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Bo Wold Nilsen,1,* Mathieu Mouhat,1,* Torbjørn Haukland,1 Ulf Thore Örtengren,1,2 James B Mercer3 1Department of Clinical Dentistry, UiT - the Arctic University of Norway, Tromsø, Norway; 2Department of Cariology, Institute of Odontology/Sahlgrenska Academy, Gothenburg, Sweden; 3Department of Medical Biology, UiT - the Arctic University of Norway, Tromsø, Norway*These authors contributed equally to this workCorrespondence: Mathieu Mouhat Email mathieu.mouhat@uit.noObjective: The study aimed to investigate factors contributing to heat development during light curing of a flowable bulk-fill resin-based composite (SDRTM, Lot # 602000876, Dentsply Sirona, Konstanz, Germany) (RBC).Materials and Methods: Temperatures were measured with calibrated thermocouples. A multi-wave light-emitting diode (LED) light curing unit (LCU) was used (Ivoclar Vivadent, Schaan, Lichtenstein). In all experiments, the RBC was first cured (cured) for 30 s and, after 5 min of recovery time, received a second LCU irradiation (post-cured) for 30 s. The exothermic reaction was measured by calculating the Δ temperature between cured and post-cured RBC. In a cylinder-shaped polymer mold, temperature was recorded inside of RBC during curing (part 1) and light transmission through RBC during curing was investigated (part 2). Pulpal temperatures were assessed in an extracted third molar during light curing (part 3). Data were statistically analyzed using one-way ANOVA (α=0.05).Results: Increased thickness of RBC led to decreased pulp chamber temperatures. Inside RBC, there was a large variation in heat development between the cured and post-cured groups (p< 0.05). The cured group absorbed more LCU irradiation than the post-cured group.Conclusion: The irradiance of the LCU seemed to be a more important factor than exothermic reaction of RBCs for pulp chamber heat development. Flowable bulk-fill RBCs can act as a pulpal insulator against LCU irradiation, despite their exothermic curing reaction.Keywords: dentistry, composite resins, LED dental curing light, pulp chamber, temperature

Purpose: The focus of this systematic review was to assess the published data concerning zirconia dental implant abutments from various aspects. Materials and Methods: To identify suitable literature, an electronic search was performed using PubMed. The keywords 'zirconia,' 'zirconium,' 'ceramic,' 'dental abutments,' 'dental implants,' 'plaque,' and 'bacteria' were included. Titles and abstracts were screened, and literature that fulfilled the inclusion criteria was selected for a full-text reading. Articles were divided into four groups: (1) studies on the mechanical properties of zirconia abutments, (2) studies on the peri-implant soft tissues around zirconia abutments, (3) studies on plaque accumulation on zirconia, and (4) clinical studies on the survival of zirconia abutments. Results: The initial literature search resulted in 380 articles. For groups 1 to 4, 11, 4, 7, and 3 articles satisfied the inclusion and exclusion criteria, respectively. Only 1 randomized clinical study was identified. Review of the selected articles showed that zirconia abutments were reliable in the anterior region from both biologic and mechanical points of view. Furthermore, zirconia abutments may represent a material surface less attractive for early plaque retention compared to titanium. Three clinical follow-up studies indicated that zirconia abutments could function without fracture and peri-implant lesions. Conclusions: Based on the reviewed literature, zirconia has the potential to be used as a dental abutment material, although some issues have to be studied further. Int J Prosthodont 2010;23:299-309. [ABSTRACT FROM AUTHOR]

Dentistry usually is 'wet work' with risk of damage to the skin barrier, and the hands may be exposed to skin irritants and contact-sensitizing substances used in dental materials or gloves. Airway irritants may also be present. This study assessed the consequences of work-related skin and airway symptoms among dentists in terms of contact with health authorities, sick leave, or changes in the professional career. A questionnaire on these factors was answered by more than 3000 Swedish dentists. Only 6% of the respondents had consulted a physician, although 22% had noted work-related skin symptoms. In 2% the skin symptoms had caused sick leave, and about 2% had reported their skin symptoms as an occupational disease. Two per cent had consulted a physician owing to work-related airway symptoms, which is a minor part of the 13% who had experienced such symptoms when in contact with dental materials. Twenty-five dentists (<1%) had been on sick leave because of work-related airway symptoms. Only 1 dentists reported change of activities or occupation owing to work-related skin or airway symptoms, and in most cases these symptoms only contributed to their decision. In summary, whereas sick leave in dentists because of musculoskeletal problems may be common, the present study shows that this is not the case for work-related skin or airway symptoms, and such symptoms seldom affect the dentists' professional career. [ABSTRACT FROM AUTHOR]

