cytological study of mucosal tissue reaction to … cobalt-chromium-based removable partial dentures...

*Assisstant Professor, Removable Prosthodontics Department, Faculty of Oral and Dental Medicine, Cairo University.**Lecturer, Oral Pathology Department, Faculty of Oral and Dental Medicine, Cairo University.

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CYTOLOGICAL STUDY OF MUCOSAL TISSUE REACTION TO DIFFERENT MODERN INTERIM ESTHETIC RESTORATIONS

Essam A. Aziz* and Nermine R. Amin**

ABSTRACT

(provisional) esthetic ones that are mainly used during socket healing or implant integration. Mucosal ridge reaction to these materials is important to guarantee optimal tissue healing circumstances.

The aim of this study was to evaluate the keratinization reaction of the supporting ridge mucosa towards two widely used interim esthetic restoration (IER) materials e.g Versacryl thermoelastic and

nd edition thermoplastic materials and to compare this reaction to that of the conventional polymethyl methacrylate (PMMA).

Material and Methods:and restored with interim (provisional) removable partial dentures (RPDs) made of either heat

nd

after denture delivery. The digital image analyser computer system was used to measure the total

Results:

Conclusion and recommendations: PMMA denture base material is recommended to be used

nd edition is mandatory to be used

Key words: nd

Essam A. Aziz and Nermine R. Amin

INTRODUCTION

The psychological impact of anterior teeth loss

presentation of the patient. This might be due to the subconscious correlation between the anterior teeth loss and advanced age. (Gobran 201117)

To achieve desirable prognosis, prosthetic treatment plan for anterior teeth loss, as in

basic requirements. These basic requirements are

and acceptable functional (masticatory and phonetic) standards together with the basic concept of preserving the natural supporting and adjacent structures in good health. (Carr et al., 20118 and Charyeva et al., 201210)

The term smile zone describes the anterior teeth and the associated soft tissues when the patient shows a greeting smile. The esthetic dentistry entails

for anterior restorations. (Beaumont 20026)

available to esthetically satisfy patients with

implant supported prostheses (Wood et al., 200437) , (Carr et al., 20118) or removable partial dentures (RPDs) that are

restorations (Carreiro et al., 20089, Ewoldsen et al., 201116, Thakral et al., 201233 and Eskandar et al., 201415 ).

restorations to choose from, yet there is a very limited range of choices for the interim esthetic restorations (IERs). These IERs, however, constitute an important treatment phase (during implant

patients before making the implant and/or tooth-

. (Wood et al., 200437, Carreiro et al., 20089 and Carr et al., 20118) They should ideally provide the optimum mucosal and bone healing circumstances to reach the desirable

(Meijer and Wolgen 200723 and Khalil 201320)

As most of the interim RPDs are used for short intervals of time, they are constructed simply from resin denture base with or without wrought wire retentive components. (Carr et al., 20118 and Ewoldsen et al., 201116)

Despite of its inherent limitations, the polymethylmethacrylate (PMMA) became the most widely used temporary denture base material since

construction and repair together with its agreeable tissue color. (Beaumont 20026 and Carr et al., 20118) These limitations are mainly summarized as the dimensional inaccuracy due to its polymerization

irritant and allergic potentials that might be due to the unavoidable presence of residual monomer. (Thomas and Nandini 201134 and Pradeep and Sreekumar 201226)

With the advent of new technologies, together with the increasing demands for esthetic

materials were introduced to satisfy and improve the esthetic quality of these IERs and also to avoid the well known disadvantages and limitations of the PMMA. (Singh et al., 201132) Thermoelastic and

denture base materials based on the philosophy of plasticizing completely pre-polymerized resins using only thermal physical processing technique without any chemical reaction. (Singh et al., 201132 and Thakral et al., 201233) A wide range of these

(polycarbonates) and polyamides (nylons) with its nd

CYTOLOGICAL STUDY OF MUCOSAL TISSUE REACTION

edition. (Prashanti et al., 201027 and Thomas and Nandini 201134)

The acetal denture base material such as Versacryl is nearly unbreakable and is a highly esthetic thermoelastic material due to its pink semi-translucent character that allows blending with the oral tissue color. These characters, together with its strength, allow the material to be made in thin sections so as to make not only a comfortable light

well. (Elawady 201014 and Eskandar et al., 201415) New generations of polyamide (nylons) denture base materials, due to their technique of fabrication, are so dense, thus lacking the porous structure as a result of absence of residual monomer. They are

strength characteristics and are also claimed to be hypoallergic. (Negrutiu et al., 200525 and Khalil 201320) nd

thermoplastic advanced monomer free denture base nd edition

was developed to improve the esthetic properties of this polyamide as it is supplied in variable tooth and soft tissue shades together with its longer color stability. It also shows increased durability due to its

