Australian Dental Journal
The official journal of the Australian Dental Association
REVIEW
Australian Dental Journal 2010; 55: 120–127
doi: 10.1111/j.1834-7819.2010.01214.x
The all-ceramic, inlay supported fixed partial denture. Part 1.
Ceramic inlay preparation design: a literature review
MC Thompson,* KM Thompson, M Swain*
*Faculty of Dentistry, The University of Sydney.
Faculty of Health Science, The University of Sydney.
ABSTRACT
The effect of cavity design is a controversial and underrated factor in the clinical success of ceramic inlays and inlay
supported prosthesis. Many articles and studies have been conducted into the advantages and disadvantages of isolated
aspects of preparation design, but lacking is a review of the most relevant papers which bring together a consensus on all the
critical features. Hence, a review and analysis of cavity depth, width, preparation taper and internal line angles is warranted
in our attempts to formulate preparation guidelines that will lead to clinically successful, all-ceramic inlay restorations and
ceramic inlay supported prosthesis.
Keywords: All-ceramic, fixed partial denture, inlay supported denture, ceramic fixed partial denture.
Abbreviations and acronyms: FEA = finite element analysis; IWC = intercuspal width; TOC = total occusal convergence.
(Accepted for publication 6 July 2009.)
INTRODUCTION
Successful restoration of the dentition has historically
depended upon simultaneously respecting the three
foundation principles of tooth preparation: mechanical
preparation to achieve retention and resistance, hence
ensuring longevity; aesthetic factors such as minimizing
the appearance of margins and display of metal; and
the biological consequences of achieving the first two
factors which concerns the health and ultimate durability of the tooth and periodontium.
Growing patient demands for aesthetic ‘‘tooth-like’’
materials and concerns about the deleterious effects of
metals has added a new consideration for the profession
to address.
Magne,1 who advocated a new ‘‘biomimetic’’
approach for restorative and prosthetic dentistry via
the use of ceramics and composite resins, heralded not
only a change in techniques, but as stated by Roeters,2
a change in treatment philosophy. As a consequence of
this major paradigm shift, the primary emphasis for
dentistry is now not the restoration of the tooth, but
rather its reinforcement and preservation.
Part 1 of this two-part investigation will review the
literature with regards to the ideal inlay preparation
120
design whilst Part 2 will present original research into
the fixed partial denture (FPD) design. Three dimensional finite element analysis will be used to create an
optimum all-ceramic bridge with regards to connector
dimensions and embrasure geometry and validated with
load-to-failure bench-top testing.
Inlay preparation design
It has become a basic tenet in dentistry that in order to
replace a missing tooth (pontic) without resorting to the
use of removable prosthetics or implants, it becomes
necessary to attach the pontic to the adjacent teeth
(abutments). Whether or not it is chosen to prepare the
abutments in an effort to improve mechanical resistance
and retention is a decision that the dentist must weigh
up against the loss of tooth structure that accompanies
such preparation and hence increased risk of tooth
fracture.
Little or no preparation to the abutments means
relying heavily upon adhesive technology with minimal
mechanical assistance. The advantages are the conservation of tooth structure and thus the diminishment of
the pulpal and periodontal consequences discussed
above. Conversely, if the decision is made to prepare
ª 2010 Australian Dental Association
Ceramic inlay preparation design
the abutments in order to impart mechanical resistance
and retention to the FPD, then varying degrees of tooth
reduction becomes necessary, with the associated
complications arising with increasing tooth preparation. It is the challenge of replacing missing teeth and
the restoration of aesthetics and function at minimal
biological cost that is of concern to every practising
dentist.3
Many articles and studies have investigated the
advantages and disadvantages of the various aspects
of preparation design and its effect on the clinical
success of ceramic inlays. Milleding et al.4 stated that
‘‘the effect of cavity design on the strength of an inlay is
a factor that is probably underrated’’.
The main factors of preparation design that influence
the longevity of the inlay ⁄ tooth complex are as follows:
cavity depth; cavity ⁄ isthmus width; preparation taper,
and the morphology of internal line angles. Figure 1
illustrates the idealized form of an MO inlay on the
lower second molar.
Tooth preparation designs advocated for posterior
ceramic restorations have been based upon recommendations made by GV Black (1836–1915) for cast metal
and amalgam, resulting in considerable tooth structure
removal, opposing walls that are too parallel and
internal line angles too steep.
