Table 2.

Characteristics of the included studies.

Sr. no.	Study Id	Place of study	Study setting	Study design	Sample size	Total sample at follow − up = N (drop out %)	Population	Method of OHE for intervention group	Method of DHE for control group	Reinforcement period	Follow-up period	Method of outcome assessment	Diagnostic accuracy/radiographic interpretation skills/proficiency score	Knowledge scores	Recall test	Satisfaction with the training	Authors' conclusions
1.	Baghdady MT et al., 2014	Toronto	University	Nonrandomized trial	Test group: 40 (22 and 18) Control group: 40 (22 and 18)	Test group: 33 (15 and 18) 17.5% Control group: 40 (22 and 18) 0% Total loss to follow-up-8.75%	Second-year students at the University of Toronto and second-year dental hygiene students from a community college dental hygiene program	Structured algorithm condition: 1. Algorithm diagnosis 1st 2. Algorithm feature 1st	Basic science condition: 1. Basic science diagnosis 1st 2. Basic science features 1st	Once at baseline	1 week	1. Diagnostic test (mean/SD) 2. Cued recall test (mean/SD)	Baseline: Test group 1. Algorithm diagnosis 1st—0.69 (0.19) 2. Algorithm feature 1st—0.60 (0.15) Control group 1. Basic science diagnosis 1st—0.69 (0.18) 2. Basic science features 1st—0.61 (0.16) 1 week: Test group 1. Algorithm diagnosis 1st—0.66 (0.17) 2. Algorithm feature 1st—0.54 (0.15) Control group 1. Basic science diagnosis 1st—0.66 (0.18) 2. Basic science features 1st—0.59 (0.14)		Baseline: Test group 1. Algorithm diagnosis 1st—0.69 (0.19) 2. Algorithm feature 1st—0.60 (0.15) Control group 1. Basic science diagnosis 1st—0.69 (0.18) 2. Basic science features 1st—0.61 (0.16) 1 week: Test group 1. Algorithm diagnosis 1st—0.72 (0.21) 2. Algorithm feature 1st—0.77 (0.08) Control group 1. Basic science diagnosis 1st—0.74 (0.08) 2. Basic science features 1st—0.72 (0.09)		Students who learned the basic science mechanisms underpinning a disease might be more likely to make a diagnosis that made sense and not rely solely on counting the number of identifiable features on the image. This instructional methodology is in line with a nonanalytical reasoning strategy, in which the student would make a holistic diagnosis based on the totality of the identified features. Thus, left to their own devices, students who learn through basic science instruction should be more likely to use a nonanalytic reasoning diagnostic strategy. Participants in the diagnosis-first condition (nonanalytic reasoning) had higher diagnostic accuracy than those in the features-first condition (analytic reasoning), regardless of their learning condition.
2.	Busanello et al., 2015	Brazil	Dental Radiology Discipline of the Dentistry School	Nonrandomized trial	Test group—32 Control group—32	No loss to follow-up Total loss to follow-up 0%	Students enrolled in the dental radiology discipline of the dentistry school	Digital learning object (DLO) without the presence of a teacher	Conventional expository classes conducted by a teacher	Three 50 min classes were held per week, for 3 weeks	3 weeks	Knowledge scores (written scores) Diagnosis accuracy (practical scores only)	Posttest: Test group—7.01 (1.18) Control group—6.06 (1.20)	Posttest: Test group—7.74 (1.40) Control group—6.64 (1.50)			The results obtained in this study suggest that students who used the DLO performed better than those who used conventional methods. This suggests that the DLO may be a useful teaching tool for dentistry undergraduates, on distance learning courses and as a complementary tool in face-to-face teaching.
