Conservative & Endodontics Portal
Dr. Mrinalini Mahajan,Senior Resident, Department of Dentistry,
All India Institute of Medical Sciences, New Delhi
Dr. Vimal Sikri, Asstt. Professor, Deptt. of Operative Dentistry,
Punjab Govt. Dental College and Hospital, Amritsar
The demise of amalgam restorations looms large in this new millennium. The increasing demand for aesthetics coupled with concern about mercury hazards has led to a growing interest in tooth coloured restorative materials for posterior teeth. Posterior composite resins seem to satisfy the requirements of both the patients and dentists. The patients get a ‘tooth as good as new’ and the dentists also achieve satisfaction since they have provided a restoration free of any known biohazards, free of corrosion, having low thermal conductivity and foremost, a restoration which strengthens the remaining tooth structure.
However, posterior composite restorations could not fully replace silver amalgam because of certain drawbacks such as inadequate wear resistance, poor marginal integrity, greater technique sensitivity, difficulty in building contacts and a common occurrence of post-operative sensitivity.
The initial studies with posterior composites reported a low wear resistance9,4,3 and poor marginal integrity, though the new improved materials and techniques show promising results7,11,6. The clinical performance of newer posterior composites has not been well documented. The present study compared three posterior composites - Tetric Ceram, Heliomolar RO, and Restorative Z-100 as regards their clinical behaviour and resistance to wear.
The present study was conducted on forty-five maxillary and mandibular first permanent molars having class II carious lesions. The patients were selected irrespective of age and the socio-economic status. Criteria for inclusion in the study were:-
Criteria for exclusion from the study were:-
The selected teeth were randomly divided into three groups viz. Group A, Group B and Group C having 15 teeth in each group. In Group A, the cavities were restored using Tetric Ceram (Vivadent/Ivoclar), in Group B, Heliomolar RO (Vivadent/Ivoclar) was used, while in Group C, the cavities were restored using Restorative Z-100 (3M Dental Products)
The clinical procedure for cavity preparation and restoration remained same for all three groups. All operative procedures were carried out under rubber dam isolation. Each cavity preparation was standardized to conform to modified Black’s principles of cavity preparation. Occlusal contacts were recorded before hand and an attempt was made to exclude them from the cavity outline; at least one centric holding contact was maintained on sound tooth structure. The cavosurface margins were not bevelled. An ultrathin stainless matrix band was used to obtain proximal contour and the restorative material was inserted in increments (Photograph 1). Initially a 0.5 mm thick increment was placed to the gingival wall extending up the facial and lingual walls. Subsequently, 1-1.5 mm increments were placed obliquely. Each increment was photocured for 40 seconds. The occlusal surface was finished using Composite Finishing Kit (Shofu). The occlusion was adjusted and polishing was done using Composite Polishing Kit (Shofu) (Photograph 2).
The restored teeth were rated using United States Public Health Services (USPHS) (Ryge) criteria (Table No. 1) at baseline and after 3, 6 and 9 months (Photograph No. 3,4). At each recall a Vinyl (Poly) Siloxane impression of the restoration was used to prepare stone casts.
The amount of wear was assessed by comparing the casts obtained at each recall visit with a set of calibrated standards fabricated modifying the Moffa-Lugassy scale (Photograph No.5). The standards were flat bottomed cylinders with depressions of known depth centered on their flat upper surface. Occlusal loss or wear represented the distance from the cavity margin to the surface of the composite restoration. Occlusal loss on both buccal and lingual sides was noted and maximum loss was recorded. When the amount of wear on a cast coincided with a particular standard it was given that value. A cast filling midway between two standards was given an intermediate value of 50% of the interval. If, however, the cast representing the restoration fell close to but did not match a given standard, an intermediate value of 25% of the interval was added or subtracted from each of the subsequent 3 monthly values of each restoration. Two examiners were trained and calibratred prior to reading of casts. The casts were read under a magnifying glass (x10) (Photograph No.6). The results were compiled and put to statistical analysis.
