Modern high powered led curing lights and their effect on pulp chamber temperature of bulk and incrementally cured composite resin.

Pulpal temperature changes induced by modern high powered light emitting diodes (LEDs) are of concern when used to cure composite resins. This study showed an increase in pulp chamber temperature with an increase in power density for all light cure units (LCU) when used to bulk cure composite resin. Amongst the three LEDs tested, the Elipar Freelight-2 recorded the highest temperature changes. Bulk curing recorded a significantly larger rise in pulp chamber temperature change than incrementally cured resin for all light types except for the Smartligh PS. Both the high powered LED and the conventional curing units can generate heat. Though this temperature rise may not be sufficient to cause irreversible pulpal damage, it would be safer to incrementally cure resins.

Effect of four over-the-counter tooth-whitening products on enamel microhardness.

OBJECTIVES: This in vitro study evaluated the effect of four over-the-counter tooth-whitening products on enamel microhardness. METHODS: Fifty enamel blocks were prepared from extracted human molar teeth. The enamel surfaces were polished up to 1200 grit fineness and the specimens randomly divided into five groups. Enamel blocks were exposed to: Rapid White (n=10); Absolute White (n=10); Speed White (n=10) and White Glo (n=10) whitening products, according to the manufacturers' instructions. As control, ten enamel blocks were kept in artificial saliva at 37 degrees C without any treatment. Microhardness values were obtained before exposure (baseline) and after 1, 7 and 14-day treatment periods using a digital hardness tester with a Vickers diamond indenter. Data were analysed using Wilcoxon Signed Rank Sum Test, one-way ANOVA and Tukey-Kramer Multiple Comparison Test (p<0.05). RESULTS: Both Rapid White and Absolute White reduced enamel microhardness. Speed White increased the microhardness of enamel, while White Glo and artificial saliva had no effect on hardness. CONCLUSIONS: Over-the-counter tooth-whitening products might decrease enamel microhardness depending on the type of product.

Leakage of teeth root-filled with GuttaFlow and a single GP cone compared to lateral condensation and warm vertical condensation.

INTRODUCTION: Root canal obturation can be time consuming and complicated. GuttaFlow is suggested for use with a simple, single cone obturating technique. AIMS AND OBJECTIVES: The aim of this study was to evaluate whether GuttaFlow and a single GP cone would produce an effective seal. METHODS: Three experimental groups were used. Group one was obturated with GP using lateral condensation, group two with GP using vertical condensation and group three using GuttaFlow and a single GP cone. Bacterial micro-leakage was tested using the two-chamber method, followed by dye penetration testing. Data was subjected to statistical analysis using the Chi Square test. RESULTS: There was no significant difference between GP using lateral condensation and GuttaFlow using a single cone for bacteria (p=0.8989) or dye (p=0.7489). GP using lateral condensation performed better than GP using vertical condensation for bacteria (p=0.0003) and dye (p=0.0006). GuttaFlow using a single cone also performed better than GP using vertical condensation for bacteria (p=0.0003) and dye (p=0.0004). CONCLUSIONS: The micro-leakage of GuttaFlow using a single cone technique is similar to that of GP using lateral condensation and less than that of GP using vertical condensation as used in this study.

Teaching approaches in South African dental schools: direct restorative procedures.

INTRODUCTION: Worldwide the use of amalgam has declined and mercury-containing products are banned in several countries. National and international opinions on amalgam were recently discussed in journals. According to surveys, significant time is spent on the teaching of amalgam in American, Canadian, Irish and United Kingdom Dental Schools. AIMS AND OBJECTIVES: To i) investigate the teaching approaches on direct restorative techniques and materials in South African Dental Schools; ii) compare the teaching approaches of the dental schools in South Africa with each other as well as with the American, Canadian, Irish and United Kingdom schools; iii) use the information of this study as baseline data for future studies on teaching approaches. METHODS: A questionnaire regarding the teaching and training of direct restorations was e-mailed to the heads of Restorative Dentistry departments in four South African Dental Schools in 2007. RESULTS: Significant time is spent on teaching and training of amalgam as a restorative material. Teaching and training on direct restorations are very similar in all South African Dental Schools. CONCLUSION: Although there is a decline in the use of amalgam worldwide, significant time is spent on teaching of amalgam restorations in South African Dental Schools and this corresponds to the curriculums of American, Canadian, Ireland and United Kingdom Dental Schools.

Non-surgical treatment of anterior open bite and its assessment using the Dawjee analysis: a case report.

