Implantology Posts

12/10/15
Rehabilitation of maxillary edentulism by means of computer-guided implant surgery and provisional prosthesis with immediate loading
Fabio Cozzolino Roberto Sorrentino Luigi De Stefano

07/11/13
Controlled Split Crest and Guided Bone Regeneration (GBR) with contemporary implant placement: rationale and limits of the clinical application in esthetic areas.
Fabio Cozzolino Dario Mari Roberto Sorrentino

24/04/13
Straumann implant guided-surgery with Codiagnostix Software and immediately-loaded prosthesis
Fabio Cozzolino Roberto Sorrentino Vincenzo Mutone

16/10/12
The Membragel Straumann liquid membrane
Fabio Cozzolino

28/09/12
Mandibular full-arch restoration with Straumann implant-supported metal mesostructures and zirconia-based prosthesis: a case report
Roberto Sorrentino Fabio Cozzolino

09/06/09
Implant positioning in the Esthetic zone
Giuseppe Cozzolino Fabio Cozzolino

14/05/09
Mini maxillary sinus elevation using Sincrest
Fabio Cozzolino Giuseppe Cozzolino

23/04/09
Sonosurgery Komet sonic tips
Ivo Agabiti

15/02/09
Controlled bone expansion
Fabio Cozzolino Giuseppe Cozzolino Anna Mariniello

27/12/08
Straumann implant with bone regeneration (GBR) by using Bio-Gide And Bio–Oss
Fabio Cozzolino Giuseppe Cozzolino Anna Mariniello

11/12/08
Bone Level Straumann implants
Fabio Cozzolino Giuseppe Cozzolino Anna Mariniello

08/11/08
Rehabilitation of complete mandibular edentulism by means of an implant-supported overdenture retained by the Locator® System
Fabio Cozzolino Carlo Montesarchio

31/10/08
Delayed loading of post-extractive Straumann implants inserted in maxillary molar area
Fabio Cozzolino Giuseppe Cozzolino Vincenzo Mutone


Rehabilitation of maxillary edentulism by means of computer-guided implant surgery and provisional prosthesis with immediate loading

Rehabilitation of maxillary edentulism by means of computer-guided implant surgery and provisional prosthesis with immediate loading

Computer-guided implantology and immediate loading with CAD-CAM screw-retained full-arch temporary prosthesis

 

A 41 year-old female patient presented with multiple missing teeth at both dental arches and a few remaining elements, among which fractured and non vital teeth. Moreover, the patient, in good general health but with poor oral hygiene, presented with reduced vertical dimension of occlusion (VDO), insufficient labial support and prosthetic space limited by macroglossia. The patient lamented severe functional problems, related both to mastication and speech, as well as serious esthetic concerns, since the maxillary teeth were not visible at all both at rest and during function.

1

Controlled Split Crest and Guided Bone Regeneration (GBR) with contemporary implant placement: rationale and limits of the clinical application in esthetic areas.

Controlled Split Crest and Guided Bone Regeneration (GBR) with contemporary implant placement: rationale and limits of the clinical application in esthetic areas.

The authors’ experience in the medium term.

 

Introduction

According to the current scientific literature, a prosthetically-guided approach should be the first choice for implant placement, even in case of horizontal/vertical alveolar bone resorption. In the last decade, different reconstructive techniques were described with the aim of restoring bone volume.

Among the available techniques, the authors widely experienced and achieved very satisfactory clinical outcomes with the “Edentulous Ridge Expansion” (E.R.E.), introduced by Dr. Bruschi and Scipioni in 1994.

This technique relies upon the healing potential of the spongy bone, associated with the elevation of a partial thickness flap to preserve the periosteum. The intra-bony gap is initially filled by a blood clot that turns into osteoid tissue in about 40 days. After about 90-120 days, the extracellular matrix progressively mineralizes and the osteoblasts mature into osteocytes.

Straumann implant guided-surgery with Codiagnostix Software and immediately-loaded prosthesis

Straumann implant guided-surgery with Codiagnostix Software and immediately-loaded prosthesis

COMPLETE MAXILLARY AND MANDIBULAR EDENTULISM TREATED WITH IMMEDIATELY-LOADED DENTAL IMPLANTS AND SCREWED FULL-ARCH TEMPORARY PROSTHESES


INITIAL SITUATION

The patient referred a clinical history of severe adult chronic periodontitis.
- (7) ortopantomografia
She has been edentulous at the maxillary arch for about 3 years while the latest extractions at the mandibular arch had been made about 6 months before the clinical examination. The patient presented with good general health and oral hygiene. She wore two removable complete dentures unsatisfactory for both function and esthetics.

