Recent Advances In Restorative Dentistry x1b3p

Recent Advances In Restorative Dentistry

By Hisham Abdelwahab Mostafa Professor Of Operative Dentistry Faculty Of Dentistry, Ainshams University

Important Notice Copy&/or modification of all or part of the following text is prohibited by law

Contents - The recent concept in restorative dentistry - Aspects in which restorative dentistry is modernized - Recent advances in diagnosis and treatment planning • • • • • • • •

Computerized Radiography: Radiovesiography Wave length dependent fiber optic transillumination Argon laser fluorescence Computerized occlusal analysis Electrical Caries Monitor ECM Caries detection dyes New concepts in treatment planning Prevention, Minimal intervention vs drill and fill, ART, Ultraconservative preparation, ozone therapy.

- Recent advances in cavity preparation • • • • • • •

Recent classification of cavities based on site and size Si/Sta Use of air abrasion technique Use of lasers in tooth preparation Use of ultrasonics in tooth preparation Stepwise excavation Chemomechanical caries removal (Caridex&Carisolv) Management of smear layer(Concept of hybridization)

- Recent advances in restorative materials and adhesives • • • • • • • •

Gallium based silver alloy Bonded amalgam restorations (Amalgam bond) Novel adhesive systems Packable and flowable composites Microhybrid non shrinking composites Glass ionomers, Compomers, Giomers and Smart restoration Ormocers and Ceromers Tooth colored inlays: -Fabricated (direct, indirect) -Machine ground (CAD/CAM, Celay) -Ready made inserts (size matching: sonic-sys, cerana) (non-size matching: megafil beta quartz inserts)

- Recent advances in manipulation techniques and equipments • Ultrasonic condensation • Incremental packing, c-factor, decoupling technique 2

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Guided polymerization: Soft start polymerization ( stepped, ramped and pulse delay) High intensity QTH polymerization(Turbo curing), PAC and LED: Recent technology in Hand pieces and rotary instruments:

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Recent Concept Of Restorative Dentistry Since the days of Greene Vandiman Black (1896), the concept of undergoing restorative therapy remained unchanged for many decades. It involved all measures by which the dentist can prepare the decayed hard tooth tissue to receive a restoration which maintains the tooth integrity, restores function, esthetics and preserves the health of the masticatory system. Later on, as early as the sixties, the scope of operative dentistry was then extended to involve all lesions affecting the hard tooth tissues, not only the carious involvement of a tooth but also other defects including fracture, erosion, abrasion, attrition, discoloration as well as the developmental and acquired defects(Anderson etal,1991). The modern concept for restorative dentistry is based on conservation and has concentrated on the importance of prevention of diseases affecting hard tooth tissue and preservation of the sound tooth structure either by taking the measures to preserve the integrity of teeth from being affected or by undergoing treatment protocols which involve the minimum intervention just necessary to restore the tooth as an active member in the masticatory apparatus and to ensure its future performance. Thus, restorative dentistry encomes the prevention, diagnosis, interception, treatment and prognosis of defects of the hard tooth structure ( Albrektsson etal, 2001). Consequently, we believe that the era and the ultimate objectives of restorative therapy is currently changing. Thus it was not unexpected to find out a dramatic change and shift from the classical believes founded as early as GV Black more than 100 years ago.

The recent advances in restorative dentistry has got four main principal files: To point out the aspects in which the restorative dentistry is modernized, one should look upon the recent advances and modifications encountered in the following views:

1. Diagnosis and treatment planning. 2. Cavity design and tooth preparation. 3. Recent advances in restorative materials and adhesives. 4. Recent advances in manipulation techniques, tools and equipments.

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The procedure of recognition of disease and its extent for achieving the plan of treatment is termed diagnosis. Apart from the traditional methods for patient examination and diagnosis, the new restorative dentistry is currently dependent on many recent methods and techniques that not only help in reaching to a prompt diagnosis for the case but also facilitate the plan of treatment and helps in explaining it to the patient to participate positively in the process of decision making to proceed during the steps for treatment.

• Computerized Radiography: According to many investigators (Richardson,1981 and Jackson,etal,1985), the digitized radiography proved to be superior than the traditional radiograph in disclosing the defects affecting the hard tooth tissue, undoubtedly, caries is of primary concern in this respect.

When large number of records are to be analyzed, the digitizer offers advantages in of speed and preparation of data for computer analysis. The computerized digital sensitivity allows for the use of up to 1024 gray levels, thus it enables the operator to distinguish the earliest changes that could affect the hard tissues especially in areas of low

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contrast. This would be usefull in particular in detection of incipient caries at the inter-proximal areas. Recent technological developments have produced a new generation of software with computer aided image analysis making it possible to drive a variety of objective measurements from approximal enamel radioluscencies corresponding to natural lesions depicted in clinical bite wing radiographs which were regularly employed for the purpose of detecting early proximal decay. Moreover, the ability of the digital radiograph to generate a scale plot of the lesion boundary as well as the estimate for the depth of penetration of the lesion enables the operator to accurately estimate the progression of decay and by follow ups, he can judge the regression or the arrest of the carious procedure (Pitts,1984). Furthermore, the ability to perform an accurate radiograph while minimizing the exposure time and omitting the procedure of film processing adds to the benefits of the technique in addition to the possibility of repeating the shots and save only of the best quality of them as a record. The filing system incorporated helps the operator to bring back the desired image in the touch of a button. On the other hand, numerous barriers still need to be overcome in the use of computers in dental radiography mostly in the part of its software. In many instances, the alteration of an image to remove artifacts or scratches needs to be documented and can not be relied on as an evidence in the legal sense (Pickens,1986). The high cost of the computerized radiograph does not encourage many of the practitioners. However, some of the equipments are introduced with a reasonable price so that a transition from traditional to computerized radiography is currently taking place.( Hess,1986)

