REVIEW
Assessment of stress distribution and displacement of complete dentures on flabby ridge with multiple occlusion schemes using finite element analysis Nanda Iswa Maysfera.
Ariyani.
Ismet Danial Nasution* ABSTRACT Keywords: Displacement of complete denture.
Finite element analysis.
Flabby ridges.
Occlusion schemes.
Stress distribution.
Loss of teeth and supporting tissues, which are functional components of the stomatognathic system, significantly affects masticatory function.
Flabby ridges are one of the soft tissue anomalies in the edentulous.
The main choice of treatment for edentulous patients with flabby ridges issues is a complete denture (CD).
Flabby ridges cause problems with the retention and stabilization of the CD which causes displacement of the denture base during function.
Lingualized and linear occlusion schemes were used to overcome the stabilization of CD by reducing stress distribution in the flabby ridge area when obtaining masticatory load.
Assessment of stress distribution and displacement of CD can be analyzed using Finite Element Analysis (FEA).
This paper describes the use of FEA to assess the stress distribution and displacement of CD on flabby ridges by simulating axial and oblique forces in lingualized and linear occlusion schemes.
The use of FEA for assessing stress distribution and displacement of CD in flabby ridges with multiple occlusion schemes has advantages in terms of accuracy and flexibility.
(IJP 2024.
:1-.
INTRODUCTION
The stomatognathic system is a complex system with several functional components that work together.
Stomatognathic components consist of teeth, bones, joints, ligaments and other supporting tissues.
1 According to the Glossary of Prosthodontic Terms, the stomatognathic system is a combination of several structures involved in speech, mastication, swallowing, and parafunctional functions.
2 Disruption one of the functional components of the stomatognathic system, such as tooth loss, will affect masticatory function, impacting quality of life and nutritional intake.
Demographic data on the elderly population indicate demand to rehabilitate edentulous patients has remained high for decades.
3 According to the 2018 National Basic Health Research Report, the proportion of edentulous cases is 2.
6 percent for people aged 55 to 64, and 9 percent for people aged 65 and up.
4 Edentulous rehabilitation with complete dentures (CD) is generally considered acceptable because it provides the desired aesthetics as well as occlusal support for mastication and allows the patient to speak normally.
The use of CD on flabby ridges will affect retention and stabilization.
Flabby ridge is a condition in which the alveolar ridge is easily moved due to bone replacement with fibrous tissue.
It is most common in the maxillary anterior, especially when the mandible still has natural anterior teeth and the maxillary ridge is weak underpressure from the mandibular anterior natural 5,6 The amount and pattern of pressure applied to the oral mucosa is an important aspect of denture treatment that affects CD stabilization and retention.
One method for achieving CD retention and stabilization is to use a lingualized and linear occlusion scheme, which aims to achieve an even stress distribution and reduce the occurrence of displacement in the CD.
3 ,8,9 The number of occlusal contacts was significantly reduced with the lingualized and linear occlusion schemes compared to the conventional occlusion scheme.
The masticatory pressure applied to the mandibular alveolar ridge with this occlusion scheme is directed towards to the center of the ridge, increasing the stability of the mandibular denture and avoiding crossbites Specialist Program in Prosthodontics.
Faculty of Dentistry.
Universitas Sumatera Utara *Corresponding author: ismetdanial@yahoo.
INDONESIAN JOURNAL OF PROSTHODONTICS
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Volume 5 Issue 1 the center of the ridge, increasing the stability of the mandibular denture and avoiding crossbites .
Finite Element Analysis (FEA) is an important research tool in dental research for biomechanical analysis.
This method has the advantages of being non-invasive, allowing visualization of overlapping structures, and allowing the determination of material properties of anatomic craniofacial structures.
This method can determine the magnitude, location, and direction of an applied force in addition to assign theoretically measurable stress points.
Furthermore, because it has no effect on the physical properties of the material being analyzed, it can be repeated as many times as necessary.
11 The use of FEA is expected to improve understanding of the stress distribution and displacement of complete dentures with flabby ridge in different occlusion schemes.
7,12
Figure 1.
Lingualized occlusion.
LITERATURE STUDIES
Figure 2.
Lingualized occlusion during lateral movement.
Figure 3.
Linear occlusion in centric and eccentric relations.
T h e E f f e c t of E d e n t u l u s on M a s t i c a t i o n Definition According to the Glossary of Prosthodontic Terms, mastication is the process of chewing food for swallowing and digestion.
