Water storage effect on marginal adaptation

Table 1.—Static Flexure Strength and Cyclic Fatigue Values Group

Code

No fiber/fiber (n)

Indirect composite resin (MPa ± SD)

Fiber-reinforced indirect composite resin (MPa ± SD)

Static control air Static control water Static aged air Static aged water Cyclic control air Cyclic control water Cyclic aged air Cyclic aged water

SUR SUW SAR SAW CUR CUW CAR CAW

15/15 15/15 15/15 15/15 25/25 25/25 25/25 25/25

106.8  20.0A 115.7  21.2A 94.1  20.5A 102.4  10.0A 78.3  15.5C 74.0  18.0C 66.7  11.2C 60.4  11.3C

242.7  43.9B 246.1  36.5B 251.6  26.8B 232.3  30.1B 199.9  12.0D 196.9  55.6D 195.7  28.8D 180.3  8.8D

Note: Different superscript uppercase letters indicate significant difference at P < .05 level. (Courtesy of Al-Darwish M, Hurley RK, Drummond JL: Flexure strength evaluation of a laboratory-processed fiber-reinforced composite resin. J Prosthet Dent 97:266-270, 2007.)

Results.—The flexure strength with static loading was comparable for the aged and nonaged groups and for the groups aged with water and those with air. However, reinforced specimens had a significantly greater flexure strength than nonreinforced specimens. Cyclic loading similarly produced a decline in flexure strength but no statistically significant differences between aged and nonaged groups or between the aging media. Cyclic loading did produce a significantly greater decline in the flexure strength of nonreinforced samples compared with that of reinforced ones. Discussion.—Incorporating fiber reinforcement into the composite resin significantly increased flexure strength in the samples tested. Specimens aged in air or water showed no difference in flexure strength. The flexure strength of specimens was significantly decreased by cyclic loading but not by static loading.

Clinical Significance.—Efforts to improve the properties of composite restoratives continue. Reported here, the addition of fiber reinforcement significantly increased the material’s flexural strength. While static loading had little impact, cyclic loading significantly reduced flexural strength. Longer-term testing, longer than 3 months, is in order.

Al-Darwish M, Hurley RK, Drummond JL: Flexure strength evaluation of a laboratory-processed fiber-reinforced composite resin. J Prosthet Dent 97:266-270, 2007 Reprints available from JL Drummond, Dept of Restorative Dentistry, College of Dentistry, Univ of Illinois at Chicago, 801 S Paulina St, Chicago, IL 60612-7212; fax: 312 996 3535; e-mail: [email protected]

Water storage effect on marginal adaptation Background.—The life expectancy of an adhesive dental restoration depends on obtaining a stress-resistant adhesion between the tooth and the restoration. Gaps between the restoration and tooth permit microleakage, discoloration of the marginal areas, postoperative sensitivity, and secondary caries. An assessment of the bond strength and marginal adaptation of etch-and-rinse and self-etch adhesives conducted by Frankenberger et al found lower bond strengths after storage. However, the comparatively hydrophobic bonding layer normally found in multistep formulations enhanced bonding performance and resistance to hydrolytic degradation. Fatigue and cumulative damage can also cause dental restorations to fail clinically. The marginal performance of adhesive restorations must be assessed in vitro under thermomechanical loading and a humid environment to simulate what will happen in the oral cavity.

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Dental Abstracts

Methods.—Sixteen groups of Class V cavities were restored with various adhesive systems. The samples were then subjected to thermal and mechanical loading with simulated dentin fluid before being stored for 18 months in water. Gold-coated polyvinylsiloxane impressions of these restorations were evaluated for marginal adaptation using a scanning electron microscope at 200 magnification. Results.—Marginal adaptation was evaluated across total margin length as well as separately for enamel margins and dentin margins (Table 2). Before storage, the percentages of marginal adaptation were relatively high. Thermomechanical loading and 18 months of water storage negatively influenced all the specimens, irrespective of the type of adhesive used. Water storage of the Scotchbond MultiPurpose samples significantly affected marginal adaptation

Table 2.—Percentages of Continuous Margins at the Total Margin Length, in Enamel and in Dentin at the Following Intervals: Before Loading (Initial), After Loading (S1) and After 18-Month Water Storage (S2). Marginal Adaptation at the Total Margin Length Differences Among S1 and S2 Groups Were Statistically Evaluated with Kruskal-Wallis and Bonferroni’s Test (P < .05) Type of adhesive

Total margin length Etch & rinse

Self-etch

Enamel margins Etch & rinse

Self-etch

Dentin margins Etch & rinse

Self-etch

Steps

Material

Initial

S1

S2

3 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1

SMPP Admira Bond James 2 FL-Bond ART Bond Tyrian SPE Contax Coltene exp. Opt. SoloPlus SE Nanobond Clearfil SE Bond OneCoatSEBond VoCo exp. Xeno III Hybrid Bond iBond

