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PubMed2004

The effect of a resin-based sealer on crown retention for three types of cement.

STATEMENT OF PROBLEM: In an effort to control postoperative sensitivity, dentin sealers are being applied following crown preparation with little knowledge of how crown retention might be affected. A previous study demonstrated no adverse effect when using a glutaraldehyde-based sealer, and existing studies have shown conflicting results for resin-based products. PURPOSE: This study determined if a resin sealer applied to prepared dentin affected retention of cemented castings when using 3 common types of luting agents. MATERIAL AND METHODS: Extracted human molars (n=55) were prepared with a flat occlusal, 20-degree taper, and 4-mm axial length. The axial surface area of each preparation was determined and specimens were distributed equally among groups (n=11). A 2-step, single-bottle adhesive system (One Step) was used to seal dentin following tooth preparation. Sealer was not used on the control specimens except for the modified-resin cement (Resinomer) specimens that required use of adhesive with cementation. Using ceramometal high noble alloy (Olympia), a casting was produced for each specimen and cemented with a seating force of 20 Kg using either zinc phosphate (Fleck's), glass ionomer (Ketac-Cem) or modified-resin cement (Resinomer) with the single-bottle adhesive. Castings were thermal cycled at 5 degrees C and 55 degrees C for 2500 cycles; then removed along the path of insertion using a universal testing machine at 0.5 mm/min. A single-factor ANOVA was used with alpha=.05. The nature of failure was also recorded and the data analyzed with a chi-square test. RESULTS: Mean dislodgment stresses for unsealed and sealed conditions were 3.7 +/- 1.0 and 2.2 +/- 0.8 MPa for zinc phosphate; 2.7 +/- 1.2 and 4.2 +/- 0.9 MPa for glass ionomer, respectively (P<.001). Retentive stress of castings cemented with modified-resin cement was 6.4 +/- 1.7 MPa. With resin sealer in combination with zinc phosphate, cement resided totally on castings in 82% of the situations and was on both surfaces without sealer. The tooth failed before casting dislodgment in 9 of 11 specimens cemented with modified-resin cement. CONCLUSIONS: Resin sealer decreased casting retentive stress by 42% when used with zinc phosphate. However, sealer use resulted in 55% increased retention when used with glass ionomer. The modified-resin cement produced the highest mean dislodgment stress, nearly always exceeding the strength of the tooth.

Analysis of Variance↗
PubMed2003

Ensuring retention for crowns and fixed prostheses.

Crowns and fixed prostheses are well-proven, accepted and routinely used restorations. However, they occasionally come loose from tooth preparations. Many things can cause these failures. In this article, I have discussed the following reasons for lack of adequate retention of crowns and fixed prostheses: inadequate tooth preparation; too much trust in dentin bonding agents and lack of adequate tooth buildup; tooth preparations that lack irregularities; improper selection of cements; and lack of postoperative occlusal adjustment.

Crowns↗
PubMed2000

Compressive shear strength of core materials and restoring techniques.

In this study, ninety extracted endodontically treated mandibular molars were mounted in acrylic resin blocks. Five groups of eighteen extracted teeth were prepared by two different techniques. A peripheral shelf 2 mm deep and 1.4 mm wide was prepared as a first technique, while TMS pins were used in the second group. The teeth were then restored with five different core materials: silver-reinforced glass-ionomer, resin-modified glass-ionomer, self-cured glass-ionomer, polyacid-modified composite resin, and titanium-reinforced composite resin. An Instron testing machine was used to apply shear force at a crosshead speed of 2 mm/min until fracture occurred. The results were obtained statistically using analysis of variance and least significant difference tests. According to the results of this study, Ti-core and composite resin were the strongest core materials when subjected to shear forces, and the most retentive preparation design was the vertical-pin design. The fractures of these materials with a vertical-pin design were mostly seen at the core and the tooth.

Analysis of Variance↗
PubMedDate not supplied

Retentiveness of dental cements used with metallic implant components.

