A systematic review published in BMC Oral Health on October 26, 2026 compared sonic-activated, preheated and flowable bulk-fill composites with conventional high-viscosity bulk-fill materials across six randomized trials. The authors found similar performance for retention, surface texture, anatomic form, secondary caries and postoperative sensitivity. Marginal adaptation and marginal discoloration remain unsettled.
Choosing a bulk-fill technique can be an equipment decision as much as a materials decision. The trials in this review, assessed as of November 2026, used dedicated equipment including SonicFill handpieces, composite warmers and a VisCalor dispenser, and the paper notes that sonic activation and preheating have been reported or suggested to improve adaptation. The review asks whether those extra steps show up in clinical outcomes. For dental professionals in Toronto, the GTA and across Canada weighing that purchase, the answer is useful, with limits worth reading closely.
What did the review examine?
The paper, by Elsaeed, Harp, Hamama and Mahmoud, appears in BMC Oral Health (volume 26). Its protocol was registered in PROSPERO under CRD42025640119, and it followed PRISMA guidelines. All four authors list the Conservative Dentistry Department at Mansoura University in Egypt as an affiliation.
The team searched MEDLINE/PubMed and ScienceDirect for trials published between January 2015 and January 2025. They identified 1,041 records and assessed 33 full-text articles. Six randomized trials met the criteria. The review required at least one year of follow-up in permanent posterior teeth, and each trial had to include at least two different categories of bulk-fill composite.
Two exclusions define what this paper can and cannot tell you. Trials comparing bulk-fill with incrementally layered conventional composite were left out, as were studies of endodontically treated teeth. This is a comparison among bulk-fill types. It does not address whether bulk-fill outperforms layering.
The authors did not run a meta-analysis, citing considerable heterogeneity in design, intervention, follow-up and outcome reporting, along with incomplete numerical data in several studies. The findings below are a narrative synthesis.
Which trials were included?
| Trial | Country | Materials or technique compared | Follow-up | Recall |
|---|---|---|---|---|
| Goda et al., 2024 | Egypt | Filtek Bulk Fill vs G-ænial Bulk Injectable, SonicFill 3 and preheated Filtek | 2 years | 100% |
| Ibrahim et al., 2024 | Egypt | X-tra Fil, non-preheated vs one, five and ten preheating cycles | 2 years | 97.6% |
| Morsy et al., 2023 | Egypt | Filtek Bulk Fill vs VisCalor bulk and SonicFill 2 | 18 months | 100% |
| Elkady et al., 2024 | Egypt | Filtek One Bulk, non-preheated vs one and ten preheating cycles | 1 year | 100% |
| Guney and Yazici, 2020 | Turkey | Tetric EvoCeram Bulk Fill vs SureFil SDR Flow | 2 years | 82.5% |
| Sajjan et al., 2022 | India | Tetric N-Ceram Bulk Fill, preheated vs ultrasonic plasticization | 1 year | 75% |
Sample sizes were modest, from 20 patients in the Morsy trial to 105 in the Elkady trial. Five trials used rubber dam isolation, and one used cotton rolls and suction. None of the six was conducted in Canada.
Where did the bulk-fill types perform alike?
Most outcomes showed no significant difference between conventional high-viscosity bulk-fill and the modified techniques.
- Retention: rates ranged from 95% to 100% across all six trials, with no significant differences.
- Anatomic form: no significant differences in any of the six trials.
- Surface texture: four trials assessed it, and none found a significant difference.
- Secondary caries: no secondary caries was documented in any included study during follow-up.
- Postoperative sensitivity: no significant differences in the trials that reported it. In the Guney and Yazici trial, one conventional bulk-fill restoration later received root canal treatment, after one year.
Where is the evidence mixed?
Margins are the unresolved issue. Four trials found no significant difference in marginal adaptation. Two, Elkady and Morsy, reported more marginal defects with conventional high-viscosity bulk-fill. In Morsy, the defects were identified by scanning electron microscopy.
