A temporary filling material may cause cusp deflection, infractions and fractures in endodontically treated teeth.

AIM: To test the hypothesis that Coltosol F might cause infractions and cusp fracture in root-filled teeth because of material expansion. METHODOLOGY: Thirty-two extracted human molar teeth were root filled and prepared with mesial-occlusal-distal (MOD) cavities with or without undercuts. The specimens were filled proximally with glass-ionomer cement and then occlusally with either Coltosol F or zinc oxide eugenol (ZOE). The tooth specimens were kept in water at 37 degrees C for a period of 20 days, and every second day the intercusp distance (ICD) of each specimen was measured in a travelling microscope, and the number of infraction lines as well as fractures were noted. RESULTS: The number of infraction lines increased in teeth filled with Coltosol F. Between day 8 and 16, seven of 16 teeth filled with Coltosol F showed fracture and exhibited a mean increase in ICD of 316 +/- 156 microm. Teeth filled with ZOE did not show an increase in number of infraction lines or in ICD, and none showed fracture. CONCLUSIONS: The hygroscopic expansion of Coltosol F in a cavity may lead to cusp deflection, infraction development and fracture. Masticatory forces will in vivo aggravate this unfavourable condition. The material is not recommended for temporary filling in root-filled teeth except for a few days.

A prospective, randomized, comparative clinical study of resin composite and glass ionomer cement for retrograde root filling.

OBJECTIVE: To compare the clinical and radiographic treatment outcome of retrograde root filling with either dentin-bonded resin composite (Retroplast, RP) or glass ionomer cement (Chelon-Silver, CS). STUDY DESIGN: A prospective, randomized clinical study of 134 consecutive patients with indication of retrograde root filling of an incisor, canine, premolar, or first molar. Either RP or CS was chosen at random as retrograde filling material. Either material was applied onto the entire resection surface after prepared slightly concave. This preparation technique makes a sealing of the entire resection surface possible and prevents marginal contraction gaps during polymerization. A total of 122 patients were available for 1-year follow-up. RESULTS: After 1 year the proportion of successful cases was significantly higher in the RP group (73%) than in the CS group (31%) (p<0.001). Doubtful healing with a need for a longer observation period was seen in 17% of the RP cases and 19% of the CS cases. The proportion of failures in the RP group (10%) was significantly lower than that in the CS group (50%) (p<0.001). Most of the unsuccessful CS cases failed due to loosening of the retrograde filling. CONCLUSIONS: Dentin-bonded RP applied onto the entire, slightly concave resection surface is a predictable apical sealant characterized by a high success rate. In contrast, retrograde root filling with CS results in an unacceptably high failure rate due to insufficient bonding strength to the concave resection surface.

Periapical healing of mandibular molars after root-end sealing with dentine-bonded composite.

AIM: The purpose was to present the frequency of periapical healing in first and second/third mandibular molars, after root-end resections sealed with a dentine-bonded resin composite. METHODOLOGY: Root-end sealing of resected mandibular molar roots was made with dentine-bonded composite (Gluma-Retroplast) as a cover on the entire slightly hollowed root-end, in an attempt to prevent leakage. RESULTS: Out of the 834 roots recalled between 6 months and 12.5 years postoperatively, 92% showed complete apical healing, 1% uncertain healing and 7% exhibited failure. The healing result of 681 first molar roots was not significantly different (P = 0.21) from that of 153 second/third molar roots, and there was no significant difference in healing between mesial and distal roots (P = 0.32 for first molars, P = 0.86 for second/third molars) or amongst six age groups (P = 0.94). In the patient group: 71-89 years, 36 roots showed an average of 97% with complete healing. Out of 25 failures who were retreated surgically, 80% showed complete healing when examined subsequently. CONCLUSION: Root-end sealing of mandibular molars with dentine-bonded resin composite is a promising technique giving 92% complete healing in cases examined between 6 months and 12 years postoperatively.

Elution of TEGDMA and BisGMA from a resin and a resin composite cured with halogen or plasma light.

Plasma arc light units for curing resin composites have been introduced with the claim of relatively short curing times. The purpose of the present study was to measure and compare elution of monomers from an experimental BisGMA-TEGDMA resin and a commercial resin composite when cured with a halogen unit and when cured with a plasma arc unit. Specimens of the materials were immersed in methanol, and the amounts of monomers released with time were analyzed by HPLC. By use of Fick's laws of diffusion, the amount of eluted monomers from the specimen at infinity was estimated. The elution from resin specimens and from resin composite specimens cured with the plasma arc light unit was 7 and 4 times higher, respectively, compared to the elution from specimens cured with the halogen unit. It was concluded that the plasma arc light curing unit did not provide optimal cure when used as recommended by the manufacturer.