The focus for the present study was to characterise dental enamel and cementum at the cervical region of healthy teeth by use of interferometry. The effect of a protein-dissolving enzyme, used for cleaning (Neutrase) on the surface topography, was also evaluated. Knowledge about the normal variation of surface topography of natural teeth is limited. In the design of artificial surfaces, intended to replace the function of lost biological surfaces, detailed knowledge of the latter is therefore of great importance. Nine health caries free premolars were used. The root cementum of three teeth was used for evaluation of Neutrase on the surface. On the six remaining teeth, the differences between the surface textures of enamel and root cementum were evaluated using 3D Interferometry. No statistical significant effect of Neutrase was identified. A significant difference between enamel and root cementum concerning surface topography using the different 3D parameters was recorded. When comparing values from the literature, the topography of artificial materials used in dentistry show similarities with the topography of the enamel and root cementum surfaces evaluated.

Objectives: The aim of this work was to investigate the release of inorganic ionic products from specimens of the polyacid-modified composite resin Dyract AP (DAP) and furthermore, to analyze the biological effect of DAP and the medium extract in human periodontal ligament (PDL) cells and mouse bone marrow cell (BMC) cultures., Methods: Ion release from DAP specimens immersed in cell culture medium was analyzed with inductively coupled plasma optical emission spectroscopy (ICP-OES). Cells were cultured with either DAP specimens or with DAP media extract and effects on cell proliferation, osteoblastic gene expression and mineralization capacity were analyzed with direct-contact tests, neutral red (NR) uptake, quantitative real-time PCR and a bone nodule formation assay., Results: ICP-OES analysis of DAP extract demonstrated a significant increase in fluoride, strontium and silica. PDL cells demonstrated normal growth pattern in the direct-contact tests with the material. DAP extracts produced a dose-dependent stimulation of cell proliferation and concomitant inhibition of osteoblast specific markers and nodule formation., Significance: The compomer may have possible bioactive properties due to ions leaching out from the filler component.

Objectives: All dental biomaterials release substances into the oral environment to a varying degree. Various preclinical biocompatibility test systems have been introduced, aiming at an evaluation of the potential risks of dental materials. Potential pathogenic effects of released substances from dental materials have been demonstrated. For the biocompatibility of a biomaterial, it is not only important that minimal diffusable substances are released when it is in body contact--the material must also fulfill the function for which it has been designed. This is also very much dependent on the material properties and its handling properties. The aim of this review was to generate an overview of the present status concerning adverse reactions among patients and personnel., Materials and Methods: A systematic review was performed using a defined search strategy in order to evaluate all MEDLINE-literature published between 1996 and 2006., Results: The compilation of the literature available has revealed that the majority of studies have been carried out on patients compared with personnel. Adverse reactions towards dental materials do occur, but the prevalence and incidence are difficult to obtain. The results were essentially based on cohort studies. Clinical trials, especially randomized-controlled trials, are in the minority of all studies investigated, with the exception of composite and bonding studies, where clinical trials, but not randomized-controlled trials, represent the majority of studies. Patients and personnel were treated separately in the manuscript. Amalgam studies show the lowest degree of verified material-related diagnosis. Even if objective symptoms related to adverse reactions with polymer resin-based materials have been reported, postoperative sensitivity dominates reports concerning composites/bondings. Verified occupational effects among dental personnel show a low frequency of allergy/toxic reactions. Irritative hand eczema seemed to be more common than in the general population., Conclusions: Patient- and personnel-related studies are of variable quality and can be improved. There is a need for a better description of the content of materials. A registry for adverse effects of dental materials would be useful to detect the occurrence of low-incidence events.

