European Journal of Oral Sciences

The present review outlines the history of monomers, used in resin composites, motivates further development, and highlights recent and ongoing research reported in the field of dental monomer systems. The monomer systems of most present‐day resin composites are based on BisGMA, developed some 40 years ago, or derivatives of BisGMA. In the remaining resin composites, urethane monomers or oligorners are used as the basis of the monomer system. The main deficiencies of current resin composites are polymerization shrinkage and insufficient wear resistance under high masticatory forces. Both factors are highly influenced by the mooonier system, and considerable efforts are being made around the world to reduce or eliminate these undesirable properties. The use of fluoride‐releasing monomer systems, some of which are under investigation, has been suggested to mitigate the negative effects of marginal gaps formed in consequence of polymerization shrinkage. The very crux of the problem has also been approached with the synthesis of potentially low‐shrinking/non‐shrinking resin composites involving ring opening or cyclopolymerizable monomers. By the use of additives with a supposed chain transfer agent function, monomer systems have been formulated that improve the degree of conversion of methacrylate double bonds and mechanical properties. Many promising monomer systems have been devised, the implementation of which may be expected to improve the longevity of resin composite fillings and expand the indications for resin composites.

Aim of the study was to compare the trimming and non‐trimming variants of the microtensile technique with the ‘micro’ push‐out test in the ability to measure accurately the bond strength of fiber posts luted inside root canals. In 15 endodontically treated teeth (Group A), fiber posts were cemented with Excite DSC in combination with Variolink II (Ivoclar‐Vivadent). In 15 roots RelyX Unicem (3M‐ESPE) was used for fiber post luting (Group B). Within each group, the bond strength of cemented fiber posts was assessed with the trimming and non‐trimming microtensile technique, as well as with the push‐out test. The great number of premature failures (16.9% in Group A, 27.5% in Group B) and the finding of high standard deviation values make questionable the reliability of the trimming microtensile technique. With the non‐trimming microtensile technique, only five sticks were obtained from a total of six roots. The remaining specimens failed prematurely during the cutting phase. With the push‐out test no premature failure occurred, the variability of the data distribution was acceptable, and regional differences in bond strength among root levels could be assessed. Relatively low values of bond strength were, in general, recorded for luted fiber posts. In conclusion, when measuring the bond strength of luted fiber posts, the push‐out test appears to be more dependable than the microtensile technique.

Children and adolescents must be examined often for occlusal caries. Diagnosis of fissure caries is difficult especially when the tooth surface appears seemingly intact. It has been shown that using traditional clinical methods, as little as 20% of teeth with fissure caries under intact surfaces were correctly recognised as such. Therefore, new methods for increasing the accuracy of diagnosis have been sought for years. Recently, a new device, based on fluorescence measurements, was introduced. The purpose of this study was to test the device under in vivo conditions in order to provide recommendations for its use in the dental office. Seven general dental practitioners examined a total of 332 occlusal surfaces in 240 patients. Caries extent was determined for each site after operative intervention (=‘gold standard’). Clinical inspection and analysis of bitewing radiographs exhibited statistically significant lower sensitivities (31–63%) than did the DIAGNOdent device (sensitivity 92%). It is recommended that the laser device is used in the decision‐making process in relation to the diagnosis of occlusal caries as a second opinion in cases of doubt after visual inspection.

Gingivitis and periodontitis are thought to result from an imbalance between those oral microorganisms which normally colonize tooth surfaces in close contact with the gingival margin, and the nature and efficiency of the host response. The bacteria are the triggering agents, but host defence mechanisms within the gingival/periodontal tissues seem to be responsible for most of the tissue damage and for the outcome and progression of the diseases. It has recently been shown that emotional or psychological load (stress) may influence immune activities directly via neurvoendocrine (hormone) messenger substances (neurotransmitters and neuropeptides) and/or indirectly via neuroendocrine (hormone) substances. This review discusses how emotional stressors and nervous and neuroendocrine responses to psychological stressors may modulate the immune response to bacteria, and thus be expected to influence the progression and course of gingivitis and periodontitis.

Different monomer structures lead to different physical and mechanical properties for both the monomers and the polymers. The objective of this study was to determine the influence of the bisphenylglycidyl dimethacrylate (BisGMA) concentration (33, 50 or 66 mol%) and the co‐monomer content [triethylene glycol dimethacrylate (TEGDMA), ethoxylated bisphenol‐A dimethacrylate (BisEMA), or both in equal parts] on viscosity (η), degree of conversion (DC), and flexural strength (FS). η was measured using a viscometer, DC was obtained by Fourier transfer Raman (FT‐Raman) spectroscopy, and FS was determined by three‐point bending. At 50 and 66% BisGMA, increases in η were observed following the partial and total substitution of TEGDMA by BisEMA. For 33% BisGMA, η increased significantly only when no TEGDMA was present. The DC was influenced by BisGMA content and co‐monomer type. Mixtures containing 66% BisGMA showed a lower DC compared with mixtures containing other concentrations of BisGMA. The BisEMA mixtures had a lower DC compared with the TEGDMA mixtures. The FS was influenced by co‐monomer content only. BisEMA mixtures presented a statistically lower FS, followed by TEGDMA + BisEMA mixtures, and then by TEGDMA mixtures. Partial or total replacement of TEGDMA by BisEMA increased η, which was associated with the observed decreases in DC and FS. Although the BisGMA content influenced the DC, it did not affect the FS results.

