Tayfun Alaçam

Analysis of stress distribution in a maxillary central incisor subjected to various post and core applications

In this study, stress distribution in a maxillary central incisor that was subjected to endodontic treatment and various post and core applications was determined by using a three-dimensional finite-element method. Cast gold post and gold core and different combinations of prefabricated stainless steel post, or a prefabricated titanium post with amalgam or composite cores were considered. In all cases, the tooth was assumed to have a porcelain crown. The primary purpose of the study was to evaluate the stress distribution due to simulated biting forces and thus investigate the reliability of different post and core applications. It was found that, within the limitations of the study, the cast gold post and gold core application yielded the best result. The second purpose of the study was to highlight the importance of using a unique stress value, which contains the effects of all the possible stress components existing upon loading in the determination of a possible failure. A resultant stress value and all the constituent components were shown in detail, and it was proved that an estimation independently based on an individual component might lead to erroneous results.

Second mesiobuccal canal detection in maxillary first molars using microscopy and ultrasonics.

The aim of this study was to investigate whether the use of operating microscope in combination with ultrasonics increased the rate of second mesiobuccal (MB2) canal detection in permanent maxillary first molar teeth. A hundred extracted human maxillary first molars were assessed. After location of the main canals, the MB2 canal was sought in all teeth first without microscopy, then with the aid of the operating microscope and finally with the combined use of the operating microscope and ultrasonics. With these techniques, the MB2 canal was detected in 62%, 67% and 74% of the teeth, respectively. The combination of the operating microscope and ultrasonics detected significantly more MB2 canals than when no microscopy was utilized (P < 0.05). Sectioning of the roots disclosed the presence of the MB2 canal in 82% of the teeth. Twenty-nine per cent of the teeth had a separate MB2 canal orifice and separate apical foramina. The results of this study suggested that the combined use of the operating microscope and ultrasonics increased the detection of MB2 canals in maxillary first permanent molars.

Fracture resistance of thin‐walled roots restored with different post systems

AIM To compare the fracture resistance of thin-walled roots after restoration with different types of post systems. METHODOLOGY One hundred and sixty-five decoronated maxillary central incisors were root filled and randomly assigned to three groups with respect to the remaining dentine thickness of root (1.0 mm, 1.5 mm, 2.0 mm). Each group was randomly divided into five equal subgroups. The subgroups were restored with one of the following post systems: polyethylene woven fibre (R), composite resin cured by light-transmitting post + glass fibre post (L), electrical glass fibre post (E), composite corono-radicular restoration (C) and cast metal post (M). Standard cores were constructed using composite resin in the first four groups. The samples were subjected to a gradually increasing force (1 mm min(-1)). The force required to fracture was recorded. The data was analysed with anova and Tukey test (P = 0.05). RESULTS The cast metal post group had the highest fracture strength (P < 0.001). There was no significant difference in fracture resistance between the other four groups. Fracture resistance was affected largely by the remaining dentine thickness in fibre post groups; however, the difference was not significant. On the contrary in the cast metal post group load failure was inversely influenced by axio-proximal dimension of dentine walls. CONCLUSION The cast post group had a higher fracture strength than resin groups. The force required to fracture the roots was similar for all fibre post systems and for all dentine thicknesses.

Interappointment Emergencies in Teeth with Necrotic Pulps

The incidence of interappointment emergencies in symptomatic and asymptomatic teeth with necrotic pulps was evaluated, and severity of flare-ups was determined by a quantitative method using a flare-up index. There were no significant differences in the incidence of flare-ups attributable to gender, age, diameter of lesion, taking analgesics, placebos, or no medication, or preoperative symptomatic or asymptomatic tooth diagnoses (p > 0.05). There were significantly more painful flare-ups in mandibular teeth than in maxillary (p < 0.05).

Analysis of stress distribution in a vertically condensed maxillary central incisor root canal

In this study, the stress distribution in a maxillary central incisor subjected to an endodontic treatment was determined by using a three-dimensional finite-element method. The tooth had a variable root canal cross-sectional area, and the canal was assumed to be filled with vertical condensation. The Clinical practice was simulated by considering the obturation in successive stages. The main aim of the study was to investigate the possibility of fracture due to the obturation process. It was found that, within the limits of the study, the likelihood of a root fracture in such a process is a remote possibility.

