F.J.M. Roeters

Comparison of Proximal Contacts of Class II Resin Composite Restorations In Vitro

This study investigated the tightness of the proximal contact when placing posterior resin composite restorations with circumferential and sectional matrix systems in an in vitro model using a special measuring device (Tooth Pressure Meter). A manikin model was used with an artificial first molar in which an MO-preparation was ground, simulating the clinical situation of an amalgam replacement. This preparation was duplicated, resulting in 160 identically prepared teeth. These teeth were divided into 8 groups (n=20). In 2 groups, circumferential matrix bands (flat or contoured) in a Tofflemire retainer were applied. In the remaining 6 groups, 3 different separation rings were combined with 2 types of sectional matrix bands. All the cavities were restored using Clearfil Photo Bond and Clearfil AP-X. The tightness of the proximal contact was measured using the Tooth Pressure Meter. Data were statistically analyzed using SPSS 12. ANOVA was used to find differences in proximal contact tightness between the groups. Tukey tests were used to find differences between the homogeneous subgroups. The use of sectional matrices combined with separation rings resulted in tighter proximal contacts compared to when circumferential systems were used (p<0.001). The use of these devices is therefore recommended when posterior resin composite restorations are placed.

Surface roughness of etched composite resin in light of composite repair

OBJECTIVES In search for clinically effective composite repair protocols, the effect of various etching protocols on the surface roughness of composite resins with different filler composition were investigated. METHODS Of two composite resins (hybrid-filled Clearfil AP-X; nano-filled Filtek Supreme XT) specimens of 3mm thick with a diameter of 7 mm were prepared (n=24). The top surface was polished with 4000-grit SiC-abrasive paper and subjected to one of eight surface treatments: (n=3): negative control (NC), 37% phosphoric acid for 20s (37PA-20s), 3% hydrofluoric acid for 20s (3HF-20s), for 120 s (3HF-120 s), 9.6% hydrofluoric acid for 20s (9.6HF-20s), for 120 s (9.6%HF-120 s), 37PA-20s followed by 9.6%HF for 120 s (37PA-20s/9.6HF-120 s) and 9.6%HF for 120 s followed by 37PA-20s (9.6HF-120s/37PA-20s). Roughness (S(a)) was measured using a 3D noncontact optical interferometer (WYKO) and surface topography imaged by SEM. Multilevel models were used to estimate the variances within a sample and between samples in each group. Using the resulting overall variances and the means for each group, the eight groups were compared consecutively using t-tests (p<0.05). RESULTS The hybrid-filled composite resin demonstrated a significantly rougher surface than the nano-filled (p<0.05). For both composites 9.6%HF-120 s, 37PA-20s/9.6HF-120 s and 9.6%HF-120 s/37PA-20s resulted in a large increase in roughness compared to the other groups (p<0.05). For the hybrid-filled, the succeeding groups (37PA-20s, 3HF-20s, 3HF-120 s and 9.6HF-20s) resulted in a statistically significant increase in surface roughness (p<0.02). For the nano-filled only a statistically significant increase in roughness was found between 3HF-20s and 3HF-120 s (p<0.001) and between 9.6HF-20s and 9.6HF-120 s (p<0.001). SEM surface characterization revealed that the hybrid-filled composite resin was much more affected by etching than the nano-filled. SIGNIFICANCE Composite resins should not be seen as a group of materials having identical properties when it comes to repair. The effect of etching will depend on the composition of the filler particles.

The effect of proximal contour on marginal ridge fracture of Class II composite resin restorations

