Vertical root fractures and dentin defects: effects of root canal preparation, filling, and mechanical cycling.
BACKGROUND
The aim of this study was to evaluate the ex vivo effects of root canal preparation, filling techniques, and mechanical cycling (MC) on the incidence of dentin defects and vertical root fractures (VRFs).


METHODS
Seventy extracted single-rooted teeth were divided into 6 groups. The first 2 groups were the unprepared and unprepared/MC groups. The other groups were prepared by using Gates Glidden drills and ProTaper Universal files up to F3 and were grouped according to the following: prepared teeth and the absence of root canal filling, passive technique, lateral compaction, and Tagger's hybrid technique. All of the groups except the unprepared group were subjected to MC (1,000,000 cycles, 90 N, 4 Hz, 37°C). The roots were then sectioned horizontally at 3, 6, and 9 mm from the apex and observed under a ×10 stereomicroscope. The defects were categorized as no defect, vertical root fracture, and other defects. The differences between the groups were analyzed by using the Fisher exact and χ(2) tests.


RESULTS
MC by itself did not influence the incidence of dentinal defects (P > .05, between the unprepared and unprepared/MC groups). The filled groups presented a similar incidence of other defects (P > .05), although VRFs were observed only when the MC was associated with pressure filling techniques (the lateral compaction and Tagger's hybrid groups).


CONCLUSIONS
MC by itself did not induce VRF. When associated with apical pressure filling techniques, however, VRF occurred in 13.3% (lateral compaction) and 33.3% (Tagger's hybrid) of the cases.
Conservative Dentistry Department, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil. myca_barreto@hotmail.com
Mirela Sangoi
MS
Barreto
Rafael do Amaral
Rdo A
Moraes
Ricardo Abreu da
RA
Rosa
Carlos Heitor Cunha
CH
Moreira
Marcus Vinícius Reis
MV
Só
Carlos Alexandre Souza
CA
Bier
D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003764:Dental Materials / Q000737:chemistry; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000293:injuries*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D004492:Edetic Acid / Q000627:therapeutic use; D004853:Epoxy Resins / Q000627:therapeutic use; D004867:Equipment Design; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D006813:Humidity; D012387:Root Canal Filling Materials / Q000627:therapeutic use; D012388:Root Canal Irrigants / Q000627:therapeutic use; D012389:Root Canal Obturation / Q000009:adverse effects*; D018915:Root Canal Preparation / Q000009:adverse effects* / Q000295:instrumentation; D012973:Sodium Hypochlorite / Q000627:therapeutic use; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D019227:Tooth Apex / Q000473:pathology; D014082:Tooth Fractures / Q000209:etiology*; D014092:Tooth Root / Q000293:injuries*
D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; D004853:Epoxy Resins; D012387:Root Canal Filling Materials; D012388:Root Canal Irrigants; C534916:epoxy resin-based root canal sealer; C533204:filtek Z350; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate; D006171:Gutta-Percha; D004492:Edetic Acid; D012973:Sodium Hypochlorite