March 1, 2004
by Jack G. Zosky, DDS, FRCD(C), FICD and Allan P. Schaffran, DDS
ABSTRACT: Historically the traditional two-stage approach to implant success utilizing the Branmark protocol emphasizes a load-free healing period as a major requirement for predictable implant integration. A single stage surgery by placing a non-submerged implant has also been shown to be successful but may be unpredictable as far as aesthetics is concerned. Technological advances in implant surface characteristics to enhance roughness and porosity demonstrate better and faster bone adaptation. Immediate loading has been proposed for the anterior aesthetic zone. With careful patient selection and attention paid to available bone and implant positioning this technique has been shown to be successful and advantageous for the patient.
Many patients who lose or are about to lose a tooth in the maxillary anterior aesthetic zone find this to be an emotionally and psychologically traumatic prospect. Options for tooth replacement in this situation provide further consternation for the patient and the treating clinician. A removable acrylic thumb partial denture has obvious and distinct disadvantages. A conventional fixed bridge requires the cutting down of healthy adjacent teeth. A bonded Maryland-like bridge cannot be considered a permanent restoration and limits hygiene access.
There are abundant data in the literature documenting aesthetic single-tooth implant-retained restorations using the traditional two-stage surgical protocol ad modem Branmark.1-3 With this protocol, however, four to six months are allotted prior to implant exposure and occlusal loading. Provisional restorations such as a thumb partial denture or an essex retainer or a temporary bonded acrylic splint may be utilized. Any of these can contribute, however, to soft tissue complications such as inflammatory response, hygiene concerns and compromised papilla reformation. Also, patient convenience, comfort and compliance can be lacking with these appliances.
A further complication of post-extraction bone resorption occurs when an implant is not placed on an immediate basis following removal of the tooth.4 An immediate implant placement will preserve the bony contours and gingival envelope but should not be done if the tooth is acutely infected or if there is buccal bone dehiscence due to vertical root fracture. Significant periapical pathology also precludes immediate placement as does the inability to remove the tooth atraumatically.5
It must be remembered that implant esthetic and functional success is predicated upon restoration-driven implant placement with preservation of peri-implant hard and soft tissue contours that are harmonious with adjacent natural teeth.6 When an anticipated implant site is insufficient in height and/or width, augmentation procedures must be utilized to optimize the deficiencies. This can be done prior to or sometimes simultaneous with implant placement and is dependant upon how to best recreate a natural dento-gingival complex with the minimum of surgical interventions.
Single-stage, non-submerged implant placement has been advocated in order to avoid a second surgery and disturbance of the biologic width. Clinical and histologic data demonstrate the predictable achievement of osseointeg ration with this technique even though provisional restorations and mastication of food will invariably cause “premature” loading of the implants.7,8 In the esthetic zone, however, the non-submergence of the implant shoulder can further complicate provisionalization and the ultimate prosthetic crown gingival margin.
A more recent technique of simultaneous extraction, implant placement and provisionalization with an immediate acrylic restoration can obviate many of the concerns described above. It is suggested that atraumatic tooth extraction with minimal or, better still, no raising of flaps with appropriate implant placement and immediate provisional crown placement will not only preserve but optimize soft tissue contours.9-11
Meticulous planning is necessary with this procedure. The alveolar housing surrounding the tooth to be removed must have the bony crest no more than 3mm apical to the buccal gingival margin and no more than 4.5mm at the interproximal height of bone to the final crown contact point12 (Figs. 1a & b).
The surgical placement of the implant must be placed with consideration of three dimensions: mesial/distal, buccal/palatal and apical/coronal. A predetermined surgical guide based on the final prosthetic crown and tooth position should be utilized to ensure proper emergence profile of the definitive restoration.
A patient with 100 percent overbite as in a Class II, Div. II occlusion would be unsuitable. Lack of buccal and/or interproximal bone would present an undesirable situation for this procedure. If the patient presents with a significant deficiency of hard and soft tissue, especially where there is preexisting absence of the interdental papilla, then a two-stage surgical approach should be utilized with the necessity of soft and hard tissue augmentation grafts.
The ability to achieve primary stability of the implant is essential with this technique. Research data shows that it is not necessarily early loading that leads to fibrous tissue rather than bony adaptation to the implant surface. Rather, it is micro-movements at the bone/implant interface, which are a result of inadequate primary stability.16
Therefore, it is essential for the surgeon to be able to identify the bone volume and density of the implant site either at the pre-surgical work-up stage or during implant osteotomy preparation. Pre-surgical work-up to determine bone quality and quantity in a patient’s bony recipient site can include CT scans. It is also imperative for the surgeon to understand the role of implant insertion torque values.