. (Khalil 201320, Dhir et al., 200713 and Ardelean et al., 20122)

The residual alveolar ridge is covered by mucoperiostium which is a type of masticatory

the ortho-keratinized cells appear as anucleated desquamated clusters of keratinocytes, while the para-keratinized cells show remnants of condensed darkly stained (pyknotic) nuclei with less tendency to form groups. (Dereci et al., 201112)

Full or partial thickness biopsies of palatal and/or ridge mucosa in patients wearing complete and

declare the effect of dentures upon the thickness

of the keratin layer of the epithelium. (Akal et al., 19971) Despite of the relative accuracy of biopsy

rendering them impractical in cases of multiple areas of interest in a large number of patients along

also represents an investigation of a limited area of the oral cavity. (Aziz 19933 and Babshet et al., 20114)

been widely and successfully used to study the epithelial changes in different body areas including the oral mucosa mainly as a cancer screening procedure. (Rajput and Tupkari 201028) The

. (Akal et al., 19971

201221)

cytology technique to study the changes in keratinization of the oral and ridge mucosa as this technique proved to be rapid, simple, less invasive and accurately representing the underlying tissues. (Aziz 19933, Akal et al., 19971, Babshet et al., 20114 and Shankar et al., 201231) It also permits repeated

layers of the epithelium without destroying the integrity of the underlying connective tissue. Thus, it doesn’t interfere with the tissue healing process. (Harinasuta and Howlett 199218)

Papanicolaou (PAP) stain is a routinely used staining technique, commonly available in oral pathology laboratories. It is a multichromatic staining technique which is used to differentiate cells in smear preparations from various body areas.

content of keratin stain yellow orange to orange brown color, parabasal cells stain faint green to blue color, while intermediate cells stain pink. (Ramulu et al., 201329)

(4) Essam A. Aziz and Nermine R. Amin

Recently, many authors recommended the use of digital analysis computer system to evaluate PAP stained cytological smears of the oral mucosa in different lesions for its accuracy, reproducibility and to avoid human subjectivity. (Decaestecker et al., 200911, Babuta et al., 20145, Sankhla et al., 201430 and Verma et al., 201536).

The keratinization changes of the oral mucosa relevant to removable prosthesis have

contradictory results. Some authors suggested that the denture bearing epithelium become more keratinized. (Markov 196822 and Jani and Bhargava 197619) Others showed decreased keratinization following the use of removable prostheses. (Harinasuta and Howlett 199218, Akal et al., 19971

201221) Thinning or loss of stratum corneum under bridge pontics were also reported. (Tolboe et al., 198735)

The use of either acrylic-based complete or cobalt-chromium-based removable partial dentures seemed to reduce the quantity and/or quality of the keratin layer. The mean values of keratinization and

lower in the complete denture group than in the partial denture group. (Akal et al., 19971)

Oral mucosal lesions associated with denture wearing represent a reaction not only to mechanical effect, but also to the type of denture base materials or may be a reaction to the microbial denture plaque.

7 and Tolboe et al., 198735)

Reviewing the dental literature revealed that the keratinization reaction of the ridge mucosa in response to removable prostheses is highly contradictory. The keratinization reaction to the modern IER base materials such as the Versacryl (as a popular type of thermoelastic acetal denture

nd edition (as a modern type of thermoplastic polyamide denture base material) has not yet gained the attention that

it deserves. However, this aspect of the denture base material biocompatibility is considered important to clarify its effect on the supporting soft tissue.

Therefore, this study was conducted to assess and evaluate the effect of two modern IERs, the

ndedition denture base materials on the keratinization reaction of ridge mucosa and compare this effect with that of the conventional heat cured acrylic interim restorations.

MATERIAL AND METHODS

Patient selection criteria

edentulous arches (having missing four incisors)

were selected from the out-patient Prosthodontic Clinic, Faculty of Oral and Dental Medicine, Cairo

included in this study. All patients were showing

no tempromandibular joint disorders. Patients were motivated and monitored for the maintenance of

with any systemic disorders that might affect the

Patient examination

candidates were done to ensure normal soft and hard supporting ridge structures free from any

roots. Participants were informed about the nature of the study and signed a written consent form.