| Category | Characteristics | Methods |
| Color match | ||
| Alpha (A) | The restoration appears to match the shade and translucency of adjacent tooth tissues | Visual inspection |
| Bravo (B) | The restoration does not match the shade and translucency of adjacent tooth tissues, but the mismatch is within the normal range of tooth shades (Within normal range : similar to silicate cement restorations for which the dentist did not quite succeed in matching tooth color by his choice among available silicate cement shades) | Visual inspection |
| Charlie (C) | The restoraiton does not match the shade and translucency of the adjacent tooth structure, and the mismatch is outside the normal range of tooth shades and translucency | Visual inspection |
| Cavosurface marginal discoloration | ||
| Alfa (A) | There is no visual evidence of marginal discoloration different from the color of the restorative material and from the color of the adjacent tooth structure | Visual inspection |
| Bravo (B) | There is visual evidence of marginal discoloration at the junction of the tooth structure and the restoration, but the discoloration has not penetrated along the restoration in a pulpal direction | Visual inspection |
| Charlie (C) | There is visual evidence of marginal discoloration at the junction of the tooth structure and the restoration that has penetrated along the restoration in a pulpal direction | Visual inspection |
| Secondary caries | ||
| Alfa (A) | The restoration is a continuation of existing anatomic form adjacent to the restoration | Visual inspection |
| Bravo (B) | There is visual evidence of dark keep discoloration adjacent to the restoration (but not directly associated with cavosurface margins) | Visual inspection |
| Anatomic contour | ||
| Alfa (A) | The restoration is a continuation of existing anatomic form or is slightly flattened. It may be overcontoured. When the side of the explorer is placed tangentially across the restoration, it does not touch two opposing cavosurface line angles at the same time | Visual inspection and explorer |
| Bravo (B) | A surface concavity is evident. When the side of the explorer is placed tangentially across the restoration, it does not touch two opposing cavosurface line angles at the same time, but the dentin or base is not exposed | Visual inspection and explorer |
| Charlie (C) | There is a loss of restorative substance such that a surface concavity is evident and the base and/or dentin is exposed. | Visual inspection and explorer |
| Marginal Integrity | ||
| Alfa (A) | The explorer does not catch when drawn across the surface of the restoration toward the tooth, or, if the explorer does not catch, there is no visible crevice along the periphery of the restoration | Visual inspection and explorer |
| Bravo (B) | The explorer catches and there is visible evidence of a crevice, which the explorer penetrates, indicating that the edge of the restoration does not adapt closely to the tooth structure. The dentin and/or the base is not exposed, and the restoration is not mobile. |
Visual inspection and explorer |
| Charlie (C) | The explorer penetrates crevice defect extended to the dento-enamel junction | Explorer |
| Surface Texture | ||
| Alfa (A) | Surface texture similar to polished enamel as determined by means of a sharp explorer | Explorer |
| Bravo (B) | Surface texture gritty or similar to a surface subjects to a white stone or similar to a composite containing supramicron-sized particles | Explorer |
| Charlie (C) | Surface pitting is sufficiently coarse to inhibit the continuous movement of an explorer across the surface | Explorer |
| Gross Fracture # | ||
| Alfa (A) | Restoration is intact and fully retained | - |
| Bravo (B) | Restoration is partially retained with some portion of the restoration still intact |
- |
| Charlie (C) | Restoration is completely missing | - |
Photograph1 : Intraoperative photograph showing Class-II cavity prepared
with rubber dam, Tofflmire band, retainer and wedges in place
Photograph 2 : Postoperative photograph showing polished composite restoration 
Photograph 3 : Composite restoration using Z-100 in tooth 26 after 9 months
Photograph 4 : Composite restoration using Tetric ceram in tooth 36 after 9 months
Photograph 5 : Calibrated standards used to assess amount of wear
Photograph 6 : Magnifying glass (X-10) to assess amount of wear
The data pertaining to the USHPS criteria rating is presented in Table 2. This was used to determine the percentage of restorations falling under each of the three categories i.e. alpha, bravo and charlie at the various recall intervals. Statistical analysis applying the chi-square test revealed no statistically significant difference between the three materials at each of the three recalls.
Results of the data involving wear measurements at each recall visit are presented in Table 3 .
