The Cervical Lesion Section Brian Pelsue Joseph Petrino by mikeholy

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									                                    The Cervical Lesion

 Section 7: Brian Pelsue, Joseph Petrino, Kris Phillips, Gary Plotz, Aimee Potasek,
          Karrie Powell, Aaron Quitmeyer, Jared Rediske, Tara Regenold


                    Evidenced Based Approach to Cervical Lesions

       When using the term “cervical lesion” it becomes essential in evidence-based

dentistry to clarify the type of cervical lesion being referred to, as both the etiology and

the manifestations of cervical lesions differ depending upon the specific type. Cervical

Lesions are first characterized into one of two groups based on the etiology of the

disease: carious cervical lesion (CCL) or non-carious cervical lesion (NCCL). NCCLs are

then further divided into three categories based again on the etiology of the lesion.

NCCLs can occur mechanically (abrasion NCCL), chemically (erosion NCCL), or

physically (abfraction NCCL). According to G.V. Black’s Cavity Classification Scheme,

any lesion or prepared cavity of the gingival third of the facial and lingual surfaces of all

teeth are class V cavities. Class V lesions typically present as crescent-shaped

decalcifications and generally follow the contour of the crest of the gingiva from the

mesial to distal line angle (Hildebrandt, 2003). Initially, both CCLs and NCCLs clinically

present as a white lesion enamel decalcification in the gingival third of buccal and/or

lingual surfaces. The likelihood of the lesion progressing on to a cavitated lesion with

possible extensive destruction and even pulpal involvement, as well as the treatment of

the lesion, depends on whether the lesion is a CCL or a NCCL.




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                                 Carious Cervical Lesions

       The etiology of carious cervical lesions (CCLs) is frequent exposure to acid,

produced by specific bacteria, which metabolize fermentable carbohydrates in the diet.

Additional host factors contribute to CCLs such as increased age, low socioeconomic

status, calculus, low fluoride exposure, hyposalivation, or environmentally induced

xerostomia via medications or radiation therapy. Dental caries is an infectious disease,

which has an end stage of tissue morbidity through dissolution of mineral and collapse of

the organic matrix. Once the bacteria Streptococcus mutans has colonized the cervical

area and proliferated with the aid of the Lactobacillus species, demineralization of the

enamel and dentin surfaces to the pulp can occur. Measures can be instituted to aid in

tooth remineralization if the CCL is arrested in the white spot form. This “white spot”

lesion presents with a chalky surface and represents a lesion that is confined to enamel.

With continued exposure to risk factors and time, the lesion passes to the dentin-enamel

junction and into dentin. At this point the lesion spreads out in a “balloon” fashion and

expands rapidly. A carious cervical lesion at this stage exhibits frank cavitation. If

cavitation has occurred, the lesion must be removed, the tooth restored operatively, and

endodontics employed if pulpal involvement exists (Hildebrandt, 2003). Cases of

multiple carious cervical lesions or “rampant caries” also exist. These situations are often

caused by frequent, large amounts of soda consumption or radiation therapy and

medication induced xerostomia. Caries disease control strategies involving diet changes,

xylitol, fluoride varnish, improved hygiene, and fluoride supplementation are often

necessary to stop the rapid progression of these multiple lesions.



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                              Non-Carious Cervical Lesions

       Non-carious cervical lesions (NCCLs) vary in appearance with some displaying

shallow depressions and others broad, disk-shaped or large, wedge-shaped defects. The

floor of the lesion can be flat, indented, or sharply angled (Levitch, 1994). At the cervical

one-third of the tooth, enamel is thinner and softer, with the enamo-dentin bond weaker

because the junction is smooth and without ridges (Goel, 1991). Enamel is irregular and

has prisms that are straight and vertical on the CEJ surface, as well as areas of non-

prismatic enamel, which thus makes the cervical area more resistant to caries because it is

less soluble in acid. This may explain why NCCL occurrence is more common than

CCLs in the cervical one third (Jukic, 1999). The etiologies of NCCLs are multifactorial,

and therefore difficult to categorize into being caused by only abrasion, erosion, or

abfraction. Although non-carious cervical lesions predominate in the elderly, NCCLs in

children can also be seen as white spot lesions on the buccal or lingual surface and most

commonly on posterior teeth. Cervical lesions typically appear near the gingival crest

within the first few years following tooth eruption. Based on clinical experience it has

been found that as the adolescent matures and the gingival crest is relocated apically, the

majority of cervical lesions do not progress to cavitation, and the majority of NCCLs

occur in the posteriors. In the Backer-Dirks experiment, 72 children with cervical lesions

were followed from 8 to 15 years with results yielding: 37 remineralized, 26 unchanged,

and 9 progressed to cavitation (Menaker, 1980). Operative restoration of cervical lesions

can therefore be contraindicated until the enamel surface has collapsed and cavitation has

occurred. The prevalence of NCCLs in the permanent dentition was evaluated when

18,555 individuals were examined and placed into one of six age groups. The prevalence

                                              3
and severity of NCCLs increased with age, and the most frequent location is on the labial

side. In the permanent dentition, mandibular premolars had the greatest number of lesions

as well as the greatest severity of NCCLs, which were due to abrasion, erosion and/or

abfraction. Severity of cervical lesions is determined most often by the tooth wear index,

which defines the depth of the lesion on a scale from 1 to 4 for each dental surface

(Borcic, 2004).

