Primate pulp response to an ultraviolet light cured restorative material

Abstract. The present toxicity study investigated the pulpal response of an experimental u.v. light cured composite product as a Class V restorative material. Seventy-eight Class V cavities were prepared on the buccofacial surfaces of cynomolgus monkeys using a high-speed, air-water spray cutting technique. The experimental product was compared to a self-curing composite resin and a zinc oxide and eugenol formula. The animals were sacrificed at 3, 14 and 60 days. All categories exhibited about the same minimal degree of pulpal response at the three-day post-operative interval. However, focal hemorrhage occurred in 80% of the u.v. light cured resin category. After 60 post-operative days, the u.v. cured resin specimens presented persistent or increasing responses as compared to the specimens treated with either a self-curing composite resin or zinc oxide and eugenol. Should this u.v. light cured resin be used as a restorative material such as employed in this study, a calcium hydroxide liner is suggested in order to minimize the pulpal responses observed 60 days post-operatively.     

Pulpal response to a new composite dental restorative material

Abstract. A new composite restorative material, Enamelite, has recently been introduced for the conservative treatment of cervical erosion and hypoplastic enamel surfaces. The pulpal response elided by the restorative material was investigated in teeth of the vervet monkey and compared to a modified zinc oxide-eugenol cement.
Buccal or labial Class V cavities were prepared in 128 teeth in six vervet monkeys. The teeth in contralateral segments were restored with the restorative and control materials, respectively. The experimental animals were killed at 4, 14 and 42 days.
The restorative and control materials exhibited about the same minimal degree of cellular displacement and inflammatory response at each of the three postoperative time intervals.
The percentage of specimens with reparative dentin increased progressively with time. At all three intervals the restorative material elicited a greater response than the control zinc oxide-eugenol cement.
The results suggest that the clinical application of the restorative material on cervical eroded or hypoplastic enamel surfaces without a protective lining is a safe procedure.     

Effects of flowable resin on bond strength and gap formation in Class I restorations.

OBJECTIVES: This study measured resin/dentin bond strengths and evaluated gap formation at the pulpal floor of occlusal composite restorations using a flowable resin as a liner with either bulk or incremental placement of the restorative composite. METHODS: Class I occlusal preparations were made in 16 extracted molars, and were randomly divided into two groups for restoration using either One-Step adhesive (OS, BISCO) and Renew composite (RW, BISCO) or OptiBond SOLO adhesive (SOLO, Kerr) and Herculite XRV composite (XRV, Kerr). A flowable resin [AEliteFlo (AE, BISCO) or Revolution (RV, Kerr)] was applied as a liner in half of the specimens of each group. The lined and unlined groups were restored with composite cured in bulk, or cured in 1.5 mm increments. After 24 h in water, the teeth were sectioned into 0.7-mm thick slabs and were examined with an optical microscope (400 x) to determine the presence of internal resin-dentin gaps. The gap-free specimens were trimmed and were subjected to microtensile bond strength testing. Specimens that contained gaps had Knoop hardness of the restorative material measured. RESULTS: All incrementally filled restorations were well adapted to the pulpal floor but nearly all bulk-cured specimens had gaps between the flowable and the hybrid composites. The use of a flowable resin increased the bond strength of OS, but not SOLO. SIGNIFICANCE: The incremental technique prevented gap formation regardless of the use of a flowable resin. In contrast, the use of a flowable composite did not guarantee gap-free restorations or improved bond strength of resin to dentin in bulk-filled restorations.     

