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At least 1,261 records · Page 70Linked to original sources
PubMed2006

Effect of design of all-ceramic resin-bonded fixed partial dentures on clinical survival rate.

In the treatment of single-tooth gaps, the resin-bonded fixed partial denture (FPD) has established itself as an alternative treatment modality. With the advent of high-strength ceramics, such as aluminum oxide ceramics, it appeared to be possible to fabricate all-ceramic resin-bonded FPDs without a metal reinforcement. However, fractures of the traditional two-retainer design of these restorations occurred quite frequently. It was proposed to change the two-retainer design to a single-retainer design with the hope that the survival rate could be improved. Nevertheless, the use of aluminum oxide ceramics can be problematic. The present study strongly suggests that the clinical performance of resin-bonded FPDs made of a high-strength glass-ceramic is in large measure dependent on their design.

Aluminum Oxide↗
PubMed2006

Bacterial colonisation of interior implant threads with and without sealing.

Premature loss of dental implants is due, apart from mechanical factors, to germrelated inflammation. Gaps and hollow spaces within the implant system, for example the gap between implant and abutment in the two-part implant system, may provide a bacterial reservoir causing or maintaining inflammation. The bacterial spectrum involved is similar to that found in periodontitis. This in vitro study aimed to scrutinise the capability of Porphyromonas gingivalis (DSM 20709), the bacterium blamed for inducing peri-implantitis, to pass the implant/abutment gap in titanium implant systems used for orthodontic anchorage and to remain vital in the interior. Additionally, the in vitro effectiveness of gutta percha for gap sealing was examined. Twelve titanium implants (Straumann, diameter: 3.3 mm, length 5.5 mm) were provided with abutments at a defined torque (20 Ncm), six of which were sealed with gutta percha before screwing in the abutment. Subsequently the implants were placed in a nutrient solution (thioglycolate boullion with haemin-menadione solution) that contained Porphyromonas gingivalis. Microbiological specimens were sampled from the implant interiors after 24 and 72 hours and analysed using culture methods. There was evidence that penetration of the periodontal pathogen Porphyromonas gingivalis to the implant interior may occur as early as after 24 hours. Microbes were also detected in the interior of implants sealed with gutta percha. The abutment/implant interface in vitro provides a microbiological leakage for the prospective peri-implantitis-inducing bacterium Porphyromonas gingivalis. Survival of the bacterium is possible in the interior, so that development of a bacterial reservoir is assumed. This in vitro trial produced no evidence that sealing with gutta percha is an effective means to prevent secondary bacterial colonisation in the implant interior.

Colony Count, Microbial↗
PubMed2006

[A comparison between the cast-bonded keeper with different dental alloys in the metallographic structure].

PURPOSE: The aim of this study is to investigate the changes of the metallographic structure of the cast-bonded keeper when cast in varied temperatures. METHODS: Three groups were included in this study: the gold alloy group, the Ni-Cr alloy group and Ti group, with the Magdisc 500 keeper as the control group. Each sample that contained a Magdisc 500 keeper was fabricated with the cast-bonded technique. Then, the samples were fabricated into a metallographic sample by polishing, smoothing and cleaning. Each sample was observed under metallographic microscope. RESULTS: There were no significant changes in the crystal size between the keeper in the gold alloy group and that in the control group. In both of the Ni-Cr alloy group and Ti group, the crystal of the keeper became larger, and this was more evident in the latter group. CONCLUSION: The keeper varied in the metallographic structure if cast-bonded with gold alloy, Ni-Cr alloy or Ti metal. The higher the casting temperature, the larger the crystal of the keeper. The results suggest that the change in the gold group is less than that in the Ni-Cr alloy group and Ti metal group.

Chromium Alloys↗
PubMed2006

[Characters of the surface of the cast-bonded keeper: an experimental study].