The Membragel Straumann liquid membrane

The Membragel Straumann liquid membrane

 

ITALIAN VERSION

 

AN INNOVATIVE APPROACH TO GUIDED BONE REGENERATION.


The Straumann® Membragel™ is a technologically advanced resorbable membrane that simplifies the clinical procedures of guided bone regeneration (GBR).
The application of the liquid membrane is very easy, fast and accurate. Once it solidifies, the Membragel stabilizes the bone graft material, acting as a barrier for 4-6 months before its resorption. Preclinical data showed that the Membragel is resorbed significantly more slowly than conventional collagen membranes, offering an excellent biocompatibility to surrounding tissues. Due to its gel consistency, it can be placed accurately onto the bone defect, over the graft material. In order to stabilize the liquid membrane, it is sufficient to extend it 1-2 mm beyond the margins of the bone defect.
The use of the Straumann® Membragel™ allows for the formation of as much regenerated bone tissue as it is achieved with conventional non resorbable ePTFE membranes.
The application of such a liquid membrane is indicated in the following guided bone regeneration procedures:

  • periimplant defects (dehiscences, fenestrations);
  • post-extractive sites;
  • horizontal bone defects.

Mandibular full-arch restoration with Straumann implant-supported metal mesostructures and zirconia-based prosthesis: a case report

Mandibular full-arch restoration with Straumann implant-supported metal mesostructures and zirconia-based prosthesis: a case report

A 63-year-old female patient presented with a severe chronic periodontitis at the mandibular arch. Only teeth 33 and 44 were present and had been used as abutments for a resin removable partial denture which did not satisfy the functional and estethic needs of the patient. Moreover, a metal-ceramic crown with a supragingival margin and a mesial metal connector was evidenced on tooth 33; the patient reported that the mandibular front teeth had been previously prepared for a metal-ceramic fixed dental prosthesis, in order to limit the discomfort due to the mobility of such teeth.At the maxillary arch, the patient wore a complete removable denture which was esthetically unsatisfactory but valid to accomplish oral functions.
edentulia mascellare

Implant positioning in the Esthetic zone

Implant positioning in the Esthetic zone

 

 ITALIAN VERSION

 

Single tooth replacement has always been one of the most complex challenges for the implantologist. Patients’ expectations nowadays are very high and the slightest error in the operation management can cause aesthetic damages of various degrees. In order to achieve a good result it is fundamental to insert the implant in a prosthetically guided position using also surgical stents: these are of paramount importance to have reference points when surgery is performed. As a matter of fact, it is not the implant that has to be positioned where the bone is present, but it is the bone that has to be regenerated where the fixture has to be inserted.

In M-D sense, the implant has to be inserted in the centre of the line that joins the adjacent teeth, although, in the case of a maxillary central incisor, the fixture can be positioned slightly more distally than the central counter-lateral due to the need to account for the mesial surplus for the permanent crown. In M-D sense extreme caution has to be taken with the residual distance between the implant and the adjacent teeth: at least 1.5 mm must be left in order to let the papilla mature. The formation of the papilla does not depend on the implant, but on the underlying bone support: as a matter of fact, the soft tissues follow the bone in its reshaping processes.

It has been proven that the average thickness of soft tissues is 4.3mm ± 1mm. Tarnow observed that the presence of the papilla depends on the distance between the bone crest and the contact point: when this distance is = 5mm the papilla will always fully mature. As soon as this distance increases to 6mm, in 50% of the occurrences, the papilla will be open and show the classic “black triangle”. For this reason, when performing a prosthetic restoration on anterior region implants, it is fundamental to try and bring the contact point as apically as possible, in order to avoid soft tissues loss.

When the M-D distance between tooth and implant is less than 1.5 mm the loss of the papilla in that area will be a certainty, due to the bone resorption of the adjacent tooth.

For this reason it is paramount to choose the implant of the right size for each site. In the case of mandibular incisors reduced diameter implants will be used. In the case of maxillary central incisors or canines 4mm diameter implants will be used. In the case of lateral incisors the choice will depend on the circumstances, according to the found spaces. In coronal-apical sense, a sunken implant will have to be inserted with the shoulder positioned 3mm more apically than the line that joins buccally the cementoenamel junction of the adjacent teeth.

Implant placement esthetic zone

Mini maxillary sinus elevation using Sincrest

Mini maxillary sinus elevation using Sincrest

 

 ITALIAN VERSION

 

MINIMALLY INVASIVE TRANSCRESTAL MAXILLARY SINUS ELEVATION

 

Inserting implants in the back of the maxilla can present considerable technical difficulties. The dentist has often to face coronally-apically reduced bone portions deriving from crestal bone reabsorption or maxillary sinus pneumatisation, especially when in the area there are extractions performed many years before.

