Oral and maxillofacial (OMF) surgery encompasses a range of surgical operations performed on the head and neck region. Surgical site wounds often disrupt the process of providing nourishment through enteral feeding, leading to malnutrition and impeding recovery from the postoperative catabolic state. The adverse effects of severe malnutrition include complications after surgery, increased susceptibility to infections, longer hospital stays, and nosocomial infections [1, 2]. Furthermore, since most patients spend over a day in the hospital following OMF surgery, there is a growing demand for receiving appropriate in-hospital services and the improvement of health-related quality of life (QOL) despite the relatively brief duration of stay [3, 4]. Thus, it is important to provide nutritionally sufficient and satisfying meals to patients after surgery. This approach not only facilitates a prompt recovery process but also contributes to their contentment with hospital services and overall health-related QOL [2]. However, it is common practice in most South Korean dental hospitals to provide patients with a predetermined postoperative diet, specifically a clear liquid diet, without any specific criteria being defined.

An OMF surgeon performs a range of surgical procedures. Major surgeries include the management of trauma, treatment of dentofacial deformities, orthognathic surgery, and oral cancer surgery. Minor surgeries encompass the surgical extraction of third molars, cyst removal, excision of benign tumors, treatment of jawbone infections, dental implant placements, and alveolar bone grafting. Typically, for complex surgeries like orthognathic or oral cancer surgery, a soft fluid diet (SFD) is recommended initially, which is then transitioned to a soft blend diet (SBD) until the wound heals and the patient can comfortably move their jaw again. However, minor surgical procedures are less likely to result in dramatic alterations to the oral environment, and the duration of hospitalization is often short [5, 6]. Nevertheless, an SFD is consistently administered even after most of the minor procedures. Such uniform treatment is usually implemented without a precise nutritional assessment. Despite the lack of empirical evidence, the practice of initially administering an SFD to inpatients has been standardized.

Unlike patients undergoing surgery in other areas of the body, individuals undergoing OMF surgeries should be assessed using newly defined post-operative nutritional and satisfaction criteria [7, 8]. Enhanced Recovery After Surgery (ERAS) is a comprehensive and patient-focused approach aimed at reducing surgical stress and accelerating the process of postoperative recovery [9]. ERAS protocols are effective in various surgical fields and lead to shorter hospital stays, faster recoveries, and fewer post-discharge complications. Focusing on 3 key phases—preadmission optimization, intraoperative treatment, and postoperative management—OMF surgeons have traditionally focused on meticulous surgical techniques and minimizing trauma during the operative phases [10]. However, there is a noticeable absence of research on the critical last stage, which is postoperative treatment. In addition, even the limited studies available have primarily examined the impact of the quantity of diet on surgical outcomes, leaving the exploration of diet types during postoperative care significantly unaddressed [11]. Furthermore, a challenge arises because the oral environment after surgery typically presents as a clean-contaminated wound, which is fragile to bacterial proliferation [12]. Consequently, this increases the likelihood of infections compared to other surgical sites [13]. Following OMF surgery, patients may experience swelling and diminished sensation, potentially impeding their ability to sense food in their mouths and leading to decreased appetite. Decreased food intake may also result from longer surgical durations and the dissection of the masticatory muscles, which can lead to restricted mouth opening or impede normal jaw function and occlusion. These factors contribute to the complexity of post-operative dietary care for OMF patients. Therefore, it is necessary to make modifications to the dietary treatment for maxillofacial patients.

Our study aims to investigate the nutritional status, and treatment prognosis by comparing a high-energy SBD against the conventional SFD in patients who have undergone OMF surgery. This research seeks to provide evidence-based recommendations for types of dietary choices after OMF surgery. The ultimate goal is to enhance treatment outcomes during hospitalization, improve health-related QOL, and elevate patient satisfaction with the hospital experience.

OMF surgery necessitates a thorough understanding of the patient's nutritional requirements. After OMF surgery, the oral cavity, which serves as the primary entrance of food, undergoes alterations. Moreover, intricate alterations in homeostasis occur following surgical intervention, often referred to as post-aggression syndrome. Following surgery, the baseline energy requirements increase by roughly 10% compared to preoperative levels [1]. A decline in a patient’s nutritional status during the perioperative period can adversely affect the wound healing process [18]. Several studies have examined the use of high-energy and high-protein nutritional supplements to enhance clinical and surgical outcomes during the postoperative period after oral surgery [6, 19]. There is a significant lack of research specifically addressing the postoperative management following OMF surgery. In addition, even the limited number of research available has primarily focused on how the amount of food consumed affects recovery while overlooking the examination of various dietary patterns throughout the postoperative phase. Previous studies have focused solely on the quantitative aspect; however, attention must also be directed toward the qualitative dimension, specifically regarding what types of food should be provided. It’s important to note that patients may find psychological comfort in the sensation of recovery associated with taking the SBD. This is because the SBD can serve as an intermediary step towards transitioning back to a normal, regular diet. Therefore, it is crucial to take into account the dietary types of post-OMF surgery patients.