Purpose: The aim of this in vitro study was to evaluate the load resistance in a conical implant system by comparing combinations of 2 different abutment head angles and 3 different retaining screw materials., Materials and Methods: The retaining screw materials (titanium alloy, gold alloy, and commercially pure titanium) were tested with abutment-head angles of 20 degrees and 45 degrees. Six groups of 10 specimens each were prepared. An oblique (30-degree) compression test was performed in a Lloyd LRX universal testing machine with the abutment attached to a superstructure with a retaining screw. All specimens were loaded until fracture or permanent deformation occurred. The results were evaluated statistically with Wilcoxon signed rank test for variance distribution (P < .05 considered significant)., Results: There were statistically significant differences in load resistance between 20-degree and 45-degree abutments. The titanium screws (titanium alloy and commercially pure) in the 45-degree abutment group had almost equal mean values, while the gold alloy had a significantly lower value. In the 20-degree abutment group, significantly higher values were found with commercially pure titanium compared to titanium alloy and gold alloy, but the difference between the values for the gold and titanium alloys was not significant., Discussion: The angulation of the abutment head played the most significant role in determining the amount of load withstood, but the material used for the screw was also relevant., Conclusion: A 45-degree abutment can be combined with a retaining screw of any of these materials to create a functional implant system. The test also substantiated that, irrespective of the retaining-screw material, a 20-degree abutment could resist loading forces of at least 900 N.

In this study we assessed the influence of pH and time on the degradation and elution of organic substances from the composite resin material, Z-100. To accomplish this, fluorescence spectrophotometry was evaluated as an appropriate technique for the identification of six organic substances (methacrylic acid, methyl methacrylate, hydroquinone, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate and 4,4'-isopropylidenediphenol) that were eluted from resin composite material stored for 24 h or 6 months at pH 4.0, 6.0 or 8.0. In addition, complementary analyses (solid-phase microextraction/gas chromatography/mass spectrometry) were carried out to identify and quantify the substances. The main substances leached from the resin composite were methacrylic acid, triethylene glycol dimethacrylate and hydroquinone. It was concluded that fluorescence spectrophotometry seems to be a suitable, non-destructive technique for the qualitative analysis of eluted organic components. Critical combinations of time and pH allowed the elution of several organic substances, predominantly methacrylic acid, triethylene glycol dimethacrylate and hydroquinone, from the model resin composite, Z-100., (Copyright Eur J Oral Sci, 2004.)

The aim of the present study was to investigate the influence of a chemo-mechanical caries removal system, Carisolv gel, on the surface topography of dental filling materials. Thirty specimens of a composite resin (Spectrum) and a compomer (Dyract AP) and 60 specimens of a glass-ionomer (Ketac-Fil Plus) were prepared. The surface topography was investigated with an optical interferometer before and after chemical exposure for 5, 10, or 20 min. Each specimen acted as its own control. The topographical part of the glass-ionomer materials was performed in two series with different drying procedures, since this material exhibits a higher sensitivity to dehydration than the other materials. The surface topographical investigations were complemented with contact angle measurements. After Carisolv gel exposure the density of summits and the developed surface area ratio (3D/2D) were slightly smaller for the composite resin and the compomer. For the minimally dried glass-ionomer material, the results indicated a reduction of the height of the surface structures, as well as a surface area enlargement, after Carisolv gel exposure. No statistically significant changes of contact angles due to Carisolv gel exposure could be detected for any material investigated. If dental filling materials of composite resin or glass-ionomer materials are exposed to Carisolv gel, no or only minor surface topographical changes can be expected. n