Preserving tooth structure is beneficial to the overall
health of the tooth and periodontal tissues. The use of
the minimally invasive bonded restoration results in less
trauma and superior prognosis.5–10 When designing a
tooth preparation, be it for restorative or prosthetic
reasons, it is imperative to balance the competing
considerations of aesthetics; preservation of tooth
structure and the periodontal complex, and maximizing
the strength of the restoration.11 Cavity geometry and
dimensions are dictated by traditions of cavity design,
the properties of the restorative material, the techniques
and technology applied and ultimately the inherent
shape of the carious lesion.12
Preparation geometry for ceramic restorations in
general, and inlays specifically, must be adapted to the
specific properties of ceramics. Possessing a low tensile
strength and high modulus of elasticity, the traditional
retention ⁄ resistance principles for cast metal restorations must be relaxed and the simplest geometry
employed.13 Low flexural strength is a limiting property
of brittle materials such as ceramics because the failure
mechanism most likely is that of tension or impact
damage rather than compression, a property of which
ceramics possess highly but is irrelevant in considerations of rupture and cyclic fatigue.14–17
The literature is conclusive in regards to the effects
of tooth preparation; it further weakens teeth and
increases the likelihood of fracture.18 Khera et al.19
examined the effects of cavity depth, isthmus width and
remaining interaxial dentine on MOD cavity preparations via the use of 3D finite element analysis (FEA). A
total of eight different cavity designs were prepared on
human premolars, divided into three groups and
compared with normal, unprepared teeth and to other
cavity designs in the same group. It was demonstrated
that the most crucial factor in the weakening of cusps
was cavity depth, with the width of the isthmus alone
being the least important.
Lin et al. studied the mechanical responses of MOD
preparations on six human second premolars with the
use of FEA. They concluded that pulpal wall depth was
the most profound determinant in the likelihood of
cuspal fracture and the deeper the pulpal depth, the
greater the risk to the restored tooth.20
In a similar study, Lin et al.21 examined the
biomechanics of 30 MOD cavity preparations on
human maxillary second premolars via FEA. Stress
levels were correlated to pulpal depth, isthmus width
Fig 1. Ideal ceramic inlay preparation design.
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121
MC Thompson et al.
Table 1. Cavity depth recommendations for minimizing tooth fracture in Class II restorations
Author
Recommendation for
cavity depth
Comments
Donly et al. (1990)23
1.5 to 2 mm
Shallow floor considered is
1.5 mm
1.5 mm
Etemadi et al. (1999)11
1.5 to 2.0 mm
Goel et al. (1992)24
Homewood (1998)25
Khera et al. (1991)19
NSR
NSR
NSR
Uniformity of depth stressed.
Cavity depth most important factor. Width does not substantially
weaken teeth if depth is shallow.
1.5 mm depth conservative Class II preparation has less marginal
leakage than 2.0 mm conventional preparation.
Study conducted on resin-bonded porcelain restorations. Rounded
internal line angles recommended.
Unfavourable stresses increased with increasing cavity depth.
Shallower cavity results in less cusp deflection.
Cavity depth most significant factor in fracture of tooth, isthmus
width the least.
Unfavourable stresses develop exponentially as cavity depth increases.
Smooth preparation with no sharp internal line angles recommended.
Banks (1990)15
Blaser et al. (1983)22
Lin et al. (2001)20
Malament and
Grossman (1987)26
Malament (1998)27
Milleding et al. (1995)4
Nadal (1962)28
Rosenstiel et al. (2001)29
Watts et al. (1995)30
1.5 to 2.0 mm
1.5 to 2.0 mm
1.5 to 2.0 mm
NSR
1.5 to 2.0 mm
Cavity depth of 1/3 to ½
bucco-lingual width.
Cavity depth recommended for ceramic strength.
Recommendation made specifically to minimize fracture of ceramic
inlay but authors found that 1.5 mm cavity depth resulted in only
2% cusp fracture rate.
Shallow floor and narrow occlusal outline recommended.
Manufacturers recommendation.
Shallower restoration depth leads to decreased prevalence of tooth
fracture.
NSR ¼ no specific recommendation.
and interaxial thickness (width of the pulpal floor from
axial wall-to-axial wall) with variations of the three
design parameters being made and analysed. The results
demonstrated that enlarging the volume of the MOD
cavity significantly increased the stresses in enamel, and
to a lesser extent dentine, with the stress intensity rising
exponentially with cavity depth. For enamel, cavity
depth is the most dominant factor influencing stress.
However, for dentine, it appears that the length of the
interaxial wall could be the most important factor.
Table 1 summarizes a number of studies evaluating
the role of cavity depth and its relation to restoration
and tooth strength. It demonstrates that a depth of 1.5
to 2 mm is ideal in minimizing tooth loss and providing
sufficient thickness of material in order to ensure
adequate functional life.
The concurrence of opinions regarding the recommended depth for cavities in order to minimize the
incidence of tooth fracture is considerable. This needs
to be balanced with the need to retain adequate bulk in
the restorative material to ensure the long-term viability
of the tooth ⁄ restoration complex. These competing
issues influencing material strength can be successfully
answered with current bonded restorations which rely
significantly less on mechanical factors than traditional
direct and cast restorations. In the case of ceramic inlay
systems, the use of a resin cement to both retain the
restoration and support the weakened tooth structure
results in good long-term success.31 Zinc phosphates
and glass-ionomer cements must be avoided. However,
the former, because of its inability to bond, and the
latter, due to its low modulus of elasticity, increases the
flexure of the inlay and thus the rate of fracture.
