Sonographic measurement of residual ridge width Mario Traxler, MD, DMD,a Christian DMD,b and Werner Lill, MD, DMDa University

of Vienna,

Dental

School,

Vienna,

versus

mapping

Ulm, MD, DMD,b

Peter

for determination

Solar, MD,

Austria

To achieve long-term success of dental implants, evaluation of the dimensions of the resorbing alveolar process must be accurate because an implant should be surrounded by at least 1 mm of bone. Estimating the thickness of bone is more difficult because the mucosal contour can mask the actual dimension of the residual ridge. With ultrasound, it is possible to analyze and visualize the diameter of maxillary or mandibular residual ridges. Data obtained from ultrasound measurement of residual ridges were compared with the data from ridge mapping with the Wilson bone caliper and the Spoerlein caliper. The ultrasound measurement produced nearly the same data at all measurement points as ridge mapping. Ultrasound also provides exact information about the location of the mental foramen and the maxillary sinus. By using all three methods the initial stage of implant treatment can be planned. (J PROSTHET DENT 1992;6'7:358-61.)

aAssistant bVisiting 10/l/30531

Professor, Department Clinician, Department

of Oral Surgery. of Oral Surgery.

Fig. 1. Wilson caliper (arrow) Wilson caliper is exact up to f to to.5 mm.

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1

and Spoerlein caliper. mm, Spoerlein caliper up

E

ven experienced implant surgeons can be misled by the apparent buccolingual dimension of the maxillary or mandibular residual ridges. l-3 When the bone is exposed, the reality of the resorbed ridge becomes apparent. An unexpected lack of dimensions can result in a sudden change of the treatment program that may not have been discussed with the patient. Ridge mapping3 allows the implant surgeon to determine the thickness of the residual bone before a mucoperiostal

Fig. 2. Spoerlein ridge.

caliper measuring

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Fig. 3. Application of a 10 MHz transducer (1) on atrophic maxillary residual ridge (2); siliconelastomer (3).

Table

I.

mandibular

Buccolingual dimension residual ridges

Measurement No. 1 2 3 4 5 6 7 8 9 10 11 Eleven sonographic patients.

Wilson caliper (mm) 5 3 6 5 4 5 6 4 5 I 3 and mechanical

of the maxillary

Spoerlein caliper (mm) 5.0 3.5 6.5 5.0 3.5 5.0 6.0 4.5 5.5 7.5 3.5 measurements

and

Sonographic measurement (mm) 5.4 3.5 6.4 4.1 3.6 5.1 6.3 4.7 5.2 7.6 3.3 were averaged

Fig. 4. A, Residual ridge of edentulous maxilla (arrow). Ultrasound beam is coming from occlusal direction. Because of vestibular concavity of alveolar process this part of bone is not delineated. B, Graphic outline with arrow indicating.~ bony crest. Striped area depicts soft tissue. for four

flap is reflected during surgery. This article describes alternative method for determining bone thickness.

an

METHOD We compared ridge mapping with sonography for analyzing the soft tissue thickness for four edentulous patients (one woman and three men 53 to 74 years of age). To obtain identical reproducible sections, the measurement points were marked with a water-insoluble pen on the crest of the residual ridge. After the sonographic measurement, the distance was measured with the Wilson caliper (WBC, Sydney South 2000, Australia) and the Sporlein (U. of Mainz, Germany) caliper (Figs. 1 and 2). The measurements were located in the premolar and frontal sections of the maxillae and mandible. For sonographic measurement, a 10 MHz mechanical sector and linear transducers (ATLUltramark 8, Advanced Technical Laboratories USA,

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Washington, D.C.) were used. To avoid near-field artifacts, a silicon elastomer was used between the transducer and the oral mucosa (Fig. 3). Distinguishing soft tissue from bone is possible because of the different impedance of the tissues. Soft tissue has a good impedance whereas bone does not. A part of the whole energy of the original ultrasound beam is reflected according to the different impedances. Bone with good reflection appears as a bright line, whereas soft tissue with poor reflection appears spotted (Figs. 4 through 6). The ridge-mapping technique involves a series of measurements with a caliper. The sharp points of the caliper penetrate the mucosa until the surface of the bone is reached. A millimeter scale near the handle of the caliper will give a reading of ridge thickness.

RESULTS The data obtained from sonographic imaging, the Wilson caliper, and Spoerlein caliper are shown in Table I. In all instances, sonographic imaging of the buccolingual dimen-

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TRAXLERETAL

B Lx-

B

-.--

Fig. 5. A, Outline of residual ridge (+); mucosa(arrow). B, Graphic outline with arrow indicating soft tissue(striped area).

sion of the maxillary and mandibular residual ridges was successful.When data of sonographicimaging were compared with the Wilson caliper and Spoerlein caliper measurement methods, the maximum deviation was 0.7 mm among the three analyses. The mental foramen can be located exactly with ultrasound (Fig. 6). Becauseof vestibular concavities of the maxillary residual ridge, the whole bone contour cannot be visualized by one beamdirection (Figs. 4 and 5). For evaluation of the contour of the residual ridge and of the body of the maxillae, the position of the transducer must be changedin the sameplane. DISCUSSION The reduction of residual ridgesis chronic, progressive, irreversible, and cumulative. The rate of bone resorption varies betweenindividuals and in different parts of the jaws in the sameindividual.’ Even though this important and basicfinding hasbeenaccepted,the contour of the soft tissuecovering the resorbedridges may often present a misleading picture of the extent of bone resorption.” Imaging methods such as computed tomography (CT)2

