Current surgical training in dentistry is based on the Halstedian apprenticeship model that was introduced over 100 years ago [1]. In this model, the assessment of technical proficiency is solely the responsibility of the surgical preceptor. However, this type of assessment can be largely subjective [2], and unreliable as the assessment is global, and not based on specific criteria. Also, it would possess poor test-retest reliability and could be affected by poor inter-observer reliability since even experienced senior surgeons have a high degree of disagreement while rating the skills of a trainee [3]. More importantly, objective assessment of surgical competence is crucial because deficiencies in training and performance are difficult to correct without factual data [2,4,5], and surgeons should be technically competent before entering operating room. Currently, training and certifying bodies are under pressure to develop new ways to assess and rate the implant surgical competence of residents.

Current methods of assessment in surgical field include written examinations, operative log books, time taken for a procedure, direct observation and assessment by trainers [2]. Recently, various types of assessment tools were developed and introduced by many researchers in medical fields. Although these newly developed methods still rely on the judgments of examiners, the inclusion of set criteria for assessing skill can remove much of the subjectivity from the evaluation process. For instance, global rating scales are utilized in the Objective Structured Assessment of Technical Skills, which is consisted of six stations where residents and trainees perform procedures on live animal or bench models in fixed time periods [6]. Hereafter, various modifications and improvements were presented in the medical fields. The McGill Inanimate System for Training and Evaluation of Laparoscopic Skills was developed to assess laparoscopic skills and to score them objectively [7], while the Objective Assessmenet of Skills in Intraocular Surgery was established to assess the ophthalmic surgery [8]. Contrarily, dexterity analysis systems such as the Advanced Dundee Endoscopic Psychomotor Trainer were developed, which was originally designed as a tool for the selection of trainees for endoscopic surgery, based on the ability of psychomotor tests to predict innate ability to perform relevant task [9]. Virtual reality simulator has also been introduced to evaluate the laparoscopic trainees, and the Minimally Invasive Surgical Trainer-Virtual Reality is one of the first virtual reality laparoscopic simulators [10].

While there are competitive attempts to develop the assessment tool in medical fields, there is no or little attempt to establish an objective assessment tool for dental implant surgery. Furthermore, pressures both from inside and outside the profession have recently resulted in the need for dental surgeons to show that they can operate well. The assessment of implant surgical technique has been a neglected field until recently, and very few training programs have objective evaluation methods of surgical skills for implants as part of their training program for residents. Therefore, the aim of this study is to develop and establish an objective assessment tool for teaching and evaluating the surgical competence for dental implant placement by residents.

In the present study, the composite iSTAR evaluation form was developed consisting of 2 parts: surgical information and task-specific checklists (Table 1, Fig. 2). The task-specific checklist assesses operative skills providing a 'structured gestalt' of implant surgical performance.

In the late 1960s, Brånemark et al. [14] introduced the concept of osseointegration whereby predictable long-term implant function could be achieved following a strict and simple protocol. This documented the installation of titanium implants involving a submerged healing phase of between 3 to 6 months depending on bone quality, followed by a delayed phase of prosthetic loading on cross-arch fixed prostheses in the edentulous jaws. However, various types of dental implants have been introduced and numerous techniques for bone augmentation and soft tissue management have been documented over the 50 years.

Task specific check list was prepared based on the standard protocol of the Brånemark Implant System [15,16], and modified principles regarding the treatment of partially edentulous jaws were included [17]. First, flap design of crestal incision is evaluated, and the decision about the inclusion of crevicular area of neighboring teeth should be made based on the space available for the implants. However, considering the fact the residents are novice in the surgical procedures, it seems necessary to properly elevate the flap so that enough view of the surgical field is acquired to avoid missing the anatomical deformities and facilitate the irrigation of the bone during drilling.

Second, bone drilling should be graded keeping in mind that excessive heating must be avoided at all times and accidental trauma from drilling must be prevented. Also, drilling must be performed with the highest precision in order to avoid unstable implant placement or over-tensioned fixation [18].

Third, implant positioning should be decided under anatomic and clinical situation, and the implant should be preferably placed in the natural tooth position both in a mesiodistal and in a buccolingual dimension. The distance between two implants should not be less than about 7 mm, measured from center to center, and the drilling point should be 3.5 to 4 mm away from the prominence of the neighboring tooth, and the following implant positions are then marked in a distal direction until reaching the area of minimum bone volume for implants [19]. Implant direction is to place the implants within the natural tooth position with normal axis be directed through the crown or the occlusal surface of the bridge to be. Regarding the buccolingual dimension, the long axis of mandibular implants will mainly be directed towards the limbus part of the incisors or the palatal cusps of the teeth in the maxilla. For implants placed in the maxilla, the corresponding inclination should be towards the incisive edges of the frontal teeth or the buccal cusps of the premolars or molars of the mandible.

Fourth, the implant fixture should be long and wide enough as possible without damaging neighboring teeth or anatomically important structures. Primary stability should be obtained and the rotation of the fixture should not be present. Hereafter, healing abutment or cover screw should be chosen based on the surgical procedures.

The main purpose of this study is to introduce to the field of dental education a method of assessment and rating for the dental implant surgery that has been proven in other medical fields to be reliable and valid. Such a standardized assessment tool is needed to ensure residents' basic competency before entering the operating room. Despite the obvious importance of ensuring the surgical competence of residents, the traditional method for assessment was inadequate and largely subjective, and the absence of objective and straightforward assessment system in dental education has inspired the development of iSTAR proposed in the present study. The goal of this article was to address the necessity of the objective assessment tool for the implant surgical skills of the residents, and to discuss the important factors that should be included in the assessment tool, not to deliver the fully validated format. Therefore, the iSTAR proposed in this preliminary study should be refined by educators in the current surgical field.

First, we understand that no guideline designed to aid can be perfect. It is the responsibility of the teaching staffs' role to implement and upgrade this assessment tool. Our hope is that the concept will be embraced as valid and ultimately adopted by residency programs as a useful measure of the surgical skills of periodontal residents. This tool will be useful not only for ensuring the basic surgical competence of residents as they progress through their training, but also for evaluating the effectiveness of teaching methods, which will ultimately enhance the quality of the treatment provided to the general patients.

Good assessment should be reliable, valid, educational, acceptable and feasible in terms of cost effectiveness and delivery [20]. The iSTAR consists of two pages of checklist and it takes minimal time to input the data. Also, it is simple to gather the meaningful information from the evaluation sheet. Therefore, it seems that iSTAR is feasible and easy to use in the operating room or during watching videotaped operation. However, this assessment tool needs to be assessed for the face and content validity, inter-rater reliability, and eventually, predictive validity. By these efforts, the specific assessment form will be further refined, and will be applied in a variety of ways in the training of residents.

In summary, our goal was to develop an objective and standardized assessment tool of implant surgical skills for the residents. Future studies will assess the face validity and content validity of this test as well as the inter-rater reliability of this format and improve the simulation typodont. Through these studies, the specific validity of the iSTAR will be further refined and ultimately benefit the residents' education. We hope the development of this objective surgical evaluation tool will lead to a nationally standardized assessment tool to facilitate future prospective multicenter studies on resident education.