In the case the reduced height is mainly due to crestal bone reabsorbtion, before inserting the implants it is necessary to coronally regenerate the bone. This is done in order to avoid using prosthesis with teeth which are too long and would cause an unfavourable crown/root ratio.

On the other hand, when the reabsorption is mainly due to a pneumatisation of the maxillary sinus, it is important to estimate the amount of remaining bone.

As a matter of fact, if the bone height is < 4mm, there is enough bone to achieve primary stabilization of the implant; in this case the operation will be carried out in a single stage performing a mini-elevation of the maxillary sinus and, at the same time, inserting the fixture.

The maxillary sinus mini elevation technique with osteotomes, explained by Summers in 1994, requires the implant site to be prepared up to 2 mm from the sinus floor. At this point, using a concave osteotome, it is time to break the 2 remaining mm of bone; the bio-material is then inserted with the help of the osteotomes, leading to the elevation of the Schneider membrane. In this technique it is the load of the bio-material that elevates the sinus floor: the osteotomes are never to enter in the maxillary sinus.

Once the sinus floor has been elevated, it is time to insert the implant. The mini-elevation technique, when usable, provides remarkable benefits in respect to the standard elevation of the sinus floor.

With this technique, it is indeed necessary for the patient to undergo just one operation, the morbility is considerably lower than in the standard elevation, vascular complications are noticeably reduced and prosthetic rehabilitation times are appreciably shortened.

One disadvantage of this technique is that the surgeon operates blindfold, without seeing directly: this greatly increases the risk of tearing Schneider membrane – sometimes being just a few tenths of millimeter thick.

In this work we will analyze a new device, made by Meta, that should make it possible to elevate the sinus floor in a safer and more controlled way.

The Sincrest is a transcrestal maxillary sinus floor elevation kit made up of burs for electric handpiece, depth stops of various heights and a manual osteotome. The manual osteotome was designed to achieve the controlled fracture of the sinus floor by the maxillary sinus mucosa without damaging it.

The patient, aged 64, non smoker, came to our observation complaining about a low chewing efficiency after the maxillary sixths were extracted many years before and not replaced with a prosthesis. The X-rays show a bone with reduced height because of the pneumatisation of the maxillary sinus.

From endo-oral X-rays made using Rinn Digital Sensor Positioning Aids and a CAT, the residual height is estimated to be less than 8 mm. It is thus decided to insert the implant and at the same time elevate transcrestally the sinus floor using the SinCrest device.

Sonosurgery Komet sonic tips

Sonosurgery Komet sonic tips

 

 ITALIAN VERSION

 

ERE (Edentulous Ridge Expansion) TECHNIQUE IN TWO STAGES.

 

In implant-supported prosthodontics there is often the need to insert implants with shapes and dimensions adequate to the teeth to be replaced, in line with the load forces and allowing the creation of an ideal emergence profile of the crowns.

These issues often force the surgeon to expand the remaining bone crest using procedures aiming at that goal. Among all the known “augmentation techniques”, a recent revision of scientific literature indicates the split-crest as one of the most highly predictable surgical methods, with a success rate of 98-100% (Chiapasco 2006) and the lowest occurrence of volumetric shrinkage during and after healing. In the case under examination, the splitcrested technique – to be more specific the ERE (Edentolous Ridge Expansion) (Bruschi and Scipioni) – was used; the surgical protocol of this technique of ridge expansion requires a partial thickness flap, not to cause cortical bone periosteum loss.

The tissue is subsequently repositioned apically; both the gingival wound and the mineralized tissue are made heal for second intention. The implant was made transmucosal by inserting the healing abutment in the surgical phase. When one faces a particularly thin ridge with little marrow or a not very elastic bone, difficult to distract, it is better to adopt the two-stage technique, allowing 40/50 days between the two operations. It is well known that in the first stage of its healing process, the bone goes through its osteoclastic phase of healing, losing part of its mineralized component and making the tissue structure much more elastic (woven bone): this feature makes it much easier to distract it.

Following the protocol, to execute the primary sagittal and release incisions – needed to plan release lines of the bone walls to distract – there is a wide choice of instruments that can be used: manual, rotary, reciprocating, piezoelectric, etc.

The latest instrument coming out for this purpose uses the micro-vibrating sonic movement of air-driven handpieces (e.g. Sonicflex kavo). Sonosurgery bonetips “sonic” instruments are made by Komet (Gebr. Basseler DE): they come in 3 shapes that are well suited to reach any place of possible operation within the mouth, even the most inaccessible. One of the most important features of these tips is to have a very thin incision section (0.2 mm), impossible to obtain with other known instruments used for this purpose, not even the piezosurgical ones.

