Fracture resistance of teeth with Class II bonded amalgam and new tooth-colored restorations

This study compared the cuspal fracture resistance of posterior teeth restored with four different adhesive restorations. Fifty sound, maxillary human premolars were randomly divided into a control group and four experimental groups with 10 teeth in each. Specimens in the first group were intact teeth that were tested as unprepared. The remaining four groups received mesio-oclusodistal cavity preparations and were restored with a hybrid composite (Filtek Z250), a packable composite (Filtek P60), an ormocer (Definite) and an amalgam (SDI Permite) with an amalgam bonding agent (Amalgam Bond Plus). All groups were stored in water at 37 degrees C for 15 days and thermocycled 1000 times between 5 degrees-55 degrees C. The specimens were preloaded five times in compression to 10 kg using two metal rods that contacted only the teeth on the cuspal inclines. The teeth were then loaded occlusally in an Instron Universal Testing Machine until fracture occurred. The means of force required to fracture the teeth in each of the five groups was analyzed using one-way ANOVA and Tukey Test. The difference between the mean cuspal fracture resistance of the unprepared control teeth and those restored with amalgam groups was found to be statistically significant (p < 0.05). No significant differences in resistance to cuspal fracture were found among the restoration groups, the unprepared control group and those teeth restored with hybrid composite, packable composite and ormocer groups (p > 0.05).

[The effect of rehabilitation of flared root canal on the fracture resistance of root and post-core system]

OBJECTIVE

To assess the effect of rehabilitation of flared root canal on the fracture resistance of root and post-core system.

METHODS

Thirty-two simulated tooth roots made of polymethyl methacrylate were divided into 4 groups, including the normal root canal group and 3 flared root canal groups. One flared root canal group was rehabilitated by light-cared composite, another group was rehabilitated by amalgam, and the third flared root conal group was not treated. Casting post and core restored every simulated tooth root. Each specimen was embedded in acrylic resin and then fixed in a special jig on the universal load-testing machine. A compressive load was applied at a 90-degree angle to the long axis of the core until fracture, at a crosshead speed of 1 mm/min; the maximum of load was recorded.

RESULTS

The means of load in normal root canal group, light-cared composite rehabilitated group, amalgam rehabilitated group, not treated group were 202.92 N, 194.60 N, 146.89 N, 142.09 N. It was shown that the load of normal root canal group is significantly greater than the load of not-treated group (P < 0.01); the light-cared composite rehabilitated group is significantly stronger than the not-treated group (P < 0.01), but there is no significant difference between the light-cared composite rehabilitated group and normal root canal group, and no significant difference between the amalgam rehabilitated group and not-treated group (P > 0.05).

CONCLUSION

The rehabilitation of flared root canal using suitable material not only changes the shape of root canal, but also increases the fracture resistance of root canal because of its thicker and stronger root canal wall which obviously improves the fracture resistance of post and core.

[The restoration of endodontically treated teeth: the minimally invasive (post-) core buildup?]

The rebuilding of endodontic treated teeth is a common situation in general dental practice. The final (post-) core buildup, with or without a crown, should protect the restoration as well as the tooth against fracture, should prevent debonding of the restoration, should not permit leakage and should provide an acceptable esthetic result. Several factors influencing these properties are described. The (post-) core buildup in relation to the concept of minimally invasive dentistry is discussed. In conclusion, there is no unambiguous guideline for restoring endodontically treated teeth. Standardised in vitro and in vivo studies are needed.

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.

Fracture resistance of teeth restored with two different post-and-core designs cemented with two different cements: an in vitro study. Part I

OBJECTIVE

The purpose of this in vitro study was to investigate fracture resistance in teeth restored with cast post and cores with and without ferrule and using two different luting cements.

