessments internationally. Furthermore, the effect of the OHS at the level of the resident and of the caregivers will be evaluated.

[Education and the dentist in 2025. An inventory of the gerodontology-programme for 5 Dutch and Flemish dental schools]. / Serie: Tandheelkundig onderwijs anno 2025. Een inventarisatie van het gerodontologie-onderwijs bij 5 Nederlandse en Vlaamse opleidingen tandheelkunde.

In a consensus meeting (September 2019) of the three Dutch and the two Flemish dental schools their current education programmes on gerodontology were presented and discussed. The aim was to examine if these programmes were in line with the most recent (inter)national guidelines, such as those of the European College of Gerodontology and the recently introduced Dutch framework Oral Health Care (2020). Therefore, the competences regarding the domain of gerodontology were analysed to assess if students were prepared adequately to meet the oral health care needs of the ageing population. In the consensus meeting a new set of competences was formulated together with a new outline for the gerodontology-programme applicable for the Dutch and Flemish dental schools.

Esthetic evaluation of single implant restorations, adjacent single implant restorations, and implant-supported fixed partial dentures: A 1-year prospective study.

BACKGROUND: Peri-implant soft tissues esthetics varies and depends on the restoration type such as implant-supported single crowns, adjacent multiple single crowns, and fixed partial dentures (FPD). PURPOSE: The aim of this prospective study was to assess the esthetic outcome of the peri-implant soft tissues of (NobelBiocare™) implant-supported single crowns, adjacent multiple single crowns, and FPD. A potential association between the esthetic risk profile and the esthetic outcome was assessed. MATERIALS AND METHODS: Between 03/11 and 03/17, 300 NobelActive implants were installed in 153 partially edentulous patients. Prior to the fabrication of the final restoration, the esthetic risk profile (ERP) of the patient was determined. The pink esthetic score (PES) and white esthetic score (WES) were assessed by three investigators at 6 and 12 months post-insertion of the final restoration. Patients' appreciation was assessed on a visual analogue scale (VAS) at the 1-year follow-up. RESULTS: The clinical acceptable limit for PES (≥6) was achieved in 56% to 68% of the single crowns at 6 and 12 months, respectively. Clinically unacceptable PES scores were recorded for 48% of the adjacent multiple single crowns and 63% of the FPDs at both time points. The association of a high ERP with WES and PESWES was noticed for single implant-supported crowns. For the latter restoration type, a ≤5 mm distance between the crestal bone level and the proximal contact positively influenced the PES and combined PESWES scores. No correlation was found between PES or WES and patient satisfaction. Mesial papilla formation was more pronounced compared to the distal one for the single implant crowns and for implant-supported FPD. CONCLUSION: When high esthetic demands are expected, assessment of ERP prior to implant treatment is advised in order to estimate a realistic outcome.

[Research agenda oral care for older people in the Netherlands and Flanders (Belgium)]. / Wetenschapsagenda 'Mondzorg voor ouderen' in Nederland en Vlaanderen.

Oral care for older people is an underexposed topic in dentistry as well as in general healthcare, while oral care professionals are increasingly confronted with frail and multimorbid older people with complex care needs. The research agenda 'Oral care for the elderly' was developed to encourage the collaboration of researchers in the Netherlands and Flanders (Belgium) to do more research in this area and in this way, to achieve an expansion and implementation of knowledge. This will make possible the provision of a socially responsible and robust basis for sustainable oral care for frail older people. The focus of the agenda is on 3 themes, namely oral health and oral function for older people; multi/interdisciplinary collaboration within primary care and the costs, benefits and long-term effect(s) of oral care throughout the entire course of life. This article provides an overview of this research agenda and the way in which it has been established.

[A view on collective oral care for frail older people: united we stand]. / Visie op de collectieve mondzorg voor kwetsbare ouderen: eendracht maakt macht.

