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PubMed2006

Reinforcement effect of polyethylene fibre in root-filled teeth: comparison of two restoration techniques.

AIM: To compare in vitro two different fibre placement techniques on reinforcement of root-filled molar teeth with mesio-occluso-distal (MOD) cavities. METHODOLOGY: Fifty sound extracted human mandibular molars were used (n = 10). Group 1 served as control. From group 2-5, endodontic access and standard MOD cavities were prepared. Following root canal treatment, group 2 was kept unrestored. In groups 3 and 4, the teeth were restored with composite resin (AP-X; Kuraray, Japan). A groove was prepared on occlusal surface of the finished restorations in group 4 from buccal to lingual direction. Polyethylene woven fibre (Ribbond; Seattle, WA, USA) was inserted in the groove in combination with flowable resin that was cured for 20 s and covered with composite resin. Cavity surfaces were covered with flowable resin in group 5, and polyethylene fibre was placed into the bed of resin in a buccal to lingual direction before the composite restoration was placed. All specimens were stored in 100% humidity at 37 degrees C for 24 h. Compressive loading of the teeth was performed by a universal testing machine at a crosshead speed of 0.5 mm min(-1) until failure. The data were recorded in Newton and submitted to anova and Tukey post hoc test. RESULTS: The mean load necessary to fracture the samples in each group was: G1: 1671.57 +/- 131.54(a); G2: 375.21 +/- 34.30(b); G3: 749.47 +/- 124.54(c); G4: 1224.36 +/- 132.17(d); G5: 926.88 +/- 118.28(e). Different superscript letters demonstrate significant difference between groups. CONCLUSIONS: Polyethylene fibre use over or under MOD composite restorations significantly increased fracture strength. However, when the fibre was placed on the occlusal surface of the restoration in buccal to lingual direction, significantly higher fracture resistance was observed.

Composite Resins↗
PubMed2006

Effect of bonded restorations on the fracture resistance of root filled teeth.

AIM: To evaluate the fracture resistance of root filled maxillary premolars restored with different techniques. METHODOLOGY: One hundred and twenty single-rooted maxillary premolar teeth were divided randomly into six groups of 20 teeth and subjected to the following procedures: group 1: intact teeth. Group 2: endodontic access cavities prepared. Group 3: MOD cavities were prepared, root canals were filled and no restoration was placed. Group 4: teeth were prepared as group 3 and restored conventionally with amalgam. Group 5: teeth were prepared as group 3 and restored with amalgam using a bonding material. Group 6: teeth were prepared as group 3 and restored with composite resin using the same bonding material. Teeth were embedded in acrylic resin and the loads for fracture strength were applied vertically with a constant speed of 1 mm min(-1). Data were evaluated statistically with anova and Tukey's tests. RESULTS: The mean force of fracture values were 1191.41, 599.86, 233.03, 494.72, 962.81 and 856.48 N for groups 1, 2, 3, 4, 5 and 6, respectively. The fracture resistance of group 5 was similar to group 1 (P > 0.05). The mean force at fracture of group 5 and group 6 was not significantly different. The fracture resistance of groups 5 and 6 was significantly higher than group 4 (P < 0.001). CONCLUSIONS: The group, restored with conventional amalgam, had the weakest resistance to fracture when compared with the bonded restorations. No statistically significant differences were found between the bonded amalgam and composite resin groups.

Acid Etching, Dental↗
PubMed2007

The use of theatre time for paediatric dentistry under general anaesthesia.

OBJECTIVE: The aim of this paper was to determine the use of theatre time for all procedures performed under general anaesthetic on a paediatric dental list. METHODS: A prospective study of paediatric dental general anaesthetic procedures was undertaken at Ninewells Hospital and Medical School, NHS Tayside, Dundee, UK. Data were collected prospectively for 71 operating lists over a 3-year period from April 2003 to March 2006. Both operator status and the procedure being undertaken were recorded. In addition, pre-anaesthetic, anaesthetic, operating and disconnection times were recorded. RESULTS: Of the 71 lists examined, 61 either finished early or on time, with a median unused time of 32.50 min (interquartile range = 19.50, 50.00 min), whilst 10 lists finished late with a median overrun time of 30.50 min (interquartile range = 9.25, 45.50 min). Comparing lists which finished late with those which were completed within time, the median pre-anaesthetic time was significantly longer (Mann-Whitney U-test, W = 20.05, P = 0.048). Overall, the theatre was in use for 78.22% of time combining pre-anaesthetic, anaesthetic, operating and disconnection times; hence, there was poor time utilization of theatre for 21.78% of the total theatre time. CONCLUSIONS: Overall, 85.9% of theatre sessions for dental procedures under general anaesthetic in children finished early or on time. Where lists finished late, the duration of the pre-anaesthetic time appeared to be the significant factor.

