Effect of the Degree of Conversion on Mechanical Properties and Monomer Elution from Self-, Dual- and Light-Cured Core Composites.

The objective of this work was to measure and correlate the degree of conversion (DC), mechanical properties and monomer elution from self-, dual- and light-cured core composites. Five samples of each of the following materials were prepared for each test: Clearfil (Core, Photo Core, Automix), Bisco (Core-Flo, Light-Core and Bis-Core). DC was determined using FTIR, compressive and flexural strength and modulus of elasticity using a universal testing machine and microhardness using Vickers hardness. Elution was measured using HPLC. One-way ANOVA with Tukey's post-test and Pearson's correlation were used to statistically analyze the data. DC of Clearfil-Dual (70.1%) and Clerafil-Photo (66.8%) were higher than Clearfil-Self (55.4%) and all Bisco materials (51.4-55.3%). Flexural strength of Clearfilwas higher than that of Bisco composites. The Microhardness of Clearfil-Dual (119.8VHN) and Clearfil-Photo (118.0VHN) were higher compared to other materials. The greatest elution was detected from self-cured materials. DC positively correlated to microhardness and compressive/flexural strength and negatively to BisGMA elution. Clearfil-Photo and Automix showed higher conversion, lower monomer elution and, generally, better mechanical properties. Self-cured composites should not be recommended for routine clinical use as their performance was inferior to dual- and light-cured composites. Microhardness may be used as an indicator of elution.

Comparison of efficacy of local hemostatic modalities in anticoagulated patients undergoing tooth extractions.

BACKGROUND/AIM: Patients receiving long-term oral anticoagulant therapy pose a clinical challenge during invasive dental procedures. The goal of this study was to compare different local hemostatic modalities after tooth extraction in patients receiving chronic Vitamin-K antagonist therapy. METHODS: Totally 90 patients with International Normalized Ratio (INR) ≤ 3.0 requiring simple extraction of one or two teeth were randomized into three groups, 30 patients in each group. The patients with the mean INR value of 2.35 ± 0.37, in whom extraction wound was sutured comprised the group A. In the group B with the mean INR of 2.43 ± 0.4, local hemostasis was achieved by placing absorbable gelatin sponges into the wound without suturing. The group C consisted of the patients with the mean INR of 2.36 ± 0.34 in whom neither gelatin sponge nor suturing were used for providing local hemostasis. Bleeding was registered as an event if other than initial hemostatic measure was needed or additional oral surgeon intervention required. RESULTS: The obtainded results show that 1 (3.3%) patient in the group A, 2 (6.7%) patients in the groups B and C manifested post-extraction bleeding. All cases of hemorrhage were easily solved with local hemostatic measures and all, except one case, were registered in the first two hours after the procedure until the dismissal. A difference between the groups was not statistically significant (χ2 = .42, p > 0.05). CONCLUSION: In therapeutically anticoagulated patients tooth extractions can be safely performed without altering the dose of anticoagulant medication if efficient local hemostasis is provided. In most cases; in patients with INR ≤ 3.0 after extraction of one or two teeth postoperative bleeding can be controlled with local pressure, without any additional local hemostatic measures.

Examination of the bioelectrical activity of the masticatory muscles during Angle's Class II division 2 therapy with an activator.

BACKGROUND/AIM: The muscles of the orofacial region have great influence on the development of dentition and occlusion formation. It is known that improper function of these muscles is one of the major etiological factors in malocclusion. A correlation between function disorders of orofacial muscle and occlusion disorders has been confirmed, as well as a correlation between the bioelectric activity of the masticatory muscles, recorded by electromyography, and bite force upon maximal voluntary contraction of these muscles. The aim of the study was to analyze the bioelectriacal activity of temporal and masseter muscles. METHODS: The sample consisted of 100 subjects of both sexes, divided into the control group (n = 30) with neutral and complete dental arches, and the study group (n = 70) of patients with distal occlusion. Electromyographic measurement of bioelectric potentials in all the subjects was conducted for the examined muscles in the physiologic rest position, central mandible occlusion, and during maximal voluntary contraction of muscles and saliva swallowing, in Angle Class I and II/2 occlusal relationships, prior to treatment, after one year of the orthodontic treatment and after the treatment with an activator. RESULTS: Comparing the values of the bioelectrical activity in the control and the study group before the treatment, a decreased muscle activity was established in all the three positions in the study group. After the first year of orthodontic treatment the results showed an elevation in the bioelectrical activity in both muscles. After treatment with an activator, the bioelectrical activity in both muscles in the study group was higher than before the treatment, as it is confirmed by a positive highly significant coefficient of correlation. CONCLUSION: In all the three measured positions of the mandible with Angle Class II/2 malocclusion, bioelectrical activity was lowest at baseline and increased during the first year of treatment, and at the end of the treatment it partially reduced close to the approximate values in normal occlusion. Research on electromyographic activity of masticatory muscles is useful in everyday clinical practice, especially in present distinctive skeletal discrepancy before, during and after orthodontic treatment, if on the bases of the results we can evaluate the treatment, but also determine the start and duration of the retention period and retention device type.

Improving mechanical properties of flowable dental composite resin by adding silica nanoparticles.