METHOD AND MATERIALS

Forty intact maxillary premolars were endodontically treated after their crowns were removed at 2.00 mm from the cementoenamel junction. Specimens were embedded in acrylic resin blocks in aluminum cylinders, 4.00 mm apical to the cementoenamel junction. Twenty specimens were ferruled, and half of the posts and cores were cemented with zinc-phosphate cement, while the other half was cemented with resin cement. The same procedures were followed for the nonferruled group. Loads were applied at an angle of 45 degrees and measured with a universal testing machine. ANOVA and Tukey test were used for statistical analyses; a significance level was established at 5%.

RESULTS

Ferruled specimens showed greater resistance than nonferruled ones, regardless of the cement used. There was no statistical difference between the group of specimens cemented with resin cement and without ferrule and the ferruled groups. The non-ferruled group with zinc-phosphate cement showed the poorest results.

CONCLUSION

A 2.00-mm cervical ferrule is important for fracture resistance of restored teeth, and resin cement has a better performance.

The use and predictable placement of Mineral Trioxide Aggregate in one-visit apexification cases

Endodontic treatment of the pulpless tooth with an immature root apex poses a special challenge for the clinician. The main difficulty encountered is the lack of an apical stop against which to compact an interim dressing of calcium hydroxide (Ca(OH)2), or the final obturation material. In these situations the unpredictability of the result, the difficulty in creating a leak-proof temporary restoration for the duration of treatment, and the difficulty in protecting the thin root from fracture may lead to complications when using traditional (Ca(OH)2-based) apexification techniques. Furthermore, given the increased mobility of today's society, lengthy treatment protocols are fraught with problems, and may not be followed through to completion. This may lead to ultimate failure of the case. Mineral Trioxide Aggregate (MTA) has recently been introduced for use in endodontics. Current literature supports its efficacy in a multitude of procedures including apexification. The focus of this paper is to propose a one-visit apexification protocol with MTA as an alternative to the traditional treatment practices with Ca(OH)2. One-visit apexification may shorten the treatment time between the patient's first appointment and the final restoration. The importance of this approach lies in the expedient cleaning and shaping of the root canal system, followed by its apical seal with a material that favours regeneration. Furthermore, the potential for fractures of immature teeth with thin roots is reduced, as a bonded core can be placed immediately within the root canal.

Fracture strength of cusp replacing resin composite restorations

PURPOSE

To assess the influence of an additional shoulder preparation on the fracture strength of a cusp-replacing direct resin composite restoration in a premolar that previously had an amalgam MOD restoration followed by fracture of a cusp.

MATERIALS AND METHODS

Two preparation designs were tested. In extracted sound premolars an MOD amalgam cavity was simulated followed by fracture of a cusp (Group A). Group B was the same as Group A but a shoulder was added along the cervical outline of the preparation. As a control group, cusp fracture was simulated but no MOD amalgam cavities were prepared. For each group, 14 preparations were made using a copy milling technique. All 42 preparations were restored using a direct resin composite restoration technique. Restorations were loaded until fracture.

RESULTS

The fracture strength of the preparation with shoulder was not significantly different from the preparation without the shoulder. The fracture strength of the preparations in the reference group, which had no resistance form, was significantly less than in Groups A and B (ANOVA, P<0.05).

[Clinical evaluation of tunnel-restoration]

OBJECTIVE

To evaluate the clinical effect of tunnel-restoration.

METHODS

35 teeth with pulpitis or periapical periodontitis caused by interproximal caries were selected. Tunnel-restoration was used after endodontic treatment. Clinical examinations were taken to follow up all the teeth at one year and two years respectively after treatment.

RESULTS

At one year after treatment, 35 cases were followed up, the rate of success was 100%. At two years after treatment, 33 cases were followed up and 2 cases were lost, the rate of success was also 100%.

CONCLUSIONS

Proximal contact point and marginal ridge of the teeth were preserved by using tunnel-restoration, which is very important to restore proximal contact, enhance the ability of resistance to fracture, and has good clinical effect.

