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At least 595 records · Page 33Linked to original sources
PubMed1998

Rigidity and retention of root canal posts.

OBJECTIVE: To test the rigidity and the retention into roots of parallel root canal posts, one a spiral vented titanium post and the other a spiral serrated, hollow, stainless steel post. A serrated, stainless steel post was used as the control. MATERIALS AND METHODS: A three-point bending test was used to test rigidity. To test retention, ten posts of each type were cemented into the roots of extracted teeth with a resin cement and the tensile loads required to remove them were compared using Student's t and Mann-Whitney U tests. RESULTS: The serrated stainless steel posts were significantly more rigid than either of the other types. The titanium posts and the stainless steel hollow posts were not significantly different in rigidity. The serrated, stainless steel posts were significantly better retained than either of the other types. The titanium posts showed greater retention than the hollow posts. CONCLUSIONS: Within the limits of the study the stainless steel, serrated posts were superior to the two newer types in terms of rigidity and retention into roots.

Cementation↗
PubMed1993

Crown retention and cyclic loading (in vitro).

Cast gold crowns were luted on extracted and prepared human teeth with zinc phosphate cement and subjected to a fatigue test by cyclic loading. The correlation between crown retention and three retention variables was determined by the fatigue test. The results show that the smallest convergence angle tested, 20 degrees, gave better retention than did angles of 40 degrees and 60 degrees, and that surface roughness, surface size, height, and base diameter of the preparations had no influence on crown retention within the parameter sizes tested.

Crowns↗
PubMedDate not supplied

Developing a tooth restorability index.

UNLABELLED: It is generally agreed that the inherent strength of a tooth is dependent on the remaining dentine. It therefore seems logical that preservation of coronal dentine is important to the survival of intra- and extra-coronal restorations. The clinical assessment of the amount of dentine needed for functional requirements and the strategic value of remaining tooth structure is currently based on clinical opinion. This paper discusses what recommendations have been published and proposes an index that may be useful in assessing the restorability of a tooth. CLINICAL RELEVANCE: An index used to assess the amount and contribution of remaining coronal dentine to resistance and retention form could be of value in treatment planning.

Dental Prosthesis Retention↗
PubMed2006

[Influence of different convergence angles on the retention of cast metal post and core].

Fifty-four simulated tooth roots made of polymethacrylate (PMMA) were divided into six groups according to the root canal convergence angles of 0 degrees, 3.93 degrees, 5.71 degrees, 7.48 degrees, 11.31 degrees, 14.71 degrees. Cast post and cores were manufactured and cemented with Zinc phosphate cement (ZP). The retention capacities of the posts were tested. The bonding strength of ZP at different convergence angles were tested with some casted wafers, and linear regression was made. So the effect of interlocking and the proportion could be calculated. With these results, we made some curvilinear regressions. The results showed that the retention of cast post declined and the bonding strength of ZP fell with the increase of convergence angles. There were significant differences in the bonding strength and retention among groups, P<0.05. The experiment indicates that the dentists should reduce the convergence angles of posts as much as possible to obtain greater retention.

Cementation↗
PubMed1994

Rotational path partial denture design: a 10-year clinical follow-up--Part I.

A conventional removable partial denture that uses a straight path of placement requires that all rests and clasps be seated simultaneously. The incorporation of a dual, curved, or rotational path of placement permits one portion of the framework to be seated first, followed by the remainder of the framework. This procedure usually permits a reduction in the number of clasps in the framework without compromising the biomechanical properties of the prosthesis. Rotational path designs that eliminate clasps reduce tooth coverage by components and often enhance esthetics, thereby contributing to improved patient acceptance.

Dental Abutments↗
PubMed1994

A new method to routinely achieve passive fit of ceramometal prostheses over Brånemark osseointegrated implants: a two-year report.

To maintain osseointegration, it is essential that the prosthesis fit with total passivity because the absence of a periodontal ligament makes the implant unable to adapt its position to a nonpassive framework. The traditional system of building a metal framework by melting over mechanized pieces--called gold cylinders in the Brånemark system--has been modified so these pieces are joined to the metal framework by means of physicochemical bonding. This bond is achieved by treating the metallic surfaces with a Silicoater system and a composite resin cement that sets in the mouth using an improved cementing protocol. In this paper, the clinical viability of this new philosophy, shown over 2 years, is presented. A total of 64 prostheses (39 maxillary and 25 mandibular) supported by 214 abutments, with an average observation period of 9 months, were evaluated. The results show that it is possible to routinely obtain a ceramometal prosthesis with a totally passive circular fitting while maintaining the possibility of retrieval, thus making postceramic soldering unnecessary.

Cementation↗
PubMed1993

Failures in the osseointegration of endosseous implants.

A total of 68 patients, 26 men and 42 women, aged 21 to 86 years, were treated with 204 endosseous implants (TPS, ITI, Bonefit, or Biolox) from 1985 to 1990. They were examined at their latest recall visit approximately 22.5 months after surgery, the range varying greatly between the implant systems used (from 4 to 60 months). Fourteen implants were lost during the observation period because of failures in osseointegration. There were no statistically significant differences in success rates between the implant systems during the observation period. The Periotest values, however, differed between the Bonefit and ITI implants in maxillae (P < .001) and mandibles (P < .01), and between successful and failed TPS implants (P < .001, unpaired t test). In four of the failures, all ITI implants, the prosthetic restorations (fixed dentures and single crowns) had been lost. All other failures were treated by using the previous complete denture. Possible causes of failure included advanced age and poor general health of the patient, complications in the surgical procedures, and compromised oral hygiene.