PURPOSE: This study is aimed to analyze the characters of the surface of the keeper after cast-bonded in varied temperatures. METHODS: Twelve keepers were divided into three groups: the gold alloy group, the Ni-Cr alloy group and the Ti group with four samples in each group. A sample that contained a Magdisc 500 keeper was fabricated with the cast-bonded technique. Then, the surface of the sample was observed under scanning electron microscope (SEM) and its elements were analyzed with the electron probe. RESULTS: The results showed that there was no oxide film on the surface of the keeper in the gold alloy group and the Ni-Cr alloy group, but there was an oxide film on the surface of the keeper in the Ti group. However, remains of the investment materials were found on the surface of the sample of three groups. CONCLUSIONS: The study suggested that the casting temperature affect the characters of the surface of the cast-bonded keeper. Gold alloy or Ni-Cr alloy is of better properties for clinical use.

Chromium Alloys↗
PubMed2006

[Comparison of the difference of the magnetic force by cast post-keepers combined with three different metals].

PURPOSE: Three different metals were used to make cast post-keepers of magnetic attachment. The magnetic force was tested and analyzed. METHODS: The cast-post keepers were combined by gold alloy, Ni-Cr alloy and Ti metal respectively. 12 samples were divided into three groups, 4 in each. Root surface structures were manufactured by these samples. The values of the magnetic force of the magnetic attachment were tested and compared using ANOVA. RESULTS: The average value of the attractive force of the keeper combined by gold alloy was 4.84N, while that of the keeper combined by Ni-Cr alloy was 4.61N and the keeper combined by Ti was 4.12N. Significant difference was found between each two samples, P<0.01. CONCLUSION: The magnetic force of the keepers combined by three different metals decreased to certain degrees, the keeper combined by gold alloy decreased the least.

Chromium Alloys↗
PubMedDate not supplied

Primary stability of a conical implant and a hybrid, cylindric screw-type implant in vitro.

PURPOSE: The differences with respect to primary stability between 2 Camlog implants, a conical implant, and a hybrid cylindric screw-type implant, were investigated in vitro. The effect of underdimensioned implant bed preparation was also studied for both implant designs. MATERIALS AND METHODS: In an in vitro model the stability of different implants in fresh porcine iliac bone blocks was measured using torque moment values, the Periotest, resonance frequency analysis, and push-out testing. RESULTS: The conical implant showed significantly higher primary stability than the cylindric hybrid implant using the insertion torque, Periotest, and push-out tests. For both types of implants, the torque moment values following under-dimensioned preparation were significantly better than those obtained following the standard drilling protocol (Conical: 25.00 vs 11.00 Ncm; Cylindrical: 11.75 vs. 5.75 Ncm). For the cylindric implant, significantly better results following under-dimensioned implant bed preparation were observed only with the insertion torque and the pushout testing values. The mean ISQ values for all groups were between 55 and 57; no statistical differences with respect to ISQ could be found. CONCLUSION: In this in vitro model conical implants showed higher primary stability than cylindric implants. The procedure of under-dimensioned drilling seemed to increase primary stability for both types of implants; however, the effect was only observable using insertion torque. RFA and Periotest, the noninvasive, clinical methods tested, did not clearly demonstrate this difference.

Animals↗
PubMed2006

Replacing an anterior metal-ceramic restoration with an all-ceramic resin-bonded fixed partial denture: a case report.

Since the first resin-bonded fixed partial denture was described, this adhesive technique for splinting mobile teeth has developed into a conservative method for replacing missing teeth. Heat-pressed all-ceramic materials have been introduced for the fabrication of 3-unit fixed partial dentures in the anterior and premolar region. This clinical report describes the replacement of a conventional partial coverage metal-ceramic resin-bonded fixed partial denture with an all-ceramic resin-bonded fixed partial denture in the anterior maxillary area.

Adult↗
PubMed2006

Compressive stress-strain behaviour of cast dental restorations in relation to luting cement distribution.

