As the numbers of women entering the health professions increase, the gender composition of dentists has been drastically changing.1) This trend is similar in Asian countries where the traditional role of women has changed dramatically in terms of career development. In 2006, females comprised of 23.0% of the dentist in South Korea and 24.2% of the dentists in Japan.2,3) Although female dentists outnumbered their male counterparts in some countries, female practitioners still exhibited various gender specific patterns in practice type (public vs. private sector), patient group, employment status, working time, etc.4-9) Furthermore, several specified studies based on dental work models have mentioned a gender difference in terms of occupational relationships, professional attitudes, academic contributions, treatment decisions, etc.4,5,7,8,10-13) However, it has been rarely studied on gender difference related to dental operation per se. One study showed that female dentists reportedly applied topical anesthesia more often than male dentists before needle injection.6) Regarding operative procedures, it is challenging to extract relevant variables for differentiating the individual performances of multiple practitioners. For example, restorative treatment, which comprises the major part of a dentist's workload, may be divided into several procedural steps, including cavity preparation, base or liner placement, filling with restorative materials, etc.14) These individual steps may vary based on scientific knowledge, clinical experience, and different maneuver. The operative procedures may be further influenced by practitioners' degree of attentiveness, caring, and other personal characteristics.7) We selected direct resin composite restoration for a representative operative model and chose relevant variables for specification. The aim of this study was to assess whether there is an independent effect of gender difference in direct resin composite restoration under consideration of background confounding factors of practitioners which might affect.

This study was based on the data acquired by a nationwide survey to investigate gender differences in operative dentistry with a specific focus on direct resin composite restoration. The survey was conducted using an electronically delivered questionnaire. The subject line of the e-mail was "A survey on esthetic bonded restoration," and the e-mail asked for participation in the linked survey. After reading a brief introduction on the survey, the recipients were able to click the icon labeled "Participation" and then proceed to the questionnaire. An electronically delivered survey has the advantages of a rapid response rate, improved ease of data collection and minimal cost when compared to traditional paper surveys sent via mail.17) However, the major drawback of an electronically delivered survey is the low response rates, which is partially due to incorrect, inactive or nonexistent e-mail addresses. In our study, information was received from 840 respondents, representing 71.4% of those who clicked to participate in the survey, 31.9% of those who viewed the e-mail, but only 6.9% of the total number of dentists who were sent the e-mail. There were a large proportion of true non-respondents who have actually received the e-mail but deleted it without opening it or chose not to participate in the survey. Previous studies on the effect of the non-response group noted that low response rates to health studies do not necessarily result in a high non-response bias.18,19) In this study, more dentists in the younger age group were included in the respondent group. Additionally, more female dentists belonged to the younger age group. However, the age and gender distributions were not significantly different between the respondents and the overall Korean dentist population (p > 0.05). The vast majority of dentists were in private practice (female, 80.2%; male, 76.2%). Relatively more female respondents (53.7%) than male respondents (29.2%) were working in a large practice which had seven employees or more. In our questionnaire, the ownership of a practice was not determined; however, it may be related to that female dentists were less likely than male dentists to own the practice as shown in other studies.6-8) Instead, female dentists were more likely to be employed in a large practice with several dental staff. Relatively more female dentists were currently finishing or had completed a specialty program in conservative dentistry. This fact reflected the current trend in Korea of a growing enrollment by female graduates in the specialty of conservative dentistry.

For class 2 resin composite restoration, we chose a distoocclusal cavity of an upper second premolar for the exemplary case, which may not be an esthetically critical area. Considering that the primary selection of material would not be direct resin composite for some respondents, we posed the question: "If you were to restore the distoocclusal cavity of the upper second premolar with resin composite, how often would you use a rubber dam?" There was no significant difference between male and female dentists in the frequency of rubber dam usage: 15.4% of female and 11.1% of male dentists always used a rubber dam, while more than 40% of both groups did not use a rubber dam in such a case. However, field isolation still seemed to be a concern, since moisture control was chosen as the most challenging part of the procedure by many respondents (females, 25.9%; males, 21.2%). Proximal contact formation was the most frequently chosen answer by both groups. A clear plastic matrix was the more preferred matrix type compared to a metal matrix; but a question concerning how to place the strip was not included in the questionnaire.

It is well known that polymerization shrinkage stress of resin composite is influenced by the configuration factor of a cavity, and incremental build up has been broadly recommended in resin composite restoration.20) Additionally, incremental layering can increase the polymerization degree of the resin composite placed in a deep cavity preparation. Generally, it is recommended that the resin composite should be cured in increments no greater than 2 mm in thickness.21) However, cavity filling in very small increments may not be desirable due to increased chair time and inclusion of porosity between the layers. It is interesting to note that female dentists tend to split the layers into smaller increments in both class 2 and class 5 restorations. Female dentists were also more likely than male dentists to take a longer time for the restoration procedure. Furthermore, this gender- specific operative pattern was clearly reflected in base or liner applications of class 5 restorations. 44.0% and 33.9% of female dentists would use flowable resin and RMGI, respectively, for the base or liner of a moderately deep V-shaped non carious lesion given as an example (Figure 1), while 34.7% and 25.8% of males gave the same answers, respectively. Flowable resin can provide a stress-relief function to compensate for polymerization shrinkage stress of the overlying resin composite and improve internal adaptation by wetting the cavity wall.22) However, the elastic bonding capacity of flowable resin was shown to be offset by its inherently high shrinkage rate.23,24) Resin-modified glass ionomer cement may be another option for a lining material with a preferable dentin bonding capacity. However, no clarified consensus exists on the efficacy of base or liner application prior to resin composite restoration, since many conflicting results have been induced from in vitro and in vivo experiments with regards to postoperative sensitivity, microleakage, bonding durability, etc.25-28) Therefore, a practitioner's inclination to use a base or liner may be related not only to evidence-based knowledge but also individual preference. Only a few studies have been performed on gender differences in dental procedures, but their findings were that operative procedures reflected gender-specific patterns. In a survey of Canadian dentists, women were more likely than men to practice recommended infection control procedures, such as wearing gloves, a mask, and protective eyewear, and being vaccinated against the hepatitis B virus.29) In a Swedish report, female dentists reported that 0.8 more of their weekly working hours were used for prosthodontic treatment compared to their male counterparts.4)

In spite of the dissimilarity in operative techniques between male and female dentists, postoperative sensitivity and debonding were chosen as the major concerns after class 5 resin composite restorations for both groups. There are several procedural steps related to postoperative complications and bonding failure such as cavity preparation, dentin and enamel bonding, resin composite placement, polymerizing light irradiation, etc. For the bonding procedure, it would be even more complicated to select clinically specific variables because of the diversity of adhesive agents and their usage.15) It is the same with the irradiating source, since various light-curing units require different irradiation times and intensities. However, more extended questions on other parts of operative procedure will derive additional valuable information on the association of gender and dental practice. Also, unbiased, well stratified sampling methods are crucial in a surveyed study, which were not properly applied in this study. Despite the limitations of this study, a gender difference was identified in several aspects of operative procedures involved in direct resin composite restoration. Future study covering other areas of dental practice will help identify the inherent characteristics of male and female clinical performance.

This study revealed differences between male and female practitioners regarding operative procedures of direct resin composite restoration. Female dentists were more likely than males to use a base or liner prior to resin composite placement, to apply resin composite in smaller increments, and to spend a longer time for the restoration procedure.