Adult↗
PubMed1998

Implant-supported prosthesis in a child with hereditary mandibular anodontia: the use of ball attachments.

This report describes the provision of an implant-supported hybrid overdenture in an 8-year-old child with mandibular anodontia. An interdisciplinary approach to treatment planning was employed. Two implant fixtures were placed in the canine regions and ball attachments connected to provide support and retention for the prosthesis. There was only one implant-related complication during the first follow-up year. Close follow-up during the child's growing years is essential for the maintenance of the peri-implant tissues and to replace the prosthesis as mandibular growth occurs.

Anodontia↗
PubMed1996

The effect of endodontic access cavity preparation and subsequent restorative procedures on molar crown retention.

Preparation of an endodontic access cavity through a full crown may affect its retention. This study was undertaken to investigate the effects on molar crown retention of endodontic access cavities and their subsequent restoration. Thirty human molars were mounted in resin, crown preparations were cut and their surface areas were determined. Vented metal copings were cemented with zinc phosphate and the forces required to displace each coping were measured using a tensile-testing machine. The copings were recemented, access cavities were cut and their surface areas determined prior to the displacement forces being re-measured. The copings were recemented, assigned to two groups, and the access cavities were restored--Group 1 with amalgam; Group 2 with glass ionomer (GIC). Displacement forces were re-measured and the copings were recemented. The occlusal margins of the access cavities were bevelled and restored again prior to displacement forces being remeasured. Mean displacement forces were - Group 1: Original (kg force), 37.86 +/- 3.97; After access cavity, 29.28 +/- 3.22; Amalgam, 50.21 +/- 4.71; Amalgam + bevel, 46.45 +/- 6.21. Group 2: Original, 42.77 +/- 4.49; After access cavity, 39.25 +/- 5.91; GIC, 48.11 +/- 3.55; GIC + bevel, 39.63 +/- 5.31. Statistical analyses with paired t tests showed that retentive values with access cavities were significantly lower than with intact crowns. Amalgam or GIC restorations increased retention beyond original values, significantly with amalgam. Bevelled occlusal margins decreased retention of crowns with restored access cavities but this was not significantly different from the original values. A significant relationship existed between total surface areas of the crown preparations, areas of the occlusal tables, and retentive values for crowns without access cavities. The access cavity area, as a proportion of the total area of the preparation, was related to the decrease in retention.

Cementation↗
PubMed1993

Fracture resistance of amalgam and composite resin cores retained by various intradentinal retentive features.

The fracture strengths of amalgam and composite resin cores retained by three types of intradentinal retentive features were compared with the fracture strength of cores retained by four self-threaded retentive pins. Composite resin cores had significantly greater resistance to fracture than amalgam cores with any of the retentive features. The fracture strength of amalgam cores retained by retentive pins was comparable to that of amalgam cores retained by a post with a countersink, but significantly higher than the strength of those retained by slots or channels. The fracture strength of composite resin cores retained by retentive pins was significantly higher than that of composite resin cores retained by any of the alternative intradentinal retentive features.

Analysis of Variance↗
PubMed2002

Incorporation of an ERA attachment for obturator framework design: a clinical report.

Swinglock framework designs have been used to retain obturators for some time. One of the problems with Swinglock designs has been loss of retention due to wear of the metal latch assembly. This clinical report describes the incorporation of an ERA attachment as the latch assembly of a Swinglock framework for an obturator. The premise behind this design was that wear would be at the expense of the nylon retention male component, which is easily interchangeable, rather than the metal component of the assembly. The life of the latch assembly, framework, and prosthesis would thereby be prolonged.

Aged↗
PubMed1999

Surface analysis of failed oral titanium implants.

The aim of the present study was to investigate the surface topography, composition, and oxide thickness of consecutively failed, oral Brånemark implants in order to determine possible causes for failure. The failure criterion was lack of osseointegration manifested as implant mobility. Ten implants were retrieved before loading (early failures) and 12 during a period of function up to 8 years (late failures). At retrieval, early losses did not display any clinical sign of infection. All late failures were radiographically characterized by peri-implant radiolucency and did not show infectious signs with one exception. No implant seemed to be lost due to peri-implantitis (plaque-induced progressive marginal bone loss). Twelve implants were analyzed by scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and depth profiling using a blind protocol. Two pristine fixtures, which underwent the same preparation as the failed implants, were used as controls. In the SEM, control samples were essentially free from macroscopic contamination, whereas failed implants contained varying amounts of tissue residues. AES showed that all surfaces consisted of Ti oxide and varying amounts of additional elements, with C dominating in most cases. Nitrogen and sometimes Na, Ca, P, Cl, S, and Si were detected. The Si contamination was most likely due to ion leaching from the glass vials used for storage. Depth profiles showed a typical oxide thickness of 5-8 nm for all samples. In conclusion, no significant changes in the oxide layer composition or thickness as a result of implantation were observed. The results do not indicate any material-related cause for the failures of these implants. Possible reasons for these failures were impaired healing, asymptomatic infection, and overload.

Adult↗