122
Habekost et al.32 evaluated the in vitro fracture
resistance of teeth restored with different designs of
ceramic restorations. One hundred and twenty sound
maxillary premolars were tested in three groups. Each
group was prepared with three indirect restorations
consisting of inlays, onlay with only lingual cuspal
coverage and onlay with buccal and palatal cuspal
coverage. Twenty intact teeth were selected as controls.
Peak load-to-fracture was measured for each specimen.
Results indicated that the fracture resistance of the teeth
was related to the quantity of hard tissue removed and
inlays showed a significantly higher fracture resistance
than onlays. This suggests that unlike in the use of
metallic materials and composite resins, where cusp
capping is often viewed as being a preferred means of
reinforcing a tooth, caution is needed for ceramic
inlays.
Bonding of inlays to teeth increases the fracture
resistance of the tooth.33–35 However, large MOD
preparations severely undermine cusps to the degree
that adhesive bonding of restorative materials does
‘‘not re-establish the fracture resistance of the tooth to
its original levels.’’16 Hence, minimizing the depth and
overall width of any tooth preparation to the amount
needed for adequate retention, resistance and convenience form must be of primary concern.
Table 2 summarizes a number of studies evaluating
the relationship between enlarged cavity widths (specifically the intercuspal width defined as the distance
between cusps) and tooth fracture strength. Universally,
the consensus is to maintain as narrow cavity width
as possible whilst maintaining acceptable strength
in the restorative material; the recommendation is 1/3
ª 2010 Australian Dental Association
Ceramic inlay preparation design
Table 2. Cavity isthmus width recommendations for minimizing tooth fracture in Class II restorations
Author
Isthmus recommendation
(as a ratio of ICW)
Bader et al. (2004)36
NSR
Blaser et al. (1983)22
NSR
37
Cavel et al. (1985)
£1/3 ICW
Christensen (1971)38
Re et al. (1982)82
£1/3 ICW
NSR
Homewood (1998)25
Joynt et al. (1987)40
NSR
1
/3 ICW
Larson et al. (1981)41
£¼ ICW
Lin et al. (2001)20
NSR
Mondelli et al. (1980)42
£¼ ICW
Osborne and Gale (1980)43
Vale (1959)44
Watts et al. (1995)30
£¼ ICW
£¼ ICW
<1/3 ICW
Comments
Relationship exists between fracture risk and dentinal support
measured by intercuspal width proportion and restoration depth.
Width of MOD preparation does not substantially weaken the tooth
if the pulpal depth is shallow.
Wider isthmus and ⁄ or more restored surfaces related to increased
fracture susceptibility.
Inlays with ICW > 1/3 have higher fracture risk.
No specific trend found between the fracture strength of restored
teeth and preparations with various sizes of faciolingual width.
Wider isthmus results in greater cusp deflection.
1
/3 ICW chosen for study, recognized that narrow ICW associated
with reduced fractures.
Proportional isthmus width is possibly the most important measure
of lost dentinal support associated with fracture resistance.
Smaller isthmus results in less stress, cavity depth most important
factor.
The narrower the isthmus, the greater the load to cause fracture.
A significant factor in preparation design.
¼ ICW provides better resistance to fracture than 1/3 ICW.
Isthmus greater than 1/3 ICW significantly weakened.
Narrower cavity width had statistically higher fracture strengths.
NSR ¼ no specific recommendation.
intercuspal width (ICW) or less, with most recommendations suggesting ¼ or less.
Total occlusal convergence (TOC), defined as ‘‘that
angle which is formed between opposing walls of a
preparation’’, is an important factor in cavity design
and yet the aspect associated with the most contention.45 For complete crown preparations, TOC was one
of the first preparation criteria given a specific quantitative value when Prothero in 1923 recommended a
range of between 2 and 5. This was later scientifically
tested by Goodacre et al.44 with the recommendation
increasing to between 6 and 7.
The current practice of minimizing the axial wall
convergence or the TOC to between 6 and 7 (or less)
in the preparation of cast metal restorations47–50 is
likely to lead to increased failure rates if used for
ceramic restorations, and should be increased to
approximately 15.
Kaufman et al.49 examined the effects of varying the
TOC angle (1, 5, 10, 15, 20) on complete veneer
crowns with controlled variations in height and diameter, and found that as the convergence approached
parallelism (at least to within 5), retention increased
geometrically – this being related to the simple effects of
geometry. No definitive recommendation was made as
to a TOC angle as it was acknowledged that many
factors influence the retention of a cast restoration (e.g.,
adaptation of the casting, texture of surfaces, elasticity
of the casting to enable it to resist deformation and
hence maintain the cement seal, etc.).
Livaditis,51 Shillingburg52 and Rosenstiel et al.29
have recommended a TOC of 5–7 for resin-bonded
cast metal, intracoronal restorations due to the
ª 2010 Australian Dental Association
increased retention offered by the friction fit of the
surfaces, whilst Jørgensen49 attributed the increased
retention to the limiting of the ‘‘paths of insertion’’ and
removal.