This feature allows to spare precious bone and, at the same time, does not cause heating; as a matter of fact, the small metal mass of the blades limits the building up of heat, which is immediately dissipated. Moreover these instruments have a bone tissue selective cutting feature and ensure the most absolute respect to the integrity of soft tissues: this is due to the slow movement, compared to other instruments, but especially because there is no need to exert pressure during the use.

Controlled bone expansion

Controlled bone expansion

 ITALIAN VERSION

NEW CONTROLLED BONE EXPANSION TECHNIQUE: MULTI-DISCIPLINE CLINICAL CASE (SURGICAL AND ORTHODONTIC PART)

PROSTHESIC PHASE

 

In implant-prosthetic rehabilitation, the presence of horizontal or vertical bone re-absorptions represents one of the most frequent anatomic limits impeding implant positioning. When bone areas are not suitable for implant positioning, reconstruction techniques can be used to restore bone anatomy. These techniques allow implant inserting of appropriate number and length for a correct dental arch restore.

In case of severe horizontal crest atrophies, the technique used to restore a correct vestibular-oral dimension, are the following:

  • regenerative techniques (Guided Bone Regeneration);
  • bone grafts;
  • expansion techniques;
  • bone distraction;
  • crest sagital osteothomy (ERE);
  • extension Crest ;
  • combined techniques (regenerative techniques, expansive techniques)

Edentulous bridge expansion (ERE) technique has been created in 1986 and presented 2 years later by Dr. Bruschi and Dr. Scipioni. The technique has been improved during the past years. Nowadays, it is used to reestablish orofacial dimensions suitable for alveolar atrophic crests during implant introduction without membrane induction and without bone-inductor or bone-conductor materials induction.

A study conducted on edentul sites treated with ERE technique confirmed that in the intraosseous rupture surgically created there is a complete bone regeneration. Interestingly, the same bone integration level is obtained on control sites treated with a traditional surgical implant technique. This technique uses the normal regenerative potential of the spongy bone, improved by a careful surgical approach with a periosteum conservation, together with recovery techniques by second intention. Intra-osseous rupture is, at first, filled by a clot; in the next days (about 40), there begins the formation of osteoid tissue that progressively (after 90-120 days) matures by increase in matrix mineralization and transformation of osteoblasts in osteocytes.

There are two principal prerequisites for bone regeneration after slit crest:

  1. a solid nutritional basis, with a minimum thickness of 1-1,5 mm of osseous flaps;
  2. an abundant blood flow necessary for newborn trabeculars.

This allows to avoid fenestrations, dehiscences or necrosis of vestibular osseous plate during the introduction and recovery phases of osteointegrated implants.

ERE technique is indicated in blade knife crests with a height of 10 mm minimum and a thickness of 4 mm minimum. It is performed by a crestal cut to release a flap of partial thickness edge in a vestibular and palatal direction. If necessary, two cuts are carried out in the mesial and distal limits of the surgical area. After the edges are raised, we proceed with cutting the bone in the crest center (5-7 mm deep); secondarily, we carry out two parallel trans-periosteal cuts. Thus, there result two vertical grooves in the vestibular cortical plan. A scalpel is inserted in the crest incision and beaten softly with a percussion hammer, until it reaches the lower part of the crack; at this point the scalpel will be used as a lever to dislocate the buccal plate in a vestibular direction.

The recovery period of implants inserted with the ERE technique is identical to the prescribed period for classic procedures. Nowadays, there seems to be a higher stability of the bone regenerated by bone expansion through time than that obtained by guided bone regeneration (GBR) techniques that tend to reabsorbed through time.

The disadvantage of the ERE technique is the risk of fracture of the vestibular wedge during the scalpel action, not being able to control the power during hammering. To avoid this risk the flap is cut at a partial thickness to guarantee blood flow of the cortical bone in case of fracture. On one hand the partial thickness flap preserves us from this risk, on the other hand not detaching the periosteum does not enable us to associate bone regeneration techniques.

Some years ago the Extension crest technique was presented.This technique, following incision in crest and bone expansion of 2 mm, is based on the insertion of a 2 mm thick distractor, activated by a screw and immediately bringing to the superior dental arch, or after a few days to the inferior arch to the crest expansion. This technique permits to control the expansion and to make it more predictable. A big disadvantage, instead, is the tool thickness. Actually, there exist 3 mm diameter implants of predictable use. Therefore, when the bone is expanded of 2 mm to introduce the Extension Crest there would be only 1 mm of expansion left for implant insertion. For all these reasons in the clinical practice during these last 4 years we tried to improve a controlled bone expansion technique that allows us to give predictability to the technique of bone expansion in order to obtain the detachment of a total thickness flap and so to associate guided osseous regeneration techniques.