OBJECTIVES To compare the marginal ridge fracture strength of Class II composite resin restorations placed with a straight or contoured matrix band using composite resins with different modulus of elasticity. METHODS In 60 artificial first molars standardized MO-preparations were ground. Two matrix systems were used: (1) A straight matrix (Standard Tofflemire Matrix, KerrHawe) in Tofflemire retainer (Produits Dentaire). (2) A contoured matrix (Standard matrix, Palodent, Dentsply). In both groups, a wooden wedge and separation ring (Composi-Tight Gold, GDS) were placed and the matrix was burnished against the adjacent tooth. Three composite resins together were used (Filtek Supreme: e-modulus 13.3 GPa (3M ESPE), Clearfil AP-X: 16.6 GPa (Kuraray) and Clearfil Majesty Posterior: 22.0 GPa (Kuraray)), resulting in six groups (n=10). Teeth were mounted into a MTS servo hydraulic testing machine (Mini Bionix II, MTS, USA) with stylus placed on the marginal ridge. Samples were loaded at a crosshead speed of 1.0mm/min until fracture occurred. Fracture resistance data were statistically analyzed using ANOVA and Scheffés post hoc test for multiple comparison of groups (p<0.05). RESULTS Contoured proximal surfaces (365.5+/-87.6N) resulted in significant stronger marginal ridges compared to straight surfaces (290.5+/-64.2N) (p<0.001). Clearfil AP-X (378.1+/-94.63N) provided a higher resistance to fracture than Filtek Supreme (301.4+/-67.3N) (p=0.001) and Clearfil Majesty Posterior (304.5+/-70.6N) (p=0.002). No differences were found between Filtek Supreme and Clearfil Majesty Posterior (p=0.890). CONCLUSION Within the limitations of this in vitro study it was shown that use of a contoured matrix results in a stronger marginal ridge of a Class II composite resin restoration.

Restoration techniques and marginal overhang in Class II composite resin restorations

OBJECTIVES The objective of the study was to compare in vitro interproximal overhang formation of Class II composite resin restoration when using different matrix systems. METHODS 240 lower left molar phantom head teeth with an MO-preparation were divided into 12 groups (n=20). In six groups a circumferential matrix (Tofflemire X-thin matrix, HaweNeos 1001-c, SuperCap) was used, combined with either a hand-instrument (PFI49 or OptraContact) or separation ring (Composi-Tight Gold). In the other six groups two sectional matrix systems were used (flexible and dead-soft), with three separation rings (Composi-Tight Gold, Contact Matrix, Palodent BiTine). Matrices were secured with wooden wedges and preparations were restored with composite resin Clearfil AP-X (Kuraray) placed and polymerized in increments. After matrix removal overhang was measured on a standardized digital macroscopic image in mm(2). For analysis a multiple linear regression model was used. RESULTS Use of circumferential matrices resulted in less overhang than sectional matrices (-0.85 mm2, p<0.001). A flexible matrix led to less overhang than dead-soft matrices (-0.54mm2, p<0.001), and no difference was found between straight and pre-contoured matrices (p=0.945). The insertion of the OptraContact resulted in a much increased overhang of 2.54 mm2 (p<0.001). The Composi-Tight Gold and the Contact Matrix System rings resulted in less overhang, -0.69 and -0.68 mm(2), respectively (both p<0.001), whereas the Palodent BiTine ring did not. CONCLUSIONS Use of circumferential matrices or sectional flexible matrices resulted in the least marginal overhang when combined with a Contact Matrix separation ring or a Composi-Tight Gold ring.

Hydrofluoric acid on dentin should be avoided.

UNLABELLED Hydrofluoric acid can be used for intra-oral repair of restorations. Contamination of tooth substrate with hydrofluoric acid cannot always be avoided. OBJECTIVES To investigate the bonding effectiveness to hydrofluoric acid contaminated dentin by, micro-tensile bond strength testing, SEM and TEM. METHODS For this study, 15 molar teeth were used of which dentin surfaces were subjected to five, different etching procedures. Group A, 37.5% phosphoric acid (Kerr Gel) (control group); group B, 37.5% phosphoric acid followed by 3% hydrofluoric acid (DenMat); group C, 37.5% phosphoric acid, followed by 9.6% hydrofluoric acid (Pulpdent); group D, 3% hydrofluoric acid followed by 37.5%, phosphoric acid; group E, 9.6% hydrofluoric acid followed by 37.5% phosphoric acid. After the bonding procedure (OptiBond FL, Kerr) a composite resin build-up (Clearfil AP-X, Kuraray), was made. After 1 week storage, specimens were prepared for micro-tensile bond testing, SEM- and, TEM-analysis. Data were analyzed using ANOVA and post hoc Tukeys HSD (p<0.05). RESULTS In the control group (solely phosphoric acid), the mean microTBS was 53.4+/-10.6 MPa, which was, significantly higher than any hydrofluoric acid prepared group (group A versus groups B-E, p<0.001). No, significant differences in microTBS were found between the 3% and 9.6% hydrofluoric acid groups: group B versus group C (13.5+/-5.5 MPa and 18.7+/-4.3 MPa, respectively) or group D versus group E (19.9+/-6.8 MPa and 20.3+/-4.1 MPa, respectively). SIGNIFICANCE Due to its adverse effect on the bond strength of composite to dentin, contact of hydrofluoric acid to dentin should be avoided.