The effect of flowable resin composite on microleakage in class V cavities

This in vitro study investigated the microleakage of flowable resin composite as a restorative material and as a liner (either light cured separately or co-cured with hybrid resin composite) in Class V cavities. A light-cured hybrid resin composite was used as a control. Twenty extracted human premolars were prepared with standardized Class V cavity outlines on the buccal and lingual surfaces. The occlusal margin of the cavities was on enamel and the gingival margin was on dentin. One bottle adhesive system (Single Bond) was used after etching enamel and dentin with 34.5% phosphoric acid for 15 seconds. The cavities were randomly divided into four groups of 10 each and restored according to the manufacturers' instructions: Group I-Hybrid resin composite (Z100); Group II-Flowable resin composite (Filtek Flow); Group III-Flowable resin composite (Filtek Flow)+Hybrid resin composite (Z100); light cured separately; Group IV-Flowable resin composite (Filtek Flow)+Hybrid resin composite (Z100); co-cured. The samples were thermocycled 200 times with a 30-second dwell time. They were then immersed in a 0.5% basic fuchsin solution for 24 hours, sectioned and analyzed by stereomicroscopy. The degree of dye penetration was recorded and analyzed with the Kruskal-Wallis and Mann-Whitney U tests. The results of this study indicate that there was no leakage at the occlusal margin for either restoration. Statistically significant differences were found among the groups at the gingival margin. No statistically significant difference was observed between the occlusal and gingival margins except in Group IV. The combination of flowable resin composite and hybrid composite light cured separately yielded the best result in this study. The most leakage was observed when this combination was co-cured. The resistance to microleakage of flowable resin composite as a restorative material is similar to that of hybrid resin composite.     

Pulpal response to chemically cured and experimental light-cured glass ionomer cavity liners

This investigation evaluated the effects of an experimental light-cured glass ionomer (LCGI) cavity liner and chemically cured Ketac-Bond glass ionomer restorative material on the pulpal tissues of monkeys. Class V cavities were prepared in 71 teeth of three adult Macaca mulatta monkeys at 7- and 35-day intervals. Ketac-Bond or LCGI cavity liners were placed in cavities with the smear layer intact (groups I and II) or with the smear layer removed (groups III and IV) and were restored with composite resin. Tissues were acquired, sectioned at 7 microns, stained for microscopic evaluation, or prepared for SEM evaluation. No statistically significant differences between materials existed at either time interval, regardless of smear layer presence. Histopathologic results demonstrated minimal pulpal reactions for groups I through IV. SEM analysis showed tenacious bonding of the LCGI material to prepared cavity walls, with absence of contraction gap formation. The results indicated excellent pulpal responses to both materials.     

Restorative pulpal and repair responses

BACKGROUND: Each year, about 90 million new restorations are placed in the United States and 200 million are replaced. Controversy surrounds the pulpal reactions and frequency of bacterial microleakage associated with common restorative materials. The authors investigated and compared pulpal reactions to different types of restorative materials. METHODS: Two hundred seventy-two teeth with standardized rectangular Class V unexposed cavities were restored with resin-based composite bonded to dentin; resin-based composite bonded to enamel; resin-modified glass ionomers, or RMGI; amalgam lined with zinc polycarboxylate, or ZnPC; amalgam lined with calcium hydroxide, or Ca(OH)2; or zinc oxide-eugenol, or ZnOE. Teeth were extracted for orthodontic reasons between 20 and 381 days later. The authors categorized pulpal responses according to standards set by the Federation Dentaire Internationale and the International Organization for Standardization. Bacteria were detected using Brown-Brenn-stained sections. Pulpal responses were evaluated using histomorphometric analysis and analysis of variance statistics. RESULTS: The results showed that RMGI was the best material for preventing bacterial microleakage, and resin-based composite bonded to enamel was the worst. In regard to minimizing pulpal inflammatory activity, ZnOE was the best material and resin-based composite bonded to enamel was the worst. In terms of maximizing odontoblast survival beneath deep cavity preparations, Ca(OH)2, was the best material and RMGI was the worst. CONCLUSIONS: The results show that bacterial microleakage, pulpal injury and repair responses varied widely with different restorative materials. CLINICAL IMPLICATIONS: The authors recommend that RMGI be used to restore teeth with cavities that are shallow to moderate in depth, with the floor of deep cavities being lined with Ca(OH)2 before the teeth are restored with RMGI.     

