Shear bond strength of zirconia-based ceramics veneered with 2 different techniques.

STATEMENT OF PROBLEM: Delamination of veneering ceramic is reported as one of the most frequent problems associated with veneered zirconia restorations. PURPOSE: The purpose of this in vitro study was to compare the shear bond strength of sintered lithium disilicate to that of pressed fluorapatite glass-ceramic on a zirconia substrate. MATERIAL AND METHODS: Thirty zirconia blocks (20×15×2.5-mm thick) were cut, sintered, and divided into 2 groups. A pressed group, a zirconia liner, was applied and sintered, and the lost-wax technique was used to fabricate fluorapatite glass-ceramic blocks (3×3×3 mm), which were pressed onto the sintered zirconia blocks. A sintered group, lithium disilicate blocks, were cut (3×3×3 mm) and sintered to the sintered zirconia blocks by using a low-fusing glass-ceramic. The thickness of the low-fusing glass-ceramic was standardized to approximately 80 µm prior to sintering. The shear bond strength levels of the specimens were tested using a universal testing machine at a crosshead speed of 1 mm/min until failure. Representative separated specimen surfaces were examined for fracture characteristics, using scanning electron microscopy at ×50 magnification. Debonding data were compared using a 2-tailed, unpaired Student t test (α=.05). RESULTS: The sintered group demonstrated mean shear bond strength values (41.2 ±6.3 MPa), which were significantly higher (P<.001) than those of the pressed group (21.3 ±4.3 MPa). CONCLUSIONS: Sintering of computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate ceramic achieved higher shear bond strength values than pressing fluorapatite glass-ceramic to zirconia substructure material.

Clinical efficacy of veneered zirconium dioxide-based posterior partial fixed dental prostheses: five-year results.

STATEMENT OF PROBLEM: In recent years, zirconium dioxide-based partial fixed dental prostheses (FDP) have been suggested as an alternative treatment to traditional metal ceramic FDPs. However, clinical studies evaluating their longevity and related complications are limited. PURPOSE: The purpose of this cohort clinical study was to assess the efficacy of zirconium dioxide-based posterior 3-unit FDPs. MATERIAL AND METHODS: Twenty 3-unit posterior FDPs (Lava) were placed in 16 participants missing a second premolar or a first molar. All participants met specific inclusion and exclusion criteria and provided informed consent. All teeth were prepared in a standardized manner: occlusal reduction of 1.5 to 2 mm; axial reduction of 1 to 1.5 mm; a 1.0 mm 360-degree rounded shoulder placed 0.5 mm subgingivally on the facial aspect and supragingivally on the lingual aspect on sound tooth structure; and rounded internal line angles. Definitive impressions were made with vinyl polysiloxane impression material. Frameworks were fabricated by using computer-aided design and computer-aided manufacturing (CAD/CAM) technology with a uniform retainer thickness of 0.6 mm and a minimal connector surface area of 9 mm(2). Restorations were luted with resin-modified glass ionomer cement (Rely-X Luting). Participants were recalled at 2 weeks, 6 months, and 12 months, and thereafter, annually for up to 60 months. Clinical fracture measurements, marginal discoloration, marginal adaptation, radiographic proximal recurrent caries, and periapical pathoses were assessed over time by using modified Ryge criteria. The probability distributions of these variables were calculated for the baseline data and for the recall data. An analysis of survival was made by using the Kaplan-Meier method. RESULTS: Eighteen FDPs were clinically evaluated at 5 years and 1 at 48 months. Fifteen were rated Alpha for fracture measurements, and 2 were rated Bravo (minor chipping of veneering porcelain and not requiring restoration replacement). Two were rated Charlie (major chipping of veneering porcelain and requiring restoration replacement). Eighteen FDPs were rated Alpha for marginal integrity, and 1 rated Bravo. All restorations were rated Alpha for marginal discoloration. One participant experienced root fracture after 60 months, while another was treated surgically for a periapical pathosis on an endodontically treated abutment. CONCLUSIONS: Zirconium dioxide-based posterior 3-unit FDPs performed well after 5 years of service.

The accuracy of implant impressions: a systematic review.

STATEMENT OF PROBLEM: Various implant impression techniques, such as the splint, pick-up, and transfer techniques, have been introduced, and some techniques may be more accurate than others. Also, clinically, some factors, including the angulation or depth of implants, may affect the accuracy of the implant impressions. PURPOSE: The purposes of this review were to: (1) investigate the accuracy of published implant impression techniques, and (2) examine the clinical factors affecting implant impression accuracy. MATERIAL AND METHODS: An electronic search was performed in June 2008 of MEDLINE, EMBASE, and Cochrane Library databases with the key words implant, implants, impression, and impressions. To be included, the study had to investigate the accuracy of implant impressions and be published in an English peer-reviewed journal. In addition, a hand search was performed to enrich the results for the time period from January 1980 to May 2008. After executing the search strategies, 41 articles were selected to be included in the review process. RESULTS: All of the selected articles were in vitro studies. Of the 17 studies that compared the accuracy between the splint and nonsplint techniques, 7 advocated the splint technique, 3 advocated the nonsplint technique, and 7 reported no difference. Fourteen studies compared the accuracy of pick-up and transfer impression techniques, and 5 showed more accurate impression with the pick-up techniques, 2 with the transfer technique, and 7 showed no difference. The number of implants affected the comparison of the pick-up and splint techniques. Eleven studies compared the accuracy of polyether and vinyl polysiloxane (VPS), and 10 of 11 reported no difference between the 2 materials. Four studies examined the effect of implant angulation on the accuracy of impressions. Two studies reported higher accuracy with straight implants, while the other 2 reported there was no angulation effect. CONCLUSIONS: The review of abutment level or implant level internal connection implants indicated that more studies reported greater accuracy with the splint technique than with the nonsplint technique. For situations in which there were 3 or fewer implants, most studies showed no difference between the pick-up and transfer techniques, whereas for 4 or more implants, more studies showed higher accuracy with the pick-up technique. Polyether and VPS were the recommended materials for the implant impressions.

