Petros
Koidis and Manda Marianthi
74
it had been prior to the immobilization. [81] Moreover, the teeth immobilization which is
achieved by splinting consists in a reduction or even an elimination of mobility only for the
period when a splint is applied. More concretely, in a Renggli and Schverzer‘s study (1974) it
is reported that those teeth splinted with a view to reducing their mobility, reacquired their
mobility at almost the same level as it had been prior to the splinting during a period of
approximately6 monthsafter splint removal. [82] In a similar study with a control group
consisting of patients without splinted teeth had been explored the reduction of mobility of
splinted teeth with telescopic crowns, which had been preserved in their position for 4 weeks.
After the fourth till the tenth week the splinting had been removed during the regular periods
of time in order to measure the tooth mobility. No statistically substantial differences were
noted between the two groups. This fact is rather expected, because after splint removal, the
same conditions reappear (biological state and load conditions), which had created the
occlusal trauma. [83]
Though, it should be mentioned that beyond the impact to occlusal trauma, currently
splinting is chosen even in cases of stabilized mobility, which, whereas
is not indicative of the
occlusal trauma and the following periodontal destruction, however affects the masticatory
ability and the stabilization of occlusal contacts, the comfort and the aesthetics of the patient,
the destabilization of which is raised from the collapse of occlusion. [23, 40]Considering the
prosthetic options for patients treated for advanced periodontal diseasethe cross-arch FPD
ofshortened dental arch concept is considered to be a conservative prosthodontic
treatment,[84-86] while splinting with cantilever cross-arch-designed FPD may be preferred
since extension to the molar area seems to provide improved esthetics, masticatory function,
occlusal stability, and properly directed occlusal forces. [87,88]
In the past, the splinting in perioprosthetic patient had been a controversial issue due to
the use of teeth with an extremely reduced but otherwise healthy periodontium as abutments
in extensive restorations, what contradicted to previous dominating views, which were based
on the Ante‘s Law. [89] However, Nyman and Ericsson (1982) have proven that the ability of
teeth with an extremely reduced periodontium (10% of the total surface of periodontal tissues
for a dental barrier) to support the fixed cross-arch restorations had been the same good in
relation to the teeth with a periodontium not so reduced after 8-11 years. [32]
In a series of studies carried out in order to record and to evaluate complications related
to the fixed cross-arch restorations in perioprosthetic patient, it was reported that they were
mostly of technical nature, not of biological / periodontal nature, and were related to the
presence of catnilevers. [90]
In 1986, Randow et al. presented a study in which they recorded the technical and
biological complications in three patient groups, which had been treated by fixed cross-arch
restorations without cantilevers, with one cantilever or with two cantilevers, respectively. In
this study they confirmed a direct correlation between the addition of cantilevers and the rate
of technical complications, which was increased over time basically for the group with the
two cantilevers. The rate of complications has almost doubled when an additional cantilever
was added, reaching 44% for restorations extending in double cantilevers bilaterally. Basic
technical complications were the retention loss and the restoration fracture. These
complications were basically related to the end-abutment, whereas the restoration fracture
was mostly located in the area of proximal connector of the end-abutment. Furthermore, a
significant correlation between the complications and the vitality of the end-abutment is
accentuated, as it concurs with the studies of Nyman (1979), Karlsson (1984), Sorensen
Biomechanics of Rehabilitating the Perioprosthetic Patient
75
(1985), and Lindquist (1998), and is explained by the fact that the end-abutment undergoes a
systematic concentration of excessive stresses when it is not alive. [33, 34, 91, 92] On the
contrary, the end-abutments in fixed cross-arch restorations with cantilevers show the greatest
possibility of necrosis, as it is confirmed by other studies.[93-96] Randow‘s group (1986) also
accentuates the same correlation, which is considered significant basically for restorations
with two cantilevers and is justified by an extensive cut ofdental substance during the
preparation of the end-abutment in order to ensure the parallelism of walls for the
optimisation of retention. [34] However, other research groups present far less rates of both
technical and biological complications during the restoration with the fixed splinting with
cantilevers. Nyman and Lyndhe (1979), in a study similar to that of Randow‘s (1986),
recorded 8% of technical complications after 5-8 years of observation, irrespective of the
presence of cantilevers. This study concurs with the study of Randow as regards the
complication type, however this rate corresponds to the complication rate that Randow et al.
attribute to restorations without cantilevers after 7 years of observation. [33] The results of
the above-mentioned study correspond to those of Lundgren and Laurell‘s, which presented a
very small rate of complications for fixed restorations extending bilaterally in double or triple
cantilevers. [97, 98] Likewise, in a three-year study of fixed cross-arch restorations with
cantilevers in Koreans, Yi et al. (2001) found respective results. [37] In essence, the last
studies formulate the view, according to which the splinting type, with regard to the presence
of cantilevers, does not affect the restoration prognosis. However, it should be mentioned that
the small rate of the last studies is attributed to special modifications conducted in relation to
the connectors‘ dimensions
of the metal framework, the type of preparations and of occlusion,
as well as the strict therapy protocol and the repeated examination that had been followed.
More precisely, the length and the width of the connectors nearly doubled in comparison with
the normal range (length: 5-6, width 4-5), the teeth preparations (mostly the end-abutment)
became parallel as far as possible, whereas the occlusal contacts were retrieved along the full
length of the dental arc without interventions in working or non-working side. [99] The
proper shaping of occlusion is a significant factor for the prognosis of restoration with
cantilevers. However, when it is not possible (patients with the skeletal Class II), it is better to
avoid the use of cantilevers. In particular, experimental studies have proven that the absence
of contact in the anterior area of a fixed cross-arch restoration with cantilevers induces stress
concentration in the area of cantilevers and the increase of the bendingmoments at the point
of junction with the end-abutment. Likewise, experimental studies carried out by Laurell and
Falk‘s research groups point out that the restitution of equivalent contacts with the rest dental
barrier causes a favourable distribution of stresses along the length of cantilevers.
Specifically, the forces that develop in the second cantilever are approximately one sixths
compared to those that develop in the first cantilever, what is explained by the root apex
bending deflection of the second cantilever in relation to the first. [100] However, premature
contacts of about 80 nm induce the reverse distribution of stresses, presenting a risk factor for
the restoration. [101] Finally, a factor which is considered significant for the prognosis of
restoration with cantilevers is the type of a competitor barrier. However, even in this case,
opinions seem to be conflicting, because Falk (1989) records an increase of dynamic fields in
the area of cantilevers when the competitor barrier is presented by the complete denture,
despite the fact that Randow et al. (1986), in a clinical study, have not found any statically
significant difference between the technical complications and the type of an opposing dental
arch. [34, 102]
Petros Koidis and Manda Marianthi
76
As shown above, the implementation of the fixed cross-arch restoration with cantilevers
may present a therapeutic reality with a very good prognosis, on the condition that
indispensable prerequisites occur as regards the therapeutic and the restorative part.
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