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At least 19 recordsLinked to original sources
PubMed1994

The periodontal-restorative interface in fixed prosthodontics: tooth preparation, provisionalization, and biologic final impressions--Part II.

The delicate dento-gingival attachment apparatus must be treated with utmost care during all phases of preparation in the crevicular region. There is little room for error within these minute dimensions. The learning objective of this article is to encourage the dentist to be ever vigilant when approaching the subcrevicular tissues during biomechanical tooth preparation, provisionalization, biologic final impressions, and final cementation. Part I, published in the January/February, 1994, issue of PP&A, discussed the emergence profile, retraction, preparation modalities, and provisionalization. Part II discusses final impressions and casts derived from information provided by morphologically correct provisionals, surgically directed provisionalization, and final functional and aesthetic rehabilitative results.

Adult↗
PubMedDate not supplied

The periodontal-restorative interface in fixed prosthodontics: tooth preparation, provisionalization, and biologic final impressions. Part I.

The delicate dento-gingival attachment apparatus must be treated with utmost respect during all preparational maneuvers in the crevicular region. There is little room for error within these minute dimensions. To avoid irreparable harm during chemo-mechanical manipulation of the attachment apparatus, the dentist must always think on a histologic level in order to respect the cellular integrity of the periodontium. The learning objective of this article is to encourage the dentist to be ever vigilant when approaching the subcrevicular tissues during biomechanical tooth preparation, provisionalization, biologic final impressions, and final cementation. Part I discusses the emergence profile, retraction, preparation modalities, and provisionalization; it is presented in this issue. Part II will cover final impressions and casts, derived from information provided by morphologically correct provisionals, surgical provisionalization, and final rehabilitative results; it will appear in the April, 1994, issue of PP&A.

Crowns↗
PubMed2001

The use of real time video magnification for the pre-clinical teaching of crown preparations.

OBJECTIVE: To investigate the effect on the undergraduate learning process of using an alternative method designed to enhance the visual demonstration of taper on full veneer crown preparations (better understanding of the value of taper on preparations early in the teaching programme in restorative dentistry). DESIGN: A comparison between the conventional teaching of full veneer crown preparations and the same teaching with the additional use of a magnified real time video display using a surgical microscope was investigated in this study. OUTCOME MEASURES: The degree of taper was measured for replica full crown preparations and results compared between different cohorts of undergraduates and experimental conditions. RESULT: Undergraduates taught using the real time video produced more accurately tapered preparations. This ability was retained over one year. CONCLUSIONS: A possible explanation for the result was that the use of magnification improved the undergraduates' precise understanding of taper by enhancing their ability to evaluate this critical measurement during the teaching process.

Calibration↗
PubMed1998

A clinical study on abutment taper and height of full cast crown preparations.

Dental students at Tokyo Medical and Dental University are taught to prepare teeth for full cast crowns with a wall taper of 2 to 5 degrees and an occlusal clearance of 1.2 to 1.5 mm. However, it is difficult to achieve such an ideal taper. The objective of this study was to examine the abutment taper and height of teeth prepared for crowns by final-year dental students under clinical supervision. To evaluate the degree of taper and height of the prepared teeth, shadowgraphs of 63 working stone dies were traced. The angles and height of the abutments were then measured on the same tracing. Only 12.7% (8 out of 63 abutments) of the prepared teeth fell within the ideal range of 2 to 5 degrees, and the average taper was 9.5 degrees (19.0 degrees convergence angle). The average abutment height varied from 4.8 mm to 6.9 mm and showed a close relationship with the abutment taper. The average taper, 9.5 degrees, of the present study was larger than the ideal taper; however, it was thought to be clinically acceptable as it is difficult to achieve the ideal taper intraorally.

Crowns↗
PubMedDate not supplied

Auxiliary retention and the role of the core in fixed prosthodontics.

Extensively damaged teeth frequently require placement of a core before preparation to receive an indirect restoration. Dentine pins have traditionally been used to enhance retention and resistance form when coronal dentine is significantly reduced; however, pins are invasive and may produce pulpal or periodontal problems. Cavity design features such as grooves, boxes or retentive pits may be better alternatives. The choice of the core material may also influence the outcome although reliable research data are scarce. Large cores should be considered to have a structural role in supporting the final restoration.

Adhesives↗
PubMed1999

Foundation restorations in fixed prosthodontics: current knowledge and future needs.