       In another study, NCCLs were found to be less than 2 mm, right-angled in shape,

and having low sensitivity. The teeth with NCCLs had prevalent wear facets, and little or

no mobility. Seventy percent of NCCLs were found to be on posterior teeth, with 65% on

the maxillary, and 46% on premolars with first premolars having the highest prevalence

of NCCLs. NCCLs are strongly correlated with age, but no difference has been found

between men and women (Aw, 2002).



                   Types of Non-Carious Cervical Lesions: Abrasion

       Abrasion NCCLs (also termed toothbrush abrasion lesions or attrition) clinically

appear well circumscribed with hard, glassy walls of sclerotic dentin and angular, notch-

like or cup-shaped defects. As they progress, abrasion NCCLs deepen and induce

gingival recession with resultant root exposure. Unlike root caries, cervical abrasion

lesions do not tend to undermine adjacent enamel. Abrasion lesions may or may not be

sensitive to touch. A hypersensitive lesion, however, indicates an active lesion that is

advancing. These abrasion lesions can then be treated with desensitizing agents or

restoration. Although abrasion cervical lesions can become carious, the etiology of the

lesion is not related to dental caries and does not require dental caries control strategies.

                                              4
(Hildebrandt, 2003). Not all abrasion lesions are restored due to their proximity to the

gingival tissues, which are healthier next to an un-restored abrasion lesion than next to an

optimal composite resin. Abrasion lesions will be restored if the lesion jeopardizes the

strength of the tooth (the restoration does not strengthen the tooth but prevents further

abrasion). Also, if the abrasion lesion is near the pulp, is esthetically displeasing,

becomes carious, or is hypersensitive it will be operatively restored (Hildebrandt, 2003).



                            Experimental Evidence: Abrasion

       In an experiment of toothbrush abrasion 45% of the 533 participants had cervical

wedge-shaped defects and 51% had gingival retraction. The common etiologic factor was

that both types of lesions occurred in the same area. Also, subjects with good oral

hygiene and those who brushed more than twice a day showed a higher frequency of

abrasion lesions. Differing tooth-brushing techniques, however, did not appear to

influence the development of the lesions (Sanges, 1976). An experiment involving dental

students over a 26-month period found the average rate of abrasion to be 0.2 microns per

day. The amount of loss did not differ between “non-abrasive” dentifrice and

conventional toothpaste (Nordbo, 1982). Another study found that excessive use of

dentifrice habitually placed and undiluted on the same area of the mouth may produce

abrasion lesions. This study also reinforced that cervical abrasion is related to good

hygiene with patients exhibiting cervical abrasions having less plaque and lower bleeding

scores than those without abrasion lesions. Young age and gingival recession were also

found to be factors of cervical abrasion (Radentz, 1976). However, in assessing a tooth

wear index on 586 adults 45 years and older, increasing tooth wear with increasing age

                                              5
was found for facial and lingual cervical surfaces. Greater tooth wear was found among

men more than women, with no significant variation between subjects of different social

class backgrounds (Donachie, 1995). Additionally, in an experiment with 250 subjects

aged 21-60, both prevalence and severity of abrasion cervical lesions increased with age.

Abrasion lesions also increased significantly with calculus index, frequency of

periodontal pockets, and reduction of the alveolar bone height. From this study, no

significant associations could be formed between abrasion and oral hygiene factors,

showing that cervical abrasion lesions are most likely related to tooth brushing but are not

related to periodontal health (Bergstrom, 1988).



                    Types of Non-Carious Cervical Lesions: Erosion

       Dental erosion can be defined as “the physical result of a pathologic, chronic,

localized loss of dental hard tissue that is chemically etched away from the tooth surface

by acid and/or chelation without bacterial involvement” (Huysmans, 2000). The critical

pH of enamel is 5.5, so essentially any solution with a lower pH that is applied frequently

and for a long duration will cause erosive NCCLs. Erosion lesions are not related to

dental caries, as the etiology of the two is different. Erosion NCCLs are caused by

intrinsic acidic chemicals, either from the stomach in the form of acid reflux disease,

regurgitation, or bulimia nervosa, or from the diet via acidic foods like citrus fruits and

acidic soft drinks. Frequent consumption of acidic, diet (sugar free) soda will not cause

cervical carious lesions but can cause cervical erosive lesions (Hildebrandt, 2003).