• Radiovesiography: The radiovesiograph is a multi-component system advocated by Dr Francis Mouyen in 1989 ( Mouyen etal,1999). It enables the operator to capture colored images from the patient mouth via an intra – oral camera and the transfer of this image to the computer to be saved there so that many options and applications could be carried out by that image. The image can be zoomed, rotated, cut or edited in the same manner as pictures captured from the computer scanner. Further manipulation of the image is possible, it includes enhancement, contrast stretching and reversing. The appearance of the image on the computer monitor and the possibility of file reopen enable the operator to share the process of decision making during planning of treatment of the case, taking in consideration the possibility of informing the patient about the existing condition and explaining the steps of treatment to be proceeded. On the other hand, alarming the patient from the unfavorable consequences that 6

could occur if such treatment is neglected . Again, as digital radiography could be an adjunct to the same equipment, a sensor for radiography can be attached instead of the intra-oral camera for radiographic purposes (Snow, 2002). The sensor can be cold sterilized and for infection control, disposable latex sheaths are used to cover it when it is in use inside the mouth. The newer versions of intra-oral cameras are very light in weight (less than 50 Grams) and the illumination for image capture is no longer a fiber-optic which is affected by aging but it became light emitting diodes which give adequate white illumination to comply with darkness inside the mouth. The focusing of the camera lens is automatic and the image could be transferred either to pc or to any other video compatible system. Some devices include a defogging feature to prevent the effect of intraoral humidity from altering the image quality. Moreover, there is a capability of freezing the images up to four images at the same timing.

• Wave length dependent fiber optic transillumination : Apart from the conventional fiber optic trans-illumination, Vaarkamp etal, in 1997 (Vaarkamp etal,1997.) advocated a technique by which the occlusal surface is imaged by a charged coupled device camera(CCD) which utilizes the light in the blue and red portions of the light spectrum during imaging. The average mineral loss of the tooth structure can be determined via analyzing the recorded image and assessment of the optical thickness difference of the tooth structure since there is a marked difference between the light transmitted through carious and non carious sites. This method can provide an assessment of the mineral loss of the suspected tooth to provide a quantitative diagnosis. A

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high intensity light is shone through the tooth and the transilluminated image of the tooth is captured by the above mentioned intra oral camera, then it is displayed on the computer screen for diagnosis.

• Argon laser fluorescence : This technique is used to quantify the mineral loss in carious lesions. The lesion is subjected to argon laser and will emit fluorescence which is different in healthy sites compared to the demineralized carious sites. (Emami etal,1996.). More recently in February 2000, a newer device was introduced , it works on the fluorescing nature of bacteria and its metabolic by-products. This fluorescence is detected into a meaningful numerical figure that can be used not only to diagnose caries but also to measure the level of cariogenic bacterial activity(Shi etal , 2000 and Featherstone , 2000).

• Computerized occlusal analysis : The problems of occlusion constitute a major issue in the establishment of dental disorders. Occlusion analysis and simulation of occlusion of a patient, remained the day dream of the dental profession. It constituted a great difficulty to analyze the problems arising from occlusal origins due to the complex nature of the human occlusal system. The search for the most atraumatic dental occlusion is an increasingly growing demand especially in the fields of restorative and reconstructive dentistry. However, in 1988, Dr William Maness (Maness,1988.) working in Tufts introduced his automated computerized sensor for analysis of the dental occlusion. The idea is to the patient occlusion on a thin

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patented 60 microns thickness disposable sensor to record instantaneously the patient bite in of location, timing and force of every tooth in . This record is transferred to a computing system which can make an actual simulation of the patient occlusion on a monitor assuming the different situations possible during centric, eccentric and functional movements. Thus, providing both qualitative and quantitative assessment of occlusion instead of the former messy only qualitative carbon marks and presenting this in a moving show. The movie can be replayed in frame by frame manner to study the occlusion. The system was termed TScan and has got many advantages as being simple to operate, dynamic viewing of occlusion, timed analysis of force during various positions of teeth and the possibility of permanent documentation and monitoring of the occlusal condition after carrying on the various treatment protocols. The T-Scan not only presented a valuable method for clinical evaluation and understanding of the occlusal problems but also it offered an important tool for teaching purposes as explained by Dr Maness, the inventor of the system. (Maness,1988).

Dr William Maness

Computerized sensor for registration of occlusion

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• Electrical Caries Monitor ECM : The existing clinical methods for caries diagnosis are unable to discriminate between lesions with or without a remineralized surface layer. The idea is that the electrical conductivity of a tooth changes with demineralization, even when the surface remains macroscopically intact. A major advantage of the ECM is to present reliable objective reading . Thus, it becomes suitable for early detection of lesions and to monitor lesion progression or recession, arrest or remineralization.(Ashley P, 1997). The ECM measures the electrical resistance of a site on the tooth ; high measurements indicating well mineralized tissue and low values are indicative of demineralized tissue. Electrical resistance measurements have demonstrated accuracy in detecting occlusal caries (Albrektsson etal, 2001)

Ricketts etal .( Ricketts etal, 1995), reported the benefits of utilizing the ECM in diagnosis of early occlusal and cervical carious lesions. Baysan etal, (Baysan etal,2000) recently in 2000, showed the definite correlation between ECM readings and th clinical findings during caries assessment as texture, hardness, size, cavitation. The researchers concluded that the ECM is a valuable method to detect incipient lesions. One of the marketed appliances is the ECM III, Lode diagnostics BV, Groningen, Netherlands.

• Caries detection dyes : Caries detection dies evolved in an attempt to solve the conflict of differentiating between affected and infected dentin and whether all doubtful dentin has to be eliminated or remineralization is possible. Fusayama in 1980, came out with a dye indicator which was 1% basic fuchsin in propylene glycol in order to replace the policy of drill and fill by a more conservative approach. More recently, Husoda and Fusayama (Husoda and Fusayama, 1984) proposed a tooth substance saving technique 10

in a more biological look and summarized the conservative technique in two man steps, the first was to use the caries detection dye and the second was stepwise excavation to remove only the infected irreversibly denaturated dentin and leave the deeper non infected reversibly denatured remineralizable dentin.