PURPOSE: The Ad Hoc Committee on Research in Fixed Prosthodontics established by the Academy of Fixed Prosthodontics publishes a yearly comprehensive literature review on a selected topic. The subject for this year is foundation restorations. METHODS: Literature of various in vitro and in vivo investigations that included technical and clinical articles was reviewed to provide clinical guidelines for the dentist when selecting methods and materials for restoration of structurally compromised teeth. Topics discussed and critically reviewed include: (1) desirable features of foundation restorations, (2) foundations for pulpless teeth, (3) historic perspectives, (4) cast posts and cores, (5) role of the ferrule effect, (6) prefabricated posts, (7) direct cores, (8) foundation restorations for severely compromised teeth, (9) problems and limitations, (10) future needs, and (11) directions for future research. CONCLUSION: This comprehensive review brings together literature from a variety of in vitro and in vivo studies, along with technique articles and clinical reports to provide meaningful guidelines for the dentist when selecting methods and materials for the restoration of structurally compromised teeth.

Dental Casting Technique↗
PubMedDate not supplied

An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 1. Outcome.

PURPOSE: This study reports on the outcome of 515 metal-ceramic fixed partial dentures (FPD) involving 1,209 abutments and 885 pontics placed by one operator in a specialist prosthodontic practice between January 1984 and December 1997. MATERIALS AND METHODS: Clinical and laboratory protocol was kept constant as much as was practical. Each FPD and abutment was given a subjective prognostic rating at the time of cementation. Patients were recalled in 1993 (review 1) and 1998 (review 2). Clinical examination by the author covered 85% of 342 FPDs at review 1 and 82% of 515 FPDs at review 2. At review 2, 37% had been in clinical service for 5 to 10 years (group b), and 34% had been in service for 10 to 15 years (group c). An objective classification protocol was used to assess outcome. RESULTS: At review 2, the FPDs had failure rates of 2%, 7%, and 11% in groups a, b, and c, respectively. There was a significant increase in the failure rate of group c at review 2 (11%) compared with review 1 (5%). Cumulative survival analysis indicated that FPDs have an expected survival rate of 96%, 87%, and 85% at 5, 10, and 15 years, respectively. The applied prognostic rating proved more accurate as clinical service time increased. Outcome was not related to number of units. Cantilevered FPDs, nonvital abutments, and anterior abutments had significantly greater failure rates. Of initially vital abutments, 2% were subsequently endodontically treated. CONCLUSION: Tooth-supported FPDs have an expected survival rate of 85% at 15 years when the described clinical and laboratory protocol is applied.

Adult↗
PubMed2005

In vitro fracture resistance of endodontically treated central incisors with varying ferrule heights and configurations.

STATEMENT OF PROBLEM: The in vitro effectiveness of a uniform circumferential ferrule has been established in the literature; however, the effect of a nonuniform circumferential ferrule height on fracture resistance is unknown. PURPOSE: This in vitro study investigated the resistance to static loading of endodontically treated teeth with uniform and nonuniform ferrule configurations. MATERIAL AND METHODS: Fifty extracted intact maxillary human central incisors were randomly assigned to 1 of 5 groups: CRN, no root canal treatment (RCT), restored with a crown; RCT/CRN, no dowel/core, restored with a crown; 2 FRL, 2-mm ferrule, cast dowel/core and crown; 0.5/2 FRL, nonuniform ferrule (2 mm buccal and lingual, 0.5 mm proximal), cast dowel/core and crown; and 0 FRL, no ferrule, cast dowel/core and crown. The teeth were prepared to standardized specifications and stored for 72 hours in 100% humidity prior to testing. Testing was conducted with a universal testing machine with the application of a static load, and the load (N) at failure was recorded. Statistical analysis was performed with a 1-way analysis of variance and the Tukey Honestly Significant Difference test (alpha=.05). The mode of fracture was noted by visual inspection for all specimens. RESULTS: There was strong evidence of group differences in mean fracture strength ( P <.0001). Following adjustment for all pairwise group comparisons, it was found that the lack of a ferrule resulted in a significantly lower mean fracture strength (0 FRL: 264.93 +/- 78.33 N) relative to all other groups. The presence of a nonuniform (0.5 to 2-mm vertical height) ferrule (0.5/2 FRL: 426.64 +/- 88.33 N) resulted in a significant decrease ( P =.0001) in mean fracture strength when compared with the uniform 2-mm vertical ferrule (2 FRL: 587.23 +/- 110.25 N), the group without RCT (CRN: 583.67 +/- 86.09 N), and the RCT-treated tooth with a crown alone (CRN/RCT: 571.04 +/- 154.86 N). The predominant mode of failure was an oblique fracture extending from the lingual margin to the facial surface just below the insertion of the tooth into the acrylic resin. CONCLUSION: The results demonstrated that central incisors restored with cast dowel/core and crowns with a 2-mm uniform ferrule were more fracture resistant compared to central incisors with nonuniform (0.5 to 2 mm) ferrule heights. Both the 2-mm ferrule and nonuniform ferrule groups were more fracture resistant than the group that lacked a ferrule.