The execution of the treatment plan for-the placement of the immediate implant, abutment and temporary acrylic crown requires a cohesive synergy between the restorative specialist, surgical specialist and laboratory technician.
This can be best demonstrated and illustrated in the following case report.
A 55-year-old Caucasian male presented with a history of a minor blow to the left central incisor a few months previous to his dental visit. The patient reported experiencing some tenderness over the labial gingiva and slight mobility.
A single periapical film was taken and revealed a horizontal fracture approximately 4mm apical to the cemento-enamel junction (Fig. 1c). The tooth exhibited M1 mobility and was non-responsive to cold stimulus and electric pulp test. The left central was slightly darker in colour than the adjacent central and lateral incisors.
The salient consideration at this juncture was the decision-making process for the ultimate restoration of the damaged tooth. If it is decided to remove the tooth, then according to a recent declaration of the Academy of Osseointegration, the single implant-supported crown should be considered as the contemporary standard of care. Root extrusion followed by endodontic treatment and post core and crown would render a poor crown/root ratio and guarded prognosis. The patient declined conventional prosthetic restorations including fixed partial denture or bonded bridge understanding these procedures involved adjacent tooth reduction.
An immediately loaded single tooth implant can obviate the need for the usual removable or bonded transitional appliance, and provide the patient with an esthetic restoration during the critical integration period.
The following immediate load technique describes a well-timed and coordinated procedure encompassing surgical, prosthetic and laboratory inventiveness.
Pre-Surgical and Prosthetic Technique
1. Maxillary and mandibular study models with the appropriate registrations are taken and mounted on a semi-adjustable articulator. A second pour is carried out by the lab technician (Fig. 2).
2. The lab tech is then instructed to prepare one set of models by “extracting” the left central incisor and prepping the socket. A 5.0 diameter implant
analog (Replace Select; Nobel Biocare, Yorba Linda, CA) is positioned at an ideal angulation and apico-gingival position (2-3mm apical to the adjacent central CEJ) (Figs. 3a & b).
3. A fixed position surgical stent is fabricated on the model to allow the surgeon to replicate the predetermined implant position as accurately as possible. A transfer assembly can assist as an extension for greater precision in stent design. A clear prosthetic shell stent is made on the original model as a back-up for temporization (Figs. 4a-c).
4. Temporary implant posts (titanium and plastic) are aligned and prepared to receive a temporary acrylic shell crown matching the mould and shade of the adjacent dentition.
5. The entire armamentarium is delivered to the restorative specialist for examination prior to surgery (Figs. 5a-c).
Initial Surgery/Prosthetic Appointment
In this case, the restorative specialist was in attendance at the time of surgery, but this is not mandatory.
1. Following buccal and palatal local anesthesia infiltration the fractured coronal portion of tooth #2.1 is removed with forceps. Note that the buccal bony wall is intact and maintains it’s convex contour and no flap is raised (Fig. 6).
2. The apical portion of the tooth is encased in bone so in order to preserve the buccal and palatal walls of the socket this portion of the root is carefully “cored-out” from the inside to the periphery with a surgical drill and fissure bur (Fig.7).
3. The fixed position surgical stent is fully seated and the initial guide drill preparation of the osteotomy is started and then completed to the pre-chosen implant length and diameter. The implant is then inserted. Note the angulation is positioned so the abutment screw is just palatal to the incisal edge in the cingulum position. Apically the implant shoulder is placed approximately 3mm above the gingival margin of the adjacent teeth (Figs. 8a-c).
4. The implant diameter ideally should “fill” the extraction socket. In this case a 5.0mm diameter tapered implant (Nobel Biocare Replace Select TiUnite Yorba Linda, CA) is used. If any voids at the coronal aspect between implant and osteotomy is noted, bone from the drilling procedure can be utilized to fill the voids. The pre-prepared temporary abutment is then hand-torqued into place (Fig. 9).
5. The temporary crown is lined and adjusted so that there is no centric or protrusive contact and the patient is cautioned to avoid direct function or load for at least two months (Figs. 10a-e).
Post Op Surgical / Prosthetic Appointment One Week
The patient is seen at one week to monitor healing and ensure accurate fit and occlusion. Note the preservation of hard and soft tissue architecture (Fig. 11).