| Groups (Materials) |
Time period | Total no. of resto- rations exami- ned |
Colour match rating | Marginal Discolour- ation rating | Marginal integrity rating | Surface texture rating |
Contour rating | Secondary Caries rating | Gross fracture rating |
||||||||||||||
| Al- pha | Bra- vo | Cha- rlie | Al- pha | Bra- vo | Cha- rlie | Al- pha | Bra- vo | Cha- rlie | Al- pha | Bra- vo | Cha- rlie | Al- pha | Bra- vo | Cha- rlie | Al- pha | Bra- vo | Cha- rlie | Al- pha | Bra- vo | Cha- rlie | |||
| Group A (Tetric Ceram) | Baseline | 15 | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - |
| 3 mths | 14 | 14 | - | - | 13 | 1 | - | 10 | 4 | - | 13 | 1 | - | 14 | - | - | 14 | - | - | 14 | - | - | |
| 6 mths | 13 | 12 | 1 | - | 11 | 2 | - | 9 | 4 | - | 12 | 1 | - | 13 | - | - | 13 | - | - | 13 | - | - | |
| 9 mths | 13 | 12 | 1 | - | 11 | 2 | - | 9 | 5 | - | 12 | 1 | - | 13 | - | - | 13 | - | - | 13 | - | - | |
| Group B (Helio- molar RO) | Baseline | 15 | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - |
| 3 mths | 14 | 14 | - | - | 13 | 1 | - | 12 | 2 | - | 14 | - | - | 14 | - | - | 14 | - | - | 14 | - | - | |
| 6 mths | 14 | 14 | - | - | 13 | 1 | - | 12 | 2 | - | 13 | 1 | - | 14 | - | - | 14 | - | - | 14 | - | - | |
| 9 mths | 14 | 14 | - | - | 13 | 1 | - | 12 | 2 | - | 13 | 1 | - | 14 | - | - | 14 | - | - | 14 | - | - | |
| Group C (Resto- rative Z100) | Baseline | 15 | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - |
| 3 mths | 15 | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | |
| 6 mths | 15 | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | |
| 9 mths | 15 | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | 15 | - | - | |
| Sr. No. | Group A (Tetric ceram) Wear (Microns) |
Group B (Heliomolar RO) Wear (Microns) |
Group C (Restorative Z-100) Wear (Microns) |
|||||||||||||||
| Tooth No. | Resto- ration | Base- line | 3 mths | 6 mths | 9 mths | Tooth No. | Resto- ration | Base- line | 3 mths | 6 mths | 9 mths | Tooth No. | Resto- ration | Base- line | 3 mths | 6 mths | 9 mths | |
| 1. | 16 | MO | 0 | 5 | 10 | 15 | 26 | MO | 0 | 0 | 0 | 5 | 36 | MO | 0 | 0 | 0 | 0 |
| 2. | 16 | MO | 0 | 0 | 0 | 0 | 26 | MO | 0 | 0 | 5 | 10 | 26 | MO | 0 | 5 | 5 | 10 |
| 3. | 46 | DO | 0 | 0 | 0 | 0 | 46 | MO | 0 | 5 | 10 | 10 | 36 | MO | 0 | 0 | 0 | 5 |
| 4. | 26 | MO | 0 | 0 | # | # | 26 | MO | 0 | 0 | 0 | 0 | 26 | MO | 0 | 0 | 0 | 0 |
| 5. | 16 | MO | 0 | 5 | 10 | 10 | 26 | DO | 0 | 0 | 5 | 5 | 36 | MO | 0 | 0 | 5 | 5 |
| 6. | 16 | DO | 0 | 0 | 0 | 0 | 46 | MO | 0 | 0 | 0 | 5 | 26 | MO | 0 | 5 | 5 | 5 |
| 7. | 36 | MO | 0 | 5 | 10 | 15 | 16 | MO | 0 | 0 | 0 | 0 | 26 | MO | 0 | 5 | 0 | 0 |
| 8. | 16 | MO | 0 | 5 | 10 | 10 | 46 | MO | 0 | 0 | 0 | 0 | 36 | MO | 0 | 0 | 5 | 0 |
| 9. | 46 | MO | 0 | 0 | 0 | 0 | 16 | MO | 0 | 0 | 5 | 10 | 26 | MO | 0 | 5 | 0 | 0 |
| 10. | 46 | MO | 0 | 0 | 0 | 5 | 16 | DO | 0 | 0 | 5 | 5 | 16 | MO | 0 | 0 | 5 | 5 |
| 11. | 36 | DO | 0 | 0 | 0 | 0 | 16 | MO | 0 | 10 | 10 | 15 | 26 | MO | 0 | 0 | 0 | 0 |
| 12. | 46 | MO | 0 | # | # | # | 46 | MO | 0 | 0 | 5 | 5 | 16 | DO | 0 | 0 | 0 | 0 |
| 13. | 36 | DO | 0 | 0 | 0 | 0 | 46 | DO | 0 | 0 | 0 | 0 | 26 | DO | 0 | 0 | 5 | 10 |
| 14. | 46 | DO | 0 | 5 | 10 | 10 | 16 | MO | 0 | 0 | 0 | 0 | 16 | DO | 0 | 0 | 0 | 0 |
| 15. | 26 | MO | 0 | 0 | 0 | 0 | 26 | MO | 0 | # | # | # | 46 | MO | 0 | 0 | 0 | 0 |
| MO = Mesio-occlusal; DO = Disto-occlusal; # = Fractured restoration | ||||||||||||||||||
Composites are rapidly becoming the materials of choice for restoration of posterior teeth. Numerous techniques for selection of material, preparation of cavity, incremental curing and finishing of restorations have been recommended from time to time.