Pulpal reactions to surface-sealed silicate cement and composite resin restorations

abstract – The effect of surface sealing and presence of bacteria in connection with pulpal response to silicate cement and composite resin restorations was tested in monkey teeth. Surface-sealing of silicates reduced the pulpal reactions to this material, whereas no such effect was observed when composites were sealed. Bacteria regularly occurred on the cavity walls except underneath zinc oxide/eugenol (ZOE) fillings and when silicates were sealed with ZOE. The frequency of bacteria was higher in teeth with unacceptable pulpal responses (44 of 49) than in teeth with acceptable reactions (48 of 79).     

Pulpal response to a new visible light-cured composite restorative material: Fotofil®

Abstract A new visible light-cured composite resin, Fotofil®, has been developed for the esthetic restoration of anterior teeth. The pulpal responses elicited by this material in unlined cavities and cavities lined with Dycal® were compared with those elicited by a negative control consisting of modified zinc oxide-eugenol cement Nobetec® and a silicate cement Syntrex®. The pulpal responses were evaluated in the permanent maxillary and mandibular incisors in vervet monkeys using labial Class V cavities prepared in a total of 240 teeth. Two teeth were filled with each material in each monkey. Groups of 10 monkeys were killed at intervals of 2 days, and 2 and 8 weeks after restoration of the teeth. The most severe pulpal responses were elicited by the unlined Fotofil® and Syntrex® restorations at all three time intervals. The Dycal® lined Fotofil® restorations elicited a milder pulp response than the Nobetec ® at 2 days and 2 weeks. No pulpal response was elicited by the latter two materials at 8 weeks. These results clearly showed that Fotofil® and Syntrex® are irritant to the dental pulp up to 8 weeks. The placement of a Dycal® liner beneath Fotofil® restorations reduced the pulpal irritation elicited by this material to levels which were lower than those elicited by the Nobetec® control at 2 days and 2 weeks.     

The effect of cavity restoration variables on odontoblast cell numbers and dental repair

OBJECTIVES: Dentinal repair following cavity restoration is dependent on several parameters including the numbers of surviving odontoblasts. The purpose of this study was to examine the effects of cavity cutting and restoration treatments on post-operative odontoblast numbers. METHODS: 353 Standardised non-exposed rectangular Class V cavities, were cut into the buccal dentin of intact 1st or 2nd premolar teeth of 165 patients, aged between nine and 25 years of age. Composite cavity restorations with various etching treatments were compared with resin-modified glass ionomer cements, enamel bonding resins, as well as polycarboxylate, calcium hydroxide, and zinc oxide eugenol materials. Following tooth extraction (20-381 days) for orthodontic reasons, the area of the reactionary dentine and the area of the odontoblasts was measured histomorphometrically. RESULTS: Odontoblast numbers and dentine repair activity were found to be influenced more by cavity restoration variables, than the choice of cavity filling materials or patient factors. The most important cavity preparation variable was the cavity remaining dentine thickness (RDT); below 0.25mm the numbers of odontoblasts decreased by 23%, and minimal reactionary dentine repair was observed. CONCLUSIONS: Odontoblast injury increased as the cavity RDT decreased. In rank order of maintaining odontoblast numbers beneath restored cavities with a RDT below 0.5mm, and using calcium hydroxide for comparison; calcium hydroxide (100%), polycarboxylate (82.4%), zinc oxide eugenol (81.3%), composite (75.5%), enamel bonding resin (49.5%) and RMGIC (42.8%). The vitality and dentine repair capacity of the pulp is dependent on odontoblast survival. Variations in the extent of odontoblast injury caused during operative procedures, may be the major underlying reason for the success or failure of restorative treatments.     