• New concepts in treatment planning : Planning the treatment for restorative therapy is getting a more biological model than the drill and fill old surgical model. The old model included tooth preparation to remove the defect and include it in a suitable design that can accommodate and retain the final restoration. On the other hand, the non surgical biological model is based on the medical therapy by controlling the causative factor and eliminating the reservoirs of the pathogenic micro-organisms. Even the intervention policy is currently changing to present a new ultraconservative approach with minimal intervention (Mount,2000) and atraumatic restorative techniques .ART (Frencken and Holmgren,1999). Recent modalities of treatment included prevention of caries by fluoridation, diet control, oral hygiene measures and immunization based on molecular biology. Another alternative is the conservative management of suspected lesions by fissure sealing, enameloplasty and preventive resin restoration. More recently, an effective and powerful method was employed which is the ozone therapy. Ozone is known to be a powerful antimicrobial agent. Studies have shown that exposure of carious dentin to O3 for 10 or 20 seconds has caused a substantial reduction in the level of cariogenic organisms. It can penetrate the bacteria and kill them in their protected niches. It can alter the bacterial metabolic activities that inhibit the process of remineralization and thus allow clinical reversal of the lesions in both root caries and occlusal surface lesions.( Baysan and Lynch 1999, 2001and Baysan etal in 2000). Ozone was first suggested to disinfect water because of its ability to inactivate microorganisms. Currently, it is used in dentistry by utilizing a special delivery system known as (Healzone). The 11

portable apparatus includes a source of oxidizing gas and a dental hand piece for delivering the gas/water to the target tooth. A cup attached to the hand piece is provided for receiving the gas and exposing a selected area of the tooth to the gas action. The tightly fitting cup includes a resilient edge for sealing the margins to prevent escape of the gas. The procedure should be followed by rinse and suction (Ebensberger etal, 2002) to eliminate gas residues since some reports indicated that excessive exposure to ozone may result in complications as eye, lung or subcutaneous emphysema.

Healozone Ozone Delivery System

Hand piece with cup for ozone delivery

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• Recent classification of cavities based on site and size Si/Sta: The traditional Black,s classification which served for identification and standardization of cavities for many years is currently debated for inefficiency in specifying the size and extent of the lesion. Mount and Hume in 1998,( Mount and Hume, 1998.), proposed a new classification that is based on site and size and was termed Si/Sta classification. It includes site1 for pits and fissures and enamel defects on the occlusal surfaces of posterior teeth and smooth surfaces on anterior teeth. Site 2 involves approximal enamel immediately below the areas with adjacent teeth. Site 3 refers to the cervical one third of the crown or exposed root. The four sizes are size 1 , which indicates minimal dentin involvement, size 2 indicates moderate dentin involvement , size 3 designates involvement beyond moderate and the restoration is designed to the remaining tooth, while in size 4, there is an extensive involvement and bulk loss of the tooth structure and hence, a more radical form of restoration will be designed. • Use of air abrasion technique: The technology of air abrasion came as early as 1940. It was an alternative to the slow speed belt driven hand piece used at that time for the removal of tooth structure. At that time, Black in 1945, published a detailed method for cavity preparation using a stream of gas–borne aluminum oxide abrasive particles to wear away and abrade the tooth structure. Eakle etal, in 1994 (Eakle etal,1994) and Goldstein and Parkins, in 1995,(Goldstein and Parkins, 1995) have demonstrated the importance of employing the air-brasive technique to match with the needs for a conservative approach in removing carious dentin and conditioning the adherend dentinal surfaces. The usual range of size of the abrasive particles utilized in the air abrasive technique is25- 50 microns while the pressure used to apply the particles ranged between 80-160 psi. The present outcome in the field of air abrasion is the Kinetic cavity preparation using K2000. The apparatus involves minute abrasive particles which are too small to be seen by the naked eye carried to the target tooth by a stream of air gently and precisely acting to remove away the decayed tooth structure. It allows the removal of such decayed part of the tissue without the removal of the healthy tooth substance unnecessarily. The resultant prepared surface was found to be ideal for

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adhesive dentistry and the application of bonded restorations. It is a precise, gentle, time saving , painless as it reduces thermo-genesis and omits the vibration of the ordinary rotary tools. It is recommended for treatment of children, pregnant women and other medically compromised patients.

Newly introduced Kavo Air abrasion system

• Use of lasers in tooth preparation: Laser is an acronym of light amplification by stimulated emission of radiation. The laser optical chamber is a resonator which comprises two mirrors, one is totally reflective to increase the excitement of the atoms by the reflection of radiation while the other is partially transmissive to emit the laser beam proper. The laser is named according to the excitation medium, accordingly, various types of lasers are available, among which the Nd-Yag (Neodymium – Ytterium/Alluminum/Garnet is most suitable for tooth preparation. The produced laser beam is then ed through a lens and the resultant radiant energy can be focused to a very small sized spot to yield the various uses of laser as cutting, vaporizing, coagulation or conditioning effects. The use of laser technology in cavity preparation was faced with many complications such as the difficulty in the localization of its effect and the enormous temperature rise (Elmortada,1995). However, the innovation of a hydrokinetic laser to employ a combination of laser energy and water spray can be utilized to rapidly remove the enamel, dentin as well as the decayed tooth ( Biolase technology incorporation). The employment of pulsed laser and the recent technology of micro and nano seconds have yielded a hope in achieving the objective of utilizing only the required laser energy to effect the procedure needed and avoid the unfavorable squeal of pulp affection ( McDonald etal, 2002).

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Special Handpiece for laser application from Kavo

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Use of ultrasonics in tooth preparation:

Generally, ultrasound is generated by either magnetostriction or by piezo electricity. Ultrasonics are usually utilized in dentistry for elimination of calculus deposits, however, drill inserts of various forms and sizes can be attached instead for cavity preparation. The sonicsys was introduced to the dental profession in the international exhibition held in Koln 1997. It consists of metallic inserts coated by diamond from one side to assure that no damage would occur if the tip s the neighboring tooth. It complies with the requirements of the minimal invasive technique of preparation. It has the advantage of providing a standard preparation to accommodate standard prefabricated inlays. There are three sizes of tips for preparing standard proximal cavities (sonicsys approx) and there is another smaller tip for ultra small proximal preparation( sonicsys micro).Each size of preparation has a corresponding prefabricated inlay that is exactly fitting its size of the preparation.