A Clinical Study on Interdental Separation Techniques

The effect of interdental separation of a special separation ring and wooden wedge was investigated. In a split-mouth design, 27 patients were randomly assigned to one of two groups (W or S). In 11 patients, an interdental wooden wedge (Hawe-Neos) was placed (group W), and in 16 patients, a separation ring (Composi-Tight Gold) was placed at the contact between teeth 4/5 and 5/6. Simultaneously, in both groups, a wooden wedge, combined with a separation ring (Composi-Tight Gold), was placed on the contact between teeth 4/5 and 5/6 (reference group W+S). To measure proximal contact tightness, frictional forces were recorded at the removal of a 0.05 mm thick metal matrix band inserted between adjacent teeth. Contact tightness was measured at contacts 4 and 5 and at 5 and 6 in the third and fourth quadrant using the Tooth Pressure Meter prior to applying separation devices (TO) five minutes after application (T1) and five minutes after removal of the devices (T2). The effect of separation was determined by calculating the differences between contact tightness before application and contact tightness with the devices in situ (T1-T0). Interdental recovery was calculated by the difference in contact tightness before application and after removal of the devices (T2-T0). To assess the presence of statistically significant differences between these measurement times, paired t-tests were applied. With each patient, either a comparison between W and W+S or S and W+S was made. For both W versus W+S and S versus W+S, paired t-tests were applied to compare differences (T1-T0 and T2-T0) between the separation devices. Within a patient, groups W and S could not be compared, therefore, to compare separation achieved between these two devices, unpaired t-tests were used. The increase in contact tightness measured at contact 4 and 5 for group W (0.98 +/- 0.26 N) was statistically significantly less compared to the increase in group S (5.48 +/- 0.88 N) (p < 0.001) or group W+S (4.62 +/- 0.68 N) (p = 0.02). No significant differences were found between groups S and W+S (p = 0.77). For all groups, five minutes after removal of the devices, the contact tightness at contact 4 and 5 and at contact 5 and 6 were still significantly weaker compared to the tightness at baseline (p < 0.02). When separation is required for restorative procedures, such as at placement of a Class II resin composite restoration, special separation rings may be more useful than wooden wedges.

Proximal marginal overhang of composite restorations in relation to placement technique of separation rings.

The aim was to investigate in vitro the marginal overhang in Class II composite restorations placed with various separation rings and placement techniques. A total of 180 Mesial-Occlusal [MO] preparations in artificial molar teeth were divided into nine groups (n=20). After placement of the sectional matrix, one of three ring systems was applied: Contact Matrix System (Danville Materials), Composi-Tight Gold (Garrison), and V-Ring (Triodent). In each group, rings were placed according to four different techniques (V-Ring placed with technique no. 2 only): 1) occlusally of the wedge, 2) on back end of the wedge, 3) between adjacent tooth and wedge, and 4) between treated tooth and wedge.After application of the adhesive resin, preparations were restored with composite Clearfil AP-X (Kuraray) and polymerized in increments. After matrix removal, overhang was measured on a standardized digital macroscopic image in millimeters squared. For analysis, analysis of variance and Tukey B were used (p<0.05).For the Contact Matrix System and Composi-Tight Gold ring, the different placement techniques had a statistically significant effect on the amount of marginal overhang (p<0.031). The V-Ring resulted in the least marginal overhang (p<0.001).None of the placement techniques and separation rings could completely prevent marginal overhang, and the placement technique has a significant influence on its occurrence.