With the inception of craniofacial surgery elaborate surgical procedures were introduced for the treatment of craniosynostosis. Recently the use of implantable springs to aid simple strip craniectomies for these conditions has been described. Having shown the feasibility of using springs for dynamic skull reshaping, several questions remain to be answered, all of them about how to control the spring action clinically. One of the most important questions concerns force. The purpose of this study was to evaluate experimentally the effect of two springs of different strengths on the growth of rabbit calvaria after strip craniectomy. Thirty-two 6-week-old rabbits were randomised into one of four groups: sham-operation where only amalgam markers were inserted after subperiostal dissection; strip craniectomy of the sagittal suture, no expansion; strip craniectomy of the sagittal suture and insertion of an expander element made of titanium molybdenum alloy (TMA); and strip craniectomy sagittal suture and insertion of an expander element made of stainless steel (SS). SS springs delivered a range of forces from 2.42-2.18 N, whereas the TMA expander elements delivered a range from 1.39-1.09 N. The parietal bone marker separation after 12 weeks was 4.9 mm in the TMA group and 7.4 mm in the SS group. This resulted in a significant increase of the calvarian height compared with control groups. Histological examination showed intramembranous bone formation in the bone gap in all groups.

Background: Several studies have shown that in soft tissue, the orientation of surface topography affects cell response. However, the response of hard tissue to the orientation is not fully understood., Purpose: This study was undertaken to determine how orientation of the microstructure of implant surfaces influences bone healing., Materials and Methods: Forty cylindrical implants were prepared with a dominant orientation of the microstructure (20 with a horizontal orientation and 20 with a vertical orientation) and investigated in vivo. Three methods for surface topographic characterization were used to investigate the topography in different resolution levels., Results: Topographic analysis showed that a clear orientation was achieved at the implant surface, and a rougher surface structure was found on the vertically oriented grooves than on the horizontal ones. The implants were inserted in the tibia of 10 New Zealand White rabbits. Pull-out tests and histomorphometric analyses of ground-sections were made after 12 weeks of healing. The pull-out test showed a higher mean value for the vertically grooved implants, but the difference was not significant. Histomorphometric analyses showed no statistically significant differences between the horizontally and the vertically grooved implants when measuring bone-to-implant contact or amount of bone area around the implant., Conclusions: No advantages could be found for either the horizontal or vertical orientation compared with each other, but further studies are needed in which implant roughness should be similar between the different topographies.

Objectives: The aim of this study was to determine whether pH and time has any influence on the sorption and solubility behaviour of composite resin materials stored in a buffer solution., Methods: Three hybrid composite restorative resin materials (Spectrum, Z-100 and ArtGlass) with different matrix structure and filler composition were studied. One hundred and twenty specimens of each material were produced according to ISO 4049. The materials were stored in McIlvain's buffer solution at different pH (4, 6 and 8) at 1, 7, 60 and 180 days. pH measurements were carried out before and after completed storage., Results: Time had a significant influence on the sorption and solubility behaviour of the composite resin materials tested. One of the materials Z-100 showed a significant mass increase and/or decrease depending on the pH of the solution. The material Spectrum was significantly influenced by pH, resulting in different sorption depending on the pH of the solution., Conclusions: Time of storage was important for the sorption and solubility behaviour of the composite resin materials tested. Comparison of solubility for one of the materials showed twice as high values in the present study as previously reported when distilled water was used as storage medium. pH in the solution seems to have an influence on the sorption and solubility behaviour of composite resin materials. The sensitivity of the sorption and solubility behaviour to time and pH of the materials tested seems to be related to the hydrophilicity of the matrix and the chemical composition of the filler.

Hand eczema and contact allergy in Swedish dentists were studied in a multidisciplinary project. The aims of the study were to establish diagnoses, to investigate the occurrence of contact allergy, in particular to (meth)acrylates, and to evaluate certain consequences of hand eczema. A postal questionnaire on skin symptoms, atopy and occupational experience was mailed to 3,500 dentists aged <65 years, and licensed 1965-1995. The response rate was 88%. Among dentists living in 3 major cities, 14.9% (n= 191) reported hand eczema during the previous year. They were invited to a clinical examination, including patch testing with a standard and a dental series. 158/191 (83%) dentists attended, and hand eczema diagnosis was confirmed in 149/158 (94%). Irritant contact dermatitis was diagnosed in 67% and allergic contact dermatitis in 28%. On patch testing, 50% presented at least 1 positive reaction. The most frequent allergens were nickel sulfate, fragrance mix, gold sodium thiosulfate and thiuram mix. 7 (5%) had positive reactions to (meth)acrylates, all to 2-hydroxyethyl methacrylate and 6 also to ethyleneglycol dimethacrylate. 38% had consulted a physician, 4% had been on sick-leave and 1% had changed occupational tasks due to hand eczema. No dentist with allergy to acrylates had been on sick-leave or changed occupation. It is concluded that dentistry is a high-risk occupation for hand eczema, and that irritant contact dermatitis is most common. The prevalence of contact allergy to acrylates was below 1% in the population of responding dentists, and in most cases did not have serious medical, social or occupational consequences.