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Various tips for ultrasonic preparation of the tooth structure

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Ultrasonic equipment used to attach preparation tips •

Stepwise excavation:

The carious process es by periods of activity in which there is increased rate of demineralization and proteolysis with resultant tooth destruction and other periods of rest in which recovery takes place and there is reparative mechanism causing remineralization by deposition of sclerotic dentin. In cases of acute caries, the activity of the lesion is enhanced due to increase of the rate of acid production while in chronic decay, there is an enhanced reparative mechanism due to decrease of virulence of the microorganisms, less production of acid and greater tooth resistance. In many instances, during management of deep carious lesions by complete one step eradication, the pulp is often approximated and may be involved by minute undetected or frank exposures. The idea of stepwise excavation is to perform peripheral dentin excavation first to change the ecology of the lesion and arrest the spread of decay so that repair can take place. This should be followed by removal of the central cariogenic biomass and the superficial necrotic dentin in a separate session as late as 2-4 months. Doing this, many pulps could be saved from injury and the removal of the minimum amount of tooth structure as a part of ART is achieved.( Bjorndal and Larsen, 2000 and Ricketts,2001). The maximum outcome of the stepwise excavation procedure can be established in combination with caries detection dyes which are able to distinguish the infected from the affected dentin such as acid red dye ( fuchsin dye) or the more recent blue dye ( Quadrant CariTest) . Thus, what is removed would be only the amount of dentin necessary to be removed. Numerous researches indicated the benefits of stepwise excavation which includes; reduced risk of pulp exposure, decreased CFU counts, an alteration of the typical cariogenic microbiota, and an increase of remineralization and repair evidenced by the formation of hard less penetrable sclerotic dentin which adds to the quality and protective capacity of the remaining dentin bridge (Leksell etal,1996,Bjorndal and Thylstrup, 1998, and Banerjee etal, 2000).

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• Chemomechanical caries removal (Caridex&Carisolv) : The ART involves the removal of only the infected carious dentin and remineralization of the reparable only affected dentin. Mchanical removal of decay using hand excavators or rotary tools would not satisfy the objectives. The original chemomechanical agent for caries removal was based on N-Monochloro-DL-2aminobutyrate (NMAB) and is currently marketed under the name Caridex. (Watson and Kidd, 1986 and RomandRoeloffs etal, 1991). The system acts by altering the secondary and /or quaternary structure of collagen in carious dentin by chlorination of the collagen. The hydrogen bonding in the collagen is disrupted rendering it more friable and easier to remove by scrapping the carious fragments away. Studies have shown that the system is efficient in eradication of more than 90% of carious dentin in 98% of cases (Albrektsson etal, 2001). The advantage of the Caridex system is that it provides painless and efficient removal of carious dentin and thus preferred than conventional mechanical removal which requires the istration of local anaesthesia. However, it was reported that it is a time consuming technique which precluded its universal adaptation. More recently, a new gel Carisolv was introduced from ( MediTeam Incorporation, Gothenburg, Sweden). It is a combination of 0.5% sodium hypochlorite and 0.1 M amino acids ( glutamine, leucine and lycine). It comes in the form of two gels, one is transparent, and the other is red. The two gels are mixed together or brought out from the tube mixer supplied and applied into the cavity. The carisolv works on the tooth substance to remove the decay evidenced by a cloudy vapor coming after action. The application of gel takes 5-8 minutes in an average case to remove the decay. The procedure is ceased when no cloud comes out on gel application then, the supplied scrappers are used to eradicate the softened dentin. The material selectively acts on denaturated collagen, that is the collagen which has lost its cross striations by the action of the cariogenic organisms and is considered as being irreparable or not liable to the process of remineralization. By applying the carisolv, only dentin decayed beyond repair is removed which matches the objectives of ART.

The carisolv gels in tube with the supplied kit of instruments

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Management of smear layer(Concept of hybridization):

The state of art in the management of smear layer is to totally remove it using phosphoric acid etching as a part of the total etch procedure before application of adhesives to both enamel and dentin. Whether total etch in a separate step or self etching adhesives are better employed remains a controversial issue. The etching time suitable for total removal of the smear unit ranges from 10-60 seconds with most of the recommendations favoring the 30 seconds. This is of quite importance to assure adequate etching effect on enamel at the same time .(Nakabayashi and Pashley, 1998)

Open tubules after dentin etching With Phosphoric acid. Partial removal Of peritubular cuff. Mag. X 18300

Collagen network at the intertubular area after etching Mag. X 36600

The success of adhesion to dentin and the adequate protection of the pulpodentinal complex after tubular patency as a result of dentin etching is achieved via the formation of the 1-5 microns thickness hybrid layer which is formed by resin infiltration of tubules and encapsulation of the collagen fibrils at the intertubular areas after application of the resin adhesive and its polymerization.

Hybridization with resin lateral branching. Mag. X 9100 19

There are two requisites necessary for hybridization to occur. The first is the preparation of dentin substrate by removal of the smear layer and the smear plugs provided that no denaturation or deformity or collapse of collagen occurs. The second requisite is the use of a suitable resin monomer that can easily impregnate and wet the dentin to infiltrate into the tubules and encapsulate the collagen fibrils projections. The process of resin impregnation is critical in the success of hybridization. ( Nakabayashi, 1996 and Nakabayashi and Pashley, 1998).

On the other hand, the presence of a non resin impregnated zone of dentin i.e. intertubular dentinal collagen non infiltrated with resin is termed hybridoid layer. The hybridoid presence is thought to adversely affect the bond, however, later studies have shown that this zone is later on remineralized( Akimoto etal, 2001).

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The search for an ideal restorative material is still going on. None of the available restoratives is free from either biologic, esthetic or mechanical limitations (Sturdevant ,2002). The evolution of new materials is very rapid and the competition in the market is too high. I would say that there is a weekly outcome in the field of restoratives to the dental profession. Some materials proved superiority while others just survived for short periods of time. All I can say is that the search is still going on. •

Gallium based silver alloy:

The vigorous attack on the toxicity of mercury with amalgam alloys in the last two decades has urged the producers to find out an alternative. Currently, many dentists do not use amalgams either convinced with the hazards of mercury, or obeying their patients. Others went for replacing old amalgam restorations with composites. However, soon dentists discovered that this was an unwise decision. (Flanders, 1992, Psarras etal,1992 and Lutz, 1996)

The Gallium based alloy is developed as a part of a program ed by the American Dental Association. It is a direct filling material which contains no mercury. It comes in the form of a powder(60.1% silver, 28.05% tin, 11.8% copper and platinum 0.05%) and a liquid ( gallium 61.98%, indium 24.99%, tin 12.98% and bisthmus 0.05%). The product suffers from some limitations especially excessive corrosion and decreased workability (Navarro etal, 1996). The melting point of gallium is about 29oc., thus, it is recommended to slightly preheat the mixing device before trituration to assure melting of gallium and enhance its wettabiliy. Some reports indicated that gallium is not free from toxicity but its vaporization at room temperature is much less compared to mercury.