2,13 The masticatory system is a complex and interconnected system of muscles, bones, ligaments, teeth, and 14 Masticatory performance is affected by factors such as the number of natural teeth, occlusal strength, and tongue 15 It is known that the number of teeth below 20 teeth can affect the efficiency, performance and masticatory ability.
Flabby Ridges According to the Glossary of Prosthodontic Terms 9 (GPT) flabby ridge is defined as excessive movable tissue.
2,17
Historically, the flabby ridge in the maxillary anterior region was a feature of the Aocombination syndromeAo as identified by Kelly The combination syndrome occurs in patients with full maxillary edentulous antagonizes the mandibular Kennedy Class I partial dentition.
5,18
Flabby ridges caused by uncontrolled tooth extraction, excessive occlusal load on the residual maxillary ridge, unstable occlusal relationships, and flabby tissue often accompanied by atrophic and knife edge ridges.
17,19 The mucosa of the flabby ridges is highly mobile and loses its attachment to the periosteal tissue that covers the bone.
Flabby ridge provides limited support for CD.
Masticatory pressure can cause displacement of the denture and loss of peripheral seal.
Flabby Ridges Classification Stefanescu C et al.
classify the flabby ridges as follows:19 By location: Upper frontal edentulous ridge .
ery ofte.
Upper fronto-lateral edentulous ridge .
Maxillary tuberosity .
Lower frontal edentulous ridge .
ery ofte.
Lower fronto-lateral edentulous ridge .
Retromolar pad .
Based on the structure: Hyperplasic, keratinized, with high antero-posterior and supero-inferior thickness.
Atrophic, thin, small antero-posterior thickness and increased supero-inferior Apparently histological normal appearance at inspection, but with increased mobilityin all directions.
Flabby Ridges Management Various managements of flabby ridges have been proposed.
INDONESIAN JOURNAL OF PROSTHODONTICS DOI 10.
46934/ijp.
Nanda Iswa Maysfera et al June 2024 both surgical and non-surgical procedures.
Surgical procedures to remove flabby ridges include pre-prosthetic treatment.
Surgical procedures on a flabby ridge usually result in the loss of a portion of the vestibular area which can affect the stability of the denture.
Either a ridge augmentation procedure using bone graft or platelet rich fibrin (PRF) can be performed but the prognosis is questionable.
The implant procedure may also be considered as part of the flabby treatment plan.
However, both augmentation and implant procedures have many factors to consider, such as patient age, history of systemic disease, surgical risks and complications, and implant failure.
9,19
Non-surgical management is a prosthodontic approach.
the principle of prosthodontics, of course, the use of an unfavorable ridge is still better than nothing.
The treatment of flabby edges with various printing methods and materials is frequently discussed in various literatures.
19 Determining the best occlusion scheme is also important for achieving denture stability in cases of flabby ridges.
Lingualized and linear occlusion are frequently used to maximize the stability, esthetics, and function of the CD in cases of severe alveolar ridge resorption and flabby ridges.
Occlusion Scheme The occlusal scheme is defined as the shape and arrangement of the occlusal contacts in natural teeth and The occlusal scheme determines the pattern of occlusal contact between opposing teeth during centric relation and the functional movement of the mandible The amount and direction of the force transmitted through the denture base to the residual ridge is determined by the quantity and intensity of this contact.
That is why the occlusal scheme is an important factor in the design of complete denture prostheses.
Over the years a number of occlusion concepts have been developed for complete dentures.
The main goal is to keep the load on the bone within physiological limits.
Lingualized and linear occlusion are the two most popular occlusion schemes for complete dentures with flabby ridges.
Lingualized Occlusion This concept was introduced by Alfred Gysi in 1927 and SH Payne in 1941: Aocusp-to-fossa occlusionAo and Pound:
Aolingualized oclusionAo.
Lingual occlusion can be defined as, a form of denture occlusion in which the maxillary lingual cusp articulates with the mandibular occlusal surface in centric working and non-working side mandibular positions (Fig.
8,20,22
Indications of a lingualized occlusion scheme are severe alveolar resorption, class II jaw relations, complete dentures on flabby ridges againts removable partial dentures and patients with parafunctional habits.
Aesthetic results can be achieved by anchoring the anatomical upper posterior teeth in lingual During lateral movement, the contact that occurs on the working side is only between the lingual cusps of the maxillary and mandibular posterior teeth, on the balancing side there is contact between the palatal cusps of the upper denture and the lingual inner curve of the buccal cusps of the lower denture, as occurs in the conventional concept of occlusion (Fig.
22,23
Advantages o f Lingualized occlusion The vertical force of masticatory pressure is concentrated at the mandibular ridge.