Patient grouping and denture construction

Patients were divided randomly into three equal groups. For group I, each patient received a

CYTOLOGICAL STUDY OF MUCOSAL TISSUE REACTION (5)

conventional acrylic partial denture using the heat

wire retentive arms encircling the labial surface of the cuspids and embedded in the acrylic denture

the conventional long curing cycle technique. (Carr et al., 20118) For group II, each patient received a thermoelastic IER made of Versacryl** denture base material constituting its retentive component

For group III, each patient received a thermoplastic nd edition*** denture base

material constituting its retentive component

For all denture types, upper and lower preliminary impressions were made in irreversible

alginate**** impression in perforated acrylic special tray constructed on double layer of modeling

record was obtained followed by acrylic teeth***** selection.

follow the basic principle of keeping them out of contact from the opposing anterior teeth in centric

* Acrostone heat cured cross linked denture base, England

**** Tropicalgin alginate, Zhermack, USA***** Vitatan cross linked acrylic teeth, Veta, German

Fig. (1): Photographs of a patient (a) before denture delivery, (b) with conventional heat cured PMMA partial denture, (c) with nd edition IER.


occluding position and from centric to any eccentric

denture teeth and the opposing natural ones was rechecked. Dentures were inspected three and seven days after delivery and followed up after two weeks,

of denture delivery. All patients were instructed to strictly follow proper dental and denture hygiene programs. (Carr et al., 20118)

For group II and III patients, soft tissue shade was obtained during the try in step together with surveying of the master cast to detect the desirable labial undercut areas in the gingival third of each

an inch were considered undesirable and blocked out. (Khalil 201320)

Duplication of the master cast was done using technosil duplicating silicone* and poured using

**

partial denture was done on the duplicate cast.

For group III patients, diatoric undercut holes

drill ***.

For all groups, the area percent of keratinized cells of the residual ridge mucosa was cytologically investigated. The investigation area was swabbed by a cotton pellet. Cytological smears were collected gently using a metal spatula and spread widely over

stain. (Aziz 19933)

Two cytological smears were collected from the mid crestal area of the residual alveolar ridge prior

months after denture delivery.

anucleated cells (ortho-keratinocytes) and the immature keratinized cells with pyknotic nuclei (para-keratinocytes). After PAP staining, keratinized cells (ortho or para) were stained orange to brown, while the parabasal cells were stained faint green-blue and the intermediate cells were stained pink.

The image analyser computer system using the software Leica Quin 500* was used to measure the area percent of the orange to brown color stained cells representing the ortho and para keratinized

the total epithelial cell populations. In addition, the area percent of the orange to brown color stained cells containing pyknotic nuclei representing the

-tion was measured.

area of keratinized cells area of total cell population

area of parakeratinized cells area of total cell population

The orange to brown stained cells were chosen for evaluation in a standard measuring frame

transferred to the monitor’s screen. These areas were masked by a green color using the computer

were collected and presented as mean and standard deviation and statistically analyzed using the three

* Technosil duplicating silicone, Bredent, Senden, Witzighausen,Germany** Bredent, Senden ,Witzighausen,Germany*** Dirtit-Multidrill, Bredent,Senden ,Witzighausen,Germany


way analysis of variance (ANOVA) test* with

each denture base material along the whole study

RESULTS

All patients in the three studied groups were

as regards their retention and esthetic qualities. However, patients of groups II and III reported higher levels of satisfaction and appraisal to their

cytological smears collected from the ridge mucosa before denture insertion showed nucleated parabasal and intermediate cells which were stained faint blue to green and pink respectively as well

which were stained orange to brown and had a

denture insertion, all groups showed predominating nucleated parabasal and intermediate cells with

of denture insertion, total keratinization began to

parakeratinized cells showed an obvious increase in

group I patients which were associated with many

I-Total Keratinization Index (TKI)

In group I (heat cured PMMA denture base

was observed. There was also a further statistically

In group II (Versacryl denture base material),

nd edition denture base


Para Keratinization Index (PKI)

In group I (heat cured PMMA denture base

In group II (Versacryl denture base material),

two weeks from denture delivery with subsequent

nd edition denture base

arrows) together with parabasal cells (faint blue to green color) and intermediate cells (pink colour), (b) few keratinized cells (red arrow), (c) clusters of orthokeratinized cells (red arrows) (d) parakeratinized cells (orange to brown color) (green


(a) in group I patients, (b) in group II patients and (c) in group III patients.

TABLE (1):

Denture base material

I II III

Mean Std. Deviation Mean Std. Deviation Mean Std. Deviation

0 time 11.1

10.9

10.9

45.4

Denture base material

I II III

Mean Std. Deviation Mean Std. Deviation Mean Std. Deviation

0 time 5.91 5.40

1.01 0.45

1.10 0.59

4.05 1.11


DISCUSSION

Discussion of methodology

As all the candidates of this study showed missing four incisors, the operator had a free hand to adjust the degree of the overbite and the overjet

guarantee absence of premature contact either in centric occluding relation or from centric to any eccentric occluding position. This was important to negate the effect of traumatic loading with subsequent frictional keratosis of the alveolar ridge mucosa that might interfere with the results of this study. (Mneizel 200324)

in this study to have the study results widely and generally applied. However, the age range of the

to avoid the effect of the menopausal hormonal changes on mucosal keratinization reaction. (Aziz 19933 and Mneizel 200324) All cases contributed in this study were also free from any systemic disorders such as anemia, hyperparathyroidism and uncontrolled diabetes mellitus that might affect the alveolar ridge mucosal tissue reaction. (Rajput and Tupkari 201028)