There is limited dental literature evaluating the retentive capabilities of luting agents when used between metal components, such as cast metal restorations cemented onto machined metal implant abutments. This study compared the retentive strengths of 5 different classes of luting agents used to cement cast noble metal alloy crowns to 8-degree machined titanium cementable implant abutments from the Straumann ITI Implant System. Sixty prefabricated 5.5-mm solid titanium implant abutments and implants were used; 30 received the standard surface preparation and the other 30 received an anodized surface preparation. Anodized implant components were used to reflect current implant marketing. Sixty castings were fabricated and randomly paired with an abutment and implant. A total of 12 castings were cemented onto the implant-abutment assemblies for each of the 5 different luting agents (zinc phosphate, resin composite, glass ionomer, resin-reinforced glass ionomer, and zinc oxide-non-eugenol). After cementation, the assemblies were stored in a humidor at room temperature prior to thermocycling for 24 hours. Each casting was pulled from its respective abutment, and the force at which bond failure occurred was recorded as retentive strength. A statistically significant difference was found between the 5 cements at P < or = .001. Of the cements used, resin composite demonstrated the highest mean retentive strength. Zinc phosphate and resin-reinforced glass-ionomer cements were the next most retentive, while glass ionomer and zinc oxide-non-eugenol cements demonstrated minimal retention. In addition, retention was not altered by the use of an anodized abutment surface.

Adhesiveness↗
PubMed2003

Post design and the optimally restored endodontically treated tooth.

The basics for the sound restoration of endodontically treated teeth have not changed despite the advent of new materials and techniques. Adequate retention for posts and crowns, resistance to cyclic shearing forces, minimal insertional stresses, and even distribution of functional stresses are prime requirements that cannot be compromised without jeopardizing the longevity of the final restoration.

Crowns↗
PubMed1999

Effect of tooth surface roughness on marginal seating and retention of complete metal crowns.

STATEMENT OF PROBLEM: Retention and marginal adaptation factors have major influence on the failure of cemented complete veneer crowns. PURPOSE: This study investigated the effect of axial surface roughness on the marginal seating and retention of silver-palladium crowns luted with zinc phosphate, glass ionomer, and resin cements. MATERIAL AND METHODS: Coarse and fine diamond stones were used to create various surface roughnesses of premolars. A milling machine was used to control the height and angle of the axial walls of tooth preparations. Ten cast metal crowns in 6 subgroups were luted with 3 cements (Phosphacap, Fuji Cap I, and Panavia 21). Marginal seating was recorded with a Digimatic indicator. Retention was determined by measuring the tensile force required to remove a metal crown with a Lloyd testing machine. RESULTS: Two-way analysis of variance revealed statistically significant differences (P <.001) in retention for both luting cements and surface roughness. No significant difference was recorded for marginal seating relative to roughness (P =.860) and interaction effects (P =.204). Tukey-HSD tests revealed substantial differences in retention among Phosphacap, Fuji Cap I, and Panavia 21 cements. Significant differences were not confirmed in marginal seating between Fuji Cap I and Phosphacap cements with coarse diamonds, and Phosphacap and Panavia 21 cements with fine diamonds. CONCLUSIONS: The best retention for complete metal crown was demonstrated for tooth preparations ground with coarse diamonds and cemented with Panavia 21 cement. Differences in axial surface roughness had no effect on the marginal seating of the complete metal crowns.

Analysis of Variance↗
PubMed2001

The use of reinforced composite resin cement as compensation for reduced post length.

STATEMENT OF PROBLEM: Cements that yield high retentive values are believed to allow use of shorter posts. PURPOSE: This study investigated the use of reinforced composite resin cement as compensation for reduced dowel length. MATERIAL AND METHODS: The retention values of stainless steel posts (parallel-sided ParaPost and tapered Dentatus in 5-, 8-, and 10-mm lengths) luted with Flexi-Flow titanium-reinforced composite resin and zinc phosphate cements were evaluated. Single-rooted extracted human teeth with crowns (n = 120), removed at the cementoenamel junction, were randomly divided into 4 groups of 30 samples each. Different post lengths were luted with either Flexi-Flow or zinc phosphate. Each sample was placed into a specialized jig and on a tensile testing machine with a crosshead speed of 2 mm/min, applied until failure. The effect of different posts and cements on the force required to dislodge the dowels was evaluated with multiple analyses of variance (ANOVA). One-way ANOVA with Scheffé contrast was applied to determine the effect of different post lengths on the retentive failure of posts luted with the 2 agents. RESULTS: Flexi-Flow reinforced composite resin cement significantly increased retention of ParaPost and Dentatus dowels (P<.001) compared with zinc phosphate. One-way ANOVA revealed no statistically significant difference (P>.05) between mean retention of both dowels luted with Flexi-Flow for all posts length used (5 mm = 8 mm = 10 mm). Mean retention values of the groups luted with zinc phosphate showed a statistically significant difference (P<.001) for the different post lengths (10 > 8 > 5 mm). Parallel-sided ParaPost dowels demonstrated a higher mean retention than tapered Dentatus dowels (P<.001). CONCLUSION: In this study, Flexi-Flow reinforced composite resin cement compensated for the reduced length of shorter parallel-sided ParaPost and tapered Dentatus dowels.

