Key words:
Fixed prosthesis - pontics - porcelain fused to metal bridges
Introduction
Pontic is the artificial tooth in the fixed or removable partial dentures; that is,
the suspended portion of the fixed partial denture (bridge) replacing the missing
natural tooth or teeth.[1] The pontic may be fabricated from cast metal or combination of metal and porcelain.[2] Designing a pontic is not simple; an exact anatomic replica of the tooth in the
space would be difficult to manage.[3] The requirements of the pontic design include esthetics, biocompatibility, function,
phonetics, patient comfort, and maintenance of healthy tissue on the edentulous ridge.[4]
[5]
[6]
[7] Pontic design selection depends on the location of the edentulous area. Controversies
exist for the gingival embrasure space and design. Some considered less plaque accumulation
with space closure while other proposed open embrasure space for oral hygiene maintenance
pontic.[8]
[9]
Pontic resembles the tooth morphology and may be altered to meet extra demands in
certain clinical scenarios such as in case of convex tissue surfaces and narrow occlusal
table.[9] Decreasing the buccolingual width lead to decrease in interferences in eccentric
movements.[7] Some authors considered normal size occlusal table, whereas other considered it
to be of minimum importance.[7]
[8]
[9] Pontic should be out of tissue contact when proceeding from facial to lingual.[10]
Different shapes of pontic are selected according to the position of the edentulous
space, amount of bone resorption, and operator’s and patient’s preferences.[11] It is recommended that the prosthodontist or the dental practitioner should advise
the dental laboratory about the shape of the desired pontic for the fixed prosthesis.[12] There is a variety of pontic designs (such as ridge lap, ovate, and conical) for
mandibular and maxillary arches [Figure 1].
Figure 1: Schematic presentation of various pontic designs; (a) Sanitary pontic; has no contact
with the edentulous ridge, (b) ridge lap pontic; forms a large concave contact replacing
the contours of a missing tooth, (c) modified ridge lap; shows illusion of a tooth
but it has all or nearly all convex surfaces for easy cleaning and minimize plaque
accumulation, (d and e) bullet/conical; rounded and cleanable smaller tip in relation
to overall size, (f) ovate; round end design currently in use where aesthetics is
a primary concern
For instance, ovate and modified ridge lap is recommended for the anterior maxilla,
sanitary and modified ridge lap for the posterior maxilla, conical, and modified ridge
lap for the anterior mandible and sanitary for the posterior mandible, respectively.[9]
[11]
[13]
[14] These guidelines should be followed to provide the patient with an acceptable prosthesis.
This survey based study was undertaken to assess the knowledge and practice of pontic
selection by the general dental practitioners (GDPs) in the light of contemporary
guidelines. Porcelain fused to metal fixed prostheses were included as these are most
commonly used prosthesis by GDPs.
Materials and Methods
This cross sectional study was conducted among the GDPs of Karachi, Pakistan. The
study protocol was approved by the Institutional Ethics Review Board at the Fatima
Jinnah Dental College, Karachi. The data were collected using a comprehensive questionnaire
over a period of 6 months (January–June 2017). A total of 100 GDPs of Karachi were
included in the study. A self administered questionnaire with multiple choices was
designed. Before its distribution, it was discussed thoroughly to ensure that the
questions were clear. Any question with ambiguity was modified and rephrased. The
questionnaire included general/demographic information related to the practitioner’s
education, experience and place of practice and an average number of a fixed prosthesis
constructed by the GDP per month. The questionnaire was further categorized to evaluate
the GDPs’ knowledge/preference about the pontic design selection and latest recommendations.
The questionnaire included various pontic designs [Figure 1] and their selection preferences according to the quadrants were enquired. Multiple
options were given, and the participant had to mark maximum two options for every
question. One of the key questions was, “did the practitioner advises the dental laboratory
about the type of pontic?”. One of the authors himself approached the practitioners
to get the questionnaire filled. After getting the consent to take part in the study
the participants were given a clear and detailed briefing about the aims and objectives
of the study. It was assured that the results obtained will be used for the study
purposes only and the information will be confidential. The questionnaires were filled
by the qualified dental practitioner only. Responses from the participants were evaluated
in terms of numbers and percentages using the SPSS Version 20 (IBM, Illinois, USA).
