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At least 19 recordsLinked to original sources
PubMed1992

Loads and designs of screw joints for single crowns supported by osseointegrated implants.

The problem of screw stability was approached in this study by calculating the maximum occlusal forces in vivo for patients with single implant restorations (which use only one screw to secure the prosthetic reconstruction to the implant). The measurements of occlusal forces together with geometric parameters for the individual patients were used to determine the necessary holding capabilities of the screw joint. Different screw designs were tried in bench test situations and the results were compared with clinical situations. A gold alloy screw with a flat head and high tightening torque (35 Ncm) produced the best results.

Bite Force↗
PubMed1992

Solving the problem of violated intermaxillary space caused by poor pre-planning and improper placement of endosseous implants: a case report.

Every dental implant patient needs thorough evaluation and pre-surgical planning. It is imperative for the practitioner to have absolute knowledge of the implant system to be used. Nevertheless, sometimes we find ourselves in very difficult, almost unrestorable, situations. Often, we cannot rely on the implant manufacturers, and we have to be ready to customize some parts in order to solve difficult clinical situations. This case report shows how customized magnet keepers were fabricated by use of plastic IME's as casting patterns in order to solve the problem of violated intermaxillary space.

Dental Alloys↗
PubMed1992

To vent or not to vent?

The complete seating of full coronal restorations during cementation is hindered by the inability of cement to flow from the internal surface of the crown, and possible binding of the crown on the tooth. Perforation venting is an effective technique to allow full seating but requires repair of the perforation. Provision of space between the crown and the tooth for cement flow is also an effective technique, and does not require repair of a perforation. Such spacing is commonly achieved with die spacer, and has the added possibility of decreasing crown deformation during cementation by diminishing binding between the crown and the tooth. A disclosing agent is effective in aiding complete seating by identifying areas of binding. These areas can subsequently be adjusted, which will allow more complete seating. The placement of an appropriate amount of cement in the crown or on the preparation is an important addition to cementation technique.

Cementation↗
PubMed2026

Clinical accuracy and short-term outcomes of intraoral photogrammetry for complete-arch implant rehabilitation: A retrospective multicentre study on 35 patients.

OBJECTIVES: To evaluate the clinical accuracy and short-term outcomes of complete-arch implant-supported fixed dental prostheses (ISFDPs) fabricated using an intraoral photogrammetry (IPG) based digital workflow in completely edentulous patients. METHODS: This multicenter retrospective clinical study included 35 patients rehabilitated with 52 complete-arch ISFDPs (10 FP1, 18 FP2 and 24 FP3 restorations) supported by 221 implants. All definitive prostheses were designed and fabricated using a fully digital workflow initiated by IPG acquisition with the Aoralscan Elite IPG® (SHINING 3D). The primary outcome was clinical accuracy, assessed at definitive prosthesis delivery through evaluation of passive fit using the Sheffield test and radiographic verification. Secondary outcomes included biologic and prosthetic complications, as well as implant and prosthesis survival rates during the follow-up. RESULTS: Passive fit was achieved in all definitive restorations (100%). Radiographic evaluation confirmed accurate marginal adaptation at the implant-prosthesis interface in all cases. No statistically significant differences in clinical accuracy were observed according to treated arch, number of supporting implants, or prosthetic design (P > .05). During a mean follow-up period of 12.1 ± 3.5 months, biologic and prosthetic complications were limited and generally minor. Implant survival was 99.5%, and prosthesis survival was 100%. CONCLUSIONS: Within the limitations of this retrospective clinical study, the IPG based workflow demonstrated high clinical accuracy and predictable short-term outcomes for complete-arch implant rehabilitation, consistently enabling passive fit and favorable prosthetic performance. CLINICAL RELEVANCE: IPG may represent a clinically reliable and predictable approach for complete-arch digital implant impression acquisition. The high rates of passive fit, together with the low incidence of biologic and prosthetic complications observed in this multicenter clinical study, support the use of IPG based workflows for the fabrication of complete-arch ISFDPs.

