Comparison of two-dimensional orthoradially reformatted computed tomography and panoramic radiography for dental implant treatment planning

Incidental Findings in Cone Beam Computed Tomography for Dental Implants in 1002 Patients

PURPOSE

The purpose of this study is to analyze the frequency and elevate the awareness of the prevalence of nondental pathology in cone beam computed tomography (CBCT) scans taken for implant placement treatment planning and postplacement evaluation. The data from the CBCT should be read by an oral and maxillofacial radiologist for proper diagnosis of dental and nondental pathology and referred to the medical specialist for proper management when necessary.

MATERIALS AND METHODS

This retrospective study analyzed 1002 consecutive CBCT scans taken at a single private practice noting the prevalence of nondental pathology in CBCT images for all dental implant procedures. All scans were taken from November 2007 to March 2020. One board certified oral and maxillofacial radiologist systemically read all scans and reported all findings in the maxilla and mandible, condyles and TMJ, paranasal sinuses, nasal fossa, pharyngeal airway, skull base and temporal bone, neck soft tissues, and cervical spine. The incidental findings, variation of normal anatomy, or pathology reported in these structures were categorized based on anatomic location and significance and the incidence was investigated.

RESULTS

Pathologies ranged from innocuous sinusitis, to more serious atherosclerotic calcification of the carotid arteries, narrowed airways, and neoplastic lesions. Fifty-one different findings were noted, of which 36 were pathologies that required referral or follow-up.

CONCLUSIONS

Incidental findings can be detected in CBCT scans for dental implants. The clinician must be familiar with the radiographic diagnosis of head and neck pathology, and/or must refer these images to an appropriate specialist for the radiographic interpretation of the full volume.

Freehand Versus Guided Surgery: Factors Influencing Accuracy of Dental Implant Placement

INTRODUCTION

Patient anatomy, practitioner experience, and surgical approach are all factors that influence implant accuracy. However, the relative importance of each factor is poorly understood. The present study aimed to identify which factors most critically determine implant accuracy to aid the practitioner in case selection for guided versus freehand surgery.

METHODS

One practitioner's ideal implant angulation and position was compared with his achieved position radiographically for 450 implants placed using a conventional freehand method. The relative contribution of 11 demographic, anatomical, and surgical factors to the accuracy of implant placement was systematically quantified.

DISCUSSION

The most important predictors of angulation and position accuracy were the number of adjacent implants placed and the tooth-borne status of the site. Immediate placement also significantly increased position accuracy, whereas cases with narrow sites were significantly more accurate in angulation. Accuracy also improved with the practitioner's experience.

CONCLUSION

These results suggest tooth-borne, single-implant cases performed later in the practitioner's experience are most appropriate for freehand placement, whereas guided surgery should be considered to improve accuracy for multiple-implant cases in edentulous or partially edentulous sites.

Effect of the different implant protocols on peri-implant bone: a 6-month prospective study in beagle dogs

OBJECTIVE

To compare the effects of different implant placement and loading protocols on the marginal bone loss (MBL) in beagles by intraoral radiography.

METHODS AND MATERIALS

61 dental implants were inserted on 9 beagle dogs at bilateral lower posteriors according to 8 different protocols: immediate implant placement and immediate loading for 3 months (IIP + IL3) or 6 months (IIP + IL6) and unloading (IIP + UL), immediate implant placement and delayed loading for 3 months (IIP + DL3) or 6 months (IIP + DL6), delayed implant placement and immediate loading for 3 months (DIP + IL3) or delayed loading for 3 months (DIP + DL3) and unloading (DIP + UL). Intraoral radiography was performed to analyze the MBL during each surgery, before and after the implant placement and at 3-month intervals after the procedure.

RESULTS

In total, 57 samples were included. There was less MBL (p<0.05) in the IIP + IL3 group (1.22 ± 0.63 mm) compared to the DIP + IL3 group (1.89 ± 0.9 mm). The longer the loading time, the more bone loss appeared in the IIP + IL group; however, the results were reversed in the IIP + DL group. The MBL during the latter 3-month period was dramatically decreased compared to the former 3-month period in the IIP + DL3 group (p<0.05).