Oral health in frail older people is often poor. There are a number of reasons for this, such as increased morbity and decreased motivation for (self) care. Good oral health is, however, very important. Studies have revealed poor oral health to cause or aggravate several medical and psychological problems. Illness and medication can, in turn, damage oral health. Oral health among the elderly should therefore be carefully monitored and maintained. This requires multidisciplinary and interprofessional collaboration on the part of healthcare professionals and others involved. Such collaboration is now still very limited; hardly anything has been written about how such collaboration in the area of oral care for frail older people should or could be organised. This article provides an overview of the possibilities and the relevant factors in the area of oral care for the elderly in promoting collaboration among healthcare professionals and others involved. All of this is under the banner of 'united we stand'.

Can the alendronate dosage be altered when combined with high-frequency loading in osteoporosis treatment?

Alendronate therapy has been associated with serious side effects. Altering the alendronate concentration and combining with high-frequency loading as mechanical intervention was explored in this animal study as a treatment for osteoporosis. The bone anabolic potency of high-frequency loading was overruled by the different alendronate dosages applied in the present study. Further exploration of reduced hormonal therapy associated with mechanical interventions in osteoporosis treatment should be sought. INTRODUCTION: The aim of the present study was to investigate the effect of alendronate (ALN) administration at two different dosages, associated or not with high-frequency (HF) loading, on the bone microstructural response. METHODS: Sixty-four female Wistar rats were used, of which 48 were ovariectomized (OVX) and 16 were sham-operated (shOVX). The OVX animals were divided into three groups: two groups were treated with alendronate, at a dosage of 2 mg/kg (ALN(2)) or at a reduced dosage of 1 mg/kg (ALN(1)) three times per week. A third OVX group did not receive pharmaceutical treatment. All four groups were mechanically stimulated via whole body vibration (WBV) at HF (up to 150 Hz) or left untreated (shWBV). ALN and HF were administered for 6 weeks, starting at 10-week post-(sh)OVX. Tibia bone structural parameters were analyzed using ex vivo microcomputed tomography. RESULTS: Trabecular bone loss and structural deterioration resulting from ovariectomy were partially restored by ALN administration, demonstrated by the improvement of trabecular patter factor (Tb.Pf), trabecular separation (Tb.Sp), and structure model index (SMI) of the ALN groups compared to that of the OVX group, regardless of the applied dosage [ALN(2) or ALN(1)] or mechanical loading regime (shWBV or WBV). However, a significant positive effect of the ALN(1) administration on trabecular (decrease of Tb.Sp and SMI) and cortical bone (increase of cortical thickness) microarchitecture compared to that of the OVX status group was observed for both loading regimes was not seen for ALN(2). Furthermore, HF loading resulted in cortical bone changes, with an increased trabeculary area and endocortical perimeter. Finally, the benefits of a combined therapy of ALN with HF loading could not be discerned in the present experimental conditions. CONCLUSIONS: The bone anabolic potency of HF loading was overruled by the ALN dosages applied in the present study. Further altering the ALN dosage combined with robust mechanical stimuli needs to be considered in osteoporosis research and eventually therapy.

Mechanical competence of ovariectomy-induced compromised bone after single or combined treatment with high-frequency loading and bisphosphonates.

Osteoporosis leads to increased bone fragility, thus effective approaches enhancing bone strength are needed. Hence, this study investigated the effect of single or combined application of high-frequency (HF) loading through whole body vibration (WBV) and alendronate (ALN) on the mechanical competence of ovariectomy-induced osteoporotic bone. Thirty-four female Wistar rats were ovariectomized (OVX) or sham-operated (shOVX) and divided into five groups: shOVX, OVX-shWBV, OVX-WBV, ALN-shWBV and ALN-WBV. (Sham)WBV loading was applied for 10 min/day (130 to 150 Hz at 0.3g) for 14 days and ALN at 2 mg/kg/dose was administered 3x/week. Finite element analysis based on micro-CT was employed to assess bone biomechanical properties, relative to bone micro-structural parameters. HF loading application to OVX resulted in an enlarged cortex, but it was not able to improve the biomechanical properties. ALN prevented trabecular bone deterioration and increased bone stiffness and bone strength of OVX bone. Finally, the combination of ALN with HF resulted in an increased cortical thickness in OVX rats when compared to single treatments. Compared to HF loading, ALN treatment is preferred for improving the compromised mechanical competence of OVX bone. In addition, the association of ALN with HF loading results in an additive effect on the cortical thickness.