Erosion lesions differ from abrasion lesions in that they involve large areas of the tooth,

and are hard, smooth, and poorly demarcated with thin, polished enamel. Restorations on

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teeth with erosive lesions tend to stand out in bold relief as the tooth surrounding the

restoration has been dissolved. Microscopically, erosive lesions appear as a honeycomb

as they involve prismatic enamel which is a demineralization pattern where either the

prism core or interprismatic areas dissolve. Peritubular dentin will respond to erosive

trauma with the dentinal tubules becoming enlarged with eventual disruption in the

intertubular areas. Sensitivity will occur if progression is rapid, while with slower

progression, a patient may be asymptomatic (Meurman, 1996). Erosion lesions caused by

stomach acids tend to be found on the occlusal surfaces of posterior teeth and the lingual

surfaces of all maxillary teeth. If diet is the cause, lesions will remain on the facial

surfaces of anterior teeth. Generally, removing the causative agent treats erosion lesions.

If teeth are hypersensitive, a desensitizing agent can be used. For more aggressive erosion

lesions, operative restorations or endodontics may be required (Hildebrandt, 2003).



                             Experimental Evidence: Erosion

        Many herbal teas have been found to be even more erosive than orange juice

(Phelan, 2003). Several studies have been conducted to determine prevention and

influence of fluoride and xylitol on erosion lesions. An in vitro study evaluated the effect

of fluoride varnish 2.26% applied 24 hours then immersed in cola pH 2.6. The results

showed treatment of enamel with topical fluoride prior to acidic challenge caused an

increase in enamel hardness and inhibition of softening which was statistically significant

(Sorvari, 1994). Another study attempted to add fluoride to acidic drinks to make them

less erosive on enamel: 645mg of solid calcium fluoride was suspended in soda and

orange juice per liter of drink. All the teeth exposed to the solutions developed erosive

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lesions. It was determined that acidic drinks are capable of dissolving large amounts of

calcium fluoride limiting the erosive-prevention effect of even high concentrations of

fluoride (Larsen, 2001). An additional study observing the effect of xylitol, fluoride, and

xylitol/fluoride combined on the erosion of enamel by acidic juices determined mineral

loss was significantly lower for xylitol/fluoride combined only when compared with pure

orange juice (Amaechi, 1997). A study comparing enamel erosion of a new sports drink

with that of water (negative control), drink with calcium, and a positive control found that

adding calcium with appropriate pH adjustment markedly reduces erosive potential. The

study involved 21 subjects with enamel loss determined at days 5, 10, and 15. The

positive control produced significantly more erosion than the sports drink at all three

points with very little erosion occurring with the sports drink, drink with calcium, and

negative control drinks (Hooper, 2004).

       The etiology of cervical erosion is vast, and an increasing awareness of the

prevalence of erosive lesions has lead to further studies in etiology and prevention. A 6-

year study involving two age groups (26-30 and 46-50 years) evaluated progression and

risk factors for erosion lesions. Progression of erosion on facial and occlusal surfaces was

found as well as wedge-shaped defects. The progression correlated with age,

consumption of dietary acids, and frequency of tooth brushing (Lussi, 2000). In an

evaluation of the progression of tooth erosion in adolescents 161 children (12.3%)

between the ages of 12 and 14 developed erosive lesions, while 351 children (26.8%)

developed new or more advanced lesions. The study also found that being male, white,

and socially deprived had a significant association with erosion progression (Dugmore,



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2003). In addition, the susceptibility of deciduous and permanent enamel to erosion has

not been found to differ (Lippert, 2004).



                          Relationship of Abrasion and Erosion

       The etiology of cervical abrasion may not be due to tooth brushing alone.

Additionally, the site specificity of cervical erosion can be influenced through cervical

abrasion. In vivo clinical investigation of the influence of constant shear forces of the oral

soft tissues against teeth demineralized by an erosive environment, has shown softened

enamel lesions exposed to abrasion by the tongue and food during mastication lose more

minerals and further abrade resulting in abraded enamel lesions. Demineralized, softened

enamel lesions that were protected from soft tissue abrasion gained more minerals from

saliva remineralization and remained as intact lesions. Soft tissue abrasion in an erosive

environment may explain the site-specificity of erosion on the palatal surfaces of upper

teeth and occlusal surfaces of molar teeth where these surfaces are constantly subjected to

shear forces from the tongue during speech, palatal surfaces during swallowing, and food

mastication (Amaechi, 2003). Another experiment theorizing that the sites of dental

erosion are saliva-dependent found the most common site of cervical lesions to be the

facial of maxillary incisors (36% of sites) and the least common site to be the lingual of

mandibular molars (1.7%). Serous saliva has a protective role and is also essential in the

formation of the salivary pellicle, which is site specific for lingual surfaces of mandibular

teeth (Young, 2002).




                                              9
                  Types of Non-Carious Cervical Lesions: Abfraction

       Historically, abfraction NCCLs were associated with abrasion lesions and thought

to be caused by tooth brushing. Both abfraction and abrasion lesions present as well

circumscribed lesions with hard, glassy walls of sclerotic dentin and angular, notch-like

or cup-shaped defects. Abfraction NCCLs today, however, are associated with tooth

flexure caused by occlusal loading. Abfraction is thus caused by a large quantity of

tensile and compressive stress concentrated in the cervical area, which releases mineral

crystals from enamel, and then dentin. A small crack in enamel develops and expands

into a larger lesion through continued forces concentrated in the area. If a slightly oblique

force is applied, the fulcrum will be near the cemento-enamel junction. Thus, abfraction

cervical lesions are determined by the orientation of occlusal forces and the position of

supporting alveolar bone. (Miller, 2003). Abfraction lesions are deeper, narrower and

more v-shaped than abrasion lesions.



