Study suggests there may be no difference between char-free and continuous-wave carbon dioxide lasers for oral mucosal biopsy


Animal studies have suggested that there is less thermal damage when excisional biopsies are performed using a carbon dioxide (CO2) laser in a char-free (CF) mode than in a continuous-wave (CW) mode. The aim of this study was to and compare the clinical and histopathologic characteristics of excisional biopsies performed with CW or CF CO2 laser (10.6μm) modes to determine whether 1 laser mode can be recommended for daily clinical practice

Patients requiring the removal of  fibrous hyperplasias of the buccal mucosa between 1 to 2 cm in diameter were randomised to have excisional biopsies with either char-free (CF)or continuous-wave (CW) mode CO2 laser.  Patietns were followed up at 2 and 4 weeks.   The primary outcomes were, the time of surgery, the number and type of intra- and postsurgical complications, and the widths of the histopathologic thermal damage zones. Secondary clinical outcomes included the postoperative pain perception (visual analog scale [VAS]) and the intake of analgesics.

  • There were 60 patients in all (36 women, 24 men) with a median age of 50.5 years.
  • Median durations of surgery were 74.5 seconds in the CW group,  83.5 seconds in the CF group. Intra-operative bleeding occurred in 16.7% of patients in the CW group and in 13.3% of patients in the CF group.
  • Median areas of histopathologic collateral damage zones were similar in the CW group (166.5 μm) and the CF group (162.5 μm).
  • There was no statistically significant difference between the VAS values of the 2 groups.
  • Analgesic intake was recorded by 16.7% of patients in the CW group and by 6.7% of patients in the CF group (P = .23, not significant).
  • No statistically significant correlation was found between areas of thermal damage zones and postoperative VAS scores.

The authors concluded

In contrast to previous animal studies, no significant difference was found in the widths of thermal damage zones between the CW and CF groups. The VAS values and analgesic intake were low in the two groups. The two CO2  laser modes are appropriate for the excision of intraoral mucosal lesions. A safety border of at least 1 mm is recommended regardless of the laser mode used.


No power calculations were presented for the sample size (30 per group)


Suter VG, Altermatt HJ, Dietrich T, Reichart PA, Bornstein MM. Does a pulsed mode offer advantages over a continuous wave mode for excisional biopsies performed using a carbon dioxide laser? J Oral Maxillofac Surg. 2012 Aug;70(8):1781-8. Epub 2012 Apr 26. PubMed PMID: 22542332.


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Derek Richards

Derek Richards is a specialist in dental public health, Director of the Centre for Evidence-Based Dentistry and Specialist Advisor to the Scottish Dental Clinical Effectiveness Programme (SDCEP) Development Team. A former editor of the Evidence-Based Dentistry Journal and chief blogger for the Dental Elf website until December 2023. Derek has been involved with a wide range of evidence-based initiatives both nationally and internationally since 1994. Derek retired from the NHS in 2019 remaining as a part-time senior lecturer at Dundee Dental School until the end of 2023.

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