3.	Cruz AD et al., 2014	Brazil	Department of oral diagnosis	Nonrandom trial	AC—60 BC—62	No loss to loss-up Total loss to follow-up 0%	First and second semesters of 2011	“B class” (BC) —distance learning using the Moodle platform	“A class” (AC)—traditional method		Immediately after course completion	Radiographic interpretation scores	Posttest: BC—6.78 (1.43) AC—7.01 (1.47)				The method of distance learning of this subject using the Moodle platform can be utilized with the same educational results as those obtained from a traditional educational setting.
4.	Howerton WB et al., 2002	North Carolina	University of North Carolina School of Dentistry	Intervention study with posttest with controls	Group 1—34 Group 2—34	Group 1—30 (11.7) Group 2—29 (14.7) Total loss to follow-up 13.2%	First-year dental students, graduating class 2004, enrolled in “Fundamentals of Dental Radiology”	Group 2—students exposed to computer-assisted instruction before exposing the initial full mouth series. An interactive computer-assisted instructional module on CD.	Group 1—students not exposed to computer-assisted instruction before exposing the initial full mouth series	Group 2—no restrictions were placed on the number of times the CD could be viewed, and students were reminded several times by email to view the CD	One week	Total error points	Postintervention: Group 2: 17.5 (11.7) Group 1: 13.6 (8.3)				Students who received an interactive CAI CD before exposing their initial full series of radiographs made more errors than those students who did not receive the CAI CD. However, those students who received the CAI CD preferred reviewing the CD and recommended the CAI CD to others.
5.	Ji et al., 2018	South Korea	Dental school	Nonrandomized trial, posttest only with controls	Test group: 40 Control group: 43	Test group: 35 (12.5%) Control group: 42 (2.3%) Total loss to follow-up 7%	Third-year students in Wonkwang Dental College	Smartphone-based training—comprised of the provision of learning materials in advance, schema assignments, group discussion activities, professor feedback, peer review, and tests (quizzes)	Traditional lecture-based training	Test group—received focused lectures for 1 week (5 days) in groups of 10 (only 1 turn in 4 weeks) Control group—received lectures for a time per 1 week (4 lectures in 4 weeks)	4 weeks	1. Satisfaction with the training 2. Quiz results		4 weeks Test group: 58.75 (2.62) Control group: 46.14 (1.856)		4 weeks Test group: 3.74 (0.610) Control group: 4.00 (0.698)	The dental radiology schema education using smartphones suggested in the present study is not a method often used in dental education, and its effects have not been verified. Nevertheless, the training requires the interest of dental educators of the current generation as a new teaching method that could be introduced in preparation for the fourth industrial revolution for dentomaxillofacial radiology practice.
6.	Kavadella A et al., 2012	Athens, Greece	School of Dentistry of the University of Athens	Nonrandomized trial—pre-post-test with controls	Test group—24 Control group—23	Test group—24 (0%) Control group—22 (4.3%) Total loss to follow-up—2.12%	10th semester (final year) in the School of Dentistry of the University of Athens	Blended group—combined face-to-face and online instruction	Conventional group	Weekly till end of course	Not mentioned	1. Students' attitudes postcourse 2. Knowledge score pre- and postcourse		Pretest: Blended group—6.3583 (1.21) Conventional group—5.8304 (1.58) Posttest: Blended group—8.0875 (1.38) Conventional group—6.8636 (1.39)		Posttest: Blended group—4.46 (0.509) Conventional group—4.43 (0.662)	Concerning student performance, students in the blended group performed significantly better in the knowledge posttest than their colleagues in the conventional group. Students also evaluated the course components in a positive way: the content, organization, educational material, and design were highly appreciated by students in both groups. Students' attitudes towards blended courses were positive: they think that blended learning is effective and motivating; it promotes active engagement and enhances self-study and self-assessment. Particularly, students in the blended group liked the combination of electronic and face-to-face teaching, the independent studying, and the availability of the online material at any time.