                          Experimental Evidence: Abfraction

       An experiment to further distinguish abfraction from abrasion lesions found

clinical signs of excessive brushing were lacking in the 61 observed abfraction lesions.

Occlusal force disturbances, however, were very consistent with the presence of

abfractions with 94.5% of abfractions associated with occlusal wear facets. Additionally,

in 77.2% of the abfractions, there was lack of canine disocclusion. To further disassociate

tooth brushing from abfraction lesions, 32.5% of the apical limits of the abfractions are

subgingival. Other etiological factors included a 40.1% correlation of abfractions with

plaque, 41.7% with calculus, and 20.4% with periodontitis. Ulceration of the gingiva

                                             10
(1.6% correlation), mobility (1.9%), and bruxism (10%) did not coincide often with

abfraction cervical lesions. Thus, teeth that loosen under occlusal loading and present a

widening of the periodontal ligament space do not present with abfractions. For these

lesions to develop, a fulcrum must be present and fulcrums can only be formed on stable

teeth (Miller, 2003). An additional study further supported the correlation of cervical

abfraction and occlusal wear, finding that the correlation between occlusal and cervical

volume loss was strong and significant (Pintado, 2000). Thus, crown flexure may cause

micro-cracking under tensile stress that leads to a loss in enamel and dentin in the

cervical area. Diagnostic criteria could be determined for susceptibility, and prevention

would be possible via enamelplasty (Pintado, 2000). High occlusal stresses were found to

disrupt bonds between hydroxyapatite crystals, causing the loss of cervical enamel (Rees,

2000). Furthermore, a review of literature of angular lesions implicated occlusal stress as

a critical component in the multifactorial etiology of cervical lesions (Spranger, 1995). If

occlusal loading is a primary etiology factor for cervical abfractions, the clinical

significance is that management of the occlusion becomes an important part of the

abfractive patient’s treatment plan (Rees, 2003).

       A different study, however, found contrary results. The study found that

continuous axially loaded teeth exhibited significantly less tooth wear possibly due to

compression effects, which may deform and shorten the tooth, increasing its bucco-

lingual diameter, and thus increasing the density of the tooth to make it less susceptible to

abfraction. Furthermore, non-axial loads were found to not significantly alter the size and

shape of cervical lesions. Upon further investigation, it was concluded that the degree of

tooth mineralization among individuals may be an important factor in the multifactorial

                                             11
etiology of tooth abfraction and may account for the variation in findings (Litonjua,

2004). A different study found strain to be concentrated near the CEJ regardless of load

direction. The character, direction, and magnitude of strain on the cervical third of the

tooth depend upon the pattern of loading. Oblique occlusal forces cause an asymmetric

pattern of strain in buccal cervical enamel that is consistent with abfraction cervical

lesions (Palamara, 2000). In an attempt to distinguish abfraction lesions from abrasion

lesions, 1,012 tooth sites with NCCL typical wedge-shaped defects were examined and

scored using the tooth wear index (designed by Smith & Knight, 1984) and the patients

interviewed as to the history of the lesions. Based on established clinical features and

histories, one-third of the NCCLs (37.7%) had occlusal wear facets, sharp margins

(which are thought to be characteristic of abfraction), and were found to be due to

abfraction. Two-thirds (62.3%) had no occlusal wear facets, and were found to be

abrasion lesions (Oginni, 2003).

       Further, etiology in the multifactorial causes of cervical abfraction lesions is

numerous. It has been found that the weakening effect of cavity preparation can

contribute to the development of abfractions by weakening tooth structure, allowing more

cuspal movement under occlusal load to the point that peak tensile and shear stresses in

the buccal cervical area were in excess of known enamel stress fracture limits (Rees,

1998). An additional study evaluated how different types of restorations affected fracture

resistance strength. Amalgam restorations were found to have a weakening effect on

fracture resistance, while composite restorations had an increase in fracture resistance due

to the adhesive compressive forces. Traumatic stress reduced fracture resistance by 85%

depending upon the degree of trauma. The same study placed impact stress on individual

                                             12
teeth, and also found the maxillary premolars and canines had the highest resistance to

fracture, which was also found to correlate with root length (Schatz, 2001). Stress profiles

of teeth were conducted to find which tooth had the greatest amount of horizontal stress

applied 1.1 mm above the CEJ. The maxillary incisor had 176.4 MPa of stress regularly

placed on it, maxillary premolar had 57.8 MPa, and the canine had 3.4 MPa of stress. The

buccal of maxillary incisors were found to have the greatest percentage of abfraction

lesions, which correlates with the larger amount of stress, placed on them at the cervical

area. This data also supports that the canines are the most fracture resistant of the

maxillary teeth (Rees, 2003).



