Molar tooth loss is more common than anterior tooth loss. 1 Now that the profession accepts that implant treatment is the first choice standard of care for such cases, 2 more general dentists will be providing both implant surgery and prosthetics to their patients. They will face the need to treat the lost first molar frequently. For successful outcomes, five considerations need to be taken into account. These are 1) implant design, 2) interdental space, 3) bone shape and quality, 4) mandibular canal location and 5) submandibular gland fossa anatomy.
METHODS
To assess the impact of these five considerations on implant treatment for the missing mandibular molar a Boolean search of Medline (http://www.pubmed.gov)using the key phrases "quality of dental implants" and "clinical performance" was conducted. Additionally, a random chart selection of missing mandibular molar patients in the author’s private practice was analyzed. Treated cases or those awaiting treatment were reviewed.
RESULTS
1) Implant design
The Boolean search of produced seventeen papers showing that the evidence on which implant therapy is based primarily comes from level-4 case series rather than the more rigorous cohort or controlled clinical trials studies. Nonetheless, fairly reliable conclusions can be reached. In a systematic review of promotional material of some 80 implant manufacturers and of the dental research literature, Jokstad et al found no clear evidence of advantages of specific morphological characteristics of dental implants. 3 From a biologic perspective, all available implant systems which have met regulatory standards of safety and effectiveness are created equal. Given that, practical considerations become uppermost.
A significant practical consideration for the general dentist is to select a system with fewer parts and fewer steps. With a large number of screw-retained parts management of the case can be a challenge. 4-6 While there can be significant benefits; these systems are best left to the specialist and to the experienced general dentist. The general dentist starting implantology will be better served with simpler systems which have a similarity to everyday crown and bridge work.
2) Interdental space considerations
The chart selection of missing mandibular molar patients showed that the size of edentulous first molar interdental space is highly variable.
It depends on the mesio-distal dimension of the lost molar and on the amount of mesial tipping and drifting of the second molar from the time of the loss of the tooth. Clinicians need to choose from one of three alternatives.
First, they can use a wide diameter implant (Figs. 1 & 2).
Secondly, they can use two standard diameter implants. The crowns can be splinted (Figs. 3 & 4) or "bicuspidized" (Figs. 5 & 6).
And third, they can bond composite material to the mesial contact point of the second molar and the distal contact point of the second bicuspid to optimize space dimensions. (Figs. 7 & 8)
3) Bone shape and quality
A random selection of cross sectional imaging reports for patients referred to radiology services from the author’s private practice was analyzed. Before the actual implant surgery, an assessment of the surgical site with cross sectional imaging can provide information which panoramic or periapical radiographs cannot. It is often useful to determine accurately the actual shape (height, width, inclination, crestal bone irregularities and submandibular gland fossa anatomy) as well as the as mandibular canal location. Cross sectional imaging will also show any pathology which needs to be eliminated before implant surgery.
Tomograms or computerized tomography scans can assess these characteristics accurately.
Lekholm and Zarb7 have identified bone shape and quality to be the major determinant of implant success. Bone shape can be assessed in the office by palpation and various x-ray methods. For more detailed and accurate assessment, cross sectional imaging gives reliable results.
No techniques for assessing bone quality are in general use in dentistry. The surgeon can assess bone quality by the "feel" of the bone during surgery.
4) Mandibular canal location
Panoramic x-ray views can be useful if, superior to the mandibular canal, there is 2mm or more of space additional to the intended implant length (Figs. 9-11).
If the amount of space superior to the mandibular canal is questionable then cross sectional imaging is needed for an accurate assessment (Fig. 12). The skilled specialist or experienced general dentist can accommodate for inadequate space in various ways.
5) Submandibular gland fossa anatomy
The anatomy of the mandible in the first molar area is highly variable (Figs. 13 & 14). To avoid perforating the buccal or lingual plate, the clinician needs to have a good understanding of it for each individual patient.
DISCUSSION
Molar tooth loss is more widespread than anterior tooth loss. 1 Throughout the entire decade the profession has accepted that implant treatment is the first choice standard of care for the replacement of the single mandibular molar. 2
Increasingly, more general dentists will be providing both surgical and prosthetic services to their patients. They will face the need to treat the lost first molar frequently. For successful outcomes, clinicians need to take into account implant design, interdental space, bone shape and quality, mandibular canal location and submandibular gland fossa anatomy.
