Exploring fiberglass post numbers for enhanced fatigue resistance in molars without coronary remnants

Vazzoler, Lais Oliveira; Rosa, Lucas Saldanha da; Velho, Helder Callegaro; Dotto, Lara; Valandro, Luiz Felipe; Bacchi, Atais; Sarkis-Onofre, Rafael; Spazzin, Aloisio Oro; Alessandretti, Rodrigo; Pereira, Gabriel Kalil Rocha

doi:10.1590/0103-6440202405946

Brasil

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ARTICLE • Braz. Dent. J. 35 • 2024 • https://doi.org/10.1590/0103-6440202405946 linkcopy

Exploring fiberglass post numbers for enhanced fatigue resistance in molars without coronary remnants

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Abstract

This study aimed to assess the fatigue resistance of molars lacking a coronary remnant, using zero, one, two, or three fiberglass posts. Forty caries/crack-free human molars with coronal portions removed at the pulp chamber floor were randomly allocated into four groups (n=10). Following endodontic treatment, posts (Whitepost DC/DC.E 0.5, 1.0, FGM) were silanized (silane agent, Angelus) and cemented with a resin cement (RelyX U200, 3M ESPE). Resin composite cores (Z350, 3M ESPE) were built, and metal crowns were fabricated and cemented using the same luting system. Samples underwent cyclic fatigue testing at 45°, applying load in the occlusal surface at 10 Hz and 100 N initial load for 10,000 cycles, with 50 N increments every 10,000 cycles until failure. Fatigue failure load and cycles for failure data were recorded and subjected to survival analysis through Kaplan-Meier and Mantel-Cox post hoc tests, and Weibull analysis. Fractography patterns of failed crowns were qualitatively analyzed. The group without posts exhibited the lowest fatigue performance (p < 0.05) for both fatigue failure load and cycles to failure. Superior fatigue performance was observed in the three-post group, followed by groups with one or two posts, corroborated by the Weibull characteristic strength parameter. Weibull moduli were similar among conditions. All specimens exhibited failure involving detachment of the restorative set (posts/core/crown) with a portion of the dental remnant, without tooth fracture. Thus, when restoring mandibular molars without crown remnants, the use of fiberglass posts promotes greater fatigue resistance to oblique loads.

Key Words: Fatigue resistance; intraradicular posts; post and core technique; survival analysis; rehabilitation of endodontically treated teeth

Groups	FFL			CFF
	Kaplan-Meier analysis and Mantel-cox post-hoc tests*	Weibull analysis**		Kaplan-Meier analysis and Mantel-cox post-hoc tests*	Weibull analysis**
	Mean (Standard Deviation)	Characteristic parameter (95% Confidence interval)	Weibull modulus (95% Confidence interval)	Mean (Standard Deviation)	Characteristic parameter (95% Confidence interval)	Weibull modulus (95% Confidence interval)
Without post	166.67 ^C (16.67)	184.30 ^C (150.50 - 222.80)	3.96 ^A (2.21 - 6.28)	23,334 ^C (3,334)	26,302 ^C (19,575 - 34,682)	2.73 ^A (1.50 - 4.37)
One post	333.33 ^B (31.18)	365.30 ^B (310.10 - 426.40)	5.01 ^A (2.61 - 8.59)	56,667 ^B (6,237)	62,700 ^B (51,288 - 75,872)	4.08 ^A (2.12 - 6.99)
Two posts	311.11 ^B (33.10)	345.90 ^B (274.70 - 429.30)	3.44 ^A (1.98 - 5.29)	52,223 ^B (6,621)	58,364 ^B (44,728 - 75,557)	2.93 ^A (1.68 - 4.52)
Three posts	494.44 ^A (55.56)	549.60 ^A (439.40 - 678.40)	3.60 ^A (1.97 - 5.76)	88,889 ^A (11,112)	99,341 ^A (77,185 -126,020)	3.19 ^A (1.74 - 5.13)

Groups	FFL (N) / CFF (Count)
Groups	100/ 10,000	150/ 20,000	200/ 30,000	250/ 40,000	300/ 50,000	350/ 60,000	400/ 70,000	450/ 80,000	500/ 90,000	550/ 100,000	600/ 110,000	650/ 120,000	700/ 130,000	750/ 140,000
Without post	0.78 (0.14)	0.44 (0.17)	0.11 (0.11)	0.0	-	-	-	-	-	-	-	-	-	-
One post	1.0	1.0	1.0	0.67 (0.16)	0.67 (0.16)	0.56 (0.17)	0.0	-	-	-	-	-	-	-
Two posts	1.0	1.0	0.89 (0.11)	0.56 (0.17)	0.22 (0.14)	0.22 (0.14)	0.22 (0.14)	0.11 (0.11)	0.0	-	-	-	-	-
Three posts	1.0	1.0	0.89 (0.11)	0.89 (0.11)	0.89 (0.11)	0.78 (0.14)	0.67 (0.16)	0.56 (0.17)	0.44 (0.17)	0.33 (0.16)	0.22 (0.14)	0.11 (0.11)	0.11 (0.11)	0.0

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[TFN1] * Different letters on these columns indicate statistical differences between evaluated conditions depicted by Kaplan-Meier and Mantel-Cox post-hoc tests (α = 0.05).

[TFN2] ** Different letters on these columns indicate statistical differences between evaluated conditions depicted by Weibull Analysis, based on the absence of overlap of 95% confidence intervals (maximum likelihood estimation).