Partial Extraction Technique
A Novel Approach to Immediate Implant Placements
There are numerous published articles and studies that illustrate what happens after a tooth is extracted. Most data indicates, with grafting or no grafting, there is an average change of 1.0-1.5mm in the alveolar ridge thickness buccal-lingually when a maxillary anterior tooth is removed.1,2
When the body senses that a tooth has been extracted, the buccal bony plate immediately begins to migrate and atrophy in a palatal direction. This shrinkage begins initially post extraction and can greatly affect the bone volume, gingival architecture, and future esthetics of potential dental implant sites.3 Over the years, cosmetically minded dentists have come to understand that maintaining pink esthetics and soft tissue architecture is far and away the biggest complicating factor for successful implant placements and is absolutely crucial for natural looking restorations in the anterior region. Dentists also understand that the underlying bone support has the greatest effect on soft tissue maintenance and preservation. Many creative techniques have been used in an attempt to bulk up deficient soft tissues or to correct reduced biotype thickness post-operatively with sometimes marginal results. Alternatively, adding pink gingival porcelain to the final restoration is a challenging esthetic endeavor at best.4
What if the body could be “tricked” into thinking that the tooth was never lost and thus maintain almost identical facial gingival architecture? What if we as clinicians could limit the surgical fatigue patients endure to get the more natural results they are seeking? The Partial Extraction Therapy (PET) surgical procedure is an innovative technique that helps overcome the dramatic bone and soft tissue changes that happen immediately upon extraction of maxillary anterior teeth. (References 5,6,7,8)
KEYWORDS: treatment planning, tooth extraction, buccal plate, socket preservation, biotype, immediate placement, soft tissue, esthetics, cosmetics, healing
“The Partial Extraction Technique has its surgical challenges, but if
performed correctly, can help eliminate many of the esthetic complications resulting from buccal bone atrophy and lost gingival architecture.”
The patient is a 44 year old female with a non-contributory medical history. She presented with a fractured post/core and crown on tooth #7 that was deemed non-restorable (Fig. 1). A 3D CBCT scan (Orthophos SL, Sirona) was taken to evaluate the tooth for periapical pathology, bone quality, and bone quantity apical to extraction site. The scan showed no pathology and 4+ mm of apical bone past the root apex. Ridge width was measured to be 6.7mm, which would facilitate a conventional diameter implant and restoration.
Preplanning and Visualization
The CBCT image data was read in SiDexis 4 reading software and subsequently scanned and opened using Galileos implant planning software (Glaxis,Sirona). Virtually planning implant cases is extremely valuable for precise implant placements and a necessary exercise to ensure proper final restoration. By examining the CBCT and practicing the case within implant planning software pre-operatively, the treating dentist was able to survey the implant site digitally, choose the correct implant body, and visualize angulations before the implant surgery is even started. When planning the implant surgery pre-operatively, any treatment decisions or modifications are made and much of the risk associated with anterior implant placement is mitigated. Pre-operative planning reduces the stress associated with anterior implant placements and also ensures a more successful procedure overall.
The virtual implant body was guided into the ideal location using the Galileos implant planning software (Fig. 2). By observing that the implant body position would engage solid bone both apically and palatally, it was ensured that the implant would have a great degree of initial primary stability.
In addition, there would be a safety zone of 2mm bone to the nasal floor. Mentally, the procedure was rehearsed and performed pre-operatively using the landmarks seen in the CBCT scan. Anatomical landmarks, such as the endodontic canal, adjacent roots, palatal bone, and the anterior root wall would guide the placement. Digital rehearsal of the surgery pre-operatively allow the practitioner to use anatomical structures like the anterior wall of the root canal system as an ideal landmark to begin mesial distal sectioning of the root (Fig. 3). After complete mesial-distal sectioning, the successful removal of palatal root segment is the next phase to be considered. The plan would be to create the initial sectional cut to a depth of 7mm and then prepare the facial root shell or socket shield to a final thickness of 1-1.5mm.
The last phase of the pre-surgical planning session considers all the possible complications that could happen during the surgery (i.e. broken buccal plate, instability of the implant on initial placement, shield exposure post-op, etc.) and how they could be corrected.