The Histological Effects of Composite Resin Materials on the Pulps of Monkey Teeth

Abstract Pulpal response of three bis glycol methacrylate composite resins. Smile®, Simulate® and Experimental Composite #2 were tested on primary and permanent monkey teeth using zinc oxide eugenol (ZOE) and silicate as controls. All materials were placed in Class V cavity preparations in Rhesus monkey teeth and evaluated at 3 days and 5 and 8 weeks. The materials were randomly placed in anterior and posterior teeth utilizing 75 primary and 75 permanent teeth. Following perfusion the teeth were prepared by routine histological procedures. The 3 day response of the composite resins was moderate, characterized by disruption of the odontoblasts, vacuolization and a mild inflammatory response underlying the cavity. At 5 weeks the formation of reparative dentin and a decrease in the inflammatory response was similar for all resins observed. At 8 weeks a slight increase in reparative dentin and a continued decrease in inflammation was noted when compared to the 5 week responses. At all time intervals ZOE produced the least pulpal response while silicate produced the most severe response.     

Histopathologic evaluation of three ultraviolet-activated composite resins on monkey pulps.

The pulpal responses of three ultraviolet-activated composite resins, Nuva-Fil, Experimental UV No. 1 and Experimental UV No. 2, were tested on adult monkey teeth using silicate and zinc oxide eugenol (ZOE) as positive and negative controls. All materials were placed in Class V cavity preparations in Rhesus monkey teeth using approximately 48 anterior and 63 posterior teeth of both the maxillary and mandibular arches. A total of 111 teeth were utilized and all materials were evaluated at 3 days, 5 and 8 weeks. Following left ventricular perfusion, the teeth were prepared for microscopic evaluation using routine histological procedures. The 3-day pulpal response of all the ultraviolet-activated composites was slight with some disruption and vacuolization in the odontoblastic layer and a slight inflammatory response. At 5 weeks there was a reduction of the inflammatory response and the formation of reparative dentin was noted for all ultraviolet composites. The 8-week pulp response was slight, characterized by a minimal inflammatory response adjacent to the zone of reparative dentin. Generally, ZOE produced the mildest response while silicate produced the most severe response at the three time intervals.     

Histopathologic Evaluation of three Ultraviolet-Activated Composite Resins on Monkey pulps

The pulpal responses of three ultraviolet-activated composite resins, Nuva-Fil®, Experimental UV #1® and Experimental UV #2®, were tested on adult monkey teeth using silicate and zinc oxide eugenol (ZOE) as positive and negative controls. All materials were placed in Class V cavity preparations in Rhesus monkey teeth using approximately 48 anterior and 63 posterior teeth of both the maxillary and mandibular arches. A total of 111 teeth were utilized and all materials were evaluated at 3 days, 5 and 8 weeks. Following left ventricular perfusion, the teeth were prepared for microscopic evaluation using routine histological procedures. The 3-day pulpal response of all the ultraviolet-activated composites was slight with some disruption and vacuolization in the odontoblastic layer and a slight inflammatory response. At 5 weeks there was a reduction of the inflammatory response and the formation of reparative dentin was noted for all ultraviolet composites. The 8-week pulp response was slight, characterized by a minimal inflammatory response adjacent to the zone of reparative dentin. Generally, ZOE produced the mildest response while silicate produced the most severe response at the three time intervals.     

Pulpal response to a newly developed MMA based resin cement for bonding tooth-colored indirect restorations

