Evaluation of the Efficiency of Dental Implants Used in the Oral Rehabilitation in Cleft Patients

Introduction

The clef patients alveolus and palate is one of the most common malformations among humans. It affects between 1: 700 and 1: 500 births and requires multidisciplinary treatment for the functional and aesthetic rehabilitation of the patient [1]. The principle that governs the treatment is the local anatomical reconstruction, being the first surgical interventions performed in the lip and palate, still, during the first year of life. These procedures allow speech, breathing and chewing functions to be performed by the patient as soon as possible, avoiding or reducing functional, nutritional and developmental sequelae [2]. The closure of the oronasal fistula and alveolar bone grafting (secondary grafting) are performed together with the orthodontic treatment between 7 and 11 years of age. The surgical procedure at the correct age allows eruption of the permanent dentition in the maxillary arch and remodelling of the graft forming the bone alveolus at the cleft site [3].

The absence of one or more teeth in the permanent dentition is reported in up to 66.5% of the fissured individuals [4]. In addition, diseases that affect the formation of dental tissues (microdontia, dentinogenesis or imperfect amelogenesis) are common in teeth adjacent to the cleft, especially in the lateral incisors [5]. It can be expected that in all the fissured there is some abnormality in anterior teeth [6]. These diseases interfere in the quality of the dental tissue that associated with the lack of local bone support and the need to remove the teeth that can interfere during the grafting, lead to a large number of absences among the alveolar fissures. With this absence of anterior teeth, occlusal problems occur that cannot be corrected by orthodontic treatment alone and may cause anterior teeth to retract, loss of overjet and deviation of the midline. To reduce or avoid these problems, the use of implants and prostheses on implants in the prosthetic space of missing teeth is indicated. This feature allows a bilaterally proportional maxillary alveolar perimeter suitable for occlusal closure with the arch mandibular [7]. The first report of the use of osseointegrated implants in patients with cleft palate was [8] in 1991, followed by successive reports of this successful use [9, 10, 11, 12]. In 1997 [13] published the first series of cases proving the effectiveness of implants in cracks.

In response to this author [14], stated that the use of dental implants for the rehabilitation of patients with fissures is already a common practice, however studies with the clinical situations of this treatment and long- term study were still needed. Carried out a systematic review [15], based on 11 articles that accompanied 484 implants installed in grafts reconstructed by grafting, and concluded that treatment with grafts and dental implants in fissured patients is feasible in the short term, less than 5 years, but the success rate in conjunction with perimplant clinical parameters are still required in evaluations above 5 years. In another systematic review [16] of 18 articles that accompanied 670 dental implants in fissures, showed a high success rate according to the authors (88.6%), with a 5-year follow-up after their installation.

The aim of this study was to analyze osseointegration and the quality of osseointegrated implants installed in alveolar fissures reconstructed by bone grafts in relation to the factors that make up the rehabilitating treatment of cleft palatal lip.

Material and Methods

For the analysis of the osseointegration and the quality of the implants installed in anatomical regions with fissures, a survey of the files of patients with cleft alveolar submitted to the rehabilitation of the cleft areas with dental implants was performed in the Centre of integral care to the fissured lip -(CAIF) - Curitiba / PR- Brazil, from January 2000 to December 2014. A total of 338 medical records were requested from the service secretariat and according to the inclusion and exclusion criteria, 93 were included in the study. Patients being both male and female, with either unilateral or bilateral fissures, submitted to bone grafting at CAIF and with medical records for data collection.

Statistical Analysis

The data was scanned into a spreadsheet of Excel for Mac software version 15.13.1 Microsoft 2015. Fischer's exact test was then applied for comparison of the data in the SPSS program IBM Statistics Desktop 22.0 for Base and all Modules Mac OS X Multilingual Assembly. In Fischer's scale the number of implants was evaluated quantitatively as a function of time (considered at least 6 months); the mean age of the patients, sex and the mean time of installation of the prosthesis over the implants. Where the following items were evaluated in the qualitative aspect, based on the Misch classification: the integration of the implants in relation to their survival, in relation to the length of the implants used and in relation to the age at which the bone graft was performed.

Results

Of the total of 120 implants installed in 93 patients, 113 (94.2%) implants remained with the prosthesis installed for at least 6 months. The mean age of the patients at implant installation was 24.7 years, ranging from 13 to 50 years of age, being 48% female and 52% male. The mean time of installation of the prosthesis after implant surgery was 18.7 months, ranging from 5 to 111 months and the time of follow-up of the prostheses was on average 6.1 years, varying from 1 to 15 years. Of the seven implants lost, two implants were replaced, two patients chose to install a fixed prosthesis, one continued the treatment in another state and two did not return after the loss.

The implants were submitted to a qualitative analysis according to the scale of Misch, et al. [18]. The results showed the following distribution: 50% of success (60 implants), 28.3% of satisfactory survival (34 implants), 7.5% of committed survival (9 implants) and 14.2% of failure (17 implants).

The age of secondary grafting was statistically relevant with higher implant quality in the group that performed the surgery at the ideal age (p = 0.001). In the comparison regarding osseointegration although all the failures were in the group above the ideal age, 7 losses, no statistical difference was observed (RR = 1.091: 95% CI 1.023 - 1.164, p = 0.074). Table 1 shows the distribution of qualitative scale data. Misch Rating

The length of the implants in the cleft areas was statistically different with five times greater integration in long implants (RR = 5.0; 95% CI 1.014-¬24.649; p = 0.028), where there were 5 losses in 46 short implants. On the other hand, long implants presented 2 losses in 74 implants. Regarding the quality of these implants (although long implants had more success than short implants), 55% and 41% respectively, this relation was not statistically proven (p = 0.164). Table 2 shows the distribution of integration data.