Humans↗
PubMed1992

Occlusal considerations in periodontal prosthetics.

The objectives in establishing a physiologic occlusion for periodontal-prosthetic patients are: (1) the minimization of lateral forces on the teeth and (2) the direction of forces along the long axis of the roots. Functional precision of occlusion is not an objective for this type of patient; rather, stability, with freedom of movement, is the goal. This paper gives an in-depth discussion of these objectives and provides an additional look at dental implant therapy and occlusion.

Dental Articulators↗
PubMed1992

Fixed implant-supported prostheses with welded titanium frameworks.

Eighty-six edentulous patients provided with Brånemark implants were randomly selected for fixed prostheses with modified framework designs. This study describes alternative laboratory techniques in which premachined titanium components are welded together to form the framework. Clinical experience, following the patients for 1 year after placement, indicates that it is a predictable technique with a similar pattern of complications as experienced by patients with cast frameworks supported by implants. The prostheses are considered to be slightly more bulky than cast frameworks, but seem to have, on a clinical level, a better fit to the implants.

Adult↗
PubMed1992

Fixture design and overload influence marginal bone loss and fixture success in the Brånemark system.

It has been documented that the long-term clinical outcome of the Brånemark system is very favourable. However, failures do occur before and after loading. This study examined the differences in marginal bone loss between standard and self-tapping fixtures and attempted to explain excessive marginal bone loss or loss of osseointegration during the first 3 years of loading. Marginal bone loss (scored on long cone radiographs) and fixture failure rate were compared for different fixture designs. For standard fixtures, in comparison with self-tapping fixtures, the failure rate was clearly higher before as well as after loading. However, for successful fixtures no difference in marginal bone loss was observed. For the conical fixtures an increased marginal bone loss around the smooth part was observed. The effect of fixture overload, marginal bone height and loss of osseointegration was examined in 69 patients with 1 and 15 patients with 2 fixed full prostheses, and in 9 patients with an overdenture in the upper jaw. Excessive marginal bone loss (more than 1 mm) after the first year of loading and/or fixture loss correlated well with the presence of overload due to a lack of anterior contact, the presence of parafunctional activity and osseointegrated full fixed prostheses in both jaws.

Adolescent↗
PubMed1992

Fatigue life of three core materials under simulated chewing conditions.

There has been an increase in the use of prefabricated post systems to restore endodontically treated teeth. Various restorative materials are being used as core buildups on these posts. The purpose of this study was to compare three core materials that are used with prefabricated stainless steel posts. Two types of prefabricated posts were placed in extracted teeth, followed by core buildups in amalgam, composite resin, or glass ionomer. The teeth were prepared for full cast crowns with the margins of the crown preparation extending 0.5 to 1.0 mm below the margins of the core buildup. Crowns were fabricated and cemented with zinc phosphate cement. A custom-designed chewing machine was used to cyclically load the teeth with vertical and horizontal forces for one million cycles or until failure occurred. Results indicated highly significant differences in the survival of the post-core-crown restorations depending on which core buildup material was used. Amalgam cores had the lowest failure rate, followed by composite resin cores. All teeth restored with crowns over glass-ionomer core buildup failed. The type of prefabricated post used had no effect on the survival of the post-core-crown restorations regardless of the core buildup used.

Bite Force↗
PubMed1992

Mechanical resistance of cemented post and core buildups for ITI-Bonefit implants.