OMF surgeons must prioritize identifying patients who are at nutritional risk and provide them with specific dietary instructions. Postoperative nutrition following oral surgery can be administered through several methods, such as a fully liquid diet, mechanically blended food, or a standard solid diet. Although the SFD, which is designed especially for patients experiencing difficulties with chewing and swallowing, does have certain benefits, the SBD provides patients with a transitional diet that closely resembles a regular diet. SBD provides better texture and composition. However, SFD is often administered even after minor OMF surgery, primarily due to concerns about potential negative effects such as wound dehiscence and infections. While these reservations are understandable, it is essential to establish criteria backed by evidence to maximize the effectiveness of postoperative nutrition. The primary objective of our study was to compare the effects of 2 different postoperative diets: SBD and SFD. Our hypothesis posited that administering SBD could result in superior postoperative outcomes in various aspects compared to routinely providing SFD. The challenge of detecting malnutrition during hospitalization is complicated because nutritional imbalances are not influenced by a single condition alone. Thus, the diagnostic methods employed for malnutrition must encompass a diverse array of anthropometric measurements, biochemical markers, and clinical symptoms [20]. So, we carried out a thorough evaluation consisting of 3 distinct parts. We conducted a subjective evaluation of patient experiences and perceptions by administering questionnaires. In terms of objective evaluation, our focus was on conducting anthropometric measurements and laboratory testing. Our study revealed a significant finding: the SBD group demonstrated consistent stability in subjective satisfaction, objective laboratory test results, and clinical follow-up results compared to the SFD group. This suggests a stronger patient preference towards the SBD, despite the possible irritation caused by the larger particles in the SBD and the somewhat unstable and sometimes painful nature of post-surgical wounds. In addition, meal satisfaction was found to be higher for the SBD. The reasons for this satisfaction within this group were more diverse, encompassing a wide range of factors such as flavor nuances and portion sizes. This is in sharp contrast to the SFD group, whose preferences were solely based on softness. The findings originated from evaluations of health-related QOL. The SBD group exhibited higher EQ-VAS scores in comparison to the SFD group. Moreover, the SFD group exhibited a decrease in physical ability during daily activities, alongside an increase in emotional distress and depressive symptoms, as shown by the EQ-5D-3L scores. The implications of these findings suggest that postoperative dietary type may have an indirect influence on the health-related QOL of patients, even when the length of hospitalization is quite short. When comparing the anthropometric data between the SFD and SBD groups, it was noticed that the SFD participants exhibited a decrease in both body weight and BMI. Conversely, the SBD group demonstrated an increase in these variables. The SFD group consumed 51.0% of the total 661 kcal provided, resulting in an average daily intake of approximately 337 kcal. In contrast, the SBD group’s intake was estimated to be around 1,104 kcal, representing 63.2% of the suggested diet of 1,747 kcal. However, this consumption was found to be less than 70% of the energy requirements for SBD individuals averaging 63.7 kg in weight, indicating that it was marginally sufficient to prevent significant weight loss during the average hospitalization period of 4.2 days. Although there was an observed increase in weight after surgery in the SBD group, it is possible that this was affected by other contributing factors. There is a lack of research on changes in body composition after OMF surgery. Nevertheless, research on gastric surgery has observed substantial reductions in overall fat and muscle mass, accompanied by an elevation in the proportion of muscle mass relative to total weight after the operation. This implies that factors other than just energy consumption may have an impact on the process of recovering after surgery and the subsequent weight changes [21, 22]. This phenomenon, however, necessitates further research to explore the implications of weight gain within the SBD patient cohort, ensuring a better understanding of nutritional adequacy and its effects.