Candidates with reported unfavorable habits

of these habits upon the mucosal keratinization reaction. (Aziz 19933, Mneizel 200324 and Babuta et al., 20145)

study as it offers a simple, rapid and non invasive technique if compared to other techniques such as partial or full thickness biopsies that interfere with the tissue healing process. (Aziz 19933, Akal et al., 19971, Rajput and Tupkari 201028 and

21)

The digital image analysis computer system method was used in this study to interpret the degree

of keratinization of the PAP stained smears to avoid the effect of human subjectivity evidenced in

enhances both precision and reproducibility of the results with less time and effort. (Decaestecker et al., 200911)

The selection of the thermoelastic Versacryl and nd edition materials was

superior esthetic qualities that permit the selection of the soft tissue shade. They also possess denser structure than the conventional PMMA that allows for a better tissue reaction. (Singh et al., 201132, Thomas and Nandini 201134, Ardelean et al., 20122 and Khalil 201320)

Reviewing the dental literature, most of the

Discussion of results

delivery for all denture base materials. This was in accordance to Mneizel 200324 who found a decrease

acrylic complete denture insertion. This was also in accordance with Akal et al., 19971 who showed that either acrylic-based complete or cobalt-chromium-based removable partial dentures reduced the quantity of the keratin layer of the palatal mucosa. This was also in accordance with Szymanska et al., 201221 who documented a decrease in the thickness of the keratin layer which

complete denture insertion. The authors stated that the decrease in keratinization was more obvious in Cobalt-Chromium and Titanium partial denture bases than in the acrylic denture bases. The previous


results could be attributed to the initial sheltering effect of the denture upon the mucosa preventing the frictional masticatory forces from inducing

for the conventional PMMA acrylic denture base

nd edition denture base materials. This was in accordance with Jani and Bahargava 197619

an increase in the thickness of the keratin layer of

also in accordance to Mneizel 200324 who recorded an increase in mean palatal keratinization after one month of acrylic complete denture delivery. The increase in keratinization seen in this study could be attributed to the effect of frictional forces of denture base materials on the ridge mucosa which was more pronounced in the rough and porous heat cured PMMA acrylic denture bases than in the denser and

nd edition denture bases.

for the heat cured PMMA acrylic denture base

continuously increasing harmful effects on the ridge mucosa. This was in accordance to Mneizel 200324 who showed an increase in mean keratinization after

This result was contradictory to Harinasuta and Howlett 199218 who reported a 50% decrease in orthkeratinization of palatal mucosa in patients who

dense structure of the metal framework together with the positive tooth support of the partial denture that decreased the mucosal irritation. As regards

nd edition denture

denoting their minimal harmful effect on the ridge mucosa compared to the effect of heat cured PMMA denture base material. This might also be attributed to the more biologically acceptable and smoother nature of the recent thermoelastic (Versacryl) and

nd edition) denture base materials.

denture base materials following the decrease

favorable and hygienic conditions of these recently delivered prostheses in all groups. However, after

heat cured PMMA denture base material showed a

nd edition denture base materials showed

Tolboe et al., 198735 who noticed changes in the form of parakeratosis resulting from poor hygiene conditions and

accumulated bacteria under bridge pontics. It is obvious that despite of the proper denture hygiene that was stressed upon and followed up throughout the whole study period for all groups, the heat cured PMMA denture base material did not provide an

to the inherent more porous nature of heat cured PMMA that favors bacterial accumulation at the tissue surface as compared to the denser Versacryl

nd edition denture base materials. It could be concluded that the use of heat cured PMMA

changes in the ridge mucosa and was manifested

nd edition denture


favorable surface density that did not encourage bacterial accumulation.

the time of denture delivery, denoting a continued

mucosa which is in accordance with the results of Pradeep and Sreekumar 201226

by Tolboe et al., 198735. Similarly, the Versacryl

was less than that at the time of denture delivery as it

nd

months of denture use. This result was in agreement with Negrutiu et al., 200525 and Khalil 201320

nd edition denture base material that could easily yield a more hygienic and biologically compatible ridge mucosal reaction.

CONCLUSIONS AND RECOMMENDATIONS

1- After two weeks of denture use, all types of interim denture bases showed favorable tissue

PMMA is recommended to be used for such short intervals due to its low cost and ease of construction. Yet, if longer duration of denture use or superior esthetic qualities is required,

to be used.

recommended to be used for moderate durations

nd edition denture base is mandatory to be used for longer duration of denture use due to its prolonged favorable tissue reaction

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cytological study of mucosal tissue reaction to … cobalt-chromium-based removable partial dentures...

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