CONCLUSIONS

The IIP + IL group seems superior to the DL protocol and the MBL changed significantly during the first three months and thereafter became stable.

EVALUATION OF THYROID RADIATION DOSE USING CONE BEAM COMPUTED TOMOGRAPHY

Cone beam computed tomography (CBCT) became common in various dental specialties over the past decade. This technology is used by dental professionals regarding the investigation of maxillofacial structures. Due to the diagnostic quality and possibility of 3D view, this method has become an additional method of human exposure to ionizing radiation. This study aims to evaluate the amount of ionizing radiation absorbed by thyroid gland using CBCT. Measurements were performed by LiF dosimeters (TLD-100), positioned on a phantom for head and neck, which was irradiated by Newtom 3G-CBCT. The average of phantom surface radiation dose at the thyroid gland was 0.48 mGy. The data obtained during this study are suitable to reference values; therefore, it is important to recall that the as low as reasonably achievable principle must be applied in all procedures, thereby safeguarding the patient and also the professional.

Validity of ridge mapping and cone beam computed tomography in dental implant therapy

AIM

The purpose of this study was to compare the validity of alveolar ridge measurements obtained with ridge mapping (RM) technique against cone beam computed tomography (CBCT) measurements.

MATERIALS AND METHODS

Twenty partially edentulous patients were recruited for implant placement in the Clinic of San Martin de Porres University. For all the measurements, a vacuum-formed stent was fabricated for each subject. A buccal and lingual point was made in the stent to provide a reference of measurement for each implant site. RM measurements with the stent were obtained before and after surgical flap reflection. Two calibrated observers made the CBCT images measurements. T-test was used for the statistical analysis. Values <0.05 were considered statistically significant. Also, specificity and sensibility of CBCT and RM were compared. Intra-class correlation coefficient (ICC)_ was measure between CBCT measurements.

RESULTS

A total of 62 implants sites were evaluated. No statistical significant differences were obtained with CBCT and RM measurements (P = 0,207). Detecting proper buccal-lingual ridge, the sensitivity and specificity were 59% and 91% for RM while CBCT obtained 92% of sensitivity and 94% of specificity. Concordance was found "good" (ICC 0.82).

CONCLUSION

Both methods provide valid measurements. Even though, we found diagnostic limitations in the RM, it demonstrated to be a useful method for its exactitude, low cost, the immediate result and no need of radiation. CBCT was recommended when the bone ridge width and height were in the less than ideal for conventional dental implant placement.

Three-dimensional imaging and guided surgery for dental implants

Clinicians worldwide are increasingly adopting guided surgical applications for dental implants. Clinicians are becoming more aware of the benefits of proper planning through advanced imaging modalities and interactive treatment planning applications. All aspects of the planning phase are based on sound surgical and restorative fundamentals. As an integral part of the implant team, dental laboratories have now moved from analog to the digital world, providing the necessary support to the new digital workflow.

Dimensional accuracy and details of the panoramic cross-sectional tomographic images: an in vitro study

INTRODUCTION

Transversal slicing system (TSS) of Planmeca PM 2002 CC is a tomographic technique which enables us to take cross-sectional views of jaws. Tomographic imaging modalities are commonly applied to acquire cross-sectional images of the jaws for preimplant assessment of bone. Among the available tomographic imaging modalities, panoramic radiography is the most accessible imaging system.

MATERIALS AND METHODS

Study was conducted using 25 mandibles, out of these five were used for linear dimensional accuracy measurement and the rest 20 were utilized to study the details within the mandible. Study was aimed to evaluate dimensional stability in the images using different parameters, such as determination of direction of slice, determination of horizontal and vertical magnification, angular distortion, three dimensional distortion and determination of details.

RESULTS

For the direction of slice and for determination of horizontal and vertical magnification change in + 5º to - 5º was in acceptable limit. In determination of details, it was found that there was great discrepancy in readings given by nonradiologist which offset the mean value which was attributed to lack of training for interpretation of the observers.

CONCLUSION

99% of the readings were in the clinically acceptable limits.