                  Conclusions Regarding Etiology of Cervical Lesions

       Carious cervical lesions typically have a unifactorial etiology (bacteria) and non-

carious cervical lesions have a multifactorial etiology (abrasion, erosion and abfraction).

Carious or non-carious cervical lesion etiologies, though, rarely occur alone. This can be

attributed to the abundance and complexity of risk factors associated with cervical

lesions. In order to diagnose and treat these lesions, it is imperative to investigate and

assess all relevant risk factors before a determination is made concerning the etiology of

the intraoral process that is occurring.



                                Restoring Cervical Lesions

       In restoring cervical lesions, one must consider the various treatment modalities,

particularly with regard to carious versus non-carious cervical lesions. Preoperative

considerations include "preventive measures such as fluoride therapy, iontophoresis,

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brushing with desensitizing dentifrices, professional application of potassium oxalate or

other tubule-occluding agents, application of dentin adhesives, occlusal adjustments,

dietary instruction, tooth brushing and oral hygiene instruction, discontinuation of poor

oral habits, and occlusal guard fabrication” (Terry et. al., 2003). Restorative therapies

may require an interdisciplinary approach, and treatments may include periodontal plastic

surgery, orthodontic measures, and operative procedures. Periodontal surgeries may

involve free autogenous mucosal grafts, subepithelial connective tissue grafts, coronally

advanced flap technique, guided periodontal tissue regeneration, and enamel matrix

derivative grafts. Restorative procedures may include use of such materials as amalgam,

conventional glass ionomers, resin-modified glass ionomers, compomers, flowable

composites, microfill composites, lab-processed composite and porcelain veneers, lab-

processed inlays and crowns, and porcelain-fused-to-metal crowns and bridges.

Orthodontically, therapies may involve up-righting, intrusion, rotation, extrusion,

restoration of a functional occlusion, and space closure (Terry et. al., 2003).

       A carious cervical lesion requires restoring the damaged tooth structure. This

approach necessitates a lesion specific cavity preparation as well as dental disease control

to stop the disease process. A non-carious cervical lesion, in contrast, may result not from

dental disease but rather, poor occlusion or dental compression to an area of the dentition.

Posterior teeth are more likely to exhibit this type of non-carious lesion because of the

great amount of occlusal and lateral forces to which they are subjected (Tar, 2002). The

treatment for this type of cervical lesion could be as simple as making an occlusal

adjustment to the area that is causing the abfraction.

       Treatment of a carious cervical lesion involves removing the damaged tooth

                                             14
structure and replacing it with a metallic or nonmetallic filling material. Metallic

restorations such as gold foils and amalgams are more likely to be used in posterior teeth

because of esthetic concerns. In the esthetic zones, the materials of choice are

conventional glass ionomers, resin modified glass ionomers, compomers, flowable

composites, and micro- and nano-filled composite materials. The use of glass ionomers is

less frequent in anterior regions of the mouth because of its opacity. However, in cases

where patients have problems with xerostomia or have had head and neck radiation, glass

ionomers are the material of choice because of the added fluoride leaching benefit. In

cases where dry mouth is not a concern, composite materials are often the better choice

because of their translucent characteristics.

       The traditional lesion-specific modality of restoring defective tooth structure in

cervical lesions requires a number of steps. The typical procedure requires cleaning the

surface, roughening it to encourage micromechanical bonding, and applying the adhesive

agent. To roughen the surface, a conditioner is applied. The conditioner of choice is

called etchant (H3PO4) and is applied to the affected area and left in place for 10

seconds. The effects of the conditioner is that it removes the smear layer, opens and

widens dentinal tubules, and demineralizes intertubular dentin. Next, the conditioner is

removed with a thorough rinsing of water and dried but not desiccated. Next, the primer

is applied to the conditioned dentin and left in situ. Primer may require the use of visual

light-cure polymerization in its attempt to bond to dentin and the adhesive resin of

choice. Finally, the adhesive is applied to the conditioned dentin. Commercial brands of

this type of system include All Bond 2, AmalgamBond Plus, and Optibond Fl to name a

few. These types of systems have evolved and currently are not used as often anymore.

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       Currently, there are two general philosophies of how to prepare the tooth of

interest before applying the material of choice. These include the total-etch technique and

the self-etch technique. The total-etch technique endeavors to remove the smear layer

completely by acid etching and rinsing as described above. The self-etch technique

integrates the smear layer as a bonding substrate. There are two types of total etch. The

first type, described above, led to the second type, which combined the primer and

adhesive in a single step. Commercial brand names of this system include Easy Bond,

One Step, Excite, etc. The self-etching techniques are two-fold. The first requires the use

of a self-etching primer which etches through the smear layer and beyond. Current

examples of this type of system include Clearfil SE Bond and Mac-Bond II. The newest

varieties combine all four steps into one, and examples of this are One-up bond F and

Prompt L-Pop.

