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Statement of Problem: Dental luting cements fail by microcrack formation and bacterial ingress or by gross failure and crown dislodgment. Both of these failure modes are related to mechanical properties and deformation., Purpose: This study evaluated those mechanical properties of cements. METHODS AND MATERIAL. Elastic modulus for 8 representative cements (zinc phosphate, polycarboxylate, glass ionomer, encapsulated glass ionomer, resin-modified glass ionomer, resin composite, and adhesive resin composite) was measured by using a nondestructive technique and evaluated for cement type and storage time (1 hour, 1 day, 1 week, 1 month, 1 year) by 2-way ANOVA (P <.05). Compressive properties (proportional limit, resilience, and toughness), ultimate strengths (compressive, diametral tensile, and flexural), and flexural toughness were determined and evaluated by 2-way ANOVA for 2 crosshead testing rates (5 and 0.5 mm/min) and cement type (P <.05)., Results: Cements varied with respect to elastic moduli, compressive proportional limit, compressive resilience, compressive strength, compressive toughness, diametral tensile strength, flexural strength, and flexural toughness. Storage time affected the elastic moduli of different materials in different ways. Elastic moduli of polycarboxylate and glass ionomer cements increased over time, whereas the other materials changed little after the first day. Crosshead rate only significantly affected compressive proportional limit and resilience., Conclusions: Luting cements differed considerably with respect to mechanical properties.

Microleakage is related to recurrent decay, inflammation of vital pulps, and reinfection of previously treated root canals. The purpose of this investigation was to compare the abilities of new adhesive cements and conventional nonadhesive controls to prevent microleakage under stainless steel crowns on primary anterior teeth. Standardized preparations were made, and stainless steel crowns were adapted. Specimens were assigned randomly to cement groups: zinc phosphate (ZP), polycarboxylate (PC), glass-ionomer (GI), resin-modified glass-ionomer (RMGI), RMGI with a dentin bonding agent (RMGI + DBA), adhesive composite resin (ACR) and zinc oxide eugenol (ZOE). Specimens were stored in water, aged artificially, stained, embedded, and sectioned, and the microleakage was measured. Group means and standard errors were calculated. ANOVA discerned differences among groups (P < 0.0001), and Turkey's multiple comparisons testing (P < 0.05) ranked the groups from least to most microleakage as follows: [RMGI + DBA, RMGI, ACR, GI], [ZP], and [PC, ZOE]. The adhesive cements significantly reduced microleakage.

This paper reviews a number of recent University of Southern California School of Dentistry clinical and laboratory research studies on marginal integrity. Marginal integrity was comprehensively investigated in many different ways. A series of studies examined cement physical properties, casting seating and microleakage, from basic laboratory investigations to multicenter clinical trials. New strong adhesive cements were shown to have many important advantages, but they have a short clinical track record and appeared to be less user-friendly than the more traditional zinc phosphate cement. Casting adjustment techniques markedly improved crown seating. Conventional and new technologies for crown fabrication were evaluated in-vivo with respect to marginal integrity. Although science and art have progressed tremendously, the perfect margin was not achieved.

