An in-office, cost effective technique for measuring width of bone using intra-oral periapical radiographs in occlusal projection.

BACKGROUND: The aim of this in vitro study was to determine the dimensions of ridge/width of bone and deviation of center of ridge using Intra Oral Periapical Radiographs (IOPA) in occlusal projection as a preprosthetic diagnostic method.
MATERIALS AND METHODS: Mandibles with edentulous space were procured and cold cure acrylic stents were fabricated. Three holes were drilled occlusally, buccally, lingually and filled with gutta percha. Then mandibles were tied to menaquine model which was fitted to a dental chair. IOPA radiographs in occlusal projection were taken. Radiographs were scanned to obtain a digital image which was analyzed using computerized software. Direct measurements were taken and compared. The position of center of ridge was compared in vitro and radiographically using student unpaired t test and width of bone was compared using Karl Pearson's coefficient test.
RESULTS: Comparisons of bucco-lingual ridge width using radiographical measurement versus in vitro method showed a mean value of 4.1930 with deviation of 0.5934 and the proposed position of center of ridge for both the methods gave a mean value of 0.2738 with deviation of 0.1164.
CONCLUSION: The findings in this study suggested that IOPA radiographs in occlusal projection can be used as a preprosthetic diagnostic method to assess the width of the alveolar bone for future flapless implant placement.

INTRODUCTION

Dental implant therapy has been used increasingly frequently for the rehabilitation of missing dentition, replacing conventional therapies in the areas of complete and partial edentulism as well as for single tooth anodontia.[1-5] Two stage submerged implant placement technique was routinely done to allow 3-4 months of undisturbed healing and load free environment for successful osseointegration.[6] In implant dentistry, surgical flap reflection may lead to soft and hard tissue loss.[78] With the rapid advancement of dental implant therapeutics, the current trend is geared more towards enhancing esthetics and patient's comfort and satisfaction. One stage surgical protocol using nonsubmerged implants has been proven successful comparable to the two stage surgical approach.[910] The acceleration of treatment time and less surgical intervention with one-stage surgical approach can significantly enhance patient's comfort, satisfaction, and acceptance.

The recent advancement in implant dentistry is flapless implant placement because of patient's preference for noninvasive procedure. Minimally invasive implant surgery allows clinicians to place implants in less time, without extensive flaps, and with less bleeding and postoperative discomfort.[11-15] The flapless placement of dental implants requires precise planning that considers the vital anatomic structures and restorative goals. Sufficient width of the alveolar ridge must be available for implant placement using a flapless technique.[11-13] Evaluation of the dimensions of the available alveolar bone is an important prerequisite for the same.[16]

Assessment of the bucco-lingual dimension of the osseous ridge is also needed for proper treatment planning.[17-19] Bone evaluation can be done by the use of panoramic and/or periapical radiographs. The bucco-lingual ridge width can be evaluated by computerized tomography (CT),[2021] Ridge mapping,[22-26] Trans tomography,[27] Ultrasonography and Direct Caliper Measurements following surgical exposure of the bone.[16]

The above methods require expensive instrumentation, surgical exposure of bone, more radiation exposure to patient and technique sensitive lab procedures. Although panaromic and IOPA radiographs produce two-dimensional image, advantages are that they provide information about length of bone, visualization of nerves and vessels, but do not provide information regarding width of bone about implant sites.[6]

Occlusal radiographs are used to determine position of impacted teeth, cysts or tumors, evaluation of fracture, locate salivary stones in the submandibular duct etc. They provide the maximum width of bone at the base of the mandible and do not give information about crestal width. That is why occlusal radiographs are not used for evaluation of width of the bone for implant placement. Till today, there is no data or report of any method using the intra oral periapical radiography in occlusal projection for assessment of ridge dimension.

So, aim of this in vitro study was to determine the dimensions of ridge/width of bone and deviation of center of ridge using Intra Oral Periapical Radiographs (IOPA) in occlusal projection as a preprosthetic diagnostic method.

MATERIALS AND METHODS

This was an in vitro study carried out in the department of Periodontology and Implantology.