       The application of the above products, however, is only as good as the technician

placing them. The key to restoring the cervical lesion is that each step is conducted in a

well-isolated area. The soft tissues must be reflected and no saliva or blood must

penetrate into the treatment area. Isolation can be achieved by the use of a retraction cord

placed in the sulcus to reflect the soft tissues, or a retractor clamp such as a 212 or S

clamp can be utilized in conjunction with a rubber dam.

       Terry et. al. point out that the "tooth flexure theory" can affect selection of a

particular restorative material for a cervical lesion. They note that "occlusal forces are

transmitted through the cusp and can become concentrated in the cervical region of the

tooth" (Terry et. al., 2003). This affects selection of the restorative material because a low

modulus of elasticity can absorb transferred energy from the occlusal surface, and

                                              16
composites with this property thus lower the transmission to the dentin-restorative

interface. For example, microfill and flowable composites have this lower modulus of

elasticity when compared with conventional and hybrid composite resins. Also, some

adhesives can add an intermediate elastic layer between the dentin and the restorative

material, further absorbing flexural deformation.

       Outlined below are five distinct groups typically used as restorative materials for

cervical lesions. The first four materials – conventional glass ionomers, resin-modified

glass ionomers, compomers, and resin composites – are useful esthetically. The fifth

material, amalgam, is regarded as a non-esthetic restorative material.

       Resin composites harden via a polymerization reaction and are considered the

toughest of the tooth-colored materials available. A wide range of resin composites are

available and vary according to the inert organic filler content. These include microfill,

flowable, hybrid. and compactable. Composites are generally defined as a mix of acrylic

and submicron glass filler. The resulting restoration is self- or light-cured and can be used

for esthetic restorations and veneers. When properly bonded to the tooth structure, micro-

leakage tends to be quite low. Clinically, this material tends to be moderately resistant to

fracture in high-load restorations and moderately resistant to wear. Composites provide

an optimal esthetic result for both carious and non-carious cervical lesions due to the

bond provided by dentin adhesive systems, and are quite useful "when fluoride is not a

consideration" (Terry et. al., 2003)

       The conventional glass ionomer restorative materials were first used in the early

1970s. The glass ionomers set via an acid-base reaction and contain a reactive inorganic

filler that has the added characteristic of leaching fluoride. This type of material,

                                              17
however, is brittle and the weakest of all the types of tooth-colored materials with respect

to mechanical properties. Advantages include biocompatibility, adhesion to tooth

structure, and ability to release, absorb, and re-release fluoride. (Burgess et. al., 2004) In

addition, Burgess points out that little leakage occurs because glass ionomer materials

have a coefficient of thermal expansion that is similar to tooth structure; thus, minimal

shrinkage occurs with setting. Disadvantages of the conventional glass ionomer include

the facts that "they are brittle, have poor wear resistance (especially in occlusal load-

bearing areas), and are technique-sensitive mainly due to their slow setting reaction"

(Burgess, 2004). While these materials are indicated for unprepared Class V non-carious

cervical lesions and prepared Class V and III lesions in high caries risk patients, they are

used less frequently today due to technique sensitivity and the availability of better

materials. In addition, they can cause "sensitivity to moisture during initial set, lengthy

setting time, which requires a second appointment for finishing and polishing, rough

surface texture, lack of translucency, and susceptibility to dehydration" (Terry et. al.,

2003).

         Resin-modified glass ionomers, also known as RMGIs, were developed as hybrids

of the conventional glass ionomer in an attempt to improve properties and handling.

These materials have such positive attributes as fluoride-release, as well as the same

recharge capability of the conventional glass ionomer. Additional benefits of RMGIs are

their higher early strength, improved resistance to fracture, and improved bonding to

tooth structure when compared with conventional glass ionomers (Burgess, 2004). They

also have the capability of immediate finishing, improved shade matching and

translucency, polishability, reduced water sensitivity, and potential for increased wear

                                              18
resistance and retention (Terry et. al., 2003). Traditionally, RMGIs have been used in

small, non-load bearing restorations, and as cavity liners and cements for crowns and

bridges (Lapinski, 2004). These RMGIs are light-activated materials that are set by an

acid-base reaction and by a methacrylate polymerization reaction (Terry, et. al., 2003).

       Compomers are, as the name suggests, a restorative material that actually blends

components of glass ionomer with resin-based composite. By incorporating filler

particles of glass ionomer into the resin monomer, a single paste light-cured material with

moderate fluoride release is produced. Compomers are poly-acid modified resin

composites which are composites with some unset constituents of glass-ionomer and are

offered in a less viscous, flowable version. This material differs from glass ionomer in

that it does not contain water, and mimics resin-based composite in handling and curing

properties (Burgess, 2004). Compomers are generally regarded as weaker materials than

resin composites.