Analysis of Variance↗
PubMed2001

[Bonding and mechanical interlocking of three kinds of luting cements in retention of complete metal crowns].

OBJECTIVE: To evaluate the effects of bonding and mechanical interlocking of three kinds of luting cements in the retention of complete metal crowns. METHODS: Zinc phosphate cement (ZP), glass ionomer cement (GI) and polycarboxylate cement (PC) are in common use for clinical treatment. In this study, these cements were selected to bond the complete crowns to molars in vitro. The retention capacities of the complete crowns were tested and compared. And apart from mechanical interlocking, the effect of bonding was tested. On this basis the interlocking capacity of the cement was calculated. RESULTS: 1. The retention capacities of complete metal crowns from the highest to least were: GI > ZP > PC. 2. The proportions of mechanical interlocking of ZP, GI and PC in the retention of complete metal crowns were 62.6%, 48.3% and 20.1% and the ratios of bonding of ZP, GI and PC were 37.4%, 51.7% and 79.9%, respectively. CONCLUSION: The effects varied with different cements in the retention of complete metal crowns because of the discrepancy in bonding and mechanical interlocking properties. Mechanical interlocking plays a prominent role when ZP or GI is used, and the role of bonding is apparent in PC.

Adhesives↗
PubMed1995

Osseointegration of Brånemark fixtures using a single-step operating technique. A preliminary prospective one-year study in the edentulous mandible.

The aim of the present prospective clinical study was to analyze the feasibility of inserting Brånemark fixtures according to a one-stage procedure including transmucosal healing and to subsequently evaluate the predictability of osseointegration as well as the potential of such implants for stabilizing complete overdentures in the edentulous mandible. Five patients (2 women, 3 men), completely edentulous in the mandible and with a mean age of 60 years, volunteered for this study. Two fixtures of various length (10-20 mm) and 3.75 mm in diameter were inserted in the lower canine regions. A standard surgical procedure including a midcrestal incision was used. After the placement of the fixtures, healing abutments, which are normally used during second-stage surgery, were inserted instead of the usual cover screws. Three months after implant placement a clinical and radiographic examination was performed to confirm the presence or absence of osseointegration of the fixtures prior to exchanging the healing abutments with the spherical attachments. Finally, different clinical (Plaque Index, Bleeding Index, probing depth, Periotest mobility) and radiographic (bone loss, peri-implant radiolucency) parameters were recorded 9 months after loading of the fixtures by means of a complete mandibular overdenture, retained by two ball attachments in the canine regions. All fixtures were perfectly stable (mean Periotest values of -2) and presented favorable peri-mplant soft tissue conditions, and no patient was complaining about any particular symptom. As far as retention and stability of their implant supported overdenture was concerned, the participants without exception considered the therapeutic result as being perfectly adequate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1998

A comparative study of retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements with stainless steel crowns--an in vitro study.

This study was conducted on 30 extracted human primary molars to assess the retentive strengths of zinc phosphate, polycarboxylate and glass ionomer cements. The teeth were embedded in resin blocks and were randomly divided into 3 groups of 10 each. The occlusal surfaces of all teeth were reduced uniformly by 1.0 to 1.5 mm. All mesial, distal undercuts were removed and sharp angles rounded. This was followed by cementing pretrimmed and precontoured stainless steel crowns on each tooth with hand pressure and storing in artificial saliva at 37 degrees C for 24 hours. Retentive strength was tested using Instron Universal Testing Machine. The load was applied starting from a zero reading and gradually increased until the cemented stainless steel crowns showed signs of movement and then the readings were recorded. It was found that retentive strengths of zinc phosphate and glass ionomer cements were statistically better (P < 0.05) when compared to the polycarboxylate cement. Negligible difference (0. 59 kg/cm2) was however observed between zinc phosphate and glass ionomer cements.