Purpose: Reduced cement flm thicknesses can improve crown seating and decrease marginal discrepancies. Improved marginal adaptation has the potential to reduce plaque accumulation, periodontal disease, and cement dissolution. Studies have indicated that dynamic seating methods can reduce seating discrepancies associated with zinc phosphate and resin cements. However, other types of cements and other dynamic techniques have not yet been studied or compared, nor has the mechanism for improved seating been fully explained. Therefore, the purpose of this study was to investigate the effect of a variety of loading methods on the film thicknesses of current types of crown and fixed partial denture cements compressed between glass plates., Materials and Methods: This study investigated the effect of three dynamic loading methods on film thickness of six representative fixed prosthodontic cements. These included zinc phosphate, resin-modified glass ionomer, encapsulated glass ionomer, adhesive composite resin, composite resin, and polycarboxylate. The method was derived from American Dental Association specifications for cement film thickness. In control groups, the cements were placed between two glass glass plates and statically loaded with a 15-kg weight. The test groups were initially similarly loaded, and then for 30 seconds further subjected to simulated repeated patient opening and closing, vibrations from an electromallet, or an ultrasonic device., Results: Mean film thicknesses ranged from 7.4 micrometers for polycarboxylate / ultrasound up to 40.3 micrometers for composite resin / static. Two-way analysis of variance revealed that the effects of material type and cementation method and their interaction all significantly affected film thickness (P < .0001). Multiple range analysis showed that dynamic methods were generally superior to static loading and that the ultrasonic method was the best overall., Conclusions: The different dynamic loading methods all significantly decreased cement film thicknesses between glass plates. The ultrasonic method was the most effective. The type of cement used also influenced film thickness. Composite resins were more affected than other materials.

Large marginal crown discrepancies are deleterious. Although previous studies have examined casting seating in vitro, few have evaluated the effects of different luting cements on in vivo seating. Hence this in vivo study compared marginal discrepancies created by different cements on cast crowns. Tooth preparations were completed according to acceptable procedures on previously intact human molars that were severely periodontally compromised and scheduled for extraction. Castings were made by conventional techniques. The castings were randomly assigned to the following luting agents: zinc phosphate cement, resin-modified glass-ionomer cement, and the same resin-modified glass-ionomer cement with a dentinal bonding agent. After 6 months the teeth were carefully extracted, embedded, and sectioned, and vertical and horizontal discrepancies were measured. Analysis of variance revealed that all cements resulted in similar discrepancies. Vertical discrepancies were considerably greater than horizontal discrepancies, and the distributions of marginal discrepancies were skewed towards upper ranges.

This study investigated the relationship between type of luting cement for artificial crowns and microleakage through dentinal tubules. Standardized preparations were made on intact human premolars, and crowns were made in a base metal alloy using conventional techniques. The castings were randomly assigned to the following luting agent groups: zinc phosphate (ZP), polycarboxylate (PC), glass ionomer (GI), phosphate ester composite resin (GMA/PE), and a composite resin with a NPG-GMA dentin bonding agent (GMA/NPG). Then they were cemented in a standardized manner. The specimens were artificially aged, stained, sectioned, and microleakage occurred through dentinal tubules toward the pulp measured. The rank in order from least to most (best to worst) leakage was GMA/NPG, GI, GMA/PE, PC, and ZP. Material GMA/NPG recorded significantly less leakage than all other materials. Therefore, the results of this study suggest that material GMA/NPG may reduce pulpal sensitivity and pathosis.

Low film thickness is critical to the clinical success of cemented castings. This study investigated the effect of luting agent-metal physico-chemical surface interactions on film thicknesses of representative luting agents. Control group luting agents were placed between two glass plates, as described by American Dental Association specifications 8, 61, and 66, and test group luting agents were positioned between glass and metal plates. The materials selected were zinc phosphate cement, polycarboxylate cement, glass ionomer cement, glass ionomer-composite resin hybrid cement and a resinous cement, with a type III gold alloy, a noble metal ceramic alloy, and a base metal ceramic alloy. A two-way analysis of variance and follow-up tests were done. The effects of the type of metal surface, type of cement, and their statistical interaction significantly affected film thickness (p < 0.0001). The type of cement had a greater affect on film thickness than the type of metal. A glass ionomer cement produced lower overall film thicknesses than other cement types, and a noble metal ceramic alloy created lower overall film thicknesses than other types of metal. American Dental Association specifications for cement film thickness did not accurately reflect normal cement use.

Standardized tooth preparations were completed on previously intact human molars in vivo, and castings were made with a precious metal ceramic alloy by conventional techniques. The castings were randomly assigned to the following luting agents: zinc phosphate, composite resin-glass ionomer hybrid, and a composite resin-glass ionomer hybrid with a dentinal bonding agent and were cemented in a standardized manner to periodontally compromised molars. After 6 months the teeth were carefully extracted, stained, embedded, and sectioned, and the in vivo microleakage was measured. ANOVA disclosed significant differences between groups, and a multiple comparisons test revealed that the zinc phosphate group leaked significantly more than other cement groups.