Ambulatory Surgical Procedures↗
PubMed1976

Abrasion of restorative materials by toothaste.

The procedure developed in this investigation is suitable for determining the abrasion resistance of restorative materials to toothbrush/dentifrice abrasion. Ideally, a restoration should have an abrasion resistance similar to that of enamel. Of the materials tested, gold was the only one that wore slightly less than enamel, whilst amalgam wore almost twice as quickly. The silicate material and composites (excluding TD.71) wear away 2-4 times faster than enamel. TD.71 and especially the unfilled resin exhibited very high rates of abrasion. After prolonged toothbrush/dentifrice abrasion, the surfaces of gold and amalgam were considerably smoother than those of the silicate and composite materials.

Dental Amalgam↗
PubMed1976

Disturbances in the contraction and co-ordination pattern of the masticatory muscles due to dental restorations. An electromyographic study.

Recent Swedish publications report that a large number of patients suffer from the mandibular dysfunction syndrome. Some theories assume that this syndrome is the result of a disturbance in blood flow through the maxillary artery. The present authors suggest, that the syndrome is caused by a disturbance in the pattern of contraction of the masticatory muscles. This hypothesis is based on the assumption that the human periodontal membrane contains mechanoreceptors which are able to exert reflex control over the pattern of contraction of the muscles during chewing. If the pattern of stimulation of these receptors is modified following dental restoration, then this could result in a disturbance of the neuromuscular pattern of the masticatory apparatus. In order to test this hypothesis, an electromyographic study was carried out in three volunteers and eight patients. The results of this study support the view that there are receptors in the human periodontal membrane which are able to control the pattern of contraction of the masticatory muscles. The hypothesis that the mandibular dysfunction syndrome is the result of a disturbance in the pattern of contraction of these muscles is pursued further in the discussion.

Adult↗
PubMed1983

A comparison of photoelastic and finite element stress analysis in restored tooth structures.

Two methods for determining internal stresses in tooth structures were compared under a specific load condition. The numerical method of the finite element method has a definite number of advantages over the experimental photoelastic method. The numerical results obtained by the first method are in reasonable conformity with those obtained by the latter. In addition the sensitivity of the finite element method towards variation of a number of relevant parameters has been studied.

Dental Restoration, Permanent↗
PubMed1984

The effect of ultrasonic scaling on the surface of Class V amalgam restorations--a scanning electron microscopy study.

Class V cavities were prepared on twelve extracted teeth and then filled with amalgam which was condensed in six cases by hand and six by mechanical means. SEM records were obtained before and after ultrasonic scaling of the restored area. They showed that such scaling had a deleterious effect on the surface of the amalgam and its marginal integrity. However the mechanically condensed specimens were less affected.

Dental Amalgam↗
PubMed1990

The effect of posterior composite restorations on the resistance of cavity walls to vertically applied occlusal loads.

The resistance of the cavity walls of non-vital premolars to vertically applied occlusal forces was studied. Standardized MOD cavities were prepared, restored, and vertical forces were applied to each of the cuspal tips by the Instron machine. Results suggest that bevelled etched-enamel margins and dentine-bonded posterior composite resin restorations significantly improved (by 33%) the resistance of the remaining cavity walls compared to amalgam restorations. In a control group, in which no restorations were carried out in the prepared cavities, the resistance of the walls was significantly smaller than in both restored groups.

Bicuspid↗
PubMed1992

Effects of ultrasonic instrumentation on microleakage in composite restorations with glass ionomer liners.

