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Some Articles on Bevelled Margins
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The articles below on the benefits of bevelling margins in Class II restorations were found at The National Library of Medicine (which provides free access to Medline searches).
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Quintessence Int 2000 Apr;31(4):231-9 Liebenberg WH. wliebenb@direct.ca The objective of this article is to introduce a new preparation design
that utilizes external axial bevels and a resin placement technique that
involves selective application of 2 resins of different viscosity to optimize
marginal integrity in large Class II restorations. The rationale behind
the intricate application of material and procedural manipulations involved
in the delivery of these complicated restorations is discussed. Am J Dent 1999 Jun;12(3):123-30 Cavity preparation factors and microleakage of Class II composite restorations filled at intraoral temperatures. Hilton TJ, Ferracane JL. Department of Biomaterials and Biomechanics, Oregon Health Sciences University, Portland 97201-3097, USA. hiltont@ohsu.edu PURPOSE: To determine if alteration of any of the following factors could
reduce microleakage following placement of Class II resin-based composites
(RBC) at intraoral temperature: cavity preparation (vertical wall bevels),
finishing technique (delayed vs. immediate), or postoperative re-bonding
(marginal sealing). An additional purpose was to determine if a decalcification/clearing
protocol was a valid technique for assessing three-dimensional microleakage.
MATERIALS AND METHODS: Twenty recently extracted human molars had standardized
Class II slot cavities prepared on the mesial and distal surfaces with
the gingival floor located on dentin. The teeth were imbedded in a stone
template, warmed to 37 degrees C and restored immediately upon removal
from the oven with visible light-cured (VLC) adhesive (All-Bond 2) and
three horizontal increments of VLC RBC (Bisfil P) using a metal matrix.
Teeth were placed into one of four groups: (1) Control; (2) The preparation
was modified to include 0.5-1.0 mm enamel bevels on the vertical walls
(facial and lingual); (3) Finishing of the RBC was delayed 24 hours; (4)
Following immediate finishing, all margins of the RBC restorations were
sealed by dentin bonding agent application. Teeth were stored at 37 degrees
C for 2 weeks, thermocycled 1000x at 5/55 degrees C, stained with silver
nitrate, underwent a decalcification and clearing protocol, and evaluated
for three-dimensional dye penetration. RESULTS: Axial-occlusal enamel
margins exhibited minimal leakage and no differences among the groups.
Vertical walls without bevels exhibited pronounced microleakage. Beveled
vertical proximal walls exhibited significantly less facial and lingual
wall microleakage compared to all other groups, and less gingival marginal
leakage compared to the control group. Am J Dent 1998 Aug;11(4):189-96 Osborne JW, Summitt JB. Department of Restorative Dentistry, School of Dentistry, University of Colorado Health Science Center, Denver 80282, USA. Extension for prevention has been an integral part of dentistry for over 100 years. Because this concept advocated the removal of sound tooth structure, it was not totally accepted at the turn of the century. The advent of the gold casting catapulted extension for prevention into general acceptance. In 1883, Webb presented a concept of "prevention of extension of decay". This concept advocated a proximal cavity preparation extending toward the buccal and lingual aspects of the tooth so that contact with adjacent teeth would not be at the margins. The separation of the margins, along with proper restoration contours, was thought to promote natural cleansing of the embrasures with saliva and fluids in the diet. GV Black's 1891 idea of "extension for prevention" was to provide extension of the preparation to the facial and lingual line angles in order to bring about "self-cleansing" margins via food excursion. Black's concept also included extending preparations through fissures to allow cavosurface margins to be on non-fissured enamel. Black integrated the extension of the proximal margins with his concept of an occlusal isthmus for a Class II amalgam preparation one-third the faciolingual width of the occlusal surface. Challenges to this concept of extension for prevention were immediate; and, by the 1950's, narrower, more conservative preparations were seen by a few as being more effective in preserving teeth. Not only occlusal width was reassessed, but the need to routinely extend proximal margins to the buccal and lingual line angles was also questioned. By the mid-1960's and early 1970's a more conservative approach to amalgam preparation was advocated and was being taught in some dental schools. Today, a standardized outline form should not be used or taught as a principle of cavity preparation. In areas where fissure caries has necessitated a preparation extending into dentin, a composite resin or dental amalgam restoration should be placed, and a fissure sealant should be used to protect remaining susceptible fissures from carious attack. This current form of the concept of extension for prevention, which is supported by clinical research, preserves sound tooth structure that, using outdated concepts, would have been cut away. Placing proximal margins in sound tooth structure that just clears an adjacent tooth is also strongly advocated. Sound enamel margins in certain areas may occasionally be left in contact with adjacent teeth for amalgam preparations. For Class II preparations for composite resin, facial or lingual proximal bevels will usually suffice to separate the margins from the adjacent tooth to allow finishing and polishing at the margins. Preventing unnecessary extension and allowing sounder tooth structure to remain is one important aspect of helping patients to maintain their teeth for their lifetimes.