The use of the scalpel cannot be foreseen and its’ power not being continuous may cause the fracture of the bone fragment with its consequent dislocation. Controlled osseous technique includes the use of manual screw expanders. Manual screw expanders can be checked more easily by the user, they allow to check with a ratcher its expansion power. In particular, they allow minimum expansion movements, each screw movement being of 0,2 mm. These screws should have a decreasing in its conical shape. This reduces expansion powers on the crest edge which is usually the weakest point.

Clinical case

The patient of this case presented a medial survey until the apex of the element n.11 caused by a root fracture not immediately diagnosed and a 3 mm diasteme between the 2 superior central teeth. The extraction of this element was thus necessary as was the consequent implant rehabilitation following 9 months from the extraction. Meanwhile, it was necessary to put a temporary prosthesis on the edentule saddle and considering that the patient wanted to fill the space between the two central teeth it was also required an orthodontic movement to improve in a mesial-distal way the space for a future implant site and the prosthetic dental crown. The patient declined at the same time the multibrackets vestibular therapy which would have allowed at the same time the maintainance of the temporary tooth.

Straumann implant with bone regeneration (GBR) by using Bio-Gide And Bio–Oss

Straumann implant with bone regeneration (GBR) by using Bio-Gide And Bio–Oss

 

 ITALIAN VERSION

 

COMPLEX MULTIDISCIPLINARY IMPLANT-ORTHODONTIC TREATMENT: ESTHETIC INVISIBLE ORTHODONTIC THERAPY COMBINED WITH IMPLANT SURGERY AND SIMULTANEOUS BONE AUGMENTATION

 

The present case report is aimed at presenting an implant treatment associated with both a simultaneous guided bone regeneration (GBR) and an orthodontic therapy. The complexity of the case required the use of a resorbable Bio-Gide membrane and a bone graft made up of autogenous bone together with Bio-Oss. Simultaneously, an esthetic orthodontic therapy was performed by means of ceramic brackets and miniscrews at the maxillary arch and using an invisible bracketless approach by means of preactivated retainers at the mandibular arch.

It is worth remembering that the type of membrane is a critical factor for the success of bone augmentation procedures. Nowadays, it is widely accepted that only non resorbable Gore-Tex membranes can guarantee a predictable result in complex bone reconstructions. Adequately stabilized resorbable membranes can be considered a viable alternative only in easier clinical cases and in the presence of a good regenerative potential. In order to properly stabilize resorbable membranes, nowadays resorbable pins are available (Resor Pin, Geistlich); differently, operative tips may be adopted, just like the use of membrane strips opportunely cut, as proposed by Prof. Massimo Simion, or creating a hole in the membrane so a sto stabilize it around the implant neck.

As to this clinical case, the patients lamented recurrent abscesses in region 14. First canine and molar class on both sides with a deep bite and mandibular crowding were evidenced.

Straumann implant with guided bone regeneration (GBR) with Bio-gide and Bio-oss
Biogide
Bio oss

A vertical radicular fracture of tooth 14 was noticed. Such tooth had been previously restored by means of a metal cast post and a metal-ceramic crown; consequently, the extraction of tooth 14 was compulsory.

In order to solve the orthodontic problems, buccal ceramic brackets were used at the maxillary arch together with mini-screws to make the opening of the deep bite faster. On the contrary, pre-activated retainers were used at the mandibular arch, in order to expand the intercanine distance and to line up the anterior mandibular teeth.

Mini screw
Orthodontic screw
Retainer
Active retainer
Orthodontic retainer

The choice of using brackets at the maxillary arch was due to the necessity of maintain a provisional resin shell in region 14. Such shell was fastened to the orthodontic wire by means of a metal ligature. In order to control the rotation of the resin shell, a continue ligature from tooth 13 to tooth 15 was made alternating the rotation spin mesially and distally to the provisional shell.

As we can also see in further cases in the present blog, to date it is preferable to avoid such a problem in the absence of teeth using rigid orthodontic wires lingually to fasten provisional crowns, so as to perform a bracketless lingual orthodontic therapy also in such cases.