In order to improve the prosthetic versatility of the ITI-Bonefit implant system, a clinical technique was tested whereby a custom made post and core buildup was cemented into implants. Specially designed threaded and serrated posts were machined in precious metal. After the posts were seated into the threaded channel of the implants, cores were built using autopolymerizing resin. Those were then cast and cemented into the implants. For the remainder of the procedure, the buildups were treated like natural abutments using conventional prosthodontic techniques. Mechanical tests were performed to assess the clinical viability of these buildups. The ultimate tensile strength of annealed posts lies in the 700-800 N range. By comparison, the pull-out resistance of posts cemented into natural roots ranged between 108 and 177 N, and the maximum pull-out resistance of manufactured abutments is about 1040 N. When the resistance against lateral forces was tested, the cemented build-ups ranged between 981 and 1128 N, whereas natural teeth fractured between 206 and 903 N depending on the diameter of the root. Manufactured abutments failed at stress levels of about 1020 N. Considering these favorable results, we conclude that the technique described above can be applied clinically for further investigation. Additionally, we suggest some modifications in implant design that would enhance the versatility of the system.

Analysis of Variance↗
PubMed1992

Influence of dimensional factors and heat treatment on permanent deformation of wrought wire clasps.

The purpose of this study is to examine the fatigue profiles of wrought wire clasps during the clinical use. Cobalt-chromium-nickel alloy wires were bent into circular beams, which dimensions and fabrication methods were similar to the clinical cases. Deflections of 0.5 mm in a normal direction were applied 10,000 times to the tips of clasp arm and permanent deformations were measured. The following results were obtained. 1) The clasp arms with larger cross sectional diameter, shorter length and smaller radius of curvature showed larger amounts of permanent deformation. 2) The amounts of permanent deformation of the clasp arm remarkably decreased by electric resistance soldering and decreased further more by heat treatment at 500 degrees C for 10 minutes after soldering regardless of the number of deflection. From the results of this study, it was concluded that dimensional factors and heat treatment influenced the permanent deformation of the wrought wire clasps remarkably. Therefore, considering these factors, wrought wire clasps could be designed to reduce permanent deformation.

Chemical Phenomena↗
PubMed1992

Effects of labial margin design on stress distribution of a porcelain-fused-to-metal crown.

PURPOSE: This study compared the stress distribution of three porcelain-fused-to-metal labial margins on a central incisor under simulated occlusal force. MATERIALS AND METHODS: The margin designs were rounded-shoulder, rounded-shoulder with a bevel, and a chamfer. RESULTS: Evaluation of mean equivalent Mises tensile stress did not show any difference at the cement-dentin and metal-cement interfaces of the three margins. The mean equivalent Mises tensile stress at the porcelain-metal interface was found to be significantly higher for rounded-shoulder when compared with the chamfer. There was no significant difference in the axial stresses along the three interfaces among the three margin designs. Statistically significant differences in radial stresses at some interfaces of the three margin designs were found. CONCLUSION: The change of cement thickness of the chamfer margin is significantly greater than that of either the rounded-shoulder or the bevelled-shoulder margin.

Crowns↗
PubMed1992

Overview of factors important in implant design.

Forty-two percent of the population over the age of 65 is totally edentulous. The use of dental implants as a means of treating these patients has accelerated in the last decade, and there are now 300,000 dental implants used in the United States. It is therefore imperative that a greater understanding of the parameters which govern the long-term success of implants be developed. In order for the effectiveness of implants to be better quantified, a fundamental, quantitative understanding of the physical parameters governing the complex synthetic material/tissue aggregate is needed. The design of an "optimal" implant requires the integration of material, physical, chemical, mechanical, biological, and economic factors. The approach taken for a specific property objective to be met should be based on a materials science approach, in which the synergistic relationships among processing, composition, structure, and properties are characterized. Implant success is a function of biomaterials and biomechanical factors, including: materials and material processing; mechanisms of implant/tissue attachment; mechanical properties; implant design; loading type; tissue properties; stress and strain distributions; initial stability and mechanisms of enhancing osseointegration; biocompatibility; and surface chemistry, mechanics, and bone-binding ability of the implant. This paper presents an overview of physical parameters important to implantology. Following a general presentation of implantology concepts, the physical parameters listed above are discussed in greater detail.

Analysis of Variance↗