Thirty immature sheep incisor teeth were tested for their fracture resistance after various treatment modalities using calcium hydroxide (CH) or a mineral trioxide aggregate material (MTA) as a root filling. The incisors, having approximately 80% of their root growth completed, were removed from jaws of slaughtered sheep and divided into four experimental groups. The pulps were extirpated from all the teeth through the open apexes. (a) Saline group: the teeth were preserved in saline for 100 days at 6 degrees C. (b) CH group: the root canals were filled with CH and sealed apically with IRM and stored as above. (c) MTA group: the canals were filled with MTA and stored as above. (d) CH+MTA group: the canals were filled with CH and sealed with IRM. After 30 days, the CH was replaced with MTA and stored as above. At the end of the 100-day storage period, all teeth were embedded in plaster of Paris and tested for fracture strength at the cervical area in an Instron testing machine. The results showed a decrease in fracture resistance (a) of the incisors with CH in the root canals after 100 days of storage, compared to (b) teeth stored in intracanal saline and (c) teeth with 30 days of CH and then filled with MTA, and (d) those filled with MTA in the canals. In conclusion, when CH was kept in the canals of immature sheep teeth for only 30 days followed by root filling with MTA there was no significant decrease in strength of the root within an observation period of 100 days. This finding may be of importance in the decision of treatment plans for teeth with pulp necrosis and immature root formation.

The loss of the plasticizers dibutylphthalate, butylphthalylbutyl glycolate, benzylbenzoate, methylsalicylate, and benzylsalicylate from four soft lining materials was measured. A 0.1% aqueous solution of triton X-100, reduced was used as immersion medium, since the solubility of plasticizer in this medium was close to that of saliva. The loss of plasticizer was monitored up to 30 d after mixing. For two of the materials, the average amount of leached dibutylphthalate within the first day exceeded the proposed tolerable daily intake (TDI) by about 11 and 32 times, respectively, for an average adult person. Similarly, for these two materials, the average daily amount within the first 30 d of leached dibutylphthalate was 2.2 and 6.6 times larger, respectively, than the TDI limit. The cumulative amount leached over 30 d for each of the four materials was 128-253 mg plasticizer g(-1). The results indicate the need for further biological evaluations of these products.

Fractured incisors were restored by reattaching the fragment to the remaining tooth structure. For this purpose, seven dentin adhesive systems were used with and without an unfilled resin (Heliobond) and the strength of the restored teeth was tested at a cross-head speed of either 1 or 500 mm/min. The hypothesis was that the strength of the reattachment would be higher when an unfilled resin was used. The dentin adhesive systems were Prime & Bond NT (PB), Excite (EX), One-Step (OS), PQ1 (PQ), SingleBond (SB), Optibond Solo Plus (OS), and an experimental adhesive (GL). Statistical analysis revealed that with all adhesives except EX, a significantly greater mean fracture strength was achieved when the adhesives were used with the resin (Heliobond). Furthermore, with all adhesives except PB, there was a significantly lower mean fracture strength when tested at 500 mm/min than at 1 mm/min. All the tested adhesives except EX should be used with an unfilled resin when restoring fractured teeth by reattachment.

Four types of resin composites (Dyract AP (DYR), Definite (DEF), Ariston pHc (ARI), and Spectrum TPH (SPE)) were tested after water storage for up to 180 days. The test parameters were flexural strength, flexural modulus, and marginal gaps at fillings in cylindrical cavities. The cavity tests were performed in two ways. One series of fillings was finished shortly after curing and the maximal gaps were followed with time during water storage. Another series was finished immediately before gap size measurement and after water storage for various periods. Absence of or reduced gap sizes at 180 days compared to 1 h or 1 day was observed for all materials and with both methods. At 180 days, DYR and ARI showed significantly smaller gap sizes than those observed with DEF and SPE. No significant differences in flexural strength were observed when means at 180 days were compared to those observed at 1 day. DEF, ARI, and SPE showed a significant increase in flexural moduli at 180 days compared to 1 day, while DYR showed none. It is concluded that fillings made of Dyract AP or Ariston pHc may show absence of or very small gap sizes between filling and cavity wall after 6 months and with no significant reduction in mechanical strength.

Bond strength between resin composite and dentin mediated by several dentin adhesives applied to dry or wet acid-etched dentin or to dry or wet acid-etched and deproteinized dentin were measured and analyzed. Human dentin were A) acid-etched and blot-dried for 1 sec (= wet), B) as A but dried with air for 10 sec (= dry). C) acid-etched and treated with hypochlorite and then dried for 1 sec, and D) as C but dried with air for 10 sec. Eight dentin adhesives were used in each group for bond strength measurements. The results were compared by means of ANOVA and the Tukey test. Collagen removal increased significantly the strength of the bond by 10 18 MPa for five adhesives when tested dry (D versus A). When tested wet, collagen removal increased the strength by 10 12 MPa for three adhesives (C versus A). Normal etched dentin showed a reduction in strength of 14 15 MPa for three of the adhesives when tested dry instead of wet (B versus A). For one dentin adhesive no significant change in bond strength due to collagen removal and/or drying conditions was observed. It was hypothesized that low technique sensitivity of an adhesive may be linked to its ability to wet and adhere to collapsed collagen fibers and to the surface of the underlying mineralized tissue. Comparisons of bond strengths obtained by using dried or wet acid-etched dentin and dried or wet acid-etched and deproteinized dentin may be useful for evaluating the efficiencies of dentin adhesives.

AIMThe 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.METHODOLOGYRoot-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.RESULTSOut 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.CONCLUSIONRoot-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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

A method was developed for measuring presence, location and extent of interfacial contraction gaps of resin-cemented ceramic inlays in dentin cavities. Cylindrical ceramic inlays were cemented using one of 12 commercially available resin composite cements to make a film thickness of 200-microns. Cross-sections revealed absence of marginal gaps but contraction gaps occurred at all dentin-cement interfaces at the cavity floors and ranged from 1.6 to 7.1 microns. This was equivalent to 0.8-3.5% of the cement film thickness and was 3-10 times greater than the wall-to-wall contraction in percent observed when resin composites are used as filling materials in 3-5 mm butt-joint dentin cavities. The results support the theory that contraction gaps developing adjacent to thin films of resin cements reach a size equivalent to the cement film thickness multiplied by the volumetric polymerization shrinkage of the cement.