7.	Lohe V et al., 2015	Wardha, India	The Department of Oral Medicine and Radiology, Sharad Pawar Dental College	Randomized controlled trial	Syndicate group—40 Traditional group—40	No loss to follow-up Total loss to follow-up—0	Final BDS students	Group A—syndicate learning method by giving five radiographs having bony lesions for discussion. The students were free to use various resource materials like class notes, books, internet, etc. They had to complete the interpretation of the given radiographs by using the standard departmental reporting method in about 2 h during their clinical posting.	Group B—traditional learning method is a teacher-centred small group method wherein the students remain comparatively passive	Only once	Immediately after discussion	Interpretation skills score in pretest and posttest	Pretest: Syndicate group—2.40 (0.98) Traditional group—2.47 (0.96) Posttest: Syndicate group—4.45 (0.71) Traditional group—3.57 (0.87)				Syndicate groups create many opportunities for creative interchange of ideas and lively and meaningful participations. This approach would ensure that, in addition to gaining subject-specific knowledge, students are also able to apply the obtained knowledge to solve problems. The present study suggests that the syndicate group is better than the traditional method and can become an appropriate method as an adjunctive instruction tool.
8.	Naik Z et al., 2015	Karnataka, India	Department of Oral Medicine and Radiology	Randomized pre-post trial	Intervention group—32 Comparison group—32	No loss to follow-up Total loss to follow-up—0	Third-year BDS students	One-minute preceptor group—students were divided into small groups of six to seven students and five different intraoral periapical+M5 radiographs of periapical diseases were discussed for a duration of 20 minutes. Then the students interpreted the intraoral radiographs under the guidance of OMP principles	Traditional group—students verbally interpreted the radiographs on a daily basis	Daily	One week	Radiographic interpretation skills, pretest and posttest scores	Pretest: Intervention group—5.30 (2.24) Traditional group—5.32 (1.34) Posttest: Intervention group—27.30 (4.76) Traditional group—17.68 (4.16)				This study supports the critical role of the radiographic interpretation in enhancing diagnostic accuracy in oral radiology. It also supports the use of the OMP model for systematic radiographic examination as a possible explanation for significant improvement of radiographic interpretation skills in a stipulated time setting. Thus, by using the “one-minute preceptor” model, student's radiographic interpretation skills had progressed from unorganized and inconsistent to systematic and consistent with clinical diagnosis, thus achieving an important skill to be a competent general dental practitioner.
9.	Nilsson TA et al., 2011	Sweden	Oral and Maxillofacial Radiology Department at the University Clinic	Randomized experimental study	Experimental group—28 Control group—29	Experimental group—20 (19.6) Control group—25 (13.8) Total loss to follow-up 21%	The seventh and ninth semesters	Simulation-based training—the participants in the experimental group trained individually using the simulator. The leader introduced the exercises and thereafter only answered questions. During training, the students were free to choose among the exercises. Training was carried out in two sessions of 45 minutes each. The time interval between the two training sessions varied from 1 day to 2 weeks.	Conventional training—the training was completed in one 90-minute session	8 months	Immediately after training and 8 months	Students' skill in interpretation of spatial information in radiographs	Pretest: Experimental group—3.20 (1.40) Control group-3.40 (1.16) Immediate: Experimental group—4.15 (1.14) Control group—3.80 (1.35) 8 months: Experimental group—4.00 (0.86) Control group—3.92 (1.32)				In conclusion, the skill of interpreting spatial relations after simulator-supported training was better eight months after training than before training. The conventional training showed a similar outcome pattern, but at a lower level. Simulator-supported training can therefore be a valuable adjunct to conventional educational methods.