CLINICAL SIGNIFICANCE

The easy availability, use of routine equipment, the low cost, low radiation dose for cross-sectional radiography make the TSS most preferred modality.

Maxillofacial Anatomy: The Mandibular Symphysis

Placement of dental implants in the anterior mandible is considered by many clinicians to be a relatively low-risk procedure. However, hemorrhagic episodes following implant placement in the mandibular symphysis are regularly reported and can have serious consequences. The use of high-resolution focused cone beam scanners has given us the ability to visualize the intricate neurovascular network of the intraforaminal region without distortion and in greater detail. Knowledge of the arterial supply and navigated implant placement in the mandibular symphysis can help to avoid these potentially life-threatening emergencies.

The effects of location of alveolar crest on the vertical bone heights on panoramic radiographs

OBJECTIVES

This study aimed to show that the horizontal relationship between the mandibular canal and the alveolar crest can influence the available bone height (ABH) measurement on panoramic radiographs.

METHODS

92 mandibular edentulous sites of panoramic computed radiographs and reformatted CT images of 77 patients were used. Selected CT images were categorized into four types according to the relative location of the peak of the alveolar crest to the mandibular canal. One oral and maxillofacial radiologist measured the ABH twice on both imaging modalities with an interval of 7 days and compared the measurement differences according to the type.

RESULTS

The absolute average value of the differences in measurement between the values of ABHs on panoramic images and CT images was 0.97 mm. Significant difference was found only between the mean values of ABHs for Type 1 (0.60 mm), where the alveolar crest is located in the buccal side or central area with respect to the mandibular canal, and Type 4 (1.46 mm), where the alveolar crest is in the lingual side to the mandibular canal (p < 0.05).

CONCLUSIONS

The relative horizontal location of the alveolar crest with respect to the mandibular canal affected the ABH measurement on panoramic radiographs. In particular, ABH is overestimated when there has been resorption of the buccal aspect of the ridge, moving the alveolar crest lingually.

Detecting bone loss along dental implants by subtraction of panoramic radiographs

OBJECTIVES

To test an extended subtraction method for measuring changes in bone along dental implants depicted on non-standardized panoramic radiographs.

MATERIAL AND METHODS

The measuring method consisted of a subtraction module extended with modules correcting gray values, correcting geometry and defining the region of interest mesial and distal of dental implants. It was applied to an archive of panoramic radiographs of implant patients who had been monitored up to 16 years.

RESULTS

Significant loss of gray value was demonstrated at a constant rate of 0.6 units per month throughout the study. This indicates gradual bone loss on the mesial and/or distal sides of the implants. Females were found to lose bone at a higher rate than males. Smokers and non-smokers, and various implant strategies yielded the same rate of bone loss.

CONCLUSIONS

The measuring method is a helpful tool to monitor changes around implants even when non-standardized radiographs are being used. Whereas changes of marginal bone level are increased five to eight times during the first year after surgery, the present method shows gradual loss of bone during 15 years after surgery.

Dental multisection CT for the placement of oral implants: technique and applications

Dental computed tomography (CT) is a diagnostic examination for the preoperative evaluation of patients who will undergo placement of oral implants. It can be performed with multidetector CT or more recently with cone-beam CT. The growing older population and the consequent development of edentulism have increased the number of imaging studies performed for preoperative evaluation of dental implantation. Thus, radiologists are becoming more frequently involved in this type of testing. Dental CT is superior to conventional x-ray techniques because superimposition and distortion are eliminated; therefore, possible complications such as injury of the neurovascular bundle and perforation of the maxillary sinuses can be avoided. This noninvasive and fast method provides accurate information about the positions of important structures to allow one to determine the implant required. Dental CT enables analysis of the state, quality, and quantity of bone on two-dimensional and three-dimensional reformatted images, and its high spatial resolution allows exact measurements of the length and width of the alveolar ridge. Inclusion of all this information in the radiology report facilitates achievement of a successful implantation.