Prosthetic stent fabrication

A total of two Mandibles with 20 edentulous spaces were procured. Along the edentulous space modeling wax of 2 mm was adapted [Figure 1]. An impression was made using alginate and cast was poured with dental stone. With the use of acrylic, a prosthetic stent was fabricated along edentulous space pertaining to the missing teeth. With the help of micro motor, a hole was drilled along the long axis of the tooth till the bur meets the cast, and the area was marked. This was marked as prosthetically driven center [Figure 2].

Figure 1

Modelling wax adapte

Figure 2

Prosthetic stent with probe denoting prosthetic center

Occlusal stent fabrication

Along the wax adapted mandible, an occlusal stent was fabricated with three holes drilled in occlusal, lingual and buccal areas [Figure 3]. The occlusal hole was drilled by placing the occlusal stent on marked prosthetically driven center on the cast then it was transferred to the mandible with the help of reamer. With respect to buccal and lingual surfaces, a linear trough was drilled and a reamer or file was probed first along the buccal side to check the resistance of bone, if no resistance was felt and then it was probed at a distance of 1 mm from previous one. Once when the resistance was felt, the area was marked with gutta percha. The same procedure was carried out along the lingual side and area where resistance felt was marked with gutta percha.

Figure 3

Occlusal stent

Radiographic procedure

The marked occlusal stent with mandible was tied to a menaquine and was fitted to dental chair. An intra-oral periapical film was placed occlusally on the occlusal stent. The occlusally projected beam was directed and radiograph was taken. Now radiograph shows three gutta percha markings (buccal, lingual and occlusal) [Figure 4]. The occlusal marking showed the prosthetic center. Using Dental Eye® (Sweden) software, the radiographic analysis was done to calculate the width of bone and center of ridge [Figure 5]. Actual width of the ridge gives bone thickness and tissue thickness. To deduct tissue thickness, an endodontic reamer was probed through the wax on both buccal and lingual side. The depth to which it penetrated was measured using measuring scale. Now the exact width of the bone was measured by deducting tissue thickness (wax thickness) from the distance between 2GP points. Dividing the width of the bone by two gave the radiographic center. So, two dots were obtained, one the prosthetic center and the other the radiographic center [Figure 6].

Figure 4

Radiographic image

Figure 5

Radiographic analysis

Figure 6

Prosthetic and radiographic center

Statistical analysis

The clinical and radiographic method was compared using student unpaired t test and to correlate the two methods, Karl Pearson's correlation coefficient test was used.

RESULTS

The clinical and radiographic methods were compared on two aspects;

Width of the bone and

Center of ridge.

The summary statistics of width of bone in two methods is shown in Table 1. The mean values of clinical and radiographical method when compared by Student's unpaired t-test were 4.2525 and 4.1335 respectively and the deviation of these two methods was 0.5934. The values were plotted in a graph which is shown in the Figure 7.

Table 1

Comparison of radiographic and in vitro procedures with respect to width of bone (mm) by Student’s unpaired t-test

Figure 7

Comparison of radiographic and in vitro procedures with respect to width of bone (mm)

The summary statistics of Proposed Position of Center of Ridge in two methods is shown in Table 2. The mean values of clinical and radiographical method when compared by Student's unpaired t-test were 0.2860 and 0.2615 and the deviation of these two methods was 0.1164. The values were plotted in a graph which is shown in the Figure 8. The deviation of the 2 methods with respect to Proposed Position of Center of Ridge and width of the bone was found to be 0.1164 and 0.5934 respectively.

Table 2

Comparison of radiographic and prosthetically driven center with respect to proposed position of center of ridge by Students unpaired t-test

Figure 8

Comparison of radiographic and prosthetically driven center with respect to proposed position of center of ridge (mm)

The sensitivity for the width of bone was 87% and specificity was 100%. The kappa measure of agreement was 0.89 [Table 3]. The sensitivity of the proposed position of center of ridge was found to be 100% and specificity was 80%. The kappa measure of agreement was 0.80 [Table 4]. Kappa measures of agreement in both methods were statistically significant (P < 0.001).