Gallium based dental alloy

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• Bonded amalgam restorations (Amalgam bond): This is a resin adhesive used with amalgam restoration after etching of enamel and conditioning of dentin. Its chemical composition is essentially 4 META (Methacryloxy chloride trimellitic dianhydride) . This is particularly useful in extensive cavities in premolars to decrease microleakage and to limit the tendency of tooth fracture. The possibility of bonding a resin composite to the facial aspects of amalgam restoration makes the system applicable to increase esthetic qualities by covering the surface of amalgam restoration. Some products are supplied with an oxyguard to counteract the oxygen inhibition of polymerization at the margins (Al-Moayad etal, 1993 and Saiku etal, 1993).

The 4 META (Amalgam bonding) kit

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Novel adhesive systems:

Bondodontics is becoming a subject of its own. The successful bonding of restorative materials to tooth tissues is the prime achievement in the modern restorative dentistry. Both chemical and micromechanical bonding to tooth structure could be well established. The bonding to enamel structure does not face the same obstacles met with dentin due to different architectures and mineral content. The acid etching invented by Bunocore (Buonocore, 1955) is still the key stone in the production of a strong and stable bond with enamel. The novel dentin adhesive systems started with the 5th. generation One bottle adhesive (Prime and bond, Dentsply, Syntac single component, 3M-Espe & Excite , Ivoclar, Vivadent). It was produced to standardize and simplify the procedure of bonding by incorporating both the primer and adhesive in a single bottle where the processes of resin impregnation and adhesive bonding are combined together. Still a total etch procedure should be carried out before application of the adhesive

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(Swift etal, 1997). However, to ensure adequate resin impregnation and

hybridization, more than one application was recommended. The research continued to eliminate the need for acid etching before application of the dentin bonding agent until a bonding agent with self etching qualities containing phosphate ester was produced under the name of (Prompt L Pop, Espe) to constitute a single bottle self etching primer/adhesive 6th. generation bonding system (Perdigao etal, 2000). The self etching system proved to produce a strong adhesive bond to both enamel and dentin together with an excellent marginal seal and possess a very simplified unique 2 steps application which are the application for 15 seconds followed by gentle spread with air stream. The simplicity and superior results has urged many clinicians to utilize the material.(Breschi etal, 1999, Nunes etal, 1999 and Frey, 2000). The self etching primer adhesive systems were blamed for the incorporation of smear layer within the hybrid layer if the primer is not agitated during application and that its highly acidic monomers incorporated to penetrate smear layer to underlying dentin can cause hypersensitivity and can interfere with polymerization of auto-polymerizable resins since this high acidity deactivates the more basic amines incorporated as catalysts in auto or dual cured resins. Moreover, as the newer generations of adhesives are becoming more hydrophilic, the adhesive may absorb water from underlying dentin(dentin perfusion) which can cause an interference with the overlying composite polymerization (Tay and Pashley, 2003, Ahmad, 2003, Ozok etal, 2004 and Tay etal, 2003).

5th. Generation single bottle adhesives Total Etch Technique

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6th Generation single bottle. Self etching primer

More recently, in 2002, a 7th generation of adhesives has erupted . The system is quite similar to the 6th generation but a desensitizing agent was added to overcome the problem of hypersensitivity (Freedman and Leinfelder, 2002). An example of this generation is the recently introduced i bond.. The material is claimed to decrease hypersensitivity in addition to the similar other properties compared to the 6th generation adhesives. (Dunn, 2003 and Van Meerbeek etal, 2003).

i Bond ( Heraeous, Kulzer) 7th. Generation adhesive system

Another development in adhesive systems is the evolution of the bioactive adhesive. This was performed by the incorporation of an antibacterial monomer (MDPB:12-Methacryloyloxydodecyl pyridinium Bromide) to a self etching adhesive system to give it a bactericidal effect. This will enable the use of the system with minimal intervention and in root caries to produce a modified sealed restoration and gives hope for success in direct pulp capping with an adhesive.(Imazato etal, 2000).

Schematic diagram showing the effect of bioactive adhesive

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Packable and flowable composites:

The invention of a condensable composite satisfied the operators due to their excellent handling characteristics. They are non sticky and moldable and easily released from the hand instruments, thus, less they are time saving and less frustrating. The material possess advanced physical and mechanical properties (Suzuk , 2001). However, the marginal adaptation of such materials suffers from a shortcoming and there is a possibility of interfacial debonding due to lack of adequate flexibility. Shrinkage during polymerization can break the established interfacial bond. The application of a flowable composite prior to the placement of packable composite will provide a stress breaking effect to prevent this debonding.(Miranden etal, 1999). The flowable composite usually has low viscosity due to decrease of its filler content.

Flowable and packable composite combination from Vivadent

Flowable composite from Bisco 25

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Microhybrid non shrinking composites:

The search for a universal composite to be suitable for use in both anterior and posterior regions has emerged a consensus that hybrid composites which has got high filler loadings up to 90% by weight of both microfined silica , borosilicate glass and quartz are suitable for use as anterior and posterior restorations. They possess excellent mechanical properties due to high filler content, polishable and has got high wear resistance and adequate translucency to produce the desired esthetics. Numerous products are available in the market with different shades. Each manufacturer claims superiority of his product. The incorporation of non shrinking monopolymer systems has added to the high performance of the materials by decreasing the resultant shrinkage of polymerization which is reflected to better bonding and reduced marginal gap formation. (Davidson, 2001).

Filtek Z250 & P 60 newer forms of microhybrid composite.

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Glass ionomers, Compomers, Giomers and Smart restoration:

The need for a fluoride releasing restorative that can directly bond to tooth structure led to the development of glass ionomer restoration. The material has a coefficient of thermal expansion close to that of the tooth structure and due to its desirable characteristics, has a wide variety of applications including restoration of cervical and root defects, core construction in addition to its use as a restorative in permanent and

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primary teeth and when its anticariogenic potential is required (Powis etal, 1982 and Thornton eal, 1986).

