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.

Oral implant placement and restoration by undergraduate students: clinical outcomes and student perceptions.

INTRODUCTION: Universities are developing and implementing implant dentistry training to prepare dental professionals for the growing treatment needs. This study describes how implant dentistry is taught at the KU Leuven and focuses on implant-related clinical outcomes. Perspectives of participating undergraduate students are analysed with a view to improve oral implant dentistry training. MATERIALS AND METHODS: Implant dentistry training at the KU Leuven consists of theoretical lectures, pre-clinical hands-on workshops and clinical (surgical/prosthetic) experience. Questionnaires were used to investigate the perceptions of students on the educational programme. Radiographs were taken at implant insertion, at healing abutment connection, at restoration/prosthesis insertion and after 1 and 2 years of functional loading. The marginal bone level was measured from the implant-abutment connection to the first visible bone-to-implant contact. RESULTS: One hundred and twelve implants were placed by 56 undergraduate students (61.5% of the total students) in 56 patients. After a follow-up time of 3 years, the cumulative implant survival rate, at implant level, was 97.1%. The mean marginal bone loss after 1 and 2 years in function was 0.35 mm and 0.39 mm, respectively. Eighty percentage of students were satisfied with the training, and they considered this sufficient preparation to perform implant placement under close supervision. CONCLUSIONS: The clinical outcome of implant treatment performed by undergraduate students under close supervision is similar to that reported by experienced clinicians/research teams. Clinical, surgical as well as restorative experience in addition to theoretical and pre-clinical training seems beneficial when implementing implant dentistry in the undergraduate programmes.

[Influence of the removable partial denture acrylic resin on oral health and quality of life]. / Influence de la prothèse amovible partielle en résine acrylique sur la santé bucco-dentaire et la qualité de vie.

OBJECTIVE: This study aims to evaluate dental decay incidence and DMF index, plaque index and gingival index, and to assess the satisfaction/dissatisfaction in acrylic removal partial denture wearers (ARPD) and in partial edentate no wearers. It aims to improve the therapeutic management in prosthetic oral rehabilitation in DR Congo. MATERIAL AND METHODS: This prospective cohort interventional randomized study on 376 patients enrolled and divided into two groups (with and without denture prosthesis) was performed in University Clinics of Kinshasa, Kinshasa Medical Center and Clinic Glory during the period August 2008 to August 2010. RESULTS: Three hundred seventy-six patients (376) with 163 men (47 ± 16 years) and 213 women (42 ± 15 years) were followed. Of the 376 patients randomized, 189 were of "prosthesis" group and 187 were in the group "without aid". Both groups were regularly reviewed every 6 months for 2 years. Ten thousand four hundred and fifty-two (10452) teeth were examined (5149 teeth to the group "prosthesis" and 5303 for the teeth "without prosthesis" group. On hundred and twenty-nine (129) teeth that presented caries, 110 (82.96 per cent) are decayed teeth in the "prosthesis" group and 19 (17.04 per cent) are in the group "without prosthesis" (p = 0.00). The index Tooth Decayed, Missing, Filled (CAD) to start of the study for each group was 0.2. Two years after the index rose to 0.3 for the group "prosthesis" and remained steady (0.2) for the group "without prosthesis". The "prosthesis" group showed plaque index (PI) and gingival index (GI) above 0.99 (SD: ± 0.28) and 1.27 (SD: ± 0.43) than normal compared to those of the "no aid" group (0.46 ± 0.15 and 0.32 ± 0.12). The differences were statistically significant for both indices between the two groups (p = 0.00). Overall satisfaction rate for the "prosthesis" group was 26.4% while for the group "without prosthesis" satisfaction rate is 80.9%. CONCLUSION: This study shows that improved oral hygiene and regular check of the RPD acrylic resin carriers become a concern for establishing a true oral health policy.

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.

Depth and lateral deviations in guided implant surgery: an RCT comparing guided surgery with mental navigation or the use of a pilot-drill template.