Cusp shape is more aesthetic than non- Nanda Iswa Maysfera et al anatomical tooth shape.
It can be used in patients with various Better food bolus penetration.
Additional stability is obtained during parafunctional movements with balanced It is easier to adjust the occlusion.
Can be used in Class II.
Class i, and crossbites.
In general, it can be said that there are no contraindications to the use of lingualized occlusion.
This occlusion scheme is used in patients who expect esthetics but minimize pressure during mastication and parafunctional movements as a result of severe ridges resorption and flabby tissue or abnormal jaw relationship and large spaces between the ridges.
Linear Occlusion The occlusal adjustment of the denture was made on the basis of a horizontal plane without anterior overlap .
verbite = .
using the maxillary posterior denture elements with nonanatomical occlusal surfaces and in contact with the occlusal surfaces of the mandibular posterior denture elements which had a straight, long and shaped shape.
narrow occlusal surface resembling a line (Fig.
3,20
Linear occlusion consists of the following basic parameters.
Zero-degree teeth .
lat plan.
are in line with the bladed teeth .
ine contac.
where the blade is in a straight line just above the crest of the ridge.
The maxillary teeth are arranged in a monoplane with relation to the occlusal plane.
There was no interference with the anterior teeth during protrusive or lateral According to Gronas and Stout, linear occlusion has the potential to generate the smallest lateral forces.
In linear occlusion, the bladed teeth are placed on the jaw that requires the most stability.
Because the lower jaw usually requires denture stability, the blade teeth in this occlusion scheme are placed on the lower jaw.
In the centric and eccentric relation, the occlusive force between the blade teeth and the zero degree teeth occurs in the vertical direction (Fig.
The location of masticatory pressure on the mandible does not change significantly in different occlusion positions.
Because there is little contact area between the plane and the blade teeth, denture displacement is reduced due to low frictional resistance.
Stress Distribution and Displacement Dentures depend on the mucosa and residual ridges for support, so it is critical to minimize excessive residual ridge resorption by distributing the occlusal load evenly.
In the absence of natural teeth, mechanoreceptors and proprioceptive functions are maintained through continuous stimulation of the denture base and oral mucosa.
As an outcome, the pattern of intraoral pressure within the oral cavity is determined by acceptable functional behaviors like mastication, swallowing, and speech, as well as parafunctional behaviors like bruxism.
Mucosal capacity continuous load from denture is a variable that depends on the level and duration of mechanical load during denture wear, there is limited knowledge about the physiological parameters for oral mucosal pain threshold.
In particular, the Pressure Pain Threshold (PPT), is a major area of concern in denture treatment because it is the maximum pressure before pain is experienced by the patient.
7 The pressure pain threshold
(PPT)
in the lower edentulous area was reported to be 630 kPa.
Occlusal forces in the range of 65-110 N, generated on premolars and molars, have been shown to be sufficient to pro-
INDONESIAN JOURNAL OF PROSTHODONTICS
DOI 10.
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Volume 5 Issue 1 According to MacEntee, support for CD is significantly cess most foods.
25 The masticatory efficiency depends not only impaired if the flabby ridges has a displacement of more than on the stability of the denture but also on the compression of 2 mm under masticatory forces.
30 According to a study (Chong mastication against the mucosa under the denture.
Chewing 1.
, displacements on the working side and balancing side and swallowing as the most frequently performed activities can reach as high as 1.
4 and 1.
6 mm, respectively.
The balancing tend to occur in a vertical direction.
6 However, movement in side shows a marked tendency to dislodge and slide on the the lateral or oblique direction has the most damaging effect foundation (Miyashita et al.
where this displacement due to displacement of the denture so that the masticatory load occurs under masticatory loads.
25 The use of lingualized and is distributed unequally over the entire supporting tissue, with linear occlusion schemes is indicated for flabby ridges because the area receiving greater stress than the other areas.
vertical forces are directed more concentrated on the mandibular Alveolar bone resorption will occur at an unpredictable rate alveolar ridge, which provides more stability to the denture.
after natural teeth are extracted and will severely destabilize the AbduoAos .
systematic review concluded that bilateral complete denture if the alveolar ridges move excessively (>2 m.
balanced or lingualized occlusion schemes were equally or are of a soft consistency under light stress.
26 In mandibular acceptable to patients in terms of mastication, aesthetics, comfort, dentures there is a large displacement of the mucosa during the and speech processing.
Improved denture quality significantly transmission of masticatory pressure especially when oblique affects masticatory performance, occlusal strength and patient forces are applied in relation to the occlusal surface.
Denture 31 Based on the research results.