PURPOSE: To evaluate the pulpal responses to a newly-developed MMA-based self-etch resin cement, when used as a luting agent for indirect resin composite restoration, and to compare the results with those obtained from a total-etch luting agent, glass-ionomer cement, and amalgam restoration. METHODS: 120 cervical cavities were prepared in monkey teeth and divided into four equal groups according to the restorative materials used: (1) the cavities were restored with resin composite inlays using a self-etch resin cement as a luting agent (M-Bond); (2) the cavities were also restored with resin composite inlays but using a total-etch resin cement as a luting agent (Super-Bond C & B); (3) the cavities were directly restored with glass-ionomer cement (Fuji II); or (4) the cavities were directly restored with amalgam (Dispersalloy). The restored teeth were extracted at 3, 30, or 90 days after restoration, then fixed in 10% neutral buffered formalin. The specimens were prepared using routine histopathological procedures. Five microm-thick sections were stained with hematoxylin and eosin or Brown & Brenn gram stain for bacterial observations. Histological responses in the pulpal tissue and bacterial penetration were observed under a light microscope and evaluated using standard scores. The results were statistically analyzed using the Kruskal-Wallis test (P< 0.05). RESULTS: At all time intervals, no significant differences of pulpal inflammatory responses between M-Bond and Super-Bond C&B were observed (P> 0.05). Both resin cements showed no serious pulpal responses, such as necrosis or abscess formation. In general, both MMA-based resin cements showed similar pulpal responses to those of glass-ionomer cement except for congestion of pulpal blood vessels at 3 days after restoration in which glass-ionomer cement exhibited a lower level than that of the MMA-based resin cements. For the group restored with amalgam, at 3 days after restoration, severe odontoblastic disorders and blood vessel congestions with a large infiltration of inflammatory cells were detected. At 30 and 90 days after restoration, slightly inflammatory irritations were observed irrespective of the materials used. Reparative dentin formation and bacterial penetration were found mostly in the group restored with amalgam.     

Pulpal effects of glass ionomer cements

Summary. The incidence of pulpal damage beneath cavities filled with ASPA, Chemfil and Chembond was studied in class I cavities in human premolar teeth after 1–10 days, 11–30 days, and 31 or more days. Cavities filled with Kalzinol or zinc oxide/eugenol acted as controls. All glass ionomer cements were accompanied by more pulpal damage than controls, but Chemfil was associated with the least changes. Bacteria were demonstrated at the material/cavity wall interface in a number of cavities with all materials, although no significant correlation was demonstrated between them and pulpal inflammation. The use of a base is recommended in cavities where large numbers of previously unaffected dentinal tubules are present.     

The effects on the dental pulp of a composite resin and two dentine bonding agents and associated bacterial microleakage

The pulpal reaction associated with a composite resin alone and composite resin used in conjunction with two dentine bonding agents was studied. Class V cavities were prepared on the labial surfaces of the canine teeth of 18 male ferrets. After acid etching of the enamel margins, the cavities were restored with either a composite resin alone or in combination with one of two dentine bonding agents, Scotchbond and Gluma. One cavity in each animal was filled with Kalzinol as a control. The animals were killed after 7, 14 and 28 days. After histological processing, the pulpal changes were assessed qualitatively and quantitatively according to standard criteria. There were variations in the pulpal response at all time intervals. The responses to the two dentine bonding agents were similar to those found with composite resin alone. No pulpal inflammation was observed in the control teeth. Gram-positive micro-organisms were identified at the interface of restoration and cavity wall, or within the dentinal tubules in virtually all cases in which pulpal inflammation was observed.     

Restorations of eroded areas

Class V erosion lesions must be restored to reinstate esthetic appearance, overcome sensitivity, or prevent further loss of tooth structure. Restoration has been a problem, but, with the advent of adhesive techniques, it is far less traumatic. The most widely advocated method currently uses composite resin as the primary restorative material with dentin bonding agents. Type III glass ionomer lining cements are also suggested to provide bonding to the dentin. This paper details the requirements for clinical success in the restoration of the Class V erosion lesion using Type II restorative esthetic glass ionomer cements as the primary restorative material with the possible addition of composite resin as a final veneer only if circumstances warrant it.     