Single and combined effect of high-frequency loading and bisphosphonate treatment on the bone micro-architecture of ovariectomized rats.

UNLABELLED: Mechanical loading at high frequency affects bone. Whether this also applies to osteoporotic bone, combined or not with bisphosphonate therapy, was investigated in this animal study through imaging. An anabolic effect of high-frequency loading on osteoporotic bone, however non-synergistic with bisphosphonates, was found, thereby revealing its potential for treatment of osteoporosis. INTRODUCTION: In an effort to elucidate the effect of high-frequency (HF) loading on bone and to optimize its potential for treatment osteoporosis, this study aimed to investigate the effect of HF loading via whole body vibration (WBV), alone or in association with bisphosphonate treatment (alendronate--ALN), on the micro-architecture of ovariectomy (OVX)-induced compromised bone. METHODS: Eighty-four female Wistar rats were ovariectomized (OVX) or sham-operated (shOVX). OVX animals were treated either with ALN (3 days/week at a dose of 2 mg/kg) or with saline solution. Each group (shOVX, OVX, ALN) was further divided into subgroups relative to the loading status (sham-WBV versus WBV) and the duration of experimental period (4 days versus 14 days). (Sham)WBV loading was applied for 10 min/day using 10 consecutive steps of HF loading (130, 135, 140, 145, 150, 130, 135, 140, 145, 150 Hz). Tibial bone structural responses to WBV and/or ALN treatment were analyzed using ex vivo micro-computed tomography. RESULTS: The animal's hormonal status displayed a major impact on the trabecular and cortical bone structural parameters. Furthermore, mechanical treatment with HF WBV increased the cortical thickness and reduced the medullar area in OVX rats. However, OVX trabecular bone was not affected by HF stimuli. Finally, ALN prevented OVX-associated bone loss, but the association of ALN with WBV did not lead to a synergistic bone response in OVX bone. CONCLUSIONS: HF WBV mechanical stimulation displayed an anabolic effect on osteoporotic cortical bone, confirming its therapeutic properties for enhancing compromised bone. Additionally, its association with bisphosphonates' administration did not produce any additive effect on the bone micro-architecture in the present study.

High-frequency loading positively impacts titanium implant osseointegration in impaired bone.

UNLABELLED: High-frequency loading via whole body vibration promotes bone formation and increases bone strength. Whether this translates to positive titanium implant osseointegration in osteoporotic bone was explored in this animal study. An anabolic effect of not only bisphosphonate treatment but also high-frequency loading on implant osseointegration in osteoporotic bone was observed. INTRODUCTION: The present study investigated the impact of high-frequency (HF) loading, applied via whole body vibration (WBV), on titanium implant osseointegration in healthy versus ovariectomy-induced compromised versus pharmacologically treated compromised bone. METHODS: A custom-made Ti implant was inserted into the metaphyseal tibia of 59 rats and left to heal for either 4 or 14 days. Rats were divided into six groups according to their hormonal and mechanical status. WBV, consisting of 10 consecutive frequency steps at an acceleration of 0.3 g, was applied daily for either 4 or 14 days. Tissue samples were processed for quantitative histology at the tibial cortical and medullar level. Data were analyzed by three-way ANOVA and by post hoc pairwise comparisons. RESULTS: The bone healing response at the interface and surrounding titanium implants was negatively influenced by osteoporotic bone conditions, mainly at the trabecular bone level. Furthermore, the administration of bisphosphonates for preventing the ovariectomy-induced impaired peri-implant response was successful. Finally, the effect of HF WBV loading on the peri-implant bone healing was dependent on the bone condition and was anabolic solely in untreated osteoporotic trabecular bone when applied for an extended period of time. CONCLUSIONS: The bone healing response to implant installation is compromised in osteoporotic bone conditions, in particular at the trabecular bone compartment. Meanwhile, not only pharmacological treatment but also mechanical loading via HF WBV can exert a positive effect on implant osseointegration in this specific bone micro-environment. The peri-implant cortical bone, however, seems to be less sensitive to HF WBV loading influences.