Avaliação de doses referenciais obtidas com exames de tomografia computadorizada de feixe cônico adquiridos com diferentes tamanhos de voxel

OBJETIVO: o objetivo deste estudo reside na avaliação do produto dose-área (DAP) e das doses de entrada na pele (DEP), empregando protocolos com tamanho de voxel diferente, obtidos com o aparelho de Tomografia Computadorizada de Feixe Cônico (TCFC) i-CAT, a fim de determinar melhores parâmetros baseados nos princípios da radioproteção. MÉTODOS: para medição do DEP foi utilizada uma câmara de ionização do tipo lápis, e para o DAP foi utilizado um aparelho PTW. Quatro protocolos foram testados, a saber: (1) 40 seg., voxel de 0,2mm e 46,72mAs; (2) 40 seg., voxel de 0,25mm e 46,72mAs; (3) 20 seg., voxel de 0,3mm e 23,87mAs; (4) 20 seg., voxel de 0,4mm e 23,87mAs. A quilovoltagem permaneceu constante (120KVp). RESULTADOS: detectou-se diferença estatisticamente significativa (p<0,001) entre os quatro protocolos, para os dois métodos de avaliação da dose de radiação (DAP e DEP). Na avaliação do DAP, os protocolos 2 e 3 promoveram uma diferença estatisticamente significativa, não sendo possível detectar qual dos protocolos na avaliação da DEP proporcionou esse resultado. CONCLUSÃO: DAP e DEP apresentam-se como métodos de avaliação para doses de radiação em tomografia computadorizada de feixe cônico, sendo necessários mais estudos para elucidar tal achado. O tamanho do voxel, isoladamente, não é capaz de interferir na dose de radiação em exames de TCFC (i-CAT). A dose de radiação para exames de TCFC (i-CAT) está diretamente relacionada ao tempo de exposição e à miliamperagem.

The use of computed tomography (CT) to estimate age in the 2009 Victorian Bushfire Victims: a case report

The development of new imaging technologies is beginning to have an impact upon medico-legal death investigation in an increasing number of jurisdictions. Computed tomography (CT) is an imaging modality which is able to provide information to investigators without the need for a physically invasive autopsy in certain circumstances. The use of post-mortem CT as an aid to the identification of the victims of the Black Saturday bushfires is discussed with particular reference to dental age estimation. A case report is presented which demonstrates the ability of this imaging modality to separate individuals based upon dental development. Whilst CT is not yet able to adequately discriminate between differing restoration types and shapes, and therefore cannot be used for dental identification in the classic sense, the ability of this imaging modality to assess dental and skeletal development for the purpose of age estimation is valid.

A simple and practical approach to evaluate implant positioning immediately after placement

With the use of the flapless technique in the placement of one-piece implants, determination of the angulation of implant placement becomes critically important. After the implant is placed, the cast is made, sectioned, and superimposed on the radiographic template to determine the angulation. This method will assist the clinician in determining the angulation of one-piece implants immediately after placement.

Instrument for extraction socket measurement in immediate implant installation

The aim of the present study was to create an instrument and a computer program for measurement of extraction sockets and for planning of the immediate replacement of teeth using screw-shaped dental implants. Ten titanium screw-shaped Osteofix Dental Implant System implants (Osteofix, Oulu, Finland) were immediately installed after extraction in nine patients, four women and five men (age 17-62 years). The measurements of fresh extraction sockets were taken at six points (mesio-buccal, buccal, disto-buccal, disto-lingual, lingual and mesio-lingual) using an instrument created by the author. The area of no contact between bone and dental implant was 11-40% (mean 31%, SD 9%), calculated by computer program. If less than 30% of the implant surface area would be in contact with the bone, immediate replacement was abandoned because sufficient primary stability could not be achieved. Guided bone regeneration was promoted by covering the implant and bone defect with deproteinized bovine bone mineral (Bio-Oss, Geistlich AG, Wolhusen, Switzerland) and bioresorbable collagen membrane (Bio-Gide, Geistlich AG), fixed in place with resorbable pins (Resor Pin, Geistlich AG). After 6 months a considerable, statistically significant (P < 0.05) defect reduction of 90% (SD 7%) was noted. It was concluded that an instrument and a computer program created for extraction socket measurement are useful in some borderline cases when there is lack of bone and the success of one-stage implantation is doubtful.

