Reconstructive materials for endodontically treated teeth

Effect of different filling materials in combination with intraradicular posts on the resistance to fracture of weakened roots

The preservation and restoration of severely weakened pulpless teeth is a difficult and relatively unpredictable procedure. This study evaluated the resistance to fracture of experimentally weakened bovine roots internally reconstructed with different filling materials in combination with prefabricated post compared with restored roots that were relatively intact. The roots of 75 mandibular bovine incisors with similar bulks were selected. Of these, 60 were internally prepared to standardized dimensions, thereby simulating weakness. All roots were filled with different restorative materials. The specimens were submitted to the fracture resistance testing with the application of a tangential compressive loading at an angle of 135 degrees in relation to the long axes of the roots. Results indicated statistically significant differences in relation to the root conditions. Weakened roots were less resistant to fracture than were controls. The roots restored with the resin cement demonstrated the lowest fracture resistance values, but statistically significant differences were observed only when compared with those restored by the resin-modified glass-ionomer cement. Resin-modified glass-ionomer cement, polyacid-modified resin composite and resin composite behaved similarly without statistically significant differences among them. None of the materials evaluated were capable of achieving the fracture resistance recorded for unweakened controls.

Resistance of core materials against torsional forces on differently conditioned titanium posts

STATEMENT OF THE PROBLEM

The separation of core materials from titanium posts, which have a low modulus of elasticity, has been identified as a problem in restorative dentistry.

PURPOSE

This study evaluated the resistance to torsional forces of various core materials adapted to differently conditioned titanium posts.

MATERIAL AND METHODS

Seven hundred and twenty specimens were tested consisting of: 6 core materials and 5 surface conditioning techniques for 2 kinds of opaquers with 10 specimens in each group (6 x 5 x 2 x 10=600) plus 6 core materials and 2 opaquers were tested and considered as control groups on nonconditioned titanium posts, each group containing 10 specimens (6 x 2 x 10=120). The custom-made pure titanium posts were conditioned with the following products: Silicoater Classical, Silicoater MD, Rocatec, Kevloc, and Siloc surface-conditioning systems. Subsequently, 6 core materials with different compositions (Durafill, Adaptic, Coradent, Ti-Core, Hytac Aplitip, and Photac-Fil Aplitip) were applied to titanium posts that were previously coated with 2 types of light-polymerized opaquers, either Artglass or Dentacolor. Sixty air-abraded titanium posts (250 microm, 30 seconds) were used as controls for each core material. Following thermocycling (5 degrees -55 degrees C, 30 seconds, 5,000 cycles), maximum torsional forces were determined with an electronic torque movement key. Data were statistically analyzed by 1-way analysis of variance followed by 2-way analysis of variance (P<.05).

RESULTS

Significantly higher mean torsional forces were observed with respect to Siloc (20.4 Newton decimeter [dNm]), Silicoater Classical (18.6 dNm), Silicoater MD (18.2 dNm), and Rocatec (17.0 dNm) systems compared with the mean for the untreated control group (14.6 dNm) (P<.001). The Kevloc system (10.4 dNm) demonstrated no significant difference compared with the control group (P>.001). The Kevloc system in combination with the Artglass opaquer and Photac-Fil Aplitip (0.00 dNm) core material showed no resistance against torsional forces. Significant differences were observed between hybrid core materials and microfilled composite, compomer, or resin-modified glass ionomer core materials (P<.001).

CONCLUSION

Within the limitations of this study, the resistance to torsional forces for the core materials on titanium posts increased with the use of chemical surface-conditioning techniques and varied in accordance with the opaquer type. Type of core material also significantly influenced the resistance after thermocycling.

Hypersensitivity to methyl methacrylate: mode of treatment

This article describes the treatment of a patient who experienced a delayed hypersensitivity reaction associated with acrylic resin. Patch testing revealed an allergy to methyl methacrylate monomer. Patients with a known or suspected allergy of this type should be treated by alternative methods. Dental procedures in which negligible contact of the oral mucosa with methyl methacrylate are presented.

Reinforced glass-ionomer cements--a review of properties and clinical use

In recent years, two new metal-reinforced Glass-ionomers have been introduced. The aim has been to develop a cement which can be used successfully as a replacement for amalgam. This paper reviews the published literature on the mechanical properties and clinical use of both the cermet and so-called 'Miracle Mix' cements. The published results do not suggest an improvement in strength or adhesion to tooth material; wear resistance is improved, however. One problem encountered in reviewing this literature is the wide variation in test methodology and hence results. In clinical use, the metal-reinforced cement has been successful in Class I and II restorations, particularly using the tunnel technique, and has potential for use in a number of other applications.

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.

Root fracture in endodontically treated teeth related to post selection and crown design

Standardized plastic analogues simulating an endodontically treated maxillary central incisor root were used to investigate the resistance to root fracture in endodontically treated teeth. Three different post and core systems were used: (1) cast post and core, (2) Para-Post Plus post, and (3) Flexi-Post post. The core build-up material selected in this study was Ketac Silver material, after which a crown preparation was made on each analogue. Two types of preparations were used: a wide chamfer margin (butt-joint) and a wide chamfer margin with a 1.0 mm circumferential bevel. An overcasting was fabricated and was permanently cemented on each preparation. Assemblies were subjected to an increasing lingual oblique force until fracture occurred. Results were tabulated using the analysis of variance (F test) and Student's t test. Beveled preparations with a concomitant final restoration provided a significant increased resistance to root fracture. Furthermore, vertical fracture occurred twice as often with nonbeveled preparations.

Fracture durability of restored functional cusps on maxillary nonvital premolar teeth

Palatal cusps of nonvital maxillary premolar teeth were restored with a coronal-radicular restoration of posterior composite resin (Occlusin), amalgam (Tytin), or cermet (Chelon-Silver). Mean fracture strength values were: 370 lb for intact premolar teeth, 266 lb for amalgam, 215 lb for posterior composite resin, and 132 lb for cermet. From this in vitro study it can be suggested that for selected endodontically treated maxillary premolar teeth, the dentist can use acid-etch-retained posterior composite resin or pin-retained high copper amalgam material for a definitive coronal-radicular restoration. The use of cermet for this purpose is contraindicated.

Guidelines for the restoration of endodontically treated teeth

Much confusion exists in the dental community regarding the restoration of endodontically treated teeth; few review articles present succinct guidelines for the restoration of these teeth. This article reviews the literature and presents guidelines for restoration of endodontically treated teeth.