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Marginal quality and fracture strength of root-canal treated mandibular molars with overlay restorations after thermocycling and mechanical loading


Dere, M; Özcan, M; Göhring, T N (2010). Marginal quality and fracture strength of root-canal treated mandibular molars with overlay restorations after thermocycling and mechanical loading. Journal of Adhesive Dentistry, 12(4):287-294.

Abstract

PURPOSE: To evaluate marginal quality, fracture modes, and loads-to-failure of different overlay restorations in rootcanal treated molars in a laboratory setup.

MATERIALS AND METHODS: Thirty-two mandibular first molars were randomly assigned to four groups (n = 8): UTR= untreated (control), RCT-COM= root canal treated (RCT)+ lab-made composite overlay, RCT-FRC= RCT+composite resin overlay with two layers of multidirectional woven glass fibers; RCT-CER: RCT+ceramic overlay. The teeth in all groups were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML with scanning electron microscopy at 200X at the tooth-to-luting composite (IF1) and luting composite-to restoration (IF2) interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Data were analyzed with ANOVA and Bonferroni correction.

RESULTS: Marginal adaptation decreased from 93 ± 3.4 to 82 ± 6.5 % at IF1 after TCML (p > 0.001) but the decrease was not significant between the groups (p = 0.8130). At IF2, ceramic overlays showed about 10% lower marginal adaptation than composite overlays (p < 0.0001). Loads-to-failure (in N) were as follows in descending order: RCT-FRC: 3619 ± 520; UTR: 3048 ± 905; RCT-COM: 2770 ± 457; RCT-CER 2036 ± 319. RCT-FRC showed significantly higher results than those of RCT-COM (p = 0.0077) and RCT-CER (p < 0.0001). Only RCT-CER showed significantly lower results than that of the control (p = 0.0019). While the fractures in the UTR occurred exclusively above the cementoenamel junction (Mode 1 and Mode 2) and were rated reparable, RCT-COM and RCT-CER showed exclusively catastrophic failures in varying modes (nodes 3 to 5). Only in group RCT-FRC, half of the specimens fractured in a reparable fracture mode (modes 1 and 2) with veneering composite delamination from the glass-fiber weaver layer.

CONCLUSION: As cusp-covering overlay restorations in root canal treated molars, composite resin overlays with and without fiber reinforcement performed similar to intact teeth with varying failure types. While intact teeth failed exclusively in reparable modes, all other restorations failed in a catastrophic manner, except half of the fiber reinforced composite group.

Abstract

PURPOSE: To evaluate marginal quality, fracture modes, and loads-to-failure of different overlay restorations in rootcanal treated molars in a laboratory setup.

MATERIALS AND METHODS: Thirty-two mandibular first molars were randomly assigned to four groups (n = 8): UTR= untreated (control), RCT-COM= root canal treated (RCT)+ lab-made composite overlay, RCT-FRC= RCT+composite resin overlay with two layers of multidirectional woven glass fibers; RCT-CER: RCT+ceramic overlay. The teeth in all groups were subjected to thermocycling and mechanical loading (TCML) in a computer-controlled masticator (1,200,000 loads, 49 N, 1.7 Hz, 3000 temperature cycles of 5°C to 50°C). Marginal adaptation was evaluated before and after TCML with scanning electron microscopy at 200X at the tooth-to-luting composite (IF1) and luting composite-to restoration (IF2) interfaces. After TCML, all specimens were loaded to failure in a universal testing machine at 0.5 mm/min. Data were analyzed with ANOVA and Bonferroni correction.

RESULTS: Marginal adaptation decreased from 93 ± 3.4 to 82 ± 6.5 % at IF1 after TCML (p > 0.001) but the decrease was not significant between the groups (p = 0.8130). At IF2, ceramic overlays showed about 10% lower marginal adaptation than composite overlays (p < 0.0001). Loads-to-failure (in N) were as follows in descending order: RCT-FRC: 3619 ± 520; UTR: 3048 ± 905; RCT-COM: 2770 ± 457; RCT-CER 2036 ± 319. RCT-FRC showed significantly higher results than those of RCT-COM (p = 0.0077) and RCT-CER (p < 0.0001). Only RCT-CER showed significantly lower results than that of the control (p = 0.0019). While the fractures in the UTR occurred exclusively above the cementoenamel junction (Mode 1 and Mode 2) and were rated reparable, RCT-COM and RCT-CER showed exclusively catastrophic failures in varying modes (nodes 3 to 5). Only in group RCT-FRC, half of the specimens fractured in a reparable fracture mode (modes 1 and 2) with veneering composite delamination from the glass-fiber weaver layer.

CONCLUSION: As cusp-covering overlay restorations in root canal treated molars, composite resin overlays with and without fiber reinforcement performed similar to intact teeth with varying failure types. While intact teeth failed exclusively in reparable modes, all other restorations failed in a catastrophic manner, except half of the fiber reinforced composite group.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Center for Dental Medicine > Clinic for Preventive Dentistry, Periodontology and Cariology
04 Faculty of Medicine > Center for Dental Medicine > Clinic for Fixed and Removable Prosthodontics
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:2010
Deposited On:06 Feb 2011 09:43
Last Modified:07 Dec 2017 06:59
Publisher:Quintessence Publishing
ISSN:1461-5185
Publisher DOI:https://doi.org/10.3290/j.jad.a17711
PubMed ID:20157656

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