Bone Level Straumann implants

Bone Level Straumann implants

 ITALIAN VERSION

STRAUMANN BONE LEVEL SUBMERGED IMPLANTS TREATED USING A NON-SUBMERGED IMPLANT TECHNIQUE: CLINICAL CASE OF AGENESIS OF TWO LATERAL INCISORS. SURGICAL PHASE OF THERAPY

Prosthetic part

The prevalence of both unilateral and bilateral agenesis of the maxillary lateral incisors is remarkable in dentistry (1). The proper treatment of such a condition requires a multidisciplinary approach and the use of a diagnostic wax up is paramount. The first step of the rehabilitation consists of a pre-surgical orthodontic treatment to harmonically distribute and balance the interdental spaces (2,3). The placement of osseointegrated implants is a complex procedure and attention must be paid to any possible esthetic and functional concern.

In case of lateral incisors agenesis, a lack of bone tissue is always present due both to the failed development of the missing tooth and to the bone resorption caused by the absence of such tooth. Moreover, a lack of attached gingiva is often evident in the area interested by the agenesis as well. Consequently, in most cases, when an implant treatment is planned, bone regeneration techniques and grafts of connective tissue are necessary to optimize the esthetic outcome.

Considering the reduced dimension of maxillary lateral incisors, the choice of the implant type is paramount as well.

Maxillary lateral incisor agenesis
Monolateral agenesis
Tooth agenesis
Bilateral agenesis
Opposing arch

The present clinical report aims at describing the case of a 23-year-old male patient showing a bilateral agenesis of the maxillary lateral incisor and microdontia of the maxillary central incisors.

The orthodontic clinical examination showed molar and canine Class I on the right side, molar Class I and head-to-head canine on the left side, deep bite and an increased interincisive angle.

An orthodontic treatment was proposed to the patient in order to optimize the dental spaces and to solve the deep bite before implant placement. The ideal treatment would have provided a reduction of the central diastema to be completed by means of laminate veneers. Such a choice would have improved the esthetic result, allowing a molar and canine Class I occlusion on both sides. Conversely, the patient did not agree with the proposed shape modification of the central incisors and the risk to renew the veneers after a long term of function.

The treatment alternative was planned by means of the mesialization of the maxillary central incisors and, then, of the maxillary posterior teeth, achieving a molar and canine Class II occlusion on both sides.

Rehabilitation of complete mandibular edentulism by means of an implant-supported overdenture retained by the Locator® System

Rehabilitation of complete mandibular edentulism by means of an implant-supported overdenture retained by the Locator® System

INTRODUCTION

The use of removable dentures stabilized by osseointegrated implants may improve the quality of life of edentulous patients. Overdentures (OVD) are removable dental prostheses that cover and rest on one or more remaining natural teeth, the roots of natural teeth and/or dental implants improving stability and reducing ridge resorption. Such implant-supported prostheses represent a compromise solution between the advantages of fixed prostheses and traditional complete removable dentures in totally edentulous patients. In scientific literature good adaptability was reported in edentulous patients provided with maxillary complete removable dentures, whereas phonetic and functional problems due to prosthesis instability were lamented by patients wearing mandibular complete removable dentures.
As to implant-supported OVDs, several advantages were pointed out just like improvement of chewing ability in comparison with traditional complete removable dentures, esthetic and phonetic improvements, lower susceptibility of the success of the rehabilitation to the optimal insertion of implants than fixed prostheses. Notwithstanding the mandibular residual ridge resorption, a sufficient amount of bone tissue often remains in the interforaminal region to properly insert at least 2 implants. The presence of 2 or 4 osseointegrated implants in such area seems not to affect the long term success of OVDs: as to retention, stability, stress distribution and peri-implant health, comparable results were noticed with both 2 or 4 interforaminal implants. High success rates were reported with mandibular OVDs, whereas higher failure rates were showed with maxillary OVDs. Success rates range between 92% and 100% and they seem not to be related to either the system of connection or the age of the patients. As to the supporting implant system, several studies obtained comparable results with both submerged and non-submerged implants. However, the use of the latter allows clinicians to perform one-step surgical procedures thus reducing the costs of the rehabilitation and the patients’ discomfort, in particular when treating old or defeated patients.
Nowadays several retention systems for OVDs are available: bar clips, solitary ball attachments, magnets, telescopic crowns. The anchorage design must be chosen after a careful evaluation of the morphology and anatomy of the edentulous arch, the position of the implants, the needs of retention, the occlusion with the antagonist arch, the hygienic habits, the economic needs and the compliance for recall of the patient.
The use of solitary attachments is advisable when a satisfactory parallelism between the implants is obtained. A non-optimal insertion of the implants can be corrected by means of ball attachments provided with angulated abutments or by the innovative anchorage system of Locator®. Solitary attachments can follow the functional distortions of the mandible because of the absence of a rigid connection; as a consequence, most of the stress concentrate at level of the symphysis avoiding implant overload. Although bars are more retentive, ball attachments are less technique sensitive, easier to clean and less costly. Controversy persists as to whether the bar clips or the ball attachments requires more maintenance. Moreover, the use bar retention systems is affected by jaw anatomy and might result in functional limitations of the tongue. The rigid connection provided by bar clips causes lower bone resorption but higher peri-implant bone stress concentration than solitary attachments do: consequently mechanical complications might occur as bars badly withstand non axial forces.
The Straumann Locator® system is a non-rigid connection anchorage using innovative solitary attachments. It is provided with self-positioning components with different height. This results in several advantages for both clinicians and patients, such as rehabilitations in case of limited denture space, easy maintenance and replacement of the retentive components, easy insertion and removing of the prosthesis. Moreover, the Locator® system can be used to compensate eventual divergence of up to 40° between two implants.