The effect of loading on peri-implant bone: a critical review of the literature.

In the 90s, there was a general belief that mechanical overloading was one of the main reasons for late implant failure. This triggered research to assess the role of mechanical loading on the establishment and the maintenance of oral implant osseointegration. Animal experimental studies indeed suggested the potential detrimental effect of excessive mechanical load on peri-implant bone, although randomised or controlled clinical trials of treatment interventions of oral implants designed to study overload are lacking. The lack of quantification of so-called overload at the implant level in the intra-oral setting is one of the main shortcomings in the literature. The level of evidence of the studies on bone response to implant loading is weak and does not indicate that overload can lead to peri-implant bone loss, except in case of inflammation. Clinical and animal experimental studies on early and immediate implant loading, however, provide information on the impact of mechanical loading on the process of osseointegration. It is obvious that micromotion between the implant and host tissues compromises osseointegration. However, in case of an efficient force transfer between implant and surrounding tissues, mechanical loading might even stimulate peri-implant bone formation and therefore osseointegration.

Ultrastructural characterization of the implant interface response to loading.

Dynamic loading can affect the bone surrounding implants. For ultrastructural exploration of the peri-implant tissue response to dynamic loading, titanium implants were installed in rat tibiae, in which one implant was loaded while the contralateral served as the unloaded control. The loaded implants received stimulation either within 24 hrs after implantation (immediate loading) or after a 28-day healing period (delayed loading) for 4, 7, 14, 21, or 28 days. The samples were processed for histology and gene expression quantification. Compared with the unloaded control, bone-to-implant contact increased significantly by immediate loading for 28 days (p < .05), but not in case of delayed loading. No effect of loading was observed on the bone formation in the implant thread areas, on the blood vessel area, and on endosteal callus formation. Loading during healing (immediate) for 7 days induced, relative to the unloaded control, a 2.3-fold increase of Runx2 in peri-implant cortical bone (p < .01) without a change in the RANKL/Opg ratio. Loading after healing (delayed) for 7 days up-regulated Runx2 (4.3-fold, p < .01) as well as Opg (22.3-fold, p < .05) compared with the unloaded control, resulting in a significantly decreased RANKL/Opg ratio. These results indicate a stimulating effect of dynamic loading on implant osseointegration when applied during the healing phase. In addition, gene expression analyses revealed molecular adaptations favoring bone formation and, at the same time, affecting bone remodeling.

Overnight storage of removable dentures in alkaline peroxide-based tablets affects biofilm mass and composition.

BACKGROUND: Clinical guidelines for denture care are available, but evidence for optimal nocturnal storage is scarce. The aim of the study was to compare the role of the overnight storage state on plaque growth and composition on acrylic removable dentures. METHODS: In a parallel-group randomized controlled trial of 51 institutionalized participants, 3 denture overnight preservation methods were considered: (i) in water, (ii) dry or (iii) in water with added alkaline peroxide-based cleansing tablet. Biofilm samples were taken on day 7 (developing biofilm - dBF) and day 14 (maturing biofilm - mBF) from a mechanically uncleaned, standardized region, situated distally to the second lower premolars. Total and individual levels of selected perio-pathogenic and commensal species (n=20), and of Candida albicans were calculated by PCR. Differences between storage conditions (water/dry/tablet) and between the samples (dBF/mBF) were assessed by means of unpaired and paired t-tests respectively, with α=5%. RESULTS: Overnight denture storage with cleansing tablet significantly decreased the total bacterial level of dBF and mBF up to 13.8%. Fn, Ec, Cs, Sc, Ao and Vp counts were particularly affected by tablet care. Significant lower amounts of Candida albicans for tablet storage compared to water preservation were recorded in dBF and mBF (-69.3 ± 3.8% and -75.9 ± 3.2% respectively). The mass and pathogenicity of dBF and mBF was equal, irrespective of the overnight storage intervention. CONCLUSIONS: The use of cleansing tablets for acrylic removable denture overnight storage reduces denture biofilm mass and pathogenicity compared to dry and water preservation, and may contribute to the overall systemic health. CLINICAL SIGNIFICANCE: Evidence-based clinical guidelines for overnight storage of removable acrylic dentures are lacking. The findings of this study indicate that alkaline peroxide-based cleansing tablets decrease bacterial and Candida levels in denture biofilms in case of poor oral hygiene. This provides evidence for a clinical guideline to minimize microbial load of dentures, thereby reducing associated systemic health risks.