Fracture resistance of teeth directly and indirectly restored with composite resin and indirectly restored with ceramic materials

PURPOSE

To evaluate the fracture resistance of teeth restored with direct and indirect restorations of composite resin and restored with indirect ceramic restorations.

MATERIAL AND METHODS

Fifty-six maxillary premolar teeth were chosen and divided at random into seven equal groups; Group 1 (control): intact teeth; Group 2: MOD cavity preparations, 1/2 intercuspal distance, with rounded internal angles, convergent walls, unrestored; Group 3: MOD cavity preparations, 1/2 intercuspal distance, divergent walls; Group 4: same preparation as Group 2, restored with direct composite resin (Single Bond/Filtek Z250-3M); Group 5: same as Group 3, restored with indirect composite resin (Artglass/Single Bond/Rely X); Group 6: same as Group 3, restored with indirect composite resin (Targis/Single Bond/Rely X); Group 7: same as Group 3, restored with indirect ceramic restoration (Empress/Single Bond/Rely X). The specimens were subjected to a compressive axial loading in a Universal testing machine at 0.5 mm/minute by means of a steel bar (8 mm in diameter).

RESULTS

The mean fracture strength obtained was: Group 1: 1.91 kN; Group 2: 1.06 kN; Group 3: 0.93 kN; Group 4: 1.45 kN; Group 5: 1.81 kN; Group 6: 1.81 kN; Group 7: 1.77 kN. The restored teeth with direct composite restoration increased the fracture resistance of Group 4 up to 76% of a level comparable with the intact teeth (Group 1). However, statistical analysis indicated no significant (P < 0.05) differences between Group 1 (intact teeth) and restored teeth groups, with direct restorations as well as indirect restorations. Both cavity preparation designs weakened the remaining tooth structure. These results demonstrated that a bonded indirect restoration could satisfactorily be an ideal option for restoring teeth weakened by wide cavity preparation.

Corono-radicular reconstruction of pulpless teeth: a mechanical study using finite element analysis

STATEMENT OF PROBLEM

Following endodontic therapy, teeth need to be protected, particularly in the cervical region, where the majority of fractures occur. The likelihood of a fracture depends on the condition of the crown and the type of reconstruction performed.

PURPOSE

This simulation study was designed to compare the effect of different corono-radicular reconstruction methods on stress transmission to dental tissues.

MATERIAL AND METHODS

The study software performed stress analysis of complex structures by finite element analysis. Seven 3-dimensional models were created, each representing a tooth embedded in a bony medium. The following parameters affecting corono-radicular restoration were studied: 2 levels of coronal destruction, core materials, post materials when present, and absence of post. The 2 levels of coronal tissue loss were (1) total tissue loss of the coronal dentin and (2) partial tissue loss of the coronal dentin with 2-mm surviving dentin walls. Teeth with 2 different levels of tissue loss (first study parameter) were reconstructed by 4 different techniques: nickel chromium (NiCr) cast post and core, NiCr post and composite core combination, carbon fiber post and composite core combination, and composite restoration without post. A NiCr crown covered each of the models and received a 30 degrees oblique occlusal load at a constant intensity of 100 N. The software computed the stresses (local tensile stress inducing cracks and compressive stress) for each of the models, comparing maximum intensity observed, localization, and concentration.

RESULTS

Whatever the type of stress (tensile or compressive), the greatest stress was observed in the cervical region, regardless of the model. Only tensile stresses potentially responsible for fractures were compared. Cervical tensile stresses exceeded 230 Pa in the absence of a ferrule and were less than 140 Pa when a ferrule was present. In the absence of a ferrule, the NiCr composite/post combination generated greater cervical stress (254 Pa) than the cast post and core (235 Pa). Results with a ferrule showed 92 Pa for the NiCr composite/post combination and 90.5 Pa for the cast post and core. In the presence of a ferrule, the tensile stress intensities generated by the composite restoration with no root canal post (139 Pa) were 51% greater than those generated by the NiCr/composite combination and approximately 26% greater than those generated by the composite/carbon combination.