This work is concerned with the performance, under dynamic compression, of the adhesives used to simulate cementation of gold crowns onto nickel chromium dies. A measurement system, based on the mounting of strain gauges onto the outer surface of the crowns, has been developed, which allows a semi-quantitative estimate of the state of adhesion. A preliminary study was carried out where miniature gauges were bonded onto the buccal, lingual, mesial and distal surfaces of gold crowns cast to fit onto a chromium-cobalt die, as a precursor to the final design of the instrumented crown. The crowns were then loaded in compression periodically measuring the strain at all four gauges. The results showed the load-strain relationship in fully, partially and uncemented crowns, along with repeated load-unload behaviour to close to the ultimate strength of the bond. The load-strain relationship is linear and repeatable and the slope varies over a factor of about 30 between the un-cemented and fully cemented crown, demonstrating that there is significant sensitivity to bond integrity. These results were used to determine the parameters for a systematic study of S-N relationships in restorative dentistry crowns.

Biomechanical Phenomena↗
PubMed2006

The effect of preparation height and taper on cement lute stress: a three-dimensional finite element analysis.

Three dimensional finite element models of an upper second premolar and molar with full veneer gold crown preparations were developed from extracted samples. The cement lute width was kept constant at 40 microm, but the height and preparation taper were varied. For both models the preparation height was either 1.5 mm (short preparation) or 3 mm (long preparation). The preparation taper was either 10 degree or 30 degree, giving a total of eight models. Each model was loaded with a 10 N horizontal load, a 10 N vertical load or a 10 N load distributed across the occlusal surface. The maximum shear stress and the maximum Von Mises' stress in the cement lute of each model were recorded. For the premolar, the maximum shear stresses ranged from 0.3-5.43 MPa and the maximum Von Mises' stress ranged from 1.44-14.98 MPa. For the molar, the maximum shear stresses ranged from 0.15-5.22 MPa and the maximum Von Mises' stress ranged from 0.3 7-15.02 MPa. The stress fields were consistently higher in the premolar with a 30 degree preparation taper compared to the 10 degree taper. The attainment of a cavity taper of 100 is still important to minimise stress in the cement lute and is particularly important in teeth with a lower preparation surface area such as a premolar

Bicuspid↗
PubMed1991

Mechanical aspects of a Brånemark implant connected to a natural tooth: an in vitro study.

Mechanical in vitro tests of the Brånemark implant disclose that the screw joint which attaches the prosthetic gold cylinder and the transmucosal abutment to the fixture forms a flexible system. This inherent flexibility seems to match well the vertical mobility of a supporting tooth connected to the implant. Calculations of vertical load distribution based on measured flexibility data demonstrate that the forces are shared almost equally between tooth and implant even without taking the flexibility of the surrounding bone or the prosthesis into account. The therapy of a single Brånemark implant connected to a natural tooth should be considered without any additional element of a flexible nature. Mechanical tests and theoretical considerations, however, indicate that the transverse mobility of the connected tooth should be limited and that the attachment of the prosthesis to the tooth should be of a rigid design to avoid gold-screw loosening.

Dental Abutments↗
PubMed1991

[The effect of bedding type on implant and abutment tooth in tooth/implant-supported bridgework].

17 distal extension cases were treated with IMZ implants supporting a fixed-removable bridge connected to a natural tooth abutment with a precision attachment. Instead of the polyoxmethylene internal shock absorber an identically dimensioned titanium element was incorporated in the implants of every second patient. Patients were monitored on a recall schedule. Implant and tooth mobility, pocket probing depth, and bone loss were the parameters evaluated. The results after a mean incorporation time of 16.5 months indicate that, at least during this initial time of function, there are no differences between a mobile and rigid bedding of the superstructure on the implants.

Aged↗
PubMed1991

[Factors involved in endosseous implant function].

Periodontometric and Periotest mobility parameters of 87 endosseous implants were studied during a period of up to 6 years. Moreover, the condition of the surrounding bone and mucosa was assessed by means of the Periodontal Index (PI). Mobility of endosseous implants was lowest during the first year of insertion and highest at the end of the study. Among all those variables that had a favorable effect on implant function, the length of the implants was in the first line. What is called the osseointegration of dental implants is no longer evident after just a short period of masticatory loading by a denture. Mobility parameters of implants then increase to those of periodontally healthy natural teeth. Improved dental hygiene and cleansing of the periimplant area reduce the incidence of pathological findings and improve the prognosis of dental implants.

Adult↗