Permeability of protective gloves by HEMA and TEGDMA in the presence of solvents.

The breakthrough times and permeation rates of two commonly used allergenic components in dentin bonding agents or resins, HEMA and TEGDMA, were measured for 5 types of latex gloves and 5 types of nitrile gloves. In addition, the breakthrough times and permeation rates for the gloves were measured for HEMA and TEGDMA when diluted with either ethanol or acetone-solvents often appearing in dentin bonding agents. The mean breakthrough times for the 5 latex gloves for HEMA and TEGDMA, concentrated, diluted in ethanol, or diluted in acetone, were 4.9, 4.8, and 2.8 min, respectively. For the 5 nitrile gloves the equivalent breakthrough times were 15.7, 9.9, and 2.8 min, respectively. There were great variations between the various gloves, and 1 nitrile glove showed a breakthrough time of 28-30 min when tested with concentrated HEMA and TEGDMA. Compared to latex gloves, nitrile gloves have a longer-lasting protection against skin contamination with methacrylates in the absence of solvents. The longer protection was reduced or not present for methacrylates diluted in organic solvents, especially acetone. In addition, the nitrile gloves showed fairly high permeation rates in the presence of this solvent. The results indicate that latex and nitrile gloves only give a limited protection against allergenic methacrylates in dentin bonding agents when they contain acetone.

Impact strength of teeth restored by fragment-bonding.

The objective of this in vitro study was to investigate the impact strength of anterior teeth that have been fractured and restored by bonding with a dentin-bonding agent and a composite resin. Twenty sheep central incisors were divided into two groups, 10 in each. One group (intact teeth) served as the control and the teeth in the other group were fractured and then bonded with a bonding agent and a low-viscous composite resin. The specimens were tested in a modified impact-testing machine (pendulum type). The mean impact strength of the intact teeth was 30.6 +/- 2.16 KJ/m2 and of the bonded teeth was 30.2 +/- 1.86 KJ/m2. Statistics revealed that the two means were not significantly different. The results related well with the fracture strength obtained by loading intact and bonded teeth at constant but low speed until fracture. It was concluded that bonding fragments to the remaining tooth structure may restore the tooth to its original strength, measured at modest velocities of the applied force. In other words, reattaching the original coronal fragment of traumatised fractured anterior teeth restored with One-Step dentin bonding system and AEliteflo composite resin would withstand a second trauma to the same extent as intact teeth.

Fracture strength of fragment-bonded teeth. Effect of calcium hydroxide lining before bonding.

PURPOSE: To measure, in vitro the strength of intact teeth, fracture-bonded teeth, and fracture-bonded teeth bonded after a preliminary calcium hydroxide lining of the dentin part of the remaining tooth. MATERIALS AND METHODS: The study used 30 young, similarly aged sheep incisors. Twenty incisors were fractured 2.5 mm from the incisal edge and another 10 incisors remained non-fractured and served as control (Group 1). Group 2 comprised 10 fractured incisors, which after 3 weeks water storage were bonded by use of acid etching and a dentin bonding agent. In Group 3, the root part of 10 fractured incisors were lined with calcium hydroxide and kept in water for 3 weeks. Then the lining was removed with a hand instrument before bonding as above. The strength of the teeth in Groups 1-3 was measured and the mean fracture strengths representing the three groups were compared by Newman-Keuls' multiple range tests at a 5% level of significance. RESULTS: The mean fracture strength of the lined teeth (9.6 MPa) was significantly different from that of intact teeth (17.8 MPa) as well as from that of the bonded but unlined teeth (15.8 MPa). The latter two means were not significantly different. It is concluded that the use of calcium hydroxide on the fracture surfaces of fractured teeth before bonding lowers the fracture strength of the restored teeth.

Drying and rewetting anterior crown fragments prior to bonding.