AIM: To assess the accuracy of guided surgery compared with mental navigation or the use of a pilot-drill template in fully edentulous patients. MATERIAL AND METHODS: Sixty consecutive patients (72 jaws), requiring four to six implants (maxilla or mandible), were randomly assigned to one of the following treatment modalities: Materialise Universal(®) mucosa, Materialise Universal(®) bone, Facilitate(™) mucosa, Facilitate(™) bone, mental navigation, or a pilot-drill template. Accuracy was assessed by matching the planning CT with a postoperative CBCT. Deviations were registered in a vertical (depth) and horizontal (lateral) plane. The latter further subdivided into BL (bucco-lingual) and MD (mesio-distal) deviations. RESULTS: The overall mean vertical deviation for the guided surgery groups was 0.9 mm ± 0.8 (range: 0.0-3.7) and 0.9 mm ± 0.6 (range: 0.0-2.9) in a horizontal direction. For the non-guided groups, this was 1.7 mm ± 1.3 (range: 0.0-6.4) and 2.1 mm ± 1.4 (range 0.0-8.5), respectively (P < 0.05). The overall mean deviation for the guided surgery groups in MD direction was 0.6 mm ± 0.5 (range: 0.0-2.5) and 0.5 mm ± 0.5 (range: 0.0-2.9) in BL direction. For the non-guided groups, this was 1.8 mm ± 1.4 (range: 0.0-8.3) and 0.7 mm ± 0.6 (range 0.0-2.9), respectively. The deviation in MD direction was significantly higher in the non-guided groups (P = 0.0002). CONCLUSION: The most important inaccuracy with guided surgery is in vertical direction (depth). The inaccuracy in MD or BL direction is clearly less. For non-guided surgery, the inaccuracy is significantly higher.

Extra short dental implants supporting an overdenture in the edentulous maxilla: a proof of concept.

OBJECTIVES: This study investigates the outcome of short implants additionally placed with longer implants to support a maxillary overdenture. MATERIALS AND METHODS: Twelve patients received six implants to support a maxillary overdenture. Only one patient still had two molars in the maxilla, while the others had no remaining teeth. The status of the opposing arch was diverse. The distal implant in each quadrant was 6 mm in height (S) and the middle implants ranged between 10 and 14 mm (L). All implants were placed following a one-stage procedure and early loaded (6 weeks). Clinical and radiological parameters were assessed 6, 12 and 24 months after loading. RESULTS: One short implant failed 2 weeks after surgery, probably due to early mobilization by the provisional prosthesis. The mean bone loss on the rough part of the implant was 0.7 mm (S) vs. 1.3 mm (L) during the first year and 0.3 mm (S) vs. 0.2 mm (L) during the second year after loading. The mean implant stability quotient values were 67 (S) vs. 70 (L) at placement and 75 (S) vs. 78 (L) after 1 year. At the 2-year follow- up, all prostheses were still stable and comfortable. CONCLUSION: An overdenture on six implants, of which two have a reduced length, might represent a successful treatment option. No significant difference could be found between both implant lengths at 2 years' follow-up. However, bone loss with short implants may increase the likelihood of failure.

Model-based guided implant insertion for solitary tooth replacement: a pilot study.

OBJECTIVE: The impact of the implant position on the restorative outcome could justify guided surgery even for the single implants particularly in the aesthetic zone and especially when a simplified concept is available. MATERIAL AND METHODS: Based on a plaster model, on which the soft tissues were mimicked (according to the thickness measured on a Cone-Beam CT), a tooth-supported, surgical template was prepared. The latter guided all drills so that even flapless implant insertion became possible. All implants were placed by students of the master-after-master training program in Periodontology. RESULTS: The prospective cohort included a total of 34 implants, all of AstraTech (Osteospeed(®)) type, which were successfully inserted in 29 patients, 16 flapless, 32 onestage. The marginal bone along the integrated implants remained stable over time, with 0.13 mm loss during the first year. The aesthetic parameters were reassuring. CONCLUSIONS: This simple model-based concept seems to be reliable for the guided placement of single implants and the pre-operative preparation of their restorations.

Sleeping vs. loaded implants, long-term observations via a retrospective analysis.

OBJECTIVE: Several theories have been presented to explain initial and secondary marginal bone loss around dental implants (e.g. microbial load, adverse loading, microbial leakage, compromised healing/adaptation of host-implant interface). MATERIAL AND METHODS: This study compared the long-term outcome (up to 12 years) of sleeping with loaded implants in the mandible via a split-mouth concept. Fourteen patients with overdentures were enrolled (10 women, mean age at implant insertion: 56 years [range: 33-71]). They presented with 28 loaded (position 33/43) and 14 sleeping implants (mostly position 31/41). At several follow-up visits, intra-oral radiographs (long-cone principle) were taken to observe marginal bone level changes. RESULTS: At each observation, compared with abutment connection, the submerged non-loaded implants showed less bone loss (P-values: 1st year 0.007, 3 years 0.000, 5 years 0.002, 8 years 0.007, 12 years 0.000) than their neighbouring functional implants. This difference was primarily due to a more significant bone loss during the first year of loading (0.8 vs. 0.1 mm respectively), since afterwards, the bone level changes remained quite similar for both implant types. CONCLUSIONS: Our data suggest that the first months of loading have a significant impact on the bone level (initial difference sleeping vs. loaded implants), followed by a more physiological bone level change afterwards. This initial difference might be explained by the adaptation of the surrounding bone to the loaded implant.

