Community hub
Recent from talks
Contribute something to knowledge base
Content stats: 0 posts, 0 articles, 1 media, 0 notes
Members stats: 0 subscribers, 0 contributors, 0 moderators, 0 supporters
Subscribers
Supporters
Contributors
Moderators
Dental composite
Dental composite resins (better referred to as "resin-based composites" or simply "filled resins") are dental cements made of synthetic resins. Synthetic resins evolved as restorative materials since they were insoluble, of good tooth-like appearance, insensitive to dehydration, easy to manipulate and inexpensive. Composite resins are most commonly composed of Bis-GMA and other dimethacrylate monomers (TEGMA, UDMA, HDDMA), a filler material such as silica and in most applications, a photoinitiator. Dimethylglyoxime is also commonly added to achieve certain physical properties such as flow-ability. Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent.
Many studies have compared the lesser longevity of resin-based composite restorations to the longevity of silver-mercury amalgam restorations. Depending on the skill of the dentist, patient characteristics and the type and location of damage, composite restorations can have similar longevity to amalgam restorations. (See Longevity and clinical performance.) In comparison to amalgam, the appearance of resin-based composite restorations is far superior.
Resin-based composites are on the World Health Organization's List of Essential Medicines.
Traditionally resin-based composites set by a chemical setting reaction through polymerization between two pastes. One paste containing an activator (not a tertiary amine, as these cause discolouration) and the other containing an initiator (benzoyl peroxide). To overcome the disadvantages of this method, such as a short working time, light-curing resin composites were introduced in the 1970s. The first light-curing units used ultra-violet light to set the material, however this method had a limited curing depth and was a high risk to patients and clinicians. Therefore, UV light-curing units were later replaced by visible light-curing systems employing camphorquinone as the photoinitiator.
In the late 1960s, composite resins were introduced as an alternative to silicates and unfulfilled resins, which were frequently used by clinicians at the time. Composite resins displayed superior qualities, in that they had better mechanical properties than silicates and unfulfilled resins. Composite resins were also seen to be beneficial in that the resin would be presented in paste form and, with convenient pressure or bulk insertion technique, would facilitate clinical handling. The faults with composite resins at this time were that they had poor appearance, poor marginal adaptation, difficulties with polishing, difficulty with adhesion to the tooth surface, and occasionally, loss of anatomical form.
In 1978, various microfilled systems were introduced into the European market. These composite resins were appealing, in that they were capable of having an extremely smooth surface when finished. These microfilled composite resins also showed a better clinical colour stability and higher resistance to wear than conventional composites, which favoured their tooth tissue-like appearance as well as clinical effectiveness. However, further research showed a progressive weakness in the material over time, leading to micro-cracks and step-like material loss around the composite margin. In 1981, microfilled composites were improved remarkably with regard to marginal retention and adaptation. It was decided, after further research, that this type of composite could be used for most restorations provided the acid etch technique was used and a bonding agent was applied.
Hybrid composites were introduced in the 1980s and are more commonly known as resin-modified glass ionomer cements (RMGICs). The material consists of a powder containing a radio-opaque fluoroaluminosilicate glass and a photoactive liquid contained in a dark bottle or capsule. The material was introduced, as resin composites on their own were not suitable for Class II cavities. RMGICs can be used instead. This mixture or resin and glass ionomer allows the material to be set by light activation (resin), allowing a longer working time. It also has the benefit of the glass ionomer component releasing fluoride and has superior adhesive properties. RMGICs are now recommended over traditional GICs for basing cavities. There is a great difference between the early and new hybrid composites.
Initially, resin-based composite restorations in dentistry were very prone to leakage and breakage due to weak compressive strength. In the 1990s and 2000s, such composites were greatly improved and have a compression strength sufficient for use in posterior teeth.
Dental composite
Dental composite resins (better referred to as "resin-based composites" or simply "filled resins") are dental cements made of synthetic resins. Synthetic resins evolved as restorative materials since they were insoluble, of good tooth-like appearance, insensitive to dehydration, easy to manipulate and inexpensive. Composite resins are most commonly composed of Bis-GMA and other dimethacrylate monomers (TEGMA, UDMA, HDDMA), a filler material such as silica and in most applications, a photoinitiator. Dimethylglyoxime is also commonly added to achieve certain physical properties such as flow-ability. Further tailoring of physical properties is achieved by formulating unique concentrations of each constituent.
Many studies have compared the lesser longevity of resin-based composite restorations to the longevity of silver-mercury amalgam restorations. Depending on the skill of the dentist, patient characteristics and the type and location of damage, composite restorations can have similar longevity to amalgam restorations. (See Longevity and clinical performance.) In comparison to amalgam, the appearance of resin-based composite restorations is far superior.
Resin-based composites are on the World Health Organization's List of Essential Medicines.
Traditionally resin-based composites set by a chemical setting reaction through polymerization between two pastes. One paste containing an activator (not a tertiary amine, as these cause discolouration) and the other containing an initiator (benzoyl peroxide). To overcome the disadvantages of this method, such as a short working time, light-curing resin composites were introduced in the 1970s. The first light-curing units used ultra-violet light to set the material, however this method had a limited curing depth and was a high risk to patients and clinicians. Therefore, UV light-curing units were later replaced by visible light-curing systems employing camphorquinone as the photoinitiator.
In the late 1960s, composite resins were introduced as an alternative to silicates and unfulfilled resins, which were frequently used by clinicians at the time. Composite resins displayed superior qualities, in that they had better mechanical properties than silicates and unfulfilled resins. Composite resins were also seen to be beneficial in that the resin would be presented in paste form and, with convenient pressure or bulk insertion technique, would facilitate clinical handling. The faults with composite resins at this time were that they had poor appearance, poor marginal adaptation, difficulties with polishing, difficulty with adhesion to the tooth surface, and occasionally, loss of anatomical form.
In 1978, various microfilled systems were introduced into the European market. These composite resins were appealing, in that they were capable of having an extremely smooth surface when finished. These microfilled composite resins also showed a better clinical colour stability and higher resistance to wear than conventional composites, which favoured their tooth tissue-like appearance as well as clinical effectiveness. However, further research showed a progressive weakness in the material over time, leading to micro-cracks and step-like material loss around the composite margin. In 1981, microfilled composites were improved remarkably with regard to marginal retention and adaptation. It was decided, after further research, that this type of composite could be used for most restorations provided the acid etch technique was used and a bonding agent was applied.
Hybrid composites were introduced in the 1980s and are more commonly known as resin-modified glass ionomer cements (RMGICs). The material consists of a powder containing a radio-opaque fluoroaluminosilicate glass and a photoactive liquid contained in a dark bottle or capsule. The material was introduced, as resin composites on their own were not suitable for Class II cavities. RMGICs can be used instead. This mixture or resin and glass ionomer allows the material to be set by light activation (resin), allowing a longer working time. It also has the benefit of the glass ionomer component releasing fluoride and has superior adhesive properties. RMGICs are now recommended over traditional GICs for basing cavities. There is a great difference between the early and new hybrid composites.
Initially, resin-based composite restorations in dentistry were very prone to leakage and breakage due to weak compressive strength. In the 1990s and 2000s, such composites were greatly improved and have a compression strength sufficient for use in posterior teeth.
Recent media
Recent media