Fractured anterior teeth can be restored by adhesive bonding of the fragment to the remaining tooth structure. This in vitro study describes the effect on fracture strength of fragments dried and rewetted for various periods of time prior to bonding. Seventy central incisors from sheep were fractured. The resulting incisal crown fragments were then stored in air at room temperature at ambient humidity (70 +/- 16%) for 5 s, 30 min, 1 h, 3 h, 6 h, 12 h, or 24 h. The apical parts of the fractured teeth were stored in water. After storage in air each fragment was then bonded to the matching apical tooth structure with a bonding agent and a low-viscosity composite resin. After water storage for 2 days, mean fracture strength was measured. Another group of teeth comprising 40 sheep central incisors was fractured and the fragments were stored in air at room temperature for 24 h as above. The fragments were then immersed in water for 10 min, 1 h, 1 day, or 7 days, prior to bonding and measurement as described above. Statistical analysis revealed that the fracture strength of the fragment-bonded teeth was unaffected by air storage of the fragment for up to 1 h prior to bonding, after which additional drying resulted in decreased fracture strength. Fragments dried for 24 h in air and rewetted by immersion in water for at least 1 day were fragment-bonded without loss of fracture strength.

Fracture strength of intact and fragment-bonded teeth at various velocities of the applied force.

Bonding of a tooth fragment to the remaining tooth substance can restore crown fracture of an anterior tooth. In this study, sheep central incisors were used. The crowns were fractured transversely and the crown fragment was bonded to the remaining tooth structure. This technique involves acid etching, use of an experimental adhesive (Gluma+) and a BisGMA/TEGDMA resin. The mean fracture strength of the restored teeth was not significantly different from that of intact teeth when tested at a rather low crosshead speed (0.5 mm/min) but different and about 30% lower when tested at a higher crosshead speed (500 mm/min). In studies aiming to test resistance to forces which might cause trauma, it might be appropriate to use a high crosshead speed.

Adhesive bonding of fragmented anterior teeth.

This in vitro study investigated the fracture strengths of fractured incisors after reattachment to the remaining tooth structure, using either Gluma dentin-bonding agent together with 1 of 13 different experimental resins or 1 of the following dentin-bonding agents: Gluma+ (experimental modification of Gluma), Panavia21, ScotchBond1 (SingleBond), All-Bond2, Dentastic, SuperBond, Prime&Bond 2.1. No significant differences were found in the experiments with various experimental resins. The fracture strength of teeth rebonded with Gluma, All-Bond2, Dentastic, SuperBond or Prime&Bond 2.1 showed mean fracture strengths in the range of 8.7-11.2 MPa, which were significantly different in all cases from that of intact teeth (16.3 MPa). Teeth bonded with Gluma+, Panavia21 or ScotchBond1 (SingleBond) showed mean fracture strengths of 15.5, 14.6, and 14.2 MPa, respectively. These fracture strengths were not significantly different from that of intact teeth.

Retrograde sealing of accidental root perforations with dentin-bonded composite resin.

Surgical treatment was performed on 100 iatrogen perforations, of which 94 showed radiolucency of bone adjacent to the perforation and 83 presence of an exposed post. The perforations were in all cases sealed with a resin composite (Retroplast) bonded to adjacent root dentin with a dentin bonding agent (Gluma). Cases were examined after approximately 1 yr (first recall) and, if necessary after 1 1/2 to 11 yr (mean: 4.1 yr) (latest recall). It was observed that the presence or absence of bone on the root between the perforation and cervix at the time of operation had no significant effect on the healing result, and that the radiographic classification "partial" healing with a border of cortical bone or a lamina dura often remained unchanged for many years. At latest recall, the healing result of 65 teeth originally having root perforation elsewhere than at the furcation was: 71% complete, 11% partial, 3% uncertain, and 15% failure. This is significantly different from the healing result of 27 molar teeth originally having perforation at the furcation: 30% complete, 41% partial, 11% uncertain, and 18% failure.

Adhesive bonding of fractured anterior teeth: effect of wet technique and rewetting agent.