When unilateral and bilateral fissured individuals were compared to dental implants, unilateral fractures were 97% successful (72 osseointegrated in 74 implants) and bilateral fractures 89% successful (41 osseointegrated in 46 implants). Values that did not statistically show difference (RR = 0.228; 95% CI 0.042 - 1.227, p = 0.063). As to the quality of the implants in these two groups, a trend of greater success was observed in unilateral individuals (41 implants with success in 74 implants) compared to bilateral implants (19 implants in 46 implants), but the groups also had no difference p = 0.92). Regarding the donor area of the cleft reconstruction graft, complementation of graft and implant marking, the groups showed no statistical difference in osseointegration and implant quality. As for the donor area in which the group and iliac crest are compared, a relation of p = 0.152 and p = 0.943 was obtained for osseointegration and quality respectively. For groups with or without graft complementation, implant placement indicated p = 0.989 and p = 0.427 for the same clinical parameters, respectively.

Two commercial brands of implants were compared, Neodent® and Signo Vinces®. The results showed that there was no statistical difference between the groups regarding osseointegration and quality (p = 0.907 and p = 0.377).

Discussion

The osseointegration rate of 94.2% of the total dental implants installed in areas of fissures corroborates with the literature findings that have similar rates in implants installed in non-cracked areas (94%, 95%, 98%) [18, 19, 20] and in fissured areas (82%, 90% and 98%) [13, 21, 22].

This percentage was also significantly close to the rates of osseointegration of implants in non-cracked patients who were previously grafted to increase local bone volume, 96% [23] and 97% [24]. These findings reinforce the hypothesis that dental implants are effective in dental rehabilitations in the clinical conditions presented by the cleft alveolar palatal as well as in patients who are not cracked, with previous grafts or not. The smaller success of short implants (<10 mm) compared to long implants (≥10 mm) is a reason for great discussion in the literature. Some authors point to clinical advantages in using longer implants, which include an increase in initial stability, greater long-term resistance to tensile and torsional forces, and a decreased risk of movement at the implant interface. However, there is no consensus that smaller implants present greater loss [25, 26, 27].

In the present study, a 5-fold loss rate was observed for short implants when compared to long implants. The use of short implants in fissures is common because the bone volume of the secondary graft undergoes a resorption of up to 55% of its volume [27]. Thus, due to the greater probability of loss, it is recommended to use the largest possible length in the implants to be installed in these areas. However, the results of the present study do not contraindicate the installation of short implants, since of the 41 short implants used in this study, 87% (36 implants) obtained osseointegration.

In fissures grafted at the ideal age, the eruption of the canine tooth in the grafted alveolus maintains a greater local bone quantity [3]. In these patients, a higher quality of installed implants was observed, and this could be pointed out as an indication of graft reconstruction surgery being performed during the ideal age. The limitation of the study in proving the greater osseointegration of the implants in patients where the reconstruction of the cleft was performed at the ideal age can be attributed to the insufficient sample size, since the ideal age group obtained 100% osseointegration.

No statistical difference was found regarding the classification of cracks. However, it was observed that 97% of the cases of patients with unilateral fissures obtained osseointegration. On the other hand, in individuals with bilateral fissures, osseointegration occurred in 87.8% of the sample. Taking into account that the literature [27, 28, 29] indicates the greater resorption of the grafts in bilateral fissures, this fact suggests the hypothesis that there may be a greater loss of the implants in places with less bone quantity.

The iliac crest and the mentum are reported as possible donor sites for the secondary graft in fissures [2, 6, 30]. In the present study, no statistical difference was observed regarding the osseointegration and quality of the implants installed in the areas that received bone from these two sites of origin of the grafts.

One of the factors in which one could expect greater success of the implants would be the grafting complementation prior to its installation. With increased local bone volume, longer implants could be installed, but this relationship has not been proven. Of the total of implants installed 32% in fissures that had complementation of the graft and 35% in fissures without complementation of the graft were of short implants. In addition, in none of them was there statistically higher osseointegration or quality.

Although the literature indicates variable indexes of osseointegration and quality in different brands of dental implants [29, 30, 31, 32, 33], the two trademarks analyzed did not demonstrate significant difference in this study. Based on these results, it can be concluded that dental implants are viable in the rehabilitation of cleft lip and palate. It is preferable to install implants with longer lengths in cracked regions. Finally, secondary grafting surgery should be performed at the ideal age, as it may contribute to increase the quality of dental implants installed in the cleft lip and palate.

Conclusion

The dental implants are viable in the rehabilitation of cleft lip and palate, presenting in this study an osseointegration rate of 94%. Regarding the clinical aspects of the fissures and rehabilitation surgeries of these cracks, the use of short dental implants had five times greater loss than when compared to the use of long implants. The bone grafting surgery that was performed at the ideal age obtained higher quality of the implants when compared to reconstruction surgery that was performed above the ideal age. The other factors analyzed were: fissure classification, graft donor area, need for graft complementation and implant marking had no influence on osseointegration and on the quality of the implants used for the rehabilitation of the cleft palate.