Anterior open bite (AOB) is a dentofacial problem occurring more commonly in race groups of African origin. Although multi-factorial, the aetiology exerts its influence in tandem with craniofacial development. Diagnosis is confirmed by a cephalometric assessment and points either to a skeletal origin, a dental source, or both. Depending on the time of diagnosis and severity of the condition, treatment can vary from interceptive procedures, orthodontics only, or a combination of orthodontic treatment and orthognathic surgery. A case study is presented of an adult female with AOB who was treated nonsurgically. The diagnosis, treatment technique and outcome are described, as well as a pre- and post-treatment evaluation of the cephalograms using the Dawjee analysis. Comparison of pre- and post-treatment cephalometric values show a definite dentofacial improvement, and identifies specific morphologic areas that have changed as a result of treatment. Transformations in anteroposterior maxillary and mandibular positions and orientation are readily detectable, as well as a repositioning of the alveolar processes. While pre and post treatment cephalometric values presented for this patient compare well, these values are case specific and cannot be implemented widely unless the analysis is applied to a larger and more representative population sample and standardised measurements have been established.

Microleakage of different amalgams bonded with dual cure resin cements.

INTRODUCTION: To reduce microleakage in high-copper amalgam restorations, bonding of amalgam was introduced. AIM: This study compared the microleakage of admixed and spherical amalgams when bonded with different bonding intermediates under thermo- and non-thermocycling conditions. METHOD AND MATERIALS: Class II butt-joint cavities were prepared in 200 extracted human molar teeth, and randomly divided into 5 groups. Calibra, Duo Cement Plus, RelyX ARC and Amalgambond Plus were applied to 4 of these groups. The fifth group was left untreated. The groups were further divided and restored with either Dispersalloy or Oralloy Magicap S. Ten specimens of each group were thermocycled between 5 degrees C and 55 degrees C, placed in basic fuchsin for 8 hours, sectioned and evaluated for dye penetration under 40X magnification. The mean microleakage scores were analysed using the chi-squared test at a confidence level of 95%. RESULTS: Microleakage of the non-bonded amalgams was significantly higher (p < 0.0001) than for the bonded amalgams (thermocycled and non-thermocycled). The microleakage of the different intermediates bonded to Dispersalloy (thermocycled and non-thermocycled) was not significantly different (p > 0.05). The microleakage of the different intermediates was not significant different except for Duo Cement compared to Calibra (p < 0.0001), RelyX (p < 0.0001) and Amalgambond (p = 0.0433) and Amalgambond compared to Calibra (p = 0.0433) and RelyX (p = 0.0433). The microleakage of the bonded amalgams was not significantly increased by thermocycling (p > 0.05). The microleakage of the two amalgams when bonded with the same resin cements (thermocycled and non-thermocycled) was not significantly different except for Duo Cement (thermocycled) (p = 0.0051) and RelyX (non-thermocycled) (p = 0.0356). CONCLUSIONS: Bonding amalgam restorations to tooth structure in butt-joint cavities will reduce microleakage of both admixed and spherical amalgam restorations. Thermal stress does not affect the bond adversely.

Effect of woven glass fibre reinforcement on the flexural strength of composites.

To measure and compare the flexural strength of composites reinforced with fibres, four groups of specimens (N = 10) were prepared from the combinations: Filtek Flow/Filtek Z250 and Esthet-X flow/Esthet-X dental composite. One group from each combination was reinforced with woven glass fibre (everStick net) and all the specimens subjected to three-point bend flexural testing. The mean and standard deviations for each test group were calculated and compared using one-way analysis of variance (ANOVA) followed by pairwise Bonferroni T-tests at a preset alpha of p < 0.05. It was found that fibre reinforcement significantly (p < 0.001) increased the flexural strength of both types of composites. As the inclusion of only one layer of glass fibre net produced an increase of approximately 30% in the flexural strength of the composite samples, it can be speculated that multiple layers would increase it even more. The use of fibre-reinforcement to strengthen directly placed composite crowns and bridges will enable the clinician to provide a more cost effective service as well as aesthetic dentistry to more patients.

Entrapment of nucleic acids in liposomes.