The efficacy of posterior three-unit zirconium-oxide-based ceramic fixed partial dental prostheses: a prospective clinical pilot study.

STATEMENT OF PROBLEM: Although zirconium-oxide-based restorations for fixed partial denture prostheses (FPDPs) are available for use, clinical studies evaluating their longevity and related complications have not been published. PURPOSE: The aim of this pilot clinical study was to assess the efficacy of zirconia-based posterior 3-unit FPDPs. MATERIAL AND METHODS: Twenty 3-unit posterior FPDPs (Lava) were placed in 16 subjects who were missing a second premolar or a first molar, met specific inclusion and exclusion criteria, and provided informed consent. All teeth were prepared in a standardized manner: occlusal reduction of 1.5 to 2 mm; axial reduction of 1 to 1.5 mm; a 1.0-mm, 360-degree rounded shoulder placed 0.5 mm subgingivally on the facial aspect and supragingivally on the lingual aspect on sound tooth structure; and rounded internal line angles. Impressions were made with vinyl polysiloxane (Express) impression material. Frameworks were fabricated using a computer-aided design/computer-assisted manufacturing technique with a retainer thickness of 0.6 mm, and a minimal connector surface area of 9 mm(2). Restorations were luted with resin-modified glass-ionomer cement (Rely X luting). Recall appointments were made after 2 weeks and 6, 12, 18, 24, and 36 months. Clinical fracture resistance, marginal discoloration, marginal adaptation, radiographic proximal recurrent decay, and periapical pathoses were assessed over time using modified Ryge criteria. The probability distributions of these variables were calculated for the baseline data as well as for recall data. RESULTS: Mean follow-up was 31.2 months. Fifteen restorations were rated Alpha in all measured parameters. Minor chipping of veneering porcelain was detected in 5 restorations rated Bravo for clinical fracture resistance and Alpha for all other assessed parameters. One restoration was rated Bravo in terms of marginal integrity at 36 months. CONCLUSIONS: Zirconia-based posterior 3-unit FPDPs performed well after short-term service.

Orthodontic extrusion and orthodontic extraction in preprosthetic treatment using implant therapy.

It has been well documented that orthodontic extrusion is a valuable adjunct to site preparation prior to implant placement. This treatment modality may also be utilized to salvage and restore an extensively damaged tooth for use as a natural abutment. By controlling the orthodontic phase, the hard and soft tissues can be manipulated into a position that permits aesthetic restoration. This article demonstrates the use of this procedure as an adjunct to site preparation and in conjunction with conventional restorative therapy.

Implants in mandibular resection.

This clinical report presents a method of satisfactorily restoring a patient with a Class V mandibular defect. Conventional restoration of this patient would have consisted of a soft tissue-supported prosthesis with its inherent instability and associated problems. The use of implants has provided stability and function unobtainable with conventional prosthesis for this patient.

Preprosthetic surgery.

Patients who require complete and removable partial dentures may find the adaptation process quicker and easier after certain pre-prosthetic surgical procedures. Incorporating selected surgical procedures into a treatment plan for removable dentures could be the determining factor between success and failure of the prosthesis. The rationale in pre-prosthetic surgery is to provide the patient an adequate restoration to function with a minimum of surgical morbidity. This article describes various procedures and considerations for their use.

Temporomandibular joint range of motion: a ratio of interincisal opening to excursive movement in a healthy population.

Range of motion is used in the examination and diagnosis of many joints. A simple method to measure and record temporomandibular joint range of motion is presented. Correlation of mandibular movement to excursive or lateral movements for a healthy population is described. The maximum incisal opening and lateral movements of 75 subjects, aged 20-50 years, were recorded. The average of maximum opening to lateral movements was found to be 4.4 to 1. A significant correlation or ratio of mandibular movement for use in diagnoses and treatment planning is discussed.

A spacer that facilitates construction of implant-supported prostheses frameworks.

This article describes a technique that uses polyvinlysiloxane (PVS) putty impression material to create adequate space between the tissue and inferior margin of a framework in pattern construction for implant supported hybrid dentures. This spacer is easily retrieved from the cast, so the dental technician can evaluate and adjust the spacer to a standardized thickness and shape it to form the framework's underside. Basic framework construction for implant hybrid dentures is also reviewed, including specific dimensions, acrylic retentive features and passive construction. PVS putty impression material is easy to obtain, maintains dimensions well and is easy to shape, making it an excellent choice for use as a spacer and a matrix to preserve the position of denture teeth during fabrication.

A method to position replacement dies accurately on a fixed partial denture master working cast.

Impressions are often remade because of insufficient detail in one of many preparations. These impressions may be salvaged with a replacement die procedure. Some transfer or replacement die procedures fail to position the dies accurately; other procedures involve many steps in the fabrication of copings. This article describes a method that quickly and accurately positions a replacement die in a fixed partial denture master working cast.

A time-saving method for performing a clinical remount procedure with complete dentures.

Occlusal disharmony is one cause of uncomfortable dentures. Remounting complete dentures to eliminate occlusal discrepancies at the time of delivery has several advantages. This time-saving method for clinically remounting complete dentures is easy and quick and helps preserve denture supporting tissues.