The laboratory findings from our investigation also yielded significant insights into the nutritional impacts of different dietary types. Various biochemical indicators can be used to evaluate nutritional status, but serum albumin, TLC, PNI, NRI, and BMI are particularly noteworthy. Numerous studies have shown that these indicators are significantly associated with nutritional status [23, 24]. An exceptionally notable observation was the behavior of albumin levels. Albumin, traditionally recognized as a significant determinant of a patient’s nutritional and overall health condition, exhibited a general decline in both the SFD and SBD groups following surgery. Nevertheless, despite the well-established significance of albumin as a predictive indicator for clinical outcomes in patients undergoing surgery, its relevance as a nutritional measure remains a matter of debate [25]. Despite evidence from other surgical disciplines suggesting that postoperative changes in albumin levels and symptoms of hypoalbuminemia are associated with increased morbidity, our findings from this clinical follow-up reinforce the critical role of albumin as a reliable marker for detecting outcomes related to recovery and mortality after OMF surgery [26, 27]. Our study identified a statistically significant difference in the trend of albumin level changes between the 2 dietary groups. Although albumin levels decreased in both groups postoperatively, the decrease was less pronounced in the SBD group (−0.3) compared to the SFD group (−0.5). This lesser reduction in the SBD group is attributed to adequate nutritional intake, which likely mitigated the body’s inflammatory response. This finding highlights the potential advantages of the SBD in supporting better postoperative recovery by preserving albumin levels more effectively than the SFD. Moreover, the extent of reduction in TLC was observed in both groups but was more significant in the SFD group, suggesting that individuals undergoing SFD treatment may be more susceptible to compromised immune function. Changes were noted in the Hgb and Hct values; however, they did not reach statistical significance. The levels of postoperative inflammatory markers, particularly ANC, showed an elevation in both groups which might have been affected by postoperative catabolic state. Notably, both the NRI and PNI exhibited a consistent decline after the surgery in both groups. The NRI, validated for its specificity and sensitivity in evaluating cancer patients, was employed to assess the risk of malnutrition. However, in our research, we employed the NRI to assess the nutritional condition after OMF surgery [2]. The study's findings showed that the average NRI scores after surgery were 102.2 for the SFD group and 107.1 for the SBD group. Based on the NRI criterion, these scores are considered to indicate a normal nutritional status. Nevertheless, there was a much larger decrease in NRI scores in the SFD group as compared to the SBD group. These data suggest that the SFD group may experience a more negative effect on their postoperative nutritional status. The PNI, which is determined by analyzing peripheral blood lymphocytes and serum albumin levels, accurately represents the immunological and nutritional condition of the individual. The PNI, derived from peripheral blood lymphocyte counts and serum albumin levels, serves as a quantifiable indicator of a patient’s immunological and nutritional state. Despite the rarity of direct claims that “a high PNI indicates better nutritional status” in the literature, a correlation is suggested by several studies demonstrating that higher PNI levels are associated with improved outcomes in conditions where nutrition plays a critical role [28, 29]. According to the results of our study, the postoperative PNI in the SBD group was 57.0, and no significant surgical complications were observed following long-term clinical observation. Nevertheless, within the SFD group, the postoperative PNI was recorded as 47.7. This was accompanied by frequent occurrences of postoperative complications, such as lethargy, discomfort, as well as complaints of pain. However, further investigation is necessary to clarify the exact connection between nutritional status after surgery and its association with this parameter [16, 17]. Upon conducting a thorough comparative study, it was observed that the SBD group had more stable data. The reduced variability in biochemical indicators seen in the SBD group emphasizes the potential superiority of the SBD and its ability to enhance postoperative outcomes.

Although the average hospital stay was considerably short in both groups, our findings reveal substantial differences in 3-month postoperative outcomes. Surprisingly, there were no post-surgery issues in the SBD group, whereas 5 out of 16 patients in the SFD group developed complications. Paradoxically, it appears that postoperative SBD creates a more advantageous setting for wound healing, thereby decreasing the occurrence of complications such as wound dehiscence. Therefore, the significance of postoperative dietary types extends to minor surgeries too, even when hospitalization time is short, highlighting their importance beyond major surgeries that require extended hospitalization. However, our investigation has some limitations. The sample size (n) was too small for parametric testing. Also, it can be considered a natural outcome that the average energy (calories) provided by SBD is higher than SFD, resulting in differences in body weight or laboratory results. However, this can be considered a significant advantage of SBD. Given that SBD can offer a variety of foods compared to SFD, SBD is considered advantageous for providing high-energy meals. Nonetheless, it was demonstrated that, when compared to SFD, SBD does not pose issues for postoperative recovery. A more thorough analysis of the nutritional composition of SFD and SBD would have been desirable. Future research has the potential to provide more meaningful results by employing a more comprehensive categorization of nutrients and studying their specific effects.

Our study concludes that the nutritionally balanced SBD is superior to the SFD for patients undergoing OMF surgery. The SBD can be provided without concerns of damaging the wound healing process or causing infection symptoms. Administering the SBD after OMF surgery not only facilitates physical recovery but also enhances satisfaction and health-related QOL, thus promoting improved healing in both physical and psychological aspects.

Supplementary Fig. 1

Questionnaire which consists of 4 parts.