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MINISTRY OF EDUCATION Univeristy of Medicine and Pharmacy of Craiova

DOCTORAL SCHOOL

NON-CARIOUS CERVICAL LESIONS –

ETIOPATHOGENIC ASPECTS

DOCTORAL THESIS

ABSTRACT

PhD Supervisor:

PROF. UNIV. DR. VERONICA MERCUŢ

PhD Student:

CAZAN (STĂNUŞI) ANDREEA

CRAIOVA

2021

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CONTENT

INTRODUCTION......................................................................................................5

CURRENT STATE OF KNOWLEDGE

1. Non-carious cervical lesions ..................................................................................5

2. Etiopathogenesis of non-carious cervical lesions...................................................5

3. Treatment of non-carious cervical lesions..............................................................5

PERSONAL CONTRIBUTION

4. Working hypothesis and general objectives............................................................6

5. Statistic study regarding the level of knowledge of non-carious cervical lesions

amongst dental practitioners.......................................................................................6

6. Highlighting the effects of occlusal forces using finite element

analysis.......................................................................................................................7

7. Highlighting the effect of stress in the cervical area of teeth using OCT..............9

8. General discussions..............................................................................................11

9. General conclusions..............................................................................................12

10. Originality and innovative character...................................................................13

SELECTIVE REFERENCES...................................................................................14

Key words: non-carious cervical lesions, tooth wear, abfraction, stress, occlusal

forces.

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INTRODUCTION

As the prevalence of non-carious cervical lesions (NCCL) grew and

specialists became aware of their importance, more studies regarding the etiology of

these lesions were conducted and published in literature, but until today a consensus

in this matter has not been accomplished.

CURRENT STATE OF KNOWLEDGE

The first section of this doctoral thesis is divided in three chapters and

presents a synthesis on terminology, classification and prevalence of non-carious

cervical lesions, following the analysis of representative national and international

publications.

Chapter 1. Non-carious cervical lesions – represent the irreversible

loss of tooth structure at the cement-enamel junction, as a result of physical and

chemical factors, not related to extreme trauma and caries [1]. These lesions were

classified according to the etiopathogenic mechanism in: abrasion, erosion and

abfraction [1]. The prevalence of NCCL varies between 5% and 85% [2].

Chapter 2. Etiopathogenesis of non-carious cervical lesions – The

etiology of NCCL is a subject widely discussed in literature. The identification of

causal factors and their degree of involvement is a controversial topic, but there is

sufficient evidence for the multifactorial etiology of non-carious cervical lesions

which includes: stress, friction and biocorrosion [2].

Chapter 3. Treatment of non-carious cervical lesions - The

treatment of non-carious cervical lesions does not refer strictly to the restoration of

lost dental tissues, but also to the identification of etiological factors and risk factors

[3]. Although several strategies have been proposed for the management of non-

carious cervical lesions, treatment plans applied by dentists vary greatly, most likely

due to lack of knowledge of the etiopathogenesis and prognosis of these lesions with

/ without treatment [4].

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PERSONAL CONTRIBUTION

The second section of this doctoral thesis consists of 3 studies.

Chapter 4: Working hypothesis and general objectives.

The working hypothesis of this scientific research started from the premise

that understanding the etiopathogenic mechanisms involved in the occurrence of

NCCL is particularly important for proper prevention and treatment. Among the

etiological factors studied over time, the role of occlusal factors enjoys special

attention and is a topic of interest for clinical and laboratory studies [5, 6].

The main objective of this research is to establish the role of excessive

occlusal forces in the pathogenesis of NCCL. Also, the research aimed to establish

the opportunity of this topic by assessing the knowledge of dentists in Romania in

this field.

Chapter 5: Statistic study regarding the level of knowledge of

non-carious cervical lesions amongst dental practitioners

The objective of this study was to determine the level of knowledge of non-

carious cervical lesions amongst dental practitioners from Romania.

Material and method. We created an electronic questionnaire, designed in

Google Forms. The questionnaire included 16 questions regarding the participant's

level of knowledge about non-carious cervical lesions.

Results and discussion. The questionnaire was completed by 253

practitioners. Of these, 96.84% answered that they feel competent in recognizing the

clinical signs of dental wear, 95.26% answered that they feel competent in discussing

dental wear with their patients, and 75.49% answered that they feel competent in

treating dental wear. The results obtained in our study are similar to those obtained

by Erickson in 2013 [7], and to those obtained by Hermont in 2011 [8].

