Effect of constant strain rate, composed of varying amplitude and frequency, of early loading on peri-implant bone (re)modelling.

AIM: Examine the effect of varying components of strain rate -- amplitude versus frequency -- while maintaining a constant strain rate of early controlled mechanical loading on implant stability, peri-implant bone mass and bone-to-implant contact. MATERIAL AND METHODS: Three groups of guinea-pigs received TiO2 -blasted implants in both tibiae. One week after installation test implants were loaded 5 days/week during 4 weeks. The contra-lateral implants were the unloaded controls. Strain rate was kept constant (1600 micro epsilon/s), while amplitude and frequency were varied per group. Implant stability was followed by resonance frequency analysis. Animals were sacrificed, and ground sections were prepared to rate bone-to-implant contact and bone mass. RESULTS: All implants (n=78) integrated uneventfully. A significant positive effect (p=0.03) of early loading on bone mass was observed in the distal medullar cavity. A significant difference in bone mass between test and control implants was evidenced between the groups (p=0.03 and 0.04). A significant increase in implant stability and bone-to-implant contact could not be shown. CONCLUSIONS: Early controlled stimulation of peri-implant bone is related to amplitude/frequency and not to strain rate as such, considering a constant stimulation time. An increase of bone mass around early-loaded implants was shown. This cortical bone model is most sensitive to low-frequency/high-amplitude stimulation.

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.

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

A total of 123 patients were followed between January 1983 and July 1998 with 140 tooth-implant connected prostheses. The age of the patients at prosthesis installation ranged from 20 to 79 years (mean 51.8). 339 (Brånemark(R) system) implants were connected to 313 teeth. The loading time ranged from 1.5 to 15 years (mean: 6.5). 123 patients were randomly selected as a control group with freestanding implant-supported prostheses only. The age of the patients at prosthesis installation ranged from 22 to 78 years (mean 52.3). The loading time for the 329 freestanding (Brånemark(R) system) implants ranged from 1.3 to 14.5 years (mean: 6.2). Evolution of the marginal bone stability around the implant in the tooth-implant connected as well as the freestanding group was studied with respect to the prognosis of the implants. Over the period from 0 to 15 years, there was significantly more marginal bone loss (0.7 mm) in tooth-implant connected versus freestanding prostheses. No significant difference in marginal bone loss was found between the non-rigid tooth-implant connected prostheses versus freestanding prostheses. However, there was a significant difference in marginal bone loss for rigid and multi-connected tooth-implant connected prostheses versus freestanding ones. The results of this study indicate that more bone is lost around implants which are rigidly connected to teeth. This suggests that bending load, which is increased in tooth-implant connected prostheses, might be responsible for this phenomenon. These observations favor the use of freestanding prostheses whenever possible. However, the clinical significance of greater bone loss in rigid versus non-rigid connections might outweigh the annoying phenomenon of tooth intrusion in the case of non-rigid tooth connection, when connection is considered.

Interdisciplinary treatment planning for orthodontic-prosthetic implant anchorage in a partially edentulous patient.

Successful orthodontic treatment is characterized by optimal anchorage control. Teeth or groups of teeth are united to counteract biomechanical reactive forces during orthodontic treatment. These classic anchorage control mechanisms are less efficient or even non-existent in partially edentulous patients who are missing multiple posterior teeth. However, osseointegrated oral implants ad modum Brånemark can provide optimal anchorage control for orthodontic tooth alignment and rehabilitation of occlusion through prosthetic implant restorations. Careful multidisciplinary planning based on complex diagnostic wax setup casts to determine exact implant location and orientation in line with future orthodontic tooth displacements and prosthetic implant crown restorations is the most important step in the overall treatment planning.

[Success of implants in the moderately resorbed edentate maxilla]. / Het succes van implanteren in de matig geresorbeerde edentate bovenkaak.

In applications of implants in the moderately resorbed maxilla factors such as bone quantity and the loading of the bone are of importance for the prognosis. Long-term studies have shown that for the maxilla the results were less good than for the mandible. The main reason for this is the condition of the bone, especially reduced bone quantity together with a thin corticalis an low bone density. Beside these factors there are also the general negative factors such as rheumatoid arthritis, osteoporosis, smoking and radiotherapy. The prognosis of implant supported prostheses is not primarily determined by the number of implants, but by the condition of the bone and to some extent by the splinting effect of the implants.