This study investigated the relationship between marginal opening and microleakage. Standardized preparations were made on intact human premolars, and copings were cast in a base metal alloy by use of conventional techniques. The castings were randomly assigned to the following luting agent groups: zinc phosphate cement, polycarboxylate cement, glass ionomer cement, phosphate ester composite resin, and a composite resin with a NPG-GMA dentinal bonding agent and were cemented in a standardized manner. The marginal openings between teeth and castings were measured, and microleakage was determined at the same points. Within the confines of the in vitro model used, no significant correlation between marginal opening and microleakage was established for either pooled data or individual luting agent groups.

This study determined and compared physical properties of six fixed prosthodontic resin composite luting agents and one control. Inorganic filler content, compressive strength, diametral tensile strength, film thickness, and Knoop hardness were determined. The amounts of filler and the physical properties varied widely among materials. One material, which contained a minimal amount of filler, underwent so much plastic deformation that its strengths could not be measured. All other materials demonstrated high strengths. The materials with the least filler demonstrated the least resistance to indentation. The material with the lowest film thickness had not set at the time of measurement, 10 minutes after mixing. Most materials had unacceptable film thicknesses. Only one material demonstrated acceptable physical properties throughout the study.

Strength parameters greatly influence the selection of luting agents. This study compared the compressive and diametral tensile strengths of six classes of new adhesive luting agents (ALAs) with zinc phosphate as the controls. The 11 materials tested were prepared according to the manufacturers' instructions for use as luting agents. Mean compressive and diametral strengths and standard errors were calculated for each luting agent (n = 10). Analysis of variance was computed (p < 0.0011) and multiple comparisons tests were performed. Compressive strengths varied from 41.5 MPa for a hydroxyapatite ALA to 178.5 MPa for a composite resin ALA. Diametral tensile strengths ranged from 8.1 MPa for a hydroxyapatite ALA to 45.1 MPa for a composite resin ALA. Conventional powder-liquid glass ionomer ALAs, an encapsulated glass ionomer ALA, a composite resin-glass ionomer hybrid ALA, and the composite resin ALAs demonstrated significantly greater compressive and diametral strengths than the zinc phosphate cements.

Luting cements are a critical, but weak, link between fixed prostheses and their supporting tooth structures. Luting cements have relatively poor physical properties compared to bulk restorative filling materials, but they must fulfill an additional series of requirements such as low film thickness. As they have a wide variety of applications, no single material can be recommended for all clinical situations. This paper reviews the properties required of luting agents, the currently available material classes of luting agents and clinical cementation procedures, and makes suggestions for specific clinical situations.

This study investigated the three-dimensional nature of crown fit and the effects of adjustment and luting. Standardized preparations were made on extracted premolars and impressions and dies made. Complete-coverage castings were fabricated using base metal alloy. The castings were placed on their respective teeth and measurements made. The castings were then adjusted using a silicone disclosing medium and remeasured. They were then assigned to one of five luting agent groups and cemented. A relative term describing tilting was defined. Casting adjustment decreased tilting and cementation increased tilting. Resin cements tilted castings significantly more than did zinc phosphate, glass-ionomer, or polycarboxylate cements.

This study determined the effect of new adhesive luting agents on the marginal seating of cast restorations. Standardized preparations were completed on freshly extracted premolars, impressions were made, and complete metal veneer crowns were cast with a base metal alloy. The castings were placed on their respective teeth and the extent of marginal opening was recorded. They were then assigned to a luting agent group: glass ionomer cement (GI), polycarboxylate cement (PC), microfilled BIS-GMA composite resin with NPG-GMA/PMDM dentinal bonding agent (GMA + NPG), microfilled BIS-GMA/phosphate ester composite resin (GMA/PE), or zinc phosphate cement (ZP). The castings were cemented and marginal openings remeasured. ANOVA revealed that the cement groups were similar before cementation (p 0.35) but were different after cementation (p < 0.0001). Tukey's multiple comparisons test identified statistically similar groups that were different from other groups and ranked them from lesser to greater marginal opening: (GI, ZP, PC) (GMA/PE, GMA + NPG).