新型自固化树脂充填Ⅴ类洞的表面边缘和内部界面适合性初探

目的探讨新型自固化树脂充填Ⅴ类洞后充填体的表面边缘和内部界面适合性。方法选用因正畸需要拔除的无龋人上颌前磨牙56颗(首都医科大学口腔医学院口腔颌面外科提供),制备Ⅴ类洞,分为2组(每组28颗)。实验组用预处理剂(Tooth primer)和新型自固化树脂(Bondfill SB)充填,对照组用自酸蚀粘接剂(Scotchbond Universal)和光固化复合树脂(Z100)充填。充填后样本牙进行疲劳实验:机械循环加载(49 N、1 Hz频率120万次)和冷热循环加载(5和55℃的水中分别浸泡1 min,共3000次),模拟口腔环境的咀嚼负荷和温度变化。疲劳实验前后样本牙浸入50%氨化硝酸银溶液并还原银离子。用扫描电镜检测分析充填体表面完整边缘百分率和内部界面银沉淀物长度。用透射电镜观察牙本质界面超微结构。结果扫描电镜显示,疲劳实验前实验组牙本质表面边缘间隙较对照组小。疲劳实验前对照组牙釉质界面银沉淀物长度[(0.67±0.15)μm]显著小于实验组[(33.54±10.27)μm](P<0.05)。疲劳实验后对照组牙釉质表面完整边缘百分率[(55.08±15.20)%]显著大于实验组[(25.15±12.47)%](P<0.05)。疲劳实验后实验组充填体表面和内部更易观察到内聚破坏。透射电镜显示,疲劳实验前对照组牙本质界面比实验组有更多的银沉淀物;疲劳实验后对照组牙本质界面破坏主要发生于混合层下方;实验组牙本质界面破坏主要发生于混合层下方和充填体内部。结论充填Ⅴ类洞时本项研究所用光固化复合树脂在牙釉质界面有较好的表面边缘和内部界面适合性,而新型自固化复合树脂在牙本质界面有良好的表面边缘和内部界面适合性。     

Polymerization Contraction Stress of Resin Composite Restorations in a Model Class I Cavity Configuration Using Photoelastic Analysis

Purpose: An important factor that contributes to deterioration of resin composite restorations is contraction stress that occurs during polymerization. The purpose of this article is to familiarize the clinician with the characteristics of contraction stress by visualizing the stresses associated with this invisible and complex phenomenon. Materials and Methods: Internal residual stresses generated during polymerization of resin composite restorations were determined using micro‐photoelastic analysis. Butt‐joint preparations simulating Class I restorations (2.0 mm ± 5.0 mm, 2.0 mm in depth) were prepared in three types of substrates (bovine teeth, posterior composite resin, and transparent composite resin) and were used to examine contraction stress in and around the preparations. Three types of composite materials (a posterior composite, a self‐cured transparent composite, and a light‐cured transparent composite) were used as the restorative materials. The self‐cured composite is an experimental material, and the others are commercial products. After treatment of the preparation walls with a bonding system, the preparations were bulk‐filled with composite. Specimens for photo‐elastic analysis, were prepared by cutting sections perpendicular to the long axis of the preparation. Fringe patterns for directions and magnitudes of stresses were obtained using transmitted and reflected polarized light with polarizing microscopes. Then, the photoelastic analysis was performed to examine stresses in and around the preparations. Results: When cavity preparations in bovine teeth were filled with light‐cured composite, a gap was formed between the dentinal wall and the composite restorative material, resulting in very low stress within the restoration. When cavity preparations in the posterior composite models were filled with either self‐cured or light‐cured composite, the stress distribution in the two composites was similar, but the magnitude of the stress was greater in the light‐cured material. When preparations in the transparent composite models were filled with posterior composite and light‐cured transparent composite material, significant stress was generated in the preparation models simulating tooth structure, owing to the contraction of both restorative materials. CLINICAL SIGNIFICANCE Polymerization contraction stress is an undesirable and inevitable characteristic of adhesive restorations encountered in clinical dentistry that may compromise restoration success. Clinicians must understand the concept of polymerization contraction stress and realize that the quality of composite resin restorations depends on successful management of these stresses.     