Numerical simulation of bone regeneration in a bone chamber.

While mathematical models are able to capture essential aspects of biological processes like fracture healing and distraction osteogenesis, their predictive capacity in peri-implant osteogenesis remains uninvestigated. We tested the hypothesis that a mechano-regulatory model has the potential to predict bone regeneration around implants. In an in vivo bone chamber set-up allowing for controlled implant loading (up to 90 microm axial displacement), bone tissue formation was simulated and compared qualitatively and quantitatively with histology. Furthermore, the model was applied to simulate excessive loading conditions. Corresponding to literature data, implant displacement magnitudes larger than 90 microm predicted the formation of fibrous tissue encapsulation of the implant. In contradiction to findings in orthopedic implant osseointegration, implant displacement frequencies higher than 1 Hz did not favor the formation of peri-implant bone in the chamber. Additional bone chamber experiments are needed to test these numerical predictions.

The influence of micro-motion on the tissue differentiation around immediately loaded cylindrical turned titanium implants.

OBJECTIVE: The aim of this study was to evaluate the effect of various degrees of implant displacement on the tissue differentiation around immediately loaded cylindrical turned titanium implants. DESIGN: The experiments were conducted in repeated sampling bone chambers placed in the tibia of 10 rabbits. Tissues could grow into the bone chambers via perforations. Due to its double structure, tissues inside the chamber could be harvested leaving the chamber intact. This allowed several experiments within the same animal. The chambers contained a cylindrical turned titanium implant that was loaded in a well-controlled manner. In each of the 10 chambers, four experiments were conducted with the following test conditions: immediate implant loading by inducing 0 (control), 30, 60 and 90 microm implant displacement, 800 cycles per day at a frequency of 1 Hz, twice a week during a period of 6 weeks. Histological and histomorphometrical analyses were performed on methylmethacrylate histological sections. An ANOVA was conducted on the dataset. RESULTS: The total tissue volume was significantly lowest in the unloaded control condition. The bone volume fraction on the other hand, was significantly larger in the unloaded and 90 microm implant displacement, compared to the 30 microm implant displacement. Bone density increased with increasing micro-motion with significantly higher values for the 60 microm- and 90 microm-test conditions compared to the unloaded situation. The chance to have bone-to-implant contact decreased in case of micro-motion at the tissues-implant interface. CONCLUSION: The magnitude of implant displacement had a statistically significant effect on the tissue differentiation around immediately loaded cylindrical turned titanium implants. Implant micro-motion had a detrimental effect on the bone-to-implant contact in an immediate loading regimen.

Numerical simulation of tissue differentiation around loaded titanium implants in a bone chamber.

The application of a bone chamber provides a controlled environment for the study of tissue differentiation and bone adaptation. The influence of different mechanical and biological factors on the processes can be measured experimentally. The goal of the present work is to numerically model the process of peri-implant tissue differentiation inside a bone chamber, placed in a rabbit tibia. 2D and 3D models were created of the tissue inside the chamber. A number of loading conditions, corresponding to those applied in the rabbit experiments, were simulated. Fluid velocity and maximal distortional strain were considered as the stimuli that guide the differentiation process of mesenchymal cells into fibroblasts, chondrocytes and osteoblasts. Mesenchymal cells migrate through the chamber from the perforations in the chamber wall. This process is modelled by the diffusion equation. The predicted tissue phenotypes as well as the process of tissue ingrowth into the chamber show a qualitative agreement with the results of the rabbit experiments. Due to the limited number of animal experiments (four) and the observed inter-animal differences, no quantitative comparison could be made. These results however are a strong indication of the feasibility of the implemented theory to predict the mechano-regulation of the differentiation process inside the bone chamber.