The statistical test (Chi square) was applied to compare the statistical significance
among groups, whereas P < 0.05 was considered as statistically significant.
Results
Out of total 100 invited practitioners, 70 (70%) participants (53 males and 17 females)
agreed to participate and completed the questionnaire. Another ten questionnaires
either incomplete or not returned by the participants were excluded. Therefore, 60
questionnaires were considered appropriate and included in the study. Only 18 (30%)
participants reported to advise the dental laboratory about the type of pontic design
while remaining 42 (70%) used to give no instructions to the dental laboratory and
to accept the pontic design provided by their dental laboratory.
The participants’ preference for choosing the pontic design for maxillary and mandibular
segments is shown in [Table 1]. For the maxillary anterior segment, the ridge lap pontic was the most common (32%)
followed by the modified ridge lap (28%) and ovate (15%). In case of the maxillary
posterior segment, the ridge lap pontic was the most common (37%) followed by sanitary
design (34%) and modified ridge lap (10%). The conical design pontic remains the least
common design for all kinds of maxillary restorations [Table 1].
For the mandibular anterior segment, the modified ridge lap (50%) was the most common
followed by ridge lap pontic (17%) and conical (13%). In case of the mandibular posterior
segment, the sanitary design (34%) was the most common followed by ridge lap pontic
(30%) and modified ridge lap (17%). The sanitary design pontic remains the least chosen
(3%) for the mandibular anterior segment and ovate (0%) for mandibular posterior restorations
[Table 1]. The collective data showed that the most popular pontic design among participant
is the ridge lap pontic (69%) followed by modified ridge lap (63%) and sanitary (47%)
pontic [Table 2]. Whereas, the ovate and conical were the least popular pontic designs.
Discussion
This study investigated whether the practicing dentist follows the contemporary guidelines
while selecting a metal ceramic pontic for fixed partial dentures. It is desired to
match the physical and mechanical properties of casting alloy and ceramic. For instance,
the gross mismatch in the thermal expansion properties of veneering ceramics and metallic
core may induce residual stresses, crack formation and potentially chipping failure.[15] To avoid metal ceramic interface failure due to residual stresses, an appropriate
thickness of the veneering porcelain is recommended.[16] The majority of the participants were males corresponding to the higher ratio of
practicing male dentists.[17]
[18] The majority of participants did not give instructions to the dental laboratory
about the pontic design. This result is very alarming in the sense that to prescribe
the pontic design to the dental laboratory is a fact and it’s the job and responsibility
of the practitioner to advise and discuss the suitable pontic design with the laboratory
technician.[12] Recommended guidelines for the laboratory prescription have mentioned pontic design
as an integral part of the prescription.[19]
[20]
The recommended designs for the anterior maxillary region are ovate and modified ridge
lap pontics. The ovate pontic has high aesthetic value, therefore, considered most
suitable in the anterior maxillary region.[14] This gives the illusion that the replaced tooth emerges from the gingiva like a
natural tooth. Certain guidelines need to be followed when considering the provision
of ovate pontic such as atraumatic extraction, long term provisional restoration and
repeated relining/modification of the provisional restoration.[21] The modified ridge lap is the second commonly recommended pontic design. However,
due to alveolar bone resorption changes need to be made in its design which can compromise
esthetic and function.[9] Hirshberg considered that oral mucosa remain healthy under the modified ridge lap.[8] This study revealed that ~57% of the GDPs are not following the contemporary guidelines
and relying on designs that may compromise esthetics in this highly esthetic zone.
