Journal of Dental Medicine
Year:2001 | Volume:14 | Issue:1 (26)|Papers Count:12

The formation of oxides on the surface of the metal is proven to contribute to the formation of strong bonding. However, The base metal alloys are expected to exhibit more oxidation than high gold alloys, increase in oxide layer thickness due to repeated firing in them can reduce the bond strength. The aim of this study was to compare the effect of repeated porcelain firing on the bond strength of two base metal alloys (Minalux and Verabond II). Sixteen metal plates (20 5 0.5) from each alloy were cast and prepared according to the manufacturers instruction. Porcelain with uniform thickness (1mm) was applied on the middle one third of metal plates. After this stage, each alloy group divided to three subgroups. Group I was fired for the second time to form the final glaze, group II and III were fired two and four more times respectively. Specimens were subjected to 3-point flexural test in a digital tritest machine. Results showed no significant differences between bond strength of two alloys. Also results showed repeated firing had no significant effect on bond strength. Due to these findings, this study support similarity of two alloys (Minalux and Verabond II) in their bond strength with porcelain.

Dry socket is one of the most common complications of teeth extractions. Etiology and pathogenesis of dry socket are not clearly known but many related predisposing factors have been discussed. According to this, a cross- sectional study was conduced at the department of oral and maxillofacial surgery (Tehran University of Medical Sciences, Oct. 97- Jul. 98). 4880 teeth were extracted which 25 of them recalled with dry socket. The relationship between the effective factors and dry sockets was evaluated. The effective factors were as follows: age, sex, site of extraction, and trauma during exctraction, infection, oral hygiene, smoking, and systemic diseases. Results showed that the incidence of dry socket was %0.5, and the number of cases observed in women was two times more than men. Also, mandibular third molars were involved more than any other areas.

Carious lesions are usually found by dentists, using bitewing radiographs, and according to the depth of the lesions, the treatment plan is designed. At the present, this technique is the most accepted one and is used generally. But it is not a perfect technique and there are some errors in determining of depth of proximal carious lesions. These errors are mainly related to the use of new high-speed films with broad density and lower voltages. In this study, dentin thickness under proximal caries in bitewing radiography was compared with its real thickness, in tooth structure. Twenty-four teeth samples with proximal caries were used. Before and after removal of carious lesions bitewing radiographs were taken and then each tooth was sectioned occlusogingivally and the thickness of dentine under proximal caries and on bitewing radiographs were measured under microscope with 0.01 mm accuracy. Mean value of dentine thickness in tooth structure was 41% of its mean thickness in bitewing radiographs, showing 59% difference (reduction). Therefore, more care should be taken in using standard technique and interpreting of bitewing radiographs by clinicians. Clinical examinations also should be performed in ideal conditions, and patients should be clinically and radiographically examined every six months.

Sialoprotein is a phosphorylated skeletal glycoprotein. The function of sialoprotein is still not fully understood. It is possible that this component participate in cell differentiation and the conversion of unmineralized matrix into mineralized structures. The purpose of the present study was to determine the serum sialoprotein concentration in-patient and normal subjects to investigate the relationship between serum sialoprotein and dentin, enamel structural differentiation. The study group consisted of 50 patients, 32 males and 18 females, aged 17-54 (with an average of 32.5 years). The control group consisted of 50 normal volunteers, 26 males and 24 females, age 22-51 (with an average of 39.60 years). The laboratory data of this group were used as a reference. Human blood was obtained from control and patient group. The blood sample was centrifuged at 3000* g for 20 min, the supernatant was discarded. Then each sample was centrifuged for 20 min at 10000 g applied to a sepharose column and eluted with 4 moll Guanidine - HCL at 50 moll tris, pH 7.4 at a flow rate of 0.5 ml/min. The fractions obtained by chromatograply were monitored by electrophoresis. Our results showed that sialoprotein control increased in patients serum (18.45+/-3.21 micro gr/L) compared to normal subjects (11.37+/-2.45 micro gr/L).

Bone osseointegration around dental implant can cause earlier stabilization and fixtion of implant and reduce healing time. Hydroxyapatite coating can affect bone osseointegration and enhance its rates. The aim of this study was to comparison of osseointegration between plasma- sprayed hydroxyapatite coated and uncoated dental implants in cats. Four endodontic implants including, vitallium and two stainless steel with and without hydroxyapatite coating were prepared and placed in mandibular canines of 20 cats after completion of root canal treatment and osseous preparation. After a healing period of 4 months, investigation by scanning electron microscopy showed significant difference in ossointegration between coated and uncoated dental implants and average bone osseointegration of coated implants was more than uncoated implants.

One of the special kinds of periodontal disease is rapidly progressive periodontitis (RPP). This form of periodontitis is an aggressive disease, which results in bone destruction and loss of periodontal attachment 4 to 5 times more than adult periodontitis or slowly progressive periodontitis. The purpose of this study was to investigate the presence of Actinobacillus actinomyctem comitans (Aa) in RPP patients. A total number of sixty samples was collected from 15 patients with RPP and cultured in anaerobic conditions. Results showed the presence of Aa in 13 patients (86.7%), while 29 samples were Aa positive (48.3%). Two of the RPP patients (13.3%) were Aa negative even after two times bacterial culturing.

Mandibular impacted third molar surgery is one of the most common surgeries in dental office. Also, antibiotic therapy is one of the most common post-operative procedures after this surgery. However, this is yet controversial. 25 patients were entered in a double blind clinical research.The patients divided into two groups. Group A were received 500 mg Ampicillin (14 patients) and group B (11 patients) were given placebo. The package of both groups was similar. In order to consider the infection, trismus, inflammation, were recorded before and after surgery. The data was analyzed. Our results showed that antibiotic therapy before surgery does not seem necessary, if the non-traumatic surgery will be in an aseptic condition.

Many different methods are suggested to restore endodontically treated teeth. Prefabricated posts can not be indicated for all teeth and cast posts require extra time and cost. In addition, with the introduction of full ceramic restorations, achieving the ideal esthetic with metal post underneath them may be problematic or impossible because the darkness of the metallic posts may show through the highly translucent all ceramic restorations. In this article the review of litature and describiton of applied methods of different procedure in restoring the root canal therapied teeth and few techniques of non metallic posts fabrication such as fiber reinforced composite and zirconium oxide posts have been described.