Mack examined the TOC angles of clinically
prepared inlay and crown dies, and compared them to
those prepared in a laboratory with the use of standard
laboratory optical measurement equipment.53 It was
concluded that the average TOC achieved in dental
practice was about 16.5 – far removed from the
textbook ideal of 5. He showed that if a dentist looked
over the preparation with a mirror and could sight all
the walls, then the minimum taper achieved is 5, 42¢.
An estimate of 12 was also made for the minimum
convergence required in order to ensure an absence of
undercutting clinically.
Ceramic restorations are fundamentally different to
cast metal restorations in numerous ways. Chief
amongst them is their very high modulus of elasticity
and presence of numerous micro-flaws on the surface
which renders them fragile in tension, hence highly
brittle and likely to fracture during the luting procedure
and under occlusal loading.11,54–56
Qualtrough and Wilson55 stressed the importance of
the bonding procedure to the overall success of the
ceramic restoration. Hypothesizing that unlike traditional cast metal inlays where the fit was critical to
success, it is the bonding procedure in ceramic systems
that may ultimately determine the longevity of the
restoration, with smaller degrees of divergence between
axial walls resulting in greater stress being imparted to
the inlay and the increased likelihood for the need of
adjustment. Unlike metals, resins and tooth structure,
123
MC Thompson et al.
ceramics are unable to elastically deform to the same
extent; hence the build-up of stresses is likely to occur
from the cementation procedure if there are any
discrepancies of fit, or if the fit is tight. The TOC angle
must be relaxed in order to accommodate the inlay,
minimizing straining and the build-up of stress.56
Table 3 demonstrates the current opinion with
regards to increasing the TOC for ceramic inlays from
the traditional 5 to 7 to approximately 20 when
ceramic restorations are utilized. Values are also given
for ceramic and metallic crowns as a comparison and a
guide as to the fluctuating historical opinions.
Classic cavity design principles as advocated by GV
Black recommended the use of flat walls and sharp
internal line angles as the best way of maximizing
the retention and especially the resistance form of
restorations – this is especially true with regards to
Class II restorations where traditionally even the
axiopulpal line angle has been left deliberately angular.
Cavity design evaluation based upon the use of 2D
photoelastic methods has revealed that any areas of
angularity within tooth preparations and restorative
materials give rise to significant stress concentrations.
The pioneering work of Noonan,69 Mahler and
Peyton70 and Haskins et al.,71 as well as others,
concluded that ‘‘rounding of internal line angles [is]
the most satisfactory modification of cavity preparation
with respect to stress within the remaining tooth
structure’’.72
The stresses that accumulate within complex shapes
is difficult mathematically to analyse. However, the use
of photoelastic analyses of these complex and deleterious stresses has provided useful data to derive optimal
design parameters for cavity preparations. Photoelasticity involves the construction of a model of the
structure from a photoelastic material, i.e., a transparent material which exhibits birefringence. The
photoelastic material exhibits birefringence upon the
application of stress and the magnitude of the stress,
and each point is displayed via the refractive indices.73
The evaluation of the stresses using this approach has
immensely helped our understanding of the need for the
Table 3. Total occlusal convergence angle recommendations
Author
TOC recommendation
57
Doyle et al. (1990)
15
Eames et al. (1978)58
El-Ebrashi et al. (1969)47
20
2.5 to 6.5
Esquivel-Upshaw et al. (2001)59
5
11
21 to 40
Etemadi et al. (1999)
Gerami-Panah et al. (2005)60
48
22
Gilboe and Teteruck (2005)
Goodacre et al. (2001)46
Jørgensen (1955)61
2 to 5
10 to 20
As parallel as possible
Leempoel et al. (1987)62
15.5 to 30.2
Mack (1980)53
5 accepted consensus
Milleding et al. (1995)4
NSR
Malament and Grossman (1987)26
Nordlander et al. (1988)50
6 to 8
5 to 10
Owen (1986)63
12
Palacios et al. (2006)64
Parker et al. (1993)65
20
8.4 for molars,
10 for premolars
NSR
Ideally 0
No difference between
8 and 16
Qualtrough and Wilson (1996)55
Schwartz (1952)66
Sobrinho et al. (1999)67
Wilson and Chan (1994)68
6 to 12
Comments
15 TOC significantly stronger than 5 on all-ceramic, complete
crowns.
20 TOC most likely to be seen clinically on complete crowns.
Stress concentration increases slightly from 0 to 15, increases
sharply at 20. Measured from models of complete crowns.
Inlays with TOC of 5 significantly more fracture resistant than those
at 20.
21 to 40 for internal tapers, 6 to 15 for external tapers, as
measured from clinical models of porcelain inlays and onlays.
22 TOC results in less stress to the gingival connector area of an
all-ceramic FPD than 12.
Recommendation for cast-metal complete crowns.
Recommendation for complete crowns
Recommendation for complete crowns. 5 TOC is twice as retentive
as 10; 20 is 62% the retention of 10 and 81% that of 5.