Table 1:
The preference of general dental practitioners for selecting pontic design for maxillary
and mandibular teeth; n (%); n=60
|
Pontic design
|
Maxillary
|
Mandibular
|
|
Anterior (%)
|
Posterior (%)
|
Anterior (%)
|
Posterior (%)
|
|
Ridge lap
|
19 (32)
|
22 (37)
|
10 (17)
|
18 (30)
|
|
Modified ridge lap
|
17 (28)
|
6 (10)
|
30 (50)
|
10 (17)
|
|
Ovate
|
9 (15)
|
2 (3)
|
6 (10)
|
0
|
|
Conical
|
0
|
2 (3)
|
8 (13)
|
7 (12)
|
|
Sanitary
|
2 (3)
|
20 (34)
|
2 (3)
|
23 (38)
|
|
Don’t know
|
13 (22)
|
8 (13)
|
4 (7)
|
2 (3)
|
|
Recommendation
|
Ovate and modified ridge lap
|
Modified ridge lap (premolars) and sanitary (molars)
|
Conical and modified ridge lap
|
Sanitary and conical
|
Table 2:
Overall general dental practitioners’ preference of pontic design selection (n=60)
|
Pontic design
|
Preference (%)
|
|
Ridge lap
|
69
|
|
Modified ridge lap
|
63
|
|
Sanitary
|
47
|
|
Don’t know
|
27
|
|
Ovate
|
17
|
|
Conical
|
17
|
The recommended designs in the posterior maxillary region are modified ridge lap and
sanitary pontics. The maxillary premolar areas are visible when viewed from the front,
especially when the patient has a wide smile curvature. Modified ridge lap is the
highly recommended design in the maxillary premolar region.[9] Maxillary molars are less visible having no esthetic value. Sanitary/hygienic pontic
is frequently used in the nonappearance zone. In sanitary type, the metallic pontic
has at least 3 mm space between the ridge and the pontic to facilitate proper cleaning.[22] Again, ~56% were not following the guidelines for the pontic selection; as ~37%
used ridge lap pontic that is highly unhygienic and may damage the ridge tissues.
The recommended designs in the mandibular anterior region are conical and modified
ridge lap pontics. Mandibular anterior teeth are partially visible and only the occlusal/incisal
two thirds of the teeth can be seen in most of the patients. The gingival or cervical
third is visible in very few patients having very thin lips or extremely wide smile.[23] However, this area has some role in phonetics.[22] Therefore, to provide phonetics and esthetics to the patients, pontic can slightly
touch the ridges, but in cases of severe resorption, pontic can be away. A conical,
bullet, or spheroid pontic is recommended in this region.[13]
[24]
The modified ridge lap pontic is also recommended in this region to complete the less
esthetic demands.[9] The results of the study showed that the practitioners are less aware of the conical
pontic and only 13% used this type of pontic. Majority of participants (50%) used
modified ridge lap pontic for the anterior mandibular region.
The recommended designs for the mandibular posterior region are sanitary, modified
ridge lap pontic and conical pontics. The mandibular posterior teeth have least esthetic
values, and only the occlusal surface is visible in phonetics and smiling. Therefore,
pontics in this region may ideally be out of gingival/tissue contact to provide good
hygiene and cleansibilty.[22] A narrow occlusal table and convex surface for easy cleaning can be used.[9] Thus, the sanitary and modified sanitary pontic designs are considered ideal for
this region. Hood et al.[6] found that sanitary designs bear higher load compared to ridge lap and modified
ridge lap pontics. A sanitary design meets the patient’s structural, functional, biological
and psychological demands.[22] Unfortunately, a few dentists do not prefer sanitary pontic design due to an unnatural
sensation of the restoration to the cheek and tongue.[22]
[25] For such cases, conical and modified ridge, lap pontics can be provided. These guideline
were followed by 67% of participants.
A considerable number of participants preferred saddle type of pontic; these findings
are in agreement with Nagarsekar et al.[12] The ridge lap pontic was preferred design in all areas of the mouth and no consideration
was given to the specific area. Modified ridge lap pontic was the second commonly
used pontic design in this study. Saddle shaped/ridge lap pontic has high esthetic
value and least chances of food particles trapping. This design gives the illusion
of a nonextracted tooth which is accepted by the patient.[26] However, this design is the most difficult to clean, because there will be food
accumulation between the tissue surface of the pontic and the alveolar ridge surface
which will lead to tissue inflammation and failure of restoration. The contemporary
guidelines are against the use of this pontic design.[9]
[27]
[28] The reasons for variability in the pontic selection should be studied further. This
study had a small sample size, and in future, a large sample size can be selected
and GDPs of other cities can be included in the study. Particular attention should
be given in case of complications in the pontic area in relation to abutment crowns
such as malalignment, narrow edentulous space, and excessive bone resorption.
Conclusions
The current study concluded that the pontic design selection is a neglected domain
in fixed partial denture provision. The contemporary guidelines are not followed with
full spirit by the GDP participants hence reported a large variability in pontic design
selection. Further studies on this topic are recommended to know the reasons for this
disparity.
Financial support and sponsorship
Nil.