The entrapment efficiency of three main methods used in the literature for the encapsulation of nucleic acids in liposomes were studied using 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes. In particular the reverse phase method, the dehydration/rehydration method, and the freeze/thawing method were compared to each other under standardised conditions, i.e. using in every case the same concentration of guest molecules (DNA, tRNA and ATP as low molecular weight analogue) and equally extruded liposomes. The percentage of entrapment strictly referred to the material localized inside the liposomes, i.e. particular care was devoted to ruling out the contribution of the nucleic acid material bound to the outer surface of the liposomes: this was eliminated by extensive enzymatic digestion prior to column chromatography. Depending on the conditions used, the percentage of the entrapped material varied between 10 and 54% of the initial amount. Further, the encapsulation efficiency was markedly affected by the salt concentration, by the size of liposomes, but to a lower degree by the molecular weight of the guest molecules. In general, we observed that the freeze/thawing encapsulation procedure was the most efficient one. In a second part of the work the freeze/thawing method was applied to encapsulate DNA (369 bp and 3368 bp, respectively) using liposomes obtained from POPC mixed with 1-10% charged cosurfactant, i.e. phosphatidylserine (PS) or didodecyldimethylammonium bromide (DDAB), respectively. Whereas PS had no significant effect, the entrapment efficiency went up to 60% in POPC/DDAB (97.5:2.5) liposomes. The large entrapment efficiency of DNA permits spectroscopic investigations of the DNA encapsulated in the water pool of the liposomes. UV absorption and circular dichroism spectra were practically the same as in water, indicating no appreciable perturbation of the electronic transitions or of the conformation of the entrapped biopolymer. This was in contrast to the DNA bound externally to the POPC/DDAB liposomes which showed significant spectral changes with respect to DNA dissolved in water.

Giant vesicles as models to study the interactions between membranes and proteins.

The interaction between polypeptides and membranes is a fundamental aspect of cell biochemistry. Liposomes have been used in this context as in vitro systems to study such interactions. We present here the case of giant vesicles (GVs), which, due to their size (radius larger than 10 microns), mimic more closely the situation observed in cell membranes and furthermore permit to study protein-membrane interactions by direct optical monitoring. It is shown that GVs formed from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine by electroformation are permeable to certain low molecular weight molecules such as the nucleic acid dye YO-PRO-1 and fluorescein diphosphate whereas conventional liposomes (large or small unilamellar liposomes) are not. In addition, it is shown that non-membrane proteins, such as DNases or RNases, added to the selected GVs from the outside, are able to convert their substrate, which is strictly localized on the internal side of the membrane. This effect is only seen in GVs (also when they are removed from the original electroformation environment) and is absent in conventional liposomes. The fact that these effects are only present in GVs obtained by electroformation and not in conventional small liposomes is taken as an indication that certain physico-chemical properties of the bilayer are affected by the membrane curvature, although the mechanism underlying such differences could not be established as yet.

Enzymatic reactions in liposomes using the detergent-induced liposome loading method.

Microcompartmentalization is a crucial step in the origin of life. More than 30 years ago, Oparin et al. proposed models based on biochemical reactions taking place in so-called coacervates. Their intention was to develop systems with which semipermeable microcompartments could be established. In the present work we follow their intuition, but we use well-characterized bilayer structures instead of the poorly characterized coacervates. Liposomes from phospholipids can be used as microreactors but they exhibit only a modest permeability and, therefore, chemical reactions occurring inside these structures are depleted after a relatively short period. Here it is shown that even highly stable liposomes from 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) can be used as semipermeable microreactors when treated with sodium cholate. Using this kind of mixed liposomes, we describe a biochemical reaction occurring inside the liposomes while the same reaction is prevented in the external medium. In addition, we show that this cholate-induced permeability of POPC bilayers can even be used to load macromolecules such as enzymes from the outside.

Polymerase chain reaction in liposomes.

BACKGROUND: Compartmentalization of biochemical reactions within a spherically closed bilayer is an important step in the molecular evolution of cells. Liposomes are the most suitable structures to model this kind of chemistry. We have used the polymerase chain reaction (PCR) to demonstrate that complex biochemical reactions such as DNA replication can be carried out inside these compartments. RESULTS: We describe the first example of DNA amplification by the PCR occurring inside liposomes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), or of a mixture of POPC and phosphatidylserine. We show that these liposomes are stable even under the high temperature conditions used for PCR. Although only a very small fraction of liposomes contains all eight different reagents together, a significant amount of DNA is produced which can be observed by polyacrylamide gel electrophoresis. CONCLUSIONS: This work shows that it is possible to carry out complex biochemical reactions within liposomes, which may be germane to the question of the origin of living cells. We have established the parameters and conditions that are critical for carrying out this complex reaction within the liposome compartment.

An introductory report on a new cephalometric method: the Dawjee analysis.