The aim of this study was to determine the effect of ultrasonic instrumentation on composite resin restorations lined with glass ionomer cement by measuring the extent of dye penetration at the restoration/tooth interface. Preparations, 2.0 mm in diameter and 2.5 mm in depth, were made with a 331 bur in 96 human molar teeth without a bevel. The teeth were restored with glass ionomer cement liners (Shofu) and one of two types of composite resin (Silux and P-30). Half of the samples were ultrasonically instrumented for 10 s. The teeth were immersed in 0.5% methylene blue dye solution and vertically sectioned. Microleakage was scored visually using a scale of 0 to 4. Statistical comparisons were made with chi 2 analysis and the Mann-Whitney U-test at the P less than 0.05 level. Microleakage was significantly different between both resin types (P less than 0.001), and between the lined and unlined resins (P less than 0.001) that were instrumented, particularly in the P-30 restorations. Although P-30 restorations exhibited much less microleakage than Silux, the use of a glass ionomer liner did not reliably reduce microleakage in either type of material after instrumentation with an ultrasonic device.

Acid Etching, Dental↗
PubMed1994

Repair of glass ionomer cements--methods for conditioning the surface of the cement to achieve bonding.

Two chemically different glass ionomer cements (Ketac Fil and ChemFil II Caps) and three different methods of conditioning the surface for repair were evaluated. Specimens of each material were prepared, aged and sectioned. The cut surfaces were treated with either phosphoric acid, polyacrylic acid or a combination of phosphoric acid followed by polyacrylic acid. Freshly mixed glass ionomer cement was injected against the treated surface and allowed to set under simulated intra-oral conditions. The specimens were then tested to failure in flexion after 7 days storage. The flexural strength of the repaired specimens was compared with that of control specimens of the same materials. The flexural strength of the repaired specimens was less than that of the controls. Treatment of the fractured surface with polyacrylic acid produced the weakest repair, and the use of phosphoric acid as the conditioning agent produced repaired specimens approximately 80% of the strength of the controls.

Acid Etching, Dental↗
PubMed1995

A study of the microstructure of some dental retention pins and prefabricated root canal posts.

Pins and root canal posts are generally considered indispensible aids in clinical restorative dentistry. To secure the long-term efficiency of pins and posts, such devices should be of sufficient strength to carry the relevant loads. It is, however, essential that their properties do not decline as a consequence of corrosion, or that corrosion of metallic pins and posts does not cause unfavourable effect in contacting biological tissues. The microstructure of certain commercially available dental retention pins and prefabricated root canal posts has been investigated using optical microscopy and standard metallographic techniques. The specimens were then examined by scanning electron microscope and energy dispersive X-ray analysis (EDAX). The results indicate differences in microstructure and condition between the types examined. The results also showed the presence of included particles in some pins and posts. These differences and the presence of inclusions may have an important bearing on service life and corrosion resistance.

Copper↗
PubMed1996

The strength of a heat-pressed all-ceramic restorative material.

A heat-pressed technique (IPS Empress, Ivoclar) has been described to construct single unit crowns, inlay/onlays and veneers using precerammed and precoloured glass-ceramic ingots. The aim of the study was to evaluate the strength of materials obtained using this technique. Strengths were determined by means of shell (disc rupture) tests. Seven groups of 10 specimens each were prepared with different combinations of core, incisal and glaze firing. Shell strength values of these seven groups varied between 167 +/- 18 and 81 +/- 9 MPa. After analysis, results showed that there was no statistical difference between groups when the core porcelain was in tension. However, there was a significant difference between those groups in which the lower surface was either core or incisal porcelain. The component thicknesses of the core and incisal materials did not change the strength of the complete specimen.

Aluminum Silicates↗
PubMed2004

Effects of various light curing methods on the leachability of uncured substances and hardness of a composite resin.

The purpose of this study was to evaluate the effect of the various light curing units (plasma arc, halogen and light-emitting diodes) and irradiation methods (one-step, two-step and pulse) using different light energy densities on the leachability of unreacted monomers (Bis-GMA and UDMA) and the surface hardness of a composite resin (Z250, 3M). Leachability of the specimens immersed for 7 days in ethanol was analysed by HPLC. Vicker's hardness number (VHN) was measured immediately after curing (IC) and after immersion in ethanol for 7 days. Various irradiation methods with three curing units resulted in differences in the amount of leached monomers and VHN of IC when light energy density was lower than 17.0 J cm(-2) (P = 0.05). However, regardless of curing units and irradiation methods, these results were not different when the time or light energy density increased. When similar light energy density was irradiated (15.6-17.7 J cm(-2)), the efficiency of irradiation methods was different by the following order: one-step > or = two-step > pulse. These results suggest that the amount of leached monomers and VHN were influenced by forming polymer structure in activation and initiation stages of polymerization process with different light source energies and curing times.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2004

The retentive effects of pre-fabricated posts by luting cements.