73.6 (13.9) 90.3 (5.4) 78.6 (12.3) 92.1 (5.9) 97.5 (2.9) 64.7 (5.3) 72.5 (14.1) 84.0 (11.3) 56.2 (17.1) 94.1 (1.7) 82.0 (7.0) 97.4 (0.9) 78.2 (16.7) 78.8 (11.6) 82.6 (7.9) 64.8 (8.1)

55.9 (12.1) 61.6 (16.7) 31.4 (16.6) 65.7 (14.4) 91.2 (3.7) 41.8 (10.2) 51.8 (15.7) 69.0 (7.0) 43.3 (13.9) 65.9 (9.8) 74.9 (10.7) 83.2 (9.3) 61.6 (23.2) 56.2 (10.6) 49.2 (16.3) 55.2 (11.0)

33.4 (16.1)) 47.0 (14.8)) 26.2 (14.6) 46.6 (13.3)) 62.9 (5.4)) 18.5 (3.2)) 20.4 (5.1)) 40.2 (11.1)) 32.1 (8.7)) 37.1 (6.7)) 55.8 (10.5)) 58.0 (11.8)) 52.3 (17.5) 42.5 (8.6)) 24.5 (12.2)) 46.5 (5.8)

3 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1

SMPP Admira Bond James 2 FL-Bond ART Bond Tyrian SPE Contax Coltene exp. Opt. SoloPlus SE Nanobond Clearfil SE Bond OneCoatSEBond VoCo exp. Xeno III Hybrid Bond iBond

64.3 (19.5) 96.6 (1.2) 95.6 (4.9) 85.3 (11.2) 96.2 (3.4) 74.4 (10.4) 87.4 (4.9) 79.5 (16.0) 36.0 (19.8) 92.2 (3.4) 73.0 (14.3) 96.2 (2.2) 69.2 (18.5) 88.9 (4.6) 68.9 (13.9) 44.9 (16.2)

55.1 (21.6) 88.7 (6.1) 64.3 (30.2) 52.4 (16.2) 82.1 (7.4) 55.9 (10.2) 65.2 (12.6) 70.8 (10.0) 17.3 (8.8) 52.2 (11.2) 64.7 (16.0) 85.4 (9.7) 45.9 (28.9) 82.9 (7.2) 25.9 (12.8) 24.6 (17.0)

40.5 (21.4) 62.8 (9.5)) 52.7 (29.4)) 39.4 (5.7) 34.7 (9.3)) 29.1 (6.4)) 36.7 (8.4)) 49.8 (18.7)) 9.3 (10.0) 28.3 (7.7)) 37.1 (11.0)) 36.7 (20.2)) 30.2 (19.0) 71.8 (14.2) 8.9 (6.4)) 10.5 (11.2))

3 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1

SMPP Admira Bond James 2 FL-Bond ART Bond Tyrian SPE Contax Coltene exp. Opt. SoloPlus SE Nanobond Clearfil SE Bond OneCoatSEBond VoCo exp. Xeno III Hybrid Bond iBond

84.2 (16.6) 82.7 (13.0) 63.9 (20.1) 99.6 (0.9) 100.0 (0) 49.0 (24.5) 56.4 (28.8) 88.9 (8.7) 81.2 (21.9) 96.7 (5.4) 96.5 (3.7) 100.0 (0) 91.9 (12.9) 69.2 (28.1) 100.0 (0) 98.2 (12.4)

54.6 (29.9) 27.9 (37.4) 3.9 (7.7) 81.8 (17.6) 97.8 (3.1) 16.2 (18.9) 21.6 (18.5) 65.5 (11.0) 71.8 (23 1) 84.6 (11.3) 87.4 (12.7) 79.2 (25.4) 83.5 (12.4) 27.5 (25.5) 77.2 (18.8) 92.2 (5.0)

25.7 (24.1) 27.3 (37.1) 0.0 (0.0) 55.3 (23.4)) 85.5 (6.4)) 4.4 (8.7) 0.0 (0.0) 29.3 (23.6)) 57.8 (17.8) 49.1 (18.7)) 84.2 (11.1) 82.8 (8.9) 82.2 (13.1) 11.6 (17.1) 45.8 (25.3)) 94.3 (5.1)

Statistical significance

A A A

A

B B

C C

B

C

B B B

C C C

A A A A

B B

C C

A

B

C

D D D D

D D D

D D D

E

F

E

F

E E E E

F F F F F

E E

F

Note: Significant differences within a group are represented with an ) (Wilcoxon signed-rank test P < .05). Levels not connected by the same letter are significantly different. Mean (SD). (Courtesy of Bortolotto T, Ferrari M, Tay F, et al: Degradation of thermo-mechanically loaded adhesive Class V restorations after 18 months of water storage. Am J Dent 20:83-89, 2007.)