RCT comparing minimally with moderately rough implants. Part 1: clinical observations.

AIM: This 1-year prospective RCT compared the outcome of minimally (turned) and moderately rough (TiUnite) implant surfaces. MATERIAL AND METHODS: Two subgroups of patients were formed; one group (n = 10) where all teeth had been extracted due to severe periodontitis, another group (n = 8) with teeth in the antagonistic jaw with a history of periodontitis and some remaining medium pockets (4-6 mm). Implants (n = 85, 43 turned & 42 TiUnite) were installed randomly in each patient. After 3-6 months of submerged healing, healing abutments were connected, followed by final abutments 2 weeks later, all with the same surface characteristics as the supporting implant. Peri-implant parameters and intra-oral radiographs were recorded up to 1 year after abutment connection. RESULTS: Two turned implants failed in the partial edentulous group during the initial healing period (CSR: 95%) and none of the TiUnite (CSR: 100%) surface. No statistically significant differences in clinical parameters could be observed between both surfaces. The partial edentulous subgroup showed more bone loss compared to the full edentulous subgroup. CONCLUSION: Moderately rough implants have a similar clinical outcome (at 1 year of loading in periodontitis susceptible patients) compared to minimally rough implants.

Patient- and clinician-reported outcomes for the additively manufactured sub-periosteal jaw implant (AMSJI) in the maxilla: a prospective multicentre one-year follow-up study.

The clinical outcomes of maxillary rehabilitation with the additively manufactured sub-periosteal jaw implant (AMSJI; CADskills BV) were evaluated in edentulous patients with a Cawood-Howell atrophy classification ≥5 in all regions of the maxilla. Fifteen consecutive patients were included in the study and followed up for 1 year. They were interviewed using a survey protocol and were examined clinically and radiographically preoperatively (T0) and at 1 (T1), 6 (T2), and 12 (T3) months after permanent upper prosthesis placement. The patients reported an increased oral health-related quality of life. The overall mean Oral Health Impact Profile-14 score at T0 was 17.20 (standard deviation (SD) 6.42). When results at T0 were compared to those at T1 (mean 8.93, SD 5.30), a statistically significant difference was seen (P = 0.001). At T3, the mean value was 5.80 (SD 4.18). Compared to T0, there was also a statistically significant difference at T3 (P = 0.001). General satisfaction based on the numerical rating scale was a mean 49.93 at T1, which was less than patient expectation prior to treatment at T0 (52.13). A higher overall value was seen at T3 (53.20) when compared to T0. Within the constraints of the short follow-up, the AMSJI appears to be a promising tool for patients with extreme jaw atrophy. The high patient expectations were met without complications.

Long-term, retrospective evaluation (implant and patient-centred outcome) of the two-implants-supported overdenture in the mandible. Part 1: survival rate.

OBJECTIVE: This retrospective analysis evaluated the long-term outcome of two implants supporting an overdenture in the mandible, as well as the significance of some confounding factors (smoking, implant length, bone quality). MATERIAL AND METHODS: All mandibular overdenture cases (n=495) treated during the past 25 years in our centre (with > or = 5 years loading of the implants) were included in this study. General information (medical history, implant data, report on surgery) was retrieved from the patient's file. A large number of patients (n=248) were willing to visit the clinic for an additional follow-up visit. For the others, information on implant survival was collected by phone (n=121), or contact was impossible (57 had died, three were hospitalized and 66 could not be reached). In the latter group, information was used, up to their last visit to the clinic. An implant was considered as surviving if it was still in function in the mouth, without clear adverse effects (pain, swelling, mobility). A failure was defined as early if it occurred within the window, insertion-final prosthesis placement; afterwards, it was considered as late. RESULTS: Most of the inserted implants (Brånemark type) were of the turned (machined) type (95.5%), the remainder was anodized (TiUnite). The anchoring system was either a bar (86.3%), ball attachments (11.7%) or magnets (1.6%), and only some patients changed from one to the other (0.4%). Kaplan-Meier analyses showed a survival rate of 95.5% after 20 years of loading. Factors that influenced the outcome included smoking (90% rate for smokers) and the surgical protocol (reduced survival rate for one-stage-placed implants). Implant length and bone quality had no impact. CONCLUSIONS: These results fully support the two-implant overdenture concept in the mandible even in the long run.

Impact of implant number, distribution and prosthesis material on loading on implants supporting fixed prostheses.

