Impact of Access Cavity Design and Root Canal Taper on Fracture Resistance of Endodontically Treated Teeth: An Ex Vivo Investigation.

INTRODUCTION: The susceptibility of endodontically treated teeth (ETT) to fracture is mainly associated with the loss of tooth structure. This study evaluated the effect of the access cavity design and taper preparation of root canals on ETT fracture resistance of maxillary molars. METHODS: For tapering assessment, 30 sound distobuccal roots of maxillary molars were randomly assigned to 1 of 3 groups (n = 10): a .04 taper, a .06 taper, or a .08 taper. Endodontic canal preparations were performed using the Twisted Files rotary system (Kerr Co, Glendora, CA). In addition, 48 intact maxillary first and second molars were randomly assigned to 1 of 3 groups (n = 16) for cavity preparation approaches: intact teeth, traditional access cavity (TAC), or conservative access cavity (CAC). Fracture resistance was tested using a universal testing machine. For statistical analysis, the level of significance was P ≤ .05. RESULTS: The .04 taper instrumentation had the highest fracture resistance (259.61 ± 52.06), and the .08 taper had the lowest (168.43 ± 59.63). The .04 and .06 groups did not differ significantly (P > .05); however, these groups differed significantly from the .08 group (P ≤ .05). Regarding the cavity preparation approaches, the 3 groups of intact teeth, CAC, and TAC showed fracture resistance mean values of 2118.85 ± 336.97, 1705.69 ± 591.51, and 1471.11 ± 435.34, respectively, with no significant difference between the CAC and TAC groups (P > .05). CONCLUSIONS: Increasing the taper of the root canal preparation can reduce fracture resistance. Moreover, access cavity preparation can reduce resistance; however, CAC in comparison with TAC had no significant impact.

Effect of water storage on ultimate tensile strength and mass changes of universal adhesives.

BACKGROUND: The aim of the present study was to evaluate the influence of water storage on micro tensile strength (µTS) and mass changes (MC) of two universal adhesives. MATERIAL AND METHODS: 10 disk-shaped specimens were prepared for each adhesive; Scotchbond Universal (SCU) All-Bond Universal (ABU) and Adper Single Bond 2 (SB2). At the baseline and after 1 day and 28 days of water storage, their mass were measured and compared to estimate water sorption and solubility. For µTS test, 20 dumbbell shaped specimens were also prepared for each adhesive in two subgroups of 1 day and 28 days water storage. RESULTS: MC was significantly lower for SCU and ABU than SB2 (P < 0.05) at both time intervals. In all three adhesives, the MC was significantly lower at 28 days compared to that at 1 day (P < 0.05). Similarly, µTS was significantly higher for SCU and ABU than SB2 at both storage intervals (P < 0.05). After 28 days, µTS increased significantly for universal adhesives (P < 0.05). CONCLUSIONS: MC and µTS of adhesives were both material and time dependent when stored in water; both universal adhesives showed less water sorption and higher values of µTS than the control group. Key words:Absorption, dental adhesives, dentin-bonding agents, solubility, tensile strength.

Endodontic repair in immature dogs' teeth with apical periodontitis: blood clot vs plasma rich in growth factors scaffold.

BACKGROUND/AIM: Different types of scaffolds have been suggested for endodontic repair procedures. The aim of this study was to compare the outcome of procedures using blood clot vs plasma rich in growth factors (PRGF) scaffold in immature teeth with apical periodontitis in dogs. MATERIALS AND METHODS: In this in vivo animal study, 20 teeth (30 canals) with open apices were divided into two groups (n = 12): (1) blood clot and (2) PRGF. Two positive and negative control groups were also selected randomly. After exposing the pulp and inducing periapical inflammation by placing a sponge soaked in a suspension of dental plaque, the root canals of both groups were flushed with sodium hypochlorite and filled with triple antibiotic paste. After 28 days, the antibiotic mixture was removed, bleeding was induced through the apical foramen, and mineral trioxide aggregate was placed over the blood clot in group one and PRGF scaffold in group two. Access cavities were then filled with composite resin. The radiographic and histological findings were compared immediately after the procedure, as well as after 3 and 6 months of follow-up. RESULTS: There was no statistically significant difference between the two experimental groups with regard to the radiographic or histological results (P > 0.05). The incidence of healed periapical radiolucency was 60% and 53.33% in groups one and two, respectively. Apical closure was noted in 60% of samples in both experimental groups. New cementum-like tissue formation was detected along the walls of the canals, and bone-like islands within the canals were also observed. CONCLUSIONS: Plasma rich in growth factors scaffold showed no advantage over blood clots regarding healing of the periapical radiolucency, radiographic apical closure and type of the newly formed soft and hard tissues.

Morphological patterns of lip prints in an Iranian population.

BACKGROUND: Lip prints are verified to be unique to an individual and stable over time; hence they have potential for human identification purposes. The aim of this study was to assess the individuality and variability of lip prints in an Iranian population for the first time. We also sought to assess the possibility of sex determination via lip printing. MATERIAL AND METHODS: Lip prints of 96 individuals including 22 males and 74 females were recorded on a plain white paper using a dark-colored lipstick and 50 mm of Scotch tape. Each lip print was divided into six sextants and studied independently by two observers using a magnifying lens to examine the lip grooves. The Suzuki and Tsuchihashi's classification was used to define the lip patterns and the data were statistically analyzed. RESULTS: In the present study, no identically similar lip prints were observed. Type V was the most predominant pattern recorded in the study sample (33.16%), followed by type I (24.13%), type II (18.75%), type IV (11.63%), type I' (9.72%) and type III (2.60%). In addition, no statistically significant difference was observed in the lip print patterns of males and females. CONCLUSIONS: It can be concluded that lip prints are unique and their analysis may enable human identification. Key words:Forensic anthropology, forensic dentistry, forensic medicine, iran, lip.