Purpose: The aim of this study was to assess the water sorption and determine the influence of water on flexural properties of a composite resin cement of 2 different viscosities., Materials and Methods: A dual-cured composite resin cement of 2 different viscosities was tested according to International Standards Organization standards for dental composite materials. The samples tested for water sorption were stored in distilled water for 7 or 60 days. The samples tested for flexural properties were divided into 2 groups and stored either wet in distilled water or dry for 1, 7, or 60 days. After storage, a flexural test was performed with 3-point bending equipment., Results: A significant increase in water sorption for both viscosities was registered as the storage time increased, but no significant difference between the 2 viscosities was recorded. Significantly lower strength and modulus were found for specimens that were wet stored for 60 days compared with the dry-stored ones, and significant changes in deflection at break were also registered. There were no differences in flexural properties between the 2 viscosities. Because of the lubricant and plasticizing effect of water on composite resin materials, the secant modulus and deflection at break seem to be valid methods to describe the complete deflection behavior., Conclusion: Water has an important effect on the flexural properties of composite resin cement after 60 days of storage time. No significant differences in water sorption and flexural properties were found between the high and low viscosities of the composite resin cement studied.

Purpose: The aims of this thesis were: 1. To study the effect of water and pH on composite resin materials in vitro by assessing sorption, solubility, monomers eluted and flexural properties. 2. To study adverse effects on the skin in dentists possibly caused by acrylic resin-based materials., Materials and Methods: Proprietary composite resin materials were used for the in vitro experiments. The tests were performed according to the ISO 4049 (1988) with the exception of McIlvaine's solution used in Study II and the storage times. The analysis of eluted monomers was performed using HPLC. The flexural properties were tested in a three-point bending equipment. The secant modulus and deflection at break were calculated for description of the viscoelastic behaviour of the material tested. To study the adverse effects on skin in dentists, a questionnaire was sent to 3500 randomly selected Swedish dentists. A response rate of 88% was achieved and the data were statistically analysed and compared with the results of two studies on skin symptoms among the general Swedish population. Dentists living in the three main cities in Sweden who had experienced hand eczema during the last 12 months were invited to a clinical examination in which a patch test was included., Results: A wide range in sorption and solubility over the test period was found, with low sorption values observed for materials containing hydrophobic matrix monomers. A maximum concentration of monomers eluted was found after 7 days of storage, and TEGDMA was the main monomer released. pH affected the sorption and solubility behaviour for two of the three materials tested. The flexural strength and modulus of the composite resin material were lowered after water storage and the secant modulus and deflection at break could describe the viscoelastic behaviour. The prevalence of dry skin and hand eczema was high in dentists compared to two age-matched general population samples investigated using identical questions. The most important predictor for adult hand eczema was found to be childhood eczema. At the clinical examination, irritant contact dermatitis was the predominant diagnosis. Seven per cent reported skin symptoms when working with acrylic resin-based material but the true prevalence of hand eczema caused by acrylates was below 1%. Contact allergy was diagnosed, however, in 50% of the dentists, mainly due to other allergens such as nickel, perfumes or rubber chemicals., Conclusions: The matrix composition was shown to be important for the sorption and solubility behaviour of the composite resin materials tested and a maximum release of monomers occurred after 7 days of storage. pH affected the water sorption and solubility behaviour. Calculation of the secant modulus and the deflection at break allowed the plasticising effect of water on composite resin material to be observed. The prevalence of hand eczema was high among dentists, with irritant contact dermatitis as the predominant diagnosis. Childhood eczema was the most important predictor for adult hand eczema. The prevalence of hand eczema owing to acrylates was below 1%.