CONCLUSION

Within the limitations of this study, it was confirmed that all simulated reconstructed teeth were more subject to stress in the cervical region. The absence of a cervical ferrule was found to be a determining negative factor, giving rise to considerably higher stress levels. When no ferrule was present, the NiCr post/composite combination generated greater cervical stress than cast post and cores. Nevertheless, the peripheral ferrule seemed to cancel the mechanical effect of the reconstruction material on the intensity of the stresses. With a ferrule, the choice of reconstruction material had no impact on the level of cervical stress. The root canal post, the purpose of which is to protect the cervical region, was also shown to be beneficial even with sufficient residual coronal dentin. In the presence of a root canal post, cervical stress levels were lower than when no root canal post was present. Moreover, the higher the elasticity modulus, the lower the stress levels.

[Techniques for immediate restoration of teeth following root canal therapy]

It is incumbent upon the dentist to restore the form and function of endodontically treated teeth. Different approaches and materials are described in the literature for restoring the missing tooth structure, either with a cast post and core or immediately with a chair-side post and core system. This article briefly reviews the available data regarding the microbiological, prosthetic, mechanical, and periodontal aspects while emphasizing the immediate approach using amalgam, composite and glass ionomer materials. The factors affecting retention of the post are presented to guide the clinician in selecting a suitable post and core system in preserving optimal root structure to prevent root fracture. Two clinical cases are presented in which tooth structure was restored using two techniques: in one, a provisional acrylic resin shell was used to house a dowel coronal-radicular amalgam core material, the other used a copper band for a composite post and core system. Both cases emphasize the ease of production and the short chair-time in the stages of crown fabrication.

The influence of a packable resin composite, conventional resin composite and amalgam on molar cuspal stiffness

Packable resin composites may offer improved properties and clinical performance over conventional resin composites or dental amalgam. This in vitro study examined the cuspal stiffness of molars restored with a packable resin composite, a conventional posterior microfilled resin composite and amalgam. Forty-eight intact caries-free human third molars were distributed into four treatment groups (n=12) so that the mean cross-sectional areas of all groups were equal. Standardized MOD cavity preparations were made and specimens restored using one of four restorative materials: (1) a spherical particle amalgam (Tytin); (2) Tytin amalgam with a dentin adhesive liner (OptiBond Solo); (3) a conventional microfilled posterior resin composite (Heliomolar); (4) a packable posterior resin composite (Prodigy Posterior). Cuspal stiffness was measured using a Bionix 200 biomaterials testing machine (MTS). Specimens were loaded vertically to 300 N at a crosshead speed of 1.0 mm/minute. Stiffness was measured at 10 intervals: (1) prior to cavity preparation (intact); (2) following cavity preparation, but before restoration; (3) seven days after restoration; then (4) 1, 2, 3, 4, 5, 6 and 12 months after restoration. All specimens were stored at 37 degrees C in deionized water throughout the study and thermocycled (5 degrees/55 degrees C; 2000 cycles) monthly for 12 months. Repeated Measures ANOVA revealed significant differences among treatment groups over time (p<0.0001). Cavity preparation reduced cuspal stiffness by more than 60%. At 12 months, the cuspal stiffness of restored teeth was, on average, 58% that of intact specimens. Neither the packable nor the conventional resin composite increased cuspal stiffness over that of amalgam.

The ferrule effect: a literature review

LITERATURE REVIEW

A ferrule is a metal ring or cap used to strengthen the end of a stick or tube. It has been proposed that the use of a ferrule as part of the core or artificial crown may be of benefit in reinforcing root-filled teeth. A review of the literature investigating this effect is presented. The literature demonstrates that a ferrule effect occurs owing to the artificial crown bracing against the dentine extending coronal to the crown margin. Overall, it can be concluded that a ferrule is desirable, but should not be provided at the expense of the remaining tooth/root structure.