The purpose of this study is to evaluate axial forces and bending moments (BMs) on implants supporting a complete arch fixed implant supported prosthesis with respect to number and distribution of the implants and type of prosthesis material. Seven oral Brånemark implants with a diameter of 3.75 mm and a length of 13 and 7 mm (short distal implant) were placed in an edentulous composite mandible used as the experimental model. One all-acrylic, one fibre-reinforced acrylic, and one milled titanium framework prosthesis were made. A 50 N vertical load was applied on the extension 10 mm distal from the most posterior implant. Axial forces and BMs were measured by calculating signals from three strain gauges attached to each of the abutments. The load was measured using three different models with varying numbers of supporting implants (3, 4 and 5), three models with different implant distribution conditions (small, medium and large) and three models with different prosthesis materials (titanium, acrylic and fibre-reinforced acrylic). Maximum BMs were highest when prostheses were supported by three implants compared to four and five implants (P < 0.001). The BMs were significantly influenced by the implant distribution, in that the smallest distribution induced the highest BMs (P < 0.001). Maximum BMs were lowest with the titanium prosthesis (P < 0.01). The resultant forces on implants were significantly associated with the implant number and distribution and the prosthesis material.

Successful outcome of splinted implants supporting a 'planned' maxillary overdenture: a retrospective evaluation and comparison with fixed full dental prostheses.

OBJECTIVE: Whereas an overdenture concept is generally accepted for the mandible, the outcome of this therapy for the maxilla remains less documented. This retrospective analysis evaluated the peri-implant parameters of implants supporting a 'planned' overdenture in the maxilla, and compared these data with those of an age-matched control group, with a fixed full dental prosthesis. MATERIAL AND METHODS: All patients with an implant-supported overdenture in the maxilla from the Leuven University Hospital (at least 12 months in function) were recalled for a thorough examination. Forty-four patients (162 implants, Brånemark type) could be enrolled. RESULTS: The mean loading time was 9 years (range: >1 to >20 years). The cumulative survival rate after 10 years of function was 99.3% if four to six interconnected implants supported the overdenture, but only 85.7% in case two non-connected implants were used as support. The marginal bone level in the former group remained stable, with changes comparable with those observed for implants supporting fixed full dental prostheses. CONCLUSIONS: These results fully support the overdenture treatment concept for the maxilla, at least when > or =4 splinted implants are used.

Resonance frequency analysis of implants in the guinea pig model: influence of boundary conditions and orientation of the transducer.

The goal of this study was to identify the parameters that must be controlled during in vivo resonance frequency measurements with a custom Osstell transducer for custom implants in the guinea pig animal model. A numerical study and in vitro measurements were performed to determine the influence of the boundary conditions as well as the transducer orientation on the resonance frequency measured by the custom Osstell transducer. In the reported guinea pig model, the type of boundary condition, the orientation of the transducer (parallel or perpendicular to the long axis of the bone) and the length of the modelled bone have a large influence on the resonance frequency values. This implies that a follow-up in time of the stability of an implant requires the boundary conditions applied to the bone in which the implant is installed as well as the orientation of the transducer to be highly repeatable. Applying controlled boundary conditions during in vivo measurements had a highly positive influence on the repeatability of the Osstell measurements. This improves the possibility of the technique to measure changes in the implant-bone interface during healing of the implant.

The resonance frequencies and mode shapes of dental implants: Rigid body behaviour versus bending behaviour. A numerical approach.

The purpose of this study was to evaluate the modal behaviour of the bone-implant-transducer (Osstell) system by means of finite element analyses. The influence of different parameters was determined: (1) the type of implant anchorage being trabecular, cortical, uni-cortical, or bi-cortical, (2) the implant diameter, (3) the length of the implant embedded in the bone, and (4) the bone stiffness. The type of anchorage determines the resulting modal behaviour of the implant-transducer system. A rigid body behaviour was found for a uni-cortical anchoring and for a homogeneous anchoring with low bone stiffness (< or =1000 MPa), whereas a bending behaviour was found for a homogeneous anchoring with a high bone stiffness (> or =5000 MPa) and for a bi-cortical anchorage. The implant dimensions influence the values for the resonance frequencies. Generally, an increase in implant diameter or implant length (in bone) results in higher resonance frequencies. This study also showed that resonance frequencies in case of rigid body behaviour of the implant-transducer system are more sensitive to changes in bone stiffness than resonance frequencies in case of bending behaviour. In conclusion, it seems that the Osstell transducer is suited for the follow-up in time of the stability of an implant, but not for the quantitative comparison of the stability of implants.

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.

Structural and Chemical Analysis of the Zirconia-Veneering Ceramic Interface.