10.	Nilsson TA et al., 2007	Sweden	Oral and Maxillofacial Radiology Department at the University Clinic	Randomized experimental study	Experimental group—28 Control group—29	No loss to follow-up Total loss to follow-up 0%	The seventh semester and ninth semester dental students	Simulation-based training—the participants in the experimental group trained individually using the simulator. The leader introduced the exercises and thereafter only answered questions. During training the students were free to choose among the exercises. Training was carried out in two sessions of 45 minutes each. The time interval between the two training sessions varied from 1 day to 2 weeks.	Conventional training—the training was completed in one 90-minute session.	No	Immediately after training	Proficiency test (radiography subtest)	Pretest: Experimental group—3.11 (1.42) Control group—3.24 (1.15) Posttest: Experimental group—4.18 (1.09) Control group—3.72 (1.39)				In conclusion, our study demonstrated that training in the radiology simulator improved skill at interpreting spatial information in radiographs utilizing parallax when evaluated immediately after training.
11.	Sodestrom T et al., 2012	Sweden	Umeå University	Randomized experimental study	Intervention group—18 Control group—18	No loss to follow-up Total loss to follow-up 0%	Fourth semester	Simulation-training group (SIM)	Conventional-training group (CON)	SIM group worked one hour with a 3D-radiology simulator to perform four structured exercises CON group studied for one hour using pairs of X-ray images shown in a PowerPoint presentation	Posttraining	Proficiency test	Pretest: SIM group—12.94 (4.29) CON group—13.11 (2.96) Posttest: SIM group—14.94 (4.35) CON group—13.00 (5.06)				The results showed that SIM groups exhibited significant development between pretest and posttest results, whereas the CON groups did not. The collaboration in the CON groups involved inclusive peer discussions, thorough interpretations of the images, and extensive use of subject-specific terminology. The SIM group discussions were much more fragmented and included more action proposals based on their actions with the simulator. The different learning conditions produced different results with respect to acquiring understanding of radiographic principles.
12.	Soltanimehr et al., 2019	Iran	Shiraz University, School of Dentistry	Experimental study	Intervention group—20 Control group—19	No loss to follow Total loss to follow-up 0%	Fourth-year dental students	Virtual group—learning management system (LMS), which included a combination of facilities such as a learning path, quizzes, weekly homework, useful links, related articles, and active interactions of students and mentors.	Traditional group—lecture-based education in a classroom setting in the presence of a mentor	Virtual group—group of students were allowed to use the LMS repeatedly during 6 weeks Traditional group—6 sessions of traditional classroom instruction, 1 h each	Immediately and 2-month follow-up	Theoretical knowledge scores clinical exams scores	Immediate clinical exam: Virtual learning: 15.13 (0.78) Traditional learning: 14.71 (0.92) Clinical exam at 2 months: Virtual learning: 14.75 (0.87) Traditional learning: 14.18 (0.95)	Immediate theoretical tests: Virtual learning: 16.60 (0.91) traditional learning: 14.89 (0.99) Theoretical tests at 2 months: Virtual learning: 15.88 (0.78) Traditional learning: 14.45 (0.83)			The virtual method was more effective than the traditional method for instruction of radiographic interpretation of bony lesions of the jaw. However, this superiority was greater for the theoretical aspect of the topic. Considering the superiority of the virtual method for teaching of theoretical topics and its equal efficacy with the traditional method for instruction of clinical reporting skills, virtual education can serve as an effective alternative to traditional classroom teaching for teaching of radiographic interpretation of bony lesions of the jaw to dental students.
13.	Vuchkova J et al., 2012	Australia	School of Dentistry at the University of Queensland	Experimental study	Group B—33 Group A—31	No loss to follow-up Total loss to follow-up 0%	Second-year undergraduate dental students	Digital tool	Conventional oral radiology textbook	Each group underwent a 1 h intervention phase involving the learning of radiographic anatomy	Immediately postintervention	Radiographic interpretation scores	Postintervention: Group B: 50.00 (12.34) Group A: 51.34 (17.08)				Although the newly constructed digital tool was not quantitatively superior to the conventional textbook in assisting dental students with their learning of radiographic interpretation, qualitative measures indicated a strong preference for the digital tool as a learning and teaching resource in radiographic interpretation.