Substance P Expression Is Elevated in Inflamed Human Periradicular Tissue

Substance P is a neuropeptide believed to be a major mediator of neurogenic inflammation. The aim of our study was to evaluate whether substance P levels are elevated in the clinical biopsies collected from inflamed periradicular or control tissue. In this study, the presence of substance P was examined in infected human periradicular granulation tissue and control tissue. Sections from 19 periradicular granulomas and pulp tissues from two healthy control teeth were examined using the immunohistochemical method. Substance P-expressing neutrophils, macrophages, and plasma cells were found in both acute and chronic periradicular granulomas. In addition, we observed the presence of neutrophils expressing substance P without concurrent clinical symptoms of acute inflammation. Our results are consistent with the hypothesis that substance P may be released from neutrophils in the inflamed region, and thus, substance P may modulate clinical inflammatory response by release from either neuronal or immunocompetent cell populations.

Evaluation of diagnostic radiopaque contrast materials used with calcium hydroxide

An evaluation of three different radiopaque materials used in combination with calcium hydroxide powder for diagnostic contrast was made. Diatrizoate meglumine (65%) and iothalamate meglumine (60%) compared favorably with barium sulfate (35%). Since barium sulfate has demonstrated problems by altering the manipulative properties of calcium hydroxide as well as demonstrating a residual radiopacity, there may be advantages to the use of resorbable diatrizoate or iothalamate compounds as alternatives. These soluble iodine compounds also make possible an excellent aqueous medium in which to mix calcium hydroxide.

Structural effects of sodium hypochlorite solution on RaCe rotary nickel-titanium instruments: an atomic force microscopy study

OBJECTIVE The aim of this study was to investigate the effect of sodium hypochlorite immersion on the surface characteristics of RaCe rotary nickel-titanium instruments using atomic force microscopy (AFM). STUDY DESIGN Four new RaCe instruments were used in this study (two 30.06 and two 30.02). One 30.06 and one 30.02 instrument were immersed in sodium hypochlorite solution for 5 min. Surface topography of the instruments was evaluated using the AFM. The instruments were analyzed on 11 points along a 3-mm section. Root mean square (RMS) values were used to compare the topographic deviations. The data were analyzed using Student t test. RESULTS Mean RMS values for NaOCl measurements were higher than the measurements on new files, and the difference was statistically significant (P < .01). CONCLUSION The AFM results show that NaOCl causes deterioration on the surface of RaCe instruments and should be used with care during clinical use because of the risk of unexpected failure.

Lactate dehydrogenase activity in periodontal ligament cells stored in different transport media.

BACKGROUND Maintaining viability of periodontal ligament cells is important after an avulsion injury occurs. OBJECTIVE This study examined cell death and compared different transport media at varying times. Lactate dehydrogenase (LD) measurements were made on root surfaces of extracted teeth for evaluating the results of breakdown and necrosis of periodontal ligament cells. STUDY DESIGN Teeth were divided into three groups. Each was immersed in one of the following storage media: Hanks balanced salt solution, Custodiol solution (an organ storage medium), or sterile saline solution. I.D. measurements (an indicator of cell death) were made at 2, 6, 24, 72, and 168 hours after extraction. RESULTS When the LD levels were compared according to the time periods, a progressive increase of cell death was found to be statistically significant (p < 0.001). However, when the effects of both time periods and the kind of storage medium on the LD levels were examined, the LD levels of the saline solution storage medium were found to be significantly higher (p < 0.001) than that of the other two groups. CONCLUSIONS Both Hanks balanced salt solution and Custodiol appeared to be suitable transport media for maintaining cell viability, whereas saline solution was not.

Incidence of postoperative pain following the use of different sealers in immediate root canal filling

Summary A clinical investigation was conducted to compare the incidence and type of postoperative pain in singlevisit endodontic therapy when different root canal sealers were utilized (lodoform, Oxpara, Endomethasone, and AH26). There was no statistical significance between the presence and type of postoperative discomfort and the type of sealer utilized.