Analysis of Variance↗
PubMed1992

Influence of low-viscosity liners on the retention of three luting materials.

A number of materials are available to protect the pulp from postoperative sensitivity. The effect of a calcium hydroxide liner and a dentinal desensitizing agent (potassium oxalate) on crown retention was investigated. Gold crowns were cemented on standardized crown preparations with zinc phosphate cement, glass-ionomer cement, or one of two resin cements. A tensile force was applied until separation occurred. The mean applied force at rupture varied greatly among the groups, indicating that the pulpal protection agent may have a distinct effect on the retention of cast restorations. In addition, other clinical factors, such as angle of convergence, crown height, and total surface area of the tooth should be considered.

Analysis of Variance↗
PubMed2003

[Circulating test and analysis of clasp retention].

OBJECTIVE: To show the trend of the retention change during the circulation of the clasp dislodging and inserting, and to discuss the proper depth of the undercut for a specific clasp. It is also a basic study for the best designing of RPD. METHODS: The Chatillon force measuring instrument was used to record the variation of the retention of Co-Cr alloy casting Akers clasp when they were dislodging from undercuts of different depths (0.25 mm, 0.50 mm, 0.75 mm) on bicuspid and molar. RESULTS: The data was analysed of Correlation and Regression by SPSS 10.0 statistic software. The variations of the retention in the circulation are obvious from the different teeth and different undercut depths. It shows an attenuation trend in circulation (P < 0.01). After 400 times dislodging, in bicuspid group, the retention of the clasp used in 0.50 mm undercut became less than the one used in 0.25 mm undercut. While the retention of the clasp used in 0.75 mm decreases most obviously, it values 0.7670 kg. In molar group, the attenuations of the retention at different depths of undercut are similar, the retentions of the clasp still rank as, from great to less, 0.75 mm, 0.50 mm and 0.25 mm, in the depth of undercut. CONCLUSION: the proper depth of the undercut for bicuspid is 0.25 mm, and 0.50 mm for molar.

Dental Clasps↗
PubMed1997

Rational predictable posthole preparation.

Restoration of the endodontically treated tooth is a common occurrence in everyday dental practice. Unfortunately, clinical posthole preparation seems to be a random technique. Even for a prefabricated post supplied with matching drills, the task is often difficult or not straightforward. Some questions inevitably arise. How long should the posthole be? How wide should the canal be prepared? How can the proper width be maintained so that the prefabricated post does not strip in the canal and lose its retention? If it is decided to use a cast post, what is the best posthole preparation to maximize retention? Is there an easy way to avoid perforating the root while preparing the canal for the post? Clinically, how can the posthole be prepared quickly, easily, and predictably every time? These key questions must be addressed when preparing the posthole.

Dental Prosthesis Retention↗
PubMed1999

Retention of adhesive cement on the tooth surface after crown cementation.

STATEMENT OF PROBLEM: Adhesive cements increase crown retention, but it is unknown if traces of cement remain undetected on the tooth surface after clinical removal of excess cement, which could exacerbate plaque retention. PURPOSE: This study measured the surface area, volume, mean depth, and maximum depth of a resin composite and a compomer luting cement left adherent on the tooth surface after removal of excess cement, as judged clinically. METHODS AND MATERIAL: Four groups of specimens (n = 48) were prepared for full coverage crowns: group AC bonding alloy with chamfer finish line, group G gold alloy with chamfer finish line, group PC porcelain with a chamfer finish line, and group PS porcelain with a shoulder finish line. Two profiles of the mesial and distal surfaces of the teeth were carried out: (1) tooth with crown seated but not cemented and (2) tooth with the crown cemented in place. Two cements and 2 methods of cement removal were studied. RESULTS: A 4-way analysis of variance for cement, crown type, method of removal, and tooth surface morphology showed that significantly greater volumes and mean depth, but not surface areas, of resin composite cement remained adherent than compomer cement (P<.05). Among crown types, significant differences were found for cement volume (group G>AC, G>PC, G>PS), cement surface area (group AC>PC, G>PC, G>PS), and maximum cement depth (group G>AC). There was no significant difference between the 2 methods of cement removal. Significantly larger surface areas and maximum depths of cement were retained on the anatomically grooved mesial surface of the maxillary first premolars than on the ungrooved distal surface. CONCLUSION: Subclinical cement retention occurred after crown cementation, which was influenced by cement, crown type, and tooth surface morphology but not method of cement removal.