Hasan A et al .
displacement is kept to a minimum during the masticatory consider the two most functionally efficient occlusion schemes, process by using an appropriate occlusion scheme.
Clinical trials namely lingual and linear occlusion.
In the lingualized occlusion have shown that denture displacement increases with the size scheme, the premolars and molars were arranged and modified of the food piece.
so that only the lingual cusps of the maxillary posterior teeth Transmission of occlusal forces in mastication is only were in contact with the central fossa of the mandibular posterior possible if the mandibular denture is in a stable condition when The linear occlusion scheme was defined as the pin-point in contact with the maxillary denture on the non-working side.
contact of the cusp tips of the bladed mandibular teeth against During in vivo studies of the masticatory process, significant the maxillary teeth that had no cusps.
denture displacements have been reported up to 1 mm, despite According to Fatihallah A, the tension generated in the the articulations being balanced.
Stabilization is achieved by lingualized occlusion scheme is much less than that produced various occlusion schemes selected by the dentist according to in the bilateral balanced occlusion scheme, this may be because the intraoral situation.
the number of occlusal contacts is reduced so that there is only Finite Element Analysis (FEA) Finite element analysisis a numerical method to get a solution A one centric stopper between the upper and lower antagonist teeth in the case of the lingualized occlusion scheme.
32 The to a problem accurately by analyzing modeling simulations.
clinical study conducted by Hameed et al.
it was found that based The advantages of using FEA: Modeling and treatment can be on the results of the radiographic evaluation, linear occlusion free-form according to the preferences of the researcher.
Mesh resulted in less resorption of the alveolar ridge than lingualized modeling is a combination of several elements.
Processing can be done in one program.
The original structure and the model The FEA study conducted by Hasan A .
showed that have identical conditions.
the maximum stress of the linear occlusion scheme was 365 MPa.
Studying the stress distribution due to this occlusal config62% higher than the lingualized occlusion scheme .
MP.
in uration is important to understand the phenomenon of load the overdenture implant.
A similar pattern was observed in the transfer not only but also to improve denture design.
Available denture and tooth bases.
the linear occlusion scheme resulted methods for studying stress analysis include photoelasticity, in a higher von-mises stress .
MP.
than the lingualized finite element analysis (FEA), and strain measurement.
The application of FEA to assess the biomechanical properties of B occlusion scheme .
MP.
On the other hand, the stress
FEA
conducted by Hasan M showed dentures, bones and teeth has grown rapidly over the last that in dentures, the maximum and minimum stresses for decade as it offers the ability to model complex geometries, bilateral balanced occlusion and lingualized schemes were not evaluate internal stress states of various components and other significantly different.
mechanical quantities.
FEA is also very effective for comparison Zmudzki J et al.
conducted an FEA study on the distribution studies where one can examine the effects of one or more of denture stress on the mandible with a load of 100 N in the parameters of interest through simulation without the need to vertical direction and 141 N in the 45A oblique direction with create multiple physical constructs or prototypes.
direct contact and delayed contact on the non-working side.
As a result, the direction of the oblique load provides greater
DISCUSSION
stress distribution and displacement, especially on the nonAccording to Pai et al flabby ridges can be defined as movable working side with delayed contact.
Quantitative assessment of soft tissue located in the superficial area of the alveolar ridge.
the stress distribution and displacement of the denture showed The flabby ridge mainly occurs when the edentulous ridge is that the occlusion scheme has an important role in maintaining opposed to the natural teeth and is considered a feature of the the stability of the CD under stress despite good adaptation of combination syndrome when it occurs in the anterior maxilla the CD base and mucosa and shape of the ridge.
There has been (Lynch and Allen, 2004.
Kelly, 1.
26 Flabby ridges are easily no research on the stress distribution and CD displacement on displaced under occlusal forces due to poor support, resulting flabby ridges on various occlusion schemes, so more research in impaired denture retention as a consequence of loss of is required.
peripheral seal (Pai et al.
INDONESIAN JOURNAL OF PROSTHODONTICS
DOI 10.
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Nanda Iswa Maysfera et al
June 2024
CONCLUSION
FEA can be used effectively to assess the stress distribution and displacement of complete dentures on the flabby ridge with lingualized and linear occlusion schemes.
Lingualized and linear occlusion schemes on flabby ridges can increase denture stabilization because occlusal forces are more concentrated on the ridges so that they can be distributed well and also reduce horizontal force during eccentric movement due to minimal occlusion contact, reducing CD displacement on the flabby SUGGESTIONS There has been no research on the stress distribution and CD displacement on flabby ridges on various occlusion schemes, so more research is required.
REFERENCES