In the present study we investigated the prevalence of self-reported hand eczema as well as subjective associations between skin symptoms and composite/bonding or other dental materials among Swedish dentists. A questionnaire on skin symptoms, atopy, occupational experience, and other background factors was sent to a random sample (n=3,500) of all dentists licensed since 1965. This group corresponds to about half of the country's occupationally active dentists. The response rate was 88%. The questionnaire had previously been validated against clinical dermatological examination of subjects reporting hand eczema. The prevalence of dry and rough skin on the hands was high (45%). Hand eczema during the previous 12 months was reported by 13.5%. Dry skin and hand eczema were more common among dentists than in two age-matched general population samples investigated using identical questions. The difference versus the general population was most pronounced (about two-fold) among male dentists. A history of childhood eczema was the most important predictor for adult hand eczema, with a prevalence ratio of 2.4 compared to dentists without childhood eczema. Seven % reported skin symptoms when working with acrylic resins, and 15% had experienced rapid itching related to protective gloves.

Purpose: The main purpose of the present experimental study was to compare five different types of crowns, cemented on implant abutments, regarding their capability to withstand loads., Materials and Methods: Three types of all-ceramic crowns, a gold-foil-reinforced porcelain crown, and, as a control, a conventional metal ceramic crown were tested. Each crown was cemented onto an Astra Tech Single-Tooth implant. The five types of crowns, three of each type, and the titanium implants were subjected to loading in Lloyd test equipment until part of them was damaged, at which point the compression value was recorded and the deflection and bending moment were calculated. Comparisons were made on the basis of these data., Results: The results showed that the all-ceramic crowns fitted with a core should be able to withstand normally occurring biting forces without difficulty. The foil crown was also judged to be acceptable, while the bending moment of the cast call-ceramic crown without a core was considered unpredictable. The values for the metal ceramic design were as predicted, ie, they were clearly the highest in the study; the superior strength of metal ceramics should still be taken into account when deciding between all-ceramic solutions and the conventional metal ceramic crown., Conclusion: It was concluded that all-ceramic crowns are weaker than conventional metal ceramic crowns: however, based on estimated maximum clinical loading (370 N in the incisor and premolar regions), In-Cream and AllCeram crowns seem to function satisfactorily on implants.

Purpose: The aims of this study were to assess changes in the microhardness and surface roughness of a dual-cured composite resin cement after water storage for different periods of time., Materials and Methods: Sixty specimens were divided into four groups comprising high- and low-viscosity cement specimens stored either dry or in water for 1 to 60 days. Microhardness and surface roughness measurements were made after 1, 7, and 60 days of storage., Results: It was found that that although interactions complicated the interpretation of the results, the water-stored samples had a significantly lower microhardness compared to the dry-stored specimens for every time interval. In addition, the high-viscosity specimens had a significantly higher microhardness compared to the low-viscosity specimens. An increased microhardness was found for all groups, except for the low-viscosity, water-stored specimens after 60 days of water storage, which was attributed to an effect of the chemical postcuring process. Although difficult to evaluate from a clinical point of view, the laser profilometry analysis revealed that a significantly increased surface roughness was found after water storage and increased storage time that was possibly caused by a deterioration of the resin-matrix surface., Conclusion: For the permanency of the interfacial luting material, a high microhardness value seems to be important.

Due to their inertness and unsurpassed aesthetic properties, ceramic materials are increasingly used as inlay materials. Based on a questionnaire, the frequency and character of complications related to ceramic inlay therapy were assessed and some important pitfalls and clinical relevant factors discussed. A majority of the dentists performed between 1 and 10 ceramic inlays per month using several different ceramic materials. As many as 85% of the dentists had observed complications in connection with ceramic inlays. Most frequency reported was hypersensitivity of a transient nature (15%). The material revealed an overall inlay fracture frequency of 5%, but the individual variations were high. Tooth fracture, loss of retention and other complications such as secondary caries, endodontic envolvement, colour mismatch and a surface and edge deterioration occurred with a varying but lower frequency. Failure analysis revealed a large number of causative factors among which cavity and inlay design, bonding procedures, selection of luting material and proper case selection were regarded as the most important. Due consideration to the strength of remaining tooth substance was found to be important in reducing the problem of hypersensitivity and the risk of tooth and inlay fracture.