This study examined the effect of seating force on the film thickness of new adhesive luting agents. The method was in compliance with American National Standards/American Dental Association Specification No. 8 for zinc phosphate cement. The materials tested were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. All materials were manipulated exactly as described in the manufacturer's instructions, and an electronic gauge with an accuracy of 0.5 micron was used. Each class of material was measured 10 times at six different seating forces. Analysis of variance and multiple comparisons testing disclosed that the seating force and class of material strongly influenced the film thicknesses of luting agents. A mathematical model describing the response of zinc phosphate cement within the range tested was reported.

This study investigated the effect of luting agent-dentinal surface interactions on the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. In the control groups the luting agents were placed between two glass plates, as described in ADA Specification No. 8, but in the test groups the luting agents were positioned between a glass and a dentinal plate. The materials selected were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. A two-way analysis of variance was performed, and t tests were computed to compare glass with the dentinal plate within each material. Zinc phosphate and glass ionomer cements exhibited a significant decrease in film thickness when measured in contact with dentin, as compared with contact with the glass plate. However, polycarboxylate cement and the resinous cement with its dentin bonding agent showed a slight nonsignificant increase when contacting dentin, as compared with the glass plate. An explanation was offered and suggestions were made regarding future research.

This study determined and compared the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. Each of the 20 materials tested was manipulated exactly as described in the manufacturers' instructions. An electronic gauge with an accuracy of 0.5 micron was recalibrated after each recording, and each luting agent was measured 10 times. The mean film thickness and standard deviation were calculated for each luting agent; an analysis of variance and a multiple comparison test were also performed. Nine materials satisfied the ADA type I specification for film thicknesses less than 25 microns, and these included a hydroxyapatite cement, glass ionomer cements, zinc phosphate cements, and polycarboxylate cements. Five other materials met the ADA type II specification for film thicknesses of less than 40 microns, and these included a glass ionomer cement, a resinous cement, a zinc phosphate cement, and glass ionomer-resinous hybrids. Six resinous cements recorded film thicknesses greater than 40 microns, and suggestions were made regarding future development and research.

This study measured the in vitro microleakage of conventional and new FPD luting agents. Standardized preparations were made on 42 freshly extracted premolars. Facial and lingual chamfer margins were placed in enamel, mesial and distal in dentin and cementum, and castings were made in Rexillium III alloy and were then cemented with a standardized technique. Six groups of seven samples were tested, (1) polycarboxylate, (2) zinc phosphate, (3) glass ionomer, (4) Den-Mat Thin Film cement, (5) Panavia Ex, and (6) Den-Mat Thin Film cement with Tenure. The ranking of groups for stain ingress was from the greatest (1) to the least (6). A one-way analysis of variance and Tukey-Student range analysis revealed significantly similar groups, p less than 0.05:(1,2,3,4) (5,6).

This in vitro study measured the microleakage of current dentin bonding agents and glass-ionomer bases. Freshly extracted human molars were prepared to a flat surface, and dentin adhesives and composite resins were applied in a plastic matrix. Samples were stored in water at 37 degrees C, thermocycled, stained with AgNO3, embedded in epoxy resin, and sectioned for evaluation of stain penetration at the composite resin/tooth interface. The reliability index of the dentin adhesives varied significantly between materials. The enamel control had essentially no microleakage, and the aluminum oxalate dentin adhesive on dentin had significantly less microleakage than other dentin adhesives tested. Present dentin adhesives were unable to prevent, but may reduce, microleakage.