Qualitative assessment of stress distribution during insertion of endodontic posts in photoelastic material.

OBJECTIVES: The purpose of this study was to investigate the stress patterns associated with prefabricated endodontic posts during the various stages of insertion according to a number of design characteristics. METHODS: In a photoelastic material with elastic properties comparable to dentin, analyses were performed of the overall stress patterns with polarized light revealing substantial differences in stresses generated by the various posts. The effects of variations in design for certain configurations of the posts were also assessed. RESULTS: One geometric feature was the retentive thread of the post. The stress patterns within the photoelastic material revealed a homogeneous distribution of stress along the entire length of the thread, and more threads induced additional stress. The stress recorded with a vent when the pitch of the thread was 0.8-1.0 mm was classified as minimal-to-mild stress. Another geometric feature considered was the head (coronal extension) of the post. Minimal stress was recorded in the material in contact with the head and the apical end of the post when the contact surface of head was more than 3 mm2. CONCLUSIONS: This study suggests that during insertion of threaded posts the least stress occurs when the head contact surface is sufficient (> or = 3 mm2). A thread with a pitch of 0.8-1.0 mm is most desirable in stress reduction. The number of windings should also be limited (less than six windings) as samples with a substantial number of windings (N = 13 or 30) produce severe stress.

Porosity in resin composite core restorations: the effect of manipulative techniques.

Forty acrylic resin duplicates of an endodontically treated and extracted human molar were restored with two resin composite materials for core restorations. Two different manipulation techniques, bulk insertion and syringe application, were used. In a simulated clinical setup, the core buildups produced by the different manipulation techniques were investigated for voids. In 20 duplicates, a post was placed to simulate a metal post and resin composite core buildup. The syringe technique produced significantly fewer incorporated voids for both resin composite core materials than did the bulk insertion technique. It was not possible to demonstrate a relationship between the presence of voids and the presence of a metal post.

Clinical performance of different post and core systems--results of a pilot study.

During the period 1974-1986, 112 post and core build-ups were inserted in 74 patients. The build-ups consisted of a metal prefabricated post (Dentatus, Unimetric or Radix) in combination with a composite core. After an average follow-up period of 7.9 years, 14 failures (12.5%) were noticed. Eight teeth could be rerestored and six teeth had to be extracted. However, when correction was made for teeth with a bad initial prognosis and for extractions not related to the build-up restoration, eight failures remained caused by failure of the build-up (7.5%). The Dentatus posts seemed to increase the risk for failure.

An analysis of durability data on post and core restorations.

An attempt was made to review the dental literature since 1970, presenting clinical data of posts and core restorations, by the use of a meta-analytic procedure. Fourteen publications were found that contained durability data on post and core systems. According to the exclusion criteria 11 studies were excluded for further analysis of the data. The survivals of these studies varied from 98.6% survival after a follow-up period of more than 10 years (F.S. Weine et al. 1991, J. Endodont. 17, 293-297) to 77.6% survival after a mean follow-up period of 5.2 years (D.H. Roberts, 1970, Br. Dent. J. 128, 117-124). The data of the three selected studies were reconstructed according to the method of Kaplan-Meier but could not be combined for an overall survival assessment because the study characteristics were too heterogeneous. Therefore the survivals were presented separately. The reconstructed survivals of the studies after 6 years were 81% survival (standard error 6%) for resin composite build-ups in combination with screw posts and 91% survival for two studies including cast posts and cores (standard errors respectively 3% and 2%). Although it was not meaningful to combine the data for an overall survival, the meta-analytic method of this study revealed homogenic survival data and as such the followed procedure is considered to be an appropriate method to obtain insights in clinical durability data.

Survival rate and failure characteristics of the all metal post and core restoration.

In this retrospective study 516 teeth restored with a cast post and core build-up were followed from 1970 till 1990. The data was derived from the dental records of 283 dental clinic patients treated by senior students. The survival rate was found to be 82% after 10 years for post and cores in the anterior region. The most frequent failure characteristic was recementation (46%), followed by rerestoration (32%). The solitary provisions in posterior teeth showed a relative high survival rate, compared with other tooth-types and locations.

[The clinical behavior of metal-composite post and core build-up. Results of a pilot study]. / Het klinisch gedrag van metaal-composiet stiftopbouwen. Resultaten van een pilot-studie.

During the period 1974-1986 112 post and core buildups were inserted in 74 patients. The buildups consisted of a metal prefabricated post (Dentatus, Unimetric or Radix) in combination with a composite core. After an average follow-up period of 7.9 years 14 failures (12.5%) were noticed. Eight teeth could be rerestored and six teeth had to be extracted. However, when correction was made for teeth with a bad initial prognosis and for extractions not related to the buildup restoration, eight failures remained caused by failure of the buildup (7.5%). Half of these concerned Dentatus posts.