A new method of lateral cephalometric analysis referred to as the Dawjee analysis is introduced. Landmarks, planes and angles are defined, and the technique is outlined. The Dawjee analysis is primarily focused on evaluating craniofacial structures in the vertical dimension and this introductory presentation demonstrates its application in both open and deep bite cases. Studies are in progress to develop a set of standardised values for this technique in a South African population sample.

Effect of saliva contamination on microleakage of a bonding system.

UNLABELLED: Saliva contamination is a major clinical problem during restorative dental treatment. Restorative systems must possess sufficient marginal sealing ability to avoid microleakage. PURPOSE: The purpose of this study was to investigate the effect of saliva contamination on the microleakage of cavities restored with Prime & Bond NT and Dyract-AP. METHOD: Cavities were prepared with occlusal margins in enamel and gingival margins in dentine on the buccal surfaces of extracted human permanent premolar teeth. The cavities were etched with phosphoric acid or a non rinse conditioner (NRC). Preparations were distributed randomly into 4 treatment groups (N = 18) consisting of two respective etching methods (phosphoric acid/NRC), each with and without saliva contamination. After the restorative process the samples were thermocycled in dye, sectioned, and scored for microleakage. RESULTS: Contamination with saliva had no significant effect on microleakage on the enamel or dentine sides where phosphoric acid was used as conditioner. Where NRC was used, significantly more microleakage was observed at the enamel sides, but significantly less at the dentine sides.

The pro sequence of lactase-phlorizin hydrolase is required for the enzyme to reach the plasma membrane. An intramolecular chaperone?

Various cDNAs coding for part or all of human pre-pro lactase-phlorizin hydrolase (pre-proLPH) were transfected into COS cells and the subcellular location of the lactase-related proteins assessed. Only the complete proLPH reached the plasma membrane. LPH without the pro sequence, and a construct containing the pro sequence and the lactase domain of mature LPH, accumulated intracellularly; the pro sequence with no mature domain was secreted. We conclude that the pro sequence is important for LPH to be transported to the cell surface.

Maturation of human lactase-phlorizin hydrolase. Proteolytic cleavage of precursor occurs after passage through the Golgi complex.

Maturation of human intestinal lactase-phlorizin hydrolase (LPH) requires that a precursor (pro-LPH) be proteolytically processed to the mature microvillus membrane enzyme (m-LPH). The subcellular site of this processing is unknown. Using low-temperature experiments and brefeldin A (BFA), intracellular transport was blocked in intestinal epithelial cells. In Caco-2 cells incubated at 18 degrees C, pro-LPH was complex-glycosylated but not cleaved, while at 20 degrees C small amounts of proteolytically processed LPH were observed. These data exclude a pre-Golgi proteolytic event. BFA completely blocked proteolytic maturation of LPH and lead to an aberrant form of pro-LPH in both Caco-2 cells and intestinal explants. Therefore, proteolytic processing of LPH is a post-Golgi event, occurring either in the trans-Golgi network, transport vesicles, or after insertion of pro-LPH into the microvillus membrane.

In vitro evaluation of two adhesive systems used with compomer filling materials.

AIM: To evaluate and compare the in-vitro shear bond strength, microleakage and dentine-restorative interface of a self-etching/self-priming dentine bonding agent with a three-component dentine-bonding agent. METHOD: For shear bond strength (SBS) testing 30 non-carious human molars were used of which 15 were tested with Non-Rinse Conditioner (NRC)/Prime&Bond NT (PBNT) and Dyract AP and 15 were tested with Scotchbond Multi-Purpose Plus (SBMP) and F2000. For the microleakage evaluation cavity preparations were made on the facial surfaces of 30 non-carious human premolars of which 15 were restored with NRC and PBNT with Dyract AP and 15 were restored with SBMP and F2000. The dentine-restorative interface was examined through a confocal scanning laser microscope (CSLM). RESULTS: The mean SBS of PBNT and SBMP were 12.8 and 18.1 MPa, respectively. The microleakage scores showed NRC/PBNT leaked on the dentine side in 13 of the 15 specimens examined. On the enamel side two of the 15 specimens showed microleakage. With SBMP no microleakage was observed on either enamel or dentine sides. The CSLM images show clear resin tag and hybrid layer formation for both the materials examined although SBMP showed better and deeper penetration into the dentine with longer resin tags. SBMP showed resin tags measuring about 150 mm while the hybrid layer measured about 5 mm. The length of the resin tags as well as the thickness of the hybrid layer for PBNT were 20 mm Pounds and 2 mm Pounds, respectively. CONCLUSIONS: The acid-etch technique of SBMP produced higher bond strength and no microleakage when compared with the self-etching/self-priming 'non-rinse technique' of NRC with PBNT. Thus it can only be speculated that SBMP should be the superior in the clinical situation.