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Fig. 6. A, Mental foramen (arrow) and residual ridge (double-arrow) are seenin sonograms.B, Graphic outline

with single arrow indicating mental foramen. Doublearrow indicates residual ridge.

and magnetic resonance (MR) have been used for the planning of dental implants. Becauseboth proceduresare complicated and expensive,their useis limited. In contrast to CT and MR, ridge mapping with the Wilson and Spoerlein calipersand sonographicmeasurementare simpleand effective methods of diagnostic measurement of ridge thickness before surgery.4,5 As the present study shows,sonographicimaging corresponds well to the ridge-mapping measurement. This finding applies to all measurementpoints of the chosen measurementplanes. Ridge mapping requires local anesthesia, which may concern patients. Ultrasound,6 being a noninvasive method, does not burden the patient. Ultrasoundexaminationscan be reproducedasoften asrequired and are easyto document by usingvideo technique or photographs. Furthermore, the useof ultrasound (Figs. 4 and 5) rendersexact information on the location of the mental foramen (Fig. 6) and the maxillary sinus. CONCLUSION Ridge mapping and ultrasound will aid the implant surgeon in the selection of patients who have adequate bone

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for placement of dental implants. As anon-invasive method, the authors prefer ultrasound to ridge mapping, especially because ultrasound provides exact information about the location of the mental foramen and the maxillary sinus. REFERENCES 1. Atwood

DA. Reduction of residual ridges: a major oral disease entity. J PROSTHET DENT 1971;26:266-71. 2. Schwartz MS, Rothman SLG, Rhodes ML, Chafetz N. Computed tomography. Part II: preoperative assessment of the maxilla for endosseus implant surgery. Int J Oral Maxillofac Implants 1987;2:143-8. 3. Wilson EJ. Ridge mapping for determination of alveolar ridge width. Int J Oral Maxillofac Implants 1989;4:41-3.

Determining the force absorption materials used in implant occlusal Roman M. Cibirka, DDS, MS,* Michael Brien R. Lang, DDS, MS,C and Christian

E. Razzoog, S. Stohler,

Spiirlein E., Stein R. Entwicklung einer zweidimensionalen Schiebelehre (Mainzer Modell). 2 Zahniirztl Implantol 1986;2:277-80. Daly CH, Wheeler JB. The use of ultrasonic thickness measurements in the clinical evaluation of the oral soft tissue. Int Dent J 1971;21:418-22. Czembirek H, Frtihwald F, Gritzmann N. Kopf-Halssonographie. 1st ed. Vienna, New York: Springer Verlag, 198867.71. Reprint requests to: DR. MARIO TRAXLER UNIVERSITATSKLINIK FUR ZAHN-, WAHRINGERSTR. 25~, A-1090

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UND KIEFERHEILKUNDE

WIEN

VIENNA AUSTRIA

quotient surfaces

for restorative

DDS, MS,b LDS, DrMedDentd

West Bloomfield, Mich., and University of Michigan, Ann Arbor, Mich. It has been hypothesized that the type of material used to form the occlusal surface of restorations retained by dental implants may impart a “dampening effect” to the bone-implant interface. This study compared the force transmitted to human bone by gold, porcelain, and resin occlusal surfaces in a simulated implant occlusal rehabilitation. A Branemark self-tapping implant was placed in a human cadaver mandible with a stacked three element strain gauge cemented to the lingual cortical plate. An Instron testing machine was used to apply an axial force, through a peanut sample, to a restoration that contained interchangeable occlusal surfaces. Applied force was divided by recorded microstrain at the bone-strain gauge junction to derive a calculated ratio, or force absorption quotient. No statistically significant difference of the force absorption quotient between the occlusal surfaces of gold, porcelain, and resin was observed. (J PROSTHET DENT 1992;67:361-4.)

0

cclusalloading of osseointegratedimplants is believed to be a determining factor in the long-term success of an implant treatment pr0gram.l Branemark et a1.2proposed a protocol for occlusal development predicated on basic physics and early clinical results. Their recommendations included acrylic resin asthe material of choice for the occlusal surfacesof implant-retained prostheses. The resiliency of acrylic resin is suggestedasa safeguard

aPrivate practice, West Bloomfield, MI. hAssociate Professor, Department of Prosthodontics. cProfessor and Chair, Department of Prosthodontics. dProfessor of Dentistry, Department of Cariology and General Dentistry. 10/l/33877

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against overstressand microfracture of the implant/bone interface. Although most acrylic resinsare burdened with technical and subjective disadvantages,the alternative of gold or porcelain occlusalsurfacesis describedas not providing resilient safeguarding to the dental implant complex.leg Researchrelated to dental implants has empirically addressedthe subject of occlusalload transfer; however, it is void of studies that quantify, through in vitro human or animal models, force absorption of restorative materials. The present investigation developed a method to scientifically apply and measurethe vertical force usedto incisea food substance.The investigation also recorded the force transmitted to human bone adjacent to an implant fixture when occluding surfaceswere made of gold, porcelain or resin.

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