CONCLUSION
General dentists who offer both implant surgery and prosthetics to their patients need to evaluate implant design, interdental space, bone shape and quality, mandibular canal location and submandibular gland fossa anatomy. Once they have taken all of these considerations into account and assuming that the patient’s medical condition allows it, they can proceed with the technical aspects of implant surgery and prosthetics with confidence. If, on the other hand, bone shape, mandibular canal location or submandibular fossa anatomy prevent routine implant treatment, the patient should be referred to a surgical specialist. OH
Tenax Dental Implant System Implants were used in all cases illustrated in this article. In 1971, Dr. Somborac published the first implant paper in the Canadian dental literature. He is in general private practice and is the co-inventor of this implant system and the founder of a Tenax Implant Inc. Over the past six years he has placed and restored over 1200 Tenax implants in his practice. He conducts continuing education courses and has assisted over 150 colleagues in both the surgical and the prosthetic phase of implant treatment.
Oral Health welcomes this original article.
REFERENCES
1. Paulander J, Axelsson P, Lindhe J, Wennstrom J. Intra-oral pattern of tooth and periodontal bone loss between the age of 50 and 60 years. A longitudinal prospective study. Acta Odontol Scand. 2004 Aug;62(4):214-22.
2. Henry PJ. Tooth loss and implant replacement. Aust Dent J. 2000 Sep;45(3):150-72.
3. Jokstad A, Braegger U, Brunski JB, Carr AB, Naert I, Wennerberg A. Quality of dental implants. Int Dent J. 2003;53(6 Suppl 2):409-43.
4. Bakaeen LG, Winkler S, Neff PA. The effect of implant diameter, restoration design, and occlusal table variations on screw loosening of posterior single- tooth implant restorations. J Oral Implantol. 2001;27(2):63-72.
5. Torrado E, Ercoli C, Al Mardini M, Graser GN, Tallents RH, Cordaro L. A comparison of the porcelain fracture resistance of screw-retained and cement-retained implant-supported metal-ceramic crowns. J Prosthet Dent. 2004 Jun;91(6):532-7.
6. Assenza B, Artese L, Scarano A, Rubini C, Perrotti V, Piattelli M, Thams U, San Roman F, Piccirilli M, Piattelli
A. Screw vs. cement-implantretained restorations: an experimental study in the beagle. Part 2. Immunohistochemical evaluation of the peri-implant tissues. J Oral Implantol.
7. Lekholm, U., and Zarb, G. A. Tissue-lntegrated Prostheses, Quintessence Publishing Co., Inc., 1985 Tenax Dental Implant System implants were used in all cases illustrated in this article.
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ABSTRACT
Posterior tooth loss is more common than anterior tooth loss. With the high documented success rates of implant treatment, using implants to replace molars lost to disease has become the first choice standard of care. Implant treatment to replace the first mandibular molar has unique considerations. General dentists who offer both implant surgery and prosthetics to their patients need to evaluate 1.) implant design, 2.) interdental space, 3.) bone shape and quality, 4.) mandibular canal location and 5.) submandibular gland fossa anatomy for each missing mandibular first molar being considered for implant restoration.
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A significant practical consideration for the general dentist is to select a system with fewer parts and fewer steps
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Lekholm and Zarb have identified bone shape and quality to be the major determinant of implant success
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Increasingly, more general dentists will be providing both surgical and prosthetic services to their patients
Photos
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Caption: FIGURE 11–PA of treated case in its fifth year of load…
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Caption: FIGURE 12–Panoramic view of a case awaiting treatment.
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Caption: FIGURE 13–Tomography showing anatomic variability of t…
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Caption: FIGURE 14–Tomography showing anatomic variability of t…
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Caption: FIGURE 1–First molar crown on a wide implant prior to …
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Caption: FIGURE 2–PA of treated case in its fourth year of load…
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Caption: FIGURE 3–Tooth 36 supported by two implants. Crown mar…
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Caption: FIGURE 4–PA of case treated with two splinted implants…
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Caption: FIGURE 5–"Bicuspidization" of the 46 supported by two …
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Caption: FIGURE 7–Tooth 46 supported by one implant. As in Fig….
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Caption: FIGURE 6–PA of treated case in its eighths year of loa…
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Caption: FIGURE 8–PA of treated case in its seventh year of loa…
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Caption: FIGURE9–Panoramic x-ray view shows adequate space for …
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Caption: FIGURE 10–Cantilever bridge replacing 36 and 35.