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 Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 3  |  Issue : 1  |  Page : 14-20

Survival times of restorative parameters vis-à-vis material combinations


Dept of Dentistry, Prince Sultan Military Medical City, India

Date of Web Publication27-Jan-2015

Correspondence Address:
Sheela Sampath
No. 393, 9th Cross, 2nd Block, Jayanagar, Bangalore - 560 011, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2321-4619.150026

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  Abstract 

Context: Two types of composite restorative modalities are compared: All-universal composite restoration (single) versus restorations done using flowable-universal composite combination (dual). Aims: To assess survival probabilities of three restorative parameters: Intactness,color match and marginal integrity.

  1. Whether the survival probabilities are influenced by restoration modality and cavity types, and if so, to what extent
  2. Clinically relevant deductions with respect to materials and clinical technique.

Settings and Design: A retrospective, case-control analytical study based on secondary data derived from documentation of evaluations of restorations placed in patients attending a primary dental care. Subjects and Methods: Data from the records of as many restorations that were routinely evaluated in the clinic, at different points in time for up to 5 years, were drawn up (2008 − 2013). The dual modality restorations were considered as 'cases' and the single modality restorations were deemed 'controls'. Statistical Analysis Used: The life-table method was applied for the survival analysis of each of the three clinical parameters. Qualitative analysis of these same parameters was also carried out using the Chi-square test with P < 0.05. Results: Survival probabilities of restoration retention (intactness) and color match were not influenced by the restorative modality, though marginal integrity's survival probability was; being slightly lower for flowable-universal combination. The subset of posterior load-bearing cavities performed similarly on all clinical parameters (survival as well as qualitatively), uninfluenced by the restorative modality. Conclusions: Overall, the lower survival of marginal integrity may necessitate sooner replacements for restorations done using flowable-universal combinations. However, in the specific case of classes I, II and built-ups i.e. posterior load bearing cavities, these might as well be restored with a combination of flowable-universal material.

Keywords: Flowable composite, longevity, universal composite


How to cite this article:
Sampath S. Survival times of restorative parameters vis-à-vis material combinations. J Res Dent 2015;3:14-20

How to cite this URL:
Sampath S. Survival times of restorative parameters vis-à-vis material combinations. J Res Dent [serial online] 2015 [cited 2019 Dec 13];3:14-20. Available from: http://www.jresdent.org/text.asp?2015/3/1/14/150026


  Introduction Top


Composite restorations are now an established method of restoring diseased/decayed teeth and more often times take precedence over traditional amalgam due to their versatility. Being inferior to amalgam when initially introduced, composite resins have undergone a sea-change in their material compositions and consequently in their properties. [1],[2],[3],[4] The performance of posterior composites has greatly improved during the past few years relatively, [5] and at least half of posterior direct restoration placements currently utilize composite materials. [6] Apart from improved longevities than in the past, due mostly to improvement in adhesivetechnologies, some of the clinical advantages of composites over amalgam and glass ionomers include estheticity, relative ease of placement and manipulation, and relatively good mechanical properties, [7] though not equal to amalgam.