The present study used a class II cavity design based on Black’s principles. Cavosurface margins were not bevelled since bevelling would lead to overextension of composite under centric stops and also the fins so created might fracture easily. Another reason why the bevel was avoided in the present study was because it facilitated detection of any material loss at or adjacent to the cavity margins. To aid in building the proximal contour a metal matrix band was preferred since it could be contoured better and offered greater resistance to condensation of composites. Clinical evaluation of the restorations was carried out after an observation period of 3, 6 and 9 months using USPHS criteria. This method was introduced in 1971 and has since been modified to suit various study designs the present study used the modified version tabulated (Table No.1).
When assessed for colour match, at 3 months, the clinical results were 100% i.e. all the restoraitons of group A (Tetric Ceram), Group B (Heliomolar RO) and Group C (Restorative Z 100) obtained alpha ratings. At six months 92.3% restorations in Group A, 100% in Group B and Group C obtained alpha ratings. Only one case in Group A at six months recall showed bravo rating. When put to statistical analysis, it was found that there was no significant difference between the three materials as regards colour match after nine months.
The results in the present study are in concurrence with the study of Silva et al12 (1999) who reported 100% colour match with restorations of Z-100 over a period of two years. However, Mazer et al7 (1992) reported 92% alpha ratings for colour match with Heliomolar RO after two years.
Evaluation for marginal discolouration at three months revealed that 92.9% restorations in Group B and 100% restorations in Group C were rated alpha. After nine months, the percentage of restorations which received an alpha rating was 84.6% in Group A, 92.9% in Group B and 100% in Group C.
At three months observation period, one restoration each of Tetric Ceram and Heliomolar RO was rated bravo. At six months, yet another restoration of Tetric Ceram obtained a bravo rating.
However, these differences were statistically non-significant.
The findings of marginal discolouration in the present study are similar to those of Mazer et al7 (1992) who reported 96% alpha ratings for Heliomolar RO after a period of two years. However, Frielich et al2 (1992) reported an incidence of 100% alpha ratings for Heliomolar RO after a three year observation period. More so, findings of 100% incidence of lack of marginal discolouration with the use of Restorative Z100 are the same as the ones presented by Silva et al12 (1999) after two years, though Puppin-Rontani et al10 (1998) reported 96.4% alpha ratings for Z-100 after 12 months.
Assessment of marginal integrity revealed that in Group A 71.4% restorations, in Group B 85.75% restorations in Group C 100% restorations received alpha ratings after three months. After six months, 69.2% restorations in Group A, 85.7% restorations in Group B and 100% in Group C were rated alpha. After nine months, the percentage of restorations given alpha ratings was 62.9% in Group A, 85.7% in Group B and 100% in Group C.
Four restorations in Group A and two restorations in Group B received bravo ratings after three months.
Differences notwithstanding no statistically significant difference was found between the three materials for marginal integrity.
The inference of the observations is that Tetric Ceram had a comparatively poor marginal integrity over a period of nine months. With Heliomolar RO the marginal integrity was rated alpha in only 85.7% cases in the present study as opposed to 100% cases reported by Frielich et al2 (1992). Mazer et al7 (1992) however, noted that during the first 12 months of service the margins along the occlusal surface began to undergo crevicing/ditching when Heliomolar RO was used for class II restorations.
The absence of such crevicing/ditching in restorations of Restorative Z100 was in agreement with the findings of Puppin-Rontani et al10 (1998) and Silva et al12(1999).
As regards surface texture, 92.95% restorations in Group A, 100% restorations in Group B and C showed smooth surfaces after three months. When assessed at six months, 92.3% cases in Group A, 100% in Group B and 100% in Group C showed alpha rating. After nine months, 92.3% cases in Group B and 92.9% in Group C were rated alpha.
One restoration in Group A after three months and one restoration in Group B at nine months were given bravo rating.