In the Elkady trial, 57.1% of non-preheated restorations kept an Alpha rating for marginal adaptation, compared with 100% across the preheated groups. In the Morsy trial, the difference surfaced only at 18 months, after all groups had held Alpha scores through 12 months.
Marginal discoloration followed the same split. The same two trials favoured preheated or sonic techniques, three found no significant difference, and Sajjan did not assess it. Neither of the two positive trials tested a flowable. Color match differed significantly in one trial, Elkady, where the ten-cycle preheated group outperformed the non-preheated group.
Those two positive trials do not settle the question. The review's own conclusion states that the evidence is "limited and insufficient to draw definitive conclusions" on marginal adaptation and marginal discoloration.
What did the trials say about repeated preheating?
Two trials tested repeated preheating at 68 °C, up to ten cycles. The Ibrahim group reported that ten cycles performed equivalently to non-preheated composite at 24 months. The Elkady group reported that no restoration in any of its three groups needed replacement or repair at 12 months.
That may be relevant if you re-warm the same composite, although the review does not say how the trial cycles compare with reuse during a clinic day, and two trials of one or two years cannot establish long-term performance. The review did not evaluate every warming protocol or every material, so results for Filtek One and X-tra Fil should not be assumed to apply to other composites.
Pro Tip: Before you budget for a composite warmer, read your composite's current instructions for use for any stated heating limits, and record the temperature and cycle count your team actually uses for a two-week sample of cases.
How much weight should Canadian practices give this?
The authors list several limitations, and they bear directly on how you read the results:
- Performance bias: all six trials were rated at high risk because operators and participants could not be blinded to the restorative materials.
- Mixed scoring systems: five trials used modified USPHS criteria and one used FDI criteria. The authors note that FDI is more sensitive to subtle change.
- Short follow-up: the longest trials ran two years, and short follow-up may miss wear, fracture and marginal deterioration.
- Incomplete reporting: wear and proximal contact were not consistently reported.
- Narrow geography: the authors caution that findings may not apply to populations in other countries.
There is also a tension within the paper. Its clinical implications section says the alternative techniques "can be confidently considered for routine clinical use," while its conclusion calls the margin evidence insufficient. The more conservative reading fits the data: these techniques appear clinically acceptable over one to two years, and the review did not assess whether any of them justifies its added cost.
Every trial but one placed composite in a single increment of up to 4 mm under conditions that were mostly rubber dam isolated. A practice in Mississauga or Scarborough placing thicker increments or working under cotton-roll isolation is working outside the conditions that dominated this evidence.
Pro Tip: If you are comparing techniques in your own practice, photograph margins at placement and at the 12-month recall. Marginal outcomes are where this review found the only recurring differences, and a dated photo record is more reliable than memory, although it may miss defects visible only under magnification.
Before buying a specific material or device, confirm its Health Canada licensing status and follow the manufacturer's instructions. This review does not address Canadian availability or licensing of any product it names.
EBIKO Dental will continue monitoring restorative research relevant to Canadian dental practices. More practice-focused coverage is available at ebiko.ca.
Sources
- Elsaeed AS, Harp YS, Hamama H, Mahmoud SH. Clinical performance of different types of posterior bulk-fill resin composite restorations in permanent teeth: a systematic review. BMC Oral Health. 2026;26.
- Publisher DOI record
Frequently Asked Questions
Q: Do preheated or sonic bulk-fill composites perform better than conventional bulk-fill?
Not consistently. A 2026 systematic review of six randomized trials, five of which used a conventional control, found no significant differences for retention, anatomic form, surface texture, secondary caries or postoperative sensitivity. Two trials reported better margins with preheated or sonic techniques, and the authors called that evidence insufficient for definitive conclusions.
Q: Is it safe to preheat bulk-fill composite more than once?
Two trials in the review tested up to ten preheating cycles at 68 °C and reported acceptable clinical results at 12 and 24 months. Those findings apply to the materials tested and do not establish long-term performance, so check your composite's instructions for use.
Q: Does this review show bulk-fill composite is as good as incremental layering?
No. The authors excluded trials comparing bulk-fill composites with incrementally layered conventional composite. The review compares bulk-fill categories with one another only.