Due to the cement nature of the material, it suffers from disintegration in the mouth and susceptible to hydration and /or dehydration. Moreover, it is a technique sensitive material during manipulation and its properties are markedly affected with imperfect handling (Teo,1986, Walls etal, 1988 and Knibbs,1988). This has led to the incorporation of resin polymers to the structure of polyalkenoates to develop the compomers (Antonucci and Stansbury, 1989 and Mitra,1991).

Compomers possess better handling characteristics, more translucent, less disintegrable and has got a better marginal adaptation compared to glass ionomers. Moreover, the pattern of fluoride release has been found to be equivalent to that of the original glass ionomers. Furthermore, the possibility of light polymerization adds to the advantages of the material (Elbadrawi, and McComb, 1998). Giomers are another addition to the glass ionomer technology by the incorporation of pre-reacted glass ionomer filler to the powder of the glass ionomer. This was performed to obtain enhanced mechanical properties. However, unlike the compomers it was noticed that this category of glass ionomers significantly release less fluoride compared to conventional glass ionomers (Yap etal, 2002). The attempts for combining composite resin and glass ionomer has led to the development of ion-releasing polyacid modified composite known as smart restoration (Van Dijken, 2002). The smart restoration elutes fluoride, calcium and hydroxyl ions when pH value drops in the oral cavity. Consequently, the material may be able to reduce plaque formation, remineralize the tooth structure, inhibit caries and neutralize acids (Heintze, 1999) .

Glass ionomer capsules (Ionofil molar) Voco, Cuxhaven,.

Compomer restorative (Dyract) Dentsply, USA.

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•

Ormocers and Ceromers:

The ormocer stands for an organically modified ceramic composite restoration. The restorative material is considered a new material that substitutes the organic fraction of resin composites (Bis GMA & UDMA) with another component which possesses an inorganic component of modified silicon dioxide in an organic methacrylate group forming a highly cross-linked matrix. The physical properties of ormocer restorative is improved, but the marginal approximation is compromised and can be decreased by utilizing a flowable composite liner better than one bottle adhesive system.(Manhart etal,2000) The ceromer is a ceramic optimized polymeric composite restoration or fiber reinforced ceramic polymeric restoration ( Targis/Vectris) where ceramic fillers are incorporated to substitute the quartz fillers. They got an improved wear resistance and excellent esthetic qualities. The material is available in LC direct restoration or LC followed by heat curing fabricated inlays which are cured in a special furnace and cemented in place with an adhesive resin cement supplied in different viscosities. The material possesses enhanced mechanical properties, excellent esthetics. Its marginal quality is optimized by utilizing a flowable composite and/or a resin cement. Undoubtedly, the inlay form can compensate for the polymerization shrinkage and is able to attain and maintain better relations with neighboring and opposing teeth (Fahl and Casellini, 1997).

Ormocer restoration(ira, Voco)

•

Ceromer restoration with supplied resin cement(Variolink,Vivadent)

Tooth colored inlays:

This category of restorations was developed to compensate for the polymerization contraction in case of direct restorations with in-situ polymerization and to enhance the mechanical properties by more completed polymerization or by using ready made blocks with high 28

physical properties ground to produce the desired inlay. Undoubtedly, direct, indirect or machinary inlays are able to produce better anatomical landmarks, occlusal and proximal relationships with better accuracy compared to the direct restorations.(Wassel etal, 1995). Apart from the material of construction of the inlay, three types of tooth colored inlays are currently available.; Fabricated inlays, either by direct or indirect technique, machine ground inlays and Ready made inlays (inserts). Repeatedly, the inlays are inserted into the corresponding preparations and luted with adhesive bonding systems and/or flowable composite or with a dual cure adhesive resin cement The ceramic inlays should be etched with hydrofluoric acid and sialanated before insertion. (Craig and Powers, 2002).

Direct inlays can be fabricated from composite resin, ceromers or ceramic. The prepared inlay cavity is lubricated, the material is packed incrementally, the increments of composite or ceromer are light cured until the preparation is filled to the margins. The inlay is removed to receive secondary polymerization by light, or by light and heat in a special polymerization apparatus for 8minutes at 110oc.. Alternatively, the indirect inlays can be constructed in the same way after an accurate impression of the preparation and the inlay is constructed on a die in the lab. The ceramic inlays are fabricated similarly as all ceramic full coverage crown (Lutz, 1996, Burke etal, 1996 and Goracci and Andreasi Bassi,1999).

Fabricated ceromer inlay

Machine ground inlays(CAD/CAM Cerec & Celay copy milling): CAD/CAM stands for computer aided design and computer aided manufacturing. The system was introduced by Mormann and Brandistini in 1988. The prepared cavity is captured by a miniatured camera and transferred to a computer linked to a milling machine. The software program in the computer gives data to the machine so that when an order of fabrication is given, the milling machine will provide the ingot of the restoration in about 10-15 minutes time. Then, the occlusal anatomy of

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the restoration is adjusted with manual grinding and finally the inlay is polished and cemented in place. The main advantage of the system is to provide the inlay in clinic in one session.(Christensen, 2001). The ceramic blocks for making the restoration are mainly constructed from feldspathic porcelain produced by Vita company. However, there is a newer version for use with Cerec III CAD/CAM (Dicor MCG) which is a glass ceramic with fluoromica crystals in a glass matrix. It has high wear resistance and possess more flexural strength. In Cerec III system, the milling machine is able to construct not only an inlay or onlay with all fine details of occlusal anatomy, but also can fabricate venners , crowns and full bridges. Moreover, the milling machine should not be placed aside of the dental unit but can be stationed away in a separate room and connected with or without a cable(remote radio control) to the computer unit. The Celay copy – milling technique fabricates the ceramic inlay after constructing a pattern from composite resin or similar material on a die. Then, a grinding machine similar to that which duplicates house keys takes part in producing the restoration from the ceramic ingot. It is important to note that as long as the ceramic blocks (ingots) do have the same color, the produced restoration will always suffer from imperfect esthetics.

CAD/CAM grinding machine Cerec With ceramic block in place.

Some inlays produced by Cerec 3 most advanced CAD/CAM technology.