Early detection of dens evaginatus appearing on the premolars and clinical management: histological study

A review of the methods for the prevention of central cusp fracture is presented, with a case of central cusp protection of a premolar by self-curing acrylic resin by early detection. The anomalous tooth was extracted for histological observation. Closure of the pulpal horn, could be accomplished by early detection and adequate treatment for the central cusp fracture of premolars. In this case, if the gradual attrition of a central cusp were not possible, a protecting the cusp using a self-curing acrylic resin would be an effective form of treatment.

Reinforcing effect of a resin glass ionomer in the restoration of immature roots in vitro

Fifty-six extracted maxillary central incisors were used for this study. The crown of each tooth was removed in order to obtain a standard length of 13 mm. Root canals were enlarged to simulate immature teeth after apexification. The apical 2 mm of the root canal was obturated with gutta-percha and AH26 sealer. The specimens were divided into two groups. Group A was unrestored and served as positive control. In group B, the canal walls were reinforced with a resin modified glass ionomer using a translucent curing post. All teeth were subjected to compressive force using an Instron testing machine until fracture occurred. Group B showed an increased resistance to fracture (456.02 +/- 172.47 N) compared with group A (263.46 +/- 98.00 N). The difference between groups was statistically significant (P < 0.005).

Resistance to fracture of endodontically treated teeth restored with different post systems

STATEMENT OF PROBLEM

Very little is known about the resistance to fracture of endodontically treated teeth restored with newly developed esthetic post systems. Purpose. This in vitro study compared the effect of 1 titanium and 3 esthetic post systems on the fracture resistance and fracture patterns of crowned, endodontically treated teeth.

MATERIAL AND METHODS

A total of 40 recently extracted human maxillary canines with their crowns removed were endodontically treated. Four groups of 10 specimens were formed. Teeth were restored with titanium, quartz fiber, glass fiber, and zirconia posts and numbered as groups 1, 2, 3, and 4, respectively. All posts were cemented with Single Bond dental adhesive system and dual-polymerizing RelyX ARC adhesive resin cement. All teeth were restored with composite cores, and metal crowns were fabricated and cemented with glass ionomer cement. Each specimen was embedded in acrylic resin and then secured in a universal load-testing machine. A compressive load was applied at a 130-degree angle to the long axis of the tooth until fracture, at a crosshead speed of 1 mm/min. One-way analysis of variance and a Tukey test were used to determine the significance of the failure loads between groups (P<.001). A non-parametric chi(2) test was conducted for evaluation of the mode of failure (P<.001).

RESULTS

The mean failure loads (kg) were 66.95, 91.20, 75.90, and 78.91 for groups 1 to 4, respectively. Teeth restored with quartz fiber posts (group 2) exhibited significantly higher resistance to fracture (P<.001) than the other 3 groups. Teeth restored with glass fiber and zirconia posts (groups 3 and 4) were statistically similar (P>.05). Fractures that would allow repair of the tooth were observed in groups 2 and 3, whereas unrestorable, catastrophic fractures were observed in groups 1 and 4 (P<.001).

CONCLUSION

Within the limitations of this study, significantly higher failure loads were recorded for root canal treated teeth restored with quartz fiber posts. Fractures that would allow repeated repair were observed in teeth restored with quartz fiber and glass fiber posts.

Fracture strength after dynamic loading of endodontically treated teeth restored with different post-and-core systems

STATEMENT OF PROBLEM

Prefabricated metal and ceramic posts can be used with direct or indirect cores as an alternative to the conventional cast post and core. It is unclear how the fracture strength of zirconia posts with composite or ceramic cores and titanium posts with composite cores compares to the fracture strength of gold posts and cores after dynamic loading.

PURPOSE

This study compared the fracture strength of endodontically treated, crowned maxillary incisors with limited ferrule length and different post-and-core systems after fatigue loading.