Starting off as unfilled/large particle filled acrylic resins, composites are now available to practitioners in a number of forms which they can utilize in different clinical situations. Some of the different physical forms in which composites are currently available include flowable, microhybrid/nanohybrid universal (stiffer composites used in anterior or posterior teeth) and packable. [8],[9] Most of the differences arise from the filler component in the composite such as size, amount, morphology, etc., The universal one, for instance, has bimodal particle sizes of 0.4−5 microns and 1−100 nm which accounts for upto 80% by volume of the resin. The flowable one on the other hand, has filler sizes ranging from 0.2−3 microns but is lesser in fraction (approx 40−60% by volume) to decrease viscosity and impart flowability. [10] The availability of composites in these different physical characteristics (flowable, packable, etc) has placed in the clinician's hand, a choice of materials with which to restore hitherto difficult, if not impossible situations. [1] For example, when the first-generation flowable composites were introduced, their mechanical properties were lower than conventional composites and were, as such, cautioned against use in high-stress areas as their longevity was expected to be low. [11] But currently available flowable composites are superior and some manufacturers recommend their use in high-stress areas too. [12],[13] Such situations arise especially in posterior teeth that require being built-up or otherwise extensively restored. When such teeth are elected to be restored directly, two options exist- 'sandwich technique', using glass ionomer as the intermediate layer below composite or restoration with all-composite material; the choice being one of clinician preference. The sandwich technique is utilized in cases of deep caries, difficult isolation and also if external margins are in dentin. In vitro studies have shown satisfactory marginal seal. [14],[15],[16] Some studies have also investigated the durability of 'sandwich' type restorations documenting 19% failure in 6 years (AFR ≈ 3%). [17],[18] However, it is not entirely without its cons. Being an inorganic material it is predisposed to acid erosion. [19] Its surface can be damaged in the presence of low pH. [20] Even after setting, further etching continues slowly for a much longer period. [21] Its ability to buffer lactic acid [22] might also be associated with loss of material by erosion. [23] Current adhesive dentistry primarily relies on the etch-rinse-bond procedure, which is considered the gold standard. [24],[25],[26] If done correctly with attention to detail, such composite restorations can lead to excellent results. But even with an all-composite restoration, marginal leakage due to polymerization shrinkage is still an issue with various degrees of microleakage and degradation of bond strength over time. [27],[28],[29],[30],[31] Albeit, restoration with all-composite does have the advantage of reinforcing remaining dental structure [32],[33] and imparting better mechanical strength compared to glass ionomer and is still widely used to restore posterior teeth and as an alternative to amalgam. [34]

When an all-composite restoration is chosen, it is usually the universal (hybrid/microhybrid/nanohybrid) composite that is chosen and is built up in an incremental fashion with a maximum depth of 2 mm for each increment. Needless to say, this is somewhat time-consuming especially in larger restorations. Further, in large cavity preparations, a composite with a stiffer consistency such as the 'universal' needs to be adapted to the cavity walls and manipulated with suitable instruments to develop proper contour and anatomy. Proper condensation of the restoration is also important to prevent voids [35] within the restoration which in turn, might be detrimental to its strength. This calls for considerable skill and dexterity on part of the operator. On the other hand, clinicians find it most useful if a material can flow and be deposited especially in tight spaces. [12] So, a solution is sought by using flowable composite in the inner layers and topping it up with a regular 'universal' (microhybrid/nanohybrid) composite. The advantages include ease of adapting the composite due to its flowable nature [13] and yet exposing only the universal composite on the occlusal (load bearing) surface, which is analogous to compensating the physical limitations of glass-ionomer by laminating it over with a stronger material (sandwich technique). [36] Additionally, the flowable nature also allows the flowable composite to create an intimate union with microstructural defects of cavity preparation prior to placingthe restorative composite. [37] Other reported advantages of using flowable composites in this manner include its role as a stress absorbing intermediate layer [38] , reduced microleakage [39],[40] and fewer voids at the interface of the restoration and tooth structure, when compared with bonding agent and resin composites alone. [41] However, the longevity of such a restoration has not been clinically evaluated, even though restoration longevity studies have themselves been the subject of many studies. Also, as far as the author's knowledge goes, longevity of individual clinical parameters (marginal integrity, color, etc.) has also not been studied thus far. A systematic review of 652 papers on directly placed materials commissioned by UK National Health Services has been published. [42],[43] Longevity of different directly placed materials was derived from the systematic review of 253 papers. [44] Many clinical studies are carried out under research environments and optimal conditions and the reported longevity may not always reflect on a general dental practice, where treatment times are constrained and the diagnostic threshold for replacement may vary.

Here, an attempt has been made to conduct an analysis in a general practice setting to assess longevity in 'real-life dentistry'. An analytical study was hence proposed to be carried out to evaluate the longevity of some of the clinical parameters of the 'dual-type' restorations described above (stiffer consistency i.e. universal composite placed over a cured flowable material) and compare them with composite restorations placed using a single type of material (universal composite only); the specific objectives being:

  • To assess survival probability figures for restorations, their marginal integrity and color match
  • To investigate if these survival probabilities are influenced by restoration modality and cavity types (build-ups, class I and class II), and if so, to what extent
  • To deduce clinically relevant information with regard to materials and clinical technique



  Subjects and method Top


Study design and setting

A retrospective, case-control analytical study based on secondary data derived from documentation of evaluations of restorations placed in patients attending primary dental care at Base 511 Polyclinic in Al Hariq, Saudi Arabia.

