A Study of a Surgical Guide for Dental Implantology

Osseointegration of endosseous implants has long been the focus of research in dental implantology, for obvious reasons. The use of Titanium became the standard quite soon, but it took decades of research to come up with the ideal shapes and surface modifications (both physical and chemical), so that today it is safe to assume that a properly placed commercially available dental implant will osseointegrate. The issue of osseointegration can thus be considered as practically resolved, and this traditional surface-oriented line of implant research now focuses on modifications to prevent complications, such as peri-implantitis (7). It must be seen, though, that for decades, the main goal was to keep the inserted implant in place, which pushed other important issues aside, such as the three- dimensional position of the inserted (and osseointegrated) implant in the bone. The lack of adequate imaging technologies also contributed to the paucity of research in this direction and clinicians - having no other option - started to plan implant positions in panoramic radiograms and perform implant surgeries relying on their ability to mentally merge those two- dimensional plans with patient anatomy. Today, this can be considered the standard approach to dental implant surgery.

The optimal positioning of the implant in the patient's bone is, in many respects, an issue of distinguished importance. First, the position of the implant has a profound impact on the fit of and stress distribution on the superstructure (i.e. crown or bridge), which, in turn, influences survival of the latter. The position of the implant also determines the distribution of stress in the supporting bone, which, ultimately, influences the long-term survival of the implant itself. In other words, a misplaced implant may be functional for some time, but will not survive in the long run. Finally, a misplaced implant can cause serious esthetic problems in the esthetic zone.

The rapid progress of information technology and digital image processing created a favorable environment for what may be called digital dentistry, including the computer-assisted, three- dimensional planning of implant surgery and the stereolithographic manufacturing of surgical guides based on such digital plans. Various systems and procedures exist, but cone-beam CT-based digital planning and the production of custom-made surgical guides are shared features. The studied SMART Guide guided system is unique in the sense that the entire process is digital, and no dental technical work is required.

The aim of such a guided system is to provide individualized patient care by a.) planning implant position(s) considering the individual patient anatomy and b.) manufacturing a custom-made surgical guide that serves to guide bone drills during the preparation of the bony bed of the planned implant. The custom-made guide is manufactured according to the digital plan. The result is a surgical accessory that exactly fits the remaining dentition of the patient (thereby stabilizing it) and ensures that the bony bed of the implant is prepared as planned. Meta-analyses show that these systems indeed allow highly accurate implant placement as compared to the plan. But is this any better than the traditional, freehand way of implant surgery and placement? Intuitively, one would answer yes, but, in fact, the question is quite difficult to answer, given the almost complete lack of studies on the accuracy of freehand implant placement. Therefore, one of the aims of this study is to make such a comparison. A further point is that in the everyday practice, surgical guides are used in either of the following three modalities: for the initiation of the bed preparation ("pilot"), for the initiation and the entire drilling process ("partial") and for the entire process including the insertion of the implant ("full"). It is assumed that the more extensively the guide is used, the more accurate the final implant position will be as compared to the plan. However, this is only an assumption, as no direct comparison is available. Therefore, it is also our aim to compare these modalities in terms of how accurate implantation they allow as compared to the plan.

The investigators hypothesize that all three guidance modalities will allow significantly more accurate implant placement than the freehand method. It is also hypothesized that the three modalities will differ in the accuracy they allow. In general, the investigators hypothesize that any form of guided implant surgery and placement yields significantly more accurate results than the freehand approach.

Primary aim Comparison of the accuracy of partially and fully guided implantation as indicated by angle deviation.

Secondary aims

The secondary aims of the study are as follows:

To compare the accuracy of the different methods as indicated by entry point deviation; To compare the accuracy of the different methods as indicated by apical deviation; To compare the accuracy of the different methods as indicated by volume overlap; To compare the influence of position (maxilla or mandible) on the accuracy of implantation; To assess the tolerability of implantation performed with surgical guide; To assess the safety of implantation performed with surgical guide; To assess dentist satisfaction with the surgical guide (custom questionnaire) To assess volunteer satisfaction (OHIP, custom questionnaire)

Inclusion criteria

• Male and female volunteers between 18 and 75 years of age
• Partial edentulousness of the mandible or maxilla
• Clinical situation fit for implantation as judged by the examining physician or principal investigator (satisfactory soft and hard tissue conditions and occlusion)
• The volunteer communicates well with the examiner and compliance can be expected.

Informed consent.

Exclusion criteria

• Pregnancy or lactation. Pregnancy is defined as the period beginning with conception and ending with birth.
• Women in their childbearing age; by definition, any woman who - unless she uses effective contraception - can get pregnant in a physiological way. Eligibility for this study presupposes that the female subject will use effective contraception until 4 weeks after the end of her participation in the study. Effective contraception is defined as any of the following:

• Barrier method: condom or diaphragm or cervical cap with spermicide. Note that spermicide in itself is not a barrier!
• Full abstinence (if this is acceptable for the subject). Periodic abstinence, like the calendar- and temperature-based methods and interrupted intercourse are not acceptable.
• Female sterilization: bilateral oophorectomy w/wo histerectomy or tubal ligation at least six weeks before participation in the study.
• Sterilization of the male partner: vasectomy (no spermia in the ejaculate). The only partner of the participating female can be a male who has undergone vasectomy.
• Hormonal contraception (oral, injection, or implanted); intrauterine device (IUD) or intrauterine system (IUS).
• Any disease (including but not exclusively the diseases of metabolism, hematological diseases, diseases of the liver, the kidneys, the lungs, the nervous system, the endocrine organs, the heart and the intestines and infectious diseases) that, in the principal investigator's opinion, has a significant effect on the subject's general health and/or means an unacceptable risk factor for the person to receive implant treatment.
• Known HIV, Hepatitis B or Hepatitis C infection.
• Any internal or psychiatric disease that, in the opinion of the principal investigator, would risk compliance with the instructions or participation until the end of the study.
• Participation in an experimental study or trial within four weeks before the randomization, or within five times the half-life of the experimental agent (whichever is longer)
• Known allergy to any component of the implant or the implant guide
• Limited mouth opening, which, in the examiner's opinion, would risk the success of the intervention
• Increased gag reflex, poor tolerance of intraoral manipulation
• Radiotherapy, irradiation of the mandible or the maxilla (either at the time of screening or in the past)
• INR>2.5
• Immunosuppressed state
• Bisphosphonate treatment (either at the time of screening or in the past)
• Alcohol or drug abuse
• Habitual smoking
• Untreated periodontitis
• Retained root in the planned insertion site
• Local infection
• Lack of dental sanitation
• Poor oral hygiene
• Infection w/wo fever