Celay key like grinding machine

pattern and inlay produced

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Ready made inlays (inserts): This group of inlays come as prefabricated inlays in different sizes. They are used to restore cavities in posterior teeth, however, the rest of preparation should be restored with packable and/or flowable composite. The inserts have the advantage of standardizing the preparation, desirable mechanical properties, efficient control of the polymerization contraction and a reduction in time of the procedure. Sonic Sys approx & sonic sys micro. These are ready made size matching prefabricated ceramic inserts for the proximal box cavity supplied in three different sizes produced by Vivadent company corresponding to the ultrasonic tips of the Sonic sys produced by Kavo. The inserts fit exactly the prepared proximal box cavity and restores the proximal with the neighboring tooth to produce the desired embrasures. The occlusal part of the preparation can be restored with packable and flowable composites if necessary. In case of small proximal cavities, a smaller size insert is available ( Sonic sys micro) while he occlusal part of the preparation may be restored with flowable composite or cavifils which are produced in compules of either 0.25 or 0.50grams. The fitting surface of ceramic inserts is usually silanated to increase the wettability by the remainder composite restoration.

Sonic sys approx

Cerana inserts. The cerana inserts are tapered cylindrical ready made size matching ceramic pieces of different sizes. After cavity preparation, the proximal part of class II preparation is drilled with the supplied corresponding cylindrical diamond point, then, the insert is fitted in place via the plastic tweezer supplied not to disturb the silanated fitting surface of the insert. Another insert is selected to fit another preparation at the occlusal surface and so on , the remaining parts of the occlusal preparation are either fitted with smaller inserts in between the previously inserted inserts or with flowable composite. The occlusal anatomy is finally adjusted after removal of the inserts handles with abrasive stones. Finally, polishing is performed for the final restoration.

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Cerana inserts

B-quatz ceramic inserts (Mega-fil) These are the first type of ready made inserts to be utilized. It is composed of a non size matching inserts. It comes in a pack of different sizes. The operator selects suitable size inserts to fit the preparation, then, the remaining part of the cavity is restored with a composite resin material. It was introduced to overcome the problem of polymerization shrinkage and waste of time during incremental packing. Moreover, the wear resistance and strength properties of the final restoration is markedly upgraded with the beta quartz inserts since it s formed of silica based glass heated to specific temperature to produce a microcrystalline translucent ceramic which is very close to the hardness of the tooth structure.

Glass ceramic inserts Megafils

Megafil inserted in prepared cavity

.

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The clinical performance of the final restoration is greatly dependent on its technique of manipulation, instrumentation and tools utilized, knowledge of the operator about the recent developments and concepts, in addition to the employment of the most updated equipments. The introduction of new materials to the field of restorative dentistry is usually accompanied by a recent technology in insertion and manipulation in an attempt to optimize the clinical utilization and the functional performance of the restorations. •

Ultrasonic condensation:

The ultrasonic condensation of amalgam restoration has increased the hazards of mercury vapor in clinics since the procedure entails a process of thermo-genesis ( Haley, 2003). On the other hand, ultrasonic packing of conventional or condensable composites was found to increase its flow and adaptation to cavity walls and margins, in addition to enhancement of polymerization due to thermo-genesis encountered (Mohsen MMA and Gilbert L, 1991). Various forms and sizes of ultrasonic tips are currently available for ultrasonic condensation of composites. They are routinely supplied with the newer forms of ultrasonic equipments. •

Incremental packing, c-factor, decoupling technique:

Bulk packing of composite resin in case of chemically activated composites was found to give satisfactory marginal sal and good physical properties. This was explained on basis of slower conversion which may give rise to a less stressful polymerization shrinkage. Moreover, the incorporation of oxygen and porosities may act as shrinkage absorber (Fusayama , 1992). On the contrary, in case of light polymerization of composite resin, irrelative of the curing depth, the polymerization shrinkage is known to be mass dependent. This necessitates the approach of layering technique to decrease the effect of polymerization shrinkage, enhance marginal adaptation and esthetic behavior of the restoration ( Neiva etal, 1998).

The increment configuration during placement of light cured composite is of great importance to control polymerization shrinkage of the restoration. C-Factor is the ratio of the free and bonded surface of the increment. It determines the amount of stress relief by flow of the material at the free surface. Thus, the horizontal layering of the increments is contented for the vertical or oblique layering since it was deduced that the minimization of the c-factor as much as possible is the key stone to the success in controlling the shrinkage pull at the margin of 33

the restoration., hence, it is advisable to separate between walls during polymerization as much as possible ( Peutzfeldt and Asmussen, 2002). Some authors recommend the use of a gingival auto-polymerizing increment in class II cavities to separate the initial increment from the body during polymerization, decoupling technique was advocated by Wilson etal in 2000, but it was debated for creating a new interface which may decrease the outcome of mechanical properties of the restoration. •

Guided polymerization:

In photo-activated composite, unlike the chemical, shrinkage vectors travel towards the light source . This is explained on basis of the high intensity of light at the surface which causes a rapid start of polymerization that pulls the rest of the polymerizing chains towards the site of initial polymerization.(Victor and Lyjan, 1994 and Yoshikawa etal, 2001). Manufacturers have introduced various shapes of curing tips to be utilized to guide the polymerization contraction, while in the critical gingival margin, the use of a light reflection wedge will be helpful to concentrate the light on the gingival area of the restoration to achieve such guidance effect.( Lutz etal, 1986 and Victor and Lyjan, 1994). The technique was termed three sited polymerization where curing is performed for buccal, lingual and gingival to effect concentration of light at the proximal cavity. ( Pereira etal, 2002). Guiding polymerization by the three –sited technique proved an improvement in the adaptation of class II cavities when compared with the conventional curing. However, Loesche in 1999 attributed the improvement in case of three sited polymerization to the reduction of light intensity rather than to guided polymerization

Curing using light reflecting wedge

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•

Soft start polymerization:

Slowing down the initial intensity of polymerization by soft start polymerization at a lower intensity 180 mw/cm2 for 10 seconds followed by full intensity polymerization at 800 mw/cm2 will cause a slow down in the conversion of double bonds of the resin monomer. Two steps of polymerization are carried out by this technique (stepped polymerization). Another method to apply the soft start polymerization is the ramped curing in which the irradiance is gradually increased from a low value to maximum intensity over a 10 seconds period after which it remains constant for the duration of exposure. The third method to apply soft start is the pulse delay in which there is an application of 10 seconds conventional curing followed by an interruption of curing for one or two minutes before completion with the same light intensity. Slowing down the initial polymerization results in a decreased pull at the margins of the restoration. The full intensity polymerization follows to complete the conversion to the maximum to attain the desired mechanical properties. Goracci and Casa de Martiniz,1993, explained the effect of reducing the intensity of light source to slow down the speed of conversion and to prevent the rapid increase of viscosity ( Trommsdorff effect ) which is likely to occur by massive emission of light intensity. Thus, it is possible by utilizing low intensity initial polymerization to obtain a slow and gradual conversion at the beginning which facilitates flow of the resin composite. Pulse delay controls the process of polymerization for sake of decreasing the contraction and improving the adaptation, yet, attaining adequate mechanical properties for the restoration. The given time probably allows for securing the established bond while the material is adequately flowy. This will prevent the forceful pull of the material from the bonded margins prematurely ( Yap etal, 2002). Moreover, the pulse delay polymerization may be in favor of attaining high mechanical properties by more cross linking of the pendant chains occurring as a result of the presence of a ceased polymerization period ( Ruggeberg etal, 1999 and Sahafi etal, 2001).

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Elipar trilight curing apparatus for soft start polymerization

•

High intensity polymerization (Turbo curing), PAC and LED:

It is well documented that the ultimate properties of direct light polymerization tooth colored restoratives are not attained except when adequate curing is performed.( Oberholzer etal, 2003).Undoubtedly, the inefficiency of curing results in diminished physical and mechanical properties of the restoration as a result of incomplete conversion and delayed hardening of the material. The result will be a decreased depth of curing, lack of strength, diminished hardness and wear resistance, insufficient bonding and loss of adaptation with subsequent failure of restoration due to inadequate retention, gross leakage and or recurrent decay as well as the inability to withstand the functional stresses which may end in fracture and excessive wear and loss of anatomical landmarks of the restoration ( Eldewani etal , 1997). In order to avoid the possibility of inadequate curing, the manufacturers produced high intensity quartz tungsten halogen lamps curing devices providing very high intensity of curing that exceeds 1000 mw/cm2. The devices were given the name turbo appliances. Other manufacturers launched other types of high performance appliances which utilizes a high energy, high pressure ionized gas in the presence of an electrical current to create an intensely bright, very high temperature light source that provides laser like curing speeds. Plasma arc curing (PAC) devices are able to perform rapid 5-10 seconds polymerization of composites having activators which absorb light in the range of 430-500 nm , a range which almost matches with the absorption curve of the camphoroquinone photo-activator present in most types of commercial composites. The power density of PAC devices was found to be at least 36

1196mw/cm2 , that is almost double that of conventional QTH appliances giving about 600mw/cm2.

Turbo curing apparatus Optilux 501 from Kerr

Apollo plasma arc curing apparatus from DMD

Two types of the current LED devices for composite curing

The most recent innovation in curing appliances in current use is the LED appliances. Light emitting diodes curing devices produce a high intensity of curing light but in a very narrow zone of wave lengths of light spectrum with peaks around 440-470 nanometers. Depending on the brand, this is ideal to be absorbed by the most common photo-initiator (camphoroquinone) which has an absorption peak of 468 nm, but is less effective for other photo-initiators that have peaks below 440 nm, such as phenyl-propanedione. The problem is that camphoroquinone is yellow in color and in some composites particularly translucent shades it cannot be used. Thus, clinical research associates recently published a listing of 37

products that may not polymerize with LED appliances. Some companies shifted the emission spectrum of their LED appliances to suit a variety of photo-initiators by combining two different diodes with a wide range of spectral emission to allow the curing of all the materials(second generation LED appliances). The advantages of LED devices are; the less power necessary to operate the unit because of their unfiltered narrow emission spectrum. Consequently, they may be powered with rechargeable batteries, making them available in light weight, cordless units. The diodes have a potential lifetime of several thousand hours instead of the range of a hundred with halogen systems. Ninety nine percent of the original energy of emitted from QTH lamps is a useless energy that must be filtered out. Noisy fans are required to help eliminate this unwanted heat, but, the LED devices have very little wasted energy and require minimum cooling.(Leonard etal, 2002 and Soh etal, 2003)

•

Recent technology in rotary tools and hand pieces:

In addition to the improvement in material of construction of the rotary cutting tools in order to improve the cutting efficiency and prolong life of the tool which may be endangered from repeated sterilization, Standardizing operative procedures is an objective of modern dentistry. Manufacturers have produced efficient tools designed to perform certain step or function. Burs are designed to prepare a conservative minimally extended cavity for composite restorations in posterior teeth having rounded ends to conform to the internal line angles of the required preparation. Others are designed to remove caries with minimum vibration. Other designs are made suitable for removal of old amalgam restorations. A newly designed rotary cutting tool is also supplied to cut and shear off full coverage crowns.

New designs of rotary tools to perform certain functions

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Modern models of high and conventional speeds hand pieces are fabricated with a more advanced technology. The body is constructed from titanium alloy which prevents rust and provide light weight and stability and to withstand repeated autoclaving. An anti-retraction technology is also supplied to prevent regurgitation of fluids for infection control purposes. Moreover, the fiber-optic illumination supplied comes out from a compacted glass nozzle which does not hinder the age of light by repeated autoclaving. Ceramic ball bearings are also incorporated to prevent wear and damage of the internal rotating parts by the extensive use or repeated sterilization. The air/water spray coolant is designed in a triple way burst for effective control of the generated heat and clearance.

New model of titanium hand piece

Maintenance of the hand pieces is also given great attention since the performance of the hand piece affects the quality of work. It is becoming very simple to just fitting the hand piece in its place in the Assisstina machine to be effectively cleaned and then lubricated with the specified cleaner and lubricant.

Assistina machine for cleaning and lubrication of hand pieces

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The most recent outcome is the Neulite technology introduced by Bien Air in which a single fiber-optic module can be plugged with either a rotary high speed or conventional contra-angle hand piece, meanwhile, the same module can be plugged with a high efficiency light curing tip to be utilized for polymerization of various resin restoratives.

Neulite technology of plug and cure

Technology is still going on, the future perspectives in restorative dentistry is very promising. Thanks to the recent advancements which have introduced a true revolution in the field of restorative dentistry which has enabled the dental clinicians to perform better and to present high quality service for their patients.

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computerized

methods

of

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