Pulpal response to an experimental adhesion promoter

Abstract The pulpal response to an experimental adhesion promoter (FTP) used in conjunction with a composite resin material, Biogloss, is described, in lined and unlined cavities. Dycal was the lining and negative control material. Standardised Class V cavities were prepared in ferret canine teeth and the pulpal responses studied after 1, 2 and 4 weeks and 6 months post-operatively. Pre-treatment of cavities with FTP causes a reduction in pulpal inflammation at 7 and 14 days compared with Biogloss. There was no obvious difference at the longer time intervals. Pre-treatment with FTP delays the ingress of microorganisms at the cavity wall/material interface but does not prevent it in the long term in this situation. The effect of FTP is not altered if the fluid is allowed to dry naturally rather than by blow drying.     

Curing units' ability to cure restorative composites and dual-cured composite cements under composite overlay

This study compared the efficacy of using conventional low-power density QTH (LQTH) units, high-power density QTH (HQTH) units, argon (Ar) laser and Plasma arc curing (PAC) units for curing dual-cured resin cements and restorative resin composites under a pre-cured resin composite overlay. The microhardness of the two types of restorative resins (Z100 and Tetric Ceram) and a dual-cured resin cement (Variolink II) were measured after they were light cured for 60 seconds in a 2 mm Teflon mold. The recorded microhardness was determined to be the optimum microhard-ness (OM). Either one of the two types of restorative resins (Z100, Tetric Ceram) or the dual cured resin cement (Variolink II) were placed under a 1.5-mm thick and 8 mm diameter pre-cured Targis (Vivadent/Ivoclar AG, Schaan, Liechtenstein) overlay. The specimens that were prepared for each material were divided into four groups depending upon the curing units used (HQTH, PAC, Laser or LQTH) and were further subdi-vided into subgroups according to light curing time. The curing times used were 30, 60, 90 and 120 seconds for HQTH; 12, 24, 36 and 48 seconds for the PAC unit; 15, 30, 45 and 60 for the Laser and 60, 120 or 180 seconds for the LQTH unit. Fifteen specimens were assigned to each sub- group. The microhardness of the upper and and lower composite surfaces under the Targis overlay were measured using an Optidur Vickers hardness-measuring instrument (G?ttfert Feinwerktechnik GmbH, Buchen, Germany). In each material, for each group, a three-way ANOVA with Tukey was used at the 0.05 level of significance to compare the microhardnesses of the upper and lower composite surfaces and the previously measured OM of the material. From the OM of each material, 80% OM was calculated and the time required for the microhardness of the upper and lower surface of the specimen to reach 100% and 80% of OM was determined. In Z100 and Tetric Ceram, when the composites were light cured for 120 seconds using the HQTH lamp, microhardnesses of the upper and lower surfaces reached OM. When they were cured with the PAC unit, only 48 seconds was needed for the upper and lower surfaces to reach OM. When they were cured using the laser, the lower surface did not reach OM in any of the groups. When the specimens were cured using the LQTH lamp, 180 seconds of curing was needed for Z100 to reach OM, whereas Tetric Ceram did not reach OM. In Z100, 60, 12, 30 and 60 seconds were needed in HQTH, PAC, Laser and LQTH, respectively, for the specimens to reach 80% OM. Tetric Ceram was needed 60,24,45 and 180 seconds to reach 80% OM. In the Variolink II specimen, microhardness of the upper and lower surfaces did not reach OM even though they were light cured with the HQTH lamp for 120 seconds. When they were cured with the PAC unit, 48 seconds was insufficient for them to reach OM. When they were cured with laser for 45 and 60 seconds, microhardness reached OM on the upper surface but not on the lower surface. However, when they were cured using the LQTH lamp, microhardness did not reach OM on the upper and lower surfaces even though the curing time was extended to three minutes. In Variolink II, 120, 36, 45 and >180 seconds were needed in HQTH, PAC, Laser and LQTH, respectively, for the specimens to reach 80% OM. In conclusion, the PAC system is the most effective curing system to cure the restorative composite and dual cured resin cement under the 1.5 mm Targis overlay, followed by the laser, HQTH and LQTH units. In addition, the restorative composites cured more efficiently than the dual-cured resin cements.