A new device for measuring density of jaw bones

OBJECTIVES

The purpose of this project was to develop a lightweight, simple device to evaluate alveolar process bone density using normal intraoral and extraoral imaging procedures.

METHODS

A simple lightweight device was constructed using barium sulfate as the major radiopaque component. The 5 x 32 x 12 mm(3) resin block has eight segments with known densities ranging from 1.304 (g/cm(3)) to 1.982 (g/cm(3)). The device was integrated into an XCP unit for standard intraoral radiographs and placed between the jaws for computer aided tomographic imaging. The relationship between the device segment densities and the optical densities of the exposed film was plotted.

RESULTS

A linear inverse relationship was found between the device segment densities and optical densities when segment densities were between 1.304 (g/cm(3)) to 1.882 (g/cm(3)). However, the relationship was non-linear for segment densities above 1.882 (g/cm(3)).

CONCLUSIONS

Normal human bone density is 1.85 (g/cm(3)), and this densitometer is useful for determination of material densities from 1.304 (g/cm(3)) to 1.882 (g/cm(3)). The device may be useful for precise bone density assessment.

A comparison of conventional panoramic radiographs with volumetric computed tomography images in the preoperative assessment of impacted mandibular third molars

PURPOSE

In the present study, we evaluated the geometric, topographic, and anatomic reliability of volumetric computed tomography (VCT) images by comparing conventional panoramic radiographs with reconstructed VCT panoramic and paraxial images before performing third molar surgery.

PATIENTS AND METHODS

A total of 6 anatomic sites on 10 patients who showed a topographic relationship between the apices of the third molar root and the mandibular canal were preoperatively assessed by 5 oral surgeons using conventional panoramic radiographs; these were complemented and compared with secondary reconstructed paraxial and panoramic VCT images.

RESULTS

The position of the apices in relation to the mandibular canal could be revealed on 94% of VCT reconstructed paraxial images. Assessment of VCT paraxial images could be facilitated by using a toolbar marker in 70% of the paraxial images. In 90% of the paraxial images, it was possible to assess the relationship of the mandibular canal and its adjacent anatomy. The visual grading scores for conventional panoramic images were significantly better on all 7 assessed anatomic sites compared with the reconstructed VCT panoramic images.

CONCLUSION

The results showed that the VCT paraxial images gave a significantly clearer perception of the mandibular nerve than conventional panoramic radiographs. However, conventional panoramic radiographs were shown to be better than the VCT reconstructed panoramic images and were therefore an invaluable tool in the "expert-derived" assessment and posed the potential for identifying the need for further VCT diagnostic procedures.

Clinical decision-making using computers: opportunities and limitations

This paper deals with the use of information technology in order to make clinical decisions in dentistry. Since there is a large number of available systems and ongoing projects using computers, we first identify and describe major streams, as well as singular specialties. We underline the need for standards for data format and exchange in addition to the ability of different systems to communicate with each other. We conclude with a five-step recommendation to transform a dental office into digital and how to implement a computer-aided clinical decision support system, which provides action-oriented support in order to reduce the likelihood of human error during dental treatment.

Accuracy of reformatted CT image for measuring the pre-implant site: analysis of the image distortion related to the gantry angle change

OBJECTIVES

In a multiplanar reconstruction CT program (CT/MPR), the altered gantry angle corresponding to the patient's position during scanning for multiplanar reformatted CT may cause distortion of the image. The aim of this study was to quantitatively assess the distortion in reformatted central panoramic and cross-sectional images owing to the change of gantry angle.

METHODS

A resin block model with four cylindrical holes and a human dry mandible were used in high resolution conventional CT scanning. A MPR software package was used for reformatted panoramic and cross-sectional images. The block and the gantry were equally inclined at 0 degrees, 15 degrees and 30 degrees. The relationship between the positional difference and depth of the hole as determined in the reformatted image, and the actual depth was analysed with respect to the gantry angle. The actual depths (H) were calculated by use of the measured depths (h) and the inclined angles: H=hxcos beta. The positional differences of the hole bases (W) were also calculated by use of the measured depths and the inclined angles: W=hxsin beta or Hxtan beta.