When asked about the recognition of clinical forms of dental wear, most

participants provided correct answers: erosion (73.5%), attrition (82.2%), abrasion

(89.7%), abrasion (66.4%). However, overall, only 18.18% simultaneously correctly

identified the four clinical forms of wear. Also, 42.3% of the participants stated that

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bruxism is a clinical form of dental wear, without knowing that this parafunction is

actually involved in the etiology of the condition in question [2].

When asked about the definition of abfraction, 66.4% of the participants

answered correctly. A similar question existed to assess the level of knowledge of

the NCCL definition, but in this case, the correct answers were in a significantly

higher percentage (83%).

Regarding the use of diet analysis as a preventive method, 36.8% of

participants stated that they did not apply it to any patient in 2019. Similar results

were obtained by Erickson in 2013 [7] and Mulic in 2012 [9]. Regarding the

materials used for the restorative treatment of these lesions, the participants stated

that they most frequently use the flowable composite.

Chapter 6: Highlighting the effects of occlusal forces using

finite element analysis

3D finite element analysis (FEA) is an effective method for simulating the

distribution of stress in various materials due to their overload and has proven to be

useful in assessing the distribution of stress in dental structures.

The proposed study aimed to highlight and evaluate stress in a virtual model

of premolar one superior as intact and with various forms of occlusal wear in the

conditions of occlusal loading with normal and excessive forces acting vertically or

horizontally, by the finite element method.

Material and method. To create the 3D virtual model of the right upper

premolar, CT images of a 14-year-old patient and the values of the modulus of

elasticity and the Poisson ration were used. All materials were considered

homogeneous, linear, and the stresses generated in the dental structures were

compared with the allowable stresses [10 - 12]. The 3D model comprised the right

upper premolar and the alveolar bone represented by a parallelepiped, as shown in

Fig. 6.1.

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Fig. 6.1. FEA model.

To simulate the effects of vertical forces on the right upper premolar, three

variants of horizontal dental wear of various degrees were imagined. An external

force F was applied to a parallelepiped-shaped block that came in contact with the

occlusal surface of the tooth at the level of the vestibular cusp. 8 occlusal loading

scenarios were created: 4 with a normal occlusal force, F = 180 N and 4 with an

excessive occlusal force, F = 532 N.

To simulate the effects of horizontal forces on the right upper premolar, three

variants of oblique wear of various degrees were imagined. A horizontal external

force F was applied to an antagonistic tooth, rigidly shaped and with complementary

occlusal relief, which came into contact with the occlusal surface of the upper

premolar one. 8 lateral occlusal loading scenarios were created: 4 for a normal

occlusal force, F = 180 N and 4 for an excessive occlusal force, F = 532 N.

Results and discussion. Analyzing the distribution of von Mises stresses in

the enamel, in the case of simulating the action of normal occlusal force with vertical

direction, values exceeded the allowable compression limit in the case of the intact

tooth at the level of the vestibular cusp. The distribution of these stresses was made

on a small and superficial area of the enamel, so we can appreciate that the risk of

cracks is small.

When applying an excessive vertical occlusal force, we registered at the level

of the enamel values of von Mises stresses higher than the admissible limit in all

cases, with the highest values in the case of the intact tooth.

Dentina

Smalț

Pulpă

Ligamentperiodontal

Os

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When applying a normal occlusal force with horizontal direction, the tensile

stresses registered in the FEA model with the intact tooth were higher than those

registered in the FEA models with various degrees of oblique wear. In the case of

teeth with various degrees of oblique wear, compression stresses with harmful values

were recorded on the oral surface. In the same area, tensile stresses with harmful

values were registered, which leads to the occurrence of the shear phenomenon.

When applying an excessive occlusal force with horizontal direction, an

overview of the amplitude and distribution of the developed tensions would lead to

the conclusion that the most affected model is the intact one. Regarding the

amplitude and distribution of compression stresses, it was observed that in the case

of the intact tooth the harmful values were distributed over the entire thickness of the

enamel. In the case of teeth with varying degrees of dental wear, the harmful values

of the compression stresses were recorded on the oral surface, in the same area where

the harmful stretching stresses were recorded. Therefore, the shear phenomenon

develops here.

In order to evaluate the biomechanical consequences deriving from the

shapes of the teeth and the variants of dental wear, the occlusal relations and the

coronary morphology are important.

Chapter 7: Highlighting the effect of stress in the cervical area

of teeth using OCT

An increased level of stress in the cervical area causes the formation of micro-

cracks, especially in the enamel. The cervical region affected in this way becomes

susceptible to abrasion and erosion [2]. One of the methods of investigating dental

tissues "in vivo" and "in vitro" is optical coherence tomography / OCT. This is an

advanced biomedical imaging technique that allows visualization of the internal

biological structure in a non-invasive manner.