Review of working dies from dental laboratory. Crowns were in place
5 to 10 years and still functioning adequately.
Whilst he accepts the consensus that the ideal TOC for inlays and
crowns is 5, 16.5 is more commonly seen clinically. 12 is the
minimum required to avoid undercutting.
Inlay preparation designs must be relaxed from the traditional
recommendations.
Recommendation for all-ceramic complete crown.
Theoretical ideal for complete crowns, but rarely seen clinically.
Average seen clinically for premolars is 8 and for molars 12.5.
Unless special jigs used, not possible to prepare teeth with TOC of less
than 12 TOC. At this angle they still perform well.
Common journal finding for all-ceramic crowns.
Calculation of limiting average taper mathematically based on ½ arc
sin (H ⁄ B). Less than this amount results in reduced resistance.
Fit must be relaxed for ceramic inlays.
Pulpal and axial walls should be perpendicular.
TOC of in-ceram crowns had no effect on their fracture strength.
However, luting with zinc phosphate achieved significantly better
results than GIC.
For extracoronal retainers, optimum thickness of cement occurs
between 6 and 12. Retention decreases significantly as TOC
reduces from 9. Larger than 25 TOC also results in significant
decrease in retention.
NSR ¼ no specific recommendation.
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ª 2010 Australian Dental Association
Ceramic inlay preparation design
Table 4. Stress analysis in dental materials and cavity preparations
Author
Findings
75
Arola et al. (1999)
13
Arnetzl and Arnetzl (2006)
Banks (1990)15
Bell et al. (1982)76
Braly and Maxwell (1981)77
Cameron (1964)78
Couegnat et al. (2006)74
Etemadi et al. (1999)11
Haskins et al. (1954)71
Kahler et al. (2006)79
Malament and Grossman (1987)26
McDonald (2001)80
Milleding et al. (1995)4
Snyder (1976)81
Soares et al. (2006)56
Vale (1959)44
Subsurface cracks introduced during cavity preparation with conventional burs may
serve as a principle source for premature restoration failure.
Geometry of cavities for ceramics must be refined and relaxed, with the simplest of
forms to increase their fracture resistance.
The transfer of distribution of stresses in an efficient manner is of equal importance to
the strength and toughness of the restorative system. Preparations for ceramics must
have smooth surfaces and rounded, smooth flowing internal and point angles.
Cuspal failure is often related to fatigue failure of the cusp, initiated from small cracks
propagating under repeated loading. Evidenced from clinical observations and
mathematical modelling.
Recognition that any inlay restoration, in particular MOD inlays weakens the
remaining tooth. Preserving the natural tooth structure, rounding of sharp line angles
and designing castings that don’t extend onto uninvolved parts of the tooth is essential.
First mention of ‘‘cracked tooth syndrome’’ and its correlation to restoration size and
postulated mechanisms for crack propagation.
Restorations not bonded to the tooth structure are most likely to fracture at the internal
line angles. Rounding of internal line angles results in reduced von Mises stress values.
Advocates rounding of all internal line angles.
Pioneering work advocating the rounding of internal line angles.
Fatigue is considered to be the principle mechanism of tooth fracture. The axiopulpal
line angle in the dentine is the site of high stress concentration, with cracks as small as
25 lm leading to failure.
Preparations for ceramics must be smooth and not have sharp line angles. Gingival
margins must be either a chamfer with a rounded gingivoaxial line angle or a rounded
shoulder.
Emphasis on rounding of internal line angles and a chamfer or rounded shoulder
finish-line for posterior ceramic restorations.
Smooth supporting surfaces and softly rounded contours reduce the degree of tensile
and bending forces.
Cavities should be prepared as conservatively as possible.
Sharp angles and knife edge prepared cusps tend to concentrate stress.
Sharp internal line angles result in increased incidence of tooth fracture.
rounding of all internal line angles, with special
emphasis on the axiopulpal line angle. Interestingly,
the stress distribution for bonded restorations is
markedly different, with peak stress values occurring
in the enamel at the site of contact with the opposing
cusp.
Couegnat et al.74 utilized structural shape optimization procedures based on FEA to derive optimized
designs for the second upper premolar. This relatively
new technique allows adaptations to be made to cavity
designs involving the build-up of material at overloaded
zones and the reduction or no build-up of material at
underloaded zones to be analysed mathematically and
displayed as a scalar function (similar to a photoelastic
image). Their results indicated that the ‘‘notches’’
which are created at internal line angles are a principle
source of stress concentration in non-bonded internal
restorations, whereas the principle source of stress for
onlays and other external restorations existed in the
restorative material itself. Rounding of all line angles
and the orientation of prepared cusps tips perpendicular to the occlusal load is recommended for the
reduction of stresses.