Unusual fracture of a mandibular second premolar: a case report.

Root fractures of posterior teeth, which are defined as fractures involving cementum, dentin, and pulp, are relatively uncommon among dental traumas. This study describes an unusual horizontal fracture of a mandibular second premolar. The tooth was asymptomatic and the fracture unnoticed until the crown broke off completely. The patient had no recollection of a causative event nor was there any evidence of previous physical trauma. The tooth was extracted, embedded in resin, sliced, and examined with different light microscopes. It was concluded that the tooth had been damaged previously but not to the extent that the pulp was seriously damaged. Resorption over a period of time eventually caused the final fracture.

Shear bond strength, microleakage, and confocal studies of 4 amalgam alloy bonding agents.

OBJECTIVE: This study was undertaken to determine the relative shear bond strengths and microleakage of 4 bonding agents to dentin and amalgam and to investigate the bonding to dentin through confocal laser scanning microscopy. METHOD AND MATERIALS: Sixty noncarious molars were restored with 1 of 4 different systems, and the shear bond strengths were determined. For the microleakage study, Class V amalgam restorations were placed in 60 noncarious teeth. The specimens were thermocycled, the teeth were sectioned, and dye penetration was assessed. For confocal examinations, the first component of the bonding adhesives was labeled with rhodamine B. Each of the adhesives was applied to 3 dentin specimens, which were examined under a confocal laser scanning microscope RESULTS: Of the 4 restorative systems tested, AmalgamBond Plus + HPA and Prime & Bond 2.1/base-catalyst showed significantly higher shear bond strengths. Prime & Bond 2.1/base-catalyst had the lowest microleakage value, which was significantly lower than that of AmalgamBond Plus + HPA and AmalgamBond Plus. AmalgamBond Plus + HPA had the highest variation in both the bond strength and microleakage values. Confocal laser scanning microscopy revealed tag formation, penetration of the bonding agents deep into the tubules, and hybrid layer formation for all 4 bonding systems. CONCLUSION: The 2 best systems, Prime & Bond 2.1/base-catalyst and, to a lesser extent, AmalgamBond Plus + HPA, utilized a supplemental bonding agent.

[Lingualized occlusion in the South African context]. / Gelingualiseerde okklusie in die Suid-Afrikaanse konteks.

The search for the ideal artificial tooth arrangement that maximizes denture stability, comfort, aesthetics, and function has occupied the dental literature for many years and still continues to do so. Of the many occlusal schemes that have been presented to the dental profession, that of lingualized occlusion has emerged as one of the more popular. The popularity of lingualized occlusion stems from the simplicity and flexibility of the concept and from its wide application to clinical practice (Parr & Ivanhoe, 1996). The registration of a repeatable correct centric jaw relation is not always possible. We don't know whether the patient will use centric relation during normal function. It is therefore useful to provide the patient with some freedom of movement around centric. lingualized occlusion provides freedom in centric. For many dentists the arrangement of artificial denture teeth into balanced occlusion is difficult and time consuming. As a result this task is most often performed by the dental technician. In the South African countryside dental laboratories are often far away. If dentists perform the arrangement of the denture teeth, time and costs can be saved. The mounting of denture teeth in lingualized occlusion is simple and fast. This will motivate dentists to arrange denture teeth themselves, with obvious benefits for both the patient and the dentist. The School of Oral Health Sciences of the University of Stellenbosch teaches this concept to its undergraduate students in order to improve the prosthetic service to the large edentulous population of South Africa.

[Polymerization shrinkage by 4 different types of dental materials]. / Polimerisasiekrimping by vier verskillende tipes tandheelkundige materiale.

Forces developing during polymerisation of dental resins cause tension in the material to increase, with possible subsequent distortion of the bond. This study was undertaken to determine and compare polymerisation shrinkage in four different light-cured dental resins. A modified dilatometer was used to determine volumetric changes during polymerisation in 60 seconds of Z250 and Filtec flow from 3 M, and DyractAP and Dyract from Dentsply. Statistical analysis revealed that Dyract Flow shrinks significantly more (P < 0.05) during polymerisation in the first, as well as the last 10 seconds when compared with the other three materials and Z250 significantly less. An increase in the amount of fillers in the composition of the material leads to a decrease in polymerisation shrinkage, while an increase in the monomer concentration gives rise to more shrinkage. Stress, that builds up during the polymerisation process, is reduced by the elasticity of the material. The shrinkage of the flowables is therefore counteracted by their reduced rigidity.