The objective of this study was to highlight and to quantitative and qualitative

evaluate by OCT, the morphological changes in the cervical areas of teeth, following

stress generated by excessive occlusal forces and establishing correlations with

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dental morphological group and degree of occlusal wear, and description of the

specific pattern each type of cervical lesion.

Material and method. For this study, 21 teeth extracted for various reasons

were selected from 33 patients over 60 years of age and with extensive partial

edentations. The Swept Laser Source OCT system developed by Thorlabs

(OCS1300SS, Thorlabs) was used to perform the experiment.

A qualitative (crack, demineralization) and quantitative (crack measurement)

assessment of dental tissue changes was performed using the Thorlabs program.

Microsoft Excel was used to centralize and interpret the data obtained by OCT

examination. The actual data processing (descriptive analysis and visual presentation

of the data) was performed in Microsoft Excel.

Resuls and discussion. Following the clinical examination and analysis of

macroscopic images of the 21 teeth included in the study, the diagnosis of occlusal

wear of various degrees was established for all teeth (Table 7.1).

Lower

molars

Upper

molars

Lower

premolars

Upper

premolars

Nr. Teeth in

total

Nr. Teeth included in the

study

8 7 2 4 21

Occluzal wear scor 1 Smith

and Knight

3 6 0 2 11

Occluzal wear scor 2 Smith

and Knight

2 0 0 2 4

Occluzal wear scor 3 Smith

and Knight

3 1 2 0 6

Non-carious cervical lesions 0 1 1 2 4

Tabel 7.1. Situation of wear to the examined teeth

The selected teeth were examined by the OCT method on all sides in the

cervical area and a maximum of 512 images were obtained for each tooth surface

analyzed. Cracks in the dental hard tissues (Fig. 7.1) and areas of structural alteration

(Fig. 7.2 – arrow indicator) appeared as signals of high intensity, differentiated by

the enamel and dentin mass.

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Fig. 7.1 PM1 Sections Fig. 7.2 mi1 Sections

The study showed that the manifestations of occlusal overload in the cervical

areas correlate with the degree of occlusal wear. Teeth with minimal occlusal wear

(Smith 1 and Knight score, representing 52.38%) showed the most changes in the

cervical area on the vestibular, oral and distal faces. The most affected mesial

cervical areas belonged to the teeth with the score 2 Smith and Knight of occlusal

wear (representing 19.04%). This result confirms the results obtained in the study

performed by the finite element method [13, 14].

Regarding the degree of damage to the axial faces, most manifestations of

occlusal stress were identified in the vestibular cervical area, followed by the oral

and distal cervical area, respectively. This result is consistent with the preferential

location of noncarious cervical lesions on the vestibular faces of the teeth.

Although the study by OCT confirmed the results of simulations by FEA,

respectively the possibility of NCCL and cracks due to occlusal overload, it remains

to be clarified under what conditions cracks occur and under what conditions NCCL

occurs, and why the latter appear preferentially on the vestibular face.

Chapter 8: General discussions

The terms used to describe non-carious cervical lesions and the etiology of

clinical forms have been the subject of discussion over time [2], but it is now

unanimously accepted that the etiology of uncarious cervical lesions is multifactorial

and includes stress, friction and biocorrosion [1, 2]. The results obtained in the study

in Chapter 5 showed that practitioners in Romania have moderate knowledge about

dental wear and non-carious cervical lesions, but consider that they are able to treat

these conditions.

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In addition, the involvement of occlusal forces in the production of these

lesions is not fully understood and therefore the treatment does not address the

mechanism of action of these forces, being in many cases doomed to failure. FEA

and OCT simulations showed that the highest concentration of stress occurs during

the application of excessive occlusal forces in the horizontal direction. Regarding the

location of the stress generated by these forces, it was recorded in the vestibular

cervical areas in particular, occlusally, but also on the proximal and oral faces. The

results of these studies overlap with Grippo's classification in 1991 [15] and with

Medeiros' 2020 study [16].

Non-carious cervical lesions in the form of abrasion, erosion, abrasion or

even in the form of cracks, will be of interest for further research because it is found

that their prevalence is increasing.

Chapter 9: General conclusions

1. Non-carious cervical lesions are a topic of interest for dental practitioners,

as demonstrated by the large number of respondents in the statistical study.

2. Dentists in Romania have a moderate level of knowledge of non-carious

cervical lesions, but nevertheless feel competent in discussing and treating this

condition.

3. Based on the study performed by the finite element method, we can

consider that occlusal overloads are the main factor in the production of non-carious

cervical lesions.