MATERIAL AND METHODS

Sixty-four caries-free, human maxillary central incisors were divided into 4 groups. After root canal treatment, Group 1 was restored with titanium posts and composite cores, Group 2 with zirconia posts and composite cores, and Group 3 with zirconia posts and heat-pressed ceramic cores. Teeth restored with cast-on gold posts and cores served as the controls (Group 4). Teeth were prepared with a circumferential shoulder including a 1 to 2 mm ferrule; all posts were cemented with an adhesive resin cement, restored with complete-coverage crowns, and exposed to 1.2 million load cycles (30 N) in a computer-controlled chewing simulator. Simultaneous thermocycling between 5 degrees C and 55 degrees C was applied for 60 seconds with an intermediate pause of 12 seconds. All specimens that did not fracture during dynamic loading were loaded until fracture in a universal testing machine at a crosshead speed of 1.5 mm/min; loads were applied at an angle of 130 degrees at the incisal edge. Fracture loads (N) and modes (repairable or catastrophic) were recorded. The Kruskal-Wallis test was used to compare fracture loads among the 4 test groups. Analyses were conducted both with and without the specimens that failed during the chewing simulation. A Fisher exact test was performed to detect group differences in fracture modes. A significance level of P<.05 was used for all comparisons.

RESULTS

The following survival rates were recorded after the chewing simulation: 93.8% (Group 1), 93.8% (Group 2), 100% (Group 3), and 87.5% (Group 4). The median fracture strengths for Groups 1 to 4 were 450 N, 503 N, 521 N, and 408 N, respectively. No significant differences were detected among the groups. The use of zirconia posts resulted in a nonsignificant lower number of catastrophic root fractures.

CONCLUSION

Within the limitations of this study, the results suggest that zirconia posts with ceramic cores can be recommended as an alternative to cast posts and cores. If a chairside procedure is preferred, zirconia or titanium posts with composite cores can be used. Clinical trials are required to verify these in vitro results.

Oral piercing in athletes: implications for general dentists

General dentists need to be aware of the growing number of athletes who display various forms of body art. Intraoral piercing and tongue jewelry place athletes at greater risk for serious medical and dental consequences that are confounded when the athlete attempts to compete while wearing a mouthguard with the tongue jewelry in place. All body jewelry should be removed during sporting events. General dentists have a professional responsibility to: become more aware of the extent and implications associated with tongue piercing in athletes to discourage athletes from having the tongue pierced; be prepared to manage postpiercing intraoral and dental complications; provide proper advice for the care and use of a mouthguard in the presence of tongue jewelry; and develop educational strategies that address the medical and dental complications of intraoral piercing.

Effects of root canal sealers on vertical root fracture resistance of endodontically treated teeth

The aim of this study was to compare vertical forces at fracture of endodontically treated mandibular incisors obturated with different types of root canal sealer. Four groups of 10 teeth each were tested; group 1 served as positive and negative controls (five teeth each), and groups 2, 3, and 4 were obturated by lateral condensation with gutta-percha and AH Plus, Tubliseal, or Ketac-Endo, respectively. All teeth were loaded vertically using a plugger tip inserted into the canal space until fracture occurred; the load at fracture and the pattern of fracture were recorded. Statistical analysis was performed using a one-way analysis of variance and post hoc Scheffé test at the 95% level of confidence. Force at fracture of roots obturated with Ketac-Endo was significantly higher than those obturated with AH Plus and Tubliseal. Most fracture lines were in a buccolingual direction. The results suggested that Ketac-Endo strengthens endodontically treated roots and may be used for weak roots, which are likely to be susceptible to vertical root fracture.

[Fracture strength of custom-fabricated celay all-ceramic post and core]

OBJECTIVE

The purpose of this study is to compare the fracture strengths of custom-fabricated Celay all-ceramic post-core, custom cast metal post-core, and prefabricated stainless steel post (Parapost) plus composite resin core with or without a 2.0 mm dentine ferrule.