Table 3

Diagnostic value of in vitro vs. radiographic (width of bone)

Table 4

Diagnostic value of in vitro vs. radiographic (proposed position of center of ridge)

DISCUSSION

The present in vitro study was done to assess the width of bone/dimensions of alveolar ridge using intra oral radiography in occlusal projection and also to locate the center of ridge.

Though there are quite other techniques for assessing ridge dimension like ridge mapping, CBCT, transtomography and direct caliper measurement following surgical exposure of the bone. Ridge mapping is a procedure that allows the implant surgeon to determine the thickness or width of the alveolar bone before a mucoperiosteal flap is reflected during surgery. The ridge-mapping technique involves a series of measurements with a specially designed caliper. The sharp points of the caliper penetrate the anesthetized mucosa until the surface of the bone is reached. A millimeter scale near the handle end of the caliper will give an accurate reading of ridge thickness.[15] However; it must be kept in mind that ridge mapping may give erroneous readings.[16]

Conventional tomography is the method of choice for obtaining cross-sectional information of small regions of interest for implant planning.[16] Tomograms before dental implant placement will help determine the height, width, inclination and undercut of the alveolar bone, as well as the location of anatomical structures such as the mandibular canal, the submandibular gland fossa, the maxillary sinus and the nasal fossa.[1718] Computer-assisted implant planning on 3D models allows the optimal assessment and investigation for implant placement, which is often difficult to predict prior to the initiation of care. The use of stereolithographic guides for the placement of dental implants is designed to provide greater control and eliminate the risks that are involved in standard implant surgery. However, the risk for deviation (transfer error from the software-planning stage to the surgical field) remains substantial.[21]

Radiographs play adjunctive role in clinical diagnosis. In dentistry, the routinely prescribed are periapical and orthopantograms. Occlusal radiographs are used when patient unable to open wide for IOPA or other reasons cannot accept periapical. The uses are for determining fractures, pathologies and in trismus conditions. Occlusal radiography shows widest width of bone (symphysis) versus the width at crest where diagnostic information is needed most. So it is not indicated for diagnostic preprosthetic phase in implant dentistry.[28]

To avoid the more radiation of bone, surgical exposure, expensive instrumentation, sensitive lab techniques, Intra oral Periapical Radiography in Occusal projection were chosen to measure the width of bone as well as center of ridge. Using the CT data of various studies, the difference between preplanned drill starting point in reference model and actual drill starting point was in the range of 0.95-1.6 mm.[2829] But comparatively the data obtained from our study has deviation for the 2 methods to be very minimal for the proposed position of center of ridge which was 0.1164 [Table 2]. Also the data for the width of the bone based on two methods were reliable with kappa measure of agreement giving the similar data. The radiographic and in vitro measurements were almost similar making the professional to opt for either of the methods. So this in office technique gives quicker, reliable and convincing results to assess the ridge dimension.

The advantages of this method are:

A routine quick chair side method

Cost effective

Also in compromised knife edge ridges.

The limitations of this study were, as it was carried out only in mandible because maxilla precludes itself with complex anatomical structures for assessment and radiographs are two dimensional images whereas CT gives three dimensional images. Especially Occlusal radiographs are exposed at steep angulation; they may be used with conventional periapical radiographs to determine the location of objects in all three dimensions.

SUMMARY AND CONCLUSION

The study was designed to overcome various limitations of the radiographs and proves that the neglected occlusal projection can be well utilized. This procedure has increased the affordability for the patients and an easy approach for the dental professional and for the patient. Following conclusions were drawn from the study.

IOPA radiographs in occlusal projection can be used as preprosthetic diagnostic to assess the width of the alveolar bone

Difference between the preprosthetic position of GP point on the template and the proposed radiographic center of the ridge was 0.1164 only and width of the bone measurement using two methods was also reliable.

Authentication of this method by conduction of human randomized controlled clinical trials with a large sample size and comparison of groups is required for the routine usage for flapless implant surgical procedures.