RESULTS

Increasing the gantry angle, increased the depth and inclination of the holes in the reformatted central panoramic images. Inclined angle (beta) was the same as gantry angle.

CONCLUSION

When the gantry angle is not at 0 degrees, certain CT/MPR programs may distort the reformatted image. If distortion occurs, the corrected position and usable length of pre-implant sites can be calculated by use of the above formula.

Use of imaging guides in preimplant tomography

OBJECTIVES

The objective of this study was to quantify the variation in use and type of imaging guides used by community-based specialists and general practitioners during dental implant treatment planning phases. The specific aim of this study was to test the hypothesis that specialists are more likely to use some form of cross-sectional imaging in conjunction with imaging guides during the preoperative assessment of dental implant procedures.

STUDY DESIGN

Records from 630 patients with implants (1640 implants) referred for cross-sectional tomography were reviewed. Imaging guide type and implant sites were noted.

RESULTS

The distribution of referring dentists by specialty was as follows: general practitioners (42.2%), periodontists (35.1%), oral and maxillofacial surgeons (13.3%), and prosthodontists (7%). Of patients referred for tomograms, 52% were referred without a surgical guide.

CONCLUSION

Specialists ordered tomograms in conjunction with imaging guides more often than did general practitioners. Prosthodontists and periodontists preferred to use more restrictive guides than did general practitioners or oral and maxillofacial surgeons.

Fabrication of imaging and surgical guides for dental implants

Research and experience have suggested that the success of dental implants depends on a well-developed and careful treatment plan approach. Historically, implant size and angulation were determined with the use of panoramic radiographs and clinical judgment during surgery. This occasionally resulted in mechanical and esthetic compromise. This article describes the step-by-step fabrication process for 4 different imaging and surgical guides. Set-up disks, which enhance the design and fabrication of guides, also are introduced. These guides are used in conjunction with cross-sectional tomography during the preimplant assessment of surgical sites.

A multifunctional, provisional, implant-retained fixed partial denture

This article describes the modification of a procedure for fabricating a laboratory-processed, metal-reinforced, acrylic resin provisional restoration that becomes an implant-retained fixed partial denture. The modification involves the incorporation of patrix and matrix components into a cast metal framework. The prosthesis can be used as an alternative to a removable radiologic stent and surgical guide. It can function as a surgical guide during implant placement and help retract the buccal mucogingival flap during implant placement. The prosthesis also can be used as an aid in locating the implant during stage II surgery. Finally, the pontics can be converted into an implant-supported provisional restoration immediately after the implant prosthetic components are attached to the uncovered implants.

Correlation between planned prosthetic and residual bone trajectories in dental implants

STATEMENT OF PROBLEM

The success of dental implant treatment relies on a well-developed treatment plan approach. Historically, implant placement was guided mainly by residual bone height and width, at times compromising prosthetic needs.

PURPOSE

This study analyzed the amount of deviation between planned prosthetic trajectory and residual bone trajectory in different areas of the maxillary and mandibular dental arches, by using a tomographic survey in conjunction with imaging/surgical guides.

METHODS AND MATERIAL

Ninety-two patients with a total of 235 implant sites were selected for the study. An imaging and surgical guide with a radiopaque indicator was constructed to determine the planned prosthetic trajectory. Cross-sectional tomograms were taken through the indicator at each implant site. The outlines of the available bone, planned prosthetic trajectory, and residual bone trajectory were traced, and the difference in the trajectory between the 2 trajectories was determined.

RESULTS

Discrepancies between the planned prosthetic and the residual bone trajectories were greater in the mandibular molar area. This site was statistically different from other site groups at P =.05 (Tukey method). Statistically, all other site groups were not significantly different.

2-D and 3-D reconstructions of spiral computed tomography in localization of the inferior alveolar canal for dental implants

OBJECTIVE

The purpose of this study was to compare and validate the accuracy of measurements on 2-dimensional and 3-dimensional reconstructions from spiral computed tomography in localization of the inferior alveolar canal.