Assessment of mechanobiological models for the numerical simulation of tissue differentiation around immediately loaded implants.

Nowadays, there is a growing consensus on the impact of mechanical loading on bone biology. A bone chamber provides a mechanically isolated in vivo environment in which the influence of different parameters on the tissue response around loaded implants can be investigated. This also provides data to assess the feasibility of different mechanobiological models that mathematically describe the mechanoregulation of tissue differentiation. Before comparing numerical results to animal experimental results, it is necessary to investigate the influence of the different model parameters on the outcome of the simulations. A 2D finite element model of the tissue inside the bone chamber was created. The differentiation models developed by Prendergast, et al. ["Biophysical stimuli on cells during tissue differentiation at implant interfaces", Journal of Biomechanics, 30(6), (1997), 539-548], Huiskes et al. ["A biomechanical regulatory model for periprosthetic fibrous-tissue differentiation", Journal of Material Science: Materials in Medicine, 8 (1997) 785-788] and by Claes and Heigele ["Magnitudes of local stress and strain along bony surfaces predict the course and type of fracture healing", Journal of Biomechanics, 32(3), (1999) 255-266] were implemented and integrated in the finite element code. The fluid component in the first model has an important effect on the predicted differentiation patterns. It has a direct effect on the predicted degree of maturation of bone and a substantial indirect effect on the simulated deformations and hence the predicted phenotypes of the tissue in the chamber. Finally, the presence of fluid also causes time-dependent behavior. Both models lead to qualitative and quantitative differences in predicted differentiation patterns. Because of the different nature of the tissue phenotypes used to describe the differentiation processes, it is however hard to compare both models in terms of their validity.

Evaluation of factors influencing the marginal bone stability around implants in the treatment of partial edentulism.

BACKGROUND: The original protocol of Brånemark to achieve predictable osseointegration for oral implants has substantially been modified. One may question whether results are influenced by those modifications, especially for the long-term prognosis. PURPOSE: The goal of the present study was to investigate the impact of those parameters that deviate from the original protocol as defined by P-I Brånemark. MATERIALS AND METHODS: In this study, 246 patients with 263 fixed partial prostheses supported by 668 Brånemark implants were followed from 1 to 15 years (mean: 6.3 yr). Radiographs were taken at the time of abutment connection, at 3 to 6 months, at 12 months, and then every 3 years. The bone level was rated mesially and distally from the implants on a total of 2588 radiographs. RESULTS: A positive relation between abutment length and marginal bone level was found (p > .0001). The maxilla (p = .03), porcelain (p = .007), long abutments (p = .008), and regular-sized diameter implants (p = .001) all exhibited more bone loss in the first 6 months. After 6 months, only long implants showed more bone loss (p = .03). CONCLUSIONS: Overall, the marginal bone level remained stable around Brånemark implants, never surpassing 2.2 mm, even after 15 years. Although longer implants lost more bone over time, this has to be interpreted with respect to higher resorption rates in less resorbed jaws.

Pre-load on oral implants after screw tightening fixed full prostheses: an in vivo study.

The fit of implant supported fixed prostheses is said to be of clinical concern because of the rigid fixation of an oral implant in its surrounding bone. The influence of the torque sequence of the set screws during fixation of implant supported fixed full prostheses on the final pre-load was investigated in vitro. No significant effect of the torque sequence of the set screws on the final pre-load was observed. The main objective of this study was to quantify and qualify the pre-load in vivo on implants supporting a fixed full prosthesis. This was performed when the prostheses were supported by all five or six implants and was repeated when the prostheses were supported by only four and three implants. A total of 13 patients with a fixed full implant supported prosthesis were selected. The existing abutments were changed for strain gauged abutments. After tightening the set screws with a torque of 10 N cm, the pre-load conditions were registered. The average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 323 N (43 N), 346 N (59 N), 307 N (60 N) 21 N cm (3 N cm) and 21 N cm (2 N cm), 23 N cm (5 N cm), respectively. In addition, the pre-load was registered after fixation of a machined gold cylinder, as delivered by the manufacturer, on each of the supporting implants, representing the 'optimal fit' situation. The corresponding average (SEM) axial forces and bending moments in case of five or six, four and three supporting implants were 426 N (36 N), 405 N (40 N), 413 N (46 N) and 8 N cm (1 N cm), 8 N cm (1 N cm), 8 N cm (1 N cm), respectively. The induced axial forces after tightening the prostheses were significantly lower then after tightening the gold cylinder in case of five or six supporting implants (P < 0.02). The induced bending moments after tightening the prostheses were statistically significantly higher (P < 0.0001) then after tightening the gold cylinder in all test conditions (five or six, four or three supporting implants). This study underlines the static load present after screw tightening implant supported fixed full prostheses.