The evolutionary links that exist between odontodes and organs that are phylogenetically related to them (teeth and scales) suggest the use of comparative approaches to study these structures. Part one of this review briefly introduces current ideas on how the pattern of odontodes and odontode‐derived tissues has been established during evolution to yield the diversity of odontode‐related organs currently observed in nature in the cranial and postcranial skeleton. This introductory survey is used to highlight aspects of the developmental processes underlying the formation of some of these organs and the resemblance their development bears to odontogenesis. Part two provides a concise survey of the diversity of tooth structure in the different classes of extant vertebrates, in particular with reference to enamel/enameloid and dentine structure, and tooth attachment. Against this background, the current state of knowledge is reviewed with regard to developmental mechanisms involved in non‐mammalian odontogenesis. Common structure and similarities in development demonstrate that teeth and odontode derivatives should not be considered subjects of separate lines of research. On the contrary, results acquired in one of these fields are relevant to the other and may disclose model species that are relevant to studies on mammalian odontogenesis.

Schley J‐S, Heussen N, Reich S, Fischer J, Haselhuhn K, Wolfart S. Survival probability of zirconia‐based fixed dental prostheses up to 5 yr: a systematic review of the literature.
Eur J Oral Sci 2010; 118: 443–450. © 2010 Eur J Oral Sci

The purpose of this systematic review was to calculate the 5‐yr survival rates of all‐ceramic zirconia‐based fixed dental prostheses (FDPs) and to analyze technical and biological complications. An electronic literature search of MEDLINE (PubMed) was conducted independently by three reviewers to identify clinical studies from 1999 to 2009 and was completed by a manual search. Keywords and inclusion and exclusion criteria were well‐defined. The search revealed 399 titles and led to the final analysis of 18 full‐text articles. Nine studies met the inclusion criteria. Extracted data were statistically calculated into 5‐yr survival rates and 5‐yr complication‐free rates by using Poisson regression analysis. In total, 310, 3‐ to 4‐unit FDPs and 20 FDPs with more than 4 units were included. The estimated 5‐yr survival rate for all FDPs was 94.29% (95% CI: 58.98–99.32); 19 FDPs were lost as a result of catastrophic failures. The 5‐yr complication‐free rate regarding technical complications was 76.41% (95% CI: 42.42–91.60) with chipping being the most frequent complication. Regarding biological complications, the 5‐yr complication‐free rate was 91.72% (95% CI: 59.19–98.53). The survival rates of zirconia‐based short‐unit FDPs are promising. However, an important improvement of the veneering systems is required, and for FDPs with more units in function, further randomized, controlled clinical trials are necessary.

Oral malodor is a significant social disability which usually has a local cause, particularly arising from the oral flora. Malodor may arise from the lingual or periodontal flora, gram‐negative anaerobes being the main organisms capable of releasing sulphur compounds, from the putrefaction of debris and other material. Volatile sulphur compounds, cadaverine and other substances appear responsible for much of the malodor. Systemic disease may underlie some cases of oral malodor. The objective assessment of malodor is still best performed by the human sense of smell (organoleptic method) but more quantifiable measures are being developed.

Although it is known that chlorhexidine application may preserve resin–dentin bonds from degradation, the lowest optimal concentration and application time have yet to be established. This study evaluated the effects of different concentrations of chlorhexidine digluconate and different application times on the preservation of resin–dentin bonds formed using two etch‐and‐rinse adhesives. In experiment 1, after acid etching, the occlusal demineralized dentin was rewetted either with water or with 0.002, 0.02, 0.2, 2, or 4% chlorhexidine for 60 s. In experiment 2, the surfaces were rewetted with water, or with 0.002% or 2% chlorhexidine for 15 or 60 s. After this, both adhesives and composite resin were applied and light‐cured. Bonded sticks (0.8 mm²) were tested under tension (0.5 mm min⁻¹) immediately or after 6 months of storage in water. Two bonded sticks from each tooth were immersed in silver nitrate and analyzed quantitatively using scanning electron microscopy. Reductions in microtensile bond strengths and higher silver nitrate uptake were observed for both adhesives when the rewetting procedure was performed with water. Stable bonds were maintained for up to 6 months under all chlorhexidine conditions tested, irrespective of the chlorhexidine concentration and application time. The use of 0.002% chlorhexidine for 15 s seems to be sufficient to preserve resin–dentin interfaces over a 6‐month period.