Three Months Post-Op
Note temporary crown at three months with excellent healing of dento-gingival complex and papilla preservation (Fig. 12). Once integration is confirmed, the temporary crown and abutment are removed and a transfer assembly is attached in preparation for an implant level impression (Figs. 13a-d). A custom cast precious implant post is fabricated along with a ceramic gold coping and a new provisional crown (Figs. 14a-c). The gold abutment is positioned and torqued to 35Ncm. The coping is fitted and a centric registration is taken for remounting. A coping pick-up impression is taken with polyvinylsiloxane material and sent to the lab for final porcelain adaptation (Figs. 15a-c). The porcelain fused to gold crown is cemented into place and the patient can now return to full function (Figs. 16a-c).
Although treatment outcome studies utilizing immediate implant placement and immediate load in the anterior aesthetic zone are limited, the preliminary data are promising.9,13-15
The most comprehensive of these is Groisman et al where 92 implants were evaluated in a prospective manner with life table analysis up to two years in function. Six of the 92 implants failed and the remaining 86 successful implants showed no soft or hard tissue adverse reactions. This success rate of 93.5 percent is comparable to data involving the more traditional two-stage, non-loading protocol of Branmark. One of the six failures was attributed to trauma sustained one day prior to surgery, which intruded the tooth and caused fracture to the buccal bone. Two of the other failures were attributed to overloading due to 100 percent overbite, which should be a contraindication to this technique. Therefore, only three of the six failed implants had no obvious reason for failure.
Implant Design and Surgical Technique
Implant surface “roughness” enhances bone to implant interface. Also a taper design or true anatomical root shape can compress bone of lesser density for better primary stability and can optimize stresses transmitted to bone.
The surgical protocol includes avoidance of a surgical flap so that bone vascularization is not compromised. Also, papillary form is maintained. Careful, atraumatic extraction is essential. The use of a surgical guide ensures proper implant positioning. The surgeon’s finger should palpate the buccal gingival wall to “feel” for possible perforation. The initial drill should rest against the palatal wall of the socket to avoid thinning of the buccal plate and a probe can be used to check the integrity of the buccal wall during osteotomy finalization.
If the bone feels fragile with little resistance to the initial drill then osteotomes can be used to compact the bony housing.
The peri-implant soft tissue envelope can demonstrate recession of approximately 0.6mm to 1.0mm and generally occurs within three months after implantation. Therefore, the temporary acrylic crown should be left in place for at least three months prior to fabrication of the final restoration. During this provisional period there should be no occlusal contact in centric occlusion or excursive movements. This provisional timeframe also allows for manipulation of the soft tissue emergence profile and papilla reformation.17
Successful and predictable achievement of immediate replacement of a single tooth via implant insertion and provisionalization with a temporary acrylic crown has become an acceptable procedure. This is particularly desirable in the anterior maxillary aesthetic zone where the essential demands of hard and soft tissue preservation must be optimized. It allows for simplification of treatment and elimination of protracted time sequences. It also provides the obvious psychological advantage to the patient and enhances patient comfort. Most importantly, the ultimate aesthetics of the final restoration can be more predictably attained.
However, the multi-faceted aspects of this surgical/prosthetic treatment present a daunting challenge to the surgical/restorative team. They should be very experienced with all aspects of implantology and especially cognizant of the criteria for success with this technique. There should be careful collaboration between surgeon, restorative dentist and lab technician as well as the patient.
It should be remembered that the maintenance and preservation of existing anatomical structures is easier that re-creating them once lost. No doubt further progress in implant design will be forthcoming as well as surgical instrumentation to enhance implant stability. In fact a new “scalloped” shoulder design of the Nobel Perfect (Nobel Biocare Yorba Linda, CA) implant has been utilized by the authors with very promising results.
Dr. Zosky is a Fellow of the International Association of Oral and Maxillofacial Surgeons and the Royal College of Dentists of Canada as well as a Fellow of the International College of Dentists and a Fellow of the Pierre Fouchard Dental Society. He currently is chief of Oral and Maxillofacial Surgery at the Orthopaedic and Arthritic Hospital in Toronto, where he also maintains a private practice.
Dr. Allan Schaffran is a Diplomate of the American Society of Osseointeg ration, a Fellow and member of the International Congress of Oral Implantology, the Academy of Osseointeg ration and
the European Academy of Osseointeg ration. He maintains a private practice and education practice in Toronto.
Thanks to Jens and Peter at Ardent Labs for their excellent work and to Judy Wilson for typing this manuscript.
Oral Health welcomes this original article.
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