Arola et al. utilized FEA to analyse the stress
distribution and potential for cyclic fatigue crack
growth within Class II amalgam cavities.75 From their
results it was concluded that subsurface cracks develª 2010 Australian Dental Association
oping in the dentine along the buccal and lingual
margins during cavity preparation can significantly
reduce fatigue life and may be the principle source for
premature restoration failure. The authors opine that it
is the instruments and techniques used in tooth
preparation that must be examined closely as cracks
as small as 25 lm can lead to fracture in 25 years.
Table 4 demonstrates the findings from a number of
studies with regards to the stresses caused by sharp
internal line angles to both tooth and restoration.
CONCLUSIONS
As a result of the above analysis, it may be concluded
that the idealized inlay preparation design should have
the following dimensions in order to best achieve a
balance between the preservation of tooth structure and
strength of material: cavity depth of between 1.5 and
2 mm; isthmus cavity width of »1/3 the intercuspal
width; TOC of »20, and rounding of all internal line
angles. However, it should be borne in mind that
clinically, preparations tend to be wider and often
deeper than recommended9 and that the presence of
existing restorations and caries will often dictate
preparations much larger than ideal. Hence, the above
dimensions are ideal recommendations that may
require changes in clinical settings.
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MC Thompson et al.
REFERENCES
25. Homewood CI. Cracked tooth syndrome–incidence, clinical
findings and treatment. Aust Dent J 1998;43:217–222.
1. Magne P, Belser U. Understanding the intact tooth and the
biomimetic principle. In: Magne P, Belser U, eds. Bonded porcelain restorations in the anterior dentition – a biomimetic
approach. Chicago: Quintessence Publishing Co., 2002:23–55.
26. Malament KA, Grossman DG. The cast glass-ceramic restoration.
J Prosthet Dent 1987;57:674–683.
2. Roeters FJM. The amalgam-free dental school. J Dent 2004;32:
371–377.
28. Nadal F. Amalgam restoration: cavity preparation, condensing
and finishing. J Am Dent Assoc 1962;65:66–77.
3. Edelhoff D, Sorensen JA. Tooth structure removal associated with
various preparation designs for anterior teeth. J Prosthet Dent
2002;87:503–509.
29. Rosenstiel SF, Land MF, Fujimoto J. Contemporary fixed prosthodontics. St. Louis: Mosby Inc., 2001.
27. Malament KA. Considerations in posterior glass-ceramic restorations. Int J Perio Rest Dent 1998;4:33–49.
4. Milleding P, Örtengren U, Karlsson S. Ceramic inlay systems:
some clinical aspects. J Oral Rehabil 1995;22:571–580.
30. Watts DC, Wilson NH, Burke FJ. Indirect composite preparation
width and depth and tooth fracture resistance. Am J Dent 1995;
8:15–19.
5. Christensen G. A void in US restorative dentistry. J Am Dent
Assoc 1995;125:244–246.
31. Bergman MA. The clinical performance of ceramic inlays: a
review. Aust Dent J 1999;44:157–168.
6. Christensen G. Has tooth structure been replaced? J Am Dent
Assoc 2002;133:103–104.
32. Habekost L de V, Camacho GB, Pinto MB, Demarco FF. Fracture
resistance of premolars restored with partial ceramic restorations
and submitted to two different loading stresses. Oper Dent
2006;31:204–211.
7. Christensen G. What has happened to conservative tooth restorations? J Am Dent Assoc 2005;136:1435–1437.
8. van Dijken J, Hasselrot L, Olofsson AL. Restorations with
extensive dentin ⁄ enamel-bonded ceramic coverage. A five-year
follow-up. Eur J Oral Sci 2001;109:222–229.
9. Edelhoff D, Spiekermann H, Yildirim M. Metal-free inlay-retained
fixed partial dentures. Quintessence Int 2001;32:269–281.
10. Ritter A, Swift E. Current restorative concepts of pulp protection.
Endod Topics 2003;5:41–47.
11. Etemadi S, Smales RJ, Drummond PW, Goodhart JR. Assessment
of tooth preparation designs for posterior resin-bonded porcelain
restorations. J Oral Rehabil 1999;26:691–697.
12. Welk DA, Laswell HR. Rationale for designing cavity preparations in light of current knowledge and technology. Dent Clin
North Am 1976;20:231–239.
33. Denehy GE, Torney DL. Internal enamel reinforcement through
micromechanical bonding. J Prosthet Dent 1976;36:171–175.
34. Eakle WS. Fracture resistance of teeth restored with Class II
bonded composite resin. J Dent Res 1986;65:149–153.
35. Morin D, DeLong R, Douglas WH. Cusp reinforcement by the
acid-etch technique. J Dent Res 1984;63:1075–1078.
36. Bader JD, Shugars DA, Martin JA. Risk indicators for posterior
tooth fracture. J Am Dent Assoc 2004;135:883–892.
37. Cavel WT, Kelsey WP, Blankenau RJ. An in vivo study of cuspal
fracture. J Prosthet Dent 1985;53:38–42.
38. Christensen G. Clinical and research advancements in cast-gold
restorations. J Prosthet Dent 1971;25:62–68.