       Another material long used for restoring cervical lesions is amalgam. This

material obviously differs from those listed above in that it is generally regarded as non-

esthetic since it does not mimic the appearance of the natural dentition. Dental amalgam

can generally be described as a mix of silver alloy powder and mercury. When these

components are combined, they can be condensed into a preparation where they will form

a solid, metal filling. This material is advantageous in that it is inexpensive, easy to use,

generally well tolerated from a biocompatibility standpoint, and has good strength in

large, high-load restorations (Lapinski, 2004). As noted above, an obvious disadvantage

of amalgam is that its shiny, silver appearance tends to make it esthetically unappealing.

Additionally, an amalgam preparation requires removal of a fairly large amount of tooth

                                              19
structure to attain adequate thickness for retention.



                          An Overview of the Clinical Evidence

Some Clinical Results

       Numerous studies conducted over the years have analyzed the efficacy and

success of these various restorative materials. Burgess et. al. compared the use of

conventional glass ionomer, resin-modified glass ionomer, compomer, and resin-based

composite in Class V restorations over a three-year period. Specifically, this study

analyzed Fuji II LC Improved (an RMGI), Dyract AP (a compomer), and Pertac III and

Synergy (both composites). They analyzed marginal discoloration, anatomic form,

surface texture, secondary caries, retention, and marginal adaptation. Their analysis

showed that overall, most of the restorations functioned well over the three years.

Comparatively, however, the Fuji II LC Improved and Pertac III were considerably

rougher than the other tested materials. The marginal adaptation of Pertac III was

determined to be much poorer than the other materials (this was attributed to the bonding

system used). Other comparisons were not deemed significant.

       A similar study evaluated various tooth-colored restorative materials in non-

carious cervical lesions over an 18-month period (Neo et. al., 1996). Eighty-three teeth

with buccal abrasion lesions were restored with a glass ionomer, a RMGI, and two resin

composites. Their analysis indicated that the glass ionomer (Fuji II Cap) had the worst

color match at baseline and at 18 months. In contrast, the RMGI (Fuji II LC) and the

resin composites had a good color match (the RMGI color match was, in fact, quite

comparable with the resin composites). The authors reported that generally, all of the

                                             20
materials presented with some marginal staining at recall, but this staining was only

statistically significant for lesions restored with one of the resin composites (APH).

Anatomically, all restorations were stable at baseline and there did not appear to be a

difference between the materials. Numerous restorations for all four of the materials lost

some degree of marginal integrity. Of the 83 restorations placed at baseline, a total of

eight were dislodged at 18 months. The resin composite (Lite Fil II) exhibited a fairly

high loss, while only one Fuji II LC restoration was lost. Restorations filled with APH

and Fuji II Cap remained intact. While this study found excellent results clinically for the

RMGIs, the authors note that the small sample size and short time of study limit the

ability to draw definite conclusions of material performance and success.

       Abdalla et. al. (1997) evaluated the two-year clinical performance of two resin-

modified glass ionomers (Fuji II LC Improved and Vitremer) and two polyacid-modified

resin composites (Dyract and Compoglass) in carious Class V lesions. Table 1, shown

below, illustrates the comparative findings of color match, anatomic form, marginal

adaptation, and cavosurface discoloration over the two years. The authors point out that

studies evaluating the clinical performance of restorative materials in abrasive Class V

lesions cannot be interpreted for carious Class V lesions since "restorations of abrasion or

erosion lesions are subjected to continued loss of tooth structure or the occurrence of

small fracture of the materials at the margin."




                                             21
      Table 1:


                                                Color
                                                Matc                     Anatomi
                                                 h                        c form
Material
                          N      A     B    C            A    B     C                A     B     C
                                                         3
Compoglass       1 year   30     30    0    0            0    0     0                30    1     0
                 2                                       2
                 years    28     28    0    0            8    0     0                28    0     0
                                                         2
Dyract           1 year   29     29    0    0            9    0     0                28    1     0
                 2                                       2
                 years    29     28    1    0            9    0     0                27    2     0
                                                         2
Fuji II LC       1 year   29     27    2    0            7    2     0                28    1     0
                 2                                       2
                 years    28     27    1    0            6    2     0                26    2     0
                                                         2
Vitremer         1 year   30     25    5    0            9    1     0                30    0     0
                 2                                       2
                 years    29     21    8    0            6    3     0                27    2     0

Table 1
N: Number of restorations      A: Alpha    B: Bravo C: Charlie



             As summarized by the numerical results above, Abdalla et. al. conclude that

      RMGI materials have a somewhat inferior performance when compared with the tested

      composite resins, particularly with regard to color stability. Incremental curing of the

      resin composite may minimize polymerization shrinkage (and thus minimize marginal

      discoloration and microleakage). Resin-modified glass ionomers, in contrast, are placed

      in one increment due to their handling characteristics. This difference in application may

      result in greater polymerization shrinkage of the RMGI material, leading to increased

      microleakage and contributing to discoloration over time.

                                                   22
           Similarly, the issue of microleakage of cervical lesions restored with resin-

modified glass ionomer and compomer restorations was explored by Toledano et. al.