The purpose of this study was to compare the retention of two different pre-fabricated posts cemented to the root canal with four different adhesive luting cements and a zinc phosphate cement. The crowns of 100 freshly extracted human mandibular central and lateral incisors were removed at the cementoenamel junction and divided into two main groups (A = ParaPost and B = Flexi-Post) and further divided into five subgroups to evaluate the effects of five different cements (Rely-X ARC, Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor) each with 10 samples. Post-holes were prepared on all of the roots following the manufacturer's instructions. Each sample was placed into a specialized jig and tensile strength tests performed by using testing machine with a crosshead speed of 0.638 cm min(-1) and force applied until failure. The data were analysed with one-way anova (Post Hoc a Scheffe's S test) and two-way anova (P < 0.001). The Flexi-Post dowels had a mean of 54.21 kg (s.d. = 9.37) and demonstrated statistically higher retention than ParaPost dowels with a mean of 33.93 kg (s.d. = 10.69) for all of the cement groups (P < 0.001). In Flexi-Post and ParaPost dowel groups; Rely-X ARC was statistically higher than the Panavia F, ParaPost Cement, Flexi-Flow Natural and Adhesor (P < 0.05). Adhesor was significantly lower than the other subgroups (P < 0.05). Resin luting cements have demonstrated very high tensile strength potential for a strong bond to dentin.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2005

Fracture resistance of class II packable composite restorations with and without flowable liners.

This study evaluated fracture resistance in class II slot packable composite restorations with and without the use of a flowable composite liner. A conventional microhybrid composite was used as a control. Thirty-six sound, caries-free human mandibulary molar teeth were used. Separate mesio-occlusal and disto-occlusal class II slot cavity preparations were made in each tooth. The prepared teeth were randomly divided into three groups of 12 teeth. Two packable composites (Surefil, Filtek P60) and one microhybrid composite (Filtek Z250) with their respective manufacturer's bonding agents were used to restore the cavities. One side of each tooth was restored with composite alone, while the other side was restored with the composite lined with that manufacturer's flowable liner. The marginal ridges of the restorations were loaded at an angle of 13.5 degrees to the long-axis of the tooth in an Instron Testing Machine until failure. The data were analysed using a one-way anova. There was no significant difference in fracture resistance between composite restorations with and without flowable liners.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2006

Partial coverage restoration systems on molars--comparison of failure load after exposure to a mastication simulator.

This in vitro study evaluated the failure load of partial coverage restorations (PCR) made of various materials cemented on natural molars after exposure to the mastication simulator. Sixty-four maxillary molars were divided into four groups of 16 test specimens each. The specimens in one group remained unprepared (group NP); the teeth in the other groups were prepared equally according to standardized guidelines and restored with the following PCR: Group GO (Gold-Pontor-MPF; Metaux Precieux SA, Metalor, Neuchatel, Switzerland), group TA (Targis; Ivoclar Vivadent AG, Schaan, Liechtenstein) and group EM (IPS-Empress; Ivoclar Vivadent AG). The restorations in group GO were cemented conventionally, while those in groups TA and EM were luted adhesively. Groups NP and GO served as control groups. All test specimens were subjected to 1.2 million cycles (F = 49 N) in a mastication simulator. Subsequently, all test specimens were loaded occlusally until fracture occurred using an universal testing machine. All specimens withstood the masticating simulation. The median (IQR = x(0.25)-x(0.75)) failure loads were as follows: group NP: 1960.3(1480.5-2227.5) N, group TA: 1478.6(1293.4-1856.7) N and group EM: 1400.1(1043.1-1721.6) N. All test specimens of group GO achieved fracture strength values which exceeded a fracture load of 5500 N. The values of group GO were statistically significantly higher than those of groups NP, TA and EM (P < 0.00001). Furthermore, the results of group NP were significantly higher (P = 0.0226) than those of group EM. The results of groups NP and TA (P = 0.2022) as well as of groups TA and EM (P = 0.5340) did not differ significantly. The median values of all PCR systems obtained were within the limits of clinical acceptance. Long-term clinical investigations which take additional parameters into consideration are required before the composite-based Targis(R) (Ivoclar Vivadent AG) material can be recommended for indirect PCR.

Compressive Strength↗