BACKGROUND/AIM: The main drawback of flowable dental composite resin is low strength compared to conventional composite resin, due to a low amount of filler, neccessary for achieving low viscosity and ease of handling. The aim of this study was to improve mechanical properties of flowable dental composite resin by adding small amount of nanoparticles, which would not compromise handling properties. METHODS: A commercially available flowable dental composite resin material was mixed with 7 nm aftertreated hydrophobic fumed silica and cured by an UV lamp. Four sets of samples were made: control sample (unmodified), the sample containing 0.05%, 0.2% and 1% nanosilica. Flexural modulus, flexural strength and microhardness were tested. One-way ANOVA followed by Tukey's test with the significance value of p < 0.05 was performed to statistically analyze the obtained results. Furthermore, differential scanning calorimetry (DSC) and SEM analysis were performed. To asses handling properties, slumping resistance was determined. RESULTS: It was found that 0.05% is the most effective nanosilica content. All the tested mechanical properties were improved by a significant margin. On the other hand, when 0.2% and 1% nanosilica content was tested, different results were obtained, some of the mechanical properties even dropped, while some were insignificantly improved. The difference between slumping resistance of unmodified and modified samples was found to be statistically insignificant. CONCLUSIONS: Low nanosilica addition proved more effective in improving mechanical properties compared to higher additions. Furthermore, handling properties are unaffected by nanosilica addition.

A biomechanical model for a new incremental technique for tooth restoration.

The objective of this study is to introduce a modified incremental technique that leads to improved marginal adaptation and to develop a mathematical model that explains the results obtained. The technique proposed is a two-step incremental technique that reduces volume of a resin that is polymerized at each step and eliminates the central point in resin, so that the stresses are additionally reduced. In the first step, the resin is placed in the cylindrical cavity with a conical dental instrument embedded in the middle of restoration. After polymerization, the conical dental instrument is removed and the conical hole is filled with the second layer of composite and polymerized. This technique is a variant of a method where singular stress point is eliminated. We modified the previous technique by introducing a conical dental instrument into the centre of the cavity. The procedure proposed was compared with the bulk and horizontal layer incremental technique. This study confirmed that the incremental type placement technique used here has better marginal adaptation than bulk technique and horizontal two-layer incremental technique although it has larger C-factor in the first step than the two-layer incremental technique. Thus, the elimination of the central point of restoration leads to better marginal adaptation. Conical shape of the cavity that is filled in the second step makes this technique easy to apply in clinical conditions. A mathematical model describing stresses in the restoration shows stress reduction as a consequence of applying the procedure proposed.

[Orthodontic-surgical therapy of retained upper canine].

INTRODUCTION: Therapy of impacted teeth is undoubtedly one of the most intriguing issues for the experts in the field of dentistry. General dental practitioners, as well as specialists in the field of pediatric dentistry, periodontology, orthodontics and particularly oral and maxillofacial surgery have been facing this challenge throughout past several years. Each of these experts can contribute to solving this problem; however, each of them alone can solve only a limited number of cases. DISCUSSION AND CONCLUSION: Since recently, the fate of impacted tooth has been determined mainly by the competence, experience and skill of the orthodontist to apply light traction in an appropriate direction once the tooth has been made surgically exposed. Oral surgeon and orthodontist should share the responsibility for a patient with impaction as they together have the necessary skill and competence required for an effective therapy. In addition, dental age of the child is to be taken into consideration, as well as his/her overall health status and potential interference with other anomalies of dental arch.

Influence of surgical sutures on wound healing.

Historical data on closing and suturing of surgical wounds describe a wide range of various suture materials. The choice of the surgical catgut, i.e. the type and diameter, depends on the locality, characteristics and condition of the tissue to be treated. From the standpoint of oral-surgical practice the following clinical parameters are of outstanding importance with respect to the selection of suture material: accumulation of soft deposits on the sutures, score of the adjacent soft tissues and dehiscence of the operative wound. Our prospective clinical study included 150 patients distributed into three groups of 50 subjects. The surgical procedure performed on each patient involved resection (apicotomy) of the tooth root end in the intercanine sector of the upper jaw. The following suture materials were applied: Black Silc 5-0, Nylon 5-0 and Vicryl 5-0. The effects of the selected sutures were evaluated according to the wound dehiscence. The effects of the applied sutures were recorded on Days 2, 5 and 7 after the surgery. The comparison of cited parameters of the investigated materials after suturing the oral mucosa revealed that none of the used material was ideal; however, a certain advantage might be given to the synthetic monofilament suture materials.

[Choice of surgical suture material used in oral cavity-clinical study].

INTRODUCTION: Historical data on closing and suturing of surgical wound describe a wide range of various suture materials. The choice of the surgical catgut, i.e. type and diameter, depends on the localization, characteristics and condition of the tissue to be treated. From the standpoint of oral-surgical practice the following clinical parameters are of the outstanding importance regarding the choice of suture material: accumulation of soft deposits on the sutures, decubitus of the adjacent soft tissues and dehiscence of the operative wound. AIM: The aim of this research was to determine the correlation between different types of suture materials and accumulation of soft deposits on the sutures, decubitus of the adjacent soft tissues and dehiscence of the operative wound. MATERIAL AND METHODS: Our prospective clinical study included 150 patients distributed into three groups of 50 subjects. The surgical procedure performed on each patient involved resection (aplicoectomy) of the tooth root end in the intercanine sector of the upper jaw. The following suture materials were applied: BLACK SILK 5-0, NYLON 5-0 and VICRYL 5-0. The effects of the selected sutures were evaluated by using several parameters: accumulation of soft deposits, wound dehiscence and decubitus of the adjacent soft tissues. The effects of the applied sutures were recorded on days 2, 5 and 7 after the surgery. CONCLUSION: The comparison of cited parameters of the investigated materials of ter suture of oral cavity mucosa revealed that none of the used material was ideal; however a certain preference might be given to the synthetic monofilament suture materials.