J Prosthet Dent 1998 Sep;80(3):274-9 Opdam NJ, Roeters JJ, Kuijs R, Burgersdijk RC. University of Nijmegen, The Netherlands. STATEMENT OF PROBLEM: The tooth preparation of a bevel is recommended
to improve marginal quality of a composite restoration. However, in small
Class II restorations, it is unclear if a bevel also contributed to a
better marginal fit. PURPOSE: This study investigated the influence of
tooth preparation design on microleakage of minimal posterior Class II
composite restorations. MATERIAL AND METHODS: Box-shaped Class II tooth
preparations for posterior composite restorations in maxillary premolars
were restored with a total etch technique. The tooth preparations were
beveled or non-beveled and the box prepared at a right angle cervically
or additionally excavated. The facial and lingual box margins were also
either beveled or unbeveled. The teeth were thermocycled and immersed
in a dye solution. After sectioning specimens, dye penetration at the
facial and palatal margins was recorded. RESULTS: A bevel-reduced microleakage
both at the cervical and ascending walls. Enamel cracks were observed
along certain unbeveled margins as recorded in this study. The additional
excavation did not contribute to reduction of microleakage. CONCLUSIONS:
Tooth preparation of a bevel is recommended for an optimal marginal seal
in small box-type Class II composite restorations.
Dent Mater J 1992 Jun;11(1):26-37 Han L, Okamoto A, Iwaku M. Niigata University School of Dentistry, Japan. In this study, enamel micro-cracks produced around composite restorations
were observed on surfaces and vertical sections, using a stereomicroscope
and a scanning electron microscope (SEM). The effects of various clinical
factors, i.e. the curing system, the marginal form and the polishing period
after filling, on the incidence of marginal enamel micro-cracks were examined.
Enamel micro-cracks were observed on all of the class 1 and 5 composite
restorations when the cavity had no marginal bevel and the restorations
were polished immediately after filling. Enamel micro-cracks distributed
approximately parallel to the cavity margin and located 0.01-0.3 mm from
the restored cavity margin. The occurrence of enamel micro-cracks was
higher in light-cured composite resin restorations than in chemical-cured
ones, for non-beveled cavities when polished 10 min or 24 hours after
filling. The occurrence of micro-cracks was reduced by marginal beveling
and delayed polishing. Actual Odontostomatol (Paris) 1989 Sep;43(167):609-18 [Article in French] Nebot D, Goldberg M, Fortier JP, Aldin P. Preparation of the cavo-surface margin for fillings with "composites
resins" is an important operative step. The good peripheral fit of
the restoration and the stability of the bond between tooth and material
depend on that preparation. How should the "bevel" be shaped?
Scan electron microscopy of long bevels and rounded bevels show that the
former seem more favorable to the fit of the filling. The section of enamel
prisms is clean. The aprismatic surface area disappears. This enables
to etch the cristallites in a more favorable axis as opposed to the rounded
bevel. J Oral Rehabil 1977 Oct;4(4):305-9 Oilo G, Jorgensen KD. Three different types of cavities: (1) with a 90 degree cavo-surface angle, (2) with a bevel at the cavity margin 0-25-0-50 mm wide, and (3) with a bevel at the cavity margin 0-5-1-0 mm wide, were prepared in extracted human teeth. Fifteen cavities of all three types were filled with Adaptic. Fifteen cavities of Type 2 and of Type 3 were filled with cosmic and the same number and types of cavities with prestige. The fillings were polished 10 min after starting the mix of the composite resins. Fractures in the enamel at the cavity margins were visualized by discoloration with methylene blue. Fractures were observed around all types of cavities, but, for all types of materials, an increased bevel at the margin gave an increased number of fillings without fractures in the enamel. However, great variations in the frequency of fractures were also observed; i.e. Adaptic showing a small frequency, Cosmic a medium and Prestige a great frequency of fillings connected with fractures at the enamel margin. . |