13. Arnetzl GV, Arnetzl G. Design of preparations for all-ceramic
inlay materials. Int J Comp Dent 2006;9:289–298.
39. Raigrodski A. Contemporary materials and technologies for
all-ceramic fixed partial dentures: a review of the literature.
J Prosthet Dent 2004;92:557–562.
14. Abu-Hassan MI, Abu-Hammed OA, Harrison A. Strains and
tensile stress distribution in loaded disc-shaped ceramic specimens. An FEA study. J Oral Rehabil 1998;25:490–485.
40. Joynt R, Wieczkowski G, Klockowski R, Davis E. Effects of
composite restorations on resistance to fracture in posterior teeth.
J Prosthet Dent 1987;57:431–435.
15. Banks RG. Conservative posterior ceramic restorations: a literature review. J Prosthet Dent 1990;63:619–626.
41. Larson TD, Douglas WH, Geistfeld RE. Effect of prepared cavities on the strength of teeth. Oper Dent 1981;6:2–5.
16. Ban S, Anusavice K. Influence of test method on failure stress of
brittle dental Materials. J Dent Res 1990;69:1791–1799.
42. Mondelli J, Steagall L, Ishiriama A, de Lima Navarro M, Soares
F. Fracture strength of human teeth with cavity preparations.
J Prosthet Dent 1980;43:419–422.
17. Fischer H, Weber M, Marx R. Lifetime prediction of all-ceramic
bridges by computational methods. J Dent Res 2003;82:238–242.
18. St-Georges AJ, Sturdevant JR, Swift EJ, Thompson JY. Fracture
resistance of prepared teeth restored with bonded-inlay restorations. J Prosthet Dent 2003;89:551–557.
19. Khera SC, Goel VK, Chen RC, Gurusami SA. Parameters of
MOD cavity preparations: a 3-D FEM study. Part II. Oper Dent
1991;16:42–54.
20. Lin CL, Chang CH, Wang CH, Ko CC, Lee HE. Numerical
investigation of the factors affecting interfacial stresses in an
MOD restored tooth by auto-meshed finite element method.
J Oral Rehabil 2001;28:517–525.
21. Lin CL, Chang CH, Ko CC. Multifactorial analysis of an MOD
restored human premolar using auto-mesh finite element
approach. J Oral Rehabil 2001;28:576–585.
22. Blaser PK, Lund MR, Cochran MA, Potter RH. Effect of designs
of Class II preparations on resistance of teeth to fracture. Oper
Dent 1983;8:6–10.
23. Donly KJ, Wild TW, Jensen ME. Posterior composite Class II
restorations; in vitro comparison of preparation designs and
restoration techniques. Dent Mater 1990;6:88–93.
24. Goel VK, Khera SC, Gurusami S, Chen RC. Effect of cavity
depth on stresses in a restored tooth. J Prosthet Dent 1992;67:
174–183.
126
43. Osborne JW, Gale EN. Failure at the margin of amalgams
affected by cavity width, tooth position and alloy selection.
J Dent Res 1980;60:681–685.
44. Vale WA. Cavity preparation and further thoughts on the high
speed. Br Dent J 1959;107:333–345.
45. Rosenstiel E. The taper of inlay and crown preparations. A
contribution to dental terminology. Br Dent J 1975;139:436–438.
46. Goodacre C, Campagni W, Aquilino S. Tooth preparations for
complete crowns: an art form based on scientific principles.
J Prosthet Dent 2001;85:363–376.
47. El-Ebrashi M, Craig R, Peyton F. Experimental stress analysis of
dental restorations. Part IV. The concept of parallelism of axial
walls. J Prosthet Dent 1969;22:346–353.
48. Gilboe D, Teteruck W. Fundamentals of extracoronal tooth
preparation. Part 1. Retention and resistance form. J Prosthet
Dent 2005;94:105–107.
49. Kaufman EG, Coelho DH, Colin LC. Factors influencing the
retention of cemented gold castings. J Prosthet Dent 1961;11:
487–502.
50. Nordlander J, Weir D, Stoffer W, Ochi S. The taper of clinical
preparations for fixed prosthodontics. J Prosthet Dent 1988;
60:148–151.
ª 2010 Australian Dental Association
Ceramic inlay preparation design
51. Livaditis GJ. Etched-metal resin-bonded intracoronal cast restorations. Part I: the attachment mechanism. J Prosthet Dent
1986;56:267–274.
68. Wilson A, Chan D. The relationship between preparation convergence and retention of extracoronal retainers. J Prosthodont
1994;3:74–78.
52. Shillingburg HT, Hobo S, Whitsett LO. Fundamentals of fixed
prosthodontics. 2nd edn. Chicago: Quintessence International,
1982.
69. Noonan MA. The use of photoelasticity in a study of cavity
preparations. J Dent Child 1949;16:24–28.
53. Mack PJ. A theoretical and clinical investigation into the taper
achieved on crown and inlay preparations. J Oral Rehabil 1980;
7:255–265.