CASE REPORT

A 63 years old non-smoker female patient was interested by complete mandibular edentulism due to previous chronic periodontitis (1,2).

Mandibular edentulous ridge

Edentulous mandible

The patient had been previously provided with a mandibular complete removable denture antagonist to a maxillary metal-ceramics full-arch bridge. The patient complained about the stability and retention of the denture asking for mechanical anchorage of the prosthesis. The lack of retention negatively influenced the patient’s social life weakening her self-consciousness as well. Moreover, she complained about limited function and bad chewing ability that had affected her food habits. Considering her psychological attitude and the economic needs, the patient was asked to sign a written consent form and it was decided to realize a new implant-supported OVD by inserting 4 Straumann implants and the innovative Locator® anchorage system.
Surgical treatment: A crestal incision was performed with a 15c Bard Parker blade and a full-thickness flap was elevated preserving a sufficient amount of keratinized mucosa on the buccal aspect of the alveolar ridge. Only one midline vertical buccal relieving incision was cut and buccal and lingual spreading sutures were executed to properly visualize the surgical site (3).

Delayed loading of post-extractive Straumann implants inserted in maxillary molar area

Delayed loading of post-extractive Straumann implants inserted in maxillary molar area

 

The high success rate of prosthetic rehabilitation by means of osseointegrated implants both in partially and totally edentulous patients currently represents the proof of power of the rules related to the biological processes of osseointegration (Romeo E. et al., 2004). The presence of an adequate percentage of bone mass is critical, facilitating the three-dimensional positioning of the implant in order to guarantee a morphologically, functionally and aesthetically optimal healing of teeth.

To note that “this percentage of bone mass” (or bone quantity) must be in adequate relationship with the antagonist arch in order to achieve the aesthetic and functional rehabilitation and also to allow the physiological transmission of the forces along the long-axis of the implant.

The reduction of the functional eccentric loads may not influence the biological osseointegration process already performed (Isidor, 1996) and, moreover, it helps to reduce the forces and the level of stress that may be dangerous for the implant and/ or prosthetic components.

Edentulous crest bone dimensions require an adequate bone thickness in vestibular-lingual and palatal direction, able to facilitate the implant insertion in a suitable position for the future prosthesic rehabilitation, whereas around the implant a bone quantity of about 1mm on both sides must be maintained. In mesial-distal direction the edentulous space should allow the re-establishment of a correct interproximal space to achieve an efficient mechanical detersion.

It is well known that the mesial-distal dimensions among the contact points of the adjoining elements must be at least 7-8 mms in order to fix correctly implants having a prosthetic base of about 5mm, similar to the “standard” – Straumann implants. In order to proceed to the implant insertion of a “standard” length, a space of at least 8 mm must be available in the crown-apical approach. After the extraction of the tooth element, a 4-6 month wait period is necessary, to obtain a highly mineralized bone able to ensure a better implant stability (Chen et al., 2004; Cardaropoli et al., 2005) .

This waiting period represents an uneasiness for the patients who insistently ask to reduce the long waiting period leading to the prosthetic implant rehabilitation.

Although there are several factors influencing the entity of the post-extractive bone healing process (i.e. pathologies caused by the extraction, surgical trauma due to the extraction, bone biotype, gingival biotype, elapsed time, etc.), there is always evidence of bone remodelling, by a reabsorption of the vestibular- cortical bone (Cardaropoli et al., 2003) that can make more complex the future displacement of the implants.
According to Carlsson and Persson, six months after the tooth extraction, a bone reabsorption equal to the 23% of the residual crest average can be observed, increasing by a further 11% after two years.

In order to reduce the long treatment periods and avoid or diminish the post-extractive bone re-absorption, clinicians use implants rapidly inserted in the post-extractive alveoli during tooth extraction (immediate post-extractive implants), or immediately after soft tissue healing (delayed post-extractive implants).