A randomised clinical trial on the influence of splinted and unsplinted oral implants in mandibular overdenture therapy. A 3-year report.

A randomised clinical trial was performed to investigate whether there is a need or advantage to splint two implants in the mandible retaining a hinging overdenture. Furthermore, patient satisfaction was evaluated for different attachment systems retaining the overdenture. Thirty-six edentulous patients were randomised into three groups of equal size and treated with either magnets, ball attachments or straight bars (reference group). After 3 years of observation no implants were lost in any of the groups. Besides, no statistically significant differences were noted for the peri-implant outcome. Although the bar group presented the highest retention force, the general satisfaction of the patients in the three groups did not differ. The patients with bar retentions showed less prosthetic complications of the retention elements but more at the level of the denture-supporting mucosa. Finally, the clinical outcome of all groups confirms that overdenture treatment demands regular controls with limited time intervals.

Patient evaluation and treatment planning.

Patient evaluation and correct treatment planning are important for the successful outcome of implant supported overdentures. The various stages may be considered as follows. An initial appointment which leads to a diagnosis and to the treatment plan, followed by the confirmation appointment where the patient is informed which is the most appropriate solution to their presenting problem. Prior to implant surgery pre-treatment and diagnostic casts are often required which assist the prosthodontist further in his treatment options. An understanding of the various factors which influence the outcome of implant placement will assist the clinician in the successful prosthetic rehabilitation of the patient.

The reliability of implant-retained hinging overdentures for the fully edentulous mandible. An up to 9-year longitudinal study.

The treatment of fully edentulous mandibles by means of implant-supported hinging overdentures has become a routine therapy, although long-term data on the success rate of implants and prostheses are lacking. This longitudinal study examined 207 consecutively treated patients who received, during the past 10 years, 449 Brånemark implants to retain a mandibular hinging overdenture, mainly on a Dolder bar. Clinical parameters and standardized radiographs taken at every recall visit with an interval of 6-12 months were used to judge the implant rigidity in the jawbone, the marginal bone level, and attachment level changes. The cumulative implant failure rate at 9 years was 3%. After loading, implant loss was concentrated during the first 12 months, with only one failure observed at 22 months. A radiographically determined bone loss of 0.7 mm was observed during the first year. From the second year, a mean annual bone loss of 0.05 mm occurred. The attachment loss, calculated as the sum of probing pocket depth plus the recession, was 0.07 mm/year and paralleled the changes in marginal bone level over time. The rigidity of the implant-bone interface revealed an increase over time, as shown by a decrease in Periotest values. The bar-overdenture complications were related to relining (23%), untightening of the retention clip (10%), and renewal of the prosthesis (7%). When magnets or ball attachments were used, more aftercare was needed. Fracture of the antagonistic full denture occurred in 7% of patients. The present data indicate that the mandibular overdenture therapy on two (Brånemark) implants is a very reliable and cost-effective treatment, even in a long-term perspective for the fixed full mandibular prosthesis and especially in elderly patients.

Biomechanics of oral implants: a review of the literature.

Considering biomechanics of oral implants, both loading on the implant itself and the transferred load to the bone need our attention. Mastication induces vertical and transverse forces, which induce axial forces and bending moments and exert stress gradients in the implant as well as in the bone. By the use of strain gauges or piezo-electric force transducers, one succeeds in precise intra-oral force measurements which make it possible to study a wide range of varying conditions in implant dentistry. A key determinant of the success or failure of an oral implant is the way mechanical stresses are transferred to the surrounding bone. The load transfer from implants to surrounding bone depends on the type of loading, the bone-implant interface, the length and diameter of the implants, the implant shape, structure of the implant surface, the superstructure and the quality and quality of the surrounding bone. Finite element analyses indicate maximum stress concentrations in the contact area of the implants with the cortical bone and around the apex of the implants in the trabecular bone. Although the precise mechanisms are not fully understood, it is clear that there is an adaptive remodelling response of the surrounding bone to the current situation.

The influence of splinting procedures on the periodontal and peri-implant tissue damping characteristics. A longitudinal study with the Periotest device.