54. Borges GA, Sophr AM, de Goes MF, Sobrinho LC, Chan D.
Effect of etching and airborne particle abrasion on the microstructure of different dental ceramics. J Prosthet Dent 2003;89:
479–488.
55. Qualtrough AJ, Wilson NH. A 3-year clinical evaluation of a
porcelain inlay system. J Dent 1996;24:317–323.
56. Soares CJ, Martins LR, Fonseca RB, Correr-Sobrinho L, Fernandes AJ. Influence of cavity preparation design on fracture
resistance of posterior Leucite-reinforced ceramic restorations.
J Prosthet Dent 2006;95:421–429.
57. Doyle MG, Munoz CA, Goodacre CJ, Friedlander LD, Moore BK.
The effect of tooth preparation design on the breaking strength
of Dicor crowns. Part 2. Int J Prosthodont 1990;3:241–248.
58. Eames WB, O’Neal SJ, Monteiro J, Miller C, Roan JD Jr, Cohen
KS. Techniques to improve the seating of castings. J Am Dent
Assoc 1978;96:432–443.
59. Esquivel-Upshaw J, Anusavice K, Yang M, Lee R. Fracture
resistance of all-ceramic and metal ceramic inlays. Int J Prosthodont 2001;14:109–114.
60. Gerami-Panah F, Rezaee S, Sedighpour L, Fahimi F, Ghodrati H.
Effect of taper on stress distribution of all-ceramic fixed partial
dentures: a 3D-FEA study. J Dent Tehran Uni Medical Sci
2005;2:109–115.
61. Jørgensen KD. The relationship between retention and convergence angle in cemented veneer crowns. Acta Odont Scad
1955;13:35–40.
62. Leempoel P, Lemmens L, Snoek P, van’t Hof M. The convergence
angle of tooth preparations for complete crowns. J Prosthet Dent
1987;58:414–416.
63. Owen CP. Retention and resistance in preparations for extracoronal restorations. Part 1. Practical and clinical studies. J Prosthet
Dent 1986;56:148–153.
64. Palacios R, Johnson G, Phillips K, Raigrodski A. Retention of
zirconium oxide ceramic crowns with three types of cement.
J Prosthet Dent 2006;96:104–114.
65. Parker M, Calverley M, Gardner M, Gunderson R. New guidelines for preparation taper. J Prosthodont Dent 1993;2:61–66.
66. Schwartz JR. Inlays and abutments. Brooklyn: Dental Items of
Interest Publishing Company, 1952.
67. Sobrinho CL, Consani S, Knowles JC. Effect of convergence angle
and luting agent on the fracture strength of in ceram crowns.
J Mater Sci Mater Med 1999;10:493–498.
ª 2010 Australian Dental Association
70. Mahler DB, Peyton FA. Photoelasticity as a research technique
for analysing stresses in dental structures. J Dent Res 1955;34:
831–838.
71. Haskins RC, Haack DC, Ireland RL. A study of stress pattern
variations in Class II cavity restorations as a result of different
cavity designs. J Dent Res 1954;33:757–766.
72. Johnson EW, Castaldi CR, Gau DJ, Wysocki GP. Stress pattern
variations in operatively prepared human teeth, studied
by three-dimensional photoelasticity. J Dent Res 1968;47:548–
558.
73. Theocaris PS, Gdoutos EE. Matrix theory of photoelasticity.
Springer series in optical science. Volume 11. Berlin and New
York: Springer-Verlag, 1979.
74. Couegnat G, Fok S, Cooper J, Qualtrough A. Structural optimization of dental restorations using the principle of adaptive
growth. Dent Mater 2006;22:3–12.
75. Arola D, Huang M, Sultan M. The failure of amalgam dental
restorations due to cyclic fatigue crack growth. J Mater Sci Mater
Med 1999;10:319–327.
76. Bell JG, Smith MC, de Pont JJ. Cuspal failures of MOD restored
teeth. Aust Dent J 1982;27:283–287.
77. Braly BV, Maxwell EH. Potential for tooth fracture in restorative
dentistry. J Prosthet Dent 1981;45:411–414.
78. Cameron CE. Cracked tooth syndrome. J Am Dent Assoc 1964;
68:405–411.
79. Kahler B, Kotousov A, Melkoumian N. On material choice and
fracture susceptibility of restored teeth: an asymptotic stress
analysis approach. Dent Mater 2006;22:1109–1114.
80. McDonald A. Preparation guidelines for full and partial coverage
ceramic restorations. Dent Update 2001;28:84–90.
81. Snyder DE. The cracked tooth syndrome and fractured posterior cusp. Oral Surg Oral Med Oral Pathol 1976;41:698–
704.
82. Re GJ, Norling BK, Draheim RN. Fracture strength of molars
containing three surface amalgam restorations. J Prosthet Dent
1982;47:185–187.
Address for correspondence:
Dr Mark C Thompson
Faculty of Dentistry
The University of Sydney
Sydney NSW 2006
Email: mthompson@pacific.net.au
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