STUDY DESIGN

Four edentulous human cadaver heads with intact mandibles were imaged in a spiral computed tomography scanner. The data were transferred to a networked computer workstation to generate 2-dimensional orthoradially reformatted and 3-dimensional volumetric images. Linear measurements of the images were made from the superior border of the inferior alveolar canal to the alveolar crest. The specimens were then dissected at corresponding locations, and physical measurements were made.

RESULTS

There were no statistically significant differences between the 2-dimensional computed tomography measurements and the physical measurements or between the 3-dimensional computed tomography measurements and the physical measurements. However, we did find a statistically significant difference between the 2-dimensional and 3-dimensional computed tomography measurements.

CONCLUSIONS

2-dimensional and 3-dimensional computed tomography images allow accurate measurements for localization of the inferior alveolar canal.

A retrospective multicenter evaluation of single tooth implant experience at three centers in the United Kingdom

STATEMENT OF PROBLEM

Implant treatment in the United Kingdom has been provided mainly in specialist, regional dental hospitals. However, increasingly, general dentists are providing implant-supported prostheses in a private office setting.

PURPOSE

This study investigated the nature, timing, and frequency of complications associated with single tooth implant therapy in a dental hospital and two dental offices.

METHODS

The dental records of 58 patients provided with 76 implants during the period of 1989-95 were reviewed retrospectively. Fifty-three single tooth crowns on implants were placed by general dentists and 23 by specialists in the dental hospital.

RESULTS

Implant survival rate was 96%. Twenty-eight guided bone regeneration procedures were required, including 13 unplanned ones. Prosthodontic complications included the need for recontouring of three crowns and the recementation of three crowns. Only two abutment screws required retightening. Peri-implant soft tissue inflammation occurred around six crowns and recession around two.

CONCLUSION

The single tooth implant-supported crown appears to be an effective and durable restorative treatment with a relatively low prevalence of postoperative complications.

Implant site assessment using panoramic cross-sectional tomographic imaging

OBJECTIVES

The purpose of this study was to evaluate the ability of two different panoramic imaging systems to produce cross-sectional images with accurate vertical dimensions of the posterior mandible.

STUDY DESIGN

Three partially edentulous human cadaver mandibles were used for this study. On each mandible, three potential implant sites were arbitrarily identified in an area between the mental foramen and the ascending ramus. Each site was imaged using two different panoramic machines. Using each image, the mandible's outline, cortical thickness, and position of the mandibular canal were traced on clear acetate film. The mandibles were then sectioned at each site to serve as a gold standard. The cadaver sections and tracings (corrected for magnification) were measured, recording the overall mandibular height, distance from the crest of the ridge to the superior aspect of the mandibular canal, and the thickness of the cortical bone at the most inferior aspect of the mandible.

RESULTS

There were no significant differences between either of the system's image measures and the gold standard when considering the distance between the crest and the mandibular canal. Differences were noted between the systems measures and the gold standard in the assessment of the cortical bone thickness and the overall mandibular height.

CONCLUSIONS

Both imaging systems can be useful for vertical measurements of a potential implant site in the posterior mandible.

A stent for presurgical evaluation of implant placement

This article describes a method of fabricating a stent with barium sulfate and stainless steel tubes for the accurate radiographic evaluation of the relationships of the predesigned superstructure, the scheduled implant placement, and the anatomic structure. The barium sulfate in the stent depicts the outline of the predesigned superstructure, and the stainless steel tubes indicate the intended location and inclination of the implants on the computed tomographic scans. In addition, this stent can be used as a surgical stent to guide the pilot drill to the desired site.

Technical note. Sagittal tomography as an adjunct to cross-sectional evaluation of select implant sites

OBJECTIVE

To supplement conventional cross-sectional tomography with a sagittal projection in order to verify the location of vital anatomical structures prior to dental implant surgery.

METHODS

A method is described that illustrates the theory, technique and benefits of incorporating sagittal tomography into the radiographic examination of a dental implant patient.

RESULTS

Local variations in the inferior-superior position of the mandibular canal or encroachment of the sinus on areas immediately adjacent to the proposed maxillary implant site can be demonstrated.

CONCLUSIONS

The additional information gained from sagittal tomography aids the clinician in appreciating the orientation and morphology of the anatomical area under examination.