The interfacial interaction of veneering ceramic with zirconia is still not fully understood. This study aimed to characterize morphologically and chemically the zirconia-veneering ceramic interface. Three zirconia-veneering conditions were investigated: 1) zirconia-veneering ceramic fired on sandblasted zirconia, 2) zirconia-veneering ceramic on as-sintered zirconia, and 3) alumina-veneering ceramic (lower coefficient of thermal expansion [CTE]) on as-sintered zirconia. Polished cross-sectioned ceramic-veneered zirconia specimens were examined using field emission gun scanning electron microscopy (Feg-SEM). In addition, argon-ion thinned zirconia-veneering ceramic interface cross sections were examined using scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectrometry (EDS) at high resolution. Finally, the zirconia-veneering ceramic interface was quantitatively analyzed for tetragonal-to-monoclinic phase transformation and residual stress using micro-Raman spectroscopy (µRaman). Feg-SEM revealed tight interfaces for all 3 veneering conditions. High-resolution transmission electron microscopy (HRTEM) disclosed an approximately 1.0-µm transformed zone at sandblasted zirconia, in which distinct zirconia grains were no longer observable. Straight grain boundaries and angular grain corners were detected up to the interface of zirconia- and alumina-veneering ceramic with as-sintered zirconia. EDS mapping disclosed within the zirconia-veneering ceramic a few nanometers thick calcium/aluminum-rich layer, touching the as-sintered zirconia base, with an equally thick silicon-rich/aluminum-poor layer on top. µRaman revealed t-ZrO2-to-m-ZrO2 phase transformation and residual compressive stress at the sandblasted zirconia surface. The difference in CTE between zirconia- and the alumina-veneering ceramic resulted in residual tensile stress within the zirconia immediately adjacent to its interface with the veneering ceramic. The rather minor chemical elemental shifts recorded in the veneering ceramic did not suffice to draw definitive conclusions regarding potential chemical interaction of the veneering ceramic with zirconia. Sandblasting damaged the zirconia surface and induced phase transformation that also resulted in residual compressive stress. Difference in CTE of zirconia versus that of the veneering ceramic resulted in an unfavorable residual tensile stress at the zirconia-veneering ceramic interface.

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.

The effect of titanium plasma-sprayed implants on trabecular bone healing in the goat.

The bone response to different titanium plasma-sprayed implants was evaluated in a goat model. Therefore, beam-shaped implants were installed into the trabecular femoral condyles of 10 goats. These implants were provided with three different titanium plasma-sprayed coatings (Ti2, Ti3 and Ti4) with a Ra of 16.5, 21.4 and 37.9 microm, respectively. An Al2O3 grit-blasted implant (Ti-un) with a Ra of 4.7 microm was used as control. After an implantation period of 3 months, the implants were evaluated histologically and histomorphometrically. Only one implant (Ti3) was not recovered after the evaluation period. Light microscopy showed a limited amount of bone for the various implants. Most of the implants showed a different degree of fibrous tissue alternating with direct bone contact. Complete fibrous encapsulation of the implants was observed in some of the sections. No signs of delamination of the plasma-sprayed coating was visible. No significant difference in bone contact were measured between the different types of implants (P > 0.05). Histomorphometrical analysis revealed significantly higher bone mass close to the implant (0-500 microm) for the Ti3, Ti4 and Ti-un implants placed in the medial femoral condyle and the Ti4 implants placed in the lateral condyle. At distance (500-1500 microm), no difference in bone mass measurements between the different implants was observed (P > 0.05).

Individualised, micro CT-based finite element modelling as a tool for biomechanical analysis related to tissue engineering of bone.

Load-bearing tissues, like bone, can be replaced by engineered tissues or tissue constructs. For the success of this treatment, a profound understanding is needed of the mechanical properties of both the native bone tissue and the construct. Also, the interaction between mechanical loading and bone regeneration and adaptation should be well understood. This paper demonstrates that microfocus computer tomography (microCT) based finite element modelling (FEM) can have an important contribution to the field of functional bone engineering as a biomechanical analysis tool to quantify the stress and strain state in native bone tissue and in tissue constructs. Its value is illustrated by two cases: (1) in vivo microCT-based FEM for the analysis of peri-implant bone adaptation and (2) design of biomechanically optimised bone scaffolds. The first case involves a combined animal experimental and numerical study, in which the peri-implant bone adaptive response is monitored by means of in vivo microCT scanning. In the second case microCT-based finite element models were created of native trabecular bone and bone scaffolds and a mechanical analysis of both structures was performed. Procedures to optimise the mechanical properties of bone scaffolds, in relation to those of native trabecular bone are discussed.