Adhesives↗
PubMed2003

Effect of a fluoride varnish on the margin leakage and retention of luted provisional crowns.

STATEMENT OF PROBLEM: Provisional crowns cemented with provisional luting agents are susceptible to washout, margin leakage, and secondary caries when placed for a prolonged period. PURPOSE: This study was conducted to determine the effect of combining a varnish containing 2.26% NaF with 2 provisional luting agents on the margin leakage and retention of provisional crowns. MATERIAL AND METHODS: Acrylic resin provisional crowns were fabricated for 8 shoulder-prepared molars. The eight provisional (N=24) crowns were luted individually with Temp-Bond (TB), Freegenol (FG), or Duraphat (DU). Specimens were thermocycled 500 times (5 degrees and 60 degrees C) with a 1-minute dwell time, stored in 100% relative humidity at 37 degrees C for 6 days, and then immersed in a 0.5% Gentian violet solution for 24 hours. Seven days after cementation, a removal test of the crowns (shear retention test) was conducted with a universal testing machine at a crosshead speed of 5 mm/min. Retention was determined as the maximum recorded force needed for crown dislodgment. DU varnish was applied to the inner surface of the dislodged crowns with no removal of the cement layer TB, FG (N=16). The crowns were relined with a 0.5-mm layer of acrylic resin and luted with a combination of luting agent and DU (TB, FG) N=16. No luting agent (NC) served as the control (N=8). Results were analyzed with the Wilcoxon matched-pairs signed-ranks test. Leakage at the margins was assessed with a 4-level dye penetration scale, and statistical differences were identified with a chi(2) test. All hypothesis testing was conducted at the 95% level of confidence. RESULTS: The mean 7-day retention forces were as follows: 44.5 N (Temp-Bond), 51.6 N (Freegenol), and 35.9 N (Duraphat). There were no significant differences among these values. Duraphat combined with Freegenol decreased the retention of provisional crowns, but Duraphat combined with Temp-Bond increased the retention of provisional crowns by 69-145%. Duraphat alone and in combination with both provisional luting agents significantly reduced margin leakage (P<.05). The least margin leakage was evident when the provisional crowns were luted with Duraphat alone. CONCLUSION: With regard to retention and margin leakage, the results of this study suggest that Duraphat varnish can be successfully used as provisional luting agent for single provisional crowns.

Acrylic Resins↗
PubMed1998

Are posts mandatory for the restoration of endodontically treated teeth?

In this era of fiscal and professional accountability, variations in the utilization of posts to improve the retention of crowns or other restorations on endodontically treated teeth are no longer acceptable. This practice ignores not only the potential for root perforations during post space preparations, but also the adhesive properties of modern resin-based materials. Since the retention of restorations hinges on many other factors, the placement of posts does not necessarily assure service quality and may even lead to deleterious changes. The need to reappraise the utilization of posts in the restoration of endodontically treated teeth cannot be overstated.

Crowns↗
PubMed2004

Computer-aided direct all-ceramic crowns: preliminary 1-year results of a prospective clinical study.

The objective of this study was to investigate the clinical performance of: (1) adhesively placed Cerec crowns with reduced stump preparations, and (2) Cerec endo crowns. The crowns were examined at baseline using modified USPHS criteria in 20 patients with 10 Cerec crowns with reduced stump preparations and 10 Cerec endo crowns. All crowns had been produced chairside with the Cerec 3 CAD/CAM method using the function mode. The crowns were machined from Vita Mk II feldspathic ceramic blocks, polished manually, and placed with dual-curing composite luting agent using a functional adhesive. After 1 year, a follow-up examination of the crowns was conducted; all 20 Cerec crowns were rated with a clinically acceptable A or B rating. Fractures or loss of retention were not observed. The method of producing and placing all-ceramic crowns with reduced stump preparations and endo crowns chairside in one appointment can be implemented successfully in private practice.

Adult↗
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↗