The patient was anesthetized by infiltration of 1 carpule 4% Septocaine 1:100,000 epinephrine and 1 carpule .5% Marcaine 1:200,000. The initial cut was done slightly anterior to the canal and fractured post in a mesial-distal direction using a #557 surgical length carbide bur in a high speed handpiece. The cut was taken to a depth of 7mm apically and evaluated periodically to confirm correct angulation. Elevation of the lingual portion of the root was started by using a spade proximator (Karl Schumacher). It is noted that the spade proximator was placed in the mesial, distal, and palatal portions of the periodontal ligament only to protect the buccal plate from undue pressure or elevations. It is also important to note that care should be taken to not put any excessive pressures on the buccal plate at anytime when attempting to separate the 2 segments. No elevators or periotomes should ever be placed in the medial-distal cut in an attempt to separate the 2 segments. If this is done, there is a much greater risk of breaking or dislodging the buccal plate and completely negating the procedural goals. If the clinician is unsure of the depth or angulation of the initial cut, it is advised to take a check film PA to evaluate and proceed cautiously. In the author’s experience, the initial cut is never as deep as first anticipated and more depth is often needed.
Elevation of the lingual segment, if done properly, should result in the tooth root coming out easily. If it does not, it is possible that the surgeon did not separate the two segments completely, requiring the operator to increase the depth of the cut apically to ensure complete separation of the 2 parts. A PA shot was taken in this case to confirm that the root tip was extracted completely and to evaluate the remaining root shield (Fig. 4). After confirmation of root tip removal, a precision start drill from the Nobel Replace kit was used to start the final osteotomy. This drill has a very sharp point which allows penetration into the bony socket without lateral deflection of the drill. It is noted that if a conventional 2.0 implant drill with a more blunt tip design were used, the drill would tend to chatter and jump around within the osteotomy or against the lingual wall, deflecting greatly from the desired path of insertion. A sharp, initial osteotomy drill was inserted into the socket to depth, then pulled back approximately 3mm. At this point, the tip of the drill was engaged into the lingual wall of the existing socket and driven 3 mm apico-lingually to create an initial osteotomy path for the final implant placement. This exercise ensures that the implant engages the lingual wall securely and establishes good initial stability. If this initial osteotomy step is not done properly, it is often difficult to bring the osteotomy back into a proper and accurate angulation.
After the correct angulation of the osteotomy was confirmed, the socket shield preparation phase was begun. A medium grit flame shaped diamond bur was chosen to prepare the root shield. The preparation of the shield was begun by smoothing the interior portion of the shield in a crescent shape, following the natural facial profile of the root itself. The preparation was extended apically 8mm and slightly interproximally on both the medial and distal aspects. The shield (root shell) was prepared further to a final thickness of 1-1.5mm using a #6 round diamond bur. Coronally, the gingival-facial aspect of the root shield was reduced so that the most coronal aspect was hidden 2mm subgingivally. This was done to create ideal esthetics and emergence profile for the future abutment. The rationale for preparing the shield portion last is that it is extremely helpful to use the full socket shield segment as an anatomical guide for the initial osteotomy. Once the shield is prepared, much of the angulation references are lost. Additionally, the clinician must note that implant osteotomy drills are not efficient at cutting tooth structure and to attempt this exercise is futile, at best. Implant drills are fantastic at preparing bone and creating osteotomies, but are very poor at reducing tooth structure itself.
The preparation of the osteotomy was finished using the Nobel Replace CC protocol with saline irrigation. A Nobel Replace CC 3.5 x 11.5 implant was placed in position 3mm below the facial zenith of the adjacent gingival margins. Initial torque value of +35 NcM was achieved and final radiographs were taken to confirm placement (Figs. 5-7).
A 15x20x3 Osteogen strip (Impladent Ltd.) was placed between the implant and the shield to graft the gap and promote initial clot formation. A custom PEEK tissue former was fabricated chair side to maintain the original shape of the root emergence profile and to retain natural soft tissue contours. The patient returned at the 4 week mark to evaluate healing. Both the implant and the PEEK abutment was stable and the buccal gingival tissue was healing nicely (Figs. 8,9).
The patient was dismissed with a followup appointment to begin the final restoration phase in 5 months (Figs. 10,11).
Anterior implant cases and their potential complications can be challenging for any restorative clinician no matter their skill level or experience. Minimizing post-operative trauma from extractions is extremely beneficial, if it can be achieved. By concentrating on bony and soft tissue preservations, the natural gingival contours are protected, thus leading to better final cosmetic outcomes. When planned and executed well, the Partial Extraction Therapy technique gives the clinician additional options for implant placements with protection of the surrounding tissues. (References 9,10,11,12)