However, in the past there has been reported a high percentage of failures, especially due to the insertion of cylindrical or smooth surface titanium implants, the use of non-absorbing membranes(often exposed to the oral cavity during their displacement), the poor knowledge on bone healing biology and the approximated surgical techniques, especially in case of immediate-loading post-extractive implants (Gher et al., 1994).

Nowadays, the use of rough surface implants (more osteofilic) with a trunk-conic shape to facilitate space reduction between the alveolar bone walls, the use of reabsorbing membranes and more sophisticated surgical techniques employed and more importantly, better scientific knowledge acquired about the bone healing process have helped to increase the average percentage of success, that is over 92-93% (Chen et al., 2004).

Today implants inserted inside the natural alveoli are defined post-extractive. They are distinguished in two types: immediate or type I (characterized by the implant insertion inside the natural alveolus immediately after the tooth extraction that is seen as part of the surgical act), and delayed or type II (characterized by the implant insertion inside the natural alveolus, 4-8 weeks after the extraction, following soft tissue healing).
Both these methods allow to use the reparative regeneration properties of the bone tissues thanks to the presence of a big quantity of growth factors in the alveolus influencing the site neovascularisation and bone cell proliferation.

The advantages of the immediate implant loading in the post-extractive alveolus are related to the reduction of the number of surgeries and the treatment period length. The disadvantages are related to the site morphology that could not be optimal for the loading and the stability of the implant, or because of cheratinization of the mucosa that could be inadequate for an optimal adaptation to the edge especially in case of a thin gingival biotype.

The delayed post-extractive implant has the advantage to have bigger quantity and volume of mucosal tissue (this makes simpler the “management” of the soft tissues) and it can be displaced in the healthy alveolus, whereas disadvantages consist in the long period of treatment (4-8 weeks) and also any possible premature reabsorption of the bone walls could make more complex the morphology of the post-extractive site.

At this point it must be specified that clinical studies regarding bone restoration show that if there is a small space (<>mm or the insertion of the post-extractive implant is associated to the presence of a reabsorption of one or more alveolar walls, then it is required to effect additional procedures for the bone restoration through the use of membranes and bone grafts (Hämmerle et al., 2004).

In both cases, it should be noted that these are very delicate methods due to difficulties in controlling different parameters taking part in the process of the bone and perimplantar mucosal tissue healing.

Till today, the post-extractive implants have been used particularly in substitution of monoradicular or biradicular teeth. Therefore, these implants are most commonly employed in the anterior areas of the oral cavity as the patients want to reduce the long treatment period especially when is involved an aesthetic area. Furthermore, the clinicians operate easily in these sites of the mouth: the access is simple, the possibility to insert the implants in optimal positions in terms of prosthetic point of view is optimal and it can be achieved a good primary stability with the result of small gap between the bone and the implant.

In posterior areas, the use of these post-extractive techniques is avoided due to the lower aesthetic demands and the presence of greater bone volume. Differently to the frontal areas, any possible post-extractive implant insertion made in the molar areas require the use of inter radicular septa (often very small) for the anchorage and in order to achieve enough stability of the implant. As a result there is a big gap between the bone walls and the implant.

In case of insertion of the implants in the mesial-distal alveoli in order to apply premolar-shaped prosthetic crowns, the nearness between them and the dental roots can often represent a local contraindication for the insertion of post-extractive implants in the alveoli. In fact, it is not possible to guarantee enough space for the detersion of the approximal surfaces of the prosthetic crowns.

The following clinical case shows a prosthetic implant rehabilitation performed through 2 delayed post-extractive implants displaced to the same level of the mesial-distal roots of a molar pulled out six weeks before.

CLINICAL CASE

A 51 year-old male patient, non smoker had the molars 36 and 37 irremediably damaged for dental decay process. (Fig.1)

Fractured teeth x-ray

The high rate of functional deficit became aggravated for the loss of the 35 clinical crown. Therefore the patient wished to restore as soon as possible a satisfactory masticatory function through a rehabilitation achieved with fixed prostheses. The lack of 27 to the antagonist arch and the presence of an interradicular septum of a big dimension due to the excessive divarication of the 36 roots allowed us to plan the orthodontic and prosthetic recovery of 35 and the insertion of two delayed post-extractive implants in the alveoli of 36 for the realization of two premolar shaped prosthetic crowns.
After the delicate extraction of 36 and 37 and the revision of the post extractive alveoli, it had been necessary to wait for 6 weeks to obtain an optimal recovery of the soft tissues (Fig.2).