Statistically, no signficant difference was detected between the three materials as regards surface texture.
No incidence of loss of anatomic contour was recorded for any of the restorations examined at each of 3, 6 and 9 months.
As regards surface texture, loss of anatomic contour and secondary caries, all the three materials seemed to perform well over a period of nine months.
These findings are in agreement with those reported by Mazer et al7 (1992), Puppin-Rontani et al10 and Silva et al12 (1999).
The percentage of restorations showing gross fracture in Group A was 6.7% after three months and nine months. In Group B, percentage of restorations showing gross fracture of restoration was 6.7% after three months, six months and nine months. The observation of the present study is that fracture occurred in few cases and that too in the early stages. This might be due to the abnormal forces which were not detected prior to restoration.
The amount of wear at each recall was quantified by comparing casts of the restoraitons with a set of standards fabricated on the lines of the Moffa-Lugassy scale8. The original scale consisted on 18 cylinders with depressions of 0, 25, 50, 75, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000mm. This scale was introduced in 1986, an age when composites exhibited considerable wear. The present generation of composites are more wear resistant and hence the need for modification of the scale to adapt it to existing needs. In the present study, a modified version was used which represented wear of 5, 10, 20, 30, 40, 50, 75, 100, 200 mm. Since the depth of the standards were very little and challenged visual acuity, a 10x magnifying glass instead of the standard 2x magnification was used for the measurements.
The mean amount of wear recorded in Group A was 1.79 mm after three months, 3.85 mm after six months and 5 mm after nine months. The mean amount of wear recorded in Group B was 1.07 mm at three months, 3.21 mm at six months and 5 mm after nine months. The mean amount of wear reported in Group C was 0.66 mm at three months, 2 mm at six months and 3.33 mm at 9 months.
These wear rates do not differ significantly when put to statistical analysis.
Mazer et al7 (1992) reported a mean wear of 55 mm of Heliomolar RO at the end of nine months and 15 mm after two years. These values are in agreement with the findings of the present study. The findings of the present study are also in concurrence with the study of Leinfelder5 (1995) who has repoted an annual wear rate of 7-8 mm for Heliomolar RO. With Tetric Ceram the mean wear recorded in the present study concurs with the annual wear rate of Tetric Ceram repoted as 7 to 8 microns by Leinfelder5 (1995).
The amount of wear recorded with Z-100 in the present study is in agreement with Leinfelder5 (1995) who has reported an annual wear rate of less than 6-7 mm for Z-100 and the study of Puppin-Rontani et al10 (1998) who observed no wear in any restoration of Z-100 at the end of 18 months.
The amount wear reported in this study was not reflected as loss of anatomic contour of the restorations when examined clinically using a mouth mirror. This could be because of the extremely low wear rates recorded. Taylor et al13 (1990) stated that the alpha-bravo transition in the USPHS system for wear occured when 97 mm of wear was recorded by the Moffa-Lugassy scale.
Since, extremely small measurements are to be carried out which are difficult, if not impossible, to measure intra-orally, therefore, indirect methods using replicas are being used. A large number of techniques are being investigated such as the 3-axis micrometer, profilometer, laser fringe patterns, moire fringes, computer controlled three-coordinate table, photo-grammetric technique etc. However, none of these techniques has enlarged infallible and a large number of them seem to be unfeasible to large volumes of samples as they require complicated technical know-how and armamentarium. As such these methods are experimental and not in wide usage.
For any wear analysis it is important to distinguish between wear in occlusal contact areas and contact free areas. In contact free areas wear is mainly because of abrasion by food bolus and also by chemical disintegration. Such type of abrasion is evident at the margins. Wear in occlusal contact areas is a more complex phenomenon involving attritition, abrasion and fatigue. Further, all wear mechanisms are superimposed by corrosive wear.
The present study measured wear in contact free areas i.e. wear primarily due to abrasion. The results obtained must be viewed with some amount of caution because the actual amount of wear might be higher when the wear in occlusal contact areas is also considered. Mair et al6 (1990) pointed out that wear due to attrition can be 3.5 times greater than due to abrasion.
The results obtained in the present study indicate that as judged from their performance over nine months the three posterior composites Tetric Ceram, Heliomolar RO and Restorative Z-100 perform satisfactorily in conservative class II restorations. Data strongly suggests that Restorative Z-100 was better suited for posterior restorations when compared with other two. However, the findings of the present study cannot be considered conclusive. Long term studies along with larger numbers of samples are required to reach a final conclusion.