PURPOSE: To compare the fracture strength of intact teeth with that of fractured crowns bonded with adhesive and a resin material on either wet or dry dentin, or dried dentin rewetted with a rewetting agent for various periods of time. MATERIALS AND METHODS: Sheep central incisors were divided into seven groups, each of 10 teeth. Group 1: Intact teeth tested for fracture strength in an Instron testing machine and used as controls. Groups 2-7 were sectioned in a vice equipped with sharp blades, 2.5 mm away from and parallel to the incisal edge. The two fracture surfaces were etched with 37% phosphoric acid for 15 s and rinsed with water for 5-6 s. Group 2: The surfaces were air-dried for 2 s. Group 3: As for Group 2 but the surfaces were rewetted with Aqua-Prep for 2 s and immediately air-blasted to remove excess. Group 4: As for Group 3, but the rewetting agent was applied for 10 s before air-blasting. Group 5: As for Group 4, but the rewetting agent was applied for 20 s. Group 6: As for Group 4, but the rewetting agent was applied for 30 s. Group 7: As for Group 2, but the surfaces were left moist after etching and rinsing by gently shaking the specimens twice. The fracture surfaces of Groups 2-7 were rebonded with All-Bond 2 adhesive system and Aeliteflo composite. After 48 hrs the restored teeth were debonded in the Instron testing machine. Fracture strengths were calculated and compared with the fracture strength of intact teeth (control group). RESULTS: Newman-Keuls' multiple range test revealed that there was a statistically significant difference between the control mean and the means of Groups 2 and 3. All other means were not significantly different. Drying of the dentin surface decreased the bonding strength, and rewetting of the dried dentin for 2 s was not sufficient to rewet the collapsed collagen fibers, as indicated by a decrease of fracture strength.

Effect of root canal contents on healing of teeth with dentin-bonded resin composite retrograde seal.

Healing results were compared among 551 infected roots apically sealed with a dentin-bonded resin composite (Gluma-Retroplast). These roots contained either 1) root filling to apex after resection, 2) insufficient root filling, or 3) empty root canals with necrotic pulp remnants. At 2- to 4-yr follow-up, complete bone healing was found to be 92%, 85%, and 81% in groups 1, 2, and 3, respectively. The results from groups 1 and 3 were significantly different, and the results from group 2 did not differ significantly from that of groups 1 or 3. Reasons for "Failures" were found to be mainly loose filling or uncovered canal. After 21 roots classified as "Failures" were reoperated, 76% of these showed "Complete Healing" after 1 yr.

Relative gap formation adjacent to ceramic inlays with combinations of resin cements and dentin bonding agents.

This study investigated the effect of combining dentin bonding agents (DBAs) with various resin cements on contraction gap formation at the cavity floor of resin-cemented ceramic inlays. Cylindrical dentin cavities were pretreated with one of five DBAs before luting of ceramic inlays with one of four dualcuring resin cements. Measurements of cross sections showed that mean gap widths were reduced from 46% to 93% compared with control specimens prepared without a DBA. The extent of the gap reduction was dependent on the type of bonding agent and resin cement. Although none of the resin cement-dentin bonding agent combinations tested were able to completely eliminate development of interfacial contraction gaps, some combinations produced considerable reductions in gap size.

Relative gap formation of resin-cemented ceramic inlays and dentin bonding agents.

The effect of dentin bonding agents (DBAs) on contraction gap formation at the cavity floor of resin-cemented ceramic inlays was investigated. Cylindrical dentin cavities were pretreated with one of 12 DBAs before luting of ceramic inlays with a dual-curing resin cement. Measurements of cross sections revealed that mean gap widths were reduced between 21% and 80% compared with control specimens prepared without a DBA. The extent of the gap reduction depended on the type of bonding agent. None of the dentin bonding agents tested were able to completely eliminate development of interfacial gaps.

Retrograde root filling with dentin-bonded modified resin composite.

A retrograde root-end cover with a special resin composite (Retroplast) combined with the dentin bonding agent Gluma (Bayer AG) has been used since 1984 by the authors. Its content of silver, added to promote radiopacity, has been found to lower the working time and storage stability of the composite and might cause discolorations. Since 1990, silver has therefore been replaced with ytterbium trifluoride, which eliminates these side effects. The purpose of this study was to compare the clinical results obtained with these two resin composites and to evaluate the healing results after several years in function. Apical fillings (351) with the modified Retroplast showed the following radiographic healing pattern 1 yr after surgery: 80% complete healing, 2% scar tissue, 12% uncertain healing, and 6% failure. No significant difference in this healing pattern was found, compared with that obtained with the silver-containing Retroplast. Cases with ytterbium trifluoride classified as scar tissue and uncertain healing at 1 yr when examined at 2 to 4 yr postoperatively showed 89% complete healing. 0% scar tissue, 1% uncertain healing, and 9% failure. This result is significantly different from that obtained 1 yr after surgery. Based on calculations, it was predicted that with time 90% will become complete healing, whereas 10% will become failure.

Self-reported occupational dermatological reactions among Danish dentists.