The aim of the present study was to evaluate the capability of the Periotest device in detecting and monitoring functional changes in the periodontal as well as in the pari-implant damping characteristics. In the first part of this study, 107 teeth were splinted by means of 40 full acrylic fixed prostheses (AFP) and another 37 teeth were splinted by means of 14 ceramometallic fixed prostheses (C-MFP). The Periotest measurements of individual teeth were done the day the fixed prostheses were cemented temporary (PTV 1), and again after a mean observation period of 27.4 days (PTV 2). In the 2nd part, 78 osseointegrated two-stage implants were splinted by means of 23 full acrylic fixed prosthesis (AFP) and other 18 implants were left without it. Using the same abutment length, Periotest measurements were performed, at abutment connections and before installation of the final prosthesis. In a 3rd part, using both implants and teeth as abutments, 29 osseointegrated implants were connected with 25 abutment teeth by means of 7 AFP. The measurements were performed at the beginning of the prosthetic treatment and 2, 4 and 6 weeks later. After splinting teeth by means of AFP for the observation period, no statistically significant reduction in PTVs was found. When on the other hand, a C-MFP was used, PTV 2 showed a significant reduction. The PTVs at abutment connection went down after a period of time, during which some implants were interconnected by means of an AFP and others were not.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of periodontal tissues damping characteristics: current concepts and clinical trials.

The reproducibility of an electronic device for the assessment of periodontal tissues damping characteristics was judged by evaluating the inter-examiner, inter-device and day to day variations of the measurements (PTVs). Nine young periodontally healthy volunteers were examined by two examiners (EX-1 and EX-2) and two devices (D-1 and D-2) in the following sequence: EX-1 D-1, EX-2 D-1, EX-1 D-2, and EX-2 D-2. PTVs were obtained at 5 different occasions during the same day. In some instances examiner 2 measured higher scores than examiner 1 with both devices. This difference was statistically significant (P = 0.05), if the total of 900 measurements was considered. The measurements of device 2 were approximately 0.5 PTV units higher, also reaching a statistical significance (P = 0.05). This difference is of limited clinical significance. The day to day variation was evaluated by comparing the scores obtained at 8 a.m. with the ones at the four other periods. The lowest scores were measured at 8 a.m. Only the 11 a.m. and the 2 p.m. measurements differed significantly. The effect of hormonal changes during the menstrual cycle and of smoking habits on PTVs were also evaluated. Ten female periodontally healthy volunteers were examined three times a week, during a period of two menstrual cycles. No significant PTV changes were found during the menstrual cycle. The effect of the smoking habit on PTVs was tested on 23 periodontally healthy patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A method for assessing the damping characteristics of periodontal tissues: goals and limitations.

The Periotest method, an objective, noninvasive clinical diagnostic method, is a dynamic procedure that measures the resistance of the periodontium to a defined impact load. It has been reported that Periotest values depend to some extent on tooth mobility, but mainly on the damping characteristics of the periodontium. Nevertheless, the real clinical meaning of the measurements and some important limitations of the Periotest measuring principle still seem to be poorly understood. In the present study, the relationship between damping characteristics of periodontal tissues and tooth mobility was investigated. The best correlations between tooth deflection and Periotest values were found for teeth showing a certain degree of clinical mobility (R2 from .79 to .91). Nevertheless, this correlation was clearly lower when only healthy subjects were examined (R2 from .43 to .54). The better correlation found for forces greater than 1.0 N indicates that the damping characteristics assessed with the Periotest method are related to secondary tooth movement. The Periotest methodology, measuring principle, and limitations are critically reviewed.

A clinical study of an intracoronal fixed partial denture attachment system.

An alternative tooth replacement system, based on pin retention, was clinically evaluated for up to 4 years in a prospective study. Thirty-two Universal Dental Anchorage anchors, supporting 28 fixed partial prostheses in 25 patients, were placed. Most of these prostheses had a cast complete crown on one abutment; on the other abutment, the UDA anchor functioned as a support for the extension pontine. After a mean observation period of 2 years, nine anchors failed. Around five of the failed anchors, caries was present; this occurred after 2 years or more of function of the prostheses. Early failure (4/9) were registered in the first year of function and were caused by loss of retention (three) or anchor fracture (one). The periodontal condition of the UDA anchor abutment teeth was not significantly different from that of the contralateral side. The number of failures, especially the number caused by recurrent caries, is cause for concern.