Data collection (cases and controls)

Patient records from 2008 to 2013 were available for collection of the following data that were recorded as per routine practice in the clinic-

  • Operator- All the restorations in this study were carried out by a single operator (author). The assessment, however, involved another trained operator to minimize bias
  • Date of initial restoration
  • Details of restoration done- cavity class, restorative materials used- flowable composite brands, microhybrid/nanohybrid composite brands
  • Date of subsequent visit by the patient (these restorations were evaluated, as elaborated further below, whenever patients presented themselves in the clinic for any reason, and not specifically recalled for evaluations alone)
  • Details of evaluation of the restoration, that included
  • 'Intactness'- scored either 0 (dislodged restoration) or 1 (intact restoration)
  • 'Color Match'- USPHS/Ryge scoring applied during evaluation
  • 'Marginal Integrity'- USPHS/Ryge scoring applied during evaluation.


Briefly, in the USPHS/Ryge scoring, Alfa (A) denotes a satisfactory restoration, Bravo (B) denotes the presence of a defect in the restoration but is clinically acceptable and does not require replacement and Charlie (C) denotes a clinical failure of the restoration. Two calibrated examiners evaluated the restorations.

Upon scanning of all records, restorations were assigned as either 'cases' or 'controls' based on the following criteria:

  • Cases: Restorations done in dual modality i.e. using two materials- flowable composite in the inner layers and universal composite (microhybrid/nanohybrid) as the outermost layer
  • Controls: Restorations done in single modality i.e. using a single type of material- universal composite (microhybrid/nanohybrid) throughout


Note 1: The type of initial restoration (single or dual modality) done was based mainly on clinical judgement and when a choice existed, either modality was chosen alternatively.

Note 2: The various composite brands used routinely in the clinic during the above period are listed in [Table 1]. However, comparison amongst these brand types did not form a part of the present study. 'Adper TM Single Bond Plus' (3M ESPE Dental Products, St. Paul, MN, USA) utilizing the total etch technique was the adhesive used with all these composites.
Table 1: Materials used

Click here to view


Study size

For the final analysis, the records of 88 restorations (31 cases, 57 controls) that were evaluated at different points in time for up to 5 years (range: 3−55 months), were drawn up.

Statistical tests

Since individual life-lengths of restorations are not known, the life-table method was applied for the survival analysis of each of the three clinical parameters of intactness, color match and marginal integrity, with respect to the two types of restorations. In this analysis, the event of interest i.e. failure, was the score of '0' for 'intactness' and the score 'C' for 'color match' and 'marginal integrity'. Further, in order to assess any contribution of cavity design on survival time of the clinical parameters of the two types of restorations under study, it (i.e. cavity design) was included as a second order control in the life-table test whenever sufficient data-points existed.

Qualitative analysis of these same parameters (again with respect to the two types of restorations) was also carried out using the Chi-square test with P < 0.05. All statistical tests were carried out using the SPSS 17.0 statistical package for Windows (Chicago, IL, USA).


  Results and discussion Top


Analysis of records presented the following distribution of either restoration [Table 2].
Table 2: Distribution of restoration modality according to classes of cavity

Click here to view


Survival times of the restorations themselves, i.e. their retention period in the cavity was measured by the parameter 'intactness'. The single-material (universal) and dual-material (flowable + universal composite) showed similar times for retention, differences not being statistically significant [Figure 1].

Survival probability at the end of 5 years was between 80 and 90% for each of the two types of restorations, which also matches with those mentioned in the literature. [45] Similarly, time to discolor, as measured by the survival analysis of the 'color match' parameter, was also found to be similar for the two types of restorations [Figure 2].
Figure 1: Intactness vs months (*Differences between the two restorative modalities not statistically significant)

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Figure 2: Color match vs months (*Differences between the two restorative modalities not statistically significant)