The influence of static and dynamic loading on marginal bone reactions around osseointegrated implants: an animal experimental study.

Although it is generally accepted that adverse forces can impair osseointegration, the mechanism of this complication is unknown. In this study, static and dynamic loads were applied on 10 mm long implants (Brånemark System, Nobel Biocare, Sweden) installed bicortically in rabbit tibiae to investigate the bone response. Each of 10 adult New Zealand black rabbits had one statically loaded implant (with a transverse force of 29.4 N applied on a distance of 1.5 mm from the top of the implant, resulting in a bending moment of 4.4 Ncm), one dynamically loaded implant (with a transverse force of 14.7 N applied on a distance of 50 mm from the top of the implant, resulting in a bending moment of 73.5 Ncm, 2.520 cycles in total, applied with a frequency of 1 Hz), and one unloaded control implant. The loading was performed during 14 days. A numerical model was used as a guideline for the applied dynamic load. Histomorphometrical quantifications of the bone to metal contact area and bone density lateral to the implant were performed on undecalcified and toluidine blue stained sections. The histological picture was similar for statically loaded and control implants. Dense cortical lamellar bone was present around the marginal and apical part of the latter implants with no signs of bone loss. Crater-shaped bone defects and Howship's lacunae were explicit signs of bone resorption in the marginal bone area around the dynamically loaded implants. Despite those bone defects, bone islands were present in contact with the implant surface in this marginal area. This resulted in no significantly lower bone-to-implant contact around the dynamically loaded implants in comparison with the statically loaded and the control implants. However, when comparing the amount of bone in the immediate surroundings of the marginal part of the implants, significantly (P < 0.007) less bone volume (density) was present around the dynamically loaded in comparison with the statically loaded and the control implants. This study shows that excessive dynamic loads cause crater-like bone defects lateral to osseointegrated implants.

Freestanding and tooth-implant connected prostheses in the treatment of partially edentulous patients. Part I: An up to 15-years clinical evaluation.

In 123 patients, 339 implants were connected to 313 teeth by means of fixed partial prostheses (test) and followed up for 1.5-15 years (mean: 6.5). In another ad random selected 123 patients, 329 implants were connected to each other by means of 123 freestanding fixed partial prostheses (control) and were followed up for 1.3-14.5 years (mean: 6.2). The aim of this study was to compare both treatment modalities with each other based on implant, tooth and prosthesis complications. The cumulative implant success, based on implant immobility and/or lack of implant fractures after loading, in the test and control groups amounted to 95% and 98.5%, respectively. Although in the test group 10 implants versus only 1 in the control group failed, a regression analysis of the survival data, based on the cox proportional hazards model, revealed no significant difference. In the test group periapical lesions (3.5%), tooth fracture (0.6%) and tooth extraction due to fatal decay or periodontitis (1%) were observed, besides tooth intrusion (3.4%) and crown cement failure (8%). Framework fracture occurred in 3 patients. In the control group, only 2 abutment screws fractured. The treatment of partial edentulism by means of oral implants was beneficial for our patients. Because of a clear tendency of more implant failures (mobility or fractures) and tooth complications in the tooth-implant connected prostheses, the freestanding solution is the primary option to be considered. To avoid intrusion of abutment teeth, the connection, if made, should be completely rigid.