Crowns↗
PubMed2006

Effect of surface treatment on retention of glass-fiber endodontic posts.

STATEMENT OF PROBLEM: The effects of surface treatment on the retention of prefabricated fiber-reinforced epoxy resin posts are not well understood because most studies measure retention shortly after cementation, without artificial aging. PURPOSE: The purpose of this study was to evaluate the effect of surface treatment on the retention of glass-fiber endodontic posts luted with resin cement and subjected to artificial aging. MATERIAL AND METHODS: Thirty-two single-rooted teeth were selected, the coronal aspect of each tooth was removed, and the remaining root received endodontic therapy. Specimens were then divided into 4 groups (n = 8). Post spaces were prepared to a depth of 10 mm by using ISO 90 rotary instruments. The tapered posts received 1 of 4 surface treatments: cleaning with alcohol (Alc), cleaning with alcohol and conditioning with ED-Primer material (Alc-ED), airborne-particle abrasion (Air), or airborne-particle abrasion and conditioning with ED-Primer material (Air-ED). All posts were luted with a composite resin luting agent (Panavia F) after conditioning the canal dentin with autopolymerizing dentin primer (ED-Primer) and without acid etching of the canal dentin. After cementation, the specimens were stored in water at 37 degrees C for 30 days and subjected to simulated aging conditions consisting of 7500 thermal cycles (5 degrees C/55 degrees C) and 300,000 mechanical loading cycles with 30 N. Retention (N) of the posts was measured with a universal testing machine with a crosshead speed of 2 mm/min. The data were analyzed using 1-way ANOVA and the Tukey HSD test (alpha = .05). The dislodged posts were also examined microscopically at x8 and x20 magnification to evaluate the mode of failure. RESULTS: The mean retentive values (N) and SDs of the test groups were as follows: Alc, 375.9 +/- 85.0; Alc-ED, 421.2 +/- 46.8; Air, 534.8 +/- 65.8; and Air-ED, 555.8 +/- 86.9. Airborne-particle-abraded posts had significantly higher retention compared with nonabraded posts (P < .001). Treating the post's surface with ED-Primer material prior to cementation had no significant effect on retention. The failure mode was purely adhesive at the resin cement-post interface for all nonabraded posts. A mixed failure mode, adhesive at the resin cement-dentin interface, at the resin cement-post interface, and cohesive in the resin cement, was observed for airborne-particle-abraded posts. CONCLUSION: Treating the surface of the posts with ED-Primer material before cementation with Panavia F cement produced no significant improvement in the retention of the posts. Airborne-particle abrasion of the surface of the post significantly improved the retention.

Air Abrasion, Dental↗
PubMed2006

Influence of remaining coronal tooth structure location on the fracture resistance of restored endodontically treated anterior teeth.

STATEMENT OF PROBLEM: A restored endodontically treated tooth is less likely to fracture when there is axial tooth structure between the core base and preparation finish line. However, an accurate prognosis requires knowing whether fracture resistance depends on a complete circumferential distribution of tooth structure or tooth structure in a specific location related to the applied force. PURPOSE: This in vitro study investigated the fracture resistance of restored endodontically treated teeth when residual axial tooth structure was limited to one half the circumference of the crown preparation. MATERIAL AND METHODS: Fifty extracted maxillary anterior teeth were sectioned 18 mm from their apices, endodontically treated, and divided into 5 groups of 10 teeth each. Four groups were prepared with full shoulder crown preparations having axial wall heights of 2 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, one half of the axial tooth structure was removed, palatally, labially, or proximally, and groups were identified according to the site of retained coronal tooth structure. For the fifth group, all axial tooth structure was removed to the level of the preparation shoulder. Thus, in 1 group the axial walls were circumferential, 360 degrees around the preparations (Complete group), in 3 groups the axial walls were continuous for 180 degrees (Palatal, Labial, and Proximal groups), and the last group had no retained coronal tooth structure incisal to the finish line (Level group). All 50 prepared teeth were then restored with quartz fiber posts (Bisco), composite resin (Bisco) cores, and metal crowns. A universal testing machine compressively loaded the tooth specimens from the palatal at a crosshead speed of 0.5 cm/min at an angle of 135 degrees to the long axis of teeth until failure occurred. A survival analysis was conducted using a log-rank test followed by Holm-Sidak pairwise tests (alpha=.05) to detect significant differences in median failure load between groups. The mode of failure was determined by visual inspection of all specimens. RESULTS: The median failure load (P<.001) was 607 N, 782 N, 358 N, 375 N, and 172 N for the Complete, Palatal, Labial, Proximal, and Level groups, respectively. The predominant mode of failure was an oblique palatal to facial root fracture for the groups with remaining coronal tooth structure. In the Level group, post debonding was the predominant mode of failure. CONCLUSION: For restored endodontically treated teeth that do not have complete circumferential tooth structure between the core and preparation finish line, the location of the remaining coronal tooth structure may affect their fracture resistance.