METHODS

A total of 60 recently extracted human maxillary central incisors were endodontically treated and divided into five groups of 12. They were given the following treatments: Group A: Celay ceramic post-core with 2.0 mm dentine ferrule, Group B: Celay ceramic post-core with no dentine ferrule, Group C: cast metal post-core with 2.0 mm dentine ferrule, Group D: cast metal post-core with no dentine ferrule, and Group E: prefabricated post and composite core with 2.0 mm dentine ferrule. All specimens were stored at 100% humidity at room temperature for 30 days before testing. Each specimen was in a special jig at a 45 degrees angle to the long axis and subjected to a load on MTS 810 universal material testing machine until failure, with crosshead speed of 0.02 cm/min. Analysis of variance followed by the Newman-Keuls pairwise multiple comparison test was used to compare the results of the groups tested.

RESULTS

There was a statistically significant difference between five groups (P < 0.01). Celay ceramic post-core with 2.0 mm dentine ferrule (758.35 N +/- 119.26 N) and cast metal post-core with 2.0 mm dentine ferrule (756.63 N +/- 166.22 N) had a significantly larger mean failure threshold for fracture than the other three groups which had no significant difference between each other. There was a statistically significant difference between the fracture resistance of Celay post-core restored teeth with and without 2.0 mm dentine ferrule.

CONCLUSION

The custom-fabricated Celay post-core could be a choice for clinical use in endodontically treated tooth when the final restoration is an all-ceramic crown and the preparation has a 2.0 mm dentine ferrule.

Preservation-based approaches to restore posterior teeth with amalgam, resin or a combination of materials

This review is a systematic assessment, from the literature, of the status quo of dental amalgam, resin-based composite and glass-ionomer restorations for carious lesions as it applies to new concepts, coupled with clinical research. Scientifically based and practical new materials and techniques are recommended to include in contemporary practice throughout the world. Clinical and laboratory studies which have been carried out in light of modern conservative principles, and in light of the current emphasis of treating dental caries as a disease process were reviewed and discussed. An approach to managing carious lesions based upon selected advantages of dental amalgam, resin-based composite and glass-ionomer technology applied to what is termed "preservation-based" approaches to restoring teeth has been synthesized. Researched evidence contradicts the notion of "extension for prevention" in favor of maintaining sound tooth structure which would translate into more patients with healthy dentitions for entire lifetimes.

Intermittent loading of teeth restored using quartz fiber, carbon-quartz fiber, and zirconium dioxide ceramic root canal posts

PURPOSE

The purpose of the investigation was to compare the performances of teeth restored with quartz fiber, carbon-quartz fiber, and zirconium-dioxide posts covered with all-ceramic crowns when subjected to a cyclic loading test performed in a wet environment.

MATERIALS AND METHODS

Forty single-rooted human lower premolars having similar dimensions were endodontically treated and mounted in acrylic resin blocks with a simulated periodontal ligament. The teeth were divided into three experimental groups and one control group. Post holes 8 mm long were prepared in the roots of the experimental groups in which quartz fiber, carbon-quartz fiber, and zirconium dioxide posts were cemented. In the control group, no posts were used. The crown buildup was made with composite resin. The teeth were covered with all-ceramic crowns and intermittently loaded at an angle of 45 degrees to the long axis of the tooth at a frequency of two loads per second.

RESULTS

Only one failure (root fracture + post fracture) was observed in each of the fiber post groups, while in the zirconium dioxide post group, six failures were observed (one crown fracture and 5 root fractures + post fractures). The Kaplan-Meier analysis of the three experimental groups showed that the survival rate of zirconium dioxide posts was significantly lower than that of both types of fiber post. All the experimental groups showed a survival rate higher than that of the control group.

CONCLUSION

Fiber posts reduced to a minimum the risk of root fractures of teeth restored with composite cores and Empress crowns under the present experimental conditions (intermittent loading in a wet environment).