Volume 53



Issue 2



2008

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for the continuous margins in dentin with respect to enamel. Water storage also caused severe degradation of the enamel margins in the Admira Bond and James 2 samples. After 18 months the James 2 samples showed complete detachment of the dentin margins. Most of the 2-step selfetch adhesive samples also developed significant marginal degradation along the enamel margins after storage. The dentin margins were similarly affected for some of these adhesives. Xeno III, a 1-step self-etch adhesive, demonstrated more marginal gaps in dentin than enamel. Discussion.—Marginal degradation of composite restorations is a clinical problem that adversely affects the longevity of the restorations. Long-term water storage caused degradation of the margins, both dentin and enamel, regardless of the adhesives used. Both etch-and-rinse and self-etch adhesive systems demonstrated similar degradation mechanisms after 18 months of water storage.

Clinical Significance.—Incomplete sealing of the dental restoration interface is a key factor in failure. While most everything deteriorates with age, how fast and to what degree this occurs is what is important. Reported here is the degree of interface integrity of popular bonding materials, initially and maintained over time, when subjected to hydrolytic activity.

Bortolotto T, Ferrari M, Tay F, et al: Degradation of thermo-mechanically loaded adhesive Class V restorations after 18 months of water storage. Am J Dent 20:83-89, 2007 Reprints available from I Krejci, Div of Cariology and Endodontology, School of Dentistry, Univ of Geneva, 19, Rue Barthe´lemyMenn, CH-1205 Geneva, Switzerland; e-mail: Ivo.Krejci@medecine. unige.ch

Endodontics Guidelines for endodontic access design Background.—Using the proper access design dramatically improves the prognosis for an endodontically treated tooth. Both internal and external anatomy must be considered in locating the root canal orifices. Maxillary molar root systems usually have 3 roots and 4 canals, but the number varies. Mandibular molar root studies indicate that the distance from the external surface of the clinical crown to the wall of the pulp chamber is uniform throughout the tooth’s circumference at the cementoenamel junction (CEJ) level. Identifying other consistencies in maxillary and mandibular first molar structures would make the dentist’s efforts to design proper access more efficient. Methods to locate appropriate pulp chamber access for maxillary and mandibular first molars based on occlusal anatomy were proposed. Methods.—In vitro studies were carried out to identify guidelines for improving access design. In the maxillary first molar tooth study, 29 extracted human maxillary first molars were used. The specimens underwent decoronation at the CEJ, with digital radiographs and occlusal photographs obtained before and after this procedure. The 3 images obtained were superimposed on one another to identify occlusal and pulpal patterns. In the mandibular first molar tooth study, 21 extracted human mandibular first molars were investigated. These specimens received amalgam restorations in their cusp tips; the orifices were filled with gutta-percha to the 3.0-mm level. Digital radiographs and occlusal photographs were taken of the complete specimens, which were then sectioned horizontally at the CEJ, with the photographs and radiographs

92

Dental Abstracts

superimposed to assess the canal orifice and occlusal surface anatomy. It was hoped that consistent landmarks could be identified that would help dentists create access openings for endodontic therapy on these first molars. Results.—In the maxillary first molar assessment, the root canal orifice showed a relationship with the occlusal landmarks that had been identified (Fig 1). Thus occlusal and intracoronal anatomy should be consistent with one another. The mesiobuccal (MB) orifices were close to the MB cusp tip in most cases. Specifically, 78% of the teeth had the MB orifice at or buccal to the line joining the MB and distolingual (DL) cusp tips. Most of these were close to the MB-distobuccal (DB) cusp tip line (Fig 2 [maxillary]). A DB orifice was generally located at or mesial to the DBmesiolingual (ML) cusp tip line. In all cases a DB orifice was mesial to the DB cusp tip. Ninety percent also had palatal orifices at or lingual to the line bisecting the DB and ML cusp tips, with 85% of these closer to the ML-DL line. The central pit was found over the pulp chamber itself in all cases. The pulp chamber was consistently located in the area relative to the greatest diameter of the clinical crown in both mesiodistal (MD) and buccolingual (BL) directions. The diameter of the tooth structure decreased at the CEJ relative to the coronal dimensions. Knowing this helps the dentist identify a more conservative access occlusally. The mandibular first molar study found that the pulp chamber occupies about 40% of the tooth’s greatest diameter in an MD direction and 30% in a BL direction. It also occupies about half the CEJ in an MD direction and 40%