(1999). In contrast to the results obtained by Abdalla et. al., this study found that resin-

modified glass ionomers showed less or similar microleakage than the polyacid-modified

composite resins that were tested. According to the study's authors, however, the Dyract

composite material tested was placed in one increment. Additionally, Toledano et. al.

used a relatively small sample of 30 non-carious molar teeth. Also, the time frame of this

particular study was one year, which is a considerably shorter amount of time than used

by some of the others (Abdalla, for example, followed the restorations with a two-year

recall).

           Chinelatti et. al. (2004) described a study looking at two different polyacid-

modified resin composites (F2000 and Freedom), and one resin modified glass ionomer

(Vitremer) in 87 different Class V restorations. Each material was tested in 29

restorations and judged based on color match, marginal discoloration, presence of caries,

anatomical form, marginal integrity, and surface texture. The results after a one-year

follow up indicated that the resin modified glass ionomer (F2000) showed the most

acceptable overall clinical performance for the above criteria. However, the RMGI had

more visible wear than the polyacid-modified resin composites.

           Folwaczny et. al. (2000) examined the clinical condition of cervical fillings after

24 months. The restorations were placed on incisors, canines, and premolars in 37

different patients. Sixty-nine of the restorations were placed on non-carious lesions, 57

restorations were placed on primary carious lesions, and 71 restorations were placed on

replacement of deficient restorations. Materials placed included composite (Tetric),

                                                23
compomer (Dyract), and resin modified glass ionomer cement (Fuji II LC and Photac-

Fil). The restorations were evaluated on the basis of color, stability, anatomical form,

surface texture, marginal integrity, marginal discoloration, and loss of filling. After the

24-month period, the composite restorations displayed superior results. The compomer

fillings performed just slightly lower than the composite restorations based on the above

criteria, whereas the RMGI restorations were rated clinically non-acceptable in at least

one or more of the criteria.

       A separate clinical study comparing cervical lesions restored with resin-modified

glass ionomer and polyacid-modified composite resin was conducted by Brackett et. al.

(1999). The purpose of this study was to evaluate clinical performance of these materials

over a one year span, and 34 pairs of restorations were placed in 31 patients using non-

carious erosion/abfraction lesions on the facial surface, restored without preparation. The

results of this study were favorable for both materials; nevertheless, the resin-modified

glass ionomer came out ahead in every category (tested categories included retention,

color match, marginal discoloration, secondary caries, anatomic form, and marginal

adaptation). Not surprisingly, the authors of this study determined RMGI to be the

superior restorative material when tested against a compomer. They do note, however,

that the poorer performance of the compomer may have been related to the isolation

method (cotton rolls rather than a rubber dam to lessen the need for local anesthesia and

to lessen trauma to the patients' gingival tissues).

       In fact, proper restoration of a cervical lesion – regardless of the esthetic material

used – is quite technique sensitive given the proximity of the gingiva and potential

problems with visibility when tissues encroach upon the lesion, and may likely factor into

                                              24
the results of any of the above studies. Chan and Adkins (2003) describe an atraumatic

approach for restoring difficult cervical lesions using resin-modified glass ionomer and

illustrate their technique with a carious cervical lesion on #25 in a 69 year-old woman.

Isolation was achieved with a cord-retained rubber dam placed around a 212 retainer.

Facial gingival tissue was then released with a blunt instrument to minimize tearing and

to allow the clamp to be placed on sound tooth structure below the lesion. (Alternatively,

the authors' note that the tissue could be excised with a #15 Bard Parker blade or

electrosurgery). A #1 band was then used to seal the margins while simultaneously

leaving room for access. Blocking resin was then injected onto the outside of the band

and the facial for the adjacent teeth and light-cured for added stability. The operator then

conditioned and filled the preparation with RMGI as usual.

       McComb et. al. (2002) compared the clinical outcomes of conventional glass

ionomer, RMGI, and composite resin restorations of cervical caries in head and neck

radiation patients suffering from xerostomia. Their study was based around the

controversy as to "whether there is less secondary caries at the margins of glass ionomer

restorations compared with other materials that do not release fluoride" McComb et. al.

(2002). Their findings indicated that secondary caries for glass ionomer and RMGI

compared with composite were reductions in excess of 80 percent in xerostomic patients

not using topical fluoride supplementation.



The Final Restoration

       When choosing a particular restorative material, it is quite important to consider

the needs of the individual patient. As noted by McComb et. al., xerostomic patients can

                                              25
benefit significantly from additional fluoride. However, the type of lesion may also play a

role in selection of restorative material.

         Terry et. al. indicates that non-carious abfraction lesions may be caused by

deflective occlusal contacts. Stress and flexing may cause loss of tooth structure in the

cervical area. In this situation, we can recall the "tooth flexure theory," in which

composites with a low modulus of elasticity (e.g., microfill and flowable) may be the

optimal restorative material.

         In addition, situations requiring optimal esthetics (all other factors excluded) can

generally be best restored with composite resin based on the general properties of this

material. Fine filler sizes, shape, orientation, and concentration create better polishing

characteristics in the small-particle hybrid and microhybrid composites (Terry et. al.,

2003).



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