4. During the simulations performed, an increased level of stress was

registered both in the vestibular and occlusal cervical area, as well as on the oral and

proximal faces.

5. The study performed by the OCT method highlighted the consequences of

occlusal overload in the form of non-carious cervical lesions and hard tissue cracks.

6. The most affected group of teeth due to non-carious cervical lesions was

that of the premolars, but due to cracks the damage was similar to premolars and

molars.

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7. Non-carious cervical lesions were highlighted mainly on the vestibular

surface, but also on the oral surface.

8. The cracks were highlighted on all sides, but more frequently the vestibular

face was the affected one.

Chapter 10: Originality and innovative character

We are not aware of any other research on the etiopathogenic mechanisms

involved in the development of non-carious cervical lesions in which the results

obtained by FEA simulation are verified by the OCT method.

The research as a whole has a unitary character, approaches the same subject

through several research methods, and the obtained results overlap, confirming the

study hypothesis regarding the involvement of occlusal overloads in the production

of necarious cervical lesions and give value to research.

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SELECTIVE REFERENCES

1. Hassan AM. Abfraction: Etiology, Treatment and Prognosis. International

Journal of Dental Sciences and Research. 2017; 5(5):125-131.

2. Soares PV, Grippo JO. Noncarious cervical lesions and cervical dentin

hypersensitivity – etiology, diagnosis and treatment.Quintessesnce Publishing; 2017.

3. Peumans M, Politano G, Van Meerbeek B. Treatment of noncarious cervical

lesions: when, why, and how. Int J Esthet Dent. 2020; 15(1): 16-42.

4. Nascimento MM, Dilbone DA, Pereira PN, Duarte WR, Geraldelj S, Delgado AJ.

Abfraction lesions: etiology, diagnosis, and treatment options. Clin Cosmet Investig

Dent. 2016; 8: 79-87.

5. Charamba CF, Needy J, Ungar PS, de Sousa FB, Eckert GJ, Hara AT. Objective

assessment of simulated non-carious cervical lesion by tridimensional digital

scanning. Clinical Oral Investigations. 2021.

6. Jakupovic S, Anic I, Ajanovic M, Korac S, Konjihodzic A, Dzankovic A.

Biomechanics of cervical tooth region and noncarious cervical lesions of different

morphology; three-dimensional finite element analysis. European Journal of

Dentistry. 2016; 10(3): 413.

7. Erickson KE. Erosive tooth wear: an investigation into knowledge and prevalence.

Masher Thesis. University of North Carolina. 2013.

8. Hermont AP, Oliveira PA, Auad SM. Tooth erosion awareness in a Brazilian

dental school. J Dent Educ. 2011; 75(12): 1620-1626.

9. Mulic A, Vidnes-Kopperud S, Skaare AB, Tveit AB, Young A. Opinions on dental

erosive lesions, knowledge of diagnosis, and treatment strategies among norwegian

dentists: a questionnaire survey. Int J Dent. 2012; 2012:716396.

10. Chun K, Choi H, Lee J. Comparison of mechanical property and role between

enamel and dentin in the human teeth. J Dent Biomech. 2014; 5: 1758736014520809.

11. Shetty P, Meshramkar R, Patil K, Nadiger RK. A finite element analysis for a

comparative evaluation of stress with two commonly used esthetic posts. European

Journal of Dentistry. 2013; 7(4): 419-22.

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12. Bramanti E, Cervino G, Lauritano F, Fiorillo L, D’Amico C, Sambataro S et al.

FEM and Von Mises analysis on prosthetic crowns structural elements: evaluation

of different applied materials. Scientific World Journal. 2017; 2017:1029574.

13. Stănuşi A, Mercuţ V, Scrieciu M, Popescu SM, Iacob MMC, Dăguci L et al.

Effects of occlusal loads in the genesis of non-carious cervical lesions – a finite

element study. Romanian Journal of Oral Rehabilitation. 2019; 11(1): 73-81.

14. Stănuşi A, Mercuţ V, Scrieciu M, Popescu SM, Iacov Crăiţoiu MM, Dăguci L,

Castravete S et al. Analysis of stress generated in the enamel of an upper first

premolar: a finite element study. Stoma Edu J. 2020; 7(1): 28-34.

15. Grippo JO. Abfractions: a new classification of hard tissue lesions of teeth. J

Esthet Dent. 1991; 3:14–19.

16. Medeiros TLM, Mutran SCAN, Espinosa DG, Faial KdCF, Pinheiro HHC et al.

Prevalence and risk indicators of non-carious cervicl lesions in male footballers.

BMC Oral Health 20. 2020; 215.