The aims of the study were to investigate the causes and prevalences of occupational dermatological reactions among Danish dentists. Questionnaires and telephone interviews with Danish dentists revealed that 37.8% reported skin reactions. In 27.2% of the cases the reactions were related to occupation, occurring with a point prevalence of 9.6%, and with a 1-yr period prevalence of 21.4%. The main causes were hand washing/soaps, latex gloves and (di)methacrylate-containing materials occurring at point prevalences of 7.1%, 1.3% and 1.7%, respectively. In addition, several other causes were reported, each occurring at relatively low frequency. Diagnosed allergic latex eczema was reported by 0.6%, but the frequency might be more than 2%, estimated on basis of reported symptoms. Allergic eczema caused by (di)methacrylate-containing materials was diagnosed among 0.7%, but estimated by the description of symptoms to be nearly 2%. The results urge for developing safer materials for dental use.

Long-term evaluation of retrograde root filling with dentin-bonded resin composite.

The purpose of this study was to investigate the long-term stability of apical retrograde root fillings using a dentin-bonded resin composite. Radiographs were used to establish the degree of healing around the apically filled roots. Patients examined were those who had previously showed complete healing 1 yr after surgery. Thirty-three of the first 34 consecutively placed resin composite apical fillings performed since the introduction of this method in 1984 were examined. Six of these fillings were examined 8 yr after surgery, and 27 of these fillings were examined 9 yr after surgery. Only one patient showed recurrence of periapical inflammation 8 yr after operation, probably caused by a root fracture. It was concluded that the bond established between dentin and the resin composite was stable during the observation period, and that the filling material had not been harmful to the surrounding tissues. If complete bone healing has been observed, it could be expected to remain stable, unless new factors, such as root fracture, occurred.

Ceramic inlay movement during polymerization of resin luting cements.

In cavities with no support for inlays, polymerization contraction of the resin cement may move the ceramic inlay axially. The purpose of this study was to determine the velocity and extent of such movement. Cylindrical ceramic inlays were placed in dentin cavities filled with one of four commercially available resin composite cements. An initial standardized 200-microns-thick cement film was created. The movement of the ceramic inlay during polymerization of one of the resin cements was measured by a dial gauge. The velocity of the inlay movement decreased exponentially with time and with a velocity constant of 0.09 min-1. The majority of the movement occurred within the first 12 min after photopolymerization and probably continued for several days, reaching an estimated value of 5.8 microns. After 1-2 d of water storage, 1-2-microns contraction gaps at the cavity floors were observed microscopically for every cement used. It is concluded that in cavities without support for the inlay, about 2/3 of the resin cement contraction results in movement of the inlay and about 1/3 results in formation of gaps at the cavity floors.

Adherence of chewing gum to dental restorative materials.

PURPOSE: To describe a method whereby chewing gum tackiness can be measured. MATERIALS AND METHODS: The chewing gum used for the experiment was V6 (Freshmint). Paladur denture base material, Silux Plus, P-50 and Heliomolar resin composites and Luxalloy amalgam were used. Squared specimens (15 x 15 x 2 mm) composed of the polymerized materials tested or set amalgam were made with a mold. As gold specimen, a gold-plated brass specimen was used, having the same dimension as specified above. A tooth enamel specimen (5 x 5 mm) was made out of flat ground human enamel from an incisor. All specimens were stored for more than 7 days in water before use, and wet ground on paper No 320 immediately before testing. The adhesion was measured by a balance equipped with a recorder and a bottom attachment, to which a chain was mounted. The end of the chain was attached to a quadratic brass plate, to which one of the above described specimen was glued by cyanoacrylate. Another brass plate, with an attached specimen of the same material, was mounted in a small vise in such way that the two specimens were parallel with and facing each other. A motor drive enabled parallel removal of the two plates from each other. The gum was chewed approximately 1 second between bites and for various periods of time. It was then pressed between the two parallel squares (mentioned above) of restorative materials or enamel, reaching a final distance of 1 mm between the plates and occupying the entire space between the plates. The study was carried out at 36 degrees C, and the two plates were wetted with fresh saliva or water immediately before placement of the chewing gum. Excess liquid was removed after the wetting, leaving a thin film. The maximal force during parallel removal of the two plates from each other was recorded. The measurements were performed eight times in each group, and the mean adhesion per surface area and SD was expressed as mN/mm(2). The measurements were repeated for some of the groups. The significance of differences between each group was tested by Newman-Keul's Multiple Range Test at a 5% level of significance. RESULTS: Adherence of chewing gum to dental restorative materials and enamel was found to decrease as follows: denture base material > resin composites = silver amalgam > gold > human enamel. The adhesion was dependent on gum base and not on the sweetening additives and reached a maximum after about 2 minutes' chewing.