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Survival of marginal integrity, however, showed significant differences (P = 0.007). Survival probability of marginal integrity at 50 months was close to 100% for the universal material, buy fell to around 60% for the flowable-universal combination [Figure 3]. Further on, this difference was not accounted for by differing cavity types (build-ups and classes I-V), as shown by the life-table tests using cavity design as the second-order control. In other words, speaking overall (i.e. considering all cavities and materials at once), marginal integrity survival did not depend on the type of cavity; rather it depended upon the restorative material, lasting a lesser time in case of flowable-universal combination. This might be expected due to the higher resin content in the flowable composite.
Figure 3: Overall marginal integrity vs months (*statistically significant differences between the two restorative modalities [P = 0.007])

Click here to view


However, to specifically analyze the case of posterior load-bearing restorations (i.e. classes I, II and build-ups), a selected-cases comparison was done, involving only these cavity types and then comparing between the two restorative modalities. Survival probabilities of intactness, color match and marginal integrity [Figure 4] for both the restorative modalities were not significantly different, statistically. That is to say, either restoration modality (single or dual material) worked well in these situations, specifically.
Figure 4: Marginal integrity of load bearing restorations vs months (*Differences between the two restorative modalities not statistically significant)

Click here to view


Since necessary data was already acquired in the above process, a related question was also explored: Did cavity types influence the survival probability (intactness) of a composite restoration, irrespective of materials used? This was done using 'cavity type' as the first order control. It was found that significant differences (P < 0.05) existed between the survival probabilities of class I cavities on one hand and classes III and V on the other hand, with the former having a greater survival function than the latter. Interestingly, no significant differences were found in survival probabilities (intactness) amongst classes I, II and build-ups [Figure 5]. This in itself might be clinically significant, in that, it strengthens the previous conclusion of similar survival rates for single and dual restorative modality for posterior load-bearing restorations.
Figure 5: Intactness by cavity type (*, a, b: Differences not statistically significant mutually, except between 'a'and'b')

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Taken together, this would mean that the survival probabilities (of intactness, color match and marginal integrity) of restorations in posterior load-bearing areas were neither influenced by the restorative modality nor by the design of the cavity.

Apart from the various tests for survival done above, purely qualitative differences between the two restorative modalities (disregarding time) were also evaluated, based on Chi-square tests. Again, no statistically significant differences were found in the same three clinical parameters. That is to say, the two restorative modalities performed equally well, quality-wise. [Figure 6] shows the combined distribution of scores for the two restoration types. (~92% of observed restorations were intact).
Figure 6: Combined % distribution of qualitative scores for the two restorative modalities (without regard to time)

Click here to view


Overall, approximately 22% of the restorations were deemed to have failed, with dislodgement being the leading cause (8.5%). Marginal deterioration and discoloration accounted for 7% and 8% of failures, respectively. Again, as stated above, these failures were not accounted for by restoration modality. No other clinical indications of failure (pulp death, sensitivity, etc) were noted at least up until the time they were examined.

Having discussed various points, however, it should also be borne in mind that the study size is relatively small. For a time-function based study such as this one, a small sample size may produce restricted findings. A bigger sample size would definitely be more representative and conclusions more definitive. Nevertheless, this small-sized study does show some pointers and could serve as a pilot investigation for bigger and preferably prospective studies.


  Conclusions Top


Within the scope of this design of study and the study size, the following inferences may be drawn:

  • Survival probabilities of restoration retention (intactness) and color match were not influenced by the restorative modality, though marginal integrity's survival probability was; being slightly lower for flowable-universal combination
  • On the other hand, survival probability of the restoration (intactness) was influenced by cavity type. Even so, the subset of posterior load-bearing cavities performed similarly on all clinical parameters (survival as well as qualitatively), uninfluenced by the restorative modality.


In an overall view (i.e. including both anterior and posterior composite restorations), even though there were no significant qualitative differences between the single and dual restorative modalities, the time period for which it remains so, especially as related to marginal integrity, may be shorter for the latter type of restorative modality (flowable + universal) than the former. This may probably necessitate sooner replacements for the flowable-universal combination.

However, in the specific case of posterior load bearing cavities (classes I, II and built-ups), these might as well be restored with a combination of flowable-universal material, producing accurate contours more easily and with the expectation that it would probably be retained for as long as a single universal material-based restoration.

Similar studies involving composite versus sandwich-technique restorations would also be relevant here.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

  [Table 1], [Table 2]



 

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