Dental Restoration Failure↗
PubMed1997

Effect of different surface textures on retentive strength of tapered posts.

STATEMENT OF PROBLEM: Tapered posts allow for the preservation of tooth substance in the fragile apical area and are advantageous in clinical situations where they conform to the root and canal configuration of endodontically treated teeth. However, their lower retention compared with passive parallel-sided or active threaded posts is a disadvantage. PURPOSE: This study determined the retentive strength of tapered titanium posts with different surface textures and examined the effect of roughening dentinal walls of the prepared post space. MATERIAL AND METHODS: Posts with four surface configurations (smooth, with and without grooves, and sandblasted, with and without grooves) were examined when cemented in extracted anterior teeth. RESULTS: The smooth post showed the lowest retentive strength. Sandblasting the smooth post more than doubled its retentive strength. The retentive strength of both smooth and sandblasted posts could be further increased by the addition of circumferential grooves. Roughening the dentinal walls of the prepared post space increased the retentive strength of sandblasted posts with and without grooves even more. CONCLUSIONS: These findings indicated that, when a tapered post is used, roughening the dentin canal wall, as well as sandblasting and grooving the post, can provide statistically significant additional resistance to dislodgment.

Analysis of Variance↗
PubMed1998

Tooth structure loss apical to preparations for fixed partial dentures when using self-limiting burs.

STATEMENT OF PROBLEM: Burs with guide pins may be used to limit the depth of tooth preparation for fixed partial dentures. The effects of guide pins on tooth structure apical to the finish line after tooth preparation for fixed partial dentures has not been recorded. PURPOSE: This in vitro study recorded loss of tooth structure within 1.0 mm apical to the finish line of teeth prepared with straight cylinder and tapered cylinder self-limiting burs and one conventional bur. MATERIAL AND METHODS: Forty-five extracted human teeth were randomly divided into three groups. The facial surface of each tooth was prepared with two types of diamond burs with guide pins and a conventional diamond for the control. The surface was profiled before and after tooth preparation. Profiled surfaces were analyzed and the groups were compared using analysis of variance and the Tukey-Kramer HSD test (alpha = 0.05). RESULTS: No significant difference was recorded between the control group and the group prepared with a round-ended tapered cylinder self-limiting pin. However, there was a statistically significant difference between the control and cylindrical pin groups, and between the two groups prepared with self-limiting diamonds. CONCLUSION: This study revealed abrasion apical to the finish line of the preparation in all groups. The cylindrical guide pin group exhibited the greatest loss of tooth surface.

Analysis of Variance↗
PubMed1999

Survival of Dicor glass-ceramic dental restorations over 14 years. Part II: effect of thickness of Dicor material and design of tooth preparation.

STATEMENT OF PROBLEM: The influence of different restorative design features on the long-term survival of Dicor glass-ceramic restorations is not well understood. PURPOSE: This study examined the relationship of different types of restorations and methods of preparation with the survival of Dicor glass-ceramic restorations functioning in vivo. MATERIAL AND METHODS: A total of 1444 Dicor glass-ceramic restorations were placed on the teeth of 417 adults. Failure was defined as a restoration that required remake because of material fracture. Survival of restorations of different types and with different methods of preparation was described by using Kaplan Meier survivor functions. Statistical significance between restoration type and preparation method was determined with the log rank test. RESULTS: Probability of survival of a typical partial coverage restoration was 92% at 11.3 years. There was no statistically significant difference between the survival of inlay or onlay restorations. For the 91 cores used for pulpless teeth, none failed over a total cumulative monitoring period of 419 years. There was no significant difference in survival of acid-etched Dicor restorations that were placed on shoulder or chamfer preparations. Thickness measured at the midpoint of the labial, lingual, mesial, distal, and midocclusal surfaces did not relate to risk of failure. CONCLUSIONS: The majority of Dicor glass-ceramic partial coverage inlay and onlay restorations and cores survived over time. Survival of restorations with either chamfer or shoulder preparations did not differ whether the restoration was acid-etched. Thickness of the restoration measured at the midaxial point of each surface did not relate to survival.

Acid Etching, Dental↗